Sheet processing apparatus and image forming system

Abstract

To provide an improved mechanism that balances between the improved alignment of sheets by combining a holding member with an ejector tray and the reduction of crash noise caused by their collision.SOLUTION: The sheet processing device includes: discharge means for discharging a bundle of sheets conveyed along a conveyance path from an outlet; loading means for loading the discharged bundle of sheets; contacting means located on the front in the discharge direction of the bundle of sheets from the outlet and abutting the upper surface of the discharged bundle of sheets; support means configured to be retractable from the outlet and to temporarily advance under the bundle of sheets and support the bundle of sheets when the bundle of sheets is discharged; and control means which controls the movement of the support means so that the support means reaches the position of the contacting means after the bundle of sheets abuts the contacting means.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a sheet processing apparatus and an image forming system. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there is known a post-processing device that is connected downstream of an image forming apparatus and performs post-processing such as an alignment process for aligning edges of sheets delivered from the image forming apparatus and a binding process for binding the sheets.

[0003] Patent Document 1 discloses a technology for supporting the posture of large sheets drawn into a processing tray in a post-processing device by a retractable tray that temporarily advances outside the device in order to prevent a decrease in sheet alignment on the processing tray. The post-processing device in Patent Document 1 also has a mechanism for further improving the alignment of the sheet stack on the processing tray by pressing the sheet stack with a belt-like member that comes into contact with the sheets drawn into the processing tray. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-265123 Summary of the Invention [Problem to be solved by the invention]

[0005] It is desirable to maintain the alignment of the sheets even when the processed sheets are discharged from the device. For example, it is conceivable to use a pressure member to hold down the discharged sheets so that the sheet orientation is not disturbed by the influence of air resistance when the sheets fall into the destination tray. However, such a pressure member must be arranged so as to overlap the sheet's discharge direction. Furthermore, if the retractable tray is used to maintain the sheet orientation, the pressure member and the retractable tray will interfere with or collide with each other. The collision between the pressure member and the retractable tray produces a collision sound that is unpleasant to the user.

[0006] In view of the above-mentioned circumstances, the present disclosure aims to provide an improved mechanism that improves sheet alignment by using a pressing member and a retractable tray in combination, while also reducing the impact noise caused by their collision. [Means for solving the problem]

[0007] According to one aspect, there is provided a sheet processing apparatus including: discharge means for discharging a sheet bundle conveyed along a conveying path from a discharge opening; stacking means on which the discharged sheet bundle is stacked; contact means located forward from the discharge opening in the discharge direction of the sheet bundle and contacting an upper surface of the discharged sheet bundle; support means configured to be able to advance and retreat from the discharge opening and temporarily advance below the sheet bundle to support the sheet bundle when it is discharged; and control means for controlling movement of the support means so that the support means reaches the position of the contact means after the sheet bundle contacts the contact means. A corresponding image forming system is also provided. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to improve the alignment of sheets by using a pressing member and a retractable tray in combination, while also reducing the impact noise caused by the impact between them. [Brief explanation of the drawings]

[0009] [Figure 1]FIG. 1 is a schematic diagram showing an example of the configuration of an image forming system according to an embodiment. [Figure 2] FIG. 2 is a perspective view illustrating an example of a configuration of a post-processing unit according to an embodiment. [Figure 3] FIG. 2 is a block diagram showing an example of the configuration of a control function of an image forming system according to an embodiment. [Figure 4] FIG. 2 is a block diagram showing an example of a detailed configuration related to a discharge control function of the post-processing device according to an embodiment. [Figure 5] 10A and 10B are perspective views showing in detail the states of the members of the bundle discharge section when the retractable tray is in the retracted position and when the retractable tray is in the advanced position. [Figure 6] 10A and 10B are schematic cross-sectional views showing the positional relationship between the main members of the bundle discharge section and the sheets when the retractable tray is in the retracted position and when the retractable tray is in the advanced position. [Figure 7] 10 is a flowchart illustrating an example of the flow of a transport control process according to an embodiment. [Figure 8] 10 is a flowchart showing an example of the flow of an appearance and haunting control process according to an embodiment. [Figure 9] 10 is a timing chart for explaining the timing of the advancement of the retractable tray. [Figure 10] FIG. 10 is a block diagram showing an example of a detailed configuration related to a discharge control function of a post-processing device according to a first modified example. [Figure 11] 10 is a flowchart showing an example of the flow of a transport control process according to a first modified example. [Figure 12] 10 is a timing chart for explaining the control of the transport speed in the first modified example. [Figure 13] FIG. 10 is a block diagram showing an example of a detailed configuration related to a discharge control function of a post-processing device according to a second modified example. [Figure 14] 10 is a flowchart showing an example of the flow of an appearance and disappearance control process according to a second modified example. [Figure 15] 10 is a timing chart for explaining the control of appearance and disappearance timing in the second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0011] <1. Overall system configuration example> FIG. 1 is a schematic diagram showing an example of the configuration of an image forming system 1s according to an embodiment. Referring to FIG. 1, the image forming system 1s includes an image forming apparatus 1, a reading apparatus 2, and a post-processing apparatus 4. The image forming apparatus 1 forms an image on a sheet (also called a recording material). The reading apparatus 2 optically reads an original document and generates read image data. The post-processing apparatus 4 is connected to the image forming apparatus 1, receives a sheet from the image forming apparatus 1, and performs post-processing, which will be described later, on the received sheet.

[0012] Generally, the technology disclosed herein is applicable to a sheet processing apparatus that performs some processing on a sheet and then discharges the sheet to the outside of the apparatus. In this embodiment, an example in which the post-processing apparatus 4 is a sheet processing apparatus will be mainly described. However, in other embodiments, the image forming apparatus may be a sheet processing apparatus.

[0013] <2. Example of reader configuration> In the example of FIG. 1 , the reading device 2 is integrated with the document feeder 3. The reading device 2 further includes a document tray 16, a drive unit 17, a first reading unit 18, a second reading unit 19, and an output tray 20. The document feeder 3 transports a document placed on the document tray 16 along a transport path to a reading position. The first reading unit 18 has an array of image sensors and optically reads the first side of the document that has reached the reading position to generate read image data. The second reading unit 19 also has an array of image sensors and optically reads the second side of the document that has reached the reading position to generate read image data. The document that has passed the reading position is output to the output tray 20. The first reading unit 18 is driven by the drive unit 17 to move horizontally, and can also optically read a document (e.g., a booklet document) placed on a document platen glass while moving.

[0014] <3. Configuration example of image forming device> In the example of FIG. 1, the image forming apparatus 1 is a monochrome printer that operates using an electrophotographic method. The image forming apparatus 1 includes an image forming unit 1b that forms an image on a sheet using a direct transfer method. The image forming unit 1b includes a process cartridge 8 and a scanner unit 15. The process cartridge 8 includes a photosensitive drum 9. The scanner unit 15 writes an electrostatic latent image on the surface of the rotating, charged photosensitive drum 9 by exposing the surface to laser light in accordance with input image data. The written electrostatic latent image is developed by supplying charged toner particles, thereby forming a toner image. The toner image is carried on the photosensitive drum 9 and reaches a transfer position between the photosensitive drum 9 and a transfer roller 10. When a copy job is executed, the input image data is read image data generated by one or both of the first reading unit 18 and the second reading unit 19 of the reading device 2. When a print job is executed, the input image data is received from an external device via a network.

[0015] The image forming apparatus 1 further includes a cassette 6 containing a stack of sheets. The sheets are separated from the cassette 6 by a feeding mechanism and transported one by one along a transport path. Registration rollers 7 correct any skew of the transported sheet and transport the sheet to a transfer position. At the transfer position, the toner image carried by the photosensitive drum 9 is transferred to the front side of the sheet. The sheet is transported from the transfer position to a fixing unit 11 downstream. The fixing unit 11 fixes the toner image to the sheet by clamping and pressurizing the sheet between a pair of rollers and heating the toner with a heating element such as a halogen lamp. When double-sided printing is performed, the sheet that has passed through the fixing unit 11 is switched back by a reversing roller 12 and transported back to the transfer position via a re-transport path 13 in an inverted state. At the transfer position, the toner image carried by the photosensitive drum 9 is transferred to the back side of the sheet. The sheet then passes through the fixing unit 11 again. After single-sided or double-sided printing, the sheet is delivered to the post-processing device 4.

