JP2018158449A - Conveyance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conveyance device capable of reducing tension fluctuation of Web, while suppressing enlargement of the device.SOLUTION: A control part 6 controls a supply current to a conveyance motor 34 so that conveyance speed of Web maintains printing conveyance speed, based on the conveyance speed of the Web detected by an encoder 36, while controlling a brake 12 so as to impart a prescribed tension to the Web, and performs control so that torque in a direction for compensating tension fluctuation of the Web corresponding to fluctuation of the supply current to the conveyance motor 34 is imparted to a web roll support shaft by a sub motor 14.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a conveyance device that conveys a web.

  There is known a printing apparatus that prints on a web by ejecting ink from an inkjet head while continuously conveying a long web as a printing medium (see, for example, Patent Document 1).

  The web printed by such a printing apparatus is supplied from a web roll in which the web is wound into a roll. As an apparatus for supplying a web from a web roll, an unwinding apparatus is known in which the web roll is rotated by a motor to unwind the web and supply it to a printing apparatus. Such an unwinding device includes a loop roller mechanism for absorbing the difference in the conveyance speed from the web conveyance speed in the printing apparatus and canceling the web tension. For this reason, an apparatus enlarges.

  Therefore, in order to suppress the enlargement of the apparatus, the function of supplying the web by rotating the web roll by the motor is not provided, and the web is unwound from the web roll by the conveyance force of the conveyance roller that conveys the web in the printing apparatus. A simple configuration has been proposed.

JP2013-71323A

  In the printing apparatus adopting the simple configuration as described above, a brake for preventing the web roll from rotating too fast and applying tension to the web is connected to a support shaft that rotatably supports the web roll. Has been.

  Here, since the web roll has a large weight, a large and high output brake is used as a brake connected to the support shaft of the web roll. Since such a brake has a low response speed, it is difficult to control the tension to suppress the fine tension fluctuation of the web. For this reason, the distance between the ink-jet head and the web fluctuates due to fluctuations in web tension, and there is a risk that the print image quality will deteriorate due to the landing deviation of the ink.

  The present invention has been made in view of the above, and an object of the present invention is to provide a transport device that can reduce fluctuations in web tension while suppressing an increase in size of the device.

  In order to achieve the above object, a first feature of a transport device according to the present invention is a web roll support shaft that rotatably supports a web roll, a transport roller that transports the web while unwinding the web roll, A conveyance motor that drives a conveyance roller, a brake that applies a torque in a direction opposite to a normal direction that is a rotation direction when the web is unwound to the web roll support shaft, the forward direction and the web roll support shaft A sub-motor that applies reverse torque; a conveyance speed detection unit that detects a conveyance speed of the web; and a control unit that controls the conveyance motor, the brake, and the sub-motor. While controlling the brake to apply tension, the web conveyance speed is determined based on the web conveyance speed detected by the conveyance speed detection unit. The value of the drive control parameter of the transport motor is controlled so as to maintain the target speed, and the torque in a direction that cancels out the tension change of the web according to the change of the value of the drive control parameter is controlled by the sub motor by the web roll support shaft. It is to control to give to.

  A second feature of the transport device according to the present invention is that the control unit applies the torque in the positive direction to the web roll support shaft during the acceleration period when the transport of the web by the transport motor is started. The sub motor is controlled to assist the rotation of the support shaft.

  A third feature of the transport apparatus according to the present invention is that the sub motor is in a short brake state when the power is shut off.

  According to the first feature of the transport apparatus according to the present invention, the control unit controls the brake so as to apply a predetermined tension to the web, and controls the drive of the transport motor so that the web transport speed maintains the target speed. Control the value of the parameter. At the same time, the control unit controls the sub-motor to apply a torque in a direction that cancels a change in the tension of the web corresponding to a change in the value of the drive control parameter to the web roll support shaft. As a result, in a simple configuration in which the conveyance roller conveys the web while unwinding it from the web roll, fine tension fluctuations of the web caused by controlling the value of the drive control parameter of the conveyance motor in order to maintain the conveyance speed of the web. It is reduced by the output torque of the sub motor. As a result, web tension fluctuations can be reduced while suppressing the increase in size of the apparatus.

