JP2013109209A - Contact charging device, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact charging device capable of improving the service life of a cleaning member without replacing the cleaning member.SOLUTION: A contact charging device 50 includes: a photosensitive drum 9; a charging roller 10; a nip forming part 300 having a bearing member 15, a guide member 17, and a spring 16 and bringing the charging roller 10 into contact with the photosensitive drum 9 to form a nip; and a cleaning sheet 22 forming a nip with the charging roller 10 to clean the charging roller 10. When the bearing member 15 is reassembled in the guide member 17 in a state where longitudinal one end and the other end of the bearing member 15 are inverted with a surface of the bearing member 15 in the side of the photosensitive drum 9 facing the photosensitive drum 9, the attitude of the bearing member 15 is transferred from a first attitude Q to a second attitude R to change the position of the nip formed by the charging roller 10 with respect to the cleaning sheet 22.

Description

  The present invention relates to a contact charging device in which a charging roller is charged while being in contact with a photosensitive drum, a process cartridge including the same, and an image forming apparatus including the same.

  2. Description of the Related Art Conventionally, in the field of image forming apparatuses, contact charging devices are known in which charging is performed by bringing a charging roller into contact with the surface of a photosensitive drum. Charging by a charging roller is widely used because of the advantage that ozone is less generated than charging by corona discharge. In an image forming apparatus provided with such a contact charging device, a very small amount of toner or an external additive contained in the toner exists on the surface of the photosensitive drum even after the development residual toner is cleaned with a cleaning member. Since the remaining materials such as the toner and the external additive described above also move to the surface of the charging roller in contact with the photosensitive drum, the surface of the charging roller is gradually contaminated and the charging performance gradually decreases.

  In order to prevent such contamination of the charging roller, an invention described in Patent Document 1 in which a cleaning unit such as a cleaning blade is provided on the charging roller is disclosed. Further, the invention described in Patent Document 2 is disclosed in which a sheet-like rubbing member is brought into contact with the charging roller to disperse dirt on the charging roller and uniform charging performance.

JP-A-6-342237 JP 2000-56544 A

  However, in the case of the invention described in Patent Document 1 or 2, there remains a problem that it takes time to replace the cleaning member for cleaning the charging roller. For example, in order to remove the cleaning member, the double-sided tape at the base end must be removed. In addition, when installing a new cleaning member, adjustment must be made so as to form a stable nip with the charging roller. Therefore, it is desirable that such a cleaning member (cleaning member) need not be replaced.

  In view of the above circumstances, an object of the present invention is to provide a contact charging device that can improve the durability of a cleaning member without replacing the cleaning member.

  In order to achieve the above object, a contact charging device of the present invention comprises an image carrier, a charging roller that contacts the surface of the image carrier and charges the surface of the image carrier, and a shaft of the charging roller. A bearing member for supporting, a guide member for guiding the operation of the bearing member, and an urging means for urging the charging roller toward the image carrier, and the charging roller is abutted against the image carrier. A nip forming unit that forms a nip by contact; and a cleaning member that is disposed to face the charging roller and forms a nip with the charging roller to clean the charging roller, and the biasing unit includes the urging unit A surface connecting the center of the urging position for urging the bearing member and the center of the image carrier is defined as a first imaginary plane, and a surface parallel to the first imaginary plane and passing through the center of the charging roller is a second imaginary plane. A virtual plane, and the first virtual plane is the second virtual plane. The attitude of the bearing member when positioned on the first surface side of the surface is the first attitude, and the attitude of the bearing member when the first virtual plane is positioned on the second surface side of the second virtual plane In the second posture, the one end and the other end in the longitudinal direction of the bearing member are reversed with the surface of the bearing member facing the image carrier facing the image carrier. When the bearing member is re-assembled into the guide member, the attitude of the bearing member changes from the first attitude to the second attitude, or from the second attitude to the first attitude. The position of the nip formed by the charging roller with respect to the cleaning member is changed.

