JP2004246386A - Multiplex image forming apparatus and method of controlling color shift in image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multiple image forming apparatus in which waiting time during ordinary operation is shortened while images with little out-of-color-registration is provided. <P>SOLUTION: The multiple image forming apparatus is equipped with ROSs (raster output scanners) 4 which form images of different colors in a superposed state, a CCD (charged coupled device) 11 which measures the test patterns for detecting the amounts of the skew displacement among the individual ROSs 4 and the amounts of the color shift other than the skew and a registration controller 12. The controller 12 compares the mounts of the skew displacement detected by a skew amount detecting means 22 with the first prescribed amount by a first comparator means 23. If the amount of the skew displacement is smaller, the controller controls the ROSs 4 so as to perform the out-of-color-registration correction other than the skew based on the amount of the out-of-color-registration other than the skew. If the amount of the skew displacement is not small, the controller controls the ROSs so as to perform the skew displacement correction for the ROSs 4 based on the amount of the skew displacement and to perform color shift correction other than the skew based on the amount of the out-of-color-registration other than the skew detected again by the detecting means 22 after the end of the skew displacement correction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a multiplex image forming apparatus used for a copying machine, a printer, a facsimile, and the like, and more particularly, to a multiplex image forming apparatus using a registration control system.

  Conventionally, a so-called tandem type color image forming apparatus has been known as a multiplex image forming apparatus for forming a color image. In this apparatus, for example, four image forming means are arranged for each color of black (K), yellow (Y), magenta (M), and cyan (C) along one transfer belt. The image forming means forms a single color image on the photosensitive drum by a ROS (Raster Output Scanner: raster output scanning device), and transfers these four images onto one transfer belt in a superimposed manner. It is configured to form a color image. In this type of multiplex image forming apparatus, since images of each color are superimposed and transferred to the same position on the transfer belt in order to form one color image, it is necessary to accurately superimpose the images of each color.

  For this reason, a registration control (register control) system that measures and corrects a so-called registration shift, which is a shift between colors to be superimposed at the same position on the transfer belt, is employed in this type of multiple image forming apparatus. I have. The registration deviation is roughly classified into a so-called skew deviation and a color deviation other than the skew deviation. The color deviation other than the skew deviation includes a deviation in the main scanning direction, a deviation in the sub-scanning direction, and a deviation in magnification. It is said that the skew deviation among these registration deviations does not fluctuate to a level at which a significant problem occurs due to thermal changes, vibrations, and the like during an image forming operation in a normal use state. On the other hand, deviations in the main scanning direction other than skew deviations are said to fluctuate due to thermal changes, vibrations, and the like during an image forming operation even in a normal use state.

  More specifically, the registration control system firstly transfers a test pattern for measuring the amount of registration deviation on the transfer belt by image forming means for each color at regular intervals, and transfers the transferred test pattern to all the transfer patterns. A registration pattern shift amount is detected by executing a test pattern sampling cycle measured by a CCD (Charged Coupled Device) arranged downstream of the image forming means. Since this pattern sampling cycle usually involves an operation of driving the ROS and the transfer belt, it requires a relatively long time, for example, about ten seconds. Next, a skew correction amount is appropriately calculated from the detected registration deviation amount, and a correction amount in the main scanning direction, a correction amount in the sub-scanning direction, and a correction amount of the magnification are appropriately calculated. When performing skew correction, mechanical adjustment is performed on the optical system of the ROS using the calculated skew correction amount. On the other hand, when correcting a color shift other than the skew shift, the electrical adjustment of the ROS electrical circuit and the signal system to the ROS is performed using the calculated color shift correction amount other than the skew. Here, especially when skew correction is performed, since all color shifts other than the skew shift generally change, the registration control cycle for the color shift other than the skew shift including the pattern sampling cycle must be performed again after the skew correction. Is required.

  As described above, first, the skew correction is not required to be performed during the normal operation unlike the color misregistration correction other than the skew, and second, the skew correction is performed by performing the pattern sampling cycle in order to perform the skew correction. It is necessary to execute the recon two times in total before and after the operation, so that the registration control including the cycle for correcting the skew (skew correction cycle) is executed only in the service mode performed by the serviceman for maintenance. That is, in the service mode, after correcting the skew, the pattern sampling cycle is executed again for color misregistration other than the skew, so that it takes time to execute the registration control. On the other hand, in the customer mode, which is a normal operation mode, a register control (register without skew) cycle including only a cycle for correcting a color shift other than a skew shift is executed without including a skew correction cycle. That is, in the customer mode, the pattern sampling cycle only needs to be executed once for color shift correction other than skew, so that it does not take much time to execute the registration control.

