Printing device and method for conveying printing medium

Abstract

A steering roller 51 (rollers 422, 475) is configured from a concave roller. Additionally, in a conveyance direction Dc, concave rollers 431, 432, 442, 444, 453 are furthermore provided between the steering roller 422 and a color printing part 32 on the downstream side of the steering roller 422. Similarly, in the conveyance direction Dc, concave rollers 476, 477 are furthermore provided between the steering roller 475 and a white printing part 33 on the downstream side of the steering roller 475.

Description

Printing device and print medium transport method

[0001] The present invention relates to a technique for transporting a print medium to a printing unit on which printing is performed by the printing unit.

[0002] Japanese Patent Application Laid-Open Nos. 2005-209499 and 2006-107093 disclose a printing device in which a printing unit prints on a print medium by ejecting ink using an inkjet method onto the print medium as it is transported in a transport direction by a transport unit. In such a printing device, if the print medium is transported in a meandering manner relative to the printing unit, printing cannot be performed in the correct position on the print medium.

[0003] JP 2019-55570 A JP 2016-43482 A

[0004] One solution is to use a steering roller that swings around a predetermined swing center. In other words, swinging the steering roller that comes into contact with the print medium can prevent the print medium from meandering relative to the printing unit. However, while this type of steering roller is effective in preventing the print medium from meandering, it can also cause wrinkles in the print medium in the transport direction.

[0005] The present invention has been made in consideration of the above-mentioned problems, and has an object to make it possible to suppress the occurrence of wrinkles in the print medium while suppressing meandering of the print medium relative to the print unit.

[0006] A printing device according to the present invention comprises a transport unit that transports a print medium along a transport direction, and a printing unit that prints on the print medium transported by the transport unit; the transport unit has a meandering correction unit that corrects meandering of the print medium at a correction position upstream in the transport direction from a printing position where the printing unit prints on the print medium, and a downstream roller having a contact surface that contacts the print medium between the printing position and the correction position; the meandering correction unit has a steering roller having a contact surface that contacts the print medium at the correction position, and a steering drive unit that oscillates the steering roller around a predetermined oscillation center; and the downstream roller and steering roller are concave rollers having regions on their contact surfaces where the diameter increases toward the ends.

[0007] A print medium transport method according to the present invention comprises the steps of transporting a print medium along a transport direction by a transport unit, and printing by a printing unit on the print medium transported by the transport unit, wherein the transport unit has a meandering correction unit that corrects meandering of the print medium at a correction position upstream in the transport direction from a printing position where the printing unit prints on the print medium, and a downstream roller having a contact surface that contacts the print medium between the printing position and the correction position, and the meandering correction unit has a steering roller having a contact surface that contacts the print medium at the correction position, and a steering drive unit that oscillates the steering roller around a predetermined oscillation center, and each of the downstream roller and the steering roller is a concave roller having an area formed on each contact surface where the diameter increases toward the end.

[0008] In the present invention (printing device, print medium transport method) configured in this manner, the steering roller is a concave roller. Therefore, the steering roller is oscillated to suppress meandering of the print medium, while the occurrence of wrinkles due to the oscillation of the steering roller can be suppressed by the steering roller, which is also a concave roller. In addition, a further concave roller is provided between the steering roller and the printing unit. Therefore, the print medium with suppressed wrinkles can be accurately transported from the steering roller to the printing unit. As a result, it is possible to suppress the occurrence of wrinkles in the print medium while suppressing meandering of the print medium relative to the printing unit.

[0009] The printing device may also be configured so that the transport unit further includes a direction-changing roller that contacts the print medium upstream of the correction position in the transport direction, and the angle of the contact area of ​​the direction-changing roller with the print medium around the center of the direction-changing roller is 35 degrees or more. Using a direction-changing roller that wraps the print medium around a wrap angle of 35 degrees or more in this way allows for a compact print medium transport path. However, a large frictional force is generated between the direction-changing roller and the print medium with such a large wrap angle. Therefore, it is conceivable that the print medium's ability to follow the oscillation of the steering roller may be reduced.

[0010] Therefore, the printing device may be configured so that the direction-changing roller is positioned upstream of the correction position in the transport direction, at a distance of at least 2.5 times the width of the print medium. By separating the direction-changing roller from the steering roller by a distance of at least 2.5 times the width of the print medium in this way, it is possible to prevent a decrease in the ability of the print medium to follow the oscillation of the steering roller.

[0011] The transport unit may further include a proximity roller that contacts the print medium and is positioned in the transport direction at a distance equal to or less than the width of the print medium from the position where the direction-changing roller contacts the print medium, and the proximity roller may be a concave roller whose contact surface contacts the print medium has an area whose diameter increases toward the edge. With this configuration, the wrap angle required to change the direction of the print medium can be distributed between the direction-changing roller and the proximity roller positioned adjacent to the direction-changing roller. Therefore, the wrap angle of the print medium around the direction-changing roller can be minimized, preventing the print medium from losing track of the oscillation of the steering roller.

