JP2014136641A - Sheet feeder and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet feeder and an image formation device that can prevent a sheet leading end from being bent and so on even if a separation roller wears away without using any dedicated electric component such as an electromagnetic clutch.SOLUTION: A sheet feeding part 24 includes a sheet loading part 30, a pickup roller 62, a feed roller 60, a retard roller 61, and a gear mechanism 28. The gear mechanism 28 includes a driving input gear 67 capable of transmitting forward rotation in a direction in which a sheet S is sent out in a sheet feeding direction to the retard roller 61, and a retard roller gear 71 capable of forward rotation of the driving input gear 67 to the retard roller 61. The driving input gear 67 has an engagement/disengagement gear part 67b1 partially provided so as to engage with the retard roller gear 71 until a sheet leading end passes through a separation nip part 63 and to disengage from the retard roller gear 71 after the sheet leading end passes through the separation nip part 63.

Description

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

  2. Description of the Related Art Conventionally, there is a sheet feeding apparatus used in an image forming apparatus such as a copying machine or a printer to which a separation system that separates and feeds sheets one by one using a retard roller and a feed roller is applied. In this method, a pickup roller that feeds out the sheet in the sheet feeding cassette, a feed roller that rotates in the same direction in synchronization with the pickup roller downstream in the sheet feeding direction, and a pressure contact with the feed roller with a predetermined pressure contact force (retard pressure) A retard roller is provided.

  In the separation method, the sheets are separated one by one at the separation nip portion between the feed roller and the retard roller. The retard roller is given a constant torque in a direction opposite to the sheet feeding direction via a torque limiter. Thereby, when two or more sheets enter the separation nip portion, the retard roller rotates in the direction opposite to the sheet feeding direction, thereby preventing the sheets from being double fed.

  In recent years, among media (sheets) used in image forming apparatuses, sheets with a large amount of paper dust or sheets containing a material that easily damages rubber on the surface of a roller are often used. It has become to. When such a medium is used, the roller surface may be worn and deteriorated in a short time, causing a problem of shortening the life of the roller.

  When the roller is worn or deteriorated, the coefficient of friction on the roller surface decreases. As a result, the retard roller may not sufficiently rotate with the feed roller. In that case, if the leading end of the sheet tries to enter the separation nip portion where the retard roller is not properly rotated, there is a possibility that the sheet feeding failure or the leading end of the sheet may be broken.

  In order to prevent this problem, a technique for controlling the timing of rotational driving in the direction opposite to the sheet feeding direction by the retard roller has been proposed. In this technique, the retard roller is forcibly rotated in the sheet feeding direction until the leading edge of the sheet fed by the pickup roller passes through the separation nip portion, and the retarding is performed after the leading edge of the sheet passes the separation nip portion. Apply reverse rotation to the roller.

  As a result, the leading edge of the sheet smoothly enters the separation nip portion by the feed roller and the retard roller that rotate in the sheet feeding direction, and the sheets that have entered the separation nip are reliably separated one by one by the reverse rotation of the retard roller. Can do. For this reason, even when the roller is worn or deteriorated, it is possible to prevent occurrence of sheet feeding failure and folding of the leading end of the sheet (see Patent Document 1).

JP-A-56-7847

  However, in the technique described in Patent Document 1, it is necessary to use a dedicated electric component (for example, an electromagnetic clutch) in order to rotate the retard roller in the sheet feeding direction. For this reason, it is difficult to use an apparatus with cost restrictions.

  The present invention is a sheet capable of preventing occurrence of sheet feeding failure and sheet tip breakage even when wear or deterioration of a separation roller such as a retard roller occurs without using a dedicated electric component such as an electromagnetic clutch. It is an object to provide a feeding device and an image forming apparatus.

