Photosensitive member unit, cartridge and electrophotographic image forming apparatus

[0001] The present invention relates to a cartridge which is mountable to and dismountable from an electrophotographic image forming apparatus and relates to an electrophotographic image forming apparatus using the cartridge.

[0002] The electrophotographic image forming apparatus forms an image on a recording material by using an electrophotographic image forming method. Examples of the electrophotographic image forming apparatus include, an electrophotographic copying apparatus, an electrophotographic printer (LED 15 printer, laser beam printer, and so on), a facsimile machine, a word processor, and the like, for example.

[0003] In an electrophotographic image forming apparatus (hereinafter, also simply referred to as “image forming apparatus”), a toner image is formed on an electrophotographic photosensitive member (photosensitive drum or drum), and the toner image is directly or indirectly transferred onto a recording material, by which an image is formed on the recording material.

[0004] In general, such an image forming apparatus requires replenishment of toner (developer) and maintenance of various members. Therefore, there is a cartridge-type image forming apparatus in which a cartridge can be mounted to and dismounted from the image forming apparatus, and the toner replenishment and maintenance operation is performed in effect by exchanging the cartridge.

[0005] The cartridge includes at least one of a drum and a process means, and is dismountably mounted to the main assembly (apparatus main assembly) of the image forming apparatus. The process means are means for forming an image, and those acting on the drum mainly include developing means, charging means, image transfer means, electric charge elimination means, cleaning means and the like. Examples of the cartridge include a process cartridge including a drum and at least one process means and being integrally mountable to and dismountable from the apparatus main assembly, a drum cartridge including a drum, a developing cartridge including a developing means, and the like. According to such a cartridge method, it becomes possible to easily perform toner replenishment and maintenance operations of the image forming apparatus.

[0006] As a structure for transmitting the driving force from the main assembly of the apparatus to the cartridge, a gear is used as shown in Japanese Patent Application Laid-Open No. S63-4252, and a coupling is used as shown in Japanese Patent Application Laid-Open No. H8-328449.

[0007] It is an object of the present invention (disclosure) to provide a development a photosensitive member unit, a cartridge, or an electrophotographic image forming apparatus.

[0008] The present invention provides at least a photosensitive member unit detachably mountable to a main assembly of an image forming apparatus, the image forming apparatus including a first main assembly side helical gear portion and a second main assembly side helical gear portion which are coaxially rotatable, the photosensitive member unit comprising a photosensitive member rotatable about a rotational axis thereof; a first unit side helical gear portion for meshing engagement with the first main assembly side helical gear portion; and a second unit side helical gear portion for meshing engagement with the second main assembly side helical gear portion, wherein a twisting direction of a tooth of the second unit side helical gear portion is the same as the twisting direction of a tooth of first unit side helical gear portion, wherein a helix angle of the tooth of the second unit side helical gear portion is larger than a helix angle of the tooth of the first unit side helical gear portion, and wherein the first unit side helical gear portion and the second unit side helical gear portion are rotatable in a state in which the first unit side helical gear portion is in meshing engagement with the first main assembly side helical gear portion, and the second unit side helical gear portion is in meshing engagement with the second main assembly side helical gear portion.

[0009] According to the present invention (the present disclosure), there is provided a development for a photosensitive member unit, a cartridge, or an electrophotographic image forming apparatus.

<Overall Structure of Image Forming Apparatus>

[0124] FIG. 2 is a sectional view of the electrophotographic image forming apparatus (image forming apparatus) 100, and the plane of the cross-section is perpendicular to a rotational axis L1 of a photosensitive drum 62 which will be described hereinafter. The image forming apparatus 100 is a laser beam printer using electrophotographic process, and a cartridge B including the photosensitive drum 62 is dismountably mounted to an apparatus main assembly A. That is, parts of the image forming apparatus 100 excluding the cartridge B is the apparatus main assembly A. When the cartridge B is mounted in the apparatus main assembly A, it is possible to form an image on a recording material (sheet material) PA such as paper.

<Structure of Main Assembly of the Apparatus>

[0125] The apparatus main assembly A includes an exposure device (laser scanner unit) 3 and a sheet tray 4 for accommodating the sheet material PA. Further, the apparatus main assembly A includes a pickup roller 5a, a feeding roller pair 5b, a transfer guide 6, a transfer roller 7, a feeding guide 8, a fixing device 9, a discharge roller pair 10, and a discharge tray 11 in the order named along a feed direction D of the sheet material PA. The fixing device 9 includes a heating roller 9a and a pressure roller 9b.

<Cartridge Structure>

[0126] Next, referring to FIGS. 3, 4, 5, 6, and 7, an overall structure of the cartridge B will be described. FIG. 3 is a cross-sectional view of the cartridge B, taken along a plane perpendicular to the rotational axis L1 of the photosensitive drum 62 which will be described hereinafter. FIGS. 4 and 5 are exploded perspective views illustrating the structure of the cartridge B. Part (a) of FIG. 6 is an exploded perspective view illustrating the structure of the drum unit 69. Part (b) of FIG. 6 is an exploded perspective view illustrating the structure of the cleaning unit. FIG. 7 is a cross-sectional view of a drive unit which transmits a driving force from the image forming apparatus A to the cartridge B. In this embodiment, the screws and the like used to connect the parts will be omitted.

[0127] The cartridge B is a process cartridge and mainly includes an electrophotographic photosensitive member and a process means acting on the electrophotographic photosensitive member. The process means includes charging means, developing means and cleaning means which will be described hereinafter. The cartridge B has a structure mainly including a cleaning unit (drum unit) 60 and a developing unit 20, and the electrophotographic photosensitive member and the process means are provided in these cleaning unit 60 or in the developing unit 20.

[0128] The longitudinal direction of the drum 62 is parallel with the direction of the rotational axis L1 of the drum 62 (direction of the rotational axis). In the drum 62, the side on which the driving force is transmitted from the apparatus main assembly A with respect to the rotational axis direction is referred to as a driving side, and the opposite side thereof in the direction is referred to as a non-driving side. Further, the direction from the non-driving side toward the driving side in the rotational axis L1 of the drum 62 (parallel to the rotational axis L1) is J direction, and the direction from the driving side toward the non-driving side is H direction. When the J direction and the H direction are referred to in the apparatus main assembly A, they are defined so as to be the same as the J direction and the H direction at the time when the cartridge B is mounted in the apparatus main assembly A.

<Cleaning Unit (Drum Unit)>

[0129] As shown in FIG. 3, the cleaning unit (drum unit) 60 includes a photosensitive drum 62, a charging roller 66, a cleaning member 77, and a cleaning frame (drum frame) 60a which supports them. The cleaning frame (drum frame) 60a includes a frame member 71 and a drum bearing member 73.

[0130] As shown in part (a) of FIG. 6, the photosensitive drum (drum) 62, which is a rotatable member, is a cylindrical electrophotographic photosensitive member, and is an aluminum cylinder having an outer peripheral surface coated with a photosensitive layer. A driving side flange (driving force receiving member) 63 is fixed, by clamping, to the end of the drum 62 on the driving side (one end side), and a non-driving side flange 64 is fixed, by clamping, to the end of the non-driving side (the other end side). A unit in which the drum 62, the driving side flange 63, and the non-driving side flange 64 are integrated (that is, a unit that can rotate integrally with the drum 62) is referred to as a drum unit 69.

[0131] In general, the cleaning unit 60 may be referred to as a drum unit, and in such a case, the drum 62 is contrasted with the developing means in the developing unit 20 from the standpoint of the means provided in the cartridge B, recognizing the entire cleaning unit 60 as a unit including the drum 62. Therefore, the drum unit as a name of the entire cleaning unit 60 is based on a concept different from that of the drum unit 69 (a unit rotatable integrally with the drum 62) in this embodiment. In the following description, the drum unit refers to a unit which can rotate integrally with the drum 62.

[0132] The drum 62, the driving side flange 63, and the non-driving side flange 64 rotate integrally around the rotational axis L1 of the drum. That is, the rotation axes of the driving side flange 63, the non-driving side flange 64, and the drum unit 69 are coaxial with the rotational axis L1 of the drum 62. Therefore, in the following, the rotation axes of the drum 62, the driving side flange 63, the non-driving side flange 64, and the drum unit 69 in the assembled drum unit 69 are all referred to as rotational axis L1.

[0133] Further, the driving side flange 63 and the non-driving side flange 64 are integrally fixed in the direction of the rotational axis L1. The driving side flange 63 and the non-driving side flange 64 are made of resin material. The driving side flange 63 includes a first gear portion 63c and a second gear portion 63d, which will be described in detail hereinafter.

[0134] As shown in part (b) of FIG. 6, the drum unit 69 is supported, rotatably around the rotational axis L1, by the drum frame 60a (frame member 71 and drum bearing member 73). Specifically, the driving side flange 63 is provided with a hole 63g coaxial with the rotational axis L1, and a shaft member 86 press-fitted into the drum bearing member 73 is inserted into the hole 63g, by which the driving side flange 63 is rotatably supported by the drum bearing member 73. The non-driving side flange 64 has a hole (not shown) coaxial with the rotational axis L1, and the shaft member 78 press-fitted into the hole 71c of the frame member 71 is inserted into this hole, by which the non-driving side flange is rotatably supported by the frame member 71. As described above, the non-driving side flange 64 and the driving side flange 63 are supported portions rotatably supported by the shaft members 86 and 78.

[0135] Further, as shown in FIG. 7, the second gear portion 63d of the driving side flange 63 is provided with a projecting portion 63d1 projecting in the H direction on the end surface on the downstream side in the H direction, and is provided with a projecting portion 63f projecting in the J direction on the upstream side in the H direction (downstream side in the J direction). In addition, the frame member 71 includes a rib 71p and a side wall 71m provided so as to extend in a direction perpendicular to the rotational axis L1. The projecting portion 63d1 is contactable with the side surface of the rib 71p, and the projecting portion 63f is contactable with the side surface of the side wall 71m. The driving side flange 63 is slidably fitted between the rib 71p and the side wall 71m by loose fitting. Therefore, it is likely that the projecting portion 63d1 contacts the side surface of the rib 71p or the projecting portion 63f contacts the side surface of the side wall 71m, but the fitting play (gap) is extremely small (about 150 μm at the maximum), and therefore, it can be said that the positioning is substantially the same in these cases. As described above, it can be said that the drum unit 69 including the driving side flange 63 is positioned in the direction of the rotational axis L1 with respect to the drum frame 60a by the rib 71p and the side wall 71m.

[0136] In this embodiment, the longitudinal direction of the cartridge B, the drum frame 60a, and the frame member 71 is a direction parallel to the direction of the rotational axis L1 of the drum 62.

[0137] Further, as shown in FIG. 3, in the cleaning unit 60, the charging roller (charging member) 66 as the charging means and the cleaning member 77 as the cleaning means are arranged in contact with the outer peripheral surface of the drum 62, respectively. The cleaning member 77 includes a rubber blade 77a, which is a blade-shaped elastic member made of rubber as an elastic material, and a support member 77b which supports the rubber blade 77a. The rubber blade 77a is in contact with the drum 62 counterdirectionally with respect to the rotational direction of the drum 62. That is, the rubber blade 77a is in contact with the drum 62 so that the free end surface thereof faces the upstream side in the rotational direction of the drum 62. Waste toner removed from the surface of the drum 62 by the cleaning member 77 is stored (accumulated) in a waste toner chamber 71b formed by the frame member 71 and the cleaning member 77. A sheet 65 for suppressing the leakage of waste toner through the gap between the frame member 71 and the drum 62 is mounted to the edge of the frame member 71 in contact with the drum 62.

[0138] Opposite end portions of the charging roller 66 in the direction of the rotational axis are rotatably supported by a charging roller bearings 67 supported by the frame member 71. A rotational axis of the charging roller 66 is substantially parallel with the rotational axis L1 of the drum 62. The charging roller 66 is pressed against the drum 62 by pressing the charging roller bearings 67 toward the drum 62 by the urging member 68. The charging roller 66 is driven by the rotation of the drum 62.

<Developing Unit>

[0139] As shown in FIG. 3, the developing unit 20 includes a developing roller 32, a magnet roller 34, a developing blade 42, a feeding member 43, a developing frame 20a which supports them, and so on. The developing frame 20a includes a developing container 23, a bottom member 22, a bearing member 24 (see FIG. 5), a bearing member 37 (see FIG. 4), a developing side cover (see FIG. 4) 26, and a developing side cover 27 (see FIG. 5). In the developing unit 20, a toner supply chamber 28 and a toner chamber 29 are formed inside by the developing container 23 and the bottom member 22.

[0140] As shown in FIGS. 4 and 5, in the toner supply chamber 28, opposite end portions of the developing roller 32 in the rotational axis direction are rotatably supported by the bearing member 24 and the bearing member 37. The bearing member 24 and the bearing member 37 are mounted to the developing container 23. The developing roller (developing member) 32 as a developing means is a cylindrical member, and a magnet roller 34 is provided inside the cylindrical member. A developing blade 42 is provided to determine (regulate) a thickness of the toner (toner layer) carried on the surface of the developing roller 32.

[0141] Spacing members 38 are mounted to the end portions of the developing roller 32 in the direction of the rotational axis, respectively, and by the spacing members 38 contacting with the surface of the drum 62, A distance of the surface of the developing roller 32 from the surface of the drum 62 is determined. Specifically, the distance is determined such that a small gap is provided between the surface of the developing roller 32 and the surface of the drum 62.

[0142] In addition, as shown in FIG. 3, a sheet 33 for preventing the toner from leaking through a gap between the developing frame 20a and abuts on the developing roller 32 is mounted to an edge portion of the bottom member 22 so as to be in contact with the developing roller 32. Further, in the toner chamber 29, a feed member (stirring member) 43 is rotatably provided. The feeding member 43 rotates to stir the toner contained in the toner chamber 29, and transports the toner from the toner chamber 29 into the toner supply chamber 28.

<Connection Between Cleaning Unit and Developing Unit>

[0143] The cartridge B is assembled by connecting the cleaning unit 60 and the developing unit 20. As shown in FIGS. 4 and 5, first, An alignment is carried out between a center of a first development boss 26a of the developing container 23 for a first hanging hole 71i on the driving side of the frame member 71 and a center of a second supporting boss 27a for a second development hanging hole 71j on the non-driving side. Then, by moving the developing unit 20 in the direction of the arrow G, the first development supporting boss 26a and the second development supporting boss 27a are fitted into the first hanging hole 71i and the second hanging hole 71j. Thereafter, by assembling the drum bearing member 73 to the cleaning unit 60, the developing unit 20 is restricted from disengaging from the cleaning unit 60. By this, the developing unit 20 is movably connected with the cleaning unit 60. Specifically, the developing unit is connected with the cleaning unit 60 rotatably (tiltably) about the first development supporting boss 26a and the second development supporting boss 27a.

[0144] In addition, as shown in FIG. 4, a first end portion 46Rb of a driving side spring (urging member) 46R is fixed to a surface 26b of the developing side cover 26, and a second end portion 46Ra contacts a surface 71k of the frame member 71 of the cleaning unit 60. Further, as shown in FIG. 5, a first end portion 46Lb of a non-driving side spring (urging member) 46L is fixed to a surface 27b of the developing side cover 27, and a second end portion 46La contacts a surface 711 of the frame member 71. The non-driving side spring 46L and the driving side spring 46R are compression springs. The urging force of these springs produces an urging force between the developing frame 20a and the cleaning frame 60a so as to press the developing roller 32 toward the drum 62. By this, as described above, the spacing member 38 is pressed against the surface of the drum 62 and is held with the gap between the surface of the developing roller 32 and the surface of the drum 62.

<Image Forming Process>

[0145] Next, the image forming process will be described. A control unit (not shown) receives a print command signal fed from a host computer or the like, and generates a print start signal based on the print command signal to start the image forming process.

[0146] When the image forming process starts, the drum 62 is first rotationally driven in a direction of arrow R (see FIGS. 2 and 3) at a predetermined peripheral speed (process speed). A charging bias voltage is applied to the charging roller 66 to substantially uniformly charge the surface (outer peripheral surface) of the drum 62. Further, as shown in FIG. 2, the exposure device (exposure means) 3 emits a laser beam L in accordance with the image information to be printed. The laser beam L passes through the laser opening 71h provided in the frame member 71 of the cartridge B, is projected to the surface of the drum 62 charged by the charging roller 66, and scans the surface of the drum 62 with the laser beam L. By this, an electrostatic latent image corresponding to the image information is formed on the photosensitive layer on the surface of the drum 62.

[0147] On the other hand, as shown in FIG. 3, in the developing unit 20, the toner (developer) T in the toner chamber 29 is stirred and fed by the rotation of the feeding member 43, into the toner supply chamber 28. The toner T is carried on the surface of the developing roller 32 by a magnetic force of the magnet roller (fixed magnet) 34. The developing roller 32 is a developer carrying member which supports the toner T on its surface to visualize (develop) the electrostatic latent image formed on the drum 62 described above with the toner. The toner T is triboelectrically charged by the developing blade 42, and the developing blade 42 regulates the thickness (layer thickness) of the layer of the toner T on the peripheral surface of the developing roller 32 to a desired thickness. Then, the toner T carried on the surface of the developing roller 32 is supplied to and adheres to the region corresponding to the electrostatic latent image of the drum 62. By this, the electrostatic latent image on the drum 62 is visualized (developed) into a toner image. It can be said that the drum 62 is an image bearing member which carries an electrostatic latent image or a toner image (developer image) on its surface.

[0148] Further, as shown in FIG. 2, in synchronism with output timing of the laser beam L, the sheet material PA stored in the sheet tray 4 at the lower portion of the apparatus main assembly A is fed out to the feed path in the main assembly A by the pickup roller 5a and the feeding roller pair 5b. Thereafter, the sheet material PA is guided by the transfer guide 6 and fed to a transfer nip provided between the drum 62 and the transfer roller (transfer means) 7. In this transfer nip, the toner image formed on the drum 62 is transferred onto the sheet material PA.

[0149] The sheet material PA on which the toner image is transferred in the transfer nip is guided by the transfer guide 8 and conveyed into the fixing device (fixing means) 9. Then, the sheet material PA passes through the fixing nip provided between the heating roller 9a and the pressure roller 9b of the fixing device 9. By pressing and heating the sheet material PA in this fixing nip, the toner image is fused to the sheet material PA and fixed thereon. The sheet material PA which has passed through the fixing nip is fed to the discharge roller pair 10 and discharged onto the discharge tray 11.

[0150] On the other hand, as shown in FIG. 3, the surface of the drum 62 after sheet material passes through the transfer nip comes into contact with the cleaning blade 77, the toner remaining on the surface of the drum 62 is removed, and the surface of the drum 62 can be used again in the above-mentioned image forming process. The toner removed from the drum 62 by the cleaning blade 77 is stored as waste toner in the waste toner chamber 71b of the cleaning unit 60.

[0151] In this embodiment, at least the charging roller 66, the exposure device 3, the developing roller 32, the transfer roller 7, and the cleaning blade 77 are process means acting on the drum 62.

<Mounting and Dismounting of Cartridge>

[0152] Next, referring to FIGS. 8, 9 and 10, the mounting of the cartridge B on the apparatus main assembly A will be specifically described. Part (a) of FIG. 8 is a sectional view of the driving side of the apparatus main assembly A with the door 13 open, and part (b) of FIG. 8 is a sectional view of the non-driving side of the apparatus main assembly A with the door 13 open. The sectional planes of part (a) of FIG. 8 and part (b) of FIG. 8 are perpendicular to the rotational axis L1. FIG. 9 is views illustrating positioning of the cartridge B in the longitudinal direction (direction of the rotational axis L1), and is sectional views of a fitting portion 15j of the apparatus main assembly A taken along a horizontal plane parallel to the rotational axis L1 (parallel with an installation surface of the apparatus main assembly A). Part (a) of FIG. 9 shows a state immediately before the cartridge B is fitted with the fitting portion 15j, and part (b) of FIG. 9 shows a state in which the cartridge B is in fitting engagement at the fitting portion 15j. Part (a) of FIG. 10 is a sectional view of the driving side of the apparatus main assembly A with the door 13 closed, and part (b) of FIG. 10 is a sectional view of the non-driving side of the apparatus main assembly A with the door 13 closed. The planes of the section of part (a) of FIG. 10 and part (b) of FIG. 10 are perpendicular to the rotational axis L1.

[0153] First, the mounting of the cartridge B on the apparatus main assembly A will be described. The apparatus main assembly A comprises a first driving side plate 15 and a non-driving side plate 16 which sandwich the cartridge B mounted on the apparatus main assembly A in the direction of the rotational axis L1. Further, a door 13 for opening and closing the insertion opening 17 is rotatably mounted on the apparatus main assembly A. The first driving side plate 15 is provided with an upper guide rail 15g and a lower guide rail 15h which guide the cartridge B when the cartridge B is mounted and dismounted. The non-driving side plate 16 is provided with an upper guide rail 16d and a lower guide rail 16e which guide the cartridge B when the cartridge B is mounted and dismounted. In addition, the drum bearing member 73 of the cartridge B is provided with a guided portion 73g and a rotation stop portion 73c, and the frame member 71 is provided with a positioned portion 71d and a rotation stop portion 71g. Therefore, the guided portion 73g and the rotation stop portion 73c are disposed on the driving side of the cartridge B, and the guided portion 73g and the rotation stop portion 73c are disposed on the non-driven side of the cartridge B.

[0154] When the door 13 of the apparatus main assembly A is opened and the insertion opening 17 formed between the first driving side plate 15 and the non-driving side plate 16 is open, the cartridge B can be inserted into and can be removed from the apparatus main assembly A through the insertion opening 17. At this time, by moving the cartridge B in a direction substantially perpendicular to the rotational axis L1 of the drum 62, the cartridge B can be inserted and mounted to and removed from the apparatus main assembly A. That is, a mounting direction M of the cartridge B to the apparatus main assembly A (part (a) of FIG. 9 and a dismounting direction thereof from the apparatus main assembly A (reverse direction to the mounting direction M) are directions substantially perpendicular to the rotational axis L1. The rotational axis L1 of the cartridge B mounted in the apparatus main assembly A is parallel to the rotational axis L2 of the drive transmission gear 81, and therefore, the mounting direction M of the cartridge B to the apparatus main assembly A and the dismounting direction thereof from the apparatus main assembly A are substantially perpendicular to the rotational axis L2. In addition, when the cartridge B is mounted to and dismounted from the apparatus main assembly A, the drum unit 69 moves integrally with the cartridge B to the apparatus main assembly A, and is mounted to and dismounted from the apparatus main assembly A. Therefore, the mounting direction of the drum unit 69 to the apparatus main assembly A and the dismounting direction thereof from the apparatus main assembly A are the same as the mounting direction M of the cartridge B to the apparatus main assembly A and the dismounting direction thereof from the apparatus main assembly A, respectively.

<Mounting and Positioning of Cartridge>

[0155] When the cartridge B is inserted into the apparatus main assembly A through the cartridge insertion opening 17, the guided portion 73g and the rotation stop portion 73c on the driving side of the cartridge B are guided by the upper guide rail 15g and the guide rail 15h, respectively. The non-driven side positioned portion 71d and the rotation stop portion 71g of the cartridge B are guided by the upper guide rail 16d and the lower guide rail 16e. By guiding the cartridge B by the guide rails of the apparatus main assembly A and inserting the cartridge B in this manner, the mounting of the cartridge B on the apparatus main assembly A is finally completed.

[0156] As shown in parts (a) and (b) of FIG. 9, the drum bearing member 73 is provided with a fitted portion 73h functioning as a positioned portion (axial direction positioned portion) to be positioned with respect to the apparatus main assembly A in the direction of the rotational axis L1. The fitted portion 73h has a recess shape (or a groove shape or a slit shape) recessed in the mounting direction M (direction perpendicular to the rotational axis L1). On the other hand, the first driving side plate 15 of the apparatus main assembly A is provided with a fitting portion 15j which can be fitted with the fitted portion 73h. The fitting portion 15j has a projection shape projecting in the direction opposite to the mounting direction MD.

[0157] In the process of inserting the cartridge B into the apparatus main assembly A, as shown in part (b) of FIG. 9, the fitted portion 73h is fitted with the fitting portion 15j, by which the position of the cartridge B in the direction of the rotational axis L1 (the longitudinal direction of the cartridge B) is determined. The fitting between the fitted portion 73h and the fitting portion 15j is loose fitting, but the fitting play (gap) is set to be extremely small (150 μm at the maximum). For this reason, it can be said that the cartridge B is positioned at substantially the same position in the direction of the rotational axis L1 regardless of whether the fitted portion 73h abuts the fitting portion 15j in either the H direction or the J direction.

[0158] Further, as shown in part (a) of FIG. 8, part (b) of FIG. 8, part (a) of FIG. 10, and part (b) of FIG. 10, the first driving side plate 15 is provided with a positioning portion 15a, a positioning portion 15b, and a rotation stop portion 15c, and the non-driving side plate 16 is provided with a positioning portion 16a, a positioning portion 16b, and a rotation stop portion 16c. Cartridge pressing members 1 and 2 are mounted to opposite ends of the door 13 in the direction of the rotational axis of the door 13 so as to be movable (rotatable) with respect to the door 13. In addition, the first driving side plate 15 and the non-driving side plate 16 is provided with pressing springs 19 and 21, respectively.

[0159] Further, as shown in FIG. 3, the drum bearing member 73 of the cartridge B has a pressed portion (urging force receiving portion) 73e, and the frame member 71 has a pressed portion (urging force receiving portion) 71n. The pressed portions 73e and 71n are provided in recess portions on the driving side and the non-driving side of the cartridge B, respectively.

[0160] As shown in part (a) of FIG. 10 and part (b) of FIG. 10, by closing the door 13, the cartridge pressing members 1 and 2 are urged toward the cartridge B by the pressing springs 19 and 21. And, the cartridge pressing members 1 and 2 abut to the pressed portions 73e and 71n, and press the pressed portions 73e and 71n by the urging force of the pressing springs 19 and 21.

