Patent Publication Number: US-2023150789-A1

Title: Sheet processing apparatus and image forming system

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a sheet processing apparatus for processing sheets and an image forming system equipped with the same. 
     Description of the Related Art 
     Sheet processing apparatuses for performing processes such as binding processes or sorting processes to sheets having images formed thereon in an image forming apparatus body are adopted as optional devices for image forming apparatuses such as electrophotographic multifunction apparatuses. 
     Hitherto, a sheet postprocessing apparatus configured to move a punching portion corresponding to sheet size by detecting a side edge portion of the sheet using a lateral registration detection sensor has been proposed (refer to Japanese Patent Application Laid-Open Publication No. H10-279170). Further, a sheet processing apparatus capable of detecting a side edge of a sheet using a line sensor and moving a punching unit in a width direction according to a detection result of the line sensor has been proposed (refer to Japanese Patent Application Laid-Open Publication No. 2021-62440). 
     The lateral registration detection sensor disclosed in Japanese Patent Application Laid-Open Publication No. H10-279170 and the line sensor disclosed in Japanese Patent Application Laid-Open Publication No. 2021-62440 are both an optical sensor that receives light by a light receiving portion. When paper dust discharged from conveyed sheets deposits on the optical sensor, the optical sensor may not be able to detect the side edge portion of the sheet correctly. Therefore, positional accuracy of the punching portion or the punching unit that moves in the width direction according to the detection result of the optical sensor may be deteriorated, and the positional accuracy of the holes punched on the sheets may also be deteriorated. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, a sheet processing apparatus includes a conveyance unit configured to convey a sheet in a sheet conveyance direction, a punching unit configured to punch a hole to the sheet being conveyed by the conveyance unit, a moving unit configured to move the punching unit in an intersecting direction intersecting the sheet conveyance direction, a detection unit arranged upstream of the punching unit in the sheet conveyance direction and configured to change an output value based on a position of an edge portion, in the intersecting direction, of the sheet being conveyed, a cleaning portion configured to clean the detection unit, and an interlocking portion configured to move the cleaning portion so as to clean the detection unit by interlocking with a movement of the punching unit in the intersecting direction. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an entire schematic view illustrating an image forming system according to a first embodiment. 
         FIG.  2 A  is a schematic diagram illustrating a punch positioned at a punching start position. 
         FIG.  2 B  is a schematic diagram illustrating a punch positioned at a punching completion position. 
         FIG.  2 C  is a schematic diagram illustrating a punch positioned at a separation position. 
         FIG.  3    is a block diagram illustrating a functional block of a postprocessing apparatus. 
         FIG.  4    is a block diagram illustrating a hardware configuration of the postprocessing apparatus. 
         FIG.  5 A  is a plan view illustrating a state in which a leading edge of a sheet has reached an inlet sensor. 
         FIG.  5 B  is a plan view illustrating a state in which a target position of a hole has reached a line sensor. 
         FIG.  5 C  is a plan view illustrating a state in which a sheet has been moved in a width direction. 
         FIG.  5 D  is a plan view illustrating a state in which a hole has been punched to the sheet. 
         FIG.  6 A  is a plan view illustrating a state in which a target position of a second hole has reached the line sensor. 
         FIG.  6 B  is a plan view illustrating a state in which the sheet has been moved in the width direction. 
         FIG.  6 C  is a plan view illustrating a state in which the sheet has been punched. 
         FIG.  6 D  is a plan view illustrating a state in which a trailing edge of the sheet has passed the line sensor. 
         FIG.  7 A  is a plan view illustrating a cleaning unit. 
         FIG.  7 B  is a plan view illustrating a state in which a punch base has been abutted against an arm. 
         FIG.  7 C  is a plan view illustrating a state in which a nonwoven fabric has moved to a cleaning completion position. 
         FIG.  8    is a flowchart illustrating a cleaning control. 
         FIG.  9 A  is a plan view illustrating a cleaning unit according to a second embodiment. 
         FIG.  9 B  is a plan view illustrating a state in which a punch base has been abutted against an arm. 
         FIG.  9 C  is a plan view illustrating a state in which a nonwoven fabric has moved to a cleaning completion position. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Explanatory embodiments for carrying out the present invention will be described below with reference to the drawings. 
     First Embodiment 
     Entire Configuration 
     An image forming system  1 S according to a first embodiment is composed of an image forming apparatus  1 , an image reading apparatus  2 , a document feeding apparatus  3 , and a postprocessing apparatus  4 . The image forming system  1 S forms an image on a sheet serving as a recording material, and subjects the sheet to processing in the postprocessing apparatus  4  according to need before outputting the same. Hereafter, the operations of respective apparatuses are described briefly, and thereafter, the postprocessing apparatus  4  will be described in detail. 
     The document feeding apparatus  3  conveys a document placed on a document tray  18  to image reading units  16  and  19 . The image reading units  16  and  19  are each an image sensor that reads image information from a document surface, and both sides of a document are read in a single document conveyance. The document having its image information read is discharged to a document discharge portion  20 . Further, by moving the image reading unit  16  in reciprocating motion by a driving device  17 , the image reading apparatus  2  can read an image information from a still document set on a platen glass, including a document such as a booklet document that cannot be conveyed by the document feeding apparatus  3 . 
