Process cartridge, assembling method for process cartridge and electrophotographic image forming apparatus

Abstract: A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, includes a cartridge frame; an electrophotographic photosensitive drum (7) having a cylinder (7a) and a photosensitive layer thereon; process means actable on said photosensitive drum; a drum shaft (30) for rotatably supporting said photosensitive drum (7) on said cartridge frame, said drum shaft (30) extending through said photosensitive drum (7) and having a length enough to be supported by said cartridge frame at one end thereof and at the other end thereof; a preventing member for preventing said drum shaft from disengaging from said cartridge frame.

Description: FIELD OF THE INVENTION AND RELATED ART The present invention relates to a process cartridge, an assembling method for the process cartridge, and an electrophotographic image forming apparatus. Corresponding prior art is known from US-A-5 371 576, JP-A-7 092 884, JP-A-1 196 089, JP-A-5 289 588. More particularly, it relates to a process cartridge which is detachably mountable relative to the main assembly of an electrophotographic image forming apparatus such as a laser beam printer, electrophotographic copying machine or facsimile machine, and an electrophotographic image forming apparatus using the same. An image forming apparatus using electrophotographic process is known which is used with the process cartridge. This is advantageous in that the maintenance operation can be, in effect, carried out by the users thereof without expert service persons, and therefore, the operativity can be remarkably improved. Therefore, this type is now widely used. Here, an electrophotographic photosensitive drum used with the process cartridge has an electroconductive base of cylindrical configuration and a photosensitive layer thereon, and a flange having a gear or the like mounted to the end portion thereof by bonding or crimping or the like. The drum is rotatably supported in a cartridge by a support shaft mounted at a predetermined position in the cartridge frame. By the mounting operation, the positioning relative to the other member in the cartridge such as a cleaning blade, receptor sheet, developing roller charging roller or the like, is accomplished. SUMMARY OF THE INVENTION Accordingly, it is a principal object of the present invention to provide a process cartridge, an assembling method for the process cartridge and an electrophotographic image forming apparatus wherein the rigidity of the shaft support for the electrophotographic photosensitive drum can be increased. It is another object of the present invention to provide a process cartridge, an assembling method for the process cartridge and an electrophotographic image forming apparatus, wherein the drum shaft is improved. It is a further object of the present invention to provide a process cartridge, an assembling method for the process cartridge, and an electrophotographic image forming apparatus, wherein the electrophotographic photosensitive drum is supported by a penetrating shaft. It is a further object of the present invention to provide a process cartridge, an assembling method for the process cartridge and an electrophotographic image forming apparatus, wherein said process cartridge comprises a cartridge frame; an electrophotographic photosensitive drum having a cylinder and a photosensitive layer thereon; process means actable on said photosensitive drum; a drum shaft for rotatably supporting said photosensitive drum on said cartridge frame, said drum shaft extending through said photosensitive drum and having a length enough to be supported by said cartridge frame at one end thereof and at the other end thereof; a preventing member for preventing said drum shaft from disengaging from said cartridge frame. According to the present invention, as defined in the independent claims, the support shaft for the electrophotographic photosensitive drum has a length enough to penetrate the electrophotographic photosensitive drum and the cartridge frame, and therefore, the rigidity of the shaft support for the electrophotographic photosensitive drum increases, so that the perpendicularity of the image is maintained even if the electrophotographic photosensitive drum receives the driving force from the device main assembly, since the axis is not deviated. The vibration during the rotation of the electrophotographic photosensitive drum is prevented, so that satisfactory image free of pitch non-uniformity can be provided. 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 as defined in the dependent claims taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of a laser beam printer. Figure 2 is a perspective view of an outer appearance of a laser beam printer. Figure 3 is a schematic illustration of a process cartridge . Figure 4 is a perspective view of an outer appearance of a process cartridge . Figure 5 is a perspective view of an outer appearance of a process cartridge . Figure 6 is a perspective view of an outer appearance of a cleaning unit and developing unit . Figure 7 shows a coupling member for combining a cleaning unit and a developing unit . Figure 8 is an illustration of mounting of a process cartridge . Figure 9 is an illustration of mounting of a process cartridge . Figure 10 is a sectional view of a photosensitive drum . Figure 11 is a sectional view of the structure around a photosensitive drum. Figure 12 is an interrelation relation view of an inner diameter of a cylinder of a photosensitive drum and an outer diameter of a gear engaging portion. Figure 13 is an illustration of a cylindricity of a photosensitive drum . Figure 14 is an illustration of a circularity of a photosensitive drum . Figure 15 is a perspective view of an outer appearance of a grounding plate . Figure 16 is an illustration of a grounding plate . Figure 17 is an illustration of a grounding plate . Figure 18 is a partial enlarged view showing a structure