SHEET FEEDING APPARATUS AND IMAGE FORMING APPARATUS

Abstract

The sheet feeding apparatus includes a sheet supporting portion, a sheet feeding portion configured to feed the sheet, a lifting unit including an urging portion and a shaft portion, wherein the damping unit includes a first gear supported rotatably on the shaft portion, a base portion, a second gear, and a damping portion, the damping unit being configured to be switched, in a state where the shaft portion is rotating, between a first state in which the damping unit damps the rotation of the shaft portion and a second state in which the damping unit does not damp the rotation of the shaft portion, and a distance between a center of rotation of the first gear and a center of rotation of the second gear is fixed regardless of whether the damping unit is in the first state or in the second state.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a sheet feeding apparatus for feeding sheets and an image forming apparatus equipped with the same.

Description of the Related Art

Hitherto, a sheet feeding cassette in which a bottom plate having sheets stacked thereon is urged by a spring toward a sheet feed roller so that the bottom plate is lifted toward the sheet feed roller is proposed (refer to Japanese Patent Application Laid-Open Publication No. H11-29226). The sheet feeding cassette is equipped with a hydraulic type damper including a pinion that meshes with a rack formed on the bottom plate and a support member that supports the pinion rotatably. The hydraulic damper generates damping force with respect to the bottom plate by the pinion relatively rotating with respect to the support member in conjunction with the lifting and lowering of the bottom plate.

When separating and feeding sheets, the bottom plate is slightly displaced in the vertical direction by the sheet feed roller, and at this time, it is preferable that damping force by the hydraulic damper does not occur so that frictional force between the sheet feed roller and the sheet supported on the bottom plate is maintained appropriately. The support member is supported swingably within a predetermined range with respect to the cassette body and in a state where the support member is swinging, the pinion will not rotate and damping force will not occur. In a state where the bottom plate is displaced in the vertical direction by the sheet feed roller, the support member swings within a predetermined range so that frictional force between the sheet feed roller and the bottom plate is maintained appropriately.

However, according to the image forming apparatus disclosed in Japanese Patent Application Laid-Open Publication No. H11-29226, the movement of the support member causes relative positions of the center of rotation of the pin and the center of rotation of the rack on the bottom plate to differ. Therefore, the swingable range of the support member was limited in order to maintain meshing of the pinion and the rack on the bottom plate, and it was not possible to set a period where damping force is generated or a period where damping force is not generated by the hydraulic damper freely.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, the sheet feeding apparatus includes a sheet supporting portion configured to support a sheet, a sheet feeding portion configured to feed the sheet supported on the sheet supporting portion, a lifting unit including an urging portion configured to urge either one of the sheet supporting portion and the sheet feeding portion to the other of the sheet supporting portion and the sheet feeding portion, and a shaft portion configured to rotate in conjunction with lifting and lowering of the one of the sheet supporting portion and the sheet feeding portion, the lifting unit being configured to lift and lower the one of the sheet supporting portion and the sheet feeding portion to the other of the sheet supporting portion and the sheet feeding portion, and a damping unit connected to the shaft portion and configured to damp rotation of the shaft portion, wherein the damping unit includes a first gear supported rotatably on the shaft portion, a base portion, a second gear meshed with the first gear and configured to relatively rotate with respect to the base portion, and a damping portion provided on the base portion and configured to damp the rotation of the shaft portion by relative rotation of the second gear with respect to the base portion, the damping unit being configured to be switched, in a state where the shaft portion is rotating, between a first state in which the damping unit damps the rotation of the shaft portion and a second state in which the damping unit does not damp the rotation of the shaft portion, and a distance between a center of rotation of the first gear and a center of rotation of the second gear is fixed regardless of whether the damping unit is in the first state or in the second state.

Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating an appearance of a printer according to a first embodiment.

FIG. 2 is a schematic drawing illustrating a configuration of a printer.

FIG. 3A is a perspective view illustrating a manual sheet feeding apparatus.

FIG. 3B is a perspective view illustrating a lifting unit.

FIG. 4A is a cross-sectional view taken in arrow X-X direction of FIG. 3B illustrating the lifting unit in a state where a linear motion member is lifted.

FIG. 4B is a cross-sectional view taken in arrow X-X direction of FIG. 3B illustrating the lifting unit in a state where the linear motion member is lowered.

FIG. 5A is a cross-sectional view taken in arrow Y-Y direction of FIG. 3B illustrating a damping unit in a state where the linear motion member is lifted.

FIG. 5B is a cross-sectional view taken in arrow Y-Y direction of FIG. 3B illustrating the damping unit in a state where the linear motion member is lowered.

FIG. 6 is a perspective view illustrating the damper.

FIG. 7A is a cross-sectional view illustrating a damping unit according to a second embodiment in a state where a linear motion member is lifted.

