JP6238750B2 - Belt conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a belt conveyance device having a configuration for suppressing the occurrence of belt meandering and an image forming apparatus having the belt conveyance device.

  Conventionally, in an image forming apparatus that outputs a color image, a belt conveyance device that conveys an endless belt called an intermediate transfer belt is used. In an image forming apparatus using this belt conveying device, a toner image is carried on a plurality of photosensitive drums, and the surface of the intermediate transfer belt is temporarily transferred from the photosensitive drum before transferring the toner images onto a sheet as a recording medium. And the transferred image is collectively transferred to a sheet to output a color image.

  The belt conveying device is also used in a sheet conveying device that conveys a sheet as a recording medium.

  A problem with such a belt conveyance device is that the belt meanders and falls off the roller due to a shift force generated in a direction perpendicular to the conveyance direction during belt conveyance. Further, when the meandering of the belt is restricted, the above-described offset force may cause waviness due to belt speed fluctuation or distortion, or the belt may be deformed and broken.

  The shifting force generated in the belt is generated by the position and shape accuracy of the roller around which the belt is wound, the influence of inhomogeneity of the belt itself, and various externally applied forces. In order to suppress the shifting force generated in the belt, it is necessary to increase the accuracy of the rollers and the belt and the accuracy of the roller position.

  However, increasing the accuracy of rollers and belts increases the number of processing steps and increases costs, and increasing the accuracy of roller positions complicates the assembly and adjustment steps. For this reason, it is difficult to realize in consideration of mass productivity, and it is necessary to suppress the meandering of the belt by providing some means.

  Therefore, conventionally, a configuration for suppressing the occurrence of meandering of the belt has been proposed.

  Specifically, Japanese Patent Application Laid-Open No. 11-223971 (Patent Document 1) includes a rib guide member that guides the rib at the end of the belt and the rib at the end of the roller in order to prevent the belt from meandering. In the image forming apparatus, a configuration is disclosed in which the grip force between the belt and the driving roller is controlled to prevent the belt from being deformed or broken.

  Japanese Patent Application Laid-Open No. 2007-15858 (Patent Document 2) discloses that when the belt meanders, the belt abuts on the belt abutment detection units at both ends of the belt control roller, and the belt abuts on the belt abutment detection unit. A configuration is disclosed in which the belt control roller is displaced by a frictional force applied in a direction in which the running position of the belt is corrected with the central support shaft as a fulcrum, thereby returning the belt to an appropriate position.

  Further, in Japanese Patent Application Laid-Open No. 2008-290875 (Patent Document 3), the belt meanders by detecting the meandering of the belt and driving a mechanism for increasing the diameter of the end of the roller based on the detection result. A configuration is disclosed in which the meandering of the belt is restricted (corrected) by increasing the diameter of the end of the roller in the direction in which the roller is positioned.

JP-A-11-223971 JP 2007-15858 A JP 2008-290875 A

  However, when belt meandering is prevented by regulating the belt offset force by the rib guide member, even if the belt can be prevented from being deformed and broken, a larger belt offset force is regulated. Occasionally, image defects such as generation of a color misregistration image due to speed fluctuation of the belt and generation of a wavy image due to distortion of the belt are caused.

  Further, when the position of the roller is displaced to prevent the meandering of the belt, a mechanism for detecting the meandering of the belt and a mechanism for displacing the roller are required, which complicates and increases the size of the belt driving device.

  Further, when the belt meandering is prevented by driving a mechanism that detects the meandering of the belt and increases the diameter of the end of the roller based on the detection result, the means for detecting the meandering of the belt, the roller A mechanism for increasing the diameter of the end of the belt and its driving means are required, which complicates the belt driving device and increases the cost.

  The object of the present invention is to reduce the belt offset force with a simple configuration even when a large offset force is generated on the belt, to prevent deformation and breakage of the belt, and to cause image defects due to belt speed fluctuations and undulations. Is to prevent.

  In order to achieve the above object, a representative configuration of the present invention includes an endless belt that rotates and moves, a support roller that supports an inner peripheral surface of the endless belt, and at least one end side in the axial direction of the support roller. And a rotatable rotating member, and a rib arranged in a band shape on the inner peripheral surface of the endless belt, and the rib and the rotating member by movement in the width direction orthogonal to the rotational movement direction of the endless belt The belt conveying device with which the contact roller has a deforming member provided at least on one end side in the axial direction of the support roller, the deforming member when the movement of the endless belt in the width direction occurs. The outer diameter is deformed by receiving the force of the rotating member in contact with the rib.

  According to the present invention, even when a large shift force is generated in the belt, the shift force of the belt can be reduced with a simple configuration. As a result, deformation and breakage of the belt can be prevented, and image defects due to belt speed fluctuations and undulations can be prevented.

Schematic perspective view of an electrophotographic image forming apparatus Cross-sectional view of an electrophotographic image forming apparatus Main cross-sectional view of photosensitive drum cartridge and intermediate transfer belt unit Cross-sectional view of photosensitive drum cartridge and intermediate transfer belt unit Figure of conventional intermediate transfer belt meandering prevention mechanism Conceptual diagram of leaning force Conceptual diagram of regulation of leaning force Sectional drawing of the offset force reduction mechanism which concerns on Example 1 of this invention. Sectional drawing which shows the time of operation | movement of the offset force reduction mechanism which concerns on Example 1 of this invention. A graph showing that the shifting force is reduced by the shifting force reduction mechanism of the present invention. A graph showing that the shifting force becomes zero by the shifting force reduction mechanism of the present invention. Sectional drawing which shows another form of the offset force reduction mechanism which concerns on Example 1 of this invention. Sectional drawing which shows the time of operation | movement of another form of the offset force reduction mechanism which concerns on Example 1 of this invention. Sectional drawing which shows the offset force reduction mechanism which concerns on Example 2 of this invention. Sectional drawing which shows the time of operation | movement of the offset force reduction mechanism which concerns on Example 2 of this invention. Sectional drawing which shows another form of the meandering prevention mechanism of the conventional intermediate transfer belt Sectional drawing of the offset force reduction mechanism which concerns on Example 3 of this invention. Sectional drawing which shows the time of operation | movement of the offset force reduction mechanism which concerns on Example 3 of this invention. Sectional drawing of the offset force reduction mechanism which concerns on Example 4 of this invention. Sectional drawing which shows the time of operation | movement of the offset force reduction mechanism which concerns on Example 4 of this invention.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, unless specifically stated otherwise, the scope of the present invention is not intended to be limited thereto.

[Example 1]
Embodiments of a belt conveyance device according to the present invention and an image forming apparatus having the belt conveyance device will be described with reference to the drawings.

  FIG. 1 is a schematic perspective view of an electrophotographic image forming apparatus according to this embodiment, and FIG. 2 is a cross-sectional view of the electrophotographic image forming apparatus according to this embodiment.

  As shown in FIGS. 1 to 2, a rotary (developer rotation) type four-cycle full-color laser printer will be described as an example of the electrophotographic image forming apparatus according to this embodiment.