  According to this registration system, it is possible to mainly correct the DC (steady) component of registration deviation depending on the mechanical accuracy of the image forming unit, the pitch between the photosensitive drums, the exposure point, and the like. Further, according to the registration control system disclosed in Japanese Patent Application Laid-Open No. 6-253151 and the like, by forming a coarse registration deviation amount measurement pattern and a fine registration deviation amount measurement pattern, mainly, DC components can be corrected with high accuracy without being affected by a DC component error caused by an AC (periodic variation) component of registration deviation depending on the rotation cycle of the roller, gear, transfer belt, or the like.

  Generally, in a multiplex image forming apparatus, it is generally desired that an image forming operation including a registration control operation be performed quickly in a normal operation mode (customer mode) while providing a high-quality image with little color shift. It is rare.

  However, according to the conventional registration control system described above, since the skew is not deviated in a normal use state and the skew correction is not performed during a normal operation, the installation surface of the apparatus is moved as a result of the user moving the image forming apparatus main body. If the skew is changed, a mechanical shock is applied to the apparatus main body, or a mechanical part or the like inside the apparatus is manipulated, the skew may be shifted to a level that causes a serious problem. In this case, a high-quality image cannot be expected until the serviceman performs the skew correction next time. Further, even if the serviceman performs maintenance, there is a possibility that a skew deviation slightly exceeding an allowable amount may be visually overlooked. Furthermore, a defect in the order of microns or a defect due to a change over time resulting from the use of a nonstandard component may not be detected during maintenance.

  On the other hand, in the above-described conventional registration control system, if the registration control cycle including the skew correction cycle is performed in the customer mode similarly to the service mode, as described above, the pattern sampling cycle is performed two times before and after the skew correction. The user has to wait for a very long time in the middle of the image forming operation because of the necessity of performing the operation twice.

  SUMMARY OF THE INVENTION It is an object of the present invention to provide a multiplex image forming apparatus that provides a high quality image with little color shift and a short waiting time during a normal operation.

In order to solve the above-mentioned problems, the present invention provides a plurality of image forming means for forming images of different colors in an overlapping manner, a sampling means for sampling a test pattern, and a skew shift amount based on a result of sampling by the sampling means. Skew shift amount calculating means for calculating
A non-skew color shift amount calculating means for calculating a color shift amount other than skew based on a result of sampling by the sampling means; and a skew shift amount calculated by the skew shift amount calculating means in the first sampling by the sampling means. Is smaller than a first threshold value, color correction other than skew is executed based on the color shift amount other than skew calculated by the non-skew color shift amount calculating means in the first sampling. Controlling the image forming means as described above, and when the skew shift amount calculated by the skew shift amount calculating means in the first sampling is not smaller than the first threshold value, Skew correction is performed by adjusting the optical system based on The second sampling is performed by the stage, and based on the result of the sampling, the non-skew color misregistration amount calculating means calculates the color misregistration amount other than the skew between the image forming means, and based on the color misregistration amount other than the skew. A control unit for controlling the image forming unit so as to execute color misregistration correction other than the skew.

According to this multiplex image forming apparatus, the plurality of image forming units form images of different colors in an overlapping manner. When performing the color shift correction between the image forming units, the skew shift amount is calculated by the skew shift amount calculating unit based on the sampling result of the sampling unit, and the color shift other than the skew is calculated by the non-skew color shift amount calculating unit. Calculate the quantity. Here, under the control of the control means, if the skew deviation calculated in the first sampling by the sampling means is smaller than the first threshold value, the image forming means calculates the skew in the first sampling. The non-skew color misregistration correction is performed based on the obtained non-skew color misregistration amount. On the other hand, if the skew deviation calculated in the first sampling is not smaller than the first threshold, the skew deviation correction is executed by adjusting the optical system based on the skew deviation and executing the correction. After the skew shift correction is completed, the second sampling is performed, and based on the result of the sampling, the non-skew color shift amount calculating means calculates the non-skew color shift amount between the image forming means. The color shift correction other than the skew is executed based on the amount. Therefore, if a value corresponding to a skew deviation large enough to immediately require skew correction is set as the first threshold, the calculated skew deviation is smaller than the first threshold. In this case, it is determined that the skew correction is unnecessary, and the color shift correction other than the direct skew is performed without performing the skew correction. As a result, only one time of detecting the amount of color shift is required, despite monitoring the amount of skew shift. If the skew deviation amount is not smaller than the first threshold value, it is determined that skew correction is necessary. After skew deviation correction is performed based on the skew deviation amount, pattern sampling is performed again, and skew correction is performed. The color misregistration other than the skew is corrected based on the color misregistration other than the skew calculated by the other color misregistration amount calculator, so that the skew correction is automatically performed appropriately even in the normal operation mode (customer mode). Will be
When skew correction is performed, two relatively long times (for example, ten and several seconds) required to calculate the amount of color shift between image forming units are required. The situation in which the time for detecting the color misregistration amount twice is required is minimized. In particular, the skew is hardly fluctuated due to thermal changes, vibrations, and the like during a normal image forming operation, and if the skew occurs, for example, several times a day or a week, the skew correction is performed until maintenance by a service person. In view of the fact that it is extremely inconvenient not to perform the high image quality maintenance, the configuration of the present invention for executing the skew correction to the minimum and surely is extremely practical and rational.
Therefore, according to the present invention, it is possible to obtain a high-quality image with little color shift by always monitoring the skew shift amount that is not necessarily corrected in the normal operation, and at the same time, to reduce the waiting time during the normal operation. it can.

