JP5244372B2 - Image forming apparatus - Google Patents

Description

 The present invention relates to an image forming apparatus.

In recent years, as one of image forming methods in an image forming apparatus using electrophotography represented by a copying machine or a printer, four colors of black (BK), yellow (Y), magenta (M), and cyan (C) are used. The color tandem system that realizes high-speed full-color printing by arranging the photosensitive drums in a row and sequentially transferring the toner images of each color formed (developed) on each photosensitive drum to paper or an intermediate transfer member is known. It has been. For example, in Patent Documents 1 and 2 listed below, in an image forming apparatus employing such a color tandem method, in order to prevent color misregistration caused by dimensional errors or mounting errors of mechanical parts such as a photosensitive drum. A technique related to the correction processing is disclosed.
JP-A-10-278338 JP 2007-30207 A

  By the way, in the image forming apparatus adopting the color tandem method, the cause of the color misregistration is not limited to the dimensional error and the mounting error of the machine parts. For example, in recent image forming apparatuses, in order to increase the speed, a configuration in which a plurality of arithmetic circuits that execute predetermined arithmetic processing based on output signals of various sensors and output various control signals is installed is adopted. Yes. These arithmetic circuits are arranged on individual boards in order to reduce the board scale, and furthermore, an oscillation circuit as a clock signal source for operating each arithmetic circuit is individually provided on each board. It is common to have. The reason for adopting a configuration in which an oscillation circuit is individually provided for each substrate (for each arithmetic circuit) in this way is that if a configuration in which a clock signal generated by an oscillation circuit on a certain substrate is supplied to another substrate is employed, This is because a high frequency causes a problem in clock transmission quality and unnecessary electromagnetic radiation increases.

  However, even when a configuration in which an oscillation circuit is provided for each substrate is employed, each oscillation circuit has a tolerance with respect to an ideal oscillation frequency, so that the oscillation frequencies of all the oscillation circuits are kept exactly the same. There is no. There is a possibility that the tolerance deviation of the oscillation frequency existing between the oscillation circuits causes the color deviation described above. Here, in order to specifically explain the color shift caused by the tolerance shift of the oscillation frequency, for example, a laser scanning unit (hereinafter referred to as a laser scanning unit) that performs exposure by irradiating the photosensitive drum with a laser by a polygon mirror. The toner image of each color formed (developed) on the photosensitive drum of each color is sequentially transferred (primary transfer) to the transfer belt, which is an intermediate transfer body, and then formed on the transfer belt. Assume an image forming apparatus that employs a color tandem method in which an image is collectively transferred (secondary transfer) onto a sheet by a secondary transfer roller.

  In such an image forming apparatus, an arithmetic circuit that generates a control clock signal of a polygon motor (motor that drives a polygon mirror) that determines the laser scanning speed of the LSU and a control clock signal of a rotating bell motor that drives the transfer belt are generated. If the oscillation circuit that supplies the clock signal is provided separately from the arithmetic circuit that performs the operation, there is a tolerance deviation in the oscillation frequency between the oscillation circuits. A speed difference is generated with respect to the moving speed of the belt, and as a result, color misregistration occurs in the sub-scanning direction of the image primarily transferred onto the transfer belt.

    The present invention has been made in view of the above-described circumstances, and includes image forming that individually includes an oscillation circuit that supplies a clock signal to an arithmetic circuit that generates a control clock signal for controlling a driving unit for each arithmetic circuit. An object of the present invention is to prevent color misregistration that occurs due to tolerance deviation of oscillation frequencies existing between oscillation circuits.

  In order to achieve the above object, the present invention provides, as a first solving means related to an image forming apparatus, an oscillation circuit that supplies a clock signal to an arithmetic circuit that generates a control clock signal for controlling a drive unit, An image forming apparatus that is provided separately for each arithmetic circuit and that includes a sensor that outputs a pulse signal having a period corresponding to the driving speed of the driving unit, wherein one of the sensors is a reference sensor, and the reference sensor An arithmetic circuit that is provided individually for each arithmetic circuit that controls other driving units excluding the driving unit whose driving speed is detected, and that controls the other driving units using the pulse signal output from the reference sensor as a clock to be measured. Each of the arithmetic circuits that control the other driving units includes a frequency counter circuit that uses the clock signal of the oscillation circuit corresponding to each of the circuits as a measurement clock. Based on the count value of the frequency counter circuit, it determines the frequency shift amount of the clock signal supplied from the oscillation circuit corresponding to itself with respect to the pulse signal, and corrects the frequency shift amount to generate the control clock signal. It is characterized by.

