JP2019095610A - Image formation device and image formation method - Google Patents

Abstract

To provide an image formation device that can correct a position deviation of a monochrome image of each color without lowering an image formation velocity.SOLUTION: An image formation device, which forms a multicolor image by overlapping a monochrome image, has: pattern formation means that forms a pattern for correcting a position deviation of the monochrome image of each color in an inter-image area from a rear end of a transfer image to a tip end of the next transfer image in a conveyance direction of the transfer image; and correction means that corrects the position deviation on the pattern. The pattern formation means is configured to form only a first pattern for correcting the position deviation in a sub-scan direction in a prescribed inter-image area; and after correcting the position deviation in the sub-scan direction, form only a second pattern for correcting the position deviation in a main scan direction in other inter-image area different from the prescribed inter-image area.SELECTED DRAWING: Figure 14

Description

  The present invention relates to an image forming apparatus and an image forming method.

  In an image forming apparatus such as a color printer for printing a multicolor image, one in which a plurality of single-color images are superimposed to form a multicolor image is known. In such an image forming apparatus, the position of superposition of single-color images of each color is shifted due to the temperature around the apparatus and the like, and the image quality may be degraded due to a change in character color or color unevenness. is there.

  In this case, the positional deviation of the monochromatic image of each color is corrected in the inter-image area from the trailing edge in the conveyance direction of the transferred image in which the monochromatic image of each color is sequentially transferred to the transfer body to the leading edge in the conveyance direction of the next transferred image. Patent Document 1 discloses a technique for forming a pattern for correcting the positional deviation and correcting a positional deviation using the pattern.

  However, in the conventional method, depending on the size and the number of patterns to be formed, the inter-image area may be long and the image forming speed may be reduced.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to correct positional deviation of single-color images of respective colors without reducing the image forming speed.

  An image forming apparatus according to an aspect of the disclosed technique is formed on each of a plurality of image carriers on which light according to image data is irradiated to form a monochromatic latent image, and the plurality of image carriers. And a plurality of developing means for developing the latent image of the single color to obtain a single color image, and a transfer body for conveying a transfer image to which the single color image is sequentially transferred. An image forming apparatus for forming a color image, wherein in the inter-image area from the rear end of the transfer image to the front end of the next transfer image in the transport direction of the transfer image, the positional deviation of the single-color image of each color A pattern forming unit that forms a pattern to be corrected; and a correction unit that corrects the positional deviation based on the pattern, the pattern Correct the misalignment A second pattern for correcting the positional deviation in the main scanning direction to another inter-image area different from the predetermined inter-image area after forming only one pattern and correcting the positional deviation in the sub-scanning direction It is characterized by forming only.

  The positional deviation of the single-color image of each color can be corrected without reducing the image forming speed.

FIG. 1 is a schematic view showing an example of the entire configuration of an image forming apparatus according to a first embodiment. FIG. 2 is a schematic view showing an example of the configuration of an image forming apparatus included in the image forming apparatus of the first embodiment. It is the schematic which shows an example of a structure of the light beam scanning device which the image forming apparatus of 1st Embodiment has. It is a block diagram which shows an example of the light beam scanning device which the image forming apparatus of 1st Embodiment has, and the hardware constitutions of the periphery of it. It is a block diagram showing an example of composition of a VCO clock generation device which an image forming device of a 1st embodiment has. It is a block diagram showing an example of composition of a writing start position control device which an image forming device of a 1st embodiment has. 5 is a timing chart showing an example of writing start position control in the main scanning direction in the image forming apparatus of the first embodiment. 5 is a timing chart showing an example of writing start position control in the sub scanning direction in the image forming apparatus of the first embodiment. FIG. 2 is a schematic view showing an example of a line memory which the image forming apparatus of the first embodiment has. FIG. 2 is a block diagram showing an example of a functional configuration of the image forming apparatus of the first embodiment. 5 is a flowchart illustrating an example of image formation control processing in the image forming apparatus of the first embodiment. FIG. 6 is a view for explaining an example of a misalignment correction pattern in the sub scanning direction in the image forming apparatus of the first embodiment. FIG. 7 is a view for explaining an example of a misalignment correction pattern in the main scanning direction in the image forming apparatus of the first embodiment. FIG. 6 is a diagram for explaining an example of a positional deviation correction method in the image forming apparatus of the first embodiment. 5 is a flowchart illustrating an example of misalignment correction processing in the image forming apparatus of the first embodiment. It is a block diagram showing an example of functional composition of an image forming device of a 2nd embodiment. It is a figure explaining an example of the position gap amendment method in the image forming device of a 2nd embodiment. 15 is a flowchart illustrating an example of formation processing of a misalignment correction pattern in the image forming apparatus of the second embodiment.

First Embodiment
A first embodiment will be described with reference to the drawings. Hereinafter, an electrophotographic image forming apparatus having a secondary transfer mechanism called a tandem system will be described as an example. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted. The terms “image formation” and “printing” used below are synonymous. Also, except when instructed in particular, "displacement" represents "displacement of single-color images of each color", and "pattern for correction" is a "predetermined pattern formed on the intermediate transfer belt for the correction of the misalignment". "Pattern of shape" is represented.

  The image forming apparatus 100 includes an intermediate transfer unit, an image forming device 20 of each color, a light beam scanning device 21, a secondary transfer unit 22, and a fixing unit 25.

  The intermediate transfer unit has an intermediate transfer belt 10 which is an endless belt, three supporting rollers 14 to 16, and an intermediate transfer member cleaning unit 17. The intermediate transfer belt 10 is wound around supporting rollers 14 to 16 and rotates clockwise. The intermediate transfer member cleaning unit 17 is provided between the second support roller 15 and the third support roller 16 and removes residual toner remaining on the surface of the intermediate transfer belt 10 after image transfer.

  The imaging device 20 is disposed between the first support roller 14 and the second support roller 15. The image forming apparatus 20 is installed in the order of yellow (Y), magenta (M), cyan (C) and black (K) in the transport direction of the intermediate transfer belt 10. The symbols in parentheses below may indicate colors.

  The image forming apparatus 20 includes a cleaning unit, a charging unit 18, a charge removing unit, a developing unit, and a photosensitive unit 40 for each color, and performs image formation for each color. The imaging device 20 may be detachable from the image forming apparatus 100.

  The light beam scanning device 21 is provided above the imaging device 20. The light beam scanning device 21 applies a laser beam to the photosensitive drums of the photosensitive unit 40 of each color in order to form an image.

  The secondary transfer unit 22 is provided below the intermediate transfer belt 10, and includes two rollers 23 and a secondary transfer belt 24. The secondary transfer belt 24 is an endless belt. Further, the secondary transfer belt 24 is hung on the two rollers 23 and rotates. Further, the roller 23 and the secondary transfer belt 24 are installed so as to push up the intermediate transfer belt 10 and to press it against the third support roller 16.

  The secondary transfer belt 24 transfers the image formed on the intermediate transfer belt 10 to the medium. The medium is, for example, a paper or a plastic sheet.

