JP2014029449A - Belt conveyance device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt conveyance device realizing an image output at significantly high speed as well as preventing image distortion and color shift by securely correcting deviation and inclination of an endless belt, and thereby realizing an output of a significantly high quality image.SOLUTION: A belt conveyance device adjusts attitude of stretching means and moves one end of the stretching means with respect to the other end in a crossing direction crossing the width direction of an endless belt by first adjustment means. The belt conveyance device adjusts attitude of the other stretching means and moves one end of the stretching means with respect to the other end in a crossing direction crossing the width direction of the endless belt by second adjustment means. The endless belt is conveyed by belt driving means, and the position of the endless belt is controlled in two width directions by respectively driving the first and the second adjustment means independently. The friction coefficient between the stretching means moved by the first adjustment means and the endless belt is made larger than the friction coefficient between the other stretching means moved by the second adjustment means and the endless belt.

Description

  The present invention relates to an image forming apparatus used for a copying machine facsimile printer and the like, and more specifically, develops a latent image formed on an image carrier to make a visible image, and superimposes a plurality of visible images to form a multicolor image. The present invention relates to a belt conveying device and an image format device.

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, an image forming apparatus using an endless belt as an intermediate transfer member that is a transfer medium or a recording sheet that is a transfer medium is known. The belt is circulated and driven by a plurality of rollers. At this time, the belt shifts in the width direction crossing the belt conveyance direction, and the belt skew in which the belt conveyance direction is inclined in the width direction occurs. Sometimes.
When the belt skew occurs, the image forming position on the transfer medium such as the intermediate transfer member or the recording paper is displaced, which causes distortion of the image. Further, monochrome images of black (hereinafter referred to as K), yellow (hereinafter referred to as Y), magenta (hereinafter referred to as M), and cyan (hereinafter referred to as C) are formed, respectively. In a color image forming apparatus configured to obtain a color image by superimposing toner images on a transfer medium, a shift in image forming position appears as a color shift between the color toner images. All of these lead to degradation of image quality, and it is necessary to take some measures for belt skew in order to obtain a high-quality image.
In order to cope with the above problem, various methods have been proposed, and one of them is a method of providing a guide member near the endless belt.

However, the force in the width direction generated in the endless belt is regulated by causing the shift guide member provided on the belt surface to abut on the end surface of the belt conveying roller, thereby suppressing the shift of the endless belt. The belt skew caused by the deviation of the guide member in the width direction and the deviation of the end face of the conveying roller cannot be suppressed, and there is a disadvantage that image distortion and color deviation occur due to the positional deviation in the width direction.
Further, when the belt is driven at a high speed, a large external force is applied to the shift guide member, and the belt and the shift guide member are likely to buckle or break, and it is difficult to increase the image output speed.

On the other hand, in Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, and Patent Document 6, the belt deviation is adjusted based on the width direction position information of the endless belt member, and the width direction of the endless belt member By correcting the latent image forming position in the width direction on the image carrier based on the tilt information, it is possible to significantly speed up image output without using a configuration that obstructs high-speed belt driving such as a shift guide member. In addition to accurately detecting and controlling the endless belt shift, it is possible to accurately detect the skew of the endless belt and correct the image forming position to prevent image distortion and color misregistration, resulting in greatly improved output image quality. Is possible.
Further, in Patent Document 7, a plurality of detection means for detecting the position of the endless belt in the belt width direction, and the deviation and skew of the endless belt are calculated based on the detection results of the plurality of detection means, and the belt is stretched. The distortion of the image is corrected by controlling the shift and skew using the two steering rollers.

On the other hand, Patent Document 8 includes a first adjustment mechanism that moves one end of the steering roller in the first direction and a second adjustment mechanism that moves one end of the steering roller in the second direction, A configuration is shown in which the adjustment mechanism is selectively used when the endless belt is moved quickly and accurately when the endless belt is adjusted.
In Patent Document 9, Patent Document 10, and Patent Document 11, in order to absorb the change in the tension in the belt width direction that occurs when the end of the endless belt is corrected by moving one end of the steering roller, other than the steering roller. A configuration is shown in which the roller is tilted in conjunction with the movement of the steering roller, and the tension in the belt width direction is made uniform, thereby preventing belt twisting and image defects due to the influence of the belt width direction tension change. .
Further, in Patent Document 12, a load sensor for detecting a tension and an actuator for controlling the tension are provided to prevent belt torsion and image defects due to the influence of a belt width direction tension change.

When correcting image distortion and color misregistration due to skew of an endless belt, such as Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, and Patent Document 6, by directly adjusting an endless belt. Therefore, if the required image formation position correction amount varies due to variations in product assembly accuracy and environmental conditions, the highly accurate correction cannot be performed. There is a limit to high image quality.
In addition, when correcting not only the shift but also the skew as in Patent Document 7, it is necessary to move one end of the two steering rollers in two different directions as specifically in the structure of Patent Document 8. . At this time, it is necessary to appropriately set the roller position and the moving direction so that the tension change in the belt width direction caused by the movement of one end of the steering roller does not become large. As one of the conditions for this purpose, it is desirable to move one end of the steering roller in a direction orthogonal to the direction in which tension is applied to the belt (the central angle direction of the belt winding angle, hereinafter the tension direction). Both the steering roller for correcting the deviation and the steering roller for correcting the skew of the belt are configured to move in a direction crossing the tension direction.
On the other hand, in Patent Document 12, since one end of the steering roller is moved in a direction other than the tension crossing direction, a belt twist or an image defect easily occurs due to the influence of the tension change in the belt width direction, and it is necessary to provide a configuration for preventing it. There is an increase in cost and an increase in the size of the device.

