JP4829597B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a color image forming apparatus such as a tandem type color copier (color PPC), a color composite apparatus (color MFP), a color facsimile apparatus, a color printer and the like using an intermediate transfer system or a collective belt transfer system. It relates to correction technology.

  In recent years, there are an increasing number of electrophotographic image forming apparatuses capable of forming color images, such as color copiers and color printers. Among them, a plurality of motors that independently rotate and drive a plurality of photosensitive drums (first image carrier), and a plurality of exposure units that respectively expose the outer peripheral surfaces of the photosensitive drums that are rotated by the motors. (Exposure unit), a plurality of development units (development unit) for developing a portion exposed by each exposure unit with a single color toner of a different color to form a single color toner image, and each development unit Each single color toner image is sequentially superimposed on the outer peripheral surface of the intermediate transfer member (second image carrier) or the transfer paper on the outer peripheral surface of the transfer conveyance belt (second image carrier) to form a composite color image. And a transfer unit (transfer means), each of which forms a single color toner image with a single color toner on each photosensitive drum, and the single color toner image is formed on the intermediate transfer member or the transfer conveyance belt. Tandem type color image forming apparatus have been increasing as you transferred and sequentially superimposed on the transfer sheet to form a composite color image.

However, in such a conventional color image forming apparatus, when the colors are superimposed on the outer peripheral surface of the intermediate transfer member or on the transfer paper, the position is shifted from the target position, and problems such as color shift occur. There was a thing. One of the causes is a fluctuation component (speed fluctuation) of one rotation (one rotation) of the photosensitive drum that is rotationally driven.
The present invention has been made in view of the above points, and an object thereof is to reduce color misregistration caused by a fluctuation component of one rotation of a first image carrier in a tandem type color image forming apparatus. .

  In order to achieve the above object, the present invention provides a plurality of motors that independently rotate and drive a plurality of first image carriers, and outer peripheral surfaces of the plurality of first image carriers that are respectively rotated by the motors. A plurality of exposure means for exposing each of the plurality of exposure means, a plurality of development means for developing a portion exposed by each exposure means with a single color toner of a different color to form a single color toner image, and each of the development means. A tandem type color image forming apparatus having transfer means for forming a composite color image by sequentially superimposing and transferring each single color toner image on the outer peripheral surface of a second image carrier or transfer paper on the outer peripheral surface. It is characterized by the following.

That is, to form a plurality of detected portions at predetermined angular intervals around the periphery of the rotating plate mounted respectively to the axis of the end faces or the respective first image bearing member of the respective first image bearing member, that each of the detection to detect the part, and face the vicinity of the outer peripheral end surface or the rotating plate of the respective first image bearing member is disposed a plurality of detection means at predetermined angular intervals, the first upper Symbol the first image bearing member Storage means for calculating and storing rotational fluctuation components generated by one rotation of each of the first image carriers based on output signals output by each of the detection means during rotation, and stored in the storage means Reference clock generation means for generating a reference clock for canceling the fluctuation component from one rotation rotation fluctuation component of each of the first image carriers, and each of the first image carriers stored in the storage means 1 turn To match the phase of the variation component, and a start signal outputting means for outputting a respective start signal to each motor, and a drive control means for driving and controlling the motor based on the reference clock generated by the reference clock generating means It is provided .

Incidentally, a time measuring means for measuring the respective time of the from the exposure timing of each exposure means for each first image bearing member to the transfer timing of each transfer means, such that each time measured by the time measuring means is aligned Further, it is preferable to further provide reference speed setting means for setting the reference speed of each motor.

According to the color image forming apparatus of the present invention, during one rotation of each first image carrier, each detection means (the rotating plate attached to the end surface of the first image carrier or the shaft of the first image carrier) is provided. The rotation fluctuation component generated by one rotation of each first image carrier is calculated and stored in the storage means based on the output signals that are output at a plurality of predetermined angular intervals facing the vicinity of the outer periphery. A reference clock for canceling the fluctuation component is generated from the rotation fluctuation component of each first image carrier stored in the means, and the rotation fluctuation of each rotation of each first image carrier stored in the storage means is generated. A start signal is output to each motor that independently rotates and drives each first image carrier so that the phases of the components are matched, and the respective motors are driven and controlled based on the reference clock. One lap of It is possible to reduce the color shift caused by fluctuation component.

