Recording medium transport device, image forming system, tilt correction method, and program

Abstract

To provide a recording medium transport device, an imaging forming system, a tilt correction method, and a program that can properly correct the tilt of the recording medium while maintaining productivity.SOLUTION: A recording medium transport device according to the present invention is provided with: a tilt detection unit for detecting a bend amount of a transported recording medium; a determination unit for determining a bend correction amount according to the detected bend amount; and a correction unit for correcting the bending of the recording medium based on the determined bend correction amount, wherein the determination unit adjusts the bend correction amount to be used for correcting the bending.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a recording medium conveying device, an image forming system, and a tilt correction method and program. [Background technology]

[0002] Conventionally, post-processing is performed by cutting paper printed by an image forming device along its four sides to produce a borderless print, or by cutting and dividing the paper into multiple pieces. In post-processing devices that perform such post-processing, if the cutting direction is tilted relative to the printed image, the quality of the print deteriorates. Therefore, when cutting paper, it is necessary to correct the tilt of the paper before cutting.

[0003] One method for correcting the skew of paper is, for example, to abut the entire width of the paper against a roller or shutter that is positioned downstream in the paper transport direction and whose rotation has been stopped. This method involves abutting the entire width of the paper against the roller or shutter and bending the paper so that the roller or shutter and the edge of the paper are parallel, and then the roller is rotated or the shutter is opened to transport the paper.

[0004] However, when correcting the skew of the paper using the above-mentioned method, the leading edge of the paper is abutted against a roller or shutter to stop the paper, causing a "bend" in the paper. This requires an interval between the sheets to correspond to the amount of time the paper is stopped, resulting in reduced productivity.

[0005] Therefore, recently, a method for correcting the skew of a paper sheet without stopping the paper sheet has been proposed. For example, Patent Document 1 discloses a method for correcting the skew of a paper sheet by detecting the skew of the paper sheet based on the position of the edge of the paper sheet in the transport direction, and rotating the paper sheet by generating a difference in the amount of rotation according to the detection result between two pairs of rollers arranged in a direction perpendicular to the transport direction. In this method, the paper sheet is rotated while being transported. Therefore, the skew of the paper sheet can be corrected without reducing productivity. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2019-48692 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, the method of Patent Document 1 has a problem that the paper does not rotate according to the target rotation amount due to the influence of the flatness, thickness, and surface friction coefficient of the paper, and the inclination of the paper cannot be properly corrected. In particular, when rotating paper after image formation, the friction coefficient of the paper surface differs from that before the image formation because an image is formed on the surface. Therefore, even if an appropriate rotation amount can be obtained for paper before image formation, an appropriate rotation amount cannot be obtained for paper after image formation.

[0008] The present disclosure has been made in consideration of the problems in the above-mentioned conventional technology, and aims to provide a recording medium conveying device, an image forming system, a tilt correction method, and a program that can appropriately correct the tilt of a recording medium while maintaining productivity. [Means for solving the problem]

[0009] A recording medium conveying device according to the present disclosure includes: a tilt detection unit that detects the amount of tilt of the conveyed recording medium; a determination unit that determines a curve correction amount according to the detected curve amount; a correction unit that corrects the skew of the recording medium based on the determined amount of skew correction; Equipped with The determination unit is The amount of correction of the curvature used for correcting the curvature is adjusted.

[0010] The tilt imaging system according to the present disclosure comprises: an image forming apparatus for forming an image on a conveyed recording medium; The recording medium conveying device and Equipped with.

[0011] The tilt correction method according to the present disclosure includes: Detects the amount of bending of the conveyed recording medium, determining a skew correction amount according to the detected skew amount; correcting the skew of the recording medium based on the determined amount of skew correction; The amount of correction of the curvature used for correcting the curvature is adjusted.

[0012] The program according to the present disclosure is The above tilt correction method is executed by a computer. Effect of the Invention

[0013] According to the present disclosure, it is possible to appropriately correct the tilt of a recording medium while maintaining productivity. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of an image forming system according to the first embodiment. [Diagram 2] FIG. 2 is a block diagram showing a main part of a control system of the image forming system according to the first embodiment. [Diagram 3] FIG. 3 is a schematic diagram illustrating an example of the configuration of the tilt correction unit in FIG. [Figure 4] FIG. 4 is a functional block diagram illustrating an example of the configuration of the control unit in FIG. [Diagram 5] FIG. 5 is a schematic diagram for explaining a conventional tilt correction process. [Figure 6] FIG. 6 is a graph for explaining the actual correction amount. [Figure 7] FIG. 7 is a flowchart showing an example of the flow of the adjustment coefficient determination process according to the first embodiment. [Figure 8]FIG. 8 is a schematic diagram for explaining correction of the inclination of the paper. [Figure 9] FIG. 9 is a timing chart for explaining detection of the paper. [Figure 10] FIG. 10 is a graph for explaining the correction amount obtained by the adjustment coefficient determination process. [Figure 11] FIG. 11 is a flowchart showing an example of the flow of the inclination correction process according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications are possible without departing from the spirit of the present disclosure. In addition, in each drawing, the same reference numerals are used to denote the same or equivalent parts, and this is common throughout the entire specification.

