JP2005089053A - Medium carrying device and image forming device provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress skew amount of a wide medium, even when the wide medium is carried by a plurality of pairs of carrying rollers. <P>SOLUTION: Images and a cut mark 60 on wide paper 2' are read by reading sensors 10a and 10b arranged on a carrying direction upstream side of a cutting position of a cutting unit. The skew amount of the wide paper 2' is detected based on a detecting time difference of the cut mark 60 on the wide paper 2' by the reading sensors 10a and 10b. Subsequently, each number of rotation of motors for driving the carrying rollers 7a and 7b is controlled to eliminate the skew amount of the wide paper 2' in a time span from a time when a cutting is performed in the vicinity of a leading end of the cut mark 60 on the wide paper 2' to a time when a cutting is performed at a trailing end of the cut mark 60 on the wide paper 2'. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a medium conveying apparatus that conveys media arranged in parallel and an image forming apparatus including the medium conveying apparatus.

In an ink jet printer that is one of image forming apparatuses, a plurality of images are continuously formed on a long sheet conveyed while being unwound from a winding unit in a printable area facing a recording head. Some are printed. In such a printer, a cut mark is printed between two adjacent images formed on a sheet. When the cut mark is detected, the paper is cut at the planned cutting positions before and after the cut mark, and is divided for each image (see, for example, Patent Document 1).
JP 2001-302074 A (FIG. 1)

  Here, in such a printer, the processing capability may be improved by performing printing almost simultaneously on two relatively narrow sheets conveyed in parallel arranged in the printable area. . Therefore, in such a printer, separate conveyance roller pairs are arranged on the upstream side of the printable area in the sheet conveyance direction so as to correspond to the conveyance paths of the two sheets. Each of these conveying roller pairs has a driving roller and a pressure roller, and the two sheets can be independently conveyed by sandwiching the sheet between them.

  In such a printer, when printing is performed on a wide sheet having a width extending over the conveyance path of two sheets, the wide sheet is nipped and conveyed by two conveyance roller pairs. Therefore, in this case, it is desirable to control the two conveying roller pairs so as to be synchronized with each other.

  However, even when the two conveying roller pairs are controlled to be synchronized with each other, the accuracy of the two conveying roller pairs (for example, individual differences between the driving roller and the pressure roller constituting the conveying roller pair, and driving the driving roller) Due to the individual differences of the motors, the conveyance force (feed amount or conveyance speed) of the two conveyance roller pairs may be different, or the balance of the conveyance load may be deteriorated, causing wide paper to skew. Thus, when the wide paper is skewed, the cutting line of the wide paper does not become parallel to the width direction of the wide paper. In particular, when a large number of images are continuously printed on a wide paper, the amount of skew feeding of the wide paper is accumulated, so that the quality of the finished print is remarkably deteriorated.

  Accordingly, a main object of the present invention is to provide a medium conveying apparatus capable of suppressing an increase in the amount of skew of a wide medium even when the wide medium is conveyed by a plurality of conveying roller pairs (conveying members). Is provided.

Means for Solving the Problems and Effects of the Invention

  The medium transport apparatus of the present invention is in a position parallel to the medium transport direction and is driven independently of each other to transport the medium, and the first and second transport members And a cutter capable of cutting a wide medium having a width straddling the first and second transport members, and a wide medium transport path corresponding to the first transport member A first sensor for detecting a first cut mark formed on a wide medium, and on a transport path of the wide medium corresponding to the second transport member, on the upstream side of the cutter in the transport direction. A second sensor that detects a second cut mark that is formed on a wide medium and is located at the same position as the first cut mark in the width direction of the wide medium, upstream of the cutter in the transport direction. And said A reference for controlling the first and second transport members based on the time when the first sensor detects the first cut mark and the time when the second sensor detects the second cut mark. Based on the reference value calculation means for calculating the value and the time at which the first sensor detects the first cut mark, the wide medium is cut at two positions sandwiching the first cut mark. Based on the cutter control means for controlling the cutter, and the reference value calculated by the reference value calculation means, the first cut mark from the time when the cutter cuts the wide medium downstream in the transport direction from the first cut mark. Transport control means for controlling the transport amount of the wide medium by the first and second transport members until the time when the wide medium is cut upstream of the transport direction so that the skew amount of the wide medium is reduced. It is provided.

  According to this configuration, from the time when the cutter cuts the wide medium downstream in the transport direction from the first cut mark to the time when the wide medium is cut upstream in the transport direction from the first cut mark, The conveyance amount of the wide medium by the first and second conveyance members is controlled so that the skew amount becomes small. Therefore, the conveyance error due to the skew of the wide medium is absorbed in the discarded portions before and after the cut mark. Accordingly, when the wide medium is cut upstream of the first cut mark in the transport direction, the cutting line of the wide medium is substantially parallel to the width direction of the wide medium.

  In the present invention, it is preferable that the transport control unit controls the transport amount of the wide medium by the first and second transport members each time the first and second cut marks are detected.

  According to this configuration, each time the first and second cut marks are detected, the conveyance amount of the wide medium by the first and second conveyance members is controlled so that the skew feeding amount of the wide medium is reduced. Therefore, it is possible to effectively suppress the accumulation of the conveyance error due to the skew of the wide medium.

  An image forming apparatus according to the present invention includes the medium conveying device according to claim 1 or 2 and an image forming unit disposed on the upstream side in the conveying direction with respect to the first and second conveying members.

  According to this configuration, when a wide medium having a width across a plurality of conveying members is cut by a cutter, the wide medium is prevented from being cut properly, so that the finished quality of the wide medium on which an image is formed Will improve.

  In the present invention, it is preferable that the first and second transport members transport the medium such that a slack portion of the medium is formed on the upstream side in the transport direction with respect to the first and second transport members.

  According to this configuration, since the slack portion can be formed in the wide medium on the upstream side in the transport direction with respect to the first and second transport members, the degree of freedom of control over the first and second transport members is large. Become.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an ink jet printer according to a first embodiment of the present invention. FIG. 2 is a partial schematic top view of the ink jet printer when printing is performed on two sheets arranged in parallel.

  An ink jet printer 1 shown in FIG. 1 includes a paper magazine (paper cassette) 4, an advance roller unit 5, an ink jet printing unit 6, a transport roller unit 7, and a cutting unit 8 in a substantially rectangular housing 30. And a discharge roller unit 9. As will be described later, the operation of each part of the ink jet printer 1 is controlled by a controller 20 (see FIG. 3) disposed in the housing 30.

