Title:
Process cartridge and electrophotographic image forming apparatus
Document Type and Number:
Kind Code:
A1

Abstract:
A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, includes a photosensitive drum; a developing roller rotatable in the same direction as that of the drum when the cartridge is mounted to the apparatus; a first separation member disposed at one end of the roller so as to provide a gap between the roller and the drum, the first separation member being contacted to the surface of the drum adjacent one end thereof; a second separation member at the other end so as to provide a gap between the developing roller and a peripheral surface of the drum, the first separation member being contacted to the drum adjacent the other end thereof; a charging roller, contacted to the drum, for charging the drum, which is rotatable with a peripheral speed difference relative to the drum by a driving force received from the assembly; and a cleaning member contacted to the drum adjacent one end thereof, the cleaning member having an effective area which is outside a developing zone of the developing roller and inside a contact region where the charging roller is contacted to the drum and which is in a region where the first separation member is contacted to the peripheral surface of the drum.

Representative Image:
Process cartridge and electrophotographic image forming apparatus
Inventors:
Morioka, Masanari (Numazu-shi, JP)
Satoh, Hiroshi (Toride-shi, JP)
Yoshida, Masahiro (Tokyo, JP)
Batori, Yoshiyuki (Mishima-shi, JP)
Matsumaru, Naoki (Shizuoka-ken, JP)
      Plaque It!

Application Number:
10/417115
Publication Date:
01/22/2004
Filing Date:
04/17/2003
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Export Citation:
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Assignee:
CANON KABUSHIKI KAISHA (Tokyo, JP)
Primary Class:
399/111
International Classes:
(IPC1-7): G03G021/16
Attorney, Agent or Firm:
FITZPATRICK CELLA HARPER & SCINTO (30 ROCKEFELLER PLAZA, NEW YORK, NY, 10112, US)
Claims:

What is claimed is:



1. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising: an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum, said developing roller being rotatable in the same direction as that of said electrophotographic photosensitive drum by the driving force received from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; a first separation member disposed at one end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent one end thereof; a second separation member disposed at the other end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said lectrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent the other end thereof; a charging roller, contacted to said electrophotographic photosensitive drum, for electrically charging said electrophotographic photosensitive drum, wherein said charging roller is rotatable with a peripheral speed difference relative to the electrophotographic photosensitive drum by a driving force received from the main assembly of the apparatus; and a cleaning member contacted to the peripheral surface of the electrophotographic photosensitive drum adjacent one end thereof, said cleaning member having an effective area which is outside a developing zone of the developing roller and inside a contact region where said charging roller is contacted to said electrophotographic photosensitive drum and which is in a region where said first separation member is contacted to the peripheral surface of said electrophotographic photosensitive drum.

2. A process cartridge according to claim 1, wherein said cleaning member includes (a) layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a non-woven fabric fixed thereto, (b) a layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a felt layer fixed thereto, (c) a layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a pile fabric fixed thereto, (d) a polyurethane foam and a high density polyurethane fixed to a part of the polyurethane foam, (e) felt, (f) polyurethane foam, or (g) non-woven fabric.

3. A process cartridge according to claim 1 or 2, wherein said first separation member and said second separation member are cap-like rollers covering a part of the peripheral surface of said developing roller.

4. A process cartridge according to claim 1 or 2, wherein there is provided no cleaning blade which is contacted to t said electrophotographic photosensitive drum in substantially entire longitudinal length thereof to remove the developer remaining on said electrophotographic photosensitive drum.

5. An electrophotographic image forming apparatus for forming an image on a recording material, to which a process cartridge is detachably mountable, said apparatus comprising: a mounting portion for detachably mounting a process cartridge, which includes, (i) an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum, said developing roller being rotatable in the same direction as that of said electrophotographic photosensitive drum by the driving-force received from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; a first separation member disposed at one end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent one end thereof; a second separation member disposed at the other end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent the other end thereof; a charging roller, contacted to said electrophotographic photosensitive drum, for electrically charging said electrophotographic photosensitive drum, wherein said charging roller is rotatable with a peripheral speed difference relative to the electrophotographic photosensitive drum by a driving force received from the main assembly of the apparatus; and a cleaning member contacted to the peripheral surface of the electrophotographic photosensitive drum adjacent one end thereof, said cleaning member having an effective area which is outside a developing zone of the developing roller and inside a contact region where said charging roller is contacted to said electrophotographic photosensitive drum and which is in a region where said first separation member is contacted to the peripheral surface of said electrophotographic photosensitive drum; and (ii) a feeding member for feeding the recording material.

6. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising: an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum, said developing roller being rotatable in the same direction as that of said electrophotographic photosensitive drum by the driving force received from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; a first separation member disposed at one end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent one end thereof; a second separation member disposed at the other end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent the other end thereof; a charging roller, contacted to said electrophotographic photosensitive drum, for electrically charging said electrophotographic photosensitive drum, wherein said charging roller is rotatable with a peripheral speed difference relative to the electrophotographic photosensitive drum by a driving force received from the main assembly of the apparatus; a cleaning member contacted to the peripheral surface of the electrophotographic photosensitive drum adjacent one end thereof, said cleaning member having an effective area which is outside a developing zone of the developing roller and inside a contact region where said charging roller is contacted to said electrophotographic photosensitive drum and which is in a region where said first separation member is contacted to the peripheral surface of said electrophotographic photosensitive drum, wherein said cleaning member includes (a) layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a nonwoven fabric fixed thereto, (b) a layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a felt layer fixed thereto, (c) a layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a pile fabric fixed thereto, (d) a polyurethane foam and a high density polyurethane fixed to a part of the polyurethane foam, (e) felt, (f) polyurethane foam, or (g) non-woven fabric, wherein said first separation member and said second separation-member are cap-like rollers covering a part of the peripheral surface of said developing roller, and wherein there is provided no cleaning blade which is contacted to t said electrophotographic photosensitive drum in substantially entire longitudinal length thereof to remove the developer remaining on said electrophotographic photosensitive drum.

7. A process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising: an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum, said developing roller being rotatable in the same direction as that of said electrophotographic photosensitive drum by the driving force received from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; a first separation member disposed at one end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent one end thereof; a second separation member disposed at the other end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent the other end thereof; a charging roller, contacted to said electrophotographic photosensitive drum, for electrically charging said electrophotographic photosensitive drum, wherein said charging roller is rotatable with a peripheral speed difference relative to the electrophotographic photosensitive drum by a driving force received from the main assembly of the apparatus; a cleaning member contacted to the peripheral surface of the electrophotographic photosensitive drum adjacent one end thereof, said cleaning member having an effective area which is outside a developing zone of the developing roller and inside a contact region where said charging roller is contacted to said electrophotographic photosensitive drum and which is in a region where said first separation member is contacted to the peripheral surface of said electrophotographic photosensitive drum, wherein said first separation member and said second separation member are cap-like rollers covering a part of the peripheral surface of said developing roller, and wherein there is provided no cleaning blade which is contacted to t said electrophotographic photosensitive drum in substantially entire longitudinal length thereof to remove the developer remaining on said electrophotographic photosensitive drum.

