JP2009184767A - Meandering compensation mechanism, and intermediate transfer unit and image forming device equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compensate meandering of an endless belt at high accuracy by finely controlling the movement of the end of the roller on which endless belt extends. <P>SOLUTION: A solid cam 51 is attached to the output shaft 55 of a motor 50 axially movable and unmovable in the rotation direction. The solid cam 51 includes a cam surface 56 for 3 rounds wherein the distance from the output shaft 55 increases gradually. One end of a swinging arm 52 swingable around an axis 65, rotatably supports one end 66 of a roller shaft 42 of a follower roller 26, and presses a roll 70 of the other end onto the cam surface 56 by urging by a pulling spring. Since the solid cam 51 can reduce lift amount for the same rotation angle compared with a plate cam (a circumference cam), it can finely control the movement of one end 66 of the roller shaft 42. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a meandering correction mechanism that corrects meandering of an endless belt, an intermediate transfer unit including the same, and an image forming apparatus.

  2. Description of the Related Art Image forming apparatuses such as color printers, copiers, and facsimile machines that use an intermediate transfer belt are known. This is a magenta (M), cyan (C), yellow (Y), and black (BK) toner image, in which one color toner image is formed on one photosensitive drum, and this is intermediate. By repeating the process of transferring onto the transfer belt for four colors, the four color toner images are superimposed on the intermediate transfer belt. Alternatively, in the case of the tandem system having four photosensitive drums, toner images of different colors are formed on the respective photosensitive drums, which are sequentially transferred onto the intermediate transfer belt and superimposed on the intermediate transfer belt. . In any case, the intermediate transfer belt is formed in an endless shape and is stretched around a plurality of rollers. When the intermediate transfer belt meanders, the transfer position of the toner image of each color to be transferred is shifted and color misregistration occurs.

In order to prevent such color misregistration, a technique for preventing meandering of the intermediate transfer belt has been proposed (see, for example, Patent Document 1). In Patent Document 1, both ends of a meandering correction roller, on which a belt is stretched, are respectively held at the tip of an arm, a swing center is provided in the middle of the arm, and a plate cam (periphery) is provided at the base end of the arm. The periphery of the cam) is brought into contact. By rotating the plate cam, the arm is swung, and the end of the roller is moved in a direction substantially perpendicular to the tension applying direction to correct the meandering of the intermediate transfer belt.
Japanese Patent Laid-Open No. 06-56294

  However, according to the above-mentioned Patent Document 1, since the movement amount of the roller end is maximized by one rotation of the plate cam, for example, the movement of the roller end with respect to the minimum controllable rotation angle of the plate cam. The amount tends to be large, and it is difficult to finely control the amount of movement. Therefore, there is a problem that it is difficult to finely correct the meandering amount. Such a problem occurs not only in the case where the belt is an intermediate transfer belt but also in, for example, a photosensitive belt (photosensitive belt), a transfer belt, a conveyance belt, and the like.

  Accordingly, the present invention provides a meandering correction mechanism capable of finely controlling the amount of movement of the end portion of the roller on which the endless belt is stretched to correct the meandering of the endless belt with high accuracy, and an intermediate including the same. An object of the present invention is to provide a transfer unit and an image forming apparatus.

  The invention according to claim 1 is attached to one end portion of a roller shaft of one roller among a plurality of rollers on which an endless belt is stretched, and has one end portion of the roller shaft in a direction substantially orthogonal to the roller shaft. The present invention relates to a meandering correction mechanism that corrects meandering of the rotating endless belt by moving the endless belt. The meandering correction mechanism according to the present invention includes: (1) a motor capable of controlling the rotation angle; and (2) rotated by the motor and having a cam surface and a guide surface on an outer peripheral portion and substantially parallel to the roller shaft. A three-dimensional cam movable in the direction of a cam shaft, wherein the cam surface gradually increases in distance from the cam shaft with rotation of the three-dimensional cam in a predetermined direction, and is a spiral exceeding at least one turn of the three-dimensional cam The three-dimensional cam formed in a spiral shape along the cam surface, the guide surface being erected on one end of the cam surface in the cam shaft direction; and (3) the roller A swing arm that is swingably supported by a swing fulcrum substantially parallel to the shaft; and a bearing portion that rotatably supports one end of the roller shaft, and the cam surface and the guide surface of the three-dimensional cam The rocking portion having a contact portion capable of contacting and separating. An arm; (4) a cam biasing member that biases the solid cam and presses the guide surface against the contact portion of the swing arm; and (5) the contact portion of the swing arm. And a pressing means for pressing the cam surface.

  The invention according to claim 2 is attached to one end portion of a roller shaft of one roller among a plurality of rollers on which an endless belt is stretched, and has one end portion of the roller shaft in a direction substantially orthogonal to the roller shaft. The present invention relates to a meandering correction mechanism that corrects meandering of the rotating endless belt by moving the endless belt. The meandering correction mechanism according to the present invention includes: (1) a motor capable of controlling the rotation angle; and (2) rotated by the motor and having a cam surface and a guide surface on an outer peripheral portion and substantially parallel to the roller shaft. A three-dimensional cam movable in the direction of a cam shaft, wherein the cam surface gradually increases in distance from the cam shaft with rotation of the three-dimensional cam in a predetermined direction, and is a spiral exceeding at least one turn of the three-dimensional cam The three-dimensional cam formed in a spiral shape along the cam surface, the guide surface being erected on one end of the cam surface in the cam shaft direction; and (3) the roller A swing arm that is swingably supported by a swing fulcrum substantially parallel to the shaft; and a bearing portion that rotatably supports one end of the roller shaft, and the cam surface and the guide surface of the three-dimensional cam Oscillating arm having a contact portion capable of contacting and separating (4) an arm biasing member that biases the swing arm to press the contact portion of the swing arm against the guide surface; and (5) the contact portion of the swing arm. Pressing means for pressing the cam surface.