Further, as a second solving means relating to the image forming apparatus, in the first solving means, as the driving unit, a transfer bell motor for driving a transfer belt as an intermediate transfer member, and a photosensitive drum surface as an exposure process. And a polygon motor for performing laser scanning, an encoder that outputs a pulse signal having a period corresponding to a rotation speed of a rotation shaft of the rotation bell motor as the reference sensor, and the operation circuit as the rotation bell motor And a second operation for generating a second control clock signal for controlling the polygon motor as an operation circuit for controlling the other drive unit. A pulse output from the encoder provided as the frequency counter circuit corresponding to the second arithmetic circuit. And a counter circuit that uses a clock signal of an oscillation circuit corresponding to the second arithmetic circuit as a measurement clock, and the second arithmetic circuit is based on the count value of the counter circuit corresponding to itself. Determining a frequency deviation amount of the clock signal supplied from the oscillation circuit corresponding to the pulse signal with respect to the pulse signal, correcting the frequency deviation amount, and generating the second control clock signal.

    Further, as a third solving means relating to the image forming apparatus, in the first solving means, as the driving unit, a transfer bell motor for driving a transfer belt which is an intermediate transfer member, and a photosensitive drum surface as an exposure process. And a polygon motor for performing laser scanning, and the reference sensor includes a beam detection sensor that outputs a pulse signal having a period corresponding to the rotation speed of the polygon motor, and controls the other drive unit. As a circuit, a first arithmetic circuit for generating a first control clock signal for controlling the rotating bell motor, and a second arithmetic circuit for generating a second control clock signal for controlling the polygon motor as the arithmetic circuit. The frequency counter circuit is provided corresponding to the first arithmetic circuit and is output from the beam detection sensor. A counter circuit using a measurement signal as a clock to be measured and a clock signal of an oscillation circuit corresponding to the first arithmetic circuit as a measurement clock, wherein the first arithmetic circuit is based on a count value of the counter circuit corresponding to itself. And determining a frequency shift amount of the clock signal supplied from the oscillation circuit corresponding to the pulse signal with respect to the pulse signal, and correcting the frequency shift amount to generate the first control clock signal. .

 According to the present invention, even when there is a deviation in the oscillation frequency between the oscillation circuits, the control clock signal generated by each arithmetic circuit is synchronized with the pulse signal output from the reference sensor. Will be maintained. That is, by supplying a control clock signal maintained in synchronization with a pulse signal output from such a reference sensor to a polygon motor and a rotary bell motor as drive units, a laser scanning speed (exposure processing speed) and It is possible to prevent a speed difference from occurring with respect to the moving speed of the transfer belt, and as a result, to prevent color misregistration from occurring in the sub-scanning direction of the image primarily transferred onto the transfer belt. Can do.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As an image forming apparatus according to this embodiment, a laser color printer adopting a color tandem method will be described as an example. FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 according to the present embodiment. As shown in FIG. 1, an image forming apparatus 100 according to the present embodiment includes image forming units 10Y, 10M, 10C, and 10B, a transfer belt 20, conveying rollers 21 and 22, primary transfer rollers 23Y and 23M, 23C, 23B, a secondary transfer roller 24, a paper cassette 25, a paper feed roller 26, a fixing device 27, and a paper discharge roller 28.

  The image forming units 10Y, 10M, 10C, and 10B are provided corresponding to four colors of yellow (Y), magenta (M), cyan (C), and black (BK), and Y in the figure. They are arranged in a line along the axial direction (sub-scanning direction), and toner images of four colors of yellow, magenta, cyan, and black are sequentially transferred to the transfer belt 20 by respective processes of charging, exposure, development, and transfer. (Primary transfer). In the following, detailed configurations of the image forming units 10Y, 10M, 10C, and 10B will be described. However, each unit is different in color of developer (toner) to be used, and the main configuration is the same. This will be described using the image forming unit 10Y.