FIG. 7B is a cross-sectional view illustrating the damping unit according to the second embodiment in a state where the linear motion member is lowered.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

Now, an image forming apparatus according to a first embodiment of the present disclosure will be described with reference to the drawings. The image forming apparatus according to the first embodiment is an image forming apparatus, such as a copying machine, a printer, a facsimile, or a multifunction device having these functions, that forms an image on a sheet and discharges the sheet on a sheet discharge tray 40. In the following embodiment, a printer 1 which is a color laser beam printer adopting an electrophotographic system is described as an example of the image forming apparatus. The printer 1 includes, as illustrated in FIGS. 1 and 2, an image forming unit 10 configured to form an image on a sheet S, a cassette sheet feeding apparatus 50, a manual sheet feeding apparatus 60 serving as a sheet feeding apparatus, a fixing roller pair 30, and sheet discharge roller pairs 31 and 32. Sheet S refers to thin sheet-like recording medium, such as paper sheet and envelope, plastic film for overhead projector (OHT), and cloth. In the following description, positional relationships of up, down, right, left, front and rear are described based on the state where the printer 1 is viewed in the front side, that is, in the viewpoint of FIG. 2.

General Configuration of Printer

The image forming unit 10 includes four process cartridges 11Y through 11BK forming toner images of four colors, which are yellow (Y), magenta (M), cyan (C) and black (BK), and scanner units 16Y through 16BK. The four process cartridges 11Y through 11BK and the scanner units 16Y through 16BK are arranged in an approximately horizontal line. The four process cartridges 11Y through 11BK and the scanner units 16Y through 16BK have similar configurations except for the difference in the colors of the formed images. Therefore, the configurations and image forming processes of only the process cartridge 11Y and the scanner unit 16Y are described, and the descriptions of process cartridges 11M through 11BK and scanner units 16M through 16BK are omitted.

The process cartridge 11Y includes a photosensitive drum 13, a charge roller 14, a developing unit 12 including a developing roller 12a, and a cleaning blade 15. The photosensitive drum 13 has an organic photoconductive layer coated on an outer periphery of an aluminum cylinder, and it is rotated by a drive motor not shown. The scanner unit 16Y includes a laser emitting portion 17a from which laser is emitted, and a polygon mirror 17b that reflects the laser beam emitted from the laser emitting portion 17a and guides the beam to the photosensitive drum 13.

When an image forming command is entered to the printer 1, an image forming process by the image forming unit 10 is started based on the image information entered, for example, from an outside computer connected to the printer 1. The scanner unit 16Y irradiates laser beams corresponding to the image information to the photosensitive drum 13 of the process cartridge 11Y. In this state, the surface of the photosensitive drum 13 is uniformly charged to predetermined polarity and potential in advance by the charge roller 14, and electrostatic latent image is formed on the surface by having laser beam irradiated from the scanner unit 16Y. The electrostatic latent image formed on the photosensitive drum 13 is developed by the developing roller 12a, and yellow (Y) toner image is formed on the photosensitive drum 13. Similarly, laser beams are irradiated from the scanner units 16Y through 16BK to the respective photosensitive drums of process cartridges 11M through 11BK, and toner images of magenta (M), cyan (C) and black (BK) are formed on the respective photosensitive drums.

An intermediate transfer belt 18 is arranged above the process cartridges 11Y through 11BK. The intermediate transfer belt 18 is stretched across a driving roller 18a and a secondary transfer counter roller 18b, and a cleaning device 20 is arranged facing the driving roller 18a. Primary transfer rollers 19a through 19d are provided on an inner side of the intermediate transfer belt 18. A secondary transfer roller 22 is provided on an opposite side of the secondary transfer counter roller 18b interposing the intermediate transfer belt 18.

In the image forming process, toner images of respective colors formed on the respective photosensitive drums are transferred via the primary transfer rollers 19a through 19d to the intermediate transfer belt 18 and conveyed on the intermediate transfer belt 18 rotated by the driving roller 18a to the secondary transfer roller 22. Primary transfer of the respective colors is performed at a matched timing to superpose the image on a toner image primarily transferred at an upstream side on the intermediate transfer belt 18. The toner remaining on the photosensitive drum 13 is removed by the cleaning blade 15.

The cassette sheet feeding apparatus 50 is arranged on a printer body la in a manner capable of being drawn out of and attached to the printer body la, and includes a cassette 51 storing sheets S, a conveyance roller 53 for feeding the sheets S stored in the cassette 51, a feed roller 54 and a retard roller 55. The cassette 51 includes a sheet supporting portion 52 on which sheets S are supported, and a spring not shown that urges the sheet supporting portion 52 upward, and the sheet supporting portion 52 is retained at a feed position where an uppermost sheet of the sheet bundle supported on the sheet supporting portion 52 is pressed against the conveyance roller 53. In feeding sheets by the cassette sheet feeding apparatus 50, along with the above-described image forming process, the sheet S supported on the sheet supporting portion 52 is sent to a sheet conveyance direction by the conveyance roller 53. Further, the feed roller 54 conveys the sheet S received from the conveyance roller 53 toward a registration roller pair 21. The retard roller 55 in pressure contact with the feed roller 54 receives input of rotary drive in a direction opposite from a rotation direction in which the sheet S is conveyed in the sheet conveyance direction, and the sheet S is separated one sheet at a time at the feed roller 54.

The manual sheet feeding apparatus 60 includes an outer cover 61 supported pivotably on the printer body la, a stacking plate 62 connected pivotably to the outer cover 61 and serving as a sheet supporting portion for supporting sheets S, and a lifting unit 80 for lifting and lowering the stacking plate 62. An end portion 62a which is an upstream end in the sheet conveyance direction of the stacking plate 62 is pivotably connected to the outer cover 61, and the stacking plate 62 is lifted by having a lower side of an end portion 62b which is a downstream end in the sheet conveyance direction of the stacking plate 62 pushed by the lifting unit 80.

