JP2014048338A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably adjust position deviations to prevent image quality degradation due to a color shift or the like based on detection results of the test pattern, even if forming processing or detecting processing of a test pattern is interrupted when the test pattern is formed outside of an image forming region in parallel with image forming processing.SOLUTION: In an image forming device 100, images of different colors are developed on a photoreceptor 120, and are superposed and transferred on an intermediate transfer belt 130 to form a color image. On the intermediate transfer belt 130, a test pattern is formed outside of an image forming region. When performing image adjustments, the test pattern is detected and detection results are stored. It is determined whether the stored detection results of the test pattern have reached a predetermined number. When it is determined that the detection results reach the predetermined number, position deviations to be adjusted are calculated based on the detection results of the test pattern, to perform image adjustments by using the calculated position deviations to be adjusted.

Description

  The present invention relates to an image forming apparatus and an image forming method that perform image process control such as color misregistration correction.

  Conventionally, electrophotographic image forming processing has been performed in image forming apparatuses such as copying machines, facsimile machines, and printers. In the electrophotographic image forming process, an electrostatic latent image is formed on a photoreceptor, the formed electrostatic latent image is developed with toner, and the developed toner image is transferred to a recording medium to form an image. . In such image forming processing, image adjustment such as positional deviation correction and density correction is conventionally performed by forming a test pattern on the intermediate transfer belt and detecting it with a sensor. However, when performing such image adjustment, normal image forming processing cannot be performed, and if it is frequently performed, the time required for image adjustment, so-called downtime increases, and the productivity of the apparatus decreases. There was a problem that. As a method for reducing this downtime, a method is proposed in which a test pattern is formed outside the image forming area in the main scanning direction in parallel with the image forming process, and correction is performed in real time by detecting it. ing.

  As a method for creating a test pattern and performing image process control, for example, in Japanese Patent Laid-Open No. 2004-228688, for the purpose of suppressing the size in the width direction of the apparatus and preventing a decrease in throughput, the paper size determination unit performs the following. When it is determined that an image to be formed for printing is a predetermined size or less and a calibration execution request is issued by the calibration execution determination unit, simultaneously with the image to be formed for printing, on the intermediate transfer belt, Image formation having a printing toner pattern forming means for forming a calibration toner pattern over a plurality of pages outside a predetermined size area, and a calibration executing means for executing calibration using the printing toner pattern An apparatus is disclosed. Further, Patent Document 2 is provided with a recording means capable of recording, detecting and erasing a binary state pattern in the sub-scanning direction on the front or back surface of the transfer body, and always recording and detecting new binary data. Thus, there is described an image forming apparatus capable of preventing color misregistration and transfer body deviation.

  In Patent Document 1, when image adjustment such as color misregistration correction or density correction is performed, a test pattern is formed outside the image forming area in parallel with the image forming process, and correction is performed in real time by detecting the test pattern. I am doing so. However, when a test pattern is formed outside the image forming area in parallel with the image forming process over a plurality of pages, the test pattern cannot be formed if transfer papers of different sizes are mixed during the image forming process. For this reason, since the number of patterns necessary for calculating the amount of misalignment is not uniform, there is a problem that correction cannot be performed and the misalignment is deteriorated. Also, when the image formation process is completed during test pattern detection or when the test pattern detection fails midway due to scratches on the intermediate transfer belt, etc., and the number of patterns necessary for calculating the misregistration amount is not complete, A similar problem occurred.

  Therefore, the present invention has been made in view of the problems of the prior art, and the object thereof is to form or detect a test pattern when a test pattern is formed outside the image forming area in parallel with the image forming process. Even if the process is interrupted, the positional deviation is surely adjusted based on the detection result of the test pattern, and the deterioration of the image quality due to the color deviation or the like is suppressed.

  The image forming apparatus according to the present invention includes a plurality of image carriers, a light irradiation unit that exposes each of the charged image carriers to form a latent image, and a latent image formed on the image carrier. An image forming unit that develops with a plurality of color developers composed of different color developers, and an intermediate transfer that moves an image formed on the image carrier to a transfer position facing the image carrier. A first transfer unit that obtains a color image by superimposing and transferring the image on a body; a second transfer unit that transfers an image transferred and formed on the intermediate transfer member to a transfer material; and an image forming process on the transfer material. A control unit for controlling each unit to perform and forming a test pattern formed on the image carrier and transferred onto the intermediate transfer member, and a test pattern detection unit for detecting the test pattern, The control unit A determination unit that stores knowledge results and determines whether or not the stored detection results have reached a predetermined number, and a detection result of the test patterns when it is determined that a predetermined number of detection results of the test patterns have been obtained. A calculation unit that calculates a misregistration adjustment amount based on the above, and an adjustment unit that performs image adjustment using the calculated misregistration adjustment amount.

  The present invention has the above-described configuration, so that when a test pattern is formed outside the image forming area in parallel with the image forming process, the test pattern detection result even if the test pattern forming process or the detecting process is interrupted Thus, it is possible to reliably adjust the misregistration based on the above and to suppress the deterioration of the image quality due to the color misregistration or the like.

