JP6066310B2 - Image forming apparatus and transfer apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus and a transfer apparatus.

  Japanese Patent Application Laid-Open No. 2004-133867 discloses an electrophotographic image forming apparatus having a photosensitive member, a cartridge that accommodates the photosensitive member, and a driving unit that transmits a driving force to the photosensitive member, and is opposed to the outer surface of the photosensitive member or the outer surface. A sliding member pressed by an elastic member is provided on one of the inner surfaces of the cartridge, and the sliding member is slid against the inner surface of the cartridge or the outer surface of the photosensitive member by driving the photosensitive member. An image forming apparatus characterized by the above is disclosed.

  In Patent Document 2, in an electrophotographic apparatus having a step of transferring a toner image formed on an endless belt-shaped photoconductor to an endless belt-shaped intermediate transfer body, the apparatus for driving the intermediate transfer body includes the intermediate transfer body. An intermediate transfer body drive roller that drives the intermediate transfer body by stretching the intermediate transfer body, and an intermediate transfer body drive gear that is fixed on the shaft of the intermediate transfer body drive roller and meshes with a drive source gear. The driving device includes a photosensitive member driving roller that stretches the photosensitive member to drive the photosensitive member, a photosensitive member driving gear that is fixed on the shaft of the photosensitive member driving roller and meshes with the intermediate transfer member driving gear. The intermediate transfer member is pressed against the photosensitive member on the photosensitive member driving roller to transfer the toner image on the photosensitive member to the intermediate transfer member, and the peripheral speed of the photosensitive member is set to the intermediate transfer member. Than circumferential speed Fast photoreceptor, an intermediate transfer body driving apparatus of an electrophotographic apparatus is disclosed in either.

  Patent Document 3 discloses an intermediate transfer device for temporarily receiving a toner image formed on an image carrier and transferring the toner image to a recording sheet, and a plurality of support rolls including a drive roll. An intermediate transfer belt that rotates in a stretched state, and a primary transfer that presses against the image carrier with the intermediate transfer belt interposed therebetween and transfers a toner image from the surface of the image carrier to the surface of the intermediate transfer belt There is disclosed an intermediate transfer apparatus including a roll, and a frictional force acting between the driving roll and the intermediate transfer belt is smaller at the center than at both sides in the width direction of the intermediate transfer belt.

JP-A-8-30059 Japanese Patent Laid-Open No. 5-289536 JP 2003-122133 A

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and a transfer apparatus that can suppress a decrease in image quality due to load fluctuations on an image carrier.

  According to a first aspect of the present invention, there is provided an image holding body for holding a toner image, a toner image forming portion for forming a toner image on the image holding body, and the image holding body in contact with the image holding body. A transfer object to which a toner image is transferred from the image carrier while moving with a difference; and a transfer object that is disposed on the opposite side of the image carrier with respect to the transfer object. A transfer member to which a voltage for transferring a toner image to the transfer body is applied; and a pressing member that presses the transfer body to a non-image forming area where the toner image of the image holding body is not formed; The pressing member is an image forming apparatus that presses the transfer target.

  According to a second aspect of the present invention, in the first aspect, the pressing member is pressed against the transferred body with a pressure stronger than a pressure when the transfer member is pressed against the transferred body. This is an image forming apparatus.

  According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the pressing member is a rotating body that rotates following the transfer target.

  The present invention according to claim 4 is the image forming apparatus according to claim 3, wherein the pressing member is mounted so as to be able to rotate on a transfer member support shaft that supports the transfer member.

  According to a fifth aspect of the present invention, the pressing member is mounted such that the pressing member can rotate on a pressing member support shaft different from the transfer member support shaft that supports the transfer member. This is an image forming apparatus.

  According to a sixth aspect of the present invention, in the pressing member, the end on the image carrier side is closer to the image carrier than the end on the image carrier side of the transfer member. 5. The image forming apparatus according to any one of 5 above.

  The present invention according to claim 7 is the image forming apparatus according to any one of claims 1 to 6, wherein the pressing member has a hardness higher than that of the transfer member.

  According to an eighth aspect of the present invention, in the moving direction of the transferred body, the pressing member is disposed in a contact region where the image holding body and the transferred member are in contact with each other. The image forming apparatus described.

  According to a ninth aspect of the present invention, there is provided a transfer body that contacts an image holding body that holds a toner image and to which a toner image is transferred from the image holding body while moving with a peripheral speed difference from the image holding body. A transfer member disposed on the opposite side of the image carrier from the image carrier, to which a voltage for transferring a toner image from the image carrier to the image carrier is applied, and the image carrier And a pressing member that presses the transfer target to a non-image forming area where a toner image of the body is not formed.

  According to the first aspect of the present invention, it is possible to suppress a decrease in image quality due to load fluctuations on the image carrier, as compared with the case where the present configuration is not provided.

