Sheet processing apparatus and image forming system

Abstract

Buckling of the uppermost sheet when the bound sheet stack is pressed by the sheet pressing paddle 320 is reduced. [Solution] When a sheet stack made of thin paper ShB is bound and discharged onto the stacking tray 300, the amount of rotation of the sheet pressure paddle 320 from its reference position to its pressing position when the sheet pressure paddle 320 presses down the sheet stack on the stacking tray 300 is made smaller than the amount of rotation of the sheet pressure paddle 320 from its reference position to its pressing position when the sheet stack made of thick paper ShA is bound and discharged onto the stacking tray 300.

Description

[Technical Field]

[0001] The present invention relates to a sheet processing apparatus that binds sheets and then discharges the sheets, and an image forming system that includes the sheet processing apparatus. [Background technology]

[0002] Patent Document 1 describes a configuration having a pressing member that presses down the top surface of the already stacked sheet bundle after the sheet bundle that has been bound by the binding unit is discharged onto the stacking tray. In the configuration described in Patent Document 1, the pressing member rotates around a rotation axis at a contact portion that abuts against the already stacked sheets while elastically deforming, thereby pressing down the top surface of the sheet bundle on the stacking tray.

[0003] This pressing member presses down on the top surface of the stack of sheets already discharged onto the stacking tray to prevent the stack of sheets from being pushed out by the next sheet bundle to be discharged. Therefore, the contact portion comes into contact with the top surface of the stack of sheets, then rotates a predetermined angle around the rotation axis and stops, causing the contact portion to elastically deform and apply a predetermined pressing force to the stack of sheets.

[0004] Here, if the basis weight of the bound sheets is, for example, 120 g / m2 or more, the force pushing out the already stacked sheets when the next sheet stack is discharged on top of the already stacked sheet stack is strong, and the pressing force of the pressing member, in other words, the stop position where the contact part contacts the already stacked sheets, rotates a predetermined angle, and stops, is set accordingly. [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] If the setting of the stop position of the pressure member described above is applied to a sheet stack that has been bound using thin paper with a basis weight of 64 g / m2 or less, as shown in Figure 50(a), when the sheet pressure member rotates while contacting the top sheet of the already stacked sheet stack SB1, the top sheet will rotate around the binding part Sh1a to which it is fixed, causing buckling Sh1b.In this state, if the next sheet stack SB2 is discharged on top of the already stacked sheet stack SB1 (Figure 50(b)), and the pressure member further presses down the discharged sheet stack (Figure 50(c)), there is a possibility that the top sheet of the already stacked sheet stack SB1 that was discharged first will be damaged. [Means for solving the problem]

[0007] a sheet pressing mechanism having a rotating shaft located on the underside of the sheets being discharged by the discharge section, a fixed portion fixed to the rotating shaft, and an elastic contact portion provided on the fixed portion, the sheet pressing mechanism rotating about the rotating shaft with the contact portion in contact with the upper surface of the sheets discharged to the stacking section and then stopping, thereby causing the contact portion to elastically deform and press down the upper surface of the sheets discharged to the stacking section; a sensor for detecting a reference position of the contact portion; and a control unit for controlling the discharge section and the sheet pressing mechanism, wherein after a first sheet bundle is discharged to the stacking section, the control unit is configured to and a second sheet bundle discharged onto the first sheet bundle, and after the leading edge of the second sheet bundle rests on the first sheet bundle, the discharge section and the sheet pressing mechanism are operated to rotate the contact portion to press the top surface of the second sheet bundle discharged onto the first sheet bundle. When the contact portion presses the first sheet bundle, the amount of rotation of the contact portion from the reference position to the stop when the binding process is performed on a sheet bundle consisting of sheets with a basis weight of 120 g / m2 or more and the sheet bundle is discharged to the stacking section is set to a first rotation amount, and the amount of rotation of the contact portion from the reference position to the stop when the binding process is performed on a sheet bundle consisting of sheets with a basis weight of 64 g / m2 or less and the sheet bundle is discharged to the stacking section is set to a second rotation amount that is smaller than the first rotation amount.

[0008] One aspect of the present invention is a sheet pressing mechanism that includes an image forming unit that forms an image on a sheet, a placing unit that places a sheet bundle consisting of multiple sheets on which an image has been formed by the image forming unit, a binding unit that performs a binding process on the sheet bundle placed on the placing unit, a stacking unit that places the sheet bundle that has been bound, a discharge unit that discharges the sheet bundle from the placing unit to the stacking unit, a rotating shaft located on the underside of the sheets discharged by the discharge unit, a fixed unit that is fixed to the rotating shaft, and an elastic abutting unit that is provided on the fixed unit, and that rotates around the rotating shaft with the abutting unit in contact with the upper surfaces of the sheets discharged to the stacking unit and then stops, so that the abutting unit elastically deforms and presses down the upper surfaces of the sheets discharged to the stacking unit, a sensor that detects a reference position of the abutting unit, and a control unit that controls the discharge unit and the sheet pressing mechanism, and, after discharging the first sheet bundle, the contact portion presses down an upper surface of the first sheet bundle, and in this state, the second sheet bundle is discharged on top of the first sheet bundle, and after a leading end of the second sheet bundle rests on top of the first sheet bundle, the discharge portion and the sheet pressing mechanism are operated to rotate the contact portion and press down an upper surface of the second sheet bundle discharged on top of the first sheet bundle, and when the contact portion presses down the first sheet bundle, a rotation amount of the contact portion from the reference position to the stop when the binding process is performed on a sheet bundle made of sheets with a basis weight of 120 g / m2 or more and the sheet bundle is discharged to the stacking portion is set to a first rotation amount, and a rotation amount of the contact portion from the reference position to the stop when the binding process is performed on a sheet bundle made of sheets with a basis weight of 64 g / m2 or less and the sheet bundle is discharged to the stacking portion is set to a second rotation amount that is smaller than the first rotation amount. The image forming system is characterized by the above. [Effects of the Invention]

[0009] According to the present invention, when a plurality of bound sheet bundles are discharged onto a stacking tray, damage to the first discharged sheet bundle can be reduced. [Brief explanation of the drawings]

[0010] [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] 1A is a view of an alignment plate on a processing tray as seen from the width direction, FIG. 1B is a view of the alignment plate as seen from the downstream side in the sheet conveying direction, and FIG. 1C is a perspective view of the alignment plate according to the first embodiment. [Figure 5] FIG. 2A is a perspective view of the periphery of a sheet pressing mechanism according to the first embodiment, and FIG. 2B is a perspective view of a sheet pressing paddle. [Figure 6] 1A is a perspective view of the periphery of a processing tray, and FIG. 1B is a cross-sectional view of the schematic configuration of the sheet processing apparatus according to the first embodiment, at the home position. [Figure 7] 1A is a diagram showing the state of the discharge roller, the state of the pick-up paddle, and the state of the trailing end drop-off member in the home position of the sheet processing apparatus according to the first embodiment, as viewed from the width direction. [Figure 8] FIG. 3 is a perspective view showing the engagement relationship between a trailing end dropping member and a raking paddle according to the first embodiment. [Figure 9] 1A is a perspective view of the periphery of a processing tray when the sheet processing apparatus according to the first embodiment discharges a sheet, and FIG. 1B is a cross-sectional view of the schematic configuration of the sheet processing apparatus. [Figure 10] 1A is a diagram showing the state of the discharge roller, the state of the pick-up paddle, and the state of the trailing end dropping member when the sheet processing apparatus according to the first embodiment is discharged, as viewed from the width direction. [Figure 11] 1A is a perspective view of the periphery of a processing tray, and FIG. 1B is a cross-sectional view of the schematic configuration of the sheet processing apparatus when the sheet processing apparatus according to the first embodiment picks up a sheet. [Figure 12]1A is a diagram showing the state of the discharge roller, the state of the pick-up paddle, and the state of the trailing end drop-off member when the sheet processing apparatus according to the first embodiment picks up a sheet, as viewed from the width direction. [Figure 13] 4 is a table showing the correspondence between each motor and each component of the sheet processing apparatus according to the first embodiment. [Figure 14] FIG. 2 is a block diagram showing a control configuration of the sheet processing apparatus according to the first embodiment. [Figure 15] 6 is a flowchart showing an example of a control flow of the sheet processing apparatus according to the first embodiment. [Figure 16] 1A is a schematic diagram of a main part of a sheet processing apparatus at a home position for a first shift discharge process according to a first embodiment, viewed from above, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 17] 1A is a schematic diagram of a main part of a sheet processing apparatus when receiving a sheet in a first shift discharge process according to a first embodiment, as viewed from above, and FIG. 1B is a schematic cross-sectional view of the configuration. [Figure 18] 1A is a schematic diagram of a main part of a sheet processing apparatus when an upper discharge roller is lowered in a first 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 a sheet processing apparatus when conveyance is stopped in a first shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 20] 1A is a schematic diagram of a main part of the sheet processing apparatus when an alignment plate moves in a first shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 21] 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 first shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 22] 1A is a schematic diagram of a main part of the sheet processing apparatus when shifting of sheets in a first shift discharge process according to a first embodiment is completed, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 23]1A is a schematic diagram of a main part of the sheet processing apparatus when the alignment plate is retracted in the first shift discharge process according to the first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 24] 1A is a schematic diagram of a main part of a sheet processing apparatus when discharging a sheet in a first shift discharging process according to a first embodiment, as viewed from above, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 25] 1A is a schematic diagram of a main part of the sheet processing apparatus when sheet discharge in the first shift discharge process according to the first embodiment is completed, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 26] 1A is a schematic diagram of a main part of the sheet processing apparatus when the leading edge of the sheet in the second shift discharge process has passed the discharge rollers according to the first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 27] 1A is a schematic diagram of a main part of the sheet processing apparatus when the rear end of the sheet in the second shift discharge process has passed through the pre-processing rollers, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 28] 1A is a schematic diagram of a main part of the sheet processing apparatus when a sheet is taken in during a second shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 29] 1A is a schematic diagram of a main part of the sheet processing apparatus when a returning member is lowered in a second shift discharge process according to a first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 30] 1A is a schematic diagram of the main parts of the sheet processing apparatus when the trailing end dropping member, the take-in paddle, and the returning member of the second shift discharge process according to the first embodiment are raised, and FIG. 1B is a schematic cross-sectional view of the configuration. [Figure 31] 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 second shift discharge process according to the first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration. [Figure 32] 1A is a schematic diagram of a main part of the sheet processing apparatus when shifting of sheets in a second shift discharge process according to a first embodiment is completed, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 33]1A is a schematic diagram of a main part of the sheet processing apparatus when the alignment plate is retracted in the second shift discharge process according to the first embodiment, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 34] 1A is a schematic diagram of a main part of the sheet processing apparatus when discharging a sheet in a second 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 35] 1A is a schematic diagram of a main part of the sheet processing apparatus when sheet discharge in the second shift discharge process according to the first embodiment is completed, and FIG. 1B is a schematic cross-sectional view of the configuration thereof. [Figure 36] FIG. 2 is a cross-sectional view of the schematic configuration of the periphery of the sheet pressure paddle, showing the home position of the sheet pressure paddle according to the first embodiment. [Figure 37] FIG. 2 is a cross-sectional view of the schematic configuration of the periphery of the sheet pressure paddle, showing a sheet receiving position of the sheet pressure paddle according to the first embodiment. [Figure 38] 3 is a schematic cross-sectional view of the periphery of the sheet pressing paddle, illustrating a state in which the sheet pressing paddle presses down a first sheet on a stack tray according to the first embodiment. FIG. [Figure 39] 1 is a schematic cross-sectional view of the periphery of the sheet pressing paddle, illustrating a state in which the sheet pressing paddle according to the first embodiment is pressing down a first sheet on a stack tray and a subsequent second sheet is being discharged. FIG. [Figure 40] 4 is a schematic cross-sectional view of the periphery of the sheet pressure paddle according to the first embodiment, showing a state in which the sheet pressure paddle starts to rotate; FIG. [Figure 41] 4 is a cross-sectional view of the schematic configuration of the periphery of the sheet pressure paddle, showing a state in which the rotation of the sheet pressure paddle according to the first embodiment is accelerating; FIG. [Figure 42] 3 is a cross-sectional view of the schematic configuration of the periphery of the sheet pressure paddle, showing a state in which rotation of the sheet pressure paddle according to the first embodiment is temporarily stopped; FIG. [Figure 43] 4 is a schematic cross-sectional view of the periphery of the sheet pressing paddle, showing a state in which the sheet pressing paddle presses down a second sheet on the stack tray according to the first embodiment. FIG. [Figure 44](a) A schematic cross-sectional view of the area around the sheet pressure paddle showing the state in which the sheet pressure paddle in the first embodiment is rotating, (b) a state in which the tip of the sheet pressure paddle is elastically swung downstream in the direction of rotation when the rotation of the sheet pressure paddle is temporarily stopped, and (c) a state in which the tip of the sheet pressure paddle is elastically swung upstream in the direction of rotation. [Figure 45] FIG. 3A is a schematic diagram showing the operation of the sheet pressing paddle according to the first embodiment when detecting the home position, and FIG. 3B is a diagram showing the operation thereof. [Figure 46] FIG. 4A is a schematic diagram showing the operation of the sheet pressing paddle according to the first embodiment when it moves from a home position to a sheet pressing position, and FIG. 4B is a diagram showing the operation thereof. [Figure 47] 3A is a schematic diagram showing the operation of the sheet pressing paddle according to the first embodiment when it moves from a sheet pressing position to a sheet pressing position for the next sheet, and FIG. 3B is a diagram showing the operation thereof. [Figure 48] FIG. 10 is an operational diagram of a staple mode according to the first embodiment. [Figure 49] FIG. 10 is an operational diagram of a staple mode according to the first embodiment. [Figure 50] FIG. 1 is a diagram illustrating a problem to be solved by the present invention. [Figure 51] 10 is a diagram comparing the rotation amount of the sheet pressing paddle according to the first embodiment between thick paper and thin paper. FIG. [Figure 52] 10 is a flowchart of sheet bundle discharge in a staple mode according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] First Embodiment The first embodiment will be described with reference to Figures 1 to 47. First, the schematic configuration of an image forming system of this embodiment will be described with reference to Figure 1.

