Developing device and power supply connection for applying developing bias voltage

Abstract: A developing device includes a rotatable developer carrying member (12) for carrying a developer to develop an electrostatic image formed on an image bearing member with a developer; wherein the developer carrying member includes a first cylindrical portion (12) and a second cylindrical portion (100) provided at an end of the first cylindrical portion (12) and supported by a bearing portion (300); a first electroconductive portion (500) extended from an outside of the second cylindrical portion (100) into an inside and electrically connected to an electroconductive portion (600) outside the developing device with a gap from an inner surface (105b) of the second cylindrical portion (100); a second electroconductive portion (400) contacted to an inner surface of the first cylindrical portion and rotatable with the first cylindrical portion and slidable on the first electroconductive portion (500); wherein a developing bias is applied to the first cylindrical portion (12) through the first and second electroconductive portions (500,400) from the electroconductive portion (600) outside of the developing device whereby the slidable contact (401,500a) between the first and second electroconductive portions is positioned within the first cylindrical portion (12).

Description: FIELD OF THE INVENTION AND RELATED ART The present invention relates to a developing device and an electric energy supply part for applying a developing bias to a developer carrying member. In a conventional apparatus for forming a multi-color image through an electrophotographic image formation process, a plurality of developing devices accommodating developers having different colors are provided on a rotary selecting mechanism; an electrophotographic photosensitive member (photosensitive drum) is electrically charged uniformly by a charging device and is selectively exposed to light so that an electrostatic latent image is formed; and the selecting mechanism is operated so as to place a developing roller as a developer carrying member (developing means) of a developing device accommodating a predetermined color developer (toner) to the photosensitive drum. The developing roller is rotated while being supplied with a developing bias so that electrostatic latent image on the photosensitive drum is developed into a toner image. The toner image is transferred onto a recording material, and the developing and transferring operations are repeated for the respective colors, thus providing a multi-color image. Recently, a process cartridge containing as a unit process means such as the photosensitive drum, the developing means actable on the photosensitive drum, the charging means, cleaning means or the like has been developed. As for a developing device or process cartridge, a proposal for a structure of an electric power supply contact of a developing bias to a developing roller (developing means) has been made in US-A-5634175 wherein a flange member of an electroconductive member is provided at an end of a developing roller; an electrode in the form of a compression coil spring is mounted to the flange member for electrical conduction; an end of the compression coil spring is contacted to a contact member which is mounted to a housing of the developing device and which is electrically conducted to the electric energy supply member provided in the main assembly of the apparatus when the developing device is mounted to the main assembly of the apparatus. US-A-5739900 shows an earthing contact for a photosensitive drum wherein a contact element makes sliding contact with the interior of the drum. Another structure for the electric power supply contact for the developing bias to the developing roller (developing means) is seen in EP-A-0549400, in which an elastic contact portion is provided in the contact member, and the elastic contact portion is contacted to the flange member of an electroconductive member provided at an end of the developing roller. In the case of the electric power supply contact structure, the compression coil spring is rotated integrally with the developing roller, and slides relative to the coil spring, and therefore, in general, grease is applied to the sliding portion. In the latter case of the electric power supply contact structure, the flange member is rotated integrally with the developing roller, and slides relative to the elastic contact member, and therefore, in general, electroconductive grease is applied to the sliding portion. In addition, in the latter electric power supply contact structure, in order to stabilize the contact pressure of the sliding contact portion to the flange member of the elastic contact member, the spring constant of the elastic contact member is desirably minimized to make the degree of deformation larger. In such a case, a space is required to assure the deformation of the elastic contact member between the developing roller and the supporting frame supporting the developing roller in the developing device or the process cartridge. SUMMARY OF THE INVENTION The present invention is concerned with a further development of the art, and it is a principal object of the present invention to provide a developing device in which a space applied by the electric power supply contact mechanism for the developer carrying member is reduced with the improved reliability of the contact portion of the electric power supply contact. It is another object of the present invention to provide an electric energy supply part for supplying electric energy (developing bias voltage) to the developer carrying member with contact electric power supply contact for supplying electric power to the developing roller. 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. