JP2007102014A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce frequency of correcting color shift, to shorten correction time and to prevent color shift regularly. <P>SOLUTION: In the color image forming apparatus MF1 equipped with a color shift correction means 501 which forms respective color patterns on an image carrier so as to detect deviation in a writing position, and corrects an image writing position in a direction where the displacement is reduced, and superposing and forming a plurality of color images on the same paper, time Time taken until next color shift correction is performed is prolonged when a color shift correction amount Δlen is under a first threshold LenL of every color, and the time Time is shortened when it is equal to or above a second threshold LenH of every color. When in-machine temperature is changed to be equal to or above a third threshold Temp from that at the previous color shift correction time, the color shift correction is performed. When the color shift correction amount is smaller than a fourth threshold LenL of every color, the third threshold Temp is changed to be large, and when it is larger than the fifth threshold LenH of every color, the third threshold Temp is changed to be small. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color image forming apparatus that forms an image of a plurality of colors on the same sheet, and in particular, in the direction of forming each color pattern on an image carrier to detect a write position shift amount and to reduce the position shift amount. The present invention relates to a color image forming apparatus including color misregistration correction means for correcting each color image writing position. This color image forming apparatus can be used in, for example, a color printer, a copying machine, and a facsimile.

  In addition to replacement and adjustment of image forming related members, color misregistration includes mechanical expansion / contraction, displacement or deformation of image forming related members due to changes in internal temperature of the color image forming apparatus and impact applied to the apparatus, and aging of the members. It also changes due to typical wear and slip changes.

Patent No. 2625130, Japanese Patent Laid-Open No. 5-188697, JP 2001-228670 A, and JP 2002-207337 A.

  Cited Document 1 proposes a color printer that performs color misregistration correction when there is a temperature change of 10 ° C. or more from the in-machine temperature immediately after power-on. Cited Document 2 presents a color printer that measures the elapsed time from power-on and increases the time interval for color misregistration correction as the elapsed time increases. Cited Document 3 presents a color printer that lengthens the time interval until the next color misregistration correction is started when the color misregistration correction amount is smaller than the reference amount. In Cited Document 4, color misregistration correction is performed when the fixing temperature is low immediately after the power is turned on. After that, after the temperature inside the machine exceeds 5 ° C., and after the color printing or color copying performed is 200. A multi-function copying machine that performs color misregistration correction after the number of sheets has been reached is presented.

  In the prior art, the color misregistration correction operation is performed when a predetermined time elapses or when the temperature inside the apparatus shows a certain amount of change. However, since this method performs color misregistration correction at the same time for all colors, there is a possibility that the color misregistration correction operation is performed depending on the color even in a state where the color misregistration correction is unnecessary as a result. Since the user cannot perform a printing operation while the color misregistration correction is being performed, it is desirable to reduce the color misregistration correction frequency and the color misregistration correction time.

  An object of the present invention is to effectively perform color misregistration correction. Specifically, the first object is to reduce the frequency of color misregistration correction, and the second object is to reduce the color misregistration correction time, and the frequency misregistration correction frequency and the color misregistration correction time can be shortened. A third object is to constantly suppress color misregistration.

(1) A plurality of colors provided with color misregistration correction means (501, FIG. 6) for forming each color pattern on the image carrier to detect the writing misregistration amount and correcting the image writing position in a direction to reduce the misregistration amount. In the color image forming device (MF1) that forms the same image on the same paper,
The color misregistration correction means (501, FIG. 6) determines, for each color, a long time (Time) until the next color misregistration correction when the color misregistration correction amount (Δlen) is small. A color image forming apparatus (MF1), wherein color misregistration correction is performed for a color that has passed.

  In addition, in order to make an understanding easy, the code | symbol of the corresponding element or the corresponding matter of the Example which is shown in drawing and mentions later in a parenthesis was added as an example for reference. The same applies to the following.

  When color misregistration correction is performed, a time (Time) until the next color misregistration correction is determined for each color, which is long when the color misregistration correction amount (Δlen) is small (FIG. 7 / FIG. 10). Since the color misregistration correction for the elapsed color is performed (FIGS. 9 and 10), the color misregistration correction for a color that is likely to cause color misregistration is high frequency, and the color misregistration correction for a color that is difficult to cause color misregistration is low frequency. Thereby, the color misregistration correction effect is high and color misregistration is constantly suppressed. Since one-time color misregistration correction is limited to the required color, shortening of the color misregistration correction time can be expected. That is, since the color misregistration correction operation more than necessary is suppressed, it is less likely that the user will wait for printing.

  (2) When the color misregistration correction amount (Δlen) is less than the first threshold value (LenL), the color misregistration correction means (501, FIG. 6) takes a time until the next color misregistration correction (Time). (2 × Time) is extended (27, 29, 31 in FIG. 7, 101 in FIG. 10), the color image forming apparatus according to (1) above.

  (3) The color image forming apparatus according to (2), further comprising means (10) for setting the first threshold (LenL) for each color (LenL-c, m, y). According to this, the approximate execution frequency of color misregistration correction for each color can be adjusted by the first threshold value (LenL) for each color (LenL-c, m, y).

  (4) The color misregistration correction means (501, FIG. 6) determines that the color misregistration correction amount (Δlen) is equal to or greater than a second threshold (LenH) higher than the first threshold (LenL). The color image forming apparatus according to (2) or (3) above, wherein time (Time) until correction is shortened ((1/2) × Time) (103 in FIG. 10). According to this, for each color, the time interval at which color misregistration correction is performed automatically converges to an interval where the color misregistration amount is in the range from the first threshold (LenL) to less than the second threshold (LenH). High color shift suppression effect.

  (4a) The above (4) further comprising means (10) for setting the first threshold (LenL) and the second threshold (LenH) for each color (LenL-c, m, y; LenH-c, m, y). A color image forming apparatus. According to this, the allowable color misregistration range for each color can be set with the first threshold value (LenL-c, m, y) and the second threshold value (LenH-c, m, y) for each color.

  (5) The color image forming apparatus further includes a temperature sensor (217) for detecting the internal temperature of the apparatus; the color misregistration correction means (501, FIG. 6) has a higher internal temperature than that in the previous color misregistration correction. The color image forming apparatus according to any one of (1) to (4), wherein color misregistration correction is performed when the threshold value (Temp) or more is changed (FIGS. 9 and 10). According to this, the color shift due to the change in the apparatus temperature is effectively suppressed.

  (6) The color misregistration correction means (501, FIG. 6) has a color misregistration correction amount (Δlen) smaller than a fourth threshold (LenL) when color misregistration correction is performed in response to the change in the internal temperature. And the third threshold value (Temp) is increased (47, 49, 51 in FIG. 8, 107 in FIG. 10), the color image forming apparatus according to (5) above. According to this, if the change in color misregistration amount due to a temperature change is small, that is, if the temperature dependency is low, the temperature change amount for automatically starting the color misregistration correction is greatly changed. The correction frequency is reduced, and the user is less likely to wait for printing.

