JP2001075324A - Image forming device and rotation controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate irregularity in the rotation of rotating members and to obtain a high definition image by computing control signals of rotation driving operations by plural driving means based on the outputs of plural rotation detecting means and controlling the plural driving means based on the obtained control signals. SOLUTION: A driving compensation computing section 305 computes a compensation value of an encoder pulse for every encoder pulse and outputs the values to an S/P converting circuit 311. An S/P converting circuit 313 latches pulse rate compensation data received from the circuit 311 for each color and outputs the data to period counter/phase signal generating circuits 317Y to 317M. The circuits 317 change the count value of a period counter based on the compensation data and generates pulses with the period of the compensated count value. Then, phase signals are generated based on the pulses, the signals are outputted to drivers 319 of step motors 203 for each color and the drivers 319 drive step motors based on the phase signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus and a rotation control device, and more particularly, to control of rotation driving of an image carrier and the like.

[0002]

2. Description of the Related Art Conventionally, there has been known an apparatus which obtains a color image at a high speed by superimposing and transferring images formed by a plurality of image forming units on a recording sheet to be conveyed.

[0003] Problems of this type of apparatus include uneven movement of a plurality of photosensitive drums and a conveyor belt and movement of the outer peripheral surface of the photosensitive drum and the conveyor belt at the transfer position of each image forming unit due to mechanical accuracy and the like. For example, the relationship of the amount differs for each color, and when the images of the respective colors are superimposed, they do not coincide with each other, resulting in a color shift (position shift).

[0004] The color shift is roughly classified into a shift in the main scanning direction and a shift in the sub-scanning direction. In addition, a steady error in which the amount of the shift is constant in one image, and a shift in the shift amount periodically. There is a non-stationary error.

[0005] Regarding the steady error, conventionally, a mark for correcting the positional deviation of each color is formed on the conveyor belt,
A misalignment is detected and corrected based on the result of reading the mark.

[0006] Regarding irregular color shifts, particularly those caused by uneven conveyance, the rotation state of the photosensitive drum and the conveyance belt is monitored, and the motor is operated so that the uneven rotation is canceled and the rotation speed becomes constant. It is conceivable to control the rotation drive.

Conventionally, the data for rotational drive control obtained in this way at the time of manufacture is stored in a memory, and the rotational drive of the motor is controlled based on the control data at the time of actual image formation. I have.

[0008]

However, conventionally, as described above, control data for canceling rotation unevenness is stored in advance in a memory, so that changes in the environment of the apparatus and changes with time are used. It is not possible to cope with fluctuations in rotation unevenness due to an error in the rotation drive unit due to the above.

[0009] Therefore, an unsteady shift occurs due to the fluctuation of the rotation unevenness, and a good image cannot be obtained.

An object of the present invention is to solve the above-mentioned problems.

It is still another object of the present invention to eliminate uneven rotation of a rotating member in an image forming apparatus and obtain a high-definition image.

[0012]

According to the present invention, a plurality of image forming units each including an image carrier and a writing unit for forming an image on the image carrier are provided. A moving body that moves to transfer an image formed on each image carrier at each transfer position of the image forming means, and a moving body provided corresponding to each of the plurality of image forming means and rotates each image carrier. A plurality of driving units for driving; a plurality of rotation detecting units for detecting a rotation state of each image carrier of the plurality of image forming units; and a plurality of rotation units provided in common to the plurality of image forming units. Calculating means for calculating a control signal for a rotational driving operation by the plurality of driving means based on an output of the detecting means; and controlling the plurality of driving means based on a control signal obtained by the calculating means And configured to include a plurality of drive control means that.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an image forming apparatus to which the present invention is applied.

The apparatus shown in FIG. 1 is provided with an image forming section for forming images of four colors, ie, yellow (hereinafter Y), magenta (hereinafter M), cyan (hereinafter C), and black (hereinafter BK). .

In the figure, 101Y, 101M, 101
C and 101BK are photosensitive drums for forming electrostatic latent images of Y, M, C and BK, respectively, and are driven by a drive unit 200 (not shown) as described later. 102Y, 102
M, 102C, and 102BK are image processing units 10
8, the photosensitive drums 101Y, 101Y
An optical unit that irradiates a laser beam onto M, 101C, and 101BK to form an electrostatic latent image, and includes a laser beam light source, a reflection mirror, and the like. As is well known, a charger, a developing device and the like are provided around each photosensitive drum.