8. An electrophotographic image forming apparatus for forming an image on a recording material, to which a process cartridge is detachably mountable, said apparatus comprising: (i) a mounting portion for detachably mounting a process cartridge, which includes, an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum, said developing roller being rotatable in the same direction as that of said electrophotographic photosensitive drum by the driving force received from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; a first separation member disposed at one end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent one end thereof; a second separation member disposed at the other end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent the other end thereof; a charging roller, contacted to said electrophotographic photosensitive drum, for electrically charging said electrophotographic photosensitive drum, wherein said charging roller is rotatable with a peripheral speed difference relative to the electrophotographic photosensitive drum by a driving force received from the main assembly of the apparatus; a cleaning member contacted to the peripheral surface of the electrophotographic photosensitive drum adjacent one end thereof, said cleaning member having an effective area which is outside a developing zone of the developing roller and inside a contact region where said charging roller is contacted to said electrophotographic photosensitive drum and which is in a region where said first separation member is contacted to the peripheral surface of said electrophotographic photosensitive drum, wherein said cleaning member includes (a) layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a nonwoven fabric fixed thereto, (b) a layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a felt layer fixed thereto, (c) a layer member structure having an elastic member of a polyurethane foam layer or a felt layer and a pile fabric fixed thereto, (d) a polyurethane foam and a high density polyurethane fixed to a part of the polyurethane foam, (e) felt, (f) polyurethane foam, or (g) non-woven fabric, wherein said first separation member and said second separation member are cap-like rollers covering a part of the peripheral surface of said developing roller, and wherein there is provided no cleaning blade which is contacted to t said electrophotographic photosensitive drum in substantially entire longitudinal length thereof to remove the developer remaining on said electrophotographic photosensitive drum; and (ii) a feeding member for feeding the recording material.

9. An electrophotographic image forming apparatus for forming an image on a recording, material, to which a process cartridge is detachably mountable, said apparatus comprising: (i) a mounting portion for detachably mounting a process cartridge, which includes, an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum, said developing roller being rotatable in the same direction as that of said electrophotographic photosensitive drum by the driving force received from the main assembly of the apparatus when said process cartridge is mounted to the main assembly of the apparatus; a first separation member disposed at one end of said developing roller so as to provide a gap between the peripheral surface of said developing roller-and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent one end thereof; a second separation member disposed at the other end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent the other end thereof; a charging roller, contacted to said electrophotographic photosensitive drum, for electrically charging said electrophotographic photosensitive drum, wherein said charging roller is rotatable with a peripheral speed difference relative to the electrophotographic photosensitive drum by a driving force received from the main assembly of the apparatus; a cleaning member contacted to the peripheral surface of the electrophotographic photosensitive drum adjacent one end thereof, said cleaning member having an effective area which is outside a developing zone of the developing roller and inside a contact region where said charging roller is contacted to said electrophotographic photosensitive drum and which is in a region where said first separation member is contacted to the peripheral surface of said electrophotographic photosensitive drum, wherein said first separation member and said second separation member are cap-like rollers covering a part of the peripheral surface of said developing roller, and wherein there is provided no cleaning blade which is contacted to t said electrophotographic photosensitive drum in substantially entire longitudinal length thereof to remove the developer remaining on said electrophotographic photosensitive drum, (ii) a feeding member for feeding the recording material.

Description:

FIELD OF THE INVENTION AND RELATED ART

[0001] The present invention relates to a process cartridge detachably mountable to an electrophotographic image forming apparatus and an electrophotographic image forming apparatus.

[0002] The electrophotographic image forming apparatus forms an image on a recording material through an electrophotographic image formation type process. Examples of the electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (laser beam printer, LED printer or the like), the facsimile machine, a word processor or a complex machine (multifunction printer or the like) or the like.

[0003] The process cartridge integrally contains an electrophotographic photosensitive drum, and charging means, developing means or cartridge, in the form of a unit or a cartridge, which is detachably mountable as a unit to a main assembly of an image forming apparatus. The process cartridge may contain the electrophotographic photosensitive drum, and at least one of charging means, developing means and cleaning means, in the form of a cartridge which is detachably mountable as a unit to the main assembly of the image forming apparatus. Furthermore, the process cartridge may contain at least developing means and electrophotographic photosensitive member in the form of a cartridge which is detachably mountable as a unit to the main assembly of the image forming apparatus.

[0004] In an image forming apparatus using an electrophotographic image forming process, a process cartridge type in which an electrophotographic photosensitive member and process means actable on said electrophotographic photosensitive member are contained as a unit in a process cartridge which is detachably mountable to the main assembly of the image forming apparatus, has been used. The process cartridge type is advantageous in that maintenance operations can be performed not by a service person but by the user in effect, and therefore, operation property has been significantly improved. Therefore, the process cartridge type is widely used in the field of image forming apparatus.

[0005] In order to provide satisfactory images by the electrophotographic image forming apparatus using such a process cartridge, it is necessary that process cartridge is mounted at a predetermined position in the main assembly of the electrophotographic image forming apparatus to establish correct connection of the interface portions such as various electrical contacts and a drive transmitting portion.

[0006] Referring to FIG. 31 , there is shown a process cartridge CR, and FIG. 32 illustrates a cartridge mounting guide GL provided in a main assembly PR of the image forming apparatus. FIG. 33 shows an image forming apparatus employing of such a process cartridge CR.

[0007] As shown in FIG. 31 - FIG. 33 , for mounting and demounting of the process cartridge CR relative to the main assembly PR of the image forming apparatus, a positioning boss CB is provided across the axis of the photosensitive drum which is the electrophotographic photosensitive member, and the main assembly PR of the image forming apparatus is provided with a mounting guide GL for guiding and positioning the positioning boss CB. When the user inserted the process cartridge CR to a predetermined position along the cartridge mounting guide GL, an abutting portion P provided in the main assembly PR of the image forming apparatus is abutted by the process cartridge CR such that rotation of process cartridge CR about the positioning boss CB is prevented. The apparatus of such a structure has been put into practice.

[0008] In the main assembly PR of the image forming apparatus having such a structure, there is a possibility that small amount of toner floats when the toner image is transferred onto a recording material or when the recording material carrying the transferred toner image is being conveyed toward the image fixing means spreads are.