(6a) A temperature sensor (217) for detecting the internal temperature of the apparatus, and each color pattern is formed on the image carrier to detect the write position shift amount and correct the image write position in a direction to reduce the position shift amount. In a color image forming apparatus (MF1) provided with color misregistration correction means (501, FIG. 6), which forms a plurality of color images on the same sheet,
The color misregistration correction means (501, FIG. 6) performs color misregistration correction when the internal temperature changes by more than the third threshold (Temp) from the previous color misregistration correction (FIG. 9, FIG. 10), and corrects color misregistration. When the amount (Δlen) is smaller than the fourth threshold value (LenL), the third threshold value (Temp) is increased (47, 49, 51 in FIG. 8, 107 in FIG. 10). .

  According to this, the color shift due to the change in the apparatus temperature is effectively suppressed. If the change in color misregistration amount due to temperature change is small, that is, if the temperature dependency is low, the temperature change amount that automatically starts color misregistration correction will change greatly, so the frequency of color misregistration correction corresponding to temperature change will be low. Therefore, it is less likely that the user will wait for printing.

  (7) When the color misregistration correction means (501, FIG. 6) has a color misregistration correction amount (Δlen) equal to or higher than a fifth threshold (LenH) higher than the fourth threshold (LenL), The color image forming apparatus according to (6) or (6a), wherein (Temp) is reduced (109 in FIG. 10). According to this, when the temperature dependency becomes high, or when the temperature change amount for starting the color misregistration correction is excessively changed by the above (6) or (6a), the temperature change automatically starting the color misregistration correction. Since the amount is reduced, the reliability of the color misregistration correction corresponding to the temperature change is high.

  (7a) The above (7) further comprising means (10) for setting the fourth threshold (LenL) and the fifth threshold (LenH) for each color (LenL-c, m, y; LenH-c, m, y). A color image forming apparatus. According to this, the allowable color shift range corresponding to the temperature change for each color is set with the fourth threshold value (LenL-c, m, y) and the fifth threshold value (LenH-c, m, y) for each color. Can do.

  (7b) The color image forming apparatus according to (7a), wherein the fourth threshold (LenL) is the same as the first threshold (LenL), and the fifth threshold (LenH) is the same as the second threshold (LenH).

  (8) The color image forming apparatus according to any one of (5) to (7b), wherein the third threshold value (Temp) is for each color (Temp-c, m, y).

  (9) The image forming apparatus responds to the image forming instruction in a standby mode waiting for an image forming instruction to each part of the image forming apparatus by switching the main power switch (main SW) from OFF to ON. A power supply device (514, 540) for supplying a standby voltage for operation and supplying a voltage for cutting off the standby voltage and returning to the standby mode in the energy saving mode when the standby mode continues for a set time; (501, FIG. 6) performs the color misregistration correction during the standby mode; the color image forming apparatus according to any one of (1) to (8) above.

  (10) The color misregistration correction means (501, FIG. 6) is configured so that a set time (15 minutes) or more elapses immediately after the main power switch is switched from off to on and is in the standby mode or before The color image forming apparatus according to (9), wherein the color misregistration correction is performed when the in-machine temperature changes by a set amount (3 ° C.) or more and is in a standby mode.

  (11) The color misregistration correction means (501, FIG. 6) includes time information (Time, Δtime) and temperature information until the next color misregistration correction is performed during the image forming operation mode and the pause mode. The color image forming apparatus according to (9) or (10), wherein (ΔTemp) and threshold values (LenL, LenH, Temp) are held in a memory in a nonvolatile manner.

  (12) The image forming apparatus according to any one of (1) to (11) includes an electrophotographic color image forming apparatus including a transfer belt (208) and a plurality of photosensitive drums arranged along the transfer belt. , A laser exposure device (512) for projecting and exposing image light to each photosensitive drum; and a primary transfer means (205) for transferring each visible image formed on each photosensitive drum to the same position on the transfer belt. , Paper feeding means (209 to 212, 215) for feeding the paper toward the transfer belt, secondary transfer means (213) for transferring the visible image on the transfer belt to the paper, and the visible image is transferred The color laser printer further comprises a fixing means (214) for fixing the visible image on the paper.

  (13) Each color image forming device is an image forming device of k (black), c (cyan), m (magenta), and y (yellow), and the color misregistration correction means (501, FIG. 6) includes k , C, and m, the color misregistration correction timing of at least one (color that requires misregistration correction) is reached, a pattern of k and “color that requires misregistration correction” is formed on the transfer belt 208, and the “deviation from k” The color laser printer according to the above (12), which detects the amount of writing position deviation of “color required for correction” and corrects the image writing position of “color required for deviation correction” in a direction to reduce the amount of positional deviation.

  (14) The image forming devices of y, m, c, and k are arranged in this order along the moving direction of the transfer belt (208) toward the secondary transfer means (213). Color laser printer.

  (15) The color laser printer (200) according to any one of (12) to (14), an image reading device (300) that generates image data representing an image projected by an optical system, and the An image forming apparatus comprising: an image data processing device (510, IPP) that converts image data generated by an image reading device into image data suitable for image formation by the color laser printer and gives the image data to the color laser printer.

  (16) The laser printer according to any one of (12) to (15), further including a controller (501) that converts document information given from outside into image data suitable for printing by the laser printer. Or an image forming apparatus.

  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

  FIG. 1 shows the appearance of a multi-function full-color digital copying machine MF1 according to an embodiment of the present invention. This full-color copying machine is roughly constituted by units of an automatic document feeder (ADF) 120, an operation board 10 (FIG. 3), a color scanner 300, a color printer 200, and a paper feed bank 35. . A LAN (Local Area Network) connected to a personal computer PC is connected to the system controller 501 (FIG. 3) in the apparatus. The facsimile controller 506 (FIG. 3) in the machine can perform facsimile communication via the exchange PBX and the public communication network PN.

  The printer 200 includes a transfer unit, and the transfer unit includes a transfer belt 208 that is an endless belt. The transfer belt 208 is wound around three support rollers and one tension roller, and is driven to rotate counterclockwise. Near the tension roller, there is a transfer body cleaning unit that removes residual toner remaining on the transfer belt 208 after image transfer.

  On the transfer belt 208 between one support roller and another support roller, Y (yellow), M (magenta), c (cyan), and k (black) colors are formed along the moving direction. The image forming unit is equipped with a transfer roller 205 facing each of the photosensitive drums 202 with the transfer belt 208 interposed therebetween. Above the image forming apparatus, there is a laser exposure unit 512 that irradiates each photoconductor drum of each color photoconductor unit with laser light for image formation. The photosensitive drum 202 is uniformly charged by the charging roller 203, and a laser that is modulated by an image signal is projected by the laser exposure unit 512 onto the charged surface. The electrostatic latent image generated thereby is developed by the developing device 204 into a toner image. This toner image is transferred to the transfer belt 208.

