Image forming device

Abstract

To prevent a focal position from being shifted due to a foreign substance on a photoreceptor drum.SOLUTION: An image forming apparatus (color printer 1) comprises: a photoreceptor drum 51 that includes a cylindrical element tube 51A and a fitting member 400 fitting to an inner peripheral surface of the element tube 51A; a rotary support member 500 that rotatably supports the fitting member 400; and an exposure head 40. The exposure head 40 includes a plurality of light emitting units (LED array 101) that is arranged in a direction of an axis of rotation of the photoreceptor drum 51, a lens array 102 that is an optical member that forms rays of light from the light emitting units into an image on the surface of the photoreceptor drum 51, and a head frame (frames 100, 200) that supports the light emitting units and the lens array 102. The rotary support member 500 has a contact surface 531 that is in contact with the exposure head 40 to regulate a distance in an optical axis direction from the lens array 102 to the photoreceptor drum 51.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a drum unit including a photosensitive drum that is exposed by an exposure head having a plurality of light emitting portions, and to an image forming apparatus. [Background technology]

[0002] Conventionally, there is known an image forming apparatus that includes a photosensitive drum, an LED head that exposes the photosensitive drum, and a spacer that is provided between the surface of the photosensitive drum and the LED head (see Patent Document 1). In this technology, the LED head abuts against the spacer, thereby maintaining the distance between the LED head and the photosensitive drum, and the focal position of the LED head is located on the photosensitive drum. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-361931 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, foreign matter such as toner adhering to the photosensitive drum may get between the spacer and the photosensitive drum or between the spacer and the LED head, causing the focal position to shift.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to prevent the focus position from being shifted due to foreign matter on the photosensitive drum. [Means for solving the problem]

[0006] In order to solve the above-mentioned problem, the image forming apparatus of the present invention comprises a photosensitive drum having a cylindrical base tube and a fitting member that fits into the inner surface of the base tube, a rotating support member that rotatably supports the fitting member, an exposure head that includes a plurality of light-emitting elements aligned in the direction of the rotation axis of the photosensitive drum, an optical element that focuses light from the light-emitting elements on the surface of the photosensitive drum, and a head frame that supports the light-emitting elements and the optical element. The rotation support member has a contact surface that contacts the exposure head and defines the distance in the optical axis direction from the optical member to the photosensitive drum.

[0007] In addition, the drum unit of the present invention is a photosensitive drum exposed by an exposure head having a plurality of light-emitting elements, an optical element that focuses light from the light-emitting elements, and a head frame, and comprises a photosensitive drum having a cylindrical base tube and an engaging member that engages with the inner surface of the base tube, and a rotation support member that rotatably supports the engaging member. The rotation support member has a contact surface that contacts the exposure head and defines the distance in the optical axis direction from the optical member to the photosensitive drum.

[0008] According to each of the above-mentioned configurations, foreign matter on the base tube is less likely to get between the exposure head and the rotating support member, so that it is possible to prevent the focal position from shifting due to a change in the distance in the optical axis direction from the optical member to the photosensitive drum. Effect of the Invention

[0009] According to the present invention, it is possible to prevent the focus position from being shifted due to foreign matter on the photosensitive drum. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic configuration of a color printer according to an embodiment of the present invention; [Diagram 2] FIG. 1 illustrates a color printer with a top cover open. [Diagram 3]FIG. 4 is a diagram showing the exposure head and the drum unit located at the retracted position. [Figure 4] FIG. 2 is a diagram showing an exposure head and a drum unit located at an exposure position. [Diagram 5] FIG. 4 is an exploded perspective view of the distance adjusting member. [Figure 6] FIG. 4 is a cross-sectional view showing a structure in the vicinity of a resin spring. [Figure 7] FIG. [Figure 8] 5A and 5B are diagrams showing the relationship between a rotation support member and a drum frame, etc. [Figure 9] 1A to 1C are diagrams showing information (dimensions) required for a spacer selection method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Next, an embodiment of the present invention will be described in detail with reference to the drawings as appropriate. In the following description, first, a schematic configuration of a color printer 1 as an example of an image forming apparatus will be briefly described, and then the configuration of the characteristic parts of the present invention will be described in detail.

[0012] In the following description, directions are described based on the user using color printer 1. That is, the left side in Fig. 1 is the "front", the right side is the "rear", the back side is the "left" and the front side is the "right". Also, the top side in Fig. 1 is the "top" and the bottom side is the "bottom".

[0013] As shown in FIG. 1, color printer 1 mainly includes a main body housing 10, a top cover 11, and a paper feed section 20 and an image forming section 30 provided within main body housing 10.

[0014] Top cover 11 is disposed on the top of main body housing 10, and is provided rotatable relative to main body housing 10 about a rear rotation shaft 11A, and opens and closes opening 10A formed in the top of main body housing 10. Specifically, top cover 11 is movable between a closed position (position in FIG. 1) where opening 10A is closed, and an open position (position in FIG. 2) where opening 10A is opened.

[0015] The paper feed unit 20 is provided at the bottom inside the main body housing 10, and mainly includes a paper feed tray 21 that stores paper P, and a paper supply mechanism 22 that supplies paper P from the paper feed tray 21 to the image forming unit 30. The paper P in the paper feed tray 21 is separated one sheet at a time by the paper supply mechanism 22 and supplied to the image forming unit 30.

[0016] The image forming section 30 mainly comprises four exposure heads 40, four process cartridges PC, a transfer unit 70, and a fixing unit 80.

[0017] The exposure head 40 has a plurality of LEDs at its tip, is held by the top cover 11 (more specifically, by a holder 12 described later) so as to be suspended from the top cover 11, and is disposed above and facing the photosensitive drum 51 described later when the top cover 11 is closed. Specifically, the exposure head 40 is capable of moving between an exposure position (position in FIG. 1) where the photosensitive drum 51 is exposed to light, and a retracted position (position in FIG. 2) that is farther away from the photosensitive drum 51 than the exposure position, by opening and closing the top cover 11. The exposure head 40 exposes the surface of the photosensitive drum 51 by causing the plurality of LEDs to blink based on image data. The structure of the exposure head 40 will be described in detail later.