[0016] It should be noted that the configurations of the image forming apparatus 1 and the reading apparatus 2 described here are merely examples. The image forming apparatus 1 may operate using other image forming methods, such as an inkjet method or an offset printing method. The image forming apparatus 1 may also be a color printer. The image forming unit 1b may also operate using an intermediate transfer method in which an image is transferred from a photosensitive drum to a sheet via an intermediate transfer body, rather than a direct transfer method. The reading apparatus 2 may not have a document feeder 3.

[0017] <4. Example of post-processing device configuration> The post-processing device 4 includes a transport path consisting of an receiving path 81, an internal path 82, a first discharge path 83, and a second discharge path 84, an upper discharge tray 25, a post-processing unit 4a, a bundle discharge unit 4b, and a lower discharge tray 37. The receiving path 81 is a path for receiving sheets from the image forming device 1. The internal path 82 is a path for transporting sheets to the post-processing unit 4a. The first discharge path 83 is a path for discharging sheets to the upper discharge tray 25. The second discharge path 84 is a path for discharging sheets from the discharge outlet 70 of the bundle discharge unit 4b to the lower discharge tray 37.

[0018] Inlet rollers 21, located near the entrance of receiving path 81, pull a sheet discharged from image forming apparatus 1 into receiving path 81 and transport it to pre-buffer rollers 22. An inlet sensor 27, located between the inlet rollers 21 and pre-buffer rollers 22, detects a sheet passing through receiving path 81. The pre-buffer rollers 22 transport the sheet to first discharge path 83. When upper discharge tray 25 is specified as the sheet discharge destination, reversing rollers 24, located in first discharge path 83, discharge the conveyed sheet to upper discharge tray 25. In this case, post-processing is not applied to the sheet delivered from image forming apparatus 1. When lower discharge tray 37 is specified as the sheet discharge destination, reversing rollers 24 switchback the sheet and transport it to internal path 82. A check valve 23 prevents the switched-back sheet from flowing back into receiving path 81. The sheet that has entered the internal path 82 is conveyed toward the post-processing section 4a by the internal discharge rollers 26, the intermediate conveyance rollers 28, and the kick-out rollers 29 in this order. The intermediate sensor 38 detects the sheet passing between the intermediate conveyance rollers 28 and the kick-out rollers 29.

[0019] In this embodiment, the post-processing unit 4a aligns multiple sheets received from the internal path 82. The post-processing unit 4a further includes a stapler 51 that can staple the aligned stack of sheets. The stack of sheets processed by the post-processing unit 4a is conveyed along the second discharge path 84 by having its trailing edge pushed by the discharge guide 34 that slides in the discharge direction X2, and is then delivered to the discharge rollers 36. The exit sensor 60, which serves as a detection unit, detects a sheet passing through a detection position (position d1, described below) on the second discharge path 84 in front of the discharge opening 70 (in front of the discharge rollers 36 in the example of FIG. 1). The pair of discharge rollers 36, which serve as a discharge unit, discharge the delivered stack of sheets from the discharge opening 70 to the lower discharge tray 37, which serves as a stacking unit. The discharged stack of sheets is stacked on the lower discharge tray 37.

[0020] The above-mentioned entrance sensor 27, intermediate sensor 38 and exit sensor 60 may be, for example, optical sensors (e.g., photointerrupters) that detect the presence of a sheet at the corresponding detection position when the incident light is blocked by the sheet.

[0021] The retractable tray 61 is a support device disposed between the second discharge path 84 and the lower discharge tray 37 and configured to be movable forward and backward from the discharge opening 70. When a sheet stack is not being discharged, the retractable tray 61 retracts to a retracted position inside the discharge opening 70. When a sheet stack is being discharged from the discharge opening 70, the retractable tray 61 temporarily advances below the sheet stack to support it. More specifically, when the leading edge of the sheet stack reaches the detection position of the exit sensor 60 and the exit sensor 60 detects the presence of the sheet stack, the retractable tray 61 waits for a certain period of time under the control of a control device (described later) and then advances from the discharge opening 70 in direction C1 below the sheet stack. The advanced retractable tray 61 supports the sheet stack on its underside and contributes to maintaining the posture of the sheet stack during discharge. After that, when the trailing edge of the sheet stack reaches the detection position, the exit sensor 60 no longer detects the presence of the sheet stack. Then, the retractable tray 61 moves in the direction opposite to the direction C1 and retreats to the original retreat position. The sheet stack that is no longer supported by the retractable tray 61 is discharged onto the lower discharge tray 37.

[0022] The presser member 62 is a plate-shaped contact member configured to be rotatable around a pivot disposed above the discharge opening 70. In a standby state, a free end portion of the presser member 62 is positioned forward in the discharge direction of the sheet stack from the discharge opening 70 (position d3 described below). The presser member 62 is pushed by the leading edge of the sheet stack discharged from the discharge opening 70 to rotate and abut against the upper surface of the sheet stack to press down the sheet stack, thereby facilitating the sheet stack falling onto the lower discharge tray 37. That is, in this embodiment, the presser member 62 cooperates with the retractable tray 61 to contribute to maintaining the posture of the sheet stack discharged onto the lower discharge tray 37. If there is no sheet stack present when the retractable tray 61 is at its advanced position where it has advanced to the maximum in direction C1, the retractable tray 61 will interfere with or collide with the presser member 62. However, in this embodiment, as a result of timing control described later, the retractable tray 61 and the pressing member 62 sandwich the sheet stack from both the top and bottom, and the retractable tray 61 and the pressing member 62 do not directly collide with each other.

[0023] The upper discharge tray 25 and the lower discharge tray 37 are configured to be movable up and down in the drawing. For example, each of the upper discharge tray 25 and the lower discharge tray 37 descends downward when a sheet is discharged to that tray. Furthermore, each tray ascends upward when a sheet is removed from that tray. This adjusts the position of the top surface of the stack of sheets stacked on each tray so that it is constant. The post-processing device 4 may also include a sheet surface sensor (not shown) for detecting the discharge of sheets to and the removal of sheets from each tray. The post-processing device 4 may also include a motor for driving each of the upper discharge tray 25 and the lower discharge tray 37. Alternatively, each of the upper discharge tray 25 and the lower discharge tray 37 may be biased upward by, for example, a spring and descend downward due to the weight of the sheets.

[0024] <5. Detailed configuration example of post-processing section> Fig. 2 is a perspective view for explaining an example of the configuration of the post-processing section 4a. Fig. 2(A) shows a state in which the upper guide 31 of the post-processing section 4a is closed, and Fig. 2(B) shows a state in which the upper guide 31 of the post-processing section 4a is open. In this embodiment, the post-processing section 4a is a processing unit that performs at least one of an alignment process for aligning a sheet bundle and a binding process for binding the sheet bundle.

[0025] As shown in FIGS. 1 and 2, the post-processing section 4a includes a pressure flag 30, an upper guide 31, a lower guide 32, an alignment section 33, a discharge guide 34, a guide drive section 35, a first reference plate 39, a stapler 51, a second reference plate 52, a pressure guide 56, and a jogger 58. The upper guide 31 and the lower guide 32 form a sheet storage space between them to accommodate sheets processed by the post-processing section 4a. Sheets discharged from the kick-out roller 29 are stacked on the lower guide 32 within the sheet storage space. The pressure flag 30 is rotatably disposed downstream of the kick-out roller 29. The pressure flag 30 presses the trailing edge of a preceding sheet discharged into the sheet storage space so that the leading edge of a subsequently discharged sheet passes above the preceding sheet. In other words, the pressure flag 30 prevents collisions between sheets discharged into the sheet storage space one after the other. The lower surface of the pressure flag 30 has a width sufficient to hold down the trailing end portions of sheets of various sizes that can be processed in the post-processing section 4a.