  A transfer belt 213 is below the transfer belt 208. The conveyor belt 213 transfers the toner image on the transfer belt 208 onto a sheet, that is, a sheet. The sheet (transfer sheet) on which the toner image is transferred is sent to the fixing unit 214 by the transport belt 213. Below the conveying belt 213 and the fixing unit 214, there is a double-sided drive unit 221 that is a sheet reversing unit that feeds a sheet immediately after an image is formed on the front surface and reverses the front and back to record an image on the back surface.

  When the start switch 17 (FIG. 4) is pressed, if there is a document on the automatic document feeder (ADF) 120, it is transported onto the contact glass of the scanner 300 and then on the contact glass when there is no document on the ADF 120. In order to read a manually placed original, the scanner 300 is immediately driven, and the first carriage and the second carriage in the scanner 300 are read and scanned. Then, light is emitted from the light source on the first carriage to the contact glass, and reflected light from the document surface is reflected by the first mirror on the first carriage and directed to the second carriage, and reflected by the mirror on the second carriage. Then, an image is formed on a CCD as a reading sensor through an imaging lens. Y, M, C, and K (Bk) color recording data are generated based on the image signal obtained by the reading sensor.

  Further, when the start switch is pushed, the transfer belt 208 starts to rotate, the image forming preparation of each unit of the image forming apparatus is started, and the image forming sequence of each color image is started. Thus, an exposure laser modulated based on each color recording data is projected onto the photosensitive drum for each color, and each color toner image is superimposed and transferred as a single image on the transfer belt 208 by each color image forming process. When the leading edge of the toner image enters the conveying belt 213, the sheet is fed to the transfer belt 213 from the registration roller pair 212, that is, the feeding roller, at a timing so that the leading edge enters the conveying belt 213 at the same time. The toner image on the belt 208 is transferred to the paper. A voltage for transferring toner is applied to the transfer belt 208 by the transfer roller 205. The sheet on which the toner image has moved is sent to the fixing unit 214 where the toner image is fixed on the sheet.

  Note that the above-described sheet is selectively rotated by driving one of the sheet feeding rollers immediately above the sheet feeding trays (also referred to as sheet feeding stages or cassettes) 209 to 211 of the sheet feeding bank 35, so that the sheet feeding bank 35 has multiple stages. A sheet is fed out from one of the paper feed trays 209 to 211, separated by one by a separation roller, put into a vertically arranged transport roller unit, transported upward, and guided to a transport path in the printer 200. The transport roller 215 transports the registration roller pair 212 to the registration roller pair 212 to stop the leading end of the sheet against the registration roller pair 212, and then rotates the registration roller pair 212 and the transport roller 215 to the transport belt 213 at the timing described above. It will be sent out. It is also possible to feed paper by inserting paper on the right side manual feed tray. When the user is inserting paper onto the manual feed tray, the printer 200 rotates the paper feed roller of the manual feed tray to separate one sheet on the manual feed tray and pull it into the manual feed path. Stop against the pair 212.

  The paper discharged after receiving the fixing process by the fixing unit 214 is guided to the discharge roller by the switching claw and stacked on a paper discharge tray (not shown). Alternatively, it is guided to the double-sided drive unit by the switching claw, reversed there and led again to the transfer position, and the image is recorded also on the back surface, and then discharged onto the paper discharge tray by the discharge roller. On the other hand, residual toner remaining on the transfer belt 208 after image transfer is removed by a transfer body cleaning unit (not shown) to prepare for image formation again.

  In order to prevent the above-described color shift (color shift) in the overlay transfer, the printer 200 uses the exposure device 512 to place the front side (hereinafter referred to as the front side in FIG. 1) and the back side on each photosensitive drum 202. A test pattern for position detection (FIG. 2) is written and developed on the back surface side (hereinafter referred to as rear in FIG. 1), transferred onto the transfer belt 208, and transferred to the transfer belt 208. By reading with the optical sensors 216f (front side) and 216r (rear side), the writing position deviation, inclination, magnification, and the like of the exposure device 512 with respect to each photosensitive drum 202 are detected, and the color deviation caused by these is eliminated. It is configured to correct the timing of writing of the exposure device 512 to the photosensitive drum. A temperature sensor 217 for detecting the in-machine temperature is arranged between the image forming unit arrays.

  FIG. 3 shows the system configuration of the electrical system of the multifunction copying machine MF1 shown in FIG. The electrical system communicates with the outside using a system controller 501 that performs overall control of the image forming apparatus, an operation board 10 of the image forming apparatus connected to the controller 501, an HDD 503 that stores image data, and an analog line. Communication control device interface board 504, LAN interface board 505, FAX control unit 506, IEEE1394 board, wireless LAN board, USB board, etc. 507 connected to general-purpose PIC bus, and engine control 510 connected to the controller via PCI bus An I / O board 513 for controlling I / O of the image forming apparatus, a scanner board (SBU) 511 for reading a copy document (image), and image data connected to the engine control 510 Painting Projecting light onto a photosensitive drum (light writing) LDB composed (laser diode board) 512 and the like.

  A reading unit 300 that optically reads an original scans the original with an original illumination light source and forms an original image on the CCD 520. An original image, that is, reflected light of light irradiation on the original is photoelectrically converted by the CCD 520 to generate R, G, B image signals.

  The communication control device interface board 504 immediately informs an external remote diagnosis device when a failure occurs in the device, and allows the service person to recognize the contents and situation of the failure part and repair them immediately. . In addition, it is also used for sending out the usage status of the device.

  The CCD 520 shown in FIG. 3 is a three-line color CCD, which generates R, G, and B image signals of EVENch (even-numbered pixel channel) / ODDch (odd-numbered pixel channel), and outputs it to an analog ASIC (Application Specific IC) of the SBU board. input. The SBU board 511 is provided with a circuit for generating an analog ASIC, CCD, and analog ASIC drive timing. The output of the CCD 520 is sampled and held by a sample and hold circuit inside the analog ASIC, then A / D converted, converted into R, G and B image data, and shading corrected, and an output I / F (interface) At 520, the data is sent to an image data processor IPP (Image Processing Processor; hereinafter simply referred to as IPP) via an image data bus.

  IPP is a programmable arithmetic processing means that performs image processing, separation generation (determination of whether an image is a character area or a photographic area: image area separation), background removal, scanner gamma conversion, filter, color correction, scaling, and image processing. , Perform printer gamma conversion and gradation processing. The image data transferred from the SBU to the IPP is corrected by the IPP for signal deterioration due to quantization of the optical system and the digital signal (signal deterioration of the scanner system) and written in the frame memory 521.

  The system controller 501 includes a ROM that controls the CPU and the system controller board, a RAM that is a working memory used by the CPU, a lithium battery, an NV-RAM that includes an SRAM backup and a clock, and a system controller board. The system bus control, frame memory control, FIFO, and other ASICs for controlling the CPU periphery and their interface circuits are mounted.