  The paper magazine 4 is a substantially rectangular parallelepiped casing, and stores winding portions 2 a and 3 a each having a long paper 2 and 3 wound in a roll shape. It is removable (detachable). As shown in FIG. 2, the winding portions 2 a and 3 a of the sheets 2 and 3 stored in the paper magazine 4 are arranged at predetermined intervals along the width direction of the sheets 2 and 3. Further, the winding portions 2a and 3a are respectively placed on driving rollers 2b and 3b that can rotate them and driven rollers 2c and 3c that rotate together with the winding portions 2a and 3a. Here, when the driving rollers 2b and 3b are rotationally driven by the controller 20, the driving rollers 2b and 3b are wound around the winding portions 2a and 3a in the direction in which the sheets 2 and 3 are unrolled or the sheets 2 and 3 are wound up. By rotating in the direction, the sheets 2, 3 wound around them can be sent out or rewound. Note that after the leading ends of the sheets 2 and 3 are supplied to the advance roller unit 5, the sheets 2 and 3 are sent out by the advance roller unit 5.

  As shown in FIG. 2, the advance roller unit 5 has paper feed roller pairs 5 a and 5 b driven by motors 22 a and 22 b controlled by the controller 20. Can be supplied respectively. The paper feed roller pair 5a, 5b has a drive roller provided below the paper transport path and a pressure roller provided on the top of the paper transport path so as to be pressure-bondable to the drive roller. Are arranged so as to correspond to the respective transport paths of the sheets 2 and 3 along the width direction of the sheet. Therefore, when the sheets 2 and 3 are arranged and conveyed in two rows, the sheets 2 and 3 can be nipped and conveyed independently.

  The ink jet printing unit 6 includes a print head 11, a carriage 12, and a transport table 13. The print head 11 has a large number of discharge nozzles (which can discharge yellow, yellow, magenta, magenta, cyan, and black color ink respectively on the lower surface (the surface facing the paper). (Not shown). Therefore, the print head 11 is desired to discharge color ink from a large number of discharge nozzles toward the front surface (upper surface in FIG. 1) of the conveyed sheets 2 and 3 based on a signal from the controller 20, respectively. Color images can be printed.

  The print head 11 may have a large number of ejection nozzles capable of ejecting black ink, and may print a black and white image. The ink jet printing unit 6 ejects liquid ink from the nozzles dot by dot and prints on the sheets 2 and 3, and employs any one of the piezo jet method, the thermal jet method, and other methods. There may be.

  The carriage 12 holds the print head 11 on the lower surface thereof, and can reciprocate with the print head 11 along the width direction of the sheets 2 and 3 by a driving mechanism (not shown). Accordingly, the print head 11 ejects ink toward the surfaces of the sheets 2 and 3 while reciprocating along a direction perpendicular to the conveying direction of the sheets 2 and 3. FIG. 2 shows a case where the carriage 12 is in a standby position (home position) when printing is not performed. The transport table 13 has a paper support surface that is the same height as the transport surfaces of the papers 2 and 3, and supports the papers 2 and 3 that are disposed to face the print head 11.

  The transport roller unit 7 is for sandwiching and transporting the sheets 2 and 3 transported between the inkjet printing unit 6 and the cutting unit 8. As shown in FIG. 2, the conveyance roller unit 7 has conveyance roller pairs 7 a and 7 b driven by motors 25 a and 25 b controlled by the controller 20, respectively. Can be supplied. The conveyance roller pair 7a, 7b has a driving roller provided below the paper conveyance path and a pressure roller provided so as to be capable of being crimped to the driving roller above the paper conveyance path. Arranged so as to correspond to the respective transport paths of the sheets 2 and 3 along the width direction. Therefore, when the sheets 2 and 3 are arranged and conveyed in two rows, the sheets 2 and 3 can be nipped and conveyed independently.

  Two reading sensors 10a and 10b are arranged above the paper conveyance path between the inkjet printing unit 6 and the conveyance roller unit 7. Each of the two reading sensors 10a and 10b is an optical sensor, and can continuously read the surfaces of the sheets 2 and 3 conveyed to the reading position facing them. The data read by the reading sensors 10a and 10b is continuously supplied to the controller 20. Accordingly, the controller 20 detects that the cut marks printed on the sheets 2 and 3 have been read by the reading sensors 10a and 10b based on the detection signals supplied from the reading sensors 10a and 10b, as will be described later. be able to.

  The cutting unit 8 includes a movable blade 8a disposed on the same side as the print head 11 with respect to the sheets 2 and 3, and a fixed blade 8b disposed to face the movable blade 8a with the sheets 2 and 3 interposed therebetween. Have. Each of the movable blade 8a and the fixed blade 8b is a rectangular blade having a width that is slightly larger than the interval between the outer ends in the width direction of the sheets 2 and 3 arranged in two rows. The movable blade 8a is controlled by the controller 20 so as to be close to or away from the fixed blade 8b, and the printed sheets 2 and 3 conveyed from the upstream side through the sheet conveyance path are transferred. It is possible to cut along the width direction by the interaction with the fixed blade 8b. By being cut in this way, the printed sheets 2 and 3 having a predetermined length are divided. The cutting unit 8 cuts based on the cut marks printed between the images on the sheets 2 and 3.

  The discharge roller unit 9 has a discharge roller pair 9 a driven by a motor 29 (see FIG. 3) controlled by the controller 20, and prints the printed sheets 2 and 3 after being cut by the cutting unit 8. It is conveyed and discharged from the discharge port 30a. The discharge roller pair 9a has a drive roller provided below the paper transport path and a pressure roller provided on the top of the paper transport path so as to be pressure-bondable with the drive roller, both of which are arranged in two rows. It is a roller having a length that is slightly larger than the interval between the widthwise outer ends of the sheets 2 and 3.

  Here, the control system of the ink jet printer 1 will be described with reference to FIG. FIG. 3 is a block diagram of a control system of the ink jet printer shown in FIG. FIG. 4 is a diagram illustrating a schematic configuration of a cut mark printed on a wide sheet. FIG. 5 is a diagram showing changes in the density of the cut mark shown in FIG.

