JP2006168921A - Post-processing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shift and put up sheet bundles for each sheet bundle to prevent carrying failure of post-processed sheet bundles, and deliver the sheet bundle on a delivery tray in a shift state. <P>SOLUTION: After the sheet bundles loaded on a post-processing tray 16 are post-processed, the sheet bundles are alternately shifted for each bundle in a paper passage width direction, the each sheet bundle is carried form the post-processing tray 16 toward a delivery port by a sheet receiving member 18, and the sheet bundle is delivered on the delivery tray 13 in the shift state by a delivery roller pair 12 disposed to the delivery port. The delivery roller pair 12 has an upper delivery roller 22 and a lower delivery roller 24 facing each other to be opened/closed, and a solenoid 40 switches the states of the upper delivery roller 22 and the lower delivery roller 24 between a closed state pinching the sheet bundle and an opened state not pinching the sheet bundle. The solenoid 40 closes the upper delivery roller 22 and the lower delivery roller 24 at predetermined timing depending on the size of the sheets. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a post-processing apparatus that performs post-processing such as stapling on a sheet bundle on which images have been formed, and an image forming apparatus such as a copying machine, printer, facsimile apparatus, and multi-function machine including these post-processing apparatuses. is there.

  Conventionally, a post-processing device is connected to or built in an image forming apparatus such as a multi-function peripheral, and a plurality of printed sheets (copy paper, OHP film, etc.) are stacked on the post-processing tray and stacked. A technique for performing post-processing such as sort processing is widely known.

  In such a post-processing apparatus, the sheet is arranged so that alignment work, which is a pre-process of post-processing, can be performed smoothly, and problems such as paper folding, wrinkling, and tearing do not occur in a thick sheet bundle after post-processing. It is necessary to smoothly feed the bundle to a sheet discharge tray or the like outside the apparatus, and various techniques for that purpose have been developed.

  For example, in the technique disclosed in Patent Document 1, as shown in FIG. 7, the discharge roller pair 100 includes a discharge lower roller 101 and a discharge upper roller 102, and both rollers 101 and 102 come into contact to form a nip. The closing position and the opening position where the rollers 101 and 102 are separated from each other and allow the sheet bundle to pass therethrough can be taken. Such a conventional post-processing device 103 presses the two rollers 101 and 102 together with the force of the spring 104 when the discharge roller pair 100 is closed, and the spring 104 when the discharge roller pair 100 is open. When the sheet size to be post-processed is separated by separating the discharge lower roller 101 and the discharge upper roller 102 against the force of the sheet (A3, B4, 11 * 17, 8.5 * 14, etc.), the large size The sheet bundle can pass through the discharge roller pair 100.

  When the solenoid 105 is turned on at the opening position of the discharge roller pair 100 described above, the lever 106 rotates clockwise, and the tip of the lever 106 presses the upstream side of the discharge upper guide 108 downward. As a result, the upper discharge guide 108 rotates clockwise with the fixed shaft 107 as a fulcrum, and the upper discharge roller 102 is separated above the lower discharge roller 101. When the upper discharge guide 108 is rotated, the fulcrum shaft 109 is moved downward, and the lower discharge guide 110 is rotated clockwise with the fulcrum shaft 111 as a fulcrum. As a result, the upper surface of the lower discharge guide 110 moves to the upper position beyond the outer peripheral surface of the lower discharge roller 101, and the sheet bundle can pass smoothly without contacting the outer peripheral surface of the lower discharge roller 101. .

  In the technique disclosed in Patent Document 2, when the rear end of the sheet bundle in the conveyance direction reaches a position 80 mm before passing through the discharge roller pair, the discharge roller pair is closed from the open state (nip state). Thus, after the majority of the sheet bundle passes through the discharge roller pair (open state), the discharge roller pair is closed to reduce the vertical deviation of the post-processed sheet bundle.

Japanese Patent Laid-Open No. 2002-167115 (7th page, FIG. 4) Japanese Patent Application Laid-Open No. 11-92019 (page 8, FIG. 1)

  However, in the prior art disclosed in Patent Document 1, when discharging a small-size sheet bundle when the discharge lower roller 101 and the discharge upper roller 102 of the discharge roller pair 100 are closed (nip state), the discharge is performed in the nip state. A deviation occurs in the upper and lower sides of the sheet bundle, and the force of the deviation is applied to the staple portion and the staple processing is easily damaged. Further, there is a risk that a sheet not subjected to the stapling process may be misaligned or misaligned (if the curl is severe or the number of sheets is large, the sheet closer to the lower discharge roller 101 is sent first). . In addition, even when a large-size sheet bundle is discharged, those that are not stapled have problems of bundle misalignment and misalignment.