  The fixing unit 25 is provided beside the secondary transfer unit 22. The medium on which the toner image has been transferred is sent to the fixing unit 25, and the fixing unit 25 fixes the image to the medium. The fixing unit 25 also has a fixing belt 26 and a pressure roller 27. The fixing belt 26 is an endless belt. The fixing belt 26 and the pressure roller 27 are disposed so as to press the pressure roller 27 against the fixing belt 26. Further, the fixing unit 25 performs heating.

  The sheet reversing unit 28 is provided below the secondary transfer unit 22 and the fixing unit 25. The sheet reversing unit 28 reverses the front and back of the fed medium. The sheet reversing unit 28 is used when forming an image on the back side after forming an image on the front side.

  The automatic document feeder (ADF) 400 conveys the medium onto the contact glass 32 when the start button of the operation panel is pressed and the medium is on the paper supply table 30. Do. On the other hand, when there is no medium on the paper supply table 30, the automatic sheet feeder 400 activates the image reading unit 300 to read the medium on the contact glass 32 placed by the user.

  The image reading unit 300 includes a first carriage 33, a second carriage 34, an imaging lens 35, a charge coupled device (CCD) 36, and a light source. The image reading unit 300 operates the first carriage 33 and the second carriage 34 to read the medium on the contact glass 32.

  Light is emitted from the light source of the first carriage 33 toward the contact glass 32. Next, the light from the light source of the first carriage 33 is reflected by the medium on the contact glass 32.

  The reflected light is reflected by the first mirror on the first carriage 33 toward the second carriage 34. Next, the light reflected by the second carriage 34 is imaged through the imaging lens 35 onto the CCD 36 which is a reading sensor.

  The image forming apparatus 100 creates image data of Y, M, C, and K, that is, each color, based on the data acquired from the CCD 36.

  When the start button of the operation panel is pressed, the image forming apparatus 100 receives an instruction to form an image from an external device such as a PC (Personal Computer), or receives an instruction to output a facsimile. Start rotating.

  When the rotation of the intermediate transfer belt 10 is started, the imaging device 20 starts an imaging process. The medium on which the toner image has been transferred is sent to the fixing unit 25. Next, when the fixing unit 25 performs a fixing process, an image is formed on the medium.

  The sheet feeding table 200 includes a sheet feeding roller 42, a sheet feeding unit 43, a separation roller 45, and a conveyance roller unit 48. The paper feed unit 43 has a plurality of paper feed trays 44, and the transport roller unit 48 has a transport roller 47.

  The paper feed table 200 selects one of the paper feed rollers 42. Next, the sheet feeding table 200 rotates the sheet feeding roller 42 to be selected.

  The sheet feeding unit 43 selects one sheet feeding tray among the plurality of sheet feeding trays 44 and feeds the medium from the sheet feeding tray 44. Next, the fed-out medium is separated into one sheet by the separation roller 45 and sent to the conveyance path 46. Subsequently, in the conveyance path 46, the medium is sent to the image forming apparatus 100 by the conveyance roller 47.

  The medium sent to the image forming apparatus 100 is sent to the registration roller 49 via the paper feed path 53. Next, the medium sent to the registration roller 49 is abutted against the registration roller 49 and stopped. Subsequently, the medium is sent to the secondary transfer unit 22 as the toner image enters the secondary transfer unit 22.

  The medium may be sent from the manual feed tray 51. When a medium is fed from the manual feed tray 51, the image forming apparatus 100 rotates the paper feed roller 50. Next, the paper feed roller 50 separates one sheet of medium from the plurality of media present on the manual feed tray 51. Subsequently, the sheet feeding roller 50 sends the separated medium to the sheet feeding path 53. Further, the medium sent to the paper feed path 53 is sent to the registration roller 49. Further, the processing after the medium is sent to the registration roller 49 is similar to, for example, the case where the medium is fed from the paper feed table 200.

  The medium is fixed by the fixing unit 25 and discharged. Further, the medium discharged from the fixing unit 25 is sent to the discharge roller 56 by the switching claw 55. Next, the discharge roller 56 sends the fed medium to the paper discharge tray 57 and discharges the medium.

  Further, the switching claw 55 may send the medium discharged from the fixing unit 25 to the sheet reversing unit 28. The sheet reversing unit 28 reverses the front and back of the fed medium. The reversed medium is subjected to image formation on the back side as in the front side, and is sent to the paper discharge tray 57.

  On the other hand, toner remaining on the intermediate transfer belt 10 is removed by the intermediate transfer member cleaning unit 17. When the toner remaining on the intermediate transfer belt 10 is removed, the image forming apparatus 100 prepares for the next image formation.

  Next, an example of the configuration of the image forming apparatus 20 included in the image forming apparatus 100 according to the present embodiment will be described with reference to FIG.

  The image forming apparatus 20 includes an intermediate transfer belt 10, an intermediate transfer member cleaning unit 17, and a secondary transfer unit 22. Furthermore, the imaging device 20 has four light beam scanning devices 21 and an imaging unit 20U for each color.

  The imaging device 20 forms images of a plurality of colors, that is, four colors, on the intermediate transfer belt 10 in an overlapping manner to form a color image. That is, the imaging device 20 performs an imaging process. Specifically, the process of image formation in the electrophotographic system includes five processes of charging, exposure, development, transfer and fixing, and the like. Among them, the imaging process is, for example, charging, exposure, development and transfer.

  In the imaging device 20, the light beam is incident on the photosensitive unit 40 from the light beam scanning device 21. A light beam modulated based on image data is incident on the photosensitive unit 40.

  A cleaning unit 13, a charging unit 18, a charge removing unit 19, and a developing unit 29 are respectively installed around each photosensitive unit 40.

  The charging unit 18 performs the process of charging. The charging process is a process in which the charging unit 18 charges the surface of the photosensitive unit 40.

  The charged photosensitive unit 40 is subjected to a process of exposure by a light beam. The process of exposure is a process in which an electrostatic latent image is formed on the surface of the photosensitive unit 40. The developing unit 29 carries out a process of development. The process of development is a process in which toner is attached to the electrostatic latent image formed on the photosensitive unit 40 to form a toner image. Further, toner is supplied to the developing unit 29 from a toner bottle.

  The developing unit 29 has a developing roller. The developing roller causes the toner to adhere to the photosensitive unit 40 in the process of development.

  Next, the toner image is transferred onto the intermediate transfer belt 10 by the transfer device 62. First, the single-color image of the first color is transferred onto the intermediate transfer belt 10, and then the single-color image is transferred in the order of the second, third and fourth colors. In this manner, four single-color images are sequentially superimposed on the intermediate transfer belt 10 to form one image in which four-color toners are superimposed.

  An image in which toners of four colors are superimposed is an example of a multicolor image. Further, an image in which toners of four colors are superimposed on the intermediate transfer belt 10 is an example of a transfer image.

  After the transfer, the discharging unit 19 discharges the photosensitive unit 40, and the cleaning unit 13 performs cleaning.

  When the transferred toner image is sent to the secondary transfer unit 22, the medium is sent to the secondary transfer unit 22. Thus, the toner image on the intermediate transfer belt 10 is transferred to the medium sent to the secondary transfer unit 22.