  As shown in FIG. 3, the controller 20 includes drive rollers 2a and 3a of the paper magazine 4, paper feed roller pairs 5a and 5b of the advance roller unit 5, transport roller pairs 7a and 7b of the transport roller unit 7, and discharge roller units. Motors 21, 22a, 22b, 25a, 25b, and 29 for driving the nine discharge roller pairs 9a are respectively connected. Further, a driver 23 connected to the print head 11 of the inkjet printing unit 6, a motor 24 for reciprocating the carriage 12, and a motor 28 for driving the movable blade 8 a of the cutting unit 8 are connected to each other. Yes. Further, the reading sensors 10 a and 10 b are connected to the controller 20.

  Therefore, the controller 20 performs predetermined processing on the image signal supplied from an input interface (not shown), and supplies a print signal including image data corresponding to the image to be printed to the print head 11 of the inkjet printing unit 6. The controller 20 also transports the papers 2 and 3 by the paper magazine 4, the advance roller unit 5, the transport roller unit 7 and the discharge roller unit 9, moves the carriage 12, discharges ink from the print head 11, and cuts it. The cutting timing of the sheets 2 and 3 by the unit 8 is controlled.

  Further, as described above, the controller 20 can recognize the positional relationship between the position of the cut mark printed on the paper and the cutting position of the cutting unit 8 based on the detection signals obtained by the reading sensors 10a and 10b. .

  The controller 20 includes a ROM that stores control programs and data for various operations related to the ink jet printer 1, and a CPU that executes various operations to generate signals for controlling the operations of the respective units of the ink jet printer 1. A member such as a RAM for temporarily storing data such as a calculation result in the CPU is included. These various members and software form a control unit 41, a deviation amount calculation unit 42, and a motor drive calculation unit 43. The deviation amount calculation unit 42 includes a cut mark determination unit 45 and a detection time storage unit 46.

  The control part 41 controls the rotation speed of the motor for driving each roller. When the skew adjustment of the wide sheet 2 ′ having a width across the conveyance path of the two sheets 2 and 3 is performed, the control unit 41 determines the conveyance roller based on the calculation result by the motor drive calculation unit 43. The motors 25a and 25b that drive the conveyance roller pairs 7a and 7b of the unit 7 are controlled.

  When the printing is performed on the wide paper 2 ′, the deviation amount calculation unit 42 is the amount of deviation in the transport direction between the one end portion in the width direction and the other end portion in the width direction at the same position in the width direction of the wide paper 2 ′. Hereinafter, simply referred to as “a displacement amount of the wide paper 2 ′”) is calculated. Here, in the deviation amount calculation unit 42, the time when the cut mark printed on the wide paper 2 ′ is read by the reading sensor 10a and the time when the cut mark printed on the wide paper 2 ′ is read by the reading sensor 10b. The deviation amount of the wide paper 2 ′ is calculated based on the time difference between the two.

  Here, in the ink jet printer 1 according to the present embodiment, when printing is performed on the wide paper 2 ′, a plurality of images 50 are continuously printed and adjacent to each other as shown in FIG. A cut mark 60 is printed between the two images 50. The cut mark 60 is a mark when the wide sheet 2 ′ is cut for each image in the cutting unit 8.

  In the present embodiment, the cut mark 60 includes two black marks 62 and 64 formed along the width direction of the wide paper 2 ′ and three marks formed along the width direction of the wide paper 2 ′. White marks 61, 63, 65. Then, the white mark 61, the black mark 62, the white mark 63, the black mark 64, and the white mark 65 are arranged in this order from the downstream side toward the upstream side in the conveyance direction of the wide paper 2 ′. Here, each of the marks 61 to 65 is a line-shaped mark extending over the entire width of the wide sheet 2 ′, and has a predetermined width a (length along the sheet conveyance direction). Therefore, the entire width of the cut mark 60 is the width 5a.

  Accordingly, the images 50 and the cut marks 60 are alternately printed on the wide paper 2 '. The end of the cut mark 60 on the downstream side in the conveyance direction (the end on the downstream side of the white mark 61 in the conveyance direction) substantially coincides with the rear end of the image 50, and the cut mark 60 on the upstream side in the conveyance direction. The end (the end on the upstream side of the white mark 65 in the transport direction) substantially coincides with the front end of the image 50.

  In the present embodiment, when the leading edge and the trailing edge of the image 50 are cut, the wide sheet 2 ′ has an end on the upstream side in the conveyance direction and an end on the downstream side in the conveyance direction of the cut mark 60. Each of them is cut at a position (scheduled cutting position) slightly within the image 50. In other words, the wide paper 2 ′ is cut at the front end portion of the image 50 at a position slightly spaced upstream of the white mark 65 of the cut mark 60 on the wide paper 2 ′ in the transport direction. Further, with respect to the rear end portion of the image 50, the wide paper 2 'is cut at a position slightly separated from the white mark 61 of the cut mark 60 on the wide paper 2' on the downstream side in the transport direction. In FIG. 4, the planned cutting position where the wide paper 2 ′ is actually cut is indicated by a one-dot chain line. As a result, it is divided into a wide sheet 2 ′ on which images 50 are printed one by one and a wide sheet 2 ′ on which cut marks 60 are printed one by one. Note that the scheduled cutting position is coincident with the upstream end of the cut mark 60 in the transport direction and the downstream end of the transport direction, and the wide sheet 2 ′ has the upstream end of the cut mark 60 in the transport direction and the transport. You may cut | disconnect just in the edge part of a direction downstream side.

  The cut mark determination unit 45 determines the cut mark 60 printed on the wide paper 2 'based on detection signals from the reading sensors 10a and 10b. Specifically, the cut mark determination unit 45 detects the density change of the image (including the cut mark) on the wide paper 2 ′ detected by the reading sensors 10a and 10b when the wide paper 2 ′ is being conveyed. The predetermined density change in the cut mark 60 is always compared. When the density change detected by the reading sensors 10a and 10b matches a predetermined density change in the cut mark 60, it is determined that the cut mark 60 is printed on that portion of the wide paper 2 '.

  Here, in the present embodiment, as described above, the cut mark 60 is configured such that the white marks 61, 63, 65 and the black marks 62, 64 are alternately arranged in the paper transport direction. Yes. Therefore, the predetermined density change of the cut mark 60 is a density corresponding to white having a length a corresponding to the mark 61 (shown as density 0 in FIG. 5) and a mark 62 as shown in FIG. The density corresponding to the black of the corresponding length a (shown as density 100 in FIG. 5), the density corresponding to the white of the length a corresponding to the mark 63, and the black of the length a corresponding to the mark 64 The change is shown in the order of the corresponding density and the density corresponding to the white color of length a corresponding to the mark 65.