[0012] [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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] Meanwhile, the image forming apparatus 100 has a plurality of cassettes 20 that store 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.

[0017] 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.

[0018] 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 document feeding device 123.

[0019] 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 102, which allows the user to input instructions (printing conditions, sheet information (such as basis weight), mode settings, etc.) to the image forming apparatus 100 and the sheet processing apparatus 200.

[0020] 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. The image forming apparatus is configured so that sheets are discharged into the internal space 130 from the discharge port 101 of the image forming apparatus main body 110. The internal space 130 is also configured so that a sheet processing device 200 and the like can be attached and detached. 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.

[0021] The sheet processing apparatus 200 is connected to the discharge port 101 and receives sheets discharged from the discharge port 101. Then, as will be described in detail later, it is possible to perform predetermined processing such as binding on these sheets.

[0022] [Sheet processing device] The configuration of the sheet processing apparatus 200 of this embodiment will be described with reference to FIGS. 2 to 12(c). The sheet processing apparatus 200 of this embodiment corresponds to a sheet stacking apparatus. 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 (the front side in FIG. 2, the front right side in FIG. 3) in the sheet width direction perpendicular to the sheet conveyance direction, and is the side where an operator operates the image forming system 1000, for example, the side where the operation panel 102 is installed. The rear side (rear (R) side) is the opposite side to the front side, and is the other side (the back side in FIG. 2, the back left side in FIG. 3) in the sheet width direction.

[0023] [Overall configuration of sheet processing device] The sheet processing apparatus 200 includes a conveying path 210A, pre-processing rollers 211A and 212A as a first conveying unit, a processing tray 220 as a loading unit, upper discharge rollers (nip members) 230A and lower discharge rollers 230B as a pair of discharge rotors (discharge units), a pick-up paddle 240A as a second conveying unit, a trailing edge drop member 250A as a sheet drop unit, an alignment unit 270A as a first and second shift unit, a return member 280, a trailing edge regulating member 290 as a striking unit, a stacking tray 300 as a stacking unit, and a sheet pressure paddle 320 as a part of a sheet pressure mechanism 1320. In this embodiment, the sheet pressure paddle 320 also functions as a discharged sheet pick-up paddle as a pick-up unit. A sheet received from the image forming apparatus 100 is conveyed to the conveying path 210A.

[0024] 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 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.

[0025] [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 as a first conveying section (a pair of conveying rotors). These are arranged in pairs so as to be spaced apart in the sheet width direction (arrow γ direction in FIG. 3 ), which intersects with the sheet conveying direction (first conveying direction, arrow β direction (left-right direction) in FIG. 2 ).

[0026] The pre-processing rollers 211A and 212A are a conveying unit, a first conveying unit, and a pair of conveying rotors that convey a sheet in a predetermined 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 conveyed from the upstream side of the sheet processing apparatus 200 and convey it to the conveying path 210A. Then, the sheet that has passed through the conveying path 210A reaches the pre-processing rollers 211A and 212A.

[0027] 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. As will be described later, 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.

[0028] [Processing tray] The processing tray 220, which serves 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 210. 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 downstream 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. At the upstream end of the processing tray 220 in the first conveying direction, a trailing edge regulating member 290 is disposed as an abutting unit against which the upstream edge in the first conveying direction of the sheet placed on the processing tray 220 abuts (the downstream edge in a second conveying direction opposite to the first conveying direction, i.e., the trailing edge of the sheet). A part of the processing tray 220 (for example, the downstream end in the first transport direction) may protrude vertically above the transport path 210A.

[0029] Furthermore, a staple unit 400 serving as a 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 the sheet stack 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 sheet or sheet stack placed on the processing tray 220 is discharged onto the stacking tray 300 by upper discharge rollers 230A and lower discharge rollers 230B, as will be described later.

[0030] [Scraping paddle] The take-in paddle 240A as a second transport unit transports the sheet on the processing tray 220 in a second transport direction opposite to the first transport direction (switchback transport). The take-in paddle 240A has a paddle unit 2401 as a rotating member, a paddle arm 2402 as a support unit that supports the paddle unit 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 unit 2401 is rotatably provided at the tip of the paddle arm 2402.

[0031] 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.

[0032] [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.

[0033] 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.

[0034] [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.

[0035] [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, a pair of discharge rollers, and a discharge section, and transport and discharge the sheet, which has been transported downstream in the first transport direction by the pre-processing rollers 211A and 212A, downstream of the processing tray 220 in the first transport direction. The upper discharge roller 230A is movable between a clamping position (contact position) where it clamps the sheet between itself and the lower discharge roller 230B, and a retracted position where it is retracted upward from the clamping position. At the clamping position, the upper discharge roller 230A clamps the sheet between itself and the lower discharge roller 230B. That is, the upper discharge roller 230A functions as a nipping member that nips the sheet between itself and the lower discharge roller 230B at the clamping position. Two upper discharge rollers 230A and two lower discharge rollers 230B are each arranged spaced apart in the sheet width direction. In this embodiment, the paddles 240A are disposed on the inner side in the width direction of the pair of paddles 240A.

[0036] The upper discharge roller 230A and the lower discharge roller 230B hold a sheet or a sheet stack at the nipping position, and, for example, the lower discharge roller 230B rotates to convey the held sheet or sheet stack. 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 nip member that can hold a sheet between itself and the lower discharge roller 230B at the nipping position, but this nip 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.

[0037] 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. 9(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.

[0038] The upper discharge roller 230A is rotatable about a rotation shaft 2301 between a clamping position and a retracted position. In other words, the upper discharge roller 230A is movable up and down between the clamping position and the retracted 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 disposed upstream in the first conveying direction of a pre-processing nip portion 211a where a sheet is clamped between the pre-processing rollers 211A and 212A, 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.

[0039] The pivot 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 nipping position. Furthermore, the upper discharge roller 230A is positioned vertically above the pre-processing nip portion 211a where the pre-processing rollers 211A and 212A nip the sheet at the retracted position, and the pivot shaft 2301 is positioned vertically above the center of the upper discharge roller 230A at the retracted position.

[0040] Because the positional relationship between the rotation shaft 2301 and the pre-processing nip portion 211a is defined as described above, when the upper discharge roller 230A is in the retracted position, it allows the sheet that has passed through the pre-processing nip portion 211a to move toward the stacking tray 300. Meanwhile, the upper discharge roller 230A moves downward from the retracted position toward the clamping position by rotating counterclockwise in FIG. 2 about the rotation shaft 2301. Then, when the upper discharge roller 230A moves to the clamping position, the sheet can be clamped between the upper discharge roller 230A and the lower discharge roller 230B.

[0041] [Matching part] The alignment unit 270A as a shift unit will be described with reference to Figures 2 and 3, as well as Figures 4(a) to 4(c). The alignment unit 270A moves in a shift direction (width direction) intersecting with the first transport direction while coming into contact with the edge of the sheet transported downstream in the first transport direction by the pre-processing rollers 211A and 212A, thereby moving the sheet in the shift direction. The alignment unit 270A has a pair of alignment plates 271A as a first shift unit and a second shift unit that are arranged to face each other in the shift direction.

[0042] The pair of alignment plates 271A 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 pair of alignment plates 271A are disposed on both width direction sides of the sheet placed on the processing tray 220 and are each movable in the width direction. The pair of alignment plates 271A extend from the upstream side to the downstream side in the first conveying direction relative to the upper discharge rollers 230A and the lower discharge rollers 230B. That is, the pair of alignment plates 271A are disposed so as to straddle the upper discharge rollers 230A and the lower discharge rollers 230B in the first conveying direction. The pair of alignment plates 271A have the same configuration. The pair of alignment plates 271A move in the shift direction by driving a front-side (F-side) alignment plate moving motor MT16 and a rear-side (R-side) alignment plate moving motor MT17 (see FIG. 13) as a first drive unit and a second drive unit. In the pair of alignment plates 271A, the alignment plate on the upstream side in the shift direction is referred to as the first shift part, and the alignment plate on the downstream side in the shift direction is referred to as the second shift part in the first shift discharge process (switchbackless shift discharge process) and the second shift discharge process (switchback shift discharge process) described later. 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.

[0043] The alignment plate 271A is formed so that its vertical width is wider on the downstream side in the first transport direction. That is, the alignment plate 271A has 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. The first plate portion 2701 has a vertically larger area than the second plate portion 2702 so that it can abut against the conveyed sheet even if the leading edge of the sheet is curled upward or downward. On the other hand, 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 drop member 250A even when the trailing end drop member 250A is positioned in a lower position. In addition, the upper edge of the second plate portion 2702 is inclined so that it becomes lower toward the upstream side in the first transport direction.

[0044] The first plate portion 2701 is formed so as to straddle the upper discharge rollers 230A and the lower discharge rollers 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 first shift discharge process 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 second shift discharge process described below.

[0045] 4(a) to 4(c), the first plate portion 2701 has a curl suppressing portion 2703 and a support portion 2704. The curl suppressing portion 2703 is provided downstream in the first conveyance direction of a discharge nip portion 230a (see FIG. 9(b) described later), which is a nip position where a sheet is sandwiched between the upper discharge roller 230A and the lower discharge roller 230B, and vertically above the discharge nip portion 230a, and suppresses the leading edge of a sheet that has curled upward. In this embodiment, the curl suppressing portion 2703 is a protruding portion that protrudes from the upper end of the first plate portion 2701 toward the inside in the width direction (the side that abuts against the sheet, the right side in FIG. 4(b)), and the leading edge of a curled sheet abuts against the protruding portion, thereby suppressing the leading edge of the sheet. In addition, an uneven portion 2705 is provided below the curl suppressing portion 2703, and depending on the state of the curl, the widthwise edge of the sheet can be caught on this uneven portion 2705, making it possible to suppress the leading edge of the curled sheet.

[0046] The support portion 2704 is provided downstream in the first conveyance direction of the discharge nip portion 230a, which is a nip position where a sheet is sandwiched between the upper discharge roller 230A and the lower discharge roller 230B, and vertically below the discharge nip portion 230a, to support the sheet from below. In this embodiment, the support portion 2704 is a protrusion that protrudes from the lower end of the first plate portion 2701 toward the inside in the width direction (the side that abuts against the sheet, the right side in FIG. 4(b)). Also, as shown in FIGS. 4(a) and 4(c), an inclined portion 2704a that is inclined downward as it goes downstream is formed at the downstream end of the support portion 2704 in the first conveyance direction. This allows the sheet supported by the support portion 2704 to be smoothly guided to the stacking tray 300. Furthermore, by supporting the sheet downstream of the discharge nip portion 230a in the first conveying direction by the support portion 2704, the area where the pair of alignment plates 271A come into contact with the side edges of the sheet can be increased compared to when the sheet is not supported.

[0047] [Loading tray] As described above, the stacking tray 300 serving as a stacking section receives sheets discharged by the upper discharge rollers 230A and the lower discharge rollers 230B. The stacking tray 300 is provided downstream of the processing tray 220 in the first transport 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 first transport 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 the drive of a stacking tray lifting motor MT20 (FIG. 13) serving as a lifting means.

[0048] At the upstream end of the stacking tray 300 in the first conveying direction, there are provided an upright surface 310a as a stacking-side regulating means for regulating the upstream end (rear end) in a predetermined 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 abutting against the upright surface 310a. The rear end presser 310b is inclined more downstream in the first conveying 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.

