JP2000250284A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease deviation in position (deviation in position that is varied periodically for each color) of AC component in a subscanning direction of a color image forming device. SOLUTION: This color image forming device is provided with a color slippage detection part 8 detecting deviation in position of a registration pattern on an intermediate transfer body, a driving motor 41 to 44 respectively rotating and driving photoreceptors 11 to 14, a motor rotation control means rotating and driving the photoreceptors 11 to 14 independently each other by carrying out rotation and drive control of driving motors 41 to 44, a photoreceptor phase detection means (21 to 24) where detection of the rotational phase of the photoreceptors 11 to 14 is carried out and a CPU 9 that controls the rotational phase of the multiple number of photoreceptors 11 to 14 by independently rotating and driving each driving motor 41 to 44 through the motor rotation control means so that the photoreceptors 12 and 14 are rotated against the rotational phase of the photoreceptor 11 that is a reference at a phase difference that counters the deviation in position of the AC component in the sub scanning direction detected at the color slippage detection part 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus which includes a plurality of laser scanning units and scans a plurality of photoconductors, and more particularly to registration of an image formed on each photoconductor in a sub-scanning direction. For controlling a color image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus employing an electrophotographic technique, a photosensitive member as an image carrier is charged by a charger, and the photosensitive member is irradiated with light according to image information to form a latent image. Is formed, the latent image is developed by a developing device, and then transferred to a sheet material or the like to form an image.

On the other hand, with the colorization of images, a plurality of image forming stations for performing the above-described image forming processes are provided, and a cyan image, a magenta image, a yellow image,
And tandem color image formation in which each color image of a black image is preferably formed on each image carrier, and a full-color image is formed by superimposing and transferring each color image on a sheet material at a transfer position of each image carrier. Devices have also been proposed. Such a tandem type color image forming apparatus includes:
Since each image forming unit is provided for each color, it is advantageous for speeding up.

However, the tandem type color image forming apparatus has a problem in how to properly perform registration (registration) of images formed by different image forming units. This is because the shift of the image forming positions of the four colors transferred to the sheet material finally appears as a color shift or a change in color tone.

Therefore, a pattern (hereinafter referred to as a “registration pattern”) serving as a reference for color misregistration is drawn in advance, a registration pattern is detected by a plurality of sensors (color misregistration detection), and the amount of misregistration is determined from the result. The calculation is performed, and the position adjustment (color shift correction) of each image is performed according to the shift amount.

Hereinafter, the operation of the conventional color image forming apparatus will be described.
The color misregistration detection operation will be described.

FIG. 14 is an explanatory view showing the structure of a conventional color image forming apparatus, FIG. 15 is a block diagram showing a control structure of a driving system in the color image forming apparatus shown in FIG. 14, and FIG. FIG. 17 is an explanatory diagram showing a configuration of a color misregistration detection unit in the image forming apparatus. FIG. 17 is an explanatory diagram showing a registration pattern on the intermediate transfer belt and an arrangement of the color misregistration detection unit in the color image forming device of FIG.

As shown in FIG. 14, a color image forming apparatus according to the present embodiment has four image forming stations Pa,
Pb, Pc, and Pd are arranged. Each of the image forming stations Pa, Pb, Pc, and Pd has photoconductors 120a, 120b, 120c, and 120d as image carriers.

Photoconductors 120a, 120b, 120c, 1
20d, each photoconductor 120a, 120b, 12
Charging means 121a, 121b, 121c, 121d for uniformly charging the surfaces of the photoconductors 0c, 120d to a predetermined potential, and charged photoconductors 120a, 120b, 120c, 120
a laser beam 122 corresponding to image data of a specific color
a, 122b, 122c, and 122d, an exposure unit 122 that is a scanning optical system that forms an electrostatic latent image by irradiating the photosensitive member 1;
Developing means 123a, 123b, 1 for visualizing the electrostatic latent images formed on 20a, 120b, 120c, 120d
23c, 123d, photoconductors 120a, 120b, 120
c, a transfer unit 1 for transferring the visualized toner image onto the endless intermediate transfer belt (intermediate transfer member) 126
Transfer devices 124a, 124b, 124c, 124 in 24
d, cleaning means 125a, 1 for removing the residual toner remaining on the photoconductors 120a, 120b, 120c, 120d after transferring the toner image from the photoconductors 120a, 120b, 120c, 120d to the intermediate transfer belt 126.
25b, 125c, and 125d are arranged respectively.

Here, the intermediate transfer belt 126 rotates in the direction of arrow A in the illustrated case. In the image forming stations Pa, Pb, Pc, and Pd, a black image, a cyan image, a magenta image, and a yellow image are formed, respectively. Then, the photoconductors 120a, 120
The single-color images of the respective colors formed on b, 120c, and 120d are sequentially transferred onto the intermediate transfer belt 126 so as to form a full-color image.

On the downstream side of the image forming stations Pa, Pb, Pc, and Pd with respect to the rotation direction of the intermediate transfer belt 126, a color misregistration detection unit (hereinafter referred to as a color misregistration detection unit) for examining a misregistration between toner images formed by respective colors. , “Sensor unit”) 133. The sensor unit 133 will be described later.

At the lower part of the apparatus, there is provided a paper feed cassette 128 containing a sheet material 129 such as printing paper. Then, the sheet material 129 is sent out from the sheet feeding cassette 128 to the sheet conveying path one by one by the sheet feeding roller 127.

An intermediate transfer belt 126 is provided on the paper transport path.
The sheet transfer roller 130 contacts the outer peripheral surface of the intermediate transfer belt 126 for a predetermined amount and transfers the color image formed on the intermediate transfer belt 126 to the sheet 129, and holds the color image transferred on the sheet 129 by the roller. Heating roller 1 for fixing to sheet material 129 by pressure and heat due to rotation
A fixing device 131 provided with 31a is arranged.

In the color image forming apparatus having such a configuration, first, the charging means 121 of the image forming station Pa is used.
The latent image of the black component color of the image information is formed on the photoreceptor 120a by the exposure unit 122a and the exposure unit 122. This latent image is visualized as a black toner image by a developing unit 123a having black toner, and is transferred as a black toner image onto the intermediate transfer belt 126 by a transfer unit 124a.

On the other hand, while the black toner image is being transferred to the intermediate transfer belt 126, the image forming station P
At b, a latent image of the cyan component color is formed, and subsequently, the developing unit 123b visualizes the cyan toner image using the cyan toner. Then, the cyan toner image is transferred to the intermediate transfer belt 126 where the transfer of the black toner image has been completed at the previous image forming station Pa by the transfer device 1 of the image forming station Pb.
The image is transferred at 24b and superimposed on the black toner image.

Thereafter, the magenta toner image and the yellow toner image are formed in the same manner, and when the superposition of the four color toner images on the intermediate transfer belt 126 is completed, the paper feed cassette 127 is fed by the paper feed roller 127. Sheet transfer roller 130 on sheet material 129 fed from
Thus, toner images of four colors are collectively transferred. Then, the transferred toner image is heated and fixed on the sheet material 129 by the fixing device 131, and a full-color image is formed on the sheet material 129.

