BELT DRIVE DEVICE, BELT DRIVE METHOD, AND IMAGE FORMING APPARATUS

Abstract

To perform fine rotation control for less than one driving step of a stepping motor to allow fine control of the belt skew of an endless belt.SOLUTION: A belt driving device comprises: an adjustment roller that stretches an endless belt and rotates and moves the belt; an inclination adjustment unit that includes a cam for adjusting the inclination of the adjustment roller to control the belt skew of the endless belt; a belt position detection unit that detects a belt position in a direction orthogonal to a belt movement direction of the endless belt; a stepping motor that drives to rotate the cam of the inclination adjustment unit; and a control output adjustment unit that, based on the belt position detected by the belt position detection unit, adjusts control output supplied to the stepping motor. In obtaining a rotation angle for less than one step of the stepping motor, the control output adjustment unit supplies the control output to the stepping motor for a time corresponding to a rotation angle less than the rotation angle for one step, of the supply time of the control output for obtaining the rotation angle for one step, and does not supply the control output for the rest of the time.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a belt driving device, a belt driving method, and an image forming apparatus. [Background technology]

[0002] Conventionally, there are known image forming devices such as copiers and printers that use an intermediate transfer belt, a photoconductor belt, or a transfer conveyor belt, which are made of an endless belt. When these endless belts rotate, they tend to deviate or meander in a direction perpendicular to their moving direction (rotation direction) (belt deviation phenomenon).

[0003] When such a phenomenon of belt deviation of an endless belt occurs, for example, in an image forming apparatus that forms a color image, the positions of the toner images of each color are shifted, resulting in color misalignment, which causes deterioration of image quality. Therefore, in a belt driving device having such an endless belt, particularly in the above-mentioned color image forming apparatus, it is necessary to prevent the occurrence of deviation or meandering of the endless belt.

[0004] For this reason, for example, Patent Document 1 (JP Patent Publication 3-288167A) discloses a method of providing registration marks at two locations on an endless belt and detecting the positions of each registration mark using a solid-state image sensor (CCD). Patent Document 1 also discloses a method of tilting at least one tension roller that tensions the endless belt based on the detection result, and moving the endless belt back and forth between the registration marks at the two locations.

[0005] Patent Document 2 (JP Patent Publication No. 11-295948) discloses a method for storing the belt edge shape of an endless belt. Patent Document 2 also discloses a method for comparing the belt edge shape and the detection result of the belt position of the endless belt, and controlling the belt deviation by changing the inclination of the tension roller of the endless belt based on the difference.

[0006] Another known method corrects belt misalignment by adjusting the inclination angle of the endless belt via a stepping motor using a belt misalignment control unit to control the position of the endless belt in the belt width direction to a reference position. Summary of the Invention [Problem to be solved by the invention]

[0007] However, because the minimum controllable drive step of a stepping motor is one drive step, rotation control is often discrete and rough. Therefore, when correcting belt misalignment by controlling the rotation of the stepping motor of the belt misalignment control unit, the problem of difficulty in correcting belt misalignment occurs because the rotation control becomes rough.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a belt driving device, a belt driving method, and an image forming apparatus that enable fine rotation control of less than one step of a stepping motor and fine control of the belt deviation of an endless belt. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems and achieve the object, the present invention provides a belt drive device comprising an adjustment roller which stretches and moves and rotates an endless belt, an inclination adjustment unit having a cam which adjusts the inclination of the adjustment roller in order to control the belt deviation of the endless belt, a belt position detection unit which detects the belt position of the endless belt in a direction perpendicular to the belt movement direction, a stepping motor which rotates and drives the cam of the inclination adjustment unit, and a control output adjustment unit which adjusts a control output supplied to the stepping motor based on the belt position detected by the belt position detection unit, wherein the control output adjustment unit, when obtaining a rotation angle of the stepping motor that is less than one step, Using an output value obtained by delta-sigma modulating the control output, During the supply time of the control output for obtaining a rotation angle of one step, the control output is supplied to the stepping motor for a time period corresponding to a rotation angle less than one step, and the control output is not supplied for the remaining time. Effect of the Invention

[0010] According to the present invention, it is possible to perform fine rotation control of a stepping motor in increments of less than one step, and it is possible to perform fine control of the belt deviation of an endless belt. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a system configuration of a printing system according to an embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of an electrophotographic image forming apparatus provided in the printing system according to the embodiment. [Diagram 3] FIG. 3 is a perspective view showing an adjustment roller for controlling the belt deviation of the intermediate transfer belt of the image forming apparatus and a cam for adjusting the inclination of the adjustment roller. [Figure 4] FIG. 4 is a diagram showing a belt position detection sensor that detects the belt position of the intermediate transfer belt. [Diagram 5] FIG. 5 is a graph showing the relationship between the belt position of the intermediate transfer belt and the detection voltage of the belt position detection sensor. [Figure 6] FIG. 6 is a diagram showing details of the cam that adjusts the inclination of the adjustment roller. [Figure 7] FIG. 7 is a block diagram showing the configuration of a belt deviation control unit for controlling the belt position of the intermediate transfer belt. [Figure 8] FIG. 8 is a diagram showing the positional fluctuation of the intermediate transfer belt, the deviation speed, and the number of control steps of the cam motor when the rotation angle of the cam motor is controlled in steps. [Figure 9] FIG. 9 is a circuit diagram of a delta sigma modulation unit provided in the belt deviation control unit of the image forming apparatus of the printing system according to the embodiment. [Figure 10] FIG. 10 is a diagram showing the positional fluctuation of the intermediate transfer belt, the deviation speed, and the number of control steps of the cam motor when the rotation angle of the cam motor is controlled in units of less than one step. [Figure 11]FIG. 11 is a diagram illustrating a modified example of the printing system according to the embodiment, in which an inkjet type image forming apparatus is provided as the image forming apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] A printing system according to an embodiment will be described below with reference to the accompanying drawings.

