JP5321379B2 - Image forming apparatus and method of correcting misalignment of image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the time required for removal of toner constituting a pattern for misalignment correction in an image forming apparatus. <P>SOLUTION: The circumferential length L of a secondary transfer roller 119, the repeating interval P of a drum clearance-correcting pattern 412 to be repeatedly drawn, a maximum value p<SB>max</SB>of sub-scanning directional width of lines included in the pattern and a minimum value g<SB>min</SB>of sub-scanning directional clearance of adjacent lines in the pattern satisfy the relation of p<SB>max</SB>&le;¾P-L¾&le;g<SB>min</SB>. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus and a method for correcting misregistration of an image forming apparatus, and more particularly to cleaning of a pattern drawn for misregistration correction.

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

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

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

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

  When the positional deviation correction as described above is performed, it is necessary to remove the toner constituting the pattern after the positional deviation correction is completed. Here, in the case of a direct transfer method in which an image is directly transferred from the photoconductors 109BK, 109M, 109C, and 109Y to the paper as shown in FIG. 14, the cleaner 118 that removes the toner is a pattern detection that is the above-described optical sensor. It can be provided on the downstream side of the sensor 117 and upstream of the point where the paper is delivered to the transport belt 105, and contamination on the back side of the paper can be avoided.

  On the other hand, in the case of the intermediate transfer system as shown in FIG. 3, the cleaner 118 cannot be provided immediately after the detection position by the pattern detection sensor 117. This is because in the normal image forming process, the image is transferred onto the sheet by the secondary transfer roller 119, and thus the pattern formed on the conveyor belt 105 cannot be removed. .

  Therefore, in the intermediate transfer type image forming apparatus, by performing the above-described misregistration correction, the misregistration correction pattern is transferred to the secondary transfer roller. As a result, the pattern transferred to the secondary transfer roller adheres to the back surface of the paper, and the paper becomes dirty. In the case of double-sided printing, the image quality is degraded.

  In order to solve such problems, in the intermediate transfer type image forming apparatus, after performing the above-described misregistration correction, a bias is applied to the conveyance belt and the secondary transfer roller to collect the toner, and cleaning is performed. ing.

  Further, when the toner for the pattern for correcting the misregistration adheres to the secondary transfer roller as dirt, a dirt prevention pattern that covers the dirt toner is formed with yellow toner and adheres to the secondary transfer roller. Thus, there has been proposed a method for preventing an apparent stain by attaching an inconspicuous yellow stain prevention pattern on the back side of the paper instead of the above-mentioned stain toner (for example, see Patent Document 2).

  When the method disclosed in Patent Document 2 is used, it is possible to prevent apparent stains, but there is no change in that excess toner adheres to the back side of the paper. In addition, there is a problem that consumption of yellow toner increases. Furthermore, when performing double-sided printing, the color of the image formed on the back side may change due to the yellow color of the anti-smudge pattern.

  In order to prevent the above-described stain on the back side of the paper without using the method disclosed in Patent Document 2, it is necessary to perform a cleaning process for collecting toner by biasing the intermediate transfer belt and the secondary transfer roller. There is. In order to reliably remove the toner attached to the intermediate transfer belt and the secondary transfer roller by this cleaning process, it is necessary to set a longer time for the cleaning process, that is, a time for collecting the toner by applying a bias. During this time, image formation and output cannot be performed, so that downtime increases and user convenience decreases.

  On the other hand, if the density of the toner forming the misregistration correction pattern, that is, the amount of toner per unit area is small, the intermediate transfer belt and the secondary transfer roller can be used while shortening the cleaning process period. The adhered toner can be reliably removed. Here, even if the toner density when developing the electrostatic latent image of the misregistration correction pattern is lowered, the pattern is repeatedly drawn in the misregistration correction operation, and the pattern is formed over a plurality of circumferences of the secondary transfer roller. When the pattern is transferred, if the pattern is transferred again to the position where the pattern was transferred in the previous round, the toner density increases.

  The present invention has been made in consideration of the above-described circumstances, and an object thereof is to shorten the time required to remove the toner constituting the misregistration correction pattern in the image forming apparatus.