[0012] In this case, the proximity roller may be located upstream of the direction-changing roller in the transport direction, and the angle formed by the area where the direction-changing roller contacts the print medium around the center of the direction-changing roller may be larger than the angle formed by the area where the proximity roller contacts the print medium around the center of the proximity roller.

[0013] The direction-changing roller may have a variety of specific configurations. For example, the direction-changing roller may be a concave roller, in which the peripheral surface that contacts the print medium has an area with a diameter that increases toward the edge, or a straight roller, in which the peripheral surface that contacts the print medium has a uniform diameter.

[0014] The printing device may also be configured so that the angle formed by the contact area of ​​the steering roller with the print medium around the center of the steering roller is greater than the angle formed by the contact area of ​​the direction-changing roller with the print medium around the center of the direction-changing roller, thereby preventing a decrease in the print medium's ability to follow the oscillation of the steering roller.

[0015] The printing device may also be configured to further include an upstream printing unit that prints on the print medium upstream of the printing unit in the transport direction, the correction position being located between the upstream printing position where the upstream printing unit prints on the print medium and the printing position in the transport direction, and the transport unit further including a direction-changing roller that contacts the print medium between the correction position and the upstream printing position in the transport direction, and the angle of the contact range of the direction-changing roller with the print medium around the center of the direction-changing roller being 85 degrees or more. In this configuration, by providing a direction-changing roller with a wrap angle of 85 degrees or more between the upstream printing unit and the printing unit, the transport path of the print medium from the upstream printing unit to the printing unit can be configured compactly. Furthermore, at least two concave rollers contact the print medium between the direction-changing roller and the printing unit. Therefore, even if wrinkles occur in the print medium due to the influence of the direction-changing roller, the wrinkles can be suppressed before the print medium is transported to the printing unit.

[0016] As described above, according to the present invention, it is possible to suppress the occurrence of wrinkles in the print medium while suppressing meandering of the print medium relative to the print section.

[0017] 1 is a front view showing a schematic representation of a printing device according to the present invention. FIG. 2 is a diagram showing a schematic representation of the relationship between the rollers provided in the printing device of FIG. 1 and the printing medium. FIG. 3 is a diagram showing a schematic representation of the relationship between the rollers provided in the printing device of FIG. 1 and the printing medium. FIG. 4 is a diagram showing a schematic representation of the relationship between the rollers provided in the printing device of FIG. 1 and the printing medium. FIG. 5 is a diagram showing a schematic representation of the mechanical configuration of a meandering correction unit provided in the printing device. FIG. 6 is a block diagram showing the electrical configuration of the meandering correction unit of FIG. 3. FIG. 7 is a diagram showing a schematic representation of an example of a concave roller. FIG. 8 is a diagram showing a schematic representation of an example of a concave roller.

[0018] Fig. 1 is a front view showing a schematic diagram of a printing device according to the present invention. Fig. 1 shows a horizontal direction X and a vertical direction Z, as well as one side X1 and the other side X2 of the horizontal direction X. The printing device 3 includes a housing 31, a color printing unit 32 disposed within the housing 31, a white printing unit 33 disposed above the color printing unit 32 within the housing 31, and a transport unit 4 that transports a print medium M using a plurality of rollers disposed within the housing 31.

[0019] The color printing unit 32 prints on the surface M1 of the print medium M, which passes the printing position P32 as the transport unit 4 transports it. The color printing unit 32 has multiple (six) head units 321 arranged along the print medium M above the print medium M at the printing position P32. Each of the multiple head units 321 is a line-type inkjet head having a horizontal length corresponding to the width of the print medium M. Each of the multiple head units 321 has a nozzle row consisting of multiple nozzles that face the surface M1 of the print medium M passing below it from above, and ejects different color inks from the nozzles using an inkjet method. Here, color ink refers to ink other than white, and includes inks such as cyan, magenta, yellow, black, orange, and blue. In this way, the multiple head units 321 of the color printing unit 32 print a color image on the surface M1 of the print medium M by ejecting color inks from above onto the surface M1 of the print medium M passing the printing position P32.

[0020] The white printing unit 33 also prints on the surface M1 of the printing medium M that passes the printing position P33 as it is transported by the transport unit 4. The white printing unit 33 has one or more head units 331 arranged above the printing medium M at the printing position P33. The head unit 331 is a line-type inkjet head having a lateral width corresponding to the width of the printing medium M. The head unit 331 has a nozzle row consisting of multiple nozzles that face the surface M1 of the printing medium M that passes below it from above, and ejects white ink from the nozzles using an inkjet method. In this way, the head unit 331 of the white printing unit 33 prints a white image on the surface M1 of the printing medium M by ejecting white ink from above onto the surface M1 of the printing medium M that passes the printing position P33.

[0021] An inlet 311 opens in the side wall on the other side X2 of the housing 31, while an outlet 312 opens in the side wall on the one side X1 of the housing 31. The transport unit 4 transports the printing medium M along a transport direction Dc from the inlet 311 to the outlet 312, passing through the color printing unit 32 and the white printing unit 33.

