Developing device, process cartridge, electrophotographic image forming apparatus and agitating member

[0002] 1. Field of the Invention

[0003] The present invention relates to a developing device, a process cartridge, an electrophotographic image forming apparatus and an agitating member. The electrophotographic image forming apparatus serves to form an image on a recording medium by using an electrophotographic image forming process and may include an electrophotographic copying machine, an electrophotographic printer (for example, a laser beam printer, an LED printer and the like), a facsimile apparatus, a word processor and the like. The process cartridge is constituted by integrally incorporating charging means, or cleaning means, developing means, and an electrophotographic photosensitive member as a cartridge unit which is detachably mountable to a main body of the image forming apparatus, or, by integrally incorporating at least one of charging means and cleaning means, developing means and an electrophotographic photosensitive member as a cartridge unit that is detachably mountable to a main body of the image forming apparatus, or by integrally incorporating developing means and an electrophotographic photosensitive member as a cartridge unit that is detachably mountable to a main body of the image forming apparatus.

[0004] 2. Related Background Art

[0005] In the past, as one of electrophotographic image forming apparatuses, there has been proposed an image forming apparatus to which a developing device or a process cartridge can be detachably mounted. The developing device or the process cartridge comprises a toner container (developer container) for containing toner (developer), and a developing chamber including a developing roller as a developer bearing member. When the developer in the toner container is consumed, the developing device or the process cartridge must be replaced by a new developing device or a new process cartridge. To this end, there is provided a developer-remaining-amount detecting device for detecting a remaining amount of the developer in the toner container.

[0006] Such a developer-remaining-amount detecting device has a metallic antenna rod extending in parallel with a longitudinal direction of the developing roller and is disposed in a passage extending from the toner container to the developing roller in the developing chamber. By applying a voltage between the antenna rod and the developing roller to measure the electrostatic capacity therebetween, the toner remaining amount can be detected. When the detected electrostatic capacity is smaller than a predetermined threshold value, it is judged that the toner amount between the antenna rod and the developing roller is small, i.e., the toner amount in the toner container is small. By detecting the change in the electrostatic capacity in this way, the absence of toner has been detected.

[0007] However, in the conventional toner-remaining-amount detecting devices, the fact that the remaining toner is little can merely be known immediately before the toner is used up, but, the user cannot know how much toner is remaining in the toner container.

[0008] An object of the present invention is to provide a developing device, a process cartridge, an agitating member and an electrophotographic image forming apparatus, in which a toner remaining amount can be detected successively.

[0009] Another object of the present invention is to provide a developing device, a process cartridge, an agitating member and an electrophotographic image forming apparatus, in which a toner remaining amount can be detected with high accuracy.

[0010] A further object of the present invention is to provide a developing device, a process cartridge, an agitating member and an electrophotographic image forming apparatus, in which a toner remaining amount is detected by using a change in electrostatic capacity.

[0011] The other object of the present invention is to provide a developing device, a process cartridge, an agitating member and an electrophotographic image forming apparatus, that have a movable antenna member for detecting a remaining amount of toner remaining in the developing device, which antenna member serves to detect the toner remaining amount on the basis of the change in electrostatic capacity between electrodes provided on the antenna member.

[0012] These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.

[0013] FIG. 1 is a perspective view showing the positional relationship between a toner feeding member and a first antenna rod, and toner-remaining-amount detecting means, according to a first embodiment of the present invention;

[0014] FIG. 2 is a vertical sectional view of an electrophotographic image forming apparatus according to a first embodiment of the present invention;

[0015] FIG. 3 is a vertical sectional view of a process cartridge detachably mountable to the electrophotographic image forming apparatus according to the first embodiment;

[0016] FIG. 4 is a schematic view showing an equivalent circuit for the toner remaining detection;

[0017] FIG. 5A is a schematic vertical sectional view of a support member, and

[0018] FIG. 5B is a right side view of FIG. 5A;

[0019] FIG. 6 is a vertical sectional view showing the state in which a toner feeding member, an antenna rod and a contact member are attached to the support member;

[0020] FIG. 7 is a perspective view of a process cartridge according to first and second embodiments of the present invention;

[0021] FIG. 8A is a vertical sectional view showing the state of toner in the process cartridge according to the first embodiment, and

[0022] FIG. 8B is a graph showing electrostatic capacity between the toner feeding member and the antenna rod in the state of FIG. 8A;

[0023] FIG. 9A is a vertical sectional view showing the state of toner in the process cartridge according to the first embodiment, and

[0024] FIG. 9B is a graph showing the electrostatic capacity between the toner feeding member and the antenna rod in the state of FIG. 9A;

[0025] FIG. 10A is a vertical sectional view showing the state of toner in the process cartridge according to the first embodiment, and

[0026] FIG. 10B is a graph showing the electrostatic capacity between the toner feeding member and the antenna rod in the state of FIG. 10A;

[0027] FIG. 11A is a vertical sectional view showing the state of toner in the process cartridge according to the first embodiment, and

