Post-processing device and image formation system

Abstract

To enable, without increasing a size of an apparatus, transporting a preceding recording medium and a subsequent recording medium such that tip positions of the preceding and subsequent recording mediums are aligned.SOLUTION: A control unit 65 is configured to: acquire a length of a preceding recording paper P1 in a transport direction X1 using a transit time of the preceding recording paper P1 obtained based on a detection result of a first detection unit 56 and a transport speed of the preceding recording paper P1; determine, based on the length of the preceding recording paper P1, in the transport direction X1, a stop timing of rotation of a retract roller 58 when a tip end of a subsequent recording paper P2 transported by forward rotation of a second transport roller 55B and a tip end of the preceding recording paper P1 are aligned in a case where the retract roller 58 is started to be driven at a reference start timing; stop the forward rotation of the retract roller 58 according to the stop timing; and cause the second transport roller 55B to rotate forward and cause the retract roller 58 to rotate backward according to the reference time timing, so as to transport, to a processing tray 52, the subsequent recording paper P2 and the preceding recording paper P1 on a retract path 54 being stacked on one another.SELECTED DRAWING: Figure 4A

Description

Technical Field

[0001] The present invention relates to a post-processing device and an image forming system, and particularly to a technique for waiting for a conveyed recording medium.

Background Art

[0002] In a post-processing device that performs post-processing on a recording paper on which an image is formed, a technique for waiting for the conveyed recording paper is known. For example, Patent Document 1 discloses a technique of winding the first sheet of a subsequent sheet group around the surface of a retraction drum and waiting while staple processing is being performed on a preceding sheet group.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described general post-processing device, the preceding recording paper that has been waited for is conveyed while being overlapped with the subsequently conveyed recording paper. At this time, it is preferable to align the leading edge positions of the preceding recording paper and the subsequently conveyed recording paper. However, if the sizes of the recording papers are different, there is a risk that the leading edge positions will not match.

[0005] In the technique disclosed in Patent Document 1, the rotation of the retraction drum is controlled so that the leading edge of the preceding recording paper reaches a predetermined position, thereby aligning the leading edge position of the preceding recording paper and the leading edge position of the subsequently conveyed recording paper. However, in the technique disclosed in Patent Document 1, a space for installing the retraction drum is required, so there is a risk that the device will become larger.

[0006] This invention has been made in view of the above circumstances, and aims to enable the transport of recording media by aligning the leading edge position of a preceding recording medium with the leading edge position of a subsequent recording medium without increasing the size of the device. [Means for solving the problem]

[0007] A post-processing device according to one aspect of the present invention comprises a processing tray, a post-processing unit that performs post-processing on a recording medium placed on the processing tray, a transport path extending toward the processing tray, a first detection unit that detects the presence or absence of a recording medium at a predetermined position on the transport path, a first transport roller that transports the recording medium along the transport path at a predetermined transport speed by rotating in a predetermined first direction, a second transport roller that transports the recording medium transported by the first transport roller toward the processing tray, a siding path provided at a position different from the transport path and extending toward the second transport roller, a second detection unit that detects the presence or absence of a recording medium at a predetermined position on the siding path, a siding roller that sends the recording medium on the siding path toward the second transport roller by rotating in a predetermined second direction, and a control unit that controls the operation of the first transport roller, the second transport roller, and the siding roller. When the rear end of the preceding recording medium passes through the transport path, the control unit rotates the second transport roller in a third direction opposite to the first direction to move the preceding recording medium to a safe path, rotates the safe path roller in a fourth direction opposite to the second direction to move the preceding recording medium in the safe path, obtains the length of the preceding recording medium in the transport direction using the passage time of the preceding recording medium determined based on the detection result of the first detection unit and the transport speed of the preceding recording medium, and starts driving the safe path roller at a predetermined reference start timing based on the detection result of the first detection unit. The rotation of the second transport roller in the first direction determines the timing at which the leading edge of the preceding recording medium and the leading edge of the preceding recording medium align when the leading edge of the preceding recording medium are being transported. The rotation of the second transport roller in the fourth direction is stopped according to the determined stopping timing, the second transport roller is rotated in the first direction, and the second transport roller is rotated in the second direction according to the reference start timing, so that the following recording medium and the preceding recording medium on the escape path are stacked and transported to the processing tray by the second transport roller.

[0008] A post-processing device according to another aspect of the present invention comprises a processing tray, a post-processing unit that performs post-processing on a recording medium placed on the processing tray, a transport path extending toward the processing tray, a first detection unit that detects the presence or absence of a recording medium at a predetermined position on the transport path, a first transport roller that transports the recording medium along the transport path at a predetermined transport speed by rotating in a predetermined first direction, a second transport roller that transports the recording medium transported by the first transport roller toward the processing tray, a siding path provided at a position different from the transport path and extending toward the second transport roller, a second detection unit that detects the presence or absence of a recording medium at a predetermined position on the siding path, a siding roller that sends the recording medium on the siding path toward the second transport roller by rotating in a predetermined second direction, and a control unit that controls the operation of the first transport roller, the second transport roller, and the siding roller. When the rear end of the preceding recording medium passes through the transport path, the control unit rotates the second transport roller in a third direction opposite to the first direction to move the preceding recording medium to a safe path, rotates the safe path roller in a fourth direction opposite to the second direction to move the preceding recording medium on the safe path in the safe path, stops the rotation of the safe path roller in the fourth direction according to a predetermined reference stop timing based on the detection result of the second detection unit, and uses the passage time of the preceding recording medium and the transport speed of the preceding recording medium, which are determined based on the detection result of the first detection unit, to determine the length of the preceding recording medium in the transport direction. When the data is acquired and the retraction roller is stopped at the reference stop timing, the start timing of the rotation of the retraction roller so that the leading edge of the preceding recording medium and the leading edge of the preceding recording medium are aligned is determined based on the length of the preceding recording medium in the transport direction. The second transport roller is then rotated in the first direction, and the retraction roller is rotated in the second direction according to the determined start timing, so that the following recording medium and the preceding recording medium on the retraction path are stacked and transported to the processing tray by the second transport roller.