  A system controller 501 has functions of a plurality of applications such as a scanner application, a facsimile application, a printer application, and a copy application, and controls the entire system. The input of the operation board 10 is decoded, and the setting of the system and the state contents are displayed on the display unit of the operation board.

  Many units are connected to the PCI bus, and image data and control commands are transferred in a time division manner by the image data bus / control command bus.

  The communication control device interface board 504 is a communication interface board between the communication control device and the controller 501. Communication with the controller 501 is connected by full-duplex asynchronous serial communication. The communication control device 522 is multi-drop connected according to the RS-485 interface standard. Communication with the remote management system is performed via the communication controller device interface board 504.

  The LAN interface board 505 is connected to an in-house LAN. It is a communication interface board between the in-house LAN and the controller 501, and is equipped with a PHY chip. The LAN interface board 505 and the controller 501 are connected by standard communication interfaces of a PHY chip I / F and an I2C bus I / F. Communication with an external device is performed via the LAN interface board 505.

  The HDD 503 is used as an application database that stores system application programs and device activation information of printers and image forming process devices, and an image database that stores image data of read images and written images, that is, image data and document data. . Both the physical interface and the electrical interface are connected to the controller through an interface compliant with ATA / ATAPI-4.

  The operation board 10 is equipped with a CPU, ROM, RAM, LCD, and ASIC (LCDC) for controlling key input. In the ROM, a control program for the operation board 10 that controls input reading and display output of the operation board 10 is written. The RAM is a working memory used by the CPU. Through communication with the system controller 501, the panel is operated to perform input for the user to input system settings, and display and input control for displaying the setting contents and status of the system to the user.

  The black (B), yellow (Y), cyan (C), and magenta (M) write signals output from the work memory of the system controller 501 are B, Y, M, LDB (Laser Diode control Board) Input to a C LD (Laser Diode) writing circuit. The LD write circuit performs LD current control (modulation control) and outputs the result to each LD.

  The engine control 510 mainly performs image creation control for image formation, and includes a CPU, an IPP that performs image processing, a ROM that contains programs necessary to control copying and printout, a RAM that is necessary for the control, and an NV -RAM is installed. The NV-RAM is equipped with an SRAM and a memory that detects power-off and stores it in the EEPROM. The I / O ASIC that also has a serial interface that transmits and receives signals to and from other CPUs that perform control is a nearby I / O (counter, fan, solenoid, motor, etc.) on which an engine control board is mounted. ASIC for controlling the). The I / O control board 513 and the engine control board 510 are connected via a synchronous serial interface.

  A sub CPU 517 is mounted on the I / O control board 513, and I / O of the image forming apparatus including analog control such as P sensor and T sensor, jam detection referring to a detection signal of a paper sensor, and paper conveyance control. Control is in progress. The interface circuit 515 is an interface circuit with various sensors and actuators (motors, clutches, solenoids).

  The power supply unit PSU 514 is a unit that supplies power to control the image forming apparatus. When the main SW is turned on (closed), commercial power is supplied. The commercial AC is supplied from the commercial power source to the AC control circuit 540, and the DC power supply PSU 514 is necessary for each control board using the AC control output controlled by the AC control circuit 540 such as rectification and smoothing. Supply DC voltage. The CPU of each control unit operates using a constant voltage generated by the DC power supply unit PSU. The AC control circuit 540 includes an AC energization circuit (heater driver) that performs energization control for energizing the fixing heater 214 and maintaining the fixing temperature constant. When the main SW is switched from OFF to ON, the AC control circuit 540 supplies commercial AC to the heater driver and DC voltage to the DC power supply 514. This is the standby mode. If there is a copy or print instruction in this state, the system controller 501 instructs the engine control 510 to copy or print, and the engine control 510 starts this. The state in which the engine control 510 is executing copying or printing is an operation mode, and power consumption is large.

  During the standby mode, the system controller 501 monitors whether a color misregistration correction start condition, which will be described later, is satisfied, and performs color misregistration correction when the start condition is satisfied. When the set time input to 10 has elapsed, the AC control circuit 540 and the DC power supply device 514 are switched to the energy saving mode. That is, the AC control circuit 540 cuts off the AC supply to the heater driver, and the DC power supply device 514 directly accesses the copying machine MF1 by the user (operation board 10 input or operation for copying or printing) or external (personal computer) DC receiving power supply circuit for DC output excluding a standby power supply circuit for supplying a voltage for recognition operation to a return electric circuit for performing power supply operation for recognizing an image request or a print request from a facsimile) and returning to an operation mode. Shut off from line. As a result, the operating voltage of the system controller 501 disappears. When the return electric circuit recognizes an access from the user or the outside in the energy saving mode, the AC control circuit 540 and the DC power supply device 514 are set in the standby mode. As a result, an operating voltage is applied to the system controller 501.

  As shown in FIG. 4, in addition to the liquid crystal touch panel 11, the operation board 10 includes a numeric keypad 15, a clear / stop key 16, a start key 17, an initial setting key 18, a mode switching key 19, a test print key 20, and a power key. There are 21. Although not shown, on the left side of the liquid crystal touch panel 11, there is an alphabet keyboard with hiragana added for inputting, setting, and abbreviated registration for URL, mail text, file name, folder name, and the like.

  The power key 21 is an operation key for instructing switching from the energy saving mode to the standby mode in which the image printing is possible and vice versa. When the power key 21 is pressed once when the energy saving mode is set, the energy saving mode is switched to the standby mode. When the power key 21 is pressed once in the standby mode, the standby mode is switched to the energy saving mode. The test print key 20 is a key for printing only one copy regardless of the set number of print copies and confirming the print result.

  By pressing the initial setting key 18, the initial state of the machine can be arbitrarily customized. When the transition time to energy saving mode is set, the threshold value that is used to determine the timing of color misregistration correction is set, the paper size stored in the machine is set, or the copy function reset key is pressed The state set to can be arbitrarily set. When the initial setting key 18 is operated, an "initial value setting" function for setting various initial values, an "ID setting" function, a "copyright registration / setting" function, an "usage record output" function, etc. A selection button to specify is displayed. The “initial value setting” function includes setting (changing) a parameter (threshold value) for “color misregistration correction”.

  On the liquid crystal touch panel 11, various function keys and messages indicating the operation states of the engine 300 and the controller board 400 are displayed. The LCD touch panel 11 is used for selecting and executing the “copy” function, “scanner” function, “print” function, “facsimile” function, “store” function, “edit” function, “register” function, and other functions. A function selection key 14 representing is displayed. An input / output screen determined for the function designated by the function selection key 14 is displayed. For example, when the “copy” function is designated, the function keys, the number of copies, and the state of the image forming apparatus are shown as shown in FIG. Messages 12 and 13 are displayed. When the operator touches a key displayed on the liquid crystal touch panel 11, the operation board 10 reads it as an operator input, and highlights the key indicating the selected function in gray indicating that it is being designated. Further, when it is necessary to specify the details of a function (for example, the type of page printing), a detailed function setting screen is popped up by touching a key. Thus, since the liquid crystal touch panel 11 uses a dot display, it is possible to graphically perform an optimal display at that time. Among the function keys 12, print color designation keys “black (BK)”, “full color”, “automatic color selection”, “blue (C)”, “red (M)” and “yellow (Y)” designation There is a key.