[0009] Such floating toner may be fused on the surface of the photosensitive drum at position where cap-like rollers are provided to the axial ends of the developing roller to be contacted to the photosensitive drum by spring force in order to maintain a predetermined gap between the photosensitive drum and the developing roller.

[0010] The amount of the fused toner gradually increases until the lifetime of the process cartridge is reached even to such an extent that block of the toner appears at the contact portion between the photosensitive drum and the cap-like roller.

[0011] If such a block of the toner is deposited at the contact portion between the photosensitive drum and the cap roller, the gap between the photosensitive drum and the developing roller varies with a result of deterioration of the developing performance of the latent image on the photosensitive drum with the toner. In addition, if the developing roller rolls on the block of the toner, vibration is produced with the possible result of non-uniformity on the resultant image in the direction perpendicular to the feeding direction of the recording material.

[0012] Moreover, if the floating toner is deposit on an un-charging region of photosensitive drum, that is, outside of a contact region relative to the charging roller, the recording material might be contaminated with the toner at the lateral ends of the recording material.

SUMMARY OF THE INVENTION

[0013] Accordingly, it is a principal object of the present invention to provide a process cartridge and an electrophotographic image forming apparatus wherein deposition of the toner is prevented at the positions outside the contact region between the photosensitive drum and charging roller and the positions where the photosensitive drum and the developing roller are contacted to each other.

[0014] It is another object of the present invention to provide a process cartridge and an electrophotographic image forming apparatus in which unnecessary deposition of the toner onto the photosensitive drum is effectively prevented.

[0015] It is a further object of the present invention to provide a process cartridge and an electrophotographic image forming apparatus in which unnecessary deposition of the toner onto the contact portion between the photosensitive drum and developing roller.

[0016] According to an aspect of the present invention, there is provided a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, said process cartridge comprising: an electrophotographic photosensitive drum; a developing roller for developing an electrostatic latent image formed on said electrophotographic photosensitive drum, said developing roller being rotatable in the same direction as that of said electrophotographic photosensitive drum by the driving force received from the main assembly of apparatus when said process cartridge is mounted to the main assembly of the apparatus; a first separation member disposed at one end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent one end thereof; a second separation member disposed at the other end of said developing roller so as to provide a gap between the peripheral surface of said developing roller and a peripheral surface of said electrophotographic photosensitive drum, said first separation member being contacted to the peripheral surface of said electrophotographic photosensitive drum adjacent the other end thereof; a charging roller, contacted to said electrophotographic photosensitive drum, for electrically charging said electrophotographic photosensitive drum, wherein said charging roller is rotatable with a peripheral speed difference relative to the electrophotographic photosensitive drum by a driving force received from the main assembly of the apparatus; and a cleaning member contacted to the peripheral surface of the electrophotographic photosensitive drum adjacent one end thereof, said cleaning member having an effective area which is outside a developing zone of the developing roller and inside a contact region where said charging roller is contacted to said electrophotographic photosensitive drum and which is in a region where said first separation member is contacted to the peripheral surface of said electrophotographic photosensitive drum.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a schematic sectional view of the image forming apparatus in one of the preferred embodiments of the present invention, in which a process cartridge in accordance with the present invention has been properly mounted, describing the general structure thereof.

[0018] FIG. 2 is a schematic sectional view of the process cartridge in the preferred embodiment of the present invention, describing the structure thereof.

[0019] FIG. 3 is a perspective view of the process cartridge in accordance with the present invention, in FIG. 2 .

[0020] FIG. 4 is another perspective view of the process cartridge in accordance with the present invention, in FIG. 2 .

[0021] FIG. 5 is an exploded perspective view of the drum frame unit of the process cartridge in accordance with the present invention.

[0022] FIG. 6 is a perspective view of the drum frame unit of the process cartridge in accordance with the present invention.

[0023] FIG. 7 is a perspective view of the side holder of the drum frame unit.

[0024] FIG. 8 is a plan view of the charge roller driving means, describing the structure thereof.

[0025] FIG. 9 is an exploded perspective view of the charge roller driving means, describing the structure thereof.

[0026] FIG. 10 is a perspective view of the process cartridge driving mechanism, in the preferred embodiment of the present invention.

[0027] FIG. 11 is a schematic sectional view of the gear train of the process cartridge driving mechanism in FIG. 10 , describing the structure thereof.

[0028] FIG. 12 is a plan view of the gear train of the process cartridge driving mechanism in FIG. 10 , describing the structure thereof.

[0029] FIG. 13 is a perspective view of the process cartridge driving mechanism, in another embodiment of the present invention, describing the structure thereof.

[0030] FIG. 14 is a schematic sectional view of the process cartridge driving mechanism in FIG. 13 , describing the structure thereof.

[0031] FIG. 15 is a plan view of the process cartridge driving mechanism in FIG. 13 , describing the structure thereof. FIG. 16 ( a ) is a perspective view of the toner sealing member in the preferred embodiment of the present invention, and FIG. 16 ( b ) is a sectional view of the same toner sealing member.

[0032] FIG. 17 is a perspective view of the toner storage-developing means frame, and frame lid, of the cartridge in the preferred embodiment of the present invention, describing how they are joined.

[0033] FIG. 18 is a drawing for describing how the toner sealing member is joined with the toner storage-developing means frame.

[0034] FIG. 19 is an exploded perspective view of the development unit of the process cartridge in accordance with the present invention.

[0035] FIG. 20 is a perspective view of the development unit in FIG. 19 .

[0036] FIG. 21 is a drawing for describing how the cleaning members of the process cartridge in accordance with the present invention are attached.

[0037] FIG. 22 is a schematic sectional view of an image forming apparatus, describing how the process cartridge is mounted into the image forming apparatus.

[0038] FIG. 23 is a schematic sectional view of the image forming apparatus, describing how the process cartridge is mounted into the image forming apparatus.

[0039] FIG. 24 is a perspective view of one of the cartridge guiding portions of the image forming apparatus in the preferred embodiment of the present invention.

[0040] FIG. 25 is a perspective view of the other cartridge guiding portion of the image forming apparatus, in the preferred embodiment of the present invention.

[0041] FIG. 26 is a drawing for describing how the process cartridge is accurately positioned relative to the image forming apparatus. FIG. 27 is a drawing for describing how the process cartridge is accurately positioned relative to the image forming apparatus.

[0042] FIG. 28 is a drawing for describing how the process cartridge is accurately positioned relative to the image forming apparatus.

[0043] FIG. 29 is a schematic drawing of one of the modifications of the contact portions of the process cartridge in accordance with the present invention.

[0044] FIG. 30 is a schematic drawing of another modification of the contact portion of the process cartridge in accordance with the present invention.

