Sheet discharge device, sheet processing device, and image forming system

Abstract

To improve lamination property of discharged sheets while maintaining productivity.SOLUTION: Control means for a sheet discharge device is configured to perform a discharge operation for causing second conveyance means to reverse a first sheet received from first conveyance means and transfer the same to third conveyance means, causing the third conveyance means to convey the first sheet toward the second conveyance means upon issuance of a detection signal from detection means in accordance with a second sheet conveyed after the first sheet, and causing the second conveyance means to discharge the first and second sheets to a lamination part in a state in which the ends of the first and second sheets in a conveyance direction are aligned and stacked.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a sheet discharge device that discharges sheets, a sheet processing device that processes sheets, and an image forming system that forms images on sheets. [Background technology]

[0002] As an option for image forming apparatuses such as electrophotographic copiers and laser beam printers, image forming systems equipped with sheet processing apparatuses (also called finishers) that perform processes such as sorting, binding, and alignment on sheets on which images have been formed are known. When the sheet processing apparatus processes multiple sets of sheets consecutively, if the sheet processing apparatus temporarily stops receiving sheets from the image forming apparatus to wait for the processing of the preceding set of sheets to finish, the productivity (throughput) of the image forming system will decrease.

[0003] Therefore, a method is known in which sheets received from the image forming device are temporarily held (buffered) while overlapping inside the sheet processing device while the sheet bundle is being processed, and then the sheet bundle is stacked on a processing tray after processing of the sheet bundle is completed.Patent Document 1 describes a configuration in which sheets received from the image forming device are held using two conveyance paths branched inside a finisher, and two sheets are stacked on top of each other and stacked on a processing tray. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 06-099070 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the sheet conveying speed is increased in order to further improve the productivity of the image forming system, the sheets tend to be discharged forcefully from the image forming device or sheet processing device, which tends to cause the stacking position of the sheets discharged to the discharge tray or other discharge destination to become distorted.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet discharge device, a sheet processing device, and an image forming system that are capable of improving the stacking capacity of discharged sheets while maintaining productivity. [Means for solving the problem]

[0007] One aspect of the present invention is A sheet ejection device, a stacking section on which sheets are stacked, a first conveying means disposed on a first conveying path extending toward the stacking section and conveying sheets toward the stacking section, a detecting means for issuing a detection signal in response to a sheet passing through the first conveying path, a second conveying means disposed on the first conveying path downstream of the first conveying means, the second conveying means reversing the conveying direction of a sheet received from the first conveying means and conveying the sheet to a second conveying path branching from the first conveying path between the first conveying means and the second conveying means, a third conveying means disposed on the second conveying path, reversing the conveying direction of a sheet and conveying the sheet, and the first conveying means, the second conveying means and a control means for controlling the third conveying means, wherein the control means is configured to execute a discharge operation of causing the second conveying means to invert the first sheet received from the first conveying means and deliver it to the third conveying means, causing the third conveying means to convey the first sheet toward the second conveying means based on the detection signal issued by the detection means in response to a second sheet being conveyed following the first sheet, and discharging the first sheet and the second sheet by the second conveying means to the stacking section in a state in which the edges of the first sheet and the second sheet in the conveying direction are aligned and the first sheet and the second sheet are overlapped. the stacking section protrudes to the outside of the device body of the sheet discharging device, and the sheet discharged above the stacking section by the second conveying means falls onto the stacking section by gravity without being conveyed by any conveying means other than the second conveying means. The sheet discharge device is characterized by the above. [Effects of the Invention]

[0008] According to the present invention, it is possible to improve the stackability of discharged sheets while maintaining productivity. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an image forming system according to a first embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of a superimposition processing unit according to the first embodiment. [Figure 3] FIG. 1 is a hardware configuration diagram of an image forming system according to a first embodiment. [Figure 4] FIG. 1 is a functional block diagram of an image forming system according to a first embodiment. [Figure 5] 5A to 5G are diagrams for explaining the operation of the superimposition processing unit according to the first embodiment. [Figure 6] 6 is a flowchart showing an example of control of the superimposition processing unit according to the first embodiment. [Figure 7] 5A to 5C are diagrams for explaining a method for controlling the amount of protrusion between sheets by the overlap processing unit according to the first embodiment. [Figure 8] 10A to 10D are diagrams for explaining a method for controlling the amount of protrusion between sheets by an overlap processing unit according to the second embodiment. [Figure 9] FIG. 10 is a functional block diagram of an image forming system according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] First Embodiment FIG. 1 is a schematic diagram of an image forming system 1S according to a first embodiment, viewed from the front. The image forming system includes an image forming apparatus 1 that forms an image on a sheet, a sheet processing apparatus 4 that processes the sheet on which the image has been formed by the image forming apparatus 1, a relay unit 14 that transports the sheet from the image forming apparatus 1 to the sheet processing apparatus 4, and an image reading apparatus 2. Note that a variety of sheets of different sizes and materials can be used as recording media, including paper such as plain paper and cardboard, surface-treated sheet materials such as plastic film, cloth, and coated paper, and sheet materials with special shapes such as envelopes and index paper. Below, a brief description of the operation of each device constituting the image forming system 1S will be given, followed by a detailed description of the operation of the sheet processing apparatus 4.

[0012] The image forming apparatus 1 has an electrophotographic image forming unit 8 as an image forming means, and a feeding device 6 that feeds sheets one by one to the image forming unit 8. The image forming unit 8 is a cartridge that integrates a photosensitive drum 9, which is an image carrier (electrophotographic photosensitive member), with a charger and a developing device that act on the photosensitive drum 9 to perform the electrophotographic process. A scanner unit 15, which serves as an exposure means, is disposed above the image forming unit 8, and a transfer roller 10, which serves as a transfer means, is disposed opposite the photosensitive drum 9. A fixing device 11, a discharge roller 12a, and a reversing roller 12b are disposed above the transfer roller 10. The fixing device 11 has a thermal fixing configuration and includes, for example, a cylindrical film, a heater unit having a heater and disposed inside the film, and a pressure roller that is pressed against the heater via the film.

[0013] A plurality of feeding devices 6 for feeding sheets are arranged below the image forming unit 8. Each feeding device 6 has a cassette 6a as a storage unit (storage cabinet, storage means) for storing a plurality of sheets, and a feeding unit 6b for feeding sheets one by one from the cassette 6a.

[0014] When the image forming apparatus 1 performs an image forming operation, the surface of the photosensitive drum 9 in the image forming section 8 is uniformly charged by a charger, and the scanner unit 15 writes an electrostatic latent image on the surface of the photosensitive drum 9 by irradiating the surface with laser light based on image information. This electrostatic latent image is developed (visualized) by toner as a developer supplied from a developing device, and a toner image is formed on the surface of the photosensitive drum 9.

[0015] In parallel with the operation of the image forming unit 8, in one of the feeding devices 6, sheets are fed one by one from a cassette 6a by a feeding unit 6b and transported toward a registration roller 7. The registration roller 7 corrects any skew in the sheet, and then sends the sheet to a transfer unit between a photosensitive drum 9 and a transfer roller 10 at a timing synchronized with the formation of a toner image by the image forming unit 8. Then, in the transfer unit, the toner image is transferred from the photosensitive drum 9 to the sheet.

[0016] The sheet that has passed through the transfer section is sent to the fixing device 11. In the fixing device, the sheet is sandwiched between a film and a pressure roller and passes through a fixing nip (the nip between the heater unit and the pressure roller), during which the toner on the sheet is heated and pressurized, thereby fixing the toner image to the sheet.

[0017] In the case of single-sided printing, the sheet that has passed through the fixing device 11 is discharged from the image forming apparatus 1 by the discharge rollers 12a and received by the relay unit 14. In the case of double-sided printing, the sheet that has a toner image formed on its first side and passed through the fixing device 11 is guided to the reversing rollers 12, is switched back and conveyed by the reversing rollers 12, and is conveyed again to the registration rollers 7 via the re-conveyance path 13. Then, after an image is formed on the second side opposite to the first side by passing through the transfer section and the fixing device 11, the sheet is delivered to the relay unit 14 by the discharge rollers 12a.

[0018] An image reading device 2 is attached to the top of the image forming apparatus 1. The image reading device 2 has a reading sensor 2s that reads image information from an original sheet, and an original transport unit that transports the original sheet to the reading sensor 2s one by one. The image forming apparatus 1 can perform both a copying operation in which an image is formed based on image information acquired by the image reading device 2, and a printing operation in which an image is formed based on image information received from an external device.