Also, 103 moves in the direction of arrow A in the figure,
A transport belt 104 for sequentially transporting the recording paper 107 to each image forming unit, a driving roller 104 connected to a drive unit including a motor, a gear, and the like, which will be described later, for driving the transport belt 103
Are driven rollers that rotate according to the movement of the conveyor belt 103 and apply a constant tension to the conveyor belt 103;
Reference numeral 6 denotes an image processing unit that processes an image signal input from the outside and outputs an image signal of each color to each optical unit.

Next, an image forming operation in the apparatus shown in FIG. 1 will be described.

At the time of image formation, when the preparation for starting printing is completed in each optical unit 102, a registration roller is driven by a control unit (not shown) to feed the recording paper 109 onto the conveyance belt 103, and to start the conveyance. The image processing unit 10 for each optical unit 102 based on the timing
6 outputs an image signal.

Then, an electrostatic latent image is formed on the photosensitive drum 101 by each optical unit 102, and toner of each color is developed by a developing unit (not shown), and is recorded at a transfer position by a transfer unit (not shown). It is transferred onto paper 107. FIG.
Is transferred in the order of Y, M, C, and BK. Thereafter, the recording paper 109 is separated from the transport belt 103, and the toner image is fixed on the recording paper by a fixing device (not shown), and is discharged outside the apparatus.

Next, control of the rotation operation of the photosensitive drum in the present embodiment will be described.

FIG. 2 shows the photosensitive drum 10 in the apparatus shown in FIG.
FIG. 2 is a diagram illustrating a configuration of one driving unit 200. The drive unit shown in FIG. 2 has the same configuration for each color and performs the same operation. In FIG. 2, the control circuit 3
00 is provided in common to the drive units 200 for each color as described later.

In FIG. 2, reference numeral 201 denotes a reduction gear for transmitting the rotation of a motor 203 to a rotating shaft 202; 202, a rotating shaft that rotates together with the photosensitive drum 101; 203, a stepping motor; and 204, concentric slits at regular intervals. A code wheel that is provided and rotates with the rotation shaft 202;
Reference numeral 205 denotes a light emitting unit and a light receiving unit.
An encoder 300 generates a pulse according to the passage of the slit 04, and a control circuit 300 controls the rotation operation of the motor 203 based on the pulse from the encoder 205 as described later.

In FIG. 2, the rotation of a motor 203 is transmitted to a rotating shaft 202 via a reduction gear 201, and the photosensitive drum 101 rotates, and the code wheel 204 rotates according to the rotation of the rotating shaft 202. With the rotation of the code wheel 204, a pulse is generated from the encoder 205 and output to the control unit 206. The control unit 206 controls the rotation operation of the motor 203 based on the pulse from the encoder 205.

FIG. 3 is a diagram for explaining rotation unevenness of the photosensitive drum 101 when the correction control of the rotation drive of the motor 203 is not performed. In FIG. 3, (a) shows the motor 20
3 shows the state of the control step 3, and FIG.
5 shows the transition of the cycle of the output pulse of FIG.
8 shows the state of the rotational position error of the drum 101 obtained by integrating the period of the output pulse of the encoder 205 shown in FIG.

As shown in the figure, when given control data is given to the motor 203, rotation of the photosensitive drum 101 within one rotation due to uneven rotation of the motor 203 or dimensional error (meshing error) of the reduction gear 201, etc. The state is not constant,
The output pulse cycle of the encoder 205 fluctuates, and a rotational position error occurs periodically. Further, the phase and amplitude of the rotational position error are different for each color, resulting in a periodic color shift (unsteady error). In the present embodiment, since the rotation cycle of the reduction gear 201 and the motor 203 is configured to be an integer fraction of one rotation of the photosensitive drum 101, the rotation unevenness is repeated at the rotation cycle of the photosensitive drum 101.

FIG. 4 is a diagram showing a state of unsteady color misregistration in the sub-scanning direction caused by uneven rotation of the photosensitive drum 101.

