JP5492797B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a composite machine using an electrophotographic method, and more particularly to an image forming apparatus that cleans toner remaining on an image carrier using a cleaning blade. Is.

  Conventional image forming apparatuses such as copying machines, printers, and facsimiles form a toner image on an image carrier, transfer the formed toner image onto a transfer medium such as paper, and then remove residual toner on the image carrier. Cleaning. The cleaned residual toner is stored in the cleaning unit or in a residual toner storage container disposed outside the cleaning unit. In order to remove the residual toner on the image carrier, a cleaning blade that is in pressure contact with the image carrier is widely used. Then, in order to remove residual toner without damaging the surface of the image carrier due to foreign matter staying between the cleaning blade and the image carrier, a method of reciprocating the cleaning blade in the axial direction of the image carrier has been proposed. Yes.

  For example, Patent Document 1 includes a drive shaft that drives a cleaning blade and a drive gear that drives the drive shaft. When the image carrier rotates, the gear for the image carrier rotates the drive gear, A configuration is disclosed in which the cleaning blade is driven to reciprocate in the axial direction of the image carrier via a cam.

  On the other hand, as shown in Patent Documents 2 and 3, there has been proposed a method of suppressing the scratch on the surface of the image carrier by reciprocating the image carrier in the axial direction instead of the cleaning blade.

JP-A-8-272271 (paragraph [0043], FIG. 2) JP-A-62-14171 JP-A-62-273586

  However, in the method of Patent Document 1, since the cleaning grade is reciprocated in the axial direction, the driving mechanism is complicated. In addition, when sealing members are attached to both ends of the cleaning unit so as to face both ends of the cleaning blade in the axial direction, a clearance is generated between both ends of the cleaning unit and the sealing member due to the reciprocating movement of the cleaning blade. In addition, the residual toner removed from the gap may be scattered outside the cleaning unit.

  Further, in the configurations of Patent Documents 2 and 3, although the serious damage so as to be manifested as vertical stripes in the output image has been reduced, there are still minute scratches (unevenness) on the surface of the image carrier. For this reason, foreign substances such as toner external additives that have passed through the cleaning blade are aggregated using the unevenness of the image carrier surface as a foothold, and toner further accumulates on the aggregated portion, resulting in a vertical spot pattern (hereinafter referred to as a dash mark) on the output image. There was a problem that it occurred.

  In view of the above problems, the present invention can clean residual toner on an image carrier with a simple configuration without damaging the surface of the image carrier, and can effectively suppress the generation of dash marks in an output image. An object of the present invention is to provide a simple image forming apparatus.

In order to achieve the above object, the present invention provides a plurality of image carriers having a photosensitive layer formed on the outer peripheral surface, a cleaning blade for cleaning residual toner on the image carriers, and adjacent to the image carriers. An endless intermediate transfer body in which toner images developed on the image carrier are sequentially stacked, and a drive mechanism that rotates the image carrier and reciprocates in the axial direction;
In an image forming apparatus comprising: an image carrier polishing mode in which the intermediate transfer member and the image carrier are brought into contact with each other with a larger linear velocity difference than during image formation during non-image formation. .

  According to the present invention, in the image forming apparatus configured as described above, the linear velocity of the image carrier in the image carrier polishing mode is smaller than that of the intermediate transfer member.

  According to another aspect of the invention, an image carrier having a photosensitive layer formed on the outer peripheral surface, a cleaning blade for cleaning residual toner on the image carrier, and a recording medium disposed adjacent to the image carrier. In an image forming apparatus comprising an endless transport member and a drive mechanism for rotating the image carrier and reciprocating in the axial direction, the transport member and the image carrier are formed at the time of non-image formation. An image carrier polishing mode in which contact is made with a larger linear velocity difference than that is executed.

  According to the present invention, in the image forming apparatus configured as described above, a linear velocity of the image carrier in the image carrier polishing mode is smaller than that of the transport member.

  The present invention also provides an image carrier having a photosensitive layer formed on the outer peripheral surface, a cleaning blade for cleaning residual toner on the image carrier, and an image carrier that is disposed adjacent to the image carrier. In the image forming apparatus comprising: a transfer member that transfers the toner image developed on the recording medium; and a drive mechanism that rotates the image carrier and reciprocates in the axial direction. And an image carrier polishing mode in which the image carrier and the image carrier are brought into contact with each other with a larger linear velocity difference than that during image formation.

  According to the present invention, in the image forming apparatus configured as described above, a linear velocity of the image carrier in the image carrier polishing mode is smaller than that of the transfer member.

  According to another aspect of the present invention, the image forming apparatus having the above configuration includes a charging device that charges the photosensitive layer on the surface of the image carrier, and applying a charging bias to the charging device during the execution of the image carrier polishing mode. It is a feature.

  In the image forming apparatus having the above-described configuration, the charging bias applied to the charging device during execution of the image carrier polishing mode is higher than the discharge start voltage and lower than the charging bias applied during image formation. It is characterized by that.

  According to the present invention, in the image forming apparatus configured as described above, the charging device charges the surface of the image carrier by applying a DC voltage to a charging member that contacts the surface of the image carrier. .

  According to the present invention, in the image forming apparatus configured as described above, the driving mechanism is fixed to one end of the rotating shaft and is fixed to the other end of the rotating shaft, and a driving input gear that inputs driving force to the rotating shaft. A first gear member, and adjacent to the first gear member, supported by the rotary shaft so as to be rotatable and slidable in the axial direction; One of a second gear member having a number of teeth different from that of the gear member, an idle gear meshing with the first gear member and the second gear member, and opposing side surfaces of the first gear member and the second gear member An annular cam surface that is provided on the side surface of the circumferential surface and has an axial distance that continuously changes in the circumferential direction, an annular cam follower that is provided on the other side surface of the cam surface and abuts the cam surface, and the cam surface and the cam follower abut The image carrier in the direction It is characterized by having a biasing member for energizing, the.

  According to the present invention, in the image forming apparatus configured as described above, one gear tooth of the first gear member and the second gear member includes a transition gear.

  According to the present invention, in the image forming apparatus having the above configuration, the cam surface and the cam follower are formed such that an axial displacement amount per unit rotation angle of the first gear member and the second gear member is constant. It is characterized by being.

