JP2001083761A - Multicolor image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure the distance between color smear detecting patterns. SOLUTION: In a multi color image forming device where the color smear detecting patterns 109 and 110 are formed by a 1st and a 2nd image forming means Y and M on an intermediate transfer belt 7, an optical sensor 108 to detect passage of patterns 109 and 110, an encoder 111 attached to a driving roll 11 driving the intermediate transfer belt 7 and a counter counting the number of pulse outputted from the encoder 111 before the 2nd pattern is detected after the 1st pattern is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type multicolor image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art FIGS. 9 and 10 are views for explaining a color shift amount detecting mechanism in a conventional multicolor image forming apparatus. First, here, in a multicolor image forming apparatus using four color toners of yellow, magenta, cyan, and black, the time difference between the vertical synchronization signals of yellow and magenta is adjusted to reduce the amount of color shift between yellow and magenta. The color misregistration detection mechanism to be measured will be described.

In FIG. 9, an endless image conveying means, that is, an intermediate transfer belt 705 as an intermediate transfer member is stretched over a driving roller 706, a driven roller 711, and a secondary transfer facing roller, and rotated in the direction of the arrow. Intermediate transfer belt 7
Along the plane portion 05, a first image forming unit 7Y having a photosensitive drum 701 for developing yellow toner, a second image forming unit 7M having a photosensitive drum 702 for developing magenta toner, A third image forming unit 7C having a photosensitive drum 703 for developing toner and a fourth image forming unit 7K having a photosensitive drum 704 for developing black toner are juxtaposed at a predetermined interval. Note that, in FIG. 9, a primary charger, an exposure device, a developing device, a transfer device, and a cleaning device constituting each image forming unit are omitted.

Further, in the vicinity of the black photosensitive drum 704, an intermediate transfer belt 70 is formed by yellow toner.
5, a yellow color misregistration detection pattern 709, which is a first pattern image for position detection, and a second position detection image formed on the intermediate transfer belt 705 with magenta toner. An LED 707 and an optical sensor 708 for detecting a magenta color misregistration detection pattern 710 as a pattern image are arranged.

As shown in FIG. 10, a conventional color misregistration detecting mechanism 800 includes an optical sensor 708 that generates an extremely low level detection signal of a color misregistration detection pattern 709, 710 formed on an intermediate transfer belt 705. An amplifier 802 that amplifies and outputs an extremely low level detection signal output from the optical sensor 708, a binarization circuit 803 that converts an analog signal output from the amplifier 802 into a digital signal, and outputs a digital signal, and a reference signal Generating circuit 806, 2
The count start / stop signal is input from the value conversion circuit 803,
Further, the encoder pulse signal output from the reference signal generation circuit 806 is input as a clock, and is output from the reference signal generation circuit 806 from when the magenta color shift detection pattern is detected to when the yellow color shift detection pattern 710 is input. Counter circuit 804, MPU 805, MP that counts how many encoder pulses are input
A vertical synchronization signal of yellow is input from U805,
Also, a counter pulse is input from the reference signal generation circuit 806 as a clock, the count value is reset at the point in time when the yellow vertical synchronization signal is input, and the counter circuit 807 counts the reference pulse output from the reference signal generation circuit 806. , The number of reference pulses counted by the counter circuit 804 from the detection of the magenta color misregistration detection pattern to the input of the yellow detection pattern from the MPU 805.
7, a count value obtained by counting reference pulses output from the reference signal generation circuit 806 during an actual printing operation is input, and a comparison is made between them. When the number of encoder pulses becomes large, a magenta vertical synchronization signal is output. Circuit 808 for outputting a signal, and a memory 813 capable of reading and writing
It has. Note that the counter circuit 809 and the comparison circuit 810, and the counter circuit 811 and the comparison circuit 81 in FIG.
2 has substantially the same functions as the counter circuit 807 and the comparison circuit 808.

In the above configuration, when the control for measuring the amount of color misregistration is started, the photosensitive drums 701 to 704 of each color and the driving roller 706 are rotated in the direction of the arrow, and the driving roller 706 is rotated.
And the intermediate transfer belt 705 rotates.
Then, the yellow color misregistration detection pattern 70 is formed on the intermediate transfer belt 705 by the yellow photosensitive drum 701.
9, a magenta color misregistration detection pattern 710 on the intermediate transfer belt 705 by the magenta photosensitive drum 702
At the same time. Next, the LED 707 is turned on, and the light from the LED 707 is reflected by the intermediate transfer belt 705 and enters the optical sensor 708. And
When the color shift detection pattern of magenta passes below the optical sensor 708 due to the rotation of the intermediate transfer belt 705, the light reflected by the intermediate transfer belt 705 is reduced by the optical sensor 7.
08 to detect. Then, a counting operation for counting the reference pulse output by the reference signal generating circuit 806 by the counter circuit 804 is started from the time when the magenta color misregistration detection pattern is detected by the optical sensor 708.

