JP5347863B2 - Optical writing apparatus, image forming apparatus, and positional deviation correction method for optical writing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately adjust a position of an image in the sub scanning direction, in an image forming apparatus with function to bring a plurality of image carriers into abutment or separation with/from an object for transferring images developed on the image carriers. <P>SOLUTION: An optical writing device forms an electrostatic latent image on a plurality of photoreceptors, wherein only a black photoreceptor draws a pattern while abutting a conveyor belt. The device performs a displacement correction A for counting a detection period and calculating a correction value, and all photoreceptors draw patterns while abutting the conveyor belt and count the detection period. Also, the device counts the detection period by abutting only the black photoreceptor and calculates an offset value of both detection periods and correction value thereof. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an optical writing apparatus, an image forming apparatus, and an optical writing apparatus misregistration correction method, and more particularly to offset correction when a part of a plurality of photoconductors is brought into contact with or separated from a conveyance body.

  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).

  The electrophotographic image forming apparatus described above includes an intermediate transfer system in which a toner image developed on a photoconductor is transferred to an intermediate transfer belt and then transferred and fixed on a sheet, and a toner developed on the photoconductor. There is a direct transfer method in which an image is directly transferred to a sheet. In either case, the toner image is transferred in a state where the photosensitive member is in contact with the transfer object to be transferred. In the following description, the intermediate transfer belt in the intermediate transfer system and the transport belt that transports the paper in the direct transfer system are collectively referred to as a transport body.

  Further, in a tandem type color image forming apparatus, when a monochrome image is formed, a photosensitive drum for forming a color other than black is separated from the above-described conveyance body. This is to prevent image disturbance due to toner leaking from a photoconductor other than black adhering to the conveyance body.

  Since the above-described conveyance body expands and contracts due to a change in the internal temperature of the image forming apparatus and the like, and as a result, a slight difference occurs in the conveyance timing of the conveyance body, the timing adjustment process disclosed in Patent Document 1 It is executed repeatedly at the timing. However, the conventional timing adjustment processing does not take into account changes when the photosensitive member and the conveying member are in contact with each other and when they are separated as described above.

  In the timing adjustment process, as described above, since the misregistration correction between the photoconductors of the respective colors is also performed, in principle, the above adjustment process is executed in a state where all the photoconductors are in contact with the conveyance body. Therefore, the result of the adjustment process is effective when all the photoconductors are in contact with the transport body.

  However, as described above, when the photoconductor for forming a color other than black transitions from a state separated from the transport body to a contact state, the transport body bends due to the contact with the photoconductor, and the above-described apparatus. Similar to expansion and contraction due to a change in internal temperature, a slight difference occurs in the transport timing of the transport body. Conversely, when a transition is made from a state in which all the photoconductors are in contact with the transport body to a state in which some of the photoconductors are separated from the transport body, the bending caused by the contact is eliminated. There is a slight difference in the transport timing. In other words, the result of the adjustment process executed when all the photoconductors are in contact with the transporting body may be inappropriate in a state where some of the photoconductors are separated.

  The present invention has been made in consideration of the above circumstances, and is an image forming apparatus having a function of contacting and separating a plurality of image carriers and a target to which an image developed on the image carrier is transferred. An object is to accurately adjust the position of the image in the sub-scanning direction.

  In order to solve the above problems, one aspect of the present invention is an optical writing device that forms an electrostatic latent image by irradiating a plurality of photoconductors arranged in the sub-scanning direction with a light beam. Based on an output signal of a light source for irradiating a beam, a light source control unit for controlling the light source to irradiate a light beam, and a sensor for imaging the surface of the carrier on which the developed image is transferred. An image detection unit that detects that an image transferred to the surface of the transport body has reached a position facing the sensor, and the image detection unit that has started drawing a predetermined pattern after the light source control unit has started drawing a predetermined pattern. A detection period counting unit that counts a detection period that is a period until a predetermined pattern is detected, and until the image detection unit detects the predetermined pattern after the light source control unit starts drawing the predetermined pattern. Base of And a reference value corresponding to one of a state in which a part of the plurality of photoconductors is in contact with the transport body and a state in which all of the plurality of photoconductors are in contact with the transport body And a correction value calculation unit for calculating a correction value for correcting the timing of irradiating the light source with the light beam based on the difference between the counted detection period and the acquired reference value A first positional deviation in which the predetermined pattern is drawn in a state where a part of the plurality of photoconductors is in contact with the transport body, and the detection period is counted and the correction value is calculated. Correction processing and second misregistration correction processing in which the predetermined pattern is drawn and the detection period is counted and the correction value is calculated in a state where the plurality of photoconductors are all in contact with the conveyance body. Toga The correction value calculating unit is configured to select the reference value from among a state in which a part of the plurality of photoconductors is in contact with the transport body and a state in which the plurality of photoconductors are all in contact with the transport body. When calculating the correction value in a state different from the state in which the values correspond to each other, the detection period in a state where all of the plurality of photoconductors are in contact with the transport body and a part of the plurality of photoconductors The correction value is calculated by applying, to the reference value, an offset value with respect to the detection period in a state in contact with the conveyance body.

  Here, in the second misregistration correction process, the predetermined pattern is drawn in a state where a part of the plurality of photoconductors is in contact with the transport body, and the detection period is counted, The offset value is preferably calculated and stored.

  The reference value is determined by the image detection unit after the light source control unit starts drawing a predetermined pattern in a state where the plurality of photoconductors are all in contact with the conveyance body. The correction value calculation unit is configured to determine, based on the counted detection period, the acquired reference value, and the calculated offset value in the first misregistration correction process. It is preferable to calculate the correction value.

