JP2003202723A - Color drift correction unit and color image forming device having the unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately correct color drift even in the case an amount of color drift is large. <P>SOLUTION: A color drift correction unit 40 has a detecting part which detects a reference toner pattern transferred to a transfer body and a toner pattern used for the detection of color drift. The unit 40 also has an optical path scanning part 41 which corrects color drift by adjusting an image forming position on a photoreceptor drum 1 in relation to the transfer body. The unit 40 further has a CPU 71 which calculates an amount of color drift from the detection result of the detecting part and corrects the color drift by controlling the optical path scanning part 41 based upon the calculated amount of color drift. In the case the amount of color drift exceeds a prescribed value, the CPU corrects color drift again. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color misregistration correction device for correcting color misregistration of a color image composed of a plurality of colors.
The present invention relates to a color image forming apparatus such as a color printer or a color copying machine which has the color misregistration correction device and forms a color image with little color misregistration.

[0002]

2. Description of the Related Art Conventionally, for example, an electrophotographic color image forming apparatus has a plurality of image forming portions each having a photosensitive drum and is provided on a recording material held on a conveyor belt for speeding up. Images of different colors are sequentially formed. The recording material is a material on which an image is formed, and includes, for example, paper, thin resin paper which is a substitute for paper, paper for overhead projectors, envelopes, sheets and the like.

A color image forming apparatus having a plurality of image forming portions may cause color misregistration (positional deviation), in which images of a plurality of colors do not match and the images are misaligned.

That is, in the color image forming apparatus, due to mechanical precision or the like, uneven rotation of a plurality of photosensitive drums or uneven movement of the conveyor belt occurs, and the outer peripheral surface of each photosensitive drum and the conveyor belt at the transfer position are different from each other. The relative positional relationship may be different for each color, and when the color images are superposed, they may not coincide with each other, resulting in color misregistration (positional misregistration).

In particular, in a color image forming apparatus having a plurality of image forming sections each having a laser scanner as an optical section and a photosensitive drum, there is an error in the distance between the laser scanner and the photosensitive drum for each image forming section. When this error differs between the image forming units, the scanning width of the laser on the photosensitive drum differs for each photosensitive drum, which may cause color misregistration.

FIGS. 16A, 16B, 16C, and 16D show colors in the main scanning direction (direction intersecting the recording material conveyance direction) or the sub-scanning direction (recording material conveyance direction). It is a figure showing various examples when there is a gap. In the figure, reference numeral 7
Indicates the original image position. Reference numerals 8a, 8b, 8
Reference characters c and 8d indicate image positions when color misregistration occurs. In order to make it easier to understand the state of color misregistration,
The two positions 7, 8a, 8b, 8c, 8d are drawn in the sub-scanning direction away from the actual state.

FIG. 16A is a diagram showing a case where a color shift occurs due to a tilt shift of a scanning line. Misalignment of the scanning lines occurs when the optical unit and the photosensitive drum are not arranged in parallel with each other. In this case, the color misregistration can be eliminated by adjusting the positions of the optical unit and the photosensitive drum or the position of the lens of the optical unit to correct the scanning line in the arrow direction.

FIG. 16B is a diagram showing a case where a color shift occurs due to variations in scanning line width (length in the main scanning direction). The variation in scanning line width occurs when the distance between the laser scanner and the photosensitive drum has an error with respect to the regular distance. In this case, fine adjustment of the image frequency (if the scanning width is long, the frequency is increased) is used to correct the width of the scanning line in the direction of the arrow, and the width of the scanning line is changed to the regular width, thereby eliminating color misregistration. It can be resolved.

FIG. 16C is a diagram showing a case where a color shift occurs due to an error in the writing start position of the main scanning line in the scanning direction. If the optical unit is a laser scanner, the error in the writing start position can be corrected by adjusting the writing start timing from the beam detection position and changing the position of the scanning line in the arrow direction. By correcting the scanning position, the color shift can be eliminated.

FIG. 16D is a diagram showing a case where a color shift occurs due to an error in the writing start position of the scanning line in the sub-scanning direction. The error of the writing start position can be corrected in the arrow direction by adjusting the writing start timing of each color from the detection of the leading edge of the recording material.

To correct these color shifts, for example,
As shown in FIG. 3, a color misregistration detection pattern is formed on the conveyor belt 3 for each color, and the color is detected by a pair of optical sensors 6a and 6b fixedly provided on both sides of the downstream portion of the conveyor belt 3. The deviation detection pattern is detected, and various adjustments as described above are performed according to the detected deviation amount.

Sub-scanning direction color shift detection patterns 9a, 9
b, 9c, 9d, 10a, 10b, 10c, 10d are
It is a pattern for detecting the amount of color misregistration in the sub-scanning direction. Main scanning direction color misregistration detection patterns 11a, 11b, 11c, 1
1d, 12a, 12b, 12c, and 12d are patterns for detecting the amount of color misregistration in the main scanning direction, and in this example, they are inclined by about 45 degrees with respect to the recording material conveyance direction. The auxiliary symbols a, b, c, and d are black (hereinafter, “B
k), yellow (hereinafter “Y”), magenta (hereinafter “M”), and cyan (hereinafter “C”).

Reference numerals tsf1 to tsf4, tmf1 to tmyf4, tsr1 to tsr4, tmr1 to tm
r4 indicates the detection timing of each pattern. The arrow indicates the moving direction of the conveyor belt 3.

