JP2006267710A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the occurrence of stripe scratches on the surface of an image carrier, and also, to suppress the occurrence of the local wear of the image carrier and turning-up of a cleaning blade. <P>SOLUTION: The cleaning blade 32 is pressurized against the surface of the photoreceptor drum 12. The photoreceptor drum 12 and an electrifying roll 14 are rotatably pivotally supported by supporting members 42 and 44. Regarding a position changing mechanism 40, by rotating a pinion 50 by a motor 52 and moving an extension part 46 and the supporting member 42 in a direction shown by an arrow A through a rack 46A, the photoreceptor drum 12 and the electrifying roll 14 are integrally moved in the axial direction. Thus, the occurrence of stripe scratches on the photoreceptor drum 12 by toner deposition on the cleaning blade 32 is reduced. Further, a contact position of the electrifying roll 14 with the photoreceptor drum 12 is not changed, and consequently, the electrified area on the photoreceptor drum 12 never enlarges up to both end parts. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes an image carrier, a contact charging roll that charges the image carrier, a cleaning blade that cleans the surface of the image carrier after transfer, and the like, and moves the image carrier in a direction perpendicular to the image traveling direction. The present invention relates to an image forming apparatus that changes a contact position with a cleaning blade.

  In general, in an image forming apparatus such as a copying machine or a printer that employs an electrophotographic method, the surface of an image carrier such as a photoconductor is charged by a contact charging roll, and the image carrier is irradiated with image light to form an electrostatic latent image. Then, the electrostatic latent image is developed with toner to form a toner image. The toner image on the image carrier is transferred to a recording medium or an intermediate transfer member, and the surface of the image carrier after the transfer is cleaned by a cleaning blade.

  In such an image forming apparatus, if the cleaning blade is always in contact with the axial direction of the image carrier, deposits such as transfer residual toner generated at the tip of the cleaning blade are the same on the image carrier. Since the contact with the peripheral surface continues, the image carrier is likely to have circumferential streaks.

  As countermeasures against such problems, for example, in order to remove deposits at the tip of the cleaning blade, a method of applying an impact to the cleaning blade, a vibration device such as a piezoelectric element is applied to the vibration blade other than the tip of the cleaning blade. Methods, a method in which a predetermined amount of reverse rotation is performed after the forward rotation of the image carrier is stopped, and a method in which the image carrier is temporarily stopped every predetermined number of times to deform the nip shape between the image carrier and the cleaning blade. ing.

  However, in the method of applying an impact to the cleaning blade, an impact sound is generated, and in the method of vibrating, there is a problem in the reliability of the vibration device. Further, in the reverse rotation operation and the method of deforming the nip shape, there is a concern that the sustainability of the effect decreases due to deformation of the cleaning blade.

In addition, there has been proposed an image forming apparatus that is provided with a drive mechanism that slides the cleaning blade in the axial direction of the image carrier and improves the cleaning performance by reciprocating the cleaning blade in the axial direction of the image carrier (for example, (See Patent Document 1).
JP 2000-356935 A

  However, in the configuration of Patent Document 1, the drive mechanism for sliding the cleaning blade in the axial direction of the image carrier is complicated, and there is a concern that reliability may be reduced. Further, there is a problem that the cleaning blade sag (permanent deformation) over time due to sliding of the cleaning blade, and the contact angle to the image carrier changes due to this.

  On the other hand, a configuration in which the image carrier is moved in the axial direction by a driving mechanism without moving the cleaning blade is also conceivable. However, when the image carrier is moved in the axial direction, the axial contact position between the image carrier and the contact charging roll changes. As a result, the area to be charged (discharge exposed area) on the surface of the image carrier charged by the minute gap discharge with the contact charging roll becomes wider as compared with the case where the image carrier is not moved. That is, since the charged area on the surface of the image carrier by the contact charging roll is displaced in the axial direction, an area that is charged only in one state with respect to the moving direction is generated on both ends of the image carrier. Since toner is difficult to be supplied to this region, the frictional force between the image carrier and the cleaning blade is increased, and the area where high frictional force is generated at both ends of the image carrier is widened. There is a problem that the wear progresses and the cleaning blade tends to bend.

  The present invention has been made in view of the above-described problems, and reduces the occurrence of streak on the surface of the image carrier due to deposits on the tip of the cleaning blade, and also locally deviates the image carrier. It is an object of the present invention to provide an image forming apparatus capable of suppressing the occurrence of wear and wobbling of a cleaning blade.

