Patent Publication Number: US-11383534-B2

Title: Liquid ejecting device and transporting method of transporting belt

Description:
The present application is based on, and claims priority from JP Application Serial Number 2019-175245, filed Sep. 26, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a liquid ejecting device and a transporting method of a transporting belt. 
     2. Related Art 
     There has been known a liquid ejecting device configured to form images and characters on a medium such as paper and cloth by causing an ejecting unit that ejects a liquid to be moved relative to the medium. For example, JP-A-2015-13455 discloses an inkjet recording device as a liquid ejecting device that includes two gripping portions disposed on left and right positions of a belt on which a recording medium is placed, and configured to be able to grip the belt, and that transports the medium by moving the gripping portion that grips the belt. 
     A micro vibration in an up-and-down direction excited by the gripping portion when the gripping portion grips the transporting belt and releases the gripped transporting belt may propagate to a printing start position of the medium supported by the transporting belt. However, since the liquid ejecting device described in JP-A-2015-13455 does not consider the vibration generated in the transporting belt at all, there has been a risk that the quality of an image printed on the medium may decrease. 
     SUMMARY 
     A liquid ejecting device includes a transporting belt configured to transport a medium in a transport direction, a head configured to move between a first end portion and a second end portion of the transporting belt in a width direction that intersects the transport direction, and eject a liquid onto the medium, a first gripping portion configured to grip the first end portion of the transporting belt, and move in the transport direction, and a second gripping portion configured to grip the second end portion of the transporting belt, and move in the transport direction, where, when the head is positioned outside the transporting belt with respect to the second end portion in the width direction, the first gripping portion performs a first operation of gripping the transporting belt and moving to a predetermined position, and releasing the gripped transporting belt, and, when the head is positioned outside the transporting belt with respect to the first end portion in the width direction, the second gripping portion performs a second operation of gripping the transporting belt and moving to a predetermined position, and releasing the gripped transporting belt. 
     The liquid ejecting device described above may further include a first detection unit configured to detect a displacement of the first gripping portion, and a second detection unit configured to detect a displacement of the second gripping portion, where the transporting belt may be transported based on a detection result of the first detection unit or the second detection unit. 
     In the liquid ejecting device described above, the first operation and the second operation may be alternately performed. 
     A transporting method of a transporting belt is a transporting method of a transporting belt of a liquid ejecting device including the transporting belt configured to transport a medium in a transport direction, a head configured to move between a first end portion and a second end portion of the transporting belt in a width direction that intersects the transport direction, and eject a liquid onto the medium supported by the transporting belt, a first gripping portion configured to grip the first end portion of the transporting belt, and move in the transport direction, and a second gripping portion configured to grip the second end portion of the transporting belt, and move in the transport direction, and includes a first operation step in which, when the head is positioned outside the transporting belt with respect to the second end portion in the width direction, the first gripping portion grips the transporting belt and moves to a predetermined position, and releases the gripped transporting belt, and a second operation step in which, when the head is positioned outside the transporting belt with respect to the first end portion in the width direction, the second gripping portion grips the transporting belt and moves to a predetermined position, and releases the gripped transporting belt. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a whole configuration of a liquid ejecting device according to Exemplary Embodiment 1. 
         FIG. 2  is a cross-sectional side view taken along a line A-A in  FIG. 1 . 
         FIG. 3  is a perspective view illustrating a configuration of a first belt displacement measuring unit. 
         FIG. 4  is a cross-sectional view taken along a line B-B in  FIG. 1 . 
         FIG. 5  is a block diagram illustrating electrical coupling of the liquid ejecting device. 
         FIG. 6  is a flowchart diagram illustrating a transporting method of a transporting belt in bidirectional printing. 
         FIG. 7  is a diagram illustrating a positional relationship between a gripping portion and a head in each step of the transporting method. 
         FIG. 8  is a diagram illustrating a positional relationship between the gripping portion and the head in each step of the transporting method. 
         FIG. 9  is a diagram illustrating a positional relationship between the gripping portion and the head in each step of the transporting method. 
         FIG. 10  is a diagram illustrating a positional relationship between the gripping portion and the head in each step of the transporting method. 
         FIG. 11  is a flowchart diagram illustrating a transporting method of the transporting belt in unidirectional printing. 