of a restraining member portion of a penetrating shaft end portion . Figure 19 is a schematic illustration showing an incorporation process of a photosensitive drum . Figure 20 is a schematic illustration showing an incorporation process of a photosensitive drum . Figure 21 is a schematic illustration showing a relation with the contact of the main assembly of the apparatus when the cartridge mounting is mounted. Figure 22 is a schematic illustration showing a relation with the contact of the main assembly of the apparatus when the cartridge mounting is mounted. Figure 23 is a partial enlarged view showing another structure of the restraining member portion of the penetrating shaft end portion . DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS {FIRST EMBODIMENT} The description will be made as to an embodiment of an electrophotographic image forming apparatus using the present invention in conjunction with the accompanying drawings. In the following embodiment, a laser beam printer is taken as an example of the electrophotographic image forming apparatus. The laser beam printer can be loaded with a process cartridge, as will be described hereinafter. Referring to Figure 1 to Figure 9, the description will be made as to a process cartridge and laser beam printer according to a first embodiment of the present invention. Figure 1 is a schematic illustration of a laser beam printer; Figure 2 is a perspective view of an outer appearance thereof; Figure 3 is a schematic illustration of the process cartridge; Figure 4 and 5 are perspective view of an outer appearances of the process cartridge; Figure 6 is perspective view of an outer appearances of a cleaning unit and a developing unit; Figure 7 shows a combination member for combining the cleaning unit and the developing unit; and Figures 8 and 9 are mounting structure illustrations of a process cartridge. Here, the description will be made as to general structures of the laser beam printer and the process cartridge and then as to the photosensitive drum and the means therearound. {GENERAL STRUCTURE} In the laser beam printer A, the beam from a laser beam source generated in accordance with image information, as shown in Figures 1 and 2, is deflected by a rotating polygonal mirror 1a, and is projected onto the electrophotographic photosensitive drum 7 through a lens 1b and reflection mirrors 1c (optical means 1) so that a latent image is formed thereon. The latent image is developed by developing means 9 into a toner image. In synchronism with the formation of the toner image, a recording medium 2 is fed from a cassette 3a through a pick-up roller 3b, feeding rollers 3c and 3d, and registration rollers 3e (feeding means 3).The toner image thus formed on the photosensitive drum 7 in an image formation portion in the form of a cartridge is transferred onto a recording medium 2 by voltage application to the transfer roller 4 as transferring means. The recording medium 2 after the toner image transfer is transported along a guide member 3f into fixing means 5 comprising a fixing roller 5b having therein a heater 5a and a driving roller 5c press-contacted to the roller 5b for urging the recording material to the fixing roller 5b, where the transferred toner image is fixed on the recording medium 2. The recording medium 2 is then transported by discharging rollers 3g, 3h and 3i and is discharged to a discharging portion 6 through a reversion feeding path 3j. A swingable flapper 3k may be operated to directly discharge it not through the reversion feeding path 3j but by the discharging rollers 3m. On the other hand, as shown in Figure 3 to Figure 5, a process cartridge B constituting the image formation portion is such that a photosensitive drum 7 having a photosensitive layer is rotated, and the surface thereof is charged uniformly by the voltage application to the charging roller 8 as charging means, and the light image from the optical means 1 is projected onto the photosensitive drum 7 through an exposure opening 26 to form the latent image, which is developed by developing means 9. In the developing means 9, toner is fed out of a toner accommodating portion 9a by toner feeding member 9b. A developing roller 9c containing therein a fixed magnet is rotated to form a toner layer having triboelectric charge provided by a development blade 9d is formed on the surface of the developing roller 9c. The toner is transferred onto the photosensitive drum 7 in accordance with the latent image to visualize it into a toner image. The transfer roller 4 is supplied with a voltage of the opposite polarity from the toner image to transfer the toner image onto the recording medium 2.After the transfer, the toner remaining on the photosensitive drum 7 is removed by a cleaning blade 10a (cleaning means 10) and is collected into a residual toner container 10b. The various parts such as the photosensitive drum 7 are accommodated in a housing constituted by combining the toner container 11 and the development frame 12 and further combining with a cleaning frame 13 into a form of a cartridge B. The process cartridge B is detachably mountable relative to a cartridge mounting means of the main assembly of the apparatus 14. When the opening and closing member 15 is opened, as shown Figures 8 and 9, there is a cartridge mounting space, and cartridge mounting guide member 16 is mounted to each of left and right inside surface of the main assembly of the apparatus 14. Each of the left and right guide members 16 comprises two guide portions 16a and 16b for guiding the dowels 13a, longitudinal guides 12a and short side guide 13b of the process cartridge B. The process cartridge B is inserted along the guides 16a and 16b, until the dowel 13a is engaged with the positioning portion 16f, and the rotation receiving portion 13c is supported by the rotation stopper portion 16g. Then, the opening and closing member 15 is closed, so that the positioning and mounting of the process cartridge B to the image forming