Sheet processing apparatus and image forming system

Abstract

To provide a configuration capable of reducing operation noise in switchbackless shift discharge processing.SOLUTION: In a case where the switchback-less shift discharge processing is performed on the small sheet S2, after the sheet is moved in the shift direction by the pair of alignment plates 271A and 271B, the sheet is discharged to the stacking tray 300 in a state where the pair of alignment plates 271A and 271B are moved from the position where the pair of alignment plates 271A and 271B nip the sheet to a position where the pair of alignment plates 271A and 271B are separated from the sheet in the sheet-width direction without stopping the pair of alignment plates 271A and 271B.SELECTED DRAWING: Figure 23

Description

[Technical Field]

[0001] The present invention relates to a sheet processing apparatus that performs a binding process on sheets, and an image forming system that includes the sheet processing apparatus. [Background technology]

[0002] Patent Document 1 describes a sheet processing device configured to perform a binding discharge process in which a sheet is transported to a processing tray, the sheet is switched back on the processing tray, the trailing end of the sheet is pressed against a trailing end regulating section, and the sheet is bound and discharged onto a stacking tray, and a switchbackless shift discharge process in which the sheet is moved in a shift direction intersecting the transport direction by a pair of alignment plates without being switched back, and is discharged onto a stacking tray.

[0003] In the switchback-less shift discharge process described above, a pair of alignment plates (alignment members) moves a sheet in the shift direction, then the pair of alignment plates move to a retracted position away from the sheet, away from the position where the sheet is clamped, and the sheet is then discharged onto the stack tray by the discharge rollers. If the pair of alignment plates are not retracted too far from the sheet at the retracted position, the sheet is guided by the pair of alignment plates when it is discharged, thereby preventing skew. On the other hand, if the pair of alignment plates are positioned too close to the sheet at the retracted position, there is a risk that one corner of the trailing edge of the sheet may come into contact with the alignment plate due to skew when the trailing edge of the sheet passes through the discharge rollers. If the corner of the trailing edge of the sheet hits the alignment plate, resistance may be created during sheet discharge, potentially causing the trailing edge of the sheet to lean against the wall at the upstream end of the stack tray in the discharge direction, resulting in poor sheet stack alignment.

[0004] Therefore, it is conceivable to move the pair of alignment plates from the above-mentioned retracted position to a further retracted position before the trailing edge of the sheet passes through the discharge rollers. In other words, it is conceivable to retract the pair of alignment plates in two stages when discharging the sheet in the switchback-less shift discharge process. This makes it possible to suppress skew when discharging the sheet and to prevent the corners of the trailing edge of the sheet from hitting the alignment plates. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-20999 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-described configuration, the operation of retracting the pair of alignment plates in two stages is more complicated than the operation of retracting them in one stage, resulting in increased operating noise.

[0007] Here, large-size sheets (large sheets) that are long in the conveying direction tend to have a large amount of skew during sheet conveyance, while small-size sheets (small sheets) that are short in the conveying direction tend to have a small amount of skew during sheet conveyance. Also, depending on the usage situation, small sheets may be used more frequently. Therefore, if the pair of alignment plates is retracted in two stages even for small sheets, the impact of increased operating noise will be significant.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a configuration that can reduce operating noise during a switchback-less shift ejection process. [Means for solving the problem]

[0009] One aspect of the present invention is a sheet conveying device including a first conveying member that conveys a sheet in a first conveying direction, a loading section that loads the sheet conveyed by the first conveying member, abutting sections against which an upstream edge of the sheet on the loading section in the first conveying direction is abutted, a second conveying member that conveys the sheet in a second conveying direction in which the upstream edge of the sheet on the loading section in the first conveying direction faces the abutting section, and second conveying members that are arranged on both sides of the sheet abutted against the abutting sections in a sheet width direction that intersects with the first conveying direction and align the sheet abutted against the abutting sections in the sheet width direction. a pair of alignment members, a drive section that moves the pair of alignment members in the sheet width direction, a binding unit that performs a binding process on a sheet bundle made up of a plurality of sheets that have been aligned in the sheet width direction by the pair of alignment members, a stacking section that stacks the bound sheets, a pair of discharge rotors that discharge the sheets in a discharge direction toward the stacking section, and a control section that controls the drive section, wherein the pair of alignment members extend from an upstream side to a downstream side of the pair of discharge rotors in the discharge direction, and the control section controls the first conveying member to move the first conveying member in the sheet width direction, a mode in which a sheet conveyed in the first conveying direction by the pair of alignment members is nipped by the pair of alignment members without being conveyed in the second conveying direction by the second conveying member, and is moved in a shift direction that is one of both sides in the sheet width direction, and then discharged to the stacking section; when the mode is executed for a sheet whose length in the first conveying direction is longer than a predetermined length, after the sheet is moved in the shift direction by the pair of alignment members, the pair of alignment members are moved to a first retracted position for restricting movement of the sheet in the sheet width direction when a skewed sheet abuts against either of the pair of alignment members in a state where the pair of alignment members are further away from the sheet in the sheet width direction than a position where the sheet is nipped, and the sheet is conveyed in the discharge direction by the pair of discharge rotors; before an upstream end of the sheet in the discharge direction passes a discharge nip portion formed by the pair of discharge rotors, the pair of alignment members are retracted to a second retracted position retracted further from the sheet than the first retracted position; and the sheet is discharged to the stacking section by the pair of discharge rotors with the pair of alignment members at the second retracted position;When the mode is executed for a sheet whose length in the first transport direction is equal to or shorter than the predetermined length, the sheet is moved in the shift direction by the pair of alignment members, and then the pair of alignment members are moved without stopping from a position where the pair of alignment members clamp the sheet to a position where the pair of alignment members are spaced apart from the sheet in the sheet width direction, and the sheet is discharged to the stacking portion by the pair of discharge rotors.

[0010] One aspect of the present invention includes an image forming unit that forms an image on a sheet, a first conveying member that conveys the sheet on which the image has been formed by the image forming unit in a first conveying direction, a loading unit that places the sheet conveyed by the first conveying member, abutting portion against which an upstream end edge of the sheet on the loading unit in the first conveying direction is abutted, a second conveying member that conveys the sheet in a second conveying direction in which the upstream end edge of the sheet on the loading unit in the first conveying direction faces the abutting portion, and a second conveying member that conveys the sheet in a second conveying direction in which the upstream end edge of the sheet on the loading unit in the first conveying direction faces the abutting portion, and a pair of alignment members arranged to align the sheets in the sheet width direction when the sheets are abutted against the abutment portion; a drive portion that moves the pair of alignment members in the sheet width direction; a binding unit that performs a binding process on a sheet bundle made up of a plurality of sheets that have been aligned in the sheet width direction by the pair of alignment members; a stacking portion that stacks the bound sheets; a pair of discharge rotating bodies that discharge the sheets in a discharge direction toward the stacking portion; and a control portion that controls the drive portion, the control unit is configured to extend from the upstream side to the downstream side with respect to the sheet conveying unit, and the control unit is capable of executing a mode in which a sheet conveyed in the first conveying direction by the first conveying member is sandwiched between the pair of alignment members without being conveyed in the second conveying direction by the second conveying member, and the sheet is moved in a shift direction that is one of both sides in the sheet width direction, and then discharged to the stacking unit; when executing the mode for a sheet whose length in the first conveying direction is longer than a predetermined length, after moving the sheet in the shift direction by the pair of alignment members, the control unit moves the pair of alignment members to a first retracted position for restricting movement of the sheet in the sheet width direction when a skewed sheet abuts against either of the pair of alignment members in a state where the pair of alignment members are spaced apart from the sheet in the sheet width direction from a position where the sheet is sandwiched, and conveys the sheet in the discharge direction by the pair of discharge rotating bodies in this state; and before an upstream end of the sheet in the discharge direction passes through a discharge nip portion formed by the pair of discharge rotating bodies, the control unit retracts the pair of alignment members to a second retracted position retracted further from the sheet than the first retracted position,an image forming system in which the pair of alignment members are in the second retracted position, the pair of discharge rotors discharge the sheet to the stacking portion, and when the mode is executed for a sheet whose length in the first transport direction is equal to or shorter than the predetermined length, the pair of alignment members move the sheet in the shift direction, and then the pair of alignment members are moved from a position where the sheet is sandwiched to a position where the pair of alignment members are spaced apart from the sheet in the sheet width direction without stopping, and the sheet is discharged to the stacking portion by the pair of discharge rotors; [Effects of the Invention]

[0011] According to the present invention, it is possible to reduce the operating noise during the switchback-less shift ejection process. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of an image forming system according to a first embodiment. [Figure 2] 1 is a cross-sectional view showing a schematic configuration of a sheet processing apparatus according to a first embodiment. [Figure 3] 1 is a schematic perspective view showing a sheet processing apparatus according to a first embodiment with an upper cover removed; [Figure 4] FIG. 4 is a side view showing the upper discharge roller and the lower discharge roller in a first separated position according to the first embodiment. [Figure 5] FIG. 4 is a side view showing the upper discharge roller and the lower discharge roller in a second separated position according to the first embodiment. [Figure 6] FIG. 2 is a plan view of a pair of alignment plates and the surrounding configuration according to the first embodiment, as viewed from above. [Figure 7] FIG. 2 is a plan view showing the pair of alignment plates and the surrounding configuration according to the first embodiment, as viewed from below. [Figure 8] 1A is a perspective view of a front-side alignment plate and its surrounding configuration according to the first embodiment, as seen from below, and FIG. 1B is a plan view of the same as seen from below. [Figure 9] 5A and 5B are schematic diagrams illustrating a clamping position, a first retracted position, and a second retracted position of a pair of alignment plates according to the first embodiment. [Figure 10] 4 is a table showing the correspondence between each motor and each component of the sheet processing apparatus according to the first embodiment. [Figure 11] FIG. 2 is a block diagram showing a control configuration of the sheet processing apparatus according to the first embodiment. [Figure 12] 6 is a flowchart showing an example of a control flow of the sheet processing apparatus according to the first embodiment. [Figure 13] 1A is a schematic diagram of a main part of a sheet processing apparatus at a home position of a switchback-less shift discharge process according to a first embodiment, as viewed from above, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 14] 1A is a schematic diagram of a main part of a sheet processing apparatus when receiving a sheet in a switchback-less shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 15] 1A is a schematic diagram of a main part of a sheet processing apparatus when an upper discharge roller is lowered in a switchback-less shift discharge process according to a first embodiment, and FIG. 1B is a cross-sectional view of the schematic configuration. [Figure 16] 1A is a schematic diagram of a main part of the sheet processing apparatus when an alignment plate moves in a switchback-less shift discharge process according to a first embodiment, and FIG. 1B is a cross-sectional view of the schematic configuration. [Figure 17] 1A is a schematic diagram of a main part of the sheet processing apparatus when a sheet is shifted by an alignment plate in a switchback-less shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration. [Figure 18] 1A is a schematic diagram of a main part of the sheet processing apparatus when shifting of a sheet is completed in a switchback-less shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 19] 1A is a schematic diagram of a main part of the sheet processing apparatus when an alignment plate is retracted in a switchback-less shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration. [Figure 20] 1A is a schematic diagram of a main part of a sheet processing apparatus when discharging a sheet in a switchback-less shift discharging process according to a first embodiment, as viewed from above, and FIG. 1B is a schematic cross-sectional view of the configuration. [Figure 21] 1A is a schematic diagram of a main part of the sheet processing apparatus when sheet discharge in the switchback-less shift discharge process according to the first embodiment is completed, and FIG. 1B is a schematic cross-sectional view of the configuration. [Figure 22] 1A and 1B are schematic diagrams showing the main parts of a sheet processing device from above when the switchback-less shift discharge process according to the first embodiment is applied to a large sheet, in which (a) the large sheet is shifted by an alignment plate, (b) the alignment plate is in a first retracted position, and (c) the alignment plate is in a second retracted position. [Figure 23] 1A and 1B are schematic diagrams showing the main parts of a sheet processing device from above when the switchback-less shift discharge process according to the first embodiment is applied to small sheets, in which (a) the state in which the small sheets have been shifted by the alignment plate and (b) the state in which the alignment plate is in the second retracted position are shown. [Figure 24] FIG. 11 is a cross-sectional view showing a schematic configuration of a sheet processing apparatus when a trailing end dropping member is lowered in a switchback-less shift discharge process according to a second embodiment. [Figure 25] 11A is a schematic diagram of a main part of a sheet processing apparatus when a sheet is shifted by an alignment plate in a switchback-less shift discharge process according to a third embodiment, and FIG. 11B is a schematic cross-sectional view of the configuration. [Figure 26] This is a cross-sectional view of the schematic configuration of a sheet processing device during binding and discharge processing in the first embodiment, in which (a) shows the state in which sheets are transported, (b) shows the state in which a sheet bundle is formed and aligned on the processing tray, and (c) shows the state in which the bound sheet bundle is discharged to the stacking tray. [Figure 27] 10 is a perspective view showing a state in which an unbound sheet bundle is formed on the stacking tray and moved in the shift direction. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] First Embodiment The first embodiment will be described with reference to Figures 1 to 24, 26 and 27. First, the schematic configuration of an image forming system of this embodiment will be described with reference to Figure 1.

