JP2010169917A - Belt conveyance device, image forming apparatus and belt meandering control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt conveyance device for coping with deviation on any side out of right and left sides in a width direction of a belt with simple constitution, and improving separability of a recording medium from the belt without deteriorating quality of an image, and an image forming apparatus and a belt meandering control method. <P>SOLUTION: The belt conveyance device includes: the belt that is tensioned and laid on a belt driving roller and a tensioning and laying roller; a variable speed roller that abuts on the inside of the belt and includes a spiral projected line formed on the surface thereof; a rotating and driving means that drives and rotates the variable speed roller; a meandering detection means that detects meandering of the belt; and a rotating and driving control means that controls the rotating and driving means based on a result of detection by the meandering detection means. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a belt conveying device, an image forming apparatus, and a belt meandering control method provided in an image forming apparatus such as a copying machine, a facsimile machine, and a printer.

  In an electrophotographic image forming apparatus, a belt transfer apparatus using an endless belt for transferring a toner image is used. The schematic configuration is such that a belt driving roller and a tension roller are arranged on the inner peripheral surface of the endless belt, and the endless belt is rotationally driven by friction with the belt driving roller. In such a belt transfer device, for example, the outer diameter varies due to a manufacturing error of the roller, or the parallelism of the mounting is distorted due to the mounting error, and the belt meanders. In the image forming system, since such belt meandering causes an image shift at the time of transfer and affects image quality, belt meandering is regulated by various means. In such an image forming apparatus, it has been proposed to arrange a separation device for separating the recording medium on the belt in order to prevent the occurrence of a paper jam due to the winding of the recording medium around the belt.

  Japanese Patent Application Laid-Open No. 2006-71818 discloses a belt transfer device in which an endless belt for transferring a toner image from an image carrier is stretched by a plurality of rollers, and at least one of the plurality of rollers. A belt meandering prevention mechanism in which a roller surface of a roller is formed by a plurality of spiral bands having different turning directions is disclosed.

  Japanese Patent Laid-Open No. 7-92820 discloses an image forming apparatus in which a recording medium is separated and conveyed by a transfer belt to form an image, and a backup roller having a large diameter in the axial direction is provided on a backup roller of a recording medium separating portion of the transfer belt. Separation member having a claw portion that is arranged with a separation roller having a small-diameter concave portion and that protrudes closer to the axis than the outer diameter of the convex portion at a position corresponding to the concave portion of the separation roller, in contact with the transfer belt surface. A belt conveying device in which is arranged is disclosed.

  Japanese Patent Application Laid-Open No. 11-334924 discloses an image forming apparatus that drives a belt stretched by a plurality of stretching rollers including a driving roller and conveys a recording medium held by the belt. When the recording medium is separated from the driving roller unit, the driving unit rotates together with the driven unit driven by the shaft, and the driven unit has a convex portion having a larger diameter than the driving unit and a concave portion having a smaller diameter than the driving unit. In addition, there is disclosed a belt conveying device in which the recording medium is corrugated in the axial direction of the driving roller, and a force for separating the recording medium from the belt is applied to improve the separation performance of the recording medium from the belt.

JP 2006-71818 A In JP-A-7-92820, Japanese Patent Laid-Open No. 11-334924

  However, the belt meandering prevention mechanism disclosed in Japanese Patent Application Laid-Open No. 2006-71818 forms a plurality of spiral bands with different turning directions by a developed V-shaped spiral band. There is a problem that a large conveying force generates stress that causes the belt to expand or contract, and a problem that a belt shift cannot be returned when the belt shift occurs.

  The belt conveying device disclosed in Japanese Patent Application Laid-Open No. 7-92820 requires precise adjustment of the position of the claw portion in order to install the claw portion in a non-contact manner with the belt, which requires high part accuracy and increases the cost. It is a factor. In addition, the recording medium is separated from the portion having the nail portion, and the separation of the recording medium is delayed in the portion without the nail portion, so that image unevenness due to the separation discharge occurs in the portion without the nail portion and the nail portion. Furthermore, when separating the recording medium, the image portion on the recording medium may be disturbed by rubbing the nail portion, and the separation of the recording medium from the belt and obtaining a high-quality image are obtained. There is a problem that it is difficult to achieve both.

