Patent Publication Number: US-10766285-B2

Title: Printing apparatus and printing method

Description:
The present application is based on, and claims priority from JP Application Serial Number 2018-063743, filed Mar. 29, 2018, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a printing apparatus and a printing method. 
     2. Related Art 
     Printing apparatuses that perform printing of images and letters by ejecting ink from a printing head onto a medium are widely used. A medium, such as paper, cloth and a sheet, is transported by a transportation roller pair disposed upstream of the printing head in the transportation direction. In this case, due to static electricity charged in the medium and the like, a part of the medium may adhere to the transportation surface of a transportation guide. Consequently, transportation of the medium may fail. 
     At a location upstream of a location where the medium is stuck, the medium forms a protruding portion due to buckling of the medium. Further, when the medium is supplied, the protruding portion is further enlarged. When being pushed into a narrow area, the protruding portion may creases or wrinkles This state is called jam. Further, when the protruding portion contacts with the printing head, the medium may stain. 
     JP-A-2016-147380 discloses a recording device for suppressing formation of the protruding portion. According to this, the recording device includes a sending unit that sends a medium. The sending unit sends the medium to a downstream side. Then, a winding unit winds and collects the medium at a location downstream of the sending unit. The sending unit and the winding unit alternately operate. Even when the sending unit sends the medium and the protruding portion is formed, the winding unit winds the medium before the protrusion is enlarged. In this manner, formation of the protruding portion is suppressed by alternately performing the sending and winding of the medium. 
     The recording device disclosed in JP-A-2016-147380 cannot detect transportation failures of the medium. When a transportation failure (jam) of the medium occurs, the protruding portion is enlarged. When the protruding portion is enlarged, the medium may be damaged, and the medium may make contact with the printing head, thus causing printing failure. In view of this, a printing apparatus that can detect transportation failures of the medium has been desired. 
     SUMMARY 
     A printing apparatus of the present application includes a transporting unit configured to transport a medium along a guide member, a winding unit disposed further downstream of the guide member than the transporting unit and configured to wind the medium, a tension applying unit including a rod member configured to press the medium between the transporting unit and the winding unit and apply tension to the medium while moving between an upper limit position and a lower limit position, and a control unit including a first detecting unit configured to detect a movement amount of the medium, and a second detecting unit configured to detect a movement amount of the rod member. The control unit detects the movement amount of the rod member every time the transporting unit transports the medium by a predetermined length, and detects a transportation failure of the medium when the movement amount of the rod member is smaller than a determination value. 
     Preferably, in the printing apparatus, a winding amount of the medium wound by the winding unit is controlled such that the medium passes through a location where the rod member is able to press the medium. 
     Preferably, the printing apparatus includes a driving unit configured to drive the tension applying unit, and when a transportation failure of the medium is detected, the control unit controls the driving unit such that a force that the tension applying unit applies to press the medium becomes greater than a force that has been applied at a time of detecting the transportation failure of the medium. 
     Preferably, in the printing apparatus, when no transportation failure of the medium is detected after the tension applying unit has intensified the force applied to press the medium, the control unit controls the driving unit to maintain the intensified force to press the medium. 
     Preferably, in the printing apparatus, when no transportation failure of the medium is detected after the tension applying unit has intensified the force applied to press the medium, the control unit controls the driving unit such that the force applied to press the medium is returned to the force that has been applied at the time of detecting the transportation failure of the medium. 
     A printing method of the present application includes transporting a medium along a guide member by a transporting unit, winding the medium by a winding unit further downstream of the guide member than the transporting unit, pressing the medium, between the transporting unit and the winding unit, by a rod member to apply tension to the medium by a rod member while moving the rod member between an upper limit position and a lower limit position, detecting a movement amount of the medium by a first detecting unit, and detecting a movement amount of the rod member by a second detecting unit, and the movement amount of the rod member is detected every time the transporting unit transports the medium by a predetermined length, and a transportation failure of the medium is detected when the movement amount of the rod member is smaller than a determination value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic perspective view illustrating a structure of a printing apparatus according to a first exemplary embodiment. 
         FIG. 2  is a schematic side sectional view illustrating a structure of the printing apparatus. 
         FIG. 3  is a schematic perspective view illustrating a configuration of a tension applying unit. 
         FIG. 4  is a schematic side sectional view illustrating a configuration of the tension applying unit. 
         FIG. 5  is an electrical block diagram illustrating a configuration of a control unit. 
         FIG. 6  is a flowchart of a printing method. 
         FIG. 7  is a schematic view for describing the printing method. 
         FIG. 8  is a schematic view for describing the printing method. 
         FIG. 9  is a schematic view for describing the printing method. 
         FIG. 10  is a schematic view for describing the printing method. 
         FIG. 11  is a schematic view for describing the printing method. 
         FIG. 12  is a drawing for describing the printing method. 
         FIG. 13  is a schematic view for describing the printing method. 
         FIG. 14  is a schematic view for describing the printing method. 
         FIG. 15  is a schematic view for describing the printing method. 
         FIG. 16  is a drawing for describing the printing method. 
         FIG. 17  is a drawing for describing the printing method. 
         FIG. 18  is a drawing for describing the printing method. 
         FIG. 19  is a drawing for describing the printing method. 
         FIG. 20  is a drawing for describing the printing method. 
         FIG. 21  is a drawing for describing the printing method. 
         FIG. 22  is a drawing for describing the printing method. 
         FIG. 23  is a flowchart of a printing method according to a second exemplary embodiment. 
         FIG. 24  is a drawing for describing the printing method. 
         FIG. 25  is a drawing for describing the printing method. 
         FIG. 26  is a drawing for describing a printing method according to a modification. 
         FIG. 27  is a drawing illustrating determination data and tension-related data in a printing medium. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments are described below with reference to the drawings. Note that the scales of the members illustrated in the drawings are changed for illustration in each drawing. 
     First Exemplary Embodiment 
     In the present exemplary embodiment, exemplary features of a printing apparatus are described with reference to the drawings. A printing apparatus and a printing method according to the first exemplary embodiment are described with reference to  FIG. 1  to  FIG. 22 .  FIG. 1  is a schematic perspective view illustrating a structure of the printing apparatus. As illustrated in  FIG. 1 , a printing apparatus  1  is an ink-jet printing apparatus of a large format of a roll-to-roll type that handles a relatively large printing medium. The printing apparatus  1  has a long shape in one direction along a horizontal direction. The longitudinal direction of the printing apparatus  1  is set as an X direction, and the left side in the drawing is set as the +X direction. A direction orthogonal to the X direction along a horizontal direction is set as a Y direction. A gravitational acceleration direction is set as a −Z direction. 
     The printing apparatus  1  includes a leg part  2 . A wheel  3  is provided on the −Z direction side of the leg part  2  and thus the printing apparatus  1  is movable. The wheel  3  is provided with a lock function that is not illustrated, and the rotation of the wheel  3  can be prohibited when the printing apparatus  1  is used. A housing part  4  is provided on the +Z direction side of the leg part  2 , and a control unit  6  configured to control the printing apparatus  1  and a printing unit  5  and the like are provided inside the housing part  4 . 
     An operation panel  7  is provided at a position on the −X direction side and on the +Z direction side of the housing part  4 . The operation panel  7  includes an operation unit  8  and a display unit  9 . The operation unit  8  is composed of a push switch and the like. When inputting a printing condition and the like and providing various instructions, an operator operates the operation unit  8 . The display unit  9  is composed of a liquid crystal display device and the like. A transportation condition setting screen and the like are displayed on the display unit  9 . 
     A notification light  10  is provided on the −X direction side with respect to the operation panel  7 . In the notification light  10 , a blue light, a green light, a yellow light and a red light are disposed side by side in the Z direction. The control unit  6  lights a light of a predetermined color in accordance with the state of the printing apparatus  1  to notify the operator of the state of the printing apparatus  1 . A speaker  11  is provided in a side surface on the −X direction side of the housing part  4 . The control unit  6  outputs a predetermined sound in accordance with the state of the printing apparatus  1  to notify the operator of the state of the printing apparatus  1 . A notification unit  12  includes the notification light  10 , the speaker  11  and the like. 
     A carriage moving unit  13 , a guide rail  14  and a carriage  15  are provided in the printing unit  5 . The carriage moving unit  13  includes a screw shaft  13   c , a motor  13   a , and an encoder  13   b . In the carriage  15 , many printing heads configured to eject ink in the form of ink drops are provided. The printing heads that are not illustrated in the drawing. Each of the screw shaft  13   c  and the guide rail  14  has a long rod shape extending in the X direction, and the carriage  15  moves along the screw shaft  13   c  and the guide rail  14 . The screw shaft  13   c  is provided with the motor  13   a  and the encoder  13   b . The carriage  15  is provided with a nut for thread engagement with the screw shaft  13   c . A ball screw is composed of the nut, the screw shaft  13   c  and the like. When the motor  13   a  rotates the screw shaft  13   c , the carriage  15  moves in the X direction. The encoder  13   b  detects the rotation angle of the screw shaft  13   c , and thus the position of the carriage  15  can be detected. 
     An outlet  16  is provided on the +Y direction side of the housing part  4 , and a printing medium  17  is output from the outlet  16  as a medium printed by the printing unit  5 . A downstream side guide part  18  is provided on the −Z direction side of the outlet  16 . The downstream side guide part  18  guides the printing medium  17  output from the outlet  16 . An infrared ray heater  21  is provided at a location opposite the downstream side guide part  18 . The printing medium  17  passes between the downstream side guide part  18  and the infrared ray heater  21 . The infrared ray heater  21  heats and dries the ink applied on the printing medium  17 . 
