JP2017219693A - Image forming apparatus and printing distortion correction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To scan a printed-out pattern image with an image reading part to detect the amount of printing distortion, and feed back the amount of printing distortion to the amount of distortion detectable by registration sensors, thereby enabling printing distortion adjustment even when the arrangement positions in a sub scanning direction of the registration sensors are shifted from each other.SOLUTION: An image forming apparatus comprises: an image reading part (document reading part 41) that reads an image; and registration sensors 72F and 72R that detect a first pattern image on a transfer belt. The registration sensors 72F and 72R are provided on one side and the other side in a direction orthogonal to the direction of movement of the transfer belt. The image forming apparatus includes a calculation part (main control part 71) that calculates the difference between the positions of the two registration sensors 72F and 72R in the direction of movement of the transfer belt on the basis of a result of reading of a second pattern image in which a printed-out pattern image is read by the image reading part 41 and a result of detection of the first pattern image performed by the registration sensors 72F and 72R.SELECTED DRAWING: Figure 2

Description

  The present invention includes an image reading unit that reads an image and a registration sensor that detects a pattern image on the transfer belt, and the registration sensor is provided on one side and the other side in a direction orthogonal to the moving direction of the transfer belt. The present invention relates to an apparatus and a printing distortion correction method for the image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus that corrects printing distortion using two registration sensors has been provided (see, for example, Patent Document 1).

  In Patent Document 1, a plurality of images of different colors are formed on an image forming medium driven at a predetermined speed by aligning the positions of the images of the respective colors, and in a predetermined arrangement direction. Two sensors (hereinafter referred to as registration sensors) that detect the image formed on the image forming medium, and an inclination amount calculation that calculates an inclination amount of the arrangement direction with respect to a direction orthogonal to the driving direction. And two correction pattern rows in which one or a plurality of correction pattern images are aligned in the driving direction at positions corresponding to the two registration sensors of the image forming medium by the image forming unit and the image forming unit, respectively. Correction pattern forming means formed with a difference in position with respect to the driving direction by the amount, detection results of the two correction pattern rows by the two sensors, and the amount of inclination. Come, the positional deviation of each color image formed against said image forming medium, the image forming apparatus is disclosed which has a positional deviation correcting means for correcting return the inclination by weight can inclined and.

JP2013-195691A

  That is, in Patent Document 1, in order to grasp the positional deviation between the two registration sensors, the arrival times of the two correction pattern rows printed on the transfer belt (image forming medium) to the registration sensor are obtained.

  However, the image forming apparatus described in Patent Document 1 is based on the premise that there is no printing misalignment in the paper transport direction on both outer sides in the direction orthogonal to the paper transport direction. The displacement of the registration sensor in the sub-scanning direction, which is the moving direction of the transfer belt, cannot be grasped.

  In other words, the print distortion can be measured by the difference in the reading timing of the two correction pattern rows by the two registration sensors, but if there is a deviation in the arrangement position of the two registration sensors in the sub-scanning direction, In other words, there is a problem that the print distortion cannot be corrected with high accuracy because there is a deviation from the print result when printing on the recording paper.

  The present invention was devised to solve such problems, and its purpose is to detect the amount of print distortion by scanning a printed pattern image with an image reading unit and detecting it with a registration sensor. An image forming apparatus and a printing distortion correction method capable of performing printing distortion adjustment with high accuracy even when there is a deviation in the position of the registration sensor in the sub-scanning direction by feeding back the printing distortion amount to the distortion amount that can be generated. Is to provide.

  In order to solve the above problems, an image forming apparatus of the present invention includes an image reading unit that reads an image, and a registration sensor that detects a first pattern image on the transfer belt, and the registration sensor moves the transfer belt. An image forming apparatus provided in one and the other of directions orthogonal to the direction, wherein a pattern image that has been printed out is read by the image reading unit and a reading result of the second pattern image and the registration sensor And a calculating unit that calculates a difference between the positions of the two registration sensors in the moving direction of the transfer belt based on the detection result of the first pattern image.

  According to this configuration, in the print distortion correction, the second pattern image for automatic void adjustment is read by the image reading unit to detect the actual print distortion amount, and this print distortion amount is fed back to the distortion amount that can be detected by the registration sensor. By doing so, even if there is a deviation in the position of the registration sensor in the sub-scanning direction, the printing distortion can be adjusted with high accuracy.

  According to the image forming apparatus of the present invention, both the reading result of the second pattern image and the detection result of the first pattern image are distortion amounts. Further, the distortion amount is a difference calculated by the calculation unit.

  The image forming apparatus according to the present invention may further include a correction amount calculation unit that calculates a correction amount from the distortion amount.

  According to the image forming apparatus of the present invention, the image forming apparatus may further include a display unit that displays the correction amount calculated by the correction amount calculation unit.

  According to the image forming apparatus of the present invention, the image forming apparatus may further include a storage unit that stores the correction amount calculated by the correction amount calculation unit.