  Further, in the belt conveying device disclosed in Japanese Patent Application Laid-Open No. 11-334924, the driving roller is clearly separated in the axial direction by the driving portion and the driven portion having the concavo-convex portion, and from the driven portion having the concavo-convex portion. Since the recording medium is separated and the separation of the recording medium from the driving unit is delayed, image unevenness due to separation discharge occurs in the driven unit and the driving unit having uneven portions. Further, since the convex portion of the driven portion is always in contact with the belt, the surface of the belt is damaged and the image quality is deteriorated.

  The present invention solves the above-described problems of the prior art, and can be applied to the left and right sides of the belt in the simple direction with a simple configuration, and can be used from a recording medium belt without degrading image quality. It is an object of the present invention to provide a belt conveying device, an image forming apparatus, and a belt meandering control method capable of improving the separability of the belt.

  In order to solve the above problems, the belt conveying device of the present invention has a variable speed with a belt stretched between a belt driving roller and a stretching roller, and a spiral protrusion formed on the surface in contact with the inside of the belt. A rotation drive means for rotating the speed variable roller, a meander detection means for detecting meandering of the belt, and a rotation drive control means for controlling the rotation drive means based on a detection result of the meander detection means; It is characterized by providing. By making the rotational speed of the speed variable roller variable with respect to the peripheral speed of the belt, there is a speed difference between the rotational speed of the speed variable roller and the peripheral speed of the belt, and the force in the direction perpendicular to the conveying direction on the belt. The belt meandering can be controlled.

  In the belt conveyance device of the present invention, the speed variable roller is a tension roller. Since the variable speed roller can also be used as a belt tension roller, the arrangement of the rollers can be reduced.

  Further, the belt conveying device of the present invention is characterized in that the variable speed roller is brought into contact with a flat portion of the belt. The position of the variable speed roller can be selected in many places with little influence on image formation.

  In the belt conveyance device of the present invention, the rotational drive control unit may be configured so that a speed difference is generated between a peripheral speed of the belt and a rotational speed of the speed variable roller according to a detection result of the meandering detection unit. It is characterized by controlling the rotation speed of the. The meandering control can be quickly performed according to the deviation of the belt.

  In the belt conveying apparatus of the present invention, the belt is used for conveying a recording medium, and the speed variable roller is disposed at a position where the recording medium is separated from the belt. The variable speed roller can be provided with meandering control and recording medium separation functions.

  Moreover, the belt conveyance device of the present invention is characterized in that the hardness of the spiral protrusion of the speed variable roller is larger than the hardness of the belt. When the speed variable roller contacts the belt, the belt deforms spirally along the spiral protrusion 102, and the meandering control and the separation of the recording medium due to the speed difference can be more effectively performed.

  The image forming apparatus of the present invention includes a latent image carrier on which an electrostatic latent image is formed, a developing device that develops the electrostatic latent image with toner and develops the toner image on the latent image carrier, A transfer belt to which the toner image of the latent image carrier is transferred, a transfer device for transferring the toner image on the transfer belt to a recording medium, and a fixing device for fixing the toner image on the recording medium, Any one of the belt conveyance devices described above is used as a recording medium conveyance unit of the transfer device. The meandering of the transfer belt at the transfer portion is controlled, and image shift during transfer can be prevented.

  The image forming apparatus of the present invention includes a latent image carrier on which an electrostatic latent image is formed, a developing device that develops the electrostatic latent image with toner and develops the toner image on the latent image carrier, A transfer belt to which the toner image of the latent image carrier is transferred, a transfer device for transferring the toner image on the transfer belt to a recording medium, and a fixing device for fixing the toner image on the recording medium, The fixing device includes a heating roller and a pressure belt, and the belt conveying device described in any one of the above is used as a recording medium conveying unit of the fixing device. The meandering of the belt at the fixing unit is controlled, and the occurrence of uneven fixing can be prevented.

  Further, the belt meandering control method of the present invention includes a belt that is stretched between a belt driving roller and a tension roller, a speed variable roller that is in contact with the inside of the belt and has a spiral protrusion formed on a surface thereof, and the speed A rotation drive means for rotating the variable roller; a rotation drive control means for controlling the rotation drive means; and a meandering detection means arranged in the width direction of the belt. A step of detecting a shift, a step of setting a speed difference between a peripheral speed of the belt and a rotation speed of the speed variable roller based on a detection result of the meandering detection unit, and the rotation driving according to the set speed difference And a step of controlling the rotation driving means by a control means. The meandering of the belt can be quickly controlled, and a high-quality image can be obtained.

