Sheet processing apparatus and image forming system

Abstract

To provide a sheet processing apparatus which corrects positional deviation due to skew of a sheet and positional deviation in the conveying direction of the sheet with respect to the position where a perforation process is performed on the sheet.SOLUTION: A sheet processing apparatus according to the present invention includes: a punching mechanism that forms a hole at a predetermined position of a conveyed sheet; a sheet deviation amount detection unit that detects the amount of skew of the sheet and the deviation amount of the conveyance center of the sheet from the center position of a conveyance path; a conveyance timing detection unit that detects the conveyance timing at which the predetermined position reaches the punching mechanism; a punching position moving mechanism that changes the position of the punching mechanism in a direction perpendicular to the sheet conveyance direction; and a control unit that controls the operation of the punching mechanism and the punching position moving mechanism. The control unit corrects the position of the punching mechanism in accordance with a first correction value calculated based on the amount of skew and the amount of deviation, and corrects the timing for performing the punching process by the punching mechanism in accordance with a second correction value calculated based on the conveyance timing.SELECTED DRAWING: Figure 9

Description

Technical Field

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

Background Art

[0002] There is known a sheet processing apparatus that performs a predetermined process on a sheet. As an example of the predetermined process, a punching process for forming holes in a sheet is known. The punching process is a process for forming holes used when binding a plurality of sheets. Therefore, it is desirable that the positions of the holes formed by the punching process (punching positions) be the same regardless of the sheet.

[0003] There is also known an image forming system including a sheet processing apparatus and configured to be able to cooperate with an image forming apparatus that forms an image on a sheet.

[0004] In order to improve the accuracy of the punching position without increasing the size and complexity of the sheet processing apparatus, a configuration is disclosed that includes a sheet deviation amount detection unit that detects the skew amount of the sheet, a conveyance timing detection unit, and a punch unit movement mechanism that is movable in a direction orthogonal to the sheet conveyance direction (see Patent Document 1).

Summary of the Invention

Problems to be Solved by the Invention

[0005] As disclosed in Patent Document 1, in a configuration in which a punching process is performed after moving a punch unit (punching unit) when the sheet is skewed, the punching position is determined by calculation based only on the skew amount of the sheet. As a result, the punching position is corrected only in the direction orthogonal to the conveyance direction. Therefore, when the sheet is skewed and there is a deviation in the registration position, the punching position is shifted as if it were rotating around the sheet rear end detection position.

[0006] That is, according to the prior art, there is a problem that the misalignment of one of the two holes formed by the punching process can be reduced, but the misalignment of the other hole increases. In this case, there is a problem that the misalignment of the holes for each sheet becomes too large and the quality of the sheet binding deteriorates.

[0007] An object of the present invention is to provide a sheet processing apparatus that corrects misalignment due to skew of a sheet and misalignment in the conveyance direction of the sheet with respect to a position where a punching process is performed on the sheet.

Means for Solving the Problems

[0008] In order to solve the above technical problems, one aspect of the present invention relates to a sheet processing apparatus, including a punching mechanism that forms a hole at a predetermined position of a conveyed sheet, a sheet displacement amount detection unit that detects the skew amount of the sheet and the displacement amount from the center position of the conveyance path of the conveyance center of the sheet, a conveyance timing detection unit that detects the conveyance timing at which the predetermined position reaches the punching mechanism, a punching position movement mechanism that variably positions the punching mechanism in a direction orthogonal to the sheet conveyance direction, and a control unit that controls the operations of the punching mechanism and the punching position movement mechanism. The control unit corrects the position of the punching mechanism according to a first correction value calculated based on the skew amount and the displacement amount, and corrects the timing at which the punching process is performed by the punching mechanism according to a second correction value calculated based on the conveyance timing.

Effects of the Invention

[0009] According to the present invention, it is possible to correct misalignment due to skew of a sheet and misalignment in the conveyance direction of the sheet with respect to a position where a punching process is performed on the sheet.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same components will be denoted by the same reference numerals, and duplicate explanations may be omitted.

[0012] [Embodiment of the Image Forming System] First, the image forming system 100 according to the embodiment of the present invention will be described. First, with reference to FIG. 1, the configuration of an inkjet type image forming apparatus, which is an embodiment of the image forming apparatus constituting the image forming system, will be described. FIG. 1 is a diagram showing the overall configuration of the image forming system 100 including the inkjet type image forming apparatus.

[0013] In FIG. 1, the overall configuration and operation of the image forming system 100, the image forming apparatus 1, and the punching processing apparatus 50 will be described. In the image forming system 100, a punching processing apparatus 50 corresponding to an embodiment of the present invention is detachably installed.

[0014] Further, the image forming apparatus 1 is a multifunction device having a copy function, a printer function, and a scanner function. A personal computer as a remote input device is connected to the image forming apparatus 1 via a communication network. Then, the user can perform various commands by communication to the image forming apparatus 1 using the personal computer to perform a desired printing (image forming operation), or manually operate operation buttons or operation keys displayed on the screen of the operation display panel 95 to perform various commands to perform a desired printing (image forming operation).

[0015] As shown in FIG. 1, a scanner 13 (document reading device) for optically reading image information of a document is installed above the image forming apparatus 1.