[Outline of image forming operation of color image forming apparatus]
The photosensitive drum (image carrier) 1 is moved in synchronization with the rotation of the intermediate transfer belt 5a stretched between the driving roller 40, the first driven roller (tension roller) 41, and the second driven roller (idler roller) 42. Rotate in the direction of the arrow in FIG. 2 (counterclockwise). The surface of the photosensitive drum 1 is uniformly charged by the charging roller 2 and a yellow image is exposed by the exposure unit 3 to form a yellow electrostatic latent image on the photosensitive drum 1. Simultaneously with the formation of the electrostatic latent image, the rotary developing device 4 is driven to dispose the yellow developing device 4Y at the developing position so that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1. A voltage having the same polarity as that of the upper charging polarity and substantially the same potential is applied to cause yellow toner to adhere to the electrostatic latent image for development. Thereafter, a voltage having a polarity opposite to that of the toner is applied to the primary transfer roller 5j in the intermediate transfer belt unit to primarily transfer the yellow toner image on the photosensitive drum 1 onto the intermediate transfer belt 5a.

  When the primary transfer of the yellow toner image is completed as described above, the next developing device rotates and is positioned at the development position facing the photosensitive drum 1, and in the same manner as in the case of yellow, magenta, cyan, For each black color, electrostatic latent image formation, development, and primary transfer are sequentially performed, and four color toner images are superimposed on the intermediate transfer belt 5a.

  During this time, the secondary transfer roller 11 is not in contact with the intermediate transfer belt 5a. At this time, the charging brush 22 and the charging roller 23 as the cleaning unit are also in a non-contact state with the intermediate transfer belt 5a.

  After the formation of the four color toner images on the intermediate transfer belt 5a, the secondary transfer roller (11 is brought into contact with the intermediate transfer belt 5a (the state shown in FIG. 2). Further, in synchronization with the rotation of the intermediate transfer belt 5a. Then, the recording medium is separated and fed one by one from the stacking means 19 by the pickup roller 18. The recording medium waiting at a predetermined position by the conveying roller pair 7d as the feeding means is connected to the intermediate transfer belt 5a. It is fed into the nip portion of the secondary transfer roller 11.

  Here, immediately before the conveying roller pair 7d, a registration sensor (not shown) is provided that detects the leading edge of the recording medium, temporarily interrupts the rotational driving force of the conveying roller pair 7d, and waits the recording medium at a predetermined position. .

  Further, a voltage having a polarity opposite to that of the toner is applied to the secondary transfer roller (transfer means) 11 so that the toner image on the intermediate transfer belt 5a is secondarily transferred collectively onto the surface of the recording medium that has been conveyed.

  The recording medium that has been secondarily transferred in this manner reaches the fixing device 8, and after fixing the toner images of a plurality of colors, the recording medium is discharged onto the discharge tray 10 above the color image forming apparatus A by the discharge roller pair 9. The image formation is completed.

  On the other hand, after the primary transfer, the cleaning charging brush 22 and the charging roller 23 are brought into contact with the intermediate transfer belt 5a, and the residual toner remaining on the intermediate transfer belt 5a is given a charge opposite to that at the time of transfer. The residual toner to which the reverse charge is applied is electrostatically attached to the photosensitive drum 1 and then collected by the cleaning blade 6 for the photosensitive drum 1.

  Here, the driving roller 40 is wider than the secondary transfer roller 11 in the width direction orthogonal to the rotation direction of the belt, and wider than the cleaning charging brush 22 and the charging roller 23. The driving roller 40 has a surface coated with rubber having a low electric resistance, and has a function as a counter electrode of the secondary transfer roller 11, the cleaning charging brush 22, and the charging roller 23.

[Intermediate transfer belt unit and photosensitive drum unit]
3 is a main cross-sectional view of the intermediate transfer belt unit 21 and the photosensitive drum unit 20, and FIG. 4 is a cross-sectional view of the intermediate transfer belt unit 21 and the photosensitive drum unit 20 of FIG.

  3 and 4, the projection of the intermediate transfer belt 5a stretched around the drive roller 40, the first driven roller (tension roller) 41, and the second driven roller (idler roller) 42 of the intermediate transfer belt unit 21 is shown. The photosensitive drum unit 20 is disposed in the direction. A waste toner box 16 is disposed in front of the photosensitive drum unit 20. The driving roller 40 of the intermediate transfer belt unit 21 is provided with a cleaning charging brush 22 and a charging roller 23 for applying a charge having a polarity opposite to that at the time of transfer to the residual toner on the intermediate transfer belt 5a.

  The photosensitive drum unit 20 is held by a right bearing 202 and a left bearing 206 so that both ends of the photosensitive drum 1 can rotate at both ends, and a predetermined rotational driving force is transmitted from the apparatus main body via a coupling 49 at the right end. It has become.

  Further, the charging roller 2 is pressed against the photosensitive drum 1 with a predetermined force by a compression spring 26 via bearings 25 at both ends, and is driven to rotate.

  Next, the intermediate transfer belt unit 21 as a belt conveying device will be described.

  The intermediate transfer belt unit 21 includes a plurality of support rollers, a driving roller 40, a first driven roller (tension roller) 41, a second driven roller (idler roller) 42, and the plurality of support rollers 40, 41, 42. The intermediate transfer belt 5a is an endless belt that is supported on the inner peripheral surface and rotates.

  The intermediate transfer belt 5 a is stretched by a driving roller 40, a first driven roller (tension roller) 41, and a second driven roller (idler roller) 42.

  The drive roller 40 is supported by a right bearing 201 and a left bearing 205 so that both ends can rotate, and a predetermined rotational drive is transmitted from the apparatus main body via a drive gear 48 of the right bearing portion.

  The bearings at both ends of the first driven roller 41 are provided with compression springs 44 so as to apply a predetermined tension to the intermediate transfer belt 5a.

  A primary transfer roller 5j is provided at a position facing the photosensitive drum 1 across the intermediate transfer belt 5a, and is pressed by a predetermined force by a compression spring 47 via bearings 46 at both ends so as to be driven to rotate. It has become.

  At least one of the bearings 46 at both ends is composed of a conductive member, and a predetermined bias is applied to the primary transfer roller 5j through the bearing 46. By applying a predetermined bias to the primary transfer roller 5j, the toner on the surface of the photosensitive drum 1 is primarily transferred onto the intermediate transfer belt 5a.

[Alignment of each color toner image of full color image]
The intermediate transfer belt 5a is provided with position detecting means for detecting the position of the intermediate transfer belt 5a in the transport direction in order to align the color toner images to be superimposed on the intermediate transfer belt 5a.

  A light reflector marker 71 is affixed outside the image forming area in the width direction orthogonal to the rotation direction of the intermediate transfer belt, and a reflective optical sensor (photo sensor) 70 is disposed at a predetermined position so as to face the marker 71. Thus, position detecting means is configured. When the optical sensor 70 detects the reflected light from the marker 71 of the light reflector, the position detecting unit detects the image writing reference position in the transport direction of the intermediate transfer belt 5a. In synchronization with the detection signal from the position detection means, a controller (control means (not shown)) controls the timing of image data writing on the photosensitive drum 1 by the exposure means 3.

  Therefore, the conveyance speed of the intermediate transfer belt 5a must be stable in order to synchronize the image writing timing. When the conveyance speed of the intermediate transfer belt 5a becomes unstable, the image writing timing cannot be synchronized and a color misregistration image is generated.