apparatus A is completed. By the positioning and the mounting, the drum gear(helical gear) 7b mounted to one end portion of the photosensitive drum 7 by press-fitting or crimping, is meshed with a driving gear 33 of the main assembly of the apparatus, and a transmission gear(spur gear) 7c mounted to the other end thereof is meshed with the gear 4a of the transfer roller 4. With the drum gear 7b of the photosensitive drum 7, a sleeve gear 9g of the developing roller 9c (helical gear) is meshed. Therefore, the rotation force of the driving gear 33 from the main assembly of the apparatus side is transmitted to the drum gear 7b, so that the photosensitive drum 7 is rotated, and the driving force is transmitted to the sleeve gear 9g through the drum gear 7b to rotate developing roller 9c. Furthermore, the driving force is transmitted through the transmission gear 7c of the photosensitive drum 7 to rotate the transfer roller 4. For the purpose of facilitating the user's handling of the process cartridge B upon the mounting-and-demounting, it is provided with a grip 17 and ribs 23 and 24, as shown in Figures 4 and 5. The process cartridge B is further provided with a drum shutter 18 (Figure 3) which opens and closes in interrelation with the mounting-and-demounting relative to the image forming apparatus A. When it is demounted from the image forming apparatus A, the shutter 18 is closed to protect the photosensitive drum 7. {HOUSING STRUCTURE} The process cartridge B of this embodiment comprises the housing constituted by combining the toner container 11, the development frame 12 and the cleaning frame 13.The structure of the housing will be described in detail. As shown in Figure 6, a toner accommodating portion 9a is formed and a toner feeding member 9b is mounted, in the toner container 11 The development frame 12 is provided with the developing roller 9c and the development blade 9d, and further with a rotatable stirring member 9e for circulating the toner in the developer chamber, adjacent the developing roller 9c. The toner container 11 and the development frame 12 are welded to each other to constitute an integral developing unit(Figure 6, (b)). To the cleaning frame 13, the photosensitive drum 7, charging roller 8 and the cleaning means 10 are mounted, and furthermore, the drum shutter member 18 for protecting the photosensitive drum 7 when the process cartridge B is dismounted from the main assembly 14, is mounted. The setting of the photosensitive drum 7 into the cleaning frame 13, will be described in detail in relation with the structure of the photosensitive drum 7. By combining the developing unit and the cleaning unit with a coupling member, the process cartridge B is constituted. More particularly, as shown in Figure 6, a rotational shaft 20 is mounted to the end portion of the arm portion 19 formed at each longitudinal end of the development frame 12 (Figure 6, (b)), and on the other hand, at the longitudinal ends of the cleaning frame 13, there are formed recesses 21 for positioning and locking the rotational shaft 20, respectively. The rotational shaft 20 is inserted into the recess 21, and the coupling member 22 having integral projection 22a, compression spring 22b and locking claw 22c shown in Figure 7 is coupled to the cleaning frame 13 by snap fitting, by which the developing unit and the cleaning unit are combined for rotation about the rotational shaft 20 relative to each other, and the developing roller 9c is urged to the photosensitive drum 7 by the weight of the developing unit. At this time, the development frame 12 is urged downwardly by the compression spring 22b mounted to the coupling member 22, by which the developing roller 9c is assuredly press-contacted to the photosensitive drum 7. Therefore, by mounting the spacer ring 9f to the opposite longitudinal ends of the developing roller 9c, the ring 9f is press-contacted to the photosensitive drum 7, so that the photosensitive drum 7 and the developing roller 9c are opposed to each other with a predetermined clearance(approx. 300µm approx. ) therebetween. The clearance between the photosensitive drum 7 and the developing roller 9c is required to be accurate since it is closely related with the density of the image, and in this embodiment, the clearance is designed as being approx. 300µm±30µm. Since the clearance is controlled only by the spacer rings 9f mounted to the end portions of the developing roller 9c, the circularity tolerance of the photosensitive drum 7 is designed as being not more than approx. 15µm to avoid the density difference, and the gap difference between the opposite end portions is not more than approx. 15µm. {STRUCTURES OF THE PHOTOSENSITIVE DRUM AND PARTS THEREAROUND} (PHOTOSENSITIVE DRUM) The photosensitive drum 7 comprises, as shown in Figure 10, a cylinder 7a of drum configuration and having a photosensitive layer on the outer peripheral surface thereof; a gear 7b meshable with a gear 33 of the main assembly (Figure 9) to receive the driving force; a gear 7c meshable with a gear 4a integrally rotatable with the transfer roller 4 to transmit the driving force thereto; and a grounding plate 31, fixed on the gear 7c, for electrical connection between the inside surface of the cylinder 7a and a penetrating shaft 30 which will be described hereinafter. The photosensitive drum 7 is rotatably supported on the cleaning frame 13 by the penetrating shaft 30, as shown in Figure 11. (PRESS-FITTING OF THE GEAR) The gears 7b and 7c have engaging portions 7b1 and 7c1 to be press-fitted into an end of the cylinder 7a. As shown in Figure 12, the outer diameters dN of the engaging portions 7b1 and 7c1 are larger than the inner diameter DS of the cylinder 7a (dN>DS). In this embodiment, the outer diameters dN of the engaging portions 7b1 and 7c1 of the gears 7b and 7c, are larger than the inner diameter DS of the cylinder 7a by approx. 