JPH09240909A - Sheet postprocessing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain size reduction and cost reduction in a device by providing an upward inclined ascendable-descendable paper discharge tray in the sheet discharge direction by a sandwiching discharge means, and arranging a paper discharge butting plate whose butting surface to come into contact with a discharge directional rear end part of plural sheets is arranged in its slant attitude to a vertical surface. SOLUTION: A sheet P discharged so that an image surface turns upward is discharged and placed on a paper discharge tray 6 by discharge roller pairs 5 through carrier roller pairs 3, a passage 13, carrier roller pairs 4 and a passage 14. In a sheet placing surface of the paper discharge tray 6, for example, an inclination is set to a range of 30 deg. to 40 deg., and an angle formed by the sheet placing surface and a sheet rear end butting reference member (a rear end reference member) 67 is set to about 90 deg.. In this way, the rear end reference member 67 is set in its slant posture, and the sheet P discharged by the discharge roller pairs 5 is slidingly dropped on the paper discharge tray 6, and the sheet rear end is sent into and brought into contact with the rear end reference member 67 by a rolling-in roller, and the sheet rear end is reliably registered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention receives a sheet on which an image is formed by an image forming apparatus such as an electrophotographic copying machine, a printer or a printing machine, automatically binds it by a stapler, and then ejects it by ejecting means. More particularly, the present invention relates to a sheet post-processing apparatus that has a staple mode and a non-staple mode (including an offset mode).

[0002]

2. Description of the Related Art A sheet post-processing device called a finisher is used as a device for collating and stapling a plurality of image-recorded sheets discharged from an image forming apparatus by the number of copies by a stapler.

The finisher has a function connected to an image forming apparatus main body such as a copying machine or a printer, and is driven in accordance with a sequence operation of a copy or print process.

Therefore, for an image forming apparatus capable of performing an image forming process at a high speed, a finisher capable of performing a function following the processing speed is required.

A finisher capable of such high-speed processing has been disclosed in Japanese Patent Application Laid-Open Nos. 60-142359 and 60-142359.
Nos. 0-158463 and 62-239169, and JP-A Nos. 62-288002 and 63-267667.
These are disclosed in JP-A-2-276691 and JP-B-5-41991.

In the sheet post-processing apparatus, the image-recorded sheets carried out from the main body of the image forming apparatus are sequentially stacked while being aligned in an intermediate stacker, and after storing a set of sheet bundles, a sheet such as a stapler is stored. The post-processed and bound sheet bundle is conveyed on a discharge belt provided at the bottom of the intermediate stacker, is further nipped by a pair of upper and lower discharge rollers, and is discharged onto a discharge tray. .

The sheet placement surface is arranged so as to be inclined so that the discharge tray is higher from the rear end toward the front end, and a sheet rear end abutting reference member is erected on the rear end side of the discharge tray. The leading edge of the sheet formed and discharged from the rear end side of the discharge tray is discharged in the direction of the distal end of the discharge tray,
After the trailing edge of the sheet passes over the sheet trailing end abutting reference member, the sheet is slid down on the discharge tray or the upper surface of the sheet placed on the discharge tray that uses the natural fall due to the weight of the sheet. A sheet stacking device that aligns the trailing edge of sheets in the sheet discharge direction by contacting with the trailing edge abutting reference member is widely used, as described in JP-A-57-48558.

The sheet post-processing apparatus disclosed in Japanese Patent Application Laid-Open No. Hei 2-233456 has a paper discharge tray that can be moved horizontally at right angles to the sheet conveyance direction. This is for changing the initial position relative to the discharge unit.

[0009]

[Problems to be Solved by the Invention]

(First Problem) FIGS. 23A, 23B, and 23C are schematic views showing a conventional sheet stacking apparatus. In the sheet stacking apparatus shown in FIG. 23A, since the angle θ1 formed by the sheet mounting surface of the sheet discharge tray T and the sheet rear end abutting reference member K is close to a right angle, the sheet is naturally dropped due to its own weight. In some cases, the trailing edge of the sheet does not return to the contact position of the winding roller R, and the trailing edge of the sheet may not reach the reference member K. In the sheet stacking apparatus shown in FIG. 23B, since the angle θ2 formed by the sheet mounting surface of the discharge tray T and the sheet rear end abutting reference member K is close to an acute angle, the sheets naturally fall due to their own weight. However, the component force in the vertical direction due to the weight of the sheet is reduced, the upper surface of the sheet is swollen, the sheets are not pressed and stacked, and the number of sheets that can be stacked is reduced. Further, as in the sheet stacking apparatus shown in FIG. 23C, the closer the angle θ2 formed by the sheet mounting surface of the sheet ejection tray T and the sheet rear end abutting reference member K is to an acute angle, the smaller the sheet ejection tray T is. At the leading edge of the sheets P stacked on top, the leading edge of the upper layer sheet hangs over the leading edge of the lower layer sheet and hangs down, and this overhang increases as the number of stacked sheets increases. Due to the weight of the sheets in the overhang portion, the upper surface of the sheets in the stacking portion swells up, the sheets are not pressed and stacked, and the number of stackable sheets is reduced.

(Second Problem) FIGS. 24A and 24B are schematic views showing a conventional sheet stacking apparatus.
FIG. 24A shows the front surface of the sheet stacking device, and FIG. The sheet P stacked on the sheet discharge tray T slides down on the upper surface of the sheet discharge tray T or the sheet P already placed on the sheet discharge tray T due to the weight of the sheet, and is brought into sliding contact with the rotating winding roller R. The upper surface of the uppermost sheet comes into contact with the sheet rear end butting reference member K. For this purpose, the upper surface detection sensor detects the upper surface of the uppermost sheet P, and drives the paper discharge tray T up and down so that the outer peripheral surface of the winding roller R and the upper surface of the uppermost sheet P come into contact with each other at a predetermined pressure. Let However, when the sheet P is a staple-processed sheet bundle, the portion of the sheet bundle having the staples ST projects and comes into strong contact with the winding roller R,
The outer peripheral surface of the winding roller R is scraped off. In particular, when a plurality of sheet bundles P are stacked on the discharge tray T, the portions of the sheet bundle P having the staples ST overlap and largely project, so that the staples ST significantly damage the outer peripheral surface of the winding roller R. To be done.

(Third Problem) Japanese Patent Laid-Open No. 63-310459
The sheet post-processing device disclosed in Japanese Patent Laid-Open Publication No. 2003-121242 detects a rising reference position when sheets are not stacked on the discharge tray, and also detects a sheet on the discharge tray when sheets are stacked on the discharge tray. A detection means for detecting the loaded amount is provided. This sheet post-processing device lowers the sheet discharge tray in response to a detection signal from a detection unit that detects the rising reference position. In FIG. 24A, in the winding operation of the sheet P by the winding roller R, if the winding roller R is in contact with the discharge tray or the upper surface of the sheet already placed on the discharge tray and is rotating, When one of the sheets discharged to the sheet lowers on the sheet discharge tray and comes into contact with the sheet trailing end abutting reference member K, the sheet is not wound around the winding roller R and sheet misalignment occurs.