[0016] Also, an intermediate transfer belt 8 is installed above the center of the image forming apparatus 1. Further, photosensitive drums 2Y, 2M, 2C, 2K (image forming units) corresponding to respective colors (yellow, magenta, cyan, black) are arranged in parallel so as to face the intermediate transfer belt 8. Furthermore, the intermediate transfer belt 8 is in pressure contact with a secondary transfer roller 15 (secondary transfer belt 16) below it to form a secondary transfer nip as an image forming unit.

[0017] As shown in FIG. 1, a charging unit 3, a developing unit 4, a cleaning unit 5, a discharging unit, etc. are arranged around the photosensitive drum 2K corresponding to black. Then, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process, discharging process) is performed on the photosensitive drum 2K, and a black image is formed on the surface of the photosensitive drum 2K.

[0018] Note that the peripheries of the other three photoreceptor drums 2Y, 2M, and 2C are also configured in substantially the same manner, and images corresponding to their respective toner colors are formed on the surfaces of the photoreceptor drums 2Y, 2M, and 2C. Hereinafter, the description of the image forming process on the other three photoreceptor drums 2Y, 2M, and 2C will be appropriately omitted, and only the description of the image forming process corresponding to black will be given.

[0019] The photoreceptor drum 2K is rotationally driven counterclockwise in FIG. 1 by the main motor. Then, at the position of the charging unit 3, the surface of the photoreceptor drum 2K is uniformly charged. This process corresponds to the charging process.

[0020] Thereafter, the surface of the photoreceptor drum 2K reaches the irradiation position of the laser light emitted from the exposure unit 7, and an electrostatic latent image corresponding to black is formed by exposure scanning in the width direction (the main scanning direction which is the direction perpendicular to the paper surface in the state facing FIG. 1) at this position. This process corresponds to the exposure process.

[0021] Note that when the image forming apparatus 1 is used as a copier, a latent image is formed on the photoreceptor drum 2K by irradiation with laser light from the exposure unit 7 based on the image information of the document read by the scanner 13. On the other hand, when the image forming apparatus 1 is used as a printer, a latent image is formed on the photoreceptor drum 2K by irradiation with laser light from the exposure unit 7 based on the image information sent from a personal computer.

[0022] Thereafter, the surface of the photoreceptor drum 2K reaches the position facing the developing unit 4, and the electrostatic latent image is developed at this position to form a black toner image. This process corresponds to the developing process.

[0023] Thereafter, the surface of the photoreceptor drum 2K reaches the position facing the intermediate transfer belt 8 and the primary transfer roller 6 (primary transfer nip), and the toner image formed on the surface of the photoreceptor drum 2K is primarily transferred to the surface of the intermediate transfer belt 8 at this position. This process corresponds to the primary transfer process. At this time, a small amount of untransferred toner remains on the photoreceptor drum 2K.

[0024] Subsequently, the surface of the photoreceptor drum 2K reaches the position facing the cleaning unit 5, and at this position, the untransferred toner remaining on the photoreceptor drum 2K is collected into the cleaning unit 5 by the cleaning blade. This process corresponds to the cleaning process.

[0025] Finally, the surface of the photoreceptor drum 2K reaches the position between the cleaning unit 5 and the charging unit 3 and facing an erasing unit (not shown), and at this position, the residual potential on the photoreceptor drum 2K is removed. Thus, a series of image forming processes performed on the photoreceptor drum 2K are completed.

[0026] Note that the above-described image forming process is also performed on the surfaces of the other photoreceptor drums 2Y, 2M, and 2C in the same manner as the black photoreceptor drum 2K. Then, the toner images of respective colors formed on the surfaces of the photoreceptor drums 2Y, 2M, 2C, and 2K are superposed and primarily transferred onto the intermediate transfer belt 8. Thus, a color image is formed on the intermediate transfer belt 8.

[0027] Thereafter, the intermediate transfer belt 8 on which the toner images of respective colors are superposed and primarily transferred reaches the position facing the secondary transfer roller 15 (secondary transfer belt 16). At this position, the secondary transfer opposing roller 9 sandwiches the intermediate transfer belt 8 and the secondary transfer belt 16 between it and the secondary transfer roller 15 to form a secondary transfer nip (image forming unit). Then, the four-color toner images formed on the intermediate transfer belt 8 are secondarily transferred onto a sheet P such as a sheet of paper conveyed to the position of this secondary transfer nip. This process corresponds to the secondary transfer process. At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 8.

[0028] Thereafter, the intermediate transfer belt 8 reaches the position of an intermediate transfer cleaning unit (not shown) between the secondary transfer nip and the primary transfer nip (primary transfer roller 6) for yellow. And at this position, deposits such as untransferred toner adhering to the surface of the intermediate transfer belt 8 are removed. Thus, a series of transfer processes performed on the intermediate transfer belt 8 are completed.

[0029] Here, the sheet P conveyed to the position of the secondary transfer nip (image forming unit) shown in FIG. 1 is conveyed from the paper feeding unit 10 disposed below the image forming apparatus 1 via a conveyance path K1 where a paper feeding roller 11, a registration roller 12, etc. are arranged. Specifically, a plurality of sheets P such as paper are stored in the paper feeding unit 10 in a stacked manner. Then, when the paper feeding roller 11 is rotationally driven in the counterclockwise direction when facing FIG. 1, the topmost sheet P is fed toward between the rollers of the registration roller 12 via the conveyance path K1.

