JP2003149902A - Color image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an effect on a color deviation detection even when impurities adhere to a transport belt. SOLUTION: A color printer is provided with a transport belt 3 which supports and carries a material to be recorded or an image formed directly, a plurality of image forming parts which are arranged along the transporting direction of the transport belt and forms an image on the material to be recorded or the transport belt, detection parts 6 which detect the widths of a plurality of color deviation detection patterns 9, 10 and 11 formed on the transport belt by the image forming parts, and a control part which changes the relative positions of the image forming parts to the transport belt on the basis of width information on the color deviation detection patterns by the detection parts, obtains the sum total of the absolute value of differences between the average of the width of each color deviation detection pattern and the width of the individual color deviation detection pattern at each place, and judges the position of the image forming part, relative to the transport belt, equivalent to the sum total of the maximum value among a plurality of sum totals to be the relative position of the occurring maximum color deviation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a color printer or a color copying machine for forming a color image on a recording material, and more particularly to a color image forming apparatus having a plurality of color image forming portions to ensure color misregistration. The present invention relates to an electrophotographic color image forming apparatus that can detect a color.

[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. If the error is different between the image forming units, the scanning width of the laser on the photosensitive drum may be different for each photosensitive drum, and color misregistration may occur.

FIGS. 7A, 7B, 7C and 7D are views showing various examples in the case where there is a color shift in the scanning direction. In the figure, reference numeral 7 indicates the original image position. Reference numerals 8a, 8b, 8c, and 8d indicate image positions when color misregistration occurs. In order to make it easier to understand the color misregistration state, two positions 7, 8a, 8b, 8c, 8d
Is drawn away from the actual state in the transport direction.

FIG. 7A is a diagram showing a case where a color shift occurs due to a tilt shift of a scanning line. The deviation of the inclination of the scanning line 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. 7B is a diagram showing a case where color misregistration occurs due to variations in the scanning line width (length in the left-right direction in the drawing). The variation of the 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. 7C is a diagram showing a case where color misregistration occurs due to an error in the writing position of the 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. 7D 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 recording material conveyance 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.

In order to correct these color misregistrations, a pair of photosensors, in which a pattern for detecting color misregistration for each color is formed on the conveyor belt, and which are fixedly provided on both sides of the downstream portion of the conveyor belt. The pattern for detection is detected by, and the above various adjustments are performed according to the detected shift amount.

However, the color misregistration includes irregular rotation mainly due to uneven rotation of the photosensitive drum, the conveyor belt and the like, and non-steady color misregistration. Of these, most of the color misregistration caused by the photosensitive drum is due to the eccentricity of the photosensitive drum, and is reproduced in the circumferential period of the drum. This color shift is caused by yellow (hereinafter referred to as “Y”),
Magenta (hereinafter referred to as "M"), cyan (hereinafter referred to as "M")
It is generated by each color of "C") and black (hereinafter referred to as "K"). Therefore, if the timing shifts as shown in FIG. 8, color shift occurs. Therefore, if the timings of the color shifts caused by the photosensitive drums that occur for each color are matched, the color shifts can be reduced.

Hereinafter, a method of adjusting the timing of color misregistration caused by the photosensitive drum for each color will be described. The numerical values in the conventional example are reference numerical values, and the conventional example is not limited to these numerical values.

FIG. 3 shows an example of a pattern for detecting color shift.
In the figure, reference numerals 9a, 10a, and 11a are C patterns which are reference color patterns. Reference numerals 9b, 10b, 1
1b is a pattern of Y, M, and K that are detection color patterns. Further, the patterns 9, 10, and 11 for detecting the color misregistration of CY, CM, and CK continuously transfer one circumference of the photosensitive drum for each color, and there are 27 patterns. To do. Reference signs tyf1 to tyf27, tyr1 to tyr27, tmf1 to tmf27, tmr1 to tmr27, tkf1 to tkf27, and tkr1
Through tkr27 indicate 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 v [mm / s]
And C is the reference color. The average value of the widths of the patterns for detecting the color shift formed by the reference color pattern and the detected color pattern (the length along the transport direction of the recording material) is dm respectively.
fY [μm], dmfM [μm], dmfK [μm],
dmrY [μm], dmrM [μm], dmrK [μ
m], the average value of the widths of the patterns for detecting the left and right color shifts of each color is: dmfY = (tyf1 + tyf2 + ... + tyf27) / 27 (Equation 1) dmrY = (tyr1 + tyr2 + ... + tyr27) / 27 (Equation 2) dmfM = (tmf1 + tmf2 + ... + Tmf27) / 27 (Equation 3) dmrM = (tmr1 + tmr2 + ... + tmr27) / 27 (Equation 4) dmfK = (tkf1 + tkf2 + ...... + tkf27) / 27 (Equation 2) 5) dmrK = (tkr1 + tkr2 + ... + kkr27) / 27 (Equation 6)

Therefore, the average value of the widths of the patterns for detecting the color shift of each color is: dmY = (dmfY + dmrY) / 2 (Equation 7) dmm = (dmfM + dmrM) / 2 (Equation 8) dmK = (dmfK + dmrK) / 2 (Equation 8) Equation 9) is obtained.

Further, the widths tyf1, tyr1, tmf1, tmr1, tkf1 of the patterns for detecting the color shift of each color are detected.
The absolute values of the differences between tkr1 and the like and the average widths dmY, dmM, and dmK of the patterns for detecting the color misregistration of the respective colors are emfY1 [μm], emfM1 [μm], and e.
mfK1 [μm], emrY1 [μm], emrM1
If [μm] and emrK1 [μm], then emfY1 = | tyf1-dmY | (Equation 10) emrY1 = | tyr1-dmY | (Equation 11) emfM1 = | tyf1-dmM | (Equation 12) emrM1 = | tyr1-dmM | (Equation 13) emfK1 = | tyf1-dmK | (Equation 14) emrK1 = | tyr1-dmK | (Equation 15)

This is done for each color, 27 lines left and right, and the maximum value e
When mY1, emm1 and emK1 are obtained, emY1 = max {emfY1, emfY2, ..., EmfY27, em rY1, emrY2, ..., EmrY27} (Equation 16) emm1 = max {emfM1, emfM2 ,. .., emfM27, em rM1, emrM2, ..., EmrM27} (Formula 17) emK1 = max {emfK1, emfK2, ..., EmfK27, em rK1, emrK2, ..., EmrK27} (Formula 17) 18).