FIG. 2 shows a case where color shift occurs between BK and Y. In FIG. 4, the whole movement amount of BK, that is, the distance of 401BK to 402BK and the whole movement amount of Y, that is, the distance of 401Y to 402Y are the same,
The phase and amplitude of rotational unevenness differ between BK and Y, and 401BK
The positions in the sub-scanning direction of the respective lines do not match in the range from 402BK to 402BK or 401Y to 402Y, and color shift occurs periodically.

In this embodiment, the control circuit 300 shown in FIG. 2 controls the motors 203 for each color to prevent such periodic color shift.

FIG. 5 is a diagram showing a configuration around a main part of the image forming apparatus including the control circuit 300. As shown in FIG. Control circuit 3 of this embodiment
Reference numeral 00 denotes a drive control circuit 303 that calculates a pulse period from the encoder 205 of the drive unit 200 for each color and generates and outputs a phase signal for the step motor for each color.
And an arithmetic processing circuit 301 for calculating and outputting the pulse rate of each step motor based on the encoder pulse period of each color from the drive control circuit 303, and motor drivers 319Y to 319BK.

In FIG. 5, each color encoder 205Y
Output pulses from .about.205BK are output to encoder cycle counters 315Y to 315BK, respectively. In this embodiment, the code wheel 204 has 1000 slits, and the encoder 205 outputs 1000 pulses in one rotation of the photosensitive drum 101. The counter 315 counts the clock CLK of a constant frequency from the time when the encoder output pulse is input, resets the count value when the next encoder pulse is input, and resets the count value at that time to the encoder pulse. The data is output to the serial / parallel conversion circuit (hereinafter, S / P conversion circuit) 313 as pulse data for each pulse.

The S / P conversion circuit 313 latches the data of the encoder pulse period of each color in an internal register, converts the data from parallel data to serial data, adds a header to the data, and adds an S / P to the S / P of the arithmetic processing circuit 301 as described later. Output to the conversion circuit 311. In the present embodiment, the S / P conversion circuit 31
3. The cycle counters 315Y to 315BK and the phase signal generation circuits 317Y to 317BK are integrally formed by an ASIC.

The S / P conversion circuit 311 is an S / P conversion circuit 3
The cycle data of the encoder pulse output from 13 is output to the encoder cycle error calculator 307. The encoder error calculator 307 compares the cycle data of the encoder pulse of each color with the reference data for each pulse based on the header, stores the error in the memory 309 for each pulse, and outputs the error to the drive correction value calculator 305. I do.

The drive correction value calculation unit 305 has a memory 309
Error data of the cycle data of the encoder pulse in a certain section centered on the same rotation position one rotation before the rotation of the photosensitive drum 101 and stored in the step motor 2.
Based on the step cycle of the same rotation position one rotation before in step 03, a correction value for canceling the error of the cycle data of the encoder pulse is calculated for each encoder pulse. A high-frequency component having no periodicity due to a tooth pitch or the like is filtered over the predetermined section to obtain correction data, and the S / P conversion circuit 31
Output to 1. This filter can use correction value averaging processing, an FIR filter, an IIR filter, or the like. Further, the drive correction value calculation unit 305, the encoder cycle error calculation unit 307, and the memory 309 are connected by a bus BUS.

The S / P conversion circuit 311 converts the pulse rate correction data from parallel data to serial data, adds a header for each color, and outputs the data to the S / P conversion circuit 313. In this embodiment, the drive correction value calculation unit 305, the encoder cycle error calculation unit 307, the memory 309, and the S / P
The conversion circuit 311 is integrally formed by a DSP.

The S / P conversion circuit 313 is the S / P conversion circuit 3
The pulse rate correction data for each color received from the latch 11 is latched, and the period counter / phase signal generation circuit 317 is latched.
Y to 317M.

The cycle counter / phase signal generation circuit 317 changes the count value of the cycle counter based on the pulse rate correction data, and generates a pulse at the cycle of the corrected count value. Then, a phase signal is generated based on the pulse, and the driver 3 of the step motor 203 for each color is generated.
19, and the driver 319 drives the stepping motor based on the phase signal.