  According to the present invention, the durability of the cleaning member can be improved without replacing the cleaning member.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus including a contact charging device according to Embodiment 1 of the present invention. It is sectional drawing etc. which show the structure of a contact charging device. It is sectional drawing which shows the structure by which the bearing member was fitted by the guide member, and is equivalent to sectional drawing seen from the arrow J direction in FIG. It is sectional drawing which shows the structure of a contact charging device, and is equivalent to sectional drawing re-assembled in the guide member with the 2nd surface and the 4th surface reversed, with a receiving hole facing the photoreceptor drum. It is sectional drawing which shows the structure of a contact charging device, and is equivalent to sectional drawing seen from the arrow J direction in FIG. FIG. 6 is a cross-sectional view illustrating a contact state between a charging roller and a cleaning sheet. 6 is a cross-sectional view illustrating a configuration of a process cartridge including a contact charging device according to Embodiment 2. FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus including a process cartridge.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, since the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions, there is no specific description. As long as the scope of the invention is not limited to these, it is not intended.

  FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus 100 including a contact charging device 50 according to Embodiment 1 of the present invention. The image forming apparatus 100 is an image forming apparatus having a duplex printing function using an electrophotographic image forming process. As shown in FIG. 1, the image forming apparatus 100 includes an image forming apparatus main body (hereinafter simply referred to as “apparatus main body”) 100A, and an image forming unit 60 for forming an image is provided inside the apparatus main body 100A. Provided. The image forming unit 60 includes a photosensitive drum 9 that is an “image carrier”, a transfer roller 13 that is a “transfer device”, and the like.

  First, the photosensitive drum 9 is obtained by applying an organic photosensitive layer (OPC) to the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm. The photosensitive drum 9 is rotatably attached to a frame (not indicated in FIG. 1) with the center of the outer diameter of the aluminum cylinder as a rotation axis, and is driven to rotate in the direction of arrow F by a driving motor (not indicated in FIG. 1). Is done. The aluminum cylinder of the photosensitive drum 9 is grounded as shown in FIG.

  Around the photosensitive drum 9, a charging roller 10, a scanner 11, a developing device 12, a transfer roller 13 and a cleaning blade 14 are arranged. The charging roller 10 (contact charging member) is a roller that contacts the surface of the photosensitive drum 9 and uniformly charges the surface of the photosensitive drum 9. The scanner 11 (laser scanner) is a device for forming an electrostatic image on the photosensitive drum 9. The developing device 12 contains an electrostatic image one-component developer (hereinafter simply referred to as “developer T”) formed on the photosensitive drum 9, and removes the electrostatic image formed on the photosensitive drum 9. Equipment for contact development. The transfer roller 13 is a roller that transfers the developed developer image to the recording material P. The cleaning blade 14 that is a “cleaning member” is a blade that cleans (cleans) the developer remaining on the photosensitive drum 9 after the transfer.

  The above-described charging roller 10 is configured as a part of the contact charging device 50, and the charging roller 10 includes a cored bar portion 10a and a rubber roller portion 10b (see FIG. 2). In addition to the charging roller 10, the contact charging device 50 includes a bearing member 15, a guide member 17, and a spring 16 made of a conductive resin. Further, the contact charging device 50 has a bias power source 19 for charging. The bias power source 19 is connected to a contact 18 (see FIG. 2) attached to the guide member 17 so that a DC bias can be applied to the charging roller 10.

  The developing device 12 includes a developing roller 12a, a supply roller 12b, a developing blade 12c, and a stirring member 12d. The developing roller 12 a (developer carrier) is a roller that contacts the photosensitive drum 9 and performs development while rotating in the forward direction (arrow G direction) with respect to the rotation of the photosensitive drum 9. The supply roller 12b (developer supply means) is a roller that rotates in the direction of the developing roller 12a and counter direction (arrow H direction) and supplies the developer T to the developing roller 12a. The developing blade 12c (regulating member) (developer regulating means) is a blade that regulates the coating amount (layer thickness) and charging amount of the developer T on the developing roller 12a. The stirring member 12d is a member that supplies the developer T to the supply roller 12b and stirs the developer T.

