JP2016137964A - Sheet feeding device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeding device and an image formation device, capable of reducing an impact sound at the time of abutment between a feeding rotating body and a sheet on a sheet loading part while promoting a stabilized feeding force by the feeding rotating body.SOLUTION: A sheet feeding device 30 includes a sheet loading part 1 which is movably supported between a standby position and a feeding position, for a sheet S to be loaded, a pressurizing spring for energizing the sheet loading part 1 from the standby position toward the feeding position, and a feeding roller 3 which feeds the sheet S loaded in the sheet loading part 1 that has moved to the feeding position.The sheet feeding device 30 includes a feeding cam 6 which rotates in synchronous with the feeding roller 3 to move the sheet loading part 1 from the feeding position to the standby position, and a buffer cam 7 and a buffer member 11 which, during moving of the sheet loading part 1 from the standby position to the feeding position by the pressurizing spring, make the sheet S loaded on the sheet loading part 1 abut for buffering, before abutment with the feeding roller 3.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a sheet feeding apparatus used in an electrophotographic copying machine, an image forming apparatus such as a printer, and an image forming apparatus provided with the sheet feeding apparatus.

  As a sheet feeding apparatus used in an image forming apparatus such as a copying machine or a printer, a sheet feeding apparatus using a friction separation method (separation pad method) is known because of its simple mechanism and low cost. This sheet feeding apparatus is attached to a sheet stacking unit for stacking sheets, a half-moon-shaped feeding roller (feeding rotating body) for feeding sheets on the sheet stacking unit, and a feeding roller and a driven roller. And a separation pad to be urged.

  In this sheet feeding apparatus, the sheet stacking unit on which the sheets are stacked is pressed against the feeding roller by a spring, the sheet on the sheet stacking unit is brought into contact with the feeding roller, and the feeding roller makes one rotation in this state. It is configured to feed the sheet every time it is done. In this apparatus, when the feeding roller rotates, the sheet stacking unit rises to contact the sheet stacked on the feeding roller, and when the feeding roller stops, the sheet stacking unit separates the sheet from the feeding roller. It is located at the standby position. The position of the sheet stacking unit when feeding the stacked sheets varies depending on the amount of stacked sheets, but the stacked sheets are in contact with the feeding roller to feed the sheets. The position of the state is set as the feeding position of the sheet stacking unit.

  If a large number of sheets are stacked on the sheet stacking unit during feeding by the feeding roller, the feeding position of the sheet stacking unit when the sheet on the sheet stacking unit comes into contact with the feeding roller and feeds And the moving distance from the standby position of the sheet stacking unit where the sheets are separated and waiting. Conversely, if the number of stacked sheets is small, the moving distance becomes large. As a result, the speed of moving the sheet stacking unit from the standby position to the feeding position during the feeding operation increases in the case of a small number of sheets as compared with the case of a large number of sheets stacked, so that the sheet comes into contact with the feeding roller. The impact will increase.

  On the other hand, there has been proposed a sheet feeding apparatus configured to reduce an impact sound at the time of collision between the feeding roller and the sheet. In this sheet feeding apparatus, a spring is provided between the feeding roller shaft and the feeding roller collar in the feeding roller unit that supports the feeding roller, and an impact when the rotating feeding roller comes into contact with the sheet is applied. Absorbed by the elasticity of the spring. Thereby, the impact sound at the time of a collision with a feeding roller and a sheet | seat is reduced (refer patent document 1).

JP 2009-179440 A

  However, the technique described in Patent Document 1 may cause the following problems. That is, the biasing force of the spring that biases the sheet stacking portion in the direction of the feeding roller is added to the biasing force of the spring that biases the feeding roller collar and the feeding roller in the sheet direction. The pressure between the sheets (sheet feeding pressure) is not stable, and the sheets cannot be fed stably one by one.

  Accordingly, the present invention provides a sheet feeding apparatus and an image that can reduce impact noise when the feeding rotating body and a sheet on the sheet stacking unit are in contact with each other while stabilizing the feeding force by the feeding rotating body. An object is to provide a forming apparatus.

  In the sheet feeding apparatus, the sheet feeding device is movably supported between a standby position and a feeding position, and a sheet stacking unit on which sheets are stacked, and the sheet stacking unit from the standby position to the feeding position. An urging unit that urges the sheet toward the feeding position, a feeding rotating body that feeds the sheets stacked on the sheet stacking unit that has moved to the feeding position, and a rotation that synchronizes with the feeding rotating body, A sheet feeding cam that moves the sheet stacking unit from the feeding position to the standby position, and a sheet stacking unit that is stacked on the sheet stacking unit when the sheet stacking unit is moved from the standby position to the feeding position by the biasing unit. Shock absorbing means for abutting and buffering the sheet before contacting the sheet feeding rotary member.

