JP2006078850A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus capable of easily detecting a fluctuation in the angular speed of each image carrier (photoreceptor drum) and adjusting the rotation phase of the image carrier, thereby greatly decreasing color misalignment. <P>SOLUTION: In the color image forming apparatus, a plurality of lines, as reference color patters, in the direction of scan by an optical part are formed at regular time-intervals in the direction of conveyance by a reference color image forming means (a1 to a18). A plurality of lines, as detection color patterns, in the direction of the scan are formed at regular time-intervals in the direction of the conveyance by a color detection image forming means so as to overlap the reference color lines (b1 to b18). The widths (A1 to A18) of lines each of which includes the reference color line and the detection color line are detected. Based upon the detected width of each line including the reference color line and the detection color line, an amount of displacement of the detection color relative to its corresponding reference color is calculated. Based upon the result of the calculation, the rotation phase of each image carrier is adjusted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color image forming apparatus such as a color copying machine or a color printer, and more particularly to the reduction of color misregistration.

  Conventionally, there is a color image forming apparatus called a so-called in-line system in which a plurality of photosensitive drums that form an image carrier are arranged in a line. This is because four photosensitive drums arranged along a transfer path of a transfer material (also referred to as a sheet) carry yellow material, while carrying and transferring the transfer material by an electrostatic transfer belt stretched by a plurality of rollers. A toner image composed of magenta, cyan, and black is sequentially transferred onto a transfer material, and a color image is formed by superimposing each color.

This configuration has attracted attention in recent years because it can perform printing at high speed.
However, since each color is formed by four photosensitive drums, a configuration in which colors are superimposed on one photosensitive drum via four conveyance paths for each color (hereinafter simply referred to as “four-pass method”). Compared to the color image forming apparatus (1)), a higher accuracy is required for rotational driving of the photosensitive drum.

  In other words, a gear train is generally used for driving the photosensitive drum, and low-frequency rotation unevenness such as one rotation component of the gear always occurs. However, in the case of the 4-pass system, the reduction ratio of the drive gear train is an integer. By combining them, it is possible to avoid the accumulated pitch error of the gears and to adjust the image forming positions of the respective colors.

  However, in the case of the in-line method, since the plurality of photosensitive drums are independent, the drive gear train is also independent, which makes it difficult to avoid the problem as in the 4-pass method described above, and the image forming positions of the respective colors are shifted. The image quality is liable to deteriorate due to color misregistration.

Conventionally, as countermeasures against this type of color misregistration, the angular velocity of the photosensitive drum or the image transferred on the transfer material is read to detect the speed unevenness, and the rotation of the motor is controlled so as to cancel the speed unevenness. As disclosed in Patent Document 1 and Patent Document 2, measures have been taken to reduce relative color misregistration by matching the rotational phase of each photosensitive drum to a desired state.
JP-A-9-146329 JP-A-10-333398

  However, in the above-described conventional example, the driving of the image carrier that forms the photosensitive drum is a reduction system via a plurality of gears. It becomes a complicated speed waveform including a component of one rotation cycle. Therefore, high-precision speed unevenness detection means and motor control are required. Even if the phase of the photosensitive drum is adjusted, the influence of the intermediate gear remains, and in order to detect driving unevenness of one rotation period of the image carrier, integration is performed. Such a complicated calculation process must be performed, and the burden on the CPU and memory is heavy.

  The present invention has been made under such circumstances, can easily detect the angular velocity unevenness of the image carrier (photosensitive drum), can adjust the rotational phase of each image carrier, It is an object of the present invention to provide a color image forming apparatus that can significantly reduce color misregistration.

  In order to solve the above problems, in the present invention, the image forming apparatus is configured as described in the following (1) and (2).