[0019] In this embodiment, the relay unit 14 is disposed in a space (also referred to as an internal discharge space) between the image forming apparatus 1 and the image reading apparatus 2 in the vertical direction (the vertical direction when the image forming system 1S is installed on a horizontal surface). The relay unit 14 transports sheets discharged from the image forming apparatus 1 in a substantially horizontal direction as viewed from the front toward the sheet processing apparatus 4, which is installed alongside the image forming apparatus 1 on the same installation surface as the image forming apparatus 1. The relay unit 14 is provided with a sheet sensor 52 as a detection means for detecting the passage of a sheet. The sheet sensor 52 is, for example, a reflective photosensor that irradiates infrared light into the transport path and detects the light reflected by the sheet passing through the transport path to determine the presence or absence of the sheet. Note that, although the image forming system 1S having the relay unit 14 has been exemplified here, a configuration in which sheets are directly transferred from the image forming apparatus 1 to the sheet processing apparatus 4 is also possible.

[0020] The image forming apparatus 1 is also provided with a display unit 5 (operation unit, operation display unit) that serves as a user interface for the image forming system 1S. The display unit 5 has a function of displaying the operating status of the system, such as jams and malfunctions, and operations required by the user, such as replacing consumables in the apparatus and removing jammed sheets. The user can also operate the touch panel function of the display of the display unit 5 or the numeric keypad to make various settings and give instructions to the image forming system 1S.

[0021] The configuration of the image forming apparatus is not limited to the direct transfer type shown in Figure 1, but may be an intermediate transfer type in which a toner image formed in an image forming unit is transferred to a sheet via an intermediate transfer body, or may be a color image forming apparatus using multiple image forming units. Also, the image forming mechanism is not limited to an electrophotographic type, but may instead employ, for example, an inkjet type printing unit or an offset printing mechanism.

[0022] (sheet processing device) The sheet processing device 4 has a sheet processing unit 71 that processes sheets, and has a function of discharging the processed sheets received from the image forming device 1 as a product. The sheet processing device 4 can also discharge the sheets received from the image forming device 1 as a product without binding them.

[0023] The sheet processing apparatus 4 is provided with an incoming path 81, an internal discharge path 82, a first discharge path 83, and a second discharge path 84 as transport paths for transporting sheets. The sheet processing apparatus 4 is also provided with an upper discharge tray 25 and a lower discharge tray 37 that protrude outward from the apparatus main body 4A (a housing having the incoming path 81, internal discharge path 82, first discharge path 83, and second discharge path 84 provided therein) as destinations for discharging sheets. The incoming path 81 is a transport path for receiving and transporting sheets from the image forming apparatus 1, and the internal discharge path 82 is a transport path for transporting sheets toward the sheet processing apparatus 71. The first discharge path 83 is a transport path for discharging sheets to the upper discharge tray 25, and the second discharge path 84 is a transport path for discharging sheets to the lower discharge tray 37. In this manner, in this embodiment, the receiving path 81 and the first discharge path 83 form a first conveyance path leading to the upper discharge tray 25 serving as a stacking section (first stacking section), and the inner discharge path 82 is provided as a second conveyance path branching off from the first conveyance path. Also, the second discharge path 84 is provided as a third conveyance path leading from the sheet processing section 71 to the lower discharge tray 37 serving as a second stacking section.

[0024] The receiving path 81 is provided with an entrance roller 21, a pre-branch roller 22, and an entrance sensor 27. The first discharge path 83 is provided with a discharge reverse roller 24, which is a reverse conveying unit. The inner discharge path 82 is provided with an inner discharge roller 26, an intermediate conveying roller 28, a kick-out roller 29, and an intermediate pre-stacking sensor 38. The second discharge path 84 is provided with a bundle discharge roller 36. The pre-branch roller 22 is a first conveying means in this embodiment, the discharge reverse roller 24 is a second conveying means in this embodiment, and the inner discharge roller 26 is a third conveying means in this embodiment. The entrance roller 21, the pre-branch roller 22, the discharge reverse roller 24, the inner discharge roller 26, the intermediate conveying roller 28, the kick-out roller 29, and the bundle discharge roller 36 are roller pairs that contact each other on their outer circumferential surfaces to form a nip portion that sandwiches and conveys sheets.

[0025] The entrance sensor 27 and the intermediate pre-stacking sensor 38 are both examples of detection means that detect the passage of a sheet at a predetermined detection position on the transport path in the sheet processing device (i.e., output a detection signal in response to the passage of a sheet). The entrance sensor 27 and the intermediate pre-stacking sensor 38 can be, for example, a reflective photosensor that irradiates infrared light into the transport path and detects the light reflected by the sheet passing through the transport path to determine the presence or absence of a sheet. The sheet detection means may also be configured to have a flag that protrudes into the transport path and detects the rotation of the flag by a photoelectric sensor such as a photointerrupter when it comes into contact with a sheet.

[0026] The following describes the sheet transport path in the sheet processing device 4. A sheet transported from the image forming device 1 via the relay unit 14 is received by the entrance rollers 21 of the sheet processing device 4 and transported to the pre-branch rollers 22 through the receiving path 81. The entrance sensor 27 detects the sheet at a detection position between the entrance rollers 21 and the pre-branch rollers 22. The pre-branch rollers 22 transport the sheet received from the entrance rollers 21 toward the first discharge path 83.

[0027] At a predetermined timing after the inlet sensor 27 detects the passage of the trailing edge of the sheet, the pre-branch rollers 22 accelerate the sheet conveying speed to a speed faster than the conveying speed in the relay unit 14. Alternatively, the sheet conveying speed by the inlet rollers 21 may be set to be faster than that of the relay unit 14, and the conveying speed may be accelerated by the inlet rollers 21 upstream of the pre-branch rollers 22. In this case, it is preferable to install a one-way clutch between the conveying rollers of the relay unit 14 and the motor that drives them, so that the conveying rollers will rotate freely even if the sheet is pulled by the inlet rollers 21.

[0028] When the sheet is discharged to the upper discharge tray 25, the discharge and reverse rollers 24 discharge the sheet received from the pre-branch rollers 22 to the upper discharge tray 25. In this case, the discharge and reverse rollers 24 decelerate to a predetermined discharge speed at a predetermined timing after the rear end of the sheet has passed the pre-branch rollers 22.

[0029] When the sheet is discharged to the lower discharge tray 37, the discharge and reverse rollers 24 switchback-convey the sheet received from the pre-branch rollers 22 and transport the sheet to the internal discharge path 82. That is, the discharge and reverse rollers 24 transport the sheet in the discharge direction toward the outside of the sheet processing device 4, and then reverse their rotation direction to transport the sheet in the opposite direction before the trailing edge of the sheet in the discharge direction passes through the discharge and reverse rollers 24. A check valve 23 is disposed at the branching point (between the pre-branch rollers 22 and the discharge and reverse rollers 24) where the internal discharge path 82 branches off from the receiving path 81 and the first discharge path 83, upstream of the discharge and reverse rollers 24 in the discharge direction. The check valve 23 functions as a guide (regulating member) that prevents the sheet, switched back by the discharge and reverse rollers 24, from flowing back into the receiving path 81. In other words, the discharge and reverse rollers 24 perform the switchback-conveyance by reversing the conveying direction of the sheet after the trailing edge of the sheet in the discharge direction passes through the check valve 23.

[0030] The inner discharge rollers 26, intermediate conveyance rollers 28, and kick-out rollers 29 arranged in the inner discharge path 82 sequentially deliver the sheets received from the discharge reversal rollers 24 and convey them toward the sheet processing unit 71. The intermediate pre-stacking sensor 38 detects the sheet between the intermediate conveyance rollers 28 and the kick-out rollers 29. The intermediate pre-stacking sensor 38 is, for example, a reflective photosensor that irradiates infrared light into the conveyance path and detects light reflected by the sheet passing through the conveyance path to determine the presence or absence of the sheet.

[0031] Here, the sheet processing device 4 has a superimposition processing unit 4B including a discharge / reverse roller 24 and an inner discharge roller 26, and is capable of performing an operation of superimposing multiple sheets conveyed one by one from the image forming apparatus 1 by the superimposition processing unit 4B. The superimposition processing unit 4B of this embodiment holds a first sheet conveyed through a receiving path 81 on an inner discharge path 82 by the discharge / reverse roller 24 and the inner discharge roller 26, and then superimposes the first sheet on a second sheet conveyed through the receiving path 81. The superimposition processing unit 4B has both a function of discharging the superimposed sheets to the upper discharge tray 25 (superimposed discharge) and a function of conveying the superimposed sheets to the sheet processing unit 71 (buffer function). The detailed configuration and operation of the superimposition processing unit 4B will be described later.

[0032] The sheet processing section 71 aligns multiple sheets received from the internal discharge path 82 and then performs binding processing at a predetermined position of the sheet stack. The sheet processing section 71 has a stapler 50 as processing means, and an intermediate stacking upper guide 31 and an intermediate stacking lower guide 32 that constitute an intermediate stacking section (processing tray) on which sheets to be processed are stacked.

[0033] A vertical alignment reference plate 39 is disposed as a reference member at the most downstream portion of the sheet processing section 71 in the conveying direction of the kick-out roller 29, and the position of the sheet stack in the vertical direction (conveying direction) is aligned by abutting the end of the sheet in the conveying direction against this. Downstream of the pressure guide 56, a half-moon roller 33 is provided which is rotatably supported by the intermediate stack upper guide 31.