  According to the image forming apparatus of the present invention, the correction amount is a value for correcting the position of the optical member of the optical scanning device in the sub-scanning direction.

  The printing distortion correction method of the present invention includes an image reading unit and a registration sensor that detects the first pattern image on the transfer belt, and the registration sensor is one of the directions orthogonal to the moving direction of the transfer belt. A printing distortion correction method for an image forming apparatus provided on the other side, the step of reading the printed pattern image by the image reading unit, the step of reading the first pattern image by the registration sensor, Based on the reading result of the second pattern image read by the image reading unit and the detection result of the first pattern image by the registration sensor, the two resist sensors in the direction orthogonal to the moving direction of the transfer belt. And a step of calculating a position difference.

  According to the printing distortion correction method of the present invention, both the reading result of the second pattern image and the detection result of the first pattern image are distortion amounts, and the correction amount is calculated from the distortion amount by the correction amount calculation unit. It is good also as a structure including the process to calculate.

  Moreover, according to the printing distortion correction method of the present invention, it may be configured to include a step of displaying the calculated correction amount on the display unit.

  Further, according to the printing distortion correction method of the present invention, it may be configured to include a step of storing the correction amount calculated by the correction amount calculation unit in the storage unit.

  Further, according to the printing distortion correction method of the present invention, it may be configured to include a step of correcting the position of the optical member of the optical scanning device in the sub-scanning direction based on the correction amount.

  According to the printing distortion correction method of the present invention, in the second and subsequent printing distortion corrections, the detection result of the first pattern image detected by the registration sensor and the correction amount stored in the storage unit. The printing distortion correction may be performed based on the above.

  According to the image forming apparatus and the printing distortion correction method of the present invention, in the printing distortion correction, the second pattern image is scanned to detect the actual printing distortion amount, and the printing distortion amount is set to the distortion amount that can be detected by the registration sensor. By feeding back, the printing distortion can be adjusted with high accuracy even if the registration sensor is displaced in the sub-scanning direction.

1 is a schematic cross-sectional view illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a block diagram illustrating a control system of an image forming apparatus according to an embodiment. It is explanatory drawing which shows typically a pair of pattern image (1st pattern image) transcribe | transferred to the both ends of the intermediate transfer belt. It is explanatory drawing which shows typically the 2nd pattern image previously registered into memory. It is explanatory drawing which shows typically an example of the 2nd pattern image when the 2nd pattern image registered into the memory is once printed out and read by the original reading part. 6 is a flowchart illustrating a processing procedure of a print distortion correction amount calculation process and a distortion adjustment process according to the first embodiment. 10 is a flowchart illustrating a processing procedure of a printing distortion correction amount calculation process according to the second embodiment. 10 is a flowchart illustrating a processing procedure of distortion adjustment processing according to the second embodiment. It is a figure which shows schematically the inside of the housing | casing of an optical scanning device seeing from an upper surface. It is a figure which shows roughly the inside of the housing | casing of an optical scanning device seeing from a side surface. It is a perspective view which shows the principal part of the optical scanning apparatus in the state which removed the upper cover.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic sectional view showing an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus 1 includes a document reading section (image reading section) 41, an apparatus main body 51, and an input operation section 52 (see FIG. 2). The apparatus main body 51 includes an image forming section 53 and a paper transport section 54. Is provided. The image forming unit 53 forms (prints) an image on a recording sheet based on the image data output from the document reading unit 41 or image data received from the outside.

  The document reading unit 41 is provided on the upper part of the apparatus main body 51, and is provided on a document placing table 43 made of transparent glass on which a sheet such as a document (hereinafter referred to as a document) is placed, and on a lower part of the document placing table 43. An optical unit 44 for reading the image and a document reading device 45 provided on the document placing table 3. The optical unit 44 is a color scanner that reads an image of a document placed on the document placement table 43 or reads an image of a document conveyed by the document reading device 45. The document reading device 45 automatically conveys the document on the document placing table 43. Further, the document reading device 45 is attached to the apparatus main body 51 so as to be pivotable by opening the front side, and the document can be placed manually by opening the document placing table 43. . In the present embodiment, the front side of the apparatus main body 51 is the front side (the operation side operated by the user).

  The document reading unit 41 automatically reads a document that is automatically transported onto the document placing table 43 or an image of a document placed on the document placing table 43. The entire image of the document read by the document reading unit 41 is sent to the image forming unit 53 as image data, and an image formed based on the image data in the image forming unit 53 is recorded on a recording sheet.

  The image data handled in the image forming apparatus 1 is data corresponding to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This corresponds to the monochrome image used. For this reason, the image forming unit 53 is provided with four developing devices 12, photosensitive drums 13, drum cleaning devices 14, and chargers 15 to form four types of toner images corresponding to the respective colors. Four image forming units Pa, Pb, Pc, and Pd are configured in association with black, cyan, magenta, and yellow, respectively.