(1) Each color image forming unit having an optical unit and an image carrier,
A plurality of transfer means for transferring an image on a conveying means for forming an endless belt that sequentially passes through the image forming portions of the respective colors, or on a recording material placed and conveyed on the conveying means;
Pattern forming means for forming a misregistration detection pattern on the conveying means;
Pattern detecting means for detecting a pattern for detecting misalignment formed on the conveying means;
Calculating means for calculating the amount of positional deviation of the detected color with respect to a reference color from the detection result of the pattern detecting means; and a phase adjusting means for adjusting the rotational phase of the image carrier based on the calculation result of the calculating means;
A color image forming apparatus comprising:
The pattern forming means forms, as the reference color pattern, a plurality of lines in the scanning direction by the optical unit at equal intervals in the transport direction by the image forming means for the reference color, and as the pattern for the detection color A plurality of lines in the scanning direction are formed by the image forming means for detection color so as to overlap with the reference color line at equal time intervals in the transport direction;
The pattern detection means detects the width of the line including the reference color line and the detection color line,
The color image forming apparatus, wherein the calculation means calculates a displacement amount of a detected color with respect to a reference color based on a width of a line including the reference color line and the detected color line detected by the pattern detection means.

(2) a plurality of image forming units each having an optical unit and an image carrier;
A plurality of transfer means for transferring an image onto a conveying means that forms an endless belt that sequentially passes through the plurality of image forming sections, or onto a recording material that is placed and conveyed on the conveying means;
Pattern forming means for forming a misregistration detection pattern on the conveying means;
Pattern detecting means for detecting a pattern for detecting misalignment formed on the conveying means;
Calculating means for calculating the amount of positional deviation of the detected color with respect to a reference color from the detection result of the pattern detecting means; and a phase adjusting means for adjusting the rotational phase of the image carrier based on the calculation result of the calculating means;
A color image forming apparatus comprising:
The pattern forming means forms a plurality of lines in the scanning direction by the optical unit at equal intervals in the transport direction by the image forming unit for the reference color as a pattern for the reference color, and as the pattern for the detection color, A plurality of lines in the scanning direction are formed by the image forming unit for the detection color so as to be alternately arranged with the reference color lines at equal time intervals in the transport direction,
The pattern detection means detects an interval between the reference color line and the corresponding detection color line,
The calculation unit calculates a positional deviation amount of the detected color with respect to the reference color based on an interval between the reference color line detected by the pattern detection unit and the corresponding detection color line. .

  According to the present invention, it is possible to easily detect the angular velocity unevenness of the image carrier (photosensitive drum), and by adjusting the rotational phase of each image carrier based on the detection result, color misregistration can be greatly improved. Can be reduced.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

FIG. 1 is a cross-sectional view illustrating a main configuration of a color image forming apparatus according to a first embodiment.
In FIG. 1, a color image forming apparatus 100 includes four electrophotographic photosensitive drums 1y, 1m, yellow, magenta, cyan, and black, which are image carriers linearly arranged in the vertical direction of FIG. 1c, 1k (hereinafter simply referred to as "photosensitive drum 1"), a transfer material transfer body that supports and conveys the transfer material S by electrostatic adsorption facing each photoconductor drum 1 A material conveying belt (endless belt) 11 is disposed.

  Each of the photosensitive drums 1 is fixed to a drum shaft 22 that is a rotating shaft of the photosensitive drum 1, and is engaged with a coupling 36 that is a first engaging member, which will be described in detail later, and the coupling 36. A rotational driving force is transmitted from a driving motor (not shown) serving as a driving source to the gear 18 on the coupling 33 side serving as a second engaging member to be coupled to be rotated in the counterclockwise direction of FIG. 1 (FIG. 2). (Refer to (a) and (b)).

  Around each photosensitive drum 1, primary chargers 2 a, 2 b, 2 c, and 2 d (hereinafter simply referred to as “charging devices”) for charging the surface of the photosensitive drum 1 uniformly in order from the upstream side in the rotation direction. Exposure unit 3a for forming an electrostatic latent image by irradiating the surface of the photosensitive drum 1 uniformly charged by the primary charger 2 with a laser beam based on image information. 3b, 3c, 3d (hereinafter simply referred to as "exposure means 3") are arranged.

