Printing device and transport control method

Abstract

To provide a printing apparatus and a conveyance control method each of which enables elimination of a wrinkle generated at a portion in a medium, near a portion conveyed by an intermediate roller pair.SOLUTION: A conveyance unit 12 has: a delivery unit 30 that delivers a medium M from a roll body 36; a conveyance roller pair 21 that conveys the medium M toward a printing portion 11; an intermediate roller pair 41 that conveys the medium M delivered by the delivery unit 30 toward the conveyance roller pair 21; a first drive unit 22 that rotates a first drive roller 21a; and a load changing unit that changes a pressing-load acting on between a second drive roller 41a and a second driven roller. A control unit 50 can perform: first control by which the load changing unit is controlled so that the pressing-load is equal to a first pressing-load when rotating the first drive roller 21a during intermittent conveyance; and second control by which the load changing unit is controlled so that the pressing-load is not generated, when stopping the rotation of the first drive roller 21a during the intermittent conveyance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a printing apparatus and a transport control method. [Background technology]

[0002] The printing device described in Patent Document 1 includes a printing unit that prints on a medium and a transport unit that transports the medium to the printing unit. The transport unit has a feed unit that feeds the medium from a roll of the medium, a transport roller pair, and an intermediate roller pair. The transport roller pair transports the medium fed by the feed unit toward the printing unit. The intermediate roller pair is located between the feed unit and the transport roller pair and transports the medium fed by the feed unit toward the transport roller pair. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-158292 Summary of the Invention [Problem to be solved by the invention]

[0004] When the printing unit repeatedly prints on a medium, the misalignment of the medium caused by printing increases, which can cause wrinkles to form on the medium during transport. For example, wrinkles may form on the medium near the point where the medium is transported by the intermediate roller pair. Because wrinkles on the medium can reduce the accuracy of printing on the medium by the printing unit, it is desirable to eliminate wrinkles that have formed on the medium. [Means for solving the problem]

[0005] A printing device that solves the above problem includes a printing unit that prints on a medium, a transport unit that transports the medium to the printing unit, and a control unit that controls the transport unit, wherein the transport unit includes a feed unit that feeds the medium from a roll of the medium wound in a roll, a transport roller pair that transports the medium fed by the feed unit toward the printing unit, and an intermediate roller pair between the feed unit and the transport roller pair that transports the medium fed by the feed unit toward the transport roller pair, wherein the transport roller pair includes a first drive roller and a first driven roller that holds the medium together with the first drive roller, and the intermediate roller pair includes a second drive roller and a second driven roller that holds the medium together with the second drive roller, The control unit has a first drive unit that rotates the first drive roller and a load change unit that changes the pressure load acting between the second drive roller and the second driven roller, and the control unit is capable of controlling the first drive unit to alternately rotate and stop rotating the first drive roller during intermittent transport in which medium transport and transport stop are alternately performed, and executing a first control to control the load change unit so that the pressure load becomes a first pressure load when the first drive roller is rotating during the intermittent transport, and a second control to control the load change unit so that the pressure load does not occur or the pressure load becomes a second pressure load that is smaller than the first pressure load when the rotation of the first drive roller is stopped during the intermittent transport.

[0006] A transport control method that solves the above problem is a transport control method for transporting a medium by a transport unit, the transport unit having a feed unit that feeds out the medium from a roll body on which the medium is wound in a roll, a pair of transport rollers that transport the medium fed out by the feed unit, and a pair of intermediate rollers between the feed unit and the pair of transport rollers that transport the medium fed out by the feed unit towards the pair of transport rollers, the pair of transport rollers having a first drive roller and a first driven roller that holds the medium together with the first drive roller, the pair of intermediate rollers having a second drive roller and a second driven roller that holds the medium together with the second drive roller, and a load changing unit that changes the pressure load acting between the second drive roller and the second driven roller, and in intermittent transport in which transport of a medium is alternately performed and transport is stopped, the first control is performed to control the first drive roller to alternately rotate and stop rotation of the first drive roller, and when the first drive roller is rotating in the intermittent transport, to control the load changing unit so that the pressure load becomes a first pressure load, and when the rotation of the first drive roller is stopped in the intermittent transport, to control the load changing unit so that the pressure load is not generated or the pressure load becomes a second pressure load that is smaller than the first pressure load. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating an embodiment of a printing device. [Figure 2] FIG. 2 is a schematic diagram showing the positional relationship between a roll body, a pair of intermediate rollers, a pair of transport rollers, and a print head. [Figure 3] FIG. 4 is a schematic diagram showing an intermediate roller pair and a load change unit. [Figure 4] FIG. 2 is a block diagram illustrating the electrical configuration of the printing apparatus. [Figure 5] 4 is a timing chart showing control by a control unit in the embodiment. [Figure 6] 10A and 10B are schematic diagrams for explaining an intermediate adjustment operation. [Figure 7] FIG. 4 is a schematic diagram for explaining first control and second control. [Figure 8] 10A and 10B are schematic diagrams for explaining an intermediate slack eliminating operation. [Figure 9] 10A and 10B are schematic diagrams for explaining the operation of eliminating slack in the feeding. [Figure 10] 10 is a timing chart showing control by a control unit in a modified example. [Figure 11] 10A and 10B are schematic diagrams for explaining a slack forming operation. DETAILED DESCRIPTION OF THE INVENTION

[0008] [First embodiment] A first embodiment of a printing device and a transport control method will be described below with reference to the drawings. The printing device is, for example, an inkjet printer that prints by ejecting ink, which is an example of a liquid, onto a medium such as paper, fabric, vinyl, plastic parts, or metal parts. The printing device is, for example, a large-format printer. A large-format printer is a printer that can print on media with a short side width of A3 (297 mm) or more.

[0009] In the drawings, the printing device is placed on a horizontal plane, with the direction of gravity indicated by the Z axis, and the directions along the horizontal plane indicated by the X and Y axes. The X, Y, and Z axes are perpendicular to each other. The direction parallel to the X axis is also called the width direction X.

[0010] <Printing device> As shown in FIG. 1, the printing device 10 includes a printing unit 11 that prints on a medium M, and a transport unit 12 that transports the medium M to the printing unit 11. In the printing device 10, the printing operation by the printing unit 11 and the transport operation by the transport unit 12 are alternately performed. The printing device 10 may also include a support table 13. The support table 13 extends in the width direction X. The support table 13 supports the medium M in a printing area where the printing unit 11 prints on the medium M.

[0011] The printing unit 11 may have a guide shaft 14, a carriage 15, a print head 16, and a carriage drive mechanism 17. The guide shaft 14 extends in the width direction X above the support base 13. The guide shaft 14 supports the carriage 15 so that the carriage 15 is movable along the guide shaft 14.

[0012] The print head 16 is mounted on the carriage 15. The print head 16 prints on the medium M supported by the support base 13 by ejecting liquid onto the medium M. The carriage drive mechanism 17 is a mechanism that moves the carriage 15 in the scanning direction XD. The printing unit 11 performs a printing operation by ejecting liquid from the print head 16 while moving the carriage 15 in the scanning direction XD along the guide shaft 14 by the carriage drive mechanism 17. The scanning direction XD may be a direction parallel to the X-axis. In this way, the printing unit 11 is a serial type, but it may also be a line type, for example.

[0013] <Transport roller pair> 2, the transport unit 12 has a transport roller pair 21 that transports the medium M toward the printing unit 11. The transport roller pair 21 has a first drive roller 21a and a first driven roller 21b. The first driven roller 21b holds the medium M between itself and the first drive roller 21a.

[0014] The first driven roller 21b rotates in accordance with the rotation of the first drive roller 21a. The transport roller pair 21 is a nip roller. The first drive roller 21a and the first driven roller 21b are each rotatable about a rotation axis extending in the width direction X. The first drive roller 21a and the first driven roller 21b may each have a cylindrical shape extending in the width direction X. The transport roller pair 21 may have one each of the first drive roller 21a and the first driven roller 21b.

[0015] <First drive unit> 1, the transport unit 12 has a first drive unit 22 that rotates the first drive roller 21a. The first drive unit 22 drives and rotates the first drive roller 21a, causing the transport roller pair 21 to transport the medium M in a transport direction YD. The transport direction YD is the length direction of the medium M. The transport direction YD may be a direction parallel to the Y axis.

[0016] The first drive unit 22 may include a transport motor 23, a transport transmission mechanism 24, and a transport rotation detection unit 25. The transport motor 23 is, for example, a DC motor. The transport motor 23 generates a transport drive torque for rotating the first drive roller 21a.

[0017] The transport transmission mechanism 24 transmits the transport drive torque generated by the transport motor 23 to the first drive roller 21a at a predetermined reduction ratio. The first drive roller 21a rotates when the transport drive torque is transmitted from the transport transmission mechanism 24.