  According to the second aspect of the present invention, it is possible to suppress a reduction in image quality due to load fluctuations on the image carrier as compared with the case where the present configuration is not provided.

  According to the third aspect of the present invention, it is possible to suppress the wear of the transfer body and the wear of the transfer member as compared with the case where the present configuration is not provided.

  According to the fourth aspect of the present invention, the device structure can be simplified as compared with the case where the present configuration is not provided.

  According to the fifth aspect of the present invention, the positional relationship between the transfer member and the pressing member can be freely determined.

  According to the sixth aspect of the present invention, it is possible to suppress deterioration in image quality due to load fluctuations on the image holding member with a simple configuration as compared with the case where the present configuration is not provided.

  According to the seventh aspect of the present invention, it is possible to suppress a reduction in image quality due to load fluctuations on the image carrier with a simple configuration as compared with the case where the present configuration is not provided.

  According to the eighth aspect of the present invention, it is possible to suppress a reduction in image quality due to load fluctuations on the image carrier as compared with the case where the present configuration is not provided.

  According to the ninth aspect of the present invention, it is possible to suppress a reduction in image quality due to load fluctuations on the image holding member as compared with the case where the present configuration is not provided.

1 is a cross-sectional view illustrating an image forming apparatus according to a first embodiment of the present invention from the front side. FIG. 2 is a cross-sectional view illustrating a toner image forming unit included in the image forming apparatus illustrated in FIG. 1 from the front side. FIG. 2 is a cross-sectional view showing the image forming apparatus shown in FIG. FIG. 4 is an enlarged cross-sectional view illustrating a part of a transfer device included in an image forming apparatus according to a second embodiment of the present invention. It is a figure explaining the positional relationship of the image holding body in the image formation which concerns on the 2nd Embodiment of this invention, a transfer member, and a press member. It is a figure explaining the positional relationship of the image holding body in the image formation which concerns on the modification of the 2nd Embodiment of this invention, a transfer member, and a press member. The relationship between the speed difference between the image carrier and the transfer body and the load on the image carrier, when the toner is attached to the image carrier and when the toner is not attached to the image carrier, respectively It is a graph shown about the case of.

Next, embodiments for carrying out 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 includes an image forming apparatus main body 12. The image forming apparatus main body 12 includes a controller 20, a communication device 22, an image forming unit 100, an optical scanning device 260, a transfer device 300, and a paper feeding device 400. Has been placed. A document reading device 500 is mounted on the upper portion of the image forming apparatus main body 12, and a sheet on which image formation has been completed is discharged to the outside of the image forming apparatus main body 12 on the right side surface of the image forming apparatus main body 12. The discharge hole 14 is formed. Here, the paper is used as a recording medium on which an image is recorded.

  In addition, a discharge tray 16 on which a sheet discharged from the image forming apparatus main body 12 through the discharge hole 14 is placed is mounted on the right side surface of the image forming apparatus main body 12. In addition, a conveyance path 600 that is a conveyance path for conveying a sheet is formed in the image forming apparatus main body 12. The image forming apparatus 10 has a printer function for printing image data received from a computer terminal or the like connected via a network or the like, and also functions as a scanner, a copier, and a facsimile. It is what has.

  The document reader 500 is placed on a glass plate 502 on which a document D on which an image to be read is written is placed, a cover member 504 that presses the document D against the glass plate 502, and the glass plate 502. And a reading optical unit 510 that reads an image written on the document D. The reading optical unit 510 is configured to illuminate a document D placed on the glass plate 502 with a light source 512 and read a reflected light image from the document D with an image reading element 514 through a mirror group and a lens. Yes. Image data read by the document reading apparatus 500 is output to the controller 20.

  The controller 20 determines in advance such as shading correction, document position shift correction, gamma correction, frame erasing, color / movement editing, and the like for image data read by the document reading device 500 or image data received from a computer terminal or the like. The obtained image processing is performed.

  The communication device 22 receives image data from, for example, a computer terminal and outputs the received image data to the controller 20.

  The image forming unit 100 forms an image based on the image data output from the controller 20, and includes, for example, four image forming units 110Y, an image forming unit 110M, an image forming unit 110C, and an image forming unit 110K. . The image forming unit 110M, the image forming unit 110C, and the image forming unit 110K are each used for forming a yellow image, used for forming a magenta image, and used for forming a cyan image. , Used to form a black image. Further, the image forming unit 110Y, the image forming unit 110M, the image forming unit 110C, and the image forming unit 110K each include a photoconductive drum 112Y, a photoconductive drum 112M, a photoconductive drum 112C, and a photoconductive drum 112K.

  Each of the photosensitive drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K is used as an image holding body that holds a toner image. Details of the image forming unit 110Y, the image forming unit 110M, the image forming unit 110C, and the image forming unit 110K will be described later.

