JP5901332B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to a tandem type image forming apparatus that exposes each photoconductor with a light beam from each exposure unit and forms images of different colors on each photoconductor.

  In an electrophotographic image forming apparatus, a photosensitive member is charged by a charger, and an exposure unit exposes the photosensitive member with a laser beam or the like according to image information to form a latent image, and the latent image is developed with toner. An image is formed by a process of transferring the developed toner image to a recording material. In a tandem color image forming apparatus, an image forming unit that executes this image forming process is provided for each color, and a toner image developed in each color is formed on each photoconductor, and a toner image on each photoconductor is formed. An image is formed by transferring the image on a recording material. For models that require a high printing speed, a method of transferring a toner image formed on a photosensitive member to an intermediate transfer member (hereinafter referred to as “belt”) and then transferring it to a recording material is the mainstream. It has become.

  When a color image is formed, the main scanning direction and / or the meandering movement (inclination in the sub-scanning direction) and the meandering movement (inclination in the sub-scanning direction) and the meandering movement (inclination in the sub-scanning direction) of the photoconductor and the belt Color misregistration in the sub-scanning direction may occur. Therefore, in order to correct the belt shift and meandering motion, first, the positions of the belt end portions are detected at two locations in the belt conveyance direction. Next, on the basis of the detection result, for example, Patent Document 1 proposes a method of adjusting the deviation or meandering of the belt by swinging the steering roller provided at the most upstream and the most downstream in the belt conveyance direction. ing.

JP 2006-76784 A

  The problem in the above-described method for detecting the position of the belt end and adjusting the deviation and meandering of the belt will be described with reference to FIG. FIG. 9 is a diagram illustrating a configuration of an image forming apparatus 200 which is an example of a conventional tandem image forming apparatus. FIG. 9A is a perspective view showing an internal configuration of the image forming apparatus 200. The main body frame 201, an exposure unit 211, a developing unit 212 including a photosensitive drum (indicated by a broken line), and a toner image are transferred to a recording sheet. For example, the belt unit 220 is used. The exposure unit 211 and the developing unit 212 are arranged corresponding to the color of the toner. The belt unit 220 is fixed so as to move up and down within the belt unit outer frame 202.

  FIG. 9B is a top view of the belt unit 220 as viewed from above the image forming apparatus 200. The belt unit 220 includes a belt frame 221, a belt 222, a transfer roller 223, a driving roller 224, a steering roller 225, a guide roller 226, a driving motor 227, a steering motor 228, an edge sensor 230, and the like. In the belt unit 220, steering is performed by two rollers provided at the most upstream side and the most downstream side in the conveyance direction of the belt 222, a driving roller 224 and a steering roller 225, and the belt 222 is driven by various rollers fixed to the belt frame 221. It is stretched.

  The displacement of the belt end can be detected by the edge sensor 230 with reference to the mounting position of the edge sensor 230. As shown in FIG. 9C, the edge sensor 230 includes a sensor arm 231, a capacitance sensor 232, an arm stay 233, and a pressing spring 234, and is installed on the belt frame 221. The axis (L-shaped center) of the sensor arm 231 is fixed to the arm stay 233, and when the belt 222 moves in the width direction (left-right direction), the vertical portion of the sensor arm 231 rotates about the axis. The capacitance sensor 232 detects the capacitance between the capacitance sensor 232 and the sensor arm 231, and can detect the distance between the capacitance sensor 232 and the sensor arm 231 based on the detected capacitance. it can. Then, the displacement in the width direction of the belt 222 can be calculated based on the detected distance.

If the displacements of the end portions of the belt 222 detected by the two edge sensors 230 are different, the conveying direction DB of the belt 222 is inclined with respect to the belt frame 221. Accordingly, the driving direction DB of the belt 222 can be adjusted and made parallel to the belt frame 221 by swinging the driving roller 224 and the steering roller 225 in the vertical direction as shown in FIG. . As shown in FIG. 9E, when the belt 222 is inclined with respect to the belt frame 221, the inclination of the belt 222 can be detected by the edge sensor 230, and the driving roller 224 and the steering roller 225 are swung. The belt conveyance direction DB can be adjusted. However, as in FIG. 9 (f), the parallel state belt frame 221 and the belt 222 is integrated, if they have inclined relative to the arrangement direction DE of the exposure unit, the edge sensor displacement of the end portion of the belt 222 230 is not detected. As a result, since the belt conveyance direction DB is not adjusted, the belt deviation and meandering are not adjusted.

  As shown in FIG. 9C, the belt frame 221 and the main body frame 201 are moved upward by an unillustrated vertical mechanism, and a belt frame side positioning pin 229 and a main body frame side positioning block 203 are used. It is connected. Since the main body frame 201 has a relatively low torsional rigidity, as shown in FIG. 9G, the main body frame 201 is likely to be twisted and deformed between the upper part and the lower part. Due to this torsional deformation, the belt frame 221 and the belt 222 may be integrated with the alignment direction DE of the exposure units, and may be inclined with respect to the alignment direction of the exposure units. However, as described above, the belt conveyance direction DB is not adjusted.

  Furthermore, the amount of heat generated from heat sources such as a fixing device and a drive motor varies depending on the printing mode and the like, and the main body frame 201 and the belt frame 221 may be deformed during printing due to heat from these heat sources. Because the amount of deformation of the main body frame 201 and the belt frame 221 also changes with time due to the amount of heat generated from the heat source that changes over time, it is difficult to cope with belt inclination adjustment.

  The present invention has been made under such circumstances, and even if the belt frame or the main body frame is deformed and the amount of deformation changes with time, the inclination between the exposure unit alignment direction and the belt conveyance direction is changed. The purpose is to reduce the color misregistration caused by.

  In order to solve the above-described problems, the present invention has the following configuration.

(1) A plurality of exposure means provided corresponding to each of the plurality of image carriers, and exposing each of the plurality of image carriers, and being exposed by the plurality of exposure means, on the plurality of image carriers. An image forming unit that develops the latent image formed on the toner image with toner, and transfers the toner images developed on the plurality of image bearing members to an endless intermediate transfer member that is rotationally driven by a rotation shaft; An image detecting means for detecting a toner image formed on the intermediate transfer member by the exposure means and the image forming means; a position detecting means for detecting a relative position between each of the plurality of exposure means and the intermediate transfer member; Formed on the plurality of image carriers by drive means for swinging the rotating shaft to control the transfer direction of the transfer body, and the inclination of the transfer direction of the intermediate transfer body and the alignment direction of the plurality of exposure means The Control means for controlling a swing amount of the rotating shaft by the drive means based on detection results of the image detection means and the position detection means so as to reduce a deviation between the toner images on the image carrier. The position detection means is provided along the widthwise end of the intermediate transfer body of the plurality of exposure means, and is opposed to the laser irradiation means for irradiating spot-like laser light. And a line sensor in which a light receiving element that detects laser light from the laser irradiation unit is linearly arranged in the width direction of the intermediate transfer body, and a support portion that supports the line sensor. The image forming apparatus is characterized in that the support portion is in contact with an end portion in the width direction of the intermediate transfer member .