         FIG. 12  is a diagram illustrating a positional relationship between the gripping portion and the head in each step of the transporting method. 
         FIG. 13  is a block diagram illustrating electrical coupling of a liquid ejecting device according to Exemplary Embodiment 2. 
         FIG. 14  is a flowchart diagram illustrating a transporting method of the transporting belt in bidirectional printing. 
         FIG. 15  is a flowchart diagram illustrating a transporting method of the transporting belt in unidirectional printing. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Exemplary embodiments will be described below with reference to the accompanying drawings. Note that, in coordinates provided in the drawings, both directions along a Z-axis are an up-and-down direction, an arrow direction is “up”, a Y-axis corresponds to a transport direction, and an arrow direction is “downstream” direction. Further, an X-axis corresponds to a width direction that intersects the transport direction. Further, a tip end side of the arrow indicating each of the axes is defined as a “plus side” and a base end side is defined as a “negative side”. 
     1. Exemplary Embodiment 1 
     1-1. Configuration of Liquid Ejecting Device 
       FIG. 1  is a plan view illustrating a whole configuration of a liquid ejecting device according to Exemplary Embodiment 1.  FIG. 2  is a cross-sectional side view taken along a line A-A in  FIG. 1 . A liquid ejecting device  100  is configured to perform printing on a medium P by moving a head  42  in a width direction of the medium P supported by a transporting belt  23  and ejecting a liquid onto the medium P. 
     As illustrated in  FIG. 1 , the liquid ejecting device  100  includes a transport unit  20  and a printing unit  40 . Each of the units of the liquid ejecting device  100  is attached to a frame  10 . 
     First, a configuration of the transport unit  20  will be described below. 
     The transport unit  20  includes the frame  10 , the transporting belt  23 , a first roller  24 , a second roller  25 , a third roller  26 , a medium support portion  30 , a pressing unit  60 , a first belt displacement measuring unit  70   a , a second belt displacement measuring unit  70   b , a first gripping portion  80   a , a second gripping portion  80   b , and the like. The transport unit  20  is configured to transport the medium P in the transport direction. As the medium P, there can be used, for example, natural fiber, cotton, silk, hemp, mohair, wool, cashmere, regenerated fiber, synthetic fiber, nylon, polyurethane, polyester, and woven cloth or non-woven cloth fabricated by mixed spinning of these fibers. To the woven cloth or non-woven cloth, a pretreatment agent for promoting a color developing property and a fixing property may be applied. 
     The frame  10  forms a rectangular parallelepiped having the Y-axis as a longitudinal direction in which a plurality of frame members are combined with each other. The first roller  24  is disposed upstream of the frame  10  in the transport direction. Both ends of the first roller  24  are rotatably supported on a support stage  24   a , where the support stage  24   a  is attached to an upper surface of the frame  10 . Further, the second roller  25  is disposed downstream of the frame  10  in the transport direction. The second roller  25  is rotatably supported on a support stage  25   a , where the support stage  25   a  is attached to the upper surface of the frame  10 . 
     The transporting belt  23  is stretched over the first roller  24  and the second roller  25 , and rotates while supporting the medium P to transport the medium P in the transport direction. More specifically, the transporting belt  23  is endlessly formed with both end portions of a band-shaped belt being coupled to each other, and is hung between two rollers of the first roller  24  and the second roller  25 . The transporting belt  23  is held in a state where a predetermined tension is applied thereto. 
     A front surface of the transporting belt  23  is provided with an adhesive layer onto which the medium P adheres. The transporting belt  23  supports the medium P bonded to the adhesive layer by the pressing unit  60  described below. This allows stretchable clothes and the like to be handled as the medium P. 
     The first roller  24  and the second roller  25  are provided at an inner side of the transporting belt  23 , and support a back surface of the transporting belt  23 . The transport unit  20  in the present exemplary embodiment includes the third roller  26  that supports the transporting belt  23  between the first roller  24  and the second roller  25 . The third roller  26  is a member that assists in supporting the transporting belt  23 , with an aim to adjust the tension of the transporting belt  23  and the like. Note that the transport unit  20  may also be configured not to include a member such as the third roller  26  that assists in supporting the transporting belt  23 . 