  According to the first, third, or fifth configuration of the present invention, since the image carrier rotates and reciprocates in the axial direction, the image carrier is retained by the foreign matter staying between the cleaning blade and the image carrier. Residual toner on the image carrier is cleaned without damaging the surface of the body. In addition, by carrying out an image carrier polishing mode in which any one of the intermediate transfer member, the conveyance member, or the transfer member is brought into contact with the image carrier with a greater linear velocity difference than during image formation during non-image formation, Fine irregularities and deposits on the body surface can be removed in a short time, and the generation of dash marks can be effectively prevented over a long period of time.

  According to the second, fourth, or sixth configuration of the present invention, the image carrier in the image carrier polishing mode in the image forming apparatus having any one of the first, third, and fifth configurations. By making the linear velocity smaller than that of the intermediate transfer member, the conveying member, or the transfer member, the polishing effect on the surface of the image carrier in the image carrier polishing mode can be further enhanced.

  According to the seventh configuration of the present invention, in the image forming apparatus having any one of the first to sixth configurations, charging for charging the photosensitive layer on the surface of the image carrier during execution of the image carrier polishing mode. By applying a charging bias to the apparatus, it is possible to improve the charge rising property and suppress the fog phenomenon in printing immediately after the execution of the image carrier polishing mode.

  According to the eighth configuration of the invention, in the image forming apparatus having the seventh configuration, the charging bias applied to the charging device during the execution of the image carrier polishing mode is higher than the discharge start voltage. By making it lower than the charging bias sometimes applied, it is possible to suppress the adhesion of the discharge product to the surface of the image carrier while maintaining the charge rising property.

  According to the ninth configuration of the present invention, in the image forming apparatus having the seventh or eighth configuration, a charging device using a contact charging method having a charging member that contacts the surface of the image carrier is used. By applying a DC voltage to the surface of the image carrier, the generation of ozone can be reduced as compared with the corona charging method. In addition, even when using a charging device with a contact charging method that easily causes scratches on the drum surface due to electric discharge and causes uneven charging due to increase or decrease in the film thickness of the photosensitive layer, halftone streaks or dash marks due to scratches on the drum surface The occurrence of image defects such as these can be effectively suppressed.

  Further, according to the tenth configuration of the present invention, in the image forming apparatus having any one of the first to ninth configurations, the photosensitive layer is scraped or scratched, which is particularly problematic when the organic photosensitive layer is used. It is possible to extend the life of the image carrier by suppressing it.

  According to the eleventh configuration of the present invention, in the image forming apparatus having any one of the first to tenth configurations, the first gear constituting the drive mechanism for rotating the image carrier and moving in the axial direction. The member, the second gear member, and the idle gear can be collectively arranged at one end of the image carrier, resulting in a space-saving configuration.

  According to the twelfth configuration of the present invention, in the image forming apparatus according to the eleventh configuration, since one gear of the first gear member and the second gear member is formed of a transition gear, the first gear member and The second gear member can reliably mesh with the idle gear, and can accurately transmit the rotational driving force.

  According to the thirteenth configuration of the present invention, in the image forming apparatus having the eleventh or twelfth configuration, when the cam surface and the cam follower rotate by a unit angle, the image carrier is displaced by a certain amount in the axial direction. The image carrier can be moved at a constant speed in the axial direction.

Schematic sectional view of a color image forming apparatus of the present invention Enlarged view of the vicinity of the image forming portion Pa in FIG. Front sectional view of the drum unit 40 including the photosensitive drum 1a, the charging device 2a, and the cleaning device 5a. Partial perspective view of the photosensitive drum 1a viewed from the drum flange 41a side The partial perspective view which shows the state which removed the gear holder 45 from FIG. Sectional drawing of the edge part by the side of the drum flange 41a of the photosensitive drum 1a The partial perspective view which looked at the drum unit 40 from the drum flange 41b side External perspective view of drum flange 41a The perspective view which looked at the 1st gear member 51 from the left side surface side (2nd gear member 53 side) of FIG. The perspective view which looked at the 1st gear member 51 from the right side surface (drum flange 41a side) of FIG. The perspective view which looked at the 2nd gear member 53 from the right side (1st gear member 51 side) of FIG. Sectional drawing of the edge part by the side of the drum flange 41a of the photosensitive drum 1a which shows the state which the axial direction distance of the 1st gear member 51 and the 2nd gear member 53 became the minimum. Sectional drawing of the edge part by the side of the drum flange 41a of the photosensitive drum 1a which shows the state which the axial direction distance of the 1st gear member 51 and the 2nd gear member 53 became the maximum. Sectional drawing which shows the positional relationship of the primary transfer roller 6a (transfer part) in the image formation part Pa, and the exposure part L to which the light from the exposure unit 4 is irradiated. Graph showing the relationship between the number of rotations of the photosensitive drum and the amount of axial movement A graph comparing the time (charge rising property) until the surface of the photosensitive drum reaches a predetermined surface potential Vo when the photosensitive layer is polished and when it is not polished Graph showing the relationship between the charging bias applied to the charging roller and the drum surface potential FIG. 4 is another schematic configuration example of the image forming apparatus according to the present invention, and is a schematic cross-section of a direct transfer type color image forming apparatus including an endless conveying belt 60 that sequentially conveys the transfer paper P to the image forming units Pa to Pb. Figure FIG. 3 is a schematic cross-sectional view of a monochrome image forming apparatus that is another example of the image forming apparatus according to the present invention and does not have a conveyance belt.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram showing the configuration of the image forming apparatus of the present invention. In the main body of the color printer 100, four image forming portions Pa, Pb, Pc, and Pd are sequentially arranged from the upstream side in the transport direction (the right side in FIG. 1). These image forming portions Pa to Pd are provided corresponding to images of four different colors (cyan, magenta, yellow, and black), and cyan, magenta, and yellow are respectively performed by charging, exposure, development, and transfer processes. And a black image are sequentially formed.

  These image forming portions Pa to Pd are provided with photosensitive drums 1a, 1b, 1c and 1d for carrying visible images (toner images) of respective colors. Here, organic photosensitive materials are disposed on the outer peripheral surface of the aluminum drum. An OPC photoreceptor in which a layer (OPC) is formed is used. Further, an intermediate transfer belt 8 that rotates clockwise in FIG. 1 by a driving means (not shown) is provided adjacent to each of the image forming portions Pa to Pd. The toner images formed on the photosensitive drums 1a to 1d are sequentially primary-transferred and superimposed on the intermediate transfer belt 8 that moves while contacting the photosensitive drums 1a to 1d, and then the secondary transfer roller. 9 is secondarily transferred onto a transfer paper P as an example of a recording medium, and further fixed on the transfer paper P in the fixing unit 7 and then discharged from the apparatus main body. For example, the image forming process for each of the photosensitive drums 1a to 1d is executed while rotating the photosensitive drums 1a to 1d counterclockwise in FIG.