(2) A plurality of exposure means provided corresponding to each of the plurality of image carriers and exposing each of the plurality of image carriers, and being exposed by the plurality of exposure means, on the plurality of image carriers. An image forming unit that develops the latent image formed on the toner image with toner, and transfers the toner images developed on the plurality of image bearing members to an endless intermediate transfer member that is rotationally driven by a rotation shaft; An image detecting means for detecting a toner image formed on the intermediate transfer body by an exposure means and the image forming means; and a plurality of exposure means provided along the widthwise ends of the intermediate transfer body, Laser irradiation means for irradiating the sheet-shaped laser light so that a part of the sheet-shaped laser light spreading in the width direction of the transfer body is blocked by the end in the width direction of the intermediate transfer body, and the laser irradiation Facing the means A light receiving element that is provided on a belt frame connected to the intermediate transfer member that is stretched, and that detects a sheet-like laser beam from the laser irradiation unit is linearly arranged in the width direction of the intermediate transfer member; A line sensor for detecting a sheet-like laser beam irradiated from the laser irradiation unit and not blocked by an end in the width direction of the intermediate transfer member, and an inclination of the belt frame with respect to the arrangement direction of the plurality of exposure units A shift on the image carrier between toner images formed on the plurality of image carriers due to an inclination between an adjustment unit for adjustment and a conveyance direction of the intermediate transfer member and an alignment direction of the plurality of exposure units Control means for controlling the amount of inclination of the belt frame by the adjustment means based on the detection results of the image detection means and the line sensor. Image forming apparatus characterized by.

  According to the present invention, even if the belt frame or the main body frame is deformed and the amount of deformation changes with time, color misregistration due to the inclination between the exposure unit alignment direction and the belt conveyance direction can be reduced.

Schematic sectional view of a color image forming apparatus of Examples 1 to 4 Configuration of the vicinity of the exposure unit and belt unit of Embodiment 1 The block diagram which shows the control system for controlling the belt conveyance direction of Examples 1-3. The flowchart which shows the control processing procedure for controlling the belt conveyance direction of Examples 1-3. The flowchart which shows the detail of the initial stage belt inclination detection process of Examples 1-3, and a belt inclination correction process. The figure which shows the structure of the belt width direction detection means in Example 2. FIG. The figure which shows the structure of the belt width direction detection means in Example 3. FIG. The figure which shows the structure of the belt unit drive means in Example 4, and the figure explaining a belt unit drive method FIG. 2 is a diagram for explaining a conventional color image forming apparatus.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Outline of image forming apparatus]
FIG. 1 is a longitudinal sectional view of an essential part of a tandem color image forming apparatus 100 (hereinafter referred to as “image forming apparatus 100”) equipped with a plurality of exposure units (exposure units). In the image forming apparatus 100, four sets of image forming units are arranged to form toner images corresponding to the respective colors of yellow (Y), magenta (M), cyan (C), and black (BK). In FIG. 1, the subscripts Y, M, C, and BK of the code indicate toner colors. Since the configuration of each image forming unit is the same, the suffixes Y, M, C, and BK are omitted in the following description unless otherwise required.

  The image forming unit includes a photosensitive drum 12, a primary charger 13, a developing device 14, a cleaning device 15, and the like. A photosensitive drum 12 as an image carrier is pivotally supported at the center of the image forming unit and is driven to rotate in the direction of the arrow. A primary charger 13 and a developing device 14 are arranged in the rotation direction facing the outer peripheral surface of each photosensitive drum 12. The primary charger 13 applies a uniform charge amount to the surface of the photosensitive drum 12. The exposure unit 11 scans and exposes the photosensitive drum 12 with a laser beam 16 modulated according to the recording image signal, and forms an electrostatic latent image on the photosensitive drum 12. The electrostatic latent image formed on the photosensitive drum 12 of each image forming unit is developed by each developing device 14 with each color (yellow, magenta, cyan, black) developer (hereinafter referred to as “toner”). Visualized as a toner image. The visualized toner image on the photosensitive drum 12 is transferred onto an intermediate transfer belt 31 (hereinafter referred to as “belt 31”), which is an intermediate transfer member. The surface of the photosensitive drum 12 is cleaned by scraping off the toner remaining on the surface of the photosensitive drum 12 without being transferred by a cleaning device 15 provided on the downstream side of the transfer position to the belt 31. Is done.

  The toner image transferred from the photosensitive drum 12 onto the belt 31 is transferred onto a recording material 22 that is a recording medium. For this reason, the cassette 21 containing the recording material 22 is disposed inside the image forming apparatus 100, and the recording material 22 fed from the cassette 21 is paired with a registration roller pair by a paper feed roller pair 23 and a paper feed guide 24. Up to 25. Then, when the registration roller pair 25 is driven in accordance with the image formation timing, the recording material 22 is conveyed to the secondary transfer unit.

  The secondary transfer unit includes an endless belt 31 stretched around a drive roller 32 and a driven roller 33, a secondary transfer roller 35, and a secondary transfer counter roller 34. The belt 31 is rotated around the drive roller 32. The driving roller 32 and the driven roller 33 can swing in the vertical direction perpendicular to the rotation direction of the belt 31, and can adjust the meandering of the belt 31. The secondary transfer roller 35 sandwiches the belt 31 and the fed recording material 22 between the secondary transfer counter roller 34 and pressurizes the belt 31 with an appropriate pressure so that the toner image on the belt 31 is recorded. 22 is transferred.

  The recording material 22 onto which the toner image has been transferred in the secondary transfer portion is carried into the fixing unit 41 and subjected to heat fixing processing. The fixing unit 41 includes a fixing roller pair 42, a conveyance guide 26, fixing heat insulating covers 43 and 44, a paper discharge roller 45, and the like. The fixing heat insulating covers 43 and 44 are configured to confine heat inside the fixing unit 41. Has been. In the fixing unit 41, the recording material 22 is guided to the fixing roller pair 42 by the conveyance guide 26, and the fixing roller pair 42 having a heat source such as a halogen heater therein heats and pressurizes the recording material 22, thereby The image is fixed on the recording material 22. The recording material 22 discharged from the fixing roller pair 42 in a state where the toner image is fixed is led out of the image forming apparatus by a paper discharge roller 45.