[0049] Furthermore, a rotation shaft 3201 (see FIG. 2 and FIG. 5A described later) of the sheet pressure paddle 320 is provided coaxially with a rotation shaft 230B1 (see FIG. 5A described later) of the lower discharge roller 230B. The rotation shaft 3201 of the sheet pressure paddle 320 does not have to be coaxial with the rotation shaft 230B1. The rotation shaft 3201 of the sheet pressure paddle 320 is located below the sheet being discharged by the upper discharge roller 230A and the lower discharge roller 230B. Specifically, the rotation shaft 3201 may be provided vertically between a discharge nip portion 230a (see FIG. 9B described later) of the pair of discharge rotors, the upper discharge roller 230A and the lower discharge roller 230B, and the upstream end of the stack tray 300 in the first conveyance direction. In this embodiment, as shown in FIG. 2, the rotation shaft 3201 of the sheet pressure paddle 320 is disposed vertically between the downstream end of the processing tray 220 in the first transport direction and the upper end of the standing surface 310a.

[0050] 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 that is lower than the first stacking position. The second stacking position is a position where the stacking tray 300, which was lowered when discharging sheets onto the stacking tray 300, switches to an upward movement. When discharging sheets, the stacking tray 300 is raised and lowered, and the sheet pressure paddle 320 rotates to transport (scrape) the sheets on the stacking tray 300 in a second transport direction that is opposite to the first transport direction. Then, the upper surface of the sheet or sheet bundle consisting of multiple sheets on the stacking tray 300 is pressed down by the sheet pressure paddle 320.

[0051] [Sheet pressure paddle surrounding structure] 5(a) and 5(b), the structure of the sheet pressing mechanism 1320 and its surroundings will be described. FIG. 5(a) is a perspective view showing the drive structure of the lower discharge roller 230B and the sheet pressing paddle 320.

[0052] The lower discharge roller 230B is driven by a discharge roller motor MT14 via a drive transmission mechanism 2300. In the illustrated example, the drive transmission mechanism 2300 is made up of a pulley and a belt, and transmits the rotational drive of the drive shaft of the discharge roller motor MT14 to a rotation shaft 230B1 of the lower discharge roller 230B. On the other hand, the sheet pressure paddle 320 is driven by a take-in motor MT15 serving as a drive unit via a drive transmission mechanism 3200. In the illustrated example, the drive transmission mechanism 3200 is made up of a pulley and a belt, and transmits the rotational drive of the drive shaft of the take-in motor MT15 to a rotation shaft 3201 of the sheet pressure paddle 320.

[0053] The rotation shaft 230B1 of the lower discharge roller 230B is configured so that the rotation shaft 3201 of the sheet pressure paddle 320 can pass through it, allowing the two sheet pressure paddles 320 on either side of the lower discharge roller 230B in the direction of the rotation axis to be arranged on one rotation shaft 3201. The rotation shaft 230B1 of the lower discharge roller 230B is rotatably supported by the rotation shaft 3201 of the sheet pressure paddle 320 via, for example, a bearing. This allows the lower discharge roller 230B and the sheet pressure paddle 320 to be driven independently by separate motors. Note that the drive transmission mechanisms 2300, 3200 may be configured using other drive transmission members, such as multiple gears, in addition to a configuration using pulleys and belts.

[0054] 5(b), the sheet pressure paddle 320 has a fixed portion 3202 fixed to a rotating shaft 3201, and a plate-shaped paddle portion 3203 serving as an elastic contact portion provided on the fixed portion 3202. The paddle portion 3203 extends from the fixed portion 3202 fixed to the rotating shaft 3201 in a direction perpendicular to the rotating shaft 3201. Furthermore, the paddle portion 3203 is formed of an elastic material such as rubber (for example, ethylene propylene rubber (EPDM) with a hardness of 30±5 HS(A) ((old JIS K6301, spring type A))). The sheet pressure paddle 320 configured in this manner rotates as the rotating shaft 3201 rotates, and as described above, picks up sheets on the stacking tray 300. Furthermore, when the paddle portion 3203 comes into contact with a sheet on the stacking tray 300 due to rotation, it elastically deforms, thereby more reliably picking up the sheet and holding down the trailing end of the sheet. The detailed operation of the sheet pressure paddle 320 will be described later.

[0055] [Drive configuration of each part] Next, the drive configuration of the upper discharge roller 230A, the pick-up paddle 240A, and the trailing-end drop-off member 250A will be described with reference to FIGS. 6(a) to 12(c). In this embodiment, the upper discharge roller 230A, the pick-up paddle 240A, and the trailing-end drop-off member 250A are configured to operate in conjunction with one another. As shown in FIG. 6(a), the drive configuration 600 includes a processing motor 610 (MT12, FIG. 13) as a drive source, a drive transmission mechanism 611, a rotating shaft 612, and a cam mechanism 613. The processing motor 610 is rotatable forward and reverse, and the drive of the processing motor 610 is transmitted to the rotating shaft 612 via the drive transmission mechanism 611. In this embodiment, the drive transmission mechanism 611 is configured with a gear train, but other drive transmission configurations, such as a configuration in which drive is transmitted by a belt, may also be used.

[0056] The rotary shaft 612 is disposed across the width above the upper discharge rollers 230A, the pick-up paddles 240A, and the trailing-end dropping member 250A. The rotation of the rotary shaft 612 operates the cam mechanism 613. The cam mechanism 613 has a first cam member 620 and a second cam member 630 that rotate together with the rotary shaft 612. The first cam member 620 is disposed between the pair of upper discharge rollers 230A and operates the upper discharge rollers 230A. The second cam members 630 are provided adjacent to each of the pair of pick-up paddles 240A and operate the pick-up paddles 240A and the trailing-end dropping member 250A.

[0057] As shown in FIG. 7(a), the first cam member 620 has a groove 621 formed on the inside thereof into which the protrusion 2303 provided on the discharge arm 2302 of the upper discharge roller 230A can enter. The groove 621 has an outer circumferential surface, i.e., the inner circumferential surface of the first cam member 620, which serves as an inner cam surface 622. The inner cam surface 622 is a cam surface whose distance from the center of rotation of the rotation shaft 612 varies depending on the phase of the rotation direction. The first cam member 620 also has an outer cam surface 623 on its outer circumferential surface. The outer cam surface 623 is also a cam surface whose distance from the center of rotation of the rotation shaft 612 varies depending on the phase of the rotation direction.

[0058] In addition to the protrusion 2303 described above, the discharge arm 2302 of the upper discharge roller 230A has an abutment portion 2304 that can abut against the outer cam surface 623 of the first cam member 620. The first cam member 620 rotates together with the rotation shaft 612 to change the abutment position (phase) between the inner cam surface 622 and the protrusion 2303 or separate them, and to change the abutment position (phase) between the outer cam surface 623 and the abutment portion 2304 or separate them, thereby rotating the upper discharge roller 230A around the rotation shaft 2301 between the clamping position and the retracted position, as described below.

[0059] As shown in FIG. 7(b), the second cam member 630 has a groove 631 formed on its inner side into which the first protrusion 2404 provided on the paddle arm 2402 of the sweeping paddle 240A can enter. The groove 631 has an outer circumferential surface, i.e., the inner circumferential surface of the second cam member 630, which serves as an inner cam surface 632. The inner cam surface 632 is a cam surface whose distance from the center of rotation of the rotation shaft 612 varies depending on the phase of the rotation direction. The second cam member 630 rotates together with the rotation shaft 612, changing the contact position (phase) between the inner cam surface 632 and the first protrusion 2404. As described below, the second cam member 630 rotates between a return position and an upper retracted position around the swing fulcrum 2403.

[0060] 7(c) and 8, a support portion 2406 that swings around a swing fulcrum 2403 together with the paddle arm 2402 of the pick-up paddle 240A and supports the end of the rotation shaft 2401a of the paddle portion 2401 is provided with a second protrusion 2405 that can enter an engagement recess 2502 formed in the trailing end dropping member 250A. When the pick-up paddle 240A rotates, the engagement recess 2502 abuts on or separates from the second protrusion 2405, thereby rotating the trailing end dropping member 250A between an upper position and a lower position around the rotation shaft 2501. The driving of the upper discharge roller 230A, the pick-up paddle 240A, and the trailing end dropping member 250A will be specifically described below.

[0061] [Home Position] 6(a) to 7(c) show the home positions (HP) of the upper discharge roller 230A, the pick-up paddle 240A, and the trailing-end drop-off member 250A. At the home positions, as shown in FIGS. 6(a) and 6(b), the upper discharge roller 230A is in the retracted position, the pick-up paddle 240A is in the upper retracted position, and the trailing-end drop-off member 250A is in the upper position.

[0062] In this state, as shown in Figure 7(a), the protrusion 2303 of the upper discharge roller 230A abuts at a position close to the center of the rotation shaft 612 of the inner cam surface 622 of the first cam member 620, so that the upper discharge roller 230A is supported by the first cam member 620.

[0063] Also, as shown in Figure 7(b), the first protrusion 2404 of the sweeping paddle 240A abuts at a position close to the center of the rotation axis 612 of the inner cam surface 632 of the second cam member 630, thereby supporting the sweeping paddle 240A on the second cam member 630.

[0064] Furthermore, as shown in Figure 7(c), the engagement recess 2502 of the trailing end dropping member 250A abuts against the second protrusion 2405 of the sweeping paddle 240A, so that the trailing end dropping member 250A is supported by the sweeping paddle 240A via the second protrusion 2405.

[0065] [Upper ejection roller lowering] Next, the operation of moving the upper discharge roller 230A from the home position (retracted position) to the clamping position will be described with reference to Figures 9(a) to 10(c). When the processing motor 610 is driven to rotate the rotation shaft 612 in a first direction (counterclockwise in Figures 10(a) and 10(b)) to lower the upper discharge roller 230A from the home position, the first cam member 620 also rotates in the same direction, and the protrusion 2303 moves along the inner cam surface 622. The inner cam surface 622 is formed so that it moves away from the center of the rotation shaft 612 when it rotates counterclockwise from the home position. Therefore, this operation causes the upper discharge roller 230A to lower.

[0066] 10(a), the inner cam surface 622 of the first cam member 620 and the protrusion 2303 are separated, and the outer cam surface 623 comes into contact with the contact portion 2304. By bringing the outer cam surface 623 into contact with the contact portion 2304 in this manner, the upper discharge roller 230A is pressed against the lower discharge roller 230B, and a predetermined nip pressure is applied between these rollers.

[0067] At this time, the second cam member 630 also rotates together with the rotary shaft 612, but as shown in FIG. 10(b), the distance from the center of the rotary shaft 612 to the position where the inner cam surface 632 abuts against the first protrusion 2404 is approximately the same as the distance at the home position. Therefore, even when the second cam member 630 rotates, the take-in paddle 240A is maintained at the home position. Because the take-in paddle 240A is maintained at the home position, the trailing end dropping member 250A is also maintained at the home position, as shown in FIG. 10(c). That is, in this state, as shown in FIG. 9(b), the upper discharge roller 230A moves to the clamping position, but the take-in paddle 240A and the trailing end dropping member 250A are maintained at their home positions.

[0068] To raise the upper discharge roller 230A, the processing motor 610 is driven to rotate the rotary shaft 612 in a second direction opposite to the first direction (counterclockwise in FIGS. 10(a) and 10(b)). This causes the first cam member 620 to rotate in the same direction as the rotary shaft 612, causing the protrusion 2303 to move along the inner cam surface 622, and the upper discharge roller 230A to rise. Then, it returns to the home position shown in FIG. 7(a).

[0069] 7(b) and 7(c) from the state of FIGS. 10(b) and 10(c), the first protrusion 2404 moves along the inner cam surface 632 of the second cam member 630. The inner cam surface 632 is formed so that the distance from the center of the rotation shaft 612 to the position where the inner cam surface 632 abuts the first protrusion 2404 does not change. Therefore, the sweeping paddle 240A remains in its home position. Because the sweeping paddle 240A is maintained in its home position, the trailing end dropping member 250A also remains in its home position.

[0070] [Lowering of the raking paddle and rear end drop member] Next, the operation of moving the pick-up paddle 240A and the trailing-end drop-off member 250A from their home positions (upper retracted positions, upper positions) to their return positions and lower positions will be described with reference to FIGS. 11(a) through 12(c). To lower the pick-up paddle 240A and the trailing-end drop-off member 250A from their home positions, the processing motor 610 is driven to rotate the rotating shaft 612 in a second direction (clockwise in FIGS. 12(a) and 12(b)) opposite to the first direction. This causes the first cam member 620 to rotate in the same direction, causing the protrusion 2303 to move along the inner cam surface 622. The inner cam surface 622 is formed so that its distance from the center of the rotating shaft 612 remains almost constant even when the inner cam surface 622 rotates clockwise from the home position. Therefore, the upper discharge roller 230A is maintained in its home position, as shown in FIG. 12(a).