5-30µm approx. Parts of end portions of the cylinder 7a are cut and bent and are engaged, after the press-fitting, with recesses 7b2 and 7c2 formed at the base portions of the engaging portions 7b1 and 7c1 of the gears 7b and 7c. Thus, the gears 7b and 7 c are press-fitted into the opposite end portions of the cylinder 7a, and thereafter, parts of the end portion of the cylinder 7a are crimped to be engaged with the recesses 7b2 and 7c2 of the gears 7b and 7c by which the cylinder 7a and the gears 7b and 7c are securedly fixed to provide a photosensitive drum assembly as shown in Figure 10. In Figure 10, designated by 31 is a grounding plate which will be described hereinafter, and is fixed to one of the gears (gear 7c). As described above, the engaging portions 7b1 and 7c1 of the gears 7b 7c are press-fitted into the end portions of the cylinder 7a, and therefore, the engaging portion of the gears receives the stress at the cylinder end portions during the crimping operation, so that the deformation of the cylinder is minimized. Therefore, as compared with a case of loose fitting of the gear into the cylinder end portion(outer diameter of gear engaging portion is smaller than inner diameter of cylinder), the circularity of the photosensitive drum 7 (particularly the circularity at the contact position relative to the spacer ring 9f) is improved, so that the clearance between the drum 7 and the developing roller 9c is maintained constant to provide good images. Figure 13 shows examples of the cylindricity data of the photosensitive drum to which the gears are mounted. The photosensitive drum showed in Figure 13, (a), is press-fitted with a gear having a press-fitting difference of approx. 30µm, and the circularities were measured at the position away from the drum end portion by 0.5mm, 2.5mm, 8.0mm, 10.0mm and 25.0mm. As shown in Figure 13, (a), the cylinder is expanded outwardly at the crimping position KS, but the cylindricity is 24.9µm, and therefore is better than the cylindricity 31.1µm of the loosely fitted photosensitive drum with approx. 30µm margin showed in Figure 13, (b). Figure 14 gives circularity data at the contact position of the spacer ring in the photosensitive drum. In this embodiment, the contact position is approx. 8.0mm away from the cylinder end portion. The circularity of the photosensitive drum in this embodiment at this position is 11.3µm (Figure 14, (a)) and is approx. one half the circularity 21.4m of the photosensitive drum which uses loose fitting, and is within the design tolerance 15µm. Image formations were carried out using the photosensitive drum, and it has been confirmed that the density non-uniformity on the print is low enough. (GROUNDING PLATE) The gear 7c has the grounding plate 31, fixed thereon, for electrical conduction by contacting with the inside surface of the cylinder 7a and with the outside surface of the penetrating shaft 30. Figure 15 is a perspective view of an outer appearance of the grounding plate 31. The grounding plate 31 is of metal material, which is phosphor bronze in this embodiment. The grounding plate 31 has a base portion 31a with a positioning hole 31a1 which is engaged with the projection 7c3 provided in the gear engaging portion 7c1, and has a contact portion 31b, for contacting to the inside surface of the cylinder 7a, having end branched portions, the contact portion 31b being crimped to the outer edges of the gear engaging portion 7c1. By press-fitting the gear 7c fixed to the grounding plate 31 into the end portion of the cylinder 7a, the contact portion 31b of the grounding plate 31 is contacted to the inside peripheral surface of the cylinder 7a. The grounding plate 31 has a plurality of first arm portions 31c (two in this embodiment) urged and contacted to the outer periphery of the penetrating shaft 30 for rotatably supporting the photosensitive drum 7. The end portions of the two first arm portions 31c are bent in a direction substantially perpendicular to the direction of insertion of the penetrating shaft 30 which will be described hereinafter, and the edge portions 31c1 are press-contacted to the outer periphery of the penetrating shaft 30. By this, the first arm portion 31c deforms outwardly from the position shown in Figure 16 to the position shown in Figure 17 in accordance with the inserting operation of the penetrating shaft 30 which will be described hereinafter. The first arm portion 31c escapes along the outer peripheral surface of the penetrating shaft 30, and therefore, the insertion of the penetrating shaft 30 is smooth even if the penetrating shaft 30 has a groove or a step, and there is no liability of deformation of the grounding plate 31. Therefore, the assembling operativity is improved. The grounding plate 31 has a second arm portion 31d extending in a direction opposite from the first arm portion 31c as shown in Figure 16s and 17, and the second arm portion 31d is contacted to a backup portion 7c4 provided in a gear engaging portion 7c1 so as to be against the force received by the first arm portion 31c when the penetrating shaft 30 is inserted. By this, when the penetrating shaft 30 is inserted, the erection and deformation of the grounding plate 31 by the force received by the first arm portion 31c can be prevented, and therefore, the contact state of the first arm portion 31c relative to the penetrating shaft 30 is stabilized. As shown in Figure 11, the two first arm portions 31c of the grounding plate 31 are deviated so as to prevent overlapping of the edge portions 31c1 at the leading edges thereof (contact portion relative to the leading edge) in the direction of the axis of the penetrating shaft 30. Thus, the contact regions of the first arm portion 31c relative to the penetrating shaft 30 are not overlapped, and the contact state of the two arm portions 31c are independent from each other, and therefore, the stabilized electrical conduction is maintained even during the rotation of the photosensitive drum 7, for example. As described hereinbefore, the two arm portions 31c have end edge portions 31c1 abutted to the outer periphery of the