  Further, the cut mark discriminating unit 45 can discriminate the cut mark 60 only between two adjacent images 50 on the wide sheet 2 ′, and does not discriminate the cut mark 60 in the image 50. Yes. Therefore, for example, even when an image having the same density change as the predetermined density change of the cut mark 60 in the image 50 is read by the reading sensors 10a and 10b, the image area is erroneously determined to be the cut mark 60. As a result, the image 50 on the wide paper 2 ′ can be prevented from being cut.

  Specifically, in the present embodiment, the reference position is set at the center position in the width direction of the cut mark 60, that is, at the center position between the two black marks 62 and 64. A length from the reference position is set in advance as a cut mark detection area in the cut mark determination unit 45. Accordingly, the cut mark determination unit 45 determines the cut mark 60 only in the set cut mark detection area. In the present embodiment, a value b slightly larger than half of the entire width 5a of the cut mark 60 is set, and the cut mark detection area in the cut mark determination unit 45 is an area having a width 2b across the reference position. It is.

  The detection time storage unit 46 stores the time when the cut mark determination unit 45 determines that the cut mark has been read for each of the reading sensors 10a and 10b.

  Then, the deviation amount calculation unit 42 calculates the deviation amount of the wide sheet 2 ′ based on the detection time difference of the cut mark by each of the reading sensors 10 a and 10 b stored in the detection time storage unit 46. In the present embodiment, the deviation amount output unit 42 calculates the deviation amount based on the conveyance amounts of the conveyance roller pairs 7a and 7b between the detection times of the cut marks detected by the reading sensors 10a and 10b. .

  The motor drive calculation unit 43 starts from the time when the wide sheet 2 ′ is cut in the cutting unit 8 in the vicinity of the end on the downstream side in the conveyance direction of the cut mark to the time in which it is cut near the end on the upstream side in the conveyance direction of the cut mark. In the meantime, the deviation amount calculated by the deviation amount calculation unit 42 is set to 0, that is, the wide sheet 2 ′ is returned to the state where the skew is not skewed, and the vicinity of the end portion on the upstream side in the transport direction of the cut mark. In order to make the scheduled cutting position substantially coincide with the cutting position of the cutting unit 8, it is for calculating how the conveying speed of the conveying roller pair 7a, 7b should be changed.

  Next, a case where printing is performed on the wide paper 2 ′ in the ink jet printer 1 according to the present embodiment configured as described above will be described with reference to FIGS. 6 to 14. FIG. 6 is a partial schematic top view of the ink jet printer when printing is performed on wide paper. FIG. 7 is a flowchart showing a skew correction procedure when printing is performed on a wide sheet. FIGS. 8 to 14 are diagrams for explaining the skew correction operation when printing is performed on a wide sheet.

  Here, in FIGS. 8 to 14, only the portions necessary for explaining the conveyance state of the wide paper 2 ′ when the wide paper 2 ′ is skew-corrected are illustrated, and the other parts are illustrated. It is omitted. Further, in FIGS. 8 to 14, an appropriate conveyance path for the wide paper 2 ′ is drawn by a one-dot chain line, and a cutting position of the cutting unit 8 is drawn by a two-dot chain line. In addition, the cut mark 60 printed on the wide paper 2 ′ is illustrated as a single band-shaped mark (shaded portion) in a simplified manner.

  When printing is performed on the wide paper 2 ′, as shown in FIG. 6, the ink jet printer 1 has a paper magazine 4 in which a winding portion 2a ′ around which the wide paper 2 ′ is wound is stored. 'Is loaded. Here, as the paper magazine 4 ′, a paper magazine 4 ′ dedicated to the wide paper 2 ′ having the driving roller 2 b ′ and the driven roller 2 c ′ is generally used.

  First, the wide paper 2 ′ unwound from the paper magazine 4 ′ is sequentially conveyed onto the conveyance table 13, and an image is printed on the wide paper 2 ′ by the inkjet printing unit 6.

  When the wide paper 2 ′ is conveyed while the image 50 and the cut mark 60 are printed, the vicinity of the portion where the cut mark 60 is printed on the wide paper 2 ′ is read sensor 10a as shown in FIG. 10b reaches the upstream vicinity of the position facing 10b. Note that FIG. 8 illustrates a case where the wide paper 2 ′ is transported in a state where the wide paper 2 ′ is inclined to the left shoulder with respect to the transport direction without being substantially displaced in the width direction of the proper transport path. Further, in the flowchart showing the skew correction procedure of FIG. 7, the subsequent procedure is described.

  As shown in FIG. 8, after the cut mark 60 reaches the vicinity of the upstream side of the position facing the reading sensors 10a and 10b, the wide sheet 2 ′ is continuously conveyed by the conveying roller pair 7a and 7b (step S101). ). At this time, the vicinity of one end in the width direction of the wide paper 2 ′ (near the left end in FIGS. 8 to 14) is sandwiched by the conveying roller pair 7a and the vicinity of the other end in the width direction of the wide paper 2 ′ (FIGS. (Near the right end) is nipped and conveyed by the conveying roller pair 7b. At this time, the control unit 20a controls the motors 25a and 25b for driving the conveying roller pairs 7a and 7b so that the rotation speeds of the motors 25a and 25b are the same.

  Then, it is determined whether at least one of the reading sensors 10a and 10b has detected the cut mark 60 on the wide paper 2 'while the wide paper 2' is being conveyed (step S102). If it is determined in step S102 that at least one of the reading sensors 10a and 10b has detected the cut mark 60 on the wide paper 2 '(S102: YES), the process proceeds to step S103. On the other hand, when it is determined in step S102 that none of the reading sensors 10a and 10b has detected the cut mark 60 on the wide paper 2 ′ (S102: NO), the process returns to step S101 to return to the wide paper. 2 'conveyance is continued. In the present embodiment, as shown in FIG. 9, the reading sensor 10a detects the cut mark 60 on the paper 2 'before the reading sensor 10b.