The yellow color misregistration detection pattern 7
When the light source 09 passes under the light sensor 708, the light sensor 708 detects that the reflected light from the intermediate transfer belt 705 decreases, and after detecting the magenta color shift detection pattern 710, the yellow color shift detection pattern 709. The counter circuit 804 counts the number of pulses output by the reference signal generation circuit 806 during the time until the detection of, and outputs the number of pulses to the MPU 805. M
The PU 805 calculates the distance between the color misregistration detection patterns from the count value input from the counter circuit 804 and the rotation speed of the driving roller 706, stores the distance in the memory 813, and ends the color misregistration amount measurement control.

[0008]

However, in a color image forming apparatus provided with a conventional color misregistration detection mechanism, a reference is required between the time when a yellow color misregistration detection pattern is detected and the time when a magenta color misregistration detection pattern is detected. The distance between the yellow color misregistration detection pattern and the magenta color misregistration detection pattern was calculated from the number of reference pulses output from the signal generation circuit 806 and the rotation speed of the drive roller 706 driving the intermediate transfer belt 705. However, there is a problem that the calculated distance is affected by an error in the rotational speed of the intermediate transfer belt 705 or uneven speed, and the distance between the color misregistration detection patterns cannot be calculated accurately.

Accordingly, an object of the present invention is to provide a multicolor image forming apparatus provided with a color misregistration amount detection mechanism capable of accurately measuring the distance between position detection pattern images.

[0010]

The above object is achieved by a multicolor image forming apparatus according to the present invention. In summary, the present invention provides a first image forming unit that forms an image corresponding to image information and also forms a first pattern image for position detection, and an image forming unit that forms an image corresponding to image information. A second pattern image that also forms a second pattern image for position detection.
Image forming means, the first image forming means and the second
Endless image conveying means sequentially passing through the image forming means,
A multicolor image forming apparatus comprising: means for detecting a distance between the first and second pattern images formed on the endless image conveying means at a distance in an image conveying direction. Means for detecting the distance between the pattern images of
A movement detecting means capable of detecting a movement of the image on the endless image carrying means, and a first means for generating a pulse signal based on the detection of the movement detecting means when the image on the endless image carrying means moves. Pulse signal generating means, second pulse signal generating means for generating a pulse signal when the first and second pattern images are detected, and the second pulse based on the result of detecting the first pattern image From detecting the pulse output from the signal generating means to detecting the pulse output from the second pulse signal generating means based on the result of detecting the second pattern image,
And a measuring means for counting the number of pulses generated by the first pulse generating means.

[0011] Based on the distance between the pattern images detected by the means for detecting the distance between the first and second pattern images, respective ones of the first image forming means and the second image forming means are determined. It is preferable to have a correction unit that corrects at least one of the image formation start timing and the image formation reference clock. The endless image conveying means is preferably an endless belt for conveying a recording medium. According to another aspect, it is preferable that the endless image forming unit is an intermediate transfer belt. According to still another aspect, it is preferable that the endless image conveying means is an intermediate transfer drum.

Preferably, the endless image conveying means is driven by a driving roller having a driving shaft, and the movement detecting means is a rotational position detecting means mounted on a shaft interlocked with the driving shaft. According to another aspect, the movement detecting means includes a position detection mark previously attached at equal intervals on the endless image conveying means, and the position detection mark when the image on the endless image conveying means moves. And a detection signal generating means for generating a detection signal when the detection is made.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multicolor image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

In the description of the present embodiment, in particular, in a multicolor image forming apparatus using four color toners of yellow, magenta, cyan and black, the time difference between the vertical synchronizing signals of yellow and magenta is adjusted to adjust the yellow and magenta. A method for measuring and correcting the color shift amount of the image will be described.

First, a multicolor image forming apparatus according to the present embodiment will be described with reference to FIGS.

The multicolor image forming apparatus according to the present embodiment includes an intermediate transfer body as an intermediate transfer member serving as an endless image conveying means for image forming stations Y, M, C, and K for yellow Y, magenta M, cyan C, and black K. The transfer belt 7 has a configuration in which the transfer belt 7 is juxtaposed along a plane portion.

Each image forming station Y, M, C, K
Are photosensitive drums 1Y, 1M, which are image carriers, respectively.
1C and 1K, around which charging device 2
Y, 2M, 2C, 2K, exposure devices 3Y, 3M, 3C, 3
K, developing devices 4Y, 4M, 4C, and 4K, and cleaning devices 6Y, 6M, 6C, and 6K.