  FIG. 5 shows a circuit block of the operation board 10. The main body of the electric control system of the operation board 10 communicates with the CPUs of the system controller 501 and the engine control 510, reads the input of the operation board 10 and controls the display on the operation board 10, and the control of the CPU 1 ROM 2 in which a program is stored 2 RAM 3 for temporarily storing data during control 3 VRAM 7 for storing drawing data of the liquid crystal touch panel 11, drawing timing control and touch of the liquid crystal touch panel 11 connected to the VRAM 7 There are a liquid crystal display controller (LCDC) 6 that performs input detection and the like, and a clock IC 5 that generates time data. A liquid crystal touch panel 11 having a CFL light source as a backlight 9 is connected to the LCDC 6. The CPU 1 is further connected to an inverter 8 that drives the CFL backlight 9, a key matrix of operation key groups 15 to 21, an LED matrix of display LEDs, an LED driver that drives these LEDs, and the like. Further, a non-volatile RAM (NVRAM) 4 for storing an image processing mode and an initial set value is connected to the data bus to which the CPU 1 is connected.

  In response to a user operation on the operation board 10, the CPU 1 of the operation board 10 reads a numeric key press, generates input numeric data, reads a start key press, and transfers a start instruction to the controller 501. , Normal copying machine operation reading and display output control, such as reading paper size switching input.

A “determination parameter table” is assigned to one memory area of the NVRAM 4. The table is composed of the following 21 registers (FIGS. 11 to 16):
Register symbol Write data Δtime c, Δtime m, Δtime y: Time of previous correction (start point of elapsed time)
Δtemp c, Δtemp m, Δtemp y: Temperature of previous correction (starting point of temperature change)
Time c, Time m, Time y: Correction interval (threshold of elapsed time)
Temp c, Temp m, Temp y: Temperature change threshold (second threshold)
Δlen c, Δlen m, Δlen y: Color misregistration correction amount (actual value)
LenL c, LenL m, LenL y: Lower limit threshold of color misregistration (for interval expansion determination: first and fourth thresholds)
LenH c, LenH m, LenH y: Upper limit threshold of color misregistration amount (for interval reduction determination: second and fifth thresholds)
Note that the register symbol in this specification and the accompanying drawings may mean the data (value represented) of the register.

  Lower limit threshold (in the present embodiment, the first threshold and the fourth threshold) LenL c, LenL m, LenL y and the upper limit threshold (in the present embodiment, the second threshold and the fifth threshold) LenHc, LenHm, and LenHy can be input (changed) from the operation board 10, and the CPU 1 reads the operator operation of the initial setting key 18 in the operation key groups 15 to 21 by "input reading". Then, a setting menu screen is displayed on the liquid crystal touch panel 11. When the operator designates an item of “setting of color misregistration correction parameter” on the setting menu screen, the CPU 1 displays the data name of each register of the above “determination parameter table” on a part of the display surface of the liquid crystal touch panel 11. A written value is displayed, and an up / down key for changing a data value is additionally displayed in each value display area of the lower and upper thresholds of the color misregistration amount. The user can change the lower limit threshold and the upper limit threshold of the color misregistration amount by clicking the up and down keys to change the display value and clicking the execution key. Although details will be described later, in the registers Δtime c, Δtime m, and Δtime y, current time data of the clock IC5 (FIG. 5) when the color misregistration correction is performed is written, and the registers Δtemp c, Δtemp m, Δtemp are registered. In y, the in-machine temperature (temperature detected by the temperature sensor 217) when color misregistration correction is performed is written.

  FIG. 6 shows an outline of color misregistration correction control by the system controller 1 shown in FIG. An operating voltage is applied to the system controller 1 by shifting to the standby mode by switching the main SW from off to on, or returning from the energy saving mode in which the main SW is on to the standby mode. At this time, if there is no information indicating the energy saving mode in the mode register (one area of the memory) that is supplied with power even in the energy saving mode and holds the mode information, the system controller 1 turns on the power by turning on the main SW (step 1 in FIG. 6). ) And initialization (step 2) is executed. In this initialization, information indicating “standby mode” is written in the mode register. When the process proceeds to the energy saving mode later, information indicating the “energy saving mode” is written in the mode register immediately before that. In the following, the word “step” is omitted in parentheses, and step no. Write numbers only.

  In the initialization (2), the registers Δtime c, Δtime m, Δtime y, Δtemp c, Δtemp m, Δtemp y, Time c, Time m, Time y, Temp c, Temp m, Temp y, and Δlen c, Δlen m and Δlen y are initialized. That is, the current time of the clock IC 5 is written in the previous time registers Δtime c, Δtime m, and Δtime y, and the current detected temperature of the temperature sensor 217, that is, the in-machine temperature, is written in the previous temperature registers Δtemp c, Δtemp m, and Δtemp y, 15 minutes are uniformly written in the correction interval registers Time c, Time m, and Time y, 3 ° C is uniformly written in the temperature change threshold registers Temp c, Temp m, and Temp y, and the color misregistration correction amount The registers Δlen c, Δlen m, and Δlen y are cleared.

  Next, “1” (high level H) representing the necessity of initial color misregistration correction immediately after the main SW is turned on is written in the register Flc (one area of the internal memory of the controller 501) (3). Next, in the standby mode in which the in-machine temperature has not changed by 3 ° C or more since the initialization and 15 minutes have elapsed, the register Flc is cleared (6, 8), and all the colors c, m, y are cleared. “C, m, y color misregistration correction 1” (9) which is color misregistration correction is executed. The contents will be described later with reference to FIG. In the standby mode in which the internal temperature changes by 3 ° C. or more before 15 minutes have elapsed, the register Flc is cleared (6, 7, 10), and “c” is the color misregistration correction for all the c, m, and y colors. , M, y color misregistration correction 2 ”(11). The contents will be described later with reference to FIG. Thereafter, color misregistration correction is required according to the color misregistration correction start conditions set in “c, m, y color misregistration correction 1” (9) or “c, m, y color misregistration correction 2” (11). No is determined for each color c, m, and y (12 to 13), and color misregistration correction is performed for the color (one, two, or all of c, m, y) determined to require color misregistration correction (15). ). In the color misregistration correction (15), the correction start condition (Time, Temp) for the next corresponding color is determined based on the correction amount of the correction result. Thereafter, until the main SW is turned off, the loop of Steps 4, 5, 12-15, and 4 is circulated to determine whether or not the color misregistration correction is necessary for each color, and the color misregistration of the color that needs the color misregistration correction. Make corrections.