  In each of the image forming units Pa, Pb, Pc, and Pd, after the toner remaining on the surface of the photosensitive drum 13 is removed and collected by the drum cleaning device 14, the surface of the photosensitive drum 13 is charged to a predetermined potential by the charger 15. The surface of the photosensitive drum 13 is exposed by the optical scanning device 11 to form an electrostatic latent image on the surface, and the electrostatic latent image on the surface of the photosensitive drum 13 is developed by the developing device 12. Then, a toner image is formed on the surface of the photosensitive drum 13. As a result, a toner image of each color is formed on the surface of each photosensitive drum 13.

  While the intermediate transfer belt 21 is moved in the direction of the arrow C while the residual toner on the intermediate transfer belt 21 is removed and collected by the belt cleaning device 25, the toner image of each color is transferred to the surface of each photosensitive drum 13 on the intermediate transfer belt 21. The toner images are sequentially transferred and overlapped to form a color toner image on the intermediate transfer belt 21.

  A nip area is formed between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26, and the recording paper conveyed through the paper conveyance path R1 is sandwiched and conveyed in the nip area (transfer nip portion). At the same time, the color toner image on the surface of the intermediate transfer belt 21 is transferred onto the recording paper. Then, the recording paper is sandwiched between the heating roller 31 and the pressure roller 32 of the fixing device 17 and heated and pressed to fix the color toner image on the recording paper.

  On the other hand, the recording sheet is pulled out from the sheet feeding tray 18 by the pickup roller 33 and conveyed through the S-shaped sheet conveying path R1 constituting the sheet conveying system 54, via the secondary transfer device 26 and the fixing device 17. Then, it is carried out to the paper discharge tray 39 via the paper discharge roller 36. In this paper conveyance path R1, after the recording paper is temporarily stopped and the leading ends of the recording paper are aligned, the color toner image is transferred at the transfer nip portion between the intermediate transfer belt 21 and the transfer roller 26a. A set of registration rollers 34 for starting the conveyance of the recording paper, a plurality of sets of conveyance rollers 35 for urging the conveyance of the recording paper, a set of paper discharge rollers 36, and the like are arranged.

  Further, when printing not only on the front side of the recording paper but also on the back side, the recording paper is conveyed in the reverse direction from each discharge roller 36 to the reverse path Rr, and the recording paper is turned upside down. The image is guided again to each registration roller 34, and the image is recorded and fixed on the back surface of the recording paper, similarly to the front surface of the recording paper, and the recording paper is carried out to the paper discharge tray 39.

  The two registration sensors 72F and 72R are disposed between the photosensitive drum 13 and the transfer nip portion of the black (K) image forming unit Pa, and detect a registration adjustment pattern on the intermediate transfer belt 21. It is. The registration sensors 72F and 72R have one (the front side of the apparatus main body 51) and the other (the apparatus main body) of the direction (hereinafter referred to as the main scanning direction) orthogonal to the moving direction of the intermediate transfer belt 21 (hereinafter referred to as the sub scanning direction). 51 are arranged in two locations on the rear side.

  FIG. 2 is a block diagram illustrating a control system of the image forming apparatus 1.

  2, the main control unit 71 includes a CPU, a RAM, a ROM, various interfaces, and the like, and an original reading unit 41, an image forming unit 53, a paper transport unit 54, an input operation unit 52, and a memory 75 are integrated. To control.

  The input operation unit 52 includes a liquid crystal display device including a plurality of input keys and a touch panel, for example. The memory (storage unit) 75 is, for example, a hard disk device (HDD), and stores various data and programs.

  The two registration sensors 72F and 72R detect a pattern image (first pattern image) for correcting printing distortion, which will be described later, in addition to the registration adjustment pattern formed on the intermediate transfer belt 21, and the detection result is mainly used. Input to the controller 71.

  In such a configuration, the main control unit 71 calculates a print distortion correction amount and performs print distortion adjustment prior to registration adjustment, for example, when the image forming apparatus 1 is inspected before shipment from the factory. That is, the main control unit 71 corresponds to a calculation unit and a correction amount calculation unit described in the claims.

<Description of Print Distortion Correction Amount Calculation Processing and Distortion Adjustment Processing According to Embodiment 1>
FIG. 3 schematically shows a pair of pattern images (first pattern images) G1, G2 transferred to both ends of the intermediate transfer belt 21. The first pattern images G1 and G2 are transferred by a black (K) image forming unit Pa. 4 is a diagram schematically showing a second pattern image registered in advance in the memory 75, and FIG. 5 is a diagram in which the second pattern image registered in the memory is once printed out on recording paper, and the document reading unit FIG. 6 is a diagram schematically showing a second pattern image when read by 41. FIG. 6 is a flowchart illustrating a processing procedure of a print distortion correction amount calculation process and a distortion adjustment process according to the first embodiment.