[0018] The process cartridges PC are arranged in parallel in the front-rear direction between the top cover 11 and the paper feed tray 21. When the top cover 11 is open (see FIG. 2), each process cartridge PC is detachable through an opening 10A in the main body housing 10. The process cartridge PC includes a drum unit 50 and a developing cartridge 60 detachable from the drum unit 50.

[0019] The drum unit 50 includes a cylindrical photosensitive drum 51, a charger 52 that charges the photosensitive drum 51, a pressure spring 53 that urges the developing cartridge 60 toward the photosensitive drum 51, a cleaning roller 54, and a drum frame 55 that supports the photosensitive drum 51, etc. The structure of the photosensitive drum 51 will be described in detail later.

[0020] The cleaning roller 54 is a roller that removes foreign matter such as toner remaining on the photosensitive drum 51. The cleaning roller 54 is in contact with the photosensitive drum 51 and is rotatable.

[0021] The developing cartridge 60 mainly includes a toner storage section 61 that stores toner, and a developing roller 62 that supplies the toner in the toner storage section 61 to the photosensitive drum 51. The developing roller 62 is movable in the radial direction of the photosensitive drum 51.

[0022] Specifically, the developing roller 62 rotates while being biased against the photosensitive drum 51 by the pressure spring 53. At this time, the developing roller 62 moves in the radial direction of the photosensitive drum 51 following the eccentricity of the photosensitive drum 51 and the developing roller 62. As a result, the biasing force of the pressure spring 53 acts stably on the contact portion between the photosensitive drum 51 and the developing roller 62, and the toner is supplied to the electrostatic latent image on the photosensitive drum 51.

[0023] The transfer unit 70 is provided between the paper feed tray 21 and the process cartridge PC. The transfer unit 70 mainly includes a drive roller 71, a driven roller 72, an endless conveyor belt 73 stretched between the drive roller 71 and the driven roller 72, and four transfer rollers 74. The outer surface of the conveyor belt 73 contacts each of the photosensitive drums 51, and each of the transfer rollers 74 is disposed inside the conveyor belt 73 so as to sandwich the conveyor belt 73 between each of the photosensitive drums 51.

[0024] The fixing unit 80 is provided behind the process cartridge PC and the transfer unit 70, and mainly includes a heating roller 81 and a pressure roller 82 disposed opposite the heating roller 81 to press the heating roller 81.

[0025] In this image forming section 30, the surface of the photoconductor drum 51 is uniformly charged by the charger 52 and then exposed by the exposure head 40, thereby forming an electrostatic latent image based on image data on the photoconductor drum 51. Then, toner is supplied to the photoconductor drum 51 from the developing roller 62, thereby making the electrostatic latent image visible and forming a toner image on the photoconductor drum 51.

[0026] The toner images formed on the photoconductor drums 51 are transferred by transfer roller 74 in order, superimposed on the paper P being transported on transport belt 73. The paper P with the transferred toner image is transported between heating roller 81 and pressure roller 82, where the toner image is thermally fixed. Thereafter, the paper P is discharged from inside main body housing 10 to the outside by transport roller 91, and placed on paper discharge tray 11B formed on the upper surface of top cover 11.

[0027] Next, the structure around the photosensitive drum 51 and the structure of the exposure head 40 will be described in detail. 3, in this embodiment, the rotation axis X1 of the photoconductor drum 51 extends in the left-right direction. In the following description, the direction in which the rotation axis X1 extends, that is, the left-right direction, will also be simply referred to as the "rotation axis direction."

[0028] The photosensitive drum 51 is rotatably supported at each end in the direction of the rotation axis by a rotation support member 500. The rotation support members 500 arranged on one end side and the other end side of the photosensitive drum 51 are supported by a drum frame 55.

[0029] The photoconductor drum 51 includes a cylindrical element tube 51A and two fitting members 400 that fit into the inner peripheral surface of the element tube 51A. The element tube 51A is made of a conductive material such as metal. A photosensitive layer is formed on the outer peripheral surface of the element tube 51A. The outer peripheral surface of the element tube 51A is also referred to as the surface. The photosensitive layer is formed over an area at least larger than the exposure area ER of the exposure head 40.

[0030] The fitting members 400 are provided on one end side and the other end side of the mother tube 51A in the rotation axis direction. The fitting members 400 are made of resin. The fitting members 400 are fitted into the inner peripheral surface of the mother tube 51A, thereby becoming rotatable together with the mother tube 51A. The fitting member 400 integrally includes a fitting portion 410 located inside the end face A1 of the mother tube 51A in the rotation axis direction, and an exposed portion 420 located outside the end face A1 of the mother tube 51A in the rotation axis direction.

[0031] The fitting portion 410 is formed in a substantially cylindrical shape. The fitting portion 410 is fitted into the inner peripheral surface of the element tube 51A. The fitting portion 410 is disposed outside the exposure range ER of the exposure head 40 in the direction of the rotation axis.

[0032] The exposed portion 420 has a supported portion 421 supported by the rotation support member 500, and a flange portion 422 protruding radially outward from the outer circumferential surface of the supported portion 421. The supported portion 421 is formed in a substantially cylindrical shape. The outer diameter of the supported portion 421 is smaller than the outer diameter of the blank tube 51A.

[0033] The flange portion 422 is formed in a substantially circular plate shape. The flange portion 422 is disposed between the supported portion 421 and the fitting portion 410 in the rotation axis direction. The flange portion 422 contacts the end surface A1 of the mother tube 51A. The outer diameter of the flange portion 422 is larger than the outer diameter of the mother tube 51A.

[0034] The fitting member 400 has a through hole 401 penetrating in the rotation axis direction. More specifically, the through hole 401 is formed from an end face of the fitting portion 410 on the inner side in the rotation axis direction to an end face of the exposed portion 420 on the outer side in the rotation axis direction. The through hole 401 also passes through the centers of the fitting portion 410 and the exposed portion 420.

[0035] One of the two fitting members 400 (the left one) has an input portion 402 to which a rotational driving force is input. The input portion 402 is formed as a recess having a non-circular shape when viewed from the direction of the rotation axis. A coupling provided in the main body housing 10 that can advance and retreat can be inserted into the input portion 402. The input portion 402 and the coupling can be engaged in the rotational direction of the photosensitive drum 51. This makes it possible to transmit the rotational driving force from the coupling to the input portion 402.

