Process cartridge and electrophotographic image forming apparatus

A process cartridge having an insertion construction for a connecting pin swingably supporting a developing unit where there are achieved an improvement in assembly property, a minimization of container deformation, and prevention of coming-off of the connecting pin due to a small press-fitting region. The connecting pin swingably supporting the developing unit is formed of a styrene-based resin composite, and, by injecting a terpene solvent from a cutout of a photosensitive drum unit frame to the outer periphery of the connecting pin, integral connection is effected between the photosensitive drum unit frame and the connecting pin, and further, between the photosensitive drum unit frame and a drum bearing member. Due to a press-fit portion between the connecting pin and the photosensitive drum unit frame, no terpene solvent flows to the developing unit side.

This application claims priority from Japanese Patent Application No. 2004-246616 filed on Aug. 26, 2004, which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process cartridge for use in a copying machine, a printer, etc. adopting an electrophotographic process, and to an electrophotographic image forming apparatus using the same.

2. Related Background Art

Here, an electrophotographic image forming apparatus is an apparatus that forms an image on a recording medium by using an electrophotographic image forming system. Examples of an electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (laser beam printer, LED printer, and the like), a facsimile machine, and a word processor.

A process cartridge is obtained by integrating charging means, developing means, or cleaning means with an electrophotographic photosensitive drum into a cartridge which is detachably mountable to an image forming apparatus main body. Apart from this, a process cartridge is obtained by integrating at least one of charging means, developing means, and cleaning means with an electrophotographic photosensitive drum into a cartridge which is detachably mountable to an image forming apparatus main body. Further, a process cartridge is obtained by integrating at least developing means with an electrophotographic photosensitive drum (hereinafter referred to as the photosensitive drum) into a cartridge which is detachably mountable to an electrophotographic image forming apparatus main body.

Conventionally, an image forming apparatus using the electrophotographic image forming process adopts a process cartridge system, in which an electrophotographic photosensitive member and process means acting thereon are integrated into a cartridge, which is detachably mountable to the image forming apparatus main body. In such a process cartridge system, the user can perform maintenance on the apparatus without relying on the serviceman, so that it is possible to achieve a substantial improvement in terms of operability. Thus, the process cartridge system is widely used for image forming apparatuses.

As shown inFIG. 2, such a process cartridge is composed of a photosensitive drum unit50having a photosensitive drum1, a charging device2, and a cleaning device, and a developing unit4having developing means for developing an electrostatic latent image on the photosensitive drum1, with their respective frames being connected together by connecting pins. As shown inFIG. 2, in a process cartridge7, the component units are connected together by mating connecting holes47(48) provided at both ends of the developing unit frame46with support holes provided at both ends of the photosensitive drum unit frame51of the photosensitive drum unit50and by inserting pins from both ends of the photosensitive drum unit50.

In effecting connection on the conventional process cartridge, metal pins are brought into press-fit-engagement with the photosensitive drum unit frame so as to involve no play, and the developing unit frame is slidably supported in the region between the press-fit engagement portions.

In addition to quality, production efficiency is required of the recent image forming apparatuses. To achieve this, it is indispensable to achieve an improvement in the assembly property of the process cartridge through simplification of the assembly, a reduction in the number of inspection steps, etc., which proves particularly effective for the process cartridge, which is a consumable article. From this viewpoint, in simplifying the components of the process cartridge and reducing the number of inspection steps, it is necessary to satisfy the requirement in terms of quality after the completion of the product and to perform a design which helps to minimize deformation after assembly and variation in assembly.

SUMMARY OF THE INVENTION

The present invention has been made with a view toward solving the above problem in the conventional art.

It is an object of the present invention to achieve an improvement in terms of assembly property.

Another object of the present invention is to prevent frame deformation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, a multicolor image forming apparatus according to an embodiment of the present invention will be described in more detail with reference to the drawings.

