JP4099912B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile using an electrophotographic system, an electrostatic recording system, etc., and in particular, in a color image forming apparatus, controls registration as an image forming position of each color. The present invention relates to a registration control system.
[0002]
[Prior art]
In recent years, documents processed in offices and the like have been rapidly colored, and image forming apparatuses such as copying machines, printers, and facsimiles that handle these documents have also been rapidly colored. Currently, these color devices have been further improved in image quality and speed as the quality of office processing in offices and the like has become higher and faster. As a color device that can meet such a requirement, for example, each color forming unit has black (K), yellow (Y), magenta (M), and cyan (C), and each image forming unit is formed. Various so-called tandem type color image forming apparatuses have been proposed and actually commercialized, which form multiple color images by transferring images of different colors onto a transfer material or intermediate transfer member to be conveyed. .
[0003]
Examples of this type of tandem color image forming apparatus include the following. As shown in FIG. 14, the tandem type color image forming apparatus includes a black image forming unit 200K that forms a black (K) image and a yellow image forming unit 200Y that forms a yellow (Y) image. And a magenta color image forming unit 200M for forming a magenta (M) color image and a cyan color image forming unit 200C for forming a cyan (C) color image. These four image forming units 200K, 200Y, 200M, and 200C are horizontally arranged at a predetermined interval. Further, the toners sequentially formed by the respective image forming units are formed below the black (K), yellow (Y), magenta (M), and cyan (C) image forming units 200K, 200Y, 200M, and 200C. An intermediate transfer belt 201 that transfers images in a state where they are superimposed on each other is disposed so as to be rotatable along the direction of the arrow. The intermediate transfer belt 201 is formed, for example, by forming a flexible synthetic resin film such as polyimide in a strip shape, and connecting both ends of the synthetic resin film formed in a strip shape by means of welding or the like. Configured. Therefore, as shown in FIG. 15, the intermediate transfer belt 201 inevitably has a seam portion 201a which is a connecting portion of the synthetic resin film.
[0004]
The black (K), yellow (Y), magenta (M), and cyan (C) image forming units 200K, 200Y, 200M, and 200C are all configured in the same manner, and these four image forming units 200K, In 200Y, 200M, and 200C, as described above, black, yellow, magenta, and cyan toner images are sequentially formed. The image forming units 200K, 200Y, 200M, and 200C for the respective colors are provided with a photosensitive drum 202. The surface of the photosensitive drum 202 is uniformly charged by a primary charging scorotron 203, and then image exposure is performed. The apparatus 204 scans and exposes image forming laser light according to image information, and forms an electrostatic latent image. The electrostatic latent image formed on the surface of the photosensitive drum 202 is developed with toner of each color of black, yellow, magenta, and cyan by the developing units 205 of the image forming units 200K, 200Y, 200M, and 200C. Thus, visible toner images are formed, and these visible toner images are transferred onto the intermediate transfer belt 201 by the transfer charger 206 in a state of being superimposed on each other. The black, yellow, magenta, and cyan toner images transferred onto the intermediate transfer belt 201 are transferred onto the transfer sheet 207 in a lump and then subjected to a fixing process by the fixing device 208. A color image is formed.
[0005]
In FIG. 14, reference numeral 209 denotes a photoreceptor cleaner, and 210 denotes an intermediate transfer belt cleaner.
[0006]
By the way, the tandem type color image forming apparatus configured as described above is a system in which toner images sequentially formed by a plurality of image forming units 200K, 200Y, 200M, and 200C are transferred onto the intermediate transfer body 201 in a multiple manner. Therefore, the transfer speed of the images formed by the image forming units 200K, 200Y, 200M, and 200C for each color is easily shifted, and the alignment of the images for each color, that is, color registration is possible. Tends to deteriorate frequently and it is difficult to maintain high image quality. This is due to manufacturing tolerances and mounting tolerances of the image exposure apparatuses 204K, 204Y, 204M, and 204C or the image forming units 200K, 200Y, 200M, and 200C as an initial one, and over time. As a result, the members constituting each of the image forming units 200K, 200Y, 200M, and 200C are thermally expanded or displaced due to a change in the internal temperature of the color image forming apparatus or an external force applied to the color image forming apparatus. Due to such as. Among these, a change in internal temperature and an external force are inevitable. For example, a daily operation such as a transfer paper replenishing operation or a paper jam recovery applies an external force to the color image forming apparatus.
[0007]
Therefore, as a conventional technique, as shown in FIG. 15, a pattern 211 for detecting a color registration shift (hereinafter abbreviated as “color registration shift”) is formed on the intermediate transfer member 201, and this color is formed. Various techniques for sampling the registration error detection pattern 211 by the detector 212 and correcting the registration error of the toner images of the respective colors have already been proposed and introduced into actual machines.
[0008]
As a technology for detecting these color registration shifts, when registering a color registration shift detection pattern, a low-cost detector can detect the color registration shift detection pattern with sufficient resolution. For example, Japanese Patent Laid-Open No. 6-118735 has already been proposed.
[0009]
In the image forming apparatus according to Japanese Patent Laid-Open No. 6-118735, as shown in FIG. 16, a pattern in which multicolored chevron marks 213K, 213Y,... Is used. The color registration misalignment amount is detected such that when the chevron pattern 211 formed on the intermediate transfer belt 210 moves along with the movement of the intermediate transfer belt 201, both ends of the pattern 211 pass under the pattern 211. The two detectors 212a and 212b arranged at the same time are used, and the intervals of the pattern 211 are measured at the timing when the pattern 211 passes under the two detectors 212a and 212b, and the color registration amount is detected. It has become.
[0010]
As shown in FIG. 16, the time interval from when the first detector 212a detects the detection reference color mark 213K (for example, black) until the detection target color mark 213Y (for example, yellow) is detected. T1A, the time interval from detection of the detection target color mark 213Y to detection of the next detection reference color mark 213K is T1B, and the second detector 212b detects the detection reference color mark 213K. T2A is the time interval from the detection of the detection target color mark 213Y until the detection of the next predetermined detection target color mark 213Y. Assuming that T2B, the main-scanning direction color registration misalignment amount Lerr and the sub-scanning direction color registration misalignment amount Perr are disclosed in JP-A-6-118735. It is calculated by the following calculation formula.
