Gear, sheet conveyance device, and image forming apparatus

A sheet conveyance device includes a rotary shaft, a conveyance roller, a driving source, and a gear. The gear rotates integrally with the rotary shaft and transmits a driving force from the driving source to the conveyance roller. The gear includes a tooth portion engaging with another gear, a wall surface forming a hole into which the rotary shaft is inserted, a deformable portion, and a pressing part. The deformable portion has a cantilever shape at least partially provided in an area provided with the tooth portion in a gear rotation axis direction. The pressing part protrudes from the wall surface toward the rotation center of the gear, and is elastically deformed by being pressed by the rotary shaft. The pressing part presses the rotary shaft toward the wall surface on a side opposite to the deformable portion in a state where the gear is attached to the rotary shaft.

BACKGROUND

Field

The present disclosure relates to a gear for transmitting a driving force, a sheet conveyance device including the gear, and an image forming apparatus.

Description of the Related Art

An image forming apparatus and an image reading apparatus each including a sheet conveyance device that conveys a sheet have been known. The sheet conveyance device of this type transmits a driving force from a driving source to a rotary shaft of a conveyance roller using a gear attached to the rotary shaft.

In such a sheet conveyance device, a configuration in which the rotary shaft is inserted into an insertion hole of the gear and the gear is attached to the rotary shaft by snap-fit has been known. The gear having such a configuration includes a cantilever-shaped deformable portion in the insertion hole into which the rotary shaft is inserted, and an engaging portion, which prevents the gear from being detached from the rotary shaft, is provided in the deformable portion. When the rotary shaft is inserted into the insertion hole of the gear, the deformable portion is pressed by the rotary shaft and is elastically deformed, and then, the engaging portion engages with an engaged portion provided in the rotary shaft. As a result, the gear is attached to the rotary shaft.

In a gear discussed in Japanese Patent Application Laid-Open No. 2020-93886, a cantilever-shaped deformable portion is provided in an area where a tooth portion of the gear is provided in a rotation axis direction. As described above, the deformable portion is provided inside the tooth portion of the gear, which makes it possible to downsize the gear and a rotary shaft as compared with a configuration in which the rotary shaft and the insertion hole are extended and the gear is screwed to the rotary shaft.

The gear attached to the rotary shaft retains an attitude to the rotary shaft by a wall surface forming the insertion hole into which the rotary shaft is inserted. In a case where a retaining force, which retains the attitude of the gear to the rotary shaft, is weak, the gear may be inclined to the rotary shaft, and a rotation center of the gear and an axial center of the rotary shaft may be misaligned. In such a case, eccentricity occurs when the gear rotates, which may cause conveyance failure and noise. To prevent the eccentricity, it is desirable to retain the attitude of the gear to the rotary shaft and to fix the gear so as not to be inclined to the rotary shaft.

In the gear including the deformable portion inside the tooth portion, however, the retaining force, which retains the attitude of the gear to the rotary shaft, is weak, because the cantilever-shaped deformable portion is easily elastically deformed. Accordingly, the gear may bend the deformable portion and be inclined, and thus the rotation center of the gear and the axial center of the rotary shaft may be misaligned, which results in eccentricity when the gear rotates.

SUMMARY

The present disclosure is directed to reduction of occurrence of eccentricity when a gear rotates, in a configuration in which a deformable portion is provided inside a tooth portion of the gear.