[0013] (System Configuration) Fig. 1 is a diagram showing the system configuration of a printing system according to a first embodiment. In Fig. 1, the printing system according to the first embodiment includes a client personal computer device (client PC) 101, a digital front end (DFE) 102, an image forming device 103, and a management server 104.

[0014] The client PC 101 includes a display unit such as a liquid crystal display, as well as input devices such as a mouse device and a keyboard device. The client PC 101 creates a print job for an image to be printed, and transmits it to the DFE 102 or the server 104.

[0015] The DFE 102 receives a print job from the client PC 101 or the management server 104 , creates drawing data using a RIP (Raster Image Processor) engine based on the received print job, and transmits the drawing data to the image forming apparatus 103 .

[0016] The image forming apparatus 103 performs an image forming operation based on the drawing data received from the DFE 102 .

[0017] The management server 104 manages print jobs received from the client PC 101. Also, in response to a request from the DFE , the management server 104 transmits the print job to the DFE .

[0018] (Configuration of Image Forming Apparatus) As an example, the image forming apparatus 103 may be an electrophotographic wet-type color image forming apparatus. Fig. 2 is a schematic diagram of the image forming apparatus 103. As shown in Fig. 2, the image forming apparatus 103 is provided with a plurality of photoconductors 1Y, 1M, 1C, and 1K that form images with different print colors. Furthermore, an intermediate transfer belt 2 is wound around a belt drive roller 3, an opposing roller 4, an adjustment roller 5, and a plurality of idler rollers 6 in a tensioned state, and is in contact with the outer periphery of each of the photoconductors 1Y, 1M, 1C, and 1K.

[0019] The intermediate transfer belt 2 is an example of an endless belt, and is made of resin such as polyimide or polyvinylidene fluoride (PVDF), or rubber such as polyurethane. A transfer roller 7 as a primary transfer section is pressed against the photoconductors 1Y, 1M, 1C, and 1K across the intermediate transfer belt 2. A non-contact transfer charger may be used as the primary transfer section.

[0020] An exposure device is provided for each of the photoconductors 1Y, 1M, 1C, and 1K. The exposure device emits an optical signal corresponding to image information color-separated by a scanner or the like from a semiconductor laser, and scans the laser light onto the photoconductors 1Y, 1M, 1C, and 1K using a polygon mirror that is rotated. In the scanning optical path, lenses for converging the light and for correcting tilt of the polygon mirror, as well as mirrors for deflecting the laser light, are provided.

[0021] Furthermore, on the outer periphery of each of the photoconductors 1Y, 1M, 1C, and 1K, there are disposed an electrostatic charger 8, a developing unit 9 as a developing section, and a cleaning member 10. A secondary transfer roller 11 is pressed against the opposing roller 4 on which the intermediate transfer belt 2 is stretched. In addition, at the bottom of the device body, there are provided a paper feed cassette that stores transfer paper as a transfer material, a paper feed roller that pulls out the transfer paper from the paper feed cassette one sheet at a time, and a registration roller 12 that sends the transfer paper P guided to the transport path to a secondary transfer roller 117.

[0022] A fixing roller and a press roller are provided above the belt drive roller 3 so as to be in contact with each other and can rotate freely, and a paper discharge roller is provided for discharging the transfer paper that passes through the fixing roller onto a paper discharge tray.

[0023] In the image forming apparatus 103 configured as above, images with different print colors are formed on the photoconductors 1Y, 1M, 1C, and 1K. Here, the image forming process for the photoconductor 1Y located on the left will be described, but the image forming processes for the other photoconductors 1M, 1C, and 1K are based on the same principle, so the description thereof will be omitted.

[0024] First, the photoconductor 1Y is uniformly charged by the charge from the charger 8 while rotating. Based on the image information separated into the first printing color, the exposure device is driven. As a result, an electrostatic latent image is formed as a latent image on the charged portion of the photoconductor 1Y. This electrostatic latent image is developed into a toner image by the developing unit 9 in the developing section. Toner images of the corresponding printing colors are formed sequentially on the other photoconductors 1M, 1C, and 1K. Then, for example, the toner images of each color, yellow, magenta, cyan, and black, are superimposed on the intermediate transfer belt 2 by the respective transfer rollers 7 and primarily transferred.

[0025] Meanwhile, the transfer paper P drawn out by the paper feed roller is maintained in a standby state with its leading edge abutting the nip portion of the registration roller 12. The transfer paper P is transported to the secondary transfer position between the secondary transfer roller 11 and the opposing roller 4 by the registration roller 12, which rotates in synchronization with the rotational motion of the photoconductors 1Y, 1M, 1C, and 1K, and the toner images on the intermediate transfer belt 2 are secondary-transferred all at once.

[0026] In this way, the transfer paper P onto which the toner images of each color are superimposed and transferred all at once is separated from the intermediate transfer belt 2, and the transferred images are fixed while being conveyed by a fixing roller and a press roller, and the paper is discharged onto a paper discharge tray by a paper discharge roller. In addition, after each primary transfer, the remaining toner adhering to the photoconductors 1Y, 1M, 1C, and 1K is removed by a cleaning member 10 consisting of a blade.

[0027] Here, the image forming device 103 transfers four color images in a superimposed manner onto the intermediate transfer belt 2. For this reason, if the intermediate transfer belt 2 becomes misaligned or meanders, color shifts occur in the toner images of each color that have been primarily transferred onto the intermediate transfer belt 2, resulting in a problem of reduced image quality of the toner images.

[0028] For this reason, in the image forming apparatus 103 provided in the printing system of the embodiment, in order to prevent deterioration of image quality due to deviation or meandering of the intermediate transfer belt 2, as shown in Fig. 2, a belt position detection sensor 20 and an inclination adjustment unit 30 including an adjustment roller 5 are provided. The adjustment roller 5, the inclination adjustment unit 30, and the belt position detection sensor 20 will be described below.