[0009] An image forming system according to another aspect of the present invention includes the above-described post-processing device and an image forming apparatus comprising an image forming unit for forming an image on a recording medium. [Effects of the Invention]

[0010] According to the present invention, the stopping or starting timing of the rotation of the retraction roller is determined based on the length of the preceding recording medium in the transport direction. Therefore, the leading edge position of the preceding recording medium and the leading edge position of the following recording medium can be aligned during transport without being affected by differences in the length of the preceding recording medium in the transport direction. Furthermore, since a retraction path is used to allow the preceding recording medium to wait, the preceding recording medium can be kept waiting without increasing the size of the device compared to the case where a retraction drum is used. [Brief explanation of the drawing]

[0011] [Figure 1] This is a cross-sectional view showing the structure of an image forming apparatus and a post-processing apparatus that constitute an image forming system. [Figure 2] This is a block diagram showing the internal configuration of an image forming apparatus and a post-processing apparatus. [Figure 3] This is a diagram showing a magnified view of a part of the post-processing device. [Figure 4A] This is a flowchart showing the first paper storage process. [Figure 4B] This is a flowchart showing the first paper storage process. [Figure 5A] This diagram shows the transport status of the preceding recording paper. [Figure 5B] This diagram shows the status of the stowage of the preceding recording paper. [Figure 5C] This diagram shows the status of the stowage of the preceding recording paper. [Figure 5D] This diagram shows the transport status of the preceding and succeeding recording sheets. [Figure 5E] This diagram shows the transport status of the preceding and succeeding recording sheets. [Figure 6A] This flowchart shows the second recording paper handling process. [Figure 6B] This flowchart shows the second recording paper handling process. [Modes for carrying out the invention]

[0012] (First Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the structures of an image forming apparatus 10 and a post-processing apparatus 50 that constitute an image forming system 100 according to the first embodiment of the present invention. FIG. 2 is a block diagram showing the internal configurations of the image forming apparatus 10 and the post-processing apparatus 50.

[0013] As shown in FIG. 1, the image forming system 100 includes an image forming apparatus 10 and a post-processing apparatus 50 connected to the image forming apparatus 10. The image forming apparatus 10 forms an image on a recording sheet as a recording medium. The post-processing apparatus 50 performs post-processing on the recording sheet on which the image has been formed by the image forming apparatus 10.

[0014] [Configuration of Image Forming Apparatus 10] As shown in FIG. 1, the image forming apparatus 10 is an inkjet recording apparatus. The image forming apparatus 10 includes an image reading unit 11, an image forming unit 12, a conveyance unit 13, a paper feeding unit 14, a conveyance mechanism 15, a display unit 16, and an operation unit 17.

[0015] The image reading unit 11 is an ADF (Auto Document Feeder) including a document conveyance unit 2 that conveys a document M placed on a document tray 1 and a scanner 4 that optically reads the document M conveyed by the document conveyance unit 2 or a document placed on a platen glass 3. The image reading unit 11 irradiates the document with the light irradiation unit of the scanner 4 and receives the reflected light with a CCD (Charge-Coupled Device) sensor to read the document and generate image data indicating a document image.

[0016] The image forming unit 12 includes line heads 5Y, 5M, 5C, and 5K corresponding to each of the colors yellow, magenta, cyan, and black. Based on image data and the like generated by the image reading unit 11, the image forming unit 12 ejects ink droplets of each color from each of the line heads 5Y, 5M, 5C, and 5K onto the recording paper P conveyed by the conveying unit 13 to form a color image.

[0017] The conveying unit 13 includes a driving roller 6A, a driven roller 6B, a tension roller 6C, a conveying belt 7, and a suction roller 8. The driving roller 6A is connected to a driving motor and rotates counterclockwise by the driving of the driving motor. The conveying belt 7 is an endless belt spanned over the driving roller 6A, the driven roller 6B, and the tension roller 6C.

[0018] The conveying belt 7 rotates counterclockwise following the rotation of the driving roller 6A. The driven roller 6B and the tension roller 6C rotate counterclockwise following the rotation of the conveying belt 7. The suction roller 8 is disposed opposite to the driven roller 6B in contact with the conveying belt 7. The suction roller 8 electrostatically adsorbs the recording paper P fed from the paper feeding unit 14 to the conveying belt 7 by charging the conveying belt 7.

[0019] The paper feeding unit 14 includes a paper feeding cassette 9A and a manual feed tray 9B. The paper feeding unit 14 feeds the recording paper P accommodated in the paper feeding cassette 9A or the manual feed tray 9B one by one into the conveyance path T1 by a pickup roller that rotates by the driving of a paper feeding motor.

[0020] The conveying mechanism 15 includes a conveyance path T1 formed from the paper feeding unit 14 through the conveying unit 13 toward the post-processing device 50, a plurality of conveying roller pairs provided near the conveyance path T1, a discharge roller pair 21, and a conveying motor. The conveying mechanism 15 conveys the recording paper P along the conveyance path T1 by rotating the conveying roller pairs and the discharge roller pair 21 by the driving of the conveying motor, and discharges it from the discharge roller pair 21 toward the post-processing device 50.

[0021] The display unit 16 is a display device composed of a liquid crystal display or an organic light-emitting diode (EL) display, etc. The display unit 16 displays various screens for each function that can be performed by the image forming apparatus 10.