  Further, between the photosensitive drum 12BK located at the most downstream side in the conveyance direction of the belt 31 and the driven roller 33, photosensors 51 and 52 as image detection means are provided on the right side and the left side in the main scanning direction, respectively. In the image forming apparatus 100, a toner pattern for color misregistration correction is formed on the belt 31 before printing is started immediately after the power is turned on and when a color misregistration adjustment request is generated, and is read by the photosensors 51 and 52. Detection "is performed. Based on the detection results of the photosensors 51 and 52, a necessary correction amount for color misregistration is calculated. Furthermore, based on the calculated correction amount, the image signal to be imaged is electrically corrected, and an appropriate color superimposition is performed by driving a correction optical system provided in the optical path of the laser beam. Adjustment “registration adjustment” is performed. Registration detection and registration adjustment consume toner, take time for color overlay adjustment, and reduce productivity. Therefore, it is desirable that the frequency of execution is low.

  In the image forming apparatus 100, in order to detect the relative positional relationship between the exposure unit 11 and the belt 31, the two exposure units 11Y and 11BK are provided with laser irradiation units 61Y and 61BK configured by LEDs, for example. Yes. Although details will be described later, the laser beams 70Y and 70BK from the laser irradiation units 61Y and 61BK are in contact with the end portions in the width direction of the belt 31 (hereinafter abbreviated as “end portions of the belt 31”). It is detected by the edge sensors 71Y and 71BK. Then, based on the detection result, the driving roller 32 and the driven roller 33 are swung to control the conveying direction of the belt 31. As a result, the shift amount of the end of the belt 31 and the meandering amount can be reduced. it can.

  By the way, when the temperature of the exposure unit 11 fluctuates, the scanning line to the photosensitive drum 12 by the laser beam 16 is deformed due to thermal deformation of the optical element group 17 in the exposure unit. As a result of the deformation of the scanning line, magnification shift, shift (horizontal shift) in the main scanning direction, shift in the sub-scanning direction (shift in the rotational direction of the photosensitive drum), tilt, and curvature (bend of the line) appear. That is, if there is a temperature difference between the exposure units 11, the scanning lines are deformed and color misregistration occurs. Therefore, in the image forming apparatus 100 of the present embodiment, the temperature in the space in which the exposure unit 11 is installed is appropriately controlled by a temperature adjusting unit (not shown), and the scanning line is deformed by thermal deformation of the optical element group 17 or the like. However, the temperature difference is kept small so that no color shift occurs.

[Exposure unit position detection]
Next, a method for detecting the relative positional relationship between the exposure unit 11 and the belt 31 in this embodiment will be described in detail. FIG. 2 is a view showing a configuration in the vicinity of the exposure unit and the belt unit. FIG. 2A is a diagram viewed from the upstream side in the conveyance direction of the belt 31. FIG. 2B is a view of the exposure unit 11Y (11BK) having the laser irradiation unit 61Y (61BK) as viewed from the width direction of the belt 31 (right direction in FIG. 2A). The conveying direction of the belt, and the arrow in the photosensitive drum 12 indicates the rotating direction. FIG. 2C is a top view of the exposure unit 11 and the belt unit as viewed from above the image forming apparatus 100. The following description will be given with respect to the laser irradiation unit 61Y provided in the yellow exposure unit 11Y. Since the laser irradiation unit 61BK provided in the black exposure unit 11BK has the same configuration, the corresponding reference numerals are described below in parentheses.

  As shown in FIG. 2A, the laser irradiation unit 61Y (61BK) is fixed to the exposure unit 11Y (11BK), and irradiates the spot-like laser beam 70Y (70BK) in a direction perpendicular to the belt 31. . The laser beam 70Y (70BK) is designed to be focused on parallel light or the line sensor 72Y (72BK), and the spot diameter is about φ10 to 20 μm.

  The edge sensor 71Y (71BK) includes a line sensor 72Y (72BK), a sensor stay 73Y (73BK), and a uniaxial guide 74Y (74BK). The sensor stay 73Y (73BK) is a support portion that supports the line sensor 72Y (72BK). Further, the sensor stay 73Y (73BK) follows the movement of the end portion of the belt 31 by being pressed against the belt 31 by the uniaxial guide 74Y (74BK) supported by the belt frame 101.

  The line sensor 72Y (72BK) is fixed to the upper part of the sensor stay 73Y (73BK) so that the alignment direction of the light receiving elements of the laser light 70Y (70BK) is substantially parallel to the width direction of the belt 31, and the laser light 70Y ( 70BK). The line sensor 72Y (72BK) reads out charges corresponding to the received light amount of the laser beam 70Y (70BK) from the light receiving elements (photodiodes) arranged in a line in a straight line by the CCD method or the CMOS method. The pitch of the light receiving elements is about several μm to 5 μm, the number of the light receiving elements is about 5000 to 7500, and the detectable range of the laser light 70Y (70BK) of the line sensor 72Y (72BK) provided at the end of the belt 31. Is approximately the number of pitches × the number of light receiving elements.

  In this embodiment, the line sensors 72Y and 72BK detect the laser beams 70Y and 70BK emitted from the two laser irradiation units 61Y and 61BK provided in the exposure units 11Y and 11BK, respectively, and calculate the spot center position. To do. The position information of the calculated spot center position indicates the distance from the end of the belt 31 of the laser irradiation unit provided in the exposure unit. A straight line DB (broken line in FIG. 2C) connecting the calculated two spot center positions and indicating the conveyance direction of the belt 31 and a direction in which the exposure units are arranged in a line (hereinafter referred to as “exposure unit alignment direction”). If the straight line DE (abbreviated as “.”) Is parallel, no color misregistration occurs. On the contrary, if the straight line DB and the straight line DE are not parallel, a shift in the main scanning direction occurs, and as a result, a color shift occurs in the image formed on the belt 31. Therefore, the conveyance direction of the belt 31 is controlled so that the straight line DB indicating the conveyance direction of the belt 31 is parallel to the straight line DE indicating the exposure unit arrangement direction.

  Accordingly, the two laser irradiation positions should be separated as much as possible. Therefore, the laser exposure units 61Y and 61BK are provided in the yellow exposure unit 11Y and the black exposure unit 11BK, which correspond to both ends of the exposure unit array. ing. Furthermore, since there are two or more laser irradiation positions, for example, a laser irradiation unit may be provided in each exposure unit. In that case, a straight line defined so as to minimize the sum of squares of the distances from the respective laser irradiation positions may be a straight line DE indicating the alignment direction of the exposure units.