[0036] A metal shaft 610 is provided in the through hole 401 of the other (right) fitting member 400. The shaft 610 is disposed at the rotation center of the fitting member 400. The length of the shaft 610 in the rotation axis direction is smaller than the length of the blank tube 51A in the rotation axis direction. More specifically, the length of the shaft 610 in the rotation axis direction is slightly larger than the length of the fitting member 400 in the rotation axis direction. Both ends of the shaft 610 protrude outward from each end face of the fitting member 400 in the rotation axis direction.

[0037] A metal earth spring 620 is provided at the end of the shaft 610 on the inside in the rotation axis direction. The earth spring 620 contacts the outer circumferential surface of the shaft 610 and also contacts the inner circumferential surface of the base tube 51A. As a result, the shaft 610 is electrically connected to the base tube 51A via the earth spring 620. When the photoconductor drum 51 is attached to the main body housing 10, the shaft 610 is electrically connected to a metal member provided in the main body housing 10 and is connected to a ground potential.

[0038] The rotation support member 500 is a member that rotatably supports the outer circumferential surface of the supported portion 421 of the fitting member 400. The rotation support member 500 is configured as a slide bearing made of resin. The rotation support member 500 is located outboard of the mother tube 51A in the direction of the rotation axis.

[0039] The rotation support member 500 has a contact surface 531 that contacts the exposure head 40. The contact surface 531 is located radially outward from the surface of the base tube 51A. More specifically, the contact surface 531 protrudes radially outward toward the exposure head 40 side from the outer circumferential surface of the flange portion 422 of the fitting member 400. The structure of the rotation support member 500 will be described in detail later.

[0040] The exposure head 40 includes a first frame 100 and a second frame 200 as examples of head frames, and a gap adjustment member 300 disposed between the second frame 200 and the drum unit 50. In more detail, the gap adjustment member 300 is disposed between the second frame 200 and a rotation support member 500 of the drum unit 50.

[0041] The first frame 100 and the second frame 200 are made of resin. The first frame 100 integrally comprises a base portion 110 that is substantially rectangular parallelepiped-shaped and elongated in the left-right direction, and two extension portions 120 that extend outward in the left-right direction from each of the left-right end faces of the base portion 110. The base portion 110 is made of resin and is open in the top-bottom direction.

[0042] The base unit 110 contains an LED array 101 and a memory 103 that stores information about the focal position. A lens array 102, which is an optical member that focuses light from the LED array 101 on the surface of the photoconductor drum 51, is provided in an opening at the bottom of the base unit 110. In other words, the base unit 110 supports the LED array 101, the lens array 102, and the memory 103. The bottom surface of the lens array 102 is an emission surface that emits light, and faces the rotation axis X1.

[0043] The LED array 101 is a semiconductor element having a plurality of light-emitting elements arranged in the direction of the rotation axis, and the photosensitive drum 51 is scanned and exposed by sequentially lighting each light-emitting element. In the following description, the direction in which the photosensitive drum 51 is scanned in the direction of the rotation axis by the plurality of light-emitting elements arranged in the direction of the rotation axis is referred to as the main scanning direction. The optical axis direction of the light emitted from the LED array 101 is simply referred to as the "optical axis direction". Furthermore, the direction perpendicular to the optical axis direction and the main scanning direction is referred to as the sub-scanning direction. In this embodiment, the sub-scanning direction is approximately the same as the front-rear direction, and therefore is also referred to as the front-rear direction as appropriate. In this embodiment, the optical axis direction is approximately the same as the up-down direction, and therefore is also referred to as the up-down direction as appropriate.

[0044] The vertical length of the extension portion 120 is smaller than the vertical length of the base portion 110. The extension portion 120 is located at the upper part of the left and right end faces of the base portion 110. The lower surface of the extension portion 120 serves as a supported surface 121 that is supported by the second frame 200. The supported surface 121 faces the rotation axis X1 side.

[0045] The second frame 200 is a resin frame that supports the first frame 100, and is supported in a suspended state by a resin holder 12 that is rotatably supported by the top cover 11. The second frame 200 integrally includes a substantially rectangular base portion 210 that is long in the left-right direction, and two protrusions 220 that support both ends of the first frame 100 in the direction of the rotation axis.

[0046] The base portion 210 has a first recess 211 , a second recess 212 , and a hole 213 . Two holes 213 are provided with a gap therebetween in the left-right direction. The holes 213 are arranged symmetrically with respect to the center in the left-right direction of the base portion 210. Each hole 213 penetrates the base portion 210 in the front-rear direction.

[0047] The holder 12 has hooks 12A for hanging the base portion 210 at positions corresponding to the holes 213. The tip of each hook 12A protrudes inward in the front-rear direction and engages with each hole 213.

[0048] The first recess 211 is a recess that opens toward the holder 12. The first recess 211 is formed on the left and right outer sides of the two left and right holes 213. A compression coil spring SP, which is a biasing member, is provided between the bottom surface of the first recess 211 and the holder 12. The compression coil spring SP biases the exposure head 40 toward the photosensitive drum 51.

[0049] The second recesses 212 are recesses that open toward one side in the front-rear direction. The second recesses 212 are formed one on each side in the left-right direction outward from the left and right first recesses 211. More specifically, the second recesses 212 are disposed at positions closer to the ends of the base portion 210 than the center in the left-right direction. The lower wall of the second recesses 212 serves as a support wall 214 that supports the distance adjustment member 300.

[0050] The lower surface of the support wall 214 serves as a second support surface F2 that supports the gap adjustment member 300 from above when the exposure head 40 is located at the exposure position (the position in FIG. 4). The second support surface F2 is disposed at a position farther from the rotation axis X1 than the first support surface F1 described below. The second support surface F2 functions as a reference surface FB that serves as a reference for determining the thickness of the spacer 320 described below. The reference surface FB is located on the lower side (photoconductor drum 51 side) of the support wall 214, that is, on the lower side of the base portion 210, and faces the rotation axis X1.