(Fourth Problem) When a large size sheet is stacked on the intermediate stacker in the staple mode, the leading edge of the sheet protrudes from the discharge roller pair and hangs down by its own weight, and when the sheet slides down on the intermediate stacker, The edge does not come into contact with the sheet trailing edge abutting reference member K, and unevenness occurs.

The sheet post-processing apparatus disclosed in Japanese Patent Laid-Open No. 63-247267 discloses a staple tray (intermediate stacker) for temporarily stacking and storing recorded sheets (sheets) before being stapled, and stapled recorded sheets. And a stacker tray (paper discharge tray) for storing the sheets, and the staple tray (intermediate stacker) can stack sheets of all sizes. Therefore, a part of the discharge tray is used as an auxiliary tray of the intermediate stacker for temporarily stacking the sheets, and the sheets stacked on the intermediate stacker are discharged across the intermediate stacker and the discharge tray via the pair of discharge rollers. This is completely different from the sheet post-processing apparatus of the present invention for the purpose of realizing the above.

(Fifth Problem) When a stapled sheet bundle and one sheet are discharged by a common pair of discharge rollers and placed on a common discharge tray, one sheet and staple Since the thickness and weight of the processed sheet bundle (for example, 50 sheets) are different, good discharge is impossible. The sheet post-processing apparatus disclosed in Japanese Patent Laid-Open No. 2-233456 uses a common discharge roller pair and a common discharge tray for the staple mode and the non-staple mode (including the offset mode). The above-mentioned problem occurs because the amount of lowering of the discharge tray does not change between the mode and the non-staple mode.

The object of the present invention is to solve the above-mentioned problems and to improve it. As a result, (1) the stacking amount of the sheets discharged onto the discharge tray is increased, (2) the damage of the winding roller is prevented, In particular, it enables good paper discharge when stacking a large number of sheets, (3) prevents winding defects due to the winding rollers and eliminates sheet misalignment, and (4) sheets when stacking large-sized sheets on the intermediate stacker. Excellent effects such as preventing unevenness in the trailing edge of the sheet due to drooping of the leading edge, compacting the sheet post-processing apparatus, and (5) enabling good discharge of a large number of sheet bundles as well as a single sheet. Sheet post-processing device (finisher)
Is provided.

[0016]

A sheet post-processing apparatus for sequentially introducing a plurality of sheets carried out from an image forming apparatus, discharging them by nipping and discharging means, and stacking them on a vertically movable discharge tray. In a sheet discharging surface having an upwardly inclined sheet stacking surface in the sheet discharging direction by the sandwiching and discharging means, and a discharging direction rear end portion of a plurality of sheets stacked on the inclined sheet stacking surface. The abutting surface to be abutted is set at an angle close to a right angle with respect to the sheet stacking surface, and the abutting surface has a paper discharge abutting plate inclined with respect to the vertical surface. Achieved by sheet post-processing equipment.

Further, the above-mentioned object is to perform a stapling mode in which sheets carried out from the image forming apparatus are bound by a stapler, and then the sheet bundle is discharged by a sandwiching and discharging means onto a sheet discharge tray which can be raised and lowered. In a sheet post-processing apparatus having a non-staple mode in which a sheet is discharged onto a discharge tray that can be raised and lowered by the sandwich discharge means, the staple mode and the non-staple mode are common discharge roller pair and discharge tray. The sheet can be ejected by means of two sensors for detecting the upper surface of the sheet placed on the paper ejection tray at different vertical heights, and in the staple mode, the lower sensor detects the sheet upper surface to eject the sheet. Holds the tray in the lower position, and in the non-staple mode, the upper sensor detects the sheet top surface detection signal. It is achieved by a sheet post-processing apparatus, characterized by elevation control the discharge tray to hold the paper discharge tray to an upper position.

Further, for the above-mentioned purpose, the sheet carried out from the image forming apparatus is introduced and discharged by the nipping and discharging means,
In a sheet post-processing device loaded on a vertically movable sheet ejection tray, a sheet ejection sensor for detecting passage of a trailing end portion of a sheet ejected by the nipping and ejecting means, and an abutting member abutting on a trailing end portion of the sheet in a sheet ejection direction. A discharge abutting plate having a surface,
A rotatable sheet discharge auxiliary rotation member that slides the sheet discharged onto the sheet discharge tray onto the rear end of the upper surface of the sheet and transfers the sheet to contact the contact surface of the sheet discharge contact plate, and the discharge sheet. The sheet discharging device includes a detection unit that detects the position of the upper surface of the sheet placed on the tray, and a control unit that controls the elevation of the sheet discharge tray by the detection unit. After the tray is lowered and the discharged sheet is brought into contact with the abutting surface of the sheet discharge abutting plate by its own weight, the sheet discharge tray is raised and the sheet discharged by the sheet discharge assisting rotation member is placed behind the sheet. This is achieved by a sheet post-processing device characterized in that it is slidably brought into contact with an end portion and is brought into contact with an abutting surface of the paper ejection abutting plate.

Further, the above-mentioned object is to stack the sheets carried out from the image forming apparatus on the intermediate stacker for alignment, perform the binding processing by the stapler, discharge the sheets by the nipping and discharging means, and place them on the vertically movable sheet discharging tray. In a sheet post-processing apparatus for stacking, when a large size sheet having a predetermined size or more is placed on the intermediate stacker, the nipping and ejecting means is opened and the leading end of the sheet is projected onto the sheet ejection tray. At the same time, the sheet ejection tray is made to stand by at an upper position where binding processing is not performed, and the leading end portion of the sheet can be held on the sheet ejection tray or on the sheet placed on the sheet ejection tray. Sheet post-processing device.

Further, the above-mentioned object is to perform a stapling mode in which sheets carried out from the image forming apparatus are bound by a stapler, and then the sheet bundle is discharged by a sandwiching and discharging means onto a vertically movable discharge tray, and a stapling mode is set. In a sheet post-processing apparatus having a non-staple mode in which a sheet is discharged onto a discharge tray that can be lifted and lowered by the nipping and ejecting means, a paper ejection sensor that detects the trailing edge of the sheet ejected from the nipping and ejecting means, An upper surface detection sensor for detecting an upper surface of a sheet placed on the paper discharge tray; a drive means for vertically moving the paper discharge tray each time the sheet is discharged from the sandwich discharge means; Control means for controlling the up-and-down drive of the discharge tray based on the output and the output of the upper surface detection sensor, and the staple mode In the emission staple mode is achieved by a sheet post-processing apparatus characterized by having different descent amount of the discharge tray.