  The space in the frame constituting the developing device 12 is used as a developer containing portion 12e for containing the developer T. Further, the gap d formed by the photosensitive drum 9 and the developing roller 12a is kept constant by the regulation roller 12f. A controller 51 is provided inside the apparatus main body 100A. The controller 51 controls driving of the photosensitive drum 9 and other internal devices of the apparatus main body 100A.

  In the image forming process, the photosensitive drum 9 rotates in the direction of arrow F, and the peripheral surface thereof is contact-charged to about 500 V by the charging roller 10 to which a DC bias of −1000 V is applied from the charging bias power source 19. The In the next electrostatic image forming step, the scanner 11 (exposure light source) (exposure means) scans and exposes the charging surface of the surface of the photosensitive drum 9 to form an electrostatic image of image information.

  In the next developing step, when the electrostatic image carried on the photosensitive drum 9 reaches a portion facing the developing roller 12a carrying the developer T, a developing bias power source (not shown) develops the developing roller. An oscillating voltage in which an AC voltage and a DC voltage are superimposed on 12a is applied. When an alternating electric field is formed between the photosensitive drum 9 and the developing roller 12a, the developer T flies and transfers to the electrostatic image formed on the surface of the photosensitive drum 9, and development is performed. The electrostatic image changes with the developer image.

  In the next transfer step, the developer image formed on the photosensitive drum 9 is transferred to the recording material P by the transfer roller 13 inside the apparatus main body 100A by the rotation of the photosensitive drum 9. In the next fixing step, the recording material P is conveyed to the fixing device 20, and the developer image is fixed by the fixing device 20, whereby a fixed image is completed on the recording material P.

  On the other hand, at the same time, in the cleaning process, the developer T remaining on the photosensitive drum 9 at the time of transfer is scraped off by the cleaning blade 14 before passing through the charging roller 10 again, and enters the waste developer container 21. Accumulated. Incidentally, the surface of the charging roller 10 is cleaned as a cleaning member of the charging roller 10 having one end fixed to a pedestal 22b (see FIG. 2) attached to the cleaning blade 14 by a double-sided tape 22a (see FIG. 2). The sheet 22 is in contact.

  FIG. 2A is a cross-sectional view showing the configuration of the contact charging device 50. FIG. 2B is a cross-sectional view showing the configuration of the bearing member 15. As shown in FIG. 2, the contact charging device 50 includes a photoreceptor drum 9 and a charging roller 10 as a contact charging member that charges the surface of the photoreceptor drum 9. The photosensitive drum 9 as a member to be charged is obtained by applying an organic photosensitive layer (OPC) to the outer peripheral surface of an aluminum cylinder having a diameter of about 20 to 50 mm, for example. The photosensitive drum 9 is rotatably attached to a frame (not shown) with the outer diameter center of the aluminum cylinder as a rotation axis, and is driven to rotate in the direction of arrow F by a driving motor (not shown). Note that the aluminum cylinder of the photosensitive drum 9 is grounded.

  On the other hand, the charging roller 10 includes a cored bar part 10a and a conductive rubber roller part 10b. Here, the outer diameter of the cored bar 2a is φ4 to φ6 mm, and the outer diameter of the rubber roller part 10b is φ8 to 12 mm. It is said. In the charging roller 10, the cored bar portion 10 a of the charging roller 10 is supported by the bearing member 15. A spring 16 is disposed adjacent to the bearing member 15. The spring 16 serving as the “biasing means” is a member that biases the charging roller 10 toward the photosensitive drum 9. The bearing member 15 is urged in a direction indicated by an arrow I (a direction toward the photosensitive drum 9) by a metal spring 16 which is an urging unit while a movable direction is restricted by the guide member 17. When the bearing member 15 receives the urging force, the rubber roller portion 10b of the charging roller 10 comes into contact with the surface of the photosensitive drum 9, and the charging roller 10 rotates while following the direction of the arrow B in accordance with the rotation of the photosensitive drum 9. To do.

