JP6201559B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus employing an electrophotographic system.

  As an electrophotographic image forming apparatus, a so-called tandem type color printer including a plurality of image carriers corresponding to each of yellow, magenta, cyan, and black is known.

  As such a tandem-type color printer, four photosensitive drums corresponding to each color are rotatably supported, and a drum unit that is slidably attached to the main body casing and a sheet that is in contact with each photosensitive drum are conveyed. There has been proposed a printer including a conveyor belt (see, for example, Patent Document 1 below).

  In this printer, the drum unit includes a bearing member for bearing the photosensitive drum. The bearing member integrally includes a cylindrical tubular portion and a pressing member provided on the tubular portion. The photosensitive drum is inserted into the cylindrical portion and pressed against the inner peripheral surface of the rear lower side of the cylindrical portion by a pressing member. As a result, the photosensitive drum is in contact with the conveyor belt in a state in which rattling in the radial direction is suppressed.

JP 2011-64884 A

  However, in the printer described in Patent Document 1, when the paper is introduced between the photosensitive drum and the conveyance belt, the photosensitive drum rattles against the pressing force of the pressing member due to contact with the paper. There is. In particular, the foremost photosensitive drum that contacts the paper first tends to be rattled.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of suppressing rattling of the first photosensitive drum and the second photosensitive drum.

(1) In order to achieve the above object, an image forming apparatus according to the present invention includes a conveyance belt, a first photosensitive drum, a second photosensitive drum, a side plate, a first urging member, and a second urging member. With. The conveyance belt is configured to convey the recording medium. The first photosensitive drum is positioned on the most upstream side in the recording medium conveyance direction by the conveyance belt. The second photosensitive drum is disposed in parallel with the first photosensitive drum, and is located downstream of the first photosensitive drum in the transport direction. The side plate is a side plate that supports the first photosensitive drum and the second photosensitive drum, and includes a first positioning portion that positions the first photosensitive drum with respect to the side plate, and a second that positions the second photosensitive drum with respect to the side plate. A positioning part. The first biasing member is configured to bias the first photosensitive drum toward the first positioning portion. The second urging member is configured to urge the second photosensitive drum toward the second positioning portion.

  The biasing force of the first biasing member is greater than the biasing force of the second biasing member.

  According to such a configuration, the first photosensitive drum disposed at the uppermost stream in the recording medium conveyance direction is positioned with respect to the side plate with a larger biasing force than the second photosensitive drum disposed downstream thereof. can do.

  Thereby, shakiness of the 1st photosensitive drum arrange | positioned in the conveyance direction most upstream can be suppressed.

  Further, by suppressing the rattling of the first photosensitive drum arranged at the most upstream in the conveying direction, the recording medium can be smoothly conveyed to the second photosensitive drum arranged downstream of the first photosensitive drum. Therefore, rattling of the second photosensitive drum can be suppressed.

As a result, rattling of the first photosensitive drum and the second photosensitive drum can be suppressed.
(2) The image forming apparatus of the present invention may further include a first bearing member and a second bearing member. The first bearing member is a first bearing member that rotatably supports an end portion of the first photosensitive drum with respect to the side plate. The first mounting portion is attached to the side plate, and the first photosensitive portion to the first photosensitive drum. A first elastic portion having elasticity and extending along the outer peripheral surface of the first elastic portion; and a first contact portion protruding from the tip of the first elastic portion toward the outer peripheral surface of the first photosensitive drum and contacting the first photosensitive drum. Prepare. The second bearing member is a second bearing member that rotatably supports an end portion of the second photosensitive drum with respect to the side plate, a second mounting portion that is attached to the side plate, and a second photosensitive drum from the second mounting portion. A second elastic portion having elasticity and a second contact portion that protrudes from the tip of the second elastic portion toward the outer peripheral surface of the second photosensitive drum and contacts the second photosensitive drum. . In this case, the first urging member may be composed of a first elastic portion and a first contact portion, and the second urging member may be composed of a second elastic portion and a second contact portion. Further, the first protrusion amount of the first contact portion toward the first photosensitive drum may be longer than the second protrusion amount of the second contact portion toward the second photosensitive drum.

  According to such a configuration, the first contact portion of the first bearing member that supports the first photosensitive drum that is disposed on the most upstream side in the transport direction supports the second photosensitive drum that is disposed on the downstream side. It is longer than the 2nd contact part of 2 bearing members.

  Therefore, the 1st elastic part of the 1st bearing member can be bent more largely than the 2nd elastic part of the 2nd bearing member.

As a result, it is possible to position the first photosensitive drum with a larger biasing force than the second photosensitive drum.
(3) The side plate has a first support hole for supporting the end portion of the first photosensitive drum via the first bearing member, and a second support for supporting the end portion of the second photosensitive drum via the second bearing member. You may have a hole. Each of the first support hole and the second support hole may have a first positioning surface and a second positioning surface extending in different directions. In this case, the first positioning portion is composed of the front 1 positioning surface and the second positioning surface of the first support hole, and the second positioning portion is composed of the first positioning surface and the second positioning surface of the second support hole. May be. The first contact portion projects in a direction between the first positioning surface and the second positioning surface of the first support hole, and the second contact portion includes the first positioning surface and the second positioning surface of the second support hole. You may protrude in the direction going between.

  According to such a configuration, the first contact portion of the first bearing member can press the end of the first photosensitive drum against the first positioning surface and the second positioning surface of the first support hole, and the second The end of the second photosensitive drum can be pressed against the first positioning surface and the second positioning surface of the second support hole by the second contact portion of the bearing member.

  Accordingly, the respective end portions of the first photosensitive drum and the second photosensitive drum can be positioned in two different directions by the first positioning surface and the second positioning surface.

As a result, the first photosensitive drum and the second photosensitive drum can be accurately positioned with respect to the side plate.
(4) The protruding direction of the first contact portion and the second contact portion may be a direction closer to the transport belt as it goes downstream in the transport direction.

According to such a configuration, the recording medium passing between the first photosensitive drum and the second photosensitive drum and the conveyance belt can be smoothly pressed against the conveyance belt.
(5) The image forming apparatus of the present invention may further include a support member that supports the first photosensitive drum and the second photosensitive drum.

