JP5287625B2 - Image forming apparatus and positional deviation correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten downtime for a user by making earlier the timing of the start of an adjustment process, in which the position of an image in a sub-scanning direction is adjusted, in an image forming apparatus. <P>SOLUTION: A writing control part 121 emits a light beam by controlling a light source 281, and performs synchronization based on the timing of the detection of a light beam at a predetermined position in the scanning range of the reflecting mirror 280. A development bias is applied before the synchronization after the start of the rotation of the reflecting mirror 280. A light beam emitted in the synchronization of the reflecting mirror 280 is used to expose a photoreceptor drum disposed downstream of a photoreceptor drum used for drawing a pattern drawn on a beginning in displacement correction. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus and a misregistration correction method, and more particularly to shortening the startup time of an optical writing apparatus.

  In recent years, there has been a tendency to digitize information, and image processing apparatuses such as printers and facsimiles used for outputting digitized information and scanners used for digitizing documents have become indispensable devices. Such an image processing apparatus is often configured as a multifunction machine that can be used as a printer, a facsimile, a scanner, or a copier by providing an imaging function, an image forming function, a communication function, and the like.

  Among such image processing apparatuses, electrophotographic image forming apparatuses are widely used in image forming apparatuses used for outputting digitized documents. In an electrophotographic image forming apparatus, an electrostatic latent image is formed by exposing a photoreceptor, and the electrostatic latent image is developed using a developer such as toner to form a toner image. Paper output is performed by transferring the toner image onto paper.

  In such an electrophotographic image forming apparatus, by aligning the timing of forming an electrostatic latent image by exposing the photosensitive member and the timing of transporting the paper, an image is formed in the correct range of the paper. Adjustments are made. In addition, in a tandem image forming apparatus that forms a color image using a plurality of photoconductors, the exposure timing of each color photoconductor is adjusted so that the images developed on the photoconductors of each color are accurately superimposed. (For example, refer to Patent Document 1). Hereinafter, these adjustment processes are collectively referred to as misalignment correction.

  In the misregistration correction as disclosed in Patent Document 1, a timing detection pattern is formed by the same operation as a normal operation such as exposure of a photosensitive member and development of an electrostatic latent image, thereby reflecting light reflection type light. The period from the start of exposure of the photosensitive member to the reading of the timing detection image pattern is counted by the sensor. And the adjustment process is performed based on the difference between the counted period and the reference value by comparing the period thus counted with a predetermined reference value.

The above-described misregistration correction is executed when the image forming apparatus is activated, when returning from the power saving state, or before image forming output is performed. FIG. 15 shows a time chart when the image forming apparatus corrects misalignment. At the time of executing the above-described misregistration correction, the image forming mechanism included in the image forming apparatus is in a pause state. Therefore, as shown in FIG. 15, first, at timing t ₀ , the motor of the reflecting mirror that operates the laser beam for exposing the photosensitive member in the main scanning direction is started and waits until the rotation of the motor is stabilized.

When the rotation of the motor is stabilized, at the timing t _1, the process for optical writing device for irradiating a laser beam synchronized with the rotation of the motor is performed. In this process, the laser beam reflected and scanned by the reflecting mirror that is irradiated and rotated by the optical writing device is incident on the synchronous detection sensor provided near the end of the scanning range, and the detection output thereby. The optical writing device receives the signal. Based on the reception timing of this detection signal, the optical writing device recognizes synchronization in the main scanning direction, that is, writing start timing of an image for one line.

When the optical writing device has completed synchronization with the rotation of the motor, at time t _2, application of the developing bias for developing an electrostatic latent image formed on the photosensitive drum is started and waits until the stabilization . Then, at the timing t ₃ when the developing bias is stabilized, the drawing of a pattern for positional deviation correction is started. As described above, various kinds of processing are required before starting the misregistration correction.

  The period required for the above-described misregistration correction is, for example, about 10 to 20 seconds, and the user needs to wait for this period. In other words, the period of the positional deviation correction is a downtime for the user, and it is desired to shorten it.

Here, as one policy for shortening the downtime for the user, it is conceivable to shorten the downtime by accelerating the end timing of the misalignment correction by increasing the timing of starting the misalignment correction. Then, in order to advance the start timing of the displacement correction, among the processes of each described in FIG. 15, it is conceivable to shorten or parallel processing performed in a period from the timing t ₀ to time t ₃ .

Here, it is considered that the motor start-up and stabilization process executed in the period from t ₀ to t ₁ and the development bias start-up and stabilization process executed in the period from t ₂ to t ₃ are parallelized. . In this case, it is possible to start the image formation of the misregistration correction pattern at the timing t2 shown in FIG. Since these processes are independent processes, it is not impossible to parallelize them.

However, in the rotation synchronization process executed in the period from t ₁ to t _2, the synchronization is performed by irradiating the laser beam for exposing the photosensitive member and causing the laser beam to enter the synchronization detection sensor. There is a possibility that the photosensitive member is exposed by the laser beam scanned by. Therefore, when the rotation synchronization processing is performed in a state where the bias is activated, the portion of the photosensitive member exposed by the laser beam is developed, and the developed image is transferred to the transfer target.

  After the rotation synchronization process is completed, pattern drawing is started for the misregistration correction process as shown in FIG. Here, as described above, when an image is transferred to the transfer target in the rotation synchronization processing, it is determined whether the image is an image formed in the rotation synchronization processing or a pattern for correcting misalignment. It becomes difficult.

  As described above, one of the reasons why it is difficult to determine whether an image has been formed in the rotation synchronization process or a pattern for correcting misalignment is that the image is formed in the rotation synchronization process. It is that it may not be formed.

  That is, in the rotation synchronization process, when the synchronization detection sensor detects the laser beam and outputs a detection signal, the irradiation of the laser beam is stopped. Therefore, if the timing at which laser beam irradiation is started is the timing before the laser beam reaches the synchronization detection sensor after passing through the photoconductor, the laser beam is irradiated before the photoconductor drum is scanned. Is stopped, the photoconductor is not exposed and no image is formed.

  In contrast, if irradiation starts after the laser beam passes through the rotation detection sensor and before passing through the photosensitive drum, the laser beam reaches the rotation detection sensor again after passing over the photosensitive member. The body is exposed and an image is formed.

  If an image different from the misregistration correction pattern is necessarily formed, the first image may be excluded from the images detected by the misregistration correction sensor. However, it is difficult to exclude an image whose formation is unknown or not only when it is formed. If the image is not formed even if it is mounted, the first pattern of the misregistration correction pattern Such a problem is considered that the positional deviation correction is not accurately executed.