The invention according to claim 3 is the meandering correction mechanism according to claim 1 or 2, wherein the swing fulcrum is disposed between the bearing portion and the contact portion in the swing arm.
It is characterized by that.

  According to a fourth aspect of the present invention, in the meandering correction mechanism according to any one of the first to third aspects, the pressing means biases the swing arm to press the contact portion against the cam surface. It is a spring member.

  According to a fifth aspect of the present invention, in the meandering correction mechanism according to any one of the first to third aspects, (1) the two three-dimensional cams have a small-diameter portion with a short cam surface distance from the cam shaft. (2) The abutting portion of the swing arm is configured as a bifurcated portion having an upper clamping portion and a lower clamping portion that are spaced apart at a constant interval, and serves as the pressing means. ) Contacting the upper clamping part with the cam surface of one of the three-dimensional cams, bringing the lower clamping part into contact with the cam surface of the other three-dimensional cam, and The cam surface is sandwiched between.

  A sixth aspect of the invention relates to an intermediate transfer unit including a transfer frame, a plurality of rollers rotatably supported by the transfer frame, and an intermediate transfer belt stretched around the plurality of rollers. The transfer unit according to the present invention corrects meandering of the rotating intermediate transfer belt by moving one end of a roller shaft of one of the plurality of rollers in a direction substantially perpendicular to the roller shaft. The meandering correction mechanism is a meandering correction mechanism according to any one of claims 1 to 5.

  A seventh aspect of the invention relates to an image forming apparatus including a sheet feeding unit that feeds a sheet and an image forming unit that forms an image on a sheet supplied from the sheet feeding unit. In the image forming apparatus according to the present invention, the image forming unit is configured to transfer an image carrier on which a toner image is formed on the surface, and a toner image formed on the surface of the image carrier, and the transferred toner image. An intermediate transfer belt for transferring the toner image to a sheet, and a meandering correction mechanism for correcting the meandering of the intermediate transfer belt, wherein the meandering correction mechanism is the meandering correction mechanism according to any one of claims 1 to 5. It is characterized by that.

  According to an eighth aspect of the present invention, there is provided an image forming apparatus comprising: a sheet feeding unit that feeds a sheet; and an image forming unit that forms an image on the sheet supplied from the sheet feeding unit. In the image forming apparatus according to the present invention, the image forming unit carries and conveys an image carrier on which a toner image is formed on a surface and a sheet onto which the toner image formed on the surface of the image carrier is transferred. 6. A meandering correction mechanism according to claim 1, further comprising: a conveyor belt; and a meandering correction mechanism that corrects meandering of the conveyor belt, wherein the meandering correction mechanism is the meandering correction mechanism according to claim 1.

  According to the meandering correction mechanism of the present invention, the three-dimensional cam has a cam surface formed in a spiral shape exceeding one round of the three-dimensional cam. For example, the three-dimensional cam has a cam surface formed only for one round. Compared with a plate cam (peripheral cam), the lift amount can be reduced for the same rotation angle, so that the movement of one end of the roller shaft can be finely controlled. That is, the meandering of the endless belt can be corrected with high accuracy.

  According to the intermediate transfer unit of the present invention, meandering of the intermediate transfer belt as an endless belt can be corrected with high accuracy. For example, when a plurality of color toner images are transferred to the intermediate transfer belt, the intermediate transfer belt is transferred. Color misregistration of a plurality of color toner images can be suppressed.

  According to the image forming apparatus of the present invention, color misregistration of a plurality of color toner images formed on a sheet can be suppressed.

  Hereinafter, the best embodiment of the present invention will be described in detail with reference to the drawings. In addition, in each drawing, the member etc. which attached | subjected the same code | symbol are the same structures, The duplication description about these shall be abbreviate | omitted suitably. Moreover, in each drawing, members and the like that are not necessary for the description are omitted as appropriate.

<Embodiment 1>
A meandering correction mechanism 1, an intermediate transfer unit 2, and an image forming apparatus 3 according to the present invention will be described with reference to FIGS. Among these, FIG. 1 is a diagram schematically showing the internal configuration of the image forming apparatus 3 when viewed from the front side (the side on which the user is located when the image forming apparatus 3 is used). 2A and 2B are diagrams illustrating the meandering correction mechanism 1 according to the first embodiment, in which FIG. 2A is a front view and FIG. 2B is a top view. FIG. 3 is a perspective view of the meandering correction mechanism 1 according to the first embodiment when viewed from the diagonally lower right side on the front side. FIG. 4 is a perspective view of the three-dimensional cam 51. 5A and 5B are diagrams illustrating the meandering correction mechanism 1A according to the second embodiment, in which FIG. 5A is a front view, FIG. 5B is a front view, and FIG. 5C is a right side view. FIG. 6 is a perspective view of the meandering correction mechanism 1 </ b> A according to the second embodiment when viewed from the upper left oblique direction on the front side. FIG. 7 is a perspective view illustrating the swing arm 91 of the second embodiment. FIG. 8 is a cross-sectional view illustrating the meandering amount detection device 80 in a direction orthogonal to the rotation direction of the intermediate transfer belt. FIG. 9 is a perspective view illustrating the meandering amount detection device 80.