  In this embodiment, the laser irradiation unit 61Y (61BK) is installed on the exposure unit 11Y (11BK), and the line sensor 72Y (72BK) is installed on the belt unit side. On the contrary, if the laser irradiation unit 61Y (61BK) is provided on the sensor stay 73Y (73BK) and the line sensor 72Y (72BK) is provided on the exposure unit 11Y (11BK), the same effect can be obtained. Furthermore, in this embodiment, the laser irradiation unit 61Y (61BK) is provided in the exposure unit 11Y (11BK). The laser irradiation unit 61Y (61BK) may be separated from the exposure unit 11Y (11BK) as long as the required accuracy is within an allowable range. For example, in the vicinity of the exposure unit of the main body frame where the exposure unit 11Y (11BK) is installed. May be installed.

  In the image forming apparatus 100 of this embodiment, as described above, the temperature in the space where the exposure unit 11 is installed is appropriately managed by a temperature adjusting unit (not shown). As a result, in this embodiment, the main body frame on which the exposure unit 11 is installed does not expand or contract due to temperature fluctuations. In addition, since each exposure unit 11 is not easily affected by external disturbances such as temperature fluctuations, the relative positional relationship between the exposure units is not greatly shifted, and the alignment direction of the exposure units is aligned on a straight line. It shall be.

[Outline of belt control system]
FIG. 3 is a block diagram schematically showing the configuration of a control system that controls the conveyance direction of the belt 31. A control unit 81 in FIG. 3 controls the entire image forming apparatus 100. The memory 82 includes a ROM and a RAM (not shown). The ROM stores a control program and data executed by the control unit 81. The RAM temporarily stores information stored in the control program executed by the control unit 81. Used to hold

  Laser beams 70Y and 70BK irradiated from the laser irradiation units 61Y and 61BK are received by a line sensor Y (hereinafter referred to as a line sensor 72Y) and a line sensor BK (hereinafter referred to as a line sensor 72BK). The line sensor 72Y and the line sensor 72BK output charge data corresponding to the amount of received light read from the light receiving element to the control unit 81. The control unit 81 calculates the spot center positions of the laser beams 70Y and 70BK on the line sensors 72Y and 72BK based on the data output from the line sensors 72Y and 72BK, and stores the laser beams 70Y and 70BK in the RAM of the memory 82. Save the spot center position data.

  Photosensor R (also referred to as “photosensor 51”) and photosensor L (also referred to as “photosensor 52”) are toners formed on the right side and the left side in the conveying direction on belt 31 in order to detect the amount of color misregistration. The pattern is read, and the read data is output to the control unit 81.

  The control unit 81 performs a predetermined process on the data output from the photosensors 51 and 52. Then, the control unit 81 decomposes the color misregistration data of each color into magnification shift, shift (left / right shift), sub-scan direction shift (shift in the rotation direction of the photosensitive drum), and tilt on the photosensitive drum. And stored in the RAM of the memory 82.

  Based on the data stored in the RAM of the memory 82, the control unit 81 uses the alignment direction of the exposure units 11Y and 11BK as a reference, the shift amount of the belt 31 (displacement amount in the belt width direction), and the meandering amount (relative to the belt conveyance direction). , The inclination of the belt end). Then, the control unit 81 calculates the driving amounts of the steering motor U36 and the steering motor D37 shown in FIG. 2 (c) in order to reduce the calculated deviation amount and meandering amount, and sends them to the motor driver U83 and the motor driver D84. Output. The motor driver U83 and the motor driver D84 drive the steering motor U36 and the steering motor D37 based on the driving amount of the steering motor output from the control unit 81. As a result, the rotation shafts of the driving roller 32 and the driven roller 33 are tilted (oscillated) in the vertical direction perpendicular to the conveying direction of the belt 31 as shown in FIG. 9D, and the conveying direction of the belt 31 is adjusted. can do.

[Control of belt conveyance direction]
FIG. 4 is a flowchart showing a control sequence for controlling the belt conveyance direction. The processing shown in FIG. 4 is executed by the control unit 81 based on a control program stored in the ROM of the memory 82, and the processing of the subsequent flowcharts is also executed by the control unit 81.

  First, in step 1 (hereinafter referred to as S1), when the image forming apparatus 100 is powered on, the control unit 81 is activated and performs predetermined initialization processing such as various error checks. Next, in S <b> 2, the control unit 81 performs belt detection 31 for each exposure unit and registration adjustment (excluding shift adjustment in the main scanning direction) and belt 31 for the exposure unit arrangement direction DE for shift adjustment in the main scanning direction. The inclination amount of the transport direction DB is calculated. Then, the control unit 81 performs an initial belt inclination detection process for calculating a target position of the exposure unit with respect to the belt 31 so that the exposure unit arrangement direction DE and the conveyance direction DB of the belt 31 are parallel to each other. Further, the control unit 81 starts a timer and resets a counter that counts the number of printed sheets in order to determine the timing of the color misregistration adjustment request.

  In S3, the control unit 81 determines whether or not there is a print request, and if so, proceeds to S4, and if not, repeats the process of S3. In S4, the control unit 81 performs belt inclination correction processing so that the position of the exposure unit with respect to the belt 31 falls within a predetermined error range from the target position calculated in S2. In S5, the control unit 81 performs the printing process by the image forming unit described above, and updates the counter that counts the number of printed sheets. In S6, the control unit 81 reads the timer value of the timer, determines whether a predetermined time has elapsed since the previous color misregistration adjustment, and determines whether a predetermined number of sheets have been printed since the previous color misregistration adjustment. To do. The control unit 81 returns to S2 if it is necessary to perform color misregistration adjustment after the elapse of a predetermined time or execution of printing for a predetermined number of sheets, and otherwise proceeds to S7. In S <b> 7, the control unit 81 determines whether or not there is a request for stopping the image forming apparatus 100. If not, the control unit 81 returns to S <b> 3.

[Belt inclination detection]
FIG. 5A is a flowchart showing a detailed control sequence of the initial belt inclination detection process executed in S2 of FIG. In FIG. 5A, the registration adjustment excluding the shift amount adjustment in the main scanning direction that can be adjusted by adjusting the inclination of the belt 31 is performed in S14. In FIG. 5A, only the inclination detection of the belt 31 is performed, and the inclination adjustment of the belt 31 is performed by the process of FIG. 5B. In S15 of FIG. 5A, the detection positions of the laser beams detected by the line sensors 72Y and 72BK are not used to detect the inclination of the belt 31. The reason is that the reference positions (end positions) of the line sensor 72Y and the line sensor 72BK do not always match, and the detection is not always performed at the same end position of the belt 31, and the belt width If they are different, a shift occurs. As a result, if the presence or absence of the inclination of the belt 31 is determined based on the detection position of the line sensor, the exposure unit alignment direction and the conveyance direction of the belt 31 may not be parallel. Therefore, in the process of S15 described later, the presence or absence of the shift amount in the main scanning direction based on the toner pattern is used to determine the presence or absence of the inclination of the belt 31.