  Thereafter, the fixing unit 25 performs the fixing process. Thus, when the process up to fixing is performed, an image is formed on the medium. The intermediate transfer member cleaning unit 17 removes four color toner images after the transfer process.

  The intermediate transfer belt 10 is an example of a transfer member, and the photosensitive unit 40 is an example of an image carrier. The developing unit 29 is an example of a developing unit.

  Further, in order to perform positional deviation correction and the like, a first sensor SEN1 and a second sensor SEN2 are provided. The first sensor SEN1 and the second sensor SEN2 are, for example, reflective optical sensors or the like. Specifically, the first sensor SEN1 and the second sensor SEN2 detect a correction pattern of a predetermined shape formed on the intermediate transfer belt 10 for positional deviation correction and the like. In the detection of the correction pattern, for example, a change in the output of the reflective optical sensor according to the correction pattern is detected. Based on the detection result, positional deviation in the main scanning direction and the sub scanning direction is corrected for each color. Note that the magnification etc. in the main scanning direction may be corrected based on the detection result.

  Each of the first sensor SEN1 and the second sensor SEN2 “is provided at a location after the transfer image is formed in the transfer image transfer direction, and detects a correction pattern for correcting the positional deviation of the single-color image. "Detection means" is an example.

  Next, an example of the configuration of the light beam scanning device included in the image forming device of the present embodiment will be described with reference to FIG. As illustrated, the light beam scanning device 21 includes a polygon mirror 11, an fθ lens 12, a LD (Laser Diode) unit 31, a folding mirror 37, a synchronization mirror 38, a synchronization lens 39, and a cylinder lens 41. , And a synchronous sensor 54. The configuration of the light beam scanning device of each color is, for example, the same. Hereinafter, the same case will be described as an example. Therefore, duplicate explanations are omitted.

  In the illustrated example, in the light beam scanning device 21, the LD unit 31 has a light source. First, the light source of the LD unit 31 is controlled based on image data and emits light.

  A light beam emitted from the LD unit 31 passes through the cylinder lens 41 and enters the polygon mirror 11. Subsequently, the polygon mirror 11 reflects the incident light beam while being rotated by a motor or the like. The light beam is deflected by rotation of the polygon mirror 11. The light beam reflected by the polygon mirror 11 passes through the fθ lens 12, is reflected by the folding mirror 37, and is scanned on the photosensitive unit 40.

  Further, as shown in the drawing, for example, a synchronous mirror 38, a synchronous lens 39, and a synchronous sensor 54 are installed at the end where writing is performed in the main scanning direction. First, the light beam passes through the fθ lens 12, enters the synchronous mirror 38, and is reflected by the synchronous mirror 38. The light beam reflected by the synchronous mirror 38 is collected by the synchronous lens 39 and enters the synchronous sensor 54. Thus, the synchronous sensor 54 detects the timing of the start of writing in the main scanning direction from the incident light beam.

  FIG. 4 is a block diagram showing an example of a light beam scanning device 21 of the imaging device 20 of the present embodiment and a hardware configuration of the periphery thereof. The illustrated configuration example is the configuration of the light beam scanning device 21 for one color.

  Connected to the light beam scanning device 21 are a polygon motor control device 211, an LD control device 212, a synchronization detection lighting control device 213, a pixel clock generation device 214, and a writing start position control device 215. . In addition, the printer control unit 1 is connected to the polygon motor control device 211 and the like. Further, to the printer control unit 1, a first sensor SEN1, a second sensor SEN2, a storage device 2, and a pixel clock generation device 214 are connected.

  The light beam emitted from the LD unit 31 is detected by the synchronous sensor 54 or the like. The synchronization sensor 54 outputs a synchronization detection signal XDETP when the light beam is detected. The synchronization detection signal XDETP is sent to the synchronization detection lighting control device 213, the pixel clock generation device 214, and the writing start position control device 215.

  The synchronization detection lighting control device 213 turns on the LD forced lighting signal BD to generate the synchronization detection signal XDETP. Next, when the LD forced lighting signal BD is turned ON, the LD control device 212 causes the LD unit 31 to emit a light beam. On the other hand, after the synchronization detection signal XDETP is output, the synchronization detection lighting control device 213 causes the LD unit 31 to emit a light beam based on the synchronization detection signal XDETP and the pixel clock signal PCLK. Specifically, the LD control device 212 causes the LD unit 31 to emit a light beam at such a timing that flare light is not generated and the synchronization detection signal XDETP can be generated. Furthermore, when the synchronization detection signal XDETP is detected, the synchronization detection lighting control device 213 generates an LD forced lighting signal BD that turns off the LD, and sends it to the LD control device 212.

  Further, the light quantity control timing signal APC of the LD is generated based on the synchronization detection signal XDETP and the pixel clock signal PCLK. Next, the light amount control timing signal APC is sent to the LD control device 212. Further, the processing based on the light quantity control timing signal APC is performed outside the image writing area. That is, at the timing when the light amount control timing signal APC is sent, control for adjusting the light amount is performed.

  The LD control device 212 causes the LD unit 31 to emit a light beam based on a signal indicating the LD forced lighting signal BD, the light amount control timing signal APC, and the image data DIMG synchronized with the pixel clock signal PCLK. Then, the light beam emitted by the LD unit 31 is incident on the polygon mirror 11. Next, the light beam deflected by the polygon mirror 11 passes through the fθ lens 12 and scans on the photosensitive unit 40.

  The polygon motor control device 211 controls the polygon motor to rotate at a predetermined number of rotations based on a control signal from the printer control unit 1.

  The writing start position control device 215 generates a signal for determining the writing start timing and the width of the image based on the control signal from the printer control unit 1, the synchronization detection signal XDETP, the pixel clock signal PCLK and the like. The signals for determining the write start timing and the image width are the main scanning control signal XRGATE and the sub scanning control signal XFGATE.

  When the first sensor SEN1 and the second sensor SEN2 detect the correction pattern, they send detection results to the printer control unit 1. Next, the printer control unit 1 calculates the amount of positional deviation based on the detection result. Subsequently, the printer control unit 1 generates correction data based on the positional deviation amount. Further, the printer control unit 1 sets the pixel clock generation device 214 and the writing start position control device 215 based on the correction data. Also, the printer control unit 1 stores the correction data in the storage device 2. That is, when image formation is performed, the correction data stored in the storage device 2 is read by the printer control unit 1 and settings of the pixel clock generation device 214 and the writing start position control device 215 are performed.

  The pixel clock generation device 214 includes a reference clock generation device 2141, a voltage controlled oscillator (VCO) clock generation device 2142, and a phase synchronization clock generation device 2143. The reference clock generation unit 2141 generates a reference clock signal FREF. The VCO clock generator 2142 generates a VCO clock signal VCLK.

  FIG. 5 is a block diagram showing a configuration example of the VCO clock generation device of the present embodiment. As illustrated, the VCO clock generation device 2142 includes a phase comparator 21421, a low pass filter (Low Pass Filter) 21422, a VCO 21423, and a 1 / N frequency divider 21424.

  The reference clock signal FREF from the reference clock generation device 2141 and the clock signal divided into 1 / N by the 1 / N divider 21424 are input to the phase comparator 21421. The phase comparator 21421 also compares the phases of the falling edges of the two input signals and outputs an error component at a predetermined current.

