JP2007010770A - Color shift correcting method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of color shift that deteriorates the quality of a formed image without lowering the throughput. <P>SOLUTION: The color shift correcting method, in which a toner pattern for detecting color shift amount is output onto a belt, the position of the toner pattern is detected, and the color shift amount is calculated from the detected position information of the toner pattern so as to correct the color shift amount to be the minimum, includes: a stage for correcting the color shift on a main scanning direction side; and a stage for correcting the color shift on a subscanning direction side. The frequency of performing the respective stages is independently changed in accordance with the variation of the color shift from the calculated color shift amount (steps B5 to B14). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color misregistration correction method for detecting and correcting a color misregistration amount, and a color image forming apparatus such as a copying machine, a printer, a facsimile, a digital multi-function peripheral, etc. that implements the color misregistration correction method.

  2. Description of the Related Art Today, electrophotographic apparatuses are increasing in color output such as color copiers and color printers in response to market demands. Particularly recently, since monochrome speeds are desired for color output, a plurality of photoconductors and individual developing devices are provided, and a single color toner image is formed on each photoconductor, and those single color toner images are sequentially formed. Tandem printers that transfer and record color images on recording paper have become mainstream.

  In the tandem printer, as shown in FIG. 12, images formed on the photoreceptors 2K, 2M, 2C, and 2Y (K, M, C, and Y indicate colors) provided for each color are displayed. Full-color images are developed by developing toner with the developing units 3K, 3M, 3C, and 3Y, and sequentially transferring onto the recording paper conveyed by the transfer belt 51 by the transfer devices 4K, 4M, 4C, and 4Y provided for each color. As shown in FIG. 13, the images formed on the photosensitive members 2K, 2M, 2C, and 2Y are temporarily transferred onto the transfer belt 51 by the transfer devices 4K, 4M, 4C, and 4Y. There is an indirect transfer type in which a full-color image formed on the transfer belt 51 is sequentially transferred onto a recording paper by a secondary transfer device 54, but the image is transferred to the recording paper. The are many things to take a configuration using a belt. In any of the methods, the images on the photosensitive members 2K, 2M, 2C, and 2Y of the respective colors are transferred onto the recording paper or the belt at different positions on the transfer belt 51, so that the moving speed of the transfer belt 51 is very small. When there is a significant change, the arrival time to the next color transfer position varies. Due to this variation, a shift occurs in the transfer position of each color, resulting in a color shift in the sub-scanning direction (belt moving direction) in the output image. In addition, since the writing units 1K, 1M, 1C, and 1Y are also independent for each color, the magnification in the main scanning direction and the writing position change due to displacement of each component due to environmental changes such as temperature. As a result, a color shift in the main scanning direction occurs in the output image.

  For this reason, the tandem printer outputs a toner pattern for detecting misregistration as shown in FIG. 14 on the transfer belt 51 before forming an actual color image, as disclosed in Japanese Patent Application Laid-Open No. H10-228707. Then, this pattern is detected by the sensor 108, and from the detection result, a deviation amount and a correction amount of each color from the normal position are calculated, and an image writing timing and a magnification are adjusted based on the correction amount, thereby causing the color deviation. Many of them have a function to correct.

  12 and 13, reference numeral 6 denotes a fixing unit, reference numeral 7 denotes a plotter control unit, reference numeral 52 denotes a driving roller, and reference numeral 53 denotes a driven roller.

Further, in Patent Document 2, engine calibration is performed with minimum downtime and minimum execution frequency, and the result is reflected in the next print so as to maintain the image quality while reducing the waiting time of the user. An image forming apparatus is disclosed.
JP 2002-244387 A JP 2003-167394 A

  However, in the case of the invention described in the cited document 1, it is possible to keep the color misregistration amount within a predetermined range by performing the color misregistration correction every fixed number of prints, but the color misregistration correction processing interrupts printing. Therefore, there is a problem that throughput is deteriorated and user convenience is deteriorated. It is also possible for the user to set the color misregistration correction interval according to the color misregistration state, but it is difficult to set the optimal number of times and the user is bothered. Become.

  The present invention has been made in view of the actual situation of the prior art, and its purpose is to improve the total throughput by shortening the time required for color misregistration correction and improve the usability of the user. The purpose of this is to prevent the occurrence of color misregistration that degrades the image quality.

  Therefore, according to the present invention, in a color image forming apparatus having a function of detecting and correcting a color misregistration amount, color misregistration correction processing in the main scanning direction and color misregistration correction processing in the sub-scanning direction are independently performed according to the detected color misregistration amount. And executed so that each is executed at an optimal execution interval.

  Specifically, the first means outputs a toner pattern for detecting the color misregistration amount on the belt, detects the position of the toner pattern, and calculates the color misregistration amount from the detected toner pattern position information. In the color misregistration correction method for correcting the color misregistration amount to a minimum, the color misregistration correction method includes a step of correcting color misregistration on the main scanning direction side and a step of correcting color misregistration on the sub scanning direction side. The execution frequency of each step is independently changed in accordance with the amount of color misregistration from the amount of color misregistration.

  The second means is characterized in that, in the first means, an interval until the next color misregistration correction is executed is changed based on the calculated color misregistration amount.

  The third means is characterized in that, in the first means, an interval until the next color misregistration correction is executed is changed in accordance with a change in temperature environment.

  The fourth means is characterized in that, in the first means, the interval until the next color misregistration correction is executed is changed in accordance with a change in image forming conditions.

  The fifth means calculates a color shift from the position information of the detected toner pattern, a means for outputting a toner pattern for detecting a color shift amount on the belt, a means for detecting the position of the toner pattern, In the image forming apparatus having a unit for correcting the color misregistration amount to a minimum, the correcting unit independently performs the color misregistration correction process on the main scanning direction side and the color misregistration correction process on the sub scanning direction side. The frequency of execution of each correction process is independently changed from the calculated color misregistration amount according to the color misregistration change amount.

  A sixth means is characterized in that, in the fifth means, the correcting means changes an interval until the next color misregistration correction is executed based on the calculated color misregistration amount.

  The seventh means further comprises means for measuring the in-machine temperature in the fifth or sixth means, and the means for correcting is the next color misregistration correction according to the amount of change in temperature measured by the measuring means. It is characterized in that the interval until execution of is changed.