Further, the present invention is a color misregistration control method for an image forming apparatus having a plurality of image forming means for forming images of different colors in a superimposed manner, wherein a step of sampling a test pattern created by the test pattern creating means, Calculating a skew shift amount between the image forming units and a color shift amount other than a skew between the image forming units based on a result of the sampling; and when the skew shift amount is smaller than a first threshold value. Executing a color shift correction other than the skew based on the color shift other than the skew; and, if the skew shift is not smaller than the first threshold, based on the skew shift. The skew deviation is corrected by adjusting the optical system, and then a test pattern is created by the test pattern creating means. The pattern is sampled by the sampling means, a color shift other than the skew between the image forming means is calculated based on the result of the sampling, and the color shift other than the skew is corrected based on the color shift other than the skew. And a step of controlling the color misregistration of the image forming apparatus.
According to this method, if the value corresponding to the skew deviation amount that is large enough to immediately require the skew correction is set as the first threshold value, the calculated skew deviation amount becomes equal to the first threshold value. If the skew correction is smaller than the above, it is determined that the skew correction is unnecessary, and the color shift correction other than the direct skew is performed without performing the skew correction. As a result, only one time of detecting the amount of color shift is required, despite monitoring the amount of skew shift. If the skew deviation amount is not smaller than the first threshold value, it is determined that skew correction is necessary. After skew deviation correction is performed based on the skew deviation amount, pattern sampling is performed again, and skew correction is performed. Since the color shift correction other than the skew is performed based on the color shift amount other than the skew, the skew correction is automatically and appropriately performed even in the normal operation mode (customer mode).
Therefore, according to the present invention, it is possible to obtain a high-quality image with little color shift by always monitoring the skew shift amount that is not necessarily corrected in the normal operation, and at the same time, to reduce the waiting time during the normal operation. it can.

  As a result, according to the present invention, by always monitoring the skew deviation amount that is not necessarily corrected during normal operation, the skew correction is performed if necessary, so that the possibility of performing the normal operation with the skew shifted is reduced. You. Therefore, the skew correction can be executed to the minimum necessary and reliably, so that the waiting time during the normal operation by the registration cycle can be reduced while realizing a high quality image with little color shift. Further, the time during which the apparatus cannot be used can be reduced by adjustment by a serviceman, and the increase in the time during which the operation of the apparatus is stopped due to the execution of the registration control can be minimized. In addition, since the skew correction is appropriately performed in the normal operation mode, the time and labor for maintenance of the serviceman are reduced. Furthermore, even if a component that does not conform to the standard is used by mistake, a defect in units of microns or a change with time can be detected and corrected.

  Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a main configuration of a tandem type color image forming apparatus according to a first embodiment of the present invention.

   In FIG. 1, a color image forming apparatus 1 is configured to be able to form a multiplex image of four colors of K (black), Y (yellow), M (magenta), and C (cyan), and has an IPS (Image). (Processing System: image processing system) 2, ROS-I / F (ROS-Interface: ROS-interface) 3k, 3y, 3m, and 3c for K, Y, M, and C colors, respectively, and K, Y, and K, respectively. ROS 4k, 4y, 4m, and 4c for M and C colors, image forming devices 5k, 5y, 5m, and 5c for K, Y, M, and C colors, a transfer belt 6, a motor 7, and a paper suction roller 8 and a belt cleaner 10.

  The IPS 2 is configured to supply write image data for each of K, Y, M, and C colors of one color image data to the ROS-I / Fs 3k, 3y, 3m, and 3c. The ROS-I / Fs 3k, 3y, 3m, and 3c are configured to supply the image data from the IPS 2 and the test pattern data for a registration controller described later to the ROSs 4k, 4y, 4m, and 4c, respectively. The ROSs 4k, 4y, 4m, and 4c as an example of the image forming unit scan ROS-I / Fs 3k, 3y, and 3m by scanning the photosensitive drums of the image forming devices 5k, 5y, 5m, and 5c with writing light. And 3c are written on the drums of the image forming apparatuses 5k, 5y, 5m, and 5c, respectively, corresponding to the write signals supplied from the image forming apparatuses 5k, 5y, 5m, and 5c. Each of the image forming devices 5k, 5y, 5m, and 5c includes a photosensitive drum, a charger, a developing device, and the like. A raster-like electrostatic latent image is sequentially written by writing light, and a toner image is formed on the drum by development. Is done.