According to such a configuration, the first photosensitive drum and the second photosensitive drum can be integrally operated by the support member.
(6) An image forming apparatus according to the present invention includes an apparatus main body, a conveyor belt, a first process cartridge, a second process cartridge, a first positioning unit, a second positioning unit, a first biasing member, A second urging member. The conveyance belt is configured to convey the recording medium within the apparatus main body. The first process cartridge is positioned on the uppermost stream side in the conveyance direction of the recording medium by the conveyance belt, and includes a first photosensitive drum. The second process cartridge includes a second photosensitive drum disposed in parallel with the first photosensitive drum, and is located downstream in the transport direction with respect to the first process cartridge. The first positioning unit positions the first process cartridge with respect to the apparatus main body. The second positioning unit positions the second process cartridge with respect to the apparatus main body. The first urging member is configured to urge the first process cartridge toward the first positioning portion. The second urging member is configured to urge the second process cartridge toward the second positioning portion.

  The biasing force of the first biasing member is greater than the biasing force of the second biasing member.

  According to such a configuration, the first process cartridge arranged at the uppermost stream in the conveyance direction of the recording medium is applied to the apparatus main body with a larger urging force than the second process cartridge arranged downstream from the first process cartridge. Can be positioned.

  Thereby, shakiness of the 1st photosensitive drum arrange | positioned in the conveyance direction most upstream can be suppressed.

  Further, by suppressing the rattling of the first photosensitive drum arranged at the most upstream in the conveying direction, the recording medium can be smoothly conveyed to the second photosensitive drum arranged downstream of the first photosensitive drum. Therefore, rattling of the second photosensitive drum can be suppressed.

  As a result, rattling of the first photosensitive drum and the second photosensitive drum can be suppressed.

  According to the image forming apparatus of the present invention, shakiness of the first photosensitive drum and the second photosensitive drum can be suppressed.

FIG. 1 is a central cross-sectional view of a printer showing a first embodiment of an image forming apparatus of the present invention. FIG. 2 is a perspective view of the drum unit shown in FIG. FIG. 3 is an explanatory view for explaining the support of the photosensitive drum with respect to the inner plate shown in FIG. 4A is a perspective view of the left bearing shown in FIG. 3 as viewed from the front right. 4B is a perspective view of the left bearing shown in FIG. 3 as viewed from the left rear. FIG. 5A is a perspective view of the right bearing shown in FIG. 3 as viewed from the left rear. FIG. 5B is a perspective view of the right bearing shown in FIG. 3 as viewed from the front right. FIG. 6A is a left side view of the left bearing corresponding to the yellow photosensitive drum. FIG. 6B is a left side view of a left bearing corresponding to magenta, cyan, and black photosensitive drums. FIG. 7 is a right side view showing a state where the left flange member of the photosensitive drum is inserted into the left bearing shown in FIG. 4A. FIG. 8A is a cross-sectional view taken along the line AA of FIG. 7 and corresponds to a yellow photosensitive drum. FIG. 8B is an enlarged view of a main part of FIG. 8A. FIG. 9A is a cross-sectional view taken along the line AA in FIG. 7 and corresponds to magenta, cyan, and black photosensitive drums. FIG. 9B is an enlarged view of a main part of FIG. 9A. FIG. 10 is an explanatory diagram illustrating a modified example of the printer.

1. Overall Configuration of Printer As shown in FIG. 1, a printer 1 as an example of an image forming apparatus is a horizontal type direct tandem color laser printer.

  In the following description, when referring to the direction, the state in which the printer 1 is placed horizontally is used as the upper and lower reference. That is, the upper side of the drawing in FIG. 1 is the upper side, and the lower side of the drawing in FIG. 1 is the lower side. Further, the left side of FIG. 1 is the front, and the right side of FIG. 1 is the rear. In addition, when the printer 1 is viewed from the front, the left and right reference is used. That is, the front side of the page of FIG. 1 is the right side, and the back side of the page is the left side. The front-rear direction is an example of the transport direction.

  The printer 1 includes a main body casing 2 as an example of an apparatus main body, a process unit 3, a scanner unit 4, a transfer unit 5, and a fixing unit 6.

  The main casing 2 is formed in a substantially box shape. The main casing 2 includes a paper feed tray 7 and a paper discharge tray 8.

  The paper feed tray 7 is disposed at the bottom of the main casing 2. The paper feed tray 7 is configured to accommodate paper P as an example of a recording medium.

  The paper discharge tray 8 is disposed on the front half of the upper wall of the main casing 2. The paper discharge tray 8 is recessed downward from the upper surface of the main casing 2 so that the paper P is placed thereon.

  The process unit 3 is disposed in the center of the main casing 2. The process unit 3 includes a drum unit 9 as an example of a support member and a plurality of developing cartridges 10.

  The drum unit 9 includes a plurality of photosensitive drums 11 and a plurality of scorotron chargers 12.

  Each of the plurality of photosensitive drums 11 is rotatably supported at the lower end portion of the process unit 3. Each of the plurality of photosensitive drums 11 corresponds to each of yellow, magenta, cyan, and black. Each of the plurality of photosensitive drums 11 is arranged in parallel at an interval in the order of yellow, magenta, cyan, and black from the front to the rear. The yellow photosensitive drum 11Y is disposed at the forefront of each of the plurality of photosensitive drums 11, and is an example of a first photosensitive drum. The magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K are arranged behind the yellow photosensitive drum 11Y, and are examples of the second photosensitive drum. Each of the plurality of photosensitive drums 11 has a substantially cylindrical shape extending in the left-right direction.

  Each of the plurality of scorotron chargers 12 corresponds to each of the plurality of photosensitive drums 11, and is disposed above and behind the corresponding photosensitive drum 11 at an interval.

  Each of the plurality of developing cartridges 10 corresponds to each of the plurality of photosensitive drums 11 and is disposed above the corresponding photosensitive drum 11. Each of the plurality of developing cartridges 10 includes a developing roller 13 and a supply roller 14. The developing cartridge 10 contains toner corresponding to each color in a space above the developing roller 13 and the supply roller 14.

