JP2009047888A - Belt shift control method, belt drive device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt driving device having a simple structure and capable of correcting and controlling a belt shift with high accuracy, and an image forming device which can prevent deterioration of image quality and is inexpensive and excellent in durability. .
According to the belt shift 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, and at least one rotating body is provided. Is a drive shaft, and is a belt shift control method in a belt drive device that drives a belt by transmitting drive torque to the belt. In the belt shift control method of the present invention, a high tension portion is formed in a region perpendicular to the belt driving direction, and the formed high tension portion is moved according to the belt shift to control the belt shift.
[Selection] Figure 5

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.

  Such a belt shift phenomenon is analyzed in Non-Patent Documents 1 to 3 for an endless belt supported by two axes. Non-Patent Documents 1 to 3 describe the belt shift phenomenon (belt skew) when the driven roller is tilted in-plane and when it is tilted out-of-plane from finite element analysis and experimental results. However, a detailed analysis of the belt shift phenomenon of a complex structure composed of a plurality of rollers such as an image forming apparatus has not yet been made.

  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. 7 is a schematic cross-sectional view showing a configuration of an image forming / transfer mechanism in a four-drum 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% (the 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. 8, a step shifting 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, and the guide roller 109 and the stoppers are stopped. 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. 9, 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.
Transactions of the Japan Society of Mechanical Engineers (C) Volume 66, No. 647 (2000-7) Paper No.99-1427 P.2128-P.2134 Transactions of the Japan Society of Mechanical Engineers (C) Vol.67, No.658 (2001-6) Paper No.00-0510 P.1749-P.1755 Transactions of the Japan Society of Mechanical Engineers (C) Volume 70 Issue 695 (2004-7) Paper No.03-1151 P.2013-P.2020 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. 8, 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. 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.

  In addition, as shown in FIG. 9, 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 driving device capable of correcting and controlling the belt deviation with high accuracy, and can prevent deterioration in image quality and is inexpensive and durable. An object of the present invention is to provide an excellent image forming apparatus.

  In order to solve the above problems, according to the belt shift 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. In the belt shift control method of the present invention, a high tension portion is formed in a region perpendicular to the belt driving direction, and the formed high tension portion is moved according to the belt shift to control the belt shift. There is a feature. Therefore, correction control for the belt shift can be performed with a simple configuration.

  Further, by changing the moving direction and moving amount of the high tension portion in accordance with the moving direction and the moving amount of the belt, the correction control of the moving belt can be performed with a simple configuration and with high accuracy.

  Furthermore, by moving a high tension portion in the direction opposite to the moving direction of the belt, correction control of the belt can be performed with a simple configuration.

  According to another aspect of the invention, a belt drive device 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 the at least one rotating body is a drive shaft. The belt is driven by transmitting driving torque to the belt. The belt drive device of the present invention detects a high tension portion forming means for forming a high tension portion in a region perpendicular to the belt drive direction, and the amount and direction of deviation of the belt in the direction perpendicular to the belt drive direction. A belt position detecting means for calculating the position of the high tension portion formed by the high tension portion forming means according to the amount and direction of the belt detected by the belt position detecting means, and the calculation It is characterized by having a moving means for moving the position of the high tension portion formed by the high tension portion forming means to the position calculated by the processing means. Therefore, correction control near the belt can be performed with a simple configuration and high accuracy.

  Further, the moving means moves the high tension portion formed by the high tension portion forming means in the direction opposite to the moving direction near the belt, thereby enabling correction control of the belt position with a simple configuration.

  Moreover, it is preferable that the high tension part forming means is composed of a rotating body or a protruding member having a non-uniform outer diameter.

  Furthermore, an image forming apparatus as another invention is characterized in that the belt driving device is mounted. Therefore, an image forming apparatus with improved image quality can be provided, and an inexpensive and durable image forming apparatus can be provided because it can be realized with a simple configuration.