  According to the present invention, the relationship between the pressing force between the feeding rotator and the sheet is simplified to stabilize the feeding force by the feeding rotator, and the contact between the feeding rotator and the sheet on the sheet stacking unit is achieved. It is possible to reduce the impact sound when touching.

1 is a cross-sectional view illustrating an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a perspective view of the sheet feeding device according to the first embodiment. FIG. 4A is an explanatory diagram of a sheet stacking unit position during a standby state of the sheet feeding device according to the first embodiment, and FIG. 5B is an explanatory diagram of a sheet stacking unit position during a feeding operation. (A) is explanatory drawing of the position of a buffer cam and a buffer member at the time of feeding standby of the sheet feeding apparatus which concerns on 1st Embodiment, (b) is the contact | abutting of a buffer cam and a buffer member at the time of feeding operation start The side view which shows a state. FIG. 4A is an explanatory diagram of a sheet stacking unit position at the start of a feeding operation of the sheet feeding apparatus according to the first embodiment, and FIG. 5B is a side view illustrating a state where the sheet stacking unit is in a feeding operation position. FIG. 3 is a side view illustrating a sheet feeding state of the sheet feeding apparatus according to the first embodiment. (A) is explanatory drawing of the position of the buffer cam and buffer member at the time of feeding standby of the sheet feeding apparatus according to the second embodiment of the present invention, and (b) is the buffer cam and buffer member at the start of feeding operation. The side view which shows the contact state of. FIG. 9 is a side view illustrating a state where a sheet stacking unit of a sheet feeding apparatus according to a second embodiment is in a feeding operation position. (A) is explanatory drawing of the position of a buffer cam and a buffer member at the time of feeding waiting of the sheet feeding apparatus concerning the 3rd embodiment of the present invention, (b) is a buffer cam and a buffer member at the time of a feeding operation start The side view which shows the contact state of.

<First Embodiment>
Hereinafter, an electrophotographic image forming apparatus such as a copying machine or a printer, and a sheet feeding apparatus mounted on the image forming apparatus will be described as an example with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus 600 equipped with the sheet feeding apparatus 30 according to the present embodiment.

[Image forming apparatus]
As shown in FIG. 1, an image forming apparatus 600 is a tandem type electrophotographic color laser printer using an intermediate transfer belt 601, and has an image forming apparatus main body (hereinafter referred to as an apparatus main body) 600a. An intermediate transfer belt unit 603 is disposed in the upper part of the apparatus main body 600a, and the sheet feeding apparatus 30 is disposed in the lower part.

  The image forming apparatus 600 includes four image forming units Y, M, C, and K that form toner images of yellow, magenta, cyan, and black, and these image forming units Y, M, C, and K In the apparatus main body 600a, they are arranged in parallel from right to left in FIG.

  Each of the image forming units Y, M, C, and K is an image forming unit of an electrophotographic image forming system, and each image forming unit Y, M, C, and K is different from each other except that a toner image of a different color is formed on the photosensitive drum of each image forming unit. The structure of the formation part is the same. Each image forming unit has a photosensitive drum 21 (21Y, 21M, 21C, 21K). Around the photosensitive drum, a charging roller 22 (22Y, 22M, 22C, 22K), a developing roller 23 (23Y, 23M, 23C, 23K), and a transfer roller 27 (27Y, 27M, 27C, 27K) are arranged as process means. Has been. Further, a laser scanner 14 that irradiates each photosensitive drum 21 with laser light corresponding to image information is disposed below each photosensitive drum 21.

  Next, image formation in each of the image forming units Y, M, C, and K will be described. That is, each photosensitive drum 21 is driven to rotate counterclockwise in FIG. In this state, the photosensitive drum 21 is charged by the charging roller 22 and irradiated with laser light from the laser scanner 14 to form a latent image (electrostatic latent image). A toner image is formed on the surface of the photosensitive drum 21 by attaching toner that adheres to the developing roller 23 to the latent image.

  A yellow toner image, which is a color separation component color of a full-color image, is formed on the surface of the photosensitive drum 21Y of the image forming unit Y, and a magenta toner image is formed on the surface of the photosensitive drum 21M of the image forming unit M. The cyan toner image is formed on the surface of the photosensitive drum 21C of the image forming unit C, and the black toner image is formed on the surface of the photosensitive drum 21K of the image forming unit K.