  The developing roller 13 is rotatably supported at the lower end portion of the developing cartridge 10 so as to be exposed rearward. Further, the developing roller 13 is in contact with the front upper end portion of the photosensitive drum 11.

  The supply roller 14 is disposed on the front upper side of the developing roller 13. The supply roller 14 is in contact with the front upper end portion of the developing roller 13.

  The scanner unit 4 is disposed at the upper end portion of the main body casing 2. As indicated by an arrow in FIG. 1, the scanner unit 4 emits a laser beam toward the photosensitive drum 11 based on the image data to expose the photosensitive drum 11.

  The transfer unit 5 is disposed below the process unit 3. The transfer unit 5 includes a driving roller 15, a driven roller 16, a conveyance belt 17, and a plurality of transfer rollers 18.

  The drive roller 15 is disposed at the rear end portion of the transfer unit 5.

  The driven roller 16 is disposed at the front end portion of the transfer unit 5 so as to be opposed to the front side of the driving roller 15 with a space therebetween.

  The conveyor belt 17 is wound around the driving roller 15 and the driven roller 16 so that the upper portion thereof is in contact with all the photosensitive drums 11. The conveyor belt 17 is moved by the drive of the driving roller 15 and the driven roller 16 so that the upper portion thereof moves from the front toward the rear.

  Each of the plurality of transfer rollers 18 corresponds to each of the plurality of photosensitive drums 11, and is disposed below the corresponding photosensitive drum 11 with the upper portion of the conveyance belt 17 interposed therebetween.

  The fixing unit 6 is disposed behind the transfer unit 5 and includes a heating roller 19 and a pressure roller 20 that contacts the heating roller 19.

  When the printer 1 starts an image forming operation, the scorotron charger 12 uniformly charges the surface of the photosensitive drum 11. Thereafter, the scanner unit 4 exposes the surface of the photosensitive drum 11. Thereby, an electrostatic latent image based on the image data is formed on the surface of the photosensitive drum 11.

  The supply roller 14 supplies the toner in the developing cartridge 10 to the developing roller 13. At this time, the toner is frictionally charged positively between the developing roller 13 and the supply roller 14 and is carried on the developing roller 13.

  The developing roller 13 supplies the carried toner to the electrostatic latent image on the surface of the photosensitive drum 11. As a result, the toner image is carried on the surface of the photosensitive drum 11.

  The paper P is transported forward and upward from the paper feed tray 7 by the rotation of various rollers, and then U-turns rearward and upward, one by one at a predetermined timing, between the yellow photosensitive drum 11Y and the transport belt 17. Paper is fed in between. Thereafter, the paper P is transported from the front to the rear by the transport belt 17. The toner image on the photosensitive drum 11 is transferred to the paper P when the paper P passes between the photosensitive drum 11 and the transfer roller 18.

Thereafter, the sheet P is heated and pressed when it passes between the heating roller 19 and the pressure roller 20. At this time, the toner image on the paper P is thermally fixed to the paper P. Thereafter, the paper P is discharged to the paper discharge tray 8.
2. Details of the Drum Unit As shown in FIGS. 2 and 3, the drum unit 9 includes a frame 31 and a plurality of bearings 30 in addition to the plurality of photosensitive drums 11 and the plurality of scorotron chargers 12 described above.
(1) Frame The frame 31 includes an inner plate 32 as an example of a pair of side plates, a pair of outer plates 33, a front plate 34, and a rear plate 35.

  Each of the pair of inner plates 32 is disposed at each of both ends in the left-right direction of the frame 31 with a space in the left-right direction. Each of the pair of inner plates 32 has a substantially rectangular flat plate shape in a side view that is long in the front-rear direction. Each of the pair of inner plates 32 is obtained by pressing a metal plate using the same press die and has the same shape. Each of the pair of inner plates 32 has a plurality of through holes 36 and a plurality of engaging portions 37.

  Each of the plurality of through holes 36 is arranged at equal intervals in the front-rear direction. Each of the plurality of through holes 36 is specifically arranged in correspondence with each of the plurality of photosensitive drums 11. The through hole 36 corresponding to the yellow photosensitive drum 11Y is an example of a first support hole. The through holes 36 corresponding to the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K are examples of second support holes. Each of the plurality of through holes 36 has a substantially circular shape in a side view. Each inner surface of the plurality of through holes 36 has a plurality of flat surfaces 38 and a plurality of curved surfaces 39 as shown in FIG.

  Each of the plurality of flat surfaces 38 is arranged at each of the front end portion, the rear end portion, the upper end portion, and the lower end portion of the through hole 36. Each of the front plane 38F and the rear plane 38R extends in the vertical direction. The rear plane 38R is an example of a first positioning surface. Each of the upper plane 38U and the lower plane 38L extends in the front-rear direction. The lower plane 38L is an example of a second positioning surface. The rear plane 38R and the lower plane 38L of the through hole 36 corresponding to the yellow photosensitive drum 11Y constitute a first positioning portion. The rear plane 38R and the lower plane 38L of the through hole 36 corresponding to the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K constitute a second positioning portion.

  Each of the plurality of curved surfaces 39 is disposed on each of the front upper end, the front lower end, the rear upper end, and the rear lower end of the through hole 36. The front upper curved surface 39 has a substantially arc shape that is recessed forward and upward, and connects the upper plane 38U and the front plane 38F. The front lower curved surface 39 has a substantially arc shape that is recessed forward and lower, and connects the lower plane 38L and the front plane 38F. The rear upper curved surface 39 has a substantially arc shape that is recessed rearward and upward, and connects the upper plane 38U and the rear plane 38R. The rear lower curved surface 39 has a substantially arc shape that is recessed rearward and lower, and connects the lower plane 38L and the rear plane 38R.

  The plurality of engaging portions 37 have a plurality of upper engaging portions 37A and a plurality of lower engaging portions 37B.

  Each of the plurality of upper engagement portions 37 </ b> A is disposed above each of the plurality of through holes 36. Each of the plurality of upper engaging portions 37 </ b> A is a concave portion that is notched downward from the upper end edge of the inner plate 32. Each of the plurality of upper engaging portions 37A has a substantially rectangular shape in side view.