[0022] The operation unit 17 includes a number of hard keys, such as a start key, for instructing the start of execution for each process that can be performed by the image forming apparatus 1. The operation unit 17 also includes a touch panel that is superimposed on the display unit 16. The user uses the operation unit 17 to input various information, such as instructions for each process that can be performed by the image forming apparatus 1.

[0023] As shown in Figure 2, the image forming apparatus 10 further comprises a control unit 18, a storage unit 19, and an interface unit 20. The control unit 18 includes a processor, RAM (Random Access Memory), and ROM (Read Only Memory), etc. The processor is, for example, a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or an ASIC (Application Specific Integrated Circuit).

[0024] The control unit 18 is electrically connected to the image reading unit 11, the image forming unit 12, the transport unit 13, the paper feeding unit 14, the transport mechanism 15, the display unit 16, the operation unit 17, the storage unit 19, and the interface unit 20.

[0025] The control unit 18 functions as a control unit 21 by executing a control program stored in the ROM or storage unit 19 by the processor. The control unit 21 may also be composed of logic circuits, independent of the operation based on the control program. The control unit 21 controls the operation of each part of the image forming apparatus 10.

[0026] The storage unit 19 is a large-capacity storage device such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive). The storage unit 19 stores various data along with various control programs for realizing the general operation of the image forming apparatus 10.

[0027] A post-processing device 50 is mounted on the interface unit 20. The interface unit 20 includes a plurality of terminals for electrical connection with the post-processing device 50.

[0028] Each part of the image forming apparatus 10 is connected to a power supply, and each part of the image forming apparatus 10 operates when power is supplied from this power supply.

[0029] [Configuration of the post-processing device 50] Figure 3 is an enlarged view of a part of the post-processing device 50. Referring to Figure 3, the post-processing device 50 includes a housing in which an inlet 51A is formed on the first side facing the image forming apparatus 10, and an outlet 51B is formed on the second side opposite to the first side. Inside the housing, the post-processing device 50 is equipped with a processing tray 52, a stapling section 53, a transport path T2, a siding path 54, a first transport roller 55A, a second transport roller 55B, a first detection unit 56, a second detection unit 57, a siding roller 58, a discharge roller 59, and a discharge tray 60.

[0030] The processing tray 52 is angled such that one end on the staple section 53 side is lower than the other end on the opposite side. A bent portion is formed at one end of the processing tray 52, which bends upward. Multiple recording papers P discharged into the processing tray 52 are aligned by one end of each recording paper P coming into contact with the bent portion.

[0031] The stapling unit 53 performs a stapling process as a post-processing step, binding the bundle S of recording paper P placed on the processing tray 52 with staples. Note that the stapling unit 53 is an example of a post-processing step as described in the claims.

[0032] The transport path T2 is formed to extend from the entrance 51A toward the processing tray 52. ​​The siding path 54 is provided at a different location from the transport path 52 (in this case, below the transport path T2) and is formed to extend toward the second transport roller 55B.

[0033] The first transport roller 55A forms a nip with the driven roller. Driven by the motor of the drive unit 62, the first transport roller 55A rotates clockwise (hereinafter referred to as "forward rotation"), thereby transporting the recording paper P conveyed from the image forming apparatus 10 through the input port 51A along the transport path T2 at a predetermined transport speed. The clockwise direction is an example of the first and fourth directions in the claims.

[0034] The second transport roller 55B forms a nip with the driven roller. The second transport roller 55B rotates in the forward direction when driven by the motor of the drive unit 62, thereby transporting the recording paper P conveyed by the first transport roller 55A toward the processing tray 52. ​​The second transport roller 55B also rotates in the counterclockwise direction (hereinafter referred to as "reverse rotation") when driven by the motor of the drive unit 62, thereby switching back the recording paper P conveyed by the first transport roller 55A and moving it to the siding path 54. Note that the counterclockwise direction is an example of the second and third directions in the claims.

[0035] The first detection unit 56 is located near the transport path T2. The first detection unit 56 detects the presence or absence of recording paper P at predetermined positions on the transport path T2. The second detection unit 57 is located near the siding path 54. The second detection unit 57 detects the presence or absence of recording paper P at predetermined positions on the siding path 54.

[0036] The first detection unit 56 and the second detection unit 57 are not particularly limited, but reflective photosensors or transmissive photosensors can be used. The first detection unit 56 and the second detection unit 57 output an ON signal when they detect the recording paper P, and an OFF signal when they do not detect the recording paper P.

[0037] The retraction roller 58 is positioned to be able to contact the recording paper P on the retraction path 54. The retraction roller 58 rotates in the forward direction when driven by the motor of the drive unit 62, moving the recording paper P on the retraction path 54 in the direction from the second transport roller 55B toward the second detection unit 57 (hereinafter referred to as the "retraction direction"). The retraction roller 58 rotates in the reverse direction when driven by the motor of the drive unit 62, feeding the recording paper P on the retraction path 54 toward the second transport roller 55B.

[0038] In this embodiment, a first stop position is predetermined on the siding path 54 for the leading edge of the A4-sized recording paper P in the siding direction, and a second stop position is predetermined for the trailing edge in the siding direction. The second detection unit 57 is provided at a position corresponding to the first stop position.

[0039] The discharge roller 59 is located above the processing tray 52. ​​The discharge roller 59 is configured to be able to move up and down by a lifting device. The discharge tray 60 is located below the discharge port 51B on the second side of the housing. The discharge roller 59, while in contact with the bundle S of recording paper P on the processing tray 52, rotates forward by the drive of the motor of the drive unit 62, thereby discharging the bundle S of recording paper P to the discharge tray 60 through the discharge port 51B.