  From the above, it is desirable to realize a configuration in which one end of the two steering rollers is moved in the crossing direction of the tension and the deviation and skew of the belt are corrected by their interaction. It has been clarified that the behavior of the belt with respect to the roller inclination varies greatly depending on the winding angle and the distance between the steering roller and the upstream roller.

10 and 13 show a configuration in which a belt is stretched around a plurality of rollers and is driven to circulate. Note that the configuration shown in FIG. 13 is a configuration in which the distance between the driven roller 112 and the driven roller 113 is shortened compared to the configuration shown in FIG.
Here, the following analysis is performed on the configuration shown in FIGS.
10 and 13, the belt 102 is rotationally driven by the driving roller 101, the tension crossing direction (steering condition 121) that is the direction in which the driven roller 111 crosses the tension direction 105, and the driven roller 112 in the tension direction 106. On the other hand, when the vehicle was tilted in the crossing direction of tension (steering condition 122), the relationship between the steering tilt angle, the belt shift speed, and the belt skew amount on the belt surface 102 was obtained.
FIG. 11 shows the result of the steering condition 121 in FIG. 10, FIG. 12 shows the result of the steering condition 122, FIG. 14 shows the result of the steering condition 121 in FIG. 13, and FIG.
In the configuration shown in FIG. 10, the belt shifting speed and the belt skew change linearly in both the steering conditions 121 and 122 as shown in FIGS. 11 and 12, whereas in the configuration shown in FIG. 13, as shown in FIGS. On the other hand, the belt shifting speed and the belt skew change linearly under the steering condition 121, but change nonlinearly under the steering condition 122.

As a result of the analysis, it can be understood that the winding angle of the belt 102 with respect to the roller is sufficiently large (135 °) in the steering condition 121, whereas the winding angle of the belt 102 with respect to the roller is not sufficient (90 °) in the steering condition 122. . In the configuration shown in FIG. 10, the distance between the driven roller 111 and the driven roller 112 is sufficiently large between the upstream roller, whereas in the configuration shown in FIG. 13, the distance between the driven roller 112 and the upstream roller (driven roller 113) is sufficient. It can be understood that this is not affecting.
In addition, it is clear that slippage in the roller thrust direction (roller axial direction) occurs between the belt 102 and the steering roller under the condition that causes nonlinear behavior (the steering condition 122 in the configuration shown in FIG. 13). became.
As described above, when the belt shift speed and the skew change non-linearly, a stable correction operation cannot be realized and it is difficult to secure a necessary correction range.

However, to ensure a sufficient belt winding angle and a sufficient distance from the upstream roller in the two steering rollers, the functional conditions and image size / cost conditions in the image forming operation of each roller are When considered, it was difficult.
Therefore, it is possible to greatly increase the image output speed without using a configuration that impedes belt high-speed driving, such as a shift guide member, and it is possible to reduce the cost with a simple configuration. Since it is possible to prevent image distortion and color misregistration by reliably correcting the rows, it is desired to realize an image forming apparatus that can greatly improve the image quality of the output image in a small size and at low cost. .

  The present invention has been made in view of the above circumstances, and can significantly increase the speed of image output and prevent image distortion and color misregistration by reliably correcting the shift and skew of the endless belt. Therefore, an object of the present invention is to realize a belt conveyance device and an image forming apparatus that can greatly improve the image quality of an output image.

  In order to solve the above problems, the invention according to claim 1 is characterized in that an endless belt stretched and conveyed by a plurality of stretching means, a belt driving means for conveying and driving the endless belt, and any one of the stretching means. A tension means for displacing the endless belt in a tension applying direction so as to apply tension to the endless belt, and adjusting the posture of any one of the tensioning means and adjusting the tension of the tensioning means. A first adjusting means for moving one end of the suspending means with respect to the other end in the crossing direction crossing the width direction of the endless belt; A second adjusting means for moving in the cross direction crossing the width direction of the endless belt with respect to the other end; and controlling the belt driving means to convey the endless belt. In the width direction Control means for independently controlling the first and second adjusting means so as to move, the one tension means moved by the first adjusting means and the endless belt, The belt conveying device is characterized in that a friction coefficient between the second tension adjusting means and the endless belt is larger than a friction coefficient between the other tensioning means moved by the second adjusting means.

  According to the present invention, the belt driving means is controlled to convey the endless belt, the first and second adjusting means are independently controlled to move the position of the endless belt in two width directions, and the first The friction coefficient between one tensioning means moved by the adjusting means and the endless belt is larger than the friction coefficient between the other tensioning means moved by the second adjusting means and the endless belt. Since belt misalignment and skew can be reliably corrected and image distortion and color misregistration can be prevented, the output image can be greatly improved in image quality.