1 is a diagram illustrating an entire embodiment of an image forming apparatus of the present invention. It is a figure which shows embodiment which applied this invention to the secondary transfer part. It is a figure which shows embodiment which applied this invention to the secondary transfer part. FIG. 3 is a diagram illustrating an embodiment in which the present invention is applied to a fixing unit. It is a figure which shows one Embodiment of a speed variable roller. It is a figure which shows the deformation | transformation state of the belt by contact | abutting to the belt of a spiral protrusion. (A) (b) It is a figure which shows the case where the rotational speed of a speed variable roller and the peripheral speed of a belt are the same. (A) (b) It is a figure which shows the case where the rotational speed of a speed variable roller is faster than the circumferential speed of a belt. (A) (b) It is a figure which shows the case where the rotational speed of a speed variable roller is slower than the circumferential speed of a belt. It is a figure for demonstrating the separation function of the recording medium of a speed variable roller. It is a figure which shows the arrangement | positioning state of the position sensor for the meandering control of a belt. It is a figure which shows the flowchart of the meandering control of a belt.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of an embodiment of an image forming apparatus according to the present invention.

  As shown in FIG. 1, the image forming apparatus 10 includes four image forming stations 15 (Y, M, C, K), an intermediate transfer belt 70, and a secondary transfer unit 80, and further includes a fixing unit 90, a user. And a display unit (not shown) formed of a liquid crystal panel, and a control unit (not shown) that controls these units and operates as an image forming apparatus.

  The image forming station 15 (Y, M, C, K) has a function of forming an image with toners of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Since the configuration of the image forming station 15 (Y, M, C, K) is the same, the image forming station 15Y will be described below.

  As shown in FIG. 1, the image forming station 15Y includes a charging unit 30Y, an exposure unit 40Y, a developing unit 50Y, and a primary transfer unit along the rotation direction of a photoconductor 20Y as an example of an image carrier. .

  The photoreceptor 20Y has a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and can rotate around a central axis. In the present embodiment, the photoreceptor 20Y rotates clockwise as indicated by an arrow. To do.

  The charging unit 30Y is a device for charging the photoconductor 20Y. From the exposure unit 40Y, a latent image is formed on the charged photoreceptor 20Y by irradiating a laser.

  The exposure unit 40Y includes a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and is charged with a modulated laser based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoconductor 20Y.

  The development unit 50Y is a device for developing the latent image formed on the photoreceptor 20Y using yellow (Y) toner. In the developing unit 50Y, a developing roller 51Y and a supply roller 52Y are disposed in a developing chamber to which toner is supplied from a replaceable toner cartridge. A regulating blade 53Y contacts the developing roller 51Y to thin the toner on the developing roller 51Y. Stratify.

  In the primary transfer unit, a primary transfer bias is applied by the primary transfer roller 65Y in the primary transfer portion B1, and the yellow toner image formed on the photoreceptor 20Y is transferred to the intermediate transfer belt 70. When the four color toners are sequentially transferred in the primary transfer portions B 1, B 2, B 3 and B 4, a full color toner image is formed on the intermediate transfer belt 70.

  The intermediate transfer belt 70 is an endless belt stretched around a belt driving roller 71a and driven rollers 71b, 71d, 71e, and 71f, and is rotationally driven while being in contact with the photoreceptor 20 (Y, M, C, K). The

  The secondary transfer unit 80 is a device for transferring a single color toner image or a full color toner image formed on the intermediate transfer belt 70 to a recording medium such as paper, film, or cloth.

  The fixing unit 90 is configured by a heating roller 90a and a pressure belt 90b, and is a device for fusing a single color toner image or a full color toner image transferred onto a recording medium to the recording medium to obtain a permanent image.

  Next, the operation of the image forming apparatus 10 configured as described above will be described. First, when an image signal and a control signal from a host computer (not shown) are input to the main controller of the image forming apparatus via an interface, the photoconductor 20Y and the developing unit are controlled by a unit controller based on a command from the main controller. The developing roller 51Y provided in 50Y, the intermediate transfer belt 70, and the like rotate. The photoconductor 20Y is sequentially charged by the charging unit 30Y at the charging position while rotating.

  The charged area of the photoconductor 20Y reaches the exposure position as the photoconductor 20Y rotates, and a latent image corresponding to yellow Y image information is formed in the area by the exposure unit 40Y.