According to an aspect of the present disclosure, a sheet conveyance device includes a rotary shaft configured to include an engaged portion having a concave-shape, a conveyance roller configured to rotate around the rotary shaft and to convey a sheet, a driving source configured to drive the conveyance roller, and a gear configured to rotate integrally with the rotary shaft and to transmit a driving force from the driving source to the conveyance roller, wherein the gear includes: a tooth portion configured to engage with another gear, a wall surface configured to form an insertion hole into which the rotary shaft is inserted, a deformable portion configured to have a cantilever shape at least partially provided in an area provided with the tooth portion in a rotation axis direction of the gear, configured to form the insertion hole together with the wall surface, and configured to be elastically deformed by being pressed by the rotary shaft when the rotary shaft is inserted into the insertion hole, an engaging part configured to protrude from the deformable portion toward a rotation center of the gear, to engage with the engaged portion of the rotary shaft when the rotary shaft is inserted while elastically deforming the deformable portion, and to prevent the rotary shaft from falling off from the insertion hole, and a pressing part configured to protrude from the wall surface toward the rotation center of the gear, configured to be elastically deformed by being pressed by the rotary shaft when the rotary shaft is inserted into the insertion hole, and configured to press the rotary shaft toward the wall surface on a side opposite to the deformable portion in a state where the gear is attached to the rotary shaft.

DESCRIPTION OF THE EMBODIMENTS

Some exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings. The following exemplary embodiments are examples embodying the present disclosure, and do not intend to limit the technical scope of the present disclosure.

First, an image forming apparatus400according to a first exemplary embodiment is described with reference toFIG.1.FIG.1is a cross-sectional view of the image forming apparatus400that is a color image forming apparatus of an intermediate transfer system using an electrophotographic process technique.

The image forming apparatus400includes a sheet feeding unit80that feeds a sheet S from a storage806, an image forming unit20that forms an image, an intermediate transfer unit30that transfers the formed image onto the sheet S, a fusing unit40that fuses a transferred toner image, a sheet discharge unit50that discharges the sheet S on which the image has been fused, to outside of the apparatus, and a cover70.

An arrow A indicates an example of a conveyance path of the sheet S, which is to be fed from the storage806and discharged onto a discharged-sheet stacking table51of the sheet discharge unit50. The sheet S is fed from the storage806by a pickup roller802, and is then conveyed to a registration roller pair12through a conveyance roller pair11. The sheet S forms a loop by the registration roller pair12so that a direction of a leading end of the sheet S is corrected.

The sheet S having passed through the registration roller pair12is conveyed to a transfer roller pair32. The sheet S is conveyed by the transfer roller pair32while abutting on an intermediate transfer belt31on which an image formed by the image forming unit20is placed as a toner image. As a result, an unfused toner image is formed on the sheet S. The sheet S on which the unfused toner image is placed is conveyed to the fusing unit40, and a fusing roller pair41performs heating or pressurizing processing to fuse the unfused toner image onto the sheet S. The sheet S on which the toner image has been fused is discharged to the discharged-sheet stacking table51by a discharge roller pair52positioned on a downstream of the fusing unit40.

In a case where the sheet S having a non-standard size is used, the sheet S is set on a multipurpose tray61, is fed from the multipurpose tray61to the conveyance roller pair11by a multiple feeding roller62, and is then conveyed to the discharged-sheet stacking table51in a manner similar to the case where the sheet S is fed from the storage806.

FIG.2is a perspective view illustrating a state where a rotary shaft200of driving rollers52ais inserted into a gear100. In the following description, a direction in which the rotary shaft200inFIG.2extends is referred to as a Y direction, a direction from a rotation center of the gear100toward a locking portion101described below is referred to as a Z direction, and a direction perpendicular to the Y direction and the Z direction is referred to as an X direction. The Y direction in which the rotary shaft200extends is a rotation axis direction of the gear100. The discharge roller pair52illustrated inFIG.1includes the driving rollers52aand driven rollers52b. The driving rollers52aas conveyance units obtain a rotational driving force from a motor90serving as a driving source through a gear91and a gear92. The driven rollers52brotate by following the driving rollers52a. As illustrated inFIG.2, the gear100is provided at an end of the rotary shaft200of the driving rollers52ato apply the rotational driving force from the motor90to the driving rollers52a. The gear100attached to the rotary shaft200engages with the gear92that transmits the rotational driving force from the motor90of the image forming apparatus400, thereby transmitting the driving force from the motor90to the rotary shaft200.