[0051] Each protrusion 220 protrudes from the lower surface of the base portion 210 toward the photoconductor drum 51. More specifically, each protrusion 220 protrudes in the optical axis direction beyond the lens array 102. Each protrusion 220 is disposed between the compression coil spring SP and the gap adjustment member 300 in the left-right direction.

[0052] Each protruding portion 220 has a third recess 223 and a fourth recess 224 that open toward one side in the front-rear direction. More specifically, the third recess 223 and the fourth recess 224 open toward the rear. The third recess 223 is formed in the upper portion of the protruding portion 220. The third recess 223 is capable of accommodating the extension portion 120 of the first frame 100 therein. The lower wall of the third recess 223 is a support wall 221 that supports the extension portion 120 of the first frame 100. The upper surface of the support wall 221 is a first support surface F1 that supports the extension portion 120 of the first frame 100 from below. The first support surface F1 faces the radially outward direction of the photosensitive drum 51. The first support surface F1 is disposed between the photosensitive drum 51 and the first frame 100 in the optical axis direction.

[0053] A part of the protruding portion 220 is disposed at the same position as the first support surface F1 in the rotation axis direction. More specifically, the photosensitive drum 51 side of the protruding portion 220 has a tip surface 225 that is perpendicular to the optical axis direction, and the tip surface 225 overlaps with the first support surface F1 when viewed from the optical axis direction.

[0054] The fourth recess 224 is disposed below the third recess 223. The above-mentioned support wall 221 is disposed between the third recess 223 and the fourth recess 224. As shown in Fig. 6, the extension portion 120 of the first frame 100 supported by the support wall 221 is attached to the protrusion 220 by a resin spring 700. The resin spring 700 is attached from the rear to prevent the user from touching it.

[0055] The resin spring 700 functions as a pressing member that presses the extension portion 120 of the first frame 100 toward the first support surface F1 and the bottom surface 223A of the third recess 223. In detail, the resin spring 700 integrally includes a first portion 710, a second portion 720, a third portion 730, a fourth portion 740, a fifth portion 750, a sixth portion 760, a seventh portion 770, and an eighth portion 780. The first portion 710 enters the fourth recess 224 and contacts the lower surface of the support wall 221. The second portion 720 extends upward from one end of the first portion 710 in the front-rear direction.

[0056] The third portion 730 extends from an upper end of the second portion 720 toward the bottom surface 223A of the third recess 223. The fourth portion 740 extends from the other end of the third portion 730 in the front-to-rear direction toward the second portion 720 at an angle relative to the third portion 730. The fifth portion 750 extends from the end of the fourth portion 740 on the second portion 720 side toward the third portion 730 at an angle relative to the third portion 730.

[0057] The sixth portion 760 extends from an end of the fifth portion 750 on the second portion 720 side toward the second portion 720 side approximately parallel to the third portion 730. The seventh portion 770 extends from an end of the sixth portion 760 on the second portion 720 side toward the first portion 710 side at an angle with respect to the third portion 730. The eighth portion 780 extends downward from a lower end of the seventh portion 770. The seventh portion 770 contacts a corner of the extension portion 120 of the first frame 100 and presses the extension portion 120 toward the first support surface F1 and the bottom surface 223A of the third recess 223.

[0058] 6, the width of the protruding portion 220 in the front-rear direction is greater than the width of the lens array 102 in the front-rear direction. The lens array 102 is disposed within the width of the protruding portion 220 in the front-rear direction.

[0059] 5, the gap adjustment member 300 includes one contact member 310 and two spacers 320. The contact member 310 is a member for determining the distance in the optical axis direction from the lens array 102 to the photosensitive drum 51 by contacting with a contact surface 531 (see FIG. 3) of the rotation support member 500.

[0060] The abutting member 310 is made of resin and integrally includes a substantially triangular main body 310A and a boss 310B that protrudes upward from the main body 310A. The width of the main body 310A in the front-rear direction narrows toward the photoconductor drum 51.

[0061] The main body 310A has a first wall 311, a second wall 312, and a third wall 313. The first wall 311 has an opposing surface F3 that faces a second support surface F2 (reference surface FB) of the second frame 200 in the optical axis direction.

[0062] The second wall portion 312 extends obliquely from one front-rear end of the first wall portion 311 downward and toward the other front-rear end. The third wall portion 313 extends from the other front-rear end of the first wall portion 311 downward and toward one front-rear end, and is connected to the lower end of the second wall portion 312. The end face on the lower side (photoconductor drum 51 side) of the corner that is the connection portion between the second wall portion 312 and the third wall portion 313 forms a contact surface F4 that abuts against the abutment surface 531 of the rotation support member 500. The contact surface F4 is a curved surface that is convex downward.

[0063] The boss 310B protrudes upward from the opposing surface F3. The boss 310B is formed in a substantially cylindrical shape. The boss 310B is supported by the support wall 214 so as to be movable in the vertical direction while being inserted into a through hole 214A formed in the support wall 214. In other words, the boss 310B functions as a supported portion supported by the support wall 214. Here, the through hole 214A is formed so as to penetrate the support wall 214 in the vertical direction. As a result, the reference surface FB has an opening facing the rotation axis X1 side.

[0064] Boss 310B has a slit 314 extending downward from its upper surface. Slit 314 is formed to open upward and penetrate boss 310B in the left-right direction. As a result, the upper part of boss 310B has a bifurcated shape that is divided in the front-rear direction.

[0065] Two claws 315 that protrude outward in the front-rear direction are formed on the outer circumferential surface of the upper end of the boss 310B. The claws 315 are capable of engaging with the upper surface of the support wall 214. The claws 315 are formed such that their height from the outer circumferential surface of the boss 310B gradually decreases toward the upper side. In other words, the outer surfaces of the claws 315 in the front-rear direction are inclined surfaces that are positioned inward in the front-rear direction toward the upper side.

[0066] As a result, when boss 310B is pressed from below into through-hole 214A of support wall 214, the forked upper part of boss 310B is elastically deformed, allowing each claw 315 to enter through-hole 214A. After each claw 315 leaves through-hole 214A, the forked upper part of boss 310B returns to its original position, allowing each claw 315 to be satisfactorily engaged with the upper surface of support wall 214.