Each of the photosensitive members 1 whose transfer has been completed is
The cleaning units 125a, 125b, 125c, and 125d remove the residual toner from the cleaning units 125a, 120b, 120c, and 120d, and prepare for the subsequent image formation.

As shown in FIG. 15, the drive system is controlled by a motor rotation control means 102 which starts a drive motor 103 in response to a control signal from a control means 101 such as a CPU for controlling the operation of the entire apparatus. The number is controlled to control the rotational drive. Here, the drive transmitting means 104 transmits the driving force taken out of the rotation shaft of the drive motor 103 by a gear or the like to the rotation moving means 105, whereby the photosensitive members 120a, 120b, 120c, 120d,
The rotation moving means 105 such as the intermediate transfer belt 126 and the heating roller 131a is driven to rotate.

When a known stepping motor (not shown) is used as the drive motor 103, the motor rotation control means 102 outputs a control signal having a frequency corresponding to the number of rotations to rotate the drive motor 103. Control the number. When a DC motor (not shown) is used as the drive motor 103, the motor rotation control means 1
02 controls the number of rotations of the drive motor 103 by, for example, a PLL control method. That is, the rotating drive motor 1
FG signal 132 that generates a frequency proportional to the number of rotations of the DC motor 03, and controls so that the phase and frequency of the FG signal 132 match a reference clock frequency (not shown); This is to perform constant-speed rotation control.

A color image is formed by the above configuration. When the power is turned on, each of the image forming stations Pa,
When replacing Pb, Pc, and Pd, a color shift occurs due to a positional shift of each of the image forming stations Pa, Pb, Pc, and Pd due to a change in the installation state of the color image forming apparatus or a temperature change in the apparatus, or a mounting shift of the scanning optical system. However, this appears as a position shift in the main scanning direction or a position shift in the sub-scanning direction.

Therefore, when the power is turned on, when each of the image forming stations Pa, Pb, Pc, and Pd is replaced and when the temperature inside the apparatus changes, a color misregistration detection and correction operation is performed.

Here, as shown in FIG. 16, the sensor unit 133 includes an image sensor (hereinafter, referred to as “CCD”) 134, a light source 135 such as a lamp, and a light source 13.
5 to the reflected light of the light applied to the intermediate transfer belt 126
It comprises a Selfoc lens array 136 for forming an image on the CD 134. Then, as shown in FIG. 17, the sensor unit 133 includes the pixels 134a, 13a in the CCD 134.
Reference numeral 4b is disposed at a position orthogonal to the rotation direction A of the intermediate transfer belt 126, and is disposed at two positions near the scanning start position and near the scanning end position of the exposure unit 122.

The operation of detecting a color shift in the above-described configuration of the sensor unit 133 will be described.

In the same manner as in the above-described printing operation, the scanning of the exposure unit 122 is started by a registration pattern such as a predetermined straight line or figure (for example, formed on a line perpendicular to the rotation direction A of the intermediate transfer belt 126). (Line including position and line including scanning end position) 137, 138, 13
9 and 140 are transferred as toner images for each color at predetermined intervals, and the sensor units 133a and 133b measure the amount of misregistration (color misregistration) of each color. For example, the positional deviation in the main scanning direction (the direction perpendicular to the direction A in FIG. 17) is caused by the registration patterns 137, 138, and 13 of each color on the intermediate transfer belt 126 as shown in FIG.
9, 140 are CCDs 137 in the sensor unit 133a.
a, the writing start position of each color in the main scanning direction is detected, and an error from a predetermined design value is detected as a position shift. In addition, as shown in FIG. 17, the misregistration in the sub-scanning direction (A direction in FIG. 17) is caused by the registration pattern 13 of each color on the intermediate transfer belt 126.
7, 138, 139 and 140 are the sensor units 133a
The position difference of each color (ΔY) is determined from the time difference (ΔT1 = T−T1, T is a predetermined design value) between the time T1 passing through the CCD 137a and a predetermined design value.
1 = ΔT1 · v). Further, for other skew errors (inclination in the main scanning direction) and magnification errors in the main scanning direction (errors in the printing area width in the main scanning direction), a registration pattern of a predetermined shape corresponding to each is formed, and detection and detection are performed. It is obtained by performing an operation.

Next, a description will be given of a correction operation for various color misregistrations detected as described above.

The position shift in the main scanning direction is corrected by independently controlling the image data writing timing of the exposure unit 122 for determining the writing start position in the main scanning direction for each color. Is done. In addition, the printing area in the sub-scanning direction is controlled by independently controlling the writing timing signal in the sub-scanning direction, which indicates the printing area in the sub-scanning direction, for each color, and the positional deviation in the sub-scanning direction is corrected. Further, a skew error and a magnification error in the main scanning direction are corrected using an image processing technique.

[0027]

However, the correction for the positional deviation in the sub-scanning direction in the above-described registration adjustment is performed by detecting a positional deviation of a certain magnitude for each color (hereinafter, referred to as "DC component"). Correction), it is not possible to perform a correction for a position shift that periodically fluctuates for each color (hereinafter, referred to as “AC component correction”).

Here, the displacement of the AC component occurs due to a speed variation on the surface of the photosensitive member of each color, a speed variation on the surface of the intermediate transfer belt, or the like. The speed fluctuation of the photoconductor surface of each color is caused by the rotation fluctuation of the driving motor for driving, the pitch fluctuation generated in the transmission gear train transmitting the driving force of the driving motor, the speed fluctuation due to the eccentric rotation of the gear, or the speed of the photoconductor itself. This is caused by speed fluctuations or the like due to eccentric rotation, and occurs when the fluctuation phase of the AC component of each color varies with the circumference of the photosensitive member as the fluctuation period. Further, the speed fluctuation of the surface of the intermediate transfer belt is caused by the rotation fluctuation of the driving motor for driving, the pitch fluctuation generated in the transmission gear train transmitting the driving force of the driving motor, the speed fluctuation due to the eccentric rotation of the gear, or the driving roller. Of the intermediate transfer belt as a fluctuation period.

Then, there is a problem that a positional deviation in the sub-scanning direction occurs due to a positional deviation of the AC component due to such a speed variation of the photosensitive member or the intermediate transfer belt, thereby deteriorating the print quality.

Accordingly, an object of the present invention is to provide a color image forming apparatus capable of reducing the displacement of the AC component in the sub-scanning direction.