  FIG. 7 shows that “c, m, y color misregistration correction 1” (9) is executed in the standby mode in which the in-machine temperature has not changed by 3 ° C. or more since the initialization immediately after the main SW is turned on and 15 minutes have elapsed. ). Here, first, in “all-color process control” (21), the image forming conditions such as c, m, y and k charging, exposure, development and transfer are all set to reference values, and the rear surface on the transfer belt 208 is set. A K (Bk), Y, C, and M image is formed on r or front f, and the image density is detected by the optical sensor 20r or 20f, and the charging roller applied voltage and exposure are adjusted so that it becomes a reference value. Adjust and set intensity and development bias. Then, “all color test pattern formation and measurement” (22) is executed. That is, under the image forming conditions (parameters) set in the “all color process control” (21), the start marks Msr and Msf are respectively formed on the transfer belt 208 on the rear r and front f as shown in FIG. And 8 sets of test patterns are formed. That is, at the rear, eight mark sets are placed within one circumference of the transfer belt 10 after the start mark Msr of black Bk at the head, 4 pitches 4d of the mark pitch d, and the set pitch (constant pitch). ) Sequentially formed by 7d + A + c. In this embodiment, eight sets including a start mark, a total of 65 marks, are formed within one circumference of the transfer belt 10.

The first mark set is a next orthogonal mark group parallel to the main scanning direction x (the width direction of the transfer belt 208),
Black Bk first orthogonal mark Akr,
Yellow Y second orthogonal mark Ayr,
A cyan C third orthogonal mark Acr, and
Magenta M 4th orthogonal mark Amr,
And the following oblique mark group forming an angle of 45 ° with respect to the main scanning direction x,
Bk's first oblique mark Bkr,
Y second oblique mark Byr,
C third oblique mark Bcr, and
M's fourth oblique mark Bmr,
Is included. The contents of the second to eighth mark sets are the same as the first mark set. The same test pattern as the above-described rear test pattern is also formed on the front at the same time. Of the symbols attached to the marks included in these test patterns, the suffix r indicates the rear side, and f indicates the front side.

  These marks are detected by the optical sensors 216r and 216f, and the mark detection signal is converted into digital data, that is, mark detection data and read. Then, the position (distribution) of the center point of each mark on the transfer belt 208 is calculated. Further, an average pattern of the rear side 8 sets (an average value group of mark positions) and a similar average pattern of the front side 8 sets are calculated. When the average pattern is calculated, the deviation amount of image formation by each of the K (Bk), Y, C, and M imaging units is calculated based on the average pattern (23), and the deviation is eliminated based on the calculated deviation amount. Then, the correction amounts for the colors c, m, and y are calculated and written in the color misregistration correction amount registers Δlen c, Δlen m, Δleny (24). Then, color misregistration correction of each color is performed for the calculated correction amount (25).

  Next, the next color misregistration correction start condition for each color is adjusted based on the color misregistration correction amount for each color (26 to 31). That is, correction is performed when the data in the color misregistration correction amount register Δlen c, that is, the current color misregistration correction amount Δlen c for color c is less than the lower limit threshold (first threshold) LenL c of the lower limit threshold register LenL c addressed to c color. The correction interval data Time c of the interval register Time c is rewritten to a value (30 minutes) twice the value represented by the data (26, 27). When the color misregistration correction amount Δlen c is equal to or greater than the lower limit threshold LenL c, the correction interval data Time c is not rewritten (changed). Similarly, if the current color misregistration correction amount Δlen m for m colors is less than the lower limit threshold value (first threshold value) LenL m addressed to m colors, the correction interval data Time m is twice the value represented by the data. Rewrite the value (30 minutes) (28, 29). When the color misregistration correction amount Δlen m is equal to or greater than the lower limit threshold LenL m, the correction interval data Time m is not rewritten. Similarly, if the current color misregistration correction amount Δlen y for the y color is less than the lower limit threshold value (first threshold value) LenL y for the y color, the correction interval data Time y is twice the value represented by the data. (30, 31). When the color misregistration correction amount Δlen y is equal to or greater than the lower limit threshold LenL y, the correction interval data Time y is not rewritten.

  When these rewriting processes are completed, the current time of the clock IC5 is written in the previous time registers Δtime c, Δtime m, and Δtime y (32), and the current temperature sensor 217 is written in the previous temperature registers Δtemp c, Δtemp m, and Δtemp y. The detected temperature, that is, the in-machine temperature is written (33).

  In FIG. 8, there is a change of 3 ° C. or more in the temperature inside the machine before 15 minutes from the initialization immediately after the main SW is turned on, and “c, m, y color misregistration correction 2 executed in the standby mode”. "(11) indicates the contents. The contents of steps 41 to 45, 52 and 53 executed here are the same as the contents of steps 21 to 25, 32 and 33 shown in FIG.

  However, here, the contents of the adjustment (46 to 51) of the next color misregistration correction start condition for each color differ based on the current color misregistration correction amount for each color. That is, if the data of the color misregistration correction amount register Δlen c, that is, the current color misregistration correction amount Δlen c of c color is less than the lower limit threshold value (fourth threshold value) LenL c of the lower limit threshold value register LenL c addressed to c color, The temperature change threshold value (third threshold value) data Temp c in the change threshold value register Temp c is rewritten with a value (6 ° C.) obtained by adding 3 ° C. to the data (46, 47). When the color misregistration correction amount Δlen c is equal to or greater than the lower limit threshold LenL c, the temperature change threshold data Temp c is not rewritten (changed). Similarly, if the color misregistration correction amount data Δlen m is less than the lower limit threshold value (fourth threshold value) LenL m addressed to m colors, the temperature change threshold value (third threshold value) Temp m is added to the data by 3 ° C. (48, 49). When the color misregistration correction amount Δlen c is equal to or greater than the lower limit threshold LenL c, the temperature change threshold Temp m is not rewritten (changed). Similarly, if the color misregistration correction amount data Δlen y is less than the lower limit threshold value (fourth threshold value) LenL y addressed to the y color, the temperature change threshold value (third threshold value) Temp y is set to 3 ° C. It is rewritten to represent the added value (6 ° C.) (50, 51). When the color misregistration correction amount Δlen y is equal to or greater than the lower limit threshold LenL y, the temperature change threshold Temp y is not rewritten (changed).