penetrating shaft 30, and therefore, the degree of deviation in the direction of the axis may be small, and the contact pressures of the two arm portions 31c can be easily made equal. The first arm portion 31c of the grounding plate 31, as shown in Figures 16 and 17, is disposed between the contact portion 31b and a positioning hole 31a1 at which the grounding plate 31 is fixed to the gear 7c. By positioning the first arm portion 31c between the fixed portions, the contact pressure of the first arm portion 31c relative to the penetrating shaft 30 is stabilized, thus providing stabilized electrical conduction. Additionally, the material can be saved, and therefore, the arrangement is economical. (penetrating shaft) The penetrating shaft 30, as shown in Figure 11, rotatably supports the photosensitive drum 7 of the above-described structure on the cleaning frame 13, and it has enough length to penetrate from one side wall 13g to the other side wall 13h of the photosensitive drum 7. The penetrating shaft 30 has an engaging portion 30a at one end portion, and is provided with a groove 30a1 for mounting a restraining member at the engaging portion edge(Figure 18). At a predetermined positions of side walls of the cleaning frame 13, there are dowels 13a1 and dowel 13a2 for engaging and supporting the opposite ends of the penetrating shaft 30. Therefore, one end of penetrating shaft 30 (engaging portion 30a) is press-fitted into an engaging hole 13a1a of the dowel 13a1, and the other end thereof is loosely fitted in the engaging hole 13a2a of the dowel 13a2 to rotatably support the photosensitive drum 7, and is fixed on the cleaning frame 13. The dowels 13a1 and 13a2 are projected outwardly beyond the cleaning frame side wall to permit enough engaging length (approx. 4-10mm approx. in this embodiment). When the cartridge is to be mounted to the main assembly, the projected portions of the dowels 13a1 and 13a2, are guided by the guide portions 16a and 16b of the main assembly shown in Figures 8 and 9, and are brought into engagement with the positioning portion 16f finally, so that the process cartridge B is mounted in the main assembly at the correct position. In this embodiment, the penetrating shaft 30 is of metal material such as iron(excavated and abraded round bar), and the cleaning frame 13 is of plastic resin material such as styrene resin material(acrylonitrile butadiene styrenc (ABS), polystyrene resin (PS) or the like) or modified polyphenylene oxide (PPO).The engaging portion 30a of the penetrating shaft 30 is press-fitted into the dowel 13a1 of the cleaning frame 13 with the press-fitting difference of approx. 10-50µm approx., and simultaneously, the inserting portion 30b at the other end is loosely fitted in the dowel 13a2. By this, rotation of the penetrating shaft 30 due to the sliding friction relative to the gears 7b and 7c at the opposite ends of the drum, is prevented. However, the cleaning frame 13 of the plastic resin material and the penetrating shaft 30 of the metal material have significantly different expansion coefficients relative to temperature change, and therefore, it is difficult to rely on the press-fitting alone for the fixing of the penetrating shaft 30. More particularly, when the temperature is higher than when the process cartridge is assembled, the engagement therebetween becomes loose with the result of liability of disengagement of the penetrating shaft 30 in the thrust direction thereof. If the press-fitting difference is increased at the engaging portion 30a of the penetrating shaft 30, the engagement may become so tight at low temperature with the result of liability of crack in the dowel 13a1 of the cleaning frame 13. To avoid these problems, the usable range of the press-fitting difference is zero or very narrow, and therefore, manufacturing is not easy. Therefore, in embodiment, a groove 30a1 is formed adjacent an end of the engaging portion of the penetrating shaft 30, as shown in Figure 18, (a), and a restraining member 32 in the form of a ring as shown in Figure 18, (b) is mounted to the groove 30a1. The restraining member 32 is of plastic resin material such as polyacetal (POM), polypropylene (PP) and has such an inner diameter relative to the outer diameter of the engaging portion 30a that they can be loosely fitted. The restraining member 32 has two projections 32a on the inner surface, and the projections 32a are projected to approx. 0.2mm approx. inside beyond the inner diameter of the restraining member 32, and have a length of approx. 1/4 of the inner circumference. When the use is made with the ring configuration restraining member 32, the restraining force in the thrust is smaller than a widely used E-type or C-type restraining member. However, the thrust force in the actual use is provided only by the spring force of the grounding electrode of the main assembly press-contacted to the end portion of the penetrating shaft 30 upon the cartridge mounting(approx. 80gf-300gf approx. in this embodiment), and therefore, the restraining member 32 is usable. The penetrating shaft 30 has a step 30c such that the diameter of the engaging portion 30a press-fitted at one side wall 13h side of the cleaning frame 13 is smaller than the diameter of the other portion and that the step 30c is abutted to the inner wall of the frame side wall upon the penetrating shaft insertion. By this structure, the insertion operation of the penetrating shaft is made easier, and the assembling operativity of the cartridge is improved. The penetrating shaft 30 in this embodiment uses an excavated and abraded round bar, and is machined only at the engaging portion 30a and groove 30a1 having smaller diameter, and therefore, the cost is low. By using the penetrating shaft 30 as a support shaft for supporting the photosensitive drum 7 on the cleaning frame 13, the rigidity of the shaft support is enhanced so that the vibration of the photosensitive drum 7, and therefore, the pitch non-uniformity can be avoided. (MOUNTING