  According to the second feature of the transport apparatus according to the present invention, the control unit applies a torque in the positive direction to the web roll support shaft during the acceleration period when the transport of the web by the transport motor is started. The sub motor is controlled to assist the rotation. Thereby, the delay in the acceleration of the web due to the moment of inertia of the web roll can be reduced, and the web can be quickly reached the target speed.

  According to the third feature of the transport apparatus of the present invention, the sub motor is in a short brake state when the power is shut off. Thereby, even if the power supply of a conveying apparatus is interrupted | blocked, it is suppressed that a web roll support shaft and a web roll rotate by the submotor of a short brake state. As a result, the web roll can be prevented from sagging due to the rotation of the web roll support shaft and the web roll due to external force.

It is a schematic block diagram of the printing apparatus provided with the conveying apparatus which concerns on embodiment. FIG. 2 is an enlarged perspective view of a main part of a web roll holding unit of the printing apparatus shown in FIG. 1. FIG. 2 is a control block diagram of the printing apparatus shown in FIG. 1. 6 is a flowchart for explaining the operation of the printing apparatus.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals.

  The following embodiments exemplify devices for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, arrangement, etc. of each component. Is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a schematic configuration diagram of a printing apparatus provided with a transport apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged perspective view of a main part of a web roll holding unit of the printing apparatus shown in FIG. FIG. 3 is a control block diagram of the printing apparatus shown in FIG. In the following description, the direction orthogonal to the paper surface of FIG. 1 is the front-rear direction, and the front surface direction is the front. Also, the top, bottom, left, and right of the paper surface in FIG.

  As shown in FIGS. 1 and 3, the printing apparatus 1 according to the present embodiment includes a web roll holding unit 2, a transport unit 3, printing units 4 </ b> A and 4 </ b> B, a winding unit 5, and a control unit 6. Is provided. The web roll holding unit 2, the conveyance unit 3, and the control unit 6 constitute a conveyance device.

  The web roll holding unit 2 holds the web roll 7. The web roll 7 is obtained by winding a web W, which is a long print medium made of film, paper, or the like, into a roll shape. As shown in FIGS. 1 to 3, the web roll holding unit 2 includes a web roll support shaft 11, a brake 12, an intermediate gear 13, a sub motor 14, and a sub motor driver 15.

  The web roll support shaft 11 supports the web roll 7 rotatably. The web roll support shaft 11 is formed in a long shape extending in the front-rear direction. The web roll support shaft 11 is made of an air shaft, for example. A web roll support shaft gear 11 a that meshes with the intermediate gear 13 is fixed to the rear end portion of the web roll support shaft 11.

  The brake 12 applies to the web roll support shaft 11 a torque (load torque) in the direction opposite to the forward direction, which is the rotational direction (clockwise direction in FIG. 1) when the web W is unwound. The brake 12 is made of a powder brake, for example.

  The brake 12 has an output shaft 12a that outputs a braking force. A brake gear 12b is attached to the output shaft 12a. When the braking force of the brake 12 is transmitted to the web roll support shaft 11 via the brake gear 12b, the intermediate gear 13, and the web roll support shaft gear 11a, a load torque is applied to the web roll support shaft 11.

  The intermediate gear 13 transmits the braking force of the brake 12 and the output torque of the sub motor 14 to the web roll support shaft gear 11a. The intermediate gear 13 meshes with a brake gear 12b, a sub motor gear 14b, which will be described later, and a web roll support shaft gear 11a.

  The sub motor 14 applies torque in the forward direction and the reverse direction to the web roll support shaft 11. The sub motor 14 has an output shaft 14a that outputs torque. A sub motor gear 14b is attached to the output shaft 14a. The output torque of the sub motor 14 is transmitted to the web roll support shaft 11 via the sub motor gear 14b, the intermediate gear 13, and the web roll support shaft gear 11a. The sub motor 14 is a low output motor that is not capable of rotating the web roll support shaft 11 on which the web roll 7 is mounted alone.

  The sub motor driver 15 drives the sub motor 14. The sub motor driver 15 has an H bridge circuit (not shown) that drives the sub motor 14 to rotate forward and backward. The sub motor driver 15 is designed so that the H bridge circuit is in a short brake mode in which the terminal of the sub motor 14 is short-circuited when the printing apparatus 1 is powered off. Thereby, when the power of the printing apparatus 1 is shut off, the sub motor 14 is in a short brake state. When the sub motor 14 is in a short brake state, a resistance force is generated against the rotation of the output shaft 14a due to an external force.