     An ink mounting part  22  is provided on the −X direction side of the downstream side guide part  18 . Ink is stored in the ink mounting part  22 . The ink is supplied to the printing heads of the carriage  15  through a tube that is not illustrated. The ink is ejected from the printing heads to the printing medium  17 . 
     A medium supply unit  23  is provided on the −Y direction side of the leg part  2 . The medium supply unit  23  supplies the printing medium  17  to the printing unit  5 . The medium supply unit  23  includes a supply shaft  24 . The printing medium  17  is wound around the supply shaft  24 , and thus a supply side roll body  25  is formed. The supply shaft  24  is provided with a supply motor  24   a  and a supply unit encoder  24   b . When the supply motor  24   a  rotates the supply shaft  24 , the printing medium  17  is supplied to the printing unit  5  from the supply side roll body  25 . The supply unit encoder  24   b  detects the rotation angle of the supply shaft  24 , and thus the supply amount of the printing medium  17  can be detected. 
     As a winding unit, a medium winding unit  26  is provided on the +Y direction side of the leg part  2 . The medium winding unit  26  winds the printing medium  17  output from the outlet  16 . The medium winding unit  26  includes a winding shaft  27 . The printing medium  17  is wound around the winding shaft  27 , and thus a winding side roll body  28  is formed. The winding shaft  27  is provided with a winding motor  27   a  and a winding unit encoder  27   b . When the winding motor  27   a  rotates the winding shaft  27 , the printing medium  17  is wound around the winding side roll body  28 . The winding unit encoder  27   b  detects the rotation angle of the winding shaft  27 , and thus the winding amount of the printing medium  17  can be detected. 
     A tension applying unit  29  is provided between the downstream side guide part  18  and the winding side roll body  28 . The tension applying unit  29  includes a tension bar  30  as a rod member. The tension bar  30  is a long rod-shaped member extending in the X direction, and applies constant tension to the printing medium  17 . With this configuration, the tension bar  30  suppresses the occurrence of wrinkles on the printing medium  17 . 
       FIG. 2  is a schematic side sectional view illustrating a structure of the printing apparatus. As illustrated in  FIG. 2 , the leg part  2  is provided with a support base  2   a  protruding in the −Y direction at a middle portion of the leg part  2  in the Z direction. A supply shaft supporting part  31  is provided on the support base  2   a . The supply shaft supporting part  31  supports the supply shaft  24 , the supply motor  24   a  and the supply unit encoder  24   b.    
     In the medium supply unit  23 , the supply motor  24   a  rotates the supply side roll body  25  in a counterclockwise direction with the X direction as an axis. With this configuration, the printing medium  17  is supplied to the printing unit  5  from the supply side roll body  25 . Note that the printing medium  17  includes various types of printing mediums, and the types of the printing medium  17  are roughly categorized into a paper type and a film type. Specific examples of the paper type include a high-quality paper, cast paper, art paper, coated paper and the like, and specific examples of the film type include synthetic paper, polyethylene terephthalate (PET), polypropylene (PP) and the like. 
     A guide member  34 , in which an upstream guide part  32 , a platen  33  and the downstream side guide part  18  are arranged in this order from the −Y direction side toward the +Y direction side, is provided between the housing part  4  and the leg part  2 . The guide members  34  in the upstream side guide part  32 , the platen  33  and the downstream side guide part  18  respectively guide the printing medium  17 . 
     A supply port  35  is provided between the upstream guide part  32  and the housing part  4 . The printing medium  17  supplied from the medium supply unit  23  is guided to the supply port  35  through the upstream side guide part  32 . A transportation roller  36  is provided between the upstream side guide part  32  and the platen  33 . The transportation roller  36  includes a transportation driving roller  36   a  and a transportation driven roller  36   b . The transportation driving roller  36   a  and the transportation driven roller  36   b  extend in the X direction intersecting the +Y direction, which is the movement direction of the printing medium  17 . The transportation driving roller  36   a  is disposed on the −Z direction side of the guide member  34 . The transportation driven roller  36   b  is disposed on the +Z direction side with respect to the transportation driving roller  36   a . The transportation driven roller  36   b  rotates to follow the rotation of the transportation driving roller  36   a.    
     The transportation roller  36  includes a spring that is not illustrated. The spring presses the transportation driven roller  36   b  against the transportation driving roller  36   a . With the transportation driven roller  36   b  pressed against the transportation driving roller  36   a , the transportation roller  36  rotates while sandwiching the printing medium  17  to send the printing medium  17  to the printing unit  5  in the +Y direction. 
     An intermediate gear  37  and a transportation motor  38  are provided on the −Z direction side of the transportation roller  36 . The transportation motor  38  is provided with a transporting unit encoder  41  as a first detecting unit, and the transporting unit encoder  41  detects the rotation angle of a shaft  38   a  of the transportation motor  38 . Teeth are formed on the shaft of the transportation driving roller  36   a , the outer periphery of the intermediate gear  37  and the shaft  38   a  of the transportation motor  38 . With this configuration, the shaft  38   a  of the transportation motor  38  and the outer periphery of the intermediate gear  37  are meshed with each other, and the outer periphery of the intermediate gear  37  and the shaft of the transportation driving roller  36   a  are meshed with each other. When the transportation motor  38  rotates the shaft  38   a , the torque of the transportation motor  38  is transmitted to the transportation driving roller  36   a  via the intermediate gear  37 . Accordingly, when the transportation motor  38  is driven and the transportation driving roller  36   a  is driven into rotation, the printing medium  17  sandwiched between the transportation driven roller  36   b  and the transportation driving roller  36   a  is transported in the +Y direction. Note that the transporting unit encoder  41  is a part of the control unit  6 . 
     A transporting unit  39  is composed of the transportation roller  36 , the intermediate gear  37 , the transportation motor  38  and the like. The transporting unit  39  transports the printing medium  17  along the guide member  34 . 
     The transporting unit encoder  41  detects the rotation angle of the shaft  38   a  of the transportation motor  38  and outputs it to a movement amount computation unit of the control unit  6 . By using the number of teeth and the diameter of the transportation driving roller  36   a , the number of teeth of the intermediate gear  37 , the number of teeth of the shaft  38   a  and the rotation angle of the shaft  38   a , the movement amount computation unit of the control unit  6  determines the movement amount of the contact surface (outer peripheral surface) with the printing medium  17  at the transportation driving roller  36   a . The movement amount of the outer peripheral surface of the transportation driving roller  36   a  is regarded as the sending amount of the printing medium  17  and is handled as the movement amount of the printing medium  17 . 
     The printing medium  17  that passed by the transportation roller  36  moves along the platen  33 . Then, the printing medium  17  past the platen  33  moves along the downstream side guide part  18 . The outlet  16  is provided between the downstream side guide part  18  and the housing part  4 . The printing medium  17  is output from the outlet  16  of the housing part  4 . The printing medium  17  past the outlet  16  moves along the downstream side guide part  18  toward the medium winding unit  26 . 
     The tension bar  30  of the tension applying unit  29  presses the printing medium  17  at a location between the transporting unit  39  and the medium winding unit  26 . The tension applying unit  29  has a configuration in which the tension bar  30  moves along the circumference of a circle about a turning axis, which is described later, as a rotation center. The tension bar  30  applies tension to the printing medium  17  while moving between the upper limit position and the lower limit position in a movement range. 
     The medium winding unit  26  is disposed further toward downstream side of the guide member  34  than the transporting unit  39 . The medium winding unit  26  wind the printing medium  17  printed by the printing unit  5  into a cylindrical shape, so as to form the winding side roll body  28 . A winding shaft supporting part  42  is provided on the leg part  2 . The winding shaft supporting part  42  sandwiches and holds the winding shaft  27 . The printing medium  17  is wound around the winding shaft  27  and thus the winding side roll body  28  is formed. 
     The carriage moving unit  13  provided inside the housing part  4  reciprocates the carriage  15  in the X direction. The X direction in which the carriage  15  moves is referred to as a main scanning direction. The carriage  15  is supported by the screw shaft  13   c  and the guide rail  14  disposed along the X direction. Thus, the carriage  15  can be reciprocated in the ±X direction by the carriage moving unit  13 . The mechanism of the carriage moving unit  13  may be a linear guide mechanism and the like as well as the ball screw. 
     The carriage  15  is provided with a head unit  43 . The head unit  43  is provided with a printing head that is not illustrated. The printing head ejects ink drops from a nozzle to the printing medium  17  that is being transported along the platen  33 . The printing head of the present exemplary embodiment is referred to also as an ink-jet head. 
     The printing apparatus  1  includes a first heater  44  and a second heater  45  in addition to the infrared ray heater  21 . The first heater  44  is disposed on the −Z direction side of the upstream side guide part  32 . The first heater  44  heats the printing medium  17  via the upstream side guide part  32 . The second heater  45  heats the printing medium  17  via the platen  33 . Since the printing medium  17  is heated, the ink landed on the printing medium  17  is easily dried. The infrared ray heater  21  dries and fixes the ink, which is still not dried, among the ink that is landed on the printing medium, before the printing medium is wound by the medium winding unit  26 . 
       FIG. 3  is a schematic perspective view illustrating a configuration of the tension applying unit. As illustrated in  FIG. 3 , the printing apparatus  1  includes a pair of the leg parts  2 . The leg part  2  on the −X direction side is a first leg part  2   b , and the leg part  2  on the +X direction side is a second leg part  2   c . A first support plate  46  is provided on the +Y direction side of the first leg part  2   b , and a second support plate  47  is provided on the +Y direction side of the second leg part  2   c.    
     The first support plate  46  is provided with a first shaft  46   a . A first arm part  48  that rotates about the first shaft  46   a  is installed on the first shaft  46   a . Likewise, the second support plate  47  is provided with a second shaft  47   a . A second arm part  49  that rotates about the second shaft  47   a  is installed on the second shaft  47   a.    