This process is performed 6 times by rotating the photosensitive drum of each detected color pattern every 60 degrees and changing the rotation start position of the photosensitive drum. The width tyf1 of the pattern for detecting the color misregistration of each color in each of the six detection color patterns,
tyr1, tmf1, tmr1, tkf1, tkr1 and the like, and the average value d of the widths of the patterns for detecting the color misregistration of each color.
Maximum values of difference from mY, dmM, dmK emY, emM,
When emK is calculated, emY = max {emY1, emY2, ..., EmY6} (Equation 19) emm = max {emM1, emM2, ..., EmM6} (Equation 20) emK = max {emK1, emK2 , ..., emK6} (Equation 21).

Widths tyf1, tyr1, and t of the pattern for detecting the color misregistration of each color in the six detection color patterns.
mf1, tmr1, tkf1, tkr1, etc., and the average values dmY, dm of the widths of the patterns for detecting the color misregistration of the respective colors.
At the position of the photosensitive drum of the detected color pattern where the maximum value emY, emm, emK of the difference between M and dmK is detected, the position where the color misregistration that occurs in one cycle of the photosensitive drum of the reference color pattern and the detected color pattern is the largest. is there. About 18 from this position
The position at which the photosensitive drum of the detected color pattern is rotated at 0 degree is the position where the color shift occurring between the detected color pattern and the reference color pattern in one cycle of the photosensitive drum is the smallest.

Therefore, the color misregistration is minimized by rotating the photosensitive drum of the detected color pattern to a position rotated about 180 degrees from the position of the photosensitive drum of the detected color pattern in which emY, emm and emK are detected. You can

In the case of handling the color misregistration detection pattern of FIG. 3, the width of the color misregistration detection pattern is 25 dots for both the reference color pattern and the detection color pattern, and the pattern width where the reference color pattern and the detection color pattern overlap is 5 do.
t, and the width of the blank portion between the patterns is 40 dots. The width here means the length along the rotating direction of the photosensitive drum, the moving direction of the belt, and the moving direction of the recording material.

[0023]

However, in the conventional color image forming apparatus, when a pair of sensors 6a and 6b detect a pattern for detecting color misregistration, it is determined that impurities are attached to the conveyor belt 3. The width of the pattern for detecting the color misregistration is detected, as shown in FIG. 9, including the amount of impurities protruding from the detected color pattern.

Therefore, in the conventional color image forming apparatus which adopts the method of detecting the position of the photosensitive drum of the detected color pattern which maximizes the width of the pattern for detecting the color shift,
It was difficult to accurately detect the color misregistration that occurs in one cycle of the photosensitive drum.

Therefore, the appearance of a color image forming apparatus having a color misregistration detection function that is not easily affected by the color misregistration detection even if impurities adhere to the conveyor belt 3 has been awaited.

It is an object of the present invention to provide a color image forming apparatus having a color misregistration detection function that is unlikely to be affected by color misregistration detection even if impurities are attached to the conveying means.

[0027]

In order to achieve the above object, a color image forming apparatus of the present invention comprises a conveying means for carrying and conveying a recording material or an image directly formed, and a conveying direction of the conveying means. A plurality of image forming means arranged in an array to form an image on the recording material or the conveying means,
Width detection means for detecting the width of a plurality of color misregistration detection patterns formed on the conveying means by the image forming means,
Based on the width information of the color misregistration detection pattern by the width detection means, the sum of the absolute values of the differences between the width of each of the color misregistration detection patterns and the width of each of the color misregistration detection patterns is conveyed. The relative position of the image forming unit with respect to the image forming unit is changed and obtained at each of a plurality of positions, and the position of the image forming unit with respect to the conveying unit corresponding to the sum of the maximum values among the plurality of the total is determined to be the maximum color shift occurrence relative. Control means for determining the position.

In order to achieve the above object, the color image forming apparatus of the present invention comprises a conveying means for carrying and conveying a recording material or an image directly formed, and the conveying means arranged along the conveying direction of the conveying means. A plurality of image forming means for forming an image on a recording material or the conveying means; a width detecting means for detecting a width of a plurality of color shift detection patterns formed on the conveying means by the image forming means; and a width detecting means Based on the width information of the color misregistration detection pattern according to, the sum of the square values of the difference between the width of each of the color misregistration detection patterns and the width of each of the color misregistration detection patterns, the image for the conveying means. The relative position of the forming means is changed to obtain it at each of a plurality of positions, and the position of the image forming means with respect to the conveying means, which corresponds to the sum of the maximum values among the plurality of the total, is set to the maximum color shift occurrence phase. It comprises a control means for determining a position.

In order to achieve the above-mentioned object, the color image forming apparatus of the present invention comprises a conveying means for carrying and conveying a recording material or an image directly formed, and the conveying means arranged along the conveying direction of the conveying means. A plurality of image forming means for forming an image on a recording material or the conveying means; an interval detecting means for detecting an interval between the reference color pattern and the detected color pattern formed on the conveying means by the image forming means; Based on the spacing information by the detection means, the sum of the average value of the spacing between each reference color pattern and the detected color pattern, the relative position of the image forming means with respect to the conveying means is obtained for each of a plurality of locations, A control unit that determines the position of the image forming unit with respect to the conveying unit that corresponds to the sum of the maximum values among the plurality of totals as the maximum color shift occurrence relative position.

The image forming means of the color image forming apparatus of the present invention has a photosensitive drum carrying a toner image, the carrying means has a belt carrying and carrying a recording material or an image, and the control means. Is the position where the photosensitive drum is rotated about 180 degrees from the position corresponding to the relative position where the maximum color misregistration occurs is set as the image forming start position.

The control means of the color image forming apparatus of the present invention does not use the detection information of the width of the color shift detection pattern when the width of the color shift detection pattern is a predetermined value or more.

The control means of the color image forming apparatus of the present invention uses the detection information of the interval between the reference color pattern and the detected color pattern when the interval between the reference color pattern and the detected color pattern is a predetermined value or more. It is supposed not to.

The predetermined value of the color image forming apparatus of the present invention is about 5 times or more the average value of the widths of the color misregistration detection patterns.

The predetermined value of the color image forming apparatus of the present invention is about 5 times or more the average value of the intervals between the reference color patterns and the detected color patterns.

In the color misregistration detection pattern of the color image forming apparatus of the present invention, the reference color pattern and the detected color pattern partially overlap each other.

[0036]

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 detection operation, but the operations for forming an image on a recording material are all the same. Therefore, the structure and operation of forming an image on a recording material will be described first, and then the color misregistration detection operation of the four embodiments will be described. The numerical values in each embodiment are reference numerical values, and the present invention is not limited to these reference numerical values. Further, 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 20 has four colors, that is,
Yellow (Y), magenta (M), cyan (C), and black (K) image forming units 21Y, 21M, 21C, 2
1K and the image forming units 21Y, 21M, 21C of the respective colors,
An endless conveyor belt (conveying means) 3 also used as a transfer belt for sequentially conveying the recording material to 21K and transferring the image from the image forming portion to the recording material, and a drive including a motor, a gear and the like not shown. Drive roller 4 which is connected to the conveying belt 3 to circulate the conveyor belt 3, a driven roller 5 which follows the conveyor belt 3 and applies a constant tension to the conveyor belt 3, and fixedly provided on both sides of the conveyor belt 3. In addition, a detection section (width detection means, interval detection means) 6 having a pair of optical sensors 6a and 6b for detecting the color misregistration detection pattern formed on the conveyor belt 3 is provided.