In order to solve the above-described problems, one embodiment of the present invention controls a light source that irradiates a photoconductor with a light beam and irradiates the light beam to form an electrostatic latent image on the photoconductor. An intermediate transfer body that temporarily holds and conveys an image formed by developing the electrostatic latent image onto a sheet, and an endless shape disposed opposite to the intermediate transfer body A transfer rotator for transferring an image held on the intermediate transfer member onto a sheet supplied between the intermediate transfer member and a sensor for imaging the surface of the intermediate transfer member. An image detection unit that detects that an image held on the surface of the intermediate transfer member has reached a position facing the sensor based on an output signal, and a predetermined pattern in which the light source control unit is configured by a plurality of lines Image detection after starting drawing A detection period counting unit that counts a detection period that is a period until the predetermined pattern is detected, and the image detection unit detects the predetermined pattern after the light source control unit starts drawing the predetermined pattern. A correction value calculation unit that calculates a correction value for correcting the timing of irradiating the light source with the light beam based on a difference between a reference value that is a reference period until the detection and the counted detection period; The light source control unit repeatedly draws the pattern, and the peripheral length L of the transfer rotating body and the pattern repeatedly drawn on the surface of the transport body the writing start position and width P in the sub-scanning direction to the drawing start position of the pattern to be written to the next, the maximum value p _m in the sub-scanning direction of the width of the lines included in the pattern and _x, and the minimum value _{g min} of the gap in the sub-scanning direction of the repeating drawn adjacent the pattern _{lines, p max} ≦ | and satisfying the relation of ≦ _{g min} | P-L.

Here, it is preferable that the number n of repeated drawing of the pattern satisfies the relationship of p _max ≦ | P−L | ≦ g _min / (n−1).

  Further, the sensor images the surface of the intermediate transfer body by exposing the intermediate transfer body and receiving reflected light, and a minimum value of the width of a line included in the pattern is determined by the exposure of the sensor. It is preferable that it is more than a spot diameter.

Furthermore, it is preferable to satisfy the relationship of p _max = | P−L |.

Furthermore, it is preferable to satisfy the relationship of | P−L | = g _min / (n−1).

  The pattern includes an oblique line pattern inclined in the sub-scanning direction, and the widths of all the lines included in the pattern are substantially the same. The width p of the line included in the pattern, the oblique line, and the sub-scan The angle θ formed by the direction preferably satisfies the relationship p / sin θ = | P−L |.

The g _min is preferably the minimum value of the interval in the sub-scanning direction between adjacent lines in the pattern.

The g _min is preferably the minimum value of the width in the sub-scanning direction from the pattern drawn at the end of the pattern to the drawing start position of the next drawn pattern.

  Furthermore, the minimum value of the interval in the sub-scanning direction of adjacent lines in the pattern, the pattern drawn at the end of the pattern, and the width in the sub-scanning direction up to the drawing start position of the next drawn pattern The minimum value is preferably the same.

  The pattern is preferably composed of a plurality of lines that do not intersect each other.

According to another aspect of the present invention, there is provided a light source control unit that controls a light source that emits a light beam to a photosensitive member to irradiate the light beam to form an electrostatic latent image on the photosensitive member; An intermediate transfer member that temporarily holds and conveys an image formed by developing an electrostatic latent image on a sheet, and an endless rotating member that is disposed to face the intermediate transfer member. A transfer rotator for transferring an image held on the intermediate transfer member onto a sheet supplied between the intermediate transfer member and an output signal of a sensor for imaging the surface of the intermediate transfer member. An image detection unit that detects that the image held on the surface of the intermediate transfer body has reached a position facing the sensor, and the light source control unit starts drawing a predetermined pattern composed of a plurality of lines. After that, the image detection unit A detection period counting unit that counts a detection period that is a period until the detection of an image, and a reference from when the light source control unit starts drawing a predetermined pattern to when the image detection unit detects the predetermined pattern An image forming unit including a correction value calculating unit that calculates a correction value for correcting a timing of irradiating the light source with a light beam based on a difference between a reference value that is a value of the period to be and the counted detection period An apparatus misalignment correction method for an apparatus, wherein the light source control unit has a circumferential length L of the transfer rotator and a pattern that is repeatedly drawn on the surface of the transport body, and the pattern is repeatedly drawn from the drawing start position of one of the patterns. and the sub-scanning direction width P to drawing start position of the pattern to be drawn in, and the maximum value p _max in the sub-scanning direction of the width of the lines included in the pattern, being the repetitive drawing And the minimum value g _min in the sub-scanning direction between adjacent lines in turn, p _max ≦ | and repeatedly ≦ g _min the pattern so as to satisfy the relation wherein the draw | P-L.

  According to the present invention, in the image forming apparatus, it is possible to shorten the time required to remove the toner constituting the misregistration correction pattern.