[0014] [Image formation system] FIG. 1 is a cross-sectional view showing a schematic configuration of an image forming system according to this embodiment. The image forming system 1000 includes an image forming apparatus 100 and a sheet processing apparatus 200. The image forming apparatus 100 may be a copier, printer, facsimile, or a multifunction device having multiple functions of these, and forms an image on a sheet such as paper or a plastic sheet. In this embodiment, the image forming apparatus 100 is an electrophotographic printer, and a sheet on which a toner image has been formed is discharged from a discharge port 101. Note that the image forming apparatus 100 may also be an inkjet image forming apparatus.

[0015] The image forming apparatus 100 of this embodiment includes an image forming apparatus main body 110 and an image reading device 120 disposed above the image forming apparatus main body 110. In the image forming apparatus main body 110, a toner image is formed on a sheet in an image forming unit 103. The image forming unit 103 of this embodiment forms a full-color toner image using toner of four colors: yellow (y), magenta (m), cyan (c), and black (k). For this reason, the image forming unit 103 has multiple image forming stations that form toner images of each color. The configuration of the image forming stations for each color is the same except for the color of the toner.

[0016] In the image forming station for each color, the surface of the photosensitive drum 10 is charged by a charging member 11 and exposed to light by an exposure device (not shown), thereby forming an electrostatic latent image on the photosensitive drum 10. This electrostatic latent image is then developed with a developer by a developing device 12 to form a toner image. The toner image formed on the photosensitive drum 10 is primarily transferred onto an intermediate transfer belt 14 by a primary transfer roller 13. Residual toner remaining on the photosensitive drum 10 after the primary transfer is removed by a drum cleaner 15.

[0017] This cycle of charging, exposure, development, primary transfer, and drum cleaning is repeated in the same way at each image forming station, and toner images of yellow, magenta, cyan, and black are transferred onto the intermediate transfer belt 14 in succession, forming a full-color toner image.

[0018] Meanwhile, the image forming apparatus 100 has a plurality of cassettes 20 as storage units for storing sheets. As a feed roller 21 rotates, the sheets stored in each cassette 20 are transported to a sheet transport path 22 and reach a registration roller 23. The registration roller 23 feeds the sheet to a secondary transfer unit 17 formed by the intermediate transfer belt 14 and a secondary transfer roller 16 in synchronization with the toner image on the intermediate transfer belt 14. The multi-color toner image formed on the intermediate transfer belt 14 is secondarily transferred onto the sheet all at once in the secondary transfer unit 17. Any residual toner and paper dust remaining on the intermediate transfer belt 14 after the secondary transfer is removed by a belt cleaner 18.

[0019] The sheet that has passed through the secondary transfer unit 17 is transported to the fixing device 30, which serves as an image heating device. The fixing device 30 has a heating roller 31 and a pressure roller 32, which form a heating nip portion that sandwiches and transports the sheet between them. The sheet transported to the fixing device 30 is heated and pressurized in the heating nip portion, and the unfixed toner image is fixed onto the sheet. The sheet with the fixed toner image is transported along the discharge transport path 24 and is discharged to the outside of the apparatus through the discharge port 101 by the discharge rollers 25, completing the series of image forming operations.

[0020] As described above, the image forming apparatus 100 of this embodiment includes the image forming apparatus main body 110 and the image reading device 120. The image reading device 120 reads an image on a document placed on the platen glass 122 using the image reading unit 121, and sends the read image signal to the image forming apparatus main body 110. In addition, an automatic document feeder (ADF) 123 that transports the document to the image reading unit 121 is disposed above the image reading device 120. The image reading device 120 can also read an image on a document fed by the automatic document feeder 123.

[0021] The image forming apparatus main body 110 has a first housing section 111 in which the image forming section 103 and the like are arranged, and a second housing section 112 in which the discharge conveying path 24 and discharge rollers 25 are arranged, and the second housing section 112 is provided above the first housing section 111. The image reading device 120 is provided above the second housing section 112. In addition, the second housing section 112 is provided with an operation panel (not shown) that allows the user to input instructions (printing conditions, mode settings, etc.) to the image forming apparatus 100 and the sheet processing apparatus 200.

[0022] In this embodiment, with this configuration, an internal space 130 is formed which is surrounded by the first housing 111, the second housing 112, and the image reading device 120. A sheet is discharged from the discharge port 101 of the image forming apparatus main body 110 into the internal space 130. A sheet processing device 200 and the like are detachably attached to this internal space 130. In this embodiment, the image forming system 1000 is configured by attaching the sheet processing device 200, but other sheet processing devices may also be attached.

[0023] The sheet processing apparatus 200 is connected to the discharge port 101 and receives sheets discharged from the discharge port 101. As will be described in detail later, the sheet processing apparatus 200 can perform predetermined processing such as binding on the sheets.

[0024] [Sheet processing device] The configuration of the sheet processing apparatus 200 of this embodiment will be described with reference to Figs. 2 to 16. First, the overall configuration of the sheet processing apparatus 200 will be described with reference to Figs. 2 and 3. In the following description, the front side (front (F) side) is one side in the sheet width direction perpendicular to the sheet conveying direction (the near side in Fig. 2, the near right side in Fig. 3) where an operator operates the image forming system 1000, for example, the side where an operation panel is installed. The rear side (rear (R) side) is the opposite side to the front side and the other side in the sheet width direction (the far side in Fig. 2, the far left side in Fig. 3).

[0025] [Overall configuration of sheet processing device] The sheet processing apparatus 200 includes a conveying path 210A, pre-processing rollers 211A and 212A as first conveying members, a processing tray 220 as a loading section, an upper discharge roller (nip member) 230A and a lower discharge roller 230B as a pair of discharge rotors (discharge section), a take-in paddle 240A as a second conveying member, a trailing end dropping member 250A as a sheet dropping section, an alignment section 270A as a first and second shift section, a return member 280, a trailing end regulating member 290 as an abutment section, a stacking tray 300 as a stacking section, and a discharge sheet take-in paddle (sheet pressing paddle) 320A as a take-in section. A sheet received from the image forming apparatus 100 is conveyed to the conveying path 210A.

[0026] The sheets conveyed from the conveying path 210A are either directly discharged to the stacking tray 300 or placed on the processing tray 220 depending on the sheet processing mode. Direct discharge to the stacking tray 300 means that the sheets are discharged to the stacking tray 300 without being conveyed back to a position on the processing tray 220 where stapling (binding) can be performed. In other words, the sheet processing apparatus 200 has a mode in which sheets stapled by the staple unit 400 are discharged to the stacking tray 300, and a mode in which sheets are discharged to the stacking tray 300 without being stapled by the staple unit 400. In this embodiment, the sheets can be aligned by a pair of alignment plates 271A and 271B of the alignment section 270A without being placed on the processing tray 220. Furthermore, sheets can also be aligned on the processing tray 220, and the sheets placed on the processing tray 220 can be stapled by the staple unit 400. Furthermore, the sheets or sheet stack placed on the processing tray 220 can be discharged onto the stacking tray 300 by a pair of discharge rotating bodies, such as an upper discharge roller 230A and a lower discharge roller 230B. The configuration of each part will be described in detail below.

[0027] [Transport path] Conveying path 210A is a path for conveying a sheet in a first conveying direction (a predetermined direction), and includes an upper guide 2101 that guides the upper surface of the sheet being conveyed, and a lower guide 2102 that guides the lower surface of the sheet. Pre-processing rollers 211A and 212A and upstream rollers (inlet rollers) 213a and 213b are arranged on conveying path 210A. These are arranged in pairs so as to be spaced apart in the sheet width direction (arrow γ direction in FIG. 3; hereinafter, simply referred to as the "width direction" or "sheet width direction") that intersects with the sheet conveying direction (first conveying direction, arrow β direction (left-right direction) in FIG. 2).

[0028] The pre-processing rollers 211A and 212A are a first transport member and a pair of transport rotors that transport a sheet in a first transport direction, and at least one of them rotates while sandwiching the sheet. The upstream rollers 213a and 213b are at least one of them that rotate while sandwiching the sheet. The upstream rollers 213a and 213b are arranged at the entrance of the sheet processing apparatus 200, and receive the sheet transported from the upstream side of the sheet processing apparatus 200 and transport it to the transport path 210A. Then, the sheet that has passed through the transport path 210A reaches the pre-processing rollers 211A and 212A.

[0029] The pre-processing rollers 211A and 212A form a pre-processing nip portion 211a that can sandwich and transport a sheet. The pre-processing nip portion 211a sandwiches the sheet and transports it in the first transport direction, and the sheet is discharged from the transport path 210A. The pre-processing rollers 211A and 212A can be brought into contact with or separated from each other, and the nip pressure can be changed.

[0030] [Processing tray] The processing tray 220 serving as a placement unit is disposed downstream of the conveying path 210A in the sheet conveying direction (first conveying direction) and vertically below the conveying path 210A. The processing tray 220 is inclined with respect to the horizontal plane so that the upstream side in the first conveying direction is lower than the downstream side. The processing tray 220 temporarily places sheets conveyed to the downstream side in the first conveying direction by the pre-processing rollers 211A and 212A. The processing tray 220 can hold multiple sheets stacked on top of each other, and an alignment unit 270A aligns the sheets in the width direction and moves them in the width direction (shifts the sheets) on the processing tray 220. In this embodiment, "shifting" refers to moving a sheet to the front and / or rear of a sheet conveyed by the pre-processing rollers 211A and 212A based on the sheet's center. The shift discharge process described below includes two patterns: moving a sheet to the front and discharging it, then discharging another sheet to the rear, and discharging a sheet based on the center and then discharging another sheet to the front or rear. Discharging a next sheet by shifting it to the front or rear of a previously discharged sheet is also considered shift discharge. At the upstream end of the processing tray 220 in the first transport direction, a trailing edge regulating member 290 is disposed as an abutment against which the upstream edge (rear end) of a sheet placed on the processing tray 220 in the first transport direction abuts. A portion of the processing tray 220 (for example, the downstream end in the first transport direction) may protrude vertically above the transport path 210A.

[0031] Furthermore, a staple unit 400 serving as a binding unit (processing section) is disposed upstream of the processing tray 220 in the first transport direction. The staple unit 400 performs a predetermined process, stapling (binding), on a sheet stack (plurality of sheets) that has been aligned in the width direction and has its trailing edge regulated by the processing tray 220. The staple unit 400 is capable of changing the staple position on the sheet stack and moves in accordance with the staple position. Note that the predetermined process may be other processes such as punching in addition to stapling. The sheets or sheet stack placed on the processing tray 220 are discharged onto the stacking tray 300 by upper discharge rollers 230A and lower discharge rollers 230B, as will be described later.

[0032] [Scraping paddle] The take-in paddle 240A as a second conveying member conveys (switchback conveys) the sheet on the processing tray 220 in a second conveying direction in which the upstream edge in the first conveying direction of the sheet is directed toward the trailing end regulating member 290. The take-in paddle 240A has a paddle portion 2401 as a rotating member, a paddle arm 2402 as a support portion that supports the paddle portion 2401, and a swing fulcrum 2403 that swingably supports the paddle arm 2402. That is, the paddle arm 2402 can swing up and down around the swing fulcrum 2403, and the paddle portion 2401 is rotatably provided at the tip of the paddle arm 2402.

[0033] The pickup paddle 240A can swing about a swing fulcrum 2403 between a return position where the paddle portion 2401 abuts against the upper surface of a sheet on the processing tray 220 to convey the sheet in the second conveyance direction, and an upper retracted position where the paddle portion 2401 is retracted above the return position. The swing fulcrum 2403 is located upstream in the first conveyance direction of a pre-processing nip portion 211a, which is a nip position where a sheet is sandwiched between the pre-processing rollers 211A and 212A, and vertically above the pre-processing nip portion 211a. The paddle arm 2402 extends downstream in the first conveyance direction from the swing fulcrum 2403, and the paddle portion 2401 is provided at its tip. As shown in FIG. 3, a pair of pickup paddles 240A are located on both sides in the width direction of an upper discharge roller 230A, which will be described later.

[0034] [Rear end drop member] A pair of trailing end drop members 250A serving as sheet droppers are provided on both sides of the pair of take-in paddles 240A. That is, the pair of trailing end drop members 250A are arranged on both sides of the take-in paddles 240A in the width direction, and as will be described later, move up and down in conjunction with the take-in paddles 240A, thereby coming into contact with the upper surface of the sheet on the upstream side in the first conveyance direction, and operating to drop the upstream end (trailing end) of the sheet toward the processing tray 220. Note that the trailing end drop members 250A may be operated by a drive separate from the take-in paddles 240A.

[0035] The trailing end dropping member 250A has a rotation shaft 2501 as a rotation center downstream in the first transport direction of the pre-processing rollers 211A and 212A, which are a pair of transport rollers. The trailing end dropping member 250A extends upstream in the first transport direction from the rotation shaft 2501 and is rotatable about the rotation shaft 2501 between an upper position above the pre-processing rollers 211A and 212A and a lower position below the pre-processing rollers 211A and 212A. By rotating from the upper position to the lower position, the trailing end dropping member 250A abuts from above against the sheet transported by the pre-processing rollers 211A and 212A and drops the sheet onto the processing tray 220 below. That is, the trailing end drop member 250A moves from a position higher than the sheet being transported in the first transport direction by the pre-processing rollers 211A, 212A to a position lower than the sheet in the vertical direction, thereby dropping the upstream end (trailing end) in the first transport direction of the sheet transported in the first transport direction by the pre-processing rollers 211A, 212A toward the processing tray 220.

