JP2020016779A - Drive control unit and image forming apparatus - Google Patents

Abstract

To provide a drive control unit that can cancel output of an even number component equal to or more than one rotation secondary component of an encoder disk.SOLUTION: A drive control unit 41 controls to drive a driving roller on the basis of an output signal of an encoder, and the encoder has a disk and three sensors 40a, 40b, 40c disposed at positions for detecting the disk and shifted by 120 degrees respectively. The drive control unit comprises: composition means that composites output signals from the sensors 40a, 40b, 40c; multiplication means that multiplies the composite signal transmitted from the composition means by 1/3; counting means that counts the 1/3-multiplied composite signal transmitted from the multiplication means; sampling means that samples a count value counted by the counting means at a predetermined timing; and feedback control means that performs feedback control to a control target value on the basis of the count value sampled by the sampling means to control to drive the drive roller.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a drive control device and an image forming apparatus.

  In a transfer apparatus using a transfer belt employed in an image forming apparatus, a color shift or banding (band-like density unevenness appearing in a halftone portion of an image due to a speed variation of the transfer belt, and an interval between halftone dots) Is likely to occur when the speed changes due to fluctuations in the speed of the mechanical system), an encoder is attached to one of a plurality of drive rollers and driven rollers that constitute the transfer device, and the rotational speed of the encoder is changed. A method of feedback-controlling the rotation speed of the drive roller according to the speed is adopted.

  However, in the above configuration, due to the influence of the concentricity processing accuracy of the disk of the encoder, when the disk is mounted on the drive roller, the center of the drive roller and the disk may be mounted in a state where they are shifted from each other. When the drive roller rotates in such a state, the disk rotates eccentrically despite the fact that the drive roller is rotating at a constant speed. Therefore, when the disk is read by a sensor (light receiver), one rotation of the drive roller is performed. The primary component appears as a shift in the sensor output, that is, the pulse signal. In order to suppress the output of the primary component of one rotation of the encoder disk, a technique has been proposed in which two sensors are arranged to face each other at 180 degrees to cancel the primary component of one rotation of the encoder disk (for example, Patent Document 1). reference).

In the technique described above, the output of the primary component of one rotation of the encoder disk can be canceled, but other components such as the secondary component of one rotation or more cannot be canceled. Of the components of such a one-rotation secondary component or more, especially the even component is caused by the printing die of the disk, or the disk itself or the driving gear of the driving roller is polygonized due to the gate position at the time of molding. It is desirable to suppress the output because it frequently occurs due to the movement.
SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems and to provide a drive control device capable of canceling the output of an even-numbered component equal to or more than a one-turn secondary component of an encoder disk, and an image forming apparatus including the same. .

  The invention according to claim 1, further comprising an encoder that detects the rotation of a driving roller that drives the endless moving member to travel or a driven roller that is driven and rotated by the movement of the endless moving member, wherein the driving roller is driven based on an output signal of the encoder. The encoder is provided with a plurality of marks or slits arranged at predetermined intervals in the circumferential direction, and a disk provided at a position shifted by 120 degrees to detect each of the marks or slits. Combining means for combining output signals of the sensors, a multiplying means for multiplying the combined signal sent from the combining means by 1/3, and a 1/3 multiplied signal sent from the multiplying means. Counting means for counting the combined signal, and sampling means for sampling a count value of the counting means at a predetermined timing , By performing feedback control on the control target value based on the sampled counted value by the sampling means, and having a feedback control means for driving and controlling the drive rollers.

  According to the present invention, since the eccentric component of the encoder disk can be removed as compared with the conventional configuration, it is possible to improve the accuracy in the feedback control of the drive motor of the endless moving member caused by the eccentricity of the encoder disk. Thus, it is possible to prevent the occurrence of color shift during image formation.