  In order to solve the above problems, an image forming apparatus according to the first aspect of the present invention includes an image carrier that carries a toner image, and a contact charging member that is disposed so as to contact the image carrier. A cleaning blade that cleans the image carrier after transferring the toner image, wherein the image carrier is moved in a direction perpendicular to the image traveling direction to Position changing means for changing the contact position, and position control means for controlling the charged area of the image carrier by the contact charging member to be the same area in a direction perpendicular to the image traveling direction of the image carrier. It is characterized by having.

  According to the first aspect of the present invention, the position changing means moves the image carrier in a direction (lateral direction) perpendicular to the image traveling direction to change the contact position with the cleaning blade. The kimono does not continue to contact the image carrier on the same circumferential surface, and it is possible to reduce the occurrence of circumferential streak on the surface of the image carrier.

  Further, when the image carrier is moved, the position control means controls the charged area of the image carrier by the contact charging member to be the same area in the direction perpendicular to the image traveling direction of the image carrier. . As a result, the charged area of the image carrier does not spread to different positions in the direction orthogonal to the image traveling direction, and toner is not easily supplied to the image carrier near both ends of the cleaning blade, and the frictional force tends to increase. The occurrence of the part can be avoided. For this reason, local wear of the image carrier is reduced in a portion of the charged region where the image carrier is likely to be deteriorated, and the occurrence of the cleaning blade is prevented from being curled.

  An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the position control unit returns the image carrier moved by the position changing unit to an image forming position. Thus, the relative positional relationship between the contact charging member and the image carrier is made constant during the image forming operation of the contact charging member.

  According to the second aspect of the present invention, the position control means makes the relative positional relationship between the contact charging member and the image carrier constant by returning the image carrier moved by the position changing means to the image forming position. Thus, the charged area of the image carrier by the contact charging member can be held in the substantially same area. For this reason, it is possible to prevent the charged area of the image carrier from spreading in a direction perpendicular to the image traveling direction, and there is a portion where the toner is difficult to be supplied to the image carrier and the frictional force tends to increase near both ends of the cleaning blade. It can be prevented from occurring.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the position control unit moves the contact charging member integrally with the image carrier, thereby moving the position charging unit. A contact position between the contact charging member and the image carrier is fixed during an image forming operation of the contact charging member.

  According to the third aspect of the present invention, the contact charging member is moved integrally with the image carrier so that the contact position between the contact charging member and the image carrier is constant, and It is possible to hold the charged area in the same area. For this reason, it is possible to prevent the charged area of the image carrier from spreading in a direction orthogonal to the image traveling direction, and there is a portion where the toner is difficult to be supplied to the image carrier and the frictional force tends to be high near both ends of the cleaning blade. It can be prevented from occurring.

  An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, wherein the contact charging member uniformly charges the image carrier. It is characterized by being a charging roll.

  According to the fourth aspect of the present invention, when the contact charging member is a charging roll that uniformly charges the image carrier, the charged area of the image carrier by the charging roll is constant in a direction orthogonal to the image traveling direction. It can be held in the area.

  An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, wherein the toner image formed on the image carrier is used as a transfer material. A transfer roll to be transferred is integrally moved with the image carrier.

  According to the fifth aspect of the present invention, since the transfer roll for transferring the toner image on the image carrier onto the transfer material is moved integrally with the image carrier, the charged area (discharge) of the image carrier by the transfer roll is moved. It is possible to hold the (exposed area) in a certain area in a direction orthogonal to the image traveling direction.

  An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to any one of the first to fifth aspects, wherein the image carrier is a cylindrical or cylindrical photosensitive drum. It is characterized by that.

  According to the sixth aspect of the present invention, when the image carrier is a cylindrical or columnar photosensitive drum, the relative position between the contact charging member and the image carrier can be held in a fixed region.

  An image forming apparatus according to a seventh aspect of the present invention is the image forming apparatus according to any one of the first to fifth aspects, wherein the image carrier is a cylindrical or columnar intermediate transfer drum. It is characterized by that.

  According to the seventh aspect of the present invention, when the image carrier is a cylindrical or columnar intermediate transfer drum, the relative position between the contact charging member and the image carrier can be held in a fixed region.