[0026] An alignment unit 33 is disposed in the upper guide 31. The alignment unit 33 includes a shaft 33b rotatably supported by the upper guide 31, an alignment roller 33a coupled to the shaft 33b, and a gear 33c for rotating the shaft 33b. The alignment roller 33a is formed of an elastic material (e.g., synthetic rubber or elastomer resin), and its outer circumferential surface is semicircular when viewed from the axial direction. The gear 33c is intermittently rotated by a driving means (not shown) in synchronization with the discharge of a sheet into the sheet storage space, thereby rotating the alignment roller 33a together with the shaft 33b. During this rotation, the alignment roller 33a contacts the upper surface of the uppermost sheet in the sheet storage space through the opening 31a in the upper guide 31 and conveys the sheet toward a pair of first reference plates 39. When the sheet strikes the first reference plates 39, the alignment roller 33a slips on the surface of the sheet and further rotates to separate from the sheet. The first reference plate 39 regulates the position of the sheet by abutting against the edge of the sheet discharged into the sheet storage space on its inner wall, which is perpendicular to the sheet conveying direction and perpendicular to the upper surface of the lower guide 32. The pressure guide 56 is a flexible plate-like member that presses against the upper surface of the sheet in the sheet storage space.

[0027] In the following description, the direction in which sheets move toward the first reference plate 39 in the post-processing section 4a is referred to as the longitudinal alignment direction X1. The opposite direction to the longitudinal alignment direction X1, i.e., the direction in which the sheet stack leaves the first reference plate 39 and is discharged from the post-processing section 4a, is referred to as the discharge direction X2. The lower guide 32 has a width sufficient to accommodate, for example, A4-sized sheets conveyed in a long-side feed manner (with the long side parallel to the longitudinal alignment direction X1). A second reference plate 52 is disposed on one side of the lower guide 32. A jogger 58 is disposed on the other side of the lower guide 32. The jogger 58 is configured to be movable in the width direction of the sheet. Together with the second reference plate 52, the jogger 58 abuts against the side of the sheet discharged into the sheet storage space to regulate the orientation of the sheet in the width direction.

[0028] The stapler 51 performs a process of stapling a stack of sheets aligned in both the vertical alignment direction X1 and the width direction within the sheet storage space. The stapler 51 may be configured to be movable, for example, in the vertical alignment direction X1 and the discharge direction X2. In this case, not only is corner stapling possible, which binds the corners of the sheet stack, but long-side stapling, which moves relative to the sheet stack and binds multiple portions located along the long side of the sheet stack, may also be possible.

[0029] The discharge guide 34 is a conveying means configured to be slidable in the discharge direction X2, and conveys the sheet bundle processed by the post-processing section 4a along the conveying path and delivers the sheet bundle to the discharge rollers 36. The upper guide 59 guides the leading edge of the sheet bundle between the pair of rollers of the discharge rollers 36.

[0030] <6. Control function configuration example> Fig. 3 is a block diagram showing an example of the configuration of the control functions of the image forming system 1s. Referring to Fig. 3, the image forming apparatus 1 includes, in addition to the image forming unit 1b, a printer control unit 100, an operation unit 103, a display unit 104, and a communication unit 105. The printer control unit 100 includes a CPU 101 and a memory 102. The post-processing device 4 includes a finisher control unit 400, a group of sensors 405, and a group of actuators 406. The finisher control unit 400 includes a CPU 401, a memory 402, an input / output (I / O) port 403, and a bus 404. The printer control unit 100 and the finisher control unit 400 are connected to each other via control signal lines and cooperate to control the operation of the image forming system 1s.

[0031] A central processing unit (CPU) 101 of the printer control unit 100 executes computer programs stored in a memory 102 to control the overall operation of the image forming apparatus 1. For example, when a copy job is instructed, the CPU 101 controls the operation of the image forming unit 1b to cause the reading device 2 to read an original and to form an image on a sheet based on the read image data input from the reading device 2. When a print job is instructed, the CPU 101 controls the operation of the image forming unit 1b to form an image on a sheet based on input image data received from an external device via a communication unit 105. The memory 102 may be any combination of a read-only memory (ROM), which is a non-volatile storage medium, and a random access memory (RAM), which is a volatile storage medium. The memory 102 stores one or more computer programs executed by the CPU 101, image data, setting data, and other data. The memory 102 may include a non-transitory computer-readable storage medium.

[0032] The operation unit 103 is a device for receiving instructions and information input from a user of the image forming system 1s. The operation unit 103 may include, for example, one or more of a button, a touch panel, a switch, a keypad, and a microphone. The display unit 104 is a device for displaying information and images to a user of the image forming system 1s. The display unit 104 may be, for example, a liquid crystal display. The communication unit 105 is an interface that mediates communication between the image forming apparatus 1 and an external device (for example, a PC (Personal Computer) or a smartphone).

[0033] The CPU 401 of the finisher control unit 400 executes computer programs stored in the memory 402 to control the overall operation of the post-processing device 4. The memory 402 may be any combination of ROM and RAM. The memory 402 stores one or more computer programs executed by the CPU 401, setting data, and other data. The memory 402 may include a non-transitory computer-readable storage medium. The CPU 401 and memory 402 are connected to an I / O port 403 via a bus 404. The I / O port 403 receives sensor signals from multiple sensors 405 included in the post-processing device 4. The multiple sensors 405 may include, for example, an entrance sensor 27, an intermediate sensor 38, and an exit sensor 60. The I / O port 403 also outputs control signals to multiple actuators 406 included in the post-processing device 4. The multiple actuators 406 may include, for example, motors for rotating or moving the rollers, guides, staplers, and joggers described above in the post-processing device 4.

[0034] The functions of the printer control unit 100 and the finisher control unit 400 may be implemented by a dedicated hardware circuit such as an ASIC (Application Specific Integrated Circuit). The functions of the printer control unit 100 and the finisher control unit 400 may also be implemented in software using a general-purpose processor such as the CPU described above. Furthermore, some or all of the functions of the finisher control unit 400 described in this specification may be implemented as functions of the printer control unit 100.

[0035] <7. Example of configuration of emission control function> 4 is a block diagram showing an example of a more detailed configuration related to the discharge control function of the finisher control unit 400 for controlling the discharge of sheets from the post-processing device 4. Referring to FIG. 4, the finisher control unit 400 includes a discharge control unit 410 and a post-processing control unit 413. The discharge control unit 410 includes a sheet control unit 411 and a tray control unit 412.

[0036] The sheet control unit 411 rotates the guide drive motor M10, and by the rotational force thereof, operates the guide drive unit 35 to slide the discharge guide 34 in the discharge direction X2. As a result, the sheet stack stacked on the lower guide 32 moves in the discharge direction X2 to the position of the discharge rollers 36. The sheet control unit 411 also rotates the roller drive motor M11, and by the rotational force thereof, operates the discharge rollers 36 to discharge the sheet stack conveyed by the discharge guide 34 from the discharge opening 70. When the discharge of the sheet stack is completed, the sheet control unit 411 operates the guide drive motor M10 in the reverse direction to slide the discharge guide 34 in the longitudinal alignment direction X1, thereby returning the discharge guide 34 to its original standby position.

[0037] The sheet control unit 411 can displace the position of the discharge rollers 36 (for example, the upper roller 36a and the lower roller 36b) by rotating the roller displacement motor M12. For example, the sheet control unit 411 causes the discharge guide 34 to convey the sheet bundle to the position of the discharge rollers 36 while the upper roller 36a and the lower roller 36b are sufficiently spaced apart. Then, when the sheet bundle reaches the position of the discharge rollers 36, the sheet control unit 411 narrows the gap between the upper roller 36a and the lower roller 36b to sandwich the sheet bundle. This allows the sheet bundle to be transferred from the discharge guide 34 to the discharge rollers 36.

[0038] The tray control unit 412 controls the movement of the retractable tray 61 so that the retractable tray 61 reaches the position of the presser member 62 after the sheet stack contacts the presser member 62. More specifically, the tray control unit 412 controls the timing of advancing the retractable tray 61 from the retracted position based on the timing when the exit sensor 60 detects that the sheet stack has reached its detection position. For example, the tray control unit 412 monitors a sensor signal from the exit sensor 60, and waits for a certain period of time when the exit sensor 60 detects the leading edge of the sheet stack being conveyed by the discharge guide 34. Then, after the waiting period has elapsed, the tray control unit 412 rotates the tray drive motor M13 to advance the retractable tray 61 from the discharge port 70. Thereafter, when the exit sensor 60 detects the trailing edge of the sheet stack, the tray control unit 412 operates the tray drive motor M13 in the reverse direction to retract the retractable tray 61 to the original retracted position.