The stepping motor according to the present embodiment has 20 rotations per revolution.
Although it is a hybrid 2-phase step motor of 0 step, the theoretical driving rate is 2000 pps, it is driven by the control circuit 300 as described above, so that it is driven at a variable step cycle corrected around the theoretical value. .

FIG. 6 shows an encoder 20 according to this embodiment.
5 is a diagram for explaining the relationship between the error of the output pulse cycle of No. 5 and the correction value of the step cycle of the step motor 203, and the rotational unevenness of the photosensitive drum 101 after the correction. FIG.

In FIG. 6, (a) shows the count value of the encoder pulse, and 1000 pulses are generated in one rotation. (B) shows the state of the control step cycle of the step motor 203, (c) shows the transition of the cycle of the output pulse of the encoder 205, and (d) shows the state of the output pulse of the encoder 205 shown in (b). Drum 1 with integrated cycle
11 shows a state of a rotational position error of 01.

For example, in FIG. 6, the current rotational position is indicated by the number of encoder pulses 500. At this time, the same position one rotation before the rotation, ie, the photosensitive position as shown in FIG. N-1 one rotation before the rotation n of the drum 101
, A fixed section around the encoder pulse number 500, for example, in this embodiment, the encoder pulse number 451 to 55
Based on the error data of the encoder pulse cycle in the section corresponding to 100 pulses indicated by 0 and the control step cycle of the step motor 203 at the same rotation position one rotation before, the control of the step motor 203 at the time of the encoder pulse 500 of the rotation n is performed. The step cycle is controlled.

Similarly, for example, when the current rotational position is indicated by the encoder pulse number 550, the rotation n
At the same position one rotation before, ie, the encoder pulse number 550
Is based on the error data of the encoder pulse cycle from encoder pulse number 501 to 600 centered on and the control step cycle of the step motor 203 at the same rotation position one rotation before the rotation of the step motor 203 at the time of the encoder pulse 550 of the rotation n. Control the control step cycle.

By controlling as described above, it is possible to reduce the fluctuation of the position of the photosensitive drum 101 as shown in FIG. 6D, and to prevent a periodic color shift of an image.

As described above, in this embodiment, since the encoder pulse cycle error in a predetermined section including the same rotation position one rotation before the rotation is used, it is possible to quickly respond to fluctuations in rotation unevenness. Therefore, the burden of calculating the error of the encoder pulse period can be reduced.

At this time, since the encoder pulse error value in the predetermined section is used after being filtered over the predetermined section, the motor control can be stably performed.

Further, by appropriately changing the length of the predetermined section, the response speed of the motor control with respect to the fluctuation of the encoder pulse cycle can be changed.

Next, transmission and reception of data between the arithmetic processing circuit 301 and the drive control circuit 303 in the control circuit 300 will be described.

FIG. 9 shows the S / P conversion circuit 311 of the arithmetic processing circuit 301 and the S / P conversion circuit 313 of the drive control circuit 303.
FIG. 4 is a diagram showing a signal flow during the period.

The serial communication lines between the S / P conversion circuits 311 and 313 are full duplex, and a total of four synchronous signal lines and four data lines are provided separately for transmission and reception. The serial communication clock is common to transmission and reception, and is always active. For example, the arithmetic processing circuit 301 outputs and the drive control circuit 303 inputs.

As shown in FIG. 7B, a synchronization signal is output one clock before the head data for synchronization of data transmission and reception. Following the synchronization signal, 24-bit data is transmitted and received in synchronization with the clock. The 24-bit data is composed of an 8-bit header indicating what the data indicates, and 16-bit main data. Each data is M
24 bits are continuously transmitted starting with SB. In this embodiment, the data type includes encoder pulse cycle data for each color output from the drive control circuit 303 and pulse rate correction data for each color output from the arithmetic processing circuit 301, and includes an 8-bit header. To identify them.

FIG. 8 is a timing chart showing the timing of data communication and arithmetic processing between the arithmetic processing circuit 301 and the drive control circuit 303.