PROCESS OF THE PHOTOSENSITIVE DRUM) Before the mounting of the photosensitive drum 7, the cleaning means 10, charging means 8 and seal or the like are mounted to the cleaning frame 13. As shown in Figure 19, the photosensitive drum 7 is placed between the both sides walls 13g 13h of the cleaning frame 13, and as shown in Figure 20, the penetrating shaft 30 is inserted from the side wall 13g side until the step 30c of the penetrating shaft 30 abuts the inner wall of the side wall 13h. The penetrating shaft 30 is first penetrated through the dowel 13a2 of the side wall 13g and through the insertion hole 7c1 of the gear 7c. At this time, the grounding plate 31 fixed to the gear 7c, changes from the state shown in Figure 16 to the state shown in Figure 17. Since the end portion of the first arm portion 31c of the grounding plate 31 is bent to the direction perpendicular to the axis, the arm portion 31c is escaped by deformation along the outer peripheral surface when the penetrating shaft 30 is inserted. Therefore, the insertion of the penetrating shaft 30 is smooth, and the deformation of the grounding plate 31 can be avoided. The edge portions 13c1 of the arm portion 13c are press-contacted at positions not overlapped in the axial direction of the penetrating shaft 30 so that the electrical connection is stabilized. Then, the penetrating shaft 30 is penetrated through the insertion hole 7b1 of the gear 7b, and the engaging portion 30a is press-fitted into the dowel 13a1 of the side wall 13h, and the shaft is further inserted until the step 13c is abutted to the inner wall of the side wall 13h. By this, the insertion is finished. The insertion hole of the gear 7b is a significantly tapered hole 7b2 to permit oblique insertion of the penetrating shaft 30. The restraining member 32 is engaged in the groove 30a1 of the penetrating shaft end portion using the dowel 13a1. By this, the disengagement of the penetrating shaft 30 in the thrust direction is prevented, and the mounting of the parts to the cleaning frame 13 is completed to provide the cleaning unit as shown in Figure 6, (b). The cleaning unit and the developing unit are coupled by the coupling member to provide the process cartridge B. (GROUNDING OF PHOTOSENSITIVE DRUM) When the process cartridge B is mounted to the main assembly 14, the dowels 13a1 and 13a2 on the side walls 13g and 13h of the cleaning frame 13 are finally engaged with the positioning portion 16f in the main assembly, so that the process cartridge B is positioned to the main assembly 14. At this time, the grounding electrode 34 of the main assembly is urged by contacting to the end surface of the penetrating shaft 30, and is deformed from the solid line position to the broken line position in Figure 21. Since the gear 7b at the drum end portion is a helical gear as shown in Figure 19, rightward thrust force in Figures 21 and 22 is produced when it receives force from the gear 33 of the main assembly. By this, the grounding electrode 34 is urged further, and is deformed until it abuts the side wall of the main assembly. The grounding electrode 34 is connected to GND of an electrical substrate in the main assembly. Therefore, the charge on the photosensitive drum 7 charged by a charging roller 8 during the image formation flows through-the photosensitive drum, grounding plate, penetration shaft, grounding electrode and the electric substrate, all of which are of metal material. Therefore, the current flows stably without storing, upon projection of the laser beam to the photosensitive drum. {OTHER EMBODIMENTS} In the above-described embodiment, two first arm portions 31c of the grounding plate 31 are provide, but the number may be three, four or more. The material of the grounding plate 31 has been described as being phosphor bronze, but another material such as SUS (stainless steel) is usable. In the above-described embodiment, the electrophotographic photosensitive member has been a drum having an end portion engagement member press-fitted and crimped. This is not limited to the electrophotographic photosensitive member, but is usable with a cylindrical member with which crimping is usable (developing roller or the like) with similar advantages. In the above-described embodiment, the outer diameter of the engaging portion 30a provided at one end of the penetrating shaft 30 is stepwisely smaller than the outer diameter of the other portion, but this feature is not inevitable, and the same diameter is usable. In this case, end portions of the penetrating shaft 30 are provided with grooves, respectively, and the restraining members 32 are inserted into the grooves using dowels 13a1 and 13a2 of the cleaning frame 13. Similarly to the above-described embodiment, the inner diameter of the engaging portion 30a of the penetrating shaft 30 is selected to provide the press-fitting relative to the side wall 13h of the frame 13. According to this structure, the preparation of the restraining member and the insertion process thereof are added to the manufacturing step of the penetrating shaft 30, but the machining process for the outer diameter is eliminated, and therefore, the manufacturing cost is reduced. In the above-described embodiment, the restraining member for the penetrating shaft has been a ring configuration member having two projections 32a, but another type is usable, for example, the restraining member may be so-called snap fit type. Figure 23 shows an example thereof. In Figure 23, (a), the restraining member is engaged, and in Figure 23, (b), there are shown a state before insertion of the restraining member and a state during insertion thereof. The restraining member 32 showed in Figure 23 is provided with two claw portions 32b which are elastically deformable, and slits 32c are formed at both sides of the claw portion 32b to permit easy elastic deformation. When the restraining member 32 is inserted into the engaging portion 30a of the penetrating shaft 30, as shown in Figure 23, (b), the claw portion 