  In the first misalignment correction process, an offset value update availability determination unit that determines whether or not the calculated and stored offset value can be updated, and the offset value can be updated. The detection period counted and stored in the second misalignment correction process that has already been executed, and the detection period counted in the first misalignment correction process that is being processed. An offset value updating unit that updates the offset value by calculating the offset value based on a difference between the offset value, and the correction value calculating unit updates the offset value in the first misalignment correction process. In this case, it is preferable to calculate the correction value using the updated offset value.

  The offset value update availability determination unit updates the offset value when a difference between a temperature at the time of execution of the second positional deviation correction process that has already been performed and a current temperature is within a predetermined range. It is preferable to determine that this is possible.

  The offset value update availability determination unit may update the offset value when the timing at which the second misalignment correction process that has already been performed is within a predetermined period from the present time. It is preferable to judge.

  Further, the transport body is an endless belt spanned by a plurality of rollers, and when at least one of the plurality of rollers moves, the surface of the transport body is inclined with respect to a horizontal direction. It is preferable to contact the part.

  Further, it is preferable that the second misregistration correction process is executed only when the electrostatic latent image is formed in a state where all of the plurality of photoconductors are in contact with the transport body.

  Further, it is preferable that the first misregistration correction process is executed when the electrostatic latent image is formed in a state where a part of the plurality of photoconductors is in contact with the transport body.

  In addition, a part of the plurality of photoconductors is a photoconductor that forms a black image, and the first misregistration correction processing forms an electrostatic latent image for forming a black image. It is preferably performed when

  The first misalignment correction process is preferably executed in a warm-up operation of the optical writing device.

  According to another aspect of the present invention, there is provided an image forming apparatus including the above-described optical writing device.

  According to still another aspect of the present invention, there is provided a positional deviation correction method for an optical writing device that forms an electrostatic latent image by irradiating a plurality of photoconductors arranged in the sub-scanning direction with a light beam. The optical writing device picks up a light source for irradiating the light beam, a light source control unit for controlling the light source to irradiate the light beam, and a surface of the carrier on which the developed image is transferred onto the photosensitive member. An image detector that detects that an image transferred to the surface of the carrier has reached a position facing the sensor based on an output signal of the sensor, and the light source controller starts drawing a predetermined pattern. A detection period counting unit that counts a detection period that is a period from when the image detection unit detects the predetermined pattern, and after the light source control unit starts drawing a predetermined pattern, the image detection unit A given pass A reference period until the detection of an error, a state in which a part of the plurality of photoconductors is in contact with the transport body, and a state in which all of the plurality of photoconductors are in contact with the transport body A reference value acquisition unit that acquires a reference value corresponding to any one of the correction value, and a correction value for correcting the timing of irradiating the light source with the light source based on the counted detection period and the acquired reference value A correction value calculation unit for calculating the light source, wherein the light source control unit draws the predetermined pattern in a state where a part of the plurality of photoconductors is in contact with the transport body, and the detection period counting unit is configured to detect the detection. A first positional deviation correction process in which the period is counted and the correction value calculation unit calculates the correction value; and the light source control unit performs the predetermined operation in a state in which the plurality of photoconductors are all in contact with the transport body. Drawing pattern The detection period counting unit counts the detection period, and the correction value calculation unit can execute a second misregistration correction process in which the correction value is calculated. The correction value in a state different from a state in which the reference value corresponds among a state in which a part of the photoconductor is in contact with the transport body and a state in which the plurality of photoconductors are all in contact with the transport body. When calculating the offset between the detection period when the plurality of photoconductors are in contact with the transport body and the detection period when a portion of the plurality of photoconductors is in contact with the transport body The correction value is calculated by applying a value to the reference value.

  According to the present invention, in an image forming apparatus having a function of abutting and separating a plurality of image carriers and a target to which an image developed on the image carrier is transferred, the position adjustment of the image in the sub-scanning direction is performed. Can be performed accurately.

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. 1 is a diagram illustrating a configuration of a print engine 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. 1 is a diagram illustrating a configuration of a print engine 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. 1 is a diagram illustrating a configuration of a print engine according to an embodiment of the present invention. It is a figure which shows the example of the information memorize | stored in the correction value memory | storage part 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. It is a figure which shows the example of judgment of which of the misalignment correction A and the misalignment correction B which concerns on embodiment of this invention is performed. It is a figure which shows the structure of the print engine which concerns on other 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 other embodiment of this invention.

  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 its gist is correction of an image writing position in the sub-scanning direction in an optical writing apparatus for forming an electrostatic latent image on a photoreceptor. is there.

  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 each of the photosensitive drums 109BK, 109M, 109C, and 109Y 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.

  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. Further, the expansion and contraction of the conveyor belt due to the temperature change in the apparatus and deterioration with the passage of time are 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 conveyor belt 105 by the photosensitive drums 109BK, 109M, 109C, and 109Y. 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. . A mode of correction of misalignment by the pattern detection sensor 117 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 for writing on the photosensitive drums 109BK, 109M, 109C, and 109Y of the respective colors are light source devices 281BK, 281Y, 281M, and 281C 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, 282Y, and 282M282C (hereinafter, generally referred to as 282) by an optical system such as an fθ lens (not shown), and further, the photosensitive drums 109BK, 109M, 109C, and 109Y are further advanced by the optical system. Is scanned to the surface.