A configuration of the gear100is described with reference toFIG.3toFIG.7.FIG.3is a perspective view of the gear100,FIG.4is a front view of the gear100,FIG.5is a cross-sectional view of the gear100as viewed from a direction of an arrow B inFIG.4,FIG.6is a cross-sectional view of the gear100as viewed from a direction of an arrow C inFIG.4, andFIG.7is an enlarged view of an area D illustrated by a dashed line inFIG.4. In the following drawings, illustration of gear teeth of a tooth portion108of the gear100is omitted.

The gear100is made of a resin material such as a polyacetal resin (POM). As illustrated inFIG.3andFIG.4, the gear100includes the tooth portion108that engages with the gear92, a wall surface110that forms an insertion hole109into which the rotary shaft200is inserted, the locking portion101that is a deformable portion for preventing the gear100from falling off from the rotary shaft200, and a side surface portion105. The wall surface110includes a planar portion102(second planar portion) and a cylindrical portion104(curved portion). The cylindrical portion104is formed to extend in the Z direction from both ends of the planar portion102in the X direction. The insertion hole109into which the rotary shaft200is inserted is formed by the wall surface110and the locking portion101.

An inner side-surface portion106illustrated inFIG.5is provided at a position recessed by one step from the side surface portion105, and the locking portion101is provided to extend in the Y direction from the inner side-surface portion106. In other words, the locking portion101is provided in an area W provided with the tooth portion108, in the rotation axis direction (Y direction inFIG.5) of the gear100. In the present exemplary embodiment, as illustrated inFIG.5, a portion extending along the Y direction of the locking portion101is partially present in the area W; however, the whole of the locking portion101can be present in the area W. The locking portion101has a cantilever shape, and includes a craw part101b. The craw part101bserves as an engaging part having a tapered shape on a front end side. When receiving a predetermined force or more in the Z direction, the locking portion101is elastically deformed from a locking root part101a. A space112for elastic deformation of the locking portion101is provided above the locking portion101in the Z direction.

As illustrated inFIG.5toFIG.7, the gear100includes a first protrusion103aand a second protrusion103bas pressing parts, in the cylindrical portion104. The first protrusion103aand the second protrusion103beach have a shape protruding from the cylindrical portion104toward a cylindrical center (rotation center of gear100) by about 0.1 mm. Further, a first tapered part103a1and a second tapered part103b1are provided at ends on a minus side in the Y direction of the first protrusion103aand the second protrusion103b, respectively. The first tapered part103a1is an inclined surface increased in height toward a plus side in the Y direction, and smoothly connect a surface of the cylindrical portion104and a top of the first protrusion103a. Likewise, the second tapered part103b1is an inclined surface smoothly connecting the surface of the cylindrical portion104and a top of the second protrusion103b.

A configuration of the rotary shaft200is described with reference toFIG.8toFIG.10.FIG.8is a perspective view of the rotary shaft200,FIG.9is a side view of the rotary shaft200, andFIG.10is a front view of the rotary shaft200.

The rotary shaft200is made of an iron material. As illustrated inFIG.8toFIG.10, the rotary shaft200includes a first shaft planar portion201, a second shaft planar portion202(first planar portion), a locking craw engaged portion203, a first shaft cylindrical portion204a, a second shaft cylindrical portion204b, and a shaft side-surface portion205. The first shaft planar portion201and the second shaft planar portion202are planar surfaces, and the first shaft cylindrical portion204aand the second shaft cylindrical portion204bare curved surfaces. The locking craw engaged portion203as an engaged portion has a concave shape, which is recessed with respect to the first shaft cylindrical portion204aand the second shaft cylindrical portion204b.

Motion when the rotary shaft200is inserted into the insertion hole109of the gear100is described.FIG.11is a perspective view illustrating a state before the rotary shaft200is inserted into the gear100.FIG.12is a perspective view illustrating a fixed state where the gear100is fixed to the rotary shaft200, andFIG.13is a cross-sectional view illustrating the fixed state where the gear100is fixed to the rotary shaft200.

