JP2009163101A - Belt skew control method, belt driving device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt driving device accurately correcting and controlling belt skew with a simple structure. <P>SOLUTION: The belt driving device includes a belt (11), and a plurality of rotating bodies (12) for supporting the belt. The tension of the belt is adjusted by at least one rotating body, with at least one rotating body serving as a driving shaft, and the belt is driven by transmitting driving torque to the belt. The belt driving device includes: control rotating bodies (13-1 and 13-2) which support the belt and coaxially rotate on both sides or one side of the rotating body that is not a driving shaft; rotational load setting mechanisms (14-1 and 14-2) which set the rotational load of the control rotating bodies; a belt skew detection means which detects the skew position and skew direction of the belt in a direction orthogonal to a belt driving direction, and a control means that adjusts the skew of the belt by setting the rotational load of the respective control rollers of the rotational load setting mechanisms according to the skew position and skew direction of the belt detected by the belt skew detection means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a belt shift control method, a belt driving device, and an image forming apparatus, and more specifically, an electrophotographic printer or an intermediate transfer belt of a copying machine, an electrophotographic printer or a thermal fixing belt of a copying machine, The present invention relates to a technique for adjusting meandering and deviation generated in a belt used in a winding device.

  In a belt driving device that drives a belt supported by a plurality of rotating bodies, it is generally ideal that the belt is conveyed in the driving direction, but the inclination of the rotating body that constitutes the driving system, The belt may meander or drive due to differences in tension between the left and right sides, if the belt is an endless belt, the difference in the circumference of the belt itself, or the electrophotographic intermediate transfer belt or heat fixing belt due to fluctuations in the external load due to paper entry, etc. It is known that there is a phenomenon that approaches a direction different from the direction.

  Several configurations have been proposed in the past for preventing such belt slippage. Patent Documents 1 and 2 propose a method for preventing the belt from meandering by inclining a roller in an in-plane or out-of-plane direction. Further, Patent Document 3 proposes to develop on a casting machine. Further, Patent Document 4 proposes a mechanism for attaching a detection ring to the roller end and generating a force for returning the belt when the detection ring is rotated by the belt. Further, Patent Document 5 and Patent Document 6 propose to prevent belt slippage by devising the shape and layout of the rotating body of the apparatus. As a simple and inexpensive method, as disclosed in Patent Document 7, it is proposed to provide steps called detents at both ends of the belt.

Here, taking the image forming apparatus as an example, a method of tilting the rollers of Patent Documents 1 to 3 and a method of providing a shift stop of Patent Document 7 will be described with reference to the drawings.
FIG. 6 is a schematic cross-sectional view showing a configuration of an image forming / transfer mechanism unit in a quadruple tandem full-color image forming apparatus. As shown in the figure, in the image forming / transfer mechanism unit in the four-drum tandem full-color image forming apparatus, an electrostatic image is formed on the photosensitive member 101 and becomes a visible image by toner. This toner image is transferred to the intermediate transfer belt 102 by the photosensitive member 101 and the first transfer portion 103 of the intermediate transfer belt 102. The intermediate transfer belt 102 is held and driven by a driving roller 104 and two driven rollers 105. Then, the toner image transferred to the intermediate transfer belt 102 is transferred to the paper 107 by the second transfer unit 106 to form an image on the paper. The quadruple tandem full-color image forming apparatus has four photoconductors 101, and each photoconductor 101 forms a different color image. This color image is superimposed on the intermediate transfer belt 102 to form a full color image, which is finally transferred to the paper 107. When a color shift phenomenon occurs when the color images of the respective colors are superimposed on the intermediate transfer belt 102, the intermediate transfer belt 102 moves to either side different from the driving direction. As a result, the superposition positions of the four colors are irregularly shifted. For example, assuming that there is 300 mm from the transfer position of the first photoconductor to the belt to the transfer position of the fourth photoconductor, there is a belt shift of 0.1% (ratio of the shift amount to the travel distance). , The color shift is 300 μm, which is an unacceptable value in terms of image quality.

