Image forming apparatus

An image forming apparatus includes a first roller, a second roller arranged downstream of the first roller in a sheet conveyance direction, the second roller including a rotation shaft and a roller body supported by the rotation shaft, a third roller arranged downstream of the second roller in the sheet conveyance direction, a first support member configured to rotatably support the first roller, a second support member configured to rotatably support the third roller, and a bearing member configured to rotatably support an end portion of the rotation shaft. The bearing member includes a first positioning portion configured to position an end portion of the first support member and a second positioning portion configured to position an end portion of the second support member.

BACKGROUND OF THE INVENTION

Field of the Invention

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

Description of the Related Art

An image forming apparatus such as a printer and a multifunction peripheral forms an image on a sheet used as a recording material while sequentially delivering and conveying the sheet between a plurality of conveyance rollers. JP 2019-095802 A discloses an image forming apparatus that forms an image on a sheet while sequentially delivering the sheet set on a sheet feed tray by a pickup roller, a feed roller, a registration roller, a transfer roller, and a sheet discharge roller.

In the image forming apparatus, in a case where relative alignment accuracy between the plurality of rollers is low, the sheet being conveyed may be skewed.

SUMMARY OF THE INVENTION

The present invention provides an image forming apparatus capable of improving relative alignment accuracy between rollers.

According to one aspect of the invention, an image forming apparatus includes a first roller configured to convey a sheet, a second roller arranged downstream of the first roller in a sheet conveyance direction and configured to convey the sheet, the second roller including a rotation shaft and a roller body supported by the rotation shaft, a third roller arranged downstream of the second roller in the sheet conveyance direction and configured to convey the sheet, a first support member configured to rotatably support the first roller, a second support member configured to rotatably support the third roller, and a bearing member configured to rotatably support an end portion of the rotation shaft in a rotational axis direction of the second roller, wherein the bearing member includes a first positioning portion configured to position 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 configured to position an end portion of the second support member in the rotational axis direction with respect to a direction orthogonal to the rotational axis direction.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings.

FIG.1is a schematic diagram of an image forming apparatus1according to the present embodiment. The image forming apparatus1is a monochrome printer that forms a monochromatic image on a sheet S serving as a recording material by using an image forming unit while conveying the sheet S. The sheet S may be various sheet materials having different sizes and materials, such as paper including plain paper and thick paper, a plastic film, cloth, a sheet material subjected to surface treatment such as a coated paper, and a sheet material having a special shape such as an envelope and index paper.

The image forming apparatus1includes an electrophotographic image forming unit1B including a process unit110, a laser scanner unit500, a transfer roller201, and a fixing unit400. The process unit110includes a photosensitive drum111serving as an image bearing member and one or more process members that act on the photosensitive drum111. The process unit110is configured as a cartridge detachable from an apparatus body1A (casing) of the image forming apparatus1.

The image forming apparatus1includes a pickup roller311, a feed roller312, a separation roller313, a conveyance roller321, counter conveyance rollers322and323, a sheet discharge roller403, and a counter sheet discharge roller404as a mechanism for conveying the sheet S. A sheet storage portion300(sheet tray) for stacking and storing the sheets S is provided in a lower portion of the apparatus body1A. A sheet discharge tray405for stacking the sheet S on which an image has been formed is provided in an upper surface portion of the apparatus body1A.

When an instruction to form an image (print job) is input to the image forming apparatus1, formation of a toner image is started in the image forming unit1B. That is, the photosensitive drum111rotates in the process unit110, and a charger uniformly charges a surface of the photosensitive drum111. The laser scanner unit500irradiates the photosensitive drum111with a laser beam on the basis of image information included in the print job. Thus, the charged surface of the photosensitive drum111is exposed, and an electrostatic latent image corresponding to the image information is written. A developing unit of the process unit110supplies a developer containing toner to the photosensitive drum111and visualizes (develops) the electrostatic latent image as a toner image. The toner image is conveyed, by rotation of the photosensitive drum111, to a transfer nip Nt that is a nip portion between the photosensitive drum111and the transfer roller201.

In parallel with the above toner image forming process, the sheets S are supplied one by one from the sheet storage portion300to the image forming unit1B. That is, the pickup roller311comes into contact with an uppermost sheet of the sheets S stacked on the sheet storage portion300and rotates, thereby feeding the sheet S from the sheet storage portion300. The sheet S fed from the sheet storage portion300is further conveyed while being separated one by one at a nip portion (separation nip Ns) between the feed roller312and the separation roller313. The sheet S passed through the separation nip Ns is nipped at a conveyance nip Nc between the conveyance roller321and the counter conveyance rollers322and is further conveyed toward a transfer nip Nt.

The separation roller313is an example of a separation member that separates the sheet S by frictional force. The separation roller313can be, for example, a rubber roller supported by a shaft fixed to a frame body of the apparatus body1A via a torque limiter. In addition, the separation member may be a retard roller to which driving force in a direction against a moving direction of a peripheral surface of the feed roller312at the separation nip Ns is input via the torque limiter, or a pad-shaped elastic member that comes into contact with the feed roller312.

