JP2018127313A - Sheet feeding device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeding device and image formation apparatus which can reduce the number of actuators used for driving a feeding unit and a lifting part and surely detect the feeding unit at the feeding position.SOLUTION: A sheet feeding device includes: a lift-up plate which lifts up an intermediate plate; a pickup roller 6 which can move to the separation position, the feeding position and the lower position; a second link member 18 which can hold the pickup roller 6 at the separation position; a sheet face detection sensor which detects that the pickup roller 6 is located at the feeding position; a motor 27; and a transmission unit 56 which can transmit the driving force from the motor 27 to the lift-up plate and the second link member 18. The transmission unit 56 has a delay mechanism which starts driving of the lift-up plate subsequently to the second link member 18.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a sheet feeding apparatus that feeds a sheet and an image forming apparatus including the sheet feeding apparatus.

  In general, an image forming apparatus such as a copying machine or a printer accommodates a sheet supplied to an image forming unit, and is configured to be able to be attached to and pulled out from an image forming apparatus main body (hereinafter referred to as an apparatus main body). It has. In this image forming apparatus, as the feeding cassette is mounted, the feeding roller descends to the feeding position for feeding the sheet and comes into contact with the sheet in the feeding cassette. Then, when the feeding roller rotates in the sheet feeding direction in accordance with the feeding signal, the sheets are sequentially fed downstream from the uppermost sheet stored in the feeding cassette. Further, when the feeding cassette is pulled out, the feeding roller is retracted upward so that the feeding roller and the sheet in the feeding cassette do not come into contact with each other.

  Conventionally, a roller holder that supports the feed roller so as to be movable up and down, a cam member that is rotated by driving of the feed motor to raise and lower the roller holder, a middle plate that supports the sheet, and a lift motor that raises and lowers the middle plate, A sheet feeding apparatus having the same has been proposed (see Patent Document 1). The cam member is controlled to rotate once by a missing tooth gear and a flapper member that is operated by a solenoid and restricts the rotation of the missing tooth gear. When the cassette for storing sheets is mounted on the apparatus main body, the solenoid and the feeding motor are driven, and the feeding roller is lowered to a predetermined position via the roller holder.

  When the feed roller is detected at a predetermined position, the feed motor is stopped and the lift motor is driven. By driving the lift motor, the middle plate rises, and the feeding roller also rises with the feeding roller in contact with the sheet on the middle plate. When the feeding roller is positioned at the feeding position, the position detection sensor detects the sensor flag attached to the roller holder, the lift motor is stopped, and the positioning of the intermediate plate is completed.

JP 2009-62158 A

  However, the sheet feeding apparatus described in Patent Document 1 uses a feeding motor and a solenoid for raising and lowering the feeding roller, and a lift motor for raising the middle plate, which causes an increase in cost. It was. In order to detect the feeding roller at the feeding position, it is necessary to lower the feeding roller in advance before the middle plate rises and the sheet on the middle plate comes into contact with the feeding roller.

  Accordingly, the present invention is configured to reduce the number of actuators used for driving the feeding unit and the ascending unit, and to reliably detect the feeding unit at the feeding position, thereby solving the above-described problem. It is an object to provide a feeding device and an image forming apparatus.

  In the sheet feeding apparatus, the present invention provides a sheet supporting unit that supports a sheet, a rising unit that raises the sheet supporting unit, a feeding member that can feed a sheet supported by the sheet supporting unit, A separation position where the feeding member is separated from the sheet supported by the sheet support portion, and a sheet which is positioned below the separation position and is supported by the sheet support portion can be fed by the feeding member. A feed unit that is movably supported between a straight feed position and a lower position located below the feed position, and a detection that detects that the feed member is located at the feed position. A holding portion that is movable to a holding position that holds the feeding member at the separation position, and a permissible position that allows the feeding member to swing toward the lower position, and a driving force. Drive source to generate and before A transmission unit capable of transmitting a driving force from a driving source to the ascending unit and the holding unit, and the transmission unit is in a state where the feeding member is located between the feeding position and the lower position And a delay mechanism that starts driving the ascending portion later than the holding portion so that the feeding member and the upper surface of the sheet supported by the sheet supporting portion come into contact with each other.

  According to the present invention, the feeding unit and the ascending unit can be driven by one drive source, so that the cost can be reduced. In addition, since a delay mechanism capable of driving transmission is provided to the holding part and the ascending part so that the feeding member and the upper surface of the sheet are in contact with each other below the feeding position, the detection part reliably detects the feeding member detection position. Can be detected.

1 is an overall schematic diagram illustrating a printer according to an embodiment. The perspective view which shows the state which pulled out the cassette from the apparatus main body. The expansion perspective view which shows the part enclosed with the dashed-two dotted line of FIG. The perspective view which shows a drive unit and a roller unit. The perspective view which shows a lift-up plate and an intermediate plate. The perspective view which shows a lifter gear and a lift up plate. The control block diagram which concerns on this Embodiment. FF sectional drawing of FIG. 4 which shows the 1st link member and 2nd link member in the state which pulled out the cassette. FF sectional drawing of FIG. 4 which shows the 1st link member and 2nd link member in the state just before mounting | wearing with a cassette. FF sectional drawing of FIG. 4 which shows the 1st link member and 2nd link member in the state which mounted | wore with the cassette. (A) is a side view showing a delay mechanism, (b) is a perspective view showing a delay mechanism, (c) is a perspective view showing a first gear, and (d) is a perspective view showing a second gear. 11A is a cross-sectional view taken along the line C-C in FIG. 11A showing the delay mechanism in a state where the motor is not driven, and FIG. 11B is a cross-sectional view in FIG. CC sectional drawing. (C) is CC sectional drawing of Fig.11 (a) which shows the delay mechanism of the state which pulled out the cassette from the apparatus main body.