     The tension bar  30  is provided so as to bridge between an end of the first arm part  48  on the +Y direction side and an end of the second arm part  49  on the +Y direction side. Further, a counter weight  50  is provided so as to bridge between the −Y direction side of the first arm part  48  and the −Y direction side of the second arm part  49 . The first shaft  46   a  and the second shaft  47   a  are disposed on the same axis. With this configuration, the tension bar  30  and the counter weight  50  rotate about the first shaft  46   a  and the second shaft  47   a  as the turning axes. 
     The tension bar  30  and the counter weight  50  function as long members that connect the first arm part  48  and the second arm part  49 . With this configuration, as viewed in the Z direction, the tension applying unit  29  forms a substantially quadrangular shape with the tension bar  30 , the counter weight  50 , the first arm part  48  and the second arm part  49  as its four sides. As a result, the torsional rigidity of the tension applying unit  29  is improved, thus achieving a structure in which the tension applying unit  29  is configured to be not easily deformed even when the tension applying unit  29  is pressed by the printing medium  17 . 
       FIG. 4  is a schematic side sectional view illustrating a configuration of the tension applying unit. As illustrated in  FIG. 4 , the second arm part  49  is provided with a flag plate  49   a  having an arc-like end portion on the −Y direction side of the second shaft  47   a . A gear is formed in the arc-like end portion of the flag plate  49   a . An intermediate gear  51  that is meshed with the gear of the flag plate  49   a  is provided on the −Y direction side of the gear of the flag plate  49   a . Further, a driving gear  52  is provided on the +Z direction side of the intermediate gear  51 . 
     As illustrated in  FIG. 3 , as a driving unit, a tension applying motor  53  is provided on the +X direction side of the second leg part  2   c . As a second detecting unit, a tension applying unit encoder  54  that detects the rotation angle of the tension applying motor  53  is provided on the +X direction side of the tension applying motor  53 . Note that the tension applying unit encoder  54  is a part of the control unit  6 . Returning back to  FIG. 4 , the driving gear  52  is provided on the rotation shaft of the tension applying motor  53 . Specifically, the driving gear  52  is formed on the rotation shaft of the tension applying motor  53 . When the tension applying motor  53  rotates the driving gear  52 , the torque output by the tension applying motor  53  is transmitted to the second arm part  49  via the driving gear  52  and the intermediate gear  51 . Then, the second arm part  49  rotates about the second shaft  47   a  as the rotation center. The tension bar  30  moves along a circumference of a circle about the second shaft  47   a  as the rotation center. The tension applying motor  53  rotates in a clockwise direction and a counterclockwise direction, and accordingly the tension bar  30  moves up and down at a position where tension is applied to the printing medium  17 . 
     At the time when the tension bar  30  contacts with the printing medium  17 , the torque output by the tension applying motor  53  acts on the tension bar  30 . Then, a force that applies tension to the printing medium  17  acts on the tension bar  30 . In this manner, the tension applying motor  53  drives the tension applying unit  29  and the tension bar  30  applies tension to the printing medium  17 . 
     The second leg part  2   c  is provided with a first sensor  55  and a second sensor  56  via a supporting part that is not illustrated in the drawing. The first sensor  55  and the second sensor  56  can be sensors that use light, magnetism, capacitance and the like. The first sensor  55  and the second sensor  56  detect whether the flag plate  49   a  is present or absent at respective locations where they are provided. The first sensor  55  and the second sensor  56  are also called proximity sensors. In other words, the first sensor  55  and the second sensor  56  are sensors that detect an end of the flag plate  49   a . Here, the flag plate  49   a  is composed of, for example, a stainless-steel sheet that does not transmit an infrared ray. Hereafter, the first sensor  55  and the second sensor  56  are described as optical sensors. Each of the first sensor  55  and the second sensor  56  is composed of a pair of a light-emitting element and a light reception element. The first sensor  55  and the second sensor  56  are turned “ON” when light emitted from the light-emitting element is received by the light reception element. Conversely, they are turned “OFF” when light is blocked between the light-emitting element and the light reception element. Accordingly, when the flag plate  49   a  is located at the first sensor  55  and the second sensor  56 , the light from the light-emitting element is blocked before reaching the light reception element, and the first sensor  55  and the second sensor  56  are turned “OFF”. When the second arm part  49  rotates about the second shaft  47   a  as the center of rotation, the end of the flag plate  49   a  reaches the first sensor  55  or the second sensor  56 . At this time, the state where the flag plate  49   a  is located at the position of the sensor is switched to a state where the flag plate  49   a  is not located at the position. Thus, the first sensor  55  and the second sensor  56  can detect the end of the flag plate  49   a.    
     When the printing apparatus  1  is activated, the control unit  6  drives the tension applying motor  53  to rotate the second arm part  49 . Then, the first sensor  55  and the second sensor  56  detect an upper end  49   c  and a lower end  49   d  of the arc-like end portion of the flag plate  49   a  in the rotational direction of thereof. The control unit  6  recognizes the movement range of the second arm part  49  and the tension bar  30 . When the upper end  49   c  on the +Z side of the flag plate  49   a  is not at the first sensor  55  whereas the flag plate  49   a  is located at the second sensor  56  (that is, when the first sensor  55  is “ON” and the second sensor  56  is “OFF”), the counter in the tension applying unit encoder  54  is reset. The control unit  6  recognizes the location where the tension bar  30  is moved up. The location of the tension bar  30  at this time is the upper limit position. This state is referred to as “the first sensor  55  detects the upper end  49   c ”. Likewise, when the lower end  49   d  on the −Z side of the flag plate  49   a  is not at the second sensor  56  whereas the flag plate  49   a  is located at the first sensor  55  (that is, when the first sensor  55  is “OFF” and the second sensor  56  is “ON”), the control unit  6  recognizes the location where the tension bar  30  is moved down. The location of the tension bar  30  at this time is the lower limit position. This state is referred to as “the second sensor  56  detects the lower end  49   d ”. That is, the tension bar  30  moves between the upper limit position and the lower limit position. 
     Note that the tension applying unit encoder  54  may not be provided on the +X direction side of the tension applying motor  53 . For example, a light-transmissive member having a scale of a predetermined resolution may be configured to be attached to the arc portion of the flag plate  49   a . With this configuration, an occurrence of an error in a position of the tension bar  30  is suppressed even when backlash occurs between the intermediate gear  51  and the driving gear  52 , for example. 
       FIG. 5  is an electrical block diagram illustrating a configuration of a control unit. In  FIG. 5 , the control unit  6  includes a central processing unit (CPU)  57  that performs various arithmetic processes as a processor, and a memory  58  that stores a variety of information as a storage unit. A carriage driving circuit  61 , a head driving circuit  62 , a supply unit driving circuit  63 , a winding unit driving circuit  64 , a transporting unit driving circuit  65  and a tension applying unit driving circuit  66  are connected with the CPU  57  via an input/output interface  67  and a data bus  68 . Further, the operation panel  7 , the notification unit  12  and a communication device  69  are connected with the CPU  57  via the input/output interface  67  and the data bus  68 . 
     The carriage driving circuit  61  is a circuit that drives the carriage moving unit  13  including the motor  13   a  and the encoder  13   b . The carriage driving circuit  61  receives an instruction signal of the CPU  57 . In accordance with the instruction signal, the carriage driving circuit  61  rotates the motor  13   a  at a predetermined rotational speed and a predetermined rotation angle. The carriage  15  is moved by the rotation of the motor  13   a.    
     The carriage driving circuit  61  converts a signal output by the encoder  13   b  into digital data and outputs it to the CPU  57 . Since the encoder  13   b  detects the movement amount of the carriage  15 , the CPU  57  receives a signal output by the carriage driving circuit  61  and recognizes the position of the carriage  15 . 
     The head driving circuit  62  is a circuit that drives the printing head provided in the head unit  43 . The head driving circuit  62  drives the printing head for ejection on the basis of printing data output by the CPU  57  to cause the printing head to eject ink from the nozzle. 
     The supply unit driving circuit  63  is a circuit that drives the supply motor  24   a  and the supply unit encoder  24   b . The supply unit driving circuit  63  receives an instruction signal of the CPU  57 . In accordance with the instruction signal, the supply unit driving circuit  63  rotates the supply motor  24   a  at a predetermined rotational speed and a predetermined rotation angle. By the rotation of the supply motor  24   a , the printing medium  17  is supplied from the medium supply unit  23  to the printing unit  5 . 
     The supply unit driving circuit  63  converts a signal output by the supply unit encoder  24   b  into digital data and outputs it to the CPU  57 . Since the supply unit encoder  24   b  detects the rotation angle of the supply side roll body  25 , the CPU  57  receives a signal output by the supply unit driving circuit  63  and recognizes the length of the printing medium  17  supplied by the supply side roll body  25 . 
     The winding unit driving circuit  64  is a circuit that drives the winding motor  27   a  and the winding unit encoder  27   b . The winding unit driving circuit  64  receives an instruction signal of the CPU  57 . In accordance with the instruction signal, the winding unit driving circuit  64  rotates the winding motor  27   a  at a predetermined rotational speed and a predetermined rotation angle. By the rotation of the winding motor  27   a , the printing medium  17  is wound from the tension applying unit  29 . 
     The winding unit driving circuit  64  converts a signal output by the winding unit encoder  27   b  into digital data and outputs it to the CPU  57 . Since the winding unit encoder  27   b  detects the rotation angle of the winding side roll body  28 , the CPU  57  receives the signal output by the winding unit driving circuit  64  and recognizes the length of the printing medium  17  that is wound around the winding side roll body  28 . 