In the above configuration, each photosensitive drum 1
Y, 1M, 1C and 1K are charged by charging devices 2Y, 2M, 2C and 2
After uniform charging with K, the exposure devices 3Y, 3
M, 3C and 3K, respectively, the photosensitive drum 1Y, 1
A latent image corresponding to the color information of each color is formed on M, 1C, and 1K. Thereafter, each latent image is visualized as a toner image by a developer (toner) by the developing devices 4Y, 4M, 4C, and 4K.

The toner images developed on the photosensitive drums 1Y, 1M, 1C, and 1K are temporarily transferred onto the intermediate transfer belt 7 by primary transfer devices 5Y, 5M, 5C, and 5K connected to high-voltage power supplies (not shown). Is primary-transferred.

On the other hand, the transfer material P is transported by the paper feed roller 9 to the secondary transfer portion T2 in synchronization with the timing of the leading edge image on the intermediate transfer belt 7.

The toner image on the intermediate transfer belt 7 is secondarily transferred from the intermediate transfer belt 7 to the transfer material P by a secondary transfer device 10 connected to a high-voltage power supply (not shown). Subsequently, the transfer material P on which the secondary transfer has been performed is conveyed to the fixing device 8, where the toner image is fixed.

After the primary transfer, each of the photosensitive drums 1Y, 1M,
The toner remaining on 1C and 1K is removed from each cleaning device 6.
Removed by Y, 6M, 6C, 6K.

Next, the features of this embodiment will be described.

As shown in FIG. 1, an image is formed on the intermediate transfer belt 7 near the black photosensitive drum 1K.
An LED 107 and an optical sensor 108 for detecting a yellow color misregistration detection pattern 109 as a first pattern image for position detection and a magenta color misregistration detection pattern 110 as a second pattern image for position detection are arranged. Have been.

On the rotating shaft 11a of the driving roller 11, a movement detecting means, that is, a rotary encoder 111 as a rotational position detecting stage is provided. The rotary encoder 111 is composed of a disc-shaped thin plate 113 having a slit 112 and a sensor 114 having a light emitting unit and a light receiving unit fixed to the main body. Light is emitted from the light emitting unit of the sensor 114 toward the side surface of the thin plate 113. To detect whether light passes through the slit 112 provided on the thin plate 113 and is incident on the light receiving portion on the opposite side, thereby detecting passage of the slit.

FIG. 3 is a block diagram of a color misregistration amount detection mechanism according to the present embodiment.

In FIG. 3, the color misregistration amount detection mechanism 200
Is a color shift detection pattern 10 on the intermediate transfer belt 7.
9 and 110, an optical sensor 201 for generating an extremely low-level detection signal, an amplifier 202 for amplifying and outputting an extremely low-level detection signal output from the optical sensor 108, and an analog signal output from the amplifier 202 as a digital signal. Binarizing circuit 20 which outputs a digital signal after conversion to
3. Rotary encoders 111, 2 provided on a rotating shaft 11a of a driving roller 11 for driving the intermediate transfer belt 7.
The count start / stop signal is input from the value conversion circuit 203,
Further, the encoder pulse signal output from the rotary encoder 111 is input as a clock, and the encoder pulse signal output from the rotary encoder 111 from the detection of the magenta color shift detection pattern 110 to the input of the yellow color shift detection pattern 109 is input. A vertical synchronization signal of yellow is input from a counter circuit 204, an MPU 205, and an MPU 205 as a measuring means for counting the number of input signals.
A counter circuit 207 that inputs an encoder pulse as a clock from the clock 11 and resets a count value when a yellow synchronization signal is input, counts an encoder pulse output from the rotary encoder 111, and a color shift of magenta from the MPU 205. After inputting the detection pattern 110, the yellow detection pattern 10
Inputting the number of encoder pulses counted by the counter circuit 207 before inputting 9, and inputting a count value obtained by counting the encoder pulses output from the rotary encoder 111 during the actual printing operation from the counter circuit 207; A comparison circuit 208 for outputting a magenta vertical synchronizing signal when the number of encoder pulses is increased by comparing the two, and the counting circuit 207
The counter circuit 209 has a function similar to that of the comparison circuit 208. The count circuit 209 and the comparison circuit 210 output a cyan vertical synchronization signal. The count circuit 211 and the comparison circuit 212 output a black vertical synchronization signal.・
A writable memory 213 is provided.