Hereinafter, the best mode for carrying out the present invention will be specifically described with reference to the drawings.
FIG. 1 is a diagram showing a first configuration example of an image forming section (image forming section) of a tandem indirect transfer type color image forming apparatus embodying the present invention.

  This color image forming apparatus is a tandem type electrophotographic apparatus (electrophotographic color copying machine, color printer, color facsimile apparatus, color composite apparatus, etc.) capable of forming a full color image, and includes a plurality of photosensitive drums 1 ( 1Y, 1C, 1M, 1B) around the developing unit 2 (2Y, 2C, 2M, 2B), the first transfer unit 3 (3Y, 3C, 3M, 3B), and the contacting / separating unit constituting the contacting / separating means (Contacting / separating mechanism) 4 (4Y, 4C, 4M, 4B) is provided.

  In this color image forming apparatus, for example, monochromatic toner images having different colors are formed on the respective photosensitive drums 1, the contact / separation parts 4 are moved (details will be described later), and the first transfer parts 3 are placed in the middle. By contacting the transfer belt 5 and bringing the intermediate transfer belt 5 and each photosensitive drum 1 into contact with each other, the monochromatic toner images on the outer peripheral surfaces of the photosensitive drums 1 are sequentially superimposed on the intermediate transfer belt 5. Transfer to form a composite color image, which is then collectively transferred onto a sheet-like transfer paper (paper), whereby a full color image can be formed.

  This color image forming apparatus can be rotated independently of each other, and a plurality of photosensitive drums (first image carriers) 1 for forming different color monochrome toner images on the outer peripheral surface, and each of the photosensitive drums 1. An intermediate transfer belt (second image carrier) 5 on which single color toner images of different colors respectively formed on the outer peripheral surface are transferred at transfer positions respectively corresponding to the respective photosensitive drums 1, and the respective first transfer units 3. A plurality of contacting / separating portions 4 for bringing the outer peripheral surface of the intermediate transfer belt 5 and the outer peripheral surface of each photosensitive drum 1 into contact with or separating from each other by moving them up and down are movable. Each of the first transfer portions 3 is selectively moved up and down by selectively rotating the push-up members 4a constituting the contact / separation portions 4 in the left-handed or right-handed direction around the support shaft 4b. Each of 5 outer peripheral surfaces Selectively contact or to separate the shooting position and the outer peripheral surface of the photosensitive drum 1.

In addition to the developing unit 2, a charging unit 6, a cleaning unit 7, a charge removal unit 8, and the like are provided around each photosensitive drum 1, and the outer peripheral surface of each photosensitive drum 1 is an exposure unit. (Laser writing unit) 9 is scanned and exposed with a laser beam corresponding to each color image modulated and emitted based on an image signal (image data), and an electrostatic latent image is formed there.
The detailed description of the image forming process performed by the charging unit 6, the exposure unit 9, the developing unit 2, the first transfer unit 3, the cleaning unit 7 and the charge removing unit 8 in this color image forming apparatus is the same as that of a known color image forming apparatus. The same thing is omitted because it is not directly related to the present invention.

When the copy mode is the four-color mode (full color mode), Y (yellow), C (cyan), M (magenta), and B (black) single-color toner images are formed on the outer peripheral surface of each photosensitive drum 1, respectively. The single color toner images are sequentially superimposed and transferred onto the intermediate transfer belt 5 by the first transfer units 3 at the transfer position (primary transfer position). Then, the composite color image superimposed on the intermediate transfer belt 5 is moved in the direction indicated by the arrow A by the intermediate transfer belt 5 that is stretched around the driving roller 21 and the driven rollers 22 and 23 and rotated. At the next transfer position, the images are transferred onto the transfer paper P by a roller-like second transfer portion (transfer roller) 24.
When the copy mode is the single-color mode, the two-color mode, or the three-color mode, only a single color toner image of a necessary color is formed on the corresponding photosensitive drum 1 among the photosensitive drums 1. Become. The same applies to the following embodiments.
The transfer paper P onto which the composite color image has been collectively transferred is discharged out of the apparatus by a transport belt 26 stretched by a second transfer portion (transfer roller) 24 and a driven roller 25.