[0028] FIG. 11B is a graph showing the electrostatic capacity between the toner feeding member and the antenna rod in the state of FIG. 11A;

[0029] FIG. 12 is a vertical sectional view of a process cartridge according to a second embodiment of the present invention;

[0030] FIG. 13 is a perspective view showing a positional relationship between a toner feeding member and an antenna rod, and toner-remaining-amount detecting means, according to the second embodiment;

[0031] FIG. 14 is a vertical sectional view of a process cartridge according to a further embodiment of the present invention;

[0032] FIG. 15 is a vertical sectional view of a process cartridge according to a further embodiment of the present invention;

[0033] FIG. 16 is a vertical sectional view of a process cartridge according to a further embodiment of the present invention;

[0034] FIG. 17 is a vertical sectional view of a process cartridge according to a further embodiment of the present invention;

[0035] FIG. 18 is a perspective view showing the positional relationship between a developing roller and a second antenna rod, and toner-remaining-amount detecting means, according to the first embodiment;

[0036] FIG. 19 is a vertical sectional view showing a fixed state of a second antenna rod;

[0037] FIG. 20 is a schematic graph showing a relationship between a ratio of cycle period p of rotation to a time t0 at which an electrostatic capacity value indicating no toner is detected, and a toner remaining amount; and

[0038] FIG. 21 is a schematic graph showing a relationship between the electrostatic capacity detected between a developing roller 9cand a second antenna rod 9i, and a toner-remaining-amount.

[0039] [First Embodiment]

[0040] Now, a first embodiment of the present invention will be fully described with reference to the accompanying drawings.

[0041] FIG. 2 is a constructural view of an electrophotographic image forming apparatus according to the first embodiment of the present invention, and FIG. 3 is a sectional view of a process cartridge detachably mountable to the electrophotographic image forming apparatus.

[0042] [Electrophotographic Image Forming Apparatus A and Process Cartridge B]

[0043] First of all, a laser beam printer A as the electrophotographic image forming apparatus according to the first embodiment will be explained with reference to FIGS. 2 and 3.

[0044] As shown in FIG. 2, the laser beam printer A serves to form an image on a recording medium (for example, recording paper, OHP sheet, cloth or the like) by using an electrophotographic image forming process. A toner image is formed on a drum-shaped electrophotographic photosensitive member (referred to as “photosensitive drum” hereinafter). More specifically, the photosensitive drum is charged by charging means, and then, a latent image corresponding to image information is formed on the photosensitive drum by illuminating the photosensitive drum with a laser beam corresponding to the image information from optical means 1. The latent image is developed by developing means to form a toner image. In sync with the formation of the toner image, a recording medium 2 is fed from a sheet feeding cassette 3aby a pick-up roller 3band is turnover-conveyed by pairs of conveying rollers 3c, 3dand a pair of registration rollers 3e. Then, the toner image formed on the photosensitive drum 7 of a process cartridge B is transferred onto the recording medium 2 by applying voltage to a transfer roller 4 as transferring means. Thereafter, the recording medium 2 on which the toner image was transferred is conveyed to fixing means 5 by a conveying guide 3f. The fixing means 5 has a driving roller 5c, and a fixing roller 5bincluding a heater 5atherein. While the recording medium 2 is being passed through the fixing means 5, heat and pressure are applied to the recording medium 2 so that the transferred toner image is fixed to the recording medium 2. Thereafter, the recording medium 2 is conveyed by pairs of discharge rollers 3g, 3h, 3iand is discharged onto a discharge tray 6 through a turn-over path 3j. The discharge tray 6 is provided on an upper surface of a main body 14 of the image forming apparatus A. Incidentally, by driving an oscillatable flapper 3k, the recording medium 2 can be discharged by a pair of discharge rollers 3mwithout passing through the turn-over path 3j. In the illustrated embodiment, the pick-up roller 3b, the pairs of conveying rollers 3c, 3d, the pair of registration rollers 3e, the conveying guide 3f, the pairs of discharge rollers 3g, 3h, 3iand the pair of discharge rollers 3mconstitute conveying means 3. Incidentally, the optical means 1 includes a laser diode 1a, a polygon mirror 1b, a lens 1cand a reflection mirror 1d.

[0045] On the other hand, as shown in FIG. 3, in the process cartridge B, while the photosensitive drum 7 having a photosensitive layer is being rotated, a surface of the photosensitive drum 7 is uniformly charged by applying voltage to a charging roller (charging means) 8. Then, in response to the image information, a laser beam from the optical means 1 irradiates the photosensitive drum 7 through an exposure opening portion 1e, thereby forming the latent image. The latent image is developed by the developing means 9 with toner. That is to say, the charging roller 8 is disposed in contact with the photosensitive drum 7 to charge the photosensitive drum 7. Incidentally, the charging roller 8 is rotatingly driven by rotation of the photosensitive drum 7. Further, the developing means 9 serves to supply the toner to a developing area of the photosensitive drum 7, thereby developing the latent image formed on the photosensitive drum 7.

