Image Forming Apparatus and Process Cartridge Detachable Thereto With Charging Member Pressure Contact Release Feature

1. Field of the Invention

This invention relates to an image forming apparatus, such as a laser-beam printer or a copier, including an image bearing member, such as a photosensitive member or a dielectric member, and a charging member for charging the image bearing member, and to a process cartridge which is detachable with respect to the image forming apparatus.

2. Description of the Related Art

In many image forming apparatuses, such as copiers or the like, process units, such as an image bearing member (a photosensitive drum), a cleaning unit, a developing unit and the like, are accommodated within a cartridge, so that they are detachable with respect to the main body of the apparatus as one body in the form of a process cartridge. In such an image forming apparatus, when any of the process units within the cartridge has come to an end of its life, or any consumable material (for example, toner within the developing unit) has been used up, the entire process cartridge is exchanged for ease of maintenance.

Chargers, such as a primary charger, a transfer charger, and the like, are disposed around the photosensitive drum so as to supply various kinds of electric charges to the photosensitive drum. A noncontact-type corona charger utilizing corona discharge, a charging roller used in contact with the photosensitive drum in the form of a roller, or the like may be used as such a charger.

If a corona charger is used as the primary charger, noxious ozone is generated during corona discharge. Accordingly, an ozone filter is required within the image forming apparatus, thereby causing an increase in production costs and also an increase in the size of the image forming apparatus.

If a contact-type charger in pressure contact with the photosensitive drum, such as a charging roller, is used as a primary charger instead of the corona charger, the generation of ozone is pevented.

However, in conventional image forming apparatuses, if there is an extended time period until the process cartridge is used after it has been manufactured, or if there is an extended time period until the process cartridge is recycled after it has been used, the charging roller stays in pressure contact with the photosensitived drum at the same portion. Hence, for example, traces caused by pressure may be produced in the charging roller and the photosensitive drum, contact portions of the charging roller and the photosensitive drum may be permanently deformed due to creep, or the photosensitive drum may be contaminated with materials contained in the charging roller, thereby degrading the obtained image. The same problems will arise also when a charging blade is used as a contact-type charger.

In order to overcome the above-described problems, a technique is disclosed, for example, in U.S. Pat. No. 5,095,335, in which a charging roller provided in the main body of an image forming apparatus is made to be in contact with or separated from a photosensitive drum provided in a process cartridge linked with mounting and detaching of the process cartridge. However, since a charging roller is not provided in the process cartridge, the mechanism of mounting and detaching the process cartridge to the image forming apparatus becomes complicated.

It is an object of the present invention to provide an image forming apparatus and a process cartridge, in which, even if an image bearing member and a charging member in contact therewith are used, traces caused by pressure, creep and contamination are not produced in the image bearing member and the charging member.

It is another object of the present invention to provide an image forming apparatus and a process cartridge, in which an image bearing member and a charging member are provided in the process cartridge, so that the mechanism of mounting/detaching the process cartridge with respect to the image forming apparatus is simplified.

It is still another object of the present invention to provide an image forming apparatus and a process cartridge, in which pressure contact between an image bearing member and a charging member can be released in a state of detaching the process cartridge from the image forming apparatus.

A process cartridge detachably mountable in an image forming apparatus, the process cartridge comprising an image bearing member for bearing an image, and a charging member, which is movable to be in releasable pressure contact with the image bearing member, for charging the image bearing member, wherein mounting of the process cartridge to the image forming apparatus is prohibited when pressure contact between the image bearing member and the charging member is released.

An image forming apparatus, including a process cartridge detachably mountable in the image forming apparatus, the process cartridge cartridge comprising an image bearing member for bearing an image, and a charging member in releasable pressure contact with the image bearing member, for charging the image bearing member, and release means for releasing the pressure contact between the image bearing member and the charging member, wherein the mounting of the process cartridge in the apparatus is prohibited when the pressure contact between the image bearing member and the charging member is released.

The foregoing and other objects, advantages and features of the present invention will become more apparent from the following detailed description taken in conjuction with the accompanying drawings.