[0067] The spacer 320 is a rectangular plate-like member sandwiched between the reference surface FB (second support surface F2) and the opposing surface F3 of the contact member 310. The spacers 320 are arranged perpendicular to the optical axis direction. The thickness (length in the optical axis direction) of each spacer 320 is the same. Here, the length of the spacer 320 in the optical axis direction is preferably, for example, 0.025 mm to 0.2 mm, and more preferably 0.05 mm to 0.1 mm.

[0068] The length of the spacer 320 in the front-rear direction is smaller than the length of the opposing surface F3 in the front-rear direction. In addition, the length of the spacer 320 in the left-right direction is smaller than the length of the opposing surface F3 in the left-right direction. The spacer 320 has a hole 321 through which the boss 310B passes.

[0069] The gap adjusting member 300 configured as above is supported in a suspended state from the second frame 200 when the exposure head 40 is located at the retracted position, as shown in Fig. 3. More specifically, the contact member 310 is supported in a suspended state from the second frame 200, and the two spacers 320 are stacked on the contact member 310 while being spaced apart from the second frame 200 in the vertical direction. In other words, the distance from the reference surface FB to the facing surface F3 when the exposure head 40 is located at the retracted position is set to a distance that allows the maximum number of spacers 320 to be installed. Here, the maximum number of spacers 320 can be appropriately set in consideration of errors during design, etc.

[0070] 4, when the exposure head 40 is located at the exposure position, the two spacers 320 are sandwiched between the reference surface FB and the opposing surface F3. In detail, when the exposure head 40 is moved from the retracted position to the exposure position, the contact member 310 first comes into contact with the contact surface 531 of the rotation support member 500, and the movement of the contact member 310 is stopped. Thereafter, the second frame 200 moves closer to the contact member 310 whose movement has been stopped, and when the reference surface FB comes into contact with the spacer 320, the movement of the second frame 200 is stopped, and the exposure head 40 is positioned in the optical axis direction. In this state, the contact surface F4 is located closer to the rotation axis X1 than the first support surface F1.

[0071] As shown in Figure 7, the rotation support member 500 is formed of resin and integrally has a cylindrical bearing portion 510, a ring-shaped flange portion 520 protruding radially outward from approximately the center of the bearing portion 510 in the direction of the rotation axis, an extension portion 530 extending radially outward from the outer circumferential surface of the flange portion 520 of the base tube 51A (see Figure 8), a guide portion 540, a rotation regulating portion 550 and a roller support portion 560.

[0072] As shown in FIG. 8, the bearing portion 510 is a portion that rotatably supports the fitting member 400. The bearing portion 510 has a pressing portion 511 that presses the fitting member 400 downward (one radial side of the blank tube 51A). The pressing portion 511 is a portion between two notches formed at two locations on one end of the bearing portion 510, and is elastically deformable in the radial direction. The pressing portion 511 is a resin spring whose tip portion 511A is inclined so as to approach the rotation axis X1, and which presses the fitting member 400 toward the rotation axis X1 with a pressing force FR. When viewed from the rotation axis direction, the pressing portion 511 is located on a straight line L1 that is perpendicular to the rotation axis X1 of the photosensitive drum 51 and passes through the abutment surface 531.

[0073] The extension portion 530 extends upward from the flange portion 520, specifically toward the abutment member 310 of the exposure head 40. The extension portion 530 has the above-mentioned abutment surface 531 at its tip. The abutment surface 531 is a flat surface perpendicular to the optical axis direction. The abutment surface 531 abuts against the abutment member 310 of the exposure head 40, thereby defining the distance in the optical axis direction from the lens array 102 to the photosensitive drum 51.

[0074] The guide portion 540 extends from the flange portion 520 in the upper right direction in the figure, more specifically, in the direction from the photosensitive drum 51 toward the developing roller 62. The guide portion 540 is adjacent to the downstream side of the extending portion 530 in the rotation direction of the photosensitive drum 51, and is connected to the extending portion 530. The guide portion 540 has a guide groove 541 that supports the shaft 62A of the developing roller 62 movably in the radial direction of the photosensitive drum 51.

[0075] The rotation regulating portion 550 is adjacent to the downstream side of the guide portion 540 in the rotation direction of the photosensitive drum 51, and is connected to the guide portion 540. The rotation regulating portion 550 has a first rotation regulating surface 551 that regulates the position of the rotation support member 500 with respect to the drum frame 55 in the rotation direction of the photosensitive drum 51. The first rotation regulating surface 551 is disposed so as to face the downstream side in the rotation direction of the photosensitive drum 51, and is capable of contacting the drum frame 55.

[0076] The roller support portion 560 is disposed between the extension portion 530 and the rotation regulating portion 550 in the rotation direction of the photosensitive drum 51. The roller support portion 560 is disposed away from the extension portion 530 and the rotation regulating portion 550 in the rotation direction. The roller support portion 560 is disposed on the opposite side of the rotation axis X1 from the rotation regulating portion 550.

[0077] The roller support portion 560 has a support hole 561 that rotatably supports the cleaning roller 54. The roller support portion 560 has a second rotation restricting surface 562 that restricts the position of the rotation support member 500 relative to the drum frame 55 in the rotation direction of the photosensitive drum 51. The second rotation restricting surface 562 is disposed to face the downstream side in the rotation direction of the photosensitive drum 51 and is capable of contacting the drum frame 55. It is sufficient that at least one of the first rotation restricting surface 551 and the second rotation restricting surface 562 is in contact with the drum frame 55 when the photosensitive drum 51 rotates.

[0078] Moreover, the second rotation restricting surface 562 is disposed at a position farther from the rotation axis X1 of the photosensitive drum 51 than the contact surface 531. Furthermore, the rotation restricting surfaces 551, 562 are provided on both sides of a straight line L1 that passes through the contact surface 531 and the rotation axis X1 of the photosensitive drum 51 in the radial direction of the photosensitive drum 51, when viewed from the rotation axis direction.

[0079] Next, a detailed description will be given of a method for manufacturing the color printer 1, more specifically, a method for assembling the exposure head 40. In the method described below, the method for selecting the spacers 320 to be placed on the left and right sides of the exposure head 40 is particularly important, and this selection method is the same for the left and right sides. Therefore, in the following, the left side will be described as a representative, and the description of the right side will be omitted.