[0029] Fig. 3 is a schematic perspective view showing the configuration of an adjustment roller 5 for controlling the belt shift of the intermediate transfer belt 2, and an inclination adjustment unit 30 for adjusting the inclination of the adjustment roller 5. In Fig. 3, the adjustment roller 5 is rotatably supported by bearings 31 and 32. The bearing 31, which serves as a fulcrum for the oscillation of the adjustment roller 5, is supported and fixed to a side plate of a belt unit in which the intermediate transfer belt 2 is disposed.

[0030] On the other hand, a bearing 32 on the swing side of the adjustment roller 5 is supported by a swing lever 33. This swing lever 33 rotates around a fulcrum shaft 34. A cam follower 35 is provided at the free end of the swing lever 33. The free end of the swing lever 33 is pulled upward by a spring 36. As a result, the cam follower 35 comes into contact with a cam 37 provided at the upper part.

[0031] The cam 37 is fixed to a camshaft 38, and a worm wheel 39 and a feeler 40 are fixed coaxially to the camshaft 38. A worm gear 42 fixed to the shaft of a cam motor 41 is disposed in mesh with the worm wheel 39. The cam motor 41 is configured as a stepping motor. A slit 40a is formed in the feeler 40, and a photosensor 43 is disposed so as to detect the slit 40a. The photosensor 43 is fixed to a sensor bracket 44. The sensor bracket 44 is provided with an elongated hole 44a for fixing with a screw or the like. The elongated hole 44a has the same shape as the curvature of the outer periphery of the feeler 40. By changing the fixing position of the elongated hole 44a, the position of the photosensor 43 can also be changed along the outer periphery of the feeler 40.

[0032] Next, the belt position detection sensor 20 is an example of a belt position detection unit, and is provided on the fulcrum side opposite to the side swung by the swing mechanism of the adjustment roller 5 described above. As shown in FIG. 4, the light emitting unit 20a and the light receiving unit 20b are arranged to sandwich the belt edge 2a of the intermediate transfer belt 2. The positional relationship between the light emitting unit 20a and the light receiving unit 20b may be the opposite to that shown in the figure. As shown in FIG. 4, the belt position detection sensor 20 includes the light emitting unit 20a made of a light emitting diode (LED) or the like, and the light receiving unit 20b made of a photodiode or the like. The light emitting unit 20a and the light receiving unit 20b are provided to sandwich the belt edge of the intermediate transfer belt 2.

[0033] The light receiving section 20b of the belt position detection sensor 20 is configured to generate a voltage upon receiving light from the light emitting section 20a, and the detected voltage differs depending on the amount of light received from the light emitting section 20a. Therefore, in Fig. 4, when the position of the belt edge 2a of the intermediate transfer belt 2 shifts to the left or right, the amount of light irradiated from the light emitting section 20a of the belt position detection sensor 20 to the light receiving section 20b changes, and as shown in Fig. 4, the detected voltage of the light receiving section 20b also changes.

[0034] For example, when the belt edge 2a of the intermediate transfer belt 2 completely blocks the light from the light-emitting element 20a, the detection voltage of the light-receiving element 20b becomes 0 V. When the light from the light-emitting element 20a completely transmits, the detection voltage of the light-receiving element 20b becomes maximum (e.g., 5 V). Here, the midpoint between 0 and maximum of the detection voltage of the light-receiving element 20b is set as the reference position of the belt position of the intermediate transfer belt 2.

[0035] As a result, when the intermediate transfer belt 2 meanders, the belt position of the intermediate transfer belt 2 can be determined by detecting the detection voltage of the light receiving portion 20b of the belt position detection sensor 20. Meanwhile, the position of the cam 37 that rocks the adjustment roller 5 also changes up and down depending on the rotation direction of the cam 37, with the position where the adjustment roller 5 is parallel to the other belt drive rollers 3 and the like as the reference position.

[0036] Next, an operation of detecting the position of the belt edge 2a of the intermediate transfer belt 2 by the belt position detection sensor 20 and controlling the belt shift of the intermediate transfer belt 2 will be described. First, the cam 37 contacts the cam follower 35 at a reference position of angle 0 as shown in Fig. 5. In this state, the inclination of the adjustment roller 5 is in a reference state where it is almost parallel.

[0037] When the intermediate transfer belt 2 rotates in a meandering manner and the position of the belt edge 2a moves, the belt position of the intermediate transfer belt 2 is detected by the belt position detection sensor 20. Based on this detection result, the cam 37 is rotated by the cam motor 42. This rotation of the cam 37 causes the swing lever 33 to swing around the fulcrum shaft 34 as the swing center. This tilts the adjustment roller 5, and the intermediate transfer belt 2 is shifted in the opposite direction to the direction biased by the meandering.

[0038] Specifically, as shown in Fig. 6, when the belt position of the intermediate transfer belt 2 is shifted from the reference position by 0.5, 1.0, 1.5, and 2.0, the inclination amount of the adjustment roller 5 is also increased by 0.1, 0.2, 0.3, and 0.4. As a result, the belt position of the intermediate transfer belt 2 is changed in proportion to the inclination amount of the adjustment roller 5. At this time, the rotation amount of the cam 37 is increased by θ1, θ2, θ3, and θ4. As a result, even if the condition of the load applied to the intermediate transfer belt 2 changes and the belt position of the intermediate transfer belt 2 is shifted from the reference position, the adjustment roller 5 is finely adjusted up and down according to the inclination state, and the deviation of the belt position of the intermediate transfer belt 2 is corrected.

[0039] In the image forming apparatus 103, the amount of inclination of the adjustment roller 5 is managed in correspondence with the number of steps of the stepping motor (cam motor 41) which is proportional to the amount of rotation of the cam 37. Here, the relationship between the actual belt shift of the intermediate transfer belt 2 and the inclination of the adjustment roller 5 is as follows.