[0036] [Return part] The returning member 280 further transports the sheet transported by the take-in paddle 240A toward the trailing end regulating member 290 as described above, toward the trailing end regulating member 290, and brings the trailing end of the sheet into contact with the trailing end regulating member 290, thereby regulating the position of the trailing end of the sheet. The returning member 280 is formed by a knurled belt 281, and by driving and rotating the knurled belt 281, further takes in the sheet transported upstream in the first transport direction by the take-in paddle 240A, and brings the trailing end into contact with the trailing end regulating member 290. The returning member 280 is movable between a contact position where it can contact the sheet and a retracted position retracted upward from the contact position, and moves to the contact position when transporting the sheet toward the trailing end regulating member 290, and to the retracted position when transporting a sheet on the processing tray 220 toward the stacking tray 300.

[0037] [Ejection roller] The upper discharge roller (upper discharge rotor) 230A and the lower discharge roller (lower discharge rotor) 230B constitute a pair of discharge rotors and a discharge section, and discharge a sheet in a discharge direction toward the stacking tray 300. That is, the upper discharge roller 230A and the lower discharge roller 230B transport and discharge the sheet, which has been transported downstream in the first transport direction by the pre-processing rollers 211A and 212A, downstream in the first transport direction from the processing tray 220. Furthermore, at least one discharge roller (discharge rotor) of the upper discharge roller 230A and the lower discharge roller 230B is movable between a nip position where the upper discharge roller 230A and the lower discharge roller 230B nip the sheet, and a separated position where the upper discharge roller 230A and the lower discharge roller 230B are spaced apart from the nip position. In this embodiment, the upper discharge roller 230A, which is one of the discharge rotors, can move to a nip position (contact position) where it nips a sheet between itself and the lower discharge roller 230B, and to a separation position where it retreats upward from the nip position and the upper discharge roller 230A and the lower discharge roller 230B are spaced apart from each other from the nip position. That is, the upper discharge roller 230A functions as a nipping member that nips a sheet between itself and the lower discharge roller 230B at the nip position. The upper discharge roller 230A and the lower discharge roller 230B are arranged in pairs, spaced apart in the width direction of the sheet. In this embodiment, they are arranged inside the pair of pick-up paddles 240A in the width direction. The lower discharge roller 230B may move vertically to move between the nip position and the separation position, or both discharge rollers 230A and 230B may move individually to move the nip position to the separation position.

[0038] The upper discharge roller 230A and the lower discharge roller 230B sandwich a sheet or a sheet stack at a nip position, and the sandwiched sheet or sheet stack is conveyed by, for example, the rotation of the lower discharge roller 230B. The upper discharge roller 230A is a driven roller that rotates following the rotation of the lower discharge roller 230B, but it may also be driven. That is, in this embodiment, the upper discharge roller 230A is a driven rotating body, and the lower discharge roller 230B is a driving rotating body. The upper discharge roller 230A also functions as a nipping member that can sandwich a sheet between itself and the lower discharge roller 230B at the nipping position, but this nipping member may be another rotating body such as a belt instead of a roller, or may be a contact member that abuts against the sheet without rotating, such as a lever member.

[0039] Furthermore, the lower discharge roller 230B may be a rotating body such as a belt instead of a roller. When the lower discharge roller 230B as the lower discharge rotating body is an endless belt, for example, this belt is stretched over a plurality of rollers, and the outer circumferential surface of the belt stretched over one of the rollers comes into contact with a nip member such as the upper discharge roller 230A to form the discharge nip portion 230a (see FIG. 19(b) described later). In this case, the rotation axis of the lower discharge rotating body is the rotation axis of the roller that stretches the belt at a position that forms the discharge nip portion 230a.

[0040] The upper discharge roller 230A is rotatable about a rotation shaft 2301 between the nip position and the separation position. In other words, the upper discharge roller 230A can move up and down between the nip position and the separation position. As will be described in detail later, there are two separation positions, and the upper discharge roller 230A can move between a first separation position and a second separation position. The upper discharge roller 230A is provided at the tip of a discharge arm 2302 serving as a support. The rotation shaft 2301 is provided coaxially with the swing fulcrum 2403 and is located upstream in the first conveying direction of the pre-processing nip portion 211a where the pre-processing rollers 211A and 212A hold the sheet, and vertically above the pre-processing nip portion 211a. The discharge arm 2302 extends downstream in the first conveying direction from the rotation shaft 2301, and the upper discharge roller 230A is provided at the tip of the discharge arm 2302. The rotation shaft 2301 does not have to be arranged coaxially with the swing fulcrum 2403, but in this embodiment, the rotation shafts of the upper discharge roller 230A and the pick-up paddle 240A are arranged coaxially.

[0041] The rotation shaft 2301 is disposed upstream in the first conveying direction of a discharge nip portion where the upper discharge roller 230A nips the sheet between the lower discharge roller 230B and the upper discharge roller 230A at the nip position. Moreover, the upper discharge roller 230A is located vertically above the pre-processing nip portion 211a where the pre-processing rollers 211A and 212A nip the sheet at the separated position, and the rotation shaft 2301 is located vertically above the center of the upper discharge roller 230A at the separated position.

[0042] Because the positional relationship between the rotation shaft 2301 and the pre-processing nip portion 211a is defined as described above, the upper discharge roller 230A allows the sheet that has passed through the pre-processing nip portion 211a to move toward the stacking tray 300 when in the separated position. Meanwhile, the upper discharge roller 230A moves downward from the separated position toward the nip position by rotating counterclockwise in FIG. 2 about the rotation shaft 2301. Then, when the upper discharge roller 230A moves to the nip position, the sheet can be sandwiched between the upper discharge roller 230A and the lower discharge roller 230B.

[0043] [First and second separation positions] As described above, the upper discharge roller 230A has a first separation position and a second separation position. Fig. 4 shows a state in which the upper discharge roller 230A is at the first separation position, and Fig. 5 shows a state in which the upper discharge roller 230A is at the second separation position, each of which shows the periphery of the upper discharge roller 230A and the lower discharge roller 230B as viewed from the side (one side in the width direction of the sheet, the front side). As shown in Fig. 4, the first separation position is a position in which the upper discharge roller 230A is further away from the lower discharge roller 230B than the nip position, and as shown in Fig. 5, the second separation position is a position in which the upper discharge roller 230A and the lower discharge roller 230B are further away from each other than the nip position, and the distance between the upper discharge roller 230A and the lower discharge roller 230B is narrower than the first separation position.

[0044] Here, the distance between the upper discharge roller 230A and the lower discharge roller 230B when they are in the first spaced position is defined as d1 ( FIG. 4 ), and the distance between the upper discharge roller 230A and the lower discharge roller 230B when they are in the second spaced position is defined as d2 ( FIG. 5 ). Furthermore, with respect to the first conveyance direction (the direction of the arrow β), the vertical height of the pair of alignment plates 271A and 271B at the same position as the rotation center O of the upper discharge roller 230A when they are in the second spaced position is defined as d3 ( FIG. 5 ). That is, as shown in FIG. 5 , if a vertical line passing through the rotation center O of the upper discharge roller 230A is defined as an imaginary line L, the height of the alignment plates 271A and 271B at the portion where the imaginary line L passes is defined as d3. The gap of the distance d2 at the second spaced position at least partially overlaps with the range of the height d3 of the pair of alignment plates 271A and 271B when viewed in the width direction.

[0045] In this embodiment, the magnitude relationship among d1, d2, and d3 is d2 < d1 < d3. For example, d1 is 12.4 mm, d2 is 5 mm, and d3 is 13 mm. Also, when viewed from one side in the width direction of the sheet, a portion including the lower end portion in the vertical direction of the upper discharge roller 230A at the second separation position and a part of the space below it are at positions overlapping the pair of alignment plates 271A and 271B. Further, the gap between the lower end portions of the alignment plates 271A and 271B where the virtual line L passes and the lower discharge roller 230B is small. Therefore, when the alignment plates 271A and 271B move in the width direction in a direction approaching the sheet, the sheet between the upper discharge roller 230A and the lower discharge roller 230B in the state at the second separation position will come into contact with the alignment plates 271A and 271B. In this embodiment, also at the first separation position, when viewed from one side in the width direction of the sheet, a portion including the lower end portion in the vertical direction of the upper discharge roller 230A and a part of the space below it are arranged to overlap the pair of alignment plates 271A and 271B. Also, when viewed from one side in the width direction of the sheet, a portion including the upper end portion in the vertical direction of the lower discharge roller 230B may also be configured to overlap the pair of alignment plates 271A and 271B.

[0046] [Alignment portion] Regarding the alignment portion 270A as a shift portion, in addition to FIGS. 2 and 3, FIGS. 6 to 9 will be used for explanation. The alignment portion 270A moves the sheet in the shift direction (sheet width direction) intersecting the first conveyance direction while being in contact with the edge along the first conveyance direction of the sheet conveyed to the downstream side in the first conveyance direction by the pre-processing rollers 211A and 212A. Such an alignment portion 270A has a pair of alignment plates 271A and 271B as a pair of alignment members arranged to face each other in the shift direction, as shown in FIGS. 6 and 7. Note that FIG. 6 is a plan view of the alignment portion 270A viewed from above in the vertical direction, and FIG. 7 is a plan view of the alignment portion 270A viewed from below in the vertical direction.

[0047] The pair of alignment plates 271A, 271B are disposed further downstream than the downstream end of the conveying path 210A in the first conveying direction and align the sheet in the width direction by moving in the width direction and abutting against the width direction edge of the sheet. In this embodiment, the alignment plates 271A, 271B are disposed on both sides of the width direction of the sheet placed on the processing tray 220 and are movable in the width direction. The pair of alignment plates 271A, 271B extend from the upstream side to the downstream side of the upper discharge roller 230A and the lower discharge roller 230B in the discharge direction. That is, the pair of alignment plates 271A, 271B are disposed so as to straddle the upper discharge roller 230A and the lower discharge roller 230B in the first conveying direction. Therefore, a portion of the pair of alignment plates 271A, 271B, including their downstream ends in the discharge direction, is located downstream of the upper discharge roller 230A and the lower discharge roller 230B in the first conveying direction. The pair of alignment plates 271A and 271B have the same configuration.

[0048] As shown in FIGS. 6 and 7, the pair of alignment plates 271A, 271B are moved in the shift direction by the drive of a front-side (F-side) alignment plate movement motor MT16 and a rear-side (R-side) alignment plate movement motor MT17, which serve as drive units. That is, a pinion gear 2711 is provided on the drive shaft of each of the F-side alignment plate movement motor MT16 and the R-side alignment plate movement motor MT17. Furthermore, a rack gear 2712 is provided on each of the alignment plates 271A, 271B. The pinion gear 2711 and the rack gear 2712 are meshed with each other. The rack gear 2712 is disposed across the width direction and moves along the width direction as the pinion gear 2711 rotates. Furthermore, the pair of alignment plates 271A, 271B are each guided along a guide shaft 2713 disposed along the width direction. That is, drive transmission units 2717 including pinion gears 2711 and rack gears 2712 are disposed between the F-side alignment plate moving motor MT16 and the R-side alignment plate moving motor MT17 and the alignment plates 271A, 271B, respectively. The drive transmission units 2717 transmit the drive of the F-side alignment plate moving motor MT16 and the R-side alignment plate moving motor MT17 to the alignment plates 271A, 271B, moving the alignment plates 271A, 271B in the sheet width direction. Such drive transmission units 2717 may have a rack-and-pinion configuration or may have other configurations, such as a pulley and belt.

[0049] As a result, by driving the F-side alignment plate moving motor MT16, the alignment plate 271A on the front side (lower side in FIGS. 6 and 7) can be moved in the width direction, and by driving the R-side alignment plate moving motor MT17, the alignment plate 271B on the rear side (upper side in FIGS. 6 and 7) can be moved in the width direction. That is, in this embodiment, the alignment plates 271A and 271B can be moved independently.

[0050] Of the pair of alignment plates 271A, 271B, in the shift discharge process described below, the alignment plate 271B on the upstream side in the shift direction (one side in the width direction, the rear side in this embodiment) is referred to as the first shift part, and the alignment plate 271A on the downstream side in the shift direction (the other side in the width direction, the front side in this embodiment) is referred to as the second shift part. Also, the motor that drives the first shift part is referred to as the first drive part, and the motor that drives the second shift part is referred to as the second drive part.

[0051] As shown in FIG. 8A, the alignment plates 271A and 271B are formed so that their vertical widths are wider on the downstream side in the first transport direction. That is, the alignment plates 271A and 271B each include a first plate portion 2701 on the downstream side in the first transport direction and a second plate portion 2702 formed so as to be continuous with the first plate portion 2701 on the upstream side in the first transport direction. While FIG. 8A shows only the alignment plate 271A, the same applies to the alignment plate 271B. The first plate portion 2701 has a vertically larger area than the second plate portion 2702 so that it can contact the conveyed sheet even if the leading edge of the sheet is curled upward or downward. Meanwhile, the second plate portion 2702 is formed so that its vertical height is lower than that of the first plate portion 2701 so that it does not interfere with the trailing end dropping member 250A even when the trailing end dropping member 250A is positioned in the lower position. The upper edge of the second plate portion 2702 is inclined so as to become lower as it approaches the upstream side in the first transport direction.