  Therefore, as shown in FIG. 7, a step shift stop member 108 is formed at both ends of the intermediate transfer belt 102, and a plurality of guide rollers 109 are provided in the drive system. When the member 108 comes into contact, the belt 108 is restricted so that the belt does not move any further.

Further, as shown in FIG. 8, one of the rollers constituting the drive system is a steering roller 110. The steering roller 110 can be tilted at an arbitrary angle (in-plane tilted) with respect to the traveling direction of the intermediate transfer belt 102, and the shifting direction of the intermediate transfer belt 102 can be controlled. Further, the belt shift detection unit 111 detects the shift state and shift amount of the intermediate transfer belt 102 and controls the steering roller 110 to prevent the belt shift. Although the image forming apparatus has been described above, the same applies to a general belt conveying apparatus, an apparatus that conveys a belt-like thing such as paper or cloth, and the like.
Patent No. 2,788,683 Japanese Patent No. 3,082,452 Patent No. 3,649,487 Japanese Patent Laid-Open No. 11-208441 Japanese Patent No. 3,419,513 Patent No. 3,720,765 JP 2006-119473 A

  However, as shown in FIG. 7, according to the shift prevention mechanism using a step called a shift stop as in Patent Document 7, there is an advantage that it can be constructed with a simple structure and at a low cost. May be a problem. In other words, there is a possibility that the detent member is always in contact with the guide surface of the guided roller to prevent the belt from deviating, and the detent member will deteriorate over time, reducing the function of preventing the belt from deviating. There is a possibility that the offset force increases due to poor adjustment and the offset stop member rides on the guide surface. In addition, the fact that the detent is always in contact with the guide surface acts as a disturbance for the belt drive system, causes fluctuations in the belt speed, and leads to a decrease in image quality. Such a point is not a problem with a low-speed machine of an image forming apparatus. However, with a high-speed machine, the belt speed is increased, so that the force transmitted to the belt is also increased, which is a problem in terms of image quality and durability.

  Further, as shown in FIG. 8, the steering roller system by tilting a predetermined rotation shaft as in Patent Documents 1 to 3 can solve the problems of durability and performance in the above-described detent, but tilts the roller itself. Therefore, a complicated mechanism is required. In particular, a control device that constantly controls the tilt angle of a roller generally controls the tilt angle of the roller by moving a link mechanism or the like by means of a rotary actuator, which increases the number of parts and makes the mechanism complicated and expensive. End up. Further, the mechanism using the detection ring proposed in Patent Document 4 is also structurally complicated and expensive, and is a mechanical shift prevention mechanism. It is difficult to improve. Further, in the case of a mechanism for preventing a shift in the structure and layout of the rotating shaft as in Patent Document 5 and Patent Document 6, there is a problem that it is weak against changes with time and initial adjustment is difficult.

  The present invention is for solving these problems, and has a simple structure and a belt deviation control method and a belt driving device capable of correcting and controlling the belt deviation with high accuracy, and prevents deterioration in image quality. An object of the present invention is to provide an image forming apparatus that is inexpensive and excellent in durability.

  In order to solve the above problems, according to the belt deviation control method of the present invention, the belt includes a belt and a plurality of rotating bodies that support the belt, and the tension of the belt is adjusted by at least one rotating body, This is a belt shift control method in a belt drive device in which at least one rotating body is a drive shaft and the belt is driven by transmitting drive torque to the belt. The belt deviation control method of the present invention is characterized in that the deviation of the belt is controlled by adjusting the linear velocity at both ends of the belt with respect to the rotating body in the traveling direction in which the belt advances with respect to the rotating body. Therefore, correction control for the belt shift can be performed with a simple configuration.

  Further, by adjusting the linear velocity at both ends of the belt with respect to the rotating body in accordance with the direction and amount of deviation of the belt, the belt deviation correction control can be performed with a simple configuration and with high accuracy.