[0040] That is, when the intermediate transfer belt 2 is biased to the left in the transport direction, the swinging side of the adjustment roller 5 is gradually tilted upward. This stops the intermediate transfer belt 2 from shifting, and a portion of the intermediate transfer belt 2 begins to shift to the right. Also, when the intermediate transfer belt 2 begins to shift to the right, the adjustment roller 5 is gradually tilted downward from the previously tilted position. By repeating this process, the amount of belt shift of the intermediate transfer belt 2 and the amount of tilt of the adjustment roller 5 converge to a small amount.

[0041] Here, if the initial belt deviation direction of the intermediate transfer belt 2 is to the right in the transport direction, the adjustment roller 5 is tilted downward. That is, the signs (+, -) in Fig. 6 indicate that the belt position of the intermediate transfer belt 2 deviates to the left with respect to the reference position (+) and deviates to the right (-), and the inclination of the adjustment roller 5 is (+) upward and (-) downward with respect to the reference position (+) and (-) respectively. The reference position of the intermediate transfer belt 2 is determined by detecting the position of the slit 40a of the filler 40 by the photosensor 43 and judging the rotation position of the cam 37.

[0042] Incidentally, the inclination of the adjustment roller 5 that causes almost no deviation of the intermediate transfer belt 2 varies depending on the unit or belt replacement, etc. Therefore, the fixed position of the photosensor 43 is changed in accordance with the intermediate transfer belt 2 and the unit, and the reference position of the intermediate transfer belt 2 is changed. This makes it possible to reduce the deviation of the intermediate transfer belt 2's belt deviation and the inclination of the adjustment roller 5, and shorten the time until the intermediate transfer belt 2's belt deviation is resolved.

[0043] In addition, when the belt edge 2a of the intermediate transfer belt 2 goes out of the detection range of the belt position detection sensor 20 due to some load fluctuation applied to the intermediate transfer belt 2, the contact point between the cam 37 and the cam follower 35 shown in Fig. 6 is set to θ6 or θ6 position, which is a change larger than the change amount of the detection range. By doing so, even in the event of an abnormality such as the intermediate transfer belt 2 being too far off, the intermediate transfer belt 2 can be quickly returned to the detection range.

[0044] Fig. 7 shows a block diagram of a belt deviation control unit 70 for controlling the belt position of the intermediate transfer belt 2. As shown in Fig. 7, the belt deviation control unit 70 includes an A / D converter 51, a control circuit 52, a memory 53, a counter 54, and a motor driver 55. The belt deviation control unit 70 also includes a delta-sigma modulation unit 60 (an example of a control output adjustment unit) which will be described later.

[0045] 7, first, the analog signal output by the belt position detection sensor 20 is converted to a digital signal by an A / D converter 51, and the digital signal is sent to a control circuit 52. This belt position information is compared with information on the number of rotations and direction of the cam motor 41 for the belt position previously stored in a memory 53, and an appropriate rotation is applied to the cam motor 41 by a motor driver 55. This process is repeated to perform belt deviation control.

[0046] 7, the control circuit 52 receives a start signal 56 from the image forming apparatus 103, and the counter 54 counts the time from the start. The counted time is compared with the time stored in the memory 53, and the belt deviation control operation is performed up to that time, and then the image forming operation is performed.

[0047] As another method, the time for one revolution of the intermediate transfer belt 2 is stored in the memory 53 and compared with the time counted by the counter 54. When the time for one revolution of the intermediate transfer belt 2 arrives, the cam motor 41 is rotated to perform belt deviation control based on the output data from the belt position detection sensor 20. This allows belt deviation control to be performed for each revolution of the intermediate transfer belt 2, and makes it possible to reduce straightness and eliminate errors in the belt edge 2a of the intermediate transfer belt 2.

[0048] (Increasing the resolution of stepping motor drive steps) Here, since the minimum driving step for controlling the rotation of the cam motor (stepping motor) 41 by the belt deviation control unit 70 shown in FIG. 7 is one driving step, the control resolution becomes coarse, and there is a risk of the position of the intermediate transfer belt 2 fluctuating even during steady state.

[0049] Specifically, FIG. 8 shows the positional fluctuation of the intermediate transfer belt 2, the deviation speed, and the number of control steps of the cam motor 41. FIG. 8(a) shows the position of the intermediate transfer belt 2 in the direction perpendicular to the conveying direction of the intermediate transfer belt 2 (the width direction of the intermediate transfer belt 2). The position of "0" is an ideal position where the intermediate transfer belt 2 does not deviate. Since the minimum driving step for controlling the rotation of the cam motor 41 is one driving step, the belt deviation control of the intermediate transfer belt 2 becomes rough, and the position of the intermediate transfer belt 2 fluctuates at the position where the deviation amount is "0". The amplitude up and down with the position of "0" as the boundary in FIG. 8(a) shows the transition of the position of the intermediate transfer belt 2 that occurs by controlling the cam motor 41 in units of one driving step.

[0050] Fig. 8(b) is a differential value of the position of the intermediate transfer belt 2 shown in Fig. 8(a), and shows the moving speed (shift speed) of the intermediate transfer belt 2. In Fig. 8(b), the shift speed is "0" at the position where the shift amount of the intermediate transfer belt 2 is "0". However, by controlling the belt shift control of the intermediate transfer belt 2 in units of one driving step as described above, the change in the shift speed also becomes large at the boundary of "0".