It is a schematic block diagram regarding embodiment which concerns on this invention. It is a schematic block diagram regarding a detection sensor. It is a block block diagram which processes the data which the detection sensor detected. It is a functional block block diagram for performing image adjustment using a test pattern. It is explanatory drawing regarding the test pattern for position shift adjustment. FIG. 6 is an explanatory diagram relating to calculation of a deviation amount based on the detection result of the misregistration adjustment test pattern shown in FIG. 5. FIG. 6 is an explanatory diagram when a test pattern is formed and detected on an intermediate transfer belt. It is explanatory drawing regarding the case where a test pattern is formed and detected in parallel with image formation processing. It is explanatory drawing regarding the case where a test pattern is formed and detected during the image formation process in which transfer papers of different sizes coexist. It is a processing flow in the case of performing misalignment adjustment processing during image formation processing.

FIG. 1 is a schematic configuration diagram relating to an embodiment of the present invention. The image forming apparatus 100 includes a light irradiation unit 101 including optical elements such as a semiconductor laser light source and a polygon mirror, and an image forming unit including a photosensitive member such as a photosensitive drum as an image carrier, a charging device, and a developing device. And a transfer unit 103 including an intermediate transfer belt and the like. The light irradiation unit 101, the image forming unit 102, and the transfer unit 103 have functions of an image forming unit and a test pattern forming unit. Examples of the image forming apparatus 100 include apparatuses such as a facsimile apparatus, a printing apparatus (printer), a copying machine, and a combination machine combining these.
The light irradiation unit 101 deflects a light beam BM emitted from a plurality of light sources (not shown), which is a semiconductor laser light source including a laser diode (hereinafter abbreviated as LD), by a polygon mirror 110 and an fθ lens. Is incident on the scanning lenses 111a and 111b. The light beam is emitted from a plurality of light sources corresponding to images of each color of yellow (Y), black (K), magenta (M), and cyan (C), passes through the scanning lenses 111a and 111b, respectively, and then reflects on the reflection mirror. Reflected by 112y to 112c.

  The light beam Y corresponding to yellow passes through the scanning lens 111a, is reflected by the reflecting mirror 112y, and enters the WTL lens 113y. Similarly to the light beam Y, the light beam K, the light beam M, and the light beam C corresponding to the respective colors of black, magenta, and cyan are also incident on the WTL lenses 113k to 113c. The WTL lenses 113y to 113c reshape the incident light beams Y to C, respectively, and then deflect the light beams Y to C toward the reflecting mirrors 114y to 114c. The respective light beams Y to C reflected by the reflecting mirrors 114y to 114c are further reflected by the reflecting mirrors 115y to 115c, and irradiated on the photosensitive drums (hereinafter abbreviated as “photosensitive members”) 120y to 120c, respectively. An exposure process is performed.

In the exposure process of the light beams Y to C on the photoconductors 120y to 120c, as described above, a plurality of optical elements are used, and the main scanning direction and sub-scanning are synchronized with the rotational operation timing of the photoconductors 120y to 120c. Irradiating in the direction forms an electrostatic latent image. In the following description, the main scanning direction with respect to the photoconductors 120y to 120c is the light beam scanning direction, and the sub-scanning direction is orthogonal to the main scanning direction, that is, the direction in which the photoconductors 120y to 120c rotate. Define.
In the photoconductors 120y to 120c, a photoconductive layer including at least a charge generation layer and a charge transport layer is formed on a conductive drum such as aluminum. The photoconductive layers are disposed corresponding to the photoreceptors 120y to 120c, respectively, and surface charges are applied by the charging devices 122y to 122c. As such a charging device, a corotron, a scorotron, a charging roller, or the like is used. The electrostatic charges applied to the photoconductors 120y to 120c by the charging devices 122y to 122c are respectively exposed by the light beams Y to C, and electrostatic latent images are formed on the charging processing surfaces by the charging devices 122y to 122c. .

  The electrostatic latent images formed on the scanned surfaces of the photoconductors 120y to 120c are respectively developed by developing devices 121y to 121c including a developing sleeve, a developer supply roller, a regulating blade, and the like, and A developer image of each color is formed on the surface to be scanned. The developer images of the respective colors carried on the scanned surfaces of the photoreceptors 120y to 120c are transferred onto the intermediate transfer belt 130 that moves in the direction of arrow D by the transport rollers 131a to 131c. Primary transfer rollers 132y to 132c are disposed to face the photoconductors 120y to 120c, respectively. In this example, the intermediate transfer belt 130 and the primary transfer rollers 132y to 132c, which are intermediate transfer members, correspond to the primary transfer unit. When the intermediate transfer belt 130 passes between the photoconductors 120y to 120c and the primary transfer rollers 132y to 132c, the developer images of the respective colors are transferred so as to sequentially overlap to form a multicolor developer image. The conveyance direction of the intermediate transfer belt 130 is set to coincide with the sub-scanning direction of the photoconductors 120y to 120c. The intermediate transfer belt 130 is conveyed to the secondary transfer unit while carrying developer images of the respective colors transferred from the scanned surfaces of the photoreceptors 120y to 120c.