Lerr = (T2A-T1A) / 2
Perr = (T2B−T1B) −Lerr
[0011]
By the way, the intermediate transfer belt 201 on which the detection pattern 211 is formed has a periodic fluctuation due to the eccentricity of a driving roll for driving the intermediate transfer belt 201 and the like. The image forming units 200K, 200Y, 200M, and 200C that form the detection patterns 211 of the respective colors also have periodic fluctuations due to the eccentricity of the photosensitive drum 202 or the like. Therefore, even if the detection patterns 211 for the respective colors are formed at predetermined intervals on the intermediate transfer belt 201, the detection reference color mark 213K and the detection target color mark 213Y detected by the two detectors 212a and 212b. Periodic fluctuations are included in the time intervals T1A, T1B, T2A, T2B, and the like.
[0012]
Therefore, if the time intervals T1A, T1B, T2A, T2B, etc. between the detection reference color mark 213K and the detection target color mark 213Y are detected as they are, the detected time intervals T1A, T1B, T2A, T2B etc. are periodically detected. Therefore, the color registration misregistration amounts Lerr and Perr in the main scanning direction and the sub-scanning direction cannot be accurately detected.
[0013]
Therefore, the reading detection of the detection pattern 211 is generally performed so as not to be affected by periodic color registration shift fluctuations. More specifically, the frequency (repetition number and interval) of the detection pattern 211 is set so as not to synchronize with a frequency that is not affected by detection, and the number of samplings is increased, or the number of samples for one cycle of the period is increased. The sampling parameters are designed to be synchronized, and a plurality of sampled detection values are averaged to reduce the influence of periodic color registration shift fluctuations, and the final detection values are calculated.
[0014]
[Problems to be solved by the invention]
However, the conventional technique has the following problems. That is, as disclosed in Japanese Patent Laid-Open No. 6-118735, as a color registration misalignment detection pattern 211, as shown in FIG. It is possible to detect the color registration misregistration detection pattern 211 with sufficient resolution by a price detector, and to correct the registration misregistration of the toner image of each color, thereby forming a high-quality color image. .
[0015]
However, even if the sampling parameter is designed so as to remove the influence of the specific frequency as described above, there is a concern that the following problems may occur. That is, when there is a long-term fluctuation represented by the cycle of the intermediate transfer belt 201, it is necessary to synchronize the sample length with this cycle. However, the detection pattern 211 is generated by the seam portion 201a of the intermediate transfer belt 201 or the like. Since there is a region that cannot be formed, even if it cannot be synchronized with a specific frequency or is synchronized, as shown in FIG. 17, the seam portion 201a of the intermediate transfer belt 201, scratches or dirt on the belt surface, etc. Due to the defect 201b, a case where the detection pattern 211 at a certain position (phase) cannot be detected inevitably occurs. In this case, even if a large number of detection patterns 211 are sampled and averaged so as not to be affected by periodic color registration deviation fluctuations, a certain position (phase) is detected. Due to the lack of sampling data of the pattern 211, the averaged color registration deviation amount is shifted by ΔV, and the influence of long period fluctuations caused by one rotation of the intermediate transfer belt 201, one rotation of the photosensitive drum 202, and the like. There was a problem that the received detection error occurred. As described above, when a detection error of ΔV occurs in the sampling data of the detection pattern 211, it is natural that each image forming unit 200K, 200Y, 200M, and 200C can accurately correct the registration error of the color image. However, there is a problem that the image quality deteriorates such as color shift.
[0016]
Also, even if the frequency components that you do not want to detect are designed to minimize the influence by setting the sampling parameters (frequency and number), the influence is not completely eliminated, and the fluctuation amplitude is particularly large. When there are a large number of frequencies, the averaged color registration shift amount is also shifted due to the influence of a large fluctuation in the amplitude, so that a detection error is generated not a little.
[0017]
Therefore, in order to improve these problems, in order to reduce periodic fluctuations, the production of the intermediate transfer belt and the drive roll that drives the intermediate transfer belt is made highly accurate, or the intermediate transfer belt and the photosensitive belt are photosensitive. It is conceivable to reduce detection errors caused by rotational fluctuations of the intermediate transfer belt and the photosensitive drum by taking measures such as complicated and highly accurate feedback control for driving the photosensitive drum.
[0018]
However, in this case, not only a significant increase in manufacturing cost is caused, but also the configuration of the apparatus becomes complicated, and in any case, a new problem is caused that a significant cost increase is caused. In addition, the above-described means cannot avoid the influence of subsequent scratches or dirt on the intermediate transfer belt.
[0019]
Accordingly, the present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to achieve an intermediate transfer member and an image carrier without incurring a complicated configuration and a significant increase in cost. Not only can the detection error of the detection pattern due to rotational fluctuations of the body, etc. be greatly reduced, it is also possible to detect the color registration shift accompanying the sampling of the detection pattern with high accuracy. Is to provide a simple image forming apparatus.
[0020]
[Means for Solving the Problems]
The invention described in claim 1 includes a plurality of image forming units and an intermediate transfer body onto which an image formed by the plurality of image forming units is transferred, and a color image forming position shift on the surface of the intermediate transfer body. Form a detection pattern,
By detecting the color image formation misregistration detection pattern by pattern detection means, the misregistration amount of the image formed by the plurality of image forming units on the surface of the intermediate transfer member is detected. Image forming apparatus A plurality of color image formation misregistration detection patterns in the same image forming unit over at least one turn of the intermediate transfer member. Equally spaced The positions of a plurality of color image formation misregistration detection patterns formed and formed by the same image forming unit Deviation amount Over one turn of the intermediate transfer member Arithmetic average value And detecting a detection error when detecting the color image forming position shift detection pattern based on Image forming apparatus It is.
[0021]
According to the first aspect of the present invention, a plurality of color image formation misregistration detection patterns are formed by the same image forming unit over at least one turn of the intermediate transfer member. Equally spaced The positions of a plurality of color image formation misregistration detection patterns formed and formed by the same image forming unit Deviation amount Over one turn of the intermediate transfer member Arithmetic average value Therefore, a plurality of color image forming position shifts are detected by the same image forming unit over at least one turn of the intermediate transfer member. Detection pattern Equally spaced By forming, the image forming position deviation detection pattern formed by the same image forming unit is basically formed by the same image forming unit because there is no position deviation at the time of color image formation. The interval measurement value of the image formation misregistration detection pattern should be essentially equal to a predetermined value, and the image formation misregistration detection pattern formed by the same image formation unit. interval Over one turn of the intermediate transfer member Arithmetic average value And the predetermined value Difference This is a detection error when detecting a color image forming position shift detection pattern.
