JP7203603B2 - Sheet processing device and image forming device - Google Patents

Description

The present invention relates to a sheet processing apparatus and an image forming apparatus that perform processing such as sorting by shifting the width direction of conveyed sheets.

2. Description of the Related Art A general conventional sheet processing apparatus sequentially conveys sheets discharged from an image forming apparatus and performs various post-processing such as sorting, as disclosed in Japanese Unexamined Patent Application Publication No. 2002-100003. Such a sheet processing apparatus creates post-processing time such as sorting by accelerating and conveying a sheet received from an image forming apparatus and separating the sheet from the succeeding sheet. A shift unit that shifts the conveyed sheets in the width direction that intersects with the predetermined conveying direction is provided, and sorting processing is possible by shifting the sheets in the width direction by a predetermined amount by the shift unit. Further, this sheet processing apparatus is provided with an auxiliary roller pair for assisting the conveyance of a sheet having a short length (conveyance length) in the conveyance direction. The pair of auxiliary rollers are separated when a sheet of a predetermined size (standard size) or larger is conveyed, and are brought into contact with each other when conveying a sheet of a shorter conveying length than the predetermined size, thereby conveying sheets of various sizes. is designed to be performed smoothly.

In recent years, users' work styles have diversified, and in the above-described sheet processing apparatus, there is a demand for sorting small-sized sheets other than general standard-sized sheets or irregular-sized sheets.

JP 2013-230891 A

However, when trying to shift in a direction intersecting the conveying direction in order to sort irregularly shaped sheets with a short conveying length such as A5 size sheets or postcard size sheets, the auxiliary roller pair may become an obstacle. . This is because if the leading edge of the sheet is nipped by the auxiliary roller pair immediately before or during the shift operation, the sheet will not be shifted or will be conveyed with an incomplete shift. As a result, there is a possibility that the scheduled sorting process cannot be performed.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a sheet processing apparatus and an image forming apparatus capable of reliably sorting and smoothly transporting even small-sized sheets having a short length in the transport direction.

In order to solve the above-described problems, the sheet processing apparatus of the present invention includes: a sheet conveying path through which a sheet is conveyed in a predetermined conveying direction; conveying means for conveying a sheet of a predetermined size in the sheet conveying path, shifting means for moving the sheet to a predetermined shift position in a direction intersecting the conveying direction; and downstream of the shifting means in the conveying direction. Auxiliary conveying means for assisting conveying of a sheet having a length in the conveying direction shorter than a predetermined size, and control means for controlling the speed of conveying by the conveying means, wherein the control means comprises: When conveying a sheet whose length in the conveying direction is shorter than a predetermined size, before the leading edge of the sheet in the conveying direction reaches the auxiliary conveying means, the sheet whose length in the conveying direction is shorter than the predetermined size is conveyed. In order to move the sheet to the shift position, the speed of the conveying means is reduced to a second conveying speed lower than the first conveying speed before or during movement of the sheet by the shift means.

According to the sheet processing apparatus of the present invention, when shifting and conveying a sheet whose length in the conveying direction is shorter than a predetermined size using the auxiliary conveying device, the first sheet is shifted before or during the shifting operation by the shifting device. Since the sheet is decelerated from the conveying speed to the second conveying speed, it can be conveyed downstream via the auxiliary conveying means after the sheet has reliably moved to the predetermined shift position. As a result, it is possible to smoothly and reliably carry out the operations from the shift operation to the transportation.

1 is a sectional view of an image forming apparatus of the present invention; FIG. 1 is a block diagram of an image forming apparatus; FIG. 1 is a cross-sectional view of a sheet processing apparatus; FIG. 1 is a block diagram of a sheet processing apparatus; FIG. FIG. 4 is a view of the lateral registration detection unit viewed from the downstream side in the transport direction; It is the figure seen from the conveyance direction downstream of a shift unit. 3A and 3B are a cross-sectional view and a perspective view showing an assist roller configuration; FIG. 4A and 4B are a perspective view and a cross-sectional view illustrating the contact and separation operation of the assist roller; FIG. It is explanatory drawing which shows the shift operation|movement of a small size sheet (a) and a standard size sheet (b). It is a flow chart of sorting processing. 4 is a timing chart of shift operation in the sorting process;

A sheet processing apparatus according to the present embodiment and an image forming apparatus including this sheet processing apparatus will be described below with reference to FIGS. 1 to 11. FIG. Components described in the following embodiments are merely examples, and the present invention according to the claims is not limited only to these components.