[0018] When the transport motor 23 is driven in the forward direction, the transport roller pair 21 rotates in the forward direction. By rotating in the forward direction, the transport roller pair 21 can transport the medium M in the transport direction YD toward the support table 13. The printing unit 11 prints on the medium M sent out from the transport roller pair 21. When the transport motor 23 is driven in the reverse direction, the transport roller pair 21 rotates in the reverse direction. By rotating in the reverse direction, the transport roller pair 21 can transport the medium M in the direction opposite to the transport direction YD.

[0019] The conveying rotation detection unit 25 detects the rotation position and rotation direction of the conveying output shaft 23a of the conveying motor 23. The conveying rotation detection unit 25 is, for example, a rotary encoder that is provided on the conveying output shaft 23a of the conveying motor 23 and is composed of a disk-shaped scale and a photointerrupter.

[0020] <Feeding section> 2, the transport unit 12 has a feeding unit 30 that feeds out the medium M from a roll 36. The roll 36 is formed by winding the medium M in a roll shape. The feeding unit 30 is disposed on the transport path 19 of the medium M, upstream of the transport roller pair 21 in the transport direction YD.

[0021] As shown in FIG. 1 , the unwinding unit 30 may have a roll holding unit 31 and a roll driving unit 32. The roll holding unit 31 holds a roll 36 rotatably about a rotation axis extending in the width direction X. The roll holding unit 31 has holders 31a that hold the ends of the roll 36. One holder 31a may be located at each end of the roll 36 in the width direction X. The holder 31a has a rotation shaft that extends in the width direction X. The rotation shaft is inserted into a core member of the roll 36.

[0022] The roll driving unit 32 has a roll motor 33, a roll transmission mechanism 34, and a roll rotation detection unit 35. The roll motor 33 is, for example, a DC motor. The roll motor 33 generates a roll driving torque for driving the roll body 36 to rotate.

[0023] The feeding unit 30 may be detachable from the printing device 10. Specifically, the roll motor 33 of the feeding unit 30 may be electrically connectable to the control unit 50 (described later) via a cable or the like.

[0024] The roll transmission mechanism 34 transmits the roll driving torque generated by the roll motor 33 to the roll holding part 31 at a predetermined reduction ratio. The roll driving torque is transmitted from the roll transmission mechanism 34 to the holder 31a, causing the holder 31a to rotate. The rotation of the holder 31a causes the roll body 36 to rotate.

[0025] When the roll motor 33 is driven in the forward direction, the roll holding unit 31 rotates in the forward direction. When the roll holding unit 31 rotates in the forward direction, it can unwind the medium M from the roll body 36 toward the transport roller pair 21. The transport roller pair 21 transports the medium M unwound by the unwinding unit 30 toward the printing unit 11. When the roll motor 33 is driven in the reverse direction, the roll holding unit 31 rotates in the reverse direction. When the roll holding unit 31 rotates in the reverse direction, it can wind the medium M onto the roll body 36.

[0026] The roll rotation detection unit 35 detects the rotation position and rotation direction of the roll output shaft 33a of the roll motor 33. The roll rotation detection unit 35 is, for example, a rotary encoder that is configured with a disc-shaped scale and a photointerrupter provided on the roll output shaft 33a.

[0027] <Intermediate Roller Pair> As shown in FIG. 2, the transport unit 12 has an intermediate roller pair 41. The intermediate roller pair 41 is located between the feed unit 30 and the transport roller pair 21 and transports the medium M fed out by the feed unit 30 toward the transport roller pair 21. The intermediate roller pair 41 has a second drive roller 41a and a second driven roller 41b. The second driven roller 41b, together with the second drive roller 41a, holds the medium M between them. The second driven roller 41b rotates in conjunction with the rotation of the second drive roller 41a. The intermediate roller pair 41 is a nip roller.

[0028] 3, the second drive roller 41a is rotatable around a drive rotation shaft 41c extending in the width direction X. The second drive roller 41a may have a cylindrical shape extending in the width direction X. The intermediate roller pair 41 may have only one second drive roller 41a.

[0029] The second driven roller 41b is rotatable around a driven rotation shaft 41d extending in the width direction X. The second driven roller 41b may have a cylindrical shape extending in the width direction X. The intermediate roller pair 41 may include multiple second driven rollers 41b. The multiple second driven rollers 41b may be spaced apart from each other in the width direction X.

[0030] The intermediate roller pair 41 is displaceable between a clamping position P1 where it can clamp the medium M, and a separated position P2. When the intermediate roller pair 41 is in the clamping position P1, it can nip the medium M. When the intermediate roller pair 41 is in the separated position P2, the second drive roller 41a and the second driven roller 41b are further apart from each other than when the intermediate roller pair 41 is in the clamping position P1. When the intermediate roller pair 41 is in the separated position P2, it is possible for the intermediate roller pair 41 to release the medium M.

[0031] In the intermediate roller pair 41 of this embodiment, the second driven roller 41b is displaceable relative to the second drive roller 41a. The displacement of the second driven roller 41b allows the intermediate roller pair 41 to be displaced between a clamping position P1 and a separated position P2. When the second driven roller 41b is in a lowered position P3 indicated by a solid line in FIG. 3, the intermediate roller pair 41 is located at the clamping position P1. When the second driven roller 41b is in a raised position P4 indicated by a two-dot chain line in FIG. 3, the intermediate roller pair 41 is located at the separated position P2.

[0032] When the intermediate roller pair 41 is in the clamping position P1, a pressing load PL acts from the second driven roller 41b to the second drive roller 41a. The magnitude of the pressing load PL when the intermediate roller pair 41 is in the clamping position P1 is also referred to as a first pressing load PL1. When the intermediate roller pair 41 is in the separated position P2, no pressing load PL is applied from the second driven roller 41b to the second drive roller 41a.

[0033] <Second drive unit> 1, the transport unit 12 may include a second drive unit 42 that drives the second drive roller 41a. The second drive unit 42 drives and rotates the second drive roller 41a, causing the intermediate roller pair 41 to transport the medium M in the transport direction YD.

[0034] The second drive unit 42 may include an intermediate motor 43, an intermediate transmission mechanism 44, and an intermediate rotation detection unit 45. The intermediate motor 43 is, for example, a DC motor. The intermediate motor 43 generates an intermediate drive torque that drives the intermediate roller pair 41.

[0035] The intermediate transmission mechanism 44 transmits the intermediate driving torque generated by the intermediate motor 43 to the second driving roller 41a at a predetermined reduction ratio. The second driving roller 41a rotates when the transport driving torque is transmitted from the intermediate transmission mechanism 44.

[0036] When the intermediate motor 43 is driven in the forward direction, the intermediate roller pair 41 rotates in the forward direction. By rotating in the forward direction, the intermediate roller pair 41 can transport the medium M in the transport direction YD toward the transport roller pair 21. When the intermediate motor 43 is driven in the reverse direction, the intermediate roller pair 41 rotates in the reverse direction. By rotating in the reverse direction, the intermediate roller pair 41 can transport the medium M in the direction opposite to the transport direction YD toward the roll body 36.

[0037] The intermediate rotation detection unit 45 detects the rotation position and rotation direction of the intermediate output shaft 43a of the intermediate motor 43. The intermediate rotation detection unit 45 is, for example, a rotary encoder that is provided on the intermediate output shaft 43a of the intermediate motor 43 and is configured with a disk-shaped scale and a photointerrupter.

[0038] <Load change section> As shown in FIG. 3, the conveying unit 12 has a load changing unit 60. The load changing unit 60 changes the pressing load PL acting between the second driving roller 41a and the second driven roller 41b. The load changing unit 60 displaces the second driven roller 41b between a lowered position P3 and an elevated position P4. In this way, the load changing unit 60 of this embodiment changes the pressing load PL acting from the second driving roller 41a to the second driven roller 41b.

[0039] The load change unit 60 may include an electric motor 61 and a rack-and-pinion mechanism 62. The rack-and-pinion mechanism 62 includes a shaft member 63, two pinions 64, two racks 65, and two support members 67. The shaft member 63 extends in the width direction X. The shaft member 63 is connected to an output shaft of the electric motor 61. One pinion 64 is fixed to each end of the shaft member 63 in the width direction X. The two racks 65 are positioned so that one rack 65 meshes with each of the two pinions 64. One support member 67 is positioned on each side of the intermediate roller pair 41 in the width direction X. The two support members 67 rotatably support both ends of the driven rotation shaft 41d of the second driven roller 41b. The rack 65 is fixed to the support member 67.

[0040] When the electric motor 61 is driven in the reverse direction while the intermediate roller pair 41 is in the clamping position P1, the second driven roller 41b moves from the lowered position P3 to the raised position P4, thereby separating from the second driving roller 41a. The intermediate roller pair 41 is now positioned at the separated position P2.

[0041] When the electric motor 61 is driven in the forward direction while the intermediate roller pair 41 is in the separated position P2, the second driven roller 41b moves from the raised position P4 to the lowered position P3, thereby approaching the second driving roller 41a. The intermediate roller pair 41 is now positioned at the clamping position P1.