  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 the present embodiment divides four light source devices into light source devices of two colors of 281BK, 281Y, and 281M, 281C, 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.

  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 image detection unit that detects that the position of the sensor 117 has been reached. When the sensor control unit 123 detects that the positional 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.

  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. Note that the writing start timing reference value according to the present embodiment is a reference value in a state where all of the photosensitive drums 109BK, 109M, 109C, and 109Y are in contact with the transport belt 105. This will be described in detail later.

  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.

  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.

  The misalignment correction pattern row 401 includes an all-drum contact pattern 410 and a black drum contact pattern 420. The all-drum contact pattern 410 is a pattern drawn in a state where all of the photosensitive drums 109BK, 109M, 109C, and 109Y are in contact with the conveyance belt 105. 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 all-drum contact pattern 410 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 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 write start timing reference value stored in the reference value storage unit 125 is the start position correction drawn after the light source device 281 starts drawing the start position correction pattern 411 according to the control of the write control unit 121. This is a reference value for the period until the pattern 411 is read by the pattern detection sensor 117 and detected by the sensor control unit 123.

  As shown in FIG. 8, the start position correction pattern 411 according to the present embodiment is configured by arranging two lines parallel to the main scanning direction in the sub scanning direction. This is because the second surface is drawn for backup when the detection of the first pattern fails.

  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.

  The black drum contact pattern 420 is a pattern drawn in a state where only the photosensitive drum 109BK is in contact with the transport belt 105. As shown in FIG. 8, when the optical writing device control unit 120 controls the light source device 281 to draw the misregistration correction mark 400, after drawing all the drum contact patterns 410, the photosensitive drums other than the photosensitive drum 109BK are drawn. A black drum contact pattern 420 is drawn after performing a separation process for separating the body drum from the conveyor belt 105.

  Note that, similarly to the start position correction pattern 411, the black drum contact pattern 420 according to this embodiment also includes two lines parallel to the main scanning direction arranged in the sub scanning direction, as shown in FIG. It is configured. This is because the second surface is drawn for backup when the detection of the first pattern fails.

  With such a configuration of the misregistration correction mark 400, drawing is performed both in a state where all the photosensitive drums are in contact with the conveyance belt 105 and in a state where only the photosensitive drum 109BK is in contact with the conveyance belt 105. It is possible to execute image positional deviation correction.

  In the present embodiment, in addition to the state where all the photosensitive drums are in contact with the conveyance belt 105, the rendered image includes the state of monochrome printing in which only the photosensitive drum 109 </ b> BK is in contact with the conveyance belt 105. An example of correcting the position of will be described. In addition to this, monochromatic printing is not limited to monochrome, and in consideration of the case of using other colors, only the photosensitive drums other than the photosensitive drum 109BK may be brought into contact with the transport belt 105.

  Even in the case of monochromatic printing, for example, when monochromatic printing is performed in colors such as red, green, and blue, two of the photosensitive drums 109M, 109C, and 109Y may be brought into contact with the conveyance belt 105. . The same applies not only to monochrome printing but also to printing that is not full color. Even in these cases, in constructing the misregistration correction mark 400, a pattern is drawn in a state corresponding to each, that is, in a state where only the photosensitive drum to be abutted is brought into contact with the reference value. By storing the reference values corresponding to the respective patterns in the storage unit 125, it is possible to perform misalignment correction as described above.

  Next, in the configuration of the print engine 26 according to the present embodiment, a mechanism for bringing the photosensitive drums 109BK, 109M, 109C, and 109Y (hereinafter collectively referred to as the photosensitive drum 109) into contact with and away from the conveyance belt 105. explain. 3 shows a state in which all the photosensitive drums 109 are separated from the transport belt 105, as shown. FIG. 9 shows a state in which all the photosensitive drums 109 and the transport belt 105 are in contact with each other.

  In order to make the transition between the state shown in FIG. 3 and the state shown in FIG. 9, the photosensitive drum 109 itself may be moved up and down, or the driving roller 107 and the driven roller 108 holding the conveyor belt 105 are moved up and down. May be. FIG. 10 is a diagram illustrating one mode when only the photosensitive drum 109BK is brought into contact with the transport belt 105. In FIG. In the embodiment of FIG. 10, the driving roller 107 and the driven roller 108 are made different in height so that the surface of the conveying belt 105 facing the photosensitive drum 109 is held in an inclined state, and only the photosensitive drum 109BK is used. It arrange | positions so that the conveyance belt 105 may be contact | abutted. This is a mode that is possible when the photosensitive drum 109BK is disposed at the end in the sub-scanning direction as in the print engine 26 according to the present embodiment.

  FIG. 11 is a diagram illustrating another mode in which only the photosensitive drum 109BK is brought into contact with the transport belt 105. In FIG. In the embodiment of FIG. 11, similarly to FIG. 10, the driving roller 107 is disposed at a position lower than the driven roller 108, and the belt height adjusting roller 118 is disposed between the photosensitive drum 109BK and the photosensitive drum 109M. And the height above the belt height adjusting roller 118 and the height above the driven roller 108 are equal. As a result, the conveyor belt 105 is supported by the belt height adjusting roller 118 and the driven roller 108, and is disposed so as to be in contact with the photosensitive drum 109BK.