[0039] When the sheets are discharged to the post-processing section 4a by the kick-out roller 29, the post-processing control section 413 rotates the longitudinal alignment motor M1, and the rotational force of the motor rotates the alignment rollers 33a of the alignment section 33, thereby aligning the sheet bundle in the longitudinal direction. The post-processing control section 413 also rotates the jogger displacement motor M2 to move the jogger 58 to a position that matches the width of the sheets, thereby aligning the sheet bundle in the width direction. The post-processing control section 413 can also rotate the stapler displacement motor M3 and the binding motor M4 according to the post-processing settings of the job received from the printer control section 100. The stapler displacement motor M3 moves the stapler 51 in the longitudinal alignment direction X1 or the discharge direction X2. The binding motor M4 causes the stapler 51, which has moved to the desired position, to bind the sheet bundle.

[0040] <8. Operation of the bundle discharge section> FIG. 5 is a perspective view showing in detail the components constituting the bundle discharge unit 4b. FIG. 5(A) shows the components of the bundle discharge unit 4b when the retractable tray 61 is in the retracted position, and FIG. 5B shows the components of the bundle discharge unit 4b when the retractable tray 61 is in the advanced position. In these figures, some components such as the sheet bundle and the frame of the bundle discharge unit 4b are omitted to show the details. FIG. 6 is a schematic cross-sectional view seen from the width direction of the sheets, showing the positional relationship between the main components of the bundle discharge unit 4b and the sheets. FIG. 6(A) shows the positional relationship when the retractable tray 61 is in the retracted position, and FIG. 6(B) shows the positional relationship when the retractable tray 61 is in the advanced position.

[0041] As described above, after the sheet stack S is aligned or stapled in the post-processing section 4a, the sheet control section 411 rotates the guide drive motor M10 and operates the guide drive section 35 to slide the discharge guide 34 in the discharge direction X2. The sheet stack S, whose rear end is pushed by the discharge guide 34, is pushed out in the discharge direction X2, and the leading end of the sheet stack S is guided by the upper guide 59 to reach the position of the discharge rollers 36 (position d2, described later). At this time, the upper roller 36a and the lower roller 36b that constitute the discharge rollers 36 are spaced apart.

[0042] When the exit sensor 60 detects the leading edge of the sheet stack S at its detection position just before the leading edge of the sheet stack S reaches the position of the discharge rollers 36, the discharge control unit 410 starts preparations for advancing the retractable tray 61. The sheet control unit 411 rotates the roller displacement motor M12 to move the upper roller 36a in the direction P1, causing the upper roller 36a and the lower roller 36b to sandwich the sheet stack S (see FIGS. 5A and 6A). Next, when the sheet control unit 411 rotates the roller drive motor M11, the discharge rollers 36 driven by the roller drive motor M11 rotate, and discharge the sheet stack S to the outside through the discharge opening 70 while sandwiching it. When the leading edge of the sheet stack S reaches the presser member 62, it pushes up the presser member 62 and rotates it.

[0043] 5, the retractable tray 61 has four comb teeth 61a, 61b, 61c, and 61d. Under the control of the tray control unit 412, the retractable tray 61 is driven by the tray drive motor M13 and starts moving in the direction C1. The tips of the comb teeth of the retractable tray 61 reach the position of the pressing member 62 slightly later than the tips of the sheet stack S (see FIGS. 5B and 6B). While the retractable tray 61 is advancing from the discharge opening 70 in this manner, the retractable tray 61 supports the sheet stack S on its underside.

[0044] When the trailing end of the sheet stack S is detected by the exit sensor 60, the tray control unit 412 reversely rotates the tray drive motor M13 to start retracting the retractable tray 61. As the retractable tray 61 retracts, the sheet stack S loses support from the retractable tray 61 and is discharged to the lower discharge tray 37. When the trailing end of the sheet stack S passes the position of the discharge roller 36, the presser member 62, which had been pushed up by the sheet stack S, returns to its original position while pressing down on the upper surface of the sheet stack S near its trailing end. The sheet control unit 411 reversely rotates the roller displacement motor M12 to move the upper roller 36a in direction P2, thereby separating the upper roller 36a and the lower roller 36b again. The sheet control unit 411 slides the discharge guide 34 in the longitudinal alignment direction X1 to return to its original standby position. In this way, the post-processing unit 4a becomes ready to accept the next sheet.

[0045] <9. Processing flow> Fig. 7 is a flowchart showing an example of the flow of the transport control process performed by the sheet control unit 411 according to this embodiment. Fig. 8 is a flowchart showing an example of the flow of the emergence control process performed by the tray control unit 412 according to this embodiment. These transport control processes and emergence control processes can be performed in parallel after the stack of sheets has been aligned or bound in the post-processing unit 4a. In the following description, processing steps will be abbreviated as S (step).

[0046] <9-1.Transport control processing> In the conveyance control process of FIG. 7, first, in S101, the sheet control unit 411 waits until the leading edge of the sheet stack S is detected by the outlet sensor 60. When the leading edge of the sheet stack S is detected, the process proceeds to S102. In S102, the sheet control unit 411 waits until the sheet stack S reaches the position of the discharge rollers 36 (a position where the upper rollers 36a and the lower rollers 36b can hold the sheet stack S). When the sheet stack S reaches the position of the discharge rollers 36, the process proceeds to S103. In S103, the sheet control unit 411 reduces the gap between the upper rollers 36a and the lower rollers 36b of the discharge rollers 36 to hold the sheet stack S between the discharge rollers 36. Next, in S104, the sheet control unit 411 starts rotating the discharge rollers 36. The sheet stack S is discharged at a speed corresponding to the rotation speed of the discharge rollers 36. Next, in S105, the sheet control unit 411 waits until a time corresponding to the length of the sheets has elapsed (i.e., until the sheet stack S has been released from the discharge rollers 36) while rotating the discharge rollers 36. When the time corresponding to the length of the sheets has elapsed, the process proceeds to S106. In S106, the sheet control unit 411 stops the rotation of the discharge rollers 36. Next, in S107, the sheet control unit 411 increases the gap between the upper roller 36a and the lower roller 36b of the discharge rollers 36, and returns the gap to its original value.

[0047] <9-2. Appearance control processing> In the retraction control process of FIG. 8, first, in S201, the tray control unit 412 waits until the leading edge of the sheet stack S is detected by the exit sensor 60. When the leading edge of the sheet stack S is detected, the process proceeds to S202. In S202, the tray control unit 412 waits until a predetermined length of time T1 has elapsed. The length of time T1 will be described in further detail later. When the length of time T1 has elapsed, the process proceeds to S203. In S203, the tray control unit 412 starts advancing the retractable tray 61 from the retracted position. Next, in S204, the tray control unit 412 advances the retractable tray 61 and waits until the retractable tray 61 has advanced to the maximum extent. When the retractable tray 61 has advanced to the maximum extent, the process proceeds to S205. In S205, the tray control unit 412 stops the advancement of the retractable tray 61. Next, in S206, the tray control unit 412 waits until the trailing end of the sheet stack S is detected by the exit sensor 60. When the trailing end of the sheet stack S is detected, the process proceeds to S207. In S207, the tray control unit 412 retracts the retractable tray 61 from the advanced position to the original retracted position.

[0048] <9-3. Timing of the emergence tray> FIG. 10 is a timing chart for explaining the timing of the advancement of the retractable tray 61, along with the positional relationship between the retractable tray 61 and the sheet stack. The horizontal axis of FIG. 10 represents the elapsed time from the point at which the discharge guide 34 starts discharging the sheet stack in the discharge direction X2. The vertical axis represents the distance along the discharge direction X2 from the position d0 (discharge start position) of the leading edge of the sheet stack at elapsed time zero. A solid line graph 91 represents the position of the leading edge of the sheet stack as it changes over time. A dashed line graph 92 represents the position of the leading edge of the retractable tray 61 as it changes over time. At elapsed time zero, the retractable tray 61 is waiting in the retracted position, and the leading edge of the retractable tray 61 is at position D1.