FIG. 1 is a pespective view illustrating an external appearance of a process cartridge according to any of first through fifth embodiments of the present invention;

FIG. 2 is a vertical, cross-sectional view of a process cartridge according to a first embodiment of the present invention;

FIG. 3 is a cross-sectional view taken along line 3--3 of the process cartridge shown in FIG. 2;

FIG. 4 is a vertical, cross-sectional view illustrating the function of the image forming apparatus shown in FIG. 1;

FIG. 5 is a vertical, cross-sectional view of a process cartridge according to a second embodiment of the present invention;

FIG. 6 is a cross-sectional view taken along line 6--6 of the process cartridge shown in FIG. 5;

FIG. 7 is a vertical, cross-sectional view illustrating the function of the process cartridge shown in FIG. 5;

FIG. 8 is a perspective view illustrating a state when 10 the process cartridge is mounted on the upper frame of the main body of the image forming apparatus;

FIG. 9 is a vertical, cross-sectional view illustrating a state after the process cartridge has been mounted on the main body of the image forming apparatus;

FIG. 10 is a substantially vertical, cross-sectional view illustrating the external shape of the process cartridge and a cartridge mounting portion in the upper frame of the main body of the image forming apparatus;

FIG. 11 is a vertical, cross-sectional view of a process cartridge according to a third embodiment of the present invention;

FIG. 12 is a cross-sectional view taken along line 12--12 of the process cartridge shown in FIG. 11;

FIG. 13 is a plan view of the upper frame of the image forming apparatus, as seen from above;

FIG. 14 is a vertical, cross-sectional view illustrating the function of the process cartridge shown in FIG. 11;

FIG. 15 is a vertical, cross-sectional view illustrating a state in which a process cartridge is mounted in the main body of an image forming apparatus according to a fourth embodiment of the present invention;

FIG. 16 is a vertical, cross-sectional view illustrating the process cartridge of the fourth embodiment;

FIG. 17 is a vertical, cross-sectional view illustrating a process cartridge according to a fifth embodiment of the present invention;

FIG. 18 is a vertical, cross-sectional view illustrating the function of the process cartridge shown in FIG. 17;

FIG. 19 is a cross-sectional view taken along line 19--19 of the image forming apparatus shown in FIG. 18;

FIG. 20 is a perspective view illustrating an external appearance of a process cartridge according to sixth and seventh embodiments of the present invention;

FIG. 21 is a vertical, cross-sectional view of a process cartridge according to a sixth embodiment of the present invention;

FIG. 22 is a cross-sectional view taken along line 22--22 of the process cartridge shown in FIG. 21;

FIG. 23 is a vertical, cross-sectional view of a process cartridge according to a seventh embodiment of the present invention; and

FIG. 24 is a cross-sectional view taken along line 24--24 of the process cartridge shown in FIG. 23.

First Embodiment

A first embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a perspective view of a process cartridge to which the present invention is applied. FIG. 2 is a vertical, cross-sectional view of the process cartridge shown in FIG. 1. FIG. 3 is a cross-sectional view taken along line 3--3 of the process cartridge shown in FIG. 2.

The process cartridge B includes at least an image bearing member and charging means, serving as process means. The process means includes, for example, charging means for charging the surface of the image bearing member, developing means for forming a toner image on the image bearing member, cleaning means for removing toner particles remaining on the surface of the image bearing member, and the like. As shown in FIGS. 2 and 3, the process cartridge B of the present embodiment disposes charging roller 10, serving as a contact charging member, developing means 12 accommodating a toner (developer), and cleaning means 13 around electrophotographic photosensitive drum 9, serving as an image bearing member. These components are covered with a housing, comprising upper and lower frames 14 and 15, so that they are provided as one body in the form of a cartridge detachable with respect to frame 16 of the main body of the image forming apparatus (see FIG. 9).

Charging roller 10, exposure means 11, and toner reservoir 12a for developing means 12 are provided in upper frame 14. Photosensitive drum 9, developing roller 12d for developing means 12, and cleaning means 13 are provided in lower frame 15.

The charging means is used for charging the surface of the photosensitive drum 9. In the present embodiment, a so-called contact charging method, as described in Japanese Patent Laid-open Application (Kokai) No. 63-149669 (1988), is used for the charging means. That is, as shown in FIG. 2, charging roller 10, to which a voltage is applied from a power supply, is provided so as to be rotatable by sliding bearings 10c within upper frame 14. The charging roller 10 comprises, for example, a metallic roller shaft 10b (for example, a conductive core made of iron, SUS (stainless steel), or the like), a layer of an elastic rubber, such as a ternary copolymer of EPDM's (ethylene propylene diene monomers), NBR (nitrile-butadiene rubber), or the like, provided thereon, and a layer of urethane rubber, in which carbon is dispersed, provided around the circumferential surface of the above-described layer, or comprises a metallic roller shaft coated with a layer of foamed urethane rubber in which carbon is dispersed. The roller shaft 10b of the charging roller 10 is mounted so as not be detached by bearing slide guide pawl 10d of upper frame 14 via sliding bearings 10c in a state in which it is slightly slidable in the directions of approaching and separating from photosensitive drum 9. Springs 10f are provided between sliding bearings 10c for supporting roller shaft 10b, and upper frame 14 drive roller shaft 10b in the direction of photosensitive drum 9, so that charging roller 10 is in pressure contact with the surface of photosensitive drum 9.