  The low pass filter 21422 removes high frequency components from the output of the phase comparator 21421 and outputs a DC voltage.

  The VCO 21423 outputs a VCO clock signal VCLK having a predetermined frequency based on the output of the low pass filter 21422.

  The 1 / N frequency divider 21424 divides the input VCO clock signal VCLK into 1 / N with the set division ratio N.

  The frequency of the reference clock signal FREF from the printer control unit 1 and the division ratio N can be set. Therefore, the frequency of the VCO clock signal VCLK is changed by setting the pixel clock generation device 214 to change the frequency of the reference clock signal FREF and the value of the division ratio N.

  Referring back to FIG. 4, the VCO clock signal VCLK input from the VCO clock generation device 2142 and the synchronization detection signal XDETP are input to the phase synchronization clock generation device 2143. Further, the phase synchronization clock generation device 2143 outputs the pixel clock signal PCLK synchronized with the synchronization detection signal XDETP to the synchronization detection lighting control device 213 or the like.

  FIG. 6 is a block diagram showing a configuration example of the writing start position control device of the present embodiment. As shown, the writing start position control device 215 has a main scanning line synchronization signal generator 2151. Also, the writing start position control device 215 has a counter 2152, a comparator 2153 and a control signal generator 2154 for main scanning and sub scanning.

  The writing start position control device 215 generates a main scanning control signal XRGATE and a sub scanning control signal XFGATE. The main scanning control signal XRGATE is generated in the main scanning direction so as to capture a signal indicating image data, that is, to indicate the write start timing of the image. On the other hand, sub-scanning control signal XFGATE is generated in the sub-scanning direction so as to indicate the acquisition of a signal indicating image data, that is, the writing start timing of the image.

  Each counter 2152 operates when the counter operation signal XLSYNC is input.

  The main scanning comparator 2153 compares the value indicated by the main scanning counter 2152 operated based on the counter operation signal XLSYNC and the pixel clock signal PCLK with the first set value SET1. The first set value SET 1 is input from the printer control unit 1. The first set value SET1 is a value determined based on the correction data.

  The control signal generator 2154 for main scanning generates a main scanning control signal XRGATE based on the comparison result output from the comparator 2153 for main scanning.

  The print start signal SRT from the printer control unit 1 is input to the sub-scanning counter 2152. The sub-scanning counter 2152 operates based on the print start signal SRT, the counter operation signal XLSYNC, and the pixel clock signal PCLK.

  The sub-scanning comparator 2153 compares the value indicated by the sub-scanning counter 2152 with the second set value SET2. The second set value SET 2 is input from the printer control unit 1. The second set value SET2 is a value determined based on the correction data.

  The control signal generator 2154 for sub scanning generates a sub scanning control signal XFGATE based on the comparison result output from the comparator 2153 for sub scanning.

  The writing start position control device 215 can correct the writing position in units of the pixel clock signal PCLK, that is, in units of one dot in the main scanning direction. On the other hand, the writing start position control device 215 can correct the writing position in units of the counter operation signal XLSYNC, that is, in units of one line, in the sub scanning direction.

  FIG. 7 is a timing chart showing an example of control of the writing start position in the main scanning direction of this embodiment. In the following description, the synchronization detection signal XDETP, the counter operation signal XLSYNC, the main scanning control signal XRGATE and the sub scanning control signal XFGATE are described as an example in which a low level is a valid signal, that is, a low active signal.

  The main scanning counter is reset by the counter operation signal XLSYNC. The main scanning counter is a counter value indicated by the main scanning counter 2152 shown in FIG.

  The main scanning counter counts up by the pixel clock signal PCLK. When the value indicated by the main scanning counter becomes the first set value SET1, the main scanning comparator 2153 outputs a signal as a comparison result. In this example, the first set value SET1 is "X". Next, when the main scanning comparator 2153 outputs a signal indicating that the first set value SET1 has been reached, the main scanning control signal generator 2154 sets the main scanning control signal XRGATE to a low level. . The main scanning control signal XRGATE is a signal that becomes low level by the image width in the main scanning direction.

  FIG. 8 is a timing chart showing an example of control of the writing start position in the sub scanning direction of the present embodiment.

  The sub-scanning counter is reset by the print start signal SRT. The sub-scanning counter is a counter value indicated by a sub-scanning counter 2152 shown in FIG.

  The sub-scanning counter counts up by the counter operation signal XLSYNC. When the value indicated by the sub-scanning counter becomes the second set value SET2, the sub-scanning comparator 2153 outputs a signal as a comparison result. In this example, the second set value SET2 is "Y". Next, when the sub-scanning comparator 2153 outputs a signal indicating that the second set value SET2 has been reached, the sub-scanning control signal generator 2154 sets the sub-scanning control signal XFGATE to the low level. Do. The sub-scanning control signal XFGATE is a signal which is at a low level by the image length in the sub-scanning direction.

  FIG. 9 is a schematic view showing an example of a line memory which the image forming apparatus 100 of the present embodiment has. The line memory LMEM shown in the figure is used, for example, at the front stage of the configuration of the image formation control apparatus 210 shown in FIG.

  The line memory LMEM stores image data fetched from a printer controller, a frame memory, a scanner or the like at a timing indicated by the sub scanning control signal XFGATE or the like. Further, it is assumed that as the image data to be stored, signals for several beams are output in synchronization with the pixel clock signal PCLK. Further, the signal output from the line memory LMEM is sent to the LD control device 212, and is controlled so that the LD lights up at the timing indicated by the signal.

  In the image forming apparatus 100 of the present embodiment, the polygon motor control device 211, the LD control device 212, the lighting control device 213 for synchronization detection, the pixel clock generation device 214, and the writing start position control device 215 are electronic circuits, for example. And other hardware. However, the present invention is not limited to this, and part or all of the processing may be realized by a CPU (Central Processing Unit) based on a program.

  On the other hand, the printer control unit 1 is realized by a CPU, a random access memory (RAM), a read only memory (ROM), an external I / F 24, and the like. However, the present invention is not limited to this, and part or all of the processing may be realized by hardware such as an electronic circuit.

  FIG. 10 is a block diagram showing an example of a functional configuration of the image forming apparatus 100 of the present embodiment. The image forming apparatus 100 includes an image forming unit 500 and a positional deviation correction unit 501. The positional deviation correction unit 501 also includes a detection unit 502.

  The image forming unit 500 forms an image based on image data. Also, using this function, the correction pattern is formed on the intermediate transfer belt 10. Therefore, the image forming unit 500 is also a pattern forming unit.

  The image forming unit 500, that is, the pattern forming unit, includes, for example, the printer control unit 1, the light beam scanning device 21, the photosensitive unit 40, the cleaning unit 13, the charging unit 18, the discharging unit 19, and the developing unit 29. , And the transfer unit 62 and the like. The pattern forming unit is an example of the “pattern forming unit”.

  The misalignment correction unit 501 is realized by, for example, a CPU of the printer control unit 1 and hardware such as an electronic circuit of the pixel clock generation device 214 and the write start position control device 215. The positional deviation correction unit 501 is an example of “a correction unit that corrects the positional deviation based on the correction pattern”.