[0030] The sheet P conveyed to the registration roller 12 temporarily stops at the position of the roller nip of the registration roller 12 where the rotational drive has stopped. Then, in synchronization with the color image on the intermediate transfer belt 8, the registration roller 12 is rotationally driven, and the sheet P is conveyed toward the secondary transfer nip (image forming unit). Thus, a desired color image is transferred onto the sheet P.

[0031] Thereafter, the sheet P onto which the color image has been transferred at the position of the secondary transfer nip is conveyed by the secondary transfer belt 16, separated from the secondary transfer belt 16, and then conveyed to the position of the fixing unit 19 by the conveyance belt 18. And at this position, the color image transferred onto the surface is fixed onto the sheet P by the heat and pressure of the fixing belt and the pressure roller. This process corresponds to the fixing process.

[0032] Thereafter, the sheet P is discharged to the outside of the image forming apparatus 1 by the discharge paper roller 25 via the discharge conveyance path K2. Further, the sheet P discharged from the image forming apparatus 1 is conveyed into the punching processing apparatus 50, and post-processing such as punching processing (punching) and binding processing is performed in the punching processing apparatus 50. And the sheet P (sheet bundle PT) subjected to the post-processing is discharged onto the discharge tray 59. Note that the configuration and operation of the punching processing apparatus 50 will be described in detail later.

[0033] In this way, a series of image forming processes (image forming operations) in the image forming apparatus 1 are completed.

[0034] Hereinafter, the punching device 50 will be described in detail. First, the sheet P discharged from the image forming apparatus 1 is fed (conveyed) into the punching device 50 by the inlet roller 51. Then, when the "normal processing mode" is selected in advance by the user on the operation display panel 95, by switching the conveyance path by the switching claw 57, the sheet P is directly discharged onto the discharge tray 59 by the discharge roller 58 via the linear conveyance path K11.

[0035] At this time, when the "punching process" is additionally selected in advance by the user on the operation display panel 95, when the sheet P passes through the punching mechanism 501, the punching mechanism 501 performs a punching process on the sheet P.

[0036] Also, when the "sorting process" is additionally selected in advance by the user on the operation display panel 95, when the sheet P is discharged onto the discharge tray 59 by the discharge roller 58, the discharge roller 58 functioning as a sorting unit moves in the width direction according to the timing of sorting the sheet P, and a sorting process is performed on the sheet P discharged onto the discharge tray 59.

[0037] On the other hand, when the "binding process mode" is selected in advance by the user on the operation display panel 95 of the image forming apparatus 1, by switching the conveyance path by the switching claw 57, the sheet P is conveyed toward the stacking unit 61 via the binding process conveyance path K12. Then, the sheet aligning unit 60 performs an aligning process in the conveyance direction and the width direction on the sheet P (sheet bundle PT) stacked on the stacking unit 61.

[0038] Specifically, when the sheet P (sheet bundle PT) is placed on the placement surface of the loading unit 61, each time, the tapping roller 56 disposed above it rotates about the rotation axis from the retracted position to a position where it contacts the uppermost sheet P. As a result, the tapping roller 56 is rotationally driven in the counterclockwise direction in FIG. 1. Consequently, the last placed sheet P is conveyed (moved) toward the end fence 62. By repeatedly executing this operation the number of times corresponding to the number of sheets P forming the sheet bundle PT, the rear ends of the plurality of sheets P (sheet bundle PT) abut against the end fence 62, and the positions of the plurality of sheets P (sheet bundle PT) in the conveyance direction are aligned.

[0039] Also, in the present embodiment, when the sheet P (sheet bundle PT) is placed on the placement surface of the loading unit 61, each time, the stopper portion 64 held on the belt surface of the conveyance belt 65 moves so as to push the leading end of the sheet P by the clockwise running of the conveyance belt 65 in FIG. 1. As a result, the sheet P is conveyed (moved) toward the end fence 62. Thereby, the rear ends of the plurality of sheets P (sheet bundle PT) abut against the end fence 62, and the positions of the plurality of sheets P (sheet bundle PT) in the conveyance direction are aligned.

[0040] Also, when the alignment process in the conveyance direction is performed on the sheet bundle PT in this way, a process for aligning the positions in the width direction of the sheet bundle PT is also performed. The alignment process in the width direction is performed by at least one of a pair of side fences (jogger fences) (not shown) installed at both ends in the width direction of the loading unit 61 moving so as to sandwich the sheet P each time the sheet P is placed on the loading unit 61. Note that the alignment process in the width direction may be performed not each time the sheet P is loaded on the loading unit 61 but after the desired number of sheets P are loaded.

[0041] Then, binding processing is performed at a predetermined position on the rear end of the sheet P (sheet bundle PT) whose conveyance direction and width direction are aligned by the sheet aligning unit 60 by the movement in the width direction of the stapler 80 that is movable in the width direction.

[0042] After that, the sheet P (sheet bundle PT) subjected to the binding process is moved obliquely upward along the inclination of the placement surface by the movement of the stopper portion 64 in the paper discharge direction, which also functions as a release claw. After passing through the discharge conveyance path K13, it is discharged onto the discharge tray 59 by the conveyance by the discharge roller 58.