[0042] <Control unit> As shown in FIG. 4, the printing device 10 includes a control unit 50. The control unit 50 controls various operations performed by the printing device 10. The control unit 50 controls the conveying unit 12. The control unit 50 may be configured as a circuit including: α: one or more processors that execute various processes according to a computer program; β: one or more dedicated hardware circuits that execute at least some of the various processes; or γ: a combination thereof. The hardware circuit is, for example, an application-specific integrated circuit. The processor includes a CPU and memory such as RAM and ROM, and the memory stores program code or instructions configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any readable medium that can be accessed by a general-purpose or dedicated computer.

[0043] The control unit 50 may be electrically connected to the transport motor 23. The control unit 50 controls the driving of the transport motor 23. That is, the control unit 50 controls the first drive unit 22. The control unit 50 may drive the transport motor 23 so that the transport roller pair 21 rotates in the forward direction when the printing conditions are met. The printing conditions may be met when a print instruction is input in response to an operation of an operation unit (not shown). The printing conditions may be met when a print instruction is input from a terminal device (not shown). The drive of the transport motor 23 causes the transport roller pair 21 to rotate in the forward direction, thereby transporting the medium M by the transport roller pair 21. The control unit 50 may drive the transport motor 23 so that the transport roller pair 21 rotates in the reverse direction. The control unit 50 may control the drive of the transport motor 23 by controlling the supply of a constant voltage power source to the transport motor 23 using PWM (Pulse Width Modulation) control.

[0044] The control unit 50 may be electrically connected to the roll motor 33. The control unit 50 may control the driving of the roll motor 33. When the printing conditions are met, the roll motor 33 may be driven so that the roll body 36 rotates in the forward direction. When the roll motor 33 is driven, the roll body 36 rotates in the forward direction, and the medium M is unwound from the roll body 36 toward the transport roller pair 21. The control unit 50 may drive the roll motor 33 so that the roll body 36 rotates in the reverse direction. The control unit 50 may control the driving of the roll motor 33 by controlling the supply of a constant voltage power source to the roll motor 33 using PWM control.

[0045] The control unit 50 may be electrically connected to the intermediate motor 43. The control unit 50 may control the driving of the intermediate motor 43. That is, the control unit 50 may control the second drive unit 42. The control unit 50 may drive the intermediate motor 43 so that the intermediate roller pair 41 rotates in the forward direction when the printing conditions are met. When the intermediate motor 43 is driven, the intermediate roller pair 41 rotates in the forward direction, causing the intermediate roller pair 41 to transport the medium M toward the transport roller pair 21. The control unit 50 may drive the intermediate motor 43 so that the intermediate roller pair 41 rotates in the reverse direction. The control unit 50 controls the driving of the intermediate motor 43 by controlling the supply of constant voltage power to the intermediate motor 43 using PWM control.

[0046] As shown in FIG. 1, the control unit 50 causes the transport unit 12 to repeatedly perform intermittent transport, thereby transporting the medium M. Intermittent transport is an operation in which the transport unit 12 alternates between transporting the medium M and stopping the transport of the medium M at a predetermined cycle. The control unit 50 controls the first drive unit 22 to alternately rotate and stop the rotation of the first drive roller 21a during intermittent transport, which alternately transports and stops the transport of the medium M. The control unit 50 causes the printing unit 11 to perform a printing operation when the transport of the medium M is stopped during intermittent transport.

[0047] When the transport unit 12 transports the medium M, the transport motor 23 drives the transport roller pair 21 to rotate in the forward direction. When the transport unit 12 transports the medium M, the roll motor 33 drives the roll body 36 to rotate in the forward direction. When the transport unit 12 transports the medium M, the intermediate motor 43 drives the intermediate roller pair 41 to rotate in the forward direction. When the transport of the medium M by the transport unit 12 stops, the drive of each of the transport motor 23, the roll motor 33, and the intermediate motor 43 may be stopped.

[0048] As shown in FIG. 4, the control unit 50 may be electrically connected to the conveying rotation detection unit 25. A pulse signal may be input to the control unit 50 from the conveying rotation detection unit 25. For example, the control unit 50 acquires the rotational position and rotational direction of the conveying output shaft 23a detected by the conveying rotation detection unit 25. The control unit 50 acquires the rotational position and rotational speed of the first drive roller 21a based on the acquired rotational position and rotational direction of the conveying output shaft 23a. The control unit 50 can perform feedback control of the first drive roller 21a based on the acquired rotational position and rotational speed of the first drive roller 21a.

[0049] The control unit 50 may be electrically connected to the roll rotation detection unit 35. A pulse signal may be input to the control unit 50 from the roll rotation detection unit 35. For example, the control unit 50 acquires the rotational position and rotational direction of the roll output shaft 33a detected by the roll rotation detection unit 35. The control unit 50 acquires the rotational position and rotational speed of the holder 31a based on the acquired rotational position and rotational direction of the roll output shaft 33a. The control unit 50 can perform feedback control of the payout unit 30 based on the acquired rotational position and rotational speed of the holder 31a.

[0050] The control unit 50 may be electrically connected to the intermediate rotation detection unit 45. A pulse signal may be input to the control unit 50 from the intermediate rotation detection unit 45. For example, the control unit 50 acquires the rotational position and rotational direction of the intermediate output shaft 43a detected by the intermediate rotation detection unit 45. The control unit 50 acquires the rotational position and rotational speed of the second drive roller 41a based on the acquired rotational position and rotational direction of the intermediate output shaft 43a. The control unit 50 can perform feedback control of the second drive roller 41a based on the acquired rotational position and rotational speed of the second drive roller 41a.

[0051] The control unit 50 may perform position feedback control and speed feedback control. The position feedback control is PID control related to the rotational positions of the first drive roller 21a, the second drive roller 41a, and the holder 31a. The speed feedback control is PID control related to the rotational speeds of the first drive roller 21a, the second drive roller 41a, and the holder 31a. When a target value for the rotational position of the first drive roller 21a is input to the control unit 50, the control unit 50 performs position feedback control. When a target value for the rotational speed of the first drive roller 21a is input to the control unit 50, the control unit 50 performs speed feedback control. Note that the feedback control may be PI control.

[0052] <Intermediate adjustment operation and feed adjustment operation> 1, the control unit 50 can control the second drive unit 42 and the feeding unit 30, and can execute an intermediate adjustment operation M1 and a feeding adjustment operation M2 by controlling the second drive unit 42 and the feeding unit 30. In the intermediate adjustment operation M1, the control unit 50 adjusts the tension T of the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 by controlling the second drive unit 42 to rotate the second drive roller 41a. In the feeding adjustment operation M2, the control unit 50 adjusts the tension T of the medium M positioned between the intermediate roller pair 41 and the feeding unit 30 by controlling the feeding unit 30.

[0053] In the intermediate adjustment operation M1, the control unit 50 may adjust the tension T of the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 to a first target tension Ta. In the feed adjustment operation M2, the control unit 50 may adjust the tension T of the medium M positioned between the intermediate roller pair 41 and the feed unit 30 to a second target tension Tb.

[0054] The control unit 50 may perform a load acquisition operation M3 and a reference current acquisition operation M4. The control unit 50 may perform an intermediate adjustment operation M1 and a payout adjustment operation M2 based on information obtained through the load acquisition operation M3 and the reference current acquisition operation M4.

[0055] In the load acquisition operation M3, the control unit 50 can acquire the intermediate roller load N1 for any rotational speed of the second drive roller 41a and the roll body load N2 for any rotational speed of the roll body 36. Previous experiments and simulations have shown that the intermediate roller load N1 has a linear relationship with the rotational speed of the second drive roller 41a. When the roll body 36 is installed in the printing device 10, the control unit 50 executes the load acquisition operation M3, which allows the control unit 50 to calculate the intermediate roller load N1 for any rotational speed of the second drive roller 41a. Previous experiments and simulations have shown that the roll body load N2 has a linear relationship with the rotational speed of the roll body 36. When the roll body 36 is installed in the printing device 10, the control unit 50 executes the load acquisition operation M3, which allows the control unit 50 to calculate the roll body load N2 for any rotational speed of the roll body 36.

[0056] In the reference current acquisition operation M4, the control unit 50 can acquire the current flowing through the intermediate motor 43 when driving the intermediate motor 43 at the same rotation speed and drive time as when transporting the medium M. In the reference current acquisition operation M4, the control unit 50 can acquire the current flowing through the roll motor 33 when driving the roll motor 33 at the same rotation speed and drive time as when transporting the medium M.

[0057] <Tension of the medium between the transport roller pair and the intermediate roller pair> We will now explain the tension T of the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41. First, we will explain the first tension T1, which is the tension T that acts on the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 when the medium M supported by the transport roller pair 21 and the intermediate roller pair 41 is transported by the transport roller pair 21 alone.