  FIG. 9 shows the contents of the color misregistration correction necessity determination (12, 13, 14) for each of the colors c, m, and y shown in FIG. In “c color misalignment correction necessity determination” (12), it is determined whether the elapsed time since the previous color misregistration correction of c color has become equal to or greater than the correction interval data Time c (61), and the elapsed time becomes equal to or greater than Time c. If so, data representing decimal number 1 for designating color misregistration correction in which the correction time interval is changed in correspondence with the correction amount after color misregistration correction is written into the register RRrc (61, 62). When the elapsed time is less than Time c, it is determined whether the amount of change in the in-machine temperature from the previous c color misregistration correction is equal to or greater than the temperature change threshold (third threshold) Temp c (63). If the temperature change amount is equal to or greater than Temp c, the register RRr c is set to a decimal number 2 that specifies color misregistration correction in a manner that changes the temperature change threshold value (third threshold value) corresponding to the correction amount after color misregistration correction. The data to be represented is written (63, 64). When the temperature change amount is less than Temp c, the register RRr c is cleared (65). That is, it is rewritten to data representing decimal 0. The contents of “m color misregistration correction necessity determination” (13) and “y color misregistration correction necessity determination” (14) are the same as the contents of “c color misregistration correction necessity determination” (12). The above-described c in the content of “Color misregistration correction necessity determination” (12) is changed to m or y.

  FIG. 10 shows the contents of “correction of color shift determined to be necessary” (15) shown in FIG. Here, a color (c, m or y) in which data representing decimal number 1 or 2 is written in the register RRr c, m, y is determined as a color misalignment correction required color (91), and color misregistration is performed. A color to be corrected and a test pattern of K (Bk) are formed on the transfer belt 208, and the position of each color test pattern is measured using the sensors 216f and 216r (92), and another color i for k (Bk) is measured. A misregistration amount (i.e., a color in which a test pattern is formed among i, c, m, y), that is, a misregistration amount is calculated (93). Next, a color misregistration correction amount corresponding to the color misregistration amount of color i is calculated and written in the correction amount register Δlen i (95), and color misregistration correction of color i is performed (95).

  Next, when this color misregistration correction is performed for the c color, “update the determination condition for the c color” (98) is performed (97, 98). In this case, whether the color misregistration correction of the c color is specified as a mode for changing the correction time interval (RRr c data is 1) or a mode for changing the temperature change threshold (RRr c data is 2). If the former is the former (99) and the current color misregistration correction amount Δlen c for c color is smaller than the lower limit threshold value (first threshold value) LenL c for c color, the correction interval register Time c is set. The correction interval data Time c is rewritten to a value twice the value represented by the data (100, 101). When the current color misregistration correction amount Δlen c is larger than the upper limit threshold value (second threshold value) LenH c addressed to the c color, the correction interval data Time c of the correction interval register Time c is ½ of the value represented by the data. (102, 103). However, when the half value is less than 15 minutes, it is rewritten to 15 minutes (104, 105). When the current color misregistration correction amount Δlen c is greater than or equal to the lower threshold (first threshold) LenL c and less than the upper threshold (second threshold) LenH−c, the correction interval data Time c is not rewritten (changed).

  In the latter case, that is, when the color misregistration correction of c color is the designation of the mode for changing the temperature change threshold (RRr c data is 2), the current color misregistration correction amount Δlen c of c color is c color. Is smaller than the lower limit threshold value (fourth threshold value) LenL c addressed to the temperature change threshold value register (temp c) temperature change threshold value (third threshold value) data Temp c, a value obtained by adding 3 ° C. to the value represented by the data (106, 107). When the current color misregistration correction amount Δlen c is larger than the upper limit threshold value (fourth threshold value) LenH c addressed to the color c, the temperature change threshold value (third threshold value) data Temp c is set to 3 ° C. from the value represented by the data. Is rewritten to indicate the value obtained by subtracting (108, 109). However, when the subtracted value is less than 3 ° C, it is rewritten to 3 ° C (110, 111). When the current color misregistration correction amount Δlen c is greater than or equal to the lower threshold (fourth threshold) LenL c and less than the upper threshold (fourth threshold) LenH−c, the temperature change threshold (third threshold) data Temp c is rewritten (changed). do not do.

  Next, the register RRc-c is cleared (112), the current time is written in the previous time register Δtime c (113), and the current in-machine temperature is written in the previous temperature register Δtemp c (114).

  When the color misregistration correction is performed for the m color, the “update judgment condition of the m color” (116) is performed (115, 116), and when the color misregistration correction is performed for the y color, the “y color judgment condition is determined. Update "(118) (117, 118). The contents of “update the determination condition for m color” (116) and “update the determination condition for y color” (118) are the same as the contents of “update the determination condition for c color” (98) described above. This is obtained by replacing c in the above description of “Updating c Color Judgment Conditions” (98) with m or y.

  Next, the outline of the above-described color misregistration correction control will be specifically described. In this embodiment, the system controller 501 sets the correction time interval (Time c, m, y) from the previous color misregistration correction as the initial value of the timing of color misregistration correction in “initialization” (2). At 15 minutes, the temperature change threshold (third threshold) Temp c, m, y from the previous color misregistration correction is set to 3 ° C. The lower limit threshold (first threshold and fourth threshold) LenL-c, m, y of the color misregistration amount set by the user from the operation board 10 is 50 μm, and the upper limit threshold (second threshold and fifth threshold) LenH-c, m , Y is set to 100 μm (FIG. 11).

  In the standby mode immediately after the main SW is turned on (immediately after 1 to 3 in FIG. 6), when the 15-minute progress is ahead of the change of 3 ° C., first, color misregistration correction of all the non-reference colors c, m, y ( 6 in FIG. 6: FIG. 7) is performed, and the color misregistration correction amount at this time is written in the correction amount register Δlen c, m, y (24 in FIG. 7). When the stored color misregistration correction amounts are Δlen c = 30 μm, Δlen m = 55 μm, Δlen y = 80 μm, and the lower threshold (first threshold) is set as LenL c = LenL m = LenL y = 50 μm The color misregistration amount that does not exceed the lower limit threshold (first threshold) is cyan c. Therefore, the next color misregistration correction time Time c of cyan c is rewritten from 15 minutes to 30 minutes. That is, cyan c is set not to perform color misregistration correction 15 minutes after the next time but to 30 minutes after skipping once (FIG. 12). By this operation, since the interval time until the color misregistration correction is set for each color of the non-reference colors c, m, and y, the elapsed time is reset. That is, the current time is written in Δtime c, Δtime m, and Δtime y. Also, the temperature change amount is reset. That is, the current temperature is written in Δtemp c, Δtemp m, and Δtemp y.

  Since the degree of color shift amount of each non-reference color is likely to be different due to the configuration of the copying machine, the user uses the operation board 10 to use the lower limit threshold (first threshold and fourth threshold) LenL c, m, y and upper limit threshold values (second threshold value and fifth threshold value) LenH c, m, y can be set for each non-reference color. For example, the lower threshold values (first threshold value, fourth threshold value) can be set as LenL c = 50 μm, LenL m = 60 μm, and LenL y = 70 μm (FIG. 13). In this case, the result of the color misregistration correction amount is Time c = Time m = 30 minutes (FIG. 14). If the cyan color shift amount Δlen c after 30 minutes is less than the lower limit threshold (first threshold) LenL c = 30 μm, Temp c = 30 minutes is changed to 60 minutes. Thereafter, similarly, if the color misregistration amount falls below the lower threshold (first threshold), Temp c = 60 minutes is changed to 120 minutes, 240 minutes,. However, for example, when the color shift amount Δlen c of cyan c is equal to or greater than the upper threshold (second threshold) LenH−c = 100 μm, if Time c = 30 minutes, Time c = 30 minutes is changed to 15 minutes. (FIG. 15). If Time c = 15 minutes, it is set as 15 minutes.