[0043] In addition, even in the binding process mode, when "perforation process" is additionally selected in advance on the operation display panel 95 by the user, when the sheet P passes through the perforation mechanism 501, the perforation mechanism 501 performs a perforation process on the sheet P.

[0044] [Embodiment of Sheet Processing Apparatus] Hereinafter, a punch processing apparatus 50 as an embodiment of the sheet processing apparatus according to the present invention will be described with reference to the drawings. FIGS. 2 to 7 are diagrams for explaining the main components, operations of the punch processing apparatus 50, displacement of the punching position due to skewing of the sheet P, and displacement of the punching position due to registration position deviation in the conveyance direction of the sheet P.

[0045] First, as shown in FIG. 2, the punch processing apparatus 50 includes a perforation mechanism 501 as a sheet processing unit, a photosensor 502 as a conveyance timing detection unit, a CIS 503 as a sheet displacement amount detection unit, and a movement mechanism 504 as a punching position movement mechanism that moves the perforation mechanism 501 to change the punching position.

[0046] The punch processing apparatus 50 also includes a control unit 510 that controls a punching correction process for correcting the position and punching operation timing of the perforation mechanism 501 based on the detection results of detecting the sheet P by the photosensor 502 and the CIS 503.

[0047] As illustrated in FIG. 2, in the conveyance path of the sheet P, the photosensor 502, the CIS 503, and the perforation mechanism 501 are arranged in order from the upstream side to the downstream side in the conveyance direction of the sheet P.

[0048] [Perforation Mechanism 501] The punching mechanism 501 performs a punching process of opening binding holes at a predetermined position on the sheet P. Specifically, a position near the rear end in the conveyance direction of the sheet P is set in advance as the predetermined position, and a punching process (punching) of opening binding holes at this predetermined position is performed. The timing of executing the punching process is based on the detection result of the photosensor 502 that the sheet P passes when being conveyed toward the punching mechanism 501. That is, the control unit 510 operates the punching mechanism 501 according to the conveyance amount or conveyance time (conveyance timing) from when the photosensor 502 detects the rear end side in the conveyance direction of the sheet P until the predetermined position reaches the position facing the punching mechanism 501.

[0049] [CIS503] Also, for the punching process on the sheet P, it is ideal that the conveyance state is such that the side edges in the width direction of the sheet P are parallel to the conveyance direction, and the conveyance direction side edge of the sheet P is orthogonal to the conveyance direction, and the punching position on the sheet P and the predetermined position are the same. However, the conveyance state of the sheet P may be inclined with respect to the conveyance path due to various conditions. That is, the side edges in the width direction of the sheet P may be in a state of being inclined rather than parallel to the conveyance direction. Also, the position in the direction orthogonal to the conveyance direction (conveyance orthogonal direction) may deviate from the predetermined position. Furthermore, the conveyance amount to the punching mechanism 501 may deviate from the predetermined conveyance amount.

[0050] Therefore, in the CIS503 as the sheet displacement amount detection unit, the position of the side edges in the width direction (width direction end of the sheet P) of the conveyed sheet P is detected a plurality of times at a predetermined detection interval. Then, based on the detection results of the plurality of times, the displacement of the position of the width direction end in the conveyance of the sheet P is detected, the skewing amount of the sheet P is determined, and the process of correcting this is executed by the operation control of the control unit 510.

[0051] Ideally, the center position of the sheet P in the width direction maintains a predetermined positional relationship with respect to the center position of the conveyance path, and it is preferable that the positions of the two holes formed by the punching mechanism 501 are line-symmetrical with respect to the virtual line passing through the center position of the conveyance path. That is, it is ideal for the sheet P to be conveyed in a state where the center position in the width direction thereof coincides with the center position of the conveyance path. However, as described above, due to various conditions, the center position of the sheet P in the width direction may deviate from the center position of the conveyance path. Also, due to the skew of the sheet, the center position of the sheet P in the width direction may shift in the inclination direction. That is, the sheet P may be displaced in the direction orthogonal to the conveyance direction.

[0052] Therefore, in the CIS 503 serving as the sheet displacement amount detection unit, the position of the width-direction end portion of the conveyed sheet P is detected, and based on this detection result, the amount by which the center position of the sheet P in the conveyance direction has deviated from a predetermined position (the conveyance orthogonal direction displacement amount) is determined. Also, the control unit 510 calculates in which direction and to what extent the center of the sheet P in the conveyance direction is displaced with respect to the center position of the conveyance path (the installation position of the following photo sensor 502). The correction value calculated here corresponds to the first correction value.

[0053] [Photo sensor 502] Also, the predetermined position (punching position) as the position where the punching process is performed on the sheet P is set in the vicinity of the rear end portion in the conveyance direction of the sheet P. That is, it is ideal to execute the punching process at the timing when the punching position with respect to the sheet P reaches the punching mechanism 501. Therefore, when performing control for conveying the sheet P at the position where the punching process is executed based on the sheet conveyance amount, starting from the time when the photo sensor 502 detects the rear end portion of the sheet P in the conveyance direction, the conveyance amount of the subsequent sheet P is calculated. Then, the sheet P is conveyed based on this conveyance amount.