As described above, the S / P conversion circuit 313 latches the encoder pulse cycle data from the cycle counter 315 for each color in an internal register. Although the rotation cycle of the drum 101 of each color is the same, the output timing of the encoder pulse of each color is asynchronous within one rotation as shown in FIG. Moves back and forth at an arbitrary timing. Therefore, the transmission of the encoder pulse cycle data from the S / P conversion circuits 313 to 311 is performed not in the order of Y, M, C, and BK, but in time series. However, it is necessary to determine the priority when the rising timing of the encoder pulse occurs simultaneously for two or more colors. If the rising edges of the Y and M encoder pulses occur at the same time, the encoder pulse is generated in the order of Y and M. Transmit the cycle data.

In FIG. 8, first, the encoder pulse cycle data of Y is obtained by the rise of the encoder pulse of Y, and is latched by the S / P conversion circuit 313. The S / P conversion circuit 313 converts the Y encoder pulse cycle data into serial data, adds a header indicating that the data is Y encoder pulse cycle data, and the S / P conversion circuit 311 is not busy (reception permission )) And confirms that it is in the state (FIG. 8B).

S / P conversion circuit 31 of arithmetic processing circuit 301
1 receives the data from the S / P conversion circuit 313, sets the communication line busy, resets the reception permission flag, and notifies the encoder cyclic error calculator 307 that there is received data. If the calculation is not being performed, the encoder cycle error calculation unit 307 inputs the data received from the S / P conversion circuit 311 and sets the reception permission flag of the S / P conversion circuit 311 to eliminate the busy state.

Then, it is identified from the header of the received data that the data is the Y encoder pulse cycle data, and an error from the reference value is calculated to calculate the drive correction value calculation unit 305 and the memory 30.
9 is output. The drive correction value calculation unit 303 calculates the pulse rate correction data as described above, and calculates the S / P conversion circuit 311.
Output to

When the operation result of the pulse rate correction data is obtained as described above, the S / P conversion circuit 311 converts the pulse rate correction data into parallel data, and further, a header indicating that the data is Y pulse rate correction data. And transmits the result to the S / P conversion circuit 313 of the drive control circuit 303. At this time, the drive control circuit 303 does not perform any arithmetic processing, and the S / P conversion circuit 313 latches the received data for each color in a register, so that it is not necessary to confirm busy, and the S / P conversion circuit 311 uses the pulse rate After calculating the correction data, the data is transmitted immediately.

In FIG. 8, M encoder pulse period data is obtained during transmission of the Y encoder pulse period data, and is latched in the register of the S / P conversion circuit 313.
At this time, the communication line is not busy, but the Y encoder pulse cycle data is being transmitted, so the transmission of the Y encoder pulse cycle data is completed.

The encoder pulse cycle data of Y is S / P
Since the arithmetic processing is performed immediately after being received by the conversion circuit 311, the busy is immediately canceled, and after the transmission of the Y encoder pulse cycle data is completed, the M encoder pulse cycle data is continuously transmitted.

In the arithmetic processing circuit 301, after receiving the M encoder pulse period data, the S / P conversion circuit 311 notifies the arithmetic section 307 that there is received data.
Since the data of Y is being calculated, the data of M is not immediately acquired by the calculation unit 307, and the calculation of the data of Y ends.
The busy is continued until the data of M is taken into the arithmetic unit 307. Hereinafter, similarly, transmission and reception of each data are performed.

The above processes will be described with reference to the flowchart of FIG.

FIG. 9A is a flowchart showing a process of transmitting encoder pulse cycle data from the drive control circuit 303 to the arithmetic processing circuit 301.

The S / P conversion circuit 313 is provided for each cycle counter 3
It is determined whether the encoder pulse period data from 15Y to 315BK has been latched (S901), and if there is data to be transmitted, a header corresponding to each data is added (S903). Then, after waiting for the transmission line L to become empty (S905), the data is transmitted (S907).

FIG. 9B is a flowchart showing the operation of the arithmetic processing circuit 301 when receiving the encoder pulse period data.

Upon receiving the encoder pulse cycle data (S909), the S / P conversion circuit 311 resets the reception permission flag (S911), sets a flag indicating that there is received data, and sets the encoder cycle error calculator 307 to receive the received data. Is notified (S913).

FIG. 9C is a flow chart for explaining the operation of the arithmetic processing circuit 301 relating to the arithmetic processing.