1 is a diagram illustrating a configuration of an image forming apparatus 1 applicable to a belt conveyance device according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating a belt deviation / skew detection unit used in the image forming apparatus 1 illustrated in FIG. 1. FIGS. 1A and 1B are diagrams illustrating a belt shift / slant adjustment unit used in the image forming apparatus 1 in FIG. 1. It is explanatory drawing of the belt skew detection method used for the image forming apparatus 1 applicable to the belt conveying apparatus concerning 7th Embodiment of this invention, and is a figure which shows a mode that belt skew occurred. It is a figure which shows the position which the belt deviation detection means installed in two places in the width direction of a belt detects a detection line before and behind skewing of a belt. It is a figure which shows the position which the belt deviation detection means installed in two places in the width direction of a belt detects a detection line before and behind skewing of a belt. It is a figure which shows the position which the belt deviation detection means installed in the position which differs in the width direction of a belt detects a detection line before and behind skewing of a belt. It is explanatory drawing for calculating the change of a skew angle from the difference of the detection interval of two belt shift | offset | difference detection means. (A) and (b) are the figures for demonstrating operation | movement of the conversion table 68a and a belt conveying apparatus. It is a figure which shows the structure (the 1) by which the belt is conventionally stretched around a some roller and circulated. It is a graph which shows the result of the steering conditions 121 in the structure shown in FIG. It is a graph which shows the result of the steering conditions 122 in the structure shown in FIG. It is a figure which shows the structure (the 2) by which the belt is stretched around the several rollers conventionally, and is circulated. It is a graph which shows the result of the steering conditions 121 in the structure shown in FIG. It is a graph which shows the result of the steering conditions 122 in the structure shown in FIG.

Embodiments of the present invention will be described below in detail with reference to the drawings.
<First Embodiment>
FIG. 1 shows a configuration of an image forming apparatus 1 that can be applied to the belt conveying apparatus according to the first embodiment of the present invention. FIG. 1 is a schematic configuration diagram illustrating a main part of an image forming apparatus that uses four photosensitive drums provided with developing devices in parallel and forms a full-color image on an intermediate transfer belt.
In this image forming apparatus 1, four image carriers (hereinafter referred to as photosensitive drums) 11, 12, 13, and 14 are rotationally driven in an arrow direction D (counterclockwise) during image formation, and the surface of each photosensitive drum. Is uniformly charged by the chargers 21, 22, 23, and 24, and then exposure is performed according to the input image information by the exposure devices 31, 32, 33, and 34 to form an electrostatic latent image.
Then, the yellow developing device 41 attaches toner to the electrostatic latent image on the photosensitive drum 11 to develop it as a yellow toner image, and the magenta developing device 42 attaches toner to the electrostatic latent image on the photosensitive drum 12. The toner is developed as a magenta toner image, the toner is attached to the electrostatic latent image on the photosensitive drum 103 by the cyan developing device 43 and developed as a cyan toner image, and the electrostatic latent image on the photosensitive drum 14 is developed by the black developing device 44. The toner is attached to the image and developed as a black toner image.
The yellow toner image, the magenta toner image, the cyan toner image, and the black toner image are in contact with the photosensitive drums 11, 12, 13, and 14 and rotate in an arrow direction D (intermediate transfer belt). 50 is primary-transferred. Then, four color toner images are superimposed on the intermediate transfer belt 50. These four color toner images are secondarily transferred to the recording material P conveyed from a paper feed cassette (not shown), so that a full color image can be obtained on the recording material P.

FIG. 2 shows a belt deviation detection unit used in the image forming apparatus 1.
A detection line 51 is formed on the surface of the intermediate transfer belt 50 at a constant position in the width direction over the entire circumference in the transport direction. A belt deviation detecting means 55 is disposed at a position facing the detection line 51 so that the position in the width direction of the detection line can be detected. The belt deviation detecting means 55 is fixed to a belt conveyance mechanism (not shown) so as to face the surface of the intermediate transfer belt 50. By detecting the position in the width direction of the detection line 51 sequentially by the belt shift detection means 55, the belt shift can be detected.
Further, as shown in FIG. 3A, two belt deviation detecting means 55a and 55b are arranged on the primary transfer surface of the intermediate transfer belt 50 at a certain interval in the belt conveyance direction. The belt skew can be detected by sequentially detecting the difference in the position in the width direction of the detection line 51 detected by the two belt deviation detecting means 55a and 55b.

  In the present embodiment, the belt shift and skew are detected by detecting the movement in the belt width direction of the detection line 51 formed in advance in the intermediate transfer belt 50 with high accuracy. For this reason, as compared with the configuration in which the position of the belt edge is detected by detecting the position of the belt edge as in Patent Document 7, the edge data measured in advance is referred to, or the periodic fluctuation of the edge position is averaged. There is no need to store the converted data in the storage means, the cost can be reduced with a simpler configuration, and it is possible to perform high-speed belt deviation detection and control without wasted time.