  The registration sensors 72F and 72R detect the first pattern images G1 and G2 conveyed in the sub-scanning direction (belt movement direction) X as the intermediate transfer belt 21 rotates, respectively. It outputs to the control part 71 (step S1).

  The main control unit 71 obtains the transfer position in the sub-scanning direction X of each first pattern image G1, G2 based on the detection timing of each first pattern image G1, G2 and the circumferential movement speed of the intermediate transfer belt 21. A distortion amount (deviation amount) α1 in the sub-scanning direction X of the pattern images G1 and G2 is calculated (step S2).

  Here, the first pattern image G2 on the front side (F) is used as a reference, and the case where the first pattern image G1 on the rear side (R) has preceded printing is defined as +. The first pattern image G1 on the rear side (R) precedes the FR reference length L in the FR direction (main scanning direction) Y (for example, 210 mm = interval between the registration sensors 72F and 72R). The amount of distortion is the distortion amount.

  More specifically, the main control unit 71 calculates a distance (deviation amount in the sub-scanning direction) from the difference between the arrival detection times of the first pattern images G1 and G2, and uses this as the distortion amount α1. Store in a predetermined area. The distortion amount α1 is a distortion amount detected by the registration sensors 72F and 72R.

  Next, the main controller 71 prints out the second pattern image registered in advance in the memory 75 on the recording paper (step S3).

  Here, as shown in FIG. 4, the second pattern image registered in the memory 75 includes 12 second pattern images having the same shape on each side of a rectangular paper frame, a total of 12 second pattern images. Yes.

  Among these, the three second pattern images G11, G12, and G13 arranged on each of two sides orthogonal to the sheet conveyance direction (the same direction as the moving direction of the intermediate transfer belt 21) are the second pattern images on the outer sides. The arrangement interval of G11 and G13 is set to be the same FR reference length L as the arrangement interval of the registration sensors 72F and 72R. Further, regarding the three second pattern images G21, G22, and G23 respectively arranged on the two sides along the paper conveyance direction, the arrangement interval L1 between the second pattern images G21 and G23 on both outer sides is not particularly limited, but It is preferable to set so that the FR reference length L is the same as the arrangement interval of the two pattern images G11 and G13.

  For the second pattern image registered in the memory 75, at least the widths W1 of the second pattern images G11, G12, and G13 in the paper transport direction (hereinafter also referred to as the X direction) are all the same. The widths W2 of the second pattern images G21, G22, and G23 in the direction orthogonal to the paper transport direction (hereinafter also referred to as the Y direction) are all set to the same width.

  Next, the main control unit 71 reads the printed recording paper with the document reading unit 41, and calculates the actual print distortion amount from the read second pattern image (step S4).

  Here, the second pattern image shown in FIG. 4 is transferred onto the intermediate transfer belt 21 by the black (K) image forming unit Pa and printed out, and the printed second pattern image is read by the document reading unit 41. If the state at that time is the state shown in FIG. 5, the main control unit 71 calculates the print distortion amount from the second pattern image shown in FIG.

  More specifically, the main control unit 71 includes two second pattern images G11, G12, and G13 arranged in alignment in the Y direction on the two outer sides corresponding to the FR reference length L. The difference between the widths in the X direction of the second pattern images G11 and G13 is calculated as the distortion amount βx in the X direction by the following equation.

X direction distortion amount βx = width W12 of G13−width W11 of G11
Next, the main control unit 71 includes two second patterns on the outer sides corresponding to the FR reference length L among the three second pattern images G21, G22, and G23 arranged in alignment in the X direction. The difference between the widths of the images G21 and G23 in the Y direction is calculated as the amount of distortion in the Y direction (deviation amount due to oblique conveyance) βy by the following equation.

Y direction distortion amount βy = width W22 of G23−width W21 of G21
Next, the main control unit 71 calculates the printing distortion amount β1 (= βx−βy) by subtracting the Y-direction distortion amount βy from the X-direction distortion amount βx.

  That is, by detecting the width of the second pattern image in a total of four locations, two locations in the X direction and two locations in the Y direction, and calculating the amount of print distortion, the distortion of the optical unit 44 and the distortion of the conveyed paper It is possible to measure the amount of distortion of printing excluding the amount (deviation amount due to oblique conveyance).

  Next, the main control unit 71 determines whether or not the printing distortion amount β1 is within a preset allowable range (for example, 0.5 mm or less) (step S5). As a result, when β1 is outside the allowable range (when it is determined Yes in step S5), the correction amount (distortion adjustment value) corresponding to the print distortion amount β1 is displayed on the display panel (display) of the input operation unit 52. (Step S6).

  When the print distortion adjustment is manual adjustment, the operator rotates the adjustment screw (knob 126 shown in FIG. 11) of the optical scanning device 11 according to the correction amount (distortion adjustment value) displayed on the display panel. To make adjustments. On the other hand, when the print distortion adjustment is automatic adjustment, the main control unit 71 drives the adjustment screw of the optical scanning device 11 according to the correction amount (distortion adjustment value) displayed on the display panel (drive motor). To adjust (step S7). Specifically, the inclination of the second fθ lens 109 (see FIG. 11 described later) of the optical scanning device 11 is adjusted. As described above, when a drive unit (drive motor) is mounted for optical adjustment, the adjustment can be completed during actual printing. The adjustment mechanism for carrying out this adjustment process will be described later in a row.