  In the image forming apparatus according to the present invention, it is possible to reduce the occurrence of circumferential streak on the surface of the image carrier, and to suppress the occurrence of local wear of the image carrier and the squeezing of the cleaning blade. Can do.

  Hereinafter, an embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 shows an image forming apparatus 10 according to the first embodiment of the present invention.

  The image forming apparatus 10 is a direct transfer type image forming apparatus in which the toner image formed on the photosensitive drum 12 is directly transferred to the recording paper P. In this image forming apparatus 10, a charging roll 14 for charging the photosensitive drum 12 from the upstream side in the rotation direction around the photosensitive drum 12 rotating in the arrow direction (image traveling direction), and a charged photosensitive drum. An optical scanning device 16 that forms an electrostatic latent image by irradiating the body drum 12 with a laser beam, and a toner is supplied to the electrostatic latent image forming portion on the photosensitive drum 12 to develop the electrostatic latent image. Thus, a developing device 18 for forming a toner image on the photosensitive drum 12 and a transfer roll 20 disposed so as to face the photosensitive drum 12 across the conveyance path of the recording paper P are arranged. Further, on the downstream side of the transfer roll 20 in the rotation direction (image traveling direction) of the photosensitive drum 12, a cleaning device 22 that cleans transfer residual toner and fog toner on the surface of the photosensitive drum 12 is disposed.

  Further, a conveyance belt 28 stretched by a drive roll 24 and a driven roll 26 is disposed on the upstream side in the conveyance direction of the recording paper P from the position where the photosensitive drum 12 and the transfer roll 20 face each other. The recording paper P is fed between the photosensitive drum 12 and the transfer roll 20 by the belt 28. Further, a fixing device 30 for fixing the toner image transferred onto the recording paper P by heating and pressurization is disposed downstream of the facing position between the photosensitive drum 12 and the transfer roll 20 in the conveyance direction of the recording paper P. It is installed.

  The cleaning device 22 includes a rubber cleaning blade 32 that is pressed against the photosensitive drum 12. The cleaning blade 32 is disposed such that the tip portion faces the upstream side in the rotation direction of the photosensitive drum 12.

  The charging roll 14 applies a DC voltage at a position in contact with the photoconductive drum 12 to uniformly charge the photoconductive drum 12 by discharge in a minute gap. The transfer roll 20 is configured to transfer the toner image on the photosensitive drum 12 onto the recording paper P by applying a transfer bias having a polarity opposite to the charging polarity of the toner.

  As shown in FIG. 2, a gear 34 is attached to the axial end portion (back side in FIG. 2) of the photosensitive drum 12, and the gear 34 meshes with a gear 38 connected to a motor 36. ing. When the motor 36 is driven, a driving force is transmitted to the photosensitive drum 12 via the gear 38 and the gear 34, and the photosensitive drum 12 rotates in the direction of the arrow shown in FIG. The drive of the motor 36 is controlled by the controller 60.

  Next, the position changing mechanism 40 that moves the photosensitive drum 12 in a direction (lateral direction or axial direction) orthogonal to the image traveling direction will be described.

  As shown in FIG. 2, a support member 42 that rotatably supports the shaft 12 </ b> A of the photosensitive drum 12 at the axial end (front side in FIG. 2) of the photosensitive drum 12 on the side opposite to the gear 34. Is arranged. A support member 44 that rotatably supports the shaft 12 </ b> A of the photosensitive drum 12 is disposed outside the gear 34 (back side in FIG. 2). The support members 42 and 44 are disposed substantially parallel to both ends of the photosensitive drum 12. The support member 42 is bent outward in the axial direction of the photosensitive drum 12, and a rack 46 </ b> A is provided above the bent extended portion 46. A rail 48 that supports the extended portion 46 so as to be movable in the axial direction (lateral direction) of the photosensitive drum 12 is disposed below the extended portion 46. The rack 46A meshes with the pinion 50, and a motor 52 is connected to the pinion 50. The motor 52 is a stepping motor, and the driving of the motor 52 is controlled by the controller 60.

  Further, the shaft 14A of the charging roll 14 is rotatably supported by support members 42 and 44 that support the photosensitive drum 12, and the photosensitive drum 12 and the charging roll 14 move together. The charging roll 14 is driven to rotate by the rotational drive of the photosensitive drum 12.