  An example of an image forming apparatus 3 according to the present invention will be described with reference to FIG. The image forming apparatus 3 shown in the figure is an electrophotographic four-color full-color printer, and employs a tandem method and an intermediate transfer method.

  The image forming apparatus 3 illustrated in FIG. 1 includes a sheet feeding unit 5, an image forming unit 6, a fixing unit 7, and a sheet refeeding unit 8 in an image forming apparatus main body 4.

  The sheet feeding unit 5 includes a plurality of sheet feeding cassettes 10, a pickup roller 11 disposed corresponding to each sheet feeding cassette 10, a feeding roller 12, a retard roller 13, and a registration roller pair 14. Is arranged. In each paper feed cassette 10, a plurality of sheets P are stored in a stacked state and fed by a pickup roller 11. The fed sheet P is prevented from being double-fed by the feeding roller 12 and the retard roller 13, and the topmost sheet P is brought into contact with the nip of the resist roller pair 14 that is stopped. The skew is corrected and paused. The temporarily stopped sheet P is then registered in synchronization with the toner image on the intermediate transfer belt (endless belt) 15 being conveyed to the secondary transfer portion T2 as the intermediate transfer belt 15 rotates in the direction of arrow R15. Supplied to the secondary transfer portion by the rotation of the roller pair 14.

  In the image forming section 6, four image forming stations 16M, 16C, 16Y, 16BK and an intermediate transfer unit 2 are disposed. The four image forming stations sequentially form magenta (M), cyan (C), yellow (Y), and black (BK) image forming stations 16M, 16C, 16Y, in order from the upstream side in the rotation direction of the intermediate transfer belt. 16BK is arranged. These four color image forming stations 16M, 16C, 16Y, and 16BK are similarly configured. The magenta image forming station 16M will be described as an example. The image forming station 16M has a photosensitive drum (image carrier) 17, a charger 18, an exposure device 20, a developing device 21, and a cleaning device 23. On the other hand, the intermediate transfer unit 2 includes a transfer frame 24 and a plurality of rollers rotatably supported by the transfer frame 24, that is, a drive roller 25, a driven roller 26, a primary transfer roller 22, and a secondary transfer counter roller 27. , A plurality of tension rollers and the like, and an endless intermediate transfer belt 15 stretched around these rollers. The intermediate transfer belt 15 rotates in the arrow R15 direction by the rotation of the driving roller 25 in the arrow direction (clockwise in FIG. 1). The entire intermediate transfer unit 2 is configured to be detachable from the image forming apparatus main body 4 from the front side, for example.

  In the magenta image forming station 16M, the photosensitive drum 17 is rotationally driven by a driving means (not shown) at a predetermined process speed (circumferential speed) in an arrow direction (counterclockwise in FIG. 1), and its surface (outer peripheral surface). ) Are uniformly charged to a predetermined polarity and potential by the charger 18. The surface of the photosensitive drum 17 after charging is exposed according to image information by the exposure device 20, and the charge of the exposed portion is removed to form an electrostatic latent image. This electrostatic latent image is developed as a magenta toner image by the developing device 21 with magenta toner attached thereto. The magenta toner image is transferred onto the intermediate transfer belt 15 by the primary transfer roller 22 at the primary transfer portion T1. After the toner image has been transferred, the transfer residual toner remaining on the surface of the photosensitive drum 17 is removed by the cleaning device 23 and used for the next image formation.

  Similarly, cyan, yellow, and black toner images formed on the respective photosensitive drums 17 at the cyan, yellow, and black image forming stations 16C, 16Y, and 16BK are transferred to the primary transfer roller at the respective primary transfer portions. 22 is primarily transferred onto the magenta toner image on the intermediate transfer belt 15 so as to be sequentially superimposed. The four color toner images superimposed on the intermediate transfer belt 15 in this way are conveyed to the secondary transfer portion T <b> 2 by the rotation of the intermediate transfer belt 15. In parallel with this, the pair of registration rollers 14 rotates to supply the sheet P to the secondary transfer portion T2. The four color toner images on the intermediate transfer belt 15 are secondarily transferred collectively onto the sheet P by the secondary transfer roller 28. The residual toner remaining on the surface of the intermediate transfer belt 15 after the secondary transfer is removed by the belt cleaner 30. On the other hand, the sheet P after the toner image is transferred is conveyed to the fixing unit 7 by the conveyance belt 31.

  The fixing unit 7 is provided with a fixing device 34 having a fixing roller 32 and a pressure roller 33 that is pressed against the fixing roller 32 and constitutes a fixing nip N. When the sheet P conveyed to the fixing device 34 passes through the fixing nip portion N, it is heated and pressed to fix the toner image on the surface. The sheet P after the toner image is fixed is discharged onto a paper discharge tray 36 by a paper discharge roller pair 35. Thereby, the four-color full-color image formation on one side of one sheet P is completed.