1 is a schematic diagram of an image forming apparatus to which an embodiment of the present invention can be applied. 1 is a schematic diagram illustrating a drive roller, a drive motor, and an encoder to which an embodiment of the present invention can be applied. It is the schematic explaining the conventional encoder disk and encoder sensor. FIG. 9 is a block diagram illustrating a conventional drive control device. FIG. 2 is a schematic diagram illustrating an encoder sensor used in an embodiment of the present invention. FIG. 2 is a block diagram illustrating a drive control device used in one embodiment of the present invention. FIG. 5 is a schematic diagram showing output waveforms of each encoder sensor in the case of one rotation primary component in one embodiment of the present invention. FIG. 5 is a schematic diagram showing output waveforms of each encoder sensor in the case of one rotation secondary component in one embodiment of the present invention. FIG. 7 is a schematic diagram showing output waveforms of each encoder sensor in the case of one-turn tertiary component in one embodiment of the present invention. FIG. 5 is a schematic diagram showing output waveforms of each encoder sensor in the case of one rotation fourth order component in one embodiment of the present invention. It is a schematic diagram showing an output waveform of each encoder sensor in the case of one rotation 16th order components in one embodiment of the present invention. FIG. 11 is a schematic diagram showing output waveforms of each encoder sensor in the case of one rotation primary component in a modification of one embodiment of the present invention. FIG. 10 is a schematic diagram showing output waveforms of each encoder sensor in the case of a one-turn secondary component in a modification of one embodiment of the present invention.

FIG. 1 shows an image forming apparatus according to an embodiment of the present invention. The laser printer 1 as an image forming apparatus includes four toner image forming units 2Y, 2M, 2C, and 4 for forming images of yellow (Y), magenta (M), cyan (C), and black (K). Has 2K. The toner image forming units 2 are arranged in the above-described order from the upstream side in the traveling direction of the transfer conveyance belt 3 that is driven to travel in the direction of arrow A.
Each toner image forming unit 2 includes a photosensitive drum 4Y, 4M, 4C, 4K as an image carrier and a developing unit 5. The toner image forming units 2 are set so that the rotation axes of the photosensitive drums 4 are parallel to each other and are arranged in parallel in the moving direction of the recording medium at predetermined intervals.

  The laser printer 1 further has an optical writing unit 6, paper feed cassettes 7, 8, a pair of registration rollers 9, and an endless movement that carries the recording medium P and passes through the transfer position of each toner image forming unit 2. The image forming apparatus includes a belt driving device 10 having a transfer / conveying belt 3 as a member, a fixing unit 11 employing a belt fixing method, and a paper discharge tray 12 on which paper P after image formation is discharged and stacked. The belt driving device 10 has a drive control device described later, and also functions as a transfer unit.

Further, the laser printer 1 has a manual feed tray 13 and a toner supply container 14, and includes well-known components such as a waste toner bottle, a two-sided reversing unit, and a power supply unit, which are not shown, inside a space S indicated by a chain line. ing.
The optical writing unit 6 includes a light source, a polygon mirror, an fθ lens, a reflection mirror, and the like, and has a well-known configuration that irradiates the surface of each photosensitive drum 4 with a laser beam while scanning it based on image data. .

The transfer conveyance belt 3 used in the belt driving device 11 is a high-resistance endless single-layer endless belt having a volume resistivity of 10 ⁹ to 10 ¹¹ Ωcm, and is made of, for example, PVDF (polyvinylidene fluoride). The transfer conveyance belt 3 is supported by a plurality of support rollers so as to pass through each transfer position facing each photosensitive drum 4.

  An entrance roller 15 is disposed at the most upstream position of each transfer position and immediately downstream of the registration roller pair 9 among the plurality of support rollers. An electrostatic attraction roller 16 is disposed at a position facing the entrance roller 15 via the transfer / conveyance belt 3. A predetermined voltage is applied from a power supply (not shown) to the electrostatic attraction roller 16, the paper P passing between the entrance roller 15 and the electrostatic attraction roller 16 is charged, and the charged paper P is transferred to the transfer conveyance belt. 3 is electrostatically attracted to the upper surface. In the belt driving device 10, a driving roller 17 is disposed at a position diagonal to the entrance roller 15. The drive roller 17 drives the transfer conveyance belt 3 to travel, and is rotationally driven in a counterclockwise direction in FIG. 1 by a motor described later.

  Transfer members 18Y, 18M, 18C, and 18K that form a transfer electric field are provided at respective transfer positions opposed to the respective photoconductor drums 4 via the transfer / transport belt 3 so as to be in contact with the back surface of the transfer / transport belt 3. Have been. Each transfer member 18 is a bias roller having a sponge or the like provided on the outer peripheral surface, and a bias voltage is applied from each bias power source (not shown). The transfer voltage is applied to the transfer / transport belt 3 by the action of the bias voltage, and a transfer electric field having a predetermined intensity is formed between the surface of the transfer / transport belt 3 and the surface of each of the photosensitive drums 4 at each transfer position.