[0052] The first plate portion 2701 is formed so as to straddle the upper discharge roller 230A and the lower discharge roller 230B from the upstream side to the downstream side in the first transport direction. This allows at least the first plate portion 2701 to come into contact with a sheet even when the sheet is discharged by a switchbackless shift discharge process, which is one of the shift discharge processes described below. The second plate portion 2702 is located above the processing tray 220 and is formed continuous with the first plate portion 2701 in the first transport direction. This allows at least the second plate portion 2702 to come into contact with a sheet placed on the processing tray 220 by a switchback shift discharge process, which is one of the shift discharge processes described below.

[0053] The first plate portion 2701 also has a curl suppressing portion 2703. The curl suppressing portion 2703 is provided vertically above the discharge nip portion 230a (see FIG. 19(b) described later), which is a nip position where the upper discharge roller 230A and the lower discharge roller 230B clamp the sheet, so as to straddle from the upstream side to the downstream side in the first conveyance direction, and to suppress the leading edge of the sheet that has curled upward. In this embodiment, the curl suppressing portion 2703 is an uneven portion formed on the inside in the width direction (the side that abuts against the sheet) from the upper end of the first plate portion 2701, and catches the widthwise edge of the curled sheet, thereby suppressing the leading edge of the sheet.

[0054] The alignment portion 270A of this embodiment further includes a biasing spring 2714 as a biasing portion that biases one (front side) alignment plate 271A of the pair of alignment plates 271A, 271B having the above-described configuration toward the other (rear side) alignment plate 271B. As shown in FIGS. 8(a) and 8(b), the front side alignment plate 271A is supported via a support portion 2715 fixed to the alignment plate 271A so as to be movable in the width direction relative to the guide shaft 2713. Meanwhile, the front side rack gear 2712 is supported via a support portion 2716 fixed to the rack gear 2712 so as to be movable in the width direction relative to the guide shaft 2713. The biasing spring 2714, which is a compression spring, is disposed between a portion of the support portion 2715 and a portion of the support portion 2716.

[0055] More specifically, the support portion 2716 of the rack gear 2712 is fitted to the guide shaft 2713 by a pair of fitting portions 2716a and 2716b that are spaced apart from each other. Meanwhile, the support portion 2715 of the alignment plate 271A is fitted to the guide shaft 2713 by a pair of fitting portions 2715a and 2715b that are spaced apart from each other. The fitting portion 2715a on the inner side (rear side) of the alignment plate 271A in the width direction is positioned outer side (front side) of the fitting portion 2716a on the inner side (rear side) of the rack gear 2712 in the width direction, and the fitting portion 2715b on the outer side of the width direction is positioned outer side of the fitting portion 2716b in the width direction. In addition, a biasing spring 2714 is arranged in a compressed state between the fitting portion 2715a of the alignment plate 271A and the fitting portion 2716b of the rack gear 2712. As a result, when the alignment plate 271A is pushed toward the front by the sheet, the biasing spring 2714 is compressed, and the alignment plate 271A moves toward the front relative to the rack gear 2712. In this state, the alignment plate 271A pushes the sheet toward the rear due to the elastic restoring force of the biasing spring 2714.

[0056] 9, the pair of alignment plates 271A, 271B can move to an alignment position (not shown) where the sheet S is aligned in the width direction, a clamping position, a first retracted position, and a second retracted position. In addition to these positions, the pair of alignment plates 271A, 271B can also move to a receiving position for receiving a sheet onto the processing tray 220 and a home position. The alignment position is a position where the sheet S that has struck the trailing edge regulating member 290 is aligned in the width direction in a switchback-less shift discharge process, which will be described later. The clamping position is a position where the sheet S is clamped in a switchbackless shift discharge process, which will be described later. The first retracted position is a position where the pair of alignment plates 271A, 271B are retracted from both widthwise edges of the sheet S further than the clamping position. The second retracted position is a position where the pair of alignment plates 271A, 271B are retracted further from both widthwise edges of the sheet S than the first retracted position. For example, the alignment position is a position where the pair of alignment plates 271A, 271B are approximately at the same position as both widthwise edges of the sheet, and may be the same position as the clamping position, or may be a position slightly retracted from both widthwise edges of the sheet from the clamping position. The clamping position is a position where the pair of alignment plates 271A, 271B abut against both widthwise edges of the sheet. The first retracted position is a position where the pair of alignment plates 271A, 271B are retracted 3 mm from both widthwise edges of the sheet. The second retracted position is a position where they are retracted 5 mm from both widthwise edges of the sheet. The receiving position is a position where they are retracted 10 mm from both widthwise edges of the sheet. The home position is a position where the alignment plates 271A, 271B are located when a job to discharge sheets to the stacking tray 300 is not being executed, and is a position further retracted from the receiving position, i.e., a position on the outer side in the width direction.

[0057] The first retraction position is a position where the distance from both widthwise edges of the conveyed sheet is reduced to prevent the sheet from skewing when the sheet is being discharged by the upper discharge rollers 230A and the lower discharge rollers 230B. In other words, the first retraction position is a position where the sheet is prevented from moving further in the widthwise direction when the discharged sheet is skewed and contacts one of the pair of alignment plates 271A, 271B. The second retraction position prevents the sheet from contacting the pair of alignment plates 271A, 271B after it leaves the discharge nip portion 230a formed by the upper discharge rollers 230A and the lower discharge rollers 230B. After the sheet leaves the discharge nip portion 230a, the sheet is no longer nipped by rollers or the like. Therefore, if the widthwise edge of the sheet contacts at least one of the pair of alignment plates 271A, 271B, the sheet may become skewed. For this reason, in this embodiment, after the trailing edge of the sheet has passed through the discharge nip portion 230a, the pair of alignment plates 271A and 271B are moved to the second retracted position.

[0058] In addition, the positions of the pair of alignment plates 271A, 271B may be slightly different from each other at the first retracted position as long as the effect of suppressing sheet skew can be obtained. Similarly, the positions of the pair of alignment plates 271A, 271B may be slightly different from each other at the second retracted position as long as the sheet does not come into contact with the pair of alignment plates 271A, 271B. Furthermore, the distances from both end edges of the sheet in the width direction at each position may also be values ​​other than those described above as long as the above requirements are met.

[0059] [Loading tray] As described above, the stacking tray 300 serving as a stacking section receives sheets discharged in the discharge direction by the upper discharge rollers 230A and the lower discharge rollers 230B. As shown in FIGS. 2 and 3, the stacking tray 300 is provided downstream of the processing tray 220 in the discharge direction and is capable of moving up and down in the vertical direction. The stacking tray 300 is inclined with respect to the horizontal plane so that the upstream side in the discharge direction is lower than the downstream side. The stacking tray 300 is supported, for example, along rails arranged in the vertical direction so as to be movable in the vertical direction, and is raised and lowered by driving a stacking tray lifting motor MT20 (FIG. 10) serving as a lifting means.

[0060] At the upstream end of the stacking tray 300 in the discharge direction, there are provided an upright surface 310a as a stacking-side regulating means for regulating the upstream end (rear end) in the discharge direction of the sheet or sheet bundle stacked on the stacking tray 300, and a rear end presser 310b for pressing the rear end of the sheet that abuts against the upright surface 310a. The rear end presser 310b is inclined more downstream in the discharge direction as it goes upward, so that even if the rear end of the sheet is curled upward, it can be pressed by this rear end presser 310b.

[0061] Furthermore, a discharged sheet sweeping paddle 320A is provided coaxially with the rotational axis of the lower discharge roller 230B. The rotational axis 3201 (see FIG. 2) of the discharged sheet sweeping paddle 320A does not have to be coaxial with the rotational axis of the lower discharge roller 230B. The rotational axis 3201 of the discharged sheet sweeping paddle 320A only needs to be provided vertically between the discharge nip portion 230a of the upper discharge roller 230A and the lower discharge roller 230B as a pair of discharge rotors and the standing surface 310a as a stacking-side abutment portion provided upstream in the discharge direction of the stacking tray 300. In this embodiment, as shown in FIG. 2, the rotational axis 3201 of the discharged sheet sweeping paddle 320A is vertically disposed between the downstream end of the processing tray 220 in the discharge direction and the upper end of the standing surface 310a.

[0062] The stacking tray 300 can be raised and lowered by a stacking tray lifting motor MT20 between a first stacking position and a second stacking position below the first stacking position. The second stacking position is a position where the stacking tray 300 switches from being lowered to being raised when discharging sheets onto the stacking tray 300. When discharging sheets, the stacking tray 300 is raised and lowered, and the discharged sheet pick-up paddle 320A rotates to transport (pick up) the sheets on the stacking tray 300 (on the stacking section) in a third transport direction in which the upstream edge in the discharge direction faces the upright surface 310a. The upper surface of the sheet or sheet stack consisting of multiple sheets on the stacking tray 300 is then pressed down by the discharged sheet pick-up paddle 320A.

[0063] [Relationship between each motor and each configuration] Figure 10 shows the relationship between each motor and each component. The columns in Figure 10 show, from left to right, the number, motor name, driving parts, operation, direction of operation during forward rotation, and direction of operation during reverse rotation. In Figure 10, processing motor MT12 is the processing motor 610 described above. As is clear from Figure 10, conveying motor MT11 drives either of the upstream rollers (inlet rollers) 213a and 213b, either of the pre-processing rollers 211A and 212A, the pick-up paddle 240A, and the returning member 280.

[0064] The processing motor MT12 also raises and lowers the pick-up paddle 240A, the trailing end drop member 250A, and the upper discharge roller (nip member) 230A. Therefore, in this embodiment, the processing motor MT12 corresponds to a moving unit that moves the upper discharge roller 230A between the nip position and the separation position (first separation position, second separation position). In addition to the above, this embodiment also includes a return lifting motor MT13 for raising and lowering the returning member 280, a discharge roller motor MT14 for driving the lower discharge roller 230B, a take-in motor (sheet pressing motor) MT15 for driving the discharged sheet take-in paddle (sheet pressing (bundle pressing) paddle) 320A, an F-side alignment plate moving motor MT16 for moving (laterally moving) the front alignment plate 271A in the width direction, an R-side alignment plate moving motor MT17 for moving (laterally moving) the rear alignment plate 271A in the width direction, an STP moving motor MT18 for moving the staple unit (STP) 400 to change the staple position, an STP motor MT19 for driving the staple unit 400 to staple the sheet bundle, and a stacking tray lifting motor MT20 for raising and lowering the stacking tray 300.

[0065] [Control configuration of sheet processing device] The control configuration of the sheet processing apparatus 200 will be described with reference to Figs. 11 and 12. Fig. 11 is a block diagram showing the motors and sensors of the sheet processing apparatus 200. Signals from these sensors are input to a control unit 203, which controls the motors. The control unit 203 is connected to a control unit of the image forming apparatus 100 so as to be able to communicate with each other, and controls the entire sheet processing apparatus 200.

[0066] Such a control unit 203 has a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The CPU controls each unit while reading a program corresponding to a control procedure stored in the ROM. In addition, working data and input data are stored in the RAM, and the CPU performs control by referring to the data stored in the RAM based on the aforementioned programs, etc.

[0067] The motors shown in FIG. 11 are as described above. Meanwhile, the sensors will be described with reference to FIG. 2. First, the entrance sensor SN11 is provided on the conveying path 210A and detects the leading edge of a sheet conveyed to the conveying path 210A. The processing upper HP sensor SN12 detects the home positions of the take-in paddle 240A, the trailing end drop member 250A, and the upper discharge roller (nip member) 230A. The return lift HP sensor SN13 detects the home position of the return member 280 (a position retracted from the processing tray 220). The processing tray sheet detection sensor SN14 detects the presence or absence of a sheet on the processing tray 220. The paddle HP sensor (sheet pressure HP sensor) SN15 detects the home position of the discharge sheet take-in paddle 320A.

[0068] The F-side alignment plate HP sensor SN16 and the R-side alignment plate HP sensor SN17 detect that the front alignment plate 271A and the rear alignment plate 271A are respectively at positions (home positions) spaced apart in the width direction from the sheets placed on the processing tray 220. The stapler movement HP sensor SN18 detects that the staple unit 400 is at the home position. The sheet detection sensor SN19 detects the top sheet placed on the stacking tray 300. The stacking tray encoder sensor SN20 detects the position of the stacking tray 300 in the lifting / lowering direction. The stacking tray lower limit position detection sensor SN21 detects the lower limit position of the stacking tray 300. The control unit 203 performs various controls, as will be described later, based on signals from these sensors.