FIG. 2 is a diagram showing a configuration example of an image forming unit of a tandem type direct transfer type color image forming apparatus embodying the present invention, and portions corresponding to those in FIG.
This color image forming apparatus can be rotated independently of each other, and a plurality of photosensitive drums (first image carriers) 1 for forming different color monochrome toner images on the outer peripheral surface, and each of the photosensitive drums 1. A transfer conveyance belt 30 for transferring different color monochromatic toner images formed on the outer peripheral surface to the transfer paper P at transfer positions corresponding to the respective photosensitive drums 1 and direct transfer to the transfer paper P. Each transfer section (first transfer section) 3 to be performed and each contact / separation section 4 for moving the transfer section 3 up and down are provided.

Each transfer unit 3 is moved up and down by moving each contact / separation unit 4, and the transfer position on the outer peripheral surface of the transfer conveyance belt 30 and the outer peripheral surface of each photosensitive drum 1 are in contact with and separated from each other with the transfer paper P interposed therebetween. Is possible. The transfer contact / separation operation control of the color image forming apparatus is the same as the transfer contact / separation operation control of the color image forming apparatus described with reference to FIG.
Further, the transfer conveyance belt 30 is stretched between a driving roller 32 and a driven roller 33 that are rotated by a conveyance driving motor 153, and rotates in an arrow direction B.

FIG. 3 is a diagram showing a second configuration example of the image forming unit of the tandem indirect transfer type color image forming apparatus embodying the present invention, and the same reference numerals are given to portions corresponding to those in FIG.
The color image forming apparatus according to the third embodiment is independently rotatable and includes four photosensitive drums (first image carrier) for forming single-color toner images having different colors of Y, C, M, and B on the outer peripheral surface. Body) 1 (1Y, 1C, 1M, 1B) and the respective monochrome toner images formed on the outer peripheral surfaces of the two photosensitive drums 1Y, 1C of the four photosensitive drums 1, respectively. At the primary transfer positions P5 and P6, the two single-color toner images respectively formed on the outer peripheral surfaces of the remaining two photosensitive drums 1M and 1B are superimposed and transferred at the primary transfer positions P7 and P8, respectively. An intermediate transfer belt (second image carrier) 40 (40A, 40B), which is one intermediate transfer body, is provided.

Each intermediate transfer belt 40 (40A, 40B) is driven to rotate by each first intermediate transfer motor 154 (154A, 154B).
The color image forming apparatus includes first transfer units 3 (3Y, 3C, 3M, 3B) and contact / separation units 4 (4Y, 4C, 4M, 4B), and the copy mode is a four-color mode. A single-color toner image is formed on the outer peripheral surface of each photosensitive drum 1, each contact / separation portion 4 is moved to raise each first transfer portion 3, and a corresponding transfer position on the outer peripheral surface of each intermediate transfer belt 40. And the respective outer peripheral surfaces of the respective photosensitive drums 1 are brought into contact with each other, and the single color toner images on the outer peripheral surfaces of the respective photosensitive drums 1 are sequentially transferred to the outer peripheral surfaces of the two intermediate transfer belts 40 in two colors. .

The color image forming apparatus also includes a second intermediate image in which the two-color toner images transferred to the outer peripheral surfaces of the two intermediate transfer belts 40A and 40B are superimposed on the secondary transfer positions P9 and P10 and transferred to the outer peripheral surface. An intermediate transfer drum (third image carrier) 41 that is a transfer body is provided, and the intermediate transfer drum 41 is rotationally driven by a second intermediate transfer motor 155.
Further, a second transfer portion (transfer roller) 42 that transfers the composite color image superimposed on the outer peripheral surface of the intermediate transfer drum 41 to the transfer paper P at the tertiary transfer position P11, and a transport belt 43 that transports the transfer paper P. And.