  Each of the plurality of lower engaging portions 37 </ b> B is disposed below each of the plurality of through holes 36. Each of the plurality of lower engaging portions 37 </ b> B is a concave portion that is notched upward from the lower end edge of the inner plate 32. Each of the plurality of lower engaging portions 37B has a substantially rectangular shape in side view.

  As shown in FIG. 2, each of the pair of outer plates 33 is disposed outward in the left-right direction of each of the pair of inner plates 32. Each of the pair of outer plates 33 is made of resin and has a substantially rectangular flat plate shape in side view that is wider in the vertical direction than each of the pair of inner plates 32.

  The front plate 34 is disposed at the front end portion of the frame 31. The front plate 34 has a substantially rectangular flat plate shape that is long in the left-right direction. The front plate 34 is constructed between the front end portions of the pair of inner plates 32.

The rear plate 35 is disposed at the rear end portion of the frame 31. The rear plate 35 has a substantially rectangular flat plate shape that is long in the left-right direction. The rear plate 35 is constructed between the rear end portions of the pair of inner plates 32.
(2) Photosensitive drum Each of the plurality of photosensitive drums 11 includes a drum body 41 and a pair of flange members 42 as shown in FIGS. 3, 8A and 9A.

  The drum main body 41 has a substantially cylindrical shape extending left and right.

  Each of the pair of flange members 42 is fitted to the left and right ends of the drum body 41 so as not to be relatively rotatable. Each of the pair of flange members 42 includes a large diameter portion 43 and a small diameter portion 44. The left flange member 42 has a drum coupling 45.

  The large diameter portion 43 is disposed at the inner end in the left-right direction of the flange member 42. The large-diameter portion 43 has a substantially cylindrical shape whose outer end in the left-right direction is closed. The outer diameter of the large diameter portion 43 is substantially the same as the inner diameter of the drum body 41. The large diameter portion 43 is inserted into the drum body 41.

  The small-diameter portion 44 protrudes outward in the left-right direction from the left-right outer wall of the large-diameter portion 43. The small diameter portion 44 has a substantially cylindrical shape sharing the central axis with the large diameter portion 43. The outer diameter of the small diameter portion 44 is smaller than the outer diameter of the large diameter portion 43.

  The drum coupling 45 is disposed at the left end of the small diameter portion 44 of the left flange member 42. The drum coupling 45 has a substantially disk shape and closes the left end portion of the small diameter portion 44 of the left flange member 42. The drum coupling 45 has a plurality of engaging recesses 46.

Each of the plurality of engaging recesses 46 is specifically arranged at the peripheral edge of the drum coupling 45 at intervals in the circumferential direction. Each of the plurality of engaging recesses 46 is recessed from the left surface of the drum coupling 45 to the right. Each of the plurality of engaging recesses 46 has a substantially rectangular shape in side view. Each of the plurality of engaging recesses 46 receives the engaging protrusion 72 of the main body coupling 71 in the main body casing 2 (see FIGS. 8A and 9A).
(3) Bearings The plurality of bearings 30 includes a plurality of left bearings 30L and a plurality of right bearings 30R.
(3-1) Left Bearing Each of the plurality of left bearings 30L specifically corresponds to each of the plurality of photosensitive drums 11 on the left side of the left inner plate 32, as shown in FIG. Four are arranged. The left bearing 30L corresponding to the yellow photosensitive drum 11Y is an example of a first bearing member. The left bearing 30L corresponding to the magenta photosensitive drum 11M, the left bearing 30L corresponding to the cyan photosensitive drum 11C, and the left bearing 30L corresponding to the black photosensitive drum 11K are examples of second bearing members. Each of the plurality of left bearings 30L includes a cylindrical portion 61 and a flange portion 62 as shown in FIGS. 4A and 4B.

  The cylinder part 61 has a substantially cylindrical shape extending left and right. The cylindrical part 61 is open at both left and right ends. The cylindrical portion 61 of the left bearing 30L corresponding to the yellow photosensitive drum 11Y is an example of a first mounting portion. The left bearing 30L corresponding to the magenta photosensitive drum 11M, the left bearing 30L corresponding to the cyan photosensitive drum 11C, and the cylindrical portion 61 of the left bearing 30L corresponding to the black photosensitive drum 11K are examples of second mounting portions. is there. The inner diameter of the cylindrical portion 61 is substantially the same as the outer diameter of the small diameter portion 44 of the flange member 42. The outer diameter of the cylindrical portion 61 is substantially the same as the inner diameter of the through hole 36 of the inner plate 32. The cylinder part 61 has a recess 65, an elastic part 63, and a protruding part 66.

  The recess 65 is disposed at the front upper end of the tube portion 61. The recessed portion 65 is recessed from the right end edge of the cylindrical portion 61 toward the left. The recess 65 has a substantially U-shape with the right end opened.

  The elastic part 63 is disposed in the recess 65. The elastic portion 63 has a substantially flat plate shape extending from the bottom surface of the recess 65, that is, from the left inner surface to the right, along the outer peripheral surface of the corresponding photosensitive drum 11. Both end edges of the elastic portion 63 in the circumferential direction of the cylindrical portion 61 are opposed to the inner surface of the concave portion 65 in the circumferential direction of the cylindrical portion 61 with a space therebetween. The elastic part 63 of the left bearing 30L corresponding to the yellow photosensitive drum 11Y is an example of a first elastic part. The elastic part 63 of the left bearing 30L corresponding to the magenta photosensitive drum 11M, the elastic part 63 of the left bearing 30L corresponding to the cyan photosensitive drum 11C, and the elastic part 63 of the left bearing 30L corresponding to the black photosensitive drum 11K This is an example of a second elastic part.