  Furthermore, developing devices 4a, 4b, 4c, and 4d (hereinafter, simply referred to as “developing device 4”) that make each color toner adhere to the surface of the photosensitive drum 1 on which the electrostatic latent image is formed to visualize the toner image. Cleaning means 6a, 6b, 6c, 6d (hereinafter simply referred to as “cleaning means 6”) for removing toner remaining on the surface of the photosensitive drum 1 after transfer are disposed.

  The photosensitive drum 1, the primary charger 2, the developing device 5, and the cleaning unit 6 are integrated into the apparatus main body 100 as process cartridges 7 a, 7 b, 7 c, and 7 d (hereinafter simply referred to as “process cartridge 7”). On the other hand, it is configured to be detachable. In addition, it has a detecting means for detecting the replacement of the process cartridge (not shown), and detects the loading state during the initialization operation.

  In addition, a transfer material conveying belt (endless belt) 11 is sandwiched between the transfer material conveying belts 11 on the surface of the photosensitive drum 1 at positions facing the respective photosensitive drums 1. Transfer rollers 12a, 12b, 12c and 12d (hereinafter simply referred to as “transfer roller 12”) serving as transfer means for transferring the toner image are arranged.

  The drive unit is positioned in front of the left side of the machine and applies a rotational driving force to the process cartridges of four colors arranged in a substantially vertical direction. Each process cartridge 7 includes a photosensitive drum 1, a developing device 4, a cleaning unit 6 and the like, and supplies all of these driving forces.

  Since the process cartridge 7 can be detached and attached independently for each color, the drive transmission unit is also arranged in a substantially vertical direction independently for each color and directly transmits to the photosensitive drum 1 that requires rotational accuracy. For example, the driving of the developing device 4 and the cleaning means 6 may be transmitted in another series. The driving force supplied to the cartridge 7 is distributed to each element by a driving system in the process cartridge 7.

  As shown in FIGS. 2A and 2B, the drive means includes a gear 18 for driving the process cartridge, a shaft portion 32a that rotates together with the gear 18, and a shaft portion. The coupling portion 33 that rotates to transmit the rotational driving force to the process cartridge 7 and the drum shaft 22 that is fixed concentrically with the photosensitive drum 1 are integrated with the positioning hole 34 for determining the position. It consists of This integral component can be a resin molded product.

  As shown in FIG. 2, the shaft portion 32a is supported by the cylinder bearing portion 35 installed on the main body side so that only the shaft portion 32a in the vicinity of the gear root is freely rotated and linearly moved. The periphery of 33 is supported to such an extent that the positioning hole 34 is determined by fitting to the drum shaft 22 described later, and does not interfere with the shaft position and does not hinder the coupling. Clearance is provided.

  Although the gear shaft is inclined due to the positional accuracy of the cylinder bearing portion 35 and the drum shaft 22, the distance from the shaft portion 32 a near the gear root to the positioning hole 34 is made sufficiently long so as not to cause any actual harm.

  The gear 18 and the integral part are movable in the axial direction, and are pressed toward the photosensitive drum 1 by a plate spring 37.

  A drum shaft 22 that rotates integrally with the photosensitive drum 1 is fixed to the photosensitive drum 1 using a parallel pin (not shown), and the drum shaft 22 is accurately positioned on the machine body via a bearing 38. Has been.

  A non-driving side (driven side) coupling 36 is fixed to the end of the drum shaft 22, and meshes with the driving side (main driving side) coupling 33 to transmit the rotational driving force.

  As shown in FIGS. 2A and 2B, the driving side coupling 33 and the non-driving side coupling 36 are triangular spiral couplings, and when driven in a predetermined direction, the two sides always engage with each other. It has become.