  According to the belt shift control method of the present invention, a high tension portion is formed in a region perpendicular to the belt driving direction, and the formed high tension portion is moved according to the belt shift to control the belt shift. 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 with respect to the roller. However, since the belt is not a complete rigidity but a flexible body, the belt is deformed and wound by the layout of the belt drive system. In FIG. 1A, when the belt 11 is wound around the belt drive system constituted by the drive roller 12 and the driven roller 13 in a deformed state, the angle of entry of the belt 11 into the drive roller 12 is determined in that state. Has been. As shown in FIG. 1B, when the belt tension between the rollers of the belt drive system is increased, the belt 11 is deformed into a shape shown by a solid line, and the belt approach angle with respect to the drive roller 12 is It can be seen that there is a change compared to the belt entry angle for the belt shape before the tension change indicated by the dotted line in the figure. That is, when the tension of the belt 11 between the rollers changes, the belt shift also changes. As can be seen from FIG. 2, which shows the relationship between the belt tension and the belt shift speed, the belt shift speed (unit length belt advances when a certain level of tension, which corresponds to the belt shift amount, starts to be applied to the belt. The length of the belt near the belt starts to change, and stops changing when the tension exceeds a certain level.

  The state near the belt also changes depending on the tension distribution in the belt main scanning direction. This phenomenon is schematically shown in FIG. 3, and the direction of the belt shift differs depending on which portion of the tension distribution in the tension distribution in the belt main scanning direction is biased in the main scanning direction. I understand that. Ideally, the belt tension distribution is constant, but due to the effects of non-parallelism due to the initial setting of the constituent rollers, variations in the belt's perimeter length distribution, and pressure roller position fluctuations when an external load is applied, the belt It is considered that tension distribution occurs in various forms. Therefore, when the belt tension distribution changes due to the influence of an external load or the like from a state where the belt is stably driven by a plurality of rotating bodies, that is, a driving roller and other driven rollers or pressure rollers, as shown in FIG. There is a belt slippage. Further, as can be seen from FIG. 4 showing the relationship between the belt left-right tension difference and the belt shift speed, the belt shift speed is generated in the direction in which the tension difference is generated according to the belt left-right tension difference. Therefore, the belt shift control method of the present invention uses such a principle to form a high tension portion in the main scanning direction between the belts, and controls the belt shift by changing the position of the high tension portion. It is. Hereinafter, an embodiment of a belt driving device of another invention to which the present invention is applied will be described.

  FIG. 5 is a schematic configuration diagram showing the configuration of the belt driving device according to the embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components. The belt driving apparatus 10 according to the present embodiment shown in the figure has a high tension for forming a high tension portion in the main scanning direction of the belt 11 between the driving roller 12 and the driven roller 13 on which the belt 11 is suspended. Part forming means 14 is arranged. In the present embodiment, the high tension portion forming means 14 is composed of a rotating body having a non-uniform outer diameter, that is, a drum-shaped roller. The high tension portion forming means 14 is not limited to a drum-shaped roller, and may be a protrusion-like member. The shape or the like need not be limited as long as the high tension portion is formed in the main scanning direction of the belt 11. The belt portion in contact with the central portion having the largest outer diameter is in the highest tension state by the high tension portion forming means 14 formed of a rotating body having a non-uniform outer diameter, that is, a drum-shaped roller. In a state where the belt drive is stable, it can be said that the high tension portion which is in contact with the central portion having the largest outer diameter of the high tension portion forming means 14 is in a balanced position where the belt is not shifted. However, as described above, the balance is lost due to an external load or the like, and the high tension portion is displaced, so that a belt shift occurs. The position of the high tension portion formed by the high tension portion forming means 14 is driven in a direction perpendicular to the belt drive in order to reduce the belt displacement or to move the belt in the direction opposite to the generated belt displacement. Variable by mechanism 15. Therefore, it is possible to change the belt shift state. As shown in FIGS. 5A and 5B, the position of the high tension portion formed by the high tension portion forming means 14 is moved in the direction of the generated belt, and the belt approaches the high tension portion of the belt. Move towards. By doing so, the belt shift occurs in the reverse direction, that is, the belt position returns. At that time, the change in the belt-closed state also changes according to the amount of change in the position of the high tension portion formed by the high tension portion forming means 14.