When the rotary shaft200is inserted into the insertion hole109of the gear100in a direction of an arrow E (Y direction) from a state illustrated inFIG.11, the cylindrical portion104of the gear100is overlapped with the first shaft cylindrical portion204aand the second shaft cylindrical portion204bof the rotary shaft200. In addition, the planar portion102of the gear100is overlapped with the first shaft planar portion201and the second shaft planar portion202. When the rotary shaft200is further inserted into the insertion hole109, the shaft side-surface portion205comes into contact with the first tapered part103a1and the second tapered part103b1that are the inclined surfaces, and then comes into contact with the first protrusion103aand the second protrusion103b. When the rotary shaft200is further pushed into the insertion hole109, the rotary shaft200advances while elastically deforming the first protrusion103aand the second protrusion103b, and then the shaft side-surface portion205of the rotary shaft200comes into contact with the craw part101bof the locking portion101. Thereafter, the rotary shaft200advances while elastically deforming the locking portion101from the locking root part101ain the Z direction. The craw part101bfinally engages with the locking craw engaged portion203to establish the fixed state illustrated inFIG.12.

In the fixed state illustrated inFIG.12, the gear100is fixed to the rotary shaft200, and the planar portion102of the gear100and the second shaft planar portion202of the rotary shaft200are in contact with each other. In addition, the first protrusion103aand the second protrusion103bare in contact with the second shaft cylindrical portion204bin a state of being elastically deformed.

In the fixed state where the gear100is fixed to the rotary shaft200, the planar portion102that is a second regulation portion of the gear100and the second shaft planar portion202that is a first regulation portion of the rotary shaft200are in contact with each other. Accordingly, in a case where the gear100rotates around the rotation axis (Y direction), the rotary shaft200also rotates in the same direction. As described above, providing the planar portion on each of the gear100and the rotary shaft200makes it possible to regulate rotation such that the gear100and the rotary shaft200are only integrally rotatable. In the present exemplary embodiment, the rotation is regulated by providing the planar portion102at one position of the gear100; however, the configuration is not limited thereto. Alternatively, a shape including a plurality of planes, for example, two planes can be used to regulate the rotation.

As described above, when the rotary shaft200is inserted into the insertion hole109of the gear100, the rotary shaft200is inserted while elastically deforming the first protrusion103aand the second protrusion103bprovided on the wall surface110forming the insertion hole109of the gear100. Further, the first protrusion103aand the second protrusion103bare in contact with the second shaft cylindrical portion204bin a state of being elastically deformed. Therefore, in the fixed state illustrated inFIG.13, the rotary shaft200is pressed against a side opposite to the locking portion101(minus side in Z direction) by an elastic force of the first protrusion103aand the second protrusion103b. In other words, the first protrusion103aand the second protrusion103bpress the rotary shaft200against the planar portion102on the side opposite to the locking portion101. On the other hand, the cylindrical portion104of the gear100is urged toward the locking portion101(plus side in Z direction) by the elastic force of the first protrusion103aand the second protrusion103b.

Since the locking portion101has the cantilever shape and is easily elastically deformed, a retaining force for retaining an attitude of the gear100to the rotary shaft200is weak. In the present exemplary embodiment, however, the attitude of the gear100to the rotary shaft200is retained by the elastic force of the first protrusion103aand the second protrusion103b, which makes it possible to prevent the gear100from bending the locking portion101and being inclined. As a result, it is possible to prevent misalignment between the rotation center of the gear100and the axial center of the rotary shaft200, and to reduce occurrence of eccentricity when the gear100rotates.