Image forming section (image forming means) 21Y, 21
M, 21C, and 21K expose the photosensitive drums 1Y, 1M, 1C, and 1K on which the electrostatic latent images are formed and the photosensitive drums 1Y, 1M, 1C, and 1K to expose the electrostatic latent images on the photosensitive drums 1Y, 1M, 1C, and 1K. It is provided with laser scanners 2Y, 2M, 2C and 2K to be formed.

When data to be printed is sent from a personal computer (PC) (not shown), the color printer 20 completes image formation according to the printer engine system and is ready for printing. Then, the color printer 20 supplies the recording material from the recording material cassette (not shown) to the conveyor belt 3. The conveyor belt 3 uses recording materials for the image forming portions 21Y, 21M, 21C, 21 of the respective colors.
Sequentially transfer to K. On the other hand, the image signals of the respective colors are sent to the laser scanners 2Y, 2M, 2C and 2K at the same timing as the conveyance of the recording material by the conveyor belt 3. An electrostatic latent image is formed on the photosensitive drums 1Y, 1M, 1C, 1K, and a toner image is developed by a developing device (not shown). The toner image is transferred to the recording material by a transfer unit (not shown).

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

FIG. 2 is a control block diagram of the pattern reading processing section (control means) 22. The pattern reading processing unit 22 includes a pattern detecting unit 13 including an LED light emitting unit (not shown), a photo sensor light receiving unit, and the like, an A / D unit 14 that digitizes an analog signal from the detecting unit 6, and a digital data calculation process. The calculation unit 15 that calculates the color shift amount and the correction value, the image output unit 16 that forms an image according to the calculation result, and the timing adjustment and various settings of each unit are performed.
The timer 12 and the CPU 17 are provided.

(First Embodiment) Hereinafter, the color printer 2 will be described.
The color misregistration detection operation of the first embodiment of No. 0 is described.

On the conveyor belt 3, patterns for detecting color shift as shown in FIG. 3 are formed on the image forming portions 21Y, 21M, 2a.
It is formed by 1C and 21K.

In the figure, reference numerals 9a, 10a and 11a
Is a pattern of C which is a reference color. Reference numerals 9b and 10
b and 11b are patterns of Y, M, and K that are detection colors, respectively. Further, the patterns 9, 10, and 11 for detecting the color misregistration of CY, CM, and CK continuously transfer one circumference of the photosensitive drum for each color, and there are 27 patterns. To do.

The widths of the patterns 9, 10 and 11 for detecting the color misregistration (the lengths along the conveying direction of the recording material (the arrow direction in FIG. 3)) are fixedly provided on both sides of the conveying belt 3. Detection unit (width detection means) 6 having a pair of optical sensors 6a and 6b
Read by

Average values dmfY, dmfM, dmfK, dmrY, d of widths of patterns for detecting left and right color shifts of respective colors.
mrM and dmrK are represented by (Equation 1) to (Equation 6). Therefore, the average value of the widths of the patterns for detecting the color misregistration of each color is expressed by (Equation 7) to (Equation 9).

Further, the widths tyf1, tyr1, tmf1, tmr1, tkf1 of the patterns for detecting the color misregistration of each color.
The absolute values of the differences between tkr1 etc. and the average widths dmY, dmM, and dmK of the patterns for detecting the color shift of each color are emfY1, emfM1, emfK1, and emr.
When Y1, emrM1, and emrK1 are given, they are represented by (Equation 10) to (Equation 15).

This is performed for each of the right and left 27 lines, and the total sum fmY1, fmM1, fmK1 is calculated (see FIG. 4).
If, fmY1 = emfY1 + emfY2 + ··· + emfY27 + emrY1 + e mrY2 + ··· + emrY27 (Equation 22) fmM1 = emfM1 + emfM2 + ··· + emfM27 + emrM1 + e mrM2 + ··· + emrM27 (Equation 23) fmK1 = emfK1 + emfK2 + ··· + emfK27 + emrK1 + e mrK2 + ··· + emrK27 (Formula 24) Becomes

This process is performed by rotating the photosensitive drum of each detected color every 60 degrees to change the rotation start position of the photosensitive drum.
Do 6 times in total. In each detection color pattern in these 6 times,
Pattern widths tyf1 and tyr for detecting the color misregistration of each color
1, tmf1, tmr1, tkf1, tkr1 and the like, and the average value dmY of the widths of the patterns for detecting the color misregistration of each color,
Maximum value f in the sum of absolute values of the difference between dmM and dmK
mY, fmM, fmK are fmY = max {fmY1, fmY2, ..., fmY6} (Formula 25) fmM = max {fmM1, fmM2, ..., fmM6} (Formula 26) fmK = max {fmK1 , FmK2, ..., fmK6} (Equation 27).

Width tyf of pattern for detecting color shift of each color
1, tyr1, tmf1, tmr1, tkf1, tkr
The position of the photosensitive drum of the detected color pattern in which the maximum value fmY, fmM, fmK in the sum of the absolute values of the differences between the first and the like and the average widths dmY, dmM, dmK of the color shift detection patterns of the respective colors is detected. Is the position where the color misregistration between the reference color pattern and the detected color pattern, which occurs in one cycle of the photosensitive drum, is the largest. The position at which the photosensitive drum of the detected color pattern is rotated about 180 degrees from this position is the position where the color shift occurring between the detected color pattern and the reference color pattern in one cycle of the photosensitive drum is the smallest.

Therefore, the color misregistration is minimized by rotating the photosensitive drum of the detected color pattern to a position rotated about 180 degrees from the position of the photosensitive drum of the detected color pattern in which fmY, fmM, and fmK are detected. You can

The above-described color misregistration detection operation control is performed by referring to FIG.
The control unit 22 shown in FIG.

FIG. 5 shows an example of the waveform obtained by the experiment when the photosensitive drum of the detected color (Y) is rotated every 60 degrees. The fmY1 of the waveform 19 in FIG.
From 2), fmY1 = 0.0 + 9.2 + 18.0 + 8
0.6 + 32.1 + 36.7 + 39.4 + 39.9 + 3
8.3 + 34.6 + 29.1 + 22.0 + 13.7 +
4.6 + 4.6 + 13.7 + 22.0 + 29.1 + 3
4.6 + 38.3 + 39.9 + 39.4 + 36.7 + 3
2.1 + 25.7 + 18.0 + 9.2 = 741.5. The unit of numerical value is μm.