[0046] In the developing means 9, the toner in a toner container 11A is fed out to a developing roller 9cby rotation of a toner feeding member 9b. While the developing roller 9cincluding a stationary magnet therein is being rotated, a toner layer, to which triboelectric charge is applied by a developing blade 9d,is formed on the surface of the developing roller 9cand the toner on the developing roller is supplied to the developing area of the photosensitive drum 7. By transferring the toner onto the photosensitive drum 7 in accordance with the latent image, the latent image is visualized as the toner image. The developing blade 9dserves to regulate the toner amount around a peripheral surface of the developing roller 9cand to apply the triboelectric charge. A toner agitating member 9efor circulating the toner in a developing chamber is rotatably supported in the vicinity of the developing roller 9c.

[0047] After the toner image formed on the photosensitive drum 7 is transferred to the recording medium 2 by applying voltage having a polarity opposite to a polarity of the toner image to the transfer roller 4, residual toner remaining on the photosensitive drum 7 is removed by cleaning means 10. In the cleaning means 10, the residual toner remaining on the photosensitive drum 7 is scraped off by an elastic cleaning blade 10aabutting against the photosensitive drum 7, and the scraped toner is collected into a removed-toner reservoir 10b.

[0048] The process cartridge B is constituted by joining a toner frame 11 having the toner container (toner containing portion) 11A containing the toner to a developing frame 12 holding the developing means 9 such as the developing roller 9cand by joining thereto a cleaning frame 13 including the photosensitive drum 7, the cleaning means 10, such as the cleaning blade 10a,and the charging roller 8. The process cartridge B can be mounted and dismounted with respect to the main body 14 of the image forming apparatus by the operator. Regarding the mounting/dismounting of the process cartridge B with respect to the main body 14 of the image forming apparatus, in FIG. 2, after an openable and closable member 35 is opened upwardly around hinges 35a, the process cartridge can be mounted along a direction shown by the arrow X and can be dismounted along a direction opposite to the direction X.

[0049] The process cartridge B is provided with the exposure opening portion 1ethrough which the light corresponding to the image information illuminate the photosensitive drum 7, and a transfer opening portion 13nthrough which the photosensitive drum 7 is opposed to the recording medium 2. The exposure opening portion 1eis formed in the cleaning frame 13.

[0050] Next, a housing of the process cartridge B according to the first embodiment will be described.

[0051] In the process cartridge B shown in the first embodiment, the photosensitive drum 7, the charging roller 8, the developing means 9 and the cleaning means 10 are contained in a housing obtained by integrally joining the toner frame 11, the developing frame 12 and the cleaning frame 13, as a cartridge. The process cartridge B is detachably mounted to cartridge-mounting means provided in the main body 14 of the image forming apparatus.

[0052] [Housing of Process Cartridge B]

[0053] In the process cartridge B according to the first embodiment, as mentioned above, the housing is constituted by joining the toner frame 11, the developing frame 12 and the cleaning frame 13. Now, the toner frame 11 and the developing frame 12 will be explained.

[0054] As shown in FIG. 3, the toner feeding member 9bis rotatably attached to the toner frame 11. Further, as shown in FIGS. 1 to 3, a first antenna rod 9hextending substantially in parallel with the toner feeding member 9bis attached to the toner frame 11 along a longitudinal direction of the toner feeding member 9b. Further, the developing roller 9c, the developing blade 9d, and a second antenna rod 9iare attached to the developing frame 12, and the agitating member 9efor circulating the toner in the developing chamber is rotatably supported in the vicinity of the developing roller 9c. An integral developing unit (second frame) D is formed by welding (ultrasonic welding in the illustrated embodiment) the toner frame 11 and the developing frame 12 together.

[0055] [Toner Remaining Amount Detecting Member]

[0056] FIG. 1 shows the positional relationship between the toner feeding member 9band the first antenna rod 9h, and toner-remaining-amount detecting means 15. Incidentally, in FIG. 1, a helical gear of a support member 16, a shaft sealing portion 16iand a toner-feeding-member driving portion 16j,which will be described later, are omitted from illustration for clarify's sake.

[0057] As shown in FIG. 1, the first antenna rod 9his integrally attached to the toner feeding member 9bformed as a crank shape with a predetermined distance therebetween.

[0058] The distance may be selected within a detectable range and so as not to clog the toner between the antenna rod and the toner feeding member and is suitably 5.5 mm to 9 mm.

[0059] The toner feeding member 9bis formed from a rod or a plate-shaped member made of non-magnetic metal, such as stainless steel, and is formed in the shape of a crank. One end 9b1 of the toner feeding member 9bis rotatably supported in a recessed portion formed in the toner frame 11 and the other end is supported by the support member 16 rotatably supported by the toner frame 11. The first antenna rod 9hhas one end attached to the toner feeding member 9bvia a holder 17aand the other end supported by the support member 16. Further, as shown in FIG. 1, the first antenna rod 9his attached to the toner feeding member 9bby another holder 17bto maintain the distance with respect to the toner feeding member 9b.