  In FIG. 3, the motors 41y, 41m, 41c and 41k (hereinafter referred to as motor 41) provided exclusively for the respective photosensitive drums 1y, 1m, 1c and 1k (hereinafter referred to as photosensitive drum 1) are engaged with the photosensitive drum 1. The photosensitive drum 1 is driven through the gear 18.

  The tooth 31 of the gear 18 is provided with a target for detecting the phase, and a phase signal is detected once per rotation by an optical or magnetic phase detector (42y, 42m, 42c, 42k) 42. can do.

  Further, an image detection sensor 44 is provided so as to face the transfer material conveyance belt 11, and an image on the transfer material conveyance belt 11 can be optically detected.

  In the configuration of this embodiment, the main component of the angular velocity unevenness is only one rotation cycle of the photosensitive drum 1, so that a pattern formed on the photosensitive drum 1 at equal time intervals is transferred to the transfer material conveying belt 11. Then, when it is read by the image detection sensor and the accumulated fluctuation component of the pattern interval is obtained, a sine waveform as shown in FIG. 4 is obtained.

  In FIG. 4, the horizontal axis represents the distance from the front end of the image, and the vertical axis represents the cumulative amount of positional deviation.

  In order to obtain the phase relationship of the four colors, processing is performed by creating and detecting one color at a time while managing the image formation start timing of each color, obtaining a sine waveform, correcting the comparison by the start timing interval, and comparing them. Just do it.

  Further, as shown in FIG. 4, when Bk is used as a reference, the color shift relative to the Bk color can be reduced by shifting the Y color by the distance y toward the image leading end. Similarly, the M color may be shifted by the distance m, and the C color may be shifted by the distance c. However, since this phase detection requires a predetermined time, if it is frequently performed, a loss of image forming time occurs.

  Therefore, a phase detector 42 that detects the phase of the gear 18 that rotates the photosensitive drum 1 is used, and phase control is usually performed based on this phase information.

  If the phase waveform detected by the phase detector 42 is in a state as shown in FIG. 5, the phase of the Y-color gear 18y is controlled so as to be turned earlier by a time yp corresponding to the distance y in FIG. , The relative color shift between the Bk color and the Y color decreases. Similarly, the M-color gear 18m may be phase-controlled so that the time m-p is faster than the distance m, and the C-color gear 18c is turned faster than the distance c by the time cp. This phase control can be performed by adjusting the speed of the motor 41.

  When such phase control is performed and the above-described phase relationship is obtained, the result is as shown in FIG. 6, and the relative color shift can be reduced to about ½ or less.

Hereinafter, the operation of this embodiment will be described.
A misregistration detection pattern as shown in FIG. 7 is formed on the transfer material conveyance belt 11 and is read by the image detection sensors 44 provided on both sides of the transfer material conveyance belt 11 to detect the misregistration amount of each color.

  FIG. 7 shows a pattern for detecting the amount of misalignment in the paper transport direction. In this example, the detected color b (hereinafter Y: yellow, M: magenta, C: cyan) on the reference color a (hereinafter Bk: black). ) (In the figure, for the sake of clarity, the image is displayed slightly shifted in the scanning direction of the exposure means). a1 to a18 and b1 to b18 indicate the detection timing of each pattern. The arrows indicate the conveyance direction of the transfer material conveyance belt 11.

  In the misregistration detection pattern, since the reference color and the detection color are arranged at the same position in the transport direction, the pattern is hardly affected by the speed unevenness caused by the transfer material transport belt 11.

  Further, as shown in FIG. 8, it can be canceled by setting the pitch of the line of the position detection pattern to an integral multiple of an interval corresponding to driving unevenness other than the photosensitive drum 1.

