JP2005208406A - Color image forming apparatus and color image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct image information so as to eliminate the influence of displacement of paper sheets and to form color images etc., with high accuracy in prescribed positions even when the paper sheets are displaced owing to a change by age. <P>SOLUTION: The image forming apparatus is equipped with: image forming units 10Y, 10M, 10C and 10K for forming the images to the paper sheets P let off from a paper feed cassette 20A etc.; an displacement sensor 11 for outputting the first displacement amount by detecting the displacement of the paper sheets P regulated in the parallel position on the downstream side of the paper feed cassette 20A; an displacement sensor 12 for outputting the second displacement amount by detecting the displacement of the paper sheets P regulated in the parallel positions on the upstream side of the image forming unit 10K; and a control means 15 for calculating a differential value from the first and second displacement amounts outputted from the offset sensors 11 and 12 and executing registering processing to determine the image forming position for the paper sheets P based on the differential value of the first and second displacement amounts. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus and a color image forming method suitable for application to a tandem (vertical) type color printer or color copier having an intermediate transfer belt, a color copier, or a combination of these. Is.

  In recent years, color printers, color copiers, and complex machines of these are often used. FIG. 8 is a conceptual diagram showing a configuration example of a direct transfer type color copying machine 200 according to a conventional example.

  The color copying machine 200 shown in FIG. 8 includes exposure means 3Y, 3M, 3C, 3K, and developing means (not shown) for yellow (Y), magenta (M), cyan (C), and black (BK) colors. 1), the photosensitive drums 1Y, 1M, 1C, and 1K, the transfer material transfer belt 90, and the fixing device 17 are provided. These Y, M, C, and BK color photosensitive drums 1Y, 1M, 1C, and 1K are arranged side by side above the transfer material transfer belt. For example, the Y-color exposure means 3Y draws an electrostatic latent image on the photosensitive drum 1Y based on arbitrary image information. A developing unit (not shown) forms a color toner image by attaching Y color toner to the electrostatic latent image drawn on the photosensitive drum 1Y. The photosensitive drum directly transfers the toner image onto the paper (transfer material) P on the transport material transfer belt. Similar processing is performed for the other M, C, and BK colors. The color toner image transferred to the paper is then fixed by the fixing device 17.

  On the other hand, as in the printing field, color copiers are also required to perform image formation positions on transfer materials with high accuracy (high accuracy registration). In a monochrome machine, in order to achieve high-precision registration, especially in the direction perpendicular to the transfer material conveyance direction, the deviation amount of the transfer material is detected using a contact-type line sensor, and the image An image forming apparatus that feeds back to a forming position has appeared.

  Also in the above-described color copying machine 200, it is possible to provide the misalignment sensor 11 in a registration mechanism unit (not shown), detect the misalignment of the paper P, and adjust the image position based on the misalignment amount. By providing the offset sensor 11 in the registration mechanism portion of the copying machine 200, the image position can be adjusted because the most upstream unit is close to the paper feed path.

  In connection with this type of misalignment detection function, Patent Document 1 discloses a method and apparatus for detecting misalignment of a circulating conveyance sheet. According to this deviation detection method, a detection sensor capable of scanning in a direction transverse to the circulation conveyance sheet is provided, and the side edge position of the sheet at the first conveyance obtained by scanning of the detection sensor is set to the side edge of the circulation conveyance sheet. After that, the deviation of the side edge position of the sheet during circulation conveyance with respect to the side edge reference position is detected. If such a detection sensor is provided in an image forming apparatus or the like, it is possible to accurately detect a deviation of a sheet that is repeatedly circulated and conveyed by a simple configuration.

  Patent Document 2 discloses an image forming apparatus, a color image forming apparatus, and a color image forming method. According to this image forming apparatus, a control unit, a main deviation detection unit, a back image deviation detection unit, and a writing unit are provided. The writing start position in the main scanning direction of the writing means in the back side image formation is controlled based on the offset information obtained when forming the image on the back side and the offset information obtained from the back side image offset detecting means. To be made. When such a control means is provided in an image forming apparatus or the like, in double-sided image formation, the front and back image forming positions are corrected without causing a large difference, and a high-quality image can be formed.

Japanese Patent Laid-Open No. 06-144647 (page 3, Fig. 1) Japanese Patent Laid-Open No. 2002-006718 (page 5, FIG. 8)

  However, the conventional color image forming apparatus has the following problems.

  i. In the color copying machine 200 shown in FIG. 8, since the most upstream unit and the paper feed path are close to each other, the offset position sensor 11 is provided in the registration mechanism (not shown) to perform image position adjustment. Since the photosensitive drums 1Y, 1M, 1C, and 1K for M, C, and BK colors are arranged side by side above the transfer material transfer belt, there is a demerit that the apparatus is increased in size.

  ii. Further, according to the color copying machine 200, since a method of directly transferring a color toner image to the paper P is adopted, it is difficult to improve the image quality.

  iii. In order to compensate for the two disadvantages of the color copying machine 200 described above, as seen in Patent Document 2, a configuration of a tandem type color image forming apparatus in which a plurality of image forming units are provided side by side is adopted, and its registration mechanism When the image position adjustment is performed by providing a deviation sensor at the part, the image forming path (path) from the most upstream image forming unit to the most downstream unit is long, whereas the feeding path is It becomes shorter on the same route as a monochrome machine.

  iv. Accordingly, the sheet misalignment detection method disclosed in Patent Document 1 is adopted for the tandem color image forming apparatus because, as described above, the apparatus is downsized and the first copy is made because the image forming path is long. Difficulties arise in terms of coexisting conflicting issues of shortening the output time (FCOT).

  Accordingly, the present invention solves the above-described problems, and enables image information to be corrected so as to eliminate the influence of the offset of the transfer material, and even when the transfer material is offset due to secular change. Another object of the present invention is to provide a color image forming apparatus and a color image forming method capable of accurately forming a color image or the like at a predetermined position.

  In order to solve the above problems, a color image forming apparatus according to the present invention is an apparatus for forming an image based on arbitrary image information, and includes a paper feeding unit and a transfer material fed from the paper feeding unit. An image forming unit that forms an image; a first detection unit that detects a shift of a transfer material whose position is regulated upstream of the sheet feeding unit and outputs a first shift amount; and the first detection unit A second detection unit provided upstream of the detection unit and in front of the position where the image is formed on the transfer material, detects a shift of the transfer material and outputs a second shift amount; The difference value is calculated from the first deviation amount output from the first detection means and the second deviation amount output from the second detection means, and the deviation amount output from the first detection means and the first deviation amount are calculated. Registration for determining the image forming position with respect to the transfer material based on the difference value between the first and second offset amounts It is characterized in that a control means for executing the Align process.