As shown in FIG. 1, the image forming apparatus 110 includes an apparatus main body 100 and a sheet processing apparatus 500 connected to the apparatus main body 100. As shown in FIG. Sheets supplied from cassettes 101 a and 101 b in apparatus main body 100 are transferred with four-color toner images by yellow, magenta, cyan, and black photosensitive drums 102 a to 102 d as image forming means, respectively. After being conveyed and having the toner image fixed thereon, the sheet is discharged from the apparatus main body 100 to the sheet processing apparatus 500 by the discharge rollers 104 .

FIG. 2 is a block diagram of an apparatus control section that controls the image forming apparatus 110. As shown in FIG. The CPU circuit section 630 has a CPU 629 , a ROM 631 and a RAM 650 . The CPU circuit portion 630 controls an image signal control portion 634 , a printer control portion 635 , a sheet processing apparatus control portion 636 and an external interface 637 . The CPU circuit unit 630 performs control according to the programs stored in the ROM 631 and the settings of the operation unit 601 . A printer control unit 635 controls the apparatus main body 100 , and a sheet processing apparatus control unit 636 controls the sheet processing apparatus 500 . The RAM 650 is used as an area for temporarily holding control data and as a work area for computation associated with control. An external interface 637 is an interface from an external computer (PC) 620 , and signals are bidirectionally exchanged between the PC 620 and the CPU circuit section 630 via the external interface 637 . Print data is sent from the PC 620 to the image signal control circuit 634 via the external interface 637 , and the image signal control circuit 634 develops the sent print data into an image and outputs the image to the printer control unit 635 . Based on the image signal output from the image signal control unit 634 to the printer control unit 635, an image is formed on the sheet by the apparatus main body 100 shown in FIG.

Next, details of the sheet processing apparatus 500 will be described. In the sheet processing apparatus 500 of the present invention, when the sheets conveyed from the apparatus main body 100 are discharged to the discharge tray, the sheets are shifted by a predetermined width in the direction intersecting the conveying direction so that the sheets can be easily sorted. It has a sorting function that can be loaded by This sorting function is performed by shift means (shift unit) 400 provided in a sheet conveying path 520 extending from the side of the discharge roller 104 (upstream side) of the apparatus main body 100 toward the upper tray 515 or the lower tray 516 (downstream side). performed by The shift unit 400 includes control means for controlling the conveying speed for smoothly shifting and conveying sheets having a conveying direction length (conveying length) shorter than a predetermined size when shifting sheets. have. In the control means of this embodiment, the reference of the conveying length of the sheet of the predetermined size is set to 182 mm, and the sheet of B5 or A5 or smaller (hereinafter referred to as a small size sheet) having a conveying length of less than 182 mm is conveyed. A conveying speed control different from that for the sheet of the predetermined size having a length of 182 mm or more is performed. In this embodiment, the sheet processing apparatus 500 can be attached to the image forming apparatus 110 as an option. Moreover, although the tray has a two-tiered structure, it may have one or three or more tiers, and the number of tiers is not limited. The configuration of the sheet processing apparatus 500 will be described below along the sheet conveying direction.

As shown in FIG. 3, the sheet processing apparatus 500 includes a sheet conveying path 520 extending from the upstream side toward the downstream side in the sheet conveying direction, and the sheet conveying path 520 provided upstream of the sheet conveying path 520. It has a sheet detection means (entrance sensor) S1 for detecting that a sheet is conveyed from the inlet roller 501 and an entrance roller 501 for guiding the sheet passing through the entrance sensor S1 to the downstream side. A sheet received by an entrance roller 501 is conveyed to an entrance conveying roller pair 502, conveying means (shift conveying roller pair) 503 and 504 in the shift unit 400, and auxiliary conveying means (assist roller pair) 505, and then discharged and conveyed. The sheets are sequentially conveyed to roller pairs 506-508.