  In S11, the control unit 81 controls the image forming unit to form a yellow toner pattern for color misregistration detection on the belt 31, and also controls the laser irradiation unit 61Y provided in the exposure unit 11Y. The line sensor 72Y is irradiated with laser light 70Y. Then, the control unit 81 stores the detection position Y0 of the laser beam 70Y detected by the line sensor 72Y in the RAM of the memory 82.

  In S12, the control unit 81 controls the image forming unit to sequentially form a magenta toner pattern and a cyan toner pattern for color misregistration detection on the belt 31. The process of S12 is executed immediately after the image forming apparatus is installed and when there is a high possibility that the exposure units are not aligned or when the exposure unit is replaced, and is omitted in other cases. be able to.

  In S13, the control unit 81 controls the image forming unit to form a black toner pattern for color misregistration detection on the belt 31, and also controls the laser irradiation unit 61BK provided in the exposure unit 11BK. The line sensor 72BK is irradiated with laser light 70BK. Then, the control unit 81 stores the detection position BK0 of the laser beam 70BK detected by the line sensor 72BK in the RAM of the memory 82.

  In S <b> 14, the toner pattern formed on the belt 31 is read by the photosensors 51 and 52 installed on the most downstream side in the belt conveyance direction, and the control unit 81 receives the read data from the photosensors 51 and 52. The control unit 81 performs predetermined processing on the data output from the photosensors 51 and 52, and shifts the color misregistration data of each color in the main scanning direction by magnification shift, shift (left / right shift), and sub-scan direction shift (up / down Shift), it is decomposed into inclinations and stored in the RAM of the memory 82. In addition, regarding the magnification deviation in the main scanning direction and the shift and inclination in the sub scanning direction that cannot be adjusted by adjusting the conveyance direction of the belt 31, the control unit 81 performs exposure of the exposure unit based on the detected color deviation data. For example, a known color misregistration adjustment process is performed by adjusting the timing.

  In S15, the control unit 81 reads the color misregistration data stored in the RAM of the memory 82, and determines whether or not the detected shift amount in the main scanning direction is within a predetermined error range. Then, if it is within the predetermined error range, the controller 81 sets the correction amounts ΔY and ΔBK of the laser beam detection positions for the laser beam detection positions Y0 and BK0 stored in the RAM of the memory 82 to 0, and proceeds to S16. . Conversely, if the shift amount in the main scanning direction is larger than the predetermined error range, the control unit 81 calculates the inclination amount θ in the conveyance direction of the belt 31 with respect to the exposure unit arrangement direction. The inclination amount θ can be calculated by the calculation formula θ = shift amount in the main scanning direction / L using L (FIG. 2C) which is the distance between the laser irradiation units 61Y and 61BK. Then, by setting the calculated inclination amount θ to 0, that is, by making the conveyance direction DB of the belt 31 parallel to the exposure unit alignment direction DE, the shift amount in the main scanning direction becomes 0, and the shift in the main scanning direction is caused. The color shift on the belt 31 can be eliminated. Therefore, the controller 81 corrects the laser beam detection position correction amount ΔY for the laser beam detection positions Y0 and BK0 stored in the RAM of the memory 82 so that the conveyance direction DB of the belt 31 is parallel to the exposure unit arrangement direction DE. , ΔBK is calculated. Since the shift amount in the main scanning direction is obtained by L × tan θ, the correction amounts ΔY and ΔBK may be determined, for example, by setting ΔY to 0, ΔBK = L × tan θ, or ΔBK to 0, and ΔY = It may be −L × tan θ. Further, when the detection position of the laser beam Y is shifted by α from the center of the line sensor 72Y so that the vicinity of the center of the line sensors 72Y and 72BK is the detection position of the laser beams 70Y and 70BK, ΔY = −α ΔBK = −α + L × tan θ. In the correction amount, since L × tan θ is the same value as the shift amount in the main scanning direction, the shift amount in the main scanning direction may be used instead of L × tan θ. Further, the signs (+ sign or-sign) of the correction amounts ΔY and ΔBK are made parallel to the exposure unit arrangement direction DE, so that the direction of adjustment of the transport direction DB of the belt 31 is adjusted (right side, left side). It is determined.

  In S16, the control unit 81 adds the correction amount ΔY calculated in S15 to the detection position Y0 of the laser light 70Y detected by the line sensor 72Y in S11, and sets the memory 82 as the target position Y0 for laser light detection in the line sensor 72Y. In the RAM. Similarly, the control unit 81 adds the correction amount ΔBK calculated in S15 to the detection position BK0 of the laser beam 70BK detected by the line sensor 72BK in S14, and uses the memory 82 as a target position BK0 for laser beam detection in the line sensor 72BK. In the RAM.

[Belt inclination correction]
FIG. 5B is a flowchart showing a detailed control sequence of the belt inclination correction process executed in S4 of FIG. In S21, the control unit 81 controls the laser irradiation unit 61Y provided in the exposure unit 11Y to irradiate the line sensor 72Y with the laser light 70Y. Then, the control unit 81 stores the detection position Y1 (position from the end of the belt 31) of the laser beam 70Y detected by the line sensor 72Y in the RAM of the memory 82.

  The position in the conveyance direction of the belt 31 when the line sensor detects the laser beam may be the same position when the initial belt inclination detection process is performed in S2 of FIG. 4 or an arbitrary position. The width of the belt 31 is not necessarily the same for the entire belt 31 due to processing accuracy at the time of manufacture. When the line sensors 72Y and 72BK detect laser light at different detection positions of the belt 31, respectively. The belt width at the detection position may be different. As a result, even if the conveyance direction of the belt 31 and the exposure unit alignment direction are parallel, if the detection position of the laser beam detected by the line sensors 72Y and 72BK, that is, the distance from the end of the belt 31, is different. If it is tilted, it may be misdetected. Therefore, in each of the line sensors 72Y and 72BK, the detection position in the transport direction of the belt 31 when detecting the laser light needs to be substantially the same position. If the start position in the conveying direction for detecting the position in the width direction on the belt 31 is determined, the position of the end of the belt 31 is detected for one round of the belt, and stored in the memory 82, the conveying direction of the belt It is possible to control the position of the belt in the width direction at any position.

  In S22, the controller 81 shifts the two positions Y0 and Y1 so that the detection position Y1 of the laser beam 70Y detected by the line sensor 72Y in S21 matches the target position Y0 calculated in S16 of FIG. The amount and the swing direction are calculated, and the driving amount of the steering motor U36 is calculated. Then, the control unit 81 drives the steering motor U36 via the motor driver U83 using the driving amount of the steering motor U36 indicating the swinging amount of the driving roller 32, thereby swinging the driving roller 32, and the belt The end position on the upstream side in the transport direction 31 is corrected.