[0022]
Therefore, by calibrating the color image formation position deviation amount detected by the color image formation position deviation detection pattern based on this detection error, the color image formation position deviation amount can be accurately detected. .
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0030]
Embodiment 1
FIG. 2 is a schematic configuration diagram showing a tandem type color electrophotographic copying machine as an image forming apparatus according to Embodiment 1 of the present invention.
[0031]
In FIG. 2, reference numeral 1 denotes a main body of a tandem type digital color copying machine, and an original reading device 4 for reading an image of the original 2 is disposed on the upper end of one end of the digital color copying machine main body 1. ing. In the digital color copying machine main body 1, image forming units 13K, 13Y, 13M, and 13C for black (K), yellow (Y), magenta (M), and cyan (C) are horizontally arranged. Are arranged at regular intervals. Further, below the four image forming units 13K, 13Y, 13M, and 13C, an intermediate transfer belt 25 that transfers toner images of respective colors sequentially formed by these image forming units in a state of being superimposed on each other, It is arrange | positioned so that rotation is possible along the arrow direction. The toner images of each color transferred onto the intermediate transfer belt 25 in a multiple manner are collectively transferred onto a transfer paper 34 as a transfer material fed from a paper feed cassette 39 or the like, and then a fixing unit 37. Thus, the toner image is fixed on the transfer paper 34 and discharged to the outside.
[0032]
FIG. 3 shows in more detail the configuration of the tandem type color electrophotographic copying machine as the image forming apparatus according to the first embodiment of the present invention.
[0033]
Here, the configuration of the present invention will be described using a tandem type color electrophotographic copying machine, but the present invention is also effective in a color printer / facsimile. The same applies to the following second and third embodiments.
[0034]
In FIG. 3, reference numeral 1 denotes a main body of a tandem type digital color copying machine. A platen cover 3 that presses a document 2 onto a platen glass 5 is disposed on an upper portion of one end side of the digital color copying machine main body 1. A document reading device 4 that reads an image of the document 2 placed on the platen glass 5 is provided. The document reader 4 illuminates a document 2 placed on a platen glass 5 with a light source 6, and reflects a reflected light image from the document 2 from a full-rate mirror 7, half-rate mirrors 8 and 9, and an imaging lens 10. The image reading element 11 composed of a CCD or the like is scanned and exposed through a reduction optical system, and the color material reflected light image of the document 2 is formed at a predetermined dot density (for example, 16 dots / mm) by the image reading element 11. It is configured to read.
[0035]
The color material reflected light image of the document 2 read by the document reader 4 is, for example, IPS 12 (three-color document reflectance data of red (R), green (G), and blue (B) (each 8 bits)). In this IPS 12, the reflectance data of the document 2 is subjected to predetermined corrections such as shading correction, positional deviation correction, brightness / color space conversion, gamma correction, frame deletion, color / moving editing, etc. Image processing is performed.
[0036]
The image data that has been subjected to the predetermined image processing by the IPS 12 as described above has four color original color material levels of yellow (Y), magenta (M), cyan (C), and black (K) (each 8 bits). As described below, black (K), yellow (Y), magenta (M), and cyan (C) image forming units 13K, 13Y, 13M, and 13C ROSs 14K, 14Y, and 14M, as described below. , 14C (Raster Output Scanner), and these ROSs 14K, 14Y, 14M, and 14C perform image exposure with laser light in accordance with document color material gradation data of a predetermined color.
[0037]
Incidentally, inside the tandem type digital color copying machine main body 1, as described above, four image forming units 13K, 13Y of black (K), yellow (Y), magenta (M), and cyan (C) are provided. , 13M, 13C are arranged in parallel in the horizontal direction with a certain interval.
[0038]
These four image forming units 13K, 13Y, 13M, and 13C are all configured in the same manner, and are roughly divided into a photosensitive drum 15 that rotates at a predetermined rotational speed in the direction of the arrow, and the photosensitive drum 15. A primary charging scorotron 16 that uniformly charges the surface of the photosensitive drum 15, an ROS 14 that forms an electrostatic latent image by exposing an image corresponding to each color on the surface of the photosensitive drum 15, and a photosensitive drum 15. The developing unit 17 develops the electrostatic latent image and the cleaning device 18.
[0039]
As shown in FIG. 3, the ROS 14 modulates the semiconductor laser 19 according to the original color material gradation data, and emits a laser beam LB from the semiconductor laser 19 according to the gradation data. The laser beam LB emitted from the semiconductor laser 19 is deflected and scanned by the rotary polygon mirror 22 via the reflection mirrors 20 and 21, and again carries an image via the reflection mirrors 20 and 21 and the plurality of reflection mirrors 23 and 24. Scanning exposure is performed on the photosensitive drum 15 as a body.
[0040]
From the IPS 12, image data of each color is supplied to the image forming units 13K, 13Y, 13M, and 13C of ROS 14K, 14Y, 14M, and 14C of each color of black (K), yellow (Y), magenta (M), and cyan (C). Are sequentially output, and laser beams LB emitted from these ROSs 14K, 14Y, 14M, and 14C in accordance with image data are scanned and exposed on the surfaces of the respective photosensitive drums 15K, 15Y, 15M, and 15C, and electrostatic latent An image is formed. The electrostatic latent images formed on the photosensitive drums 15K, 15Y, 15M, and 15C are respectively black (K), yellow (Y), magenta (M), and cyan by the developing units 17K, 17Y, 17M, and 17C. It is developed as a toner image of each color (C).
[0041]
Black (K), yellow (Y), magenta (M), and cyan (C) are sequentially formed on the photosensitive drums 15K, 15Y, 15M, and 15C of the image forming units 13K, 13Y, 13M, and 13C. The toner images of the respective colors are transferred in multiple by primary transfer rolls 26K, 26Y, 26M, and 26C onto an intermediate transfer belt 25 as an intermediate transfer member disposed below each of the image forming units 13K, 13Y, 13M, and 13C. The The intermediate transfer belt 25 is wound around the drive roll 27, the stripping roll 28, the steering roll 29, the idle roll 30, the backup roll 31, and the idle roll 32 with a constant tension. A drive roll 27 that is rotationally driven by a dedicated drive motor with excellent constant speed (not shown) is circulated at a predetermined speed in the direction of the arrow. As the transfer belt 25, for example, a flexible synthetic resin film such as polyimide is formed in a band shape, and both ends of the synthetic resin film formed in the band shape are connected by means such as welding, thereby providing an endless belt. What was formed in the shape is used. Therefore, as shown in FIG. 4, the intermediate transfer belt 25 inevitably has a seam portion 25a which is a connecting portion of the synthetic resin film.