  The optical scanning device 260 is a device that scans light based on image data output from the controller 20, and includes, for example, four optical scanning units 262Y, an optical scanning unit 262M, an optical scanning unit 262C, and an optical scanning unit 262K. . The optical scanning unit 262Y, the optical scanning unit 262M, the optical scanning unit 262C, and the optical scanning unit 262K irradiate light to the photosensitive drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K, respectively. And used as a latent image forming apparatus for forming an electrostatic latent image.

  The transfer device 300 includes an intermediate transfer belt 302. The intermediate transfer belt 302 is in contact with the photoconductive drum 112Y, the photoconductive drum 112M, the photoconductive drum 112C, and the photoconductive drum 112K, and surrounds the photoconductive drum Y, the photoconductive drum 112M, the photoconductive drum 112C, and the photoconductive drum 112K. While being moved with a speed difference, the toner image is used as a transfer target to which a toner image is transferred from the photosensitive drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K.

  More specifically, the intermediate transfer belt 302 rotates in the direction of arrow a shown in FIG. 1 with a circumferential speed difference from the photosensitive drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K. However, the toner images are transferred from the photosensitive drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K. Here, in this embodiment, the peripheral speed of the intermediate transfer belt 302 is determined to be faster than the peripheral speeds of the photosensitive drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K. . The peripheral speed of the intermediate transfer belt 302 is determined so as to be faster than the peripheral speeds of the photosensitive drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K. You may determine so that it may become slower than the peripheral speed of the drum 112M, the photoconductive drum 112C, and the photoconductive drum 112K.

  The intermediate transfer belt 302 is band-shaped and endless, and is formed, for example, by forming a flexible synthetic resin film such as polyimide in a band shape and connecting both ends of the formed synthetic resin film by welding or the like. Can be used.

  The intermediate transfer belt 302 is wound around the support roll 310, the support roll 312, the support roll 314, the support roll 316, the support roll 318, and the support roll 320, which are, for example, six support rolls so as to be rotatable. Is supported. At least one of the six support rolls is used as a drive transmission member that transmits drive to the intermediate transfer belt 302. In this embodiment, the support roll 310 is used as a drive transmission member, and the intermediate transfer belt is rotated in the direction of arrow a by rotating the support roll 310 in response to drive transmission from a drive motor (not shown). Driven to rotate.

  The transfer device 300 includes, for example, four primary transfer rolls 330Y, a primary transfer roll 330M, a primary transfer roll 330C, and a primary transfer roll 330K that are four primary transfer rolls. The primary transfer roll 330Y, the primary transfer roll 330M, the primary transfer roll 330C, and the primary transfer roll 330K are respectively an intermediate transfer belt from the photosensitive drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K. It is used as a transfer member (primary transfer member) to which a transfer voltage for transferring a toner image is applied to 302.

  The primary transfer roll 330 </ b> Y, the primary transfer roll 330 </ b> M, the primary transfer roll 330 </ b> C, and the primary transfer roll 330 </ b> K are each arranged inside the intermediate transfer belt 302, and each is a photosensitive member with respect to the intermediate transfer belt 302. The drum 112Y, the photosensitive drum 112M, the photosensitive drum 112C, and the photosensitive drum 112K are disposed on the opposite side.

  The transfer device 300 includes a secondary transfer roll 390. The secondary transfer roll 390 is used as a transfer member (secondary transfer member) for transferring a toner image from the intermediate transfer belt 302 to a sheet, and is pressed against the support roll 318 via the intermediate transfer belt 302. ing.

  In addition, the transfer device 300 includes a cleaning device 394. The cleaning device 394 cleans the intermediate transfer belt 302 by removing the toner remaining on the surface of the intermediate transfer belt 302 after the toner image is transferred onto the sheet by the secondary transfer roll 390.

  The paper feeding device 400 is a device that supplies paper to the conveyance path 600, and includes a storage container 402 that stores the paper so as to be stacked, and an uppermost sheet among the paper stacked in the storage container 402. It has a delivery roll 404 that sends out a certain sheet to the conveyance path 600.

  The transport path 600 is a transport path for transporting paper from the paper feeding device 400 to the discharge tray 16, and the above-described delivery roll 404 and transport in order from the upstream side in the paper transport direction along the transport path 600. A roll 610, a transport roll 612, a registration roll 614, the above-described support roll 318 and secondary transfer roll 390, a transport device 620, a transport device 630, and a fixing device 180 are disposed.

  The transport roll 610 and the transport roll 612 transport the paper sent out by the delivery roll 404 toward the registration roll 614. The registration roll 614 is formed by the image forming unit 100 by temporarily stopping the movement of the leading end of the sheet being sent to the downstream side in the conveyance direction by the conveyance roll 612, and is formed by the primary transfer roll 330Y and the primary transfer roll 330M. The leading edge of the sheet is matched with the timing at which the toner image transferred to the intermediate transfer belt 302 by the primary transfer roll 330C and the primary transfer roll 330K reaches the contact portion between the secondary transfer roll 390 and the intermediate transfer belt 302. The movement of the department is resumed.