  The transfer paper P onto which the toner image is transferred is accommodated in a paper cassette 16 at the lower part of the apparatus, and is conveyed to the secondary transfer roller 9 via the paper feed roller 12a and the registration roller pair 12b. A sheet made of dielectric resin is used for the intermediate transfer belt 8, and a (seamless) belt having no seam is mainly used. A blade-shaped belt cleaner 19 for removing toner remaining on the surface of the intermediate transfer belt 8 is disposed on the downstream side of the secondary transfer roller 9 with respect to the rotation direction of the intermediate transfer belt 8.

  Next, the image forming units Pa to Pd will be described. There are charging devices 2a, 2b, 2c and 2d for charging the photosensitive drums 1a to 1d and image information on the photosensitive drums 1a to 1d around and below the photosensitive drums 1a to 1d, which are rotatably arranged. The exposure unit 4 for exposing the toner, the developing devices 3a, 3b, 3c and 3d for forming toner images on the photosensitive drums 1a to 1d, and the developer (toner) remaining on the photosensitive drums 1a to 1d are removed. Cleaning devices 5a to 5d are provided.

  When the start of image formation is input by the user, the surfaces of the photosensitive drums 1a to 1d are first uniformly charged by the charging devices 2a to 2d, and then the light irradiation is performed on the surfaces of the photosensitive drums 1a to 1d by the exposure unit 4. Then, electrostatic latent images corresponding to the image data are formed on the respective photosensitive drums 1a to 1d. Each of the developing devices 3a to 3d includes a developing roller disposed so as to face the photosensitive drums 1a to 1d, and each of the developing devices 3a to 3d is filled with a predetermined amount of a two-component developer including yellow, cyan, magenta, and black toners. This toner is supplied onto the photosensitive drums 1a to 1d by the developing rollers of the developing devices 3a to 3d, and electrostatically adheres to the electrostatic latent image formed by exposure from the exposure unit 4. A toner image is formed.

  Then, the primary transfer rollers 6a to 6d apply an electric field at a predetermined transfer voltage between the primary transfer rollers 6a to 6d and the photosensitive drums 1a to 1d, and yellow, cyan, magenta, and the like on the photosensitive drums 1a to 1d. A black toner image is primarily transferred onto the intermediate transfer belt 8. These four color images are formed with a predetermined positional relationship predetermined for forming a predetermined full-color image. Thereafter, the toner remaining on the surfaces of the photosensitive drums 1a to 1d is removed by the cleaning devices 5a to 5d in preparation for the subsequent formation of a new electrostatic latent image.

  The intermediate transfer belt 8 is stretched around a plurality of suspension rollers including a driven roller 10 and a drive roller 11, and the intermediate transfer belt 8 rotates clockwise as the drive roller 11 is rotated by a drive motor (not shown). Is started, the transfer paper P is conveyed from the registration roller 12b to the secondary transfer roller 9 provided adjacent to the intermediate transfer belt 8 at a predetermined timing, and the nip portion (secondary transfer nip portion) with the intermediate transfer belt 8 is transferred. ), The full color image is secondarily transferred onto the transfer paper P. The transfer paper P onto which the toner image is transferred is conveyed to the fixing unit 7.

  The transfer paper P conveyed to the fixing unit 7 is heated and pressurized when passing through the nip portion (fixing nip portion) of the pair of fixing rollers 13, and the toner image is fixed on the surface of the transfer paper P, so that a predetermined full color is obtained. An image is formed. The transfer paper P on which the full-color image is formed is distributed in the transport direction by the branching portion 14 that branches in a plurality of directions. When an image is formed on only one side of the transfer paper P, it is discharged as it is onto the discharge tray 17 by the discharge roller 15.

  On the other hand, when images are formed on both sides of the transfer paper P, a part of the transfer paper P that has passed through the fixing unit 7 is once projected from the discharge roller 15 to the outside of the apparatus. Thereafter, the transfer paper P is distributed to the paper transport path 18 by the branching section 14 by rotating the discharge roller 15 in the reverse direction, and is transported again to the registration roller pair 12b with the image surface reversed. Then, after the next image formed on the intermediate transfer belt 8 is transferred by the secondary transfer roller 9 to the surface of the transfer paper P where the image is not formed, and conveyed to the fixing unit 7 to fix the toner image. , And discharged to the discharge tray 17.

  FIG. 2 is an enlarged view of the vicinity of the image forming portion Pa in FIG. Since the image forming units Pb to Pd have basically the same configuration, description thereof is omitted. Around the photosensitive drum 1a, a charging device 2a, a developing device 3a, a cleaning device 5a, and a charge eliminating lamp 20 are disposed along the drum rotation direction (counterclockwise in FIG. 2), and the intermediate transfer belt 8 is interposed therebetween. The primary transfer roller 6a is arranged.

  The charging device 2 a includes a charging roller 21 that contacts the photosensitive drum 1 a and applies a charging bias (DC voltage) to the drum surface, and a charging cleaning roller 23 for cleaning the charging roller 21. In the present invention, in order to reduce the amount of generated ozone and reduce the cost of a charging bias power source (not shown), a charging bias consisting only of a DC voltage is applied to the charging roller 21. Alternatively, a method of applying a bias in which an AC bias is superimposed on may be used.

  The developing device 3a is a two-component developing type having two stirring and conveying screws 25, a magnetic roller 27, and a developing roller 29, and a toner thin film is applied to the developing roller 29 using a magnetic brush that stands on the surface of the magnetic roller 27. A layer is formed, and a developing bias having the same polarity (positive) as the toner is applied to the developing roller 29 to cause the toner to fly on the drum surface.

  The cleaning device 5 a has a cleaning blade 31 and a toner discharge screw 33. A neutralizing lamp 20 is disposed between the cleaning device 5a and the charging device 2a. The neutralization lamp 20 removes residual charges on the surface of the drum by irradiating the surface of the photosensitive drum 1a with light.