     The image forming apparatus  1  is an electrophotographic apparatus equipped with a direct transfer-type image forming unit  1 B. The image forming unit  1 B includes a cartridge  8  equipped with a photosensitive drum  9 , and a laser scanner unit  15  arranged above the cartridge  8 . When performing an image forming operation, a surface of the photosensitive drum  9  in rotation is charged, and an electrostatic latent image is formed on the drum surface by the laser scanner unit  15  exposing the photosensitive drum  9  based on the image information. The electrostatic latent image borne on the photosensitive drum  9  is developed into a toner image by charged toner particles, and the toner image is conveyed to a transfer portion where the photosensitive drum  9  and a transfer roller  10  oppose one another. A control unit of the image forming apparatus  1  executes the image forming operation by the image forming unit  1 B based on the image information read by the image reading units  16  and  19  or the image information received from an external computer via a network. 
     The image forming apparatus  1  includes a plurality of sheet feeding apparatuses  6  that feed sheets serving as recording materials one at a time. The sheet fed from the sheet feeding apparatus  6  is subjected to skew correction at a registration roller  7 , and then transferred to the transfer portion where the toner image borne on the photosensitive drum  9  is transferred to the sheet. A fixing unit  11  is arranged downstream of the transfer portion in a sheet conveyance direction. The fixing unit  11  includes a rotary member pair that nips and conveys the sheet, and a heating element such as a halogen lamp that heats the toner image, and the toner image on the sheet is heated and pressed to fix the image. 
     When discharging the sheet on which an image has been formed to the exterior of the image forming apparatus  1 , the sheet having passed through the fixing unit  11  is conveyed via a horizontal conveyance portion  14  to the postprocessing apparatus  4 . In the case of a sheet to which image forming to the first surface has been completed in duplex printing, the sheet having passed through the fixing unit  11  is transferred to a reverse roller  12 , subjected to switchback conveyance by the reverse roller  12 , and is conveyed again to the registration roller  7  via a reconveyance portion  13 . Then, the sheet passes through the transfer portion and the fixing unit  11  again where an image is formed on the second surface, before being conveyed to the postprocessing apparatus  4  via the horizontal conveyance portion  14 . 
     The image forming unit  1 B described above is one example of an image forming unit for forming an image on a sheet, and it is also possible to adopt an intermediate transfer-type electrophotographic unit in which a toner image formed on a photoreceptor is transferred to a sheet via an intermediate transfer body. Further, a printing unit adopting an inkjet system or an offset printing system can also be used as the image forming unit. 
     Postprocessing Apparatus 
     The postprocessing apparatus  4  serving as a sheet processing apparatus includes a punching process portion  4 A for subjecting sheets to a punching process, and a binding process portion  4 B for subjecting the sheets to a binding process, wherein the sheets received from the image forming apparatus  1  is subjected to the punching process and the binding process before the sheets are discharged as a sheet bundle. Further, the postprocessing apparatus  4  can simply discharge the sheets received from the image forming apparatus  1  without subjecting the sheets to the punching process or the binding process. 
     The postprocessing apparatus  4  is equipped with a reception path  81 , an inner sheet discharge path  82 , a first sheet discharge path  83 , and a second sheet discharge path  84  that serve as a conveyance path for conveying sheets, and is further provided with an upper sheet discharge tray  25  and a lower sheet discharge tray  37  serving as a sheet discharge destination to which the sheets are discharged. The reception path  81  serving as a first conveyance path is a conveyance path through which the sheet received from the image forming apparatus  1  is conveyed, and the inner sheet discharge path  82  serving as a second conveyance path is a conveyance path that extends downward from the reception path  81  to guide the sheet toward the binding process portion  4 B. The first sheet discharge path  83  is a conveyance path that discharges the sheet to the upper sheet discharge tray  25 , and the second sheet discharge path  84  serving as a third conveyance path is a conveyance path that extends along the sheet discharge direction and through which the sheet is guided to the lower sheet discharge tray  37 . 
     The sheet discharged from the horizontal conveyance portion  14  of the image forming apparatus  1  is received by an inlet roller  21  serving as a conveyance unit arranged on the reception path  81 , and conveyed through the reception path  81  toward a pre-reverse roller  22 . An inlet sensor  27  detects the sheet at a detection position between the inlet roller  21  and the pre-reverse roller  22 . The pre-reverse roller  22  conveys the sheet received from the inlet roller  21  toward the first sheet discharge path  83 . 
     At a predetermined timing after the inlet sensor  27  has detected the passing of a trailing edge of a sheet, the pre-reverse roller  22  is accelerated such that a conveyance speed of the sheet is raised to a speed faster than the conveyance speed at the horizontal conveyance portion  14 . It is also possible to set the conveyance speed of the sheet by the inlet roller  21  to be greater than the speed at the horizontal conveyance portion  14  and accelerate the conveyance speed at the inlet roller  21  arranged upstream of the pre-reverse roller  22 . In that case, it is preferable to install a one-way clutch between a conveyance roller of the horizontal conveyance portion  14  and a motor that drives the roller, such that the conveyance roller rotates idly when the sheet is pulled by the inlet roller  21 . 
     If a discharge destination of the sheet is the upper sheet discharge tray  25 , a reverse roller  24  discharges the sheet received from the pre-reverse roller  22  to the upper sheet discharge tray  25 . In that case, the reverse roller  24  is decelerated to a predetermined sheet discharge speed at a predetermined timing after the trailing edge of the sheet has passed the pre-reverse roller  22 . 
     If the discharge destination of the sheet is the lower sheet discharge tray  37 , the reverse roller  24  serving as a reverse portion performs a switchback conveyance of reversing the sheet received from the pre-reverse roller  22  and conveys the sheet to the inner sheet discharge path  82 . A check valve  23  is arranged at a branch portion where the reception path  81  and the inner sheet discharge path  82  are branched from the first sheet discharge path  83  upstream of the reverse roller  24  in the sheet discharge direction of the reverse roller  24 . The check valve  23  has a function to restrict the sheet having been switched back by the reverse roller  24  from being conveyed back to the reception path  81 . The pre-reverse roller  22  starts to rotate in the reverse direction at a timing at which the trailing edge of the sheet passes through the check valve  23 . 