  The bearing member 15 is made of conductive resin, and a bias can be applied to the charging roller 10 from a bias power source 19 connected via a spring 16 and a contact 18 attached to the frame. The bias power source 19 is grounded and can output a DC bias of −500V to −1500V.

  By applying this bias to the charging roller 10 that rotates while being driven in the direction of the arrow B while being in contact with the surface of the photosensitive drum 9, the peripheral surface of the photosensitive drum 9 that is driven to rotate in the direction of the arrow F is approximately 0 to 0. It can be uniformly charged to a desired charging potential within a range of 1000V. Here, the bias power supply 19 is connected to the DC power supply, but may be connected to the AC power supply.

  On the other hand, on the surface of the charging roller 10, a cleaning sheet 22 having one end fixed by a double-sided tape 22a is in contact with a pedestal 22b attached to the frame. The cleaning sheet 22, which is a “cleaning member”, is a sheet member that is disposed so that the tip side portion faces the charging roller 10 and forms a nip with the charging roller 10 to clean the charging roller 10. The cleaning sheet 22 has a fixed end 22x that is fixed to the apparatus main body 100A other than the guide member 17, and a free end 22y that is the other end of the fixed end. The cleaning sheet 22 needs to be assembled to the frame with high accuracy so that a portion that does not come into contact with the charging roller 10 due to undulation, warpage, or the like is generated, and cleaning of the charging roller 10 is not incomplete.

  Here, the free length L1 of the cleaning sheet 22 is 6 to 10 mm, the contact length L2 with the charging roller 10 is 4 to 8 mm, and the penetration amount Δ into the charging roller 10 is 1 to 2 mm. However, when the undulation amount at the free end of the cleaning sheet 22 exceeds 1 mm, the cleaning sheet 22 may not contact the charging roller 10 at that portion.

  In order to avoid this problem, the frame is warped in advance when the cleaning sheet 5 is fixed to the frame. Then, after the cleaning sheet 22 is attached in a straight state, the warping of the frame body is released, and tension is applied to the cleaning sheet 22 in the direction of the core metal 2a (shaft) of the charging roller 10. In this case, a polyimide sheet having a thickness of 25 to 75 μm is used. However, other materials and thicknesses may be used if the same effect can be obtained for cleaning of the charging roller 10. I do not care.

  Next, the bearing member 15 and the peripheral configuration to which the bearing member 15 is attached, which is a feature of the contact charging device 50 of the present embodiment, will be described. The bearing member 15 is a member that supports the cored bar portion 10 a that is the shaft of the charging roller 10. The bearing member 15 has a receiving hole 15 d that is a “first receiving hole” that opens toward the photosensitive drum 9 and receives the cored bar portion 10 a that is the “shaft” of the charging roller 10. Can be opened and closed by bending. Therefore, the receiving hole 15d bends and opens when the cored bar part 10a is inserted, and closes when the cored bar part 10a is completely inserted to prevent the cored bar part 10a from being unintentionally removed. In particular, the receiving hole 15d has an arcuate opening edge on the opening side. A receiving hole 15d is provided in a first surface H1 described later, and the cored bar 10a is inserted into the receiving hole 15d. The receiving hole 15d is formed narrow on the opening side.

  The bearing member 15 has a boss 15a on the second surface H2 corresponding to the back surface of the first surface H1. The boss 15 a is a convex portion for supporting the spring 16 in order to press the charging roller 10 against the photosensitive drum 9. The boss 15a is inserted into the end of the spring 16 and fixed.