[0060] FIG. 5A is a vertical sectional view of the support member 16, and FIG. 6 is a sectional view showing a state in which the toner feeding member 9b, the first antenna rod 9h, a contact member 16dand toner seal members 16a, 16b, 16care attached to the support member 16. Further, FIG. 7 is a perspective view of the process cartridge according to the first embodiment, as viewed from below.

[0061] The support member 16 shown in FIGS. 5A and 5B has a helical gear 16f, a contact member support portion 16h, a journal-cum-sealing portion 16i, and a toner-feeding-member driving portion 16j. The contact-member support portion 16his provided with a rectangular recessed portion 16qextending radially from an outer periphery of the support portion 16h. The toner feeding member driving portion 16jis provided at its outer periphery with a circumferential groove portion 16e. A fitting through hole 16kfor the toner-feeding member 9bis formed in the support member 16 at a center of the support member 16. An antenna rod fitting hole 16mis extending through the support member 16 from an inner side (right in FIG. 5A) to the recessed portion 16qin parallel with the hole 16k.Inlets of the holes 16k,16mat the inner side have enlarged diameter portions to provide seal-member fitting holes 16a1, 16b1.

[0062] The support member 16 is provided at its end of the inner side with a hollow portion 16nat a center thereof, and the fitting holes 16k,16mextend to the left (FIG. 5A) from a bottom of the hollow portion 16n. A peripheral wall of the hollow portion 16nis provided with a radially running through slot 16pinto which an arm portion 9b2 of the toner-feeding member 9band an arm portion 9h2 of the first antenna rod 9hare just fitted.

[0063] As shown in FIG. 6, a shaft end portion 9bl of the toner-feeding member 9bis fitted into the fitting hole 16kof the support member 16. The arm portion 9b2 of the toner feeding member 9bis fitted into the slot 16pof the support member 16. Further, the shaft end portion 9h1 of the first antenna rod 9his fitted into the fitting hole 16mof the support member 16. The arm portion 9h2 of the first antenna rod 9his fitted into the slot 16pof the support member 16. The toner-feeding-member 9band the first antenna rod 9hare designed so that they are fitted from the right toward the left in FIG. 6. And, the member 9band the rod 9hare sealed by the toner seal members 16a, 16bpreviously fitted in the toner-seal fitting holes 16a1, 16b1. Further, a hollow cylindrical contact member 16dhaving an incised contact portion 16d1 formed in a part of the circumference of the contact member 16dis also previously fitted into the contact-member support portion 16hof the support member 16 so that the incised contact portion 16d1 is lightly bent in the recess portion 16qof the support member 16 to provide the contact portion 16d1. The shaft end portion 9h1 of the first antenna rod 9his inserted into the fitting hole 16mto urge the bent contact portion 16d1 so that the bent contact portion 16d1 of the contact member 16delastically urges the end surface of the first antenna rod 9hto thereby make a reliable electrical connection.

[0064] The toner-feeding member 9bis attached to extend through the fitting hole 16kof the support member 16, so that an end portion 18b1 (FIG. 1) of the contact member 18bprovided on the toner frame 11 elastically urges an exposed end surface 9b3 of the toner-feeding member 9bto thereby make a reliable electrical connection.

[0065] The support member 16 is constructed as mentioned above and is attached to the toner frame 11 in a unit. In this case, in order to prevent toner from leaking out, the toner-seal member 16cis fitted into and secured to the hole 11aof the toner frame 11 between the toner frame 11 and the journal-cum-sealing portion 16iof the support member 16. Dislodgment-preventing members or detent members (E type retaining rings in the illustrated embodiment) (not shown) for preventing the support member 16 from coming off from the toner frame 11 are disposed in the groove portion 16e.

[0066] Further, the support member 16 is provided at its end with the helical gear 16f, which is rotatingly driven by a driving source (not shown). Thus, the support member 16 is biased in an axial direction (right) of a rotational shaft by a thrust force from the helical gear 16fto thereby further effectively prevent the support member 16 from coming off.

[0067] Further, as shown in FIG. 1, along the toner frame 11, there are provided a contact member 18acontacting a part of an outer periphery of the contact member 16dand acting as a contact, and a contact member 18bcontacting the end surface of the toner-feeding member 9band acting as a contact. As shown in FIG. 7, parts of the contact members 18a, 18bare exposed from the bottom surface (along which the recording medium passes) of the toner frame 11 so that, when the process cartridge is mounted to the main body 14 of the image forming apparatus, the contact members 18a, 18bcontact contacts (not shown) of the main body of the image forming apparatus, thereby providing electrical connection. Through these contacts, bias is applied to the toner feeding member 9b.

[0068] [Toner-remaining-amount Detecting Mechanism]

[0069] Next, a toner-remaining-amount detecting mechanism regarding the first antenna rod 9bof the process cartridge B according to the illustrated embodiment will be explained.