  FIG. 3 is a front sectional view of the drum unit 40 including the photosensitive drum 1a, the charging device 2a, and the cleaning device 5a. Hereinafter, the drum unit disposed in the image forming unit Pa will be described. However, the drum units disposed in the image forming units Pb to Pd have the same configuration, and thus description thereof will be omitted. Further, the charging device 2a and the cleaning device 5a are not shown.

  Drum flanges 41a and 41b are inserted and fixed at both ends of the photosensitive drum 1a, and a drum shaft 42 is fixed at the center of the drum flanges 41a and 41b so as to penetrate the inside of the photosensitive drum 1a. .

  A drive input gear 43 is fixed to an end portion of the drum shaft 42 that protrudes from the drum flange 41b side to the outside of the drum unit housing 40a. A pressing spring 44 is disposed between the drum flange 41b and the inner wall surface of the drum unit housing 40a. The photosensitive drum 1a is urged in the direction of arrow A by the pressing spring 44. On the other hand, on the drum flange 41a side, a plurality of gears (described later) constituting a driving mechanism 50 (described later) for reciprocating the photosensitive drum 1a in the axial direction (left-right direction in the figure) while rotating the photosensitive drum 1a are arranged. A gear holder 45 that covers each gear is mounted. The gear holder 45 is fixed to the drum unit housing 40a. The drive input gear 43 and the pressing spring 44 constitute a part of the drive mechanism 50.

  4 is a partial perspective view of the photosensitive drum 1a viewed from the drum flange 41a side, FIG. 5 is a partial perspective view of the photosensitive drum 1a with the gear holder 45 removed, and FIG. 6 is a drum of the photosensitive drum 1a. FIG. 7 is a partial perspective view of the drum unit 40 as viewed from the drum flange 41b side. The drive mechanism 50 for the photosensitive drum 1a will be described with reference to FIGS.

  The drive mechanism 50 includes a drive input gear 43 that inputs a driving force to the drum shaft 42, a first gear member 51 that is fixed to the drum flange 41a, and a second gear member 53 that is rotatably fitted to the drum flange 41a. And an idle gear 55 that meshes with the first gear member 51 and the second gear member 53, and a pressing spring 44 that presses the drum flange 41b toward the drum flange 41a.

  8 is an external perspective view of the drum flange 41a, and FIGS. 9 and 10 show the first gear member 51 on the left side (second gear member 53 side) and the right side (drum flange 41a side) in FIG. 6, respectively. FIG. 11 is a perspective view of the second gear member 53 viewed from the right side surface (first gear member 51 side) of FIG. As shown in FIG. 8, the drum flange 41a has a concave shape toward the inside of the photosensitive drum 1a. A cylindrical bearing portion 60 to which the drum shaft 42 is fixed is formed at the center of the drum flange 41 a, and engaging claws 61 are projected from three locations on the outer peripheral surface of the bearing portion 60.

  As shown in FIGS. 9 and 10, the first gear member 51 includes first gear teeth 51a, a cam follower 51b, and an engaging recess 51c. The first gear teeth 51 a are spur gears formed on the outer peripheral surface of the first gear member 51. The cam follower 51 b is an annular protrusion that protrudes from the side surface of the first gear member 51 and abuts on the cam surface 53 b of the second gear member 53. The cam follower 51b has a maximum portion (convex portion) 511 and a minimum portion (concave portion) 512 so that the axial distance is always changed (displaced) by a predetermined amount with respect to the unit rotation angle in the circumferential direction of the first gear member 51. One place is formed 180 degrees apart. The engaging recess 51c engages with an engaging claw 61 formed in the bearing portion 60 of the drum flange 41a.

  As shown in FIG. 11, the second gear member 53 has second gear teeth 53a and a cam surface 53b. The second gear teeth 53 a are spur gears that are formed on the outer peripheral surface of the second gear member 53 and have one fewer tooth than the first gear teeth 51 a of the first gear member 51. Further, the second gear teeth 53a are formed by shifting so that the pitch circle diameter matches the pitch circle diameter of the first gear teeth 51a. By configuring the second gear teeth 53a with a transfer gear, an idle gear 55, which will be described later, reliably meshes with the first gear teeth 51a and the second gear teeth 53a.

  Instead of reducing the number of teeth of the second gear teeth 53a, the first gear teeth 51a may be a transition spur gear having one less number of teeth than the second gear teeth 53a. Also, the number of teeth on one of the first and second gear teeth 51a, 53a may be reduced by two or more.

  The cam surface 53b is formed in an annular shape on the left side surface of the second gear member 53 so as to face the cam follower 51b of the first gear member 51, and is formed so that the axial distance is different (displaced) in the circumferential direction. . The cam surface 53b has a maximum portion (convex portion) 531 and a minimum portion (concave portion) 532 so that the axial distance always changes (displaces) by a predetermined amount with respect to the unit rotation angle in the circumferential direction of the second gear member 53. Are formed one by one apart by 180 °.

  And according to the contact position of the cam follower 51b and the cam surface 53b, the cam follower 51b moves relative to the cam surface 53b in the axial direction. Here, since the side surface of the second gear member 53 having the cam surface 53b is in contact with the gear holder 45, and the gear holder 45 is in contact with the drum unit housing 40a, the second gear member 53 is in the axial direction (see FIG. 6). Movement to the left is restricted.

  Therefore, the first gear member 51 having the cam follower 51b presses the drum flange 41a in the axial direction (right direction in FIG. 6), and the photosensitive drum 1a together with the drum flanges 41a and 41b resists the urging force of the pressing spring 44. Move together. In addition, you may provide the maximum part 511,531, and the minimum part 512,532 of the cam follower 51b and the cam surface 53b facing each other in the position which divides | segments a circumferential surface. When two or more maximum portions 511 and 531 and minimum portions 512 and 532 are provided, the cam follower 51b and the cam surface 53b can be stably brought into contact with each other. Alternatively, a cam surface may be formed on the first gear member 51 and a cam follower may be provided on the second gear member 53.

  The idle gear 55 includes a spur gear that meshes with the first gear teeth 51a and the second gear teeth 53a. The rotation shaft 55 a of the idle gear 55 is rotatably supported by bearing portions 45 a and 45 b of the gear holder 45.

  The pressing spring 44 is a coil spring that presses the drum flange 41b in the left direction in FIG. 6, and biases the cam follower 51b in a direction in which the cam follower 51b contacts the cam surface 53b.