  Furthermore, a belt drive device according to another invention includes a belt and a plurality of rotating bodies that support the belt, the tension of the belt is adjusted by at least one rotating body, and at least one rotating body is a drive shaft. The belt is driven by transmitting driving torque to the belt. The belt driving device of the present invention includes a control rotator that supports the belt and rotates coaxially on both sides or one side of the rotator that is not a drive shaft, and a rotation load setting mechanism that sets a rotation load of the control rotator. Belt deviation detection means for detecting the belt deviation position and deviation direction perpendicular to the belt driving direction, and each control roller of the rotational load setting mechanism according to the belt deviation position and deviation direction detected by the belt deviation detection means And a control means for adjusting the deviation of the belt by setting the rotational load. Therefore, correction control near the belt can be performed with a simple configuration and high accuracy.

  The rotational load setting mechanism preferably has a brake mechanism or a motor.

  Further, the control means performs a predetermined calculation from the position deviation between the target belt position and the belt position detected by the belt position detection means, and sets the rotational load of each control roller of the rotational load setting mechanism. Is output. Therefore, stable belt driving is possible even if the belt deviation fluctuates due to environmental changes or changes over time.

  An image forming apparatus as another invention is characterized in that the belt is an endless belt and the belt driving device is mounted. Therefore, it is possible to provide an image forming apparatus with improved high-quality image quality and low cost and excellent durability.

  According to the belt deviation control method of the present invention, the deviation of the belt is controlled by adjusting the linear velocity at both ends of the belt with respect to the rotating body in the traveling direction in which the belt advances with respect to the rotating body. Therefore, correction control near the belt can be performed with a simple configuration and high accuracy.

  First, the principle of the belt deviation control method of the present invention will be outlined with reference to FIG. It has been found that the belt shift phenomenon in the belt drive system is determined by the belt entrance angle (traveling direction) with respect to the roller. Therefore, the belt shift phenomenon can be eliminated by controlling the belt entrance angle (traveling direction) with respect to the roller. As a method of changing the traveling direction of the belt, there is a method of giving a speed difference at both ends of the belt as shown in FIG. This method is the same principle as when the left and right caterpillars of an endless track vehicle have a speed difference, they are bent toward the slower caterpillar side. In FIG. 1A, the belt runs straight when both sides are constant speed. FIG. 1B shows a case where the belt linear velocity is slow on the left side, and as a result, the belt moves to the left side. Embodiments of a belt driving device to which the principle of the present invention is applied will be described below.

  FIG. 2 is a schematic configuration diagram showing the configuration of the belt driving device according to the first embodiment of the present invention. The belt 11 in the belt driving device 10 of the present embodiment shown in the figure includes a driving roller (not shown) and a driven roller having a first control roller 13-1 and a second control roller 13-2 on both sides. 12 is suspended. The first and second control rollers 13-1 and 13-2 on both sides can rotate independently of the driven roller 12, and each of the first and second control rollers 13-1 and 13-2. Both ends of the belt 11 are in contact with a part of the rotation surface. The first and second control rollers 13-1 and 13-2 have first and second rotational load setting mechanisms 14-1 and 14-2, respectively. This is a mechanism that can change the rotational loads of the first and second control rollers 13-1 and 13-2. As a rotational load setting mechanism, there are a method using a torque control type motor and a method using a brake. When a torque control type motor is used, it can be increased or decreased with respect to the belt conveying speed. Since it is possible to make a large speed difference on both sides, such as increasing the speed of one side and decelerating the other side, it is possible to obtain a large control range with respect to the belt. However, when a motor is used, a counter electromotive force is generated particularly when the motor is decelerated with respect to the belt conveyance speed. Therefore, a load is applied to the motor driver and a configuration for this is necessary. On the other hand, when a brake is used, it can only be decelerated. When the brake is used, fine rotational load control is necessary so as not to cause a heavy load on the belt in order not to reduce the conveying speed of the belt itself. As a brake mechanism capable of such control, there is a powder brake. A rotational load torque almost linear with respect to the input current amount can be obtained.