[0016] <Embodiment 1> Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings. The image forming system according to the first embodiment is capable of forming an image on paper (recording medium) such as a sheet of paper. Note that, in the following, an example will be described in which paper is used as the recording medium, but the recording medium is not limited to paper, and other media such as cloth may also be used.

[0017] [Configuration of image forming system 1] Fig. 1 is a schematic diagram showing an example of the configuration of an image forming system 1 according to the present embodiment 1. Fig. 2 is a block diagram showing a main part of a control system of the image forming system 1 according to the present embodiment 1. As shown in Fig. 1, the image forming system 1 includes an image forming apparatus 100, a paper feed section 200, a reading section 300, a post-processing section 500, a paper discharge section 400, and the like.

[0018] The image forming apparatus 100 is an intermediate transfer type color image forming apparatus that utilizes electrophotographic process technology. That is, the image forming apparatus 100 primarily transfers the toner images of each color, CMYK, formed on a photoconductor onto an intermediate transfer body, and then superimposes the four color toner images on the intermediate transfer body, and then secondarily transfers them onto paper to form an image. CMYK stands for C (cyan), M (magenta), Y (yellow), and K (black).

[0019] The image forming apparatus 100 employs a tandem system in which photoconductors corresponding to the four colors, CMYK, are arranged in series in the running direction of an intermediate transfer body, and toner images of each color are transferred sequentially to the intermediate transfer body in a single step.

[0020] As shown in FIG. 2, the image forming system 1 includes an image processing unit 10, an image forming unit 20, a fixing unit 30, a paper transport unit 40, an operation display unit 50, a communication unit 71, a memory unit 72, a control unit 600, a paper feeding unit 200, a reading unit 300, a post-processing unit 500, and a paper discharge unit 400.

[0021] The image processing unit 10 includes a circuit for performing image processing on input image data according to initial settings or user settings, etc. The image forming unit 20 is controlled based on the image data that has been subjected to the image processing.

[0022] The image forming section 20 includes an image forming unit 21, an intermediate transfer unit 22, and a secondary transfer unit 23. The image forming unit 21 forms an image using color toners of each color component based on image data from the image processing section 10. For example, the image is formed using color toners of each color component of Y (yellow), M (magenta), C (cyan), and K (black).

[0023] The image forming unit 21 has, for each color, an exposure device, a developing device, a photosensitive drum, a charging device, a drum cleaning device, etc. Since known technologies can be adopted for the exposure device, the developing device, the photosensitive drum, the charging device, and the drum cleaning device, detailed description thereof will be omitted here.

[0024] The intermediate transfer unit 22 includes an intermediate transfer belt and the like. The intermediate transfer belt is stretched in a loop shape around a number of support rollers and travels in the direction of arrow A. The support rollers include a backup roller, a primary transfer roller, a drive roller, and other rollers, but these are not shown here. The intermediate transfer belt is pressed against the photosensitive drum, thereby transferring a toner image from the photosensitive drum to the intermediate transfer belt.

[0025] The intermediate transfer unit 22 may be configured to include a belt cleaning device having a plate-shaped belt cleaning blade or the like that is in sliding contact with the surface of the intermediate transfer belt. The belt cleaning device removes residual toner and the like that remains on the surface of the intermediate transfer belt after the secondary transfer.

[0026] The secondary transfer unit 23 includes a secondary transfer roller, etc. The secondary transfer roller is in pressure contact with the intermediate transfer belt, so that a secondary transfer nip is formed between the intermediate transfer belt and the secondary transfer roller.

[0027] In the secondary transfer unit 23, when the paper is transported to the secondary transfer nip, the toner images of each color carried on the intermediate transfer belt are transferred onto the paper at once. The paper onto which the toner images have been transferred is transported toward the fixing unit 30 by the secondary transfer roller.

[0028] Incidentally, the secondary transfer unit 23 may be a belt-type secondary transfer unit having a secondary transfer belt stretched around a plurality of support rollers, instead of a roller-type secondary transfer unit having a secondary transfer roller or the like.

[0029] The fixing unit 30 includes a fixing roller and a pressure roller. The fixing roller is heated to a predetermined fixing temperature, and the pressure roller forms a fixing nip between the fixing roller and the pressure roller to sandwich and transport the paper. In the fixing unit 30, the toner image is fixed to the paper by heating and pressurizing the paper, which has been secondarily transferred and transported, in the fixing nip.

[0030] The paper transport section 40 includes a transport path section 41. The transport path section 41 is composed of, for example, a path for transporting the paper, a plurality of transport rollers, and a drive motor for driving the transport rollers to rotate. The transport path section 41 transports the paper supplied from the paper feed section 200 to the secondary transfer unit 23 and the fixing section 30, and then transports the paper to the paper discharge section 400.

[0031] In the transport path section 41, a registration roller pair 41a is provided upstream of the secondary transfer unit 23 in the paper transport direction D. The registration roller pair 41a adjusts the transport timing and direction (angle) of the paper transported to the secondary transfer unit 23.