     An inner sheet discharge roller  26 , an intermediate conveyance roller  28 , and a kick-out roller  29  serving as rotary member pairs arranged on the inner sheet discharge path  82  convey the sheets received from the reverse roller  24  sequentially toward the binding process portion  4 B. When performing buffering of sheets, the inner sheet discharge roller  26  stops temporarily while nipping a preceding sheet. Then, the inner sheet discharge roller  26  rotates in the reverse direction in synchronization with a succeeding sheet moving toward the reverse roller  24 , and buffers the sheets by superposing the preceding sheet to the succeeding sheet in a first sheet discharge path. Buffering of a plurality of sheets is made possible regardless of sheet lengths by repeating switchback of the inner sheet discharge roller  26 . 
     A pre-intermediate stacking sensor  38  detects the sheet between the intermediate conveyance roller  28  and the kick-out roller  29 . An optical sensor for detecting the presence or absence of a sheet at the detection position using light can be used as the inlet sensor  27  and the pre-intermediate stacking sensor  38 , and passing of the leading edge or the trailing edge of the sheet or the presence or absence of a jammed sheet can be detected thereby. 
     The binding process portion  4 B includes an intermediate lower guide  31 , a longitudinal alignment roller  32 , a longitudinal alignment reference plate  33 , a bundle discharge guide  34 , a guide driving unit  35 , and a stapler and a width alignment mechanism which are not shown, serving as a supporting portion on which the sheets are supported. The sheets sent from the inner sheet discharge path  82  are stacked on the intermediate lower guide  31  and abutted against the longitudinal alignment reference plate  33  by the longitudinal alignment roller  32 . Thereby, alignment of sheets in the sheet conveyance direction is performed. 
     Next, the sheets are aligned in a width direction orthogonal to the sheet conveyance direction by a width alignment mechanism not shown and bound by a stapler not shown. The sheet bundle bound by the stapler is pushed out by the bundle discharge guide  34  driven by the guide driving unit  35 , and transferred via the second sheet discharge path  84  to a bundle discharge roller  36 . Then, the sheet bundle is discharged to the exterior of the apparatus by the bundle discharge roller  36  serving as a discharge portion and stacked on the lower sheet discharge tray  37 . 
     The upper sheet discharge tray  25  and the lower sheet discharge tray  37  are both capable of moving up and down with respect to a casing of the postprocessing apparatus  4 . The postprocessing apparatus  4  is equipped with a sheet surface detection sensor for detecting an upper surface position of the sheet on the upper sheet discharge tray  25  and the lower sheet discharge tray  37 , and when either one of the sensors detects a sheet, the corresponding tray is lowered. If the sheet surface detection sensor detects that the sheet on the upper sheet discharge tray  25  or the lower sheet discharge tray  37  has been removed, the corresponding tray is lifted. Therefore, the upper sheet discharge tray  25  and the lower sheet discharge tray  37  are controlled to be lifted and lowered such that an upper surface of the stacked sheet is maintained at a fixed level. 
     Punching Process Portion 
     Next, the punching process portion  4 A will be described in detail. The punching process portion  4 A includes, as illustrated in  FIGS.  2 A to  2 C , the inlet roller  21  for conveying a sheet SH in a sheet conveyance direction D 1 , the inlet sensor  27 , a side edge detection unit  305 , a punching unit  62 , and a shift unit not shown. The side edge detection unit  305  includes a lighting unit  63  and a line sensor  61 , wherein the lighting unit  63  and the line sensor  61  are arranged to oppose one another with the reception path  81  (refer to  FIG.  1   ) interposed therebetween. The side edge detection unit  305  is arranged upstream of the punching unit  62  in the sheet conveyance direction D 1 . The inlet sensor  27  is arranged upstream of the side edge detection unit  305  in the sheet conveyance direction D 1 , and output signals are changed when a leading edge  506  (refer to  FIG.  5 A ) which is a downstream edge of the sheet in the sheet conveyance direction D 1  passes through. 
     The line sensor  61  serving as a detection unit extends in a width direction of the sheet SH orthogonal to the sheet conveyance direction D 1 , and output signals serving as output values are changed based on a position of an edge portion of the sheet SH in the width direction. More specifically, the line sensor  61  is composed of an optical sensor, and the output value thereof is changed based on a boundary position of density difference on the line sensor  61  that appears by the light irradiated from the lighting unit  63  being blocked by the sheet SH. Thereby, the side edge position which is the edge portion of the sheet SH in the width direction can be detected. 
     The punching unit  62  is a rotary punching unit including a punch  202  that rotates in an R 1  direction about a shaft center  201  serving as an axis, and a die  205  that rotates in an R 2  direction opposite to the R 1  direction about a shaft center  204 . Gears not shown having the same number of teeth are provided on the shaft centers  201  and  204 , and the gears are meshed with one another. More specifically, drive from a punch motor M 1  is entered to the gear provided on the shaft center  204  of the die  205 , and the gear is meshed with a gear provided on the shaft center  201  of the punch  202 . 