[0051] FIG. 8(c) shows the number of control steps of the cam motor 41. The "0" in the center is the 0 drive step, which indicates a state in which the cam motor 41 is not rotating. With this 0 drive step as a boundary, the plus directions such as "+1" and "+2" indicate drive steps for driving the cam motor 41 to rotate in the forward direction. Also, the minus direction such as "-1" indicates drive steps for driving the cam motor 41 to rotate in the opposite direction to the forward direction. As shown in FIG. 8(c), if the rotation of the cam motor 41 is controlled in units of one drive step, as shown in FIG. 8(a), a problem occurs in which the position of the intermediate transfer belt 2 fluctuates throughout the entire process, with the deviation amount at the "0" position as a boundary.

[0052] For this reason, in the printing system of the embodiment, when obtaining a rotation angle of less than one step of cam motor 41, the control output is supplied to cam motor 41 for a time period corresponding to a rotation angle of less than one step during the supply time of the control output for obtaining a rotation angle of one step, and the control output is not supplied for the remaining time. Cam motor 41 rotates while the control output is being supplied. For this reason, the supply time of the control output for one step can be divided into a "time for supply" and a "time for not supplying" according to the rotation angle of less than one step that is desired to be obtained, thereby controlling the rotation of cam motor 41 to a rotation angle of less than one step.

[0053] (Configuration and operation of delta-sigma modulation section) As one example, the rotation angle of the cam motor 41 can be controlled by delta-sigma modulation. That is, in the printing system according to the embodiment, as shown in Fig. 7, a delta-sigma modulation unit 60 is provided in the belt deviation control unit 70 of the image forming apparatus 103. The delta-sigma modulation unit 60 converts the rotation angle into an integer by delta-sigma modulation, and drives the cam motor 41 based on the integer value.

[0054] Fig. 9 is a circuit diagram of the delta-sigma modulation section 60. As shown in Fig. 9, the delta-sigma modulation section 60 includes an adder 71, an integrator 72, a comparator (hysteresis comparator) 73, and a 1-bit digital-to-analog converter (1-bit DAC) 74.

[0055] The adder 71 has a first input terminal (+) and a second input terminal (-). The output of the motor driver 55 is supplied to the first input terminal (+). In addition, the output of the 1-bit DAC 74 is negatively fed back and supplied to the second input terminal (-).

[0056] The output terminal of the adder 71 is connected to the input terminal of the integrator 72. The output terminal of the integrator 72 is connected to the input terminal of the comparator 73. The output of the comparator 73 is supplied to the cam motor 41 and also to a 1-bit DAC 74. The 1-bit DAC 74 converts the output of the comparator 73 into an analog signal and negatively feeds it back to the second input terminal (-) of the adder 71.

[0057] In the delta-sigma modulation unit 60, the integrator 72 integrates the control output (analog value) of the rotation angle of the cam motor 41 output from the control circuit 52 via the motor driver 55, and when the value becomes "1", the comparator 73 binarizes the value and supplies it to the cam motor 41. The output from the comparator 73 is also converted to an analog value by a 1-bit DAC 74 and negatively fed back to the second input terminal (-) of the adder 71. The integrator 72 integrates the difference between the control output of the step angle output from the control circuit 52 via the motor driver 55 and the output of the comparator 73. The delta-sigma modulation unit 60 repeats such operations.

[0058] As a result, instead of rounding the control output of the rotation angle to an integer, a delta-sigma modulation process is applied to the decimal of the angle to be output, and an output that is a pseudo target decimal rotation angle can be obtained. Specifically, when the rotation angle is set to, for example, 0.25, it was necessary to set it to 0 steps in the past. However, in the printing system of the embodiment, the delta-sigma modulation unit 60 sets 3 / 4 seconds to 0 steps and the remaining 1 / 4 seconds to 1 step, so that the cam motor 41 can be rotated in 0.25 steps. Note that in this example, 1 / 4 seconds may be set to 1 step and the remaining 3 / 4 seconds to 0 steps. This makes it possible to reduce the occurrence of deviation of the intermediate transfer belt 2 during steady state, etc.

[0059] FIG. 10 is a diagram showing how the deviation of the intermediate transfer belt 2 is reduced by the delta-sigma modulation process. In the case of FIG. 10, similarly to FIGS. 8(a) to 8(c), FIG. 10(a) shows the position of the intermediate transfer belt 2 in a direction (width direction of the intermediate transfer belt 2) perpendicular to the conveying direction of the intermediate transfer belt 2. FIG. 10(b) shows the differential value of the position of the intermediate transfer belt 2 shown in FIG. 10(a) and indicates the moving speed (deviation speed) of the intermediate transfer belt 2. FIG. 10(c) shows the number of control steps of the cam motor 41, and indicates how the cam motor 41 is rotated and controlled in fine steps less than one step.

[0060] The printing system of the embodiment can control the rotation of the cam motor 41 to a rotation angle of less than one step, so that the shift of the intermediate transfer belt 2 can be finely controlled to reduce the amount of shift during steady state, etc., as shown in Figures 10(a) to 10(c).

[0061] (Effects of the embodiment) As is clear from the above description, the printing system according to the embodiment can achieve the following effects.

[0062] 1. Even if the reference position of the adjustment roller 5 is shifted from the center position when controlling the actual belt deviation, the inclination of the adjustment roller 5 can be controlled around the shifted position, and the belt deviation can be controlled with high precision. This improves image quality.

[0063] 2. When the intermediate transfer belt 2 is out of the detection range of the position detection sensor 20, the inclination amount of the adjustment roller 5 is made larger than the proportional relationship. This prevents the intermediate transfer belt 2 from shifting too far and becoming difficult to control, and allows the belt shift to be quickly returned to the control range.

[0064] 3. The position detection sensor 20 of the intermediate transfer belt 2 is provided on the fulcrum side of the adjustment roller 5. This makes it possible to almost completely eliminate the inclination of the adjustment roller 5 on this fulcrum side, and to reduce the vibration of the intermediate transfer belt 20 at the location where the position detection sensor 20 is provided. This allows the position detection sensor 20 to be made small.