Further, as described above, when the rotary shaft200is inserted into the insertion hole109of the gear100, the shaft side-surface portion205comes into contact with the first tapered part103a1and the second tapered part103b1, and then comes into contact with the first protrusion103aand the second protrusion103b. If the first tapered part103a1and the second tapered part103b1that are the inclined surfaces are not provided, the first protrusion103aand the second protrusion103bmay be scraped when the shaft side-surface portion205comes into contact with the first protrusion103aand the second protrusion103b. In contrast, in the present exemplary embodiment, the shaft side-surface portion205first comes into contact with the first tapered part103a1and the second tapered part103b1that are the inclined surfaces, whereby making it possible to prevent the first protrusion103aand the second protrusion103bfrom being scraped.

Positions of the first protrusion103aand the second protrusion103bthat are the pressing parts are not limited to the positions described in the present exemplary embodiment. The positions of the first protrusion103aand the second protrusion103bthat are the pressing parts are described with reference toFIG.5andFIG.7. InFIG.7, a straight line connecting a point f that is the rotation center of the gear100and a center of the locking portion101is defined as a line g (first straight line), and a straight line perpendicular to the line g is defined as a line h (second straight line). The line g is the straight line parallel to the Z direction, and the line h is the straight line parallel to the X direction. In the present exemplary embodiment, the first protrusion103aand the second protrusion103bthat are the pressing parts are provided near the locking portion101as illustrated inFIG.7. The positions of the first protrusion103aand the second protrusion103b, however, are not limited thereto, and it is sufficient to provide the first protrusion103aand the second protrusion103bat positions to press the rotary shaft200, which has been inserted into the insertion hole109, toward the side opposite to the locking portion101. In other words, it is sufficient to provide the first protrusion103aand the second protrusion103bon the locking portion101side (deformable portion side) relative to the line h illustrated inFIG.7, in the cylindrical portion104.

In the present exemplary embodiment, the first protrusion103aand the second protrusion103bare present in a range closer to the craw part101b(plus side in Y direction) than the locking root part101ain the cylindrical portion104as illustrated inFIG.5. However, the first protrusion103aand the second protrusion103bare not necessarily present in the whole of the range closer to the craw part101bthan the locking root part101ain the cylindrical portion104. Further, the first protrusion103aand the second protrusion103bcan be present up to a side opposite to the craw part101b(minus side in Y direction) beyond the locking root part101ain the cylindrical portion104. In other words, it is sufficient for the first protrusion103aand the second protrusion103bto be at least partially present in the range closer to the craw part101bthan the locking root part101a. Thus, it is possible to urge the cylindrical portion104of the gear100toward the locking portion101(plus side in Z direction) within a range where the retaining force retaining the attitude of the gear100to the rotary shaft200is weak.

In the present exemplary embodiment, two convex portions, namely, the first protrusion103aand the second protrusion103bare provided as the pressing parts; however, the pressing part(s) can be provided at one position or three or more positions. Further, the first protrusion103aand the second protrusion103bthat are the pressing parts according to the present exemplary embodiment each have a convex shape extending in the Y direction; however, the shape of the pressing parts are not limited thereto. Alternatively, a convex portion can be provided at one position, or a plurality of convex portions can be arranged.

In the present exemplary embodiment, the configurations of the rotary shaft200of the driving rollers52aof the discharge roller pair52and the gear100are described. The configurations of the rotary shaft200and the gear100can be applied to a driving system of a conveyance unit other than the discharge roller pair52, such as the pickup roller802, the conveyance roller pair11and the registration roller pair12. Further, the above-described configurations of the gear100and the rotary shaft200are applicable to a gear and a rotary shaft thereof not including a conveyance unit, such as the gear91and the gear92. In the present exemplary embodiment, the configuration in which the gear100is used for sheet conveyance in the image forming apparatus400has been described; however, the gear100can be used for sheet conveyance in an image reading apparatus or other apparatuses.