[General Construction of the Multicolor Image Forming Apparatus]

First, the general construction of the multicolor image forming apparatus will be schematically described with reference toFIG. 1.FIG. 1is a longitudinal sectional view showing the general construction of a full-color laser beam printer100, which is a form of a multicolor image forming apparatus.

The multicolor image forming apparatus100shown inFIG. 1is equipped with four electrophotographic photosensitive drums1(1a,1b,1c, and1d), which are arranged side by side in the vertical direction. The photosensitive drums1are rotated counterclockwise as shown inFIG. 1by driving means (not shown). Around the photosensitive drums1, there are sequentially arranged, in the rotating direction, charging devices2(2a,2b,2c, and2d) for uniformly charging the surfaces of the photosensitive drums1, scanner units3(3a,3b,3c, and3d) for applying laser beams based on image information to form electrostatic latent images on the photosensitive drums1, developing devices4(4a,4b,4c, and4d) for causing toners to adhere to the electrostatic latent images to develop them into toner images, an electrostatic transfer device5for transferring the toner images on the photosensitive drums1to a transfer material R, cleaning devices6(6a,6b,6c, and6d) for removing transfer residual toner from the surfaces of the photosensitive drums1after transfer, etc. Here, the photosensitive drums1, the charging devices2, the developing devices4, and the cleaning devices6are integrated into process cartridges7(7a,7b,7c, and7d). In the following, the above components will be sequentially described, starting from the photosensitive drums1.

Each photosensitive drum1is formed by providing a photoconductive layer on the outer peripheral surface of an aluminum cylinder with a diameter, for example, of 24 mm. Each photosensitive drum1is rotatably supported at both ends by support members; by transmitting driving force from a drive motor (not shown) to one end, it is rotated counterclockwise.

As the charging devices2, it is possible to use contact charging type ones. Each charging member is formed as a conductive roller, which is brought into contact with the surface of the photosensitive drum1, and a charging bias voltage is applied to this roller, thereby uniformly charging the surface of the photosensitive drum1. This embodiment adopts a reversal developing system, so that the surfaces of the photosensitive drums1are charged to a negative polarity.

The scanner units3apply, by laser diodes (not shown), image light corresponding to image signals to polygon mirrors9(9a,9b,9c, and9d), which are rotated at high speed by scanner motors (not shown). The image light reflected by the polygon mirrors9is used to selectively perform exposure on the surfaces of the photosensitive drums1that have undergone charging to thereby form electrostatic latent images.

Referring toFIG. 2, the developing devices4will be described. The developing devices4are formed by toner containers respectively containing yellow, magenta, cyan, and black toners; in each of them, the toner in the developing unit frame46is fed to a toner supply roller43by a feeding mechanism42. The toner supply roller43rotates clockwise as shown inFIG. 2, supplying toner to a developing sleeve40, which serves as a developer carrier, and scraping away toner from the developing sleeve40after development on the photosensitive drum1.

The toner supplied to the developing sleeve40is applied to the outer periphery of the developing sleeve40, which rotates clockwise as shown inFIG. 2, by means of a developing blade44held in press contact with the outer periphery of the developing sleeve40, and, at the same time, receives charge.

Then, by applying a developing bias to the developing sleeve40opposed to the photosensitive drum1with a latent image formed thereon, development with toner is performed on the photosensitive drum1in accordance with the latent image.

The electrostatic transfer device5is equipped with an electrostatic conveyor belt11opposed to all the photosensitive drums1a,1b,1c, and1dand adapted to run while in contact therewith. The electrostatic conveyor belt11consists, for example, of a resin film or a multi-layer film-like member formed by providing a resin layer on a rubber base layer. The electrostatic conveyor belt11is stretched between a driving roller13, driven rollers14aand14b, and a tension roller15; it holds the transfer material R on the left-hand outer peripheral surface as shown inFIG. 1by an electrostatic attracting force, and runs so as to bring the transfer material R into contact with the photosensitive drums1. In this way, the transfer material R is conveyed to transfer positions by the electrostatic conveyor belt11, and the toner images on the photosensitive drums are transferred to the transfer material R.