     The transporting unit driving circuit  65  is a circuit that drives the transportation motor  38  and the transporting unit encoder  41 . The transporting unit driving circuit  65  receives an instruction signal of the CPU  57 . In accordance with the instruction signal, the transporting unit driving circuit  65  rotates the transportation motor  38  at a predetermined rotational speed and a predetermined rotation angle. By the rotation of the transportation motor  38 , the printing medium  17  is supplied to the printing unit  5 . 
     The transporting unit driving circuit  65  converts a signal output by the transporting unit encoder  41  into digital data and outputs it to the CPU  57 . Since the transporting unit encoder  41  detects the rotation angle of the transportation driving roller  36   a , the CPU  57  receives the signal output by the transporting unit driving circuit  65  and recognizes the length of the printing medium  17  that is transported by the transportation roller  36 . 
     The tension applying unit driving circuit  66  is a circuit that drives the tension applying motor  53  and the tension applying unit encoder  54 . The tension applying unit driving circuit  66  receives an instruction signal of the CPU  57 . In accordance with the instruction signal, the tension applying unit driving circuit  66  causes the tension applying motor  53  to output a predetermined torque. From the torque output by the tension applying motor  53 , tension is applied to the printing medium  17 . 
     The tension applying unit driving circuit  66  converts a signal output by the tension applying unit encoder  54  into digital data and outputs it to the CPU  57 . Since the tension applying unit encoder  54  detects the rotation angle of the second arm part  49  corresponding to the position of the tension bar  30 , the CPU  57  receives the signal output by the tension applying unit driving circuit  66  and recognizes the position of the tension bar  30 . 
     The operation panel  7  includes the operation unit  8  and the display unit  9 . The operator operates the operation unit  8  to input various printing conditions. Then, the operation panel  7  outputs the input information to the CPU  57 . Then, the CPU  57  causes the display unit  9  to display a message to the operator. 
     The notification unit  12  includes the notification light  10 , the speaker  11  and the like. The notification unit  12  notifies the state of the printing apparatus  1  with sound and light to the operator. When an abnormality occurs in the printing apparatus  1 , warning sound and strong light are output so that the operator can realize the notification even when the operator is away from the printing apparatus  1 . 
     The communication device  69  is a device that communicates with a peripheral device  70 . The communication device  69  receives printing data from the peripheral device  70  by communicating with the peripheral device  70 . Further, a printing start signal and various data used in printing are received. 
     The memory  58  is a concept including semiconductor memories such as a RAM and a ROM, and external storage devices such as a hard disk. The memory  58  stores a program  71  in which an operation control procedure of the printing apparatus  1 , a determination procedure of a transportation failure and the like are described. Further, the memory  58  stores printing data  72  that is data for printing of the printing unit  5 . Further, the memory  58  stores determination data  73  that is data for the CPU  57  to determine whether the state of the printing apparatus  1  is normal or abnormal. Further, the memory  58  stores tension-related data  74  that is data of the tension to be applied to the printing medium  17 . Further, the memory  58  includes various storage areas including a storage area that functions as a temporally file, a work area and the like for the CPU  57 . 
     The CPU  57  controls the operation of the printing apparatus  1  in accordance with the program  71  stored in the memory  58 . The CPU  57  includes various functional parts for achieving functions. Specifically, the CPU  57  includes a carriage control unit  75  as a functional part. The carriage control unit  75  performs controls of the movement speed, the movement direction, the movement position and the like of the carriage  15 . The carriage control unit  75  outputs, to the carriage driving circuit  61 , a parameter for controlling the operation of the carriage  15 . The carriage control unit  75  outputs, to the carriage driving circuit  61 , an instruction signal of the start and stop of the operation of the carriage  15 . In accordance with the instruction signal output by the carriage control unit  75 , the carriage driving circuit  61  causes the carriage moving unit  13  to move the carriage  15 . 
     Further, the CPU  57  includes a printing head control unit  76 . The printing head control unit  76  controls the ejection of the ink ejected from a plurality of printing heads provided in the head unit  43 . The printing head control unit  76  outputs, to the head driving circuit  62 , data of ejecting timing of each printing head. The head driving circuit  62  drives the printing head in accordance with the data of the ejecting timing. The printing head control unit  76  performs the control of the ejecting timing by using the location information of the carriage  15  input by the carriage control unit  75 . 
     Further, the CPU  57  includes a material supply removal control unit  77 . The material supply removal control unit  77  outputs, to the supply unit driving circuit  63 , an instruction signal of the rotational speed, the rotation start, the rotation stop and the like of the supply motor  24   a . The material supply removal control unit  77  increases the rotational speed of the supply motor  24   a  as the diameter of the supply side roll body  25  decreases. The material supply removal control unit  77  controls the speed of the printing medium  17  supplied to the printing unit  5  by the medium supply unit  23  at a constant speed. 
     The material supply removal control unit  77  outputs, to the winding unit driving circuit  64 , an instruction signal of the rotational speed of the winding motor  27   a . The material supply removal control unit  77  receives data of the rotation angle of the second arm part  49  output by the tension applying unit encoder  54 . With reference to the data of the rotation angle, the material supply removal control unit  77  outputs, to the winding unit driving circuit  64 , an instruction signal of the rotation start, the rotation stop and the like of the winding motor  27   a.    
     The range of the location where the tension bar  30  can apply tension to the printing medium  17  is limited. This range is referred to as a tension applying possible range. When the tension bar  30  is within the tension applying possible range, the printing medium  17  passes through a location where the tension bar  30  can press the printing medium  17 . With an instruction signal of the material supply removal control unit  77 , the winding amount of the printing medium  17  wound by the medium winding unit  26  is controlled such that the printing medium  17  passes through the location where the tension bar  30  can press the printing medium  17 . When the amount of the printing medium  17  that is wound by the medium winding unit  26  is small, the printing medium  17  slackens, and consequently the tension bar  30  cannot press the printing medium  17 . When the medium winding unit  26  winds the printing medium  17  such that the printing medium  17  is not slackened, the tension bar  30  can press the printing medium  17 . Further, the tension bar  30  can be moved in accordance with the movement of the printing medium  17 . 
     Further, the CPU  57  includes a tension control unit  78 . The tension control unit  78  outputs an instruction signal of a torque of the tension applying motor  53  to the tension applying unit driving circuit  66 . By changing the torque of the tension applying motor  53 , the tension applied to the printing medium  17  by the tension applying unit  29  is changed. Thus, the tension control unit  78  controls the tension applied to the printing medium  17  via the tension applying unit driving circuit  66 , the tension applying motor  53 , the first arm part  48 , the second arm part  49  and the tension bar  30 . 
     Further, the CPU  57  includes a transportation control unit  81 . The transportation control unit  81  outputs an instruction signal of the rotational speed, the rotation start, the rotation stop and the like of the transportation motor  38  to the transporting unit driving circuit  65 . The transportation control unit  81  receives the output of the transporting unit encoder  41  via the transporting unit driving circuit  65 . The transporting unit encoder  41  outputs data corresponding to the movement amount of the printing medium  17 . The transportation control unit  81  recognizes the movement amount of the printing medium  17  and controls the movement speed of the printing medium  17  at a predetermined speed. 
     Further, the CPU  57  includes a movement amount computation unit  82 . The movement amount computation unit  82  receives data of the rotation angle of the rotation shaft of the transportation motor  38  that is output by the transporting unit encoder  41 . The movement amount computation unit  82  multiplies the rotation angle of the rotation shaft of the transportation motor  38  with a predetermined coefficient to compute the movement amount of the printing medium  17 . A first detecting unit  83  is composed of the transporting unit encoder  41 , the movement amount computation unit  82  and the like. The first detecting unit  83  detects the movement amount of the printing medium  17  and outputs movement amount information indicating the movement amount of the printing medium  17  to a transportation failure detecting unit  86 . 
     Further, the CPU  57  includes a bar position computation unit  84 . The bar position computation unit  84  receives data of the rotation angle of the rotation shaft of the tension applying motor  53  that is output by the tension applying unit encoder  54 . The rotation angle of the rotation shaft of the tension applying motor  53  is multiplied by a predetermined coefficient to compute the rotation angle of the tension bar  30 . Since the tension bar  30  rotates around the second shaft  47   a  as the center of rotation, the bar position computation unit  84  can calculate the position of the tension bar  30 . A second detecting unit  85  is composed of the tension applying unit encoder  54 , the bar position computation unit  84  and the like. The second detecting unit  85  detects the position of the tension bar  30  and outputs, to the transportation failure detecting unit  86 , the rod member location information indicating the position of the tension bar  30 . 
     Further, the CPU  57  includes the transportation failure detecting unit  86 . The transportation failure detecting unit  86  receives the movement amount of the printing medium  17  that is detected by the transporting unit encoder  41 . Further, the transportation failure detecting unit  86  receives data indicating the position of the tension bar  30  that is output by the tension applying unit encoder  54 . When the tension bar  30  is not moving while the printing medium  17  is moving, it is determined that a transportation failure of the printing medium  17  is caused, and thus the transportation failure of the printing medium  17  is detected. In this manner, when the printing medium  17  is transported at the transporting unit  39 , the transportation failure detecting unit  86  in the control unit  6  determines the movement state of the printing medium  17  at the tension applying unit  29  on the basis of the movement amount information and the rod member location information. 
     When the printing medium  17  adheres to the guide member  34 , the printing medium  17  does not move at the tension applying unit  29 . At this time, the transportation failure detecting unit  86  determines that the printing medium  17  is not moving at the tension applying unit  29  and the printing medium  17  is moving at the transporting unit  39 . As a result, the printing apparatus  1  can detect the transportation failure of the printing medium  17 . 
     Further, the CPU  57  includes a functional part that is not illustrated. For example, the CPU  57  performs a control of displaying the state of the apparatus and displaying information relating to measurement on the display unit  9 . Further, the CPU  57  performs a control of driving the notification unit  12  when an abnormality is caused in the printing apparatus  1 . 