  According to the color image forming apparatus of the present invention, when an image is formed based on arbitrary image information, the first detection unit detects a deviation of the transfer material whose position is regulated on the upstream side of the paper supply unit. Then, the first deviation amount is output to the control means. Further, the second detection means provided upstream of the first detection means and in front of the position where the image is formed on the transfer material is, for example, a transfer whose position is restricted by the second position restriction means. The deviation of the material is detected and the second deviation amount is output to the control means. On the premise of this, the control means calculates the difference value from the first deviation amount output from the first detection means and the second deviation amount output from the second detection means, and the first deviation value is calculated. Registration processing for determining the image forming position with respect to the transfer material is executed based on the deviation amount output from the detecting means and the difference value between the first and second deviation amounts.

  Therefore, the control unit can correct the writing position of the image information so that the deviation amount of the transfer material in the image forming unit becomes a predetermined value. The image forming unit forms an image based on the corrected image information on the transfer material fed from the paper feeding unit. In addition, even if the characteristics of the paper feed (feed) path change due to secular change, and the amount of deviation generated between the first detection means and the second detection means changes, the statistical Or the image position is corrected in consideration of the difference value between the first and second offset amounts obtained in the previous paper feed, so that a color image or the like can be accurately printed at a predetermined position on the transfer material. Can be formed.

  A color image forming method according to the present invention is a tandem color image forming method in which a color image is formed on a transfer material fed from a paper feeding system by the image forming system, and the position is regulated on the upstream side of the paper feeding system. The first deviation amount is obtained by detecting the deviation of the transfer material to be detected, and then the second deviation is detected by detecting the deviation of the transfer material whose position is regulated in front of the position where the image is formed on the transfer material. And the difference value is calculated from the first and second offset amounts acquired here, and the difference value between the first offset amount and the first and second offset amounts is calculated. The image forming position with respect to the transfer material is determined based on this.

  According to the color image forming method of the present invention, when an image is formed on the transfer material fed from the paper feeding system by the image forming system, the difference value of the offset amount of the transfer material in the image forming system is set to a predetermined value. Thus, the image information writing position can be corrected. Moreover, even if the characteristics of the paper feed path change due to secular change and the first and second offset amounts change, the statistically obtained or the first obtained by the previous paper feed Since the image position is corrected in consideration of the difference value between the first and second offset amounts, a color image or the like can be accurately formed at a predetermined position on the transfer material.

  According to the color image forming apparatus of the present invention, when an image is formed based on arbitrary image information, the shift amount of the transfer material that is position-regulated on the upstream side of the paper feeding system and the front side of the image forming system And a control unit that calculates a difference value from the deviation amount of the transfer material whose position is regulated in step, and executes a registration process for determining an image forming position with respect to the transfer material based on the difference value of the deviation amount. .

  With this configuration, it is possible to correct the writing position of the image information so that the difference value of the shift amount of the transfer material in the image forming unit becomes a predetermined value. Moreover, even when the deviation of the paper feed path changes due to aging and the amount of deviation generated between the first detection means and the second detection means changes, it was obtained statistically. Alternatively, since the image position is corrected in consideration of the difference value between the first and second offset amounts obtained in the previous paper feed, a color image or the like can be formed accurately at a predetermined position on the transfer material. it can. Accordingly, it is possible to provide a color image forming apparatus having a highly accurate registration function for aligning the image forming position with the transfer material.

  According to the color image forming method of the present invention, when an image is formed on the transfer material fed out from the paper feeding system by the image forming system, a deviation of the transfer material whose position is regulated upstream of the paper feeding system is detected. The first deviation amount is obtained, and then, the second deviation amount is obtained by detecting the deviation of the transfer material whose position is regulated in front of the position where the image is formed on the transfer material, A difference value is calculated from the first and second deviation amounts acquired here, and based on the first deviation amount and the difference value between the first and second deviation amounts calculated here. The position of the image forming system with respect to the transfer material is determined (register processing).

  With this configuration, it is possible to correct the writing position of the image information so that the difference value of the deviation amount of the transfer material in the image forming system becomes a predetermined value. Moreover, even if the characteristics of the paper feed path change due to secular change and the first and second offset amounts change, the statistically obtained or the first obtained by the previous paper feed Since the image position is corrected in consideration of the difference value between the first and second offset amounts, a color image or the like can be accurately formed at a predetermined position on the transfer material.

  A color image forming apparatus and a color image forming method according to embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a conceptual diagram showing a configuration example of a color copying machine 100 as an embodiment of the present invention.
In this embodiment, when an image is formed on the basis of arbitrary image information, the image forming apparatus includes a control unit that executes a registration process. The difference value is calculated from the deviation amount of the transfer material whose position is regulated in front of the position where the image is formed on the material, and the image forming position with respect to the transfer material is determined based on the difference value of these deviation amounts. Thus, the writing position of the image information can be corrected so that the difference value of the deviation amount of the transfer material in the image forming means becomes a predetermined value, and the characteristics of the paper feed path change due to the secular change. Even if the second offset amount changes, the image position is considered in consideration of the difference value between the first and second offset amounts obtained statistically or obtained by the previous paper feed. Corrects the color image at a predetermined position on the transfer material with high accuracy. It is obtained so as to form a.

  A color copying machine 100 shown in FIG. 1 is an example of a color image forming apparatus, and is an apparatus that forms a color image based on arbitrary image information. The color copying machine 100 includes a copying machine main body 101 and an image reading device 102. An image reading device 102 including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the copying machine main body 101. The document 30 placed on the document table of the automatic document feeder 201 is conveyed by a conveying means, and one or both sides of the document are scanned and exposed by the optical system of the document image scanning exposure device 202 to reflect the document image. Incident light is read by the line image sensor CCD.

  The analog image signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit (not shown) to become digital image data Din. The image data Din is converted into image data Dy, Dm, Dc, Dk for Y, M, C, BK colors, and then image writing units (exposure means) 3Y, 3M, 3C, constituting the image forming means 60. Sent to 3K.