  The image forming apparatuses 5k, 5y, 5m and 5c synchronize each toner image corresponding to image data on a recording sheet 100 supplied by a sheet suction roller 8 on a transfer belt 6 driven by a motor 7. The toner images corresponding to the test pattern data for the registration control are directly transferred onto the transfer belt 6. The belt cleaner 10 is configured to remove the test pattern directly transferred to the transfer belt 6 from the transfer belt 6.

   In FIG. 1, the color image forming apparatus 1 further includes a CCD 11, a registration controller 12, and skew correction devices 13k, 13y, 13m, and 13c for K, Y, M, and C colors built in ROSs 4k, 4y, and 4m, respectively. It has.

  The CCD 11 is disposed downstream of the image forming devices 5 k, 5 y, 5 m, and 5 c of the transfer belt 6 and upstream of the belt cleaner 10, and measures a test pattern formed on the transfer belt 6.

  The registration controller 12 generates test pattern data including, for example, K, Y, M, and C as shown in FIG. 2, and outputs the test pattern data for each of K, Y, M, and C colors to the ROS-I / F3k. , 3y, 3m and 3c. The ROSs 4k, 4y, 4m, and 4c receive the supply of the write test pattern data for each of K, Y, M, and C corresponding to the set pattern at a predetermined timing, and use the write light to generate the image forming apparatuses 5k, 5y. Instead of the image data from the IPS 2, a raster image corresponding to the test pattern data is written on the drums 5m and 5c. At this time, by not supplying the recording paper 100, the test pattern is directly transferred onto the transfer belt 6 by the image forming devices 5k, 5y, 5m, and 5c.

  Further, the registration controller 12 samples a skew shift amount, a shift amount in the main scanning direction, a shift amount in the sub-scanning direction, and a shift amount of magnification, which are color shift amounts other than the skew shift, from the test pattern measured by the CCD 11, respectively. It is configured as follows. Then, after determining whether or not the sampled skew deviation amount is smaller than a predetermined threshold, according to the determination result, a registration control cycle including skew deviation correction is performed, It is configured to perform a registration cycle excluding the correction.

  The skew correction device 13 is configured to perform color misregistration correction by adjusting the optical systems of the image forming devices 5k, 5y, 5m, and 5c according to the correction amounts calculated in this manner.

  FIG. 3 shows a main configuration of the registration controller 12 in FIG. 1 together with the CCD 11 and the skew correction device 13.

   In FIG. 3, the registration controller 12a includes a state detection unit 21, a skew amount detection unit 22, a first comparison unit 23, a second comparison unit 24, a flag storage unit 25, a skew amount storage unit 26, and a skew correction amount calculation. It comprises means 27.

  The state detection device 21 detects a predetermined color misregistration correction start state, and instructs the start of a registration control cycle. The predetermined color misregistration correction start state includes, for example, paper jam clearance, power-on, a high-temperature state observed during continuous operation, and transfer module setting.

  The skew detection unit 22 samples the skew deviation from the test pattern measured by the CCD 11.

  The first comparing unit 23 compares a first predetermined amount as a first threshold value with the sampled skew deviation amount. As the first predetermined amount, a value corresponding to a skew deviation large enough to immediately require skew correction is set in advance. More specifically, if the skew deviation amount is set to a value corresponding to the deviation amount indicating that the skew deviation amount has approached the limit of the allowable range of the registration control system, the skew before the allowable amount is exceeded. Since correction is performed, it is preferable from the viewpoint of maintaining high image quality. However, in order to reduce the number of times of skew correction requiring two test pattern samplings in one registration cycle and to reduce the waiting time during operation, the first predetermined amount is a skew deviation. Preferably, the value is set to a value corresponding to a deviation amount indicating that the amount slightly exceeds the limit of the allowable range of the registration control system.

  The second comparing unit 24 compares the second threshold value with the sampled skew shift amount. As the second threshold value, a value corresponding to the minimum skew deviation amount at which meaningful skew correction can be performed in consideration of the skew correction resolution of the color image forming apparatus 1 is set in advance. More specifically, if the skew correction resolution is set to a value corresponding to one step, the skew correction can be improved as long as there is room for improving the skew deviation. However, while there is no problem if the skew deviation falls within the practical range, a value corresponding to a plurality of steps of the skew correction resolution may be set in order not to execute the skew correction too frequently. .

  When the skew deviation amount compared by the second comparing unit 24 is larger than the second threshold value, the flag storage unit 25 sets 1 to a flag and stores the flag signal as a flag signal. If it is not large, the flag is set to 0. This flag is information indicating whether to include skew correction in the next registration cycle.