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an illustration of a major part of a main assembly of a developing device and an electrophotographic image forming apparatus according to an embodiment of the present invention. Figure 2 is an illustration of mounting a developing device to a rotary unit of the electrophotographic image forming apparatus. Figure 3 is an illustration of mounting the developing device to the rotary unit of the electrophotographic image forming apparatus. Figure 4 is a sectional view of a major part of a yellow developing device (magenta developing device or cyan developing device) to be mounted to the electrophotographic image forming apparatus. Figure 5 is a sectional view of a major part of a black developing device to be mounted to the electrophotographic image forming apparatus. Figure 6 is a perspective view illustrating an opening state of a shutter of a developing device. Figure 7 is a perspective view of a developing device as seen from an opposite side of Figure 6. Figure 8 is an exploded perspective view of a developing device. Figure 9 is a perspective view of an outer appearance of an end surface of a developing roller. Figure 10 is a sectional view of a developing roller. Figure 11 is a sectional view of a developing roller taken along a direction perpendicular to a direction of Figure 10. Figure 12 is a sectional view of a developing roller taken along a line perpendicular to an axis thereof. Figure 13 is a sectional view of a developing roller taken along a line perpendicular to the axis. Figure 14 is a schematic illustration of an electric energy supplying structure to the developing roller. Figure 15 is a perspective view of an outer appearance of a holder member. Figure 16 is a perspective view of an outer appearance of a roller electrode plate (second electroconductive portion). Figure 17 is an illustration of a contact portion of a frame electrode plate (third electroconductive portion) and an electrode shaft (first electroconductive portion) which are integral, according to another embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS The description will be made as to the embodiments of the present invention in conjunction with the accompanying drawings. In the following description, !"longitudinal direction!" of a developing device means a direction parallel to the direction of mounting-and-demounting of the developing device relative to a main assembly of an electrophotographic image forming apparatus, which is also parallel to a surface of a recording material and crossing with (substantially perpendicular to) a feeding direction of the recording material. Referring to Figures 1 to 11, the description will be made as to the electrophotographic image forming apparatus according to this embodiment. (General arrangement of electrophotographic image forming apparatus) Referring to Figure 1, the description will be made as to a general arrangement of the electrophotographic image forming apparatus in the form of a color electrophotographic image forming apparatus. Figure 1 shows a general arrangement of a color laser beam printer which is an example of a color electrophotographic image forming apparatus. The color laser beam printer (electrophotographic image forming apparatus) comprises an image formation station including an electrophotographic photosensitive member 1 in the form of a drum (photosensitive drum) rotating at a constant speed, rotatable developing devices D (Dy, Dm, Dc, Db), and an intermediary transfer member 4 for carrying a color image superimposedly transferred thereonto by the image formation station and for transferring the color image onto a transfer material P (recording material) such as a recording paper, OHP sheet or the like fed from a sheet feeder by feeding means 5. The transfer material P now having the transferred color image is fed to a fixing portion 7 where the color image is fixed on the transfer material P, and is then discharged to a discharging portion 8 provided at a top of the apparatus, by discharging rollers 5f. The rotatable developing devices D are individually detachably mountable to a main assembly 30 of the printer as a main assembly of the electrophotographic image forming apparatus. The description will be made as to various parts of the electrophotographic image forming apparatus. (Process Cartridge) A process cartridge U used in the electrophotographic image forming apparatus of this embodiment contains as a unit the photosensitive drum 1 and a cleaner container 9a of a cleaning device 9 which function as a holder for the photosensitive drum 1. The process cartridge U is detachably mountablely supported on the main assembly 30 of the printer, and can be easily exchanged as a unit when the lifetime of the photosensitive drum 1 is reached. The photosensitive drum 1 of the present invention comprises an aluminum cylinder having a diameter of approx. 50 mm aluminum cylinder and an organic photoconductive layer on the outside thereof, and is rotatably supported on the cleaner container 9a of the cleaning device 9. Around the photosensitive drum 1, there are provided a cleaning blade (cleaning means) 9b for removing the toner remaining on the photosensitive drum 1 and primary charging means 2 for uniformly charging the surface of the photosensitive drum 1. The photosensitive drum 1 is rotated in a couterclockwise direction in the Figure in accordance with the image forming operation by a driving force from a driving motor at one of the opposite ends of the drum. (Charging Means) The charging means 2 charges the drum through a contact charging method, wherein an electroconductive roller is contacted to the photosensitive drum 1, and the electroconductive roller is supplied with a voltage, by which the surface of the photosensitive drum 1 is uniformly charged. (Exposure Means) The photosensitive drum 1 is exposed to image light using a k said photosensitive drum 1 k. More particularly, when an image signal is supplied to a laser diode, the laser diode projects image light corresponding to the image signal to the polygonal mirror 3a. The polygonal mirror 3a is rotated at a high speed, and the image light reflected by the polygonal mirror 3a is selectively projected via imaging lens 3c and reflection mirrors 3d to the surface of the photosensitive drum 1 which is rotating at a constant speed so that electrostatic latent image is formed on the photosensitive drum 1. (Developing Device) The developing device D includes the four developing devices Dy, Dm, Dc, Db for effecting development to provide yellow, magenta, cyan and black images, respectively. The developing devices D are detachably mountablely supported on a rotary unit 11 which rotates about a shaft 10 as shown in Figure 1 to Figure 3. In the image forming operation, the rotary unit 11 supporting the developing devices D rotates about the shaft 10 so as to face a predetermined one of the developing devices D to the photosensitive drum 1 and stop it there, and then the developing roller 12 as the developing means is positioned relative to the photosensitive drum 1 with a fine clearance (approx. 