[Meander prevention mechanism for intermediate transfer belt]
Next, the meandering prevention mechanism of the intermediate transfer belt 5a will be described with reference to FIG.

  The endless belt-like intermediate transfer belt 5a as an intermediate transfer member is made of a resin film such as polyvinylidene fluoride (PVDF) or polyimide (PI), and includes a driving roller 40, a first driven roller 41, and a second driven roller 42. The three rollers are stretched.

  The surface of the drive roller 40 is coated on the surface of an aluminum pipe or the like with a rubber layer having a large friction coefficient μ in order to reliably transmit the rotational force to the intermediate transfer belt. That is, the surface layer of the drive roller 40 is a rubber layer.

  The driven roller 41 is composed of an aluminum pipe or the like, and has a smooth surface and a low friction coefficient μ. As shown in FIGS. 4 and 5, ribs 5b made of an elastic material such as polyurethane foam or urethane rubber are arranged in a strip shape on the back surfaces of both ends of the intermediate transfer belt 5a. The ribs 5b are adhered to both ends of the inner peripheral surface of the intermediate transfer belt 5a with an adhesive such as a double-sided tape so as to maintain the straightness of the ribs over the entire circumference (one round).

  At both ends of the drive roller 40, a rotating member 100 having substantially the same diameter as the drive roller 40 and having a slope on one side is rotatably provided. Between the rotating member 100 and the drive roller 40, a spacer (not shown) made of a material having a small friction coefficient μ such as Teflon (registered trademark) is provided.

  Further, the first driven roller 41 and the second driven roller (idler roller) 42 are provided with both end portions of the roller at positions sufficiently separated from the rib 5b so as not to restrict the rib 5b described above.

  The rib 5b of the intermediate transfer belt 5a is brought into contact with the inclined wall of any one of the rotary members 100 described above when the intermediate transfer belt 5a is displaced in the width direction, and moves. Be regulated. As a result, the intermediate transfer belt 5a is stably rotated without dropping from each roller.

  FIG. 6 shows the concept of the offset force of the intermediate transfer belt 5a. If the belt driving force F (hereinafter also referred to as belt tension) from the driving roller 40, the friction coefficient μ between the driving roller 40 and the intermediate transfer belt 5a, and the drag T perpendicular to the roller generated by the belt tension F, the offset force f = It is expressed by μ · T.

  Accordingly, the shift force f increases as the roller inclination θ, the friction coefficient μ of the intermediate transfer belt 5a, and the belt driving force F increase.

  Here, when the intermediate transfer belt 5a is restricted by the inclined wall of the rotating member 100, if the offset force f is large, the intermediate transfer belt 5a is deformed and wavy. Then, the toner image on the photosensitive drum 1 is not normally primary-transferred onto the intermediate transfer belt 5a, and an abnormal image called a wavy image may occur.

  In addition, when the offset force f is larger, the rib 5b rides on the inclined wall of the rotating member 100, and the intermediate transfer belt 5a is dropped from each roller, or the intermediate transfer belt 5a is deformed. May break.

  FIG. 7 is a conceptual diagram of the regulation of the shifting force that abuts the rib 5b of the intermediate transfer belt 5a against the rotating member 100 provided at both ends of the driving roller 40. FIG.

  The rib 5b restricted by the rotating member 100 moves by a moving amount x in the moving direction, where α is the restricting angle of the rotating member 100, and y is the riding amount of the rib 5b, y = x · tan (α). Become. Here, when the restriction angle α is constant, the movement amount x is proportional to the magnitude of the shifting force f.

  Accordingly, the ride amount y decreases as the movement amount x or the regulation angle α decreases.

  If the carry amount y is large, the conveyance speed of the intermediate transfer belt 5a becomes unstable, and the image writing timing cannot be synchronized as described above, resulting in a color misregistration image. Therefore, it is important to reduce the carry amount y. It is.

  When the restriction angle α is large, the shifting force f is almost perpendicular to the inclined surface of the rotating member 100, and a large restriction force can be secured. However, since the amount of riding y increases, a color misregistration image easily occurs. .

  On the other hand, when the regulation angle α is small, the regulation force with respect to the shifting force f is also small. Therefore, when the rib 5b rides on the rotating member 100, the intermediate transfer belt 5a is likely to drop off from each roller.

  That is, there is a limit to reducing the riding amount y only by reducing the restriction angle α.

  For this reason, it is important to reduce the movement amount x, that is, the shifting force f, in order to achieve both an image that is not broken due to dropping or deformation of the intermediate transfer belt 5a, and that is free of color shift and waviness.

[Intermediate transfer belt offset force reduction mechanism]
Next, a mechanism for reducing the offset force f of the intermediate transfer belt 5a, which is a feature of the present invention, will be described with reference to FIGS.

  FIG. 8 is a cross-sectional view showing a state where the intermediate transfer belt 5a is conveyed without meandering.

  In addition to the meandering prevention mechanism of the intermediate transfer belt 5 a shown in FIG. 5, a holding member 50 is provided between both ends of the driving roller 40 and the rotating member 100. Further, between the both ends of the driving roller 40 and the holding member 50, a deforming member 30 is provided that has substantially the same diameter as the driving roller 40 and whose outer periphery contacts the inner peripheral surface of the intermediate transfer belt 5 a.

  The holding member 50 is held (supported) on the shaft of the drive roller 40 so that the rotation direction rotates integrally with the drive roller 40, but the axial direction is not fixed and the rotation of the drive roller 40 is not fixed. It can move in the axial direction on the shaft.

  The deformable member 30 is a ring-shaped elastic body made of rubber having a large friction coefficient μ in order to reliably transmit the rotational force of the drive roller 40 to the intermediate transfer belt 5a, and the inner diameter side is held by press fitting into the holding member 50. Has been.

  Therefore, the deformable member 30 rotates together with the drive roller 40 and functions as a member that rotates and moves the intermediate transfer belt 5 a together with the drive roller 40.

  Here, the rotating member 100 is provided so as to be coaxially rotatable with respect to the holding member 50, and is not fixed in the axial direction, and can move in the axial direction on the same axis.

  Note that the end of the other driving roller 40 (not shown) has the same configuration, so that it can cope with the meandering direction of the intermediate transfer belt 5a which is left or right in the width direction.

  In FIG. 8, since the intermediate transfer belt 5a does not meander, there is a gap between the rib 5b and the rotating member 100.

  FIG. 9 is a cross-sectional view showing a state where the intermediate transfer belt 5a is meanderingly conveyed on the left side in the axial direction (one axial end side).

  In FIG. 9, the intermediate transfer belt 5a meanders and moves to one end side in the axial direction. Therefore, there is no gap between the rib 5b on the other end side in the axial direction and the rotating member 100, the rib 5b contacts the rotating member 100, and the offset force f of the intermediate transfer belt 5a passes through the rib 5b. It is in a state of hanging on.

  The belt offset force f applied to the rotating member 100 via the rib 5 b is also applied to the deformable member 30 via the holding member 50. Therefore, the deformation member 30 sandwiched between the end portion of the drive roller 40 that does not move in the axial direction and the holding member 50 that can move in the axial direction is deformed mainly by receiving compressive stress in the axial direction.