[0042]
The black (K), yellow (Y), magenta (M), and cyan (C) toner images transferred onto the transfer belt 25 in a multiple manner are transferred to the backup roll 31 by a secondary transfer roll 33. The transfer sheet 34 that has been secondarily transferred onto the transfer sheet 34 by the pressure contact force and electrostatic force and onto which the toner images of the respective colors have been transferred is conveyed to the fixing device 37 by the two conveyance belts 35 and 36. The transfer paper 34 onto which the toner images of the respective colors have been transferred undergoes a fixing process with heat and pressure by a fixing device 37 and is discharged onto a discharge tray 38 provided outside the copying machine main body 1.
[0043]
As shown in FIG. 3, the transfer paper 34 has a predetermined size from any one of a plurality of paper feed cassettes 39, 40, 41, and a pair of paper feed rollers 42 and a pair of paper transport rollers 43, 44. , 45 is temporarily transported to the registration roll 47 via a paper transport path 46. The transfer paper 34 supplied from any one of the paper feed cassettes 39, 40, 41 is sent onto the intermediate transfer belt 25 by a registration roll 47 that is rotationally driven at a predetermined timing.
[0044]
In the four image forming units 13K, 13Y, 13M, and 13C of black, yellow, magenta, and cyan, as described above, toner images of black, yellow, magenta, and cyan are respectively set to predetermined colors. It is formed sequentially at the timing.
[0045]
The photosensitive drums 15K, 15Y, 15M, and 15C, after the toner image transfer process is completed, the residual toner and paper dust are removed by the cleaning devices 18K, 18Y, 18M, and 18C, and the next image formation is performed. Prepare for the process. Further, residual toner is removed from the intermediate transfer belt 25 by a belt cleaner 48.
[0046]
By the way, in this embodiment, a color registration misalignment detection pattern is formed on the intermediate transfer belt 25 at a predetermined timing, and this color registration misalignment detection pattern is detected, and each image forming unit 13K, 13Y, After correcting the color registration misalignment of 13M and 13C, a color image is formed.
[0047]
As shown in FIG. 6, the color registration misalignment detection pattern 50 includes a first chevron mark 51KK made of the first reference color, a second chevron mark 51YY made of the second measured color, A pattern in which all of the colors to be measured are combined using the third chevron mark 51KY mark composed of the first color and the second color as one unit is used. The combination of the patterns 50 shown in FIG. 5 is one block for the reference color and the target color. When this pattern is actually used, it is repeatedly sampled for several blocks as shown in FIG. Here, the first embodiment of the present invention will be described on the assumption that the sample of one turn of the intermediate transfer belt 25 is assumed.
[0048]
FIG. 7 is a perspective view showing the pattern detector 60 for detecting the color registration deviation.
[0049]
In FIG. 7, reference numeral 61 denotes a housing of the pattern detector 60, and 62 a and 62 b denote two light emitting elements that respectively illuminate the color registration misalignment detection pattern 50 formed on the intermediate transfer belt 25. Reference numerals 63b, 64a, and 64b denote two sets of light receiving elements that respectively receive reflected light from different mountain-shaped marks 51 of the color registration misalignment detection pattern 50 formed on the intermediate transfer belt 25. As the two light emitting elements 62a and 62b, for example, LEDs that emit light having a specific wavelength or light having a predetermined wavelength distribution are used. These light emitting elements 62a and 62b are arranged on the intermediate transfer belt 25. These one detection positions are arranged so as to illuminate from opposite diagonal directions inclined by a predetermined angle. The two sets of light receiving elements 63a, 63b and 64a, 64b are arranged in such a manner that the center portions are in contact with each other and the both end portions are inclined downward by a predetermined angle with respect to the horizontal direction. 63b and 64a and 64b, and the light receiving elements 63a, 63b and 64a and 64b are set so that the detection timing and the detection angle of the reflected light are different from each other, as shown in FIG.
[0050]
As shown in FIG. 8, when the pattern detector 60 detects the color registration deviation detection pattern 50 formed on the intermediate transfer belt 25, the pattern detector 60 uses the linear marks 51 of the color registration deviation detection pattern 50 to detect the color registration deviation detection pattern 50. As shown in FIG. 8A, a smooth mountain-shaped waveform is first output from one light receiving element 63b, and after some delay, the other light receiving element 63a also shows in FIG. 8B. Thus, a smooth mountain-shaped waveform is output. Then, by amplifying the waveforms output from these two light receiving elements 63b and 63a, or by taking the difference and then amplifying it, as shown in FIG. After falling, an output waveform that rises in a large mountain shape is obtained. Therefore, by taking the difference between the waveforms output from the two light receiving elements 63a and 63b, as shown in FIG. 8D, it is possible to detect a color registration deviation without using a high-precision sensor such as a CCD. It becomes possible to detect the linear mark 51 of the pattern 50 with high resolution and high accuracy.
[0051]
FIG. 9 is a block diagram showing an embodiment of the color registration misalignment correction apparatus according to the first embodiment.
[0052]
In FIG. 9, reference numeral 70 denotes a CPU for controlling the image forming operation of the tandem type digital color copying machine and the detection and calibration operation of the color registration misalignment, and 71 denotes the image forming operation executed by the CPU 70, the detection of the color registration misalignment, and ROM storing software programs for controlling the calibration operation, etc. 72 is an LED driver for lighting the LEDs constituting the light emitting elements 62a and 62b of the pattern detector 60, 73 is a light receiving element 63a of the pattern detector 60, PWM circuit (pulse width modulation circuit) 60 for controlling the threshold value for sampling data at 63b, 64a and 64b, and 60 at the three ends of the intermediate transfer belt 25 in the width direction, for example, at three ends (if necessary, both end portions 74, a pattern detector for detecting a color registration misalignment detection pattern formed on the A counter for measuring a time interval between predetermined pulses (rising) at the time of detecting a color registration error detection pattern output from these pattern detectors 60 based on a reference clock pulse, 75 is also based on a command from the CPU 70 Then, the original 2 is transferred to the ROSs 14Y, 14M, 14C, and 14BK of the image forming units 13Y, 13M, 13C, and 13BK of yellow (Y), magenta (M), cyan (C), and black (BK) at a predetermined timing. An image output circuit for outputting image information for forming the color registration error detection pattern 50 or an image output circuit 76 for outputting the color registration error detection pattern 50, respectively, indicates a registration pattern storage ROM for storing the image information of the color registration error detection pattern 50 in advance. is there.