  The automatic document feeder 201 described above is provided with automatic double-sided document conveying means. The automatic document feeder 201 continuously reads the contents of a large number of documents 30 fed from the document placement table at once, and stores the document contents in a storage means (electronic RDH function). This electronic RDH function is conveniently used when copying the contents of a large number of documents by the copying function or when transmitting a large number of documents 30 by the facsimile function.

  The copying machine main body 101 constitutes a tandem type color image forming apparatus, and a plurality of sets of image forming units (image forming systems) 10Y, 10M, 10C, 10K each having an image forming body for each color, and an endless intermediate A transfer belt 6, a paper feeding / conveying means including a refeeding mechanism (ADU mechanism), a fixing device 17 for fixing a toner image, and a feeding for feeding a transfer material (hereinafter referred to as paper) P to an image forming system. And paper means 20.

  The paper feeding unit 20 is provided below the image forming system. The sheet feeding means 20 is composed of, for example, three sheet feeding cassettes 20A, 20B, and 20C. The image forming unit 60 includes four image forming units 10Y, 10M, 10C, and 10K in order to form a color image on the paper P fed from the paper supply unit 20. The image forming unit 10Y that forms a yellow (Y) image includes a photosensitive drum 1Y as an image forming body that forms a Y-color toner image, and a Y-color charging disposed around the photosensitive drum 1Y. Means 2Y, exposure means 3Y, developing device 4Y, and image forming body cleaning means 8Y.

  An image forming unit 10M for forming a magenta (M) color image includes a photosensitive drum 1M as an image forming body for forming an M color toner image, an M color charging unit 2M, an exposure unit 3M, and a developing device 4M. And an image forming member cleaning means 8M. An image forming unit 10C for forming a cyan (C) color image includes a photosensitive drum 1C as an image forming body for forming a C toner image, a charging unit 2C for C color, an exposure unit 3C, and a developing device 4C. And an image forming member cleaning means 8C. An image forming unit 10K that forms a black (BK) color image includes a photosensitive drum 1K as an image forming body that forms a BK color toner image, a charging unit 2K for BK color, an exposure unit 3K, and a developing device 4K. And an image forming member cleaning means 8K.

  The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit. Development by the developing devices 4Y, 4M, 4C, and 4K is performed by reversal development in which a development bias in which an AC voltage is superimposed on a DC voltage having the same polarity (negative polarity in this embodiment) as the polarity of the toner to be used is applied. . The intermediate transfer belt 6 is wound around a plurality of rollers and is rotatably supported. Each of the Y, M, C, and BK colors formed on each of the photosensitive drums 1Y, 1M, 1C, and 1K. A toner image is transferred.

  Here, an outline of the image forming process will be described below. Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is applied with a primary transfer bias (not shown) having a polarity opposite to that of the toner to be used (positive polarity in this embodiment). The rollers 7Y, 7M, 7C, and 7K are sequentially transferred (primary transfer) onto the rotating intermediate transfer belt 6 to form a synthesized color image (color image: color toner image). The color image is transferred from the intermediate transfer belt 6 to the paper P.

  The paper P accommodated in the paper feed cassettes 20A, 20B, and 20C is fed by the feed roller 21 and the paper feed roller 22A provided in the paper feed cassettes 20A, 20B, and 20C, respectively, and the transport rollers 22B, 22C, 22D, After passing through the registration rollers 23 and 28 and the like, the sheet is conveyed to the secondary transfer roller 7A, and the color image is collectively transferred to one surface (front surface) on the paper P (secondary transfer).

  The paper P on which the color image has been transferred is fixed by the fixing device 17, is sandwiched between the paper discharge rollers 24, and is placed on a paper discharge tray 25 outside the apparatus. The transfer residual toner remaining on the peripheral surfaces of the photosensitive drums 1Y, 1M, 1C, and 1K after the transfer is cleaned by the image forming body cleaning means 8Y, 8M, 8C, and 8K, and enters the next image forming cycle.

  At the time of double-sided image formation, the paper P formed on one side (front surface) and discharged from the fixing device 17 is branched off from the sheet discharge path by the branching unit 26, and constitutes a sheet feeding and conveying unit. After passing through the circulation sheet passing path 27A, the front and back are reversed by a reversing conveyance path 27B which is a refeed mechanism (ADU mechanism), passes through the refeed conveyance section 27C, and merges at the sheet feeding roller 22D. The reversely conveyed paper P is conveyed again to the secondary transfer roller 7A through the registration rollers 23 and 28, and a color image (color toner image) is collectively transferred onto the other surface (back surface) of the paper P.

  The paper P on which the color image has been transferred is fixed by the fixing device 17, is sandwiched between the paper discharge rollers 24, and is placed on a paper discharge tray 25 outside the apparatus. On the other hand, after the color image is transferred to the paper P by the secondary transfer roller 7A, the residual toner is removed by the intermediate transfer belt cleaning means 8A from the intermediate transfer belt 6 that has separated the curvature of the paper P.

The time of forming these images, 52.3~63.9kg / m ² (1000 sheets) as the paper P about thin and 64.0~81.4kg / m ² (1000 sheets) of approximately plain paper, 83 .0~130.0kg / m ² (1000 sheets) about cardboard and 150.0kg / m ² (1000 sheets) about super thick paper is used. The thickness of the paper P (paper thickness) is about 0.05 to 0.15 mm.

  The copying machine main body 101 is provided with a control means 15 for detecting the amount of deviation of the sheet P fed out from the paper feed tray 20A and the like, and for eliminating the difference value of the amount of deviation, the image forming units 10Y, 10M, The writing position of the image information at 10C and 10K is corrected.

FIG. 2 is a conceptual diagram showing an example of the arrangement of the displacement sensors 11 and 12 in the color copying machine 100.
On the upstream side of the paper feed cassette 20A shown in FIG. 2, a first registration mechanism 71 as an example of a first position restricting means is provided, and operates to restrict the position of the paper P (parallel position restriction). To do. The first registration mechanism 71 has a first displacement sensor 11, a first registration roller 23, a first registration sensor 41, a first paper feed motor 72, and a first paper feed clutch 73. Yes. The deviation sensor 11 is an example of a first detection unit. In order to detect where the end position of the paper P is, the deviation sensor 11 detects the deviation of the position-controlled paper P and detects the first deviation. Output quantity. The first deviation amount is output to the control means 15 as a deviation detection signal Sd1.