[0058] When the medium M supported by the transport roller pair 21 and the intermediate roller pair 41 is transported by the transport roller pair 21 alone, the medium M is pulled by the first drive roller 21a. This causes the second drive roller 41a to rotate in the forward direction. An intermediate roller load N1, which is the load required to rotate the intermediate roller pair 41, is generated on the intermediate roller pair 41. At this time, the first tension T1 is expressed by the following equation (1). The first proportionality constant k1 is a constant set based on the results of experiments and simulations conducted in advance. The first radius R1 is the radius of the second drive roller 41a.

[0059] T1=k1×N1 / R1 … (1) Next, the first tension T1 when the medium M is fed using the transport roller pair 21 and the intermediate roller pair 41 will be described. In this case, a first output torque Tq1 that rotates the second drive roller 41a in the forward direction is generated in the second drive roller 41a. As a result, a torque obtained by subtracting the first output torque Tq1 from the intermediate roller load N1 acts on the second drive roller 41a. The first tension T1 at this time can be expressed by the following equation (2):

[0060] T1=k1×(N1-Tq1) / R1 … (2) From the above formulas (1) and (2), the first output torque Tq1 of the second drive roller 41a can be expressed by the following formula (3).

[0061] Tq1=N1-{(R1 / k1)×T1} … (3) From the above equation (3), the first proportionality constant k1, the first radius R1, which is the radius of the second drive roller 41a, and the intermediate roller load N1 are known values. The first target tension Ta is input as the first tension T1 in the above equation (3). This makes it possible to calculate the first output torque Tq1 of the second drive roller 41a required to generate the first target tension Ta in the medium M located between the transport roller pair 21 and the intermediate roller pair 41.

[0062] The first target tension Ta is set to a value that maintains the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 in a state where it does not skew or break. The first target tension Ta is set according to the characteristics of the medium M based on the results of experiments and simulations conducted in advance. The set first target tension Ta is associated with the characteristics of the medium M and stored in the control unit 50. Information regarding the characteristics of the medium M may be input to the control unit 50 by the user through an operation unit (not shown). The control unit 50 may select the first target tension Ta based on the input information regarding the characteristics of the medium M.

[0063] <Tension of the medium between the intermediate roller pair and the feeding section> The tension T of the medium M positioned between the intermediate roller pair 41 and the feeding section 30 will be described below. First, the second tension T2 will be described, which is the tension T acting on the medium M positioned between the intermediate roller pair 41 and the feeding section 30 when the medium M supported by the intermediate roller pair 41 and the feeding section 30 is transported by the intermediate roller pair 41 alone.

[0064] When the medium M supported by the intermediate roller pair 41 and the feeding unit 30 is transported by only the intermediate roller pair 41, the medium M is pulled by the second drive roller 41a. This causes the roll body 36 to rotate in the forward direction. A roll body load N2, which is the load required to rotate the roll body 36, is generated on the roll body 36. At this time, the second tension T2 is expressed by the following equation (4). The second proportionality constant k2 is a constant set based on the results of experiments and simulations conducted in advance. The second radius R2 is the radius of the roll body 36.

[0065] T2=k2×N2 / R2 … (4) Next, the second tension T2 when the medium M is fed using the intermediate roller pair 41 and the unwinding unit 30 will be described. In this case, a second output torque Tq2 that rotates the roll body 36 in the forward direction is generated in the roll body 36. As a result, a torque obtained by subtracting the second output torque Tq2 from the roll body load N2 acts on the roll body 36. The second tension T2 at this time can be expressed by the following equation (5).

[0066] T2=k2×(N2-Tq2) / R2 … (5) From the above formulas (4) and (5), the second output torque Tq2 of the roll body 36 can be expressed by the following formula (6).

[0067] Tq2=N2-{(R2 / k2)×T2} … (6) From the above equation (6), the second proportionality constant k2, the second radius R2 that is the radius of the roll body 36, and the roll body load N2 are known values. By inputting the second target tension Tb into the second tension T2 in the above equation (6), it is possible to calculate the second output torque Tq2 of the roll body 36 that is required to generate the second target tension Tb in the medium M located between the intermediate roller pair 41 and the unwinding unit 30.

[0068] The second target tension Tb is set to a value that maintains the medium M positioned between the intermediate roller pair 41 and the feeding unit 30 in a state where it does not skew or break. The second target tension Tb is set according to the characteristics of the medium M based on the results of experiments and simulations conducted in advance. The set second target tension Tb is associated with the characteristics of the medium M and stored in the control unit 50. The control unit 50 may select the second target tension Tb based on information regarding the characteristics of the medium M that has been input.

[0069] 4, the control unit 50 may be electrically connected to the electric motor 61. The control unit 50 controls the driving of the electric motor 61. That is, the control unit 50 controls the load changing unit 60.

[0070] The control unit 50 is capable of executing a first control C1. In the first control C1, the control unit 50 controls the load change unit 60 so that the pressing load PL becomes a first pressing load PL1 when the first drive roller 21a is rotated during the intermittent transport of the medium M. The control unit 50 is capable of executing a second control C2. In the second control C2, the control unit 50 controls the load change unit 60 so that the pressing load PL does not occur when the rotation of the first drive roller 21a is stopped during the intermittent transport of the medium M.

[0071] The control unit 50 may execute the second control C2 every time the rotation of the transport roller pair 21 stops. When the rotation of the first drive roller 21a stops during intermittent transport of the medium M, the control unit 50 may execute the first control C1 after executing the second control C2.

[0072] <Media transport control method> Next, an example of a transport control method for transporting the medium M by the transport unit 12 will be described. In Fig. 5, the horizontal axis represents time. In Fig. 5, the vertical axis represents the rotation speeds of the transport roller pair 21, the intermediate roller pair 41, the electric motor 61, and the roll holding unit 31. In Fig. 5, + rotation speed represents the rotation speed during forward rotation drive, and - rotation speed represents the rotation speed during reverse rotation drive.

[0073] 5, at time t1, the control unit 50 controls the second drive unit 42 to drive the intermediate roller pair 41 in the forward direction while performing the intermediate adjustment operation M1. Specifically, the control unit 50 controls the second drive unit 42 to drive the intermediate roller pair 41 in the forward direction while stopping the drive of the transport roller pair 21. In this embodiment, the drive start timing of the intermediate roller pair 41 is earlier than the drive start timing of the transport roller pair 21.

[0074] 6, in the intermediate adjustment operation M1 of the present embodiment, the control unit 50 forms slack 95 in the medium M between the transport roller pair 21 and the intermediate roller pair 41. The control unit 50 drives the intermediate motor 43 in the forward direction to maintain the slack 95 in the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41, while maintaining the tension T at the first target tension Ta.

[0075] 5, at time t2, the control unit 50 drives the transport motor 23 in the forward direction to rotate the transport roller pair 21 in the forward direction. At time t2, the control unit 50 drives the roll motor 33 in the forward direction to rotate the roll holding unit 31 in the forward direction. The medium M is transported from the transport roller pair 21 in the transport direction YD.

[0076] The control unit 50 controls the roll motor 33 of the feeding unit 30 to drive the roll holding unit 31 in the forward direction while performing the feeding adjustment operation M2. By driving the roll motor 33 in the forward direction, the control unit 50 maintains the tension T in the medium M located between the intermediate roller pair 41 and the feeding unit 30 at the second target tension Tb.

[0077] The slack 95 described above is formed between the transport roller pair 21 and the intermediate roller pair 41, allowing the transport roller pair 21 to smoothly start transporting the medium M. Furthermore, the intermediate roller pair 41, which is driven to rotate forward first, can rotate forward without delaying the acceleration of the transport roller pair 21 due to its own inertia or the like.

[0078] The control unit 50 continues driving the transport motor 23, intermediate motor 43, and roll motor 33 in the forward direction until time t3. As a result, the forward driving of the transport roller pair 21, intermediate roller pair 41, and roll holder 31 continues until time t3. A predetermined transport amount of medium M is transported from the transport roller pair 21 between time t2 and time t3. In this embodiment, the period from time t2 to time t3 corresponds to the time when the first drive roller 21a is rotating during the intermittent transport of medium M. At time t3, the control unit 50 stops driving the transport motor 23, intermediate motor 43, and roll motor 33.

[0079] The control unit 50 executes the second control C2 at time t4 after stopping the drive of the transport motor 23, the intermediate motor 43, and the roll motor 33. The control unit 50 may execute the second control C2 on the condition that the forward rotation drive of the transport motor 23 is stopped. In the second control C2, the control unit 50 controls the load change unit 60 so that the pressing load PL does not occur when the rotation of the first drive roller 21a is stopped due to the intermittent transport of the medium M.

[0080] 5 and 7, in the second control C2, the control unit 50 drives the electric motor 61 in the reverse direction. As a result, the second driven roller 41b is displaced from the lowered position P3 to the raised position P4. The intermediate roller pair 41 is displaced from the clamping position P1 where the medium M can be clamped to the separated position P2 where no pressing load PL is generated.