     Thereby, the punch  202  and the die  205  are rotated synchronously by the punch motor M 1  such that a blade edge  202   a  of the punch  202  and a hole portion  205   a  of the die  205  engage with each other. The punch motor M 1  is configured to provide drive such that a circumferential speed of the blade edge  202   a  of the punch  202  becomes the same as a speed of the sheet SH in the sheet conveyance direction D 1 , to enable punching to be performed while conveying the sheet SH. The punch motor M 1  is composed of a stepping motor, but it can also be composed of a motor adopting other driving methods, such as a DC brushless motor. 
       FIG.  2 A  is a schematic diagram illustrating a state in which the punch  202  is positioned at a punching start position.  FIG.  2 B  is a schematic diagram illustrating a state in which the punch  202  is positioned at a punching completion position.  FIG.  2 C  is a schematic diagram illustrating a state in which the punch  202  is positioned at a separation position. The punch  202  rotating in the R 1  direction starts to contact the sheet SH at the punching start position illustrated in  FIG.  2 A , and engages with the die  205  at the punching completion position illustrated in  FIG.  2 B . Then, the punch  202  separates from the sheet SH at the separation position illustrated in  FIG.  2 C . By rotating the punch  202  at a predetermined timing after a leading edge of the sheet SH has been detected by the inlet sensor  27 , punching can be performed with various hole pitches to the sheet SH during conveyance. 
     A rotational position of the punch  202  is detected by a punch position sensor S 1 . The punching unit  62  is provided with a shielding plate not shown that rotates integrally with the punch  202 , and the punch position sensor S 1  changes the output signal depending on whether the optical path is shielded by the shielding plate or the optical path is opened. For example, in the present embodiment, while the punch  202  is positioned between the punching start position and the separation position in the R 1  direction, the optical path of the punch position sensor S 1  is shielded by the shielding plate having a fan shape. That is, when the punch  202  is positioned at the punching start position, the optical path of the punch position sensor S 1  starts to be blocked by the shielding plate, and when the punch  202  reaches the separation position, the optical path of the punch position sensor S 1  starts to be opened. 
     The rotational position of the punch  202  is controlled by both the detection of the rotational position by the punch position sensor S 1  and pulses from the punch motor M 1  composed of the stepping motor. In the present embodiment, the punch  202  is configured to stand by at a home position upstream of the punching start position in the R 1  direction. 
     Further, a shift unit (not shown) for shifting the punching unit  62  in a width direction W (refer to  FIG.  5 A ) orthogonal to the sheet conveyance direction D 1  is provided on the punching process portion  4 A. According to the present embodiment, the width direction W serving as an intersecting direction is a direction orthogonal to the sheet conveyance direction D 1 , but it can be any direction as long as the direction intersects the sheet conveyance direction D 1 . The shift unit includes, as illustrated in  FIG.  7 A , a punch base  70  that retains the punching unit  62  and serving as a moving unit that is movable in the width direction W together with the punching unit  62 , and a feed screw mechanism not shown for moving the punch base  70  in the width direction W. The feed screw mechanism is driven by a shift motor M 2 . Further, it is also possible to move the punch base  70  in the width direction W by a gear train or a belt being driven by the shift motor M 2 , instead of the feed screw mechanism. 
     The punching unit  62  and the punch base  70  move in a forward (Fwd) direction by rotating the shift motor M 2  in a normal direction, and move in a reverse (Rvs) direction opposite to the forward direction by rotating the shift motor M 2  in a reverse direction. The forward and reverse directions are directions parallel to the width direction W. The punching unit  62  moves from the home position in the width direction to the forward direction to thereby approach the center in the width direction W of the conveyance path, i.e., the reception path  81 . Further, the punching unit  62  moves from the home position in the width direction to the reverse direction to thereby move away from the center in the width direction W of the conveyance path, i.e., the reception path  81 . The shift motor M 2  is composed of a pulse motor, and the position of the punching unit  62  in the width direction W is managed by the number of pulses entered to the shift motor M 2  with the home position in the width direction set as the reference. 
     Control System 
     Next, a control system of the postprocessing apparatus  4  according to the present embodiment will be described.  FIG.  3    is a block diagram illustrating a functional block of the postprocessing apparatus  4 , and  FIG.  4    is a block diagram illustrating a hardware configuration of the postprocessing apparatus  4 . As illustrated in  FIGS.  3  and  4   , the postprocessing apparatus  4  includes a controller  301 , an engine control unit  302 , and a postprocessing control unit  303 , wherein the postprocessing control unit  303  includes functional blocks such as a conveyance control unit  309 , a sensor control unit  310 , and a punch control unit  308 . 
     The conveyance control unit  309  controls the conveyance of the sheet SH, and the sensor control unit  310  detects a side edge  507  (refer to  FIG.  5 B ) serving as an edge portion of the sheet SH in the width direction W. The punch control unit  308  controls the punching unit  62  such that punching is performed to a desired position on the sheet SH. 
     Further, the postprocessing control unit  303  includes a hardware configuration such as a CPU  320 , a ROM  321 , and a RAM  322 . The CPU  320  reads various programs stored in the ROM  321  and performs calculation. The RAM  322  is used as a work area of the CPU  320 . 
     The image transmitted from an external apparatus  300  such as a server or a computer is expanded and adjusted by the controller  301 , and the controller  301  instructs the engine control unit  302  to perform the image forming operation. Whether to perform punching of the sheet SH is instructed through a touch panel not shown attached to the image forming apparatus  1 , the image reading apparatus  2 , or the document feeding apparatus  3 , or by the external apparatus  300 , which is sent to the postprocessing control unit  303  via the controller  301 . 