  When the drive input gear 43 is rotationally driven by a drive source such as a motor (not shown), the drum shaft 42 to which the drive input gear 43 is fixed rotates, and the photosensitive drum is integrated with the drum flanges 41a and 41b to which the drum shaft 42 is fixed. 1a also rotates. Further, the first gear member 51 rotates integrally with the drum flange 41a by the engagement between the engagement recess 51c of the first gear member 51 and the engagement claw 61 of the drum flange 41a.

  When the first gear member 51 is driven to rotate, the idle gear 55 that meshes with the first gear teeth 51 a rotates, and further, the second gear teeth 53 a that mesh with the idle gear 55, that is, the second gear member 53 rotates. As a result, the first gear member 51 and the second gear member 53 rotate in the same direction, but due to the difference in the number of teeth between the first gear teeth 51a and the second gear teeth 53a, the first gear member 51 and the second gear member 53 are rotated. The members 53 rotate at different peripheral speeds. When the first and second gear members 51 and 53 rotate at different peripheral speeds, the contact position between the cam follower 51b and the cam surface 53b changes, and the biasing force of the pressing spring 44 is resisted according to the contact position. Then, the photosensitive drum 1a rotates (thrust movement) in the axial direction while rotating.

  As shown in FIG. 12, the first gear member 51 and the maximum portion 511 of the cam follower 51b and the minimum portion 532 of the cam surface 53b, and the minimum portion 512 of the cam follower 51b and the maximum portion 531 of the cam surface 53b are in contact with each other. The axial distance from the second gear member 53 is minimized, and the photosensitive drum 1a moves to the second gear member 53 side (to the left in FIG. 3).

  When the first gear member 51 further rotates, the photosensitive drum 1a gradually moves to the right from the state of FIG. Then, as shown in FIG. 13, the maximum portion 511 of the cam follower 51b and the maximum portion 531 of the cam surface 53b are in contact with each other, and the minimum portion 512 of the cam follower 51b and the minimum portion 532 of the cam surface 53b are opposed to each other. The distance in the axial direction between the gear member 51 and the second gear member 53 becomes the maximum, and the photosensitive drum 1a moves to the drive input gear 43 side (to the right in FIG. 3). When the first gear member 51 further rotates from the state of FIG. 13, the state returns to the state of FIG.

  As described above, since the photosensitive drums 1a to 1d rotate and reciprocate in the axial direction, the photosensitive member is in a state where residual toner is clogged in the cleaning blade 31 (see FIG. 2) that contacts the photosensitive drums 1a to 1d. There is no possibility that the same positions on the surfaces of the drums 1a to 1d are repeatedly rubbed. Therefore, the residual toner on the photosensitive drums 1a to 1d is cleaned without damaging the surfaces of the photosensitive drums 1a to 1d. Instead of rotating the first gear member 51, the second gear member 53 may be fixed to the drum flange 41a and driven to rotate.

  Here, in the image forming portions Pa to Pd of the respective colors, in order to clean the photosensitive drums 1a to 1d by the cleaning blade 31, the photosensitive drums 1a to 1d move in the axial direction during image formation. There is a risk of color misregistration in the axial direction during primary transfer of toner images of the respective colors by the primary transfer rollers 6a to 6d. A configuration for suppressing this color shift will be described with reference to FIGS. FIG. 14 is a cross-sectional view showing the image forming portion Pa, and FIG. 15 is a graph showing the relationship between the number of rotations of the photosensitive drum and the amount of movement in the axial direction. 14 shows the image forming portion Pa shown in FIG. 2 from the back side of the drawing. Further, since the same applies to the image forming units Pb to Pd, description thereof is omitted.

  As shown in FIG. 14, the primary transfer roller 6 a (transfer unit) is separated from the exposure unit L irradiated with light from the exposure unit 4 by an angle W in the circumferential direction. In the present embodiment, the angle W is set to 162.5 °, and the angle between the cleaning blade 31 and the charging device 2a is set to 129.28 °.

  Further, the number of teeth of the first gear teeth 51a (see FIG. 9) is set to 24, and the number of teeth of the second gear teeth 53a (see FIG. 11) is set to 23. Furthermore, the cam follower 51b and the cam surface 53b are formed such that a constant axial distance always changes (displaces) with respect to the unit rotation angle, and the maximum axial displacement of the cam follower 51b relative to the cam surface 53b (FIG. 12, (See FIG. 13) is set to 0.5 mm.

  In the drive mechanism 50 set in this way, when the first gear member 51 is rotated by the rotational drive of the drive input gear 43, the photosensitive drum 1a reciprocates as shown by the solid line in FIG. In FIG. 15, the horizontal axis represents the number of rotations of the photosensitive drum 1a, and the vertical axis represents the axial movement amount of the photosensitive drum 1a. The photosensitive drum 1a reciprocates once during 23 rotations (8280 ° rotation) and moves 0.5 mm in the axial direction at 11.5 rotations (4140 ° rotation).

  Now, since the angle W from the primary transfer roller 6a to the exposure portion L is 162.5 °, the axial movement amount of the photosensitive drum 1a while the photosensitive drum 1a rotates by the angle W is 162.5 / 4140 × 0.5 (mm) ≈0.0196 mm = 19.6 μm, and the axis moves 19.6 μm. That is, the electrostatic latent image formed by the exposure unit 4 is developed into a toner image by the developing roller 29 and is shifted by 19.6 μm before being transferred onto the intermediate transfer belt 8 by the primary transfer roller 6a. Accordingly, the maximum amount of deviation between any two colors at the time of primary transfer is 19.6 × 2 = 39.2 μm.

  Here, the color misregistration between the two colors is at a level that causes no practical problem as long as it is not more than the diameter (here 42 μm) of one dot of the color point forming the image. Therefore, if the amount of axial movement of each of the photosensitive drums 1a to 1d during image formation is 21 μm or less, the color shift of the toner image by each of the photosensitive drums 1a to 1d is within an allowable range.

  According to the configuration of the present embodiment, since the photosensitive drums 1a to 1d are rotated and reciprocated in the axial direction by the drive mechanism 50, the foreign matter staying between the cleaning blade 31 and the photosensitive drums 1a to 1d. However, there is no risk of scraping the same portion of the photosensitive drums 1a to 1d in the axial direction. Therefore, residual toner on the photosensitive drums 1a to 1d can be cleaned by using the cleaning blade 31 without damaging the photosensitive layers on the surfaces of the photosensitive drums 1a to 1d.