  The protruding portion 66 is disposed at the right end portion of the elastic portion 63. The protruding portion 66 protrudes from the inner peripheral surface of the elastic portion 63, that is, the rear lower surface, radially inward of the cylindrical portion 61, that is, rearward and downward, and extends in the circumferential direction of the cylindrical portion 61. The protrusion 66 of the left bearing 30L corresponding to the yellow photosensitive drum 11Y is an example of a first contact portion, and constitutes a first urging member together with the elastic portion 63 of the left bearing 30L corresponding to the yellow photosensitive drum 11Y. To do. The protrusion 66 of the left bearing 30L corresponding to the magenta photosensitive drum 11M, the protrusion 66 of the left bearing 30L corresponding to the cyan photosensitive drum 11C, and the protrusion 66 of the left bearing 30L corresponding to the black photosensitive drum 11K. Each of them is an example of a second contact portion, and an elastic portion 63 of the left bearing 30L corresponding to the magenta photosensitive drum 11M, an elastic portion 63 of the left bearing 30L corresponding to the cyan photosensitive drum 11C, and a black photosensitive member. A second urging member is configured together with each of the elastic portions 63 of the left bearing 30L corresponding to the drum 11K.

  Here, as shown in FIG. 6A, FIG. 6B, FIG. 8B and FIG. 9B, the protrusion length as the first protrusion amount of the protrusion 66 of the left bearing 30L corresponding to the yellow photosensitive drum 11Y, The length L2 in the direction connecting the rear and lower sides is the protrusion length as the second protrusion amount of the protrusion 66 of the left bearing 30L corresponding to each of the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K. That is, it is longer than the length L1 in the direction connecting the front upper side and the rear lower side.

  As shown in FIGS. 4A and 4B, the flange portion 62 projects radially outward from the outer peripheral surface at the center in the left-right direction of the cylindrical portion 61 and extends in the circumferential direction of the cylindrical portion 61. The collar portion 62 has a substantially annular shape. The flange portion 62 has a pair of engaging portions 64.

Each of the pair of engaging portions 64 is disposed on the upper end portion and the lower end portion of the flange portion 62 one by one. The upper engaging portion 64 protrudes upward from the upper end edge of the flange portion 62 and is bent rightward. The lower engaging portion 64 protrudes downward from the lower end edge of the flange portion 62 and is bent rightward.
(3-2) Right Bearing As shown in FIG. 3, each of the plurality of right bearings 30 </ b> R specifically corresponds to each of the plurality of photosensitive drums 11 on the left side of the right inner plate 32. Four are arranged. The right bearing 30R corresponding to the yellow photosensitive drum 11Y is an example of a first bearing member. The right bearing 30R corresponding to the magenta photosensitive drum 11M, the right bearing 30R corresponding to the cyan photosensitive drum 11C, and the right bearing 30R corresponding to the black photosensitive drum 11K are examples of second bearing members. Each of the plurality of right bearings 30R includes a cylindrical portion 51 and a flange portion 52, as shown in FIGS. 5A and 5B.

  The cylinder part 51 has a substantially cylindrical shape extending left and right. As for the cylinder part 51, the left end part is open | released and the right end part is closed. The cylindrical portion 51 of the right bearing 30R corresponding to the yellow photosensitive drum 11Y is an example of a first mounting portion. The right bearing 30R corresponding to the magenta photosensitive drum 11M, the right bearing 30R corresponding to the cyan photosensitive drum 11C, and the cylindrical portion 51 of the right bearing 30R corresponding to the black photosensitive drum 11K are examples of second mounting portions. is there. The inner diameter of the cylindrical portion 51 is substantially the same as the outer diameter of the small diameter portion 44 of the flange member 42. The outer diameter of the cylindrical portion 51 is substantially the same as the inner diameter of the through hole 36 of the inner plate 32. The cylinder part 51 has a recess 55, an elastic part 53, and a protruding part 56.

  The concave portion 55 is disposed at the front upper end portion of the cylindrical portion 51. The recessed part 55 is recessed from the left end edge of the cylinder part 51 toward the right. The recess 55 has a substantially U-shape with the left end opened.

  The elastic part 53 is disposed in the recess 55. The elastic portion 53 has a substantially flat plate shape extending from the bottom surface of the concave portion 55, that is, from the right inner surface toward the left. Both end edges of the elastic portion 53 in the circumferential direction of the cylindrical portion 51 are opposed to the inner surface of the concave portion 55 in the circumferential direction of the cylindrical portion 51 with a space therebetween. The elastic part 53 of the right bearing 30R has the same shape as the elastic part 63 of the left bearing 30L. That is, the width of the elastic portion 53 of the right bearing 30R, that is, the circumferential dimension is the same as the width of the elastic portion 63 of the left bearing 30L. The thickness of the elastic portion 53 of the right bearing 30R, that is, the radial dimension is the same as the thickness of the elastic portion 63 of the left bearing 30L. Further, the left-right dimension of the elastic part 53 of the right bearing 30R is the same as the left-right dimension of the elastic part 63 of the left bearing 30L. The elastic portion 53 of the right bearing 30R corresponding to the yellow photosensitive drum 11Y is an example of a first urging member and a first elastic portion. The elastic part 53 of the right bearing 30R corresponding to the magenta photosensitive drum 11M, the elastic part 53 of the right bearing 30R corresponding to the cyan photosensitive drum 11C, and the elastic part 53 of the right bearing 30R corresponding to the black photosensitive drum 11K FIG. 3 is an example of a second urging member and a second elastic portion.

  The protruding portion 56 is disposed at the left end portion of the elastic portion 53. The projecting portion 56 projects from the inner peripheral surface of the elastic portion 53, that is, the rear lower surface, radially inward of the cylindrical portion 51, that is, rearward and downward, and extends in the circumferential direction of the cylindrical portion 51. The protrusion 56 of the right bearing 30R corresponding to the yellow photosensitive drum 11Y is an example of a first contact portion, and constitutes a first biasing member together with the elastic portion 53 of the right bearing 30R corresponding to the yellow photosensitive drum 11Y. . The protrusion 56 of the right bearing 30R corresponding to the magenta photosensitive drum 11M, the protrusion 56 of the right bearing 30R corresponding to the cyan photosensitive drum 11C, and the protrusion 56 of the right bearing 30R corresponding to the black photosensitive drum 11K. Each is an example of the second contact portion, and the elastic portion 53 of the right bearing 30R corresponding to the magenta photosensitive drum 11M, the elastic portion 53 of the right bearing 30R corresponding to the cyan photosensitive drum 11C, and the black photosensitive drum. A second urging member is configured together with each of the elastic portions 53 of the right bearing 30R corresponding to 11K.