[0053]
In this embodiment, the CPU 70 controls the image forming operation of the tandem type digital color copying machine, or immediately after the tandem type digital color copying machine is turned on, or the copying machine. The CPU 70 moves onto the intermediate transfer belt 25 at a predetermined timing such as when the temperature in the main body 1 changes by a predetermined temperature or more, when a predetermined number of copies are made by the copying machine, when the front cover is opened and closed, and so on. A color registration misalignment detection pattern 50 as shown in FIGS. 4 to 6 is formed, and this color registration misalignment detection pattern 50 is detected by the pattern detector 60 to be a target for a reference color pattern. Detects how much the color registration shift detection pattern 50 formed by the image forming units 13Y, 13M, and 13C is shifted. , And is configured to perform a control to calibrate the color shift.
[0054]
By the way, as shown in FIG. 9, the CPU 70 outputs predetermined image information to the ROSs 14K, 14Y, 14M, and 14C of the image forming units 13K, 13Y, 13M, and 13C of the respective colors via the image output circuit 75. As a result, a color registration deviation detection pattern 50 as shown in FIGS. 4 to 6 is repeatedly formed on the intermediate transfer belt 25.
[0055]
The interval at which the color registration misalignment detection pattern 50 is repeatedly formed, that is, the frequency of the color registration misalignment detection pattern 50 is generally designed so as to eliminate periodic fluctuations in image formation. . For example, when the circumferential length of the photosensitive drum 15 is 250 mm and the circumferential length of the belt driving roll 27 is 100 mm, the periodic fluctuation due to the photosensitive drum 15 occurs every 250 mm and the periodic fluctuation due to the belt driving roll 27 occurs every 100 mm. It will be. When the fluctuation of the cycle is long to some extent, such as the period of one rotation of the photosensitive drum 15, the period of the pattern 1 block is shortened as much as possible, and the color registration shift is within the period fluctuation of one rotation of the photosensitive drum 15. It is desirable to set so that the detection pattern 50 is sampled as much as possible. Further, in the case of fluctuations with a relatively short cycle such as the belt drive roll 27, it is desirable to set at a frequency that is asynchronous with this cycle.
[0056]
At the time of actual image output, the fluctuation of the photosensitive drum 15 and the belt driving roll 27 becomes a combined fluctuation. In this embodiment, the frequency of the color registration deviation detection pattern 50 is increased, and the belt driving roll 27 The period (frequency) of the pattern 50 is set so as to be asynchronous with the period. Due to the configuration of the pattern 50, the pattern is limited by the detected color registration deviation amount and the characteristics of the pattern detector 60. For example, the minimum block formation length that can be formed with the minimum pattern interval is 50 mm (here, the reference color and the three target colors If the combination of 3 blocks is 1 block), the period of 50 mm is the highest frequency in the pattern period shown in FIG. 6, but is not desirable because it synchronizes with the frequency of the belt drive roll 27. Therefore, since the minimum block formation length of 60 to 70 mm is not synchronized with the belt drive roll 27 and becomes a high frequency, it is an appropriate set value. Assuming that the circumference of the intermediate transfer belt 25 is 2000 mm, it is possible to form a color registration misalignment detection pattern 50 of 33 blocks in the circumference of the belt with a block length of 60 mm. Here, the design of the block frequency of the pattern 50 has been described for the two fluctuation factors of the photosensitive drum 15 and the belt driving roll 27. However, in the actual image forming apparatus, the photosensitive drum 15 and the belt driving roll 27 are driven. It is necessary to consider other fluctuation factors such as the drive system to be used.
[0057]
However, even if the design parameters of the pattern 50 are designed so as to reduce the detection error due to periodic fluctuations as described above, as described in the problem of the prior art, long-period fluctuations (for example, photosensitive drums and belts). If the color registration error detection pattern 50 cannot be detected at a specific phase of the belt seam portion 25a or the defect 25b such as a scratch on the belt, the color registration error detection pattern is detected. The detection values of the main scanning direction color registration misalignment amount Lerr and the sub-scanning direction color registration misalignment amount Perr based on the pattern 50 are expected to have a certain amount of detection error. For example, when color registration fluctuations due to periodic fluctuations of the photosensitive drum 15 and the intermediate transfer belt 25 occur with an amplitude of several tens to hundreds of μm as shown in FIG. It is conceivable that the thickness is about ten to several μm.
[0058]
In addition, it may be difficult to set the pattern period of the color registration misalignment detection pattern 50 so that the influence of periodic fluctuations caused by the photosensitive drum 15 and the intermediate transfer belt 25 is zero. Sometimes an inappropriate pattern frequency is set and a large detection error may occur.
[0059]
Therefore, in this embodiment, the detection error of the color registration misregistration amount Lerr in the main scanning direction and the color registration misregistration amount Perr in the sub-scanning direction based on the color registration misregistration detection pattern is reduced as follows. It is. The procedure will be described below.
[0060]
In the first embodiment, calibration of a detection error at the time of reading caused by an inappropriate pattern frequency will be described.
[0061]
That is, in the first embodiment, as shown in FIG. 1, prior to the detection operation of the color registration displacement amount Lerr in the main scanning direction and the color registration displacement amount Perr in the sub scanning direction based on the color registration displacement detection pattern 50. Then, a pattern block 55 composed of mountain-shaped marks 51 that replaces all the blocks of the color registration displacement detection pattern 50 with a single color (for example, black) is formed on the intermediate transfer belt 25 at the same interval as the normal pattern 50. Perform the action.
[0062]
Then, the block of the pattern 55 to be replaced with a single color (for example, black) formed on the intermediate transfer belt 25 is detected by the pattern detector 60, and similarly to the normal pattern 50, the time intervals T1A, T1B, T2A, T2B is obtained, and based on these time intervals T1A, T1B, T2A, T2B, the main scanning direction color registration deviation amount Lerr and the sub-scanning direction color registration deviation amount Perr for each pattern 55 are calculated by the following calculation formulas. To do.