<First Embodiment>
〔overall structure〕
A printer 1 as an image forming apparatus according to the present embodiment is an electrophotographic laser beam printer that forms a monochrome toner image. As shown in FIG. 1, the printer 1 includes a sheet feeding device 14 that feeds stacked sheets, and an image forming unit 50 that forms an image on the fed sheets. The printer 1 also includes a fixing device 11 that fixes the image transferred to the sheet, and a discharge roller pair 12 that can discharge the sheet to the discharge tray 13.

  When an image formation command is output to the printer 1, an image forming process by the image forming unit 50 is started based on image information input from an external computer or the like connected to the printer 1. The image forming unit 50 includes a process cartridge 2, a laser scanner 3, and a transfer roller 4. The process cartridge 2 includes a photosensitive drum 2a rotating in the direction of arrow A, a charging roller 2b, a developing roller 2c and a cleaning blade 2e arranged along the photosensitive drum 2a, a toner container 2d, and a waste toner container 2f. Have. The process cartridge 2 can be attached to and detached from the apparatus main body 1 </ b> A of the printer 1.

  The laser scanner 3 irradiates the photosensitive drum 2a with laser light based on the input image information. At this time, the photosensitive drum 2a is charged in advance by the charging roller 2b, and an electrostatic latent image is formed on the photosensitive drum 2a when irradiated with laser light. Thereafter, the electrostatic latent image is developed by the developing roller 2c, and a monochrome toner image is formed on the photosensitive drum 2a.

  In parallel with the image forming process described above, the sheet S is fed from the sheet feeding device 14. The sheet feeding device 14 has a cassette 5 as a drawer portion that is supported so as to be attached to and pulled out from the apparatus main body 1A in a direction perpendicular to the sheet S feeding direction. The intermediate plate 33 as a supporting sheet supporting portion is supported so as to be movable up and down. The sheet S supported by the intermediate plate 33 is fed by a pickup roller 6 as a feeding member, and the sheet S fed by the pickup roller 6 is fed by a feed roller 7 and a separation roller 8 that presses against the feed roller 7. Separated one by one.

  The separation roller 8 has a built-in torque limiter. When one sheet is conveyed to the separation nip formed by the feed roller 7 and the separation roller 8, the separation roller 8 is driven to rotate by the feed roller 7. Thus, the limit value of the torque limiter is set. When a plurality of sheets are conveyed to the separation nip, the separation roller 8 stops without being driven by the feed roller 7. Note that driving may be input to the separation roller 8 so that the sheet is conveyed in the direction opposite to the sheet conveying direction by the feed roller 7. In the present embodiment, only one cassette 5 is provided, but a plurality of cassettes capable of supporting different sized sheets are provided, and sheets are selected according to the sheet size selected from the plurality of cassettes. You may send it.

  The sheets S separated one by one by the feed roller 7 and the separation roller 8 are conveyed to the registration roller pair 10 by the conveyance roller pair 9, and the skew is corrected by the registration roller pair 10. A toner image on the photosensitive drum 2 a is transferred to the sheet S conveyed at a predetermined conveyance timing by the registration roller pair 10 by an electrostatic load bias applied to the transfer roller 4. The residual toner remaining on the photosensitive drum 2a is collected in a waste toner container 2f by the cleaning blade 2e.

  The sheet S on which the toner image is transferred is given predetermined heat and pressure by the heating roller 11a and the pressure roller 11b of the fixing device 11, and the toner is melted and fixed (fixed). The sheet S that has passed through the fixing device 11 is conveyed to the discharge roller pair 12 by the conveyance roller pair 51 and 52, and is discharged to the discharge tray 13 by the discharge roller pair 12.

[Sheet feeding device]
Next, the sheet feeding device 14 will be described. FIG. 2 is a perspective view illustrating a state in which the cassette 5 is pulled out from the sheet feeding device 14. In FIG. 2, for convenience, some parts such as an exterior and a frame are omitted. FIG. 3 is an enlarged perspective view showing a portion surrounded by a two-dot chain line in FIG. FIG. 4 is a perspective view showing only components used for explaining the present invention from FIG.

  As shown in FIG. 2, the cassette 5 includes a pair of side regulation plates 5 a that regulate the position of the end portion in the width direction of the sheet S, and a rear end regulation that regulates the position of the upstream end of the sheet S in the sheet conveyance direction. And a plate 5b. As shown in FIG. 3, the apparatus main body 1 </ b> A is provided with a drive unit 15, a roller unit 16, a lever member 19, a first link member 17, and a second link member 18.

  As shown in FIG. 4, the roller unit 16 includes a drive shaft 20 that is rotatably supported by the apparatus main body 1A (see FIG. 2), a roller shaft 16 that is rotatably supported relative to the drive shaft 20, and a pickup roller 6. And a holder 22 that is swingably supported.

  A feed roller 7 (see FIG. 1) is fixed to the drive shaft 20 connected to the paper feed motor 40 (shown in FIG. 7), and a feed gear (not shown) is fixed to one end of the feed roller 7. ing. The rotation of the feed gear is transmitted to a pickup gear (not shown) fixed to one end of the pickup roller 6 via a gear train (not shown). Thereby, the feed roller 7 and the pickup roller 6 are rotated by the rotation of the drive shaft 20.

  As shown in FIG. 4, a pressing plate 24 that is rotatably supported by the drive shaft 20 and extends in the width direction is fastened to the holder 22, and the pressing plate 24 is a torsion coil spring 53 serving as a feeding and feeding unit. Is pressed downward. The torsion coil spring 53 is loosely fitted to the drive shaft 20, one end is connected to the apparatus main body 1 </ b> A (see FIG. 2), and the other end is connected to the pressing plate 24. The urging force of the torsion coil spring 53 is transmitted to the holder 22 via the pressing plate 24, thereby urging the pickup roller 6 toward the lower position. The pickup unit 6, the holder 22, and the pressing plate 24 constitute a feeding unit 55.