  The registration roller 23 is clutch-driven using a paper feed motor 72 as a driving force. When feeding the paper P, the registration roller 23 and the paper feed motor 72 are connected, and the rotational force is transmitted from the paper feed motor 72 to the registration roller 23. When stopping the paper P, the registration roller 23 and the paper feed motor 72 are disconnected, and the rotational force from the paper feed motor 72 to the registration roller 23 is “cut off”.

  In addition, a second registration mechanism 82 serving as an example of a second position restricting unit is provided below the image forming unit 10K illustrated in FIG. 2 and upstream of the first registration mechanism 71. It operates so as to detect the edge of the paper P collected by the registration unit and improve the alignment accuracy. The second registration mechanism 82 includes a second displacement sensor 12, a second registration roller 28, a second registration sensor 42, and a second paper feed motor 81. The deviation sensor 12 is an example of a second detection unit, and detects the deviation of the paper P, which is regulated in parallel on the front side of the position where the image is formed on the transfer material, and calculates the second deviation amount. Output. The second deviation amount is output to the control means 15 as a deviation detection signal Sd2.

  The registration roller 28 is driven by a paper feed motor 81. When feeding the paper P, the rotational force is transmitted from the paper feed motor 81 to the registration roller 28. When stopping the paper P, the paper feed motor 81 is stopped, and the rotational force to the registration roller 28 is stopped. Each of the sensors 11 and 12 uses a reflection type light transmitting / receiving element (such as a photocoupler).

  In this example, the intermediate transfer belt 6 and the image forming units 10Y, 10M, 10C, and 10K have a function of circulating the paper P and forming a color image on both surfaces of the paper P. 12 is shared by the feeding path for forming the front surface and the feeding path for forming the back surface of the paper P circulated by the intermediate transfer belt 6 and the image forming units 10Y, 10M, 10C, and 10K.

FIG. 3 is a conceptual diagram illustrating an example of functions of the offset sensors 11 and 12 in the color copying machine 100.
The deviation sensor 11 shown in FIG. 3 detects the deviation of the paper P with respect to the paper P fed out from the paper feed tray 20A and the like, and outputs a deviation detection signal Sd1 to the control means 15. The deviation sensor 12 detects the deviation of the paper P at time t 2 and outputs a deviation detection signal Sd 2 to the control means 15. A two-dot chain line indicates a case where the paper P is shifted to the left.

  ε is the difference between the distances S1 and S2, and is the difference between the paper P when there is no deviation and the paper P that has produced the deviation. S1 is a distance from a certain reference position to the left end when there is no deviation of the paper P. S2 extends from the same reference position to the left end when the paper P is displaced in the paper feeding process from the displacement sensor 11 to the displacement sensor 12 due to mechanical component tolerance or assembly variation. Distance.

  In this example, the control means 15 recognizes the amount of deviation of the paper P based on the first and second deviation detection signals Sd1, Sd2, and adds this difference value to the first deviation detection signal Sd1. Thus, the image information writing position in the image forming units 10Y, 10M, 10C, and 10K is corrected so as to eliminate the difference value of the deviation amount.

  FIG. 4 is a block diagram illustrating a configuration example of a control system in the color copying machine 100. The color copying machine 100 shown in FIG. 4 has a control means 15 for performing image registration with high accuracy so as to detect the supply deviation (shift) of the paper P and align the image position with the paper position. ing. The control unit 15 includes the image forming units 10Y, 10M, 10C, and 10K, the operation panel 48, the image processing unit 70, the first and second registration mechanism units 71 and 82, the transport paper discharge unit 83, and the timing signal generation circuit 84. And the image reading apparatus 102 are connected.

  The control unit 15 includes a CPU (Central Processing Unit) 57, a ROM (Read Only Memory) 58, and a work RAM (Random Access Memory) 59. The ROM 58 stores system program data for controlling the entire copying machine. The RAM 59 temporarily stores control commands when various modes are executed. When the power is turned on, the CPU 57 reads the system program data from the ROM 58, starts up the system, and controls the entire copying machine. The CPU 57 adjusts the Y color, M color, and C color writing timing, the CLK frequency, the horizontal and vertical inclinations, and the like according to the correction amount of each error factor.

  Although not shown, the operation panel 48 is connected to the control means 15 and includes an operation tool configured from a touch panel and a display unit configured from a liquid crystal display panel. The operation panel 48 uses GUI (Graphic User Interface) type input means. A power switch and the like are provided on the operation panel 48. For example, the display unit performs a display operation in conjunction with the operation tool. The operation panel 48 is operated when selecting image forming conditions and the paper feed cassettes 20A to 20C. Note that image forming conditions, paper cassette selection information, and the like set on the operation panel 48 are output to the CPU 57 as operation data D3.

  The image reading apparatus 102 is connected to the control means 15 and reads an image from the original 30 shown in FIG. 1 and outputs digital image data Din to the control means 15. The control means 15 inputs the image data Din, and performs color conversion processing on the Y color image data Dy, the M color image data Dm, the C color image data Dc, and the BK color image data Dk. The image processing unit 70 includes an image memory 33Y and a PWM circuit 43Y for Y color, an image memory 33M and a PWM circuit 43M for M color, an image memory 33C and a PWM circuit 43C for C color, and an image memory for BK color. 33K and PWM circuit 43K.

  A timing signal generation circuit 84 is connected to the control means 15 described above. Based on the image formation start trigger signal St input from the control means 15, the motor control signal Sm2 for the second registration roller, the Y color image data Dy. Read control signal (hereinafter referred to as Y V-Valid signal), M color image data Dm read control signal (hereinafter referred to as M V-Valid signal), C color image data Dc read control signal (hereinafter referred to as C) V-Valid signal) and a read control signal for K-color image data Dk (hereinafter referred to as K-V-Valid signal) are generated and output.

  An image memory 33Y is connected to the control means 15, and the image data Dy input from the control means 15 is stored. The image processing unit 70 reads the image data Dy from the image memory 33Y based on the Y V-Valid signal, performs image processing, and transfers the image data Dy after the image processing to the PWM circuit 43Y. The PWM circuit 43Y performs pulse width modulation on the image data Dy and outputs a laser driving signal Sy for Y color.