[0022] The transport unit 4 has an entrance unit 41 provided below the color printing unit 32, an ascending transport unit 42 provided on one side X1 of the color printing unit 32, an upward transport unit 43 provided above the color printing unit 32, a descending transport unit 44 provided on the other side X2 of the color printing unit 32, and an introduction transport unit 45 provided on the other side X2 of the color printing unit 32. The entrance unit 41, the ascending transport unit 42, the upward transport unit 43, the descending transport unit 44, and the introduction transport unit 45 transport the printing medium M along the transport direction Dc from the entrance 311 toward the color printing unit 32.

[0023] The carry-in unit 41 has a plurality of rollers 411, 412, 413 arranged in order along the conveyance direction Dc facing one side X1, and conveys the printing medium M carried in through the carry-in entrance 311 to the one side X1 by the rollers 411, 412, 413. The upward conveyance unit 42 has a plurality of rollers 421, 422 arranged in order along the conveyance direction Dc facing upward, and conveys the printing medium M conveyed by the carry-in unit 41 upward by the rollers 421, 422. The upward conveyance unit 43 has a plurality of rollers 431, 432 arranged in order along the conveyance direction Dc facing the other side X2, and conveys the printing medium M conveyed by the upward conveyance unit 42 to the other side X2 by the rollers 431, 432. The downward transport unit 44 has a plurality of rollers 441, 442, 443, and 444 arranged in order along the transport direction Dc facing downward, and transports the printing medium M transported by the upward transport unit 43 downward by the rollers 441, 442, 443, and 444. The introduction transport unit 45 has a plurality of rollers 451, 452, and 453 arranged in order along the transport direction Dc facing one side X1, and transports the printing medium M transported by the downward transport unit 44 to one side X1 by the rollers 451, 452, and 453. In this way, the printing medium M reaches the printing position P32 where the color printing unit 32 prints on the surface M1 of the printing medium M.

[0024] Furthermore, the transport unit 4 has a color transport unit 46 that supports the print medium M from below at the printing position P32 facing the color printing unit 32, and the print medium M that has passed through the introduction transport unit 45 enters the color transport unit 46. This color transport unit 46 has a plurality of rollers 461 arranged from the other side X2 to the one side X1, and each roller 461 contacts the back surface M2 of the print medium M from below. In this way, the front surface M1 of the print medium M supported at the printing position P32 by the color transport unit 46 faces upward, and each head unit 321 of the color printing unit 32 ejects color ink while facing the front surface M1 of the print medium M from above at the printing position P32.

[0025] Furthermore, the transport unit 4 has a reverse transport unit 47 that turns upside down twice the printing medium M transported from the color transport unit 46 to one side X1. This reverse transport unit 47 has multiple rollers 471-479 arranged in order along the transport direction Dc from printing position P32 to printing position P33, and transports the printing medium M transported from printing position P32 to one side X1 by the color printing unit 32 toward printing position P33 using the rollers 471-479. In particular, the rollers 471-477 of the reverse transport unit 47 turn upside down the printing medium M twice while contacting the back surface M2 of the printing medium M. In other words, the reverse transport unit 47 transports the printing medium M transported from the color transport unit 46 downward using the rollers 471 and 472, and then changes the traveling direction of the printing medium M to the other side X2 using the roller 472 and transports it, thereby turning upside down the front surface M1 and back surface M2 of the printing medium M. Next, the reverse transport unit 47 transports the printing medium M from one side X1 to the other side X2 using multiple rollers 473, 474, and then transports the printing medium M upward using rollers 475 to 478. Furthermore, the reverse transport unit 47 changes the traveling direction of the printing medium M to one side X1 using roller 478, thereby again inverting the front surface M1 and back surface M2 of the printing medium M upside down, and transports the printing medium M toward printing position P33 using roller 479. In this way, the transport unit 4 transports the printing medium M from printing position P32 to printing position P33 while inverting the printing medium M upside down twice.

[0026] The transport unit 4 also has a white transport unit 48 that supports from below the printing medium M at the printing position P33 opposite the white printing unit 33, and the printing medium M that has been inverted twice upside down by the reversing transport unit 47 enters the white transport unit 48. This white transport unit 48 has a roller 481 that contacts the back surface M2 of the printing medium M from below. In this way, the front surface M1 of the printing medium M supported at the printing position P33 by the white transport unit 48 faces upward, and the head unit 331 of the white printing unit 33 ejects white ink while facing the front surface M1 of the printing medium M from above at the printing position P33.

[0027] The transport unit 4 also has an unloading unit 49 located above the upper transport unit 43. The unloading unit 49 has a plurality of rollers 491 to 493 arranged in order on one side X1, and each of the rollers 491 to 493 contacts the back surface M2 of the print medium M from below. The unloading unit 49 transports the print medium M transported by the white transport unit 48 to one side X1 using the plurality of rollers 491 to 493, thereby unloading the print medium M from the unloading opening 312 of the housing 31.