The conveyor belt 43 is stretched between the driving roller 44 and the driven roller 45, and rotates in the arrow direction C when the driving roller 44 is rotated by the driving motor 156.
The transfer contact / separation operation control of the color image forming apparatus is the same as the transfer contact / separation operation control of the color image forming apparatus described with reference to FIG.

Next, a control system related to motor control in the color image forming apparatus shown in FIG. 1 will be described with reference to FIG. The control systems related to the motor control in the color image forming apparatus shown in FIGS. 2 and 3 are substantially the same, and the description of these control systems is omitted.
4 is a block diagram showing a configuration example of a control system related to motor control in the color image forming apparatus shown in FIGS. 1 to 3, and FIG. 5 is a schematic diagram showing an example of a rotation detector in the control system.

The color image forming apparatus shown in FIG. 1 includes an image forming apparatus control unit 200 and motor control units 211 (211Y, 211C, 211M, and 211B). It functions as clock generation means, drive control means, and registration adjustment means.
The image forming apparatus control unit 200 includes a CPU 201, a memory 202, and a clock generation circuit 203.
A CPU 201 is a central processing unit that comprehensively controls the entire color image forming apparatus.
The memory 202 is a storage means constituted by a ROM that stores a program including the program according to the present invention and other fixed data, a RAM that stores readable and writable data, a nonvolatile raw memory, and the like.

The clock generation circuit 203 is a means for generating various clocks including a reference PLL clock described later.
The image forming apparatus control unit 200 and each motor control unit 211 start / stop driving at least each motor 151 (151Y, 151C, 151M, 151B) to each motor control unit 211. For outputting a start / stop signal (START / STOP) to instruct, a speed signal (reference PLL clock) for controlling the speed of each motor 151, and a rotation direction signal (CW / CCW) for instructing the rotation direction of each motor 151 Connected via signal line. The image forming apparatus controller 200 and each motor controller 211 are connected to a power source and a ground, respectively.

Therefore, the image forming apparatus control unit 200 can individually set the rotation speed of each motor 151 with respect to each motor control unit 211, and can rotationally drive each motor 151 at a different speed. Further, each motor 151 is connected to each photosensitive drum 1 through a gear or the like, and is driven and transmitted.
The photosensitive drum 1Y is rotated by a motor 151Y, and the rotation is controlled by a motor control unit 211Y. The photosensitive drum 1C is rotated by a motor 151C, and the rotation is controlled by a motor control unit 211C. The photosensitive drum 1M is rotated by a motor 151M, and the rotation is controlled by a motor control unit 211M. The photosensitive drum 1B is rotated by a motor 151B, and the rotation is controlled by a motor control unit 211B.

  For example, a rotating plate 300 as shown in FIG. 5 is attached to the central axis of each photosensitive drum 1. In the vicinity of the outer periphery of each rotary plate 300, four slits 301 are arranged at intervals of 90 degrees (predetermined angular intervals). Further, in order to detect these slits 301, two FSP sensors (rotation detectors composed of photosensors) 302 are arranged at intervals of 180 degrees (predetermined angular intervals) facing the vicinity of the outer periphery of each rotary plate 300. Has been. Therefore, each FSP sensor 302 outputs 4 pulses per rotation of the photosensitive drum 1. Further, a home position sensor for detecting a slit (home position slit) 301 at the home position (home position) at the same time as the FSP sensor 302 immediately below the FSP sensor 302 disposed near the transfer position of the rotating plate 300. 303 is also provided. The home position slit 301 has a longer length in the longitudinal direction than the other three slits 301 so that it can be detected by the home position sensor 303.

  Note that the four slits 301 can be arranged at intervals of 90 degrees near the outer periphery of the end surface of the photosensitive drum 1. In that case, in order to detect each slit 301, two FSP sensors 302 are arranged at an interval of 180 degrees so as to face the vicinity of the outer periphery of the end surface of the photosensitive drum 1. Further, instead of the slit 301, another detected part such as a mark can be used. Furthermore, a sensor (detection means) other than the FSP sensor 302 can be used. Furthermore, the number of detected parts such as slits and the number of sensors and the arrangement angle interval may be changed.