  In addition, the cleaning blade 31 can be fixed to the cleaning devices 5a to 5d, for example, and the configuration of the seal portion of the cleaning devices 5a to 5d is simplified, so that the toner is scattered outside the cleaning devices 5a to 5d. There is nothing to do. Further, since the photosensitive drums 1a to 1d are rotated and reciprocated in the axial direction by using a single driving source (motor), the configuration is simplified and the cost is reduced.

  Further, since the first gear member 51, the second gear member 53, and the idle gear 55 constituting the drive mechanism 50 are accommodated inside the concave shape of the drum flange 41a, the space-saving configuration is achieved. In addition, since the drive mechanism 50 is less likely to be contaminated by the scattered toner, it is possible to suppress the occurrence of malfunction of the drive mechanism 50 and to extend the life of the image forming apparatus.

  By the way, even if the photosensitive drums 1a to 1d are reciprocated in the axial direction as described above, the generation of minute scratches (unevenness) on the surfaces of the photosensitive drums 1a to 1d is not completely eliminated. For this reason, foreign matters such as toner external additives that have passed through the cleaning blade 31 aggregate along the flaws, and if toner accumulates in areas where the irregularities are large, a dash mark may be generated in the output image.

  Therefore, in the image forming apparatus of the present invention, a polishing operation (hereinafter referred to as photosensitive photosensitive member) in which the photosensitive drums 1a to 1d and the intermediate transfer belt 8 are brought into contact with each other with a predetermined linear velocity difference in each of the image forming units Pa to Pd. The body polishing mode).

  Even during image formation, the linear velocity of the intermediate transfer belt 8 is slightly (approximately 0.3%) faster than the photosensitive drums 1a to 1d. That is, in the photoconductor polishing mode, the photoconductor drum is brought into contact with the photoconductor drums 1a to 1d by the primary transfer rollers 6a to 6d, the backup roller, and the guide roller (not shown) during non-image formation. The rotation is performed with a greater linear velocity difference between 1a to 1d and the intermediate transfer belt 8 than during image formation.

  The surface of the photosensitive drums 1a to 1d is executed by executing this photosensitive member polishing mode when the image forming apparatus is started from the power-off state or the sleep (power saving) mode to the printing start state, or for every predetermined number of printings. The minute irregularities and deposits can be removed in a short time, and the generation of dash marks can be effectively prevented over a long period of time.

  The greater the linear velocity difference between the photosensitive drums 1a to 1d and the intermediate transfer belt 8 during execution of the photosensitive drum polishing mode, the higher the polishing effect. However, the amount of abrasion of the photosensitive layer increases and the photosensitive drums 1a to 1d increase. Life is shortened. Therefore, it is preferable to set the linear velocity difference between the photosensitive drums 1a to 1d and the intermediate transfer belt 8 to an appropriate value depending on the type and thickness of the photosensitive layer.

  Further, when a linear velocity difference is provided between the photosensitive drums 1a to 1d and the intermediate transfer belt 8, the linear velocity of the intermediate transfer belt 8 may be increased as compared with the linear velocity of the photosensitive drums 1a to 1d. preferable. At this time, the linear velocity of the intermediate transfer belt 8 may be made larger than that at the time of image formation, or the linear velocity of the photosensitive drums 1a to 1d may be made smaller than that at the time of image formation.

  Incidentally, it is known that when the photosensitive layer on the surface of the photosensitive drum is polished, the charging performance of the photosensitive layer changes. FIG. 16 is a graph comparing the time (charge rising property) until the surface of the photosensitive drum reaches a predetermined surface potential Vo (for example, 600 V) when the photosensitive layer is polished and when it is not polished. .

  As shown in FIG. 16, when the photosensitive layer is not polished (solid line in FIG. 16), the surface potential at the first rotation of the drum is slightly low, but reaches the predetermined surface potential Vo after the second rotation. To do. On the other hand, when the photosensitive layer is polished (broken line in FIG. 16), the charge rising property decreases, so the surface potential increases stepwise and reaches a predetermined surface potential Vo after rotating the drum several times (after time R). To do. That is, it can be understood that it takes more time for the surface potential of the photosensitive drum to reach Vo when the application of the charging bias is started after execution of the photosensitive member polishing mode than when the photosensitive member polishing mode is not executed.

  Therefore, in order to improve the rising property of charging when printing is performed after execution of the photoconductor polishing mode, it is preferable to apply a charging bias (charging aging) to the charging roller 21 during execution of the photoconductor polishing mode. .

  However, when a charging bias having the same voltage as that during normal image formation is applied to the charging roller 21 during execution of the photoconductor polishing mode, discharge products such as NOx and SOx are generated by the discharge from the charging roller 21. When this discharge product adheres to the photosensitive drums 1a to 1d, fine irregularities are formed on the drum surface. As a result, polishing in the photoconductor polishing mode cannot catch up, and a dash mark is generated after long-term use.

  On the other hand, when charging aging is not performed in the photoconductor polishing mode, the adhesion of discharge products to the photoconductor drums 1a to 1d is suppressed, so that generation of a dash mark can be avoided. However, as described above, the rising property of charging when printing is performed after execution of the photoconductor polishing mode is deteriorated, and a fog phenomenon may occur in an image immediately after the start of printing. In order to prevent this fogging phenomenon, if the charge rising time is secured after execution of the photoconductor polishing mode, the printing waiting time for the user becomes long.

  FIG. 17 is a graph showing the relationship between the charging bias applied to the charging roller and the drum surface potential. As shown in FIG. 17, when the charging bias is gradually increased, the drum surface potential does not increase until the discharge start voltage (Vth), and is proportional to the charge bias from the point where the discharge start voltage (Vth) is exceeded. It can be seen that the drum surface potential is rising. At the time of image formation, by applying a predetermined charging bias Vdc (for example, +1.4 V), the drum surface is charged to a predetermined surface potential Vo (for example, 600 V).

  Here, by lowering the charging bias applied to the charging roller 21 during charging aging to the vicinity of the discharge start voltage Vth (for example, +700 V) (hatched region in FIG. 17), the charge rising property after execution of the photoconductor polishing mode is also maintained. As a result, it was found that adhesion of discharge products was also suppressed.