1 is a block diagram illustrating a hardware configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a functional configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a configuration of a print engine according to an embodiment of the present invention. It is a top view which shows the structure of the optical writing apparatus which concerns on embodiment of this invention. It is a sectional side view which shows the structure of the optical writing apparatus which concerns on embodiment of this invention. It is a block diagram which shows the control part of the optical writing apparatus which concerns on embodiment of this invention. It is a figure which shows the information memorize | stored in the reference value memory | storage part which concerns on embodiment of this invention. It is a figure which shows the example of the pattern drawn in the position shift correction operation | movement which concerns on embodiment of this invention. It is a figure which shows the detail of the pattern for drum space | interval correction | amendment which concerns on embodiment of this invention. FIG. 6 is a diagram illustrating a state where a drum interval correction pattern according to an embodiment of the present invention is transferred to a secondary transfer roller. FIG. 6 is a diagram illustrating a state where a drum interval correction pattern according to an embodiment of the present invention is transferred to a secondary transfer roller. FIG. 6 is a diagram illustrating a state where a drum interval correction pattern according to an embodiment of the present invention is transferred to a secondary transfer roller. FIG. 6 is a diagram illustrating a state where a drum interval correction pattern according to an embodiment of the present invention is transferred to a secondary transfer roller. It is a figure which shows the structure of the print engine which concerns on a direct transfer format.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the present embodiment, an image forming apparatus as an MFP (Multi Function Peripheral) will be described as an example. The image forming apparatus according to the present embodiment is an electrophotographic image forming apparatus, and the positional deviation correction after performing the positional deviation correction of the image in the optical writing apparatus for forming the electrostatic latent image on the photosensitive member. The gist thereof is to shorten the period required for removing the pattern drawn in FIG.

  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, a plurality of image forming units (electrophotography) are sequentially arranged from the upstream side in the conveying direction of the conveying belt 105 along the conveying belt 105 on which the images formed and superimposed by the image forming units 106 of the respective colors are temporarily transferred. Process section) 106BK, 106M, 106C, 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 and the drive roller 107 function as a drive unit that moves the conveyor 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 by the paper feed roller 102 and the separation roller 103 in order from the uppermost one, and the secondary transfer roller 119 and the secondary belt that is the opposite portion of the transport belt 105. It is conveyed to the transfer unit. In the secondary transfer portion, the toner image formed on the conveyance belt 105 is transferred onto the sheet by the function of the secondary transfer roller 110. That is, the conveyance belt 105 functions as an intermediate transfer member. Further, the secondary transfer roller 119 functions as a transfer rotator.

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

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

  This toner image is transferred onto the conveyance belt 105 by the action of the transfer unit 115BK at a position (transfer position) where the photosensitive drum 109BK and the conveyance belt 105 abut. By this transfer, an image of black toner is formed on the conveyance belt 105. 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 conveying belt 105 to which the black toner image is transferred by the image forming unit 106BK is conveyed to the next image forming unit 106M side by the rotational drive by the driving roller 107. 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 and transferred onto the already formed black image. Is done.

  The transport belt 105 is further transported to the next image forming units 106C and 106Y, and a cyan toner image formed on the photoconductive drum 109C and a yellow toner formed on the photoconductive drum 109Y by the same operation. The image is superimposed and transferred. In this way, a full color image is formed on the conveyor belt 105. The conveyance belt 105 on which the full-color superimposed image is formed proceeds to the position facing the above-described secondary transfer roller 119, and the toner image formed on the conveyance belt 105 in the secondary transfer portion is secondarily transferred to the sheet. The Further, the sheet on which the toner image is transferred is discharged to the outside of the image forming apparatus after the image is fixed by the fixing device 116.

  In such an image forming apparatus 1, errors in the interaxial distances of the photosensitive drums 109 BK, 109 M, 109 C, and 109 Y, parallelism errors in the photosensitive drums 109 BK, 109 M, 109 C, and 109 Y, and deflection in the optical writing device 111. The toner images of each color do not overlap at positions that should originally overlap due to errors in the installation of mirrors, writing timing errors of electrostatic latent images on the photosensitive drums 109BK, 109M, 109C, and 109Y. May occur.

  Further, due to the same reason, the image is transferred to a range outside the range where the image should originally be transferred on the conveyance belt 105, and the range outside the range where the image is originally transferred on the paper that is the final transfer target. The image may be transferred to 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 conveyance belt 105 by the photosensitive drums 109BK, 109M, 109C, and 109Y, and is used for correction drawn on the surface of the conveyance belt 105. A light emitting element for irradiating the pattern and a light receiving element for receiving reflected light from the correction pattern are included. As shown in FIG. 3, the pattern detection sensor 117 is supported on the same substrate along the direction orthogonal to the conveyance direction of the conveyance belt 105 on the downstream side of the photosensitive drums 109BK, 109M, 109C, and 109Y. . The mode of positional deviation correction will be described in detail later.

  A cleaner 118 is provided in order to remove the toner of the pattern drawn on the conveyance belt 105 and prevent the sheet conveyed by the conveyance belt 105 from being stained in such misalignment correction. As shown in FIG. 3, the cleaner 118 is pressed against the conveyor belt 105 on the downstream side of the secondary transfer roller 119 and on the upstream side of the photosensitive drum 109 in the conveyance direction of the conveyor belt 105. This is a blade and is a developer removing unit that scrapes off toner adhering to the surface of the conveying belt 105.