Further, the manual sheet feeding apparatus 60 includes a conveyance roller 63 serving as a sheet feeding portion for feeding sheets S stacked on the stacking plate 62. The sheet S stacked on the stacking plate 62 abuts against the conveyance roller 63 by the lifting of the stacking plate 62 and is separated from the conveyance roller 63 by the lowering of the stacking plate 62 by the lifting unit 80. While feeding sheets by the manual sheet feeding apparatus 60, in parallel with the above-described image forming process, the sheets S stacked on the stacking plate 62 are sent by the conveyance roller 63 toward a registration roller pair 21.

The registration roller pair 21 corrects skewing of the sheet S by abutting against a leading edge of the sheet in the sheet conveyance direction and conveys the sheet toward the secondary transfer roller 22 at a matched timing with the advancement of the image forming process by the image forming unit 10. A full-color toner image formed on the intermediate transfer belt 18 is transferred to the sheet S by secondary transfer bias applied to the secondary transfer roller 22 at a nip formed by the secondary transfer counter roller 18b and the secondary transfer roller 22. Predetermined heat and pressure are applied from the fixing roller pair 30 to the sheet S on which the toner image is transferred, by which toner is melted and fixed. The sheet S having passed through the fixing roller pair 30 is destaticized by a destaticizing member not shown, before being discharged by sheet discharge roller pairs 31 and 32 onto a sheet discharge tray 40. After toner image has been transferred, toner remaining on the surface of the intermediate transfer belt 18 is removed by the cleaning device 20.

Further, the printer 1 includes a control unit 200 composed of a computer and including a CPU 201 and a memory 202. The memory 202 includes a ROM 202a that stores programs controlling respective units, and a RAM 202b that stores data temporarily. The CPU 201 is connected via an input/output circuit to respective driving sources and sensors, communicating with respective units and controlling operations thereof. Detailed Configuration of Manual Sheet Feeding Apparatus

As illustrated in FIGS. 3A and 3B, the manual sheet feeding apparatus 60 includes a sheet feed frame 64 serving as a frame unit fixed to the printer body 1a, and a sheet feed shaft 63a rotatably supported on the sheet feed frame 64 and having the conveyance roller 63 attached thereto. FIG. 3A is a perspective view illustrating the manual sheet feeding apparatus 60, and FIG. 3B is a perspective view illustrating the lifting unit 80. A drive gear 63d that rotates by a feed motor M serving as a driving source is attached to a first end of the sheet feed shaft 63a. Further, the lifting unit 80 including a pivot shaft 65 serving as a shaft portion that extends in parallel with the sheet feed shaft 63a and a drive transmission mechanism 70 that transmits the driving force of the feed motor M to the pivot shaft 65 is attached to the sheet feed frame 64. A damping unit 90 capable of applying damping force to the rotation of the pivot shaft 65 is connected to the pivot shaft 65. That is, the damping unit 90 damps the rotation of the pivot shaft 65.

The lifting unit 80 includes, as illustrated in FIGS. 4A and 4B, a gear 81 fixed to the pivot shaft 65, and a linear motion member 82 that serving as a pressing portion connected to the gear 81 and that is capable of being lifted and lowered and also capable of abutting against and pressing an end portion 62b of the stacking plate 62. FIG. 4A is a cross-sectional view taken in arrow X-X direction of FIG. 3B illustrating the lifting unit 80 in a state where the linear motion member 82 is raised, and FIG. 4B is a cross-sectional view taken in arrow X-X direction of FIG. 3B illustrating the lifting unit 80 in a state where the linear motion member 82 is lowered. The linear motion member 82 is urged toward the end portion 62b by a pressing spring 83 serving as an urging portion provided therein and maintained in a state where an upper end portion 82b is abutted against the end portion 62b. The lifting unit 80 lifts the stacking plate 62 by the lifting of the linear motion member 82 and lowers the stacking plate 62 by its own weight by the lowering of the linear motion member 82.

Further, a rack portion 82a that meshes with the gear 81 is formed on the linear motion member 82, and the rack portion 82a moves in conjunction with the gear 81. In a state where the linear motion member 82 is lifted by the pressing spring 83, the gear 81 pivots in an arrow B direction illustrated in FIG. 4A. Meanwhile, in a state where the gear 81 pivots in an arrow C direction illustrated in FIG. 4B opposite to the arrow B direction, the linear motion member 82 is lowered against the urging force of the pressing spring 83. In FIG. 4A, the stacking plate 62 is positioned at a lifted position where the conveyance roller 63 is capable of feeding the sheet supported on the stacking plate 62. In FIG. 4B, the stacking plate 62 is positioned at a lowered position where the conveyance roller 63 is separated from the sheet supported on the stacking plate 62. As described, the lifting unit 80 lifts and lowers the stacking plate 62 between a lifted position and a lowered position.

