JP5146130B2 - Belt drive device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a belt driving device and an image forming apparatus including the belt driving device.

  In a belt driving device that travels infinitely by rotating an endless belt, such as an intermediate transfer belt in an image forming apparatus, meandering is a change in the width direction of the endless belt that is a direction perpendicular to the rotating direction during traveling. Need to control. As a method for controlling the meandering of the endless belt in the width direction, a method for controlling the meandering of the belt by controlling the inclination of a roller that stretches the belt (hereinafter referred to as a steering method) is known. An edge sensor for detecting the edge (end in the width direction) position of the endless belt is provided as the steering type belt driving device, and a roller (hereinafter referred to as a steering roller) that performs an inclination operation based on the position information is provided. There is a method for controlling the tilt. When detecting the fluctuation of the edge position of the belt, both of the meandering component of the belt and the distortion component of the belt edge shape generated at the time of manufacturing and processing the belt are included. For this reason, as a method for removing the distortion component of the belt edge shape that occurs during belt manufacturing and processing, the edge shape data for one belt revolution is stored and stored as the edge sensor detection data. A method is used in which edge shape data is compared to extract only the meandering component of the belt, and the amount of meandering of the belt is restored by tilting the steering roller. This method has a problem that a large amount of memory is required to store edge shape data for one belt revolution. In addition, when the edge shape data for one round of the belt changes due to deterioration over time, there is a problem that an accurate belt meandering component cannot be detected.

  For example, in Patent Document 1, for the purpose of suppressing the meandering of the intermediate transfer belt of the image forming apparatus, the belt edge sensor compares the detection result of the edge position for one round of the belt with the stored edge shape data, and the belt. A meandering correction method is disclosed in which only the meandering component is extracted, the belt meandering position is calculated and feedback control is performed to operate the tilt of the steering roller so that the belt always circulates at the reference position in the width direction.

In Patent Document 2, a plurality of target reference positions are provided for the purpose of shortening the time until the position in the width direction of the belt is returned to the reference position at the time of power-on, job start, and job switching. And a method of controlling the belt so as to guide the belt to a reference position at which it is easy to quickly and stably travel.
Japanese Patent Laid-Open No. 11-295948 JP 2004-78082 A

  In the meandering correction method for the intermediate transfer belt disclosed in Patent Document 1, in the case of a minute displacement from the reference position of the belt or a slow meandering, the meandering correction of the belt is easily performed by feedback control. However, if the deviation of the belt from the reference position is abrupt or large, as when the job of the image forming apparatus is started or switched, it takes time to return the belt to the reference position. End up. If image formation is performed during such meandering correction, the image may be distorted or color misregistration may occur.

  Furthermore, in this intermediate transfer belt, edge shape data for at least one round of the belt is stored for correction of meandering, and the meandering amount of the belt is always calculated by comparing the edge shape data with the measurement data by the edge sensor. doing. For this reason, the intermediate transfer belt must be provided with a storage device and an arithmetic unit for that purpose.

  In the meandering correction method for the intermediate transfer belt disclosed in Patent Document 2, a plurality of reference positions for stably running the belt are provided, so that it is relatively easy to return to the reference position in response to a significant belt position variation. It is. However, during the return of the belt to the reference position, the meandering of the belt continues, and image formation cannot be performed, resulting in a waiting time for return. Also in this intermediate transfer belt, it is necessary to store edge shape data for at least one round of the belt for correction of meandering and to calculate the meandering amount of the belt by comparing the edge shape data with measurement data by the edge sensor. Therefore, it is the same as the intermediate transfer belt disclosed in Patent Document 1 that a storage device and an arithmetic device for this purpose must be provided. In particular, as the belt length increases as in a full-color image forming apparatus, the memory for storing edge shape data also requires a large capacity. Further, even if the edge shape data of the belt is stored, the edge shape data needs to be re-stored when the edge shape of the belt changes due to belt replacement or deterioration over time.

  In view of the above problems, an object of the present invention is to provide a belt driving device capable of quickly suppressing meandering in the width direction of an endless belt and controlling the endless belt normally, and an image forming apparatus including the belt driving device.

The present invention is a belt driving device including a plurality of rollers including a driving roller and an endless belt that is stretched around the plurality of rollers and rotates in a width direction with respect to a predetermined portion of the endless belt that is rotating. A plurality of detection devices arranged at intervals with respect to the circulation direction for detecting a position, and an endless belt in the circulation from detection positions of the predetermined portions detected by at least two detection devices among the plurality of detection devices A calculation device that calculates a fluctuation speed in the width direction of the control unit, a control device that controls a position in the width direction of the endless belt based on the calculated fluctuation speed, and a detection device that detects the endless belt detected by each of the detection devices. By comparing the average values of the positions of the predetermined portions over one or more rounds, the relative position of each of the plurality of detection devices with respect to the width direction of the endless belt And a position detecting device for detecting the belt drive device.