     The inlet sensor  27 , the lighting unit  63 , the line sensor  61 , the punch motor M 1 , the punch position sensor S 1 , the shift motor M 2 , and a shift sensor S 2  are connected to the postprocessing control unit  303 . An ON signal or an OFF signal is output from the inlet sensor  27  to the postprocessing control unit  303 . An ON signal or an OFF signal is output from the postprocessing control unit  303  to the lighting unit  63 . A timing signal notifying a timing to start detection by the line sensor  61  is output from the postprocessing control unit  303  to the line sensor  61 , and image data is output from the line sensor  61  to the postprocessing control unit  303 . 
     A driving signal is output from the postprocessing control unit  303  to the punch motor M 1  via a motor driver. Similarly, a driving signal is output from the postprocessing control unit  303  to the shift motor M 2  via a motor driver. A sensor signal composed of an ON signal, which is a high voltage signal, or an OFF signal, which is a low voltage signal, is output from the punch position sensor S 1  to the postprocessing control unit  303 . When the optical path of the punch position sensor S 1  is shielded by the shielding plate mentioned above, an ON signal is output from the punch position sensor S 1 . When the optical path is opened, an OFF signal is output from the punch position sensor S 1 . 
     Similarly, a sensor signal composed of an ON signal or an OFF signal is output from the shift sensor S 2  to the postprocessing control unit  303 . As illustrated in  FIGS.  7 A to  7 C , a light shielding portion  70   a  is provided on the punch base  70 . When the optical path of the shift motor M 2  composed of the optical sensor is shielded by the light shielding portion  70   a , an ON signal is output from the shift sensor S 2 , and when the optical path is opened, an OFF signal is output from the shift sensor S 2 . That is, the shift sensor S 2  serving as a movement detection unit varies the signals serving as the output value based on the position of the punch base  70 . 
     Punching Operation 
     Next, a punching operation performed to the sheet SH will be explained. In the present embodiment, a case in which a two-hole punch mode of punching two holes to each sheet SH is illustrated as an example, especially with the sheet SH skewed. In  FIGS.  5 A to  5 D  and  FIGS.  6 A to  6 D , reference number  250  denotes a center of the punch  202  in a punching completion position, hereinafter referred to as a punch center  250 . Further, target positions P 1  and P 2  illustrated on the sheet SH are target positions of holes to be punched by the punch  202 , which are indicated in dashed lines. When holes are punched to the target positions P 1  and P 2 , holes P 1 ′ and P 2 ′ are indicated in solid lines. The target position P 1  is positioned downstream of the target position P 2  in the sheet conveyance direction D 1 , and it shows a position of the hole to be punched first on the sheet SH. The target position P 2  is a position of the hole to be punched second on the sheet SH. 
     When a punching operation of punching holes P 1 ′ and P 2 ′ to the sheet SH is started, as shown in  FIG.  5 A , the leading edge  506  of the sheet SH conveyed by the inlet roller  21  is detected by the inlet sensor  27 , and the signal of the inlet sensor  27  is switched. In this stage, holes P 1 ′ and P 2 ′ on the sheet SH are not yet punched, such that they are indicated by dashed lines. At this time, the conveyance control unit  309  of the postprocessing control unit  303  detects the reaching of the sheet SH to a punch area, and instructs preparation of edge portion detection of the sheet SH to the sensor control unit  310  and instructs preparation of punching operation to the punch control unit  308 . 
     When the sheet SH is conveyed further by the inlet roller  21 , as illustrated in  FIG.  5 B , the target position P 1  reaches the line sensor  61 . By detecting a density difference at a boundary of the area covered by the sheet SH and the area not covered by the sheet SH, the line sensor  61  detects the position of the side edge  507  in the width direction W of the sheet SH positioned at a position where the target position P 1  and the line sensor  61  overlap in the sheet conveyance direction D 1 . 
     The postprocessing control unit  303  determines that the target position P 1  has reached the line sensor  61  after a predetermined time has elapsed from the detection of the leading edge  506  of the sheet SH by the inlet sensor  27 . The predetermined time is set according to the target position of the hole set in advance. Further, in a case where the sheet SH is skewed, the detection timing of the leading edge  506  is slightly varied compared to the case where the sheet SH is not skewed, but the error of output value of the line sensor  61  based on the difference of detection timing is so small that it can be ignored. 
     The postprocessing control unit  303  calculates a first movement distance of the punching unit  62  based on the position of the punch center  250  of the punching unit  62  managed by the shift sensor S 2  and the shift motor M 2  and the position of the side edge  507  detected by the line sensor  61 . The first movement distance is a difference of position in the width direction W between the punch center  250  and the position of the side edge  507  detected in  FIG.  5 B . 
     Next, the postprocessing control unit  303  drives the shift motor M 2  to move the punching unit  62  for a first movement distance in the width direction W, as illustrated in  FIG.  5 C , such that the punch center  250  and the target position P 1  are aligned in the width direction W. The movement of the punching unit  62  in the width direction W is completed before the target position P 1  reaches the punch center  250  and before the blade edge  202   a  (refer to  FIG.  2 A ) of the punch  202  rotated by the punch motor M 1  contacts the sheet SH. 
       FIG.  5 D  is a plan view illustrating a state in which the punch center  250  corresponds to the target position P 1  and a hole P 1 ′ has been punched by the punch  202 . In this state, the punch  202  is positioned at the punching completion position, and the punch  202  is driven by the punching motor M 1  in correspondence with this timing. 
     If the sheet SH is conveyed further by the inlet roller  21 , as illustrated in  FIG.  6 A , the target position P 2  reaches the line sensor  61 . The line sensor  61  detects the position of the side edge  507  in the width direction W of the sheet SH positioned at a position in which the target position P 2  and the line sensor  61  overlap in the sheet conveyance direction D 1  by detecting the density difference at the boundary between the area covered by the sheet SH and the area not covered by the sheet SH. 