  Furthermore, the belt cleaner 118 according to the present embodiment includes a function of collecting toner adhering to the conveyance belt 105 by applying a bias voltage. By applying a bias voltage having a polarity opposite to the charge of the toner, the toner adhering to the conveyance belt 105 can be peeled off and adsorbed to the belt cleaner 118.

  Note that when the toner charge is mixed in positive and negative, the belt cleaner 118 vibrates the bias voltage positively and negatively. As a result, toner having either positive or negative charge can be peeled off from the conveying belt 105 and adsorbed to the belt cleaner 118.

  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.

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

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

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

  The sensor control unit 123 includes a function of controlling the pattern detection sensor 117 and adjusting the light amount of the light emitting elements included in the pattern detection sensor 117. That is, the sensor control unit 123 also functions as a light amount adjustment unit. When adjusting the light amount of the light emitting element, the sensor control unit 123 drives the light emitting element with a predetermined power, and irradiates the white background of the conveyance belt 105 on which nothing is drawn. And based on the value of the output signal of the light receiving element which received the reflected light, the irradiation light quantity of the light emitting element is judged and adjusted.

  For example, if the output signal of the light receiving element is lower than a predetermined target value, the sensor control unit 123 performs the same process again after increasing the driving power of the light emitting element. On the other hand, if the output signal of the light receiving element is higher than a predetermined target value, the sensor control unit 123 performs the same process again after increasing the driving power of the light emitting element. By repeating such processing, the sensor control unit 123 adjusts the driving power of the light emitting element so that the driving power of the light emitting element becomes a target value, and as a result, the irradiation light amount of the light emitting element is adjusted to an appropriate level. The

  By adjusting the amount of light reflected from the conveyor belt 105 to a predetermined target value, the S / N ratio by the light receiving element is improved, and the pattern of the misalignment correction mark 400 can be detected with high accuracy.

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

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

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

  In addition to the functional configuration shown in FIG. 6, the optical writing device control unit 120 according to the present embodiment has a function of controlling the driving roller 107 that rotates the conveyor belt 105, a function of controlling the belt cleaner 118, and secondary transfer. A bias is applied to the roller 119 to control a process of removing from the secondary transfer roller 119 the pattern drawn in the positional deviation correction and transferred to the secondary transfer roller 119. That is, the optical writing device control unit 120 functions as a cleaning control unit.

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

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

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

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

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

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

  When the positional deviation correction using the positional deviation correction mark 400 as shown in FIG. 8 is executed and completed, the optical writing device control unit 120 controls the driving roller 107 to continue the rotation of the conveying belt 105, and A cleaning process is performed to apply a bias voltage to the secondary transfer roller 119 and remove the misregistration correction marks 400 transferred to the secondary transfer roller. As a result, the toner transferred to the secondary transfer roller 119 is removed by the positional deviation correction, and the secondary transfer roller is cleaned, so that the toner adheres to the back surface of the paper in the secondary transfer portion, and the paper becomes dirty. Can be prevented.

  In this cleaning process, the toner remaining on the conveying belt 105 side without being transferred to the secondary transfer roller 119 side is removed by the cleaner 118. During this period, the optical writing device 120 performs control such as oscillating the bias voltage of the belt cleaner 118 positively or negatively, and peels off the toner adhering to the conveyance belt 105.

  When the charge of the toner is only one of positive and negative, the vibration of the bias voltage is not necessary. In this case, the optical writing device control unit 120 applies a bias voltage having a charge opposite to the charge of the toner, and peels off the toner attached on the transport belt 105. Also, the bias voltage of the belt cleaner 118 may be applied during normal operation. In this case, the optical writing device control unit 120 only controls the driving roller 107 to continue the conveyance belt 105 without changing the control during the cleaning process.

  When performing misalignment correction using the misalignment correction pattern 400 as shown in FIG. 8, as described above, the pattern detection sensor 117 irradiates the surface of the conveyor belt 105 with a light emitting element, and receives the reflected light as a light receiving element. And outputs a detection signal corresponding to the amount of received light. And the sensor control part 123 detects a pattern based on the output signal of the pattern detection sensor 117. FIG.

  Here, the amount of light incident on the light receiving unit of the pattern detection sensor 117 according to the present embodiment is the strongest when the reflecting surface is white, becomes weaker as the color of the reflecting surface becomes darker, and the reflecting surface is black. In some cases. Therefore, the sensor control unit 123 detects a pattern when the signal intensity output from the pattern detection sensor 117 is weak, that is, when the signal intensity is lower than a predetermined threshold value.

  Here, there are disturbances such as deposits and scratches other than the pattern on the transport belt 105. When the light irradiated by the light emitting element is irradiated by this disturbance, the amount of light incident on the light receiving element is reduced as compared with the case where a completely white surface is irradiated. Therefore, the threshold value that the sensor control unit 123 applies to the output signal of the pattern detection sensor 117 in order to detect the pattern needs to be set as low as possible so that the change of the signal due to the disturbance can be ignored.