At the transfer nip Nt, by a predetermined bias voltage (transfer voltage) being applied to the transfer roller201, the toner image is transferred from the photosensitive drum111to the sheet S. The sheet S to which the toner image has been transferred is subject to fixing process in the fixing unit400. The fixing unit400has a heat fixing configuration including a first rotary member and a second rotary member that convey the sheet S while nipping the sheet S at a fixing nip Nf and a heating unit that heats the image on the sheet S. The first rotary member is, for example, a flexible tubular film or roller. The second rotary member is, for example, a roller having an elastic layer on its outer peripheral portion. The heating unit can be a heater board in which a pattern of a heating resistor formed on a ceramic substrate, or a halogen lamp that emits radiant heat.

The sheet S passed through the fixing nip Nf is discharged to the outside of the apparatus body1A by a sheet discharge roller pair including the sheet discharge roller403and the counter sheet discharge roller404and is stacked on the sheet discharge tray405. The above path from the sheet storage portion300to the sheet discharge tray405via the plurality of rollers is a first conveyance path P1(main conveyance path) of the image forming apparatus1.

In order to form images on both surfaces of the sheet S, the sheet S having a first surface on which the image has been formed by the above image forming operation is fed to a second conveyance path P2(duplex conveyance path, re-conveyance path) by reverse conveyance by the sheet discharge roller pair. The second conveyance path P2is a conveyance path that branches from the first conveyance path P1at a part downstream of the fixing nip Nf in a sheet conveyance direction of the first conveyance path P1and joins the first conveyance path P1at a part upstream of the separation nip Ns between the conveyance roller321and the counter conveyance rollers322. The sheet S fed to the second conveyance path P2is conveyed while being nipped between the conveyance roller321and the counter conveyance roller323and is conveyed to the first conveyance path P1again. Then, an image is formed on a second surface opposite to the first surface while the sheet S is passing through the transfer nip Nt and the fixing nip Nf, and thereafter the sheet S is discharged by the sheet discharge roller pair.

Rollers and Guide Members

Rollers and guide members included in the image forming apparatus1will be described with reference toFIGS.2to10.

In the following description, a rotational axis direction of the photosensitive drum111is defined as an X-axis direction. A vertical direction (a direction opposite to a direction of gravity) when the image forming apparatus1is installed on a horizontal plane is defined as a Z-axis direction. A direction orthogonal to the X-axis direction and the Z-axis direction is defined as a Y-axis direction. The X-axis direction is preferably orthogonal to the Z-axis direction. The X-axis direction is also a sheet width direction (a direction orthogonal to the sheet conveyance direction) of the sheet conveyed in the first conveyance path P1and the second conveyance path P2.

FIG.2is a cross-sectional view of a part of the image forming apparatus1, which is taken along a plane perpendicular to the X-axis direction.FIG.2illustrates arrangement of the rollers and guide members arranged in a part from the sheet storage portion300to the transfer roller201in the first conveyance path P1.

As illustrated inFIG.2, the pickup roller311, the feed roller312, the separation roller313, the conveyance roller321, the counter conveyance rollers322, the photosensitive drum111, and the transfer roller201are arranged along the first conveyance path P1. The separation nip Ns formed by the feed roller312and the separation roller313is located downstream of the pickup roller311in the sheet conveyance direction in the first conveyance path P1. The conveyance nip Nc formed by the conveyance roller321and the counter conveyance rollers322is located downstream of the separation nip Ns. The transfer nip Nt formed by the photosensitive drum111and the transfer roller201is located downstream of the conveyance nip Nc.

The feed roller312is an example of a first roller that conveys a sheet. The conveyance roller321is an example of a second roller that includes a rotation shaft and a roller body supported by the rotation shaft, is arranged downstream of the first roller in the sheet conveyance direction, and conveys the sheet. The transfer roller201is an example of a third roller that is arranged downstream of the second roller in the sheet conveyance direction and conveys the sheet. The second conveyance rollers322are each an example of a fourth roller that comes into contact with the second roller and nips and conveys the sheet together with the second roller. Note that the first to fourth rollers are not limited to the examples described herein and may be roller members that convey a sheet at other positions in the image forming apparatus.

The pickup roller311, the feed roller312, and the photosensitive drum111are to be brought into contact with the first surface of the sheet S fed from the sheet storage portion300. The separation roller313, the conveyance roller321, and the transfer roller201are to be brought into contact with the second surface of the sheet S fed from the sheet storage portion300.

The pickup roller311, the feed roller312, and the photosensitive drum111are each rotationally driven in a clockwise direction inFIG.2by driving force transmitted from a motor serving as a driving source. The conveyance roller321is rotationally driven in a counterclockwise direction inFIG.2by the driving force transmitted from the motor. The transfer roller201and the counter conveyance rollers322can be rotated by force received from their opposing rollers or may be rotationally driven by the driving force transmitted from the driving source.