  Thereafter, returning to step S1, the first pattern images G1, G2 are detected by the registration sensors 72F, 72R, and the distortion amount (deviation amount) of the pattern images G1, G2 in the sub-scanning direction X is calculated in step S2. In step S3, the second pattern image is printed on the recording paper, and the recording paper printed in step S4 is read by the document reading unit 41. The actual print distortion amount is calculated from the read second pattern image. To do. In step S5, it is determined whether the printing distortion amount β1 is within a preset allowable range (for example, 0.5 mm or less).

  The main control unit 71 carries out the processes in steps S1 to S4 until it is determined in step S5 that the print distortion amount β1 is within a preset allowable range (for example, 0.5 mm or less).

  When it is determined in step S5 that the printing distortion amount β1 is within a preset allowable range (for example, 0.5 mm or less) (that is, NO is determined in step S5), the main control unit 71 The distortion correction amount γ (= α1) is obtained by subtracting the printing distortion amount β1 calculated from the second image pattern read by the document reading unit 41 from the distortion amount α1 detected by the registration sensors 72F and 72R obtained at that time. -Β1) is calculated (step S8), and the calculated distortion correction amount γ is stored (registered) in a predetermined area of the memory 75 (step S9).

  That is, according to the first embodiment, by calculating the distortion correction amount γ, the correlation between the distortion of the printing itself (deviation amount) and the deviation of the attachment positions of the registration sensors 72F and 72R in the sub-scanning direction is calculated. Become.

  In this way, the initial print distortion adjustment is completed at the time of factory shipment.

  In the first embodiment, when the initial adjustment is repeated, the processing in steps S1 to S7 is repeated, and when it is determined that the print distortion amount β1 is within a preset allowable range (for example, 0.5 mm or less), A value obtained by subtracting the printing distortion amount β1 from the distortion amount α1 obtained at this time is registered in the memory 75 as a distortion correction amount γ. That is, in the first embodiment, the distortion correction amount γ obtained when the print distortion adjustment is completed is registered. In this case, the printed second pattern image has a substantially square angle, and the print distortion amount β1 is 0.5 mm or less. Accordingly, the distortion correction amount γ registered in the memory 75 becomes a value very close to the distortion amount α1 detected by the registration sensors 72F and 72R that have been adjusted at that time.

<Description of Print Distortion Correction Amount Calculation Processing and Distortion Adjustment Processing According to Embodiment 2>
FIG. 7 is a flowchart illustrating a processing procedure of a printing distortion correction amount calculation process according to the second embodiment, and FIG. 8 is a flowchart illustrating a processing procedure of a distortion adjustment process according to the second embodiment. In the second embodiment, the pattern images shown in FIGS. 3 to 5 are commonly used.

  The registration sensors 72F and 72R detect the first pattern images G1 and G2 conveyed in the sub-scanning direction (belt movement direction) X as the intermediate transfer belt 21 rotates, respectively. It outputs to the control part 71 (step S11).

  The main control unit 71 obtains the transfer position in the sub-scanning direction X of each first pattern image G1, G2 based on the detection timing of each first pattern image G1, G2 and the circumferential movement speed of the intermediate transfer belt 21. A distortion amount (deviation amount) α1 in the sub-scanning direction X of the pattern images G1 and G2 is calculated (step S12). The process of step S12 is the same as the process of step S2 of FIG.

  Next, the main controller 71 prints out the second pattern image registered in the memory 75 in advance on the recording paper (step S13).

  Next, the main control unit 71 reads the printed recording paper by the document reading unit 41, and calculates the actual print distortion amount β1 (= βx−βy) from the read second pattern image (step S14). . The process of step S14 is the same as the process of step S4 of FIG.

  Next, the main control unit 71 subtracts the print distortion amount β1 calculated from the second image pattern read by the document reading unit 41 from the distortion amount α1 detected by the registration sensors 72F and 72R, thereby correcting the distortion correction amount γ ( = Α1-β1) (step S15), and the calculated distortion correction amount γ is stored (registered) in a predetermined area of the memory 75 (step S16).

  Thus, the printing distortion correction amount calculation process is completed, and the printing distortion adjustment process is subsequently performed.

  That is, the registration sensors 72F and 72R respectively detect the first pattern images G1 and G2 conveyed in the sub-scanning direction (belt movement direction) X with the circumferential movement of the intermediate transfer belt 21, and the respective detection results. Is output to the main control unit 71 (step S21).