The secondary transfer unit includes a secondary transfer belt 133 and conveying rollers 134a and 134b. The secondary transfer belt 133 is conveyed in the direction of arrow E by the conveyance rollers 134a and 134b. A sheet P, which is a transfer material such as high-quality paper or a plastic sheet, is supplied to the secondary transfer unit from a sheet storage unit T such as a paper feed cassette by a conveyance roller 135. In the secondary transfer unit, a secondary transfer bias is applied to transfer the multicolor developer image carried on the intermediate transfer belt 130 onto the paper P held by suction on the secondary transfer belt 133. The sheet P on which the multicolor developer image is transferred is conveyed to the fixing device 136 by the secondary transfer belt 133.
The fixing device 136 includes a fixing member 137 having a fixing roller containing silicone rubber, fluorine rubber, or the like. The fixing device 136 presses and heats the paper P and the multicolor developer image, and discharges the paper 138. As a result, the paper P is discharged out of the image forming apparatus 100 as a printed material P ′.
The intermediate transfer belt 130 transfers the multicolor developer image onto the paper P, and after the developer remaining on the surface is removed by a cleaning unit 139 including a cleaning blade, is conveyed to perform the next image forming process. The

In the vicinity of the conveyance roller 131a, a plurality of detection sensors 5a to 5c for detecting a test pattern for correcting image forming processing conditions when forming a color image formed on the intermediate transfer belt 130 are provided. . Examples of the test pattern include a misregistration correction test pattern and a density correction test pattern.
Each of the detection sensors 5a to 5c can be a detection sensor such as a known light-reflective photosensor. Image adjustment using a test pattern is performed based on the detection results detected by the detection sensors 5a to 5c. For example, various misregistration amounts including skew (inclination) of each color with respect to the reference color, main scanning registration misregistration amount, sub-scanning registration misregistration amount, and main scanning magnification error are calculated, and various misregistrations relating to image adjustment are calculated based on the calculation results. Correct the amount. Then, based on the deviation amount thus obtained, the image forming processing conditions (color misregistration correction, density correction, etc.) when forming a color image on the intermediate transfer belt 130 are corrected.

  FIG. 2 is a schematic configuration diagram relating to the detection sensor 5a. In addition, since the internal structure of the detection sensors 5a-5c is common, description is abbreviate | omitted about the detection sensors 5b and 5c. The detection sensor 5a includes one light emitting unit 10a, two light receiving units 11a and 12a, and a condenser lens 13a. The light emitting unit 10a is a light emitting element that emits light, and for example, an infrared light LED that generates infrared light, a laser light emitting element, or the like is used. In this example, the light receiving unit 11a is a regular reflection type light receiving element, and the light receiving unit 12a is a diffuse reflection type light receiving element. As the light receiving portions 11a and 12a, any known phototransistor can be used, and a light receiving element including a photodiode, an amplifier circuit, and the like can also be used.

In the detection sensor 5a, the light L1 emitted from the light emitting unit 10a passes through the condenser lens 13a and then reaches the test pattern (not shown) of the intermediate transfer belt 130. A part of the light L1 is specularly reflected by the test pattern forming region and the developer layer that forms the test pattern to become specularly reflected light L2, and is retransmitted through the condenser lens 13a and received by the light receiving unit 11a. The incident angle of the light L1 with respect to the test pattern formation region and the reflection angle of the regular reflection light L2 incident on the light receiving unit 11a with respect to the test pattern formation region are set to be equal. Therefore, the light receiving unit 11a can accurately receive the regular reflection light L2.
Further, part of the light L1 is diffusely reflected by the test pattern forming region and the developer layer that forms the test pattern to become diffusely reflected light L3, and is retransmitted through the condenser lens 13a and received by the light receiving unit 12a.

FIG. 3 is a block configuration diagram for processing data detected by the detection sensor. Detection sensors 5a to 5c, which are test pattern detection units, include light emitting units 10a to 10c and light receiving units 11a to 11c and 12a to 12c, respectively. The control unit of the image forming apparatus 100 includes a CPU 1, a ROM 2, a RAM 3, an input / output (I / O) port 4, and a light emission amount control unit 14a to 14c as functional units related to processing of data detected by the detection sensors 5a to 5c. , Amplification units (AMP) 15a to 15c, filter units 16a to 16c, analog / digital (A / D) conversion units 17a to 17c, first-in first-out (FIFO) memory units 18a to 18c And sampling control units 19a to 19c.
The ROM 2 stores various programs necessary for the CPU 1 to control the image forming apparatus 100. The CPU 1 performs various processes such as a process for forming a test pattern on the intermediate transfer belt 130, a process for detecting the formed test pattern, and a process for calculating a correction amount from the detected result and executing a correction. The program which consists of the procedure which is executed is also stored.