The moving speed of the conveyor belt 3 is vmm / s, B
With k as a reference color, color shift patterns 9b, 9 in the sub-scanning direction
The theoretical distances between the colors c, 9d, 10b, 10c, 10d and the Bk sub-scanning direction color shift patterns 9a, 10a are set to dsYmm, dsMmm, dsCmm, and the sub-scanning direction color shift detection patterns 9a, 9b for the respective colors are set. , 9c, 9d,
10a, 10b, 10c and 10d and main scanning direction color misregistration detection patterns 11a, 11b, 11c, 11d and 12a.
The measured distances between 12b, 12c, and 12d are set to d
mfBkmm, dmfYmm, dmfMmm, dmfC
mm, dmrBkmm, dmrYmm, dmrMmm,
When dmrCmm is set, the color shift amounts δesY, δesM, and δesC of the respective colors in the sub-scanning direction are: δesY = v * {(tsf2-tsf1) + (tsr2-tsr1)} / 2−dsY (Formula 1) δesM = V * {(tsf3-tsf1) + (tsr3-tsr1)} / 2−dsM (Equation 2) δesC = v * {(tsf4-tsf1) + (tsr4-tsr1)} / 2−dsC (Equation 3) ).

With respect to the main scanning direction, the color shift amounts δemf and δemr for each of the left and right colors are as follows: dmfBk = v * (tmf1-tsf1) (Equation 4) dmfY = v * (tmf2-tsf2) (Equation 5) dmfM = v * (Tmf3-tsf3) (Equation 6) dmfC = v * (tmf4-tsf4) (Equation 7) and dmrBk = v * (tmr1-tsr1) (Equation 8) dmrY = v * (tmr2-tsr2) (Equation 9) ) DmrM = v * (tmr3-tsr3) (Equation 10) dmrC = v * (tmr4-tsr4) (Equation 11) From, δemfY = dmfY-dmfBk (Equation 12) δemfM = dmfM-dmfBk (Equation 13 = δem) dmfC-dmfBk (Equation 14) and δemrY = dmrY-dmrBk (Equation 15) δemrM = dmrM-dm Become bk (Equation 16) δemrC = dmrC-dmrBk (Equation 17).

Therefore, the deviation direction can be determined from the positive or negative of the calculation result, and δemfY, δemfM, δemfC, δ.
From the emrY, δemrM, and δemrC, the writing start position is (δemrY−δemfY), (δemrM−δe
The main scanning width of each color is corrected from (mfM) and (δemrC−δemCf).

[0017]

However, in the conventional color image forming apparatus, depending on the color misregistration correction method, when the color misregistration amount becomes large and the correction amount becomes large, the correction error increases and the color misregistration correction accuracy increases. Was sometimes reduced. In particular,
The effect of the means for actuating the lens or the mechanical mechanism using the actuator is large.

Therefore, there has been proposed a color image forming apparatus capable of performing a coarse adjustment mode and a fine adjustment mode in the color misregistration correction operation. However, since this color image forming apparatus always performs the color misregistration correction operation in the coarse adjustment mode and the fine adjustment mode, it requires a long time for the color misregistration correction. Furthermore, a complicated judgment is required as to whether or not to carry out the coarse adjustment mode.

According to the present invention, a plurality of color misregistration correction operations are not performed, the color misregistration correction operation time is shortened in most color misregistration correction operations, and the judgment criterion is not complicated.
Provided are a color misregistration correction device that can perform color misregistration correction with high accuracy even when the amount of color misregistration is large, and a color image forming apparatus that includes the color misregistration correction device in the apparatus main body to form a color image with less color misregistration. The purpose is to

[0020]

In order to achieve the above object, the color misregistration correction apparatus according to the present invention is a reference in which a toner image formed for each of a plurality of image forming units is transferred to a transfer-receiving member to which the toner images are sequentially transferred. A color misregistration correction device that detects a toner pattern and a color misregistration detection toner pattern to correct color misregistration, and detects the reference toner pattern and the color misregistration detection toner pattern transferred to the transfer target. Means, a color shift correcting means for correcting the color shift by correcting the image forming position of the image forming means with respect to the transferred material, and a color shift amount calculated from the detection result of the detecting means, and the calculated color shift A correction control unit that controls the color misregistration correction unit based on the amount to correct the color misregistration, and the correction control unit again corrects the color misregistration when the color misregistration amount exceeds a specified value. I'll do It has become.

When the correction control means of the color misregistration correction device of the present invention performs the color misregistration correction again, the detection means:
The reference toner pattern and the color misregistration detection toner pattern formed again on the transfer target are detected.

The color misregistration correction means of the color misregistration correction device of the present invention has a plurality of types, and the correction control means selectively selects the plurality of types of color misregistration correction means based on the detection result of the detection means. It is designed to be used.

The color misregistration correction means of the color misregistration correction device according to the present invention has a mechanical mechanism section that is operated by an actuator section, and the correction control section controls the actuator section based on the detection result of the detection section. The color misregistration correction is performed under control.

There are a plurality of types of the color misregistration correction means of the color misregistration correction device of the present invention, and among the plurality of color misregistration correction means,
At least one color misregistration correction unit has a mechanical mechanism unit that is operated by an actuator unit, and the correction control unit selectively uses the plurality of types of color misregistration correction units based on the detection result of the detection unit. It is supposed to do.

The color misregistration correction means of the color misregistration correction device according to the present invention includes color misregistration correction means for correcting color misregistration in the main scanning direction, color misregistration correction means for correcting color misregistration in the sub-scanning direction, and There is a color misregistration correction unit that corrects color misregistration in both the scanning direction and the sub-scanning direction.

There are a plurality of types of the color shift correction means of the color shift correction apparatus of the present invention, and at least one of the color shift correction means operates under the control of the correction control means to operate the optical path of the image exposure. It has an optical path operation unit that operates.

The optical path operating unit of the color misregistration correction device of the present invention includes a correction lens disposed between the exposure unit and the toner image carrier and capable of changing the direction of the exposure, and the correction lens. And an actuator portion that is displaced in a direction intersecting the optical path.

The optical path operating unit of the color misregistration correction device of the present invention is a correction lens which is arranged between the exposure unit and the toner image carrier and is capable of changing the scanning width of the exposure in the main scanning direction. , And an actuator section for moving the correction lens toward and away from the toner image carrier.

The specified value of the color misregistration correction device of the present invention is
It is a value of the color shift amount due to the inclination of the color shift detection toner pattern with respect to the reference toner pattern in the sub-scanning direction.