A mode in which a belt cleaning device 19 having a brush roller and a cleaning blade makes the surface of the brush roller and the tip of the cleaning blade contact the surface of the transfer transport belt 3 at a position facing the drive roller 17 via the transfer transport belt 3. It is arranged in. The belt cleaning device 19 removes foreign matters such as residual toner adhered on the transfer and conveyance belt 3.
A tension roller 20 is disposed in the vicinity of the drive roller 17 so as to push the outer peripheral surface of the transfer / transport belt 3, and the function of the tension roller 20 is used to reduce the winding angle of the transfer / transport belt 3 around the drive roller 17. We have secured a large amount. In the vicinity of the tension roller 20, an urging force in a direction of pressing outward by the urging force of the spring 22 is applied to the transfer conveyance belt 3 while being in contact with the inner peripheral surface of the transfer conveyance belt 3. A tension roller 21 for applying tension to the roller 3 is provided.

Next, an image forming operation by the laser printer 1 will be described.
First, the paper P is fed from one of the paper feed cassettes 7 and 8 or the manual feed tray 13, and the fed paper P is guided by a guide plate (not shown). The transported sheet P is transported by each transport roller along a transport path indicated by a dashed line, and is temporarily stopped at the registration roller pair 9.
On the other hand, at the time of forming a color image, each photosensitive drum 4 is rotated clockwise in each of the four toner image forming sections 2, and each photosensitive drum 4 is uniformly charged on its outer peripheral surface by a charging member (not shown). You. Each charged surface is irradiated with laser light of an image to be formed by the optical writing unit 6 to form an electrostatic latent image. Thereafter, each electrostatic latent image is visualized by each developing unit 5, and a toner image corresponding to each color is formed on the outer peripheral surface of each photosensitive drum 4.

  As described above, the paper P temporarily stopped at the registration roller pair 9 is fed at a predetermined timing by the rotation of the registration roller pair 9, and is transferred to each transfer position while being electrostatically attracted onto the transfer conveyance belt 3. Conveyed sequentially. Each color toner image formed on each photoconductor drum 4 in each toner image forming unit 2 is sequentially formed at a different image forming timing so as to be superimposed on the sheet P at each transfer position. When P passes through each transfer position, it is transferred onto the sheet P under the action of the above-described transfer electric field and nip pressure. A full color toner image is formed on the sheet P by the superimposed transfer. After the transfer of the toner image, the surface of each photoconductor drum 4 is cleaned by a photoconductor cleaning device 23 provided around the photoconductor drum 4, and is further subjected to static elimination by a static eliminator (not shown) to prepare for the next image formation.

  After the full-color toner image is formed on the sheet P on which the full-color toner image is fixed, the fixing unit 11 fixes the full-color toner image on the sheet P, and then moves in either the first discharge direction B or the second discharge direction C according to the state of the switching guide 24. . When the paper is discharged onto the paper discharge tray 12 from the first discharge direction B, the paper is discharged and stacked in a so-called face-down state with the image surface facing downward. On the other hand, when the paper is discharged in the second discharge direction C, the paper is conveyed to a post-processing device such as another sorter or a binding device (not shown), or is re-formed for double-sided image formation via a switchback unit. The sheet is conveyed toward the registration roller pair 9. Through the above series of operations, the laser printer 1 forms a full-color image on the paper P.

  In a tandem-type image forming apparatus such as the laser printer 1 described above, it is important to superimpose toner images of each color with high positional accuracy in order to prevent occurrence of color misregistration. However, the drive roller 17, the entrance roller 15, the tension roller 20, the transfer conveyance belt 3 and the like constituting the belt drive device 10 have a production error of several tens of μm at the time of producing parts. Due to this error, a fluctuation component generated when each component makes one rotation is transmitted to the transfer conveyance belt 3, and the conveyance speed of the paper P fluctuates.

Due to fluctuations in the transport speed of the paper P (traveling speed of the transfer transport belt 3), when transferring the toner image on each photoconductor drum 4 to the paper P, a slight shift occurs in each timing, and a sub-shift in the paper transport direction occurs. Color shift occurs in the scanning direction. In particular, in an apparatus that forms an image with minute dots of about 1200 × 1200 DPI, a timing shift of several μm is conspicuous as a color shift.
Therefore, the belt driving device 10 detects the rotation speed of the driving roller 17 based on a detection signal (output pulse signal) of an encoder provided on the shaft of the driving roller 17, and performs feedback control of the rotation of the driving roller 17 to thereby transfer and transfer the image. The belt 3 is running at a constant speed.