  The latent image formed on the photoreceptor 20Y reaches the development position as the photoreceptor 20Y rotates, and is developed by the development unit 50Y. Thereby, a toner image is formed on the photoreceptor 20Y.

  The toner image formed on the photoconductor 20Y reaches the position of the primary transfer portion B1 as the photoconductor 20Y rotates, and is transferred to the intermediate transfer belt 70 by the primary transfer unit. At this time, in the primary transfer unit, a primary transfer voltage having a polarity opposite to the charging polarity of the toner is applied from the primary transfer roller 65Y. As a result, the four color toner images formed on the respective photoreceptors 20 (Y, M, C, K) are transferred to overlap the intermediate transfer belt 70, and a full color toner image is formed on the intermediate transfer belt 70. Is done.

  The intermediate transfer belt 70 is driven by transmitting a driving force from a belt driving means such as a motor via a belt driving roller 71a.

  The full color toner image formed on the intermediate transfer belt 70 is transferred to a recording medium such as paper by the secondary transfer unit 80. In the secondary transfer unit 80, a belt driving roller 71a as a backup roller and a secondary transfer roller 82 face each other with the intermediate transfer belt 70 interposed therebetween. A secondary transfer voltage having a polarity opposite to that of the toner is applied from the secondary transfer roller 82, and the toner image transferred to the intermediate transfer belt 70 is secondarily transferred to a recording medium. The recording medium is transported from the paper feed tray to the secondary transfer unit 80 via a paper feed roller, a gate roller 94, and a transport guide 94a.

  The recording medium on which the full color toner image is transferred by the secondary transfer unit 80 is conveyed to the fixing unit 90 via the conveyance guide 94b. The fixing unit 90 includes a heating element such as a halogen heater, the temperature of which is controlled to a predetermined fixing temperature, and a heating roller 90a that is rotationally driven, and a pressure belt that is stretched between two stretching rollers 90c and 90d. 90b. The toner image is fused to the recording medium by being heated and pressurized by the fixing unit 90. After passing through the fixing unit 90, the recording medium is discharged by a discharge roller 95 through a conveyance guide 95a.

  On the other hand, the photosensitive member 20 (Y, M, C, K) is neutralized by a neutralizing unit (not shown) after passing through the primary transfer portions B1, B2, B3, B4 to form the next latent image. To prepare for charging.

  An intermediate transfer belt cleaning device (not shown) is installed on the driven roller 71b side of the intermediate transfer belt 70 after the secondary transfer, and cleans the intermediate transfer belt 70 after the secondary transfer.

  FIG. 2 is a view showing an embodiment in which the variable speed roller 100 for belt meandering control according to the present invention is in contact with the inner flat portion of the intermediate transfer belt 70 of the secondary transfer unit 80.

  In the secondary transfer unit 80, a belt driving roller 71a is positioned between stretching rollers 71d and 71f around which the intermediate transfer belt 70 is wound, and the secondary transfer roller 82 is used as a backup roller with the belt driving roller 71a as a backup roller. To form a secondary transfer portion. The recording medium is conveyed to the secondary transfer portion via the gate roller 94 and the conveyance guide 94a, and a secondary transfer voltage having a polarity opposite to that of the toner is applied from the secondary transfer roller 82, and the toner transferred to the intermediate transfer belt 70 is transferred. Secondary transfer of the image to the recording medium. The recording medium on which the toner image is transferred is discharged by the discharging device 96. The moving direction of the intermediate transfer belt 70 is changed by a stretching roller 71d. The recording medium to which the toner image has been transferred is separated from the intermediate transfer belt 70 whose movement direction is changed by the stretching roller 71d, and is conveyed to the fixing unit 90, which is the next step, via the conveyance guide 94b.

  When the intermediate transfer bell 70 meanders, an image shift at the time of transfer occurs and the image quality is lowered. Further, if the recording medium after the secondary transfer is not separated from the intermediate transfer belt 70, the recording medium is wound around the tension roller 71d and a paper jam occurs. In particular, when the recording medium is thin paper, many paper jams occur due to winding. In order to prevent image quality deterioration and paper jam, a variable speed roller 100 having a belt meandering control function and a recording medium separation function is positioned at the end of the secondary transfer section and the recording medium conveyance path. Arranged so as to be in contact with the inner flat portion of the intermediate transfer belt 70 between the support rollers 71d. By arranging the variable speed roller 100 in contact with the flat surface inside the intermediate transfer belt 70, the meandering of the intermediate transfer belt 70 is controlled, and the recording medium after the secondary transfer is separated from the intermediate transfer belt 70, It is conveyed to the fixing unit 90 via the conveyance guide 94b. In the case of sharing only the belt meandering control function, the position of the variable speed roller 100 in contact with the inner flat portion of the intermediate transfer belt 70 is not limited to the secondary transfer portion shown in FIG. It may be between the secondary transfer portion and the primary transfer portion that have little influence on image formation.