[0032] The operation display unit 50 is composed of, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit and an operation unit. The display unit displays various operation screens, image status display, and operation status of each function according to a display control signal input from the control unit 600. The operation unit includes various operation keys such as a numeric keypad and a start key, and outputs operation signals to the control unit 600 upon receiving various input operations by the user.

[0033] Paper feed unit 200 is disposed upstream of image forming apparatus 100 in paper transport direction D, and is connected to image forming apparatus 100. Paper feed unit 200 has a plurality of paper feed trays 201, 202, and 203, and each of paper feed trays 201, 202, and 203 stores sheets of paper (standard paper or special paper) identified based on basis weight or size, etc., for each preset type. Based on an instruction from image forming apparatus 100, paper feed unit 200 supplies the specified paper to image forming apparatus 100.

[0034] Reading unit 300 is disposed between paper feed unit 200 and image forming apparatus 100, and is connected to paper feed unit 200 on the upstream side and to image forming apparatus 100 on the downstream side in paper transport direction D. Reading unit 300 has a media sensor 301 that reads paper transported from paper feed unit 200. Media sensor 301 is disposed, for example, above the path along which paper is transported, facing the paper being transported, and is configured to read the front (upper) side of the paper being transported.

[0035] For example, a CCD (Charge Coupled Device) or a CIS (Contact Image Sensor) is used as the media sensor 301. Also, for example, a line sensor extending over a width equal to or greater than the width of the paper (width in a direction perpendicular to the paper transport direction D), such as a line scanner or a line sensor camera, is used as the media sensor 301.

[0036] The media sensor 301 acquires paper information, which is information related to paper. The media sensor 301 acquires, as the paper information, for example, the size of the paper (paper width, paper length, etc.) and the paper position.

[0037] The paper discharge section 400 is disposed downstream of the post-processing section 500 in the paper transport direction D, and is connected to the image forming apparatus 100 via the post-processing section 500. The paper discharge section 400 has a paper discharge tray 401 and a purge tray 402, and discharges the transported paper to the paper discharge tray 401 or the purge tray 402.

[0038] The paper output tray 401 outputs paper on which an image has been formed by the image forming apparatus 100. The purge tray 402 outputs paper whose paper size does not satisfy a predetermined condition as a result of the paper size being read by the reading unit 300. For example, if the paper size read by the reading unit 300 does not satisfy a predetermined condition, the paper output unit 400 may output paper on which an image has not been formed by the image forming apparatus 100 from the purge tray 402, as indicated by the dashed-dotted arrow in FIG.

[0039] The post-processing unit 500 is disposed between the image forming apparatus 100 and the paper discharge unit 400 in the paper conveying direction D. The post-processing unit 500 is connected to the image forming apparatus 100 on the upstream side and to the paper discharge unit 400 on the downstream side. The post-processing unit 500 performs a predetermined post-processing as necessary on the paper on which an image has been properly formed. For example, the post-processing unit 500 performs various post-processing such as folding the paper, punching holes in the paper, gluing the paper, and cutting the paper. In the present embodiment 1, the post-processing unit 500 has a skew correction unit 501, a cutting unit 502, and a purge tray 503. The post-processing unit 500 corresponds to the "recording medium conveying device" of this disclosure.

[0040] The skew correction unit 501 corrects the skew of a sheet conveyed from the image forming apparatus 100. Fig. 3 is a schematic diagram showing an example of the configuration of the skew correction unit 501 in Fig. 1. As shown in Fig. 3, the skew correction unit 501 has two correction roller pairs 511a and 511b, a first skew detection unit 512, and a second skew detection unit 513.

[0041] The pair of correction rollers 511a and 511b are arranged along a direction perpendicular to the conveying direction of the paper. The pair of correction rollers 511a and 511b sandwich and convey the paper. The respective pairs of correction rollers 511a and 511b are controlled by the control unit 600 so as to be rotated and driven individually.

[0042] In the present embodiment 1, the correction roller pairs 511a and 511b can be driven at different rotation speeds during the adjustment coefficient determination process and the tilt correction process described below. The correction roller pairs 511a and 511b can rotate the paper being transported by being driven at different rotation speeds to generate a linear speed difference. The correction roller pairs 511a and 511b correspond to the "correction unit" of this disclosure.

[0043] The first skew detection unit 512 and the second skew detection unit each detect the skew of the transported paper. The first skew detection unit 512 and the second skew detection unit each include two optical sensors arranged at a predetermined interval in a direction perpendicular to the paper transport direction.

[0044] The first skew detection unit 512 has two optical sensors arranged at a predetermined interval in a direction perpendicular to the paper transport direction. The first skew detection unit 512 detects a change in the amount of received light that occurs when the edge of the paper in the transport direction passes over each optical sensor. Based on the detection result, the control unit 600 detects the skew of the paper at the position of the first skew detection unit 512.