[0028] Of the rollers included in the transport unit 4, rollers 451, 471, and 491 are drive rollers that drive the print medium M in the transport direction Dc. Rollers 421 and 472 (direction-changing rollers) are straight rollers that contact the print medium M with a circumferential surface having a uniform diameter regardless of position in the width direction (in other words, the direction in which the central axes of rollers 421 and 472 extend). Rollers 413, 422, 431, 432, 442, 444, 453, 474, 475, 476, and 477 are concave rollers. The specific configuration of the concave rollers will be described later.

[0029] 2A to 2D are diagrams showing the relationship between the rollers and the print medium M provided in the printing apparatus of Fig. 1. Next, the relationship between each roller and the print medium M will be explained using these diagrams.

[0030] As shown in Figure 2A, the print medium M that comes into contact with the roller 421 curves along the shape of the roller 421 and is wound around the roller 421. As a result, the roller 421 wraps the print medium M at a wrap angle θ421. Here, the wrap angle is the angle formed around the center of the roller by the contact area of ​​the roller where the roller comes into contact with the print medium, and corresponds to the angle formed around the center of the roller between both ends of the contact area in the transport direction Dc. This is also true for any roller other than the roller 421. The roller 421 is a large wrap angle roller with a wrap angle θ421 of 35 degrees or more.

[0031] The roller 413 adjacent to the roller 421 on the upstream side of the roller 421 in the transport direction Dc wraps the print medium M at a wrap angle θ413. The wrap angle θ413 is smaller than the wrap angle θ421. For example, the wrap angle θ421 is approximately 70 degrees, and the wrap angle θ413 is approximately 20 degrees. The length L1 of the print medium M transported by the transport unit 4 from the roller 413 to the roller 421 is less than the width W ( FIG. 3 ) of the print medium M. Here, the length of the print medium M between the two rollers 413 and 421 is the length of the print medium M between the downstream end of the contact area where the upstream roller 413 contacts the print medium M in the transport direction Dc and the upstream end of the contact area where the downstream roller 421 contacts the print medium M. This is the same for any two rollers.

[0032] As described above, the printing medium M passes through roller 413 and roller 421 in order and then reaches roller 422. As shown in FIG. 2B , roller 422 wraps the printing medium M at a wrap angle θ422. The wrap angle θ422 is greater than the wrap angle θ421. As will be described later, this roller 422 is a steering roller, and the range of the wrap angle θ422 at which roller 422 contacts the printing medium M corresponds to a correction position P422 at which the steering roller corrects the meandering of the printing medium M. The length L2 ( FIG. 1 ) of the printing medium M from roller 421 to roller 422 is longer than a predetermined roller span Re extending upstream from the correction position P422 in the transport direction Dc. The starting point of this roller span Re is the upstream end of the correction position P422 in the transport direction Dc. The roller span Re is the range between the steering roller and the large wrap angle roller, and no large wrap angle roller is disposed within the roller span Re. In other words, there are no rollers with a large wrap angle in the roller span Re. The length of the roller span Re is at least 2.5 times the width W of the print medium M. Note that there is no restriction on rollers with a wrap angle of less than 35 degrees being placed in the roller span Re.

[0033] As shown in FIG. 2C , roller 472 wraps around printing medium M at wrapping angle θ472. Roller 472 is a large wrapping angle roller with a wrapping angle θ472 of 35 degrees or more. In this example in particular, wrapping angle θ472 is 85 degrees or more. As described above, printing medium M that has passed roller 472 passes through rollers 473 and 474 before reaching roller 475. As shown in FIG. 2D , roller 475 wraps around printing medium M at wrapping angle θ475. Wrapping angle θ475 is larger than wrapping angle θ472. As will be described later, roller 475 is a steering roller, and the range of wrapping angle θ475 in which roller 475 contacts printing medium M corresponds to correction position P475 where the steering roller corrects meandering of printing medium M. The length L3 (FIG. 1) of the print medium M from roller 472 to roller 475 is longer than the predetermined roller span Re provided upstream from correction position P475 in the transport direction Dc. This roller span Re is as described above. Note that because the wrap angle of roller 474 is less than 35 degrees, there is no restriction on roller 474 being positioned within the roller span Re.

[0034] As described above, rollers 422 and 475 are steering rollers that correct meandering of print medium M based on the position in the width direction (the direction perpendicular to the plane of the paper in FIG. 1 ) of print medium M. In other words, an edge sensor Se that detects the position of the edge in the width direction of print medium M is provided for each of rollers 422 and 475 (the edge sensor Se is preferably provided downstream of rollers 422 and 475 in the transport direction Dc), and each of rollers 422 and 475 corrects meandering of print medium M by displacing by an angle according to the detection result of the corresponding edge sensor Se.

[0035] Fig. 3A is a perspective view showing a schematic overview of the mechanical configuration of the meandering correction unit 5 provided in the printing device, Fig. 3B is an elevation view showing a schematic overview of the mechanical configuration of the meandering correction unit provided in the printing device, and Fig. 4 is a block diagram showing the electrical configuration of the meandering correction unit of Fig. 3. The meandering correction unit 5 of Figs. 3A and 3B uses a so-called end pivot method to correct meandering of the printing medium M. Fig. 3 shows the width W of the printing medium M, in other words, the dimensions of the printing medium M in the width direction Dw.