In the above configuration, when the control for measuring the amount of color misregistration is started, the photosensitive drums 1Y, 1M, 1C, and 1K for the respective colors
Then, the drive roller 11 is rotated in the direction of the arrow, and the intermediate transfer belt 7 is driven by the rotation of the drive roller 11. Then, an image of a yellow color shift pattern 109 is formed on the intermediate transfer belt 7 from the yellow photosensitive drum 1Y, and a color shift pattern 110 of magenta is formed on the intermediate transfer belt 7 from the magenta photosensitive drum 1M.
Next, the LED 107 is turned on, and the light from the LED 107 is reflected by the intermediate transfer belt 7 and is incident on the optical sensor 108. When the color shift pattern of magenta passes below the optical sensor 108 due to the rotation of the intermediate transfer belt 7, the optical sensor 108 detects that the reflected light from the intermediate transfer belt 7 decreases. Then, the optical sensor 10
From the time when the magenta color misregistration detection pattern 110 is detected by 8, a counting operation is started by the counter circuit 204, which counts the pulses output from the rotary encoder 111 and detected by passing through the slit 112.

Then, the yellow color misregistration detection pattern 1
When 09 passes below the optical sensor 108, the counting operation of the number of times that the slit 112 output by the rotary encoder 111 has passed is stopped when the optical sensor 108 detects that the reflected light from the intermediate transfer belt 7 decreases. Then, the counter circuit 204 counts the number of pulses output by the rotary encoder 111 during the time from when the magenta color shift detection pattern 110 is detected to when the yellow color shift detection pattern 109 is detected, and the number of pulses is counted. Output to MPU 205. MP
U205 stores the count value input from the counter circuit 204 in the memory 213, and ends the color shift amount measurement control.

Next, when the original image forming operation starts,
The MPU 205 outputs a yellow vertical image synchronization signal, and the counter circuit 207 resets the count value when the yellow vertical image synchronization signal is input, inputs an encoder pulse, and compares the count value with a comparison circuit 208. The comparison circuit 208 receives an input from the rotary encoder 111 during the time from the detection of the magenta color shift detection pattern 110 measured in the color shift amount measurement control by the MPU 205 to the detection of the yellow color shift detection pattern 109. Input from the counter circuit 207, and outputs a magenta vertical image synchronizing signal based on the comparison result of the number of encoder pulses during the printing operation. Works.

By the same color shift amount measurement control and image forming operation, the time difference between the magenta vertical image synchronizing signal and the cyan vertical image synchronizing signal, and the time difference between the cyan and black vertical image synchronizing signals are obtained. By controlling the time difference, the amount of color misregistration of the image forming operation of all colors is measured,
And can be corrected.

As described above, according to this embodiment, the distance between the color misregistration detection patterns can be accurately measured.

In the above embodiment, the time difference between the yellow vertical synchronizing signal and the magenta vertical synchronizing signal, the time difference between the magenta and cyan vertical synchronizing signals, and the vertical difference between the cyan and black vertical signals. The method of adjusting the time difference between the synchronization signals has been described. However, this is not the case with other colors, such as the time difference between the vertical synchronization signals of yellow and cyan, the time difference between the vertical synchronization signals of yellow and black, and the vertical direction of magenta black. The time difference of the synchronizing signal can be adjusted in the same manner as in the above-described embodiment, and furthermore, the distance between each color is measured at the same time.
Various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIGS. In the description of the present embodiment, in particular, in a multicolor image forming apparatus using four color toners of yellow, magenta, cyan, and black, the time difference between the vertical synchronization signals of yellow and magenta is adjusted to adjust the color shift between yellow and magenta. A method for detecting the amount will be described.

FIG. 4 shows a multicolor image forming apparatus according to this embodiment.

In FIG. 4, yellow Y, magenta M,
Cyan C, black K image forming stations Y, M,
A configuration is provided in which C and K are juxtaposed along a paper transport belt 27 which is an endless image transport means stretched over a driving roller 31 and a driven roller 32. Each of the image forming stations Y, M, C, and K includes a photosensitive drum 21Y, 21
M, 21C and 21K, around which charging devices 22Y, 22M, 22C and 22K and an exposure device 23, respectively.
Y, 23M, 23C, 23K, developing devices 24Y, 24
M, 24C, 24K, and a cleaning device 26Y,
26M, 26C and 26K are provided.

Each of the image forming stations Y,
In M, C, and K, the photosensitive drums 21Y, 21M, 2
1C and 21K are charged to the charging devices 22Y, 22M, 22C and 22
Exposure devices 23Y, 23M, 23C, 2
3K, the photosensitive drums 21Y, 21M, 21C, 21
K is caused to form a latent image corresponding to the color information of each color. afterwards,
Each of the latent images is visualized as a toner image with toner by the developing devices 24Y, 24M, 24C, and 24K.