The specified value of the color misregistration correction device of the present invention is
It is a value of a color misregistration correction amount due to an inclination of the color misregistration detection toner pattern with respect to the reference toner pattern in the sub-scanning direction.

The specified value of the color misregistration correction device of the present invention is
This is the value of the color shift amount due to the difference in the main scanning direction width of the color shift detection toner pattern with respect to the reference toner pattern.

The specified value of the color misregistration correction device of the present invention is
This is a value of a color misregistration correction amount due to a difference in width in the main scanning direction of the color misregistration detection toner pattern with respect to the reference toner pattern.

The specified value of the color misregistration correction device of the present invention is
This is the value of the color shift amount due to the position shift of the color shift detection toner pattern with respect to the reference toner pattern in the main scanning direction.

The specified value of the color misregistration correction device of the present invention is
This is a value of a color misregistration correction amount due to a misregistration in the main scanning direction of the color misregistration detection toner pattern with respect to the reference toner pattern.

The specified value of the color misregistration correction device of the present invention is
It is a value of a color shift amount due to a position shift of the color shift detection toner pattern with respect to the reference toner pattern in the sub-scanning direction.

The specified value of the color misregistration correction device of the present invention is
It is a value of a color shift correction amount due to a position shift of the color shift detection toner pattern with respect to the reference toner pattern in the sub-scanning direction.

In order to achieve the above object, the color image forming apparatus of the present invention is provided with a plurality of exposure units that emit light of image information, and the exposure units are provided corresponding to the respective exposure units. A plurality of toner image carriers capable of carrying toner images of different colors that have been exposed to light and a color misregistration correction device of any one of the above are provided, and the toner image of the toner image carrier is transferred to the transfer target. It has become.

The transfer medium of the color image forming apparatus of the present invention is a conveyor belt for sequentially conveying the recording material to the plurality of toner image carriers.

The transfer medium of the color image forming apparatus of the present invention is a recording medium placed on a conveyor belt and sequentially conveyed to the plurality of toner image carriers.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color printer which is a color image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings. The color printer of the present embodiment has four embodiments for the color misregistration correction operation, but the operations for forming an image on a recording material are all the same. Therefore, first, the configuration and operation for forming an image on a recording material will be described, then the configuration and operation of the color misregistration correction device will be described, and finally, the color misregistration correction operation of the four embodiments will be described. In addition, the same formula as the conventional one is used as it is. Further, the same parts are designated by the same reference numerals.

(Color Printer) FIG. 1 is an overall schematic perspective view of a color printer which is a color image forming apparatus according to an embodiment of the present invention.

The color printer 30 has four colors, that is,
Black (Bk), Yellow (Y), Magenta (M),
Cyan (C) image forming units (image forming means) 31B
k, 31Y, 31M, 31C, and the image forming unit 31 of each color
An endless conveyor belt 3 which also serves as a transfer belt for sequentially conveying the recording material P to C, 31M, 31Y and 31Bk;
A drive roller 4 which is connected to a drive unit (not shown) composed of a motor, a gear, etc. and circulates the conveyor belt 3, and the conveyor belt 3
The driven roller 5 that follows the rotation of the conveyor belt 3 and applies a constant tension to the conveyor belt 3, and the pattern for detecting the color shift formed on the conveyor belt 3 that is fixedly provided on both sides of the conveyor belt 3 are detected. A detection unit (detection means) 6 having a pair of optical sensors 6a and 6b is provided.

Image forming units 31Bk, 31Y, 31M, 3
1C is a photosensitive drum (toner image carrier) 1Bk, 1Y, 1M, 1C on which an electrostatic latent image is formed, and an electrostatic latent image is formed on the photosensitive drum 1Bk, 1Y, 1M, 1C by performing exposure according to an image signal. Laser scanner (exposure unit) 2Bk, 2 for forming an image
It is equipped with Y, 2M, 2C and the like.

When data to be printed is sent from a personal computer (PC) (not shown), the color printer 30 finishes image formation according to the printer engine system and becomes ready for printing. Then, the color printer 30 supplies the recording material P to the conveyor belt 3 from a recording material cassette (not shown). The conveyor belt 3 transfers the recording material P to the image forming portions 31C, 31M, 31Y of the respective colors.
It is sequentially transported to 31 Bk. On the other hand, the image signals of the respective colors are sent to the laser scanners 2C, 2M, 2Y and 2Bk at the same timing as the conveyance of the recording material P by the conveying belt 3. An electrostatic latent image is formed on the photosensitive drums 1C, 1M, 1Y, 1Bk, and a toner image is developed by a developing device (not shown). The toner image is transferred to the recording material P by a transfer unit (not shown).

The color printer according to the present embodiment is Bk,
The toner images are sequentially transferred to the recording material P in the order of Y, M, and C colors. Note that the order of colors is not limited to this order. After that, the recording material P is separated from the conveyor belt 3, the toner image is fixed by heat by a fixing device (not shown), and the recording material P is discharged to the outside.

The image forming section does not have to include the image forming sections for four colors. A black image forming unit 31Bk that serves as a color reference and an image forming unit for at least one other color may be provided.

(Color misregistration correction device) FIGS. 2 (a) and 2
FIG. 16B is a correction of inclination in the sub-scanning direction according to the embodiment of the present invention (for example, correction corresponding to FIG. 16A) and correction of main scanning line width (overall magnification in the main scanning direction) (for example, FIG.
FIG. 7 is a schematic diagram of a color misregistration correction device that performs (correction corresponding to (b)).

The color misregistration correction device 40 includes an optical path operation unit (color misregistration correction means) 41 shown in FIG. 2 and an engine control unit 78 shown in FIG. The engine control unit 78 may include at least the CPU 71.