  The holder 22 has a separation position where the pickup roller 6 is separated from the sheet S (see FIG. 8), a feeding position where the pickup roller 6 is in contact with the sheet S and can feed the sheet S, and a lower position (see FIG. 10). ), The pickup roller 6 is supported so as to be swingable. The feeding position is located below the separation position, and the lower position is located below the feeding position. The feeding unit 55 supports the pickup roller 6 so as to be movable to a separation position, a feeding position, and a lower position.

  The lever member 19 has a contact portion 19a that can rotate in the E1 direction and the E2 direction around a rotation shaft 19b that extends in the vertical direction and that can contact the downstream end in the mounting direction of the cassette 5. . The first link member 17 as the pressing portion can be rotated in the C1 direction and the C2 direction around the rotation shaft 17d extending in parallel with the axial direction of the drive shaft 20, and C1 is provided by the torsion coil spring 54 as the urging portion. Is biased in the direction. The first link member 17 has a pressed portion 17c that is pressed by the contact portion 19a of the lever member 19, and the torsion coil spring 54 is pressed by the pressed portion 17c being pressed by the contact portion 19a. It rotates in the C2 direction against the urging force. That is, the first link member 17 is linked to the attaching / detaching operation of the cassette 5 in the apparatus main body 1 </ b> A via the lever member 19. Further, the first link member 17 is formed with a first pressing surface 17 a and a second pressing surface 17 b at the upper end portion, and the first pressing surface 17 a can press the side end portion 24 a of the pressing plate 24. . The second pressing surface 17b is formed slightly below the first pressing surface 17a, and a step portion is formed by the first pressing surface 17a and the second pressing surface 17b. The biasing force of the torsion coil spring 54 is set to be larger than the biasing force of the torsion coil spring 53.

  The 2nd link member 18 as a holding | maintenance part is supported so that the movement to the D1 direction and D2 direction which are perpendicular directions is possible. The second link member 18 is formed on the opposite side of the first contact surface 18 b that can contact the second press surface 17 b of the first link member 17 and the first contact surface 18 b, and is on the side end of the press plate 24. And a second contact surface 18c that can contact the portion 24a. Further, a rack portion 18 a is formed at the lower end portion of the second link member 18, and the rack portion 18 a meshes with the one-way gear 26 of the drive unit 15. The second link member 18 is movable up and down between the most elevated holding position (see FIG. 8) and the most lowered allowable position (see FIG. 10). The second link member 18 holds the feeding unit 55 at the holding position so that the pickup roller 6 is located at the separation position. In addition, the second link member 18 permits the movement of the feeding unit 55 at the permissible position so that the pickup roller 6 can swing between the separated position and the lower position.

[Drive unit]
As shown in FIG. 4, the drive unit 15 includes a motor 27 that generates a driving force, a worm gear pair 25 as a restricting portion, an intermediate gear 29, a lifter drive gear 28, and a one-way gear 26. Yes. The worm gear pair 25, the intermediate gear 29, the lifter driving gear 28, and the one-way gear 26 constitute a transmission unit 56 that can transmit the driving force of the motor 27 to the lift-up plate 31 (see FIG. 5) and the intermediate plate 33. .

  The driving force of the motor 27 is transmitted to the intermediate gear 29 through the worm gear pair 25. The driving force transmitted to the intermediate gear 29 is transmitted to the second link member 18 via the first gear 81 and the one-way gear 26 of the intermediate gear 29. The one-way gear 26 incorporates a one-way clutch 26 a that transmits a driving force from a motor 27 as a driving source to the second link member 18 and interrupts the driving force from the second link member 18. Further, the first gear 81 and the second gear 82 of the intermediate gear 29 rotate integrally, so that the lift-up plate 31 (see FIG. 5) is transferred from the second gear 82 via the lifter drive gear 28 and the lifter gear 30. The driving force of the motor 27 is transmitted.

  The worm gear pair 25 has a cylindrical worm 25a as a worm driven by a motor 27, and a worm wheel 25b meshing with the cylindrical worm 25a. The worm gear pair 25 can set a large reduction ratio in one stage. That is, when the motor 27 is stopped, the movement of the one-way gear 26 and the rack portion 18a of the second link member 18 can be restricted by the large reduction ratio of the worm gear pair 25. Instead of the worm gear pair 25, a spur gear train having a large reduction ratio set through several stages may be used.

  As shown in FIG. 5, the lifter drive gear 28 meshes with a lifter gear 30 as a second gear provided integrally with the lift-up plate 31. The lift-up plate 31 and the lifter gear 30 constitute a rising portion 31C. As shown in FIG. 6, the lift-up plate 31 can be rotated around a rotation shaft 32, and the intermediate plate 33 can be pushed up by the lift portion 31a. When the lifter drive gear 28 rotates in the arrow H direction in FIG. 5, the lifter gear 30 rotates in the arrow K direction. Then, the lift-up plate 31 rotates upward about the rotation shaft 32, and the lift part 31a pushes up the intermediate plate 33 from below. As a result, the intermediate plate 33 rotates upward with the rotation shaft 34 as a fulcrum.

  As shown in FIGS. 4 and 5, the holder 22 is provided with a flag member 83. The apparatus main body 1A has a paper surface detection sensor 84 (see FIG. 7) as a detection unit for detecting the presence or absence of the flag member 83. ) Is provided. The paper surface detection sensor 84 is configured by a photo sensor, for example. When the intermediate plate 33 is raised as described above, the pickup roller 6 that is in contact with the sheet S on the intermediate plate 33 is also raised together with the holder 22. When the pickup roller 6 reaches the feeding position, the paper surface detection sensor 84 detects the flag member 83 and the motor 27 is stopped. In this state, feeding of the sheet S is started.