[0070] As shown in FIGS. 1 and 3, the process cartridge B according to the illustrated embodiment includes the first antenna rod 9hextending substantially in parallel with the toner-feeding member 9band integrally attached to the toner-feeding member 9band adapted to detect the amount of toner between the toner feeding member 9band the antenna rod 9h.The first antenna rod 9hserves to detect the amount of toner between the toner-feeding member 9band the antenna rod 9hsuccessively and forms a part of the toner-remaining-amount detecting means 15.

[0071] Now, the toner-remaining-amount detecting means 15 having the first antenna rod 9hwill be fully explained. The toner-remaining-amount detecting means 15 is provided in the main body 14 of the image forming apparatus.

[0072] The toner-remaining-amount detecting means 15 is operated every about 10 msec to detect the toner remaining amount between the toner-feeding member 9band the first antenna rod 9h.

[0073] That is to say, the toner-remaining-amount detecting means 15 detects the electrostatic capacity between the toner-feeding member 9bto which the developing bias is being applied and the first antenna rod 9hand estimates the toner-remaining-amount in the toner container 11A on the basis of the value of the detected electrostatic capacity. As shown in FIG. 4, the toner-remaining-amount detecting means 15 mainly includes a load-resistor 15cand a voltmeter 15d.

[0074] Now, an equivalent circuit will be explained with reference to FIG. 4.

[0075] An AC power source 15aand a DC power source 15bare connected to the toner-feeding member 9bso that an electric current obtained by superposing an alternate current on a direct current flows through the toner-feeding member 9b. The toner-feeding member 9bassumes a first electrode C1 and the first antenna rod 9hopposed to the toner-feeding member 9bassumes a second electrode C2 thereby to provide a capacitor C.

[0076] In such an equivalent circuit, the electrostatic capacity of the capacitor C is varied with a dielectric constant between the electrodes C1 and C2. The dielectric constant is changed in accordance with the amount of toner between the toner-feeding member 9band the first antenna rod 9h. Accordingly, the magnitude of the differential waveform of AC components of the developing bias generated on both ends of the load-resistor 15cof the toner-remaining-amount detecting means 15 is varied in accordance with a change in the toner amount between the toner feeding member 9band the first antenna rod 9h, so that, by measuring such a signal by the voltmeter 15d, the toner-remaining-amount in the toner container 11A can be detected.

[0077] Next, the change in electrostatic capacity between the toner-feeding member 9band the first antenna rod 9hdetected in this way will be fully described.

[0078] FIGS. 8A and 8B through FIGS. 11A and 11B show processes in which the toner in the process cartridge B according to the first embodiment is gradually consumed; in particular, FIGS. 8B, 9B, 10B and 11B are graphs showing the relationship between the electrostatic capacity between the toner-feeding member 9band the first antenna rod 9h(ordinate) and the used time of the process cartridge B (abscissa) in each process.

[0079] As shown in FIG. 8A, when an upper surface 19 of the toner is located above a rotating area of the toner feeding member 9b, the toner always exists between the toner-feeding member 9band the first antenna rod 9hso that the electrostatic capacity does not change as shown the straight line u in FIG. 8B.

[0080] The toner-feeding member 9band the first antenna rod 9hare rotated simultaneously. As shown in FIGS. 9A and 10A, in the case where the toner upper surface 19 is located within the rotating area of the toner-feeding member 9b, a state in which the toner exists between the toner feeding member 9band the first antenna rod 9hwhen the toner feeding member 9band the first antenna rod 9hare below the toner upper surface 19 and a state in which the toner does not exist between the toner-feeding member 9band the first antenna rod 9hwhen the toner feeding member 9band the first antenna rod 9hare above the toner upper surface 19 are repeated periodically. In this way, the electrostatic capacity detected on the basis of the presence/absence of the toner between the toner-feeding member 9band the first antenna rod 9his periodically changed over a cycle period p. As the toner is gradually consumed, in one cycle period p, a time period t0 of the electrostatic capacity indicating the absent of toner (no toner) (value below the broken line L in FIGS. 9B and 10B) is gradually lengthened.

[0081] And, as shown in FIG. 11A, when the toner is consumed until the toner upper surface 19 reaches below the rotating area of the toner-feeding member 9b, the toner does not exist completely between the toner-feeding member 9band the first antenna rod 9h, with the result that, as shown in FIG. 11B, the detected electrostatic capacity has always a value indicating no toner and does not change.

[0082] That is to say, the toner-remaining-amount in the rotating area of the toner feeding member 9bcan be successively detected by always monitoring the electrostatic capacity between the toner-feeding member 9band the first antenna rod 9h, by dividing the values of the electrostatic capacity on the basis of the period p of rotation of the toner-feeding member 9band by checking the ratio of the time period of the value of the electrostatic capacity indicating no toner (or toner exists) within the period p.