  In a preferred aspect of the present invention, the control device sets the fluctuation speed in the width direction of the endless belt to zero.

The present invention is a belt driving device including a plurality of rollers including a driving roller and an endless belt that is stretched around the plurality of rollers and rotates in a width direction with respect to a predetermined portion of the endless belt that is rotating. A plurality of detection devices arranged at intervals with respect to the circulation direction for detecting a position, and an endless belt in the circulation from detection positions of the predetermined portions detected by at least two detection devices among the plurality of detection devices An arithmetic device that calculates the amount of variation in the width direction of the computer and the position in the width direction of a predetermined location detected by at least two detection devices of the plurality of detection devices based on the calculated amount of variation are identically controlled By comparing the average value of the position of the predetermined portion over one or more rounds of the endless belt detected by each of the detection devices. A position detecting device that detects a relative position of the plurality of detecting devices with respect to a width direction of the endless belt .

  In a preferred aspect of the present invention, the predetermined portion is an edge of the endless belt or a mark attached on the endless belt.

  According to a preferred aspect of the present invention, the arithmetic device is configured such that the predetermined positions of the detection devices are based on the intervals in the circumferential direction of the detection devices in the plurality of detection devices and the traveling speed of the endless belt in the circumferential direction. The belt driving device according to claim 1, wherein the detection timing is calculated.

  A preferable aspect of the present invention is the belt driving device including a traveling speed detecting device that detects a traveling speed of the endless belt.

  In a preferred aspect of the present invention, the belt driving device is characterized in that the travel speed of the endless belt is a target travel speed of the endless belt.

  In a preferred aspect of the present invention, the belt driving device is characterized in that the running speed of the endless belt is calculated from an interval in a circumferential direction of each of the detection devices and a detection time for a predetermined location of each detection device. .

  In a preferred aspect of the present invention, the control device controls the position in the width direction of the endless belt based on a plurality of the fluctuation speeds or a plurality of the fluctuation amounts.

  In a preferred aspect of the present invention, the arithmetic device uses an average value of the plurality of fluctuation speeds or an average value of the plurality of fluctuation amounts as an average fluctuation speed or an average fluctuation amount, respectively, and the control device includes the average fluctuation speed or the average fluctuation amount. The belt driving device according to claim 1, wherein the position of the endless belt in the width direction is controlled based on a fluctuation amount.

  In a preferred aspect of the present invention, the arithmetic device uses an average value of the plurality of fluctuation speeds or an average value of the plurality of fluctuation amounts as an average fluctuation speed or an average fluctuation amount, respectively, and the plurality of fluctuation speeds or the plurality of fluctuation amounts. Of these, the average value excluding the difference between the average fluctuation speed or the average fluctuation amount is a predetermined value or more is set as the corrected average fluctuation speed or the corrected average fluctuation quantity, and the control device is configured to correct the corrected average fluctuation speed. Alternatively, the belt driving device is characterized in that the position in the width direction of the endless belt is controlled based on the corrected average fluctuation amount.

  In a preferred aspect of the present invention, when the position in the width direction of the endless belt detected by any of the plurality of detection devices exceeds a reference value, the control device detects the endless detected by the plurality of detection devices. The belt driving device according to claim 1, wherein the belt driving device is controlled so that a position in a width direction with respect to a predetermined portion of the belt is within a reference value.

  The present invention is an image forming apparatus including any one of the belt driving devices described above.

  According to the present invention, it is possible to provide a belt driving device that can quickly suppress meandering of the endless belt in the width direction and control the endless belt to a normal circulation, and an image forming apparatus including the belt driving device.

  The belt driving device of the present invention is a belt driving device comprising a plurality of rollers including a driving roller and an endless belt that is stretched around the plurality of rollers, and the predetermined position of the endless belt that is rotating A plurality of detection devices are provided which detect the position in the width direction with respect to the outer circumference and are spaced apart from each other in the circumferential direction. This detection device is, for example, an edge sensor that measures an edge portion of a belt. In addition, as long as a predetermined portion of the belt can be detected, a CCD sensor or other position detecting means for measuring the position of the mark attached to the central portion of the belt or the vicinity of the edge may be used. The predetermined portion may be an edge, a center of the endless belt, or a back side of the endless belt, but is a specific portion of the belt whose position can be detected by at least two sensors. The plurality of detection devices are arranged such that at least two detection devices are arranged at intervals with respect to the belt circumferential direction, and the endless belt travels while circulating between a plurality of rollers on which the endless belt is stretched. The position in the width direction of the same predetermined portion can be detected with a time difference.