  At this time, the deformable member 30 that has received the compressive stress in the axial direction is also deformed in the radial direction according to Hooke's law. Specifically, since the inner diameter of the deformable member 30 is fixed to the holding member 50 and does not change, the outer diameter increases. In other words, the deformation member 30 on the other end side, which has substantially the same diameter as the drive roller 40 and the undeformed deformation member 30 on one end side in the axial direction before deformation, is deformed on the drive roller 40 and one end side after deformation. It becomes slightly larger than the outer diameter of the deformable member 30 that does not exist.

  Here, the intermediate transfer belt 5a has a property of meandering (moving) in a direction in which the outer diameter is slightly larger when the outer diameter of either end of the driving roller 40 is slightly larger. Therefore, an attempt is made to meander in the direction of the deformable member 30 that is slightly larger than the outer diameter of the drive roller 40 due to the deformation, and a shifting force fgmax is generated in that direction. That is, the rotational speed of the portion of the intermediate transfer belt 5a that contacts the deformable member 30 on the other end side becomes faster than the rotational speed of the portion that does not contact the deformable member 30 on the other end side. A shifting force fgmax for moving the intermediate transfer belt 5a is generated on the other end in the width direction.

  FIGS. 10 and 11 are graphs relating to the shifting force generated in the intermediate transfer belt 5a. The vertical axis represents the shifting force and the horizontal axis represents time. As shown in FIG. 9, the rib 5b and the rotating member 100 start to contact each other. The time is shown as ts.

  Here, the shift force fgmax generated by the deformation of the deformation member 30 is a force in a direction opposite to the shift force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30 is deformed. It shows as the power of.

  Therefore, when the deforming member 30 is deformed, the difference between the shifting force f and the shifting force fgmax becomes the shifting force generated by the intermediate transfer belt 5a after the deformation member 30 is deformed. Here, since the shifting force after deformation acts opposite to the shifting force before deformation, the shifting force generated by the intermediate transfer belt 5a after the deformation member 30 is deformed deforms the deformation member 30. It becomes smaller than the offset force f of the previous intermediate transfer belt 5a. As a result, the deformation amount of the deformation member 30 is reduced, and the shifting force fgmax generated by the intermediate transfer belt 5a due to the deformation of the deformation member 30 is also reduced.

  That is, the deformation amount of the deformation member 30 finally converges at a certain place as shown in FIG. As shown in FIG. 10, when fs is a shift force generated by the intermediate transfer belt 5a after the deformation of the deformation member 30 is converged and fg is a shift force generated by the deformation of the deformation member 30, fs = f−fg. . Thus, the shifting force fs generated by the intermediate transfer belt 5a after the deformation of the deforming member 30 converges is reduced by the shifting force fg generated by the deformation of the deforming member 30.

  As a result, the belt is prevented from being deformed and broken due to the belt offset force f, and image defects such as a color shift image due to the speed fluctuation of the belt and a wavy image due to the distortion of the belt are generated. The belt can be driven without any problems.

  Further, as shown in FIG. 11, particularly when the shifting force fgmax generated by the deformation of the deformation member 30 is larger than the shifting force f of the intermediate transfer belt 5 a before the deformation member 30 is deformed, the deformation member 30. The offset force fs generated by the intermediate transfer belt 5a after the deformation of (2) converges is zero, that is, the amount of deformation of the deformable member 30 is f = fg, and the intermediate transfer belt 5a does not meander at all.

  Up to this point, the method of changing the outer diameter of the end of the member that drives the intermediate transfer belt 5a by the deformation of the deformable member 30 provided at the end of the driving roller 40 has been described. May be the end of the drive roller 40 itself.

  As described above, in this embodiment, in addition to the mechanism for preventing the meandering of the intermediate transfer belt 5a by restricting the rib 5b disposed on the end of the intermediate transfer belt 5a with the inclined surface of the rotating member 100, the driving is performed. Between the both ends of the roller 40 and the rotating member 100, the deformable member 30 having the same diameter as the driving roller 40 and the outer periphery contacting the inner surface of the intermediate transfer belt 5a is provided.

  As a result, even when a large shifting force is generated in the intermediate transfer belt, the shifting force of the belt can be reduced with a simple configuration. As a result, it is possible to prevent the belt from being deformed and broken due to the belt offset force, and to be compact without image defects such as a color shift image due to the belt speed fluctuation and a wavy image due to the belt being distorted. A color electrophotographic image forming apparatus can be realized.

  Up to this point, as a mechanism for reducing the shifting force of the intermediate transfer belt 5a when the deforming member 30 is deformed by receiving the shifting force f and the outer diameter becomes large, the deforming member 30 is compressed mainly in the axial direction by the shifting force f. However, the present invention is not limited to this.

  Next, as a modification of the shifting force reduction mechanism of the intermediate transfer belt 5a when the deforming member 30 receives the shifting force f and deforms to increase the outer diameter, the deformation member 30 is deformed by the shifting force f with reference to FIGS. A mechanism for reducing the shifting force of the intermediate transfer belt 5a when the member 30 is deformed by receiving a tensile stress mainly in the radial direction will be described.

  FIG. 12 is a sectional view showing a state in which the intermediate transfer belt 5a is conveyed without meandering.

  In addition to the meandering prevention mechanism of the intermediate transfer belt 5 a shown in FIG. 5, a first pressing member 60 and a second pressing member 61 are provided between both ends of the driving roller 40 and the rotating member 100. Further, a deforming member 30 is provided between the first pressing member 60 and the second pressing member 61 so as to have substantially the same diameter as the driving roller 40 and the outer periphery contacts the inner surface of the intermediate transfer belt 5a.

  The first pressing member 60 is fixed to the driving roller 40, and the second pressing member 61 is not fixed, and can move in the axial direction on the rotating shaft of the driving roller 40.

  Moreover, the 1st press member 60 and the 2nd press member 61 are the shapes which have the inclined surface in the contact surface (one side) with the deformation member 30 intervening. Further, the first pressing member 60 and the second pressing member 61 are formed with a rubber layer having a large friction coefficient μ on the surface in order to reliably transmit the rotational force of the driving roller 40 to the deformation member 30.

  The deformable member 30 is a ring-shaped elastic body made of rubber having a large friction coefficient μ in order to reliably transmit the rotational force of the drive roller 40 to the intermediate transfer belt 5a. It is held between the two pressing members 61.

  Therefore, the deformable member 30 rotates integrally with the first pressing member 60 and the driving roller 40, and functions as a member that rotates and moves the intermediate transfer belt 5 a together with the driving roller 40.

  Here, the rotating member 100 is provided so as to be coaxially rotatable with respect to the second pressing member 61, and is not fixed in the axial direction but is movable in the axial direction on the same axis.

  The other end side of the other drive roller 40 (not shown) has the same configuration, so that it can cope with the meandering direction of the intermediate transfer belt 5a on either the left or right side in the width direction.

  In FIG. 12, since the intermediate transfer belt 5a does not meander, there is a gap between the rib 5b and the rotating member 100.

  FIG. 13 is a cross-sectional view showing a state where the intermediate transfer belt 5a is meanderingly conveyed on the left side in the axial direction (one axial end side).