[0161] By this, on the driving side, the positioned portion 73g of the cartridge B contacts the positioning portion 15a and the positioning portion 15b of the apparatus main assembly A, and the rotation stop portion 73c contacts the rotation stop portion 15c of the apparatus main assembly A. By this, the driving side portion of the drum frame 60a of the cartridge B is positioned in a direction perpendicular to the rotational axis L1 and rotation about the axis parallel to the rotational axis L1 is restricted. On the non-driven side, the positioned portion 71d of the cartridge B abuts to the positioning portions 16a and 16b of the apparatus main assembly A, and the rotation stop portion 71g abuts to the rotation stop portion 16c of the apparatus main assembly A. By this, the non-driving side portion of the drum frame 60a of the cartridge B is positioned in the direction perpendicular to the rotational axis L1, and rotation about the axis parallel to the rotational axis L1 is restricted.

[0162] By positioning the drum frame 60a of the cartridge B with respect to the apparatus main assembly A in this manner, the drum unit 69 positioned with respect to the drum frame 60a is also indirectly positioned with respect to the apparatus main assembly A.

<Drive Transmission to Drum Unit>

[0163] Next, a structure for transmitting the drive from the apparatus main assembly A to the drum unit 69 and the drum 62 will be described. FIG. 1 is a perspective view of a portion for transmitting the drive from the apparatus main assembly A to the drum unit 69. FIG. 11 is an exploded perspective view illustrating a support structure of the drive transmission gear 81 of the apparatus main assembly A. FIG. 12 is a perspective view illustrating a drive transmission unit of the apparatus main assembly A. Part (a) of FIG. 13 is an illustration schematically showing the drive transmission gear 81 of the apparatus main assembly A. Part (b) of FIG. 13 is an illustration schematically showing the driving side flange 63 of the cartridge B. In part (a) of FIG. 13 and part (b) of FIG. 13, an addendum circle of the gear is shown for the gear tooth. FIG. 14 is an illustration schematically showing a drive transmission structure from the drive transmission gear 81 of the apparatus main assembly A to the driving side flange 63 of the cartridge B.

<Drive Structure on Apparatus Main Assembly Side>

[0164] As shown in FIG. 11, the apparatus main assembly A includes a motor (not shown), an idler gear 80, a drive transmission gear 81, a second driving side plate 83, a main frame 84, a driving shaft 82, and a compression spring 85. The driving force of the motor is transmitted from the idler gear 80 to the drive transmission gear 81. The idler gear 80 and the drive transmission gear 81 are supported by the driving shaft 82 so as to be coaxially rotatable and movable in the direction of the rotational axis. One end 82a of the driving shaft 82 is fixed to the hole 83a of the second driving side plate 83, and the other end 82b thereof is supported by the hole 84a of the main frame 84. The driving shaft 82 is provided so that the rotational axis of the drive transmission gear 81 is parallel with the rotational axis L1 of the drum 62 when the cartridge B is mounted in the apparatus main assembly A.

[0165] In addition, the compression spring 85 is provided between the other end 80b of the idler gear 80 and the second driving side plate 83, so that the idler gear 80 is urged in the H direction of the rotational axis direction. As described above, the J direction and the H direction in the apparatus main assembly A are defined to be coincident with the J direction and the H direction of the cartridge B having been mounted on the apparatus main assembly A. As a result, as shown in FIG. 11, the J direction is the direction from the idler gear 80 toward the second driving side plate 83 along the rotational axis of the idler gear 80, and the H direction is the direction opposite thereto.

[0166] One end 80a of the idler gear 80 is provided with a recess 80a1 recessed in the direction of the rotational axis. On the other hand, one end 81a of the drive transmission gear 81 is provided with a projection 81a1 projecting in the direction of the rotational axis at a position facing the recess 80a1 of the idler gear 80. By engagement of the recess 80a1 of the idler gear 80 with the projection 81a of the drive transmission gear 81, the drive force is transmitted from the idler gear 80 to the drive transmission gear 81, and the drive transmission gear 81 is rotated integrally. The projection-recess relationship between the recess 80a1 and the projection 81a1 may be reversed.

[0167] As will be described hereinafter, the drive transmission gear 81 mesh-engages with the driving side flange 63 of the cartridge B to transmit the drive force. As shown in part (d) of Figure luring performing the above-mentioned image forming process operation, the initial operation after mounting the cartridge B, and the preparatory operation of the image forming process (collectively referred to as “driving”), the drive transmission gear 81 is rotated in the I direction to rotate the driving side flange 63 in the K direction. That is, the driving direction (rotational direction) of the drive transmission gear 81 during driving is the I direction, and the driving direction (rotational direction) of the driving side flange 63 during driving is the K direction. As the drive transmission gear 81 and the driving side flange 63 are viewed from the driving side to the non-driving side along the H direction, the I direction is a clockwise direction and the K direction is a counterclockwise direction.

<Drive Transmission Gear 81>

[0168] As shown in FIGS. 1, 12 and part (a) of FIG. 13, the drive transmission gear 81 includes a first main assembly gear portion (first main assembly side gear portion, first main assembly side helical tooth gear portion) 81c and a second main assembly gear portion (second main assembly side gear portion, second main assembly side helical tooth gear portion) 81d are provided which are coaxial with each other, as an helical tooth gear portion. The first main assembly gear portion 81c is located on the downstream side, in the H direction (upstream side in the J direction), with respect to the second main assembly gear portion 81d. The first main assembly gear portion 81c includes a plurality of first main assembly helical teeth 81ct, and the second main assembly gear portion 81d includes a plurality of second main assembly helical teeth 81dt. The first main assembly helical tooth 81ct and the second main assembly helical tooth 81dt both have involute tooth profiles. The first main assembly gear portion 81c and the second main assembly gear portion 81d are integrally resin-molded and are integrally rotatable. In addition, twisting directions of the first main assembly gear portion 81c and the second main assembly gear portion 81d are the same, and the tooth surfaces are twisted so as to shift in the I direction as go in the J direction. Further, as shown in part (a) of FIG. 13, a helix angle α2 of the second main assembly gear portion 81d is larger than a helix angle α1 of the first main assembly gear portion 81c (that is, α1<α2 is satisfied). Furthermore, the numbers of teeth of the first main assembly gear portion 81c and the second main assembly gear portion 81d are the same.

<Driving Side Flange 63>

[0169] On the other hand, as shown in FIGS. 1, part (b) of FIG. 6 and part (b) of FIG. 13, the driving side flange 63 is coaxially provided with the first gear portion (first unit side gear portion, first unit side helical gear portion) 63c as the helical gear portion, and a second gear portion (second unit side gear portion, second unit side helical gear portion, second helical gear portion) 63d. The first gear portion 63c is disposed on a downstream side, in the H direction (upstream side in the J direction), of the second gear portion 63d. That is, the first gear portion 63c is disposed between the second gear portion 63d and the drum 62 in the direction of the rotational axis L1. The first gear portion 63c includes a plurality of first helical teeth (first projections) 63ct provided at different positions in a circumferential direction about the rotational axis L1, and the second gear portion 63d includes a plurality of second helical teeth (second projections) 63dt provided at different positions in the circumferential direction about the rotational axis L1. The first helical teeth 63ct and the second helical teeth 63dt are both involute teeth and are projections projecting in the radial direction centered on the rotational axis L1. The first gear portion 63c and the second gear portion 63d are integrally molded of resin and rotate integrally, and therefore, the first gear portion 63c and the second gear portion 63d can be said to be a first rotating portions and a second rotating portion which are rotatable integrally with each other. The first gear portion 63c meshes with the first main assembly gear portion 81c of the drive transmission gear 81, and the second gear portion 63d meshes with the second main assembly gear portion 81d of the drive transmission gear 81.

[0170] As shown in FIG. 1, twisting directions of the first gear portion 63c and the second gear portion 63d of the driving side flange 63 are the same, and the tooth surfaces twisted so as to shift in the K direction as go in the J direction. The twisting direction of the first gear portion 63c and the second gear portion 63d is opposite to the twisting direction of the first main assembly gear portion 81c and the second main assembly gear portion 81d of the drive transmission gear 81. Further, as shown in part (b) of FIG. 13, a helix angle α2 of the second gear portion 63d is larger than a helix angle α1 of the first gear portion 63c (that is, α1<α2 is satisfied). The helix angle α1 of the first gear portion 63c is the same as the helix angle α1 of the first main assembly gear portion 81c, and the helix angle α2 of the second gear portion 63d is the same as the helix angle α2 of the second main assembly gear portion 81d. In addition, the numbers of the teeth of the first gear portion 63c and the second gear portion 63d of the driving side flange 63 are the same. Further, a width (tooth width) W63c (Wc, Wc1) of the first helical tooth (first projection) 63ct measured in the direction of the rotational axis L1 is larger than a width (tooth width) W63d (Wd) of the second helical tooth (second projection) 63dt measured in the direction of the rotational axis L1. That is, the first gear portion 63c and the second gear portion 63d is each provided with at least one tooth such that the tooth width Wc of the first helical tooth (tooth, first projection) 63ct measured in the direction of the rotational axis L1 and the tooth width Wd of the second helical tooth (tooth, second projection) 63dt measured in the direction of the rotational axis L1 satisfy the following formula A1.
Wc>Wd  (Formula A1).
In other words, when the width (tooth width) of the first helical tooth 63ct having the largest width (tooth width) measured in the direction of the rotational axis L1 of the first gear portion 63c is Wc1, the second gear portion 63d has a second helical tooth (second projection) 63dt having a width (tooth width) measured in the direction of the rotational axis L1 which is smaller than Wc1.

[0171] As will be described in detail hereinafter, while the driving side flange 1763 is driven by the drive transmission gear 1781 in a balanced state, the drive force FD received by a first gear portion 1763c is higher than a restricting force FB received by a second gear portion 1763d, and therefore, such a relationship is preferable.

[0172] In addition, the larger a width (meshing width), in the direction of the rotational axis L1, of the portion where the first gear portion 63c in meshing engagement (contact) with the first main assembly gear portion 81c and a meshing engagement width of the second helical tooth gear portion 63c with the second main assembly gear portion 81d, the better the drive transmission accuracy. However, if the meshing width is set larger than necessary, the widths of the first gear portion 63c and the second gear portion 63d in the direction of the rotational axis L1 are large, and the driving side flange 63, the drum unit 69, the cartridge B, and eventually the apparatus main assembly A are upsized. Therefore, the tooth width Wc1 of the first helical tooth (tooth) 63ct having the largest tooth width in the first gear portion 63c and the tooth width Wd1 of the second helical tooth (tooth) 63dt having the largest tooth width in the second gear portion 63d preferably satisfies the following formula A2, more preferably formula A3.
Wd1≤(⅘)·Wc1  (A2)
Wd1≤(¾)·Wc1  (A3)

[0173] Further, from a standpoint of the strength of the second helical tooth (tooth) 63dt of the second gear portion 63d, it is preferable that the second helical tooth (tooth) 63dt has a tooth width of a certain level or more, and it is preferable that the tooth width Wc1 and the tooth width Wd1 satisfies the following formula A4.
Wd1≥( 1/10)·Wc1  (formula A4).

[0174] In addition, as shown in FIG. 14, meshing pitch circle diameters D63c and D63d of the first gear portion 63c and the second gear portion 63d in the meshing between the driving side flange 63 and the drive transmission gear 81 are set to be substantially the same. Further, addendum circle diameters Dt63c and Dt63d of the first gear portion 63c and the second gear portion 63d are also set to be substantially the same. Similarly, the meshing pitch circle diameters D81c and D81d of the first main assembly gear portion 81c and the second main assembly gear portion 81d are set to be substantially the same. By this, the meshing between the first gear portion 63c and the first main assembly gear portion 81c and the meshing between the second gear portion 63d and the second main assembly gear portion 81d can be appropriately meshed without tip tooth bearing.

[0175] In order to set the meshing pitch circular diameters D63c and D63d of the first gear portion 63c and the second gear portion 63d to be substantially the same, it is preferable that the shapes of the first gear portion 63c and the second gear portion 63d are as follows.

[0176] Specifically, it is preferable that the addendum circle diameter Dt63c of the first gear portion 63c is larger than a dedendum circle diameter Db63d of the second gear portion 63d, or is larger than 0.8 times (further preferably 0.9 times) the addendum circle diameter Dt63d of the second gear portion 63d. In addition, it is preferable that the addendum circle diameter Dt63c of the first gear portion 63c is preferably smaller than 1.1 times the addendum circle diameter Dt63d of the second gear portion 63d.

[0177] Further, it is preferable that the dedendum circle diameter Db63c of the first gear portion 63c is smaller than the addendum circle diameter Dt63d of the second gear portion 63d. Furthermore, the dedendum circle diameter Db63c of the first gear portion 63c is preferably larger than 0.9 times the dedendum circle diameter Db63d of the second gear portion 63d.

[0178] Moreover, it is preferable that the addendum circle diameter Dt63d of the second gear portion 63d is larger than the dedendum circle diameter Db63c of the first gear portion 63c, or is larger than 0.8 times (further preferably 0.9 times) the addendum circle diameter Dt63c of the first gear portion 63c. Further, the addendum circle diameter Dt63d of the second gear portion 63d is preferably smaller than 1.1 times the addendum circle diameter Dt63c of the first gear portion 63c.

[0179] Further, the dedendum circle diameter Db63d of the second gear portion 63d is preferably smaller than the addendum circle diameter Dt63c of the first gear portion 63c. Further, the dedendum circle diameter Db63d of the second gear portion 63d is preferably larger than 0.9 times the dedendum circle diameter Db63c of the first gear portion 63c.

[0180] Here, the relationship between these dimensions is expressed using the diameters of the first gear portion 63c and the second gear portion 63d, but it is a matter of course that the relationship remains the same even if the diameters are replaced with radii. In addition, in the embodiments which will be described hereinafter, examples in which the teeth of the first gear portion 63c and the second gear portion 63d are replaced with a plurality of projections including various shapes will be shown. In such cases, the addendum circle is a circle drawn as a rotation locus when the free end (point) most remote from the rotational axis L1 among the tips of the plurality of projections rotates, and the diameter/radius of this circle is the addendum circle diameter/radius.

[0181] In order to make the meshing pitch circle diameters D63c and D63d the same while making the helix angles of the first gear portion 63c and the second gear portion 63d different, as described above, the modules and/or the amounts of gear profile shifts are made different between the first gear portion 63c and the second gear portion 63d. Similarly, for the drive transmission gear 81, the modules and/or the amounts of gear profile shifts are different between the first main assembly gear portion 81c and the second main assembly gear portion 81d.

[0182] In addition, the driving side flange 63 includes a cylindrical portion (intermediate portion, small diameter portion, shaft portion) 63e between the first gear portion 63c and the second gear portion 63d in the direction of the rotational axis L1. The maximum diameter D63e centered on the rotational axis L1 of the cylindrical portion 63e is smaller than the addendum circle diameter Dt63c of the first gear portion 63c and the addendum circle diameter Dt63d of the second gear portion 63d. Further, in this embodiment, the maximum diameter D63e centered on the rotational axis L1 of the cylindrical portion 63e is smaller than the dedendum circle diameter Db63c of the first gear portion 63c and the dedendum circle diameter Db63d of the second gear portion 63d. However, the maximum diameter D63e centered on the rotational axis L1 of the cylindrical portion 63e is not limited to the above unless it comes into contact with the drive transmission gear 81 while the driving side flange 63 is being driven by the drive transmission gear 81. Further, as will be described hereinafter in Embodiments 22 and 23, the structure may be such that the distance (radius) R63e from the rotational axis L1 to the outer diameter of the cylindrical portion 63e is at least temporarily smaller than the addendum circle radius Rt63ct of the first gear portion 63c or the addendum circle radius Rt63d of the second gear portion 63d, so that the driving side flange 63 and the drive transmission gear 81 can be in meshing engagement with each other to transmit the drive force.

[0183] Here, the relationship between these dimensions is expressed using the diameters of the first gear portion 63c, the second gear portion 63d, and the cylindrical portion 63e, but it is a matter of course that the relationships remain the same even if the diameters are replaced with radii. The shape of the cylindrical portion 63e does not have to be a cylindrical shape centered on the rotational axis L1. For example, various shapes such as a polygonal prism shape and a shape that is not symmetrical with respect to the rotational axis L1 can be used. In such cases, a diameter of the circle drawn as the rotation locus of the point most remote with respect to the rotational axis L1 in the intermediate portion 63e is the above-mentioned maximum diameter D63e when the driving side flange 63 rotates, and the radius of the circle is the maximum of the radius R63e.

[0184] By providing the cylindrical portion 63e, the second gear portion 63d can be arranged at a position away from the drum 62 (more downstream side in the J direction) so as not to contact the first gear portion 81c. Similarly, the first gear portion 63c can be placed at a position close to the drum 62 (more downstream in the H direction) so as not to contact the second main assembly gear portion 81d. That is, by providing the cylindrical portion 63e, a gap g is provided between the first gear portion 81c and the second gear portion 63d in the direction of the rotational axis L1. By this, when the cartridge B is mounted to the apparatus main assembly A, the first gear portion 63c is prevented from contacting the second main assembly gear portion 81d, and the second gear portion 63d is prevented from contacting the first main assembly gear the portion 81c, in the direction of the rotational axis L1. In addition, when the drive transmission gear 81 is driven and the drive transmission gear 81 is moved to a balanced position, the first main assembly gear portion 81c is prevented from contacting the second gear portion 63d, and the second main assembly gear portion 81d is prevented from contacting the first gear portion 63c. A width of the cylindrical portion 63e measured in the direction of the rotational axis L1 will be described in detail hereinafter.

<Drive Transmission to Developing Roller>

[0185] FIG. 15 is an illustration of a structure of drive transmission from the driving side flange 63 to the developing roller 32. The developing roller 32 is fixed to the developing roller shaft 31, and a developing roller gear 30 is provided at one end on the driving side of the developing roller shaft 31 so as to be movable in the direction of the rotational axis of the developing roller shaft 31. The developing roller gear 30 is rotatable integrally with the developing roller shaft 31 and the developing roller 32. That is, the developing roller gear 30 is provided so as to be able to transmit the driving force to the developing roller shaft 31 and the developing roller 32. The developing roller gear 30 is meshing engagement with the first gear portion 63c of the driving side flange 63 to transmit the driving force thereto.

[0186] Alternatively, the developing roller gear 30 may be engaged with the second gear portion 63d to transmit the driving force. However, by employing a structure in which the developing roller gear 30 meshes with the first gear portion 63c, the length of the developing roller shaft 31 in the rotational axis direction can be reduced as compared with the structure in which the developing roller gear 30 meshes with the second gear portion 63d.

<Drive Transmission Operation>

[0187] Next, referring to FIGS. 16, 17, 19, 20, and 21, the meshing operation between the drive transmission gear 81 and the driving side flange 63 will be described in the order from the mounting of the cartridge B.

[0188] Part (a) of FIG. 16 is a schematic view of the drive transmission gear 81 and the driving side flange 63 as viewed along the rotational axis direction. Part (b) of FIG. 16 is a sectional view of the drive transmission gear 81 taken along a line AF-AF. In the drawings subsequent to part (b) of FIG. 16, the shaded (hatched) portions in the Figures are sections of the tooth portions of the gear and the portion between adjacent shaded portions correspond to a part of the gear including the intertooth space portions of the gear. Part (c) of FIG. 16 is a sectional view of the driving side flange 63 taken along a line AF-AF. Part (d) of FIG. 16 is a sectional view of the drive transmission gear 81 taken along the line AF-AF before mounting the cartridge. Part (e) of FIG. 16 is a sectional view, taken along the line AF-AF, of the drive transmission gear 81 and the driving side flange 63 after mounting of the cartridge B and before start of the driving operation.

[0189] FIG. 17 is sectional views, taken along the line AF-AF which is in contact with the meshing pitch circle between of the drive transmission gear 81 and the driving side flange 63 immediately after the start of the drive, in which part (a) of FIG. 17, part (b) of FIG. 17, part (c) of FIG. 17, and part (d) of FIG. 17 shows states with elapse of time.

[0190] Part (a) of FIG. 19, part (b) of FIG. 19, and part (c) of FIG. 19 are illustrations of the drive transmission gear 81 and the driving side flange 63 as viewed along the H direction.

[0191] Part (a) of FIG. 21 is a view of the drive transmission gear 81 and the driving side flange 63 as viewed along the direction perpendicular to the rotational axis direction. Part (b) of FIG. 21 is a sectional view, taken along a line AD-AD, of the first main assembly gear portion 81c during the driving operation. Part (c) of FIG. 21 is a sectional view, taken along the line AD-AD, of the second main assembly gear portion 81d during the driving operation.

<Engagement when Cartridge B is Mounted>

[0192] As shown in part (d) of FIG. 16, in the drive transmission gear 81 before mounting the cartridge B, the other end 81e of the drive transmission gear 81 is abutted against a surface 84b of the main frame by the urging force F1 of the compression spring 85, so that the drive transmission gear 81 is held thereby. By abutting and holding the drive transmission gear 81 against the abutting surface 84b in this manner, the initial position of the drive transmission gear 81 in the rotational axis direction is fixed, so that the meshing with the driving side flange 63 can be stabilized.

[0193] When the cartridge B is mounted to the apparatus main assembly A along the mounting direction M (M direction), the driving side flange 63 is brought into meshing engagement with the drive transmission gear 81 as shown in part (a) of FIG. 19. Here, the force required to rotate the driving side flange 63 is larger than the force required to rotate the drive transmission gear 81. Therefore, the drive transmission gear 81 is rotated in the I direction (clockwise direction) by the movement of the driving side flange 63 in the M direction. At this time, as shown in part (e) of FIG. 16, the first main assembly gear portion 81c or the second main assembly gear portion 81d of the drive transmission gear 81 is brought into contact the first gear portion 63c or the second gear portion 63d of the driving side flange 63, and is pressed in the M direction. A thrust force F3 in the H direction is applied to the drive transmission gear 81. However, since the other end 81e of the drive transmission gear 81 abuts against the abutting surface 84b of the main frame 84 and receives the reaction force F4, the drive transmission gear 81 cannot move in the H direction.

<Operation after Start of Driving>

[0194] Next, a case where the driving side flange 63 is driven in order to perform an initial operation, a preparatory operation for image formation, and the like will be described. As shown in part (b) of FIG. 19, the drive transmission gear 81 is rotated by a motor (not shown) of the apparatus main assembly A and rotates in the I direction. By this, the driving side flange rotates in the K direction. It is assumed that immediately after the start of rotation of the drive transmission gear 81 in the I direction, the second main assembly gear portion 81d of the drive transmission gear 81 first meshes with the second gear portion 63d of the driving side flange 63 to transmit the driving force thereto, as shown in part (a) of FIG. 17. Then, the second main assembly gear portion 81d applies a thrust force in the H direction to the second gear portion 63d. However, the driving side flange 63 is prevented from moving in the H direction by the rib 71p, and receives a reaction force in the J direction corresponding to the thrust force in the H direction. Therefore, the second main assembly gear portion 81d receives a thrust force F5 in the J direction due to the action of the reaction force received from the second gear portion 63d. The drive transmission gear 81 moves in the J direction by this thrust force F5.

[0195] When the drive transmission gear 81 moves in the J direction with further rotation, as shown in part (b) of FIG. 17, the first gear portion 63c also brought into meshing engagement with the first main assembly gear portion 81c, so that the first main assembly gear portion 81c A receives a thrust force F6. The direction of the thrust force F6 is the J direction which is the same as that of the thrust force F7 received by the meshing engagement of the second main assembly gear portion 81d with the second gear portion 63d. By this, the drive transmission gear 81 moves further in the J direction.

[0196] When the drive transmission gear 81 further rotates and moves in the J direction, the second main assembly gear portion 81d becomes out of engagement with the second gear portion 63d, as shown in part (c) of FIG. 17. On the other hand, the meshing engagement between the first gear portion 81c and the first gear portion 63c is maintained, and a thrust force F8 is applied to the first gear portion 81c in the J direction. At this time, the drive transmission gear 81 rotates the driving side flange 63 only through the engagement between the first main assembly gear portion 81c and the first gear portion 63c. That is, the tooth surface 81c1, on the downstream side in the I direction, of the first main assembly gear portion 81c and the tooth surface 63c1, on the upstream side in the I direction, of the first gear portion 63c are in contact with each other.

[0197] This is effected because the helix angle α2 of the second main assembly gear portion 81d of the drive transmission gear 81 is larger than the helix angle α1 of the first main assembly gear portion 81c (α2>α1). Details will be described below, referring to part (b) of FIG. 21 and part (c) of FIG. 21. It is assumed that the drive transmission gear 81 is moved by the amount of movement LL in the J direction by the thrust force through the engagement with the driving side flange 63. In parts (b) and (c) of FIG. 21, the first main assembly gear portion 81c and the second main assembly gear portion 81d are shown by a solid line before movement and a broken line after movement, respectively. The amounts of movement of the first main assembly gear portion 81c and the second main assembly gear portion 81d in the rotational direction by this movement can be expressed by LL/tan α1 and LL/tan α2, respectively. Based on the relationship between the helix angles α1 and α2, the movement amount LL/tan α2 in the rotational direction of the second main assembly gear portion 81d is larger than the movement amount LL/tan α1 in the rotational direction of the first main assembly gear portion 81c (LL/tan α1<LL/tan α2). As will be understood, the movement amount in the rotational direction corresponding to the movement amount LL in the J direction is larger in the second main assembly gear portion 81d than in the first main assembly gear portion 81c. Therefore, even if the first main assembly gear portion 81c and the first gear portion 63c are engaged with each other, the second main assembly gear portion 81d is separated from the second gear portion 63d.