  The main control unit 71 obtains the transfer position in the sub-scanning direction X of each first pattern image G1, G2 based on the detection timing of each first pattern image G1, G2 and the circumferential movement speed of the intermediate transfer belt 21. A distortion amount (deviation amount) α1 in the sub-scanning direction X of the pattern images G1 and G2 is calculated (step S22).

  Next, the main control unit 71 subtracts the distortion correction amount γ stored (registered) in the memory 75 from the calculated distortion amount (deviation amount) α1 of each pattern image G1, G2 in the sub-scanning direction. The corrected distortion amount is calculated (step S23).

  Next, the main control unit 71 determines whether or not distortion adjustment is necessary based on the calculated corrected distortion amount (step S24). Specifically, when the corrected distortion amount is zero or within a predetermined fixed amount (when it is determined No in step S24), it is determined that the distortion adjustment is unnecessary, and the distortion adjustment process is completed. .

  On the other hand, when the corrected distortion amount is zero or exceeds a predetermined fixed amount (when determined Yes in step S24), the correction amount corresponding to the calculated corrected distortion amount ( (Distortion adjustment value) is displayed on the display panel of the input operation unit 52 (step S25).

  Here, when the print distortion adjustment is manual adjustment, the operator performs the adjustment by rotating the adjustment screw of the optical scanning device 11 according to the correction amount (distortion adjustment value) displayed on the display panel. On the other hand, when the print distortion adjustment is automatic adjustment, the main control unit 71 drives the adjustment screw of the optical scanning device 11 according to the correction amount (distortion adjustment value) displayed on the display panel (drive motor). To adjust (step S26). Specifically, the inclination of the second fθ lens 109 (see FIG. 11) of the optical scanning device 11 described later is adjusted. The adjustment process at this time will be briefly described later with an example of an adjustment mechanism.

  Thereafter, returning to step S21 again, the first pattern images G1, G2 are detected by the registration sensors 72F, 72R, and the distortion amount (deviation amount) α1 in the sub-scanning direction of each pattern image G1, G2 is calculated in step S22. In step S23, the distortion correction amount γ is subtracted from the distortion amount (deviation amount) α1 to calculate the corrected distortion amount. In step S24, it is determined whether or not the corrected distortion amount is zero or within a predetermined fixed amount. When the main control unit 71 repeatedly performs such processing in steps S21 to S26 until it is determined in step S24 that the corrected distortion amount is zero or within a predetermined fixed amount, distortion adjustment is performed. Complete the process.

  That is, according to the second embodiment, by calculating the distortion correction amount γ, the correlation between the distortion of the printing itself (deviation amount) and the deviation of the attachment positions of the registration sensors 72F and 72R in the sub-scanning direction X is calculated. become.

  In this way, the initial print distortion adjustment is completed at the time of factory shipment.

  In the first and second embodiments, the printing distortion correction amount calculation process and the distortion adjustment process at the time of shipment from the factory (that is, the first time) have been described. Since it is the same as the adjustment processing procedure described with reference to FIG. 8 of the second embodiment, detailed description thereof is omitted here.

  That is, in the second and subsequent distortion adjustments, processing such as print output of the second pattern image and reading by the document reading unit 41, which is necessary in the first processing, becomes unnecessary, and the distortion amount α1 detected by the registration sensors 72F and 72R. And the distortion correction amount γ registered in the memory 75 can be used to adjust printing distortion. That is, the perpendicularity of the printed image can be obtained.

  In the subsequent registration adjustment, black (K) does not need to be adjusted, but the tilt adjustment of the second fθ lens 109 corresponding to each color of cyan (C), magenta (M), and yellow (Y) is performed. The adjustment may be made according to the adjustment value displayed on the display panel as before.

<Another embodiment of print distortion correction amount calculation processing>
In the print distortion correction amount calculation processing described in the first embodiment, the two second pattern images G21, G22, and G23 arranged on the sides along the paper transport direction (X direction) are the second patterns on the outer sides. The arrangement interval between the images G21 and G23 is set to the same FR reference length L (= 210 mm) as the arrangement interval between the second pattern images G11 and G13, but the arrangement interval between the second pattern images G21 and G23 on both outer sides is as follows. The FR reference length L (= 210 mm) is not necessarily required. For example, it may be set to 400 mm or the like.

  In this case, it is necessary to convert the Y-direction distortion amount βy (= width W22 of G23−width W21 of G21) into 210 mm which is the FR reference length L.

That is, if the Y-direction distortion after conversion is βy1,
βy1 = βy × 210/400
It becomes.

  Next, the main control unit 71 calculates the printing distortion amount β2 (= βx−βy1) by subtracting the Y direction distortion amount βy1 from the X direction distortion amount βx.

  Therefore, in the first and second embodiments, the process of each step shown in FIGS. 6 and 7 may be performed using this β2 instead of β1. After each step, the main control unit 71 subtracts the printing distortion amount β2 calculated from the second image pattern read by the document reading unit 41 from the distortion amount α1 detected by the registration sensors 72F and 72R. The value may be stored (registered) in a predetermined area of the memory 75 as a distortion correction amount γ (= α1-β2).