  The eighth means further comprises means for measuring the environmental temperature of the equipment installation environment in any of the fifth to seventh means, and the means for correcting the temperature change amount measured by the measurement means. Accordingly, the interval until the next color misregistration correction is executed is changed.

  The ninth means further comprises means for detecting a magnification change in the main scanning direction in any one of the fifth to eighth means, and the correcting means sets the magnification change amount detected by the detecting means. Accordingly, the interval until the next color misregistration correction is executed is changed.

  According to a tenth means, in any one of the fifth to ninth means, the belt is a transport belt for transporting a sheet onto which an image is directly transferred.

  An eleventh means is the intermediate transfer belt according to any one of the fifth to ninth means, wherein the belt is an intermediate transfer belt on which an image is primarily transferred and the transferred image is transferred onto a sheet at a secondary transfer position. It is characterized by that. In the embodiment described later, the process of correcting the color misregistration in the main scanning direction is performed in steps A3 to A13, and the process of correcting the color misregistration in the sub-scanning direction is performed in steps A2 and A14 through A22. Changing the interval until the next color misregistration correction is executed based on the amount of misregistration is performed by changing the interval until the next color misregistration correction is performed according to the change of the temperature environment in steps C5 to C22. Changing the interval until the next color misregistration correction is executed according to the change in the image forming conditions corresponds to steps E5 to E17.

  Further, a means for outputting a toner pattern is applied to the entire image forming element formed via the plotter control unit 7 according to an instruction from the CPU 100, a means for detecting the position is the toner mark sensor 108 and the CPU 100, and a means for correcting is the CPU 100. Further, the means for measuring correspond to the temperature detection sensor 109, respectively.

  According to the present invention, the color misregistration correction process on the main scanning direction side and the color misregistration correction process on the sub-scanning direction side are executed independently, and each of the above described color misregistration amounts is calculated according to the amount of color misregistration change. Since the execution frequency of the correction process is changed independently, it is possible to reduce the time required for color misregistration correction, thereby causing color misregistration that reduces the quality of the formed image without reducing throughput. Can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<First Embodiment>
FIG. 1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. In the figure, an image forming apparatus according to this embodiment includes a CPU 100, a ROM 101, a RAM 102, a parameter memory 103, a synchronization detection detection unit 104, a synchronization detection sensor 114, an operation display unit 105, a plotter 106, an I / O unit 107, a toner. The mark sensor 108, temperature detection sensor 109, motor control unit 110, motor driver circuit 111, motor 112, and system bus 113 are basically configured.

  The CPU 100 is a central processing unit that executes a program written in the ROM 101 and controls each part of the apparatus. The ROM 101 is a read only memory in which a program for the CPU 100 to control each part of the apparatus and fixed data used for control are stored. A RAM 102 is a random access memory used to develop a work area when the CPU 100 executes a program for controlling each part of the apparatus and an image to be printed. The parameter memory 103 is a non-volatile memory for storing data related to the operation of the apparatus even when the power is shut down and for storing data that is referred to at the next operation, and is a battery-backed SRAM or EEPROM. Consists of. The parameter memory 103 stores data that is updated when color misregistration correction is performed, such as a color misregistration correction execution interval, a color misregistration correction pattern parameter, and a color misregistration correction amount.

  The synchronization detection detection unit 104 measures a change in magnification in the main scanning direction of the optical system by counting signals from the synchronization detection sensor 114 using a clock inside the system. The synchronization detection sensor 114 is arranged on the writing side and the writing end side of each of the CMYK four colors in the writing unit, and outputs a signal on a pulse when a writing signal passes. The synchronization detection detection unit 104 counts the interval between pulses from the synchronization detection sensor 114 on the writing side and the writing end side with a clock, compares the measured value with a reference value, and performs a magnification correction process based on the comparison result. Do.

  The operation display unit 105 includes operation keys for the user to set the device and the like, and a display unit such as a liquid crystal display for displaying the operation state and message of the device to the user. The plotter 106 is a part that performs an operation of forming and outputting an image on a recording paper 70 (see FIG. 2), and is controlled by the plotter control unit 7. A detailed configuration of the plotter 106 is shown in FIG. The I / O unit 107 includes an input / output port, and controls input and output of the toner mark sensor 108 and other sensors.

  The toner mark sensor 108 is a sensor that detects a toner mark generated on the transfer belt 51. When the optical sensor is used, the transfer belt 51 is irradiated with light, a toner mark for measuring the color misregistration amount generated on the transfer belt 51 is detected, and information for measuring the color misregistration amount is obtained. . An example of the toner mark is as shown in FIG. The temperature detection sensor 109 is a sensor for detecting an environmental temperature and / or an in-machine temperature, and detects an ambient temperature in which the image forming apparatus is installed and / or an in-machine temperature of the image forming apparatus by using a temperature sensor such as a thermistor. Is.

  The motor 112 is a motor that drives each part of the image forming apparatus according to the present embodiment, and is controlled by a drive signal supplied from the motor control circuit 110 via the motor drive circuit 111. The system bus 113 is a signal line for the above-described units to exchange data. Specifically, the system bus 113 is configured as a set of a data bus, an address bus, a control bus, and an I / O bus.

  FIG. 2 is a diagram showing a schematic configuration of the plotter unit 106. In the figure, a plotter 106 is of an electrophotographic tandem type, and four drum-shaped photoconductors 2K, 2M, 2C, and 2Y and images formed on the photoconductors 2K, 2M, 2C, and 2Y are displayed. It comprises a belt-like transport device (transfer belt 51) that transports the recording paper 70 so as to be sequentially transferred onto the recording paper 70 at the transfer positions of the respective transfer devices 4K, 4M, 4C, 4Y provided for each color. This is a direct transfer type configuration and corresponds to FIG.