[0083] FIG. 20 is a schematic view showing the relationship between a ratio of one cycle period p of rotation to a time period for which the electrostatic-capacity value indicating no toner is detected, and the toner-remaining amount. As shown in FIG. 20, in a range 100, the toner-remaining-amount can be successively detected by always monitoring the ratio of p/t0.

[0084] Detection of the toner-remaining-amount after the toner in the toner frame 11 was decreased below the rotating area of the toner feeding member 9bis effected by using a second antenna rod 9iprovided in the toner frame 11. Now, a successive toner-remaining-amount detecting mechanism using the second antenna rod 9iwill be fully explained.

[0085] FIG. 18 shows the relationship between the developing roller 9cand the second antenna rod 9i, and toner-remaining-amount detecting means 25, and FIG. 19 shows a fixing state of the second antenna rod 9i.

[0086] As shown in FIG. 18, the second antenna rod 9ihas a bent one end and is attached to the developing frame 12 (not shown here) with a constant distance between the developing roller 9cand the second antenna rod 9i.

[0087] The second antenna rod 9iis formed from a rod or a plate-shaped member made of non-magnetic metal, such as stainless steel, and has one end bent in a shape of a hook and attached to the toner frame 11 as shown in FIG. 19. The other end 9jof the second antenna rod 9iis supported in a recessed portion 11cof the toner frame 11, and the one end of the antenna rod 9iis secured and sealed by a toner-seal member 11bfitted into and attached to an antenna hole lid of the toner frame 11. The toner-seal member 11bis formed in a shape of a ring and made of an elastic material, and compressed between the second antenna rod 9iand the antenna hole 11d.

[0088] The bent one end of the second antenna rod 9iis located outside the toner frame 11 and forms a contact 18c. Namely, as shown in FIG. 7, the contact 18cis exposed to the bottom surface (along which the recording medium passes) of the toner frame 11 so that, when the process cartridge B is mounted to the main body 14 of the image forming apparatus, the contact 18ccontacts a contact (not shown) of the main body 14 of the image forming apparatus, thereby providing an electrical connection. Similarly, the developing roller 9cis also provided with a contact (not shown) exposed to the bottom surface of the developing frame 12 so that, when the process cartridge B is mounted to the main body 14 of the image forming apparatus, the contact (not shown) is contacted with a contact (not shown) of the main body 14 of the image forming apparatus, thereby providing an electrical connection. Through these contacts, a developing bias is applied to the developing roller 9c, and the second antenna rod 9iis connected to the second toner-remaining-amount detecting means 25.

[0089] Next, a toner-remaining-amount detecting mechanism for the second antenna rod 9iof the process cartridge B according to the illustrated embodiment will be explained.

[0090] As shown in FIGS. 3 and 18, the process cartridge B according to the illustrated embodiment is provided with the second antenna rod 9iextending substantially in parallel with the developing roller 9cand is adapted to detect the amount of toner between the developing roller 9cand the second antenna rod 9i.

[0091] The second antenna rod 9iserves to detect the amount of toner between the developing roller 9cand the second antenna rod 9iand forms a part of the second toner-remaining-amount detecting means 25.

[0092] The toner-remaining-amount detecting means 25 of the second antenna rod 9iis similar to the above-mentioned first toner-remaining-amount detecting means 15 and serves to detect the toner-remaining amount by detecting the electrostatic capacity between the developing roller 9cand the second antenna rod 9i.

[0093] The electrostatic capacity detected by the second antenna rod 9iis varied with the amount of toner between the developing roller 9cand the second antenna rod 9i. As the toner is gradually decreased between the developing roller 9cand the second antenna rod 9i, the electrostatic capacity detected by the second antenna rod 9iis reduced accordingly, and, when the toner does not exist between the developing roller 9cand the second antenna rod 9i, the electrostatic capacity does not change from a certain value. That is to say, while the electrostatic capacity detected by the second antenna rod 9iis being changed, the amount of toner between the developing roller 9cand the second antenna rod 9ican be estimated on the basis of the value of the electrostatic capacity, thereby successively detecting the toner-remaining amount between the developing roller 9cand the second antenna rod 9i.

[0094] FIG. 21 is a schematic view showing the relationship between the electrostatic capacity detected between the developing roller 9cand the second antenna rod 9i, and the toner-remaining-amount. As shown in FIG. 21, in a range 101, the toner-remaining amount can successively be detected by always monitoring the electrostatic capacity detected between the developing roller 9cand the second antenna rod 9i.

[0095] Further, in the illustrated embodiment, the toner-remaining-amount is successively detected substantially throughout the service life of the process cartridge B by using both the first and second antenna rods 9h, 9i. Such detection is as follows.

[0096] The first and second antenna rods 9h, 9iare positioned so that the ranges 100 and 101 shown in FIGS. 20 and 21 are overlapped without fail.

[0097] As shown in FIG. 11A, when the amount of toner in the toner container 11A is decreased below the rotating area of the toner-feeding member 9b, the value of the first electrostatic capacity detected by the first antenna rod 9hbecomes constant.