[0045] In the following, for ease of explanation, "the control unit 600 detects the tilt of the paper based on the change in the amount of received light detected by the optical sensor of the first tilt detection unit 512 (or the second tilt detection unit 513)" may be simply expressed as "the tilt of the paper is detected by the first tilt detection unit 512 (or the second tilt detection unit 513)."

[0046] The second tilt detection unit 513 is disposed downstream in the transport direction from the first tilt detection unit 512. Similar to the first tilt detection unit 512, the second tilt detection unit 513 has two optical sensors disposed at a predetermined interval in a direction perpendicular to the transport direction of the paper. The second tilt detection unit 513 detects a change in the amount of received light that occurs when an end of the paper in the transport direction passes over each optical sensor. Based on the detection result, the control unit 600 detects the tilt of the paper at the position of the second tilt detection unit 513.

[0047] 1, cutting unit 502 performs processing to cut the paper whose skew has been corrected by skew correction unit 501. Cutting unit 502 has a slitter 521, a CD perforation cutting unit 522, an FD perforation cutting unit 523, and a CD cutting unit 524 on the conveyance path.

[0048] The slitter 521 cuts the paper in the feed direction. The CD perforation cutting unit 522 cuts the paper in a perforated shape in a cross direction perpendicular to the paper feed direction. The FD perforation cutting unit 523 cuts the paper in a perforated shape in the paper feed direction. The CD cutting unit 524 cuts the paper in a cross direction perpendicular to the paper feed direction.

[0049] The above-mentioned configuration of the cutting unit 502 is merely an example, and is not limited to this example. As the cutting unit 502, for example, some of the above-mentioned slitter 521, CD perforation cutting unit 522, FD perforation cutting unit 523, and CD cutting unit 524 may be provided, or other units may be provided.

[0050] The purge tray 503 is disposed downstream of the skew correction unit 501 in the paper transport direction, and discharges paper transported under predetermined conditions. For example, in the first embodiment, the purge tray 503 discharges adjustment paper used in the adjustment coefficient determination process described later and used when determining an adjustment coefficient.

[0051] The control unit 600 is connected to the above-mentioned image processing unit 10, image forming unit 20, fixing unit 30, paper transport unit 40, operation display unit 50, communication unit 71, storage unit 72, paper feed unit 200, reading unit 300, post-processing unit 500, and paper discharge unit 400. The control unit 600 issues various instructions to each of these units and executes predetermined processes.

[0052] In the first embodiment, control unit 600 performs adjustment coefficient determination processing and tilt correction processing. The details of adjustment coefficient determination processing and tilt correction processing will be described later.

[0053] The control unit 600 includes a CPU (Central Processing Unit) 601, a ROM (Read Only Memory) 602, and a RAM (Random Access Memory) 603. The CPU 601 reads out a program corresponding to the processing contents from the ROM 602, loads it in the RAM 603, and centrally controls the operation of each block of the image forming system 1 in cooperation with the loaded program. At this time, various data such as a LUT (Look Up Table) stored in the storage unit 72 is referenced. The storage unit 72 is configured, for example, with a non-volatile semiconductor memory (so-called flash memory) or a hard disk drive.

[0054] The control unit 600 transmits and receives various data to and from an external device (e.g., a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. The control unit 600 receives, for example, image data transmitted from an external device, and forms an image on a sheet based on this image data (input image data). The communication unit 71 is formed, for example, of a communication control card such as a LAN card.

[0055] Fig. 4 is a functional block diagram showing an example of the configuration of control unit 600 in Fig. 2. As shown in Fig. 4, control unit 600 has an information acquisition unit 611, a bending amount detection unit 612, a correction amount calculation unit 613, a rotation control unit 614, an adjustment coefficient determination unit 615, and a storage unit 616.

[0056] The information acquiring unit 611 acquires detection results indicating that a sheet has been detected from the first tilt detecting unit 512 and the second tilt detecting unit 513. Although not shown, the information acquiring unit 611 can also acquire sheet information read by the media sensor 301 disposed in the reading unit 300.

[0057] The skew amount detection unit 612 detects the amount of skew indicating the inclination of the paper based on the detection result of the paper acquired by the information acquisition unit 611. The amount of skew is a physical amount indicating the state related to the inclination of the paper, and is, for example, the angle of the front end of the paper with respect to the direction perpendicular to the paper transport direction.

[0058] The correction amount calculation unit 613 calculates the amount of correction for correcting the skew of the paper based on the amount of skew detected by the skew amount detection unit 612 .

[0059] Rotation control unit 614 controls the rotation of correction roller pair 511a and 511b based on the correction amount calculated by correction amount calculation unit 613. Specifically, rotation control unit 614 generates a linear speed difference between correction roller pair 511a and 511b, and rotates the paper conveyed to skew correction unit 501 by the calculated correction amount.

[0060] The adjustment coefficient determination unit 615 determines the adjustment coefficient α based on the amount of skew detected by the skew amount detection unit 612. The adjustment coefficient α is a coefficient for the amount of correction calculated by the correction amount calculation unit 613, and is used to appropriately rotate the paper by the original amount of correction. A specific method for determining the adjustment coefficient α will be described later.