     Next, the printing method performed by the printing apparatus  1  is described with reference to  FIG. 6  to  FIG. 22 .  FIG. 6  is a flowchart of the printing method. In the flowchart of  FIG. 6 , step S 1  to step S 4  are performed in parallel. Further, step S 5  to step S 7  and step S 9  to step S 10  are performed in parallel with step S 1  to step S 4 . 
     Step S 1  is a supplying process. In this process, the medium supply unit  23  supplies the printing medium  17  to the guide member  34 . Next, the process proceeds to step S 8 . Step S 8  is a print completion determining process. This process is a process determining whether the planned printing is completed. When the planned printing is not completed, the process proceeds to step S 1  to step S 5 . When the planned printing is completed, the printing process is terminated. 
     Step S 2  is a transporting process. In this process, the transporting unit  39  transports the printing medium  17  along the guide member  34 . Then, in this process, the first detecting unit  83  detects the movement amount of the printing medium  17  and outputs movement amount information indicating the movement amount of the printing medium  17  to the transportation failure detecting unit  86 . Next, the process proceeds to step S 8 . Step S 3  is a printing process. In this process, the printing unit  5  performs printing on the printing medium  17 . Next, the process proceeds to step S 8 . Step S 4  is a tension applying process. In this process, the tension bar  30  applies tension to the printing medium  17  by pressing the printing medium  17  while moving between the upper limit position and the lower limit position at a location between the transporting unit  39  and the medium winding unit  26 . Next, the process proceeds to step S 8 . 
     Step S 5  is a bar position detecting process. In this process, the second detecting unit  85  detects the position of the tension bar  30  and outputs rod member location information indicating the position of the tension bar  30  to the transportation failure detecting unit  86 . Next, the process proceeds to step S 6 . Step S 6  is a transportation failure determining process. In this process, the transportation failure detecting unit  86  of the control unit  6  determines the slackness of the printing medium  17  on the basis of the movement amount information and the rod member location information. The transportation failure detecting unit  86  determines the transportation state on the basis of the slackness of the printing medium  17 . When the printing medium  17  is slack, it is determined that a transportation failure occurs. When there is no transportation failure, the process proceeds to step S 7 . When there is a transportation failure, the process proceeds to step S 9 . 
     Step S 7  is a winding process. In this process, at a location further downstream of the guide member  34  than the transporting unit  39 , the medium winding unit  26  winds the printing medium  17 . Next, the process proceeds to step S 8 . Step S 9  is a tension determining process. In this process, the intensity of the tension applied to the printing medium  17  by the tension bar  30  is determined. When the intensity of the tension is smaller than a determination value, the process proceeds to step S 10 . The determination value is defined as a threshold value regarding the movement amount of the rod member when the printing medium  17  is transported. For example, the determination value is determined based on an experiment. When the intensity of the tension is equal to or greater than the determination value, the process proceeds to step S 11 . 
     Step S 10  is a tension changing process. In this process, the intensity of the tension applied to the printing medium  17  by the tension bar  30  is increased. When the transportation failure detecting unit  86  detects a transportation failure of the printing medium  17  in the control unit  6 , the tension control unit  78  controls the tension applying motor  53  to cause the force applied by the tension applying unit  29  to press the printing medium  17  to be greater than the force at the time when the transportation failure of the printing medium  17  has been detected. Next, the process proceeds to step S 8 . Step S 11  is a notifying process. In this process, the CPU  57  drives the notification unit  12  to notify the operator of an abnormality state of the printing apparatus  1 . After the notifying step is terminated, the printing process is terminated. Through the above-mentioned processes, the processes in which the printing unit  5  performs printing on the printing medium  17  is completed. 
       FIG. 7  to  FIG. 22  are drawings or schematic views for describing the printing method. Next, with reference to  FIG. 7  to  FIG. 22 , the printing method will be described in detail in correspondence with the steps illustrated in  FIG. 6 . 
       FIG. 7  corresponds to the supplying process of step S 1 . As illustrated in  FIG. 7 , the material supply removal control unit  77  causes the supply unit driving circuit  63  to drive the supply motor  24   a . When the supply motor  24   a  rotates, the printing medium  17  is supplied to the guide member  34 . The supply unit encoder  24   b  detects the rotation angle of the supply shaft  24  and outputs it to the supply unit driving circuit  63 . The supply unit driving circuit  63  controls the rotation angle of the supply shaft  24  in accordance with the variation of the diameter of the supply side roll body  25 . Then, the printing medium  17  is supplied from the supply side roll body  25  at a predetermined supply speed. 
       FIG. 8  corresponds to the transporting process of step S 2  and the printing process of step S 3 . As illustrated in  FIG. 8 , at step S 2 , the transportation control unit  81  causes the transporting unit driving circuit  65  to drive the transportation motor  38 . When the transportation motor  38  rotates, the printing medium  17  is transported along the guide member  34 . The transporting unit encoder  41  detects the rotation angle of the transportation driving roller  36   a  and outputs it to the transporting unit driving circuit  65 . Receiving the data of the rotation angle of the transportation driving roller  36   a , the transporting unit driving circuit  65  controls the transportation amount of the printing medium  17  transported by the transportation roller  36 . 
     At step S 3 , the carriage control unit  75  causes the carriage driving circuit  61  to drive the motor  13   a . When the motor  13   a  rotates, the carriage  15  moves along the guide rail  14 . The encoder  13   b  detects the rotation angle of the motor  13   a  and outputs it to the carriage driving circuit  61 . Receiving data of the rotation angle of the motor  13   a , the carriage driving circuit  61  controls the carrying speed of the carriage  15 . 
     In parallel with transportation of the printing medium  17  and movement of the carriage  15 , ink  87  is ejected from the nozzle of the printing head in the head unit  43 . The printing head control unit  76  receives the printing data  72  from the memory  58 . Then, when the nozzle is located at a location opposite the location where the ink  87  is planned to be placed, the ink  87  is ejected from the nozzle. The carriage control unit  75 , the transportation control unit  81  and the printing head control unit  76  perform drawing on the printing medium  17  in cooperation with each other. Since the printing medium  17  has been heated by the first heater  44  and the second heater  45 , the ink  87  is easily dried. Further, since the infrared ray heater  21  dries the ink  87 , the ink  87  is dried before the printing medium  17  reaches the medium winding unit  26 . 
       FIG. 9  to  FIG. 14  correspond to the tension applying process of step S 4 , the bar position detecting process of step S 5  and the winding process of step S 7 . Step S 4  and step S 5  are performed in parallel. As illustrated in  FIG. 9 , at step S 4 , the tension bar  30  is located at an upper limit position  30   a  in the state where the printing medium  17  is wound around the medium winding unit  26 . At this time, the first sensor  55  detects the upper end  49   c.    
     The tension bar  30  rotates around the second shaft  47   a . The rotation angle of the tension bar  30  is set as a tension bar angle  88  as the movement amount of the rod member. The tension bar angle  88  is set to 0 degree when the tension bar  30  is located at the upper limit position  30   a . The tension control unit  78  causes the tension applying unit driving circuit  66  to drive the tension applying motor  53 . The tension applying motor  53  is a direct-current motor. Since the torque of the tension applying motor  53  is proportional to the current, the tension applying unit driving circuit  66  can readily control the torque of the tension applying motor  53  by controlling the current flowing through the tension applying motor  53 . 
     The tension applying unit driving circuit  66  outputs, to the bar position computation unit  84 , the rotation angle of the driving gear  52  that is detected by the tension applying unit encoder  54 . The bar position computation unit  84  multiplies the rotation angle of the driving gear  52  with a predetermined coefficient to calculate the tension bar angle  88 . Since the distance between the second shaft  47   a  and the tension bar  30  is constant, the tension bar angle  88  corresponds to the position of the tension bar  30 . 
     As illustrated in  FIG. 10 , in the medium winding unit  26 , the transporting unit  39  transports the printing medium  17  while the winding motor  27   a  does not rotate the winding side roll body  28 . At this time, the length of the printing medium  17  located between the downstream side guide part  18  and the medium winding unit  26  increases. Then, since the tension bar  30  is rotated at a constant torque by the tension applying motor  53 , the tension bar  30  is moved down in the −Z direction. Constant tension acts on the printing medium  17  by the tension bar  30 . The tension bar  30  rotates about the second shaft  47   a , and thus the tension bar angle  88  increases. 
     As illustrated in  FIG. 11 , when the tension bar  30  is moved down, the lower end  49   d  of the second arm part  49  rotates about the second shaft  47   a  and the second sensor  56  detects the lower end  49   d . The position of the tension bar  30  at this time is a lower limit position  30   b . In this manner, in the tension applying unit  29 , the tension bar  30  presses the printing medium  17  between the transporting unit  39  and the medium winding unit  26 , and applies tension to the printing medium  17  while moving between the upper limit position  30   a  and the lower limit position  30   b . The tension bar angle  88  is maximized at the lower limit position  30   b.    
       FIG. 12  illustrates a relationship between the feed amount of the printing medium  17  and the tension bar angle  88 . In  FIG. 12 , a vertical axis indicates the tension bar angle  88 , and the angle is greater on the upper side of the vertical axis than on the lower side. The tension bar angle  88  varies between the upper limit position  30   a  and the lower limit position  30   b  of the tension bar  30 . A horizontal axis indicates a cumulative feed amount of the medium, which corresponds to the amount of the printing medium  17  fed by the transporting unit  39 . In the drawing, the cumulative feed amount of the medium is larger on the right side of the horizontal axis than on the left side. The cumulative feed amount of the medium increases with time passing. An angle transition line  90  indicates variation of the tension bar angle  88 . 