  In FIG. 13, the intermediate transfer belt 5a meanders and moves to one end side in the axial direction. Therefore, there is no gap between the rib 5b on the other end side in the axial direction and the rotating member 100, the rib 5b contacts the rotating member 100, and the offset force f of the intermediate transfer belt 5a passes through the rib 5b. It is in a state of hanging on.

  The offset force f applied to the rotating member 100 via the rib 5 b is also applied to the deformable member 30 via the second pressing member 61. Therefore, the deformation member 30 is sandwiched between the first pressing member 60 that contacts both ends of the driving roller 40 that does not move in the axial direction and the second pressing member 61 that can move in the axial direction. The sandwiched deformation member 30 is deformed by receiving a tensile stress mainly in the radial direction from the inclined surfaces (contact surfaces) of the first pressing member 60 and the second pressing member 61.

  At this time, the deformable member 30 that has received a tensile stress in the radial direction is stretched and deformed, and the outer diameter is increased. Therefore, the deformation member 30 on the other end side in the axial direction, which is substantially the same diameter as the drive roller 40 before the deformation, is larger than the outer diameter of the drive roller 40 and the deformation member 30 on the one end side in the axial direction after the deformation. Slightly larger.

  Here, the intermediate transfer belt 5a has a property of meandering (moving) in a direction in which the outer diameter is large when the outer diameter of either end of the driving roller 40 is slightly larger. Therefore, the intermediate transfer belt 5a tries to meander (move) in the direction of the deformable member 30 on the other end side in the axial direction, which is slightly larger than the outer diameter of the drive roller 40 due to deformation, and a shifting force is generated in that direction. .

  The shift force generated by the deformation of the deformation member 30 is a force in a direction opposite to the shift force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30 is deformed. Therefore, as described above, the shifting force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30 is deformed can be reduced or zero.

  Up to this point, in the description of the first embodiment, when a biasing force is generated in the intermediate transfer belt 5a, the ribs 5b disposed at both ends of the intermediate transfer belt 5a are regulated by the inclined surfaces of the rotating member 100, thereby causing the intermediate transfer belt. Although the configuration having the mechanism for preventing the meandering of 5a has been described as an example, the configuration is not limited thereto. The rib 5b and the rotating member 100 of the intermediate transfer belt 5a may be used in a belt conveyance device provided only at one end portion in the axial direction.

  As described above, in this embodiment, in addition to the mechanism for preventing the meandering of the intermediate transfer belt 5a by restricting the rib 5b disposed on the end of the intermediate transfer belt 5a with the inclined surface of the rotating member 100, the driving is performed. A first pressing member 60 and a second pressing member 61 are provided between both ends of the roller 40 and the rotating member 100, and the driving roller 40 and the first pressing member 60 and the second pressing member 61 are provided between the first pressing member 60 and the second pressing member 61. A deformable member 30 having substantially the same diameter and an outer periphery contacting the inner surface of the intermediate transfer belt 5a is provided.

  As a result, even when a large shifting force is generated in the intermediate transfer belt, the shifting force of the belt can be reduced with a simple configuration. As a result, it is possible to prevent the belt from being deformed and broken due to the belt offset force, and to be compact without image defects such as a color shift image due to the belt speed fluctuation and a wavy image due to the belt being distorted. A color electrophotographic image forming apparatus can be realized.

[Example 2]
In the above-described embodiment, the shift force reducing mechanism in which the outer diameter of the deformation member 30 is increased by receiving the belt shift force f has been described. A mechanism for reducing the shifting force of the intermediate transfer belt 5a having a configuration with a small diameter will be described.

  Next, as a deviation force reducing mechanism according to the second embodiment, the deviation force reducing mechanism of the intermediate transfer belt 5a having a configuration in which the outer diameter of the deformable member 30 is reduced by receiving the belt deviation force f with reference to FIGS. Will be described.

[Intermediate transfer belt offset force reduction mechanism]
FIG. 14 is a cross-sectional view showing a state where the intermediate transfer belt 5a is conveyed without meandering.

  In addition to the meandering prevention mechanism of the intermediate transfer belt 5 a shown in FIG. 5, holding members 51 </ b> L and 51 </ b> R are provided between both ends of the driving roller 40 and the rotating member 101. Further, deforming members 30L and 30R are provided between the holding members 51L and 51R and the driving roller 40 so as to have substantially the same diameter as the driving roller 40 and the outer periphery thereof contacts the inner peripheral surface of the intermediate transfer belt 5a.

  The holding members 51L and 51R are held (axially supported) on the shaft of the driving roller 40 so that the rotating direction rotates integrally with the driving roller 40, but the axial direction is not fixed, and the driving roller 40 It can move in the axial direction on the rotation axis.

  Here, the rotating member 101 rotatably provided on the drive roller 40 has substantially the same diameter as the drive roller 40 at both ends. Further, the rotating member 101 has inclined surfaces with which the ribs 5bL and 5bR provided on the intermediate transfer belt 5a can come into contact with both surfaces on one end side and the other end side in the axial direction, and are integrated through the one end side and the other end side. Yes.

  Further, when the rotating member 101 moves in the width direction orthogonal to the rotational movement direction of the intermediate transfer belt 5a, the tubular ribs 101L and 101R at the center in the width direction come into contact with the holding members 51L and 51R. .

  The deformable members 30L and 30R are ring-shaped elastic bodies formed of rubber having a large friction coefficient μ in order to reliably transmit the rotational force of the driving roller 40 to the intermediate transfer belt 5a, and the holding members 51L and 51R are arranged on the inner diameter side. Is held by press fitting.

  Therefore, the deformable members 30L and 30R rotate together with the drive roller 40, and function as members that rotate and move the intermediate transfer belt 5a together with the drive roller 40.

  Further, compression springs 80L and 80R are provided between the holding members 51L and 51R and the rib 40a inside the driving roller 40, and a spring force is always applied to the holding members 51L and 51R in the axial direction.

  Both end portions of the drive roller 40 have the same configuration, and can cope with the meandering direction of the intermediate transfer belt 5a which is left or right in the width direction.

  The spring force applied to the holding members 51L and 51R is also applied to the deformable members 30L and 30R. Therefore, both end portions of the drive roller 40 that do not move in the axial direction and the deformation members 30L and 30R sandwiched between the holding members 51L and 51R are deformed mainly by receiving compressive stress in the axial direction.

  At this time, the deformable members 30L and 30R that have received the compressive stress in the axial direction are also deformed in the radial direction by the Hooke's law. Specifically, the inner diameters of the deformable members 30L and 30R are fixed to the holding members 51L and 51R and do not change, so that the outer diameter becomes larger. That is, the deformable members 30L and 30R that have received compressive stress in the axial direction are slightly larger than the outer diameter of the drive roller 40, and the deformable members 30L and 30R at both ends have substantially the same diameter.

  In FIG. 14, since the intermediate transfer belt 5a does not meander, there is a gap between the ribs 5bL and 5bR and the rotating member 101.

  FIG. 15 is a cross-sectional view showing a state in which the intermediate transfer belt 5a is meanderingly conveyed on the left side in the axial direction (one axial end side).