As illustrated inFIG.2, a first conveyance guide331, a second conveyance guide332, and a third conveyance guide333are arranged along the first conveyance path P1. The first conveyance guide331guides the sheet S between the separation nip Ns and the conveyance nip Nc and in the vicinity of the counter conveyance rollers322. The second conveyance guide332guides the sheet S in a part of the second conveyance path P2and in the vicinity of the conveyance roller321. The third conveyance guide333is arranged downstream of the second conveyance guide332in the sheet conveyance direction in the first conveyance path P1and guides the sheet S between the conveyance nip Nc and the transfer nip Nt and around the transfer roller201.

A part of the first conveyance guide331and a part of the second conveyance guide332face each other across the first conveyance path P1(i.e., with the first conveyance path P1being interposed between them) in the vicinity of the conveyance nip Nc. The first conveyance guide331and the second conveyance guide332can guide the sheet S fed from the sheet storage portion300to the conveyance nip Nc. The third conveyance guide333can guide the sheet having passed through the conveyance nip Nc to the transfer nip Nt. The first conveyance guide331guides the first surface of the sheet S fed from the sheet storage portion300. The second conveyance guide332and the third conveyance guide333guide the second surface of the sheet S fed from the sheet storage portion300.

The first conveyance guide331is an example of a first support member that rotatably supports the first roller. The third conveyance guide333is an example of a second support member that rotatably supports the third roller.

Outline of Support Configuration

FIG.3is a schematic diagram (exploded diagram) illustrating a support configuration of the first conveyance guide331, the second conveyance guide332, and the third conveyance guide333. In the present embodiment, a bearing member334rotatably supporting the conveyance roller321supports the first conveyance guide331, the second conveyance guide332, and the third conveyance guide333. The first conveyance guide331supports the feed roller312and the counter conveyance rollers322. The third conveyance guide333supports the transfer roller201. As described below, the first conveyance guide331and the third conveyance guide333are positioned by the bearing member334, thereby determining positions of the feed roller312and the transfer roller201with respect to the conveyance roller321.

In the present embodiment, the support configuration of each conveyance guide and the conveyance roller321is substantially the same on both sides in the X-axis direction (a rotational axis direction of the conveyance roller321). In the following description, the support configuration on one side in the X-axis direction will be described, but a corresponding support configuration is also provided on the opposite side in the X-axis direction. For example, in addition to the bearing member334and the frame335inFIG.3, one bearing member (second bearing member) and one frame (second frame) having the same configuration as the bearing member334and the frame335in a symmetrical shape are arranged on the opposite side in the X-axis direction.

Support Configuration of Conveyance Roller

The support configuration of the conveyance roller321will be described with reference toFIG.4.FIG.4is a perspective view illustrating the support configuration of the conveyance roller321.

As illustrated inFIG.4, the bearing member334has a first boss334b, a second boss334a, a hole334c, and a connecting portion334d. The first boss334bis a first positioning portion of the present embodiment, and the second boss334ais a second positioning portion and a third positioning portion of the present embodiment.

Both the first boss334band the second boss334aare projections extending in the X-axis direction and have an arc surface (cylindrical surface) extending in the X-axis direction. The hole334cis formed inside the second boss334aand extends in the X-axis direction. The second boss334aand the first boss334bare arranged to have a space in a direction intersecting the X-axis direction and are integrally formed via the connecting portion334d. The second boss334aand the hole334care coaxially arranged (on a rotational axis of the conveyance roller321). The bearing member334is supported by the frame335.

The frame335has a hole335a, a rectangular hole335b, a first groove335c, a first rib335d, a second groove335e, a second rib335f, and a third rib335g. Both the hole335aand the rectangular hole335bare through holes penetrating the frame335from the outside to the inside thereof in the X-axis direction. The first groove335cand the second groove335ehave a groove shape provided on an inner side surface of the frame335in the X-axis direction. The first rib335dand the second rib335fhave a plate shape extending in the direction intersecting the X-axis direction (preferably, the Y-axis direction and the Z-axis direction). The frame335is fixed to the frame body of the apparatus body1A.

The frame335is an example of a restriction member or regulation member that restricts/regulates rotation or positions of the first support member and the second support member. The first groove335cis an example of a first rotation restriction portion that restricts the rotation of the first support member. The second groove335eis an example of a second rotation restriction portion that restricts the rotation of the second support member. The first rib335dis an example of a first position regulation portion that regulates the position of the first support member in the X-axis direction (the rotational axis direction of the second roller). The third rib335gis an example of a second position regulation portion that regulates the position of the second support member in the X-axis direction.

The second boss334aof the bearing member334is engaged with (fitted into) the hole335aof the frame335, and the first boss334bof the bearing member334is engaged with (fitted into) the rectangular hole335bof the frame335. Thus, a position and posture of the bearing member334are regulated. The hole335aof the frame335is an example of a first engagement portion that is engaged with the second boss334aof the bearing member334to position the bearing member334in a direction orthogonal to the X-axis direction. The rectangular hole335bof the frame335is an example of a second engagement portion that is engaged with the first boss334bof the bearing member334to restrict rotation of the bearing member334when viewed in the X-axis direction.