[0081] At time t5, the control unit 50 stops the reverse driving of the electric motor 61 associated with the second control method C2. As a result, the position of the second driven roller 41b is maintained at the raised position P4. The position of the intermediate roller pair 41 is maintained at the separated position P2. The position of the intermediate roller pair 41 is maintained at the separated position P2 until the first control method C1 is executed by the control unit 50 at time t6. Therefore, it can be said that the control unit 50 of this embodiment executes the second control method C2 during the period from time t4 to time t6.

[0082] 5, at time t6, the control unit 50 executes the first control process C1. The control unit 50 starts the first control process C1 after executing the second control process C2 when the rotation of the first drive roller 21a is stopped due to the intermittent transport of the medium M. In the first control process C1, the control unit 50 controls the load change unit 60 so that the pressing load PL becomes the first pressing load PL1.

[0083] 5 and 7, in the first control C1, the control unit 50 drives the electric motor 61 in the forward direction. As a result, the second driven roller 41b is displaced from the raised position P4 to the lowered position P3. The intermediate roller pair 41 is displaced from the separated position P2 to the clamping position P1. When the intermediate roller pair 41 is in the clamping position P1, the pressing load PL becomes the first pressing load PL1.

[0084] At time t7, the control unit 50 stops the reverse driving of the electric motor 61 associated with the first control process C1. As a result, the position of the second driven roller 41b is maintained at the lowered position P3. The position of the intermediate roller pair 41 is maintained at the clamping position P1. The pressing load PL acting from the second driven roller 41b to the second drive roller 41a is maintained at the first pressing load PL1. The position of the intermediate roller pair 41 is maintained at the clamping position P1 until the next second control process C2 is executed by the control unit 50. Therefore, it can be said that the control unit 50 of this embodiment executes the first control process C1 during the period from time t6 until the next execution of the second control process C2.

[0085] As shown in FIG. 5, after the first control C1 is executed, the control unit 50 executes the intermediate slack elimination operation M5 at time t8. That is, the control unit 50 executes the first control C1 while the rotation of the first drive roller 21a is stopped during the intermittent transport of the medium M, and then executes the intermediate slack elimination operation M5. In the intermediate slack elimination operation M5, the control unit 50 controls the second drive unit 42 to rotate the second drive roller 41a in the direction opposite to the direction in which the medium M is transported toward the transport roller pair 21. The intermediate slack elimination operation M5 eliminates slack 95 in the medium M located between the transport roller pair 21 and the intermediate roller pair 41. By performing the intermediate slack elimination operation M5, it is possible to eliminate a transport error that occurs during the transport operation for the medium M located between the transport roller pair 21 and the intermediate roller pair 41. The transport error is the difference in the transport amount between both ends of the medium M in the width direction X.

[0086] 8, in intermediate slack elimination operation M5, the control unit 50 drives the intermediate roller pair 41 in the reverse direction using speed feedback control with the intermediate slack elimination speed as the target speed. The intermediate slack elimination speed is set according to the characteristics of the medium M based on the results of experiments and simulations conducted in advance. Note that in addition to the speed feedback control, the control unit 50 may simultaneously perform torque feedback control with the intermediate slack elimination torque as the target torque. Like the intermediate slack elimination speed, the intermediate slack elimination torque is set according to the characteristics of the medium M based on the results of experiments and simulations conducted in advance.

[0087] 5, after execution of first control C1, at time t8, the control unit 50 executes a feeding slack elimination operation M6. In the feeding slack elimination operation M6, the control unit 50 drives the roll motor 33 to rotate the roll holding unit 31. As the control unit 50 performs the feeding slack elimination operation M6, slack 95 of the medium M located between the intermediate roller pair 41 and the feeding unit 30 is eliminated. The feeding slack elimination operation M6 is an operation that eliminates a transport error that occurs during the transport operation for the medium M located between the intermediate roller pair 41 and the feeding unit 30.

[0088] As shown in Figure 9, in the feeding slack elimination operation M6, the control unit 50 drives the roll holding unit 31 in the reverse direction using speed feedback control with the feeding slack elimination speed as the target speed. The feeding slack elimination speed is set according to the characteristics of the medium M based on the results of experiments and simulations conducted in advance. Note that in addition to the speed feedback control, the control unit 50 may simultaneously perform torque feedback control with the feeding slack elimination torque as the target torque. Like the feeding slack elimination speed, the feeding slack elimination torque is set according to the characteristics of the medium M based on the results of experiments and simulations conducted in advance. The rate of increase of the feeding slack elimination speed may be smaller than that of the intermediate slack elimination speed. The upper limit of the feeding slack elimination speed may be greater than that of the intermediate slack elimination speed.

[0089] 5, at time t9, when the tension T acting on the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 reaches a predetermined value, the control unit 50 ends the intermediate slack elimination operation M5. At time t10, when the tension T acting on the medium M positioned between the intermediate roller pair 41 and the feed unit 30 reaches a predetermined value, the control unit 50 ends the feed slack elimination operation M6.

[0090] At time t11, the control unit 50 causes the transport unit 12 to restart the transport operation of the medium M. The control unit 50 may cause the printing unit 11 to print on the medium M during the period from time t10, when the feeding slack elimination operation M6 ends, to time t11. With the start of the transport operation of the medium M, the control unit 50 causes the first drive roller 21a to rotate forward. At this time, with the execution of the first control C1 by the control unit 50, the position of the intermediate roller pair 41 is maintained at the clamping position P1. The pressing load PL acting from the second driven roller 41b to the second drive roller 41a is maintained at the first pressing load PL1. Therefore, in the first control C1, the control unit 50 controls the load change unit 60 so that the pressing load PL becomes the first pressing load PL1 when rotating the first drive roller 21a during intermittent transport of the medium M. In this embodiment, the period from time t3 to time t11 corresponds to the time when the rotation of the first drive roller 21a is stopped during the intermittent transport of the medium M.

[0091] After time t11, the control unit 50 stops the rotation of the transport roller pair 21 and the intermediate roller pair 41 associated with the transport of the medium M, and then the control unit 50 again executes the second control C2. After executing the second control C2, the control unit 50 executes the first control C1. The control unit 50 of the present embodiment executes the second control C2 every time the rotation of the transport roller pair 21 stops.

[0092] <Operation of the First Embodiment> The operation of this embodiment will be described. The control unit 50 executes the second control C2 when the rotation of the first drive roller 21a is stopped during intermittent transport of the medium M. In the second control C2, the control unit 50 drives the electric motor 61 of the load change unit 60 in the reverse direction. The second driven roller 41b is displaced from the lowered position P3 to the raised position P4. The intermediate roller pair 41 is displaced from the clamping position P1 to the separated position P2. When the intermediate roller pair 41 is in the separated position P2, no pressing load PL is applied from the second driven roller 41b to the second drive roller 41a. Therefore, the medium M is not clamped between the second drive roller 41a and the second driven roller 41b. As the intermediate roller pair 41 is displaced from the clamping position P1 to the separated position P2, wrinkles that have occurred in the medium M near the location of transport by the intermediate roller pair 41 can be eliminated.

[0093] The control unit 50 executes the first control C1 while rotating the first drive roller 21a during intermittent transport of the medium M. In the first control C1, the control unit 50 drives the electric motor 61 of the load change unit 60 in the forward direction. The second driven roller 41b is displaced from the raised position P4 to the lowered position P3. The intermediate roller pair 41 is displaced from the separated position P2 to the clamping position P1. When the intermediate roller pair 41 is in the clamping position P1, the pressing load PL acting from the second driven roller 41b on the second drive roller 41a becomes the first pressing load PL1. Therefore, the medium M can be clamped between the second drive roller 41a and the second driven roller 41b. With the medium M clamped by the intermediate roller pair 41, printing on the medium M by the printing unit 11 and transport of the medium M by the transport roller pair 21 and the intermediate roller pair 41 can be performed.

[0094] <Effects of the first embodiment> The effects of this embodiment will be described. (1) When the control unit 50 stops the rotation of the first drive roller 21a during intermittent transport, it executes the second control C2, which controls the load change unit 60 so that the pressing load PL is not generated. Therefore, when the second control C2 is executed, the load acting on the medium M from the intermediate roller pair 41 is smaller than when the first control C1 is executed. Therefore, it is possible to eliminate wrinkles that have occurred in the medium M near the location where the intermediate roller pair 41 is transporting the medium M.

[0095] (2) The control unit 50 executes the second control C2 every time the rotation of the transport roller pair 21 stops. Therefore, the control unit 50 executes the second control C2 more frequently than when the control unit 50 executes the second control C2 every time the rotation of the transport roller pair 21 stops multiple times. Therefore, wrinkles that have occurred in the medium M can be eliminated more frequently.

[0096] (3) When the rotation of the first drive roller 21a is stopped during intermittent transport, the control unit 50 executes the second control C2 and then the first control C1. Therefore, the first drive roller 21a can start rotating with the pressing load PL of the intermediate roller pair 41 set to the first pressing load PL1. Therefore, the medium M can be transported while being appropriately sandwiched by the intermediate roller pair 41.