[0080] As shown in Fig. 9(a), first, the LED array 101, the lens array 102, and the memory 103 are assembled to the first frame 100. After that, the first frame 100 is set in an inspection device. Next, light is emitted from the LED array 101, and a first distance D1 from the supported surface 121 of the first frame 100 to the focal point FP is measured. Note that since there are two supported surfaces 121, one on the left side and one on the right side, the first distance D1 is measured on both the left and right sides. After that, the measured first distance D1 is recorded in the memory 103.

[0081] 9(b), for the second frame 200, for example, a second distance D2 from the left reference plane FB to the left first support plane F1 is measured and acquired (acquisition process). The first support plane F1 is a plane that supports the supported surface 121 of the first frame 100. Therefore, the second distance D2 corresponds to the distance from the reference plane FB to the supported surface 121 in a state in which the first frame 100 is assembled to the second frame 200. The second distance D2 is acquired on both the left and right sides of the second frame 200. By recording the measurement result of the first distance D1 in the memory 103, it becomes possible to measure the first distance D1 and the second distance D2 in different processes or factories.

[0082] After that, the first distance D1 is obtained from the memory 103 of the first frame 100 to be assembled into the second frame 200 (obtaining process). Then, based on the first distance D1 and the second distance D2, the focal position of the exposure head 40 with respect to the reference surface FB is obtained (obtaining process). In detail, the first distance D1 and the second distance D2 are added together to calculate and obtain the distance D3 from the reference surface FB to the focal point FP, that is, the focal position of the exposure head 40 with respect to the reference surface FB.

[0083] 9(c), for the left contact member 310 attached to the left reference surface FB, the length D4 in the optical axis direction from the facing surface F3 to the contact surface F4 is measured and acquired (acquisition step). The same is done for the right side.

[0084] Then, the number of spacers 320 is selected based on the distance D3 and length D4 corresponding to the focal position (selection step). More specifically, the difference between the distance D3 and the length D4 is calculated, and the number of spacers 320 required to fill this difference is determined. Here, if the length of the spacer 320 in the optical axis direction is T1, the number N of spacers 320 can be derived from the following formula (1). N = (D3-D4) / T1 (1)

[0085] After the number of spacers 320 is determined, that number of spacers 320 are attached to the bosses 310B of the contact members 310, and then the contact members 310 are attached to the second frame 200. As a result, the selected number of spacers 320 are assembled between the reference surface FB and the opposing surface F3 (assembly step).

[0086] As described above, the following effects can be obtained in this embodiment. Since the contact surface 531 with which the exposure head 40 comes into contact is provided on the rotation support member 500 that supports the fitting member 400, which is a member different from the base tube 51A, foreign matter on the base tube 51A is less likely to get between the exposure head 40 and the rotation support member 500. Therefore, according to this embodiment, the distance in the optical axis direction from the lens array 102 to the photosensitive drum 51 can be accurately defined, so that shifting of the focal position can be suppressed.

[0087] Since the rotating support member 500 is positioned outward in the direction of the rotation axis from the base tube 51A, the abutment surface 531 can be moved away from the surface of the base tube 51A in the direction of the rotation axis, thereby further preventing foreign matter on the base tube 51A from entering between the abutment surface 531 and the exposure head 40.

[0088] Since the outer diameter of supported part 421 of fitting member 400 is smaller than the outer diameter of mother tube 51A, the contact area between supported part 421 and rotation support member 500 can be made smaller than in a structure in which the outer diameter of the supported part is larger than the outer diameter of the mother tube. As a result, wear of supported part 421 or rotation support member 500 can be suppressed.

[0089] Since the fitting member 400 has the flange portion 422, when the fitting member 400 is fitted into the mother tube 51A, the flange portion 422 comes into contact with the end face of the mother tube 51A, making it easy to position the fitting member 400 relative to the mother tube 51A.

[0090] Since the abutment surface 531 is provided at the tip of the extension portion 530 extending in the radial direction of the blank tube 51A, the extension portion 530 can bring the abutment surface 531 closer to the abutment member 310 of the exposure head 40. Therefore, the amount of protrusion of the abutment member 310 protruding from the second frame 200 towards the abutment surface 531 can be reduced, and the shape of the exposure head 40 can be simplified.

[0091] By positioning the abutment surface 531 radially outward from the surface of the base tube 51A, the abutment surface 531 can be moved radially away from the surface of the base tube 51A, thereby better preventing foreign matter on the base tube 51A from entering between the abutment surface 531 and the exposure head 40.

[0092] By making the abutment surface 531 flat and the contact surface F4 curved, the abutment surface 531 and the contact surface F4 can be in line contact, so that the distance in the optical axis direction from the lens array 102 to the photosensitive drum 51 can be accurately determined.

[0093] By making the contact surface 531 a plane perpendicular to the optical axis direction, the exposure head 40 can slide on the contact surface 531 in the sub-scanning direction perpendicular to the optical axis direction, so that the contact surface 531 is prevented from getting in the way when positioning the exposure head 40 in the sub-scanning direction.

[0094] Since both the fitting member 400 and the rotation support member 500 are made of resin, it is easy to form the shapes of the fitting member 400 and the rotation support member 500. Furthermore, the fitting member 400 and the rotation support member 500 can form a sliding bearing.

[0095] Since the fitting member 400 is pressed to one radial direction by the pressing portion 511 provided on the rotation support member 500, it is possible to suppress fluctuations in the distance between the focal position of the exposure head 40 and the surface of the photosensitive drum 51. In addition, by applying resistance to the rotation of the photosensitive drum 51, it is possible to suppress uneven rotation.

[0096] By arranging the pressing portion 511 on a straight line L1 that is perpendicular to the rotation axis X1 of the photosensitive drum 51 and passes through the abutment surface 531 when viewed from the rotation axis direction, the direction in which the photosensitive drum 51 is shifted can be made to approximately coincide with the optical axis direction of the exposure head 40, so that the distance in the optical axis direction from the lens array 102 to the photosensitive drum 51 can be accurately determined.