  The skew amount storage unit 26 stores the skew deviation amount sampled by the skew amount detection unit 22. In particular, it is preferable that the skew amount storage means 26 be composed of a nonvolatile memory such as a nonvolatile RAM (Random Access Memory), together with the flag storage means 25. In this case, the skew correction is appropriately performed using the skew deviation amount detected in the previous registration control cycle even at the time of startup after the power of the color image forming apparatus 1 has been once turned off or in the subsequent registration control cycle. can do.

  Further, when the skew amount storage means 26 is constituted by a non-volatile memory, the color shift amount including the skew shift amount and the color shift correction amount including the skew correction amount are overwritten only when the sample state is good. You may make it memorize | store. Here, whether or not the sample state is good can be determined from the image width, contrast, background level, and the like of the sampled pattern. In this case, if the stored color shift amount is adopted as the reference correction value for the next registration cycle, a stable correction state can be ensured regardless of temperature changes due to seasonal changes or changes in the installation environment. High correction accuracy can be ensured even in the correction immediately after insertion. This is extremely advantageous as compared with the conventional technique using a uniform reference correction value regardless of the four seasons. Further, even in the case of an abnormality in which sampling of the test pattern becomes impossible for some reason, by using the stored latest correction amount and the like, it is possible to minimize deterioration in image quality.

  The skew correction amount calculating means 27 calculates a skew correction amount from the skew deviation amount stored in the skew amount storage means 26 before executing the skew deviation correction.

  The registration controller 12a also has a function of correcting a color shift other than a skew (not shown). More specifically, the registration controller 12a has a shift in the main scanning direction which is a color shift amount other than the skew shift from the test pattern measured by the CCD 11. Color shift amount detection means for sampling the amount of shift, the amount of shift in the sub-scanning direction, and the amount of shift in magnification, and calculating means for calculating a color shift correction amount other than skew from the sampled color shift amounts other than skew. ing.

  As a result, as described in detail later, when the state detecting unit 21 detects the color misregistration correction start condition, the skew correcting unit 13 outputs the detected skew amount to the first predetermined amount based on the output of the first comparing unit 23. If the skew correction amount is larger than the skew correction amount, the skew correction amount calculation unit 27 calculates the skew correction amount from the skew deviation amount stored in the skew amount storage unit 26. The skew correction for the ROS 4 is executed based on the calculation result.

  Next, regarding the operation of the color image forming apparatus 1 of the present embodiment, there are three cases of (1) a normal color image forming operation, (2) a registration control operation without skew correction, and (3) a registration control operation with skew correction. This will be described below.

(1) Normal Color Image Forming Operation In a normal color image forming operation, the IPS 2 converts the write image data of each color K, Y, M, and C for one color image data into ROS-I / F3k, ROSs 4k, 4y, 4m and 4c are respectively supplied through 3y, 3m and 3c. The ROSs 4k, 4y, 4m, and 4c respectively write the corresponding raster images by scanning the drums of the image forming devices 5k, 5y, 5m, and 5c with the writing light. The image forming devices 5k, 5y, 5m, and 5c develop a raster-like electrostatic latent image written on the drum to form a toner image. The transfer belt 6 is driven in the forward direction by a motor 7, and the paper suction roller 8 supplies the recording paper 100 onto the transfer belt 6. The image forming devices 5k, 5y, 5m, and 5c transfer the respective toner images to the recording paper 100 on the transfer belt 6 while synchronizing, and synthesize a color image. The color image formed on the recording paper 100 is discharged from the color image forming apparatus after undergoing a heat fixing process or the like.

(2) When the registration control operation state detecting means 21 in the case where the skew correction is not performed detects a predetermined color misregistration correction start condition, the registration controller 12 determines, for example, K, Y, M and C as shown in FIG. A test pattern for automatic registration misregistration correction is generated, and the write image data corresponding to each of the K, Y, M, and C colors corresponding to the test pattern is stored in the ROS 4k via the ROS-I / Fs 3k, 3y, 3m, and 3c. , 4y, 4m and 4c, respectively. In response to this, the ROSs 4k, 4y, 4m, and 4c write the raster images corresponding to the test patterns on the drums of the image forming devices 5k, 5y, 5m, and 5c, respectively, using the writing light. At this time, by not supplying the recording paper 100, the test pattern is directly transferred onto the transfer belt 6 by the image forming devices 5k, 5y, 5m, and 5c. When the CCD 11 measures the test pattern on the transfer belt 6, the registration controller 12 detects the amount of color shift other than skew based on the measurement result, and also detects the amount of skew shift. In the case (2), the skew correction is not performed because the skew deviation amount is smaller than the first predetermined amount and the flag is not set in the flag storage unit 25. A color shift correction amount other than the skew is calculated based on the detected non-skew color shift amount. The registration controller 12 performs an electrical adjustment on an electric circuit of the ROS 4 and a signal system to the ROS 4 based on the calculation result. For example, the write timing of ROS4 is adjusted. By the above-mentioned registration control operation, color shift other than skew is corrected.