[0061] The storage unit 616 stores various data and the like used by each unit of the control unit 600. For example, the adjustment coefficient α determined in the adjustment coefficient determination process is stored in the storage unit 616. The storage unit 616 also stores arithmetic expressions and the like used by the bend amount detection unit 612 and the correction amount calculation unit 613.

[0062] [Operation of image forming system 1] The operation of image forming system 1 according to the first embodiment having the above configuration will be described. In image forming system 1, when an image is formed on paper, which is a recording medium, the paper is stored in paper feed trays 201, 202, and 203 of paper feed unit 200. The paper fed from paper feed unit 200 is then transported to reading unit 300, where paper information such as paper size is read, and then the paper is transported to image forming device 100. The paper transported to image forming device 100 has an image formed (hereinafter referred to as "printed") in image forming device 100, and is then transported to post-processing unit 500.

[0063] The paper conveyed to the post-processing section 500 undergoes a skew correction process, whereby the skew of the paper is corrected in the skew correction section 501. Then, the paper whose skew has been corrected undergoes a predetermined post-processing in the cutting section 502, and is conveyed to the paper discharge section 400.

[0064] [Tilt correction processing] The skew correction process according to the first embodiment will be described. As described above, the paper on which an image has been formed by the image forming apparatus 100 is transported to the post-processing section 500, where post-processing such as cutting is performed. At this time, if the paper transported to the post-processing section 500 is tilted, the cutting direction will be tilted with respect to the formed image, and the quality of the printed matter will decrease. Therefore, before the post-processing is performed on the paper, it is necessary to rotate the paper and correct the skew.

[0065] Fig. 5 is a schematic diagram for explaining a conventional tilt correction process. As shown in Fig. 5, the configuration for performing the conventional tilt correction process is a configuration in which the second tilt detection unit 513 is removed from the configuration of the tilt correction unit 501 according to the first embodiment (see Fig. 3). That is, the conventional tilt correction unit 1501 has two correction roller pairs 511a and 511b, and a first tilt detection unit 512.

[0066] In this case, in the skew correction unit 1501, the first skew detection unit 512 detects the amount of skew x indicating the skew of the paper. Then, the skew correction unit 1501 generates a linear speed difference between the pair of correction rollers 511a and 511b so that the detected amount of skew x becomes "0". For example, in this example, the linear speed of the pair of correction rollers 511a is controlled to be slower than the linear speed of the pair of correction rollers 511b. This rotates the paper being transported, and the skew of the paper is corrected.

[0067] However, in the conventional skew correction process, there are cases where the skew of the paper cannot be properly corrected. Fig. 6 is a graph for explaining the actual correction amount. In Fig. 6, the horizontal axis indicates the amount of paper skew before correction, and the vertical axis indicates the amount of correction. The dashed line is a correction line indicating the target correction amount for the amount of paper skew, and the solid line is a correction line indicating the actual correction amount for the amount of paper skew.

[0068] As shown by the dashed line in Fig. 6, when the amount of skew is "x", the target correction amount is "-x". However, as shown by the solid line in Fig. 6, the actual correction amount is insufficient compared to the target correction amount, resulting in the paper tilt not being eliminated. Note that the actual correction line passes through the origin, just like the target correction line. This shows that similar results tend to be obtained even when the type of paper used is changed.

[0069] This is believed to be because the actual rotation of the paper does not properly follow the control amount for the pair of correction rollers 511a and 511b due to the influence of the friction coefficient of the paper surface, the flatness and thickness of the paper, etc., and the paper cannot be rotated as intended. In particular, when rotating paper after image formation, this phenomenon is noticeable because the friction coefficient of the paper surface differs from that before the image formation due to the image formed on the surface.

[0070] Therefore, in the present embodiment 1, a skew correction process is performed to appropriately correct the skew of the paper by adjusting the amount of correction for the skew of the paper and rotating the paper with a correction amount such that the amount of rotation of the paper is approximately the same as the target correction amount.

[0071] (Determination of adjustment coefficient α for correction amount) In the skew correction process according to the first embodiment, an adjustment coefficient α is set for a target correction amount. The adjustment coefficient α is a coefficient set for the correction amount for rotating the paper according to the target correction amount. In other words, if the amount of paper skew is "x", the correction amount after adjustment is "-αx".

[0072] Here, the adjustment coefficient α is a value that is determined by the state of the paper, such as the friction coefficient. Therefore, the adjustment coefficient α needs to be determined, for example, at a stage prior to the image formation mode (print mode) in which an image is formed on the paper. In the first embodiment, the adjustment coefficient α is determined by performing an adjustment coefficient determination process in an adjustment coefficient determination mode that is performed prior to the image formation mode.

[0073] In the following, first, the adjustment coefficient determination process for determining the adjustment coefficient α will be described, and then the skew correction process for correcting the skew of the paper will be described.

[0074] (Adjustment coefficient determination process) 7 is a flowchart showing an example of the flow of the adjustment coefficient determination process according to the present embodiment 1. First, in the adjustment coefficient determination process, at least one adjustment sheet is prepared, which is a sheet for adjustment coefficient determination and has a similar condition to the sheet used in the image forming mode.

