Image forming apparatus

Abstract

To improve relative alignment accuracy between rollers.SOLUTION: An image forming apparatus comprises a first roller, a second roller arranged downstream of the first roller, a third roller arranged downstream of the second roller, a first support member that rotatably supports the first roller, a second support member that rotatably supports the third roller, and a bearing member that rotatably supports an end portion of a rotation shaft in a rotational axis direction of the second roller. The bearing member includes a first positioning portion that positions an end portion of the first support member in the rotational axis direction with respect to a direction orthogonal to the rotational axis direction and a second positioning portion that positions an end portion of the second support member in the rotational axis direction with respect to the direction orthogonal to the rotational axis direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image forming apparatus that forms an image on a sheet.

Background Art

[0002] Image forming apparatuses such as printers and multifunction devices form an image on a sheet while sequentially delivering and conveying the sheet used as a recording material between a plurality of conveying rollers. Patent Document 1 describes an image forming apparatus that forms an image on a sheet while sequentially delivering a sheet set on a feed tray by a pickup roller, a feed roller, a registration roller, a transfer roller, and a discharge roller.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In an image forming apparatus, when the relative alignment accuracy between a plurality of rollers is low, the sheet being conveyed may tilt.

[0005] Therefore, an object of the present invention is to provide an image forming apparatus capable of improving the relative alignment accuracy between rollers.

Means for Solving the Problems

[0006] One aspect of the present invention is an image forming apparatus comprising: a first roller for conveying a sheet; a rotating shaft; a roller body supported on the rotating shaft; a second roller positioned downstream of the first roller in the sheet conveying direction and conveying the sheet; a third roller positioned downstream of the second roller in the sheet conveying direction and conveying the sheet; a first support member that rotatably supports the first roller; a second support member that rotatably supports the third roller; and a bearing member that rotatably supports the end of the rotating shaft in the direction of the rotation axis of the second roller, wherein the bearing member has a first positioning portion that positions the end of the first support member in the direction of the rotation axis with respect to a direction perpendicular to the direction of the rotation axis; and a second positioning portion that positions the end of the second support member in the direction of the rotation axis with respect to a direction perpendicular to the direction of the rotation axis. [Effects of the Invention]

[0007] According to the present invention, the relative alignment accuracy between rollers can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] A cross-sectional view showing a part of an image forming apparatus according to an embodiment. [Figure 3] A schematic diagram showing the support configuration of the roller and guide member according to the embodiment. [Figure 4] A perspective view showing the support configuration of a conveying roller according to an embodiment. [Figure 5] Perspective views (a, b) of the first transport guide and feed roller according to the embodiment. [Figure 6] A perspective view showing the support configuration of the first transport guide according to this embodiment. [Figure 7] A cross-sectional view showing a portion of the first transport guide and frame according to an embodiment. [Figure 8] Perspective views (a, b) of the second transport guide according to the embodiment. [Figure 9]A perspective view showing the support configuration of the second transport guide according to the embodiment. [Figure 10] A perspective view (a) of a third transport guide according to an embodiment and a perspective view (b) showing its support configuration. [Figure 11] A cross-sectional view of an image forming apparatus showing the rear cover in a closed state (a) and in an open state (b) according to the embodiment. [Modes for carrying out the invention]

[0009] The embodiments relating to this disclosure will be described below with reference to the drawings.

[0010] Figure 1 is a schematic diagram of the image forming apparatus 1 according to this embodiment. The image forming apparatus 1 is a monochrome printer that forms a single-color image on a sheet S, which is used as a recording material, by an image forming unit while the sheet S is being transported. A variety of sheet materials of different sizes and materials can be used as the sheet S, including paper such as plain paper and cardboard, plastic film, cloth, sheet materials with surface treatments such as coated paper, and sheet materials with special shapes such as envelopes and index paper.

[0011] The image forming apparatus 1 includes an electrophotographic image forming section 1B, which includes a process unit 110, a laser scanner unit 500, a transfer roller 201, and a fuser 400. The process unit 110 is configured as a cartridge that can be attached to and detached from the main body 1A (housing) of the image forming apparatus 1, comprising a photosensitive drum 111 as an image carrier and one or more process members that act on the photosensitive drum 111.

[0012] Furthermore, the image forming apparatus 1 includes a pickup roller 311, a feed roller 312, a separation roller 313, a transport roller 321, transport rollers 322, 323, a discharge roller 403, and a discharge roller 404 as a mechanism for transporting the sheets S. A sheet storage section 300 (sheet tray) for loading and storing the sheets S is provided at the bottom of the apparatus body 1A. A discharge tray 405 for loading the image-formed sheets S is provided on the top surface of the apparatus body 1A.

[0013] When an execution instruction for image formation (print job) is input to the image forming apparatus 1, the formation of a toner image is started in the image forming unit 1B. That is, in the process unit 110, the photosensitive drum 111 rotates, and a charger uniformly charges the surface of the photosensitive drum 111. The laser scanner unit 500 irradiates the photosensitive drum 111 with laser light based on the image information included in the print job. As a result, the surface of the charged photosensitive drum 111 is exposed, and an electrostatic latent image corresponding to the image information is written. The developing device of the process unit 110 supplies a developer containing toner to the photosensitive drum 111, and visualizes (develops) the electrostatic latent image as a toner image. This toner image is conveyed to the transfer nip Nt, which is the nip portion between the photosensitive drum 111 and the transfer roller 201, by the rotation of the photosensitive drum 111.

[0014] In parallel with the above toner image forming process, sheets S are supplied one by one from the sheet storage unit 300 to the image forming unit 1B. That is, the pickup roller 311 rotates in contact with the uppermost sheet of the sheets S stacked in the sheet storage unit 300, and feeds out the sheet S from the sheet storage unit 300. The sheet S fed out from the sheet storage unit 300 is further conveyed in a state of being separated one by one at the nip portion (separation nip Ns) of the feed roller 312 and the separation roller 313. The sheet S that has passed through the separation nip Ns is sandwiched between the conveyance roller 321 and the conveyance roller 322 at the conveyance nip Nc, and is further conveyed toward the transfer nip Nt.