A second exemplary embodiment is described with reference toFIG.14toFIG.18. In the above-described first exemplary embodiment, the configuration, in which the planar portion102as the second regulation portion of the gear100and the second shaft planar portion202as the first regulation portion of the rotary shaft200regulate rotation of the gear100and the rotary shaft200around the Y direction, has been illustrated. In contrast, in the second exemplary embodiment, a configuration using a pin300to regulate rotation of the gear100and the rotary shaft200around the Y axis is described. A gear100aand a rotary shaft200adescribed in the second exemplary embodiment are used to transmit the rotational driving force from the motor90to the driving rollers52afor conveying a sheet in the image forming apparatus400, as with the gear100and the rotary shaft200described in the first exemplary embodiment. In the second exemplary embodiment, configurations other than the gear100aand the rotary shaft200aof the image forming apparatus400are similar to those of the first exemplary embodiment, so that descriptions thereof are omitted.

FIG.14is a perspective view of the gear100a, andFIG.15is a perspective view of the rotary shaft200a.FIG.18is a cross-sectional view illustrating a fixed state where the gear100ais fixed to the rotary shaft200a. As illustrated inFIG.18, the gear100aincludes the tooth portion108, the locking portion101, and the side surface portion105, as with the above-described gear100. Further, as illustrated inFIG.14, the wall surface110forming the insertion hole109of the gear100aincludes only the cylindrical portion104, and the first protrusion103aand the second protrusion103bsimilar to the gear100described in the first exemplary embodiment are provided in the cylindrical portion104. The gear100aincludes a first pin fitting portion107aand a second pin fitting portion107bas the second regulation portions, and a first press-in part111a, a second press-in part111b, a third press-in part111c, and a fourth press-in part111dare provided inside the first pin fitting portion107aand the second pin fitting portion107b.

As with the above-described rotary shaft200, the rotary shaft200aillustrated inFIG.15includes the locking craw engaged portion203, the first shaft cylindrical portion204a, and the second shaft cylindrical portion204b. The rotary shaft200afurther includes a pin insertion hole206into which the pin300is inserted, and the pin300as the first regulation portion is inserted into the pin insertion hole206.

FIG.16is a perspective view illustrating a state before the rotary shaft200ais inserted into the gear100a, andFIG.17is a perspective view illustrating a state where the gear100ais fixed to the rotary shaft200a. As illustrated inFIG.16, the rotary shaft200ais inserted into the gear100ain the Y direction. At this time, the rotary shaft200ais inserted while elastically deforming the first protrusion103aand the second protrusion103bof the gear100a. Further, the rotary shaft200aadvances while elastically deforming the locking portion101from the locking root part101ain the Z direction. The craw part101bfinally engages with the locking craw engaged portion203to establish the fixed state illustrated inFIG.17andFIG.18.

In the fixed state illustrated inFIG.17andFIG.18, the first protrusion103aand the second protrusion103bare in contact with the second shaft cylindrical portion204bin a state of being elastically deformed. As in the first exemplary embodiment, the cylindrical portion104of the gear100ais urged toward the locking portion101(plus side in Z direction) by the elastic force of the first protrusion103aand the second protrusion103b, thereby preventing the gear100afrom bending the locking portion101and being inclined. As a result, occurrence of eccentricity of the gear100ais suppressed.

Further, when the rotary shaft200ais inserted into the gear100a, the pin300fits into the first pin fitting portion107aand the second pin fitting portion107b. An internal distance between the first press-in part111aand the second press-in part111bprovided in the first pin fitting portion107ais made smaller than a width of the pin300, and the pin300is fixed in a state where the first press-in part111aand the second press-in part111bare elastically deformed. The second pin fitting portion107balso has a configuration similar to the configuration of the first pin fitting portion107a. As a result, it is possible to prevent delay caused by backlash when the gear100aand the rotary shaft200aintegrally rotate.

As illustrated inFIG.17andFIG.18, when the gear100arotates around the Y direction in the state where the gear100ais fixed to the rotary shaft200a, the rotary shaft200aalso rotates in the same direction by the pin300. As described above, the rotation can be regulated using the pin300such that the gear100aand the rotary shaft200aare only integrally rotatable.

This application claims the benefit of Japanese Patent Application No. 2020-143827, filed Aug. 27, 2020, which is hereby incorporated by reference herein in its entirety.