On the other hand, encoders 152 (152Y, 152C, 152M, 152B) are respectively attached to the shafts of the motors 151, and PLL (Phase Locked Loop) control of the motors 151 is performed by the output pulses of the encoders 152. Can do.
Further, the exposure position (position exposed by the exposure unit 9) and the transfer position (position where the toner image formed on the outer peripheral surface of the photosensitive drum 1 is transferred to the intermediate transfer belt 5 on the outer peripheral surface of each photosensitive drum 1. The measurement sensors 304 are respectively disposed so as to face the surface between them. The measurement sensor 304 detects toner adhering to the outer peripheral surface of the photosensitive drum 1 (the output changes with respect to the toner), whereby the transfer timing (the outer periphery of the photosensitive drum 1 is changed) from the exposure timing by the exposure unit 9. This is used to measure the time until the toner image formed on the surface is transferred to the intermediate transfer belt 5.

Here, processing related to PLL control of the motor 151 (reference clock generation, motor drive, etc.) will be described with reference to FIG. Since the processes related to the four motors 151 are the same, only the process related to one motor 151 will be described here.
FIG. 6 is a timing chart showing an example of the relationship between signals generated during the PLL control of the motor 151.
The image forming apparatus control unit 200 outputs a target PLL reference clock to the motor control unit 211 to drive the motor 151.

Next, the interval between the output pulses of the FSP sensor 302 from the time point when the home position slit 301 (home position) of the rotating plate 300 (home position) is detected by the FSP sensor 302 (not shown) is measured clock generator (of the clock generation circuit 203 of FIG. 4). Time is measured by detecting a measurement clock (waveform 3) generated from a part), and pulse intervals T1, T2, T3 (waveform 2) are determined.
Then, A and a (waveform 4) are derived from Equation 1, and the fluctuation waveform of one round (one rotation) of the assumed photosensitive drum 1 is calculated.

Subsequently, a reference PLL clock (waveform 6) is generated so as to cancel the calculated fluctuation component, and the pulse width is written in the memory (RAM) 202 in order from the home position and stored.
After measuring the rotational fluctuation of the photosensitive drum 1 in this way and storing the measurement result (pulse width of the reference PLL clock) in the memory 202, the reference PLL clock having the pulse width is output and is output to the shaft of the motor 151. PLL control is performed via the motor control unit 211 so that the phase coincides with the output signal (waveform 5) of the encoder 152 provided, and the motor 151 is driven to rotate.
The above-described rotation fluctuation measurement of the photosensitive drum 1 is performed at the time of color misregistration measurement or factory shipment, and the measurement result is stored in the memory 202. However, the measurement result at the time of factory shipment is stored in the nonvolatile raw memory.

FIG. 7 shows the fluctuation component of one rotation of each photosensitive drum 1 related to the PLL control of the four motors 151 that respectively rotate and drive the four photosensitive drums 1 (1Y, 1C, 1M, 1B).
As described above, the image forming apparatus control unit 200 generates a reference PLL clock so as to cancel the fluctuation component for each photosensitive drum 1, and the fluctuation component (rotation) of one rotation of each photosensitive drum 1. A start signal for instructing the start of driving of each motor 151 is output so that the phases (a, -b, c, -d) of (variation) are matched.

FIG. 8 is a block diagram for explaining the details of the processing by the drive control unit that performs phase adjustment and variable speed of each motor 151. For convenience of illustration, illustration of the motor control units 211C and 211M and their peripheral portions is omitted.
The drive control unit 500 corresponds to a part that performs processing related to PLL control of each motor 151 of the image forming apparatus control unit 200 of FIG. The function as the drive control unit 500 can be realized by the CPU 201, the memory 202, and the clock generation circuit 203.
The drive control unit 500 performs the following processing.