Further, the CPU 1 reads out a program from the ROM 2 as necessary, and performs overall control of the image forming apparatus 100. The CPU 1 monitors the detection signals from the light receiving portions 11a to 11c at an appropriate timing, and emits light so that the intermediate transfer belt 130 and the light emitting portions 10a to 10c can be reliably detected even if they are deteriorated. The light emission amounts are controlled by the amount control units 14a to 14c so that the levels of the light reception signals from the light reception units 11a to 11c are always constant. As described above, the CPU 1 and the ROM 2 function as a control unit that controls the operation of the entire image forming apparatus.
The write control unit 20 includes a device that can set the output frequency very finely, for example, a clock generator using a VCO (Voltage Controlled Oscillator), and performs write control using the set output frequency as an image clock. . The writing control unit 20 outputs the image data transmitted from the controller 22 to the LD lighting control unit 21 based on the pixel clock, and writes the image on the photosensitive member by controlling the lighting of the LD according to the image data. It has become. The controller 22 outputs predetermined pattern data corresponding to the test pattern together with the image data. Based on the write control signal from the CPU 1, the controller 22 outputs the image data in the image forming area and the image forming area as will be described later. The test pattern arranged corresponding to the detection position outside the area is written.

Next, processing of data detected by the detection sensors 5a to 5c will be described with reference to FIG. The CPU 1 executes a program stored in the ROM 2 using the RAM 3 as a work area, and controls the light emission amount control units 14a to 14c via the I / O port 4 when detecting a test pattern to be described later. A light beam having a required light amount is emitted from each of the light emitting units 10a to 10c of 5a to 5c.
First, the test pattern is irradiated with a light beam from the light emitting unit 10a of the detection sensor 5a, and the reflected light is received by the light receiving units 11a and 12a of the detection sensor 5a. The light receiving units 11a and 12a transmit detection data signals corresponding to the amounts of received light beams to the amplification unit 15a. The detection data signal is amplified by the amplifying unit 15a and transmitted to the filter unit 16a, and the filter unit 16a transmits only the signal component of the line detection data to the A / D conversion unit 17a. In the A / D converter 17a, the detection data is converted from analog data to digital data. The digital data converted by the A / D conversion unit 17a is sampled by the sampling control unit 19a and stored in the FIFO memory unit 18a.

As for the detection sensor 5b, similarly to the detection sensor 5a, sampled digital data is generated and stored in the FIFO memory unit 18b for the detection data signals transmitted from the light receiving units 11b and 12b. Similarly to the detection sensor 5a, the detection sensor 5c generates sampled digital data for the detection data signal transmitted from the light receiving units 11c and 12c and stores the sampled digital data in the FIFO memory unit 18c. Thus, after the detection of the test pattern is completed, the stored detection data is loaded into the CPU 1 and the RAM 3 via the I / O port 4 and the data bus, and the CPU 1 performs a predetermined arithmetic processing and performs a positional deviation adjustment amount. Ask for.
Based on the adjustment amount obtained from the detection result of the test pattern, the CPU 1 performs setting for the writing control unit 20 in order to perform processing such as setting the writing start timing and changing the pixel clock frequency.

  FIG. 4 is a functional block configuration diagram for performing image adjustment using a test pattern. The control unit 200 includes a test pattern formation unit 200a, a calculation unit 200b, a determination unit 200c, and an adjustment unit 200d. As will be described later, the test pattern forming unit 200a forms a predetermined test pattern at detection positions in the image forming area and outside the image forming area. The calculation unit 200b calculates various deviation amounts of the test pattern based on the detection result of the test pattern transmitted from the test pattern detection unit 201, and calculates the positional deviation adjustment amount based on the various deviation amounts of the predetermined number of test patterns. To do. Then, the calculation unit 200b stores the calculation result in the storage unit 202. The determination unit 200c determines whether or not the test pattern is normally detected. If the test pattern is normally detected, the determination unit 200c stores the test pattern in the storage unit 202 and counts the number of the test patterns. Judge whether or not. The adjustment unit 200d performs image adjustment based on the calculated shift amount. The control unit 200 corrects the image forming conditions according to the adjusted deviation amount, controls the light irradiation unit 101, the image forming unit 102, and the transfer unit 103, and performs image forming processing.

  By using the detection results of a predetermined number of test patterns for the calculation of the positional deviation adjustment amount, the positional deviation can be adjusted with high accuracy. For example, a plurality of test patterns may be formed over a length corresponding to the image forming area of one transfer sheet, and the misregistration may be adjusted based on the detection results of the plurality of sets of test patterns. Thus, it is possible to reliably adjust the positional deviation in units of transfer paper.

