JP2019056887A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can adjust skew of a laser beam with a simple configuration.SOLUTION: An image forming apparatus comprises: a groove 57 into which a rotation shaft 39 of a photoreceptor drum is inserted; an exposure device that irradiates the photoreceptor drum with a laser beam to form an electrostatic latent image on the photoreceptor drum; and an adjustment member 65 that moves the rotation shaft 39 in a vertical direction in the groove 57 to adjust skew of the laser beam.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus including a photosensitive drum on which an electrostatic latent image is formed.

  In an electrophotographic image forming apparatus, a photosensitive drum is exposed by laser light output from an optical element of an exposure apparatus, and an electrostatic latent image is formed on the photosensitive drum. At this time, if the laser beam and the photosensitive drum are slightly displaced, skew (distortion) occurs in the image on the photosensitive drum, resulting in color misregistration. Generally, since a plurality of parts are interposed between the optical element and the photosensitive drum, it is difficult to accurately position both of them.

  Patent Document 1 includes an exposure device arranged to have an inclination with respect to the rotation axis of the photosensitive drum, and the peripheral speed of the photosensitive drum is set so that the inclination of the toner image is the same as the inclination of the exposure device. An image forming apparatus for finely adjusting the image is disclosed. Patent Document 2 discloses an image forming apparatus including an exposure device that finely adjusts a mirror with a stepping motor.

JP-A-8-146317 JP 2000-98685 A

  However, when the exposure apparatus described in Patent Document 1 and Patent Document 2 has a configuration for finely adjusting the components in the exposure apparatus, the configuration and control become complicated and the exposure apparatus becomes large. There is.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus capable of adjusting the skew of a laser beam with a simple configuration.

  In order to achieve the above object, an image forming apparatus of the present invention includes a groove into which a rotating shaft of a photosensitive drum is inserted, an exposure apparatus that forms an electrostatic latent image by irradiating the photosensitive drum with laser light, And an adjustment member that adjusts the skew of the laser beam by moving the rotation shaft in the vertical direction in the groove.

  In the image forming apparatus according to the aspect of the invention, the groove has a side edge along a vertical direction, the adjustment member is rotatably provided, and comes into contact with the rotation shaft inserted into the groove obliquely from below. An outer peripheral edge having an arc shape that presses the rotation shaft against the side edge and supports the rotation shaft together with the side edge, and the outer periphery is formed so that the radius from the rotation center of the adjustment member is different, The contact position between the outer peripheral edge and the rotation shaft may be changed by rotating the adjustment member, and the position where the rotation shaft is pressed against the side edge may move in the vertical direction.

  In the image forming apparatus according to the aspect of the invention, the outer peripheral edge may include a plurality of arcs arranged along the rotation direction of the adjustment member and having different radii from the rotation center.

  In the image forming apparatus of the present invention, the outer peripheral edge may be formed such that a radius from the rotation center gradually increases along the rotation direction of the adjustment member.

  The image forming apparatus according to the present invention may further include an urging member that urges the rotating shaft inserted into the groove downward.

  In the image forming apparatus of the present invention, the image forming apparatus includes a unit including the photosensitive drum, the unit is provided corresponding to a plurality of colors including black, the plurality of units are arranged in parallel, and the adjustment member is , At least corresponding to the unit arranged at a position farthest from the unit corresponding to black.

  In the image forming apparatus according to the aspect of the invention, in the exposure apparatus, an incident angle of the laser beam to the photosensitive drum is greater than 0 degree with respect to a normal direction perpendicular to a tangential direction of the surface of the photosensitive drum. It may be characterized by being set within a range of 45 degrees or less.

  According to the present invention, the rotation position of the photosensitive drum is moved in the vertical direction by the adjusting member to adjust the writing position of the laser beam, so that the writing position can be finely adjusted with a simple configuration.