The drive transmission mechanism 70 includes, as illustrated in FIGS. 3A and 3B, a gear 71 that rotates by driving force of the feed motor M, a control gear 72 capable of being meshed with the gear 71, a control cam 74 connected to the control gear 72, and a cam follower 75 capable of abutting against the control cam 74. The cam follower 75 is connected to the pivot shaft 65 and pivots integrally with the pivot shaft 65. In the present embodiment, each position of the cam follower 75, the pivot shaft 65, the gear 81 and the linear motion member 82 in a state where the sheet S supported on the stacking plate 62 is separated from the conveyance roller 63 is defined as a separated position. Each position of the cam follower 75, the pivot shaft 65, the gear 81 and the linear motion member 82 in a state where the sheet S supported on the stacking plate 62 is abutted against the conveyance roller 63 is defined as an abutted position. Each of the pivot shaft 65, the cam follower 75 and the gear 81 moves from the separated position to the abutted position by pivoting in the arrow B direction by urging force of the pressing spring 83.

The control gear 72 includes a chipped tooth gear 72a having a gear part that meshes with the gear 71 and a chipped tooth part where a gear is not formed, and an engagement part 72b to which a claw 76a of a solenoid 76 that controls the operation of the control gear 72 can be engaged, the control gear 72 rotating together with the control cam 74. The claw 76a of the solenoid 76 is urged toward the engagement part 72b by a spring not shown, and when the solenoid 76 is set to on state, the claw 76a is separated from the engagement part 72b against the urging force of a spring not shown. Further, in a state where the claw 76a of the solenoid 76 is engaged with the engagement part 72b and the control gear 72 is stopped, the chipped tooth part of the chipped tooth gear 72a is opposed to the gear 71 and driving force will not be transmitted from the gear 71 to the control gear 72.

In a state where the engagement part 72b and the claw 76a are engaged, the control cam 74 of the control gear 72 abuts against the cam follower 75 and positions the cam follower 75 at the separated position. That is, in a state where the engagement part 72b and the claw 76a are engaged, as illustrated in FIGS. 3A, 3B and 4B, each of the cam follower 75, the pivot shaft 65, the gear 81 and the linear motion member 82 is positioned at the separated position. The cam follower 75 positioned at the separated position is abutted against the control cam 74 and regulated from rotating so that the linear motion member 82 is positioned at the separated position against the urging force of the pressing spring 83. If the control cam 74 rotates in an arrow A direction in this state, the control cam 74 is separated from the cam follower 75. Then, the linear motion member 82 is moved upward by urging force of the pressing spring 83, and as illustrated in FIGS. 3A, 3B and 4A, each of the cam follower 75, the pivot shaft 65, the gear 81 and the linear motion member 82 is positioned at the abutted position.

Now, the operation of the lifting unit 80 in a state where sheets are fed continuously will be described. In standby state, the linear motion member 82 is positioned at the separated position, the claw 76a of the solenoid 76 is engaged with the engagement part 72b of the control gear 72, and the chipped tooth part of the chipped tooth gear 72a opposes to the gear 71. If a sheet feed job is entered, the feed motor M is driven, by which the conveyance roller 63 and the gear 71 are rotated. Then, the solenoid 76 turns from off state to on state, and the claw 76a is separated from the engagement part 72b. The control gear 72 starts to rotate in the arrow A direction by a spring 73 provided in the control gear 72, and the gear part of the chipped tooth gear 72a is meshed with the gear 71. In a state where the control cam 74 rotates in the arrow A direction together with the control gear 72 rotated by driving force of the gear 71, the control cam 74 is separated from the cam follower 75. Thereby, the linear motion member 82 is lifted toward the abutted position by urging force of the pressing spring 83. In a state where the sheet S supported on the stacking plate 62 is abutted against the conveyance roller 63, the sheet S is fed.

After the conveyance roller 63 has been abutted against the sheet S for a predetermined time, the cam follower 75 is pressed by the control cam 74 rotating in the arrow A direction, and the pivot shaft 65 and the gear 81 are rotated in the arrow C direction illustrated in FIG. 4B. In a state where the gear 81 rotates in the arrow C direction, the linear motion member 82 meshing with the gear 81 is lowered from the abutted position toward the separated position against the urging force of the pressing spring 83. Then, in a state where the linear motion member 82 is positioned at the separated position, the claw 76a of the solenoid 76 in the off state engages with the engagement part 72b and returns to the standby state. As described, the operation of the lifting unit 80 corresponding to one sheet is completed, and thereafter, the solenoid 76 is turned on and off in response to the feeding of a subsequent sheet S. As described, the control gear 72 is controlled to rotate once by driving force of the feed motor M, and the lifting unit 80 operates in a state where one rotation of the control gear 72 corresponds to one cycle.

Detailed Configuration of Damping Unit

The damping unit 90 includes, as illustrated in FIGS. 5A, 5B and 6, a shaft-side gear 91 serving as a first gear connected to the pivot shaft 65, and a damper 95 that is supported pivotably on the sheet feed frame 64 and meshed with the shaft-side gear 91. FIG. 5A is a cross-sectional view taken in arrow Y-Y direction of FIG. 3B illustrating the damping unit 90 in a state where the linear motion member 82 is lifted, FIG. 5B is a cross-sectional view taken in arrow Y-Y direction of FIG. 3B illustrating the damping unit 90 in a state where the linear motion member 82 is lowered, and FIG. 6 is a perspective view illustrating the damper 95.