Further, the above-mentioned object is to perform a stapling mode in which sheets carried out from the image forming apparatus are bound by a stapler, and then the sheet bundle is discharged by a sandwiching and discharging means onto a discharge tray which can be raised and lowered. In a sheet post-processing apparatus having a non-staple mode in which a sheet is discharged onto a discharge tray that can be lifted and lowered by the nipping and ejecting means, a paper ejection sensor that detects the trailing edge of the sheet ejected from the nipping and ejecting means, An upper surface detection sensor for detecting an upper surface of a sheet placed on the paper discharge tray; a drive means for vertically moving the paper discharge tray each time the sheet is discharged from the sandwich discharge means; Control means for controlling the up-and-down drive of the discharge tray based on the output and the output of the upper surface detection sensor, and the staple mode In the emission staple mode is achieved by a sheet post-processing apparatus characterized by having different fall time of the output tray.

[0022]

Next, an embodiment of a sheet post-processing apparatus according to the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a sectional view showing the structure of the sheet post-processing apparatus (finisher). The sheet post-processing apparatus is installed with its position and height adjusted so that the receiving portion of the sheet P coincides with the discharge port of the main body of the image forming apparatus (copier, printer, etc.), and corresponds to the operation of the main body of the image forming apparatus. Connected to a control system to be driven.

The conveying path of the sheet P connected to the sheet conveying downstream of the inlet roller pair 1 of the receiving section is the upper first conveying path 100, the middle second conveying path 200 and the lower third conveying path.
It is branched into three systems of the transport path 300 and has a switching gate G
The sheet P is fed to one of the transport paths by selecting the angle occupied by 1, G2, and G3.

FIG. 2 (a) is a schematic diagram showing the conveyance path of the sheet P by the first conveyance path 100 (one-dot chain line), FIG. 2 (b).
3A is a schematic diagram showing the conveyance path of the sheet P by the second conveyance path 200 (one-dot chain line), FIG. 3A is a schematic diagram showing the conveyance path of the sheet P by the third conveyance path 300 (one-dot chain line), FIG. FIG. 6B is a schematic diagram (one-dot chain line) showing the conveyance path of the sheet P by the fourth conveyance path 400.

(1) First Conveying Path 100 (Printer Mode, Image Face Down Discharge) In FIG. 2A, the sheet P discharged from the image forming apparatus main body in the image face up direction is the inlet roller pair 1 Of the second transfer gate G2, which is a second conveyance path 200, which is sandwiched by the pair of conveyance rollers 2 and is conveyed through the passage 11 below the upper first switching gate G1. After passing through the passage 12, passing through the conveying roller pair 3, the passage 13, and the conveying roller pair 4, it is temporarily stopped and then switched back by the conveying roller pairs 2, 3 and 4 which are converted into the reverse rotation drive, and the first After passing through the passage 15 above the switching gate G1 and the passage 16 above the switching gate G1, the sheet is discharged face-down on the sheet discharge tray 8 on the upper outside of the machine by the pair of discharge rollers 7 and placed in page order. It

(2) Second transport path 200 (copy mode,
Non-Staple Mode Including Image Surface Upward Discharge and Offset Paper Discharge) In FIG. 2B, the sheet P discharged from the image forming apparatus main body in the image surface upward direction (face up) is conveyed by the entrance roller pair 1. The passage 12 above the first switching gate G1 at the upper side passes through the passage 11 below the first switching gate G1 and is sandwiched by the pair of conveying rollers 2 and is the second conveying path 200. Passing through
After passing through the conveying roller pair 3, the passage 13, the conveying roller pair (shift roller pair) 4, and the passage 14, the sheet is discharged and placed on the sheet discharge tray 6 outside the apparatus with the image surface facing upward by the discharge roller pair (sandwiching and discharging means) 5. To be done. In an automatic document feeder (ADF) connected to the image forming apparatus, exposure processing is performed from the final document, and a copy of the final page on which the image formation processing is performed is sequentially sent to a sheet post-processing apparatus, and the image is directed upward. The sheets are stacked on the discharge tray 6 in page order.

(3) Third transport path 300 (copy mode,
Image-Side Upward Discharge, Staple Mode) In FIG. 3A, a copy of the last page image-formed in the image forming apparatus main body is discharged in the image-up upward direction (face-up), and the sheet post-processing apparatus is sequentially performed. The sheet P fed to the sheet is conveyed by the pair of entrance rollers 1 and is conveyed to the passage 1 below the upper first switching gate G1.
1 and is sandwiched by the pair of transport rollers 2 and passes through the passage 17 below the third switching gate G3, which is the third transport path 300 and diagonally below, to the pair of transport rollers 9 and the path 18.
Then, it is sent to the staple processing unit 20.

The sheet P nipped and conveyed by the pair of conveying rollers 21 on the downstream side of the passage 18 is discharged into the space above the intermediate stacker 22 which is inclined, and is stacked on the intermediate stacker 22 or the intermediate stacker 22. After contacting the upper surface of the sheet P and further sliding up, the trailing edge of the sheet is discharged from the pair of transport rollers 21, and then the sheet P starts to descend due to its own weight and slides down on the inclined surface of the intermediate stacker 22. The sheet abutting surface (stopper member) 31 in the vicinity of the stapler (binding means) 30 is abutted and stopped. The conveyance assisting rotation member (roll-in member) 23 rotated by a belt wound around a pulley that rotates coaxially with the lower roller 21B of the conveyance roller pair 21 slides on the upper surface of the sliding sheet P, so that the sheet P When the switch back is performed, the stopper member 31 is caused by the sliding contact action of the conveyance assisting member 23.
Be sure to make contact with.

Reference numeral 24 denotes a pair of alignment members movably provided on both side surfaces of the intermediate stacker 22. The matching member 24
Is movable in a direction orthogonal to the sheet conveying direction, and when the sheet P is received on the intermediate stacker 22, the sheet P is opened wider than the sheet width and the intermediate stacker 2 is opened.
When the sheet 2 slides down and comes into contact with the stopper member 31 and stops, the side edges in the width direction of the sheet are tapped to align the width of the sheet bundle. At this stop position, when a predetermined number of sheets P are stacked and aligned on the intermediate stacker 22, the stapler 30 performs a binding process (stapling process) to bind the sheet bundle.