32b is deformed to permit smooth insertion. When it is further inserted, the claw portion 32b is engaged with the groove 30a1 so that the penetrating shaft 30 is stopped. With this structure, the claw portion 32b having the restraining member function is easily elastically deformed, and therefore, the degree of engagement of the claw with the groove is required to be larger. Further, in each of the preceding embodiments, the process cartridge B is of a type which is used to form a monochrome image, but t present invention is also applicable to a multicolor process cartridge, which comprises two or more developing means and is used to form a multicolor image (image of two colors, three colors, or full-color). As for the electrophotographic photosensitive member, it is not limited to the aforementioned photosensitive drum 7. The present invention is also applicable to the following. To begin with, the photoconductive material is usable as the photoconductive material, amorphous silicone, amorphous selenium, zinc oxide, titanium oxide, organic photoconductor (OPC), or the like is usable. Further, as for the configuration of a base member on which the configuration of a base member on which t photosensitive material is placed, a base member in the form of a drum or a belt is used. For example, in the case of the base member of t drum type, the photoconductive material is coated, deposited or placed by the like means on a cylinder of aluminum alloy or the like. As for the developing method, the present invention is compatible with various well-known methods such as the double component magnetic brush developing method, cascade developing method, touch down developing method, cloud developing method, and the like. Further, as to the structure of the charging means, the so-called contact charging method is employed in the first embodiment, but the present invention is also applicable to other conventional charging methods such as the one in which a metallic shield of aluminum or the like is placed on three sides of a tungsten wire, and positive or negative ions generated by applying a high voltage to the tungsten wire are transferred onto the surface of the photosensitive drum to charge it uniformly. Further, the aforementioned charging means may be of the blade type (charging blade), pad type, block type, rod type, wire type, or the like, in addition to the roller type described above. As for the method for cleaning the residual toner on the photosensitive drum, the cleaning means may be constituted of a blade, fur brush, magnetic brush or the like. Process cartridge is provided at least with an electrophotographic photosensitive member or the like and at least one process means. The process cartridge may be a cartridge which is detachably mountable to a main assembly of an image forming apparatus and which contains as an unit an electrophotographic photosensitive member and charging means. The process cartridge may be a cartridge which is detachably mountable to a main assembly of an image forming apparatus and which contains as an unit an electrophotographic photosensitive member and developing means. The process cartridge may be a cartridge which is detachably mountable to a main assembly of an image forming apparatus and which contains as an unit an electrophotographic photosensitive member and cleaning means. The process cartridge may be a cartridge which is detachably mountable to a main assembly of an image forming apparatus and which contains as an unit an electrophotographic photosensitive member and two or more process means. The process cartridge means a cartridge having as a unit an electrophotographic photosensitive member, and charging means, developing means and cleaning means, which is detachably mountable to a main assembly of an image forming apparatus. It may include as a unit an electrophotographic photosensitive member and at least one of charging means, developing means and cleaning means. It may include as a unit developing means and an electrophotographic photosensitive member. In the foregoing, the description has been made as to a laser beam printer as an exemplary image forming apparatus, but he present invention is applicable to an electrophotographic copying machine, facsimile machine, word processor or anther image forming machine. As described in the foregoing, according to this embodiment, the rigidity of the shaft support for the electrophotographic photosensitive drum can be increased at low cost by using a penetrating shaft for the electrophotographic photosensitive drum. Therefore, even if the electrophotographic photosensitive drum receives the driving force from the main assembly, the shaft axis is not deviated, thus maintaining the high image quality. Additionally, the vibration of the electrophotographic photosensitive drum during the driving is prevented, and therefore, the image free of the pitch non-uniformity is produced. Additionally, the support shaft has at least one end press-fitting portion relative to the cartridge frame, and a mounting portion for a shaft restraining member is provided at the end portion, and the restraining member is of elastic member in the form of a ring and has an engaging portion for engagement with the mounting portion of the support shaft, by which the assembling process is simplified without deterioration the shaft restraining effect. 