Next, each of the photosensitive drums 21Y, 21M,
Transfer Devices 25Y and 25 Opposed to 21C and 21K
Each of the photosensitive drums 21Y, 21Y on the transfer material P sucked and conveyed to the transfer conveyance belt 27 by M, 25C, and 25K.
The toner images formed on 21M, 21C, and 21K are superimposed and transferred, and the unfixed toner image is fixed on the transfer material P by a fixing device 28 as a fixing unit.

After the transfer, each of the photosensitive drums 21Y, 21M,
The cleaning device 2 removes the toner remaining on 21C and 21K.
Removed by 6Y, 26M, 26C, 26K.

As shown in FIG. 5, in the vicinity of the black photosensitive drum 304, a yellow color misregistration detection pattern 309 formed on the paper transport belt 305 by yellow toner and a magenta toner A first LED for detecting a magenta color misregistration detection pattern 310 having an image formed on the paper transport belt 27 by the
307, an optical sensor 308, and a second LED 312 and a second optical sensor 313 for detecting a position detection mark 311 provided in advance on the paper transport belt 27 are arranged.

FIG. 6 is a block diagram of the color misregistration amount detection mechanism according to this embodiment.

In FIG. 6, a color shift amount detection mechanism 400
Is a color shift detection pattern 30 on the paper transport belt 27.
9, 310 which generate the very low level detection signal.
, An amplifier 402 that amplifies and outputs an extremely low level detection signal output from the first optical sensor 308, and converts an analog signal output from the amplifier 402 into a digital signal, and then outputs a digital signal. 2
The digitizing circuit 403, the second optical sensor 313 and the second optical sensor 31 that detect the position detection mark 311 disposed on the paper transport belt 27 and generate an extremely low level detection signal.
An amplifier 414 that amplifies and outputs an extremely low-level detection signal output from 3; a binarization circuit 415 that outputs a digital signal after converting an analog signal output from the amplifier 414 into a digital signal; The count start / stop signal is input from the circuit 403 and the binarization circuit 4
15, the detection signal of the position detection mark 311 output as a clock is input, the magenta color shift detection pattern 310 is detected, and then the yellow color shift detection pattern 3 is detected.
The counter circuit 404 counts the number of encoder pulses output from the binarization circuit 415 until the input of the input signal 09, the MPU 405, and the MPU 405 input a yellow vertical synchronization signal. , The detection signal of the position detection mark 311 is input as a clock, the count value is reset at the time when the yellow vertical synchronization signal is input, and the detection signal of the position detection mark 311 output from the binarization circuit 415 is counted. The number of encoder pulses counted by the counter circuit 404 from the input of the magenta color misregistration detection pattern 309 to the input of the yellow detection pattern 309 from the counter circuit 407 and the MPU 405 Binary conversion during actual printing operation A count value obtained by counting the detection signals of the position detection mark 311 output from 415 is input, and a comparison is made between them to output a magenta vertical synchronization signal when the number of detection signals of the position detection mark 311 increases. The comparison circuit 408, the counter circuit 407, and the comparison circuit 408, which have the same functions as the above-described counter circuit 408, output the synchronization signal in the vertical direction of cyan and the comparison circuit 410, and output the synchronization signal in the vertical direction of black. The circuit includes a circuit 411, a comparison circuit 412, and a readable / writable memory 413.

In the above arrangement, when the control for measuring the amount of color misregistration starts, the photosensitive drums 21Y, 21M, 21
C, 21K and the drive roller 31 are rotated in the direction of the arrow, and driven by the rotation of the drive roller 31, the paper transport belt 2 is rotated.
7 rotates. Then, the yellow photosensitive drum 21Y
Accordingly, the yellow color misregistration detection pattern 309 is simultaneously formed on the paper conveyance belt 27 and the magenta color misregistration detection pattern 310 is simultaneously formed on the paper conveyance belt 305 by the magenta photosensitive drum 21M. Next, the first LED 3
07 is turned on, the light from the first LED 307 is reflected by the paper transport belt 305, and is incident on the first optical sensor 308. Then, the rotation of the paper transport belt 27 causes the magenta color misregistration detection pattern 310 to be detected by the first optical sensor 3.
08, the first optical sensor 308 detects that the light reflected by the paper transport belt 27 decreases. Also, the second LED 312 is turned on, and the second LED 312 is turned on.
312 is reflected by the paper transport belt 27,
The light enters the second optical sensor 313. When the color shift detection pattern 310 of magenta passes under the first optical sensor 308 due to the rotation of the paper transport belt 305, the second optical sensor 308 detects that the reflected light by the paper transport belt 305 decreases. I do. The counter circuit 404 counts the number of pulses detected by the passage of the position detection mark 311 output by the second optical sensor 313 from the time when the magenta color misregistration detection pattern is detected by the first optical sensor 308. Start.