  FIG. 12 is a diagram illustrating an example in which two photosensitive drums are brought into contact with the conveyance belt 105 as a modification of FIG. In the embodiment of FIG. 12, similarly to FIG. 10, the driving roller 107 is disposed at a position lower than the driven roller 108, and the belt height adjusting roller 118 is disposed between the photosensitive drum 109M and the photosensitive drum 109C. And the height above the belt height adjusting roller 118 and the height above the driven roller 108 are equal. As a result, the conveyor belt 105 is supported by the belt height adjusting roller 118 and the driven roller 108, and is disposed so as to contact only the photosensitive drums 109BK and 109M.

  FIG. 13 is a view showing still another aspect in the case where only the photosensitive drum 109BK is brought into contact with the transport belt 105. In FIG. In the embodiment shown in FIG. 13, the driving roller 107 and the driven roller 108 are arranged in the same manner as in FIG. 3, and between the photosensitive drum 109BK and the driven roller 108, and between the photosensitive drum 109BK and the photosensitive drum 109M. The belt height adjusting roller 118 is provided between the two belt height adjusting rollers 118 so that the upper heights of the two belt height adjusting rollers 118 are equal and higher than the driving roller 107 and the driven roller 108. As a result, the conveying belt 105 is supported by the two belt height adjusting rollers 118 and disposed so as to contact the photosensitive drum 109BK.

  By such a contact / separation mechanism between the photosensitive drum 109 and the conveyor belt 105, for example, when the state of FIG. 9 is changed to the state of FIG. 10, the arrangement of the driving roller 107 and the driven roller 108 changes. As a result, the conveyor belt 105 may slightly expand and contract. As a result, a shift occurs in the timing at which the image formed on the photosensitive drum 109 is transferred to the paper transported by the transport belt 105, resulting in a positional shift of the image transferred on the paper.

  Further, when the conveyance speed of the conveyance belt 105 changes due to the expansion and contraction of the conveyance belt 105, in addition to the above-described image misalignment, the images formed on the photosensitive drums 109BK, 109M, 109C, and 109Y are transferred to the sheet. As a result, a color shift occurs in the image transferred onto the paper, that is, a color shift.

  In the state of FIG. 9, the photosensitive drum 109BK and the transport belt 105 are in contact with each other at the lowest point in the vertical direction of the photosensitive drum 109BK, but in the state of FIG. 10, the transport belt 105 is inclined. Therefore, the contact position between the photosensitive drum 109BK and the transport belt 105 changes. This also causes a shift in the timing at which the image formed on the photoconductive drum 109 is transferred to the sheet transported by the transport belt 105, resulting in a positional shift of the image transferred on the sheet.

  The shift due to the change in the contact position between the photosensitive drum 109BK and the transport belt 105 as shown in FIG. Therefore, the misregistration correction mechanism according to this embodiment is particularly effective in the print engine 26 that employs the contact / separation mechanism as shown in FIG. The contact / separation mechanism of the print engine 26 as shown in FIG. 9 can be realized, for example, by providing a mechanism that raises or lowers only the height of the drive roller 107, and thus is advantageous in terms of cost compared to other aspects. There is.

  Further, since the frictional force when the conveying belt 105 is conveyed changes due to the change in the number of the photosensitive drums 109 in contact with the conveying belt 105, the conveying speed of the conveying belt 105 may change. . As a result, the above-described image misregistration and image color misregistration may occur. Further, in the case of FIGS. 11 and 12, since the conveyor belt 105 is expanded and contracted by the belt height adjusting roller 118, as described above, there is a possibility that image misregistration and color misregistration occur.

  The gist of the present embodiment is to perform a correction operation using such a misregistration correction mark 400 as described in FIG. 8 with respect to such problems of misregistration and color misregistration. In the present embodiment, of the misregistration correction marks 400 shown in FIG. 8, a correction operation (hereinafter referred to as misregistration correction A) executed by drawing only the black drum contact pattern 420, and misregistration. Any one of the correction operations (hereinafter referred to as misalignment correction B) executed by drawing all the correction marks 400 is selectively executed.

  As described with reference to FIG. 3, the image forming apparatus 1 according to the present embodiment is capable of full-color printing including the four-color photosensitive drums 109. By performing the above-described misregistration correction B, the image writing position and A positional deviation correction B for correcting the color deviation of each color is fundamental. Therefore, among the reference values described in FIG. 7, not only the drum interval reference value but also the writing start timing reference value is a state where all the photosensitive drums 109 are in contact with the conveyance belt 105 as shown in FIG. The reference value in (hereinafter referred to as contact state) is stored.

  Further, by drawing all the patterns included in the misregistration correction mark 400, the optical writing device control unit 120 causes the start position correction pattern 411 to be detected (period from the start of exposure to detection) and the black drum. The difference from the detection period of the contact pattern 420 can be calculated. By storing this difference as an offset value in the correction value storage unit 126, the image transfer position in a state as shown in FIGS. 10, 11 and 13 (hereinafter referred to as a separated state) is corrected to a suitable position. Is possible.

  In the case of the misalignment correction A, as described above, the pattern to be drawn is only the black drum contact pattern 420. However, in the case of executing monochrome printing, the photosensitive drum on which an image is drawn is the photosensitive drum. Since only 109BK is used, it is not necessary to consider the color misregistration correction between the drums, and it is sufficient to correct only the image writing position, which is sufficient. In monochrome printing, since the photosensitive drums other than the photosensitive drum 109BK are in the separated state, it is desirable to perform the positional deviation correction in a state in which the photosensitive drums are separated, which is also effective in this respect. .