[0049] The leading edge of the sheet stack, pushed by the discharge guide 34 and starting to move, reaches the detection position d1 of the exit sensor 60 at time t1. The discharge control unit 410, for example, starts a timer at this time and begins monitoring the passage of time. At time t2, the leading edge of the sheet stack reaches position d2, where the discharge rollers 36 can clamp the sheet stack. The sheet control unit 411 can determine that the leading edge of the sheet stack has reached position d2, for example, based on the timer measuring time length T2 (= t2 - t1). From time t2 to time t3, the discharge guide 34 stops operating, and the leading edge of the sheet stack is maintained at position d2. During this time, the upper roller 36a and the lower roller 36b of the discharge rollers 36 narrow the gap and clamp the sheet stack. At time t3, the discharge rollers 36 start rotating, and the leading edge of the sheet stack moves again in the discharge direction X2. At time t4, the tray control unit 412 starts advancing the retractable tray 61. The tray control unit 412 can determine the timing to start advancing the retractable tray 61, for example, based on the timer measuring the time length T1 (= t4 - t1). At time t5, the leading edge of the sheet stack reaches position d3 where it abuts against the pressing member 62. At this time, the leading edge of the retractable tray 61 is positioned a distance L1 behind the leading edge of the sheet stack. At time t6, the leading edge of the retractable tray 61 reaches the maximum advanced position D2, and the retractable tray 61 stops. The tray control unit 412 can determine the timing to stop the retractable tray 61, for example, based on the timer measuring the time length T3 (= t6 - t1). At time t7, the trailing edge of the sheet stack reaches position d1. The length L shown in the figure S corresponds to the length of the sheet. When the exit sensor 60 detects the trailing end of the sheet stack at time t7, the tray control section 412 starts retracting the retractable tray 61.

[0050] In one embodiment, the movement speed of the discharge guide 34 (the sheet stack transport speed up to time t2) and the speed at which the discharge rollers 36 discharge the sheet stack (the sheet stack discharge speed after time t3) may both be 200 mm / s. If the distance between the detection position d1 of the exit sensor 60 and the position d2 of the discharge rollers 36 is 20 mm, the time length T2 = 100 ms. The time length (t3 - t2) during which the discharge of the sheet stack is stopped depends on the displacement speed of the upper roller 36a and the lower roller 36b and may be, for example, 300 ms. If the distance between the position d2 of the discharge rollers 36 and the position d3 of the pressure member 62 is 20 mm, the leading edge of the sheet stack reaches the position d3 of the pressure member 62 at time t5, 100 ms after the discharge rollers 36 resume movement at time t3.

[0051] The advance speed of the retractable tray 61 may also be 200 mm / s. By setting the advance speed of the retractable tray 61 to the same value as the discharge speed of the sheet stack, the sheet stack can be stably supported while the retractable tray 61 is advanced. The timing t4 at which the retractable tray 61 starts to advance depends on the distance L1 between the leading edge of the sheet stack and the leading edge of the retractable tray 61, and the position D1 of the leading edge of the retractable tray 61 at the retracted position. For example, in the above-mentioned embodiment, L1 may be 10 mm, and T1 (= t4 - t1) may be 450 ms.

[0052] 7 to 9, the sheet stack reaches position d3 of the pressure member 62 earlier than the retractable tray 61, lifting the pressure member 62, so the retractable tray 61 does not directly collide with the pressure member 62. This reduces the collision noise caused by the collision between the retractable tray 61 and the pressure member 62. Furthermore, until the sheet stack is fully discharged from the discharge opening 70, the sheet stack is held down by the pressure member 62 on the upper surface and supported by the retractable tray 61 on the lower surface, improving the alignment of the sheet stack. In this way, in this embodiment, it is possible to achieve both improved sheet alignment by using the pressure member 62 and the retractable tray 61 in combination and reduced collision noise caused by the collision between the two members.

[0053] <10. Variations> In the previous section, an example was described in which the discharge speed of the sheet stack and the advance speed of the retractable tray 61 were both constant. However, these speeds may change during discharge. The advance speed of the retractable tray 61 may be different from the discharge speed of the sheet stack. The finisher control unit 400 of the post-processing device 4 may variably set one or both of the discharge speed of the sheet stack and the advance speed of the retractable tray 61. In addition, the finisher control unit 400 may variably set the timing at which the retractable tray 61 starts to advance from the retracted position. Two modified examples related to such control are described below.

[0054] <10-1. First modified example> In the first modified example, the finisher control unit 400 variably sets the discharge speed at which the discharge rollers 36 discharge the sheet bundle. More specifically, the finisher control unit 400 sets the discharge speed of the sheet bundle to one of two or more candidate speeds based on the type of sheets included in the sheet bundle. As an example, assume that one type of sheet is plain paper and the other type of sheet is cardboard, which is thicker than plain paper. A cardboard sheet bundle tends to generate a louder impact noise when colliding with the pressure member 62 than a plain paper sheet bundle. Therefore, when a cardboard sheet bundle is discharged, the finisher control unit 400 reduces the impact noise by setting the discharge speed at which the sheet bundle collides with the pressure member 62 to a speed (second speed V2) slower than the normal discharge speed (first speed V1). In this case, too, the movement of the retractable tray 61 is controlled so that the retractable tray 61 reaches the position of the pressure member 62 after the sheet bundle contacts the pressure member 62.

[0055] In this modified example, the configurations of the image forming system 1s, image forming device 1, reading device 2, and post-processing device 4 may be the same as those described above, except for the parts related to the discharge control function of the post-processing device 4 shown in Figure 10.

[0056] 10 is a block diagram showing an example of a more detailed configuration related to the discharge control function of post-processing device 4 according to this modification. Referring to Fig. 10, finisher control unit 400 of post-processing device 4 includes post-processing control unit 413, sheet information acquisition unit 420, and discharge control unit 430. Discharge control unit 430 includes sheet control unit 431 and tray control unit 432.

[0057] The sheet information acquisition unit 420 acquires type information indicating the type of sheet to be transferred from the image forming apparatus 1 to the post-processing device 4 from the printer control unit 100 of the image forming apparatus 1. As an example, the type information may be an identifier or name identifying the type, such as "plain paper" or "cardboard." As another example, the type information may be a numerical value indicating a characteristic value, such as the thickness or basis weight of the sheet. The printer control unit 100 may accept a user's designation of the sheet type via the operation unit 103 and output type information indicating the accepted type to the sheet information acquisition unit 420. Alternatively, the image forming apparatus 1 or the post-processing device 4 may have a sensor for automatically measuring the thickness or basis weight of the sheet, and the sheet information acquisition unit 420 may determine the sheet type based on sensor data from the sensor. The sheet information acquisition unit 420 outputs the acquired type information to the discharge control unit 430.

[0058] Similar to the sheet control unit 411 described above, the sheet control unit 431 controls the discharge guide 34 to transport the sheet bundle stacked on the lower guide 32 of the post-processing unit 4a to the position of the discharge rollers 36. When the sheet bundle reaches the position of the discharge rollers 36, the sheet control unit 431 narrows the gap between the upper roller 36a and the lower roller 36b to sandwich the sheet bundle.

[0059] In this modification, the sheet control unit 431 sets a discharge speed for discharging the sheet bundle from the discharge opening 70 based on type information input from the sheet information acquisition unit 420. For example, if the type information indicates that the type of sheets constituting the sheet bundle is “plain paper,” the sheet control unit 431 sets the discharge speed to a first speed V1. On the other hand, if the type information indicates that the type of sheets constituting the sheet bundle is “cardboard,” the sheet control unit 431 sets the discharge speed to a second speed V2 slower than the first speed V1. The sheet control unit 431 rotates the roller drive motor M11 at a rotational speed corresponding to the set discharge speed, and the rotational force of the motor rotates the upper roller 36a and the lower roller 36b of the discharge roller 36, thereby discharging the sheet bundle from the discharge opening 70. If the type of sheets is “cardboard,” when the leading edge of the sheet bundle reaches the position of the presser member 62, the sheet control unit 431 may compensate for a relative delay in the discharge of the sheet bundle by setting the discharge speed to a third speed V3 faster than the second speed V2. In this case, the third speed V3 may be faster than the first speed V1.