  The bearing member 15 includes guide ribs 15b and 15c on the third surface H3 and the fourth surface H4 corresponding to the side surfaces orthogonal to the first surface H1 and the second surface H2. The guide ribs 15b and 15c are configured to engage with the guide grooves 17b and 17c of the guide member 17 so as to be linearly movable in the guide member 17 (see FIG. 3). The guide member 17 is a member that guides the operation of the bearing member 15. The guide member 17 includes a receiving portion 17a of the spring 16 positioned on the inner bottom surface, and guide grooves 17b and 17c which are positioned on the inner side surface and form engaging portions with the guide ribs 15b and 15c of the bearing member 15. . The movable direction of the bearing member 15 is restricted by guide grooves 17b and 17c provided in the guide member 17, and is limited to the arrow D direction. The nip forming portion as the “nip forming means” includes the bearing member 15, the guide member 17, the spring 16, and the like described above, and forms the nip by bringing the charging roller 10 into contact with the photosensitive drum 9.

  The guide member 17 has a receiving hole 17d that is a “second receiving hole” that opens toward the photosensitive drum 9 and receives and guides the bearing member 15, and the receiving hole 17d is opened and closed by being bent. It is free. Accordingly, the receiving hole 17d bends and opens when the bearing member 15 is inserted, and closes when the bearing member 15 is completely inserted, thereby preventing the bearing member 15 from being removed without permission. In particular, the receiving hole 17d of the bearing member 15 has a claw portion formed on the opening side. The force with which the guide member 17 restricts the removal of the bearing member 15 is set to be stronger than the force with which the bearing member 15 restricts the removal of the cored bar portion 10 a of the charging roller 10.

  Here, a surface connecting the center J1 of the biasing position where the spring 16 biases the bearing member 15 and the center J2 of the photosensitive drum 9 is defined as a first virtual plane X. In addition, a plane that is parallel to the first virtual plane X and passes through the center J3 of the charging roller 10 is defined as a second virtual plane Y.

  Further, the posture of the bearing member 15 when the second virtual plane Y is located on the first surface X1 side of the first virtual plane X is defined as a first posture Q. The posture of the bearing member 15 when the second virtual plane Y is located on the second surface X2 side of the first virtual plane X is defined as a second posture R. Therefore, when the cored bar portion 10a of the charging roller 10 is fitted into the receiving hole 15d of the bearing member 15, the center J1 of the cored bar portion 10a is positioned on the first surface X1 side of the virtual plane X in the case of FIG. However, the first posture Q is shifted from the virtual plane X.

  3 is a cross-sectional view showing a configuration in which the bearing member 15 is fitted to the guide member 17, and corresponds to a cross-sectional view seen from the direction of arrow J in FIG. As shown in FIG. 3, the guide ribs 15b and 15c of the bearing member 15 and the guide grooves 17b and 17c of the guide member 17 have a bilaterally symmetrical shape on the surface where each is provided. Therefore, the bearing member 15 can be reassembled with the third surface H3 and the fourth surface H4 reversed while the receiving hole 15d faces the photosensitive drum 9 (FIGS. 4 and 5). reference). This will be described later with reference to FIGS.

  Further, the guide member 17 has the above-described guide grooves 17b and 17c on the inner side surface, and an abutting portion 17e (abutting surface) on the inner bottom surface. When the charging roller 10 is incorporated in the bearing member 15, the end faces of both ends of the cored bar portion 10 a of the charging roller 10 come into contact with the abutting portions 17 e of the guide member 17, so that the movement of the charging roller 10 is restricted in the axial direction. The 3 shows only the configuration of one end of the charging roller 10, the configuration of the other end is the same (the same applies to FIG. 5).

  FIG. 4 is a cross-sectional view showing the configuration of the contact charging device 50. The contact charging device 50 is reassembled into the guide member with the second surface H3 and the fourth surface H4 reversed while directing the receiving hole 15d toward the photosensitive drum 9. It corresponds to a sectional view. FIG. 5 is a cross-sectional view showing the configuration of the contact charging device 50, and corresponds to a cross-sectional view seen from the direction of arrow J in FIG. As can be seen from FIGS. 4 and 5, one end of the bearing member 15 in the longitudinal direction and the other with the surface (first surface H1) of the bearing member 15 facing the photosensitive drum 9 facing the photosensitive drum 9. The bearing member 15 is re-assembled into the guide member 17 with the end portion turned in the opposite direction. Then, the posture of the bearing member 15 shifts from the first posture Q to the second posture R. In this case, in the case of FIG. 4, the center J <b> 1 of the cored bar portion 10 a is located on the second surface X <b> 2 side of the virtual plane X and is displaced with respect to the virtual plane X.