  In order to lower the threshold value set in the sensor control unit 123, it is necessary to reduce the amount of light incident on the light receiving element when the irradiation light is applied to the pattern, that is, the amount of reflected light. Here, in order to reduce the amount of reflected light as much as possible, when the pattern drawn on the transport belt 105 is transported and passes through the spot of light irradiated by the light emitting element, the entire range of the spot is the pattern range. To be included. That is, it is preferable that the line width of the pattern is made larger than the spot diameter so that a period in which the light emitted from the light emitting element does not irradiate the white surface of the conveyor belt 105 occurs.

  Thereby, when the pattern drawn on the conveyance belt 105 is conveyed and passes the detection position of the pattern detection sensor 117, specifically, the spot range of the irradiation light by the light emitting element, the spot range is included in the pattern range. As a result, there is a period in which the white surface of the conveyor belt 105 is not irradiated, so the minimum value of the signal corresponding to the amount of reflected light is low, and the amount of light is zero when the pattern is black. Accordingly, when the sensor control unit 123 detects a pattern based on the output signal of the pattern detection sensor 117, the threshold value applied to the signal can be set low, and the above-described disturbance of the conveyance belt 105 such as scratches and adhered matter The influence of can be eliminated.

  In such an image forming apparatus 1 and the optical writing apparatus 111, the gist of the present embodiment is that the toner per unit area of the toner transferred to the secondary transfer roller 119 side is shortened in order to shorten the period for performing the cleaning process described above. The purpose is to reduce the amount, that is, the toner density. Therefore, the repetition interval of the drum interval correction pattern 412 that is repeated in the misregistration correction mark 400 according to the present embodiment does not overlap the secondary transfer roller 119 so that it does not overlap when transferred to the secondary transfer roller 119. It is set based on the length. Hereinafter, the repetition interval of the drum interval correction pattern 412 in the misregistration correction mark 400 according to the present embodiment will be described in detail.

FIG. 9 is a diagram showing details of patterns included in the drum interval correction pattern 412 and the repetition interval of the drum interval correction pattern according to the present embodiment. In FIG. 9, the width p _{1 in} the sub-scanning direction of the sub-scanning direction correction pattern 413 and the width p _{2 in} the sub-scanning direction of the main scanning direction correction pattern 414 are shown.

In FIG. 9, as an example of the sub-scanning direction interval of each pattern included in the drum interval correction pattern 413, the sub-scanning direction interval g ₁ between the sub-scanning direction correction patterns 413, and the main scanning direction correction distance g ₂ in the sub-scanning direction of the pattern 414 to each other is shown. Also, the sub-scanning direction between g ₃ of the sub-scanning direction correction pattern 413 and the main scanning direction correction pattern 414 shown in phrase point in the main scanning direction.

  As shown in FIG. 9, the repeated interval of the drum interval correction pattern 412 that is repeatedly drawn is from the leading pattern 413 a drawn at the beginning of the sub-scanning direction correction pattern 413 to the next drawn drum interval correction pattern. This is indicated by an interval P to the leading pattern 413a included in 412. In FIG. 9, the circumferential length L of one turn of the secondary transfer roller 119 is shown in comparison with the repetition interval P.

Such a repetition interval P and the peripheral length L of the secondary transfer roller 119 satisfy the relationship represented by the following formula (1).

In Expression (1), “p _max ” is the largest value of p ₁ and p ₂ shown in FIG. 9, that is, the maximum value of the width of the pattern included in the drum interval correction pattern 412 in the sub-scanning direction. . In the present embodiment, since towards _{p 2} is greater than _{p 1, p max} is _{p 2.}

In Expression (1), “g _min ” is adjacent in the sub-scanning direction in the values exemplified by g 1, g 2, and g 3 in FIG. 9, that is, in the pattern included in the drum interval correction pattern 412. This is the minimum value of the interval between two patterns. In the present embodiment, since the value of _{g 1} is the _{smallest, g min} is _{g 1.}

  Under this premise, formula (1) will be described. First, “P−L” indicates the difference between the repetition interval P and the circumferential length L of the secondary transfer roller 119. In other words, when the drum interval correction pattern 412 is repeatedly drawn, the drum interval correction pattern 412 for the first round is transferred to the secondary transfer roller, and the drum interval correction pattern 412 for the second week is further transferred. Is transferred to the secondary transfer roller, the amount of deviation between the first pattern 413a in the first round and the first pattern 413a in the second week is shown.

  When the drum interval correction pattern 412 is repeatedly drawn twice or three times, the previously drawn drum interval correction pattern 412 and the newly drawn drum interval correction pattern 412 do not overlap each other. The purpose of this embodiment is to define the amount of deviation, and the writing control unit 121 draws the drum interval correction pattern 412 by controlling the light source device 281 in accordance with the definition.