  In S23, the control unit 81 controls the laser irradiation unit 61BK provided in the exposure unit 11BK to irradiate the line sensor 72BK with the laser light 70BK. Then, the control unit 81 stores the detected position of the laser beam 70BK detected by the line sensor 72BK (position from the end of the belt 31) in the RAM of the memory 82 as BK1.

  In S24, the control unit 81 calculates the shift amount and the swing direction of the two positions BK0 and BK1 so that the detection position BK1 of the laser beam 70BK detected by the line sensor 72BK matches the target position BK0 calculated in S16. Then, the driving amount of the steering motor D37 is calculated. Then, the controller 81 drives the steering motor D37 via the motor driver D84 using the driving amount of the steering motor D37 indicating the swinging amount of the driven roller 33, so that the driven roller 33 swings and the belt The position of the end portion 31 on the downstream side in the transport direction 31 is corrected.

  In S25, the controller 81 determines whether the difference between the detection position Y1 of the laser beam 70Y detected in S21 and the target position Y0 of the laser beam 70Y calculated in S16 of FIG. 5A is greater than a predetermined specified value. Judge whether. The control unit 81 returns to S21 if the difference between the two detection positions Y1 and Y0 is greater than a predetermined specified value, and proceeds to S26 if it is less than the predetermined specified value.

  In S26, the controller 81 determines whether the difference between the detection position BK1 of the laser beam 70BK detected in S23 and the target position BK0 of the laser beam 70BK calculated in S16 of FIG. 5A is larger than a predetermined specified value. Judge whether. If the difference between the two detection positions BK1 and BK0 is larger than a predetermined specified value, the process returns to S23, and if it is equal to or smaller than the predetermined specified value, the process is terminated.

  As described above, according to this embodiment, even if the belt frame or the main body frame is deformed and the amount of deformation changes with time, color misregistration due to the inclination between the exposure unit alignment direction and the belt conveyance direction is prevented. Can be reduced. As a result, the present embodiment has an effect of reducing color misregistration caused by shifting each color image in the main scanning direction. In addition, the belt conveyance direction can be adjusted based on the alignment direction of the exposure units, and color misregistration caused by belt deviation and meandering can be reduced, reducing the frequency of registration detection and registration adjustment that is performed regularly using toner patterns. There is also an effect that can be done. Further, since the belt conveyance direction is controlled based on the alignment direction of the exposure units, it is not necessary to excessively increase the torsional rigidity of the main body frame, and the weight of the image forming apparatus can be reduced.

  In this embodiment, the belt inclination control is performed by a driving roller and a driven roller which are steering rollers. When the tilt in the sub-scanning direction caused by the tilt between the alignment direction of the exposure units and the belt conveyance direction is allowed, and only the shift in the main scanning direction is corrected, the exposure is not performed by controlling the belt conveyance direction by the steering roller. It may be handled by adjusting the unit writing timing.

  In this embodiment, the case of an image forming apparatus employing an independent exposure unit for each toner color is described. However, two colors are stored in one exposure unit, or all the colors are stored in one exposure unit. The present invention can also be applied to the case of an image forming apparatus. In this case, in order to detect the relative positional relationship between the exposure unit and the belt, when two colors are one exposure unit, at least one or more exposure units, and when all colors are one exposure unit, at least one Two or more laser irradiation units are provided. Furthermore, in this embodiment, color is superimposed on the belt 31 in the order of yellow, magenta, cyan, and black. However, the color order is not limited to this, and the arrangement of each color can be freely set. Can be set.

  In the first embodiment, the laser irradiation unit emits a spot-shaped laser beam, and the line sensor detects the spot center position of the irradiated laser beam. The present embodiment is different from the first embodiment in that the laser irradiation unit irradiates a sheet-shaped (band-shaped) laser beam, and the line sensor detects the width of the detected laser beam. Except for the configuration of the laser irradiation unit and the line sensor described in FIG. 6, the configuration of the other image forming apparatuses is the same as that of the first embodiment, and thus the description thereof is omitted.

[Exposure unit position detection]
FIG. 6 is a view of the configuration in the vicinity of the exposure unit 11 and the belt unit of this embodiment, as viewed from the upstream side in the conveyance direction of the belt 31. FIG. 6 shows a characteristic configuration of this embodiment, and the photosensitive drums 12Y and 12BK are omitted. As shown in FIG. 6, the position detection means of the exposure unit 11Y (11BK) includes a laser irradiation unit 62Y (62BK) and a line sensor 76Y (76BK) that can irradiate a sheet-like laser beam 75Y (75BK). Yes. The laser irradiation unit 62Y (62BK) is installed in the exposure unit 11Y (11BK) so that about half of the spreading direction of the laser beam 75Y (75BK) to be irradiated (width direction of the belt 31) is blocked by the belt 31. Yes. The line sensor 76Y (76BK) is installed on the belt frame 101 so as to face the laser irradiation unit 62Y (62BK), and detects the sheet-like laser light 75Y (75BK) that has passed without being blocked by the belt 31. .

  Of the positions at both ends of the sheet-like laser beam 75Y (75BK) detected by the line sensor 76Y (76BK), the position corresponding to the edge (end) side of the belt 31 is C, and the opposite position is S. . It can be seen from FIG. 6 that the distance between the position C and the position S indicates the distance from the end of the belt 31 of the laser irradiation unit 62Y (62BK) provided in the exposure unit 11Y (11BK). Therefore, if the distance between the position C and the position S is the same in the laser irradiation units 62Y and 62BK, it can be said that the exposure unit alignment direction and the conveyance direction of the belt 31 are parallel. On the contrary, if the distance between the position C and the position S in the laser irradiation units 62Y and 62BK is different, it can be understood that the alignment direction of the exposure units and the conveyance direction of the belt 31 are not parallel.

  5A and 5B described in the first embodiment, the detection positions of the laser light detected by the line sensor are read as follows, so that FIGS. 5A and 5B are obtained. The described control sequence can be applied to the second embodiment as it is. That is, Y0 which is the detection position of the laser beam 70Y in S11 of FIG. 5A is changed to the laser beam width (SY0−CY0) calculated from the difference between SY0 and CY0 which is the detection position of the sheet-like laser beam 75Y. replace. Similarly, BK0, which is the detection position of the laser beam 70BK in S13 of FIG. 5A, is changed from the difference between SBK0 and CBK0, which is the detection position of the sheet-like laser light 75BK, to the width (SBK0− Replace with CBK0). Accordingly, in S15 of FIG. 5A, the inclination amount θ of the belt 31 is calculated using the equation θ = ((|) using L (FIG. 2C) which is the distance between the laser irradiation units 62Y and 62BK. SBK0−CBK0 | − | SY0−CY0 |) / L). Further, if the sign of the difference (| SBK0−CBK0 | − | SY0−CY0 |) is positive, it can be seen that the belt 31 is inclined to the right in the transport direction. If the sign of the difference is negative, the belt It can be seen that 31 is inclined to the left in the transport direction. Although the shift amount in the main scanning direction can be calculated by L × tan θ, (| SBK0−CBK0 | − | SY0−CY0 |) may be used as the shift amount in the main scanning direction. Based on the calculated shift amount in the main scanning direction, the control unit 81 can calculate an inclination correction amount that makes the inclination of the belt 31 with respect to the alignment of the exposure units zero by the method described in the first embodiment. . In S16, the control unit 81 calculates a target position (a target width of the laser light (a distance between the position C and the position S)) of the laser light detection in the line sensors 76Y and 76BK to which the obtained inclination correction amount is added.