The first conveyance guide331, the second conveyance guide332, the third conveyance guide333, the feed roller312, the conveyance roller321, and the transfer roller201are arranged such that at least part thereof is located on one side of the frame335in the X-axis direction. The bearing member334is attached to the frame335from the other side of the frame335and is arranged such that at least a part thereof is located on the other side of the frame335. The second boss334aand the first boss334bof the bearing member334penetrate the frame335from the other side to the one side of the frame335through the hole335aand the rectangular hole335bof the frame335.

That is, the bearing member334is positioned with the second boss334aserving as a positioning center (reference) in at least one direction orthogonal to the X-axis direction by the engagement between the second boss334aand the hole335a. The second boss334aand the hole335arestrict movement of the bearing member334with respect to the frame335in at least one of the Y-axis direction and the Z-axis direction, preferably in any arbitrary direction orthogonal to the X-axis direction. An inner diameter of the hole335ais set to be equal to an outer diameter of the second boss334aor to be slightly larger than the outer diameter of the second boss334ain consideration of tolerance.

The engagement between the first boss334band the rectangular hole335brestricts rotation (change in posture) of the bearing member334about the second boss334a. That is, even if the bearing member334attempts to rotate about the second boss334a, the first boss334binterferes with a lower surface or upper surface of the rectangular hole335b. Thus, the bearing member334does not rotate. A width of the rectangular hole335bin the Y-axis direction can be set slightly larger than an outer diameter of the first boss334bso as to allow tolerance of the frame335.

Instead of the hole-shaped engagement portions, a projection to be fitted into a hole shape (recess portion) provided in the bearing member334may be provided in the frame335to serve as the first engagement portion or the second engagement portion.

The conveyance roller321includes a rotation shaft321aextending in the X-axis direction serving as the rotational axis direction and a plurality of rubber rollers321bsupported by the rotation shaft321a. The rubber rollers321bare roller bodies that come into contact with the sheet S.

The conveyance roller321is rotatably supported by the bearing member334by an end portion of the rotation shaft321ain the X-axis direction being engaged with (fitted into) the hole334cof the bearing member334. Here, a gear (not illustrated) is provided at one end portion of the rotation shaft321ato receive driving force for rotationally driving the conveyance roller321from the motor provided in the apparatus body1A.

Support Configuration of First Conveyance Guide and Feed Roller

A support configuration of the first conveyance guide331and the feed roller312will be described with reference toFIGS.5A and5BtoFIG.7.FIGS.5A and5Bare perspective views of the first conveyance guide331and the feed roller312as viewed from different angles.FIG.6is a perspective view illustrating the support configuration of the first conveyance guide331.FIG.7is a cross-sectional view of a part of the first conveyance guide331and the frame335, which is taken along a plane perpendicular to the Y-axis direction in a state in which the first conveyance guide331is assembled to the image forming apparatus1.

As illustrated inFIGS.5A and5B, the first conveyance guide331has a guide portion331d(first guide portion; see alsoFIG.2) that forms the first conveyance path P1and a bearing portion331ethat rotatably supports the feed roller312. The first conveyance guide331supports an arm member310that rotatably supports the pickup roller311. The arm member310is swingable (rotatable) with respect to the first conveyance guide331so as to raise and lower the pickup roller311. The feed roller312and the pickup roller311are rotationally driven by transmitting driving force from the motor provided in the apparatus body1A to a roller shaft312aof the feed roller312.

As illustrated inFIG.5B, the first conveyance guide331rotatably supports the plurality of counter conveyance rollers322. Each of the counter conveyance rollers322is rotatably held by a holder337. The holder337is supported by the first conveyance guide331via a pressing member338(elastic member, spring member). The pressing member338urges the holder337so as to bring the counter conveyance rollers322into pressure contact with the conveyance roller321in a state in which the first conveyance guide331is assembled to the image forming apparatus1.

As illustrated inFIGS.5A,5B, and6, a rectangular hole331a, a projection331b, and a slit331care provided at an end portion of the first conveyance guide331in the X-axis direction. The rectangular hole331ahas a rectangular (preferably square) opening as viewed in the X-axis direction and has a hole shape formed in the X-axis direction. The projection331bhas a projecting shape projecting in the X-axis direction. The projection331bof the present embodiment has a rectangular shape elongated in the Z-axis direction as viewed in the X-axis direction (a plate shape of which a thickness direction is the Y-axis direction). The slit331chas a groove shape formed in the direction intersecting the X-axis direction. The slit331cof the present embodiment has a groove shape (seeFIG.7) opening downward in the Z-axis direction and extending in the Z-axis direction and the Y-axis direction.

The rectangular hole331aof the first conveyance guide331is engaged with (fitted into) the first boss334bof the bearing member334, and the projection331bof the first conveyance guide331is engaged with (fitted into) the first groove335cof the frame335. Thus, a position and posture of the first conveyance guide331are regulated.