  The conveying device 620 and the conveying device 630 transfer a sheet of paper in which the toner image is transferred to the upper surface in the gravity direction and the unfixed toner image is placed on the upper surface in the gravity direction from the lower side in the gravity direction. It is conveyed toward the fixing device 180 while being supported. The fixing device 180 uses, for example, heat and pressure to fix the toner image placed on the upper surface of the paper on the upward surface of the paper.

  FIG. 2 shows an image forming unit 110Y, an image forming unit 110M, an image forming unit 110C, and an image forming unit 110K. The image forming unit 110Y, the image forming unit 110M, the image forming unit 110C, and the image forming unit 110K have the same configuration although the color of the toner to be used and the color of the toner image to be formed are different. Therefore, these image forming units will be collectively referred to as the image forming unit 110 below. 2 shows a primary transfer roll 330Y, a primary transfer roll 330M, a primary transfer roll 330C, and a primary transfer roll 330K. Since the primary transfer roll 330M, the primary transfer roll 330C, and the primary transfer roll 330K have the same configuration, these primary transfer rolls will be collectively referred to as the primary transfer roll 330 below.

  As shown in FIG. 2, the image forming unit 110 makes the surface of the photosensitive drum 112 uniform before forming the latent image on the photosensitive drum 112 by the optical drum 260 and the optical drum 260 described above. A charging device 120 for charging the toner and a toner image forming unit for forming a toner image on the photosensitive drum 112. The latent image formed on the surface of the photosensitive drum 112 by the optical scanning device 260 is used with toner. The developing device 130 for developing and the surface of the photosensitive drum 112 are cleaned, and the toner remaining on the surface of the photosensitive drum 112 after the transfer of the toner image to the intermediate transfer belt 302 by the primary transfer roll 330 is removed is cleaned. Device 140.

  As shown in FIG. 2, the primary transfer roll 330 is connected to a power supply 332 that applies a voltage for transferring a toner image from the photosensitive drum 112 to the intermediate transfer belt 302 to the primary transfer roll 330. Yes. Here, the voltage applied to the primary transfer roll 330M, the primary transfer roll 330C, and the primary transfer roll 330K may be the same voltage for all four primary transfer rolls. On the other hand, different voltages may be applied to each.

  In addition, press rolls 370 are arranged at positions outside the both ends in the longitudinal direction of the primary transfer roll 330. The pressing roll 370 is used as a pressing member that presses the intermediate transfer belt 302 against the photosensitive drum 112. 2 shows only the pressure roll 370 disposed on the front side (the front side in the drawing) of the image forming apparatus main body 12, the pressure roll 370 is the primary transfer roll 330 as described above. One is arranged at a position outside the both ends in the longitudinal direction, and two are arranged for one primary transfer roll 330 (see FIG. 3).

  FIG. 3 is a cross-sectional view showing a cross-section of the AA plane in FIG. 1. FIG. 3 shows the photosensitive drum 112K, the intermediate transfer belt 302, the primary transfer roll 330K, and the peripheral portion thereof. Yes. As described above, the image forming unit 110Y, the image forming unit 110M, the image forming unit 110C, and the image forming unit 110K have the same configuration, and the primary transfer roll 330Y, the primary transfer roll 330M, the primary transfer roll 330C, and The primary transfer rolls 330K have the same configuration. Therefore, the primary transfer roll 330K and its peripheral configuration, which will be described below, the primary transfer roll 330Y and its peripheral configuration, the primary transfer roll 330M and its peripheral configuration, and the primary transfer roll 330C and its peripheral configuration. The configuration is the same.

  As shown in FIG. 3, the primary transfer roll 330 </ b> K includes a shaft portion 334 and a roll body portion 336. Bearings 338 that support the shaft portion 334 so that the shaft portion 334 can rotate are respectively attached to both ends of the shaft portion 334. The roll body 336 is fixed to the shaft 334 and rotates integrally with the shaft 334. Here, the primary transfer roll 330K does not rotate when driving is transmitted from, for example, a motor or the like, but comes into contact with the intermediate transfer belt 302 and rotates along with the intermediate transfer belt 302. As the material of the roll body 336, a conductive and elastic material can be used, for example, conductive rubber or the like can be used.

  A biasing member 342 is attached to each of the two bearings 338. The urging member 342 is a member for urging the primary transfer roll 330 and the pressing roll 370 together toward the photosensitive drum 112K side, and the primary transfer roll 330K and the two pressing rolls 370 are The photosensitive drum 112K is a member that is pressed against the intermediate transfer belt 302 that is a member positioned on the opposite side. When the primary transfer roll 330K and the pressure roll 370 are pressed against the intermediate transfer belt 302, the intermediate transfer belt 302 is pressed against the photosensitive drum 112K.