[0060] In this modification, the tray control unit 432 monitors the sensor signal from the exit sensor 60, similar to the tray control unit 412 described above. After the leading edge of the sheet stack conveyed by the discharge guide 34 is detected by the exit sensor 60, the tray control unit 432 waits for a certain period of time and then starts advancing the retractable tray 61 from the retracted position. The length of the waiting time before the retractable tray 61 starts advancing may be fixed regardless of the type information input from the sheet information acquisition unit 420. Alternatively, the tray control unit 432 may variably set the length of the waiting time before the retractable tray 61 starts advancing based on the type information input from the sheet information acquisition unit 420. For example, if the type information indicates that the type of sheets constituting the sheet stack is “plain paper,” the tray control unit 432 sets the length of the waiting time to a first value T1. On the other hand, if the type information indicates that the type of sheets constituting the sheet stack is “cardboard,” the tray control unit 432 sets the length of the waiting time to a second value T1b greater than the first value T1. The advance speed of the retractable tray 61 in this modification may be fixed regardless of the type information input from the sheet information acquisition unit 420, and may be equal to the above-described first speed V1, for example. When the trailing end of the sheet stack is detected by the exit sensor 60, the tray control unit 432 retracts the retractable tray 61 to the original retracted position.

[0061] FIG. 11 is a flowchart showing an example of the flow of conveyance control processing performed by the sheet control unit 431 according to this modified example. Referring to FIG. 11, first, in S301, the sheet control unit 431 waits until the leading edge of the sheet stack is detected by the outlet sensor 60. When the leading edge of the sheet stack is detected, the process proceeds to S302. In S302, the sheet control unit 431 waits until the sheet stack reaches the position of the discharge rollers 36. When the sheet stack reaches the position of the discharge rollers 36, the process proceeds to S303. In S303, the sheet control unit 431 reduces the gap between the upper roller 36a and the lower roller 36b of the discharge rollers 36, causing the discharge rollers 36 to clamp the sheet stack. The subsequent process branches depending on the type of sheet indicated by the type information acquired by the sheet information acquisition unit 420. When the type information indicates a sheet to be discharged at a low speed (for example, "cardboard"), the process proceeds to S305. On the other hand, if the type information does not indicate that the sheet should be discharged at a low speed, the process proceeds to S308.

[0062] In S305, the sheet control unit 431 sets the rotation speed of the discharge rollers 36 to a speed corresponding to the discharge speed V2 and starts rotating the discharge rollers 36. This starts discharging the sheet stack at the discharge speed V2. Next, in S306, the sheet control unit 431 continues discharging the sheet stack and waits until the leading edge of the sheet stack reaches the position of the presser member 62. When the leading edge of the sheet stack reaches the position of the presser member 62, the process proceeds to S307. In S307, the sheet control unit 431 increases the rotation speed of the discharge rollers 36 to a speed corresponding to a discharge speed V3 that is higher than the discharge speed V2.

[0063] In S308, the sheet control unit 431 sets the rotation speed of the discharge rollers 36 to a speed corresponding to the discharge speed V1, and starts the rotation of the discharge rollers 36. This starts the discharge of the sheet stack at the discharge speed V1.

[0064] Next, in S309, the sheet control unit 431 continues discharging the sheet bundle while waiting until the sheet bundle is released from the discharge rollers 36. When the sheet bundle is released from the discharge rollers 36, the process proceeds to S310. In S310, the sheet control unit 431 stops the rotation of the discharge rollers 36. Next, in S311, the sheet control unit 431 increases the gap between the upper roller 36a and the lower roller 36b of the discharge rollers 36, and returns the gap to the original gap.

[0065] 12 is a timing chart showing the positional relationship between the retractable tray 61 and the sheet stack in this modified example when the sheet stack is made up of sheets that should be discharged at a slow speed (sheets that are likely to cause a louder collision noise). A solid line graph 93 represents the position of the leading edge of the sheet stack, which changes over time. A dashed line graph 94 represents the position of the leading edge of the retractable tray 61, which changes over time.

[0066] The leading edge of the sheet stack, pushed by the discharge guide 34 and starting to move, reaches the detection position d1 of the exit sensor 60 at time t1. The discharge control unit 430, for example, starts a timer at this time and starts monitoring the passage of time. At time t2, the leading edge of the sheet stack reaches position d2 of the discharge rollers 36. From time t2 to time t3, the leading edge of the sheet stack is maintained at position d2, and the upper roller 36a and the lower roller 36b of the discharge rollers 36 reduce the gap between them to hold the sheet stack. At time t3, the discharge rollers 36 start rotating, and the leading edge of the sheet stack moves in the discharge direction X2 at discharge speed V2 (i.e., a speed slower than the example in FIG. 9). At time t4', the tray control unit 432 starts advancing the retractable tray 61. The tray control unit 432 can determine the timing to start advancing the retractable tray 61, for example, based on the timer measuring time length T1b (= t4' - t1). At time t5', the leading edge of the sheet stack reaches position d3 where it contacts the pressure member 62. At this time, the leading edge of the retractable tray 61 is positioned a distance L2 behind the leading edge of the sheet stack. At time t5', the sheet control unit 431 increases the rotation speed of the discharge rollers 36, and the leading edge of the sheet stack moves in the discharge direction X2 at discharge speed V3. At time t6', the leading edge of the retractable tray 61 reaches the maximum advanced position D2, and the retractable tray 61 stops. The tray control unit 432 can determine the timing to stop the retractable tray 61 based on, for example, the timer measuring time length T3b (= t6' - t1). At time t7', the trailing edge of the sheet stack reaches position d1. When the exit sensor 60 detects the trailing edge of the sheet stack, the tray control unit 432 starts retracting the retractable tray 61.

[0067] In this modified example, the movement speed of the discharge guide 34, the speed at which the pair of rollers of the discharge rollers 36 close (the standby time from time t2 to time t3), the advancement speed of the retractable tray 61, and positions d1, d2, d3, D1, and D2 are the same as those in the above-described embodiment. In this case, if time length T1b is equal to time length T1, the distance L2 between the leading edge of the sheet stack and the leading edge of the retractable tray 61 at time t5' when the leading edge of the sheet stack reaches position d3 is shorter than the distance L1 in the above-described embodiment. For example, if the distance between positions d2 and d3 is 20 mm and the discharge speed V2 is 150 mm / s, the time required from time t3 to time t5' is 133 ms, which is 33 ms longer than in the above-described embodiment. During this time, the retractable tray 61 advances an additional 67 mm (= 200 mm / s × 0.33 s), resulting in L2 = 3.3 mm. When the sheet size is A4 size (the length of the long side along the discharge direction is 297 mm) and the pair of rollers of the discharge rollers 36 pinches the sheet at a position 20 mm from the leading edge, the discharge distance of the sheet stack by the discharge rollers 36 is 277 mm (297 mm - 20 mm). In this case, the time required from time t3 to time t7 in the above-described embodiment is 1385 ms, which is the discharge distance of 277 mm divided by the discharge speed of 200 mm / s. Therefore, in this modified example, if the discharge speed V3 after reaching the presser member 62 is set to 205.3 mm / s (= (277 mm - 20 mm) / (1385 ms - 133 ms)), the discharge completion timing t7' becomes equal to the timing t7 in the above-described embodiment. In this case, the productivity of the post-processing device 4 can be maintained constant regardless of the type of sheet.

[0068] In this modified example, the discharge speed of the sheet stack when the leading edge of the sheet stack reaches position d3 of the presser member 62 is variably set depending on the type of sheets, so that it is possible to reduce the actual collision noise when a sheet that is likely to cause a louder collision noise is discharged. Also, by setting the discharge speed until the leading edge of the sheet stack reaches position d3 of the presser member 62 relatively low and then increasing the discharge speed after the sheet stack reaches position d3, it is possible to compensate for the decrease in productivity that accompanies the reduction in collision noise.

[0069] The sheet control unit 431 may change the discharge speed of the sheet bundle at a timing different from the timing when the leading edge of the sheet bundle reaches position d3 of the presser member 62. The sheet control unit 431 may also change the discharge speed of the sheet bundle multiple times instead of just once. For example, the sheet control unit 431 may gradually reduce the discharge speed before the leading edge of the sheet bundle reaches position d3 of the presser member 62. The sheet control unit 431 may also temporarily increase the discharge speed to a speed faster than the above-mentioned speed V1 after the leading edge of the sheet bundle reaches position d3 of the presser member 62 to eliminate the delay, and then reduce the discharge speed to speed V1.