The fmY2 of the waveform 20 is f
mY2 = 58.4 + 53.6 + 46.0 + 35.8 + 2
3.8 + 10.4 + 3.5 + 17.2 + 30.0 + 4
1.2 + 50.1 + 56.4 + 59.6 + 59.6 + 5
6.4 + 50.1 + 41.2 + 30.0 + 17.2 +
3.5 + 10.4 + 23.8 + 35.8 + 46.0 + 5
It is 3.6 + 58.4 + 60.0 = 1032. In addition,
The unit of the numerical value is μm.

Since fmY1 <fmY2, fmY = 1032 μm from (Equation 25). The position where the waveform 20 is obtained on the drum of the detection color (Y) (relative position where the maximum color misregistration occurs)
To about 180 degrees. This can minimize color misregistration. This position is the image formation start position where the image formation is started on the recording material.

On the other hand, in the conventional example, the pattern widths tyf1, tyr1, tmf1, tmr1, tkf for detecting the color shift are detected.
Since the absolute value of the difference between 1, tkr1 and the like and the average value of the pattern widths for detecting the color misregistration of each color is selected to be the largest, the waveform 19 and the waveform 20 are compared in the example of FIG. emY1 = 80.6 from (Equation 16)
μm, and emY2 of the waveform 20 is em from (Equation 16)
Y2 = 60.0 μm. In FIG. 5, reference numeral 19b indicates the pattern width of the pattern having the maximum difference from the average value of the pattern width of the waveform 19. Also, reference numeral 20
Symbols a and 20b indicate the pattern width of the pattern having the maximum difference from the average value of the pattern width of the waveform 20.

Since emY1> emY2, emY = 80.6 μm from (Equation 19). The detected color (Y) drum is rotated to a position rotated about 180 degrees from the position where the waveform 19 is obtained.

Here, in the waveforms 19 and 20, the color shift due to the photosensitive drum has a larger amplitude in the waveform 20. This proves the usefulness of the present invention in that the color printer of the present embodiment is unlikely to be affected by impurities adhering to the conveyor belt 3.

The above experimental results show that yellow (Y)
However, it is needless to mention that similar results can be obtained for image forming units of other colors.

Therefore, the color printer of this embodiment is
Even if impurities are attached to the conveyor belt 3, the color misregistration can be reliably detected and the color misregistration can be corrected accurately, so that a high-quality image can be formed on the recording material.

(Second Embodiment) Next, the color misregistration detection operation of the second embodiment of the color printer 20 will be described.

The pattern shown in FIG. 3 is also used in the color misregistration detection operation of the second embodiment. On the conveyor belt 3, patterns 9, 10, 11 for color shift detection as shown in FIG. 3 are formed by image forming portions 21Y, 21M, 21C, 21K.

The widths of the color shift detection patterns 9, 10 and 11 are read by a detection section (width detection means) 6 having a pair of optical sensors 6a and 6b fixedly provided on both sides of the conveyor belt 3. .

Average values dmfY, dmfM, dmfK, dmrY, d of widths of patterns for detecting left and right color shifts of respective colors.
mrM and dmrK are represented by (Equation 1) to (Equation 6). Therefore, the average value of the widths of the patterns for detecting the color misregistration of each color is expressed by (Equation 7) to (Equation 9).

Further, the widths tyf1, tyr1, tmf1, tmr1, tkf1 of the patterns for detecting the color misregistration of the respective colors.
The difference between tkr1 and the like and the average values dmY, dmM, and dmK of the widths of the patterns for detecting the color misregistration of the respective colors,
emfY1, emfM1, emfK1, emrY1, e
If mrM1 and emrK1 are set, (Equation 10) to (Equation 1)
It is represented by 5).

This is done for each of the right and left 27 lines, and the square
When the sum gmY1, gmM1, gmK1 is calculated,   gmY1 = (emfY1)^Two+ (EmfY2)^Two+ ... + (emfY27) ^Two + (EmrY1)^Two+ (EmrY2)^Two+ ・ ・ ・ + (EmrY27)^Two                                                               (Equation 28)   gmM1 = (emfM1)^Two+ (EmfM2)^Two+ ・ ・ ・ + (EmfM27) ^Two + (EmrM1)^Two+ (EmrM2)^Two+ ・ ・ ・ + (EmrM27)^Two                                                               (Formula 29)   gmK1 = (emfK1)^Two+ (EmfK2)^Two+ ・ ・ ・ + (EmfK27) ^Two + (EmrK1)^Two+ (EmrK2)^Two+ ・ ・ ・ + (EmrK27)^Two                                                               (Equation 30) Becomes

This process is repeated 6 times by rotating the photosensitive drum of each detected color pattern every 60 degrees and changing the rotation start position of the photosensitive drum. The width tyf1 of the pattern for detecting the color misregistration of each color in each of the six detection color patterns,
tyr1, tmf1, tmr1, tkf1, tkr1 and the like, and the average value d of the widths of the patterns for detecting the color misregistration of each color.
Maximum value g in the sum of squares of the differences with mY, dmM, and dmK
mY, gmM, and gmK are gmY = max {gmY1, gmY2, ..., GmY6} (Formula 31) gmM = max {gmM1, gmM2, ..., GmM6} (Formula 32) gmK = max {gmK1 , GmK2, ..., GmK6} (Equation 33).

Width tyf of pattern for detecting color shift of each color
1, tyr1, tmf1, tmr1, tkf1, tkr
1 and the average value dmY, dmM, dmK of the widths of the patterns for detecting the color shift of each color, the maximum value gmY, gmM, gmK in the sum of squares of the differences, the position of the photosensitive drum of the detected color pattern, This is the position where the color deviation between the reference color pattern and the detected color pattern that occurs in one cycle of the photosensitive drum is the largest. The position at which the photosensitive drum of the detected color pattern is rotated about 180 degrees from this position is the position where the color shift occurring between the detected color pattern and the reference color pattern in one cycle of the photosensitive drum is the smallest.

Therefore, the color misregistration is minimized by rotating the photosensitive drum of the detected color pattern to a position rotated about 180 degrees from the position of the photosensitive drum of the detected color pattern in which gmY, gmM and gmK are detected. You can

The color misregistration detection operation control described above is performed by referring to FIG.
The control unit 22 shown in FIG.