  FIG. 3 is a diagram showing an embodiment in which the variable speed roller 100 for belt meandering control according to the present invention is a stretch roller. In this embodiment, a belt meandering control variable speed roller 100 that also serves as a tension roller is disposed at the position of the tension roller 71d positioned at the end of the recording medium conveyance path. Since the variable speed roller 100 also serves as a stretching roller, the arrangement of the rollers can be reduced, the meandering of the intermediate transfer belt 70 is controlled, and the recording medium after the secondary transfer is separated from the intermediate transfer belt 70, It is conveyed to the fixing unit 90 via the conveyance guide 94b. When only the belt meandering control function is shared, the position of the variable speed roller 100 as the stretching roller is not limited to the position shown in FIG. 3, and the primary transfer from the secondary transfer unit has little influence on image formation. It may be a stretch roller between the parts.

  FIG. 4 is a view showing an embodiment in which the variable speed roller 100 for belt meandering control according to the present invention is applied to the fixing unit 90.

  The fixing unit 90 includes a heating element such as a halogen heater, the temperature of which is controlled to a predetermined fixing temperature, and a heating roller 90a that is rotationally driven, and a pressure belt that is stretched between two stretching rollers 90c and 90d. 90b. If meandering occurs in the pressure belt 90b, uneven fixing occurs, which affects the image quality. In order to control the meandering of the pressure belt 90b and to improve the separation of the recording medium, the speed is applied to the flat portion inside the pressure belt 90b upstream of the stretching roller 90c located at the end of the recording medium conveyance path. The variable roller 100 is placed in contact. By arranging the variable speed roller 100 in contact with each other, the meandering of the pressure belt 90b is controlled, and the fixed recording medium is separated from the pressure belt 90b and conveyed to the paper discharge roller 95 through the conveyance guide 95a. The paper is discharged. A variable speed roller for belt meandering control and recording medium separation may also be used as the stretching roller 90c. When only the belt meandering control function is shared, the position of the speed variable roller 100 that contacts the flat surface inside the pressure belt 90b is not limited to the position shown in FIG. It may be a position between the tension rollers 90c and 90d.

  FIG. 5 is a view showing an embodiment of a variable speed roller 100 for belt meandering control according to the present invention.

  In the variable speed roller 100, a spiral protrusion is continuously formed on the surface of a cylindrical cylindrical body integrated with the shaft 101. A rotation driving means 103 is disposed at one end of the shaft 101 and is driven to rotate.

  The rotation drive means 103 is controlled by a rotation drive control unit (not shown) and makes the rotation speed of the speed variable roller 100 variable. As the rotation driving means 103, for example, a pulse motor whose rotation speed can be controlled by the number of pulses is used. Further, the hardness of the spiral protrusion 102 of the variable speed roller 100 is made larger than the hardness of the intermediate transfer belt 70 or the pressure belt 90b. As a result, when the speed variable roller 100 abuts against the intermediate transfer belt 70 or the pressure belt 90b, it is deformed in a spiral shape along the spiral protrusion 102 as shown in FIG.

  7 to 9 are diagrams for explaining the function of the belt meandering control of the speed variable roller 100.

  7A and 7B are diagrams illustrating a case where the rotational speed V1 of the speed variable roller 100 by the rotational driving unit 103 and the peripheral speed V2 of the intermediate transfer belt 70 or the pressure belt 90b are V1 = V2.

  When V1 = V2, a force in a direction perpendicular to the belt conveyance direction is not applied to the intermediate transfer belt 70 or the pressure belt 90b.

  FIGS. 8A and 8B are diagrams showing a case where the rotational speed V1 of the speed variable roller 100 by the rotational driving unit 103 and the peripheral speed V2 of the intermediate transfer belt 70 or the pressure belt 90b are V1> V2.