Upon receiving a notification from the S / P converter 311 that there is received data (S915), the encoder cycle error calculator 307 inputs the received data from the S / P converter 311 (S917), and The reception permission flag of 311 is set (S919). Next, the type of the received data is identified based on the header of the received data (S92).
1) The pulse rate correction data is calculated by the drive correction value calculation unit 305 based on the identification data as described above (S923) and output to the S / P conversion circuit 311 (S9).
25).

In this embodiment, if the number of slits of the code wheel 204 is 1000 and the number of rotations is 100 rpm,
The average period of the encoder pulse is 600 μs, and the transmission period of the encoder pulse period data from the drive control circuit 303 to the arithmetic processing circuit 301 is 150 μs on average for four colors. Further, the transfer time and the calculation time of the transmission data and the reception data overlap, and in this embodiment, each processing time is set shorter than 150 μs. The data transfer time is about 24 μs even if the serial clock is 1 MHz. Since the calculation time varies greatly depending on the calculation content, it cannot be said unconditionally, but 20 MIPS (20 MHz)
In the DSP, the 100th-order FIR processing is 50 μs, and the processing is sufficiently completed within 150 μs even if other processing is added.

As described above, in this embodiment, when the control data of the motor of each color is calculated and generated based on the encoder pulse cycle data of each color, the arithmetic processing circuit is commonly used for each color. Can be downsized,
It is possible to perform highly accurate positional deviation correction with an inexpensive configuration.

Next, a second embodiment of the present invention will be described.

FIG. 10 is a diagram showing a configuration of a main part of a control circuit 300 according to the second embodiment. Components similar to those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof will be omitted. Hereinafter, portions different from the circuit of FIG. 5 will be described.

In the circuit of FIG. 10, the bus between the arithmetic processing circuit 301 and the drive control circuit 303 is connected instead of serial communication. That is, the arithmetic processing circuit 301 and the drive control circuit 303 are connected by a clock by the bus 325, a data bus, an address bus, a read / write, and an interrupt signal.

For example, when the arithmetic processing circuit 301 is constituted by a DSP and the drive control circuit 303 is constituted by an ASIC,
Although the number of connected signals increases as compared with the circuit of FIG. 5,
Each internal circuit configuration can be simplified, and the data transmission / reception time is reduced.

In FIG. 10, the bus I / F 3 of the drive processing circuit 303 responds to the rise of each encoder pulse.
From 23, an interrupt occurs to the bus I / F 321 of the arithmetic processing circuit 301. Bus I / of the arithmetic processing circuit 301
F321 reads data from a register that stores an interrupt factor indicating which data was interrupted in the bus I / F 323, and the interrupt is Y, M, C,
After determining any one of the BKs, the encoder pulse cycle data is read out from the register of the corresponding color in the bus I / F 323, and the encoder pulse cycle calculator 307 is notified. After that, arithmetic processing is performed in the same manner as in the above-described embodiment,
The pulse rate correction data is obtained and written to the register of the bus I / F 321 corresponding to the color.

The bus I / F 321 outputs the pulse rate correction data to the bus I / F 323,
323 outputs the received pulse rate correction data to the cycle counter / phase signal generation circuit 317 of the corresponding color.

As described above, also in this disassembly, similarly to the circuit of FIG. 5, the arithmetic processing of the encoder pulse cycle data of each color is performed by the arithmetic processing circuit common to each color. The displacement can be corrected.

Next, a third embodiment of the present invention will be described.

FIG. 11 is a diagram showing a configuration of a driving section 200 according to a third embodiment of the present invention.

In FIG. 11, a reduction gear 201, a rotating shaft 202, an encoder wheel 204, and an encoder 20
5 is the same as the configuration in FIG. Reference numeral 206 denotes a DC brushless motor, which rotates the photosensitive drum 101 via the reduction gear 201, generates an FG pulse with the rotation, and outputs the generated FG pulse to the control unit 300. The control unit 300 controls the output pulse of the encoder 205 and the motor 2
The rotation operation of the motor 206 is controlled based on the FG pulse from 06. Also, the configuration in FIG. 11 is provided for each color similarly to the configuration in FIG. 2, and the control circuit 300 is provided in common for each color.