  Then, the belt driving device according to the present invention calculates the fluctuation speed in the width direction of the endless belt during the rotation from the detection position of the predetermined portion detected by at least two detection devices of the plurality of detection devices. And a control device for controlling the position of the endless belt in the width direction based on the calculated fluctuation speed. The arithmetic unit calculates the fluctuation speed in the width direction of the endless belt from the position information of the predetermined position of the endless belt detected by the at least two detection devices, or while the predetermined position of the endless belt travels between at least two detection devices. Calculate the amount of variation. And a control apparatus controls the position of the width direction of an endless belt according to this fluctuation speed or fluctuation amount. As a preferred control method, the fluctuation speed or fluctuation amount in the width direction of the endless belt may be set to zero. That is, the control device performs control to control the same position in the width direction of a predetermined portion of the running endless belt detected by at least two detection devices.

  Preferably, the arithmetic device according to the present invention sets the detection timing for a predetermined portion of each detection device based on the interval between the detection devices in the circumferential direction of the plurality of detection devices and the traveling speed of the endless belt in the circumferential direction. Can be calculated. Here, the travel speed of the endless belt may be a target travel speed of the endless belt, that is, a design travel speed. Note that there may be a plurality of design travel speeds, and in that case, the travel speed selected in the rounding operation may be used. Further, the arithmetic device may calculate the traveling speed of the endless belt in the circumferential direction from the arrangement interval of the detection device in the circumferential direction and the detection time at a predetermined location detected by each detection device.

  The control device can control the position in the width direction of the endless belt based on the plurality of fluctuation speeds or the plurality of fluctuation amounts calculated by the arithmetic device. The arithmetic unit sets the average value of the plurality of fluctuation speeds or the average value of the plurality of fluctuation amounts as the average fluctuation speed or the average fluctuation amount, respectively, and the control device determines the width direction of the endless belt based on the average fluctuation speed or the average fluctuation amount. The position of the can also be controlled. Further, each of the fluctuation speeds or fluctuation amounts whose difference from the average fluctuation speed or the average fluctuation amount is a predetermined value or more is regarded as noise and removed. The average value is calculated as a corrected average fluctuation speed or a corrected average fluctuation amount, and the control device can also control the position of the endless belt in the width direction based on the corrected average fluctuation speed or the corrected average fluctuation amount.

  The belt driving device of the present invention preferably includes a position detection device that detects the relative positions of the plurality of detection devices in the width direction of the endless belt. In order to measure the relative position of the same endless belt in the width direction of the endless belt with a plurality of detection devices, the relative position of each detection device in the width direction of the endless belt must be clear. In terms of device design, there is no problem because each detection device is placed at a predetermined position, but in case the respective detection devices move relative to each other, the relative positions of the multiple detection devices in the width direction of the endless belt are detected. It is preferable to provide a position detecting device. The position detection device detects the relative position of each detection device by comparing the average value of the position of the edge or end mark on the endless belt detected by each detection device over one lap of the endless belt. I can do it.

  When the position in the width direction of the endless belt detected by any one of the plurality of detection devices exceeds a reference value, the control device detects the endless belt detected by the plurality of detection devices. It is preferable to control the position in the width direction with respect to the predetermined location to be within a reference value. In normal control, the position in the width direction of the endless belt detected by one of the detection devices does not exceed the reference value, but if the movement in the width direction due to meandering of the endless belt is accumulated, the endless belt is accumulated. The belt may deviate greatly from the design reference position during travel. In such a case, for example, in the case of an intermediate belt of an image forming apparatus, there is a possibility that an image is formed beyond the play allowance of the endless belt. In order to prevent this, when the deviation in the width direction of the endless belt exceeds a certain reference value, it is preferable to perform control for forcibly moving the endless belt to a design reference position or reference range.

  An image forming apparatus provided with any of the belt driving apparatuses of the present invention described above and applied to, for example, an intermediate transfer belt driving apparatus can perform suitable image formation. In particular, in an image forming apparatus having a structure in which images of respective colors are superimposed on the intermediate transfer belt with a time difference like a tandem type full-color image forming apparatus, it is strictly required to control the meandering of the intermediate transfer belt in the width direction. Therefore, the use of the belt driving device of the present invention is preferable.

(Embodiment)
Specific embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an intermediate transfer belt driving device in an image forming apparatus which is a kind of belt driving device of the present invention. In FIG. 1, an intermediate transfer belt 1 composed of an endless belt is stretched with a predetermined tension by a driving roller 2, a steering roller 3, a repulsive roller 4, and a driven roller 5. On the intermediate transfer belt 1, along the belt running direction X, photosensitive drums 6, 7, 8, corresponding to each color of yellow (Y), cyan (C), magenta (M), and black (K) are provided. 9 are arranged in order. A secondary transfer roller 11 is disposed opposite to the repulsive roller 4.

  Two edge sensors 14 and 15 are arranged on the travel path of the intermediate transfer belt 1 so that the edge position of the intermediate transfer belt 1 can be detected. In FIG. 1, it is arranged between the driving roller 2 and the repulsive roller 4 downstream of the driving roller 2, but the arrangement of the two edge sensors 14, 15 is not limited to this position. However, the two edge sensors 14 and 15 are arranged so that the edge position on the same side of the intermediate transfer belt 1 can be detected.