Lerr = (T2A-T1A) / 2
Perr = (T2B−T1B) −Lerr
[0063]
The main scanning direction color registration deviation amount Lerr calculated based on the blocks of the single-color patterns 55 formed at a predetermined block frequency over the entire circumference of the surface of the intermediate transfer belt 25, and the sub-scanning direction color registration deviation. The value of the quantity Perr is arithmetically averaged. Then, in the block of the monochromatic pattern 55 formed by the same image forming unit 13BK, the linear marks 56 of each pattern 55 should be formed on the intermediate transfer belt 25 at a predetermined interval. If the factors based on the periodic fluctuations of the belt 25 and the photosensitive drum 25 are removed by arithmetic averaging, values of the main scanning direction color registration deviation amount Lerr and the sub scanning direction color registration deviation amount Perr obtained as a result are obtained. Should both be zero.
[0064]
Here, when the deviation ΔV of about 10 to several μm is calculated instead of being zero as shown in FIG. 10, the value is a defect 25b such as a seam portion 25a of the intermediate transfer belt 25 or a scratch on the belt surface. It can be said that this is a detection error caused by.
[0065]
More specifically, as shown in FIG. 1, the blocks of single-color patterns 55 formed at a predetermined block frequency are formed by the same image forming unit 13BK over the entire circumference of the surface of the intermediate transfer belt 25. Therefore, there is no so-called color registration misalignment in the blocks of the single-color patterns 55, as in the case where the blocks of the pattern 50 are formed by the black image forming unit 13BK and the yellow image forming unit 13Y. The main-scanning direction color registration shift amount Lerr and the sub-scanning-direction color registration shift amount Perr caused by misalignment between the image forming units and the shift in image formation timing do not occur, and these color registration shifts in the main scanning direction do not occur. The value of the amount Lerr and the sub-scanning direction color registration shift amount Perr should be essentially zero.
[0066]
However, when the pattern detector 60 detects the blocks of the single-color patterns 55 formed on the intermediate transfer belt 25, the positional deviation caused by the rotational fluctuation of the intermediate transfer belt 25 and the photosensitive drum 15 is caused. As a matter of course, even in the case of the block of each monochrome pattern 55, the values of the main scanning direction color registration deviation amount Lerr and the sub-scanning direction color registration deviation amount Perr are periodically changed as shown in FIG. Fluctuating.
[0067]
Therefore, as shown in FIG. 1, a block of each monochrome pattern 55 is formed at a predetermined block frequency over the entire circumference of the surface of the intermediate transfer belt 25, and based on these blocks of each monochrome pattern 55, a main block is formed. The values of the color misregistration amount Lerr in the scanning direction and the color misregistration amount Perr in the sub-scanning direction are respectively obtained, and the arithmetic average of the values of the color registration misregistration amount Lerr in the main scanning direction and the color registration misalignment amount Perr in the sub-scanning direction can be obtained. For example, the factors based on the periodic fluctuations are canceled out, and the values of the main scanning direction color registration misalignment amount Lerr and the sub-scanning direction color registration misalignment amount Perr obtained as a result of the arithmetic average should be essentially zero. .
[0068]
Therefore, if the values of the main scanning direction color registration deviation amount Lerr and the sub-scanning direction color registration deviation amount Perr obtained as a result of the arithmetic average do not become zero as shown in FIG. A detection error based on the fact that the block of the monochromatic pattern 55 cannot be detected due to the seam portion 25a of the intermediate transfer belt 25 or the defect 25b such as a scratch on the belt surface.
[0069]
Therefore, a detection error amount measurement cycle using a monochromatic pattern block is provided in this way before the actual color registration error detection cycle, and the detection error amount ΔV is grasped. By calibrating the amount of deviation calculated in the actual color registration deviation detection cycle with detection error data obtained in advance, it is possible to detect color registration deviation that does not include a detection error.
[0070]
This will be specifically described. In the detection error amount measurement cycle, the color registration error detection error amount corresponding to the reference color detection target color is 7 μm in the process direction, the lateral direction is −5 μm, and the color registration error amount of the detection target color with respect to the reference color in the color registration error detection cycle is Assuming that the process is 56 μm and the lateral 42 μm, calibration is performed based on the detection error amount, and the final color registration misalignment detection value may be the process −49 μm and the lateral 37 μm.
[0071]
By doing so, the detection error of the detection pattern 50 due to the rotational fluctuation of the intermediate transfer belt 25, the photosensitive drum 15 and the like can be significantly reduced without complicating the configuration and significantly increasing the cost. Needless to say, it is possible to detect the color registration shift accompanying the sampling of the detection pattern 50 with high accuracy.
[0072]
Embodiment 2
FIG. 11 shows a second embodiment of the present invention. The same reference numerals are given to the same parts as those in the first embodiment. In the first embodiment, the color registration misalignment detection cycle is described. The detection error detection cycle is provided before. In the second embodiment, the detection error is grasped and the detection data is calibrated simultaneously using the color registration error detection cycle. This relates to the calibration of detection errors that occur when the sample length is not synchronized with long period fluctuations.
[0073]
FIG. 11 shows an arrangement in which a part of the pattern 50 used for color registration misalignment detection is omitted by the number of blocks to be detected. In the figure, TIA2 / T2A2 indicates an interval in the second color pattern to be detected. Here, attention is paid to the interval data T2B1 and T1C1 of the pattern 50. These intervals T2B1 and T1C1 indicate the intervals of the same color pattern such as yellow colors and black colors. That is, T2B1 is an interval formed between color registration misalignment detection target colors (for example, yellow colors), and T1C1 is an interval between reference colors (for example, black colors). If there is no periodic fluctuation in the reference color and the detection target color, the difference between the measured value and the design value of the same color should be the same (the difference between the measured value and the design interval value is This is caused by the difference between the design value of the rotational speed of the photosensitive drum / belt and the actual speed). When the difference between the measured value and the design value in the two interval data is different, the difference is caused by the periodic color registration fluctuation amount of the color registration detection target color with respect to the reference color.
[0074]
The detection error is calculated from the periodic color registration fluctuation calculated from the interval data. A specific example will be described below.