  However, transfer paper sizes are mixed in a print job for performing a series of image forming processes, and test pattern formation at a detection position outside the image forming area is interrupted, and a predetermined number of test pattern detection results are obtained. There may not be. Even in such a case, if a test pattern can be formed on the next transfer paper and the test pattern can be detected, it is determined that a predetermined number of test pattern detection results have been obtained together with the already obtained test pattern detection results. The amount of misalignment adjustment can be calculated based on the obtained predetermined number of test pattern data. For this reason, even when the formation of the test pattern is interrupted in the middle, it is possible to reliably adjust the misalignment and suppress degradation of the image quality as much as possible. The interruption of the test pattern formation may be interrupted by the end of the print job in addition to the transfer paper size, but even in such a case, it can be dealt with by determining whether a predetermined number of test pattern detection results have been obtained. Further, when a test pattern is detected abnormally due to a scratch on the surface of the intermediate transfer belt even though the test pattern is formed, a normal test pattern detection result cannot be obtained. Even in such a case, it is possible to cope with the detection result of the predetermined number of test patterns by obtaining the normal detection result of the next test pattern.

FIG. 5 is an explanatory diagram relating to a test pattern for adjusting misalignment. FIG. 5A is a waveform example relating to the detection result of the misregistration adjustment test pattern, and FIG. 5B is a diagram showing a set of marks in the misregistration adjustment test pattern. FIG. 6 is an explanatory diagram regarding the calculation of the deviation amount based on the detection result of the misregistration adjustment test pattern shown in FIG.
The misregistration adjustment test pattern is a mark having a predetermined pattern for alignment for specular reflection light, and as shown in FIG. 5B, horizontal lines formed in the order of the colors Y, K, M, and C The pattern and the hatched pattern are one set (part indicated by reference numeral 30 in the figure), and eight sets are arranged in the sub-scanning direction, and a test pattern consisting of three columns corresponding to the detection sensors 5a to 5c.
The horizontal line pattern is four linear patterns of each color formed with a predetermined width and a predetermined length along the main scanning direction X1 of the photoconductors 120y to 120c, and the oblique line pattern is the main scanning direction of the photoconductors 120y to 120c. These are four diagonal patterns of each color formed at a predetermined inclination angle (for example, 45 °) with a predetermined width and a predetermined length with respect to X1 and the sub-scanning direction X2.

The misregistration adjustment test patterns are formed by forming eight sets of horizontal line patterns and diagonal line patterns corresponding to the colors Y to C on the photoconductors 120y to 120c, transferring them onto the intermediate transfer belt 130, and combining them. 5 is formed. In FIG. 5B, the locus where the centers of the detection sensors 5 a to 5 c move in the sub-scanning direction X <b> 2 on the intermediate transfer belt 130 is indicated by alternate long and short dashed lines 31 a to 31 c, and as illustrated in FIG. 5B, the alternate long and short dashed lines 31 a to 31 c When passing through the center of the test pattern for positional deviation adjustment, an ideal locus without positional deviation is obtained.
5 and 6, horizontal line patterns and diagonal line patterns are arranged on the intermediate transfer belt 130 in the order of Y, K, M, and C from the upstream side in the sub-scanning direction X2 (the conveyance direction of the intermediate transfer belt 130). Although an example is shown, the order of the colors of the horizontal line pattern and the diagonal line pattern can be changed as appropriate, and may be arranged in another order.

  Three mark rows of a test pattern for positional deviation adjustment formed on the intermediate transfer belt 130 are detected by detection sensors 5a to 5c arranged in the main scanning direction. The waveform shown in FIG. 5A shows one of the detection results of the detection sensors 5a to 5c, but the waveform of the other detection results can be obtained because the same waveform is obtained. Since the detection sensors 5a to 5c detect the surface of the intermediate transfer belt 130 in portions other than the horizontal line pattern and the diagonal line pattern, when the regular reflection light is received on the surface of the intermediate transfer belt 130, the detection level is set. Assuming the reference level, the detection level is lowered at the horizontal line pattern and the diagonal line pattern formed in each color as shown in FIG. 5A. In FIG. 5A, a threshold voltage level (voltage value) Vth indicated by a broken line is set. Therefore, even when the detection level is lowered due to contamination of the intermediate transfer belt 130, the detection accuracy can be improved by detecting the position where the level drop is detected from the threshold voltage value Vth as the position of the horizontal line pattern or the oblique line pattern. Can do.

The detection sensors 5a to 5c detect the positions of the horizontal line patterns and the oblique line patterns for the eight sets of the positional deviation adjustment test patterns, and based on the detection results, the other colors for the reference color (black in FIG. 6: K) are detected. The skew (color: yellow: Y, cyan: C, magenta: M), main scanning registration deviation, sub-scanning registration deviation, and main scanning magnification error are calculated, and the skew, main scanning registration deviation, and sub-scanning registration deviation are calculated. In addition, it is possible to obtain adjustment values for various shift amounts of the main scanning magnification error.
Further, if the detection sensor 5a to 5c detects the mark rows for three rows and calculates the average value of each detection result, the skew, sub-scanning registration deviation, main scanning registration deviation, and main scanning magnification error deviation are calculated from the calculation results. By obtaining the amount, the shift amount of each color can be obtained with high accuracy. By adjusting the shift amount of each color in this way, it is possible to form a high-quality image with very little shift between the colors. Various adjustment amounts, calculation of adjustment amounts, and execution commands for image forming correction processing based on the adjustment amounts are performed by the adjustment unit 200d. The detected misalignment adjustment test pattern is removed by the cleaning unit 139 in FIG.