[0069] Next, the control flow of each mode of this embodiment will be described with reference to Fig. 12. In this embodiment, there are three modes: a straight discharge mode in which sheets sent to the sheet processing apparatus 200 are discharged directly to the stacking tray 300 without undergoing any predetermined processing; a shift mode in which sheets sent to the sheet processing apparatus 200 are shifted in the width direction (shifted) and discharged to the stacking tray 300 in order to sort the sheets discharged to the stacking tray 300; and a staple mode in which sheets sent to the sheet processing apparatus 200 are stapled as a predetermined processing and then discharged to the stacking tray 300. Each of these modes is selected by the user via the operation panel of the image forming apparatus 100 or a PC connected via a network or the like.

[0070] In this embodiment, the user can manually set the mode or automatically set the mode based on the paper type (sheet length), and in the shift mode, the user can select either of the two shift discharge processes (switchbackless shift discharge process and switchback shift discharge process) described below depending on the desired output.

[0071] In the staple mode as the binding and discharging process, as shown in FIGS. 26(a) to 26(c), the sheet S (FIG. 26(a)) conveyed downstream in the first conveyance direction by the pre-processing rollers 211A and 212A is conveyed in the second conveyance direction by the pick-up paddle 240A on the processing tray 220, and the downstream edge (trailing edge) of the sheet in the second conveyance direction is abutted against the trailing edge regulating member 290, that is, the trailing edge of the sheet is regulated. Then, by driving the alignment unit 270A (the pair of alignment plates 271A) by the F-side alignment plate movement motor MT16 and the R-side alignment plate movement motor MT17, the sheet abutted against the trailing edge regulating member 290 by the alignment unit 270A is moved in the sheet width direction and positioned at the binding position. That is, the alignment process is performed. In this embodiment, the sheet is aligned by hitting the sheet from both sides in the sheet width direction using the pair of alignment plates 271A and 271B. By repeating this operation of regulating the rear ends of the sheets and the alignment process, a sheet bundle is formed on the processing tray 220 (FIG. 26(b)). Thereafter, the sheet bundle positioned at the binding position is stapled, and the stapled sheet bundle is discharged onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B (FIG. 26(c)). In the following shift mode, a shift operation of sheets that are not to be bound is performed using the pair of alignment plates 271A, 271B, the F-side alignment plate moving motor MT16, and the R-side alignment plate moving motor MT17 that were used in the alignment process when forming the sheet bundle in this staple mode.

[0072] The shift mode includes a case where a shift operation is performed on a sheet (first sheet, small-size sheet) having a first length in the sheet conveyance direction (first conveyance direction), and a case where a shift operation is performed on a sheet (second sheet, large-size sheet) having a second length in the first conveyance direction that is longer than the first length. A small-size sheet (also referred to as a small sheet) is, for example, a sheet whose length in the first conveyance direction is equal to or shorter than a predetermined length, and a large-size sheet (also referred to as a large sheet) is, for example, a sheet whose length in the first conveyance direction is longer than a predetermined length. The predetermined length is, for example, the so-called A4 portrait size, in which an A4-size sheet is fed in the portrait direction (the direction in which the lengthwise direction is the conveyance direction). In the shift mode, a productivity-priority mode that prioritizes productivity and an alignment-priority mode that prioritizes sheet alignment can be selected and executed. In either shift mode, the sheet can be shifted in both directions, from the rear side to the front side and from the front side to the rear side (the shift direction is bidirectional).

[0073] The productivity priority mode as a switchbackless shift discharge process is a mode in which a sheet transported downstream in the first conveying direction by the pre-processing rollers 211A, 212A is not transported in the second conveying direction by the pick-up paddle 240A, but instead a switchbackless shift operation is performed to move (shift) the sheet in the shift direction by the alignment section 270A (a pair of alignment plates 271A) by driving the F side alignment plate moving motor MT16 and the R side alignment plate moving motor MT17, and the sheet is discharged onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B.

[0074] The alignment priority mode as a switchback shift discharge process is a mode in which a sheet transported downstream in the first transport direction by pre-processing rollers 211A, 212A is transported in the second transport direction on processing tray 220 by pick-up paddle 240A, and after the downstream edge of the sheet in the second transport direction is abutted (regulated) against trailing end regulating member 290, a switchback shift operation is performed in which the sheet is moved (shifted) in the shift direction by alignment section 270A (a pair of alignment plates 271A) by driving F-side alignment plate moving motor MT16 and R-side alignment plate moving motor MT17 without stapling by staple unit 400, and the sheet is then discharged onto stacking tray 300 by upper discharge rollers 230A and lower discharge rollers 230B.

[0075] When control is started, the control unit 203 determines whether the discharge mode is the straight discharge mode, the shift mode, or the staple mode (S1). If the straight discharge mode is selected, the sheets sent to the sheet processing device 200 are discharged one by one onto the stacking tray 300 without undergoing any predetermined processing (S2).

[0076] If the shift mode is selected in S1, it is determined whether the sheet size is a large size sheet or a small size sheet (S3). If it is a small size sheet, it is determined whether productivity is prioritized (S4). If productivity is prioritized, the sheet discharged from the conveying path 210A is not conveyed in the second conveying direction by the processing tray 220, but is shifted by the alignment unit 270A and discharged to the stacking tray 300 (S5). If productivity is not prioritized in S4, the sheet discharged from the conveying path 210A is picked up into the processing tray 220, and is shifted by the alignment unit 270A on the processing tray 220 and discharged to the stacking tray 300 (S6). If the sheet is a large size sheet in S3, the process also proceeds to S6.

[0077] In S1, if the staple mode is selected, the sheet discharged from the conveying path 210A is conveyed in the second conveying direction by the pick-up paddle 240A on the processing tray 220, and the downstream edge of the sheet in the second conveying direction is abutted against the trailing edge regulating member 290. In other words, the trailing edge of the sheet is regulated. After regulating the trailing edge of the sheet, the F-side alignment plate movement motor MT16 and the R-side alignment plate movement motor MT17 are driven to position (align) the sheet at the binding position by the alignment unit 270A (the pair of alignment plates 271A). These sheet trailing edge regulation and alignment operations are repeated to form a sheet bundle on the processing tray 220 (S7). Then, the sheet bundle is stapled (S8). The stapled sheet bundle is then discharged to the stacking tray 300 (S9).

[0078] [Switchback-less shift discharge processing (productivity priority mode)] Of the two shift discharge processes described above, the operation of the sheet processing apparatus 200 in the switchback-less shift discharge process will be described. In the switchback-less shift discharge process of this embodiment, first, a sheet is conveyed in the first conveyance direction by the pre-processing rollers 211A and 212A. Next, with the upper discharge roller 230A and the lower discharge roller 230B in the first separation position, the downstream end (leading end) in the first conveyance direction of the sheet conveyed in the first conveyance direction by the pre-processing rollers 211A and 212A passes between the upper discharge roller 230A and the lower discharge roller 230B (a pair of discharge rotors), and when the upstream end (trailing end) in the first conveyance direction of the sheet passes the pre-processing rollers 211A and 212A, the sheet is sandwiched between the pair of alignment plates 271A and 271B without being conveyed in the second conveyance direction by the pick-up paddle 240A. In this state, the pair of alignment plates 271A, 271B are moved in a shift direction, which is either one of the widthwise directions, to perform a shift operation to move the position of the sheet in the shift direction. Next, after this shift operation, the pair of alignment plates 271A, 271B are retracted in the widthwise direction from the sheet that has undergone the shift operation, and the upper discharge roller 230A and the lower discharge roller 230B are moved to the nip position, and then the sheet is discharged onto the stacking tray 300 by the upper discharge roller 230A and the lower discharge roller 230B.

[0079] The switchbackless shift discharge process will be described in more detail with reference to FIGS. 13(a) through 24(b). As shown in FIGS. 13(a) and 13(b), when a sheet S has not yet been conveyed to the conveying path 210A, the upper discharge roller 230A, the pick-up paddle 240A, and the trailing-end drop member 250A are all located at their home positions. In particular, the upper discharge roller 230A and the lower discharge roller 230B are located at their first separation positions. Furthermore, the pair of alignment plates 271A and 271B are located at their home positions, which are the positions where they are furthest apart from each other.

[0080] 14(a) and 14(b), when the sheet S is conveyed to the entrance of the conveying path 210A, the pair of alignment plates 271A and 271B move closer to each other from their home positions and wait at a receiving position to receive the sheet S. Also, even in this state, the upper discharge roller 230A, the pick-up paddle 240A, and the trailing end dropping member 250A are all positioned at their home positions.

[0081] Next, with the upper discharge roller 230A and the lower discharge roller 230B in the first separation position, the downstream end (leading edge) of the sheet S in the first conveyance direction passes through the pre-processing nip portion 211a of the pre-processing rollers 211A and 212A, and then the leading edge of the sheet S passes between the upper discharge roller 230A and the lower discharge roller 230B. Then, as shown in FIGS. 15(a) and 15(b), the upper discharge roller 230A is moved to the second separation position. The relationship between the first separation position and the second separation position is as described above with reference to FIGS. 4 and 5. The second separation position is a position where the upper discharge roller 230A is further lowered from the first separation position. At this time, the pick-up paddle 240A and the trailing edge drop-off member 250A remain in their home positions.

[0082] 16(a) and 16(b), when the upstream end (rear end) of the sheet S in the first conveying direction passes through the pre-processing nip portion 211a of the pre-processing rollers 211A and 212A with the upper discharge roller 230A positioned at the second separation position, the sheet S is nipped by the pair of alignment plates 271A and 271B without being picked up by the pick-up paddle 240A and while the sheet S is moving in the first conveying direction. That is, the pair of alignment plates 271A and 271B are moved to a widthwise position (clamping position) that matches the size of the sheet S, and the sheet S is nipped by the pair of alignment plates 271A and 271B from both sides in the widthwise direction (both sides in the shift direction). The timing at which the pair of alignment plates 271A, 271B start moving may be before or after the trailing end of the sheet S has passed through the pre-processing nip portion 211a, as long as the trailing end of the sheet S has passed through the pre-processing nip portion 211a when the sheet S is sandwiched between the pair of alignment plates 271A, 271B.

[0083] In this embodiment, the movement speed of the pair of alignment plates 271A, 271B can be changed. Specifically, by changing the drive speeds of the F-side alignment plate movement motor MT16 and the R-side alignment plate movement motor MT17, the movement speed of the pair of alignment plates 271A, 271B is changed between when the pair of alignment plates 271A, 271B move to sandwich a sheet and when the pair of alignment plates 271A, 271B shift a sheet in the switchback-less shift discharge process. In this embodiment, when the sheet S, whose trailing edge has passed through the pre-processing nip portion 211a, is not conveyed in the second conveyance direction by the take-in paddle 240A and is being nipped between the pair of alignment plates 271A and 271B while the sheet S is moving in the first conveyance direction, the movement speed at which the F-side alignment plate movement motor MT16 and the R-side alignment plate movement motor MT17 move the pair of alignment plates 271A and 271B from the receiving position to the nipping position where the sheet is nipped is set slower than the movement speed at which the F-side alignment plate movement motor MT16 and the R-side alignment plate movement motor MT17 move the pair of alignment plates 271A and 271B during the shift operation. For example, the movement speed when the sheet S is nipped between the pair of alignment plates 271A and 271B is 261 mm / sec, and the movement speed during the shift operation is 313 mm / sec.

[0084] This is because if the movement speed when the sheet S is sandwiched between the pair of alignment plates 271A, 271B is fast, the pair of alignment plates 271A, 271B may come into strong contact with the edge of the sheet S, which may cause skew in the sheet S. On the other hand, during the shift operation, the movement speed of the pair of alignment plates 271A, 271B is increased to improve productivity. Note that the movement speed of the pair of alignment plates 271A, 271B during the shift operation may be the same as the movement speed when the sheet S is sandwiched between the pair of alignment plates 271A, 271B.

[0085] Furthermore, when the sheet S is sandwiched between the pair of alignment plates 271A and 271B, the movement speed of the front-side alignment plate 271A and the movement speed of the rear-side alignment plate 271B are set to be the same. After the sheet S is sandwiched between the pair of alignment plates 271A and 271B, the pair of alignment plates 271A and 271B are simultaneously moved in the shift direction to perform the shift operation. However, in this embodiment, when the sheet S is sandwiched between the pair of alignment plates 271A and 271B, the timing at which the alignment plates 271A and 271B start moving is staggered. Specifically, when shifting the sheet to the front side, the rear-side alignment plate 271B is moved first, and then the front-side alignment plate 271A is moved.

[0086] As described above, in this embodiment, the front-side alignment plate 271A is biased toward the rear side by the biasing spring 2714 (see FIGS. 7 to 8(b)). Therefore, by moving the rear-side alignment plate 271B first as described above, the rear-side alignment plate 271B, which does not have a biasing spring, contacts the sheet first, and then the front-side alignment plate 271A, which has the biasing spring 2714, contacts the sheet. This allows the biasing spring 2714 to efficiently absorb the force generated when the sheet is sandwiched between the pair of alignment plates 271A and 271B, improving sheet alignment. If the front-side alignment plate 271A, which has a biasing spring, were to contact the sheet first, the biasing force of the biasing spring 2714 could cause the sheet to fly toward the rear side, potentially disrupting sheet alignment. For this reason, in this embodiment, the alignment plate without the biasing spring is moved first so that it contacts the sheet first.