  Similarly in FIG. 5B, the width of the laser beam (SY1) calculated from the difference between SY1 and CY1 as the detection position of the sheet-like laser beam 75Y as Y1 as the detection position of the laser beam 70Y at S21. Replace with -CY1). Furthermore, BK1, which is the detection position of the laser beam 70BK in S23 of FIG. 5B, is the laser beam width (SBK1-CBK1) calculated from the difference between SBK1 and CBK1, which is the detection position of the sheet-like laser beam 75BK. Replace with With these replacements, the control unit 81 can correct the inclination of the belt 31 by the drive control (swing control) of the drive roller 32 and the driven roller 33 as in the first embodiment.

  As described above, according to this embodiment, even if the belt frame or the main body frame is deformed and the amount of deformation changes with time, color misregistration due to the inclination between the exposure unit alignment direction and the belt conveyance direction is prevented. Can be reduced. In particular, according to the present embodiment, the mechanism (sensor stays 73Y, 73BK, uniaxial guides 74Y, 74BK) for moving the line sensors 72Y, 72BK in the first embodiment in contact with the end of the belt 31 can be eliminated. . In this embodiment, the laser irradiation unit is provided in the exposure unit and the line sensor is provided on the belt frame. However, the laser irradiation unit is provided on the belt frame and the line sensor is provided on the exposure unit. The effect is obtained.

  The laser irradiation units 61Y and 61BK in the first embodiment and the laser irradiation units 62Y and 62BK in the second embodiment are attached to the outside of the exposure units 11Y and 11BK as independent devices, and have a laser light source inside. In this embodiment, a part of the laser beam 16 that exposes the photosensitive drum 12 is extracted from the exposure unit 11 (the suffixes of Y and BK are omitted) and used as a laser irradiation unit, as in the first and second embodiments. Is different. Except for the configuration of the laser irradiation unit using the exposure unit described in FIG. 7, the configuration of the other image forming apparatuses is the same as that of the first embodiment, and thus the description thereof is omitted.

[Exposure unit position detection]
FIGS. 7A and 7B are views showing an exposure unit 11 used in the first embodiment and an exposure unit 18 that is an alternative to the laser irradiation unit 61. FIG. 7A is a top view of the exposure unit 18 as viewed from the upper direction of the image forming apparatus 100, and FIG. 7B is a view of the exposure unit 18 as viewed from the upstream side in the conveyance direction of the belt 31. FIG.

  7A and 7B, the laser light 16 emitted from the laser light source 90 is reflected and scanned by the rotating polygon mirror 91, passes through the optical element group 92, and is reflected by the mirror 93. Scanning exposure is performed on the photosensitive drum 12 in the direction of the arrow in FIG. A part of the laser beam 16 is reflected by the mirror 94 and is incident on a laser detection sensor 95 used for aligning the writing position of the scanning exposure light. Further, a part of the laser beam 16 is reflected by the mirrors 94 and 96, passes through the optical system 97, is reflected by the mirror 98, and is a laser for detecting the position of the exposure unit 18 from the end of the belt 31. Used as laser light 70 of the irradiation unit. The line sensor having the configuration described in the first embodiment can be used as it is, and the inclination detection and the inclination correction processing of the belt 31 are described in FIGS. 5A and 5B of the first embodiment. The control sequence can also be applied as it is in this embodiment.

  Next, FIGS. 7C to 7E are views showing an exposure unit 19 that is an alternative to the exposure unit 11 and the laser irradiation unit 62 used in the second embodiment. 7C is a top view of the exposure unit 19 viewed from the upper direction of the image forming apparatus 100, FIG. 7D is a view of the exposure unit 19 viewed from the upstream side in the conveyance direction of the belt 31, and FIG. e) is a view of the exposure unit 19 as seen from the width direction of the belt 31. FIG. A part of the laser beam 16 is cut out into a sheet shape, reflected by the mirrors 94 and 96, passes through the optical system 97, then reflected by the mirror group 99, and the position of the exposure unit 19 from the end of the belt 31. Used as laser light 75 of the laser irradiation unit for detection. The line sensor having the configuration described in the second embodiment can be used as it is. Further, the inclination detection and inclination correction processing of the belt 31 is performed in the present embodiment as it is by replacing the control sequence described in FIGS. 5A and 5B of the first embodiment in the same manner as in the second embodiment. Can be applied.

  As described above, according to this embodiment, even if the belt frame or the main body frame is deformed and the amount of deformation changes with time, color misregistration due to the inclination between the exposure unit alignment direction and the belt conveyance direction is prevented. Can be reduced. In particular, according to this embodiment, there is no need to separately provide a laser irradiation unit independent of the exposure unit for detecting the relative positional relationship between the exposure unit and the belt.

  In the first to third embodiments described above, the tilt correction of the belt 31 is performed using the driving roller 32 and the driven roller 33 which are steering rollers. This embodiment differs from the second embodiment in which a uniaxial drive unit is used instead of a steering roller as a tilt correction unit of the belt 31, and the laser irradiation unit and line sensor having the same configuration are used. is there. Except for the configuration described with reference to FIG. 8, the configuration of the other image forming apparatuses is the same as that of the first embodiment, and a description thereof will be omitted.