A cutout is formed in a part of the sheet stacking surface of the intermediate stacker 22, and a plurality of discharge belts 27 wound around a drive pulley 25 and a driven pulley 26 are rotatably driven. . A discharge claw 28 is formed integrally with a part of the discharge belt 27, and the tip thereof draws an elliptical locus as shown by a dashed line in the figure. The stapled sheet bundle P has the rear end of the sheet P held by the discharge claws 28 of the discharge belt 27, is placed on the discharge belt 27, and slides on the placement surface of the intermediate stacker 22 to be obliquely upward. It is pushed up and advances to the nip position of the discharge roller pair (sandwiching discharge means) 5. The sheet bundle P nipped by the rotating discharge roller pair 5 is discharged and stacked on the discharge tray 6 with the image surface facing upward.

(4) Fourth transport path 400 (copy mode,
Sheet Discharging Upward on Image Surface In FIG. 3B, the sheet P discharged upward from the image forming apparatus main body is conveyed by the pair of entrance rollers 1, and is conveyed substantially vertically upward to the switching gate. After passing through a passage (fourth transport passage) 400 on the back side of G1, and further passing through an upper passage 16, the discharge roller pair 7 discharges the image onto the discharge tray 8 on the upper side of the machine with the image surface facing upward (face up). It

FIG. 4 is a block diagram showing the drive system of the sheet post-processing apparatus. The motor M1 is connected to the timing belts B1, B
The drive roller 9A (left roller) of the transport roller pair 9 of the third transport path 300 is rotated via the second drive path 2, and the drive roller 2 of the transport roller pair 2 of the second transport path 200 is rotated via a gear train.
A (lower roller), the drive roller 3A (lower roller) of the transport roller pair 3 and the drive roller 4A (upper roller) of the transport roller pair 4 are rotated. Further, the driving roller 1A (right roller) of the entrance roller pair 1 of the receiving unit is rotated via the timing belt B3, and the driving roller 7A (lower roller) of the discharge roller pair 7 is further rotated via the timing belt B4.

The motor M2 has timing belts B5, B.
The upper drive (hereinafter, referred to as upper roller) roller 5A of the discharge roller pair 5 is rotated via 6 and the lower drive roller (hereinafter, referred to as lower roller) 5B of the discharge roller pair 5 is passed through the gear train and the timing belt B7. To rotate. Further, the pulley that drives the lower roller 5B rotates the drive pulley 25 via the timing belt B8 and rotates the discharge belt 27.

The motor M4 drives and rotates the drive pulley 61 via the gear train, and rotates the wire 63 that winds the drive pulley 61 and the driven pulley 62 above. On a part of the wire W, the base of the paper discharge tray 6 is locked by the locking member 6
It is fixed by 4. The paper discharge tray 6 can be moved up and down along the rail member 66 by a roller 65 rotatably supported by a base thereof sliding on a rail member 66 and rotating the wire 63.

FIG. 5 is a sectional view showing the staple processing unit 20 and the paper discharge unit, and FIG. 6 is a plan view of the staple processing unit 20.

In FIG. 6, the two aligning members 24 are arranged symmetrically with respect to the center line CL and can move simultaneously in the direction orthogonal to the conveying direction of the sheet P. The left and right alignment members 24 are fixed to the timing belt 32,
It slides on the guide bar 33 and moves. The timing belt 32 rotates from the stepping motor M6 via an intermediate gear train. The alignment member 24 shown in FIG. 6 is in the home position. This home position position is the protrusion (detected portion) 24A provided on the alignment member 24.
And a home position detecting sensor 34 provided in the intermediate stacker 22. The alternate long and short dash line shown in FIG. 6 indicates sheets P of various sizes. In this embodiment, as an example, A3 size, B4 size, 11 ″ × 17 ″,
Sheets P of various sizes having lengths in the longitudinal direction of 8.5 ″ × 14 ″ were set as large size sheets, and sheets P having lengths shorter than this were set as small size sheets. The distance L from the stopper surface (abutting surface) m of the stopper member 31 in the vicinity of the stapler 30 that abuts the sheet to the nip position n of the discharge roller pair 5 is set to a position that distinguishes the large size from the small size. Set. That is, each of the small-sized sheets P has a length in the transport direction,
Since it is shorter than the distance L, it is placed on the upstream side of the discharge roller pair 5. On the other hand, since each of the large-sized sheets P has a length in the transport direction that is longer than the distance L, the leading end thereof projects from the nip position of the discharge roller pair 5 to the downstream side, and the sheet P is discharged onto the discharge tray 6. Also placed. The nip portion of the discharge roller pair 5 is controlled to be opened and closed in order to place this large size sheet P for alignment and stapling.

In FIG. 5, the discharge roller pair 5 is composed of an upper roller 5A and a lower roller 5B which are connected to the motor M2 shown in FIG. The lower roller 5B is driven and rotated at a fixed position. The upper roller 5A, which can be driven and rotated, is supported by the holding member 51, and can swing about the support shaft 52 along an arcuate long groove 53 provided in a side plate of the apparatus main body. That is, the pinion gear g1 on the drive shaft of the motor M5
Is decelerated via a gear train composed of gears g2, g3, g4, g5 to rotate the disc 54. An eccentric pin 55, which is planted at an eccentric position of the disc 54, is rotatably connected to one end of a crank lever 56. The other end of the crank lever 56 is rotatably engaged with a pin 57 provided on the holding member 51. When the pinion gear g1 of the motor M5 is driven to rotate and the disc 54 is rotated halfway through the gear train, the crank lever 56 moves to move the holding member 51 holding the upper roller 5A around the support shaft 52. And swings clockwise along the long groove 53. When the rotating disk 54 makes a half rotation and the detected portion 58 provided on the disk 54 passes through the optical path of the photointerrupter type sensor PS5, the driving of the motor M5 is stopped and the upper roller 5A ejects the sheet. Stop with the passage open.

FIG. 7 is a sectional view showing a state in which the upper roller 5A of the discharge roller pair opening / closing driving means 50 is opened and stopped. In this discharge path open state, a large-sized sheet is carried into the intermediate stacker 22 from the intermediate stacker inlet section roller pair 21, and is aligned and stapled.

FIG. 8 is a sectional view showing the standby state of the lower discharge roller unit and the upper discharge roller unit. FIG. 9 shows FIG.
FIG. 6 is a sectional view taken along the line A in FIG. The lower roller unit includes a rotating shaft 501 rotatably supported on both side walls of the sheet post-processing apparatus main body and a pulley 502 fixed to one shaft end thereof, a plurality of lower rollers 5B having a rubber layer on the peripheral surface, and a peripheral surface. And a plurality of winding rollers (sponge rollers) 5C having a flexible elastic material layer, and is driven and rotated by the motor M2 via the belt B7 around the pulley 502.