[0034] The half-moon roller 33 is a moving member (paddle member, conveying member) for abutting the sheet that has passed the kick-out roller 29 against the longitudinal alignment reference plate. After the trailing edge of the sheet passes the intermediate stack pre-sensor 38, the half-moon roller 33 conveys the sheet toward the longitudinal alignment reference plate 39 at a predetermined timing. The contact pressure of the half-moon roller 33 against the sheet is adjusted so that the sheet slips on the sheet when it is in contact with the longitudinal alignment reference plate 39. A flexible presser guide 56 is fixed to the intermediate stack upper guide 31, and presses the sheet in the sheet processing unit 71 downward with a predetermined pressure force to prevent the sheet from lifting up. In addition, downstream of the kick-out roller 29, a stack presser flag 30 is rotatably supported. The stack presser flag 30 prevents the trailing edge of the sheet from lifting up so that the trailing edge of the sheet already stacked in the sheet processing unit 71 does not interfere with the leading edge of the subsequent sheet being discharged by the kick-out roller 29.

[0035] When alignment of a predetermined number of sheets (multiple sheets that will become part of the product after processing) is completed on the intermediate stacking section, the stapler 50 performs a binding operation. Then, a bundle discharge guide 34 serving as a pushing member driven by a guide drive unit 35 moves from the standby position in FIG. 1 toward the bundle discharge rollers 36 (bundle discharge direction), thereby pushing out the sheet bundle from the intermediate stacking section. The bundle discharge direction is the opposite direction to the sheet discharge direction to the intermediate stacking section by the kick-out rollers 29. When the leading edge of the sheet bundle in the bundle discharge direction reaches the bundle discharge rollers 36, the bundle discharge guide 34 stops and returns to the standby position again. The bundle discharge rollers 36 serving as discharge means (fourth conveying means) discharge the sheet bundle received from the bundle discharge guide 34 onto a lower discharge tray 37.

[0036] Both the upper discharge tray 25 and the lower discharge tray 37 are movable up and down relative to the housing of the sheet processing device 4. Sheet presence sensors 51, 53 that detect the presence or absence of sheets on the trays are arranged on the upper discharge tray 25 and the lower discharge tray 37, respectively. The sheet presence sensors 51, 53 are, for example, reflective photosensors that determine the presence or absence of sheets by irradiating infrared light above the tray loading surface and detecting light reflected from the sheets. The sheet processing device 4 also has a sheet surface detection sensor that detects the top surface position of the sheets on the upper discharge tray 25 and the lower discharge tray 37 (sheet stacking height).

[0037] When the sheet surface detection sensor detects a sheet, the corresponding upper discharge tray 25 or lower discharge tray 37 is lowered in the direction A2 or B2. Furthermore, when the sheet presence / absence sensors 51, 53 detect that a sheet has been removed from the upper discharge tray 25 or lower discharge tray 37, the tray is raised in the direction A1 or B1. The upper discharge tray 25 and the lower discharge tray 37 are controlled to rise and fall in accordance with the amount of sheets stacked so that the top surfaces of the stacked sheets are positioned vertically below the discharge / reversal roller 24 or the bundle discharge roller 36. In this embodiment, the upper discharge tray 25 as the first stacking unit and the lower discharge tray 37 as the second stacking unit are each controlled to rise and fall by motor drive, but may also be configured to be able to rise and fall by a biasing means such as a spring.

[0038] The stapler 50 is an example of a processing means, and a sorting mechanism for sorting sheets or a center-folding processing section for center-folding a plurality of sheets to form a book may be provided.

[0039] (Superimposition processing unit) 2 shows an enlarged view of the overlap processing unit 4B. The sheet transport path (receiving path 81) between the entrance roller 21 and the pre-branch roller 22 is formed by the entrance upper guide 40 and the entrance lower guide 41. The sheet transport path (internal discharge path 82) between the internal discharge roller 26 and the intermediate transport roller 28 is formed by the internal discharge upper guide 46 and the internal discharge lower guide 47. The transport guide that guides the sheet from the same side as the entrance upper guide 40 between the pre-branch roller 22 and the discharge reverse roller 24 is referred to as the inverting upper guide 42. Furthermore, the transport guide that guides the sheet from the same side as the internal discharge lower guide 47 between the discharge reverse roller 24 and the internal discharge roller 26 is referred to as the inverting lower guide 43. The first discharge path 83 is formed by the inverting upper guide 42 and the inverting lower guide 43.

[0040] The sheet conveyed by the inlet rollers 21 is guided to the pre-branch rollers 22 by the upper inlet guide 40 and the lower inlet guide 41. An inlet sensor 27 is disposed in the upper inlet guide 40. The inlet sensor 27 may be a reflective photosensor that irradiates infrared light toward the receiving path 81 and detects the light reflected from the sheet to determine the presence or absence of a sheet at the detection position. In this case, a hole larger than the diameter of the spot light of the inlet sensor 27 is provided in the part of the lower inlet guide 41 facing the inlet sensor 27 so that the infrared light is not reflected when no sheet is passing through.

[0041] A check valve 23 is disposed downstream of the pre-branch roller 22 at a location where the receiving path 81 and the internal discharge path 82 branch off from the first discharge path 83. The check valve 23 is rotatably supported by a rotating shaft 23a relative to the internal discharge upper guide 46. The check valve 23 is constantly biased by a spring (not shown) in the direction C2 (clockwise in the drawing) toward a position (position in FIG. 2) where the tip of the check valve 23 overlaps with the reverse upper guide 42 as viewed from the axial direction of the rotating shaft 23a (the sheet width direction). The spring constant of the spring is set to a magnitude sufficient to rotate the check valve 23 in the direction C1 (counterclockwise in the drawing) against the biasing force of the spring when the sheet delivered from the pre-branch roller 22 contacts the check valve 23. Therefore, the check valve 23 allows the sheet conveyed from the pre-branch roller 22 toward the discharge reverse roller 24 to pass through. Furthermore, when the trailing end of the sheet in the receiving path 81 passes through the check valve 23, the check valve 23 rotates in the C2 direction to prevent the sheet from flowing back from the discharge / reverse roller 24 to the pre-branch roller 22.

[0042] The discharge / reverse roller 24 is made up of an upper roller 24a and a lower roller 24b. In this embodiment, a driving force is input to both the upper roller 24a and the lower roller 24b, and the rotations of the upper roller 24a and the lower roller 24b are always synchronized.

[0043] The discharge and reversing rollers 24 are configured so that they can be brought into contact (closing operation) and separated (opening operation) by a plunger solenoid 45. Specifically, one end of a separating lever 44 is connected to the roller shaft of the upper roller 24a, and the separating lever 44 is supported rotatably around a lever fulcrum shaft 44a relative to the upper reversing guide 42. A solenoid connection shaft 44b provided at the other end of the separating lever 44 is connected to the plunger of the plunger solenoid 45.

[0044] When the plunger solenoid 45 is energized, the plunger is attracted in the direction D1 by magnetic force, causing the separation lever 44 to rotate in the direction E1, and the discharge / reverse roller 24 enters a separated state (a state in which the nip portion of the pair of rollers is open). When the plunger solenoid 45 is de-energized, the upper roller 24a comes into contact with the lower roller 24b due to the biasing force of a pressure spring 48 connected to the roller shaft of the upper roller 24a, and the discharge / reverse roller 24 enters a contact state (a state in which the nip portion is closed). At this time, the separation lever 44 rotates in the direction E2 as the upper roller 24a moves, and the plunger of the plunger solenoid 45 moves in the direction D2. Note that the mechanism for opening and closing the discharge / reverse roller 24 may be, for example, a mechanism in which the separation lever 44 is swung by a cam rotated by the driving force of a motor.

[0045] The inner discharge rollers 26 are a pair of rollers adjacent to the discharge reverse rollers 24 in the sheet transport direction in the inner discharge path 82, and are a pair of rollers that can rotate forward and backward. That is, the inner discharge rollers 26 can transport a sheet in both a direction from the discharge reverse rollers 24 toward the sheet processing unit 71 (hereinafter referred to as the G1 direction) and a direction from the sheet processing unit 71 toward the discharge reverse rollers 24 (hereinafter referred to as the G2 direction).

[0046] (Hardware configuration) Next, the hardware configuration of the image forming system 1S according to this embodiment will be described with reference to Fig. 3. Fig. 3 is a diagram showing the hardware configuration of the image forming system 1S, mainly showing the portion relating to the configuration of the sheet processing apparatus 4. A video controller 601 controls the entire image forming system 1S including the image forming apparatus 1 and the sheet processing apparatus 4, and an engine control unit 602 controls the image forming apparatus 1.