  In addition, as in the prior art of Patent Document 2, if a single position is bound as a stapling process for a sheet bundle by simply nipping a fixed position (80 mm) from the rear end in the sheet bundle conveyance direction, When the sheet bundle is discharged to the discharge tray, the plurality of discharged sheet bundles are inclined and fall off. In such a case, a plurality of sheet bundles after the stapling process may be discharged while being shifted (shifted) alternately in the sheet passing width direction. The center of gravity in the direction protrudes from the push-up member that receives and conveys the rear end of the sheet bundle, and conveyance failure occurs such that the sheet bundle is inclined and conveyed during conveyance. Therefore, as in Patent Document 2, if the nipping is performed at a position 80 mm from the rear end in the sheet bundle conveyance direction and the most part of the sheet bundle is pushed up, the discharge roller pair is closed. The sheet bundle is inclined or dropped during conveyance before the sheet nips the sheet bundle.

  Therefore, the present invention provides a post-processing device and an image forming apparatus that can shift a sheet bundle after the post-processing for each sheet bundle so as not to cause a conveyance failure and discharge the sheet bundle in a shifted state on a paper discharge tray. The purpose is to provide.

In the first aspect of the invention, a plurality of sheets are stacked on the post-processing tray, and after the post-processing is performed on the plurality of sheet bundles, each sheet bundle is alternately shifted in the sheet passing width direction. In a post-processing apparatus that transports each sheet bundle from a post-processing tray toward a discharge port by a sheet transport unit, and discharges the sheet bundle in a shifted state onto a discharge tray by a pair of discharge rollers disposed at the discharge port.
The pair of discharge rollers has a discharge upper roller and a discharge lower roller that are opposed to be opened and closed,
Drive means for switching the discharge upper roller and the discharge lower roller between a closed state in which a sheet bundle is sandwiched and discharged and an open state in which the sheet bundle is not sandwiched;
The lower discharge roller and the upper discharge roller are closed at a predetermined timing according to the sheet size or the number of sheets by the driving means.

  According to a second aspect of the present invention, in the post-processing apparatus according to the first aspect, the predetermined timing is performed a predetermined time after the leading end in the conveyance direction of the sheet bundle reaches the discharge roller pair. Features.

  According to a third aspect of the present invention, in the post-processing apparatus according to the first aspect, the predetermined timing is performed after a predetermined time from the start of conveyance of the sheet bundle by the sheet conveying unit.

  According to a fourth aspect of the present invention, in the post-processing apparatus according to any one of the first to third aspects, the rear end side in the sheet bundle conveying direction is nipped as the sheet size of the sheet bundle is larger.

  According to a fifth aspect of the present invention, in the post-processing apparatus according to any one of the first to fourth aspects, the rear end side in the sheet bundle conveying direction is nipped as the number of sheets in the sheet bundle increases.

  According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising: an image forming unit that forms an image on a sheet; and the post-processing apparatus according to any one of the first to fifth aspects that performs post-processing on the image-formed sheet. .

  According to the present invention, the lower discharge roller and the upper discharge roller provided at the discharge port are closed at a predetermined timing in accordance with the sheet size or the number of sheets, so that the post-processed sheet bundle does not cause a conveyance failure. Thus, the bundle can be raised in the shifted state, and the sheet can be discharged onto the discharge tray without any deviation of the sheet bundle. Further, even when post-processing is performed on a small-size sheet bundle, it is possible to prevent the sheet bundle from being damaged by the nip of the discharge roller pair.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Schematic configuration of post-processing apparatus and image forming apparatus including the same)
FIG. 1 shows a schematic configuration of a post-processing apparatus 1 and an image forming apparatus 2 having the same according to an embodiment of the present invention.