As shown in FIG. 3, on the conveyor belt (transferred body) 3, the image forming portions 31Bk, 31Y, 31 are formed.
Sub-scanning direction color shift detection patterns 9a, 9b, 9c, 9d, 10a, 10 for detecting the amount of color shift in the sub-scanning direction by the photosensitive drums 1Bk, 1Y, 1M, 1C of M and 31C.
b, 10c, 10d, and main-scanning-direction color shift detection patterns 11a, 11b, 11c, 11 for detecting the amount of color shift in the main scanning direction by inclining about 45 degrees with respect to the recording material P transport direction.
It is assumed that d, 12a, 12b, 12c and 12d are formed.

Among the plurality of sub-scanning direction color misregistration detection patterns, the patterns indicated by reference numerals 9a and 10a are reference patterns (reference toner patterns), and the remaining reference numerals 9b and 9a.
The patterns indicated by c, 9d, 10b, 10c and 10d are
It is a detection pattern (color shift detection toner pattern).

Further, among the plurality of main-scanning-direction color misregistration detection patterns, the patterns denoted by reference numerals 11a and 12a are reference patterns (reference toner patterns), and the remaining reference numeral 1
The patterns indicated by 1b, 11c, 11d, 12b, 12c and 12d are detection patterns (color shift detection toner patterns).

These detection patterns may be formed on the recording material (transferred material) P conveyed by the conveyor belt 3 by the photosensitive drums 1Bk, 1Y, 1M and 1C.

The optical path operating unit 41 of the color misregistration correction device 40 is
The image forming unit 31 is incorporated between the laser scanner 2 and the photosensitive drum 1. The laser scanner 2 has a polygon mirror 13 and a folding mirror 14.

The optical path operating section 41 of the color misregistration correction device 40 is
A correction lens 15 that corrects the inclination of the main scanning line and the width of the main scanning line, a tilt correction motor (actuator unit) 17 that is a drive source that tilts (displaces) the correction lens 15,
A tilt correction cam 18 for tilting the correction lens 15 by rotating the motor 17 and a holding unit 16 are provided. The holding unit 16 holds a correction lens 15, a motor 17 for tilt correction, and a cam 18 for tilt correction. The main scanning width correction motor (actuator unit) 19 has a screw 20 for moving the holding unit 16 up and down. When the screw 20 rotates, the correction lens 15 moves toward and away from the photosensitive drum 1.

Correction of inclination of main scanning line (see FIG. 16 for example)
The correction corresponding to (a) is performed as follows.
One of the correction lenses 15 is in contact with a cam 18 attached to the output rotation shaft 17a of the motor 17. When the motor 17 operates and the cam 18 rotates, one end of the correction lens 15 moves in the rotation direction of the photosensitive drum 1. The incident position of the laser beam (exposure) L deflected by the polygon mirror 13 and reflected by the folding mirror 14 is the photosensitive drum 1.
2A to the front and back direction of the paper surface of FIG. That is,
The correction lens 15 changes the direction of the laser light (exposure) L.

When the correction lens 15 tilts to the right in FIG. 2B, the incident position on the photosensitive drum 1 also moves to the right.
In this way, by operating the motor 17 according to the detected color shift amount, the inclination in the sub-scanning direction can be corrected. Therefore, the correction lens 15, the motor 17, the cam 1
Reference numeral 8 and the like constitute color misregistration correction means for correcting the inclination of the main scanning line in the sub-scanning direction.

The main scanning line width correction is performed as follows (for example, the correction corresponding to FIG. 16B). Holding part 16
Is connected to the output rotary shaft of the main scanning width correction motor 19 via a screw 20. When the motor 19 operates and the output shaft rotates, the holding portion 16 moves up and down by the screw 20, and the correction lens 15 moves up and down. The ratio of the optical path length between the correction lens 15 and the folding mirror 14 and the optical path length between the correction lens 15 and the photosensitive drum 1 changes. Since the laser light is refracted by the correction lens 15, when the ratio changes, the scanning width of the laser light (exposure) L on the photosensitive drum 1 changes. When the correction lens 15 moves to the upper side, the scanning width on the photosensitive drum 1 becomes shorter. When moved to the lower side, the scanning width becomes wider. In this way, by operating the motor 19 according to the detected color shift amount, the main scanning width can be corrected. Therefore, the correction lens 15, the screw 20, the motor 19 and the like constitute color misregistration correction means for correcting the width of the main scanning line.

FIG. 4A is a graph for explaining the correction error of the width in the main scanning direction (for example, the correction corresponding to FIG. 16B). FIG. 4B is a graph for explaining the correction error of the tilt in the sub-scanning direction (for example, the correction corresponding to FIG. 16A). The motor 19 (M
1) and 17 (M2), and the vertical axis shows the color shift correction amount.

Both the movement amount and the correction amount are relative amounts with reference to before the start of movement (0). The straight lines a and d indicate the ideal correction amount for the movement amount. Straight lines b, c, e, f
Indicates the actual correction amount for the operation amount. Δb, Δ
c, Δe, and Δf represent correction errors for the movement amounts M1 and M2.

Dimensional error between the screw 20 and the cam 18,
Due to the optical error of the correction lens 15, the motor 19,
The correction amounts of the main scanning width and the tilt with respect to the operation (rotation) amount of 17 are different from the ideal values. The error amount increases as the operation amount increases.

6 to 8 show correction of the writing position in the sub-scanning direction according to the embodiment of the present invention (for example, FIG. 16).
It is a figure explaining the control regarding the correction equivalent to (d). The block diagram of FIG. 6 and the block diagram of FIG. 9 described later are partially the same, and are incorporated in the image formation control unit (color misregistration correction unit) 72 of FIG.

The horizontal sync signal from the horizontal sync signal generator 51 is sent to the polygon motor phase controller 53 which controls the polygon motor driver 52. The horizontal synchronization signal is output for each surface of the polygon mirror 13 in synchronization with the rotation of the polygon mirror 13 driven by the polygon motor drive unit 52. The horizontal synchronization signal is used to control the image forming position in the main scanning direction. The image data is transmitted to the laser scanner in synchronization with the horizontal synchronizing signal output line by line in the image forming area. A vertical synchronization signal from a counter (not shown) in the CPU (correction control means) 71 of FIG.
It is generated in synchronization with the conveyance of the recording material in the sub-scanning direction, and is used to control the image forming position in the sub-scanning direction.