[0070] <10-2. Second modified example> In the second modified example, the finisher control unit 400 of the post-processing device 4 variably sets the timing at which the retractable tray 61 advances from the retracted position. More specifically, the finisher control unit 400 sets the waiting time length until the retractable tray 61 advances to one of two or more candidate values ​​based on the type of sheets included in the sheet stack. As an example, assume that one type of sheet is plain paper and the other type of sheet is thin paper, which is thinner than plain paper. A sheet stack made of thin paper is more likely to bend than a sheet stack made of plain paper and to lose its posture due to sagging of the leading edge protruding from the leading edge of the retractable tray 61. Therefore, when a sheet stack made of thin paper is discharged, the finisher control unit 400 sets the waiting time length until the retractable tray 61 advances to a value shorter than the normal waiting time length. This shortens the distance between the leading edge of the sheet stack and the leading edge of the retractable tray 61, preventing the sheet stack from losing its posture due to sagging of the leading edge. In this case as well, the movement of the retractable tray 61 is controlled so that the retractable tray 61 reaches the position of the pressing member 62 after the sheet stack abuts against the pressing member 62 .

[0071] In this modified example, the configurations of the image forming system 1s, image forming device 1, reading device 2, and post-processing device 4 may be the same as those described above, except for the parts related to the discharge control function of the post-processing device 4 shown in Figure 13.

[0072] 13 is a block diagram showing an example of a more detailed configuration related to the discharge control function of post-processing device 4 according to this modified example. Referring to Fig. 13, finisher control unit 400 of post-processing device 4 includes post-processing control unit 413, sheet information acquisition unit 420, and discharge control unit 440. Discharge control unit 440 includes sheet control unit 411 and tray control unit 442.

[0073] In this modification, the tray control unit 442 monitors the sensor signal from the exit sensor 60, similar to the tray control unit 412 described above. After the leading edge of the sheet stack conveyed by the discharge guide 34 is detected by the exit sensor 60, the tray control unit 442 waits for a certain period of time and then starts advancing the retractable tray 61 from the retracted position. The tray control unit 442 sets the waiting time length before advancing the retractable tray 61 based on the type information input from the sheet information acquisition unit 420. For example, if the type information indicates that the type of sheets constituting the sheet stack is “plain paper,” the tray control unit 442 sets the waiting time length to a first value T1. On the other hand, if the type information indicates that the type of sheets constituting the sheet stack is “thin paper,” the tray control unit 442 sets the waiting time length to a second value T1c smaller than the first value T1. The advancing speed of the retractable tray 61 in this modification may be constant regardless of the type of sheets, or may change during the advance. When the trailing end of the sheet stack is detected by the outlet sensor 60, the tray control section 442 retracts the retractable tray 61 to the original retracted position.

[0074] 14 is a flowchart showing an example of the flow of the appearance / retraction control process performed by the tray control unit 442 according to this modified example. Referring to FIG. 14, first, in S401, the tray control unit 442 waits until the leading edge of the sheet stack is detected by the outlet sensor 60. When the leading edge of the sheet stack is detected, the process proceeds to S402. The subsequent process branches depending on the type of sheet indicated by the type information acquired by the sheet information acquisition unit 420. If the type information indicates a sheet that is prone to bending (for example, "thin paper"), the process proceeds to S403. On the other hand, if the type information does not indicate a sheet that is prone to bending, the process proceeds to S407.

[0075] In S403, the tray control unit 442 waits until a time length T1c set for sheets that are easy to bend has elapsed. After the time length T1c has elapsed, the process proceeds to S404. In S404, the tray control unit 442 starts advancing the retractable tray 61 from the retracted position at a fourth speed V4 that is slower than the first speed V1. Next, in S405, the tray control unit 442 waits until the leading edge of the sheet stack reaches the position of the pressing member 62. When the leading edge of the sheet stack reaches the position of the pressing member 62, the process proceeds to S406. In S406, the tray control unit 442 increases the advancing speed of the retractable tray 61 from the fourth speed V4 to a fifth speed V5.

[0076] Meanwhile, in S407, the tray control unit 442 waits until the time length T1 set for normal sheets has elapsed. After the time length T1 has elapsed, the process proceeds to S408. In S408, the tray control unit 442 starts advancing the retractable tray 61 from the retracted position at a first speed V1.

[0077] After that, in S409, the tray control unit 442 advances the retractable tray 61 and waits until the retractable tray 61 advances to the maximum extent. When the retractable tray 61 advances to the maximum extent, the process proceeds to S410. In S410, the tray control unit 442 advances the retractable tray 61 ofNext, in S411, the tray control section 442 waits until the trailing end of the sheet stack is detected by the exit sensor 60. When the trailing end of the sheet stack is detected, the process proceeds to S412. 1 In step 2, the tray control unit 442 retracts the retractable tray 61 from the advanced position to the original retracted position.

[0078] 15 is a timing chart showing the positional relationship between the retractable tray 61 and the sheet stack in this modified example when the sheet stack is made up of sheets that are easily bent. The solid line graph 91 is the same as that shown in FIG. 9. The dashed line graph 96 shows the position of the tip of the retractable tray 61 that changes over time in this modified example.

[0079] The leading edge of the sheet bundle that has been pushed by the discharge guide 34 and started to move reaches the detection position d1 of the outlet sensor 60 at time t1. The discharge control unit 440, for example, starts a timer at this point and begins monitoring the passage of time. At time t2, the leading edge of the sheet bundle reaches the position d2 of the discharge roller 36. Between time t2 and time t3, the position of the leading edge of the sheet bundle is maintained at position d2, and the upper roller 36a and the lower roller 36b of the discharge roller 36 reduce the gap to sandwich the sheet bundle. At time t4´´, the tray control unit 442 starts the advancement of the retractable tray 61 at the advancement speed V4. The tray control unit 442 can, for example, determine the timing at which the retractable tray 61 should start advancing based on the timer measuring a time duration T1c (T1c < T1). At time t3, the rotation of the discharge roller 36 starts, and the leading edge of the sheet bundle moves in the discharge direction X2 at the discharge speed V1. At some point between time t3 and time t5, the leading edge of the sheet bundle overtakes the leading edge of the retractable tray 61. At time t5, the leading edge of the sheet bundle reaches the position d3 where it abuts against the pressing member 62. At this time, the leading edge of the retractable tray 61 is located a distance L3 behind the leading edge of the sheet bundle. The distance L3 is shorter than the distance L1 described above. At time t5, the tray control unit 442 raises the advancement speed of the retractable tray 61 to speed V5. At time t6´´, the leading edge of the retractable tray 61 reaches the maximum advancement position D2, and the retractable tray 61 stops. At time t7, the trailing edge of the sheet bundle reaches the position d1. When the trailing edge of the sheet bundle is detected by the outlet sensor 60, the tray control unit 442 starts the retraction of the retractable tray 61.

[0080] In this modified example, the movement speed of the discharge guide 34, the speed at which the pair of rollers of the discharge rollers 36 close (the waiting time from time t2 to time t3), the discharge speed of the sheet stack, and positions d1, d2, d3, D1, and D2 are the same as those in the above-described embodiment. Furthermore, position d2 of the discharge rollers 36 coincides with position D1 of the leading edge of the retractable tray 61, which is in the retracted position. In this case, for example, if time length T1c is 380 ms, the retractable tray 61 begins advancing 20 ms earlier than time t3. Furthermore, the discharge speed V1 of the sheet stack is 200 mm / s, and the distance between positions d2 and d3 is 20 mm. Therefore, if the advancing speed V4 of the retractable tray 61 is 150 mm / s, at time t5, the leading edge of the retractable tray 61 is positioned a distance L3 of 2 mm behind the leading edge of the sheet stack that has reached position d3 of the pressure member 62. This is one-fifth of the distance L1 of 10 mm in the above-described embodiment. Furthermore, if the distance between the position d3 of the pressure member 62 and the maximum advanced position D2 of the retractable tray 61 is 40 mm, by increasing the advancement speed of the retractable tray 61 to a speed V5 = 210 mm / s at time t5, the leading edge of the retractable tray 61 will catch up with the leading edge of the sheet stack at position D2 at time t6''.

[0081] In this modified example, the distance between the leading edge of the sheet stack and the leading edge of the retractable tray 61 while the sheet stack is being discharged is shortened depending on the type of sheet, thereby suppressing the deterioration of alignment caused by sagging when sheets that are prone to bending are discharged.