300 µm) therefrom, and then develops the electrostatic latent image. During the color image formation, the rotary unit 11 rotates one full turn for one full turn of the intermediary transfer member 4, and the yellow developing device Dy, the magenta developing device Dm, the cyan developing device Dc and the black developing device Db carries out the developing process in the order named. In Figure 4, the yellow developing device Dy is shown as being positioned to the position facing to the process cartridge U. The developing device Dy feeds the toner from the toner container 63a to the toner supplying roller 19 by a toner feeding mechanism 15, non- magnetic one component toner (developer) is applied in the form of a thin layer onto an outer periphery of a developing roller 12 rotating in a counterclockwise direction in the Figure by means of a toner supplying roller 19 rotating in the counterclockwise direction and a developing blade 16 press-contacted to the outer periphery of the cylindrical developing roller 12 (developer carrying member), during which the toner is given charge (triboelectric charge). By applying a developing bias voltage to the developing roller 12 opposed to the photosensitive drum 1 on which the formation is formed, the toner is deposited to the photosensitive drum 1 in accordance with the latent image. The toner development is carried out for each of the magenta developing device Dm, the cyan developing device Dc and the black developing device Db through the similar mechanism. The developing roller 12 of each of the developing devices D is connected with a driver (unshown), and a high voltage source for the color development provided in the main assembly 30 of the printer when the developing device D is rotated to the development position. The developing roller and the electric energy supplying structure for the developing roller will be described hereinafter. The developing device Dy, the magenta developing device Dm and the cyan developing device Dc shown in Figure 4 have the same structure. In each of the color developing devices Dy, Dm, Dc, the toner supplying roller 19 having a peripheral surface moving in direction opposite from the moving direction of the peripheral surface of the developing roller 12 is rotatably mounted to the developing member supporting frame 63A which is a frame constituting a part of the cartridge frame 63. The black developing device Db shown in Figure 5 does not have a toner supplying roller. The toner (developer) is deposited onto the developing roller 12 by the magnetic force and depositing force, and the toner layer thickness is regulated by a developing blade 16 contacted to the peripheral surface of the developing roller 12, and also, triboelectric charge is produced on the toner. (Intermediary Transfer Member) The intermediary transfer member 4 functions to receive a plurality of toner image which are sequentially and superposedly transferred thereonto from the intermediary transfer member 4 (1 next transfer), and transfer the superposed toner images all together onto the transfer material P (2 next transfer). The transferring device 4 is provided with an intermediary transfer belt 4a which travels in the direction indicated by an arrow R4. The intermediary transfer belt 4a in this embodiment is extended around three rollers, namely, a driving roller 4b a 2next transfer pair roller 4c and a follower roller 4d. Adjacent the follower roller 4d, there is provided a confining roller. The confining roller 4j is movable between a position where it urges the intermediary transfer belt 4a to the photosensitive drum 1 and a position where the transfer belt 4a is away from the photosensitive drum 1. The intermediary transfer belt 4a travels in the direction indicated by an arrow R4 by rotation of the driving roller 4b. A cleaning unit 4e which is movable toward and away from the surface of the intermediary transfer belt 4a is provided at a predetermined position outside the intermediary transfer belt 4a. The cleaning unit 4e functions to remove the untransferred toner which remains on the intermediary transfer belt 4a after the 2next transfer which transfers the toner images all together onto the transfer material P. The cleaning unit 4e brings the charging roller 4f into contact with the intermediary transfer belt 4a to apply to the toner the charge having a polarity opposite from that during the transfer operation. The toner now having the opposite polarity charge is electrostatically attracted to the photosensitive drum 1, and thereafter, is collected by means of the cleaning device 9 for the photosensitive drum 1 which will be described hereinafter. The cleaning method for the intermediary transfer belt 4a is not limited to the electrostatic cleaning, and may be a blade, a fur brush (mechanical) or the like or a combination thereof. (Cleaning Device) The cleaning device (cleaning means) removes the toner remaining on the photosensitive drum 1 after the transfer of the toner onto the intermediary transfer member 4, by the cleaning blade 9b, thus cleaning the photosensitive drum 1. The removed toner T is accumulated in the cleaner container 9c. The cleaner container 9c has such a capacity that it does not become full before the lifetime o the photosensitive drum 1, and therefore, the cleaner container 9c is exchanged with fresh one together with the exchange of the photosensitive drum 1. (Sheet Feeder) The sheet feeder 5 functions to feed the transfer material P to the image formation station, and comprises a cassette 5a accommodating a plurality of transfer material P, a sheet feeding roller 5b, a feeding roller 5c1, and a retarding roller 5c2 for double feeding prevention, a sheet feeding guide 5g and a registration roller 5e. During the image forming operation, the sheet feeding roller 5b is rotated with the image forming operation to feed the transfer materials P one by one from the cassette 5a and guides it by the guiding plate 5g to the registration roller 5e via a feeding roller 5c1. During the image forming operation, the operation of registration roller 5e driven in a predetermined sequences includes a non- rotation period in which the transfer