FIG. 12 is a diagram showing the configuration of the control circuit 300 according to the present embodiment and the essential parts around it. 12, a detailed description of the same configuration as in FIG. 5 is omitted.

FIG. 12 differs from the circuit of FIG. 5 in the configuration of the period counter / phase signal generation circuit 317.

That is, in FIG. 12, the arithmetic processing circuit 3
01 is output from the S / P conversion circuit 313 to the register 327 of each color.

The motor 206 for each color is provided with an FG generator for generating an FG signal. The comparison circuit 329 uses the correction data stored in the register 327 and the F of the motor 206.
The G pulse is compared with the period of the G pulse, and data indicating an error therebetween is output to the filter 331. The filter 331 performs gain adjustment and phase compensation processing on the output data from the comparison circuit 329, and outputs the data to the driver 333. The driver 333 converts the error data output from the filter 331 into a PWM signal, and controls the driving of the motor 206 based on the PWM signal.

In this embodiment, the number of rotations of the motor 206 is 12
00 rpm, FG pulse is 100 pulses per one rotation of the motor, and the reference pulse frequency on the theoretical value is 2 KHz (120 kHz).
0 rpm / 60 × 100), but is controlled as described above by the control circuit 208, so that it is driven at a speed corrected around the theoretical value.

As described above, instead of the step motor, the DC
Even in the case where a motor is used, the rotation drive of the photosensitive drum can be controlled in the same manner as in the above-described embodiment, and color shift of an image due to an aperiodic error can be eliminated.

In the above-described embodiment, one of the rotations is performed.
Although the encoder pulse cycle error in a predetermined section including the same rotation position before rotation is used, the encoder pulse cycle error in the predetermined section for a plurality of rotations immediately before the rotation is used, and an average value and weighted data thereof are used. You may.

Further, in the above-described embodiment, the driving unit 200 shown in FIG. 2 or FIG. 12 is used for controlling the rotation of the photosensitive drum 101. It may be used for control.

Although the latent image is formed on the photosensitive drum in the apparatus shown in FIG. 1, a photosensitive member on a belt may be used.
The configuration shown in FIG. 2 or FIG. 12 can be applied to the rotation control of the driving roller in this case.

The motor of the drive source may be another motor such as a DC servo motor with a brush.

The encoder may be of a reflection type in addition to the optical encoder.

A magnetic rotary encoder using an MR element or the like may be used instead of the code wheel and the optical encoder.

In the above-described embodiment, an image is formed using a light beam. However, the invention can be applied to an apparatus for forming an image using, for example, an LED head.

Further, in the above-described embodiment, the rotation cycle of the reduction gear and the motor is set to an integral fraction of one rotation of the photosensitive drum, the transport helmet and the drive roller. It is also possible to set the value to an integral one of two rotations of the driving roller. In this case, the control shown in FIG. 5 may be performed for a predetermined section before and after the same rotation position of the immediately preceding cycle as a center, with two rotations of the photosensitive drum and the conveyance belt driving roller as one cycle.

In each circuit of FIG. 5 or FIG.
Although the cycle counter 315 outputs the count value of the clock between encoder pulses as cycle data, other than this, for example, the cycle counter is a free-run counter of about n bits (8 to 10 bits), and an encoder pulse is input. The count value itself at the point of time may be output to the arithmetic processing circuit 301.

[0094]

As described above, according to the present invention,
An unsteady error due to uneven rotation of the rotating member can be prevented, and a high-definition image can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram illustrating a configuration of a photosensitive drum driving unit in the apparatus of FIG. 1;

FIG. 3 is a diagram for explaining a control operation of the photosensitive drum.

FIG. 4 is a diagram for explaining an unsteady error.

FIG. 5 is a diagram showing a configuration of a main part around a control circuit in FIG. 2;

FIG. 6 is a diagram for explaining a control operation of the photosensitive drum according to the configuration of FIG. 2;

FIG. 7 is a diagram illustrating a state of transmission / reception data in the circuit of FIG. 5;

8 is a timing chart showing a state of data communication and processing in the circuit of FIG. 5;

FIG. 9 is a flowchart showing the operation of the circuit of FIG. 5;

FIG. 10 is a diagram illustrating another configuration of the control circuit of FIG. 1;

11 is a diagram showing another configuration of the photosensitive drum driving unit in the apparatus of FIG.