First, the portion of “p _max ≦ P−L” will be described. This is because, when the drum interval correction pattern 412 to be repeatedly drawn is transferred to the secondary transfer roller 119, like the leading patterns 413a, This is to prevent the corresponding patterns from overlapping each other. Here, the reason why it is defined as p _max will be described with reference to FIG.

In FIG. 10, when the drum interval correction pattern 412 is transferred to the secondary transfer roller 119 for two rounds, the first round pattern is indicated by a solid line and the second round pattern is indicated by a broken line. As shown in FIG. 10, if p _max in the equation (1) is defined as p _min , that is, p ₁ according to the present embodiment, the sub-scanning direction correction patterns 413 overlap each other as shown in FIG. However, the main scanning direction correction patterns 414 that are wider in the sub-scanning direction than that overlap. Therefore, the “PL” needs to be at least p _max or more.

Next, the portion of “PL ≦ g _min ” will be described. This is because when the drum interval correction pattern 412 is drawn with a shift of “PL” in the second round, each pattern is displayed. This is intended to fit in the margin between patterns drawn in the previous circumference. This will be described with reference to FIG.

FIG. 11 shows the pattern of the first turn as a solid line and the pattern of the second turn as a broken line when the drum interval correction pattern 412 is transferred to the secondary transfer roller 119 for two turns, as in FIG. ing. By defining the maximum value of “PL” as g _min , the pattern drawn in the second round is drawn in the margin between each pattern as shown in FIG. It is drawn without overlapping the pattern.

  FIG. 11 shows the case where the drum interval correction pattern 412 for two rounds is transferred to the secondary transfer roller 119, but as described in FIG. 8, the drum interval correction pattern 412 is repeatedly drawn. Is done. Therefore, it is desirable that all the drum interval correction patterns 412 included in the misregistration correction mark 400 do not overlap when transferred to the secondary transfer roller 119. Such an example is shown in FIG.

In FIG. 12, when the number of repetitions of the drum interval correction pattern 412 included in the misregistration correction mark 400 is 5, the secondary transfer roller 119 does not overlap all five drum interval correction patterns 412. The state of being transcribed is shown. In such an aspect, conditions that are more severe than those of the above formula (1) need to be satisfied, and specifically, the following formula (2) needs to be satisfied.

In Expression (2), “n” is the number of repetitions of the drum interval correction pattern 412 described above, and is “5” in the example of FIG. The expression (2) will be described. In the portion of “PL ≦ (g _min ) / (n−1)”, the pattern deviation amount for each turn is set to be smaller than the expression (1). It stipulates. The narrower interval is an interval of a blank space in which a pattern is to be stored, and “g _min ” is divided by the number of times the drum interval correction pattern 412 is repeated from the second round onward, that is, “n−1”. It is an interval.

When the equation (2) is transformed, “(| P−L |) (n−1) ≦ g _min ” is obtained, and this is performed every turn after the pattern of the first round is transferred to the secondary transfer roller 119. The total shift amount of the pattern “n−1” times after the second round transferred with a shift of “| P−L |”, that is, “(| P−L |) (n−1)” is It is shown that all can be included in the interval of “g _min ”. When such a condition is satisfied, as shown in FIG. 12, the drum interval correction pattern 412 repeatedly drawn on the misregistration correction mark 400 is transferred to the secondary transfer roller 119 without overlapping. .

Note that, as a premise of the formula (2), the following formula (3) must be satisfied.

In consideration of Equation 3, since it is preferable that p _max is small, the width in the sub scanning direction of each pattern included in the misregistration correction mark 400 is preferably narrow and the g _min is large. A wider width between adjacent patterns in the scanning direction is better. However, the width of each line included in the misregistration correction mark 400 needs to secure a certain width as described above, and is preferably larger than the spot diameter of the irradiation light of the light emitting element of the pattern detection sensor 117. Further, if the width between adjacent patterns in the sub-scanning direction is widened, the width of the misregistration correction mark 400 in the sub-scanning direction is widened, and as a result, the time required for misalignment correction is increased. Therefore, the width between adjacent patterns in the sub-scanning direction needs to be as narrow as possible.

Considering these, it is preferable that the repetition interval P and the peripheral length L of the secondary transfer roller 119 have a relationship represented by the following expression (4).

  When the condition of Expression (4) is satisfied, the pattern of the misregistration correction mark 400 is secured in the pattern in the sub-scanning direction while ensuring the spot diameter of the irradiation light of the light emitting element of the pattern detection sensor 117. The time required for correcting the misalignment can be reduced by narrowing the interval between them as much as possible and narrowing the width of the misalignment correcting mark 400 in the sub-scanning direction.

Furthermore, in the above embodiment, the case where p _max = p ₂ has been described as an example. However, the thickness of each line included in the sub-scanning direction correction pattern 413 and each line included in the main-scanning direction correction pattern 414 is _Pmax is equal to “p ₁ = p _min ” and the angle formed by each line included in the main scanning direction correction pattern 414 and the sub-scanning direction is “θ”. Identified.