  The transport unit 3 transports the web W. The transport unit 3 includes guide rollers 21 to 30, 20 head lower support members 31, a meandering control unit 32, a pair of transport rollers 33, a transport motor 34, a transport motor driver 35, and an encoder (Claims). 36).

  The guide rollers 21 to 30 guide the web W transported in the transport unit 3. The guide rollers 21 to 20 are driven to rotate by the web W being conveyed. The guide rollers 21 to 30 are formed in a long shape extending in the front-rear direction. A guide path of the web W in the transport unit 3 is formed by the guide rollers 21 to 30, the head lower support member 31, the transport roller 33, and meander control rollers 37 and 38 of the meander control unit 32 described later.

  The guide rollers 21 and 22 guide the web W between the web roll 7 and the meandering control unit 32. The guide roller 21 is disposed in the vicinity of the right side of the web roll holding unit 2. The guide roller 22 is disposed between the guide roller 21 and a meandering control roller 37 of a meandering control unit 32 described later.

  The guide rollers 23 to 29 guide the web W between the meandering control unit 32 and the conveyance roller 33. The guide roller 23 is disposed on the left side of a meandering control roller 38 of a meandering control unit 32 described later. The guide roller 24 is disposed above the guide roller 23. The guide roller 25 has the same height as the guide roller 24 and is disposed on the right side of the guide roller 24. The guide roller 26 is disposed below the guide roller 25 and at a position higher than the guide roller 23. The guide roller 27 is disposed on the left side of the guide roller 26, in the vicinity of the right side of the web W between the guide rollers 23 and 24, and at the same height as the guide roller 26. The guide roller 28 is disposed on the lower right side of the guide roller 27. The guide roller 29 is disposed slightly below the right side of the guide roller 28.

  The guide roller 30 guides the web W between the conveyance roller 33 and the winding unit 5. The guide roller 30 is disposed in the vicinity of the left side of the winding unit 5.

  The head lower support member 31 supports the web W under the head unit 51 described later between the guide rollers 24 and 25 and between the guide rollers 26 and 27. The head lower support member 31 is formed in a long shape extending in the front-rear direction. Ten head support members 31 are arranged between the guide rollers 24 and 25 and between the guide rollers 26 and 27, respectively. Two head lower support members 31 are arranged immediately below each head unit 51. Between the guide rollers 24 and 25 and between the guide rollers 26 and 27, the 10 head lower support members 31 are arranged so that the web W draws a convex arch upward.

  The meander control unit 32 corrects the meandering of the web W. The meandering control unit 32 includes meandering control rollers 37 and 38, a meandering control motor 39, and a meandering control motor driver 40.

  The meandering control rollers 37 and 38 are rollers for guiding the web W and correcting the meandering of the web W. The meandering control rollers 37 and 38 are formed in a long cylindrical shape extending in the front-rear direction. The meandering control rollers 37 and 38 are driven to rotate by the web W being conveyed. The meandering control rollers 37 and 38 are configured such that the angle of the axial direction with respect to the width direction (front-rear direction) of the web W can be adjusted. The meandering control roller 37 is disposed on the right side of the guide roller 22. The meandering control roller 38 is disposed above the meandering control roller 37.

  The meandering control motor 39 controls the meandering control rollers 37 and 38 around the axis parallel to the left and right direction in order to adjust the angle of the axial direction of the meandering control rollers 37 and 38 with respect to the width direction (front-rear direction) of the web W. Rotate. The meander control motor driver 40 drives the meander control motor 39.

  The pair of transport rollers 33 transport the web W toward the winding unit 5 while nipping the web W. By the conveyance of the web W by the conveyance roller 33, the web roll support shaft 11 and the web roll 7 are rotated, and the web W is unwound from the web roll 7. The pair of transport rollers 33 is disposed between the guide rollers 29 and 30.

  The carry motor 34 drives the carry roller 33 to rotate. The carry motor driver 35 drives the carry motor 34.

  The encoder 36 is connected to the guide roller 24 and outputs a pulse signal for each predetermined rotation angle of the guide roller 24.

  The printing units 4A and 4B print images on the front surface and the back surface of the web W, respectively. The printing unit 4 </ b> A is disposed in the vicinity of the upper portion of the web W between the guide rollers 24 and 25. The printing unit 4B is disposed in the vicinity of the upper portion of the web W between the guide rollers 26 and 27. Each of the printing units 4A and 4B includes five head units 51.