[0075] When the adjustment sheet is transported to the skew correction unit 501 of the post-processing unit 500, in step S1, the information acquisition unit 611 of the control unit 600 acquires the detection result of the adjustment sheet from the first skew detection unit 512. Then, based on the acquired detection result, the skew amount detection unit 612 detects a first skew amount S1 indicating the skew of the adjustment sheet transported to the skew correction unit 501. The first skew amount S1 is detected based on the timing when the sheet passes over the two optical sensors of the first skew detection unit 512.

[0076] Fig. 8 is a schematic diagram for explaining the correction of the skew of the paper. Fig. 9 is a timing chart for explaining the detection of the paper. As shown in Fig. 8, the paper conveyed to the skew correction unit 501 is conveyed by the pair of correction rollers 511a and 511b that rotate at the same linear speed.

[0077] At this time, each optical sensor provided in first skew detection unit 512 detects the passage of the paper as the paper passes over the optical sensor, and if the paper is transported without being skewed, the leading edge of the paper passes over each optical sensor at the same time. On the other hand, if the paper is transported at an angle, the leading edge of the paper passes over each optical sensor at different times, as shown in Fig. 9. Specifically, the leading edge of the paper passes over one of the two optical sensors, and then passes over the other optical sensor with a delay after the first optical sensor.

[0078] Here, the separation distance, which is the distance between the two optical sensors of the first skew detection unit 512 in the direction perpendicular to the transport direction, is known. The transport speed of the paper is also known. Therefore, the skew amount detection unit 612 can calculate the first skew amount S1 of the paper from the separation distance between the two optical sensors, the transport speed of the paper, and the detection time difference caused by the difference in the timing of the paper passing detected by the two optical sensors.

[0079] 7, next, in step S2, correction amount calculation unit 613 calculates a correction amount based on the detected first skew amount S1. Then, rotation control unit 614 controls correction roller pair 511a and 511b so as to generate a linear speed difference. This rotates the paper being transported, and the skew of the paper is corrected.

[0080] Next, in step S3, the information acquisition unit 611 acquires the detection result of the adjustment sheet from the second skew detection unit 513. Then, the skew amount detection unit 612 detects the second skew amount S2 of the adjustment sheet based on the acquired detection result. A specific method for detecting the second skew amount S2 is the same as the method for detecting the first skew amount S1.

[0081] In step S4, the adjustment coefficient determination unit 615 determines the adjustment coefficient α based on the first bend amount S1 and the second bend amount S2.

[0082] Here, a specific method for determining the adjustment coefficient α will be described. Fig. 10 is a graph for explaining the correction amount obtained by the adjustment coefficient determination process. Since the first bend amount is S1 and the second bend amount is S2, a correction line with a slope of "(S2-S1) / S1" is obtained as shown in Fig. 10. This is based on the fact that the correction line obtained from the results of actually measuring the bend amount passes through the origin.

[0083] On the other hand, when the amount of bending detected by the first tilt detection unit 512 is "x", the target amount of correction is "-x", whereas the actual amount of correction is "(S2-S1) / S1×x". Therefore, the insufficient amount of correction is the value shown in formula (1). -x-(S2-S1) / S1×x=-(S2 / S1)x ···(1)

[0084] Therefore, the true correction amount for the amount of bending "x" is the target correction amount "-x" plus the insufficient correction amount "-(S2 / S1)x" as shown in formula (2). -x-(S2 / S1)x=-(S1+S2) / S1×x ···(2)

[0085] That is, the adjustment coefficient α in this case is "(S1+S2) / S1×x".

[0086] 7, in step S5, adjustment coefficient determination unit 615 stores the adjustment coefficient α determined in step S4 in memory unit 616. Then, the adjustment paper used to determine adjustment coefficient α is transported to cutting unit 502 in the subsequent stage, but is discharged from purge tray 503 without being cut.

[0087] In this example, the adjustment coefficient α is determined using one adjustment sheet, but the present invention is not limited to this, and the adjustment coefficient α may be determined using multiple adjustment sheets. In this case, for example, the skew amount detection unit 612 detects the first skew amount S1 and the second skew amount S2 for each adjustment sheet. Then, the adjustment coefficient determination unit 615 determines the adjustment coefficient α using the average value of each skew amount.

[0088] (Tilt correction processing) When the adjustment coefficient α is determined by the above-mentioned adjustment coefficient determination process, a skew correction process is performed to correct the skew of the paper using the adjustment coefficient α. Fig. 11 is a flowchart showing an example of the flow of the skew correction process according to the first embodiment. The skew correction process is usually performed during an image formation mode in which an image is formed on paper.

[0089] When the paper is transported to the skew correction unit 501, in step S11, the information acquisition unit 611 acquires the detection result of the paper from the first skew detection unit 512. Then, the skew amount detection unit 612 detects the skew amount x of the paper transported to the skew correction unit 501 based on the acquired detection result.