  An operation procedure when a color image is formed using the image forming apparatus provided with the intermediate belt driving device of this embodiment will be described. When the image forming apparatus receives a press of a start button or a print instruction, the photosensitive drums 6, 7, 8, 9, the intermediate transfer belt 1, and the secondary transfer roller 11 start rotating at substantially equal speeds. Then, each color image corresponding to each image information is written on the photoconductive drums 6, 7, 8, and 9, and each color image is primarily transferred to the intermediate transfer belt 1. At the same time, the recording paper 13 is conveyed from the paper feed tray or the manual feed tray, and the paper image is formed at the same timing as the image formed on the intermediate transfer belt 1 reaches the secondary transfer roller 11 and the repulsive roller 4. The part reaches between the secondary transfer roller 11 and the repulsive roller 4. Then, the image on the intermediate transfer belt 1 is secondarily transferred to the recording paper between the secondary transfer roller 11 and the repulsive roller 4.

  In such a series of image forming operations, when so-called meandering occurs in which the intermediate transfer belt 1 moves in the width direction (a direction orthogonal to the circumferential direction of the intermediate transfer belt 1), each color image is respectively transferred to the photosensitive drum 6, When primary transfer is performed from 7, 8, 9 onto the intermediate belt 1, a relative shift occurs in the position of each color image, and this appears as color shift or color unevenness in the output image. In view of this, the intermediate transfer belt driving apparatus of the present invention incorporates a configuration in which the steering roller 3 is inclined in order to correct the meandering of the intermediate transfer belt 1.

  When the intermediate transfer belt 1 is traveling while being circulated between the excess rollers, the edge sensors 14 and 15 always detect the edge of the intermediate transfer belt 1 and output an analog signal corresponding to the edge position. Based on the analog signal, the steering motor 16 is driven to rotate the eccentric cam 17. The eccentric cam 17 moves one end of the steering rod 18 up and down as it rotates. The steering rod 18 is like a lever rod having a fulcrum near the center, and the other end also serves as a bearing for one shaft on the same side as the edge sensors 14 and 15 of the steering roller 3 are arranged. Yes. When one end of the steering rod 18 moves up and down, one shaft of the steering roller 3 coupled to the other end moves up and down in the direction opposite to the one end. Since the other shaft of the steering roller 3 is coupled to a bearing that does not move, when one shaft of the steering roller 3 moves up and down, the steering roller 3 is inclined relative to the other roller, and the intermediate transfer belt 1 The meandering state changes.

  In the case of the configuration shown in FIG. 1, the intermediate transfer belt 1 circulates in the direction of arrow X, and when one shaft of the steering roller 3 coupled to the steering rod 18 moves in the direction of arrow Y, the intermediate transfer belt that is running The force to move to the back side of the page is applied to 1. When one shaft of the steering roller 3 coupled to the steering rod 18 moves in the direction of arrow Z, a force that moves toward the front side of the paper surface is applied to the running intermediate transfer belt 1.

  In the first embodiment, this action is used to apply a force to move the intermediate transfer belt 1 in the reverse direction by an amount corresponding to the meandering amount of the edge detected by the edge sensors 14 and 15. One axis is moved to tilt the axis. As a result, the stress of the meandering and the stress due to the inclination of the steering roller 3 are balanced, and the moving speed of the intermediate transfer belt 1 in the width direction becomes 0. At that time, the meandering is stopped and the belt circulates normally.

  FIG. 2 shows the control state of the displacement in the belt width direction and the fluctuation speed in the belt driving device of the present invention and the conventional belt driving device. In FIG. 2, the horizontal axis represents the time for which the belt travels, the vertical axis represents the position in the width direction of the predetermined position of the belt edge, and the upper figure represents the width of the predetermined position of the belt edge. It represents the direction variation speed. A solid line indicates the movement of the predetermined position in the belt driving apparatus of the present invention, and a broken line indicates the movement of the conventional belt driving apparatus.

First, variations in the position in the belt width direction will be described. When the driving of the belt driving device was started at time t ₀ , the belt width direction position X was X ₁ . Reference position design of the belt drive is a X _0, the drive start time, etc., it is often deviated from the reference position X _0.

Therefore, belt drive detects the belt widthwise position X ₁ by the time t ₁ by the edge sensor. If a conventional belt driving device, back to the reference position X ₀ it takes until time t ₂ as shown in broken lines, where the belt is controlled so as to run stably. Then, the position in the width direction of the belt from time _{t 1} to _{t 2} is moving (meandering) from _{X 1} to _{X 0.} For this reason, this period is a waiting time during which image formation is not possible. If this is described with reference to the upper diagram showing the fluctuation speed in the belt width direction, the fluctuation speed of the belt is zero even if the position in the width direction is deviated from the reference position. However, the conventional belt driving apparatus measures the edge position and does not measure the fluctuation speed in the width direction of the edge position. For this reason, in order to return the position in the width direction to the reference position, the belt moves (meanders) from time t ₁ to time t ₂ at the speed v ₁ . During this belt movement period, the belt driving device cannot be used for image formation or the like.