  Similarly, an image memory 33M is connected to the control means 15, and image data Dm input from the control means 15 is stored. The image processing unit 70 reads out the image data Dm from the image memory 33M based on the M V-Valid signal, performs image processing, and transfers the image data Dm after the image processing to the PWM circuit 43M. The PWM circuit 43M performs pulse width modulation on the image data Dm and outputs a laser driving signal Sm for M color.

  An image memory 33C is connected to the control means 15 and image data Dc input from the control means 15 is stored. The image processing unit 70 reads the image data Dc from the image memory 33C based on the C V-Valid signal, performs image processing, and transfers the image data Dc after the image processing to the PWM circuit 43C. The PWM circuit 43C performs pulse width modulation on the image data Dc and outputs a C-color laser drive signal Sc.

  Further, an image memory 33K is connected to the control means 15, and image data Dk input from the control means 15 is stored. The image processing unit 70 reads the image data Dk from the image memory 33K based on the K V-Valid signal, performs image processing, and transfers the image data Dk after the image processing to the PWM circuit 43K. The PWM circuit 43K performs pulse width modulation on the image data Dk and outputs a laser drive signal Sk for BK color.

  The laser drive signal Sy described above is output to an image writing unit (exposure means) 3Y constituting the image forming unit 10Y. The image writing unit 3Y has a Y-color laser diode (hereinafter referred to as Y-LD). The Y-LD generates a laser beam for Y color having a predetermined intensity based on the laser drive signal Sy. The Y-color laser beam is main-scanned on the photosensitive drum 1Y rotating in the sub-scanning direction, and an electrostatic latent image is written on the photosensitive drum 1Y. The electrostatic latent image written on the photosensitive drum 1Y is developed by a Y-color toner member. The Y color toner image on the photosensitive drum 1Y is transferred to the intermediate transfer belt 6 that rotates in the sub-scanning direction (primary transfer).

  Similarly, the laser drive signal Sm is output to the image writing unit (exposure unit) 3M constituting the image forming unit 10M. The image writing unit 3M has a laser diode for M color (hereinafter referred to as M-LD). The M-LD generates laser beam light for M color having a predetermined intensity based on the laser drive signal Sm. The laser beam for M color is main-scanned on the photosensitive drum 1M that rotates in the sub-scanning direction, and an electrostatic latent image is written on the photosensitive drum 1M. The electrostatic latent image written on the photosensitive drum 1M is developed by an M-color toner member. The M color toner image on the photosensitive drum 1M is transferred to the intermediate transfer belt 6 that rotates in the sub-scanning direction (primary transfer).

  The laser drive signal Sc described above is output to an image writing unit (exposure means) 3C constituting the image forming unit 10C. The image writing unit 3C has a C-color laser diode (hereinafter referred to as C-LD). The C-LD generates C-color laser beam light having a predetermined intensity based on the laser drive signal Sc. The laser beam for C color is main-scanned on the photosensitive drum 1C rotating in the sub-scanning direction, and an electrostatic latent image is written on the photosensitive drum 1C. The electrostatic latent image written on the photosensitive drum 1C is developed by a C-color toner member. The C toner image on the photosensitive drum 1C is transferred to the intermediate transfer belt 6 that rotates in the sub-scanning direction (primary transfer).

  Further, the laser drive signal Sk is output to an image writing unit (exposure means) 3K constituting the image forming unit 10K. The image writing unit 3K has a laser diode for K color (hereinafter referred to as K-LD). The K-LD generates laser beam light for BK color having a predetermined intensity based on the laser drive signal Sk. The laser beam for BK color is main-scanned on the photosensitive drum 1K that rotates in the sub-scanning direction, and an electrostatic latent image is written on the photosensitive drum 1K. The electrostatic latent image written on the photosensitive drum 1K is developed by a BK color toner member. The BK color toner image on the photosensitive drum 1K is transferred to the intermediate transfer belt 6 that rotates in the sub-scanning direction (primary transfer).

  The control unit 15 is connected to the first registration mechanism 71 and operates to regulate the position of the paper P. For example, the registration roller 23 is clutch-driven using a paper feed motor 72 controlled by a motor control signal Sm1 as a driving force. When feeding the paper P, the registration roller 23 and the paper feed motor 72 are connected via the paper feed clutch 73, and the rotational force is transmitted from the paper feed motor 72 to the registration roller 23. When stopping the paper P, the registration roller 23 and the paper feed motor 72 are disconnected by the paper feed clutch 73, and the rotational force from the paper feed motor 72 to the registration roller 23 is “cut off”.

  Further, the deviation sensor 11 and the registration sensor 41 are connected to the control means 15. The displacement sensor 11 detects the displacement of the sheet P whose parallel position is restricted and outputs a displacement detection signal Sd1 to the control unit 15 in order to detect where the end position of the sheet P is. The registration sensor 41 detects whether or not the paper P has arrived and outputs a paper detection signal Sh1.

  The second registration mechanism unit 82 operates so as to detect the edge of the sheet P gathered by the registration unit and align it with high accuracy. For example, the registration roller 28 is driven by a paper feed motor 81 controlled by a motor control signal Sm2. When feeding the paper P, the paper feed motor 81 rotates the registration roller 28. When stopping the paper P, the paper feed motor 81 stops and the registration roller 23 also stops. As a result, the transport discharge unit 83 transports and feeds the paper P from the paper feed cassette 20A, 20B or 20C to the image forming system, or discharges the paper P from the paper discharge tray 25 or the like.

  Further, the deviation sensor 12 and the registration sensor 42 are connected to the control means 15. The deviation sensor 12 detects the deviation of the sheet P whose parallel position is restricted, and outputs a deviation detection signal Sd2 to the control means 15. The registration sensor 42 detects the arrival of the paper P and outputs a paper detection signal Sh2. In this example, the control means 15 recognizes the deviation amount of the paper P based on the deviation detection signals Sd1 and Sd2, and the deviation amount from the reference position becomes a predetermined value as shown in FIG. In this way, the image forming units 10Y, 10M, 10C, and 10K operate to correct the image information writing position.

