JP2018101146A - Belt conveyance device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt conveyance device that is flexibly designed and securely corrects slippage and skew of a belt, and an image forming apparatus with a simple configuration that can prevent image distortion and color shift.SOLUTION: A belt conveyance device comprises a plurality of stretching means and an endless belt stretched by the plurality of stretching means. The plurality of stretching means includes driving means that drives the endless belt, and adjustment means that each have one end moving relative to the other end in a direction orthogonal to the width direction of the endless belt. The belt conveyance device conveys the endless belt with the driving means and corrects the position of the endless belt with the adjustment means. The coefficient of friction between the endless belt and at least one stretching means located on the upstream side in the conveyance direction of the endless belt with respect to the adjustment means is made smaller than the coefficient of friction between the endless belt and two stretching means adjacent to each other in the conveyance direction of the endless belt with respect to the at least one stretching means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a belt conveying device in which an endless belt member is stretched by a plurality of stretching rollers and rotationally drives the belt member, and an image forming apparatus such as a copying machine, a facsimile, and a printer using the belt conveying device. Is.

  2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, an image forming apparatus using an endless belt as a transfer means for an intermediate transfer belt as a transfer medium or a recording sheet as a transfer medium is known. The belt used in these devices is circulated and driven by a plurality of rollers. At this time, the belt position moves in the direction perpendicular to the belt conveyance direction (main scanning direction) and the belt conveyance direction. In some cases, the belt skews incline in the main scanning direction.

  When the belt is skewed, the image forming position on the transfer medium such as the intermediate transfer belt or the recording paper is shifted, which causes image distortion. 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 that obtains 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 the 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 main scanning direction generated on the endless belt is regulated by abutting a deviation guide member provided on the belt surface against the end face of the belt conveying roller, thereby suppressing the deviation of the endless belt. For this reason, there is a problem in that the skew of the belt due to the deviation in the main scanning direction of the shift guide member formed on the belt and the deviation of the end face of the conveying roller cannot be suppressed, and image distortion and color deviation due to positional deviation in the main scanning direction occur. . 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.

  In order to solve the above problem, the belt is adjusted based on the endless belt member main scanning direction position information, and the main scanning direction latent image forming position on the image carrier is corrected based on the endless belt member main scanning direction position information. A forming apparatus is known (see, for example, Patent Documents 1 to 6). The image forming apparatus having such a configuration can significantly increase the image output speed without using a shift guide member or the like that obstructs high-speed driving of the belt, and accurately detects the shift of the endless belt. Can control. In addition, by accurately detecting the skew of the endless belt and correcting the image forming position, image distortion and color misregistration can be prevented, and the quality of the output image can be improved.

  However, the image forming apparatuses described in Patent Documents 1 to 6 do not directly correct the inclination of the endless belt. For this reason, when the required image forming position correction amount varies depending on variations in product assembly accuracy and environmental conditions, the detected skew of the belt cannot be corrected with high accuracy, and the image quality of the output image cannot be improved.

  In order to solve the above-described problem, the belt includes a plurality of detection means for detecting the position of the endless belt in the belt width direction, and calculates the deviation and skew of the endless belt based on the detection results of the plurality of detection means. 2. Description of the Related Art An image forming apparatus that corrects distortion of an image by using two steering rollers that stretch the belt and controlling skew and skew is known (see, for example, Patent Document 7).

  In addition, the first adjustment mechanism that moves one end of the steering roller in the first direction and the second adjustment mechanism that moves one end of the steering roller in the second direction are accurate when moving the endless belt quickly. There is known an image forming apparatus capable of adjusting the shift of the endless belt by using different adjustment mechanisms depending on the movement of the belt (for example, see Patent Document 8).

  However, the image forming apparatuses described in Patent Document 7 and Patent Document 8 need to correct the belt shift and the belt skew by independently tilting the two steering rollers. Therefore, in the case where the correction sensitivity obtained with respect to the inclination of each steering roller and the linearity of the sensitivity in the necessary correction range are sufficiently ensured, the restrictions on the layout of the rollers that stretch the belt increase.

  As a configuration for improving the correction sensitivity, it is well known to increase the steering roller diameter. However, the image forming apparatus having such a configuration causes an increase in the size of the apparatus and cannot reduce the cost.

  In order to solve the above-described problem, the two adjacent steering rollers are integrally tilted to increase the correction amount of the position in the belt width direction, and the friction coefficient of the two steering rollers is set to be higher than that of the other rollers. A configuration is known in which the grip of the steering roller and the belt in the correction operation is maintained by performing a surface treatment so as to increase (see, for example, Patent Document 9). With such a configuration, the same effect as that of increasing the steering roller diameter can be obtained, and the correction sensitivity can be improved.

  In addition, a configuration is known in which a pressing roller that presses the belt from the outer peripheral surface side is provided in the vicinity of the steering roller, the winding of the belt around the steering roller is increased, and the frictional force between the steering roller and the belt is increased (for example, (See Patent Document 10). With such a configuration, it is intended to improve the correction sensitivity.

  However, the image forming apparatuses described in Patent Document 9 and Patent Document 10 have a problem that the belt position correction sensitivity cannot be improved depending on layout conditions.