Transfer rollers12(12a,12b,12c, and12d) are arranged side by side so as to be in contact with the inner side of the electrostatic conveyor belt11and at positions opposed to the four photosensitive drums1a,1b,1c, and1d. At the time of transfer, a bias of positive polarity is applied to the transfer rollers12, and a charge of positive polarity is applied to the transfer material R through the electrostatic conveyor belt11. Due to an electric field generated in this process, the toner image6fnegative polarity on each photosensitive drum1is transferred to the transfer material R held in contact with the photosensitive drum1.

A sheet feeding portion16serves to feed and convey the transfer materials R to the image forming portions, and has a sheet feeding cassette17containing the plural transfer materials R. When performing image formation, a feeding roller18(semicircular roller) and registration rollers19are rotated in accordance with the image forming operation, feeding one by one the transfer materials R in the sheet feeding cassette17; in this process, the leading end of each transfer material R abuts the registration rollers19to stop temporarily and forms a loop before being fed to the electrostatic conveyor belt11by the registration rollers19in synchronism with the running of the electrostatic conveyor belt11in terms of image writing positions.

A fixing portion20serves to fix toner images in a plurality of colors transferred to each transfer material R, and is composed of a rotary heating roller21aand a pressurizing roller21bbrought into press contact therewith and adapted to apply heat and pressure to the transfer material R. That is, the transfer material R to which the toner images on the photosensitive drums1have been transferred is conveyed by the pressurizing roller21bwhen passing the fixing portion20, and, at the same time, receives heat and pressure from the heating roller21a. As a result, toner images in a plurality of colors are fixed to the surface of the transfer material R.

In the image forming operation, the process cartridges7a,7b,7c, and7dare sequentially driven in accordance with the printing timing, and as they are thus driven, the photosensitive drums1a,1b,1c, and1dare rotated counterclockwise. Then, the scanner units3respectively corresponding to the process cartridges7are sequentially driven. By this driving, the charging rollers2impart uniform charge to the peripheral surfaces of the photosensitive drums1, and the scanner units3perform exposure on the peripheral surfaces of the photosensitive drums1in accordance with image signals to form electrostatic latent images on the peripheral surfaces of the photosensitive drums1. Developing sleeves40in the developing devices4cause toner to be transferred to the low potential portions of the electrostatic latent images to form toner images (i.e., perform development) on the peripheral surfaces of the photosensitive drums1.

The registration rollers19start rotation to feed the transfer material R to the electrostatic conveyor belt11such that the leading end of the toner image on the peripheral surface of the most upstream photosensitive drum1is brought through rotation to a point where it is opposed to the electrostatic conveyor belt11simultaneously with the start of printing on the transfer material R at that point.

The transfer material R is held in press contact with the outer periphery of the electrostatic conveyor belt11by being nipped between an electrostatic attraction roller22and the electrostatic conveyor belt11, and, by applying a voltage to the gap between the electrostatic conveyor belt11and the electrostatic attraction roller22, a charge is induced in the transfer material R which is a dielectric, and the dielectric layer of the electrostatic conveyor belt11, causing the transfer material to be electrostatically attracted to the outer periphery of the electrostatic conveyor belt11. In this way, the transfer material R is attracted to the electrostatic conveyor belt11in a stable manner and transferred to the most downstream transfer portion.

While the transfer material R is thus conveyed, the toner images on the photosensitive drums1are sequentially transferred to the transfer material R by electric fields generated between the photosensitive drums1and the transfer rollers12.

The transfer material R to which toner images in four colors have been transferred is separated from the electrostatic conveyor belt11due to the curvature of the belt driving roller13, and is carried into the fixing portion20. After the toner images have been thermally fixed to it by the fixing portion20, the transfer material R is discharged to the exterior of the apparatus main body from a discharging portion24by discharging rollers23, with the image side facing downwards.