     Then, the postprocessing control unit  303  calculates a second movement distance of the punching unit  62  based on the punch center  250  of the punching unit  62  and a position of the side edge  507  detected by the line sensor  61 . The second movement distance is a difference between the punch center  250  and the position of the side edge  507  detected in  FIG.  6 A  in the width direction W. 
     Next, the postprocessing control unit  303  drives the shift motor M 2  to move the punching unit  62  for a second movement distance in the width direction W, as illustrated in  FIG.  6 B , such that the punch center  250  and the target position P 2  are aligned in the width direction W. The movement of the punching unit  62  in the width direction W is completed before the target position P 1  reaches the punch center  250  and before the blade edge  202   a  (refer to  FIG.  2 A ) of the punch  202  rotated by the punch motor M 1  contacts the sheet SH. 
       FIG.  6 C  is a plan view illustrating a state in which the punch center  250  corresponds to the target position P 2  and a hole P 2 ′ has been punched by the punch  202 . In this state, the punch  202  is positioned at the punching completion position, and the punch  202  is driven by the punch motor M 1  in correspondence with this timing. 
       FIG.  6 D  is a plan view illustrating a state after a trailing edge  508  of the sheet SH has passed the line sensor  61 . The holes P 1 ′ and P 2  are punched as targeted on the target positions P 1  and P 2  of the sheet SH. In  FIG.  6 D , the shift motor M 2  is not driven after punching a hole to the target position P 2 , but the shift motor M 2  can be driven such that the punching unit  62  is returned to the home position in the width direction (refer to  FIG.  5 A ) to prepare for the arrival of the subsequent sheet to the punch area. 
     As described, by detecting the position of the side edge  507  of the sheet SH by the line sensor  61  for each of the target positions P 1  and P 2 , the position of the punching unit  62  in the width direction W can be adjusted highly accurately and holes can be punched as targeted on the target positions P 1  and P 2 . The abovementioned operation is repeated if there are three or more holes to be punched on the sheet SH. 
     Cleaning Unit 
     Next, a cleaning unit  410  for cleaning the line sensor  61  will be described with reference to  FIGS.  7 A to  7 C . As illustrated in  FIG.  7 A , the line sensor  61  includes a transparent member  161  having a detection surface  161   a  opposed to a surface of the sheet conveyed by the inlet roller  21  (refer to  FIG.  1   ), and a plurality of light receiving elements  162  that are arranged in the width direction W to receive light having passed through the transparent member  161 . A Contact Image Sensor (CIS), a Charge Coupled Device (CCD) sensor, or a Complementary Metal Oxide Semiconductor (CMOS) sensor can be used, for example, as the line sensor  61 . 
     The cleaning unit  410  includes an arm  401  that pivots about a pivot shaft  403 , a nonwoven fabric  400  supported by a first end portion of the arm  401 , and a coil spring  402  urging the arm  401 . A contact portion  401   a  against which the punch base  70  abuts is provided on a second end portion of the arm  401 . The second end portion of the arm  401  is positioned on an opposite side interposing the pivot shaft  403  from the first end portion on which the nonwoven fabric  400  is attached. The arm  401  is urged by the coil spring  402  in an R 4  direction illustrated in  FIG.  7 B  about the pivot shaft  403 , and is positioned at a standby position illustrated in  FIG.  7 A  by being abutted against a stopper not shown. 
     The punch base  70  retaining the punching unit  62  includes the light shielding portion  70   a  extending in the width direction W and a pressing portion  70   b  capable of pressing the contact portion  401   a  of the arm  401 . As illustrated in  FIG.  7 A , in a state where the punching unit  62  and the punch base  70  are positioned at the home position in the width direction and the arm  401  of the cleaning unit  410  is positioned at the standby position, the pressing portion  70   b  is separated from the contact portion  401   a.    
     When the punching unit  62  and the punch base  70  move in a reverse direction by the shift motor M 2  rotating in the reverse direction, as illustrated in  FIG.  7 B , the pressing portion  70   b  of the punch base  70  presses the contact portion  401   a  of the arm  401 . Thereby, the arm  401  pivots in an R 3  direction about the pivot shaft  403  against an urging force of the coil spring  402 . In  FIG.  7 B , the shift sensor S 2  has its optical path shielded by the light shielding portion  70   a , and the output signal is changed from OFF to ON. In this state, the nonwoven fabric  400  attached to the arm  401  starts to abut against the detection surface  161   a  of the transparent member  161  of the line sensor  61 . 
     Then, when the punching unit  62  and the punch base  70  move further toward the reverse direction, as illustrated in  FIG.  7 C , the arm  401  pivots further in the R 3  direction. Thereby, the nonwoven fabric  400  is rubbed against the detection surface  161   a  to thereby clean the paper dust as deposit deposited on the detection surface  161   a . As described, the arm  401  serving as an interlocking portion and a pivot member moves the nonwoven fabric  400  serving as a cleaning portion by interlocking with the movement of the punching unit  62  in the width direction W. Paper dust is discharged from the sheets SH being conveyed. The deposits deposited on the detection surface  161   a  are not limited to paper dust, and it can be a filler added to the sheets SH or other types of dust. 