  Specifically, an analysis performed on the belt position correction sensitivity due to a difference in layout conditions will be described. For the analysis, one driving roller, four driven rollers and an endless belt were used. 6 shows the layout condition 1 used for the analysis, and FIG. 7 shows the layout condition 2. Layout condition 1 and layout condition 2 are the diameter of each roller, the circumferential length of endless belts 506 and 606, the positional relationship between first driven rollers 501 and 601 and second driven rollers 502 and 602, and the first to third driven rollers. The main conditions, such as the belt winding range angle, are common. On the other hand, the interval between the second driven rollers 502 and 602 that are also the steering rollers and the third driven rollers 503 and 603 on the upstream side in the belt conveyance direction is different, and the interval X2 of the layout condition 2 is equal to the interval X1 of the layout condition 1. The interval is about half.

  When the driving rollers 505 and 605 are rotationally driven, the endless belts 506 and 606 are conveyed in the belt conveying direction, and the second driven rollers 502 and 602 are tilted in a direction perpendicular to the tension direction, the second driven rollers 502 and 605 The relationship between the belt position correction sensitivity in the belt width direction (main scanning direction) obtained with the inclination A of 602 and the belt position correction sensitivity in the belt width direction obtained with the inclination 2.5A of the second driven rollers 502 and 602. Is shown in FIG. The correction sensitivity obtained with the slope A of the layout condition 1 is at least twice the correction sensitivity obtained with the slope A of the layout condition 2. From the results of this analysis, it can be seen that if the distance between the second driven rollers 502 and 602 and the adjacent roller on the upstream side in the belt conveyance direction is large, the belt position correction sensitivity is improved.

  Further, the correction sensitivity obtained with the slope 2.5A of the layout condition 1 is about 2.5 times the correction sensitivity obtained with the slope A. This indicates that the correction sensitivity for the inclination in the layout condition 1 is a behavior close to a linear behavior. On the other hand, the correction sensitivity obtained with the slope 2.5A of the layout condition 2 is about twice the correction sensitivity obtained with the slope A. This indicates that the correction sensitivity with respect to the inclination in the layout condition 2 has a non-linear behavior in which the inclination and the correction sensitivity are not proportional. From the result of this analysis, it can be seen that if the distance between the second driven rollers 502 and 602 and the adjacent roller on the upstream side in the belt conveyance direction is large, the belt position correction sensitivity with respect to the inclination approaches linear behavior.

  Next, the relationship between the axial force acting on the belt from each roller and the posture of the belt deformed by this force will be described. FIG. 9 shows the relationship between the axial force acting on the belt 506 from each of the rollers 501 to 505 and the posture of the belt 506 deformed by this force in the case of the inclination A in the layout condition 1. FIG. 10 shows the relationship between the axial force acting on the belt 606 from each of the rollers 601 to 605 and the posture of the belt 606 deformed by this force in the case of the inclination A in the layout condition 2. FIG. 11 shows the relationship between the axial force acting on the belt 506 from each of the rollers 501 to 505 and the posture of the belt 506 deformed by this force when the inclination is 2.5A in the layout condition 1. FIG. 12 shows the relationship between the axial force acting on the belt 606 from each of the rollers 601 to 605 and the posture of the belt 606 deformed by this force when the inclination is 2.5A in the layout condition 2. In both the layout conditions 1 and 2, the axial force acting on the belt from each roller is caused by the second driven rollers 502 and 602 that are steering rollers and the adjacent third driven rollers 503 and 603 on the upstream side in the belt conveyance direction. Thus, the force is in the opposite direction. Due to the influence of the force acting on the belts 506 and 606, the postures of the belts 506 and 606 are changed between the second driven rollers 502 and 602 and the adjacent third driven rollers 503 and 603 on the upstream side in the belt conveyance direction. It deforms greatly in the width direction. On the other hand, the belt posture hardly deforms at other roller positions.

  In the case of the inclination A, the axial force acting on the belt between the second driven roller and the third driven roller is not significantly different between the layout condition 1 and the layout condition 2. On the other hand, the posture (position) of the belt in the belt width direction between the second driven roller and the third driven roller is deformed more greatly in the layout condition 1 than in the layout condition 2. This is because, under the layout condition 1, the distance between the second driven roller 502 and the third driven roller 503 is large, and the deformation is greatly caused by the axial force acting on the belt 506. From the result of this analysis, the deformation of the belt posture is greatly influenced by the deformation between the second driven roller and the third driven roller, and the layout condition 1 is larger than the layout condition 2. Further, since the belt entry angle with respect to the roller, which is the principle of belt position correction, is larger in the layout condition 1 than in the layout condition 2, the belt position correction sensitivity is larger in the layout condition 1 than in the layout condition 2.

  Further, in the case of the layout condition 1, the deformation of the posture of the belt 506 in the belt width direction between the second driven roller 502 and the third driven roller 503 is approximately the same as when the inclination is 2.5A. 2.5 times. For this reason, the belt position correction sensitivity is improved by about 2.5 times when the inclination is 2.5A and when the inclination is A. On the other hand, in the case of the layout condition 2, the deformation of the posture of the belt 606 in the belt width direction between the second driven roller 602 and the third driven roller 603 is approximately the same as that when the inclination is 2.5A. It has doubled. For this reason, the correction sensitivity of the belt position is only improved about twice as much as when the inclination is 2.5A. This is because, under the layout condition 2, the distance between the second driven roller 602 and the third driven roller 603 is small, and the belt 606 is difficult to deform with respect to the axial force. In the layout condition 2, the second driven roller 602 and the third driven roller 603 exert opposite forces in the axial direction acting on the belt 606 against deformation of the belt 606 in the belt width direction. Exceeding the allowable range. Therefore, an axial slip occurs between the belt 606 and the roller. For this reason, even if the inclination of the steering roller is increased and the mutually opposite forces in the axial direction acting on the belt 606 increase between the steering roller and the adjacent roller on the upstream side in the belt conveyance direction, Due to the sliding with the roller, the deformation of the belt 606 does not increase, and the correction sensitivity cannot be increased.