[0015] Note that the separation roller 313 is an example of a separating member that separates the sheet S by frictional force, and for example, a rubber roller supported via a torque limiter on a shaft fixed to the frame of the apparatus main body 1A can be used. In addition, a retard roller that inputs a driving force in a direction opposite to the moving direction of the peripheral surface of the feed roller 312 at the separation nip Ns via a torque limiter, or a pad-shaped elastic member that abuts on the feed roller 312 may be used as the separating member.

[0016] At the transfer nip Nt, a predetermined bias voltage (transfer voltage) is applied to the transfer roller 201, so that the toner image is transferred from the photosensitive drum 111 to the sheet S. The sheet S onto which the toner image has been transferred is subjected to a fixing process in the fixing device 400. As the fixing device 400, a configuration of a heat fixing method including a first rotating body and a second rotating body that sandwich and convey the sheet S at the fixing nip Nf, and a heating means for heating the image on the sheet S is used. The first rotating body is, for example, a flexible cylindrical film or roller. The second rotating body is, for example, a roller having an elastic layer on its outer peripheral portion. As the heating means, a heater substrate on which a pattern of a heating resistor is formed on a ceramic substrate or a halogen lamp that emits radiant heat can be used.

[0017] The sheet S that has passed through the fixing nip Nf is discharged to the outside of the apparatus main body 1A by a pair of discharge rollers including a discharge roller 403 and a discharge roller 404, and is stacked on a discharge tray 405. The path from the sheet storage unit 300 through a plurality of rollers to the discharge tray 405 is the first conveyance path P1 (main conveyance path) of the image forming apparatus 1.

[0018] When forming images on both sides of the sheet S, the sheet S on which the image has been formed on the first side by the above-described image forming operation is sent to the second conveyance path P2 (double-sided conveyance path, re-conveyance path) by reverse conveyance of the pair of discharge rollers. The second conveyance path P2 branches from the first conveyance path P1 on the downstream side of the fixing nip Nf in the sheet conveyance direction of the first conveyance path P1, and merges with the first conveyance path P1 on the upstream side of the separation nip Ns between the conveyance roller 321 and the conveyance roller 322. The sheet S sent to the second conveyance path P2 is sandwiched and conveyed by the conveyance roller 321 and the conveyance roller 323, and is conveyed back to the first conveyance path P1. Then, after an image is formed on the second side opposite to the first side while the sheet S passes through the transfer nip Nt and the fixing nip Nf, the sheet S is discharged by the pair of discharge rollers.

[0019] (Rollers and Guide Members) Using FIGS. 2 to 10, the rollers and guide members included in the image forming apparatus 1 will be described.

[0020] In the following description, the rotation axis direction of the photosensitive drum 111 is defined as the X-axis direction. The vertical direction (opposite direction to the direction of gravity) when the image forming apparatus 1 is installed on a horizontal plane is defined as the Z-axis direction. The direction perpendicular to the X-axis direction and the Z-axis direction is defined as the Y-axis direction. Preferably, the X-axis direction is perpendicular to the Z-axis direction. The X-axis direction is also the sheet width direction (direction perpendicular to the sheet transport direction) of the sheet transported by the first transport path P1 and the second transport path P2.

[0021] Figure 2 is a cross-sectional view of a part of the image forming apparatus 1, cut in a plane perpendicular to the X-axis direction. Figure 2 shows the arrangement of rollers and guide members located in the section of the first transport path P1 from the sheet storage section 300 to the transfer roller 201.

[0022] As shown in Figure 2, a pickup roller 311, a feed roller 312 and a separation roller 313, a transport roller 321 and a transport roller 322, a photosensitive drum 111 and a transfer roller 201 are arranged along the first transport path P1. With respect to the sheet transport direction in the first transport path P1, the separation nip Ns formed by the feed roller 312 and the separation roller 313 is located downstream of the pickup roller 311. The transport nip Nc formed by the transport roller 321 and the transport roller 322 is located downstream of the separation nip Ns. The transfer nip Nt formed by the photosensitive drum 111 and the transfer roller 201 is located downstream of the transport nip Nc.

[0023] The feed roller 312 is an example of a first roller that conveys a sheet. The conveying roller 321 has a rotating shaft and a roller body supported by the rotating shaft, and is positioned downstream of the first roller in the sheet conveying direction, and is an example of a second roller that conveys the sheet. The transfer roller 201 is an example of a third roller that is positioned downstream of the second roller in the sheet conveying direction, and conveys the sheet. The conveying roller 322 is an example of a fourth roller that contacts the second roller and, together with the second roller, grips and conveys the sheet. Note that the first to fourth rollers are not limited to the examples given here, and may be roller members that convey the sheet at other positions in the image forming apparatus.

[0024] The pickup roller 311, feed roller 312, and photosensitive drum 111 contact the first surface of the sheet S fed from the sheet storage section 300. The separation roller 313, transport roller 321, and transfer roller 201 contact the second surface of the sheet S fed from the sheet storage section 300.

[0025] The pickup roller 311, feed roller 312, and photosensitive drum 111 are each driven to rotate clockwise in the figure by a driving force transmitted from a motor acting as a drive source. The transport roller 321 is driven to rotate counterclockwise in the figure by a driving force transmitted from a motor. The transfer roller 201 and transport roller 322 can be configured to rotate driven by the force they receive from the opposing roller, but they may also be driven to rotate by a driving force transmitted from a drive source.

[0026] Furthermore, as shown in Figure 2, a first conveyor guide 331, a second conveyor guide 332, and a third conveyor guide 333 are arranged along the first conveyor path P1. The first conveyor guide 331 guides the sheet S between the separation nip Ns and the conveyor nip Nc and near the conveyor roller 322. The second conveyor guide 332 guides the sheet S in part of the second conveyor path P2 and near the conveyor roller 321. The third conveyor guide 333 is positioned downstream of the second conveyor guide 332 with respect to the sheet conveying direction in the first conveyor path P1, and guides the sheet S between the conveyor nip Nc and the transfer nip Nt and around the transfer roller 201.