  When performing the misalignment correction A, what is required is the detection period of the black drum contact pattern 420 in the separated state as shown in FIGS. Here, as described above, the write start timing reference value stored in the reference value storage unit 125 is a value in the contact state, and thus cannot be applied as it is. On the other hand, by applying the offset value obtained in the positional deviation correction B, the positional deviation correction of the writing start position in the separated state is performed using the writing start timing reference value stored in the reference value storage unit 125. Can be done accurately.

  Further, in the present embodiment, the write start timing reference value stored in the reference value storage unit 125 may be only the contact state value as shown in FIG. In contrast, the storage area of the reference value storage unit 125 can be reduced.

  Note that the write start timing reference value stored in the reference value storage unit 125 can be used as the reference value in the separated state. However, since the write start timing reference value in the current image forming apparatus is a value based on the contact state, when the write start timing reference value is set as the reference value in the separated state, the load due to the specification change increases. . On the other hand, the above-described embodiment can be easily applied to the current image forming apparatus by setting the writing start timing reference value to the reference value in the contact state as in the conventional case.

  Next, information stored in the correction value storage unit 126 will be described with reference to FIG. As shown in FIG. 14, the correction value storage unit 126 according to the present embodiment stores “positional deviation correction A execution information”, “positional deviation correction B execution information”, and “correction value information”. “Position misalignment correction A execution information” includes “execution date and time”, “in-machine temperature”, and “black drum contact pattern count value”.

  “Execution date and time” and “in-machine temperature” are information indicating the date and time when the positional deviation correction A was executed last and the temperature in the image forming apparatus 1, respectively. When recording the “in-machine temperature”, in addition to recording the temperature by providing a thermometer inside the image forming apparatus 1, the temperature is estimated by estimating the temperature according to the operation status of the image forming apparatus 1. Can also be recorded.

  The “black drum contact pattern count value” is the output signal from the pattern detection sensor 117 after the light source device 281 starts exposing the photosensitive drum 109BK to draw the black drum contact pattern 420. This is information indicating a period until the black drum contact pattern 420 is detected based on the count value by the count unit 122.

  Further, as shown in FIG. 14, “position deviation correction B execution information” includes “execution date and time”, “in-machine temperature”, “start position correction pattern count value”, “drum interval correction pattern count value”, “ Black drum contact pattern count value ”. “Execution date / time” and “in-machine temperature” are the same as the information of the same name included in the “position shift correction A execution information” described above.

  The “start position correction pattern count value” is the sensor control unit 123 after the light source device 281 starts exposure of the photosensitive drum 109BK to draw the start position correction pattern 411 among the patterns shown in FIG. Is information indicating a period until the start position correction pattern 411 is detected based on the output signal of the pattern detection sensor 117, and indicates a count value by the counting unit 122.

  In the “drum interval correction pattern count value”, the light source device 281 starts exposure of the photosensitive drums 109BK, 109M, 109C, and 109Y in order to draw the drum interval correction pattern 412 among the patterns shown in FIG. Information indicating a period until the sensor control unit 123 detects each pattern included in the drum interval correction pattern 412 based on the output signal of the pattern detection sensor 117, and indicates a count value by the counting unit 122.

  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, and each pattern is composed of a plurality of lines. Therefore, the “drum interval correction pattern count value” includes a plurality of count values corresponding to a plurality of lines. The “black drum contact pattern count value” included in the “position shift correction B execution information” is the same as the information of the same name included in the “position shift correction A execution information” described above.

  “Correction value information” includes “contact state write start timing correction value”, “separated state write start timing correction value”, “offset value”, and “color shift correction value”. The “contact state write start timing correction value” is a value calculated based on the “start position correction pattern count value” described above and the “write start timing reference value” stored in the reference value storage unit 125. Yes, the correction value is referred to by the writing control unit 121 when image formation is executed in the contact state.

  The “separated state write start timing correction value” is the same as the “black drum contact pattern count value”, the “write start timing reference value” stored in the reference value storage unit 125, and the “offset value” shown in FIG. It is a value calculated based on this. The writing control unit 121 refers to the “separated state writing start timing correction value” when driving the light source device 281 in image formation in the separated state.

  The “offset value” is a value calculated as the difference between the “start position correction pattern count value” and the “black drum contact pattern count value”. Here, as the “black drum contact pattern count value”, either the value of “positional deviation correction A execution information” or the value of “positional deviation correction B execution information” is used. Which will be used will be described in detail later.

  The “color shift correction value” is a value calculated based on the “drum interval correction pattern count value” described above, and is a correction value for correcting the color shift described above. That is, the “color misregistration correction value” is individually stored for each photosensitive drum 109.

  Next, the misregistration correction operation of the image forming apparatus 1 according to the present embodiment, that is, specific processing when each information shown in FIG. 14 is stored in the correction value storage unit 126 will be described with reference to FIG. To do. FIG. 15 is a flowchart showing processing of the optical writing device control unit 120 in the misregistration correction operation of the image forming apparatus 1 according to the present embodiment. As shown in FIG. 15, when the optical writing device control unit 120 starts the misregistration correction operation, it first determines whether it is misregistration correction A or misregistration correction B (S1501).

  FIG. 16 is a table showing the determination method in S1501. As shown in FIG. 16, in the present embodiment, the misregistration correction B is performed only when the misregistration correction is performed before and during the color printing, and the misalignment correction A is performed in other cases. This is to reduce the amount of color toner consumption by setting the timing for performing the misregistration correction B to the minimum necessary timing. In addition, since the time required for processing is shorter when only the black drum contact pattern 420 is drawn than when all the misalignment correction marks 400 shown in FIG. 8 are drawn, the response time to the user's instruction is shortened, and the user Convenience can be improved.