  From the above analysis results, in order to increase the belt position correction sensitivity and make the belt position correction sensitivity close to linear with respect to the tilt of the steering roller, and to ensure a sufficient belt position correction range by steering, It can be seen that it is effective to ensure a large distance between the roller and the roller positioned upstream in the belt conveyance direction. However, such a configuration is a great restriction on the layout.

  In addition, the friction coefficient between the tension roller and the belt is made smaller than the friction coefficient between the two rollers adjacent to the upstream side and the downstream side in the belt conveyance direction of the tension roller and the belt, so that the axial direction of the tension roller from the belt An image forming apparatus that can reduce the influence of a force acting on the belt and prevent the belt from twisting is known (see, for example, Patent Document 11).

  However, there is a demand for a belt conveyance device that can cope with a further flexible design and reliably correct the deviation and skew of the belt, and further, an image forming apparatus having a simple configuration capable of preventing image distortion and color misregistration.

  The present invention has been made in view of the above-described problems, and is a belt transport device that can flexibly correct belt deviation and skew feeding, and can easily prevent image distortion and color misregistration. An object of the present invention is to provide an image forming apparatus having a configuration.

In order to solve the above-described problem, a belt conveying device according to claim 1 of the present invention is provided.
A plurality of stretching means;
An endless belt stretched around the plurality of stretching means,
The plurality of stretching means,
Driving means for driving the endless belt;
Adjusting means in which one end moves relative to the other end in a direction perpendicular to the width direction of the endless belt,
In the belt conveying apparatus that conveys the endless belt by the driving means and corrects the position of the endless belt by the adjusting means,
The coefficient of friction between the endless belt and the at least one stretching means positioned upstream in the transporting direction of the endless belt with respect to the adjusting means is such that the transporting direction of the endless belt with respect to the at least one stretching means. The friction coefficient between two adjacent stretching means and the endless belt is smaller than the friction coefficient.

  According to the present invention, it is possible to provide an inexpensive image forming apparatus with a simple configuration that can reliably correct the deviation and skew of the endless belt and prevent image distortion and color misregistration.

1 is a configuration diagram schematically illustrating an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view illustrating an embodiment of a belt deviation detecting unit of the image forming apparatus illustrated in FIG. 1. FIG. 6 is an explanatory diagram illustrating first to fifth aspects of the belt conveyance device of the image forming apparatus illustrated in FIG. 1. FIG. 10 is an explanatory diagram illustrating a sixth aspect of the belt conveyance device of the image forming apparatus illustrated in FIG. 1. FIG. 10 is an explanatory diagram illustrating a seventh aspect of the belt conveyance device of the image forming apparatus illustrated in FIG. 1. It is explanatory drawing explaining the conventional belt conveying apparatus. It is explanatory drawing explaining the conventional belt conveying apparatus. It is a graph explaining the conventional belt conveying apparatus. It is a graph explaining the conventional belt conveying apparatus. It is a graph explaining the conventional belt conveying apparatus. It is a graph explaining the conventional belt conveying apparatus. It is a graph explaining the conventional belt conveying apparatus. 2 is a graph illustrating a belt conveyance device of the image forming apparatus illustrated in FIG. 1. 2 is a graph illustrating a belt conveyance device of the image forming apparatus illustrated in FIG. 1. 2 is a graph illustrating a belt conveyance device of the image forming apparatus illustrated in FIG. 1.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of an image forming apparatus to which the present invention is applied. FIG. 1 shows an image for forming a full-color image on an intermediate transfer belt as an endless belt (intermediate transfer member) using four image carriers (hereinafter referred to as photosensitive drums) in which developing devices as developing units are arranged side by side. It is a schematic block diagram which shows the principal part of a formation apparatus. In this image forming apparatus, at the time of image formation, the four photosensitive drums 101Y, 102M, 103C, and 104Bk are rotationally driven in the directions of arrows (counterclockwise), and the surfaces thereof are uniformly made by the chargers 111, 112, 113, and 114. Charges up. Thereafter, exposure is performed in accordance with input image information (image data) by the exposure devices 121, 122, 123, and 124, and an electrostatic latent image (latent image) is formed in the latent image forming unit. The yellow developing device 131Y attaches toner to the electrostatic latent image on the photosensitive drum 101Y to develop it as a yellow toner image, and the magenta developing device 132M attaches toner to the electrostatic latent image on the photosensitive drum 102M. Then, the toner is developed as a magenta toner image, and the cyan developing device 133C attaches the toner to the electrostatic latent image on the photosensitive drum 103C to develop it as a cyan toner image, and the black developing device 134Bk develops it on the photosensitive drum 104Bk. A toner is attached to the electrostatic latent 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 101Y, 102M, 103C, and 104Bk, and rotate in the direction of an arrow 200 (intermediate transfer belt). Primary transfer is performed on the top. Then, four color toner images are superimposed on the intermediate transfer belt 200. These four color toner images are secondarily transferred to a recording material P conveyed from a paper feed cassette (not shown) by a secondary transfer means (not shown), thereby obtaining a full color image.