  As the urging member 342, for example, a coil spring formed of a metal having elasticity can be used. When a coil spring is used as the urging member 342, one end of the coil spring is attached to the bearing 338, and the other end of the coil spring is attached to the main body frame 18 that forms a part of the image forming apparatus main body 12. The

  The two pressing rolls 370 are arranged at positions outside the roll main body 336 in the longitudinal direction of the primary transfer roll 330K so that the outer peripheral surfaces thereof are in contact with the intermediate transfer belt 302, and each of them is a bearing 340. It is mounted so that it can be rotated with respect to the shaft part 334 using the. Therefore, the pressing roll 370 rotates with the intermediate transfer belt 302 independently of the shaft portion 334 and the roll main body portion 336.

  As shown in FIG. 2, the two pressing rolls 370 are in contact with the photosensitive drum 112 and the intermediate transfer belt 302 in the moving direction of the intermediate transfer belt 302, that is, the photosensitive drum 112. The intermediate transfer belt 302 is disposed in a region where a nip portion is formed.

  As described above, the pressing roll 370 is rotated with respect to the intermediate transfer belt 302 and is driven by the intermediate transfer belt 302, so that the pressing roll 370 is fixed and the pressing roll 370 is not rotated. Compared with the case where the belt is mounted on the intermediate transfer belt 302, the portion of the intermediate transfer belt 302 that contacts the pressing roll 370 is less likely to be worn. Further, since the pressing roll 370 is configured to rotate independently of the roll main body 336 using the bearing 340, compared to the case where the pressing roll 370 and the roll main body 336 rotate as one body, The load applied to the intermediate transfer belt 302 is reduced, the intermediate transfer belt 302 is less likely to deteriorate, and the portion of the intermediate transfer belt 302 in contact with the pressing roll 370 is less likely to be worn. Further, since the pressing roll 370 is mounted on the shaft portion 334 as described above, the configuration of the image forming apparatus 10 is compared with the case where a member for mounting the pressing roll 370 is provided separately from the shaft portion 334. It will be easy.

  The pressing roll 370 presses the intermediate transfer belt 302 against the non-image forming area P1 where the toner image on the photosensitive drum 112K is not formed. Here, P1 in FIG. 3 indicates an area where the toner image of the photosensitive drum 112K is not formed, and P2 in FIG. 3 indicates an image forming area where the toner image of the photosensitive drum 112K is formed. The toner image formed by the image forming unit 110K is transferred to the image forming area P2 by the primary transfer roll 330K.

  More precisely, the image forming area P2 is an area where a toner image can be formed, and the toner image is not always formed in the entire part of the image forming area P2. For example, after a series of image formation is completed and the surface of the photosensitive drum 112K is cleaned by the cleaning device 140, no toner image is formed in the image forming area P2. Further, for example, in the intermediate transfer belt 302, a region where a toner image transferred to one sheet is transferred and a region where a toner image transferred to the next sheet is transferred. In general, no toner is formed between the positions.

  The pressing roll 370 is pressed against the intermediate transfer belt 302 with a pressure stronger than the pressure when the primary transfer roll 330K is pressed against the intermediate transfer belt 302. For this reason, the pressing roll 370 has an end 370a on the photosensitive drum 112K side closer to the photosensitive drum 112K than the end 330a of the primary transfer roll 330K on the photosensitive drum 112K side. It has come to be. In the image forming apparatus 10 according to the first embodiment, since the two pressing rolls 370 are attached to the shaft portion 334 of the primary transfer roll 330K, the diameter of the pressing roll 370 is changed to that of the primary transfer roll 330K. If it is made larger than just the roll main body 336, the end portion 370a on the photosensitive drum 112K side of the pressing roll 370 is larger than the end portion 330a of the primary transfer roll 330K on the photosensitive drum 112K side. It comes to be in a position close to.

  Moreover, as a material of the press roll 370, resin etc. which are insulators can be used, for example. Further, the pressing roll 370 has higher hardness than the roll main body 336K of the primary transfer roll 330K.

  For example, when images are continuously formed on a plurality of sheets, a toner image and a toner image are formed on the intermediate transfer belt 302 in the moving direction of the intermediate transfer belt 302 as described above. It is mixed with areas that are not. The friction between the photosensitive drum 112K and the intermediate transfer belt 302 is larger when no toner adheres to the photosensitive drum 112K and the intermediate transfer belt 302 (when a toner image is not formed). The toner is attached to at least one of the photosensitive drum 112K and the intermediate transfer belt 302, and the toner is smaller when the toner exists between the photosensitive drum 112K and the intermediate transfer belt 302.