  As shown in FIG. 1, a sheet (copy paper, OHP film, etc.) 4 sent out from the paper feed tray 3 is printed with an image forming unit 5, and then a discharge roller pair on the image forming apparatus main body 6 side. 7 is sent to the sheet conveyance path 8 of the post-processing apparatus 1. In addition, since the punching operation to the sheet 4 in the post-processing is performed by the punch unit 9 set in the sheet conveyance path 8, the following post-processing is, for convenience of description, stapling processing excluding the punching operation, etc. It shall be said. The sheet 4 sent to the sheet conveyance path 8 of the post-processing apparatus 1 is guided to the discharge roller pair 12 through the discharge path 11 by the branching claw 10 when not post-processed, and the discharge tray 13 by the discharge roller pair 12. Sent out. In addition, the sheet 4 sent to the sheet conveyance path 8 of the post-processing apparatus 1 is sent to the post-processing unit 15 via the post-processing conveyance path 14 by the branching claw 10 when post-processing. The post-processing unit 15 includes an upper unit 28 and a lower unit 29, a post-processing tray 16, a folding unit 19 for folding the stapled sheet bundle at the center, and the like.

  2 and 3 are a front view and a side view of the lower unit 29. The post-processed sheet 4 sent to the post-processing unit 15 is transported downward, and its rear end (the rear end in the transport direction from the post-processing unit 15 to the paper discharge tray 13) is a sheet receiving member (sheet transport means). 18 is received. The sheet receiving member 18 is attached to a belt 52 that is wound around two rotating shafts 50 and 51. The sheet receiving member 18 stands by at a predetermined position in the belt moving direction according to the size of the sheet to be used. A rotating shaft 58 is provided at the upper end of the lower unit 29, and another belt 60 is wound around the rotating shaft 58 and the rotating shaft 50. The belt 60 is provided with a protrusion 59 that presses the leading edge of the sheet (the leading edge in the conveyance direction to the paper discharge tray 13) for sheet alignment (see FIG. 3).

  In the lower unit 29, a pair of upper guides 53 and a pair of lower guides 54 are provided side by side in the sheet passing width direction (direction orthogonal to the sheet discharge direction) to guide the sheet in the transport direction. The pair of upper guides 53 and lower guides 54 are movable in the sheet passing width direction symmetrically with respect to the center line A. In the middle of the upper guide 53 and the lower guide 54, a pair of both-end support members 55 are juxtaposed in the sheet passing width direction. The both-end support member 55 is for receiving the rear end of the sheet bundle when performing stapling, and has a substantially L-shaped receiving metal plate 56. The both end support members 55 are interlocked with the corresponding lower guides 54 via operation levers 57. When the length of the sheet in the conveyance direction is smaller than the predetermined sheet size, the pair of lower guides 54 are spread outward, the lower guides 54 press the operation lever 57, and both end support members 55 are supported by the operation lever 57. Is pushed down and moved to a reference position that supports the trailing edge of the sheet as shown by the solid line in FIG. When the length of the sheet in the conveyance direction is longer than the predetermined sheet size, the pair of lower guides 54 is narrowed inward, the operation lever 57 is rotatable, and both end support members 55 push the operation lever 57 up, It moves to the retracted position as shown by the broken line in FIG.

  Thus, when the length of the sheet in the conveyance direction is smaller than the determined sheet size, the plurality of sheets 4 stacked on the post-processing tray 16 received by the sheet receiving member 18 are moved downward by moving the belt 60 downward. After lightly pressing the leading edge of the sheet toward the sheet receiving member 18 with the protrusion 59 to align and align the leading edge of the sheet, post-processing such as a stable process is performed by the post-processing means 17. The post-processing means 17 has a center binding stapler 17 ′ provided at a symmetrical position with respect to the center line A in FIG. 2, and an oblique binding stapler 17 ″ provided at the right end in FIG. When the length in the direction is smaller than the predetermined sheet size, the both-end support member 55 is waiting at the reference position, so that the sheet receiving member 18 moves to the reference position, The rear end of the sheet bundle is stably supported by the sheet receiving member 18 and the both end support members 55.

  When the length of the sheet in the conveyance direction is longer than the predetermined sheet size, after the sheet receiving member 18 moves to the reference position, the pair of lower guides 54 is narrowed, and both end support members 55 are rotated to the retracted position. Then, the sheet receiving member 18 moves downward, and the rear end of the sheet bundle is supported only by the sheet receiving member 18. Then, the plurality of sheets 4 moved downward by the sheet receiving member 18 are lightly pressed by the protrusions 59 toward the sheet receiving member 18 by the protrusions 59 and aligned to align the leading ends of the sheets, and then the belts 52 and 60 are aligned. Are simultaneously moved upward, the sheet receiving member 18 is moved upward, and once again moved to the reference position, and then the stapling process is performed.