  In FIG. 15, the intermediate transfer belt 5a meanders and moves to one end side in the axial direction. Therefore, there is no gap between the rib 5bR on the other axial end side and the rotating member 101, the rib 5bR comes into contact with the rotating member 101, and the offset force f of the intermediate transfer belt 5a is transmitted through the rib 5bR. It is in a state of hanging on.

  Further, since the rotating member 101 is also moved to one end side in the axial direction, the circular rib 101L at the center is in contact with the holding member 51L.

  Here, the offset force f applied to the rotating member 101 on the other axial end side is also applied to the deformable member 30L via the holding member 51L. Since the shifting force f is a force in a direction opposite to the spring force of the compression spring 80L, the compressive stress applied to the deformation member 30L is reduced. Therefore, the deformation amount of the deformation member 30L is also reduced.

  At this time, the deformation member 30L has a small deformation amount, so that the outer diameter is also reduced. On the other hand, the outer diameter of the deformation member 30R provided at the end of the drive roller 40 on the opposite side (one axial end side) is It remains unchanged. Therefore, compared to the outer diameter of the deformable member 30R at the end of the belt on which the belt offset force f is applied (one axial end side), the side on which the belt offset force f is not applied (the other axial end side). The outer diameter of the deformable member 30L becomes slightly smaller.

  Here, as described above, the intermediate transfer belt 5a has a property of meandering (moving) in a direction in which the outer diameter is large when the outer diameter of either end of the driving roller 40 is slightly larger. Therefore, the intermediate transfer belt 5a tries to meander (move) in the direction of the deformable member 30R whose outer diameter is slightly larger than the outer diameter of the drive roller 40, compared to the deformable member 30L whose outer diameter is reduced by deformation. A shifting force is generated in that direction.

  The shift force generated by the deformation of the deformation member 30L is a force in a direction opposite to the shift force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30L is deformed. Therefore, as described above, the shifting force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30L is deformed can be reduced or zero.

  So far, the configuration has been described in which the outer diameter of the end portion of the member that drives the intermediate transfer belt 5a is changed by the deformation of the deformable members 30L and 30R provided at the end portion of the drive roller 40. However, the outer diameter changes. What is to be done may be the end of the drive roller 40 itself.

  As described above, in this embodiment, in addition to the mechanism for preventing the meandering of the intermediate transfer belt 5a by restricting the ribs 5bL and 5bR arranged at both ends of the intermediate transfer belt 5a with the inclined surface of the rotating member 101. In addition, holding members 51L and 51R are provided between both ends of the driving roller 40 and the rotating member 101, and the outer periphery of the driving roller 40 and the holding members 51L and 51R are approximately the same diameter as the driving roller 40 and the outer periphery thereof is an intermediate transfer. Deformation members 30L and 30R that contact the inner surface of the belt 5a are provided. Further, compression springs 80L and 80R are provided between the holding members 51L and 51R and the rib 40a inside the drive roller 40. The holding members 51L and 51R are always subjected to a spring force in the axial direction via the rotating member 101, and the deforming members 30L and 30R at both ends are configured to be slightly larger than the outer diameter of the driving roller 40.

  As a result, even when a large shifting force is generated in the intermediate transfer belt, the shifting force of the belt can be reduced with a simple configuration. As a result, it is possible to prevent the belt from being deformed and broken due to the belt offset force, and to be compact without image defects such as a color shift image due to the belt speed fluctuation and a wavy image due to the belt being distorted. A color electrophotographic image forming apparatus can be realized.

Example 3
In the first and second embodiments, when a biasing force is generated in the intermediate transfer belt 5a, the rib 5b of the intermediate transfer belt 5a is regulated by the inclined surface of the rotating member 100 or the rotating member 101 to meander the intermediate transfer belt 5a. The image forming apparatus having a mechanism for preventing the above has been described.

  However, the present invention is not limited to this, and a meandering prevention mechanism that restricts the shift direction of the intermediate transfer belt 5a by bringing both ends of the intermediate transfer belt 5a into contact with the regulating member as shown in FIG. The present invention can also be applied to an image forming apparatus having the same.

[Meander prevention mechanism for intermediate transfer belt]
Next, another embodiment of the meandering prevention mechanism for the intermediate transfer belt 5a will be described with reference to FIG.

  FIG. 16 is a cross-sectional view showing another form of the meandering prevention mechanism for the intermediate transfer belt, and a regulating member 90 is provided at both ends of the drive roller 40.

  When a biasing force is generated in the intermediate transfer belt 5a, the end of the intermediate transfer belt 5a is regulated by the wall of the regulating member 90, and the intermediate transfer belt 5a is stably rotated without dropping from each roller.

[Intermediate transfer belt offset force reduction mechanism]
Next, another form of the mechanism for reducing the offset force f of the intermediate transfer belt 5a will be described with reference to FIGS.

  FIG. 17 is a cross-sectional view showing a state where the intermediate transfer belt 5a is conveyed without meandering.

  In addition to the meandering prevention mechanism of the intermediate transfer belt 5 a shown in FIG. 16, holding members 55 are provided at both ends of the driving roller 40. Further, between the both ends of the driving roller 40 and the holding member 52, there is provided a deforming member 30 that is substantially the same diameter as the driving roller 40 and whose outer periphery contacts the inner peripheral surface of the intermediate transfer belt 5a.

  The holding member 52 is fixed to the drive roller 40 in the rotation direction, but is not fixed in the axial direction, and can move in the axial direction on the rotation axis of the drive roller 40.

  The deformable member 30 is a ring-shaped elastic body made of rubber having a large friction coefficient μ in order to reliably transmit the rotational force of the drive roller 40 to the intermediate transfer belt 5a, and the inner diameter side is held by press fitting into the holding member 52. Has been.

  Therefore, the deformable member 30 rotates together with the drive roller 40 and functions as a member that rotates and moves the intermediate transfer belt 5 a together with the drive roller 40.

  Further, a compression spring 81 is provided between the regulating member 90 and the left bearing 205, and a spring force is always applied to the holding member 52 in the axial direction via the regulating member 90.

  The other end of the driving roller 40 (not shown) has the same configuration, and a compression spring 81 is provided between the regulating member 90 and the right bearing, and the holding member 52 is interposed via the regulating member 90. Spring force is always applied in the axial direction. As a result, the meandering direction of the intermediate transfer belt 5a can cope with either the left or right of the width direction.

  Since the spring force applied to the restricting member 90 is also applied to the deformable member 30, the deformable member 30 sandwiched between both ends of the drive roller 40 that does not move in the axial direction and the holding member 52 is mainly a shaft. It will be deformed by receiving compressive stress in the direction.

  At this time, the deformable member 30 that has received the compressive stress in the axial direction is also deformed in the radial direction according to Hooke's law. Specifically, since the inner diameter of the deformable member 30 is fixed to the holding member 52 and does not change, the outer diameter increases. That is, the deformable member 30 that has received a compressive stress in the axial direction is slightly larger than the outer diameter of the drive roller 40, and the deformable members 30 at both ends have substantially the same diameter.

  In FIG. 17, since the intermediate transfer belt 5a does not meander, there is a gap between the end of the intermediate transfer belt 5a and the regulating member 90.

  FIG. 18 is a cross-sectional view showing a state where the intermediate transfer belt 5a is meanderingly conveyed to the right side in the axial direction (the other end side in the axial direction).