[0040] As shown in Figure 2, the post-processing device 50 further comprises a control unit 61, a drive unit 62, a storage unit 63, and an interface unit 64. The control unit 61 includes a processor, RAM, and ROM, etc. The processor is, for example, a CPU, MPU, or ASIC. The control unit 61 is electrically connected to the drive unit 62, the storage unit 63, the interface unit 64, the stapling unit 53, the first detection unit 56, and the second detection unit 57.

[0041] The control unit 61 functions as a control unit 65 by executing a control program stored in the ROM or storage unit 63 by the processor. The control unit 65 may also be composed of logic circuits, independent of the operation based on the control program. The control unit 65 controls the operation of each part of the post-processing unit 50.

[0042] The drive unit 62 includes a plurality of motors connected to each of the first conveyor roller 55A, the second conveyor roller 55B, the retraction roller 58, and the discharge roller 59. The drive unit 62 rotates each of the first conveyor roller 55A, the second conveyor roller 55B, the retraction roller 58, and the discharge roller 59 by driving each of the motors.

[0043] The storage unit 63 is a large-capacity storage device such as an SSD (Solid State Drive) or an HDD (Hard Disk Drive). The storage unit 63 stores various data along with various control programs for realizing the general operation of the post-processing device 50. As one of the various control programs, the storage unit 63 stores a first program for executing the first recording paper saving process according to the first embodiment.

[0044] The control unit 65 operates according to the first program, and when the rear end of the preceding recording paper P1 passes through the transport path T2, it reverses the second transport roller 55B to move the preceding recording paper P1 to the siding path 54, rotates the siding roller 58 forward to move the preceding recording paper P1 on the siding path 54 in the siding direction X2, obtains the length of the preceding recording paper P1 in the transport direction X1 using the passage time of the preceding recording paper P1 and the transport speed of the preceding recording paper P1, which are determined based on the detection result of the first detection unit 56, and starts driving the siding roller 58 at a predetermined reference start timing based on the detection result of the first detection unit 56. In the process, the timing at which the stopping of the rotation of the receptacle roller 58 aligns with the leading edge of the preceding recording paper P2, which is being transported by the forward rotation of the second transport roller 55B, is determined based on the length of the transport direction X1 of the preceding recording paper P1. The forward rotation of the receptacle roller 58 is stopped according to the determined stopping timing, the second transport roller 55B is started to rotate forward, and the receptacle roller 58 is rotated in reverse according to the reference start timing, thereby executing the first recording paper receptacle process in which the following recording paper P2 and the preceding recording paper P1 on the receptacle path 54 are stacked and transported to the processing tray 52 by the second transport roller 55B.

[0045] The image forming apparatus 10 is connected to the interface unit 64. The interface unit 64 includes a plurality of terminals for electrical connection with the image forming apparatus 10.

[0046] Each part of the post-processing device 50 is connected to a power supply, and each part of the post-processing device 50 operates when power is supplied from this power supply.

[0047] [Operation] Figures 4A and 4B are flowcharts showing the first recording paper retraction process. Figure 5A shows the transport status of the preceding recording paper P1. Figures 5B and 5C show the retraction status of the preceding recording paper P1. Figures 5D and 5E show the transport status of the preceding recording paper P1 and the following recording paper P2.

[0048] The operation of the image forming system 100 during the execution of the first recording paper retraction process will be described below with reference to Figures 4A to 5E, etc. In this embodiment, the length of the transport direction X1 of the preceding recording paper P1 is assumed to be 210 mm or more.

[0049] [Operation of the image forming apparatus 10] The user places two original documents M on the document tray 1 of the document transport unit 2. The user then uses the touch panel on the operation unit 17 to input a first instruction to set the number of copies to "2" and a second instruction to perform stapling every two documents, and then presses the start key on the operation unit 17. When the control unit 21 of the image forming apparatus 10 detects that the start key has been pressed, it transmits a control signal indicating the second instruction to the post-processing device 50 via the interface unit 20.

[0050] The control unit 21 also instructs the image reading unit 11 to read the original documents M that are being transported one by one by the original document transport unit 2 and generate image data showing two pages of original document images. The control unit 21 also instructs the transport mechanism 15 to transport the four sheets of recording paper P sequentially along the transport path T1 toward the post-processing device 50, and instructs the image forming unit 12 to sequentially form the two pages of original document images shown by the generated image data on the four transported sheets of recording paper P, repeating the page order twice.

[0051] [Operation of the post-processing device 50] When the control unit 65 of the post-processing device 50 receives the above-mentioned control signal through the interface unit 64, it controls the drive unit 62 to rotate the first transport roller 55A and the second transport roller 55B in the forward direction. Here, it is assumed that two sheets of recording paper P, from the first to the second, have been sequentially transported from the image forming apparatus 10 through the loading port 51A. The two sheets of recording paper P are sequentially transported along the transport path T2 in the transport direction X1 by the forward rotation of the first transport roller 55A and the second transport roller 55B.

[0052] As the rear end of each of the two recording papers P passes the second transport roller 55B in the transport direction X1, gravity causes them to fall into the processing tray 52. ​​Each of the two recording papers P moves along the incline of the processing tray 52 and stops when one end contacts the bend of the processing tray 52. ​​When the control unit 65 discharges the number of recording papers P (in this case, two recording papers P) indicated by the second instruction into the processing tray 52, it instructs the stapling unit 53 to perform stapling on the bundle S of the two recording papers P placed on the processing tray 52, and also starts the execution of the first recording paper holding process shown in Figures 4A and 4B.

[0053] In the first recording paper retraction process, the control unit 65 first controls the drive unit 62 to rotate the first transport roller 55A and the second transport roller 55B in the forward direction (step S10). As a result, as shown in Figure 5A, the control unit 65 transports the third preceding recording paper P1, which is transported from the image forming apparatus 10 via the input 51A, along the transport path T2 at a predetermined transport speed in the transport direction X1.