That is, the first conveyance guide331is positioned with the first boss334b(first positioning portion) of the bearing member334serving as the positioning center (reference) in at least one direction orthogonal to the X-axis direction. The rectangular hole331aand the first boss334brestrict movement of the first conveyance guide331with respect to the bearing member334in at least one of the Y-axis direction and the Z-axis direction, preferably in any arbitrary direction orthogonal to the X-axis direction. The movement of the first conveyance guide331with respect to the bearing member334is preferably restricted in a first direction orthogonal to the X-axis direction and a second direction orthogonal to both the X-axis direction and the first direction. In the present embodiment, the movement of the first conveyance guide331in the Y-axis direction and/or in the Z-axis direction with respect to the bearing member334is restricted. A width and height (lengths of two sides of the rectangle) of the rectangular hole331aare set to be equal to the outer diameter of the first boss334bor slightly larger than the outer diameter of the first boss334bin consideration of tolerance.

The engagement between the projection331band the first groove335cof the frame335restricts rotation (change in posture) of the first conveyance guide331about the first boss334b. That is, even if the first conveyance guide331attempts to rotate about the first boss334b, the projection331binterferes with a lower surface or upper surface of the first groove335c. Thus, the first conveyance guide331does not rotate.

The first positioning portion may be a recess portion into which a boss (projecting portion) provided in the first conveyance guide331(first support member) is fitted.

A positioning configuration of the first conveyance guide331in the X-axis direction will be described with reference toFIG.7. Both the slit331cof the first conveyance guide331and the first rib335dof the frame335extend in the direction intersecting the X-axis direction. A width of the slit331cin the X-axis direction is set to be equal to a width of the first rib335din the X-axis direction or to be slightly larger than the width of the first rib335din consideration of tolerance. Therefore, in a state in which the slit331cis engaged with the first rib335d, movement of the first conveyance guide331in the X-axis direction with respect to the frame335is restricted. That is, the first conveyance guide331is positioned in the X-axis direction by the engagement of the slit331cand the first rib335d.

In the positioning configuration of the first conveyance guide331in the X-axis direction, a rib (projecting portion) in the direction intersecting the X-axis direction may be formed in the first conveyance guide331, and a slit (recess portion) to be engaged with the rib may be formed in the frame335.

Support Configuration of Second Conveyance Guide

A support configuration of the second conveyance guide332will be described with reference toFIGS.8A,8B, and9.FIG.8Ais a perspective view of the second conveyance guide332.FIG.8Bis a perspective view illustrating a support configuration of the second conveyance guide332.

As illustrated inFIG.8A, the second conveyance guide332has a guide portion332d(see alsoFIG.2) that forms the first conveyance path P1and the second conveyance path. The guide portion332dhas an opening portion332efor allowing each rubber roller321bof the conveyance roller321to project into the first conveyance path P1.

As illustrated inFIG.8B, a hole332a, a projection332b, and a slit332care provided at an end portion of the second conveyance guide332in the X-axis direction. The hole332ais a through hole penetrating, in the X-axis direction, a side surface of the second conveyance guide332in the X-axis direction. The projection332bhas a projecting shape projecting outward in the X-axis direction from the side surface of the second conveyance guide332in the X-axis direction. The slit332chas a groove shape formed in the direction intersecting the X-axis direction. The slit332cof the present embodiment has a groove shape opening downward in the Z-axis direction and extending in the Z-axis direction and the Y-axis direction.

The hole332aof the second conveyance guide332is engaged with (fitted into) the second boss334aof the bearing member334, and the projection332bof the second conveyance guide332is engaged with (fitted into) the second groove335eof the frame335. Thus, a position and posture of the second conveyance guide332are regulated.

That is, the second conveyance guide332is positioned with the second boss334aof the bearing member334serving as the positioning center (reference) in at least one direction orthogonal to the X-axis direction. The hole332aand the second boss334arestrict movement of the second conveyance guide332with respect to the bearing member334in at least one of the Y-axis direction and the Z-axis direction, preferably in any arbitrary direction orthogonal to the X-axis direction. The movement of the second conveyance guide332with respect to the bearing member334is preferably restricted in the first direction orthogonal to the X-axis direction and the second direction orthogonal to both the X-axis direction and the first direction. In the present embodiment, the movement of the second conveyance guide332in the Y-axis direction and/or in the Z-axis direction with respect to the bearing member334is restricted. An inner diameter of the hole332ais set to be equal to the outer diameter of the second boss334aor to be slightly larger than the outer diameter of the second boss334ain consideration of tolerance.

The engagement between the projection332band the second groove335eof the frame335restricts rotation (change in posture) of the second conveyance guide332about the second boss334a. That is, even if the second conveyance guide332attempts to rotate about the second boss334a, the projection332binterferes with a side surface (one of side surfaces on both sides in the Y-axis direction) of the second groove335e. Thus, the second conveyance guide332does not rotate.