A lateral registration detection unit 300 is provided upstream of the shift unit 400 . The lateral registration detection unit 300 is activated when the user selects the sorting process using the operation unit 601, and the direction (hereinafter referred to as the sheet width direction) that intersects the predetermined conveying direction of the sheets sorted by the shift unit 400. is detected. When the position in the sheet width direction is detected by the lateral registration detection unit 300, the shift unit 400 moves in the direction intersecting the sheet conveying direction to a predetermined sorting position based on the detection result. As shown in FIG. 9, this movement is based on the center line O of the conveying direction of the sheets P1 and P2, and shifts in one of two directions intersecting the center line O (vertical direction in the figure). This shift amount is set in consideration of the positional deviation amount in the sheet width direction detected by the lateral registration detection unit 300 .

If the sheet shifted by the shift unit 400 is of a standard size with a conveying length of 182 mm or more, it is conveyed toward the discharge conveying roller pair 506 without being nipped by the assist roller pair 505 on the downstream side. On the other hand, if the sheet is a small size sheet with a conveying length of less than 182 mm, the sheet is nipped by the assist roller pair 505 and conveyed toward the discharge conveying roller pair 506 . Then, while being nipped by the discharge conveying roller pairs 506 , 507 , 508 , the sheet is conveyed to the switching flapper 509 arranged downstream. The sheet switched by the switching flapper 509 is stacked on an upper tray 515, which is one of stacking means, from the first discharge roller pair 510, or conveyed to the second discharge roller pairs 511 to 514, and They are loaded on a lower tray 516 which is a loading means. The switching flapper 509 is switched by ON/OFF of a solenoid (not shown). Sheets stacked on the upper tray 515 are aligned in a direction crossing the sheet discharge direction by an upper tray aligning member 517, and sheets stacked on the lower tray 516 are aligned by a lower tray aligning member 518 as alignment means.

Next, the sheet processing apparatus control section 636 that controls the sheet processing apparatus 500 will be described with reference to FIG. FIG. 4 shows an example of the control configuration, but it is not limited to this. can be

The sheet processing apparatus control unit 636 includes a CPU 701, a RAM 702, a ROM 703, an I/O 705, a network interface 704, a communication interface 706, and the like. The CPU 701 also controls the transport control unit 707 via the I/O 705 . The conveying control unit 707 includes a lateral registration detection drive motor M1, a shift motor M2 for moving the shift unit 400, a shift conveying motor M3 for conveying the sheet nipped by the shift unit 400, and a sheet conveyed from the shift unit 400. A pre-buffer transport motor M4, an entrance sensor S1, a lateral registration detection HP sensor S2, a lateral registration detection sensor S3, a shift unit HP sensor S4, and an assist roller contact solenoid 436 are included. Reference positions are detected by the sensors S1 to S4, and the motors M1 to M4 and the assist roller contact solenoid 436 are controlled based on the detection results.