  Subsequently, it is determined whether or not both of the reading sensors 10a and 10b have simultaneously detected the cut marks 60 on the wide paper 2 '(step S103). If it is determined in step S103 that both the reading sensors 10a and 10b have simultaneously detected the cut marks 60 on the wide paper 2 ′ (S103: YES), the process proceeds to step S109, and the wide paper 2 is detected. 'Will continue to be transported. That is, when both of the reading sensors 10a and 10b detect the cut mark 60 on the wide paper 2 ′ at the same time, it is determined that the wide paper 2 ′ is not skewed (the deviation amount is 0). The conveyance of the wide paper 2 ′ is continued as it is.

  On the other hand, if it is determined in step S103 that both of the reading sensors 10a and 10b have not simultaneously detected the cut marks 60 on the wide paper 2 '(S103: NO), the process proceeds to step S104. That is, when both of the reading sensors 10a and 10b do not detect the cut mark 60 on the wide paper 2 ′ at the same time, it is determined that the wide paper 2 ′ is skewed (the shift amount is not 0). Thus, the skew of the wide paper 2 ′ is corrected as follows. In the present embodiment, as described above, since the reading sensor 10a detects the cut mark 60 on the sheet 2 ′ before the reading sensor 10b, it is determined that the wide sheet 2 ′ is skewed. .

  Here, the time when one of the reading sensors 10a and 10b that previously detected the cut mark 60 on the wide paper 2 'detected the cut mark 60 is stored in the detection time storage unit 46 (step S104). In the present embodiment, the time when the reading sensor 10a detects the cut mark 60 is stored. Subsequently, the conveyance of the wide paper 2 'is continued (step S105). At this time, the control unit 20a controls the rotation speeds of the motors 25a and 25b that drive the conveying roller pairs 7a and 7b to be the same.

  Then, it is determined whether or not the other sensor that has previously detected the cut mark 60 has detected the cut mark 60 on the wide paper 2 '(step S106). If it is determined in step S106 that the other sensor has detected the cut mark 60 on the wide paper 2 '(S106: YES), the process proceeds to step S107. Here, the time when the other sensor detects the cut mark 60 on the wide paper 2 'is stored in the detection time storage unit 46 (step S107). In the present embodiment, in step S106, it is determined whether or not the reading sensor 10b has detected the cut mark 60. In step S107, the reading sensor 10b has detected the cut mark 60 as shown in FIG. The time is stored.

  On the other hand, if it is determined in step S106 that the other sensor has not detected the cut mark 60 on the wide paper 2 ′ (S106: NO), the process returns to step S105 to convey the wide paper 2 ′. Will continue.

  Thereafter, the shift amount calculation unit 42 calculates the shift amount of the wide paper 2 '(step S108). In the present embodiment, in the deviation amount calculation unit 42, the width from the pair of transport rollers 7a and 7b increases from the detection time by one sensor stored in the detection time storage unit 46 to the detection time by the other sensor. Based on the transport amount given to the sheet 2 ′, the shift amount of the wide sheet 2 ′ is calculated.

  That is, the deviation amount calculated by the deviation amount calculation unit 42 is such that the vicinity of one end in the width direction of the wide paper 2 ′ corresponding to one sensor is greater than the vicinity of the other end in the width direction of the wide paper 2 ′ corresponding to the other sensor. In other words, the wide paper 2 'is skewed by an amount corresponding to the amount of deviation. In the present embodiment, the vicinity of the left end of the wide paper 2 ′ corresponding to the reading sensor 10a is conveyed ahead of the vicinity of the right end of the wide paper 2 ′ corresponding to the reading sensor 10b. 'Is tilted to the left with respect to the transport direction.

  Then, the wide paper 2 'is further conveyed (step S109). At this time, the number of rotations of the motors 25a and 25b that drive the conveying roller pairs 7a and 7b is controlled by the control unit 20a so that both are the same. Then, the tip of the cut mark 60 on the wide paper 2 '(the end on the downstream side in the transport direction) reaches the cutting position of the cutting unit 8 (step S110). In the present embodiment, as shown in FIG. 11, the wide paper 2 ′ is inclined to the left with respect to the conveyance direction, and therefore, the vicinity of the left end portion of the front end of the cut mark 60 on the wide paper 2 ′. The cutting position of the cutting unit 8 is reached before the vicinity of the right end portion.

  Subsequently, the wide paper 2 'is cut in the vicinity of the front end of the cut mark 60 by the cutting unit 8 (step S111). Here, in the present embodiment, cutting is performed when the vicinity of the left end of the front end of the cut mark 60 on the wide sheet 2 ′ reaches the cutting position of the cutting unit 8. At this time, the right end of the front end of the cut mark 60 is cut. The vicinity does not reach the cutting position of the cutting unit 8. Accordingly, as shown in FIG. 12, the vicinity of the left end portion of the front end of the cut mark 60 on the wide paper 2 ′ substantially coincides with the cutting position, so that the vicinity of the left end portion of the wide paper 2 ′ is almost shifted from the planned cutting position. Cut at no position. On the other hand, since the vicinity of the right end of the front end of the cut mark 60 on the wide paper 2 ′ is on the upstream side of the cutting position in the transport direction, the vicinity of the right end of the wide paper 2 ′ is downstream of the planned cutting position in the transport direction. It is cut at a position shifted to the side.

  Then, it is determined whether or not the wide paper 2 'is skewed (there is a deviation amount) (step S112). If it is determined in step S112 that the wide paper 2 'is skewed (S112: YES), the process proceeds to step S113.

  Here, if the conveyance of the wide sheet 2 ′ by the conveyance roller pair 7a and 7b is continued with the rotation speeds of the motors 25a and 25b of the conveyance roller pair 7a and 7b being kept the same, the wide sheet 2 ′ is maintained. The vicinity of the left end of the rear end (the end on the upstream side in the transport direction) of the upper cut mark 60 reaches the cutting position of the cutting unit 8 before the vicinity of the right end.