The waveform obtained when the photosensitive drum of the detected color (Y) is rotated every 60 degrees obtained by the experiment is shown in FIG. The gmY1 of the waveform 19 is gmY1 = 0.0 + 85.1 + 32 from (Equation 28).
2.3 + 6496.4 + 1029.4 + 1349.0 +
1551.8 + 1594.6 + 1468.4 + 120
0.0 + 846.5 + 483.1 + 187.2 + 21.
6 + 21.6 + 187.2 + 483.1 + 846.5 +
1200.0 + 1468.4 + 1594.6 + 155
1.8 + 1349.0 + 1029.4 + 661.1 + 3
It is 22.3 + 85.1 = 27435.5. The unit of numerical value is μm.

GmY2 of the waveform 20 is calculated from (Equation 28) as g
mY2 = 3408.5 + 2874.9 + 212.6 +
1283.8 + 564.8 + 108.6 + 12.2 + 2
96.1 + 900.0 + 1695.3 + 2512.9 +
3178.9 + 3551.5 + 3551.5 + 317
8.9 + 2512.9 + 1695.3 + 900.0 + 2
96.1 + 12.2 + 108.6 + 564.8 + 128
3.8 + 212.6 + 2874.9 + 3408.5 +
3600.0 = 48600.2. The unit of numerical value is μm.

Since gmY1 <gmY2, gmY = 48600.2 μm from (Equation 31). The drum of the detected color (Y) is rotated from the position where the waveform 20 is obtained (relative position where maximum color misregistration occurs) to the position where it is rotated about 180 degrees. This position is the image formation start position where the image formation is started on the recording material. This can minimize color misregistration.

On the other hand, in the conventional example, the pattern widths tyf1, tyr1, tmf1, and tmr of the patterns for detecting the color misregistration.
Since the absolute value of the difference between 1, tkf1, tkr1 and the like and the average value of the widths of the patterns for detecting the color shift of each color is selected as the largest absolute value, comparing waveforms 19 and 20 as shown in FIG. EmY1 of the waveform 19 is emY from (Equation 16)
1 = 80.6 μm, and emY2 of the waveform 20 is (equation 1
According to 6), emY2 = 60.0 μm.

Since emY1> emY2, emY = 80.6 μm from (Equation 19). The detected color (Y) drum is rotated to a position rotated about 180 degrees from the position where the waveform 19 is obtained.

Here, in the waveforms 19 and 20, the waveform 20 has a larger color shift due to the photosensitive drum. This proves the usefulness of the present invention in that the color printer of the present embodiment is unlikely to be affected by impurities adhering to the conveyor belt 3.

The above experimental results show that yellow (Y)
However, it is needless to mention that similar results can be obtained for image forming units of other colors.

Therefore, the color printer of this embodiment is
Even if impurities are attached to the conveyor belt 3, the color misregistration can be reliably detected and the color misregistration can be corrected accurately, so that a high-quality image can be formed on the recording material.

(Third Embodiment) Next, the color misregistration detection operation of the third embodiment of the color printer 20 will be described.

The color misregistration detection operation of the third embodiment is performed as shown in FIG.
Use the pattern shown in. As shown in FIG.
The pattern for color misregistration detection as shown in FIG.
It is formed by Y, 21M, 21C and 21K. The horizontal line pattern is formed on the conveyor belt 3 in the order of Y31, M32, C33, and K34 at a constant interval of 27 for each color. Of the horizontal line patterns, C33 is a reference color pattern. Y31, M32M, and K34 are detection color patterns. The width of the pattern for detecting the color misregistration has a pair of optical sensors 6a and 6b fixedly provided on both sides of the conveyor belt 3.
It is read by a detection unit (interval detection means) 6 having a.

In the horizontal line pattern of Y31, M32, C33, and K34 in FIG. 6, the interval of each color is set to the cycle of the driving roller 4 of the conveyor belt 3, and the horizontal line of the same color is used for each photosensitive drum 1Y, 1M, 1C. , 1K per cycle. t
yf1 to tyf27, tyr1 to tyr27, tm
f1 to tmf27, tmr1 to tmr27, tcf
1 to tcf27, tcr1 to tcr27, tkf1
To tkf27, tkr1 to tkr27 indicate the detection timing of each pattern, and the arrow indicates the moving direction of the conveyor belt 3.

Average values dm1fY, dm1fM, dm1fK, dm1r of the pattern gaps for detecting the color shift of the detected color patterns 31, 32, 34 with respect to the reference color pattern 33.
Y, dm1rM, and dm1rK are represented by the following (formula 34) to (formula 39).

[0084]   dm1fY = (| tyf1-tcf1 | + | tyf2-tcf2 | + ... + | Tyf27-tcf27 |) / 27 (Formula 34)   dm1rY = (| tyr1-tcr1 | + | tyr2-tcr2 | + ... + | Tyr27-tcr27 |) / 27 (Formula 35)   dm1fM = (| tmf1-tcf1 | + | tmf2-tcf2 | + ... + | Tmf27-tcf27 |) / 27 (Formula 36)   dm1rM = (| tmr1-tcr1 | + | tmr2-tcr2 | + ... + | Tmr27-tcr27 |) / 27 (Formula 37)   dm1fK = (| tkf1-tcf1 | + | tkf2-tcf2 | + ... + | Tkf27-tcf27 |) / 27 (Formula 38)   dm1rK = (| tkr1-tcr1 | + | tkr2-tcr2 | + ... + | Tkr27-tcr27 |) / 27 (Formula 39) Becomes

Therefore, the average value between the patterns for detecting the color shift of each detected color pattern with respect to the reference color pattern is: dm1Y = (dm1fY + dm1rY) / 2 (Formula 40) dm1M = (dm1fM + dm1rM) / 2 (Formula 41) dm1K = (Dm1fK + dm1rK) / 2 (Equation 42)

Further, the difference between the pattern interval for detecting the color shift of each detected color pattern with respect to the reference color pattern and the average value dm1Y, dm1M, dm1K between the patterns for detecting the color shift of each detected color pattern with respect to the reference color pattern. The absolute values of em1fY1 [μm], em1fM1
[Μm], em1fK1 [μm], em1rY1 [μ
m], em1rM1 [μm], and em1rK1 [μm], em1fY1 = || tyf1-tcf1 | -dm1Y | (Formula 43) em1rY1 = || tyr1-tcr1 | -dm1Y | (Formula 44) em1fM1 = || -Tcf1 | -dm1M | (Formula 45) em1rM1 = || tmr1-tcr1 | -dm1M | (Formula 46) em1fK1 = || tkf1-tcf1 | -dm1K | (Formula 47) em1rK1 = || tkr1-tcr1 | -dm1 | (Equation 48)

This is performed for each of the left and right 27 lines for each color, and the total sum em1Y1, em1M1, em1K1 is calculated.