material P is at rest, and a rotation period in which the transfer material P is fed to the intermediary transfer member 4, by which the image on the photosensitive member is aligned with the transfer material P for the next transfer step. (Fixing Portion) The fixing portion 7 fixes the toner image the toner image transferred onto the transfer material P from the intermediary transfer member 4. The fixing portion 7 comprises a fixing roller 7a for applying heat to the transfer material P and a pressing roller 7b for press-contacting the transfer material P to the fixing roller 7a, the rollers 7a, 7b are hollow rollers and contain therein respective heaters. One of the rollers are driven to feed the transfer material P. The transfer material P carrying the toner image is fed by the fixing roller 7a and the pressing roller 7b, during which toner is fixed on the transfer material P by heat and pressure. (Mounting of Developing Device to Main Assembly of the Image Forming Apparatus) Referring to Figures 2 and 3, the description will be made as to mounting of the developing device. First, an unshown switch on the main assembly 30 of the printer is depressed, in response to which the rotary unit 11 is rotated until the position thereof for the developing device D to be mounted comes to a predetermined mounting position. Then, a cover 18 for a developing device inserting opening 17 formed in a part of the main assembly 30 of the printer, is opened. Normally, the inserting opening 17 is kept closed by the cover 18. A guiding rib 70 provided on a side surface of a shutter 64, which will be described in detail hereinafter (Figure 6), of the developing device D is brought into alignment with a cartridge guide 59 (Figure 2) provided on an inner wall of the rotary unit 11 in the main assembly 30 of the printer, and then developing device D is pushed in (Figure 3). A grip portion 63f (Figure 7) provided on the cartridge frame 63 of the developing device D is pushed in the direction of an arrow shown in Figure 2 by hand(s), by which only the cartridge frame 63 rotates while the shutter 64 is fixed on the rotary unit 11 to expose the developing roller 12, thus establishing the operable state. (Shutter Structure) Referring to Figure 6 to Figure 8, the shutter 64 will be described. As shown in Figure 8, each of the longitudinal end walls 64e, 64f of the shutter 64 is provided with a round hole 64a, and by engagement between the round hole 64a and the projected portions 63c and, 63g, the shutter 64 is rotatably mounted to the cartridge frame 63. As shown in Figures 6, 7, the shutter 64 is movable between a position where it covers the developing roller 12 and a retracted position where the developing roller 12 is exposed, and when the developing device D is dismounted from the main assembly 30 of the printer, the shutter 64 is closed. Therefore, the developing device D is protected from dust or the like deposition and/or the damage of the developing roller 12. Adjacent the projected portion 63c of the cartridge frame 63, a locking member 71 for locking the shutter 64 in the closed state. The locking member 71 has an engaging portion 71b and an arm portion 71a having an elasticity. On the other hand, at a predetermined position in the wall 64e of the shutter 64, an engaging recess 64t is provided for engagement. By this, when the shutter 64 is closed, the said engaging portion 71b is engaged with the engaging recess 64t so that shutter 64 is locked in the closed state to prevent the shutter from being inadvertently opened. When the developing device D is mounted to the main assembly 30 of the printer, the locking is automatically released to open. The side wall 64e of the shutter 64 is provided with a round hole 64u, and a side wall 63h of the cartridge frame 63 is provided with a semi-spherical projection 63d correspondingly. Therefore, when the shutter 64 is in the closed state, the round hole 64u is engaged with the semi-spherical projection 63d, so that even if the locking of the shutter 64 is released, the cartridge frame 63 is not rotatably relative to the shutter 64 to an unstable position. (Structure of Developing Roller and Structure of Electric Power Supply Contact to Developing Roller) Referring to Figure 9 to Figure 16, the description will be made as to the structure of the developing roller and the structure of the electric power supply contact to the developing roller. Figure 9 is a perspective view of an outer appearance of an end surface of the developing roller in the embodiment; Figure 10 is a sectional view of the developing roller; Figure 11 is a sectional view of the developing roller taken along a perpendicular plane; Figure 12 and 13 is a sectional view of the developing roller taken along a perpendicular plane; Figure 14 is a schematic illustration of an electric power supply contact for the developing roller; Figure 15 is a perspective view of an outer appearance of a holder member; and Figure 16 is a perspective view of an outer appearance of a roller electrode plate which is a second electroconductive portion. As shown in Figures 10, 11, an end of a large diameter portion (first cylindrical portion) of the developing roller 12 is provided with a flange member (second cylindrical portion) 100 in the form of a shaft made of metal material such as aluminum. The outer diameter of the flange member 100 is smaller than an outer diameter of the large diameter portion. The flange member 100 has a press-fitting portion 105c, which is press- fitted into inner a press-fitting circumference 12c of the developing roller 12 so as to be non- rotatable relative to the large diameter portion of the developing roller 12. The flange member 100 of this embodiment is provided with a press-fit portion 105c into which the developing roller 12 is press-fitted, a mounting hole 105a into which an insulative holder member 300 which will be described hereinafter is press-fitted. The mounting hole 105a is provided radially inside of the press-fit portion 105c adjacent the press-fit portion 105c. The flange member 100, as shown in Figure 9, is provided with an engaging shaft portion 103 extending from a shaft portion 104 which is in turn extended axially from an end of the developing roller 12. The engaging shaft portion 103 is provided with parallel flats 101 and an arcuate abutment portion 102. To the engaging shaft portion 