For example, when the phases of the photosensitive drums 1 (1Y, 1C, 1M, 1B) of the respective colors are matched with the Y photosensitive drum 1Y as a reference, the rotation of the photosensitive drums 1 of the respective colors is adjusted to the Y phase. The rotational speed of each motor 151 is adjusted so that the phases of the four photosensitive drums 1 coincide.
When the four phases coincide with each other, each reference PLL clock is generated from the data stored in the memory 202 (measurement result of the rotation variation of each photosensitive drum 1), and is output to each motor control unit 211.

Each motor control unit 211 is configured by a dedicated IC, and the phase (frequency) of the reference PLL clock input from the drive control unit 500 and the phase of the output signal of the encoder 152 attached to the shaft of the motor 151 ( The PLL control of the corresponding motor 151 is performed so that the frequency matches, but when the phase matches (LOCKs), the PLL LOCK signal is output to the drive control unit 500.
When the LOCK signal is input from all the motor control units 211, the drive control unit 500 determines that image formation is possible.

Further, development is performed from the exposure timing, and the time until the toner image formed thereby is detected by the measurement sensor 304 is calculated from the pulse width of the reference PLL clock stored in the memory 202. Since the time from the detection of the toner image by the measurement sensor 304 to the transfer position can be calculated from the design, the time from the exposure position to the transfer position can be determined. However, the mounting position of the measurement sensor 304 and the accuracy of the measurement sensor 304 are required.
Then, the color misregistration is reduced by adjusting the rotation speed of the photosensitive drum 1 of each color so that the time from the exposure position of each color to the transfer is matched. The rotation target speed of the photosensitive drum 1 of each color is determined by a speed magnification determined by a preset target speed, and when the pulse width of the reference PLL clock stored in the memory 202 is read, the clock multiplied by the speed magnification is used. It becomes the width and the speed setting value.

FIG. 9 is a diagram for explaining each color station and pattern for detecting color misregistration.
The image forming apparatus control unit 200 shown in FIG. 4 includes a station for each color of Y (yellow), C (cyan), M (magenta), and B (black) and a pattern (detection pattern) for detecting a color (position) deviation of each color. P1 and P2 are transferred onto the intermediate transfer belt 5. For example, in the case of the detection pattern P1, a pattern is formed by superimposing the colors Y, C, and M on the basis of the B color and changing the overlapping amount little by little. The detection pattern P1 is irradiated with light from a light source 501 that is an LED or LD (laser diode), the reflected light is detected by a photosensor 502, and the amount of deviation from the target position of each color is detected using the detected amount. calculate.

When the detection pattern P2 is used, a certain line (detection pattern P2) is transferred onto the intermediate transfer belt 5 of each color in the main scanning direction, which is a direction orthogonal to the rotation direction of the intermediate transfer belt 5. The line transferred onto the intermediate transfer belt 5 is irradiated with light from the light source 501, the reflected light is detected by the photosensor 502, and the amount of deviation is calculated from the target position of the line (detection pattern P2). To do.
Further, there is a method in which a color CCD is used as a color (position) deviation detection method, and the color (position) deviation of each color is detected from the output result of RGB.
Note that the image forming apparatus control unit 200, the light source 501, and the photosensor 502 function as color misregistration amount detection means.

The present invention can be implemented by the above configuration and operation control.
In this way, each photoconductor drum 1 (first image carrier) is rotationally driven by a gear or the like to each color motor (photoconductor drive motor) 151, and the phase of the rotational fluctuation of each photoconductor drum 1 is matched. In addition, since the rotational speed is differentiated, it is possible to reduce the color misregistration caused by the fluctuation component of one rotation of the photosensitive drum 1 with an inexpensive and energy-saving device.

  As is apparent from the above description, according to the present invention, it is possible to reduce color misregistration caused by a fluctuation component of one turn of the first image carrier. Therefore, if this invention is used, a high-performance and highly reliable color image forming apparatus capable of forming a color composite image without color misregistration can be provided.