[Control unit]
FIG. 7 is a control block diagram of the present embodiment. As shown in FIG. 7, the control unit 70 provided in the apparatus main body 1A includes a CPU 71, a ROM 72 that stores a program for controlling each unit, and a RAM 73 that temporarily stores data. A motor 27 and a paper feed motor 40 are connected to the output side of the control unit 70, and a cassette presence / absence sensor 74 that detects that the cassette 5 is mounted on the apparatus main body 1 </ b> A is connected to the input side of the control unit 70. The paper surface detection sensor 84 is connected. The cassette presence / absence sensor 74 as a detection unit is configured by, for example, a switch sensor or an optical sensor.

[Operation of feeding unit, middle plate and its surroundings]
Next, operations of the feeding unit 55, the intermediate plate 33, and the peripheral configuration will be described. In a state where the cassette 5 is mounted on the apparatus main body 1A, the first link member 17 is pressed against the cassette 5 via the lever member 19, and the first pressing surface 17a is at the lowest position, and the second link The member 18 is held at an allowable position. When the cassette 5 is pulled out from the apparatus main body 1 </ b> A, the cassette 5 is separated from the lever member 19. Then, the pressing of the first link member 17 by the lever member 19 is released, and the first link member 17 is rotated in the C1 direction by the torsion coil spring 54 (see FIG. 4) as shown in FIG. As the first link member 17 rotates in the C1 direction, the first pressing surface 17a of the first link member 17 presses the side end 24a of the pressing plate 24 upward, and the pickup roller 6 is positioned at the separation position. . The holder 22 is positioned in contact with a stopper (not shown) provided in the apparatus main body 1 </ b> A at the separation position of the pickup roller 6. When the pickup roller 6 is located at the separated position, the pickup roller 6 is located at a position where it does not interfere with the sheets S stacked on the intermediate plate 33.

  At the same time, the second pressing surface 17b (see FIG. 4) of the first link member 17 presses the first contact surface 18b of the second link member 18, and the second link member 18 moves to the holding position. At this time, the one-way gear 26 is driven by the rack portion 18 a of the second link member 18, but the one-way clutch 26 a built in the one-way gear 26 drives from the one-way gear 26 to the first gear 81 of the intermediate gear 29. Not transmitted. For this reason, when the cassette 5 is pulled out, the driving force is not transmitted to the lifter driving gear 28 and the worm wheel 25b via the intermediate gear 29. Further, when the second link member 18 is positioned at the holding position, the elastic force of the torsion coil spring 53 is applied from the pressing plate 24 in the direction of pushing down the second link member 18. However, since the second link member 18 is biased upward via the first link member 17 by the torsion coil spring 54 having a larger elastic force than the torsion coil spring 53, the second link member 18 is maintained in the holding position.

  On the other hand, when the cassette 5 is pulled out from the apparatus main body 1 </ b> A, the lifter gear 30 is separated from the lifter drive gear 28 together with the cassette 5. Thereby, the middle plate 33 of the cassette 5 is lowered by its own weight. At this time, since the driving force is not transmitted to the lifter drive gear 28 as described above, the friction between the lifter drive gear 28 and the lifter gear 30 is small, and the cassette 5 can be pulled out easily.

  When the cassette 5 is attached to the apparatus main body 1A, the downstream end in the insertion direction of the cassette 5 comes into contact with the contact portion 19a of the lever member 19 immediately before the cassette 5 is attached to the apparatus main body 1A. As a result, the lever member 19 rotates in the E1 direction (see FIG. 4), and as shown in FIG. 9, the first link member 17 rotates in the C2 direction in conjunction with this. Then, the first pressing surface 17 a of the first link member 17 is separated from the side end portion 24 a of the pressing plate 24. At this time, the feeding unit 55 is slightly swung downward by the urging force of the torsion coil spring 53 (see FIG. 4), and comes into contact with the second contact surface 18c of the second link member 18 located at the holding position. Held. A force is applied to the second link member 18 in a direction in which the second link member 18 is pushed downward by its own weight and the biasing force of the torsion coil spring 53, but the second link member 18 is maintained at the holding position by the reduction ratio of the worm gear pair 25. The position where the feeding unit 55 is slightly swung downward is also a separation position where the pickup roller 6 does not interfere with the sheets S stacked on the intermediate plate 33.

  In the state where the cassette 5 is pulled out, the second contact surface 18c of the second link member 18 and the first pressing surface 17a of the first link member 17 are also in contact with the side end portion 24a of the pressing plate 24. May be. In this configuration, even if the first link member 17 is separated from the pressing plate 24, the feeding unit 55 does not swing slightly downward. Further, the first link member 17 may be directly rotated in the C2 direction by the cassette 5 without using the lever member 19. For example, the pressed portion 17c of the first link member 17 is directly pressed by an inclined surface or the like provided in the cassette 5, and the pressed portion 17c is swung in a direction orthogonal to the mounting direction of the cassette 5, thereby causing the first link. The member 17 may be rotated in the C2 direction.

  When the cassette 5 is attached to the apparatus main body 1A and the attachment of the cassette 5 is detected by the cassette presence / absence sensor 74 (see FIG. 7), the motor 27 is driven by the controller 70. When the motor 27 is driven, as shown in FIG. 10, the intermediate gear 29, the lifter drive gear 28, and the one-way gear 26 rotate in the arrow G direction, the arrow H direction, and the arrow J direction, respectively. As the one-way gear 26 rotates in the J direction, the second link member 18 moves in the D2 direction from the holding position toward the allowable position via the rack portion 18a. When the second link member 18 is lowered, the rack portion 18a and the one-way gear 26 are disengaged during the movement. Then, the second link member 18 is stopped when the first contact surface 18b contacts the second pressing surface 17b of the first link member 17, and is maintained at the allowable position. Further, when the second link member 18 moves in the D2 direction, the feeding unit 55 urged downward by the torsion coil spring 53 rotates following the second link member 18. The second link member 18 stops by contacting the second pressing surface 17b of the first link member 17, and the pressing plate 24 of the feeding unit 55 contacts the first pressing surface 17a of the first link member 17. And stop. At this time, the pickup roller 6 is located at the lower position.