103, a drive transmitting member in the form of a gear 200 is mounted. The gear 200 is provided with an engaging hole 201 engageable with the parallel flats the engaging shaft portion 103, and by the engagement therebetween, they are rotatable integrally with the developing roller 12. An abutment portion 102 at the inboard end of flat 101 is contacted to the developing roller 12 side surface of the gear 200 to determine the mounting position of the gear 200 to the engaging shaft portion 103. To the other end of the developing roller 12, an unshown flange member (small diameter portion) is non- rotatably mounted to the developing roller 12 in the similar manner as with the flange member 100, and the flange member and the shaft portion 104 provided on the flange member 100 is supported by the bearing portion (unshown) provided in the developing device D. The gear 200 is rotated by a driving source (unshown) provided in the main assembly 30 of the printer to rotate the developing roller 12. In this embodiment, both of the flange members 100 are made of lateral such as aluminum. Therefore, the support rigidity for the developing roller 12 is improved. Accordingly, the accuracy of rotation of the developing roller 12 is improved. In this embodiment, the flange member 100 and an electrode shaft 500 (first electroconductive portion) are not contacted with each other. Therefore, the developing bias is not supplied from the flange member 100. The description will be made as to the structure in the developing roller 12. The flange member 100 is provided with a mounting hole 105a for mounting a holder member 300 which will be described hereinafter and a through hole 105b through which the electrode shaft 500 is penetrated, and they are arranged along an axis of the developing roller 12. The holder member 300 has a press-fit portion 301 which is press-fitted into a mounting hole 105a provided radially inside of the press-fit portion 105c of the flange member 100. Thus, in this embodiment, the mounting hole 105a is formed adjacent the press-fit portion 105c of the flange member 100 (radially inside of the press-fit portion 105c), and the press-fit portion 301 of the holder member 300 is press- fitted into the mounting hole 105a, so that outer diameter of the press-fit portion 105c can be made slightly larger. By doing so, the press-fitting force between the flange member 100 of the developing roller 12 and the press-fit portion 105c is raised so that reliability of the fastening of the flange member 100 relative to the developing roller is assured. The holder member 300 is provided with a cylindrical portion 302 having a diameter which is smaller than the inner diameter of the large diameter portion of the developing roller 12 and which is larger than the press-fit portion 301. To an end of the cylindrical portion 302, a second electroconductive portion (electric energy supply part) of electroconductive material (for example, a Cu alloy, Fe, gold, stainless steel, or the like), in the form of an electrode plate (roller electrode plate) 400 is fixed. More particularly, the roller electrode plate 400 is fixed to the free end of the cylindrical portion 302 by a disk-like substrate 404 functioning as a base formed to have substantially the same outer diameter as the outer diameter of the cylindrical portion 302. The substrate 404 of the roller electrode plate 400 and the cylindrical portion 302 of the holder member 300 are fixed to each other by welding, ultrasonic welding, bonding or the like. The roller electrode plate 400 has first arm portions (first contact portions) 402 at diametrically opposite positions of the substrate 404, which are contacted to the inner surface of the large diameter portion of the developing roller 12 so as to be electrically connected. The first arm portion 402, as shown in figures 10 and 16, is provided such that force is applied against a direction of removal of the holder member 300 from the flange member 100. The first arm portion 402 is disposed downstream of the base 404 with respect to the direction of the force which the second arm portion 401 receives from the first electroconductive portion 500. Therefore, the holder member 300 is prevented from separating from the flange member 100. The roller electrode plate 400 is provided with a second arm portion (second contact portion) 401 elastically contacted to the elastic of the contact portion 500a electrode shaft 500 which will be described hereinafter, at a radially outer end position of the substrate 404. The second arm portion is extended in a direction perpendicular to the first arm portion 402 (Figures 12, 13). The first arm portions 402 and the second arm portion 401 are extended in directions crossing with the substrate 404. The first arm portion 402 and the second arm portion 401 are extended in different directions. The first arm portions 402 and the second arm portion 401 are provided by bending parts of the substrates 404. The second arm portion 401 is connected to the substrate 404 through the elastic portion 403 extending in a direction parallel to the axis direction of the developing roller 12. The elastic portion 403 enters the cut-away portion 302a (Figures 12, 15), and retains such that second arm portion 401 is opposed to the engaging hole 304 which will be described hereinafter, in the cylindrical portion 302. The holder member 300 has a partition wall 303 between the press-fit portion 301 and the cylindrical portion 302, and an engaging hole 304 is formed in the partition wall 303. The engaging hole 304 is provided adjacent a position where the contact portion 500a of the electrode shaft 500 and the arm portion 401 of the second are contacted to each other. On the other hand, as shown in Figure 14, a third electroconductive portion in the form of an electrode plate (frame electrode plate) 600 is mounted to a developing member supporting frame 63A constituting a part of the cartridge frame 63. The frame electrode plate 600 is provided with a contact portion 600a so as to be exposed to outside through a hole portion 63v formed in the developing member supporting frame 63A. When the developing device D is mounted to the main assembly 30 of the printer, it is electrically connected to an electrode member (unshown) (main assembly side electroconductive portion) electrically connected to a voltage source provided in the