  When image formation is also performed on the back side, the sheet P that has been turned upside down by the flappers 37 and 38 disposed in the sheet refeeding unit 8, the reversing path 40, and the like passes through the refeeding path 41 and the like. Then, the toner image is supplied again to the image forming unit 6, and the toner image is transferred to the back surface in the same manner as described above. After that, the toner image is fixed and then discharged onto the paper discharge tray 36. This is the end of the description of the image forming apparatus 3.

  The meandering correction mechanism 1 according to the present invention is attached to a driven roller 26 on which an intermediate transfer belt 15 is stretched, and corrects meandering of the intermediate transfer belt 15. Here, as described above, the intermediate transfer belt 15 is a constituent element of the intermediate transfer unit 2, and is stretched around a plurality of rollers rotatably supported by the transfer frame 24. The meandering correction mechanism 1 is attached to one end of the roller shaft 42 of the driven roller 26 which is one of the plurality of rollers.

  2 and 3, the meandering correction mechanism 1 includes a motor 50, a solid cam 51, a swing arm 52, a compression spring 53 as a cam biasing member, and a tension spring 54 as a pressing means. It has.

  The motor 50 is supported by the transfer frame 24 so that its output shaft (cam shaft) 55 is substantially parallel to the roller shaft 42 of the driven roller 26. As the motor 50, a step motor capable of obtaining a rotation angle corresponding to the number of input pulses can be used. A servo motor can also be used. A solid cam 51 is attached to the output shaft 55 of the motor 50.

  The three-dimensional cam 51 has an external shape such that the outer peripheral surface (outer peripheral portion) of the truncated cone is stepped. A cam surface 56 having a predetermined width is spirally formed on the outer peripheral surface of the three-dimensional cam 51. Here, the predetermined width refers to a width that can be effectively rolled without disengaging a roller (contact portion) 70 of the swing arm 52 described later. Of the two end faces in the direction of the output shaft 55 in the three-dimensional cam 51, when the side with the smaller end face is the small diameter part 57 and the side with the larger end face is the large diameter part 58, the cam surface 56 is From the small diameter part 56 to the large diameter part 57, it is formed in a spiral shape so that the distance from the output shaft 55 gradually increases. The cam surface 56 has an end edge 60 on the small diameter portion 56 side and an end edge 61 on the large diameter portion 57 side. A guide surface 62 is erected vertically. The guide surface 62 is formed in a spiral shape along the cam surface 56 in the same manner as the cam surface 56. As shown in FIG. 4, in the present embodiment, the cam surface 56 and the guide surface 62 are formed over almost three rounds of the three-dimensional cam 51. Of the cam surface 56, the end located closest to the small diameter portion 57 is the start end 63, the end located closest to the large diameter portion 58 is the end end 64, and further from the center of the output shaft 55 to the start end 63. If the distance from the center of the output shaft 55 to the end portion 64 is d2, the cam surface 56 makes three rounds, that is, by rotating 1080 degrees (= 360 degrees × 3), the lift amount is It will increase by d2-d1. Further, in this embodiment, the cam surface is viewed from the direction in which the first round 56a and the second round 56b, and the second round 56b and the third round 56c are orthogonal to the output shaft 55. , Appear to be adjacent. That is, the first round 56a and the second round 56b are connected by the guide surface 62 while forming a step. The same applies to the second round 56b and the third round 56c. The height of the guide surface 62 as a step, that is, the height of the guide surface 52 in the radial direction is such that when the guide surface 62 is pressed against the roller 70 of the swing arm 52 by a compression spring 53 described later, the roller 70 is moved. The height is set so as not to deviate from the guide surface 62. In the present embodiment, the three-dimensional cam 51 is movable in the direction along the output shaft 55 with the large-diameter portion 58 facing the motor 50 side with respect to the output shaft 55 of the motor 50, and in the circumferential direction. It is attached non-rotatably. That is, the three-dimensional cam 51 rotates in the same direction as the output shaft 55 rotates, and can move in the axial direction.

  As shown in FIG. 2A, the swing arm 52 is formed in a plate shape and is supported so as to be swingable. The oscillating arm 52 is formed in a rectangular plate shape having a horizontal dimension that is longer than a vertical dimension. A shaft (swinging fulcrum) 65 is passed through in the front-rear direction substantially at the center of the swinging arm 52 in the vertical and horizontal directions. The shaft 65 is supported on the base end side by the transfer frame 24 and is arranged substantially in parallel with the roller shaft 42 described above. The tip end side penetrates the swing arm 52 and is attached with a stopper (not shown). Therefore, the swing arm 52 is prevented from unnecessarily moving in the front-rear direction. The shaft 65 is the swing center of the swing arm 52.