In the middle of the plurality of lower rollers 5B and the plurality of sponge rollers 5C, one discharge guide plate 503 is swingably supported around a support shaft 504. The paper discharge guide plate 503 is lifted up by a coil spring (spring member) 505 stretched between the discharge roller upper units described later, and comes into contact with a stopper 507 via a cushioning material 506. At the time of this contact, the upper surface of the paper discharge guide plate 503 protrudes above the outer peripheral surface of the sponge roller 5C.

The upper roller 5A of the discharge roller upper unit is
The discharge roller upper unit includes a rotation shaft 511 rotatably supported on both side walls of the discharge roller upper unit and having a pulley 512 fixed to one shaft end, and the same as the discharge roller lower unit via the belt B6 around which the pulley 512 is wound. It is driven and rotated by the motor M2.

The holding member 51 of the discharge roller upper unit is
As described with reference to FIG. 7, it is possible to swing about the support shaft 52, and the cover upper portion 51A comes into contact with the stopper 513 of the sheet post-processing apparatus main body to stop the swing. The support shaft 52
An arm member 514 that rotatably supports both shaft ends of the rotary shaft 511 of the discharge roller upper unit, and a lever member 515 that engages with a pin 517 planted in a plunger 516 of the solenoid SD are fixed to this. It is possible to swing together. The solenoid SD is the upper roller 5
The pressure contact with the lower roller 5B of A and the release thereof are driven. A stopper member 518 is provided at the bottom of the arm member 514 and outside the sheet passage area. The distal end of the stopper member 518 is installed such that the gap s is maintained between the upper roller 5A and each peripheral surface of the paper discharge guide plate 503. The sheet P held by the shift roller pair 4 can smoothly pass between the upper roller 5A and the lower roller 5B that are separated by the gap s without contacting the sponge roller 5C.

FIG. 10 is a sectional view of the discharge roller upper unit and the discharge roller lower unit at the time of discharging the sheet. When a voltage is applied to the solenoid SD from the stopped state, the plunger 516 is attracted and the pin 517 is attached to the lever member 5.
15 is rotated counterclockwise about the support shaft 52 against the biasing force of the return spring. The arm member 514 that is integral with the support shaft 52 is also rotated counterclockwise, and the stopper member 5
The leading end of 18 abuts against the upper surface of the paper discharge guide plate 503 and pushes it down, and the upper roller 5A comes into pressure contact with the lower roller 5B and stops. In this pressed state, the sheet discharged from the shift roller pair 4 is pressed and sandwiched and discharged onto the sheet discharge tray 6. Alternatively, the sheet bundle after the stapling process is
And the upper roller 5A
The lower roller 5 </ b> B and the lower roller 5 </ b> B are pressed to each other and discharged from the nip position to the discharge tray 6.

FIG. 11 is a sectional view of the discharge roller upper unit and the discharge roller lower unit showing a state in which the sheet bundle P is discharged from the discharge roller pair 5. In the figure, PS2 is a paper ejection sensor, and 520 is an actuator of the paper ejection sensor PS2, which detects the passage of the rear end of the sheet bundle P and detects the completion of paper ejection. When the completion of discharging the sheet bundle P is detected, the energization of the solenoid SD is stopped and the initial state shown in FIG. 8 is restored.

Although the sheet post-processing apparatus connected to the copying machine is shown in the embodiment of the present invention, the sheet post-processing apparatus used by connecting to the image forming apparatus such as a printer or a facsimile or a light printing machine is used. It is also applicable to.

Next, an embodiment according to the present invention which solves the first problem will be described with reference to FIG. FIG. 12 (a)
FIG. 4 is a schematic view showing a discharged sheet stacking unit of the sheet post-processing apparatus according to the present invention. Inclination angle θ3 (for example, 30 ° to 40 °) of the sheet mounting surface of the paper discharge tray 6 with respect to the horizontal plane.
Is an angle required for the sheet discharged onto the sheet discharge tray 6 or the sheet surface placed on the sheet discharge tray to slide down reliably. Further, the angle θ4 formed by the sheet stacking surface of the sheet discharge tray 6 and the sheet trailing end abutting reference member (hereinafter referred to as the trailing end reference member) 67 is preferably closer to 90 °.
Therefore, the rear end reference member 67 is inclined at the angle α with respect to the vertical plane V. Here, when θ4 = about 90 ° is set, the inclination angle α of the rear end reference member 67 is equal to the inclination angle θ of the discharge tray 6.
It is almost equal to 3. By setting the trailing end reference member 67 in such an inclined manner, the sheet P discharged by the pair of discharge rollers 5 slides down on the discharge tray, and the trailing end of the sheet is set by the winding roller 5C. It is possible to make sure that the rear ends of the sheets are substantially perpendicular to each other and to align them. However, if the trailing edge reference member 67 is inclined at the inclination angle α, the sheet post-processing apparatus main body becomes large in size.

FIG. 12B is a schematic view showing another embodiment of the discharged sheet stacking unit of the sheet post-processing apparatus according to the present invention. The sheet placement surface of the discharge tray 6 is a sheet P.
Sheet mounting surface 6A having a large inclination angle θ3 for occupying a wide area including the front end of the sheet, and a gentle inclination angle θ5 for mounting the sheet near the rear end of the sheet (for example, 10 ° to 20 °) And the sheet mounting surface 6B having The rear end reference member 67 is set at an inclination angle θ4 (about 90 °) with respect to the sheet mounting surface 6B having the inclination angle θ5. That is,
The rear end reference member 67 is arranged so as to be inclined with respect to the vertical plane VP at an inclination angle β. The inclination angle β is substantially equal to the inclination angle θ5 and can be set to be significantly smaller than the inclination angle α, so that the sheet post-processing apparatus main body can be downsized and the sheet rear end alignment can be surely achieved. To be done.

Next, an embodiment according to the present invention for solving the second problem will be described with reference to FIG. FIG. 13 (a)
FIG. 6 is a sectional view showing an upper limit position of the paper discharge tray 6 in the non-staple mode. On the upper part of the rear end reference member 67,
A photo interrupter type tray upper limit sensor PS6 and a swingable actuator 68 are installed. When the sheet ejection tray 6 is driven to rise and one end portion 68A of the actuator 68 comes into contact with the upper surface of the sheet ejection tray 6 or the upper surface of the sheet P placed on the sheet ejection tray 6, the actuator 68 The other tip portion 68B of the other end is the upper limit sensor P.
The light detection unit in S6 is opened to switch it off, and the driving of the paper discharge tray 6 is stopped. The stop position of the paper discharge tray 6 is a position where the upper surface of the paper discharge tray 6 or the upper surface of the sheet P placed on the paper discharge tray 6 is pressed against the winding roller 5C with a predetermined pressure. In this state, the rotating winding roller 5C constantly presses the sheet P at a predetermined pressure to feed the sheet P to the trailing edge reference member 67 and align the trailing edge. As the number of sheets P stacked on the discharge tray 6 increases, the discharge tray 6 is driven downward,
The uppermost surface of the sheets P stacked on the paper discharge tray 6 is detected and controlled by the tray upper limit sensor PS6 and the actuator 68, and is always held at a constant upper surface height.
The outer peripheral surface of the winding roller 5C is brought into pressure contact with a predetermined pressure.