The damper 95 includes a holder 96 serving as a base portion that is supported movably with respect to the sheet feed frame 64, and a damper gear 98 serving as a second gear that is meshed with the shaft-side gear 91 and supported rotatably around a rotation shaft 97 with respect to the holder 96. In the manual sheet feeding apparatus 60, the holder 96 is supported pivotably around the rotation shaft 97 with respect to the sheet feed frame 64, and the distance between a center of rotation 91a of the shaft-side gear 91 and the rotation shaft 97 serving as a center of rotation of the damper gear 98 is always fixed. The damper gear 98 relatively rotates in an arrow D direction with respect to the sheet feed frame 64 by the shaft-side gear 91 pivoting in the arrow B direction, and the damper gear 98 relatively rotates in an arrow E direction by the shaft-side gear 91 pivoting in the arrow C direction.

A damping portion 99 that damps rotation of the pivot shaft 65 by the damper gear 98 relatively rotating with respect to the holder 96 is disposed inside the holder 96. Further, the damping unit 90 includes regulating portions 92a and 92b that allow movement of the holder 96 within a predetermined range with respect to the sheet feed frame 64 and that regulate movement of the holder 96 by abutting against the holder 96. That is, the holder 96 is supported with play on the sheet feed frame 64. The regulating portion 92a is arranged downstream in the arrow D direction with respect to the holder 96, and the regulating portion 92b is arranged downstream in the arrow E direction with respect to the holder 96. Further, positions of the regulating portions 92a and 92b are adjustable with respect to the sheet feed frame 64. For example, a rotary-type oil damper or air damper is used as the damper 95, but any type of rotary damper can be adopted.

Moreover, according to the manual sheet feeding apparatus 60, damping force of the damping portion 99 is greater than a resistance such as friction between the sheet feed frame 64 and the holder 96. Therefore, in a state where the holder 96 is not abutted against the regulating portions 92a and 92b, the damper gear 98 does not relatively rotate with respect to the holder 96 when the holder 96 relatively rotates with respect to the sheet feed frame 64. Meanwhile, in a state where the holder 96 abuts against and is regulated from rotating by the regulating portions 92a and 92b, the holder 96 does not relatively rotate with respect to the sheet feed frame 64, and the damper gear 98 relatively rotates with respect to the holder 96. That is, the damping unit 90 is capable of being switched between a first state where rotation of the pivot shaft 65 is damped and a second state where rotation of the pivot shaft 65 is not damped according to whether the holder 96 is relatively rotated with respect to the sheet feed frame 64 when the pivot shaft 65 is pivoting. The damping unit 90 is in the second state when it is separated from the regulating portions 92a and 92b, and is in the first state when the holder 96 is abutted against the regulating portions 92a and 92b and regulated from rotating.

In a state where the linear motion member 82 is positioned at the separated position, the holder 96 is positioned at a position illustrated by a broken line in FIG. 5A. Then, as described above, in a state where the linear motion member 82 is lifted from the separated position toward the abutted position, the pivot shaft 65 pivots in the arrow B direction, and the damper gear 98 and the holder 96 rotate in the arrow D direction. That is, in the damping unit 90, the holder 96 is not abutted against the regulating portion 92a immediately after rotation of the damper gear 98 has started, so that the holder 96 rotates relatively with respect to the sheet feed frame 64, but the damper gear 98 does not rotate relatively with respect to the holder 96. Therefore, in the manual sheet feeding apparatus 60, immediately after starting of rotation of the pivot shaft 65 in a state where the damping unit 90 is in the second state, the cam follower 75, the pivot shaft 65, the gear 81 and the linear motion member 82 move.

In a state where the shaft-side gear 91 pivots further in the arrow B direction together with the pivot shaft 65, the holder 96 abuts against the regulating portion 92a. Thereby, in the manual sheet feeding apparatus 60, relative rotation of the holder 96 with respect to the sheet feed frame 64 is stopped, and relative rotation of the damper gear 98 with respect to the holder 96 is started. Therefore, according to the manual sheet feeding apparatus 60, the damping unit 90 is set to the first state when a certain time has elapsed after starting of rotation of the pivot shaft 65. In other words, the damping unit 90 is switched from the second state to the first state when the stacking plate 62 moves on the way to lifted position from the lowered position. Further according to the manual sheet feeding apparatus 60, in the first state, the cam follower 75, the pivot shaft 65, the gear 81 and the linear motion member 82 move, and the sheet S supported on the stacking plate 62 abuts against the conveyance roller 63. The position of the regulating portion 92a should preferably be adjusted so that the damping unit 90 is set to the first state immediately before the sheet S supported on the stacking plate 62 collides against the conveyance roller 63.

Furthermore, the cam follower 75 is pressed by the control cam 74 rotating in the arrow A direction, and as illustrated in FIG. 5B, the pivot shaft 65 rotates in the arrow C direction. By the pivot shaft 65 rotating in the arrow C direction, the linear motion member 82 meshing with the gear 81 fixed to the pivot shaft 65 is lowered from the abutted position toward the separated position against urging force of the pressing spring 83. In the damping unit 90, the damper gear 98 and the holder 96 are rotated in the arrow E direction by the pivot shaft 65 and the shaft-side gear 91 pivoting in the arrow C direction. The holder 96 relatively rotates in the arrow E direction with respect to the sheet feed frame 64 and abuts against the regulating portion 92b. Then, the control gear 72 rotates to a release position, by which the claw 76a of the solenoid 76 is reengaged with the engagement part 72b and rotation is stopped.