  FIG. 3 is a schematic configuration diagram showing the operation of the belt driving apparatus according to the first embodiment. Here, the first and second rotational load setting mechanisms 14-1 and 14-2 are used when a brake is used. The normal belt 11 has a desired belt position (shown by a solid line), but when the belt 11 is at a close belt position (shown by a broken line), the traveling direction of the belt 11 needs to be changed from an arrow A to an arrow B. Therefore, if the brake of the second rotational load setting mechanism 14-2 on the right side in the figure is turned on and the brake of the first rotational load setting mechanism 14-1 on the left side in the figure is turned off, the result will be the right side in the figure. The traveling angle (traveling direction) of the belt 11 changes from the arrow A to the arrow B. In order to change the traveling angle (traveling direction) of the belt 11 on the left side in the figure, the brake of the second rotational load setting mechanism 14-2 is turned OFF, and the brake of the first rotational load setting mechanism 14-1 is It should be ON. Further, in the belt driving device 10 of the first embodiment, the first and second control rollers having the first and second rotational load setting mechanisms 14-1 and 14-2 on both sides of the driven roller 12, respectively. 13-1 and 13-2 are provided, respectively, but a control roller having a fixed load setting mechanism may be provided on one side of the driven roller 12 for control. In this case, the belt shift control is performed only in one direction.

  According to the belt driving apparatus of this embodiment, since the belt is not forcibly deformed unlike the steering system, the stress on the belt is small, which is convenient for the life of the belt itself. In addition, since the control is for the rotating body, the configuration of the movable portion is simplified as compared with the steering method or the like. The steering system requires an arm mechanism that extends to the center of the tilt with respect to the roller shaft, and it is difficult to reduce the size. In the present invention, however, it is advantageous in that the configuration is only around the shaft. is there.

  By the way, when the belt is actually driven, a change in the surrounding length of the belt itself occurs due to changes in the external environment such as changes in humidity and temperature. In the image forming apparatus, the print paper enters and contacts the cleaning roller. Due to the external load caused by the belt, the belt shift state always changes. That is, even if the belt deviation does not occur in the initial state, the deviation occurs during operation. Therefore, in FIG. 4 showing the configuration of the belt driving apparatus according to the second embodiment of the present invention, in the belt driving apparatus of the present embodiment, the belt deviation amount (belt deviation position) during driving is detected by the belt deviation sensor 15. The first and second rotational load setting mechanisms 14-1 and 14-2 are controlled and driven on the basis of the amount of belt deviation detected by the control unit 16 so as to be on both sides of the driven roller. The rotational loads of the first and second control rollers 13-1 and 13-2 are changed. As a result, a speed difference occurs between the left and right sides of the belt 11, and the deviation of the belt 11 is dynamically controlled. The belt deviation sensor 15 includes a method of detecting the position by contacting the belt end, a method of optically detecting a mark on the belt, and the like. The belt deviation sensor 15 outputs a belt deviation amount at regular time intervals. The belt shift phenomenon itself is not a periodic component but a linear characteristic, and a high sensing frequency is not necessary. In general, sufficient detection and control are possible if there are about 10 detections during one revolution of the belt. However, the belt offset position output from the sensor may cause many errors depending on the sensing method. For example, in the method of detecting the belt end portion, deformation of the belt itself, a belt cut error, and the like are generated, and in particular, belt deviation fluctuation of one belt period occurs. Therefore, it is necessary to remove this periodic component and the like. Therefore, the amount of belt deviation detected by the belt deviation sensor 15 is supplied to the periodic component cut filter 16-1 in the control unit 16. This periodic component cut filter 16-1 is a digital filter, and the periodic component is removed by cutting the waveform component of a specific period from the belt-side position data. Then, the belt rotation amount detected by the belt deviation sensor 15 via the periodic component cut filter 16-1 in the control unit 16 with respect to the belt deviation position stored in the control table 16-2 as shown in FIG. Each control value (first and second brake control values) of the belt rotation load corresponding to the amount of belt deviation detected by the belt deviation sensor 15 is read from the control value of the load, and each control value of the read belt rotation load is read out. Thus, the rotational loads of the first and second control rollers 13-1 and 13-2 are changed by controlling and driving the rotational loads of the first and second rotational load setting mechanisms 14-1 and 14-2. it can. Therefore, the belt shift can be controlled dynamically.