  Measure the color relative to the reference color by fixing the rotation phase of the reference color, detecting the rotation phase of the detected color with respect to the reference color by shifting it by a certain predetermined angle, and repeating the above detection. As the relationship between the rotation phase and the amplitude of the above, a waveform as shown in FIG. 9 is obtained, and the optimum phase of each color can be easily determined.

In FIG. 9, the vertical axis indicates the amplitude of the detected color misregistration amount with respect to the reference color, and the horizontal axis indicates the rotational phase of the detected color with respect to the reference color. It is necessary to obtain a waveform over one period). The amplitude of the positional deviation amount of the photosensitive drum 1 of the detected color with respect to the positional deviation detection pattern reference color is:
ΔC ₁ (θ) = MAX (Ac1, Ac2,... Ac17, Ac18) −MIN (Ac1, ac2,... Ac17, ac18) / 2 (Formula 1)
ΔY ₁ (θ) = MAX (Ay1, Ay2,... Ay17, Ay18) −MIN (A1, A2,... Ay17, Ay18) / 2 (Formula 2)
ΔM ₁ (θ) = MAX (Am1, Am2,... Am17, Am18) −MIN (Am1, Am2,... Am17, Am18) / 2 (Formula 3)
The width in the conveyance direction of the line in which the reference color and the detection color are overlapped is detected.

  Further, there is a method of shortening the time by roughly adjusting the rotational phase of the photosensitive drum 1 of the detected color with respect to the reference color and then finely adjusting the rotational phase.

  In this method, for example, first, a displacement pattern is detected at intervals of 120 ° with respect to the reference phase. Using the detection result, a phase range having a small amplitude of the positional deviation amount is determined. Next, a phase shift pattern is detected by finely changing the phase within the phase range to determine a phase range having a small amplitude of the position shift amount. This operation is repeated, and finally the phase where the amplitude of the positional deviation amount is minimum is set as the optimum phase.

  By feeding back the phase detection result to the rotational phase control of the motor 41, color misregistration can be reduced.

  In the case where there are a plurality of speed irregularities other than those caused by the transfer material conveyance belt 11, the moving average process is performed for the pitch of the line of the misregistration detection pattern as in the following formula, whereby the speed irregularity of the photosensitive drum 1 is performed. Can be easily extracted.

ΔC ₁ (θ) = MAX (Average (Ac1, Ac2, Ac3), Average (Ac2, Ac3, Ac4)... Average (Ac15, Ac16, Ac17), Average (Ac16, Ac17, Ac18)) − MIN (Average) (Ac1, Ac2, Ac3), Average (Ac2, Ac3, Ac4) ... Average (Ac15, Ac16, Ac17), Average (Ac16, Ac17, Ac18)) / 2 (Formula 4)
ΔY ₁ (θ) = MAX (Average (Ay1, Ay2, Ay3), Average (Ay2, Ay3, Ay4)... (Ay1, Ay2, Ay3), Average (Ay2, Ay3, Ay4) ... Average (Ay15, Ay16, Ay17), Average (Ay16, Ay17, Ay18)) / 2 (Formula 5)
ΔM ₁ (θ) = MAX (Average (Am1, Am2, Am3), Average (Am2, Am3, Am17), Average (Am15, Am16, Am17), Average (Am16, Am17, Am18)) − MIN (Average) (Am1, Am2, Am3), Average (Am2, Am3, Am4) ... Average (Am15, Am16, Am17), Average (Am16, Am17, Am18)) / 2 (Formula 6)

  As described above, according to the present embodiment, it is possible to easily detect the angular velocity unevenness of the photosensitive drum, and by adjusting the rotational phase of each photosensitive drum based on the detection result, the color misregistration is greatly increased. Can be reduced.

  In this embodiment, it is assumed that the optimum phase calculation and the optimum phase determination in which the amplitude of the positional deviation amount is minimized are automatically performed by the CPU that controls the apparatus. Part of it can be left to the operator.