     The detection surface  161   a  can be divided into an area AR 1  and an area AR 2 , and the area AR 1  can be further divided into an area AR 11  and an area AR 12 . The area AR 1  is an area from a left edge portion  161 L of the detection surface  161   a  to a position P 11 , wherein the position P 11  is a position where a side edge portion, or left edge portion, of a minimum size sheet to which the punching unit  62  can punch holes passes. The area AR 2  is an area from the position P 11  to a right edge portion  161 R of the detection surface  161   a . The area AR 11  is an area from the left edge portion  161 L to a position P 10 , wherein the position P 10  is a position where a side edge portion, or left edge portion, of a maximum size sheet to which the punching unit  62  can punch holes passes. The area AR 12  serving as a predetermined area is an area from the position P 11  to the position P 11 . 
     The postprocessing apparatus  4  according to the present embodiment can punch holes to sheets of various sizes, such that a position of the side edge portion, or left edge portion, of the sheet passing above the line sensor  61  differs according to the sheet size. The paper dust discharged from the sheets tends to deposit on the area through which the sheets pass through the detection surface  161   a , that is, in the areas AR 12  and AR 2 . However, since the area AR 2  is the area through which the sheet passes regardless of the size of the sheet, such that paper dust deposited on the area AR 2  will be removed by the sheet itself when the sheet passes above the line sensor  61 . Therefore, the nonwoven fabric  400  should preferably be designed to clean at least the area AR 12 , and in the present embodiment, it is configured to clean the area AR 1  including the area AR 11  and the area AR 12 . Meanwhile the nonwoven fabric  400  will not clean the area AR 2  due to the reason described above. 
     If it is determined that cleaning of the line sensor  61  is required, the punch control unit  308  (refer to  FIG.  3   ) rotates the shift motor M 2  in the reverse direction to swing the nonwoven fabric  400  from the position illustrated in  FIG.  7 A  to the position illustrated in  FIG.  7 C , and thereafter rotates the shift motor M 2  in the normal direction. Thereby, the punching unit  62  and the punch base  70  are returned to the home position in the width direction illustrated in  FIG.  7 A , and the arm  401  pivots in the R 4  direction by the urging force of the coil spring  402 . Thus, the nonwoven fabric  400  returns to the position illustrated in  FIG.  7 A . 
     Cleaning Control 
     Next, cleaning control by the cleaning unit  410  is described in further detail with reference to the flowchart of  FIG.  8   . The punching unit  62  is defined to be positioned at a punch position correction area when the shift sensor S 2  is OFF, and the punching unit  62  is defined to be positioned at a sensor cleaning area when the shift sensor S 2  is ON. The punch position correction area is an area in which the punching unit  62  moves in the width direction W during punching, and the sensor cleaning area is an area adjacent to the punch position correction area in the width direction W and in which the punching unit  62  moves in the width direction W during cleaning of the line sensor  61 . 
     When cleaning control is started, the postprocessing control unit  303  starts to initialize the postprocessing apparatus  4  (step S 601 ). The cleaning control is started, for example, by the power of the postprocessing apparatus  4  being turned on, and initialization of the postprocessing apparatus  4  includes cleaning of the line sensor  61  and the movement of the punching unit  62  in the home position in the rotational direction, for example. 
     Next, the postprocessing control unit  303  confirms whether there is a residual paper remaining in the postprocessing apparatus  4  (step S 602 ), and determines whether there is a residual paper (step S 603 ). If there is a residual paper (Step S 603 : Yes), the postprocessing control unit  303  displays a notification that there is a residual paper on the touch panel, for example (step S 604 ), and ends the processing. 
     If there is no residual paper (step S 603 : No), the cleaning control by the cleaning unit  410  is continued, and a search for the width direction home position of the punching unit  62  is started (step S 605 ). That is, the postprocessing control unit  303  determines whether the shift sensor S 2  is ON (step S 606 ). If the shift sensor S 2  is ON (step S 606 : Yes), the postprocessing control unit  303  starts to rotate the shift motor M 2  in the normal direction (step S 607 ), and determines whether the shift sensor S 2  has turned OFF (step S 608 ). If the shift sensor S 2  is still ON (step S 608 : No), the normal rotation of the shift motor M 2  is continued. 
     When the shift sensor S 2  is turned OFF in step S 608 , or when the shift sensor S 2  is OFF from the beginning in step S 606  (step S 606 : No), the procedure advances to step S 609 . In this state, the punching unit  62  is positioned within the punch position correction area since the search for the width direction home position has been completed. 
     Next, the postprocessing control unit  303  starts to rotate the shift motor M 2  in the reverse direction, and the punching unit  62  is moved to the sensor cleaning area (step S 609 ). Then, the postprocessing control unit  303  determines whether the shift sensor S 2  is ON (step S 610 ). If the shift sensor S 2  is still OFF (step S 610 : No), the reverse rotation of the shift motor M 2  is continued. In other words, the shift motor M 2  serving as a drive source drives based on the output value of the shift sensor S 2  and moves the punch base  70  in the width direction W. 
     When the shift sensor S 2  is turned from OFF to ON (step S 610 : Yes), the postprocessing control unit  303  continues the reverse rotation of the shift motor M 2  for an additional time T 1  from when the shift sensor S 2  has been turned ON. At a timing prior to the turning ON of the shift sensor S 2 , the pressing portion  70   b  of the punch base  70  starts pressing the contact portion  401   a  of the arm  401  of the cleaning unit  410 . Thereby, the arm  401  pivots in the R 3  direction, and the nonwoven fabric  400  moves to the cleaning completion position illustrated in  FIG.  7 C , by which the cleaning of the detection surface  161   a  of the line sensor  61  is completed. After elapse of time T 1 , the postprocessing control unit  303  stops the driving of the shift motor M 2  (step S 611 ). 