  Therefore, when the wide paper 2 ′ is skewed as described above, when the planned cutting position near the rear end of the cut mark 60 on the wide paper 2 ′ reaches the cutting position of the cutting unit 8, In order to set the deviation amount of the wide paper 2 ′ to 0 (to match the planned cutting position in the vicinity of the rear end of the cut mark 60 on the wide paper 2 ′ with the cutting position of the cutting unit 8), The motor drive calculation unit 43 uses various data to calculate how many seconds the conveyance speed of the two conveyance roller pairs 7a and 7b related to conveyance should be changed to a speed of cm / s, respectively (step S113). That is, in the present embodiment, in order to prevent the planned cutting position near the rear end of the cut mark 60 on the wide paper 2 ′ from being inclined at the cutting position of the cutting unit 8, the left end in the width direction of the wide paper 2 ′. It is calculated how to change the conveyance speed of the conveyance roller pair 7a that sandwiches the vicinity of the portion and the conveyance roller pair 7b that sandwiches the vicinity of the right end of the wide sheet 2 ′ in the width direction. Here, while the skew correction of the wide paper 2 ′ is being performed, the transport roller pair 7 a and 7 b are maintained in a rotated state and do not stop.

  The positions facing the reading sensors 10a and 10b and the cutting position of the cutting unit 8 are separated by a predetermined distance, and the distance between them is constant. Therefore, the motor 25a, 25b is controlled by the control unit 20a from the time when the reading sensor 10a, 10b detects the cut mark 60 to the time when the cut mark 60 reaches the cutting position of the cutting unit 8, and is conveyed. The transport amount (number of pulses) applied from the roller pair 7a, 7b to the wide sheet 2 ′ is a predetermined value.

  Therefore, in the present embodiment, when the cutting unit 8 cuts in the vicinity of the front end portion of the cut mark 60 on the wide paper 2 ′, the control unit 20a performs the conveyance roller pair rather than the motor 25b that drives the conveyance roller pair 7b. This means that a drive signal is supplied to the motor 25a that drives the motor 7a so that the motor 25a is transported in advance by the amount of deviation calculated by the deviation amount calculator 42.

  Therefore, the motor drive calculation unit 43 sets the planned cutting position near the rear end of the cut mark 60 from the time when the cutting unit 8 cuts near the front end of the cut mark 60 on the wide paper 2 ′ to the cutting position of the cutting unit 8. A drive signal that is transported by the amount of deviation calculated by the deviation amount calculation unit 42 more than the drive signal supplied to the motor 25a that drives the pair of conveyance rollers 7a before reaching the conveyance roller pair 7b. The rotational speeds of the motors 25a and 25b are calculated so as to be supplied to the driving motor 25b.

  Based on the calculation result in the motor drive calculation unit 43, the controller 20 appropriately changes the number of rotations of the motors 25a and 25b connected to the conveyance roller pair 7a and 7b, whereby the conveyance roller pair 7a and 7b. The wide paper 2 ′ is conveyed while the rotation speed is controlled (step S114).

  At this time, since the wide paper 2 ′ is cut in the vicinity of the tip of the cut mark 60, the wide paper 2 ′ sandwiched between the transport roller pair 7a and 7b of the transport roller unit 7 is transported more than that. It is not connected to the wide sheet 2 'sandwiched between the discharge roller pair 9a of the discharge roller unit 9 on the downstream side in the direction. Therefore, the shift amount of the wide sheet 2 ′ on the upstream side in the transport direction from the cutting position of the cutting unit 8 can be corrected by transporting while controlling the rotation speed of the pair of transport rollers 7 a and 7 b.

  On the other hand, if it is determined in step S112 that the wide sheet 2 'is not skewed (S112: NO), the process proceeds to step S115, and the conveyance of the wide sheet 2' is continued. At this time, the control unit 20a controls the rotation speeds of the motors 25a and 25b that drive the conveying roller pairs 7a and 7b to be the same.

  When the planned cutting position near the rear end of the cut mark 60 on the wide paper 2 ′ reaches the cutting position of the cutting unit 8 (step S116), the wide paper 2 ′ is placed behind the cut mark 60 by the cutting unit 8. Cut along the edge (step S117). Here, in the present embodiment, when the rear end of the cut mark 60 on the wide paper 2 ′ reaches the cutting position of the cutting unit 8, as shown in FIG. 13, the cut mark 60 on the wide paper 2 ′. The planned cutting position in the vicinity of the rear end substantially coincides with the cutting position. Accordingly, the wide paper 2 ′ is cut by the cutting unit 8 along the planned cutting position near the rear end of the cut mark 60.

  In this way, as shown in FIG. 14, the cut is made at a position shifted from the planned cutting position near the tip of the cut mark 60 on the wide paper 2 ′, and at the planned cutting position near the rear end of the cut mark 60. The portion cut along is cut off and discarded. Here, the discarding portion 75 of the wide paper 2 ′ is composed of a region 70 on which the cut mark 60 is printed and a correction region 71 downstream of the region 70 in the transport direction. The area 70 on which the cut mark 60 is printed is rectangular. Here, the width (length in the transport direction) x of the region 70 is slightly smaller than the width 5a of the cut mark 60 (each of the upstream end portion in the transport direction and the downstream end portion in the transport direction of the cut mark 60 and the planned cutting position). Is longer). On the other hand, the correction area 71 has a substantially triangular shape. That is, since the vicinity of the left end portion of the front end of the cut mark 60 on the wide paper 2 ′ is cut at a position that hardly deviates from the planned cutting position, the left end portion of the correction area 71 has an acute angle (the width is almost zero). is there). Since the vicinity of the right end portion of the front end of the cut mark 60 on the wide paper 2 ′ is cut at a position shifted to the downstream side in the transport direction from the planned cutting position, the right end portion of the correction area 71 has a width y. Yes.

  Accordingly, the width of the left end portion of the disposal portion 75 is substantially the same width x as the width of the region 70, and the width of the right end portion thereof is the sum of the width x of the region 70 and the maximum width y of the correction region 71. The width is z. As described above, the waste portion 75 of the wide sheet 2 ′ has the substantially triangular correction area 71, so that the conveyance error due to the skew of the wide medium 2 ′ is absorbed. In the present embodiment, for the sake of explanation, the case where the skew amount of the wide paper 2 ′ is relatively large is described as an example, and therefore the maximum width y of the correction region 75 is shown large. The correction area 75 is not so large, and the maximum width y of the correction area 75 is small. In particular, as in the present embodiment, each time one cut mark 60 formed between adjacent images on the wide medium 2 ′ is detected, the skew correction amount of the wide medium 2 ′ is corrected. Therefore, the maximum width y of the correction area 75 is very small.

  Here, in the present embodiment, when the control unit 41 controls the two transport roller pairs 7a and 7b separately so that the deviation amount of the wide paper 2 ′ becomes 0, the transport roller pair 7a, Both are controlled, maintaining the state which does not stop rotation of 7b. Therefore, wrinkles can be prevented from occurring on the wide paper 2 '.