  On the other hand, an intermediate transfer belt unit 603 having an intermediate transfer belt 601 to which a toner image is transferred from each photosensitive drum 21 is disposed above the image forming portions Y, M, C, and K. The intermediate transfer belt 601 includes a stretching roller 25 disposed on the image forming unit Y side, a stretching roller 26 disposed on the image forming unit K side, and a secondary transfer facing member disposed above the stretching roller 26. It is stretched by a roller 602T. The tension roller 26 is a roller that drives the intermediate transfer belt 601 in the direction of the arrow F (clockwise direction) so that the speed of the surface of the intermediate transfer belt is substantially the same as the speed of the surface of each photosensitive drum. It is rotated by the drive source.

  The primary transfer rollers 27 (27Y, 27M, 27C, 27K) are arranged between the stretching rollers 25, 26 so as to face the photosensitive drums 21 of the image forming units Y, M, C, K with the intermediate transfer belt 601 interposed therebetween. ) Is arranged. A primary transfer nip T21 (T21Y, T21M, T21C, T21K) is formed between each photosensitive drum 21 and each primary transfer roller 27. A primary transfer bias is applied at the primary transfer nip T21, and the toner images on the photosensitive drums are primarily transferred onto the intermediate transfer belt.

  A secondary transfer roller 602 is disposed downstream of the primary transfer nip T21 in the rotation direction of the intermediate transfer belt 601 so as to face the secondary transfer counter roller 602T with the intermediate transfer belt 61 interposed therebetween. The secondary transfer roller 602 presses the secondary transfer counter roller 602T via the intermediate transfer belt 601. The intermediate transfer belt 601 and the secondary transfer roller 602 form a secondary transfer nip portion T2. The toner image on the intermediate transfer belt 601 is secondarily transferred onto a sheet conveyed to the secondary transfer nip T2 by applying a secondary transfer bias at the secondary transfer nip T2.

  A belt cleaner 608 that scrapes off toner remaining without being transferred at the secondary transfer nip T2 is disposed at a position facing the stretching roller 25 downstream of the intermediate transfer belt 601 in the rotation direction of the secondary transfer nip T2. ing.

  A fixing device 604 is disposed downstream of the secondary transfer nip T2 in the sheet conveyance direction. The fixing device 604 includes a fixing roller (heating roller) 604a and a pressure roller 604b that is pressed against the fixing roller 604a. In this embodiment, an image is formed on the sheet S fed from the sheet feeding device 30 by the image forming portions Y, M, C, K, the secondary transfer nip portion T2, and the fixing device 604. An image forming unit 610 is configured.

  Next, a process for forming a four-color toner image on a sheet will be described. A control unit 605 that controls the image forming operation of the image forming apparatus 600 is disposed in the apparatus main body 600a. A control unit 605 serving as a control unit forms toner images of yellow, magenta, cyan, and black on the photosensitive drums 21 of the image forming units Y, M, C, and K based on the print start signal. Each toner image is sequentially superimposed and transferred onto the intermediate transfer belt 601 at the primary transfer nip T21, formed as a four-color toner image on the intermediate transfer belt 601, and moves to the secondary transfer nip T2. .

  Further, the control unit 605 controls driving of the feeding roller 3 provided in the sheet feeding device 30 and the conveyance roller pair 13 provided in the conveyance path. Then, the control unit 605 rotates the feeding roller 3 to separate and feed the sheets S stacked on the sheet stacking unit 1 one by one, and further rotates the conveying roller pair 13 to register the sheet S. It is conveyed to the pair of ration rollers 12.

  The registration roller pair 12 introduces the sheet S into the secondary transfer nip T2 in accordance with the timing at which the toner image on the intermediate transfer belt reaches the secondary transfer nip T2. Then, by applying a secondary transfer bias to the secondary transfer nip portion T2, four color toner images on the intermediate transfer belt 601 are secondarily transferred onto the sheet. Further, the sheet S that has passed through the secondary transfer nip portion T2 is conveyed to the fixing device 604 and heated and pressed, whereby an unfixed toner image is fixed on the sheet. As a result, four color toner images are formed on the sheet.

[Sheet feeding device]
Next, details of the sheet feeding apparatus 30 according to the present embodiment using a friction separation type separation means such as a so-called separation pad or separation roller will be described with reference to FIGS. 2, 3A, and 3B. explain. 2 is a perspective view showing the sheet feeding device 30. FIG. 3A is an explanatory diagram of the position of the sheet stacking unit 1 when the sheet feeding apparatus 30 according to the present embodiment is in a standby state, and FIG. 3B is a sheet feeding apparatus according to the present embodiment. FIG. 10 is an explanatory diagram of the position of the sheet stacking unit 1 during 30 feeding operations.