  One end portion (left end portion in FIG. 2) of the swing arm 52 is a bearing portion 68 that rotatably supports one end portion 66 of the roller shaft 42. That is, the one end portion 66 of the roller shaft 42 penetrates one end portion of the swing arm 52 from the rear to the front, and the retainer 67 is attached. As a result, when the swing arm 52 swings about the above-described shaft 65, the one end portion 66 of the roller shaft 42 moves up and down substantially in the vertical direction, that is, in the direction substantially perpendicular to the tension applying direction to the intermediate transfer belt 15. Go up and down. The other end portion of the roller shaft 42 is rotatably supported by a normal bearing (not shown), and when the one end portion 66 of the roller shaft 42 moves up and down, the roller shaft 42 is inclined. The inclination angle of the roller shaft 42 is approximately 1 degree in the vertical direction, and the length of the roller shaft 42 is sufficiently long with respect to the inclination angle (for example, about 350 mm).

  At the other end (right end in FIG. 2) of the swing arm 52, a roller 70 serving as a contact portion is rotatably supported. The roller 70 is pressed substantially from above with respect to the cam surface 56 of the three-dimensional cam 51 and from the front side with respect to the guide surface 62. In the present embodiment, the center of the output shaft 55 is configured to be located between the center of the roller shaft 42 and the rotation center of the roller 70. That is, when the roller 70 rolls following the cam surface 56 due to the rotation of the three-dimensional cam 51, the vertical movement amount of the rotation center of the roller 70 is the same as the vertical movement amount of the roller shaft 42 as it is. It is supposed to be. However, the moving direction in the vertical direction is reversed.

  The compression spring 53 as a cam urging member is interposed between the motor 50 and the three-dimensional cam 51 on the output shaft 55 of the motor 50. The solid cam 51 is urged toward the distal end side of the output shaft 55 by the compression spring 53. As a result, the guide surface 62 of the three-dimensional cam 51 is pressed against the side surface of the roller 70 of the swing arm 52. In other words, when the biased guide surface 62 presses the roller 70, the roller 70 is prevented from being detached from the cam surface 62.

  In this embodiment, the tension spring 54 as a pressing means is attached to a part (not shown) of the transfer frame 24 on the base end side (upper end side), and on the left end side of the swing arm 52 on the front end side (lower end side). And attached to the upper end side. As a result, the swing arm 52 is biased upward on the left end side with the bearing portion 68 around the shaft 65, and as a result, the right end side with the roller 70 is biased downward. It is pressed with an appropriate pressing force.

  In the meandering correction mechanism 1 configured as described above, the solid cam 51 is disposed at the home position when the driven roller 26 is disposed at the home position, that is, the roller shaft 42 of the driven roller 26 is disposed horizontally. The roller 70 of the swing arm 52 is brought into contact with the cam surface 56 of the three-dimensional cam 51 arranged. Here, the home position of the three-dimensional cam 51 is 1.5 when the three-dimensional cam 51 is in the arrow direction (counterclockwise) in FIG. 2B from the state where the roller 70 is in contact with the start end 63 of the cam surface 56. Rotate. That is, the state in which the roller 70 is in contact with the intermediate point of the second round 56 b on the spiral cam surface 56 for a total of three rounds is the home position of the three-dimensional cam 51. From this state, when the solid cam 51 rotates in the arrow direction (clockwise) in FIG. 2B, the distance from the output shaft 55 of the contact portion of the roller 70 on the cam surface 56 decreases. The right end side of the swing arm 52 descends around the shaft 65, the left end side rises, and the one end portion 66 of the roller shaft 42 rises. Conversely, when the three-dimensional cam 51 rotates in the direction of the arrow (counterclockwise) in FIG. 2B, the distance from the output shaft 55 of the contact portion of the roller 70 on the cam surface 56 increases. The right end side of the swing arm 52 is raised around the shaft 65, the left end side is lowered, and the one end portion 66 of the roller shaft 42 is lowered. By repeating the forward / reverse rotation of the motor 50 as appropriate based on the output of the meandering amount detection device 80 described below, the end of the roller shaft can be raised and lowered to suppress meandering of the intermediate transfer belt 15. .

  The meandering amount detection device 80 will be described with reference to FIGS. In these drawings, the intermediate transfer belt 15 is illustrated in a simplified manner. The meandering amount detection device 80 includes an inclined shaft 81 supported by the transfer frame 24 in the vicinity of the end of the intermediate transfer belt 15 in the belt width direction, an inclined roller 82 supported rotatably by the inclined shaft 81, A film encoder 83 integrated with the inclined roller 82 and a photo interrupter for detecting a slit 84 of the film encoder 83 are provided. The center of the inclined shaft 81 is set in a state inclined by 45 degrees with respect to the intermediate transfer belt 15 on a virtual plane orthogonal to the rotation direction of the intermediate transfer belt 15 (the direction of the arrow R15 in FIG. 9). The inclined roller 82 is formed in a truncated cone shape, and a through hole through which the inclined shaft 81 passes is formed at the center. As shown in FIG. 8, one bus line in the inclined roller 82 is parallel to the intermediate transfer belt 15 in the uppermost position. A circular film encoder 83 is attached to the lower surface of the inclined roller 82. The outer peripheral side of the film encoder 83 protrudes outward from the lower surface of the inclined roller 82, and a number of slits (notches) 84 are provided at equal intervals in the protruding portion. The photo interrupter 85 has a light emitting portion 86 on one side and a light receiving portion 87 on the other side so as to sandwich the protruding portion of the film encoder 83. When the slit 84 comes to a position corresponding to the light emitting unit 86 and the light receiving unit 87 with the rotation of the inclined roller 82, the light emitted from the light emitting unit 86 passes through the slit 84 and reaches the light receiving unit 87. . On the other hand, when the portion other than the slit 84 comes to the corresponding position, the light from the light emitting portion 86 does not reach the light receiving portion 87. By counting the number of slits 84 per unit time by the photo interrupter 85, the number of rotations of the inclined roller 82 can be detected.