[0027] Parts of the first transport guide 331 and the second transport guide 332 face each other across the first transport path P1 near the transport nip Nc. The first transport guide 331 and the second transport guide 332 can guide the sheet S fed from the sheet storage unit 300 to the transport nip Nc. The third transport guide 333 can guide the sheet that has passed through the transport nip Nc to the transfer nip Nt. The first transport guide 331 guides the first surface of the sheet S fed from the sheet storage unit 300. The second transport guide 332 and the third transport guide 333 guide the second surface of the sheet S fed from the sheet storage unit 300.

[0028] The first transport guide 331 is an example of a first support member that rotatably supports the first roller. The third transport guide 333 is an example of a second support member that rotatably supports the third roller.

[0029] (Summary of support structure) Figure 3 is a schematic diagram (exploded view) showing the support configuration of the first transport guide 331, the second transport guide 332, and the third transport guide 333. In this embodiment, a bearing member 334 that rotatably supports the transport roller 321 supports the first transport guide 331, the second transport guide 332, and the third transport guide 333. The first transport guide 331 supports the feed roller 312 and the transport roller 322. The third transport guide 332 supports the transfer roller 201. As will be explained below, the positions of the feed roller 312 and the transfer roller 201 relative to the transport roller 321 are determined by the positioning of the first transport guide 332 and the third transport guide 333 by the bearing member 334.

[0030] In this embodiment, the support configurations for each transport guide and transport roller 321 are substantially the same on both sides in the X-axis direction (the direction of the rotation axis of the transport roller 321). The following description will explain the support configuration on one side in the X-axis direction, but a corresponding support configuration is also provided on the opposite side in the X-axis direction. For example, in addition to the bearing member 334 and frame 335 shown in Figure 3, one bearing member and frame having the same configuration as the bearing member 334 and frame 335 and a symmetrical shape are each arranged on the opposite side in the X-axis direction.

[0031] (Support configuration for conveyor rollers) The support configuration of the conveyor roller 321 will be explained using Figure 4. Figure 4 is a perspective view showing the support configuration of the conveyor roller 321.

[0032] As shown in Figure 4, the bearing member 334 has a first boss 334b, a second boss 334a, a hole 334c, and a connecting portion 334d. The first boss 334b ​​is the first positioning portion in this embodiment, and the second boss 334a is the second and third positioning portions in this embodiment.

[0033] The first boss 334b ​​and the second boss 334a are projections extending in the X-axis direction and have arcuate surfaces (cylindrical surfaces) extending in the X-axis direction. That is, the hole 334c is formed inside the second boss 334a and extends in the X-axis direction. The second boss 334a and the first boss 334b ​​are spaced apart in a direction intersecting the X-axis direction and are integrally formed via a connecting portion 334d. The second boss 334a and the hole 334c are arranged coaxially (on the rotation axis of the conveyor roller 321). The bearing member 334 is supported by the frame 335.

[0034] The frame 335 has a hole 335a, a square hole 335b, a first groove 335c, a first rib 335d, a second groove 335e, a second rib 335f, and a third rib 335g. The hole 335a and the square hole 335b are through holes that penetrate from the outside to the inside of the frame 335 in the X-axis direction. The first groove 335c and the second groove 335e are groove shapes provided on the inner side surface of the frame 335 in the X-axis direction. The first rib 335d and the second rib 335f are plate-shaped and extend in directions intersecting the X-axis direction (preferably in the Y-axis and Z-axis directions). The frame 335 is fixed to the frame of the device body 1A.

[0035] Frame 335 is an example of a restricting member that restricts the rotation or position of the first support member and the second support member. The first groove 335c is an example of a first rotation restricting part that restricts the rotation of the first support member. The second groove 335e is an example of a second rotation restricting part that restricts the rotation of the second support member. The first rib 335d is an example of a first position restricting part that restricts the position of the first support member in the X-axis direction (the direction of the rotation axis of the second roller). The third rib 335g is an example of a second position restricting part that restricts the position of the second support member in the X-axis direction.

[0036] The position and orientation of the bearing member 334 are restricted by the engagement (fitting) of the second boss 334a of the bearing member 334 with the hole 335a of the frame 335, and the engagement (fitting) of the first boss 334b ​​of the bearing member 334 with the square hole 335b of the frame 335. The hole 335a of the frame 335 is an example of a first engagement portion that positions the bearing member 334 in a direction perpendicular to the X-axis direction by engaging with the second boss 334a of the bearing member 334. The square hole 335b of the frame 335 is an example of a second engagement portion that restricts the rotation of the bearing member 334 when viewed in the X-axis direction by engaging with the first boss 334b ​​of the bearing member 334.

[0037] In the X-axis direction, the first transport guide 331, the second transport guide 332, the third transport guide 333, the feed roller 312, the transport roller 321, and the transfer roller 201 are positioned such that at least a portion of them is located on one side of the frame 335. The bearing member 334 is attached to the frame 335 from the other side, and at least a portion of it is positioned on the other side of the frame 335. The second boss 334a and the first boss 334b ​​of the bearing member 334 penetrate the frame 335 from one side to the other through the holes 335a and square holes 335b of the frame 335.

[0038] In other words, the bearing member 334 is positioned with respect to at least one direction perpendicular to the X-axis direction, with the second boss 334a as the positioning center (reference) by the engagement of the second boss 334a and the hole 335a. The second boss 334a and the hole 335a are configured to restrict the movement of the bearing member 334 relative to the frame 335 with respect to at least one of the Y-axis direction and the Z-axis direction, preferably any direction perpendicular to the X-axis direction. The inner diameter of the hole 335a is equal to the outer diameter of the second boss 334a, or set to be slightly larger than the outer diameter of the second boss 334a, taking tolerances into consideration.