  The control means 15 calculates a difference value from the deviation detection signals Sd1 and Sd2 (deviation amounts) output from the deviation sensors 11 and 12, and a first deviation amount output from the deviation sensor 11; Registration processing for determining an image forming position on the paper P based on the difference value between the first and second offset amounts is executed. For example, the control unit 15 performs a statistical process such as calculating an average value of the past 10 measurement (detection) values of the difference value of the deviation amount of the paper P, and the deviation amount of the paper P is calculated based on the statistical process. A correction value is calculated so that the difference value becomes a predetermined value. In this way, it is possible to perform correction so as to eliminate the temporal change in the amount of feed deviation obtained by analyzing the statistical difference value.

  Further, as another embodiment, the control unit 15 relates to the deviation detection signal Sd1 output from the deviation sensor 11 acquired last time with respect to a correction value for setting the difference value of the deviation amount of the paper P to a predetermined value. The current image information is corrected based on the difference value of the shift detection signal Sd2 output from the shift sensor 12. The previously acquired correction value is recorded in the nonvolatile memory 14. Thus, a color image is formed by the image forming units 10Y, 10M, 10C, and 10K on the paper P fed from the paper cassette 20A, 20B, or 20C based on the corrected image data Dy, Dm, Dc, and Dk. can do.

FIG. 5 is a conceptual diagram showing an example of correction of the image forming position in the color copying machine 100.
A white triangle mark on the photosensitive drum 1Y shown in FIG. 5 is a Y color image forming start position (a writing position of image information for Y color). The laser beam for Y color is scanned on the photosensitive drum 1Y rotating in the sub-scanning direction, and an electrostatic latent image is written on the photosensitive drum 1Y. The electrostatic latent image written on the photosensitive drum 1Y is developed by a Y-color toner member. The Y color toner image on the photosensitive drum 1Y is transferred to the intermediate transfer belt 6 that rotates in the sub-scanning direction (primary transfer). The Y color toner image transferred to the intermediate transfer belt 6 is transferred to the paper P as it is, or is superimposed on the other color toner images. The color toner image on the intermediate transfer belt 6 is transferred to the paper P (secondary transfer).

  A white triangle mark on the paper P shown in FIG. 5 is an image forming position (image transfer start position). The paper P indicated by the solid line is a case where there is no deviation. In this example, a color toner image is formed from the image transfer start position while maintaining the preset left margin of the paper P. The color toner image transferred onto the paper P is separated from the intermediate transfer belt 6 and then fixed.

  The sheet P shown by the two-dot chain line in FIG. 5 is a case where a shift of α occurs on the left side. In this example, when a color image is formed without any correction, the image is formed in a state where the image transfer start position is shifted to the right by α from the preset left margin of the paper P. With respect to the left side of the sheet P, the black triangle mark on the photosensitive drum 1Y is a corrected Y color image forming start position (a writing position of image information for Y color). In this example, correction is performed so that the Y color image forming start position is shifted to the left by α.

  When such correction is performed, the laser beam for Y color is subjected to main scanning with the writing position advanced by α with respect to the photosensitive drum 1Y rotating in the sub-scanning direction, and the electrostatic latent image is applied to the photosensitive drum 1Y. Written. The electrostatic latent image written on the photosensitive drum 1Y is developed by a Y-color toner member. The Y color toner image on the photosensitive drum 1Y is transferred to the intermediate transfer belt 6 that rotates in the sub-scanning direction (primary transfer). The Y color toner image transferred to the intermediate transfer belt 6 is transferred to the paper P as it is, or is superimposed on the other color toner images. The color toner image on the intermediate transfer belt 6 is transferred to the paper P (secondary transfer).

  A black triangle mark on the paper P indicated by a two-dot chain line in FIG. 5 is an image forming position (image transfer start position). In this example, it is possible to form a color toner image from a corrected image transfer start position while maintaining the preset left margin of the paper P. Then, the color toner image transferred to the paper P is separated from the intermediate transfer belt 6 and then subjected to a fixing process. Similar correction processing is performed for the other colors, that is, the M color, the C color, and the BK color. The description is omitted. As described above, even when the paper P is fed by being shifted by α to the left side, an image can be formed at a predetermined position from the left end portion of the paper P in the same manner as when there is no deviation.

  Next, a color image forming method according to the present invention will be described. 6A to 6L are time charts showing an example of image forming timing and an example of deviation detection in the color copying machine 100. FIG.

  In this embodiment, the color copying machine main body is provided with two-stage registration mechanism portions 71 and 82, and offset sensors 11 and 12 are provided in the vicinity of the exits of the registration mechanism portions 71 and 82, and upstream of the sheet feeding. Based on the sensor output of a certain first registration mechanism unit 71, the deviation of the image is corrected (image position adjustment), the sensor value of the first registration mechanism unit 71, the sensor value of the second registration mechanism unit 82, and The difference value is statistically collected and continuously collected, and the correction is performed by adding the difference value to the offset correction value. Even for a machine with a long imaging path such as a color tandem machine, The crossover image position can be registered (positioned) with high accuracy on the paper position.

  The image forming units 10Y, 10M, 10C, and 10K in the image forming units 10Y, 10M, 10C, and 10K and the second registration mechanism unit 82 (the front end of the paper) are based on the image forming start trigger signal St output from the control unit 15 to the timing signal generation circuit 84. ) Is determined.

  Under these image forming conditions, first, an image forming start trigger signal St as shown in FIG. 6A is output from the control means 15 to the timing signal generating circuit 84. When the image formation start trigger signal St rises, the image forming means 60 is shown in FIG. 6B almost in synchronization with the fall of the image formation start trigger signal St (delayed by the time ta from the rise). As described above, the Y V-Valid signal rises, and the most upstream unit, that is, the Y-color image forming unit 10Y is under image formation.

  Further, as shown in FIG. 6C, the M V-Valid signal rises with a delay of time tb from the rise of the image formation start trigger signal St, and the image forming unit 10M for M color is under image formation. Further, as shown in FIG. 6D, the C V-Valid signal rises with a delay of time tc from the rise of the image forming start trigger signal St, and the C color image forming unit 10C is in the process of forming an image. Furthermore, as shown in FIG. 6E, the BK V-Valid signal rises with a delay of time td from the rise of the image formation start trigger signal St, and the most downstream unit, that is, the BK color image forming unit 10K is activated. The image is being created.