  When the motor 52 is driven, a driving force is transmitted to the rack 46A through the pinion 50, and the extending portion 46 moves along the rail 48, whereby the photosensitive drum 12 supported by the support members 42 and 44 is pivoted. Move in the direction (lateral direction). At this time, since the cleaning blade 32 is fixed, the contact position in the axial direction between the cleaning blade 32 and the photosensitive drum 12 changes when the photosensitive drum 12 moves in the axial direction (lateral direction).

  Further, since the charging roll 14 is supported by the support members 42 and 44, the photosensitive drum 12 and the charging roll 14 move together, and the contact position in the axial direction between the charging roll 14 and the photosensitive drum 12. Will not change.

  Further, the shaft 20A of the transfer roll 20 is rotatably supported by support members 62 and 64 that are arranged substantially parallel to both ends. The transfer roll 20 is rotated in the arrow direction shown in FIG. 1 by a motor (not shown).

  Next, the operation of the image forming apparatus 10 will be described.

  First, the entire image forming operation will be described, and then the unique action in the present embodiment will be described.

  As shown in FIG. 1, when the photosensitive drum 12 rotates in the direction of the arrow, the surface of the photosensitive drum 12 is first charged to a substantially uniform potential by the charging roll 14. When the photosensitive drum 12 further rotates, the surface of the photosensitive drum 12 is exposed by the optical scanning device 16, and the potential of the exposed portion of the photosensitive drum 12 is lowered to form an electrostatic latent image. The electrostatic latent image on the photosensitive drum 12 is conveyed to the developing device 18, and toner charged to the same polarity as the charging polarity of the photosensitive drum 12 is electrically attached to the potential lowering portion of the photosensitive drum 12. The electrostatic latent image is developed.

  Thereafter, when the photosensitive drum 12 is further rotated, the recording paper P is conveyed between the transfer roll 20 and the photosensitive drum 12 by the conveying belt 28 in accordance with the timing, and at the same time, the recording paper P has a polarity opposite to that of toner. A transfer bias is applied. As a result, the toner is electrically attracted to the transfer roll 20 and the toner image on the photosensitive drum 12 is transferred to the recording paper P. The toner image transferred to the recording paper P is heated and pressed by the fixing device 30 and fixed on the recording paper P.

  Further, after the transfer of the toner image, the surface of the photosensitive drum 12 moves to a contact position of the cleaning blade 32, and residual toner on the surface of the photosensitive drum 12 is removed and collected in the cleaning device 22.

  In the image forming apparatus 10, after the image formation is continued for a predetermined time, the photosensitive drum 12 is moved in the axial direction (lateral direction). The movement of the photosensitive drum 12 in the axial direction is performed during non-image formation.

  As shown in FIG. 2, the controller 60 drives the motor 52 and moves the extending portion 46 in the direction of arrow A through the rack 46 </ b> A by the rotation of the pinion 50. As a result, the photosensitive drum 12 supported by the support members 42 and 44 moves in the axial direction (lateral direction), and the contact position in the axial direction between the cleaning blade 32 of the cleaning device 22 and the photosensitive drum 12 changes. At this time, the movement amount of the photosensitive drum 12 in the axial direction (lateral direction) is preferably about 0.5 mm to 3 mm.

  As a result, the deposits collected at the tip of the cleaning blade 32 are prevented from continuing to contact the photosensitive drum 12 on the same peripheral surface, and the occurrence of streak on the surface of the photosensitive drum 12 is reduced over a long period of time. be able to.

  Further, the charging roll 14 is supported by the support members 42 and 44, and the photosensitive drum 12 and the charging roll 14 are integrally moved in the axial direction (lateral direction). Therefore, when the photosensitive drum 12 moves in the direction of arrow B as shown in FIG. 3A (state A), and when it moves in the direction of arrow C as shown in FIG. 3B (state B). Thus, the movement amount a of the charging roll 14 and the movement amount a of the photosensitive drum 12 coincide with each other, and the contact position in the axial direction between the charging roll 14 and the photosensitive drum 12 does not change. Therefore, the charging area of the charging roll 14 does not change between the state A and the state B, and the discharge exposed area (charged area) of the photosensitive drum 12 becomes the same area as shown in FIG. For this reason, the discharge exposure area of the photosensitive drum 12 does not extend to both ends in the axial direction, and a portion where the toner is difficult to be supplied to the photosensitive drum 12 and the frictional force tends to be high is generated near both ends of the cleaning blade 32. Can be avoided. As a result, it is possible to suppress the occurrence of local wear of the photosensitive drum 12 in the easily exposed area subject to deterioration, or the occurrence of the cleaning blade curling.