1 is a cross-sectional view schematically showing an internal structure of a color printer according to an embodiment of the present invention. FIG. 3 is a perspective view showing an image forming frame on which a drum unit is mounted in the color printer according to the embodiment of the present invention. 1 is a perspective view showing a drum unit in a color printer according to an embodiment of the present invention. In the color printer which concerns on one Embodiment of this invention, it is a front view which shows the mounting division of a right side board. In the color printer which concerns on one Embodiment of this invention, it is a front view which shows the adjustment board and dial gear in the state which removed the right side board. In the color printer which concerns on one Embodiment of this invention, it is a front view which shows the 1st axis | shaft, the 2nd axis | shaft, and a convex part in the state which removed the right side board. In the color printer which concerns on one Embodiment of this invention, it is the perspective view which looked at the mounting division of the right side board from diagonally forward. In the color printer which concerns on one Embodiment of this invention, it is sectional drawing which shows an adjustment board and a dial gear. In the color printer which concerns on one Embodiment of this invention, it is a front view which shows an adjustment board. In the color printer which concerns on one Embodiment of this invention, it is a perspective view which shows a dial gear. In the color printer which concerns on one Embodiment of this invention, it is a reverse view which shows a dial gear. In the color printer which concerns on one Embodiment of this invention, it is sectional drawing of a dial gear. In the color printer according to an embodiment of the present invention, FIG. FIG. 6 is a diagram schematically illustrating a method for adjusting a skew of laser light in a color printer according to an embodiment of the present invention. In the color printer which concerns on one Embodiment of this invention, it is a front view which shows the modification of an adjustment board.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

  First, the overall configuration of a color printer 1 as an image forming apparatus will be described with reference to FIG. FIG. 1 is a front view schematically showing the internal configuration of the color printer. In the following description, the left side of FIG. 1 is the front side (front side) of the color printer 1, and the horizontal direction is based on the direction of the color printer 1 viewed from the front side. Fr, Rr, L, and R shown in the drawings respectively indicate the front side, the rear side, the left side, and the right side of the color printer 1.

  The apparatus main body 2 of the color printer 1 includes a paper feed cassette 3 that stores paper P, a paper feed device 5 that feeds the paper P from the paper feed cassette 3, and an image that forms a full-color toner image on the paper P. A forming unit 7, a fixing device 9 that fixes the toner image on the paper, and a paper discharge device 13 that discharges the paper P on which the toner image is fixed to the paper discharge tray 11 are provided. The paper P is sent out from the paper feed cassette 3 by the paper feeding device 5, and after the full-color toner image is transferred in the image forming unit 7, the toner image is fixed in the fixing device 9, and is discharged from the paper discharge device 13 to the paper discharge tray. 11 is discharged.

  The image forming unit 7 includes an image forming unit 17, an exposure device 19 disposed below the image forming unit 17, and four toner containers 21 disposed above the image forming unit 17. Four toner containers 21 store toners (developers) of four colors (yellow, magenta, cyan, and black), respectively.

  Next, the image forming unit 17 will be described with reference to FIGS. FIG. 2 is a perspective view showing an image forming frame on which the drum unit and the developing unit are mounted.

  The image forming unit 17 includes four drum units 23, four developing units 25, an intermediate transfer unit 27, and an image forming frame 29 (see FIG. 2) on which the drum unit 23 and the developing unit 25 are supported. Yes. The four drum units 23 and the four developing units 25 correspond to each color of toner.

  Next, the drum unit 23 will be described with reference to FIG. FIG. 3 is a perspective view of the drum unit.

  The drum unit 23 as a unit including the photosensitive drum 31 on which the electrostatic latent image is formed includes a charging device 33 that charges the photosensitive drum 31 and a cleaning device 35 that removes toner remaining on the surface of the photosensitive drum 31. And are provided integrally. Flange members 37 are fixed to the openings at both ends of the photosensitive drum 31, respectively. A rotating shaft 39 passes between the flange members 37. Push levers 41 are inserted into both ends of the rotating shaft 39. Between the pressing lever 41 and the rotating shaft 39, a spring 43 as an urging member for urging the rotating shaft 39 downward is interposed.

  The charging device 33 and the cleaning device 35 are sequentially arranged along the outer circumferential surface of the photosensitive drum 31 along the rotation direction of the photosensitive drum 31.