[0097] (4) The control unit 50 can perform an intermediate adjustment operation M1 that adjusts the tension T of the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 by controlling the second drive unit 42 to rotate the second drive roller 41a. Therefore, the intermediate adjustment operation M1 can eliminate any transport error that occurs in the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 while the medium M is being transported. The control unit 50 can perform a feed adjustment operation M2 that adjusts the tension T of the medium M positioned between the intermediate roller pair 41 and the feed unit 30 by controlling the feed unit 30. Therefore, the feed adjustment operation M2 can eliminate any transport error that occurs in the medium M positioned between the intermediate roller pair 41 and the feed unit 30 while the medium M is being transported. Therefore, the transport roller pair 21 can transport the medium M with high accuracy.

[0098] (5) The control unit 50 executes an intermediate slack elimination operation M5, which controls the second drive unit 42 to rotate the second drive roller 41a in the direction opposite to the direction in which the medium M is transported toward the transport roller pair 21. The intermediate slack elimination operation M5 eliminates the slack 95 of the medium M located between the transport roller pair 21 and the intermediate roller pair 41. Therefore, the accumulated transport error and the accumulated error in the amount of slack in the width direction X can be reset for the medium M located between the transport roller pair 21 and the intermediate roller pair 41.

[0099] [Second embodiment] A second embodiment of the printing apparatus and the transport control method will be described below with reference to the drawings. Note that the second embodiment differs from the first embodiment in the frequency with which the control unit 50 executes the second control C2. In other respects, the second embodiment is the same as the first embodiment. In the second embodiment, descriptions of the same configuration as the first embodiment will be omitted where appropriate.

[0100] In this embodiment, the control unit 50 executes the second control C2 each time the rotation of the transport roller pair 21 is stopped multiple times. In this embodiment, the control unit 50 executes the second control C2 each time the rotation of the transport roller pair 21 is stopped twice. In this case, for example, if the control unit 50 executes the second control C2 after the rotation of the transport roller pair 21 is stopped, the control unit 50 does not execute the second control C2 after the rotation of the transport roller pair 21 is stopped the next time. In this manner, in this embodiment, the control unit 50 alternately executes and does not execute the second control C2 at the timing when the rotation of the transport roller pair 21 is stopped. Note that the control unit 50 may execute the second control C2 each time the rotation of the transport roller pair 21 is stopped three or more times.

[0101] 5, when the control unit 50 executes the second control process C2, the control unit 50 executes the second control process C2 in the same manner as in the first embodiment during the period from time t4 to time t6. As a result, the intermediate roller pair 41 is displaced from the clamping position P1 to the separated position P2. As in the first embodiment, the control unit 50 executes the first control process C1 after executing the second control process C2. As a result, the intermediate roller pair 41 is displaced from the separated position P2 to the clamping position P1.

[0102] 5, when the control unit 50 does not execute the second control C2, the control unit 50 does not drive the electric motor 61 to rotate when the rotation of the first drive roller 21a is stopped. The control unit 50 continues to execute the first control C1 until the rotation of the first drive roller 21a, which has started to rotate again, is stopped. This causes the position of the intermediate roller pair 41 to remain at the clamping position P1.

[0103] According to this embodiment, the same effects as those of the first embodiment can be obtained. <Effects of the second embodiment> The effects of this embodiment will be described.

[0104] (6) The control unit 50 executes the second control C2 each time the rotation of the conveyance roller pair 21 is stopped multiple times. Therefore, the frequency with which the control unit 50 executes the second control C2 is reduced compared to when the control unit 50 executes the second control C2 each time the rotation of the conveyance roller pair 21 is stopped. Therefore, the load acting on the load change unit 60 due to the execution of the second control C2 can be reduced.

[0105] <Example of change> The above-described embodiments can be modified as follows: The above-described embodiments and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0106] As shown in FIG. 10 , the control unit 50 may be capable of executing an intermediate adjustment operation M1 and a slack formation operation M7. In the intermediate adjustment operation M1, the control unit 50 adjusts the tension T of the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 by controlling the second drive unit 42 to rotate the second drive roller 41a, as in the above embodiment. The control unit 50 may execute the slack formation operation M7 between time t10, when the feeding slack elimination operation M6 ends, and time t11, when the transport operation of the medium M starts again. Specifically, the control unit 50 starts the slack formation operation M7 at time t12, which is after time t10 but before time t11. The control unit 50 ends the slack formation operation M7 at time t13. In this case, the control unit 50 may cause the printing unit 11 to print on the medium M between time t13, when the slack formation operation M7 ends, and time t11, when the transport operation of the medium M starts again.

[0107] As shown in FIG. 11 , in slack formation operation M7, the control unit 50 controls the feeding unit 30 to feed the medium M from the roll 36 toward the transport roller pair 21, thereby forming slack 95 in the medium M located between the intermediate roller pair 41 and the feeding unit 30. Specifically, in slack formation operation M7, the control unit 50 drives the roll motor 33 in the forward direction by position feedback control, with the slack formation position set as the target position. The slack formation position is a rotational position at which a predetermined amount of slack is pulled out of the roll 36. The control unit 50 ends the slack formation operation M7 when the rotational position based on the pulse signal from the roll rotation detection unit 35 reaches the slack formation position. When the slack formation operation M7 ends, slack 95 is formed in the medium M located between the intermediate roller pair 41 and the roll holding unit 31. The control unit 50 may perform a feeding slack elimination operation M6 to eliminate the slack 95 formed in the slack formation operation M7.

[0108] According to the above modification, the following effects can be obtained. (7) The control unit 50 can execute an intermediate adjustment operation M1 to adjust the tension T of the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 by controlling the second drive unit 42 to rotate the second drive roller 41a. Therefore, the intermediate adjustment operation M1 can eliminate any transport error that occurs in the medium M positioned between the transport roller pair 21 and the intermediate roller pair 41 during transport of the medium M. The control unit 50 can execute a slack forming operation M7 to form slack 95 in the medium M positioned between the intermediate roller pair 41 and the feed unit 30 by controlling the feed unit 30 to feed the medium M from the roll body 36 toward the transport roller pair 21. This makes the intermediate roller pair 41 less susceptible to the effects of eccentricity, tilt, and the like of the roll body 36. As a result, it is possible to suppress a decrease in transport accuracy in the intermediate roller pair 41 and, ultimately, in the transport roller pair 21. Therefore, the transport roller pair 21 can transport the medium M with high precision.

[0109] In the second control C2, when the rotation of the first drive roller 21a is stopped during intermittent transport of the medium M, the control unit 50 may control the load change unit 60 to change the pressure load PL to a second pressure load PL2 that is smaller than the first pressure load PL1. In this case, the second pressure load PL2 is preferably equal to or smaller than 10 percent of the first pressure load PL1. The second pressure load PL2 may be greater than 10 percent of the first pressure load PL1. In this case, the pressure load PL acting from the second driven roller 41b to the second drive roller 41a during execution of the second control C2 is smaller than that during execution of the first control C1. Therefore, the load acting from the intermediate roller pair 41 on the medium M during execution of the second control C2 is smaller than that during execution of the first control C1. Therefore, execution of the second control C2 can eliminate wrinkles that have occurred in the medium M near the location transported by the intermediate roller pair 41.

[0110] The load change unit 60 may change the pressing load PL acting from the second drive roller 41a to the second driven roller 41b. In this case, for example, the load change unit 60 may change the pressing load PL by displacing the second drive roller 41a. In other words, the load change unit 60 may be any unit that changes the pressing load PL acting between the second drive roller 41a and the second driven roller 41b.

[0111] The control unit 50 may omit the execution of the intermediate slack eliminating operation M5. The control unit 50 may omit the execution of the feeding slack eliminating operation M6. The control unit 50 may omit execution of the intermediate adjustment operation M1. When the control unit 50 omits execution of the intermediate adjustment operation M1, for example, the control unit 50 rotates the intermediate roller pair 41 by the intermediate motor 43 in a manner in which a preset intermediate drive torque is generated. The control unit 50 may omit execution of the payout adjustment operation M2. When the control unit 50 omits execution of the payout adjustment operation M2, for example, the control unit 50 rotates the roll holding unit 31 by the roll motor 33 in a manner in which a preset roll drive torque is generated. When the control unit 50 omits execution of both the intermediate adjustment operation M1 and the payout adjustment operation M2, the control unit 50 may omit execution of the load acquisition operation M3 and the reference current acquisition operation M4.

[0112] The timing for executing the first control C1 by the control unit 50 is when the rotation of the first drive roller 21a is stopped during the intermittent transport of the medium M, and is not limited to after the second control C2 is executed. For example, the control unit 50 may execute the first control C1 after the second control C2 is executed and at the timing when the rotation of the first drive roller 21a starts.