  The present invention provides a sheet feeding apparatus, a sheet stacking unit on which sheets are stacked, a feeding roller that feeds the sheets stacked on the sheet stacking unit in a sheet feeding direction, and a sheet fed by the feeding roller A conveying roller for conveying the sheet in the sheet feeding direction, and a separation nip portion is formed by pressure contact with the conveying roller, and when two or more sheets are fed into the separation nip portion, the direction opposite to the sheet feeding direction A separation roller for separating the sheets one by one, a drive input gear capable of transmitting a positive rotation in the direction of feeding the sheet in the sheet feeding direction to the separation roller, and the separation roller provided on the separation roller side. A separation roller gear capable of transmitting the forward rotation of the drive input gear to the separation roller, and the separation roller until the leading edge of the sheet passes through the separation nip portion. And a gear mechanism having an engagement / disengagement gear portion that is partially provided so as to be disengaged from the separation roller gear after the leading edge of the sheet has passed through the separation nip portion. .

  According to the present invention, it is possible to prevent occurrence of sheet feeding failure and sheet leading edge breakage even when wear or deterioration of a separation roller such as a retard roller occurs without using dedicated electric parts such as an electromagnetic clutch. The apparatus configuration can be realized at a low cost.

1 is a schematic sectional view showing a laser beam printer in an embodiment according to the present invention. (A)-(e) is a figure which shows the structure of the sheet feeding apparatus in this embodiment. FIGS. 5A to 5D are diagrams illustrating a state before starting JOB of the sheet feeding apparatus according to the present embodiment. FIGS. FIGS. 5A to 5D are diagrams illustrating a state immediately before the termination of the retard roller forced forward rotation of the sheet feeding device in the present embodiment. FIGS. 5A to 5D are diagrams illustrating states after the retard roller forced forward rotation of the sheet feeding device according to the present embodiment is completed. FIGS. 4A to 4D are diagrams illustrating a state immediately before the end of the forward rotation of the retard roller in a state where two sheets have entered the separation nip portion of the sheet feeding device according to the present embodiment. FIGS. 4A to 4D are diagrams illustrating a state after the end of forced forward rotation of a retard roller in a state where two sheets have entered the separation nip portion of the sheet feeding device according to the present embodiment.

<First Embodiment>
Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. First, an image forming apparatus including a sheet feeding device will be described with reference to FIG. FIG. 1 is a schematic sectional view showing a laser beam printer as an image forming apparatus according to the present invention.

  As shown in FIG. 1, a full-color laser beam printer (hereinafter “printer”) 1 includes a printer main body (hereinafter “apparatus main body”) 1A serving as an image forming apparatus main body. The apparatus main body 1A includes an image forming section 1B, a fixing section 20 as a fixing unit, and an image reading apparatus 2 as an upper apparatus installed substantially horizontally above the apparatus main body 1A. In the apparatus main body 1A, a control unit 18 is disposed as a control unit that controls each unit of the apparatus.

  A discharge space P for discharging a sheet is formed between the image reading apparatus 2 and the apparatus main body 1A. A toner cartridge 15 is disposed below the discharge space P, and a plurality of sheet stacking sections 30 on which sheets S are stacked are disposed below the apparatus main body 1A.

  The image forming unit 1B employs a four-drum full-color system, and forms a toner image of four colors of laser scanner 10 and yellow (Y), magenta (M), cyan (C), and black (K) 4. The process cartridge 11 is included.

  Each process cartridge 11 includes a photosensitive drum 12 as a photosensitive member, a charger 13 as a charging unit, a developing unit 14 as a developing unit, and a cleaner (not shown) as a cleaning unit. Further, the image forming unit 1B includes an intermediate transfer unit 1C above the process cartridge 11.

  The intermediate transfer unit 1C includes an intermediate transfer belt 16 as an image carrier that is wound around a driving roller 16a and a tension roller 16b. The intermediate transfer unit 1 </ b> C includes a primary transfer roller 19 that is provided inside the intermediate transfer belt 16 and abuts against the inner surface of the intermediate transfer belt 16 at a position facing the photosensitive drum 12. The intermediate transfer belt 16 is composed of a film-like member and is in contact with each photosensitive drum 12. The intermediate transfer belt 16 is rotated in the arrow direction by a driving roller 16a driven by a driving unit (not shown).