  The detection unit 502 is realized by, for example, a first sensor SEN1 and a second sensor SEN2. The positional deviation correction unit 501 is an example of a “detection unit that detects a pattern”.

  The details of the positional deviation correction process will be described later.

  FIG. 11 is a flowchart showing an example of image formation control processing in the image forming apparatus 100.

  When the start button of the operation panel of the image forming apparatus 100 is pressed, the printer control unit 1 instructs the polygon motor control device 211 to rotate the polygon motor in step S1101. The polygon motor is a motor that rotates the polygon mirror 11 at a predetermined rotational speed. The polygon motor control device 211 controls a polygon motor.

  Subsequently, in step S1103, the printer control unit 1 transmits correction data for correcting the writing start positions of the main scanning and the sub scanning, the main scanning magnification, and the like to each control device. Correction data is set in each control unit.

  Subsequently, in step S1105, the synchronization detection lighting control device 213 instructs the LD unit 31 to light the LD, and performs an APC (Automatic Power Control) operation or the like to light the LD at a predetermined light amount.

  Subsequently, in step S1107, the respective control devices interlock to perform image formation.

  Subsequently, in step S1109, the printer control unit 1 confirms the presence or absence of an image to be formed next.

  If there is an image to be formed next, the process returns to step S1107 to perform image formation again. Next, if there is no image to be formed, the printer control unit 1 instructs the LD control device 212 to turn off the LD in step S1111.

  Subsequently, in step S1113, the printer control unit 1 instructs the polygon motor control device 211 to stop the rotation of the polygon motor, and ends the process of image formation control.

  Next, a correction pattern in the image forming apparatus 100 of the present embodiment and a positional deviation correction process using the correction pattern will be described.

  The printer control unit 1 outputs pattern data corresponding to a correction pattern in the main scanning or sub scanning direction described later to the LD control device 212. Then, the LD control device 212 turns on the LD of the LD unit 31 based on the pattern data to form a latent image corresponding to the correction pattern on the photoconductor unit 40 of each color. Then, the formed latent image of each color is developed with toner, and the toner image is transferred onto the intermediate transfer belt 10. In the image forming apparatus 100, the correction pattern is thus formed on the intermediate transfer belt 10.

  FIG. 12 shows an example of the correction pattern in the sub scanning direction in the image forming apparatus of the present embodiment. The correction pattern in the sub-scanning direction is a horizontal line image as shown. Horizontal line images of Y, M, C, and K colors are formed on the intermediate transfer belt 10 along the “belt moving direction” in the figure.

  The patterns K1 and K2 are K-color images, and the patterns C1 and C2 are C-color images. The patterns M1 and M2 are M-color images, and the patterns Y1 and Y2 are Y-color images.

  The correction patterns in the sub scanning direction are formed at two positions on both sides of the intermediate transfer belt 10 in the “light beam scanning direction” in the drawing. The “belt movement direction” and the conveyance direction of the transfer image and the sub-scanning direction are synonymous with each other. A pair of Y, M, C, and K horizontal line images is an example of the “first pattern”.

  In FIG. 12, a correction pattern in which the patterns K1, C1, M1, and Y1 form one set is detected by the first sensor SEN1. In addition, a correction pattern in which the patterns K2, C2, M2, and Y2 form one set is detected by the second sensor SEN2.

  Outputs of the first sensor SEN1 and the second sensor SEN2 accompanying the movement of the intermediate transfer belt 10 in the “belt moving direction” are sent to the printer control unit 1. The printer control unit 1 calculates the amount of positional deviation in the sub-scanning direction of each color with respect to the K color.

  That is, at the output of the first sensor SEN1, positional deviation in the sub scanning direction with respect to the pattern K1 of each of the patterns C1, M1, and Y1 is calculated. At the output of the second sensor SEN2, positional deviation in the sub-scanning direction with respect to the pattern K2 of each of the patterns C2, M2 and Y2 is calculated.

  The case of detecting the positional deviation of the C color in the sub scanning direction with respect to the K color will be specifically described as an example. A specification value of a time until detection of a C-color pattern after detection of a K-color pattern by the first sensor SEN1 or the second sensor SEN2 is set as Tcs. The time until the pattern C1 is detected after the detection of the pattern K1 by the first sensor SEN1 is TKC1, and the time after the detection of the pattern K2 by the second sensor SEN2 to the detection of the pattern C2 is TKC2.

  The detection results of the first sensor SEN1 and the second sensor SEN2 are output to the printer control unit 1. The printer control unit 1 calculates the positional deviation amount ΔTcs of the C color with respect to the K color in the sub-scanning direction by the following equation (1). The unit of positional deviation is time.

・・・・・・・（１）
プリンタ制御部１は、位置ずれ量ΔＴｃｓに相当するライン数を補正データとして算出し、書出開始位置制御装置２１５に出力する。書出開始位置制御装置２１５は、補正データを用いて、副走査方向の書出開始位置を決定するＸＦＧＡＴＥ信号のタイミングを補正する。

・ ・ ・ ・ ・ ・ ・ ・ ・ (1)
The printer control unit 1 calculates the number of lines corresponding to the positional deviation amount ΔTcs as correction data, and outputs the correction data to the writing start position control device 215. The writing start position control device 215 uses the correction data to correct the timing of the XFGATE signal that determines the writing start position in the sub-scanning direction.

  The above description has been made taking C color as an example, but the same applies to M and Y colors. Further, the correction pattern is not limited to the horizontal line image, and may be another pattern as long as it is possible to detect positional deviation for each color in the sub scanning direction.

  In the present embodiment, after the positional deviation in the sub scanning direction is corrected, a pattern for positional deviation correction in the main scanning direction is formed on the intermediate transfer belt 10.

  FIG. 13 shows an example of the correction pattern in the main scanning direction in the image forming apparatus of this embodiment. The correction pattern in the main scanning direction is an oblique line image as shown. The diagonal line images of Y, M, C, and K colors are formed on the intermediate transfer belt 10 along the “belt movement direction” in the figure.

  Patterns K3 and K4 are K-color images, and patterns C3 and C4 are C-color images. The patterns M3 and M4 are M-color images, and the patterns Y3 and Y4 are Y-color images.

  The correction patterns in the main scanning direction are formed at two positions on both sides of the intermediate transfer belt 10 in the “light beam scanning direction” in the drawing. The “light beam scanning direction” is synonymous with the main scanning direction. In addition, a pair of Y, M, C, and K diagonal line images are an example of the “second pattern”.

  In FIG. 13, a correction pattern in which the patterns K3, C3, M3 and Y3 form one set is detected by the first sensor SEN1, and a correction pattern in which the patterns K4, C4, M4 and Y4 form one set is It is detected by the second sensor SEN2.

  Outputs of the first sensor SEN1 and the second sensor SEN2 accompanying the movement of the intermediate transfer belt 10 in the “belt moving direction” are sent to the printer control unit 1.