  Here, the protruding length of the protruding portion 56 of the right bearing 30R is the same as the protruding length of the protruding portion 66 of the left bearing 30L. That is, the projecting length as the first projecting amount of the projecting portion 56 of the right bearing 30R corresponding to the yellow photosensitive drum 11Y corresponds to each of the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K. This is longer than the protruding length as the second protruding amount of the protruding portion 56 of the right bearing 30R.

  The flange portion 52 projects radially outward from the outer peripheral surface at the center in the left-right direction of the cylindrical portion 51 and extends in the circumferential direction of the cylindrical portion 51. The collar portion 52 has a substantially annular shape. The flange portion 52 has a pair of engaging portions 54.

Each of the pair of engaging portions 54 is disposed on the upper end portion and the lower end portion of the flange portion 52 one by one. The upper engaging portion 54 protrudes upward from the upper end edge of the flange portion 52 and is bent rightward. The right end portion of the upper engaging portion 54 has a hook shape protruding downward. The lower engaging portion 54 protrudes downward from the lower end edge of the flange portion 52 and is bent rightward. The right end portion of the lower engaging portion 54 has a hook shape protruding upward.
3. Assembling State of Photosensitive Drum As shown in FIGS. 3 and 7, the left end portion of the cylindrical portion 61 of the left bearing 30 </ b> L is fitted in the through hole 36 of the left inner plate 32. The upper engaging portion 64 of the left bearing 30 </ b> L is engaged with the upper engaging portion 37 of the left inner plate 32. The lower engaging portion 64 of the left bearing 30 </ b> L is engaged with the lower engaging portion 37 of the left inner plate 32. Thereby, the left bearing 30L is supported by the left inner plate 32 so as not to be relatively rotatable.

  Further, the front end portion of the cylindrical portion 61 of the left bearing 30 </ b> L is in contact with the flat surface 38 </ b> F in front of the through hole 36. The rear end portion of the cylindrical portion 61 of the left bearing 30L is in contact with the flat surface 38R behind the through hole 36. The upper end portion of the cylindrical portion 61 of the left bearing 30L is in contact with the flat surface 38U above the through hole 36. The lower end portion of the cylindrical portion 61 of the left bearing 30L is in contact with the flat surface 38L below the through hole 36. Further, the outer peripheral surface of the cylindrical portion 61 of the left bearing 30 </ b> L is spaced from the curved surface 39.

  The small diameter portion 44 of the left flange member 42 of the photosensitive drum 11 is fitted in the cylindrical portion 61 of the left bearing 30L so as to be relatively rotatable. Thus, the left end portion of the photosensitive drum 11 is supported by the left inner plate 32 through the left bearing 30L so as to be relatively rotatable.

  Here, the small-diameter portion 44 of the left flange member 42 of the photosensitive drum 11 is in contact with the inner peripheral surface 61A at the rear lower side of the cylindrical portion 61 of the left bearing 30L.

  Further, the protruding portion 66 of the left bearing 30L is in contact with the outer peripheral surface of the small diameter portion 44 of the left flange member 42 of the photosensitive drum 11 as shown in FIGS. 7, 8B and 9B. The elastic part 63 of the left bearing 30 </ b> L is bent so that the right end moves forward and upward by the protrusion length of the protrusion 66. That is, the elastic portion 63 of the left bearing 30L causes the small-diameter portion 44 of the left flange member 42 of the photosensitive drum 11 to move against the inner peripheral surface 61A below the rear portion of the cylindrical portion 61 of the left bearing 30L. Energized. Thus, the photosensitive drum 11 is pressed between the rear plane 38R and the lower plane 38L of the left inner plate 32 via the left bearing 30L, and the left inner plate 32 in the radial direction thereof. Is positioned with respect to the rear plane 38R and the lower plane 38L.

  More specifically, the elastic portion 63 of the left bearing 30L corresponding to the yellow photosensitive drum 11Y is the elasticity of the left bearing 30L corresponding to each of the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K. It is bent larger than the part 63.

  Accordingly, the elastic portion 63 of the left bearing 30L corresponding to the yellow photosensitive drum 11Y is more than the elastic portion 63 of the left bearing 30L corresponding to each of the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K. With a large biasing force, the yellow photosensitive drum 11Y is biased against the inner peripheral surface 61A on the rear lower side of the cylindrical portion 61 of the corresponding left bearing 30L.

  Further, as shown in FIG. 3, the right end portion of the cylindrical portion 51 of the right bearing 30 </ b> R is fitted in the through hole 36 of the right inner plate 32. The upper engaging portion 54 of the right bearing 30 </ b> R is engaged with the upper engaging portion 37 of the right inner plate 32. The lower engaging portion 54 of the right bearing 30 </ b> R is engaged with the lower engaging portion 37 of the right inner plate 32. Thus, the right bearing 30R is supported by the right inner plate 32 so as not to be relatively rotatable.

  The small diameter portion 44 of the right flange member 42 of the photosensitive drum 11 is fitted in the cylindrical portion 51 of the right bearing 30R so as to be relatively rotatable. Thus, the right end portion of the photosensitive drum 11 is supported by the right inner plate 32 through the right bearing 30R so as to be relatively rotatable.

  Although not shown, the small diameter portion 44 of the right flange member 42 of the photosensitive drum 11 is similar to the small diameter portion 44 of the left flange member 42 on the inner peripheral surface below the rear portion of the cylindrical portion 51 of the right bearing 30R. Touching.