FIG. 3A shows a belt shift / slant adjustment unit used in the image forming apparatus 1.
The intermediate transfer belt 50 is stretched by a plurality of substantially parallel rollers, and is driven in the belt conveyance direction by one drive roller 61 among them. While the driving roller 61 and the driven rollers 62 and 63 are fixed at predetermined positions, both ends of the rotating shaft of the roller 64 as a tension roller are urged in the tension directions indicated by arrows D1 and D2, and the intermediate transfer belt 50 is It is stretched with almost constant tension. Both ends of the rotating shaft of the roller 64 which is also a steering are supported by pivot bearing portions 64a and 64b so as to be swingable in the crossing direction of the roller rotating shaft, and one end side is supported by the actuator 67 as the first adjusting means in the tension crossing direction. D3 is supported so as to be reciprocally movable.
Both ends of the rotating shaft of the steering roller 65 are supported by pivot bearing portions 65a and 65b so as to be swingable in the roller rotating shaft crossing direction D4, and one end side thereof is moved in the tension crossing direction by an actuator 66 as a second adjusting means. It is supported so that it can reciprocate.

FIG. 3B shows the control unit 68 used in the image forming apparatus 1.
The control unit 68 is based on the belt shift detection information and the belt skew detection information indicating the shift in the width direction detected by the pair of belt shift detection means 55a and 55b arranged at different positions on the intermediate transfer belt 50. Then, the actuators 66 and 67 are driven, and the steering rollers 64 and 65 are swung so as to correct the generated movement and inclination in the belt width direction.
The control unit 68 controls a motor 69 that rotates the drive roller 61 so as to convey the intermediate transfer belt 50, and makes the actuators 66 and 67 independent so as to move the position of the intermediate transfer belt 50 in two width directions. To control.

With reference to Fig.3 (a), the belt conveying apparatus which concerns on 1st Embodiment of this invention is demonstrated.
In the belt conveying apparatus according to the first embodiment, the friction coefficient μ1 between the steering roller 64 and the intermediate transfer belt 50 that is rotationally driven by the actuator 67 that is the first adjusting means is the second adjusting means. The friction coefficient between the steering roller 65 and the intermediate transfer belt 50 that is rotationally driven by a certain actuator 66 is larger than the friction coefficient μ2, that is, μ1> μ2.
In the present embodiment, there are limitations on the conditions for image formation and the peripheral length of the intermediate transfer belt 50 for downsizing the image forming apparatus.
For this reason, the layout configuration is such that when the steering roller 64 is swung, the shifting force acting on the intermediate transfer belt 50 from the steering roller 64 increases.
However, it is possible to prevent the intermediate transfer belt 50 from slipping between the steering roller 64 having a large friction coefficient μ1 and the intermediate transfer belt 50. Further, the belt shift and skew sensitivity generated in the intermediate transfer belt 50 on the steering roller 65 by the rotational drive of the actuator 66 does not change nonlinearly as shown in FIG. 15, and stable correction control is realized. And a sufficient correction range can be secured.
As a result, it is possible to significantly increase the speed without using a configuration that obstructs the high-speed driving of the belt, such as a conventionally used shifting guide member, and to prevent a problem caused by slipping of the belt. It is possible to realize a belt conveyance device capable of performing a line correction operation.

Second Embodiment
With reference to Fig.3 (a), the belt conveying apparatus which concerns on 2nd Embodiment of this invention is demonstrated.
In the belt conveyance device according to the second embodiment, the control unit 68 drives the actuators 67 and 66, which are first and second adjusting means, independently of each other, so that the steering rollers 64 are driven by the actuators 67 and 66. , 65 are independently driven to control the position of the intermediate transfer belt 50 in the direction crossing the belt conveyance direction D5 and the belt inclination with respect to the belt conveyance direction.
Accordingly, in this embodiment, even if the layout configuration of the image forming apparatus is limited, the moving direction of the steering rollers 64 and 65 that are independently driven by the actuators 67 and 66 is the tension crossing direction. Therefore, as described above, there is no tension change in the width direction of the intermediate transfer belt 50, and the twist and image defect that occur in the intermediate transfer belt 50 can be suppressed.
Also, by driving the actuators 67 and 66 as the first and second adjusting means independently of each other, one end of the steering rollers 64 and 65 (stretching means) is intermediately transferred to the other end by the actuators 67 and 66. The direction of movement in the crossing direction of the tension that crosses the width direction of the belt crosses the center angle direction (direction in which tension is applied to the belt) of the belt winding angle in the steering rollers 64 and 65 (stretching means). By being in the tension crossing direction, there is no tension change in the width direction of the intermediate transfer belt 50, and twisting and image defects that occur in the intermediate transfer belt 50 can be suppressed.

<Third Embodiment>
With reference to Fig.3 (a), the belt conveying apparatus which concerns on 3rd Embodiment of this invention is demonstrated.
In the belt conveyance device according to the third embodiment, the winding angle θ1 at which the intermediate transfer belt 50 is wound around the steering roller 64 (stretching means) that is rotationally driven by the actuator 67 that is the first adjusting means is 2 is characterized by being smaller than a winding angle θ2 around which the intermediate transfer belt 50 is wound around a steering roller 65 (stretching means) rotated by an actuator 66 that is an adjusting means, that is, θ1 <θ2.
In FIG. 3A, the winding angle θ1 of the intermediate transfer belt 50 wound around the steering roller 64 is smaller than the winding angle θ2 of the intermediate transfer belt 50 wound around the steering roller 65. It is difficult to change this depending on conditions for transferring an image to the intermediate transfer belt 50 as a recording material.
For this reason, the steering roller 64, 65 is swung to correct the position of the intermediate transfer belt 50, so that slippage in the belt shift direction is likely to occur in the steering roller 64.