  According to the first and second embodiments, the distortion amount α1 of the first pattern image (resist pattern) and the distortion amount β1 or β2 on the printed recording sheet are continuously (that is, almost simultaneously). ) Obtained by detecting. In particular, the distortion amount β1 or β2 can be detected before the optical adjustment as in the second embodiment, but after the optical adjustment is completed as in the first embodiment, that is, when β1 or β2 becomes the minimum, It is preferable to calculate the correction amount γ.

<Description of adjustment mechanism>
Next, the configuration of the optical scanning device 11 will be described with reference to FIGS. 9 and 10 are diagrams schematically showing the inside of the housing of the optical scanning device 11 of FIG. 1 as viewed from the top and side surfaces. FIG. 10 also shows the photosensitive drum 13. FIG. 11 is a perspective view showing a main part of the optical scanning device 11 with the upper lid removed.

  The optical scanning device 11 guides each light beam BM emitted from the four semiconductor lasers 101 to each reflecting surface of the polygon mirror 102 that is rotationally driven in the direction of the arrow by each optical element such as a mirror or a lens. The beam BM is reflected by each reflecting surface of the polygon mirror 102 and deflected, and each reflected light beam BM is guided to each photosensitive drum 13 by each optical element such as a mirror or a lens, and each light beam BM is used for each light beam BM. The photosensitive drum 13 is scanned.

  From the semiconductor laser 101 to the polygon mirror 102, four collimating lenses 103, four first reflecting mirrors 104, a cylindrical lens 105, and a second reflecting mirror 106 are arranged in the order from the four semiconductor lasers 101 to the polygon mirror 102. Has been.

  Next, from the polygon mirror 102 to the photosensitive drum 13, a first fθ lens 107, an exit folding mirror 108, and a second fθ lens 109 are arranged in the order from the polygon mirror 102 to the photosensitive drum 13.

  The second fθ lens 109 (optical member) condenses the light beams BM of parallel light so as to have a predetermined beam diameter on the photosensitive drum 13 in the sub-scanning direction X, and the first fθ in the main scanning direction Y. Each light beam BM that has been converged by the lens 107 is directly incident on the photosensitive drum 13.

  As shown in FIG. 11, four lens holders 113 are bridged on the first and second side portions 111 and 112 of the housing 110 of the optical scanning device 11, and each second fθ lens is placed on each lens holder 113. 109 is installed. At the first side portion 111, the end portion 113a of each lens holder 113 is moved in the sub-scanning direction X, and each lens holder 113 rotates in the arrow direction Q about each axis 118 of the second side portion 112. Along with this, each second fθ lens 109 rotates, and the inclination angle of each second fθ lens 109 in the sub-scanning direction X is adjusted. The adjustment of the inclination angle of each second fθ lens 109 is performed to eliminate the inclination (skew) of the scanning line on the surface of each photosensitive drum 13.

  As a mechanism for moving the end 113a of each lens holder 113 in the sub-scanning direction X, a gear unit 121 is provided at the end 113a of each lens holder 113.

  The end 113a of the lens holder 113 moves in a direction approaching the gear unit 121 by a biasing force of a kick spring (not shown), and the end 113a of the lens holder 113 is pressed against the tip of the screw screw 122 of the gear unit 121. Alternatively, the end 113 a of the lens holder 113 is pressed against the tip of the screw screw 122 of the gear unit 121 through the spacer 114.

  The gear unit 121 includes a screw screw 122, a crown gear 123 through which the screw screw 122 passes, a pinion gear 125 that meshes with the crown gear 123, and a knob 126 that is fixed to one end of the shaft of the pinion gear 125. Yes.

  The shaft of the pinion gear 125 is rotatably supported through a hole (not shown) of the first side portion 111, and a knob 126 is fixed to one end of this shaft. A cross groove is formed on the end face of the knob 126 so as to be fitted to a Phillips screwdriver.

  In the gear unit 121 having such a configuration, a Phillips screwdriver is fitted in the cross groove on the end face of the knob 126, the knob 126 (pinion gear 125) is rotated in one direction, and the crown gear 123 is rotated in conjunction with this. When rotated in the turning direction, the screw screw 122 rotates in the clockwise direction, the screw screw 122 moves in a direction approaching the end 113a of the lens holder 113, and the tip of the screw screw 122 is subjected to a biasing force of a kick spring (not shown). Accordingly, the end portion 113a (or the spacer 114 and the end portion 113a) of the lens holder 113 is pushed and displaced.

  Further, when a Phillips screwdriver is fitted in the cross groove on the end face of the knob 126, the knob 126 (pinion gear 125) is rotated in the other direction, and the crown gear 123 is rotated counterclockwise, the screw screw 122 is anti-clockwise. By rotating clockwise, the screw screw 122 moves away from the end 113a of the lens holder 113, and the end 113a (or the spacer 114 and the end 113a) of the lens holder 113 is moved by the biasing force of a kick spring (not shown). It moves following the tip of the screw screw 122.