[0047] The main control unit 603 controls the sheet processing apparatus 4. A signal line 604 is a signal line for transmitting serial commands from the video controller 601 to the engine control unit 602, and a signal line 605 is a signal line for transmitting commands from the video controller 601 to the main control unit 603 via serial communication. A signal line 606 is a signal line for transmitting serial status data from the engine control unit 602 to the video controller 601 in response to a command, and a signal line 607 is a signal line for transmitting serial status data from the main control unit 603 to the video controller 601 via serial communication. When performing image formation operations, the video controller 601 transmits serial commands to the engine control unit 602 and the main control unit 603 and receives status data from the engine control unit 602 and the main control unit 603, thereby performing control. In this way, when a plurality of devices are connected and the image forming system 1S is operating, the video controller 601 controls and manages the status of each device and maintains consistency in operation between the devices.

[0048] The main control unit 603 has a CPU 608 that controls various operations of the sheet processing apparatus 4, and a RAM 609 that temporarily stores control data required for the operation of the sheet processing apparatus 4. The main control unit 603 also has a non-volatile ROM 610 that stores programs and control tables required for the operation of the sheet processing apparatus 4. The main control unit 603 also has a communication unit 611 that performs communication processing with the video controller 601, a system timer 612 that generates timing required for various controls, and an I / O port 613 that inputs and outputs control signals to various units within the sheet processing apparatus 4. The main control unit 603 is a control IC to which these elements are connected via a bus 614.

[0049] Input signals from the entrance sensor 27 and the sheet presence sensors 51 and 53 of the upper discharge tray 25 and the lower discharge tray 37 are transmitted to the main control unit 603 via input circuits 615, 626, and 628. Control signals from the main control unit 603 are transmitted to the entrance motor 641, the pre-branch motor 642, the discharge reversal motor 643, the internal discharge motor 644, or the plunger solenoid 45 via drive circuits 618, 619, 620, 621, and 623. This controls the driving of each actuator.

[0050] (function block) Next, functional blocks of this embodiment will be described with reference to Fig. 4. A main control unit 603 in Fig. 4 has a function of executing the sheet conveying operation of the sheet processing apparatus 4. The main control unit 603 has at least the functions of a communication unit 611, a system timer 612, a sheet conveying control unit 701, a sensor control unit 720, a motor control unit 721, and a solenoid control unit 722.

[0051] The sensor control means 720 is a means for inputting signals from the entrance sensor 27 and the sheet presence / absence sensor 51 of the upper discharge tray 25 to the sheet transport control means 701. The sheet transport control means 701 is composed of an overlapping transport control means 711 and a sheet number control means 712. The sheet transport control means 701 controls the motor control means 721 and the solenoid control means 722 based on the input from the sensor control means 720, thereby realizing the operations of the overlapping processing unit 4B, the upper discharge tray 25, and the lower discharge tray 37. The overlapping transport control means 711 controls the transport of sheets to the overlapping processing unit 4B and the upper discharge tray 25 while managing the position of the sheets mainly based on the input from the sensor control means 720.

[0052] When a job for forming images continuously on a plurality of sheets is executed, the sheet count control unit 712 manages the number of sheets to be superimposed in the superimposition processing unit 4B. Based on the maximum number of sheets that can be superimposed by the superimposition processing unit 4B (superimposable number of sheets), the current number of superimposed sheets, and sheet information, the sheet count control unit 712 determines whether to transport the superimposed sheets toward the upper discharge tray 25 or the sheet processing unit 71, or to continue superimposing subsequent sheets.

[0053] The inlet motor 641 drives the inlet roller 21, the pre-branch motor 642 drives the pre-branch roller 22, and the discharge / reverse motor 643 drives the discharge / reverse roller 24. The inner discharge motor 644 drives the inner discharge roller 26, and the plunger solenoid 45 drives the separation lever 44. The operations of these drives will be described in detail later.

[0054] (Overlapping discharge operation) 5(a) to 5(f), an overview of the operation (superimposed discharge operation) in which the superimposed conveyance control means 711 superimposes and discharges multiple sheets using the superimposed processing unit 4B will be described. Hereinafter, of the sheets to be subjected to the superimposed discharge operation, the first sheet (first sheet) conveyed from the image forming apparatus 1 to the sheet processing apparatus 4 will be referred to as sheet S1, and the second sheet (second sheet) conveyed will be referred to as sheet S2. Furthermore, the conveying speed of the pre-branch rollers 22, discharge reversal rollers 24, and inner discharge rollers 26 before acceleration (conveying speed in the relay unit 14) will be referred to as V1, and the conveying speed after acceleration will be referred to as V2.

[0055] Roughly speaking, in the overlapping discharge operation, the discharge reverse rollers 24 (second conveying section) reverse the sheet S1 received from the pre-branch rollers 22 (first conveying section) and deliver it to the inner discharge rollers 26 (third conveying section) (FIGS. 5(a) to 5(d)). Next, based on the detection signal emitted by the entrance sensor 27 (detecting section) in response to the sheet S2 being conveyed following the sheet S1, the inner discharge rollers 26 (third conveying section) convey the sheet S1 toward the discharge reverse rollers 24 (second conveying section) (FIG. 5(e)). Then, with the edges of the sheets S1 and S2 in the conveying direction aligned and the sheets S1 and S2 overlapping each other, the discharge reverse rollers 24 (second conveying section) discharge the sheets S1 and S2 onto the upper discharge tray 25 (stacking section) (FIG. 5(f)).

[0056] FIG. 5(a): When the trailing edge of the preceding sheet S1 passes the entrance sensor 27, the pre-branch roller 22 and the discharge / reverse roller 24 are accelerated from speed V1 to speed V2. By accelerating the conveying speed of the sheet S1, the sheet interval required for switchback can be secured between the sheet S1 and the succeeding sheet S2, even if the image forming apparatus 1 is a high-performance machine with high throughput. However, if the sheets S1 and S2 do not collide, the conveying speed at the entrance sensor 27 may not be accelerated. In that case, the conveying speed in the superposition processing unit 4B may be unified at V1. Also, at the time of FIG. 5(a), the discharge / reverse roller 24 is conveying the sheet S1 in the direction F2.

[0057] 5(b): The conveyance of the sheet S1 is temporarily stopped when the trailing edge of the sheet S1 moves a predetermined distance after passing the inlet sensor 27 and passes through the check valve 23. The "predetermined distance" is the distance at which the trailing edge of the sheet S1 in the F2 direction passes through the check valve 23 and does not reach the nip portion of the discharge reverse roller 24.

[0058] 5(c): The discharge / reverse roller 24 changes its rotation direction and conveys the sheet S1 in the F1 direction at a speed V2. Before the leading edge of the sheet S1 in the F1 direction reaches the inner discharge roller 26, the inner discharge roller 26 starts to drive, and the inner discharge roller 26 further conveys the sheet S1 in the G1 direction.

[0059] 5(d): When the sheet S1 is sandwiched between the inner discharge rollers 26 and the leading edge of the sheet S1 in the G1 direction (F1 direction) passes the inner discharge rollers 26 and is conveyed a predetermined distance, the conveyance of the sheet S1 is stopped. The "predetermined distance" is shorter than the distance required for the leading edge of the sheet S1 to reach the intermediate conveyance rollers 28. The upper roller 24a of the discharge reverse rollers 24 is moved in the E1 direction by the separation lever 44 at the timing when the sheet S1 is sandwiched between the inner discharge rollers 26, and is separated from the lower roller 24b. The discharge reverse rollers 24 are driven to separate before the leading edge of the succeeding sheet S2 reaches the discharge reverse rollers 24.

[0060] FIG. 5(e): After the trailing edge of the succeeding sheet S2 passes the entrance sensor 27, the pre-branch roller 22 and the discharge / reverse roller 24 are accelerated to a speed V2, similar to that of the preceding sheet S1. After the trailing edge of the sheet S2 passes the entrance sensor 27 and a predetermined time T_wait has elapsed, the inner discharge roller 26 begins rotating again toward the discharge / reverse roller 24, and the sheet S1 is transported in the G2 direction. The predetermined time T_wait will be explained later. When the relative speeds of the sheets S1 and S2 become equal, the upper roller 24a of the discharge / reverse roller 24 is driven in the E2 direction and contacts the lower roller 24b, and the discharge / reverse roller 24 simultaneously grips the sheets S1 and S2. At this point, the leading edges of the sheets S1 and S2 in the F2 direction are aligned. The rotational speed of the discharge / reverse roller 24 is adjusted to be equal to the speed V2, which is the transport speed of the sheets S1 and S2, before gripping the sheets S1 and S2.

[0061] 5(f): When the trailing edge of sheet S2 passes through check valve 23, sheets S1 and S2 become sheet bundle S' whose leading and trailing edges are aligned in the F2 direction. If the discharge destination of sheet bundle S' is set to upper discharge tray 25, sheet bundle S' is discharged to upper discharge tray 25 by discharge reversal rollers 24 while maintaining speed V2.