  When the oblique line image is used as the correction pattern, the detection timing of the correction pattern by the first sensor SEN1 and the second sensor SEN2 changes according to the positional deviation of the image in the main scanning direction and the magnification error. Here, the magnification in the main scanning direction refers to the imaging magnification of the image formed on the photosensitive unit 40 by the fθ lens 12 in the light scanning direction. The magnification error in the main scanning direction refers to the error of magnification caused by the fluctuation of the characteristics such as the refractive index and the surface shape of the fθ lens 12.

  Since the image is a diagonal line image, originally, the detection timing of the correction pattern changes also by the positional deviation of the image in the sub scanning direction. However, in the present embodiment, the correction pattern in the main scanning direction is formed immediately after correcting the positional deviation of the image in the sub scanning direction. Therefore, there is no positional deviation of the image in the sub scanning direction at this time. Therefore, the first sensor SEN1 and the second sensor SEN2 can detect a change in the detection timing of the correction pattern depending only on the position of the image in the main scanning direction and the deviation of the magnification.

  The case of detecting the magnification error and the positional deviation amount of the C color in the main scanning direction with respect to the K color will be specifically described as an example. A specification value of time until detection of the pattern C3 after detection of the pattern K3 by the first sensor SEN1 is set to Tcm. The time until the pattern C3 is detected after the detection of the pattern K3 by the first sensor SEN1 is TKC3, and the time after the detection of the pattern K4 by the second sensor SEN2 to the detection of the pattern C4 is TKC4.

  The printer control unit 1 calculates a magnification error in the main scanning direction from the difference between the time TKC3 and the time TKC4. The unit of magnification error is time.

  The magnification error is corrected by varying the frequency of the pixel clock signal PCLK by the pixel clock generation device 214 according to the calculated magnification error.

  Next, the printer control unit 1 subtracts, from the time TKC3, the time change by the magnification error correction at the position where the first sensor SEN1 is installed and the time Tcm, the main scanning direction of the C color for the K color The positional deviation amount ΔTcm is calculated.

  Next, the printer control unit 1 calculates the number of dots corresponding to the positional deviation amount ΔTcm as correction data, and outputs the correction data to the writing start position control device 215. The writing start position control device 215 uses the correction data to correct the timing of the XRGATE signal that determines the writing start position in the main scanning direction.

  The above description has been made taking C color as an example, but the same applies to M and Y colors. Further, the correction pattern is not limited to the oblique line image, and may be another pattern as long as it is possible to detect positional deviation for each color in the main scanning direction. For example, it may be a pattern obtained by horizontally reversing the patterns K3, C3, M3, and Y3 in FIG.

  Next, with reference to FIG. 14, an area where the correction pattern is formed on the intermediate transfer belt 10, the formed correction pattern, and a method of detecting the amount of misalignment using the same will be described.

  FIG. 14 schematically shows the intermediate transfer belt 10 moving in the belt moving direction indicated by the arrow. On the intermediate transfer belt 10, toner images of four colors, that is, "image 1" to "image 9" which are transfer images are formed.

  An area between the rear end of each transfer image and the front end of the next transfer image in the belt movement direction, that is, the conveyance direction of the transfer image, is an example of the inter-image area. A first sensor SEN1 and a second sensor SEN2 are installed at locations where toner images of four colors are formed in the transfer direction of the transfer image.

  In the inter-image area between "image 1" and "image 2", two sets of "pattern 1" are formed on the first sensor SEN1 side, and two sets of "pattern 1" are formed on the second sensor SEN 2 side There is. Similarly, in the inter-image region between "image 2" and "image 3", two sets of "pattern 1" are formed on the first sensor SEN1 side, and two sets of "pattern 1" are formed on the second sensor SEN 2 side It is done. Here, “pattern 1” is a positional deviation correction pattern in the sub scanning direction, that is, a horizontal line image.

  The first sensor SEN1 is located in an inter-image area between an “image 2” and an “image 3”, and in an “inter-image area” between an “image 1” and an “image 2”. The two sets of "pattern 1" formed are detected. For example, in the case of C color, detection results of four sets of “pattern 1” are transmitted to the printer control unit 1, and the positional deviation amount TKC1 by the first sensor SEN1 is calculated by averaging these.

  The misalignment amount TKC2 is similarly calculated in the second sensor SEN2. The positional deviation amounts TKC1 and TKC2 are substituted into the equation (1), and the positional deviation amount ΔTcs in the sub-scanning direction is acquired. The misregistration amounts in the sub-scanning direction of the M and Y colors are similarly acquired.

  When the outputs of the first sensor SEN1 and the second sensor SEN2 are combined, a total of eight detection results are averaged, and the detection error is reduced according to the number of times of averaging.

  Based on the acquired positional displacement amount ΔTcs, correction data of the XFGATE signal is calculated. The correction data is stored in the storage device 2 and set in the printer control unit 1.

  The time when the correction is reflected on the image formation is determined by the setting of the image writing position and the installation position of the first sensor SEN1 and the second sensor SEN2. In the present embodiment, the correction is reflected at the time when the “image 5” is formed. The image writing position is a value that determines the writing timing, and the installation position of the first sensor SEN1 and the second sensor SEN2 is a value that determines the detection timing.

  In the inter-image area immediately after the positional deviation amount in the sub-scanning direction is corrected, that is, in the present embodiment, in the area between “image 5” and “image 6”, “pattern 2” is 2 on the first sensor SEN 1 side. Two sets of “pattern 2” are formed on the second sensor SEN 2 side.

  Similarly, in the inter-image area between "image 6" and "image 7", two sets of "pattern 2" are formed on the first sensor SEN1 side, and two sets of "pattern 2" are formed on the second sensor SEN2 side It is done. Here, “pattern 2” is a misalignment correction pattern in the main scanning direction, that is, an oblique line image.

  In the inter-image area between “image 5” and “image 6”, “After correcting the positional deviation in the sub-scanning direction, the region between the first and second sensors SEN An example of the inter-image area of After the positional deviation in the sub scanning direction is corrected, the second pattern is formed in the first inter-image area passing through the place where the first sensor SEN1 and the second sensor SEN2 are installed, to obtain an image forming speed of It is possible to suppress the decrease and correct the positional deviation of the single color image of each color.

  The first sensor SEN1 is located in an inter-image area between the “image 6” and the “image 7” and in the two sets of “pattern 2” formed in the inter-image area between the “image 5” and the “image 6”. The two sets of "pattern 2" formed are detected. For example, in the case of C color, four sets of detection results of “pattern 2” are transmitted to the printer control unit 1, and a time TKC3 corresponding to the positional deviation amount by the first sensor SEN1 is calculated by averaging these.

  Similarly, in the second sensor SEN2, the time TKC4 corresponding to the positional deviation amount is calculated. The magnification error in the main scanning direction and the positional deviation amount ΔTcm are acquired from the times TKC3 and TKC4 corresponding to the positional deviation amount. Magnification errors and misregistration amounts in the main scanning direction of M and Y colors are similarly acquired.

  The outputs of the first sensor SEN1 and the second sensor SEN2 are combined, and a total of eight detection results are averaged to reduce detection errors. Based on the acquired magnification error, correction data of the pixel clock frequency is calculated, and correction data of the XRGATE signal is calculated based on the positional shift amount ΔTcm. The correction data is stored in the storage device 2 and set in the printer control unit 1.