  Referring to FIG. 1 again, the developing unit 25 includes a developing device that develops the electrostatic latent image formed on the photosensitive drum 31 with toner.

  The intermediate transfer unit 27 includes an endless intermediate transfer belt 47 and four primary transfer rollers 49 disposed in a hollow portion of the intermediate transfer belt 47. The apparatus main body 2 is provided with a secondary transfer roller 48 facing the intermediate transfer belt 47 behind the intermediate transfer unit 27.

  The image forming frame 29 will be described with reference to FIG. The image forming frame 29 is a rectangular cylindrical frame member having a front side plate 29a and a rear side plate 29b opposed in the front-rear direction, and a left side plate 29c and a right side plate 29d opposed in the left-right direction. On the left side plate 29c and the right side plate 29d, four mounting sections S in which the drum unit 23 and the developing unit 25 are mounted are formed in parallel in the front-rear direction. The four mounting sections S are arranged in the order of yellow, magenta, cyan, and black from the front to the rear of the image forming frame 29.

  A flange receiving groove 51 is formed in each mounting section S of the left side plate 29c. The flange receiving groove 51 is notched downward from the upper edge of the left side plate 29c.

  Each mounting section S of the right side plate 29d will be described with reference to FIGS. In this example, the mounting section S (frontmost mounting section) of the drum unit 23 and the developing unit 25 corresponding to yellow toner will be described. FIG. 4 is a front view showing the mounting section of the right side plate, FIG. 5 is a front view showing the adjustment plate and the dial gear with the right side plate removed, and FIG. 6 is the first shaft with the right side plate removed. FIG. 7 is a perspective view of the mounting section as seen obliquely from the front, and FIG. 8 is a cross-sectional view showing the adjustment plate and the dial gear.

  As shown in FIGS. 4 and 7, each mounting section S of the right side plate 29 d is formed with a recess 55 that is recessed from the outside to the inside. The recess 55 is formed with a groove 57 cut out from the upper edge of the right side plate 29d. When the drum unit 23 is mounted in the mounting section S, the rotation shaft 39 of the photosensitive drum 31 is inserted into the groove 57. The groove 57 has a pair of side edges 57a along the vertical direction, and a bottom edge 57b that protrudes downward and curves in an arc shape. The width of the groove 57 is slightly wider than the diameter of the rotating shaft 39. The corner between the upper edge of the right side plate 29d and the pair of side edges 57a of the groove 57 is chamfered in an arc shape.

  Further, in each mounting section S, a lower opening 59 and a lateral opening 61 are formed below the groove 57 and obliquely forward and downward, respectively. When the drum unit 23 and the developing unit 25 are mounted in the mounting section S, the charging device 33 included in the drum unit 23 is exposed from the lower opening 59, and the developing device of the developing unit 25 is exposed from the lateral opening 61. Yes. Both openings 59 and 61 communicate with the recess 55. In addition, a first hole 55 a and a second hole 55 b are formed in the recess 55 between the groove 57 and the lateral opening 61.

  As shown in FIGS. 5 and 8, between the groove 57 and the lateral opening 61, an adjustment plate 65 as an adjustment member and a dial gear 67 are provided inside the concave portion 55 of the right side plate 29d. ing.

  As shown in FIGS. 5, 6, and 8, the adjustment plate 65 is rotatably supported between a first inner plate 29e and a right plate 29d provided inside the right plate 29d, and the dial gear 67 is The second inner plate 29f provided on the inner side of the right side plate 29d and the right side plate 29d are rotatably supported. The first inner plate 29e is provided with a first shaft 29g extending horizontally in the right direction. The first shaft 29g is inserted through the first hole 55a of the right side plate 29d. The second inner plate 29f is provided with a second shaft 29h extending horizontally in the right direction. The second shaft 29h is inserted through the second hole 55b of the right side plate 29d. Further, as shown in FIGS. 6 and 8, the second inner plate 29f is formed with a convex portion 29i extending horizontally rearward from the second shaft 29h.