[0087] In this embodiment, the pair of alignment plates 271A, 271B are located 10 mm from both ends of the sheet at the receiving position. When the pair of alignment plates 271A, 271B are moved toward the clamping position to sandwich the sheet, the rear-side alignment plate 271B is moved 10 mm toward the front, and the front-side alignment plate 271A is moved 10.5 mm toward the rear. When the pair of alignment plates 271A, 271B sandwich the sheet, the front-side alignment plate 271A pushes the sheet toward the rear, thereby aligning the sheet. At this time, the biasing spring 2714 absorbs the reaction force from the sheet when the front-side alignment plate 271A pushes the sheet, thereby preventing the sheet from bending. After moving 10.5 mm toward the rear to push the sheet, the front-side alignment plate 271A returns 0.5 mm toward the front. As a result, the pair of alignment plates 271A, 271B are positioned at the clamping position with the sheet sandwiched and aligned.

[0088] In this embodiment, the amount of movement when the sheet is sandwiched between the pair of alignment plates 271A and 271B is different between the side with the biasing spring and the side without the biasing spring, but it may be the same. That is, the amount of movement on the front side may be the same as the amount of movement on the rear side.

[0089] Note that a biasing spring may be provided on the rear alignment plate, and the front alignment plate without a biasing spring may be configured to strike the sheet first. Furthermore, in the switchback shift discharge process, the sheet is shifted on the processing tray 220, and the sheet is sandwiched between the pair of alignment plates 271A, 271B in order to perform the shifting operation by the same operation as described above. Furthermore, in both the switchbackless shift discharge process and the switchback shift discharge process, when the sheet is sandwiched between the pair of alignment plates 271A, 271B, the pair of alignment plates 271A, 271B may be moved approximately simultaneously to strike the sheet approximately simultaneously. Even in this case, sheet alignment is less likely to be disturbed than when the alignment plate with a biasing spring strikes the sheet first.

[0090] After the sheet S is sandwiched between the pair of alignment plates 271A and 271B as described above, the sheet S is moved in the shift direction while sandwiched between the pair of alignment plates 271A and 271B, as shown in FIGS. 17(a) and 17(b). That is, a shift operation is performed. After the shift operation is completed, the upper discharge roller 230A is lowered to the nip position, as shown in FIGS. 18(a) and 18(b), and the sheet S is nipped between the upper discharge roller 230A and the lower discharge roller 230B. After the sheet S is nipped between the upper discharge roller 230A and the lower discharge roller 230B, the pair of alignment plates 271A and 271B are moved from the sheet S to a first retracted position, as shown in FIGS. 19(a) and 19(b). In this example, the shift direction is from the rear side to the front side, so of the pair of alignment plates 271A, 271B, the front side alignment plate 271A is one alignment plate and the rear side alignment plate 271B is the other alignment plate.

[0091] 20(a) and 20(b), the lower discharge roller 230B is rotated to discharge the sheet S nipped between the upper discharge roller 230A and the lower discharge roller 230B onto the stacking tray 300. At this time, after the shift operation by the pair of alignment plates 271A and 271B, the pair of alignment plates 271A and 271B are moved from the nipping position to the first retracted position from the sheet that has been shifted, and the sheet is then conveyed in the discharge direction by the upper discharge roller 230A and the lower discharge roller 230B.

[0092] Next, before the upstream end (rear end) in the discharge direction of the sheet conveyed by the upper discharge roller 230A and the lower discharge roller 230B passes through the discharge nip portion 230a formed by the upper discharge roller 230A and the lower discharge roller 230B at the nip position, the pair of alignment plates 271A and 271B are moved from the first retracted position to the second retracted position. Then, with the pair of alignment plates 271A and 271B in the second retracted position, the sheet is discharged onto the stacking tray 300 by the upper discharge roller 230A and the lower discharge roller 230B.

[0093] That is, in this embodiment, while the sheet S is being nipped and conveyed by the upper discharge rollers 230A and the lower discharge rollers 230B, the pair of alignment plates 271A and 271B are positioned at a first retracted position that is closer to the sheet than the second retracted position. This prevents skew of the sheet S when it is discharged. Then, before the trailing edge of the sheet S passes through the discharge nip portion 230a, the pair of alignment plates 271A and 271B are moved to the second retracted position. This prevents the trailing edge of the sheet S from coming into contact with the pair of alignment plates 271A and 271B when it is not being nipped by the upper discharge rollers 230A and the lower discharge rollers 230B.

[0094] In the present embodiment, as described above, the pair of alignment plates 271A, 271B are disposed so as to straddle the upper discharge roller 230A and the lower discharge roller 230B in the first transport direction, and a portion of the pair of alignment plates 271A, 271B, including their downstream ends in the first transport direction, is located downstream of the discharge nip portion 230a in the first transport direction. Therefore, if the pair of alignment plates 271A, 271B are positioned at the first retracted position even after the trailing edge of the sheet S has passed through the discharge nip portion 230a, there is a risk that the sheet S will come into contact with the portion of the pair of alignment plates 271A, 271B that is downstream of the discharge nip portion 230a.

[0095] If the sheet S comes into contact with the pair of alignment plates 271A, 271B before being conveyed by the upper discharge rollers 230A and the lower discharge rollers 230B, this creates resistance when the sheet S is discharged, and there is a risk that the stackability of the sheet S will be reduced, such as the rear end of the sheet S leaning against the upright surface 310a when it is stacked on the stacking tray 300. For this reason, in this embodiment, the pair of alignment plates 271A, 271B are moved to the second retracted position before the rear end of the sheet S passes through the discharge nip portion 230a, so that the sheet S that is not nipped by the upper discharge rollers 230A and the lower discharge rollers 230B is less likely to come into contact with the pair of alignment plates 271A, 271B.

[0096] On the other hand, if the pair of alignment plates 271A, 271B are positioned at the second retracted position from the start of the discharge operation of the sheet S, there is a risk that the sheet S may become skewed while being conveyed by the upper discharge rollers 230A and the lower discharge rollers 230B. For this reason, in this embodiment, while the sheet S is being conveyed by the upper discharge rollers 230A and the lower discharge rollers 230B, the pair of alignment plates 271A, 271B are positioned at the first retracted position as much as possible to suppress skew of the sheet S. Then, by moving the pair of alignment plates 271A, 271B to the second retracted position before the trailing edge of the sheet S passes through the discharge nip portion 230a, a decrease in the stacking capacity of the sheet S on the stacking tray 300 is suppressed.

[0097] In this embodiment, the timing at which the pair of alignment plates 271A, 271B start moving to the first retracted position after the shift operation is after the sheet S has been nipped by the upper discharge roller 230A and the lower discharge roller 230B. The timing at which the pair of alignment plates 271A, 271B start moving from the first retracted position to the second retracted position is when the trailing edge of the sheet S is located, for example, 10 mm before (upstream in the first conveying direction) the discharge nip point (the central position of the discharge nip portion 230a in the first conveying direction).

[0098] That is, in this embodiment, with the pair of alignment plates 271A, 271B in the first retracted position, the upper discharge rollers 230A and the lower discharge rollers 230B nip the sheet S and transport it a predetermined amount (until the trailing edge of the sheet S is positioned 10 mm before the discharge nip point), and then the pair of alignment plates 271A, 271B move to the second retracted position to discharge the sheet S onto the stacking tray 300. Note that in this embodiment, the speed at which the sheet S is transported by the upper discharge rollers 230A and the lower discharge rollers 230B (discharge speed) is reduced at the timing when the pair of alignment plates 271A, 271B start to move from the first retracted position to the second retracted position. This prevents the position of the discharged sheet S from being disturbed on the stacking tray 300 while suppressing a decrease in productivity.

[0099] The above-mentioned "position where the rear end of the sheet S is 10 mm before the discharge nip point" may be slightly earlier or later. The timing of moving the pair of alignment plates 271A, 271B from the first retracted position to the second retracted position and the timing of slowing down the discharge speed may be different. The discharge speed may not be slowed down.

[0100] 21(a) and 21(b), after the sheet S is discharged onto the stacking tray 300, the sheet S is picked up by the discharged sheet pick-up paddle 320A and further presses down the rear end of the sheet S. At this time, the pair of alignment plates 271A and 271B move from the second retracted position to the receiving position to receive the next sheet.

[0101] In the case of such a switchback-less shift discharge process (productivity priority mode), there is no operation of conveying the sheet S in the second conveying direction on the processing tray 220 (switchback conveyance), so the shift operation of the sheet S can be performed faster than when it is performed on the processing tray 220. Note that the productivity priority mode is preferably applicable to small-sized sheets, but may also be performed on large-sized sheets. In other words, it may be performed on all sheets that are shifted and discharged without being stapled.

[0102] In particular, in this embodiment, in the switchback-less shift discharge process, the sheet conveyed by the pre-processing rollers 211A and 212A is nipped between the pair of alignment plates 271A and 271B and shifted as is, without being nipped between the upper discharge roller 230A and the lower discharge roller 230B. This further increases the speed of the switchback-less shift discharge process. That is, as in the configuration described in Patent Document 1, the sheet conveyed by the pre-processing rollers 211A and 212A is nipped between the upper discharge roller 230A and the lower discharge roller 230B, and then the nip is released before the sheet is sandwiched between the pair of alignment plates 271A and 271B and shifted. In contrast, in this embodiment, there is no need to nip the sheet between the upper discharge roller 230A and the lower discharge roller 230B and then release the nip. This further increases the speed of the switchback-less shift discharge process, thereby improving productivity.

[0103] [Alignment plate retraction position according to sheet size] 19(a) to 20(b), regardless of the sheet size, the sheet is conveyed in the discharge direction with the pair of alignment plates 271A, 271B moved to the first retracted position after the shift operation, and the pair of alignment plates 271A, 271B is moved to the second retracted position before the trailing edge of the sheet passes through the discharge nip portion 230a. However, if the pair of alignment plates 271A, 271B is retracted in two stages like this every time, the operating noise increases.

[0104] That is, when the pair of alignment plates 271A, 271B is retracted in two stages, the pair of alignment plates 271A, 271B repeatedly moves and stops. As described above, drive transmission units 2717 including pinion gears 2711 and rack gears 2712 are disposed between the F-side alignment plate movement motor MT16 and the R-side alignment plate movement motor MT17 and the alignment plates 271A, 271B, respectively. Therefore, when the pair of alignment plates 271A, 271B moves simultaneously, sound is generated from the drive transmission units 2717 in addition to the sound from the motors. Therefore, repeated movement and stopping of the pair of alignment plates 271A, 271B increases the operating noise. Furthermore, repeated movement and stopping of the pair of alignment plates 271A, 271B increases the load on the mechanism that moves the pair of alignment plates 271A, 271B.

[0105] On the other hand, large-size sheets (large sheets) that are long in the conveying direction tend to have a large amount of skew during sheet conveyance, while small-size sheets (small sheets) that are short in the conveying direction tend to have a small amount of skew during sheet conveyance. For this reason, when performing the switchback-less shift discharge process on small sheets, it is not necessary to retract the pair of alignment plates 271A, 271B in two stages. For this reason, when the switchback-less shift discharge process is applied to both small and large sheets, the retraction operation of the pair of alignment plates 271A, 271B during sheet discharge in the switchback-less shift discharge process differs depending on the sheet size.

[0106] Specifically, when the switchback-less shift discharge process (productivity priority mode) is performed on a sheet S1 (large sheet) whose length in the first conveyance direction is longer than a predetermined length, the pair of alignment plates 271A, 271B are retracted in two stages, as in the case described above with reference to Figures 19(a) to 20(b). That is, as shown in Figure 22(a), the sheet S1 is moved in the shift direction by the pair of alignment plates 271A, 271B, and then, as shown in Figure 22(b), the pair of alignment plates 271A, 271B are moved to a first retracted position that is farther away from the sheet S1 in the sheet width direction than the position where the sheet S1 is sandwiched, and the sheet S1 is conveyed in the discharge direction by the upper discharge rollers 230A and the lower discharge rollers 230B. Next, before the upstream end (rear end) of the sheet S1 in the discharge direction passes through the discharge nip portion 230a formed by the upper discharge roller 230A and the lower discharge roller 230B, the pair of alignment plates 271A, 271B are retracted to a second retracted position further retracted from the sheet S1 than the first retracted position, and as shown in Figure 22(c), with the pair of alignment plates 271A, 271B in the second retracted position, the sheet S1 is discharged onto the stacking tray 300 by the upper discharge roller 230A and the lower discharge roller 230B.

[0107] On the other hand, when the switchback-less shift discharge process (productivity priority mode) is performed on a sheet (small sheet) S2 whose length in the first conveyance direction is equal to or shorter than a predetermined length, as shown in FIG. 23A, the sheet S2 is moved in the shift direction by the pair of alignment plates 271A and 271B, and then, as shown in FIG. 23B, the pair of alignment plates 271A and 271B are moved from the position where they clamp the sheet to a position where the pair of alignment plates 271A and 271B are spaced apart from the sheet in the sheet width direction without stopping, and then the sheet S2 is discharged onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B. In this embodiment, after the sheet S2 is moved in the shift direction by the pair of alignment plates 271A and 271B, the pair of alignment plates 271A and 271B are moved to the second retracted position without stopping at the first retracted position, and then the sheet S2 is discharged onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B. That is, the pair of alignment plates 271A and 271B are moved to the second retracted position in one step, and the sheet S is discharged onto the stacking tray 300.