main assembly 30 of the printer. To the frame electrode plate 600, an electrode shaft 500 (first electroconductive portion) made of circular column shaped or cylindrical electroconductive material is mounted and is electrically connected. As for a connecting method between the electrode shaft 500 and the frame electrode plate 600, crimping method, caulking method or a method in which a contact portion is provided in the frame electrode plate 600 to which an electrode shaft 500 is elastically contacted, or the like, is usable. Alternatively, an electrode shaft 500 is fastened on an unshown electroconductive member (for example, plate of stainless steel) by crimping or the like, and the electroconductive member and the frame electrode plate 600 are electrically connected. Furthermore, the electrode shaft 500 and the contact portion 600a of the frame electrode plate 600 may be integrally formed, and it may be mounted to the developing member supporting frame 63A. The electrode shaft 500 is provided at an end of the shaft portion 500b with a contact portion (sliding contact portion) 500a for electrical connection with the roller electrode plate 400. The contact portion 500a is preferably spherical from the standpoint of smooth sliding contact of the second arm portion 401 of the roller electrode plate 400 when the developing roller 12 is rotated. In order to minimize the wearing due to sliding motion, grease is preferably present at the contact portion between the contact portion 500a and the arm portion 401. As shown in Figure 14, a shaft portion 500b of the electrode shaft 500 is penetrated through a through hole 105b formed in the flange member 100 with a gap from the inner surface of the through hole 105b, and is engaged with an engaging hole 304 provided in the holder member 300. The contact portion 500a is contacted by the second arm portion 401 of the electrode plate 400 with an urging force toward the frame electrode plate 600. The dimensions of the inner diameter of the engaging hole 304 and the outer diameter of the electrode shaft 500 are selected in consideration of the part accuracy and the part mounting accuracy or the like, it is preferable that with the worst value within the tolerance for the part accuracy and the mounting accuracy, the outer diameter portion of the electrode shaft and the engaging hole are relatively slidable with a small pressure. Since the outer diameter portion of the electrode shaft and the engaging hole may relatively slide, the holder member 300 is preferably made of a resin material having a good slidability such as a polyacetal resin material or the like. When the developing device D provided with such an electric power supply contact is mounted to the main assembly 30 of the printer, the unshown electrode member of the main assembly 30 of the printer is connected to the contact portion 600a provided in the frame electrode plate 600 are contacted to each other, by which the developing bias can be supplied to the developing roller 12 through the frame electrode plate 600, the electrode shaft 500, the contact portion 500a, second arm portion 401 of the electrode plate 400, first arm portions 402 thereof. In the developing device D provided with an electric power supply contact having such a structure, the second arm portion 401 of the roller electrode plate 400 preferably has a low spring constant since then even when the developing roller 12 moves in a longitudinal direction due to the existence of the gap between the developing roller 12 and the developing member supporting frame 63A or the like when the developing roller 12 is rotated, a proper contact pressure is maintained between the electrode shaft 500 and the contact portion 500a. To accomplish this, it is effective to make the elastic portion 403 (Figure 14) between the second arm portion 401 and the first arm portion 402. In this embodiment, the second arm portion 401 is provided in the developing roller 12, the proper contact pressure can be provided between the second arm portion 401 and the contact portion 500a of the electrode shaft 500 without losing the longitudinal direction space of the developing device D. More particularly, it is not necessary to provide, between the developing roller 12 and the developing member supporting frame 63A, a space for permitting deflection of the second arm portion 401 to provide proper contact pressure between the second arm portion 401 and the contact portion 500a of the electrode shaft 500. If the first electroconductive portion is directly slid on the inner surface of the developing roller, and the developing bias is applied, the electrical conduction at the sliding portion is not stabilized, and therefore, it is preferable to provide a second electroconductive portion on which the first electroconductive portion is slid. In the electric power supply contact of this embodiment, the holder member 300 fixed to the inside of the developing roller 12 through the flange member 100 is provided with an engaging hole 304 for engagement with the contact portion (sliding contact portion) 500a of the electrode shaft 500 which slides on the second arm portion 401 of the roller electrode plate 400, and therefore, the range in which the roller electrode plate 400 and the electrode shaft 500 are contacted (sliding range) can be substantially regulated. Therefore, the contact portion 500a of the electrode shaft 500 is prevented from being out of place, so that reliability of the electric power supply contact is remarkably improved. Since the sliding contact between the contact portion 500a of the electrode shaft 500 and the second arm portion 401 of the roller electrode plate 400 is provided in the developing roller 12, the sliding contact portion is permitted to be supplied with electroconductive lubricant such as electroconductive grease since the electroconductive lubricant does not leak to outside of the developing roller 12. Particularly, in this embodiment, the sliding contact is disposed inside of the flange member 100 in the longitudinal direction of the developing roller, so that grease is not easily leaked out. In this embodiment, the developer is a nonmagnetic one component developer, and therefore it is rather easily scattered, and therefore, the sliding contact is preferably within the developing roller. Additionally, since the sliding contact between the contact portion 