  The present invention has been made in consideration of the above circumstances, and aims to shorten the downtime for the user by advancing the start timing of the adjustment process for adjusting the position of the image in the sub-scanning direction in the image forming apparatus. And

  In order to solve the above problems, according to one embodiment of the present invention, a light source that irradiates a plurality of photoconductors arranged in the sub-scanning direction is controlled to irradiate the light beam, and the photoconductor is statically placed on the photoconductor. A light source control unit for forming an electrostatic latent image, and voltage control for controlling a voltage applied between the photosensitive member and a developing unit when the electrostatic latent image formed on the photosensitive member is developed with a developer. And the image transferred on the surface of the carrier has reached a position facing the sensor based on an output signal of a sensor that images the surface of the carrier on which the developed image is transferred onto the photosensitive member. And a detection period counting unit that counts a detection period from when the light source control unit starts drawing a predetermined pattern to when the image detection unit detects the predetermined pattern. And the light source control unit A reference value acquisition unit that acquires a reference value that is a value of a reference period from when image drawing starts to when the image detection unit detects the predetermined pattern; and the counted detection period and the A correction value calculation unit that calculates a correction value for correcting the timing of irradiating the light source with the light beam based on the difference between the acquired reference values, and the light source control unit controls the light source to emit light. Irradiating a beam and performing synchronization with the rotation of the rotating reflector based on the detection timing of the light beam at a predetermined position in the scanning range of the rotating reflector that scans the irradiated light beam in the main scanning direction, The voltage control unit starts application of a voltage between the photosensitive member and the developing device before the rotation reflector starts rotating and the light source control unit synchronizes with the rotation reflector, and the light source The controller The light beam irradiated when synchronizing with the rotation of the reflecting mirror is arranged on the downstream side in the transport direction of the transport body with respect to the first photoconductor for drawing the pattern drawn at the head of the predetermined pattern. In the period when the image detection unit detects the pattern drawn at the head, the pattern drawn at the head reaches a position corresponding to the sensor. This is a predetermined period before and after the theoretical value, and the predetermined period is a distance from the transfer position of the first photoconductor to the transfer position of the second photoconductor than the period during which the transport body is transported. It is characterized by a short period.

  Here, it is preferable that the first photoconductor is disposed on the most upstream side in the transport direction of the transport body among the plurality of photoconductors arranged in a row.

  Further, it is preferable that the second photoconductor is arranged on the most downstream side in the transport direction of the transport body among the plurality of photoconductors arranged in a row.

  Further, it is preferable that the predetermined period is a period shorter than a period in which the transport body is transported between transfer positions of adjacent photoreceptors in the plurality of photoreceptors arranged side by side.

  The light beam applied to the first photoconductor and the light beam applied to the second photoconductor are scanned by the same surface among the plurality of reflecting surfaces included in the rotary reflecting mirror. It is preferable.

  Further, it is preferable that the light source control unit stops the irradiation of the light beam in response to the detection of the light beam in synchronization with the rotation of the rotary reflecting mirror.

  Further, it is preferable that the light beam irradiated when the light source control unit synchronizes with the rotation of the rotary reflecting mirror is a light beam irradiated on the photosensitive member developed with a color other than black.

  The light source control unit preferably starts drawing the predetermined pattern within a predetermined period after detecting the light beam in synchronization with the rotation of the rotary reflecting mirror.

  Further, it is preferable that a theoretical value at which a pattern drawn at the head reaches a position corresponding to the sensor is the reference value.

  According to another aspect of the present invention, an electrostatic latent image is formed on the photoconductor by controlling a light source that irradiates a light beam to a plurality of photoconductors arranged in the sub-scanning direction. A light source controller, a voltage controller for controlling a voltage applied between the photosensitive member and a developing device when the electrostatic latent image formed on the photosensitive member is developed with a developer, and the photosensitive member An image for detecting that an image transferred to the surface of the carrier has reached a position facing the sensor based on an output signal of a sensor that images the surface of the carrier to which the developed image is transferred. A detection unit, a detection period counting unit that counts a detection period from when the light source control unit starts drawing a predetermined pattern to when the image detection unit detects the predetermined pattern, and the light source control Starts drawing a predetermined pattern A reference value acquisition unit that acquires a reference value that is a value of a reference period until the image detection unit detects the predetermined pattern, and a difference between the counted detection period and the acquired reference value And a correction value calculation unit for calculating a correction value for correcting a timing for irradiating the light source with the light beam based on the position correction method in the optical writing device of the image forming apparatus, wherein the light source control unit includes: , Controlling the light source to irradiate the light beam, and scanning the irradiated light beam in the main scanning direction based on the detection timing of the light beam at a predetermined position in the scanning range of the rotating reflector. The voltage control unit performs synchronization between the photosensitive member and the developing unit before the rotation reflecting mirror starts rotating and the light source control unit synchronizes with the rotating reflection mirror. Application of pressure is started, and when the light source control unit synchronizes with the rotation of the rotary reflecting mirror, the conveyance is performed more than the first photoconductor that draws a pattern drawn at the head in the predetermined pattern. A theory that irradiates a second photoconductor disposed on the downstream side of the body conveyance direction with a light beam, and that the image detection unit reaches a position where the pattern drawn at the head corresponds to the sensor. The interval between the transfer position of the first photoconductor and the transfer position of the second photoconductor is a period before and after the value, and is drawn at the head in a period shorter than the period in which the transport body is transported. It is characterized by detecting a pattern.

  According to the present invention, in the image forming apparatus, the start timing of the adjustment process for adjusting the position of the image in the sub-scanning direction can be advanced, and the downtime for the user can be shortened.

1 is a block diagram illustrating a hardware configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a functional configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a configuration of a print engine according to an embodiment of the present invention. It is a top view which shows the structure of the optical writing apparatus which concerns on embodiment of this invention. It is a sectional side view which shows the structure of the optical writing apparatus which concerns on embodiment of this invention. It is a block diagram which shows the control part of the optical writing apparatus which concerns on embodiment of this invention. It is a figure which shows the information memorize | stored in the reference value memory | storage part which concerns on embodiment of this invention. It is a figure which shows the example of the pattern drawn in the position shift correction operation | movement which concerns on embodiment of this invention. It is a flowchart which shows the position shift correction operation | movement which concerns on embodiment of this invention. FIG. 3 is a diagram illustrating a configuration of a print engine according to an embodiment of the present invention and a position of a drawn pattern. FIG. 3 is a diagram illustrating a configuration of a print engine according to an embodiment of the present invention and a positional relationship between drawn patterns. FIG. 4 is a diagram illustrating a configuration of a print engine according to an embodiment of the present invention and a positional relationship between conveyed patterns. It is a figure which shows the time series in the position shift correction operation | movement which concerns on embodiment of this invention, and the position shift correction operation which concerns on a prior art. It is a figure which shows the positional relationship of the structure of the print engine which concerns on other embodiment of this invention, and the pattern conveyed. It is a figure which shows the time series in the position shift correction operation | movement which concerns on a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, an image forming apparatus as an MFP (Multi Function Peripheral) will be described as an example. The image forming apparatus according to the present embodiment is an electrophotographic image forming apparatus, and the timing for completing the correction of the image writing position in the optical writing apparatus for forming an electrostatic latent image on the photosensitive member is advanced. It is a gist.

  FIG. 1 is a block diagram illustrating a hardware configuration of an image forming apparatus 1 according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 according to the present embodiment includes an engine that executes image formation in addition to the same configuration as an information processing terminal such as a general server or a PC (Personal Computer). That is, the image forming apparatus 1 according to the present embodiment includes a CPU (Central Processing Unit) 10, a RAM (Random Access Memory) 11, a ROM (Read Only Memory) 12, an engine 13, an HDD (Hard Disk Drive) 14, and an I / O. F15 is connected via the bus 18. Further, an LCD (Liquid Crystal Display) 16 and an operation unit 17 are connected to the I / F 15.