(3) Registration control operation for skew correction In this case (3), the operation is further divided into a case where a flag is set in the flag storage unit 25 or a case where the flag is not set.
(3-1) When the flag is not set in the flag storage unit 25, the operation is the same as that in the above (2) until the registration controller 12 detects the color shift amount other than the skew and the skew shift amount. . In the case (3-1), since the skew deviation amount is larger than the first predetermined amount, the skew correction amount is calculated based on the detected skew deviation amount. Based on the calculation result, the skew correction device 13 performs mechanical adjustment on the optical system of the ROS 4. For example, the angle of a mirror constituting the optical system of the ROS 4 is adjusted. Thereafter, the registration controller 12 generates a test pattern again, and the CCD 11 measures the test pattern on the transfer belt 6. An amount of color shift correction other than skew is calculated based on the amount of color shift other than skew detected from the test pattern. Based on the calculation result, an electrical adjustment is made to an electrical circuit of the ROS 4 and a signal system to the ROS 4. Add. By the above-described registration control operation, the skew shift and the color shift other than the skew are corrected. In this case, even when the registration controller 12 generates a test pattern again, the amount of skew deviation is detected from the test pattern measured by the CCD 11 to prepare for the next registration cycle.
(3-2) When the flag is set in the flag storage unit 25, the skew correction amount calculation unit 27 is based on the skew deviation amount stored in the skew amount storage unit 26, which is the previously detected skew deviation amount. Calculates the skew correction amount. Based on the calculation result, the skew correction device 13 performs mechanical adjustment on the optical system of the ROS 4. Thereafter, the registration controller 12 generates a test pattern, and the CCD 11 measures the test pattern on the transfer belt 6. Based on the non-skew color misregistration detected from the test pattern, a non-skew color misregistration correction amount is calculated. Add. In this case, even when the registration controller 12 generates a test pattern, the amount of skew deviation is detected from the test pattern measured by the CCD 11 to prepare for the next registration cycle.

The operation of the first embodiment will be described with reference to the flowchart of FIG.
In FIG. 7, first, it is determined whether or not there is a request for registration deviation correction based on a flag in the flag storage unit 25 (step S1). If it is determined that there is a request (step S1: NO), the skew correction amount is calculated from the skew deviation amount stored in the skew amount storage means 26 at the time of the previous registration control, and the skew correction is executed based on the calculation result. (Step S2). At this point, the skew deviation detected during the previous registration control is eliminated. Subsequently, a test pattern sampling process is performed to measure the amount of color shift other than skew (step S3). If it is determined in step S1 that there is no request (step S1: YES), the process directly proceeds to step S3 (step S3).

  Next, each color shift amount including the skew shift amount is calculated (step S4), and it is determined whether the skew shift amount is zero, that is, whether the skew shift amount is smaller than the second predetermined amount (step S5). If it is determined to be zero (step S5: YES), the amount of color misregistration correction other than skew is calculated (step S6), and the amount of color misregistration correction other than skew is set for each image forming unit (step S7). The process ends.

  If it is determined in step S5 that the skew deviation is not zero (step S5: NO), a skew deviation correction amount is calculated from the skew deviation amount (step S8), and it is determined whether the skew deviation amount is allowable (step S9). ). If it is determined that the skew correction is acceptable (step S9: YES), the skew correction amount is stored (step S10), and a flag is set in the flag storage unit 25 so as to request execution of the skew correction at the beginning of the next cycle. From (step S11), the process proceeds to step S6.

  If it is determined in step S9 that it is not acceptable (step S9: NO), skew correction is executed based on the skew correction amount obtained in the current sample (step S12), and sampling processing of the test pattern is performed (step S12). S13) After calculating the color misregistration amount other than the skew (step S14), the process proceeds to step S6. As described above, the operation of the first embodiment is performed.

Next, a tandem type color image forming apparatus according to a second embodiment of the present invention will be described. The second embodiment is different from the first embodiment only in the configuration of the registration controller, and other configurations are the same.
FIG. 4 shows the configuration of the registration controller of the second embodiment. In FIG. 4, the same components as those of the first embodiment shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

  In FIG. 4, the registration controller 12b does not include the skew amount storage means 26 for storing the skew amount in the first embodiment shown in FIG. A skew amount storage unit 28 for storing the correction amount is provided. That is, the second embodiment is configured to store the skew correction amount for the next registration cycle instead of the skew deviation amount of the first embodiment.