[0031]

In order to solve this problem, a color image forming apparatus according to the present invention comprises a plurality of photosensitive members provided corresponding to respective color toner images to be developed, and a plurality of photosensitive members. A plurality of charging means for uniformly charging the surface of the photoconductor, and an exposure means for irradiating the charged photoconductor with laser light corresponding to image data of a specific color to form an electrostatic latent image. A plurality of developing means provided for each photoconductor to visualize an electrostatic latent image formed on the photoconductor, and a single-color image of each color provided on each photoconductor and formed on the photoconductor. A plurality of transfer means for successively superimposing and transferring images on an intermediate transfer member to form a composite image, and a color shift detecting a positional shift of an AC component in a sub-scanning direction in a registration pattern of each color formed on the intermediate transfer member. A detection unit; A plurality of drive motors for rotationally driving the respective photoconductors; a plurality of motor rotation control means for rotationally controlling the drive motors to respectively rotate the plurality of photoconductors independently of each other; Photoconductor phase detection means for detecting the rotation phase of the, from the rotation phase of the plurality of photoconductors detected by the photoconductor phase detection means, the other photoconductor relative to the reference predetermined photoconductor rotation phase, The drive motors are driven independently via motor rotation control means so as to rotate with a phase difference that cancels out the position shift of the AC component in the sub-scanning direction detected by the color shift detection unit, and the rotational phases of the plurality of photosensitive members are rotated. And control means for controlling the

As a result, the rotational phases of the plurality of photoconductors are accurately controlled, so that the displacement of the AC component in the sub-scanning direction can be reduced, and the printing quality can be improved.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention provides a plurality of photoconductors provided corresponding to each color toner image to be developed, and a photoconductor provided for each photoconductor. A plurality of charging units for uniformly charging the photosensitive member, an exposure unit for irradiating a laser beam corresponding to image data of a specific color onto the charged photosensitive member to form an electrostatic latent image, And a plurality of developing means for visualizing the electrostatic latent image formed on the photoconductor, and a single color image of each color formed on the photoconductor is provided on each of the photoconductors sequentially on the intermediate transfer body. A plurality of transfer means for forming a composite image by overlapping transfer; a color shift detecting unit for detecting a positional shift of an AC component in a sub-scanning direction in a registration pattern of each color formed on the intermediate transfer body; The body that rotates the body Drive motor, a plurality of motor rotation control means for rotationally controlling the drive motors to respectively drive the plurality of photoconductors independently of each other, and a photoconductor phase detection means for detecting the rotation phase of each photoconductor And from the rotational phases of the plurality of photoconductors detected by the photoconductor phase detecting means, the other photoconductors are moved in the sub-scanning direction detected by the color misregistration detection unit with respect to the reference rotational phase of the predetermined photoconductor. Control means for controlling the rotation phases of a plurality of photosensitive members by independently driving the drive motors via motor rotation control means so as to rotate with a phase difference that cancels out the positional deviation of the AC components. This is a forming device, and has an effect that the rotational phase of a plurality of photoconductors can be controlled with high accuracy, and the displacement of the AC component in the sub-scanning direction can be reduced.

According to a second aspect of the present invention, there is provided a color image forming apparatus according to the first aspect, further comprising a memory for storing a detected value of the registration pattern detected by the color misregistration detecting section. There is an effect that it is possible to reduce the number of detection processes for the registration pattern of each color.

According to a third aspect of the present invention, in the first or second aspect of the invention, the control means activates any one of the reference drive motors by the motor rotation control means, and then controls the motor rotation control. This is a color image forming apparatus in which the remaining drive motors are sequentially activated by means to correct the rotational phase of the photoreceptor, and has an effect that the rotational phase of the photoreceptor can be easily controlled.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the motor rotation control means controls the number of rotations of the drive motor by PLL control. The means is a P input to the motor rotation control means.
This is a color image forming apparatus that corrects the rotation phase of the photoconductor by controlling the phase of a reference clock serving as a reference for LL control, and has an effect that the rotation phase of the photoconductor can be accurately controlled. .

According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the phase control of the reference clock, which is a reference of the PLL control, rotates all the drive motors. This is a color image forming apparatus that is performed in a state where the photosensitive member is rotated, and has an effect that the rotation phase of the photosensitive member can be controlled with high accuracy.

According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the control means uses one of the plurality of photosensitive members as a reference. A color image forming apparatus that controls the rotation phase of each photoconductor by controlling the phase of a reference clock to control the phase of each of the other photoconductors relative to the photoconductor in a direction that delays the phase of the other photoconductor. This has the effect that the rotation phase can be controlled with high accuracy.

According to a seventh aspect of the present invention, in the first aspect of the present invention, a predetermined frequency is obtained by dividing a system clock which is a basic clock for electrical operation of the device. A frequency divider for generating a clock; and pulse generating means for generating a pulse for temporarily stopping the operation of the frequency divider. The frequency divider generates a reference clock and controls the phase of the reference clock. A color image forming apparatus,
This has the effect that the rotational phase of the photoreceptor can be controlled accurately.

According to an eighth aspect of the present invention, in the invention according to any one of the first to seventh aspects, the phase control of the reference clock, which is a reference of the PLL control, uses the system clock as a minimum unit. This is a color image forming apparatus to be performed, and has an effect that the phase of a reference clock for PLL control can be controlled with the accuracy of a system clock.

According to a ninth aspect of the present invention, in the first aspect of the present invention, the control means controls the start timing of the plurality of drive motors to control the drive motor and the photosensitive motor. A first step of correcting the rotational phase of the body, and correcting the rotational phase of the drive motor and the photoconductor by controlling the phase of a reference clock input to the motor rotation control means while rotating the plurality of drive motors. This is a color image forming apparatus that executes the second step, and has an effect that the rotational phase of the photoconductor can be easily and accurately controlled in a short time.

According to a tenth aspect of the present invention, in the first aspect of the present invention, the control means corrects the rotational phase of the photoreceptor after turning on the power of the apparatus. This is a color image forming apparatus, and has an effect that even if the rotation phase of any of the photoconductors is shifted before the power is turned on, it is possible to perform control so that the rotation is performed at an appropriate rotation phase after correction.

According to an eleventh aspect of the present invention, in the invention according to any one of the first to ninth aspects, the control means corrects the rotational phase of the photoreceptor and controls the photoreceptor and the developing means. This is a color image forming apparatus to be performed after replacing or adjusting any of the image stations configured so that even if the rotational phase of any of the photoconductors is shifted, the image is rotated at the corrected rotational phase. It has the effect that control becomes possible.

According to a twelfth aspect of the present invention, in the first aspect of the present invention, the control means corrects the rotational phase of the photoreceptor to print a paper jam. This is a color image forming apparatus that performs after the paper jam processing to remove the paper. Even if the rotation phase of any of the photoconductors is deviated by the paper jam processing, it is possible to control the photoconductor to rotate at the correct rotation phase after the correction. It has the effect of becoming.

According to a thirteenth aspect of the present invention, in any one of the first to ninth aspects, the control means corrects the rotational phase of the photosensitive member before the start of the printing operation. This is a color image forming apparatus, and has an effect that even if the rotation phase of any of the photoconductors is shifted during standby, it is possible to control the photoconductor to rotate at an appropriate rotation phase after correction.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In the present embodiment, illustration and description of the same configuration and operation as those of the conventional color image forming apparatus described above are omitted.