  For this reason, for example, when the tip of the area where the toner image is transferred from the photosensitive drum 112Y, the photosensitive drum 112M, and the photosensitive drum 112C of the intermediate transfer belt 302 reaches a position where it contacts the photosensitive drum 112K, Thus, the friction between the photosensitive drum 112K and the intermediate transfer belt 302 is reduced. If the pressing roll 370 is not provided, even if the photosensitive drum 112K is controlled to rotate at a constant speed, the tip of the portion of the intermediate transfer belt 302 onto which the toner image is transferred. There is a possibility that the speed of the photosensitive drum 112K may change abruptly at the timing when the portion reaches the position where the photosensitive drum 112K comes into contact with the photosensitive drum 112K, for example, because the photosensitive drum 112K slips with respect to the intermediate transfer belt 302. . If the speed of the photosensitive drum 112K is suddenly changed, a defect occurs in an image, for example, a streak is formed in a direction substantially perpendicular to the traveling direction of the intermediate transfer belt 302.

  In contrast, in the image forming apparatus 10 according to the first embodiment, the intermediate transfer belt 302 biases the non-image forming area P1 where the toner image on the photosensitive drum 112K is not formed. It is pressed by the action of the pressing roll 370 and the like. The frictional force between the intermediate transfer belt 302 and the non-image forming area P1 where the toner image of the photosensitive drum 112K is not formed is different from that of the image forming area P2, and the photosensitive drum 112K and the intermediate transfer belt 302 The toner does not decrease due to the presence of toner during the period. Therefore, in the image forming apparatus 10 according to the first embodiment, the photosensitive drum 112K is unlikely to slip with respect to the intermediate transfer belt 302, and the speed fluctuation of the photosensitive drum 112K hardly occurs.

  FIG. 4 is an enlarged view of a part of the transfer device 300 included in the image forming apparatus according to the second embodiment of the present invention. FIG. 5 shows a photoconductor in the transfer device 300 shown in FIG. A positional relationship among the drum 112K, the intermediate transfer belt 302, the primary transfer roll 330K, and the pressing roll 370 is schematically shown.

  In the image forming apparatus 10 according to the first embodiment described above, the two pressing rolls 370 are attached so as to be able to rotate on the shaft portion 334 of the primary transfer roll 330K (see FIG. 3). reference). In contrast, in the image forming apparatus 10 according to the second embodiment, as shown in FIG. 4, the pressing roll 370 rotates integrally with the support shaft 372 on the support shaft 372 different from the shaft portion 334. It is attached so that it can. Here, the support shaft 372 is used as a support shaft for a pressing member.

  As shown in FIG. 4, a pressing roll 370 is attached to one end of the support shaft 372, and a bearing 374 is attached to the other end of the support shaft 372. A biasing member 376 is attached to the bearing 374. The biasing member 376 is a member for biasing the pressing roll 370 toward the photosensitive drum 112K, and the pressing roll 370 is photosensitive. The body drum 112K is a member that presses against the intermediate transfer belt 302 that is a member positioned on the opposite side. As the urging member 376, for example, a coil spring formed from an elastic metal can be used. When a coil spring is used as the urging member 376, one end of the coil spring is attached to the bearing 374, and the other end of the coil spring is attached to the main body frame 18 that forms a part of the image forming apparatus main body 12. The

  In the image forming apparatus 10 according to the second embodiment, as in the image forming apparatus 10 according to the first embodiment described above, the peripheral speed V1 of the intermediate transfer belt 302 is the peripheral speed V2 of the photosensitive drum 112K. It is determined to be faster. For this reason, in the direction in which the intermediate transfer belt 302 moves, the intermediate transfer belt 302 is pulled downstream in the movement direction on the downstream side of the nip portion N where the photosensitive drum 112K and the intermediate transfer belt 302 are in contact. It becomes a state. On the other hand, in the portion upstream of the nip portion N in the moving direction of the intermediate transfer belt 302, the movement of the intermediate transfer belt 302 to the downstream side is restricted by the nip portion N, so that the intermediate transfer belt 302 is slackened. It becomes a state.

  In the image forming apparatus 10 according to the second embodiment, as in the image forming apparatus 10 according to the first embodiment described above, the pressing roll 370 is an intermediate member independent of the primary transfer roll 330K. It rotates with the transfer belt 302 and rotates. Further, the pressing roll 370 has a contact area where the photosensitive drum 112 and the intermediate transfer belt 302 are in contact with each other in the moving direction of the intermediate transfer belt 302, that is, a nip portion N is formed between the photosensitive drum 112 and the intermediate transfer belt 302. It is arranged in the area.

  In the image forming apparatus 10 according to the second embodiment, as in the image forming apparatus 10 according to the first embodiment described above, the pressing roll 370 is an area where the toner image on the photosensitive drum 112K is not formed. The intermediate transfer belt 302 is pressed against the non-image forming area P1.