A positioning configuration of the second conveyance guide332in the X-axis direction will be described with reference toFIG.9. Both the slit332cof the second conveyance guide332and the second rib335fof the frame335extend in the direction intersecting the X-axis direction. A width of the slit332cin the X-axis direction is set to be equal to a width of the second rib335fin the X-axis direction or to be slightly larger than the width of the second rib335fin consideration of tolerance. Therefore, in a state in which the slit332cis engaged with the second rib335f, movement of the second conveyance guide332in the X-axis direction with respect to the frame335is restricted. That is, the second conveyance guide332is positioned in the X-axis direction by the engagement of the slit332cand the second rib335f.

In the positioning configuration of the second conveyance guide332in the X-axis direction, a rib (projecting portion) in the direction intersecting the X-axis direction may be formed in the second conveyance guide332, and a slit (recess portion) to be engaged with the rib may be formed in the frame335.

Support Configuration of Third Conveyance Guide and Transfer Roller

A support configuration of the third conveyance guide333and the transfer roller201will be described with reference toFIGS.10A and10B.FIG.10Ais a perspective view of the third conveyance guide333.FIG.10Bis a perspective view of the support configuration of the third conveyance guide333.

As illustrated inFIG.10A, the third conveyance guide333has a guide portion333d(second guide portion; see alsoFIG.2) that forms the first conveyance path P1. The third conveyance guide333rotatably supports the transfer roller201. Both end portions of a shaft portion of the transfer roller201are rotatably held by a holder201h. The holder201his supported by the third conveyance guide333via a pressing member201p(elastic member, spring member; seeFIG.2). The pressing member201purges the holder201hso as to bring the transfer roller201into pressure contact with the photosensitive drum111in a state in which the third conveyance guide333is assembled to the image forming apparatus1.

As illustrated inFIGS.10A and10B, a hole333aand a slit333bare provided at an end portion of the third conveyance guide333in the X-axis direction. The hole333ais a through hole penetrating, in the X-axis direction, a side surface of the third conveyance guide333in the X-axis direction. The slit333bhas a groove shape formed in the direction intersecting the X-axis direction. The slit333bof the present embodiment has a groove shape opening downward in the Z-axis direction and extending in the Z-axis direction and the Y-axis direction.

When the hole333aof the third conveyance guide333is engaged with (fitted into) the second boss334aof the bearing member334, a position of the third conveyance guide333is regulated.

That is, the third conveyance guide333is positioned with the second boss334a(second positioning portion) of the bearing member334serving as a positioning center (reference) in at least one direction orthogonal to the X-axis direction. The hole333aand the second boss334arestrict movement of the third conveyance guide333with respect to the bearing member334in at least one of the Y-axis direction and the Z-axis direction, preferably in any arbitrary direction orthogonal to the X-axis direction. The movement of the third conveyance guide333with respect to the bearing member334is preferably restricted in the first direction orthogonal to the X-axis direction and the second direction orthogonal to both the X-axis direction and the first direction. In the present embodiment, the movement of the third conveyance guide333in the Y-axis direction and/or in the Z-axis direction with respect to the bearing member334is restricted. An inner diameter of the hole333ais set to be equal to the outer diameter of the second boss334aor to be slightly larger than the outer diameter of the second boss334ain consideration of tolerance.

The second positioning portion may be a recess portion into which a boss (projecting portion) provided in the third conveyance guide333(second support member) is fitted.

Here, the hole332aof the second conveyance guide332and the hole333aof the third conveyance guide333are engaged with the second boss334aof the bearing member334at different positions in the X-axis direction. That is, in the present embodiment, a part of the second boss334ais the second positioning portion that positions the second support member (third conveyance guide), and another part of the second boss334ais the third positioning portion that positions the guide member (second conveyance guide332). Therefore, a length L1(FIG.9) of the second boss334aof the bearing member334projecting in the X-axis direction from the hole335aof the frame335is at least larger than the sum of lengths of the hole332aof the second conveyance guide332and of the hole333aof the third conveyance guide333in the X-axis direction.

A positioning configuration of the third conveyance guide333in the X-axis direction will be described with reference toFIG.10B. Both the slit333bof the third conveyance guide333and the third rib335gof the frame335extend in the direction intersecting the X-axis direction. A width of the slit333bin the X-axis direction is set to be equal to a width of the third rib335gin the X-axis direction or to be slightly larger than the width of the third rib335gin consideration of tolerance. Therefore, in a state in which the slit333bis engaged with the third rib335g, movement of the third conveyance guide333in the X-axis direction with respect to the frame335is restricted. That is, the third conveyance guide333is positioned in the X-axis direction by the engagement of the slit333band the third rib335g.

Although the third conveyance guide333of the present embodiment is positioned in the X-axis, Y-axis, and Z-axis directions as described above, the rotation (change in posture) of the bearing member334about the second boss334ais not restricted by the bearing member334or the frame335. That is, the third conveyance guide333is supported by the bearing member334so as to be rotatable about the second boss334a. Because the third conveyance guide333is rotatable, the process unit110(or another detachment unit) is easily detached as described below.