FIG. 12 is a diagram showing a configuration of a main part around a control circuit of FIG. 11;

Claims (17)

[Claims] A plurality of image forming units each having an image carrier and a writing unit for forming an image on the image carrier; and an image formed on each image carrier of the plurality of image forming units. A moving body that moves to transfer at a transfer position, and is provided corresponding to each of the plurality of image forming units;
A plurality of driving units for driving each image carrier to rotate; a plurality of rotation detecting units for detecting a rotation state of each image carrier of the plurality of image forming units; a plurality of rotation detecting units commonly provided for the plurality of image forming units. Calculating means for calculating a control signal for a rotational driving operation by the plurality of driving means based on outputs of the plurality of rotation detecting means; and controlling the plurality of driving means based on a control signal obtained by the calculating means. An image forming apparatus, comprising: a plurality of drive control units for controlling. 2. The method according to claim 1, wherein the arithmetic processing unit detects a rotation speed error of the plurality of driving units based on outputs of the plurality of rotation detection units, and obtains the control signal based on the rotation speed error. The image forming apparatus according to claim 1. 3. The apparatus according to claim 2, wherein said calculating means includes a speed error detecting means for detecting a rotational speed error of said driving means, and a filter means for filtering an output of said speed error detecting means. Image forming apparatus. 4. The image processing apparatus according to claim 1, wherein the driving unit includes an encoder that generates a pulse according to rotation of the image carrier, and the arithmetic unit calculates the control signal based on a period of the encoder pulse of the plurality of image carriers. The image forming apparatus according to claim 1, wherein: 5. The calculating means has an error detecting means for comparing a cycle of the encoder pulse with a reference cycle and detecting an error therebetween, and calculates the control signal based on the error detection result. The image forming apparatus according to claim 4, wherein: 6. A method according to claim 4, wherein each of said plurality of rotation detecting means has a counter for counting a predetermined clock, and outputs a count value of said counter according to said encoder pulse to said calculating means. The image forming apparatus as described in the above. 7. The image forming apparatus according to claim 1, wherein said driving means includes a step motor. 8. An image forming apparatus according to claim 7, wherein said drive control means changes a drive step cycle of said step motor based on said control signal. 9. The image forming apparatus according to claim 1, wherein said driving means includes a DC brushless motor. 10. The image forming apparatus according to claim 1, wherein the driving unit includes a driving source and a transmission mechanism for transmitting a driving force from the driving source to the image carrier. 11. An image forming apparatus according to claim 1, wherein said plurality of rotation detecting means and said calculating means are constituted by independent circuits and connected by a common serial communication line. 12. The plurality of rotation detecting means and the plurality of drive control means are integrally formed, and a control signal obtained by the arithmetic means is sent to the plurality of drive control means via the serial communication line. The image forming apparatus according to claim 11, wherein the image is output. 13. An image forming apparatus according to claim 1, wherein said plurality of rotation detecting means and said calculating means are constituted by independent circuits and are connected by a common bus. 14. The control means calculates the control signal based on a rotation state of the drive means in a predetermined section around a same rotational position as a current rotational position before the rotation. The image forming apparatus according to claim 1. 15. A moving body driving means for transporting and driving the moving body, a second rotation detecting means for detecting a rotation state of the moving body driving means, and controlling a driving operation of the moving body driving means. 2. The control device according to claim 1, further comprising a second drive control unit, wherein the calculation unit generates a control signal of a drive operation by the moving body drive unit based on an output of the second rotation detection unit. 3. Image forming device. 16. The moving body includes an endless conveyance belt that places and conveys a recording material, and the moving body driving unit includes a roller-shaped drive motor that rotates while suspending the endless conveyance belt. The image forming apparatus according to claim 15, wherein: 17. An apparatus for controlling the rotation drive of each image carrier in a plurality of image forming units each having an image carrier, wherein the device is provided in common to the plurality of image forming units, and A rotation control device comprising: a calculation circuit that calculates a plurality of control signals for controlling rotation driving.