  The control value of the belt rotation load is an increase / decrease value with respect to the current rotation load. If you want to move the belt in a certain direction, whether to increase or decrease the rotation load, and which side to control the control roller? , Shows. Further, the data stored in the control table 16-2 is calculated experimentally. Based on the control value read from the control table 16-2, the first and second rotational load setting mechanisms 14-1 and 14-2 are operated. Further, the deviation position output from the belt deviation sensor 15 can be controlled so that the belt position is always the ideal position by using the value of the distance between the ideal belt conveyance position and the actual position. Become.

  By the way, when the belt shift phenomenon occurs, in the image forming apparatus including the belt driving device, the image is distorted particularly in the belt shift direction. In particular, in a color image forming apparatus as shown in FIG. 6, when a belt shift occurs in the middle of image formation, a belt forming four color images (cyan, magenta, yellow, and black images). Therefore, the relative position shift of each color image pattern on the belt occurs, resulting in color shift and image quality deterioration. Therefore, it is possible to prevent the deterioration of the image quality by mounting the belt driving device of the present invention described above or using the belt shift control method.

  The present invention is not limited to the above embodiments, and it goes without saying that various modifications and substitutions are possible as long as they are described in the scope of the claims.

It is a figure which shows the principle of the belt deviation control method of this invention. It is a schematic block diagram which shows the structure of the belt drive device which concerns on the 1st Embodiment of this invention. It is a schematic block diagram which shows the operation | movement in the belt drive device of 1st Embodiment. It is a schematic block diagram which shows the structure of the belt drive device which concerns on the 2nd Embodiment of this invention. FIG. 6 is a characteristic diagram illustrating a relationship of a control value of a belt rotation load with respect to a belt shift position. FIG. 3 is a schematic cross-sectional view illustrating a configuration of an image forming / transfer mechanism in a quadruple tandem full-color image forming apparatus. It is a figure which shows the structure of the conventional belt deviation | shift prevention mechanism. It is a perspective view which shows another structure of the conventional belt deviation | shift prevention mechanism.

Explanation of symbols

10; belt drive device; 11; belt; 12; driven roller;
13-1, 13-2; control roller,
14-1, 14-2; rotational load setting mechanism, 15: belt deviation sensor,
16; control unit, 16-1; periodic component cut filter,
16-2: Control table.

Claims (7)

A belt and a plurality of rotating bodies that support the belt; tension of the belt is adjusted by at least one rotating body; at least one rotating body is a drive shaft; and a driving torque is transmitted to the belt. A belt driving device for driving the belt by:
A belt deviation control method, comprising: adjusting a linear velocity of both ends of the belt with respect to the rotating body in a traveling direction in which the belt advances with respect to the rotating body to control the deviation of the belt.   The belt shift control method according to claim 1, wherein a linear velocity at both ends of the belt with respect to the rotating body is adjusted according to a shift direction and a shift amount of the belt. A belt and a plurality of rotating bodies that support the belt; tension of the belt is adjusted by at least one rotating body; at least one rotating body is a drive shaft; and a driving torque is transmitted to the belt. In the belt driving device for driving the belt by
A control rotating body that supports the belt and rotates coaxially on both sides or one side of the rotating body that is not a drive shaft;
A rotational load setting mechanism for setting the rotational load of the control rotor;
Belt deviation detection means for detecting the position and direction of deviation of the belt in the direction orthogonal to the belt driving direction;
Control means for adjusting the belt deviation by setting the rotational load of each control roller of the rotational load setting mechanism according to the belt deviation position and deviation direction detected by the belt deviation detection means. A belt driving device characterized by the above.   The belt driving device according to claim 3, wherein the rotational load setting mechanism includes a brake mechanism.   The belt driving device according to claim 3, wherein the rotational load setting mechanism includes a motor.   The control means performs a predetermined calculation from a position deviation between the target belt position and the belt position detected by the belt position detection means, and sets the rotational load of each control roller of the rotational load setting mechanism. The belt driving apparatus according to claim 3, wherein a control value is output.   An image forming apparatus, wherein the belt is an endless belt, and the belt driving device according to claim 3 is mounted.

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