  In the case of V1> V2, the intermediate transfer belt 70 or the pressure belt 90b with which the spiral protrusion 102 of the speed variable roller 100 abuts depends on the speed difference between the speed variable roller 100 and the intermediate transfer belt 70 or the pressure belt 90b. As the reaction force, a force in an anti-spiral direction opposite to the spiral direction of the spiral protrusion 102 of the variable roller 100 is applied, and the intermediate transfer belt 70 is perpendicular to the belt conveyance direction indicated by the arrow in FIG. Alternatively, the pressure belt 90b is moved closer.

  FIGS. 9A and 9B are diagrams illustrating a case where the rotational speed V1 of the speed variable roller 100 by the rotational driving unit 103 and the peripheral speed V2 of the intermediate transfer belt 70 or the pressure belt 90b are V1 <V2.

  When V1 <V2, the intermediate transfer belt 70 or the pressure belt 90b with which the spiral protrusion 102 of the speed variable roller 100 abuts depends on the speed difference between the speed variable roller 100 and the intermediate transfer belt 70 or the pressure belt 90b. As a reaction force, a force in the spiral direction of the spiral protrusion 102 of the variable roller 100 is applied, and the intermediate transfer belt 70 or the pressure belt 90b is moved in a direction orthogonal to the belt conveyance direction indicated by the arrow in FIG. I will stop.

  A deviation in a direction perpendicular to the conveying direction of the intermediate transfer belt 70 or the pressure belt 90b is detected based on data of a position detection sensor arranged in the vicinity of the intermediate transfer belt 70 or the pressure belt 90b. Based on the detected data, the rotational drive means 103 is controlled by a rotational drive control means (not shown), and the rotational speed V1 of the recording medium separating roller 100 and the peripheral speed V2 of the intermediate transfer belt 70 or the pressure belt 90b. A speed difference is provided between them, and a force in a direction perpendicular to the belt conveyance direction is generated on the intermediate transfer belt 70 or the pressure belt 90b to correct the deviation of the belt. A belt meandering control method by the position sensor will be described later.

  FIG. 10 is a diagram illustrating a function of separating the recording medium from the belt of the variable speed roller 100.

  The speed variable roller 100 is disposed in contact with a separation portion of the recording medium 200 from the intermediate transfer belt 70 or the pressure belt 90b serving as a conveying unit for the recording medium 200. A spiral protrusion 102 is continuously formed on the surface of the variable speed roller 100. Since the hardness of the spiral protrusion 102 of the speed variable roller 100 is greater than the hardness of the intermediate transfer belt 70 or the pressure belt 90b, when the speed variable roller 100 contacts the intermediate transfer belt 70 or the pressure belt 90b. The intermediate transfer belt 70 or the pressure belt 90 b is deformed in a spiral shape along the spiral protrusion 102. As a result, a complicated undulation that the recording medium 200 cannot follow on the surface of the intermediate transfer belt 70 or the pressure belt 90b is generated, and a gap is formed between the recording medium 200 and the intermediate transfer belt 70 or the pressure belt 90b. The separability of the medium 200 from the intermediate transfer belt 70 or the pressure belt 90b can be improved.

  FIG. 11 is a diagram illustrating an arrangement state of the position sensors A, B, C, and D arranged on the intermediate transfer belt 70 or the pressure belt 90b for meandering control by the speed variable roller 100.

  The position sensors A, B, C, and D are arranged on a straight line along a direction orthogonal to the conveyance direction of the intermediate transfer belt 70 or the pressure belt 90b. As the position sensors A, B, C, and D, for example, a light emitting element and a light receiving element are used, and the intermediate transfer belt 70 or the pressure belt 90b is an optical path between the light emitting elements and the light receiving elements of the position sensors A, B, C, and D. The position of the end of the belt is detected by shutting off.

  FIG. 12 is a flowchart of meandering control of the intermediate transfer belt 70 or the pressure belt 90b by the position sensors A, B, C, and D in FIG.

  (1) First step: It is determined whether or not the intermediate transfer belt 70 or the pressure belt 90b is at the position of the position sensor A. If the determination is YES, the intermediate transfer belt 70 or the pressure belt 90b is on the right side. And move the belt to the left side at high speed. If the determination is NO, the process proceeds to the second step.

  (2) Second step: It is determined whether or not the intermediate transfer belt 70 or the pressure belt 90b is at the position of the position sensor B. If YES is determined, the intermediate transfer belt 70 or the pressure belt 90b is on the right side. The belt is moved to the left side at a low speed. If the determination is NO, the process proceeds to the third step.