[0088]   em1Y1 = em1fY1 + em1fY2 + ... + em1fY27 + em1 rY1 + em1rY2 + ... + em1rY27 (Formula 49)   em1M1 = em1fM1 + em1fM2 + ... + em1fM27 + em1 rM1 + em1rM2 + ... + em1rM27 (Formula 50)   em1K1 = em1fK1 + em1fK2 + ... + em1fK27 + em1 rK1 + em1rK2 + ... + em1rK27 (Formula 51) Becomes

This processing is performed 6 times in total by rotating the photosensitive drum of each detected color pattern every 60 degrees and changing the rotation start position of the photosensitive drum. Pattern intervals tyf1, tyr1, and tmf for detecting color misregistration of each detected color pattern with respect to the reference color pattern in each of the six detected color patterns.
1, tmr1, tkf1, tkr1, etc. and the maximum value em1Y, em1M, em1K in the sum of the absolute values of the differences between the average values dm1Y, dm1M, dm1K between the patterns for detecting the color shift of each detected color pattern with respect to the reference color pattern.
Is em1Y = max {em1Y1, em1Y2, ..., Em1Y6} (Equation 52) em1M = max {em1M1, em1M2, ..., Em1M6} (Equation 53) em1K = max {em1K1, em1K2, ... ···· Em1K6} (Equation 54)

The absolute value of the difference between the pattern distance for detecting the color shift of each detected color pattern with respect to the reference color pattern and the average value dm1Y, dm1M, dm1K between the patterns for detecting the color shift of each detected color pattern with respect to the reference color pattern. The position of the photosensitive drum of the detected color that has detected the maximum values em1Y, em1M, and em1K in the sum of the values is the position where the color misregistration that occurs in the photosensitive drum one cycle of the reference color pattern and the detected color pattern is the largest. The position at which the photosensitive drum of the detected color is rotated about 180 degrees from this position is the position where the color shift occurring between the detected color and the reference color pattern in one revolution cycle of the photosensitive drum is the smallest.

Therefore, the color misregistration can be minimized by rotating the detected-color photosensitive drum to a position rotated by about 180 degrees from the position of the detected-color photosensitive drum detecting gm1Y, gm1M, and gm1K. .

The color misregistration detection operation control described above is performed by referring to FIG.
The control unit 22 shown in FIG.

The waveform obtained when the photosensitive drum of the detected color (Y) was rotated by 60 degrees obtained by the experiment is the same as that shown in FIG. The em1Y1 of the waveform 19 is em1Y1 = 0.0 + 9.2 + 18.0 + from (Formula 49).
80.6 + 32.1 + 36.7 + 39.4 + 39.9 +
38.3 + 34.6 + 29.1 + 22.0 + 13.7 +
4.6 + 4.6 + 13.7 + 22.0 + 29.1 + 3
4.6 + 38.3 + 39.9 + 39.4 + 36.7 + 3
2.1 + 25.7 + 18.0 + 9.2 = 741.5. The unit of numerical value is μm.

The em1Y2 of the waveform 20 is calculated from (Equation 49).
em1Y2 = 58.4 + 53.6 + 46.0 + 35.8
+ 23.8 + 10.4 + 3.5 + 17.2 + 30.0 +
41.2 + 50.1 + 56.4 + 59.6 + 59.6 +
56.4 + 50.1 + 41.2 + 30.0 + 17.2 +
3.5 + 10.4 + 23.8 + 35.8 + 46.0 + 5
It is 3.6 + 58.4 + 60.0 = 1032. In addition,
The unit of the numerical value is μm.

Since em1Y1 <em1Y2, (Equation 5
From 2), em1Y = 1032 μm. Detection color (Y)
The drum is rotated from the position where the waveform 20 is obtained (the relative position where the maximum color misregistration occurs) to the position where it is rotated about 180 degrees. This can minimize color misregistration. This position is the image formation start position where the image formation is started on the recording material.

On the other hand, in the conventional example, the pattern widths tyf1, tyr1, tmf1, tmr1, t of the color misregistration detection pattern are used.
Since the value with the largest absolute value of the difference between kf1, tkr1, etc. and the average value of the pattern width is selected, when waveform 19 and waveform 20 as shown in FIG. 5 are compared, emY1 of waveform 19 is calculated from (Equation 16). emY1 = 80.6 μm, waveform 2
EmY2 of 0 is emY2 = 60.0 μm from (Equation 16)
Is.

Since emY1> emY2, emY = 80.6 μm from (Equation 19). The detected color (Y) drum is rotated to a position rotated about 180 degrees from the position where the waveform 19 is obtained.

In the waveforms 19 and 20, the waveform 20 has a larger amplitude in the color misregistration caused by the photosensitive drum. This proves the usefulness of the present invention in that the color printer of the present embodiment is unlikely to be affected by impurities adhering to the conveyor belt 3.

The above experimental results show that yellow (Y)
However, it is needless to mention that similar results can be obtained for image forming units of other colors.

Therefore, the color printer of this embodiment is
Even if impurities are attached to the conveyor belt 3, the color misregistration can be reliably detected and the color misregistration can be corrected accurately, so that a high-quality image can be formed on the recording material.

(Fourth Embodiment) Next, the color misregistration detection operation of the color printer 20 according to the fourth embodiment will be described.

The color misregistration detection operation of the fourth embodiment is, so to speak, a threshold value is set for the color misregistration information in the color misregistration detection operation of the first embodiment, and information having extremely different values is treated as abnormal information. It is supposed to be deleted.

On the conveyor belt 3, color shift detection patterns as shown in FIG. 3 are formed on the image forming portions 21Y, 21M, 21.
It is formed by C and 21K. The detection pattern is the same as the conventional one. The pattern width for detecting the color misregistration is read by the detection unit 6 having a pair of optical sensors 6a and 6b fixedly provided on both sides of the conveyor belt 3.

Average values dmfY, dmfM, dmfK, dmrY, dm of pattern widths for detecting left and right color shifts of respective colors.
rM and dmrK are represented by (Formula 1) to (Formula 6).
Therefore, the average value of the pattern width for detecting the color misregistration of each color is expressed by (Equation 7) to (Equation 9).

Further, the pattern width t for detecting the color misregistration of each color
yf1, tyr1, tmf1, tmr1, tkf1, t
The absolute value of the difference between kr1 and the like and the average values dmY, dmM, and dmK of the pattern widths for detecting the color shift of the respective colors is emfY1, emfM1, emfK1, and emrY.
1, emrM1, and emrK1 are represented by (Equation 10) to (Equation 15).

This is performed for each of the right and left 27 lines, and the total sum fmY1, fmM1, fmK1 is calculated from (Equation 22) to (Equation 2).
4).