[0108] The retracted position of the pair of alignment plates 271A and 271B when the sheet S2 is discharged onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B may be the second retracted position or the first retracted position. In the case of the first retracted position, after the sheet S2 is moved in the shift direction, the pair of alignment plates 271A and 271B are moved to the first retracted position without moving to the second retracted position, and the sheet S2 is discharged onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B. That is, the pair of alignment plates 271A and 271B are moved to the first retracted position in one step, and the sheet S is discharged onto the stacking tray 300. Furthermore, after the sheet S2 is moved in the shift direction by the pair of alignment plates 271A and 271B, the position to which the pair of alignment plates 271A and 271B is moved may be a position other than the first retracted position or the second retracted position. That is, the pair of alignment plates 271A and 271B may be moved in one step, in other words, without stopping midway, from the clamping position where the sheet is clamped to a position spaced apart in the sheet width direction.

[0109] As described above, small sheets have a small amount of skew during sheet transport, so unlike large sheets, there is no problem even if the pair of alignment plates 271A, 271B are not positioned at the first retracted position to guide the sheet when transporting the sheet in the discharge direction. Furthermore, even if the pair of alignment plates 271A, 271B are not positioned at the second retracted position before the trailing edge of the sheet passes through the discharge nip 230a, the possibility of the corner of the trailing edge of the sheet hitting either of the alignment plates 271A, 271B is low. Therefore, in this embodiment, for small sheets, the pair of alignment plates 271A, 271B are moved to the second retracted position or the first retracted position in one step after the sheet moves in the shift direction.

[0110] When the control unit 203 executes the switchback-less shift discharge process (productivity priority mode) for the sheet (small sheet) S2, the control unit 203 discharges the first sheet onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B while the pair of alignment plates 271A, 271B are in a position spaced apart in the sheet width direction from the sheet S2 (in this embodiment, the second retracted position or the first retracted position). After that, the control unit 203 moves the pair of alignment plates 271A, 271B from the position spaced apart in the sheet width direction (in this embodiment, the second retracted position or the first retracted position) to a receiving position for receiving the next sheet without stopping the pair of alignment plates 271A, 271B, and receives the next sheet. That is, when the pair of alignment plates 271A, 271B are moved from the position spaced apart in the sheet width direction (in this embodiment, the second retracted position or the first retracted position) to the receiving position, the pair of alignment plates 271A, 271B are moved in one step. The same applies to the case of a large sheet. That is, when the switchbackless shift discharge process (productivity priority mode) is performed on the sheet (large sheet) S1, the pair of alignment plates 271A, 271B are in the second retracted position, and the first sheet is discharged onto the stacking tray 300 by the upper discharge roller 230A and the lower discharge roller 230B, and then the pair of alignment plates 271A, 271B are moved from the second retracted position to the receiving position for receiving the next sheet without stopping, and the next sheet is received in that state.

[0111] This reduces the operating noise when performing the switchbackless shift discharge process on small sheets. Especially when small sheets are frequently used, the reduced operating noise improves usability. It also reduces the load on the mechanism that moves the pair of alignment plates 271A and 271B.

[0112] In the case of large sheets, either the switchback-less shift discharge process or the switchback-shift discharge process may be performed, but regardless of the sheet size, the switchback-shift discharge process may be performed when performing a staple mode in which a sheet stack is bound, and the switchback-less shift discharge process may be performed when the sheets are moved in the shift direction and discharged without binding (when performing a shift mode).When performing the switchback-less shift discharge process on large sheets, the pair of alignment plates 271A, 271B are retracted in two stages, and when performing the switchback-less shift discharge process on small sheets, the pair of alignment plates 271A, 271B are retracted in one stage.

[0113] [Formation of sheet stacks by shift discharge processing] Here, in this embodiment, a process will be described in which sheets are shifted one by one in the shift direction and discharged onto the stacking tray 300 without being bound, thereby forming a sheet bundle consisting of multiple unbound sheets. For example, as shown in FIG. 27, there is a case in which multiple unbound sheet bundles are discharged onto the stacking tray 300 by shifting them relative to each other in the shift direction (this is called a sorting and discharging process). This sorting and discharging process is performed as follows. First, a sheet is conveyed in the first conveyance direction by the pre-processing rollers 211A and 212A, and then, without conveying the sheet conveyed by the pre-processing rollers 211A and 212A in the second conveyance direction by the pick-up paddle 240A, and while the sheet S is moving in the first conveyance direction, the pair of alignment plates 271A and 271B are driven by the front-side (F-side) alignment plate moving motor MT16 and the rear-side (R-side) alignment plate moving motor MT17, so that the sheet is sandwiched between the pair of alignment plates 271A and 271B and moved in the shift direction. Next, the sheets moved in the shift direction by the pair of alignment plates 271A, 271B are discharged one by one to the shift position on the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B, and this is repeated multiple times to stack a first unbound sheet bundle. Next, the sheets transported by the pre-processing rollers 211A, 212A are discharged one by one to a position on the stacking tray 300 shifted upstream in the shift direction from the shift position, without being transported in the second transport direction by the pick-up paddle 240A, by the upper discharge rollers 230A and the lower discharge rollers 230B, and this is repeated multiple times to stack a second unbound sheet bundle. Note that "stacking a sheet bundle" here refers to forming a sheet bundle on the stacking tray 300. Even in the case of a single sheet bundle as in this embodiment, "stacking a sheet bundle" refers to discharging multiple sheets one by one onto the stacking tray 300 to form a sheet bundle on the stacking tray 300.

[0114] In the sorting and discharging process, the second sheet bundle may be stacked by discharging the sheets one by one onto the stacking tray 300 using the pair of alignment plates 271A in the direction opposite to the shift direction of the first sheet bundle, or by discharging the sheets one by one onto the stacking tray 300 in the position in the shift direction conveyed by the pre-processing rollers 211A and 212A without moving them in the direction opposite to the shift direction of the first sheet bundle (same as in the straight discharge mode). Essentially, as shown in FIG. 27 , it is sufficient that the first sheet bundle and the second sheet bundle are stacked with a shift in the shift direction. Alternatively, a sheet bundle may be stacked on the stacking tray 300 before the first sheet bundle, in the position in the shift direction conveyed by the pre-processing rollers 211A and 212A, without moving them in the direction opposite to the shift direction of the first sheet bundle, and then the first sheet bundle may be moved in the shift direction and stacked on the stacking tray 300.

[0115] When stacking the second sheet bundle on the stacking tray 300, if the sheets are discharged onto the stacking tray 300 at the same position in the shift direction as conveyed by the pre-processing rollers 211A and 212A without moving in the opposite direction to the shift direction of the first sheet bundle, the sheets may be discharged after only width alignment by the pair of alignment plates 271A before being discharged by the upper discharge rollers 230A and the lower discharge rollers 230B. This improves the alignment of the second sheet bundle on the stacking tray 300. Also, even in the straight discharge mode only, the sheets may be width-aligned one by one by the pair of alignment plates 271A before being discharged onto the stacking tray 300.

[0116] Such a sorting and discharging process includes a sorting process and a grouping process. For example, when discharging 10 sets of sheets, each set consisting of five sheets, the sorting process is a process of shifting the sheet bundle one by one and stacking them on the stacking tray 300. The grouping process is a process of shifting the 10 sheets of the first page, the 10 sheets of the second page, ..., the 10 sheets of the fifth page, and stacking them on the stacking tray 300. The sorting process and the grouping process can be selected by the user, for example, from the operation panel of the image forming apparatus 100 or an external terminal such as a PC (personal computer) connected via a network. Then, a command for the process selected by the user is sent from the image forming apparatus 100 to the sheet processing apparatus 200A, and the sheet processing apparatus 200A executes the process.

[0117] The sorting and discharging process also includes a process in which, when jobs with different contents are successively input to image forming system 1000A, the sheet bundle is shifted for each job and stacked on stacking tray 300. For example, consider a case in which person A inputs a job to form a bundle of 10 sheets as a first job, and then person B inputs a job to form a bundle of 5 sheets as a second job. In this case, the sheet bundle for the first job is shifted in the shift direction and stacked on stacking tray 300, and then the sheet bundle for the second job is stacked on stacking tray 300 without being shifted or by moving it in the opposite direction to the shift direction.

[0118] In this embodiment, the above-described switchback shift discharge process (alignment priority mode) and sorting discharge process can be executed as processes for shifting and discharging sheets without binding them. The sorting discharge process includes the above-described switchbackless shift discharge process (productivity priority mode).

[0119] In the switchbackless shift discharge process, sheets are shifted one by one and discharged onto the stacking tray 300. In this case, if the shifted sheets are simply stacked on the stacking tray 300 to form a sheet bundle, the alignment of the sheets on the stacking tray 300 may be degraded. Furthermore, even if an attempt is made to form a sheet bundle on the stacking tray 300 and then to pick up the sheets using the discharged sheet pick-up paddle 320A, only the top sheet of the sheet bundle will be picked up, which may result in a deterioration in the alignment of the sheets. Therefore, in this embodiment, as described above with reference to FIGS. 21(a) and 21(b), after the sheets are discharged onto the stacking tray 300, the sheets are picked up by the discharged sheet pick-up paddle 320A.

[0120] That is, when forming a sheet stack shifted onto stacking tray 300 (on the stacking section) without binding, the shift discharge process and the take-in process are repeatedly performed on multiple sheets to form a sheet stack consisting of multiple sheets on stacking tray 300. The shift discharge process is a process in which sheets are shifted by alignment section 270A and the sheets shifted by alignment section 270A are discharged onto stacking tray 300 by upper discharge rollers 230A and lower discharge rollers 230B, and is the above-mentioned switchback-less shift discharge process. The take-in process is a process in which the sheets discharged onto stacking tray 300 are transported in the third transport direction by discharge sheet take-in paddle 320A.

[0121] Furthermore, when the shift discharge process and the take-in process are repeated, take-in paddle 320A stops at a position on stacking tray 300 where it presses down on the top surface of the sheet it has taken in until the next sheet is discharged (until the trailing edge of the sheet passes through the nip point between upper discharge roller 230A and lower discharge roller 230B). Then, when the next sheet is discharged onto stacking tray 300, take-in paddle 320A rotates to take in the sheet and further press down on the trailing edge of the sheet. This makes it possible to prevent the next sheet from shifting the sheet already taken in on stacking tray 300.

[0122] This improves the alignment of the sheet bundle when forming an unbound sheet bundle moved in the shift direction on the stacking tray 300. That is, by shifting the sheet and discharging it onto the stacking tray 300, and then picking up the sheet with the discharged sheet pick-up paddle 320A, the sheet discharged onto the stacking tray 300 can be abutted against the upright surface 310a provided at the upstream end of the stacking tray 300 in the first conveying direction. Then, by repeating this operation for each sheet, the alignment of the sheet bundle discharged onto the stacking tray 300 can be improved.

[0123] This operation can also be performed in the switchback shift discharge process. That is, when the switchback shift discharge process is performed, a sheet bundle is usually formed on the processing tray 220 and then discharged onto the stacking tray 300. However, it is also possible to shift the sheets one by one on the processing tray 220 and discharge them onto the stacking tray 300. Even in this case, by performing a scraping process on each sheet discharged onto the stacking tray 300, the alignment of the sheet bundle discharged onto the stacking tray 300 can be improved.

[0124] Furthermore, even when forming a second sheet stack on the stacking tray 300 or in the straight discharge mode, the alignment of the second sheet stack or the sheet stack formed by being discharged in the straight discharge mode can be improved by performing the above-mentioned scraping process on the sheets discharged one by one onto the stacking tray 300.

[0125] <Second embodiment> The second embodiment will be described with reference to FIG. 24. In the first embodiment described above, in the switchbackless shift discharge process, when the leading edge of the sheet passes between the upper discharge roller 230A and the lower discharge roller 230B, the upper discharge roller 230A is moved to the second separation position (see FIG. 15(b)). In contrast, in this embodiment, when the trailing edge of the sheet passes through the pre-processing nip portion 211a, the trailing edge dropping member 250A is moved from the upper position to the lower position. Since the other configurations and functions are the same as those of the first embodiment described above, the same configurations are denoted by the same reference numerals, and description and illustration thereof will be omitted or simplified. The following description will focus on the differences from the first embodiment.

[0126] In this embodiment, when switchback-less shift discharge processing is performed, the sheet S is conveyed toward the pre-processing rollers 211A and 211B via the conveying path 210A, as in the case shown in FIGS. 13A to 14B. Then, as shown in FIG. 24, when the leading edge of the sheet S conveyed in the first conveying direction by the pre-processing rollers 211A and 211B passes between the upper discharge roller 230A and the lower discharge roller 230B and the trailing edge of the sheet S passes the pre-processing rollers 211A and 211B, the trailing edge dropping member 250A is moved from the upper position to the lower position. As a result, the sheet S is dropped onto the processing tray 220, and both widthwise edges of the sheet S face the pair of alignment plates 271A and 271B over a wide range in the first conveying direction.