Next, details of the lateral registration detection unit 300 will be described with reference to FIG. FIG. 5 is a view of the lateral registration detection unit 300 viewed from the downstream side in the sheet conveying direction. In the lateral registration detection unit 300, when the sheet passes through the transport path 309 composed of the pair of transport guides 307 and 308, the lateral registration sensor S3 detects the edge of the sheet in the sheet width direction. A position in the sheet width direction is specified. Bearings 303 and 304 are provided in the lateral registration detection sensor S3. The bearings 303 and 304 are configured to be movable in the direction of arrow X along guides 305 and 306 fixed to the sheet processing apparatus 500, respectively. Further, the lateral registration detection sensor S3 is previously moved to a position corresponding to the sheet size based on sheet size information input from the operation unit 601 of the apparatus main body 100 . The lateral registration detection sensor S3 has a recess, and detects the sheet width direction end portion of the sheet entering the recess. A drive source for moving the lateral registration detection sensor S3 is a lateral registration detection drive motor M1. A timing belt 311 is driven by a pulley 313 provided in the lateral registration detection drive motor M1 and a pulley 312 fixed to the sheet processing apparatus 500 . The lateral registration detection sensor S3 and the timing belt 311 are connected by a fixing plate 310 so that the lateral registration detection sensor S3 can be moved as the timing belt 311 is driven. At this time, the home position of the lateral registration detection sensor S3 is determined by detecting the fixing plate flag portion 310a provided on the fixing plate 310 with the lateral registration detection HP sensor S2 attached to the sheet processing apparatus 500. FIG. From this home position, the lateral registration detection drive motor M1 is driven by a predetermined number of pulses to move to a position corresponding to the sheet size.

FIG. 6 is a diagram of the shift unit 400 viewed from the downstream side in the sheet conveying direction. In the shift unit 400, a conveying path 423 is configured by conveying guides 403a and 403b. The conveying path 423 is configured such that the sheet can be nipped and conveyed by shift conveying rollers 503a, 503b, 504a, and 504b (see FIG. 3). The shift conveying roller pair 503, 504 is connected to the shift conveying motor M3 via gears 415, 416, and is configured to rotate forward and backward according to the rotation of the shift conveying motor M3. The shift conveying roller pairs 503, 504 and conveying guides 403a, 403b are supported by frames 405, 406, 407, 408. As shown in FIG. Bearings 409 , 410 , 411 , 412 fixed to frames 405 , 406 , 407 , 408 are configured to be movable along guides 413 , 414 . Frames 405 , 406 , 407 and 408 are also connected to timing belt 418 by fixing plate 419 . The fixed plate 419 is configured to be movable via a timing belt 418 by a shift motor M2 and pulleys 420 and 421. As shown in FIG. The home position of the shift unit 400 is determined by detecting the flag portion 406a in the frame 406 with the shift unit HP sensor S4 attached to the sheet processing apparatus 500. FIG.

7 and 8 show the configuration of the assist mechanism 430 centering on the assist roller pair 505. FIG. A drive gear 435 is mounted on the shaft of the assist roller pair 505 . Driving of the pre-buffer transport motor M4 is transmitted via a timing belt 431 to a pulley 433 and a pulley 432 provided on the shaft of the discharge transport roller pair 506 downstream of the assist roller pair 505 . A gear 434 that meshes with a driving gear 435 is attached coaxially to the pulley 433, and the assist roller pair 505 and the discharge conveying roller pair 506 are simultaneously driven by the pre-buffer conveying motor M4. The assist roller pair 505 is normally in a separated state as shown in FIG. 8(c). It is controlled by the sheet processing apparatus control unit 636 so as to come into contact only when conveying a small size sheet whose conveying pitch is less than the conveying pitch of the pair 506 .

An assist roller contact solenoid 436 is used for contacting the assist roller pair 505 . A solenoid link 438 is provided at the tip of the assist roller contact solenoid 436 via a spring pin 437 . A roller holder 441 is connected to the end of the solenoid link 438 opposite to the spring pin 437 to support the roller shaft 442 of the assist roller pair 505 . As shown in FIG. 8C, when the assist roller contact solenoid 436 is turned on, the iron core 443 of the assist roller contact solenoid 436 to which the spring pin 437 is attached moves in the arrow Z direction. Following this, the solenoid link 438 rotates in the direction of the arrow R with the rotating shaft 440 as the center of rotation, and the roller holder 441 moves in the direction of the arrow Y, pushing the roller shaft 442 of the assist roller pair 505 . abuts.