Then, the yellow color shift detection pattern 3
When the first optical sensor 308 detects that the reflected light from the paper transport belt 27 decreases when the optical sensor 09 passes under the first optical sensor 308, the pulse output from the second optical sensor 313 changes. The counting operation is stopped, and the counter circuit 404 counts the number of pulses output by the binarization circuit 415 during the time from the detection of the magenta color shift detection pattern 310 to the detection of the yellow color shift detection pattern 309. I do. The counter circuit 404 outputs the count value to the MPU 405,
In step 05, the count value input from the counter circuit 404 is stored, and the color shift amount measurement control ends.

When the original image forming operation starts,
The MPU 405 outputs a yellow vertical image synchronization signal, and the counter circuit 407 resets the count value when the yellow vertical image synchronization signal is input, inputs an encoder pulse, and compares the count value with the comparison circuit 408. Output to The comparison circuit 408 is an MPU 405
From the second optical sensor 313 that has detected the position detection mark 31 during the time from the detection of the magenta color shift detection pattern 310 measured in the color shift amount measurement control to the detection of the yellow color shift detection pattern 109. The number of input encoder pulses is input, and the count value of the pulses detected by the position detection mark 311 during the printing operation is input from the counter circuit 407. Based on the comparison result of the numbers, the vertical direction of magenta is determined. In order to output the image synchronization signal.

By the same color shift amount measurement control and image forming operation, the time difference between the magenta vertical image synchronizing signal and the cyan vertical image synchronizing signal, and the time difference between the cyan and black vertical image synchronizing signals. , It is possible to measure and correct the color shift amount of the image forming operation for all colors.

As described above, according to this embodiment, the distance between the color misregistration detection patterns can be accurately measured.

In the above-described embodiment, the time difference between the yellow vertical synchronizing signal and the magenta vertical synchronizing signal, the time difference between the magenta and cyan vertical synchronizing signals, and the vertical difference between cyan and black The method of adjusting the time difference between the synchronization signals has been described. However, this is not the case with other colors, such as the time difference between the vertical synchronization signals of yellow and cyan, the time difference between the vertical synchronization signals of yellow and black, and the vertical direction of magenta black. The time difference between the synchronization signals can be adjusted in the same manner as in the above-described embodiment, and the distance between the colors can be measured at the same time.
Various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIGS. In the description of the present embodiment, in particular, in a multicolor image forming apparatus using four color toners of yellow, magenta, cyan, and black, the time difference between the vertical synchronization signals of yellow and magenta is adjusted to adjust the color shift between yellow and magenta. A method for detecting the amount will be described.

FIG. 7 schematically shows a multicolor image forming apparatus of this embodiment.

In FIG. 7, an intermediate transfer drum 505 as an intermediate transfer body as an endless image conveying means is rotated in the direction of an arrow. A photoreceptor drum 501 for forming an image using yellow toner, a photoreceptor drum 502 for forming an image using magenta toner, and an image forming using cyan toner along the peripheral surface of the intermediate transfer drum 505. And a photosensitive drum 504 for forming an image with black toner are arranged side by side at a predetermined interval. A charging device, an exposure device, a developing device, and a cleaning device that contribute to image formation are arranged around each of the photosensitive drums 501 to 504, but are omitted in the drawing. Similarly, a transfer device for transferring the toner image transferred from the photosensitive drums 501 to 504 to the intermediate transfer drum 505 onto a recording material, and a fixing device for fixing the toner image to the recording material are also omitted in the drawing. ing.

In the vicinity of the black photosensitive drum 504, a yellow color misregistration detection pattern 50 formed on the intermediate transfer drum 505 with yellow toner is formed.
9 and the intermediate transfer drum 5 with magenta toner.
05, a magenta color misregistration detection pattern 510, and a yellow and magenta color misregistration detection pattern 50
An LED 507 and an optical sensor 508 for detecting 9, 510 are arranged. Further, the intermediate transfer drum 50
A rotary encoder 511 is provided at one end of a drive shaft 506 that drives the motor 5. Rotary encoder 5
Eleven. Disc-shaped thin plate 513 having slit 512
And a sensor 514 having a light-emitting unit and a light-receiving unit fixed to the main body. Light is emitted from the light-emitting unit of the sensor 514 toward the side surface of the thin plate 513, and transmitted through a slit 512 provided on the thin plate 513. Then, by detecting whether or not light has entered the opposite light receiving portion, the passage of the slit 512 is detected.

FIG. 8 is a block diagram of the color misregistration amount detection mechanism according to this embodiment.