1 is a diagram illustrating a first configuration example of an image forming unit (image forming unit) of a tandem indirect transfer type color image forming apparatus embodying the present invention. 1 is a diagram illustrating a configuration example of an image forming unit of a color image forming apparatus of a tandem type direct transfer system embodying the present invention. It is a figure which shows the 2nd structural example of the image creation part of the color image forming apparatus of a tandem type indirect transfer system which implements this invention. FIG. 4 is a block diagram illustrating a configuration example of a control system related to motor control in the color image forming apparatus illustrated in FIGS. 1 to 3. It is the schematic which shows an example of the rotation detector in the control system of FIG.

FIG. 6 is a timing diagram illustrating an example of a relationship between signals generated during PLL control of each motor 151 in FIG. 5. FIG. 6 is a timing chart showing a fluctuation component of one rotation of each photosensitive drum 1 related to PLL control of each motor 151 that rotationally drives each photosensitive drum 1 in FIG. 5. FIG. 6 is a block diagram for explaining details of processing by a drive control unit that performs phase alignment and variable speed of each motor 151 in FIG. 5. It is a figure for demonstrating the station and pattern of each color for detecting a color shift.

Explanation of symbols

1 (1Y, 1C, 1M, 1B): photoconductor drum 2 (2Y, 2C, 2M, 2B): developing unit 3 (3Y, 3C, 3M, 3B): first transfer unit (transfer unit)
4 (4Y, 4C, 4M, 4B): contact / separation portions 5, 40 (40A, 40B): first intermediate transfer belt (intermediate transfer belt)
6: Charging unit 7: Cleaning unit 8: Neutralizing unit 9: Exposure unit 21, 32, 44: Driving roller 22, 23, 25, 33, 45: Driven roller 24, 42: Second transfer unit (transfer roller) 26, 43: Conveying belt 30: Transfer conveying belt 41: Intermediate transfer drum 50: Second intermediate transfer belt 61: Third transfer unit (transfer roller)
151 (151Y, 151C, 151M, 151B): Motor 152 (152Y, 152C, 152M, 152B): Encoder 200: Image forming apparatus controller 201: CPU 202: Memory 203: Clock generation circuit 211 (211Y, 211C, 211M, 211B): motor control unit 300: rotating plate 301: slit 302: FSP sensor 303: home position sensor 304: measurement sensor
500: Drive control unit 501: Light source 502: Photo sensor

Claims (2)

A plurality of motors for independently rotating the plurality of first image carriers;
A plurality of exposure means for exposing the outer peripheral surfaces of the plurality of first image carriers respectively rotated by the motors;
A plurality of developing means for developing a portion exposed by each of the exposure means with a single color toner of a different color to form a single color toner image;
A tandem type image forming apparatus including: a transfer unit configured to form a composite color image by sequentially superimposing and transferring each single color toner image formed by each developing unit on the outer peripheral surface of the second image carrier or a transfer sheet on the outer peripheral surface; A color image forming apparatus,
And forming a plurality of detected portions at predetermined angular intervals around the periphery of the rotating plate mounted respectively to the axis of the end faces or the respective first image bearing member of the first image bearing member, the respective detection target portion to detect, it arranged a plurality of the detection means at predetermined angular intervals so as to face respectively the the outer periphery near the end surface or the rotating plate of each of the first image bearing member,
Storage means for calculating and storing a rotational fluctuation component generated by one rotation of each first image carrier in response to a plurality of output signals output from each detection means during one rotation of each first image carrier. When,
Reference clock generation means for generating a reference clock for canceling the fluctuation component from the rotation fluctuation component of one rotation of each of the first image carriers stored in the storage means ;
Start signal output means for outputting a start signal to each of the motors so as to match the phase of the rotational fluctuation component of one rotation of each of the first image carriers stored in the storage means;
And drive control means for the driving and controlling the motors based on the reference clock generated by the reference clock generating means
Color image forming apparatus, wherein a is provided. The color image forming apparatus according to claim 1.
And time measuring means for measuring the respective time from the exposure timing by the exposure unit to the transfer timing of each of the transfer means relative to each first image bearing member,
A reference speed setting means for setting each of said reference speed of each motor so that each time fits measured by the time measuring means
Color image forming apparatus according to claim, further provided with.