[0062] 5(g): On the other hand, when the discharge destination of the sheet bundle S' is set to the lower discharge tray 37, the discharge reverse rollers 24 are temporarily stopped when the trailing edge of the last sheet (sheet S2 in this case) added to the sheet bundle S' passes through the check valve 23. Thereafter, the discharge reverse rollers 24 transport the sheet bundle S' toward the sheet processing unit 71 at a speed V2.

[0063] This completes the operation of overlapping and discharging the two sheets S1 and S2 while aligning them in the overlapping processing unit 4B (overlapping and discharging operation). When image formation is performed continuously on a large number of sheets, the overlapping and discharging operation is repeated to stack two sheets on the upper discharge tray 25.

[0064] Here, the advantages of this embodiment will be explained in comparison with the case where sheets S1 and S2 are discharged one by one without performing the overlapping discharge operation. When sheets S1 and S2 are discharged one by one, there is a possibility that the position and posture of sheets S1 and S2 that have passed through the discharge / reversal roller 24 may become distorted before they land on the upper surface of the upper discharge tray 25 or on the upper surface of a sheet on the upper discharge tray 25. This is because sheets S1 and S2 are subjected to air resistance and move back and forth and left and right as they fall when viewed from above.

[0065] In contrast, in this embodiment, the sheets S1 and S2 are discharged in a superimposed state with their positions aligned in the sheet conveyance direction, making it less likely that the positions and postures of the sheets S1 and S2 will be disturbed. Comparing a stack of sheets discharged by superimposing discharge and sheets discharged individually, the projected area of ​​the sheets (stack) seen from above is the same, but the weight of the stack of sheets is twice that of a single sheet, making it less susceptible to air resistance. Therefore, even if the sheet discharge speed by the discharge / reversal roller 24 is increased to improve the productivity of the image forming system 1S and the sheet processing device 4, a decrease in sheet stackability can be suppressed. In other words, this embodiment can improve the sheet stackability on the upper discharge tray 25 while maintaining productivity. Furthermore, this embodiment allows sheets to be discharged superimposed with a simpler and more compact configuration than a method of discharging sheets after overlapping and aligning them in an intermediate stacking unit, such as the sheet processing unit 71.

[0066] In this embodiment, the upper discharge tray 25 serving as a stacking section protrudes outside the apparatus main body 4A, and sheets discharged above the upper discharge tray 25 by the discharge and reversal rollers 24 fall onto the upper discharge tray 25 by gravity without being transported to any transport section other than the discharge and reversal rollers 24. Even in such a configuration that is relatively susceptible to the influence of air resistance, it is possible to improve the stacking ability of sheets on the upper discharge tray 25 by performing the overlapping discharge operation.

[0067] (3 or more sheets stacked and ejected) Although the above describes the transport of two sheets, the sheet processing device 4 of this embodiment can perform an overlapping discharge operation in which three or more sheets are aligned, overlapped on top of each other, and discharged onto the upper discharge tray 25 in the overlapping processing unit 4B.

[0068] When performing the overlap discharge operation for three sheets, first, two sheets S1 and S2 are overlapped in the procedure described above using Figures 5(a) to (f), and then the discharge / reverse roller 24 is rotated in the reverse direction again from the state of Figure 5(f) to transport the sheet bundle S' in the G1 direction. Then, the operation performed on sheet S1 in Figures 5(c) to (f) is performed on the sheet bundle S', while the operation performed on sheet S2 in Figures 5(c) to (f) is performed on the third sheet S3 (third sheet).

[0069] As a result, the sheet bundle S' is temporarily held by the inner discharge rollers 26 of the inner discharge path 82, and then, when a predetermined time T_wait has elapsed since the entrance sensor 27 detected the trailing end of the third sheet S3, the inner discharge rollers 26 convey the sheet bundle S' in the direction G2. Thereafter, the discharge reverse rollers 24, which had been open, close, and the three sheets S1, S2, and S3 are simultaneously sandwiched between the discharge reverse rollers 24. When the trailing end of sheet S3 passes through the check valve 23, a sheet bundle is formed in which the leading and trailing ends of the three sheets S1, S2, and S3 are aligned.

[0070] When the number of sheets in the overlapping discharge operation is three, the sheet stack is discharged directly in the G2 direction by the discharge reverse rollers 24 and stacked on the upper discharge tray 25. When the number of sheets in the overlapping discharge operation is four or more, the discharge reverse rollers 24 again transport the sheet stack in the G1 direction and repeat the same operations as those in Figures 5(c) to (f), thereby increasing the number of overlapping sheets.

[0071] The sheet count control means 712 manages the number of sheets to be superimposed in the superimposition processing unit 4B based on the number of sheets that can be superimposed in the superimposition processing unit 4B and information on the sheets to be conveyed. That is, the sheet count control means 712 determines whether the sheet conveyed to the superimposition processing unit 4B should be immediately conveyed (discharged) toward the upper discharge tray 25 or the sheet processing unit 71, or whether the sheet should be superimposed on the subsequent sheet.

[0072] As an example of a determination method, when the number of sheets that can be superimposed in the superimposition processing unit 4B is N, the sheet count control unit 712 creates a sheet bundle of N-1 sheets and discharges it to the upper discharge tray 25. In other words, when executing a job in which multiple sheets are discharged to the stacking unit, the control unit of this embodiment repeatedly performs a superimposed discharge operation as a discharge operation so that the multiple sheets are discharged to the stacking unit in a state in which they are stacked in units of a preset number of sheets. Furthermore, when it is determined that the Nth sheet is the last sheet in the job, the number of sheets to be superimposed is set to N, thereby avoiding the Nth sheet being discharged alone to the upper discharge tray 25.

[0073] As a specific example, in the configuration example of this embodiment, the number of sheets that can be superimposed in the superimposition processing unit 4B is five. In this case, the sheet count control unit 712 repeatedly executes the superimposition discharge operation for four sheets at a time, and stacks a sheet bundle consisting of four sheets on the upper discharge tray 25. Here, if it is determined that the fifth sheet is the final sheet and that the final sheet will be discharged alone if the superimposition discharge operation for four sheets is completed, the sheets are discharged to the upper discharge tray 25 by performing the superimposition discharge operation for five sheets including the final sheet. If the final sheet is still superimposed on another sheet even after the superimposition discharge operation for four sheets is completed, the sheet bundle is discharged to the upper discharge tray 25 when a sheet bundle including the final sheet is formed.

[0074] In other words, when executing a job to discharge a predetermined number of sheets to the upper discharge tray 25, the sheet count control unit 712 changes the number of sheets in the sheet bundle formed by the overlapping discharge operation in accordance with the value of the predetermined number so that each of the predetermined number of sheets is always discharged to the upper discharge tray 25 in a state where it is included in a sheet bundle consisting of two or more sheets formed by the overlapping discharge operation. In other words, the control unit of this embodiment changes the number of sheets to be stacked in the overlapping discharge operation in accordance with the number of sheets to be discharged by the job so that each of the multiple sheets to be discharged during the job is discharged to the stacking section in a state where it is stacked on one of the other sheets. This prevents a decrease in sheet stackability due to a single sheet being discharged to the upper discharge tray 25. Note that the method for controlling the number of sheets in the overlapping discharge operation is not limited to this as long as it can prevent a single sheet from being discharged. For example, in the above example, the number of sheets to be stacked in the overlapping discharge operation may be 4, . . . , 4, 3, or 2.

[0075] (How to calculate T_wait) Here, the timing management (how to obtain the above-mentioned T_wait) performed by the overlapping conveyance control means 711 in order to align the leading edges of the sheets S1 and S2 in the overlapping processing unit 4B will be described.

[0076] 7(a) shows the positional relationship between sheets S1 and S2 at the moment when the trailing edge of sheet S2 is detected by the inlet sensor 27. Distance L1 is the distance from the detection position of the inlet sensor 27 to the nip position of the discharge / reverse rollers 24 (the length measured along the receiving path 81 and the first discharge path 83). Distance L2 is the distance from the position where the leading edge of the inverted sheet S1 passes through the inner discharge rollers 26, moves a predetermined distance d1, and stops, to the nip portion of the discharge / reverse rollers 24 (the length measured along the first discharge path 83 and the inner discharge path 82).

[0077] 7(b) shows the positional relationship between sheets S1 and S2 at the time when sheet S1 starts to be conveyed in the F2 direction (G2 direction) from the state shown in FIG. 7(a) and the conveying speed of sheet S1 becomes equal to the conveying speed of sheet S2. It is assumed that at this point, the rear ends of sheets S1 and S2 in the F2 direction are misaligned by a protrusion amount Kt.

[0078] FIG. 7(c) shows the transition of the speeds of sheets S1 and S2 during the operation shown in FIGS. 7(a) and 7(b). A in the figure indicates the moment when the entrance sensor 27 detects the trailing edge of sheet S2 and the pre-branch roller 22 starts accelerating from speed V1 to speed V2 at a constant acceleration, as shown in FIG. 7(a). B in the figure indicates the timing when sheet S2 completes acceleration to speed V2. C in the figure indicates the timing when a predetermined time T_wait has elapsed after the entrance sensor 27 detects the trailing edge of sheet S2, that is, the timing when the inner discharge roller 26 starts conveying sheet S1 in the G2 direction. D in the figure indicates the timing when the relative speed (speed difference) between sheets S1 and S2 becomes zero, as shown in FIG. 7(b).