  On the other hand, as shown in FIGS. 4A and 4B, in the system in which the charging roll 114 is fixed and only the photosensitive drum 112 moves in the axial direction, the photosensitive drum 112 moves in the arrow B direction ( The contact position in the axial direction between the charging roll 114 and the photosensitive drum 112 changes between the state A) and the movement in the arrow C direction (state B). For this reason, the charging area of the charging roll 114 with respect to the photosensitive drum 112 changes between the state A and the state B, and the discharge exposed area (charged area) of the photosensitive drum 12 is in the state A as shown in FIG. And the state B are different areas. For this reason, a discharge exposure region only in the state A and a discharge exposure region only in the state B are generated at both axial ends of the photosensitive drum 112. In this state, near the both ends of the cleaning blade 32, toner is hardly supplied to the photosensitive drum 112, and a portion where the frictional force tends to be high is generated, and local wear of the photosensitive drum 112 occurs in the discharge exposure area where deterioration tends to occur. May occur, or the cleaning blade 32 may be bent.

  As described above, according to the present embodiment, it is possible to suppress the occurrence of local wear of the photoconductive drum 112 and wobbling of the cleaning blade 32.

  In the present embodiment, when the photosensitive drum 12 is moved in the axial direction, the charging roll 14 is moved integrally. However, by rotating the transfer roll 20 on the support members 42 and 44 so as to be rotatable, The photosensitive drum 12, the charging roll 14, and the transfer roll 20 may be moved integrally. In this configuration, when a transfer bias is applied to the transfer roll 20, it is possible to prevent the discharge exposed area (charged area) of the photosensitive drum 12 by the transfer roll 20 from moving to a different position in the axial direction. That is, the discharge exposure area of the photosensitive drum 12 by the charging roll 14 and the transfer roll 20 is the same area in the axial direction, and the discharge exposure area does not spread at both ends in the axial direction. For this reason, it is possible to further suppress the occurrence of local wear of the photoconductive drum 12 and wobbling of the cleaning blade.

  Next, an image forming apparatus according to a second embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 5, the image forming apparatus 70 is provided with a position changing mechanism 71 that moves the photosensitive drum 12 in the axial direction (lateral direction). In the position changing mechanism 71, a support member 72 that rotatably supports the shaft 12B of the photosensitive drum 12 is disposed at an axial end portion (front side in FIG. 5) of the photosensitive drum 12. An extending portion 46 is provided on the support member 72. Further, the shaft 14B of the charging roll 14 is rotatably supported by a support member 74 provided separately from the support member 72 and a support member 76 disposed in parallel thereto. In this configuration, the charging roll 14 does not move when the photosensitive drum 12 moves in the axial direction (lateral direction). A motor 78 is connected to the shaft B of the charging roll 14 outside the support member 76 so that the charging roll 14 rotates.

  Driving of the motor 78, the motor 52, and the motor 36 is controlled by the controller 80. The motor 52 is a stepping motor, and the position of the photosensitive drum 12 is controlled by controlling the number of pulses. The controller 80 drives the motor 52 to move the photosensitive drum 12 in the axial direction to change the contact position with the cleaning blade 32, and then returns the photosensitive drum 12 to a predetermined position (home position) during image formation. Perform such control.

  Next, the operation of the image forming apparatus 70 will be described.

  After the image formation is continued for a predetermined time, the controller 80 drives the motor 52 to move the photosensitive drum 12 in the axial direction (lateral direction). At this time, the controller 80 controls the position of the photosensitive drum 12 by controlling the number of pulses of the motor 52. Thereby, the contact position in the axial direction between the cleaning blade 32 and the photosensitive drum 12 is changed, and the deposits accumulated at the tip of the cleaning blade 32 are prevented from continuing to contact the photosensitive drum 12 on the same circumferential surface. Generation of streak on the surface of the photosensitive drum 12 can be reduced over a long period of time.