  In the paper feed system, before the start of the image formation start trigger signal St, the paper feed clutch 73 shown in FIG. 6G is turned on and becomes high level (power transmission state; hereinafter referred to as “H” level). The paper P is fed out from the paper feed cassette 20A or the like. Thereafter, the paper feed clutch 73 is turned off with a delay of the loop formation time tf in the paper arrival detection period of the registration sensor 41 shown in FIG. 6 (F), and from the “H” level to the low level (power non-transmission state; hereinafter “ L ”level) and the conveyance of the paper P is stopped.

  Thereafter, after a predetermined time delay, as shown in FIG. 6H, after the registration roller 23 is turned on (driven) and transits from the “L” level (stop state) to the “H” level (rotation state), It is turned off again to make a transition to the “L” level, and then further turned on to make a transition to “H” level. The offset sensor 11 shown in FIG. 6 (I) detects the offset amount of the paper P during the off period of the registration roller 23, that is, during the “L” level section. In addition, the leading edge of the paper P, which is regulated in parallel in the first half ON period of the registration roller 23, is sent to the sensor position to detect the deviation amount. In the second half ON period, the paper P is removed from the first registration mechanism unit 71. It is conveyed to the second registration mechanism unit 82.

  The motor control signal Sm2 for the second registration roller is determined based on the rising time of the image forming start trigger signal St. In this example, the paper P is conveyed to the image forming system in synchronization with the rise of the motor control signal Sm2 after the control adjustment time te has elapsed from the rise time of the image formation start trigger signal St.

  In this example, the registration roller 23 is turned off and transits from the “H” level to the “L” level with a delay of the loop formation time tg from the paper arrival detection start time of the registration sensor 42 shown in FIG. Then, the paper feed motor 81 is turned on, and the registration roller 28 is turned on (driven) as shown in FIG. 6 (K), and transits from the “L” level (stop state) to the “H” level (rotation state). Later, it turns off again and transits to the “L” level, and then further turns on and transits to the “H” level. The offset sensor 12 shown in FIG. 6 (L) detects the offset amount of the paper P in the off period of the registration roller 28, that is, in the section of “L” level. In the first half of the registration roller 28, the leading edge of the parallel regulated paper P is sent to the sensor position, and the amount of deviation is detected. In the second half of the registration period, the paper P is removed from the second registration mechanism 82. It is conveyed to the fixing device 17.

  As described above, on the assumption that an image is formed on the paper P fed out from the paper feeding system by the image forming system, the paper P whose parallel position is restricted by the first registration mechanism unit 71 on the upstream side of the paper feeding system. The first deviation amount is acquired by detecting the deviation. Thereafter, a deviation of the sheet P whose parallel position is regulated by the second registration mechanism 82 on the front side of the image forming system is detected to obtain a second deviation amount. Thereby, a difference value is calculated from the first and second offset amounts acquired in FIGS. 6 (I) and 6 (L). The CPU 57 determines the position of the image forming system with respect to the paper P based on the first deviation amount detected in advance and the difference value between the first and second deviation amounts calculated here. .

  FIG. 7 is a flowchart illustrating an example of updating difference data related to the displacement sensors 11 and 12. In this embodiment, an average value of the past 10 times is calculated based on the current difference data and the past 9 difference data, and the average value is used as the difference data between the latest deviation sensor 11 and the deviation sensor 12. Take the case of updating as an example.

  Under these update conditions, in step A1 of the flowchart shown in FIG. 7, the CPU 57 shifts the deviation amount of the sheet P in the first registration mechanism portion 71 and the deviation amount of the sheet P in the second registration mechanism portion 82. Get the latest data of the difference value.

  Thereafter, in step A2, the output value of the offset sensor 11 is acquired, and it is determined whether or not it is appropriate. At this time, the CPU 57 compares the preset reference value with the output value of the deviation sensor 11. For example, when the output value of the deviation sensor 11 is equal to or lower than the upper limit reference value and is equal to or higher than the lower limit reference value, it is determined that the output value of the deviation sensor 11 is appropriate. If the output value of the deviation sensor 11 exceeds the upper reference value or is less than the lower reference value, it is determined that the output value of the deviation sensor 11 is inappropriate.

  If it is determined that the output value of the deviation sensor 11 is appropriate, the process proceeds to step A4. If the output value of the deviation sensor 11 is inappropriate, the process proceeds to step A3 and the previous deviation data is replaced with the output value of the deviation sensor 11. Thereafter, the process proceeds to step A4, and difference data between the deviation sensor 11 and the deviation sensor 12 is added to the output value of the deviation sensor 11.

  In step A5, the control unit 15 corrects the image writing position. At this time, according to the example of the sheet P ′ shown by the two-dot chain line in FIG. 5, the deviation is caused by α on the left side. The image data Dy is corrected so that the Y-color image forming start position is shifted to the left by α on the photosensitive drum 1Y with respect to the left side deviation of the sheet P ′ (see the black Δ mark in FIG. 5). ). When such correction is performed, the laser beam for Y color is subjected to main scanning with the writing position advanced by α with respect to the photosensitive drum 1Y rotating in the sub-scanning direction, and the electrostatic latent image is applied to the photosensitive drum 1Y. Written.

  Thereafter, the process proceeds to step A6, where the output value of the offset sensor 12 is acquired, and it is determined whether or not it is appropriate. At this time, the CPU 57 compares the preset reference value with the output value of the deviation sensor 12. For example, when the output value of the deviation sensor 12 is equal to or lower than the upper limit reference value and is equal to or higher than the lower limit reference value, it is determined that the output value of the deviation sensor 12 is appropriate. Further, when the output value of the deviation sensor 12 exceeds the upper limit reference value or is less than the lower limit reference value, it is determined that the output value of the deviation sensor 12 is inappropriate.

  When the output value of the deviation sensor 12 is appropriate, the process proceeds to step A7, and difference data between the deviation sensor 11 and the deviation sensor 12 is calculated. And it transfers to step A8 and calculates the average value of the past 10 times based on this difference data and the past 9 difference data, and this average value is the latest offset sensor 11 and the offset sensor 12. Update as the difference data. The updated difference data is stored in the nonvolatile memory 14.

  If the output value of the offset sensor 12 is inappropriate in step A6, the process proceeds to step A9, and the difference data between the offset sensor 11 and the offset sensor 12 is not updated and remains unchanged. The value is held in a non-volatile memory. Thereafter, returning to step A1, the CPU 57 continues the above-described processing.