[0039] Furthermore, the bearing member 334 is restricted from rotating (changing its orientation) around the second boss 334a by the engagement of the first boss 334b ​​and the square hole 335b. In other words, even if the bearing member 334 tries to rotate around the second boss 334a, the first boss 334b ​​interferes with the lower or upper surface of the square hole 335b, so the bearing member 334 does not rotate. The width of the square hole 335b in the Y-axis direction can be set to be slightly larger than the outer diameter of the first boss 334b ​​in order to allow tolerances for the frame 335.

[0040] Alternatively, instead of a hole-shaped engaging portion, a projection that fits into a hole-shaped (recessed) portion provided in the bearing member 334 may be provided on the frame 335 to serve as the first or second engaging portion.

[0041] The conveyor roller 321 has a rotating shaft 321a extending in the X-axis direction, which is the direction of the rotation axis, and a plurality of rubber rollers 321b supported by the rotating shaft 321a. The rubber rollers 321b are roller bodies that come into contact with the sheet S.

[0042] The conveyor roller 321 is rotatably supported by the bearing member 334, by engaging (fitting) the end of the rotating shaft 321a in the X-axis direction with the hole 334c of the bearing member 334. Here, a gear (not shown) is provided at one end of the rotating shaft 321a and is configured to receive driving force from a motor provided on the device body 1A to rotate the conveyor roller 321.

[0043] (Support configuration of the first transport guide and feed roller) The support configuration of the first transport guide 331 and the feed roller 312 will be explained using Figures 5(a, b) to 7. Figures 5(a, b) are perspective views of the first transport guide 331 and the feed roller 312 from different angles. Figure 6 is a perspective view showing the support configuration of the first transport guide 331. Figure 7 is a cross-sectional view of the first transport guide 331 and a part of the frame 335 when the first transport guide 331 is assembled to the image forming apparatus 1, cut by a plane perpendicular to the Y-axis direction.

[0044] As shown in Figures 5(a, b), the first transport guide 331 has a guide portion 331d (see also Figure 2) that forms the first transport path P1 and a bearing portion 331e that rotatably supports the feed roller 312. The first transport guide 331 also supports an arm member 310 that rotatably supports the pickup roller 311. The arm member 310 is swingable (rotatable) relative to the first transport guide 331 to raise and lower the pickup roller 311. The feed roller 312 and the pickup roller 311 are rotationally driven by a motor provided in the device body 1A that transmits driving force to the roller shaft 312a of the feed roller 312.

[0045] As shown in Figure 5(b), the first transport guide 331 rotatably supports a plurality of transport rollers 322. Each transport roller 322 is rotatably held by a holder 337. The holder 337 is supported by the first transport guide 331 via a pressurizing member 338 (elastic member, spring member). The pressurizing member 338 biases the holder 337 so that the transport rollers 322 are pressed against the transport rollers 321 when the first transport guide 331 is assembled to the image forming apparatus 1.

[0046] As shown in Figures 5(a, b) and 6, the X-axis end of the first transport guide 331 is provided with a rectangular hole 331a, a projection 331b, and a slit 331c. The rectangular hole 331a has a rectangular (preferably square) opening when viewed in the X-axis direction and is formed in the X-axis direction. The projection 331b is a convex shape that protrudes in the X-axis direction. In this embodiment, the projection 331b is an elongated rectangular shape in the Z-axis direction (plate-like with the Y-axis direction as the thickness direction) when viewed in the X-axis direction. The slit 331c is a groove shape formed in a direction intersecting the X-axis direction. In this embodiment, the slit 331c is a groove shape that opens downward in the Z-axis direction and widens in the Z-axis and Y-axis directions (see Figure 7).

[0047] The square hole 331a of the first transport guide 331 engages (fits) with the first boss 334b ​​of the bearing member 334, and the projection 331b of the first transport guide 331 engages (fits) with the first groove 335c of the frame 335, thereby restricting the position and orientation of the first transport guide 331.

[0048] In other words, the first transport guide 331 is positioned with respect to at least one direction perpendicular to the X-axis direction, with respect to the first boss 334b ​​(first positioning part) of the bearing member 334 as the positioning center (reference). The rectangular hole 331a and the first boss 334b ​​are configured to restrict the movement of the first transport guide 331 relative to the bearing member 334 with respect to at least one of the Y-axis direction and the Z-axis direction, preferably any direction perpendicular to the X-axis direction. It is preferable that the movement of the first transport guide 331 relative to the bearing member 334 is restricted with respect to a first direction perpendicular to the X-axis direction and a second direction perpendicular to both the X-axis direction and the first direction. In this embodiment, the movement of the first transport guide 331 relative to the bearing member 334 is restricted with respect to the Y-axis direction and the Z-axis direction. The width and height (length of two sides of the rectangle) of the rectangular hole 331a are set to be equal to the outer diameter of the first boss 334b, or slightly larger than the outer diameter of the first boss 334b, taking tolerances into consideration.

[0049] Furthermore, the first transport guide 331 is restricted from rotating (changing its posture) around the first boss 334b ​​by the engagement of the projection 331b with the first groove 335c of the frame 335. In other words, even if the first transport guide 331 tries to rotate around the first boss 334b, the projection 331b interferes with the lower or upper surface of the first groove 335c, so the first transport guide 331 does not rotate.

[0050] The first positioning portion may also be a recess into which a boss (protrusion) provided on the first transport guide 331 (first support member) fits.

[0051] The positioning configuration of the first transport guide 331 in the X-axis direction will be explained using Figure 7. The slit 331c of the first transport guide 331 and the first rib 335d of the frame 335 both extend in a direction intersecting the X-axis direction. The width of the slit 331c in the X-axis direction is equal to the width of the first rib 335d in the X-axis direction, or is set to be slightly larger than the width of the first rib 335d considering tolerances. Therefore, when the slit 331c is engaged with the first rib 335d, the movement of the first transport guide 331 in the X-axis direction relative to the frame 335 is restricted. In other words, the engagement of the slit 331c and the first rib 335d positions the first transport guide 331 with respect to the X-axis direction.