[0097] Since the engaging portion 410 of the engaging member 400 is positioned outside the exposure range ER of the exposure head 40 in the direction of the rotation axis, it is possible to prevent the portion on the photosensitive drum 51 corresponding to the exposure range ER from being deformed due to the engagement of the engaging member 400.

[0098] A metal shaft 610 electrically connected to the base tube 51A is provided at the rotation center of the right fitting member 400, so that the base tube 51A can be electrically connected to the main body of the apparatus via the shaft 610.

[0099] Since the left fitting member 400 is provided with the input portion 402 to which the rotational driving force is input, the rotational driving force can be input to the fitting member 400 satisfactorily, and the photosensitive drum 51 can be rotated satisfactorily.

[0100] Since the left and right rotation support members 500 are supported by the drum frame 55, the photosensitive drum 51 and each of the rotation support members 500 can be integrated into a unit by the drum frame 55.

[0101] Since rotation control surfaces 551, 562 are provided on the rotation support member 500 having the abutment surface 531 for positioning the exposure head 40 in the optical axis direction, it is possible to prevent the rotation support member 500 from vibrating in the rotational direction and causing the focal position to shift.

[0102] By arranging the second rotation restriction surface 562 at a position farther from the rotation axis X1 than the abutment surface 531, rotation restriction can be performed at a position farther from the rotation axis X1, so that rotation restriction can be performed efficiently. Also, since vibration at the abutment surface 531 is smaller than vibration at the second rotation restriction surface 562 (vibration in the rotational direction), the positioning of the exposure head 40 by the abutment surface 531 can be maintained well.

[0103] Since the rotation restriction surfaces 551, 562 are provided on both sides of the straight line L1 passing through the abutment surface 531 and the rotation axis X1, vibration in the rotational direction can be effectively suppressed.

[0104] By providing the second rotation control surface 562 on the roller support portion 560 that supports the cleaning roller 54, the cleaning roller 54 can be supported by the roller support portion 560 in which vibration in the rotational direction is suppressed, so that the cleaning roller 54 can be accurately positioned relative to the photosensitive drum 51.

[0105] Since the guide portion 540 is provided on the rotation support member 500 in which vibration in the rotation direction is suppressed by the rotation restricting surfaces 551, 562, the developing roller 62 can be positioned with high accuracy in the rotation direction relative to the photosensitive drum 51.

[0106] Since spacers 320 are provided between the reference surface FB of the second frame 200 and the abutment member 310, even if the focal position of the exposure head 40 relative to the reference surface FB is not in an appropriate position due to manufacturing errors of the frames 100, 200 or the abutment member 310, the focal position can be accurately determined by appropriately selecting the number of spacers 320.

[0107] Since the spacer 320 is plate-shaped, the error in the thickness (length in the optical axis direction) of the spacer 320 can be made extremely small.

[0108] Since the spacers 320 all have the same thickness, when assembling the exposure head 40, an operator can easily adjust the focal position by simply changing the number of spacers 320.

[0109] By making the contact member 310 movable in the optical axis direction relative to the second frame 200, when the exposure head 40 is pressed against the photosensitive drum 51, the second frame 200 moves relative to the contact member 310, and the spacer 320 can be sandwiched between the reference surface FB and the contact member 310. Therefore, compared to a structure in which the contact member is fixed to the second frame with screws or the like with the spacer sandwiched between the contact member and the second frame, costs can be reduced by not providing mounting members such as screws.

[0110] Since the spacer 320 has the hole 321 through which the boss 310B of the contact member 310 penetrates, the spacer 320 can be prevented from shifting relative to the contact member 310.

[0111] By providing a compression coil spring SP that biases the exposure head 40 toward the photosensitive drum 51, the biasing force of the compression coil spring SP can bring the reference surface FB, the spacer 320 and the abutment member 310 into close contact with each other, thereby accurately determining the focal position.

[0112] Since the reference surface FB is provided on the second frame 200, which is a separate component from the first frame 100 on which optical components such as the LED array 101 are provided, it is possible to prevent the force applied to the reference surface FB when the exposure head 40 is pressed against the photosensitive drum 51 from being transmitted to the optical components provided on the first frame 100.

[0113] Since the supported surface 121 of the first frame 100 faces the rotation axis X1, like the light emission surface of the lens array 102, the position of the focal point FP relative to the supported surface 121 can be measured and obtained with high precision, and thus the focal point position relative to the reference surface FB can be obtained with high precision.

[0114] By positioning the second support surface F2 at a position farther from the rotation axis X1 than the first support surface F1, the amount by which the spacing adjustment member 300 protrudes from the surface of the exposure head 40 facing the photosensitive drum 51 (the tip surface of the protrusion 220) can be reduced, thereby preventing the spacing adjustment member 300 from interfering with other members when the exposure head 40 is moved toward the photosensitive drum 51.

[0115] The protrusion 220, which is positioned at approximately the same position in the rotational axis direction as the first support surface F1 that supports the first frame 100, protrudes toward the photosensitive drum 51 further than the lens array 102, so that the lens array 102 can be well protected by the protrusion 220.

[0116] Since the width of the protrusion 220 in the sub-scanning direction is greater than the width of the lens array 102 in the sub-scanning direction, the lens array 102 can be well protected by the wide protrusion 220.

[0117] Since the width of the main body 310A of the abutment member 310 in the sub-scanning direction becomes narrower toward the photosensitive drum 51, it is possible to prevent the abutment member 310 from interfering with other members when the exposure head 40 is moved toward the photosensitive drum 51.

[0118] The present invention is not limited to the above-described embodiment, but can be used in various forms as exemplified below. In the following description, the same reference numerals are used to designate components having substantially the same structures as those in the above-described embodiment, and the description thereof will be omitted.

[0119] In the above embodiment, the outer diameter of the supported part 421 is smaller than the outer diameter of the mother tube 51A, but the present invention is not limited to this, and the outer diameter of the supported part 421 may be, for example, larger than the outer diameter of the mother tube 51A. By making the outer diameter of the supported part 421 different from the outer diameter of the mother tube 51A in this way, a step is formed between the outer circumferential surface of the supported part 421 and the surface of the mother tube 51A, so that it is possible to prevent foreign matter on the mother tube 51A from entering between the supported part 421 and the rotation support member 500, as compared to a structure in which the outer circumferential surface of the supported part and the surface of the mother tube are flush with each other. The outer diameter of the supported part 421 may be the same as the outer diameter of the mother tube 51A.