FIG. 1 is a block diagram showing a photoconductor driving circuit in a color image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the phase of a home signal of each color of YMC with respect to a home signal of K by the CPU of FIG. FIG. 3 is a flowchart showing the calculation procedure of the set value of the shift time and its processing, and FIG.
FIG. 4 is a timing chart in which the phase shift time from the peak timing of the AC component of the sub-scanning position shift is detected from the falling timing of the home signal of each color, and FIG. 4 shows the phase of the AC component of the KCMY color shift in the sub-scanning direction. Phase shift time TmemC, TmemM, TmemY of the home signal of each color CMY with respect to the home signal of K at the time
FIG. 5 is a flowchart showing the overall processing of correcting the AC component of the positional deviation in the sub-scanning direction by the CPU in FIG. 1, and FIG. 6 is a drive motor for each color photoconductor in the color image forming apparatus in FIG. FIG. 7 is a flowchart showing the sub-scanning AC component correction process by the start timing control of FIG. 8, and FIG. 7 is a timing chart showing the start / stop timing control of the drive motor when the initial process is not performed in the color image forming apparatus of FIG. 9 is a timing chart showing drive motor start / stop timing control when initial processing is performed in the color image forming apparatus of FIG. 1; and FIG. 9 is a diagram showing each color drive motor started after the drive motor of FIG. Time interval T
delayC (setting value), TdelayM (setting value),
FIG. 10 is a timing chart showing a recalculation process of TdelayY (set value), FIG. 10 is a timing chart showing a phase correction operation of a reference clock input to the PLL control circuit of FIG. 1, and FIG. 11 is input to the PLL control circuit of FIG. FIG. 12 is a flowchart showing the process of correcting the AC component in the sub-scanning direction by controlling the phase of the reference clock. FIG. 12 shows that the phase of the other photoconductor with respect to the photoconductor of K in FIG. 13 is a timing chart of each home signal in the case. FIG. 13 is a timing chart of each home signal in the case where there is a photoconductor in which the phase of the other photoconductor with respect to the photoconductor of K in FIG. It is a timing chart.

In FIG. 1, photosensitive members 11 to 14 are provided in image forming stations Pa, Pb, Pc, and Pd of black K, cyan C, magenta M, and yellow Y in FIG. 120a, 1
These are the same as 20b, 120c, and 120d.

It is composed of one magnetic pattern (not shown) arranged for detecting the home position on the surface of the photoconductors 11 to 14 and a Hall element (not shown) for detecting the same. Photoconductor phase detecting means 21 to 24 are provided for outputting the output of the Hall element as a home signal within one rotation period of the photoconductor and detecting the rotational phase of each of the photoconductors 11 to 14. From the photoconductor phase detecting means 21 to 24, the K home signal 31, the C home signal 32, the M home signal 33, and the Y home signal 34 of the photoconductors 11 to 14 are output.
Are respectively output. These home signals 31, 3
2, 33 and 34 are input to a CPU (control means) 9, whereby the CPU 9 detects the rotational phase of the photoconductors 11 to 14.

Driving motors 41 to 44 are provided to rotationally drive the photoconductors 11 to 14 independently of each other. A known DC motor is used for each of the drive motors 41 to 44, and a hall element (not shown) for detecting a rotation speed is provided inside. The frequency signals FG1 to FG4 from the hall elements are converted into PLL (phase-to-phase) signals. (Lock / loop) control circuits 51-54.

The PLL control circuits 51 to 54 include reference clocks CK1 to CK4 obtained by dividing the system clock SCK, which is the basic clock for the electrical operation of the device generated by the clock generator 61, with the frequency dividers 71 to 74. ON / OFF control signals CTL1 to CTL for performing ON / OFF control of the rotation of each of the drive motors 41 to 44 from the CPU 9.
4 has been entered. Each of the PLL control circuits 51 to 54 receives the input reference clock CK1 to CK.
4 and the frequency signals FG1 to FG4 so that the phases and frequencies thereof match each other, thereby controlling the rotation speeds of the drive motors 41 to 44, whereby the drive motors 41 to 44 rotate at a constant speed corresponding to the reference clock frequency. .

Further, there are provided pulse generating means 81 to 84 for generating one-shot pulses for a period independently set by the CPU 9, and the length (valid period) of the one-shot pulse is determined by the system clock SCK. It is set as an integral multiple of the period. The one-shot pulse is input to the frequency dividers 71 to 74 as a disable (Disable) signal for stopping the frequency division operation of the frequency dividers 71 to 74.

Further, the color misregistration detecting unit 13 shown in FIG.
3, the detection result of the AC component which is the periodic fluctuation component of each color detected by the color misregistration detection unit 8, and the respective photoconductors 11 detected by the photoconductor phase detection units 21 to 24.
Based on the detection results of the rotation phases 14, the home signal 3 of each color of YMC with respect to the home signal 31 of K
A non-volatile memory (memory) 7 for calculating the set values of the phase shift times 2 to 34 and storing the calculation results is provided.

The non-volatile memory 7 preferably includes an EEP
A ROM (electrically erasable / erasable ROM), a flash memory, or the like can be used, but any memory may be used as long as data is not lost even when the power is turned off. The power is turned off by a backup battery, etc.
If a mechanism is provided to prevent data loss even if
A memory such as M may be used.

The CPU 9 detects the rotation phase of each of the photoconductors 11 to 14 by the photoconductor phase detection means, and controls the timing of CTL1 to CTL4 to perform ON / OFF control of the rotation of the respective drive motors 41 to 44. And the pulse generators 81 to 84 and the frequency divider 71
By controlling the phases of the reference clocks CK1 to CK4 input to the PLL control circuits 51 to 54 by
Control is performed such that the photoconductors 11 to 14 of each color rotate at a predetermined phase shift time stored in the nonvolatile memory 7.

The operation of the driving circuit for the photoconductors 11 to 14 according to the present embodiment configured as described above will be described with reference to timing charts and flowcharts shown in FIGS.

First, using the flowchart of FIG.
The calculation procedure of the set value of the phase shift time of the home signal of each color of YMC with respect to the home signal of K by the PU 9 and the processing thereof will be described.

In order to detect the AC component of the displacement in the sub-scanning direction, first, a K registration pattern is formed on the intermediate transfer belt 126 by the photoconductor 11 (S
1). This registration pattern 137-140
As shown in FIG. 17, a straight line including a scanning start position and a straight line including a scanning end position of the exposure unit 122 are formed on a line orthogonal to the traveling direction A of the intermediate transfer belt 126 at predetermined intervals. Images are sequentially transferred and formed.

Next, the registration patterns 137 to 140 are detected by the color shift detecting section 8, and the AC component of the positional shift in the sub-scanning direction is detected (S2). That is,
As shown in FIG.
7 to 140 are CCDs 137 in the sensor unit 133a.
a (T1 = T−T1, where T is a predetermined design value) between the time T1 passing through a and a predetermined design value, and the displacement of each color from the transport speed v (ΔY1 = ΔT1 · v).
Is detected by calculating. Then, this calculation is sequentially performed for each of the registration patterns 137 to 140 to detect a position shift in the sub-scanning direction. The detected positional deviation in the sub-scanning direction is caused by a variation in the speed of the surface of the photoconductor 11 or a variation in the speed of the surface of the intermediate transfer belt 126.
Contains C component. Therefore, in order to extract only the AC component caused by the speed fluctuation of the photoconductor 11, the detection data is subjected to a filtering process such as a band-pass filter. In this manner, as shown in FIG. 3, the speed fluctuation component of the photoconductor 11 corresponding to K can be detected as indicated by the AC component of K. The AC component fluctuates in one rotation cycle Topc to indicate a speed fluctuation due to the eccentricity of the photoconductor 11 or the like.