Next, a specific method for calculating various misalignment amounts when a misalignment adjustment test pattern is detected will be described with reference to FIG. In FIG. 6, the case where the detection sensor 5a detects the misalignment adjustment test pattern will be described, but the same applies to the other detection sensors 5b and 5c.
The detection sensor 5a detects the mark train of the misalignment adjustment test pattern at a predetermined sampling time interval, and transmits the detection result to the CPU 1 as described with reference to FIG. When the CPU 1 receives the detection result from the detection sensor 5a, the CPU 1 calculates the interval of each color of the horizontal line pattern and the length of the interval between the horizontal line pattern and the corresponding oblique line pattern based on the detection result and the sampling time interval. By calculating the interval value in this way and comparing the interval values, various shift amounts can be calculated.
First, in calculating the sub-scanning registration deviation amount (position deviation amount in the sub-scanning direction), the detection data of the horizontal line pattern is used to calculate the reference color (K) pattern and the target color Y, M, and C patterns. The interval value (y1, m1, c1) between them is calculated and compared with the default interval values (y0, m0, c0) stored in advance. Then, the difference (y1-y0, m1-m0, c1-c0) between the detected interval value and the default interval value is set as the sub-scanning registration deviation amount of each color of Y, M, and C with respect to the reference color (K). Can do.

In calculating the main scanning registration deviation amount (position deviation amount in the main scanning direction), first, the interval values (y2, k2, m2, c2) of the horizontal line pattern and the diagonal line pattern of K to C are calculated. Using these calculated interval values, the difference between the interval value of the reference color (K) and the interval values of other colors is calculated. That is, the difference between the interval values between K and Y (k2−y2), the difference between the interval values between K and M (k2−m2), and the difference between the interval values between K and C (k2−c2) are calculated. . Since the oblique line pattern is inclined by a predetermined angle (for example, 45 °) with respect to the main scanning direction, when there is a deviation in the main scanning direction, the interval between the horizontal line pattern and the reference color interval Therefore, these differences can be used as the main scanning registration deviation amount.
The skew and main scanning magnification error can also be obtained by combining the detection results of the detection sensors 5a to 5c. The skew can be acquired by calculating the difference in the sub-scanning registration deviation amount calculated from the detection results of the detection sensors 5a and 5c. The main scanning magnification error can be obtained by calculating the difference between the main scanning registration deviation amounts of the detection sensors 5a and 5b and the detection sensors 5b and 5c.

  Then, based on the various shift amounts calculated in this way, shift amount adjustment processing is performed. Ideally, adjustment is made so that the amount of deviation is eliminated, but as will be described later, adjustment processing for the amount of deviation is performed so as to minimize image quality degradation in accordance with the curve characteristics of the scanning line. Based on the adjustment of the deviation amount, an image correction process for correcting the image forming process condition when forming a color image on the intermediate transfer belt 130 is executed. The correction processing can be performed, for example, by correcting the light emission timings of the light beams Y to C corresponding to the respective colors with respect to the photoconductors 120y to 120c in accordance with the shift amount. It can also be performed by adjusting the tilt of the reflecting mirror that reflects the light beam. Adjustment of the tilt of the reflection mirror is performed by driving a stepping motor attached to the reflection mirror. Further, it is possible to perform correction in accordance with the adjustment of the shift amount by changing the image data itself.

  FIG. 7 is an explanatory diagram when a test pattern is formed and detected on the intermediate transfer belt 130. The detection sensors 5a and 5c are disposed opposite to the detection positions outside the image forming area at both ends of the intermediate transfer belt 130, and the detection sensor 5b is positioned at the detection position in the image forming area at the center of the intermediate transfer belt. Opposed. Since the detection sensors 5a and 5c are arranged opposite to the detection position outside the image forming area, they can be detected by forming a test pattern in the sub-scanning direction X2 in parallel with the image forming process. Since the detection sensor 5b is disposed opposite to the detection position in the image forming area, a test pattern is formed between the sheets on which the transfer paper is image-formed, after the print job is completed, or immediately after the apparatus is turned on. Can be detected.

  FIG. 8 is an explanatory diagram regarding a case where a test pattern is formed and detected in parallel with the image forming process. The width H in the main scanning direction of the image forming region G to be subjected to image forming processing is narrower than the width of the intermediate transfer belt 130, and test patterns are formed on both ends of the intermediate transfer belt 130 on both sides, and the detection sensors 5a and 5c. Is detected. When image adjustment is performed by forming a test pattern in parallel with the image formation processing, the image formation processing is stopped when image adjustment is performed, so that the so-called downtime is not generated, and the efficiency of the image formation processing is improved. There is an advantage not to lower. Since the detection sensor 5b is disposed opposite to the center of the intermediate transfer belt, a test pattern cannot be formed during the image forming process, and no detection operation is performed.