[0098] The main body 14 of the image forming apparatus according to the illustrated embodiment is provided with control means (not shown) for interchanging between the first and second toner-remaining-amount detecting means.

[0099] When the fact that the first electrostatic capacity, detected by the first antenna rod 9his not changed periodically, is detected by the control means (not shown) of the main body 14 of the image forming apparatus, the detection system of the toner remaining amount is interchanged, by the control means in a software manner, to the detection of toner-remaining amount effected by using the second electrostatic capacity detected by the second antenna rod 9iand the second toner-remaining-amount detecting means 25. After the interchanging, the toner remaining amount is detected by using the second antenna rod 9iand the second toner-remaining-amount detecting means 25 as mentioned above.

[0100] Naturally, since the respective relationships between the electrostatic capacities obtained from the antenna rods and the toner-remaining amount are not the same, control means (not shown) for calculating the estimated toner-remaining amount based on the detected electrostatic capacity must be interchanged at the same time when the detection system is interchanged to match the corresponding antenna rod. In this case, the interchanging may be effected in a software manner as mentioned above.

[0101] As mentioned above, by interchanging the detection system of the toner-remaining amount by using the first and second antenna rods 9h,9i,the toner-remaining amount can successively be detected substantially throughout the service life of the process cartridge B.

[0102] With the arrangement as mentioned above, the remaining amount of toner in the toner container 11A can successively be detected on the basis of the change in electrostatic capacity between the toner-feeding member 9band the first antenna rod 9hand the change in electrostatic capacity between the developing roller 9cand the second antenna rod 9i,and, thus, by informing the user of the detected toner-remaining amount successively through informing means, such as a monitor, the user can easily know the amount of toner remaining in the process cartridge B. Incidentally, the electrostatic capacity between the developing roller 9cand the second antenna rod 9iis created by the developing bias applied to the developing roller 9c.

[0103] In the above-mentioned arrangement, the closer the toner container approaches a cylindrical shape, the greater the effect is achieved.

[0104] [Second Embodiment]

[0105] Now, a second embodiment of the present invention will be explained with reference to the accompanying drawings. Incidentally, in the second embodiment, since the main constructions of the electrophotographic image forming apparatus and the process cartridge B are the same as those in the first embodiment, an explanation thereof will be omitted.

[0106] FIG. 12 is a sectional view of a process cartridge B according to the second embodiment. Further, FIG. 13 shows the positional relationship between a toner-feeding member 9band a first antenna rod 9h,and toner-remaining-amount detecting means 15. Incidentally, a support member 16 is illustrated similar to FIG. 1.

[0107] In the first embodiment of the present invention, the distance between the toner-feeding member 9band the first antenna rod 9his widely set not to clog the toner therebetween. However, since the narrower such distance, the greater the change in electrostatic capacity detected by the first antenna rod 9h,detecting accuracy is improved accordingly.

[0108] Thus, in the second embodiment of the present invention, the distance between the toner-feeding member 9band the first antenna rod 9his decreased as narrow as possible so long as the developing bias applied to the toner feeding member 9bdoes not leak to the first antenna rod 9h.Such a distance is preferably about 2 mm to 5.5 mm.

[0109] Further, an elastic member (plastic sheet in the illustrated embodiment) 20 having an L-shaped cross-section is disposed within the toner container 11A to be in contact with the toner feeding member 9band the first antenna rod 9hat an uppermost position of rotation of the toner-feeding member 9b.The elastic member 20 is so located that a distal end 20aof the member contacts the toner between the toner feeding member 9band the first antenna rod 9hin a whole longitudinal area of the toner-feeding member 9band is fixedly held by the toner container 11A via an elastic-member holding member 21. Further, the elastic member 20 has sufficient elasticity to drop the toner between the toner-feeding member 9band the first antenna rod 9hby shock or vibration when the elastic member comes into contact with the rotating toner-feeding member 9band not to prevent the toner-feeding member 9bfrom rotating.

[0110] Further, as shown in FIG. 13, a cut-away portion 16gis formed in a part of periphery of the contact member 16dslidingly contacting the contact member 18ato interrupt the electrical connection (between these contacts) for a very short time, and the timing of the interruption is synchronized with the timing of contact between the elastic member 20 and the toner feeding member 9b.A signal indicating the interruption is detected by the toner-remaining-amount detecting means 15, and a time period from the signal to an area in which the toner exists is monitored.

[0111] That is to say, as shown in FIG. 12, in a state in which the toner upper surface 19 is located within the rotating area of the toner-feeding member 9bas a result that the toner is consumed, when the toner feeding member 9band the first antenna rod 9hare rotated to move to the toner non-existing area from the toner existing area through the toner upper surface 19, the toner may be clogged between the toner-feeding member 9band the first antenna rod 9h.In this state, the toner non-existing area cannot be detected. To avoid such inconvenience, the toner between the toner-feeding member 9band the first antenna rod 9his surely scraped off by the elastic member 20. And, a time period t22 from a time when the toner is scraped off to a time when the toner-feeding member 9band the first antenna rod 9hreach the toner upper surface 19 again (in the state in which there is no toner between the toner-feeding member 9band the first antenna rod 9h) is detected on the basis of the change in electrostatic capacity similar to the first embodiment of the present invention.