FIG. 2 shows a driving mechanism of the driving roller 17 in a conventional configuration. The drive roller 17 is connected to a drive motor 24 via a timing belt (not shown), and is driven to rotate in proportion to the rotation speed of the drive motor 24. Then, the transfer conveyance belt 3 is driven to travel as the drive roller 17 rotates.
As shown in FIG. 2, an encoder shaft 25 is provided on an extension of the center axis of the drive roller 17, and an encoder disk 26 shown in FIG. An encoder disk 26 having a plurality of marks or slits formed on a peripheral surface is mounted inside an encoder cover 27, and the encoder disk 26 reads the plurality of marks or slits by encoder sensors 28a and 28b.

  When the encoder cover 27 is removed, the encoder sensors 28a and 28b, the encoder disk 26, and the encoder shaft 25 are attached as shown in FIG. In this conventional configuration, the two encoder sensors 28a and 28b are arranged at positions 180 degrees opposite to each other, and the primary components of one rotation are canceled by reading the encoder disk 26 by the encoder sensors 28a and 28b. . Each of the encoder sensors 28a and 28b has a light emitting unit and a light receiving unit. The light emitting unit and the light receiving unit sandwich the encoder disk 26 and read a plurality of marks or slits.

  In the above-described configuration, when the encoder disk 26 is press-fitted into the encoder shaft 25, an error of about several μm occurs in the mounting process between the encoder shaft 25 and the encoder disk 26, and it is practically impossible to eliminate the error. is there. For this reason, when the encoder disk 26 rotates in an eccentric state with respect to the encoder shaft 25, a shift occurs in each cycle of the encoder disk 26. In order to eliminate this, the encoder sensors 28a and 28b are arranged at positions facing each other by 180 degrees, and the phases of the sine waves detected by the encoder sensors 28a and 28b are shifted by 180 degrees. Therefore, by combining these two detection results, the above-described shift can be canceled.

FIG. 4 is a block diagram of a control unit including a drive control device of the belt drive device 10 in the laser printer 1. The control unit 29 shown in FIG. 4 digitally controls a drive pulse of the drive motor 24 based on output pulse signals of the encoder sensors 28a and 28b.
The control unit 29 includes a CPU 30, a RAM 31, a ROM 32, an I / O control unit 33, a drive motor IF 34, a driver 35, a detection I / O unit 36, a bus 37, and the like. The CPU 30 is a central processing unit that performs overall control of the laser printer 1 such as receiving image data from an external device 38 such as a personal computer and controlling transmission and reception of control commands to and from the external device 38 based on a program in the ROM 32. It is.

The CPU 30 operates according to a program in the ROM 32, and functions as a sampling unit and a feedback control unit by using the encoder sensors 28a and 28b.
A RAM 31, a ROM 32, an I / O control unit 33, a drive motor IF 34, and a detection I / O unit 36 are mutually connected to the CPU 30 via a bus 37.
The RAM 31 is a readable / writable memory used as a work memory used when the CPU 30 performs control and an image memory used when developing image data.
The ROM 32 is a read-only memory that stores fixed data of a program executed by the CPU 30.

The I / O control unit 33 controls input and output of signals to and from each load 39 such as a motor, a clutch, a solenoid, and a sensor according to an instruction from the CPU 30.
The drive motor IF 34 controls the rotation drive of the drive motor 24 by outputting a drive pulse signal to the drive motor 24 via the driver 35 according to a drive command from the CPU 30. Since this rotation drive control is performed according to the frequency of the drive pulse signal, it is possible to variably control the traveling drive speed of the transfer conveyance belt 3.

  Output pulse signals from the encoder sensors 28a and 28b are output to the detection I / O unit 36. The detection I / O unit 36 functioning as a synthesizing unit processes output pulses from the encoder sensors 28a and 28b and converts them into digital values. The detection I / O unit 36 includes a plurality of counters including a counting unit for counting the number of output pulses of the encoder sensors 28a and 28b. Then, the value of the counter is multiplied by a predetermined conversion constant of the number of pulses versus angular displacement to convert the value into a digital value corresponding to the angular displacement of the shaft of the drive roller 17. A signal of a digital value corresponding to the angular displacement of the encoder disk 26 is sent to the CPU 30 via the bus 37.