  Then, the position of the nip formed by the charging roller 10 with respect to the cleaning sheet 22 changes. That is, the position of the nip has moved to the front end side of the cleaning sheet 22. Conversely, when the bearing member 15 originally has the second posture R, the bearing member 15 may change from the second posture R to the first posture Q to change the position of the nip. Is possible. As a feature of the contact charging device 50, it can be said that the cross-sectional center of the receiving hole 17 d is eccentric with respect to the cross-sectional center of the bearing member 15.

  FIG. 6 is a cross-sectional view showing a contact state between the charging roller 10 and the cleaning sheet 22. 6A shows a contact state when the bearing member 15 is incorporated in the state of FIG. 2, and FIG. 6B shows a contact state when the bearing member 15 is incorporated in the state of FIG. Show. 6A and 6B, the nip portion of the cleaning sheet 22 with the charging roller 10 is changed so as not to overlap before and after the bearing member 15 is reassembled.

  In the prototype, when the outer dimension of the rubber portion 2b of the charging roller 10 is φ12 mm in the state shown in FIG. 6A, the nip width formed by the charging roller 10 and the cleaning sheet 22 is about 0.5 mm. It became. In addition, the dimension between the virtual plane X and the virtual plane Y was shifted to 0.4 mm. With this setting, when the bearing member is reassembled with the third surface H3 and the fourth surface H4 reversed, it is possible to avoid overlapping of the nip formed by the charging roller 10 and the cleaning sheet 22.

  Next, the procedure for maintenance of the contact charging device and reuse of the cleaning sheet described above will be described. When replacing the charging roller 10 or reusing the frame, the cleaning sheet 22, and the cleaning sheet mounting member (double-sided tape 22a, pedestal 22b), the following procedure is used.

  (A) The photosensitive drum 9 is removed from the frame (not indicated in the figure). (I) Remove the charging roller 10 from the bearing member 15. (Iii) The bearing member 15 is once removed from the guide member 17 and assembled again into the guide member 17 from the direction shown in FIG. 3 to the direction shown in FIG. (E) A new charging roller 10 is assembled to the bearing member 15. (O) The photosensitive drum 9 is attached to the frame (not indicated in the figure).

  According to such a configuration, the surface of the newly incorporated charging roller 10 and the unused portion of the cleaning sheet 22 come into contact with each other, and excellent cleaning performance can be obtained without replacing the cleaning sheet 22. Therefore, the charging performance of the contact charging device can be maintained over a long period of time. In addition, the above-described effects can be obtained without disassembling or replacing the cleaning sheet 22 and the frame, and the labor related to the maintenance and reuse of the contact charging device 50 can be reduced.

  FIG. 7 is a cross-sectional view illustrating a configuration of the process cartridge 23 including the contact charging device 50 according to the second embodiment. FIG. 8 is a cross-sectional view illustrating a configuration of an image forming apparatus 200 including the process cartridge 23. In the configuration of the process cartridge 23 and the image forming apparatus 200 of the second embodiment, the same configurations and effects as those of the contact charging device 50 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted as appropriate. Even if the reference numeral is not attached, the configuration of the contact charging device 50 is the same as that of the first embodiment. In the configuration of the second embodiment, the contact charging device 50 is incorporated in the process cartridge 23, or the process cartridge 23 is detachably attached to the apparatus main body 200A (image forming apparatus main body). Mainly different from Example 1.

  In the process cartridge 23, the photosensitive drum 9, the charging roller 10 and the support mechanism thereof, the developing device 12, the cleaning blade 14, and the waste developer container 21 described in the first embodiment are integrated, and are detachable from the apparatus main body 100A. It has become a structure. The process cartridge 23 can be separated into the photosensitive drum 9, the charging roller 10 and its supporting means, the cleaning blade 14, a frame 25 incorporating the waste developer container 21, and the developing device 12.