In FIG. 8, a color misregistration amount detecting mechanism 600 is shown.
The color shift detection pattern 5 on the intermediate transfer drum 505
09, 510 for generating an extremely low level detection signal, an amplifier 602 for amplifying and outputting an extremely low level detection signal output from the optical sensor 508, and an analog signal output from the amplifier 602 as a digital signal. Binarization circuit 6 which outputs a digital signal after conversion to
03, drive shaft 506 for driving the intermediate transfer drum 505
A count start / stop signal is input from the rotary encoder 511 provided above, a binarization circuit 603, an encoder pulse signal output from the rotary encoder 511 is input as a clock, and a magenta color shift detection pattern 510 is input. By the time the rotary encoder 51
A counter circuit 604 for counting the number of encoder pulses output from 1; an MPU 605;
A vertical synchronization signal of yellow is input from the MPU 605, a reference pulse is input as a clock from the rotary encoder 511, and the count value is reset when the vertical synchronization signal of yellow is input, and is output from the rotary encoder 511. The number of encoder pulses counted by the counter circuit 604 from the input of the magenta color misregistration detection pattern 510 from the MPU 605 to the input of the yellow detection pattern 509 from the MPU 605, A count value obtained by counting reference pulses output from the rotary encoder 511 during an actual printing operation is input from the counter circuit 607, and the count value is compared. When the number of encoder pulses becomes large, the magenta vertical synchronization signal is input. 608, which has the same functions as the counting circuit 607 and the comparing circuit 608, and outputs a synchronizing signal in the vertical direction of cyan and a comparing circuit 610, and outputs a synchronizing signal in the vertical direction of black. Counting circuit 611 and comparing circuit 61
2 and a readable / writable memory 613.

In the above configuration, when the control for measuring the amount of color misregistration starts, the photosensitive drums 501 to 504 and the drive shaft 506 of each color are rotated in the direction of the arrow, and the intermediate transfer drum 505 is driven by the rotation of the drive shaft 506. Rotate. Then, a yellow color misregistration detection pattern 509 is formed on the intermediate transfer drum 505 by the yellow photosensitive drum 501, and a magenta color misregistration detection pattern 510 is formed on the intermediate transfer drum 505 by the magenta photosensitive drum 502 at the same time. Next, the LED 507 is turned on and LE
The light from D 507 is reflected by the intermediate transfer drum 505 and is incident on the optical sensor 508. Then, the rotation of the intermediate transfer drum 505 causes the magenta color shift pattern 5 to move.
When the light 10 passes below the optical sensor 508, the optical sensor 508 detects that the reflected light from the intermediate transfer drum 505 decreases. Then, from the point when the magenta color shift detection pattern 509 is detected by the optical sensor 508,
The counter circuit 604 starts a counting operation of counting the pulses output from the rotary encoder 511 and detected by passing through the slit 512.

Then, the yellow color misregistration detection pattern 5
When the optical sensor 508 detects that the reflected light from the intermediate transfer drum 505 decreases when the optical sensor 09 passes under the optical sensor 508, the counting operation of the number of times the slit 512 output by the rotary encoder 511 has passed is stopped. Then, the counter circuit 604 counts the number of pulses output by the rotary encoder 511 during the time from when the magenta color misregistration detection pattern 510 is detected to when the yellow color misregistration detection pattern 509 is detected. Output to MPU 605.
The MPU 605 stores the count value input from the counter circuit 604 in the memory 613, and ends the color shift amount measurement control.

When the original image forming operation starts,
The MPU 605 outputs a yellow image synchronization signal in the vertical direction, and the counter circuit 607 resets the count value when the yellow image synchronization signal is input, inputs an encoder pulse, and compares the count value with the comparison circuit 608. The comparison circuit 608 receives an input from the rotary encoder 511 during the time from the detection of the magenta color shift detection pattern 510 measured in the color shift amount measurement control by the MPU 605 to the detection of the yellow color shift detection pattern 509. The number of encoder pulses thus input is input, and the count value of the encoder pulse 511 during the printing operation is input from the counter circuit 607, and a magenta vertical image synchronization signal is output based on the comparison result of the numbers. Works like that.

By the same color shift amount measurement control and image forming operation, the time difference between the magenta vertical image synchronizing signal and the cyan vertical image synchronizing signal, and the time difference between the cyan and black vertical image synchronizing signals. , It is possible to measure and correct the color shift amount of the image forming operation for all colors.

As described above, according to this embodiment, the distance between the color misregistration detection patterns can be accurately measured.