[0054] After the processing in step S10, the control unit 65 repeatedly determines that it has not detected the preceding recording paper P1 (NO in step S11) until the preceding recording paper P1 is detected by the first detection unit 56. When the first detection unit 56 outputs an ON signal and an OFF signal to the control unit 65 as the preceding recording paper P1 passes, the control unit 65 determines that it has detected the preceding recording paper P1 (YES in step S11), and uses the passage time of the preceding recording paper P1, which is determined based on the detection result of the first detection unit 56, and the transport speed of the preceding recording paper P1 to obtain the length of the transport direction X1 of the preceding recording paper P1 (step S12).

[0055] In this case, the control unit 65 obtains the length of the transport direction X1 of the preceding recording paper P1 by multiplying the time from the input of the ON signal to the input of the OFF signal by the transport speed of the preceding recording paper P1. After the processing in step S12, as shown in Figure 5B, the control unit 65 controls the drive unit 62 to reverse the rotation of the second transport roller 55B just before the trailing end of the preceding recording paper P1 in the transport direction X1 passes through the transport path T2 and then through the second transport roller 55B (step S13). As a result, the control unit 65 moves the preceding recording paper P1 to the siding path 54.

[0056] After the processing in step S13, the control unit 65 controls the drive unit 62 to rotate the retractor roller 58 in the forward direction as shown in Figure 5C (step S14). As a result, the control unit 65 moves the preceding recording paper P1 on the retractor path 54 in the retraction direction X2. After the processing in step S14, the control unit 65 determines the timing at which the forward rotation of the retractor roller 58 stops so that the leading edge of the following recording paper P2, which is transported by the forward rotation of the second transport roller 55B, and the leading edge of the preceding recording paper P1 are aligned, based on the length of the transport direction X1 of the preceding recording paper P1, assuming that the retractor roller 58 was started to be driven at the reference start timing (step S15).

[0057] Here, the control unit 65 is assumed to have pre-set the detection point of the leading edge of the preceding recording paper P1 in the retraction direction X2 by the second detection unit 57 as a reference stop timing assuming an A4 size recording paper P. Specifically in step S15, the control unit 65 first determines whether the length of the transport direction X1 of the preceding recording paper P1 exceeds a predetermined reference length (in this case, "210 mm"). If the control unit 65 determines that the length of the transport direction X1 of the preceding recording paper P1 is the same as the predetermined reference length (i.e., the preceding recording paper P1 is A4 size), it sets the stop timing of the retraction roller 58 to the reference stop timing.

[0058] On the other hand, if the control unit 65 determines that the length of the transport direction X1 of the preceding recording paper P1 exceeds the reference length, it calculates the difference between the length of the transport direction X1 of the preceding recording paper P1 and the reference length. The control unit 65 determines the stopping timing of the retraction roller 58 to be the time obtained by dividing the above difference by the moving speed of the preceding recording paper P1 on the retraction path 54 from the reference stopping timing.

[0059] After the processing in step S15, the control unit 65 repeatedly determines that it has not detected the leading edge of the retraction direction X2 of the preceding recording paper P1 until the second detection unit 57 detects the leading edge of the retraction direction X2 (NO in step S16). When the leading edge of the retraction direction X2 of the preceding recording paper P1 passes, the second detection unit 57 outputs an ON signal to the control unit 65, and the control unit 65 determines that it has detected the leading edge of the retraction direction X2 (YES in step S16), and controls the drive unit 62 to stop the forward rotation of the retraction roller 58 according to the determined stopping timing (step S17).

[0060] As a result, the preceding recording paper P1 is placed on the siding path 54 with its rear end in the siding direction X2 coinciding with a predetermined second stop position. After the processing in step S17, the control unit 65 controls the drive unit 62 to rotate the first transport roller 55A and the second transport roller 55B in the forward direction (step S18). As a result, the control unit 65 transports the fourth subsequent recording paper P2, which is transported from the image forming apparatus 10 via the input 51A, along the transport path T2 in the transport direction X1, as shown in Figure 5D.

[0061] At this point, since the stapling process is already complete, the control unit 65 controls the lifting device to lower the discharge roller 59 to contact the bundle S of recording paper P on the processing tray 52, and controls the drive unit 62 to rotate the discharge roller 59 in the forward direction. As a result, the control unit 65 discharges the bundle S of recording paper P on the processing tray 52 to the discharge tray 60 via the discharge port 51B.

[0062] After the processing in step S18, the control unit 65 repeatedly determines that it has not detected the subsequent recording paper P2 (NO in step S19) until the first detection unit 56 detects the subsequent recording paper P2. When the first detection unit 56 outputs an ON signal and an OFF signal to the control unit 65 as the subsequent recording paper P2 passes, the control unit 65 determines that it has detected the subsequent recording paper P2 (YES in step S19) and controls the drive unit 62 to reverse the rotation of the retraction roller 58 according to a predetermined reference start timing (step S20).

[0063] Here, the control unit 65 has pre-set a predetermined time (in this case, 0.5 seconds) after the input of the OFF signal by the first detection unit 56 when the subsequent recording paper P2 passes, as the reference start timing, assuming an A4 size recording paper P.

[0064] As a result of the process in step S20, the control unit 65 moves the leading recording paper P1 on the siding 54 in the direction X3 toward the second transport roller 55B, as shown in Figure 5E. When the leading recording paper P1 reaches the second transport roller 55B, the leading recording paper P1 and the following recording paper P2 are transported to the processing tray 52 by the second transport roller 55B with their leading edge positions in the respective transport direction X1 coinciding and overlapping.