  As described above, according to the ink jet printer 1 of the present embodiment, the rear end of the cut mark 60 on the wide paper 2 ′ from the time when the cut near the front end of the cut mark 60 on the wide paper 2 ′ is performed. Until the cutting is performed in the vicinity, the skew amount of the wide medium 2 ′ gradually decreases, and the vicinity of the rear end of the cut mark 60 on the wide paper 2 ′ reaches the cutting position of the cutting unit 8. In addition, the rotational speeds of the motors 25a and 25b for driving the conveying roller pairs 7a and 7b are controlled separately so that the skew amount of the wide medium 2 ′ is almost eliminated. Therefore, when the wide medium 2 ′ is cut in the vicinity of the rear end of the cut mark 60, it is possible to prevent the wide medium 2 ′ from being cut properly. As a result, the finished quality of the wide medium 2 'on which the image is printed is improved.

  Further, each time a cut mark 60 formed between adjacent images on the wide medium 2 ′ is detected, the motor 25a that drives the pair of conveying rollers 7a and 7b so that the skew amount of the wide medium 2 ′ is eliminated. 25b is controlled, it is possible to effectively suppress the accumulation of transport errors due to the skew of the wide medium 2 ′.

  Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 15 is a diagram showing a schematic configuration of an ink jet printer according to the second embodiment of the present invention. FIG. 16 is a block diagram of a control system of the ink jet printer shown in FIG.

  The ink jet printer 101 of the second embodiment is different from the ink jet printer 1 of the first embodiment in that a slack portion is formed on the paper between the ink jet printing unit 6 and the cutting unit 8. It is a point that can be. The other configuration of the ink jet printer 101 is the same as that of the ink jet printer 1 of FIG.

  In the ink jet printer 101, as shown in FIG. 15, conveyance roller units 107 and 108 and reading sensors 10a and 10b are arranged between the ink jet printing unit 6 and the cutting unit 8 in order from the upstream side. . Here, the transport roller units 107 and 108 have the same configuration as the transport roller unit 7 of the first embodiment, and printing is performed on two sheets 2 and 3 arranged in parallel. In this case, the sheets 2 and 3 can be sandwiched and conveyed independently of each other.

  Accordingly, as shown in FIG. 16, the transport roller unit 107 includes transport roller pairs 107 a and 107 b driven by motors 125 a and 125 b controlled by the controller 20. The transport roller unit 108 includes the controller 20. The conveyance roller pairs 108a and 108b are respectively driven by motors 126a and 126b controlled by the motor.

  A space is provided between the transport roller units 107 and 108 below the paper transport path on the downstream side of the transport roller unit 107. Therefore, when the papers 2 and 3 longer than the interval between them are transported between the transport roller units 107 and 108, a slack portion of the photographic papers 2 and 3 is formed between them. Become.

  That is, for example, when the sheets 2 and 3 are nipped and conveyed by the conveyance roller units 107 and 108, the conveyance speed by the conveyance roller unit 107 is faster than the conveyance speed by the conveyance roller unit 108, or the sheet 2 3 when a portion closer to the winding parts 2a and 3a is held between and transported by the transport roller unit 107 in a state where a part of the front end side of 3 is sandwiched and held by the transport roller unit 108. A slack portion of the sheets 2 and 3 is formed between the transport roller units 107 and 108. Further, when printing is performed on the wide paper 2 ′, a slack portion of the wide paper 2 ′ can be formed between the transport roller units 107 and 108 as in the case of the paper 2 and 3.

  Therefore, according to the ink jet printer 101 of the present embodiment, the same effects as those of the ink jet printer 1 of the first embodiment can be obtained. In addition, since the slack portion of the wide paper 2 ′ can be formed between the transport roller units 107 and 108, printing within the inkjet printing unit 6 is irrelevant within the length of the slack portion of the wide paper 2 ′. In addition, the rotational speeds of the motors 125a, 125b, 126a, and 126b that drive the conveying roller pairs 107a, 107b, 108a, and 108b can be changed to correct the skew of the wide sheet 2 ′.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various design changes can be made as long as they are described in the claims. Is. For example, in the first and second embodiments described above, when the planned cutting position in the vicinity of the rear end of the cut mark 60 of the wide paper 2 ′ reaches the cutting position of the cutting unit 8, the wide paper 2 ′ is slanted. Although the case where skew correction is performed so that the line amount becomes 0 has been described, the present invention is not limited to this. Accordingly, the skew amount of the wide paper 2 ′ when the planned cutting position near the rear end of the cut mark 60 on the wide paper 2 ′ reaches the cutting position of the cutting unit 8 is the same as that of the cut mark 60 on the wide paper 2 ′. Even if skew correction is performed so that the scheduled cutting position near the leading edge is cut by the cutting unit 8 (has reached the cutting position of the cutting unit 8), it is smaller than the skew amount of the wide sheet 2 ′. Good.

  In the first and second embodiments described above, the reference for controlling the conveying roller pairs 7a and 7b based on the time difference at which the reading sensors 10a and 10b read the cut marks 60 on the wide paper 2 ′, respectively. Although the case where the deviation amount of the wide paper 2 ′ as a value is calculated has been described, the present invention is not limited to this. Accordingly, when the reading sensors 10a and 10b are not arranged at the same position with respect to the conveyance direction of the wide paper 2 ′, the distance between the reading sensors 10a and 10b in the conveyance direction of the wide paper 2 ′ and the width of the wide paper 2 ′. The shift amount of the wide paper 2 ′ may be calculated based on the time when the reading sensors 10a and 10b read the cut marks 60 on the wide paper 2 ′ in consideration of the conveyance speed.

  In the first and second embodiments described above, the skew correction of the wide medium 2 ′ is performed every time one cut mark 60 formed between the images on the wide medium 2 ′ is detected. Although the case has been described, skew correction of the wide medium 2 ′ may be performed each time a plurality of cut marks 60 formed between images on the wide medium 2 ′ are detected.

  Further, in the first and second embodiments described above, when the skew correction of the wide medium 2 ′ is performed, the control unit 41 does not stop the rotation of the two transport roller pairs 7a and 7b. However, the controller 41 may stop only one of the two transport roller pairs 7a and 7b and control only the other rotation.