Therefore, image formation on the intermediate transfer belt 50 is performed by setting the friction coefficient μ1 between the steering roller 64 and the intermediate transfer belt 50 to a value larger than the friction coefficient μ2 between the steering roller 65 and the intermediate transfer belt 50. In addition to satisfying the above conditions, stable correction control can be realized and a sufficient correction range can be secured.
As a result, it is possible to significantly increase the speed without using a conventionally used shift guide member or the like, which is an obstacle to high-speed belt driving, and more reliable shift by preventing problems caused by belt slippage. It is possible to realize a belt conveyance device capable of performing a skew correction operation and having stable and reliable functions and operations.

<Fourth embodiment>
With reference to Fig.3 (a), the belt conveying apparatus which concerns on 4th Embodiment of this invention is demonstrated.
In the belt conveyance device according to the fourth embodiment, the distance d1 between the steering roller 64 (stretching means) and the driven roller 63 (stretching means) adjacent to the upstream side in the belt conveyance direction is the steering roller 65 ( The distance d2 between the tensioning means) and the steering roller 64 (stretching means) adjacent to the upstream side in the belt conveying direction is smaller, that is, d1 <d2.
In FIG. 3A, the distance d1 between the steering roller 64 and the driven roller 63 adjacent to the upstream side is smaller than the distance d2 between the steering roller 65 and the steering roller 64 adjacent to the upstream side. This is to prevent an increase in cost due to an increase in the peripheral length of the intermediate transfer belt 50 and an increase in the size of the image forming apparatus.

Here, since the position of the intermediate transfer belt 50 is corrected, slippage between the rollers and the intermediate transfer belt 50 caused by swinging the steering rollers 64 and 65 easily occurs on the steering roller 64.
Therefore, the friction coefficient between the steering roller 64 and the intermediate transfer belt 50 is set to a value larger than the friction coefficient between the steering roller 65 and the intermediate transfer belt 50, thereby reducing the cost and downsizing the image forming apparatus. In addition, the stable correction control can be realized and a sufficient correction range can be secured.
As a result, it is possible to significantly increase the speed without using a conventionally used shift guide member or the like, which is an obstacle to high-speed belt driving, and more reliable shift by preventing problems caused by belt slippage. A belt conveyance device capable of performing a skew correction operation can be realized in a small size and at a low cost.

<Fifth Embodiment>
With reference to Fig.3 (a), the belt conveying apparatus which concerns on 5th Embodiment of this invention is demonstrated.
In the belt conveyance device according to the fifth embodiment, the surface on which the steering roller 64 (stretching means) that is rotationally driven by the actuator 67 serving as the first adjustment means contacts the intermediate transfer belt is adjacent in the belt conveyance direction. The driven roller 63 and the steering roller 65, which are two stretching means, have a friction coefficient larger than that of the surface in contact with the intermediate transfer belt 50.
In FIG. 3A, the friction coefficient of the surface where the steering roller 64 is in contact with the intermediate transfer belt 50 is set to be larger than the friction coefficient of the surface where the driven roller 63 and the steering roller 65 are in contact with the intermediate transfer belt 50, respectively. The configuration can be realized by processing the roller surface of the steering roller 64 to have a larger surface roughness than the roller surfaces of the driven roller 63 and the steering roller 65. In addition, the surface of the steering roller 64 can be realized by applying a surface coat with a high friction coefficient such as rubber resin.
As described above, the friction coefficient of the surface where the steering roller 64 is in contact with the intermediate transfer belt 50 is set to be larger than the friction coefficient of the surface where the driven roller 63 and the steering roller 65 are in contact with the intermediate transfer belt 50. It is possible to prevent a trouble caused by slipping of the belt, and to realize a belt conveyance device capable of performing a reliable deviation / skew correction operation at low cost.

<Sixth Embodiment>
With reference to Fig.3 (a), the belt conveying apparatus which concerns on 6th Embodiment of this invention is demonstrated.
In the belt conveying apparatus according to the sixth embodiment, the steering roller 64 (stretching means) that is rotationally driven by the actuator 67 serving as the first adjusting means has two stretching means that are adjacent in the belt conveying direction. The driven roller 63 and the steering roller 65 are stretched on a surface different from the surface of the intermediate transfer belt 50, and the steering roller 64 that is rotationally driven by the actuator 67 as the first adjusting means is stretched. The surface of the intermediate transfer belt 50 is characterized in that the friction coefficient is larger than the surface of the intermediate transfer belt 50 on which the driven roller 63 and the steering roller 65 which are adjacent two stretching means are stretched.
In FIG. 3A, the surface of the intermediate transfer belt 50 with which the steering roller 64 abuts is different from the surface with which the driven roller 63 and the steering roller 65 abut. Here, by making the friction on the surface of the intermediate transfer belt 50 on the side where the steering roller 64 abuts larger than the surface on the side where the driven roller 63 and the steering roller 65 abut, the same effect as in the sixth embodiment can be obtained. It is possible to obtain.
Specifically, it can be realized by processing the surface on the side where the steering roller 64 abuts with a surface roughness larger than the surface on the side where the driven roller 63 and the steering roller 65 abut. Further, this can be realized by a two-layer structure in which the surface is formed of a material having a high friction coefficient such as a rubber-based resin.
As a result, it is possible to prevent problems due to slippage of the intermediate transfer belt, and to realize a belt conveyance device that can perform a reliable deviation / skew correction operation at low cost.