     The medium support portion  30  is provided at the inner side of the transporting belt  23  and between the first roller  24  and the second roller  25 . The medium support portion  30  is a beam member  31  having a beam shape elongated in the width direction of the medium P that intersects the transport direction, and a length of the beam member  31  is longer than a width of the transporting belt  23 . Both ends of the beam member  31  constituting the medium support portion  30  are supported by a support stage  31   a  attached onto the frame  10 . The medium support portion  30  supports the transporting belt  23  in a printing area PA illustrated in  FIG. 1  from below with three beam members  31 . The printing area PA is an area of the transporting belt  23  that overlaps the head  42  in a plan view from the Z-axis when a carriage  43  constituting the printing unit  40  described below moves in the width direction. Note that the present exemplary embodiment exemplifies a configuration in which the transporting belt  23  in the printing area PA is supported by the three beam members  31 , but the number of the beam members  31  may be two, or four or more, and the beam member  31  may be a plate member having a plate shape. 
     The pressing unit  60  is provided on an upstream side of the printing region PA, and presses the medium P supplied on the transporting belt  23  toward a pressing unit support portion  63 . The pressing unit  60  is formed in a cylindrical shape or a columnar shape, is provided rotatably in a circumferential direction, and rotates along the transport direction of the medium P. The pressing unit  60  is supported to be reciprocally movable along the transport direction. The pressing unit  60  is moved by a pressing unit driving portion  62  in the transport direction and in a direction opposite to the transport direction while pressing the medium P downward from above along the Z-axis. 
     The pressing unit support portion  63  is provided at the inner side of the transporting belt  23  and between the first roller  24  and the medium support portion  30 . The pressing unit support portion  63  has a plate shape and is configured to be able to support the pressing unit  60  via the transporting belt  23 . A range in which the pressing unit support portion  63  is formed corresponds to a movement range of the pressing unit  60 . Specifically, a length of the pressing unit support portion  63  along the X-axis corresponds to a length of the pressing unit  60  along the X-axis, and a length of the pressing unit support portion  63  along the Y-axis corresponds to a movement range of the pressing unit  60  along the Y-axis. The pressing unit support portion  63  is supported by four support stages  63   a  attached to the upper surface of the frame  10 . The medium P supplied on the front surface of the transporting belt  23  is pressed against the transporting belt  23  between the pressing unit  60  and the pressing unit support portion  63 . This allows the medium P to reliably adhere onto the adhesive layer provided on the front surface of the transporting belt  23 , and to prevent the medium P from floating up over the transporting belt  23 . Note that the transporting belt may be of an electrostatic adsorption type belt for adsorbing the medium P with static electricity. 
       FIG. 3  is a perspective view illustrating a configuration of the first belt displacement measuring unit.  FIG. 4  is a cross-sectional view taken along a line B-B in  FIG. 1 . Note that the second belt displacement measuring unit  70   b  is configured to be symmetrical to the first belt displacement measuring unit  70   a  with respect to a center line of the transporting belt  23  in the width direction that intersects the transport direction. Thus, an illustration of a perspective view illustrating a configuration of the second belt displacement measuring unit  70   b  will be omitted. 
     The first belt displacement measuring unit  70   a  is provided on the upstream side of the printing unit  40 , and is positioned on a positive side of the transporting belt  23  along the X-axis. 
     The first belt displacement measuring unit  70   a  includes a first scale portion  75   a  provided along the transport direction, a first detection unit  85   a  that detects a displacement relative to the first scale portion  75   a , and the first gripping portion  80   a  that is configured so as to integrally move with the first detection unit  85   a , grips an end portion on the positive side along the X-axis that is a first end portion  23   a  of the transporting belt  23  in the width direction, and moves with the transporting belt  23  in the transport direction. The first detection unit  85   a  detects the displacement of the first gripping portion  80   a , namely, the displacement of the transporting belt  23  at the first end portion  23   a.    
     The first belt displacement measuring unit  70   a  includes a base  71  having a rectangular parallelepiped form elongated along the transport direction of the medium P, a scale bonded portion  73  provided above the base  71 , the first gripping portion  80   a  that is provided on the base  71  and moves along a guide rail  72  extending along the Y-axis, a first movement mechanism  77   a  for moving the first gripping portion  80   a  in both directions along the transport direction, and the like. 