  In the image forming apparatus configured as shown in FIG. 2, the image data is first decomposed into image data of cyan (C), magenta (M), yellow (Y), and black (K) by the plotter control unit 7. Are converted into data for each color for writing. The photosensitive drums 2K, 2M, 2C, and 2Y are exposed to the laser light output from the writing units 1K, 1M, 1C, and 1Y, and the photosensitive layers on the photosensitive drums 2K, 2M, 2C, and 2Y correspond to the image data. An electrostatic latent image is formed. The electrostatic latent images formed on the photosensitive drums 2K, 2M, 2C, and 2Y are developed by the developing devices 3K, 3M, 3C, and 3Y corresponding to the respective colors, and become toner images of the respective colors. The developed toner image is fed from the paper feed cassette 71 and sequentially transferred onto the recording paper 70 supplied to the transfer unit 4, and four colors are superimposed on the recording paper 70 to form a color image.

  The transfer unit 4 includes transfer belts 51 that are in contact with the photosensitive drums 2K, 2M, 2C, and 2Y of the respective colors and transfer devices (transfer roller units) 4K, 4M, 4C, and 4Y that are opposed to the photosensitive drums 2K, 2M, 2C, and 2Y. Consists of. The recording paper 70 is conveyed in an electrostatically attracted state on the transfer belt 51, and the toner image is transferred to the recording paper 70 at the position where it contacts the photosensitive drums 2 K, 2 M, 2 C, and 2 Y.

  The transfer belt 51 is an endless belt, is stretched between the driving roller 52 and the driven roller 53, and is driven to operate at a constant speed by a motor 112 connected to the shaft of the driving roller 52. A cleaning device 54 is installed on the downstream side of the driving roller 52 in the rotation direction of the transfer belt 51 to clean an unnecessary toner image on the surface of the transfer belt 51. As the transfer belt 51, for example, a belt in which all layers of the belt are formed of fluorine-based resin, polycarbonate resin, polyimide resin, or a part of the belt is used. A fixing unit 6 is provided on the downstream side of the transfer belt 51 in the conveyance direction. In the fixing unit 6, the recording paper 70 to which the toner images of the respective colors are transferred is fixed on the recording paper 70 by heating and pressurizing and output.

  In this embodiment, the direct transfer type printer has been described. However, the present invention can be similarly applied to an indirect transfer type printer as shown in FIG.

  In the image forming apparatus configured as described above, the following color misregistration correction processing is performed.

  In the color misregistration correction process, as shown in FIG. 14 described above, four strip-shaped toner patterns 11K, 11M, 11C, and 11Y having different colors formed on both sides in the main scanning direction on the transfer belt 51 are marked with toner marks. The detection is performed by the sensor 108, the color misregistration amount between the patterns 11K, 11M, 11C, and 11Y of the respective colors is detected, and the writing timing is adjusted so that the color misregistration amount becomes a predetermined value or less. Is called.

 In the direct transfer method shown in FIG. 10, the toner patterns 11K, 11M, 11C, and 11Y are indirect transfer shown in FIG. 11 at a position facing the nearest position on the downstream side in the rotation direction of the transfer belt 51 of the drive roller 52. In the system, the drive roller 52 is formed at a position facing the nearest position on the upstream side in the rotation direction of the transfer belt 51. The patterns 11K, 11M, 11C, and 11Y are formed of a series of strip-shaped patterns in accordance with the arrangement of the toner mark sensor 108 at a plurality of locations in the main scanning direction in the same manner as in normal image formation. It is formed by transferring from 2Y. In this embodiment, although it arrange | positions in two places, it is good also as a structure which arrange | positions a pattern three or more places according to the number of sensors. The pattern itself is visualized by the CPU 100 by reading the parameter data of the pattern stored in the parameter memory 103 from the plotter control unit 7 through the above-described steps.

  In any case, at the time of color misregistration correction, the recording paper 70 is not passed, but the toner pattern for misregistration detection shown in FIG. 14 is output on the transfer belt 51, and this pattern is detected by the toner mark sensor 108. From the detection result, the CPU 100 detects and corrects the deviation amount of each color from the normal position. As shown in FIG. 3, each pattern includes four parallel linear patterns 11-1 and four diagonal line patterns 11-2. The pairs are arranged at regular intervals in the sub-scanning direction, and a plurality of sets are repeated and formed along the moving direction of the transfer belt 51. In this embodiment, four colors of yellow (Y), cyan (C), magenta (M), and black (K) are formed. Here, it is shown that a positional deviation indicated by ΔM in the horizontal magenta pattern 11M and Δ (Mo−Ko) to Δ (M−K) occurs in the interval between the black and magenta patterns.

  Each part not specifically described is configured in the same manner as the direct transfer type printer shown in FIG. 12 and functions in the same way.

FIG. 4 is a flowchart showing a processing procedure of color misregistration correction processing using this toner pattern, and is executed by the CPU 100.
When performing color misregistration correction (step A1), first, it is selected whether to perform color misregistration correction in the main scanning direction or correction processing in the sub scanning direction (step A2). When execution of the color misregistration correction process in the sub-scanning direction is selected (step A2-Yes), the processes after step A14 are executed.

  When obtaining the amount of color misregistration in the sub-scanning direction, a toner pattern that repeats only the horizontal line is output as shown in FIG. 5 (step A14). The toner pattern is formed on the transfer belt 51 through each photoconductor. Since the color misregistration amount in the sub-scanning direction can be obtained by using only the horizontal lines of four colors, when obtaining the color misregistration amount in the sub-scanning direction, as shown in FIG. By outputting only the horizontal line patterns 11Y, 11M, 11C, and 11K, the pattern output and detection is performed as compared with the case of outputting the patterns 11-1 and 11-2 in which the horizontal lines and the diagonal lines are combined as shown in FIG. It is possible to reduce the time required for the process.

  Next, the color misregistration detection toner patterns 11Y, 11M, 11C, and 11K (11-1) formed on the transfer belt 51 are detected by the toner mark sensor 108, and the position information of each line pattern is detected (step A15). ), A shift amount in the sub-scanning direction is calculated from the detected edge information of each line pattern 11-1, and a correction amount that minimizes the shift between the colors is calculated. The calculated shift amount and correction amount are stored in the parameter memory 103 and used as correction values until the next color shift correction process (step A16).