[0036] As shown in FIG. 3A , the meandering correction unit 5 is a device that corrects meandering of the printing medium M while converting the transport direction of the printing medium M from a first transport direction Dc1 to a second transport direction Dc2. The first transport direction Dc1 is, for example, a horizontal direction, and the second transport direction Dc2 is, for example, a vertically upward direction, but is not limited thereto. The meandering correction unit 5 mainly includes a steering roller 51 around which the printing medium M is wound and which rotates about a central axis A51, an edge sensor Se that detects the edge of the printing medium M, and a swing mechanism 52 that swings the steering roller 51. When the swing mechanism 52 swings the steering roller 51 in response to the output of the edge sensor Se, the steering roller 51 swings around a swing center C51 located upstream in the first transport direction Dc1.

[0037] A more detailed mechanical configuration of the meandering correction unit 5 will be described with reference to Fig. 3B, which is a bottom view of the meandering correction unit 5 as seen from the direction of arrow A in Fig. 3A.

[0038] The meandering correction unit 5 has a steering roller 51, which comes into contact with the printing medium M at correction position P5. The rollers 422 and 475 described above each correspond to the steering roller 51 of the meandering correction unit 5. This steering roller 51 is a concave roller. Furthermore, the meandering correction unit 5 has an edge sensor Se (not shown in FIG. 3B ) that detects the position of the edge of the printing medium M in the width direction Dw, downstream of the steering roller 51 in the transport direction Dc. Here, the width direction Dw is perpendicular to the transport direction Dc and corresponds to the width direction of the printing medium M.

[0039] The meandering correction unit 5 has a swing mechanism 52 that swings the steering roller 51 around a swing center C51. The swing mechanism 52 has a pair of bearings 53 that support both ends of the steering roller 51, and a frame 54 that supports the bearings 53. The pair of bearings 53 support the steering roller 51 rotatably around the central axis A51 of the steering roller 51. The frame 54 has a base plate 541 that is arranged parallel to the steering roller 51, and a pair of support plates 542 that protrude from both ends of the base plate 541 toward the steering roller 51, and the pair of bearings 53 are respectively attached to the pair of support plates 542.

[0040] Furthermore, the swing mechanism 52 has a pair of rollers 551 and a pair of stays 552 that respectively support the pair of rollers 551, and each roller 551 is rotatable about a rotation axis perpendicular to the central axis A51. Furthermore, the swing mechanism 52 has a pair of roller supports 56 that respectively support the pair of rollers 551. The roller support 56 has a slope plate 561 that abuts against the peripheral surface of the roller 551, and a support plate 562 that protrudes from the slope plate 561 toward the roller 551 and supports the roller 551. The pair of slope plates 561 are inclined in opposite directions to each other, and the pair of rollers 551 move along the slope of the pair of slope plates 561 that abut against them.

[0041] The swing mechanism 52 also has a frame 57, which has a base plate 571 parallel to the width direction Dw. A pair of stays 573 protrude from the base plate 571 toward the pair of roller supports 56, and the pair of roller supports 56 are respectively attached to the pair of stays 573. In this way, the pair of roller supports 56 are supported by the base plate 571. The frame 57 also has a support plate 572 protruding from one end of the base plate 571 in the conveying direction Dc, and the support plate 572 faces the support plate 542 of the frame 54 from the outside in the width direction Dw.

[0042] The swing mechanism 52 also has an actuator 58 that swings the frame 54 relative to the frame 57. The actuator 58 is provided between the support plate 572 and the support plate 542 in the width direction Dw and is connected to them. The actuator 58 is a cylinder that swings the frame 54 by extending and contracting a rod 581. Driving the actuator 58 causes the steering roller 51 to swing around a swing center C51.

[0043] The end pivot type meandering correction unit 5 shown in FIG. 3 has the advantage that it can be easily configured by simply attaching a swing mechanism 52 to the roller of an existing printing device.

[0044] 4, the meandering correction unit 5 has a control unit 59. This control unit 59 is a processor such as a CPU (Central Processing Unit), and adjusts the angle at which the steering roller 51 swings around the swing center C51 in accordance with the position of the edge of the printing medium M detected by the edge sensor Se, thereby adjusting the position in the width direction Dw of the printing medium M being transported by the steering roller 51. This corrects the meandering of the printing medium M.

[0045] As described above, concave rollers are used in the conveying unit 4. Next, the configuration of the concave rollers will be described. Figures 5A to 5C are diagrams that schematically show examples of concave rollers.

[0046] The concave roller 61 in Fig. 5A is rotatable around the center line A61, with both ends 611 in the direction of the center line A61 of the concave roller 61 (in other words, the width direction Dw) supported by bearings. The concave roller 61 has a circumferential surface (contact surface) 612 with which the print medium M comes into contact between the ends 611. The diameter DI of the concave roller 61 changes depending on the position. In other words, a concave shape in which the diameter DI increases from the center of the concave roller 61 to the end 611 along the center line A61 is provided over the entire circumferential surface 612 of the concave roller 61. The circumferential surface 612 having such a concave shape comes into contact with the print medium M. In this way, the circumferential surface (contact surface) 612 of the concave roller 61 has a region in which the diameter increases toward the end.