The process cartridge B further includes pressure-releasing pieces 40 for separating charging roller 10 from photosensitive drum 9. As shown in FIG. 3, pressure-releasing pieces 40 are supported on upper frame 14 so as to be rotatable around fulcrums 40c provided in upper frame 14 in the vicinity of both ends of charging roller 10 in the longitudinal direction. As shown in FIG. 2, pressure-releasing pieces 40 raise charging-roller shaft 10b by their distal-end portions 40a, serving as pressure-releasing portions, so that charging roller 10 does not contact photosensitive drum 9.

When the operator intends to use the process cartridge B, he rotates pressure-releasing pieces 40 in the direction of arrow D, as seen in FIG. 2, by holding respective gripping members 40b of pressure-releasing pieces 40. Thus, distal-end portions 40a of pressure-releasing pieces 40 are detached from shaft 10b of charging roller 10, and sliding bearings 10c move along bearing slide guide pawl 10d by the force of springs 10f, whereby charging roller 10 also moves. Hence, charging roller 10 becomes in pressure contact with photosensitive drum 9 (see FIG. 4). Thereafter, as shown in FIGS. 8 and 9, the process cartridge B is mounted in the main body of the image forming apparatus. When the cartridge B has been mounted in the main body of the apparatus, a state, in which a power supply provided in the main body of the image forming apparatus can apply a voltage to the charging member, is provided.

In FIG. 9, original-mount glass la is movable in the vertical direction as viewed in FIG. 9, and is connected to a driving device so as to perform reciprocating movement. Original 2 on original-mount glass 1a is illuminated by illuminating lamp 1c1 during the forward or backward movement of original-mount glass 1a. Light reflected by original 2 is imaged onto photosensitive drum 9, which rotates in the direction of the arrow and which has been uniformly charged by charging roller 10, via short-focus lens array 1c2 to form a latent image. The latent image becomes a developed image by toner particles supplied from developing roller 12d of developing means 12, and the developed image moves to the position of transfer roller 6. On the other hand, a sheet of transfer material 4, fed from sheet-feeding tray 3 in the direction of arrow "a" by sheet-feeding roller 3a, is fed by registration roller 5c1 with a timing to coincide with the developed image, and is provided with a transfer bias potential by transfer roller 6. The developed image on photosensitive drum 9 is transferred onto the sheet of transfer material 4, which is then separated from photosensitive drum 9 and is fed to fixing device 7 by conveying devices 5d and 5e. The image is fixed on the sheet in fixing device 7, and the sheet is discharged outside the image forming apparatus.

In the present embodiment, upper frame 19 of the main body is mounted on frame 16 of the main body of the image forming apparatus so as to be rotatable around hinge 1c3, and can take the positions shown in FIGS. 8 and 9. FIG. 8 illustrates the mounting/detaching position of process cartridge B with respect to image forming apparatus A. Guide rails 31 and 32 provided in process cartridge B slide into guide grooves 29b and 29c, parallel to photosensitive drum 9, provided in upper frame 19 of the main body, whereby process cartridge B is mounted in upper frame 19 of the main body. Process cartridge B is accommodated within main body 16 of the apparatus by rotating upper frame 19 around hinge 1c3.

As shown in FIG. 10, guide grooves 29b and 29c of upper frame 19 of the main body are provided in opening 29a, which is substantially analogous in shape to process cartridge B and in which process cartridge B can be accommodated. Opening notches 29d are provided at portions of side plate 29 of upper frame 19 of the main body which forms opening 29a. When pressure-releasing pieces 40 are at positions of not supporting charging roller 10, i.e., when gripping members 40b are in an oblique state, gripping members 40b enter opening notches 29d, so that process cartridge B can be inserted into upper frame 19 of the main body from opening 29a. On the other hand, when charging roller 10 is supported by Pressure-releasing pieces 40 and is separated from photosensitive drum 9, i.e., when gripping members 40b are substantially orthogonal to the edge of opening 29a, gripping members 40b contact side plate 29 of main-body upper frame 19, so that process cartridge B cannot enter opening 29a of main-body upper frame 19. Thus, a foolproof mechanism is provided.