Next, the details of the sheet sorting process will be described. In order to start the shift operation of the sheet by the shift unit 400, the roller positioned on the upstream side of the shift unit 400 must be in a free state in which it does not nip the sheet. For this reason, the trailing edge of the sheet has passed through the inlet conveying roller pair 502, or the entrance conveying roller pair 502 and the inlet roller pair 502 are arranged so that the shifting operation can be started in the shift unit 400 before passing through the inlet conveying roller pair 502. The roller pair 501 also needs to be spaced apart. Further, in the shift unit 400 of the present invention, the shift conveying roller pair 503 and 504 move the sheet in the width direction while conveying the sheet in a nipped state. The leading edge must have passed through the shift conveying roller pair 503 . Furthermore, it is a condition that the leading edge of the sheet is not nipped by the assist roller pair 505 . Regarding this point, when the sheet to be conveyed is of a standard size having a predetermined conveying length or longer, the assist roller pair 505 is spaced apart (see FIG. 8), so there is no problem. Without the nip of the roller pair 505, the sheet cannot be conveyed smoothly to the downstream side. Therefore, it is necessary to complete the movement by the shift unit 400 before the leading edge of the sheet reaches the assist roller pair 505 . This is because if the leading edge of the sheet is nipped by the assist roller pair 505 before the movement by the shift unit 400 is completed, the sheet cannot be moved in the sheet width direction by the shift unit 400 .

As described above, in the sheet processing apparatus 500 of the present invention, in order to sort small-size sheets, the leading edge in the sheet conveying direction passes through the pair of shift conveying rollers 503, and the trailing edge in the sheet width direction passes through the inlet. It is necessary to start moving the sheet in the sheet width direction after passing through the pair of conveying rollers 502 and complete the movement of the sheet before the leading edge of the sheet reaches the pair of assist rollers 505 . Therefore, in the present invention, when sorting small size sheets is selected, the sheet conveying speed of the pair of shift conveying rollers 503 and 504 in the sheet conveying direction is shifted while the shift unit 400 is moving the sheet in the sheet width direction. The sheet processing apparatus control unit 636 controls so as to decelerate or stop at a speed slower than that at the start. By decelerating or stopping the sheet while moving in the sheet width direction in this way, the movement of the shift unit 400 in the sheet width direction can be completed before the leading edge of the sheet reaches the assist roller pair 505 . After the movement of the shift unit 400 is completed, the shift conveying motor M3 is accelerated again to convey the sheet downstream. Note that before the shift unit 400 starts moving the sheet, the shift conveying roller pair 503 and 504 stops conveying the sheet when the leading edge of the sheet is upstream of the assist roller pair 505, and after the shift unit 400 moves the sheet, the shift conveying roller It is also possible to control the pair 503, 504 to be driven again for transport. However, with this control method, the sheet stops for a long time, which may lead to a decrease in productivity. On the other hand, in the sheet processing apparatus 500 of the present invention, while the sheet is moved in the sheet width direction by the shift unit 400, it is controlled so as to decelerate or stop the sheet conveyance, thereby minimizing the sheet stop time. It is possible to prevent a decrease in productivity.

Next, a procedure for sorting sheets in the sheet processing apparatus 500 of the present invention will be described with reference to FIGS. 9 to 11. FIG. 9A shows an A5 size sheet P1 having a length (conveyance length) of 148 mm in the conveying direction, and FIG. 9B shows an A4 size sheet P2 having a conveying length of more than 148 mm. The state is shown schematically. As shown in FIG. 9A, in the case of the A5 size sheet P1, the sheet conveying speed is changed from the first conveying speed V1 to the second conveying speed V2, which is accelerated from the steady conveying speed V0 set in the apparatus main body 100. is conveyed toward the shift unit 400 in a state of being decelerated to . As a result, the movement of the shift unit 400 toward the predetermined shift position in the sheet width direction is completed before the leading edge of the sheet P<b>1 reaches the assist roller pair 505 . Then, the sheet is accelerated from this shift position to a conveying speed V3, which is faster than the conveying speed V2, and conveyed downstream via the pair of discharge conveying rollers 506 to 508 via the pair of assist rollers 505. FIG. On the other hand, the A4 size sheet P2 is conveyed toward the shift unit 400 at the sheet conveying speed V1. At this time, the leading edge of the sheet P2 reaches the assist roller pair 505, but since the assist roller pair 505 is separated, the shift operation by the shift unit 400 is hindered while the sheet P2 is nipped by the shift conveying roller pairs 503 and 504. can be done without Then, the sheet is conveyed to the downstream side through the discharge conveying roller pairs 506 to 508 while maintaining the conveying speed V1.