[0047] The concave roller 62 in FIG. 5B is rotatable around the center line A62, with both ends 621 of the concave roller 62 in the direction of the center line A62 (in other words, the width direction Dw) supported by bearings. The concave roller 62 has a circumferential surface (contact surface) 622 that comes into contact with the print medium M between the ends 621. The diameter DI of the concave roller 62 changes depending on the position. In particular, the circumferential surface 622 of the concave roller 62 has a central straight region 622A and concave regions 622B on both sides of the straight region 622A. The straight region 622A has a straight shape with a constant diameter DI regardless of the position in the direction of the center line A62. The concave region 622B has a concave shape with a diameter DI that increases from the center of the concave roller 62 toward the end 621 along the center line A62. The peripheral surface 622 having such a straight shape and a concave shape comes into contact with the print medium M. In this manner, the peripheral surface (contact surface) 622 of the concave roller 62 has a region (concave region 622B) whose diameter increases toward the end.

[0048] The concave roller 63 in FIG. 5C is rotatable around the center line A63, with both ends 631 of the concave roller 63 in the direction of the center line A63 (in other words, the width direction Dw) supported by bearings. The concave roller 63 has a circumferential surface 632 (contact surface) that comes into contact with the print medium M between the ends 631. The diameter DI of the concave roller 63 varies with position. In particular, the circumferential surface 632 of the concave roller 63 has a central straight region 632A, concave regions 632B on both sides of the straight region 632A, and straight regions 632C on both sides of each concave region 632B. The straight region 632A has a straight shape with a constant diameter DI regardless of position in the direction of the center line A63. The concave region 632B has a concave shape with a diameter DI that increases from the center of the concave roller 63 toward the end 631 along the center line A63. The straight region 632C has a straight shape with a constant diameter DI regardless of the position in the direction of the center line A63. The circumferential surface 632 having such a straight shape, concave shape, and straight shape comes into contact with the print medium M. In this way, a region (concave region 632B) whose diameter increases toward the end is formed on the circumferential surface 632 of the concave roller 63.

[0049] In the embodiment described above, the steering roller 51 (roller 422, 475) is configured as a concave roller 61, 62, or 63. Therefore, the steering roller 51 is oscillated to suppress meandering of the print medium M, and the steering roller 51, which is also a concave roller, can suppress the occurrence of wrinkles due to the oscillation of the steering roller 51. Furthermore, concave rollers 431, 432, 442, 444, and 453 are further provided between the steering roller 422 and the color printing unit 32 downstream of the steering roller 422 (in other words, printing position P32) in the transport direction Dc. Similarly, concave rollers 476 and 477 are further provided between the steering roller 475 and the white printing unit 33 downstream of the steering roller 475 (in other words, printing position P33) in the transport direction Dc. Therefore, the print medium M with reduced wrinkles can be accurately transported from the steering roller 422 to the color print section 32, and from the steering roller 475 to the white print section 33. As a result, it is possible to suppress the occurrence of wrinkles in the print medium M while suppressing meandering of the print medium M relative to each of the color print section 32 and the white print section 33.

[0050] The transport unit 4 also has a roller 421 (direction-changing roller) that contacts the print medium M upstream of the correction position P422 in the transport direction Dc, and the wrap angle θ421 formed by the contact area of ​​the roller 421 with the print medium M around the center of the roller 421 is 35 degrees or greater. The transport unit 4 also has a roller 472 (direction-changing roller) that contacts the print medium M upstream of the correction position P475 in the transport direction Dc, and the wrap angle θ472 formed by the contact area of ​​the roller 472 with the print medium M around the center of the roller 472 is 35 degrees or greater. By using rollers 421 and 472 that wrap the print medium M around a wrap angle of 35 degrees or greater in this way, the transport path for the print medium M can be configured compactly. However, a large frictional force is generated between the rollers 421 and 472 and the print medium M due to such a large wrap angle. Therefore, it is conceivable that the ability of the print medium M to follow the oscillation of the rollers 422 and 475, which are steering rollers, may decrease.

[0051] Therefore, roller 421 (direction changing roller) is positioned upstream of correction position P422 in the transport direction Dc, at a distance from correction position P422 that is at least 2.5 times the width W of print medium M. By separating roller 421 from roller 422 (steering roller) by a length at least 2.5 times the width W of print medium M in this way, it is possible to suppress a decrease in the ability of print medium M to follow the oscillation of roller 422.

[0052] Similarly, roller 472 (direction changing roller) is positioned upstream of correction position P475 in the transport direction Dc, at a distance from correction position P475 that is at least 2.5 times the width W of print medium M. By separating roller 472 from roller 475 (steering roller) by a length at least 2.5 times the width W of print medium M in this way, it is possible to suppress a decrease in the ability of print medium M to follow the oscillation of roller 475.