In the above-described embodiment, the time difference between the vertical synchronizing signal for yellow and the vertical synchronizing signal for magenta, the time difference for the vertical synchronizing signal between magenta and cyan, and the vertical difference between cyan and black. The method of adjusting the time difference between the synchronization signals has been described. However, this is not the case with other colors, such as the time difference between the vertical synchronization signals of yellow and cyan, the time difference between the vertical synchronization signals of yellow and black, and the vertical direction of magenta black. The time difference of the synchronizing signal can be adjusted in the same manner as in the above-described embodiment, and furthermore, the distance between each color is measured at the same time.
Various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0062]

As is apparent from the above description, according to the multicolor image forming apparatus of the present invention, the means for detecting the distance between the first and second pattern images is provided on the endless image conveying means. Movement detection means capable of detecting movement of the image, first pulse signal means for generating a pulse signal based on the detection of the movement detection means when the image on the endless image conveyance means moves, A second pulse signal generating means for generating a pulse signal when the first and second pattern images are detected, and detecting a pulse output from the second pulse generating means based on a result of detecting the first pattern image Then, the number of pulses generated by the first pulse generation means is counted during a time period until the detection of the pulse output from the second pulse generation means based on the result of detecting the second pattern image. Total By having a means,,
The distance between pattern images for detecting color misregistration can be accurately calculated, and a high-quality image can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a main part of a multicolor image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a multicolor image forming apparatus according to a first embodiment.

FIG. 3 is a block diagram of a color misregistration amount detection mechanism according to the first embodiment.

FIG. 4 is an explanatory diagram illustrating a main part of a multicolor image forming apparatus according to a second embodiment.

FIG. 5 is a configuration diagram illustrating a multicolor image forming apparatus according to a second embodiment.

FIG. 6 is a block diagram of a color misregistration amount detection mechanism according to a second embodiment.

FIG. 7 is an explanatory diagram illustrating a main part of a multicolor image forming apparatus according to a third embodiment.

FIG. 8 is a block diagram of a color misregistration amount detection mechanism according to a third embodiment.

FIG. 9 is an explanatory diagram illustrating an example of a conventional multicolor image forming apparatus.

FIG. 10 is a block diagram illustrating an example of a conventional color misregistration amount detection mechanism.

[Explanation of symbols]

7 Intermediate Transfer Belt (Intermediate Transfer Body / Endless Image Conveying Means) 27 Paper Conveying Belt (Endless Image Conveying Means) 111 Rotary Encoder
Moving means) 204 Counter circuit (measuring means) Y, M, C, K Image forming means

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA16 DA38 DA50 DE02 DE04 EB04 EC03 EC06 EC20 ED02 ED06 ED24 EE01 EE02 EE03 EE04 EE07 EF09 2H030 AA01 AB02 AD12 AD17 BB23 BB42 BB53 BB56 2H032 AA05 BA01 BA01 BA01 BA01 BA08

Claims (7)

[Claims] A first image forming means for forming an image corresponding to the image information and also forming a first pattern image for position detection; and forming an image corresponding to the image information and detecting the position. Image forming means for also forming a second pattern image for use, an endless image conveying means sequentially passing through the first image forming means and the second image forming means, and an endless image conveying means Means for detecting the distance between the first and second pattern images formed on the image at a distance in the image transport direction, wherein the distance between the first and second pattern images is Means for detecting the movement of the image on the endless image conveying means, and a pulse based on the detection of the movement detecting means when the image on the endless image conveying means moves. Generate signal A first pulse signal generating means for detecting the first and second pattern images, a second pulse signal generating means for generating a pulse signal when detecting the first and second pattern images, and a second pulse signal generating means for detecting the first pattern image. 2 from the detection of the pulse output from the second pulse signal generation means to the detection of the pulse output from the second pulse signal generation means based on the result of detection of the second pattern image. And a measuring means for counting the number of pulses generated by the first pulse signal generating means. 2. A method according to claim 1, wherein said first image forming means and said second image forming means determine a distance between said first and second pattern images based on a distance between said pattern images detected by said means for detecting a distance between said first and second pattern images. 2. The multicolor image forming apparatus according to claim 1, further comprising a correction unit configured to correct at least one of a start timing of each image formation and a reference clock of the image formation. 3. The multicolor image forming apparatus according to claim 1, wherein said endless image conveying means is an endless belt for conveying a recording medium. 4. The multicolor image forming apparatus according to claim 1, wherein said endless image forming means is an intermediate transfer belt. 5. The multicolor image forming apparatus according to claim 1, wherein said endless image conveying means is an intermediate transfer drum. 6. The endless image conveying means is driven by a driving roller having a driving shaft, and the movement detecting means is a rotational position detecting means mounted on a shaft interlocked with the driving shaft. The multicolor image forming apparatus according to any one of claims 1 to 5, wherein 7. The movement detecting means detects a position detection mark previously attached at equal intervals on the endless image conveying means and the position detection mark when an image on the endless image conveying means moves. 6. A multicolor image forming apparatus according to claim 1, further comprising: a detection signal generating means for generating a detection signal.