  That is, by generating the charging bias applied to the charging roller 21 during the charge aging higher than the discharge start voltage Vth and lower than the charging bias Vdc applied during image formation, discharge generation is maintained while maintaining the charge rising property. Occurrence of a dash mark can be avoided by suppressing adhesion of objects. Since the discharge start voltage Vth varies depending on the type and thickness of the photosensitive layer formed on the photosensitive drums 1a to 1d, an appropriate charging bias may be set according to the specifications of the photosensitive drums 1a to 1d.

  Although the case where the photoconductor drums 1a to 1d are simultaneously polished has been described here, only one specific photoconductor drum or a plurality of photoconductor drums can be polished. The execution procedure of the photoconductor polishing mode is basically the same as that in the case where four are simultaneously performed. However, in order to prevent a difference in linear velocity between the photoconductor drum and the intermediate transfer belt 8 without performing polishing, It is necessary to rotate and stop in synchronization with the movement and stop of the transfer belt 8.

  Further, as shown in FIG. 18, an endless conveying belt 60 that sequentially conveys the transfer paper P to the image forming portions Pa to Pb instead of the intermediate transfer belt 8 is in contact with the lower portions of the photosensitive drums 1a to 1d. In the case of the direct transfer type color printer 100 arranged in FIG. 1, the photosensitive member polishing mode is executed by driving the conveying belt 60 with a linear velocity difference with respect to the photosensitive drums 1a to 1d during non-image formation. Can do.

  In the color printer 100 shown in FIG. 18, the developing devices 3 a to 3 d are of a one-component developing type, and include LED heads 4 a to 4 d that individually expose the photosensitive drums 1 a to 1 d in place of the exposure unit 4. Yes. The configuration of other parts is basically the same as that in FIG.

  In addition, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in each of the above embodiments, the present invention is applied to a color image forming apparatus of an intermediate transfer type and a direct transfer type. However, the present invention is not limited to this and may be applied to a monochrome image forming apparatus.

  For example, when the monochrome image forming apparatus has a transport belt for transporting transfer paper, the transport belt is driven with a linear speed difference with respect to the photosensitive drum in the same manner as the direct transfer type color image forming apparatus. The body polishing mode can be executed. Further, in the case of the monochrome image forming apparatus 101 having no conveyance belt as shown in FIG. 19, the transfer roller 70 for transferring the toner image onto the transfer paper is in contact with the photosensitive drum 1. The photoconductor polishing mode can be executed by rotating 70 with a linear velocity difference with respect to the photoconductor drum 1. Note that the above-described problem of color misregistration does not occur when applied to a monochrome image forming apparatus. Hereinafter, the effects of the present invention will be described in more detail with reference to examples.

  In the image forming apparatus (FS-C2026 MFP remodeled by Kyocera Mita) as shown in FIG. 1, whether or not the photosensitive drum is moved in thrust, whether or not the photosensitive body polishing mode is executed, the surface state of the photosensitive drum, the generation of dashes, And the relationship with the charge rising property was investigated. The test was performed with the system linear speed set at 160 mm / sec.

  As a test method, the photosensitive drums 1a to 1d are reciprocated once during 23 rotations with a maximum thrust amount of 0.5 mm, and the linear velocity of the intermediate transfer belt 8 is set to the linear speed of the photosensitive drums 1a to 1d. The present invention 1 is a case where the photosensitive member polishing mode of + 3.0% of the speed is executed once for every 500 sheets (30 seconds) and no charging bias is applied to the charging roller 21 during the photosensitive member polishing mode. The present invention 2 shows a case where a charging bias of the same voltage (+1.4 kV) as that at the time of image formation is applied to the present invention 2, and a case where a charging bias similar to the discharge start voltage (+700 V) is applied to the charging roller 21 of the present invention 3. did. On the other hand, the case where both the thrust movement of the photosensitive drums 1a to 1d and the photosensitive member polishing mode are not executed is Comparative Example 1, and the case where the thrust movement of the photosensitive drums 1a to 1d is performed but the photosensitive member polishing mode is not executed is a comparative example. 2.

  When a test image having a printing rate of 4% consisting of characters and lines is continuously printed using the image forming apparatuses of the present invention 1 to 3 and comparative examples 1 and 2 in a normal temperature and humidity environment (25 ° C., 50% RH). The generation of halftone streaks due to scratches on the drum surface, the generation of dash marks, and the charge rising property were evaluated.

  The photosensitive drums 1a to 1d used in the present invention 1 to 3 and comparative examples 1 and 2 were positively charged single layer OPC drums having a diameter of 30 mm. Further, a charging roller 21 made of epichlorohydrin rubber having a diameter of 12 mm was used. The evaluation results are shown in Table 1.

  As is clear from Table 1, in Comparative Example 1 in which neither the thrust movement of the photosensitive drum nor the photosensitive member polishing mode was performed, halftone streaks due to drum scratches occurred after printing 120k (120,000) sheets. In Comparative Example 2 in which only the thrust movement of the photosensitive drum was performed, the halftone streaks were eliminated, but a dash mark was generated after printing 80k (80,000) sheets.

  On the other hand, in the first aspect of the present invention in which the photosensitive drum is thrust-moved and the photosensitive member polishing mode is executed, both the halftone streak and the dash mark are eliminated. However, since no charging bias was applied to the charging roller, the charge rising property was poor, and fogging was observed at the leading edge of the first image after execution of the photoconductor polishing mode.

  Further, in the second aspect of the present invention in which the charging bias of the same voltage as that at the time of image formation was applied during the photoconductor polishing mode, the halftone streaks were eliminated and the charge rising property was good, but 80k (80,000) sheets were printed. A dash mark occurred later. This is presumably because the discharge product adheres to the drum surface due to the application of the charging bias and fine irregularities are formed, and the toner adheres to the concave or convex portions, so that a dash mark is easily generated. Further, in the third aspect of the present invention in which the charging bias having the same voltage as that at the time of image formation was applied during the photoconductor polishing mode, generation of both halftone streaks and dash marks was eliminated, and the charge rising property was also good.

  INDUSTRIAL APPLICABILITY The present invention can be used in image forming apparatuses such as copying machines, printers, facsimiles, and composite machines using electrophotography, and in particular, cleaning toner remaining on an image carrier using a cleaning blade. The image forming apparatus can be used.