[0079] Hereinafter, the elapsed time from A to D is referred to as T_Merge. Time T1 represents the time required for the pre-branch roller 22 to accelerate from speed V1 to speed V2 (the elapsed time from A to B). Time T2 represents the time required for the pre-branch roller 22 to accelerate to speed V2 and then for the inner discharge roller 26 to start rotating (the elapsed time from B to C). From the definitions of T1, T2, and T_wait, T_wait = T1 + T2. Time T3 represents the time required for the sheet S1 to accelerate at a constant acceleration from a stopped state and reach speed V2 (the elapsed time from C to D).

[0080] From the above explanation, the distance X2 that the sheet S1 travels from the state in Figure 7(a) to the state in Figure 7(b) is the distance that the sheet S1 travels from C to D in Figure 7(c), and can be expressed by the following equation (1). X2=(V2×T3) / 2 (1)

[0081] Furthermore, the distance X1 that the sheet S2 travels from the state in Figure 7(a) to the state in Figure 7(b) is the distance that the sheet S2 travels from A to D in Figure 7(c), and can be expressed by the following equation (2). X1=(V1+V2)×T1 / 2+V2×(T2+T3) (2)

[0082] From the positional relationship between the sheets S1 and S2 at the timing of FIG. 7(b), the relationship of the following formula (3) holds. L1-X1=L2-X2-Kt (3)

[0083] Substituting equations (1) and (2) into equation (3), expanding and rearranging it, we obtain the following equation (4). L1-L2+Kt =(T1 / 2)×V1+(T1 / 2+T2+T3 / 2)×V2 (4)

[0084] Substituting T_wait = T1 + T2 into the above equation (4) and rearranging, the waiting time T_wait from when the rear end of sheet S2 passes through the entrance sensor 27 until the inner discharge roller 26 starts transporting sheet S1 for the protrusion amount Kt can be calculated using the following equation (5). T_wait=(L1-L2+Kt) / V2 -(T1 / 2) × V1 / V2 + (T1-T3) / 2 (5)

[0085] To align the leading and trailing edges of the sheets S1 and S2 when they are overlapped, the waiting time T_wait can be calculated by setting Kt=0 in the above formula (5). By starting conveyance of the sheet S1 by the inner discharge rollers 26 based on the calculated T_wait, it is possible to form a sheet bundle S' in which the leading and trailing edges of the sheets S1 and S2 are aligned. In other words, the predetermined time (T_wait) from the detection of the sheet S2 by the inlet sensor 27 to the start of conveyance of the sheet S1 by the inner discharge rollers 26 is set in advance so that the edges of the sheets S1 and S2 in the conveyance direction are aligned at the discharge reverse rollers 24. Furthermore, when three or more sheets are overlapped, the same value of T_wait can be used to form a sheet bundle in which the leading and trailing edges of each sheet are aligned.

[0086] (Control example) Next, an example of a control method for the sheet processing apparatus 4 that realizes the overlapping discharge operation described with reference to Figures 5(a-f) will be described with reference to the flowchart in Figure 6. This flow is executed every time the main control unit 603 of the sheet processing apparatus receives from the video controller 601 a notification that one sheet will be discharged from the image forming apparatus 1. Unless otherwise specified, each step of this flow is executed by the overlapping conveyance control means 711 in Figure 4.

[0087] In the following description, the "first sheet" refers to the sheet that is first transported to the sheet processing device 4 among the sheets that make up the sheet bundle to be superimposed in the superimposition processing unit 4B. For example, when sheets are superimposed in groups of four and discharged onto the upper discharge tray 25, the "first sheet" refers to the sheet (4n+1th sheet) that is transported to the sheet processing device 4 after the last sheet of the previous sheet bundle. Furthermore, the "last sheet" refers to the sheet (4nth sheet in the above example) that is last transported to the sheet processing device 4 among the sheets that make up the sheet bundle to be superimposed in the superimposition processing unit 4B.

[0088] Step S101: The entrance roller 21 and the pre-branch roller 22 start to rotate at a speed V1. The process proceeds to S102. If the entrance roller 21 and the pre-branch roller 22 are already rotating at the speed V1, they continue to rotate. Step S102: Determine whether the current sheet is the first sheet. If Yes, proceed to S103; if No, proceed to S106.

[0089] Step S103: The discharge / reverse roller 24 is brought into contact with the upper discharge tray 25 and starts to rotate at a speed V1 in a direction (G2 direction) for conveying the first sheet toward the upper discharge tray 25 (see sheet S1 in FIG. 5A). The process proceeds to S104. Step S104: It is determined whether the trailing edge of the first sheet has passed through the entrance sensor 27. If Yes, the process proceeds to S105; if No, the process proceeds to S104. Step S105: The pre-branch roller 22 and the discharge / reverse roller 24 are accelerated to a speed V2 (see the sheet S1 in FIG. 5(a)). The process proceeds to S111.

[0090] Step S106: It is determined whether the trailing edge of the current sheet (second or subsequent sheet) has passed through the entrance sensor 27. If Yes, the process proceeds to S107; if No, the process proceeds to S106. Step S107: The pre-branch roller 22 and the discharge / reverse roller 24 are accelerated to a speed V2. As a result, the conveying speed of the current sheet is accelerated from the speed V1 to V2 (see sheet S2 in FIG. 5(d)). The process proceeds to S108. Step S108: It is determined whether a predetermined time T_wait has elapsed since the trailing edge of the current sheet passed through the entrance sensor 27. If Yes, the process proceeds to S109; if No, the process proceeds to S108. Step S109: The inner discharge rollers 26 start rotating again at the speed V2 in the direction (F2 direction) in which the sheet is conveyed toward the discharge reverse rollers 24 (see the sheet S1 in FIG. 5(d)). The process proceeds to S110. Step S110: When the conveying speed of the sheet (stack) conveyed by the internal discharge rollers 26 and the current sheet become equal, the upper roller 24a of the discharge reverse rollers 24 is moved in the E2 direction and brought into contact with the lower roller 24b (see FIG. 5(e)). As a result, the sheet (stack) conveyed by the internal discharge rollers 26 and the current sheet are simultaneously sandwiched between the discharge reverse rollers 24 (see FIG. 5(e)). The process proceeds to S111.

[0091] Step S111: Determine whether the current sheet is the final sheet. If Yes, proceed to S112; if No, proceed to S115.

[0092] Step S112: The sheet stack including the last sheet is discharged onto the upper discharge tray 25 (see FIG. 5(f)). That is, the sheet conveyance by the discharge reverse roller 24 and the inner discharge roller 26, which was started in S107 and S109, is continued, and a predetermined number of sheets with their leading and trailing ends aligned are discharged onto the upper discharge tray 25 together with the current sheet. Step S113: It is determined whether the rear end of the sheet stack has passed the discharge / reverse roller 24. If Yes, the process proceeds to S114, and if No, the process proceeds to S113. Step S114: The pre-branch roller 22 is decelerated to a speed V1, the discharge reverse roller 24 and the inner discharge roller 26 are stopped, and this flow ends. Note that if the current sheet is also the last sheet in the job (if no more sheets are being conveyed from the image forming apparatus 1), the entrance roller 21 and the pre-branch roller 22 are also stopped in S114.

[0093] Step S115: It is determined whether the rear end of the current sheet (a sheet other than the final sheet) has passed through the check valve 23. If Yes, the process proceeds to S116, and if No, the process proceeds to S115. Step S116: The discharge / reverse roller 24 and the inner discharge roller 26 are temporarily stopped (see the sheet S1 in FIG. 5B). The process proceeds to S117. Step S117: The discharge / reverse roller 24 and the inner discharge roller 26 start to rotate at a speed V2 in a rotation direction for conveying the sheets (stack) in the reverse direction (F1 direction, G1 direction) (see sheet S1 in FIG. 5(c)). The process proceeds to S118. Step S118: It is determined whether the leading edge of the sheets (stack) has passed the inner discharge roller 26. If Yes, the process proceeds to S119; if No, the process proceeds to S118. Step S119: The upper roller 24a of the discharge and reverse roller 24 is separated from the lower roller 24b. The process proceeds to S120. Step S120: At a position where the leading edge of the sheet (stack) has been conveyed a predetermined distance after passing the inner discharge roller 26, the pre-branch roller 22 is decelerated to speed V1, the discharge reverse roller 24 and the inner discharge roller 26 are stopped, and this flow ends. As a result, the sheet (stack) that is the target of the overlapping discharge operation and that can still be overlapped with other sheets is held in a state where it is sandwiched between the inner discharge roller 26 (see sheet S1 in FIG. 5(d)). The timing of steps S109, S113, S115, S118, etc. can be determined based on the timing signal of the system timer 612 (FIG. 6). For example, the timing is determined based on the operation history of the discharge reverse roller 24 and the inner discharge roller 26 from the time the trailing edge of the sheet S1 is detected by the inlet sensor 27.