The stapled sheet bundle is discharged by being alternately shifted in the sheet passing width direction in order to prevent the sheet bundle from being stacked and tilted to prevent dropping. For this reason, the sheet bundle for which the stapling process has been completed, the pair of upper guides 53 are alternately moved to shift positions (not shown) at both ends in the sheet passing width direction, and the sheet receiving member 18 raises the bundle from that position. The
(Configuration of discharge roller pair)
4 to 6 are diagrams showing a configuration of the discharge roller pair 12 according to the embodiment of the present invention, and are configuration diagrams of a portion indicated by K in FIG.

  The discharge roller pair 12 includes a discharge upper guide 21 that is supported on the apparatus main body 20 side so that the middle portion in the longitudinal direction is rotatable, and a discharge upper roller 22 that is rotatably supported on one end 21 a side of the discharge upper guide 21. And a lower discharge guide 23 supported on the apparatus main body 20 side so that the middle part in the longitudinal direction is rotatable, and a lower discharge roller 24 supported rotatably on the apparatus main body 20 side. A plurality of the discharge roller pairs 12 are arranged at appropriate intervals in the sheet passing width direction (direction orthogonal to the sheet discharge direction), and the sheet of any size to be subjected to the post-processing of the post-processing apparatus 1 is reliably conveyed. It can be done.

  Among these, the discharge lower guide 23 is rotatably supported by the frame 26 on the apparatus main body 20 side by a support pin 25 at its longitudinal intermediate portion. The discharge lower guide 23 is configured such that a counterclockwise rotation moment is generated with respect to the rotation fulcrum (support pin 25) by its own weight. The lower discharge guide 23 has an end 23a on the lower discharge roller 24 side from the outer peripheral surface of the lower discharge roller 24 in a closed state where the lower discharge roller 24 and the upper discharge roller 22 form a nip P. Is also supported by a locking member 27 formed on the frame 26 on the apparatus main body 20 side so that it is also retracted.

  Further, a substantially U-shaped groove 30 (U-shaped groove) that opens toward the tip is formed on the other end 23 b side of the lower discharge guide 23. The U-shaped groove 30 is adapted to engage with a connecting pin 31 protruding from the other end 21b of the discharge upper guide 21, which will be described later, with a gap. Here, the gap amount between the connecting pin 31 and the U-shaped groove 30 is configured to produce the maximum separation dimension between the lower discharge roller 24 and the upper discharge roller 22. The lower discharge guide 23 guides the movement of the sheet by the sheet guide plate portion 23c.

  The upper middle portion of the discharge upper guide 21 is rotatably supported by a support pin 25 common to the lower discharge guide 23. The discharge upper guide 21 is biased by a spring 37 in a direction in which an intermediate portion presses the discharge upper roller 22 toward the discharge lower roller 24, and the other end 21 b side separates the discharge upper roller 22 from the discharge lower roller 24. It is energized by a solenoid (driving means) 40. The solenoid 40 is on (energized) and off (cut off) by control means (not shown). The upper discharge guide 21 is attached to the other end 21b side so that a connecting pin 31 that engages with the U-shaped groove 30 of the lower discharge guide 23 with a gap protrudes from the side surface.

  A solenoid 40, a lever 42 rotatably supported on the frame 26 via a support pin 41, an end 42 a of the lever 42, and an operation rod 43 of the solenoid 40 are connected to the frame 26 on the apparatus body 20 side. And a connection ring 44 such as a wire. When the solenoid 40 is turned on (energized), the lever 42 is pulled by the operation rod 43 of the solenoid 40, the lever 42 is rotated clockwise, and the other end (tip) 42b of the lever 42 is discharged. By pushing the other end 21 b side of the guide 21, the discharge upper guide 21 is rotated around the support pin 25 (clockwise).

  As described above, when a sheet not subjected to post-processing is discharged onto the discharge tray 13 by the discharge roller pair 12, the discharge upper guide 21 is pressed by the spring force of the spring 37, and the sheet is discharged via the discharge upper guide 21. The upper roller 22 is pressed against the discharge lower roller 24. As a result, a nip P is formed at the contact portion between the discharge upper roller 22 and the discharge lower roller 24, and the sheet is sent out onto the discharge tray 13 by the discharge roller pair 12.