FIG. 13B is a sectional view showing the upper limit position of the paper discharge tray 6 in the staple mode. A photo interrupter type tray upper limit sensor PS7 is provided above the rear end reference member 67 and below the tray upper limit sensor PS6.
And a swingable actuator 69 are installed.
When the paper discharge tray 6 is driven to rise, the actuator 69
When one of the leading end portions 69A contacts the upper surface of the stapled sheet bundle P placed on the paper discharge tray 6,
The other tip portion 69B of the actuator 69 opens the photodetection portion of the tray upper limit sensor PS7 to bring it into a switch-off state, and stops the driving of the paper discharge tray 6. The stop position of the paper discharge tray 6 is a position having a gap a at which the sheet bundle P placed on the paper discharge tray 6 does not contact the winding roller 5C. In this state, the sheet bundle P discharged from the discharge roller pair 5 is placed on the discharge tray 6,
The trailing end of the sheet bundle P enters below the winding roller 5C, contacts the trailing end reference member 67, and stops. Output tray 6
As the number of sheet bundles P stacked on the sheet discharge tray 6 increases, the discharge tray 6 is driven downward, and the uppermost surface of the sheet bundle P stacked on the sheet discharge tray 6 has the tray upper limit sensor PS7.
And the detection is controlled by the actuator 69, and the gap a is constantly maintained.

Next, an embodiment according to the present invention for solving the third problem will be described with reference to FIGS. 14, 15 and 16. FIG. 14 is a schematic diagram showing the process of discharging and stacking the sheets P on the discharge tray 6 in the non-staple mode, FIG. 15 is a block diagram of the lifting control of the discharging tray 6, and FIG. 16 is a lifting control of the discharging tray 6. It is a flowchart.

(1) One sheet is nipped by the pair of discharge rollers 5 and discharged, and when the discharge sensor PS2 detects the passage of the trailing end of the sheet, the motor drive circuit causes the motor M4 for raising and lowering the discharge tray. To start lowering the discharge tray 6. FIG. 14A shows a sheet discharge state before the sheet discharge tray 6 starts to descend.

(2) The discharge tray 6 is lowered, and the tip end portion 6 of the actuator 69 is in contact with the upper surface of the discharge tray 6 or the uppermost surface of the sheet P placed on the discharge tray 6.
9A swings, and when the other end 69B opens the photodetector of the tray upper limit sensor PS7 and switches it off,
The lowering of the discharge tray is stopped, and at this time, a gap b is formed between the upper surface of the discharge tray 6 or the uppermost surface of the sheet P placed on the discharge tray 6 and the outer peripheral surface of the winding roller 5C.
Is formed.

(3) When the timer in the control means 70 is started by switching off the tray upper limit detection sensor PS7 and the timer counts up a predetermined time,
The motor drive circuit starts driving the motor M4 to start raising the paper discharge tray 6 and reduce the gap b. The sheet P discharged onto the upper surface of the sheet discharge tray 6 or the uppermost surface of the sheet P placed on the sheet discharge tray 6 descends between the lowering and the rising of the sheet discharging tray 6, and The trailing edge of the sheet passes below the winding roller 5C, and the trailing edge of the sheet is rotated by the winding roller 5C and the upper surface of the paper discharge tray 6 or the uppermost surface of the sheet P placed on the paper discharge tray 6. It is pressed and pinched and abuts on the rear end reference member 67. In this way, when the trailing edge of the sheet P passes through the winding roller 5C, the gap b is formed, so that the trailing edge of the curled sheet P hits the outer peripheral surface of the winding roller 5C and a conveyance failure occurs. , The rear end of the sheet is not misaligned.

(4) The paper ejection tray 6 is raised so that the upper surface of the paper ejection tray 6 or the uppermost surface of the sheet P placed on the paper ejection tray 6 contacts the actuator 69 and rocks. As a result, when the tray upper limit sensor PS7 is switched on, the motor drive circuit stops driving the motor M4, and the raising of the discharge tray 6 is stopped.

(5) The above-described lowering and raising operations of the discharge tray 6 are performed each time one sheet P is discharged, and the tray upper limit sensor PS7 and the tray upper limit sensor PS7 are activated at the timing when the trailing edge of the sheet enters the winding roller 5C. A gap b is formed for each sheet discharge by driving the motor M4 by a timer. As a result, sheet misalignment due to defective winding is prevented.

Next, an embodiment according to the present invention for solving the fourth problem will be described with reference to FIGS. 17, 18 and 19. FIG. 17 is a cross-sectional view of essential parts of the staple processing unit 20 in the staple mode. FIG. 17A shows a sheet bundle P _A of small size placed on the intermediate stacker 22 and the trailing end of the sheet abuts the stopper member 31. 6B shows a state in which the large-sized sheet bundle P _B is placed on the intermediate stacker 22.
The state where the rear end of the sheet is brought into contact with the stopper member 31 is shown. FIG. 18 is a block diagram of the elevation control of the discharge tray 6, FIG.
Reference numeral 9 is a flowchart for raising and lowering the discharge tray 6.

As shown in FIG. 5, the small-sized sheets P _A are stacked on the intermediate stacker 22 and, after the stapling process, are discharged onto the discharge tray 6 stopped at the standby position in the staple mode. (See FIG. 17A). However, in such a configuration, the large size sheet P _B
As described with reference to FIG. 7, the discharge roller pair 5 is opened so that the leading end of the sheet is ejected from the discharge roller pair 5 to the outside of the machine. That is, the rear end of the large-sized sheet P _B contacts the stopper member 31 near the stapler 30,
The sheet is placed on the intermediate stacker 22, and on the lower roller 5B and the take-in roller 5C of the discharge roller pair 5 which are not rotating, and the sheet front end is projected outside the machine. Of the large size sheets P _B , in particular, in the case of the largest size 11 ″ × 17 ″ size sheet or A3 size sheet, the sheet leading edge protruding out of the machine is as the sheets are stacked. Hanging down, lower roller 5
B and the winding roller 5C are curved and wound. In such a state, the sheet P conveyed from the intermediate stacker inlet portion roller pair 21 and fed into the intermediate stacker 22 is curved at the leading edge of the sheet and is prevented from advancing, so that the sheet P extends along the inclined surface of the intermediate stacker 22. It doesn't slip
There is a problem in that the sheets do not come into contact with the stopper member 31 and the sheets are not aligned.