FIG. 2 is a diagram showing an embodiment of the belt deviation detecting means according to the present invention.
A detection line 201 is formed on the surface of the intermediate transfer belt 200 at a fixed position in the main scanning direction over the entire circumference in the transport direction. At a position facing the detection line, belt deviation / skew detection means 205 is arranged so that the position of the detection line in the main scanning direction can be detected. By sequentially detecting the position of the detection line in the main scanning direction, the belt shift can be detected. In addition, as shown in FIG. 13, two belt deviation / skew detection means 205 are arranged on the primary transfer surface of the intermediate transfer belt 200 at a certain interval in the sub-scanning direction. The belt skew can be detected by sequentially detecting the difference between the positions of the detection lines in the main scanning direction detected by the two belt deviation / skew detection means 205. In this configuration, the belt shift / skew is detected by detecting the belt main scanning direction movement of the detection line 201 formed on the belt with high accuracy in advance. Therefore, the belt shift / skew is detected by detecting the position of the belt edge. Compared with a configuration to detect (for example, see Japanese Patent Application Laid-Open No. 2000-233843), it is necessary to refer to edge data measured in advance or to store data obtained by averaging periodic fluctuations in edge positions in a storage unit. However, it is possible to detect and control the belt at high speed without waste time with a lower cost configuration.

  Next, various aspects of the relationship between the driven roller and the intermediate transfer belt, which are characteristic configurations of the present invention, will be described. In addition, about the equivalent structure in each aspect, a corresponding code | symbol is attached | subjected and detailed description is abbreviate | omitted. Various aspects of the relationship between the driven roller and the intermediate transfer belt can be used singly or in combination of two or more aspects.

A first aspect of the relationship between the driven roller and the intermediate transfer belt will be described.
The intermediate transfer belt 200 is stretched by a plurality of rollers 211, 212, 213, 214, and 215 as substantially parallel stretching means, and in the belt conveyance direction by a driving roller 211 as one of the driving means. It is driven. The driving roller 211 and the driven rollers 212, 213, and 214 are fixed at predetermined positions. On the other hand, the steering roller 215 as an adjusting means corrects a shift generated in the intermediate transfer belt 200, and both ends of the rotating shaft of the steering roller 215 can be swung in a direction orthogonal to the roller rotating shaft by a pivot bearing or the like. In addition to being supported, one end side is supported by an actuator 216 which is a belt deviation correction means so as to be reciprocally movable in the direction of the arrow. Further, the steering roller 215 as a tension applying unit urges the intermediate transfer belt 200 with a substantially constant tension by urging both ends of the rotation shaft in the tension direction indicated by the arrow.

  Based on information from the belt deviation / skew detection means 205, the actuator 216 is driven, and the steering roller 215 is swung so that the belt moves in the direction opposite to the generated belt main scanning direction movement. It is controlled within a certain range, and it is possible to suppress the belt shift without providing a shift guide member or the like.

  The friction coefficient between the driven roller 214 and the intermediate transfer belt 200 is smaller than the friction coefficient between the steering roller 215 and the driven roller 213 adjacent to the intermediate transfer belt 200 in the belt conveyance direction. Specifically, the surface roughness of the surface (roller surface) of the driven roller 214 on which the intermediate transfer belt 200 is stretched is set so that the steering roller 215 and the driven roller 213 adjacent to the belt transfer direction and the intermediate transfer belt 200 are stretched. The processing is smaller than the surface roughness of the surface to be processed (roller surface). Alternatively, a surface coating with good lubricity such as a fluororesin is applied to the roller surface of the driven roller 214, or a surface coating with a material having high friction such as rubber is applied to the roller surfaces of the steering roller 215 and the driven roller 213. It is feasible by.

  By swinging the steering roller 215 to correct the belt, the belt posture is deformed by the axial force generated from the steering roller 215. The intermediate transfer belt 200 is inclined due to the deformation of the belt posture. Here, the friction coefficient between the driven roller 214 and the intermediate transfer belt 200 is smaller than the friction coefficient between the adjacent steering roller 215 and driven roller 213 and the intermediate transfer belt 200. Therefore, the inclination of the intermediate transfer belt 200 is generated not with respect to the driven roller 214 but with respect to the upstream driven roller 213. In the driven roller 213, an axial force opposite to the steering roller 215 acts on the intermediate transfer belt 200. The posture of the intermediate transfer belt 200 is greatly deformed in the intermediate transfer belt width direction between the steering roller 215 and the driven roller 213.

  For this reason, the belt position correction sensitivity with respect to the tilt of the steering roller 215 is increased, the belt position correction sensitivity with respect to the tilt of the steering roller 215 is made to be nearly linear, and the belt position correction range by the steering roller 215 is sufficiently secured. can do.

Here, the relationship between the driven roller and the intermediate transfer belt will be described in detail using analysis results.
For the analysis, one driving roller, four driven rollers and an endless belt were used. 6 shows the layout condition 1 used for the analysis, and FIG. 7 shows the layout condition 2. Layout condition 1 and layout condition 2 are the diameter of each roller, the circumferential length of endless belts 506 and 606, the positional relationship between first driven rollers 501 and 601 and second driven rollers 502 and 602, and the first to third driven rollers. The main conditions such as the belt winding range angle are the same. On the other hand, the interval between the second driven rollers 502 and 602 that are also the steering rollers and the third driven rollers 503 and 603 on the upstream side in the belt conveyance direction is different, and the interval X2 of the layout condition 2 is about the interval X1 of the layout condition 1. The interval is half.