  By applying a positive transfer bias from the primary transfer roller 19 to the intermediate transfer belt 16, each color toner image having a negative polarity on the photosensitive drum 12 is sequentially transferred to the intermediate transfer belt 16 in a multiple transfer manner. As a result, a color image is formed on the intermediate transfer belt. A secondary transfer roller 17 constituting a secondary transfer unit that transfers a color image formed on the intermediate transfer belt to the sheet S is provided at a position facing the driving roller 16a of the intermediate transfer unit 1C. .

  A fixing unit 20 is disposed above the secondary transfer roller 17, and a first discharge roller pair 25a, a second discharge roller pair 25b, and a double-sided reversing unit 1D as a reversing discharge unit are disposed at the upper left part of the fixing unit 20. Has been placed. The double-side reversing unit 1D has a reversing roller pair 26 as a sheet reversing and conveying roller capable of normal and reversal, and a reconveying path R that conveys a sheet on which an image is formed to the image forming unit 1B again. . The image forming unit 1B, the secondary transfer unit (17), and the fixing unit 20 constitute an image forming unit according to the present invention that forms an image on the sheet S fed from the sheet stacking unit 30.

  A sheet feeding unit 24 as a sheet feeding device that feeds the sheets S stacked on the sheet stacking unit 30 downstream is disposed downstream of each sheet stacking unit 30 in the sheet feeding direction.

  In the above configuration, image information read by the image reading device 2 or image information input from an external device such as a personal computer (not shown) is subjected to image processing and then converted into an electrical signal to be a laser scanner of the image forming unit 1B. 10 is transmitted.

  In the image forming unit 1B, the surface of the photosensitive drum 12 of each process cartridge 11 is scanned with laser light corresponding to image information of yellow, magenta, cyan, and black component colors emitted from the laser scanner 10. As a result, the surface of the photosensitive drum 12 whose surface is uniformly charged to a predetermined polarity and potential by the charger 13 is sequentially exposed, and yellow, magenta, cyan on the photosensitive drum of each process cartridge 11 respectively. And an electrostatic latent image of black are sequentially formed.

  Thereafter, the electrostatic latent image is developed and visualized with each color toner of yellow, magenta, cyan and black, and each color toner image on each photosensitive drum is formed by the primary transfer bias applied to the primary transfer roller 19. The images are sequentially superimposed and transferred onto the intermediate transfer belt 16. As a result, a toner image is formed on the intermediate transfer belt 16.

  On the other hand, the sheet S sent out from the sheet feeding unit 24 passes through the registration roller pair 40 and is sent to the secondary transfer unit constituted by the drive roller 16 a and the secondary transfer roller 17. In the secondary transfer portion, the toner images formed by the image forming portion 1B are transferred onto the sheet S at once.

  Subsequently, the sheet S to which the toner image has been transferred in this manner is conveyed to the fixing unit 20 and receives heat and pressure at the fixing unit 20 to fix the toner image as a color image. Thereafter, the sheet S on which the color image is fixed is discharged to the discharge space P by the first discharge roller pair 25a and stacked on the stacking portion 23 formed to protrude from the bottom surface of the discharge space P.

  Next, an outline of the configuration and operation of the sheet feeding unit 24 in the present embodiment will be described with reference to FIG. 2A is a schematic cross-sectional view of the sheet feeding unit 24, FIG. 2B is a diagram showing a relationship in the thrust direction of the sheet feeding unit 24, and FIGS. e) is a cross-sectional view taken along lines AA, BB, and CC in FIG.

  The sheet feeding unit 24 includes a pickup roller 62 and a separation roller pair 22 as a sheet separation unit including a feed roller 60 and a retard roller 61. The retard roller 61 as a separation roller has a retard roller gear 71 as a separation roller gear which is provided on the retard roller side (separation roller side) and can transmit the positive rotation of the drive input gear 67 to the retard roller 61. A conveyance roller pair 21 that conveys the fed sheet S to the secondary transfer unit is disposed downstream of the separation roller pair 22.