  Next, the adjustment plate 65 will be described with reference to FIG. FIG. 9 is a front view of the adjustment plate.

  The adjustment plate 65 is a disk-shaped member, and includes a cylindrical shaft hole portion 71, a substantially semicircular adjustment portion 73 provided on one side (rear side) with the shaft hole portion 71 as a center, And a substantially semicircular gear portion 75 provided on the other side (front side) with the shaft hole portion 71 as a center. A first arc 77, a second arc 78, and a third arc 79 are formed in order along the circumferential direction on the outer peripheral edge of the adjustment portion 73. The first arc 77, the second arc 78, and the third arc 79 have different radii from the center of the shaft hole 71, and the radii gradually increase in this order. As an example, the difference in radius between adjacent arcs is 0.1 mm. Adjacent arcs are connected by a step 80 along the radial direction. Gear teeth 81 are formed on the gear portion 75 at a predetermined interval along the circumferential direction. Furthermore, an arc-shaped rib 83 is formed in the gear portion 75 along the inside of the gear tooth 81. The tips of the ribs 83 are formed in a semicircular cross section.

  The adjustment plate 65 includes a component A in which the shaft hole portion 71 and the adjustment portion 73 are integrally formed, a component B in which the gear portion 75 and the shaft hole 85 are formed, and a shaft hole portion 71 and the shaft hole 85. It is formed by overlapping and joining so as to be coaxial. The part A is made of sheet metal material, and the part B is made of resin. The configuration of the adjustment plate 65 is not limited to this configuration.

  As shown in FIGS. 5 and 8, the adjustment plate 65 is supported by the first shaft 29g of the first inner plate 29e with the rib 83 facing the right side plate 29d. Specifically, the first shaft 29g is inserted through the shaft hole 71 of the adjustment plate 65, and the shaft hole 71 passes through the first hole 55a. Thereby, the adjustment plate 65 is supported so as to be rotatable about the first shaft 29g and not movable in the axial direction. When the adjustment plate 65 rotates, the tip end surface of the rib 83 slides against the inner surface of the right side plate 29d. Further, as shown in FIG. 5, a part of the outer peripheral edge of the adjustment portion 73 is exposed in the lower end portion of the groove 57 from the obliquely lower front side.

  Next, the dial gear 67 will be described with reference to FIG. 10 and FIGS. 11A and 11B. 10 is a perspective view of the dial gear, FIG. 11A is a rear view of the dial gear, and FIG. 11B is a cross-sectional view of the dial gear.

  The dial gear 67 is a disk-shaped member, and includes a shaft hole portion 91, and a gear portion 93 and a rack portion 95 provided coaxially with the shaft hole portion 91. The outer diameter of the rack portion 95 is larger than the outer diameter of the gear portion 93. The gear portion 93 is formed with gear teeth 97 that can mesh with the gear teeth 81 of the gear portion 75 of the adjustment plate 65 along the outer peripheral edge. Rack teeth 99 are formed in the rack portion 95 at predetermined intervals along the outer peripheral edge.

  An annular groove 101 is formed around the shaft hole portion 91 on one surface of the dial gear 67 (the surface on the gear portion 93 side). As shown in FIGS. 11A and 11B, an annular rib 103 is formed around the shaft hole portion 91 on the other surface (the surface on the rack portion 95 side) of the dial gear 67. A plurality of (for example, five) recesses 105 are formed in the rib 103 at equal central angles along the circumferential direction. Both side surfaces of each recess 105 are inclined outward in the circumferential direction.