[0065] 4. Since the inclination of the adjustment roller 5 can be changed and adjusted with respect to the reference position, the reference position of the adjustment roller 5 can be easily adjusted when assembling the drive device for the intermediate transfer belt 2 or when replacing the intermediate transfer belt 2. Therefore, the detection range for the belt position of the intermediate transfer belt 2 can be narrowed.

[0066] 5. The intermediate transfer belt 2 is rotated at a constant rate to adjust the inclination of the adjustment roller 5, and image formation is started after controlling the deviation of the intermediate transfer belt 2. As a result, even when the meandering width of the intermediate transfer belt 2 becomes large, such as immediately after assembly of the belt drive device for the intermediate transfer belt 2 or immediately after the belt is replaced, image formation can be started after the meandering width of the intermediate transfer belt 2 is reduced. This makes it possible to prevent deterioration of image quality.

[0067] 6. The position detection sensor 20 in the direction perpendicular to the conveying direction of the intermediate transfer belt 2 detects the belt edge of the intermediate transfer belt 2. Therefore, even if a detection mark is not provided on the intermediate transfer belt 2, the belt deviation of the intermediate transfer belt 2 can be detected.

[0068] 7. The edge position of the same part in the moving direction of the intermediate transfer belt 2 is detected for each rotation of the intermediate transfer belt 2, and belt deviation control is performed based on the result. This makes it possible to eliminate straightness errors in the belt edge shape, and to perform belt deviation control of the intermediate transfer belt 2 with high accuracy.

[0069] 8. As an example, using delta-sigma modulation processing, during the supply time of the control output to obtain a rotation angle of one step, the control output is supplied to the cam motor 41 for a time period corresponding to a rotation angle less than one step, and the control output is not supplied for the remaining time. This makes it possible to obtain a rotation angle of less than one step of the cam motor 41, and to perform fine rotation control of the cam motor 41. Therefore, the deviation of the intermediate transfer belt 2 during steady state, etc. can be finely adjusted, and image quality can be further improved.

[0070] (Modification) In the above embodiment, image forming apparatus 103 has been described as an electrophotographic wet color image forming apparatus, but an inkjet image forming apparatus shown in Fig. 11 may also be used. Inkjet image forming apparatus 103 shown in Fig. 11 includes a paper feed unit 501, an image forming unit 506, a drying unit 502, and a paper discharge unit 503.

[0071] In the image forming apparatus 103, an image is formed on paper P, which is a recording material as a sheet material fed from a paper feed unit 501, by an image forming unit 506 using ink, which is a liquid for image formation. Then, after the ink adhering to the paper is dried in a drying unit 502, the paper is discharged from a paper discharge unit 503.

[0072] (Paper feed section) The paper feed section 501 includes a paper feed tray 511 on which a plurality of papers P are stacked, a feed device 512 that separates and sends out the papers P one by one from the paper feed tray 511, and a pair of registration rollers 513 that sends the papers P to the image forming section 506.

[0073] As the feeding device 512, any feeding device such as a device using rollers or a device using air suction can be used. After the leading edge of the paper sent out from the paper feed tray 511 by the feeding device 512 reaches the pair of registration rollers 513, the pair of registration rollers 513 is driven at a predetermined timing to feed the paper to the image forming unit 506. There is no limitation on the configuration of the paper feeding unit 501 as long as it can send out the paper P to the image forming unit 506.

[0074] (Image forming section) The image forming section 506 includes a receiving drum 561 that receives the fed paper P, a paper carrying drum 562 that carries the paper P transported by the receiving drum 561 on its outer surface and transports it, an ink ejection section 564 that ejects ink toward the paper P carried by the paper carrying drum 562, and a transfer drum 565 that transfers the paper P transported by the paper carrying drum 562 to the drying section 502.

[0075] The paper P transported from the paper feed unit 501 to the image forming unit 506 has its leading edge gripped by a paper gripper provided on the surface of the receiving cylinder 561, and is transported as the surface of the receiving cylinder 561 moves. The paper P transported by the receiving cylinder 561 is delivered to the paper carrying drum 562 at a position opposite the paper carrying drum 562.

[0076] A paper gripper is also provided on the surface of the paper carrying drum 562, and the leading edge of the paper is gripped by the paper gripper. In addition, a plurality of suction holes are formed in a dispersed manner on the surface of the paper carrying drum 562, and a suction device 563 generates a suction air current in the direction toward the inside of the paper carrying drum 562 at each suction hole. The leading edge of the paper P transferred from the receiving cylinder 561 to the paper carrying drum 562 is gripped by the paper gripper, and the paper P is adsorbed to the surface of the paper carrying drum 562 by the suction air current, and is transported as the surface of the paper carrying drum 562 moves.

[0077] The ink ejection unit 564 ejects four colors of ink, C (cyan), M (magenta), Y (yellow), and K (black), to form an image, and is provided with liquid ejection heads 564C, 564M, 564Y, and 564K, one for each ink. There is no limitation on the configuration of the liquid ejection heads 564C, 564M, 564Y, and 564K, and any configuration may be adopted as long as they eject liquid. If necessary, a liquid ejection head that ejects special ink such as white, gold, or silver, or a liquid ejection head that ejects liquid that does not form an image, such as a surface coating liquid, may be provided.

[0078] The ejection operation of each of the liquid ejection heads 564C, 564M, 564Y, and 564K of the ink ejection unit 364 is controlled by a drive signal corresponding to image information. When the paper P held on the paper carrying drum 562 passes through an area facing the ink ejection unit 564, each color ink is ejected from the liquid ejection heads 564C, 564M, 564Y, and 564K, and an image corresponding to the image information is formed. There are no limitations on the configuration of the image forming unit 506, so long as it deposits liquid on the paper P to form an image.