<Seventh embodiment>
An image forming apparatus according to a seventh embodiment of the present invention will be described with reference to FIGS.
FIG. 4 is an explanatory diagram of belt skew detection and shows how belt skew occurs.
In FIG. 4, due to the influence of the inclination of each roller that conveys the intermediate transfer belt 50, the intermediate transfer belt 50 is conveyed in a direction inclined at an oblique angle θ on the image transfer surface. Therefore, the image formed on the image transfer surface is inclined at the skew angle θ, and the transfer position on the intermediate transfer belt of the image formed on each photoconductive drum is shifted in the width direction. That is, image distortion and color misregistration in a color image occur.
In addition, the position where the belt deviation detecting means 75a and 75b detect the detection line 51 provided for detecting the movement in the belt width direction also changes due to the influence of the belt skew angle θ. Here, two detection lines 51 provided for detecting the movement of the belt in the width direction are formed in two places in the width direction of the belt, and the belt shift detection means 75a and 75b are placed in positions opposite to the belt main scanning. FIG. 5 shows the positions at which the belt deviation detection means 75a and 75b detect the detection lines before and after the belt skew when arranged in the respective directions.

In FIG. 5, when the skew angle of the intermediate transfer belt 50 changes, the line detection interval at the two detection positions in the width direction changes. Therefore, the change in the belt skew angle is detected by detecting the change in the interval. It is possible to detect. Normally, the image forming position is adjusted when the image forming apparatus is started. However, the belt skew angle change that occurs after the image forming position adjustment is adjusted according to the belt skew angle change. By correcting the image forming position in the width direction on the intermediate transfer belt 50 by the second adjusting means, it is possible to correct image distortion and color misregistration in a color image.
In FIG. 5, when the image forming position adjustment (before the belt skew change), the detection interval of the two belt deviation detecting means 75a and 75b is L1, and the detection interval after the belt skew change is L2, L1 <L2. In some cases, it can be seen in FIG. 4 that the belt transfer surface has rotated in a direction (counterclockwise) in which the skew angle θ increases. Here, if the skew angle before the belt skew change is θ1, the skew angle after the belt skew change is θ2, and the distance between the two detection lines 51a and 51b in the belt width direction is L, as shown in FIG. Furthermore, the change in the skew angle (θ2−θ1) can be detected from the change in the detection interval (L2−L1) of the belt deviation detection means 75a and 75b.

However, as shown in FIG. 6, when the same position is detected in the width direction of the detection line 51 by the two belt deviation detecting means 75a and 75b, the change in the skew angle θ from the state of the skew angle 0 is detected. The detection intervals of the two belt deviation detection means 75a and 75b are L1 <L2 when the skew angle is + (counterclockwise in the figure) and-(clockwise in the figure).
In this case, even if the amount of change in the skew angle can be detected, the direction of the change cannot be detected. Therefore, a means for separately detecting the skew change direction is required for correcting the image forming position. Therefore, as shown in FIG. 7, the skew angle θ is + (counterclockwise in the figure) by detecting different positions in the width direction of the detection lines 51a and 51b by the two belt deviation detecting means 75a and 75b. In this case, L1 <L2, and in the case of − (clockwise in the figure), L1> L2, and the change amount and change direction of the skew angle θ can be detected.

Here, as shown in FIG. 8, when the image forming position is adjusted by the first and second adjusting means (before the belt skew change), the detection interval of the pair of belt deviation detecting means 75a and 75b is set to L1, The detection interval after the belt skew change is L2.
When L1 <L2, it can be understood that the belt transfer surface has rotated in the direction in which the skew angle θ increases (counterclockwise) in the drawing. The skew angle before the belt skew change is θ1, the skew angle after the belt skew change is θ2, the distance between the two detection lines 51a and 51b in the belt width direction is L, and the two belt shift detectors 75a and 75b. If the interval in the sub-scanning direction of the detected position is M, from FIG.
L1 × cos θ1 = L + M × sin θ1
L2 × cos θ2 = L + M × sin θ2
The relationship holds.
Since θ1 and θ2 are very small angles, if sin θ1 = θ1, sin θ2 = θ2, and cos θ1 = cos θ2 = 1,
L1 = L + M × θ1
L2 = L + M × θ2
It becomes.
Therefore, L2−L1 = M × (θ2−θ1), and the change in the skew angle (θ2−θ1) can be obtained from the change in the detection interval of the belt deviation detection means 75a and 75b (L2−L1).