  As shown in FIGS. 2, 3 (a), and 3 (b), a half-moon-shaped feeding roller 3 is provided so as to be positioned in the vicinity of the leading end of the uppermost sheet of the plurality of sheets S stacked on the sheet stacking unit 1. It has been. A rotating shaft 4 extends in the width direction (direction of arrow E) perpendicular to the sheet feeding direction (direction of arrow B in FIG. 2) for feeding the sheet S on the sheet stacking unit 1. A feeding roller 3 is attached to the central portion of the rotating shaft 4 in the axial direction. The feeding roller 3 is rotated in the direction of feeding the sheet S (the direction of arrow A in FIG. 3A) by the rotation of the rotating shaft 4 during the feeding operation. The feeding roller 3 has an arc-shaped (half-moon shaped) friction conveying unit that feeds the sheet S in contact with the upper surface of the sheet S on the sheet stacking unit. The shape of the feeding roller 3 is not limited to an arc shape, and the outer periphery may be circular.

  A separation pad 5 is disposed on the opposite side of the sheet feeding path of the feeding roller 3, and this separation pad 5 is pressed in the direction of the feeding roller 3 by a pad spring 5 a formed of a compression spring. . The sheet stacking unit 1 is supported by a rotating shaft 1a so that the rear end side in the sheet feeding direction is pivotable, and is pressed in a direction approaching the feeding roller 3 by a pressing spring 2 formed of a compression spring. The pressing spring 2 constitutes a biasing unit that biases the sheet stacking unit 1 from the standby position toward the feeding position. In this embodiment, a separation pad is used as the separation unit. However, a separation roller attached to a fixing unit such as a frame of the sheet stacking unit 1 via a torque limiter may be used as the separation unit.

  Based on the print start signal, the control unit 605 (see FIG. 1) transmits a drive signal to the drive motor 18 (FIG. 1) as drive means for driving the feed roller 3 to rotate. A drive transmission mechanism 31 is disposed between the drive motor 18 and the feed roller 3 as shown in FIG. The drive motor 18 (FIG. 1) is driven based on the print start signal, and the drive transmission mechanism 31 transmits the drive force of the drive motor 18 to the feed roller 3 and is driven every time the feed roller 3 makes one rotation. Cancel transmission. One sheet S is fed by one rotation of the feeding roller 3. The drive transmission mechanism 31 is configured to repeat rotation and stop for each rotation of the feeding roller 3 by a one-rotation clutch using a solenoid (not shown), a missing gear 32, and the like (one rotation control). . In this embodiment, a one-rotation clutch having a solenoid and a toothless gear is used for one-rotation control of the feeding roller 3, but one-turn control is performed by controlling drive transmission by turning on / off the electromagnetic clutch. May be performed.

  A rotating shaft 4 extending in the width direction is supported at the front end portion of a frame 30 a as a main body of the sheet feeding device 30, and the feeding roller 3 is held on the rotating shaft 4. Feed cams 6 are fixed to both ends of the rotary shaft 4 in the axial direction so as to rotate with the feed roller 3 at a predetermined phase. The feeding cam 6 may not be provided on the rotating shaft 4. For example, the feeding cam 6 may be provided on another shaft so as to rotate in conjunction with the rotation of the rotating shaft 4 and synchronized with the feeding roller 3 in a predetermined phase relationship. And rotate it.

  The pair of feeding cams 6 are provided coaxially with the feeding roller 3 and rotate integrally with the feeding roller 3. The feeding cam 6 at the time of waiting for feeding pushes down the raising / lowering cam follower (elevating / lowering part) 1b fixed on the same axis as the sheet stacking part 1 against the urging force of the pressing spring 2. The stacking unit 1 is in a standby position where the sheet S and the feeding roller 3 are separated from each other.

  When the rotation of the drive motor 18 is transmitted to the rotary shaft 4 via the drive transmission mechanism 31, the feed roller 3 and the feed cam 6 rotate together with the rotary shaft 4. Further, the lifting cam followers (lifting parts) 1b are respectively provided with corresponding feeding cams 6 at both ends in the width direction (direction of arrow E) orthogonal to the sheet feeding direction (direction of arrow B) of the sheet stacking section 1. It is provided opposite to. The elevating cam follower 1 b is provided in the sheet stacking unit 1 and is engaged with a feeding cam 6 that rotates integrally with the feeding roller 3, thereby moving the sheet stacking unit 1 toward and away from the feeding roller 3.

  The sheet stacking unit 1 is pushed up by the pressing spring 2 in the direction of arrow G in FIG. When the rotation is transmitted to the feeding roller 3, the feeding cam 6 rotates in the direction of the arrow A (the sheet feeding direction) together with the feeding roller 3, and the elevating cam follower 1b follows the feeding cam 6. . When the feeding cam 6 and the elevating cam follower 1 b are separated from each other, the sheet S on the sheet stacking unit 1 is pressed against the feeding roller 3 by the pressing spring 2 and is fed out by the rotating feeding roller 3. Then, the fed sheet S is separated and fed one by one by the separation action by the separation pad 5 and the feeding roller 3, and sent to the downstream conveying roller pair 13 (FIG. 1).