  As shown in FIGS. 5 and 8, in the dial gear 67, the shaft hole portion 91 is inserted into the second shaft 29h of the second inner plate 29f with the gear portion 93 facing the inner surface of the right side plate 29d. ing. As shown in FIG. 8, a spring 111 is interposed between the groove 101 of the dial gear 67 and the right side plate 29d. The spring 111 urges the dial gear 67 in the direction of the second inner plate 29 f along the axial direction of the dial gear 67. Accordingly, one of the plurality of recesses 105 (see FIGS. 11A and 11B) formed in the rib 103 is engaged with the projections 29i of the second inner plate 29f, and the rotation of the dial gear 67 is restricted. The gear teeth 97 of the gear portion 93 mesh with the gear teeth 81 of the gear portion 75 of the adjustment plate 65 so that the adjustment plate 65 and the dial gear 67 are engaged. Further, as shown in FIG. 7, the rack teeth 99 of the rack portion 95 are viewed from the lateral opening 61 of the right side plate 29d when viewed obliquely from the front.

  When the dial gear 67 is rotated in one direction, the adjustment plate 65 rotates in the opposite direction to the dial gear 67. Thereby, the position where the outer peripheral edge of the adjustment portion 73 of the adjustment plate 65 is exposed in the lower end portion of the groove 57 changes. That is, by rotating the dial gear 67, any of the first arc 77, the second arc 78, and the third arc 79 of the adjustment plate 65 can be exposed in the lower end portion of the groove 57.

  Further, the dial gear 67 is restricted from rotating with respect to the right side plate 29 d at a position where any one of the arcs of the adjustment plate 65 is exposed in the lower end portion of the groove 57. Specifically, when the dial gear 67 is rotated, one inclined side surface of the concave portion 105 engaged with the convex portion 29i comes into contact with the convex portion 29i, and the inclined side surface is guided in a direction away from the convex portion 29i. The rib 103 rides on the convex portion 29i against the urging force. When the dial gear 67 is further rotated, the dial gear 67 is eventually urged toward the convex portion 29i by the spring 111, and the next concave portion 105 is engaged with the convex portion 29i. At this time, a click feeling is given to the rotation of the dial gear 67. By appropriately setting the center angle of each arc of the adjustment plate 65, the number of the concave portions 105 of the dial gear 67, the number of gear teeth of the dial gear 67 and the gear teeth of the gear portion of the adjustment plate 65, etc. When the dial gear 67 is rotated until it is obtained, one of the arcs of the adjustment plate 65 is exposed in the lower end portion of the groove 57.

  When the drum unit 23 is mounted in the mounting section S described above, the left flange member 37 of the photosensitive drum 31 is inserted into the flange receiving groove 51 of the left plate 29c, as shown in FIG. Further, as shown in FIG. 4, the right end of the rotation shaft 39 of the photosensitive drum 31 is inserted into the groove 57 of the right side plate 29d. As described above, in the lower end portion of the groove 57, the outer peripheral edge (for example, the first arc 77) of the adjustment portion 73 of the adjustment plate 65 is exposed obliquely from below. When the rotating shaft 39 is inserted into the groove 57, the outer peripheral edge abuts the rotating shaft 39 obliquely from the lower left and presses the rotating shaft 39 against the side edge 57 a on the rear side of the groove 57. As an example, the contact position between the outer peripheral edge of the adjustment plate 65 and the rotation shaft 39 is a position of 45 degrees with respect to a perpendicular passing through the center of the rotation shaft 39. Thereby, the rotating shaft 39 is positioned by the outer peripheral edge of the adjusting portion 73 of the adjusting plate 65 and the side edge 57a of the groove 57.

  Further, each pressing lever 41 engages with the right side plate 29 d, and the spring 43 presses the rotating shaft 39 downward against the pressing lever 41. Thus, the rotating shaft 39 is pressed against the outer peripheral edge of the adjustment portion 73 of the adjustment plate 65 and the side edge 57a of the groove 57 by the spring 43.

  Referring to FIG. 1 again, the exposure device 19 is disposed below the image forming unit 17. The exposure device 19 irradiates the photosensitive drum 31 of each drum unit 23 with laser light. The incident angle of the laser light with respect to the tangential direction on the surface of the photosensitive drum 31 is zero, and the laser light is incident from a direction inclined about 10 degrees with respect to the normal direction perpendicular to the tangential direction.