[0071] Meanwhile, the second cam member 630 also rotates in the same direction together with the rotary shaft 612, and the first protrusion 2404 moves along the inner cam surface 632. The inner cam surface 632 is formed so that when it rotates clockwise from the home position, it moves away from the center of the rotary shaft 612. Therefore, this movement causes the sweeping paddle 240A to descend and move to the return position.

[0072] At this time, the trailing end dropping member 250A also descends together with the take-in paddle 240A. In this embodiment, the trailing end dropping member 250A has a positioning portion 2503 that is positioned at the lower position by engaging with the upper guide 2101 of the conveying path 210A when it rotates from the upper position to the lower position. The positioning portion 2503 is provided at the upper end of a protruding portion 2504 that protrudes upward from the leading end (upstream end in the first conveying direction) of the trailing end dropping member 250A. The protruding portion 2504 also serves to regulate the leading end of the sheet conveyed toward the pre-processing nip portion 211a, upstream of the pre-processing nip portion 211a in the first conveying direction, when the trailing end dropping member 250A is in the lower position.

[0073] The positioning portion 2503 is an engagement portion provided on the upper end of the protrusion 2504 so as to be able to engage with the upper guide 2101, and by abutting against the upper surface of the upper guide 2101, prevents the trailing end dropping member 250A from descending any further. The engagement recess 2502 is formed so as to be separated from the second protrusion 2405 in this state. Therefore, the trailing end dropping member 250A is disengaged from the sweeping paddle 240A and is positioned at a lower position by the positioning portion 2503.

[0074] As a result, even if the take-in paddle 240A reaches the return position, the trailing end dropping member 250A is positioned at the lower position and does not move further downward due to the engagement between the positioning portion 2503 and the upper guide 2101. In this state, as shown in Figure 11(b), the take-in paddle 240A and the trailing end dropping member 250A move to the return position and the lower position, and the upper discharge roller 230A is positioned at the home position.

[0075] 1 to 11(b), the protrusion 2504 and the positioning portion 2053 shown in Fig. 12(c) are omitted. Such protrusion 2504 and positioning portion 2053 may be omitted, in which case a separate positioning mechanism may be provided to position the trailing-end dropping member 250A at the lower position. For example, positioning may be performed by engaging the engagement recess 2502 with the second protrusion 2405 at the lower position.

[0076] To raise the sweeping paddle 240A and the trailing-end dropping member 250A, the motor 610 is driven to rotate the rotary shaft 612 in a first direction (counterclockwise in FIGS. 12(a) and 12(b)). This causes the second cam member 630 to rotate in the same direction as the rotary shaft 612, causing the first protrusion 2404 to move along the inner cam surface 632 and lifting the sweeping paddle 240A. At this time, the second protrusion 2405 re-engages with the engaging recess 2052, and this engagement also lifts the trailing-end dropping member 250A. The sweeping paddle 240A and the trailing-end dropping member 250A then return to their home positions shown in FIGS. 6(a) to 7(c).

[0077] 7(a) from the state of Fig. 12(a), the protrusion 2303 moves along the inner cam surface 622 of the first cam member 620, but the inner cam surface 622 is formed so that the distance from the center of the rotation shaft 612 to the position where the inner cam surface 622 abuts against the protrusion 2303 does not change. Therefore, the upper discharge roller 230A remains at the home position.

[0078] In this embodiment, when the rotating shaft 612 is rotated from the home position in the counterclockwise direction in Figures 7(a) to 7(c), the upper discharge roller 230A descends, and the take-in paddle 240A and the trailing end drop-off member 250A are maintained at the home position. On the other hand, when the rotating shaft 612 is rotated from the home position in the clockwise direction in Figures 7(a) to 7(c), the upper discharge roller 230A is maintained at the home position, and the take-in paddle 240A and the trailing end drop-off member 250A descend.

[0079] 10(a) through 10(c) when the rotation shaft 612 is rotated clockwise in FIGS. 10(a) through 10(c) with the upper discharge roller 230A in the clamping position shown in FIG. 10(a), the upper discharge roller 230A rises, and the take-in paddle 240A and the trailing-end drop-off member 250A are maintained in their home positions. On the other hand, when the rotation shaft 612 is rotated counterclockwise in FIGS. 12(a) through 12(c) with the take-in paddle 240A and the trailing-end drop-off member 250A in their returned and lowered positions, the upper discharge roller 230A is maintained in its home position, and the take-in paddle 240A and the trailing-end drop-off member 250A are raised.

[0080] Figure 13 shows the relationship between each motor and each component. The columns in Figure 13 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 13, processing motor MT12 is the processing motor 610 described above. As is clear from Figure 13, 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.

[0081] Further, the processing motor MT12 moves up and down the pick-up paddle 240A, the trailing end dropping member 250A, and the upper discharge roller (nip member) 230A. In this embodiment, in addition to the above, the motors provided include a return lift 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 pressure motor) MT15 for driving the discharge take-in paddle (sheet pressure (bundle pressure) paddle) 320, 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 lift motor MT20 for raising and lowering the stacking tray 300.

[0082] [Control configuration of sheet processing device] The control configuration of the sheet processing apparatus 200 will be described with reference to Figs. 14 and 15. Fig. 14 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 serves as control means, and the motors are controlled by the control unit 203. 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.

[0083] 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.

[0084] The motors shown in FIG. 14 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 the 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 sheet pressure paddle 320.

[0085] 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.

[0086] Next, the control flow of each mode of this embodiment will be described with reference to FIG. 15. 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 process 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. Sheet information (basis weight, size, etc.) may also be input via the PC.

[0087] In this embodiment, the user can manually set the mode, or the mode can be automatically set based on the paper type (sheet length), and in the shift mode, whether to select the first shift discharge process or the second shift discharge process described below can be set appropriately depending on the output desired by the user.

[0088] In the staple mode for the binding and discharging process, a sheet 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, i.e., the trailing edge of the sheet is regulated. Then, the alignment unit 270A (the pair of alignment plates 271A) is driven by the F-side alignment plate movement motor MT16 and the R-side alignment plate movement motor MT17, thereby moving the sheet abutted against the trailing edge regulating member 290 by the alignment unit 270A in the sheet width direction (the same direction as the shift direction) and positioning it at the binding position. In other words, the alignment process is performed. In this embodiment, the pair of alignment plates 271A is used for center alignment, and the sheets are aligned by hitting them from both sides in the sheet width direction. Repeating this operation of regulating the trailing edge of the sheet and the alignment process forms a stack of sheets on the processing tray 220. Thereafter, the sheet bundle positioned at the binding position is stapled, and the stapled sheet bundle is discharged by the upper discharge rollers 230A and the lower discharge rollers 230B onto the stacking tray 300. In the following shift mode, the pair of alignment plates 271A, the F-side alignment plate moving motor MT16, and the R-side alignment plate moving motor MT17 used in the alignment process when forming the sheet bundle in this staple mode are used to perform a shift operation for sheets that are not to be bound.

[0089] 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 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 is, for example, a sheet whose length in the first conveyance direction is longer than the 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).

[0090] The productivity priority mode as the switchbackless shift discharge process and the first 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 is instead moved (shifted) 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 is then discharged onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B.

[0091] In the alignment priority mode as the switchback shift discharge process and the second shift discharge process, a sheet conveyed downstream in the first conveyance direction by the pre-processing rollers 211A and 212A is conveyed in the second conveyance direction by the take-in paddle 240A on the processing tray 220, and the downstream edge of the sheet in the second conveyance direction is abutted against (regulated by) the trailing edge regulating member 290. Then, without stapling by the staple unit 400, a switchback shift operation is performed in which the sheet is moved (shifted) 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. This will be described in detail later.

[0092] 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).

[0093] 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.

[0094] 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).

[0095] The operation of the sheet processing apparatus 200 in the first shift discharge process and the second shift discharge process in the shift mode will be described with reference to FIGS. 16(a) to 35(b).

[0096] [First shift discharge process (productivity priority mode)] First, the first shift discharge process (productivity priority mode) of the shift mode will be described with reference to Figures 16(a) to 25(b). As shown in Figures 16(a) and 16(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 each located at their home positions. Also, the pair of alignment plates 271A are located at their home positions, which are the positions where they are furthest apart from each other.

[0097] 17(a) and 17(b), when the sheet S is conveyed to the entrance of the conveying path 210A, the pair of alignment plates 271A move closer to each other from their home positions and wait at the receiving position to receive the sheet. 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.

[0098] 18(a) and 18(b), when the downstream end (leading edge) 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 and the leading edge of the sheet S passes through the lower discharge roller 230B, the upper discharge roller 230A starts to descend. For example, when the leading edge of the sheet S reaches a position 10 mm downstream from the nip position where the upper discharge roller 230A and the lower discharge roller 230B nip the sheet, the upper discharge roller 230A is lowered so that the gap between the upper discharge roller 230A and the lower discharge roller 230B becomes 2 mm. In other words, the upper discharge roller 230A is positioned closer to the lower discharge roller 230B than the retracted position, and is positioned at a separated position where the upper discharge roller 230A and the lower discharge roller 230B are separated from each other. At this time, the pick-up paddle 240A and the trailing end dropping member 250A remain in their home positions.

[0099] 19(a) and 19(b), when the upstream end (trailing end) of the sheet S in the first transport direction passes through the pre-processing nip portion 211a of the pre-processing rollers 211A and 212A, the upper discharge roller 230A is lowered to the nipping position, and the sheet is nipped between the upper discharge roller 230A and the lower discharge roller 230B. Furthermore, the rotation of the lower discharge roller 230B is stopped. For example, when the trailing end of the sheet S reaches a position 10 mm downstream from the pre-processing nip portion 211a, the upper discharge roller 230A is positioned at the nipping position. As a result, the sheet S is nipped between the upper discharge roller 230A and the lower discharge roller 230B, and transport is stopped.

[0100] 20(a) and 20(b), the upper discharge rollers 230A are raised to the separated position, and the pair of alignment plates 271A are moved to widthwise positions that match the size of the sheet S. As a result, the sheet S is sandwiched from both sides in the widthwise direction (both sides in the shift direction). Note that, because the sheet S is sandwiched between the pair of alignment plates 271A, even if the upper discharge rollers 230A are raised to the separated position, the sheet S is prevented from shifting in the first conveying direction or the second conveying direction.

[0101] Then, as shown in FIGS. 21A and 21B, the sheet S is moved in the shift direction while being sandwiched between the pair of alignment plates 271A. That is, a shift operation is performed. After the shift operation is completed, as shown in FIGS. 22A and 22B, the upper discharge roller 230A is lowered to the sandwiching position, and the sheet S is again 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 are retracted from the sheet S as shown in FIGS. 23A and 23B. In this example, since the shift direction is from the rear side to the front side, the rear alignment plate of the pair of alignment plates 271A is referred to as the first shift unit, and the front alignment plate is referred to as the second shift unit. In addition, the rear alignment plate moving motor MT17 is referred to as the first drive unit, and the front alignment plate moving motor MT16 is referred to as the second drive unit. Conversely, when the shift direction is from the front side to the rear side, the front alignment plate of the pair of alignment plates 271A is the first shift part, and the rear alignment plate is the second shift part. Also, the front alignment plate moving motor MT16 is the first drive part, and the rear alignment plate moving motor MT17 is the second drive part.

[0102] 24(a) and 24(b), the lower discharge roller 230B is rotated, and the sheet S nipped between the upper discharge roller 230A and the lower discharge roller 230B is discharged onto the stacking tray 300. After the sheet S is discharged onto the stacking tray 300, the sheet pressing paddle 320 picks up the sheet S and further presses down the rear end of the sheet S, as shown in FIGS. 25(a) and 25(b). At this time, the pair of alignment plates 271A moves to the receiving position to receive the next sheet.

[0103] In such a 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 it 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.

[0104] [Second shift discharge process (alignment priority mode)] Next, the second shift discharge process (alignment priority mode) of the shift mode will be described using Figures 26(a) to 35(b). Note that the alignment priority mode may be performed for small-sized sheets, but here we will describe the case where it is performed for large-sized sheets. The state in which sheet S has not yet been transported to transport path 210A and the state in which sheet S has been transported to the entrance of transport path 210A are the same as Figures 16(a) to 17(b) shown in the first shift discharge process.

[0105] 26(a) and 26(b), in the second shift discharge process, even when the downstream end (leading edge) 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 and the leading edge of the sheet S passes through the lower discharge roller 230B, the upper discharge roller 230A does not descend. That is, in this state, the upper discharge roller 230A, the pick-up paddle 240A, and the trailing edge drop member 250A remain positioned at their home positions.