In this way, the control unit 68 changes the skew angle based on the change in the belt width interval in the width direction (L2-L1) detected by the pair of belt deviation detection means provided at regular intervals in the width direction. Further, the image forming position in the width direction on the intermediate transfer belt 50 can be corrected by the first and second adjusting means based on the change in the skew angle.
4 to 8, the skew (rotation) of the intermediate transfer belt 50 is regarded as the skew (rotation) around the central portion of the belt shift detection means 75b. The adjustment means always performs belt deviation correction with reference to the belt deviation detection means 75b, and controls so that the detection line 51 provided on the intermediate transfer belt 50 always passes through the central portion of the belt deviation detection means 75b. Further, the belt deviation detection means 75a and 75b have a detection unit on a straight line that vertically crosses the central portion thereof, and the position of the detection line 51 that intersects the detection unit can be known.

The control unit 68 shown in FIG. 3A uses the first and second adjustment means based on the movement amount (L2-L1) of the belt 50 in the width direction detected by the belt deviation detection means 75a and 75b, respectively. By independently driving, the position of the belt 50 is controlled to move in the width direction, and the detection line 51 provided on the intermediate transfer belt 50 always passes through the center of the belt deviation detecting means 75a and 75b. Control. Here, the control unit 68 controls the first and second adjusting means to incline the rollers other than the steering roller to correct the belt skew. Here, since the belt shift changes by correcting the belt skew, the belt shift can be corrected.
That is, in FIG. 3A, the control unit 68 knows that the belt shift and skew adjustment sensitivity by the actuator 66 and the belt shift and skew adjustment sensitivity by the actuator 67 are known and stable and constant. The driving amounts s1 and s2 respectively indicating the ratios for driving the actuators 66 and 67 according to the belt deviation detection information (movement amount in the width direction of the belt 50) are optimally set in advance and stored in the conversion table 68a.

As shown in FIG. 9A, in the conversion table 68a, the movement amount (L2-L1) of the belt 50 in the width direction obtained from the belt deviation detection information detected by the belt deviation detection means 75a and 75b, the actuator Drive amounts s1 and s2 for 66 and 67 are stored.
Next, the operation of the belt conveyance device will be described with reference to the flowchart shown in FIG.
First, in step S10, it is determined whether the belt is being conveyed. The control unit 68 proceeds to step S15 when the belt is being conveyed, and ends the process when the belt is not being conveyed.
In step S15, a movement amount (L2-L1) is calculated. That is, the control unit 68 calculates the amount of movement (L2-L1) in the width direction of the belt 50 from the belt deviation detection information detected by the belt deviation detection means 75a and 75b.
Next, in step S20, a drive amount corresponding to the movement amount (L2-L1) is obtained. That is, the control unit 68 reads and obtains the drive amounts s1 and s2 from the conversion table 68a based on the movement amount (L2-L1).
Next, in step S25, the actuator is driven according to the drive amount, and the process returns to step S10. That is, the control unit 68 drives the actuators 66 and 67 according to the obtained drive amounts s1 and s2.

Here, the control unit 68 obtains the driving amounts s1 and s2 that respectively indicate the ratio of driving the actuators 66 and 67 according to the belt skew detection information detected by the belt deviation detecting means 75a and 75b. The actuators 66 and 67 are driven according to the driving amounts s1 and s2.
Since the tearing rollers 64 and 65 are moved in the tension crossing direction by the two actuators 66 and 67, the intermediate transfer belt 50 is moved in the belt width direction on the respective tearing rollers 64 and 65. In this manner, it is possible to control the shift and skew of the intermediate transfer belt 50 so as to independently move in the belt width direction.
Thus, the belt shift is controlled within a certain range by controlling the detection line 51 provided on the intermediate transfer belt 50 so as to always pass through the central portion of the belt shift detection means 75a and 75b, and the belt shift is suppressed. In addition, the belt skew is controlled within a certain range, and image distortion and color misregistration can be prevented.
In this embodiment, there is no use of a configuration that hinders belt high-speed driving, such as a conventionally used shift guide member, so that it is possible to significantly increase the speed and prevent problems due to belt slippage. By doing so, it is possible to realize a belt conveyance device capable of performing a reliable deviation / skew correction operation.