  The image forming unit 10Y includes a photosensitive drum 11Y, a charger 12Y, an exposure device 13Y, and a developing device 14Y. The photosensitive drum 11Y is a cylindrical electrostatic latent image carrier having a rotation axis in the X-axis direction (main scanning direction) in the figure, and faces the primary transfer roller 23Y with the transfer belt 20 sandwiched therebetween. As shown in FIG. The charger 12Y extends along the rotation axis direction (that is, the X-axis direction) of the photoconductor drum 11Y, and discharges negatively charged electric charges toward the surface of the photoconductor drum 11Y. The surface of the drum 11Y is uniformly charged (charging process).

  The exposure unit 13Y is composed of a laser scanning unit (LSU) including a laser light source (not shown), a polygon motor, and the like, and a photosensitive member by rotating the polygon motor with laser light emitted from the laser light source. By scanning along the main scanning direction of the drum 11Y, negative charges at predetermined positions on the surface of the photosensitive drum 11Y are erased, and an electrostatic latent image corresponding to a yellow image is formed (exposure processing). That is, the laser scanning speed (exposure processing speed) is determined by the rotational speed of the polygon motor, and this polygon motor is controlled by a second control clock signal supplied from a second arithmetic circuit 37 described later. is there.

 The developing device 14Y extends along the rotational axis direction of the photosensitive drum 11Y, receives toner supplied from a yellow toner cartridge (not shown), and discharges the toner toward the surface of the photosensitive drum 11Y. Thus, a toner image corresponding to the electrostatic latent image formed by the exposure process is formed on the surface of the photosensitive drum 11Y (development process). The toner image thus formed on the surface of the photosensitive drum 11Y is transferred onto the transfer belt 20 that moves in the Y-axis direction between the photosensitive drum 11Y and the primary transfer roller 23Y (primary transfer processing). ). Specifically, a predetermined transfer voltage is applied to the primary transfer roller 23Y, and the transfer belt 20 is positively charged, whereby the toner image formed on the surface of the photosensitive drum 11Y is transferred onto the transfer belt 20. .

  The image forming units 10M, 10C, and 10B have the same configuration as the image forming unit 10Y described above. In other words, the image forming unit 10M includes a photosensitive drum 11M, a charger 12M, an exposure device 13M, and a developing device 14M. A toner image corresponding to a magenta image formed on the surface of the photosensitive drum 11M is photosensitive. The image is transferred onto the transfer belt 20 that moves in the Y-axis direction between the body drum 11M and the primary transfer roller 23M. The image forming unit 10C includes a photosensitive drum 11C, a charger 12C, an exposure device 13C, and a developing device 14C. A toner image corresponding to a cyan image formed on the surface of the photosensitive drum 11C is photosensitive. The toner image is transferred onto the transfer belt 20 that moves in the Y-axis direction between the body drum 11C and the primary transfer roller 23C. The image forming unit 10B includes a photosensitive drum 11B, a charger 12B, an exposure device 13B, and a developing device 14B. A toner image corresponding to a black image formed on the surface of the photosensitive drum 11B is a photosensitive member. The toner image is transferred onto the transfer belt 20 that moves in the Y-axis direction between the body drum 11B and the primary transfer roller 23B.

  As described above, the image forming units 10Y, 10M, 10C, and 10B sequentially transfer the toner images corresponding to the yellow, magenta, cyan, and black images onto the transfer belt 20 that is an intermediate transfer member, and thereby form one toner. It is superimposed on the image. The transfer belt 20 reciprocates in the Y-axis direction (sub-scanning direction) by the rotation of the conveying rollers 21 and 22, and the moving speed and the image forming speed (development) by the image forming units 10Y, 10M, 10C, and 10B. The speed until the processing is completed is synchronously controlled so that no color misregistration occurs when the toner images are sequentially transferred and superimposed on the transfer belt 20. The moving speed of the transfer belt 20 is determined by a rotation bell motor (not shown) for rotationally driving the conveying rollers 21 and 22, and the rotation bell motor is supplied with a first control clock supplied from a first arithmetic circuit 32 described later. It is controlled by a signal.