  Further, the protruding portion 56 of the right bearing 30R is in contact with the outer peripheral surface of the small diameter portion 44 of the right flange member 42 of the photosensitive drum 11 in the same manner as the protruding portion 66 of the left bearing 30L. The elastic portion 53 of the right bearing 30 </ b> R is bent so that the left end portion moves forward and upward by the protruding length of the protruding portion 56. That is, the elastic portion 53 of the right bearing 30R attaches the small diameter portion 44 of the flange member 42 on the right side of the photosensitive drum 11 to the inner peripheral surface of the lower portion of the cylindrical portion 51 of the right bearing 30R. It is fast. Accordingly, the photosensitive drum 11 is pressed between the rear plane 38R and the lower plane 38L of the right inner plate 32 via the right bearing 30R, and the right inner plate 32 in the radial direction thereof. Is positioned with respect to the rear plane 38R and the lower plane 38L.

  More specifically, the elastic portion 53 of the right bearing 30R corresponding to the yellow photosensitive drum 11Y is the elasticity of the right bearing 30R corresponding to each of the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K. It is bent larger than the portion 53.

Accordingly, the elastic portion 53 of the right bearing 30R corresponding to the yellow photosensitive drum 11Y is more than the elastic portion 53 of the right bearing 30R corresponding to each of the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K. With a large biasing force, the yellow photosensitive drum 11Y is biased against the inner peripheral surface of the corresponding lower portion of the cylindrical portion 51 of the right bearing 30R.
4). In the state where the sheet transport process unit is mounted in the main body casing 2 during image formation, as shown in FIGS. 8A and 9A, the engagement protrusion 72 of the main body coupling 71 in the main body casing 2 is formed by the photosensitive drum. 11 is engaged with the engaging recess 46 of the drum coupling 45. Thereby, the main body coupling 71 and the drum coupling 45 are connected to each other so as not to be relatively rotatable.

  At this time, the main body coupling 71 presses the drum coupling 45 to the right, and the photosensitive drum 11 is pressed against the right inner plate 32 via the right bearing 30R. Thus, the photosensitive drum 11 is positioned on the right inner plate 32 via the right bearing 30R in the left-right direction.

  When the above-described image forming operation is performed, the paper P is supplied between the yellow photosensitive drum 11Y and the conveyance belt 17 as shown in FIG.

  At this time, when the leading edge of the paper P is changed to the yellow photosensitive drum 11Y, a front-upward impact may be applied to the yellow photosensitive drum 11Y.

  Here, since the yellow photosensitive drum 11Y is more strongly biased rearward and downward by the corresponding left bearing L and right bearing R, rattling is suppressed when an impact is applied due to a collision with the paper P. Is done.

  Thereafter, the paper P is supplied between the magenta photosensitive drum 11 </ b> M and the conveyance belt 17.

  At this time, the leading edge of the sheet P is in close contact with the upper surface of the conveyance belt 17 when passing between the yellow photosensitive drum 11K and the conveyance belt 17, and in this state, the magenta photosensitive drum 11M and the conveyance belt 17 Supplied during.

  Therefore, when the paper P is supplied between the magenta photosensitive drum 11M and the conveyance belt 17, the leading edge of the paper P is smoothly supplied between the magenta photosensitive drum 11M and the conveyance belt 17, and the leading edge of the paper P is supplied. And the magenta photosensitive drum 11 </ b> M contact with each other is reduced as compared with the case where the leading edge of the paper P is supplied between the yellow photosensitive drum 11 </ b> Y and the conveyance belt 17.

  Thereby, rattling of the magenta photosensitive drum 11M can also be suppressed.

  Similarly, rattling of the cyan photosensitive drum 11C and the black photosensitive drum 11K can be suppressed.

Thus, in the above-described image forming operation, shakiness of a plurality of photosensitive drums can be suppressed.
5. Operation and Effect (1) According to this printer 1, as shown in FIGS. 8B and 9B, the yellow photosensitive drum 11Y arranged at the most upstream in the transport direction of the paper P, that is, the foremost, is arranged downstream from it. The magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K can be positioned with respect to the inner plate 32 with a larger urging force.

  As a result, the rattling of the yellow photosensitive drum 11Y can be suppressed.

  Further, by suppressing the rattling of the yellow photosensitive drum 11Y, the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K that are disposed downstream of the yellow photosensitive drum 11Y are smooth. Further, the paper P can be conveyed, and rattling of the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K can be suppressed.

As a result, rattling of the plurality of photosensitive drums 11 can be suppressed.
(2) According to the printer 1, as shown in FIGS. 8B and 9B, the protruding lengths L2 of the protruding portions 56 and 66 of the left bearing 30L and the right bearing 30R that support the yellow photosensitive drum 11Y are as follows. It is longer than the projecting length L1 of the protrusions 56 and 66 of the left bearing 30L and the right bearing 30R that support the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K disposed downstream thereof.

  Therefore, the elastic portions 53 and 63 of the left bearing 30L and the right bearing 30R that support the yellow photosensitive drum 11Y are replaced with the left bearing 30L and the right bearing that support the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K. It can be bent larger than the elastic portions 53 and 63 of the bearing 30R.

As a result, the yellow photosensitive drum 11Y can be positioned relative to the inner plate 32 with a larger biasing force than the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K.
(3) Also, according to the printer 1, as shown in FIG. 7, the end portions of the plurality of photosensitive drums 11 are formed in the through holes 36 of the inner plate 32 by the corresponding protrusions 56 and 66 of the bearing 30. It is possible to press against the rear plane 38R and the lower plane 38L.

  Thereby, each edge part of the some photosensitive drum 11 can be positioned in the front-back direction and an up-down direction by the back plane 38R and the lower plane 38L.

As a result, each of the plurality of photosensitive drums 11 can be accurately positioned with respect to the inner plate 32.
(4) Further, according to the printer 1, as shown in FIG. 7, the protrusions 56 and 66 of the bearing 30 are in the direction closer to the transport belt 17 toward the downstream side in the transport direction of the paper P, that is, the rear lower side. Protruding.

Therefore, the paper P passing between each of the plurality of photosensitive drums 11 and the conveyance belt 17 can be smoothly pressed against the conveyance belt 17.
(5) Moreover, according to this printer 1, as shown in FIG. 1, the drum unit 9 which supports the some photosensitive drum 11 is provided.

Therefore, the drum unit 9 can integrally operate the plurality of photosensitive drums 11.
6). Modification A modification of the printer will be described with reference to FIG. In addition, in the printer of the modified example, the same reference numerals are given to the same members as those in the above-described embodiment, and the description thereof is omitted.