[0059] Sheet postprocessing apparatus according to the present invention, the sheet size, the sheet discharge tray 6 and controls to change the standby position, the large size sheet P _B the intermediate stacker 22
When the sheets are stacked on the sheet, as shown in FIG. 17B, the sheet discharge tray 6 is raised to the standby position in the offset mode, and the sheet front end protruding from the intermediate stacker 22 is placed on the upper surface of the sheet discharge tray 6 or the sheet discharge tray 6. The sheet bundle P placed on the tray 6 is supported so as to come into contact with the uppermost surface of the sheet bundle P. As a result, the leading edge of the sheet is lifted, and the sheet P on the intermediate stacker 22 is easily lowered to come into contact with the stopper member 31. Further, by using the vertically movable sheet ejection tray 6 as an auxiliary tray of the intermediate stacker 22 on which the sheets P are placed before the stapling process, the intermediate stacker 2
2 can be downsized, and the sheet post-processing device can be made compact.

A sheet of 11 ″ × 17 ″ size or A
When stacking 10 or more large size sheets such as 3-size sheets, the discharge tray 6 is raised to the upper offset mode standby position and made to stand by, and the leading end portion of the sheets conveyed onto the intermediate stacker 22 is It is supported on the upper surface of the sheet discharge tray 6 or the uppermost surface of the sheet bundle P placed on the sheet discharge tray 6. Upon completion of the stapling operation, the paper discharge tray 6 is lowered for a certain period of time, and after the paper discharge sensor PS2 detects that the sheet bundle P has been discharged onto the paper discharge tray 6, the paper discharge tray 6 is raised. Stop all offset mode standby position again.

However, when a large number of large sheets are stacked with a small number of sheets less than 10 sheets, the staples of the sheet bundles already placed on the discharge tray 6 overlap each other, and this portion overlaps. Only thicker (Fig. 24 (b)
(See), the tray upper limit sensor PS7 that detects the upper surface of the sheet bundle on the discharge tray protrudes higher than the detection surface, and the upper portion of the staple needle bites into the outer peripheral surface of the winding roller 5C and is damaged. In order to prevent this, when stacking less than 10 large sheets, the discharge tray 6 is not raised and is set to the standby position in the staple mode shown in FIG. 17A.

Next, an embodiment for solving the fifth problem will be described with reference to FIGS. 20, 21 and 22. When a stapled sheet bundle and one sheet are discharged by a common discharge roller pair and placed on a common discharge tray,
Since one sheet and a staple-processed sheet bundle (for example, 50 sheets) have different thicknesses and weights, good ejection is impossible. The present invention solves this problem. FIG. 20 is a block diagram of the elevation control of the paper ejection tray 6, FIG. 21 is a flowchart of the elevation control of the paper ejection tray 6, and FIG. 22 is a timing chart of the elevation control of the paper ejection tray 6. Is.

The time from when the paper discharge sensor PS2 detects the passage of the rear end portion of the sheets (or the stapled sheet bundle) P discharged from the intermediate stacker 22 to the start of the lowering of the paper discharge tray 6 is A, The time during which the discharge tray 6 is descending is set to B, and the times A and B are set to different times in the offset mode and the staple mode. Paper discharge tray 6 in both offset mode and staple mode operations
Table 1 shows the descent time and the descent distance.

[0064]

[Table 1]

Since the staple-processed sheet bundle is generally thick, as shown in Table 1, in the staple mode, the lowering time of the discharge tray 6 is made longer than that in the staple mode, and the lowering distance is increased, so that Good paper discharge is achieved by setting the stop position of the paper discharge tray 6 when receiving the sheet P discharged to the first position to a position larger than the maximum sheet bundle thickness.

[0066]

According to the sheet post-processing apparatus of the present invention, the staple mode discharging means and the non-staple mode (including the shift processing) discharging means are combined into one structure, thereby making the apparatus compact and simplifying the mechanism. The reduction of manufacturing cost was achieved. In addition, misalignment of the stapled sheet bundle discharged onto the sheet discharge tray and sheets discharged one by one, scattering, and damage to the discharge roller were prevented, and good sheet discharge was achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a sheet post-processing apparatus of the present invention.

FIG. 2 is a schematic diagram showing a sheet conveyance path by a first conveyance path, and a schematic diagram showing a sheet conveyance path by a second conveyance path.

FIG. 3 is a schematic view showing a sheet conveyance path by a third conveyance path and a schematic view showing a sheet conveyance path by a fourth conveyance path.

FIG. 4 is a configuration diagram showing a drive system of the sheet post-processing apparatus.

FIG. 5 is a cross-sectional view showing a staple processing unit and a paper discharge unit.

FIG. 6 is a plan view of a staple processing unit.

FIG. 7 is a cross-sectional view showing a state in which an upper roller of a discharge roller pair is opened and stopped.

FIG. 8 is a sectional view showing a standby state of a discharge roller lower unit and a discharge roller upper unit.

9 is a cross-sectional view taken along arrow A in FIG.

FIG. 10 is a cross-sectional view of a discharge roller upper unit and a discharge roller lower unit during sheet discharge.

FIG. 11 is a cross-sectional view showing a state in which a sheet bundle is discharged from a discharge roller pair.

FIG. 12 is a schematic diagram showing a discharged sheet stacking unit of the sheet post-processing apparatus according to the present invention.

FIG. 13 is a cross-sectional view showing the upper limit position of the discharge tray in the non-staple mode and the staple mode.

FIG. 14 is a schematic diagram showing a process of discharging and stacking sheets on a discharge tray in a non-staple mode.

FIG. 15 is a block diagram of a lift control of a discharge tray.

FIG. 16 is a flowchart for raising / lowering a discharge tray.

FIG. 17 is a cross-sectional view of a main portion of a staple processing unit on which a small-sized sheet bundle is placed and a main-part sectional view of a staple processing unit on which a large-sized sheet bundle is placed in a staple mode.

FIG. 18 is a block diagram of a lifting / lowering control of the discharge tray.

FIG. 19 is a flowchart for raising / lowering control of the sheet discharge tray.

FIG. 20 is a block diagram of a lifting / lowering control of the discharge tray.

FIG. 21 is a flowchart for raising and lowering a discharge tray.

FIG. 22 is a timing chart of raising / lowering control of the discharge tray.

FIG. 23 is a schematic view showing a conventional sheet stacking device.

FIG. 24 is a schematic view showing a front surface and a side surface of a conventional sheet stacking device.