  The head unit 51 has an inkjet head (not shown), and prints an image by ejecting ink from the nozzles of the inkjet head onto the web W. In each of the printing units 4A and 4B, the five head units 51 eject inks of different colors.

  The winding unit 5 winds the web W printed by the printing units 4A and 4B. The winding unit 5 includes a winding shaft 56, a winding motor 57, and a winding motor driver 58.

  The winding shaft 56 winds and holds the web W. The winding shaft 56 is formed in a long shape extending in the front-rear direction.

  The winding motor 57 rotates the winding shaft 56 in the clockwise direction in FIG. The web W is wound around the winding shaft 56 by the rotation of the winding shaft 56. The take-up motor driver 58 drives the take-up motor 57.

  The control unit 6 controls the operation of the entire printing apparatus 1. The control unit 6 includes a CPU, RAM, ROM, hard disk, and the like.

  When performing the printing operation, the control unit 6 drives the transport motor 34 and the winding motor 57 to transport the web W, and drives the head unit 51 of the printing units 4A and 4B to print an image on the web W.

  During the conveyance of the web W, the control unit 6 controls the brake 12 so as to apply a predetermined tension to the web W, and the conveyance speed is determined to be a predetermined print conveyance based on the conveyance speed of the web W detected by the encoder 36. The power supplied to the conveyance motor 34 is controlled so as to maintain the speed. Here, in the present embodiment, it is assumed that the drive control parameter for controlling the power supplied to the transport motor 34 is a current. That is, the control unit 6 controls the supply current to the transport motor 34 so that the transport speed of the web W maintains the print transport speed.

  Further, the control unit 6 controls the sub motor 14 to apply a torque in a direction that cancels the tension variation of the web W according to the variation of the supply current to the conveyance motor 34 to the web roll support shaft 11.

  Next, the operation of the printing apparatus 1 will be described.

  FIG. 5 is a flowchart for explaining the operation of the printing apparatus 1. The process of the flowchart in FIG. 5 starts when the printing apparatus 1 receives a print job from an external apparatus such as a personal computer.

  In step S <b> 1 of FIG. 4, the control unit 6 starts driving the transport motor 34, the winding motor 57, and the sub motor 14.

  When the driving of the transport motor 34 is started, the rotation of the transport roller 33 is started and the transport of the web W is started. The conveyance roller 33 conveys the web W toward the winding unit 5 while unwinding the web W from the web roll 7. Accordingly, the web roll support shaft 11 and the web roll 7 rotate in the forward direction (clockwise direction in FIG. 1). After the start of conveyance, the conveyance speed of the web W is accelerated.

  The sub motor 14 is driven so as to apply a torque in the positive direction to the web roll support shaft 11. Thereby, the sub motor 14 assists the rotation of the web roll support shaft 11 and the web roll 7 in order to increase the acceleration of the web W and shorten the acceleration period.

  In addition, when the winding motor 57 starts to be driven, the winding shaft 56 starts to rotate in the clockwise direction in FIG. Thereby, the winding shaft 56 starts to wind the web W sent by the transport roller 33.

  Next, in step S <b> 2, the control unit 6 determines whether or not the web W conveyance speed has reached the print conveyance speed based on the web W conveyance speed detected by the encoder 36. Specifically, the control unit 6 calculates the rotation speed of the guide roller 24 based on the output pulse signal of the encoder 36, and calculates the conveyance speed of the web W according to the rotation speed. Then, the control unit 6 determines whether or not the calculated transport speed of the web W has reached the print transport speed. When it is determined that the conveyance speed of the web W has not reached the printing conveyance speed (step S2: NO), the control unit 6 repeats step S2.

  When it is determined that the conveyance speed of the web W has reached the printing conveyance speed (step S2: YES), the control unit 6 stops the sub motor 14 in step S3. That is, the control unit 6 stops the sub motor 14 when the acceleration period at the start of conveyance of the web W ends.

  In step S <b> 3, the control unit 6 starts constant speed conveyance control of the web W at the printing conveyance speed and starts tension control of the web W.