  In the present embodiment, the determination mode of the positional deviation correction A and the positional deviation correction B will be described using an example as shown in FIG. 16, but other conditions can be used. For example, there may be a case where the contents of a job are not yet known during a warm-up operation such as when the power is turned on or when returning from a standby state or a power saving state. In this case, it is possible to refer to the past execution history of image formation output and execute misregistration correction A if there is more monochrome printing, and perform misregistration correction B if there is more color printing. It is.

  If the result of S1501 is the timing of the misregistration correction A (S1501 / YES), the write control unit 121 draws only the black drum contact pattern 420 among the patterns shown in FIG. And the count unit 122 starts counting (S1502). The process of S1502 includes a process of changing the arrangement state of the photosensitive drum 109 or the conveyance belt 105 to make the separation state.

  After the process of S1502, when the sensor control unit 123 detects the black drum contact pattern 420 based on the output signal of the pattern detection sensor 117 (S1503), the count unit 122 detects the detection period of the black drum contact pattern 420, that is, In S1503, the count value for the period from the start of counting in S1502 to the detection is acquired (S1504) and input to the correction value calculation unit 124. In S <b> 1504, 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 calculating unit 124 acquires a plurality of count values from the counting unit 122, the correction value calculating unit 124 obtains an average value thereof (S1505) and corrects the correction value as the “black drum contact pattern count value” of the “positional deviation correction A execution information”. The data is stored in the storage unit 126. Further, the correction value calculation unit 124 also stores “execution date and time” and “in-machine temperature” of “positional deviation correction A execution information” at the same time.

  After completing the processing up to S1505, the optical writing device control unit 120 proceeds to determine whether to update the “offset value” information already stored in the correction value storage unit 126. This process is executed by the correction value calculation unit 124. That is, the correction value calculation unit 124 functions as an offset value update availability determination unit. First, the correction value calculation unit 124 refers to the current in-machine temperature and also refers to the “in-machine temperature” of the “position shift correction B execution information” stored in the correction value storage unit 126, and the difference between the two values. Is determined to be within a predetermined range (S1506).

  If it is determined in S1506 that the difference in the in-machine temperature is outside the predetermined range (S1506 / NO), the correction value calculation unit 124 cancels the update of the offset value, and stores the average value obtained in S1505 and the reference value. Based on the “write start timing reference value” stored in the unit 125 and the “offset value” already stored in the correction value storage unit 126, a “separated state write start timing correction value” is calculated and stored as a correction value The data is stored in the unit 126 (S1509), and the process is terminated.

  On the other hand, if it is determined in S1506 that the difference in the in-machine temperature is within the predetermined range (S1506 / YES), the correction value calculation unit 124 then stores the “position deviation correction B stored in the correction value storage unit 126. With reference to the “execution date / time” information of “execution information”, it is determined whether the information is within a predetermined period, such as within one month (S1507).

  In the determination of S1507, when the “positional deviation correction B execution information” is not information within a predetermined period (S1507 / NO), the correction value calculation unit 124 cancels the update of the offset value and is obtained in S1505. Based on the average value, the “write start timing reference value” stored in the reference value storage unit 125, and the “offset value” already stored in the correction value storage unit 126, the “separated state write start timing correction value” Is calculated and stored in the correction value storage unit 126 (S1509), and the process ends.

  On the other hand, if it is determined in S1507 that the “positional deviation correction B execution information” is information within a predetermined period (S1507 / YES), the correction value calculation unit 124 has already corrected to update the offset value. The “start position correction pattern count value” of the “position shift correction B execution information” stored in the value storage unit 126 is acquired, and the acquired “start position correction pattern count value” and the “black drum” obtained in S1505 are acquired. A difference from the “contact pattern count value” is calculated to obtain an “offset value”, which is stored in the correction value storage unit 126 (S1508). That is, the correction value calculation unit 124 functions as an offset value update unit.

  Then, the correction value calculation unit 124 performs “separation state writing” based on the average value obtained in S1505, the “write start timing reference value” stored in the reference value storage unit 125, and the calculated “offset value”. The “start timing correction value” is calculated and stored in the correction value storage unit 126 (S1508), and the process ends.

  The processes from S1502 to S1509 are the process of positional deviation correction A. Here, the offset value update determination described above will be described. In the present embodiment, as described above, it is determined whether or not the offset value needs to be updated on condition of “in-machine temperature” and “execution date and time”. This is because the “start position correction pattern count value” is required to update the offset value. In order to newly obtain the “start position correction pattern count value”, the above-described various adverse effects are present. Since it is necessary to execute the deviation correction B, this is equivalent to determining whether or not the “start position correction pattern count value” already stored in the correction value storage unit 126 can be used.

  In order to use the “start position correction pattern count value” that is already stored, the state of the transport belt 105 when the “start position correction pattern count value” is counted needs to be close to the current state. Furthermore, it is preferable that they are the same. This is because if the offset value is calculated using the “start position correction pattern count value” counted in a state in which the expansion / contraction state of the transport belt 105 is different, an inaccurate offset value is likely to be calculated. is there.

  In the present embodiment, considering the thermal expansion and contraction due to temperature changes and changes over time as factors for changing the state of the conveyor belt 105, the current state and the last time when the misregistration correction B is executed for each condition. When the state is close, it is determined that the state of the transport belt 105 is close and the “start position correction pattern count value” already stored in the correction value storage unit 126 can be used. As a result, when the condition is satisfied, the offset value can be updated without executing the misregistration correction B having various problems as described above.