  Further, when the post-processed sheet bundle is discharged onto the discharge tray 13 by the discharge roller pair 12, the solenoid 40 is energized, and the solenoid 40 rotates the lever 42 in the clockwise direction. The top end 42b of the discharge upper guide 21 presses the upper surface of the discharge upper guide 21 on the other end 21b side, and the discharge upper guide 21 is rotated clockwise with the support pin 25 as a rotation fulcrum. As a result, the discharge upper roller 22 rotatably supported on the one end 21 a side of the discharge upper guide 21 is separated from the discharge lower roller 24. When the upper discharge guide 21 rotates clockwise with the support pin 25 as a pivot, the connecting pin 31 attached to the other end 21 b of the upper discharge guide 21 contacts the lower edge of the U-shaped groove 30 of the lower discharge guide 23. . The position where the connecting pin 31 contacts the lower edge of the U-shaped groove 30 of the lower discharge guide 23 is the maximum separation position between the upper discharge roller 22 and the lower discharge roller 24. The maximum dimension at which the discharge upper roller 22 is separated from the discharge lower roller 24 is set to such a dimension that a sheet bundle in which 50 sheets of A4 size copy paper having a basis weight of about 80 g / m 2 can be passed. Has been.

One end 23a of the lower discharge guide 23 is separated from the locking member 27 on the apparatus main body 20 side, and rotates clockwise with the upper discharge guide 21 around the support pin 25 as a rotation center. When the 23a side rotates to a position protruding from the outer peripheral surface of the lower discharge roller 24, the operation of the solenoid 40 is maintained and the posture is maintained. In this way, the lower end (back side) of the sheet bundle sent out from the post-processing unit 15 by the sheet receiving member 18 by the one end 23a side of the lower discharge guide 23 projecting from the outer surface of the lower discharge roller 24. However, it does not come into contact with the outer surface of the lower discharge roller 24, and the front end side of the sheet bundle passes smoothly without being caught in the gap between the lower discharge roller 24 and the upper discharge roller 22. Note that the discharge roller pair 12 has a large sheet size of the sheet bundle to be post-processed, and at the time of sheet alignment operation in the post-processing unit 15, the leading end in the sheet conveyance direction when discharging the sheet bundle is the discharge lower roller 24 and the discharge upper roller 22. Even in the case where it is necessary to project the nip P beyond the nip P, the nip P is separated. Thereby, the alignment work of the large-size sheet bundle is smoothly performed.
(Sheet bundle discharge operation by post-processing device)
In the present embodiment, when the sheet bundle is discharged from the post-processing unit 15 by the sheet receiving member 18, if the sheet detection sensor 47 detects passage of the leading end of the sheet bundle in the conveyance direction, the solenoid 40 is connected to the solenoid 40 after a predetermined time. When the energization is interrupted or the sheet bundle bundling operation (conveying operation) is started by the sheet receiving member 18, the energization to the solenoid 40 is interrupted after a predetermined time. When the energization of the solenoid 40 is interrupted, the sheet bundle raised to the discharge port is sandwiched by closing the discharge lower roller 24 and the discharge upper roller 22 and is sent out onto the paper discharge tray 13.

  For example, in FIG. 2 and FIG. 3, when the sheet receiving member 18 is moved in the belt direction to move the sheet bundle to a reference position for post-processing and staple the sheet bundle, the sheet bundle is passed in the sheet width direction. The staple is moved to the staple position. For example, when stapling is performed at a symmetrical position with respect to the center of the sheet width, the pair of upper guides 53 are moved in the sheet width direction, and stapling is performed by the center binding stapler 17 '. Further, when stapling at one corner of the sheet bundle, the pair of upper guides 53 is moved to the right end (FIG. 2) in the sheet width direction, and stapling is performed by the oblique binding stapler 17 ″. The bundle is moved to one shift position in the paper width direction (position to raise the bundle), and the sheet bundle is raised and discharged by the sheet receiving member 18. Since the sheet receiving member 18 is attached to the belt 52, 3, the sheet bundle is raised by the sheet receiving member 18 to the position of the rotary shaft 50, and thereafter, the sheet bundle is transferred to the protrusion 59 and discharged to the discharge roller pair 12 by the protrusion 59. The protrusion 59 is the upper end of the movement. Until the belt 60 is rotated counterclockwise, the rear side of the tray is moved back to the original position, and the stapled second sheet is returned. The sheet bundle is moved to the other shift position in the paper width direction (position to raise the bundle), and the sheet bundle is raised and discharged by the sheet receiving member 18. Thus, when there are a plurality of sheet bundles, the shift position is set. Even when the sheet bundle is not stapled, the sheet bundle is moved alternately to the shift position in the same manner, and the sheet bundle is raised by the sheet receiving member 18 and discharged.