  A “color image forming apparatus” that is Embodiment 2 will be described with reference to FIG. Since the hardware configuration of the present embodiment is the same as that of the first embodiment, the description of the first embodiment is used and described below.

  A misregistration detection pattern as shown in FIG. 10 is formed on the conveyor belt 3 and is read by a pair of sensors 44 provided on both sides of the conveyor belt to detect the misregistration amount of each color. FIG. 10 is a diagram showing a pattern for detecting a positional deviation amount in the paper transport direction. In this example, the detected color b (hereinafter Y: yellow, M: magenta, C) is added to the reference color a (hereinafter Bk: black). : Cyan) are arranged alternately with respect to the transport direction. c1 to c9 and d1 to d9 indicate the detection timing of each pattern, and the arrows indicate the conveyance direction of the transfer material conveyance belt 11.

  In the misregistration detection pattern, the corresponding reference color and detection color (c1, d1, etc. are given the same numbers) are arranged at positions close to the transport direction. 11 is less likely to be affected by the uneven speed.

  As shown in FIG. 8, it can be canceled by setting the line pitch of the misregistration detection pattern to an integral multiple of the driving unevenness other than the photosensitive drum 1.

  The rotation phase of the reference color is fixed, the rotation phase of the detection color with respect to the reference color is shifted by a predetermined angle, the pitch between the reference color and the detection color is detected, and the above detection is repeated. Thus, a waveform as shown in FIG. 9 is obtained for the relationship between the rotation phase and amplitude of the measurement color with respect to the reference color, and the optimum phase of each color can be easily determined.

As in the first embodiment, the amplitude of the positional deviation amount of the photosensitive drum 1 of the detected color with respect to the positional deviation detection pattern reference color is the same as in the first embodiment.
ΔC ₁ (θ) = MAX (Bc1, Bc2,... Bc17, Bc18) −MIN (Bc1, Bc2,... Bc17, Bc18) / 2 (Formula 1)
ΔY ₁ (θ) = MAX (By1, By2,... By17, By18) −MIN (B1, B2,... By17, By18) / 2 (Formula 2)
ΔM ₁ (θ) = MAX (Bm1, Bm2,... Bm17, Bm18) −MIN (Bm1, Bm2,... Bm17, Bm18) / 2 (Formula 3)
It is represented by

  Further, there is a method of shortening the time by roughly adjusting the rotational phase of the photosensitive drum 1 of the detected color with respect to the reference color and then finely adjusting the rotational phase.

  In this method, for example, first, a displacement pattern is detected at intervals of 120 ° with respect to the reference phase. Using the detection result, a phase range having a small amplitude of the positional deviation amount is determined. Next, a phase shift pattern is detected by finely changing the phase within the phase range to determine a phase range having a small amplitude of the position shift amount. This operation is repeated, and finally the phase where the amplitude of the positional deviation amount is minimum is set as the optimum phase.

  By feeding back the phase detection result to the rotational phase control of the motor 41, color misregistration can be reduced.

  In the case where there are a plurality of speed irregularities other than those caused by the transfer material conveyance belt 11, the moving average process is performed for the pitch of the line of the misregistration detection pattern as in the following formula, whereby the speed irregularity of the photosensitive drum 1 is performed. Can be easily detected.

ΔC ₁ (θ) = MAX (Average (Bc1, Bc2, Bc3), Average (Bc2, Bc3, Bc4)... (Bc1, Bc2, Bc3), Average (Bc2, Bc3, Bc4) ... Average (Bc15, Bc16, Bc17), Average (Bc16, Bc17, Bc18)) / 2 (Formula 4)
ΔY ₁ (θ) = MAX (Average (By1, By2, By3), Average (By2, By3, By4)... Average (By15, By16, By17), Average (By16, By17, By18)) − MIN (Average) (By1, By2, By3), Average (By2, By3, By4) ... Average (By15, By16, By17), Average (By16, By17, By18)) / 2 (Formula 5)
ΔM ₁ (θ) = MAX (Average (Bm1, Bm2, Bm3), Average (Bm2, Bm3, Bm4)... (Bm1, Bm2, Bm3), Average (Bm2, Bm3, Bm4) ... Average (Bm15, Bm16, Bm17), Average (Bm16, Bm17, Bm18)) / 2 (Formula 6)

  As described above, also in this embodiment, the same effect as that of Embodiment 1 can be obtained.