[0054] Or, when performing control for conveying the sheet P at the position where the punching process is to be executed based on the number of sheet conveyance times, the conveyance time of the subsequent sheet P is calculated starting from the time when the photosensor 502 detects the trailing end portion in the conveyance direction of the sheet P. Then, the sheet P is conveyed based on this number of times.

[0055] Then, at the timing when the conveyance corresponding to the determined conveyance amount or number of times is executed, the control unit 510 executes the punching process by the punching mechanism 501. The correction value of the conveyance amount or number of times calculated here corresponds to the second correction value.

[0056] [Control unit 510] The control unit 510 controls the operations of the moving mechanism 504, the punching mechanism 501, and the conveyance mechanism that conveys the sheet P. The control unit 510 controls the moving mechanism 504 based on the skew amount and the deviation amount of the center position calculated based on the detection result of the CIS 502 and the detection result of the sheet P by the photosensor 502, so as to vary the position of the punching mechanism 501 in the direction orthogonal to the conveyance direction of the sheet P. Then, the control unit 510 operates the punching mechanism 501 based on the conveyance timing of the sheet P to execute the punching process.

[0057] [Control block according to this embodiment] Here, with reference to FIG. 3, the hardware configuration of the control unit 510 in the punching device 50 will be described. As shown in FIG. 3, the control unit 510 includes a CPU 511, a ROM 512, and an I / F 513. Further, the punching device 50 includes a punch movement motor 514 that constitutes the moving mechanism 504, a punch punching motor 515 that executes the punching operation by the punching mechanism 501, a conveyance motor 516 for conveying the sheet P toward the punching mechanism 501, a CIS 503, and a photosensor 502.

[0058] The detection results in the CIS503 and the photosensor 502 are notified to the CPU 511 via the I / F 513. The CPU 511 calculates the skew amount and the displacement amount described above by a predetermined punching process program. Based on the calculated skew amount, displacement amount, etc., the CPU 511 controls the operations of the punch movement motor 514, the punch punching motor 515, and the conveyance motor 516 via the I / F 513. By this control, as described above, the punching process can be executed at a predetermined punching position.

[0059] Note that detailed explanations regarding the correction of the position of the punching mechanism 501 leading to the punching process and the correction of the operation timing will be described later.

[0060] [Structure of the punching mechanism 501] Next, the structure of the punching mechanism 501 will be described with reference to FIG. 4. As shown in FIG. 4, the punching mechanism 501 includes a fixed part 70a and a movable part 70b provided with a blade part 70b1.

[0061] The movable part 70b is held by the housing of the punching mechanism 501 so as to be movable in the vertical direction. The movable part 70b is biased upward by a tension spring 70d, and a cam 70c abuts on the upper part thereof. Then, with the sheet P interposed between the fixed part 70a and the movable part 70b, the cam 70c rotates under the control of the control unit 510, and the movable part 70b is pushed downward against the biasing force of the tension spring 70d. Then, when the blade part 70b1 of the movable part 70b enters the hole part 70a1 of the fixed part 70a through the sheet, a punch hole is formed in the sheet. Note that the punching mechanism 501 is not limited to the one using such a cam mechanism, and for example, a mechanism using a link mechanism may be used.

[0062] [Method for calculating the sheet skew amount and method for calculating the center position in the conveyance orthogonal direction] Next, the method for calculating the "sheet skew amount" in the present embodiment and the method for calculating the center position of the sheet P in the direction orthogonal to the conveyance direction, that is, the center position in the width direction of the sheet P, which is the center position in the conveyance orthogonal direction as the center position of the skew sheet P, will be described with reference to FIG. 5.

[0063] As already described, the CIS503 as the sheet deviation amount detection unit is composed of a plurality of sensors arranged to extend in a direction orthogonal to the conveyance direction of the sheet P. Each of these plurality of sensors detects the sheet P. The CIS503 is configured as a sensor for detecting the position of the end portion in the width direction of the sheet P being conveyed toward the punching mechanism 501. By the CIS503, while conveying the sheet P to the punching mechanism 501, the end portions in the width direction of the sheet P are detected a plurality of times at predetermined time intervals or in accordance with a predetermined conveyance amount. The control unit 510 compares the detection results, determines the change in the position of the end portion in the width direction of the sheet P, and thereby calculates the degree of inclination (sheet skew amount) of the sheet P.

[0064] Also, based on the positions of the sensors that detect the end portions of the sheet P among the plurality of sensors provided in the CIS503, the displacement from the center position in the conveyance path of the sheet P can be detected. Based on this detection result, the control unit 510 calculates the degree of displacement (conveyance center displacement amount) of the sheet P.

[0065] In the following description, the "direction orthogonal to the conveyance direction of the sheet P" may be referred to as the "conveyance orthogonal direction of the sheet P". Also, for the sake of convenience, the sheet P in the ideal state where the sheet P is conveyed straight without being displaced in the conveyance orthogonal direction is referred to as the "ideal sheet Pi".

[0066] As shown in FIGS. 5(a) and 5(b), when the sheet P is inclined with respect to the conveyance direction, the CIS503 detects the width end portions of the sheet P at different positions on the conveyance path. The position of the width end portion in FIG. 5(a) is different from the position of the width end portion in FIG. 5(b).