As described, while the control gear 72 rotates once, the stacking plate 62 moves from the lowered position to the lifted position by being pressed by the linear motion member 82 lifted by urging force of the pressing spring 83, and thereafter, moves from the lifted position to the lowered position by the gear 81 lowering the linear motion member 82 against urging force of the pressing spring 83. The pivot shaft 65 rotates in the arrow B direction serving as the first direction in a state where the stacking plate 62 moves from the lowered position to the lifted position, and rotates in the arrow C direction serving as the second direction that is opposite to the arrow B direction in a state where the stacking plate 62 moves from the lifted position to the lowered position. Further, the holder 96 is rotatable in the arrow D direction serving as the third direction by rotation of the pivot shaft 65 in the arrow B direction, and rotatable in the arrow E direction as the fourth direction that is opposite to the arrow D direction by the rotation of the pivot shaft 65 in the arrow C direction. The regulating portion 92a serving as the first regulating part regulates rotation of the holder 96 in the arrow D direction, and the regulating portion 92b serving as the second regulating part regulates rotation of the holder 96 in the arrow E direction.

As described, according to the printer 1, the rotational speed of the pivot shaft 65 can be reduced in the first state of the damping unit 90, so that noise generated when the sheet S supported on the stacking plate 62 abuts against the conveyance roller 63 can be reduced. Further, the damping unit 90 is switchable between the first state and the second state, and the rotation speed of the pivot shaft 65 can be prevented from being constantly set to low speed by damping force, so that cycle time of the image forming process can be prevented from being deteriorated.

Actually, the damping unit 90 is in a second state from when the stacking plate 62 has started to be lifted until immediately before the sheet S on the stacking plate 62 collides against the conveyance roller 63, and the damping unit 90 will be in the first state at a timing where the noise caused by the collision of the sheet S and the conveyance roller 63 becomes relatively small. The switching timing of the first state and the second state of the damping unit 90 can be changed by adjusting the positions of the regulating portions 92a and 92b with respect to the sheet feed frame 64. According to the present embodiment, level of meshing of the shaft-side gear 91 and the damper gear 98 is always fixed since the distance between the center of rotation 91a of the shaft-side gear 91 and the rotation shaft 97 serving as the center of rotation of the damper gear 98 is fixed, regardless of whether the damping unit 90 is in the first state or in the second state. Therefore, the timing to switch the damping unit 90 to the first state and the second state can be varied freely by adjusting the rotation phase of the shaft-side gear 91 and the holder 96 or by adjusting the positions of the regulating portions 92a and 92b. By appropriately setting the timing in which the damping unit 90 is set to the second state, effective noise reduction is realized while preventing deterioration of cycle time of the image forming process.

Second Embodiment

Next, a second embodiment will be described. The configurations similar to the first embodiment are either not shown or denoted with the same reference numbers and descriptions thereof are omitted. As illustrated in FIGS. 7A and 7B, a damping unit 110 capable of damping rotation of the pivot shaft 65 is connected to the pivot shaft 65. FIG. 7A is a cross-sectional view taken in arrow Y-Y direction of FIG. 3 illustrating the damping unit 110 in which the linear motion member 82 is lifted, and FIG. 7B is a cross-sectional view taken in arrow Y-Y direction of FIG. 3 illustrating the damping unit 110 in which the linear motion member 82 is lowered. The damping unit 110 includes a shaft-side gear 111 serving as a first gear connected to the pivot shaft 65, and a damper 115 that is fixed to the sheet feed frame 64 and meshing with the shaft-side gear 111. The pivot shaft 65 includes a pin 65e serving as an engagement portion formed in an I shape when viewed in the axial direction. The shaft-side gear 111 includes a hole portion 111a serving as an engaged portion where the pin 65e is engaged pivotably for a predetermined angle without abutting against the shaft-side gear 111. As described, the shaft-side gear 111 is connected with play so that it is relatively pivotable for a predetermined angle to the pivot shaft 65.

The damper 115 includes a holder 116 serving as a base portion fixed by a screw 117 so as not to pivot with respect to the sheet feed frame 64, and the damper gear 98 supported rotatably around the rotation shaft 97 on the holder 116. In other words, the holder 116 of the damper 115 is supported in a non-movable manner with respect to the sheet feed frame 64. In the manual sheet feeding apparatus 60, the distance between a center of rotation 111b of the shaft-side gear 111 and the rotation shaft 97 serving as a center of rotation of the damper gear 98 is always fixed.

In the manual sheet feeding apparatus 60, in order to lift the stacking plate 62, the pivot shaft 65 start pivoting in the arrow B direction, similar to the first embodiment. As illustrated in FIG. 7A, in a state where the pivot shaft 65 pivots in the arrow B direction, at first, the pivot shaft 65 rotates relatively with respect to the shaft-side gear 111, but the shaft-side gear 111 will not rotate until the pin 65e of the pivot shaft 65 is engaged with the hole portion 111a. Thus, the damper gear 98 will not rotate relatively with respect to the holder 116. Therefore, in a state where the pivot shaft 65 is in the area of play with respect to the shaft-side gear 111, that is, where the pivot shaft 65 pivots relatively for a predetermined angle, the damping unit 110 is in a second state where rotation of the pivot shaft 65 is not damped. Thereby, the stacking plate 62 is first lifted in a state where the damping unit 110 is in the second state. If the pin 65e of the pivot shaft 65 engages with the hole portion 111a and the pivot shaft 65 starts rotating integrally with the shaft-side gear 111, the damper gear 98 meshing with the shaft-side gear 111 will rotate relatively with respect to the holder 116. Thereby, the damping unit 110 is switched from the second state to the first state where rotation of the pivot shaft 65 is damped. If the damping unit 110 is in the second state, the stacking plate 62 is lifted and abutted against the conveyance roller 63 via the sheet S.