[0198] When the drive transmission gear 81 further continues to rotate and moves to the driving side J, the tooth surface 81d2, on the upstream side, in the I direction of the second main assembly gear portion 81d finally comes into contact with the tooth surface (contact portion) 63d2, on the downstream side in the I direction, of the second gear portion 63d, as shown in part (d) of FIG. 17. The surface 81c1 of the first main assembly gear portion 81c and the surface 63c1 of the first gear portion 63c maintain contact with each other. That is, in this state, the first main assembly gear portion 81c of the drive transmission gear 81 presses the tooth surface (contact portion) 63c1 by the tooth surface 81c1 to rotate the driving side flange 63, and the tooth surface 81d2 of the second main assembly gear portion 81d of the drive transmission gear 81 contacts the tooth surface 63d2, so that the drive transmission gear 81 is sandwiched by the driving side flange 63. Then, the movement of the drive transmission gear 81 in the direction of the rotational axis L1 stops. The position in the direction of the rotational axis L1 at this time is a balanced position. A state in which the drive transmission gear 81 rotates at the balanced position and is driven to effect the drive transmission to the driving side flange 63 will be described.

[0199] In the balanced state, the force F9, the force F10, and the force F1 are applied to the drive transmission gear 81 in the direction of the rotational axis L1. The force F9 is the thrust force in the J direction which the first main assembly gear portion 81c receives by the meshing engagement with the first gear portion 63c, and the force F1 is the thrust force in the H direction which the second main assembly gear portion 81d receives by the meshing engagement with the second gear portion 63d, and the force F1 is the urging forces of the compression spring 85. In addition, the driving side flange 63 receives a force from the drive transmission gear 81 and is positioned by the side wall 71m or the rib 71p in the direction of the rotational axis L1, and a reaction force F11 is produced which balances with the force received from the drive transmission gear 81. Part (d) of FIG. 17 shows a case in which the drive transmission gear 81 is positioned in contact with the side wall 71m. When friction is ignored in the balanced state, the force F9, the force F10, the force F1, and the force F11 are balanced, and the drive transmission gear 81 and the driving side flange 63 are positioned in the direction of the rotational axis L1.

[0200] Further, the driving side flange 63 is sandwiched (contacted) between the first main assembly gear portion 81c and the second main assembly gear portion 81d of the drive transmission gear 81 and receives the following forces in the K direction (rotational direction). That is, the tooth surface (contact portion) 63c1 of the first gear portion 63c is in contact with the first main assembly gear portion 81c existing on the upstream side in the K direction (first circumferential direction), and it receives the driving force FD as the force of the component for rotating the driving side flange 63 the in the direction K (predetermined direction). At the same time, the tooth surface (contact portion) 63d2 of the second gear portion 63d is in contact with the second main assembly gear portion 81d existing on the downstream side in the K direction (first circumferential direction), and it receives a restricting force (braking force) FB as the force of the component in the direction which suppresses (restricts) the rotation of the driving side flange 63 in the direction K. Therefore, it can be said that the first gear portion 63c is a driving force receiving portion which receives the driving force FD, and the second gear portion 63d is the restricting force receiving portion which receives the restricting force FB. The driving force FD is larger than the restricting force FB.

[0201] Here, since the second gear portion 63d is integrally provided with the first gear portion 63c in the rotational direction, the structure is such that the second gear portion 63d cannot rotate relative to the first gear portion 63c in the opposite direction K. Strictly speaking, since the driving side flange 63 is made of resin and deformation of teeth and members occurs, the second gear portion 63d subjected to the restricting force FB is slightly rotated in the direction opposite to the K direction relative to the first gear portion 63c, and then the rotation thereof stops and the position thereof is fixed. Therefore, the restricting force FB received by the second gear portion 63d acts on (is transmitted to) the first gear portion 63c. By the same principle, the driving force FD received by the first gear portion 63d acts on (is transmitted to) the second gear portion 63d.

[0202] The state in which the first gear portion 63c receives the driving force FD and the second gear portion 63d receives the restricting force FB in this manner is a state that there is no play (backlash) in the rotational direction (I direction) between the driving side flange 63 and the drive transmission gear 81, that is, a backlashless state. In this manner, the driving side flange 63 is rotationally driven in the K direction with the backlashless state maintained. While the drive is transmitted by engaging with each other in the backlashless state, the drive transmission with high rotation accuracy is accomplished.

[0203] In addition, the width (tooth width) W63c of the first helical tooth (first projection) 63ct measured in the direction of the rotational axis L1 is larger than the width (tooth width) W63d of the second helical tooth (second projection) 63dt in the direction of the rotational axis L1. In other words, the second gear portion 63d has a second helical tooth (second projection) 63dt which is narrower than the first helical tooth 63ct, which has the largest width (tooth width) of the first gear portion 63c in the direction of the rotational axis L1.

[0204] If the second main assembly gear portion 81d and the second gear portion 63d do not come into contact with each other at the start of driving, and the first main assembly gear portion 81c and the first gear portion 63c come into contact with each other, The driving starts from the state shown in part (c) of FIG. 17 without going through the state shown in part (b) of FIG. 17. Then, according to the same principle as described above, the balanced state shown in part (d) of FIG. 17 is reached. That is, from the state shown in part (c) of FIG. 17, the drive transmission gear 81 moves in the J direction by the thrust force F8 to reach the balanced state shown in part (d) of FIG. 17.

<Disengagement when Dismounting Cartridge B>

[0205] Next, referring to FIGS. 18, 19, and 20, the meshing disengagement operation between the drive transmission gear 81 and the driving side flange 63 when the cartridge B is dismounted after the end of driving operation will be described. FIG. 18 is a sectional view taken along a line AF-AF in contact with the meshing pitch circle between the drive transmission gear 81 and the driving side flange 63 when the cartridge B is to be dismounted after the end of driving operation, and the time elapses in the order of part (a) of FIG. 18 and part (b) of FIG. 18. FIG. 20 is a schematic view of the drive transmission gear 81 and the driving side flange 63 as viewed along the H direction.

[0206] As shown in part (c) of FIG. 19, the cartridge B is dismounted in the take-out direction N

(N direction) and removed from the apparatus main assembly A. The N direction is opposite of the M direction. As described above, the force required to rotate the driving side flange 63 is larger than the force required to rotate the drive transmission gear 81. Therefore, the drive transmission gear 81 is rotated in the K direction (counterclockwise direction) by the movement of the driving side flange 63 in the N direction. At this time, as shown in part (a) of FIG. 18, when the driving side flange 63 moves in the N direction, the first gear portion 63c presses the first main assembly gear portion 81c. In addition, FIG. 20 shows the positional relationship between the driving side flange 63 that moves in the N direction and the drive transmission gear 81, in which a solid line indicates the state before the movement in the N direction, and a broken line indicates the state after the movement. The distance between the rotation center (rotational axis) L1 of the driving side flange 63 and the rotation center (rotational axis) L2 of the drive transmission gear 81 changes from a distance LA to a distance LB as the driving side flange 63 moves in the N direction (LA<LB)

[0207] By this, the meshing position of the teeth of the first gear portion 63c and the first main assembly gear portion 81c gradually moves toward the teeth tops. Therefore, as shown in part (b) of FIG. 18, the backlash of the meshing in the rotational direction increases, and gap AL between the surface 63d2 of the second gear portion 63d and the tooth surface 81d2 of the second main assembly gear portion 81d increases. When a gap AL is provided between the tooth surfaces, the force from the second gear portion 63d does not act on the drive transmission gear 81, and the thrust force F16 in the J direction by the engagement between the first main assembly gear portion 81c and the first gear portion 63c acts. As a result, when the cartridge B is dismounted, the drive transmission gear 81 gradually moves in the J direction while rotating in the K direction, and finally the meshing between the first gear portion 63c and the first main assembly gear portion 81c is disappears. By this, the engagement between the driving side flange 63 and the drive transmission gear 81 is released.

<Helix Angle Setting>

[0208] Next, referring to FIG. 46, the helix angles of the first gear portion 63c and the second gear portion 63d, which are preferable, will be described. Part (a) of FIG. 46 and part (b) of FIG. 46 are sectional views of the second gear portion 63d and the second main assembly gear portion 81d, taken along a line AF-AF in contact with the meshing pitch circle between the drive transmission gear 81 and the driving side flange 63.

[0209] The description will be made as to the setting of the helix angle α1 of the first gear portion 63c and the helix angle α2 of the second gear portion, in the case that the first gear portion 63c is the gear portion which receives the driving force FD and the second gear portion 63d is the gear portion which receives the restriction force FB as described above. First, as a premise, since the first gear portion 63c is the gear portion which receives the driving force FD and the second gear portion 63d is the gear portion that receives the restriction force FB, the helix angle α2 is larger than the helix angle α1 (α2>α1). If the helix angle α2 is smaller than the helix angle α1, drive transmission cannot be performed in a backlashless state. That is, the thrust force applied by the first gear portion 63c to the first main assembly gear portion 81c and the thrust force applied by the second gear portion 63d to the second main assembly gear portion 81d do not balance, and therefore, the position of the drive transmission gear 81 in the direction of the rotational axis L1 is not determined at a balanced position, and.

[0210] The helix angle α1 of the first gear portion 63c of the driving side flange 63 is preferably 10° or more (α1≥10°), further preferably 15° or more (α1≥15°), and even further preferably 20° or more (α1≥20°). The reason is that, in general, if the tooth width (the width of the gear tooth in the direction of the rotational axis L1) is the same, the larger the helix angle, the larger the meshing ratio and the higher the rotation accuracy. The helix angle α1 is preferably 40° or less (α1≤40°), further preferably 35° or less (α1≤35°). The reason is that, in general, when the helix angle is large, the moldability by the mold deteriorates.

[0211] On the other hand, the helix angle α2 of the second gear portion 63d of the drum gear 63 is preferably 40° or less (α2≤40°), further preferably 35° or less (α2≤35°). The reason is that, in general, when the helix angle is large, the moldability by the mold deteriorates. In addition, the helix angle α2 of the second gear portion 63d of the drum gear is preferably 20° or more (α2≥20°), and further preferably 25° or more (α2≥25°). The reason is that, as shown in part (a) of FIG. 46 and part (b) of FIG. 46, the larger the helix angle α2, the larger the width E in the rotational direction (K direction) of the contact surface with the second main assembly gear portion 81d. In this embodiment, the helix angle α2 is 35°.

[0212] If the width E is small, when the second gear portion 63d receives the thrust force F9 (see part (d) of FIG. 17 received by the first gear portion 63c, the tooth surface of the second gear portion 63d is deformed, and the second main assembly gear portion 81d enters like a wedge and moves, and the positioning in the direction of the rotational axis L1 becomes unstable. Therefore, it is necessary to assure a certain width E in order to reliably receive the thrust force F9 to position the drive transmission gear 81 in the direction of the rotational axis L1.

[0213] In view of the above-described analysis as a whole, the helix angle α1 is preferably 10° or more and 40° or less (15°≤α1≤40°), further preferably 15° or more and 40° or less (15°≤α1≤40°), and further preferably 20° or more and 35° or less (20°≤α1≤35°). The helix angle α2 is preferably 20° or more and 40° or less (20°≤α2≤40°), and further preferably 25° or more and 35° or less (25°≤α2≤35°). In this embodiment, the helix angle α1 is 20° and the helix angle α2 is 35°, satisfying the above conditions.

<Width of Cylindrical Portion 63e>

[0214] Next, the width (length) of the cylindrical portion 63e in the direction of the rotational axis L1 will be described. Part (a) of FIG. 47 is a schematic view of the driving side flange 63 and the drive transmission gear 81 when the cartridge B is mounted, as viewed in a direction perpendicular to the rotational axis L1. Part (b) of FIG. 47 is a schematic view of the driving side flange 63 and the drive transmission gear 81 during the driving operation, as viewed through a direction perpendicular to the rotational axis L1.

[0215] As described above, by providing the cylindrical portion 63e, the first gear portion 63c is prevented from contacting the second main assembly gear portion 81d, and the second gear portion 63d is prevented from contacting the first main assembly gear portion 81c, with respect to the direction of the rotational axis L1. Further, by providing the cylindrical portion 63e, when the drive transmission gear 81 is driven and the drive transmission gear 81 moves to the balanced position, the first main assembly gear portion 81c is prevented from contacting the second gear portion 63d, and the second main assembly gear portion 81d is prevented from contacting the first gear portion 63c. That is, by providing the cylindrical portion 63e, a gap g is formed between the first gear portion 81c and the second gear portion 63d in the direction of the rotational axis L1. Therefore, in the following description, the width (length) of the cylindrical portion 63e measured in the direction of the rotational axis L1 is synonymous with the width (length) of the gap g measured in the direction of the rotational axis L1.

[0216] The above-mentioned contact may occur in the following two situations. First, as shown in part (a) of FIG. 47, when the cartridge B is mounted on the apparatus main assembly A, the other end 81e of the drive transmission gear 81 is held in contact with the abutting surface 84b of the main frame 84. Second is the state in which the drive transmission gear 81 is driven and being moved toward the balanced position, as shown in part (b) of FIG. 47.

[0217] The positions of the first gear portion 63c and the second gear portion 63d of the driving side flange 63, the positions of the first main assembly gear portion 81c and the second main assembly gear portion 81d of the drive transmission gear 81, and the balanced position may be different depending on the following factors. Specifically, (1) a tolerance in the direction of the rotational axis L1 of related portions such as the driving side flange 63, the drive transmission gear 81, and the cleaning frame (drum frame) 60a, (2) a tolerance related to the distance between the rotational axis L1 of the driving side flange 63 and the rotational axis L2 of the drive transmission gear 81, (3) a tolerance of phase in the rotational direction of the teeth of the first gear portion 63c and the second gear portion 63d of the driving side flange 63, (4) a tolerance of the phase in the rotational direction between the teeth of the first main assembly gear portion 81c and the second main assembly gear portion 81d of the drive transmission gear 81, (5) deformation of the teeth due to the maximum drive load, and thermal expansion and contraction of the driving side flange 63 and the drive transmission gear 81. In consideration of these factors, the width (length) We of the cylindrical portion 63e (or the gap g) in the direction of the rotational axis L1 is selected.

[0218] Specifically, the width We is selected so that, the following Formula B1 is satisfied in which the width (tooth width, length) measured in the direction of the rotational axis L1 of the teeth of the first gear portion 63c is Wc as a reference,
We≥Wc/5  (Formula B1).

[0219] In addition, as the width We increases, the width in the direction of the rotational axis L1 of the cartridge B increases, and therefore, in order to downsize the cartridge B and the apparatus main assembly A, the width We is to be selected so as not to be larger than necessary. In view of the standpoint, it is further preferable to satisfy the following formula B2.
We≤Wc  (Formula B2).

[0220] In this embodiment, Wc=8.6 mm and We=2.3 mm, satisfying the above formulas B1 and B2. In the case that the tooth width Wc of the first gear portion 63c is not constant, the tooth width Wc1 of the tooth having the largest tooth width is deemed to be the tooth width Wc.

[0221] In addition, as will be understood from part (b) of FIGS. 13, 14 and 47 it is preferable for the width We to satisfy the following formula B3, in which Wd is the width (tooth width, length) of the teeth of the second gear portion 63c in the direction of the rotational axis L1.
We≤Wd  (Formula B3)
<Rotation Accuracy>

[0222] Hereinafter, referring to FIGS. 22 and 49, the reason why the rotation accuracy is improved in the backlashless state will be described. Part (a) of FIG. 22 is a view of the drive transmission gear 81 and the driving side flange 63 as viewed along the direction perpendicular to the rotational axis direction. Part (b) of FIG. 22 is a partial sectional view of the meshing engagement portion of an ordinary helical tooth gears 51 and 53 as a comparative example. Part (c) of FIG. 22 is a partial sectional view taken along a line AD-AD in contact with the meshing pitch circle of the drive transmission gear 81 and the driving side flange 63. Part (d) of FIG. 22 is a partial perspective view of the helical tooth gear 51. Part (e) of FIG. 22 is a partial perspective view of the drive transmission gear 81. FIG. 49 is a graph comparing the drive transmission error when the alignment of the driving side flange 63 and the helical tooth gear 53 is off.

[0223] As shown in part (b) of FIG. 22, in gear drive, the tooth surfaces of the helical tooth gears on the driving side and the driven side may mesh with each other without being parallel in a tooth line direction due to molding accuracy, play and deformation of the shaft portion. Such a state is generally called a misaligned state. When the alignment of the helical tooth gear (driving side) 51 and the helical tooth gear (driven side) 53, which are general helical tooth gears, is off by β°, the helical tooth gears 51 and 53 are at one end of the tooth surface in the axial direction, with the result that the meshing rate is significantly reduced as compared with the state where the meshing is performed only at the position and the alignment is not deviated. By this, the rotation accuracy at the time of drive transmission is extremely deteriorated. Part (d) of FIG. 22 shows a region in which the tooth surface of the helical tooth gear 51 meshes with the helical tooth gear 53 when the alignment is deviated, and the width of this region is defined as the width LP.

[0224] On the other hand, as shown in part (c) of FIG. 22, the driving side flange 63 is rotated while the first gear portion 63c and the second gear portion 63d of the driving side flange 63 sandwiches the first main assembly gear portion 81c and the main assembly gear portion 81d of the drive transmission gear 81. By this, a pinching force FC (that is, rotary drive brake) acting on the second main assembly gear portion 81d is generated. A reaction force of the pinching force FC is added to the force applied to the tooth surface of the first main assembly gear portion 81c in a direction of pressing the first gear portion 63c in the I direction, resulting in the force FB. On the other hand, when the same load torque is driven in the conventionally used helical tooth gear 51, no such additional force is produced to the force FA applied to the tooth surface of the helical tooth gear 51. Therefore, the force FB applied to the tooth surface of the first main assembly gear portion 81c of this embodiment is larger than the force FA applied to the tooth surface of the helical tooth gear 51. Part (e) of FIG. 22 shows a region of the tooth surface of the first main assembly gear portion 81c of the drive transmission gear 81 which is in meshing engagement with the first gear portion 63 of the driving side flange 63 when the alignment is deviated, in which a width of this region is LQ. Since the force FB is larger than the force FA, when the width LP in part (d) of FIG. 22 and the width LQ in part (e) of FIG. 22 are compared, the width LQ is larger than the width LP. Therefore, when the alignment is deviated, the decrease in the overlapping meshing ratio between the first main assembly gear portion 81c and the first gear portion 63c is smaller than that between the helical tooth gears 51 and 53.

[0225] FIG. 49 is a graph showing measurement results of the drive transmission errors to the driven side helical tooth gear 53 and driving side flange 63 with respect to the amount of misalignment, when the ordinary helical tooth gears 51 and 53 and the drive transmission gear 81 and the driving side flange 63 of this embodiment are used. In the helical tooth gear 51 and 53, and, the drive transmission gear 81 and the driving side flange 63, the gear specifications such as the number of teeth and the backlash amount in the inter-axis direction of 0.15 mm and the conditions such as the load torque are 0.25 N·m and rotation speed 270 rpm were the same, and the shaft and gear are fitted without play. Here, the drive transmission error (%) is a ratio of the experimental rotation pitch deviation data to the ideal rotation pitch in the gear meshing period. For example, if the ideal rotation pitch is 0.7258 mm and the amount of experimental deviation data from the ideal rotation pitch is 0.00036 mm, the result is 0.05% (=(0.00036/0.7258)×100). In addition, the alignment deviation amount (°) is 0° when the axes of the meshing gears are parallel to each other, and is an angle (see parts (b) and (c) of FIG. 22) between the axes when the axis of the gear is tilted on the driven side is tilted so that the tooth line directions of the gears is tilted by an angle β. As shown in this graph, when the alignment is deviated, the deterioration of the rotational accuracy of the driving side flange 63 of this embodiment is suppressed as compared with that in the ordinary helical tooth gear 53. Therefore, it can be said that the drive transmission structure using the drive transmission gear 81 and the driving side flange 63 of this embodiment is more resistant to misalignment than the drive transmission structure using an ordinary helical tooth gear.

<Wear of Drive Transmission Gear>

[0226] Next, referring to FIG. 24, the wear of the drive transmission gear 81 and the helical tooth gear 101 will be described below. Part (a) of FIG. 24 is a schematic illustration of a drive transmission structure using a conventional helical tooth gear. Part (b) of FIG. 24 is a schematic illustration of the drive transmission structure of this embodiment. As shown in part (a) of FIG. 24, when rotational driving is performed by the helical tooth gear 101, the helical tooth gear 101 receives a thrust force (force in the axial direction) FD provided by the meshing engagement force. By this, the helical tooth gear 101 moves in the H direction toward the non-driving side, and the end surface 101a of the helical tooth gear abuts and slides on the abutting surface 184b of the main frame 84, and therefore, they are worn. On the other hand, as shown in part (b) of FIG. 24, in the drive transmission gear 81 of this embodiment, the position thereof in the direction of the rotational axis L1 is determined by the driving side flange 63 and the spring 85 (not shown) during driving, and therefore, the end surface 81e in the H direction and the end surface 81f in the J direction of the drive transmission gear 81 do not slide because a gap AA is formed between the main frame 84 and the second driving side plate 83. Therefore, wear of the two end surfaces 81e and 81f of the drive transmission gear 81, the main frame 84, and the second driving side plate 83 can be suppressed, and the durability can be improved.

<Comparison with Conventional Coupling Drive>

[0227] Next, referring to FIGS. 26 and 27, a comparison with a structure in which the drum is driven by the conventional coupling will be described. Part (a) of FIG. 26 is a sectional view of a drive transmission portion of a conventional coupling drive, and the sectional plane includes a rotational axis of the coupling. Part (b) of FIG. 26 is a sectional view of the drive transmission unit of this embodiment, which is a sectional view including the rotational axis (L1) of the driving side flange 63 and the rotational axis of the drive transmission gear 81. FIG. 27 is a graph showing amount of deformations in the coupling drive and the drive transmission gear.

[0228] As shown in part (a) of FIG. 26, in the conventional coupling drive, a driving side flange 263 provided with a projection coupling 263a including a twisted polygonal prism shape is mounted to the end of the drum 62 of the cartridge. The drum flange 263 has a support portion 263b which is a cylindrical portion having a diameter smaller than the diameter of the drum 62. The apparatus main assembly has a drive transmission gear 281 with a recess coupling 281a into which the coupling 263a is inserted and engaged.

[0229] The coupling 263a is provided at the end of the driving side flange 263 in the direction of the rotational axis. Therefore, the twist amount of the driving side flange 263 during drive in the coupling drive is larger than the twist amount of the driving side flange 63 in the gear drive of this embodiment shown in part (b) of FIG. 26. FIG. 27 shows simulation results of the deformation amounts of the drive members (drum flange 263, driving side flange 63) in the rotational direction, and as will be understood, the amount of deformation in the gear drive (drive with the driving side flange 63) is smaller than in the coupling drive (driving at drum flange 263). Here, the amount of deformation of the drive member in the rotational direction will be described. This amount of deformation is the amount of displacement of a drive transmission point to the drum 62 in the rotational direction when the drum 62 sides of the drum coupling 263 and the driving side flange 63 are fixed, and the same static load torque of 0.25 N·m is applied to the engaging portion with the drive input member 281 or the meshing engagement portion with the drive transmission gear 81. The drive transmission point is a point fixed on the drum 62. And, the displacement amount is converted into the displacement amount when there is no twist at a predetermined point on the surface of the drum 62. Due to this difference in the amounts of deformation of the drive members, the change in the amount of deformation of the drive member when the load torque of the cartridge B changes, and the fluctuation of the rotation speed of 62 are smaller in the gear drive than in the coupling drive. That is, the density unevenness of the image in the rotational direction of the drum 62 on the image when the load torque fluctuation of the cartridge B occurs (caused by variation of the pitch between the scanning lines in the sub-scanning direction resulting when scanning the surface of the drum 62 with the laser beam L (pitch variation)) can be suppressed keep the pitch variation. As described above, with the drive transmission structure of the driving side flange 63 and the drive transmission gear 81 of the above-described embodiment, the deterioration of the rotational accuracy of the drum 62 with respect to the load torque fluctuation can be suppressed as compared with the conventional coupling drive structure.

[0230] In addition, as compared with the conventional coupling drive from another standpoint, in the case of the conventional coupling drive, it is necessary to provide a retracting mechanism for advancing and retreating the coupling 263a on the main assembly side in the direction of the rotational axis to permit mounting and dismounting the cartridge B.

[0231] Next, referring to FIG. 28, this retracting mechanism will be described. Part (a) of FIG. 28 is a sectional view of the drum 62 of the retracting mechanism in cross-section including the rotational axis. Part (b) of FIG. 28 is a schematic sectional view of an image forming apparatus provided with a retracting mechanism. Parts (c) and (d) of FIG. 28 are sectional views of the drive transmission gear 281 and the retracting mechanism, and the section thereof includes the rotational axis of the drive transmission gear 281.

[0232] The main assembly of the coupling-driven image forming apparatus is equipped with a retracting mechanism including a link 210, a cylindrical cam 212, and a compression spring 214. One end of the link 210 is connected with an opening/closing door 211 of the apparatus main assembly A. The other end of the link 210 is connected, coaxially with the drive input member 281, with a cylindrical cam 212 rotatably provided between the drive input member 281 and the side wall 213. In addition, as shown in part (a) of FIG. 28, the cylindrical cam 212 has a slope 212d, a projection surface 212c, and a recess surface 212e with height difference in the rotational direction on one end surface in the axial direction. Further, the side wall 213 has a slope 213e, a projection surface 213f, and a recess surface 213g at locations facing the slope 212d, the projection surface 212c, and the recess surface 212e, respectively. Furthermore, as shown in part (d) of FIG. 28, the drive transmission gear 281 is urged in the H direction by the compression spring 214.

[0233] As shown in part (b) of FIG. 28, by the operation of opening the door 211, the cylindrical cam 212 is rotated in the I direction by way of the link 210, and the cylindrical cam 212 and the projection surfaces 212c and 213f provided on the side wall 213 come into contact with each other, so that the cylindrical cam 212 is moved in the J direction. By the operation of the cylindrical cam 212 in the J direction, as shown in part (c) of FIG. 28, the cylindrical cam 212 moves the drive input member 281 in the J direction against the urging force of the compression spring 214. By this, the drive input member 281 is moved away from the drum flange 263 (see part (a) of FIG. 26 to disengage the coupling 281a from the coupling 263a (see part (a) of FIG. 26. As a result, the cartridge B can be dismounted.