  FIG. 3B is an explanatory diagram of the position of the sheet stacking unit 1 during the feeding operation of the sheet feeding device 30. As shown in FIG. 3B, at the time of the feeding operation, the rotation roller 4 is rotated to rotate the feeding roller 3, and the cam follower 1b of the sheet stacking unit 1 that has been pushed down by the feeding cam 6 is released. . As a result, the sheet stacking unit 1 moves suddenly in the direction in which the sheet S is brought into contact with the feeding roller 3 by the urging force of the pressing spring 2.

  When the sheet stacking unit 1 moves to the feeding position where the sheet S and the feeding roller 3 contact each other, the uppermost sheet S is fed by the rotation of the feeding roller 3 and separated one by one by the separation pad 5. The When the feeding roller 3 rotates once, the sheet stacking unit 1 is returned to the standby position by the feeding cam 6 again. The position of the sheet stacking unit 1 when feeding the stacked sheets varies depending on the amount of the stacked sheets S, but the stacked sheets S come into contact with the feeding roller 3 and the sheets S are moved. The position in the feeding state is set as the feeding position of the sheet stacking unit.

  The sheet stacking unit 1 constitutes a sheet stacking unit that stacks the sheets S and can move between the standby position and the feeding position. The feeding roller 3 constitutes a feeding rotating body that rotates in the feeding direction of the sheets S stacked on the sheet stacking unit 1 moved to the feeding position.

  FIG. 4A is a view for explaining the positions of the buffer cam 7 and the buffer member 11 at the time of feeding standby constituting the buffer means. In FIG. 4A, a feed roller 3 and a feed cam 6 (not shown in FIG. 4A) and a pair of buffer cams 7 are fixed on the rotating shaft 4 with a predetermined phase. The pair of buffer cams 7 are provided with arc-shaped sliding contact surfaces 7 b, are fixed to both sides in the axial direction of the feed roller 3, and are coaxial with the feed roller 3 and the feed cam 6. And rotates integrally with the feeding cam 6.

  As shown in FIGS. 4A and 4B, a guide member 8 that guides the upper surface of the sheet S when being fed is provided between the sheet S on the sheet stacking unit 1 and the feeding roller 3. Has been placed. The guide member 8 is composed of an elastically deformable sheet member such as a flexible sheet metal or a PET (polyethylene terephthalate) film. The rear end portion of the sheet feeding device 30 is supported by a frame 30a (see FIG. 2), which is displaceable via the support portion 15, and is disposed above the sheet S on the sheet stacking portion. . A pair of buffer members 11 that face the pair of buffer cams 7 rotated to a predetermined position (positions shown in FIGS. 4B and 5A) so as to come into contact with each other are supported at the distal end portion of the guide member 8. Has been. The guide member 8 constitutes a support means for supporting the buffer member 11. The buffer member 11 is made of an elastic member such as a foam material or a rubber material. The buffer member 11 is configured to buffer the sheet S on the sheet stacking unit 1 that moves from the standby position to the feeding position in a state in which the arcuate sliding contact surface 7b of the buffer cam 7 rotated to the predetermined position is in contact. 7 is configured so as to be received in cooperation. In this embodiment, the buffer member 11 is provided on the guide member 8 that guides the sheet. However, the buffer member 11 is attached to the frame 30a and has a flexible support member that does not have a guide function. (Supporting means) may be supported.

  By supporting the buffer member 11 at the tip of the guide member 8 supported at the rear end in this way, the arcuate sliding contact surface 7b of the tip 7a of the rotating buffer cam 7 is made to move against the buffer member 11. Can be reliably slid and moved.

  As shown in FIG. 4A, the buffer cam 7 in the feed standby state in which the feed roller 3 is stopped is in a separated position that is not in contact with the buffer member 11 on the guide member 8. The buffer cam 7 is provided coaxially with the feed roller 3 and is configured to rotate integrally with the feed roller 3 and the feed cam 6. Further, the buffer member 11 is configured such that the sheet S on the sheet stacking unit (on the sheet stacking unit) passes through the guide member 8 in a state in which the buffer unit 11 is in contact with the buffer cam 7 immediately before the sheet stacking unit 1 reaches the feeding position. It is comprised so that it may contact | abut. That is, before the upper surface of the sheet S on the sheet stacking unit 1 comes into contact with the feeding roller 3 while the sheet stacking unit 1 moves from the standby position to the feeding position, the upper surface of the sheet on the sheet stacking unit 1 is It abuts against the buffer member 11 via the guide member 8. At this time, the impact is alleviated by the elasticity of the buffer member 11.