  In the operation of the second embodiment, the skew correction amount calculated in a certain registration control cycle is stored in the skew amount storage means 28, and in the next registration control cycle, the skew correction is performed based on the stored skew correction amount. Is executed. As a result, there is no need to perform an operation immediately before executing the skew correction, so that there is an advantage that the skew correction can be executed more quickly. The other operations are the same as those of the first embodiment, and the description is omitted.

Next, a tandem type color image forming apparatus according to a third embodiment of the present invention will be described. The third embodiment is different from the first embodiment only in the configuration of the registration controller, and the other configurations are the same, so the description thereof will be omitted.
FIG. 5 shows the configuration of the registration controller of the third embodiment. In FIG. 5, the same components as those of the first embodiment shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

  In FIG. 5, the registration controller 12c is not provided with the skew amount storage means 26 for storing the skew amount in the first embodiment shown in FIG. That is, the third embodiment does not have a configuration for storing the skew deviation amount and the skew correction amount in preparation for the next registration cycle as in the first and second embodiments. The skew correction is performed based on the skew correction amount obtained by executing the pattern sampling. In the third embodiment, the first predetermined amount used for the first comparison means 23 is set to a value corresponding to the limit of the allowable range of the registration control system. On the other hand, the second predetermined amount used in the second comparing means 24 is set to a value corresponding to a deviation amount indicating that the skew deviation amount has approached the limit of the allowable range of the registration control system.

  In the operation of the third embodiment, when the amount of skew deviation exceeds the first predetermined amount, the skew correction is immediately executed within the registration cycle. On the other hand, if the skew deviation amount does not exceed the first predetermined amount but exceeds the second predetermined amount, a flag is set in the flag storage means 25, and the skew correction is executed first in the next registration cycle. . As a result, according to the present embodiment, the skew correction is performed when the skew is about to exceed the allowable range, so that the skew deviation can be kept within the allowable range while the number of time-consuming skew corrections is reduced.

The operation of the third embodiment will be described in detail with reference to the flowchart of FIG.
In FIG. 8, first, the state detection means 21 determines whether registration deviation correction is necessary (step S21). Unless it is determined that it is necessary (step S21: NO), the normal operation is continued. If it is determined that the skew is necessary (step S21: YES), it is determined whether the flag of the skew flag storage unit 25 is 0 (step S22). If the flag is not 0, that is, if the flag is 1 (step S22: NO), a skew correction cycle is executed (step S23), and then a registration control cycle other than the skew correction is executed (step S24). If the flag is 0 at step S22 (step S22: YES), a registration control cycle other than the skew correction is executed (step S24).

  Next, it is determined whether or not the amount of skew deviation detected in the registration cycle other than the skew correction is smaller than a second predetermined amount (step S25). If it is smaller (step S25: YES), the process returns to step S21. If it is not smaller (step S25: NO), it is further determined whether or not the skew deviation detected in the registration control cycle other than the skew correction is smaller than a first predetermined amount (step S26). If it is smaller (step S26: YES), the flag of the flag storage unit 25 is set to 1 so as to start from the skew correction cycle at the next registration control cycle (step S27), and returns to step S21. If not smaller (step S26: NO), the process proceeds to step S23 described above.

Next, a tandem type color image forming apparatus according to a fourth embodiment of the present invention will be described. The fourth embodiment is different from the first embodiment only in the configuration of the registration controller, and the other configurations are the same.
FIG. 6 shows the configuration of the registration controller of the fourth embodiment. In FIG. 6, the same components as those of the first embodiment shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

  6, the registration controller 12d does not include the skew amount storage means 26, the second comparison means 24, and the flag storage means 25 for storing the skew amount in the first embodiment shown in FIG. That is, in the fourth embodiment, the skew deviation amount and the skew correction amount are stored and a flag for requesting the execution of the skew correction is set in preparation for the next registration cycle as in the first to third embodiments. When skew correction is performed, skew correction is always performed based on the skew correction amount obtained by executing pattern sampling. In the fourth embodiment, the skew correction is immediately executed selectively based on the comparison result of the first comparing unit 23. As the first threshold value, a value corresponding to a skew deviation amount large enough to immediately require skew correction is set.

  In the operation of the fourth embodiment, if the detected amount of skew deviation is smaller than the first threshold value, it is determined that skew correction is unnecessary, and skew correction is not performed. The color shift correction is performed. As a result, in this registration cycle, only the time required to detect the color shift amount for one time is required. If the skew deviation amount is not smaller than the first threshold value, it is determined that skew correction is necessary, and the skew deviation correction is immediately executed based on the detected skew deviation amount.

  As a result, according to the present embodiment, the situation where the time for detecting the color misregistration amount twice during one registration control cycle is required is minimized.