  The secondary transfer roller 24 is installed so as to face the transport roller 21 with the transfer belt 20 sandwiched therebetween, and the paper P is fed from the paper cassette 25 to the secondary transfer roller 24 and the transfer belt 20 by the paper feed roller 26. , The toner image formed on the transfer belt 20 is collectively transferred onto the paper P (secondary transfer process). The paper P on which the toner image is formed by such secondary transfer processing is conveyed to the fixing device 27.

  The fixing device 27 is composed of a heating roller 27a and a pressure roller 27b arranged to face each other, and heats and presses the paper P conveyed between the heating roller 27a and the pressure roller 27b. The toner image is fixed on the paper P (fixing process). As a result, a desired full-color image is formed on the paper P. The paper P on which the full-color image is formed is discharged outside the apparatus main body by the paper discharge roller 28.

  On the other hand, FIG. 2 is a block diagram of a main part of the image forming apparatus 100 described above. In FIG. 2, for convenience of explanation, a motor including a first arithmetic circuit 31 that supplies a first control clock signal to the above-described bell motor and a second arithmetic circuit 36 that supplies a second control clock signal to a polygon motor. Only the control circuit is shown. As shown in FIG. 2, the motor control circuit of the image forming apparatus 100 includes a first oscillation circuit 30, an encoder 31, a first arithmetic circuit 32, a rotation bell motor 33, a second oscillation circuit 34, a counter circuit 35, and the like. , A sensor 36, a second arithmetic circuit 37, and a polygon motor 38.

  The first oscillation circuit 30 generates a first clock signal having the clock frequency fa and outputs the first clock signal to the first arithmetic circuit 32. The encoder 31 is installed in the vicinity of the rotary shaft of the rotary bell motor 33, and a first arithmetic circuit 32 generates a pulse signal (hereinafter referred to as an encoder pulse signal) having a period corresponding to the rotational speed of the rotary shaft of the rotary bell motor 33. And output to the counter circuit 35.

  The first arithmetic circuit 32 generates a first control clock signal for driving the rotary bell motor 33 based on the first clock signal and the encoder pulse signal, and supplies the first control clock signal to the rotary bell motor 33. Specifically, the first arithmetic circuit 32 divides the first clock signal to generate the first control clock signal, and based on the encoder pulse signal, the rotation speed of the rotating bell motor 33, that is, the transfer belt 20 , And the feedback control of the frequency dividing process is performed so that the detected movement speed matches the target speed.

  The second oscillation circuit 34 generates a second clock signal having the clock frequency fb and outputs it to the counter circuit 35 and the second arithmetic circuit 37. The counter circuit 35 is a frequency counter using the encoder pulse signal as a clock to be measured and the second clock signal as a measurement clock, and a count value representing the result of measuring the period of the encoder pulse signal using the second clock signal as a second arithmetic circuit. To 37. The sensor 36 is a sensor for detecting information necessary for generating the second control clock signal such as the driving start timing and driving stop timing of the polygon motor, and outputs an output signal representing this information to the second arithmetic circuit 37. To do.

  The second arithmetic circuit 37 is a second clock for driving the polygon motor 38 based on the second clock signal supplied from the second oscillation circuit 34, the count value output from the counter circuit 35, and the output signal of the sensor 36. A control clock signal is generated, and the second control clock signal is supplied to the polygon motor 38. Specifically, the second arithmetic circuit 37 generates a second control clock signal by dividing the second clock signal by a predetermined dividing ratio, and corrects the dividing ratio according to the count value. It has a function to do.

  As described above, in the image forming apparatus 100 according to the present embodiment, in order to increase the speed, predetermined drive processing is executed based on the output signals of various sensors, and the drive units (the rotation bell motor 33 and the polygon motor 38) are installed. A configuration is employed in which a plurality of arithmetic circuits (first arithmetic circuit 32 and second arithmetic circuit 37) that generate control clock signals (first control clock signal and second control clock signal) for control are installed. Further, the first arithmetic circuit 32 and the second arithmetic circuit 37 are individually provided with oscillation circuits (first oscillation circuit 30 and second oscillation circuit 34) that are clock signal sources for operating the respective arithmetic circuits. The first oscillation circuit 30 and the second oscillation circuit 34 have tolerances with respect to ideal clock frequencies (fa, fb), respectively, and the first oscillation circuit 30 and the second oscillation circuit 34 It is assumed that there is a clock frequency tolerance gap between them.