     The scale bonded portion  73  spans between column portions  73   a  and  73   b  provided perpendicularly to both ends of the base  71  along the Y-axis being a longitudinal direction. The scale bonded unit  73  in the first belt displacement measuring unit  70   a  includes a protruding portion that protrudes in an eaves shape on a negative side along the X-axis, and a part thereof overlaps the transporting belt  23  in the plan view. 
     The first scale portion  75   a  is provided on a lower surface of the protruding portion of the scale bonded portion  73 . A magnetic scale in which magnets having different polarities are alternately disposed is used in the first scale portion  75   a  according to the present exemplary embodiment. 
     The first gripping portion  80   a  includes a gripping base  81 , a guide block  82 , an elastic member  83 , and the like. The gripping base  81  has a rectangular plate shape elongated in the width direction of the transporting belt  23 . An end portion  81   c  of the gripping base  81  on the negative side along the X-axis substantially coincides with a side wall  73   c  of the scale bonded portion  73  on the negative side along the X-axis in the plan view, and overlaps the transporting belt  23 . An end portion  81   d  of the gripping base  81  on the positive side along the X-axis protrudes more than a side wall  71   d  of the base  71  on the positive side along the X-axis in the plan view. The guide block  82  is provided on a bottom surface of the gripping base  81 . A recessed groove that corresponds to a shape of the guide rail  72  protruding in a protruding shape from an upper surface of the base  71 , and opens to a negative side along the Z-axis in a side view from the Y-axis is formed in the guide block  82 . With the guide block  82  and the guide rail  72  engaging each other, the first gripping portion  80   a  is configured to be reciprocally movable along the transport direction. 
     The elastic member  83  is provided on an upper surface of the gripping base  81 . The elastic member  83  has a rectangular plate shape shorter than the gripping base  81 . An end portion  83   d  of the elastic member  83  on the positive side along the X-axis is bonded to the gripping base  81  substantially at the center of the gripping base  81 . An end portion  83   c  of the elastic member  83  on the negative side along the X-axis substantially coincides with the end portion  81   c  of the gripping base  81  on the negative side along the X-axis in the plan view. The end portion  81   c  of the gripping base  81  and the end portion  83   c  of the elastic member  83  have a slightly wider gap than a thickness of the transporting belt  23 . The first gripping portion  80   a  is configured to be able to grip the first end portion  23   a  of the transporting belt  23  between the end portion  81   c  of the gripping base  81  and the end portion  83   c  of the elastic member  83  by an elastic force of the elastic member  83 . Carbon fiber and the like can be used as a material of the elastic member  83 . 
     The first gripping portion  80   a  includes a ferromagnetic body  84  on the upper surface of the elastic member  83  that does not overlap the transporting belt  23  in the plan view. Iron, nickel, cobalt, and the like can be used as the ferromagnetic body  84 . 
     Further, a first switching unit  74   a  that switches the first gripping portion  80   a  between a gripping state and a non-gripping state is provided at a position on a lower surface of the gripping base  81  of the first gripping portion  80   a , and facing the ferromagnetic body  84 . The switching unit  74  includes an electromagnet and a driving portion, and the ferromagnetic body  84  is attracted to the first switching portion  74   a  by a magnetic force generated when a current is passed through the electromagnet by the driving portion. At this time, the elastic member  83  elastically deforms toward the gripping base  81 , resulting in the gripping state in which the transporting belt  23  is gripped between the gripping base  81  and the elastic member  83  by the elastic force. Further, when the current passing through the electromagnet is cut off, the first gripping portion  80   a  is brought into the non-gripping state from the gripping state. 
     The first detection unit  85   a  is provided at a position on the upper surface of the end portion  83   c  of the elastic member  83 , and facing the first scale portion  75   a . The first detection unit  85   a  includes a hall element, an MR element, or the like configured to convert a change in a magnetic field into an electrical signal, and detects the displacement relative to the first scale portion  75   a . The first detection unit  85   a  according to the present exemplary embodiment is provided on a pedestal for disposing the first detection unit  85   a  close to the first scale portion  75   a . The first detection unit  85   a  integrally moves with the first gripping portion  80   a.    