  The CPU 10 is a calculation unit and controls the operation of the entire image forming apparatus 1. The RAM 11 is a volatile storage medium capable of reading and writing information at high speed, and is used as a work area when the CPU 10 processes information. The ROM 12 is a read-only nonvolatile storage medium, and stores programs such as firmware. The engine 13 is a mechanism that actually executes image formation in the image forming apparatus 1.

  The HDD 14 is a nonvolatile storage medium capable of reading and writing information, and stores an OS (Operating System), various control programs, application programs, and the like. The I / F 15 connects and controls the bus 18 and various hardware and networks. The LCD 16 is a visual user interface for the user to check the state of the image forming apparatus 1. The operation unit 17 is a user interface such as a keyboard and a mouse for the user to input information to the image forming apparatus 1.

  In such a hardware configuration, a program stored in a recording medium such as the ROM 12, the HDD 14, or an optical disk (not shown) is read into the RAM 11 and operates according to the control of the CPU 10, thereby configuring a software control unit. A functional block that realizes the functions of the image forming apparatus 1 according to the present embodiment is configured by a combination of the software control unit configured as described above and hardware.

  Next, the functional configuration of the image forming apparatus 1 according to the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating a functional configuration of the image forming apparatus 1 according to the present embodiment. As shown in FIG. 2, the image forming apparatus 1 according to the present embodiment includes a controller 20, an ADF (Auto Document Feeder) 110, a scanner unit 22, a paper discharge tray 23, a display panel 24, and a paper feed table. 25, a print engine 26, a paper discharge tray 27, and a network I / F 28.

  The controller 20 includes a main control unit 30, an engine control unit 31, an input / output control unit 32, an image processing unit 33, and an operation display control unit 34. As shown in FIG. 2, the image forming apparatus 1 according to the present embodiment is configured as a multifunction machine having a scanner unit 22 and a print engine 26. In FIG. 2, the electrical connection is indicated by solid arrows, and the flow of paper is indicated by broken arrows.

  The display panel 24 is an output interface that visually displays the state of the image forming apparatus 1 and is an input when the user directly operates the image forming apparatus 1 or inputs information to the image forming apparatus 1 as a touch panel. It is also an interface (operation unit). The network I / F 28 is an interface for the image forming apparatus 1 to communicate with other devices via the network, and uses an Ethernet (registered trademark) or a USB (Universal Serial Bus) interface.

  The controller 20 is configured by a combination of software and hardware. Specifically, a control program such as firmware stored in a nonvolatile recording medium such as the ROM 12 and the nonvolatile memory and the HDD 14 and the optical disk is loaded into a volatile memory (hereinafter referred to as a memory) such as the RAM 11 to control the CPU 10. The controller 20 is configured by a software control unit configured according to the above and hardware such as an integrated circuit. The controller 20 functions as a control unit that controls the entire image forming apparatus 1.

  The main control unit 30 plays a role of controlling each unit included in the controller 20 and gives a command to each unit of the controller 20. The engine control unit 31 serves as a drive unit that controls or drives the print engine 26, the scanner unit 22, and the like. The input / output control unit 32 inputs a signal or a command input via the network I / F 28 to the main control unit 30. The main control unit 30 controls the input / output control unit 32 and accesses other devices via the network I / F 28.

  The image processing unit 33 generates drawing information based on the print information included in the input print job under the control of the main control unit 30. The drawing information is information for drawing an image to be formed in the image forming operation by the print engine 26 as an image forming unit. The print information included in the print job is image information converted into a format that can be recognized by the image forming apparatus 1 by a printer driver installed in an information processing apparatus such as a PC. The operation display control unit 34 displays information on the display panel 24 or notifies the main control unit 30 of information input via the display panel 24.

  When the image forming apparatus 1 operates as a printer, first, the input / output control unit 32 receives a print job via the network I / F 28. The input / output control unit 32 transfers the received print job to the main control unit 30. When receiving the print job, the main control unit 30 controls the image processing unit 33 to generate drawing information based on the print information included in the print job.

  When drawing information is generated by the image processing unit 33, the engine control unit 31 performs image formation on the paper conveyed from the paper feed table 25 based on the generated drawing information. That is, the print engine 26 functions as an image forming unit. A document on which an image has been formed by the print engine 26 is discharged to a discharge tray 27.

  When the image forming apparatus 1 operates as a scanner, the operation display control unit 34 or the input / output unit is operated in accordance with a user operation on the display panel 24 or a scan execution instruction input from an external PC or the like via the network I / F 28. The control unit 32 transfers a scan execution signal to the main control unit 30. The main control unit 30 controls the engine control unit 31 based on the received scan execution signal.

  The engine control unit 31 drives the ADF 21 and conveys the document to be imaged set on the ADF 21 to the scanner unit 22. Further, the engine control unit 31 drives the scanner unit 22 and images a document conveyed from the ADF 21. If no original is set on the ADF 21 and the original is directly set on the scanner unit 22, the scanner unit 22 takes an image of the set original under the control of the engine control unit 31. That is, the scanner unit 22 operates as an imaging unit.

  In the imaging operation, an imaging element such as a CCD included in the scanner unit 22 optically scans the document, and imaging information generated based on the optical information is generated. The engine control unit 31 transfers the imaging information generated by the scanner unit 22 to the image processing unit 33. The image processing unit 33 generates image information based on the imaging information received from the engine control unit 31 according to the control of the main control unit 30. Image information generated by the image processing unit 33 is stored in a storage medium attached to the image forming apparatus 1 such as the HDD 40. That is, the scanner unit 22, the engine control unit 31, and the image processing unit 33 work together to function as a document reading unit.

  The image information generated by the image processing unit 33 is stored in the HDD 40 or the like as it is according to a user instruction or transmitted to an external device via the input / output control unit 32 and the network I / F 28. That is, the ADF 21 and the engine control unit 31 function as an image input unit.

  Further, when the image forming apparatus 1 operates as a copying machine, the image processing unit 33 generates drawing information based on the imaging information received by the engine control unit 31 from the scanner unit 22 or the image information generated by the image processing unit 33. To do. Based on the drawing information, the engine control unit 31 drives the print engine 26 as in the case of the printer operation.

  Next, the configuration of the print engine 26 according to the present embodiment will be described with reference to FIG. As shown in FIG. 3, the print engine 26 according to the present embodiment includes a configuration in which image forming units 106 of respective colors are arranged along a conveyor belt 105 that is an endless moving unit, which is a so-called tandem type. It is what is said. That is, along the transport belt 105 that transports the paper (recording paper) 104 separated and fed by the paper feed roller 102 and the separation roller 103 from the paper feed tray 101, the transport belt 105 is sequentially transported from the upstream side in the transport direction. A plurality of image forming units (electrophotographic process units) 106BK, 106M, 106C, and 106Y are arranged.