[0045] FIG. 31 is a perspective view of a process cartridge in accordance with the prior arts.

[0046] FIG. 32 is a perspective view of one of the cartridge guiding portions of an image forming apparatus in accordance with the prior arts.

[0047] FIG. 33 is a schematic sectional view of an image forming apparatus in accordance with the prior arts, which is properly holding the process cartridge in accordance with the prior arts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] Hereinafter, a combination of a process cartridge and an electrophotographic image forming apparatus, in accordance with the present invention, will be described in more detail with reference to the appended drawings.

[0049] In the following description of the present invention, the lengthwise direction of a process cartridge means the direction intersectional (roughly perpendicular) to the direction in which a process cartridge is mounted into, or removed from, the main assembly of an image forming apparatus. It is parallel to the surface of recording medium, and is intersectional (roughly perpendicular) to the direction in which the recording medium is conveyed. The right or left direction means the right or left direction of the recording medium as the recording medium is seen from the rear side in terms of the recording medium conveyance direction. The top surface of a process cartridge means the surface of the process cartridge which will be on the top side after the proper mounting of the process cartridge in the main assembly of an image forming apparatus, and the bottom surface of the process cartridge means the surface of the process cartridge which will be on the bottom side after the proper mounting of the process cartridge in the apparatus main assembly.

[0050] FIG. 1 shows one of the preferred embodiments of an electrophotographic image forming apparatus in accordance with the present invention. In this embodiment, a process cartridge B shown in FIG. 2 is removably mountable in this electrophotographic image forming apparatus. FIG. 1 is a schematic drawing for describing the structure of this electrophotographic image forming apparatus, which is properly holding the process cartridge B in FIG. 2 . FIG. 2 is a schematic drawing for describing the structure of the process cartridge B.

[0051] As for the order of description, the general structure of the process cartridge B and the general structure of the electrophotographic image forming apparatus employing the process cartridge B will be first described. Then, the structure of the mechanism of the image forming apparatus main assembly for guiding the process cartridge B when the process cartridge B is mounted into, or removed from, the main assembly of the electrophotographic image forming apparatus will be described.

[0052] (General Structure)

[0053] Referring to FIG. 1 , the electrophotographic image forming apparatus A (which hereinafter will be referred to simply as “image forming apparatus”) in this embodiment is a laser beam printer, and has an electrophotographic photoconductive member 7 in the form of a drum (which hereinafter will be referred to simply as “photoconductive drum”), as an image bearing member, which comprises an aluminum cylinder, and a photoconductive layer, that is, a layer of organic photoconductive substance, coated on the entirety of the peripheral surface of the aluminum cylinder.

[0054] A beam of light carrying image formation information is projected onto the photoconductive drum 7 from an optical system 1 , forming a latent image on the photoconductive drum 7 . This latent image is developed into a toner image with the use of developer (which hereinafter may be referred to as “toner”).

[0055] In synchronism with the formation of the toner image, a single or plurality of sheets of recording medium 2 in the sheet feeder cassette 3 a are fed one by one into the apparatus main assembly by the combination of a pickup roller 3 b , and a pressing member 3 c kept pressed against the pickup roller 3 b , and are conveyed further inward by a conveying means 3 f.

[0056] The toner image formed on the photoconductive drum 7 in the process cartridge B is transferred onto the recording medium 2 by applying voltage to a transfer roller 4 as a transferring means. Then, the recording medium 2 is conveyed to a fixing means 5 by the conveying means 3 f.

[0057] The fixing means 5 comprises: a driving roller 5 a , a heater 5 b , a supporting member 5 c , and a rotational fixing member 5 d . The rotational fixing member 5 d is a cylinder formed of sheet of a certain substance, and is supported by the supporting member 5 c . The heater 5 b is in the hollow of the rotational fixing member 5 d . The fixing means 5 fixes the unfixed toner image on the recording medium 2 to the recording medium 2 , by the application of heat and pressure to the recording medium 2 while the recording medium 2 is passed through the fixing means 5 . After the fixation, the recording medium 2 is further conveyed and discharged into the delivery area 6 , by a pair of discharge rollers 3 d.

[0058] (Process Cartridge)

[0059] On the other hand, the process cartridge B comprises an electrophotographic photoconductive member, and a minimum of one processing means. As for the processing means, there are, for example, a charging means for charging the electrophotographic photoconductive member, and a developing means for developing a latent image formed on the electrophotographic member.

[0060] Referring to FIGS. 1 and 2 , the process cartridge B in this embodiment comprises the photoconductive drum 7 , as an electrophotographic photoconductive drum, having a photoconductive layer, a charge roller 8 as a charging means, a developing means 10 , and an exposure opening 9 . In operation, while the photoconductive drum 7 is rotated, the peripheral surface of the photoconductive drum 7 is uniformly charged by the application of voltage to the charge roller 8 , and the uniformly charged portion of the peripheral surface of the photoconductive drum 7 is exposed to an optical image projected from the optical system 1 , forming a latent image. Then, the latent image is developed by the developing means 10 .

[0061] The developing means 10 in this embodiment comprises a toner storage-developing means frame 10 f 1 , a frame lid 10 f 2 , a rotational toner conveyance roller 10 b as a toner conveying means, a development roller 10 d (in which a magnet 10 c is stationarily disposed) as a rotational developing member, and a development blade 10 e . The toner storage-developing means frame 10 f 1 and frame lid 10 f 2 are joined, creating a toner chamber (toner storage) 10 a in which toner (magnetic single-component developer) is stored, and a development chamber 10 i . In operation, the toner in the toner chamber 10 a is sent out into the development chamber 10 through the opening (toner passage) 10 k of the toner storage-developing means frame 10 f 1 , by the toner conveyance roller 10 b . In the development chamber 10 i , the development roller 10 d is rotated, and a layer of triboelectrically charged toner is formed on the peripheral surface of the rotating development roller 10 d . Then, the toner is transferred onto the peripheral surface of the photoconductive drum 7 from the toner layer on the development roller 10 d , in the pattern of the latent image on the photoconductive drum 7 , developing the latent image into a visual image, that is, a toner image.

[0062] Next, the toner image is transferred onto the recording medium 2 by the application of a voltage, opposite in polarity to the toner image, to a transfer roller 4 . The transfer residual toner, that is, the toner remaining on the photoconductive drum 7 after the toner image transfer, is recovered during the following rotational cycle of the photoconductive drum 7 . More specifically, during the following rotational cycle of the photoconductive drum 7 , the peripheral surface of the photoconductive drum 7 is charged by the charge roller 8 with the presence of the transfer residual toner on the peripheral surface of the photoconductive drum 7 , and another latent image is formed on the peripheral surface of the photoconductive drum 7 by exposure, and then, the residual toner from the preceding rotational cycle of the photoconductive drum 7 is recovered by the fog prevention bias (difference Vback between the potential level of the DC voltage applied to the developing apparatus and the surface potential level of the photoconductive member) during the development of the latent image. In this embodiment, a cleaning means such as a cleaning blade for removing the transfer residual toner on the photoconductive drum 7 is not provided.