  Further, the rotation of the lifter drive gear 28 in the direction of arrow H raises the intermediate plate 33 as described above. At this time, as will be described later, the intermediate plate 33 starts to rise later than the movement from the second link member 18 by the delay mechanism 85 (see FIG. 11) including the intermediate gear 29. Then, as the intermediate plate 33 is raised, the pickup roller 6 of the feeding unit 55 located at the lower position and the sheet S on the intermediate plate 33 come into contact with each other. In a state where the pickup roller 6 and the sheet S are in contact with each other, the feeding unit 55 is raised as the middle plate 33 is raised. When the paper surface detection sensor 84 detects that the feeding unit 55 is raised and the pickup roller 6 is located at the feeding position, the control unit 70 stops the motor 27. Thereby, the positioning of the intermediate plate 33 and the feeding unit 55 is completed, and the pickup roller 6 is pressed against the upper surface of the sheet S through the pressing plate 24 and the holder 22 by the elastic force of the torsion coil spring 53. A sheet feeding pressure with the sheet S is set. As described above, since the pickup roller 6 moves to the lower position after the cassette 5 is completely mounted, the pickup roller 6 comes into contact with the sheet S during the mounting operation of the cassette 5 and the sheet S becomes wrinkled. It can be prevented from being torn.

  The pickup roller 6 can continuously feed out the sheet by transmitting the drive of the sheet feeding motor 40 at a predetermined interval while being in pressure contact with the sheet S. When the upper surface of the sheet S is lowered due to the decrease in the sheet S and the pickup roller 6 is removed from the feeding position, the paper surface detection sensor 84 does not detect the flag member 83 provided in the holder 22. The control unit 70 drives the motor 27 based on the detection signal from the paper surface detection sensor 84, and the pickup roller 6 is controlled to move to the feeding position. In the state where the intermediate plate 33 is lifted by the ascending portion 31C, the intermediate plate 33 is maintained without being lowered due to the reduction ratio of the worm gear pair 25.

[Delay mechanism]
Next, the delay mechanism 85 will be described in detail. As shown in FIGS. 11A and 11B, the delay mechanism 85 includes an intermediate gear 29 and a coil spring 35 (see FIG. 12A) as a biasing member built in the intermediate gear 29. The The intermediate gear 29 is disposed coaxially with the first gear 81 and the first gear 81 interposed in the drive transmission path between the motor 27 and the second link member 18, and between the motor 27 and the lift-up plate 31. And a second gear 82 interposed in the drive transmission path.

  As shown in FIG. 11C, the first gear 81 is formed with a boss 81a, a rib 81b, and a first contact surface 81c, and the coil spring 35 is press-fitted into the boss 81a. . As shown in FIG. 11 (d), the second gear 82 includes a spring receiver 82 a that can contact the coil spring 35, an insertion portion 82 b into which the rib 81 b of the first gear 81 is inserted, and a first contact surface. And a second contact surface 82c provided so as to be able to contact and separate from 81c. The rib 81b of the first gear 81 and the insertion portion 82b of the second gear 82 are ribs for preventing erroneous assembly so that the first gear 81 and the second gear 82 are correctly assembled. Then, the second gear 82 is attached to the first gear 81 by the snap fit 81d provided in the first gear 81 in a state where the rib 81b is inserted into the insertion portion 82b. At this time, as shown in FIG. 12A, the second gear 82 is relative to the first gear 81 within the range of the angle α between the first contact surface 81c and the second contact surface 82c. It can be rotated.

  12A is a sectional view taken along the line CC in FIG. 11A showing the delay mechanism 85 in a state where the cassette 5 is mounted on the apparatus main body 1A and the motor 27 is not driven. FIG. 12B is a cross-sectional view taken along the line C-C in FIG. 11A showing the delay mechanism 85 in a state where the sheet is fully loaded on the intermediate plate and the motor 27 is driven. FIG. 12C is a cross-sectional view taken along the line CC in FIG. 11A showing the delay mechanism 85 in a state where the cassette is pulled out from the apparatus main body 1A.

  As shown in FIG. 12A, when the cassette 5 is mounted on the apparatus main body 1A and the motor 27 is not driven, the first contact surface 81c of the first gear 81 and the second contact of the second gear 82 are provided. The surfaces 82c are separated. The natural length L1 of the coil spring 35 is such a length that the coil spring 35 is not sandwiched between the first gear 81 and the second gear 82 when the second gear 82 is assembled to the first gear 81. Is set.

  When the cassette 5 is mounted on the apparatus main body 1A, the lifter drive gear 28 and the lifter gear 30 are engaged with each other, so that a load torque in the direction opposite to the direction rotated by the drive of the motor 27 acts on the second gear 82. To do. This load torque is generated based on the sliding resistance of the gear train of the lifter drive gear 28 and the lifter gear 30, the weight of the lift-up plate 31 and the intermediate plate 33, the weight of the seat, and the like. Even when the sheets of the intermediate plate 33 are not stacked, the second gear 82 is subjected to load torque due to the sliding resistance of the gear train and the weight of the lift-up plate 31 and the intermediate plate 33. That is, the load torque is a value whose magnitude changes mainly according to the weight (loading amount) of the sheets.