[Construction of the Process Cartridge]

Next, a process cartridge according to the present invention will be described in more detail with reference toFIGS. 2,3A, and3B.FIGS. 2,3A, and3B are a main sectional view and perspective views of the process cartridge7containing toner.

The process cartridges7a,7b,7c, and7drespectively containing yellow, magenta, cyan, and black toners are of the same construction.

The process cartridge7is composed of the photosensitive drum unit50equipped with the electrophotographic photosensitive drum1serving as the image bearing member (hereinafter referred to as the photosensitive drum1), the charging means, and the cleaning means, and the developing unit4having the developing means for developing electrostatic latent images on the photosensitive drum1.

The photosensitive drum unit50has the photosensitive drum unit frame51. At the ends of the photosensitive drum unit frame51, there are provided bearing members30rotatably supporting the photosensitive drum. That is, the photosensitive drum unit frame51supports the photosensitive drum1through the intermediation of the bearing members. In the periphery of the photosensitive drum1, there are arranged a primary charging means2for uniformly charging the photoconductive layer provided on the outer peripheral surface of the photosensitive drum1, a cleaning blade60for removing developer remaining on the photosensitive drum1after transfer (residual toner), and a flexible sheet member80. Further, the residual toner (waste toner) removed from the surface of the photosensitive drum1by the cleaning blade60is accommodated in a waste toner chamber55provided at the rear of the photosensitive drum unit frame. Further, the abutment condition for the flexible sheet member80is set such that while the transfer residual toner on the drum passes the portion of the flexible sheet member80in contact with the drum and reaches the position of the cleaning blade60, the residual toner removed from the drum by the cleaning blade60does not leak to the exterior of the photosensitive drum unit frame51.

The developing unit4is composed of the developing sleeve40rotating in the direction of the arrow Y while maintaining a minute gap between itself and the photosensitive drum1, and developing frames45aand45bcontaining toner.

The developing frames45aand45bare connected to each other (by ultrasonic welding or the like) to form a developing unit frame46.

The developing sleeve40is rotatably supported by the developing unit frame46through the intermediation of bearing members, and, in the periphery of the developing sleeve40, there are arranged the toner supply roller43rotating in the direction of the arrow Z while in contact with the developing sleeve40, and the developing blade44. Further, inside the developing unit frame46, there is provided a toner feeding mechanism42for agitating the contained toner and feeding it to the toner supply roller43.

Then, by mating the connecting holes47and48provided at the ends of the developing unit frame46with the support holes provided at the ends of the photosensitive drum unit frame51of the photosensitive drum unit50and inserting the pins49from both ends of the photosensitive drum unit50, a suspension structure is obtained in which the entire developing unit4is supported so as to be swingable with respect to the photosensitive drum unit50.

Further, the developing unit4is constantly urged around the support holes by a pressurizing spring so as to hold the developing sleeve40in contact with the photosensitive drum1. At the time of development, the toner contained in the toner container41is carried to the toner supply roller43by the toner feeding mechanism42. The toner supply roller43rotating in the direction of the arrow Y is rubbed against the developing sleeve40rotating in the direction of the arrow Z to thereby supply the toner to the developing sleeve40, causing it to be carried by the developing sleeve40. As the developing sleeve40rotates, the toner carried by the developing sleeve40reaches the developing blade44, which regulates the toner to form a predetermined thin toner layer, imparting a predetermined amount of charge thereto. As the developing sleeve40rotates, the toner turned into a thin layer on the developing sleeve40is carried to the developing portion where the photosensitive drum1and the developing sleeve40are in close proximity to each other, and, in the developing portion, a developing bias is applied to the developing sleeve40from a power source (not shown), whereby the toner adheres to the electrostatic latent image formed on the surface of the photosensitive drum1, thereby developing the latent image. The toner remaining on the surface of the developing sleeve40without contributing to the development of the electrostatic latent image is returned to the developing device as the developing sleeve40rotates, and is separated from the developing sleeve40and recovered at the position where the developing sleeve40is rubbed against the toner supply roller43. The recovered toner is mixed with the residual toner through agitation by the toner feeding mechanism42.