This process is performed by rotating the photosensitive drum of each detected color every 60 degrees, changing the rotation start position of the photosensitive drum,
Do 6 times in total. Pattern widths tyf1, tyr1, tmf for detecting color shift of each color in each of the six detection colors.
1, tmr1, tkf1, tkr1, etc., and the average value dmY, dmM, dm of the pattern width for detecting the color shift of each color.
Maximum values fmY, fmM, in the sum of absolute values of the difference of K,
fmK is expressed by (Expression 25) to (Expression 27).

The maximum value fmY, fmM, fmK in the sum of the absolute values of the difference between the pattern width for detecting the color shift of each color and the average value dmY, dmM, dmK of the pattern width is detected. This is the position where the color deviation between the reference color pattern and the detected color pattern that occurs in one cycle of the photosensitive drum is the largest. The position where the photosensitive drum of the detected color is rotated about 180 degrees from this position is the position where the color shift between the detected color pattern and the reference color pattern that occurs in one cycle of the photosensitive drum is the smallest.

Therefore, the color misregistration is minimized by rotating the photosensitive drum of the detected color pattern to a position rotated about 180 degrees from the position of the photosensitive drum of the detected color pattern in which fmY, fmM, and fmK are detected. You can

The color misregistration detection operation control described above is performed in FIG.
The control unit 22 shown in FIG.

The waveform obtained when the photosensitive drum of the detected color (Y) is rotated by 60 degrees obtained by the experiment is shown in FIG. However, unlike the first embodiment, 19a in FIG.
Change to 0.0 μm.

When the waveform 19 and the waveform 20 are compared in the example of FIG. 5, emY1 of the waveform 19 is emY1 =
0.0 + 9.2 + 18.0 + 500.0 + 32.1 + 3
6.7 + 39.4 + 39.9 + 38.3 + 34.6 + 2
9.1 + 22.0 + 13.7 + 4.6 + 4.6 + 13.
7 + 22.0 + 29.1 + 34.6 + 38.3 + 39.
9 + 39.4 + 36.7 + 32.1 + 25.7 + 18.
It is 0 + 9.2 = 1160.9. The unit of numerical value is μm.

The fmY2 of the waveform 20 is f
mY2 = 58.4 + 53.6 + 46.0 + 35.8 + 2
3.8 + 10.4 + 3.5 + 17.2 + 30.0 + 4
1.2 + 50.1 + 56.4 + 59.6 + 59.6 + 5
6.4 + 50.1 + 41.2 + 30.0 + 17.2 +
3.5 + 10.4 + 23.8 + 35.8 + 46.0 + 5
It is 3.6 + 58.4 + 60.0 = 1032. In addition,
The unit of the numerical value is μm.

Since fmY1> fmY2, fmY = 1160.9 μm from (Equation 25). The detected color (Y) drum is rotated to a position rotated about 180 degrees from the position where the waveform 19 is obtained.

Here, in the waveforms 19 and 20, the amplitude of the color shift due to the photosensitive drum is larger in the waveform 20. Therefore, as indicated by reference numeral 19a in FIG. 5, a problem occurs when an extremely large amount of color misregistration is detected in the average value of the color misregistration amounts.

Therefore, in order to solve the above problem, a threshold value is set by comparing with the average value of the color misregistration amount, and the color misregistration amount equal to or more than the threshold value is excluded. The threshold value is about 5 times the average value of the color shift amount. When the threshold value dt1 = 200 μm, fmY1 of the waveform 19 is fmY1 = 0.0 + 9.2.
+ 18.0 + 32.1 + 36.7 + 39.4 + 39.9
+ 38.3 + 34.6 + 29.1 + 22.0 + 13.7
+ 4.6 + 4.6 + 13.7 + 22.0 + 29.1 + 3
4.6 + 38.3 + 39.9 + 39.4 + 36.7 + 3
2.1 + 25.7 + 18.0 + 9.2 = 660.9. The unit of numerical value is μm.

Therefore, since fmY1 <fmY2, fmY = 1032 μm from (Equation 25). Detection color (Y)
The drum is rotated from the position where the waveform 20 is obtained (the relative position where the maximum color misregistration occurs) to the position where it is rotated about 180 degrees. This position is the image formation start position where the image formation is started on the recording material.

In the waveforms 19 and 20, the waveform 20 has a larger amplitude in the color misregistration caused by the photosensitive drum. This proves the usefulness of the present invention in that the color printer of the present embodiment is unlikely to be affected by impurities adhering to the conveyor belt 3.

The above experimental results show that yellow (Y)
However, it is needless to mention that similar results can be obtained for image forming units of other colors.

Therefore, the color printer of this embodiment is
Even if impurities are attached to the conveyor belt 3, the color misregistration can be reliably detected and the color misregistration can be corrected accurately, so that a high-quality image can be formed on the recording material.

Note that the threshold value is set to 5 times the average amount of color misregistration and information that is far apart from the others is excluded by the threshold value also in the second and third embodiments. be able to.

Although the above-described respective configurations according to the present invention have been described as being applied to the image forming apparatus using the carrying means for carrying and carrying the recording material, the present invention is not limited to this.

For example, images from a plurality of image forming units are
The present invention can also be applied to an image forming apparatus using a so-called intermediate transfer member, which directly transfers and carries and conveys it. This is an apparatus in which images of respective colors are sequentially transferred and superposed on an intermediate transfer member to form a color image and then collectively transferred to a conveyed recording material. Even in an image forming apparatus using this intermediate transfer member, for the purpose of preventing color misregistration,
This is because it is necessary to create a color shift detection pattern on the intermediate transfer member, read the shift amount, and perform a correction operation based on the result.

[0124]

According to the color image forming apparatus of the present invention, the difference between the average value of the widths of the color misregistration detection patterns and the width of each color misregistration detection pattern is determined based on the width information of the color misregistration detection pattern by the width detection means. The absolute value of the image forming means is calculated for each of a plurality of positions by changing the relative position of the image forming means with respect to the conveying means, and the position of the image forming means with respect to the conveying means corresponding to the sum of the maximum values is maximized. Since the control unit for determining the relative position of occurrence of color misregistration is provided, even if impurities are attached to the transport unit, the color misregistration can be accurately detected without being substantially affected by the color misregistration detection. It is possible to form a high-precision multicolor color image on the recording material.

In the color image forming apparatus of the present invention, the square of the difference between the average value of the widths of the color misregistration detection patterns and the width of each color misregistration detection pattern is based on the width information of the color misregistration detection pattern by the width detection means. The total value is obtained by changing the relative position of the image forming means with respect to the conveying means, and obtaining it at each of a plurality of positions,
Since a control unit that determines the position of the image forming unit with respect to the conveying unit corresponding to the sum of the maximum values among the plurality of totals is the relative position where the maximum color misregistration occurs, impurities may be attached to the conveying unit. In this case, the color shift can be accurately detected and a highly accurate multicolor color image can be formed on the recording material without being substantially affected by the color shift detection.