The guide portion333dthat guides the sheet at the transfer roller201and in the vicinity thereof is located downstream of the conveyance roller321in the sheet conveyance direction (above the conveyance roller in the Z-axis direction). Therefore, the hole333aand the slit333bof the third conveyance guide333are provided at a leading edge of the arm portion projecting upstream (downward) from an upstream end (lower end) of the guide portion333din the sheet conveyance direction.

Opening and Closing Operation of Third Conveyance Guide

As illustrated inFIGS.11A and11B, in the present embodiment, the process unit110is detachable from a back surface side (one side in the Y-axis direction) of the apparatus body1A.FIG.11Aillustrates a state in which a back cover340is closed, andFIG.11Billustrates a state in which the back cover340is open.

As illustrated inFIGS.1,11A, and11B, the image forming apparatus1includes the back cover340as an opening/closing member. The apparatus body1A has an opening portion OP that opens in the Y-axis direction. The back cover340is rotatably supported by the apparatus body1A. The back cover340is movable (openable and closable) between a closed position (FIG.11A) at which the back cover340covers the opening portion OP of the apparatus body1A as viewed in the Y-axis direction and an open position (FIG.11B) at which the back cover340allows the opening portion OP of the apparatus body1A to be exposed as viewed in the Y-axis direction. The back cover340in the closed position forms a side surface of the apparatus body1A in the Y-axis direction.

As illustrated inFIG.11A, the back cover340and the third conveyance guide333have guide portions340aand333efacing each other in a state in which the back cover340is located at the closed position. In a state in which the back cover340is located at the closed position, the second conveyance path P2is formed between the guide portions340aand333e. As illustrated inFIG.11B, when the back cover340is moved to the open position, the guide portion340aof the back cover340is separated from the guide portion333eof the third conveyance guide333. Therefore, the second conveyance path P2is opened, and thus a user can easily remove a sheet jammed in the second conveyance path P2.

The user can rotate (open) the third conveyance guide333by opening the back cover340, then gripping the third conveyance guide333, and pulling the third conveyance guide in an arrow direction inFIG.11A. In this operation, the third conveyance guide333rotates about the second boss334a(FIG.10) coaxial with the rotation shaft321aof the conveyance roller321. In other words, the third conveyance guide333and the conveyance roller321rotate around one rotational axis.

By opening the third conveyance guide333, a part of the first conveyance path P1is opened, and thus it is possible to easily remove a sheet jammed in the first conveyance path P1. When the third conveyance guide333is opened, the process unit110is exposed as viewed from the outside of the image forming apparatus1in the Y-axis direction (FIG.11B). Therefore, the user can grip the process unit110and remove and attach the process unit through the opening portion OP of the apparatus body1A.

As described above, the third conveyance guide333is supported to be rotatable about the second boss334aof the bearing member334, that is, about the rotation shaft321aof the conveyance roller321. Hereinafter, it will be described that this configuration enables reduction in size of the image forming apparatus.

In a case where a center of rotation of the third conveyance guide333is provided above the rotation shaft321aof the conveyance roller321, the center of rotation may interfere with a detachment path of the process unit110(an area indicated by dotted lines inFIG.11B) as viewed in the X-axis direction. When a support portion that rotatably supports the third conveyance guide333is arranged outside the detachment path of the process unit110in the X-axis direction in order to avoid the interference, the size of the image forming apparatus increases in the X-axis direction.

In a case where the center of rotation of the third conveyance guide333is provided below the rotation shaft321aof the conveyance roller321, a rotation path of the third conveyance guide333may interfere with the rotation shaft321aof the conveyance roller321. When the support portion that rotatably supports the third conveyance guide333is arranged outside the conveyance roller321in the X-axis direction in order to avoid the interference, the size of the image forming apparatus increases in the X-axis direction. Further, when the support portion that rotatably supports the third conveyance guide333is arranged below the conveyance roller321and on the back surface side (left side inFIG.11A) thereof in order to avoid the interference, the size of the image forming apparatus increases in the Y-axis direction.

Meanwhile, in the present embodiment, the center of rotation of the third conveyance guide333is coaxial with the rotation shaft321aof the conveyance roller321in the configuration in which the third conveyance guide333is openable. Therefore, it is possible to reduce the size of the image forming apparatus while improving workability of jam handling and detachment of the process unit.

Advantages of the Present Embodiment

According to the present embodiment, the first support member supporting the first roller and the second support member supporting the third roller are both positioned by the bearing member supporting the second roller. That is, the end portion of the first conveyance guide331(first support member) supporting the feed roller312(first roller) is positioned by the first boss334b(first positioning portion) of the bearing member334in a direction orthogonal to the X-axis direction (rotational axis direction of the second roller). Further, the end portion of the third conveyance guide333(second support member) supporting the transfer roller201(third roller) is positioned by the second boss334a(second positioning portion) of the bearing member334in a direction orthogonal to the X-axis direction.