  The plurality of image forming units 106BK, 106M, 106C, and 106Y have the same internal configuration except that the colors of the toner images to be formed are different. The image forming unit 106BK forms a black image, the image forming unit 106M forms a magenta image, the image forming unit 106C forms a cyan image, and the image forming unit 106Y forms a yellow image. In the following description, the image forming unit 106BK will be described in detail. However, since the other image forming units 106M, 106C, and 106Y are the same as the image forming unit 106BK, the image forming units 106M, 106C, and 106Y are similar to the image forming unit 106BK. As for each of the components, only the symbols distinguished by M, C, and Y are displayed in the drawing in place of the BK attached to each component of the image forming unit 106BK, and the description thereof is omitted.

  The conveying belt 105 is an endless belt, that is, an endless belt that is stretched between a driving roller 107 and a driven roller 108 that are rotationally driven. The drive roller 107 is driven to rotate by a drive motor (not shown), and the drive motor, the drive roller 107, and the driven roller 108 function as a drive unit that moves the conveyance belt 105 that is an endless moving unit. .

  At the time of image formation, the paper 104 stored in the paper feed tray 101 is sent out in order from the top, and the first image forming unit 106BK is conveyed by the conveyance belt 105 that is attracted to and rotated by the conveyance belt 105 by electrostatic adsorption action. Where the black toner image is transferred. That is, the conveyance belt 105 functions as a conveyance body that conveys a sheet that is an image transfer target.

  The image forming unit 106BK includes a photoconductor drum 109BK as a photoconductor, a charger 110BK arranged around the photoconductor drum 109BK, an optical writing device 111, a developing device 112BK, a photoconductor cleaner (not shown), and a static eliminator. 113BK and the like. The optical writing device 111 is configured to irradiate the respective photosensitive drums 109BK, 109M, 109C, and 109Y (hereinafter collectively referred to as the photosensitive drum 109) with a laser beam.

  At the time of image formation, the outer peripheral surface of the photosensitive drum 109BK is uniformly charged by the charger 110BK in the dark, and then writing is performed by a laser beam corresponding to the black image from the optical writing device 111. An image is formed. The developing device 112BK visualizes the electrostatic latent image with black toner, thereby forming a black toner image on the photosensitive drum 109BK.

  This toner image is transferred onto the sheet 104 by the action of the transfer unit 115BK at a position (transfer position) where the photosensitive drum 109BK and the sheet 104 on the conveying belt 105 contact each other. By this transfer, an image of black toner is formed on the paper 104. After the transfer of the toner image is completed, unnecessary toner remaining on the outer peripheral surface of the photosensitive drum 109BK is wiped off by the photosensitive cleaner, and then the charge is removed by the charge eliminator 113BK, and waits for the next image formation.

  As described above, the sheet 104 on which the black toner image is transferred by the image forming unit 106BK is transported to the next image forming unit 106M by the transport belt 105. In the image forming unit 106M, a magenta toner image is formed on the photosensitive drum 109M by a process similar to the image forming process in the image forming unit 106BK, and the toner image is superimposed on the black image formed on the paper 104. And is transcribed.

  The sheet 104 is further conveyed to the next image forming units 106C and 106Y, and a cyan toner image formed on the photoconductive drum 109C and a yellow toner image formed on the photoconductive drum 109Y by the same operation. Are superimposed on the sheet 104 and transferred. In this way, a full color image is formed on the sheet 104. The sheet 104 on which the full-color superimposed image is formed is peeled off from the conveying belt 105 and the image is fixed by the fixing device 116, and then discharged to the outside of the image forming apparatus.

  In such an image forming apparatus 1, errors in the interaxial distances of the photosensitive drums 109 BK, 109 M, 109 C, and 109 Y, parallelism errors in the photosensitive drums 109 BK, 109 M, 109 C, and 109 Y, and deflection in the optical writing device 111. The toner images of each color do not overlap at positions that should originally overlap due to errors in the installation of mirrors, writing timing errors of electrostatic latent images on the photosensitive drums 109BK, 109M, 109C, and 109Y. May occur. Further, the positional deviation may occur again even after the positional deviation is corrected due to the expansion / contraction of the conveyor belt due to the temperature change in the apparatus or deterioration with time.

  For the same reason, the image may be transferred to a range that is outside the range where the image is originally transferred on the paper to be transferred. As such misregistration components, skew, sub-scan registration error, magnification error in the main scanning direction, registration error in the main scanning direction, and the like are mainly known.

  A pattern detection sensor 117 is provided to correct such positional deviation. The pattern detection sensor 117 is an optical sensor for reading a misregistration correction pattern transferred onto the conveyance belt 105 by the photosensitive drums 109BK, 109M, 109C, and 109Y, and is used for correction drawn on the surface of the conveyance belt 105. A light emitting element for irradiating the pattern and a light receiving element for receiving reflected light from the correction pattern are included. As shown in FIG. 3, the pattern detection sensor 117 is supported on the same substrate along the direction orthogonal to the conveyance direction of the conveyance belt 105 on the downstream side of the photosensitive drums 109BK, 109M, 109C, and 109Y. . The details of the pattern detection sensor 117 and the mode of positional deviation correction will be described in detail later.

  Next, the optical writing device 111 according to the present embodiment will be described. FIG. 4 is a view of the optical writing device 111 according to the present embodiment as viewed from above. FIG. 5 is a cross-sectional view of the optical writing device according to the present embodiment as viewed from the side. As shown in FIGS. 4 and 5, the laser beams to be written on the photosensitive drums 109BK, 109M, 109C, and 109Y of the respective colors are light source devices 281BK, 281M, 281C, and 281Y as light sources (hereinafter collectively referred to as the light source device 281). ). Note that the light source device 281 according to the present embodiment includes a semiconductor laser, a collimator lens, a slit, a prism, a cylinder lens, and the like.

  The laser beam emitted from the light source device 281 is reflected by the reflecting mirror 280. Each laser beam is guided to mirrors 282BK, 282M, 282C, and 282Y (hereinafter collectively referred to as 282) by an optical system such as an fθ lens (not shown), and further, the photosensitive drums 109BK, 109M, and 109C are further advanced by the optical system. , 109Y is scanned.

  The reflecting mirror 280 is a hexahedral polygon mirror, and can rotate by scanning the laser beam corresponding to the line in the main scanning direction per polygon mirror surface. The optical writing device 111 according to this embodiment divides the four light source devices into light source devices of two colors of 281BK, 281M, and 281C, 281Y, and performs scanning using different reflecting surfaces of the reflecting mirror 280. It is possible to write on four different photosensitive drums at the same time with a more compact configuration than the scanning method using only one reflecting surface.

  In addition, a horizontal synchronization detection sensor 283 is provided in the vicinity of the scanning start position in the range where the laser beam is scanned by the reflecting mirror 280. When the laser beam emitted from the light source device 281 enters the horizontal synchronization detection sensor 283, the timing of the scanning start position of the main scanning line is detected, and the control device that controls the light source device 281 and the reflecting mirror 280 are synchronized. Be taken.

  Next, a control block of the optical writing device 111 according to the present embodiment will be described with reference to FIG. FIG. 6 is a diagram illustrating a functional configuration of the optical writing device control unit 120 that controls the optical writing device 111 according to the present embodiment and a connection relationship between the light source device 281, the horizontal synchronization detection sensor 283, and the pattern detection sensor 117. .