500a of the electrode shaft 500 and the second arm portion 401 of the roller electrode plate 400 is disposed in the holder member 300, the sliding contact, when the holder member 300 fixed to the roller electrode plate 400 is mounted to the flange member 100, is free of deformation due to external force or the like. Furthermore, since the electrode portion or the like is not exposed to outside in the developing roller 12 per se, the handling of the developing roller per se is easy. In the developing device of this embodiment, a holder member 300 having the contact (first arm portion 402) for contact to the inner surface of the developing roller 12 and a sliding contact (contact portion 500a) for contact to the electrode shaft 500, is disposed in the developing roller 12, and an engaging hole 304 for engagement with the engagement is provided adjacent the sliding contact. The holder member 300 is made of a high slidability material, and is fixed to a flange member 100 fixed to the end of the developing roller 12. The developing member supporting frame 63A of the developing device D has a contact for contact with a main assembly of the electrophotographic image forming apparatus (main assembly 30 of the printer), and the electrode shaft 500 and the sliding contact are press-contacted to apply a developing bias to the developing roller 12. (Other Embodiments) In the developing device D of the embodiment, the roller electrode plate 400 (second electroconductive portion) and the contact portion 500a of the electrode shaft 500 (first electroconductive portion) are provided at the end of the electrode shaft 500, but the present invention is not limited to this, and the outer surface of the electrode shaft 500, for example, may be contacted to the roller electrode plate 400 (second electroconductive portion). In such a case, the configuration of the first arm portion 401 provided in the roller electrode plate 400 is modified easily by one skilled in the art. In the developing device D of the foregoing embodiments, the connecting method among the flange member 100, the developing roller 12, the flange member 100 are press-fitting, but the present invention is not limited to this, and, for example, they may be bonded by adhesive material. As regards fastening of the flange member 100 to the developing roller 12, an end of the developing roller 12 is bent and cut, and is engaged into a hole portion formed in the flange member 100. In this embodiment, the developing device D functions to develop a multi-color image, but the present invention is not limited to this, and is applicable to a process cartridge or the like capable of forming monochromatic images. For example, the photosensitive drum and the developing device shown in Figure 5 are constituted into a cartridge. Here, the process cartridge, for example, comprises an electrophotographic photosensitive member and at least one process means. As for the types of the process cartridge, there are, in addition to those disclosed hereinbefore, a type in which, for example, an electrophotographic photosensitive member, a developing means and a charging means are unified integrally into a cottage which is detachably mountable to the main assembly of the electrophotographic image forming apparatus, a type in which an electrophotographic photosensitive member and a developing means are unified integrally into a cartridge which is detachably mountable to a main assembly of apparatus, a type in which an electrophotographic photosensitive member, a developing means, a charging means and cleaning means are unified integrally into a cartridge which is detachably mountable to a main assembly of an electrophotographic image forming apparatus, they tied in which an electrophotographic photosensitive member and two or more of the process means are combined integrally into a cartridge which is detachably mountable to a main assembly of an electrophotographic image forming apparatus. The process cartridge may contain an electrophotographic photosensitive member and additionally at least one of charging means, developing means and cleaning means as a unit which constitutes a cartridge which is detachably mountable to a main assembly of an electrophotographic image forming apparatus. The process cartridge is mounted to or demounted from the main assembly of the apparatus by the user. This means that maintenance of the apparatus is carried out, in effect, by the user. In the above-described, the electrophotographic photosensitive member has been described as photosensitive drum, but the electrophotographic photosensitive member is not limited to such a photosensitive drum, but the following is usable. The photosensitive member may be a photoconductor which may be an amorphous silicon, amorphous selenium, zinc oxide, titanium oxide, organic photoconductor (OPC) or the like. The photosensitive member may be in the form of a drum, a belt or another rotatable member, or a sheet, or the like. Generally, however, a drum or a belt is used, and in the case of a drum type photosensitive member, a cylinder of aluminum alloy or the like is coated with a photoconductor by evaporation or application or the like. The structure of the charging means described in the foregoing is of a so-called contact type charging method, but a known charging means comprising a tungsten wire which is enclosed with a metal shield of aluminum or the like at three sides, wherein positive or negative ions generated by application of a high voltage to said tungsten wire are directed to the surface of the photosensitive drum to uniformly charge the surface, is usable. The charging means may be a roller type as described in the foregoing, a blade type (charging blade), a pad type, a block type, a rod type, a wire type or the like. As for a cleaning method for removing toner remaining on the photosensitive drum, a blade, a fur brush, a magnetic brush or the like is usable. In the foregoing environment, a laser beam printer has been described in the foregoing as an example of the electrophotographic image forming apparatus, but the present invention is not limited thereto, and the present invention is applicable to an electrophotographic copying machine, a facsimile machine, a facsimile machine or the like of an electrophotographic type. 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 scope of the following claims.