[Attachment/Detachment of the Process Cartridge to/from the Image Forming Apparatus Main Body]

Next, the method of attaching/detaching the process cartridge7to/from the image forming apparatus main body100will be described with reference toFIG. 4. As shown inFIG. 4, the image forming apparatus main body100is equipped with a front cover101, which is provided so as to be rotatable. Further, inside the front cover101, an electrostatic transfer device5is rotatably provided. With the front cover101and the electrostatic transfer device5being open, the process cartridge7is detachably mountable to the image forming apparatus main body100. In the vicinity of the photosensitive drum support portions at the ends of the process cartridge7, there are provided grip members90, which protrude on the front cover side of the main body when the cartridge is attached/detached.

A guide rail portion (not shown) provided in the image forming apparatus main body100and an insertion guide portion (not shown) provided on the process cartridge7are engaged with each other, whereby the process cartridge7is detachably mountable to the image forming apparatus main body100.

Next, Embodiment 1 of the present invention will be described with reference toFIGS. 5 through 10.

First, connection between a connecting pin71, serving as a connecting member, and the photosensitive drum unit frame51will be described.

The connection between the photosensitive drum unit frame51and the connecting pin71is effected as follows.

The connecting pin71is composed of small diameter portions71bat the ends and a large diameter portion71cat the center.

The connection between the small diameter portions71bof the connecting pin71and the photosensitive drum unit frame51is effected by press fitting.

The connection between the large diameter portion71cof the connecting pin71and the photosensitive drum unit frame51is effected by the following connections: connection through adhesion, by an adhesive consisting of a terpene solvent, of a part or all of a fitting portion S where there is a minute gap between the large diameter portion71cof the connecting pin71and the photosensitive drum unit frame51, and connection through press fitting of the large diameter portion71cand the small diameter portions71bof the connecting pin71into the photosensitive drum unit frame51.

The method of injecting the adhesive for effecting connection between the large diameter portion71cof the connecting pin71and the photosensitive drum unit frame51will be described.

In the photosensitive drum unit frame51, a cutout52is formed in the portion into which the connecting pin71is fitted, and the cutout52serves as the injection inlet for the terpene solvent serving as the adhesive. The terpene solvent injected through the injection inlet flows into a flow passage (first flow passage) for the adhesive for connecting the photosensitive drum unit frame51and the connecting pin71to each other. More specifically, the supplied solvent fills the fitting portion S, using, as the first flow passage, a gap which communicates with the injection inlet and which is between the inner peripheral portion53aof the photosensitive drum unit frame and the outer peripheral portion71aof the connecting pin, thus effecting integral connection.

The portion where the connection between the large diameter portion71cof the connecting pin71and the photosensitive drum unit frame51is effected by press fitting extends over the range indicated by reference symbol E, which is 1 to 3 mm from a wall end surface51cof a recess51bof the photosensitive drum unit frame51. Thus, due to the portion E, where the press fitting is effected, the terpene solvent is prevented from flowing to the developing unit frame side.

It is desirable for the supply of terpene solvent to the fitting portion to be effected by a capillary phenomenon. In view of this, a slight contact or a minute gap is desired in the fitting portion. In this embodiment, the fitting engagement between the inner peripheral portion53aof the photosensitive drum unit frame and the outer peripheral portion71aof the connecting pin is H9/g9.

By thus diminishing the press fitting region between the photosensitive drum unit frame and the connecting pin, the requisite insertion force for the connecting pin71is reduced, thereby achieving an improvement in terms of productivity. Further, since as little stress as possible is imparted to the photosensitive drum unit frame51, the distortion of the photosensitive drum unit frame is mitigated, and it is possible to achieve an improvement in terms of the arrangement accuracy of the photosensitive drum and the cleaning blade.

Due to its symmetrical configuration, the connecting pin71of this embodiment allows assembly with no directional limitation.