[0067] That is, in the sensors that make up the CIS503, the positional relationship between the sensors that detect the sheet P and the sensors that do not detect the sheet P changes as the sheet P is conveyed. Based on this difference in positional relationship, the sheet skew fee is calculated. Here, the amount of deviation in the direction orthogonal to the conveyance direction when the sheet P is relatively upstream, which is the amount of deviation from the position of the end portion in the conveyance direction of the ideal sheet Pi, is designated as "a1". Also, the amount of deviation in the direction orthogonal to the conveyance direction when the sheet P is relatively downstream, which is the amount of deviation from the position of the end portion in the conveyance direction of the ideal sheet Pi, is designated as "a2". Based on these "a1" and "a2", the degree of inclination (skew amount) of the sheet P with respect to the ideal sheet Pi can be calculated.

[0068] Also, based on the skew amount, the control unit 510 can calculate the amount of deviation of the conveyance center of the sheet P. Specifically, the CIS503 consists of a plurality of reflection type photo sensors arranged in parallel in the direction orthogonal to the conveyance direction of the sheet P (corresponding to the width direction of the sheet P). Note that the reflection type photo sensor consists of a light emitting element and a light receiving element. The CIS503 corresponds to a line sensor that optically detects the position of the side edge of the sheet P.

[0069] Then, among the plurality of reflection type photo sensors (sensors that make up the CIS503) arranged in parallel in the direction orthogonal to the conveyance direction, the control unit 510 determines the boundary portion between these sensors by identifying the "sensors that detect the sheet P" and the "sensors that do not detect the sheet P". As a result, the control unit 510 can determine the position of the side edge of the sheet P.

[0070] If the position of the side edge of the sheet P is determined, since the dimension in the width direction of the sheet P is preset, the position corresponding to half of the dimension in the width direction of the sheet P in the orthogonal direction from the side edge is determined as the center in the conveyance direction of the sheet P.

[0071] That is, in order to calculate the sheet skew amount, the degree of inclination from the ideal sheet Pi is calculated using the result of the CIS503 detecting the widthwise end portions of the sheet P. Then, taking into account the degree of inclination, the conveyance center deviation amount indicating in which direction and by how much the center position in the width direction of the sheet P is displaced at the rear end side of the conveyance path is calculated. As a result, the position of the sheet center Pc, which should be on the conveyance path center Tc as the conveyance path center position in the case of the ideal sheet Pi (sheet center position), can be calculated.

[0072] When sheets P having different sizes in the direction orthogonal to the conveyance direction are conveyed, the normal positions of their side edges (the side edge positions of the ideal sheet Pi) will change, so information regarding the size of the sheet P is required. Such information regarding the size of the sheet P can be obtained based on the information of the sheet P input by the user via the operation display panel 95.

[0073] [Calculation of Conveyance Direction Position] Next, the calculation of the conveyance direction position will be described with reference to FIG. 6. As shown in FIG. 6, the photosensor 502 as the conveyance timing detection unit is disposed on the conveyance path of the sheet P. The position of the photosensor 502 where it is attached and its position in the conveyance direction are referred to as the "photosensor attachment position 502Sp". Also, the attachment position of the punching mechanism 501 in the conveyance direction of the sheet P is referred to as the punching mechanism attachment position 501Mp.

[0074] Here, the timing for performing the punching process on the sheet P corresponds to the timing when the sheet P is conveyed by the distance from when the photosensor 502 detects the rear end side in the conveyance direction of the sheet P until the punching position 501Dp of the sheet P reaches the punching mechanism 501.

[0075] The sheet conveyance amount Pa, which is the conveyance amount of this sheet P, is calculated by the difference between the distance from the photosensor mounting position 502Sp to the punching mechanism mounting position 501Mp and the distance to the punching position 501Dp of the sheet P defined by the dimension in the conveyance direction of the sheet P (the length of the sheet P). Here, the photosensor mounting position 502Sp and the punching mechanism mounting position 501Mp are predetermined in the specifications of the punching device 50. Also, the dimension in the conveyance direction of the sheet P (the length of the sheet P) is clear at a preset value. The punching position 501Dp is defined by the length of the sheet P.

[0076] Therefore, at the photosensor 502, when the trailing edge in the conveyance direction of the sheet P (the sheet trailing edge) is detected, and the sheet P is conveyed by the difference between the trailing edge of the length dimension of the sheet P and the punching position 501Dp from the distance from the above photosensor mounting position 502Sp to the punching mechanism mounting position Mp, the punching position 501Dp will reach the punching mechanism mounting position Mp. By operating the punching mechanism 501 at the timing when the punching position 501Dp reaches the punching mechanism mounting position Mp, a hole can be formed at the predetermined punching position 501Dp.

[0077] Here, as illustrated in FIG. 6(b), assume a situation where the posture of the sheet P during conveyance is inclined with respect to the ideal sheet Pi. In this case (when there is an obliquity in the sheet P), the distance between the sheet center Pc and the photosensor 502 is calculated as the correction amount Co. When the sheet center Pc is ahead of the photosensor mounting position 502Sp (when it is on the downstream side), the difference (correction amount Co) is subtracted from the sheet conveyance amount Pa. Also, when the sheet center Pc is behind the photosensor mounting position 502Sp (when it is on the upstream side), the difference (correction amount Co) is added to the sheet conveyance amount Pa to convey the sheet P. This correction amount Co corresponds to the second correction value.