  The time when the correction is reflected on the image formation is determined by the setting of the image writing position and the installation position of the first sensor SEN1 and the second sensor SEN2. In the present embodiment, the correction is reflected at the time when the “image 9” is formed.

  From “image 9” onward, an image in which both the positional deviation in the sub scanning direction and the positional deviation in the main scanning direction are corrected is formed.

  The number of correction patterns formed in one inter-image area is not limited to two, and may be further increased as long as it can be formed in one inter-image area. The larger the number of correction patterns, the more the detection error can be reduced by averaging, which is preferable.

  In addition, the number of inter-image areas forming the pattern is not limited to two, and may be further increased. As the number of inter-image areas forming the correction pattern increases, the detection error can be reduced by averaging. However, as the number of inter-image areas increases, it takes longer to correct the positional deviation. The positional deviation correction with an increase in the number of inter-image areas is suitable when outputting many images continuously, that is, when the number of printed sheets is large. This is because even if it takes some time to correct the misregistration, the correction result can be reflected on more printings.

  In this embodiment, only one type of correction pattern is formed in one inter-image area, that is, a correction pattern for displacement correction in the sub scanning direction or a correction pattern for displacement correction in the main scanning direction. . If two types of correction patterns are formed in one inter-image area, the inter-image area becomes longer in the transport direction by that amount, and the image forming speed decreases.

  The printer control unit 1 controls the timing at which the positional deviation correction process is performed. For example, the printer control unit 1 executes printing by the image forming apparatus every time the number of sheets reaches a predetermined number, or monitors the temperature around the place where the image forming apparatus is installed, and the temperature change more than specified Execute when there is.

  Next, an example of the positional deviation correction process will be described with reference to FIG.

  First, in step S 1501, the pattern formation unit forms “pattern 1” for correcting positional deviation in the sub scanning direction in the inter-image area on the intermediate transfer belt 10.

  Subsequently, in step S1503, the first sensor SEN1 and the second sensor SEN2 detect "pattern 1", and output the detection result to the printer control unit 1.

  Subsequently, in step S1505, the printer control unit 1 calculates the amount of positional deviation for each color of K in the sub-scanning direction based on the outputs of the first sensor SEN1 and the second sensor SEN2. When a plurality of sets of “pattern 1” are formed, an average value of these detection results is calculated.

  Subsequently, in step S1507, the printer control unit 1 determines whether to execute the positional deviation correction processing based on the calculated positional deviation amount. In this determination, for example, when the positional deviation amount is 1/2 or more of the resolution of the correction, it is determined that the correction process is to be performed.

  Subsequently, in the case of executing the correction processing, the printer control unit 1 calculates correction data from the positional deviation amount in step S1509. The correction data here is a set value of the XFGATE signal that determines the writing start position in the sub-scanning direction.

  Subsequently, in step S1511, the data of the storage device 2 is updated with the correction data.

  Subsequently, in step S1513, the corrected XFGATE signal is set in the writing start position control device 215. After setting, image formation is performed by the corrected XFGATE signal.

  If it is determined in step S1507 that the correction process is not to be performed, the correction data is not updated or set.

  Subsequently, in step S1515, the pattern formation unit forms “pattern 2” for correcting positional deviation in the main scanning direction in the inter-image area on the intermediate transfer belt 10.

  Subsequently, in step S 1517, the first sensor SEN 1 and the second sensor SEN 2 detect “pattern 2”, and output the detection result to the printer control unit 1.

  Subsequently, in step S1519, the printer control unit 1 calculates the amount of positional deviation for each color of K in the main scanning direction based on the outputs of the first sensor SEN1 and the second sensor SEN2. When a plurality of sets of "pattern 2" are formed, an average value of these detection results is calculated.

  Subsequently, in step S1521, the printer control unit 1 determines whether or not to execute the positional deviation correction processing based on the calculated positional deviation amount. In this determination, for example, when the positional deviation amount is 1/2 or more of the resolution of the correction, it is determined that the correction process is to be performed.

  Subsequently, in the case of executing the correction processing, the printer control unit 1 calculates correction data from the positional deviation amount in step S1523. The correction data here are a setting value of the pixel clock frequency that determines the magnification in the main scanning direction and a setting value of the XRGATE signal that determines the writing start position in the main scanning direction.

  Subsequently, in step S1525, the data of the storage device 2 is updated with the correction data.

  Subsequently, in step S1525, the corrected XRGATE signal is set in the writing start position control device 215, and the corrected pixel clock frequency is set in the pixel clock generation device 214. After setting, image formation is performed with the corrected XRGATE signal and the pixel clock frequency.

  As described above, according to the present embodiment, one type of correction pattern to be formed in one inter-image area on the intermediate transfer belt in order to detect a shift in the main scanning direction, for example, a diagonal line image Can only As compared with the case where a plurality of types of correction patterns, for example, horizontal line images and oblique line images, are formed in one inter-image area, the length in the conveyance direction of the inter-image area can be shortened. Further, the time and frequency of forming the correction pattern can be suppressed. Thereby, the positional deviation of the single-color image of each color can be corrected without reducing the image forming speed.

Furthermore, in addition to the above, detection errors can be reduced by forming a plurality of sets of the same pattern.
Second Embodiment
Next, a positional deviation correction method in the image forming apparatus of the second embodiment will be described. Descriptions of parts that overlap the first embodiment will be omitted, and differences will be described.

  Depending on the size of the medium on which an image is formed and the speed of image formation, the inter-image area on the intermediate transfer belt 10 may be elongated in the transport direction. For example, when the size of the medium on which an image is formed is large, the inter-image area in the transport direction becomes long in order to secure the time for temperature adjustment of the fixing unit 25. The size of the medium is, for example, the size of a sheet represented by A4 size or A3 size. In the following, the length of the inter-image area in the transport direction is simply referred to as the length of the inter-image area.

  As described above, when the number of correction patterns formed in one inter-image area can be increased, the number of times of averaging for misalignment detection can be increased, so that detection errors can be reduced. Therefore, in the present embodiment, it is detected that the inter-image area becomes long due to an external factor such as the size of the medium, and the number of correction patterns formed in the inter-image area is increased according to the length to average the detection. The number of conversions is increasing.

  Note that “an inter-image area becomes longer due to an external factor” means that the inter-image area becomes longer due to factors other than misregistration correction rather than an inter-image area becoming long for misregistration correction. doing.

  FIG. 16 is a block diagram showing an example of a functional configuration of the image forming apparatus 100a of the present embodiment. The image forming apparatus 100a includes an image forming unit 500, a positional deviation correction unit 501, an area length detection unit 503, a pattern number determination unit 504, an image length detection unit 505, and an area number determination unit 506. doing.

  The area length detection unit 503 detects the length of the inter-image area. For example, when the inter-image area becomes longer according to the size of the medium, the printer control unit 1 can grasp the size of the medium when performing the image formation. For example, when the user of the image forming apparatus 100a selects the size of a sheet on which an image is to be formed through the operation panel, the printer control unit 1 recognizes the selected sheet size, that is, the size of the medium. Alternatively, the printer control unit 1 grasps the size of the medium by reading the sheet size prepared in the image forming apparatus 100a with an optical document sensor or the like.