  Then, in step A17, correction of the sub-scanning resist is performed using the correction amount calculated in step A16. After the correction in step A16, the color misregistration detection pattern is output again in a state reflecting the correction result of the color misregistration correction process in step A16, and the pattern after the color misregistration correction is formed on the transfer belt 51 (step S16). A18). The uncorrected toner pattern first formed on the transfer belt 51 is cleaned by the cleaning device 54 and removed from the transfer belt 51 after detection by the toner mark sensor 108.

  The line pattern 11-1 after color misregistration correction formed in step A18 is detected again by the toner mark sensor 108, and each position information of the line pattern 11-1 is detected (step A19). From the detected edge information of each line pattern 11-1, a shift amount in the sub-scanning direction is calculated in the same manner as in step A16, and a correction amount that minimizes the shift between these colors is calculated (step A20).

  Next, it is determined whether or not the color misregistration amount between the patterns after the color misregistration correction is smaller than a predetermined value (Δd) (step A21). If smaller than Δd (step A21-Yes), the process is performed. End (step A22). If it is greater than Δd (No at Step A21), the correction amount is calculated again from the position information detected at Step A19, and the processes after Step 17 are repeated.

  By performing the above-described series of processing, the amount of color misregistration between colors in the sub-scanning direction can be adjusted to a value smaller than a predetermined value (Δd).

  Also on the main scanning side, it is possible to adjust the color misregistration amount between each color to a value smaller than a predetermined value (Δd) by executing the procedures (A5) to (A13) as in the sub-scanning correction. Become.

  On the main scanning side, as shown in FIG. 3, the color misregistration amount is detected by using patterns 11-1 and 11-2 that are output by combining horizontal lines and diagonal lines. That is, if the sub-scan correction is not performed in step A2, it is further checked whether or not the main-scan correction is performed (step A3). If it is not the main-scan correction, the process is terminated (step A4). If it is main scanning correction, a main scanning correction pattern, that is, toner patterns 11-1 and 11-2 output in combination with the horizontal line and the diagonal line in FIG. 3 are output (step A5). The subsequent processing is the same as the procedure for correcting the shift amount in the sub-scanning direction except that the format of the toner pattern is different, and will be described briefly.

  When obtaining the amount of color misregistration in the main scanning direction, as shown in FIG. 3, the YMCK horizontal line pattern 11-1 (11Y, 11M, 11C, 11K) and the oblique pattern 11-2 (11Y, 11M, 11C, 11K) is repeatedly output. In step A6, the color misregistration detection toner patterns 11-1 and 11-2 formed on the transfer belt 51 are detected by the toner mark sensor 108, the position information of each line pattern is detected, and each detected line pattern 11 is detected. The shift amount in the main scanning direction is calculated from the edge information of −1 and 11-2, and the correction amount that minimizes the shift between these colors is calculated. The calculated shift amount and correction amount are stored in the parameter memory 103 and used as correction values until the next color shift correction process (step A7).

  In step A8, registration correction in the main scanning direction is performed using the correction amount calculated in step A7. After the correction in step A8, the color misregistration detection pattern is output again in a state reflecting the correction result of the color misregistration correction process in step A8, and the pattern after the color misregistration correction is formed on the transfer belt 51 (step A9). The color mark corrected line patterns 11-1 and 11-2 formed in step A9 are detected again by the toner mark sensor 108, and position information of the line patterns 11-1 and 11-2 is detected (step A10). . From the detected edge information of each line pattern 11-1, a deviation amount in the sub-scanning direction is calculated in the same manner as in step A7, and a correction amount that minimizes the deviation between these colors is calculated (step A11).

  Next, it is determined whether or not the color misregistration amount between the patterns after the color misregistration correction is smaller than a predetermined value (Δd) (step A12). If smaller than Δd (step A12-Yes), the process is performed. End (step A13). If it is greater than Δd (No at Step A12), the correction amount is calculated again from the position information detected at Step 10, and the processes after Step A8 are repeated.

  By performing the series of processes described above, the amount of color misregistration between colors in the main scanning direction can be adjusted to a value smaller than a predetermined value (Δd).

  Here, the color misregistration correction process is performed once, and the color misregistration detection pattern is output again with the correction result reflected, and the color misregistration amount is set to a predetermined value or less, but priority is given to shortening the processing time. When doing, it is good also as operation | movement which complete | finishes by the process to step A5-A7 and step A14-A16.

  The first embodiment includes means for independently executing color misregistration correction processing on the main scanning direction side and color misregistration correction on the sub scanning direction side, and color misregistration on the main scanning direction side according to the amount of color misregistration change. By changing the correction execution frequency and the color shift correction execution frequency in the sub-scanning direction side to optimum values, the time required for color shift correction is shortened. Therefore, in this embodiment, processing is performed according to the procedure shown in the flowchart of FIG.

  In the processing procedure according to this flowchart, when a preset number of pages are output during continuous printing, the color misregistration amount of the output image is always kept within a certain range by interrupting printing and performing color misregistration correction processing. It is a structure that can be accommodated.

  When this processing is started (step B1), first, the power is turned on (step B2), and an initialization operation for printing preparation (step B3) is performed. When the initialization operation is completed, if the print request is not issued, the process waits as it is (step B4). When a print request is issued, the process proceeds to normal image output processing (step B4-Yes).

  In the image output processing, first, color misregistration correction processing (step B5) is executed. In the color misregistration correction process (step B5), as described in the previous section, toner patterns 11-1 and 11-2 for color misregistration detection are formed on the transfer belt 51, and the patterns 11-1 and 11-2 are used as toners. This is a process for detecting the amount of color misregistration from the value detected by the mark sensor 108 and adjusting the registration and magnification in the main scanning direction and sub-scanning direction to minimize the color misregistration of the four colors. Further, since the calculated shift amount and correction amount are used as correction values until the next color shift correction process, they are stored in the parameter memory 103. Here, the color misregistration correction processing during the initialization operation is performed in both the main scanning and sub-scanning directions. This processing corresponds to the processing procedure of FIG. 4 described above.

  When the color misregistration correction process (step B5) is completed, the printing process is executed in a state where the correction amount stored in the parameter memory is reflected, and one page of image is output (step B6). For each page output, the number of output sheets from the previous color misregistration correction is counted up (step B7). Here, the counter for the main scanning direction is n, and the counter for the sub scanning direction is m. Next, it is determined whether or not the counted number n has reached a preset number of pages (N pages) (step B8). When the preset number of pages (N pages) is reached, it is determined that there is a possibility that the amount of color misregistration in the main scanning direction is larger than the allowable range, and color misregistration correction processing in the main scanning direction is performed. Execute (Step B11).