  By combining the buffer cam 7 and the buffer member 11 having such a simple configuration, when the sheet stacking unit 1 moves from the standby position to the feeding position, the sheets stacked on the sheet stacking unit 1 are fed to the feeding roller 3. It is possible to constitute a buffer means for receiving and buffering before the contact. In addition to the configuration in which the buffer cam 7 and the buffer member 11 are combined, the buffer unit is a single unit that receives and buffers the sheet S on the sheet stacking portion that moves to the feeding position before coming into contact with the feeding roller 3. It is also possible to arrange and configure such elastic members.

  4B is a side view showing a state where the buffer cam 7 and the buffer member 11 are in contact with each other at the start of the feeding operation, and FIG. 5A is a sheet stacking at the start of the feeding operation. It is a figure explaining the position of the part.

  As shown in FIG. 4B, at the start of the feeding operation, the feeding roller 3 and the buffer cam 7 rotate, so that the buffer cam 7 contacts the buffer member 11 (predetermined position). Rotate. Here, the guide member 8 swings in a direction approaching the lower sheet S (downward in the drawing) when the buffer cam 7 contacts the buffer member 11.

  Subsequently, as shown in FIG. 3A, when the sheet stacking portion 1 that has been pushed down by the feeding cam 6 is released along with the rotation of the feeding roller 3, the sheet stacking portion 1 is attached to the pressing spring 2. The sheet S abruptly moves upward from the standby position in contact with the feeding roller 3 by the force.

  As shown in FIG. 5A, when the sheet stacking unit 1 moves upward from the standby position, the uppermost sheet S stacked on the sheet stacking unit 1 is placed on the lower surface of the guide member 8. Abut. At this time, since the buffer member 11 on the guide member 8 is held in contact with the buffer cam 7, the impact force of the sheet stacking unit 1 is reduced by the elasticity of the buffer member 11.

  FIG. 5B is a side view showing a state in which the sheet stacking unit 1 is in the feeding operation position, and FIG. 6 is a side view showing a sheet feeding state of the sheet feeding apparatus 30. When the buffer cam 7 rotates while abutting against the buffer member 11 and rotates to a position away from the buffer member 11 shown in FIG. 5B, the guide member 8 returns to the original position for guiding the sheet S as shown in FIG. Return to position. The sheet stacking unit 1 moves up to a feeding position where the sheet S and the feeding roller 3 come into contact with each other. That is, when the buffer cam 7 rotates while contacting the buffer member 11 and rotates to the position shown in FIG. 5B where the buffer cam 7 does not contact the buffer member 11, the sheet S stacked on the sheet stacking unit 1 is fed. 3 abuts. In this state, the uppermost sheet S1 is fed by the rotation of the feeding roller 3, and is conveyed toward the conveying roller pair 13 (see FIG. 1) along the conveying guide portion 9 as shown in FIG.

  According to the present embodiment, when the sheet stacking unit 1 moves from the standby position (the position in FIG. 3A) to the feeding position (the position in FIG. 3B), the sheet S on the sheet stacking unit is fed. Before contacting the feed roller 3, the buffer cam 7 contacts the buffer member 11 of the guide member 8. As a result, the sheet S abuts against the buffer cam 7 via the buffer member 11 and then abuts against the feeding roller 3 as the buffer cam 7 moves, thereby suppressing the impact force when the sheet S contacts the feeding roller 3. Is done. Accordingly, it is possible to realize a configuration that reduces the occurrence of sheet displacement and abnormal noise due to impact with a simple configuration.

  That is, in the present embodiment, the buffer cam 7 is provided on the rotating shaft 4 of the feeding roller 3 and the buffer member 11 is provided on the guide member 8, so that the sheet stacking unit 1 waits at the start of the feeding operation. While moving from the position to the feeding position, the following effects can be obtained. That is, when the sheet stacking unit 1 moves from the standby position to the feeding position, the buffer member 11 in a state of contacting the buffer cam 7 before the sheet S on the sheet stacking unit contacts the feeding roller 3. After the sheet S is brought into contact with the sheet S, it can be brought into contact with the feeding roller 3. Therefore, the impact force at the time of contact between the sheet S rising together with the sheet stacking unit 1 and the feeding roller 3 is once reduced by the buffer member 11 and the buffer cam 7, and then the sheet S can be brought into contact with the feeding roller 3. Therefore, it is possible to easily obtain a configuration capable of effectively reducing the impact force. As a result, it is possible to reduce the occurrence of sheet displacement and abnormal noise.