The detected color shift amount is, for example, reference numeral 9a,
Reference numerals 9b, 9c, 9d, 10b, 10c, and 10d are used for the sub-scanning direction color misregistration detection pattern of the reference color 10a.
The detection pattern color indicated by is 9/4 (that is, 2 (1 /
4)) If there is a line error, correct it as follows.
However, at this time, if the above-described inclination correction in the sub-scanning direction has been performed, the correction operation is performed by calculating a correction amount that also takes into consideration the variation amount of the write start position due to the inclination correction.

For example, as shown in FIG. 8, the color shift in the unit of one line is corrected by increasing or decreasing the count number of the horizontal synchronizing signal from the vertical synchronizing signal to the start of the image formation in the unit of line. . For example, when delaying by two lines, the count number of the horizontal synchronizing signal from the vertical synchronizing signal to the start of image formation is set to +2. Correction within one line is performed by controlling the surface phase of the polygon.

The reference horizontal synchronization signals of the reference horizontal synchronization signal generation unit 54 are four signals generated by the internal timer of the CPU 71 of the printer at equal intervals during one line period. The surface phase of the polygon is controlled so that the horizontal synchronizing signal of each color is synchronized with a desired phase among the four phases of the reference horizontal synchronizing signal. So if you want to delay 1/4 line,
As shown in FIG. 8, the reference phase is switched from the 1/4 phase to the 2/4 phase. Therefore, the CPU 71, the image formation control unit 72, and the like constitute a color misregistration correction unit that corrects the writing start position in the sub-scanning direction.

FIGS. 9 and 10 show correction of the write start position in the main scanning direction according to the embodiment of the present invention (for example, FIG. 16C).
FIG. 6 is a diagram for explaining an operation regarding correction (corresponding to the above). The image processing unit 73 in FIG. 9 shows a part of the image processing unit 73 in FIG.

When the detected color shift amount has an error of 9/4 (that is, 2 (1/4)) dots in the detected color with respect to the reference color, the correction is performed as follows. For example, the amount of color misregistration in 1-dot units is obtained by changing the count number of the image clock from the horizontal synchronization signal of the horizontal synchronization signal generation unit 51 to the position where image data transmission is started (the position where image formation is started). To do. For example, when delaying by 2 dots, the count number is set to +2. Correction within 1 dot is performed by controlling the synchronization phase of the horizontal synchronization signal. The sampling clock shown in FIG. 10 of the video clock generation unit 55 has a frequency four times that of the image clock in order to control the synchronization phase of the horizontal synchronization signal. Of the four clocks from the rising edge of the horizontal synchronizing signal, the image clock (4
Output) to control the phase of the image clock with respect to the horizontal synchronizing signal. Therefore, in the case of delaying by 1/4 dot, the sampling phase is switched from 1/4 phase to 2/4 phase as shown in FIG.

Based on the signal from the video clock generator 55, the video data generator 56 drives the laser drive 57.
Drive control.

In FIG. 5, the pattern detection control unit 74 of the engine control unit 78 outputs the detection signal of the detection unit 6 to the CPU 7
It is supposed to be sent to 1. Color misregistration correction value holding unit 75
Stores the color shift correction amount calculated by the COU 71. The memory 76 is adapted to store specified values and the like described later. The CPU 71 detects detection patterns (color deviation detection toner patterns) 9b, 9c for the reference patterns (reference toner patterns) 9a, 10a, 11a, 12a based on the color deviation detection result of the detection unit 6.
9d, 10b, 10c, 10d, 11b, 11c, 11
The color misregistration correction amounts are calculated by obtaining the color misregistration amounts with respect to d, 12b, 12c, and 12d, and are stored in the color misregistration correction value holding unit 75. Further, CPU (correction control means)
Reference numeral 71 denotes a tilt correction motor (actuator) 17 which is a drive source for tilting (displacement) the correction lens 15 via the actuator control unit 77 in accordance with the color misregistration correction amount, and the correction lens 15 to the photosensitive drum. A motor (actuator) for correcting the main scanning width that moves closer to and away from 1
The color misregistration correction is performed by controlling 19 and.

The CPU 81 of the image control section 80 controls the image processing section 73 to perform image processing.

FIG. 11 is a flow chart for explaining a correction operation according to the first embodiment of the present invention, which is equivalent to the correction operation of FIGS. 16 (a) to 16 (d), for example. Therefore, the color misregistration amount in FIG. 11 is a generic term for the color misregistration amount in the main scanning line inclination correction, the main scanning line width correction, the main scanning direction writing position correction, and the sub-scanning direction writing position correction. The amount of color shift.

After the color misregistration correction is started (the color misregistration correction is started, S1
01), the internal counter n of the CPU 71 is initialized (n
= 1, n = n + 1, S102, S103). Color misregistration sub-scanning direction color misregistration detection patterns 9a, 9 as shown in FIG.
b, 9c, 9d, 10a, 10b, 10c, 10d, main scanning direction color misregistration detection patterns 11a, 11b, 11c,
11d, 12a, 12b, 12c, 12d on the conveyor belt 3, image forming units 31Bk, 31Y, 31M, 31C.
(Color shift pattern formation, S104), and a pair of sensors 6a, 6 fixedly provided on both sides of the conveyor belt 3.
It is read by the sensor unit 6 having b (color shift pattern detection, S105).

The above pattern may be formed on the recording material instead of being formed on the conveyor belt 3.

Then, the CPU 71 uses the expressions 4 to 17
Then, the color misregistration amount between the respective colors is calculated for each of the four color misregistration items as shown in FIG. 16 (color misregistration amount calculation, S106), and the correction amount for correcting the calculated color misregistration amount is calculated ( The color misregistration correction amount is calculated, S107). Furthermore, the CPU 71
Performs actuator operation, counter setting, and synchronization timing setting (color misregistration correction execution, S108). Figure 4
In the graph, the correction error increases when the color shift amount is large and the color shift correction amount is large.