  The timing at which the energization to the solenoid 40 is interrupted (nip) is preferably the rear end in the sheet conveyance direction as close to the stapling position as possible in consideration of bundle deviation and misalignment. However, when the sheet bundle is bundled by the sheet receiving member 18, as shown in FIG. 2, the sheet bundle is moved in the width direction by the upper guide 53 from the start of the bundle raising until the upper end of the upper guide 53 is passed. There is no problem because both ends are guided, but there is nothing to guide both ends in the width direction after passing through the upper guide 53. Therefore, if the center of gravity in the width direction of the sheet bundle protrudes from the sheet receiving member 18, the sheet bundle may be inclined and become unstable during conveyance or may be caught, resulting in conveyance failure. For example, when the sheet bundle is shifted in the sheet width direction and discharged, the center of gravity of the sheet bundle in the width direction protrudes from the sheet receiving member 18, and the sheet bundle may be inclined during conveyance or may be poorly conveyed. For this reason, in the present embodiment, an appropriate position of the sheet bundle is nipped so as not to cause a bundle shift or misalignment at the time of nip and to prevent a conveyance failure.

  For example, if the sheet bundle after the stapling process is A4 length or smaller, the sheet detection sensor 47 detects the leading edge of the sheet bundle and then is 1/3 of the sheet size in the conveyance direction. When passing through, energization to the solenoid 40 is cut off (OFF) and nip is performed. For example, in the case of A4 horizontal size, a nip of approximately 1/3 of the total length from the front end in the sheet conveyance direction is niped. To do. In this way, the position of 1/3 of the entire length from the front end in the sheet conveying direction is nipped so that the sheet bundle does not incline after passing through the upper guide 53. Further, since the nipping is performed at 1/3 of the total length from the front end in the sheet conveying direction, it is possible to prevent the small-size sheet bundle after the stapling process from being damaged by the nip.

  If the sheet bundle after the stapling process is larger than the A4 length (B4, A3, etc.), the lower discharge roller 24 and the upper discharge roller 22 are initially opened in order to prevent damage to the sheet bundle. The sheet bundle is shifted on the lower discharge roller 24 without contacting the outer surface of the lower discharge roller 24, and then the sheet receiving member 18 raises the bundle. The timing at which the solenoid 40 is shut off (OFF) to close the lower discharge roller 24 and the upper discharge roller 22 is 2/5 from the leading edge of the sheet conveying direction after the sheet receiving member 18 starts the bundle raising operation. This is done when passing. For example, in the case of B4 vertical size, a nip of about 145 mm, which is 2/5 of the total length from the front end of the sheet conveyance direction, and in the case of A3 vertical size, nip of about 167 mm, which is 2/5 of the total length from the front end of the sheet conveyance direction. To do. In this way, a position that is 2/5 of the total length from the front end in the sheet conveying direction is nipped so that the sheet bundle does not tilt even after passing through the upper guide 53 as in the case of a size smaller than the A4 length. Yes. Therefore, in the case of a size smaller than the A4 length and a large size such as B4 and A3 larger than the A4 length, the sheet position where the discharge lower roller 24 and the discharge upper roller 22 are closed becomes the rear end side as the sheet size increases. (Timing is delayed).

Further, in the present embodiment, the timing at which the energization to the solenoid 40 is cut off (OFF) is delayed as the number of sheet bundles increases, and the rear end side is nipped. For example, if the number of sheet bundles is 50 sheets or more, when the discharge lower roller 24 and the discharge upper roller 22 are closed (niped) at a position that has passed half of the sheet size in the conveyance direction from the leading edge in the conveyance direction, If the timing for performing the same operation is the same, the larger the number of sheet bundles, the weaker the nip force, and the larger the deviation amount of the bundles. For this reason, the nip timing is changed every 10 sheet bundles, and the closing timing of the lower discharge roller 24 and the upper discharge roller 22 is delayed as the number of sheet bundles increases. For example,
For a bundle of 10 sheets or less, the sheet detection sensor 47 nips 50 msec from ON.

  For a bundle of 20 sheets or less, the sheet detection sensor 47 nips 100 msec from ON.