  As shown in FIG. 6, the optical writing device control unit 120 according to the present embodiment includes a writing control unit 121, a counting unit 122, a sensor control unit 123, a correction value calculation unit 124, a reference value storage unit 125, and a correction value storage unit. 126. The optical writing device 111 according to the present embodiment includes information processing mechanisms such as the CPU 10, RAM 11, ROM 12, and HDD 14 as described in FIG. 1, and the optical writing device control unit 120 as shown in FIG. Similar to the controller 20 of the forming apparatus 1, a control program stored in the ROM 12 or the HDD 14 is loaded into the RAM 11 and is operated under the control of the CPU 10.

  The writing control unit 121 is a light source control unit that controls the light source device 281 in accordance with a synchronization detection signal from the horizontal synchronization detection sensor 283 based on image information input from the engine control unit 31 of the controller 20. In addition to driving the light source device 281 based on the image information input from the engine control unit 31, the write control unit 121 also draws a pattern for correcting misalignment in the misalignment correction process described above. 281 is driven. The correction value generated as a result of this misalignment correction processing is stored in the correction value storage unit 126 shown in FIG. 6, and the writing control unit 121 uses the light source based on the correction value stored in this correction value storage unit 126. The timing for driving the device 281 is corrected.

  Further, the writing control unit 121 includes a function of acquiring a detection signal from the horizontal synchronization detection sensor 283 and performing synchronization with the rotation of the reflecting mirror 280 as described with reference to FIG. Further, when the electrostatic latent image formed on the photosensitive drum 109 is developed with toner as a developer, the writing control unit 121 and the photosensitive drums 109BK, 109M, 109C, and 109Y and the developing units 112BK and 112M are developed. , 112C, 112Y also functions as a voltage control unit that controls the voltage applied between them.

  In the misregistration correction process, the count unit 122 starts counting at the same time when the writing control unit 121 controls the light source device 281 to start exposure of the photosensitive drum 109BK. The count unit 122 stops counting when the sensor control unit 123 detects the pattern based on the output signal of the pattern detection sensor 117. As a result, in the above-described misregistration correction processing, the count unit 122 controls the light source device 281 to start the exposure of the photosensitive drum 109BK in the above-described misregistration correction process. It functions as a detection period counting unit that counts the detection period until a pattern is detected. Hereinafter, this count value is referred to as a write start count value. Further, the count unit 122 counts the detection timings of the continuously drawn patterns in the positional deviation correction process for correcting the deviation of the toner images of the respective colors. Hereinafter, this count value is referred to as a drum interval count value.

  The sensor control unit 123 is a control unit that controls the pattern detection sensor 117. As described above, the misregistration correction pattern formed on the conveyance belt 105 is subjected to pattern detection based on the output signal of the pattern detection sensor 117. It is an arrival determination unit that determines that the position of the sensor 117 has been reached. When the sensor control unit 123 determines that the position deviation correction pattern has reached the position of the pattern detection sensor 117 as described above, the sensor control unit 123 inputs a detection signal to the count unit 122. That is, the sensor control unit 123 functions as an image detection unit.

  The correction value calculation unit 124 calculates a correction value based on the reference value stored in the reference value storage unit 125 based on the count result by the counting unit 122. That is, the correction value calculation unit 124 functions as a reference value acquisition unit and a correction value calculation unit. FIG. 7 shows an example of reference values stored in the reference value storage unit 125. As shown in FIG. 7, the reference value storage unit 125 stores a writing start timing reference value and a drum interval reference value.

  The write start timing reference value is a period from when the write control unit 121 controls the light source device 281 to start exposure of the photosensitive drum 109BK to when the pattern detection sensor 117 detects a pattern for correcting misalignment. Is the reference value. That is, the correction value calculation unit 124 compares the write start count value with the write start timing reference value among the count values by the count unit 122, and calculates a correction value based on the difference between the two.

  The drum interval reference value is a reference value of the detection timing for each of the continuously drawn patterns as described above. That is, the correction value calculation unit 124 compares the drum interval count value with the drum interval reference value among the count values of the counting unit 122, and calculates a correction value based on the difference between the two. The correction value calculated in this way is stored in the correction value storage unit 126 as described above. Thus, by storing the correction value in the correction value storage unit 126, the writing control unit 121 can drive the light source device 281 with reference to the correction value.

  Next, the misregistration correction operation according to the present embodiment will be described with reference to FIG. FIG. 8 is a diagram showing marks (hereinafter referred to as misalignment correction marks) drawn on the transport belt 105 by the light source device 281 controlled by the writing control unit 121 in the misalignment correction operation according to the present embodiment. It is. As shown in FIG. 8, the misregistration correction mark 400 according to this embodiment includes a plurality of misregistration correction pattern rows 401 in which various patterns are arranged in the sub-scanning direction (this embodiment). 3) are arranged side by side. In FIG. 8, the solid line represents the pattern drawn by the photosensitive drum 109BK, the dotted line represents the photosensitive drum 109Y, the broken line represents the photosensitive drum 109C, and the alternate long and short dash line represents the pattern drawn by the photosensitive drum 109M.

  As shown in FIG. 8, the pattern detection sensor 117 has a plurality (three in the present embodiment) of sensor elements 170 in the main scanning direction, and each misalignment correction pattern row 401 includes each sensor element. It is drawn at a position corresponding to 170. Accordingly, the optical writing control device 120 can detect a pattern at a plurality of positions in the main scanning direction, and can improve the accuracy of the misregistration correction operation by calculating the average value of each.

  As illustrated in FIG. 8, the misalignment correction pattern row 401 includes a start position correction pattern 411 and a drum interval correction pattern 412. As shown in FIG. 8, the drum interval correction pattern 412 is repeatedly drawn. The start position correction pattern 411 is a pattern drawn in order to count the write start count value described above. The start position correction pattern 411 is also used for correcting the detection timing when the sensor control unit 123 detects the drum interval correction pattern 412.

  As shown in FIG. 8, the start position correction pattern 411 according to this embodiment is a line drawn by the photosensitive drum 109BK and parallel to the main scanning direction. In the start position correction using the start position correction pattern 411, the optical writing device control unit 120 performs a write start timing correction operation based on the read signal of the start position correction pattern 411 by the pattern detection sensor 117. In other words, the writing start timing reference value stored in the reference value storage unit 125 is the same as the drawn black after the light source device 281 starts drawing the black pattern on the photosensitive drum 109BK in the start position correction pattern 411. This value is a reference value for the period until the pattern is read by the pattern detection sensor 117 and detected by the sensor control unit 123.

  As the name suggests, the drum interval correction pattern 412 is a pattern drawn to count the drum interval count value described above. As shown in FIG. 8, the drum interval correction pattern 412 includes a sub-scanning direction correction pattern 413 and a main scanning direction correction pattern 414. The optical writing device control unit 120 corrects the positional deviation in the sub-scanning direction of each of the photosensitive drums 109BK, 109M, 109C, and 109Y based on the reading signal of the sub-scanning direction correction pattern 413 by the pattern detection sensor 117. Based on the read signal of the scanning direction correction pattern 414, the positional deviation correction of each photosensitive drum in the main scanning direction is performed.