  On the other hand, when restarting the image forming operation, the controller 80 controls the number of pulses of the motor 52 to return the position of the photosensitive drum 12 in the axial direction to a predetermined position (home position). For this reason, the contact position in the axial direction between the photosensitive drum 12 and the charging roll 14 does not change during image formation. Further, the contact position in the axial direction between the photosensitive drum 12 and the transfer roll 20 does not change. For this reason, the discharge exposure area of the photosensitive drum 12 by the charging roll 14 and the transfer roll 20 becomes the same area in the axial direction, and the discharge exposure area does not spread at both ends in the axial direction. Accordingly, it is possible to avoid the occurrence of a portion where the toner is not easily supplied to the photosensitive drum 12 and the frictional force is likely to be increased near both ends of the cleaning blade 32, and local wear and the like of the photosensitive drum 12 in the discharge exposure region. It is possible to prevent the cleaning blade 32 from wobbling.

  Next, an image forming apparatus according to a third embodiment of the present invention will be described.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 6, in this image forming apparatus 90, cyan (C), magenta (M), yellow (Y), and black (K) toners are placed around the photosensitive drum 12 from the upstream side in the rotation direction. Four developing devices 18C, 18M, 18Y, and 18K that are housed respectively are arranged.

  An intermediate transfer drum 92 is disposed on the downstream side of the four developing devices 18C, 18M, 18Y, and 18K facing the photosensitive drum 12. A motor (not shown) is connected to the intermediate transfer drum 92 and is driven to rotate in the direction of the arrow.

  Although not shown, the intermediate transfer drum 92 is made of a cylindrical member, and a transfer charger (not shown) is disposed at a position facing the photosensitive drum 12 inside the intermediate transfer drum 92, so that the toner image on the photosensitive drum 12. Is transferred onto the intermediate transfer drum 92.

  A transfer roll 94 is disposed on the downstream side of the photosensitive drum 12 in the rotation direction of the intermediate transfer drum 92 so as to be in contact with the intermediate transfer drum 92. Then, the recording paper P is conveyed between the intermediate transfer drum 92 and the transfer roll 94, and the toner image on the intermediate transfer drum 92 is transferred onto the recording paper P by the transfer roll 94.

  A cleaning device 96 is disposed downstream of the transfer roll 94 in the rotation direction of the intermediate transfer drum 92. The cleaning device 96 is provided with a cleaning blade 98 that comes into contact with the intermediate transfer drum 92 to remove residual toner on the surface of the intermediate transfer drum 92 after transfer.

  Further, the intermediate transfer drum 92 can be moved in the axial direction (lateral direction) by a position changing mechanism (not shown) similar to the position changing mechanism 40 shown in FIG. The transfer roll 94 is integrally supported by an intermediate transfer drum 92 and a support member (not shown) (see FIG. 2), and the intermediate transfer drum 92 and the transfer roll 94 move together in the axial direction. It is the composition to do.

  Next, the operation of the image forming apparatus 90 will be described.

  In this image forming apparatus 90, the photosensitive drum 12 is uniformly charged by the charging roll 14, and a laser beam corresponding to a cyan image is irradiated on the photosensitive drum 12 by the optical scanning device 16, so that the photosensitive drum 12 is statically irradiated. An electrostatic latent image is formed. This electrostatic latent image is developed by a developing device 18C containing cyan toner, and a cyan toner image is formed on the photosensitive drum 12. This cyan toner image is transferred to the intermediate transfer drum 92 by the action of a transfer charger (not shown). At this time, on the downstream side of the moving direction of the intermediate transfer drum 92, the transfer roll 94 and the cleaning device 96 are retracted from the intermediate transfer drum 92 by a moving mechanism (not shown).

  Similarly, a magenta toner image is formed on the photosensitive drum 12 through charging of the photosensitive drum 12, exposure, and development with magenta toner, and this magenta toner image is superimposed on the cyan toner image on the intermediate transfer drum 92 and transferred. Is done. Further, after the photosensitive drum 12 is charged, exposed, and developed with yellow toner, the yellow toner image on the photosensitive drum 12 is transferred to the intermediate transfer drum 92 so as to be superimposed, and the photosensitive drum 12 is charged, exposed, and exposed. After developing with black toner, the black toner image on the photosensitive drum 12 is transferred onto the intermediate transfer drum 92 in an overlapping manner. As a result, the multicolor toner images are superimposed on the intermediate transfer drum 92.