Then, when the above formula (4) and the formula (5) are integrated, the repetition interval P and the peripheral length L of the secondary transfer roller 119 have the relationship represented by the following formula (6).

When Expression (6) is satisfied, as described above, the width “p _min ” of each line included in the misregistration correction mark 400 is ensured to be equal to or larger than the spot diameter of the irradiation light of the light emitting element of the pattern detection sensor 117. However, the width of g _min can be made as narrow as possible. Accordingly, it is possible to reduce the time required for the positional deviation correction by narrowing the width of the positional deviation correction mark 400 in the sub-scanning direction.

  In the case of the condition of Expression (6), when the drum interval correction pattern 412 is transferred to the secondary transfer roller 119, as shown in FIG. 12, the pattern having the widest width in the sub-scanning direction (in this embodiment, The main scanning direction correction pattern 414) is transferred to the secondary transfer roller 119 so as to be spread without gaps. Therefore, the drum interval correction pattern 412 that is repeatedly drawn is not transferred on the secondary transfer roller 119 in an overlapping manner, and the toner density transferred to the secondary transfer roller 119 can be suppressed in the positional deviation correction. .

  In the above-described cleaning process, it is necessary to remove the toner by applying a bias for a longer period as the density of the toner transferred and adhered to the secondary transfer roller 119 is higher. On the other hand, as in this embodiment, by suppressing the density of the toner transferred to and adhered to the secondary transfer roller 119, it is possible to reduce the time required for the cleaning process after the positional deviation correction is completed. .

9 to 12 exemplify a case where “L <P”, the second round pattern is upstream of the first round pattern in the sub-scanning direction, that is, FIG. The image is transferred by shifting downward as indicated by 10. Although not particularly problematic in FIG. 12, in addition to the above-mentioned condition “g _min ”, “g _rear ” shown in FIG. 12, that is, among the lines included in the drum interval correction pattern 412 The interval between the tail pattern 414a arranged at the tail and the writing start position of the next drum interval correction pattern 412 to be drawn, that is, the head pattern 413a needs to be equal to or greater than “g _min ”.

Even if “g _rear ” is equal to or less than “g _min ”, the same effect as described above can be obtained by satisfying the following expression (7).

Equation (7) shows that when “g _rear ” is equal to or less than “g _min ”, each pattern drawn with a shift every time repeated drawing is divided into the last pattern 414a and the next pattern to be drawn next 413a. It is an expression that regulates that it falls between. This is because the definition of “g _min ” is not “the minimum value of the interval values of two patterns adjacent to each other in the sub-scanning direction in the pattern included in the drum interval correction pattern 412” but “repetitively drawn. In the drum interval correction pattern 412, the minimum value of the interval between two patterns adjacent in the sub-scanning direction is synonymous with the above-described equation (2).

Note that, as described above, the purpose of shortening the time required for misalignment correction by reducing the width of the misalignment correction mark 400 in the sub-scanning direction is “in the pattern included in the drum interval correction pattern 412. In addition, “g _min ” as “minimum value of the interval value between two patterns adjacent to each other in the sub-scanning direction” and “g _rear ” are preferably the same.

  Further, when “P <L”, the same effect as described above can be obtained. In this case, as shown in FIG. 13, the pattern of the second round is transferred with a shift to the downstream side in the sub-scanning direction from the pattern of the first round, that is, upward as shown in FIG.

  In the above embodiment, the case where the number of repetitions of the drum interval correction pattern 412 in the misalignment correction mark 400 is five as an example. It may be 6 times or more.

  Further, in the above embodiment, as an example of a pattern that is repeatedly drawn in the positional deviation correction, as shown in FIG. 9, drum interval correction including a sub-scanning direction correction pattern 413 and a main scanning direction correction pattern 14 is performed. Although the pattern 412 has been described as an example, this is only an example, and other patterns can be similarly applied as long as the conditions of the expressions (1) to (7) described above are satisfied. It is.

  Here, as the misalignment correction pattern, it is preferable that the lines constituting the pattern do not intersect each other. In the case of a pattern where lines intersect, even when the pattern is repeatedly transferred to the secondary transfer roller 119, even if the corresponding lines are shifted in the sub-scanning direction so as not to overlap each other, non-corresponding lines intersect. It is. However, when corresponding lines overlap each other, as described in FIG. 10, an overlapping area is generated over the entire range of the lines. On the other hand, when the non-corresponding lines intersect, the area is slight. Therefore, there are few demerits when shortening the cleaning period which is the gist of this embodiment.