  Further, in the image forming apparatus 10 according to the second embodiment, as in the image forming apparatus 10 according to the first embodiment described above, the pressing roll 370 has the primary transfer roll 330K as the intermediate transfer belt 302. The intermediate transfer belt 302 is pressed with a pressure stronger than the pressure when pressed against the intermediate transfer belt 302. In order for the pressing roll 370 to be pressed against the intermediate transfer belt 302 with a pressure stronger than the pressure when the primary transfer roll 330K is pressed against the intermediate transfer belt 302, the urging member 342 is used. The strength of biasing the bearing 338 and the strength of the biasing member 376 pressing the bearing 374 may be adjusted, for example, by selecting a coil spring to be used.

  In the image forming apparatus 10 according to the second embodiment, as in the image forming apparatus 10 according to the first embodiment described above, the pressing roll 370 has an end portion 370a on the photosensitive drum 112K side. The photosensitive drum 112K is positioned closer to the photosensitive drum 112K than the end 330a of the primary transfer roll 330K on the photosensitive drum 112K side. More specifically, in the image forming apparatus 10 according to the second embodiment, the end portion 370a on the photosensitive drum 112K side is more photosensitive than the end portion 330a of the primary transfer roll 330K on the photosensitive drum 112K side. Positions of a shaft (not shown) that supports the photosensitive drum 112K, a shaft portion 334 of the primary transfer roll 330K, and a support shaft 372 that supports the pressing roll 370 so as to be close to the body drum 112K. Is stipulated.

  4 and 5, of the two pressing rolls 370 provided in the vicinity of the primary transfer roll 330K, only the pressing roll 370 disposed on the rear side (left side in FIG. 4) in the image forming apparatus main body 12. However, the configuration of the pressing roll 370 disposed on the front side in the image forming apparatus main body 12 is the same as the pressing roll 370 positioned on the rear side described above. The configuration of the image forming apparatus 10 according to the second embodiment is the same as that of the image forming apparatus according to the above-described first embodiment, except for the part that has been described as to the difference from the image forming apparatus 10 according to the first embodiment. 10, the description of the same part is omitted.

  FIG. 6 schematically shows the positional relationship among the photosensitive drum 112K, the intermediate transfer belt 302, the primary transfer roll 330K, and the pressing roll 370 in the image forming apparatus 10 according to the modification of the second embodiment of the present invention. Has been. In the image forming apparatus 10 according to the second embodiment described above, the peripheral speed V1 of the intermediate transfer belt 302 is determined to be faster than the peripheral speed V2 of the photosensitive drum 112K. On the other hand, in this modification, the peripheral speed V2 of the photosensitive drum 112 and the peripheral speed of the intermediate transfer belt 302 are set so that the peripheral speed V2 of the photosensitive drum 112K is higher than the peripheral speed V1 of the intermediate transfer belt 302. V1 is defined.

  For this reason, in the direction in which the intermediate transfer belt 302 moves, the intermediate transfer belt 302 is moved downstream by the photosensitive drum 112K on the upstream side of the nip portion N, which is a position where the photosensitive drum 112K contacts the intermediate transfer belt 302. It will be pulled to the state. On the other hand, in the portion downstream of the nip portion N in the moving direction of the intermediate transfer belt 302, the intermediate transfer belt 302 is sent downstream from the nip portion N by the photosensitive drum 112K, whereby the intermediate transfer belt 302 is moved. It becomes loose.

  In the image forming apparatus 10 according to the modified example of the second embodiment, the pressing roll 370 moves the intermediate transfer belt 302 in the moving direction as in the image forming apparatus 10 according to the second embodiment described above. The photosensitive drum 112 and the intermediate transfer belt 302 are in contact with each other, that is, in the region where the nip portion N is formed between the photosensitive drum 112 and the intermediate transfer belt 302. However, the position at which the nip portion N is formed is different from that of the image forming apparatus 10 according to the second embodiment. In the image forming apparatus 10 according to the modification of the second embodiment, the nip portion N is an intermediate position. The transfer belt 302 is formed at a position upstream of the image forming apparatus 10 according to the second embodiment in the moving direction.

  FIG. 7 shows an experimental apparatus for moving the photosensitive drum 112K and the intermediate transfer belt 302 in contact with each other, for example, used in the image forming apparatus 10 according to the first embodiment. As a result of measuring the change in load torque applied to the photosensitive drum 112 when the speed difference between the photosensitive drum 112 and the intermediate transfer belt 302 is changed, the result of measuring the change in the load torque applied to the photosensitive drum 112 is shown. It is the graph shown about. In FIG. 7, the speed difference of the photosensitive drum 112K with respect to the peripheral speed of the intermediate transfer belt 302 is shown on the horizontal axis, and the load torque of the photosensitive drum 112K is shown on the vertical axis.