     In the horizontal axis, the winding side roll body  28  is stopped in a winding stop region  91 , whereas the winding side roll body  28  winds the printing medium  17  in a winding operation region  92 . The winding stop region  91  and the winding operation region  92  are performed alternately. The proportion of the winding stop region  91  is larger than the proportion of the winding operation region  92 . For example, every time when the printing medium  17  is transported multiple times (two times or greater) by the transporting unit  39 , the winding side roll body  28  is rotated. As the angle transition line  90  indicates, the tension bar angle  88  increases in the winding stop region  91 . 
     That is, the tension bar  30  moves down. In the winding operation region  92 , the tension bar angle  88  decreases more quickly than in the winding stop region  91 . That is, the tension bar  30  moves up. In this manner, the tension bar  30  applies tension to the printing medium  17  while the tension bar  30  moves. 
       FIG. 13  illustrates a state where the tension bar  30  has reached the lower limit position  30   b . The bar position computation unit  84  outputs the tension bar angle  88  to the material supply removal control unit  77  by using the output of the tension applying unit encoder  54 . When the tension bar  30  reaches lower limit position  30   b , the material supply removal control unit  77  causes the winding side roll body  28  to rotate at step S 7  to wind the printing medium  17 . 
       FIG. 14  illustrates a state where the tension bar  30  reaches the upper limit position  30   a . The tension bar  30  is moved up by winding the printing medium  17  by rotating the winding side roll body  28 . Also at this time, the bar position computation unit  84  outputs the tension bar angle  88  to the material supply removal control unit  77  by using the output of the tension applying unit encoder  54 . When the tension bar  30  reaches the upper limit position  30   a , the material supply removal control unit  77  stops the rotation of the winding side roll body  28  to stop the winding of the printing medium  17 . 
       FIG. 15  to  FIG. 22  correspond to the transportation failure determining process of step S 6 , the tension determining step of step S 9 , the tension changing process of step S 10  and the notifying process of step S 11 . As illustrated in  FIG. 15 , when static electricity acts on the printing medium  17  and the printing medium  17  adheres to the downstream side guide part  18 , the transporting unit  39  transports the printing medium  17  and consequently a protrusion  17   a , which results from buckling of the printing medium  17  in a protruding shape, is formed. The location where the protrusion  17   a  is formed is indefinite. When the protrusion  17   a  contacts with the head unit  43 , the protrusion  17   a  is stained with the ink  87 . In addition, the printing medium  17  is wrinkled and creased, which results in printing failure. 
     When static electricity acts on the printing medium  17  and the printing medium  17  adheres to the downstream side guide part  18 , the printing medium  17  does not advance toward the medium winding unit  26  from the guide member  34 . In  FIG. 16 , the vertical axis and the horizontal axis are identical to those of  FIG. 12 . In the drawing, the interval between each vertical broken line indicates a cycle of one rotation of the transportation driving roller  36   a . The transportation failure detecting unit  86  determines the presence or absence of a transportation failure for each rotation of the transportation driving roller  36   a . That is, the transportation failure detecting unit  86  performs the determination at the timing indicated with the broken lines. 
     In a normal region  93  in the drawing, the printing medium  17  is normally transported. In an abnormality region  94 , a part of the printing medium  17  is adhered to the guide member  34 . At this time, the tension bar angle  88  increases in the normal region  93 . Meanwhile, the tension bar angle  88  does not change in the abnormality region  94 . The transportation failure detecting unit  86  determines the presence or absence of a transportation failure at a determination timing  95  of the abnormality region  94 . The transportation failure detecting unit  86  detects the tension bar angle  88  every time when the transporting unit  39  transports the printing medium  17  by a predetermined length, and, when the tension bar angle  88  is smaller than a determination value  96 , the transportation failure detecting unit  86  detects a transportation failure of the printing medium  17 . 
     In this manner, the transportation failure detecting unit  86  determines a transportation failure of the printing medium  17  by using only the tension bar angle  88  without computing the movement amount of the printing medium  17  (the length of the track of the tension bar  30 ) on the basis of the product of the tension bar angle  88  and the distance of the tension bar  30  from the first shaft  46   a  (the second shaft  47   a ). Thus, the transportation failure detecting unit  86  can save the time required for computing the movement amount of the printing medium  17 , and therefore can detect a transportation failure in a short time. 
       FIG. 17  illustrates a relationship between the cumulative feed amount of the printing medium  17  and the variation of the tension bar angle  88 . In  FIG. 17 , the vertical axis indicates variation of the tension bar angle  88 , and the variation is larger on the upper side of the vertical axis than on the lower side. The vertical axis indicates the difference of the variation of the tension bar angle  88  for each rotation of the transportation driving roller  36   a . The horizontal axis is identical to that of  FIG. 12 . 
     An angle variation transition line  97  indicates a change of the variation of the tension bar angle  88 . In the normal region  93 , the angle variation transition line  97  gradually declines. In the abnormality region  94 , the angle variation transition line  97  abruptly declines since the printing medium  17  does not move. Then, the angle variation transition line  97  falls below the determination value  96 . Since the angle variation transition line  97  is smaller than the determination value  96  in the determination timing  95 , the transportation failure detecting unit  86  determines that a transportation failure is caused. 
       FIG. 18  illustrates a relationship between the feed amount of the printing medium  17  and the force applied by the tension bar  30  to press the printing medium  17 . In  FIG. 18 , the vertical axis indicates a tension bar pressing force, which is the force applied by the tension bar  30  to press the printing medium  17 , and corresponds to a torque applied by the tension applying motor  53 . Tension is applied to the printing medium  17  in accordance with the tension bar pressing force. In the drawing, the pressing force is greater on the upper side than on the lower side. The horizontal axis is identical to that of  FIG. 12 . A pressing force transition line  98  remains constant in the normal region  93 . When it is determined that a transportation failure is caused at the determination timing  95  at step S 6 , the pressing force transition line  98  is compared with a pressing force determination value  101  at step S 9 . The pressing force determination value  101  is a threshold for determinating the abnormality of the tension bar pressing force. That is, it is determined that abnormality is caused when the tension bar pressing force is greater than the pressing force determination value  101 . 
     When the pressing force transition line  98  is smaller than the pressing force determination value  101 , the tension applying unit driving circuit  66  increases the current flowing through the tension applying motor  53  by an instruction signal of the tension control unit  78 . As a result, the pressing force applied by the tension bar  30  on the printing medium  17  increases. In this manner, when the transportation failure detecting unit  86  detects a transportation failure of the printing medium  17 , the tension control unit  78  controls the tension applying motor  53  to cause the force applied by the tension applying unit  29  to press the printing medium  17  to be greater than the force at the time when the transportation failure of the printing medium  17  has been detected. 
       FIG. 19  illustrates the angle transition line  90  after the pressing force applied by the tension bar  30  on the printing medium  17  is increased. The vertical axis and the horizontal axis are identical to those of  FIG. 12 . The angle transition line  90  indicates a state where the printing medium  17  does not adhere to the downstream side guide part  18  as a result of the increase of the pressing force applied by the tension bar  30  on the printing medium  17  in the determination timing  95 . 
       FIG. 20  illustrates the pressing force transition line  98  after the pressing force applied by the tension bar  30  on the printing medium  17  is increased. The vertical axis and the horizontal axis are identical to those of  FIG. 18 . As indicated by the pressing force transition line  98 , the pressing force is intensified after the determination timing  95  so as to maintain the pressing force applied on the printing medium  17  even in the normal region  93 . That is, when no transportation failure of the printing medium  17  is detected after the force applied by the tension applying unit  29  to press the printing medium  17  has been intensified, the tension control unit  78  controls the tension applying motor  53  to maintain the intensified force applied to press the printing medium  17 . 
       FIG. 21  illustrates the angle transition line  90  after the pressing force applied by the tension bar  30  on the printing medium  17  is increased. The vertical axis and the horizontal axis are identical to those of  FIG. 12 . The angle transition line  90  indicates that a state where the printing medium  17  adheres to the downstream side guide part  18  is maintained even after the pressing force applied by the tension bar  30  on the printing medium  17  is increased at the determination timing  95 . 
       FIG. 22  illustrates the pressing force transition line  98  after the pressing force applied by the tension bar  30  on the printing medium  17  is increased. The vertical axis and the horizontal axis are identical to those of  FIG. 20 . As indicated by the pressing force transition line  98 , the pressing force is in the abnormality region  94  even when the pressing force is intensified after the determination timing  95 . That is, the printing medium  17  is still adhered to the guide member  34 . 
     At this time, step S 6 , step S 9  and step S 10  are performed continuously. As a result, the pressing force applied by the tension bar  30  on the printing medium  17  is increased for each rotation of the transportation driving roller  36   a . In this manner, when a transportation failure of the printing medium  17  is detected, the tension control unit  78  controls the tension applying motor  53  to cause the force applied by the tension applying unit  29  to press the printing medium  17  to be greater than the force at the time when the transportation failure of the printing medium  17  has been detected. When the adhesion power of the printing medium  17  to the guide member  34  is relatively small, the printing medium  17  can be detached from the guide member  34  by increasing the tension of the printing medium  17 . 
     Then, at an abnormality determination timing  102  when the pressing force applied by the tension bar  30  on the printing medium  17  exceeds the pressing force determination value  101 , the process proceeds from step S 9  to step S 11 . Thereafter, the CPU  57  drives the notification unit  12  to terminate the printing process. 
     As described above, according to the present exemplary embodiment, the following advantages are achieved. 
     (1) According to the present exemplary embodiment, the transporting unit  39  transports the printing medium  17  along the guide member  34 . The transporting unit encoder  41  detects the movement amount of the printing medium  17  and outputs movement amount information indicating the movement amount of the printing medium  17  to the transportation failure detecting unit  86 . The medium winding unit  26  is disposed downstream of the transporting unit  39  in the guide member  34 . At a location between the transporting unit  39  and the medium winding unit  26 , the tension bar  30  of the tension applying unit  29  presses the printing medium  17  to apply tension to the printing medium  17 . By applying tension to the printing medium  17 , the medium winding unit  26  can wind the printing medium  17  with high quality. 