[0075]
Assume that the block length of the pattern 50 is 60 mm, the peripheral length of the intermediate transfer belt 25 is 2000 mm, the sample length is 1800 mm, and the design value interval between T2B1 and T1C1 is 3 mm. The error between the design value and the actual measurement value of the pattern interval of T2B1 / T1C1 is calculated for each block, and error data for the number of samples at the sample length of 1800 mm is averaged. When the error of T2B1 after averaging is 30 μm and the error of T1C1 is 25 μm, the difference of 5 μm becomes a detection error due to color registration fluctuation. These detection errors are calculated before the actual color registration deviation amount is calculated, and the color registration deviation amount is calculated after the interval data is calibrated. That is, for the T2B1 / T1C1 data detected for each block, the color registration shift detection error is subtracted by 5 μm from the measured data. If the color registration deviation amount is calculated from the calibrated interval data, it is possible to calculate the color registration deviation amount from which the detection error is removed.
[0076]
In this way, using the normal color registration misalignment detection pattern 50, the same reference color mark interval and the same detection target color mark interval are used to determine the same reference color mark interval. By subtracting the mark interval between the detection target colors, the detection error of the color registration deviation of the target color can be obtained simultaneously with the normal pattern detection. Therefore, the color registration displacement amount calibration operation can be performed quickly, and the time required for the entire color registration displacement amount calibration operation and correction operation can be shortened.
[0077]
In the second embodiment, the pattern interval is described as a distance for convenience of explanation, but it may be performed at a time interval.
[0078]
Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.
[0079]
Embodiment 3
FIG. 12 shows a third embodiment of the present invention. The same parts as those of the first embodiment will be described with the same reference numerals. The third embodiment is different from the first embodiment. The toner images formed by the image forming units on the intermediate transfer body belt are not transferred once in a multiple manner, but on the transfer paper 34 carried on the transfer material transport belt 90 as a transfer material carrier. In this configuration, the toner images formed by the image forming unit are directly transferred in multiple layers.
[0080]
In the figure, reference numerals 91 and 92 denote driving rolls and driven rolls that stretch the transfer material conveyance belt 90, and 93 denotes a paper conveyance roll for conveying the transfer paper 34 onto the transfer material conveyance belt 90.
[0081]
Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.
[0082]
Embodiment 4
FIG. 13 shows a fourth embodiment of the present invention. In the fourth embodiment, unlike the first embodiment, on the photosensitive drum as the image carrier, every rotation of the photosensitive drum. In this configuration, toner images of different colors are sequentially formed, and the toner images are transferred onto the intermediate transfer member in a state of being superimposed on each other.
[0083]
FIG. 13 shows a color electrophotographic copying machine as an image forming apparatus according to Embodiment 4 of the present invention. Here, the configuration of the present invention will be described using a copying machine, but the present invention is also effective in a color printer / facsimile.
[0084]
In FIG. 13, reference numeral 101 denotes a main body of a color electrophotographic copying machine, and an automatic document transport for automatically transporting the original 102 in a state of being separated one by one on the upper part of the main body 101 of the color electrophotographic copying machine. An apparatus 103 and an original reading apparatus 104 that reads an image of the original 102 conveyed by the automatic original conveying apparatus 103 are provided. The document reader 104 illuminates a document 102 placed on a platen glass 105 with a light source 106, and reflects a reflected light image from the document 102 from a full-rate mirror 107, half-rate mirrors 108 and 109, and an imaging lens 110. The image reading element 111 composed of a CCD or the like is scanned and exposed through the reduction optical system, and the color material reflected light image of the original 2 is scanned at a predetermined dot density (for example, 16 dots / mm) by the image reading element 111. It is supposed to read.
[0085]
The color material reflected light image of the document 2 read by the document reading device 4 is subjected to image processing, for example, as document reflectance data of three colors of red (R), green (G), and blue (B) (8 bits each). The image processing apparatus 112 sends predetermined correction data such as shading correction, position shift correction, brightness / color space conversion, gamma correction, frame deletion, color / moving editing, etc. to the reflectance data of the document 2. Image processing is performed.
[0086]
The image data subjected to the predetermined image processing by the image processing apparatus 112 as described above is an original of four colors of yellow (Y), magenta (M), cyan (C), and black (BK) (8 bits each). The color material gradation data is sent to a ROS 113 (Raster Output Scanner), and the ROS 113 performs image exposure with laser light in accordance with the original color material gradation data.
[0087]
An image forming unit A capable of forming a plurality of toner images having different colors is disposed inside the color electrophotographic copying machine main body 101. This image forming means A mainly develops a photosensitive drum 117 as an image carrier on which an electrostatic latent image is formed and a plurality of different colors by developing the electrostatic latent image formed on the photosensitive drum 117. And a rotary type developing device 119 as developing means capable of forming a toner image.
[0088]
As shown in FIG. 13, the ROS 113 modulates a semiconductor laser (not shown) according to the original reproduction color material gradation data, and emits a laser beam LB from the semiconductor laser according to the gradation data. The laser beam LB emitted from the semiconductor laser is deflected and scanned by the rotary polygon mirror 114, and is scanned and exposed on the photosensitive drum 117 as an image carrier through the f · θ lens 115 and the reflecting mirror 116.
[0089]
The photosensitive drum 117 on which the laser beam LB is scanned and exposed by the ROS 113 is rotationally driven at a predetermined speed in the direction of the arrow by a driving unit (not shown). The surface of the photosensitive drum 117 is charged in advance with a predetermined polarity (for example, negative polarity) and potential by the primary charging scorotron 118, and then the laser beam LB is scanned and exposed in accordance with the original reproduction color material gradation data. As a result, an electrostatic latent image is formed. The electrostatic latent image formed on the photosensitive drum 117 includes four color developing devices 119Y, 119M, 119C, and 119BK of yellow (Y), magenta (M), cyan (C), and black (BK). The rotary developing device 119 reversely develops, for example, with a toner (charged color material) charged to a negative polarity that is the same polarity as the charged polarity of the photosensitive drum 117 to form a toner image of a predetermined color. The toner image formed on the photosensitive drum 117 is negatively charged by the pre-transfer charger 120 as necessary to adjust the amount of charge.
[0090]
The toner images of the respective colors formed on the photosensitive drum 117 are transferred onto a primary transfer roll as a first transfer unit on an intermediate transfer belt 121 as an intermediate transfer member disposed below the photosensitive drum 117. Multiple transfer is performed by 122. The intermediate transfer belt 121 is moved at the same moving speed as the peripheral speed of the photosensitive drum 117 by a driving roll 123, a driven roll 124a, a tension roll 124b, and a backup roll 125 as an opposing roll constituting a part of the secondary transfer means. It is supported so as to be rotatable along the arrow direction.