  In the image forming unit 7, after the photosensitive drum 31 is charged by the charging device 33, exposure corresponding to the image data is performed by the exposure device 19, and an electrostatic latent image is formed on the photosensitive drum 31. . The electrostatic latent image is developed into a toner image by a developing device. The toner image is transferred from the photosensitive drum 31 to the intermediate transfer belt 47 by the primary transfer roller 49 of the intermediate transfer unit 27. The toner images developed by the four drum units 23 and the four developing units 25 are transferred to the intermediate transfer belt 47, whereby a full-color toner image is formed on the intermediate transfer belt 47. The full-color toner image is transferred from the intermediate transfer belt 47 to the paper P by the secondary transfer roller 48. Further, the toner remaining on the photosensitive drum 31 is removed by the cleaning device 35. The sheet on which the full-color toner image is transferred is conveyed to the fixing device 9 and fixed, and is discharged from the paper discharge device 13 to the paper discharge tray 11.

  A procedure for moving the rotation shaft 39 of the photosensitive drum 31 in the vertical direction in the image forming unit 17 having the above-described configuration will be described with reference to FIGS. 5, 7, 8, and 12. FIG. 12 is a view showing the rotation shaft in the groove (the spring 43 is not shown).

  As shown by the solid line in FIG. 12, the rotation shaft 39 is vertically moved by the outer peripheral edge (first arc 77 in this example) of the adjustment portion 73 of the adjustment plate 65 and the side edge 57a of the groove 57 of the right side plate 29d. It is positioned. A position where the rotating shaft 39 is pressed against the side edge 57a is defined as P1. When the rotary shaft 39 is moved upward, as shown in FIGS. 7 and 8, a finger is put through the lateral opening 61, the finger is put on the rack tooth 99 of the rack portion 95 of the dial gear 67, and the dial gear 67. Is rotated clockwise in FIG. When the dial gear 67 is rotated until a click feeling is obtained, the second arc 78 of the adjustment portion 73 of the adjustment plate 65 is exposed in the lower end portion of the groove 57, and as shown by the chain line in FIG. 78 abuts on the rotary shaft 39. Since the radius of the second arc 78 is larger than that of the first arc 77, the contact position with the rotating shaft 39 moves upward to push the rotating shaft 39 outward in the radial direction of the adjustment plate 65. Since the rotation shaft 39 is pressed against the side edge 57a and the outward movement in the radial direction is restricted, it moves upward in the vertical direction along the side edge 57a. A position where the rotating shaft 39 is pressed against the side edge 57a is defined as P2. As an example, the moving distance from P1 to P2 is 0.28 mm.

  When the rotary shaft 39 is further moved upward, the dial gear 67 is further rotated in the clockwise direction in FIG. 5 until a click feeling is obtained. Then, the third arc 79 of the adjustment portion 73 of the adjustment plate 65 is exposed in the lower end portion of the groove 57, and the third arc 79 comes into contact with the rotation shaft 39 as indicated by a two-dot chain line in FIG. Since the radius of the third arc 79 is larger than that of the second arc 78, the contact position with the rotary shaft 39 moves further upward, and the rotary shaft 39 moves in the vertical direction along the side edge 57a. The position at which the rotating shaft 39 is pressed against the side edge 57a is P3. As an example, the moving distance from P2 to P3 is also 0.28 mm.

  When the rotary shaft 39 is moved downward, the dial gear 67 is rotated counterclockwise in FIG. When the dial gear 67 is rotated until a click feeling is obtained, the second arc 78 of the adjustment portion 73 of the adjustment plate 65 is exposed in the lower end portion of the groove 57, and the second arc 78 comes into contact with the rotation shaft 39. Since the second arc 78 has a smaller radius than the third arc 79, the contact position with the rotary shaft 39 moves downward, and moves downward along the side edge 57a in the vertical direction.

  As described above, by operating the dial gear 67 to rotate the adjustment plate 65, the contact position between the outer peripheral edge of the adjustment plate 65 and the rotary shaft 39 changes. Since the position where the rotary shaft 39 is pressed against the side edge 57a moves in the vertical direction according to the radius of the outer peripheral edge at the contact position, the photosensitive drum 31 can be moved in the vertical direction. As an example, the photosensitive drum 31 can be moved in steps of 0.28 mm.