On the other hand, the belt drive of the present invention, the two edge sensors during the time t ₁ to t _2, detects that there is no variation in the belt width direction position. If there is no change in the position in the belt width direction, it is determined that the belt is normally circulated without meandering at that time, and a job such as image formation becomes possible. In general, the belt has a certain margin at the end, and the variation in the belt position due to the start of operation of the belt driving device or the impact of job switching is a variation sufficiently within the margin. In the belt drive device of the present invention, this characteristic is used to minimize the time until the belt can stably run without meandering regardless of the design reference position. As can be seen from the above diagram showing the fluctuation speed in the belt width direction, since the belt normally circulates when the fluctuation speed in the belt width direction is 0, the belt driving device of the present invention is started from time t _1. It turns out that it can be used normally.

In the example shown in the figure, and from the time t ₁ to t ₂ in the conventional belt drive, but a from the time t ₁ in the belt driving device of the present invention to t ₂ is assumed equal, the belt of the present invention In the drive device, two edge sensors are arranged, and by narrowing the arrangement interval, the presence or absence of the meandering of the belt can be detected in a shorter time.

Next, the operation when the belt starts to meander for some reason while the belt drive device is in operation will be described. Meandering of the belt begins at time t ₃ in FIG. 2, and detects the meandering from time t ₃ to t _4. In conventional belt drive, halt the meandering serpentine from the time t ₄ when the detected and an attempt move further from the belt lateral shift position X ₂ to X ₀ is (meandering). For this reason, control is performed to change the fluctuation speed in the belt width direction from v ₂ to v ₁ , and the process waits until time t ₅ when the belt moves in the belt width direction fluctuation position X ₂ to X ₀ . From this time t ₄ to t ₅ , the belt moves in the width direction at the fluctuation speed v ₁ and cannot be used as a belt driving device.

On the other hand, when the belt began meanders in the belt driving apparatus of the present invention, and detects the meandering from time t ₃ to t _4. In the belt driving device of the present invention, the belt meandering speed or the amount of displacement in the width direction of a predetermined position of the belt detected by two edge sensors is detected. In FIG. 2, the movement from the belt width direction fluctuation position X ₁ to X ₃ in the lower figure is detected from the fluctuation speed v ₂ in the belt width direction in the upper figure or the time t ₃ to t ₄ . Then, the changing speed of the belt width direction so as to be 0 at time t _4, or the belt lateral shift position to stop at X _3, controls the steering device. In this case, it is possible to normal operation from the time t ₄ the belt drive, the image forming and the like can be performed immediately.

  FIG. 3 is a control block diagram of the belt driving device of the present invention. On the other hand, FIG. 8 is a control block diagram of a conventional steering type belt driving apparatus. Before describing the belt driving device of the present invention, control of a conventional steering type belt driving device will be described with reference to FIG.

  In a conventional steering type belt driving device, the position of the belt is controlled based on information from one edge sensor. For this reason, the configuration for performing the position control in the width direction of the belt includes the above-described three mechanical mechanisms of the steering motor, the steering roller, and the edge sensor, mainly the control unit, the motor driver, the A / D converter, the calculation unit, and the memory. Part of the controller. The control unit compares the amount of variation between the target position in the width direction of the belt, which is the input information, and the actual position, which is information from the edge sensor, and determines the steering amount (the number of steps of the steering motor) corresponding to the amount of variation of the belt. ) Is output to the motor driver. On the other hand, the motor driver drives the steering motor according to the control information from the control unit, and controls the tilt angle θ (t) of the steering roller by this driving.

  On the other hand, the edge sensor detects the edge position of the belt and outputs an analog value E (t) corresponding to the edge position. The problem here is the content of the information contained in E (t). If the edge portion of the intermediate transfer belt is flat, this E (t) is equal to the belt edge position fluctuation, and the control system may have a simple configuration. In reality, however, the edges of the intermediate transfer belt often have irregularities in manufacturing and processing. Therefore, the edge sensor output E (t) is obtained by adding the position fluctuation amount W (t) due to the belt meandering and the belt edge shape data P (t).

  The edge sensor output is input to an A / D converter and converted from an analog signal to a digital signal. Usually, in order to remove a noise component included in an analog signal, digital signal values obtained by performing A / D conversion a plurality of times are averaged and leveled to obtain an edge sensor output E (t).

  The storage unit stores the edge shape data in advance, and as described above, the edge sensor output E (t) is calculated from the position variation amount W (t) due to the belt meander and the belt edge shape data P (t). In order to control the meandering of the belt with high accuracy, the belt edge shape data P (t) component is removed from the edge sensor output E (t), and only the position variation W (t) component is used. It is necessary to compare with the target position. Therefore, the edge data P (t) for one belt revolution is stored in advance in the storage unit, and the edge shape data at a predetermined belt position is subtracted from the edge sensor output E (t) and compared with the target position. Yes.