Therefore, when the maximum value of the detected color deviation amount exceeds the specified value E1 which is predetermined and stored in the memory 76, (max (color deviation amount)> specified value E1,
S109), the CPU 71 again sets the image forming unit 31B.
k, 31Y, 31M, 31C photosensitive drums 1Bk, 1
A sub-scanning direction color misregistration detection pattern and a main scanning direction color misregistration detection pattern are formed on the conveyor belt 3 by Y, 1M, and 1C, and color misregistration detection and correction operations are repeated. At this time, C
The PU 71 counts up the internal counter n of the CPU 71 (n = n + 1, S103), and even after the color misregistration detection and correction operations are repeated again, the maximum value of the detected color misregistration amount exceeds the predetermined specified value E1. If (n>
1, S109), it is determined that there is an abnormality and an error occurs (error, S112). When the detected maximum value of the color misregistration amount is equal to or smaller than the predetermined specified value E1, the color misregistration correction operation ends (color misregistration correction end, S110).

The above correction operation is repeated once, but may be repeated a plurality of times.

Normally, the color misregistration correction operation is automatically executed at an appropriate timing in order to prevent the color misregistration from deteriorating beyond the specified value. Therefore, when the maximum value of the detected color deviation amount exceeds the predetermined specified value E1, it is limited to such a situation that the environment in which the printer is installed changes greatly immediately after the assembly, during the initial installation, and during the power OFF period. Become.

(Second Embodiment) FIG. 12 shows a second embodiment of the present invention.
According to the embodiment, the color misregistration correction operation due to the tilt in the sub-scanning direction (for example, the correction operation corresponding to FIG. 16A) and the color misregistration correction operation due to the difference in the main scanning width (for example, FIG. 16).
It is a flow chart for explaining (correction operation equivalent to (b)). Only the parts different from the first embodiment will be described.

In the color misregistration correction method associated with the operation of the motors 17 and 19, as shown in FIG. 4, when the color misregistration amount is large and the color misregistration correction amount is large, the correction error increases. However, the correction based on the electrical count value and the synchronization timing has a large amount of color misregistration, and the correction error does not increase even when the amount of color misregistration correction is large.

In the present embodiment, the motors 17 and 19 are operated to correct the inclination in the sub-scanning direction and the main scanning width.
Among the detected color misregistration amounts, the color misregistration amounts of inclination (tilt (color misregistration amount)> specified value E2, S113) and main scanning width (main scanning width (color misregistration amount)> specified value E2, S114) are set in advance. When the specified value is exceeded, the color misregistration detection and correction operation is repeated again.

(Third Embodiment) FIG. 13 shows a third embodiment of the present invention.
A prescribed value for color misregistration correction (for example, correction corresponding to FIG. 16A) due to inclination in the sub-scanning direction according to the embodiment,
Color misregistration correction due to difference in main scanning width (see, for example, FIG.
It is a flow chart for explaining operation when a specified value of (correction equivalent to (b)) is different. That is, the prescribed value E3 ≠ the prescribed value E4. Only parts different from the first and second embodiments will be described.

As shown in FIG. 4, the color misregistration amount is large in the color misregistration correction of the inclination in the sub-scanning direction and the color misregistration correction of the main scanning width accompanied by the operation of the motors 17 and 19 (see FIG. 2). The correction error that increases when the color misregistration correction amount is large may differ. Therefore, the prescribed value for determining whether or not to repeat the color misregistration detection and correction operation is individually set again. If the inclination exceeds the specified value E3 among the detected color deviation amounts (inclination (color deviation amount)> specified value E3, S11
5) When the main scanning width exceeds the specified value E4 (main scanning width (color shift amount)> specified value E4, S116), respectively,
The color misregistration detection and correction operations are repeated.

(Fourth Embodiment) FIG. 14 shows correction of the main scanning width (overall magnification) according to the fourth embodiment (for example, FIG. 16).
It is a figure explaining the operation | movement regarding the correction | amendment equivalent to (b). The block diagram of FIG. 14 is the image processing unit 7 shown in FIG.
A part within 3 is shown.

A part of the image processing section 73 is composed of a PLL circuit. X'tal61 and X'tal61
1 / N _R frequency divider 62 that divides the output of 1 / N _F, 1 / N _F frequency divider 63 that divides the image clock output, 1 / N _R frequency divider 62 and 1 / N _F frequency divider 63 Comparator 64 that outputs pulses with different polarities and widths according to the phase difference between the outputs of the
And a low-pass filter 65 that smoothes the output of the phase comparator 64, and a VCO whose output frequency differs depending on the input voltage.
(Voltage controlled oscillator) 66.

The image clock frequency f _V is f _V = (N _F / N _R ) * f _X (Equation 18), where _{F X} is the frequency of X'tal, and N _R (integer) and N _F (integer) ) and by fine-tuning in the CPU67, _{f V} it can be fine-tuned. The main scanning width is corrected by changing the set values E6 of N _R and N _F according to the detected color shift amount. For example, when the amount of color misregistration is detected in the direction in which the width is narrow, the ratio of N _R and N _F is reduced to reduce f _V (longer period).

FIG. 15 shows a color misregistration correction operation due to an inclination in the sub-scanning direction according to the fourth embodiment of the present invention (for example, FIG. 16).
It is a flow chart for explaining (correction equivalent to (a)). Only parts different from the first to third embodiments will be described.

In this embodiment, the color misregistration correction method involving the operation of the motors 17 and 19 only corrects the inclination in the sub-scanning direction. Therefore, in the detected color shift amount, when the tilt color shift amount exceeds a predetermined specified value E5 (tilt (color shift amount)> specified value E5, S117), the color shift detection and correction operation is repeated again. .