  In FIG. 6, when the rotating feeding roller 3 protrudes downward from the notch 8d (see FIG. 2) of the buffer member 11 and contacts the sheet S to feed, the buffer cam 7 and the buffer member 11 is not in contact. For this reason, the pressing force between the feeding roller 3 and the sheet S is not affected.

<Second Embodiment>
Next, a second embodiment of the present invention will be described with reference to FIGS. 7 (a), (b) and FIG. FIG. 7A is a diagram for explaining the positions of the buffer cam 7 and the buffer member 11 at the time of waiting for feeding. FIG. 7B shows the buffer cam 7 against the buffer member 11 at the start of feeding operation. FIG. 8 is a side view showing a state where the sheet stacking unit 1 is in the feeding operation position. Note that differences from the first embodiment will be described in detail. The same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the description thereof is omitted.

  As shown in FIG. 7A, the buffer cam 7 in the present embodiment is integrally provided with a rotatable driven roller (roller) 7d at the tip. In FIG. 7A, the buffer cam 7 and the driven roller 7 d at the time of feeding standby when the feeding roller 3 is stopped are in a separated position where they do not contact the buffer member 11 on the guide member 8.

  At the start of the feeding operation, as shown in FIG. 7B, the feeding roller 3 and the buffer cam 7 rotate in the same phase, so that the buffer cam 7 comes into contact with the buffer member 11 (a predetermined position). Position). When the driven roller 7d at the tip of the buffer cam 7 abuts on the buffer member 11 and is driven to rotate, the guide member 8 swings in the direction toward the sheet S (downward in the figure).

  Next, with the rotation of the feeding roller 3, the sheet stacking unit 1 suddenly moves upward from the standby position where the sheet S contacts the feeding roller 3, and the uppermost sheet stacked on the sheet stacking unit 1. The sheet S comes into contact with the lower surface of the guide member 8. At this time, since the buffer member 11 on the guide member 8 is in contact with the driven roller 7d of the buffer cam 7 as shown in FIG. 7B, the shock force is temporarily reduced by the buffer member 11 and the buffer cam 7.

  Subsequently, with the rotation of the buffer cam 7, the driven roller 7d abuts against the buffer member 11 while rotating, and when the buffer cam 7 rotates to a position where the driven roller 7d shown in FIG. The member 8 returns to the original position for guiding the sheet S. Accordingly, the sheet stacking unit 1 moves to a feeding position where the feeding roller 3 is brought into contact with the sheet S. As described above, the buffer cam 7 of the present embodiment includes the driven roller (driven rotor) 7 d that rotates following the buffer member 11 when rotating while contacting the buffer member 11. The configuration using the driven roller 7d can be similarly applied to both the first embodiment described above and the second embodiment described later.

  Also in the present embodiment described above, as in the first embodiment, the sheet S is moved to the feeding roller 3 by the buffer member 11 and the buffer cam 7 while the sheet stacking unit 1 moves from the standby position to the feeding position. The impact force at the time of contact can be reduced. In this embodiment, by providing the rotatable driven roller 7d at the contact portion of the buffer cam 7 with the buffer member 11, the sliding resistance of the buffer cam 7 can be reduced by the driven roller 7d. The movement of the buffer cam 7 that moves while abutting can be made smoother. As a result, the buffer member 11 can be formed of a material having a coefficient of friction or a material that is not slidable with the buffer cam 7, so the material of the buffer cam 7 is selected as compared with the configuration of the first embodiment. It becomes possible to expand the range.

<Third Embodiment>
Next, a third embodiment of the present invention will be described with reference to FIGS. 9 (a) and 9 (b). FIG. 9A is a diagram for explaining the positions of the buffer cam 7 and the buffer member 11 when waiting for feeding, and FIG. 9B shows the buffer cam 7 when starting the feeding operation. It is a side view which shows the state which the buffer member 11 contact | abutted. Note that differences from the first embodiment will be described in detail. The same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the description thereof is omitted.

  The guide member 8 in the present embodiment is made of a relatively hard plate-like member such as a sheet metal or plastic, and swings with respect to the support portion 15 via a rotation fulcrum 8c as shown in FIG. 9A. Supported as possible. Further, the swinging spring 10 constituted by a tension spring is urged in the direction of the feeding roller 3, and the swinging operation exceeding the position of FIG. ing. In FIG. 9A, the buffer cam 7 in the standby state in which the feeding roller 3 is stopped is in a separated position where it does not contact the buffer member 11 on the guide member 8.

  As described above, the guide member 8 in the present embodiment is supported in such a manner that the rear end portion is swingably supported by the support portion 15 provided in the frame 30a (see FIG. 2) which is the apparatus main body, and in the direction toward the buffer cam 7. It is composed of a biased plate member.