Next, the rotational phase of the photoconductor 11 is detected from the K home signal 31 from the K photoconductor phase detecting means 21, and the AC of the positional deviation in the sub-scanning direction detected by the color misregistration detector 8 is detected. The phase shift time from the peak position of the component is detected (S3). Specifically, as shown in FIG. 3, the home signal 31 of K becomes Lo level once in one rotation cycle Topc of the photoconductor 11 corresponding to K, and the AC component of the displacement of K in the sub-scanning direction. Also fluctuates in one rotation cycle Topc, and K falls from the fall timing of the home signal 31 of K.
The phase shift time TacK from the peak position of the AC component of the sub-scanning position shift is detected.

Next, it is determined whether or not the processing of S1 to S3 has been completed for all colors (S4). Here, since the detection processing of the phase shift time from the fall timing of the home signal to the peak position of the AC component of the sub-scanning position shift has not been performed yet for CMY, CMY is sequentially detected.
The detection process for MY is performed, and TacC for C, TacM for M, and TacY for Y are similarly detected.

Next, the AC of the displacement of each color in the sub-scanning direction is shown.
The phase shift times TmemC, T of the CMY home signals with respect to the K home signal when the phases of the components are matched.
memMm and TmemY are calculated, and these are stored in the nonvolatile memory 7 (S5). Specifically, as shown in FIG. 4, the operation is performed for TmemC, TacK <TacC.
At the time, TmemC = Topc− (TacC−Tac
K), when TacK> TacC, TmemC = Tac
Calculated by K-TacC, and in the case of FIG.
It is calculated using the arithmetic expression of acC.

Similarly, for TmemM, TacK <T
When acM, TmemmM = Topc- (TacM-T
acK), when TacK> TacM, TmemmM = T
Calculated by acK-TacM, and in the case of FIG.
<Calculated using the TacM equation.

Similarly, for TmemY, TacK <T
When acY, TmemY = Topc- (TacY-T
acK), when TacK> TacY, TmemY = T
Calculated by acK-TacY, and in the case of FIG.
> TacY is used to calculate.

TmemC and Tm obtained as described above
The set value of each phase shift time of emm and TmemY is stored in the nonvolatile memory 7, and an AC component correction of a position shift in the sub-scanning direction (hereinafter, referred to as “sub-scan AC component correction” as necessary) is performed. Read when.

Next, using the flowchart of FIG.
The overall processing of the operation of correcting the AC component of the displacement in the sub-scanning direction by the PU 9 will be described.

In order to perform sub-scan AC component correction, first, C
The set value Tmem of the phase shift time of the home signals 32 to 34 of each color of YMC with respect to the home signal 31 of K by the PU 9
It is determined whether the setting process of C, TmemM, and TmemY has been completed (S11). If the setting process has not been performed, the above-described processes of S1 to S5 shown in FIG. 3 are performed (S13). Also, the set values TmemC and Tmem have already been set.
After the setting process of M, TmemY, the setting values TmemC, TmemM, Tme are read from the nonvolatile memory 7.
mY is read (S12), the phases of the photoconductors 11 to 14 are corrected based on the read set values, and the sub-scanning AC
A component correction operation is performed (S14).

As described above, once the set values TmemC, Tmemm, and TmemY of the phase shift times of the home signals 32 to 34 of the YMC colors with respect to the K home signal 31 are set (processes of S1 to S5), Only reads the correction data from the non-volatile memory 7 and
Component correction processing S14 may be performed, and the processing can be shortened.

Next, the sub-scanning AC component correction processing by the start timing control of the drive motors 41 to 44 of the photoconductors 11 to 14 of each color will be described with reference to the flowchart of FIG.

First, each image station P after power is turned on.
a, Pb, Pc, Pd, cleaning of the photoconductors 11 to 14, temperature control of the heating roller 131 a in the fixing unit 31, detection of various color misregistration, correction operation, etc. It is determined (S21), and if the initial processing has not been performed, the K drive motor 41
Are started, the CMY drive motors 42 to 44 are sequentially started at predetermined time intervals (default values) (S2).
6).

More specifically, as shown in FIG. 7, the drive is started by setting the ON / OFF control signal CTL1 of the K drive motor 41 to Lo, and after a predetermined time interval TdelayC (default value), the drive of C is started. The motor is started by setting the motor ON / OFF control signal CTL2 to Lo, and similarly, Tdela
After yM (default value) and TdelayY (default value), the drive motors 43 and 44 are activated respectively. Here, the reason why the CMY drive motors 42 to 44 are shifted from the K drive motor 41 by a predetermined time and activated is as follows.
Since a large current flows through the drive motors 41 to 44 at startup,
This is to prevent the starting current from increasing due to the simultaneous starting, reduce the load on the power supply (not shown), and prevent the power supply capacity from increasing. As described above, each of the drive motors 41 to 44 is
TdelayC (default value), Tde
By setting layerM (default value) and TdelayY (default value),
Can be prevented from occurring at the same time.

After starting the drive motors 41 to 44, KC
The photoconductors 11 to 14 are obtained from the home signals 31 to 34 of the respective colors MY.
And the phase delay times TiniC, TiniM, and TiniY of the CMY home signals 32-34 with respect to the K home signal 31 are detected (S
27). In this state, various color misregistration detection processes are performed, and the above-described K home signal 31 is calculated and the phase shift time set values of the YMC home signals 32 to 34 (S1 to S5) are also processed.

Next, when the drive motors 41 to 44 are stopped, first, the ON / OFF control signal C
TL1 is set to Hi, and then stopped. Then, after a predetermined time interval TdelayC (default value), the ON / OFF control signal CTL2 of the drive motor of C is set to Hi, and stopped in the same manner as in the above-described startup. , TdelayM (default value) and TdelayY (default value), the drive motors 43 and 44 are respectively stopped (S2).
8). The reason why the CMY drive motors 42 to 44 are shifted with respect to the K drive motor 41 by a predetermined time and stopped is to maintain the phase relationship of the photoconductors 11 to 14 after the stop in the same state as before the start. .

Next, TiniC, Ti detected in S27
Using the set values of the phase shift times of niM, TiniY, and TmemC, TmemM, and TmemY stored in the nonvolatile memory 7, the photoconductors 11 to 14 are moved to the predetermined phase shift times stored in the nonvolatile memory 7. The predetermined time intervals TdelayC of the drive motors 42 to 44 of the respective colors that are started after the K drive motor 41 is started so as to rotate at the set values TmemC, Tmemm, and TmemY.
(Set value), TdelayM (set value), Tdelay
Y (set value) is calculated and reset (S29). That is, TdelayC (set value) = TdelayC (default value) -TiniC + TmemC, TdelayM
(Setting value) = TdelayM (default value)-Tin
iM + TmemM, TdelayY (set value) = Tde
The calculation is performed as: layY (default value) −TiniY + TmemY, and after the next drive motors 41 to 44 start the K drive motor 41, each CMY drive motor 4
2 to 44 are sequentially activated at predetermined time intervals TdelayC (set value), TdelayM (set value), and TdelayY (set value).