The suspension portion49of the developer container is swingably supported, with a minute gap between itself and the large diameter portion71cof the connecting pin71.

Next, the connection between the photosensitive drum unit frame51and the drum bearing members30will be described.

The connection between the photosensitive drum unit frame51and each drum bearing member30is effected by a terpene solvent injected through an injection inlet52.

Here, the adhesive flow passage (second flow passage) for effecting the connection between the photosensitive drum unit frame51and the drum bearing member30is connected to the first adhesive flow passage for effecting the connection between the photosensitive drum unit frame51and the connecting pin71. Thus, by injecting the terpene solvent into the terpene solvent injection inlet52, it is possible to effect the connection between the photosensitive drum unit frame51and the drum bearing member30and the connection between the photosensitive drum unit frame51and the connecting pin71by a single process, thereby achieving an improvement in terms of productivity. This will be described more specifically. The joint surface T of the photosensitive drum unit frame51(the shaded area inFIG. 6) has minute protrusions and recesses (not shown) and a recess (slit)54constituting the second flow passage extending from the hole53in fit-engagement with the connecting pin71. It is desirable for the supply of the terpene solvent to the joint surface T to be effected by a capillary phenomenon. Thus, it is desirable for the recess54, communicating with the terpene solvent injection inlet52and constituting the flow passage to the joint surface T, to have a width of 0.1 to 2 mm and a depth of 0.1 to 2 mm, and it is desirable for the flow passage formed by the recess54to have a sectional area of 4 mm or less. In a flow passage having a sectional area larger than 4 mm2, a capillary phenomenon does not occur easily, and the supply of terpene solvent to the joint surface T has a tendency to become difficult. In this embodiment, the recess has a width of 0.5 mm and a depth of 0.5 mm, and is situated within the range of the minute protrusions and recesses.

The terpene solvent having passed through the fit-engagement portion of the first flow passage and supplied to the portion in the vicinity of the joint surface T, is spread from the flow passage over the entire joint surface T due to the capillary phenomenon of the recess of the second flow passage and the minute protrusions and recesses formed around the same, with the result that the surfaces of the photosensitive drum unit frame51and the drum bearing member30are integrally joined together (see the arrows inFIG. 6).

When the terpene solvent having passed through the first flow passage is to be spread over the entire joint surface by the second flow passage, the supply thereof to the joint surface by utilizing a capillary phenomenon is rather difficult if the gaps between the components to be joined together are large. On the other hand, when the surfaces to be joined together are being firmly pressed against each other and the contact strength is high, a capillary phenomenon does not occur easily, either, making the supply of terpene solvent rather difficult. Thus, it is desirable that the portions to be joined together be in close proximity to or in slight contact with each other; in this regard, it is also desirable, as indicated by reference symbol M inFIG. 7, to provide minute protrusions and recesses in at least one of the joint surfaces so as to define a space allowing the terpene solvent to be spread over the joint surface by a capillary phenomenon. Such protrusions and recesses consist, for example, of wrinkles whose average depth (Rz) preferably ranges from 20 to 40 μm. When the depth exceeds 40 μm, the connection of the trough portions of the wrinkles with the mating component is rather insufficient, with the result that the joint strength tends to be reduced as a whole.

In the joint portion of this embodiment, the wrinkles are formed in the joint surface51aof the photosensitive drum unit frame51and the mating joint surface30aof the drum bearing member30is flat.

As shown inFIG. 8, a hole31is formed in a part of the drum bearing member30so as to be opposed to a position where the recess54is partly visible. Here, the region of the recess54that can be checked through the hole31is indicated by reference symbol54a. As described above, the injected terpene solvent flows from the injection inlet through the recess54constituting the second flow passage to pervade the joint surface T, so that, during that process, it is possible to check from outside how the solvent passes through the recess54a. Further, if the passing of the terpene solvent is not ascertained in real time, it can be ascertained after a fixed period of time has elapsed since the surface gloss of the recess54achanges after the passage of the terpene solvent.