[0106] 27(a) and 27(b), when the upstream end (trailing end) of the sheet S in the first transport direction passes through the pre-processing nip portion 211a of the pre-processing rollers 211A and 212A, the pick-up paddle 240A starts to descend. Then, as shown in FIGS. 28(a) and 28(b), the pick-up paddle 240A is moved to the returned position and the trailing end dropping member 250A is moved to the lowered position, so that the sheet S is dropped onto the processing tray 220 and the pick-up paddle 240A transports the sheet S in the second transport direction.

[0107] 29(a) and 29(b), the return member 280 (knurled belt 281) is also lowered, and the sheet S is conveyed in the second conveyance direction by the take-in paddle 240A and the return member 280, until the trailing end of the sheet S abuts against the trailing end regulating member 290. Thereafter, as shown in FIGS. 30(a) and 30(b), the take-in paddle 240A, the trailing end dropping member 250A, and the return member 280 are raised. In this state, as shown in FIGS. 31(a) and 31(b), of the pair of alignment plates 271A, only the alignment plate 271A (first shift portion) on the upstream side in the shift direction (upper side in FIG. 31(a)) is moved toward the sheet S, and the sheet S is further moved in the shift direction by this alignment plate 271A. That is, in the second shift discharge process, the sheet S is shifted by moving the alignment plate 271A on the upstream side in the shift direction without being sandwiched between the pair of alignment plates 271A. The alignment plate 271A on the downstream side (lower side in FIG. 31(a)) waits at the receiving position when the shift operation starts, and moves from this receiving position in the shift direction according to the shift amount of the sheet S. Note that, during the shift operation by the alignment plate 271A, the knurled belt 281 may be brought into contact with the upper surface of the sheet while rotating. This causes the shift operation to be performed with the rear end of the sheet abutting against the rear end regulating member 290, stabilizing the behavior of the sheet.

[0108] The reason why the downstream alignment plate 271A is not moved from the receiving position toward the sheet S in this way is that, in the second shift discharge process, the shift operation can be performed with multiple sheets placed on the processing tray 220. That is, when performing the shift operation for the second and subsequent sheets, if the downstream alignment plate 271A is moved from the receiving position toward the sheet, the first sheet will also be pushed and moved by this downstream alignment plate 271A, which may disrupt the alignment of the first sheet.

[0109] When the shift operation of the sheet S is completed, the upper discharge rollers 230A are lowered to the nipping position, and the sheet S is nipped between the upper discharge rollers 230A and the lower discharge rollers 230B, as shown in Figures 32(a) and 32(b). After the sheet S is nipped between the upper discharge rollers 230A and the lower discharge rollers 230B, the pair of alignment plates 271A are retracted from the sheet S, as shown in Figures 33(a) and 33(b). In this example, the case where the second shift discharge process is performed on one sheet S will be described, but when the second shift discharge process is performed on two or more sheets, the upper discharge rollers 230A are raised from this state, and the shift operation of the second and subsequent sheets is performed in the same manner as for the sheet S described above.

[0110] When discharging a sheet that has undergone a shift operation, with the upper discharge roller 230A positioned at the nipping position, i.e., in the state shown in FIGS. 33(a) and 33(b), the lower discharge roller 230B is rotated as shown in FIGS. 34(a) and 34(b), and the sheet S nipped between the upper discharge roller 230A and the lower discharge roller 230B is discharged onto the stacking tray 300. After the sheet S has been discharged onto the stacking tray 300, the sheet pressing paddle 320 picks up the sheet S and further presses down the rear end of the sheet S, as shown in FIGS. 35(a) and 35(b). At this time, the pair of alignment plates 271A moves to the receiving position to receive the next sheet.

[0111] In this way, in the alignment priority mode, the sheets S are aligned and shifted on the processing tray 220, so the alignment of the sheets S can be improved compared to the productivity priority mode. However, in the alignment priority mode, the sheets must be temporarily placed on the processing tray 220, so processing takes longer than in the productivity priority mode. However, in the case of large-size sheets, processing within the image forming apparatus 100 also takes time. Therefore, when the alignment priority mode is executed for large-size sheets, the shift operation can be performed with productivity suited to the productivity of the image forming apparatus 100, and further, the alignment of the sheets can be improved. Note that the productivity priority mode described above may also be executed for large-size sheets.

[0112] In this embodiment, when performing the staple mode, the first shift discharge process, and the second shift discharge process, each process is performed using a common drive source, the front alignment plate moving motor MT16 and the rear alignment plate moving motor MT17, and a common alignment plate 271A, which reduces costs compared to a configuration that requires separate alignment plates and drive sources for each process.

[0113] In the above example, the shift operation in the first shift discharge process and the second shift discharge process was performed with the upper discharge roller 230A separated from the lower discharge roller 230B. However, the shift operation may be performed with a lower nip pressure between the upper discharge roller 230A and the lower discharge roller 230B. That is, in the above example, the drive mechanism 600 for moving the upper discharge roller 230A functions as a discharge rotor moving member that moves the upper discharge roller 230A to the nip position, the separated position, and even the retracted position. However, the drive mechanism 600 may also function as a discharge rotor nip pressure switching mechanism that switches the nip pressure at which the upper discharge roller 230A and the lower discharge roller 230B nip the sheet between a first nip pressure and a second nip pressure that is weaker than the first nip pressure. The shift operation may also be performed with the nip pressure set to the second nip pressure. The first nip pressure is a nip pressure when the sheet is discharged between the upper discharge roller 230A and the lower discharge roller 230B.

[0114] In the above example, the shift operation is performed after the sheet passes through the pre-processing nip portion 211a of the pre-processing rollers 211A and 212A during the first shift discharge process. However, the shift operation may be performed while the sheet is in the pre-processing nip portion 211a. One of the pre-processing rollers 211A and 212A may be movable between a clamping position where the rollers clamp the sheet and a spaced position where the rollers are spaced apart, and the pre-processing rollers 211A and 212A may be moved to the spaced position during the shift operation during the first shift discharge process. The nip pressure of the pre-processing rollers 211A and 212A may be switchable between a first nip pressure and a second nip pressure weaker than the first nip pressure, and the second nip pressure may be used during the shift operation during the first shift discharge process. The mechanisms for switching the nip pressure of the pre-processing rollers 211A and 212A and for moving the rollers between the clamping position and the spaced position may be the same as those in the second embodiment. Alternatively, small-size sheets may be shifted by the pair of alignment plates 271A after their trailing edges have passed through the pre-processing nip portion 211a, and large-size sheets may be shifted by the pair of alignment plates 271A after their leading edges have passed through the discharge nip portion 230a and before their trailing edges have passed through the pre-processing nip portion 211a. This brings the contact points of the pair of alignment plates 271A for large-size sheets closer to the center of gravity of the sheets, thereby reducing the force with which the sheets rotate during the shift operation.

[0115] Furthermore, in the above example, when the first shift discharge process is performed, the pair of alignment plates 271A are moved in the shift direction while the sheet S is between the upper discharge roller 230A and the lower discharge roller 230B and the upper discharge roller 230A is positioned at the separation position (or in the second nip pressure state) to shift the sheet S. Similarly, when the second shift discharge process is performed, the pair of alignment plates 271A are moved in the shift direction while the sheet S is between the upper discharge roller 230A and the lower discharge roller 230B and the upper discharge roller 230A is positioned at the separation position (or in the second nip pressure state) to shift the sheet S. Furthermore, when performing staple mode, when aligning the sheet S on the processing tray 220 in the sheet width direction, the sheet S is similarly aligned in the sheet width direction by moving the pair of alignment plates 271A in the shift direction while the sheet S is positioned between the upper discharge roller 230A and the lower discharge roller 230B and the upper discharge roller 230A is positioned at the separated position (or in the second nip pressure state).

[0116] In other words, when shifting the sheet S using the pair of alignment plates 271A in the first shift discharge process, it is necessary to release the nip of the members nipping the sheet S (or change the nip pressure to the second nip pressure), but the nip release mechanism (the mechanism that moves the upper discharge roller 230A between the clamping position and the separated position) is not provided exclusively for the first shift discharge process, but is also used for the second shift discharge process and the staple mode. Therefore, in the first embodiment described above, the nip release mechanism is shared compared to the second embodiment described later, and the staple mode, the first shift discharge process, and the second shift discharge process can be performed at a lower cost.

[0117] [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 binding, thereby forming a sheet bundle consisting of multiple unbound sheets. For example, multiple unbound sheet bundles may be discharged onto the stacking tray 300 by shifting them relative to each other in the shift direction. As a process for shifting and discharging sheets without stapling in this way, in this embodiment, the above-mentioned switchback shift discharge process (alignment priority mode) and switchbackless shift discharge process (productivity priority mode) can be executed.

[0118] In the switchbackless shift discharge process, sheets are shifted one by one and discharged onto the stacking tray 300. At this time, 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 sweep the sheets using the sheet pressure paddle 320 after a sheet bundle is formed on the stacking tray 300, only the top sheet of the sheet bundle will be sweeped, which may result in a deterioration in the alignment of the sheets. Therefore, in this embodiment, as described above with reference to FIGS. 25(a) and 25(b), after the sheets are discharged onto the stacking tray 300, the sheets are sweeped in by the sheet pressure paddle 320.

[0119] That is, when a sheet stack shifted onto the stacking tray 300 (on the stacking section) without being bound is formed, the shift discharge process and the take-in process are repeatedly performed on a plurality of sheets to form a sheet stack consisting of a plurality of sheets on the stacking tray 300. The shift discharge process is a process in which the sheets are shifted by the alignment section 270A and the sheets shifted by the alignment section 270A are discharged onto the stacking tray 300 by the upper discharge rollers 230A and the 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 the stacking tray 300 are conveyed in the second conveyance direction by the sheet pressure paddle 320.

[0120] Furthermore, when the shift discharge process and the take-in process are repeated, the take-in paddle 320 stops at a position on the stacking tray 300 where it presses down on the top surface of the sheet it has taken in after taking in the sheet until the next sheet is discharged (until the trailing edge of the sheet passes the nip point of the discharge roller 230). Then, when the next sheet is discharged onto the stacking tray 300, the take-in paddle 320 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 the stacking tray 300.

[0121] 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 scraping the sheet with the sheet pressing paddle 320, 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.

[0122] 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, as described above with reference to Figures 35(a) and 35(b), by performing a scraping process on each sheet discharged onto the stacking tray 300, it is possible to improve the alignment of the sheet bundle discharged onto the stacking tray 300.

[0123] [Sheet pressure paddle operation] Next, the operation of the sheet pressure paddle 320 as a pressure member will be described with reference to FIGS. 36 to 47. As described above, the sheet pressure paddle 320 presses down the upper surface of a sheet discharged onto the stacking tray 300. The sheet pressure paddle 320 rotates around the rotation shaft 3201, causing the paddle portion 3203 to abut against the upper surface of the sheet. At this time, if the paddle portion 3203 abuts against the upper surface of the sheet with force, a collision noise may be generated. For this reason, in this embodiment, the take-in motor MT15 rotates the sheet pressure paddle 320 from a state in which it is pressing down on a sheet stacked on the stacking tray 300, temporarily stops the rotation before pressing down the upper surface of the next sheet discharged by the upper discharge rollers 230A and the lower discharge rollers 230B, and then starts the rotation again, thereby driving the sheet pressure paddle 320 to press down the upper surface of the next sheet discharged onto the stacking tray 300 at a rotation speed slower than the fastest rotation speed of the sheet pressure paddle 320 before the sheet pressure paddle 320 was temporarily stopped. The specific details will be explained below.

[0124] First, Figure 36 shows the home position (HP) of the sheet pressure paddle 320. The home position is a position above the stacking tray 300 where the paddle portion 3203 of the sheet pressure paddle 320 does not interfere with other members and prevents the paddle portion 3203 from becoming distorted. For example, when waiting for a job, the sheet pressure paddle 320 is located at the home position. A flag 321 is provided on the rotation shaft 3201 of the sheet pressure paddle 320, and when the sheet pressure paddle 320 is located at the home position, the flag 321 is detected by the paddle HP sensor SN15.

[0125] Here, since the sheet pressure paddle 320 rotates around the rotation shaft 3201, the paddle portion 3203 passes by the processing tray 220 side. For this reason, as shown in FIG. 36, a recess 3204 is formed on the processing tray 220 side, through which the paddle portion 3203 can pass when the sheet pressure paddle 320 rotates. That is, since the sheet pressure paddle 320 rotates around the rotation shaft 3201, it rotates counterclockwise in FIG. 36 from above the stacking tray 300 toward the processing tray 220 side, passes by the processing tray 220 side, and returns to above the stacking tray 300 again. For this reason, a recess 3204 is formed at the downstream end of the processing tray 220 in the predetermined direction, at a position corresponding to the sheet pressure paddle 320 in the width direction, so as to be recessed toward the upstream side in the predetermined direction. The paddle portion 3203 passes by the recess 3204 when the sheet pressure paddle 320 rotates.