[0094] As described above, according to this embodiment, when multiple sheets conveyed continuously are discharged to the stacking section, the overlapping processing section 4B can discharge the multiple sheets in an overlapping state with their edges aligned. This makes it possible to improve the stacking ability of the sheets in the stacking section while maintaining productivity. Furthermore, since an intermediate tray with a sheet alignment function does not need to be provided in the sheet processing apparatus for the purpose of discharging sheets in an overlapping state onto the upper discharge tray 25, it is possible to avoid an increase in the size of the apparatus and the resulting increase in costs.

[0095] In the configuration example of this embodiment, the maximum number of sheets that can be superimposed by the superimposition processing unit 4B (number of sheets that can be superimposed) is described as five, but the number of sheets that can be superimposed can be changed as appropriate depending on the specific configuration of the superimposition processing unit 4B and the required performance.

[0096] (Buffer operation when processing in the sheet processing section) The superimposition processing unit 4B of this embodiment can also operate as a buffer unit that overlaps and holds sheets received from the image forming apparatus 1 during processing when sheets are processed in the sheet processing unit 71. By performing the buffer operation, collisions of sheets in the sheet processing unit 71 can be avoided without reducing the productivity of the image forming apparatus 1, thereby improving the productivity of the image forming system 1S.

[0097] When performing the buffering operation, the operation of the overlapping processing unit 4B is basically the same as the overlapping discharge operation, except that the overlapping sheet bundle is transported to the sheet processing unit 71 via the internal discharge path 82. That is, in the operation shown in Figures 5(a) to 5(f), the overlapping sheet bundle as shown in Figure 5(f) is not discharged to the upper discharge tray 25, but is transported to the sheet processing unit 71 via the internal discharge rollers 26 and the like. After the sheet bundle is transported to the sheet processing unit 71 by the buffering operation, subsequent sheets that do not need to be buffered are switched back one by one by the discharge reversal rollers 24 and transported to the sheet processing unit 71.

[0098] In the buffer operation, the protrusion amount Kt (FIG. 7B) may be set so that the leading edges (ends) of the stacked sheets are offset by a predetermined distance. In this case, it is preferable to set the protrusion amount Kt so that the sheet located at the bottom in the sheet processing unit 71 (sheet S1 in FIG. 7B) protrudes further downstream in the sheet conveying direction toward the sheet processing unit 71. This allows the half-moon roller 33 to come into contact with each sheet of the stack of sheets stacked by the buffer operation, thereby enabling effective alignment. In particular, it is preferable that the protrusion amount Kt be greater than the distance from the contact position of the half-moon roller 33 with the sheet to the longitudinal alignment reference plate 39.

[0099] In this way, the overlap processing unit 4B of this embodiment has both the function of performing an overlap discharge operation when a sheet is discharged outside the sheet processing device 4 without being processed by the sheet processing unit 71, and the function of buffering sheets to be processed by the sheet processing unit 71. This makes it possible to reduce the size and cost of the device compared to a configuration in which two mechanisms for overlapping sheets are provided to achieve each function.

[0100] <Second embodiment> In the first embodiment, a method for improving stacking performance by an overlapping discharge operation in which sheets are discharged in an overlapping state has been described. In the second embodiment, in the overlapping discharge operation described in the first embodiment, the standby position of the overlapping sheets is changed according to the length of the sheets in the conveying direction. Hereinafter, elements with the same reference numerals as those in the first embodiment have substantially the same configurations and functions as those in the first embodiment, and their description will be omitted.

[0101] In the bundle discharge operation described in the first embodiment, after the transport direction of the preceding sheet S1 is reversed by the operation from FIG. 5(a) to FIG. 5(d), consider at what position the sheet S1 should be stopped (FIG. 5(d)). Hereinafter, the length of the sheet S1 in the transport direction is defined as Ls. The length of the sheet S1 from the nip position of the discharge reverse roller 24 to the end S1a of the sheet S1 on the G1 direction side (the inner discharge roller 26 side) is defined as L2. The length of the sheet S1 from the nip position of the discharge reverse roller 24 to the end S1b protruding outward from the sheet processing device 4 relative to the nip position is defined as L3. The relationship between Ls, L2, and L3 is Ls = L2 + L3.

[0102] 8(a) and 8(b), the length Ls of a sheet having a long length in the conveying direction (for example, an A4 sheet fed in the long-side feed direction) is denoted by Ls1, and the length Ls of a sheet having a short length in the conveying direction (for example, an A5 sheet fed in the long-side feed direction) is denoted by Ls2. Ls1 is an example of the first length, and Ls2 is an example of the second length.

[0103] In this embodiment, regardless of whether the length Ls of the sheet S1 is Ls1 or Ls2, the length L3 by which the end S1b of the sheet S1 protrudes from the discharge / reverse roller 24 is set to be equal to or less than Lmax (a predetermined value). The predetermined value Lmax is set to a value that has been considered in advance so that the end S1b of the sheet S1 (or a stack of sheets) protruding by the length Lmax from the nip position of the discharge / reverse roller 24 does not lean against the upper discharge tray 25 as shown in FIG. 8C. If the end S1b of the temporarily stopped sheet S1 leans against the upper discharge tray 25, it may rub against the stack of sheets St on the upper discharge tray 25 when the sheet S1 is later discharged, causing the position of the stack of sheets St to become distorted.

[0104] The discharge and reversing rollers 24 are designed to have a shape that, when a sheet is sandwiched between them, causes the cross section of the sheet to be slightly curved (or wavy) along the sheet width direction when the sandwiched sheet is viewed downstream in the sheet discharge direction. For example, the upper roller 24a and the lower roller 24b are configured to have their portions (rollers) that come into contact with the sheet alternately in the sheet width direction and their outer peripheral surfaces partially overlap when viewed in the sheet width direction, forming so-called comb rollers.

[0105] As described above, the discharge / reverse roller 24 conveys the sheets while giving them a curved shape, so that the sheet stack S' stacked by the overlapping discharge operation is discharged while maintaining a substantially straight posture without the end S1b drooping, as shown in Fig. 8(d). This reduces the possibility that the sheet stack S' will rub against the upper surfaces of the stack of sheets St stacked on the upper discharge tray 25, disrupting the stacking of the sheets St.

[0106] Fig. 9 is a functional block diagram of an image forming system 1S according to this embodiment. Compared to the first embodiment shown in Fig. 4, the overlapping conveyance control means 711 is different in that it includes a stop position control means 713 in addition to a sheet number control means 712. The stop position control means is a means for controlling the position at which the preceding sheet is temporarily stopped when multiple sheets are overlapped in the overlapping processing unit 4B.

[0107] The stop position control means 713 determines L2 by the following formula (6) based on the length Ls of the sheet in the conveying direction obtained from the video controller 601 via the communication means 611. L2=Ls-Lmax (6)

[0108] The control method of the sheet processing apparatus 4 is basically the same as the method of the first embodiment described with reference to FIG. 6. In the first embodiment, in step S120, the discharge reverse roller 24 and the inner discharge roller 26 are stopped at a position where the leading edge of the sheet S1 has been conveyed a predetermined distance (predetermined distance d1 in FIG. 7B) after passing the inner discharge roller 26. Instead, in this embodiment, the discharge reverse roller 24 and the inner discharge roller 26 are stopped when the sheet S1 has been conveyed a distance d2 corresponding to L2 calculated by the above formula (6) after passing the inner discharge roller 26. This distance d2 is a variable whose value changes depending on the sheet length Ls, where d4 is the distance from the nip position of the discharge reverse roller 24 to the inner discharge roller 26. The timing at which the leading edge of the sheet S1 has been conveyed the distance d2 after passing the inner discharge roller 26 can be determined based on a timing signal from a system timer 612 (FIG. 6). For example, it is determined based on the operation history of the discharge reverse roller 24 and the inner discharge roller 26 from the time when the rear end of the sheet S1 is detected by the entrance sensor 27. Other timing management (such as the method of determining the above-mentioned T_wait) performed by the overlapping conveyance control means 711 is the same as in the first embodiment.

[0109] The above-described method changes the standby position where the sheet S1 is temporarily stopped according to the sheet length Ls, thereby making it possible to keep the protruding length L3 of the sheet S1 at the time of the temporary stop equal to or less than the predetermined value Lmax. This prevents the end S1b of the sheet S1, which is temporarily stopped to wait for the subsequent sheet S2, from drooping and rubbing against the stack of sheets St already stacked on the upper discharge tray 25 during the process of overlapping the sheets S1 and S2 in the overlapping unit 4B. As a result, the possibility of the sheet S1 dragging the stack of sheets St when the sheets S1 and S2 are subsequently discharged is reduced, resulting in misalignment of the stack of sheets St. This improves the stackability of discharged sheets of various sizes. Furthermore, even if the sheet S1 has a curl (a tendency to curve), the temporarily stopped sheet S1 is less likely to curl significantly outside the discharge / reversal roller 24, reducing the possibility of the end S1b of the sheets S1 and S2 being curled when they are discharged.