[0234] Further, as shown in part (b) of FIG. 28, with the closing operation of the door 211, the cylindrical cam 212 is rotated in a direction opposite to the I direction while the cylindrical cam 212 and the slopes 212d and 213e are in contact with each other provided on the side wall 213, by way of the link 210. During this rotation, the cylindrical cam 212, the side wall 213, and the drive input member 281 becomes out of contact with each other in the rotational axis direction, and as shown in part (d) of FIG. 28, the drive input member 281 becomes rotatable in the H direction by the urging force of the compression spring 214. By this, the drive input member 281 moves in a direction approaching the drum flange 263 (see part (a) of FIG. 26, and the coupling 281a and the coupling 263a become engageable with each other.

[0235] As described above, the conventional coupling drive requires, a retracting mechanism, and there is a possibility that the size of the apparatus main assembly or the cost increases correspondingly to the amount of the retracting mechanism. However, in the case of gear drive as in this embodiment, the cartridge B can be mounted and dismounted without such a retracting mechanism.

[0236] Next, Modified Example 1 will be described. In the above-described embodiment, the first main assembly gear portion 81c and the second main assembly gear portion 81d of the drive transmission gear 81 have the same number of teeth, but the numbers of teeth do not necessarily have to be the same. However, the reduction ratio between the first main assembly gear portion 81c of the drive transmission gear 81 and the first gear portion 63c of the driving side flange 63, and the second gear of the second main assembly gear portion 81d of the drive transmission gear 81 and the second gear portion 63d of the driving side flange 63 need to be the same. For example, in the case that the number of teeth of the first gear portion 81c of the drive transmission gear is 20, the number of teeth of the first gear portion of the drum gear is 30, and therefore, the reduction ratio is 2:3, the reduction ratio is the same 2:3 if, the number of teeth of the second main assembly gear portion 81d of the drive transmission gear is 40 and the number of teeth of the second gear portion 63d of the driving side flange 63 is 60. In this case as well, the gear of the drive transmission gear 81 can be sandwiched by the first gear portion 63c and the second gear portion 63d of the driving side flange 63, and therefore, it is possible to establish the backlashless state in the rotational direction.

[0237] Next, Modified Example 2 will be described. In this Modified Example, the first gear portion 181c and the second gear portion 181d of the drive transmission gear 181 have different numbers of teeth, and the number of teeth on one side is not an integer multiple of the number of teeth on the other side. The first gear portion 163c and the second gear portion 163d of the driving side flange 163 also have different numbers of teeth, and the number of teeth on one side is not an integer multiple of the number of teeth on the other side. These points are different from those in the above-described embodiment of this Modified Example, and the structures of this Modified Example and the above-mentioned embodiment are the same except for these different points and the structures associated therewith, and therefore, the explanation thereof is omitted.

[0238] Also in this Modified Example, it is possible to establish the backlashless state in the rotation direction as in the above-described embodiment. However, due to the setting of the numbers of teeth as described above, in the structure of this modified example the meshing phase of the gear with respect to the drive transmission gear 181 of the driving side flange 163 is not unique. Referring to FIG. 25, as to the structure in which the meshing phase is not uniquely determined, the position where the drive transmission gear 181 is positioned in the axial direction (balanced) will be described. Part (a) of FIG. 25 is a schematic illustration of a drive transmission structure using the drive transmission gear 81 of this embodiment described above. Part (b) of FIG. 25 is an illustration of a drive transmission portion using the drive transmission gear 181 and the driving side flange 163 of the modified example. Part (c) of FIG. and part (d) of FIG. 25 show a state in which the drive transmission gear 181 is in a balanced position after the drive transmission gear is driven.

[0239] Comparing part (c) of FIG. 25 and part (d) of FIG. 25, the drive transmission gear 181 and the driving side flange 163 are in meshing engagement with each other, but the meshing ways at the meshing engagement portions are different from each other. Specifically, part (c) of FIG. 25 shows a state in which a tooth top of the first gear portion 181c of the drive transmission gear 181 and a tooth top of the second gear portion 181d are in phase alignment with each other at the meshing engagement portion between the driving side flange 163 and the drive transmission gear 181, and the tooth top of the first gear portion 163c of the driving side flange 163 and the tooth top of the second gear portion 163d are in phase alignment with each other. In part (d) of FIG. 25 shows a state in which the tooth top of the first gear portion 181c of the drive transmission gear 181 and the tooth top of the second gear portion 181d are in phase alignment with each other at the meshing engagement portion, and the tooth top of the first gear portion 163c of the driving side flange 163 and the intertooth space of the second gear portion 163d are in phase alignment with each other.

[0240] When the numbers of teeth of the first gear portion 181c and the second gear portion 181d of the drive transmission gear 181 are different from each other, the phases of the tooth tops of the first gear portion 181c and the second gear portion 181d are different from each other depending on the phase of the gear in the rotational direction. For example, there are a position Q1 in which the tooth top portion 181cs of the tooth of the first gear portion and the tooth top 181ds of the second gear portion are in phase alignment with each other, and, a position Q2 in which the tooth top portion 181cs of the first gear portion and the intertooth space 181dv of the second gear portion are in phase alignment with each other, as well, depending on the phase in the rotational direction of the gear. This also applies to the relationship between the first gear portion 163c and the second gear portion 163d of the drum gear 163. As a result, as shown in part (c) of FIG. 25 and part (d) of FIG. 25, The balanced position of the drive transmission gear 181 relative to the driving side flange 163 in the axial direction is different, depending on an initial (before drive) meshing phase between the drive transmission gear 181 and the driving side flange 163 in the rotational direction. Part (c) of FIG. 25 shows the case where the balance position of the drive transmission gear 181 is the most downstream side in the H direction, and part (d) of FIG. 25 shows the case where the balance position of the drive transmission gear 181 is the most downstream side in the J direction. The amount of change of the balanced position can be expressed by the amount of deviation of a boundary between the first gear portion 181c and the second gear portion 181d of the drive transmission gear 181, with reference to an intermediate line between the first gear portion 163c and the second gear portion 163d of the driving side flange 163, for example. That is, in the state of part (c) of FIG. 25, the deviation amount LD in the J direction, and in the state of part (d) of FIG. 25, the deviation amount LE in the H direction, and therefore, sum (LD+LE) of the deviation amount LD and the deviation amount LE is the amount of change of the balanced position in this Modified Example.

[0241] In the case that the first gear portion 181c comes into contact with the second gear portion 163d or the second gear portion 181d comes into contact with the main assembly frame 184, or the second gear portion 181d comes into contact with the first gear portion 163c before the drive transmission gear 181 reaches the balanced position, the backlashless state cannot be established even if the driving operation is carried out. Therefore, in this Modified Example, the distance LF (width of the cylindrical portion 163e) between the first gear portion 163c and the second gear portion 163d of the driving side flange 163 and/or the gap LG between the drive transmission gear 181 and the main assembly frame 184 is selected, taking into consideration the amount of change in the balanced position

(LD+LE)

[0242] On the other hand, in the structure of this embodiment shown in part (a) of FIG. 25, the numbers of teeth of the first main assembly gear portion 81c and the second main assembly gear portion 81d are the same, and the positional relationship between the tooth top 81cs and the tooth top 81ds of the first main assembly gear portion 81c and the second main assembly gear portion 81d is not changed by the phase in the rotational direction. Therefore, the balanced position where the position of the drive transmission gear 81 is determined in the axial direction with respect to the driving side flange 63 does not change. That is, it is not necessary to pay attention to the amount of change in the balanced position (LD+LE), which had to be considered in the modified example. Therefore, in this embodiment, the gap (width of the cylindrical portion 63e) between the first gear portion 63c and the second gear portion 63d of the driving side flange 63 can be designed to be smaller than that of the modified example, and the cartridge B can be downsized. In addition, the apparatus main assembly A of this embodiment can be designed in which the gap between the drive transmission gear 81 and the main assembly frame 84 is smaller than that of the modified example. By this, the cartridge B and/or the apparatus main assembly A can be downsized.

[0243] Next, a modified example will be described in which the main modifications are in portions other than the drive transmission structure itself of the driving side flange 63 or the drive transmission gear 81.

<Application to Cleanerless Structure>

[0244] In the above-described embodiment, in the cartridge B, the toner remaining on the drum 62 without being transferred is scraped off by the rubber blade 77a into contact with the drum 62 and is stored in the waste toner chamber 71b (FIG. 3). However, the cartridge B may have a cleanerless structure. In other words, the drive transmission structure of the driving side flange 63 and the drive transmission gear 81 of the above-described embodiment may be applied to the cartridge having the cleanerless structure.

[0245] FIG. 23 is a cross-sectional view of the cartridge B having the cleanerless structure. The cartridge B having a cleanerless structure is structured and controlled so that the residual toner on the drum 62 can be recovered by the developing roller 32. Therefore, the cartridge B does not have a rubber blade in contact with the drum 62, a rubber blade being a resistance against rotation of the drum 62, and for this reason, the torque required for rotation of the drum 62 is smaller in the cleanerless structure as compared with the structure having the rubber blade 77a in contact with the drum 62 by the amount corresponding to the absence of the rubber blade 77a. As a result, the rotation speed of the drum 62 tends to fluctuate due to the influence of the impact when the sheet material PA is fed. In other words, the rotation accuracy of the drum 62 may deteriorate. By applying the drive transmission structure of the driving side flange 63 and the drive transmission gear 81 of the above-described embodiment, the drum 62 can be driven with transmission between the driving side flange 63 and the drive transmission gear 81 in a backlashless state. For this reason, it is possible to suppress the rotation accuracy deterioration of the drum 62 attributable to, the absence of the rubber blade, as compared with the structure in which the drive is transmitted with the backlash and play in the rotational direction existing between the driving side flange and the drive member on the main assembly side.

<Application to Structures without Magnet Rollers 34>

[0246] Further, in the above-described embodiment, the developer carrying member in which a magnet roller 34 is provided in a developing roller 32 has been described, but an elastic roller in which the magnet roller is not provided may be used.

<Application to the Structure in which the Developing Roller Gear 30 is Engaged with the Second Gear Portion 63d>

[0247] Further, in the above-described embodiment, the structure in which the developing roller gear 30 is in meshing engagement with the first gear portion 63c of the driving side flange 63 has been described. However, the developing roller gear 30 may be structured to be in meshing engagement with the second gear portion 63d. Referring to FIG. 29, such a case will be described. FIG. 29 is a schematic view illustrating the engagement between the driving side flange 63 and the developing roller gear 30. The developing roller gear 130 fixed to the end of the developing roller shaft 31 meshes with the second gear portion 63d. Since the second gear portion 63d has the larger helix angle than the first gear portion 63c, the meshing ratio also increases accordingly. Therefore, the developing roller gear 130 which meshes with the second gear portion 63d can have a smaller tooth width than the developing roller gear 30 which meshes with the first gear portion 63d.

<Application to Drive Transmission Structure from Driving Side Flange to Developing Roller Gear>

[0248] Further, the same structure as the driving force transmission structure from the drive transmission gear 81 to the driving side flange 63 may be further applied to the drive force transmission structure from the driving side flange 63 to the developing roller gear 230. Such a case will be described with reference to FIG. 30. FIG. 30 is a perspective view of the cartridge B. The developing roller gear 230 includes a first developing gear portion 230c and a second developing gear portion 230d which mesh with the first gear portion 63c and the second gear portion 63d of the driving side flange 63, respectively. When the driving side flange 63 is driven, the developing roller gear 230 moves in the direction of the rotational axis L1 by the same principle in the above-described embodiment, so that the drive transmission gear 81 moves in the direction of the rotational axis L1 and reaches the balanced position. In the state the developing roller gear 230 is in the balanced position, the developing roller gear 230 is driven in a backlashless state with respect to the driving side flange 63, so that the misalignment and the deterioration of the rotational accuracy of the developing roller 32 in the load fluctuates can be suppressed.

<Application to the Structure of the Driving the Developing Roller Gear not Through the Driving Side Flange>

[0249] Further, the driving force may be transmitted to the developing roller 532 not through the driving side flange 63. FIG. 44 is a partial perspective view of the cartridge B showing a drive train to the developing roller 532. For the sake of better illustration, a part of the frame of the cartridge B is not shown.

[0250] As shown in FIG. 44, the developing roller 532 is not structured to received the driving force from the driving side flange 63, but is structured to received the driving force by way of another path. Specifically, the cartridge B is provided with a development coupling member 89 which can be engaged with a coupling member (not shown) of the apparatus main assembly A for driving the developing roller. Further, the cartridge B is provided with idler gears 90 and 91 which mesh with the gear portion 89a of the development coupling member 89, and is provided with a developing roller gear 530 which meshes with the idler gear 91 at one end of the shaft of the developing roller 532. With this structure, the developing roller 530 is driven by transmitting the driving force received by the development coupling member 89 by way of the idler gears 90 and 91 and the developing roller gear 530. Therefore, the driving of the development coupling member 89 can be controlled separately from the drive of the driving side flange 63, and the development coupling member 89 can be driven while the driving side flange 63 is not, for example.

<Application to Drive Transmission Structure to Rotatable Members Other than Drums>

[0251] The driving side flange 63 is mounted to the end of the drum 62, but it is possible that the developing roller gear 30 is provided with the first gear portion 63c, the second gear portion 63d, and the cylindrical portion 63e, and the drive transmission gear 81 drives the developing roller 30. Further, the object to be driven by the drive transmission gear 81 is not limited to a developer carrier such as a drum 62 and a developing roller 30 which carries the toner (developer). The object to be driven by the drive transmission gear 81 may be, a feed member (or agitator member) 43 for transporting (or stirring) toner, a charging roller 66, or a supply member for supplying toner to the developing roller 30, for example. Further, when the object to be driven by the drive transmission gear 81 is a member other than the drum 62 included in the cartridge B, the cartridge B may be a cartridge including no photosensitive member such as the drum 62.

[0252] Next, referring to FIG. 31, Embodiment 2 will be described below. In this embodiment, the structures of the first gear portion and the second gear portion provided on the driving side flange are different from those in Embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0253] FIG. 31 is a sectional view of a meshing engagement portion between the drive transmission gear 81 and the driving side flange 263, and the sectional plane is in contact with meshing pitch circles therebetween. The driving side flange 263 is provided with a first gear portion (first unit side gear portion) 263c and a second gear portion (second unit side gear portion) 263d. The first gear portion 263c includes a plurality of first flat teeth (first projections) 263ct having a tooth width which is sized so as to be insertable between the teeth of the first main assembly gear portion 81c. The second gear portion 263d includes a plurality of second flat teeth (second projections) 263dt having a tooth width which is sized so as to be insertable between the teeth of the second main assembly gear portion 81d. In addition, the width (tooth width) of the first flat tooth 263ct measured in the direction of the rotational axis L1 is larger than the width (tooth width) of the second flat tooth 263dt measured in the direction of the rotational axis L1. The plurality of first flat teeth and the plurality of second flat teeth are projections projecting in the radial direction with respect to the rotational axis L1 and are arranged at positions different in the circumferential direction about the rotational axis L1.

[0254] Also when such a driving side flange 263 is used, by the drive transmission gear 81 rotating in the I direction, the drive transmission gear 81 is moved to the balanced position and establishes a backlashless state as in Embodiment 1. That is, the first main assembly gear portion 81c meshes with the first gear portion 263c and receives the reaction force of the driving force FD and the thrust force F209 in the J direction from the contact point (contact portion) CP1 of the first gear portion 263c. The second main assembly gear portion 81d meshes with the second gear portion 263d and receives the reaction force of the restricting force FB and the thrust force F210 in the H direction from the contact point (contact portion) CP2 of the second gear portion 263d. Also with this, the drive transmission gear 81 is sandwiched between the first gear portion 263c and the second gear portion 263d of the driving side flange 263 in the rotational direction in the axial direction, so that the backlashless state is provided as in Embodiment 1.

[0255] Next, referring to FIG. 32, Embodiment 3 will be described. In this embodiment, the structures of the first gear portion and the second gear portion provided on the driving side flange are different from those in Embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0256] FIG. 32 is an illustration of a driving side flange 363. The driving side flange 363 is provided with a first gear portion 363c and a second gear 363d1. The first gear portion (first unit side gear portion) 363c includes a plurality of first helical tooth gears (first projections) 363ct provided by being divided into a plurality of portions in the direction of the rotational axis L1. Although the plurality of first helical tooth gears (projections) 363ct are provided by dividing in the direction of the rotational axis L1, they function as one helical tooth substantially extending in the direction of the rotational axis L1 with respect to the first main assembly gear portion 81c. Further, the tooth surface of the plurality of first helical tooth gears (projections) 363ct is a plurality of force receiving portions which receive force from the first main assembly gear portion 81c. Therefore, it can be said that the plurality of force receiving portions which receive the force from the first main assembly gear portion 81c are provided over the plurality of first helical tooth gears (first projections) 363ct. It can be said that the tooth surfaces of the plurality of first helical tooth gears (projections) 363ct constitute helical tooth surfaces provided by dividing into a plurality portions in the direction of the rotational axis L1, or they constitute a plurality of helical tooth surfaces which are provided by dividing in the circumferential direction centered on the rotational axis L1 of the driving side flange 363. As described above, the plurality of helical tooth-shaped projections 363ct constitute one tooth of the first main assembly gear portion 81c and one tooth of the corresponding helical tooth gear.

[0257] The tooth surfaces of the plurality of second helical tooth gears (projections) 363dt are force receiving portions which receive force from the second main assembly gear portion 81d. Therefore, it can be said that the plurality of force receiving portions which receive the force from the second main assembly gear portion 81d are provided over the plurality of second helical tooth gears (second projections) 363dt. The second gear portion (second unit side gear portion) 363d includes a plurality of second helical tooth gears (projections) 363dt provided by being divided into a plurality of portions in the direction of the rotational axis L1. Although the plurality of second helical tooth gears (second projections) 363dt are provided by dividing in the direction of the rotational axis L1, they function substantially as one helical tooth extending in the direction of the rotational axis L1, with respect to the second main assembly gear portion 81d. In addition, it can be said that the tooth surfaces of the plurality of second helical tooth gears (projections) 363dt constitute a plurality of helical tooth surfaces provided by dividing in the direction of the rotational axis L1, or they constitute helical tooth surfaces which are provided by dividing in the circumferential direction with respect to the rotational axis L1 of the driving side flange 363. As described above, the plurality of helical tooth-shaped projections 363dt constitute one helical tooth corresponding to one tooth of the second main assembly gear portion 81d.

[0258] Therefore, also when such a driving side flange 363 is used, by the drive transmission gear 81 rotating in the I direction, the drive transmission gear 81 is moved to the balanced position and establishes a backlashless state as in Embodiment 1.

[0259] Next, referring to FIG. 33, Embodiment 4 will be described. In this embodiment, the structures of the first gear portion and the second gear portion provided on the driving side flange are different from those in Embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0260] The driving side flange 463 has two gear portions (first unit side gear portion and second unit side gear portion) as with the first gear portion 63c and the second gear portion 63d of the driving side flange 63 of Embodiment 1. At least one of the two gear portions has a missing tooth portion (apparently, a portion where the teeth of the gear are intermittently missing) 463L. Part (a) of FIG. 33 is a view of the driving side flange 463 and the drive transmission gear 81 meshing with each other in a cross-section perpendicular to the rotational axis L1. Part (b) of FIG. 33 is a graph showing the change in the number of teeth of the meshing gear. When the meshing ratio between the gear portion of the driving side flange 463 and the gear portion of the drive transmission gear 81 is N teeth with truncating after the decimal point, the gear portion of the driving side flange 463 may have tooth missing portion 463L at every N−1 tooth at the maximum. By satisfying this condition, even if the tooth missing portion 463L is provided, there are one or more teeth which are in meshing engagement with the drive transmission gear 81 (the meshing ratio is 1 or more). With such a structure, by the drive transmission gear 81 rotating in the I direction, the drive transmission gear 81 moves to the balanced position to establish a backlashless state as in Embodiment 1. As shown in part (b) of FIG. 33, the number of gear teeth of the driving side flange 463 which meshes with each gear portion of the drive transmission gear 81 changes during driving.

[0261] Next, referring to FIG. 34, Embodiment 5 will be described. In this embodiment, the structures of the first gear portion and the second gear portion which are provided on the driving side flange are different from those in Embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0262] The driving side flange 563 is provided with two gear portions (first unit side gear portion and second unit side gear portion) as with the first gear portion 63c and the second gear portion 63d of the driving side flange 63 of Embodiment 1. At least one of the two gear portions has a tooth missing portion 563L. Part (a) of FIG. 34 is a view of the driving side flange 563 and the drive transmission gear 81 meshing with each other in a cross-section perpendicular to the rotational axis L1. Part (b) of FIG. 34 is an illustration showing changes in the number of teeth of the meshing gears. As shown in part (a) of FIG. 34, as is different from the driving side flange 463 of Embodiment 4, the teeth of the driving side flange 563 are not arranged at regular intervals in the circumferential direction. That is, it can be said that the size of the plurality of tooth missing portions 563 in the circumferential direction is not constant, or the apparent amount of all the tooth missing portions 563 is not the same. In other words, it will suffice if they are arranged in the rotational direction at intervals LI, LJ which are natural number (1, 2, . . . ) multiple of the minimum pitch LH between adjacent teeth. Even if such a tooth missing portion 563 is provided, it will suffice if there is at least one meshing tooth (the meshing ratio is 1 or more). With such a structure, by the drive transmission gear 81 rotating in the I direction, the drive transmission gear 81 moves to the balanced position to establish a backlashless state as in Embodiment 1. As shown in part (b) of FIG. 34, the number of gear teeth of the driving side flange 463 which mesh with each gear portion of the drive transmission gear 81 changes.

[0263] Next, referring to FIG. 35, Embodiment 6 will be described below.

[0264] In this embodiment, the structures of the first gear portion and the second gear portion provided on the driving side flange are different from those in Embodiment 1. Specifically, the first gear portion 63c and the second gear portion 63d of Embodiment 1 each have an involute tooth profile helical tooth, but this embodiment is different, in that the helical tooth does not have an involute tooth profile. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0265] FIG. 35 is a perspective view of the driving side flange 763. The driving side flange 763 has a first gear portion (first unit side gear portion) 763c and a second gear portion (second unit side gear portion) 763d. The first gear portion 763c includes a plurality of first projections 763ct, and the second gear portion 63d includes a plurality of second projections 763dt. The first projection 763ct and the second projection 763dt are projections projecting in the radial direction relative to the rotational axis L1, and the cross-sectional shape in the cross-section perpendicular to the rotational axis L1 is trapezoidal having a width narrowing toward the free end. In addition, the first projection 763ct and the second projection 763dt are helical teeth which are twisted around the rotational axis L1. Even with such a structure, the first gear portion 763c and the second gear portion 763d function as helical tooth gears in the meshing engagement with the drive transmission gear 81. Therefore, by the drive transmission gear 81 rotating in the I direction, the drive transmission gear 81 moves to the balanced position to establish a backlashless state as in Embodiment 1.

[0266] The cross-sectional shape of the first projection 763ct and the second projection 763dt is not limited to the trapezoid, but may be a projection shape such as a rectangle, a triangle, or a curved shape, or a shape with chamfered corners.

[0267] Next, referring to FIG. 36, Embodiment 7 will be described. In this embodiment, the structures of the first gear portion and the second gear portion provided on the driving side flange are different from those in Embodiment 1. Specifically, the twisting directions are reversed as compared with the first gear portion 63c and the second gear portion 63d of Embodiment 1. In harmonization with this structure, the twisting directions of the first main assembly gear portion and the second main assembly gear portion of the drive transmission gear are also reversed as compared with Embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0268] FIG. 36 is a schematic view illustrating the engagement between the drive transmission gear 881 and the driving side flange 863. As shown in FIG. 36, the twisting directions of the first gear portion (first unit side gear portion) 863c and the second gear portion (second unit side gear portion) 863d of the driving side flange 863 are such that the tooth surface shift in the I direction as go in the J direction. The twisting directions of the first gear portion 881c and the second gear portion 881d of the drive transmission gear 881 is such that the tooth surface shift in the K as go in the J direction.

[0269] Since the twisting direction is opposite to that of Embodiment 1, the direction of the thrust force F21 applied to the drive transmission gear 881 by the meshing engagement during driving of the drive transmission gear 881 is also opposite to that of Embodiment 1. Therefore, in moving to the balanced position in the axial direction, a space having a width LK for the drive transmission gear 881 to move in the H direction is required. For this reason, a compression spring 185 for urging the drive transmission gear 881 in the J direction is provided, so that the drive transmission gear 881 is placed in abutment against the positioning portion 83b of the second driving side plate 83 before mounting the cartridge B.

[0270] Also with such a structure, by the drive transmission gear 881 rotating in the I direction, the drive transmission gear 881 moves to the balanced position to establish a backlashless state as in Embodiment 1.

[0271] Next, referring to FIG. 37, Embodiment 8 will be described. This embodiment has a different structure in which the cartridge B is mounted to the main assembly of the apparatus as compared with Embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0272] FIG. 37 is a perspective view of an image forming apparatus 800. In the image forming apparatus 800, the inserting direction for inserting the cartridge B into the apparatus main assembly A is parallel to or substantially parallel to the rotational axis L1 of the drum 62. Even if the cartridge B is completely inserted in the direction parallel to the rotational axis L1, the driving side flange 63 and the drive transmission gear (not shown) of the apparatus main assembly A cannot mesh with each other because there is a distance between them in the direction perpendicular to the rotational axis L1. Thereafter, by closing the door 211, the cartridge B is displaced at least in the direction VD perpendicular to the rotational axis L1 by the lift-up mechanism (not shown) provided in the apparatus main assembly A in connection with the door 211, and the driving side flange 63 and the drive transmission gear (not shown) of the apparatus main assembly A are meshed with each other.