[0052] Furthermore, as a positioning configuration for the first transport guide 331 in the X-axis direction, a rib (protrusion) may be formed on the first transport guide 331 in a direction intersecting the X-axis direction, and a slit (recess) that engages with this rib may be formed on the frame 335.

[0053] (Support configuration of the second transport guide) The support configuration of the second transport guide 332 will be explained using Figures 8(a, b) and 9. Figure 8(a) is a perspective view of the second transport guide 332. Figure 8(b) is a perspective view showing the support configuration of the second transport guide 332.

[0054] As shown in Figure 8(a), the second transport guide 332 has a guide portion 332d (see also Figure 2) that forms the first transport path P1 and the second transport path. The guide portion 332d is provided with an opening 332e for allowing the rubber roller 321b of the transport roller 321 to protrude into the first transport path P1.

[0055] As shown in Figure 8(b), the X-axis end of the second transport guide 332 is provided with a hole 332a, a projection 332b, and a slit 332c. The hole 332a is a through hole that penetrates the X-axis side surface of the second transport guide 332 in the X-axis direction. The projection 332b is a convex shape that protrudes outward in the X-axis direction from the X-axis side surface of the second transport guide 332. The slit 332c is a groove shape formed in a direction intersecting the X-axis direction. In this embodiment, the slit 332c is a groove shape that opens downward in the Z-axis direction and widens in the Z-axis and Y-axis directions.

[0056] The hole 332a of the second transport guide 332 engages (fits) with the second boss 334a of the bearing member 334, and the projection 332b of the second transport guide 332 engages (fits) with the second groove 335e of the frame 335, thereby restricting the position and orientation of the second transport guide 332.

[0057] In other words, the second transport guide 332 is positioned with respect to at least one direction perpendicular to the X-axis direction, with respect to the second boss 334a of the bearing member 334 as the positioning center (reference). The hole 332a and the second boss 334a are configured to restrict the movement of the second transport guide 332 relative to the bearing member 334 with respect to at least one of the Y-axis direction and the Z-axis direction, preferably any direction perpendicular to the X-axis direction. It is preferable that the movement of the second transport guide 332 relative to the bearing member 334 is restricted with respect to a first direction perpendicular to the X-axis direction, and a second direction perpendicular to both the X-axis direction and the first direction. In this embodiment, the movement of the second transport guide 332 relative to the bearing member 334 is restricted with respect to the Y-axis direction and the Z-axis direction. The inner diameter of the hole 332a is equal to the outer diameter of the second boss 334a, or set to be slightly larger than the outer diameter of the second boss 334a, taking tolerances into consideration.

[0058] Furthermore, the second transport guide 331 is restricted from rotating (changing its posture) around the second boss 334a by the engagement of the projection 332b with the second groove 335e of the frame 335. In other words, even if the second transport guide 332 tries to rotate around the second boss 334a, the projection 332b interferes with the side surface of the second groove 335e (either of the sides on either side in the Y-axis direction), so the second transport guide 332 does not rotate.

[0059] The positioning configuration of the second transport guide 332 in the X-axis direction will be explained using Figure 9. The slit 332c of the second transport guide 332 and the second rib 335f of the frame 335 both extend in a direction intersecting the X-axis direction. The width of the slit 332c in the X-axis direction is equal to the width of the second rib 335f in the X-axis direction, or is set to be slightly larger than the width of the second rib 335f, taking tolerances into consideration. Therefore, when the slit 332c is engaged with the second rib 335f, the movement of the second transport guide 332 in the X-axis direction relative to the frame 335 is restricted. In other words, the engagement of the slit 332c and the second rib 335f positions the second transport guide 332 with respect to the X-axis direction.

[0060] Furthermore, as a positioning configuration for the second transport guide 332 in the X-axis direction, a rib (protrusion) may be formed on the second transport guide 332 in a direction intersecting the X-axis direction, and a slit (recess) that engages with this rib may be formed on the frame 335.

[0061] (Support configuration for the third transport guide and transfer roller) The support configuration of the third transport guide 333 and the transfer roller 201 will be explained using Figures 10(a, b). Figure 10(a) is a perspective view of the third transport guide 333. Figure 10(b) is a perspective view showing the support configuration of the third transport guide 333.

[0062] As shown in Figure 10(a), the third transport guide 333 has a guide portion 333d (see also Figure 2) that forms the first transport path P1. The third transport guide 333 also rotatably supports the transfer roller 201. Both ends of the shaft portion of the transfer roller 201 are rotatably held by a holder 201h. The holder 201h is supported by the third transport guide 333 via a pressurizing member 201p (elastic member, spring member; see Figure 2). The pressurizing member 338 biases the holder 337 so that the transfer roller 201 is pressed against the photosensitive drum 111 when the third transport guide 333 is assembled to the image forming apparatus 1.

[0063] As shown in Figure 10(a, b), the X-axis end of the third transport guide 333 is provided with a hole 333a and a slit 333b. The hole 333a is a through hole that penetrates the X-axis side of the third transport guide 333 in the X-axis direction. The slit 333b is a groove shape formed in a direction intersecting the X-axis direction. In this embodiment, the slit 333c is a groove shape that opens downward in the Z-axis direction and widens in the Z-axis and Y-axis directions.

[0064] The position of the third transport guide 333 is restricted when the hole 333a of the third transport guide 333 engages (fits) with the second boss 334a of the bearing member 334.

[0065] In other words, the third transport guide 333 is positioned with respect to at least one direction perpendicular to the X-axis direction, with respect to the second boss 334a (second positioning portion) of the bearing member 334 as the positioning center (reference). The hole 333a and the second boss 334a are configured to restrict the movement of the third transport guide 333 relative to the bearing member 334 with respect to at least one of the Y-axis direction and the Z-axis direction, preferably any direction perpendicular to the X-axis direction. It is preferable that the movement of the third transport guide 333 relative to the bearing member 334 is restricted with respect to a first direction perpendicular to the X-axis direction and a second direction perpendicular to both the X-axis direction and the first direction. In this embodiment, the movement of the third transport guide 333 relative to the bearing member 334 is restricted with respect to the Y-axis direction and the Z-axis direction. The inner diameter of the hole 333a is equal to the outer diameter of the second boss 334a, or set to be slightly larger than the outer diameter of the second boss 334a considering tolerances.