     The first movement mechanism  77   a  moves the first gripping portion  80   a  in the gripping state in the transport direction, and moves the first gripping portion  80   a  in the non-gripping state in the direction opposite to the transport direction via a movement lever  78  that couples the gripping base  81  of the first gripping portion  80   a  to the first movement mechanism  77   a . The first movement mechanism  77   a  has a rectangular parallelepiped shape elongated in the transport direction, and is fixed to the side wall  71   d  of the base  71  on the positive side along the X-axis. A recessed guide groove extending in the transport direction is formed in an upper surface and a lower surface of the first movement mechanism  77   a.    
     The movement lever  78  includes a pedestal  78   a  including a protruding protrusion that corresponds to a shape of the guide groove, and a long handle portion  78   b  extending from the pedestal  78   a  along the Z-axis. An upper end of the long handle portion  78   b  is coupled to the gripping base  81 . The movement lever  78  is configured to be reciprocally movable along the Y-axis with the guide groove of the first movement mechanism  77   a  and the pedestal  78   a  engaging each other. As the first moving mechanism  77   a , there can be employed, for example, a mechanism combined of a ball screw and a ball nut, a linear guide mechanism, or the like. As the driving portion that drives the first moving mechanism  77   a , there can be employed, for example, a variety of motors such as a stepping motor, a servomotor, and a linear motor or an air cylinder. 
     The second belt displacement measuring unit  70   b  is provided on the upstream side of the printing unit  40 , and is positioned on the negative side of the transporting belt  23  along the X-axis. 
     The second belt displacement measuring unit  70   b  includes a second scale portion  75   b  provided along the transport direction, a second detection unit  85   b  that detects a displacement relative to the second scale portion  75   b , and the second gripping portion  80   b  that is configured so as to integrally move with the second detection unit  85   b , grips an end portion on the negative side along the X-axis that is a second end portion  23   b  of the transporting belt  23  in the width direction, and moves with the transporting belt  23  in the transport direction. The second detection unit  85   b  detects the displacement of the second gripping portion  80   b , namely, the displacement of the transporting belt  23  at the second end portion  23   b . Further, a second switching unit  74   b  that switches the second gripping portion  80   b  between the gripping state and the non-gripping state is provided at the second gripping portion  80   b.    
     The second belt displacement measuring unit  70   b  includes a base  71  having a rectangular parallelepiped form elongated along the transport direction of the medium P, a scale bonded portion  73  provided above the base  71 , a second movement mechanism  77   b  for moving the second gripping portion  80   b  in both directions along the transport direction, and the like. 
     The second belt displacement measuring unit  70   b  is configured to be symmetrical to the first belt displacement measuring unit  70   a  in the width direction. The second gripping portion  80   b , the second scale portion  75   b , the second detection unit  85   b , the second movement mechanism  77   b , and the second switching unit  74   b  included in the second belt displacement measuring unit  70   b  have the same configuration as that of the respective corresponding components of the first belt displacement measuring unit  70   a , and thus description of the configuration will be omitted. 
     Note that the present exemplary embodiment indicates the configuration in which the first and second detection units  85   a  and  85   b  integrally move with the first and second gripping portions  80   a  and  80   b , and the first and second scale portions  75   a  and  75   b  are fixed, but a configuration in which the first and second scale portions integrally move with the first and second gripping portions, and the first and second detection units are fixed may be used. 
     Further, the present exemplary embodiment exemplifies a so-called magnetic encoder that obtains a relative displacement between the first scale portion  75   a  and the first detection unit  85   a  and a relative displacement between the second scale portion  75   b  and the second detection unit  85   b  through a change in magnetic field, but an optical encoder that obtains the displacement through an optical change may also be used. 
     The configuration of the transport unit  20  is described above. Note that the transport unit  20  may also be configured to be able to be coupled to a medium supply unit that supplies the medium P at the upstream of the transporting belt  23  in the transport direction. For example, the medium supply unit rotatably supports the medium P of a band-shape wound in a rolled shape, rolls out the medium P of a rolled shape by rotating the medium P, and then supplies the medium P to the transporting belt  23 . Further, the transport unit  20  may also be configured to be able to be coupled to a medium winding unit that winds up the medium P at the downstream of the transporting belt  23  in the transport direction. For example, the medium winding unit includes a winding shaft that rotatably supports the medium P, and rotates the winding shaft to wind up the medium P of a band-shape into a rolled shape. 