  That is, the drum interval reference value stored in the reference value storage unit 125 is the drum interval correction value that is drawn after the light source device 281 starts drawing the drum interval correction pattern 412 under the control of the writing control unit 121. Each line included in the pattern 412 for use is a value serving as a reference for a period until the line is read by the pattern detection sensor 117 and detected by the sensor control unit 123.

  In such an aspect of the image forming apparatus 1 and the misregistration correction operation, the gist of the present embodiment is that the position required by starting the misregistration correction operation is shortened by shortening the period required to start the misregistration correction operation. It is to shorten the downtime for the user by advancing the completion timing of the deviation correction operation. The misregistration correction operation according to this embodiment will be described with reference to FIG.

  FIG. 9 is a flowchart showing the misalignment correction operation according to this embodiment. When the misregistration correction operation is started, first, a motor that rotates the reflecting mirror 280 in the optical writing device 111 is activated, and in the image forming units 106BK, 106M, 106C, and 106Y, the developing devices 112BK, 112M, 112C, The developing bias for 112Y to develop the electrostatic latent image is activated (S901).

  When the motor is started, it waits until the motor speed is stabilized (S902 / NO). When the motor speed is stabilized (S902 / YES), the optical writing device 111 is synchronized with the motor. Irradiate a light beam (S903). As shown in FIG. 3, the optical writing device 111 can individually irradiate a light beam corresponding to each of the photosensitive drums 109BK, 109M, 109C, and 109Y. Here, the optical writing device 111 according to the present embodiment irradiates only the light beam for exposing the photosensitive drum 109Y in S903. This is one of the gist according to the present embodiment. Note that the synchronization timing of the photosensitive drums other than the photosensitive drum 109Y can be calculated based on the synchronization timing of the photosensitive drum 109Y.

  As described in FIG. 4, the optical writing device 111 continues to output the light beam until the horizontal synchronization detection sensor 283 detects the light beam and outputs a detection signal to the optical writing device control unit 120 (S904 / NO). ). If the irradiation start timing of the light beam in S903 is after passing through the horizontal synchronization detection sensor 283 and before passing through the mirror 282Y in the scanning direction shown in FIG. 4, the light beam is guided to the photosensitive drum 109Y, and is exposed to light. An electrostatic latent image is formed on the body drum 109Y.

  Here, since the developing bias has already been activated in S901, the electrostatic latent image formed on the photosensitive drum 109Y is developed by the developing device 112Y and transferred onto the conveying belt 105. Thereby, as shown in FIG. 10, the surplus pattern 402 is formed on the conveyance belt 105. The surplus pattern 402 is an extra pattern, and the gist of the present embodiment is to prevent the surplus pattern 402 from causing a problem in the subsequent misalignment correction.

  When the horizontal synchronization detection sensor 283 detects the light beam and outputs a detection signal to the optical writing device control unit 120 (S904 / YES), the writing control unit 121 of the optical writing device control unit 120 performs irradiation for the above-described synchronization detection. The light source device 281 is controlled to stop the irradiation of the light beam, and the misalignment correction mark 400 shown in FIG. 8 is drawn, and the count unit 122 starts counting (S905). As described with reference to FIG. 8, since the leading pattern of the misregistration correction mark 400 is the start position correction pattern 411, the start position correction pattern 411 is generated by the photosensitive drum 109BK as shown in FIG. Formed and transferred onto the conveyor belt 105.

  Note that the interval from “YES” in S904 to S905 is very short, and as shown in FIG. 11, the surplus pattern 402 formed between S903 and S904 is almost moved from the position of the photosensitive drum 109Y. Not done. When the start position correction pattern 411 that is the first pattern reaches the detection position of the pattern detection sensor 117 after the image formation of the position deviation correction mark 400 is started in S905, the sensor control unit 123 causes the pattern detection sensor 117 to start. The start position correction pattern is detected based on the output signal (S906).

  Here, the pattern detection sensor 117 and the sensor control unit 123 according to the present embodiment do not always detect a pattern, but detect a pattern only during a predetermined period. In the case of the present embodiment, the sensor control unit 123 starts from the exposure for the optical writing device 111 to draw the start position correction pattern 411 until the start position correction pattern 411 reaches the pattern detection sensor 117. That is, the pattern is detected from a predetermined period before the write start timing reference value described in FIG.

  Here, the predetermined period is a maximum value that can be considered as an error between the actual detection timing of the start position correction pattern 411 and the above-described theoretical value. It is. Therefore, when the predetermined period is 10 mm, the sensor control unit 123 detects the start position correction pattern 411 in a period of 10 mm before and after the writing start timing reference value, that is, a period of 20 mm.

  In the transition from S904 to S905, the writing control unit 121 sets the horizontal synchronization timing in accordance with the output signal of the horizontal synchronization detection sensor 283, and then starts drawing the misregistration correction mark 400 within a predetermined period. To do. This predetermined period is, for example, the half of the detection period of the above-described start position correction pattern 411, that is, the maximum value considered as an error between the actual detection timing of the start position correction pattern 411 and the above-described theoretical value. is there. Not only this value but also the start timing of misalignment correction can be advanced by making the transition from S904 to S905 as early as possible.

  An example of the timing at which the start position correction pattern 411 reaches the detection position of the pattern detection sensor 117 is shown in FIG. As shown in FIG. 12, at the timing when the start position correction pattern 411 reaches the detection position of the pattern detection sensor 117, the surplus pattern 402 is further conveyed further. Therefore, when the sensor control unit 123 detects the start position correction pattern 411 in the detection period as described above, the surplus pattern 402 is not detected, and the surplus pattern 402 is detected by the start position correction pattern 411. This will not cause a problem.

  When the sensor control unit 123 detects the start position correction pattern 411, the count unit 122 acquires the above-described count value based on the detection result (S907) and inputs it to the correction value calculation unit 124. In S <b> 907, the count unit 122 acquires the count value for each of the plurality of sensor elements 170 and inputs the count value to the correction value calculation unit 124.

  When the correction value calculation unit 124 acquires a plurality of count values from the count unit 122, the correction value calculation unit 124 obtains an average value thereof (S908), calculates a correction value based on the average value and the reference value described above, and stores the correction value. The data is stored in the unit 126 (S909), and the process is terminated. With such processing, the misregistration correction operation according to the present embodiment is completed.

The effects of the misregistration correction operation according to this embodiment will be described with reference to FIGS. 13 (a) and 13 (b). FIG. 13A is a diagram showing a time series when starting the misregistration correction operation according to the present embodiment, and FIG. 13B is a diagram showing a time series according to the prior art. As shown in FIG. 13 (a), the positional deviation correcting operation according to the present embodiment, the optical writing device 111, the timing t _0, performs activation and activation of the developing bias motor for first rotating the reflecting mirror 280. Thus, the rotational speed of the motor is stabilized, then, at the timing t _1, it executes the rotation synchronization process.