[0273] The drive operation after the driving side flange 63 and the drive transmission gear (not shown) meshing engagement with each other is the same as in Embodiment 1, and the drive transmission gear moves to the balanced position to establish the backlashless state as in Embodiment 1.

[0274] When the cartridge B is displaced at least in the direction VD perpendicular to the rotational axis L1 by the lift-up mechanism, the cartridge B may be displaced not only in the direction perpendicular to the rotational axis L1 but also in the direction of the rotational axis L1. Further, the lift-up mechanism may be structured to rotate the cartridge B around an axis perpendicular to the rotational axis L1 and displace the driving side flange 63 in the direction VD perpendicular to the rotational axis L1.

[0275] Further, instead of the structure in which the door 211 is closed to operate the lift-up mechanism after the cartridge B is inserted into the apparatus main assembly A, the cartridge B may be displaced at least in the direction VD perpendicular to the rotational axis L1 in the process of inserting the cartridge B into the apparatus main assembly A. Specifically, at the initial stage of the insertion stroke of the cartridge B into the apparatus main assembly A, the cartridge B is guided by a guide (not shown) so as to move the cartridge B in a direction parallel to the rotational axis L1. Then, at the final stage of the insertion stroke, the cartridge B is guided by a guide (not shown) so as to displace the cartridge B in a direction VD perpendicular to at least the rotational axis L1. In this manner, the structure may be such that the moving direction (mounting direction) of the cartridge B changes during the insertion process.

[0276] Next, referring to FIG. 38, Embodiment 9 will be described. In this embodiment, the structures of the first gear portion and the second gear portion provided on the driving side flange are different from those in Embodiment 1. Specifically, in this embodiment, the arrangement of a first gear portion 963c and a second gear portion 963d in the direction of the rotational axis L1 is reversed as compared with that of the first gear portion 63c and the second gear portion 63d of Embodiment 1. In harmonization with this structure, the positions of the first main assembly gear portion and the second main assembly gear portion of the drive transmission gear in the direction of the rotational axis L1 are also reversed as compared with Embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0277] FIG. 38 is a schematic view illustrating the meshing engagement between the drive transmission gear 981 and the driving side flange 963. The driving side flange 963 is provided with the first gear portion (first unit side gear portion) 963c and the second gear portion (second unit side gear portion) 963d. The helix angle of the second gear portion 963d is larger than that of the first gear portion 963c. The first gear portion 963c is arranged on the downstream side (driving side), in the J direction, of the second gear portion 963d. That is, the second gear portion 963d is disposed between the first gear portion 963c and the drum 62 in the direction of the rotational axis L1. Similarly, the drive transmission gear 981 is provided with a first gear portion 981c which meshes with the first gear portion 963c and a second gear portion 981d which meshes with the second gear portion 963d. The positions of them in the direction of the rotational axis L1 is opposite to that in Embodiment 1.

[0278] Also with such a structure, by the drive transmission gear 981 being driven, the drive transmission gear 981 moves to the balanced position. During the subsequent driving operation, the first gear portion 963c receives the driving force FD (see part (d) of FIG. 17) and the second gear portion 963d receives the restricting force FB (see part (d) of FIG. 17) as in Embodiment 1, so that the backlashless state is established.

[0279] Here, the end portion, on the driving side (downstream side in the J direction), of the drum unit 969 in which the driving side flange 963 and the drum 62 are integrated is rotatably supported by the shaft member 86 (see also FIG. 4). Further, the first gear portion 963c is disposed at a position closer to a root portion of the shaft member 86 than the second gear portion 963d. Further, in the driving side flange 963, the force applied to the tooth surface of the first gear portion 963c which receives the drive force FD is larger than that of the second gear portion 963d which receives the restricting force FB. Therefore, the driving force FD may act so as to cause the rotational axis L1 of the drum unit 969 to tilt, and therefore, the drum 62 may be tilted with respect to the ideal rotational axis L1. However, as in this embodiment, by disposing the first gear portion 963c which receives the driving force FD at a position closer to the root portion of the shaft member 86 than the second gear portion 963d, the tilting of the rotational axis L1 of the drum unit 969 nine six nine attributable to the reception of the driving force FD can be suppressed.

[0280] Next, referring to FIG. 39, Embodiment 10 will be described below. In this embodiment, the structures of the first gear portion and the second gear portion provided on the driving side flange are different from those in Embodiment 1. Specifically, the positions and widths of the first gear portion 63c and the second gear portion 63d of Embodiment 1 in the direction of the rotational axis L1 are the same, but in this embodiment, the positions and widths, in the direction of the rotational axis L1, of the teeth are not the same, as is different from embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0281] FIG. 39 is a sectional view of the meshing engagement portion between the drive transmission gear 81 and the driving side flange 1063, and the sectional plane is in contact with the meshing pitch circles therebetween. The driving side flange 1063 is provided with a first gear portion (first unit side gear portion) 1063c and a second gear portion (second unit side gear portion) 1063d. The first gear portion 1063c includes a plurality of first helical teeth (first projections) 1063ct having different widths and positions in the direction of the rotational axis L1. The second gear portion 1063d includes a plurality of second helical teeth (second projections) 1063dt having different widths and positions in the direction of the rotational axis L1.

[0282] In the case of this structure, the meshing ratio is different from that in the case where the driving side flange 63 of Embodiment 1 is used, but the first gear portion 1063c and the second gear portion 1063d function as helical gears similarly to the first gear portion 63c and the second gear portion 63d, respectively. Therefore, as the drive transmission gear 81 rotating in the I direction, the drive transmission gear 81 moves to the balanced position so that the backlashless state is established as in Embodiment 1.

[0283] Next, referring to FIG. 40, Embodiment 11 will be described. In this embodiment, the structure of the second gear portion provided on the driving side flange is different from that in Embodiment 1. Specifically, the second gear portion 63d of Embodiment 1 is an helical tooth gear, but in this embodiment, it is a spur tooth gear, as is different from embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0284] FIG. 40 is a sectional view of the meshing engagement portion between the drive transmission gear 81 and the driving side flange 1163, and the sectional plane is in contact with the meshing pitch circles therebetween. The driving side flange 1163 is provided with a first gear portion (first unit side gear portion) 1163c and a second gear portion (second unit side gear portion) 1163d. The first gear portion 1163c is the same as the first gear portion 63c of Embodiment 1. The second gear portion 1163d includes a plurality of second flat teeth (teeth, second projections) 1163dt. The plurality of second flat teeth 1163dt are flat teeth having a tooth width and a tooth thickness which are sized so as to be insertable between the teeth (intertooth portion) of the second main assembly gear portion 81d of the drive transmission gear 81. Therefore, the width (tooth width) of the second flat tooth (second projection) 1163dt in the direction of the rotational axis L1 is smaller than the width (tooth width) of the first gear portion 1163c in the direction of the rotational axis L1. In other words, the second gear portion 1163d has a second flat tooth (second projection) 1163dt having a narrower width than the first helical tooth having a largest width (tooth width), in the direction of the rotational axis L1, of the first gear portion 1163c.

[0285] The rotational direction (I direction) or circumferential width (length) of the second projection 1163dt is smaller than the rotational direction (I direction) or circumferential width (length) of one tooth of the first gear portion 1163c. In other words, the second gear portion 1163d includes a second projection 1163dt which is narrower in the rotational direction (I direction) or the circumferential direction as compared with the first helical tooth having the largest rotational direction (I direction) or circumferential direction width (length) of the first gear portion 1163c.

[0286] Further, the second projection 1163dt has a contact portion CP2 which contacts the second main assembly gear portion 81d. As shown in FIG. 40, the contact portion CP2 is provided at the corner portion of the second projection 1163dt. The corner portion (contact point CP2) is provided so that the corner portion (contact point CP2) comes into contact with one tooth of the second main assembly gear portion 81d only at one point in the direction of the rotational axis L1. The radius of curvature of this corner portion can be set to a desired value, and the corner portion may have a sharper shape by making the radius of curvature smaller, or a less sharp corner may be formed by increasing the radius of curvature, as in the second projection 1363dt shown in Embodiment 13 which will be described hereinafter.

[0287] When the drive transmission gear 81 is driven, the drive transmission gear 81 receives a thrust force F1109 in the J direction and moves in the J direction in the same manner as in Embodiment 1. Then, the surface 81d2 on the upstream side in the I direction of the second main assembly gear portion 81d comes into contact with the contact portion CP2 of the second flat tooth 1163dt of the second gear portion 1163d, and receives the thrust force F1110 in the H direction. Therefore, the drive transmission gear 81 is positioned at the balanced position in the same principle as in Embodiment 1 to establish the backlashless state. Further, in the backlashless state, with respect to the driving in the rotational direction, the first gear portion 1163c receives the driving force FD and the second gear portion 1163d receives the restricting force FB at the contact portion CP2 of the second flat tooth 1163dt.

[0288] Next, referring to FIG. 41, Embodiment 12 will be described. In this embodiment, the structure of the second gear portion provided on the driving side flange is different from that in Embodiment 1. Specifically, the helix angle of the second gear portion 63d of Embodiment 1 is larger than the helix angle of the first gear portion 63c, but such is not the case in the helix angle of the second gear portion 1263d of this embodiment. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0289] FIG. 41 is a sectional view of the meshing engagement portion between the drive transmission gear 81 and the driving side flange 1263, and the sectional plane is in contact with the meshing pitch circles therebetween. The driving side flange 1263 is provided with a first gear portion (first unit side gear portion) 1263c and a second gear portion (second unit side gear portion) 1263d. The first gear portion 1263c is the same as the first gear portion 63c of Embodiment 1. The second gear portion 1263d includes a plurality of second helical teeth (teeth, second projections) 1263dt. The helix angle of the plurality of second helical teeth 1263dt is the same as the helix angle of the helical teeth of the first gear portion 1263c. Further, similarly to the plurality of second helical teeth 1163dt of Embodiment 11, the plurality of second helical teeth 1263dt have tooth widths and tooth thicknesses which are sized so as to be insertable between the teeth (intertooth portion) of the second main assembly gear portion 81d of the drive transmission gear 81. Therefore, the width (tooth width) of the second helical tooth (second projection) 1263dt measured in the direction of the rotational axis L1 is smaller than the width (tooth width) of the first gear portion 1263c measured in the direction of the rotational axis L1. In other words, the second gear portion 1263d includes a second helical tooth (second projection) 1263dt having a narrower width than that of the first helical tooth having a largest width (tooth width) in the direction of the rotational axis L1 of the first gear portion 1263c.

[0290] Further, the rotational direction (I direction) or the circumferential width (length) of the second projection 1263dt is smaller than the rotational direction (I direction) or the circumferential width (length) of one tooth of the first gear portion 1263c. In other words, the second gear portion 1263d includes a second projection 1263dt having a rotational direction (I direction) or circumference width narrower than that of the first helical tooth having a largest rotational direction (I direction) or circumferential direction width (length) of the first gear portion 1263c.

[0291] Further, the second projection 1263dt has a contact portion CP2 which contacts the second main assembly gear portion 81d. As shown in FIG. 40, the contact portion CP2 is provided at the corner portion of the second projection 1263dt. The corner portion (contact point CP2) is provided so that the corner portion (contact point CP2) contacts one tooth of the second main assembly gear portion 81d only at one point in the direction of the rotational axis L1. The radius of curvature of this corner portion can be set to a desired value, and the corner portion may have a sharper shape by making the radius of curvature smaller, or less sharp corner may be formed by increasing the radius of curvature, as in the second projection 1363dt shown in Embodiment 13 which will be described hereinafter.

[0292] By the drive transmission gear 81 being driven, the drive transmission gear 81 receives the thrust force F1209 in the J direction and moves in the J direction as in the first embodiment. Then, the surface 81d2, on the upstream side in the I direction, of the second main assembly gear portion 81d comes into contact with the contact portion CP2 of the second helical tooth 1163dt of the second gear portion 1263d, and receives the thrust force F1210 in the H direction. Therefore, the drive transmission gear 81 is positioned at the balanced position in the same principle as in Embodiment 1, so that the backlashless state is established. Further, in the backlashless state with respect to the driving in the rotational direction, the first gear portion 1263c receives the driving force FD and the second gear portion 1263d receives the restricting force FB at the contact portion CP2 of the second helical tooth 1263dt.

[0293] Next, referring to FIG. 42, Embodiment 13 will be described below. In this embodiment, the structure of the portion corresponding to the second gear portion provided on the driving side flange is different from that in Embodiment 1. Specifically, the second gear portion 63d of Embodiment 1 is an helical tooth gear, but in this embodiment, it is a plurality of cylindrical projections, as is different from embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0294] Part (a) of FIG. 42 is a perspective view of the driving side flange 1363. Part (b) of FIG. 42 is a sectional view of the meshing engagement portion between the drive transmission gear 81 and the driving side flange 1363, and the sectional plane is in contact with the meshing pitch circles therebetween.

[0295] The driving side flange 1363 is provided with a first gear portion (first unit side gear portion) 1363c and a second gear portion (second unit side gear portion) 1363d. The first gear portion 1363c is the same as the first gear portion 63c of Embodiment 1.

[0296] The second gear portion 1363d includes a plurality of cylindrical second projections (teeth) 1363dt projecting in the radial direction of the rotational axis L1 from the tooth bottom cylindrical portion (base cylinder portion) 1363Bd extending along the rotational axis L1. The second gear portion 1363d is a rotating portion which rotates integrally with the first gear portion 1363c. The plurality of second projections 1363dt are arranged at the same position (on the same plane perpendicular to the rotational axis L1) with respect to the direction of the rotational axis L1.

[0297] Further, the tips S of the plurality of second projections 1363dt are arranged on a predetermined circumference centered on the rotational axis L1 as viewed along the rotational axis L1, and are arranged at equal intervals in the circumferential direction. The addendum circle of the second gear portion 1363d is a circle as a rotation locus drawn by the free end S that is most remote from the rotational axis (rotational axis L1) of the second gear portion 1363d among the free ends S of the plurality of second projections 1363dt when the driving side flange 1363 rotates. In this embodiment, the shapes of all the second projections 1363dt are the same, and therefore, the distances of the free ends S of all the second projections 1363dt from the rotational axis L1 are the same, so that all the free ends S draw the same rotation locus. Further, the diameter/radius of the circle of this rotation locus is the addendum circle diameter/addendum circle radius of the second gear portion 1363d.

[0298] The plurality of second projections 1363dt are projections having a width in the direction of the rotational axis L1 and a width in the rotational direction (I direction) which are sized so as to be insertable between the teeth (intertooth portion) of the second main assembly gear portion 81d of the drive transmission gear 81. Therefore, the width of the second projection 1363dt measured in the direction of the rotational axis L1 is smaller than the width (tooth width) of the first gear portion 1363c measured in the direction of the rotational axis L1. In other words, the second gear portion 1363d has the second projection 1363dt having a width in the direction of the rotational axis L1 narrower than that of the first helical tooth having the largest width (tooth width), in the direction of the rotational axis L1, of the first gear portion 1363c. The rotational direction (I direction) or circumferential direction width (length) of the second projection 1363dt is larger than the rotational direction (I direction) or circumferential width (length) of one tooth of the first gear portion 1363c. In other words, the second gear portion 1363d includes a second projection 1363dt having a rotational direction (I direction) or circumferential width smaller than that of the first helical tooth having the largest rotational direction (I direction) or circumferential direction width (length) of the first gear portion 1363c.

[0299] Further, the second projection 1363dt has a contact portion CP2 which contacts the second main assembly gear portion 81d. As shown in part (b) of FIG. 42, the contact portion CP2 is on the curved portion of the surface of the second projection 1363dt. The curved portion of the surface of the second projection 1363dt can be said to be a corner portion. The corner portion (contact point CP2) is provided so that the corner portion (contact point CP2) contacts one tooth of the second main assembly gear portion 81d only at one point in the direction of the rotational axis L1. The radius of curvature of this corner can be set to a desired value, and the radius of curvature may be made smaller to form a corner with a sharper shape, or the radius of curvature may be made larger to form a less sharp corner.

[0300] When the drive transmission gear 81 is driven, the drive transmission gear 81 receives a thrust force in the J direction and moves in the J direction, as in Embodiment 1. Then, the surface 81d2 on the upstream side in the I direction of the second main assembly gear portion 81d comes into contact with the contact portion CP2 of the second projection 1363dt of the second gear portion 1163d, and receives the thrust force F1310 in the H direction. Therefore, the drive transmission gear 81 is positioned at the balanced position in the same principle as in Embodiment 1, and the backlashless state is established. Further, in the backlashless state, the first gear portion 1363c receives the driving force FD, and the second gear portion 1363d receives the restricting force FB at the contact portion CP2 of the second projection 1363dt with respect to the driving in the rotational direction.

[0301] Thus, the second gear portion 1363d can engage with other gears such as the second main assembly gear portion 81d by using the plurality of second projections 1363dt and can receive the rotational driving force and/or the thrust force, and therefore, in this respect, it can be regarded as a kind of gear.

[0302] Further, the plurality of second projections 1363dt are not limited to a cylindrical shape, and may have at least a shape which projects in the radial direction relative to the rotational axis L1 and may be a polygonal column shape, for example. Further, all the plurality of second projections 1363dt do not have to have the same shape.

[0303] Next, referring to FIG. 43, Embodiment 14 will be described. In this embodiment, the structure of the portion corresponding to the second gear portion provided on the driving side flange is different from that in Embodiment 1. Specifically, the second gear portion 63d of Embodiment 1 is an helical tooth gear, but in this embodiment, it is a plurality of cylindrical projections, as is different from embodiment 1. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted. Further, in the comparison with Embodiment 13, this embodiment is different therefrom only in the arrangement of the plurality of cylindrical projections.

[0304] Part (a) of FIG. 43 is a sectional view of the teeth and projections of the driving side flange 1463, and the sectional plane thereof is in contact with a circle centered on the rotational axis L1. Part (b) of FIG. 43 is a sectional view of the meshing engagement portion between the drive transmission gear 81 and the driving side flange 1463, and the sectional plane thereof is in contact with the meshing pitch circles therebetween.

[0305] The driving side flange 1463 is provided with a first gear portion (first unit side gear portion) 1463c and a second gear portion (second unit side gear portion) 1463d. The first gear portion 1463c is the same as the first gear portion 63c of Embodiment 1.

[0306] The second gear 1463d includes a plurality of cylindrical second projections 1463dt projecting in the radial direction relative to the rotational axis L1. The second gear portion 1463d is a rotatable portion which is rotatable integrally with the first gear portion 1463c. The plurality of second projections 1463dt are arranged at positions shifted in the direction of the rotational axis L1.

[0307] Further, the free end S (see part (a) of FIG. 42) of the plurality of second projections 1463dt are arranged on a predetermined circumference centered on the rotational axis L1 as viewed along the rotational axis L1. The plurality of second projections 1463dt are projections having a width measured in the direction of the rotational axis L1 and a width measured in the rotational direction (I direction) which are sized such that it can be inserted between the teeth (intertooth portion) of the second main assembly gear portion 81d of the drive transmission gear 81. Further, the plurality of second projections 1463dt are inserted between the teeth (intertooth portion) of the second main assembly gear portion 81d of the drive transmission gear 81, and are placed at positions where they can receive the restricting force FB from the second main assembly gear portion 81d in the backlashless state. Specifically, as shown in part (a) of FIG. 43, a plurality of imaginary twisted lines (helical lines) L9 twisted at the same angle as the helix angle α2 of the second main assembly gear portion 81d are drawn on the cylindrical surface centered on the rotational axis L1 at a predetermined pitch P9. This pitch P9 is the same as the pitch of the drive transmission gear 81 in the direction perpendicular to the tooth surface of the plurality of second helical teeth 81dt of the second main assembly gear portion 81d. Then, the plurality of second projections 1463dt are arranged so as to satisfy the following conditions in relation to the plurality of twisted lines L9. The condition is that a plurality of twisted lines L9 can be arranged such that some of the plurality of twisted lines L9 are in contact with some of the plurality of second projections 1463dt, and none of the plurality of twisted lines L9 passes through the cross-section of the plurality of second projections 1463dt. This embodiment can perform the same function as the plurality of second projections 1363dt of Embodiment 13, that is, by arranging the plurality of second projections 1463dt so as to satisfy such the condition, the plurality of second projections 1463dt receive the restricting force FB from the second main assembly gear portion 81d in a backlashless state. In addition, similarly to Embodiment 13, the corner portion (contact point CP2) of the second projection 1463dt is provided such that at only one corner portion (contact point CP2) in the direction of the rotational axis L1, it can contact with one tooth of the second main assembly gear portion 81d.

[0308] When the drive transmission gear 81 is driven, as shown in part (b) of FIG. 43, the drive transmission gear 81 receives the thrust force F1409 and moves in the J direction as in embodiment 1. And, the surface 81d2, on the upstream side in the I direction, of the second main assembly gear portion 81d comes into contact with the contact portion CP of the second projection 1463dt of the second gear portion 1463d, and receives the thrust force F1410 in the H direction. Therefore, the drive transmission gear 81 is positioned at the balanced position in the same principle as in Embodiment 1 to establish the backlashless state. In addition, in the backlashless state, the first gear portion 1463c receives the driving force FD, and the second gear portion 1463d receives the restricting force FB at the contact portion CP2 of the second projection 1463dt, with respect to the driving in the rotational direction.

[0309] Since the second gear portion 1463d can engage with other gears such as the second main assembly gear portion 81d and can receive the rotational driving force and/or the thrust force by using the plurality of second projections 1463dt, it can be regarded as a kind of gear, in this respect.

[0310] Further, the shapes of the plurality of second projections 1463dt are not limited to a cylindrical shape, and may have a shape which projects at least in the radial direction relative to the rotational axis L1, and all the plurality of second projections 1463dt do not have to have the same shape.

[0311] Next, referring to FIG. 45, Embodiment 15 will be described. The drive transmission structure in the cartridge B is different from that of Embodiment 1. Part (a) of FIG. 45 is a partial sectional view of the cartridge B in the neighborhood of the drum 62, taken along a line including the rotational axis L1. Part (b) of FIG. 45 is a view of the drum 62 and the developing roller 632 of the cartridge B as viewed in a direction perpendicular to the rotational axis L1.

[0312] The gear that meshes with the drive transmission gear 81 does not have to be integrally fixed to the end of the drum 62. As shown in part (a) of FIG. 45, the driven gear 1563 which meshes with the drive transmission gear 81 is rotatably supported at both end portions by a shaft 1578 fixed to one end of the cleaning frame 1571. That is, the shaft 1578 supports the driven gear 1563 in a state of penetrating the driven gear 1563. The driven gear 1563 is a first gear portion (first unit side gear portion) 1563c which is an helical tooth gear having a helix angle α1 and a second gear portion (second unit side gear portion) 1563d which is an helical tooth gear having a helix angle α2, similarly to the first gear portion 63c and the second gear portion 63d provided on the driving side flange 63 of Embodiment 1. In addition, a developing roller gear 632 is provided integrally with a developing gear 630 in meshing engagement with the second gear portion 1563d of the driven gear 1563 at one end of the developing roller 632, and a drum drive gear 92 is provided integrally with the developing roller 632 at the other end of the developing roller 632. Further, a drum gear 93 which meshes with the drum drive gear 92 is integrally mounted to one end of the drum 62 by clamping or the like, and is rotatably supported by the drum shaft. Furthermore, a drum flange 1564 is mounted to the other end of the drum by clamping or the like, and is rotatably supported by a shaft 1578. With such a structure, the driving force received by the driven gear 1563 from the drive transmission gear 81 is transmitted to the drum 62 in the order of the developing roller gear 630, the developing roller 632, the drum drive gear 92, and the drum gear 93.

[0313] Next, referring to FIG. 48, Embodiment 15 will be described. In this embodiment, the structures of the portions corresponding to the first gear portion and the second gear portion provided on the driving side flange, as is different from those in Embodiment 1. Specifically, the first gear portion 63c and the second gear portion 63d of Embodiment 1 are helical tooth gears, but in this embodiment, each gear portion is provided by a plurality of projections (projections form each tooth of the gears), as is different therefrom. Since the other points are the same as those in Embodiment 1, the description thereof will be omitted.

[0314] Part (a) of FIG. 48 is a sectional view of the teeth and projections of the driving side flange 1663, and the sectional plane thereof is in contact with a circle centered on the rotational axis L1. Part (b) of FIG. 48 is a sectional view of the meshing engagement portion between the drive transmission gear 81 and the driving side flange 1663, and the sectional plane is in contact with the meshing pitch circles therebetween.

[0315] The first gear portion (first unit side gear portion, first unit side helical tooth gear portion) 1663c includes a plurality of cylindrical first projections 1663ct projecting in the radial direction with respect to the rotational axis L1 from the tooth bottom cylindrical portion (base cylinder portion) extending along the rotational axis L1. The plurality of first projections 1663ct are arranged at the same position and at different positions with respect to the direction of the rotational axis L1.

[0316] In addition, the free ends S (see part (a) of FIG. 42) of the plurality of first projections 1663ct are arranged on a predetermined circumference centered on the rotational axis L1 as viewed along the rotational axis L1. The plurality of first projections 1663ct are projections having a width in the direction of the rotational axis L1 and a width in the rotational direction (I direction) having which are sized such that it can be inserted between the teeth (intertooth portion) of the first main assembly gear portion 81c of the drive transmission gear 81. In addition, the plurality of first projections 1663ct are disposed at the positions so that they are inserted between the teeth (intertooth portion) of the first main assembly gear portion 81c of the drive transmission gear 81, and to receive the driving force FD from the first main assembly gear portion 81c in the backlashless state. Specifically, as shown in part (a) of FIG. 48, a plurality of imaginary twisted lines L15 twisted at the same angle as the helix angle α1 of the first main assembly gear portion 81c on the cylindrical surface centered on the rotational axis L1 (helical line) are drawn at the predetermined pitch P11. This pitch P11 is the same as the pitch in the direction perpendicular to the tooth surface of the plurality of first helical teeth 81ct of the first main assembly gear portion 81c of the drive transmission gear 81. Then, the plurality of first projections 1663dt are arranged so as to satisfy the following conditions in relation to the plurality of twisted lines L5. The condition is that the plurality of twisted lines L11 can be arranged so that some of the plurality of twisted lines L15 are in contact with some of the plurality of first projections 1663ct, and none of the plurality of twisted lines L11 pass through the cross-sections of the plurality of first projections 1663ct. By arranging the plurality of first projections 1663ct so as to satisfy such a condition, the plurality of first projections 1663ct mesh with the first main assembly gear portion 81c in the backlashless state and rotate to receive the driving force FB.