  As described above, according to the color copying machine and the color image forming method as the embodiments according to the present invention, when forming a color image based on arbitrary image data Dy, Dm, Dc and Dk, 2 registration mechanism sections 71 and 82, and the upstream side of the feeding path before the start of image formation, while minimizing the feeding deviation between the registration mechanism sections 71 and 82. The deviation amount of the paper P detected by the deviation sensor 11 is fed back to the image forming position. On the assumption of this, the control means 15 calculates a difference value from the first and second offset amounts output from the first and offset sensors 12, and the difference between the first and second offset amounts is calculated. A registration process for determining an image forming position on the paper P with further consideration of the value is executed.

  Therefore, the control unit 15 can correct the writing position of the image data Dy, Dm, Dc, and Dk so as to eliminate the difference value of the deviation amount of the paper P under the image forming unit. The image forming units 10Y, 10M, 10C, and 10K form a color image based on the corrected image data Dy, Dm, Dc, and Dk on the paper P fed out from the paper feed cassette 20A and the like. In addition, even when the characteristics (gradation, etc.) change with time due to wear of the paper feed roller and the paper P is offset from the control target position, the difference between the first and second offset amounts. Since the image forming position on the paper P is determined based on the statistical processing of values, a color image or the like can be accurately formed at a predetermined position on the paper P.

  As a result, it is possible to provide the color copying machine 100 capable of downsizing the apparatus and registering it for a long period of time with high accuracy without delaying (damaging) the first copy output time (FCOT). By using the deviation sensors 11 and 12 in common with the paper feeding path for double-sided copying, even in the double-sided copying mode, the surface is corrected by the deviation sensors 11 and 12 provided in the registration mechanism unit 71. Regarding the back side deviation correction, the correction can be performed based on the data of the front side deviation sensor or the non-volatile data.

  The present invention is extremely suitable when applied to a tandem type color printer or copier having an intermediate transfer belt and forming a color image, a multi-function machine thereof, or the like.

1 is a conceptual diagram illustrating a configuration example of a color copying machine 100 as an embodiment of the present invention. 3 is a conceptual diagram illustrating an example of arrangement of offset sensors 11 and 12 in the color copying machine 100. FIG. 3 is a conceptual diagram illustrating an example of functions of offset sensors 11 and 12 in the color copying machine 100. FIG. 2 is a block diagram illustrating a configuration example of a control system in the color copying machine 100. FIG. 3 is a conceptual diagram illustrating an example of correction of an image forming position in the color copying machine 100. FIG. (A) to (L) are time charts showing an example of image formation timing and an example of deviation detection in the color copying machine 100. 6 is a flowchart illustrating an example of updating difference data related to the deviation sensors 11, 12. It is a conceptual diagram which shows the structural example of the color copying machine 200 which concerns on a prior art example.

Explanation of symbols

1Y, 1M, 1C, 1K Photosensitive drum (image forming body)
3Y, 3M, 3C, 3K Image writing unit (image forming means)
4Y, 4M, 4C, 4K developing device (image forming means)
6 Intermediate transfer belt (image forming body)
10Y, 10M, 10C, 10K Image forming unit (image forming means)
11 First displacement sensor (first detection means)
12 Second displacement sensor (second detection means)
14 Non-volatile memory (storage means)
DESCRIPTION OF SYMBOLS 15 Control means 17 Fixing device 23 1st registration roller 28 2nd registration roller 48 Operation panel 60 Image formation means 71 1st registration mechanism part (1st position control means)
82 Second registration mechanism (second position regulating means)
DESCRIPTION OF SYMBOLS 100 Color copier 101 Copier main body 102 Image reading apparatus 201 Automatic document feeder 202 Document image scanning exposure apparatus

Claims (8)

A tandem color image forming apparatus that forms a color image based on arbitrary image information,
Paper feeding means;
Image forming means for forming an image on a transfer material fed from the paper feeding means;
First detecting means for detecting a deviation of the transfer material whose position is regulated upstream of the paper feeding means and outputting a first deviation amount;
A second upstream side of the first detection means and on the front side of the position where an image is formed on the transfer material, and detects a shift of the transfer material and outputs a second shift amount; Detection means;
A difference value is calculated from the first deviation amount outputted from the first detection means and the second deviation amount outputted from the second detection means, and outputted from the first detection means. A color image forming apparatus comprising: a control unit that executes a registration process for determining an image forming position with respect to the transfer material based on a deviation amount and a difference value between the first and second deviation amounts. . The control means includes
The writing position of the image information in the image forming means is determined by using a difference with respect to a predetermined value of the sum of the difference values of the deviation amount output from the first detection means and the first and second deviation amounts as a correction amount. The color image forming apparatus according to claim 1, wherein correction is performed. First position regulating means for regulating the position of the transfer material upstream of the paper feeding means;
And a second position restricting means provided on the upstream side of the first position restricting means and in front of the position where the image is formed on the transfer material and restricting the position of the transfer material. The color image forming apparatus according to claim 1. The control means includes
Statistically processing a difference value between the first and second offset amounts;
The color image forming apparatus according to claim 1, wherein a correction value is calculated from the statistically processed difference value and a first deviation amount output from the first detection unit. The control means includes
This time based on the difference value between the first and second offset amounts acquired at the time of the previous paper feeding and the correction amount obtained from the first offset amount output from the first detection means acquired this time. The color image forming apparatus according to claim 1, wherein the image information is corrected. The image forming unit includes:
The transfer material is circulated and has a function of forming images on both sides of the transfer material,
The first and second detection means include
2. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is shared by a feeding path for forming the front surface of the transfer material and a feeding path for forming the back surface of the transfer material circulated by the image forming means. The control means includes
Determining whether the first and second offset amounts are included in a predetermined range,
2. The color image according to claim 1, wherein when the first or second deviation amount is out of the predetermined range, an image forming position on the transfer material is determined using a previous correction value. Forming equipment. A tandem color image forming method for forming a color image on an image forming system on a transfer material fed from a paper feeding system,
A first deviation amount is obtained by detecting a deviation of the transfer material, the position of which is regulated on the upstream side of the paper feed system, and then the position regulation is performed on the front side of the position where an image is formed on the transfer material Detecting the displacement of the transfer material to obtain a second displacement amount;
A difference value is calculated from the acquired first and second offset amounts,
A color image forming method, wherein an image forming position with respect to the transfer material is determined based on the first deviation amount and a difference value between the first and second deviation amounts.

Images