  In this state, the transfer roll 94 and the cleaning device 96 are brought into contact with the intermediate transfer drum 92 by a moving mechanism (not shown), and the recording paper P is conveyed between the intermediate transfer drum 92 and the transfer roll 94 at a predetermined timing. Is done. Then, the multicolor toner image on the intermediate transfer drum 92 is transferred to the recording paper P by the action of the transfer roll 94, and the toner image is fixed by a fixing device (not shown) to form a full color image.

  In such an image forming apparatus 90, after the image forming operation is continued for a predetermined time, the intermediate transfer drum 92 is moved in the axial direction (lateral direction) by a position changing mechanism (not shown). As a result, the deposits collected at the tip of the cleaning blade 98 are prevented from continuing to contact the intermediate transfer drum 92 on the same peripheral surface, and the occurrence of streak on the surface of the intermediate transfer drum 92 is reduced over a long period of time. be able to.

  At this time, since the intermediate transfer drum 92 and the transfer roll 94 move together, the contact position in the axial direction between the intermediate transfer drum 92 and the transfer roll 94 does not change. For this reason, the discharge exposure area (charged area) of the intermediate transfer drum 92 by the transfer roll 94 becomes the same area, and the discharge exposure area does not spread to both ends in the axial direction. Accordingly, it is possible to avoid the occurrence of a portion where the toner is hardly supplied to the intermediate transfer drum 92 and the frictional force tends to be high near both ends of the cleaning blade 98, and the local wear of the intermediate transfer drum 92 is caused in the discharge exposure region. It is possible to prevent the cleaning blade 98 from being twisted.

  In the third embodiment, the photosensitive drum 12 is used, but the present invention can also be applied to a configuration using an endless photosensitive belt that moves around by a plurality of support rolls.

1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a perspective view showing a position changing mechanism for moving the photosensitive drum in the axial direction in the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a side view showing a discharge exposed area of a photosensitive drum by a charging roll of the image forming apparatus according to the first embodiment of the present invention. It is a side view showing a discharge exposure area of a photosensitive drum by a charging roll of an image forming apparatus according to a comparative example. FIG. 10 is a perspective view showing a position changing mechanism for moving a photosensitive drum in an axial direction in an image forming apparatus according to a second embodiment of the present invention. It is a schematic block diagram which shows the image forming apparatus which concerns on 3rd Embodiment of this invention.

Explanation of symbols

10 Image forming apparatus 12 Photosensitive drum (image carrier)
14 Charging roll (contact charging member)
16 Optical scanning device 18 Developing device 20 Transfer roll 22 Cleaning device 32 Cleaning blade 34 Gear 36 Motor 38 Gear 40 Position changing mechanism (position changing means)
42 Support member (position control means)
44 Support member (position control means)
46A Rack 46 Extension portion 48 Rail 50 Pinion 52 Motor (Position control means, position change means)
60 controller (position control means, position change means)
62 Support member 70 Image forming apparatus 71 Position change mechanism (position change means)
72 support member 74 support member 76 support member 78 motor 80 controller (position control means, position change means)
90 Image forming apparatus 92 Intermediate transfer drum (image carrier)
94 Transfer roll 96 Cleaning device 98 Cleaning blade P Recording paper (transfer material)

Claims (7)

An image having an image carrier on which a toner image is carried, a contact charging member disposed so as to be in contact with the image carrier, and a cleaning blade for cleaning the image carrier after the toner image is transferred. A forming device,
Position changing means for changing the contact position with the cleaning blade by moving the image carrier in a direction perpendicular to the image traveling direction;
Position control means for controlling the charged region of the image carrier by the contact charging member to be the same region in a direction orthogonal to the image traveling direction of the image carrier;
An image forming apparatus comprising:   The position control means returns the image carrier moved by the position changing means to the image forming position, thereby allowing the relative position between the contact charging member and the image carrier during the image forming operation of the contact charging member. The image forming apparatus according to claim 1, wherein the relationship is constant.   The position control means moves the contact charging member integrally with the image carrier so that a contact position between the contact charging member and the image carrier is constant during an image forming operation of the contact charging member. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the contact charging member is a charging roll that uniformly charges the image carrier.   The transfer roll for transferring the toner image formed on the image carrier to a transfer material is moved integrally with the image carrier, and moved according to any one of claims 1 to 3. The image forming apparatus described.   The image forming apparatus according to claim 1, wherein the image carrier is a cylindrical or columnar photosensitive drum.   The image forming apparatus according to claim 1, wherein the image carrier is a cylindrical or columnar intermediate transfer drum.

Images