10 and 11 show a series of processing flows and operation timings for the A5 size sheet P1. First, the user selects the sorting process of A5 lateral feed (A5L) on the operation unit 601 (720). As a result, the lateral registration detection unit 300 and the shift unit 400 are moved to the receiving position of the sheet P1 corresponding to the A5 size (721), the assist roller contact solenoid 436 is turned ON, and the assist roller pair 505 is brought into contact (721). 722).

The sheet on which the image is formed by the apparatus main body 100 is conveyed into the sheet processing apparatus 500 at the regular conveying speed V0 set by the apparatus main body 100 (723), and the leading edge of the sheet passes the entrance sensor S1 (OFF→ON). Detect 724 to do so. When the inlet sensor S1 is turned from OFF to ON, the sheet conveying speed is accelerated from the steady conveying speed V0 to the first conveying speed V1 (V0<V1) (725) in order to advance the sorting process after a predetermined time t1 has elapsed from ON. ). After that, the trailing edge of the sheet is detected to pass the entrance sensor S1 (726), and when it is detected that S1 is turned from ON to OFF, the shift unit 400 is detected after a predetermined time t2 has elapsed from the time when it was turned OFF. The sheet conveying speed of the inner shift conveying motor M3 is reduced from the first conveying speed V1 to the second conveying speed V2 (V1>V2) (727). Further, after a predetermined time t3 has passed since S1 was turned OFF, the shift motor M2 is turned ON, and the shift unit 400 starts moving at a predetermined speed in the sheet width direction intersecting the sheet conveying direction (728). ). At this time, the shift conveying motor M3 may be temporarily stopped so that the second conveying speed V2 of the sheet conveying speed becomes zero. At the operation timing shown in FIG. 11, the shift motor M2 is turned ON after the sheet conveying speed of the shift conveying motor M3 changes to the second conveying speed V2. However, when the trailing edge of the sheet passes through the nip point of the pair of entrance conveying rollers 502, the sheet conveying speed of the shift conveying motor M3 reaches the first conveying speed V1 before it is reduced to the second conveying speed V2. , the shift motor M2 may be turned on to start moving in the sheet width direction intersecting the sheet conveying direction.

When the shift unit 400 completes the movement of the sheet being conveyed or stopped to the shift position at the sheet conveying speed V2 (729), the third conveying speed V3 higher than the second conveying speed V2 and the (730). This third conveying speed V3 can be arbitrarily set according to the processing capacity toward the upper tray 515 or the lower tray 516 via the switching flapper 509 on the downstream side. By setting the third conveying speed V3 to be equal to or higher than the first conveying speed V1, it is possible to speed up the discharge of the sheet, but there is no problem even if the speed is the same as the first conveying speed V1.

After that, when the leading edge of the sheet passes the assist roller pair 505 toward the discharge conveying roller pairs 506 to 508 (731), the lateral registration detection unit 300 and the shift unit 400 move to the subsequent sheet receiving position (732). The above operation is repeated (733) until such a series of processes is completed. When the sheet has been carried in from the apparatus main body 100, the assist roller contact solenoid 436 is turned off (734), and the assist roller pair 505 is separated. Then, the lateral registration detection unit 300 and the shift unit 400 move to their home positions and wait until the next sheet is started to be carried (735).

By repeating the above operations, it is possible to smoothly perform the sorting process even for small-sized sheets whose length in the conveying direction is shorter than the predetermined size, and to improve the productivity of a series of printing processes from image formation to discharge. can be done.