     Next, a configuration of the printing unit  40  will be described. The printing unit  40  includes the head  42 , the carriage  43 , a carriage moving unit  45 , and the like. 
     The printing unit  40  is disposed above the transport unit  20 . The head  42  ejects the liquid onto the medium P supported by the transporting belt  23  to print an image and the like on the medium P. A plurality of the heads  42  are mounted on the carriage  43  in a replaceable manner. The head  42  mounted on the carriage  43  moves between the first end portion  23   a  and the second end portion  23   b  of the transporting belt  23  in the width direction by the carriage moving unit  45 . Each of the heads  42  is supplied with, as the liquid, a color ink such as cyan (C), magenta (M), yellow (Y), black (K), and the like, a preprocess liquid, postprocess liquid, or the like. The head  42  includes a piezoelectric element as a driving portion configured to eject the liquid from a nozzle corresponding to each liquid toward the medium P positioned in the printing region PA. 
     The carriage moving unit  45  is attached to a support frame  15  extending from the frame  10  to the positive side along the Z-axis, and is positioned above the transporting belt  23 . The carriage moving unit  45  includes a guide rail  46  extending along the X-axis. The head  42  is supported by the guide rail  46  in a state reciprocally movable with the carriage  43  along the X-axis. 
     The carriage moving unit  45  includes a moving mechanism for causing the carriage  43  to move along the guide rail  46 , and a driving portion that drives the moving mechanism. As the moving mechanism, there can be employed, for example, a mechanism combined of a ball screw and a ball nut, a linear guide mechanism, or the like. As the driving portion, there can be employed, for example, a variety of motors such as a stepping motor, a servomotor, and a linear motor. The motor is driven to cause the moving mechanism to move the head  42  together with the carriage  43  along the X axis direction. 
       FIG. 5  is a block diagram illustrating electrical coupling of the liquid ejecting device. Next, an electrical configuration of the liquid ejecting device  100  will be described with reference to  FIG. 5 . 
     The liquid ejecting device  100  includes a control unit  1  that controls each component included in the liquid ejecting device  100 . The control unit  1  is configured to include an interface (I/F) unit  2 , a Central Processing Unit (CPU)  3 , a control circuit  4 , a storage unit  5 , and the like. The CPU  3  is coupled to each component via a bus. 
     The I/F unit  2  is coupled to an input device  6 , is configured to transmit/receive data between the input device  6  that handles an input signal and an image and the control unit  1 , and receives print data and the like generated in the input device  6 . The input device  6  is constituted by a computer and the like. In the present exemplary embodiment, a block diagram in which the input device  6  is integrally formed with the liquid ejecting device  100  is illustrated, but the input device  6  may be separately formed from the liquid ejecting device  100 . 
     The CPU  3  is an arithmetic processing device for performing various types of input signal processing, and an overall control of the liquid ejecting device  100  in accordance with a program stored in the storage unit  5  and the print data received from the input device  6 . 
     The storage unit  5  serves as a storage medium configured to secure a region for storing the program, a working region, and the like of the CPU  3 , and includes a storage element such as a Random Access Memory (RAM), an Electrically Erasable Programmable Read Only Memory (EEPROM), or the like. The control circuit  4  is a circuit coupled to each driving portion of the head  42 , the carriage moving unit  45 , the first switching unit  74   a , the first movement mechanism  77   a , the second switching unit  74   b , and the second movement mechanism  77   b , and configured to generate a control signal for controlling the driving of the head  42 , the carriage moving unit  45 , the first switching unit  74   a , the first movement mechanism  77   a , the second switching unit  74   b , the second movement mechanism  77   b , and the like, based on the print data and the arithmetic result of the CPU  3 . 
     Further, the CPU  3  is coupled to the first detection unit  85   a  and the second detection unit  85   b  via the bus. The CPU  3  calculates the displacement of the first gripping portion  80   a  moved by the first movement mechanism  77   a , based on a detection result output from the first detection unit  85   a , and calculates the displacement of the second gripping portion  80   b  moved by the second movement mechanism  77   b , based on a detection result output from the second detection unit  85   b.    