  When the endless belts 506 and 606 are rotationally driven by the driving rollers 505 and 605 and the second driven rollers 502 and 602 are inclined in the direction orthogonal to the tension direction, the belt width obtained by the inclination A of the steering rollers 502 and 602 FIG. 8 shows the relationship between the belt position correction sensitivity in the direction (main scanning direction) and the belt position correction sensitivity in the belt width direction obtained by the inclination 2.5A of the steering rollers 502 and 602.

  FIG. 13 shows that in the layout condition 2, the friction coefficient between the belt 606 and the third driven roller 603 is about 1/3 of the conventional one (hereinafter referred to as the conventional friction coefficient condition) and the conventional one. It is the figure which compared the belt position correction sensitivity with what (henceforth the friction coefficient conditions of this invention) what did. When the belt 606 is rotationally driven by the driving roller 605 and the second driven roller 602 as the steering roller is tilted in a direction (steering conditions) perpendicular to the tension direction with respect to the belt 606, the steering roller inclination A The relationship between the belt position correction sensitivity in the belt width direction (main scanning direction) obtained at this time and the belt position correction sensitivity obtained when the steering roller tilt is 2.5A is shown.

  As shown in FIG. 13, the belt position correction sensitivity at the inclination A of the steering roller 602 is about 1.8 times as high as that of the conventional friction coefficient condition. From this analysis result, it can be seen that a greater belt position correction sensitivity can be obtained by reducing the frictional force between the belt 606 and the roller 603 adjacent to the upstream side of the steering roller 602 in the belt conveyance direction. In addition, the correction sensitivity at the inclination 2.5A of the steering roller 602 is about 2.5 times that at the inclination A, and it can be seen that the relationship of the correction sensitivity to the inclination of the steering roller 602 approaches a linear behavior.

  14 and 15 show the axial force acting on the belt 606 from each roller and the posture of the belt 606 deformed by the force under the friction coefficient condition of the present invention under the layout condition 2. 14 shows a case where the steering roller 602 has an inclination A, and FIG. 15 shows a case where the steering roller 602 has an inclination of 2.5A. The large axial force acting from the roller 602 to the belt 606 is a fourth driven roller 602 that is a steering roller and a fourth driven roller 603 that is further upstream of the third driven roller 603 adjacent to the upstream side in the belt conveyance direction. And the driven roller 604 of FIG. Due to the force, the posture of the belt 606 is largely deformed in the width direction between the driven roller 602 and the driven roller 604. On the other hand, the posture of the belt 606 is hardly deformed at other roller positions. Further, the deformation in the width direction of the posture of the belt between the second driven roller 602 and the fourth driven roller 604 is about 2 when the steering roller inclination is 2.5A and the steering roller inclination is A. .5 times. Therefore, the deformation state of the entire belt is about 2.5 times, and the belt position correction sensitivity is about 2.5 times.

From the above results, the following actions can be considered.
First, the posture of the belt is deformed by an axial force acting on the belt from the steering roller due to the inclination of the steering roller.
Second, due to the deformation of the belt posture, an axial force opposite to the steering roller acts on the roller adjacent to the steering roller on the upstream side in the belt conveyance direction due to the inclination of the belt.
Third, the smaller the frictional force between the roller adjacent to the steering roller and the belt conveyance direction and the belt, the smaller the force acting on the belt from this roller, and the smaller the deformation of the belt posture.
Fourth, when the frictional force between the roller adjacent to the steering roller and the upstream side in the belt conveyance direction and the belt is small, the upstream roller has a large axial direction opposite to the steering roller due to the inclination of the belt. Power works.
Fifth, the greater the friction between the roller and the belt, the greater the force acting on the belt from the roller and the greater the deformation of the belt posture.

  Under the conventional friction coefficient conditions, the distance between the second driven roller and the third driven roller that generates an axial force in the opposite direction to the belt is small, and the belt is difficult to deform with respect to the axial force. However, under the friction coefficient condition of the present invention, the roller that generates the axial force in the opposite direction to the belt becomes the second driven roller and the fourth driven roller, and the interval between the rollers can be increased. Therefore, the belt position correction sensitivity by the steering roller can be increased, and the belt position correction sensitivity with respect to the tilt of the steering roller can be made closer to linear.

  Next, a second aspect regarding the relationship between the driven roller and the intermediate transfer belt will be described. In the second mode, an additional driven roller (not shown) other than the driven roller 214 is disposed between the steering roller 215 and the driven roller 213 for the image forming operation, and the intermediate transfer belt 200 is stretched. May be. In this case, the friction coefficient of the further arranged driven roller and driven roller 214 and the intermediate transfer belt 200 is smaller than the friction coefficient of the steering roller 215, the driven roller 213 and the intermediate transfer belt 200. With such a configuration, the intermediate transfer belt 200 can be deformed between the steering roller 215 and the driven roller 213 without the posture of the intermediate transfer belt 200 being deformed by the further arranged driven roller. The same effect as the above-described aspect can be obtained.

  Next, a third aspect regarding the relationship between the driven roller and the intermediate transfer belt will be described. In the third mode, the surface of the intermediate transfer belt 200 with which the driven roller 214 abuts is different from the surface of the intermediate transfer belt 200 with which the driven roller 213 and the steering roller 215 abut. Here, the friction of the surface on the side where the driven roller 214 abuts on the intermediate transfer belt 200 is set to be lower than the friction on the surface on the side where the driven roller 213 and the steering roller 215 abut on the intermediate transfer belt 200. An effect equivalent to that of the above-described aspect can be obtained.