  Further, the amount of belt deviation is quantitatively determined, and the amount of movement of the position of the high tension portion formed by the high tension portion forming means 14 is determined according to the amount, and the high tension portion forming means is actually moved by that amount. The position of the high tension part formed by 14 is moved. For this purpose, belt deviation detecting means 16 is provided at the end of the belt 11 of the belt driving device 10 in the main scanning direction, and information on the deviation speed and the deviation direction of the belt 11 detected by the belt deviation detecting means 16 is provided. Is supplied to the arithmetic processing means 17. The belt deviation detecting means 16 is a sensor that measures changes in the end position of the belt 11 in a contact or non-contact manner, and arranges a detection target at a predetermined position on the belt 11 to capture the movement amount of the target. Such an optical sensor may be used. Then, the calculation processing means 17 calculates the position where the high tension portion of the belt 11 is set based on the information on the speed and direction of the belt 11 detected by the belt deviation detection means 16. Further, based on FIG. 6 showing the correlation between the detected belt shift speed and the amount of movement of the position of the high tension portion formed by the high tension portion forming means 14 for correcting the shift speed, the high tension portion The amount of movement is calculated so that the position of the high tension portion formed by the forming means 14 comes to the calculated position. The movement amount information is supplied to the drive mechanism 15 to be driven. Further, it is possible to check the change in the belt shift speed by the belt shift detection means 16 after driving. If the belt 11 is not in a desired state, further information on the current shift speed and shift direction of the belt 11 is calculated. 17 and the belt deviation control similar to the above is repeated.

  Further, when the belt shift phenomenon occurs, the image forming apparatus including the belt driving device may cause image distortion particularly in the belt shift direction. In particular, in a quadruple tandem color image forming apparatus as shown in FIG. 7, if a belt shift occurs in the middle of image formation, four color images (cyan, magenta, yellow, and black images) are displayed. Since the position of the formed belt is shifted at each image forming portion, a relative positional shift of each color image pattern on the belt occurs, and finally, color shift occurs and image quality deteriorates. . Therefore, it is possible to prevent the image quality from being deteriorated by mounting the above-described belt driving device of the present invention or using the belt shift control method.

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

It is a figure which shows the principle of the belt deviation control method of this invention. FIG. 6 is a characteristic diagram showing a relationship of belt shift speed with respect to belt tension. It is a figure which shows the mode of a belt | deviation shift by the tension distribution of a belt main scanning direction. FIG. 6 is a characteristic diagram illustrating a relationship between a belt left-right tension difference and a belt shift speed. It is a schematic block diagram which shows the structure of the belt drive device which concerns on one embodiment of this invention. FIG. 6 is a characteristic diagram showing a correlation between a belt shift speed and a movement amount of a position of a high tension portion. 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; drive roller;
13; driven roller, 14; high tension portion forming means,
15; drive mechanism, 16; belt deviation detecting means, 17; arithmetic processing means.

Claims (7)

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, the at least one rotating body is a drive shaft, and a driving torque is transmitted to the belt A belt driving device for driving a belt,
A belt shift control method comprising: forming a high tension portion in a region in a direction perpendicular to the belt driving direction; and moving the formed high tension portion according to the belt shift to control the belt shift.   2. The belt shift control method according to claim 1, wherein the moving direction and the moving amount of the high tension portion are varied in accordance with the shift direction and the shift amount of the belt.   The belt shift control method according to claim 1 or 2, wherein a high tension portion is moved in a direction opposite to a moving direction of the belt shift. 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, the 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,
A high tension portion forming means for forming a high tension portion in a region perpendicular to the belt driving direction;
Belt position detecting means for detecting the amount and direction of deviation of the belt in the direction orthogonal to the belt driving direction;
Arithmetic processing means for calculating the position of the high tension portion formed by the high tension portion forming means according to the amount and direction of belt deviation detected by the belt position detecting means;
A belt driving device comprising: a moving means for moving a position of a high tension portion formed by the high tension portion forming means to a position calculated by the calculation processing means.   5. The belt driving device according to claim 4, wherein the moving means moves a high tension portion formed by the high tension portion forming means in a direction opposite to a moving direction closer to the belt.   6. The belt driving device according to claim 4, wherein the high tension portion forming means is constituted by a rotating body or a protruding member having a non-uniform outer diameter.   An image forming apparatus comprising the belt driving device according to claim 4.

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