     The tension applying unit encoder  54  detects the position of the tension bar  30  and outputs rod member location information indicating the position of the tension bar  30  to the transportation failure detecting unit  86 . When the transporting unit  39  transports the printing medium  17 , the tension of the printing medium  17  is reduced in a period until the medium winding unit  26  operates. When the tension bar  30  applies tension to the printing medium  17 , the position of the tension bar  30  moves. Movement amount information and rod member location information are input to the transportation failure detecting unit  86 . The transportation failure detecting unit  86  determines the movement amount of the printing medium  17  at the transporting unit  39  on the basis of the movement amount information. Further, the transportation failure detecting unit  86  recognizes the moving state of the printing medium  17  at the tension applying unit  29  on the basis of the rod member location information. 
     Thus, the transportation failure detecting unit  86  can detect the movement state of the printing medium  17 , which indicates whether the printing medium  17  is moving at the tension applying unit  29  when the transporting unit  39  is moving the printing medium  17 . When the printing medium  17  adheres to the guide member  34 , the printing medium  17  does not move at the tension applying unit  29 . At this time, the transportation failure detecting unit  86  determines that the printing medium  17  is not moving at the tension applying unit  29  and the printing medium  17  is moving at the transporting unit  39 . As a result, the printing apparatus  1  can detect the transportation failure of the printing medium  17 . 
     (2) According to the present exemplary embodiment, the movement amount computation unit  82  detects the transporting length of the printing medium  17  transported by the transporting unit  39 . Then, when the transporting length of the printing medium  17  transported by the transporting unit  39  becomes equal to the length corresponding to one rotation amount of the transportation driving roller  36   a , the bar position computation unit  84  detects the movement amount of the tension bar  30 . Then, when the variation of the tension bar angle  88  is smaller than the determination value  96 , a transportation failure of the printing medium  17  is detected. 
     The transportation failure detecting unit  86  determines a transportation failure of the printing medium  17  by using only the variation of the tension bar angle  88  without computing the variation of the movement amount of the printing medium  17  on the basis of the product of the variation of the tension bar angle  88  and the distance of the tension bar  30  from the first shaft  46   a  (the second shaft  47   a ). Thus, the transportation failure detecting unit  86  can save the time required for computing the movement amount of the printing medium  17 , and therefore can detect a transportation failure in a short time. 
     (3) According to the present exemplary embodiment, the medium winding unit  26  controls the winding amount of the printing medium  17 . Then, the printing medium  17  is caused to pass through at a location where the tension bar  30  can press the printing medium  17 . When the amount of the printing medium  17  that is wound by the medium winding unit  26  is small, the printing medium  17  slackens, and consequently the tension bar  30  cannot press the printing medium  17 . When the medium winding unit  26  winds the printing medium  17  such that the printing medium  17  is not slackened, the tension bar  30  can press the printing medium  17 . Further, the tension bar  30  can be moved in accordance with the movement of the printing medium  17 . 
     (4) According to the present exemplary embodiment, the printing apparatus  1  includes the tension applying motor  53  that drives the tension applying unit  29 . When the transportation failure detecting unit  86  detects a transportation failure of the printing medium  17 , the tension control unit  78  causes the tension applying motor  53  to intensify the force applied by the tension applying unit  29  to press the printing medium  17 . When the adhesion power of the printing medium  17  to the guide member  34  is small, the printing medium  17  can be detached from the guide member  34  by increasing the tension of the printing medium  17 . 
     (5) According to the present exemplary embodiment, when no transportation failure of the printing medium  17  is detected, the tension control unit  78  causes the tension applying motor  53  to maintain the force applied by the tension applying unit  29  to press the printing medium  17  at a high value. Thus, since strong tension is applied to the printing medium  17 , the adhesion of the printing medium to the guide member again can be reduced. 
     (6) According to the present exemplary embodiment, the tension applying unit  29  presses the tension bar  30  against the printing medium  17  so as to apply tension to the printing medium  17  at a location between the transporting unit  39  and the medium winding unit  26 . By applying tension to the printing medium  17 , the medium winding unit  26  can implement high quality winding of the printing medium  17 . When the transporting unit  39  transports the printing medium  17 , the tension of the printing medium  17  is reduced at a location downstream of the transporting unit  39 . When the tension bar  30  applies tension to the printing medium  17 , the position of the tension bar  30  moves. The transportation failure detecting unit  86  receives movement amount information and rod member location information. The transportation failure detecting unit  86  receives the movement amount information and recognizes the movement amount of the printing medium  17  at the transporting unit  39 . Further, the transportation failure detecting unit  86  receives the rod member location information and recognizes the degree of the movement of the printing medium  17  at the tension applying unit  29 . 
     Thus, the transportation failure detecting unit  86  can detect the movement state of the printing medium  17 , which indicates whether the printing medium  17  is moving at the tension applying unit  29  when the transporting unit  39  is moving the printing medium  17 . When the printing medium  17  adheres to the guide member  34 , the printing medium  17  does not move at the tension applying unit  29 . At this time, the transportation failure detecting unit  86  determines that the printing medium  17  is not moving at the tension applying unit  29  and the printing medium  17  is moving at the transporting unit  39 . As a result, the printing apparatus  1  can detect the transportation failure of the printing medium  17 . 
     Second Exemplary Embodiment 
     Next, an exemplary embodiment of the printing apparatus is described with reference to  FIG. 23  to  FIG. 25 . The present exemplary embodiment differs from the first exemplary embodiment in that a tension reducing process of step S 12  is performed after the winding process of step S 7  illustrated in  FIG. 6 . Note that, the descriptions for the points identical to those of the first exemplary embodiment are omitted. 
       FIG. 23  is a flowchart of a printing method. That is, in the present exemplary embodiment, the tension reducing process of step S 12  is performed after the winding process of step S 7  as illustrated in  FIG. 23 . 
     When it is determined that there is no transportation failure at the transportation failure determining process of step S 6 , the process proceeds to step S 7 . At the winding process of step S 7 , the medium winding unit  26  winds the printing medium  17 . Next, the process proceeds to step S 12 . Step S 12  is a tension reducing process. In this process, the force applied by the tension bar  30  to press the printing medium  17  is returned to the force at the time when the transportation failure of the printing medium  17  has been detected. Next, the process proceeds to step S 8 . 
       FIG. 24  and  FIG. 25  are drawings for describing a printing method. Next, with reference to  FIG. 24  and  FIG. 25 , a printing method will be described in detail in correspondence with the steps illustrated in  FIG. 23 .  FIG. 24  illustrates the angle transition line  90  after the pressing force applied by the tension bar  30  on the printing medium  17  is increased. The vertical axis and the horizontal axis are identical to those of  FIG. 12 . At the determination timing  95 , the pressing force applied by the tension bar  30  on the printing medium  17  is increased. 
     The transportation failure continues while the transportation driving roller  36   a  rotates two times after the determination timing  95 . Then, when the transportation driving roller  36   a  has rotated two and half times after the determination timing  95 , the transportation failure is eliminated and the tension bar  30  rotates. That is, the tension bar  30  moves to the medium winding unit  26  side. 
     In the transportation failure determining process of step S 6  at a determination timing  105  after the transportation failure is eliminated, the transportation failure detecting unit  86  determines that there is no transportation failure. Next, the process proceeds to the winding step of step S 7 . In the winding process, the tension applying unit  29  has not reached the lower limit position  30   b , and therefore winding of the printing medium  17  is not performed. Accordingly, the tension bar angle  88  increases. 
       FIG. 25  illustrates the pressing force transition line  98  after the pressing force applied by the tension bar  30  on the printing medium  17  is increased. The vertical axis and the horizontal axis are identical to those of  FIG. 18 . As the pressing force transition line  98  indicates, the force applied by the tension bar  30  to press the printing medium  17  is intensified after the determination timing  95 . In the abnormality region  94 , the force applied to press the printing medium  17  is increased for each rotation of the transportation driving roller  36   a . In the present exemplary embodiment, a tension bar pressing force, which is the force applied by the tension bar  30  to press the printing medium  17 , is increased in three levels. 
     Then, at step S 12 , at the determination timing  105  when the normal region  93  is set, the pressing force applied on the printing medium  17  is reset to the original state. That is, when no transportation failure of the printing medium  17  is detected after the force applied by the tension applying unit  29  to press the printing medium  17  has been intensified, the tension control unit  78  controls the tension applying motor  53  to return the force applied to press the printing medium  17  to the force at the time when the transportation failure of the printing medium  17  has been detected. Next, the process proceeds to step S 8 . 
     As described above, according to the present exemplary embodiment, the following advantages are achieved. 
     (1) According to the present exemplary embodiment, when no transportation failure of the printing medium  17  is detected, the tension control unit  78  causes the tension applying motor  53  to weaken the pressing force of the tension bar  30  to return the force applied by the tension applying unit  29  to press the printing medium  17  to the original force. Thus, when the printing medium  17  is easily applied by strong tension, deformation of graphics printed on the printing medium  17  can be reduced. 
     Note that, the present exemplary embodiment is not limited to the above-described exemplary embodiment, it should be understood by those skilled in the art that various modifications and alterations may occur in so far as they are within the spirit and technical scope of the present disclosure. Such modified examples are described below. 
     Modified Example 1 
     In the second exemplary embodiment, the tension bar pressing force is increased in three levels at the determination timing  95 .  FIG. 26  is a drawing for describing a printing method, and illustrates the pressing force transition line  98  after the pressing force applied by the tension bar  30  on the printing medium  17  is increased. The vertical axis and the horizontal axis are identical to those of  FIG. 18 . As indicated by the pressing force transition line  98 , in the present modification, the tension bar pressing force, which is the force applied by the tension bar  30  to press the printing medium  17 , has been intensified in three levels. 