  Specifically, the surface on the side where the driven roller 214 abuts on the intermediate transfer belt 200 is processed with a surface roughness smaller than the surface on the side where the driven roller 213 and the steering roller 215 abut on the intermediate transfer belt 200. . Alternatively, the surface of the side on which the driven roller 214 abuts on the intermediate transfer belt 200 may have a two-layer structure in which the surface is formed of a material having good lubricity such as a fluororesin. Alternatively, the surface on the side where the steering roller 215 and the driven roller 213 are in contact with the intermediate transfer belt 200 may be processed with a larger surface roughness than the surface on the side where the driven roller 214 is in contact with the intermediate transfer belt 200. Further, the surface on the side where the steering roller 215 and the driven roller 213 come into contact with the intermediate transfer belt 200 may be formed of a material having a large friction such as rubber resin.

  Next, a fourth aspect regarding the relationship between the driven roller and the intermediate transfer belt will be described. In the fourth aspect, in FIG. 13, the driven roller 214 is supported in a fixed state that does not rotate about the axis. That is, when the intermediate transfer belt 200 is traveling, the driven roller 214 and the intermediate transfer belt 200 are in a sliding state. Therefore, the friction coefficient between the driven roller 214 and the intermediate transfer belt 200 is a dynamic friction coefficient. On the other hand, the driven roller 213 and the steering roller 215 are supported so as to be rotatable about an axis. Therefore, the friction coefficient of the driven roller 213, the steering roller 215, and the intermediate transfer belt 200 is a static friction coefficient. As a result, the coefficient of friction between the driven roller 214 and the intermediate transfer belt 200 becomes smaller than the coefficient of friction between the driven roller 213, the steering roller 215, and the intermediate transfer belt 200, and the same effect as the above-described aspect can be obtained. Can do.

  Next, a fifth aspect of the relationship between the driven roller and the intermediate transfer belt will be described. In the fifth aspect, in the analysis result described above, the axial force acting from the roller to the belt by the steering generates a large reverse force between the steering roller and the upstream roller in the belt conveyance direction. As a result, it has been found that the belt largely deforms the posture of the belt in the belt width direction between the steering roller and the upstream roller in the belt conveyance direction. As a result of further analysis, when the belt winding angle of the adjacent roller on the upstream side in the belt conveyance direction of the steering roller is small, specifically, when the belt winding angle is smaller than about 40 degrees, the roller acts on the belt. The axial force is smaller. For this reason, it has been found that the deformation of the posture of the belt in the belt width direction in this roller is also reduced. Here, the belt wrap angle of the roller refers to an angle in a range where the belt is in contact with the entire circumference of the roller. That is, the belt winding angle is a central angle of the roller with respect to a range where the belt is in contact with the outer peripheral surface of the roller.

  This is the same as the behavior when the friction coefficient between the intermediate transfer belt 200 and the roller is small. Specifically, the large force in the reverse direction acts on the large axial force acting on the intermediate transfer belt 200 from the steering roller 215. The roller having a small belt winding angle of about 40 degrees or less (see FIG. (Not shown), the roller 214 has the shortest transport distance upstream of the steering roller 215 and the intermediate transfer belt in the transport direction. Therefore, the belt 200 is greatly deformed in the width direction between the roller 214 and the steering roller 215. As a result, an effect equivalent to the above-described aspect can be obtained.

  Next, a sixth aspect of the relationship between the driven roller and the intermediate transfer belt will be described. In the sixth aspect, as shown in FIG. 4, the intermediate transfer belt 200 is stretched by a plurality of substantially parallel rollers, and is driven in the intermediate transfer belt conveyance direction by one drive roller 211 among them. Yes. The driving roller 211 and the driven rollers 212 and 213 are fixed at predetermined positions. On the other hand, both ends of the rotating shaft of the steering roller 215 as the tension applying means are urged in the tension direction indicated by the arrow. The intermediate transfer belt 200 is stretched with a substantially constant tension.

  Further, the steering roller 215 is supported at both ends of the rotating shaft of the steering roller 215 as a adjusting means so as to be swingable in a direction orthogonal to the roller rotating shaft by a pivot bearing or the like. Then, one end side thereof is supported by an actuator 216 serving as a belt deviation correcting unit so as to be reciprocally movable in the arrow direction. Then, it is possible to correct the deviation generated in the intermediate transfer belt 200.

  Further, the steering roller 224 as the second adjusting means is supported at both ends of the rotating shaft of the steering roller 224 so as to be swingable in a direction orthogonal to the roller rotating shaft by a pivot bearing or the like. Then, one end side thereof is supported by an actuator 217 as a belt skew feeding correcting means so as to be reciprocally movable in the arrow direction. Then, it is possible to correct the skew generated in the intermediate transfer belt 200.

  The actuator 216 is driven based on information from the belt deviation / skew detection unit 205 and swings the steering roller 215 so that the intermediate transfer belt 200 moves in the direction opposite to the generated movement in the intermediate transfer belt main scanning direction. Move. Therefore, the belt shift is controlled within a certain range, and the belt shift can be suppressed without providing a shift guide member or the like.