[0079] (Drying section) The drying section 502 includes a drying mechanism 521 for drying the ink attached to the paper P in the image forming section 506, and a transport mechanism 522 for transporting the paper P transported from the image forming section 506. The paper P transported from the image forming section 506 is received by the transport mechanism 522, then transported to pass through the drying mechanism 521, and delivered to the paper discharge section 503. When passing through the drying mechanism 521, the ink on the paper P is subjected to a drying process, whereby liquid components such as water in the ink evaporate, the ink is fixed on the paper P, and curling of the paper P is suppressed.

[0080] (Paper ejection section) The paper discharge unit 503 includes a paper discharge tray 531 on which a plurality of sheets of paper P are stacked. The sheets of paper P transported from the drying unit 502 are sequentially stacked and held on the paper discharge tray 531. Note that there are no limitations on the configuration of the paper discharge unit 503 as long as it can discharge the sheets of paper P.

[0081] (Other functional parts) The image forming apparatus 103 includes a paper feed unit 501, an image forming unit 506, a drying unit 502, and a paper discharge unit 503, but other functional units may be added as appropriate. For example, a pre-processing unit that performs pre-processing of the image formation may be added between the paper feed unit 501 and the image forming unit 506. Also, a post-processing unit that performs post-processing of the image formation may be added between the drying unit 502 and the paper discharge unit 503.

[0082] Examples of the pre-processing section include a processing liquid application process that applies a processing liquid to the paper P to react with the ink and suppress bleeding, but there is no particular restriction on the content of the pre-processing section. Examples of the post-processing section include a paper inversion and transport process that inverts the paper on which an image has been formed in the image forming section 506 and transports it again to the image forming section 506 to form images on both sides of the paper P, a process that binds multiple sheets of paper P on which images have been formed, a correction mechanism that corrects paper deformation, or a cooling mechanism that cools the paper, but there is no particular restriction on the content of the post-processing section.

[0083] Even when such an inkjet type image forming apparatus 103 is used, the same effects as those of the above-described embodiment can be obtained.

[0084] Finally, the above-described embodiments are presented as examples, and are not intended to limit the scope of the present invention. This novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention.

[0085] For example, "paper" is not limited to paper, but may include OHP film (polyester film), cloth, glass, substrates, etc., and may be any material to which ink droplets or other liquids can be attached. Furthermore, "paper" includes what is called a recording medium, recording medium, recording paper, recording paper, etc. Furthermore, image formation, recording, printing, copying, and printing are all synonymous terms.

[0086] Furthermore, an "inkjet printer device" may form an image by ejecting liquid onto a medium such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, ceramics, etc. Furthermore, "image formation" includes not only forming images such as characters or figures on a medium, but also forming meaningless images such as patterns on a medium (simply causing liquid (droplets) to land on the medium).

[0087] In addition, unless otherwise specified, the term "ink" is not limited to what is called ink, but is used as a general term for all liquids that can form images, including recording liquids, fixing treatment liquids, liquids, etc. For example, "ink" includes DNA (Deoxyribonucleic Acid) samples, resists, pattern materials, resins, etc., as well as water-based latex inks for sign graphics.

[0088] Furthermore, the term "image" is not limited to flat images, but also includes images formed in a three-dimensional form or three-dimensional objects.

[0089] The present invention can also be applied to single-function machines such as printers, facsimile machines, and copiers, or to multifunction machines comprising these.

[0090] Furthermore, as the device for ejecting liquid, not only a device capable of ejecting liquid onto an object onto which the liquid can adhere, but also a device that ejects liquid into air or liquid may be used.

[0091] This "liquid ejecting device" may include means for feeding, transporting, and discharging objects onto which the liquid can be attached, as well as other pre-processing devices and post-processing devices.

[0092] In addition, the term "liquid ejection device" is not limited to devices that use ejected liquid to visualize meaningful images such as characters and figures, but also includes devices that form patterns that have no meaning in themselves.

[0093] Furthermore, "something to which a liquid can adhere" means something to which a liquid can adhere at least temporarily, something to which the liquid adheres and sticks, something to which the liquid adheres and penetrates, etc. Specific examples include media such as paper, recording paper, film, cloth, and other recording media, electronic boards, electronic components such as piezoelectric elements, powder layers, organ models, and test cells, and unless otherwise specified, includes all things to which a liquid can adhere.

[0094] The material to which the liquid can adhere may be any material to which the liquid can adhere, even temporarily, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, or ceramics.

[0095] The "liquid" may be any liquid having a viscosity and surface tension that allows it to be discharged from the head, and is not particularly limited, but it is preferable that the viscosity is 30 mPa·s or less at room temperature and pressure, or by heating or cooling. More specifically, it is a solution, suspension, emulsion, etc. that contains a solvent such as water or an organic solvent, a colorant such as a dye or pigment, a functionalizing material such as a polymerizable compound, a resin, or a surfactant, a biocompatible material such as DNA, amino acids, proteins, calcium, an edible material such as a natural dye, etc. These can be used for applications such as inkjet ink, surface treatment liquid, components of electronic elements or light-emitting elements, and liquids for forming electronic circuit resist patterns.

[0096] Furthermore, the "liquid ejection device" may be a device in which a liquid ejection head and an object to which liquid can be attached move relatively, but is not limited to this. Specific examples include a serial type device in which a liquid ejection head moves, a line type device in which a liquid ejection head does not move, etc.

[0097] Other examples of "liquid ejecting devices" include a treatment liquid application device that ejects a treatment liquid onto paper to apply the treatment liquid to the surface of the paper for purposes such as modifying the surface of the paper, and an injection granulation device that ejects a composition liquid in which raw materials are dispersed through a nozzle to granulate fine particles of the raw materials.

[0098] Furthermore, the pressure generating means used in the "liquid ejection head 564" is not limited. For example, in addition to a piezoelectric actuator (which may use a laminated piezoelectric element), a thermal actuator using an electrothermal conversion element such as a heating resistor, or an electrostatic actuator consisting of a vibration plate and an opposing electrode may be used.