Regarding the means for correcting the color misregistration, various kinds other than the means described in the present embodiment have been proposed, and the present invention is not limited to the means described in the above embodiment.

The color misregistration amount and the color misregistration correction amount are essentially equivalent to each other. Therefore, the criterion for repeating the color shift correction operation may be the calculated color shift correction amount, instead of the detected color shift amount described in the present embodiment.

The above color printer (color image forming apparatus) is provided with the color misregistration correction device capable of surely correcting the color misregistration, so that a high quality image can be formed on the recording material.

Although the color printers of the above embodiments are configured to sequentially form color toner images on the recording material conveyed on the conveyor belt 3, the conveyor belt (intermediate transfer member) Even in a color printer in which a plurality of color toner images are formed on a transfer belt and the color toner images are transferred to the transfer material at once, a high quality image can be similarly formed on the recording material.

In the optical path operating unit 41 of the above embodiment, the motor 17 for tilt correction and the motor 19 for main scanning width correction are actuators, and the cam 18 for tilt correction for tilting the correction lens 15 and the holding unit. The screw 20 for raising and lowering 16 is a mechanical mechanism.

Although not shown, the relative position between the photosensitive drum 1 and the laser scanner 2 can be adjusted to correct the color misregistration. In this case, a mechanism for changing the position of the photosensitive drum 1 serves as a mechanical mechanism unit, and a motor for operating the mechanical mechanism unit serves as an actuator unit. Further, a mechanism for changing the position of the laser scanner 2 serves as a mechanical mechanism unit, and a motor for operating the mechanical mechanism unit serves as an actuator unit.

[0094]

The color misregistration correction apparatus according to the present invention detects the same color misregistration again only when the detected color misregistration amount or the calculated correction amount exceeds a predetermined specified value.
Since the correction operation is repeated, there is no need to have a plurality of color misregistration correction operations, the color misregistration correction operation time is not increased in the majority color misregistration correction operation, and the judgment criterion is not complicated. Even if the amount of color shift is large, it is possible to perform color shift correction with high accuracy.

Further, the color misregistration correction apparatus of the present invention repeats the same color misregistration detection and correction operations again only in the minimum necessary case. Therefore, in most color misregistration correction operations, color misregistration correction is performed. Color misregistration can be highly accurately corrected even when the amount of color misregistration is large without increasing the operation time.

[Brief description of drawings]

FIG. 1 is an overall perspective view of a printer that is an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a color misregistration correction device that corrects an inclination in the sub-scanning direction and a main scanning line width (overall magnification in the main scanning direction) according to the embodiment of the present invention. FIG. 6A is a diagram of the color misregistration correction device as viewed from the recording material conveyance direction. (B) It is the figure which looked at the color shift correction device of (a) from the right side.

FIG. 3 is a plan view of a sub-scanning direction color misregistration detection pattern and a main scanning direction color misregistration detection pattern formed on a conveyor belt.

FIG. 4 is a graph showing the degree of color misregistration correction error. (A) A graph showing a correction error of the main scanning width. (B) A graph showing a correction error of a tilt in the sub-scanning direction.

5 is a schematic control block diagram of the entire printer of FIG. 1. FIG.

FIG. 6 is a block diagram showing a part of the inside of the image formation control unit of FIG.

FIG. 7 is an explanatory diagram in the case of performing correction by increasing or decreasing the number of counts of the horizontal synchronization signal from the vertical synchronization signal to the start of image formation in line units.

FIG. 8 is a diagram illustrating an operation regarding correction of a writing position in a sub-scanning direction.

9 is a block diagram showing a part inside the image formation control unit and a part inside the image processing unit of FIG. 5;

FIG. 10 is a diagram for explaining a correction operation of a writing position in the main scanning direction.

FIG. 11 is a flowchart illustrating a color misregistration correction operation according to the first embodiment.

FIG. 12 is a flowchart illustrating a color misregistration correction operation according to the second embodiment.

FIG. 13 is a flowchart illustrating a color misregistration correction operation according to the third embodiment.

FIG. 14 is a block diagram showing a part of the image processing unit of FIG.

FIG. 15 is a flowchart illustrating a color misregistration correction operation according to the fourth embodiment.

FIG. 16 is a diagram showing various examples when there is a color shift in the main scanning direction or the sub scanning direction. FIG. 7A is a diagram showing a case where a color shift occurs due to a shift in the inclination of a scanning line. FIG. 7B is a diagram showing a case where color misregistration occurs due to variation in scanning line width. FIG. 6C is a diagram showing a case where a color shift occurs due to an error in a writing position of a scanning line in a main scanning direction. FIG. 6D is a diagram showing a case where a color shift occurs due to an error in the writing position of the scanning line in the sub-scanning direction.

[Explanation of symbols]

P Recording material (transferred material) 1Bk, 1Y, 1M, 1C Photosensitive drum (toner image carrier) 2Bk, 2Y, 2M, 2C Laser scanner (exposure part) 3 Conveyor belt (transferred material) 6 Detection part (detection) 7) Original image position 8 Image position 9a in the case where there is a color shift 9a Transport direction color shift detection pattern (reference toner pattern) 9b, 9c, 9d Transport direction color shift detection pattern (color shift detection toner pattern) 10a Transport direction color Misregistration detection pattern (reference toner pattern) 10b, 10c, 10d Transport direction Color misregistration detection pattern (color misregistration detection toner pattern) 11a Main scanning direction Color misregistration detection pattern (reference toner pattern) 11b, 11c, 11d Main scanning direction Color shift detection pattern (color shift detection toner pattern) 12a Color shift detection pattern in the main scanning direction (reference toner) -Patterns 12b, 12c, 12d Patterns for detecting color deviation in the main scanning direction (color deviation detection toner patterns) 15 Correction lens 16 Correction lens, tilt correction motor, and tilt correction cam holder 17 Tilt correction motor (actuator) 19 Motor for main scanning width correction (actuator part) 30 Color printer (color image forming device) 31Bk, 31Y, 31M, 31C Image forming part (image forming means) 40 Color misregistration correction device 41 Optical path operating part (color misregistration correction part) 67 CPU 71 CPU (correction control unit) 72 Image formation control unit (color shift correction unit) 73 Image processing unit 75 Color shift correction value holding unit 76 Memory 77 Actuator control unit 78 Engine control unit 80 Image control unit 81 CPU