Second Embodiment

Next, a description will be provided of a second embodiment of the present invention with reference to FIGS. 5 through 7. In FIGS. 5 through 7, components having the same functions as in the first embodiment are indicated by the same reference characters, and a description thereof will be omitted.

While in the first embodiment, charging roller 10 is provided as charging means, in the present embodiment, charging blade 10h is provided. Charging blade 10h is fixed to one arm of blade holder 10e, having the shape of a belt crank, rotatably pivoted on upper frame 14 around shaft 10g. Blade holder 10e is rotated in a counterclockwise direction around shaft 10g by springs 10f provided between upper frame 14 and blade holder 10e, whereby charging blade 10h is driven toward photosensitive drum 9.

FIG. 6 is a cross-sectional view taken along line 6--6 shown in FIG. 5. In the present embodiment, pressure-releasing pieces 40 for separating charging blade 10h from photosensitive drum 9 are rotatably supported on upper frame 14 around fulcrums 40c provided on upper frame 14 in the vicinity of two ends 51 of blade holder 10e in the longitudinal direction, and rotate charging blade 10h and blade holder 10e in a clockwise direction, as viewed in FIG. 7, around shaft 10g by raising the arm of blade holder 10e, to which charging blade is not fixed, by distal-end portions 40a of the pressure-retaining pieces 40. Thus, charging blade 10h does not contact photosensitive drum 9 (see FIG. 5).

When using process cartridge B, in the same manner as described in the first embodiment, in FIG. 5, pressure-releasing pieces 40 are rotated in the direction of arrow D by grasping gripping members 40b of pressure-releasing pieces 40 to provide a state in which charging blade 10h is in pressure contact with photosensitive drum 9, as shown in FIG. 7, and process cartridge B is mounted in the main body of the image forming apparatus as shown in FIGS. 8 and 9.

At that time, as shown in FIG. 10, if it is intended to mount process cartridge B in image forming apparatus A when pressure-releasing pieces 40 are in a pressure-releasing state shown in FIG. 5, gripping members 40b of the pieces do not coincide with notches 20d provided in opening 20a of upper frame 19 of the main body of the image forming apparatus. Hence, process cartridge B cannot be mounted.

Third Embodiment

The external appearance of the process cartridge used in a third embodiment of the present invention is the same as in the first and second embodiments, as represented by the perspective view shown in FIG. 1. FIG. 11 is a vertical, cross-sectional view of the image forming apparatus of the third embodiment. The same components as in the first embodiment are indicated by the same reference characters, and a description thereof will be omitted. A description will be provided of only a portion around the charging roller which differs.

Pressure-releasing pieces 40 for separating charging roller 10 from photosensitive drum 9 are provided in process cartridge B. As shown in FIG. 12, pressure-releasing pieces 40 are supported around fulcrums 40c provided in upper frame 14 at two ends of charging roller 10 in the longitudinal direction, and are driven in a counterclockwise direction, as viewed in FIG. 11, around fulcrums 40c by tension springs 40e, each provided between spring-holding bracket 14a of upper frame 14 and spring holder 40d provided at distal-end portion 40a of the piece, whereby distal-end portions 40a of the pieces raise shaft 10b of charging roller 10, so that charging roller 10 does not contact photosensitive drum 9.

The ratio of the force of compression spring 10f provided between bearing 10c and upper frame 14 as in the first embodiment to the force of the above-described tension spring 40e is appropriately determined. Gripping members 40b are not manually operated. When no force is applied to gripping members 40b, as shown in FIG. 11, pressure-releasing pieces 40 are rotated around fulcrums 40c in a counterclockwise direction by the force of tension springs 40e against the force of compression springs 10f to raise roller shaft 10b while grasping it by distal-end portions 40a of the pieces, so that charging roller 10 is separated from photosensitive drum 9.

When mounting the above-described process cartridge B in main body A of the image forming apparatus, as shown in FIGS. 13 and 14, grooves 41, serving as pressure-release operation means, are provided in upper frame 19 of the main body of the apparatus. Gripping members 40b of pressure-releasing pieces 40 of the process cartridge contact entrance slopes 41a of groove 41. Thereafter, pressure-releasing pieces 40 are rotated around fulcrums 40c in a clockwise direction, as viewed in FIG. 11, against the force of tension springs 40e so as to contact pressure-releasing piece contact surfaces 41b. Thus, as shown in FIG. 14, distal ends 40a of pressure-releasing pieces 40 are disengaged from charging-roller shaft 10b engaged therewith, and charging roller 10 is driven toward photosensitive drum 9 by compression springs 10f.