  On the other hand, if the conditions of “in-machine temperature” and “execution date / time” are not satisfied, the update of “offset value” is canceled. Therefore, strictly speaking, as the processing in S1509, a value different from the exact “offset value” is used. It may be used. However, even if an inaccurate offset value is used, the resulting image position shift is in units of microns. Normally, when an image is formed on the paper surface, the outer peripheral portion of the paper is in millimeters. Since there is a margin more than the unit, it does not become a big problem.

  If the result of S1501 is the timing of the misalignment correction B (S1501 / NO), the writing control unit 121 controls the light source device 281 so as to draw the entire misalignment correction mark 400 shown in FIG. The counting unit 122 starts counting (S1510). In the processing of S1510, after the photosensitive drum 109 and the conveying belt 105 are in the contact state shown in FIG. 9, the entire drum contact pattern 410 shown in FIG. 8 is drawn, and then the separation shown in FIGS. This is a process of drawing the black drum contact pattern 420 shown in FIG. 8 after the transition to the state.

  After the process of S1510, when the sensor control unit 123 detects each pattern included in the misregistration correction mark 400 based on the output signal of the pattern detection sensor 117 (S1511), the count unit 122 determines based on the detection result. “Start position correction pattern count value”, “drum interval correction pattern count value”, and “black drum contact pattern count value” are acquired and input to the correction value calculation unit 124 (S1512). In S1512, 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, as in S1504.

  When the correction value calculation unit 124 acquires a plurality of count values from the counting unit 122, the correction value calculation unit 124 obtains an average value of them (S1513), and calculates “start position correction pattern count value” of “position shift correction B execution information”, “drum” The correction value storage unit 126 stores the interval correction pattern count value ”and the“ black drum contact pattern count value ”, respectively. Further, the correction value calculation unit 124 also stores “execution date and time” and “in-machine temperature” of “positional deviation correction B execution information” at the same time.

  Further, the correction value calculation unit 124 calculates the difference between the “start position correction pattern count value” and the “black drum contact pattern count value” to obtain an “offset value”, and stores it in the correction value storage unit 126. (S1514). Further, the correction value calculation unit 124 determines “contact” based on the average value of the “start position correction pattern count value” obtained in S1513 and the “write start timing reference value” stored in the reference value storage unit 125. The “state write start timing correction value” is calculated and stored in the correction value storage unit 126 (S1515), and the process ends. With such processing, the misregistration correction operation according to the present embodiment is completed.

  As described above, the image forming apparatus 1 according to the present embodiment calculates the offset value by performing the displacement correction in the contact state and the separation state, and calculates the correction value at the time of contact. B and positional deviation correction A for calculating a correction value at the time of separation by performing positional deviation correction in the separation state using the offset value obtained by the positional deviation correction B can be executed. Thereby, it is possible to correct an image position shift due to a difference in conveyance timing of the conveyance belt 105 between the contact state and the separation state.

  Further, the number of times that the misregistration correction mark 400 shown in FIG. 8 is drawn can be reduced by limiting the misregistration correction B to cases where it is necessary to correct the color misregistration of each color, such as when performing color printing. Can be reduced. Thereby, it is possible to reduce the consumption amount of the color toner. Further, when the misregistration correction B is performed, it is necessary to draw the entire misregistration correction mark 400 shown in FIG. 8, but when the misregistration correction A is performed, only the black drum contact pattern 420 needs to be rendered. Therefore, it is possible to reduce the time required for correcting the misalignment and improve the response speed of the apparatus with respect to the user's instruction.

  In the above-described embodiment, as illustrated in FIGS. 3 and 9, the method of directly transferring an image from the photosensitive drum 109 onto the sheet surface of the sheet conveyed by the conveying 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. 17, the above embodiment is applied even to an intermediate transfer system 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 embodiment, as shown in FIG. 8, the start position correction pattern 411 and the black drum contact pattern 420 are described as an example, which is composed of only two lines parallel to the main scanning direction. did. This is a necessary and sufficient configuration because the main purpose is correction of the image writing start position, that is, correction of the position in the sub-scanning direction.

  On the other hand, in the misregistration correction A according to the present embodiment, as described above, only the black drum contact pattern 420 is drawn, so the main scanning direction correction pattern 414 is not drawn and the main scanning direction is not drawn. No misalignment correction is performed. As described above, the case where the misregistration correction A is executed is a case where it is not necessary to consider the color misregistration of each color, such as monochrome printing. Since it is a deviation that is absorbed, it is not a big problem. However, as shown in FIG. 18, as the black drum contact pattern 420, the positional deviation in the main scanning direction may be corrected in the positional deviation correction A, including the hatched pattern. As a result, the image can be transferred to a more appropriate position on the paper.

  Further, in the above embodiment, as shown in S1506 to S1508 in FIG. 15, in the case of performing the positional deviation correction A, the offset value update necessity determination (S1506, S1507) and the offset value update process (S1508). The case of executing is described as an example. However, as described above, in monochrome printing, the offset value shift is not a big problem, and thus the processing of S1506 to S1508 may be omitted.