  Therefore, when the knob 126 is reciprocated, the end 113a of the lens holder 113 reciprocates in the sub-scanning direction X. Since the lens holder 113 is supported so as to be rotatable about the axis 118 of the second side portion 112, the second fθ lens 109 is centered on the axis 118 as the end portion 113a of the lens holder 113 is moved. Thus, the tilt angle of the second fθ lens 109 in the sub-scanning direction X is adjusted.

  Therefore, the adjustment in step S7 of FIG. 6 and step S26 of FIG. 8 described above is that the operator adjusts the distortion by rotating the knob 126 according to the rotation direction and the number of clicks displayed on the display panel. become. In the case of automatic adjustment in which the drive motor is connected to the knob 126, the main control unit 71 converts the adjustment amount into the rotation direction and the number of pulses of the drive motor (pulse motor), and drives the drive motor. The distortion is adjusted by outputting a control instruction to the unit.

  The adjustment mechanisms shown in FIGS. 9 to 11 are merely examples, and various adjustment mechanisms have been proposed in the past, and these conventionally known adjustment mechanisms can be applied to the present invention.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and should not be interpreted limitedly. The scope of the present invention is set forth in the claims, and is not restricted by the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming device 11 Optical scanning device 12 Developing device 13 Photosensitive drum 14 Drum cleaning device 15 Charger 17 Fixing device 21 Intermediate transfer belt 41 Document reading unit (image reading unit)
43 Document Placement Table 45 Document Reading Device 51 Device Main Body 52 Input Operation Unit 53 Image Forming Unit 54 Paper Conveying System 71 Main Control Units 72F, 72R Registration Sensor 75 Memory (Storage Unit)
109 second fθ lens (optical member)
121 Gear unit 122 Screw screw 123 Crown gear 125 Pinion gear 126 Knob Pa, Pb, Pc, Pd Image forming unit

Claims (13)

An image reading unit that reads an image and a registration sensor that detects a first pattern image on the transfer belt, and the registration sensor is an image provided in one and the other direction perpendicular to the moving direction of the transfer belt A forming device,
Based on the reading result of the second pattern image obtained by reading the printed pattern image by the image reading unit and the detection result of the first pattern image by the registration sensor, the 2 in the moving direction of the transfer belt. An image forming apparatus comprising a calculation unit that calculates a difference between positions of two registration sensors. The image forming apparatus according to claim 1,
The image forming apparatus, wherein both the reading result of the second pattern image and the detection result of the first pattern image are distortion amounts. The image forming apparatus according to claim 2,
The image forming apparatus, wherein the distortion amount is a difference calculated by the calculation unit. The image forming apparatus according to claim 2, wherein:
An image forming apparatus comprising a correction amount calculation unit that calculates a correction amount from the distortion amount. The image forming apparatus according to claim 4,
An image forming apparatus comprising: a display unit that displays a correction amount calculated by the correction amount calculation unit. The image forming apparatus according to claim 4, wherein:
An image forming apparatus comprising a storage unit that stores a correction amount calculated by the correction amount calculation unit. An image forming apparatus according to any one of claims 4 to 6,
The image forming apparatus according to claim 1, wherein the correction amount is a value for correcting the position of the optical member of the optical scanning device in the sub-scanning direction. An image reading unit; and a registration sensor that detects a first pattern image on the transfer belt, wherein the registration sensor is provided in one of the directions perpendicular to the moving direction of the transfer belt and the other of the image forming apparatus. A printing distortion correction method,
A step of reading the printed pattern image by the image reading unit;
Reading the first pattern image by the resist sensor;
The two registration sensors in the direction orthogonal to the moving direction of the transfer belt based on the reading result of the second pattern image read by the image reading unit and the detection result of the first pattern image by the registration sensor. And a step of calculating a difference between the positions of the print distortion correction method. The printing distortion correction method according to claim 8,
Both the reading result of the second pattern image and the detection result of the first pattern image are distortion amounts, and includes a step of calculating a correction amount from the distortion amount by a correction amount calculation unit. Method. The printing distortion correction method according to claim 9,
A printing distortion correction method comprising: a display unit including a step of displaying the calculated correction amount on a display unit. The printing distortion correction method according to claim 9 or 10, wherein:
A printing distortion correction method comprising: storing a correction amount calculated by the correction amount calculation unit in a storage unit. A printing distortion correction method according to any one of claims 9 to 11, comprising:
A printing distortion correction method comprising a step of correcting the position of the optical member of the optical scanning device in the sub-scanning direction based on the correction amount. The printing distortion correction method according to claim 11 or 12,
In the second and subsequent printing distortion correction, the printing distortion correction is performed based on the detection result of the first pattern image detected by the registration sensor and the correction amount stored in the storage unit. Printing distortion correction method.

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