  For example, as shown in FIG. 12B, when the motor 27 is driven in a state where sheets are fully loaded on the intermediate plate 33, the first gear 81 rotates in the arrow G direction. At this time, the position of the second gear 82 is maintained by the load torque, and when the first gear 81 rotates, the coil spring 35 contracts between the first gear 81 and the second gear. That is, as the first gear 81 rotates, the urging force (elastic force) acting on the second gear 82 from the coil spring 35 increases. When this urging force exceeds the load torque acting on the second gear 82, the second The gear 82 is pressed by the coil spring 35 and rotates in the arrow G direction.

  In a state where the sheets are fully loaded on the intermediate plate 33, the urging force of the coil spring 35 does not exceed the load torque acting on the second gear 82, the first gear 81 rotates by an angle α, and the first contact surface 81c The second contact surface 82c contacts. At this time, the length L2 of the coil spring 35 is set to be equal to or greater than the contact height of the coil spring 35. The contact height is the height when all the spring wires are in contact with each other. Further, since the second link member 18 is set to move to the permissible position (see FIG. 10) by the rotation of the first gear 81 by the angle α, the pickup roller 6 is positioned at the lower position. Yes.

  The pickup roller 6 passes through the feeding position while the first gear 81 rotates by the angle α. For example, even if the paper surface detection sensor 84 detects the flag member 83 for a predetermined time after the motor 27 is turned on. The controller 70 ignores the ON signal of the paper surface detection sensor 84. Thereby, even if the pickup roller 6 passes through the feeding position while the pickup roller 6 moves from the separated position to the lower position after the motor 27 is turned on, the control unit 70 does not stop the motor 27. Further, the paper surface detection sensor 84 may have two detection elements in the vertical direction, and the paper surface detection sensor 84 may transmit an ON signal to the control unit 70 only when the feeding unit 55 is raised.

  When the motor 27 further rotates while the first contact surface 81c and the second contact surface 82c are in contact with each other, the delay mechanism 85 is operated with the first gear 81 and the second gear 82 being integrated. Rotate. The state in which the first gear 81 and the second gear 82 rotate integrally as described above is referred to as a second state, and the state in which the first gear 81 rotates and the second gear 82 does not rotate is referred to as a first state. In the second state, the middle plate 33 rises due to the rotation of the second gear 82, and the upper surface of the sheet S on the middle plate 33 comes into contact with the pickup roller 6. Further, when the second gear 82 rotates, the feeding unit 55 rises following the sheet S on the intermediate plate 33 against the biasing force of the torsion coil spring 53. When the paper surface detection sensor 84 detects that the pickup roller 6 is located at the feeding position, the control unit 70 stops the motor 27. Even after the motor 27 stops, the second link member 18 does not move unless the cassette 5 is removed from the apparatus main body 1A due to the large reduction ratio of the worm gear pair 25 acting on the second gear 82.

  In the second state, since the first gear 81 rotates together with the second gear 82, the second link member 18 is driven by the motor 27 until the motor 27 stops even after the pickup roller 6 is positioned at the lower position. Tries to move down. For this reason, for example, the rack portion 18a of the second link member 18 is formed with a missing gear, and the missing gear portion of the missing gear is opposed to the one-way gear 26 at a position where the second link member 18 is located at the allowable position. It may be configured. Accordingly, when the second link member 18 is positioned at the allowable position, the driving force is not transmitted from the one-way gear 26 to the second link member 18. Further, the rack portion 18a may be configured to be detached from the one-way gear 26 while the second link member 18 is lowered toward the allowable position, and a stopper that stops the second link member 18 at the allowable position may be provided. .

  In addition, when no sheets are stacked on the intermediate plate 33 or when a small number of sheets are stacked, the second gear 82 is in the first state before the first contact surface 81c and the second contact surface 82c contact each other. It starts to rotate with the gear 81. Hereinafter, the case where the number of sheets stacked is small, including the case where sheets are not stacked, will be referred to. That is, when the first gear 81 rotates, the coil spring 35 contracts, and the biasing force that acts on the spring receiver 82a of the second gear 82 from the coil spring 35 increases. When the urging force exceeds the load torque applied to the second gear 82, the delay mechanism 85 rotates with the first gear 81 and the second gear 82 integrally. A state in which the first gear 81 and the second gear 82 rotate together in a state where the first contact surface 81c and the second contact surface 82c are not in contact with each other is also referred to as a second state. At this time, the time from when the first gear 81 starts to rotate until the second gear 82 starts to rotate is the time when the first contact surface 81c and the second contact surface 82c come into contact with each other and the rotation starts. This time is shorter than the time, and this time varies depending on the weight (loading amount) of the sheet supported by the intermediate plate 33.

  The operating length L of the coil spring 35 in a state where the first gear 81 and the second gear 82 start to rotate together with the first contact surface 81c and the second contact surface 82c not contacting each other is L2. <L <L1 is satisfied. As described above, when the second gear 82 starts to rotate together with the first gear 81 before the first contact surface 81c and the second contact surface 82c contact each other, the pickup roller 6 is positioned at the lower position. Before, the middle plate 33 starts to rise. The pickup roller 6 contacts the sheet S on the intermediate plate 33 in a state where the pickup roller 6 is located between the feeding position and the lower position. In this state, the intermediate plate 33 rises before the pickup roller 6 is positioned at the lower position. However, the upper surface of the sheet S on the intermediate plate 33 is located at a position where the lowered pickup roller 6 is lowered from the feeding position. It is necessary to abut. Therefore, the urging force of the coil spring 35 is set so that at least the middle plate 33 starts to rise after the pickup roller 6 is lowered to the feeding position by the second link member 18.