[0090] In step S12, the correction amount calculation unit 613 reads out the adjustment coefficient α stored in the storage unit 616. In step S13, the correction amount calculation unit 613 calculates an adjusted correction amount “−αx” based on the detected amount of bending x and the adjustment coefficient α read out from the storage unit 616.

[0091] In step S14, rotation control unit 614 controls correction roller pair 511a and 511b so as to generate a linear speed difference based on the calculated adjustment correction amount "-αx". This rotates the paper being transported, and the skew of the paper is corrected. Then, the paper with the skew corrected is transported to cutting unit 502 at the downstream stage.

[0092] In this way, in the first embodiment, an adjusted correction amount that is a true correction amount that takes into account the adjustment coefficient α determined by the adjustment coefficient determination process is used, and therefore the skew of the paper is appropriately corrected.

[0093] As described above, in the image forming system 1 according to the first embodiment, the adjustment correction amount is calculated based on the adjustment coefficient α and the correction amount based on the amount of skew of the paper obtained from the detection result by the first skew detection unit 512. Then, based on the calculated adjustment correction amount, the correction roller pair 511a and 511b are controlled to correct the skew of the paper. At this time, the paper rotates based on the adjustment correction amount using the adjustment coefficient α while being transported. Therefore, the skew of the paper can be appropriately corrected while maintaining productivity.

[0094] <Embodiment 2> Next, the present embodiment 2 will be described. The present embodiment 2 differs from the above-mentioned embodiment 1 in that a plurality of adjustment coefficients α are stored. In the present embodiment 2, the same reference numerals are used for the parts common to the embodiment 1, and detailed description thereof will be omitted.

[0095] The adjustment coefficient α applied during the skew correction process differs depending on the paper conditions, such as the paper used and the state of the formed image, etc. Therefore, in the above-described first embodiment, it is necessary to perform the adjustment coefficient determination process and determine the adjustment coefficient α to be applied every time the paper conditions change.

[0096] However, if the adjustment coefficient α is determined by performing the adjustment coefficient determination process every time an image is formed, the image formation process is interrupted each time, which may reduce productivity. Therefore, in the second embodiment, a plurality of adjustment coefficients α determined up to that point are stored, and during the skew correction process, the adjustment coefficient α selected by the user is applied to correct the skew of the paper.

[0097] First, in the second embodiment, each time an adjustment coefficient determination process is performed, the determined adjustment coefficient α is stored in the storage unit 616. Then, when an inclination correction process is performed, a plurality of adjustment coefficients α stored in advance in the storage unit 616 are displayed on the operation display unit 50. The adjustment coefficient α to be applied is selected by the user from the plurality of adjustment coefficients α displayed in this manner. At this time, the user selects an appropriate adjustment coefficient α in consideration of the type of paper to be used for image formation, etc.

[0098] Next, when the skew correction process is started during the image formation mode (print mode), the skew amount detection unit 612 of the control unit 600 detects the amount of skew x of the paper conveyed to the skew correction unit 501, as in the first embodiment. Next, the correction amount calculation unit 613 calculates the adjustment correction amount "-αx" based on the detected amount of skew x and the adjustment coefficient α selected by the user. Then, the rotation control unit 614 controls the correction roller pair 511a and 511b based on the calculated adjustment correction amount "-αx". This rotates the conveyed paper, and the skew of the paper is corrected.

[0099] In this way, in the second embodiment, a plurality of adjustment coefficients α are stored in advance, and the inclination of the paper is corrected using an appropriate adjustment coefficient α selected by the user. Therefore, as in the first embodiment, the inclination of the paper can be appropriately corrected. Also, when forming an image on the paper, it is no longer necessary to perform the adjustment coefficient determination process, and image formation is not interrupted, so that productivity can be maintained.

[0100] [Variations] Next, a description will be given of a modification of the present embodiment 2. In the modification of the present embodiment 2, an appropriate adjustment coefficient α is automatically selected from a plurality of adjustment coefficients α.

[0101] In a modification of the second embodiment, each time an adjustment coefficient determination process is performed, the determined adjustment coefficient α is stored in the storage unit 616. Here, the adjustment coefficient α is associated with the paper information acquired by the media sensor 301 of the reading unit 300 and stored in the storage unit 616.

[0102] When the skew correction process is performed, the media sensor 301 of the reading unit 300 acquires paper information of the paper being conveyed. Next, the control unit 600 refers to the storage unit 616 and reads out from the storage unit 616 the adjustment coefficient α associated with the acquired paper information.

[0103] Next, when the skew correction process is started during the image formation mode (print mode), the skew amount detection unit 612 of the control unit 600 detects the amount of skew x of the paper conveyed to the skew correction unit 501, as in the first embodiment. The correction amount calculation unit 613 calculates the adjustment correction amount "-αx" based on the detected amount of skew x and the adjustment coefficient α read from the storage unit 616. Then, the rotation control unit 614 controls the correction roller pair 511a and 511b based on the calculated adjustment correction amount "-αx". This rotates the conveyed paper, and the skew of the paper is corrected.