  Next, with reference to FIG. 13, the adjustment of the skew of the laser beam of the exposure device 19 will be described. FIG. 13 is a diagram for explaining the relationship between the moving direction of the photosensitive drum and the skew.

  In general, the skew of the laser beam is adjusted by displacing the laser beam in the circumferential direction of the photosensitive drum 31. In other words, the photosensitive drum 31 is displaced in a direction (X direction) orthogonal to the normal direction (Y direction) of the surface of the photosensitive drum 31 as shown in the leftmost diagram of FIG. Here, the shift of the writing position by the laser light between when moved in the Y direction and when moved in the X direction will be described. The incident angle with respect to the normal direction of the incident direction of the laser beam is φ.

  As shown in the middle diagram of FIG. 13, the deviation of the laser beam writing position when the photosensitive drum 31 is moved by a distance D in the Y direction is α. α decreases as the incident angle φ approaches zero. On the other hand, as shown in the rightmost diagram of FIG. 13, the deviation of the laser beam writing position when the photosensitive drum 31 is moved by the same distance D in the X direction is β. As shown in FIG. 13, β is larger than α.

  As described above, the shift amount of the writing position is higher when the photosensitive drum 31, that is, the rotation shaft 39, is moved in the X direction than when it is moved in the Y direction. In other words, the ratio (adjustment sensitivity) of the writing position deviation amount with respect to the movement amount of the rotating shaft 39 is lower in the Y direction than in the X direction. In general, in the adjustment operation, fine adjustment is easier when the adjustment sensitivity is lower. When the adjustment sensitivity is high, high accuracy is required for the adjustment work, which is disadvantageous in the manufacturing process. Therefore, in this case, the adjustment sensitivity is lower when the rotary shaft 39 is moved in the Y direction than when the rotary shaft 39 is moved in the X direction, and the adjustment is facilitated.

  When the incident angle φ is 45 degrees, the amount of deviation of the writing position is the same when the rotary shaft 39 is displaced in the X direction and when it is displaced in the Y direction. In the case of 0 degree, the writing position does not shift even if the rotation axis is displaced in the Y direction. Therefore, the incident angle of incident light is set to be greater than 0 degree and 45 degrees or less.

  As described above, according to the color printer 1 of the present invention, the writing shaft is adjusted in accordance with the skew of the laser beam with respect to the axial direction of the photosensitive drum 31 by moving the rotating shaft 39 of the photosensitive drum 31 in the vertical direction. Therefore, the adjustment sensitivity of the adjustment work can be lowered. Furthermore, the rotating shaft 39 can be moved in the vertical direction by rotating the adjusting plate 65 provided in the image forming unit 17 using the dial gear 67. Therefore, the writing position can be finely adjusted according to the skew of the laser beam with respect to the axial direction of the photosensitive drum 31 with a simple configuration.

  Further, after the rotating shaft 39 is positioned by the arc of any of the adjusting portions 73 of the adjusting plate 65 and the side edge 57a of the groove 57, the rotating shaft 39 remains within the same arc even if the adjusting plate 65 is slightly displaced. Since it is pressed, the position of the rotating shaft 39 in the vertical direction does not change. Therefore, fluctuations in the position of the photosensitive drum 31 can be suppressed. The number of arcs is not limited to three, but may be two or four or more.

  Further, since the rotary shaft 39 is biased downward by the spring 43 in the groove 57, the movement of the rotary shaft 39 in the groove 57 can be prevented.

  The adjustment plate 65 and the dial gear 67 are provided in the mounting section S in which the drum unit 23 corresponding to yellow toner is mounted. That is, by providing the adjustment plate 65 and the dial gear 67 in the mounting section S of the drum unit 23 mounted at the position farthest from the drum unit 23 corresponding to the black toner, the color misregistration can be corrected efficiently. it can. However, it can also be provided in all the mounting sections S. In the present embodiment, the right end portion of the rotation shaft 39 can be adjusted by the adjustment plate 65, but the left end portion of the rotation shaft 39 may be adjusted by the adjustment plate 65. Alternatively, both ends may be adjusted with the adjustment plate 65.