  The pickup roller 62 constitutes a feeding roller that feeds the sheets S stacked on the sheet stacking unit 30 in the sheet feeding direction H. The feed roller 60 constitutes a conveyance roller that conveys the sheet S fed by the pickup roller 62.

  The retard roller 61 rotates in the direction of feeding the sheet S in the sheet feeding direction H in a state where the separation nip portion 63 is formed in contact with the feed roller 60. The retard roller 61 constitutes a separation roller that rotates in the direction opposite to the sheet feeding direction and separates the sheets S one by one when two or more sheets S are fed into the separation nip portion 63.

  In the present embodiment, rotation in the direction in which the sheet S is fed in the sheet feeding direction H is referred to as normal rotation, and rotation in the direction in which the sheet S is fed in the direction I opposite to the sheet feeding direction is referred to as reverse rotation.

  As shown in FIGS. 2A to 2E, in the sheet feeding unit 24, the pickup roller 62 abuts on the downstream side in the sheet feeding direction H of the uppermost sheet S1 in the stacked sheet bundle S. Yes. The pickup roller 62 sends the uppermost sheet S1 to the separation nip portion 63 formed by the pressure contact between the feed roller 60 and the retard roller 61. Thereafter, the uppermost sheet S <b> 1 is sent out by a feeding force received from the separation nip portion 63.

  Here, the retard roller 61 is forcibly forced for a certain period of time without using an electric component such as an electromagnetic clutch, which is a feature of the sheet feeding unit 24, and without using a return drive (for example, a reverse drive of the feed motor M). A configuration for realizing reverse rotation after rotating in the forward direction will be described.

  That is, the sheet feeding unit 24 includes a gear mechanism 28. The gear mechanism 28 includes a pickup roller gear (first transmission gear) 66, a drive input gear 67, an engagement / disengagement gear portion 67b1, an idler gear 70, a retard roller gear 71, a feed roller gear (second transmission gear) 68, a pickup idler. A gear 65 and the like are included. The gear mechanism 28 transmits the forward rotation generated by the feeding motor M from the drive input gear 67 to the pickup roller 62, the feed roller 60, and the retard roller 61, respectively.

  The drive input gear 67 is configured to be divided into all tooth portions 67a and missing tooth portions 67b adjacent to each other in the axial direction. This drive input gear 67 is rotated by receiving a drive from a feeding motor M that rotates only in one direction (forward rotation), and rotates forward through the engagement / disengagement gear portion 67b1, idler gear 70, and retard roller gear 71. 61.

  All the teeth 67a mesh with the feed roller gear 68 to transmit the drive to the feed roller gear 68, and rotate the feed roller 60 at the other end via a feed roller shaft 69 that fixes and supports the feed roller gear 68 at one end. Let

  A pickup roller input gear 64 is fixed on the feed roller shaft 69 adjacent to the feed roller 60. The pickup roller input gear 64 transmits driving to a pickup roller gear 66 that is mounted coaxially with the pickup roller 62 via a pickup idler gear 65. For this reason, the pickup roller 62 can be rotated synchronously with the feed roller 60 by driving the feed motor M that generates normal rotation.

  An engagement / disengagement gear portion 67b1 is formed only on a part of the circumference of the toothless portion 67b of the drive input gear 67, and is attached coaxially to the retard roller 61 from the engagement / disengagement gear portion 67b1 via the idler gear 70. Drive is transmitted to the retard roller gear 71.

  The engagement / disengagement gear portion 67b1 provided in the drive input gear 67 meshes with the retard roller gear 71 until the leading end of the sheet passes the separation nip portion 63, and after the leading end of the sheet passes the separation nip portion 63, the retard roller gear 71. It is provided in part so that it may detach from. That is, the engagement / disengagement gear portion 67b1 meshes with the retard roller gear 71 coaxial with the retard roller 61 and transmits the normal rotation until the leading edge of the sheet S to be sent passes through the separation nip portion 63. The engagement / disengagement gear portion 67b1 releases the meshing with the retard roller gear 71 after the leading edge of the sheet S passes through the separation nip portion 63.