[0053] The transport unit 4 also includes a roller 413 (proximity roller) that contacts the print medium M and is positioned at a distance (length L1) equal to or less than the width W of the print medium M from the position (range of wrap angle θ421) where the roller 421 (direction changing roller) contacts the print medium M in the transport direction Dc. The roller 413 is a concave roller that contacts the print medium M with a peripheral surface having an area where the diameter DI increases toward the edge. With this configuration, the wrap angle required to change the direction of the print medium M can be distributed between the roller 421 (direction changing roller) and the roller 413 that is positioned proximate to the roller 421. Therefore, the wrap angle of the print medium M around the roller 421 can be minimized, preventing a decrease in the ability of the print medium M to follow the oscillation of the roller 422.

[0054] Furthermore, the wrap angle θ422 formed around the center of the roller 422 by the contact area of ​​the roller 422 (steering roller) with the printing medium M is greater than the wrap angle θ421 formed around the center of the roller 421 by the contact area of ​​the roller 421 (direction changing roller) with the printing medium M. This makes it possible to prevent a decrease in the ability of the printing medium M to follow the oscillation of the roller 422.

[0055] Similarly, the wrap angle θ475 formed around the center of the roller 475 by the contact area of ​​the roller 475 (steering roller) with the printing medium M is greater than the wrap angle θ472 formed around the center of the roller 472 by the contact area of ​​the roller 472 (direction changing roller) with the printing medium M. This makes it possible to prevent a decrease in the ability of the printing medium M to follow the oscillation of the roller 475.

[0056] The transport unit 4 also includes a white printing unit 33 (printing unit) and a color printing unit 32 (upstream printing unit) that prints on the print medium M upstream of the white printing unit 33 in the transport direction Dc. The correction position P475 is located between the printing position P32 where the color printing unit 32 prints on the print medium M and the printing position P33 where the white printing unit 33 prints on the print medium M in the transport direction Dc. The transport unit 4 also includes a roller 472 (direction-changing roller) that contacts the print medium M between the printing position P33 and the printing position P32 in the transport direction Dc. In particular, the wrap angle θ472 formed around the center of the roller 472 by the contact range of the roller 472 with the print medium M is 85 degrees or more. In this configuration, by providing the roller 472 with a wrap angle θ472 of 85 degrees or more between the color printing unit 32 and the white printing unit 33, the transport direction Dc of the print medium M from the color printing unit 32 to the white printing unit 33 can be made compact. Furthermore, at least two concave rollers (roller 475 and concave rollers 476, 477) come into contact with the print medium M between roller 472 and the white print section 33. Therefore, even if wrinkles occur in the print medium M due to the influence of roller 472, the wrinkles can be suppressed before the print medium M is transported to the white print section 33.

[0057] In the embodiment described above, the printing medium M corresponds to an example of the "printing medium" of the present invention, the conveying direction Dc corresponds to an example of the "conveying direction" of the present invention, the conveying unit 4 corresponds to an example of the "conveying unit" of the present invention, the color printing unit 32 or the white printing unit 33 corresponds to an example of the "printing unit" of the present invention, the printing position P32 or the printing position P33 corresponds to an example of the "printing position" of the present invention, the meandering correction unit 5 corresponds to an example of the "meandering correction unit" of the present invention, and the rollers 431, 432, 442, 444, 453 or the rollers 476, 477 are examples of the "downstream rollers" of the present invention. the steering roller 51 (i.e., roller 422, roller 475) corresponds to an example of the "steering roller" of the present invention, the swinging mechanism 52 corresponds to an example of the "steering drive unit" of the present invention, the printing device 3 corresponds to an example of the "printing device" of the present invention, roller 421 or roller 472 corresponds to an example of the "direction changing roller" of the present invention, roller 413 corresponds to an example of the "proximity roller" of the present invention, the color printing unit 32 corresponds to an example of the "upstream printing unit" of the present invention, and the printing position P32 corresponds to an example of the "upstream printing position" of the present invention.

[0058] The present invention is not limited to the above-described embodiment, and various modifications other than those described above are possible without departing from the spirit of the present invention. For example, the specific configuration of the concave roller is not limited to the concave rollers 61, 62, or 63. In other words, various rollers having a concave shape can be used as the concave roller.

[0059] For example, it is not necessary for all of rollers 431, 432, 442, 444, and 453 to be concave rollers. Similarly, it is not necessary for all of rollers 476 and 477 to be concave rollers.

[0060] Furthermore, the positional relationship between the roller 413 (proximity roller) and the roller 421 (direction changing roller) is not limited to the above example. That is, the roller 413 may be disposed downstream of the roller 421 in the conveyance direction Dc.

[0061] Furthermore, the magnitude relationship between the wrap angle θ422 of the roller 422 and the wrap angle θ421 of the roller 421 can also be arbitrary. Therefore, the wrap angle θ422 and the wrap angle θ421 may be equal, or the wrap angle θ422 may be smaller than the wrap angle θ421.