[0317] The second gear portion (second unit side gear portion, second unit side helical tooth gear portion) 1663d includes a plurality of cylindrical second projections 1663dt projecting in the radial direction relative to the rotational axis L1. The second gear portion 1663d is a rotatable portion which rotates integrally with the first gear portion 1663c. The plurality of second projections 1663dt are arranged at positions shifted with respect to the direction of the rotational axis L1.

[0318] Further, the free ends S (see part (a) of FIG. 42) of the plurality of second projections 1663dt are arranged on a predetermined circumference centered on the rotational axis L1 as viewed along the rotational axis L1. The plurality of second projections 1663dt are projections having a width in the direction of the rotational axis L1 and a width in the rotational direction (I direction) which are sized such that that they can be inserted between the teeth (intertooth portion) of the second main assembly gear portion 81d of the drive transmission gear 81. In addition, the plurality of second projections 1663dt are disposed at the positions such that they can be inserted between the teeth (intertooth portion) of the second main assembly gear portion 81d of the drive transmission gear 81, and can receive the restricting force FB from the second main assembly gear portion 81d in a backlashless state. Specifically, as shown in part (a) of FIG. 48, a plurality of imaginary twisted lines L14 twisted at the same angle as the helix angle α2 of the second main assembly gear portion 81d on the cylindrical surface centered on the rotational axis L1 (helical line) are drawn at a predetermined pitch P10. This pitch P10 is the same as the pitch in the direction perpendicular to the tooth surface of the plurality of second helical teeth 81dt of the second main assembly gear portion 81d of the drive transmission gear 81. And, the plurality of second projections 1663dt are arranged so as to satisfy the following conditions in relation to the plurality of twisted lines L14. The condition is that a plurality of the twisted lines L14 can be arranged such that some of the plurality of twisted lines L14 are in contact with some of the plurality of second projections 1663dt, and none of the plurality of twisted lines L14 pass through the cross-section of the plurality of second projections 1663dt. By arranging a plurality of second projections 1663dt so as to satisfy such a condition, the plurality of second projections 1663dt can perform the same function as the plurality of second projections 1363dt of Embodiment 13 can be performed, that is, the projections makes the meshing engagement with the second main assembly gear portion 81d to rotate in a backlashless state and receives the restricting force FB.

[0319] As shown in part (b) of FIG. 48, when the drive transmission gear 81 is driven, the drive transmission gear 81 moves in the J direction as in Embodiment 1. This is because the first main assembly gear portion 81c comes into contact with the plurality of first projections 1663ct and receives a thrust force in the J direction. In the drive transmission gear 81 which has moved in the J direction, the surface 81d2 on the upstream side in the I direction of the second main assembly gear portion 81d finally comes into contact with the contact portion CP2 of the second projection 1663dt of the second gear portion 1663d, and receives the thrust force F1610 in the H direction. In addition, the surface 81c1 on the downstream side in the I direction of the first main assembly gear portion 81c comes into contact with the contact portion CP1 of the first projection 1663ct of the first gear portion 1663c and receives the thrust force F1609 in the J direction. Therefore, the drive transmission gear 81 is positioned at the balanced position in the same principle as in Embodiment 1, and the backlashless state is established. Further, in the backlashless state, the first gear portion 1663c receives the driving force FD and the second gear portion 1663d receives the restricting force FB at the contact portion CP of the second projection 1463dt with respect to the driving in the rotational direction.

[0320] The first gear portion 1663c can engage with other gears such as the first main assembly gear portion 81d by using the plurality of first projections 1663ct, it can receive a rotational driving force and/or the thrust force, and therefore, in this respect, it can be regarded as a kind of gear (helical tooth gear). That is, it can be said that the surfaces of the plurality of first projections 1663ct (plural contact portions CP1) constitute a plurality of helical tooth surfaces provided by division in the direction of the rotational axis L1, or constitute the helical tooth surfaces provided by division into a plurality of parts in the circumferential direction and centered on the rotational axis L1 of the driving side flange 1663.

[0321] Therefore, by connecting the plurality of contact portions CP1, the twisted line L15 can be defined. The plurality of first projections 1663ct are arranged so as to be contactable with one tooth of the first main assembly gear portion 81c at a plurality of positions separated from each other in the direction of the rotational axis L1. It can be said that the plurality of contact portions CP1 capable of simultaneously contacting one tooth of the first main assembly gear portion 81c are provided at positions separated from each other with respect to the direction of the rotational axis L1. In this manner, it can be said that the plurality of first projections 1663ct separately arranged in the direction of the rotational axis L1 constitute one tooth (helical tooth) which meshes with one tooth of the first main assembly gear portion 81c. Therefore, the plurality of first projections 1663ct function as helical tooth gears, and the first gear portion 1663c is the first helical tooth gear portion.

[0322] In addition, a circle drawn as the rotation locus when the free end (point) most remote from the rotational axis L1 among the free ends of the plurality of first projections 1663ct is rotated is the addendum circle of the first gear portion 1663c, and the diameter of the circle is the addendum circle.

[0323] Similarly, the second gear portion 1663d can engage with other gears such as the second main assembly gear portion 81d by using the plurality of second projections 1663dt, and can receive a rotational driving force and/or a thrust force, and therefore, in this respect, it can be regarded as a kind of gear. That is, it can be said that the surfaces of the plurality of second projections 1663dt (plural contact portions CP2) constitute a plurality of helical tooth surfaces provided by division in the direction of the rotational axis L1, or constitute the helical tooth surfaces provided by division into a plurality of parts in the circumferential direction and centered on the rotational axis L1 of the driving side flange 1663.

[0324] Therefore, by connecting the plurality of contact portions CP2, the twisted line L14 can be defined. The plurality of second projections 1663dt are arranged so as to be contactable with one tooth of the second main assembly gear portion 81d at the plurality of positions separated from each other in the direction of the rotational axis L1. It can be said that the plurality of contact portions CP2 capable of simultaneously contacting one tooth of the second main assembly gear portion 81d are provided at positions separated from each other in the direction of the rotational axis L1. In this manner, it can be said that the plurality of second projections 1663dt separately arranged in the direction of the rotational axis L1 constitute one tooth (helical tooth) which meshes with one tooth of the second main assembly gear portion 81d. Therefore, the plurality of second projections 1663dt function as a helical tooth gear, and the second gear portion 1663d is a second helical tooth gear portion.

[0325] Further, a circle drawn as the rotation locus when the free end (point) most remote from the rotational axis L1 among the free ends of the plurality of second projections 1663dt is the addendum circle of the second gear portion 1663d, and the diameter of the circle is the addendum circle.

[0326] Further, each of the plurality of first projections 1663ct and the plurality of second projections 1663dt is not limited to a cylindrical shape, and may have a shape that projects at least in the radial direction relative to the rotational axis L1. Further, the plurality of first projections 1663ct do not have to be a plurality of completely separated projections, and may include a plurality of contact portions CP1. For example, the cross-sectional shape in the tangential direction perpendicular to the radial direction relative to the rotational axis L1 may have a shape like a staircase in which parts of the cross-sectional shape portions are connected. The same applies to the plurality of second projections 1663dt. Further, all the plurality of first projections 1663ct may not have the same shape, and all the plurality of second projections 1663dt may not have the same shape.

[0327] Embodiment 17 differs from Embodiment 1 in the following points. First, the layout of the structure in the apparatus main assembly A to which the cartridge B is mountable is different. As a result, the attitude of the cartridge B in the apparatus main assembly A is different. In addition, the support structure of a driving side flange 1763 and an engagement structure of a drive transmission gear 1781 and an idler gear 1780 are different. A drive transmission structure to a developing roller 1732 is the same as that of other Modified Example of Embodiment 1. Further, the positional relationship between the first gear portion which receives the driving force FD and the second gear portion which receives the restricting force FB in the axial direction is the same as those of Embodiment 9. Other points are the same as in Embodiment 1, and detailed description thereof will be omitted. Further, among the elements in this embodiment, the element corresponding to the element of Embodiment 1 (example: drum 62) (example: drum 1762) is associated with the corresponding element of Embodiment 1 (for example, reference numeral “1762” corresponds to “62”). Regarding these elements, the matters not specifically explained are the same as the corresponding elements of Embodiment 1.

<Configuration of Main Assembly of Apparatus>

[0328] FIG. 50 is a cross-sectional view of the apparatus main assembly A to which the cartridge B is mounted (the cross-sectional plane is perpendicular to the rotational axis L1). The apparatus main assembly A of the image forming apparatus 17100 comprises an exposure device (laser scanner unit) 1703 and a sheet tray 1704 for accommodating the sheet material PA. Further, the apparatus main assembly A comprises a pickup roller (not shown), a feeding roller pair 1705b, a transfer guide 1706, a transfer roller 1707, a feeding guide 1708, a fixing device 1709, a discharge roller pair 1710, and a discharge tray 1711, provided along a transfer path of the sheet material PA.

<Attitude of Cartridge B in Apparatus Main Assembly A>

[0329] As shown in FIG. 50, the cartridge B is positioned in the apparatus main assembly A with the cleaning unit 1760 and the developing unit 1720 placed substantially horizontally. At this time, the transfer roller 1707 is below the drum 1762.

<Support Structure for Drum Unit 1769 by Cleaning Unit 1760>

[0330] Next, referring to part (a) of FIG. 51, part (b) of FIG. 51, part (a) of FIG. 52, part (b) of FIG. 52, part (c) of FIG. 52, FIG. 58, and FIG. 59, the support structure of the drum unit 1769 by the cleaning unit 1760 will be described.

[0331] Part (a) of FIG. 51 is an exploded perspective view of the cleaning unit 1760, and shows a state in which the cleaning unit 1760 is viewed from the developing unit side so that the inside of the drum bearing member 1773 can be seen. Part (b) of FIG. 51 is an exploded perspective view of the cleaning unit 1760, and shows a state in which the cleaning unit 1760 is viewed from the developing unit side so that the outside of the drum bearing member 1773 can be seen. Part (a) of FIG. 52 is a perspective view of the drum bearing member 1773 as viewed from the inside. Part (b) of FIG. 52 is a cross-sectional view of a guided portion 1773g of the drum bearing member 1773 which supports the driving side flange 1763 taken along a cross-sectional plane perpendicular to the rotational axis L1. Here, this cross-sectional view shows a state in which the cross-section is viewed from the inside of the drum bearing member 1773. Part (c) of FIG. 52 is a sectional view of, the portion adjacent to the driving side flange 1763 of the cartridge B mounted on the apparatus main assembly A, taken along a plane including rotational axis L1 and perpendicular to the mounting direction M (see FIG. 57) of the cartridge B to the apparatus main assembly A. FIG. 58 is a cross-sectional view of the cleaning unit 1760 and the drive transmission gear 1781 as viewed from the outside of the drum bearing member 1773, and the cross-sectional plane thereof passes through a hole 1773d of the drum bearing member 1773 which supports the driving side flange 1763 and perpendicular to the rotational axis L1. FIG. 59 is a partial perspective view of the neighborhood of the driving side flange 1763 of the cartridge B.

[0332] As shown in part (a) of FIG. 51 and part (b) of FIG. 51, the cleaning unit 1760 includes a frame member 1771 and a drum bearing member 1773 fixed to the frame member 1771, which constitute a drum frame which supports the drum 1762. The driving side flange 1763 is provided with a cylindrical projection (supported portion) 1763g centered on the rotational axis L1 and projecting outward (downstream in the J direction) from the end surface of the first gear portion 1763c in the rotational axis L1 so as to project from the end of the driving side flange 1763 toward the downstream side in the J direction. The drum bearing member 1773 is provided with a hole 1773d recessed in the direction of the rotational axis L1 (J direction) for supporting the projection 1763g. As shown in part (a) of FIG. 52 and part (b) of FIG. 52, the inner peripheral surface of the hole 1773d has surfaces 1773e and 1773f and two circumferential surfaces 1773h and 1773i, each of which is parallel to the rotational axis L1. In addition, the two surfaces 1773e and 1773f are not parallel to each other and are arranged so as to provide a substantially V-shaped recess shape as viewed in the rotational axis L1 direction. The surface 1773e and the surface 1773f are support surfaces (support portions) having supporting points which contact and support the projections 1763g. As shown in FIG. 58, the substantially V-shaped recess shape provided by the two surfaces 1773e and 1773f is oriented against a force FH parallel to a force FG starting at the rotational axis L1 so as to receive the meshing engagement force FG between the tooth surfaces of the gears when the driving force is transmitted from the driving transmission gear 1781 to the driving side flange 1763. Specifically, a bisector of an angle formed by the extension line of the surface 1773e and the extension line of the surface 1773f as viewed along the rotational axis L1 and the force FH is substantially parallel with the force FH. The orientations of the two surfaces 1773e and 1773f are not limited to this example, and may be selected, taking into account various forces which apply loads to the driving side flange 1763.

[0333] After the drum unit 1769 is incorporated inside the frame member 1771, the drum bearing member 1773 is mounted to the frame member 1771 and fixed, so that the projection 1763g of the driving side flange 1763 fits the hole 1773d of the drum bearing member 1773. By this, the drum unit 1769 is rotatably supported by the frame member 1771 and the drum bearing member 1773. In addition, as shown in FIG. 59 and part (b) of FIG. 114, in the completed state as the cartridge B, parts of the driving side flange 1763 (a part of the first gear portion 1363c and the second gear portion 1363d) and the drum 1762 are not covered by the drum frame (drum bearing member 1773 and frame member 1771) but is exposed to an outside of the cartridge B. That is, it can be said that the drum frame has an opening to expose a part of the driving side flange 1763 (a part of the first gear portion 1363c, a part of the second gear portion 1363d, and so on) and a part of the drum 1762 toward the outside.

[0334] As shown in part (c) of FIG. 52, when the cartridge B is mounted in the apparatus main assembly A, the arc surface of the guided portion 1773g contacts two positioning portions 1715a of a first driving side plate 1715 of the apparatus main assembly A, and the position of the rotational axis L1 of the cartridge B with respect to the apparatus main assembly A is determined in two directions perpendicular to the rotational axis (the mounting direction M and the orthogonal direction MP perpendicular to the mounting direction M) (see FIG. 57). The guided portion 1773g is a projecting portion having a shape projecting outward (J direction) in the direction of the rotational axis L1, and the above-mentioned hole 1773d is provided inside the projecting portion. The apparatus main assembly A is provided with a pressing member (not shown) which presses the cartridge B so as to press the guided portion 1773g toward the two positioning portions 1715a. In addition, the meshing force FG on the tooth surface of the gears at the time of transmitting the driving force from the driving transmission gear 1781 to the driving side flange 1763 also acts to press the guided portion 1773g toward the two positioning portions 1715a. Further, the force of the transfer roller 1707 (see FIG. 50) to press the drum 1762 also acts to press the guided portion 1773g toward the positioning portions 1715a in the orthogonal direction MP.

[0335] At least a part of the guided portion 1773g, at least a part of the two flat surface portions 1773f and 1773e, and at least a part of the projection 1763g are placed at the same position in the direction of the rotational axis L1. In other words, at least a part of the guided portion 1773g, at least a part of the two flat portions 1773f and 1773e, and at least a part of the projection 1763g are arranged on one surface perpendicular to the rotational axis L1. By such an arrangement relationship, it is possible to suppress such deformation that the drum bearing member 1773 is inclined with respect to the rotational axis L1, and it is possible to suppress inclination (tilt) of the driving side flange 1763 with respect to the rotational axis L1. As a result, deterioration of the meshing engagement accuracy between the driving side flange 1763 and the drive transmission gear 1781 can be suppressed. Further, by abutting the projections 1763g against the two flat surface portions 1773f and 1773e, the play of the fitting is gathered in one direction (the direction along the bisector of the angle formed between the extension line of the flat surfaces 1773e and 1773f as viewed along the rotational axis L1), by which the positional accuracy of the driving side flange 1763 in the direction perpendicular to the rotational axis L1 is improved, and the deterioration of the meshing engagement accuracy with the drive transmission gear 1781 can be suppressed.

[0336] In this embodiment, the projection 1763g is integrally formed with the driving side flange 1763, but the projection 1763g may be formed of another part of metal or the like and press-fitted into the driving side flange 1763.

[0337] Next, positioning of the driving side flange 1763 in the axial direction will be described. As shown in part (a) of FIG. 51 and part (b) of FIG. 51, the first gear portion 1763c of the driving side flange 1763 is provided with a projecting portion 1763c1 slightly projecting in the H direction on the end surface on the downstream side in the H direction, and is provided with a projection 1763f slightly projecting in the J direction is provided on the end surface on the downstream side (upstream side in the H direction) in the J direction. Further, the frame member 1771 includes a rib 1771p and a side wall 1771m provided so as to extend in a direction perpendicular to the rotational axis L1. The projecting portion 1763c1 is in contact with the side surface of the rib 1771p, and the projection 1763f is in contact with the side surface of the side wall 1771m. The driving side flange 1763 is slidably fitted and held between the rib 1771p and the side wall 1771m in the direction of the rotational axis L1. By this, the driving side flange 1763 is positioned on the frame member 1771 in the direction of the rotational axis L1, and as a result, the position of the drum unit 1769 in the frame member 1771 is determined.

<Mounting and Dismounting of Cartridge B Relative to Apparatus Main Assembly a, and Positioning within Apparatus Main Assembly A>

[0338] Part (a) of FIG. 113 is a view of the cartridge B mounted in the apparatus main assembly A installed on the horizontal installation surface, as viewed in the direction (K direction) along the rotational axis L1, and the horizontal direction is HD and the vertical direction is VD. A plane perpendicular to the rotational axis L1 is parallel to the vertical direction VD. Part (b) of FIG. 113 is a view of the cartridge B as viewed along the HD1 direction parallel to the horizontal HD shown in part (a) of FIG. 113. Part (a) of FIG. 114 is a view of the cartridge B as viewed along the VD1 direction parallel to the vertical VD shown in part (a) of FIG. 113. Part (b) of FIG. 114 is a view of the cartridge B as viewed along the VD2 direction parallel to the vertical VD shown in part (a) of FIG. 113. As will be understood from FIG. 50 as viewed along the direction of the rotational axis L1, a straight line connecting the rotation center of the developing roller 1732 and the rotation center of the photosensitive drum 1762 (rotational axis L1) are substantially parallel to the mounting direction M. Therefore, the mounting direction M in the following description can be read as a direction perpendicular to the rotational axis L1 and parallel to the straight line connecting the rotation center of the developing roller 1732 and the rotation center of the photosensitive drum 1762 (rotational axis L1).

[0339] Similar to Embodiment 1, the mounting direction M of the cartridge B to the apparatus main assembly A and the removing direction from the apparatus main assembly A (the direction opposite to the mounting direction M) are directions substantially perpendicular to the rotational axis L1. In addition, the mounting direction of the drum unit 69 to the apparatus main assembly A and the dismounting direction from the apparatus main assembly A are the same as the mounting direction M of the cartridge B to the apparatus main assembly A and the dismounting direction from the apparatus main assembly A, respectively.

[0340] As shown in part (a) of FIG. 113, the drum bearing member 1773 is provided with a guided portion 1773s1, a guided portion 1773s2, and a guided portion 1773s3 in addition to the guided portion 1773g described above. These guided portions are projections having shapes projecting in the direction of the rotational axis L1 from the main assembly portion of the drum bearing member 1773. When the cartridge B is mounted on the apparatus main assembly A and taken out from the apparatus main assembly A, it comes into contact with and guided by a guide portion (not shown) provided on the apparatus main assembly A. As shown in other Figures, the guided portion 1773s1 may be omitted. The guided portion 1773s3 may also be omitted in consideration of necessity. However, it is made more stable to mount and dismount the cartridge B by providing the guided portion 1773s1 and the guided portion 1773s3. In addition, the guided portion 1773s1 is a projection which is long in the mounting direction M (or is long in the direction perpendicular to the rotational axis L1 and parallel to the straight line connecting the rotation center of the developing roller 1732 and the rotation center of the photosensitive drum 1762 (rotational axis L1). By making the guided portion 1773s1 a long projection in this manner, the stiffness of the drum bearing member 1773 is enhanced. Further, although the guided portion 1773s1 and the guided portion 1773g are provided as one connected projection, they may be provided as separate projections. However, the stiffness of the drum bearing member 1773 is enhanced when it is provided as one connected projection.

[0341] In addition, as described above, in the state that the cartridge B is mounted in the apparatus main assembly A, the guided portion 1773g contacts the two positioning portions 1715a of the apparatus main assembly A and the position of the rotational axis L1 of the cartridge B with respect to the apparatus main assembly A is determined in two directions perpendicular to the rotational axis L1 (mounting direction M and the orthogonal direction MP) (see part (c) of FIG. 52 and FIG. 57). Further, by the guided portion 1773s2 being brought into contact with the positioning portion of the apparatus main assembly A (not shown), the position (attitude) of the cartridge B with respect to the apparatus main assembly A is determined in the rotational direction about the rotational axis L1.

[0342] Furthermore, the positioning of the cartridge B with respect to the apparatus main assembly A in the direction of the rotational axis L1 is the same as that of Embodiment 1. Specifically, as shown in part (b) of FIG. 113 and part (a) of FIG. 114, the drum bearing member 1773 has a recess fitted portion 1773h recessed along the mounting direction M, and into the fitted portion 1773h, the projection fitting portion projecting along the mounting direction M (not shown) of the apparatus main assembly A is fitted, so that the position of the cartridge B with respect to the apparatus main assembly A in the direction of the rotational axis L1 is determined.

[0343] Further, as shown in part (a) of FIG. 113, the drum bearing member 1773 is provided with a substantially cylindrical developing unit support portion 1773b extending in the direction of the rotational axis L1. The developing unit support portion 1773b supports a cylindrical portion 1721a which is placed surrounding a development coupling member 1789 and the coupling portion 1789a of the frame 1721 of the developing unit 1720, so as to be rotatable (swingable) around the rotational axis DA. The rotational axis DA is coaxial with the rotational axis of the development coupling member 1789 and parallel to the rotational axis L1. The developing unit 1720 can rotate (swing) about the rotational axis DA in the DS direction relative to the cleaning unit 1760, by receiving a force from a force applying portion (not shown) of the apparatus main assembly A at the force receiving portion 1721b of the frame 1721 of the developing unit 1720. By this rotation, the developing roller 1732 can be spaced from the drum 1762.

[0344] Further, as shown in part (a) of FIG. 113, as the cartridge B is viewed in the direction of the rotational axis L1, the guided portion 1773s2 is disposed on the straight line LT passing through the rotational axis L1 and the rotational axis DA, and in a direction parallel with the line LT, the developing unit support portion 1773b and the rotational axis DA are disposed between the rotational axis L1 and the guided portion 1773s2. Therefore, the cleaning unit 1760 can securedly support the relatively heavy developing unit 1760. Thus, it can be said that the developing unit support portion 1773b and the rotation axis DA are disposed between the rotational axis L1 and the guided portion 1773s2, in any of the mounting direction M (or the longitudinal direction of the guided portion 1773s1), the orthogonal direction MP perpendicular to the mounting direction M (or the direction perpendicular to the longitudinal direction of the guided portion 1773s1), the horizontal direction HD, and the vertical direction VD.

[0345] Further, when the region are divided into two regions by a straight line LT, as the cartridge B is viewed in the direction of the rotational axis L1, the guided portion 1773s1 is disposed in one region and the guided portion 1773s3 is disposed in the other region, and therefore, the attitude of the cartridge B during mounting and dismounting of the cartridge B is stabilized.