  The constant speed conveyance control of the web W at the printing conveyance speed is based on the conveyance speed of the web W detected by the encoder 36 and is supplied to the conveyance motor 34 so as to maintain the conveyance speed constant at the printing conveyance speed (target speed). It controls power. The reason why the conveyance speed of the web W is kept constant is to prevent the landing deviation of the ink discharged from the head unit 51 to the web W and to obtain a good print image quality.

  Specifically, the control unit 6 calculates the rotation speed of the guide roller 24 based on the output pulse signal of the encoder 36, and calculates the conveyance speed of the web W according to the rotation speed. Then, the control unit 6 controls the supply current to the transport motor 34 so that the difference between the calculated transport speed and the print transport speed is eliminated. Thereby, the conveyance speed of the web W by the conveyance motor 34 is controlled to match the printing conveyance speed.

  By such constant speed conveyance control, even when the conveyance speed of the web W fluctuates minutely due to unevenness of the thickness of the web W or the like, control is performed to suppress the fluctuation of the conveyance speed and maintain the printing conveyance speed.

  Here, when the supply current to the conveyance motor 34 varies due to the above-described constant speed conveyance control, the output torque of the conveyance motor 34 varies, and as a result, fine tension fluctuations occur in the web W. The tension control of the web W is performed in order to apply a predetermined tension to the web W and to suppress fine tension fluctuations of the web W caused by performing the above-described constant speed conveyance control.

  Specifically, when the acceleration period of the web W ends, that is, when the conveyance speed of the web W reaches the print conveyance speed, the control unit 6 activates the brake 12. Then, the control unit 6 controls the brake 12 so that a predetermined load torque for applying a predetermined tension to the web W is applied to the web roll support shaft 11.

  Here, when the outer diameter of the web roll 7 is reduced by the unwinding of the web W, the brake force of the brake 12 is used to maintain the load torque applied to the web roll support shaft 11 and maintain the tension of the web W. Need to be larger. For this reason, the control unit 6 maintains the load torque applied to the web roll support shaft 11 by gradually increasing the braking force according to the reduction in the outer diameter of the web roll 7 detected by a sensor (not shown). Then, the brake 12 is controlled.

  Further, the control unit 6 cancels the tension fluctuation of the web W according to the fluctuation of the value of the supply current to the conveyance motor 34 in order to suppress the tension fluctuation of the web W caused by the above-described constant speed conveyance control. Control is performed so that torque is applied to the web roll support shaft 11 by the sub motor 14.

  Specifically, when the supply current to the conveyance motor 34 increases, the control unit 6 controls the sub motor 14 to apply a positive torque to the web roll support shaft 11. Thereby, when the output torque of the conveyance motor 34 increases due to an increase in the supply current to the conveyance motor 34 and the tension of the web W increases, the load torque applied to the web roll support shaft 11 is reduced, thereby reducing the web W Suppresses the increase in tension.

  On the other hand, when the supply current to the conveyance motor 34 decreases, the sub motor 14 is controlled so as to apply a reverse torque to the web roll support shaft 11. Thereby, when the output torque of the conveyance motor 34 decreases due to the decrease in the supply current to the conveyance motor 34 and the tension of the web W decreases, the load torque applied to the web roll support shaft 11 is increased, thereby increasing the web W Suppresses the decrease in tension.

  After starting the constant speed conveyance control and tension control of the web W as described above, in step S4 of FIG. 4, the control unit 6 controls the printing units 4A and 4B to perform printing on the web W based on the print job. Let it begin.

  Next, in step S5, the control unit 6 determines whether printing based on the print job is finished. If it is determined that printing based on the print job has not ended (step S5: NO), the control unit 6 repeats step S5.

  If it is determined that printing based on the print job has been completed (step S5: YES), in step S6, the control unit 6 stops the transport motor 34, the take-up motor 57, and the brake 12. Thereby, conveyance of the web W is complete | finished and a series of operation | movement is complete | finished.

  When the printing operation based on the print job as described above is completed in the middle of the web roll 7, the printing apparatus 1 holds the web roll 7 in the web roll holding unit 2, and the web W is pulled along the conveyance path of the conveyance unit 3. It will be in a standby state while being turned. In this state, the power supply of the printing apparatus 1 may be cut off.