  (3) Third step: It is determined whether or not the intermediate transfer belt 70 or the pressure belt 90b is at the position of the position sensor C. If the determination is YES, the intermediate transfer belt 70 or the pressure belt 90b is left and right. Judge not to stop and do not move the belt. When determination is NO, it transfers to a 4th process.

  (4) Fourth step: It is determined whether or not the intermediate transfer belt 70 or the pressure belt 90b is at the position of the position sensor DC. If it is determined YES, the intermediate transfer belt 70 or the pressure belt 90b is on the left side. The belt is moved slightly to the right at a low speed. When the determination is NO, it is determined that the intermediate transfer belt 70 or the pressure belt 90b is largely shifted to the left side, and the belt is moved at a high speed on the right side.

  10: image forming apparatus, 15 (Y, M, C, K): image forming station, 20 (Y, M, C, K): photoconductor, 30 (Y, M, C, K): charging unit, 40 (Y, M, C, K): exposure unit, 50 (Y, M, C, K): development unit, 65 (Y, M, C, K): primary transfer roller, 70: intermediate transfer belt, 71a: Belt drive roller, 71b, 71d, 71e, 71f: tension roller, 80: secondary transfer unit, 82: secondary transfer roller, 90: fixing unit, 90a: heating roller, 90b: pressure belt, 90c, 90d: Stretching roller, 94: gate roller, 94a, 94b: conveyance guide, 95: discharge roller, 95a: conveyance guide, 96: static elimination device, 100: variable speed roller, 101: shaft, 102: spiral ridge, 103: Drive Means, 200: recording medium

Claims (9)

A belt stretched between a belt drive roller and a stretch roller;
A variable speed roller that is in contact with the inside of the belt and has a spiral protrusion formed on the surface;
A rotation driving means for rotating the speed variable roller;
Meander detection means for detecting meandering of the belt;
Rotation drive control means for controlling the rotation drive means based on the detection result of the meander detection means;
A belt conveying device comprising: The belt conveyance device according to claim 1, wherein the speed variable roller is a tension roller. The belt conveyance device according to claim 1, wherein the speed variable roller is brought into contact with a flat portion of the belt. The rotation drive control means controls the rotation drive means so that a speed difference is generated between a peripheral speed of the belt and a rotation speed of the speed variable roller according to a detection result of the meandering detection means. The belt conveyance device according to any one of 1 to 3. 5. The belt conveyance device according to claim 1, wherein the belt is used for conveyance of a recording medium, and the speed variable roller is disposed at a position where the recording medium is separated from the belt. The belt conveying device according to any one of claims 1 to 5, wherein a hardness of the spiral protrusion of the speed variable roller is made larger than a hardness of the belt. A latent image carrier on which an electrostatic latent image is formed;
A developing device for developing the electrostatic latent image with toner and developing the toner image on the latent image carrier;
A transfer belt onto which the toner image of the latent image carrier is transferred;
A transfer device for transferring the toner image of the transfer belt to a recording medium;
A fixing device for fixing a toner image on the recording medium;
With
An image forming apparatus using the belt conveyance device according to claim 1 as a recording medium conveyance unit of the transfer device. A latent image carrier on which an electrostatic latent image is formed;
A developing device for developing the electrostatic latent image with toner and developing the toner image on the latent image carrier;
A transfer belt onto which the toner image of the latent image carrier is transferred;
A transfer device for transferring the toner image of the transfer belt to a recording medium;
A fixing device for fixing a toner image on the recording medium;
With
7. The image forming apparatus according to claim 1, wherein the fixing device includes a heating roller and a pressure belt, and the belt conveying device according to claim 1 is used as a recording medium conveying unit of the fixing device. A belt stretched between a belt drive roller and a stretch roller;
A variable speed roller that is in contact with the inside of the belt and has a spiral protrusion formed on the surface;
A rotation driving means for rotating the speed variable roller;
Rotation drive control means for controlling the rotation drive means;
Meander detection means arranged in the width direction of the belt;
With
Detecting the deviation of the belt by the meander detection means;
Setting a speed difference between the peripheral speed of the belt and the rotational speed of the speed variable roller based on the detection result of the meandering detection means;
Controlling the rotation drive means by the rotation drive control means according to the set speed difference;
A belt meandering control method characterized by comprising:

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