[0126] In this embodiment, a moving mechanism 221 (a rack-and-pinion mechanism in this embodiment) for moving the alignment plate 271A in the width direction is provided inside the processing tray 220. Because this moving mechanism 221 is provided across the width direction, the recessed portion 3204 can only be recessed up to the front of the moving mechanism 221. That is, in this embodiment, the recessed portion 3204 cannot be recessed to an amount corresponding to the length of the sheet pressure paddle 320. On the other hand, because the paddle portion 3203 of the sheet pressure paddle 320 has elasticity, the paddle portion 3203 passes through the recessed portion 3204 by elastic deformation, as shown in FIG. 40 , which will be described later.

[0127] 37 shows the sheet receiving position of the sheet pressure paddle 320. The sheet receiving position is the position of the sheet pressure paddle 320 when receiving a sheet onto the stacking tray 300. When there is no sheet on the stacking tray 300, the sheet receiving position is the position where the paddle portion 3203 of the sheet pressure paddle 320 abuts against the upper surface of the stacking tray 300 in an elastically bent state. On the other hand, when there is a sheet on the stacking tray 300, the sheet receiving position is the position where the paddle portion 3203 of the sheet pressure paddle 320 abuts against the upper surface of the sheet on the stacking tray 300 in an elastically bent state, as shown in FIG.

[0128] 38 to 43, an operation of pressing down the top surface of a sheet discharged onto the stacking tray 300 by the sheet pressure paddle 320 will be described. Here, an operation of pressing down the next, second sheet S2 by the sheet pressure paddle 320 will be described in a state in which the first sheet S1 is being pressed down on the stacking tray 300 by the sheet pressure paddle 320. In addition, the following description will be given of a case in which a sheet conveyed by the pre-processing rollers 211A and 212A is delivered to the upper discharge rollers 230A and the lower discharge rollers 230B and is discharged onto the stacking tray 300 by the upper discharge rollers 230A and the lower discharge rollers 230B as is, but the operation of the sheet pressure paddle 320 is similar in the case of the discharge operation of the other sheets described above.

[0129] First, Fig. 38 shows a state in which a first sheet S1 stacked on the stacking tray 300 is being pressed down by the sheet pressing paddle 320, while a second sheet S2, which is the sheet following the first sheet S1, is being transported by the pre-processing rollers 211A and 212A. While the second sheet S2 is being nipped and transported between the upper discharge rollers 230A and the lower discharge rollers 230B, the sheet pressing paddle 320 continues to press down the first sheet S1, as shown in Fig. 39. Because the sheet pressing paddle 320 presses down the first sheet S1 in this way, even if the leading edge of the second sheet abuts against the first sheet S1 when the second sheet S2 is transported on top of the first sheet S1, it is possible to prevent the first sheet S1 from shifting.

[0130] As shown in Fig. 40, while the second sheet S2 is being nipped and conveyed between the upper discharge roller 230A and the lower discharge roller 230B, the sheet pressing paddle 320 starts to rotate counterclockwise in the figure. At this time, the paddle portion 3203 enters the recessed portion 3204 while elastically deforming. Then, as shown in Fig. 41, after the rear end (upstream end in the predetermined direction) of the second sheet S2 passes through the discharge nip portion 230a between the upper discharge roller 230A and the lower discharge roller 230B, the paddle portion 3203 jumps out of the recessed portion 3204 and the rotation accelerates. At this time, the third sheet S3, which is the sheet next to the second sheet S2, is being nipped and conveyed between the pre-processing rollers 211A and 212A.

[0131] 42, the sheet pressure paddle 320 temporarily stops rotating before the paddle portion 3203 contacts the second sheet S2. That is, the sheet pressure paddle 320 rotates from a state in which it is pressing down on the first sheet S1 stacked on the stack tray 300, and temporarily stops rotating before pressing down on the top surface of the next second sheet S2 discharged by the upper discharge rollers 230A and the lower discharge rollers 230B. The position at which the sheet pressure paddle 320 temporarily stops rotating is a position at which, when the sheet pressure paddle 320 temporarily stops rotating, the leading edge of the paddle portion 3203 elastically swings downstream in the rotation direction, but does not come into contact with the first sheet S1 stacked on the stack tray 300. That is, because the paddle portion 3203 has elasticity as described above, when the rotation of the sheet pressure paddle 320 stops, the leading edge elastically swings downstream in the rotation direction due to inertia. For this reason, in this embodiment, the stop position of the sheet pressing paddle 320 is set in consideration of the amplitude of the elasticity of the paddle portion 3203 .

[0132] On the other hand, as described below, the sheet pressure paddle 320 temporarily stops rotating and then starts rotating again to press down the upper surface of the sheet on the stacking tray 300. Therefore, from the viewpoint of suppressing collision noise, it is not preferable to make the rotation speed of the sheet pressure paddle 320 too fast after restarting rotation. If the position where the sheet pressure paddle 320 temporarily stops rotating is too far from the stacking tray 300, the rotation speed of the sheet pressure paddle 320 after restarting rotation will be slow, which will take time to press down the sheet, resulting in reduced productivity. Therefore, from the viewpoint of productivity, it is preferable to temporarily stop the rotation of the sheet pressure paddle 320 as close to the stacking tray 300 as possible.

[0133] In this embodiment, the position at which the sheet pressure paddle 320 temporarily stops rotating is above the stacking tray 300 and at a position where the paddle portion 3203 in an unelastically deformed state is approximately parallel to the horizontal direction, as shown in Fig. 42. This position can be set appropriately taking into consideration the positional relationship between the stacking tray 300 and the rotation shaft 3201 of the sheet pressure paddle 320, the angle of the stacking surface of the stacking tray 300 relative to the horizontal direction, and the like, and it is preferable that the timing at which the sheet pressure paddle 320 temporarily stops rotating satisfies the following points.

[0134] First, the timing at which the sheet pressure paddle 320 temporarily stops rotating is the timing at which the paddle 3203 is located upstream in the rotation direction of the contact position where the paddle 3203 contacts the top surface of the stack tray 300, up to a position 180° upstream in the rotation direction of the contact position. In this embodiment, since the paddle 3203 passes through the recess 3204 as described above, if the paddle 3203 stops while located within the recess 3204, rotation will resume thereafter, and the paddle 3203 may elastically restore when it protrudes from the recess 3204, which may cause the operation of the sheet pressure paddle 320 to become unstable. For this reason, it is preferable that the timing at which the sheet pressure paddle 320 temporarily stops rotating is at least after the paddle 3203 has passed the recess 3204.

[0135] As described above, the rotation shaft 3201 of the sheet pressure paddle 320 is provided coaxially with the rotation shaft 230B1 of the lower discharge roller 230B (see FIG. 5A). Therefore, in this embodiment, it is preferable that the timing at which the sheet pressure paddle 320 temporarily stops rotation is the timing at which the paddle portion 3203 is located downstream in the rotation direction of the nip point between the upper discharge roller 230A and the lower discharge roller 230B. Note that the nip point is the point when the pair of rollers contact each other at a point, and is the central position of the width in the sheet conveyance direction when the pair of rollers contact each other with a width in the sheet conveyance direction.

[0136] As described above, after the sheet pressure paddle 320 temporarily stops rotating, the sheet pressure paddle 320 starts rotating again. At this time, the sheet pressure paddle 320 rotates at a rotation speed slower than the fastest rotation speed of the sheet pressure paddle 320 before it temporarily stopped. Then, as shown in FIG. 43, the sheet pressure paddle 320 presses down the upper surface of the second sheet S2 discharged onto the stacking tray 300. At this time, the next third sheet S3 is being nipped and conveyed between the upper discharge roller 230A and the lower discharge roller 230B, and the above-described operations shown in FIGS. 39 to 43 are repeated for the third sheet S3 as well.

[0137] It is preferable that the timing for the sheet pressure paddle 320 to stop rotating and then start rotating again be as soon as possible after the rotation for productivity has stopped. However, because the paddle portion 3203 has elasticity, if the timing at which the tip of the paddle portion 3203 sways downstream in the rotation direction due to its elasticity coincides with the timing at which the sheet pressure paddle 320 resumes rotation, the paddle portion 3203 will sway downstream in the rotation direction due to its elasticity, causing the paddle portion 3203 to come into strong contact with the sheet, resulting in a louder collision noise.

[0138] Therefore, in this embodiment, when the sheet pressure paddle 320 temporarily stops rotating, the tip of the paddle portion 3203 elastically swings downstream in the rotation direction, and then the tip of the paddle portion 3203 elastically swings upstream in the rotation direction. This point will be explained using Figures 44(a) to 44(c). First, Figure 44(a) shows a state in which the sheet pressure paddle 320 is rotating to press down the sheet S discharged onto the stacking tray 300.

[0139] Next, as shown in FIG. 44(b), when the rotation of the sheet pressure paddle 320 temporarily stops, the tip of the paddle portion 3203 elastically swings downstream in the rotation direction. Thereafter, as shown in FIG. 44(c), the tip of the paddle portion 3203 that swung downstream in the rotation direction returns in the opposite direction due to the elasticity of the paddle portion 3203, and swings upstream in the rotation direction. In this embodiment, the rotation of the sheet pressure paddle 320 is resumed at the timing when the paddle portion 3203 is swinging upstream in the rotation direction. Then, after the paddle portion 3203 swings upstream in the rotation direction, the paddle portion 3203 is made to come into contact with the sheet S on the stack tray 300 before it starts to swing downstream in the rotation direction again due to its elasticity.

[0140] As described above, in this embodiment, when the sheet pressure paddle 320 presses down the upper surface of a sheet discharged onto the stacking tray 300, the sheet pressure paddle 320 is operated so that the rotation of the sheet pressure paddle 320 is stopped temporarily and then restarted at a rotation speed slower than the fastest rotation speed of the sheet pressure paddle 320 before the sheet pressure paddle 320 was stopped. This makes it possible to prevent the paddle portion 3203 of the sheet pressure paddle 320 from coming into forceful contact with the sheet on the stacking tray 300, thereby reducing collision noise.

[0141] Furthermore, as described above, the timing for resuming rotation of the sheet pressure paddle 320 is set to the timing when the paddle portion 3203 is elastically swung upstream in the rotation direction, so compared to when rotation is resumed at the timing when the paddle portion 3203 is swung downstream in the rotation direction, it is possible to prevent the paddle portion 3203 from coming into forceful contact with the sheets on the stack tray 300. This makes it possible to further reduce collision noise.

[0142] Next, the operation of the sheet pressure paddle 320 of this embodiment will be described in more detail with reference to FIGS. 45(a) to 47(b). First, FIGS. 45(a) and 45(b) show the operation of detecting the home position of the sheet pressure paddle 320. As described above, the sheet pressure paddle 320 rotates by driving the take-in motor MT15. In this embodiment, the take-in motor MT15 is a pulse motor. FIG. 45(a) shows the sheet pressure paddle 320 making one rotation at a constant speed. In FIG. 45(a), the path of the sheet pressure paddle 320 is schematically shown as an arc path. The position of the sheet pressure paddle 320 shown in FIG. 45(a) is the sheet receiving position (i.e., the holding position), as in FIG. 37, but in FIG. 45(a), the paddle portion 3203 is not elastically deformed as in FIG. 37. FIG. 45(b) is a diagram showing the relationship between the position of the sheet pressure paddle 320, the elapsed time, and the speed (pps) of the take-in motor MT15 at that time.

[0143] When a sheet is received on the stacking tray 300 during a job, the sheet pressure paddle 320 is located at the sheet receiving position shown in FIG. 37. This position is also the position where the sheet is pressed down if there is a sheet on the stacking tray 300, so in FIG. 45(b), this position is referred to as the "pressing position." During the home position detection operation, rotation begins from this pressing position. In this embodiment, the take-in motor MT15 rotates once at a constant speed of, for example, 600 pps during the home position detection operation. At this time, the home position is detected when a flag 321 provided on the rotation shaft 3201 passes the paddle HP sensor SN15.

[0144] 46(a) and (b) show the operation of moving the sheet pressure paddle 320 from the home position to the pressing position. FIG. 46(a) is a diagram showing the sheet pressure paddle 320 rotating from the home position to the pressing position. FIG. 46(a) schematically shows the path of movement of the sheet pressure paddle 320 as an arc path. Similarly to FIG. 45(a), FIG. 46(a) shows the state in which the sheet pressure paddle 320 is in the sheet receiving position (i.e., the pressing position) without elastic deformation of the paddle portion 3203. FIG. 46(b) is a diagram showing the relationship between the position of the sheet pressure paddle 320, the elapsed time, and the speed (pps) of the take-in motor MT15 at that time.