  On the edge of the intermediate transfer belt 15 in the belt width direction, a convex portion 88 having a triangular cross section is formed toward the back surface. The convex portion 88 contacts the generatrix of the inclined roller 82 and rotates the inclined roller 82. When the intermediate transfer belt 15 meanders, the position of the convex portion 88 moves along the generatrix. For example, when the intermediate transfer belt 15 meanders in the direction of the arrow a, the convex portion 88 comes into contact with the portion of the bus bar on the large diameter side of the inclined roller 82, so that the rotational speed of the inclined roller 82 is reduced. On the other hand, if the intermediate transfer belt 15 meanders in the direction of the arrow b, the convex portion 88 comes into contact with the smaller diameter side of the inclined roller 82 in the bus line, and the rotational speed of the inclined roller 82 increases. Therefore, the meandering amount of the intermediate transfer belt 15 and the meandering speed in the direction of the arrow a or the direction of the arrow b can be detected by detecting the rotational speed of the inclined roller 82 by the photo interrupter 85.

  The detection result of the meandering amount detection device 80 is transmitted to the control means 90 shown in FIG. The control means 90 has a storage means (not shown). In this storage means, the relationship between the detection result of the meandering amount detection device 80 and the rotation angle of the motor 50 corresponding thereto is stored as a table. Stored. Based on the detection result of the meandering amount detection device 80, the control means 90 controls the rotation angle of the motor 50 and rotates the three-dimensional cam 51 as compared with the data in the table. Thereby, the movement of the roller shaft 42 is controlled via the swing arm 52. By controlling the roller shaft 42, meandering of the intermediate transfer belt 15 is suppressed. At this time, since the predetermined lift amount is realized by three rounds of the three-dimensional cam 51, for example, when compared with a plate cam (peripheral cam) of the prior art, the lift is the same for the same rotation angle. Since the amount can be reduced, the movement of the one end portion 66 of the roller shaft 42 can be finely controlled. That is, the meandering of the intermediate transfer belt 15 can be corrected with high accuracy. In the above description, the predetermined lift amount is realized by three rounds of the three-dimensional cam 51. However, in principle, the effect can be obtained if at least one round of the three-dimensional cam 51 is exceeded. Can do.

<Embodiment 2>
A second embodiment of the meandering correction mechanism 1A will be described with reference to FIGS. As shown in the figure, the meandering correction mechanism 1A includes a motor 50, two solid cams 51, a swing arm 91, and a bifurcated portion (contact portion) 92 of the swing arm 91 as a pressing means. I have.

  The motor 50 is the same as that in the first embodiment. That is, the motor 50 is supported by the transfer frame 24 so that the output shaft 55 is substantially parallel to the roller shaft 42 of the driven roller 26. As the motor 50, a step motor can be used.

  The three-dimensional cams 51A and 51B are attached to the output shaft 55 of the motor 50 so as to be axially movable and circumferentially immovable in a state where the two cams are joined so that the respective small diameter portions 57 are aligned. Yes. The shape of each of the three-dimensional cams 51A and 51B is the same as that of the three-dimensional cam 51 of the first embodiment, and a detailed description thereof will be omitted. However, each of the three-dimensional cams 51A and 51B has a helical cam surface 56 and a guide surface 62.

  The swing arm 91 is formed in a substantially plate shape that is long in the left-right direction, and is swingably supported by a shaft 65 that protrudes forward from the transfer frame 24 at substantially the center in the left-right direction, as in the first embodiment. ing. A bearing portion that rotatably supports one end portion 66 of the roller shaft 42 of the driven roller 26 is formed on the left end side. On the right end side of the swing arm 91, a bifurcated portion 92 is formed as a pressing means. The bifurcated portion 92 is configured by a plate-like upper clamping portion 93 and a lower clamping portion 94 that extend rightward. The upper clamping portion 93 and the lower clamping portion 94 are formed in parallel to each other, and the position in the front-rear direction is back and forth from the center C in the front-rear direction of the swing arm 91 (see the dashed line in FIG. 5B). It is arranged so that it can be distributed. The upper clamping portion 93 contacts the cam surface 56 and the guide surface 62 of the three-dimensional cam 51A on the side close to the motor, and the lower clamping portion 94 contacts the gum surface 56 and the guide surface 62 of the three-dimensional cam 51B on the side far from the motor. It comes to contact.