[0346] Further, as shown in part (b) of FIG. 113, part (a) of FIG. 114 and part (b) of FIG. 114, the drum frame of the cleaning unit 1760 includes the above-mentioned drum bearing member (first bearing member) 1773 and the frame member 1711, and in addition, it includes a non-driving side drum bearing member (second bearing member) 1712 mounted to the frame member 1711. In the drum unit 1769, the driving side flange 1763 (first flange member) is rotatably supported by the drum bearing member 1773 as described above. On the other hand, the non-driving side flange (second flange member) 1764 of the drum unit 1769 is rotatably supported by the non-driving side drum bearing member 1712. The non-driving side flange 1764 is a member fixed to the downstream end portion of the drum 1762 in the H direction. That is, the drum bearing member (first bearing member) 1773 is placed at the first end of the frame in the direction of the rotational axis L1 of the drum frame, and the non-driving side drum bearing member (secondly bearing member) 1712 is placed at the second end opposite to the first end. Of the two ends of the drum 62 in the direction of the rotational axis L1, the first end of the photosensitive member is an end located closer to the first end of the frame than the second end of the frame, and the second end of the photosensitive member on the opposite side of the first end is an end located at a position closer to the second end of the frame than the first end of the frame. As will be understood from part (a) of FIGS. 114 and 114 (b) a non-driving side drum bearing member 1712 includes a projecting shape portion 1712a having a shape projecting downstream in the mounting direction M. Here, as will be understood from FIG. 50, as viewed along the direction of the rotational axis L1, a straight line connecting the rotation center of the developing roller 1732 and the rotation center of the photosensitive drum 1762 (rotational axis L1) is parallel with the mounting direction M. Therefore, the projecting shape portion 1712a has a shape projected toward the downstream of the drum bearing member 1773 or the drum 1762, with respect to a direction which is perpendicular to the rotational axis L1 and which is directed from the rotation center of the developing roller 1732 toward the rotation center of the photosensitive drum 1762 (direction substantially parallel to the mounting direction M). A memory board 1740 on which a non-volatile memory chip is mounted is mounted to the projecting shape portion 1712a. The memory board 1740 is provided with an electrode portion (electrode surface) 1740a which is a surface that is electrically connected with the non-volatile memory chip and is electrically connectable by contacting an electrode portion on the main assembly side (not shown) of the apparatus main assembly A. With respect to the direction of the rotational axis L1, the electrode portion 1740a is provided at a position close to the end portion (the end portion of the second frame) on the side (non-driving side) opposite to the end portion (first frame end portion) on the side (driving side) where the drum bearing member 1773 and the driving side flange 1763 are provided. Specifically, with respect to the direction of the rotational axis L1, the region where the electrode portion 1740a is provided is a region including a position of the end portion (second end portion of the photosensitive member) on the downstream side in the H direction of the drum 1762. However, with respect to the direction of the rotational axis L1, the region where the electrode portion 1740a is provided may be located close to the outside the drum frame (or outside of the cartridge B) than the position of the end portion (second end portion of the photosensitive member), on the downstream side in the H direction, of the drum 1762. Further, with respect to the direction of the rotational axis L1, of the region where the electrode portion 1740a is provided and the region where the non-driving side flange 1764 is provided are at least partly at the same position (at least partly overlap). However, with respect to the direction of the rotational axis L1, the region where the electrode portion 1740a is provided is closer to the outside of the drum frame (or the outside of the cartridge B) than the region where the non-driving side flange 1764 is disposed (downstream side position in the H direction). In addition, the electrode portion 1740a is disposed on the downstream side of the rotational axis L1 and the photosensitive drum 1762 with respect to the mounting direction M. Further, the electrode portion 1740 is disposed on the downstream side of the rotational axis L1 or the photosensitive drum 1762 with respect to the direction which is perpendicular to the rotational axis L1 and which is directed from the rotation center of the developing roller 1732 toward the rotation center of the photosensitive drum 1762 (direction substantially parallel to the mounting direction M). Furthermore, the memory board 1740 is supported by the cleaning unit 1760 in an attitude in which the electrode portion (electrode surface) 1740a is oriented perpendicular to the mounting direction M.

<Driving Side Flange 1763>

[0347] Next, referring to part (b) of FIG. 54 and FIG. 60, the driving side flange 1763 will be described. Part (b) of FIG. 54 is a schematic cross-sectional view of the gear portion of the driving side flange 1763. The cross-section is a plane in contact with a meshing pitch circle at the time of meshing with the drive transmission gear 1781. Part (a) of FIG. 60 and part (b) of FIG. 60 are sectional views of the drum unit 1769 in the neighborhood of the driving side flange 1763, taken along a plane including the rotational axis L1.

[0348] The driving side flange 1763 includes a first gear portion (first unit side gear portion, first unit side helical tooth gear portion) 1763c and a second gear portion (second unit side gear portion, second unit side helical tooth gear portion) 1763d as helical tooth gear portions, and they are coaxial with each other. The first gear portion 1763c is disposed on the upstream side in the H direction (downstream side in the J direction) with respect to the second gear portion 1763d. That is, the second gear portion 1763d is disposed between the first gear portion 1763c and the drum 1762 in the direction of the rotational axis L1. The first gear portion 1763c includes a plurality of first helical teeth (teeth, first projections) 1763ct arranged at different positions in the circumferential direction about the rotational axis L1, and the second gear portion 1763d includes a plurality of second helical teeth (teeth, second projections) 1763dt arranged at different positions in the circumferential direction about the rotational axis L1. The first helical tooth 1763ct and the second helical tooth 1763dt both have involute tooth profiles, and are projections projecting in the radial direction with respect to the rotational axis L1. The first gear portion 1763c and the second gear portion 1763d are integrally resin-molded and integrally rotatable, and therefore, it can be said that the first gear portion 1763c and the second gear portion 1763d are integrally rotatable first and second rotatable portions. The first gear portion 1763c meshes with the first main assembly gear portion 1781c of the drive transmission gear 1781, and the second gear portion 1763d meshes with the second main assembly gear portion 1781d of the drive transmission gear 1781.

[0349] The twisting directions of the first gear portion 1763c and the second gear portion 1763d of the driving side flange 1763 is the same, and the tooth surface is twisted so as to go in the K direction as goes in the J direction. The twisting direction of the first gear portion 1763c and the second gear portion 1763d is opposite to the twisting direction of the first main assembly gear portion 1781c and the second main assembly gear portion 1781d of the drive transmission gear 1781. In addition, as in Embodiment 1, the helix angle of the second gear portion 1763d is larger than the helix angle of the first gear portion 1763c. The helix angle of the first gear portion 1763c is the same as the helix angle of the first main assembly gear portion 1781c which will be described hereinafter, and the helix angle of the second gear portion 1763d is the same as the helix angle of the second main assembly gear portion 1781d which will be described hereinafter. Further, the numbers of teeth of the first gear portion 1763c and the second gear portion 1763d of the driving side flange 1763 are the same.

[0350] Further, as shown in part (a) of FIG. 60, the width (tooth width) Wc of the first helical tooth (tooth, first projection) 1763ct measured in the direction of the rotational axis L1 is larger than the width (tooth width) Wd of the second helical tooth (tooth, second projection)1763dt measured in the direction of the rotational axis L1. That is, each of the first gear portion 1763c and the second gear portion 1763d has at least one tooth satisfying the following formula A1, wherein Wc is tooth width of the first helical tooth 1763ct (tooth, first projection) in the direction of the rotational axis L1, and Wd is tooth width of the second helical tooth 1763dt in the direction of the rotational axis L1:Wc>Wd. (Formula A1). While the driving side flange 1763 is being driven by the drive transmission gear 1781 in a balanced state, the driving force FD received by the first gear portion 1763c is larger than the restricting force FB received by the second gear portion 1763d, and therefore, it is preferable to satisfy such a relationship.

[0351] Further, the width (engagement width), in the rotational axis L1, of the portion where the first gear portion 1763c meshes (contacts) with the first main assembly gear portion 1781c and the engagement width of the second helical tooth gear portion 1763c with the second main assembly gear portion 1781d are preferably larger since then the drive transmission accuracy is better. However, if the meshing width is set to be larger than necessary, the widths of the first gear portion 1763c and the second gear portion 1763d in the direction of the rotational axis L1 is large, and the driving side flange 1763, the drum unit 1769, the cartridge B, and eventually the apparatus main assembly A will be upsized. Therefore, the tooth width Wc1 of the first helical tooth (teeth) 1763ct having the widest tooth width in the first gear portion 1763c and the tooth width Wd1 of the second helical tooth (teeth) 1763dt having the widest tooth width in the second gear portion 1763d preferably satisfy preferably satisfies the following Formula A2, further preferably formula A3.
Wd1≤(⅘)·Wc1  (Formula A2)
Wd1≤(¾)·Wc1  (Formula A3).

[0352] Further, from the standpoint of the strength of the second helical tooth (teeth) 1763dt of the second gear portion 1763d, it is preferable that the second helical tooth (teeth) 1763dt has a tooth width of a certain level or more, and the tooth width Wc1 and the tooth width Wd1 satisfy the following formula A4.
Wd1≥( 1/10)·Wc1  (Formula A4).

[0353] Further, the width (length) We of the cylindrical portion 1763e (or the gap g) in the direction of the rotational axis L1 is selected so as to satisfy the formulas B1, B2 and B3 with reference to the widths Wc and Wd, as in Embodiment 1.

[0354] When the tooth width Wc of the first gear portion 1763c is not constant, it is assumed that the tooth width Wc1 of the tooth having the widest tooth width is taken as the tooth width.
We≥Wc/5  (Formula B1)
We≤Wc  (Formula B2)
We≤Wd  (Formula B3).

[0355] In this embodiment, the tooth width of each tooth of the first gear portion 1763c is the same, the tooth width of each tooth of the second gear portion 1763d is also the same, the tooth width Wc is 8.2 mm, and the tooth width Wd is 5.2 mm. The width We is 3.1 mm.

[0356] In addition, as shown in part (b) of FIG. 60, the meshing pitch circle diameters D63c and D63d of the first gear portion 1763c and the second gear portion 1763d in the meshing between the driving side flange 1763 and the drive transmission gear 1781 are substantially the same. Similarly, the meshing pitch circle diameters of the first main assembly gear portion 1781c and the second main assembly gear portion 1781d are substantially the same. By this, the meshing between the first gear portion 1763c and the first main assembly gear portion 1781c and the meshing between the second gear portion 1763d and the second main assembly gear portion 1781d can be appropriate without tooth tip hitting.

[0357] Further, as in Embodiment 1, the addendum circle diameter Dt63c of the first gear portion 1763c and the dedendum circle diameter Db63d of the second gear portion 1763d are substantially the same such that the meshing with the first main assembly gear portion 1781c and the second main assembly gear portion 1781d establishes an proper meshing engagement without tooth top hitting.

[0358] Specifically, it is preferable that the size of the addendum circle diameter Dt63c of the first gear portion 1763c is larger than that of the dedendum circle diameter Db63d of the second gear portion 1763d, or larger than 0.8 times (further preferably 0.9 times) than the addendum circle diameter Dt63d of the second gear portion 1763d. In addition, the size of the addendum circle diameter Dt63c of the first gear portion 1763c is preferably smaller than 1.1 times the addendum circle diameter Dt63d of the second gear portion 1763d.

[0359] Further, it is preferable that the size of the dedendum circle diameter Db63c of the first gear portion 1763c is smaller than that of the addendum circle diameter Dt63d of the second gear portion 1763d. Further, the size of the dedendum circle diameter Db63c of the first gear portion 1763c is preferably larger than that of 0.9 times the dedendum circle diameter Db63d of the second gear portion 1763d.

[0360] Furthermore, the size of the addendum circle diameter Dt63d of the second gear portion 1763d is larger than that of the dedendum circle diameter Db63c of the first gear portion 1763c, or larger than 0.8 times (further preferably 0.9 times) of the addendum circle diameter Dt63c of the first gear portion 1763c. Further, the size of the addendum circle diameter Dt63d of the second gear portion 1763d is preferably smaller than 1.1 times the addendum circle diameter Dt63c of the first gear portion 1763c.

[0361] Further, it is preferable that the size of the dedendum circle diameter Db63d of the second gear portion 1763d is smaller than that of the addendum circle diameter Dt63c of the first gear portion 1763c. Further, the size of the dedendum circle diameter Db63d of the second gear portion 1763d is preferably larger than 0.9 times the dedendum circle diameter Db63c of the first gear portion 1763c.

[0362] In this embodiment, the addendum circle diameter Dt63c, the pitch circle diameter D63c, and the dedendum circle diameter Db63c of the first gear portion 1763c are 22.3 mm, 21.1 mm, and 19.6 mm, respectively. The addendum circle diameter Dt63d, pitch circle diameter D63d, and dedendum circle diameter Db63d of the second gear portion 1763d are 22.1 mm, 21.1 mm, and 19.8 mm, respectively. The diameter of the cylindrical portion 1763e is 17.5 mm

[0363] Further, the modules and/or amounts of addendum modification are made different between the first gear portion 1763c and the second gear portion 1763d such that the meshing pitch circle diameters D63c and D63d are the same while making the helix angles of the first gear portion 1763c and the second gear portion 1763d different from each other. Similarly, as for the drive transmission gear 1781, the modules and/or amounts of addendum modification are made different between the first main assembly gear portion 1781c and the second main assembly gear portion 1781d.

[0364] In addition, the driving side flange 1763 is provided with a cylindrical portion (intermediate portion, small diameter portion, shaft portion) 1763e between the first gear portion 1763c and the second gear portion 63d in the direction of the rotational axis L1. The maximum diameter D63e centered on the rotational axis L1 of the cylindrical portion 1763e is smaller than the addendum circle diameter Dt63c of the first gear portion 1763c and the addendum circle diameter Dt63d of the second gear portion 1763d. Further, in this embodiment, the maximum diameter D63e centered on the rotational axis L1 of the cylindrical portion 1763e is smaller than the dedendum circle diameter Db63c of the first gear portion 1763c and the dedendum circle diameter Db63d of the second gear portion 1763d. However, the maximum diameter D63e centered on the rotational axis L1 of the cylindrical portion 1763e is not limited to such a condition if there is no contact with the drive transmission gear 1781 while the driving side flange 1763 is being driven by the drive transmission gear 1781. As will be described hereinafter in Embodiments 22 and 23, the structure may be such that a distance (radius) R63e from the rotational axis L1 to the outer diameter of the cylindrical portion 1763e is at least temporarily smaller than the addendum circle radius Rt63ct of the first gear portion 1763c or the addendum circle radius Rt63d of the second gear portion 1763d so that the driving side flange 1763 and the drive transmission gear 1781 are engaged with each other to transmit the drive force.

[0365] It is self-evident that the portions showing the relationship between these dimensions using various diameters of the first gear portion 1763c, the second gear portion 1763d, and the cylindrical portion 1763e apply also when the diameter is replaced with a radius.

<Drive Transmission Gear 1781>

[0366] Next, referring to FIG. 53 and part (a) of FIG. 54, the drive transmission gear 1781 of the apparatus main assembly A which meshes with the driving side flange 1763 will be described. Part (a) of FIG. 53 and part (b) of FIG. 53 are exploded perspective views of the peripheral portion of the drive transmission gear 1781 of the apparatus main assembly A, in which part (a) is a view as seen from the second driving side plate 1783 side, and part (b) is a view as seen from the main frame 1784 side. Part (a) of FIG. 54 is a schematic sectional view of the gear portion of the drive transmission gear 1781. The sectional plane is in contact with the meshing pitch circle at the time of meshing with the driving side flange 1763.

[0367] The drive transmission gear 1781 coaxially includes a first main assembly gear portion (first main assembly helical tooth gear portion) 1781c and a second main assembly gear portion (second main assembly helical tooth gear portion) 1781d as helical tooth gear portions. The first main assembly gear portion 1781c is arranged on the upstream side in the H direction (downstream side in the J direction) with respect to the second main assembly gear portion 1781d. The first main assembly gear portion 1781c includes a plurality of first main assembly helical teeth 1781ct, and the second main assembly gear portion 1781d includes a plurality of second main assembly helical teeth 1781dt. The first main assembly helical tooth 1781ct and the second main assembly helical tooth 1781dt have both involute tooth profiles. The first main assembly gear portion 1781c and the second main assembly gear portion 1781d are integrally resin-molded and integrally rotatable. In addition, the twisting directions of the first main assembly gear portion 81c and the second main assembly gear portion 81d are the same, and the tooth surface is twisted so as to be displaced in the I direction as goes in the J direction. Further, similarly to Embodiment 1, the helix angle of the second main assembly gear portion 1781d is larger than the helix angle of the first main assembly gear portion 1781c. Furthermore, the number of teeth of the first main assembly gear portion 81c and the second main assembly gear portion 81d are the same. In the state that the cartridge B is mounted on the apparatus main assembly A, the first gear portion 1763c meshes with the first main assembly gear portion 1781c, and the second gear portion 1763d meshes with the second main assembly gear portion 1781d.

[0368] FIG. 112 is a perspective view of another structure example of the drive transmission gear 1781. As shown in FIG. 112, a rib-shaped portion (projecting portion, radial projection main portion) 1781p projecting in the radial direction with respect to the rotational axis L2 may be provided between the first main assembly gear portion 1781c and the second main assembly gear portion 1781d in the direction of the rotational axis L2. Depending on the manufacturing method of the drive transmission gear 1781, it may be possible to improve the molding accuracy, suppress the deterioration, or reduce the manufacturing cost, by providing the rib-shaped portion 1781p. The diameter of the rib-shaped portion 1781p is about the same as the diameter of the addendum circle of the first main assembly gear portion 1781c and the diameter of the addendum circle of the second main assembly gear portion 1781d. The rib-shaped portion 1781p may be provided over the entire circumference or may be provided only partially in the circumferential direction centered on the rotational axis L2. Here, by providing the driving side flange 1763 with the cylindrical portion 1763e, a gap g is formed between the first gear portion 1763c and the second gear portion 1763d in the direction of the rotational axis L1 (see FIG. 60 and so on). Because of the provision of this gap g, even when the drive transmission gear 1781 has the rib-shaped portion 1781p, the rib-shaped portion 1781p and the driving side flange 1763 are prevented from coming into contact with each other, and the drive transmission gear 1781 and the gear portions of the driving side flange 1763 can be properly meshed with each other. At this time, the rib-shaped portion 1781p is inserted (entered) into the gap g between the first gear portion 1763c and the second gear portion 1763d.

[0369] As shown in part (a) of FIG. 53 and part (b) of FIG. 53, the apparatus main assembly A comprises a motor (not shown), an idler gear 1780, a drive transmission gear 1781, a second driving side plate 1783, a main frame 1784, a driving shaft 1782, a reinforcing member 1798 and a compression spring 1785. The second driving side plate 1783 is a member corresponding to the second driving side plate 83 of Embodiment 1. The driving force from the motor is transmitted to the drive transmission gear 1781 by way of the idler gear 1780. The idler gear 1780, the drive transmission gear 1781, and the reinforcing member 1798 are supported by the driving shaft 1782 which is a fixed shaft, so as to be rotatable coaxially with the rotational axis L2 as the rotational axis and movable in the direction of the rotational axis L2. One end of the driving shaft 1782 is fixed to the second driving side plate 1783, and the other end 1782b is fitted in and supported by a hole 1784a of the main frame 1784. The driving shaft 1782 is provided so that the rotational axis L2 of the drive transmission gear 1781 is parallel to the rotational axis L1 of the drum 62 in a state where the cartridge B is mounted on the apparatus main assembly A.

[0370] A compression spring 1785 is provided between the other end 1780b of the idler gear 1780 and the second driving side plate 1783, and the idler gear 1780 is urged (H direction) toward the main frame 1784 with respect to the direction of the rotational axis L2. A recess portion 1780a recessed in the direction of the rotational axis L2 is provided at the end of the idler gear 1780 opposing the drive transmission gear 1781, and a projection (driving force transmission portion) 1780a1 is provided inside the recess portion 1780a.

[0371] At the end of the drive transmission gear 1781 opposing the idler gear 1780, a projection 1781a1 projecting in the direction of the rotational axis L2 is provided at a position opposing the recess 1780a1 of the idler gear 1780. The projection 1781a1 has a surface 1781e at the upstream end and a slope 1781h at the downstream end, in the rotational direction I. The surface 1781e is perpendicular to the plane perpendicular to the rotational axis L2, and the slope 1781h is inclined with respect to the plane perpendicular to the rotational axis L2. By engaging the projection 1780a1 of the idler gear 1780 and the surface 1781e of the projection 1781a1 with each other, the driving force is transmitted from the idler gear 1780 to the drive transmission gear 1781, so that they rotate integrally in the rotational direction I.

[0372] On the other hand, when the drive transmission gear 1781 rotates relative to the idler gear 1780 in the rotational direction I, the slope 1781h of the projection 1781a1 of the drive transmission gear 1781 is brought into contact with the projection 1780a1 of the idler gear 1780. By this, a force acts tending to separate the idler gear 1780 from the drive transmission gear 1781 in the rotational axis L2 direction, and the idler gear 1780 moves in the J direction against the spring force of the compression spring 1785, and the projection 1780a1 rides over the projection 1781a1, and therefore, the structure is such that the driving force in the rotational direction I is not transmitted from the drive transmission gear 1781 to the idler gear 1780. In the process of mounting the cartridge B inn the apparatus main assembly A, the drive transmission gear 1781 may be rotated in the rotational direction I by engagement with the driving side flange 1763, but on such occasion, the driving force in the rotational direction I is not transmitted to the idler gear 1780 from the drive transmission gear 1781 due to the above-described structure. Therefore, when the user mounts the cartridge B, it is not necessary to rotate the motor for driving the idler gear 1780 or the photosensitive drum 1762, so that the load required when mounting the cartridge B in the apparatus main assembly A can be reduced.

[0373] Further, the drive transmission gear 1781 is provided with a hole 1781f, and an engaging portion 1781g having a shape of a plurality of recesses and projections is provided on the inner peripheral portion thereof. The reinforcing member 1798 is provided with an engaging portion 1798b having a shape of a plurality of recesses and projections on an outer peripheral portion thereof, and is inserted into the hole 1781f. The engaging portion 1781g of the drive transmission gear 1781 and the engaging portion 1798b of the reinforcing member 1798 are in meshing engagement with each other. The reinforcing member 1798 contacts the driving shaft 1782 and is directly supported by the driving shaft 1782, and the drive transmission gear 1781 is indirectly supported by the driving shaft 1782 by way of the reinforcing member 1798. However, the drive transmission gear 1781 may be structured to be directly supported by the driving shaft 1782.

[0374] However, in the case of manufacturing the drive transmission gear 1781 having a relatively large diameter by resin molding as in this embodiment, it is preferable that the drive transmission gear 1781 is supported by the driving shaft 1782 by way of the reinforcing member 1798, because it is advantageous from the standpoint of both molding accuracy and strength. This is because when a gear having a relatively large radial wall thickness (radial distance from the inner peripheral surface of the hole through which the shaft passes to the dedendum circle of the gear) is produced in one resin molded member, it is necessary to provide a lightening shape in order to avoid deterioration of gear molding accuracy due to the resin sink marks and so on. When the lightening shape is provided, the strength of the gear may decrease. Therefore, in this embodiment, without the drive transmission gear 1781 being directly supported by the driving shaft 1782, a separate resin-molded reinforcing member 1798 is provided to provide a resin-molded drive transmission gear 1781, by which while suppressing the deterioration of the molding accuracy of the above, it is possible to suppress the decrease in strength.

<Drive Transmission Operation>

[0375] Next, referring to FIGS. 54 and 55, the meshing operation between the drive transmission gear 1781 and the driving side flange 1763 will be described. Part (c) of FIG. 54, part (d) of FIG. 54, part (a) of FIG. 55, part (b) of FIG. 55 and part (c) of FIG. 55 are schematic sectional views in the meshing engagement portion between the gear portion of the drive transmission gear 1781 and the gear portion of the driving side drum flange 1763. The sectional plane is in contact with the meshing pitch circle between the drive transmission gear 1781 and the driving side flange 1763. Part (c) of FIG. 54, part (d) of FIG. 54, part (a) of FIG. 55, part (b) of FIG. 55, and part (c) of FIG. 55 all show states after the drive transmission gear 1781 is started, with elapse of time.

[0376] First, in a state where the cartridge B is not mounted to the main assembly A, the drive transmission gear 1781 is urged in the H direction by the compression spring 1785 and abuts against the main frame 1784 as shown in part (a) of FIG. 54.

<Operation after Starting Drive>

[0377] After the cartridge B is mounted in the main assembly A, the drive transmission gear 1781 is driven by a motor (not shown) of the apparatus main assembly A by way of the idler gear 1780 (see FIG. 53) to rotate in the I direction. The driving side flange 1763 receives a driving force from the drive transmission gear 1781 that rotates in the I direction and rotates in the K direction.

[0378] The case will be described in which the force FD is first transmitted through the meshing engagement between the second main assembly gear portion 1781d of the drive transmission gear 1781 and the second gear portion 1763d of the driving side flange 1763, immediately after the start of rotation of the drive transmission gear 1781 in the I direction, as shown in part (c) of FIG. 54. The second main assembly gear portion 1781d produces a thrust force which pushes the second gear portion 1763d in the H direction. However, the driving side flange 1763 is constrained from moving in the H direction by the rib 1771p (see part (a) of FIG. 51), and receives a reaction force in the J direction corresponding to the thrust force in the H direction. Therefore, the second main assembly gear portion 1781d receives a thrust force F5 in the J direction due to the action of the reaction force received from the second gear portion 1763d. This thrust force F5 moves the drive transmission gear 1781 in the J direction.

[0379] When the drive transmission gear 1781 moves in the J direction while with further rotation continued, as shown in part (d) of FIG. 54, the first gear portion 1763c is also brought into meshing engagement with the first main assembly gear portion 1781c to transmit the drive force FD, and at the same time, a thrust force F6 is generated in the first main assembly gear portion 1781c. The thrust force F6 is the same thrust force in the J direction as the thrust force F5 previously received by the second main assembly gear portion 1781d by meshing with the second gear portion 1763d. By this, the drive transmission gear 1781 further moves in the J direction.

[0380] When the drive transmission gear 1781 further rotates and moves in the J direction, the second main assembly gear portion 1781d becomes out of meshing engagement with the second gear portion 1763d, as shown in part (a) of FIG. 55. On the other hand, the meshing engagement between the first gear portion 1781c and the first gear portion 1763c is maintained, and the first gear portion 1781c receives the thrust force F8 in the J direction. At this time, the drive transmission gear 81 transmits the drive force FD only by the engagement between the first main assembly gear portion 1781c and the first gear portion 1763c, to rotate the driving side flange 1763.

[0381] When the drive transmission gear 1781 further rotates and moves in the J direction, the second main assembly gear portion 1781d finally brought into contact with the downstream side (in I direction) of the tooth surface (contact portion) 1763d2 of the second gear portion 1763d as shown in part (b) of FIG. 55 and part (c) of FIG. 55. The surface 1781c1 of the first main assembly gear portion 1781c and the surface 1763c1 of the first gear portion 1763c maintain in contact with each other. That is, the teeth of the first gear portion 1763c contacts the first main assembly gear portion 1781c disposed on the upstream side in the I direction, and the teeth of the second gear portion 1763d contacts the second main assembly gear portion 1781d disposed on the downstream side in the I direction. In addition, the first gear portion 1763c and the second gear portion 1763d are integrally molded with resin, and therefore, the teeth of the first gear portion 1763c are fixed so as not to move (rotate) in the I direction relative to the teeth of the second gear portion 1763d, and the teeth of the second gear portion 1763d are fixed so as not to move (rotate) in the I direction relative to the teeth of the first gear portion 1763c. Therefore, in this state, the first main assembly gear portion 1781c of the drive transmission gear 1781 presses the tooth surface (contact portion) 1763c1 on the tooth surface 1781c1 to rotate the driving side flange 1763, and the tooth surface 1781d2 of the second main assembly gear portion 1781d of the drive transmission gear 1781 contacts with the tooth surface 1763d2, it is sandwiched by the driving side flange 1763. Then, the movement of the drive transmission gear 1781 in the direction of the rotational axis L1 stops. The position of the drive transmission gear 1781 at this time in the direction of the rotational axis L1 is a balanced position.