  As shown in FIG. 7, a bearing member 15, a guide member 17, and a metal spring 16 as a biasing unit are incorporated in the process cartridge 23 as a supporting unit for the charging roller 10. In addition, a bias is applied to the charging roller 10 from a bias power supply 19 for charging mounted in the image forming apparatus 200 (see FIG. 8). First, a contact 26 (formed of a metal fitting) is attached inside the process cartridge 23. A contact 27 is attached outside the process cartridge 23. A contact 28 is attached to the apparatus main body 200 </ b> A at a position corresponding to the contact 27. With this configuration, the bias power source 19 is electrically connected to the charging roller 10 via the contact 28, the contact 27, the contact 26, the contact 18 (see FIG. 2), and the spring 16.

  In addition, the receiving hole 15d of the cored bar portion 10a of the charging roller 10 is provided on a surface orthogonal to the surface on which the guide ribs 15b and 15c of the bearing member 15 are provided, as shown in FIGS. Then, only 0.4 mm (dimension k in FIGS. 3 and 5) from the virtual plane X passing through the center of the rotation axis of the photosensitive drum 9 and parallel to the biasing direction by the spring 16 (the direction of arrow I in FIG. 2). It is provided by shifting. In addition, the guide ribs 15b and 15c of the bearing member 15 and the guide grooves 17b and 17c of the guide member 17 have a symmetrical shape on the surface where each is provided. Therefore, as shown in FIGS. 3 and 5, it is possible to incorporate the bearing member 15 by inverting it in the direction orthogonal to the regulating direction of the guide member 17.

  Next, an example of an operation when performing reproduction in the process cartridge of this embodiment will be described. In the reproduction procedure described below, only the used charging roller 10 and developing device 12 are replaced with new ones. The process cartridge can be reused without replacing the cleaning sheet 22, the mounting member for the cleaning sheet 22 (double-sided tape 22a, pedestal 22b), the cleaning blade 14, and the frame 25 (waste developer container 21). It is.

  (A) Remove the used developing device 12 from the frame. (Ii) Remove the photosensitive drum 9 from the frame (not indicated in the figure). (Iii) The charging roller 10 is removed from the bearing member 15. (E) The developer in the waste developer container is sucked from the opening formed in the cleaning blade 14 by removing the photosensitive drum 9, and the inside of the container is cleaned. (V) The bearing member 15 is once removed from the guide member 17 and assembled again into the guide member 17 from the direction shown in FIG. 3 to the direction shown in FIG. () A new charging roller 10 is assembled to the bearing member 15. (I) The photosensitive drum 9 is attached to the frame (not indicated in the figure). (C) A new developing device 12 is attached to the frame.

  According to the configuration of the first or second embodiment, the configuration is as follows. That is, the first surface H1 of the bearing member 15 on the photosensitive drum 9 side is in a state in which one end portion and the other end portion in the longitudinal direction of the photosensitive drum 9 are reversed, and the bearing member 15 is moved to the guide member 17. Re-install. Then, the nip position with the charging roller 10 formed on the surface of the cleaning sheet 22 is changed.

  Here, it is assumed that after using the contact charging device 50, inconveniences such as damage and deposits occur at the nip position with the charging roller 10 formed on the surface of the cleaning sheet 22. Even in this case, a nip position different from the nip position before reuse on the surface of the cleaning sheet 22 can be set as the nip position during reuse. In brief, the surface of the newly incorporated charging roller 10 comes into contact with the unused portion of the cleaning sheet 22, and the unused portion of the cleaning sheet 22 cleans the charging roller 10. Therefore, excellent cleanability can be obtained without replacing the cleaning sheet 22.

  As a result, the durability of the cleaning sheet 22 is improved even if the cleaning sheet 22 is not replaced. As a result, the image forming apparatuses 100 and 200 can output a good output image over a long period of time. In addition, the cleaning sheet 22 and other members can be obtained without being disassembled or replaced, and the labor related to the reuse of the process cartridge 23 can be reduced.