Claims: A developing device comprising: a rotatable developer carrier member (12) for carrying a developer to develop an electrostatic image formed on an image bearing member (1) with a developer: wherein said developer carrier member includes a first cylindrical portion (12) and a second cylindrical portion (100) provided at an end of the first cylindrical portion and supportable by a bearing portion; characterised in that the developing device further includes an electric power supply path comprising: a first electroconductive portion (500) extending from an outside of said second cylindrical portion into an inside thereof and electrically connectable to an electroconductive portion outside said developing device, and spaced from an inner surface of said second cylindrical portion; a second electroconductive portion (400) contacted to an inner surface of said first cylindrical portion and when in use rotating with said first cylindrical portion and when in use sliding on said first electroconductive portion; wherein a contact portion (401) of said second electroconductive portion relative to said first electroconductive portion urges said first electroconductive portion toward the outside of said second cylindrical portion; and wherein a developing bias from said electroconductive portion outside of said developing device is connectable to the first cylindrical portion through said first and second electroconductive portions. An apparatus according to claim 1, further comprising a third electroconductive portion (600), provided in a frame of said developing device, for electrically connecting said first electroconductive portion to said electroconductive portion outside of said developing device. An apparatus according to claim 1 or claim 2, wherein an outer diameter of said second cylindrical portion is smaller than an outer diameter of said first cylindrical portion. An apparatus according to any of claims 1 to 3, wherein said second cylindrical portion is a flange portion fixed to said first cylindrical portion. An apparatus according to any preceding claim, wherein said first electroconductive portion is provided with a shaft portion (500b) extended from an outside of said second cylindrical portion thereinto and having an end (500a) contacted to said second electroconductive portion. An apparatus according to any preceding claim, wherein a sliding contact portion (500a, 401) between said first electroconductive portion and said second electroconductive portion is disposed inboard of said second cylindrical portion in a longitudinal direction of said developer carrying member. An apparatus according to claim 4, further comprising a holder member (300) supporting said second electroconductive portion and fixed to an inside surface of said developer carrier member. An apparatus according to claim 7, wherein the holder member (300) supporting said second electroconductive portion is fixed to an inside of said flange portion. An apparatus according to claim 8, further comprising a fixing portion (301) for fixing said flange portion and said holder member adjacent a portion of said flange fixed to said first cylindrical portion. An apparatus according to any of claims 7 to 9, wherein said first electroconductive portion is provided with a shaft portion (500b) extended from an outside of said second cylindrical portion thereinto, and said holder member (300) is provided with an engaging hole (304) engaged with said shaft portion adjacent a sliding contact portion (500a, 401) of said first electroconductive portion and said second electroconductive portion. An apparatus according to claim 7, wherein a sliding contact portion (500a, 401) between said first electroconductive portion and said second electroconductive portion is positioned within the holder member (300). An apparatus according to claim 1, wherein said second electroconductive portion (400) has a first arm portion (402) press-contacted to said first cylindrical portion (12) and a second arm portion (401) press-contacted to said first electroconductive portion (500), said first arm portion is disposed downstream of a base portion (404) of said second electroconductive portion in a direction of a force which is received by said second arm portion from said first electroconductive portion. A process cartridge (U) detachably mountable to a main assembly (30) of an image forming apparatus and including a developing apparatus according to any preceding claim.

Inventors: AKUTSU TAKASHI, BATORI YOSHIYUKI, NODA SHINYA, SASAGO YOSHIKAZU, SASAKI TERUHIKO, TERADA ICHIRO, AKUTSU, TAKASHI, BATORI, YOSHIYUKI, NODA, SHINYA, SASAGO, YOSHIKAZU, SASAKI, TERUHIKO, TERADA, ICHIRO
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 2000
Main classification: G03G15
IPC codes: G03G15, G03G21