[0063] The process cartridge B, which will be described in more detail later, is removably mounted into the cartridge mounting portion of the main portion, that is, the main assembly AO, of the image forming apparatus A, while being guided by the pair of guiding portions of the process cartridge B, which are located at the lengthwise ends of the process cartridge B, one for one.

[0064] The process cartridge B comprises a drum holding frame 102 , which is one of the main sections of the cartridge frame, and the toner storage-developing means frame 10 f 1 , which constitutes another of the main sections of the cartridge frame. The drum holding frame 102 and toner storage-developing means frame 10 f 1 are joined to form a drum frame unit C and a development unit D.

[0065] (Drum Frame Unit C)

[0066] Referring to FIGS. 3 - 7 , the drum frame unit C, and the various members, for example, the photoconductive drum 7 , charge roller 8 , etc., making up the drum frame unit C, will be described.

[0067] Photoconductive Drum 7

[0068] Referring to FIGS. 5 and 6 , the photoconductive drum 7 is provided with a drum gear 7 a , which is solidly attached to one of the lengthwise ends of the photoconductive drum 7 . The drum gear 7 a comprises a triangular coupling portion 7 a 1 , a first helical gear portion 7 a 2 , and a second helical gear portion 7 a 3 . The triangular coupling portion 7 al is a driving force receiving portion by which the driving force from the image forming apparatus main assembly A 0 is received, and is in the form of a twisted triangular pillar. The first helical gear portion 7 a 2 is a driving force transmitting portion by which the driving force is transmitted to the charge roller 8 . The second helical gear portion 7 a 3 is a driving force transmitting portion by which the driving force is transmitted to the development unit D. Although not shown, to the other lengthwise end of the photoconductive drum 7 , a flange is fixed, and to the flange, an electrode for grounding the photoconductive drum 7 is integrally attached.

[0069] The photoconductive drum 7 , charge roller 8 , etc., are internally held by the drum supporting frame 102 . More specifically, one end of the photoconductive drum 7 , from which the driving force is transmitted to the photoconductive drum 7 , is rotatably supported by the drum holding frame 102 , with the interposition of a side holder 107 integrally comprising a drum bearing 107 b , and the other end of the photoconductive drum 7 is rotatably supported by the drum holding frame 102 , with the interposition of the drum supporting shaft 100 . The diameter of the photoconductive drum 7 is in a range from 20 mm to 40 mm.

[0070] The second helical gear portion 7 a 3 of the drum gear 7 a is located close to one of a pair of spacer rings 10 m which determine the distance between the axes of the development roller 1 d and photoconductive drum 7 . Therefore, the positional relationship, in terms of pitch circle, between the second helical gear portion 7 a 3 and development roller gear 10 n is precisely maintained.

[0071] Charge Roller 8

[0072] The charge roller 8 comprises a shaft 8 b , and a contact portion 8 a . The contact portion 8 a is placed in contact with the photoconductive drum 7 , and is an elastic member formed on the peripheral surface of the shaft 8 b in a manner to wrap the shaft 8 b . The measurement of the shaft 8 b in its axial direction is greater than the measurement of the contact portion 8 a in its axial direction, extending beyond both ends of the contact member 8 a . The two portions extending from two ends of the contact portion 8 a , one for one, will be referred to as shaft portions 8 b 1 and 8 b 2 . The shaft 8 b and contact portion 8 a constitute integral parts of the charge roller 8 . The diameter of the charge roller 8 is in a range of 8-20 mm.

[0073] Between the peripheral surface of the photoconductive drum 7 and the peripheral surface of the contact portion 8 a of the charge roller 8 , a layer of electrically conductive microscopic particles is present. The electrical conductive microscopic particles used in this embodiment are microscopic zinc oxide particles (having a resistance of 1,500 ω·cm, and a permeability of 35%). They are formed by air-classifying the particles (secondary particles) created by applying pressure to particles (primary particles) of zinc oxide, the diameters of which are in a range of 0.1-0.3 μm. They are 1.5 μm in volume average particle diameter. In terms of particle size distribution, the particles no more than 0.5 μm in size constitute 35% of the volume, and particles no less than 5 μm in size constitute zero to several percentages of the volume.

[0074] Charge Roller Bearing 103

[0075] The shaft portions 8 b 1 and 8 b 2 of the charge roller 8 are fitted with charge roller bearings 103 b and 103 a , respectively, which are roughly C-shaped in cross section, and which are in contact with the shaft portions 8 b 1 and 8 b 2 , respectively, by their internal surface, with respect to their C-shaped cross sections.

[0076] Further, the charge roller bearings 103 a and 103 b each have a locking portion (unshown) which engages with a part of the drum supporting frame 102 in such a manner that enables the assembly comprising the charge roller 8 and charge roller bearings 103 to move relative to the photoconductive drum 7 .

[0077] Compression Coil Spring 104

[0078] Between the drum supporting frame 102 and the pair of charge roller bearings 103 a and 103 b , a pair of compression coil springs 104 , as elastic members, are disposed, one for one. One end of the lengthwise ends of each compression coil spring 104 is fitted around the spring holder portion of the corresponding charge roller bearing 103 a ( 103 b ), and the other end is fitted around the corresponding spring holder portion of the drum supporting frame 102 . The charge roller 8 is kept pressed on the peripheral surface of the photoconductive drum 7 by these compression coil springs 104 .

[0079] More specifically, in order to keep the theoretical amount of the penetration of the charge roller 8 into the photoconductive drum 7 at 0.2 mm, a pair of compression springs, each of which exerts an operational load of 340 gf are disposed on the left and right sides, one for one. The spring constant of each compression coil spring 104 is equivalent to a compression amount of approximately 3 mm.

[0080] In this embodiment, the theoretical amount of the penetration of the charge roller 8 into the photoconductive drum 7 is controlled only by controlling the amount of the pressure applied by the pair of compression coil springs 104 .

[0081] (Structure of Charge Roller Driving Mechanism)

[0082] Referring to FIGS. 5 - 12 , the structure of the mechanism for driving the charge roller 8 will be described. FIGS. 7 - 12 describe the gear train of the process cartridge.

[0083] Drum Gear 7 a

[0084] Referring to FIG. 11 , the photoconductive drum 7 in this embodiment comprises the drum cylinder 7 A and the photoconductive layer coated on the entirety of the peripheral surface of the drum cylinder 7 A. To one end of the drum cylinder 7 A, a drum gear 7 a is solidly attached. The drum gear 7 a transmits the rotational driving force to the charge roller 8 , and also to the transfer roller 4 and development roller 10 d.