  Below 30 sheets, the sheet detection sensor 47 nips 150 msec from ON.

  Below 40 sheets, the sheet detection sensor 47 nips 200 msec from ON.

  For 50 sheets or less, the sheet detection sensor 47 nips 250 msec from ON.

Further, in order to nip the same sheet position from the front end of the sheet conveying direction, the timing at which the energization to the solenoid 40 is cut off (OFF) may be made faster as the sheet bundle discharge speed is faster. For example, when a nip is performed at a position 60 mm from the detection of the leading edge of the sheet (a position １ ／ from the leading edge in the sheet conveyance direction),
When the discharge speed is 400 mm / sec, the sheet detection sensor 47 nips 150 msec from ON.

  When the discharge speed is 500 mm / sec, the sheet detection sensor 47 nips 120 msec from ON.

  When the discharge speed is 600 mm / sec, the sheet detection sensor 47 nips 100 msec from ON.

However, when the discharge speed is increased, a displacement force generated in the vertical direction of the sheet bundle is applied to the staple portion and is easily damaged. In this embodiment, the nip position should be the rear end of the sheet. . For example, taking an A4 vertical sheet bundle as an example:
When the discharge speed is 400 mm / sec, nipping is performed at a position 100 mm from the leading edge of the sheet.

  When the discharge speed is 500 mm / sec, nipping is performed at a position 150 mm from the leading edge of the sheet.

  When the discharge speed is 600 mm / sec, nipping is performed at a position 200 mm from the leading edge of the sheet.

  The post-processing apparatus and the image forming apparatus of the present invention can be used in combination with an image reading apparatus such as a scanner, and can be used for post-processing a sheet bundle after image reading.

1 is a schematic configuration diagram of a post-processing apparatus and an image forming apparatus of the present invention. It is a front view of the lower unit of a post-processing apparatus. It is a cross-sectional side view same as the above. It is a figure which shows the structure of the discharge roller pair of a post-processing apparatus. It is an external appearance perspective view by the side of the discharge port of the discharge roller pair (closed state) of a post-processing apparatus. It is an external appearance perspective view by the side of the discharge port of the discharge roller pair (open state) of a post-processing apparatus. It is a figure which shows the structure of the discharge roller pair of the conventional post-processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Post-processing apparatus, 2 ... Image forming apparatus, 4 ... Sheet, 5 ... Image forming part, 12 ... Discharge roller pair, 13 ... Paper discharge tray, 16 ... Post-processing tray, 18 ... Sheet receiving member, 21 ... upper discharge guide, 22 ... upper discharge roller, 23 ... lower discharge guide, 24 ... lower discharge roller, 40 ... solenoid

Claims (6)

After stacking a plurality of sheets on the post-processing tray and performing post-processing on the plurality of sheet bundles, the sheets are alternately shifted in the sheet passing width direction for each sheet bundle, and the post-processing tray for each shifted sheet bundle A post-processing device that conveys the sheet bundle from the sheet discharge unit toward the discharge port and discharges the sheet bundle in a shifted state onto the discharge tray by a pair of discharge rollers disposed at the discharge port
The pair of discharge rollers has a discharge upper roller and a discharge lower roller that are opposed to be opened and closed,
Drive means for switching the discharge upper roller and the discharge lower roller between a closed state in which a sheet bundle is sandwiched and discharged and an open state in which the sheet bundle is not sandwiched;
The post-processing apparatus, wherein the lower discharge roller and the upper discharge roller are closed at a predetermined timing according to a sheet size or the number of sheets by the driving unit.   2. The post-processing apparatus according to claim 1, wherein the predetermined timing is performed a predetermined time after the leading end in the conveyance direction of the sheet bundle reaches the discharge roller pair.   The post-processing apparatus according to claim 1, wherein the predetermined timing is performed after a predetermined time from the start of conveyance of the sheet bundle by the sheet conveyance unit.   The post-processing apparatus according to claim 1, wherein the rear end side of the sheet bundle in the conveyance direction is nipped as the sheet size of the sheet bundle is larger.   5. The post-processing apparatus according to claim 1, wherein the rear end side of the sheet bundle in the conveyance direction is nipped as the number of sheets in the sheet bundle increases. An image forming apparatus comprising: an image forming unit that forms an image on a sheet; and a post-processing device according to claim 1 that performs post-processing on the image-formed sheet.

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