100 apparatus main body 110 image forming apparatus 400 shift unit (shift means)
430 assist mechanism 436 assist roller contact solenoid 500 sheet processing device 501 inlet roller 502 inlet conveying roller pair 503, 504 shift conveying roller pair (conveying means)
503a, 503b, 504a, 504b shift conveying roller 505 assist roller pair (auxiliary conveying means)
506, 507, 508 discharge conveying roller pair 509 switching flapper 510 first discharging roller pair 511, 512, 513, 514 second discharging roller pair 515 upper tray 516 lower tray 520 sheet conveying path 636 sheet processing apparatus controller (control means)
M1 lateral registration detection driving motor M2 shift motor M3 shift conveying motor M4 pre-buffer conveying motor S1 inlet sensor (sheet detecting means)
S2 Lateral registration detection HP sensor S3 Lateral registration detection sensor S4 Shift unit HP sensor V0 Regular conveying speed V1 First conveying speed V2 Second conveying speed V3 Third conveying speed

Claims (8)

a sheet conveying path along which a sheet is conveyed in a predetermined conveying direction; conveying means provided in the sheet conveying path for conveying a sheet of a predetermined size at a predetermined first conveying speed in the conveying direction; and the sheet conveying path a shift unit provided in the sheet width direction intersecting the conveying direction to move the sheet to a predetermined shift position in the sheet width direction; Auxiliary conveying means for assisting conveyance of short sheets, and control means for controlling the speed of conveying by the conveying means,
When conveying a sheet whose length in the conveying direction is shorter than the predetermined size, the control means controls the length of the sheet in the conveying direction from the predetermined size before the leading edge of the sheet in the conveying direction reaches the auxiliary conveying means. A sheet processing apparatus that reduces the speed of the conveying means to a second conveying speed that is slower than the first conveying speed before the shift means starts moving the sheet so as to move a sheet having a short length to the shift position. . a sheet conveying path along which a sheet is conveyed in a predetermined conveying direction; conveying means provided in the sheet conveying path for conveying a sheet of a predetermined size at a predetermined first conveying speed in the conveying direction; and the sheet conveying path a shift unit provided in the sheet width direction intersecting the conveying direction to move the sheet to a predetermined shift position in the sheet width direction; Auxiliary conveying means for assisting conveyance of short sheets, and control means for controlling the speed of conveying by the conveying means,
When conveying a sheet whose length in the conveying direction is shorter than the predetermined size, the control means controls the length of the sheet in the conveying direction from the predetermined size before the leading edge of the sheet in the conveying direction reaches the auxiliary conveying means. A sheet processing apparatus for reducing the speed of the conveying means to a second conveying speed lower than the first conveying speed while the sheet is moved by the shifting means so as to move a sheet having a short length to the shift position. the control means includes sheet detection means for detecting that a sheet has been conveyed to the sheet conveying path on the upstream side of the shift means in the conveying direction;
3. The sheet processing apparatus according to claim 1, wherein the control means controls the shift means to move the sheet to the predetermined shift position based on the result of sheet detection by the sheet detection means. 4. After the sheet is conveyed for a predetermined period of time after the sheet is detected by the sheet detecting means , the control means starts the shift operation of the sheet by the shift means and controls the speed reduction of the sheet conveying speed. The sheet processing apparatus according to . After the sheet is moved to the predetermined shift position by the shift means, the control means shifts the conveying means from the first conveying speed to a third conveying speed faster than the second conveying speed. 3. The sheet processing apparatus according to claim 1, wherein speed is controlled. 6. The sheet processing apparatus according to claim 5 , wherein the third conveying speed is equal to or higher than the first conveying speed. The auxiliary conveying means is composed of a pair of rollers capable of contacting and separating from the sheet,
3. When a sheet having a length in the conveying direction shorter than the predetermined size is conveyed, the roller pair abuts, and when a sheet of the predetermined size is conveyed, the roller pair separates. The sheet processing apparatus according to . 8. An image forming apparatus, comprising: the sheet processing apparatus according to claim 1 , provided inside an image forming apparatus main body for forming an image on a sheet.

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