[0110] Depending on the configuration of the device, the range of the value of L2 may be limited. For example, a lower limit may be set for the length of L2 so that the conveyance of the sheet S1 is temporarily stopped after the end S1a of the sheet S1 is nipped by the inner discharge rollers 26. In this case, the lower limit of L2 may be set to a value obtained by adding a margin for more reliably nipping the end S1a between the inner discharge rollers 26 to the distance from the nip position of the discharge reversal rollers 24 to the nip position of the inner discharge rollers 26.

[0111] Furthermore, suppose that the conveyance of sheet S1 is temporarily stopped after the end S1a of sheet S1 passes through the inner discharge rollers 26 and then reaches the intermediate conveyance rollers 28 (FIG. 1). In this case, to overlap sheets S1 and S2, the conveyance direction needs to be reversed in synchronization with the inner discharge rollers 26 and driven up to the intermediate conveyance rollers 28. To maintain a simple configuration in which the intermediate conveyance rollers 28 are driven in only one direction, an upper limit is set for L2. In this case, the upper limit of L2 can be set to a value obtained by subtracting a margin for more reliably preventing the end S1a from contacting the intermediate conveyance rollers 28 from the distance from the nip position of the discharge reversal rollers 24 to the nip position of the intermediate conveyance rollers 28.

[0112] Furthermore, the change of the standby position according to the length of the sheet in the transport direction, as described in this embodiment, only needs to be performed when the sheet is discharged to the upper discharge tray 25. When the sheet is discharged to the lower discharge tray 37, the sheet stack S' is ultimately discharged from the overlap processing unit 4B toward the sheet processing unit 71, and is unlikely to interfere with the sheets stacked on the upper discharge tray 25. Therefore, when the sheet is discharged to the lower discharge tray, the distance from when the sheet is reversed to when it stops after passing through the inner discharge rollers 26 may be determined regardless of the length of the sheet in the transport direction.

[0113] (Variation) In the first and second embodiments, the internal discharge path 82 as the second conveyance path is described as being connected to the sheet processing unit 71, but the second conveyance path may be configured to be connected to a discharge destination other than the sheet processing unit 71. For example, the sheet processing unit 71 may be omitted, and the sheet conveyed via the internal discharge path 82 may be discharged to the lower discharge tray 37 without being processed. Also, the second conveyance path may be configured as a dead end that does not communicate with the outside of the sheet processing device 4.

[0114] In addition, in embodiments 1 and 2, a sheet discharge device of a sheet processing device 4 that is provided separately from the image forming device 1 is described, but the present technology can also be applied to a sheet discharge device that discharges sheets from the image forming device 1 or other devices that handle sheets.

[0115] (Other embodiments) The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that realizes one or more functions. [Explanation of symbols]

[0116] 1...image forming apparatus / 1S...image forming system / 4...sheet processing device / 22...first conveying means (pre-branching roller) / 24...second conveying means (discharge reversal roller) / 25...loading section (upper discharge tray) / 26...third conveying means (internal discharge roller) / 27...detection means (entrance sensor) / 71...sheet processing section / 81, 83...first conveying path (receiving path, first discharge path) / 82...second conveying path (internal discharge path) / 603...control means (main control section)

Claims

1. A sheet discharge device, a loading section on which sheets are loaded; a first conveying means disposed on a first conveying path extending toward the stacking portion, for conveying a sheet toward the stacking portion; a detection means for generating a detection signal in response to a sheet passing through the first conveying path; a second conveying means disposed on the first conveying path downstream of the first conveying means, the second conveying means reversing a conveying direction of the sheet received from the first conveying means and conveying the sheet to a second conveying path branched off from the first conveying path between the first conveying means and the second conveying means; a third conveying means disposed on the second conveying path, the third conveying means reversing a conveying direction of the sheet and conveying the sheet; a control means for controlling the first conveying means, the second conveying means, and the third conveying means; Equipped with The control means causing the second conveying means to invert the first sheet received from the first conveying means and deliver it to the third conveying means; causing the third conveying means to convey the first sheet toward the second conveying means based on the detection signal issued by the detecting means in response to a second sheet being conveyed following the first sheet; and discharging the first sheet and the second sheet to the stacking portion by the second conveying means in a state in which the first sheet and the second sheet are overlapped with each other with their edges in the conveying direction aligned. configured to perform a discharge operation; the stacking portion protrudes to the outside of the device body of the sheet discharge device, The sheet discharged above the stacking unit by the second conveying means falls onto the stacking unit by gravity without being conveyed by any conveying means other than the second conveying means. A sheet discharge device characterized by:

2. the control means is configured to, during the discharge operation, cause the third conveying means to convey the first sheet toward the second conveying means at a timing when a predetermined time has elapsed since the detection means issued the detection signal in response to the second sheet, the predetermined time is set in advance so that edges of the first sheet and the second sheet in the conveying direction are aligned in the second conveying means.

2. The sheet ejection device according to claim 1.

3. the control unit is capable of forming a sheet bundle of three or more sheets including the first sheet and the second sheet in the discharging operation, and discharging the sheet bundle to the stacking portion by the second conveying unit.

3. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

4. when executing a job to discharge a plurality of sheets onto the stacking section, the control unit repeatedly executes the discharge operation so that the plurality of sheets are discharged onto the stacking section in a state where the sheets are stacked in units of a preset number of sheets.

4. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

5. the control means changes the number of sheets to be stacked in the discharge operation during the job in accordance with the number of sheets to be discharged by the job so that each of the plurality of sheets is discharged to the stacking section in a state where it is stacked on any one of the other sheets; 5. The sheet ejection device according to claim 4.

6. the control means, when stopping the conveyance of the first sheet by the third conveying means after the first sheet has been delivered to the third conveying means, changes a stop position of the leading edge of the first sheet in a direction from the second conveying means toward the third conveying means in accordance with the length of the first sheet in the sheet conveying direction so that a distance from the third conveying means to the stop position when the first sheet has a first length is longer than a distance from the third conveying means to the stop position when the first sheet has a second length that is shorter than the first length.

6. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

7. The control means changes the stopping position of the leading edge of the first sheet in the direction from the second conveying means toward the third conveying means according to the length of the first sheet in the sheet conveying direction when the conveyance of the first sheet by the third conveying means is stopped after the first sheet has been handed over to the third conveying means, and the control means sets the stop position so that, in a state in which the conveyance of the first sheet by the third conveying means is stopped, a length of the first sheet protruding toward the stacking section relative to the second conveying means is equal to or less than a predetermined value regardless of the length of the first sheet.

6. The sheet ejection device according to claim 1, wherein the sheet ejection device is a sheet ejection device.

8. The stacking unit is a first stacking unit, and the sheet conveyed via the second conveying path is stacked on a second stacking unit. the control means executes control to change the stop position of the first sheet when the first sheet and the second sheet are discharged to the first stacking section, and does not execute control to change the stop position of the first sheet when the first sheet and the second sheet are discharged to the second stacking section.

8. The sheet ejection device according to claim 6, wherein the sheet ejection device is a sheet ejection device.

9. The sheet ejection device according to any one of claims 1 to 8, a sheet processing section that processes sheets conveyed via the second conveying path; A sheet processing apparatus comprising:

10. The control unit is capable of performing a buffer operation in which, instead of the discharge operation, a plurality of sheets transported to the first transport path from outside the sheet processing device while the sheets are being processed in the sheet processing unit are superimposed by the first transport unit, the second transport unit, and the third transport unit, and then transported to the sheet processing unit after the processing in the sheet processing unit. The sheet processing apparatus according to claim 9 .

11. the control unit controls the buffer operation so that the edges of the sheets stacked by the buffer operation in the conveying direction are shifted from each other. The sheet processing apparatus according to claim 10 .

12. the sheet processing section includes an intermediate stacking section disposed within the device body, a reference member provided downstream of the intermediate stacking section in a sheet discharge direction from the second conveying path to the intermediate stacking section, a moving member that moves and aligns the sheet discharged to the intermediate stacking section toward the reference member, and a pushing member that pushes out the sheet that has been processed in the sheet processing section in a direction opposite to the discharge direction, The loading section is a first loading section, and a second loading section is provided below the first loading section; a third transport path extending from the intermediate stacking section toward the second stacking section below the first transport path, The sheets processed in the sheet processing section are stacked on the second stacking section. The sheet processing apparatus according to claim 10 .

13. an image forming device that forms an image on a sheet; a sheet processing apparatus according to any one of claims 9 to 12; An image forming system comprising:

Images