Next, the operation of the motor control circuit of the image forming apparatus 100 according to the present embodiment configured as described above will be described.
First, the first arithmetic circuit 32 generates a first control clock signal by dividing the first clock signal supplied from the first oscillation circuit 30 and supplies the first control clock signal to the rotary bell motor 33 and is output from the encoder 31. Based on the encoder pulse signal, the rotational speed of the rotating bell motor 33, that is, the moving speed of the transfer belt 20, is detected, and feedback control of the frequency dividing process is performed so that the detected moving speed matches the target speed.

  On the other hand, if the count value output from the counter circuit 35 is N1, the count value N1 represents the result of measuring the period of the encoder pulse signal (frequency fc) with the second clock signal (frequency fb). = Fb / fc. Here, the frequency fc of the encoder pulse signal is sufficiently low (for example, assumed to be about 1/1000) as compared with the clock frequency fb of the second clock signal and the clock frequency fa of the first clock signal. Assuming that the clock frequency fb of the signal is an ideal value with no tolerance, the value of the count value N1 should always be “1000”.

 However, when there is a tolerance in the clock frequency fb of the second clock signal, for example, the value of the count value N1 increases or decreases in accordance with the tolerance, such as “1001” or “999”. That is, the increase / decrease from the value “1000” in this ideal case is the frequency shift amount of the second clock signal with respect to the encoder pulse signal. For example, when the count value N1 becomes “1001”, it can be determined that the frequency shift amount of the second clock signal with respect to the encoder pulse signal is “+1/1000” (shifted by 1/1000 to the high frequency side). . Further, for example, when the count value N1 is “999”, it is determined that the frequency shift amount of the second clock signal with respect to the encoder pulse signal is “−1/1000” (shifted by 1/1000 to the low frequency side). be able to.

  As described above, the second arithmetic circuit 37 generates the second control clock signal by dividing the second clock signal by a predetermined division ratio, and corrects the division ratio according to the count value N1. It has a function to do. That is, for example, when the count value N1 is “1001”, the second arithmetic circuit 37 determines that the frequency shift amount of the second clock signal with respect to the encoder pulse signal is “+1/1000”, and this frequency The frequency division ratio is corrected so that the shift amount is canceled (for example, if the initial frequency division ratio is “500”, it is corrected to “499”).

  By the operation as described above, the first control clock generated by the first arithmetic circuit 32 even when there is a tolerance shift in the clock frequencies fa and fb of the first oscillation circuit 30 and the second oscillation circuit 34. Since the signal and the second control clock signal generated by the second arithmetic circuit 37 are maintained in synchronization with the encoder pulse signal, the laser scanning speed (exposure processing speed) and the moving speed of the transfer belt 20 Can be prevented from occurring, and as a result, it is possible to prevent color misregistration from occurring in the sub-scanning direction of the image primarily transferred onto the transfer belt 20.

  Note that it is desirable not to count the encoder pulse signal as it is by the counter circuit 35, but to count every rotation of the rotation shaft (positive multiple rotation). By counting the encoder pulse signal in this way, it is possible to absorb a count error caused by variations in mechanical tolerances of the rotary bell motor 33, the encoder 31, and other mechanical parts.

Further, the present invention is not limited to the above embodiment, and the following modifications can be considered.
FIG. 3 is a block diagram showing a modification of the motor control circuit in the image forming apparatus 100 according to the present embodiment. In FIG. 3, the same components as those in FIG. As shown in FIG. 3, the motor control circuit of the modification differs from the motor control circuit shown in FIG. 2 in that a pulse signal (hereinafter referred to as a BD pulse) having a period corresponding to the rotational speed (laser scanning speed) of the polygon motor 38 is used. BD (Beam Detector) sensor 40 is provided, and counter circuit 35 ′ outputs a BD pulse signal output from BD sensor 40 as a clock to be measured and from first oscillation circuit 30. The first clock signal is used as a measurement clock, and a count value representing the result of measuring the period of the BD pulse signal using the first clock signal is output to the first arithmetic circuit 32. In addition, the second arithmetic circuit 37 ′ in the modification has a function of generating the second control clock signal by dividing the second clock signal output from the second oscillation circuit 34 by a predetermined division ratio. It does not have a function of correcting the frequency division ratio. On the other hand, the first arithmetic circuit 32 ′ in the modified example generates the first control clock signal by dividing the first clock signal by a predetermined division ratio, and the division ratio is set according to the count value N2. It has a function to correct.