When detaching process cartridge B from the main body A of the image forming apparatus, gripping members 40b of pressure-releasing pieces 40 are separated from contact surfaces 41b of grooves 41 in upper frame 19 of the main body which gripping members 40b have contacted. Hence, in FIG. 14, pressure-releasing pieces 40 are rotated around fulcrums 40c in a counterclockwise direction by tension springs 40e, whereby distal ends 40a of pressure-releasing pieces 40 engage with charging-roller shaft 10b, so that charging roller 10 is separated from photosensitive drum 9. If gripping members 40b of pressure-releasing pieces 40 do not move because of some reason when cartridge B is mounted in the main body A of the image forming apparatus, gripping members 40b are not guided along slopes 41a. That is, in a state in which roller 10 is separated from drum 9, gripping members 40b contact slopes 41a, and cartridge B cannot be mounted in main body A of the image forming apparatus.

Fourth Embodiment

Next, a description will be provided of a fourth embodiment of the present invention with reference to FIGS. 15 and 18. In FIGS. 18 and 18, components having the same functions as in the third embodiment are indicated by the same reference characters, and a description thereof will be omitted.

In the third embodiment, a case, in which process cartridge B is detached from the main body A of the image forming apparatus from the axial direction of charging roller 10 (see FIG. 8), has been described. In the present embodiment, however, a case, in which process cartridge B is mounted from a direction orthogonal to the axis of the charging roller (the direction of arrow J in FIG. 18), will be described.

When mounting process cartridge B in the main body A of the image forming apparatus, as shown in FIG. 15, process cartridge B is inserted from the direction of arrow J in upper frame 19 of main body A of the image forming apparatus, and is secured by securing means (not shown). At that time, as shown in FIG. 16, gripping members 40b of pressure-releasing pieces 40, which have separated charging roller 10 from photosensitive drum 9 by grasping roller shaft 10b by distal ends 40a of the pieces, contact contact surface 42 of upper frame 19 of the main body of the image forming apparatus provided as pressure-release operation means, and pressure-releasing pieces 40 rotate around fulcrums 40c in a clockwise direction, so that charging roller 10 is in pressure contact with photosensitive drum 9. On the other hand, when detaching process cartridge B from main body A of the apparatus, gripping members 40b of presure-releasing pieces 40 draw away contact surface 42, whereby pressure-releasing pieces 40 rotate around fulcrums 40c in a counterclockwise direction by the force of tension springs 40e, so that charging roller 10 is separated from photosensitive drum 9. If gripping members 40b of pressure-releasing pieces 40 do not move because of some reason when cartridge B is mounted in main body A of the image forming apparatus, i.e., in a state in which roller 10 is separated from drum 9, cartridge B cannot be mounted in main body A of the image forming apparatus.

Fifth Embodiment

Next, a description will be provided of a fifth embodiment of the present invention with reference to FIGS. 17 through 19. The present embodiment is substantially the same as the second embodiment. In the present embodiment, charging blade 10h is provided as charging means for the process cartridge. Charging blade 10h is fixed to blade holder 10e rotatably pivoted on upper frame 14 around shaft 10g. Blade holder 10e is rotated around shaft 10g in a counterclockwise direction by springs 10f, whereby blade 10h is driven toward photosensitive drum 9. As in the second embodiment, the process cartridge B also includes pressure-releasing pieces 40 for the charging means. When process cartridge B is detached from the main body A of the image forming apparatus, charging blade 10h is separated from photosensitive drum 9 by pressure-releasing pieces 40, as shown in FIG. 17. When process cartridge B is mounted in the main body A of the image forming apparatus, pressure-releasing pieces 40 do not prevent the driving of charging blade 10h toward photosensitive drum 9, as shown in FIG. 18. The image forming apparatus to which the present embodiment is applied includes either grooves 41 having entrance slopes 41 a in upper frame 14 of the main body as in the third embodiment, or contact surface 42 at side plate 29 of upper frame 19 of the main body A of the image forming apparatus as in the fourth embodiment.

Sixth Embodiment

FIG. 20 is a perspective view of a process cartridge according to a sixth embodiment of the present invention. FIG. 21 is a vertical, cross-sectional view of the image forming apparatus shown in FIG. 20. FIG. 22 is a cross-sectional view taken along line 22--22 shown in FIG. 21.