Specific examples of the inspection means include visual inspection by the inspector, various apparatuses, such as means for measuring displacement of the recess54aby a laser displacement meter, and means for performing photographing by a photographing device using a CCD camera (image processing device) and analyzing and judging the obtained image by an analysis device. As compared with the conventional destructive inspection through sampling, all of the above-mentioned means make it possible to perform total inspection very easily; further, there are no cartridges to be disposed of, thereby achieving a substantial improvement in terms of production efficiency.

In this embodiment, the injection of the terpene solvent is performed with the terpene solvent injection inlet placed at the top position, facilitating the pervasion of the solvent by the gravitational force. However, there are no particular limitations regarding the injection attitude as long as the solvent can pervade the entire joint area. In this embodiment, the injection amount is 10 to 50 μl.

In the present invention, there are no particular limitations regarding the frame and components to be joined together as long as they consist of a styrene-based resin composite that can be dissolved in a terpene solvent. Examples of a styrene-based resin composite that can be suitably used as the cartridge material include high-impact polystyrene (HIPS), which is a rubber-modified styrene-based material. In order to achieve an improvement in impact resistance, this material is obtained by mixing a rubber-like polymer or a rubber-like copolymer with polystyrene (PS), which is inexpensive and of satisfactory fluidity.

Further, examples of the terpene-based solvent used for connection in the present invention include d-limonene, 1-limonene, dl-limonene, d-α-pinene, d-β-pinene, α-terpinene, β-terpinene, γ-terpinene, terpinolene, 2-carene, d-3-carene, 1-3-carene, and phellandrene. Of those, d-limonene, 1-limonene, and dl-limonene are preferably used. Of those, d-limonene which provides the highest solubility of the styrene-based resin is particularly preferably used.

Next, Embodiment 2 of the present invention will be described with reference toFIG. 12.

In Embodiment 1, the inner peripheral portion32of each drum bearing member30has, between itself and the outer peripheral portion71aof the connecting pin71, a gap small enough not to allow intrusion of terpene solvent by a capillary phenomenon. In Embodiment 2, in contrast, there is secured, between the inner peripheral portion32of each drum bearing member30and the outer peripheral portion71aof the connecting pin71, a gap large enough to allow intrusion of terpene solvent by a capillary phenomenon. Due to this arrangement, the three components (the connecting pin71, the photosensitive drum unit frame51, and the drum bearing member30) can be joined together by a single injection of terpene solvent.

Next, Embodiment 3 of the present invention will be described with reference toFIGS. 13 and 14.

In the connecting pin71described with reference to Embodiment 1, a communication hole72is formed so as to extend in the axial direction, and, further, a slit73is formed in the portion of the large diameter portion of the connecting pin corresponding to the cutout (the terpene solvent injection inlet)52formed in the photosensitive drum unit frame. Further, the fit-engagement of the small diameter portion71bof the connecting pin71and the photosensitive drum unit frame51is effected in H9/g9 with a minute gap therebetween. Due to this construction, a flow passage for the terpene solvent is also formed in the communication hole72, making it possible to effect connection by adhesive of the small diameter portion71band the photosensitive drum unit frame51by the terpene solvent supplied from the injection inlet52. Further, by effecting press-fitting between the small diameter portion71band part of the photosensitive drum unit frame51, it is possible to realize a construction in which no terpene solvent flows to the developer container side.

Next, Embodiment 4 of the present invention will be described with reference toFIG. 15.

A connecting pin70formed of a conductive styrene-based resin composite can also serve as a contact. More specifically, the connecting pin70comes into contact with a main body contact102that is in electrical contact with a high-voltage unit in the image forming apparatus main body100, and a high-voltage current is applied to an electrode plate80of the process cartridge7through the connecting pin70to supply electricity to the charging device2. The electrode plate80is equipped with a cut-and-raised portion80a, which is in contact with the connecting pin70. The electrode plate80effects connection between the connecting pin70and the charging device2.