  Next, Example 3 will be described with reference to FIG.

  FIG. 11 is a cross-sectional explanatory diagram illustrating the configuration of a “color image forming apparatus” according to the third embodiment. In addition, about the component similar to the above-mentioned Example 1, description of Example 1 is used and description here is abbreviate | omitted.

  In this embodiment, as shown in FIG. 11, the toner image formed on the surface of the photosensitive drum 1 facing the photosensitive drum 1 serving as a plurality of image carriers arranged in parallel in the horizontal direction is subjected to primary transfer. An intermediate transfer belt 54 serving as an intermediate transfer member is stretched by a driving roller and a driven roller, and a secondary transfer device 55 is disposed at a position facing the driven roller with the intermediate transfer belt 54 interposed therebetween. .

  In the same manner as in the first embodiment, the toner images formed on the respective photosensitive drums 1 are transferred to the intermediate transfer belt 54 by the action of the transfer units 56a, 56b, 56c, and 56d (hereinafter simply referred to as “transfer unit 56”). The primary transfer.

  On the other hand, the transfer material S fed from the paper feed cassette 50 by the pickup roller 51 is separated and fed one by one by a separation means (not shown), and then sent to the registration roller pair 53 by the conveying roller pair 52. By the pair 53, the toner image conveyed between the intermediate transfer belt 54 and the secondary transfer device 55 at a predetermined timing and primarily transferred to the intermediate transfer belt 54 by the action of the secondary transfer device 55 is secondarily transferred. The

  After the toner image is fixed by the fixing device 21, the transfer material S onto which the toner image has been transferred is conveyed by a discharge roller pair 57 and discharged onto a discharge tray 24 provided on the upper part of the apparatus main body 200.

  In the above configuration, as in the first and second embodiments, a misregistration detection pattern is formed on the intermediate transfer member 54, the pattern is detected by the image detection sensor 44, and the misregistration amount is calculated based on the detection result. By adjusting the rotational phase of the photosensitive drum based on the calculation result, the same effect as in the first and second embodiments can be obtained.

FIG. 3 is a longitudinal sectional view showing the main configuration of a color image forming apparatus that is Embodiment 1. The figure which shows the structure of the drive part of a photoconductive drum, and a drive transmission part. The figure which shows the principal part structure of the drive part of a photosensitive drum, and a control system The figure which shows the state of the color shift of each color before phase adjustment The figure showing the state of the signal which detected the phase of the gearwheel which rotationally drives a photosensitive drum The figure which shows the state which eliminated the color shift of each color after phase adjustment of a photoconductive drum The figure which shows the pattern for position shift detection, and its example of arrangement The figure which shows the amount of position shifts with respect to a reference color when driving unevenness other than the photosensitive drum is canceled The figure which shows the change of the position shift amplitude when changing the rotation phase of a photoconductive drum. The figure which shows the pattern for position shift detection in Example 2, and its example of arrangement | positioning. Sectional drawing which shows the principal part structure of the color image forming apparatus which is Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 3 Exposure means 7 Process cartridge 100 Color image forming apparatus

Claims (6)