[0127] In this state, the sheet S is not conveyed in the second conveying direction by the pick-up paddle 240A, but is sandwiched between the pair of alignment plates 271A, 271B and shifted, as in the first embodiment shown in FIG. 16(a) and subsequent figures, and the sheet S is discharged. By dropping the sheet S onto the processing tray 220 by the trailing end dropping member 250A in this way, the sheet S can be more reliably sandwiched between the pair of alignment plates 271A, 271B. This improves sheet alignment.

[0128] In this embodiment, as shown in FIG. 24, when the trailing-end dropping member 250A is moved to the lower position, the take-in paddle 240A also moves from the upper retracted position to the return position. This is because the configurations of the various components are interlocked by the cam mechanism 613 described above. In this embodiment, as described with reference to FIG. 16, the take-in paddle 240A can rise independently by the amount of the gap between the second protrusion 2405 when the take-in paddle 240A is in the return position and the portion of the engagement recess 2502 located above the second protrusion 2405. Therefore, after the sheet S is dropped by the trailing-end dropping member 250A, the take-in paddle 240A is raised from the return position by the amount of the gap described above, so that the take-in paddle 240A is separated from the sheet S. This prevents the take-in paddle 240A from interfering with the sheet shifting operation by the pair of alignment plates 271A and 271B.

[0129] Furthermore, the trailing end dropping member 250A may be configured to return to the upper position immediately after dropping the sheet S onto the processing tray 220. For example, the trailing end dropping member 250A may start moving to the upper position before the pair of alignment plates 271A, 271B sandwich the sheet S, or the trailing end dropping member 250A may start moving before the shift operation. Furthermore, the trailing end dropping member 250A may be configured not to be linked to the pick-up paddle 240A, for example, by being driven separately from the pick-up paddle 240A.

[0130] <Third embodiment> The third embodiment will be described with reference to FIGS. 25(a) and 25(b). In the first embodiment described above, after the leading edge of the sheet S conveyed in the first transport direction by the pre-processing rollers 211A and 211B passes between the upper discharge roller 230A and the lower discharge roller 230B and the trailing edge of the sheet S passes through the pre-processing rollers 211A and 211B, the sheet S is sandwiched between the pair of alignment plates 271A and 271B and then shifted (see FIGS. 16(a) to 17(b)). In contrast, in this embodiment, the sheet is not sandwiched between the pair of alignment plates 271A and 271B, and while the sheet is moving in the first transport direction, one of the alignment plates is moved in the shift direction to perform the shift operation. Since the other configurations and operations are the same as those of the first embodiment described above, the same components are denoted by the same reference numerals, and their description and illustration will be omitted or simplified. The following description will focus on the differences from the first embodiment.

[0131] In the first embodiment described above, a configuration was described in which the switchback-less shift discharge process is performed for small-size sheets and the switchback-less shift discharge process is performed for large-size sheets in the shift mode. In this embodiment, in the switchback-less shift discharge process for small-size sheets, two types of switchback-less shift discharge processes can be further performed depending on the sheet size.

[0132] That is, in this embodiment, two types of switchback-less shift discharge processes can be performed: a first shift discharge process and a second shift discharge process. The first shift discharge process is performed when the sheet conveyed by the pre-processing rollers 211A and 212A is a first size, and the second shift discharge process is performed for a second size sheet whose length in the first conveyance direction is shorter than that of the first size sheet conveyed by the pre-processing rollers 211A and 212A. The first shift discharge process is the switchback-less shift discharge process described in the first or second embodiment. The second shift discharge process may also be performed in the sorting discharge process described in FIG. 27.

[0133] 15(a) and 15(b) of the first embodiment, the operation shown in Fig. 25 is performed without performing the operations shown in Fig. 16(a) and 16(b). That is, when the leading edge of the sheet S conveyed in the first conveying direction by the pre-processing rollers 211A and 212A passes between the upper discharge roller 230A and the lower discharge roller 230B and the trailing edge of the sheet S passes the pre-processing rollers 211A and 212A, the sheet S is not conveyed in the second conveying direction by the take-in paddle 240A, and while the sheet S is moving in the first conveying direction, the alignment plate 271B on one side in the width direction of the pair of alignment plates 271A and 271B is moved in a shift direction (a predetermined shift direction) that is a direction toward the other side in the width direction, thereby performing a shift operation to move the position of the sheet S in the shift direction. In this embodiment, since the shift direction is toward the front side, the alignment plate on one side is the rear side alignment plate 271B, and the alignment plate on the other side is the front side alignment plate 271A.

[0134] Here, the second size sheets for which the second shift discharge process is performed are, for example, B5 size sheets or smaller sheets, and are sheets such that the center of gravity G of the sheet S is located within the range of the alignment plate 271A when the alignment plate 271B on one side abuts against the widthwise end of the sheet S, as shown in Fig. 25. As long as the second size sheets satisfy this requirement, they vary depending on the configuration and size of the sheet processing device, and are not limited to sheets of B5 size or smaller.

[0135] In this way, when one of the alignment plates 271A contacts the widthwise end of the sheet S, that is, when the leading edge of the sheet S passes between the upper discharge roller 230A and the lower discharge roller 230B and the trailing edge of the sheet S passes through the pre-processing rollers 211A and 212A, and the center of gravity G of the sheet S overlaps with the alignment plate 271A when viewed from the widthwise direction, a shift operation can be performed by directly contacting the one of the alignment plates 271A without sandwiching the sheet between the pair of alignment plates 271A and 271B.

[0136] If the second shift discharge process is performed on a sheet whose center of gravity G is not within the range of the alignment plate 271A in the above state, for example, a sheet whose center of gravity G is located further downstream than the downstream end of the alignment plate 271A in the first conveying direction, the sheet may be tilted when it hits the alignment plate 271A. For this reason, the switchback-less shift discharge process (i.e., the first shift discharge process) described in the first and second embodiments is performed on such a sheet.

[0137] After the shift operation by the one-side alignment plate 271A, the one-side alignment plate 271A is retracted in the width direction from the sheet S that has been shifted, and the upper discharge roller 230A and the lower discharge roller 230B are moved to the nip position. Then, the sheet is discharged onto the stacking tray 300 by the upper discharge roller 230A and the lower discharge roller 230B.

[0138] In this embodiment, the sheet is not sandwiched between the pair of alignment plates 271A, 271B, and the shift operation is performed by moving one of the alignment plates in the shift direction, which further speeds up the switchbackless shift discharge process and improves productivity.

[0139] <Other embodiments> In the above-described embodiments, the sheet processing apparatus 200 is configured to be disposed within the internal space 130 of the image forming apparatus 100. However, the sheet processing apparatus of the present invention may be configured, for example, to be attached to the side of the image forming apparatus. The sheet processing apparatus may also be configured to be controlled by a control unit provided in the image forming apparatus. In other words, the control unit may be located within the sheet processing apparatus or the image forming apparatus, as long as it is capable of controlling the sheet processing apparatus within the image forming system. [Explanation of symbols]

[0140] 100 Image forming device 103 Image forming unit 200 Sheet processing device 203 Control unit 211A, 212A: Pre-processing rollers (first conveying members) 220 Processing tray (mounting section) 230A···Upper discharge roller (discharge rotor) 230B Lower discharge roller (discharge rotor) 240A···Scraping paddle (second conveying member) 271A, 271B: Alignment plate (alignment member) 290 Rear end regulating member (butting portion) 300···Loading tray (loading section) 400 Staple unit (binding unit) 1000···Image forming system MT16 Front side (F side) alignment plate movement motor (drive unit) MT17 Rear side (R side) alignment plate movement motor (drive unit)

Claims

1. a first conveying member that conveys the sheet in a first conveying direction; a placement portion on which the sheet conveyed by the first conveying member is placed; an abutting portion against which an upstream edge of the sheet on the sheet placement portion in the first transport direction abuts; a second conveying member configured to convey the sheet in a second conveying direction in which an upstream edge of the sheet on the sheet placement portion in the first conveying direction faces the abutting portion; a pair of alignment members that are arranged on both sides of the sheet abutted against the abutting portion with respect to a sheet width direction intersecting the first conveying direction, and that align the sheet abutted against the abutting portion in the sheet width direction; a drive unit that moves the pair of alignment members in the sheet width direction; a binding unit that performs a binding process on a sheet bundle made up of a plurality of sheets that have been aligned in the sheet width direction by the pair of alignment members; a stacking section for stacking the bound sheets; a pair of ejection rotors that eject the sheets in an ejection direction toward the stacking section; a control unit that controls the drive unit; Equipped with the pair of alignment members extend from the upstream side to the downstream side of the pair of discharge rotors in the discharge direction, the control unit is capable of executing a mode in which the sheet conveyed in the first conveying direction by the first conveying member is sandwiched between the pair of alignment members without being conveyed in the second conveying direction by the second conveying member, and is moved in a shift direction that is one of both sides in the sheet width direction, and then discharged to the stacking unit, When the mode is executed for a sheet whose length in the first transport direction is longer than a predetermined length, after the sheet is moved in the shift direction by the pair of alignment members, the pair of alignment members are moved to a first retracted position for restricting movement of the sheet in the sheet width direction when a skewed sheet abuts against either of the pair of alignment members while being spaced apart from the sheet in the sheet width direction relative to a position where the sheet is sandwiched, and the sheet is conveyed in the discharge direction by the pair of discharge rotors in this state; before an upstream end of the sheet in the discharge direction passes through a discharge nip portion formed by the pair of discharge rotors, the pair of alignment members are retracted to a second retracted position retracted further from the sheet than the first retracted position; and the sheet is discharged to the stacking portion by the pair of discharge rotors while the pair of alignment members are at the second retracted position; When the mode is executed for a sheet whose length in the first transport direction is equal to or shorter than the predetermined length, the sheet is moved in the shift direction by the pair of alignment members, and then the pair of alignment members are moved without stopping from a position where the pair of alignment members clamp the sheet to a position where the pair of alignment members are spaced apart from the sheet in the sheet width direction, and the sheet is discharged to the stacking portion by the pair of discharge rotors. Sheet handling device.

2. When the mode is executed for a plurality of sheets whose lengths in the first transport direction are equal to or shorter than the predetermined length, the control unit discharges a first sheet to the stacking unit by the pair of discharge rotors in a state in which the pair of alignment members are positioned apart from the sheet in the sheet width direction, and then receives the next sheet in a state in which the pair of alignment members are moved from the positions apart in the sheet width direction to a receiving position for receiving the next sheet without stopping. The sheet processing apparatus according to claim 1 .

3. The sheet conveying mechanism further includes a drive transmission unit that transmits the drive of the drive unit to the pair of alignment members and moves the pair of alignment members in the sheet width direction. The sheet processing apparatus according to claim 1 or 2.

4. an image forming unit that forms an image on a sheet; a first conveying member that conveys a sheet on which an image has been formed by the image forming unit in a first conveying direction; a placement portion on which the sheet conveyed by the first conveying member is placed; an abutting portion against which an upstream edge of the sheet on the sheet placement portion in the first transport direction abuts; a second conveying member configured to convey the sheet in a second conveying direction in which an upstream edge of the sheet on the sheet placement portion in the first conveying direction faces the abutting portion; a pair of alignment members that are arranged on both sides of the sheet abutted against the abutting portion with respect to a sheet width direction intersecting the first conveying direction, and that align the sheet abutted against the abutting portion in the sheet width direction; a drive unit that moves the pair of alignment members in the sheet width direction; a binding unit that performs a binding process on a sheet bundle made up of a plurality of sheets that have been aligned in the sheet width direction by the pair of alignment members; a stacking section for stacking the bound sheets; a pair of ejection rotors that eject the sheets in an ejection direction toward the stacking section; a control unit that controls the drive unit; Equipped with the pair of alignment members extend from the upstream side to the downstream side of the pair of discharge rotors in the discharge direction, the control unit is capable of executing a mode in which the sheet conveyed in the first conveying direction by the first conveying member is sandwiched between the pair of alignment members without being conveyed in the second conveying direction by the second conveying member, and is moved in a shift direction that is one of both sides in the sheet width direction, and then discharged to the stacking unit, When the mode is executed for a sheet whose length in the first transport direction is longer than a predetermined length, after the sheet is moved in the shift direction by the pair of alignment members, the pair of alignment members are moved to a first retracted position for restricting movement of the sheet in the sheet width direction when a skewed sheet abuts against either of the pair of alignment members while being spaced apart from the sheet in the sheet width direction relative to a position where the sheet is sandwiched, and the sheet is conveyed in the discharge direction by the pair of discharge rotors in this state; before an upstream end of the sheet in the discharge direction passes through a discharge nip portion formed by the pair of discharge rotors, the pair of alignment members are retracted to a second retracted position retracted further from the sheet than the first retracted position; and the sheet is discharged to the stacking portion by the pair of discharge rotors while the pair of alignment members are at the second retracted position; When the mode is executed for a sheet whose length in the first transport direction is equal to or shorter than the predetermined length, the sheet is moved in the shift direction by the pair of alignment members, and then the pair of alignment members are moved without stopping from a position where the pair of alignment members clamp the sheet to a position where the pair of alignment members are spaced apart from the sheet in the sheet width direction, and the sheet is discharged to the stacking portion by the pair of discharge rotors. Imaging system.

5. The sheet conveying mechanism further includes a drive transmission unit that transmits the drive of the drive unit to the pair of alignment members and moves the pair of alignment members in the sheet width direction. The image forming system according to claim 4 .

Images