  Next, it is determined whether the counted number m has reached a preset number of pages (M pages) (step B9). When the preset number of pages (M pages) is reached, it is determined that the color misregistration amount in the sub-scanning direction may be larger than the allowable range, and color misregistration correction processing in the main scanning direction is performed. Execute (Step B13). If the set number of pages (M or N pages) has not been reached, it is determined whether or not it is the last page (step B10). If it is not the last page, the process returns to step B6 to display the next page. Output. If it is the last page, the output process is terminated and the process returns to step B4 to shift to a standby state for the next print request.

  When the number of pages (N pages) set in advance in step B8 is reached, it is determined that the main scanning color misregistration amount may be larger than the allowable range as described above, and the main scanning direction is determined. The color misregistration correction process is executed (step B11). Since the calculated shift amount and correction amount are used as correction values until the next color shift correction process, the contents of the parameter memory 103 are updated and stored. Further, the main scanning direction counter is cleared (step B12), and the process returns to step B6 to output the next page. If the number of pages (M pages) set in advance in step B9 has been reached, it is determined that the sub-scanning color misregistration amount may be larger than the allowable range, and the color in the sub-scanning direction is determined. Deviation correction processing is executed (step B13). Since the calculated shift amount and correction amount are used as correction values until the next color shift correction process, the contents of the parameter memory 103 are updated and stored. Further, the counter for the sub-scanning direction is cleared (step B14), and the process returns to step B6 to output the next page.

  Through the series of processes described above, it is possible to independently execute the color misregistration correction process in the main scanning direction and the color misregistration correction process in the sub-scanning direction at intervals set for each.

  In this description, the color misregistration correction process in the main scanning direction and the color misregistration correction process in the sub scanning direction are executed independently, but the execution timing of the main scanning color misregistration correction and the sub scanning color misregistration correction are performed. If they match, the time required for color misregistration correction may be shortened by executing them simultaneously. Even when the next main scanning color misregistration correction execution timing and sub scanning color misregistration correction execution timing are within a certain range, the time required for color misregistration correction can be reduced by executing the main scanning and sub scanning correction simultaneously. It shall be shortened.

  As described above, according to the present embodiment, during color misregistration correction, color misregistration correction processing on the main scanning direction side and color misregistration correction on the sub scanning direction side can be performed independently, and only necessary correction processing is selectively performed. By executing this, the time required for color misregistration correction can be shortened. As a result, total throughput can be improved and user convenience can be improved.

<Second Embodiment>
In the first embodiment, the time required for color misregistration correction is shortened by independently executing the color misregistration correction processing on the main scanning direction side and the color misregistration correction on the sub scanning direction side. However, since the environment in which the device is installed and the user's usage status such as the amount and interval of printing are not constant, the set color misregistration correction interval is not always the optimum interval. For this reason, color misregistration correction is performed more than necessary depending on the situation, the throughput deteriorates and user convenience deteriorates, and even if the color misregistration increases, the correction processing is not performed and the color misaligned image is displayed. There is a risk of output.

  Therefore, in this embodiment, when the preset number of pages is output during continuous printing, the color misregistration amount of the output image is always kept within a certain range by temporarily interrupting printing and performing color misregistration correction processing. At this time, the interval until the next color misregistration correction process is changed according to the color misregistration amount detected at the time of color misregistration correction.

FIG. 7 is a flowchart showing the processing procedure of the second embodiment.
When this process is started (step C1) and the power is turned on (step C2), an initialization operation for printing preparation (step C3) is performed. When the initialization operation is completed, if the print request is not issued, the process waits as it is (step C4). When a print request is issued, the process proceeds to normal image output processing (step C4-Yes).

  In the image output processing, first, color misregistration correction processing (step C5) is executed. In the color misregistration correction process (step C5), as described above, toner patterns 11-1 and 11-2 for color misregistration detection are formed on the transfer belt 51, and these patterns 11-1 and 11-2 are used as toner mark sensors. In this processing, the amount of color misregistration is obtained from the detected value and the registration and magnification in the main scanning direction and sub-scanning direction are adjusted to minimize the color misregistration of the four colors. Further, since the calculated shift amount and correction amount are used as correction values until the next color shift correction process, they are stored in the parameter memory 103. Here, the color misregistration correction processing during the initialization operation is performed in both the main scanning and sub-scanning directions.

  When the color misregistration correction process (step C5) is completed, the printing process is executed in a state where the correction amount stored in the parameter memory is reflected, and one page of image is output (step C6). For each page output, the number of output sheets from the previous color misregistration correction is counted up (step C7). Here, the counter for the main scanning direction is n, and the counter for the sub scanning direction is m. Next, it is determined whether the counted number n has reached a preset number of pages (N pages) (step C8). When the preset number of pages (N pages) is reached, it is determined that there is a possibility that the amount of color misregistration in the main scanning direction is larger than the allowable range, and color misregistration correction processing in the main scanning direction is performed. Execute (Step C11).

  Next, it is determined whether the counted number m has reached a preset number of pages (M pages) (step C9). When the preset number of pages (M pages) is reached, it is determined that the color misregistration amount in the sub-scanning direction may be larger than the allowable range, and color misregistration correction processing in the main scanning direction is performed. Execute (Step C13).

  If the set number of pages (M or N pages) has not been reached, it is determined whether or not it is the last page (step C10). If it is not the last page, the process returns to step C6 to output the next page. To do. If it is the last page, the output process is terminated and the process returns to step C4 to shift to a standby state for the next print request. As described above, when the number of pages (N pages) set in advance in step C8 has been reached, it is determined that the main scanning color misregistration amount may be larger than the allowable range, and the main scanning direction is determined. The color misregistration correction process is executed (step C11). Since the calculated shift amount and correction amount are used as correction values until the next color shift correction process, the contents of the parameter memory 103 are updated and stored. Further, the main scanning direction counter is cleared (step C12).