If the initial process is performed in S21, after the K drive motor 41 is started, each of the CMY drive motors 42 to 44 is sequentially turned over at a predetermined time interval Tdela.
yC (set value), TdelayM (set value), Tdel
It is started with ayY (set value) (S22).

Specifically, as shown in FIG. 8, the drive is started by setting the ON / OFF control signal CTL1 of the K drive motor 41 to Lo, and then after a predetermined time interval TdelayC (set value), ON / OFF control signal CTL
2 to Lo and start up.
After (set value) and TdelayY (set value), the drive motors 43 and 44 are activated respectively.

The photoconductors 11 to 14 have a predetermined phase shift time set value TmemC,
It rotates at TmemM and TmemY, but slightly fluctuates due to fluctuations in the start and stop times of the drive motors 41 to 44 due to load fluctuations. Therefore, the drive motors 41 to 44
, The rotational phases of the photoconductors 11 to 14 are detected from the home signals 31 to 34 of the KCMY colors, and the K home signal 3 is detected.
CMY home signals 32 to 3 based on 1
4, the phase delay time TsetC, TsetM, TsetY
Is detected (S23), and the next start timing is recalculated. For TsetC, TsetM and TsetY, T
setC @ TmemC, TsetM @ Tmemm, Ts
The relationship of etY ≒ TmemY is established. In this state, the printing operation described in the conventional example is performed.

Next, the drive motors 41 to 44 are stopped.
Here, first, the ON / OFF control signal CTL1 of the K drive motor 41 is set to Hi and stopped, and the ON / OFF control of the C drive motor is performed after a predetermined time interval TdelayC (set value), similarly to the above-described start-up. The signal CTL2 is set to Hi and stopped, and similarly, TdelayM (set value), TdelayM
After the delay Y (set value), the drive motor 43,
44 are stopped (S24). K drive motor 4
The reason why the CMY drive motors 42 to 44 are shifted from each other by a predetermined time and then stopped is to maintain the phase relationship of the photoconductors 11 to 14 after stopping in the same state as before starting.

Next, the Tset detected in S23
Using the set values of the phase shift times of TmemC, TmemM, and TmemY stored in the nonvolatile memory 7, the drive motor 41 of K is used.
A predetermined time interval TdelayC (set value) between the drive motors 42 to 44 of the respective colors to be started after the start of the operation, Tdela
yM (set value) and TdelayY (set value) are recalculated and the next start timing is reset (S25).

Here, the resetting of TdelayC (set value) for C will be specifically described. Usually Tm
emC-TsetC becomes substantially a value close to 0 by controlling the start timing of the drive motor 42 of C, and its absolute value does not exceed Topc / 2. Therefore, as shown in FIG. 9A, -Topc / 2 <TmemC-
When TsetC <Topc / 2, TdelayC (set value) = TdelayC (set value) + TmemC−Ts
The start timing is reset as etC.

However, as shown in FIG.
In the state of mCＣTopc, if the home signal 32 of C shifts in the direction in which the phase is delayed after the correction by the start timing control, TsetC ≒ 0, and TmemC−TsetC.
> TopcC / 2. Therefore, TmemC-T
When setC> Topc / 2, TdelayC (set value) = TdelayC (set value) + TmemC-Tse
The start timing is reset as tC-Topc.

As shown in FIG. 9C, Tmem
In the state of C ≒ 0, C
Is shifted in the direction in which the phase advances, Ts
etC ≒ Topc, and TmemC−TsetC <−
TopcC / 2. Therefore, TmemC-Ts
When etC <−Topc / 2, TdelayC (set value) = TdelayC (set value) + TmemC−Tse
The start timing is reset as tC + Topc. Similarly, TdelayM (set value) for M and TdelayY (set value) for Y are obtained by calculation and reset.

In the next start-up of the drive motors 41 to 44, after the K drive motor 41 is started, the CMY drive motors 42 to 44 are sequentially turned on for a predetermined time interval Tdelay.
C (set value), TdelayM (set value), Tdela
By starting at yY (set value) and repeating the processing from S22 to S25, the drive motors 41 to 4
4, the sub-scanning AC component correction can be performed.

Next, using the flowcharts and timing charts of FIGS.
The sub-scanning AC component correction processing by the phase control of the 44 PLL reference clocks CK1 to CK4 will be described.

The sub-scanning AC by the start timing control of the drive motors 41 to 44 of the photoconductors 11 to 14 of each color described above.
In contrast to the component correction processing, this correction processing
By controlling the respective rotation phases during the rotation of .about.44, the phase control of the photoconductors 11 to 14 is performed, and the sub-scanning AC component correction processing is performed.

Here, the reference clock CK1 inputted to the PLL control circuit 51 for controlling the K drive motor 41 in the case of controlling the rotation phase of the K drive motor 41 is used.
Will be described. However, the same is performed for each color of MCY.

As shown in FIG. 10, the CPU 9 generates a pulse so that the pulse generating means 81 corresponding to K outputs a one-shot pulse corresponding to the cycle of the system clock SCK or a predetermined correction cycle T that is an integral multiple thereof. Means 8
1 is set. At this time, the frequency divider 71 is prohibited from performing the frequency dividing operation during the period in which the one-shot pulse (correction period T) is being output. The clock CK1 is in a state where the phase is shifted by T and delayed. By repeating this operation n times, the phase of the reference clock CK1 is shifted by a period corresponding to a total of n × T as shown in the figure.

The PLL control circuit 51 receives the reference clock CK
1 to synchronize the frequency signal FG1 with the drive motor 4
1 temporarily lowers the rotation speed. As a result, the frequency of the frequency signal FG1 temporarily decreases, but as a result of the PLL control, the rotational phase of the drive motor 41 is changed to the correction cycle nxT
Just shift. Therefore, the phase of the photoconductor 11 driven by the drive motor 41 is also shifted by the correction period n × T.

The phase of the photosensitive member 11 can be shifted by time m × n × T by repeating the above-described operation of correcting the reference clock CK1 having the correction period n × T by m times. In this way, the phase of the photoconductor 11 can be controlled using the correction cycle T as a minimum unit. Similarly, the reference clocks CK2, CK3, and CK4 are used to control the phases of the photoconductors 12 to 14.

Using the flowchart of FIG.
The process of correcting the AC component in the sub-scanning direction by controlling the phase of the reference clock input to the control circuit will be described.

First, the drive motors 41 to 44 of the respective colors are started, and as shown in FIG.
The rotational phases of the photoconductors 11 to 14 are detected from
, The phase delay times TphC, TphM,
TphY is detected (S31).

Next, using the set values of the phase shift times of TmemC, TmemM, and TmemY stored in the nonvolatile memory 7, TphC,
Difference from TphM, TphY TsubC, TsubM, T
SubY is calculated (S32). That is, TsubC
= TmemC-TphC, TsubM = TmemM-T
Calculate as phM, TsubY = TmemY-TphY.