  Further, it is the memory of this belt position that becomes a problem. Especially in the case of a large machine, the length of the intermediate transfer belt is long and uses a huge memory capacity. Further, when stored in the volatile memory, the data is lost when the power is turned off, and it is necessary to always obtain the data again after the power is turned on. In the image forming apparatus, there are a lot of data that must be stored in the nonvolatile memory, such as data at the time of stopping due to an error and the cumulative number of prints, so if there is room to store the belt position information in the nonvolatile memory Few. Increasing the capacity of the non-volatile memory leads to an increase in substrate area and cost.

  This control method is position feedback control in which control is performed by comparing the position of the target belt with the actually measured position. The position feedback control is performed so that the position of the belt always becomes the target position. If the belt position is shifted even a little, the position is returned to the target position. For this reason, the belt often fluctuates in the width direction, and it may take time for the position in the width direction of the belt to become stable. There is a possibility of generating. For example, it is assumed that the intermediate transfer belt is traveling while maintaining a position of +100 μm from the target position. In this state, the meandering speed is 0 μm / s and no color shift occurs. However, position feedback control is performed here, and the belt is moved by −100 μm in an attempt to return the belt to the target position.

  Furthermore, in the conventional belt driving device, when the belt is replaced, as well as when the shape changes even a little due to deterioration of the belt over time or removal due to maintenance, the position fluctuation amount due to the belt meandering cannot be obtained accurately. It is necessary to re-store the edge shape data.

  FIG. 3 is a control block diagram illustrating a method for controlling the belt driving device of the present invention, corresponding to FIG. 8 which is a control block diagram of a conventional belt driving device. In the belt driving device of the present invention, two belt edge sensors are used to perform speed feedback control for controlling the fluctuation speed of the belt position or fluctuation amount feedback control for controlling the fluctuation amount of the belt position. As a configuration for performing steering control, a steering motor, a steering roller, a mechanical mechanism of two edge sensors 14 and 15, a controller, an A / D converter, a calculator, and a controller of a calculator are provided.

  In the belt driving device of the present invention, the input information is the target meandering speed of the belt (the meandering speed refers to the fluctuation speed in the width direction of the belt) or the position fluctuation amount of the belt within a predetermined time, that is, meandering. The speed or position fluctuation amount is set to zero. In the control method based on the target meandering speed, the control unit compares the target meandering speed (normally the target meandering speed is 0) with the meandering speed of the circulating belt, and corresponds to the meandering speed of the belt. The steering amount (the number of steps of the steering motor) is output to the motor driver. On the other hand, the motor driver drives the steering motor according to the control information from the control unit, and the tilt angle θ (t) of the steering roller is controlled by this driving.

On the other hand, the two edge sensors 14 and 15 detect the same edge position, which is a predetermined portion of the belt, and output analog output values E1 (t) and E2 (t) corresponding to the edge positions. As described above, since the edge sensor output is obtained by adding the position variation amount W (t) due to the belt meandering and the belt edge shape data P (t), the belt rotation direction at a predetermined time t. The edge position E1 (t) measured by the edge sensor 14 on the upstream side is
E1 (t) = W (t) + P (t) (1)
It is represented by Formula (1).

Here, paying attention to the edge shape data P (t) component of the intermediate transfer belt, if it takes τ seconds to reach the edge sensor 15 after one point on the belt passes the edge sensor 14, the edge sensor The output E2 (t) of 15 is
E2 (t) = W (t) + P (t−τ) (2)
It is represented by Formula (2).

The calculation unit determines the data acquisition timing of the edge sensor input to the A / D converter. The analog outputs of the edge sensors 14 and 15 are continuously input to the A / D converter, but this analog value is used to instruct the timing for A / D conversion. This timing is instructed to the A / D converter so that the timing for fetching the data of the edge sensor 15 is τ seconds after the timing of fetching the data of the edge sensor 15, where t1 is the timing for fetching the data of the edge sensor 14. The analog value data acquired by the edge sensor 14 in this way is
E1 (t1) = W (t1) + P (t1) (3)
Similarly, the analog value data acquired by the edge sensor 15 is
E2 (t1 + τ) = W (t1 + τ) + P (t1) (4)
It becomes.

  The acquired data is converted into a digital value by an A / D converter. E1 (T1) and E2 (T2 + τ) converted to digital values are output from the A / D converter to the calculation unit, and the calculation unit calculates the meandering speed. Speed feedback control can be performed by comparing this meandering speed with a target speed (= 0). Further, when performing fluctuation amount feedback control, E1 (T1) and E2 (T2 + τ) may be directly compared and controlled so that this difference becomes zero. A detailed method for calculating the meandering speed will be described later.

  In the belt drive device of the present invention, it is not necessary to store the edge shape data required for the conventional belt drive device, and the consumption of memory capacity can be suppressed. In addition, since the edge shape data P (t) is not used for control, the output of the two edge sensors always includes the latest edge information even if the edge shape changes due to time degradation or removal due to maintenance. Further, the meandering speed of the belt and the fluctuation amount within the measurement time can be obtained accurately.