     Next, the postprocessing control unit  303  rotates the shift motor M 2  in the normal direction again such that the punching unit  62  is moved to the width direction home position in the punch position correction area (step S 612 ). Then, the postprocessing control unit  303  determines whether the shift sensor S 2  has turned OFF (step S 613 ). If the shift sensor S 2  is still ON (step S 613 : No), the normal rotation of the shift motor M 2  is continued. 
     When the shift sensor S 2  is turned from ON to OFF (step S 613 : Yes), the postprocessing control unit  303  continues the normal rotation of the shift motor M 2  for an additional time T 2  before stopping the shift motor M 2  (step S 614 ). Thereby, the punching unit  62  stops at the width direction home position within the punch position correction area. As described, the cleaning control is ended. 
     In the flowchart illustrated in  FIG.  8   , cleaning control of the cleaning unit  410  has been described taking the turning on of power of the postprocessing apparatus  4  as an example, but the present technique is not limited thereto. For example, the processing of steps S 605  to S 614  can be performed at the timing when a job of punching holes to the sheets is started or when the job is completed. Further, it is also possible to count the number of sheets passing through the line sensor  61  and to clean the detection surface  161   a  of the line sensor  61  for each predetermined number of sheets. 
     As described, by providing the cleaning unit  410  on the postprocessing apparatus  4  and cleaning the detection surface  161   a  of the line sensor  61  by the cleaning unit  410 , the detection accuracy of the side edge  507  of the sheet by the line sensor  61  can be improved. Thereby, the positioning accuracy in the width direction W of the punching unit  62  can be improved, and holes can be punched highly accurately on the sheet. 
     Further according to the present embodiment, when the punching unit  62  moves in the width direction W by the shift motor M 2 , the nonwoven fabric  400  moves in an interlocked manner via the arm  401 . Thus, the nonwoven fabric  400  can be moved by the shift motor M 2  even if a motor for moving the nonwoven fabric  400  is not specifically provided, such that downsizing of the apparatus and cutting down of costs can be realized. 
     Further according to the present embodiment, only the area AR 1  is configured to be cleaned in the detection surface  161   a  of the line sensor  61 , and the area AR 2  is not cleaned. Therefore, the cleaning time of the line sensor  61  by the cleaning unit  410  can be cut down. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described. According to the second embodiment, the area of the detection surface  161   a  of the line sensor  61  cleaned by the nonwoven fabric  400  differs from the first embodiment. Therefore, similar configurations as the first embodiment are either not shown in the drawings or denoted by the same reference numbers. 
     According to the present embodiment, as illustrated in  FIG.  9   , the nonwoven fabric  400  cleans an entire area AR 20  of the detection surface  161   a  of the line sensor  61 . That is, the cleaning area of the detection surface  161   a  by the nonwoven fabric  400  can be adjusted arbitrarily according to the length of the nonwoven fabric  400 , the distance from the pivot shaft  403  to the contact portion  401   a  or the nonwoven fabric  400 , or the positional relationship between the light shielding portion  70   a  of the punch base  70  and the shift sensor S 2 . 
     As described, by providing the cleaning unit  410  on the postprocessing apparatus  4  and cleaning the entire area AR 20  of the detection surface  161   a  of the line sensor  61  by the cleaning unit  410 , the detection accuracy of the side edge  507  of the sheet by the line sensor  61  can be improved. Thereby, the positioning accuracy of the punching unit  62  in the width direction W can be improved, and holes can be punched highly accurately on the sheets. 
     OTHER EMBODIMENTS 
     In any of the embodiments described above, the cleaning control of the line sensor  61  by the cleaning unit  410  caused the nonwoven fabric  400  to move once in reciprocating motion on the detection surface  161   a , but the present technique is not limited thereto. For example, by repeating the steps S 609  to S 613  of  FIG.  8   , the nonwoven fabric  400  can be made to move in reciprocating motion for a number of times on the detection surface  161   a.    
     In any of the embodiments described above, the punch base  70  directly presses the arm  401  to pivot the arm  401  such that the nonwoven fabric  400  cleans the line sensor  61 , but the present technique is not limited thereto. For example, it is possible to adopt a configuration in which the punch base  70  and the arm  401  are mutually connected via a gear train and the arm  401  is pivoted in linkage with the movement of the punching unit  62  and the punch base  70 . Further, the nonwoven fabric  400  is not limited to being pivoted about the pivot shaft  403  by the arm  401 , and for example, it may be attached to a slide member and moved in sliding motion in the width direction W. 
     In any of the embodiments described above, the nonwoven fabric  400  of the cleaning unit  410  is moved in linkage with the movement of the punching unit  62  and the punch base  70  in the width direction W, but the present technique is not limited thereto. For example, the arm  401  can be driven by a motor other than the shift motor M 2 , and the nonwoven fabric  400  can be swung thereby. For example, a conveyance motor M 3  can be used as the motor for driving the arm  401 , or an additional motor can be provided. 
     In any of the embodiments described above, the nonwoven fabric  400  is used as a cleaning portion for removing paper dust, but the present embodiment is not limited thereto. For example, woven fabric, flocking sheet or other members can be used instead of the nonwoven fabric  400 , and the materials thereof are not limited. However, the cleaning portion for removing paper dust should preferably not damage or charge the detection surface  161   a  of the line sensor  61 . 
     In any of the embodiments described above, the image forming apparatus  1  adopting an electrophotographic system has been described, but the present technique is not limited thereto. For example, the present technique can be adopted in an inkjet-type image forming apparatus for forming images on sheets by discharging ink through nozzles. 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2021-186730, filed Nov. 17, 2021, which is hereby incorporated by reference herein in its entirety.