Each color image forming unit having an optical unit and an image carrier, respectively.
A plurality of transfer means for transferring an image on a conveying means for forming an endless belt that sequentially passes through the image forming portions of the respective colors, or on a recording material placed and conveyed on the conveying means;
Pattern forming means for forming a misregistration detection pattern on the conveying means;
Pattern detecting means for detecting a pattern for detecting misalignment formed on the conveying means;
A computing means for computing a positional deviation amount of the detected color with respect to a reference color from the detection result of the pattern detecting means;
Phase adjusting means for adjusting the rotational phase of the image carrier based on the calculation result of the calculating means;
A color image forming apparatus comprising:
The pattern forming means forms, as the reference color pattern, a plurality of lines in the scanning direction by the optical unit at equal intervals in the transport direction by the image forming means for the reference color, and as the pattern for the detection color A plurality of lines in the scanning direction are formed by the image forming means for detection color so as to overlap with the reference color line at equal time intervals in the transport direction;
The pattern detection means detects the width of the line including the reference color line and the detection color line,
The calculating means calculates a positional deviation amount of the detected color with respect to the reference color based on a width of the line including the reference color line and the detected color line detected by the pattern detecting means. Color image forming apparatus. A plurality of image forming units each having an optical unit and an image carrier;
A plurality of transfer means for transferring an image onto a conveying means that forms an endless belt that sequentially passes through the plurality of image forming sections, or onto a recording material that is placed and conveyed on the conveying means;
Pattern forming means for forming a misregistration detection pattern on the conveying means;
Pattern detecting means for detecting a pattern for detecting misalignment formed on the conveying means;
Calculating means for calculating the amount of positional deviation of the detected color with respect to a reference color from the detection result of the pattern detecting means; and a phase adjusting means for adjusting the rotational phase of the image carrier based on the calculation result of the calculating means;
A color image forming apparatus comprising:
The pattern forming means forms a plurality of lines in the scanning direction by the optical unit at equal intervals in the transport direction by the image forming unit for the reference color as a pattern for the reference color, and as the pattern for the detection color, A plurality of lines in the scanning direction are formed by the image forming unit for the detection color so as to be alternately arranged with the reference color lines at equal time intervals in the transport direction,
The pattern detection means detects an interval between the reference color line and the corresponding detection color line,
The calculating means calculates a positional deviation amount of the detected color with respect to the reference color based on an interval between the reference color line detected by the pattern detecting means and the corresponding detected color line. A color image forming apparatus. The color image forming apparatus according to claim 1 or 2,
The phase adjusting means adjusts the rotational phase of the measurement color image carrier relative to the rotational phase of the reference color image carrier to the phase relationship determined to be optimum,
The phase relationship determined to be optimal is that the rotation phase of the image carrier for the reference color is fixed, and the rotation phase of the image carrier for the detection color with respect to the rotation phase of the image carrier for the reference color is a predetermined value. The method of detecting the amount of misregistration of the detected color with respect to the reference color by adjusting for each angle is performed over at least one period of the driving unevenness of the image carrier, and the amplitude of the detected misregistration amount and the reference color Based on the relationship of the rotational phase of the measured color to the reference color, the relationship of the rotational phase of the measured color with respect to the reference color having the minimum amplitude is obtained, and the phase relationship that is determined to be optimum is based on the relationship of the calculated rotational phase. A color image forming apparatus. The color image forming apparatus according to claim 3.
When obtaining the optimum phase relationship, first, the rotational phase of the measurement color with respect to the reference color is greatly changed to detect the positional deviation at each rotational phase, and further rotate around the rotational phase with a small amount of positional deviation. A color image forming apparatus characterized in that a phase shift is detected finely to detect a positional shift at each rotational phase, and a rotational phase with a small amount of positional shift has a phase relationship that is determined to be optimal. The color image forming apparatus according to claim 1 or 2,
The color misregistration detection pattern is characterized in that the line-to-line pitch is an integral multiple of an interval corresponding to a driving unevenness period caused by a motor and gears for rotating an image carrier and a developing device. The color image forming apparatus according to claim 1 or 2,
A color image forming apparatus, characterized in that a moving average process is performed on the pitch of the lines when calculating the positional deviation amount by the calculating means.

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