     Then, at the determination timing  105  at step S 12  after the normal region  93  is set, the level of the pressing force applied on the printing medium  17  is reduced one by one to reset the state to the original state. By gradually changing the pressing force in this manner, the influence of the tension bar  30  on the printing medium  17  can be reduced. 
     Modified Example 2 
     In the first exemplary embodiment, one type of the printing medium  17  is used. In the printing apparatus  1 , printing may be performed on multiple types of the printing mediums  17  by replacing the printing mediums  17 . At this time, the determination data  73  and the tension-related data  74  stored in the memory  58  may be set for each the printing medium  17 .  FIG. 27  illustrates determination data and tension-related data of printing mediums. In the table of  FIG. 27 , examples of the item names of the elements are described in the first line, and examples of data are described in the second and subsequent lines. 
     The medium names are described in the first column of the table. Names for distinguishing the printing mediums  17  are described as the medium names. The materials are described in the second column of the table. The names of the materials of the printing mediums  17  are described as the materials. In a case that the printing medium  17  is a laminated medium of a plurality of sheets, the names of a plurality of materials are described. 
     The thickness is described in the third column of the table. The load-bearing capacity of the printing medium  17  differs depending on the thickness. The angle variation determination value is described in the fourth column of the table. The angle variation determination value corresponds to the determination value  96  of  FIG. 17 . The pressing force determination value is described in the fifth column of the table. The pressing force determination value corresponds to the pressing force determination value  101  of  FIG. 18 . The pressing force increase amount is described in the sixth column of the table. The pressing force increase amount is the increase of the pressing force applied by the tension bar  30  on the printing medium  17  for each rotation of the transportation driving roller  36   a  in the abnormality region  94  of  FIG. 25 . 
     The pressing force reduction pattern is described in the seventh column of the table. The pressing force reduction pattern is a reduction pattern of the pressing force applied by the tension bar  30  on the printing medium  17  for each rotation of the transportation driving roller  36   a  after shifting from the abnormality region  94  to the normal region  93 . The type in which the tension bar pressing force is maintained even after shifting from the abnormality region  94  to the normal region  93  as in  FIG. 20  of the first exemplary embodiment is “1”. The type in which the tension bar pressing force is immediately reset to the original state after shifting from the abnormality region  94  to the normal region  93  as in  FIG. 25  of the second exemplary embodiment is “2”. The type in which the tension bar pressing force is reset to the original state stepwise after shifting from the abnormality region  94  to the normal region  93  as in  FIG. 26  of modification  1  is “3”. 
     The determination data  73  and the tension-related data  74  as those described in the table is provided in the memory  58  for each medium name. The transportation failure detecting unit  86  and the tension control unit  78  perform determination and control with reference to the determination data  73  and the tension-related data  74 . In this manner, the determination data  73  and the tension-related data  74  are set in association with the material and the thickness of the printing medium  17 . Thus, the damage of the printing medium  17  by an excessively strong tension bar pressing force can be reduced. 
     Modified Example 3 
     In the first exemplary embodiment, the movement amount computation unit  82  computes the movement amount of the printing medium  17  by multiplying the rotation angle of the rotation shaft of the transportation motor  38  with a predetermined coefficient. Then, the transportation failure detecting unit  86  detects a transportation failure with reference to the movement amount of the printing medium  17 . The transportation failure detecting unit  86  may receive data of the rotation angle of the rotation shaft of the transportation motor  38  output by the transporting unit encoder  41 . Further, the transportation failure detecting unit  86  may detect a transportation failure with reference to the rotation angle of the rotation shaft of the transportation motor  38 . Since the time for computing the movement amount of the printing medium  17  can be saved, the time for detecting a transportation failure can be shortened. 
     Contents derived from the exemplary embodiments will be described below. 
     A printing apparatus includes: a transporting unit configured to transport a medium along a guide member; a winding unit disposed further downstream of the guide member than the transporting unit and configured to wind the medium; a tension applying unit including a rod member configured to press the medium between the transporting unit and the winding unit and apply tension to the medium while moving between an upper limit position and a lower limit position; and a control unit including a first detecting unit configured to detect a movement amount of the medium, and a second detecting unit configured to detect a movement amount of the rod member, and the control unit detects the movement amount of the rod member every time the transporting unit transports the medium by a predetermined length, and detects a transportation failure of the medium when the movement amount of the rod member is smaller than a determination value. 
     With this configuration, the transporting unit transports the medium along the guide member. The winding unit is disposed on the downstream side of the transporting unit and the guide member in the movement direction of the medium. The downstream side is the traveling direction side when the medium moves. Then, the rod member of the tension applying unit between the transporting unit and the winding unit presses the medium to apply tension to the medium. By applying tension to the medium, the winding unit can implement high quality winding of the medium. 
     The control unit includes a first detecting unit and a second detecting unit. Then, the first detecting unit detects the movement amount of the medium. Then, the second detecting unit detects the movement amount of the rod member. When the transporting unit transports the medium, the tension of the medium is reduced until the winding unit operates. Then, when the rod member applies tension to the medium, the position of the rod member changes. The control unit determines the movement amount of the medium at the transporting unit on the basis of the movement amount information. Further, the control unit recognizes the degree of the movement of the medium (medium movement state) at the tension applying unit on the basis of the rod member location information. 
     Thus, the control unit can detect the medium movement state, which indicates whether the medium is moving at the tension applying unit when the transporting unit is moving the medium. When the medium adheres to the guide member, the medium does not move at the tension applying unit. At this time, the control unit determines that the medium is moving at the transporting unit and the medium is not moving at the tension applying unit. Specifically, when the transporting length of the medium transported by the transporting unit becomes equal to a predetermined length, the control unit detects the movement amount of the rod member. Then, when the movement amount of the rod member is smaller than a determination value, a transportation failure of the medium is detected. As a result, the printing apparatus can detect a transportation failure of the medium. 
     Preferably, in the printing apparatus, a winding amount of the medium wound by the winding unit is controlled such that the medium passes through a location where the rod member is able to press the medium. 
     With this configuration, the winding amount of the medium wound by the winding unit is controlled. Then, the medium is caused to pass through a location where the rod member is capable of pressing the medium. When the amount of the medium wound by the winding unit is small, the medium slackens, and consequently the rod member cannot press the medium. Since the winding unit winds the medium before the medium slackens, the rod member can press the medium. Thus, the rod member can be moved in accordance with the movement of the medium. 
     Preferably, the printing apparatus includes a driving unit configured to drive the tension applying unit, and when a transportation failure of the medium is detected, the control unit controls the driving unit such that a force that the tension applying unit applies to press the medium becomes greater than a force that has been applied at a time of detecting the transportation failure of the medium. 
     In this configuration, the printing apparatus includes a driving unit that drives the tension applying unit. When the control unit detects a transportation failure of the medium, the control unit causes the driving unit to intensify the force applied by the tension applying unit to press the medium. When the adhesion power of the medium to the guide member is small, the medium can be detached from the guide member by increasing the tension of the medium. 
     Preferably, in the printing apparatus, when no transportation failure of the medium is detected after the tension applying unit has intensified the force applied to press the medium, the control unit controls the driving unit to maintain the intensified force to press the medium. 
     With this configuration, when no transportation failure of the medium is detected, the control unit causes the driving unit to maintain the intensified force applied by the tension applying unit to press the medium. Thus, since strong tension is applied to the medium, the medium adhering to the guide member again can be reduced. 
     Preferably, in the printing apparatus, when no transportation failure of the medium is detected after the tension applying unit has intensified the force applied to press the medium, the control unit controls the driving unit such that the force applied to press the medium returns to the force that has been applied at the time detecting the transportation failure of the medium. 
     With this configuration, when no transportation failure of the medium is detected, the control unit causes the driving unit to weaken the force applied by the tension applying unit to press the medium to return to the original force. Thus, in the case that the medium to which strong tension is applied is easily extended, deformation of graphics printed on the medium can be reduced. 
     A printing method includes: transporting a medium along a guide member by a transporting unit; winding the medium by a winding unit further downstream of the guide member than the transporting unit; pressing the medium, between the transporting unit and the winding unit, by a rod member to apply tension to the medium while moving between an upper limit position and a lower limit position; detecting a movement amount of the medium by a first detecting unit; and detecting a movement amount of the rod member by a second detecting unit. The movement amount of the rod member is detected every time the transporting unit transports the medium by a predetermined length, and a transportation failure of the medium is detected when the movement amount of the rod member is smaller than a determination value. 
     According to the method, the transporting unit transports the medium along the guide member. The winding unit winds the medium the downstream side of the guide member with respect to the transporting unit. The rod member applies tension to the medium by pressing the medium while moving between the upper limit position and the lower limit position at a location between the transporting unit and the winding unit. By applying tension to the medium, the winding unit can implement high quality winding of the medium. 
     When the transporting unit transports the medium, the tension of the medium is reduced. Then, the position of the rod member moves when the rod member applies tension to the medium. The first detecting unit detects the movement amount of the medium, and the second detecting unit detects the movement amount of the rod member. The control unit detects the movement amount of the rod member at every time when the transporting unit transports the medium by a predetermined length. 
     Thus, the control unit can detect the medium movement state, which indicates whether the medium is moving at the tension applying unit when the transporting unit is moving the medium. When the medium adheres to the guide member, the medium does not move at the tension applying unit. At this time, the medium is moving at the transporting unit, and the medium is not moving at the tension applying unit. Then, when the movement amount of the rod member is smaller than a determination value, the control unit detects a transportation failure of the medium. As a result, the printing apparatus can detect a transportation failure of the medium.