  The shaft of the pickup roller 62, the shaft of the pickup idler gear 65, the feed roller shaft 69, the retard roller shaft 72, the shaft 67c of the drive input gear 67, the shaft of the idler gear 70, etc. are connected to the main body of the apparatus via support means (not shown). It is supported on the 1A side.

  The retard roller shaft 72 is rotatably supported by the apparatus main body 1A, the retard roller 61 is fixed to one end, and the other end is connected to a torque limiter 74 supported by a fixing portion 75 provided in the apparatus main body 1A. The parts are connected. Further, a retard roller gear 71 is fixed on the retard roller shaft 72 between the retard roller 61 and the torque limiter 74.

  The rotation transmitted to the toothless portion 67 b of the drive input gear 67 is transmitted from the engagement / disengagement gear portion 67 b 1 to the retard roller gear 71 via the idler gear 70 and transmitted to the retard roller 61. A torsion coil spring 73 is arranged between the retard roller gear 71 and the torque limiter 74 on the retard roller shaft 72.

  The torsion coil spring 73 has one end connected to the retard roller gear 71 and the other end connected to the torque limiter 74. A torque limiter 74 having a known structure in which an inner ring member having a smaller diameter than the external part is inserted into the cylindrical external part and a coil spring is interposed between the external part and the inner ring member is used. Can do. In this case, the other end of the torsion coil spring 73 is connected to the inner ring member of the torque limiter 74. When the torque acting between the inner ring member and the external part is small, the torque limiter 74 rotates together with the inner ring member and the external part in one direction. Rotate. And when an inner ring member reversely rotates with respect to an external component, both will lock. The torsion coil spring 73 and the torque limiter 74 constitute a torsion mechanism.

  The torsion coil spring 73 charges a return rotational force to the retard roller 61 while being forwardly rotated by the gear mechanism 28 or while being rotated along with the rotation of the feed roller 60. That is, the torsion mechanism having the torsion coil spring 73 is charged with a reverse rotational force that rotates the retard roller 61 in a direction opposite to the normal rotation via the torque limiter 74 when the forward rotation is applied. Then, a reverse rotational force is applied to the retard roller 61 when the forward rotation is released.

  The winding direction of the torsion coil spring 73 is set so that the torsion coil spring 73 is wound by the retard roller 61 that is rotated by being imparted with a normal rotation.

  A home position sensor 76 for detecting that the drive input gear 67 has made one rotation is disposed at a position adjacent to the toothless portion 67 b of the drive input gear 67. A detection signal from the home position sensor 76 is transmitted to the control unit 18 as control means. The control unit 18 controls the driving of the feeding / feeding motor M based on the detection signal.

  In the present embodiment described above, the drive is transmitted from the gear mechanism 28 to the retard roller 61 for a predetermined time from the start of sheet feeding, and after the leading edge of the fed sheet S has passed through the separation nip portion 63, the retard roller. The drive transmission to 61 is cut off. The torsion coil spring 73 and the torque limiter 74 generate a rotational load in the direction in which the retard roller 61 is rotated in the reverse direction. The torque limiter 74 applies a rotational load to the retard roller 61 via the torsion coil spring 73 when the retard roller 61 rotates in the sheet feeding direction.

  A configuration for realizing a desired operation in the sheet feeding unit 24 having the above configuration will be described in detail with reference to FIGS. 3 to 7, (a) is a diagram showing the relationship in the thrust direction of the sheet feeding unit 24 (corresponding to FIG. 2 (b)), and FIGS. 3 to 7 (b) and (c). ) And (d) are views of FIGS. 3 to 7A taken along lines DD to XX and viewed in the direction of the arrows, respectively.

  3A to 3D show a state before the sheet feeding is started. In this state, when a sheet feeding start signal is input to the control unit 18 from an external input means such as an operation panel (not shown) of the apparatus main body 1A or a personal computer, the control unit 18 controls the feeding motor M to drive input. The gear 67 is rotated.