[0066] The second positioning portion may also be a recess into which a boss (protrusion) provided on the third transport guide 333 (second support member) fits.

[0067] Here, the hole 332a of the second transport guide 332 and the hole 333a of the third transport guide 333 engage with the second boss 334a of the bearing member 334 at different positions relative to each other with respect to the X-axis direction. In other words, in this embodiment, a portion of the second boss 334a is a second positioning portion that positions the second support member (third transport guide), and the other portion of the second boss 334a is a third positioning portion that positions the guide member (second transport guide 332). Therefore, the length L1 (Figure 9) by which the second boss 334a of the bearing member 334a protrudes in the X-axis direction relative to the hole 335a of the frame 335 is at least greater than the sum of the X-axis lengths of the holes 332a and 333a of the second transport guide 332 and the third transport guide 333.

[0068] The positioning configuration of the third transport guide 333 in the X-axis direction will be explained using Figure 10(b). The slit 333b of the third transport guide 333 and the third rib 335g of the frame 335 both extend in a direction intersecting the X-axis direction. The width of the slit 333b in the X-axis direction is equal to the width of the third rib 335g in the X-axis direction, or is set to be slightly larger than the width of the third rib 335g considering tolerances. Therefore, when the slit 333b is engaged with the third rib 335g, the movement of the third transport guide 333 in the X-axis direction relative to the frame 335 is restricted. In other words, the engagement of the slit 333b and the third rib 335g positions the third transport guide 333 in the X-axis direction.

[0069] Incidentally, although the third transport guide 333 of this embodiment is positioned in the X, Y, and Z axis directions as described above, its rotation (change in posture) around the second boss 334a of the bearing member 334 is not restricted by the bearing member 334 or the frame 335. That is, the third transport guide 333 is supported by the bearing member 334 so as to be rotatable around the second boss 334a. By making the third transport guide 333 rotatable, the process unit 110 (or other detachable units) can be easily attached and detached, as will be explained below.

[0070] Furthermore, the transfer roller 201 and the guide portion 333d that guides the sheet around it are located downstream of the conveyor roller 321 in the sheet conveying direction (upward in the Z-axis direction). For this reason, the hole portion 333a and the slit 333b of the third conveyor guide 333 are provided at the tip of the arm portion that protrudes upstream (downward) from the upstream end (lower end) of the guide portion 333d in the sheet conveying direction.

[0071] (Opening and closing operation of the third transport guide) As shown in Figures 11(a, b), in this embodiment, the process unit 110 is configured to be detachable from the rear side (one side in the Y-axis direction) of the main body 1A of the apparatus. Figure 11(a) shows the rear cover 340 in the closed position, and Figure 11(b) shows the rear cover 340 in the open position.

[0072] As shown in Figures 1 and 11(a, b), the image forming apparatus 1 has a rear cover 340 as an opening / closing member. The apparatus body 1A is provided with an opening OP that opens in the Y-axis direction. The rear cover 340 is rotatably supported by the apparatus body 1A. The rear cover 340 is movable (opens and closes) between a closed position (Figure 11(a)) that covers the opening OP of the apparatus body 1A when viewed in the Y-axis direction, and an open position (Figure 11(b)) that exposes the opening OP of the apparatus body 1A when viewed in the Y-axis direction. When the rear cover 340 is in the closed position, it constitutes the Y-axis side surface of the apparatus body 1A.

[0073] As shown in Figure 11(a), the rear cover 340 and the third transport guide 333 have guide portions 340a and 333e that face each other when the rear cover 340 is in the closed position. When the rear cover 340 is in the closed position, a second transport path P2 is formed between the guide portions 340a and 333e. As shown in Figure 11(b), when the rear cover 340 moves to the open position, the guide portion 340a of the rear cover 340 separates from the guide portion 333e of the third transport guide 333. This opens the second transport path P2, allowing the user to easily remove any sheets jammed in the second transport path P2.

[0074] The user can rotate (release) the third transport guide 333 by opening the rear cover 340, grasping the third transport guide 333, and pulling it in the direction of the arrow in Figure 11(a). At this time, the third transport guide 333 rotates around the second boss 334a (Figure 10), which is coaxial with the rotation axis 321a of the transport roller 321. In other words, the third transport guide 333 and the transport roller 321 are configured to rotate around a single rotation axis.

[0075] By opening the third transport guide 333, a portion of the first transport path P1 is opened, making it easy to remove any sheets jammed in the first transport path P1. Furthermore, when the third transport guide 333 is opened, the process unit 110 is exposed when viewed from outside the image forming apparatus 1 in the Y-axis direction (Figure 11(b)). Therefore, the user can grasp the process unit 110 and remove and install it through the opening OP in the apparatus body 1A.

[0076] As described above, the third transport guide 333 is supported so as to be rotatable around the second boss 334a of the bearing member 334, that is, around the rotation axis 321a of the transport roller 321. This configuration makes it possible to miniaturize the image forming apparatus.

[0077] If the pivot point of the third transport guide 333 is set above the rotation axis 321a of the transport roller 321, the pivot point may interfere with the attachment / detachment trajectory of the process unit 110 (the area shown by the dotted line in Figure 11(b)) when viewed in the X-axis direction. To avoid interference, if the support portion that rotatably supports the third transport guide 333 is placed outside the attachment / detachment trajectory of the process unit 110 in the X-axis direction, the size of the image forming apparatus in the X-axis direction will increase.

[0078] Furthermore, if the pivot point of the third transport guide 333 is located below the rotation axis 321a of the transport roller 321, the rotation trajectory of the third transport guide 333 may interfere with the rotation axis 321a of the transport roller 321. To avoid interference, if the support portion that rotatably supports the third transport guide 333 is placed outside the transport roller 321 in the X-axis direction, the size of the image forming apparatus in the X-axis direction will increase. Also, to avoid interference, if the support portion that rotatably supports the third transport guide 333 is placed below and on the rear side (left side in Figure 11(a)) of the transport roller 321, the size of the image forming apparatus in the Y-axis direction will increase.