As described, according to the printer 1, the rotational speed of the pivot shaft 65 can be reduced in the first state of the damping unit 110, so that noise generated when the sheet S supported on the stacking plate 62 abuts against the conveyance roller 63 can be reduced. The damping unit 110 can be switched between the first state and the second state, so that the rotational speed of the pivot shaft 65 can be prevented from being constantly reduced by damping force, so that the deterioration of cycle type of the image forming process can be prevented.

The switching timing for switching between the first state and the second state of the damping unit 110 can be changed by varying the shape of the pin 65e of the pivot shaft 65 and the hole portion 111a of the shaft-side gear 111. According to the present embodiment, since the distance between the center of rotation 111b of the shaft-side gear 111 and the rotation shaft 97 serving as the center of rotation of the damper gear 98 is fixed regardless of whether the damping unit 110 is in the first state or in the second state, the level of meshing of the shaft-side gear 111 and the damper gear 98 is fixed. Therefore, the switching timing of the first state and the second state of the damping unit 90 can be changed freely. Thereby, noise can be reduced effectively while preventing deterioration of cycle time of the image forming process by appropriately setting the period in which the damping unit 110 is set to the second state.

In the first embodiment, the holder 96 is formed rotatably around the rotation shaft 97 serving as the center of rotation of the damper gear 98, but the present invention is not restricted thereto. For example, the holder 96 can be supported rotatably on the sheet feed frame 64 around the center of rotation 91a of the shaft-side gear 91. In that case, in a state where rotation is not regulated by the regulating portions 92a and 92b, the holder 96 rotates around the center of rotation 91a, and the damper gear 98 revolves around the center of rotation 91a without relatively rotating with respect to the holder 96.

In the first and second embodiments, the shaft-side gears 91 and 111 and the damper gear 98 are connected in a directly meshing manner, but the present invention is not limited to such arrangement, and they can be connected in an indirectly meshed manner with other gears interposed therebetween. Further according to the first and second embodiments, damping force is generated by the damping units 90 and 110 formed with play with respect to the rotation of the pivot shaft 65, but the present invention is limited to this arrangement. For example, a configuration can be adopted where a spring clutch is disposed between the pivot shaft 65 and the shaft-side gear 91 so that the shaft-side gear 91 rotates after a predetermined time has elapsed from the starting of rotation of the pivot shaft 65.

Further according to the first and second embodiments, the printer 1 is configured so that the stacking plate 62 is lifted and lowered, but the present invention is not limited to this example, and a configuration can be adopted where the conveyance roller 63 is lifted and lowered and the damping unit 90 or 110 applies damping force to the lifting and lowering of the conveyance roller 63. The printer 1 is not limited to the present embodiments as long as either one of the stacking plate 62 and the conveyance roller 63 is designed to urge the other. The printer 1 adopts a configuration where the damping unit 90 or 110 is arranged on the manual sheet feeding apparatus 60, but the present invention is not limited to this example, and a configuration can be adopted where the damping unit 90 or 110 is arranged on the cassette sheet feeding apparatus 50.

Further according to the first and second embodiments, the printer 1 is configured so that the conveyance roller 63 and the pivot shaft 65 are driven by the feed motor M, but the present invention is not limited to this example, and the conveyance roller 63 and the pivot shaft 65 can be driven by different motors. Further according to the first and second embodiments, the printer 1 adopts a configuration where the transmission path between the feed motor M and the pivot shaft 65 is connected in a disconnectable manner by the drive transmission mechanism 70, but the present invention is not limited to this example, and they can be connected by other clutch mechanisms such as an electromagnetic clutch.

Further according to the first and second embodiments, the printer 1 is configured as a color laser beam printer adopting an electrophotographic system, but the present invention is not limited thereto, and it can be configured as an inkjet printer in which ink is discharged through nozzles to form images on sheets.

Other Embodiments

Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2018-088927, filed May 2, 2018, which is hereby incorporated by reference herein in its entirety.

Claims

1. A sheet feeding apparatus comprising:

a sheet supporting portion configured to support a sheet;

a sheet feeding portion configured to feed the sheet supported on the sheet supporting portion;

a lifting unit comprising an urging portion configured to urge either one of the sheet supporting portion and the sheet feeding portion to the other of the sheet supporting portion and the sheet feeding portion, and a shaft portion configured to rotate in conjunction with lifting and lowering of the one of the sheet supporting portion and the sheet feeding portion, the lifting unit being configured to lift and lower the one of the sheet supporting portion and the sheet feeding portion to the other of the sheet supporting portion and the sheet feeding portion; and

a damping unit connected to the shaft portion and configured to damp rotation of the shaft portion,

wherein the damping unit comprises a first gear supported rotatably on the shaft portion, a base portion, a second gear meshed with the first gear and configured to relatively rotate with respect to the base portion, and a damping portion provided on the base portion and configured to damp the rotation of the shaft portion by relative rotation of the second gear with respect to the base portion, the damping unit being configured to be switched, in a state where the shaft portion is rotating, between a first state in which the damping unit damps the rotation of the shaft portion and a second state in which the damping unit does not damp the rotation of the shaft portion, and

a distance between a center of rotation of the first gear and a center of rotation of the second gear is fixed regardless of whether the damping unit is in the first state or in the second state.