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2C362 AA48 BA51 BA52 BA70 BA71                       BA84 BA90 BB37 BB46 CA22                       CA23 CA39 CB73 DA03                 2H027 DA09 DE02 EA18 EB04 EC03                       ED04                 2H030 AA01 AB02 AD16 BB02 BB21                       BB43 BB56                 2H200 FA04 GA12 GA23 GA34 GA44                       GA47 GB22 GB41 JA02 JA30                       JB06 JB50 LA11 LA12 PB16                       PB39

Claims (20)

[Claims] 1. A color misregistration for correcting a color misregistration by detecting a reference toner pattern and a color misregistration detection toner pattern transferred to a transfer body to which toner images formed by a plurality of image forming units are sequentially transferred. A correction device, which detects a reference toner pattern and the color shift detection toner pattern transferred to the transfer target, and corrects an image forming position of the image forming unit with respect to the transfer target. Color misregistration correction means for correcting color misregistration, and correction control for calculating a color misregistration amount from the detection result of the detection means and controlling the color misregistration correction means based on the calculated color misregistration amount to correct the color misregistration. And a correction unit that corrects the color shift again when the amount of color shift exceeds a specified value. 2. When the correction control unit performs the color misregistration correction again, the detection unit detects the reference toner pattern and the color misregistration detection toner pattern formed again on the transfer target. The color misregistration correction device according to claim 1. 3. There are a plurality of types of color misregistration correction means,
The color shift correction device according to claim 1, wherein the correction control unit selectively uses the plurality of types of color shift correction units based on a detection result of the detection unit. 4. The color misregistration correction unit has a mechanical mechanism unit that is actuated by an actuator unit, and the correction control unit controls the actuator unit based on the detection result of the detection unit to cause color misregistration. The color misregistration correction device according to any one of claims 1 to 3, wherein correction is performed. 5. There are a plurality of types of color misregistration correction means,
At least one of the plurality of color misregistration correction means has a mechanical mechanism section that is actuated by an actuator section, and the correction control means is based on the detection result of the detection means. 5. The color shift correction device according to claim 1, wherein the color shift correction means is selectively used. 6. The color misregistration correction unit includes a color misregistration correction unit that corrects color misregistration in the main scanning direction, a color misregistration correction unit that corrects color misregistration in the sub-scanning direction, and a main scanning direction and a sub-scanning direction. 6. The color misregistration correction device according to claim 1, further comprising a color misregistration correction unit that corrects both color misregistrations of 7. There are a plurality of types of color misregistration correction means,
7. At least one of the color misregistration correction means has an optical path operation section that is operated under the control of the correction control means to operate the optical path of the image exposure. The color misregistration correction device according to item 1. 8. The optical path manipulating section is disposed between the exposing section and the toner image carrier and has a correcting lens capable of changing the direction of the exposure, and the correcting lens intersects the optical path. The color misregistration correction device according to claim 7, further comprising: an actuator unit that displaces in a direction in which the color misregistration is performed. 9. The optical path manipulating section is disposed between the exposing section and the toner image carrier, and has a correcting lens capable of changing a scanning width of the exposure in a main scanning direction, and the correcting lens. The color misregistration correction device according to claim 7, further comprising: an actuator unit that moves closer to and away from the toner image carrier. 10. The color misregistration correction device according to claim 1, wherein the specified value is a value of a color misregistration amount due to an inclination of the color misregistration detection toner pattern with respect to the reference toner pattern in the sub-scanning direction. . 11. The color misregistration correction according to claim 1, wherein the specified value is a value of a color misregistration correction amount due to an inclination of the color misregistration detection toner pattern with respect to the reference toner pattern in the sub-scanning direction. apparatus. 12. The color according to claim 1, wherein the specified value is a value of a color shift amount due to a difference in width in the main scanning direction of the color shift detection toner pattern with respect to the reference toner pattern. Deviation correction device. 13. The color shift correction amount according to claim 1, wherein the specified value is a value of a color shift correction amount due to a difference in a main scanning direction width of the color shift detection toner pattern with respect to the reference toner pattern. Color shift correction device. 14. The color shift correction according to claim 1, wherein the specified value is a value of a color shift amount due to a position shift of the color shift detection toner pattern with respect to the reference toner pattern in a main scanning direction. apparatus. 15. The color shift according to claim 1, wherein the specified value is a value of a color shift correction amount due to a position shift of the color shift detection toner pattern in the main scanning direction with respect to the reference toner pattern. Correction device. 16. The color shift correction according to claim 1, wherein the specified value is a value of a color shift amount due to a position shift of the color shift detection toner pattern with respect to the reference toner pattern in the sub-scanning direction. apparatus. 17. The color shift according to claim 1, wherein the specified value is a value of a color shift correction amount due to a position shift of the color shift detection toner pattern with respect to the reference toner pattern in the sub-scanning direction. Correction device. 18. A plurality of exposure portions that emit light of image information, and a plurality of exposure portions that are provided corresponding to the respective exposure portions and that can carry toner images of different colors by being exposed to the corresponding exposure portions. A color image forming apparatus comprising: a toner image carrier; and the color misregistration correction device according to claim 1, wherein the toner image of the toner image carrier is transferred to a transfer target. 19. The color image forming apparatus according to claim 18, wherein the transfer target is a transport belt that sequentially transports a recording material to the plurality of toner image bearing members. 20. The color image forming apparatus according to claim 18, wherein the transfer target is a recording material that is placed on a transfer belt and is sequentially transferred to the plurality of toner image bearing members. .