[0099] In addition, the terms "image formation," "recording," "printing," "imaging," "printing," "shaping," and the like in this application are all the same. It is a synonym.

[0100] Moreover, the "liquid ejection head 564" is housed in a "liquid ejection unit." This liquid ejection unit is an assembly of components related to ejecting liquid, in which functional parts and mechanisms are integrated with the liquid ejection head 564. For example, the "liquid ejection unit" includes a combination of at least one of the following components with the liquid ejection head: a head tank, a carriage, a supply mechanism, a maintenance and recovery mechanism, and a main scanning movement mechanism.

[0101] Here, integration includes, for example, a liquid ejection head, a functional part, and a mechanism that are fixed to each other by fastening, bonding, engaging, etc., and one is held movably relative to the other. Also, the liquid ejection head, the functional part, and the mechanism may be configured to be detachable from each other.

[0102] For example, there are liquid ejection units in which the liquid ejection head and the head tank are integrated together, and there are also liquid ejection units in which the liquid ejection head and the head tank are integrated together by being connected to each other by a tube, etc. Here, a unit including a filter can be added between the head tank and the liquid ejection head of these liquid ejection units.

[0103] Furthermore, there is a liquid ejection unit in which the liquid ejection head and the carriage are integrated.

[0104] In some liquid ejection units, the liquid ejection head is movably supported by a guide member that constitutes a part of the scanning movement mechanism, and the liquid ejection head and the scanning movement mechanism are integrated together, and in some liquid ejection units, the liquid ejection head, the carriage, and the main scanning movement mechanism are integrated together.

[0105] Furthermore, there is a liquid ejection unit in which a cap member, which is part of the maintenance and recovery mechanism, is fixed to a carriage on which the liquid ejection head is attached, thereby integrating the liquid ejection head, carriage, and maintenance and recovery mechanism.

[0106] In addition, some liquid ejection units have a head tank or a liquid ejection head to which a flow path component is attached, and a tube is connected to the liquid ejection head, and the liquid is supplied from a liquid storage source to the liquid ejection head via the tube.

[0107] The main scanning movement mechanism includes the guide member alone, and the supply mechanism includes the tube alone and the loading unit alone.

[0108] Such embodiments and modifications of the embodiments are intended to be included within the scope and spirit of the invention, and are included in the scope of the invention and its equivalents as described in the claims. [Explanation of symbols]

[0109] 2 Intermediate transfer belt 2a Belt edge of intermediate transfer belt 3 Belt drive roller 4 Counter Roller 5 Adjustment roller 6 Idler roller 7 Transfer roller 8. Charger 9 Development Unit 20 Belt position detection sensor 30 Tilt adjustment means 41 Cam motor 51 A / D converter 52 Control circuit 53 Memory 54 Counter 55 Motor Driver 60 Delta Sigma Modulation Section 70 Belt shift control unit 71 Adder 72 Integrator 73 Comparator 74 1-bit DAC 101 Personal computer equipment 102 Digital Front End (DFE) 103 Image forming device [Prior art documents] [Patent documents]

[0110] [Patent Document 1] Japanese Patent Application Publication No. 3-288167 [Patent Document 2] Japanese Patent Application Publication No. 11-295948

Claims

1. An adjustment roller that stretches and rotates the endless belt; a tilt adjustment unit including a cam for adjusting the tilt of the adjustment roller in order to control the belt deviation of the endless belt; a belt position detection unit that detects a belt position in a direction perpendicular to a belt moving direction of the endless belt; a stepping motor that rotates the cam of the tilt adjustment unit; a control output adjustment unit that adjusts a control output supplied to the stepping motor based on the belt position detected by the belt position detection unit; Equipped with the control output adjustment unit, when obtaining a rotation angle of the stepping motor that is less than one step, uses an output value obtained by delta-sigma modulating the control output to supply a control output to the stepping motor for a time period corresponding to a rotation angle that is less than one step during a supply time of the control output for obtaining a rotation angle of one step, and does not supply the control output for the remaining time. Belt drive.

2. The control output adjustment unit supplies a control output to the stepping motor for a time period during which the output value is 1.

2. The belt drive device according to claim 1,

3. When the endless belt is within a detection range of the belt position detection unit, the tilt amount of the adjustment roller is adjusted and controlled in proportion to the amount of fluctuation in the belt position, and when the endless belt is out of the detection range of the belt position detection unit, the tilt amount of the adjustment roller is controlled to be greater than the maximum tilt amount that can be taken when the endless belt is within the detection range.

3. The belt drive device according to claim 1, wherein:

4. The inclination adjustment of the adjustment roller is performed by tilting the opposite side of the adjustment roller with one side of the adjustment roller as a fulcrum, and the belt position detection unit is provided on the fulcrum side of the adjustment roller.

4. The belt drive device according to claim 3,

5. A belt driving method for a belt driving device including an adjustment roller that stretches and moves / rotates an endless belt, an inclination adjustment unit having a cam that adjusts the inclination of the adjustment roller in order to control a belt deviation of the endless belt, a belt position detection unit that detects a belt position in a direction perpendicular to a belt moving direction of the endless belt, and a stepping motor that rotates and drives the cam of the inclination adjustment unit, a control output adjustment unit that adjusts a control output to be supplied to the stepping motor based on the belt position detected by the belt position detection unit, comprising a control output adjustment step of, when obtaining a rotation angle of the stepping motor less than one step, using an output value obtained by delta-sigma modulating the control output, supplying the control output to the stepping motor for a time period corresponding to a rotation angle less than one step during a supply time of the control output for obtaining a rotation angle of one step, and not supplying the control output for the remaining time A belt drive method comprising:

6. An image forming apparatus comprising the belt driving device according to claim 1 .

Images