[0112] With the arrangement as mentioned above, on the basis of the change in electrostatic capacity between the toner-feeding member 9band the first antenna rod 9hand the change in electrostatic capacity between the second antenna rod 9iand the developing roller 9cdetected by the similar arrangement as the first embodiment, the remaining amount of toner in the toner container 11A can successively be detected with high accuracy. By informing the user of the detected toner-remaining amount successively through the informing means such as a monitor, the user can easily the how amount of toner remaining in the process cartridge B. Incidentally, in the illustrated embodiment, as shown in FIG. 2, a display portion 100 is provided. The display portion 100 can successively indicate the toner-remaining amount by moving a pointer 100a.In the above-mentioned embodiments, as an example in which the agitating portion is provided with the antenna portion, the toner feeding member 9band the first antenna rod 9hwas explained. However, the agitating portion may be constituted by a non-conductive plastic sheet and first and second electrodes may be provided on the plastic sheet.

[0113] In the process cartridge B according to the second embodiment of the present invention, since the cut-away portion 16gdetects the optimum posture timing of the toner-feeding member 9b,so long as the electrical connection is interrupted at that timing, it is not limited to the cut-away portion. For example, in place of the cut-away portion. For example, in place of the cut-away portion, a non-conductive coating or a projection may be provided.

[0114] Alternatively (instead of the interruption due to the cut-away portion 16g), for example, as shown in FIG. 14, a sensor 23 for detecting falling of the elastic member 20 (for example, detecting a movement of a rod or a plate-shaped member rotated by the falling of the elastic member) may be provided in a direction along which the elastic member 20 is fallen, thereby detecting the optimum posture timing starting the toner detection of the toner-feeding member 9b.

[0115] Further, as shown in FIG. 15, in place of the elastic member 20, an arrangement in which a plate-shaped rigid member 24ahaving an L-shaped cross-section is rotatably supported by a hinge portion 24bat its proximal end so that the plate-shaped member 24asuspended from the hinge portion 24bby its own weight may be used. In this case, by using the arrangement including the cut-away portion 16gdescribed in connection with the second embodiment, the optimum posture timing of the toner-feeding member 9bstarting the toner detection may be detected.

[0116] Further, the cross-section of each of the elastic member 20 and the plate-shaped member 24ais not limited to the L-shape, but, for example, as shown in FIGS. 16 and 17, a free end or distal end of the elastic member 20 may be formed as a plurality of leveled or curved surface portions arranged in a line, such as plate-shaped end portions 20bor semi-circular end portions 20cwhich can be opposed to a space between the toner-feeding member 9band the first antenna member 9hto achieve the same effect.

[0117] In the above-mentioned embodiments, while the process cartridge detachably mountable to the main body of the electrophotographic image forming apparatus, and the electrophotographic image forming apparatus to which the process cartridge can detachably be mounted and which is adapted to form the image on the recording medium were explained, the present invention can be applied to a developing device detachably mountable to a main body of an electrophotographic image forming apparatus, and an electrophotographic image forming apparatus to which a developing device can detachably be mounted and which is adapted to form an image on a recording medium. Further, the present invention can also be applied to an electrophotographic image forming apparatus in which a process cartridge is not used. In addition, according to the above-mentioned embodiments, while an example in which the movable antenna member is provided on the agitating member was explained, the present invention is not limited to the example.

[0118] As mentioned above, according to the present invention, in the developing device, the antenna member is moved through the toner within the toner-containing portion and the toner remaining-amount is detected on the basis of the change in electrostatic capacity between the electrodes of the antenna member so that the toner-remaining amount in the moving area of the antenna member can successively be detected with high accuracy, thereby providing a developing device in which a service life thereof can easily be guessed by the user.

[0119] Further, according to the present invention, the first antenna member is movable and serves to detect the remaining amount of toner in the toner-containing portion. And, since the second antenna member is fixed and, since the second antenna member detects the toner remaining amount on the basis of the change in electrostatic capacity between the second antenna member and the developing member, the remaining amount of almost all of toner in the toner-containing portion can successively be detected with high accuracy, thereby providing a developing device in which a service life thereof can easily be guessed by the user.

[0120] Since the movable antenna member also acts as an agitating member, it is not required that an additional agitating member is provided.

[0121] The above-mentioned effects or advantages can be achieved by a process cartridge including developing means having the same construction as that of the above-mentioned developing device.

[0122] Further, according to the electrophotographic image forming apparatus to which the developing device or the process cartridge can detachably be mounted, the service life of the developing device or the process cartridge can be estimated with leaving a margin.

[0123] While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.