[0079] In contrast, in this embodiment, the third transport guide 333 is configured to be openable, and the rotation center of the third transport guide 333 is made coaxial with the rotation axis 321a of the transport roller 321. This makes it possible to improve the workability of jam processing and attaching / detaching the process unit while also achieving miniaturization of the image forming apparatus.

[0080] (Advantages of this embodiment) According to this embodiment, the bearing member supporting the second roller positions the first support member supporting the first roller and the second support member supporting the third roller. Specifically, the end of the first transport guide 331 (first support member) supporting the feed roller 312 (first roller) is positioned by the first boss 334b ​​(first positioning part) of the bearing member 334 with respect to a direction perpendicular to the X-axis direction (the rotation axis direction of the second roller). Similarly, the end of the third transport guide 333 (second support member) supporting the transfer roller 201 (third roller) is positioned by the second boss 334a (second positioning part) of the bearing member 334 with respect to a direction perpendicular to the X-axis direction.

[0081] This makes it easier to ensure accuracy in the relative position of the rotation axis of the second roller and the rotation axis of the first roller compared to, for example, when the first support member and the second support member are positioned by a member other than the bearing member of the second roller. Also, it makes it easier to ensure accuracy in the relative position of the rotation axis of the second roller and the rotation axis of the third roller compared to when the first support member and the second support member are positioned by a member other than the bearing member 334. Therefore, the configuration of this embodiment makes it possible to improve the relative alignment accuracy between the rollers. By improving the relative alignment accuracy between the rollers, tilting and rotation of the sheet during transport are suppressed, so that positional displacement and deformation of the image formed on the sheet can be reduced.

[0082] Furthermore, the bearing member 334 rotatably supports the rotation axis 321a of the transport roller 321 (second roller) at the hole 334c of the second boss 334a. In addition, the bearing member 334 positions the second support member (third transport guide 333) that supports the third roller (transfer roller 201) with the second boss 334a (second positioning part) which is coaxial with the hole 334c and provided on the outer circumference of the hole 334c. This further improves the relative positional accuracy of the second roller and the third roller.

[0083] Furthermore, the first support member (first transport guide 331) that supports the first roller (feed roller 312) may also be positioned by the second boss 334a (second positioning portion) of the bearing member 334. That is, the bearing member has a hole that rotatably supports the rotation axis of the second roller, and it is preferable that at least one of the first positioning portion and the second positioning portion is provided coaxially with the hole and on the outer circumference of the hole. This makes it possible to improve the relative positional accuracy between the second roller and at least one of the first roller and the third roller.

[0084] In this embodiment, the first transport guide 331 as the first support member and the third transport guide 333 as the second support member are guide members having guide portions 331d and 333d, respectively, for guiding the sheet. Since the two guide members, the first support member and the second support member, are positioned by the same bearing member, the relative positional accuracy of the guide members can be improved, and stable sheet transport can be achieved.

[0085] Furthermore, in this embodiment, the first transport guide 331 (first support member) and the second transport guide 332 (guide member) facing the guide portion 331d of the first transport guide 331 are positioned by the bearing member 334. Also, the second transport guide 332 (guide member) and the third transport guide 333 (second support member) located on the same side as the second transport guide 332 with respect to the transport path and downstream of the second transport guide 332 in the sheet transport direction are positioned by the bearing member 334. As a result, the accuracy of the gap width between the first transport guide 331 and the second transport guide 332 (width of the transport path in the sheet thickness direction) can be improved, and the step difference between the second transport guide 332 and the third transport guide 333 can be reduced. This enables more stable sheet transport.

[0086] Furthermore, the frame 335, which acts as a regulating member, has a first rib 335d (first position regulating part) that regulates the position of the first transport guide 331 in the X-axis direction, and a third rib 335g (second position regulating part) that regulates the position of the third transport guide 333 in the X-axis direction. In other words, the first transport guide 331, which acts as a first support member, and the third transport guide 333, which acts as a second support member, have their positions in the X-axis direction (direction of the rotation axis of the second roller) regulated by the same member, the frame 335. This allows the first support member and the second support member to be positioned with respect to the rotation axis direction of the second roller with a simple configuration.

[0087] Furthermore, the frame 335, acting as a restricting member, has a first groove 335c that restricts the rotation of the first transport guide 331 around the first boss 334b ​​(first positioning part). The frame 335 also has a second groove 335e that restricts the rotation of the third transport guide 333 around the second boss 334a (second positioning part). In other words, the first transport guide 331, acting as a first support member, and the third transport guide 333, acting as a second support member, have their rotations restricted by the same component, the frame 335. This allows the angles of the first and second support members to be stabilized with a simple configuration.

[0088] (modified version) In this embodiment, a configuration was described in which both the first support member supporting the first roller and the second support member supporting the third roller are guide members that guide the sheet. However, the configuration is not limited to this, and the first support member and the second support member may not have the function of guiding the sheet.

[0089] (Other embodiments) In this embodiment, a configuration in which the process unit 110 can be attached to and detached from the rear side of the apparatus body 1A was described as an example of a detachable unit. However, this technology is not limited to this. For example, this technology may be applied to an image forming apparatus using an intermediate transfer belt, in which the intermediate transfer belt unit can be attached to and detached from the rear side of the apparatus body 1A.

[0090] Furthermore, although this embodiment illustrates an image forming apparatus equipped with an electrophotographic image forming unit 1B, this technology may also be applied to an image forming apparatus equipped with an inkjet image forming unit or an offset printing mechanism as the image forming unit.