Therefore, accuracy of a relative position between the rotational axis of the second roller and the rotational axis of the first roller can be easily secured, as compared with a case where, for example, the first support member and the second support member are positioned by a member different from the bearing member of the second roller. Further, accuracy of a relative position between the rotational axis of the second roller and the rotational axis of the third roller can be easily secured, as compared with a case where the first support member and the second support member are positioned by a member different from the bearing member334. Therefore, the configuration of the present embodiment can improve a relative alignment accuracy of the rollers. When the relative alignment accuracy of the rollers is improved, skew and turning of a sheet being conveyed can be reduced. This makes it possible to reduce positional deviation and deformation of an image formed on the sheet.

The bearing member334rotatably supports the rotation shaft321aof the conveyance roller321(second roller) in the hole334cof the second boss334a. The bearing member334positions the second support member (third conveyance guide333) supporting the third roller (transfer roller201) by the second boss334a(second positioning portion) provided coaxially with the hole334con the outer peripheral side of the hole334c. This makes it possible to further improve relative positional accuracy between the second roller and the third roller.

The first support member (first conveyance guide331) supporting the first roller (feed roller312) may also be positioned by the second boss334a(second positioning portion) of the bearing member334. That is, the bearing member preferably has a hole that rotatably supports the rotation shaft of the second roller, and at least one of the first positioning portion and the second positioning portion is preferably provided coaxially with the hole on the outer peripheral side of the hole. This makes it possible to improve relative positional accuracy between the second roller and at least one of the first roller and the third roller.

In the present embodiment, the first conveyance guide331serving as the first support member and the third conveyance guide333serving as the second support member are guide members having the guide portions331dand333d(first guide portion and second guide portion) for guiding a sheet. The first support member and the second support member, which are two guide members, are positioned by the same bearing member. This makes it possible to improve relative positional accuracy of the guide members and therefore to achieve stable sheet conveyance.

Further, in the present embodiment, the first conveyance guide331(first support member) and the second conveyance guide332(guide member) facing the guide portion331dof the first conveyance guide331are positioned by the bearing member334. The second conveyance guide332(guide member) and the third conveyance guide333(second support member) located on the same side as the second conveyance guide332with respect to the conveyance path and located downstream of the second conveyance guide332in the sheet conveyance direction are positioned by the bearing member334. Therefore, it is possible to improve accuracy of a width of a gap between the first conveyance guide331and the second conveyance guide332(a width of the conveyance path in a sheet thickness direction) and therefore to reduce a step between the second conveyance guide332and the third conveyance guide333. Accordingly, further stable sheet conveyance can be achieved.

The frame335serving as a restriction member/regulation member includes the first rib335d(first position regulation portion) that regulates the position of the first conveyance guide331in the X-axis direction and the third rib335g(second position regulation portion) that regulates the position of the third conveyance guide333in the X-axis direction. That is, the positions of the first conveyance guide331serving as the first support member and the third conveyance guide333serving as the second support member are regulated in the X-axis direction (the rotational axis direction of the second roller) by the same member, i.e., the frame335. This makes it possible to position the first support member and the second support member in the rotational axis direction of the second roller with a simple configuration.

The frame335serving as the restriction member/regulation member has the first groove335cthat restricts rotation of the first conveyance guide331about the first boss334b(first positioning portion). The frame335further has the second groove335ethat restricts rotation of the third conveyance guide333about the second boss334a(second positioning portion). That is, the rotation of the first conveyance guide331serving as the first support member and the third conveyance guide333serving as the second support member is restricted by the same member, i.e., the frame335. This makes it possible to stabilize angles of the first support member and the second support member with a simple configuration.

Modification Example

In the present embodiment, a mode has been 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 a sheet. The present technology is not limited thereto, and the first support member and the second support member may not have a function of guiding a sheet.

OTHER EXAMPLES

In the present embodiment, the configuration in which the process unit110is detachable from the back surface side of the apparatus body1A has been described as an example of the detachable unit. However, the present technology is not limited thereto. For example, in the image forming apparatus including an intermediate transfer belt, the present technology may be applied to a configuration in which an intermediate transfer belt unit is detachable from the back surface side of the apparatus body1A.

In the present embodiment, the image forming apparatus including the electrophotographic image forming unit1B has been described as an example, but the present technology may be applied to an image forming apparatus including an inkjet image forming unit or an offset printing mechanism as the image forming unit.

The present technology is not limited to the image forming apparatus body storing the image forming unit and may be applied to an apparatus used together with the image forming apparatus body in the image forming apparatus. Examples of such an apparatus include an image reading apparatus that reads image information from a document sheet and transmits the image information to an image forming apparatus body and a sheet processing apparatus (finisher) that performs processing such as a binding process on a sheet on which an image has been formed by the image forming apparatus body.

OTHER EMBODIMENTS

This application claims the benefit of Japanese Patent Application No. 2021-205729, filed on Dec. 20, 2021, which is hereby incorporated by reference herein in its entirety.