Then, at timing t _2, when the rotation synchronization process is completed, because it is already started developing bias, you are possible to start drawing of the positional deviation correction mark 400 as it is. In contrast, in the case of the prior art shown in FIG. 13 (b), to start the developing bias after the timing t _2, the start of drawing the positional deviation correction mark 400 includes a later timing t ₃ than the timing t ₂ Become.

  As described above, the timing of writing the misregistration correction mark 400 by the misregistration correction operation according to the present embodiment can be advanced by the time required for starting and stabilizing the developing bias as compared with the prior art. In addition, the completion timing of the misalignment correction operation can be advanced, and the downtime for the user can be shortened.

  Furthermore, in the misregistration correction operation according to the present embodiment, the following countermeasures are taken to avoid problems due to patterns that may be drawn by performing rotation synchronization processing with the development bias activated. It has been broken. That is, rotation synchronization is performed by irradiating a laser beam for exposing the photosensitive drum 109Y arranged on the most downstream side among the plurality of photosensitive drums 109 arranged in the sub-scanning direction. A photoconductor 109BK for drawing a start position correction pattern 411 drawn at the top of the position deviation correction mark 400 is arranged on the most upstream side in the sub-scanning direction.

  Due to such an arrangement relationship, as shown in FIG. 11, the surplus pattern 402 and the start position correction pattern 411 drawn on the photosensitive drum 109Y by the irradiation of the laser beam in synchronization with the rotation are the photosensitive drum 109BK. And the photosensitive drum 109Y. Therefore, when the sensor control unit 123 detects the start position correction pattern 411 in the detection period described above, the surplus pattern 402 has already been transported downstream of the pattern detection sensor 117 as shown in FIG. Yes.

  As described above, the pattern detection sensor 117 detects the pattern on the conveyance belt 105 according to the control of the sensor control unit 123 within a range of 10 mm before and after the predetermined reference value, and adjacent photoconductors. Since the transfer position of the drum 109 is generally separated by about 60 mm, the surplus pattern 402 is not detected when the start position correction pattern 411 is detected. For this reason, the surplus pattern 402 does not cause a problem in the detection of the start position correction pattern 411, and the optical writing device control unit 120 can accurately perform the positional deviation correction.

  As described above, in the image forming apparatus according to the present embodiment, the other photosensitive elements arranged on the downstream side in the sub-scanning direction with respect to the photosensitive drum that draws the pattern drawn at the head of the misregistration correction mark. The body drum synchronizes the rotation of the reflector motor. Thus, even if the pattern is drawn by performing the rotation synchronization of the motor after the transfer bias is activated, the pattern does not cause a problem in correcting the positional deviation. Therefore, in the image forming apparatus, the start timing of the adjustment process for adjusting the position of the image in the sub-scanning direction can be advanced, and the downtime for the user can be shortened.

  In the above-described embodiment, as illustrated in FIG. 3, a system in which an image is directly transferred from the photosensitive drum 109 onto the sheet surface of the sheet conveyed by the conveyance belt 105 has been described as an example. That is, the case where the conveyance belt 105 as a conveyance body conveys a sheet has been described as an example.

  In addition, as shown in FIG. 14, the above embodiment is applied even to an intermediate transfer method in which an image formed by being transferred from the photosensitive drum 109 onto the conveying belt 105 is further transferred onto the paper surface. It is possible to obtain the same effects as described above. In this case, the conveyance belt 105 which is an intermediate transfer belt conveys an image as a conveyance body.

  In the above-described embodiment, the case where the photosensitive drum 109BK draws the start position correction pattern 411 and performs rotation synchronization in the photosensitive drum 109Y has been described as an example. However, the gist of the present embodiment is that the mirror motor is reflected by another photosensitive drum disposed downstream in the sub-scanning direction from the photosensitive drum that draws the pattern drawn at the head of the position deviation correction mark. Is to perform the rotation synchronization. Therefore, the photosensitive drum that draws the start position correction pattern 411 and the photosensitive drum that performs rotation synchronization are not limited to the above modes.

  As described above, the transfer positions of adjacent photosensitive drums 109 are generally separated by about 60 mm. In order to make the effect more reliable, the start position correction pattern 411 is drawn on the photosensitive drum arranged on the most upstream side in the sub-scanning direction as in the above embodiment, and arranged on the most downstream side. Although it is preferable to perform rotation synchronization in the photosensitive drum, the problem can be solved in the same manner as described above even when the photosensitive drum for drawing the start position correction pattern 411 and the photosensitive drum for rotation synchronization are adjacent to each other. Can do. That is, the photosensitive drum 109BK may draw the start position correction pattern 411, and rotation synchronization may be performed on the photosensitive drum 109M.

  Alternatively, the start position correction pattern 411 may be drawn by the photosensitive drum 109C, and rotation synchronization may be performed on the photosensitive drum 109Y. The color of the start position correction pattern 411 is preferably black from the viewpoint of pattern detection accuracy based on the presence or absence of diffuse reflection light. Therefore, it is preferable that the start position correction pattern 411 is drawn by the photosensitive drum 109BK as in the above embodiment.

  Further, the arrangement order of the photosensitive drums 109 as shown in FIG. 3 is an example, and other arrangement orders can be adopted. Even in such a case, the rotation of the mirror motor is rotated by another photosensitive drum disposed downstream in the sub-scanning direction from the photosensitive drum that draws the pattern drawn at the head of the misalignment correction mark. By performing synchronization, the same effect as described above can be obtained.

  In the above embodiment, in S903 of FIG. 9, the optical writing device 111 emits only the light beam for exposing the photosensitive drum 109Y, and the synchronization timing of the other photosensitive drums is the photosensitive drum 109Y. The calculation based on the synchronization timing in FIG. In addition, for example, in FIG. 4, only one of the light beams scanned by the same surface of the reflecting mirror 280 may be irradiated.

  For example, as a modification of the above-described embodiment, the light source devices 281M and 281C shown in FIG. 4 emit light beams to perform rotation synchronization, the light source device 281BK is synchronized with the light source device 281M, and the light source device 281Y is the light source device. The synchronization timing may be calculated based on the synchronization timing of 281C. Even in this case, the mirror motor is rotated by another photosensitive drum arranged downstream in the sub-scanning direction from the photosensitive drum that draws the pattern drawn at the head of the position correction mark. By performing synchronization, the same effect as described above can be obtained. In addition, the synchronization timing can be set with higher accuracy.

  In the above embodiment, the period during which the sensor control unit 123 detects the start position correction pattern 411 is around a predetermined period of the theoretical value until the start position correction pattern 411 reaches the pattern detection sensor 117. There has been described an example in which the predetermined period is 10 mm. In the above-described embodiment, the predetermined period needs to be at least shorter than the period during which the conveyance belt 105 is conveyed, from the transfer position of the photosensitive drum 109BK to the transfer position of the photosensitive drum 109Y. .

  In other words, the predetermined period is the interval from the transfer position of the photosensitive drum on which the start position correction pattern 411 is drawn to the transfer position of the photosensitive drum irradiated with the light beam that synchronizes the rotation of the reflecting mirror 280. The period is shorter than the period during which the conveyor belt 105 is conveyed. More preferably, the period is shorter than the period during which the conveying belt 105 is conveyed between the transfer positions of adjacent photosensitive drums.