  Furthermore, since it is possible to adjust the rotating shaft 39 in the vertical direction using the adjustment plate 65 in a range where the incident angle φ is greater than 0 degree and 45 degrees or less, the incident angle φ is within a relatively wide range. Can be set. Therefore, a margin can be obtained in the arrangement of the exposure device 19 and the arrangement of the image forming unit 17.

  Next, another example of the adjustment plate 65 will be described with reference to FIG. FIG. 14 is a plan view showing an adjustment plate according to another example.

  The adjustment plate 65 of this example is formed such that the outer peripheral edge of the adjustment portion 73 gradually increases or decreases in radius along the circumferential direction. As an example, the difference between the minimum radius d1 and the maximum radius d2 is 0.2 mm.

  In this adjustment plate 65, the radius of the outer peripheral edge is continuously changing, so that the position where the rotating shaft 39 is pressed against the side edge 57a of the groove 57 can be changed steplessly.

  In the present embodiment, the adjustment plate 65 is rotated using the rotatable dial gear 67, but instead of the dial gear 67, a rack member that moves on a straight line may be used. Alternatively, the adjustment plate 65 may be directly rotated without using the dial gear 67. Alternatively, the adjustment plate 65 may be rotated by a stepping motor.

  Note that the above description of the embodiment of the present invention describes a preferred embodiment of the image forming apparatus according to the present invention, and thus may have various technically preferable limitations. The technical scope of the present invention is not limited to this embodiment unless specifically described to limit the present invention. Furthermore, the constituent elements in the embodiments of the present invention described above can be appropriately replaced with existing constituent elements, and various variations including combinations with other existing constituent elements are possible. The description of the embodiment of the present invention is not intended to limit the content of the invention described in the claims.

1 Color printer (image forming device)
19 Exposure device 23 Drum unit (unit)
29 Image creation frame
31 Photosensitive drum 39 Rotating shaft 43 Spring (biasing member)
57 Groove 57a Side edge 65 Adjustment plate (Adjustment member)
77, 78, 79 arc

Claims (7)

A groove into which the rotating shaft of the photosensitive drum is inserted;
An exposure device that irradiates the photosensitive drum with laser light to form an electrostatic latent image;
An image forming apparatus comprising: an adjustment member configured to adjust the skew of the laser beam by moving the rotation shaft in the vertical direction in the groove. The groove has a side edge along the vertical direction,
The adjustment member is rotatably provided and has an arcuate shape that abuts the rotation shaft inserted into the groove obliquely from below and presses the rotation shaft against the side edge to support the rotation shaft together with the side edge. Has an outer periphery,
The outer peripheral edge is formed to have different radii from the rotation center of the adjustment member, and by rotating the adjustment member, a contact position between the outer peripheral edge and the rotation shaft changes, and the rotation shaft The image forming apparatus according to claim 1, wherein a position pressed against the side edge moves in a vertical direction.   The image forming apparatus according to claim 2, wherein the outer peripheral edge includes a plurality of arcs arranged along a rotation direction of the adjustment member and having different radii from the rotation center.   The image forming apparatus according to claim 2, wherein the outer peripheral edge is formed such that a radius from the rotation center gradually increases along a rotation direction of the adjustment member.   The image forming apparatus according to claim 1, further comprising an urging member that urges the rotating shaft inserted into the groove downward. A unit including the photosensitive drum;
The units are provided corresponding to a plurality of colors including black, the plurality of units are arranged in parallel,
The image forming apparatus according to claim 1, wherein the adjustment member corresponds at least to the unit disposed at a position farthest from the unit corresponding to black.   In the exposure apparatus, an incident angle of the laser beam to the photosensitive drum is set in a range of greater than 0 degree and not more than 45 degrees with respect to a normal direction perpendicular to a tangential direction of the surface of the photosensitive drum. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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