[0078] [Calculation of Position in the Direction Orthogonal to Conveyance] Next, the calculation of the position in the direction orthogonal to the conveyance in the punching processing apparatus 50 according to the present embodiment will be described with reference to FIG. 7. The punching position 501Dp orthogonal to the sheet conveyance direction operates the punching mechanism 501 at a position obtained by adding the skew amount of the sheet P at the punching position 501Dp and the deviation amount from the conveyance path center Tc to a preset position.

[0079] Here, the skew amount of the sheet P at the punching position 501Dp is calculated by adding the deviation amount from the conveyance path center Tc based on the skew amount of the sheet P to the preset punching position 501Dp of the sheet P. Based on this calculation result, the moving mechanism 504 is operated to change the setting of the position of the punching position 501Dp in the direction orthogonal to the conveyance of the punching mechanism 501.

[0080] [Explanation of Problems in the Prior Art] Here, regarding the problems in the prior art, the reference numerals used above will be used for the explanation. As shown in FIG. 8, for the direction orthogonal to the conveyance direction of the sheet P, the punching position 501Dp is determined by calculating a correction amount for a predetermined position from the sheet conveyance position deviation amount and the skew amount calculated by the CIS 502. However, for the conveyance direction of the sheet P, since the punching position 501Dp is determined with respect to a predetermined position from the rear end of the sheet detected by the photosensor 502, the position is shifted as if the sheet P is rotated around the rear end position in the conveyance direction of the sheet P detected by the photosensor 502.

[0081] As shown in FIG. 8(b), the amount of positional deviation between the ideal hole position Hi and the actual hole position HL is such that the hole closer to the photosensor 502 is smaller, but the other hole is significantly shifted (FIG. 8(b)).

[0082] [Embodiment of Punching Position Correction Processing in the Present Invention] Next, an embodiment of the punching position correction process according to the present invention, which can solve the problems in the prior art described with reference to FIG. 8, will be described with reference to FIGS. 9 and 10. Note that FIG. 10 is an enlarged view of the circular region R shown in FIG. 9(a). As shown in FIGS. 9 and 10, for the direction orthogonal to the sheet conveyance direction, a correction amount Co with respect to a predetermined position is calculated from the sheet P conveyance position deviation amount and the skew amount calculated by the CIS502.

[0083] Also, as shown in FIG. 10, for the sheet conveyance direction, a correction amount Co with respect to the skew amount in the sheet conveyance direction of the rear end of the sheet P detected by the photosensor 502 and the sheet center Pc calculated by the CIS502 is calculated. The punching position 501Dp is determined taking this correction amount Co into account. As a result, as shown in FIG. 9(b), even when the sheet P is skewed and displaced from the sheet conveyance position, the punching position is displaced with reference to the center TC of the rear end side of the sheet.

[0084] Therefore, as shown in FIG. 9(b), an overlapping portion is formed between the ideal hole position Hi and the actual hole position HL. Thereby, it is possible to suppress the displacement when the sheet bundle PT is bound using the stitched holes.

[0085] [Flow of the punching process according to the present embodiment] Next, the flow of the punching process including the punching position correction process described above will be described using the flowchart of FIG. 11.

[0086] First, the rear end position of the sheet P in the conveyance direction is detected by the photosensor 502 (S1101).

[0087] Subsequently, the skew amount of the sheet P and the sheet P conveyance position deviation amount from the conveyance path center are calculated by the CIS502 (S1102).

[0088] Subsequently, it is determined whether the detection of the skew amount was successful (S1103: Yes). If the skew amount has been detected (S1103: Yes), the punching position 501Dp in the direction orthogonal to the sheet conveyance is calculated (S1104). Also, the sheet center Pc is calculated (S1105). From these results, the punching position 501Dp in the sheet conveyance direction is calculated (S1106).

[0089] If the skew amount has not been detected (S1103: No), the control unit 510 determines whether there is a previous value of the punching position 501Dp (S1109). If there is a previous value (S1109: Yes), the previous value is applied to the sheet conveyance direction and the position in the direction orthogonal to the sheet (S1110). If there is no previous value (S1109: No), the initial value is applied (S1111). When the initial value is applied, the punching position 501Dp becomes the initial setting position.

[0090] By the above processing, the punching mechanism 501 is moved to the set punching position 501Dp (S1107). Then, the punching process is executed at a predetermined timing (S1108).

[0091] According to the punching process according to the present embodiment, when the sheet P is skewed, the punching position 501Dp in the sheet conveyance direction is calculated from the position where the rear end in the conveyance direction of the sheet P detected by the photosensor 502 as the conveyance timing detection unit and the distance from the center of the rear end side in the conveyance direction of the sheet P, and the position orthogonal to the sheet conveyance direction calculated from the skew amount detected by the photosensor 502 and the punching position in the sheet conveyance direction.