[0065] According to the first embodiment, the control unit 65 obtains the length of the transport direction X1 of the preceding recording paper P1 using the passage time of the preceding recording paper P1 and the transport speed of the preceding recording paper P1, which are determined based on the detection result of the first detection unit 56, and determines the timing at which the rotation of the retraction roller 58 stops when the leading edge of the following recording paper P2, which is transported by the forward rotation of the second transport roller 55B, aligns with the leading edge of the preceding recording paper P1, when the retraction roller 58 is started to be driven at the reference start timing, based on the length of the transport direction X1 of the preceding recording paper P1.

[0066] Therefore, the leading edge position of the leading edge

[0067] Furthermore, according to the first embodiment, if the length of the transport direction X1 of the preceding recording paper P1 is the same as a predetermined reference length, the control unit 65 determines the stopping timing of the retraction roller 58 to a predetermined reference stopping timing based on the detection result of the second detection unit 57. If the length of the transport direction X1 of the preceding recording paper P1 exceeds the reference length, the control unit 65 calculates the difference between the length of the transport direction X1 of the preceding recording paper P1 and the reference length, and determines the stopping timing of the retraction roller 58 to be a time elapsed from the reference stopping timing by the time obtained by dividing the above difference by the moving speed of the preceding recording paper P1 on the retraction path 54.

[0068] In this way, the stopping timing of the retractable roller 58 is determined using the reference stopping timing corresponding to the reference length and the movement speed of the preceding recording paper P1, so the stopping timing can be determined easily and accurately.

[0069] (Second Embodiment) The image forming system 100 according to the second embodiment of the present invention has the same configuration as the image forming system 100 according to the first embodiment, except that the storage unit 63 of the post-processing device 50 stores a second program for executing a second recording paper saving process in place of the first program. The same configuration and operation as the image forming system 100 according to the first embodiment will not be described again below.

[0070] In the second embodiment, the control unit 65 of the post-processing device 50 operates according to the second program, so that when the rear end of the preceding recording paper P1 passes through the transport path T2, it reverses the rotation of the second transport roller 55B to move the preceding recording paper P1 to the escape path 54, rotates the escape roller 58 forward to move the preceding recording paper P1 on the escape path 54 in the escape direction X2, stops the forward rotation of the escape roller 58 according to a predetermined reference stop timing based on the detection result of the second detection unit 57, and uses the passage time of the preceding recording paper P1 and the transport speed of the preceding recording paper P1, which are determined based on the detection result of the first detection unit 56, to process the preceding recording paper P The length of the transport direction X1 is obtained, and the start timing of the rotation of the receptacle roller 58 when the receptacle roller 58 is stopped at a reference stop timing is determined based on the length of the transport direction X1 of the preceding record paper P1, so that the leading edge of the following record paper P2 transported by the forward rotation of the second transport roller 55B aligns with the leading edge of the preceding record paper P1. The second transport roller 55B is then rotated forward, and the receptacle roller 58 is rotated in the reverse direction according to the determined start timing, thereby executing a second record paper receptacle process in which the following record paper P2 and the preceding record paper P1 on the receptacle path 54 are stacked and transported to the processing tray 52 by the second transport roller 55B.

[0071] [Operation of the post-processing device 50] Figures 6A and 6B are flowcharts showing the second recording paper retraction process. The operation of the image forming system 100 during the execution of the second recording paper retraction process will be described below with reference to Figures 6A and 6B, etc. In this embodiment, the length of the transport direction X1 of the preceding recording paper P1 is assumed to be 210 mm or more.

[0072] [Operation of the post-processing device 50] The control unit 65 of the post-processing device 50, in the same manner as described above, starts the execution of the second recording paper retraction process shown in Figures 6A and 6B when it instructs the stapling unit 53 to perform stapling on the bundle S of recording paper P placed on the processing tray 52.

[0073] In the second recording paper retraction process, the control unit 65 executes the processes of steps S30 to S34 in the same manner as the processes of steps S10 to S14 in the first recording paper retraction process. After the process of step S34, the control unit 65 repeats the process of determining that the leading edge of the retraction direction X2 of the preceding recording paper P1 has not been detected (NO in step S35) until the second detection unit 57 detects the leading edge of the retraction direction X2 of the preceding recording paper P1.

[0074] As the leading edge of the preceding recording paper P1 in the retraction direction X2 passes, the second detection unit 57 outputs an ON signal to the control unit 65. The control unit 65 determines that the leading edge of the retraction direction X2 has been detected (YES in step S35), and controls the drive unit 62 to stop the forward rotation of the retraction roller 58 according to the reference stop timing (step S36). Here, the control unit 65 assumes that the detection point of the leading edge of the preceding recording paper P1 in the retraction direction X2 by the second detection unit 57 is set in advance as a reference stop timing assuming an A4 size recording paper P. As a result, the preceding recording paper P1 is placed on the retraction path 54 with the leading edge of the retraction direction X2 coinciding with a predetermined first stop position.

[0075] After the processing in step S36, the control unit 65 determines the start timing of the reverse rotation of the retractor roller 58, based on the length of the transport direction X1 of the preceding record paper P1, when the retractor roller 58 is stopped at the reference stop timing, so that the leading edge of the following record paper P2 transported by the forward rotation of the second transport roller 55B aligns with the leading edge of the preceding record paper P1 (step S37). Here, the control unit 65 has set a predetermined time (in this case, 0.5 seconds) elapsed from the time the OFF signal is input by the first detection unit 56 as the following record paper P2 passes, as the reference start timing assuming an A4 size record paper P.

[0076] In step S37, specifically, the control unit 65 first determines whether the length of the transport direction X1 of the preceding recording paper P1 exceeds a predetermined standard length (in this case, "210 mm"). If the control unit 65 determines that the length of the transport direction X1 of the preceding recording paper P1 is the same as the standard length (i.e., the preceding recording paper P1 is A4 size), it sets the start timing of the retractable roller 58 to the standard start timing.