  Next, as shown in FIG. 9B, when the feeding operation is started, the feeding roller 3 and the buffer cam 7 rotate in the same phase, so that the buffer cam 7 contacts the buffer member 11. Rotate to (predetermined position). Here, the guide member 8 swings in a direction approaching the sheet S on the sheet stacking unit 1 (downward in the drawing) when the buffer cam 7 contacts the buffer member 11.

  Next, as the feeding roller 3 rotates, the sheet stacking unit 1 suddenly moves upward from the standby position where the sheet S comes into contact with the feeding roller 3, and the uppermost layer stacked on the sheet stacking unit 1. The sheet S comes into contact with the lower surface of the guide member 8. At this time, since the buffer member 11 on the guide member 8 is in contact with the sliding contact surface 7 b of the buffer cam 7, the impact force is temporarily reduced by the buffer member 11 and the buffer cam 7.

  The buffer cam 7 rotates while contacting the buffer member 11, and when the buffer cam 7 rotates to a position away from the buffer member 11, the guide member 8 returns to the original position where the sheet S is guided by the swing spring 10. As a result, the sheet stacking unit 1 moves to a feeding position where the sheet S and the feeding roller 3 abut.

  As described above, according to the present embodiment, as in the first and second embodiments, the buffer on the guide member 8 is moved while the sheet stacking unit 1 moves from the standby position to the feeding position. The impact force when the sheet S comes into contact with the feeding roller 3 by the member 11 can be reduced. According to the present embodiment, even when the total weight of the guide member 8 and the buffer member 11 is increased, the buffer member 11 on the guide member 8 is biased toward the buffer cam 7 by the swing spring 10. be able to. Thereby, when the buffer cam 7 rotates to a position where it does not contact the buffer member 11, the guide member 8 can be reliably returned to the original position where the sheet S is guided.

  DESCRIPTION OF SYMBOLS 1 ... Sheet stacking part (sheet stacking means) / 1b ... Elevating cam follower (elevating part) / 2 ... Pressing spring (biasing means) / 3 ... Feeding roller (feeding rotating body) / 6 ... Feeding cam / 7 11 ... buffer cam, buffer member (buffer means) / 7d ... driven roller (driven rotor) / 8 ... guide member (sheet-like member, plate-like member) / 10 ... swing spring / 30 ... sheet feeding device / 30a ... Frame (apparatus body) / 600 ... Image forming apparatus / 610 ... Image forming means / B ... Sheet feeding direction / S ... Sheet

Claims (8)

A sheet stacking unit that is supported movably between the standby position and the feeding position and stacks sheets;
Biasing means for biasing the sheet stacking means from the standby position toward the feeding position;
A feeding rotator for feeding sheets stacked on the sheet stacking means moved to the feeding position;
A feeding cam that rotates in synchronization with the feeding rotating body and moves the sheet stacking unit from the feeding position to the standby position;
A buffer for buffering the sheets stacked on the sheet stacking means before contacting the feeding rotating body when the sheet stacking means is moved from the standby position to the feeding position by the biasing means. Means,
A sheet feeding apparatus characterized by that. The buffer means is
A buffer cam provided coaxially with the feeding rotating body and the feeding cam, and rotating integrally with the feeding rotating body and the feeding cam;
A buffer member that cooperates with the buffer cam to receive the sheets stacked on the sheet stacking means that moves from the standby position to the feeding position with the buffer cam rotated to a predetermined position in contact with the buffer cam. And having
The sheet feeding apparatus according to claim 1. Comprising support means arranged to be positioned on the upper surface of the sheet on the sheet stacking means,
The buffer member is supported by the support means so as to be able to contact the buffer cam rotated to the predetermined position.
The sheet feeding apparatus according to claim 2, wherein the sheet feeding apparatus is a sheet feeding apparatus. The support means is composed of a sheet-like member.
The sheet feeding apparatus according to claim 3. The support means includes a plate-like member that is supported by a support portion provided in the apparatus main body so that a rear end portion thereof is swingable and is biased in the direction of the buffer cam.
The sheet feeding apparatus according to claim 3. The support means has a function of guiding a sheet sent out from the sheet stacking means.
The sheet feeding apparatus according to claim 3, wherein the sheet feeding apparatus is a sheet feeding apparatus. The buffer cam has a driven rotating body that rotates following the rotation while contacting the buffer member.
The sheet feeding apparatus according to claim 2, wherein the sheet feeding apparatus is a sheet feeding apparatus. A sheet feeding device according to any one of claims 1 to 7,
Image forming means for forming an image on a sheet fed from the sheet feeding device,
An image forming apparatus.

Images