  In the above-described embodiment, the printer 1 includes the drum unit 9 including the plurality of photosensitive drums 11 and the plurality of developing cartridges 10 corresponding to the plurality of photosensitive drums 11.

  On the other hand, in this modified example, the printer includes a plurality of process cartridges 81 each having the photosensitive drum 11, specifically, four corresponding to each color. The process cartridge 81 including the yellow photosensitive drum 11Y is an example of a first process cartridge. The process cartridge 81 including the magenta photosensitive drum 11Y, the process cartridge 81 including the cyan photosensitive drum 11C, and the process cartridge 81 including the black photosensitive drum 11K are examples of the second process cartridge. In FIG. 10, one of the plurality of process cartridges 81 is shown for convenience. Although not shown, the process cartridge 81 includes a developing roller 13 and a supply roller 14 and stores toner.

  In the above-described embodiment, the photosensitive drum 11 is pressed rearward and downward toward the transport belt 17 by the elastic portion 53 of the left bearing 30L and the elastic portion 63 of the right bearing 30R.

  On the other hand, in this modification, as shown in FIG. 10, the process cartridge 81 is pressed downward toward the transport belt 17 by the biasing member 82 in the main body casing 2. As a result, the photosensitive drum 11 is pressed downward toward the transport belt 17 and positioned relative to the positioning portion 83 in the main body casing 2. That is, the urging force of the urging member 82 acts on the photosensitive drum 11.

  The urging member 82 corresponding to the yellow process cartridge 81 is an example of a first urging member. The urging member 82 corresponding to the magenta process cartridge 81, the cyan process cartridge 81, and the black process cartridge 81 is an example of a second urging member. The positioning unit 83 corresponding to the yellow process cartridge 81 is an example of a first positioning unit. The positioning unit 83 corresponding to the magenta process cartridge 81, the cyan process cartridge 81, and the black process cartridge 81 is an example of a second positioning unit.

  In this modification, the urging force of the urging member 82 that urges the yellow process cartridge 81 is set larger than the urging force of the urging member 82 that urges the magenta, cyan, and black process cartridges 81. ing.

  According to the modification, the yellow process cartridge 81 disposed in the uppermost stream in the conveyance direction of the paper P, that is, the frontmost process cartridge 81 is biased more than the magenta, cyan, and black process cartridges 81 disposed downstream thereof. Thus, positioning with respect to the main casing 2 can be performed.

  As a result, the rattling of the yellow photosensitive drum 11Y can be suppressed.

  Further, by suppressing the rattling of the yellow photosensitive drum 11Y, the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K that are disposed downstream of the yellow photosensitive drum 11Y are smooth. Further, the paper P can be conveyed, and rattling of the magenta photosensitive drum 11M, the cyan photosensitive drum 11C, and the black photosensitive drum 11K can be suppressed.

  As a result, rattling of the plurality of photosensitive drums 11 can be suppressed.

DESCRIPTION OF SYMBOLS 1 Printer 11Y Yellow photosensitive drum 11M Magenta photosensitive drum 11C Cyan photosensitive drum 11K Black photosensitive drum 30L Left bearing 30R Right bearing 51 Cylindrical part 53 Pressing part 56 Protruding part 61 Cylindrical part 63 Pressing part 66 Protruding part 81 Process cartridge 82 Biasing member 83 Positioning part L1 Projection length L2 Projection length P Paper

Claims (4)

A conveyor belt configured to convey a recording medium;
A first photosensitive drum positioned on the most upstream side in the conveyance direction of the recording medium by the conveyance belt;
A second photosensitive drum disposed in parallel with the first photosensitive drum and positioned downstream in the transport direction with respect to the first photosensitive drum;
A side plate for supporting the first photosensitive drum and the second photosensitive drum, the first positioning portion positioning the first photosensitive drum with respect to the side plate; and the first positioning portion positioning the second photosensitive drum with respect to the side plate. A side plate comprising two positioning parts;
A first bearing member that rotatably supports an end portion of the first photosensitive drum with respect to the side plate; a first mounting portion that is attached to the side plate; and A first elastic portion that extends along the outer peripheral surface and has elasticity, and protrudes from the tip of the first elastic portion toward the outer peripheral surface of the first photosensitive drum with a first protruding amount, and contacts the first photosensitive drum. A first contact portion, which is a first contact portion that presses the first photosensitive drum toward the first positioning portion with a first urging force generated by bending the first elastic portion. A first bearing member;
A second bearing member that rotatably supports an end of the second photosensitive drum with respect to the side plate; a second mounting portion that is attached to the side plate; and A second elastic portion that extends along the outer peripheral surface and has elasticity, and protrudes from the tip of the second elastic portion toward the outer peripheral surface of the second photosensitive drum with a second protrusion amount, and contacts the second photosensitive drum. A second contact portion, wherein the second contact portion presses the second photosensitive drum toward the second positioning portion with a second urging force generated by the second elastic portion being bent. A second bearing member;
With
The first protrusion amount is longer than the second protrusion amount,
The image forming apparatus according to claim 1, wherein the first urging force is larger than the second urging force . The side plate supports a first support hole for supporting an end portion of the first photosensitive drum via the first bearing member, and a second support for supporting an end portion of the second photosensitive drum via the second bearing member. A support hole,
Each of the first support hole and the second support hole has a first positioning surface and a second positioning surface extending in different directions,
The first positioning portion is configured by the first positioning surface and the second positioning surface of the first support hole,
The second positioning portion is configured by the first positioning surface and the second positioning surface of the second support hole,
The first contact portion protrudes in a direction between the first positioning surface and the second positioning surface of the first support hole,
The image forming apparatus according to claim 1, wherein the second contact portion projects in a direction between the first positioning surface and the second positioning surface of the second support hole. 3. The image according to claim 1 , wherein a protruding direction of the first contact portion and the second contact portion is a direction closer to the transport belt as it goes downstream in the transport direction. 4. Forming equipment. The image forming apparatus according to claim 1, further comprising a support member that supports the first photosensitive drum and the second photosensitive drum.

Images