  In order to explain the effect of the first embodiment, each operation and each state with respect to time in the first embodiment and the comparative example are schematically shown in FIGS.

  As shown in FIG. 9, according to the first embodiment, even if a skew deviation within the allowable range occurs at time T1, if the registration control is performed twice thereafter, the flag is set by the first registration control, and Since skew correction is performed at the second registration control, skew deviation can be eliminated at time T2.

  On the other hand, as shown in FIG. 10, according to the comparative example in which the skew deviation correction is not performed in the normal operation, the skew deviation within the allowable range occurs at the time T1, and thereafter, the maintenance is not performed by the service person. As long as this skew shift continues to exist.

  In order to further explain the effect of the third embodiment, FIG. 11 schematically shows each operation and each state with respect to the time of the third embodiment.

  As shown in FIG. 11, according to the third embodiment, even if a large skew deviation exceeding the allowable range occurs at the time T3, the skew correction is also performed in the subsequent registration control cycle. Can eliminate the skew deviation. That is, even if maintenance is not performed by a serviceman, such a large skew deviation can be automatically corrected.

  The color image forming apparatus described above can be used for a copying machine, a printer, a facsimile, and the like. In the above embodiment, the case of four colors of K, Y, M, and C has been described. However, the present invention is not limited to the four colors, but may be applied to an apparatus that forms a multiplexed image by overlaying a plurality of arbitrary colors. Applicable.

FIG. 1 is a block diagram of a color image forming apparatus according to an embodiment of the present invention. FIG. 3 is a plan view showing an example of a measurement pattern for registration control used in an embodiment of the present invention. FIG. 2 is a block diagram of a registration controller used in the first embodiment of the present invention. FIG. 9 is a block diagram of a registration controller used in a second embodiment of the present invention. FIG. 13 is a block diagram of a registration controller used in a third embodiment of the present invention. FIG. 14 is a block diagram of a registration controller used in a fourth embodiment of the present invention. 5 is a flowchart illustrating the operation of the first embodiment of the present invention. 9 is a flowchart illustrating the operation of the third embodiment of the present invention. 5 is a time chart illustrating the operation of the first embodiment of the present invention. 9 is a time chart illustrating an operation of a comparative example. 9 is a time chart illustrating the operation of the third example of the present invention.

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 1 ... Color image forming apparatus, 2 ... IPS, 3 ... ROS-I / F, 4 ... ROS, 5 ... Image forming apparatus, 6 ... Transfer belt, 7 ... Motor, 8 ... Paper suction roller, 10 ... Belt cleaner, 11 .. CCD, 12 registration controller, 13 skew correction device, 21 state detection means, 22 skew amount detection means, 23 first comparison means, 24 second comparison means, 25 flag storage means 26: Skew amount storage means, 27: Skew correction amount calculation means, 28: Skew correction amount storage means, 24: Second comparison means

Claims (2)

A plurality of image forming means for forming images of different colors in an overlapping manner;
Sampling means for sampling a test pattern;
Skew shift amount calculating means for calculating a skew shift amount based on a result of sampling by the sampling means;
A non-skew color misregistration amount calculating means for calculating a non-skew color misregistration amount based on a sampling result of the sampling means;
If the skew shift calculated by the skew shift calculating means in the first sampling by the sampling means is smaller than a first threshold, the non-skew color shift calculating means in the first sampling Controlling the image forming means so as to execute the color shift correction other than the skew based on the color shift amount other than the skew calculated by the formula (1), and calculating the skew shift calculated by the skew shift amount calculating means in the first sampling. If the amount is not smaller than the first threshold value, the skew deviation correction is performed by adjusting the optical system based on the skew deviation amount, and then the second sampling is performed by the sampling means. Based on the result of the sampling, the image is calculated by the color misregistration amount calculating means other than the skew. Control means for calculating an amount of color misregistration other than skew between forming means, and controlling the image forming means to execute color misregistration other than the skew based on the amount of color misregistration other than the skew. A multiplex image forming apparatus. A color misregistration control method for an image forming apparatus having a plurality of image forming units for forming images of different colors in an overlapping manner,
Sampling the test pattern created by the test pattern creating means;
Calculating a skew shift amount between the image forming units and a color shift amount other than a skew between the image forming units based on a result of the sampling;
Performing a non-skew color shift correction based on the non-skew color shift amount when the skew shift amount is smaller than a first threshold value;
When the skew deviation amount is not smaller than the first threshold value, the skew deviation correction is executed by adjusting the optical system based on the skew deviation amount, and then the test pattern is formed by the test pattern creating means. Create, sample the test pattern, calculate the amount of color shift other than the skew between the image forming units based on the result of the sampling, and correct the color shift other than the skew based on the amount of color shift other than the skew. And a step of executing a color misregistration control method for an image forming apparatus.

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