  Further, the distance in the height direction between the upper clamping portion 93 and the lower clamping portion 94 is set to be constant. This interval is such that when the upper clamping portion 93 comes into contact with the portion of the cam surface 56 of the three-dimensional cam 51A that is farthest from the output shaft 55, the lower clamping portion 94 of the cam surface 56 of the three-dimensional cam 51B The portion that is closest to the output shaft 55 comes into contact. On the contrary, when the upper clamping portion 93 comes into contact with the portion of the cam surface 56 of the three-dimensional cam 51A that is the closest to the output shaft 55, the lower clamping portion 94 of the cam surface 56 of the three-dimensional cam 51B Of these, the portion farthest from the output shaft 55 comes into contact. As described above, in the swing arm 91 having the bifurcated portion 92 constituted by the upper clamping portion 93 and the lower clamping portion 94, one of the upper clamping portion 93 and the lower clamping portion 94 is always in contact with the cam surface 56. Thus, a so-called positive cam is formed. For this reason, the tension spring 54 as a pressing means for urging the swing arm 52 against the cam surface 56 of the three-dimensional cam 51, which is necessary in the first embodiment, is unnecessary. That is, the forked portion 92 acts as a pressing means.

  Also in the meandering correction mechanism 1A of the present embodiment, the same operational effects as those of the first embodiment can be obtained. That is, since the three-dimensional cams 51A and 51B can reduce the lift amount with respect to the same rotation angle as compared with the plate cam (peripheral cam) of the prior art, the movement of the one end portion 66 of the roller shaft 42 can be performed. It can be finely controlled. That is, the meandering of the intermediate transfer belt 15 can be corrected with high accuracy.

  In the first embodiment described above, the solid cam 51 is configured to be movable in the axial direction and the swing arm 52 is configured to be immovable in the axial direction. However, the reverse is also possible. 2A, the shaft 65 is extended to the front side, a stopper 95 is provided, and a compression spring 96 as a swing arm urging member is provided between the stopper 95 and the swing arm 52. To intervene. As a result, the entire swing arm 52 can be urged backward. On the other hand, the three-dimensional cam 51 is fixed to the output shaft 55 of the motor 50 so as not to move in the axial direction. Further, the compression spring 53 is omitted. Thereby, there can exist an effect substantially equivalent to Embodiment 1. FIG. In the second embodiment, similarly, the three-dimensional cams 51A and 51B can be configured to be immovable in the axial direction, and the swing arm 91 can be configured to be movable in the axial direction.

  In the first and second embodiments described above, the shaft 65 serving as the swing center of the swing arms 52 and 91 is set between the bearing portion 68 and the roller 70 or the bifurcated portion 92. The swing arms 52 and 91 are extended to the left, and a shaft serving as a swing center is disposed on the left side of the bearing portion 68. Conversely, the swing arms 52 and 91 are extended to the right. It is also possible to arrange an axis serving as a swing center on the right side of the roller 70 or the bifurcated portion 92. However, when the swing arm 52 is used, the position of the tension spring 54 is appropriately changed so that the roller 70 is pressed against the cam surface 56.

  In the above description, the meandering correction mechanism 1, 1 </ b> A according to the present invention is applied to the intermediate transfer belt 15 as an example. However, the meandering correction mechanism 1, 1 </ b> A according to the present invention is not limited to this, For example, in the tandem four-color image forming apparatus 3, a conveyance belt (not shown) that carries the sheet P on the surface and conveys the sheet P to the image forming station of each color, or in the single-color image forming apparatus 3, the sheet P is formed on the surface. The present invention can also be applied to a conveying belt that is carried and conveyed, a photosensitive belt formed in a belt shape, and the like.

  In the above description, the meandering correction mechanism 1, 1 </ b> A according to the present invention is described as an example applied to a four-color full-color image forming apparatus 3 of an electrophotographic system, a tandem system, and an intermediate transfer system. The meandering correction mechanisms 1 and 1A according to the invention are not limited to this, and can be applied to various image forming apparatuses having an endless belt such as an ink jet type image forming apparatus.

  The present invention is not limited to the intermediate transfer belt 15 and the image forming apparatus 3, and can be widely used to correct meandering of a general endless belt.

2 is a diagram schematically showing an internal configuration of the image forming apparatus 3 when viewed from the front side (a side where a user is positioned when the image forming apparatus 3 is used). FIG. It is a figure explaining the meandering correction mechanism 1 of Embodiment 1, (a) is a front view, (b) is a top view. It is the perspective view which looked at the meandering correction mechanism 1 of Embodiment 1 from the diagonally lower right side of the front side. It is a perspective view of a solid cam. It is a figure explaining the meandering correction mechanism 1 of Embodiment 2, (a) is a front view, (b) is a front view, (c) is a right view. It is the perspective view which looked at the meandering correction mechanism 1 of Embodiment 2 from the diagonally left upper side of the front side. FIG. 6 is a perspective view for explaining a swing arm according to a second embodiment. 4 is a cross-sectional view in a direction orthogonal to the rotation direction of the intermediate transfer belt 15 for explaining the meandering amount detection device. FIG. It is a perspective view explaining a meandering amount detection apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,1A ... Meander correction mechanism, 2 ... Intermediate transfer unit, 3 ... Image forming apparatus, 4 ... Image forming apparatus main body, 5 ... Sheet feeding part, 6 ... Image forming part, 7 ... Fixing , 8... Sheet refeeding section, 15... Intermediate transfer belt (endless belt), 17... Photosensitive drum (image carrier), 24... Transfer frame, 26. ... Roller shaft, 50 ... Motor, 51, 51A, 51B ... Solid cam, 52, 91 ... Swing arm, 53 ... Compression spring (cam biasing member), 54 ... Tension spring (spring member, pressure) Means), 56... Cam surface, 62... Guide surface, 65... Shaft (swinging fulcrum), 57... Small diameter portion, 66. (Contact portion), 92... Forked portion (pressing means, contact portion), 93... Upper clamping portion, 94. Lifting unit, 96 ...... compression spring (with the swing arm urging member), P ...... sheet