<Eighth Embodiment>
With reference to FIGS. 1 and 3A, an image forming apparatus according to an eighth embodiment of the present invention will be described.
In the image forming apparatus according to the eighth embodiment, as shown in FIG. 1, an exposure apparatus that is a latent image forming unit that forms a latent image on the image carrier 11, 12, 13, 14 based on image data. 31, 32, 33, 34, developing devices 41, 42, 43, 44 that are developing units that visualize the latent image formed in the latent image forming unit, and a visible image formed on the image carrier An intermediate transfer belt 50, which is an intermediate transfer body for primary transfer of the toner image, and secondary transfer means for transferring a transfer image on the intermediate transfer body onto a recording material, on a plurality of image carriers 11, 12, 13, 14 In the image forming apparatus 1 that forms a multi-color image by sequentially transferring the formed visible image onto the intermediate transfer member, the intermediate transfer belt 50 that is an intermediate transfer member is the first to seventh embodiments described above. And the first and second adjusting means. And adjusting Ri of the intermediate transfer member widthwise position and the intermediate transfer member to the image formed of the color shift.
By applying the belt conveyance device (see FIG. 3A) described in the first to seventh embodiments to the intermediate transfer belt mechanism of the image forming apparatus 1 as shown in FIG. The configuration can reduce the cost, and by reliably correcting the shift and skew of the intermediate transfer belt, it is possible to stably control the shift of the intermediate transfer belt and to reliably correct the color misregistration of the image.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 11 ... Image carrier, 11 ... Photosensitive drum, 12 ... Photosensitive drum, 14 ... Photosensitive drum, 21 ... Charger, 31 ... Exposure apparatus, 41 ... Yellow developing device, 41 ... Developing device , 42 ... Magenta developer unit, 43 ... Cyan developer unit, 44 ... Black developer unit, 50 ... Intermediate transfer belt, 51 ... Detection line, 51a, 51b ... Detection line, 55a, 55b ... Belt deviation detection means, 61 ... Drive roller 62 ... driven roller, 63 ... driven roller, 64 ... steering roller, 64a, 64b ... pivot bearing part, 65 ... steering roller, 65a, 65b ... pivot bearing part, 66 ... actuator, 67 ... actuator, 68 ... control part, 69 ... motor, 75a, 75b ... belt deviation detecting means,

JP 2009-180884 A JP 2010-204255 A JP 2010-217300 A JP 2010-217301 A JP 2011-002632 A JP 2011-022549 A JP 2000-233843 A JP 2007-163695 A JP 2001-147601 A JP 2002-91185 A JP 2009-25475 A JP 2011-95571 A

Claims (9)

An endless belt stretched and conveyed by a plurality of stretching means;
Belt driving means for conveying and driving the endless belt;
Tensioning means for supporting any one of the stretching means so as to be displaceable in the tension applying direction so as to apply tension to the endless belt, and biasing in the tension applying direction;
First adjusting means for adjusting the posture of any one of the stretching means and moving one end of the stretching means in the crossing direction crossing the width direction of the endless belt with respect to the other end;
A second adjusting means for adjusting the posture of the other stretching means, and for moving one end of the stretching means in the crossing direction crossing the width direction of the endless belt with respect to the other end;
Control means for controlling the belt driving means to convey the endless belt, and independently controlling the first and second adjusting means so as to move the position of the endless belt in the two width directions; In a belt conveyance device provided with
The coefficient of friction between the one tension means moved by the first adjustment means and the endless belt is between the other tension means moved by the second adjustment means and the endless belt. A belt conveying device having a coefficient of friction larger than that of the belt.   The direction in which one end of the stretching means is moved in the crossing direction with respect to the other end by the first and second adjusting means is a direction crossing the central angle direction of the belt winding angle in the stretching means. The belt conveyance device according to claim 1, wherein:   The control means controls the position of the endless belt in the direction crossing the belt conveying direction and the belt inclination with respect to the belt conveying direction by independently driving the first and second adjusting means. The belt conveying device according to claim 2.   The belt conveyance device according to claim 2, wherein a winding angle around which the endless belt is wound around the one stretching means is smaller than a winding angle around which the endless belt is wound around the stretching means.   The distance between the one tensioning means and the tensioning means adjacent to the upstream side in the belt conveyance direction is smaller than the distance between the other tensioning means and the tensioning means adjacent to the upstream side in the belt conveyance direction. The belt conveyance device according to claim 2.   3. The surface of the one stretching means in contact with the endless belt has a larger coefficient of friction than the surface of two stretching means adjacent in the belt conveyance direction in contact with the endless belt. The belt conveying apparatus as described.   The one stretching means stretches a surface different from the surface of the endless belt stretched by two stretching means adjacent to each other along the belt conveyance direction, and the first adjusting means stretches the first stretching means. The belt conveying device according to claim 1 or 2, wherein a surface of the endless belt has a larger coefficient of friction than a surface of the endless belt stretched by two adjacent stretching means. Belt deviation detecting means for detecting the amount of movement of the endless belt in the width direction;
The control means drives the first and second adjustment means independently based on the movement amount in the width direction detected by the belt deviation detection means, thereby moving the endless belt in the width direction. The belt conveying device according to claim 1, wherein the belt conveying device is controlled so that a detection line provided on the endless belt always passes through a central portion of the belt deviation detecting means. A latent image forming unit that forms a latent image on the image carrier based on the image data;
A developing unit that visualizes the latent image formed in the latent image forming unit;
An intermediate transfer body for primary transfer of a visible image formed on the image carrier;
Secondary transfer means for transferring the transfer image on the intermediate transfer member to a recording material,
In an image forming apparatus for forming a multi-color image by sequentially transferring visible images formed on a plurality of the image bearing members onto the intermediate transfer member,
The intermediate transfer body is the belt conveyance device according to any one of claims 1 to 7, and the intermediate transfer body and the position of the intermediate transfer body in the width direction and the intermediate transfer body by the first and second adjusting units. An image forming apparatus that adjusts color misregistration of an image formed thereon.

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