[0077] On the other hand, if the control unit 65 determines that the length of the transport direction X1 of the preceding recording paper P1 exceeds the reference length, it calculates the difference between the length of the transport direction X1 of the preceding recording paper P1 and the reference length. The control unit 65 determines the start timing of the retraction roller 58 to be a time elapsed from the reference start timing by the time obtained by dividing the above difference by the moving speed of the preceding recording paper P1 on the retraction path 54.

[0078] After the processing in step S37, the control unit 65 controls the drive unit 62 to rotate the first transport roller 55A and the second transport roller 55B in the forward direction (step S38). As a result, the control unit 65 causes the fourth subsequent recording paper P2, which is transported from the image forming apparatus 10 through the input port 51A, to be transported along the transport path T2 in the transport direction X1, as shown in Figure 5D.

[0079] At this point, since the stapling process is already complete, the control unit 65 controls the lifting device to lower the discharge roller 59 to contact the bundle S of recording paper P on the processing tray 52, and controls the drive unit 62 to rotate the discharge roller 59 in the forward direction. As a result, the control unit 65 discharges the bundle S of recording paper P on the processing tray 52 to the discharge tray 60 via the discharge port 51B.

[0080] After the processing in step S38, the control unit 65 repeatedly determines that it has not detected the following recording paper P2 (NO in step S39) until the first detection unit 56 detects the following recording paper P2. When the first detection unit 56 outputs an ON signal and an OFF signal to the control unit 65 as the following recording paper P2 passes, the control unit 65 determines that it has detected the following recording paper P2 (YES in step S39) and controls the drive unit 62 to rotate the retraction roller 58 in reverse according to the determined start timing (step S40).

[0081] As a result of the process in step S40, the control unit 65 moves the leading recording paper P1 on the siding 54 in a direction X3 toward the second transport roller 55B, as shown in Figure 5E. When the leading recording paper P1 reaches the second transport roller 55B, the leading recording paper P1 and the following recording paper P2 are transported to the processing tray 52 by the second transport roller 55B with their leading edge positions in the transport direction X1 aligned and overlapping.

[0082] According to the second embodiment, the control unit 65 obtains the length of the transport direction X1 of the preceding recording paper P1 using the passage time of the preceding recording paper P1 and the transport speed of the preceding recording paper P1, which are determined based on the detection result of the first detection unit 56, and determines the start timing of rotation of the retraction roller 58 so that the leading edge of the following recording paper P2, which is transported by the forward rotation of the second transport roller 55B, and the leading edge of the preceding recording paper P1 are aligned when the retraction roller 58 is driven and stopped at the reference stop timing, based on the length of the transport direction X1 of the preceding recording paper P1.

[0083] Therefore, the leading edge position of the leading edge position of the leading edge position of the leading edge position of the following leading edge position of the

[0084] Furthermore, according to the second embodiment, if the length of the transport direction X1 of the preceding recording paper P1 is the same as a predetermined reference length, the control unit 65 determines the start timing of the retractable roller 58 to a predetermined reference start timing based on the detection result of the first detection unit 56. If the length of the transport direction X1 exceeds the reference length, the control unit 65 calculates the difference between the length of the transport direction X1 and the reference length, and determines the start timing of the retractable roller 58 to be a time elapsed from the reference start timing by the time obtained by dividing the above difference by the moving speed of the preceding recording paper P1 on the retractable path 54.

[0085] In this way, the start timing of the retractable roller 58 is determined using the reference start timing corresponding to the reference length and the movement speed of the preceding recording paper P1, so the start timing can be determined easily and accurately.

[0086] (Other variations) In the above embodiment, the post-processing device 50 was equipped with a stapling unit 53 as a post-processing unit, but the present invention is not limited to such an embodiment. For example, the post-processing device 50 may be equipped with a paper folding unit that performs a folding process on the recording paper P on the processing tray 52, or a punching unit that performs a hole punching process on the recording paper P on the processing tray 52, as a post-processing unit.

[0087] Furthermore, in the above embodiment, the control unit 65 started executing the first recording paper retraction process or the second recording paper retraction process while the stapling unit 53 was performing the stapling process, but the present invention is not limited to such an embodiment. For example, the control unit 65 may start executing the first recording paper retraction process or the second recording paper retraction process when the stapling process is completed.

[0088] Furthermore, in the above embodiment, the control unit 65 moved only one sheet of recording paper P to the siding 54, but the present invention is not limited to such an embodiment. For example, the control unit 65 may move two sheets of recording paper P to the siding 54. In this case, the control unit 65 may determine the stopping or starting timing of the rotation of the siding roller 58 for the second sheet of recording paper P based on the length of the transport direction X1 of the second sheet of recording paper P, or it may determine the stopping or starting timing based on the longer of the lengths of the transport directions X1 of the first and second sheets of recording paper P.

[0089] Furthermore, in the above embodiment, the image forming unit 12 etc. formed an image on recording paper P, but the present invention is not limited to such an embodiment. The image forming unit 12 etc. may record images on other recording media, not just recording paper P. Examples of other recording media include OHP (Overhead Projector) sheets.

[0090] It should be noted that the present invention is not limited to the configuration of the above embodiment and various modifications are possible. For example, in the above embodiment, a color multifunction printer is used as the image forming apparatus 10, but this is merely one example, and other image forming apparatuses such as a monochrome multifunction printer, a copier, or a facsimile machine may be used. Furthermore, the image forming apparatus 10 is not limited to an inkjet recording device; a laser image forming apparatus may also be used.