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 Cleaner,
119 secondary transfer 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,
171 light emitting element,
172 specular reflection light receiving element,
173 diffuse reflection light receiving 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,
411 start position correction pattern,
412 Drum interval correction pattern,
413 Sub-scanning direction correction pattern,
413a head pattern,
414 main scanning direction correction pattern;
414a tail pattern

JP 2008-299311 A JP 2008-224955 A

Claims (11)

A light source controller that controls a light source that emits a light beam to the photosensitive member to irradiate the light beam to form an electrostatic latent image on the photosensitive member; and
An intermediate transfer member that temporarily holds and conveys an image formed by developing the electrostatic latent image on a sheet;
An endless rotator disposed opposite to the intermediate transfer member, the transfer rotator transferring an image held on the intermediate transfer member onto a sheet supplied between the intermediate transfer member and the intermediate transfer member. When,
An image detection unit that detects that an image held on the surface of the intermediate transfer member has reached a position facing the sensor based on an output signal of a sensor that images the surface of the intermediate transfer member;
A detection period counting unit that counts a detection period from when the light source control unit starts drawing a predetermined pattern configured by a plurality of lines until the image detection unit detects the predetermined pattern;
A difference between a reference value that is 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 the counted detection period. A correction value calculation unit for calculating a correction value for correcting the timing of irradiating the light beam with the light source based on
The light source control unit repeatedly draws the pattern,
A circumferential length L of the transfer rotator;
A width P in the sub-scanning direction from the drawing start position of one pattern to the drawing start position of the pattern drawn next in the pattern repeatedly drawn on the surface of the carrier;
A maximum value p _max of the width of the line included in the pattern in the sub-scanning direction;
The minimum value g _min of the interval in the sub-scanning direction of adjacent lines in the repeatedly drawn pattern is:
An image forming apparatus satisfying a relationship of p _max ≦ | P−L | ≦ g _min . The number n of times the pattern is repeatedly drawn is
The image forming apparatus according to claim 1, wherein a relationship of p _max ≦ | P−L | ≦ g _min / (n−1) is satisfied. The sensor images the surface of the intermediate transfer member by exposing the intermediate transfer member and receiving reflected light thereof,
The image forming apparatus according to claim 1, wherein a minimum value of a width of a line included in the pattern is equal to or larger than a spot diameter of exposure by the sensor. The image forming apparatus according to claim 3, further satisfying a relationship of p _max = | P−L |. The image forming apparatus according to claim 4, further satisfying a relationship of | P−L | = g _min / (n−1). The pattern includes a hatched pattern inclined in the sub-scanning direction,
The widths of all lines included in the pattern are substantially the same,
A line width p included in the pattern;
An angle θ formed by the oblique line and the sub-scanning direction is
The image forming apparatus according to claim 5, wherein a relationship of p / sin θ = | P−L | is satisfied. The image forming apparatus according to claim 1, wherein the g _min is a minimum value of an interval between adjacent lines in the pattern in the sub-scanning direction. 8. The g _min is a minimum value of the width in the sub-scanning direction from the pattern drawn at the end of the pattern to the drawing start position of the next drawn pattern. The image forming apparatus according to any one of the above.   The minimum value in the sub-scanning direction of adjacent lines in the pattern, the pattern drawn at the end of the pattern, and the minimum value in the sub-scanning direction up to the drawing start position of the next drawn pattern The image forming apparatus according to claim 8, wherein   The image forming apparatus according to claim 1, wherein the pattern includes a plurality of lines that do not intersect each other. A light source controller that controls a light source that emits a light beam to the photosensitive member to irradiate the light beam to form an electrostatic latent image on the photosensitive member; and
An intermediate transfer member that temporarily holds and conveys an image formed by developing the electrostatic latent image on a sheet;
An endless rotator disposed opposite to the intermediate transfer member, the transfer rotator transferring an image held on the intermediate transfer member onto a sheet supplied between the intermediate transfer member and the intermediate transfer member. When,
An image detection unit that detects that an image held on the surface of the intermediate transfer member has reached a position facing the sensor based on an output signal of a sensor that images the surface of the intermediate transfer member;
A detection period counting unit that counts a detection period from when the light source control unit starts drawing a predetermined pattern configured by a plurality of lines until the image detection unit detects the predetermined pattern;
A difference between a reference value that is 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 the counted detection period. And a correction value calculation unit for calculating a correction value for correcting a timing for irradiating the light source with the light beam based on the image forming apparatus,
The light source controller is
A circumferential length L of the transfer rotator;
A width P in the sub-scanning direction from the drawing start position of one pattern to the drawing start position of the pattern drawn next in the pattern repeatedly drawn on the surface of the carrier;
A maximum value p _max of the width of the line included in the pattern in the sub-scanning direction;
The minimum value g _min of the interval in the sub-scanning direction of adjacent lines in the repeatedly drawn pattern is:
A positional deviation correction method for an image forming apparatus, wherein the pattern is repeatedly drawn so as to satisfy a relationship of p _max ≦ | P−L | ≦ g _min .

Images