  The actuator 217 is driven based on information from the belt deviation / skew detection means 205 and swings the steering roller 224 so that the intermediate transfer belt 200 moves in the direction opposite to the generated movement in the intermediate transfer belt main scanning direction. Move. Therefore, the belt skew is controlled within a certain range, and image distortion and color misregistration can be prevented.

  The friction coefficient between the steering roller 224 and the intermediate transfer belt 200 is set to a value smaller than the friction coefficient between the adjacent steering roller 215 and driven roller 213 and the intermediate transfer belt 200. Therefore, the belt position correction sensitivity by the steering roller 215 can be increased, and the belt position correction sensitivity with respect to the tilt of the steering roller 215 can be made closer to a linear shape.

  In order to correct the belt shift, it is necessary to change the posture of the belt by the steering roller and the upstream roller in the belt conveyance direction. On the other hand, the skew of the belt can be corrected by changing the inclination of the belt carried out from the roller with respect to the inclination of the belt carried into the roller according to the inclination of the roller. Therefore, it is not affected by the distance between the steering roller and the upstream roller in the belt conveyance direction, or the friction between the steering roller and the belt.

  Next, a seventh aspect regarding the relationship between the driven roller and the intermediate transfer belt will be described. In the seventh aspect, as shown in FIG. 5, the intermediate transfer belt 200 is stretched by a plurality of substantially parallel rollers, and is driven in the belt conveyance direction by one drive roller 211 among them. The driving roller 211 and the driven rollers 212 and 213 are fixed at predetermined positions. On the other hand, both ends of the rotating shaft of the steering roller 234 as tension applying means are urged in the tension direction indicated by the arrow. The belt is stretched with a substantially constant tension.

  Further, the steering roller 234 as the second adjusting means is supported at both ends of the rotation shaft of the steering roller 234 by a pivot bearing or the like so as to be swingable in a direction orthogonal to the roller rotation shaft. Then, one end side thereof is supported by an actuator 217 as a belt skew feeding correcting means so as to be reciprocally movable in the arrow direction. Then, it is possible to correct the skew generated in the intermediate transfer belt 200.

  Further, the steering roller 225 as an adjusting means is supported at both ends of the rotating shaft of the steering roller 225 by a pivot bearing or the like so as to be swingable in a direction orthogonal to the roller rotating shaft. Then, one end side thereof is supported by an actuator 216 serving as a belt deviation correcting unit so as to be reciprocally movable in the arrow direction. Then, it is possible to correct the deviation generated in the intermediate transfer belt 200.

  The actuator 216 is driven based on information from the belt deviation / skew detection means 205 and swings the steering roller 225 so that the intermediate transfer belt 200 moves in the direction opposite to the generated movement in the intermediate transfer belt main scanning direction. Move. Therefore, the belt shift is controlled within a certain range, and the belt shift can be suppressed without providing a shift guide member or the like.

  The actuator 217 is driven based on information from the belt deviation / skew detection unit 205 and swings the steering roller 234 so that the intermediate transfer belt 200 moves in the direction opposite to the generated movement in the intermediate transfer belt main scanning direction. Move. Therefore, the belt skew is controlled within a certain range, and image distortion and color misregistration can be prevented.

  The friction coefficient between the steering roller 234 and the intermediate transfer belt 200 is set to a value smaller than the friction coefficient between the adjacent steering roller 225 and the driven roller 213 and the intermediate transfer belt 200. Therefore, the belt position correction sensitivity by the steering roller can be increased, and the belt position correction sensitivity with respect to the tilt of the steering roller can be made closer to linear.

  The steering roller 225 applies an axial force to the intermediate transfer belt 200 to deform the posture of the belt. Therefore, an axial reaction force acts on the steering roller 225 from the intermediate transfer belt 200.

  In general, the tension roller has a configuration in which both ends thereof are urged by a spring or the like, and therefore an unnecessary inclination is generated by a reaction force from the belt. Therefore, when the steering roller 225 is a tension roller, the belt 200 may be twisted.

  However, when the steering roller 234 is a tension roller as in this embodiment, the friction coefficient between the steering roller 234 and the belt 200 is small, and the reaction force received from the belt 200 is also small. Therefore, unnecessary inclination hardly occurs and the problem of occurrence of twisting of the belt 200 can be avoided.

  By applying the belt conveyance device according to at least one of the first to seventh aspects to the intermediate transfer belt mechanism of the image forming apparatus as shown in FIG. 1, the deviation and skew of the endless belt are reliably corrected. it can. As a result, it is possible to provide a small and simple image forming apparatus that stably controls the shift of the intermediate transfer belt and reliably corrects the color misregistration of the image.

  The embodiment of the present invention has been described with respect to the secondary transfer type image forming apparatus. However, the present invention is not limited to this mode, and is applicable to a direct transfer type photographic image forming apparatus. Specifically, each toner image formed on a plurality of electrostatic latent image carriers (photosensitive members) is transported as a recording material as a transporting means for transporting each electrostatic latent image carrier, the recording material, and the recording material. By applying pressure and electric force to the toner in the vicinity of the transfer nip formed by the belt, the toner is sequentially superimposed and transferred onto a recording material such as transfer paper, and after a fixing operation by pressing and heating, a final color image is obtained. . Then, by applying the belt conveying device of at least one of the first to seventh aspects to the recording material conveying belt of the image forming apparatus, the deviation and skew of the endless belt can be reliably corrected, and the intermediate transfer belt It is possible to provide a small-sized and simple image forming apparatus that stably controls the shift and reliably corrects the color misregistration of the image.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this. It should be noted that the materials and dimensions of each component introduced in the above-described embodiment are merely examples, and it is needless to say that various materials and dimensions can be selected within a range where the effects of the present invention can be exhibited.