[0085] The drum gear 7 a is solidly attached to one end of the drum cylinder 7 A, as described above, and its axial line coincides with that of the drum cylinder 7 A. The drum gear 7 a comprises the helical gear portions 7 a 2 and 7 a 3 , and a shaft portion 7 a 4 . The helical gear portions 7 a 2 and 7 a 3 are the gear proper portions of the drum gear 7 a , and are on the outward side of the drum cylinder 7 A in terms of the axial direction of the drum cylinder 7 A. The shaft portion 7 a 4 constitutes the center portion of the drum gear 7 a , and which overlaps the helical gear portions 7 a 2 and 7 a 3 , in terms of the radius direction of the drum gear 7 a . In other words, the helical gear portions 7 a 2 and 7 a 3 are cylindrical, and the shaft portion 7 a 4 is extended in the holes of the cylindrical helical gear portions 7 a 2 and 7 a 3 , with its axial line coinciding with those of the cylindrical helical gear portions 7 a 2 and 7 a 3 .

[0086] Thus, there is a cylindrical gap 7 a 5 between the peripheral surface of the shaft portion 7 a 4 and the internal surfaces of the cylindrical helical gear portions 7 a 2 and 7 a 3 . This cylindrical space 7 a 5 constitutes the space into which the bearing portion 107 b of the side holder 107 fits as the photoconductive drum 7 is attached to the cartridge frame (drum holding frame 102 ), so that the shaft portion 7 a 4 is rotatably supported by the bearing portion 107 b.

[0087] The drum gear 7 a also comprises the triangular coupling portion 7 a 1 , that is, a projection constituting the coupling means on the cartridge side, which projects from the outward end of the shaft portion 7 a 4 . As the process cartridge B is mounted into the apparatus main assembly AO, this projection 7 a 1 engages with the coupling means of the apparatus main assembly, that is, a driving force transmitting member 200 ( FIG. 24 ). More specifically, the driving force transmitting member 200 has a roughly triangular recess, and the projection 7 al fits into this recess to receive the rotational driving force from the apparatus main assembly A 0 . The projection 7 al is twisted around its rotational axis, and its cross section perpendicular to its rotational axis is polygonal. The recess of the driving force transmitting member 200 is twisted around the rotational axis of the driving force transmitting member 200 , and its cross section perpendicular to the rotational axis of the driving force transmitting member 200 is polygonal.

[0088] The drum gear 7 a in this embodiment is structured so that the end surface of the shaft portion 7 a 4 is on the inward side by an amount of E relative to the outward end surface of the helical gear 7 a , more specifically, the end surface of the helical gear portion 7 a 2 . Thus, the projection 7 al partially overlaps the helical gear portion 7 a 2 in terms of the radius direction of the helical gear 7 a . With the provision of this structural arrangement, the drum gear 7 a in this embodiment is wider in terms of its axial direction, being therefore superior, in terms of physical strength as well as meshing ratio, than a drum gear in accordance with the prior arts. Thus, it is possible to an excellent image.

[0089] Also with the provision of the above described structural arrangement, the shaft portion 7 a 4 is rotationally supported by the bearing portion 107 b of the side holder 107 , which is in the cylindrical space 7 a 5 between the peripheral surface of the shaft portion 7 a 4 and the inward surface of the cylindrical gear proper portions of the drum gear 7 a . Therefore, the repulsive force resulting from the meshing of the gears are caught directly below the teeth of the gears, assuring that the repulsive force does not work in the direction to bend the photoconductive drum 7 . Therefore, it is assured that the photoconductive drum 7 is rotationally driven in the preferable manner.

[0090] As described above, the drum gear 7 a in this embodiment has the first helical gear portion 7 a 2 , which is on the outward side in terms of the lengthwise direction of the cylinder 7 A, and the second helical gear portion 7 a 3 , which is on the inward side. The first and second helical gear portions 7 a 2 and 7 a 3 are disposed next to each other, with their rotational axes coinciding. In terms of the diameter at the tooth tip (that is, diameter at root of gorge), the first helical gear portion 7 a 2 is smaller than the second helical gear portion 7 a 3 . With the provision of this structural arrangement, the optimal number of teeth can be selected for the drum gear 7 a , in accordance with the optimal numbers of revolution of the development roller 10 d and charge roller 8 .

[0091] In this embodiment, the first and second helical gear portions 7 a 2 and 7 a 3 are made different in the direction of twist. More specifically, as seen from the drum side, the first helical gear portion 7 a 2 is twisted rightward, whereas the second helical gear portion 7 a 3 is twisted leftward. Thus, as the photoconductive drum 7 in the process cartridge B in the image forming apparatus main assembly AO is rotated, the first helical gear portion 7 a 2 pushes the gear, which is being driven by the helical gear portion 7 a 2 , in the direction opposite to the location of the drum cylinder 7 A, that is, inward of the process cartridge B, whereas the second helical gear portion 7 a 3 pushes the gear, which is being driven by the helical gear portion 7 a 3 , in the direction opposite to the location of the helical gear 7 a , that is, outward direction of the process cartridge B.

[0092] Also in this embodiment, the gear portion 110 b of a geared coupler 110 , which transmits the rotational driving force to the charge roller 8 , is pushed in the direction opposite to the location of the gear portion 10 b in terms of the lengthwise direction of the charge roller 8 , that is, inward of the process cartridge B indicated by an arrow mark in FIG. 11 .

[0093] Idler Gear 111

[0094] An idler gear 111 is a step gear having two gear portions 111 a and 111 b different in diameter, and is rotationally supported by the shaft 102 c ( FIG. 5 ) which is a part of the drum supporting frame 102 . The end portion of the shaft 102 c is supported by the side holder 107 , being prevented from being broken off by the force resulting from the driving of the idler gear 111 by the gear in mesh with the idler gear 111 .

[0095] The two gear portions 111 a and 111 b of the idler gear 111 are in mesh with the gear portion 110 b of the geared coupler 110 , and the first helical gear portion 7 a 2 of the drum gear 7 a , respectively, and transmit the rotational driving force from the drum gear 7 a to the gear portion 110 b of the geared coupler 110 .

[0096] Geared Coupler 110

[0097] The geared coupler 110 has the aforementioned gear portion 110 b , and the coupler proper portion 110 a integral with the gear portion 110 b . As will be evident from FIG. 9 , the coupler proper portion 110 a of the geared coupler 110 is shaped like a pair of parallel cylinders connected by a roughly rectangular plate placed between their peripheral surfaces. The pair of the cylindrical portions of the coupler proper portion 110 a are symmetrical with respect to the rotational axis of the coupler proper portion 110 a . The gear portion 10 b of the geared coupler 110 meshes with the aforementioned idler gear 111 and transmits the rotational driving force.