  Further, since the speed feedback control or the fluctuation amount feedback control is performed, if the meandering speed or the fluctuation amount within the measurement time is zero, the manipulated variable becomes zero. For example, when the belt is running while maintaining a position deviated by +100 μm in the width direction from the reference position, the meandering speed and the amount of fluctuation within the measurement point are 0 μm / s and 0 μm, and the state is maintained as it is. You are in control. For this reason, the time required for returning the deviation of +100 μm, which was necessary in the conventional belt driving device, is not required, and normal operation can be performed as it is.

  That is, in the belt driving device of the present invention, in order to prevent color misregistration of the image forming apparatus due to the belt meandering, if the belt meandering speed is 0 (if the belt does not fluctuate in the width direction at that time). Good, taking advantage of the fact that the belt does not always have to be in the target position. In the belt driving device used for the image forming apparatus or the like, the vicinity of the end of the belt is not used for image formation and is allowed to play. Therefore, in the meandering width during normal belt running, the range of this allowance is provided. There is no problem even if the belt is running and the belt is running relatively deviated from the reference position.

  FIG. 4 is an enlarged view of the periphery of the edge sensors 14 and 15 in the belt driving apparatus of the present invention shown in FIG. FIG. 5 is a flowchart for explaining the data acquisition flow of the arithmetic unit in the belt driving device of the present invention.

In FIG. 4, if the distance between the edge sensors 14 and 15 is a [mm] and the running speed (circumferential speed) of the belt 1 is b [mm / s], one point which is an arbitrary part of the belt 1 is The time τ from passing through the sensor 14 to passing through the sensor 15 is
[Τ = a / b]

  Therefore, in the arithmetic unit, the distance a between the edge sensors 14 and 15 and the traveling speed b of the belt 1 are stored in advance, and as shown in FIG. Position data is acquired, τ = a / b is obtained, it is confirmed that time τ has elapsed, and position data is acquired by the edge sensor 15 after time τ. Thereby, the position data of the same part on the belt can be acquired by the edge sensors 14 and 15.

  At this time, the belt speed b may be the design speed of the belt speed in the belt drive device, or if the belt speed sensor actually has a speed sensor such as an encoder or a speed detector such as an encoder, The detection result may be used. In the arithmetic unit, the timing t1 for performing A / D conversion of the sensor 14 is arbitrarily set, and the sensor 15 may be instructed to perform A / D conversion at t1 + τ. This operation is always repeated while the edge sensor is operating, that is, while steering control is being performed.

FIG. 6 is a flowchart for explaining the calculation of the belt meandering speed by the arithmetic device in the belt driving device of the present invention. As described above, when the analog output of the sensor 14 is subjected to A / D conversion at time t1, the result is expressed by the above-described equation (3), and the analog output of the sensor 15 is converted to A / D at time t1 + τ. The result when D conversion is performed is expressed by Equation (4).
Therefore, the position fluctuation amount due to the belt meandering during the time τ is obtained by subtracting the A / D conversion value E1 (t1) of the sensor 14 from the A / D conversion value E2 (t1 + τ) of the sensor 15.
E2 (t1 + τ) −E1 (t1)
= {W (t1 + τ) + P (t1)}-{W (t1) + P (t1)}
= W (t1 + τ) −W (t1) (5)
Represented as:

The position fluctuation amount due to the meandering of the belt during the time τ is obtained by removing the belt edge shape data from the output of the edge sensor, and the position fluctuation amount due to the meandering of the belt at the positions of the sensor 14 and the sensor 15 during the time τ is expressed by the equation (5). ). Therefore, by dividing the position fluctuation amount due to the belt meandering during the time τ by the time τ, the meandering speed v (t1) from the time t1 to t1 + τ is
v (t1) = {W (t1 + τ) −W (t1)} / τ (6)
Represented as: In the belt driving device of the present invention, the meandering speed v (t1) may be controlled to be zero.

  When the sensor output can be calculated at a sufficiently fast cycle with respect to the control cycle of the speed feedback control, the meandering speed calculated from multiple sensor outputs is averaged, and the average meandering speed is calculated. It becomes possible to prevent malfunction. For example, FIG. 7 shows a calculation flow of the average meandering speed by the arithmetic unit when data acquisition and meandering speed calculation are performed by five sensors during the control period.

  In the calculation flowchart of the calculation device shown in FIG. 7, the data acquisition timing of the edge sensor 14 is t1 to t5, respectively, and the meandering speeds v (t1), v (t2), v (t3), v (t4) and v (t5) are calculated, and the average of these five meandering speeds is calculated as the meandering speed v (tn).

  The belt driving device of the present invention can be effectively used as, for example, an intermediate transfer belt of an image forming apparatus. Further, the present invention can be effectively applied to a recording medium conveying device of an image forming apparatus or other conveying device using a belt that requires control in the width direction.