Upon receiving a drive command from the CPU 30 via the bus 37, the drive motor IF 34 functioning as a multiplying unit generates a pulse-like control signal having a drive frequency designated on the basis of the drive command and outputs the control signal to the driver 35. I do.
The driver 35 includes a power semiconductor element (for example, a transistor) and the like. The driver 35 operates based on a pulse-like control signal input from the drive motor IF 34 and outputs a drive pulse signal to the drive motor 32, that is, applies a pulse-like drive voltage. As a result, the drive of the drive motor 24 is controlled at a speed proportional to the drive frequency specified by the drive command of the CPU 30.
Thus, the additional value is controlled so that the angular displacement of the encoder disk 26 becomes the target angular displacement, and the drive roller 17 rotates at a constant angular speed at a constant angular speed. The angular displacement of the encoder disk 26 is detected by the encoder sensors 28a and 28b and the detection I / O unit 36, taken into the CPU 30, and the control is repeated.

The RAM 31 has an encoder measured by driving the drive motor 24 at a constant speed without executing an image forming process in addition to a function used as a work memory and an image memory when the CPU 30 performs control. It also has a function as a data memory for storing detected angular displacement error data for one rotation of the disk corresponding to the eccentricity of the disk 26, that is, data sampled at regular intervals.
Since the RAM 31 is a volatile memory, the above-described detected angular displacement error data is stored in a nonvolatile memory such as an EEPROM (not shown), and the detected angular displacement error data is stored when the power is turned on or when the drive motor 24 is started. It is also possible to develop on the RAM 31.

In the above-described conventional configuration, there is a problem that the one-turn primary component of the encoder disk 26 can be canceled, but the one-turn secondary component or more and even-number components cannot be canceled. For this reason, appropriate feedback control of the drive roller 17 cannot be performed, and as a result, color shift has occurred during image formation.
The present invention is to solve such a problem. Hereinafter, one embodiment of the present invention will be described.

FIG. 5 shows a drive control device for a drive motor according to an embodiment of the present invention. In the figure, an encoder disk 26 is attached to an encoder shaft 25 in the same manner as described above, and three encoder sensors 40a, 40b, and 40c are arranged around the encoder disk 25 with a shift of 120 degrees from each other.
FIG. 6 is a block diagram of a control unit including a drive control device of the belt drive device 10 used in one embodiment of the present invention. The control unit 41 as the drive control device illustrated in FIG. 6 is different from the control unit 29 illustrated in FIG. 4 in that the drive unit is driven based on output pulse signals of the encoder sensors 40a, 40b, and 40c instead of the encoder sensors 28a and 28b. The only difference is that the drive pulse of the motor 24 is digitally controlled, and the other configuration is the same.

7 to 11 are diagrams illustrating composite waveforms when signals are obtained by the encoder sensors 40a, 40b, and 40c according to the embodiment of the present invention.
FIG. 7 shows an output waveform in the case of one rotation primary component, FIG. 8 shows an output waveform in the case of one rotation secondary component, FIG. 9 shows an output waveform in the case of one rotation tertiary component, and FIG. 11 shows an output waveform in the case of a component, and FIG. 11 shows an output waveform in the case of a sixteenth-order component in one rotation.

  As shown in FIG. 7, FIG. 8, and FIG. 10, the total waveform of each encoder sensor 40a, 40b, and 40c as shown by a bold solid line in the center in one rotation primary component, one rotation secondary component, and one rotation sixteenth component. Becomes 0, and the total waveform becomes 3 only for the one-turn cubic component shown in FIG. This is because the output waveforms of the encoder sensors 40a, 40b, and 40c completely coincide with each other only in the third-order multiple component, and some waveforms overlap. This is because when the phases of the output waveforms are shifted by 120 degrees, the waveforms cancel each other out.

  As described above, according to the present invention, the encoder includes three encoder sensors 40a, 40b, and 40c for detecting a plurality of marks or slits provided on the encoder disk 26, and the encoder sensors 40a, 40b, and 40c are mutually connected. Since they are arranged at positions shifted by 120 degrees, the output signals from the encoder sensors 40a, 40b, and 40c are respectively combined, and the combined signal is multiplied by ３ to obtain a signal other than the third-order multiple component. Output can be offset. Thereby, since the eccentric component of the encoder disk can be removed as compared with the conventional configuration, it is possible to improve accuracy in feedback control of the drive motor of the endless moving member caused by the eccentricity of the encoder disk, and The occurrence of color misregistration during formation can be prevented.