  On the other hand, the length of the inter-image area necessary according to the size of the medium is grasped in advance based on experiments and the like. Therefore, by receiving information on the size of the medium from the printer control unit 1, the region length detection unit 503 can detect that the inter-image region becomes long and how long it becomes.

  The pattern number determination unit 504 determines the number of correction patterns to be generated in the inter-image area from the length of the inter-image area detected by the area length detection unit 503. Since the length in the transport direction per set of correction patterns is known in advance, the pattern number determination unit 504 can determine the number of correctable patterns that can be formed based on the length of the inter-image area. .

  FIG. 17 shows an example of how four correction patterns are formed in one inter-image area when the number of correction patterns to be formed is increased when the inter-image area becomes long.

  FIG. 18 shows an example of the flow of forming processing of a correction pattern in the present embodiment.

  First, in step S1801, an inter-image area can be formed based on the length L of the correction pattern in the conveyance direction, the length X of the inter-image area in the conveyance direction, and the distance Y between the transferred image and the correction pattern in the conveyance direction. The number N of correction patterns is calculated. In this case, the largest integer N for which X> L · N + Y holds may be obtained.

  Subsequently, in step S1803, the calculated number of correction patterns is formed in the inter-image area.

  Subsequently, in step S1805, it is determined whether the inter-image area for forming the correction pattern has ended. If it is determined that the process has been completed, the formation of the correction pattern is ended. If it is determined that the process has not been completed, a correction pattern is formed in the next inter-image area.

  As described above, the detection error can be reduced and positional deviation correction accuracy can be improved by increasing the number of times of averaging the detection of the correction pattern by utilizing the fact that the inter-image region is elongated due to an external factor. Also in this case, the image forming speed does not decrease due to misalignment correction.

  The interval Y between the transferred image and the correction pattern is an interval Y that does not affect the image formation, that is, the printing, and that the correction pattern can be normally detected when forming the correction pattern. Obtain and set in advance.

  In addition, the region length detection unit 503 is an example of “a region length detection unit that detects the length of the inter-image region in the transport direction”. The pattern number determination unit 504 is an example of “a pattern number determination unit that determines the number of patterns used for correction based on the output of the region length detection unit”.

  On the other hand, in the case where the averaging number of times of detection of correction patterns necessary for securing detection accuracy is grasped in advance by experiments etc., the number of corrections necessary for averaging in one inter-image area If it is not possible to form the pattern for correction, the necessary number of correction patterns are formed in a plurality of inter-image areas.

  In this case, based on the length of the inter-image area detected by the area length detection unit 503, the area number determination unit 506 determines the number of inter-image areas required to form the correction pattern. Alternatively, based on the size of the transferred image in the transport direction detected by the image length detection unit 505, the area number determination unit 506 determines the number of inter-image areas required to form the correction pattern.

  By forming the correction pattern in accordance with the number of inter-image areas determined in this manner, it is possible to correct the positional deviation of the single-color image of each color without reducing the image forming speed.

  While examples of embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and various modifications may be made within the scope of the present invention as set forth in the claims. Modifications and changes are possible.

Reference Signs List 1 printer control unit 2 storage device 10 intermediate transfer belt 11 polygon mirror 12 fθ lens 13 cleaning unit 14 to 16 support roller 17 intermediate transfer member cleaning unit 18 charging unit 19 charge removal unit 20 imaging device 21 light beam scanning device 210 image formation control Device 211 polygon motor controller 212 LD controller 213 lighting controller for synchronization detection 214 pixel clock generator 215 writing start position controller 22 secondary transfer unit 23 roller 24 secondary transfer belt 25 fixing unit 29 developing unit 31 LD unit DESCRIPTION OF SYMBOLS 40 Photosensitive body unit 54 Synchronization sensor 62 Transfer device 100, 100a Image forming apparatus 300 Image reading unit 400 Automatic sheet feeding device 500 Image forming unit 501 Misalignment correction unit 502 Detection unit 503 area length detection unit 504 pattern number determination unit 505 image length detection unit 506 area number determination unit SEN1, SEN2 first sensor, second sensor

JP 2008-073894 A

Claims (8)

A plurality of image carriers on which light according to image data is irradiated to form a monochrome latent image and a latent image of the monochrome formed on each of the plurality of image carriers is developed, and a monochrome image is formed. An image forming apparatus comprising: a plurality of developing units; and a transfer body for conveying a transferred image on which the single-color image is sequentially transferred, wherein the single-color image is superimposed to form a multicolor image.
Pattern forming means for forming a pattern for correcting the positional deviation of the single-color image of each color in an inter-image area from the rear end of the transferred image to the front end of the next transferred image in the transfer direction of the transferred image; ,
Correction means for correcting the positional deviation based on the pattern;
The pattern forming means forms only a first pattern for correcting the positional deviation in the sub scanning direction in a predetermined inter-image area, corrects the positional deviation in the sub scanning direction, and then performs the predetermined inter-image area. An image forming apparatus, wherein only a second pattern for correcting the positional deviation in the main scanning direction is formed in another inter-image area different from the image forming apparatus. The correction means is
The image forming apparatus according to claim 1, further comprising a detection unit provided at a position after the multicolor image is formed in the transport direction and detecting the pattern.   3. The apparatus according to claim 2, wherein the pattern forming unit forms the second pattern in the first inter-image area passing through the portion after correcting the positional deviation in the sub scanning direction. Image forming device.   The detection means detects each of a plurality of the patterns formed in one inter-image area or a plurality of inter-image areas, and outputs an average value of each detection result. The image forming apparatus according to 2 or 3.   Area length detection means for detecting the length of the inter-image area in the transport direction; and pattern number determination means for determining the number of the patterns used for the correction based on the output of the area length detection means. The image forming apparatus according to any one of claims 1 to 4, comprising.   The image forming apparatus according to claim 5, wherein the region length detection unit detects a size of a medium on which the multicolor image is formed.   The image length detection unit detects the length of the transferred image in the transport direction, and the pattern is formed based on the output of one of the area length detection unit and the image length detection unit. 7. The image forming apparatus according to claim 5, further comprising area number determining means for determining the number of inter-image areas. A step of irradiating a plurality of image carriers with light according to image data to form a monochrome latent image, and developing the monochrome latent images formed on each of the plurality of image carriers. An image forming method comprising: forming a single color image; and conveying a transferred image to which the single color image is sequentially transferred, wherein the single color image is superimposed to form a multicolor image.
Forming a pattern for correcting positional deviation of the single-color image of each color in an inter-image area from the rear end of the transferred image to the front end of the next transferred image in the transport direction of the transferred image; ,
Correcting the positional deviation based on the pattern;
In the pattern forming step, only the first pattern for correcting the positional deviation in the sub scanning direction is formed in a predetermined inter-image area, and after correcting the positional deviation in the sub scanning direction, the predetermined inter-image area An image forming method characterized in that only the second pattern for correcting the positional deviation in the main scanning direction is formed in another inter-image area different from the above.

Images