[0091] Furthermore, the configuration and processing of the above embodiment shown using Figures 1 to 6B are merely one embodiment of the present invention, and the present invention is not intended to be limited to such configuration and processing. [Explanation of Symbols]

[0092] 100 Post-processing systems 10 Image forming apparatus 12 Image forming unit 50 Post-processing equipment 52 processing trays 53 Staple section 54 Escape Route 55B Second conveyor roller 56 First detection unit 57 Second detection unit 58 Retreat Roller 65 Control Unit T2 transport path

Claims

1. Processing tray and A post-processing unit that performs post-processing on the recording medium placed on the processing tray, A transport path extending toward the processing tray, A first detection unit that detects the presence or absence of the recording medium at a predetermined position on the transport path, A first conveyor roller rotates in a predetermined first direction to convey the recording medium along the conveyor path at a predetermined conveying speed, A second transport roller rotates in the first direction to transport the recording medium that has been transported by the first transport roller toward the processing tray, A refuge path is provided at a different location from the aforementioned transport path and extends toward the second transport roller, A second detection unit that detects the presence or absence of the recording medium at a predetermined position on the aforementioned refuge path, A retraction roller that rotates in a predetermined second direction to send the recording medium on the retraction path toward the second transport roller, The system comprises a control unit that controls the operation of the first transport roller, the second transport roller, and the retractable roller, The control unit, The first transport roller and the second transport roller are rotated in the first direction to transport the preceding recording medium along the transport path. When the first detection unit detects the preceding recording medium, it obtains the length of the preceding recording medium in the transport direction using the passage time of the preceding recording medium determined based on the detection result of the first detection unit and the transport speed of the preceding recording medium. When the rear end of the preceding recording medium passes through the transport path, the second transport roller is rotated in a third direction opposite to the first direction to move the preceding recording medium into the retraction path. The retraction roller is rotated in a fourth direction opposite to the second direction, thereby moving the preceding recording medium on the retraction path in the retraction direction. When the retractor roller is started to drive at a predetermined reference start timing based on the detection result of the first detection unit, the timing at which the rotation of the retractor roller stops aligning the leading edge of the preceding recording medium with the leading edge of the preceding recording medium, which is being transported by the rotation of the second transport roller in the first direction, is determined based on the length of the transport direction of the preceding recording medium, and the rotation of the retractor roller in the fourth direction is stopped according to the determined stop timing. The first transport roller and the second transport roller are rotated in the first direction to transport the subsequent recording medium along the transport path. A post-processing device comprising: when the first detection unit detects the subsequent recording medium, the retraction roller rotates in the second direction according to the reference start timing, thereby stacking the subsequent recording medium and the preceding recording medium on the retraction path and transporting them to the processing tray by the second transport roller.

2. The control unit, If the length of the preceding recording medium in the transport direction is the same as a predetermined reference length, the stop timing is determined to a predetermined reference stop timing based on the detection result of the second detection unit. The post-processing device according to claim 1, wherein if the length in the transport direction exceeds the reference length, the difference between the length in the transport direction and the reference length is calculated, and the stop timing is determined to be a time elapsed from the reference stop timing by a time obtained by dividing the difference by the moving speed of the preceding recording medium on the siding path.

3. Processing tray and A post-processing unit that performs post-processing on the recording medium placed on the processing tray, A transport path extending toward the processing tray, A first detection unit that detects the presence or absence of the recording medium at a predetermined position on the transport path, A first conveyor roller rotates in a predetermined first direction to convey the recording medium along the conveyor path at a predetermined conveying speed, A second transport roller rotates in the first direction to transport the recording medium that has been transported by the first transport roller toward the processing tray, A refuge path is provided at a different location from the aforementioned transport path and extends toward the second transport roller, A second detection unit that detects the presence or absence of the recording medium at a predetermined position on the aforementioned refuge path, A retraction roller that rotates in a predetermined second direction to send the recording medium on the retraction path toward the second transport roller, The system comprises a control unit that controls the operation of the first transport roller, the second transport roller, and the retractable roller, The control unit, The first transport roller and the second transport roller are rotated in the first direction to transport the preceding recording medium along the transport path. When the first detection unit detects the preceding recording medium, it obtains the length of the preceding recording medium in the transport direction using the passage time of the preceding recording medium determined based on the detection result of the first detection unit and the transport speed of the preceding recording medium. When the rear end of the preceding recording medium passes through the transport path, the second transport roller is rotated in a third direction opposite to the first direction to move the preceding recording medium into the retraction path. The retraction roller is rotated in a fourth direction opposite to the second direction, thereby moving the preceding recording medium on the retraction path in the retraction direction. Based on the detection result of the second detection unit, the rotation of the retractable roller in the fourth direction is stopped according to a predetermined reference stop timing. When the retraction roller is stopped at the reference stop timing, the start timing of the rotation of the retraction roller at which the leading edge of the preceding recording medium and the leading edge of the preceding recording medium are aligned with the leading edge of the preceding recording medium, which is being transported by the rotation of the second transport roller in the first direction, is determined based on the length of the preceding recording medium in the transport direction. The first transport roller and the second transport roller are rotated in the first direction to transport the subsequent recording medium along the transport path. A post-processing device in which, when the first detection unit detects the subsequent recording medium, the retraction roller is rotated in the second direction according to the determined start timing, and the subsequent recording medium and the preceding recording medium on the retraction path are stacked together and transported to the processing tray by the second transport roller.

4. The control unit, If the length of the preceding recording medium in the transport direction is the same as a predetermined reference length, the start timing is determined to a predetermined reference start timing based on the detection result of the first detection unit. The post-processing device according to claim 3, wherein if the length in the transport direction exceeds the reference length, the difference between the length in the transport direction and the reference length is calculated, and the start timing is determined to be a time elapsed from the reference start timing by a time obtained by dividing the difference by the moving speed of the preceding recording medium on the siding path.

5. A post-processing device according to any one of claims 1 to 4, An image forming system including an image forming apparatus having an image forming unit for forming an image on the recording medium.

Images