[0113] The printing device 10 may be a liquid ejection device that jets or ejects liquids other than ink. The state of the liquid ejected as minute droplets from the liquid ejection device includes granular, teardrop-like, and string-like tails. The term "liquid" as used herein refers to any material that can be ejected from the liquid ejection device. For example, the term "liquid" refers to any state in which a substance is in its liquid phase, including fluids such as high or low viscosity liquids, sols, gel water, other inorganic solvents, organic solvents, solutions, liquid resins, liquid metals, and metal melts. The term "liquid" refers not only to a single state of matter, but also to solid functional material particles, such as pigments and metal particles, dissolved, dispersed, or mixed in a solvent. Representative examples of liquids include inks and liquid crystals, as described in the above embodiments. Here, "ink" encompasses various liquid compositions, such as general water-based inks and oil-based inks, as well as gel inks and hot-melt inks. Specific examples of liquid ejection devices include devices that eject liquids containing dispersed or dissolved materials such as electrode materials and color materials used in the manufacture of liquid crystal displays, electroluminescent displays, surface-emitting displays, and color filters. The liquid ejection device may be a device that ejects bioorganic materials used in biochip manufacture, a device used as a precision pipette to eject sample liquids, a textile printing device, a microdispenser, or the like. The liquid ejection device may be a device that ejects lubricating oil with pinpoint accuracy onto precision machinery such as watches and cameras, or a device that ejects transparent resin liquids such as ultraviolet-curing resins onto substrates to form micro-hemispherical lenses, optical lenses, and the like used in optical communication elements. The liquid ejection device may also be a device that ejects etching liquids such as acids or alkalis to etch substrates, etc.

[0114] [Note] The technical concepts and effects that can be understood from the above-described embodiment and modified examples will be described below.

[0115] (A) A printing device comprising: a printing unit that prints on a medium; a transport unit that transports the medium to the printing unit; and a control unit that controls the transport unit, wherein the transport unit comprises a feed unit that feeds the medium from a roll of the medium wound in a roll, a transport roller pair that transports the medium fed by the feed unit toward the printing unit, and an intermediate roller pair between the feed unit and the transport roller pair that transports the medium fed by the feed unit toward the transport roller pair, wherein the transport roller pair comprises a first drive roller and a first driven roller that holds the medium together with the first drive roller, and the intermediate roller pair comprises a second drive roller and a second driven roller that holds the medium together with the second drive roller, and The control unit has a first drive unit that rotates the first drive roller, and a load change unit that changes the pressure load acting between the second drive roller and the second driven roller, and the control unit controls the first drive unit to alternately rotate and stop rotating the first drive roller during intermittent transport in which medium transport and transport stop are alternately performed, and is capable of executing a first control that controls the load change unit so that the pressure load becomes a first pressure load when the first drive roller is rotating during the intermittent transport, and a second control that controls the load change unit so that the pressure load does not occur or the pressure load becomes a second pressure load that is smaller than the first pressure load when the rotation of the first drive roller is stopped during the intermittent transport.

[0116] With this configuration, when the control unit stops rotation of the first drive roller during intermittent transport, the control unit executes second control, which controls the load change unit so that no pressure load is applied or the pressure load is a second pressure load that is smaller than the first pressure load. Therefore, when the second control is executed, the load applied to the medium from the intermediate roller pair is smaller than when the first control is executed. This makes it possible to eliminate wrinkles that have occurred in the medium near the point of transport by the intermediate roller pair.

[0117] (B) In the printing device, the control unit executes the second control every time the rotation of the pair of transport rollers stops. According to this configuration, the control unit executes the second control each time the rotation of the transport roller pair stops. Therefore, the frequency with which the control unit executes the second control increases compared to when the control unit executes the second control each time the rotation of the transport roller pair stops multiple times. Therefore, wrinkles that have occurred in the medium can be eliminated more frequently.

[0118] (C) In the printing device, the control unit executes the second control each time the rotation of the pair of transport rollers is stopped multiple times. According to this configuration, the control unit executes the second control each time the rotation of the conveying roller pair is stopped multiple times. Therefore, the frequency with which the control unit executes the second control is reduced compared to when the control unit executes the second control each time the rotation of the conveying roller pair is stopped. Therefore, the load acting on the load change unit due to the execution of the second control can be reduced.

[0119] (D) In ​​the printing device, when the rotation of the first drive roller is stopped during the intermittent transport, the control unit executes the second control and then the first control. With this configuration, when the rotation of the first drive roller is stopped during intermittent transport, the control unit executes the second control and then the first control. This allows the first drive roller to start rotating with the pressing load on the intermediate roller pair set to the first pressing load. This allows the medium to be transported while being appropriately sandwiched between the intermediate roller pair.

[0120] (E) In the printing device, the second pressing load is 10 percent or less of the first pressing load. (F) In the printing device, the transport unit has a second drive unit that drives the second drive roller, and the control unit is capable of performing an intermediate adjustment operation that adjusts the tension of the medium located between the transport roller pair and the intermediate roller pair by controlling the second drive unit to rotate the second drive roller, and a feed adjustment operation that adjusts the tension of the medium located between the intermediate roller pair and the feed unit by controlling the feed unit.

[0121] According to this configuration, the control unit can perform an intermediate adjustment operation to adjust the tension of the medium located between the transport roller pair and the intermediate roller pair by controlling the second drive unit to rotate the second drive roller. Therefore, the intermediate adjustment operation can eliminate any transport error that occurs in the medium located between the transport roller pair and the intermediate roller pair during transport of the medium. The control unit can perform a feed adjustment operation to adjust the tension of the medium located between the intermediate roller pair and the feed unit by controlling the feed unit. Therefore, the feed adjustment operation can eliminate any transport error that occurs in the medium located between the intermediate roller pair and the feed unit during transport of the medium. Therefore, the transport roller pair can transport the medium with high precision.

[0122] (G) In the printing device, the transport unit has a second drive unit that drives the second drive roller, and the control unit is capable of performing an intermediate adjustment operation that adjusts the tension of the medium located between the transport roller pair and the intermediate roller pair by controlling the second drive unit to rotate the second drive roller, and a slack formation operation that forms slack in the medium located between the intermediate roller pair and the feed unit by controlling the feed unit to feed the medium from the roll body toward the transport roller pair.

[0123] According to this configuration, the control unit can perform an intermediate adjustment operation to adjust the tension of the medium located between the transport roller pair and the intermediate roller pair by controlling the second drive unit to rotate the second drive roller. Therefore, the intermediate adjustment operation can eliminate transport errors that occur in the medium located between the transport roller pair and the intermediate roller pair during medium transport. The control unit can perform a slack formation operation to create slack in the medium located between the intermediate roller pair and the feed unit by controlling the feed unit to feed the medium from the roll toward the transport roller pair. This makes the intermediate roller pair less susceptible to the effects of eccentricity or tilt of the roll. As a result, it is possible to suppress a decrease in transport accuracy in the intermediate roller pair, and ultimately a decrease in transport accuracy in the transport roller pair. Therefore, the transport roller pair can transport the medium with high precision.

[0124] (H) In the printing device, the transport unit has a second drive unit that drives the second drive roller, and the control unit performs the second control and then the first control when the rotation of the first drive roller is stopped during the intermittent transport, and performs the first control when the rotation of the first drive roller is stopped during the intermittent transport, and then performs an intermediate slack elimination operation to eliminate slack in the medium located between the transport roller pair and the intermediate roller pair by controlling the second drive unit to rotate the second drive roller in a direction opposite to the direction in which the medium is transported toward the transport roller pair.

[0125] With this configuration, the control unit executes an intermediate slack elimination operation that controls the second drive unit to rotate the second drive roller in a direction opposite to the direction in which the medium is transported toward the transport roller pair. The intermediate slack elimination operation eliminates slack in the medium positioned between the transport roller pair and the intermediate roller pair. Therefore, it is possible to reset the accumulated transport error and accumulated slack amount error in the width direction for the medium positioned between the transport roller pair and the intermediate roller pair.

[0126] (I) A transport control method for transporting a medium by a transport unit, the transport unit having a feed unit that feeds out the medium from a roll body on which the medium is wound in a roll, a transport roller pair that transports the medium fed out by the feed unit, and an intermediate roller pair between the feed unit and the transport roller pair that transports the medium fed out by the feed unit toward the transport roller pair, the transport roller pair having a first drive roller and a first driven roller that holds the medium together with the first drive roller, the intermediate roller pair having a second drive roller and a second driven roller that holds the medium together with the second drive roller, the transport unit rotating the first drive roller The device has a first drive unit and a load change unit that changes the pressure load acting between the second drive roller and the second driven roller, and is capable of controlling the first drive unit to alternately rotate and stop rotation of the first drive roller during intermittent transport in which medium transport and transport stop are alternately performed, and executing a first control that controls the load change unit so that the pressure load becomes a first pressure load when the first drive roller is rotating during the intermittent transport, and a second control that controls the load change unit so that the pressure load does not occur or becomes a second pressure load that is smaller than the first pressure load when the rotation of the first drive roller is stopped during the intermittent transport.