  In FIG. 18, the intermediate transfer belt 5a meanders and moves to the right in the axial direction. Therefore, there is no gap between the end of the intermediate transfer belt 5a and the regulating member 90, and the shifting force f of the intermediate transfer belt 5a is applied to the regulating member 90.

  Since the offset force f applied to the regulating member 90 is a force in a direction opposite to the spring force of the compression spring 81, the compressive stress applied to the deformation member 30 is reduced. Therefore, the deformation amount of the deformation member 30 is also reduced.

  At this time, the deformation member 30 has a small deformation amount, so that the outer diameter is also small. On the other hand, the deformation member 30 provided at the end of the driving roller 40 on the opposite side (one axial end side) (not shown) The outer diameter remains unchanged. Therefore, the outer diameter of the deformable member 30 at the end opposite to the side to which the belt offset force f is applied is slightly smaller than that of the deformable member 30 at the end to which the belt offset force f is applied. Will become bigger.

  Here, as described above, the intermediate transfer belt 5a has a property of meandering (moving) in a direction in which the outer diameter is large when the outer diameter of either end of the driving roller 40 is slightly larger. Therefore, the intermediate transfer belt 5a tries to meander (move) in the direction of the deformable member 30 whose outer diameter is slightly larger than the outer diameter of the drive roller 40, compared to the deformable member 30 whose outer diameter is reduced by deformation. A shifting force is generated in that direction.

  The shift force generated by the deformation of the deformation member 30 is a force in a direction opposite to the shift force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30 is deformed. Therefore, as described above, the shifting force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30 is deformed can be reduced or zero.

  Up to this point, the method of changing the outer diameter of the end of the member that drives the intermediate transfer belt 5a by the deformation of the deformable member 30 provided at the end of the driving roller 40 has been described. May be the end of the drive roller 40 itself.

  As described above, in this embodiment, the both ends of the intermediate transfer belt 5a and the regulating member 90 are brought into contact with each other, and in addition to the mechanism for preventing the meandering of the intermediate transfer belt 5a, the driving roller 40 is held at both ends. The member 52 is provided, and the deformable member 30 is provided between the both end portions of the drive roller 40 and the holding member 52 so as to have substantially the same diameter as the drive roller 40 and the outer periphery contacts the inner surface of the intermediate transfer belt 5a. Further, a compression spring 81 is provided between the regulating member 90 and both side bearings. A spring force is always applied to the holding member 52 in the axial direction via the regulating member 90, and the deformable members 30 at both ends are configured to be slightly larger than the outer diameter of the drive roller 40.

  As a result, even when a large shifting force is generated in the intermediate transfer belt, the shifting force of the belt can be reduced with a simple configuration. As a result, it is possible to prevent the belt from being deformed and broken due to the belt offset force, and to be compact without image defects such as a color shift image due to the belt speed fluctuation and a wavy image due to the belt being distorted. A color electrophotographic image forming apparatus can be realized.

Example 4
In the third exemplary embodiment, in an image forming apparatus having a meandering prevention mechanism that restricts the shift direction of the intermediate transfer belt 5a by bringing the end of the intermediate transfer belt 5a into contact with the restriction member, the image forming apparatus is deformed by receiving the belt shift force f. The shift force reducing mechanism having a configuration in which the outer diameter of the member 30 is reduced has been described. In this embodiment, the shift force reducing mechanism of the intermediate transfer belt 5a having a configuration in which the outer diameter of the deformable member 30 is increased by receiving the shift force of the belt. Will be described.

  Next, as a deviation force reducing mechanism according to the fourth embodiment, the deviation force reducing mechanism of the intermediate transfer belt 5a configured to increase the outer diameter of the deformable member 30 by receiving the belt deviation force f using FIGS. Will be described.

[Intermediate transfer belt offset force reduction mechanism]
FIG. 19 is a sectional view showing a state in which the intermediate transfer belt 5a is conveyed without meandering.

  As shown in FIG. 19, in addition to a mechanism for preventing meandering of the intermediate transfer belt 5a by abutting the end of the intermediate transfer belt 5a against the regulating member 91, holding members 53L and 53R are provided at both ends of the driving roller 40. It has been. Further, deforming members 30L and 30R are provided between both ends of the driving roller 40 and the holding members 53L and 53R. The deforming members 30L and 30R have substantially the same diameter as the driving roller 40 and the outer periphery contacts the inner surface of the intermediate transfer belt 5a.

  Although the holding members 53L and 53R are held so as to rotate integrally with the drive roller 40, the holding members 53L and 53R are not fixed in the axial direction and can be moved in the axial direction on the same axis.

  Here, the regulating member 91 provided on the drive roller 40 is integrated through one end side and the other end side in the axial direction.

  When the regulating member 91 moves in the width direction orthogonal to the rotational movement direction of the intermediate transfer belt 5a, the circular ribs 91L and 91R provided outside the holding members 51L and 51R are in contact with the holding members 51L and 51R. It comes to touch.

  The deformable member 30 is a ring-shaped elastic body made of rubber having a large friction coefficient μ in order to reliably transmit the rotational force of the drive roller 40 to the intermediate transfer belt 5a, and the inner diameter side is press-fitted into the holding members 53L and 53R. Is held by.

  Therefore, the deformable members 30L and 30R rotate together with the drive roller 40, and function as members that rotate and move the intermediate transfer belt 5a together with the drive roller 40.

  In FIG. 19, since the intermediate transfer belt 5a does not meander, there is a gap between the end of the intermediate transfer belt 5a and the regulating member 91.

  FIG. 20 is a cross-sectional view showing a state where the intermediate transfer belt 5a is meanderingly conveyed to the right side in the axial direction (the other end side in the axial direction).

  In FIG. 20, the intermediate transfer belt 5a meanders and moves to the right in the axial direction. Therefore, there is no gap between the end portion of the intermediate transfer belt 5a on the right side in the axial direction and the regulating member 91, the belt end portion comes into contact with the regulating member 91, and the offset force f of the intermediate transfer belt 5a is applied to the regulating member 91. It is in a hanging state.

  Further, since the restricting member 91 has also moved to the right in the axial direction, the circular rib 91L provided outside the holding member 53L is in contact with the holding member 53L.

  The offset force f applied to the restricting member 91 is also applied to the deformable member 30L via the holding member 53L, so that it is sandwiched between the end of the driving roller 40 that does not move in the axial direction and the holding member 53L. The deformable member 30L is deformed by receiving a compressive stress mainly in the axial direction.

  At this time, the deformable member 30L which has received the compressive stress in the axial direction is also deformed in the radial direction according to Hooke's law. Specifically, the deformation member 30L has an inner diameter that is fixed to the holding member 53L and does not change, so the outer diameter increases, but on the other hand, the deformation provided at the end of the drive roller 40 on the opposite side (the right side in the axial direction). The outer diameter of the member 30R remains unchanged. Therefore, the outer diameter of the deformable member 30L at the end on the side where the belt offset force f is applied is slightly smaller than that of the deformable member 30R at the end opposite to the side where the belt offset force f is applied. Will become bigger.