  Next, processing for changing the execution reference value of the color misregistration correction processing is performed according to the color misregistration amount detected in the main scanning color misregistration correction processing in step C11. The color misregistration amount Δd calculated in the color misregistration correction process is compared with a preset error range Δd (step C15), and the color misregistration amount Δd calculated in the color misregistration correction process is set in advance. If greater than Δd1, the process proceeds to step C16, where the number N of pages, which is the main scanning color misregistration correction interval, is changed to a value of N−α, and the setting value is set in a direction that facilitates the color misregistration correction processing. change. On the other hand, if it is smaller than the error range Δd1, the process proceeds to step C17. If the color misregistration amount is smaller than the set value Δd2 in step C17, the process proceeds to step C18, where the number N of pages, which is the main scanning color misregistration correction interval, is changed to a value of N + α, and the color misregistration correction processing is executed. Change the setting value in the direction that makes it difficult to perform.

  The value of N obtained here is stored in the parameter memory 103, and this value is used as a reference value for the next determination of color misregistration correction.

  When the color misregistration amount is between the set values Δd1 and Δd2, the value of the number N of pages, which is the execution interval of the main scan color misregistration correction, is not changed, and the print processing is continued under the same conditions as in the past. Execute.

Δd1 and Δd2 here are
Δd2 <color misregistration allowable value <Δd1
It is a value with the relationship. When the process of changing the execution reference value of the color misregistration correction process is completed, the process returns to step C6 to output the next page.

  When the number of pages (M pages) set in advance in step C9 is reached, it is determined that the sub-scanning color misregistration amount may be larger than the allowable range, and color misregistration correction in the sub-scanning direction is performed. Processing is executed (step C13). Since the calculated shift amount and correction amount are used as correction values until the next color shift correction process, the contents of the parameter memory 103 are updated and stored.

  In the sub-scanning direction, similarly to the main scanning direction, processing for changing the execution reference value of the color misregistration correction processing is performed according to the color misregistration amount detected by the color misregistration correction processing. Since the content of the process is the same as steps C12 to C18, detailed description of the process of steps C14 to C22 is omitted.

  In the above-described series of processes, the color misregistration correction process in the main scanning direction and the color misregistration correction process in the sub-scanning direction are performed independently at intervals set to each other. By updating the execution interval of the color misregistration correction process according to the amount of color misregistration, it is possible to maintain the optimum execution interval following the variation of the color misregistration amount.

  In the above description, the color misregistration correction process in the main scanning direction and the color misregistration correction process in the sub scanning direction are executed independently, but the execution timing of the main scanning color misregistration correction and the sub scanning color misregistration correction are performed. If they match, the time required for color misregistration correction may be shortened by executing them simultaneously. Even when the next main scanning color misregistration correction execution timing and sub scanning color misregistration correction execution timing are within a certain range, the time required for color misregistration correction can be reduced by executing the main scanning and sub scanning correction simultaneously. It can be shortened.

  As described above, according to the present embodiment, in addition to the effects of the first embodiment, the interval until the next color misregistration correction is executed is changed according to the color misregistration amount detected at the time of color misregistration correction. Even when the environment in which the device is installed or the usage status of the user changes, the color misregistration amount can be maintained within a certain range.

<Third Embodiment>
In the first and second embodiments, the color misregistration correction processing on the main scanning direction side and the color misregistration correction on the sub scanning direction side are executed independently to reduce the time required for color misregistration correction. However, since the environment in which the device is installed and the user's usage status such as the amount and interval of printing are not constant, the set color misregistration correction interval is not always the optimum interval. For this reason, color misregistration correction is performed more than necessary depending on the situation, the throughput deteriorates and user convenience deteriorates, and even if the color misregistration increases, the correction processing is not performed and the color misaligned image is displayed. There is a risk of output.

  Therefore, in this embodiment, the color misregistration correction processing in the first and second embodiments has a function of detecting a temperature change of the device, and executes the next color misregistration correction according to the detected temperature change amount. The interval until is changed.

  In this embodiment, since the color misregistration correction processing execution interval is adjusted according to the temperature change, the temperature change is measured using the temperature detection sensor 109. The temperature detection sensor 109 is installed in the vicinity of the temperature of the lens in the writing unit or in the vicinity of the lens, and measures the temperature change of the lens. This is because, as a cause of color misregistration on the main scanning side, the influence of the change in main scanning magnification due to the temperature change of the lens inside the writing unit is dominant, so the main scanning is performed by monitoring the temperature of the lens or its vicinity. This is because it is possible to predict a change in color shift on the side.

FIG. 8 is a flowchart showing the processing procedure of the third embodiment.
When this process is started (step D1) and the power is turned on (step D2), an initialization operation for printing preparation (step D3) is performed. When the initialization operation (step D3) ends, if no print request has been issued, the process stands by (step D4). When a print request is issued, the process proceeds to image output processing (step D4-Yes).

  In the image output process, first, a color misregistration correction process (step D5) is executed, and a temperature measurement value at that time is performed (step D6). The temperature is measured using a temperature detection sensor 109 such as a thermistor. The output signal of the temperature detection sensor 109 is A / D converted by the I / O unit 107 and converted to temperature. The temperature detected here is the temperature at the time of color misregistration correction, and is used to determine whether to perform color misregistration correction.

  When the color misregistration correction process (step D5) ends, the printing process is executed in a state where the correction amount stored in the parameter memory 103 is reflected, and one page of image is output (step D7). For each page output, the number of output sheets from the previous color misregistration correction is counted up (step D8). Next, for each page output, the temperature is measured, and Δt, which is the difference between the measured temperature T ′ and the temperature T0 measured at the time of color misregistration correction, is greater than a preset reference value T of the temperature change amount. (Step D10). When the difference Δt is larger than a preset reference value T of the temperature change amount, it is determined that the color shift amount in the main scanning direction may be larger than the allowable range, and the color in the main scanning direction is determined. Deviation correction processing is executed (step D14).

  Thereafter, the color misregistration correction processing in the main scanning direction and the color misregistration correction processing in the sub scanning direction depending on the number of pages output in steps D12 to D17 are the same as the processing in steps B8 to B14 of FIG. 6 in the first embodiment. Since the process is executed, detailed description is omitted.