[0092] Thereby, the positions of the respective holes can be calculated and punched based on the center with the sheet P instead of the center of the conveyance path reference, and the deviation amount of the stitching holes due to the skew or registration deviation of the sheet P can be suppressed.

[0093] Note that the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the technical gist thereof. All technical matters included in the technical idea described in the claims are the subject of the present invention. The above embodiments show preferred examples, but those skilled in the art can realize various modifications from the disclosed content. Such modifications are also included in the technical scope described in the claims.

[0094] The content of the present invention is as follows, for example. <1> A punching mechanism for forming a hole at a predetermined position of the conveyed sheet, A sheet deviation amount detection unit that detects the skew amount of the sheet and the deviation amount from the center position of the conveyance path of the conveyance center of the sheet, A conveyance timing detection unit that detects the conveyance timing at which the predetermined position reaches the punching mechanism, A punching position moving mechanism that varies the position of the punching mechanism in a direction orthogonal to the sheet conveyance direction, A control unit that controls the operations of the punching mechanism and the punching position moving mechanism, Comprising, The control unit, Corrects the position of the punching mechanism according to a first correction value calculated based on the skew amount and the deviation amount, Corrects the timing for executing the punching process by the punching mechanism according to a second correction value calculated based on the conveyance timing, A sheet processing apparatus characterized by the above. <2> The control unit operates the punching mechanism so as to form the hole at a position obtained by adding the skew amount and the deviation amount to the initial setting position of the predetermined position, The sheet processing apparatus according to <1> above. <3> The control unit, Calculate the first correction value as a value for correcting the inclination of the sheet with respect to the sheet conveyance direction, the deviation between the sheet center position as the center position of the sheet in the orthogonal direction of the sheet and the conveyance path center position as the center position in the conveyance path. Calculate the second correction value as a value for correcting the timing of operating the punching mechanism based on the distance between the position where the conveyance timing detection unit detects the rear end of the sheet in the conveyance direction and the center position of the rear end side of the sheet calculated based on the skew amount. The sheet processing apparatus according to <1> or <2>. <4> The control unit When the sheet center position is located downstream of the conveyance timing detection unit in the sheet conveyance direction, perform the control so that the position corresponding to the distance obtained by subtracting the second correction value becomes the predetermined position. When the sheet center position is located upstream of the conveyance timing detection unit in the sheet conveyance direction, perform the control so that the position corresponding to the distance obtained by adding the second correction value becomes the predetermined position. The sheet processing apparatus according to <3>. <5> An image forming apparatus that forms an image of a sheet, The sheet processing apparatus according to any one of <1> to <4> that forms a hole in the sheet on which an image is formed in the image forming apparatus, An image forming system, characterized by comprising the above.

Explanation of Signs

[0095] 1: Image forming apparatus 100: Image forming system 501: Punching mechanism 502: Photo sensor 502Sp: Photo sensor mounting position 504: Moving mechanism 510: Control unit 511: CPU 512: ROM 513: I / F 514: Punch movement motor 515: Punch perforation motor 516: Conveyor motor

Prior art documents

Patent documents

[0096]

Patent Document 1

Claims

1. A punching mechanism for forming a hole at a predetermined position of a conveyed sheet; A sheet deviation amount detection unit for detecting the skew amount of the sheet and the deviation amount of the conveyance center of the sheet from the center position of the conveyance path; A conveyance timing detection unit for detecting the conveyance timing at which the predetermined position reaches the punching mechanism; A punching position moving mechanism for varying the position of the punching mechanism in a direction orthogonal to the sheet conveyance direction; A control unit for controlling the operations of the punching mechanism and the punching position moving mechanism; Comprising: The control unit: Corrects the position of the punching mechanism according to a first correction value calculated based on the skew amount and the deviation amount, Corrects the timing for executing the punching process by the punching mechanism according to a second correction value calculated based on the conveyance timing. A sheet processing apparatus characterized by the above.

2. The control unit operates the punching mechanism so as to form the hole at a position obtained by adding the skew amount and the deviation amount with respect to the initial setting position of the predetermined position. The sheet processing apparatus according to Claim 1.

3. The control unit: Calculates the first correction value as a value for correcting the inclination of the sheet with respect to the sheet conveyance direction and the deviation between the sheet center position as the center position of the sheet in the orthogonal direction of the sheet and the conveyance path center position as the center position in the conveyance path, Calculates the second correction value as a value for correcting the timing of operating the punching mechanism based on the distance between the position where the conveyance timing detection unit detects the rear end in the conveyance direction of the sheet and the center position of the rear end side of the sheet calculated based on the skew amount. The sheet processing apparatus according to Claim 1 or 2.

4. The control unit: When the sheet center position is located downstream of the conveyance timing detection unit in the sheet conveyance direction, performs the control so that a position corresponding to the distance obtained by subtracting the second correction value becomes the predetermined position, When the sheet center position is located upstream of the conveyance timing detection unit in the sheet conveyance direction, performs the control so that a position corresponding to the distance obtained by adding the second correction value becomes the predetermined position. The sheet processing apparatus according to Claim 3.

5. An image forming apparatus for forming an image of a sheet; The sheet processing apparatus according to Claim 1 for forming a hole in the sheet on which an image is formed in the image forming apparatus. An image forming system characterized by comprising the above. ​

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