[0127] According to this method, when the rotation of the first drive roller is stopped during intermittent conveyance, a second control is executed to control the load change unit so that no pressure load is applied or the pressure load is a second pressure load that is smaller than the first pressure load. Therefore, when the second control is executed, the load applied to the medium from the intermediate roller pair is smaller than when the first control is executed. Therefore, wrinkles that have occurred in the medium near the point of conveyance by the intermediate roller pair can be eliminated. [Explanation of symbols]

[0128] C1...first control, C2...second control, M...medium, M1...intermediate adjustment operation, M2...feed adjustment operation, M5...intermediate slack elimination operation, M7...slack formation operation, PL...pressing load, PL1...first pressing load, PL2...second pressing load, T...tension, 10...printing device, 11...printing unit, 12...conveying unit, 21...conveying roller pair, 21a...first driving roller, 21b...first driven roller, 22...first driving unit, 30...feeding unit, 36...roll body, 41...intermediate roller pair, 41a...second driving roller, 41b...second driven roller, 42...second driving unit, 50...control unit, 60...load changing unit, 95...slack.

Claims

1. a printing unit that prints on the medium; a transport unit that transports a medium to the printing unit; a control unit that controls the transport unit, The conveying unit is a feeding unit that feeds out the medium from a roll body on which the medium is wound in a roll shape; a pair of transport rollers that transport the medium fed by the feeding unit toward the printing unit; an intermediate roller pair disposed between the feeding section and the pair of transport rollers, for transporting the medium fed by the feeding section toward the pair of transport rollers; the transport roller pair includes a first drive roller and a first driven roller that sandwiches the medium together with the first drive roller; the intermediate roller pair includes a second drive roller and a second driven roller that pinches the medium together with the second drive roller, The conveying unit is a first driving unit that rotates the first driving roller; a load change unit that changes a pressing load acting between the second drive roller and the second driven roller, the control unit controls the first drive unit so that the first drive roller alternates between rotating and stopping rotation during intermittent transport in which transport and stopping of the medium are alternately performed; executing a first control for controlling the load changing unit so that the pressing load becomes a first pressing load when the first driving roller is rotated during the intermittent conveyance; controlling the load change unit so that the pressing load becomes the first pressing load when the rotation of the first driving roller is stopped and the second driving roller is rotated during the intermittent conveyance; a second control that controls the load change unit so that the pressing load is not generated or becomes a second pressing load that is smaller than the first pressing load when the rotation of the first drive roller is stopped and the rotation of the second drive roller is stopped during the intermittent transport;

2. A printing unit that prints on a medium; a transport unit that transports a medium to the printing unit; a control unit that controls the transport unit, The conveying unit is a feeding unit that feeds out the medium from a roll body on which the medium is wound in a roll shape; a pair of transport rollers that transport the medium fed by the feeding unit toward the printing unit; an intermediate roller pair disposed between the feeding section and the pair of transport rollers, for transporting the medium fed by the feeding section toward the pair of transport rollers; the transport roller pair includes a first drive roller and a first driven roller that sandwiches the medium together with the first drive roller; the intermediate roller pair includes a second drive roller and a second driven roller that pinches the medium together with the second drive roller, The conveying unit is a first driving unit that rotates the first driving roller; a load change unit that changes a pressing load acting between the second drive roller and the second driven roller, the control unit controls the first drive unit so that the first drive roller alternates between rotating and stopping rotation during intermittent transport in which transport and stopping of the medium are alternately performed; executing a first control for controlling the load changing unit so that the pressing load becomes a first pressing load when the first driving roller is rotated during the intermittent conveyance; a second control is executable to control the load changing unit so that the pressing load is not generated or is set to a second pressing load that is smaller than the first pressing load when the rotation of the first driving roller is stopped during the intermittent conveyance; A printing device characterized in that, when the rotation of the first drive roller is stopped during the intermittent transport and the feed-out unit is rotated, the load change unit is controlled so that the pressing load becomes a first pressing load.

3. 3. The printing apparatus according to claim 1, wherein the control unit executes the second control every time the rotation of the pair of transport rollers stops.

4. 3. The printing apparatus according to claim 1, wherein the control unit executes the second control each time the rotation of the pair of transport rollers is stopped a plurality of times.

5. A printing device described in any one of claims 1 to 4, characterized in that the control unit performs the second control and then the first control when the rotation of the first drive roller is stopped during the intermittent transport.

6. 6. The printing apparatus according to claim 1, wherein the second pressing load is equal to or less than 10 percent of the first pressing load.

7. the transport unit has a second drive unit that drives the second drive roller, A printing device described in any one of claims 1 to 6, characterized in that the control unit is capable of performing an intermediate adjustment operation to adjust the tension of the medium located between the transport roller pair and the intermediate roller pair by controlling the second drive unit to rotate the second drive roller, and a feed adjustment operation to adjust the tension of the medium located between the intermediate roller pair and the feed unit by controlling the feed unit.

8. the transport unit has a second drive unit that drives the second drive roller, The printing device described in any one of claims 1 to 7, characterized in that the control unit is capable of performing an intermediate adjustment operation to adjust the tension of the medium located between the transport roller pair and the intermediate roller pair by controlling the second drive unit to rotate the second drive roller, and a slack formation operation to form slack in the medium located between the intermediate roller pair and the feed unit by controlling the feed unit to feed the medium from the roll body toward the transport roller pair.

9. The printing device described in Claim 8, characterized in that the control unit controls the load change unit so that the pressing load becomes the first pressing load when performing the slack forming operation.

10. the transport unit has a second drive unit that drives the second drive roller, The control unit When the rotation of the first driving roller is stopped during the intermittent transport, the second control is executed and then the first control is executed; A printing device described in any one of claims 1 to 9, characterized in that when the rotation of the first drive roller is stopped during the intermittent transport, after executing the first control, an intermediate slack elimination operation is performed to eliminate slack in the medium located between the transport roller pair and the intermediate roller pair by controlling the second drive unit to rotate the second drive roller in the opposite direction to the direction in which the medium is transported toward the transport roller pair.

11. The printing device described in Claim 10, characterized in that the control unit controls the load change unit so that the pressing load becomes the first pressing load when performing the intermediate slack elimination operation.

12. A transport control method for transporting a medium by a transport unit, comprising: The conveying unit is a feeding unit that feeds out the medium from a roll body on which the medium is wound in a roll shape; a pair of transport rollers that transport the medium fed by the feeding unit; an intermediate roller pair disposed between the feeding section and the pair of transport rollers, for transporting the medium fed by the feeding section toward the pair of transport rollers; the transport roller pair includes a first drive roller and a first driven roller that sandwiches the medium together with the first drive roller; the intermediate roller pair includes a second drive roller and a second driven roller that pinches the medium together with the second drive roller, The conveying unit is a first driving unit that rotates the first driving roller; a load change unit that changes a pressing load acting between the second drive roller and the second driven roller, In intermittent transport in which transport of a medium is alternately performed and transport stop is performed, the first drive unit is controlled so that the first drive roller is alternately rotated and stopped from rotating; executing a first control for controlling the load changing unit so that the pressing load becomes a first pressing load when the first driving roller is rotated during the intermittent conveyance; controlling the load change unit so that the pressing load becomes the first pressing load when the rotation of the first driving roller is stopped and the second driving roller is rotated during the intermittent conveyance; a second control that controls the load change unit so that the pressing load is not generated or is a second pressing load that is smaller than the first pressing load when the rotation of the first drive roller is stopped and the rotation of the second drive roller is stopped during the intermittent conveyance,

13. A transport control method for transporting a medium by a transport unit, comprising: The conveying unit is a feeding unit that feeds out the medium from a roll body on which the medium is wound in a roll shape; a pair of transport rollers that transport the medium fed by the feeding unit; an intermediate roller pair disposed between the feeding section and the pair of transport rollers, for transporting the medium fed by the feeding section toward the pair of transport rollers; the transport roller pair includes a first drive roller and a first driven roller that sandwiches the medium together with the first drive roller; the intermediate roller pair includes a second drive roller and a second driven roller that pinches the medium together with the second drive roller, The conveying unit is a first driving unit that rotates the first driving roller; a load change unit that changes a pressing load acting between the second drive roller and the second driven roller, In intermittent transport in which transport of a medium is alternately performed and transport stop is performed, the first drive unit is controlled so that the first drive roller is alternately rotated and stopped from rotating; executing a first control for controlling the load changing unit so that the pressing load becomes a first pressing load when the first driving roller is rotated during the intermittent conveyance; a second control is executable to control the load changing unit so that the pressing load is not generated or is set to a second pressing load that is smaller than the first pressing load when the rotation of the first driving roller is stopped during the intermittent conveyance; a control unit for controlling the load change unit so that the pressing load becomes a first pressing load when the rotation of the first drive roller is stopped and the feeding unit is rotated during the intermittent conveyance;

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