200 Intermediate transfer belt (an example of an endless belt)
211, 212, 213, 214, 215 Roller (an example of stretching means)
211 Driving roller (an example of driving means)
215 Steering roller (an example of adjusting means and tension applying means)
224 Steering roller (an example of second adjusting means)
225 Steering roller (an example of adjusting means)
234 Steering roller (an example of second adjusting means and tension applying means)

JP 2009-180884 A JP 2010-204255 A Japanese Patent No. 5257169 JP 2010-217301 A JP 2011-2632 A JP 2011-22549 A Japanese Patent No. 3976924 Japanese Patent No. 4967328 JP 2009-151097 A JP 2009-282196 A JP 2012-233976 A

In order to solve the above-described problem, a belt conveying device according to claim 1 of the present invention is provided.
A plurality of stretching means;
An endless belt stretched around the plurality of stretching means,
The plurality of stretching means,
Driving means for driving the endless belt;
Adjusting means in which one end moves relative to the other end in a direction perpendicular to the width direction of the endless belt,
In the belt conveying apparatus that conveys the endless belt by the driving means and corrects the position of the endless belt by the adjusting means,
The coefficient of friction between the endless belt and the at least one tensioning means, which is positioned upstream of the adjustment means in the conveying direction of the endless belt , is fixed with respect to the at least one tensioning means. The coefficient of friction is smaller than the coefficient of friction between two endless belts adjacent in the conveying direction of the endless belt and the endless belt.

Claims (10)

A plurality of stretching means;
An endless belt stretched around the plurality of stretching means,
The plurality of stretching means,
Driving means for driving the endless belt;
Adjusting means in which one end moves relative to the other end in a direction perpendicular to the width direction of the endless belt,
In the belt conveying apparatus that conveys the endless belt by the driving means and corrects the position of the endless belt by the adjusting means,
The coefficient of friction between the endless belt and the at least one stretching means positioned upstream in the transporting direction of the endless belt with respect to the adjusting means is such that the transporting direction of the endless belt with respect to the at least one stretching means. A belt conveying device characterized by having a smaller coefficient of friction between two adjacent stretching means and the endless belt.   The coefficient of friction of the surface of the at least one stretching means positioned on the upstream side in the conveying direction of the endless belt with respect to the adjusting means is the surface of the endless belt. The belt conveyance device according to claim 1, wherein the belt conveyance device has a coefficient of friction smaller than a friction coefficient of a surface stretched by the endless belt of two stretching means adjacent to each other in the conveyance direction. The surface of the endless belt, which is stretched by at least one stretching means positioned upstream in the conveying direction of the endless belt with respect to the adjusting means, is in the conveying direction of the endless belt with respect to the at least one stretching means. A surface different from the surface of the endless belt on which two adjacent stretching means are stretched;
The surface of the endless belt, which is stretched by at least one stretching means positioned upstream in the conveying direction of the endless belt with respect to the adjusting means, is in the conveying direction of the endless belt with respect to the at least one stretching means. The belt conveyance device according to claim 1 or 2, wherein a friction coefficient is smaller than a surface of the endless belt stretched by two adjacent stretching means. At least one stretching means positioned upstream in the conveying direction of the endless belt with respect to the adjusting means stretches the endless belt in a sliding state,
The two stretching means adjacent to the at least one stretching means in the conveying direction of the endless belt are rollers that are driven to rotate by conveying the endless belt. The belt conveyance device according to one item.   At least one stretching means positioned upstream in the conveying direction of the endless belt with respect to the adjusting means, except for the stretching means whose belt winding angle is approximately 40 degrees or less, in the conveying direction of the endless belt, The belt conveyance device according to any one of claims 1 to 4, wherein a distance from the adjustment unit is the shortest. At least one stretching means positioned upstream in the conveying direction of the endless belt with respect to the adjusting means has a first end that moves relative to the other end in a direction perpendicular to the width direction of the endless belt. 2 adjustment means,
The belt conveying device according to claim 1, wherein the endless belt is conveyed by the driving unit, and the position of the endless belt is corrected by the second adjusting unit.   7. The adjusting means and the second adjusting means correct the position of the endless belt in a direction orthogonal to the conveying direction of the endless belt and the inclination of the endless belt with respect to the conveying direction of the endless belt. The belt conveyance apparatus as described in.   The belt conveying apparatus according to claim 6, wherein the second adjusting unit is a tension applying unit that applies tension to the endless belt. On the image carrier,
A latent image forming unit that forms a latent image based on 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 a transfer image on the intermediate transfer member to a recording material,
In an image forming apparatus that forms a multi-color image by sequentially transferring visible images formed on a plurality of image carriers onto an intermediate transfer member,
The image forming apparatus according to claim 1, wherein the intermediate transfer member is a belt conveyance device according to claim 1. On the image carrier,
A latent image forming unit that forms a latent image based on image data;
A developing unit that visualizes the latent image formed in the latent image forming unit;
Conveying means for conveying a recording material to a position where a visible image formed on the image carrier is transferred;
A transfer means for transferring a visible image on the image carrier 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 image carriers onto a recording material,
The image forming apparatus according to claim 1, wherein the conveying unit is the belt conveying device according to claim 1.

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