Next, TsubC, TsubM, Tsub
It is determined whether there is a negative Y (S33). If there is no negative Y, as shown in FIG. 12, the phases of the other photoconductors 12 to 14 with respect to the K photoconductor 11 are set at predetermined positions. Since all the phase shift times are set ahead of the set values TmemC, TmemM, and TmemY, the phases of the reference clocks CK2, CK3, and CK4 are set to TsubC and TsubC.
After delaying by subM and TsubY, control is performed such that the other photoconductors 12 to 14 rotate at predetermined set values TmemC, TmemM, and TmemY of the respective phase shift times with respect to the K photoconductor 11 (S34).

In S33, TsubC, TsubM,
When there is a negative one among TsubY, as shown in FIG. 13, the phases of the other photoconductors 12 to 14 with respect to the K photoconductor 11 are set to predetermined values TmemC and T of predetermined phase shift times.
Some photoconductors are later than memM, TmemY. In the case of FIG. 13, the C photoconductor 12 and the M photoconductor 13 correspond to this. Therefore, first, the phase of the photoconductor whose phase is the most delayed with respect to the photoconductor 11 of K is K
TsubC, TsubM, and TsubY such that the photoconductor 11 rotates at a predetermined set value of each phase shift time with respect to the photoconductor 11.
Minimum value min (TsubC, TsubM, Tsu
bY) is detected (negative value), and the phase of the reference clock CK1 is delayed by its absolute value to delay the phase of the K photoconductor 11 (S35). Here, in the case of FIG. 13, the C photoconductor 12 whose phase is the most delayed with respect to the K photoconductor 11 is set to a predetermined phase shift time T with respect to the K photoconductor 11.
In order to rotate at memC, the absolute value of TsubC is K
Of the photoconductor 11 is delayed.

Next, the phases of the reference clocks CK2, CK3 and CK4 are set to Tsub, respectively.
C-min (TsubC, TsubM, TsubY),
TsubM-min (TsubC, TsubM, Tsu
bY), TsubY-min (TsubC, Tsub
(M, TsubY), and the other photoconductors 12 to 14 are controlled to rotate at the set values TmemC, TmemM, and TmemY of the respective phase shift times with respect to the K photoconductor 11 (S36).

As described above, the drive motors 41 to 4 for the respective colors are used.
4 while the PLL reference clocks CK1 to CK
By controlling the phase of K4, the drive motors 41 to 44 can be controlled.
, The phase control of the photoconductors 11 to 14 can be performed to correct the sub-scanning AC component.

Further, the photoconductors 11 to 14 of the respective colors described above.
A first step of performing the sub-scanning AC component correction process (S21 to S29) by controlling the start timing of the drive motors 41 to 44, and the drive motors 41 to 44 in a state where the drive motors 41 to 44 are started and rotated. PLL reference clock C
By performing in combination with the second step of performing the sub-scanning AC component correction process (S31 to S36) by the phase control of K1 to Ck4, the highly accurate sub-scanning AC component correction process can be performed in a shorter time. it can.

The home signal 31 of K described above.
The setting process of the phase shift time of the home signals 32 to 34 of the respective colors YMC and the sub-scanning AC component correction process are performed after the power supply of the apparatus is turned on or the plurality of image stations Pa, Pb, P
This is performed after replacement or adjustment of any of c and Pd, after a jam process for removing a paper sheet that has been jammed due to the paper not being properly conveyed in the apparatus during a printing operation, or before the printing operation is started. As a result, the photoconductor 11
Even if the rotational phase varies due to the speed fluctuation of the AC components of (1) to (14), the correction control can be performed.

[0099]

As described above, according to the present invention, the rotational phases of a plurality of photoconductors are controlled with high accuracy, and the displacement of the AC component in the sub-scanning direction can be reduced. The effect is obtained.

As a result, an effective effect that the print quality can be improved can be obtained.

If a memory for storing the detected value of the registration pattern is provided, an effective effect is obtained that the number of detection processes for each color registration pattern can be reduced.

If the reference drive motor is started and then the remaining drive motors are sequentially started to correct the rotational phase of the photosensitive member, the rotational phase of the photosensitive member can be easily controlled. That is, an effective effect is obtained.

The motor rotation control means controls the rotation speed of the drive motor by PLL control, and the control means controls the phase of a reference clock which is input to the motor rotation control means and serves as a reference for the PLL control. If the phase is corrected, an effective effect that the rotation phase of the photoreceptor can be accurately controlled can be obtained.

If the phase control of the reference clock is performed while all the drive motors are rotated, it is possible to control the rotation phase with high accuracy while the photosensitive member is rotated. Is obtained.

The rotational phase of the photosensitive member is controlled by controlling the phase of the reference clock with reference to any one of the photosensitive members and controlling the phase of each of the other photosensitive members with respect to the corresponding photosensitive member. For example, an effective effect that the rotation phase of the photoreceptor can be accurately controlled can be obtained.

When the reference clock is generated by the frequency divider and the phase of the reference clock is controlled, an effective effect that the rotational phase of the photosensitive member can be controlled with high accuracy can be obtained.

If the phase control of the reference clock is performed using the system clock as the minimum unit, there is an effective effect that the phase of the reference clock for PLL control can be controlled with the accuracy of the system clock.

A first step of controlling the start timings of the plurality of drive motors to correct the rotational phases of the drive motors and the photosensitive members, and a reference to input to the motor rotation control means while the plurality of drive motors are rotating. By executing the second step of correcting the rotation phase of the drive motor and the photoconductor by controlling the phase of the clock, the rotation phase of the photoconductor can be easily and accurately controlled in a short time. Is obtained.

If the rotation phase of the photoconductor is corrected after the power supply of the apparatus is turned on, even if the rotation phase of any of the photoconductors is shifted before the power is turned on, the correction is performed with the proper rotation phase. An effective effect that it is possible to control to rotate is obtained.

If the rotation phase of the photoconductor is corrected after replacing or adjusting any image station including the photoconductor and the developing means, the rotation phase of any photoconductor is shifted. This also provides an effective effect that it is possible to perform control so as to rotate at an appropriate rotational phase after the correction.

If the rotation phase of the photosensitive member is corrected after the jam processing for removing the printing paper that has caused the paper jam, the correction can be performed even if the rotation phase of any of the photosensitive members is shifted due to the jam processing. Thus, it is possible to obtain an effective effect that control can be performed so as to rotate at an appropriate rotation phase.

If the rotation phase of the photoconductor is corrected before the start of the printing operation, even if the rotation phase of any of the photoconductors is shifted during standby, the rotation is corrected at the correct rotation phase. An effective effect that control can be performed so that

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a photoconductor driving circuit in a color image forming apparatus according to an embodiment of the present invention;

FIG. 2 is a diagram showing Y to K home signal by the CPU of FIG. 1;
Flow chart showing the calculation procedure and the processing of the set value of the phase shift time of the home signal of each color of MC

FIG. 3 is a timing chart in which a phase shift time from a fall timing of a home signal of each KCMY color to a peak position of an AC component of a sub-scanning position shift is detected.