  If the change in the internal temperature becomes 3 ° C. or more before 15 minutes have passed since the previous color misregistration correction, for example, when the state shown in FIG. 16 is reached, first, the non-reference colors c, m, y color misregistration correction (11 in FIG. 6: FIG. 8) is performed. The rest is the same as the time interval described above. For example, if the cyan color shift amount Δlen c falls below the lower limit threshold (fourth threshold) LenL c, Temp c is doubled to 6 ° C. Conversely, when the color shift amount Δlen c of cyan c exceeds the upper threshold (fifth threshold) LenH c in the state of Temp c = 6 ° C., Temp c = 6 ° C. is returned to 3 ° C.

  The above-described color misregistration correction for all the non-reference colors c, m, y (9 in FIG. 6: FIG. 7) or the color misregistration correction for all the non-reference colors c, m, y (11 in FIG. 6: FIG. 8). After executing the above, while the copying machine MF1 is in the standby mode, the above-described color misregistration correction necessity determination (12 to 14 in FIG. 6: the content is FIG. 9) is substantially repeated at regular intervals. During the operation mode in which image formation is performed in accordance with a user instruction and during the energy saving mode, the color misregistration correction necessity determination (12 to 14 in FIG. 6) is not executed. Then, when it is necessary to correct the color misregistration of any color in the determination of necessity of correction (12 to 14 in FIG. 6), that is, data representing decimal number 1 or 2 in at least one of the registers RR c, m, y. Is written, color misregistration correction (15 in FIG. 6: content in FIG. 10) determined to be necessary is executed.

  In the above embodiment, the reference color is K (Bk), but K (Bk) color misregistration correction may be performed using Y, M, or C as the reference color. The above embodiment is an electrophotographic copying machine in which the respective color image forming units are arranged in tandem. However, other types of electrophotographic image forming that can transfer a visible image onto a transfer medium even if the tandem arrangement is not used. The present invention can be similarly applied to an image forming apparatus (for example, an ink jet printer) that can form a visible image on a paper transport belt, even if the apparatus is not an electrophotographic system.

1 is a longitudinal sectional view of a multi-function full-color copying machine according to an embodiment of the present invention. FIG. 2 is a plan view of the transfer belt 208 shown in FIG. 1 as viewed from above a loop. FIG. 2 is a block diagram showing an outline of an image processing system of the copying machine shown in FIG. 1. FIG. 4 is an enlarged plan view of the operation board 10 shown in FIG. 3. It is a block diagram which shows the outline | summary of the input-output processing system of the operation board 10 shown in FIG. 4 is a flowchart showing an outline of color misregistration correction control executed by an engine control 510 of the system controller 501 shown in FIG. 3. It is a flowchart which shows the content of "c, m, y color shift correction 1" (9) shown in FIG. It is a flowchart which shows the content of "c, m, y color shift correction 2" (11) shown in FIG. 7 is a flowchart showing the contents of “c color misregistration correction necessity determination” (12), “m color misregistration correction necessity determination” (13), and “y color misregistration correction necessity determination” (14) shown in FIG. It is a flowchart which shows the content of "the color shift correction | amendment of the color determined to be important" (15) shown in FIG. FIG. 6 is a block diagram showing register symbols in the determination parameter table allocated to one memory area of NVRAM 4 which is a nonvolatile memory shown in FIG. 5 and data written in the register, and is a block diagram of “initialization” (2) in FIG. A part of the setting data immediately after is shown. It is a block diagram which shows an example of the data changed by "c, m, y color shift correction 1" (9) of the determination parameter table. It is a block diagram which shows the other example of the setting data immediately after "initialization" (2) of FIG. 6 of the determination parameter table. It is a block diagram which shows the other example of the data changed by "c, m, y color shift correction 1" (9) of the determination parameter table. It is a block diagram which shows one example of the data changed by the color shift correction after "c, m, y color shift correction 1" (9) of the determination parameter table. It is a block diagram which shows an example of the data changed by "c, m, y color shift correction 2" (11) of the determination parameter table.

Explanation of symbols

10: Operation board 300: Color document scanner 120: Automatic document feeder 200: Color printer PC: Personal computer PBX: Exchanger PN: Communication line 512: Optical writing unit 204: Charging roller 205: Transfer roller 208: Transfer belts 209 to 211 : Paper feed tray 212: Registration roller pair 213: Conveying belt 214: Fixing unit 514: Power supply device

Claims (9)

Multiple color images are formed on the same sheet with color misregistration correction means that forms each color pattern on the image carrier, detects the misregistration amount, and corrects the image writing position in a direction to reduce the misregistration amount. In the color image forming apparatus
The color misregistration correcting means determines, for each color, a time until the next color misregistration correction, which is long when the color misregistration correction amount is small, and performs color misregistration correction for the color after the time has elapsed. A characteristic color image forming apparatus.   2. The color image forming apparatus according to claim 1, wherein the color misregistration correction unit extends a time until the next color misregistration correction is performed when the color misregistration correction amount is less than a first threshold value.   The color image forming apparatus according to claim 2, further comprising: a first threshold value for each color.   4. The color misregistration correction unit according to claim 2, wherein the color misregistration correction unit shortens the time until the next color misregistration correction is performed when the correction amount of the color misregistration is equal to or greater than a second threshold higher than the first threshold. Color image forming apparatus.   The color image forming apparatus further includes a temperature sensor that detects an internal temperature of the apparatus; and the color misregistration correction unit performs color misregistration correction when the internal temperature changes by a third threshold value or more from the previous color misregistration correction; The color image forming apparatus according to claim 1.   6. The color according to claim 5, wherein the color misregistration correction unit increases the third threshold when the color misregistration correction amount when performing color misregistration correction corresponding to the change in the internal temperature is smaller than a fourth threshold. Image forming apparatus.   The color image forming apparatus according to claim 6, wherein the color misregistration correction unit decreases the third threshold when the correction amount of the color misregistration is equal to or greater than a fifth threshold higher than a fourth threshold.   The color image forming apparatus according to claim 5, wherein the third threshold value is for each color. When the main power switch is switched from off to on, the image forming apparatus receives a standby voltage for operating in response to the image forming instruction in each part of the image forming apparatus in a standby mode waiting for the image forming instruction. And a power supply device that supplies a voltage for cutting off the standby voltage and returning to the standby mode when the standby mode continues for a set time; and the color misregistration correcting means is configured to output the color during the standby mode. The color image forming apparatus according to claim 1, wherein deviation correction is performed.

Images