  As described above, the cause of the color misregistration in the main scanning direction is mainly due to the temperature change of the lens. Therefore, by increasing the determination reference value N of the color misregistration correction processing based on the number of pages on the main scanning side, It is possible to execute the correction process only when color misregistration occurs due to a temperature change, instead of performing correction at regular intervals.

  Further, as in the second embodiment, a criterion for correcting color misregistration under the condition based on the temperature change amount from the next time according to the actual color misregistration amount when the color misregistration correction is performed under the temperature change condition. When the detected color misregistration amount is smaller than the set value, the value Δt is changed to a value of Δt + α so that the color misregistration correction is difficult to execute. Further, when the detected color misregistration amount is larger than the set value, a process of changing Δt to a value of Δt−α and adjusting in a direction in which color misregistration correction can be easily performed may be performed.

  As described above, according to the present embodiment, in addition to the effects of the first and second embodiments, the amount of change in temperature during printing is monitored, and color misregistration correction is executed according to the amount of change in temperature. As a result, even when the environment where the machine is installed changes or when the user's usage changes, the color misregistration correction is executed at an optimal interval, so that the accuracy of detecting the color misregistration amount can be maintained. It becomes possible.

  Further, by performing the color misregistration correction only when the temperature change is large, it is possible to eliminate the need for performing the color misregistration more than necessary, and to improve user convenience.

  Note that the environmental temperature at the location where the image forming apparatus is installed may cause color misregistration. In such a case, the installation environment temperature can be detected by the temperature detection sensor 109, and this factor can also be added.

<Fourth Embodiment>
In the first and second embodiments, the time required for color misregistration correction can be shortened by independently executing the color misregistration correction processing on the main scanning direction side and the color misregistration correction on the sub scanning direction side. . However, since the environment in which the device is installed and the user's usage status such as the amount and interval of printing are not constant, the set color misregistration correction interval is not always the optimum interval. For this reason, color misregistration correction is performed more than necessary depending on the situation, the throughput deteriorates and user convenience deteriorates, and even if the color misregistration increases, the correction processing is not performed and the color misaligned image is displayed. There is a risk of output.

  Therefore, in the present embodiment, the color misregistration correction process in the first embodiment has a function of detecting a magnification change in the main scanning direction until the next color misregistration correction is executed according to the detected amount of magnification change. The interval of was changed.

  In this embodiment, since the color misregistration correction processing execution interval is adjusted according to the change in magnification in the main scanning direction, the change in magnification is measured using the synchronization detection sensor 114 and the synchronization detection detection unit 104. The synchronization detection detection unit 104 measures a change in magnification in the main scanning direction of the optical system by counting signals from the synchronization detection sensor 114 using a clock inside the system. The synchronization detection sensor 114 is arranged on the writing side and the writing end side in the writing unit, and outputs a signal on a pulse when a writing signal passes. The synchronization detection detection unit 104 detects the magnification value in the main scanning direction by counting the intervals of pulses from the writing side sensor and the writing end side sensor with a clock.

FIG. 9 is a flowchart showing the processing procedure of the fourth embodiment.
When this process is started (step E1) and the power is turned on (step E2), an initialization operation for printing preparation (step E3) is performed. When the initialization operation (step E3) is completed, if no print request is issued, the process waits as it is (step E4). When a print request is issued, the process proceeds to image output processing (step E4-Yes).

  In the image output processing, first, color misregistration correction processing (step E5) is executed, and at that time, the magnification setting value is measured using the synchronization detection sensor 114 (step E6). The magnification value detected here is used as a magnification setting value at the time of color misregistration correction, and is used for determination of execution of color misregistration. When the color misregistration correction process (step E5) is completed, the printing process is executed in a state where the correction amount stored in the parameter memory 103 is reflected, and one page of image is output (step E7).

  For each page output, the number of output sheets from the previous color misregistration correction is counted up (step E8). Next, magnification is measured for each page output (step E9), and Δz, which is the difference between the measured magnification Z ′ and the magnification Z0 measured at the time of color misregistration correction, is a preset reference for the amount of magnification change. It is determined whether the value is greater than Z (step E10). If it is larger than the reference value Z of the magnification change amount set in advance, it is determined that the color misregistration amount in the main scanning direction may be larger than the allowable range, and color misregistration correction processing in the main scanning direction is performed. Execute (Step E14).

  Thereafter, the color misregistration correction processing in the main scanning direction and the color misregistration correction processing in the sub scanning direction based on the number of pages output in steps E11 to E17 are the same as the processing in steps B8 to B14 of FIG. 6 in the first embodiment. Since it is a process, detailed description is omitted.

  As described above, the cause of color misregistration in the main scanning direction is predominantly caused by a change in magnification. Therefore, by making the determination reference value N for color misregistration correction processing based on the number of pages on the main scanning side a large value, The correction process can be executed only when a color shift occurs due to a change in magnification.

  Further, as in the second embodiment, the color misregistration correction is performed under the condition based on the amount of change in magnification from the next time according to the actual color misregistration amount when the color misregistration correction is performed under the condition based on the change in main scanning magnification. Therefore, when the detected color misregistration amount is smaller than the set value, Δz is changed to a value of Δz + α, and is adjusted in a direction that makes it difficult to perform color misregistration correction. If the detected color misregistration amount is larger than the set value, Δz may be changed to a value of Δz−α to perform a process of adjusting the direction in which color misregistration correction can be easily performed.

  As described above, according to this embodiment, in addition to the effects of the first and second embodiments, the amount of change in the main scanning magnification is monitored during printing, and color misregistration correction is performed according to the amount of change in magnification. By executing, color misregistration correction is performed at optimal intervals even when the environmental condition where the machine is installed or when the user's usage status changes. It becomes possible to maintain.

  Further, by performing color misregistration correction only when the amount of change in magnification is large, it is possible to eliminate unnecessary color misregistration correction and improve user convenience.