  When other effects are exemplified, the following can be said. Since it is not necessary to attach and detach the cleaning sheet 22, labor and time required for reusing the contact charging device 50 can be reduced. Even if the cleaning sheet 22 remains the same member, the charging roller 10 can maintain excellent chargeability over a long period of time, and a good image can be obtained over a long period of time.

  Next, according to the configuration of the first or second embodiment, the cleaning sheet 22 has the fixed end 22x fixed to the apparatus main body 100A, and the leading end side becomes the free end 22y. The free end 22 y rubs against the surface of the charging roller 10, and a stable nip is formed between the cleaning sheet 22 and the charging roller 10. As a result, the charging roller 10 can be cleaned with a simple configuration including only the cleaning sheet 22 and fixing means for fixing the cleaning sheet 22 to a frame or the like.

  Further, the dimension of the photosensitive drum 9 and the transfer roller in the direction orthogonal to the image traveling direction is set according to the maximum image width formed by the image forming apparatus 100, and it is not necessary to set the dimension wider than necessary. In addition, since the photosensitive drum 9 and the transfer roller 13 can be fixedly arranged, the configuration around the photosensitive drum 9 can be simplified, and maintenance is improved.

9 Photosensitive drum (image carrier)
10 Charging roller 15 Bearing member 16 Spring (biasing means)
17 Guide member 22 Cleaning sheet (cleaning member)
50 Contact charging device 300 Nip forming part (nip forming means)
J1 center J2 center J3 center X first virtual plane Y second virtual plane Q first posture R second posture

Claims (6)

An image carrier;
A charging roller that contacts the surface of the image carrier and charges the surface of the image carrier;
A bearing member that supports the shaft of the charging roller; a guide member that guides the operation of the bearing member; and a biasing unit that biases the charging roller toward the image carrier. Nip forming means for forming a nip in contact with the image carrier;
A cleaning member disposed opposite to the charging roller and forming a nip with the charging roller to clean the charging roller,
A surface connecting the center of the biasing position where the biasing unit biases the bearing member and the center of the image carrier is defined as a first virtual plane, and the center of the charging roller is a plane parallel to the first virtual plane. The surface passing through is the second virtual plane, the posture of the bearing member when the first virtual plane is located on the first surface side of the second virtual plane is the first posture, and the first virtual plane is the When the posture of the bearing member when positioned on the second surface side of the second imaginary plane is the second posture,
The bearing member is placed in the guide member in a state where one end and the other end in the longitudinal direction of the bearing member are reversed with the surface of the bearing member facing the image carrier facing the image carrier. In this case, the bearing member moves from the first posture to the second posture, or from the second posture to the first posture, and the charging roller with respect to the cleaning member moves. A contact charging device, wherein a position of a nip to be formed is changed. The bearing member has a first receiving hole that opens toward the image carrier and receives the shaft of the charging roller, and the first receiving hole is openable and closable by bending,
2. The contact charging device according to claim 1, wherein a cross-sectional center of the first receiving hole is eccentric in a direction along the first virtual plane with respect to a cross-sectional center of the bearing member. The guide member has a second receiving hole that opens toward the image carrier and receives and guides the bearing member, and the second receiving hole can be opened and closed by bending,
3. The contact according to claim 2, wherein the force by which the guide member restricts removal of the bearing member is set to be stronger than the force by which the bearing member restricts removal of the shaft of the charging roller. Charging device.   2. The sheet member according to claim 1, wherein the cleaning member is a sheet member having a fixed end that is fixed to the image forming apparatus main body other than the guide member, and a free end that is the other end of the fixed end. The contact charging device according to claim 3.   5. A process cartridge comprising the contact charging device according to claim 1 and detachably attached to an image forming apparatus main body.   An image forming apparatus comprising the contact charging device according to claim 1 or the process cartridge according to claim 5.

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