[0120] The contact surface 531 may be perpendicular to the optical axis toward the rotation axis X1 of the photosensitive drum 51. For example, the contact surface 531 may be parallel to the contact surface of the conveyor belt 73 (see FIG. 1) with the photosensitive drum 51, or may not be parallel to the contact surface.

[0121] In the above embodiment, the abutment surface 531 is a flat surface and the contact surface F4 is a curved surface, but the present invention is not limited to this, and the abutment surface may be a curved surface and the contact surface may be a flat surface. Also, the curved surface may be a spherical surface. In this case, the abutment surface and the contact surface can be in point contact.

[0122] In the above embodiment, the head frame is configured with two frames 100, 200, but the present invention is not limited to this. For example, the head frame may be configured with one frame. In this case, optical components such as a light emitting section and a distance adjusting member may be provided on one head frame.

[0123] In the above embodiment, the guide portion 540 movably supports the developing roller 62 which rotates in contact with the photosensitive drum 51, but the guide portion 540 may be configured to be provided with a separation mechanism which moves the developing roller 62 to a separated position where it does not contact the photosensitive drum 51, and to support the developing roller 62 movably between the contact position and the separated position.

[0124] The materials of the fitting members, the rotation support members, and other components are not limited to those in the above embodiment, and various materials can be selected and used. Furthermore, the rotation support members do not need to be plain bearings, and may be rolling bearings or the like.

[0125] In the above embodiment, the present invention is applied to a color printer 1, but the present invention is not limited to this, and the present invention may be applied to other image forming devices, such as a copying machine or a multifunction machine.

[0126] Furthermore, the elements described in the above-described embodiment and modified examples may be implemented in any combination. [Explanation of symbols]

[0127] 1. Color printer 40 Exposure head 51 Photoconductor drum 51A bare pipe 100 1st frame 101 LED Array 102 Lens Array 200 2nd Frame 400 Fittings 500 Rotating support member 531 Contact surface

Claims

1. A main body housing; a drum unit including a photosensitive drum rotatable in a rotation axis direction and a drum frame supporting the photosensitive drum, the drum unit being detachable from the main body housing; an exposure head having a plurality of light-emitting units aligned in the direction of the rotation axis, a lens array that focuses light from the light-emitting units on the surface of the photosensitive drum, a head frame that supports the light-emitting units and the lens array, and a contact member that contacts the drum unit to determine the distance from the lens array to the photosensitive drum, the exposure head being movable between an exposure position where the photosensitive drum can be exposed and a retracted position retracted from the exposure position; A holder for supporting the head frame; a spring that biases the head frame from the holder toward the photosensitive drum, the photosensitive drum includes a cylindrical mother tube having a photosensitive layer formed on an outer peripheral surface thereof, and fitting members provided at one end side and the other end side of the mother tube in the rotation axis direction, the fitting members fitting into an inner peripheral surface of the mother tube, the drum unit includes a support member that supports one end side and the other end side of the photosensitive drum in the rotation axis direction and has an abutment surface that abuts against the abutment member, the drum frame supports the support member at one end side and the other end side in the rotation axis direction of the photosensitive drum, The image forming apparatus, wherein the drum unit is detachably attached to the main body when the exposure head is in the retracted position.

2. The image forming apparatus described in Claim 1, characterized in that the engaging member on one end side in the direction of the rotational axis has a concave shape from the direction of the rotational axis, and has an input portion into which a rotational driving force is input by inserting a coupling provided in the main body housing.

3. the fitting member on the other end side in the rotational axis direction has a through hole penetrating in the rotational axis direction, 3. The image forming apparatus according to claim 2, further comprising a metal shaft disposed within the through hole, which provides electrical conductivity between the base tube and a metal member of the main body housing when the drum unit is attached to the apparatus main body.

4. The image forming device described in Claim 1, characterized in that the head frame has a first frame that supports the light-emitting unit and the lens array, and a second frame that supports the first frame from the opposite side to the photosensitive drum in the optical axis direction of the lens array and receives the biasing force of the spring.

5. 5. The image forming apparatus according to claim 4, wherein the spring is provided on the inside of the contact member in the direction of the rotation axis.

6. The head frame has a through hole penetrating in the optical axis direction of the lens array, 2. The image forming apparatus according to claim 1, wherein the contact member has a contact surface that contacts the drum unit and a boss that is inserted into the through hole.

7. a cover for opening and closing the opening of the main body housing; the exposure head is located at the retracted position with the cover open, 2. The image forming apparatus according to claim 1, wherein the drum unit is detachable through the opening when the cover is open.

8. A main body housing; a process cartridge detachably attached to the main body housing, the process cartridge including a photosensitive drum rotatable in a rotation axis direction, a drum frame supporting the photosensitive drum, a toner storage section for storing toner, and a developing roller for supplying the toner in the toner storage section to the photosensitive drum; an exposure head including a plurality of light-emitting units aligned in the direction of the rotation axis, a lens array that focuses light from the light-emitting units on the surface of the photosensitive drum, a head frame that supports the light-emitting units and the lens array, and a contact member that contacts the process cartridge to define a distance from the lens array to the photosensitive drum, the exposure head being movable between an exposure position where the photosensitive drum can be exposed and a retracted position retracted from the exposure position; A holder for supporting the head frame; a spring that biases the head frame from the holder toward the photosensitive drum, the photosensitive drum includes a cylindrical mother tube having a photosensitive layer formed on an outer peripheral surface thereof, and fitting members provided at one end side and the other end side of the mother tube in the rotation axis direction, the fitting members fitting into an inner peripheral surface of the mother tube, the process cartridge includes a support member that supports one end side and the other end side of the photosensitive drum in the rotation axis direction and has an abutment surface that abuts against the abutment member, the drum frame supports the support member at one end side and the other end side in the rotation axis direction of the photosensitive drum, The image forming apparatus according to claim 1, wherein the process cartridge is detachably mountable to the main body when the exposure head is in the retracted position.

Images