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,
118 Belt height adjustment roller 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,
410 All drum contact pattern,
411 start position correction pattern,
412 Drum interval correction pattern,
413 Sub-scanning direction correction pattern,
414 main scanning direction correction pattern;
420 Black drum contact pattern

JP 2008-299311 A

Claims (13)

An optical writing device that forms an electrostatic latent image by irradiating a plurality of photoconductors arranged in the sub-scanning direction with a light beam,
A light source for irradiating the light beam;
A light source controller that controls the light source to emit a light beam;
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 value of a reference period from when the light source control unit starts drawing a predetermined pattern to when the image detection unit detects the predetermined pattern, and a part of the plurality of photoconductors is the transport body A reference value acquisition unit that acquires a reference value corresponding to any one of the state in contact with the photosensitive member and the state in which the plurality of photosensitive members are in contact with the transport body;
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 first misalignment correction process in which the predetermined pattern is drawn in a state in which a part of the plurality of photoconductors is in contact with the transport body, and the detection period is counted and the correction value is calculated;
A second misregistration correction process is performed in which the predetermined pattern is drawn and the detection period is counted and the correction value is calculated in a state where all of the plurality of photoconductors are in contact with the transport body. And
The correction value calculation unit corresponds to the reference value among a state in which a part of the plurality of photoconductors is in contact with the transport body and a state in which the plurality of photoconductors are all in contact with the transport body. When the correction value is calculated in a state different from the state where the plurality of photosensitive members are in contact with each other, the detection period and a part of the plurality of photosensitive members are in contact with the conveying member. An optical writing apparatus, wherein the correction value is calculated by applying an offset value with respect to the detection period in a contact state to the reference value.   In the second misalignment correction process, the predetermined pattern is drawn in a state where a part of the plurality of photoconductors is in contact with the transport body, the detection period is counted, and the offset value is set. The optical writing apparatus according to claim 1, wherein the optical writing apparatus is calculated and stored. The reference value is a period from when the light source control unit starts drawing a predetermined pattern in a state where all of the plurality of photoconductors are in contact with the conveyance body until the image detection unit detects the predetermined pattern. It is the value of the reference period,
The correction value calculation unit calculates the correction value based on the counted detection period, the acquired reference value, and the calculated offset value in the first misalignment correction processing. The optical writing device according to claim 1. In the first misalignment correction process, an offset value update availability determination unit that determines whether the calculated and stored offset value can be updated, and a determination that the offset value can be updated. The detection period counted and stored in the second misalignment correction process that has already been executed, and the detection period counted in the first misalignment correction process that is being processed. An offset value updating unit that updates the offset value by calculating the offset value based on the difference,
The correction value calculation unit, when the offset value is updated in the first misalignment correction process, calculates the correction value using the updated offset value. Optical writing device.   The offset value update availability determination unit can update the offset value when the difference between the temperature at the time of execution of the second positional deviation correction process already executed and the current temperature is within a predetermined range. The optical writing device according to claim 4, wherein the optical writing device is determined as follows.   The offset value update availability determination unit determines that the offset value can be updated when a timing at which the second positional deviation correction process that has already been performed is within a predetermined period from the present time. The optical writing device according to claim 4, wherein the optical writing device is an optical writing device.   The transport body is an endless belt spanned between a plurality of rollers, and when at least one of the plurality of rollers moves, a surface thereof is inclined with respect to a horizontal direction and a part of the photoreceptor. The optical writing device according to claim 1, wherein the optical writing device is in contact with the optical writing device.   2. The second misregistration correction process is executed only when the electrostatic latent image is formed in a state where all of the plurality of photoconductors are in contact with the transport body. 8. The optical writing device according to any one of 7 to 7.   The first misalignment correction process is performed when the electrostatic latent image is formed in a state where a part of the plurality of photosensitive members is in contact with the transport body. The optical writing device according to any one of 1 to 8. A part of the plurality of photoconductors is a photoconductor that forms a black image,
The optical writing apparatus according to claim 9, wherein the first misregistration correction process is executed when an electrostatic latent image for forming a black image is formed.   The optical writing apparatus according to claim 1, wherein the first misalignment correction process is executed in a warm-up operation of the optical writing apparatus.   An image forming apparatus comprising the optical writing device according to claim 1. A method of correcting misalignment of an optical writing device for forming an electrostatic latent image by irradiating a plurality of photosensitive members arranged in the sub-scanning direction with a light beam,
The optical writing device comprises:
A light source for irradiating the light beam;
A light source controller that controls the light source to emit a light beam;
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 period value from when the light source control unit starts drawing a predetermined pattern to when the image detection unit detects the predetermined pattern, and a part of the plurality of photoconductors is transported. A reference value acquisition unit that acquires a reference value corresponding to any one of a state in contact with a body and a state in which all of the plurality of photosensitive members are in contact with the transport body;
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 counted detection period and the acquired reference value;
The light source control unit draws the predetermined pattern in a state where a part of the plurality of photoconductors is in contact with the transport body, the detection period counting unit counts the detection period, and the correction value calculation unit A first misalignment correction process for calculating the correction value;
The light source control unit draws the predetermined pattern in a state where the plurality of photoconductors are all in contact with the conveyance body, the detection period counting unit counts the detection period, and the correction value calculation unit is configured to perform the correction. Second misregistration correction processing for calculating a value can be executed,
The correction value calculation unit corresponds to the reference value among a state in which a part of the plurality of photoconductors is in contact with the transport body and a state in which the plurality of photoconductors are all in contact with the transport body. When the correction value is calculated in a state different from the state where the plurality of photosensitive members are in contact with each other, the detection period and a part of the plurality of photosensitive members are in contact with the conveying member. An offset correction method for an optical writing device, wherein the correction value is calculated by applying an offset value with respect to the detection period in a contact state to the reference value.

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