  In this example, four test patterns corresponding to one detection sensor are formed for each of the image forming regions G along the sub-scanning direction as four sets 30 of horizontal line patterns and diagonal line patterns. Then, eight sets corresponding to the two image forming areas G are used as one set for adjusting the positional deviation. By using the test patterns of the two image forming regions, the noise component can be removed by increasing the number of patterns to be detected and averaging them, and the accuracy of positional deviation adjustment can be improved. The timing for forming such a test pattern is preferably the timing at which misalignment is likely to occur. For example, when the number of continuous image forming processes reaches 10 pages or more, the temperature rises at a predetermined location in the apparatus. The case where it becomes 1 degreeC or more is mentioned.

  FIG. 9 is an explanatory diagram regarding a case where a test pattern is formed and detected during an image forming process in which transfer sheets of different sizes are mixed. In this example, image forming areas G1 and G2 having different widths in the main scanning direction are set. The image forming area G1 is set to an area corresponding to the horizontal size of A4 size, and the image forming area G2 is set to A3 size. It is set in the area corresponding to the nobi size. The width H2 of the image forming region G2 in the main scanning direction is set to be wider than the width H1 of the image forming region G1 in the main scanning direction, and both sides of the image forming region G2 are disposed close to both side ends of the intermediate transfer belt 130. ing. As shown in FIG. 1, the intermediate transfer belt 130 is composed of an endless belt stretched around a conveying roller, but in FIG. 9, the entire belt is shown in a schematic developed state. .

  In FIG. 9, test patterns can be formed on both sides of the image forming region G1, but the test pattern formation is temporarily interrupted because there are no regions where test patterns can be formed on both sides of the image forming region G2. . When the next image forming area G1 is set, the test pattern formation is resumed. Then, the test pattern is formed and detected before the interruption is stored, and the test pattern is formed after the interruption and the detection result is obtained based on the detection result before and after the interruption. A misalignment adjustment process is performed. In this way, even during image formation processing where transfer papers of different sizes coexist, even if test pattern formation is interrupted, a predetermined number of test patterns can be reliably formed and detected, and misalignment adjustment can be performed accurately. It can be done well.

  FIG. 10 is a processing flow in the case of performing misalignment adjustment processing during image formation processing. Such misalignment adjustment processing is performed, for example, when the number of consecutive image forming processes is 10 pages or more, or when the temperature rise at a predetermined location in the apparatus is 1 ° C. or more. First, it is determined whether or not the next page for image formation processing is the last page of the print job being executed (S1), and if it is the last page (S1; YES), return without performing misregistration adjustment processing. Process. If it is not the last page (S1; NO), whether the size of the image forming area of the page to be image-formed next is smaller than the A3 size, that is, whether a test pattern can be formed on both outer sides of the image forming area. (S2), and if it is not smaller than the A3 size (S2; NO), the return process is performed without performing the misalignment adjustment process. If the size is smaller than the A3 size (S2; YES), a test pattern is formed along the sub-scanning direction on both outer sides of the image forming area and the detection process is executed (S3). For example, four test patterns can be formed as shown in FIG. In the test pattern detection process, for example, there may be a detection error such as misrecognizing the number of test patterns due to scratches on the surface of the intermediate transfer belt. If it is determined (S4) and a detection error occurs (S4; YES), return processing is performed. If a detection error has not occurred (S4; NO), the test pattern detection result is stored in the storage unit (S5).

  Then, it is determined whether or not a predetermined number of test pattern detection results necessary for performing misalignment adjustment processing are obtained (S6), and when a predetermined number of test pattern detection results are not obtained (S6; NO). Return processing is performed. Test pattern formation and detection processing are repeatedly performed until a predetermined number of test pattern detection results are obtained. For example, as shown in FIG. 9, at the stage where the detection results of four sets of test patterns are obtained, it is determined that the detection results of eight sets of test patterns, which is a predetermined number, are not obtained. The adjustment process is interrupted. Then, when four sets of test patterns are obtained in the next misalignment adjustment process, it is determined that a predetermined number of eight sets of test pattern detection results have been obtained, and the process proceeds to the next process. When the detection results of a predetermined number of test patterns are obtained (S6; YES), the amount of adjustment for misregistration is calculated using the obtained test pattern detection results (S7), and the misregistration correction process is performed. This is executed (S8) and return processing is performed.

In the print job shown in FIG. 9, the image forming process is performed in the order of the transfer paper size A4 size horizontal size → A3 size novi size → A4 size horizontal size, so the processing flow is as follows. First, the next page to be subjected to the image forming process is not the last page of the print job but is A4 size, and assuming that the test pattern is formed and the detection is successful, the following processing is performed.
Step S1 (No)-> Step S2 (Yes)-> Step S3-> Step S4 (No)-> Step S5-> Step S6 (No)-> Return The next page is not the last page of the print job, but the A3 size nobi size, Since the test pattern cannot be formed on both outer sides of the image forming area, the following processing is performed.
Step S1 (No) → Step S2 (No) → Return Therefore, the return process is performed while storing and holding the test pattern detection result obtained on the previous page.
If it is the last page of a print job of an A3 size nobi size page (the next A4 size horizontal size page is not subjected to image formation processing), the following processing is performed.
Step S1 (Yes) → Return In this case, a predetermined number of test patterns are stored together with the next test pattern detection result while the test pattern detection result is stored and held until the next misalignment adjustment process is performed. The calculation of the misalignment adjustment amount and the misalignment correction process are not executed until it is obtained.