[0098] As the rotational driving force is transmitted to the charge roller 8 through the geared coupler 110 , the geared coupler 110 is subjected to the force generated in the direction perpendicular to the rotational axis of the geared coupler 110 by the idler gear 111 in mesh with the gear portion 10 b of the geared coupler 110 . Thus, in order to minimize the effect of this force, it is desired that the geared coupler 110 is supported at both ends in terms of its axial direction. Therefore, the geared coupler 110 is provided with a shaft portion 110 c having a predetermined diameter. The shaft portion 110 c is between the coupler proper portion 11 a and gear portion 110 b , and its rotational axis coincides with that of the geared coupler 110 . It is rotationally borne by the wall of a through hole 108 ( FIG. 5 ) of the drum supporting frame 102 . As the process cartridge B is driven, the gear portion 110 b is pushed inward of the process cartridge B, indicated by the arrow mark in FIG. 11 , as described above. Therefore, while the process cartridge B is driven, the inward lateral surface of the gear portion 110 b of the geared coupler 110 remains in contact with the lip portion of the through hole 108 , assuring that the charger roller 8 remains stable while it is rotationally driven.

[0099] Referring to FIG. 5 , the geared coupler 110 is also provided with a hole 110 d with a predetermined diameter, which is located on the side opposite to the shaft portion 110 c in terms of the axial direction of the geared coupler 110 . The geared coupler 110 is rotationally supported by the shaft portion 106 a of a supporting member 106 , which is attached to the drum supporting frame 102 , along with the side holder 107 .

[0100] The geared coupler 110 couples with the first coupling portion 112 a of an intermediary coupler 112 , and transmits the rotational driving force.

[0101] Intermediary Coupler 112

[0102] FIG. 8 is a sectional view of the coupled combination of the geared coupler 110 , intermediary coupler 112 , and coupler 109 , describing how-they are coupled. The drawing shows only the coupler proper portion 110 a of the geared coupler 110 , and only the coupler proper portion 109 c of the coupler 109 .

[0103] In FIG. 8 , the coupler proper portion 110 a is hatched in order to differentiate the coupler proper portion 110 a from the coupler proper portion 109 c.

[0104] Referring to FIG. 9 , the intermediary coupler 112 is sandwiched between the coupler 109 and geared coupler 110 . The intermediary coupler has a second coupling portion 112 b , which is on coupler 109 side of the intermediary coupler 112 , and a pair of first coupling portions 112 a , which is on the geared coupler 110 side. The second coupling portion 112 b is a hole elongated in the direction perpendicular to axial direction of the intermediary coupler 112 , and into which the coupler proper portion 109 c fits. Each of the pair of first coupling portions 112 a is a hole open at the peripheral surface of the coupler 112 as well as one of the lateral surfaces of the coupler 112 . Its bottom wall in terms of the radius direction of the coupler 112 is rounded, and its bottom wall in terms of the axial direction of the coupler 112 is flat. The pair of first coupling portions 112 a are where the pair of couplers proper portions 110 a of the geared coupler 110 fit one for one.

[0105] The first coupling portions 112 b in the form of an elongated hole is symmetrical with respect to the rotational axis of the intermediary coupler 112 , and the pair of the first coupling portions 112 a in the form of a groove are symmetrically positioned relative to each other with respect to the axial line of the intermediary coupler 112 . The first and second coupling portions 112 a and 112 b are positioned so that the center line of the first coupling portion 112 a parallel to the lengthwise direction of the first coupling portion 112 a , and the center line of each of the pair of second coupling portions 112 b parallel to the lengthwise direction of the second coupling portion 112 b , do not become parallel to each other, that is, the angle between them does not become zero; preferably, they are positioned so that the two lines become perpendicular to each other, as shown in FIG. 8 .

[0106] Coupler 109

[0107] In order to receive the force for rotationally driving the charge roller 8 , the charge roller 8 is provided with the coupler 109 as a driving force catching member, which is attached to one end of the shaft portion 8 b 1 of the charge roller 8 . More specifically, one end of the shaft portion 8 b 1 of the charge roller 8 is given a D-shaped cross section, and is put through the-D-shaped center hole of the coupler 109 .

[0108] The coupler 109 has a pair of the couplers proper portions 109 c in the form of a cylindrical projection, which are symmetrically positioned relative to each other with respective to the axial line of the coupler 109 . These couplers proper portions 109 c fit into the pair of second coupling portions 112 b of the intermediary coupler 112 , one for one, and catch the rotational driving force.

[0109] The first coupling portion 112 a of the intermediary coupler 112 is in the form of an elongated hole. Therefore, while the intermediary coupler 112 and geared coupler 110 are in the properly coupled state, that is, while the projection 110 a is properly situated in the hole 112 a , there is a certain amount of play between the end surface of the coupling portion 112 a and the peripheral surface of the corresponding projection 110 a , in terms of the lengthwise direction of the coupling portion 112 a , allowing the projection 111 a to slide in the lengthwise direction of the coupling portion 112 a.

[0110] Further, the pair of second coupling portions 112 b are in the form of a groove with an open end extending in the radius direction of the coupler 112 . Therefore, while the intermediary coupler 112 and coupler 109 are in the properly coupled state, in other words, while each projection 109 c is properly situated in the corresponding hole 112 b , there is a certain amount of play between the internal surface of the hole 112 b and the peripheral surface of the corresponding projection 109 c , allowing the projection 109 c to slide in the lengthwise direction of the hole 112 b.

[0111] As described above, the charge roller 8 is rotated in such a direction that in the contact area between the charge roller 8 and photoconductive drum 7 , the peripheral surface of the charge roller 8 moves in the direction opposite to the direction in which the peripheral surface of the photoconductive drum 7 moves. Therefore they rub against each other, increasing the frequency at which a given point of the peripheral surface of the charge roller 8 (photoconductive drum 7 ) comes into contact with the peripheral surface of the photoconductive drum 7 (charge roller 8 ).

[0112] (Structure of Mechanism for Driving Development Roller 10 d , Transfer Roller 4 , and Toner Conveyance Roller 10 b )

[0113] As described above, the drum gear 7 a drives the charge roller 8 with the interposition of the idler gear 111 and geared coupler 110 . It also drives the development roller 10 , transfer roller 4 , and toner conveying member (conveyance roller) 10 b , as shown in FIG. 10 .