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 process cartridge (B) detachably mountable to a main assembly of an electrophotographic image forming apparatus (14), comprising: a cartridge frame (11,12,13); an electrophotographic photosensitive drum (7) having a cylinder (7a) and a photosensitive layer thereon; process means (8,9,10) actable on said photosensitive drum; a drum shaft (30) for rotatably supporting said photosensitive drum on said cartridge frame (13), said drum shaft extending through said photosensitive drum and supported by said cartridge frame (11,12,13) at its respective ends; longitudinal projections (13a1,13a2) projecting outwardly from lateral walls of said cartridge frame, said projections having respective holes (13a1a,13a2a) with which the respective ends of said drum shaft (30) are engaged; and a preventing member for preventing said drum shaft (30) from disengaging from said cartridge frame (13), characterised in that said preventing member (32) has an inside surface with an inward projection which is engaged with a groove (30a1) formed in an outer periphery of one end of said drum shaft (30), wherein said preventing member (32) is disposed inside an outer end of one of said projections (13a1) in a longitudinal direction of said photosensitive drum (7). A cartridge according to claim 1, wherein said one end of said drum shaft is prevented from disengaging from said cartridge frame by said preventing member press-fitted in said cartridge frame. A cartridge according to claim 1 or 2, wherein said preventing member is in the form of a ring having an inside surface with an inward projection which is engaged with a groove formed in an outer periphery of said drum shaft, and wherein said preventing member is of plastics resin material, and said drum shaft is of metal. A cartridge according to claim 3, wherein the cartridge frame is of acrylonitrile butadiene styrene (ABS) resin material, polystyrene resin (PS) resin material or polyphenylene oxide (PPO) resin material, and said preventing member is of polyacetal (POM) resin material or polypropylene (PP) resin material, and the metal is steel. A cartridge according to any preceding claim, wherein said projections are engageable by guides on the main assembly to guide the process cartridge relative to the main assembly when said process cartridge is mounted to said main assembly. A cartridge according to any preceding claim, wherein said cartridge frame comprises a cleaning frame (13) supporting the photosensitive drum and the process means which includes a charging member and the cleaning member, a developing frame (12) supporting a developing member (9c) as the process means and a toner container (11) for containing toner to be used by the developing member, wherein said cleaning frame and said developing frame are rotatable relative to each other, and wherein said projections (13a1,13a2) are provided on respective lateral walls of said cleaning frame. A cartridge according to any preceding claim, wherein said photosensitive drum is provided with a spur gear (7c) at one longitudinal end thereof for transmitting driving force to a transfer roller provided in said main assembly and a helical gear (7b) at the other longitudinal end for receiving driving force from the main assembly, and wherein said preventing member (32) is located nearer to said other longitudinal end than said one longitudinal end. A cartridge according to claim 7, further comprising a grounding member (31) in the cylinder of said photosensitive drum, said grounding member being contacted to an inner surface of said cylinder and an outer surface of said drum shaft for grounding said photosensitive drum to the main assembly, and wherein said grounding member is mounted to said spur gear (7c). A cartridge according to claim 7 or claim 8, wherein said helical gear (7b) is provided with a through hole through which said drum shaft is penetrated, and said hole is tapered (7b2) from a drum shaft entrance side to the opposite side. A method for assembling the process cartridge according to any previous claim which is detachably mountable to a main assembly of an image forming apparatus and comprises an electrophotographic photosensitive drum (7) and process means actable on said photosensitive drum, wherein said photosensitive drum has a cylinder and a photosensitive layer thereon, said method comprising: (a) a positioning step of positioning the photosensitive drum (7) between cartridge frames (13g,13h); (b) drum shaft inserting step including inserting a drum shaft (30) for rotatably supporting the photosensitive drum on said cartridge frames into a hole (13a2a) formed in a longitudinal projection (13a2) of a first frame portion (13g) of the cartridge frame from an outside of the first frame portion adjacent one longitudinal end portion of said photosensitive drum, penetrating the drum shaft through the photosensitive drum, and inserting the drum shaft penetrating the photosensitive drum into a hole (13a1a) formed in a longitudinal projection (13a1) of a second frame portion (13h) of the cartridge frame from an inside of the second frame portion adjacent the other longitudinal end portion of said photosensitive drum, wherein the ends of the drum shaft are supported on the first frame portion and the second frame portion of the cartridge frame respectively; and (c) mounting on the drum shaft, at a position disposed inside the outer end of one of said projections (13a1,13a2) in the longitudinal direction of said photosensitive drum a preventing member (32) for preventing the drum shaft from disengaging from the cartridge frame. A method according to claim 10, wherein one end of the drum shaft is press-fitted in the cartridge frame, and the other end is prevented from being disengaged by said preventing member. A method according to claim 10 or claim 11, wherein the preventing member (32) is in the form of a ring having an inside surface with an inward projection which is engaged with a groove formed in an outer periphery of said drum shaft when the preventing member is mounted on the drum shaft. A method according to any of claims 10 to 12, wherein the preventing member is mounted on the drum shaft after said drum shaft inserting step. An electrophotographic image forming apparatus, for forming an image on a recording material, comprising a process cartridge according to any of claims 1 to 9.

Inventors: MIYABE SHIGEO, NOMURA YOSHIYA, SASAGO YOSHIKAZU, MIYABE, SHIGEO, NOMURA, YOSHIYA, SASAGO, YOSHIKAZU
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1996
Main classification: G03G21
IPC codes: G03G15, G03G21