  The operation of this modified example configured as described above will be described below. The second arithmetic circuit 37 ′ generates a second control clock signal by dividing the second clock signal supplied from the second oscillation circuit 34 and supplies the second control clock signal to the polygon motor 38. As a result, the polygon motor 38 is driven to rotate, and laser scanning (exposure processing) is performed on the photosensitive drum. At this time, a BD pulse signal having a period corresponding to the rotation speed (laser scanning speed) of the polygon motor 38 is output from the BD sensor 40 to the counter circuit 35 '.

  On the other hand, if the count value output from the counter circuit 35 ′ is N2, the count value N2 represents the result of measuring the period of the BD pulse signal (frequency fd) with the first clock signal (frequency fa). N2 = fa / fd. Here, the frequency fd of the BD pulse signal is a sufficiently low value (for example, assumed to be about 1/1000) as compared with the clock frequency fa of the first clock signal and the clock frequency fb of the second clock signal. If the clock frequency fa of the signal is an ideal value with no tolerance, the value of the count value N2 should always be “1000”.

 However, when there is a tolerance in the clock frequency fa of the first clock signal, for example, the value of the count value N2 increases or decreases according to the tolerance, such as “1001” or “999”. That is, the increase / decrease from the value “1000” in this ideal case becomes the frequency shift amount of the first clock signal with respect to the BD pulse signal. For example, when the count value N2 is “1001”, the first arithmetic circuit 32 ′ determines that the frequency shift amount of the first clock signal with respect to the BD pulse signal is “+1/1000”, and this frequency shift. The division ratio is corrected so that the amount is canceled.

By the operation as described above, the first control generated by the first arithmetic circuit 32 ′ even when there is a tolerance shift in the clock frequencies fa and fb of the first oscillation circuit 30 and the second oscillation circuit 34. Since the clock signal and the second control clock signal generated by the second arithmetic circuit 37 ′ are maintained in synchronization with the BD pulse signal, the laser scanning speed (exposure processing speed) and the transfer belt 20 It is possible to prevent a speed difference from occurring with respect to the moving speed, and as a result, it is possible to prevent a color shift from occurring in the sub-scanning direction of the image primarily transferred onto the transfer belt 20. .
In this modification as well, it is desirable that the counter circuit 35 ′ does not count the BD pulse signal as it is, but counts every rotation of the polygon motor 38 (positive multiple rotation).

  2 and 3, two arithmetic circuits, a first arithmetic circuit 32 (32 ′) that controls the rotation bell motor 33 and a second arithmetic circuit 37 (37 ′) that controls the polygon motor 38. However, even if each of the arithmetic circuits is individually provided with the oscillation circuit, the calculation circuit and the pair of oscillation circuits are further provided. The present invention can be applied. For example, one reference sensor (the encoder 31 in the example of FIG. 2 and the BD sensor 40 in the example of FIG. 3) is determined, and a counter circuit is individually provided for each of the other arithmetic circuits excluding the arithmetic circuit corresponding to the reference sensor. The pulse signal output from the reference sensor may be supplied to all the counter circuits.

  2 and 3, the polygon motor 38 and the rotation bell motor 33 are described as driving units. However, as the other driving unit, a control clock signal is supplied from an arithmetic circuit and an oscillation circuit is provided. The present invention can be applied to any drive unit that is affected by a frequency tolerance shift existing between them. Although the laser color printer has been described as an example of the image forming apparatus 100, the present invention is not limited to this. The present invention is not limited to this, and a plurality of devices such as a copying machine (copying machine) and a multifunction machine (printer, copying machine, FAX machine, etc.). It can also be applied to those having a function.