In FIGS. 20 through 22, the same components as in the first embodiment are indicated by the same reference characters except members for approaching/separating charging roller 10 relative to photosensitive drum 9, and a description of the same components will be omitted.

Process cartridge B includes pressure-releasing pieces 40 for separating charging roller 10 from photosensitive drum 9. As shown in FIG. 22, pressure-releasing pieces 40 are supported on upper and lower frames 14 and 15 at two ends of charging roller 10 in the longitudinal direction. Distal-end portions 40a of the pieces raise shaft 10b of charging roller 10, so that charging roller 10 does not contact photosensitive drum 9.

When using process cartridge B, pressure-releasing pieces 40 are pulled by grasping gripping members 40b and detached from process cartridge B, so that charging roller 10 is in pressure contact with photosensitive drum 9. Then, process cartridge B is mounted in upper frame 19 of main body A of the image forming apparatus, as shown in FIGS. 8 and 9.

At that time, if pressure-releasing pieces 40 for charging roller 10 are not detached from process cartridge B, gripping members 40b of pressure-releasing pieces 40 contact sides 16a and 16b of outer cover 16 of main body A of the image forming apparatus when closing upper frame 19 of the main body on main body A of the image forming apparatus, so that upper frame 19 of the main body A of the image forming apparatus cannot be completely closed.

Seventh Embodiment

Next, a description will be provided of a seventh embodiment of the present invention with reference to FIGS. 23 and 24. In FIGS. 23 and 24, components having the same functions as in the sixth embodiment will be indicated by the same reference characters, and a description thereof will be omitted.

While charging roller 10 is provided as charging means in the sixth embodiment, charging blade 10h is provided in the present embodiment. Charging blade 10h is fixed to blade holder 10e rotatably pivoted on upper frame 14 around shaft 10g. Blade holder 10e is rotated around shaft 10g in a counterclockwise direction by springs 10f, whereby blade 10h is driven toward photosensitive drum 9. FIG. 24 is a cross-sectional view taken along line 24--24 shown in FIG. 23. In the present embodiment, pressure-releasing pieces 40 for separating charging blade 10h from photosensitive drum 9 are supported on upper and lower frames 14 and 15 in the vicinity of two ends 51 of blade holder 10e in the longitudinal direction. Blade holder 10e is raised by distal-end portions 40a of the pieces, whereby charging blade 10h does not contact photosensitive drum 9.

As in the sixth embodiment, in the present embodiment, in a state in which pressure-releasing pieces 40 for charging roller 10 are mounted in process cartridge B, process cartridge B cannot be mounted in the main body A of the image forming apparatus.

In the above-described embodiments, the description that cartridge B cannot be mounted in the main body A of the image forming apparatus in a state in which the pressure contact state between the image bearing member and the charging member is released indicates that cartridge B cannot be mounted at a predetermined position (a position where an image forming operation can be performed) of the main body A of the image forming apparatus.

In the present invention, by providing pressure-releasing means so that charging means in pressure contact with an image bearing member is separated from the image bearing member when a process cartridge is not used, it is possible to prevent traces by pressure, creep, contamination, and the like from being produced in the image bearing member and the charging means, and thereby to prevent problems in the obtained image. If such pressure release is performed until a process cartridge is used after it has been manufactured, or when a process cartridge for a certain color is replaced by a process cartridge for another color, or until a process cartridge is recycled after it has been used, the above-described effects can be obtained, and the image bearing member and the charging means can be used as they are.

In the present invention, by arranging the process cartridge in the above-described pressure-release state so that it cannot be mounted in the main body of the image forming apparatus, it is possible to prevent problems in the obtained image caused by malfunction of the charging means for the image bearing member.

According to the present invention, an image forming apparatus includes a process cartridge detachable to the main body of the image forming apparatus. The process cartridge includes at least an image bearing member, and contact charging means in pressure contact with the image bearing member disposed therearound. The process cartridge also includes pressure-releasing means capable of contacting/separating the charging means relative to the image bearing member, and pressure-release operation means operating so that the charging means can contact and separate from the image bearing member linked with the pressure-releasing means when mounting and detaching the process cartridge relative to the main body of the image forming apparatus. Thus, when the process cartridge is mounted in the image forming apparatus, the contact charging means is in pressure contact with the image bearing member, and when the process cartridge is detached from the image forming apparatus, the contact charging means is separated from the image bearing member. Accordingly, no particular attention is needed when mounting and detaching the process cartridge relative to the image forming apparatus.

While the present invention has been described with respect to what is presently considered to be the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.