     The control unit  1  generates a first current control signal for controlling a driving portion that generates a magnetic force in the first switching unit  74   a . The first switching unit  74   a  switches the first gripping portion  80   a  between the gripping state and the non-gripping state, based on the first current control signal. 
     The control unit  1  generates a first movement mechanism control signal for controlling the driving portion of the first movement mechanism  77   a , based on the calculated displacement of the first gripping portion  80   a , and performs feedback control of the first movement mechanism  77   a . In other words, the transporting belt  23  is transported based on a detection result of the first detection unit  85   a.    
     For example, the control unit  1  performs a first operation in which the first gripping portion  80   a  grips the transporting belt  23  and moves to a predetermined position in the transport direction, and releases the gripped transporting belt  23  by the control of the first switching unit  74   a  by the first current control signal and the control of the first movement mechanism  77   a  by the first movement mechanism control signal. 
     The control unit  1  generates a second current control signal for controlling a driving portion that generates a magnetic force in the second switching unit  74   b . The second switching unit  74   b  switches the second gripping portion  80   b  between the gripping state and the non-gripping state, based on the second current control signal. 
     The control unit  1  generates a second movement mechanism control signal for controlling the driving portion of the second movement mechanism  77   b , based on the calculated displacement of the second gripping portion  80   b , and performs feedback control of the second movement mechanism  77   b . In other words, the transporting belt  23  is transported based on a detection result of the second detection unit  85   b.    
     For example, the control unit  1  performs a second operation in which the second gripping portion  80   b  grips the transporting belt  23  and moves to a predetermined position in the transport direction, and releases the gripped transporting belt  23  by the control of the second switching unit  74   b  by the second current control signal and the control of the second movement mechanism  77   b  by the second movement mechanism control signal. 
     The control unit  1  performs an image forming operation of generating a head control signal for controlling the driving portion of the head  42  and a carriage control signal for controlling the driving portion of the carriage moving unit  45 , ejecting the liquid droplet to the medium P by causing the head  42  moved by the carriage  43  to eject the liquid. 
     The control unit  1  causes any one of the first operation and the second operation, and the image forming operation to be alternately performed, and thus an image based on the image data is printed on the medium P. 
     1-2. Transporting Method in Bidirectional Printing 
       FIG. 6  is a flowchart diagram illustrating the transporting method of the transporting belt in the bidirectional printing.  FIGS. 7 to 10  are diagrams illustrating a positional relationship between the gripping portion and the head in each step of the transporting method. Next, the transporting method of the transporting belt  23  in the bidirectional printing of the liquid ejecting device  100  will be described with reference to  FIGS. 6 to 10 . 
     Step S 101  is a first gripping step of gripping the transporting belt  23  by the first gripping portion  80   a . As illustrated in  FIG. 7 , when the head  42  is positioned outside the transporting belt  23  with respect to the second end portion  23   b  in the width direction, the control unit  1  generates the magnetic force in the first switching unit  74   a , and brings the first gripping portion  80   a  in the non-gripping state into the gripping state of gripping the first end portion  23   a  of the transporting belt  23 . At this time, a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the first end portion  23   a  gripped by the first gripping portion  80   a.    
     Step S 102  is a first movement step of moving the first gripping portion  80   a  in the gripping state in the transport direction. As illustrated in  FIG. 8 , the control unit  1  drives the first movement mechanism  77   a , and moves the first gripping portion  80   a  in the gripping state of gripping the transporting belt  23  from upstream to downstream in the transport direction to a predetermined position. The transporting belt  23  is transported in the transport direction together with the first gripping portion  80   a , and the medium P on the transporting belt  23  is transported to a predetermined position based on print data. 
     Step S 103  is a first release step of releasing the gripped first gripping portion  80   a . The control unit  1  demagnetizes the magnetic force of the first switching unit  74   a , and brings the first gripping portion  80   a  in the gripping state into the non-gripping state in which the transporting belt  23  is not gripped. At this time, a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the first end portion  23   a  that has been gripped by the first gripping portion  80   a.    
     Note that step S 101  to step S 103  are a first operation step of performing the first operation in which the first gripping portion  80   a  grips the transporting belt  23  and moves to the predetermined position, and releases the gripped transporting belt  23 . 