  Further, in the first and second embodiments described above, the wide paper 2 ′ is transported in a state where the wide paper 2 ′ is skewed upwardly to the left with respect to the transport direction without almost deviating in the width direction of the proper transport path. However, the present invention is not limited to this, and the wide sheet 2 ′ is transported in a state where the wide sheet 2 ′ is skewed upward to the right with respect to the transport direction with almost no deviation in the width direction of the proper transport path. It is the same even if there is.

  In the first and second embodiments described above, as the cut mark 60, the white mark 61, the black mark 62, and the white mark 63 that extend in a line shape along the width direction of the wide paper 2 ′. Although the case where the marks arranged in the order of the black mark 64 and the white mark 65 are printed has been described, the present invention is not limited to this, and the configuration of the cut mark 60 can be arbitrarily changed. Therefore, even when the cut mark includes a plurality of line-shaped or belt-shaped marks, their width and the interval between two adjacent marks can be arbitrarily changed. In addition, the cut mark is not necessarily a line-shaped or belt-shaped mark, and may be a plurality of marks that are spaced apart from each other in the width direction of the wide paper 2 ′ or the width direction of the wide paper 2 ′. May be one mark extending in a line along the line.

  In the first and second embodiments described above, the case where the cut mark 60 is printed on the surface of the wide paper 2 ′ in the inkjet printing unit 6 has been described. It may be formed on the back surface of 2 ′. Moreover, it is not necessarily printed by the inkjet printing unit 6, and may be formed by a dedicated device for forming a cut mark. Therefore, the cut mark does not necessarily need to be printed, and may be composed of one or a plurality of punch holes.

  In the first and second embodiments described above, the ink jet printer 1 that prints an image on the wide paper 2 ′ by ejecting ink from the print head 11 has been described. For example, the image forming apparatus may be an image forming apparatus other than an ink jet printer, such as a photographic processing apparatus that forms an image by performing exposure processing on photographic paper as a medium. When the present invention is applied to a photographic processing apparatus, the exposure method may be an analog exposure method or a digital exposure method, and the same effects as in the present embodiment can be obtained. it can. Further, in the case of a photographic processing apparatus that forms an image by performing exposure processing on photographic paper, even if a cut mark is formed together with the image, the cut mark is detected by a sensor before development processing is performed. In this case, the cutting unit is preferably arranged at a position where the developed photographic paper can be cut.

1 is a diagram illustrating a schematic configuration of an ink jet printer according to a first embodiment of the present invention. FIG. 4 is a partial schematic top view of an ink jet printer when printing is performed on two sheets arranged in parallel. It is a block diagram about the control system of the ink jet printer of FIG. It is a figure which shows schematic structure of the cut mark printed on a wide paper. It is a figure which shows the density change of the cut mark shown in FIG. FIG. 4 is a partial schematic top view of an ink jet printer when printing is performed on a wide sheet. 6 is a flowchart illustrating a skew correction procedure when printing is performed on a wide sheet. It is a figure for demonstrating the operation | movement of skew correction when printing is performed with respect to a wide paper. It is a figure for demonstrating the operation | movement of skew correction when printing is performed with respect to a wide paper. It is a figure for demonstrating the operation | movement of skew correction when printing is performed with respect to a wide paper. It is a figure for demonstrating the operation | movement of skew correction when printing is performed with respect to a wide paper. It is a figure for demonstrating the operation | movement of skew correction when printing is performed with respect to a wide paper. It is a figure for demonstrating the operation | movement of skew correction when printing is performed with respect to a wide paper. It is a figure for demonstrating the operation | movement of skew correction when printing is performed with respect to a wide paper. It is a figure which shows schematic structure of the inkjet printer which concerns on the 2nd Embodiment of this invention. FIG. 16 is a block diagram of a control system of the ink jet printer of FIG. 15.

Explanation of symbols

1, 101 Inkjet printer (image forming apparatus)
2, 3 paper (medium)
2 'Wide paper (wide media)
7 Conveying roller unit 7a Conveying roller pair (first conveying member)
7b Conveying roller pair (second conveying member)
8 Cutting unit (cutter)
10a Reading sensor (first sensor)
10b Reading sensor (second sensor)
20 controller 41 control unit (cutter control means; conveyance control means)
42 Deviation amount calculation unit (reference value calculation means)
43 motor drive calculation unit 45 cut mark determination unit 46 detection time storage unit 50 image 60 cut mark (first cut mark; second cut mark)
108 Conveying roller unit 108a Conveying roller pair (first conveying member)
108b Conveying roller pair (second conveying member)

Claims (4)

First and second transport members that are parallel to the transport direction of the medium and that are driven independently of each other to transport the medium;
A cutter that is disposed on the downstream side in the transport direction with respect to the first and second transport members and is capable of cutting a wide medium having a width straddling the first and second transport members;
A first sensor that detects a first cut mark formed on the wide medium on the wide medium conveyance path corresponding to the first conveyance member and upstream of the cutter in the conveyance direction;
It is formed on the wide medium on the wide medium conveyance path corresponding to the second conveyance member and upstream of the cutter in the conveyance direction, and is the same as the first cut mark in the width direction of the wide medium. A second sensor for detecting a second cut mark at a position;
To control the first and second transport members based on the time when the first sensor detects the first cut mark and the time when the second sensor detects the second cut mark. A reference value calculating means for calculating the reference value of
Cutter control means for controlling the cutter so that the wide medium is cut at two positions sandwiching the first cut mark based on the time when the first sensor detects the first cut mark;
Based on the reference value calculated by the reference value calculation means, the wide medium on the upstream side of the first cut mark from the time when the cutter cuts the wide medium on the downstream side of the first cut mark. And a conveyance control means for controlling the conveyance amount of the wide medium by the first and second conveyance members up to the time of cutting the sheet so that the skew feeding amount of the wide medium becomes small. Medium transport device.   2. The conveyance control unit according to claim 1, wherein the conveyance control unit controls the conveyance amount of the wide medium by the first and second conveyance members each time the first and second cut marks are detected. Medium transport device. The medium conveying device according to claim 1 or 2,
An image forming apparatus comprising: an image forming unit disposed upstream of the first and second transport members in the transport direction. 4. The medium according to claim 3, wherein the first and second transport members transport the medium such that a slack portion of the medium is formed on the upstream side in the transport direction with respect to the first and second transport members. The image forming apparatus described in 1.

Images