Claims (8)

Among a plurality of rollers on which an endless belt is stretched, the roller shaft is attached to one end portion of a roller shaft of one roller, and the one end portion of the roller shaft is moved in a direction substantially perpendicular to the roller shaft, In the meandering correction mechanism for correcting the meandering of the endless belt,
A motor whose rotation angle can be controlled;
A solid cam that is rotated by the motor and has a cam surface and a guide surface on an outer peripheral portion and is movable in a cam shaft direction substantially parallel to the roller shaft, the cam surface being a predetermined direction of the solid cam The guide surface is formed at one end of the cam surface in the direction of the cam shaft, the distance from the cam shaft gradually increasing with the rotation of the cam. The three-dimensional cam that is erected and spirally formed along the cam surface;
A swing arm that is swingably supported by a swing fulcrum substantially parallel to the roller shaft, the bearing portion rotatably supporting one end portion of the roller shaft, the cam surface of the solid cam, and the guide The swing arm having an abutting portion capable of contacting and separating from a surface;
A cam biasing member that biases the solid cam and presses the guide surface against the contact portion of the swing arm;
Pressing means for pressing the abutting portion of the swing arm against the cam surface;
A meandering correction mechanism characterized by that. Among a plurality of rollers on which an endless belt is stretched, the roller shaft is attached to one end portion of a roller shaft of one roller, and the one end portion of the roller shaft is moved in a direction substantially perpendicular to the roller shaft, In the meandering correction mechanism for correcting the meandering of the endless belt,
A motor whose rotation angle can be controlled;
A solid cam that is rotated by the motor and has a cam surface and a guide surface on an outer peripheral portion and is movable in a cam shaft direction substantially parallel to the roller shaft, the cam surface being a predetermined direction of the solid cam The guide surface is formed at one end of the cam surface in the direction of the cam shaft, the distance from the cam shaft gradually increasing with the rotation of the cam. The three-dimensional cam that is erected and spirally formed along the cam surface;
A swing arm that is swingably supported by a swing fulcrum substantially parallel to the roller shaft, the bearing portion rotatably supporting one end portion of the roller shaft, the cam surface of the three-dimensional cam, and the guide An oscillating arm having an abutting portion capable of contacting and separating from the surface;
An arm biasing member that biases the swing arm and presses the contact portion of the swing arm against the guide surface;
Pressing means for pressing the abutting portion of the swing arm against the cam surface;
A meandering correction mechanism characterized by that. The swing fulcrum is disposed between the bearing portion and the contact portion in the swing arm,
The meandering correction mechanism according to claim 1 or 2, characterized in that The pressing means is a spring member that urges the swing arm to press the contact portion against the cam surface.
The meandering correction mechanism according to any one of claims 1 to 3, wherein the meandering correction mechanism is provided. The two three-dimensional cams are coupled so that the small diameter side where the distance of the cam surface from the cam shaft is close to each other, and the abutting portion of the swing arm is separated from an upper holding portion and a lower The upper clamping part is brought into contact with the cam surface of one of the three-dimensional cams, and the lower clamping part is brought into contact with the cam surface of the other three-dimensional cam. Abutting and sandwiching the cam surface between the upper clamping part and the lower clamping part,
The meandering correction mechanism according to any one of claims 1 to 3, wherein the meandering correction mechanism is provided. In an intermediate transfer unit comprising a transfer frame, a plurality of rollers rotatably supported by the transfer frame, and an intermediate transfer belt stretched around the plurality of rollers,
A meandering correction mechanism that corrects meandering of the rotating intermediate transfer belt by moving one end of a roller shaft of one of the plurality of rollers in a direction substantially perpendicular to the roller shaft;
The meandering correction mechanism is the meandering correction mechanism according to any one of claims 1 to 5.
An intermediate transfer unit characterized by that. In an image forming apparatus including a sheet feeding unit that feeds a sheet and an image forming unit that forms an image on a sheet supplied from the sheet feeding unit,
The image forming unit includes:
An image carrier on which a toner image is formed on the surface;
An intermediate transfer belt that transfers the toner image formed on the surface of the image carrier and transfers the transferred toner image to a sheet;
A meandering correction mechanism for correcting meandering of the intermediate transfer belt,
The meandering correction mechanism is the meandering correction mechanism according to any one of claims 1 to 5.
An image forming apparatus. In an image forming apparatus including a sheet feeding unit that feeds a sheet and an image forming unit that forms an image on a sheet supplied from the sheet feeding unit,
The image forming unit includes:
An image carrier on which a toner image is formed on the surface;
A conveyor belt that carries and conveys a sheet onto which a toner image formed on the surface of the image carrier is transferred;
A meandering correction mechanism for correcting meandering of the conveyor belt,
The meandering correction mechanism is the meandering correction mechanism according to any one of claims 1 to 5.
An image forming apparatus.

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