[0382] In the balanced state, as shown in part (b) of FIG. 55, a force F9, a force F10, and a force F1 are applied to the drive transmission gear 1781 with respect to the direction of the rotational axis L1. The force F9 is a thrust force in the J direction received by the first main assembly gear portion 1781c by the meshing engagement force with the first gear portion 1763c, the force F10 is a thrust force in the H direction received by the second main assembly gear portion 1781d by the meshing engagement force with the second gear portion 6173d, and the force F1 is an urging forces of the compression spring 1785 received by way of the idler gear 1780. In addition, the driving side flange 1763 receives a force from the drive transmission gear 1781, to abut to the rib 1771p or the side wall 1771m, so that it, is positioned with respect to the direction of the rotational axis L1, and a reaction force F11 is produced, in the direction of the rotational axis L1, which balances with the thrust force received from the drive transmission gear 1781. Part (b) of FIG. 55 shows a case where the driving side flange 1763 is positioned in contact with the rib 1771p. In the balanced state, with respect to the direction of the rotational axis L1, if frictions are ignored, the force F9, the force F10, the force F1, and the force F11 are balanced, so that the drive transmission gear 1781 and the driving side flange 1763 are in a state of being positioned in the direction of the rotational axis L1.

[0383] Further, as shown in part (c) of FIG. 55, in the balanced state, the driving side flange 1763 is sandwiched (contacted) between the first main assembly gear portion 1781c and the second main assembly gear portion 1781d of the drive transmission gear 1781 in the K direction (rotational direction), so that it is in a state of receiving the following forces. That is, the tooth surface (contact portion) 1763c1 of the first gear portion 1763c contacts the first main assembly gear portion 1781c disposed on the upstream side in the K direction (first circumferential direction), by which it receives the driving force FD as the force having a component in the direction of rotating the driving side flange 1763 in the K direction (predetermined direction). At the same time, the tooth surface (contact portion) 1763d2 of the second gear portion 1763d contacts the second main assembly gear portion 1781d disposed on the downstream side in the K direction (first circumferential direction), by which it receives the restricting force (braking force) FB as the force having a component in the direction which suppresses (restricts) the rotation of the driving side flange 1763 in the K direction. Therefore, it can be said that the first gear portion 1763c is a driving force receiving portion which receives the driving force 1-D, and the second gear portion 1763d is a restricting force receiving portion which receives the restricting force FB. Part (b) of FIG. 55 shows the reaction force FF of the driving force FD received by the first main assembly gear portion 1781c and the reaction force FE of the restricting force FB received by the second main assembly gear portion 1781d.

[0384] Further, when the first main assembly gear portion 1781c of the drive transmission gear 1781 first meshes with the first gear portion 1763c of the driving side flange 1763 and transmits the driving force FD immediately after the start of rotation of the drive transmission gear 1781 in the I direction, the state shown in part (d) of FIG. 54 or part (a) of FIG. 55 results. Thereafter, the drive transmission gear 1781 moves in the J direction toward the driving side while transmitting the drive force FD to the first gear portion 1763c in the same manner as described above, and the state changes to the balanced state shown in part (b) of FIG. 55 and part (c) of FIG. 55.

[0385] As described above, also in this embodiment, the state in which the first gear portion 1763c receives the driving force FD and the second gear portion 1763d receives the restricting force FB is a backlashless state of no backlash (backlash) in the direction (I direction) between the driving side flange 1763 and the drive transmission gear 1781. In this manner, the driving side flange 1763 is rotationally driven in the K direction while maintaining the backlashless state. While the drive is transmitted by engaging with each other in the backlashless state, the drive transmission with high rotation accuracy is possible.

[0386] Further, with respect to the direction of the rotational axis L1, the first gear portion 1763c is arranged at a position closer to the projection 1763g which is a supported portion supported by the surface 1773e and the surface 1773f than the second gear portion 1763d. In the driving side flange 1763, a larger force applied to the tooth surface of the first gear portion 1763c which receives the driving force FD than that of the second gear portion 1763d which receives the restricting force FB. Therefore, the driving force FD acts to cause the rotational axis L1 of the drum unit 1769 to tilt, and the drum 1762 may be tilted with respect to the ideal rotational axis L1. However, as in this embodiment, by arranging the first gear portion 1763c which receives the driving force FD at a position closer to the projection 1763g which is the supported portion than the second gear portion 1763d, it is possible to suppress the tilting of the rotational axis L1 of the drum unit 1769 attributable to the driving force FD is received.

<Drive Transmission Structure Developing Roller 1732>

[0387] Further, the driving force transmission structure to the developing roller 1732 in this embodiment is similar to that described in other Modified Examples of Embodiment 1 to transmit the driving force referring to FIG. 44, which engages with the coupling member of the apparatus main assembly A so that the driving force is transmitted to the developing roller 532 by way of the input development coupling member 89.

[0388] Referring to FIGS. 56 and 57 the specific structure will be described. Part (a) of FIG. 56 is a perspective view of a drive train which drives the developing roller 1732 of the developing unit 1720. Part (b) of FIG. 56 is a partial perspective view of the developing unit 1720 in the neighborhood of the coupling member 1789. Part (c) of FIG. 56 is a perspective view of the cartridge B. FIG. 57 is a partial perspective view of the apparatus main assembly A in the neighborhood of the main assembly side coupling member 1799.

[0389] The developing unit 1720 includes a development coupling member 1789 having a coupling portion 1789a and a gear portion 1789b, an idler gear 1790 which meshes with the gear portion 1789b, an idler gear 1791 which meshes with the idler gear 1790, and the developing roller gear 1730 which is fixed to one end of the shaft portion of the developing roller 1732 and meshes with the idler gear 1791, wherein they constitute a developing drive train for driving the developing roller 1732.

[0390] In the apparatus main assembly A, a main assembly side coupling member 1799 driven by a motor (not shown) is supported by a first driving side plate 1715. The main assembly side coupling member 1799 is provided so as to be movable in the direction of the rotational axis. The driving force is transmitted from the main assembly side coupling member 1799 to the development coupling member 1789 by integrally rotating the coupling portion 1789a of the main assembly side coupling member 1799 and the development coupling member 1789 in an engaged state. Then, the driving force is transmitted from the development coupling member 1789 to the developing roller 1732 in the order of the idler gears 1790, 1791, and the developing roller gear 1730.

[0391] Further, the developing unit 1720 is provided with a toner moving member (stirring member) (not shown) which stirs or conveys the toner in the toner accommodating container, and the driving force received by the development coupling member 1789 is transmitted, by way of another gear, to the toner moving member to drive the toner moving member.

[0392] The member driven by the driving force from the development coupling member 89 is not limited to the above-mentioned developing roller 1732 and the toner moving member (not shown), but it may be some member other than the drum unit 1769 included in the cartridge B (for example, a charging member, a seal member, a cleaning member, and so on). Therefore, the member to which the driving force is transmitted from the development coupling member 1789 (the member connected to the development coupling member 1789 so as to be able to transmit the driving force) is not limited to the developing roller 1732.

[0393] As described above, the apparatus main assembly A is provided with two systems of driving force output means, that is, the drive transmission gear 1781 and the main assembly side coupling member 1799 as the driving force output means to the cartridge B. By this, it possible to perform control such as drive-stopping one of the drive transmission gear 1781 and the main assembly side coupling member 1799 while driving the other. As a specific example, it is possible to control such that the developing roller 1732 is driven while the drum 1762 is stopped.

[0394] In addition, in the cartridge B, the driving side flange 1763 is not included in the development drive train for driving the developing roller 1732 or the member connected to the development coupling member 1789 so as to transmit the driving force. Therefore, even if the user rotates the drum 1762 in the state in which the cartridge B has been removed from the apparatus main assembly A, the member connected, for drive transmission, to the developing roller 1732 or the development coupling member 1789 is prevented from rotating in accordance with the rotation of is the drum 1762. Therefore, it is possible to reduce the possibility that the developing roller 1732 or the development coupling member 1789 and the member connected so as to be able to transmit the driving force are unnecessarily driven to cause toner leakage or the like.

[0395] As described above, in this embodiment, the developing roller 1732 is driven by the driving force inputted to the development coupling member 1789, but the driving force may be transmitted from the driving side flange 1763 to the developing roller gear 1730 as in Embodiment 1 to drive the developing roller 1732.

[0396] As described above, according to this embodiment, the same effect as that of the first embodiment can be provided. Further, the elements of each of the above-described embodiments can be applied to the structure of this embodiment. In particular, the structures of the first helical tooth (first projection) 1763ct of the first gear portion 1763c of the driving side flange 1763 and the second helical tooth (second projection) 1763dt of the second gear portion 1763d may be modified to Use the helical teeth, spur teeth, projections and the like shown in embodiment 2, 3, 4, 5, 6, 10, 11, 12, 13, 14, or 16.

[0397] This embodiment is different from embodiment 17 in that a ring-shaped elastic member is provided so as to cover the driving side flange 1763. The other points are the same as in Embodiment 17, and detailed description thereof will be omitted. In addition, among the elements in this embodiment, the elements corresponding to the elements of Embodiment 1 are assigned the reference numerals associated with the corresponding elements of Embodiment 1. Regarding these elements, the matters not specifically explained are the same as the corresponding elements of Embodiment 1.

[0398] FIG. 61 is a partial perspective view of the drum unit 1869 in the neighborhood of the driving side flange 1863. FIG. 62 is a cross-sectional view of the second gear portion 1863d and the second main assembly gear portion 1881d, and the cross-sectional plane thereof is perpendicular to the rotational axis L1.

[0399] The driving side flange 1863 has the same shape as the driving side flange 1763 of embodiment 17. In this embodiment, the elastic ring 1801, which is the ring-shaped elastic member which can be elastically deformed, is provided so as to cover the entire outer or a part of the outer circumference of the second gear portion (second unit side gear portion) 1863d.

[0400] The elastic ring 1801 is a thin film rubber or sponge, and the thickness is preferably about 0.01 to 1 mm for rubber such as nitrile rubber and about 1 to 6 mm for sponge. Further, it is desirable that the inner diameter of the elastic ring before being mounted to the driving side flange 1863 is about 0.5 to 0.9 times the outer diameter of the second gear portion 1863d. In this embodiment, the outer diameter of the second gear portion 1863d is Φ20 mm, and an inner diameter of the elastic ring 1801 is Φ14 mm. When the outer diameter of the second gear portion 1863d is Φ20 mm, it is desirable that the inner diameter of the elastic ring 1801 is appropriately selected in the range of Φ10 mm to 18 mm, which is slightly smaller than Φ20 mm. If it is larger than Φ18 mm, it may disengage from the second gear portion 1863d, and if it is smaller than Φ10 mm, the force tightening the second gear portion 1863d is so strong that the second gear portion 1863d may be deformed.

[0401] As shown in FIG. 62, when the cartridge B is mounted to the apparatus main assembly A, the elastic ring 1801 is elastically deformed so as to follow the shapes of the second helical tooth 1863dt of the second gear portion 1863d and the second helical tooth 1781dt of the drive transmission gear 81, so that the second gear portion 1863d and the second main assembly gear portion 1781d are in meshing engagement with each other by way of the elastic ring 1801. Further, the first gear portion (first unit side gear portion) 1863c meshes with the first main assembly gear portion 1781c.

[0402] When the drive transmission gear 1781 rotates in the direction of the arrow I, a force is transmitted to the second gear portion 1863d from the second main assembly gear portion 1781d by way of the elastic ring 1801. Therefore, the second gear portion 1863d provides the same function as the second gear portion 1763d of embodiment 17. That is, when the drive transmission gear 1781 rotates in the arrow I direction, there is no backlash (backlash) in the rotational direction (I direction) between the driving side flange 1863 and the drive transmission gear 1781, that is, the backlashless state results, as in the case of embodiment 17.

[0403] The elastic ring 1801 may be provided, at an inner peripheral portion of the driving side flange 1863, with a plurality of projections projecting in the direction toward the rotational axis L1 to fill the plurality of gaps 1863ds of the plurality of second helical teeth 1863dt of the second gear portion 1863d in a state in which the cartridge B is not in contact with the drive transmission gear 1781 such as before mounting the cartridge B to the apparatus main assembly A.

[0404] Further, in this embodiment, the elastic ring 1801 is provided on the outer periphery of the second gear portion 1863d, but the elastic ring 1801 may be provided on the entire or a part of the outer circumference of the first gear portion 1863c, or on the entire or parts of the outer circumferences of both of the second gear portion 1863d and the first gear portion 1863c. Also in these cases, the force is transmitted between the tooth surfaces of the respective gears by way of the elastic ring 1801. Therefore, the first gear portion 1863c and the second gear portion 1863d provide the same functions as the first gear portion 1763c and the second gear portion 1763d of the embodiment 17. In other words, when the drive transmission gear 1781 rotates in the arrow I direction, there is no backlash (backlash) in the rotational direction (I direction) between the driving side flange 1863 and the drive transmission gear 1781, that is, a backlash-less state results.

[0405] Further, the driving side flange 1863 has the same shape as the driving side flange 1763 of embodiment 17, but the addendum shape of the gear and the size of the gear may be appropriately changed in consideration of the thickness of the elastic ring 1801 and the like.

[0406] As described above, according to this embodiment, the same effect as that of embodiment 17 can be obtained. Further, the elements of each of the above-described embodiments can be applied to the structure of this embodiment. In particular, the structures of the first helical tooth (first projection) 1863ct of the first gear portion 1863c of the driving side flange 1863 and the second helical tooth (second projection) 1863dt of the second gear portion 1863d may be modified to use the helical teeth, the spur teeth, the projections and the like of Embodiment 2, 3, 4, 5, 6, 10, 11, 12, 13, 14, or 16.

[0407] In this embodiment, as compared with Embodiment 17, the difference is that the rotational axis (L19, and so on) of the first gear portion (external tooth gear portion 1902b, and so on) which receives the driving force FD and the rotational axis (L1) of the second gear portion (1963d) which receives the regulatory force FB are not coaxial but parallel. The other points are the same as in the embodiment 17, and the detailed description thereof will be omitted. In addition, among the elements in this embodiment, the elements corresponding to the elements of Embodiment 1 are assigned the reference numerals associated with the corresponding elements of Embodiment 1. Regarding these elements, the matters not specifically explained are the same as the corresponding elements of Embodiment 1.

<Drum Unit 1969>

[0408] FIG. 63 is a partial perspective view of the drum unit 1969. As shown in FIG. 63, the driving side flange 1963 of the drum unit 1969 includes an internal gear portion 1963f, a second gear portion 1963d, a projection 1963g, a small diameter portion 1963e, and a flange portion 1963h with the drum rotational axis L1 as the center. The internal gear portion 1963f is a spur tooth gear. The drum unit 1969 further includes a gear 1902, which will be described in detail hereinafter (FIG. 65 and the like). The gear 1902 includes an external tooth gear portion 1902b as a first gear portion and an internal tooth gear portion 1902a which meshes with the internal gear portion 1963f.

[0409] The projection 1963g has a generally cylindrical shape, and is provided so as to project from the internal gear portion 1963f in the direction opposite to the drum 1962 side (downstream side with respect to the J direction) along the drum rotational axis L1. The small diameter portion (cylindrical portion) 1963e has a generally cylindrical shape, and is provided so as to project beyond the internal gear portion 1963f toward the drum side (downstream side in the H direction) 1962 along the drum rotational axis L1. The second gear portion 1963d is an helical tooth having a helix angle α2 as in embodiment 17, and is provided on the drum 1962 side (downstream side in the H direction) of the small diameter portion 1963e. The flange portion 1963h has a thin disk shape having a diameter equal to or larger than the diameter of the drum 1962, and is provided on the drum 1962 side (downstream side in the H direction) of the second gear portion 1963d.

<Support Structure for Drum Unit 1969>

[0410] Next, referring to FIGS. 64, 65, 66, and 67, the structure for supporting the drum unit 1969 will be described.

[0411] FIG. 64 is a side view (viewed in a direction perpendicular to the rotational axis L1) of the cleaning unit 1960 to which the drum unit 1969 is mounted. FIG. 65 is an exploded perspective view of a driving side portion of the cleaning unit 1960. FIG. 66 is a partial sectional view of the cleaning unit 1960 in the neighborhood of the driving side flange 1963, and the sectional plane thereof includes the rotational axis L1. FIG. 67 is a partial cross-sectional view of the cleaning unit 1960, which is a cross-section, as viewed along the J direction, of perpendicular to the rotational axis L1 and passing through the internal gear portion 1963f.

[0412] As shown in FIG. 64, the cleaning frame 1960a of the cleaning unit 1960 supports the drum unit 1969. The cleaning frame 1960a of the cleaning unit 1960 comprises a frame member 1971 and a drum bearing member 1973. The cleaning frame 1971 is provided with a drum sliding portion 1971g.

[0413] The driving side flange 1963 is rotatably supported by the drum bearing member 1973 in the same manner as in embodiment 17. Similarly to that described in Embodiment 17, when the drive transmission gear 1781 rotates in a predetermined direction after the driving side flange 1963 of the drum unit 1969 engages with the drive transmission gear 1781, the driving side flange 1963 rotates in interrelation with the drive transmission gear 1781, and as described above, and a thrust force in the H direction is produced in the drum unit 1969. By this thrust force, the non-driving side flange 1964 and the drum sliding portion 1971g are brought into contact with each other, and the movement of the drum unit 1969 in the H direction is restricted.

[0414] As shown in FIG. 65, the bearing member 1973 is supported by the frame member 1971. In the frame member 1971, a cylindrical portion 19710b, which is a positioning portion relative to the bearing member 1973, is provided so as to project toward the drum unit 1969 side. In the bearing member 1973, a cylindrical portion 19730r, which is a positioning portion relative to the frame member 1971, is provided so as to project toward the drum unit 1969 side.

[0415] The inner peripheral surface 19710d of the cylindrical portion 19710b is formed in an arc shape, and is provided at such a position that the center of the arc is on the drum rotational axis L1. In addition, the outer peripheral surface 19730b of the cylindrical portion 19730r is formed in an arc shape, and is provided at such a position that the center of the arc is on the drum rotational axis L1. On the other hand, the outer peripheral surface 19710c of the cylindrical portion 19710b is formed in the shape of an arc surface, but the central axis L19 of the arc surface (coaxial with the rotational axis L19 of the gear 1902) is provided, in parallelism with but not coaxial with the drum rotational axis L1. In other words, the outer peripheral surface 19710c of the cylindrical portion 19710b is provided at a position eccentric with respect to the inner peripheral surface 19710d.

[0416] The outer peripheral surface 19710c of the cylindrical portion 19710b rotatably supports the gear 1902 about the rotational axis L19. The gear 1902 has a generally cylindrical shape and includes, coaxially with the rotational axis L19 of the cylinder, the internal tooth gear portion 1902a on the inner peripheral side, and the external tooth gear portion 1902b as the first gear portion (first unit side gear portion) on the outer peripheral side. The internal tooth gear portion 1902a is a flat tooth, and the external tooth gear portion 1902b is an helical tooth having a helix angle α1, and has the same the number of teeth as that of the second gear portion (second unit side gear portion) 1963d of the driving side flange 1963. In addition, a support portion 1902c is provided on one end side of the gear 1902, and a cylindrical portion 1902d is provided on the other end side. The support portion 1902c has a generally cylindrical shape, and is provided along the rotational axis L19 so as to project beyond the external tooth gear portion 1902b and the internal tooth gear portion 1902a in the direction away from the drum 1962 (downstream side in the J direction). The cylindrical portion 1902d has a generally cylindrical shape, and is provided along the rotational axis L19 so as to project beyond the external tooth gear portion 1902b and the internal tooth gear portion 1902a toward the drum 1962 side (downstream side in the H direction).

[0417] As shown in FIG. 66, the inner peripheral surface (supported portion) of the support portion 1902c engages with the outer peripheral surface 19710c of the cylindrical portion 19710b, and the gear 1902 is supported on the frame member 1971 rotatably about the rotational axis L19. In addition, the outer peripheral surface 19730b of the cylindrical portion 19730r engages with the inner peripheral surface 19710d of the cylindrical portion 19710b, and the bearing member 1973 is positioned and supported by the frame member 1971. The driving side flange 1963 penetrates the inner peripheral portion of the gear 1902 and is provided on the cleaning frame 1960a. In the driving side flange 1963, the projection 1963g is rotatably supported by the bearing member 1973 on the rotational axis L1 as with the case of the embodiment 17.

[0418] Further, as shown in FIG. 67, the internal gear portion 1963f of the driving side flange 1963 is a spur gear and has the same number of teeth as the internal gear portion 1902a of the gear 1902. The internal gear portion 1902a of the gear 1902 is provided so as to be fitted into the internal gear portion 1963f, and the tooth surfaces of the internal tooth gear portion 1902a and the internal gear portion 1963f engage with each other in the rotational direction. That is, the internal gear portion 1902a and the internal gear portion 1963f are in meshing engagement with each other so as to be able to transmit the rotational driving force.

[0419] As described above, the outer peripheral surface 19710c of the cylindrical portion 19710b of the frame member 1971 is provided at a position eccentric with respect to the inner peripheral surface 19710d. Therefore, the gear 1902 supported by the outer peripheral surface 19710c is engaged with the inner peripheral surface 19710d at an eccentric position with respect to the driving side flange 1963 supported by way of the bearing member 1973. That is, the gear 1902 and the driving side flange 1963 are rotatably arranged in a state that the rotational axis L19 and the rotational axis L1 are parallel and non-coaxial with each other, and the rotation driving force can be transmitted to each other. In FIG. 67, the positions of the rotational axis L19 and the rotational axis L1 are shown by the intersections between horizontal chain lines extend in left-right direction and a vertical line extending vertically, and the difference between the horizontal line corresponding to the rotational axis L19 and the horizontal line corresponding to the rotational axis L1 can be seen. In addition, the gear 1902 can also be referred to as a non-coaxial rotating member connected to the driving side flange 1963 so as to be able to transmit a driving force.

<Transmission of Driving Force to Drum Unit 1969>

[0420] Next, referring to FIGS. 68 and 69, the driving force transmission to the drum unit 1969 will be described. FIG. 68 is a sectional view illustrating an engaged state between the drum unit 1969 and the drive transmission gear 1781, and the sectional plane thereof includes the rotational axis L1. FIG. 69 is a cross-sectional view illustrating the engaged state between the drum unit 1969 and the drive transmission gear 1781, taken along a plane perpendicular to the rotational axis L1 and passing through the internal gear portion 1963f the J direction of a cross-section, as viewed in the J direction.

[0421] As shown in FIG. 68, as in embodiment 17, the second main assembly gear portion 81d of the drive transmission gear 1781 meshes with the second gear portion 1963d of the driving side flange 1963. In addition, the first main assembly gear portion 1781c of the drive transmission gear 1781 meshes with the external tooth gear portion (first gear portion) 1902b of the gear 1902, and the internal gear portion 1902a of the gear 1902 engages with the internal gear portion 1963f of the driving side flange 1963.

[0422] As shown in FIG. 69, by rotation of the drive transmission gear 1781 in the direction of the arrow I, the gear 1902 receives the driving force by the meshing engagement between the external tooth gear portion 1902b and the first main assembly gear portion 1781c, so that the gear 1902 rotates in the direction of the arrow KW about the rotational axis L19. At this time, the internal gear portion 1902a engages with the internal gear portion 1963f of the driving side flange 1963 in the rotational direction, and transmits the driving force to the driving side flange 1963. By this, the driving side flange 1963 rotates in the direction of arrow K about the rotational axis L1.

[0423] By the rotation of the drive transmission gear 1781 in the direction of arrow I, the external tooth gear portion 1902b receives a thrust force in the direction of arrow H (see FIG. 68) because of the meshing with the first main assembly gear portion 1781c. For this reason, as shown in FIG. 68, the gear 1902 moves in the arrow H direction, the cylindrical portion 1902d abuts to the end surface of the second gear portion 1963d of the driving side flange 1963, and the movement of the gear 1902 in the arrow H direction is restricted (stopped).

[0424] On the other hand, the drive transmission gear 1781 receives a thrust force due to meshing with the external tooth gear portion 1902b and moves in the direction of arrow J. Then, similarly to embodiment 17, the second main assembly gear portion 1781d moves to the balanced position where it engages with the second gear portion 1963d of the driving side flange 1963, and the movement in the direction of the rotational axis L1 stops.

[0425] In this balanced state, the external tooth gear portion (first gear portion) 1902b receives the driving force FD from the first main assembly gear portion 1781c. The gear 1902 can be regarded as a rigid assembly, and therefore, this driving force FD is transmitted to the driving side flange 1963 by the meshing (engagement) between the internal gear portion 1902a and the internal gear portion 1963f. That is, the driving side flange 1963 is in a state of receiving the drive force FD by way of the gear 1902. In addition, the driving side flange 1963 is in a state that the second gear portion 1963d receives the restriction force (braking force) FB from the second main assembly gear portion 1781d. The teeth of the second gear portion 1963d are fixed so as not to move (rotate) in the direction opposite to the I direction relative to the teeth of the first gear portion 1902b. Therefore, the drum unit 1969 (drum 1962, driving side flange 1963, and gear 1902) is driven in a backlashless state. For this reason, the same effect as that of Embodiment 17 can be provided also when the structure of this Embodiment is used.