[Belt inclination correction]
FIG. 8A is a diagram of the configuration in the vicinity of the exposure unit and the belt unit of the present embodiment as viewed from the upstream side in the conveyance direction of the belt 31. FIG. 8A shows a characteristic configuration of the present embodiment, and the photosensitive drums 12Y, 12BK and the like are omitted. Further, the laser irradiation unit 62Y (62BK) and the line sensor 76Y (76BK) capable of irradiating the sheet-like laser beam 75Y (75BK) for detecting the position of the exposure unit 11Y (11BK) are the same as those in the second embodiment. The description is omitted. In FIG. 8A, the main body frame 201 and the belt unit outer frame 202 are connected by a positioning pin 229 and a positioning block 203. The belt frame 101 is connected to the belt unit outer frame 202 by uniaxial driving units 103Y and 103BK. For example, an air cylinder, a piezoelectric actuator, or the like can be used for the uniaxial drive units 103Y and 103BK. The belt frame 101 has bearing mechanisms 102 at least at three locations so that the belt frame 101 can move smoothly on the belt unit outer frame 202. The belt 31 includes only a fixed roller having no steering mechanism, and is stretched and integrated with the belt frame 101. Based on the edge positions S and C of the sheet-like laser light detected by the line sensors 76Y and 76BK, the control unit 81 calculates the inclination of the conveyance direction of the belt 31 with respect to the exposure unit arrangement direction. Then, the control unit 81 calculates the driving amounts of the uniaxial driving units 103Y and 103BK necessary for making the conveyance direction of the belt 31 parallel to the exposure unit arrangement direction. Then, the driver 85 drives the uniaxial drive units 103Y and 103BK based on the drive amount instructed from the control unit 81.

  FIGS. 8B and 8C are views showing a state in which the straight line DB indicating the conveyance direction of the belt 31 is adjusted (parallel) to the alignment direction DE of the exposure units in the present embodiment. It is. FIG. 8B is a diagram showing a state in which the main body frame 201 has undergone torsional deformation at the upper part provided with the exposure unit and the lower part provided with the belt unit. In FIG. 8B, the belt frame 101 and the belt unit outer frame 202 are parallel to each other, but are in a twisted positional relationship with the exposure unit 11 connected to the main body frame, and with respect to the alignment direction DE of the exposure units 11. The conveyance direction DB of the belt 31 is inclined. In FIG. 8C, as a result of the uniaxial driving units 103Y and 103BK driving the belt frame 101, the belt frame 101 is inclined with respect to the belt unit outer frame 202, but the belt 31 conveyance direction DB and the exposure unit 11 are arranged. It is a figure which shows a mode that the direction DE became parallel.

  As described above, according to this embodiment, even if the belt frame or the main body frame is deformed and the amount of deformation changes with time, color misregistration due to the inclination between the exposure unit alignment direction and the belt conveyance direction is prevented. Can be reduced. In particular, according to the present embodiment, the belt inclination can be corrected by two simple uniaxial driving units without using a complicated steering mechanism having many components.

  In addition, two position data (two edge positions S and C) can be obtained by one line sensor by detecting the end of the belt in the width direction using the sheet-shaped laser light and the line sensor of the present embodiment. Therefore, by adding a steering mechanism having a steering roller to the present embodiment and combining the steering roller and the uniaxial drive unit, the conveyance direction of the belt can be controlled. That is, the belt conveying direction can be controlled by driving the uniaxial driving unit based on the data of the edge position S and controlling the steering roller based on the data of the edge position C. For example, in this embodiment, the torsional rigidity of the main body frame can be kept low, and as a result, the large torsional deformation that occurs is driven into the tilt control range of the steering mechanism by the uniaxial drive unit, and the remaining tilt is It can be controlled by a steering mechanism.

11Y, 11M, 11C, 11BK Exposure units 12Y, 12M, 12C, 12BK Photosensitive drum 31 Intermediate transfer belt 32 Drive roller 33 Driven rollers 51, 52 Photo sensor 61Y, 61BK Laser irradiation unit 72Y, 72BK Line sensor 81 Control unit

Claims (5)

A plurality of exposure means provided corresponding to each of the plurality of image carriers, and exposing each of the plurality of image carriers;
The latent images formed on the plurality of image carriers are developed with toner by being exposed by the plurality of exposure units, and the toner images developed on the plurality of image carriers are rotated by a rotation shaft. Image forming means for transferring to an endless intermediate transfer body,
Image detecting means for detecting a toner image formed on the intermediate transfer member by the plurality of exposure means and the image forming means;
Position detecting means for detecting a relative position between each of the plurality of exposure means and the intermediate transfer member;
Drive means for swinging the rotating shaft to control the conveying direction of the intermediate transfer member;
The image is arranged such that a deviation on the image carrier between toner images formed on the plurality of image carriers due to an inclination between a conveyance direction of the intermediate transfer member and an alignment direction of the plurality of exposure units is reduced. Control means for controlling a swing amount of the rotating shaft by the drive means based on detection results of the detection means and the position detection means;
Equipped with a,
The position detection means is provided along end portions in the width direction of the intermediate transfer body of the plurality of exposure means, and is provided facing a laser irradiation means for irradiating a spot-like laser beam. A line sensor in which a light receiving element for detecting a laser beam from the laser irradiation means is linearly arranged in the width direction of the intermediate transfer body, and a support part for supporting the line sensor,
The image forming apparatus , wherein the support portion is in contact with an end portion in the width direction of the intermediate transfer member . A plurality of exposure means provided corresponding to each of the plurality of image carriers, and exposing each of the plurality of image carriers;
The latent images formed on the plurality of image carriers are developed with toner by being exposed by the plurality of exposure units, and the toner images developed on the plurality of image carriers are rotated by a rotation shaft. Image forming means for transferring to an endless intermediate transfer body,
Image detecting means for detecting a toner image formed on the intermediate transfer member by the plurality of exposure means and the image forming means;
A part of the sheet-like laser light that is provided along the widthwise end of the intermediate transfer member of the plurality of exposure means and spreads in the width direction of the intermediate transfer member is the edge in the width direction of the intermediate transfer member. Laser irradiation means for irradiating a sheet-like laser beam so as to be blocked by the unit;
A light receiving element, which is provided on a belt frame connected to the stretched intermediate transfer member so as to face the laser irradiation unit and detects a sheet-like laser beam from the laser irradiation unit, has a width of the intermediate transfer member. A line sensor for detecting a sheet-shaped laser beam that is linearly arranged in a direction, is irradiated from the laser irradiation unit, and is not blocked by an end portion in the width direction of the intermediate transfer member;
An adjusting means for adjusting an inclination of the belt frame with respect to an arrangement direction of the plurality of exposure means;
The image is arranged such that a deviation on the image carrier between toner images formed on the plurality of image carriers due to an inclination between a conveyance direction of the intermediate transfer member and an alignment direction of the plurality of exposure units is reduced. An image forming apparatus comprising: a detection unit; and a control unit configured to control an inclination amount of the belt frame by the adjustment unit based on a detection result of the line sensor. The laser beam by the laser irradiation means for irradiating the image forming apparatus according to claim 1 or 2, characterized in that a laser beam emitted from the laser light source of the exposure means. The laser beam said laser irradiation means for irradiating comprises said laser irradiation means, according to claim 1 or 2, characterized in that a laser beam emitted from different laser light source is a laser light source of the exposure means Image forming apparatus. It said image detecting means, the read toner pattern formed on the intermediate transfer member, the image forming apparatus according to any one of claims 1 and detecting the color misregistration 4.

Images