1 is a schematic configuration diagram of an image forming apparatus 100 according to an embodiment of the present invention. 1 is a block configuration diagram of a motor control circuit in an image forming apparatus 100 according to an embodiment of the present invention. 5 is a modification of the motor control circuit in the image forming apparatus 100 according to an embodiment of the present disclosure.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 10Y, 10M, 10C, 10B ... Image forming unit, 20 ... Transfer belt, 21, 22 ... Conveyance roller, 23Y, 23M, 23C, 23B ... Primary transfer roller, 24 ... Secondary transfer roller, 25 ... paper cassette, 26 ... feed roller, 27 ... fixer, 28 ... discharge roller, 30 ... first oscillation circuit, 31 ... encoder, 32 ... first arithmetic circuit, 33 ... bell motor, 34 ... second oscillation Circuit 35 ... Counter circuit 36 ... Sensor 37 ... Second arithmetic circuit 38 ... Polygon motor 40 ... BD sensor

Claims (3)

An oscillation circuit that supplies a clock signal to an arithmetic circuit that generates a control clock signal for controlling the motor by dividing the clock signal is provided for each of the arithmetic circuits, and according to the rotational speed of the motor An image forming apparatus including a sensor that outputs a pulse signal having a period,
One rotation of the motor that is provided individually for each arithmetic circuit that controls other motors excluding the motor whose rotational speed is detected by the reference sensor, and one of the sensors is output from the reference sensor. A frequency counter circuit that uses each pulse signal as a clock to be measured and uses a clock signal of an oscillation circuit corresponding to each of the arithmetic circuits that control the other motors as a measurement clock;
Each of the arithmetic circuits that control the other motors, based on the count value of the frequency counter circuit corresponding to itself, sets a frequency shift amount with respect to the pulse signal of the clock signal supplied from the oscillation circuit corresponding to the motor. Determining, correcting the frequency division ratio of the clock signal so that the frequency deviation amount is canceled, and generating the control clock signal,
An image forming apparatus. The motor includes a transfer bell motor for driving a transfer belt as an intermediate transfer member, and a polygon motor for performing laser scanning on the surface of the photosensitive drum as an exposure process,
As the reference sensor, an encoder that outputs a pulse signal having a period corresponding to the rotation speed of the rotation shaft of the rotary bell motor,
As the arithmetic circuit, a first arithmetic circuit for generating a first control clock signal for controlling the rotating bell motor, and a second control clock for controlling the polygon motor as an arithmetic circuit for controlling the other motor. A second arithmetic circuit for generating a signal,
As the frequency counter circuit, provided corresponding to the second arithmetic circuit, a pulse signal output from the encoder is a clock to be measured, and a clock signal of an oscillation circuit corresponding to the second arithmetic circuit is a measurement clock. With a counter circuit,
The second arithmetic circuit determines a frequency shift amount with respect to the pulse signal of the clock signal supplied from the oscillation circuit corresponding to the second arithmetic circuit based on a count value of the counter circuit corresponding to the second arithmetic circuit, and the frequency shift amount The second control clock signal is generated by correcting the frequency division ratio of the clock signal so that is canceled .
The image forming apparatus according to claim 1. The motor includes a transfer bell motor for driving a transfer belt as an intermediate transfer member, and a polygon motor for performing laser scanning on the surface of the photosensitive drum as an exposure process,
As the reference sensor, a beam detection sensor that outputs a pulse signal having a cycle according to the rotation speed of the polygon motor,
As an arithmetic circuit for controlling the other motor, a first arithmetic circuit for generating a first control clock signal for controlling the rotating bell motor, and a second control clock for controlling the polygon motor as the arithmetic circuit A second arithmetic circuit for generating a signal,
The frequency counter circuit is provided corresponding to the first arithmetic circuit, the pulse signal output from the beam detection sensor is a clock to be measured, and the clock signal of the oscillation circuit corresponding to the first arithmetic circuit is a measurement clock With a counter circuit
The first arithmetic circuit determines a frequency deviation amount of the clock signal supplied from the oscillation circuit corresponding to the first arithmetic circuit with respect to the pulse signal based on a count value of the counter circuit corresponding to the first arithmetic circuit, and the frequency deviation amount The first control clock signal is generated by correcting the frequency division ratio of the clock signal so that is canceled .
The image forming apparatus according to claim 1.

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