[0114] As described above, the first helical gear portion 7 a 2 is indirectly in mesh, with the interposition of the idler gear 111 , with the gear portion 110 b of the geared coupler 110 attached to one end of the shaft of the charge roller 8 , and transmits the rotational driving force to the charge roller 8 . Further, the first helical gear portion 7 a 2 is meshes with a gear 4 a attached to one end of the shaft of the transfer roller 4 , and transmits the rotational driving force to the transfer roller 4 at the same time as it transmits the rotational driving force to the charge roller 8 .

[0115] The second helical gear portion 7 a 3 of the drum gear 7 a is in mesh with the gear 10 n attached to one end of the shaft of the development roller 10 d , and rotationally drives the development roller 10 d . Further, the gear 10 n of the development roller 10 d is indirectly in mesh, with the interposition of an idler gear lot, that is, a step gear, and an idler gear 10 u , that is, a step gear, with a gear 10 v attached to one end of the conveyance roller. 10 b , and transmits the rotational driving force to the conveyance roller 10 b.

[0116] In this embodiment, the drum gear 7 a has the first and second helical gear portions 7 a 2 and 7 a 3 , which are different in the direction in which their teeth are twisted, as described above. The development roller 10 d has the development roller gear 10 n attached to one end of the development roller 10 d . This development roller gear 10 n is in mesh with the second helical gear portion 7 a 3 of the drum gear 7 a , and is rotationally driven by the drum gear 7 a , as described above.

[0117] The transfer roller 4 has the transfer roller gear 4 a attached to one end of the transfer roller 4 . This transfer roller gear 7 a is in mesh with the first helical gear portion 7 a 2 of the drum gear 7 a , and is rotationally driven by the drum gear 7 a.

[0118] For the improvement of positional accuracy, the first helical gear portion 7 a 2 of the drum gear 7 a in this embodiment is twisted in the direction to push the development roller 10 d in the outward direction indicated by an arrow mark in FIG. 11 , whereas the second helical gear portion 7 a 3 of the drum gear 7 a is twisted in the direction to push the charge roller 8 and transfer roller 4 in the inward direction indicated by the arrow mark in FIG. 11 as described above.

[0119] Further, due to the structural constraint of the gear driving apparatus, the second helical gear portion 7 a 3 of the drum gear 7 a is smaller in width in terms of its axial direction than the first helical gear portion 7 a 2 of the drum gear 7 a.

[0120] Also in this embodiment, the second helical gear portion 7 a 3 of the drum gear 7 a is made larger in pitch circle diameter than the first drum gear 7 a 2 of the drum gear 7 a.

[0121] In this embodiment, the diameter of the photoconductive drum 0.7 is 24 mm, and the diameter of the charge roller 8 is 18 mm. Further, the diameter of the development roller 1 d is 12 mm.

[0122] Also in this embodiment, the peripheral velocity of the development roller 10 d is roughly 118% of that of the photoconductive drum 7 , and the peripheral velocity of the charge roller 8 is roughly 80% of that of the photoconductive drum 7 .

[0123] Also in this embodiment, the charge roller 8 is rotated in such a direction that in the contact area between the photoconductive drum 7 and charge roller 8 , the peripheral surface of the charge roller 8 moves in the direction opposite to the direction in which the peripheral surface of the photoconductive drum 7 moves, and the development roller 10 d is rotated in such a direction that in the area in which the peripheral surfaces of the photoconductive drum 7 and development roller 10 d are closest to each other, the peripheral surfaces of the photoconductive drum 7 and development roller 1 d move in the same direction. In other words, the photoconductive drum 7 and charge roller 8 rotate in the clockwise direction, and the development roller 10 d rotates in the counterclockwise direction, as shown in FIG. 1 . Further, the conveyance roller 10 b is rotated in the clockwise direction.

[0124] Next, referring to FIGS. 13 - 15 , another example of a gear train in accordance with the present invention will be described.

[0125] The helical drum gear 7 a of the gear train shown in FIGS. 10 - 12 has the first helical gear portion 7 a 2 , which is on the outward side in terms of the lengthwise direction of the cylinder 7 A, and the second helical gear portion 7 a 3 , which is on the inward side. In comparison, the helical gear 7 a of the gear train shown in FIGS. 13 - 15 has only one gear portion (similar to helical gear portion 7 a 2 ), which plays both the role played by the first helical gear portion 7 a 2 of the drum gear 7 a of the gear train shown in FIGS. 10 - 12 , and the role played by the second helical gear portion 7 a 3 of the drum gear 7 a shown in FIGS. 10 - 12 .

[0126] Also in the case of the example of a gear train in accordance with the present invention, shown in FIGS. 13 - 15 , the drum gear 7 a is in mesh with the idler gear 111 , gear 4 a , and gear 10 n ; the outward side of the drum gear 7 a , in terms of its axial direction, is in mesh with the idler gear 111 and gear 4 a , and the inward side of the drum gear 7 a is in mesh with the gear 10 n.

[0127] The gear train in shown in FIGS. 10 - 12 , and the gear train shown in FIGS. 13 - 15 are virtually the same in structure, except for the structure of the drum gear 7 a . Therefore, the components, members, portions, etc., of the former, which are the same as the counterparts in the latter, are given the identical referential numerals, and they will not be described here.

[0128] Next, the structure of the gear train, shown in FIGS. 13 - 15 , for driving the charge roller 8 , transfer roller 4 , development roller 10 d , etc., will be described in comparison to the gear train shown in FIGS. 10 - 12 .

[0129] (Structure of Side Holder)

[0130] Referring to FIGS. 5 - 7 , the structure of the side holder 107 will be described.

[0131] As described before, the side holder 107 has: a hole 107 a for the reinforcement of the shaft 102 for supporting the idler gear 111 ; a bearing portion 107 b for rotationally bearing the photoconductive drum 7 ; and a coupler of joggles 107 h and 107 i for precisely positioning the side holder 107 relative to the drum holding frame 102 .

[0132] Further, the side holder- 107 has a through hole 107 c ( FIG. 5 ), through which an assembly tool for aligning the teeth of the drum gear 7 a and the teeth of the idler gear 111 is inserted into the internal space of the side holder 107 , in order to mesh the drum gear 7 a and idler gear 111 during the process cartridge assembly.

[0133] (Assembly of Process Cartridge)

[0134] Method for Assembling Drum Supporting Frame Unit C

[0135] Referring again to FIG. 5 , the assembling of the drum supporting frame unit C will be described.

[0136] First, an electrical contact member 113 for supplying the charge roller 8 with bias, and a couple of drum end cleaning members 114 ( 114 a and 114 b ), are attached to the drum supporting frame 102 . The. cleaning members 114 will be described later in detail.

[0137] As described before, the shaft portions 8 b 1 and 8 b 2 of the charge roller 8 are rotationally borne by the bearing 103 a