2. The sheet feeding apparatus according to claim 1, further comprising a frame unit configured to support the base portion rotatably, and

wherein the damping unit comprises a regulating portion provided on the frame unit and configured to allow rotation of the base portion within a predetermined range and to regulate the rotation of the base portion by abutting against the base portion, the damping unit being configured to be in the second state if the base portion is separated from the regulating portion and in the first state if the rotation of the base portion is regulated by the base portion being abutted against the regulating portion.

3. The sheet feeding apparatus according to claim 2, wherein the base portion is supported on the frame unit rotatably around the center of rotation of the second gear.

4. The sheet feeding apparatus according to claim 2, wherein a position of the regulating portion is adjustable with respect to the frame unit.

5. The sheet feeding apparatus according to claim 2, wherein the sheet supporting portion is configured to be lifted and lowered by the lifting unit between a lifted position where the sheet feeding portion is capable of feeding the sheet supported on the sheet supporting portion and a lowered position where the sheet feeding portion is separated from the sheet supported on the sheet supporting portion, and the damping unit is switched from the second state to the first state in a case where the sheet supporting portion moves on the way to the lifted position from the lowered position.

6. The sheet feeding apparatus according to claim 5, wherein the lifting unit comprises a gear fixed to the shaft portion, and a pressing portion comprising a rack portion configured to mesh with the gear, the pressing portion being urged by urging force of the urging portion to press the sheet supporting portion toward the lifted position.

7. The sheet feeding apparatus according to claim 6, wherein the lifting unit comprises a driving source, and a control gear configured to be rotated by driving force of the driving source,

during one rotation of the control gear, the sheet supporting portion is configured to move from the lowered position to the lifted position by being pressed by the pressing portion lifted by urging force of the urging portion, and thereafter, move from the lifted position to the lowered position by the gear lowering the pressing portion against urging force of the urging portion, and

the shaft portion rotates in a first direction in a state where the sheet supporting portion moves from the lowered position to the lifted position and rotates in a second direction opposite to the first direction in a state where the sheet supporting portion moves from the lifted position to the lowered position.

8. The sheet feeding apparatus according to claim 7, wherein the base portion is configured to rotate in a third direction by the rotation of the shaft portion in the first direction and also configured to rotate in a fourth direction opposite to the third direction by the rotation of the shaft portion in the second direction, and

the regulating portion comprises a first regulating part configured to regulate the rotation of the base portion in the third direction and a second regulating part configured to regulate the rotation of the base portion in the fourth direction.

9. The sheet feeding apparatus according to claim 8, wherein positions of the first regulating part and the second regulating part are respectively adjustable with respect to the frame unit.

10. The sheet feeding apparatus according to claim 1, wherein the shaft portion is connected with play to the first gear such that the shaft portion is relatively pivotable within a predetermined angle with respect to the first gear, and

the damping unit is configured to be in the second state in a case where the shaft portion pivots within a range of play with respect to the first gear, and in the first state in a case where the shaft portion rotates integrally with the first gear.

11. The sheet feeding apparatus according to claim 10, further comprising a frame unit configured to support the base portion in a non-movable manner.

12. The sheet feeding apparatus according to claim 10, wherein the shaft portion comprises an engagement portion, and

the second gear comprises a hole portion in which the engagement portion is pivotable for the predetermined angle without abutting against the second gear.

13. The sheet feeding apparatus according to claim 10, wherein the sheet supporting portion is configured to be lifted and lowered by the lifting unit between a lifted position where the sheet feeding portion is capable of feeding the sheet supported on the sheet supporting portion and a lowered position where the sheet feeding portion is separated from the sheet supported on the sheet supporting portion, and

the damping unit is switched from the second state to the first state in a case where the sheet supporting portion moves on the way to the lifted position from the lowered position.

14. The sheet feeding apparatus according to claim 13, wherein the lifting unit comprises a gear fixed to the shaft portion, and a pressing portion comprising a rack portion configured to mesh with the gear, the pressing portion being urged by urging force of the urging portion to press the sheet supporting portion toward the lifted position.

15. The sheet feeding apparatus according to claim 14, wherein the lifting unit comprises a driving source, and a control gear configured to be controlled to rotate once by driving force of the driving source,

during one rotation of the control gear, the sheet supporting portion is configured to move from the lowered position to the lifted position by being pressed by the pressing portion lifted by urging force of the urging portion, and thereafter, move from the lifted position to the lowered position by the gear lowering the pressing portion against urging force of the urging portion, and

the shaft portion rotates in a first direction in a state where the sheet supporting portion moves from the lowered position to the lifted position and rotates in a second direction opposite to the first direction in a state where the sheet supporting portion moves from the lifted position to the lowered position.

16. An image forming apparatus comprising:

the sheet feeding apparatus according to claim 1; and

an image forming unit configured to form an image on a sheet fed from the sheet feeding apparatus.