[0091]
On the intermediate transfer belt 121, four colors of yellow (Y), magenta (M), cyan (C), and black (BK) are formed on the photosensitive drum 117 according to the color of the image to be formed. All or part of the toner image is transferred in a state of being sequentially superimposed by the primary transfer roll 122. The toner image transferred onto the intermediate transfer belt 121 is transferred to a secondary transfer position at a predetermined timing on a transfer sheet 126 as a recording medium, a backup roll 125 that supports the intermediate transfer belt 121, Transfer is performed by the pressure contact force and electrostatic attraction force of the secondary transfer roll 127 that constitutes a part of the second transfer unit that is in pressure contact with the backup roll 125. As shown in FIG. 13, the transfer sheet 126 is fed from any one of a plurality of sheet feeding cassettes 128, 129, 130, and 131 serving as recording medium accommodation members disposed in the lower part of the color electrophotographic copying machine main body 101. Paper of a predetermined size is fed by feed rolls 128a, 129a, 130a, 131a. The fed transfer sheet 126 is transported to the secondary transfer position of the intermediate transfer belt 121 by a plurality of transport rolls 132 and registration rolls 133 at a predetermined timing. Then, as described above, a predetermined color toner image is transferred onto the transfer sheet 126 from the intermediate transfer belt 121 by the backup roll 125 and the secondary transfer roll 127 as secondary transfer means. It has become so.
[0092]
The transfer sheet 126 onto which the toner image of a predetermined color is transferred from the intermediate transfer belt 121 is separated from the intermediate transfer belt 121 and then conveyed to the fixing device 135 by the conveying belt 134. Thus, the toner image is fixed on the transfer sheet 126 by heat and pressure, and in the case of single-sided copying, the toner image is directly discharged onto the discharge tray 136 and the color image copying process is completed.
[0093]
On the other hand, in the case of duplex copying, the transfer sheet 126 on which the color image is formed on the first surface (front surface) is not discharged onto the discharge tray 136 as it is, but the conveyance direction is changed downward by a reversing gate (not shown). Then, the tri-roll 137 and the reverse roll 138 with which the three rolls are pressed are temporarily transported to the reverse passage 139. Then, the transfer sheet 126 is conveyed to the double-sided passage 140 by the reversing roll 138 which is now reversed, and is temporarily conveyed to the registration roll 133 by the conveying roll 141 provided in the double-sided passage 140 and stopped. The transfer sheet 126 is started to be conveyed again by the registration roll 133 in synchronization with the toner image on the intermediate transfer belt 121, and the transfer / fixing process of the toner image is performed on the second surface (back surface) of the transfer sheet 126. After being performed, it is discharged onto the discharge tray 136.
[0094]
In FIG. 13, reference numeral 142 denotes a cleaning device for removing residual toner, paper dust, and the like from the surface of the photosensitive drum 117 after the transfer process is completed, and reference numeral 143 denotes an intermediate transfer for cleaning the intermediate transfer belt 121. Belt cleaners 144 indicate manual feed trays.
[0095]
Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.
[0096]
【The invention's effect】
As described above, according to the present invention, the detection error of the detection pattern due to the rotational fluctuation of the intermediate transfer member or the image carrier is greatly reduced without complicating the configuration and significantly increasing the cost. As a matter of course, it is possible to provide a color image forming position deviation detecting device capable of detecting a color registration deviation accompanying sampling of a detection pattern with high accuracy, and an image forming apparatus using the same. can do.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a color registration misalignment detection pattern used in a color image formation position misalignment detection apparatus according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a digital color copying machine as an image forming apparatus to which a color image forming position deviation detecting apparatus according to Embodiment 1 of the present invention is applied.
FIG. 3 is a block diagram showing a digital color copying machine as an image forming apparatus to which a color image forming position shift detecting apparatus according to Embodiment 1 of the present invention is applied.
FIG. 4 is a perspective view showing an intermediate transfer belt.
FIG. 5 is an explanatory diagram showing a color registration misalignment detection pattern used in the color image forming position misalignment detecting apparatus according to the first embodiment of the present invention.
FIG. 6 is an explanatory diagram showing a color registration misalignment detection pattern used in the color image forming position misalignment detecting apparatus according to the first embodiment of the present invention.
FIG. 7 is a perspective configuration diagram showing a pattern detector.
FIG. 8 is an explanatory diagram showing a detection state of the pattern detector.
FIG. 9 is a block diagram illustrating a color registration misalignment correction circuit.
FIG. 10 is an explanatory diagram illustrating a detection state of a detection error of the color registration error correction circuit.
FIG. 11 is an explanatory diagram showing a color registration misalignment detection pattern used in the color image forming position misalignment detecting apparatus according to the second embodiment of the present invention.
FIG. 12 is a block diagram showing a digital color copying machine as an image forming apparatus to which a color image forming position deviation detecting apparatus according to Embodiment 3 of the present invention is applied.
FIG. 13 is a block diagram showing a digital color copying machine as an image forming apparatus to which a color image forming positional deviation detecting apparatus according to Embodiment 4 of the present invention is applied.
FIG. 14 is a block diagram showing a digital color copying machine as an image forming apparatus to which a conventional color image forming position deviation detecting device is applied.
FIG. 15 is an explanatory diagram showing a color registration misalignment detection pattern used in a conventional color image formation misregistration detection apparatus.
FIG. 16 is an explanatory diagram showing a color registration misalignment detection pattern used in a conventional color image forming position misalignment detection apparatus.
FIG. 17 is an explanatory diagram illustrating a detection state of a detection error of the color registration misalignment correction circuit.
[Explanation of symbols]
50: Color registration error detection pattern, 51KK: First mark, 51YY: Second mark, 51KY: Third mark, 55: Color registration error detection pattern of the same color, 56K: Mark.

Claims (1)

A plurality of image forming units;
An intermediate transfer body onto which images formed by the plurality of image forming units are transferred,
Forming a color image forming position shift detection pattern on the surface of the intermediate transfer member,
In the image forming apparatus for detecting the amount of positional deviation of the image formed by the plurality of image forming units on the surface of the intermediate transfer body by detecting the color image formation positional deviation detection pattern by a pattern detection unit,
Forming a plurality of color image formation misregistration detection patterns at equal intervals with the same image forming unit over at least one turn of the intermediate transfer member;
The color image formation position shift detection based on the arithmetic average value of the position shift amounts of the plurality of color image formation position shift detection patterns formed by the same image forming unit over one turn of the intermediate transfer member. An image forming apparatus characterized by obtaining a detection error when detecting a pattern for use.

Images