FIG. 12 shows an output waveform in the case of a one-rotation primary component for explaining a modification of the embodiment of the present invention, and FIG. 13 shows an output waveform in the case of the same rotation secondary component.
In this modification, when any one of the three encoder sensors 40a, 40b, and 40c fails and becomes unusable, feedback control is performed by the remaining two encoder sensors. In this case, feedback control is performed by combining the output signals of the two encoder sensors in the detection I / O unit 36 and multiplying the combined signal sent from the detection I / O unit 36 by the drive motor IF 34. Is carried out.

Even when the feedback control is performed by the two encoder sensors as described above, the two sensors are arranged at a distance of 120 degrees, so that one rotation is primary, one rotation secondary, one rotation quaternary, and one rotation tenth. The total is 1 except for the third-order multiple component of one rotation, such as the sixth order, and the total is 2 for the multiple component of the one-turn third-order component. Can be. As a result, even when the control is performed by two encoder sensors, it is possible to obtain an operational effect that is not provided by the conventional configuration.
When two out of three encoder sensors become unusable due to a failure, feedback control is performed by the remaining one encoder sensor, for example, as in the conventional technology described in Japanese Patent No. 4719043. . If all three encoder sensors become unusable due to a failure, the execution of the feedback control is stopped.

  In the above-described embodiments and modified examples, examples in which a laser printer is used as an image forming apparatus have been described. However, the present invention is not limited to this, and can be applied to a plotter, a facsimile, a multifunction peripheral, and the like. Further, in the present embodiment and the modified example, the configuration in which the paper P is used as the recording medium on which an image is formed has been described. However, the recording medium is not limited to the paper P, and is thick paper, postcard, envelope, plain paper, thin paper. , Coated paper (coated paper, art paper, etc.), tracing paper, OHP sheet, OHP film, resin film, etc., as long as it is a sheet-like substance capable of forming an image. Good.

  As described above, the preferred embodiments of the present invention have been described. However, the present invention is not limited to such specific embodiments, and unless otherwise specified in the above description, the present invention described in the claims is not limited thereto. Various modifications and changes are possible within the scope of the gist. The effects described in the embodiments of the present invention merely exemplify the most preferable effects resulting from the present invention, and the effects according to the present invention are limited to those described in the embodiments of the present invention. is not.

  For example, in the above-described embodiment, the transfer / conveying belt 3 is shown as an endless moving member. However, the endless moving member is not limited to this. For example, each of the photosensitive belt and the transfer / conveying belt 3 used in place of the photosensitive drum 4 may be used. The present invention may be applied to an intermediate transfer belt on which the toner image from the photosensitive drum 4 is intermediately transferred, a recording medium transport belt for transporting the paper P, or the like as an endless moving member.

1 Image forming apparatus (laser printer)
3 Endless moving member (transfer and conveyor belt)
17 drive roller 26 encoder disk 30 sampling means, feedback control means (CPU)
34 Multiplication means (drive motor IF)
36 combining means, counting means (detection I / O part)
40a, 40b, 40c Encoder sensor 41 Drive control device (control unit)

Japanese Patent No. 4719043

Claims (6)

An encoder that detects the rotation of a driven roller that travels and drives the endless moving member or a driven roller that is driven and rotated by the movement of the endless moving member, controls driving of the driving roller based on an output signal of the encoder,
The encoder has a disk in which a plurality of marks or slits are arranged at predetermined intervals in a circumferential direction, and three sensors arranged at positions shifted by 120 degrees for detecting the marks or slits, respectively. And
Combining means for combining output signals of the sensors;
Multiplying means for multiplying the combined signal sent from the combining means by 1/3;
Counting means for counting the 1/3 multiplied synthesized signal sent from the multiplying means;
Sampling means for sampling the count value of the counting means at a predetermined timing;
A drive control device comprising: feedback control means for controlling the drive of the drive roller by performing feedback control on a control target value based on the count value sampled by the sampling means. The drive control device according to claim 1,
The drive control device, wherein the feedback control means performs the feedback control based on output signals from two normal sensors when one of the sensors fails. The drive control device according to claim 1 or 2,
The drive control device, wherein the feedback control means performs the feedback control based on an output signal from one normal sensor when two of the sensors fail. The drive control device according to any one of claims 1 to 3,
The drive control device, wherein the feedback control means stops the feedback control when all the sensors fail. A drive control device according to any one of claims 1 to 4,
An endless moving member driven and controlled by the drive control device. The image forming apparatus according to claim 5,
The image forming apparatus according to claim 1, wherein the endless moving member includes at least one of a photoreceptor belt, a transfer belt, an intermediate transfer belt, and a recording medium transport belt.

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