  3A to 3D, the drive is transmitted from all the teeth 67a of the drive input gear 67 to the feed roller gear 68, and the feed roller shaft 69 rotates. Accordingly, the uppermost sheet S1 of the sheet bundle S is fed toward the separation nip portion 63 by rotating the feed roller 60 and the pickup roller 62.

  On the other hand, since the driving force is transmitted from the engagement / disengagement gear portion 67b1 of the toothless portion 67b to the retard roller shaft 72 via the idler gear 70 and the retard roller gear 71, the retard roller 61 also rotates in the sheet feeding direction.

  That is, immediately after the start of feeding, all of the feed roller 60, the retard roller 61, and the pickup roller 62 are rotated in the sheet feeding direction. When all the rollers 60, 61, 62 are rotating in the sheet feeding direction, the engaging / disengaging gear portion 67b1 of the toothless portion 67b of the drive input gear 67 is engaged with the idler gear 70 (FIG. 3A). To (d) to the states of FIGS. 4 (a) to (d)).

  The sheet S fed while all the rollers are rotating in the sheet feeding direction allows the leading end to smoothly enter the separation nip portion 63, and the separation nip portion 63 is not damaged without being damaged. Pass smoothly.

  Further, while all the rollers are rotating in the sheet feeding direction, the torsion coil spring 73 is wound and the retard roller gear 71 and the torque limiter 74 are united when fully wound. Thereafter, the retard roller 61 and the retard roller gear 71 are driven to be rotated by overcoming the force of the torque limiter 74 in response to driving from the toothless portion 67 b of the drive input gear 67.

  When the drive input gear 67 further rotates and the meshing between the engagement / disengagement gear portion 67b1 of the missing tooth portion 67b and the idler gear 70 is released as shown in FIGS. 5 (a) to 5 (d), the retard roller 61 is Driving in the reverse direction from the wound torsion coil spring 73 is applied.

  Here, when the number of sheets positioned in the separation nip portion 63 is one, the retard roller 61 receives a force in the following direction due to the frictional force of the sheet S. In response to this force, the retard roller 61 overcomes the force generated by the torque limiter 74 while rotating the torsion coil spring 73 and rotates in the sheet feeding direction.

  On the other hand, as shown in FIGS. 6A to 6D, when the engagement between the engagement / disengagement gear portion 67b1 and the idler gear 70 is released, if there are a plurality of sheets S positioned in the separation nip portion 63, the winding is tightened. The retard roller 61 is reversely rotated by the force of the torsion coil spring 73. Accordingly, as shown in FIGS. 7A to 7D, the leading end of the sheet that is in contact with the retard roller 61 is returned to the separation nip portion 63. In FIG. 6B and FIG. 7B, S1 is the uppermost sheet, and S2 is the second sheet.

  Further, when only one sheet S is fed to the separation nip portion 63 and the next sheet S enters the separation nip portion 63, the reverse rotation operation of the retard roller 61 by the torsion coil spring 73 is immediately performed. Occurs. For this reason, a plurality of sheets are not sent simultaneously.

  As described above, in the present embodiment, the state where the retard roller 61 is rotating in the sheet feeding direction is continued while the engagement / disengagement gear portion 67b1 of the missing tooth portion 67b is engaged with the idler gear 70. That is, the rotation amount in the sheet feeding direction H is determined according to the range setting of the missing tooth portion 67b.

  From the viewpoint of preventing simultaneous feeding (multiple feeding) of a plurality of sheets and preventing damage to the leading end of the sheet, it is desirable that the retard roller 61 is switched to the reverse rotation operation immediately after the leading end of the sheet passes the separation nip portion 63.

  When the drive input gear 67 makes one revolution, the sheet feeding operation ends. At this time, since the home position sensor 76 detects that the drive input gear 67 has made one rotation, the control unit 18 stops the feeding motor M based on this detection.