  Here, as described above, the intermediate transfer belt 5a has a property of meandering (moving) in a direction in which the outer diameter is large when the outer diameter of either end of the driving roller 40 is slightly larger. Therefore, the intermediate transfer belt 5a tries to meander (move) in the direction of the deformable member 30L that is slightly larger than the outer diameter of the drive roller 40 due to deformation, and a shifting force is generated in that direction.

  The shift force generated by the deformation of the deformation member 30L is a force in a direction opposite to the shift force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30L is deformed. Therefore, as described above, the shifting force f acting in the direction in which the intermediate transfer belt 5a meanders before the deformation member 30L is deformed can be reduced or zero.

  Up to this point, the method of changing the outer diameter of the end portion of the member that drives the intermediate transfer belt 5a by the deformation of the deformation members 30L and 30R provided at the end portion of the driving roller 40 has been described. What is to be done may be the end of the drive roller 40 itself.

  In the description of the fourth embodiment up to this point, when the offset force is generated in the intermediate transfer belt 5a, the belt end portion is regulated by the walls of the regulating members 91 arranged at both ends of the driving roller 40, thereby performing the intermediate transfer. Although the configuration having a mechanism for preventing meandering of the belt 5a has been described, the configuration is not limited to this. In this embodiment, the regulating member 91 and the deforming member 30 may be used in a belt conveyance device provided only at one end portion in the axial direction.

  As described above, in this embodiment, in addition to the mechanism for preventing the meandering of the intermediate transfer belt 5a by bringing the end of the intermediate transfer belt 5a into contact with the regulating member 91, both ends of the drive roller 40 are provided. Holding members 53L and 53R are provided, and further, deformation members 30L and 30R having substantially the same diameter as the driving roller 40 and the outer periphery contacting the inner surface of the intermediate transfer belt 5a are provided between both ends of the driving roller 40 and the holding members 53L and 53R. It was configured as follows.

  As a result, even when a large shifting force is generated in the intermediate transfer belt, the shifting force of the belt can be reduced with a simple configuration. As a result, it is possible to prevent the belt from being deformed and broken due to the belt offset force, and to be compact without image defects such as a color shift image due to the belt speed fluctuation and a wavy image due to the belt being distorted. A color electrophotographic image forming apparatus can be realized.

  In the above-described embodiment, a printer is exemplified as the image forming apparatus, but the present invention is not limited to this. For example, the image forming apparatus may be another image forming apparatus such as a copying machine or a facsimile machine, or another image forming apparatus such as a multi-function machine combining these functions. Further, the image forming apparatus provided with the belt conveying device described above is not limited to an image forming apparatus using an intermediate transfer member (endless belt). For example, an image forming apparatus that uses a recording medium carrier (endless belt) and sequentially superimposes and transfers the toner images of the respective colors onto the recording medium carried on the recording medium carrier. The same effect can be obtained by applying the present invention to a belt conveying device used in these image forming apparatuses.

A ... Image forming apparatus 1 ... Photosensitive drum 5a ... Intermediate transfer belts 5b, 5bL, 5bR ... Rib 30 ... Deformation member 30L, 30R ... Deformation member 40 ... Drive roller 40a ... Rib 41 ... First driven roller (tension roller)
42 ... 2nd driven roller (idler roller)
50 ... Holding members 51L, 51R ... Holding member 52 ... Holding members 53L, 53R ... Holding member 60 ... First pressing member 61 ... Second pressing member 80L, 80R ... Compression spring 81 ... Compression spring 90 ... Restriction member 91 ... Restricting members 91L, 91R ... ribs 100, 101 ... rotating members 101L, 101R ... ribs

Claims (15)

An endless belt that rotates, a support roller that supports the inner peripheral surface of the endless belt, a rotating member that is provided on at least one end side in the axial direction of the support roller, and that is rotatable, and an inner peripheral surface of the endless belt A belt conveying device in which the rib and the rotating member come into contact with each other by movement in a width direction orthogonal to the rotational movement direction of the endless belt,
A deformable member provided on at least one end side in the axial direction of the support roller, the deformable member of the rotating member contacting the rib when the endless belt moves in the width direction. A belt conveying device characterized in that an outer diameter is deformed by receiving a force.   When the endless belt moves to the other end side in the width direction, the rotation speed of the one end side of the endless belt is faster than the rotation speed of the other end side, so that the endless belt is moved in the width direction. The belt conveying device according to claim 1, wherein the belt conveying device is moved to one end side of the belt.   The belt conveying device according to claim 1, wherein the rotating member and the deforming member are also provided on the other end side in the axial direction, respectively.   4. A holding member that is supported by a shaft of the support roller and holds the deforming member, wherein the deforming member is a ring-shaped elastic body. The belt conveyance apparatus as described in.   2. The deformation member according to claim 1, wherein when the endless belt moves in the width direction, an outer diameter of the deformable member is increased by receiving a force of the rotating member that comes into contact with the rib. The belt conveyance apparatus as described in any one of Claim 4.   The deformable member has an outer diameter larger than that of the support roller, and when the endless belt moves in the width direction, the outer diameter is reduced by receiving the force of the rotating member in contact with the rib. The belt conveyance device according to any one of claims 1 to 5, characterized by these. An endless belt that rotates, a support roller that supports an inner peripheral surface of the endless belt, and a regulating member that is disposed on at least one end side in the axial direction of the support roller, and the rotational movement direction of the endless belt In the belt conveyance device in which the end of the endless belt and the regulating member abut on each other by moving in the width direction orthogonal to the
And a deformable member provided on at least one end side in the axial direction of the support roller, and the deformable member contacts an end of the endless belt when the endless belt moves in the width direction. A belt conveying device, wherein the outer diameter is deformed by receiving the force of the regulating member.   When the endless belt moves to the other end side in the width direction, the rotation speed of the one end side of the endless belt is faster than the rotation speed of the other end side, so that the endless belt is moved in the width direction. The belt conveying device according to claim 7, wherein the belt conveying device is moved to one end side of the belt.   The belt conveying device according to claim 7 or 8, wherein the regulating member and the deforming member are also provided on the other end side in the axial direction, respectively.   10. A holding member that is supported by a shaft of the support roller and holds the deforming member, wherein the deforming member is a ring-shaped elastic body. The belt conveyance apparatus as described in.   The outer diameter of the deformable member is increased by receiving the force of the restricting member that contacts the end of the endless belt when the endless belt moves in the width direction. The belt conveyance device according to any one of claims 7 to 10.   The deformable member has an outer diameter larger than that of the support roller, and when the movement of the endless belt in the width direction occurs, the deformable member receives the force of the restriction member that contacts the end of the endless belt. The belt conveying device according to claim 7, wherein the belt conveying device is reduced.   The belt conveyance device according to any one of claims 1 to 12, wherein a surface layer of a support roller to which the deformable member is fixed is a rubber layer. An image carrier;
The belt conveyance device according to any one of claims 1 to 13, further comprising an endless belt that carries an image formed on the image carrier.
Transfer means for transferring the image transferred to the endless belt to a recording medium;
An image forming apparatus comprising: An image carrier;
A belt conveyance device according to any one of claims 1 to 13, comprising an endless belt that carries and conveys a recording medium;
Transfer means for transferring an image formed on the image carrier to a recording medium carried on the endless belt;
An image forming apparatus comprising:

Images