  From FIG. 7, when there is no speed difference between the photosensitive drum 112K and the intermediate transfer belt 302, a load is applied to the photosensitive drum 112K regardless of whether there is toner between the photosensitive drum 112K and the intermediate transfer belt 302. I understand that there is no. As the speed difference between the photosensitive drum 112K and the intermediate transfer belt increases, the load torque on the photosensitive drum 112K increases regardless of whether there is toner between the photosensitive drum 112K and the intermediate transfer belt 302. You can see it grows.

  Further, from FIG. 7, the case where there is no toner between the photosensitive drum 112K and the intermediate transfer belt 302 corresponds to the speed difference than the case where there is toner between the photosensitive drum 112K and the intermediate transfer belt 302. It can be seen that the increase in the load on the photosensitive drum 112K is large.

  As described above, the load torque applied to the photosensitive drum 112K differs depending on whether or not there is toner between the photosensitive drum 112K and the intermediate transfer belt 302. For this reason, for example, when the tip of the area where the toner image is transferred from the photosensitive drum 112Y, the photosensitive drum 112M, and the photosensitive drum 112C of the intermediate transfer belt 302 reaches a position where it contacts the photosensitive drum 112K, As a result, the load torque applied to the photosensitive drum 112K changes, for example, the photosensitive drum 112K slips with respect to the intermediate transfer belt 302, and the speed of the photosensitive drum 112K may change abruptly. If the speed of the photosensitive drum 112K is suddenly changed, a defect occurs in an image, for example, a streak is formed in a direction substantially perpendicular to the traveling direction of the intermediate transfer belt 302.

  For this reason, in the image forming apparatus 10 according to each embodiment of the present invention described above, the pressure roller 370 presses the intermediate transfer belt 302 to the non-image forming area P1 where the toner image is not formed on the photosensitive drum 112, thereby The change in the speed due to the load fluctuation of the body drum 112 is suppressed, and the speed change is generated in the photosensitive drum 112 so that the image quality is hardly deteriorated.

  As described above, the present invention can be used for image forming apparatuses such as copying machines, facsimile machines, and printers, and transfer apparatuses used in these image forming apparatuses.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 12 ... Image forming apparatus main body 112 ... Photosensitive drum 130 ... Developing apparatus 300 ... Transfer apparatus 302 ... Intermediate transfer belt 330 ... Primary transfer roll 330a ... End 334 ... Shaft 336 ... Roll body 338 ... Bearing 340 ... Bearing 342 ... Biasing member 370 ... Pressing roll 370a ... End 372 ...・ Support shaft 374 ... Bearing 376 ... Biasing member P1 ... Non-image forming area

Claims (5)

An image carrier for holding a toner image;
A toner image forming unit for forming a toner image on the image carrier;
A transferred body to which a toner image is transferred from the image holding body while contacting the image holding body and moving with a difference in peripheral speed with the image holding body , the image holding body and the transferred body being The transferred body in which the area where the toner image is not formed and the area where the toner image is formed alternately reach the position where the
A transfer member that is disposed on the opposite side of the image carrier from the image carrier and to which a voltage for transferring a toner image from the image carrier to the image carrier is applied;
A pressing member that presses the transferred body against a non-image forming area where a toner image of the image holding body is not formed;
I have a,
The pressing member is
The transfer member is pressed against the transferred body with a pressure stronger than the pressure when the transfer member is pressed against the transferred body;
It consists of a rotating body that rotates following the transfer object,
An image forming apparatus mounted so as to be able to rotate on a transfer member support shaft that supports the transfer member . The pressing member, an image forming apparatus according to claim 1, wherein an end portion of the image carrier side is positioned closer to the image carrier than the end of the image holding side of the transfer member. The pressing member, an image forming apparatus having a high hardness according to claim 1 or 2, wherein than the transfer member. The pressing member, the in the direction of movement of the transfer member, the image carrier and the image forming apparatus according to claim 1 to 3, wherein any one and the transfer member is disposed in the contact area in contact. A transferred object to which a toner image is transferred from the image holding body while contacting the image holding body holding a toner image and moving with a difference in peripheral speed from the image holding body, the image holding body and the image holding body The transferred body in which the area where the toner image is not formed and the area where the toner image is formed alternately reach the position where the transferred body is in contact ;
A transfer member that is disposed on the opposite side of the image carrier from the image carrier and to which a voltage for transferring a toner image from the image carrier to the image carrier is applied;
A pressing member that presses the transferred body against a non-image forming area where a toner image of the image holding body is not formed;
I have a,
The pressing member is
The transfer member is pressed against the transferred body with a pressure stronger than the pressure when the transfer member is pressed against the transferred body;
It consists of a rotating body that rotates following the transfer object,
A transfer device mounted so as to be able to rotate on a transfer member support shaft that supports the transfer member .

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