  When the leading edge of the sheet S fed by one rotation of the drive input gear 67 reaches the downstream conveying roller pair 21, the sheet S is sandwiched and pulled out by the nip portion, toward the secondary transfer portion (17). Be transported. At this time, if it is necessary to feed the next sheet, the drive is transmitted from the feed motor M to the drive input gear 67 at an arbitrary timing.

  In the present embodiment, the retard roller 61 is provided with a configuration in which the retard roller 61 is rotated in the reverse direction by the torsion mechanism (73, 74), and the retard roller 61 can be made highly durable without using an electric component such as an electromagnetic clutch. Can be realized. That is, the retard roller 61 is forcibly rotated in the forward direction for a predetermined time without using electric parts such as an electromagnetic clutch and without performing return driving (reverse rotation driving of the feeding motor M). The configuration can be realized. Therefore, even when the retard roller 61 is worn and no longer rotates following the feed roller 60, it is possible to reliably prevent inconveniences such as sheet feeding failure and sheet tip breakage.

  In the present embodiment, since the return drive is not performed by the reverse rotation of the feed motor M, the load applied to the feed motor M is small compared to the configuration with the return drive by the reverse rotation of the motor. Therefore, it is possible to use a motor with a small torque, and it is possible to realize the laser beam printer 1 that can be reduced in size, saved in space, and reduced in cost.

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus (laser beam printer), 1B, 17, 20 ... Image forming part (image forming part, secondary transfer roller, fixing part), 22 ... Separation roller pair, 24 ... Sheet feeding apparatus (sheet feeding) Part), 28 ... gear mechanism, 30 ... sheet stacking part, 60 ... conveying roller (feed roller), 61 ... separation roller (retard roller), 62 ... feeding roller (pickup roller), 63 ... separation nip part, 66 ... First transmission gear (pickup roller gear), 67 ... drive input gear, 67b1 ... engagement / disengagement gear portion, 68 ... second transmission gear (feed roller gear), 71 ... separation roller gear (retard roller gear), 73,74 ... Torsion mechanism (torsion coil spring, torque limiter), H ... sheet feeding direction, I ... direction opposite to sheet feeding direction, S ... sheet

Claims (4)

A sheet stacking unit on which sheets are stacked;
A feeding roller for feeding out the sheets stacked on the sheet stacking unit in a sheet feeding direction;
A conveying roller for conveying the sheet fed by the feeding roller in the sheet feeding direction;
A separation nip portion is formed by pressure contact with the conveying roller, and when two or more sheets are fed into the separation nip portion, the sheet is separated into one sheet by rotating in a direction opposite to the sheet feeding direction. A separation roller;
A drive input gear capable of transmitting a normal rotation in the direction of feeding the sheet in the sheet feeding direction to the separation roller, and a separation provided on the separation roller side and capable of transmitting the positive rotation of the drive input gear to the separation roller A roller gear, and the drive input gear meshes with the separation roller gear until the leading edge of the sheet passes through the separation nip portion, and is separated from the separation roller gear after the leading edge of the sheet passes through the separation nip portion. And a gear mechanism having a partially provided engaging / disengaging gear portion,
A sheet feeding apparatus characterized by that. The gear mechanism is
The first and second transmission gears are connected to the feeding roller and the conveying roller, respectively, and the forward rotation is transmitted from the drive input gear to the feeding roller via the first transmission gear. And transmitting to the transport roller via the second transmission gear.
The sheet feeding apparatus according to claim 1, wherein When rotating with the forward rotation, the reverse rotation force that rotates the separation roller in a direction opposite to the forward rotation is charged via a torque limiter, and the forward rotation by the gear mechanism is released. A torsion mechanism having a torsion coil spring that imparts the reverse rotational force to the separation roller at the time,
The sheet feeding apparatus according to claim 1, wherein the sheet feeding apparatus is a sheet feeding apparatus. A sheet feeding apparatus according to any one of claims 1 to 3,
An image forming unit that forms an image on a sheet fed from the sheet stacking unit,
An image forming apparatus.

Images