[Explanation of symbols]

1 Inlet Roller Pair 2, 3, 9 Conveyor Roller Pair 4 Conveyor Roller Pair (Shift Roller Pair, Offset Roller Pair) 5 Discharge Roller Pair (Nipping Discharge Means) 7 Discharge Roller Pair 5A Upper Roller (Upper Drive Roller) 5B Lower Roller (Lower drive roller) 5C Rolling roller (sponge roller) 6,8 Paper discharge tray 11, 12, 13, 14, 15, 16, 17, 18, 1
9 Passage 20 Staple Processing Section 21 Conveying Roller Pair (Intermediate Stacker Inlet Roller Pair) 22 Intermediate Stacker 27 Discharging Belt 28 Discharging Claw 30 Stapler 31 Stopper Member 50 Discharging Roller Opening / Closing Means 67 Sheet Rear End Abutting Reference Member (Discharging Paper) Abutment plate,
Rear end reference member) 70 Control means 100 First transport path 200 Second transport path 300 Third transport path 400 Fourth transport path M1, M2, M3, M4, M5, M6 Motor P sheet, sheet bundle PS1 Inlet sensor PS2 Paper discharge sensor PS3 Stacker inlet sensor PS6, PS7 Tray upper limit sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Toshitaka Matsumoto 1-5-10 Sakaemachi, Asaka-shi, Saitama Prefecture (72) Hirohiko Okabe 47 47, 1067 Wakamatsucho, Tokorozawa-shi, Saitama Prefecture

Claims (8)

[Claims] 1. A sheet post-processing apparatus in which a plurality of sheets carried out from an image forming apparatus are sequentially introduced, discharged by sandwiching and ejecting means, and stacked on a vertically movable sheet ejection tray, wherein the sheets by the sandwiching and ejecting means are disposed. A stackable sheet discharge tray having a sheet stacking surface that is inclined upward in the discharge direction, and a sheet stacking surface that abuts the trailing end of the plurality of sheets stacked on the inclined sheet stacking surface in the discharge direction. A paper discharge abutting plate which is set to an angle close to a right angle with respect to the surface, and the abutting surface is inclined with respect to the vertical surface;
A sheet post-processing apparatus comprising: 2. The sheet post-processing apparatus according to claim 1, wherein the sheet discharge tray can be moved up and down along a contact surface of the inclined sheet discharge contact plates. 3. A sheet discharged onto a sheet discharge tray is slidably brought into contact with an abutting surface of the sheet discharge abutting plate near the upper end portion of the sheet discharge abutting plate. The sheet post-processing apparatus according to claim 1, further comprising a rotatable sheet discharge auxiliary rotation member. 4. A staple mode in which sheets carried out from an image forming apparatus are bound by a stapler, and then a sheet bundle is discharged by a sandwiching and ejecting means onto a sheet discharge tray that can be raised and lowered, and sheets are stapled without being bound. In a sheet post-processing apparatus having a non-staple mode for discharging onto a discharge tray that can be raised and lowered by the sandwich discharge means, the staple mode and the non-staple mode discharge the sheet by a common discharge roller pair and discharge tray. It is possible to provide two sensors for detecting the upper surface of the sheet placed on the sheet discharge tray at different vertical heights, and in the staple mode, the sheet upper surface detection signal from the lower sensor is used to position the sheet discharge tray downward. In the non-staple mode, the upper sensor raises the output tray with the sheet upper surface detection signal. Sheet post-processing apparatus, characterized by elevation control the discharge tray to hold the position. 5. A sheet post-processing apparatus, which introduces a sheet carried out from an image forming apparatus, discharges it by a nipping and discharging means, and stacks it on a vertically movable paper ejection tray, A paper discharge sensor for detecting passage of the rear end, a paper discharge abutting plate having an abutting surface for abutting the rear end of the sheet in the sheet discharge direction, and a rear end of the upper surface of the sheet discharged on the paper discharge tray. A rotatable sheet discharge assisting rotation member that slides the sheet and transfers the sheet to contact the contact surface of the sheet discharge contact plate, and a detection unit that detects the upper surface position of the sheet placed on the discharge tray. And a control means for controlling the elevating and lowering of the paper discharge tray by the detection means, the paper discharge tray is lowered every time the sheet is discharged by the sandwiching and discharging means, and the discharged sheet is discharged against the discharge plate. Butt After being brought into contact with the surface by its own weight, the paper discharge tray is raised and brought into sliding contact with the rear end portion of the sheet discharged by the paper discharge auxiliary rotation member to come into contact with the contact surface of the paper discharge contact plate. A sheet post-processing apparatus characterized by the above. 6. A sheet after being loaded from an image forming apparatus, stacked on an intermediate stacker, aligned, bound by a stapler, discharged by a sandwiching discharge means, and stacked on a vertically movable discharge tray. In the processing apparatus, when a large-sized sheet of a predetermined size or more is placed on the intermediate stacker, the nipping and ejecting means is opened, the leading end of the sheet is projected onto the paper ejection tray, and the paper is ejected. A sheet post-processing, characterized in that the paper tray is made to stand by at an upper position where binding processing is not performed, and the leading end portion of the sheet can be held on the discharge tray or on a sheet placed on the discharge tray. apparatus. 7. A staple mode in which sheets carried out from an image forming apparatus are bound by a stapler, and then a sheet bundle is discharged by a sandwiching and ejecting means onto a paper discharge tray that can be raised and lowered, and sheets are stapled without binding processing. A sheet post-processing apparatus having a non-staple mode in which a sheet is ejected onto a sheet ejection tray that can be moved up and down by the nipping and ejecting means, and a sheet ejection sensor that detects a trailing edge of the sheet ejected from the nipping and ejecting means, An upper surface detection sensor for detecting the upper surface of the sheet placed on the tray, a driving means for driving the paper discharge tray up and down every time the sheet is discharged from the nipping and discharging means, an output of the paper discharge sensor and the upper surface. Control means for controlling the up-and-down drive of the discharge tray based on the output of the detection sensor, and the staple mode and the non-staple mode. Sheet post-processing apparatus characterized by a in, with different descent amount of the discharge tray. 8. A staple mode in which sheets carried out from the image forming apparatus are bound by a stapler and then the sheet bundle is ejected by a nipping and ejecting means onto a sheet discharge tray that can be moved up and down, and sheets are stapled without being bound. A sheet post-processing apparatus having a non-staple mode in which a sheet is ejected onto a sheet ejection tray that can be moved up and down by the nipping and ejecting means, and a sheet ejection sensor that detects a trailing edge of the sheet ejected from the nipping and ejecting means, An upper surface detection sensor for detecting the upper surface of the sheet placed on the tray, a driving means for driving the paper discharge tray up and down every time the sheet is discharged from the nipping and discharging means, an output of the paper discharge sensor and the upper surface. Control means for controlling the up-and-down drive of the discharge tray based on the output of the detection sensor, and the staple mode and the non-staple mode. Sheet post-processing apparatus characterized by a in, with different falling time of the output tray.