[0091] Furthermore, this technology may be applied not only to the main body of the image forming apparatus that houses the image forming unit, but also to devices used together with the main body of the image forming apparatus. Examples of such devices include an image reading device that reads image information from a document sheet and transmits it to the main body of the image forming apparatus, and a sheet processing device (finisher) that performs processing such as binding on the sheet on which the image has been formed by the main body of the image forming apparatus. [Explanation of Symbols]

[0092] 110...Unit (Process Unit) / 111...Image Carrier (Photosensitive Drum) / 201...Third Roller (Transfer Roller) / 300...Sheet Storage Section / 312...First Roller (Feed Roller) / 331...First Support Member (First Conveyor Guide) / 331d...Guide Section / 321...Second Roller (Conveyor Roller) / 321a...Rotating Shaft / 321b...Roller Body (Rubber Roller) / 322...Fourth Roller (Conveyor Roller) / 332...Guide Member (Second Conveyor Guide) / 333...Second Support Member (Third Conveyor Guide) / 33 3d...Guide section / 334...Bearing member / 334a...Second positioning section, third positioning section (second boss) / 334b...First positioning section (first boss) / 334c...Hole / 335...Restricting member (frame) / 335a...First engagement section (hole) / 335b...Second engagement section (square hole) / 335c...First rotation restricting section (first groove) / 335d...First position restricting section (first rib) / 335e...Second rotation restricting section (second groove) / 335g...Second position restricting section (third rib) / 340...Opening / closing member (back cover) / P1...Conveyor path

Claims

1. A first roller for conveying a sheet; a second roller having a rotation shaft and a roller body supported by the rotation shaft, the second roller being disposed downstream of the first roller in a sheet conveying direction and configured to convey the sheet; a third roller disposed downstream of the second roller in the sheet conveying direction and configured to convey the sheet; a first support member that rotatably supports the first roller; a second support member that rotatably supports the third roller; a bearing member that rotatably supports an end of the rotation shaft in a rotation axis direction of the second roller; A frame supporting the bearing member; Equipped with the bearing member has a first positioning portion that positions an end of the first support member in the rotational axis direction with respect to a direction perpendicular to the rotational axis direction, and a second positioning portion that positions an end of the second support member in the rotational axis direction with respect to the direction perpendicular to the rotational axis direction, At least a portion of the second roller is disposed on one side of the frame in the direction of the rotation axis, and the bearing member is disposed on the other side of the frame in the direction of the rotation axis.

1. An image forming apparatus comprising:

2. The second positioning portion has a hole portion, The rotation shaft of the second roller is rotatably supported by the hole portion of the second positioning portion.

2. The image forming apparatus according to claim 1,

3. The second positioning portion and the hole portion are arranged coaxially.

3. The image forming apparatus according to claim 2,

4. The first support member has a first guide portion that guides the sheet, The second support member has a second guide portion that guides the sheet.

4. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

5. A guide member for guiding the sheet is further provided, The bearing member further includes a third positioning portion that positions an end portion of the guide member in the direction of the rotation axis in a direction perpendicular to the direction of the rotation axis.

5. The image forming apparatus according to claim 4.

6. The first guide portion and the guide member face each other across a conveying path for the sheet, the second guide portion is disposed on the same side as the guide member with respect to a conveying path of the sheet and downstream of the guide member in the sheet conveying direction.

6. The image forming apparatus according to claim 5,

7. the second support member is rotatable about a rotation axis of the second roller between a position where the sheet transport path is formed and a position where the sheet transport path is opened.

7. The image forming apparatus according to claim 4, wherein the image forming apparatus is a multi-color image forming apparatus.

8. A device body having an opening; an opening / closing member movable with respect to the device body between a closed position that covers the opening and an open position that exposes the opening; a unit detachable from the device body; Further comprising: the second support member is rotatable to a position where the unit can be attached and detached through the opening when the opening / closing member is in an open state.

8. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

9. The unit includes an image carrier and at least one process member acting on the image carrier.

9. The image forming apparatus according to claim 8,

10. a first rotation restricting portion that restricts rotation of the first support member around the first positioning portion; a second rotation restricting portion that restricts rotation of the second support member around the second positioning portion; Further comprising:

9. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

11. The first rotation regulating portion and the second rotation regulating portion are provided on the frame.

11. The image forming apparatus according to claim 10.

12. The frame has a first engagement portion arranged coaxially with the second roller, and a second engagement portion arranged at a position different from the first engagement portion when viewed in the direction of the rotation axis, When the first engagement portion engages with the bearing member, the bearing member is positioned in a direction perpendicular to the rotation axis direction, When the second engagement portion is engaged with the bearing member, rotation of the bearing member is restricted when viewed in the rotation axis direction.

12. The image forming apparatus according to claim 11.

13. a first position restricting portion that restricts a position of the first support member in the direction of the rotation axis; a second position restricting portion that restricts a position of the second support member in the direction of the rotation axis; Further comprising:

10. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

14. The first position regulating portion and the second position regulating portion are provided on the frame.

14. The image forming apparatus according to claim 13.

15. The frame has a first engagement portion arranged coaxially with the second roller, and a second engagement portion arranged at a position different from the first engagement portion when viewed in the direction of the rotation axis, When the first engagement portion engages with the bearing member, the bearing member is positioned in a direction perpendicular to the rotation axis direction, When the second engagement portion is engaged with the bearing member, rotation of the bearing member is restricted when viewed in the rotation axis direction.

15. The image forming apparatus according to claim 14.

16. An image carrier; a sheet storage section for storing a sheet; Further comprising: the first roller is a feed roller that feeds the sheet from the sheet storage unit, the third roller is a transfer roller that transfers a toner image from the image carrier to the sheet, the second roller is a conveying roller that conveys the sheet conveyed from the feed roller toward a nip portion between the image carrier and the transfer roller; 9. The image forming apparatus according to claim 1, wherein the first and second electrodes are arranged in a first direction.

17. The sheet conveying device further includes a fourth roller that contacts the second roller and conveys the sheet together with the second roller, The first support member rotatably supports the fourth roller.

13. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus.

18. The first positioning portion and the second positioning portion are engaged with the frame.

13. The image forming apparatus according to claim 1, wherein the image forming apparatus is a multi-layered image forming apparatus.

Images