  The urging force that the coil spring 35 acts on the second gear 82 is set to be larger than the load torque based on the sliding resistance of the gear train of the second gear 82 and the lifter drive gear 28. Thereby, when the cassette 5 is pulled out, the urging force of the coil spring 35 causes the second gear 82 and the first gear 81 to rotate before the first contact surface 81c and the second contact surface 82c contact each other. Even if the delay mechanism 85 is set to start, the delay mechanism 85 reliably shifts from the second state to the first state. Even when the amount of sheets S is small, the sliding resistance of the gear train and the lift-up plate 31 and the intermediate plate 33 are set so that the delay mechanism 85 is in the second state when the motor 27 is driven. The biasing force of the coil spring 35 may be larger than the load torque due to its own weight.

  When the cassette 5 is pulled out from the apparatus main body 1A from the state shown in FIG. 12B, the load torque acting on the second gear 82 is reduced, and the first force is applied by the urging force of the coil spring 35 as shown in FIG. The first contact surface 81c and the second contact surface 82c are separated again. Accordingly, by pulling out the cassette 5 from the apparatus main body 1A, the first gear 81 and the second gear 82 are separated by an angle α as in FIG. 12A, and the delay mechanism 85 is moved from the second state to the first state. Transition to the state.

  As described above, the provision of the delay mechanism 85 causes a time difference in rotational driving between the first gear 81 and the second gear 82, and the lift-up plate 31 starts to be driven later than the second link member 18. Thus, the pickup roller 6 and the sheet S on the intermediate plate 33 can be brought into contact with each other in a state where the pickup roller 6 is positioned between the lowered position or the feeding position and the lower position. For this reason, the pickup roller 6 rising together with the intermediate plate 33 and the sheet S can be reliably detected at the feeding position, and jamming and conveyance failure can be prevented. For example, when the pickup roller 6 and the sheet S are in contact with each other with the pickup roller 6 positioned above the feeding position, the feeding unit 55 that rises with the sheet S cannot be detected at the feeding position.

  In addition, since the coil spring 35 is provided between the first gear 81 and the second gear 82, the first gear 81 and the second gear according to the weight (loading amount) of the sheets S stacked on the intermediate plate 33. The time difference at which the motor 82 starts rotating is adjusted. That is, in a state where the sheets S are fully loaded on the intermediate plate 33, the time from when the pickup roller 6 starts to descend until the intermediate plate 33 starts to rise is when the amount of sheets S on the intermediate plate 33 is small. Longer than that. However, since the sheets S are fully loaded, the upper surface of the sheets S stacked on the intermediate plate 33 is already positioned at a high position, and the distance that the intermediate plate 33 ascends before the pickup roller 6 is positioned at the feeding position. Is shorter than when the amount of stacked sheets S is small.

  On the other hand, in a state where the amount of sheets S stacked on the intermediate plate 33 is small, the time from when the pickup roller 6 starts to descend until the intermediate plate 33 starts to rise is shorter than when the amount of sheets S stacked is large. . At this time, the second gear 82 starts rotating together with the first gear 81 before the first gear 81 completes the rotation of the angle α. Since the upper surface of the sheet S stacked on the intermediate plate 33 is lower than when full, the distance that the intermediate plate 33 rises before the pickup roller 6 is positioned at the feeding position is long.

  As described above, the drive start timing of the intermediate plate 33 differs depending on the weight of the sheets S stacked on the intermediate plate 33, from when the motor 27 starts to drive until the feeding unit 55 is positioned at the feeding position. The time of is almost leveled. The pickup roller 6 and the intermediate plate are kept in a state where the feeding unit 55 is positioned between the feeding position and the lower position regardless of the weight (loading amount) of the sheets S stacked on the intermediate plate 33. 33 can be brought into contact with the sheet S.

  Moreover, the raising / lowering operation | movement of the feeding unit 55 and the lift up plate 31 can be implement | achieved by the one motor 27, and the number of actuators to be used can be reduced and cost can be reduced. Further, the lever member 19 and the second link member 18 can position the pickup roller 6 at a position that does not interfere with the sheet S when the cassette 5 is inserted into the apparatus main body 1A, thereby preventing jamming. In addition, since the motor 27 does not rotate in the reverse direction, there is no need to add an extra electric circuit or the like.

  In this embodiment, the motor 27 is used as a drive source. However, the present invention is not limited to the motor, and a solenoid or other actuator may be used. Further, the delay mechanism 85 is constituted by the first gear 81, the second gear 82, and the coil spring 35. However, the present invention is not limited to this. You may comprise.

  In this embodiment, the delay mechanism 85 is configured to return from the second state to the first state using the coil spring 35. However, the present invention is not limited to this, and an elastic member such as rubber is used instead of the coil spring 35. A magnet or the like may be used. Further, the coil spring 35 may be omitted, and the motor 27 may be configured to rotate reversely when the cassette 5 is pulled out from the apparatus main body 1A.

  In the present embodiment, when the sheet S is fully loaded on the intermediate plate 33, the first contact surface 81c of the first gear 81 and the second contact surface 82c of the second gear 82 are in contact with each other. Although the first gear 81 and the second gear 82 are configured to rotate integrally, the present invention is not limited to this. For example, the second gear 82 may be pressed by the coil spring 35 and rotated as in the case where the sheet S is hardly stacked on the intermediate plate 33. On the other hand, even when the sheet S is hardly stacked on the intermediate plate 33, the first gear 81 and the second gear 82 rotate together by the first contact surface 81c and the second contact surface 82c contacting each other. You may comprise.

  In this embodiment, the electrophotographic printer 1 has been described. However, the present invention is not limited to this. For example, the present invention can be applied to an inkjet image forming apparatus that forms an image on a sheet by ejecting ink liquid from a nozzle.