  When the power of the printing apparatus 1 is cut off, the brake 12 is stopped, so that the braking force by the brake 12 does not act on the web roll support shaft 11. On the other hand, in the printing apparatus 1, as described above, when the power is cut off, the sub motor 14 enters the short brake state. In the sub-motor 14 in the short brake state, a resistance force against the rotation of the output shaft 14a is generated, so that the rotation of the web roll support shaft 11 is prevented.

  For this reason, even if the web roll 7 is held by the web roll holding unit 2 and the power of the printing apparatus 1 is shut off in a state where the web W is drawn around the conveyance path of the conveyance unit 3, the web roll support shaft 11 and the web It is possible to prevent the roll 7 from rotating and the web W from sagging in the transport unit 3. Thereby, it is suppressed that the web W contacts the inkjet head of the head unit 51.

  As described above, in the printing apparatus 1, the control unit 6 controls the brake 12 so as to apply a predetermined tension to the web W, while the web W conveyance speed is maintained at the print conveyance speed to the conveyance motor 34. Control the supply current. At the same time, the control unit 6 controls the sub-motor 14 to apply a torque in a direction that cancels out the tension variation of the web W according to the variation in the supply current to the conveyance motor 34 to the web roll support shaft 11.

  Thereby, in a simple configuration in which the transport roller 33 transports the web W while unwinding it from the web roll 7, the fineness of the web W generated by controlling the supply current to the transport motor 34 in order to maintain the transport speed of the web W. Tension fluctuation is reduced by the output torque of the sub motor 14. As a result, according to the printing apparatus 1, fluctuations in the tension of the web W can be reduced while suppressing an increase in the size of the apparatus.

  Further, in the printing apparatus 1, the control unit 6 applies the torque in the positive direction to the web roll support shaft 11 during the acceleration period at the start of conveyance of the web W to assist the rotation of the web roll support shaft 11. To control. Thereby, the delay in the acceleration of the web W due to the moment of inertia of the web roll 7 can be reduced, and the web W can be quickly reached to the printing conveyance speed (target speed). Therefore, the time from the start of conveyance of the web W to the start of printing can be reduced.

  Further, in the printing apparatus 1, the sub motor 14 is in a short brake state when the power is shut off. Thereby, even if the power supply of the printing apparatus 1 is interrupted, the rotation of the web roll support shaft 11 and the web roll 7 is suppressed by the sub motor 14 in the short brake state. As a result, it is possible to prevent the web W from sagging due to rotation of the web roll support shaft 11 and the web roll 7 due to external force.

  In the above-described embodiment, the drive control parameter of the carry motor 34 is the current. However, the present invention is not limited to this, and may be a voltage or the like.

  In the embodiment described above, the encoder 36 is used to detect the conveyance speed of the web W. However, the present invention is not limited to this, and a laser Doppler velocimeter or the like may be used.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

DESCRIPTION OF SYMBOLS 1 Printing apparatus 2 Web roll holding | maintenance part 3 Conveyance part 4A, 4B Printing part 5 Winding part 6 Control part 7 Web roll 11 Web roll support shaft 12 Brake 13 Intermediate | middle gear 14 Sub motor 15 Sub motor driver 33 Conveyance roller 34 Conveyance motor 35 Conveyance Motor driver 36 Encoder

Claims (3)

A web roll support shaft that rotatably supports the web roll;
A transport roller for transporting the web while unwinding from the web roll;
A transport motor for driving the transport roller;
A brake that applies a torque in the direction opposite to the forward direction, which is the rotational direction when the web is unwound, to the web roll support shaft;
A sub motor that applies torque in the forward direction and the reverse direction to the web roll support shaft;
A conveyance speed detection unit for detecting the conveyance speed of the web;
A controller for controlling the transport motor, the brake, and the sub motor,
The control unit controls the brake so as to apply a predetermined tension to the web, and controls the conveyance so that the web conveyance speed maintains a target speed based on the web conveyance speed detected by the conveyance speed detection unit. Controlling the value of the drive control parameter of the motor and controlling the sub-motor to apply a torque in a direction that cancels the change in the tension of the web in accordance with the change in the value of the drive control parameter to the web roll support shaft. Characteristic transport device.   The control unit controls the sub motor to assist the rotation of the web roll support shaft by applying the torque in the positive direction to the web roll support shaft during an acceleration period at the start of web transport by the transport motor. The conveying apparatus according to claim 1.   The transport apparatus according to claim 1, wherein the sub motor is in a short brake state when the power is shut off.