<Fifth Embodiment>
FIG. 10 is a diagram illustrating a schematic configuration of an image forming apparatus according to the fifth embodiment. In the present embodiment, the image forming apparatus according to the first or fourth embodiment is applied to a direct transfer type printer that directly transfers an image from a photosensitive member (4K, 4M, 4C, 4Y) onto a recording sheet. Only the detection position of the toner mark sensor 108 is different from the example of FIG. In other words, the toner mark sensor 108 is provided on the lower surface side of the transfer belt 51 in the drawing on the fixing side (downstream side in the paper conveyance direction). At the time of color misregistration correction, the recording paper is not passed, and a toner pattern for detecting the color misregistration amount shown in FIG. 14 is created on the transfer belt 51, and this pattern is detected by the toner mark sensor 108. Detects the amount, calculates the optimum correction amount for the detected displacement amount, and uses the correction amount to adjust the writing timing and magnification setting value in the main scanning and sub-scanning directions, thereby correcting color misregistration. Other parts that are not particularly described are configured in the same manner as the first to fourth embodiments described above and function in the same manner.

  According to the present embodiment, the effects of the first and second embodiments can be obtained by a direct transfer tandem color printer.

<Sixth Embodiment>
FIG. 11 is a diagram showing a schematic configuration of an image forming apparatus according to the sixth embodiment. In the present embodiment, the image forming apparatus according to the first or fourth embodiment transfers an image once from the photoconductor (4K, 4M, 4C, 4Y) onto the transfer belt 51, and again transfers the image onto the recording paper. The image forming apparatus has an indirect transfer type configuration. At the time of color misregistration correction, the recording paper is not passed, and a toner pattern for detecting the color misregistration amount shown in FIG. 14 is created on the transfer belt 51, and this pattern is detected by the toner mark sensor 108. Detects the amount, calculates the optimum correction amount for the detected displacement amount, and uses the correction amount to adjust the writing timing and magnification setting value in the main scanning and sub-scanning directions, thereby correcting color misregistration. Other parts that are not particularly described are configured in the same manner as the first to fourth embodiments described above and function in the same manner.

  According to the present embodiment, the effects of the first and second embodiments can be obtained with an indirect transfer tandem color printer.

1 is a block diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of a plotter unit of an image forming apparatus according to a first embodiment of the present invention. FIG. 4 is an enlarged view illustrating an example of a toner pattern for detecting a displacement in a main scanning direction. It is a flowchart which shows the process sequence of the color shift correction process in the 1st Embodiment of this invention. FIG. 4 is a diagram illustrating an example of a toner pattern for detecting a displacement in a sub-scanning direction. 6 is a flowchart illustrating a processing procedure of color misregistration correction processing according to the first embodiment. 10 is a flowchart illustrating a processing procedure of color misregistration correction processing according to the second embodiment. 10 is a flowchart illustrating a processing procedure of color misregistration correction processing according to a third embodiment. 14 is a flowchart illustrating a processing procedure of color misregistration correction processing according to a fourth embodiment. It is a figure which shows schematic structure of the printer of the direct transfer system which concerns on 5th Embodiment. It is a figure which shows schematic structure of the printer of the indirect transfer system which concerns on 6th Embodiment. It is a figure which shows schematic structure of the printer of the direct transfer system currently implemented. It is a figure which shows schematic structure of the printer of the indirect transfer system currently implemented conventionally. It is a figure which shows the example of the pattern for color misregistration amount detection implemented conventionally.

Explanation of symbols

1K, 1M, 1C, 1Y Writing unit 2K, 2M, 2C, 2Y Photosensitive drum 3K, 3M, 3C, 3Y Developer 4K, 4M, 4C, 4Y Transfer device 7 Plotter controller 11-1, 11-2 Pattern 51 Transfer belt 70 recording paper,
100 CPU
101 ROM
102 RAM
103 Parameter memory 106 Plotter 108 Toner mark sensor 109 Temperature detection sensor

Claims (11)

A toner pattern for detecting the color misregistration amount is output on the belt, the position of the toner pattern is detected, the color misregistration amount is calculated from the detected toner pattern position information, and the color misregistration amount is minimized. In the color misregistration correction method to be corrected,
Correcting the color misregistration on the main scanning direction side;
Correcting the color misregistration on the sub-scanning direction side;
A color misregistration correction method, wherein the execution frequency of each step is independently changed from the calculated color misregistration amount according to a color misregistration change amount.   The color misregistration correction method according to claim 1, wherein an interval until the next color misregistration correction is executed is changed based on the calculated color misregistration amount.   2. The color misregistration correction method according to claim 1, wherein an interval until the next color misregistration correction is executed is changed according to a change in temperature environment.   2. The color misregistration correction method according to claim 1, wherein an interval until the next color misregistration correction is executed is changed according to a change in image forming conditions. A means for outputting a toner pattern for detecting a color misregistration amount on the belt, a means for detecting the position of the toner pattern, and calculating the color misregistration amount from the detected toner pattern position information, so that the color misregistration amount is minimized. And an image forming apparatus having a means for correcting so that
The correcting unit independently executes a color misregistration correction process on the main scanning direction side and a color misregistration correction process on the sub scanning direction side, and determines the color misregistration amount from the calculated color misregistration amount according to a color misregistration change amount. An image forming apparatus, wherein the execution frequency of each correction process is changed independently.   The image forming apparatus according to claim 5, wherein the correcting unit changes an interval until the next color misregistration correction is performed based on the calculated color misregistration amount. Further comprising means for measuring the in-machine temperature;
The image forming apparatus according to claim 5, wherein the correcting unit changes an interval until the next color misregistration correction is performed according to a change amount of the temperature measured by the measuring unit. Further comprising means for measuring the environmental temperature of the equipment installation environment,
8. The correction unit according to claim 5, wherein the correction unit changes an interval until the next color misregistration correction is performed according to a change amount of the temperature measured by the measurement unit. The image forming apparatus described in 1. Means for detecting a change in magnification in the main scanning direction;
9. The correction unit according to claim 5, wherein the correction unit changes an interval until the next color misregistration correction is executed in accordance with a magnification change amount detected by the detection unit. The image forming apparatus described in 1.   The image forming apparatus according to claim 5, wherein the belt is a conveyance belt that conveys a sheet onto which an image is directly transferred.   10. The belt according to claim 5, wherein the belt is an intermediate transfer belt on which an image is primarily transferred and the transferred image is transferred onto a sheet at a secondary transfer position. Image forming apparatus.

Images