[0082] The tray control unit 442 may change the advancement speed of the retractable tray 61 at a timing different from the timing when the leading edge of the sheet stack reaches position d3 of the presser member 62. The tray control unit 442 may also change the advancement speed of the retractable tray 61 multiple times instead of just once. The leading edge of the retractable tray 61 may overtake the leading edge of the sheet stack after the leading edge of the sheet stack reaches position d3 of the presser member 62. Furthermore, the tray control unit 442 may set the waiting time length T1c to a value equal to T1, advance the retractable tray 61 at an advancement speed faster than the discharge speed of the sheet stack, and decelerate the retractable tray 61 after the leading edge of the retractable tray 61 has come sufficiently close to the leading edge of the sheet stack.

[0083] <11. Summary> 1 to 15, various embodiments, examples, and modifications of the technology according to the present disclosure have been described. According to the above-described embodiments, the control unit of the sheet processing apparatus controls the movement of the retractable tray so that the retractable tray reaches the position of the presser member after the sheet stack discharged from the discharge port abuts against the presser member. Therefore, by using the presser member and the retractable tray in combination, it is possible to improve the alignment of the sheets and reduce the impact noise caused by the impact between the presser member and the retractable tray.

[0084] In the above-described embodiment, the control unit controls the timing of advancing the retractable tray from the retracted position based on the timing at which the sensor detects that the sheet bundle has reached a detection position on the conveyance path. In this way, by controlling the timing of advancing the retractable tray based on the timing of conveyance of the sheet bundle, it is easy to advance the retractable tray while maintaining an appropriate positional relationship between the sheet bundle and the retractable tray.

[0085] In one embodiment, the control unit may start advancing the infeed tray at a second time point (t4) that is a first time period (T1) after the sensor detects that the sheet stack has reached the detection position. In this case, the sheet stack is discharged a desired distance during the first time period, thereby creating a sufficient distance between the leading edge of the sheet stack and the leading edge of the infeed tray. In this embodiment, the discharge of the sheet stack from the discharge opening may start at a third time point (t3) that is earlier than the second time point (t4), and the advancing speed of the infeed tray may be set equal to the discharge speed of the sheet stack. This allows the sheet stack to be stably discharged while maintaining a constant distance between the leading edge of the sheet stack and the leading edge of the infeed tray, effectively maintaining the alignment of the sheet stack.

[0086] In a first modification, the control unit variably sets the discharge speed of the sheet bundle based on the type of sheets constituting the sheet bundle. This allows for flexible reduction of collision noise caused by a collision between the sheet bundle and the pressing member. For example, when processing a type of sheet that is likely to produce a loud collision noise, the discharge speed of the sheet bundle can be set to a second speed (V2) slower than the first speed (V1), thereby preventing the occurrence of a loud collision noise that is unpleasant to users. Furthermore, after the sheet bundle contacts the pressing member, the discharge speed can be changed from the second speed (V2) to a faster third speed (V3), thereby compensating for a decrease in productivity caused by a temporary reduction in the discharge speed.

[0087] In a second variation, the control unit variably sets the first time length based on the type of sheets constituting the sheet stack. This allows for flexible adjustment of the distance between the leading edge of the sheet stack and the leading edge of the inlet / outlet tray, effectively preventing deterioration of the sheet stack alignment. For example, when a type of sheet that is prone to bending is being processed, the first time length to wait before the inlet / outlet tray advancement begins is set to a second value (T1b) shorter than the first value (T1), thereby preventing excessive drooping of the leading edge of the sheet stack preceding the inlet / outlet tray. Additionally or alternatively, when a type of sheet that is prone to bending is being processed, the advance speed of the inlet / outlet tray may be variably set so that the distance between the leading edge of the sheet stack being ejected and the leading edge of the inlet / outlet tray is shorter than when the type of sheet that is prone to bending is being processed. This approach also prevents excessive drooping of the leading edge of the sheet stack preceding the inlet / outlet tray.

[0088] In the above-described embodiment, the presser member is configured to be rotatable about a pivot shaft, and after the sheet stack contacts the presser member, the presser member is pushed by the sheet stack and rotates. In this case, even without actively controlling the movement of the presser member when the sheet stack is discharged, it is possible to press the upper surface of the sheet stack and promote discharge onto the discharge tray with a simple configuration.

[0089] <12. Other embodiments> The above-described embodiment can also be realized in the form of a process in which a program for realizing one or more functions is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program, or by a circuit (e.g., ASIC) that realizes one or more functions.

[0090] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0091] 1s: image forming system, 1: image forming apparatus, 4: post-processing apparatus, 4a: post-processing section, 34: discharge guide (conveying means), 36: discharge roller (discharge means), 37: lower discharge tray (loading means), 60: exit sensor (detecting means), 61: retractable tray (supporting means), 62: pressing member (contact means), 70: discharge port, 410, 430, 440: discharge control section (controlling means), S: sheet stack

Claims

1. a discharge means for discharging the sheet bundle conveyed along the conveying path from a discharge port; a stacking means for stacking the discharged sheet bundle; a contact means positioned forward of the discharge opening in the sheet bundle discharge direction and contacting an upper surface of the discharged sheet bundle; a support means configured to be able to advance and retreat from the discharge port, and to temporarily advance below the sheet bundle to support the sheet bundle when the sheet bundle is discharged; a control means for controlling the movement of the support means so that the support means reaches the position of the abutment means after the sheet stack abuts against the abutment means; A sheet processing apparatus comprising:

2. The sheet processing apparatus includes: a detection unit for detecting that the sheet stack has reached a detection position on the conveying path; Furthermore, the control means controls the timing of advancing the support means from the retracted position based on the timing at which the detection means detects that the sheet stack has reached the detection position. The sheet processing apparatus according to claim 1 .

3. 3. The sheet processing apparatus according to claim 2, wherein the control means starts the advancement of the support means at a second point in time when a first length of time has elapsed since the detection means detected that the sheet stack has reached the detection position.

4. the control means causes the discharge means to start discharging the sheet bundle at a third time point that is earlier than the second time point; a discharge speed at which the discharge means discharges the sheet stack is equal to an advance speed at which the support means advances; The sheet processing apparatus according to claim 3 .

5. 4. The sheet processing apparatus according to claim 3, wherein the control unit variably sets the first time length based on the type of sheets constituting the sheet bundle.

6. The control means If the type of sheets constituting the sheet bundle is a first type, the first time length is set to a first value; When the type of sheets constituting the sheet bundle is a second type that is more easily bent than the first type, the first time length is set to a second value that is smaller than the first value. The sheet processing apparatus according to claim 5 .

7. 4. The sheet processing apparatus according to claim 3, wherein the control means variably sets one or both of the first time length and the advance speed of the support means so that the distance between the leading edge of the sheet bundle and the leading edge of the support means during discharge of the sheet bundle when the type of sheets constituting the sheet bundle is a first type is shorter than the distance between the leading edge of the sheet bundle and the leading edge of the support means during discharge of the sheet bundle when the type of sheets constituting the sheet bundle is a second type that is more easily bent than the first type.

8. 2. The sheet processing apparatus according to claim 1, wherein said control means variably sets a discharge speed at which said discharge means discharges said sheet bundle based on the type of sheets constituting said sheet bundle.

9. The control means When the type of sheets constituting the sheet bundle is a first type, the discharge speed is set to a first speed; When the type of sheets constituting the sheet bundle is a third type that is more likely to generate a louder impact noise than the first type, the discharge speed is set to a second speed that is slower than the first speed. The sheet processing apparatus according to claim 8 .

10. 10. The sheet processing apparatus according to claim 9, wherein the control unit changes the discharge speed from the second speed to a third speed faster than the second speed after the sheet bundle contacts the contact unit when the type of sheets constituting the sheet bundle is the third type.

11. The abutment means is configured to be rotatable around a rotation axis, After the sheet stack contacts the contact means, the contact means is pushed by the sheet stack and rotates. The sheet processing apparatus according to claim 1 .

12. The sheet processing apparatus includes: a processing unit that performs at least one of an alignment process for aligning the sheet bundle and a binding process for binding the sheet bundle; a conveying means for conveying the sheet bundle processed by the processing means along the conveying path and delivering the sheet bundle to the discharging means; The sheet processing apparatus of claim 1 , further comprising:

13. an image forming device that forms an image on a sheet; a sheet processing apparatus according to any one of claims 1 to 12, which is connected to the image forming apparatus and receives and processes sheets from the image forming apparatus; An image forming system comprising:

Images