[0104] In this manner, in the modified example of the second embodiment, a plurality of adjustment coefficients α are stored in association with the paper information, and the paper skew is corrected using an appropriate adjustment coefficient α selected based on the paper information of the paper used for image formation. Therefore, similar to the second embodiment, the paper skew can be appropriately corrected while maintaining higher productivity.

[0105] Although the first and second embodiments have been described above, the present disclosure is not limited to the first and second embodiments described above, and various modifications and applications are possible within the scope of the present disclosure. For example, the functions related to the adjustment coefficient determination process and the tilt correction process of the control unit 600 may be included in the post-processing unit 500.

[0106] Also, the adjustment coefficient determination process may be performed in an image forming mode (printing mode) using the first sheets of the multiple sheets used as adjustment sheets to determine the adjustment coefficient α, instead of in the adjustment coefficient determination mode. When the adjustment coefficient α is determined in this manner, normal image formation is performed on the remaining sheets using the adjustment coefficient α. [Explanation of symbols]

[0107] 1. Image forming system 50 Operation display section 100 Image forming device 200 Paper feed section 300 Reading unit 301 Media Sensor 400 Paper output section 500 Post-processing section 501 Tilt correction unit 502 Cutting section 503 Purge Tray 511a, 511b Correction roller pair 512 First tilt detection unit 513 Second tilt detection unit 600 Control section 601 CPU 602 ROM 603 RAM 611 Information Acquisition Department 612 Bending amount detection unit 613 Correction amount calculation unit 614 Rotation control section 615 Adjustment Coefficient Determination Unit 616 Storage section

Claims

1. a tilt detection unit that detects the amount of tilt of the conveyed recording medium; a determination unit that determines a curve correction amount according to the detected curve amount; a correction unit that corrects the skew of the recording medium based on the determined amount of skew correction; Equipped with The determination unit is Adjusting the amount of correction of the bend used for correcting the bend Recording medium transport device.

2. The determination unit is Calculating an adjustment correction amount for adjusting the amount of curvature correction based on the amount of curvature correction and a preset adjustment coefficient; The correction unit is The skew of the recording medium is corrected based on the calculated adjustment correction amount. The recording medium transport device according to claim 1 .

3. The tilt detection unit is a first skew detection unit that detects a first amount of skew of the conveyed recording medium; a second skew detection unit that is disposed downstream of the first skew detection unit in a conveying direction of the recording medium and detects a second skew amount of the recording medium; having The determination unit is determining a first bend correction amount based on the first bend amount; The adjustment coefficient is determined based on the first amount of skew and the second amount of skew detected by the second tilt detection unit in a state in which the amount of skew of the recording medium has been corrected by the first amount of skew correction. The recording medium transport device according to claim 2 .

4. The apparatus further includes a storage unit for storing the determined adjustment coefficient. The recording medium transport device according to claim 2 .

5. The determination unit is When the first bending amount is "S1" and the second bending amount is "S2", "-(S1+S2) / S1×x" is calculated as the adjustment correction amount for the first bending amount "x". The recording medium transport device according to claim 3 .

6. When a plurality of sheets of the recording medium are conveyed, The determination unit is determining the adjustment coefficient using at least a first recording medium among the plurality of recording media as an adjustment recording medium; The remaining skew of the recording medium is corrected based on the adjustment correction amount obtained by the determined adjustment coefficient. The recording medium transport device according to claim 2 .

7. The recording medium conveying apparatus further includes a purge tray that is disposed downstream of the correction unit in the conveying direction of the recording medium and that discharges the adjusted recording medium. The recording medium transport device according to claim 6.

8. The storage unit is storing a plurality of said adjustment factors; The correction unit is Correcting the curl of the recording medium based on a selected adjustment coefficient from among the plurality of adjustment coefficients. The recording medium transport device according to claim 4 .

9. The storage unit is storing each of the plurality of adjustment coefficients in association with recording medium information; The determination unit is reading the adjustment coefficient associated with the recording medium information of the recording medium; The correction unit is The bending of the recording medium is corrected based on the read adjustment coefficient. The recording medium transport device according to claim 8.

10. a media sensor arranged upstream of the correction unit and acquiring the recording medium information of the recording medium being conveyed The recording medium transport device according to claim 9.

11. The correction unit is The rollers are arranged in pairs, each of which can be rotated individually, and are spaced apart in a direction perpendicular to the conveying direction of the recording medium. The recording medium transport device according to claim 1 .

12. The correction unit is A linear speed difference is generated between the two pairs of rollers based on the adjusted correction amount. The recording medium transport device according to claim 11.

13. The tilt detection unit includes a plurality of optical sensors. The recording medium transport device according to claim 1 .

14. an image forming apparatus for forming an image on a conveyed recording medium; A recording medium conveying device according to any one of claims 1 to 13, Equipped Image forming system.

15. Detects the amount of bending of the conveyed recording medium, determining a skew correction amount according to the detected skew amount; correcting the skew of the recording medium based on the determined amount of skew correction; Adjusting the amount of correction of the bend used for correcting the bend Tilt correction method.

16. A program for causing a computer to execute the tilt correction method according to claim 15.

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