[0145] The operation of moving the sheet pressure paddle 320 from the home position to the pressure position is performed, for example, when a job including an operation of discharging multiple sheets onto the stacking tray 300 is executed, before the first sheet of the job is discharged onto the stacking tray 300. In this embodiment, the rotation operation of the sheet pressure paddle 320 is performed by first accelerating the rotation speed of the sheet pressure paddle 320 to a first speed (maximum speed in this embodiment), and then decelerating from the first speed to a second speed to temporarily stop the rotation of the sheet pressure paddle 320. The position and timing of the temporary stop are as described above. Then, the sheet pressure paddle 320 is moved to the pressure position at the second speed, which is lower than the first speed. At this position, the sheet pressure paddle 320 waits for the sheet to be discharged onto the stacking tray 300.

[0146] Specifically, the rotation of the sheet pressure paddle 320 is accelerated to 1000 pps from the home position to an angle of 2.25°, and then rotated at a constant speed of 1000 pps for an angle of 37.5°. Then, the rotation of the sheet pressure paddle 320 is decelerated from 1000 pps to 600 pps for an angle of 2.25°, and the rotation of the sheet pressure paddle 320 is temporarily stopped. The rotation of the sheet pressure paddle 320 is then resumed and rotated at a constant speed of 600 pps for an angle of 108°. This positions the sheet pressure paddle 320 at the pressing position. At this time, the sheet pressure paddle 320 temporarily stops rotating and then contacts the top surface of the stack tray 300 at a second, slower speed, thereby reducing the impact noise.

[0147] The distance traveled by the sheet pressure paddle 320 when it moves from the home position to the pressing position is smaller than the distance traveled when it makes one revolution from the pressing position and returns to the pressing position. Therefore, the movement of the sheet pressure paddle 320 at this time may be performed without stopping its rotation. At this time, the sheet pressure paddle 320 is moved from the home position to the pressing position at a second speed. In this case, it takes a long time to move the sheet pressure paddle 320 from the home position to the pressing position. However, the timing for moving the sheet pressure paddle 320 from the home position to the pressing position is the start of a job, before the sheet is discharged onto the stack tray 300, so there is ample time. Therefore, even if this time takes, it has almost no effect on productivity.

[0148] 47(a) and (b) show the operation of the sheet pressure paddle 320 when it rotates once from the pressing position and moves back to the pressing position to press down the top surface of a sheet discharged onto the stacking tray 300. FIG. 47(a) is a diagram showing the sheet pressure paddle 320 rotating once from the pressing position. FIG. 47(a) schematically shows the path of the sheet pressure paddle 320 as an arc. Similarly to FIG. 45(a), FIG. 47(a) shows the state in which the sheet pressure paddle 320 is in the sheet receiving position (i.e., the pressing position) without elastic deformation of the paddle portion 3203. FIG. 47(b) is a diagram showing the relationship between the position of the sheet pressure paddle 320, the elapsed time, and the speed (pps) of the take-in motor MT15 at that time.

[0149] The operation of the sheet pressure paddle 320 rotating once from the pressing position is performed, for example, when a job including an operation of discharging multiple sheets onto the stacking tray 300 is executed and the first and subsequent sheets of the job are discharged onto the stacking tray 300. In this embodiment, the sheet pressure paddle 320 first starts rotating at a slow second speed, and then accelerates its rotation speed to a first speed (maximum speed in this embodiment). This is because, as described above, the sheet pressure paddle 320 also functions as a discharged sheet pick-up paddle. That is, the sheet pressure paddle 320 picks up sheets on the stacking tray 300 toward the upright surface 310a (FIG. 2). At this time, if the sheet pressure paddle 320 rotates too fast, there is a risk of the sheets being damaged, such as by buckling. Alternatively, when the paddle portion 3203 separates from the sheet, the strain stored in the sheet is released, and the sheet moves in a direction away from the standing surface 310a, which may affect the alignment of the sheet.

[0150] The reason why the sheet pressure paddle 320 starts rotating at the slow second speed and then changes to the fast first speed is because the paddle portion 3203 passes through the recessed portion 3204 when the sheet pressure paddle 320 is rotated from the pressing position. That is, if the sheet pressure paddle 3200 is rotated at the fast first speed when the paddle portion 3203 passes through the recessed portion 3204, a large load will be applied to the paddle portion 3203 due to friction with the recessed portion 3204. For this reason, in this embodiment, the sheet pressure paddle 320 starts rotating at the slow second speed, and continues to rotate at the second speed until the paddle portion 3203 is partway through passing through the recessed portion 3204, and then the rotation of the sheet pressure paddle 320 is accelerated before the paddle portion 3203 leaves the recessed portion 3204.

[0151] Next, after rotating at a first speed, the rotation of the sheet pressure paddle 320 is decelerated from the first speed to a second speed and temporarily stopped. The position and timing of the temporary stop are as described above. Then, the sheet pressure paddle 320 is moved to the pressing position at the second speed, which is slower than the first speed. This causes the sheet pressure paddle 320 to press down on the top surface of the sheet being discharged onto the stacking tray 300.

[0152] Specifically, the sheet pressure paddle 320 rotates at a constant speed of 600 pps from the pressure position to an angle of 10°, and then the rotation speed of the sheet pressure paddle 320 is accelerated to 1000 pps until the angle reaches 2.25°. The sheet pressure paddle 320 then rotates at a constant speed of 1000 pps for an angle of 237.5°. Next, the rotation speed of the sheet pressure paddle 320 is decelerated from 1000 pps to 600 pps for an angle of 2.25°, and then the rotation of the sheet pressure paddle 320 is temporarily stopped. In this embodiment, the rotation of the sheet pressure paddle 320 is stopped for a predetermined time (30 ms in the illustrated example). Note that the time for which the rotation of the sheet pressure paddle 320 is temporarily stopped varies depending on the length and hardness of the sheet pressure paddle 320. The sheet pressure paddle 320 then resumes rotation and rotates at a constant speed of 600 pps for an angle of 108°. As a result, the sheet pressure paddle 320 is positioned at the pressure position. At this time, the sheet pressure paddle 320 is temporarily stopped from rotating, and then comes into contact with the upper surface of the stacking tray 300 at a second slow speed, thereby reducing the impact noise.

[0153] In the above description, the rotation of the sheet pressure paddle 320 is temporarily stopped from the operation for the first sheet of the job. However, for the first sheet, the sheet pressure paddle 320 may be rotated at a low speed (for example, the second speed) without stopping its rotation, so that the sheet pressure paddle 320 presses down the top surface of the sheet. That is, unlike the second and subsequent sheets, the first sheet does not undergo a pressing operation beforehand, so there is ample time before the sheet pressure paddle 320 presses down the top surface. Therefore, for the first sheet, for example, the start timing of the rotation of the sheet pressure paddle 320 can be earlier than the operation for the second and subsequent sheets. Therefore, the first sheet can be pressed down by rotating the sheet pressure paddle 320 at a constant speed, the second speed, and if the paddle portion 3203 abuts against the top surface of the sheet at the low speed, the impact noise is reduced.

[0154] On the other hand, for the second and subsequent sheets, as described with reference to FIGS. 38 to 43, it is necessary to perform the sheet pressing operation by the sheet pressing paddle 320 so as to keep up with the conveyance timing of the successively conveyed sheets. For this reason, if the sheet pressing paddle 320 is rotated at a constant speed using the second speed as in the case of the first sheet, the pressing operation for the next sheet will not be completed in time. In this case, it is conceivable to widen the sheet conveyance interval so as to keep up with the pressing operation for the next sheet, but this would result in reduced productivity. Therefore, in this embodiment, the sheet pressing paddle 320 is operated as described above for at least the second and subsequent sheets of a job, i.e., for the next sheet when sheets are already stacked on the stacking tray 300.

[0155] That is, when the sheet pressure paddle 320 rotates while pressing down on a sheet stacked on the stacking tray 300, it accelerates its rotational speed to a first speed, then decelerates from the first speed to a second speed, stops rotating, and then rotates at the second speed to press down on the top surface of the next sheet discharged onto the stacking tray 300. This reduces impact noise while suppressing a decrease in productivity. It is preferable that the deceleration rate from the first speed to the second speed be set to a rate that allows a large speed difference without promoting plastic deformation of the paddle portion 3203. That is, if the plastic deformation of the paddle portion 3203 increases due to the acceleration of the deceleration, it takes a long time for the vibration of the paddle portion 3203 to converge when the paddle portion 3203 is stopped. On the other hand, if the speed difference between the first speed and the second speed is large, the sheet pressure paddle 320 can be stopped for a long time, but if the speed difference is large, the vibration of the paddle portion 3203 is difficult to converge. In this embodiment, the deceleration rate from the first speed to the second speed is preferably, for example, between 60% and 80%. If the second speed is less than 60% of the first speed, the rotation speed of the sheet pressure paddle 320 becomes too slow, resulting in reduced productivity. On the other hand, if the second speed is more than 80% of the first speed, the rotation speed of the sheet pressure paddle 320 may be too fast and may not be able to sufficiently reduce the impact noise.

[0156] The operation of the sheet pressing mechanism 1320 in the staple mode as the binding and discharging process will be described in detail below. First, the basic operation in the staple mode will be described with reference to Figures 48 and 49.

[0157] FIG. 48(a) shows a state in which the sheet S is being conveyed to the processing tray 220 by the pre-processing rollers 211A and 212A. The sheet S is switchback-conveyed using the pick-up paddle 240A and the return member 280, and the trailing edge of the sheet S is abutted against the trailing edge regulating member 290, and the sheet width is aligned by the alignment section 270A. This process is repeated for multiple sheets to form a sheet bundle SB1 on the processing tray 220 (FIG. 48(b)). Thereafter, the sheet bundle SB1 formed on the processing tray 220 is bound by the staple unit 400, and the bound sheet bundle SB1 is discharged onto the stacking tray 300 using the discharge rollers 230A and 230B. After the sheet bundle SB1 is discharged onto the stacking tray 300, the sheet pressing mechanism 1320 rotates the sheet pressing paddle 320 to press down the upper surface of the sheet bundle SB1 (FIG. 48(c)).

[0158] Thereafter, the next sheet bundle SB2 is formed on the processing tray 220 and stapled by the staple unit 400 (FIG. 49(a)). The stapled sheet bundle SB2 is discharged onto the stacking tray 300, but at this time, the sheet pressure paddle 320 holds down the sheet bundle SB1 so that the leading edge of the sheet bundle SB2 does not push the sheet bundle SB1 stacked on the stacking tray 300 in the discharge direction (FIG. 49(b)). Once the sheet bundle SB2 is discharged onto the sheet bundle SB1, the sheet pressure mechanism 1320 rotates the sheet pressure paddle 320 to press down the top surface of the sheet bundle SB2 (FIG. 49(c)). The sheet pressure paddle 320 may start rotating before the trailing edge of the sheet bundle SB2 passes the discharge rollers 230A and 230B (before the sheet bundle SB2 is completely discharged), but it starts rotating at least after the leading edge of the sheet bundle SB2 reaches the sheet bundle SB1.

[0159] Here, we will explain the issues that arise when thin sheets with a basis weight of 64 g / m or less are stapled, discharged onto stacking tray 300, and pressed down by sheet pressing paddle 320. As described above, sheet pressing paddle 320 is designed to prevent the alignment of sheet stacks from becoming poor when a previously discharged sheet stack SB1 is pushed out by a subsequently discharged sheet stack SB2 and discharged onto stacking tray 300. However, sheet pressing paddle 320 also has the function of knocking down sheets with upward curled trailing ends onto stacking tray 300, and therefore is configured to rotate around rotation axis 3201 located below the sheets being discharged by upper discharge roller 230A and lower discharge roller 230B.

[0160] Since the sheet processing device 200 of this embodiment is an internal finisher, the angle of the stacking tray 300 (the angle of inclination upward from the upstream side to the downstream side in the discharge direction) is smaller than that of an external finisher, so that sheets discharged onto the stacking tray 300 do not easily return toward the standing surface 310a. Therefore, particularly in an internal finisher, sheets discharged onto the stacking tray 300 are pulled toward the standing surface 310a to improve alignment. The sheet processing device 200 of this embodiment performs this pulling operation using a sheet pressing paddle 320,

[0161] When pressing down on the top surface of a stack of sheets with this configuration, the paddle portion (contact portion) 3203 of the sheet pressing paddle 320 comes into contact with the sheets and then rotates a predetermined amount to press down on the sheets by applying a certain amount of pressure to prevent the sheets from being pushed out. This configuration allows the paddle portion 3203 to elastically deform and press down on the sheets.