[0062] Furthermore, the magnitude relationship between the wrap angle θ475 of the roller 475 and the wrap angle θ472 of the roller 472 can also be arbitrary. Therefore, the wrap angle θ475 and the wrap angle θ472 may be equal, or the wrap angle θ475 may be smaller than the wrap angle θ472.

[0063] Various specific configurations can be assumed for the rollers 421 and 472 (direction-changing rollers). For example, the rollers 421 and 472 may be concave rollers 61, 62, or 63.

[0064] Furthermore, the configuration for changing the direction of the print medium M from the color printing unit 32 to the white printing unit 33 is not limited to using the roller 472, i.e., the large wrap angle roller. In other words, the print medium M may be transported from the color printing unit 32 to the white printing unit 33 by gradually changing the direction of the print medium M using multiple rollers with a wrap angle of less than 35 degrees. The same applies to the roller 421.

[0065] Furthermore, the roller span Re does not need to be 2.5 times or more the width W of the printing medium M, but may be 1 time or more.

[0066] Furthermore, the method for printing on the print medium M is not limited to the inkjet method, but may be a gravure printing method.

[0067] The present invention is applicable to all techniques for transporting a print medium to a printing unit on which printing is performed by the printing unit.

[0068] 3...Printing device 32...Color printing section 33...White printing section 4...Conveying section 413...Roller 421...Roller 422...Roller 431432...Roller 472...Roller 475...Roller 476...Roller 5...Meandering correction section 51...Steering roller 52...Swinging mechanism Dc...Conveying direction M...Printing medium P32...Printing position P33...Printing position

Claims

1. A printing device comprising: a transport unit that transports a print medium along a transport direction; and a printing unit that prints on the print medium transported by the transport unit, wherein the transport unit has a meandering correction unit that corrects meandering of the print medium at a correction position upstream in the transport direction from a printing position where the printing unit prints on the print medium, and a downstream roller having a contact surface that contacts the print medium between the printing position and the correction position, wherein the meandering correction unit has a steering roller having a contact surface that contacts the print medium at the correction position, and a steering drive unit that oscillates the steering roller around a predetermined oscillation center, and the downstream roller and the steering roller are concave rollers whose contact surfaces are formed with areas whose diameters increase toward the ends.

2. A printing device as described in claim 1, wherein the transport section further has a direction-changing roller that contacts the printing medium upstream of the correction position in the transport direction, and the angle formed by the range in which the direction-changing roller contacts the printing medium around the center of the direction-changing roller is 35 degrees or more.

3. A printing device according to claim 2, wherein the direction-changing roller is disposed upstream of the correction position in the transport direction, at a distance of at least 2.5 times the width of the print medium from the correction position.

4. The printing device described in claim 2, wherein the transport section further has a proximity roller that contacts the print medium and is arranged at a distance equal to or less than the width of the print medium from the position where the direction-changing roller contacts the print medium in the transport direction, and the proximity roller is a concave roller in which an area whose diameter increases toward the edge is formed on the contact surface that contacts the print medium.

5. A printing device according to claim 4, wherein the proximity roller is disposed upstream of the direction-changing roller in the transport direction.

6. A printing device according to claim 4 or 5, wherein the angle formed by the area where the direction-changing roller contacts the printing medium around the center of the direction-changing roller is greater than the angle formed by the area where the proximity roller contacts the printing medium around the center of the proximity roller.

7. A printing device according to claim 2, wherein the direction-changing roller is a concave roller having a peripheral surface with an area whose diameter increases toward the end, the contact surface that comes into contact with the printing medium.

8. The printing device according to claim 2, wherein the direction-changing roller is a straight roller that contacts the printing medium with a peripheral surface having a uniform diameter.

9. The printing device of claim 2, wherein the angle formed by the area where the steering roller contacts the printing medium around the center of the steering roller is greater than the angle formed by the area where the direction-changing roller contacts the printing medium around the center of the direction-changing roller.

10. A printing device as described in claim 1, further comprising an upstream printing unit that prints on the print medium upstream of the printing unit in the transport direction, wherein the correction position is provided between the upstream printing position where the upstream printing unit prints on the print medium in the transport direction and the printing position, wherein the transport unit further has a direction-changing roller that contacts the print medium between the correction position and the upstream printing position in the transport direction, and wherein the angle formed by the range where the direction-changing roller contacts the print medium around the center of the direction-changing roller is 85 degrees or more.

11. A print medium transport method comprising: a step of transporting a print medium along a transport direction by a transport unit; and a step of printing by a printing unit on the print medium transported by the transport unit, wherein the transport unit has a meandering correction unit that corrects meandering of the print medium at a correction position upstream in the transport direction from a printing position where the printing unit prints on the print medium, and a downstream roller having a contact surface that contacts the print medium between the printing position and the correction position, wherein the meandering correction unit has a steering roller having a contact surface that contacts the print medium at the correction position, and a steering drive unit that swings the steering roller around a predetermined swing center, and wherein each of the downstream roller and the steering roller is a concave roller having an area formed on each contact surface where the diameter increases toward the end.

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