FIG. 4 shows a phase shift time TmemC of a home signal of each color of CMY with respect to a home signal of K when the phase of the AC component of the position shift in the sub-scanning direction of each color of KCMY is matched.
Timing chart for detecting TmemM and TmemY

FIG. 5 is a diagram illustrating an example of the positional deviation A in the sub-scanning direction by the CPU of FIG.
Flowchart showing the overall processing of the C component correction operation

FIG. 6 is a flowchart showing a sub-scanning AC component correction process in the color image forming apparatus of FIG.

FIG. 7 is a timing chart showing start / stop timing control of a drive motor when initial processing is not performed in the color image forming apparatus of FIG. 1;

FIG. 8 is a timing chart showing start / stop timing control of a drive motor when initial processing is performed in the color image forming apparatus of FIG. 1;

9 shows a time interval TdelayC (set value) of each color drive motor which is started after the drive motor of K in FIG. 1 is started,
TdelayM (set value), TdelayY (set value)
Timing chart showing recalculation processing

10 is a timing chart showing a phase correction operation of a reference clock input to the PLL control circuit of FIG.

11 is a flowchart showing a process of correcting an AC component in the sub-scanning direction by controlling the phase of a reference clock input to the PLL control circuit of FIG. 1;

12 is a timing chart of each home signal in a case where the phases of other photoconductors with respect to the photoconductor of K in FIG. 1 are all ahead of the set value of each phase shift time.

13 is a timing chart of each home signal in the case where there is a photoconductor in which the phase of another photoconductor with respect to the photoconductor of K in FIG. 1 is behind the set value of each phase shift time.

FIG. 14 is an explanatory diagram illustrating a configuration of a conventional color image forming apparatus.

FIG. 15 is a block diagram showing a control structure of a driving system in the color image forming apparatus of FIG.

16 is an explanatory diagram illustrating a configuration of a color misregistration detection unit in the color image forming apparatus in FIG.

FIG. 17 is an explanatory diagram showing the arrangement of a registration pattern and a color misregistration detection unit on an intermediate transfer belt in the color image forming apparatus of FIG. 14;

[Explanation of symbols]

 Reference Signs List 7 Non-volatile memory (memory) 8 Color shift detecting unit 9 CPU (control means) 11 to 14 Photoconductor 21 to 24 Photoconductor phase detecting means 41 to 44 Drive motor 51 to 54 PLL control circuit 61 Clock generator 71 to 74 minutes Circuit 81-84 Pulse generating means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tadayuki Kajiwara 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F-term (reference) 2H027 DA09 DA17 DC14 DE10 EC03 EC10 ED02 ED24 EE02 EE03 EE04 EE08 EF01 EF06 EF13 EK04 EK06 FA28 HA06 HA08 HA12 HB05 HB06 HB14 2H030 AB02 AD16 AD17 BB36 BB42 BB63 BA31H01 BAH

Claims (13)

[Claims] A plurality of photoconductors provided corresponding to each color toner image to be developed; a plurality of charging means provided for each of the photoconductors, for uniformly charging the surface of the photoconductor; An exposure unit that irradiates a laser beam corresponding to image data of a specific color onto the charged photoconductor to form an electrostatic latent image; and an exposure unit that is provided for each of the photoconductors and is formed on the photoconductor. A plurality of developing means for visualizing the electrostatic latent image; provided for each of the photoconductors; and a single-color image of each color formed on the photoconductor is sequentially superimposed and transferred onto an intermediate transfer body to form a composite image. A plurality of transfer units, a color shift detecting unit for detecting a positional shift of an AC component in a sub-scanning direction in a registration pattern of each color formed on the intermediate transfer body, and a rotational drive of each of the photoconductors You A plurality of drive motors; a plurality of motor rotation control means for rotationally controlling the drive motors to rotate the plurality of photoconductors independently of each other; and a photodetector for detecting a rotation phase of each of the photoconductors Body phase detection means, and from the rotation phases of the plurality of photoconductors detected by the photoconductor phase detection means, the rotation of the other photoconductor relative to a predetermined rotation phase of the photoconductor as a reference, The drive motors are independently driven to rotate by the motor rotation control means so as to rotate with a phase difference that cancels out the displacement of the AC component in the sub-scanning direction detected by the detection unit, thereby rotating the plurality of photoconductors. A color image forming apparatus, comprising: control means for controlling a phase. 2. The color image forming apparatus according to claim 1, further comprising a memory for storing a detected value of the registration pattern detected by said color misregistration detecting section. 3. The control means activates any one of the reference drive motors by the motor rotation control means, and then sequentially activates the remaining drive motors by the motor rotation control means to cause the photosensitive member to rotate. 3. The color image forming apparatus according to claim 1, wherein the rotation phase is corrected. 4. The motor rotation control means controls the number of rotations of the drive motor by PLL control, and the control means controls the phase of a reference clock which is input to the motor rotation control means and serves as a reference for PLL control. The rotation phase of the photoconductor is corrected by performing the correction.
4. The color image forming apparatus according to claim 3. 5. The color according to claim 1, wherein the phase control of the reference clock, which is a reference of the PLL control, is performed while all the drive motors are rotated. Image forming device. 6. The control means controls the phase of the reference clock with reference to any one of the plurality of photoconductors to control the phase of the other photoconductor relative to the other photoconductor. The color image forming apparatus according to any one of claims 1 to 5, wherein the rotation phase of each of the photoconductors is controlled by controlling the phase to be delayed. 7. A frequency divider for generating a predetermined clock by dividing a system clock which is a basic clock for electrical operation of the device, and a pulse for generating a pulse for temporarily stopping the operation of the frequency divider The color image forming apparatus according to any one of claims 1 to 6, further comprising a generator, wherein the frequency divider generates the reference clock and controls the phase of the reference clock. 8. The color image forming apparatus according to claim 1, wherein the phase control of the reference clock serving as a reference of the PLL control is performed using the system clock as a minimum unit. . 9. A first step of controlling the start timing of the plurality of drive motors to correct the rotational phase of the drive motor and the photoconductor, and causing the plurality of drive motors to rotate. A step of controlling the phase of the reference clock input to the motor rotation control means to correct the rotation phases of the drive motor and the photosensitive member in the state of being rotated. ~
9. The color image forming apparatus according to claim 8. 10. The color image forming apparatus according to claim 1, wherein said control means corrects the rotational phase of said photoconductor after turning on a power supply of said apparatus. 11. The apparatus according to claim 11, wherein said control means corrects the rotational phase of said photosensitive member after replacement or adjustment of any image station including said photosensitive member and said developing means. Item 10. The color image forming apparatus according to any one of Items 1 to 9. 12. The apparatus according to claim 1, wherein said control means corrects the rotational phase of said photosensitive member after a jam process for removing a paper sheet having a paper jam. Color image forming apparatus. 13. A color image forming apparatus according to claim 1, wherein said control means corrects the rotational phase of said photosensitive member before starting a printing operation.