Pa to Pd Image forming section 1a to 1d Photosensitive drum (image carrier)
2a to 2d Charging device 3a to 3d Developing device 4 Exposure unit 5a to 5d Cleaning device 6a to 6d Primary transfer roller 8 Intermediate transfer belt (intermediate transfer member)
9 Secondary transfer roller 21 Charging roller (charging member)
31 Cleaning blade 40 Drum unit 40a Drum unit housing 41a, 41b Drum flange (flange member)
42 Drum shaft (Rotating shaft)
43 Drive input gear 44 Pressing spring (biasing member)
45 Gear holder 50 Drive mechanism 51 First gear member 51a First gear tooth 51b Cam follower 53 Second gear member 53a Second gear tooth 53b Cam surface 55 Idle gear 511, 531 Maximum portion 512, 532 Minimum portion 60 Conveying belt (conveying member) )
70 Transfer roller (transfer member)
100 color image forming apparatus 101 monochrome image forming apparatus

Claims (11)

A plurality of image carriers having a photosensitive layer formed on the outer peripheral surface;
A cleaning blade for cleaning residual toner on the image carrier;
An endless intermediate transfer member that is arranged adjacent to each of the image carriers and on which the developed toner images are sequentially stacked;
A drive mechanism for rotating the image carrier and reciprocating in the axial direction;
In an image forming apparatus comprising:
Performing an image carrier polishing mode in which the intermediate transfer member and the image carrier are brought into contact with each other with a larger linear velocity difference than that during image formation during non-image formation ;
The drive mechanism includes a drive input gear that is fixed to one end of a rotation shaft of the image carrier and inputs a driving force to the rotation shaft, a first gear member that is fixed to the other end of the rotation shaft, and the first gear member. A second gear having a number of teeth different from that of the first gear member is supported adjacent to the gear member so as to be rotatable on the rotating shaft and slidable in the axial direction, and supported in a stationary manner in the axial direction with respect to the unit housing. A gear member, an idle gear that meshes with the first gear member and the second gear member, and a circumferential surface provided on one of the opposing side surfaces of the first gear member and the second gear member. An annular cam surface having a continuously changing axial distance, an annular cam follower provided on the other side surface and in contact with the cam surface, and the image carrier is biased in a direction in which the cam surface and the cam follower are in contact with each other. And an urging member
The image forming apparatus , wherein the cam surface and the cam follower are formed such that an axial displacement amount per unit rotation angle of the first gear member and the second gear member is constant .   The image forming apparatus according to claim 1, wherein a linear velocity of the image carrier in the image carrier polishing mode is smaller than that of the intermediate transfer member. An image carrier having a photosensitive layer formed on the outer peripheral surface;
A cleaning blade for cleaning residual toner on the image carrier;
An endless transport member that is disposed adjacent to the image carrier and transports a recording medium;
A drive mechanism for rotating the image carrier and reciprocating in the axial direction;
In an image forming apparatus comprising:
Executing an image carrier polishing mode in which the conveying member and the image carrier are brought into contact with each other with a larger linear velocity difference than that during image formation during non-image formation ;
The drive mechanism includes a drive input gear that is fixed to one end of a rotation shaft of the image carrier and inputs a driving force to the rotation shaft, a first gear member that is fixed to the other end of the rotation shaft, and the first gear member. A second gear having a number of teeth different from that of the first gear member is supported adjacent to the gear member so as to be rotatable on the rotating shaft and slidable in the axial direction, and supported in a stationary manner in the axial direction with respect to the unit housing. A gear member, an idle gear that meshes with the first gear member and the second gear member, and a circumferential surface provided on one of the opposing side surfaces of the first gear member and the second gear member. An annular cam surface having a continuously changing axial distance, an annular cam follower provided on the other side surface and in contact with the cam surface, and the image carrier is biased in a direction in which the cam surface and the cam follower are in contact with each other. And an urging member
The image forming apparatus , wherein the cam surface and the cam follower are formed such that an axial displacement amount per unit rotation angle of the first gear member and the second gear member is constant .   The image forming apparatus according to claim 3, wherein a linear velocity of the image carrier in the image carrier polishing mode is smaller than that of the transport member. An image carrier having a photosensitive layer formed on the outer peripheral surface;
A cleaning blade for cleaning residual toner on the image carrier;
A transfer member disposed adjacent to the image carrier and transferring a toner image developed on the image carrier onto a recording medium;
A drive mechanism for rotating the image carrier and reciprocating in the axial direction;
In an image forming apparatus comprising:
Performing an image carrier polishing mode in which the transfer member and the image carrier are brought into contact with each other with a larger linear velocity difference than that during image formation during non-image formation ;
The drive mechanism includes a drive input gear that is fixed to one end of a rotation shaft of the image carrier and inputs a driving force to the rotation shaft, a first gear member that is fixed to the other end of the rotation shaft, and the first gear member. A second gear having a number of teeth different from that of the first gear member is supported adjacent to the gear member so as to be rotatable on the rotating shaft and slidable in the axial direction, and supported in a stationary manner in the axial direction with respect to the unit housing. A gear member, an idle gear that meshes with the first gear member and the second gear member, and a circumferential surface provided on one of the opposing side surfaces of the first gear member and the second gear member. An annular cam surface having a continuously changing axial distance, an annular cam follower provided on the other side surface and in contact with the cam surface, and the image carrier is biased in a direction in which the cam surface and the cam follower are in contact with each other. And an urging member
The image forming apparatus , wherein the cam surface and the cam follower are formed such that an axial displacement amount per unit rotation angle of the first gear member and the second gear member is constant .   6. The image forming apparatus according to claim 5, wherein a linear velocity of the image carrier in the image carrier polishing mode is smaller than that of the transfer member.   7. The charging device according to claim 1, further comprising: a charging device that charges the photosensitive layer on the surface of the image carrier, wherein a charging bias is applied to the charging device during the execution of the image carrier polishing mode. The image forming apparatus described in 1. 8. The image according to claim 7, wherein a charging bias applied to the charging device during execution of the image carrier polishing mode is set to a value higher than a discharge start voltage and in the vicinity of the discharge start voltage. Forming equipment.   9. The image forming apparatus according to claim 7, wherein the charging device charges the surface of the image carrier by applying a DC voltage to a charging member that contacts the surface of the image carrier. .   The image forming apparatus according to claim 1, wherein the photosensitive layer is an organic photosensitive layer. The image forming apparatus according to claim 1, wherein one gear tooth of the first gear member and the second gear member is formed of a transition gear .