Configuration diagram of belt driving device of the present invention Graph showing belt width displacement and fluctuation speed Control block diagram of belt driving device of the present invention Enlarged view of the edge sensor Flow chart of data acquisition by arithmetic unit Arithmetic flow chart of arithmetic unit Flowchart of calculation for averaging five acquired data by the calculation device Control block diagram of a conventional steering belt drive

Explanation of symbols

1 Intermediate transfer belt (endless belt)
2 Driving roller 3 Steering roller 4 Repulsive roller 5 Driven roller 6 Photosensitive drum (yellow)
7 Photosensitive drum (cyan)
8 Photosensitive drum (magenta)
9 Photosensitive drum (black)
10 drive motor 11 secondary transfer roller 13 recording paper (recording medium)
14 Edge sensor (detection device)
15 Edge sensor (detection device)
16 Steering motor 17 Eccentric cam 18 Steering rod

Claims (13)

A belt drive device comprising a plurality of rollers including a drive roller, and an endless belt that is stretched around the plurality of rollers,
Detecting the position in the width direction with respect to a predetermined portion of said endless belt of orbiting, and a plurality of detecting devices arranged at a distance with respect to the circumferential direction,
An arithmetic device that calculates a fluctuation speed in the width direction of the endless belt during the rotation from the detection position of the predetermined portion detected by at least two detection devices among the plurality of detection devices;
A control device for controlling the position in the width direction of the endless belt based on the calculated fluctuation speed;
By comparing the average values of the positions of the predetermined portions over one or more rounds of the endless belt detected by the detection devices, the relative positions of the plurality of detection devices with respect to the width direction of the endless belts are calculated. A position detection device to detect;
A belt drive device comprising:   2. The belt driving device according to claim 1, wherein the control device sets a fluctuation speed in a width direction of the endless belt to zero. A belt drive device comprising a plurality of rollers including a drive roller, and an endless belt that is stretched around the plurality of rollers,
A plurality of detection devices arranged at intervals with respect to the circumferential direction for detecting a position in the width direction with respect to a predetermined portion of the endless belt during circulation;
An arithmetic unit that calculates a fluctuation amount in a width direction of the endless belt during the rotation from a detection position of the predetermined portion detected by at least two detection devices of the plurality of detection devices;
A control device that controls the same position in the width direction of a predetermined location detected by at least two detection devices among the plurality of detection devices based on the calculated variation amount;
By comparing the average values of the positions of the predetermined portions over one or more rounds of the endless belt detected by the detection devices, the relative positions of the plurality of detection devices with respect to the width direction of the endless belts are calculated. A position detection device to detect;
A belt drive device comprising:   The belt driving device according to any one of claims 1 to 3, wherein the predetermined portion is an edge of the endless belt or a mark attached to the endless belt.   The arithmetic device calculates detection timings for predetermined positions of the detection devices based on the intervals in the rotation direction of the detection devices in the plurality of detection devices and the traveling speed of the endless belt in the rotation direction. The belt drive device according to any one of claims 1 to 4, wherein   The belt driving device according to claim 5, further comprising a traveling speed detection device that detects a traveling speed of the endless belt.   The belt driving device according to claim 5 or 6, wherein the travel speed of the endless belt is a target travel speed of the endless belt.   5. The travel speed of the endless belt is calculated from an interval with respect to the rotation direction of each of the detection devices and a detection time with respect to a predetermined location of each of the detection devices. The belt driving device described.   The belt drive according to claim 1, wherein the control device controls a position in a width direction of the endless belt based on a plurality of the fluctuation speeds or a plurality of the fluctuation amounts. apparatus. The arithmetic device, an average value of a plurality of fluctuation speeds or an average value of a plurality of fluctuation amounts as an average fluctuation speed or an average fluctuation amount, respectively,
The belt drive device according to claim 9, wherein the control device controls a position in a width direction of the endless belt based on the average fluctuation speed or the average fluctuation amount. The arithmetic device uses an average value of the plurality of fluctuation speeds or an average value of the plurality of fluctuation amounts as an average fluctuation speed or an average fluctuation amount, respectively, and the average of the plurality of fluctuation speeds or the plurality of fluctuation amounts, respectively. The average value excluding the fluctuation rate or the difference between the average fluctuation amount and the predetermined value is a corrected average fluctuation speed or the corrected average fluctuation amount,
The belt drive device according to claim 9, wherein the control device controls a position in a width direction of the endless belt based on the corrected average fluctuation speed or the corrected average fluctuation amount. When the position in the width direction with respect to a predetermined location of the endless belt detected by any of the plurality of detection devices exceeds a reference value,
The control device according to any one of claims 1 to 11, wherein the controller controls so as to be within a reference value position in the width direction with respect to a predetermined portion of said endless belt detected by the plurality of detection devices Belt drive device. An image forming apparatus comprising the belt driving device according to any one of claims 1 to 12.

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