[0162] In this configuration, when sheet stack SB1 made of thin paper ShB with a basis weight of 64 g / m2 or less is pressed and rotated by sheet pressure paddle 320, the stiffness of sheets ShB is weak, causing the top sheet to rotate around binding portion Sh1a, creating a buckled portion Sh1b, and in this state, sheet pressure paddle 320 stops to prevent it from being pushed out by the next sheet stack SB2 (Figure 50(a)). If the next sheet stack SB2 is discharged in this state on top of the buckled sheet (Figure 50(b)), and sheet pressure paddle 320 is further rotated to press down on sheet stack SB2 from above (Figure 50(c)), the buckled portion Sh1b may be crushed, potentially damaging sheet stack SB1. Furthermore, if the sheet stack SB2 is discharged onto the buckled sheets, the top sheet of the sheet stack SB2 will also buckle due to the sheet pressing paddle 320. If this process is repeated multiple times, the buckled portions will overlap and rise, and the leading edge of the sheet being transported from the pre-processing rollers 211A and 212A may collide with the raised portion, causing transport problems.

[0163] Therefore, the sheet processing device 200 of this embodiment performs a binding process on the thin paper ShB and discharges it onto the stacking tray 300, and controls the sheet pressing mechanism 1320 to reduce buckling of the top sheet when pressed down by the sheet pressing paddle 320, as described below.

[0164] First, thick paper ShA with a basis weight of 120 g / m2 or more has a high stiffness, and when the next sheet bundle SB2 is discharged, a strong force is exerted to push out the already stacked sheet bundle SB1. Therefore, a strong pressing force is required when the sheet pressing paddle 320 presses down the already stacked sheet bundle SB1. For this reason, the control unit 203 sets the rotation amount (first rotation amount ra1) from when the flag 321 provided on the rotation shaft 3201 passes the paddle HP sensor SN15 (this position is called the reference position) until it stops (pressing position) to 130 degrees (Figure 51(a)).

[0165] This allows the sheet stack made of thick paper ShA with a basis weight of 120 g / m2 or more to be pressed with an appropriate pressing force. Furthermore, because thick paper ShA is not prone to buckling in the first place, even if the sheet pressing paddle 320 is rotated and pressed at this rotation amount, buckling hardly occurs.

[0166] On the other hand, thin paper ShB having a basis weight of 64 g / m2 or less has low stiffness, and if the sheet pressure paddle 320 is rotated and pressed by the same amount of rotation as for thick paper ShA, there is a high possibility that the top sheet will buckle. Therefore, when binding a sheet stack made of thin paper ShB having a basis weight of 64 g / m2 or less, discharging the sheet stack onto the stacking tray 300, and pressing the sheet stack with the sheet pressure paddle 320, the control unit 203 of this embodiment sets the rotation amount (second rotation amount ra2) from when the flag 321 passes the paddle HP sensor SN15 (reference position) until it stops (pressure position) to 70 degrees, which is less than the first rotation amount ra1 (FIG. 51(b)).

[0167] This shortens the distance the paddle 3203 rotates after contacting the top sheet of the stack of thin paper ShB, reducing buckling of the top sheet. At this time, the pressing force on the stack of sheets is smaller than that of thick paper ShA. However, since thin paper ShB is weak and the pushing force of the next sheet bundle Sh2 is weak, it is sufficient to apply a pressing force that can counter this pushing force. In other words, the second rotation amount ra2 is set within a range that reduces buckling of the top sheet and prevents it from being pushed out by the next sheet bundle SB2 (70 degrees in this embodiment).

[0168] Furthermore, after the next sheet bundle SB2 is discharged onto the sheet bundle SB1 while the first sheet bundle SB1 is being pressed down by the sheet press paddle 320, the sheet bundle SB2 presses down the top sheet of the sheet bundle SB1, so even if the sheet press paddle 320 is rotated from the pressing position to press down the sheet bundle SB2, the top sheet is unlikely to buckle. Therefore, the control unit 203 rotates the sheet press paddle 320 to press down the sheet bundle SB2 after the leading edge of the sheet bundle SB2 is placed on the sheet bundle SB1.

[0169] In this way, by changing the rotation amount of the sheet pressing paddle 320 according to the basis weight of the sheets, it is possible to reduce buckling when pressing down a sheet stack made of thin paper ShB. The first rotation amount ra1 and the second rotation amount ra2 can be set appropriately depending on the arrangement of the sensor SN15, the shape of the flag 321, etc.

[0170] Furthermore, since there is no problem whether the first rotation amount ra1 or the second rotation amount ra2 is applied to sheets whose basis weight is between 64 g / m2 and 120 g / m2, in this embodiment, the threshold (predetermined basis weight) is set to 105 g / m2, and the rotation amount of the sheet pressure paddle 320 is set to the first rotation amount ra1 when the basis weight is greater than 105 g / m2, and the rotation amount of the sheet pressure paddle 320 is set to the second rotation amount ra2 when the basis weight is 105 g / m2 or less. Note that a third rotation amount between the first rotation amount ra1 and the second rotation amount ra2 may be set for sheets whose basis weight is between 64 g / m2 and 120 g / m2.

[0171] 52 is a flowchart relating to sheet bundle discharge in staple mode, which shows in detail step S9 "Discharge bundle onto stack tray" in the flowchart shown in FIG.

[0172] The control unit 203 first discharges the stapled sheet bundle SB1 onto the stacking tray 300 (St1). At this time, the control unit 203 determines whether the basis weight of the sheets is equal to or less than a predetermined basis weight (105 g / m2 in this embodiment, as described above) (St2). If the basis weight is greater than the predetermined basis weight (thick paper ShA), the control unit 203 sets the rotation amount of the pressure paddle 320 to a first rotation amount ra1 (St3). The sheet pressure paddle 320 rotates by the first rotation amount ra1 and stops, thereby pressing down the sheet bundle SB1 discharged onto the stacking tray 300 (St5). On the other hand, if the basis weight is equal to or less than the predetermined basis weight in St2 (thin paper ShB), the control unit 203 sets the rotation amount of the pressure paddle 320 to a second rotation amount ra2 (St4). The sheet pressure paddle 320 rotates by the second rotation amount ra2 and stops, thereby pressing down the sheet bundle SB1 discharged onto the stacking tray 300 (St5). The control unit 203 may set the rotation amount when it receives sheet information.

[0173] Furthermore, as described above, the sheet processing apparatus 200 of this embodiment can execute not only the staple mode but also the straight discharge mode and the shift mode. In this case, the rotation amount of the sheet pressure paddle 320 when pressing down the sheets discharged onto the stacking tray 300 with the sheet pressure paddle 320 is set to a rotation amount greater than the second rotation amount ra2 regardless of the sheet basis weight, and in this embodiment, it is set to the same rotation amount as the first rotation amount ra1. This is because a certain degree of pressing force is required because sheets that have not been bound are easily pushed out by the next sheet being discharged. In other words, the rotation amount does not have to be the same as the first rotation amount ra1 as long as the pressing force is sufficient to prevent previously stacked sheets from being pushed out by the next sheet being discharged, and can be set as appropriate.

[0174] In addition, in the staple mode of this embodiment, the binding process is performed by the staple unit 400 using staples, but the binding process may also be performed on the sheet stack by a binding unit such as a pressure binding unit without using staples.

[0175] Furthermore, although the present embodiment shows a mode in which binding processing is performed on the corners of the sheet stack (FIG. 50), two-point binding processing may also be performed in which two-point binding processing is performed on the sheet ends that abut against the trailing end regulating member 290. In this case as well, the sheet pressing paddle 320 is rotated by a first rotation amount ra1 for a sheet stack made of thick paper ShA, and is rotated by a second rotation amount ra2 for a sheet stack made of thin paper ShB.

[0176] <Other embodiments> In the above-described embodiments, the sheet processing apparatus 200, 200A is configured to be disposed in the internal space 130 of the image forming apparatus 100, but the sheet processing apparatus of the present invention may be configured to be attached to the side of the image forming apparatus, for example. Also, the sheet processing apparatus may be configured to be controlled by the control unit 1003 provided in the image forming apparatus. [Explanation of symbols]

[0177] 100, 100A... Image forming device 103 Image forming unit 200, 200A... Sheet processing device (sheet stacking device) 211A, 212A... Pre-processing rollers (first conveying section, pair of conveying rotating bodies) 220 Processing tray (mounting section) 230A···Upper discharge roller (discharge section, discharge rotor) 230B Lower discharge roller (discharge section, discharge rotor) 230B1 Rotating shaft 300, 300A Loading tray (loading section) 320, 320A... Sheet holding paddle (holding member) 400 Staple unit (processing section) 1000, 1000A... Image formation system 3201 Rotating shaft 3202...Fixed part 3203 Paddle part (contact part) MT15···Scraping motor (drive unit)

Claims

1. a loading section for loading a sheet stack consisting of a plurality of sheets; a binding unit that performs a binding process on the sheet bundle placed on the sheet stack placement section; a stacking section for stacking the bound sheet bundle; a discharge section that discharges the sheet bundle from the placement section to the stacking section; a sheet pressing mechanism having a rotating shaft located on the underside of the sheet being discharged by the discharge section, a fixed section fixed to the rotating shaft, and an elastic contact section provided on the fixed section, the sheet pressing mechanism rotating around the rotating shaft with the contact section in contact with the upper surface of the sheet discharged to the stacking section and then stopping, thereby causing the contact section to elastically deform and press down the upper surface of the sheet discharged to the stacking section; a sensor for detecting a reference position of the contact portion; a control unit that controls the discharge unit and the sheet pressing mechanism, The control unit After a first sheet bundle is discharged to the stacking portion, the contact portion presses down an upper surface of the first sheet bundle, and in this state, a second sheet bundle is discharged onto the first sheet bundle, and after a leading end of the second sheet bundle is placed on the first sheet bundle, the contact portion is rotated to operate the discharge portion and the sheet pressing mechanism so as to press down an upper surface of the second sheet bundle discharged onto the first sheet bundle, When the contact portion presses the first sheet bundle, the amount of rotation of the contact portion from the reference position to the stop when the binding process is performed on the sheet bundle made up of sheets with a basis weight of 120 g / m2 or more and the sheet bundle is discharged to the stacking portion is defined as a first amount of rotation, and the amount of rotation of the contact portion from the reference position to the stop when the binding process is performed on the sheet bundle made up of sheets with a basis weight of 64 g / m2 or less and the sheet bundle is discharged to the stacking portion is defined as a second amount of rotation that is smaller than the first amount of rotation. A sheet processing apparatus characterized by:

2. the sheet processing apparatus is capable of executing an unstitched discharge mode in which sheets that are not to be bound are discharged one by one to the stacking portion, The sheet processing apparatus according to claim 1, characterized in that, when a sheet having a basis weight of 64 g / m2 or less is discharged to the stacking section in the unstitched discharge mode, the control unit increases the amount of rotation of the contact portion from the reference position to the stop when pressing the sheet discharged to the stacking section to more than the first amount of rotation.

3. an image forming unit that forms an image on a sheet; a sheet stacking section for stacking a plurality of sheets on which images have been formed by the image forming section; a binding unit that performs a binding process on the sheet bundle placed on the sheet stack placement section; a stacking section for stacking the bound sheet bundle; a discharge section that discharges the sheet bundle from the placement section to the stacking section; a sheet pressing mechanism having a rotating shaft located on the underside of the sheet being discharged by the discharge section, a fixed section fixed to the rotating shaft, and an elastic contact section provided on the fixed section, the sheet pressing mechanism rotating around the rotating shaft with the contact section in contact with the upper surface of the sheet discharged to the stacking section and then stopping, thereby causing the contact section to elastically deform and press down the upper surface of the sheet discharged to the stacking section; a sensor for detecting a reference position of the contact portion; a control unit that controls the discharge unit and the sheet pressing mechanism, The control unit After a first sheet bundle is discharged to the stacking portion, the contact portion presses down an upper surface of the first sheet bundle, and in this state, a second sheet bundle is discharged onto the first sheet bundle, and after a leading end of the second sheet bundle is placed on the first sheet bundle, the contact portion is rotated to operate the discharge portion and the sheet pressing mechanism so as to press down an upper surface of the second sheet bundle discharged onto the first sheet bundle, When the contact portion presses the first sheet bundle, the amount of rotation of the contact portion from the reference position to the stop when the binding process is performed on the sheet bundle made up of sheets with a basis weight of 120 g / m2 or more and the sheet bundle is discharged to the stacking portion is defined as a first amount of rotation, and the amount of rotation of the contact portion from the reference position to the stop when the binding process is performed on the sheet bundle made up of sheets with a basis weight of 64 g / m2 or less and the sheet bundle is discharged to the stacking portion is defined as a second amount of rotation that is smaller than the first amount of rotation. An image forming system comprising:

Images