1 image forming apparatus,
10 CPU,
11 RAM,
12 ROM,
13 engine,
14 HDD,
15 I / F,
16 LCD,
17 Operation part,
18 Bus,
20 controller,
21 ADF,
22 Scanner unit,
23 Output tray,
24 display panels,
25 Paper feed table,
26 print engine,
27 Output tray,
28 Network I / F,
30 Main control unit,
31 engine control unit,
32 Input / output control unit,
33 Image processing unit,
34 Operation display control unit,
101 paper feed tray,
102 paper feed roller,
103 separation roller,
104 paper,
105 Conveyor belt,
106BK, 106C, 106M, 106Y Image forming unit,
107 driving roller,
108 driven roller,
109BK, 109C, 109M, 109Y photosensitive drum,
110BK charger,
111 optical writing device,
112BK, 112C, 112M, 112Y Developer,
113BK, 113C, 113M, 113Y
115BK, 115C, 115M, 115Y transfer device,
116 fixing device,
117 pattern detection sensor,
120 optical writing device controller,
121 write controller,
122 counting part,
123 sensor control unit,
124 correction value calculation unit,
125 reference value storage unit,
126 correction value storage unit,
170 sensor element,
280 reflector,
281,281BK, 281Y, 281M, 281C Light source device,
282, 282BK, 282Y, 282M, 282C Mirror 283 Horizontal synchronization detection sensor 400 Misalignment correction mark,
401 misalignment correction pattern sequence,
402 patterns,
411 start position correction pattern,
412 Drum interval correction pattern,
413 Sub-scanning direction correction pattern,
414 Main scanning direction correction pattern

JP 2008-299311 A

Claims (10)

A light source controller that controls a light source that emits a light beam to a plurality of photoconductors arranged in the sub-scanning direction to form an electrostatic latent image on the photoconductor by irradiating the light beam;
A voltage control unit that controls a voltage applied between the photoconductor and a developing unit when developing the electrostatic latent image formed on the photoconductor with a developer;
Detecting that the image transferred to the surface of the carrier has reached a position facing the sensor based on an output signal of a sensor that images the surface of the carrier to which the image developed on the photoconductor is transferred An image detector to perform,
A detection period counting unit that counts a detection period from when the light source control unit starts drawing a predetermined pattern until the image detection unit detects the predetermined pattern;
A reference value acquisition unit that acquires a reference value that is a value of a reference period from when the light source control unit starts drawing a predetermined pattern until the image detection unit detects the predetermined pattern;
A correction value calculation unit that calculates a correction value for correcting the timing of irradiating the light source with a light beam based on the difference between the counted detection period and the acquired reference value;
The light source control unit controls the light source to irradiate a light beam, and based on the detection timing of the light beam at a predetermined position in a scanning range of a rotating reflector that scans the irradiated light beam in a main scanning direction. Synchronize with the rotation of the rotating reflector,
The voltage control unit starts application of a voltage between the photosensitive member and the developing device before the rotary reflector starts rotating and the light source control unit synchronizes with the rotary reflector,
The light beam emitted when the light source control unit synchronizes with the rotation of the rotary reflecting mirror is transported by the transport body rather than the first photosensitive body that draws a pattern drawn at the head of the predetermined pattern. A light beam applied to a second photoconductor disposed downstream of the direction,
The period in which the image detection unit detects the pattern drawn at the head is a predetermined period before and after the theoretical value at which the pattern drawn at the head reaches the position corresponding to the sensor, and the predetermined period. Is an image forming apparatus characterized in that an interval from the transfer position of the first photosensitive member to the transfer position of the second photosensitive member is a period shorter than a period in which the conveyance member is conveyed.   2. The image forming apparatus according to claim 1, wherein the first photosensitive member is disposed on the most upstream side in the conveying direction of the conveying member among the plurality of arranged photosensitive members.   3. The image forming apparatus according to claim 1, wherein the second photoconductor is disposed on the most downstream side in the transport direction of the transport body among the plurality of photoconductors arranged side by side.   4. The predetermined period is a period shorter than a period in which the transport body is transported between transfer positions of adjacent photoreceptors in the plurality of photoreceptors arranged in a row. The image forming apparatus described.   The light beam applied to the first photoconductor and the light beam applied to the second photoconductor are scanned by the same surface among a plurality of reflecting surfaces included in the rotary reflecting mirror. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   6. The image forming apparatus according to claim 1, wherein the light source control unit stops the irradiation of the light beam in response to the detection of the light beam in synchronization with the rotation of the rotary reflecting mirror. apparatus.   The light beam irradiated when the light source control unit synchronizes with the rotation of the rotary reflecting mirror is a light beam irradiated on the photosensitive member developed with a color other than black. The image forming apparatus according to any one of 1 to 6.   8. The light source control unit according to claim 1, wherein the light source control unit starts drawing the predetermined pattern within a predetermined period after detecting the light beam in synchronization with the rotation of the rotary reflecting mirror. An image forming apparatus according to claim 1.   9. The image forming apparatus according to claim 1, wherein a theoretical value at which a pattern drawn at the head reaches a position corresponding to the sensor is the reference value. A light source controller that controls a light source that emits a light beam to a plurality of photoconductors arranged in the sub-scanning direction to form an electrostatic latent image on the photoconductor by irradiating the light beam;
A voltage control unit that controls a voltage applied between the photoconductor and a developing unit when developing the electrostatic latent image formed on the photoconductor with a developer;
Detecting that the image transferred to the surface of the carrier has reached a position facing the sensor based on an output signal of a sensor that images the surface of the carrier to which the image developed on the photoconductor is transferred An image detector to perform,
A detection period counting unit that counts a detection period from when the light source control unit starts drawing a predetermined pattern until the image detection unit detects the predetermined pattern;
A reference value acquisition unit that acquires a reference value that is a value of a reference period from when the light source control unit starts drawing a predetermined pattern until the image detection unit detects the predetermined pattern;
Optical writing of an image forming apparatus including a correction value calculation unit that calculates a correction value for correcting the timing of irradiating the light source with a light beam based on the difference between the counted detection period and the acquired reference value A method of correcting misalignment in an apparatus,
The light source control unit controls the light source to irradiate a light beam, and based on the detection timing of the light beam at a predetermined position in a scanning range of a rotating reflector that scans the irradiated light beam in a main scanning direction. Synchronize with the rotation of the rotating reflector,
The voltage control unit starts application of a voltage between the photoconductor and the developing device before the rotary reflector starts rotating and the light source control unit synchronizes with the rotary reflector,
When the light source control unit synchronizes with the rotation of the rotary reflecting mirror, the light source control unit is downstream in the transport direction of the transport body from the first photoconductor that draws a pattern to be drawn at the head of the predetermined pattern. Irradiating the second photoconductor disposed on the light beam,
The image detector is a period before and after the theoretical value at which the pattern drawn at the head reaches the position corresponding to the sensor, and the transfer of the second photoconductor from the transfer position of the first photoconductor. A positional deviation correction method, wherein a pattern drawn at the head is detected in a period shorter than a period in which the conveyance body is conveyed.

Images