  1: Image forming apparatus (printer) / 1A: apparatus main body / 5: drawer part (cassette) / 6: feeding member (pickup roller) / 14: sheet feeding apparatus / 17: pressing part (first link member) / 18: holding portion (second link member) / 25: restricting portion (worm gear pair) / 25a: worm (cylindrical worm) / 25b: worm wheel / 26a: one-way clutch / 27: drive source (motor) / 31C: ascending portion / 33: Sheet support part (medium plate) / 35: Biasing member (coil spring) / 50: Image forming part / 53: Feeding and feeding part (torsion coil spring) / 54: Biasing part (torsion coil spring) / 55: Feeding Feed unit / 56: Transmission unit / 81: First gear / 81c: First contact surface / 82: Second gear / 82c: Second contact surface / 84: Detection unit (paper surface detection sensor) / 85: Delay mechanism

Claims (16)

A sheet support part for supporting the sheet;
A raising part for raising the seat support part;
A feeding member capable of feeding a sheet supported by the sheet support portion;
A separation position where the feeding member is separated from the sheet supported by the sheet support portion, and a sheet which is positioned below the separation position and is supported by the sheet support portion can be fed by the feeding member. A feeding unit that is movably supported between a lower feeding position and a lower position located below the feeding position;
A detection unit for detecting that the feeding member is located at the feeding position;
A holding portion movable to a holding position for holding the feeding member at the separated position and an allowable position for allowing the feeding member to swing toward the lower position;
A driving source for generating a driving force;
A transmission unit capable of transmitting a driving force from the driving source to the ascending unit and the holding unit,
The transmission unit is configured so that the feeding member and the upper surface of the sheet supported by the sheet support portion are in contact with each other in a state where the feeding member is located between the feeding position and the lower position. Having a delay mechanism that starts driving the ascending portion later than the holding portion;
A sheet feeding apparatus characterized by that. The delay mechanism is disposed coaxially with the first gear interposed in the drive transmission path between the drive source and the holding unit, and is driven between the drive source and the ascending unit. A second state in which the first gear rotates and the second gear does not rotate, and the first gear and the second gear rotate integrally. Can take the state,
The sheet feeding apparatus according to claim 1. The time from the start of rotation of the first gear to the start of rotation of the second gear varies depending on the weight of the seat supported by the seat support portion.
The sheet feeding apparatus according to claim 2, wherein the sheet feeding apparatus is a sheet feeding apparatus. The delay mechanism includes a biasing member that is interposed between the first gear and the second gear and biases the first gear and the second gear so as to be in the first state.
The sheet feeding apparatus according to claim 2, wherein the sheet feeding apparatus is a sheet feeding apparatus. The delay mechanism enters the second state when an urging force acting on the second gear from the urging member exceeds a load torque acting on the second gear.
The sheet feeding apparatus according to claim 4, wherein the sheet feeding apparatus is a sheet feeding apparatus. The load torque is a value corresponding to the weight of the sheet supported by the sheet support portion.
The sheet feeding apparatus according to claim 5, wherein the sheet feeding apparatus is a sheet feeding apparatus. The first gear has a first contact surface;
The second gear has a second contact surface provided so as to be able to contact and separate from the first contact surface,
The delay mechanism enters the second state when the first contact surface and the second contact surface contact each other.
The sheet feeding apparatus according to claim 2, wherein the sheet feeding apparatus is a sheet feeding apparatus. An apparatus main body that supports the feeding unit, the detection unit, the holding unit, the drive source, and the transmission unit;
A drawer part that supports the sheet support part and the ascending part, and can be attached to and pulled out from the apparatus main body,
The delay mechanism shifts from the second state to the first state by being pulled out from the apparatus main body.
The sheet feeding device according to claim 2, wherein the sheet feeding device is a sheet feeding device. The transmission unit has a restricting portion that restricts the holding portion from moving from the holding position to the permissible position when the drive source is stopped.
The sheet feeding apparatus according to claim 8, wherein the sheet feeding apparatus is a sheet feeding apparatus. The restricting portion includes a worm and a worm wheel.
The sheet feeding device according to claim 9. A pressing part capable of pressing the feeding unit and the holding part;
An urging portion that urges the pressing portion so that the feeding member moves from the lower position to the separated position and the holding portion moves from the allowable position to the holding position;
The transmission unit is disposed in a drive transmission path between the delay mechanism and the holding unit, and transmits a driving force from the driving source to the holding unit and cuts off a driving force from the holding unit. Having
The sheet feeding apparatus according to claim 9 or 10, wherein the sheet feeding apparatus is a sheet feeding apparatus. In a state where the drawer portion is pulled out from the apparatus main body, the drawer portion is separated from the pressing portion, and the holding portion is positioned at the holding position by the pressing portion biased by the biasing portion. The feeding member is located at the separated position;
In a state where the drawer portion is mounted on the apparatus main body, the drawer portion abuts against the pressing portion against the urging force of the urging portion, and the regulation portion is in a state where the holding portion is separated from the pressing portion. Held in the holding position by the part,
The sheet feeding apparatus according to claim 11. A feeding / feeding unit that biases the feeding unit toward the lower position;
The urging force of the feeding and sending urging unit is set to be smaller than the urging force of the urging unit.
The sheet feeding apparatus according to claim 11, wherein the sheet feeding apparatus is a sheet feeding apparatus. When the driving source is driven in a state where the drawer portion is mounted on the apparatus main body, the holding portion moves toward the allowable position.
The sheet feeding device according to claim 8, wherein the sheet feeding device is a sheet feeding device. The feeding unit rises following the raising portion in a state where the feeding member is in contact with the upper surface of the sheet supported by the sheet supporting portion raised by the raising portion.
The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus. A sheet feeding device according to any one of claims 1 to 15,
An image forming unit that forms an image on a sheet fed from the sheet feeding device,
An image forming apparatus.

Images