In the color image forming apparatus of the present invention, the sum of the average value of the intervals between the reference color patterns and the detected color patterns is calculated as the relative position of the image forming means with respect to the conveying means, based on the distance information obtained by the distance detecting means. Since it is provided with a control unit that determines the position of the image forming unit with respect to the conveying unit corresponding to the sum of the maximum values as the maximum color misregistration occurrence relative position. Even if impurities are attached to the conveying means, the color misregistration can be detected accurately without being affected by the color misregistration detection, and a highly accurate multicolor color image can be recorded on the recording material. Can be formed.

[Brief description of drawings]

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

FIG. 2 is a block diagram of a control unit of the color printer of FIG.

FIG. 3 is a diagram for explaining a pattern for color shift detection that detects a color shift based on a difference in width.

FIG. 4 is a graph for explaining processing of a detection result obtained from a pattern for detecting color misregistration according to the embodiment of the present invention.

FIG. 5 is a graph showing a tendency of the pattern width of a pattern for detecting color shift according to the embodiment of the present invention to be read by a sensor for detecting color shift.

FIG. 6 is a diagram for explaining a pattern for detecting color misregistration that detects color misregistration based on a difference in interval.

FIG. 7 is a diagram for explaining various examples when there is a color shift in the 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 (length in the left-right direction in the drawing). FIG. 6C is a diagram showing a case where color misregistration occurs due to an error in the writing start position of the scanning line in the 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 recording material conveyance direction.

FIG. 8 is a graph for explaining color misregistration that occurs in a photosensitive drum circumferential cycle. (A) is a graph of a reference color shift amount and a detected color shift amount. (B) is a graph showing the difference between the reference color shift amount and the detected color shift amount.

FIG. 9 is a graph showing a tendency of a value obtained by reading a pattern width of a pattern for color misregistration detection with a sensor for color misregistration detection.

[Explanation of symbols]

1Y, 1M, 1C, 1K Photosensitive drums 2Y, 2M, 2C, 2K Laser scanner 3 Conveying belt (conveying means) 6 Detecting section (width detecting means, interval detecting means) 6a, 6b Optical sensor 9, 10, 11 Color shift detection Patterns 9a, 10a, 11a reference color patterns 9b, 10b, 11b detection color pattern 19b pattern width 20a, 20b of the pattern 19 having the largest difference from the average value of the pattern width of the waveform 19 and the average value of the pattern width of the waveform 20 The pattern width of the pattern having the maximum difference 20 Color printer (color image forming apparatus) 21Y, 21M, 21C, 21K Image forming unit (image forming unit) 22 Control unit (control unit) 31, 32, 34 Detection color pattern 33 Reference Color pattern

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/14 G03G 21/00 372 F term (reference) 2H027 DA22 DA23 DA32 DE02 DE07 DE09 EB04 EC04 EC06 EC07 EC10 EC18 EC20 ED02 ED06 EE01 EE02 EE07 EF08 EF09 ZA07 2H030 AA01 AB02 AD17 BB02 BB16 BB42 2H200 FA16 GA12 GA23 GA30 GA34 GA40 GA44 GA47 JB06 JB49 JB50 JC03 JC19 JC20 LA12 PA12 PA19 PA24 PB11 PB16 PB16 PB16 PB16 P39

Claims (9)

[Claims] 1. A conveying means for carrying and conveying a recording material or an image directly formed thereon, and a plurality of images arranged along the conveying direction of the conveying means to form an image on the recording material or the conveying means. Forming means, width detecting means for detecting the width of a plurality of color shift detection patterns formed on the conveying means by the image forming means, and based on width information of the color shift detecting pattern by the width detecting means, The sum of the absolute value of the difference between the average width of the color shift detection pattern and the width of each of the color shift detection patterns is obtained for each of a plurality of positions by changing the relative position of the image forming unit with respect to the conveying unit. And a control unit that determines the position of the image forming unit with respect to the conveying unit corresponding to the sum of the maximum values among the plurality of totals as the maximum color misregistration occurrence relative position. Color image forming apparatus. 2. A conveying means for carrying and conveying a recording material or an image directly formed thereon, and a plurality of images arranged along the conveying direction of the conveying means to form an image on the recording material or the conveying means. Forming means, width detecting means for detecting the width of a plurality of color shift detection patterns formed on the conveying means by the image forming means, and based on width information of the color shift detecting pattern by the width detecting means, The sum of square values of the difference between the width of the color shift detection pattern and the width of each of the color shift detection patterns is obtained at each of a plurality of positions by changing the relative position of the image forming unit with respect to the conveying unit. And a control unit that determines the position of the image forming unit with respect to the conveying unit corresponding to the sum of the maximum values among the plurality of totals as the maximum color misregistration occurrence relative position. Color image forming apparatus. 3. A conveying means for carrying and conveying a recording material or an image directly formed thereon, and a plurality of images arranged along the conveying direction of the conveying means to form an image on the recording material or the conveying means. Forming means, interval detecting means for detecting an interval between the reference color pattern and the detected color pattern formed on the conveying means by the image forming means, and each reference color pattern based on the interval information by the interval detecting means. The total of the average value of the interval with the detection color pattern, the relative position of the image forming means with respect to the conveyance means is obtained for each of a plurality of positions, among the plurality of the total,
A color image forming apparatus comprising: a control unit that determines a position of the image forming unit with respect to the conveying unit corresponding to a total of maximum values as a maximum color misregistration occurrence relative position. 4. The image forming means has a photosensitive drum carrying a toner image, the carrying means has a belt carrying a carrying material or an image, and the control means has a maximum color deviation. 4. The color image forming apparatus according to claim 1, wherein a position where the photosensitive drum is rotated about 180 degrees from a position corresponding to a relative position is set as an image forming start position. 5. The control unit does not use the detection information of the width of the color shift detection pattern when the width of the color shift detection pattern is equal to or larger than a predetermined value. Color image forming apparatus. 6. The control means does not use the detection information of the interval between the reference color pattern and the detected color pattern when the interval between the reference color pattern and the detected color pattern is a predetermined value or more. The color image forming apparatus according to claim 3. 7. The color image forming apparatus according to claim 5, wherein the predetermined value is about 5 times or more an average value of widths of the color misregistration detection patterns. 8. The color image forming apparatus according to claim 6, wherein the predetermined value is about 5 times or more an average value of the intervals between the reference color patterns and the detected color patterns. 9. The color image forming apparatus according to claim 1, wherein the color misregistration detection pattern is formed by partially overlapping the reference color pattern and the detected color pattern.