Next, suppose that the page subjected to image formation processing subsequent to the A3 size nobi size page is not the last page of the print job but the A4 size landscape size page, and the test pattern is formed and the detection is successful. It becomes processing like this.
Step S1 (No) → Step S2 (Yes) → Step S3 → Step S4 (No) → Step S5 → Step S6 (Yes) → Step S7 → Step S8 → Return If a test pattern detection error occurs, The process proceeds from step S4 to the return process. In this case, the test pattern detection result remains stored and held until the next misalignment adjustment process is performed, together with the next test pattern detection result. The calculation of the misalignment adjustment and the misalignment correction processing are not executed until a predetermined number of test patterns are obtained.

As described above, when the transfer paper size is mixed in a print job that performs a series of image forming processes, and test pattern formation at the detection position outside the image forming area is interrupted, the print job is terminated. Even when the test pattern detection result is not continuously obtained, such as when a test pattern detection abnormality occurs due to a scratch or the like on the surface of the intermediate transfer belt although the test pattern is formed, If it is possible to form a test pattern on the next transfer paper and detect the test pattern, if it is determined that a predetermined number of test pattern detection results have been obtained together with the test pattern detection results already obtained The amount of misalignment adjustment can be calculated based on the obtained predetermined number of test pattern data. For this reason, even when the formation of the test pattern is interrupted in the middle, it is possible to reliably adjust the misalignment and suppress degradation of the image quality as much as possible.
In the example described above, the test pattern detection results for two pages are used as the predetermined number of test patterns. However, the test pattern detection results for three or more pages may be used.

  DESCRIPTION OF SYMBOLS 1 ... CPU, 2 ... ROM, 3 ... RAM, 4 ... I / O port, 5a-5c ... detection sensor, 10a-10c ... light emission part, 11a-11c ... -Light receiving part, 12a-12c ... Light receiving part, 13a-13c ... Condensing lens, 14a-14c ... Light emission amount control part, 15a-15c ... Amplifying part, 16a-16c ... Filter , 17a-17c ... A / D converter, 18a-18c ... FIFO memory, 19a-19c ... sampling controller, 20 ... write controller, 21 ... LD lighting control , 22 ... controller, 100 ... image forming apparatus, 101 ... light irradiation unit, 102 ... image forming unit, 103 ... transfer unit, 130 ... intermediate transfer belt.

JP 2010-256618 A JP 2004-157152 A

Claims (5)

A plurality of image carriers, a light irradiation unit that exposes each of the charged image carriers to form a latent image, and a plurality of latent images formed on the image carrier are made of developers of different colors. An image forming unit that develops with a color developer and an image formed on the image carrier are superimposed and transferred onto an intermediate transfer member that moves at a transfer position facing the image carrier, and a color image is transferred. A first transfer unit to be obtained, a second transfer unit to transfer an image transferred and formed on the intermediate transfer member to a transfer material, and the image carrier to control each unit so as to perform an image forming process on the transfer material A control unit that forms a test pattern that is formed and transferred onto the intermediate transfer member, and a test pattern detection unit that detects the test pattern,
The control unit stores the detection result of the test pattern and determines whether or not the stored detection result has reached a predetermined number, and determines that a predetermined number of detection results of the test pattern have been obtained. An image forming apparatus comprising: a calculation unit that calculates a misregistration adjustment amount based on the detection result of the test pattern, and an adjustment unit that performs image adjustment using the calculated misregistration adjustment amount.   The image forming apparatus according to claim 1, wherein the predetermined number of the test patterns are the test patterns for a plurality of pages.   3. The image forming apparatus according to claim 1, wherein the determination unit determines the test pattern detection result in the next test pattern formation process when it is determined that the test pattern formation process is interrupted. An image forming apparatus that determines whether or not the total number has reached a predetermined number.   4. The image forming apparatus according to claim 1, wherein when the determination unit determines that a detection abnormality has occurred during the test pattern detection process, the determination unit performs the next test pattern detection process. 5. An image forming apparatus for determining whether or not a predetermined number of test pattern detection results are combined. A plurality of image carriers are charged and exposed to form a latent image, and the latent images formed on the image carrier are developed with a plurality of color developers, each of which has a different color, and intermediate transfer is performed. An image forming method in which a color image is formed by transferring and superimposing on a body, and the color image transferred and formed on the intermediate transfer body is transferred to a transfer material,
Detecting test patterns formed on the image carrier and transferred onto the intermediate transfer member, storing the detection results, and determining whether the stored detection results of the test patterns are a predetermined number; When it is determined that a predetermined number of test pattern detection results have been obtained, a positional deviation adjustment amount is calculated based on the test pattern detection result, and image adjustment is performed using the calculated positional deviation adjustment amount. Image forming method.

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