     Step S 104  is a first return step of moving the first gripping portion  80   a  in the non-gripping state in the direction opposite to the transport direction. As illustrated in  FIG. 9 , the control unit  1  drives the first movement mechanism  77   a , and moves the first gripping portion  80   a  in the non-gripping state from downstream to upstream in the transport direction to the original position. 
     Note that, in step S 104 , the control unit  1  controls the head  42  and the carriage moving unit  45 , based on the print data, and performs the image forming operation of causing the head  42  to eject the liquid while moving the carriage  43  from the second end portion  23   b  side to the first end portion  23   a  side of the transporting belt  23 . The image forming operation may start simultaneously with step S 103  or may start between step S 104  and step S 105 . As illustrated in  FIG. 8 , the micro vibration generated in step S 101  and step S 103  is excited at the first end portion  23   a  away from the head  42  positioned on the second end portion  23   b  side that is the printing start position of the image forming operation. The micro vibration propagating through the transporting belt  23  is attenuated before reaching the printing start position. 
     Step S 105  is a second gripping step of gripping the transporting belt  23  by the second gripping portion  80   b . As illustrated in  FIG. 9 , when the head  42  is positioned outside the transporting belt  23  with respect to the first end portion  23   a  in the width direction, the control unit  1  generates the magnetic force in the second switching unit  74   b , and brings the second gripping portion  80   b  in the non-gripping state into the gripping state of gripping the second end portion  23   b  of the transporting belt  23 . At this time, a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the second end portion  23   b  gripped by the second gripping portion  80   b.    
     Step S 106  is a second movement step of moving the second gripping portion  80   b  in the gripping state in the transport direction. As illustrated in  FIG. 10 , the control unit  1  drives the second movement mechanism  77   b , and moves the second gripping portion  80   b  in the gripping state of gripping the transporting belt  23  from upstream to downstream in the transport direction to a predetermined position. The transporting belt  23  is transported in the transport direction together with the second gripping portion  80   b , and the medium P on the transporting belt  23  is transported to a predetermined position based on the print data. 
     Step S 107  is a second release step of releasing the gripped second gripping portion  80   b . The control unit  1  demagnetizes the magnetic force of the second switching unit  74   b , and brings the second gripping portion  80   b  in the gripping state into the non-gripping state in which the transporting belt  23  is not gripped. At this time, a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the second end portion  23   b  that has been gripped by the second gripping portion  80   b.    
     Note that step S 105  to step S 107  are a second operation step of performing the second operation in which the second gripping portion  80   b  grips the transporting belt  23  and moves to the predetermined position, and releases the gripped transporting belt  23 . 
     Step S 108  is a second return step of moving the second gripping portion  80   b  in the non-gripping state in the direction opposite to the transport direction. As illustrated in  FIG. 7 , the control unit  1  drives the second movement mechanism  77   b , and moves the second gripping portion  80   b  in the non-gripping state from downstream to upstream in the transport direction to the original position. 
     Note that, in step S 108 , the control unit  1  controls the head  42  and the carriage moving unit  45  based on the print data, and performs the image forming operation of causing the head  42  to eject the liquid while moving the carriage  43  from the first end portion  23   a  side to the second end portion  23   b  side of the transporting belt  23 . The image forming operation may start simultaneously with step S 107  or may start between step S 108  and step S 101  when step S 101  to step S 108  are repeatedly performed. As illustrated in  FIG. 9 , the micro vibration generated in step S 105  and step S 107  is excited at the second end portion  23   b  away from the head  42  positioned on the first end portion  23   a  side that is the printing start position of the image forming operation. The micro vibration propagating through the transporting belt  23  is attenuated before reaching the printing start position. 
     Step S 101  to step S 108  are repeatedly performed, and the first operation by the first gripping portion  80   a  and the second operation by the second gripping portion  80   b  are alternately performed, and thus the transporting belt  23  is sequentially transported in the transport direction. The control unit  1  sequentially performs the image forming operation by the bidirectional printing on the medium P transported by the transporting belt  23 , and thus a desired image is formed on the medium P. 
     1-3. Transporting Method in Unidirectional Printing 
       FIG. 11  is a flowchart diagram illustrating the transporting method of the transporting belt in the unidirectional printing.  FIG. 12  is a diagram illustrating a positional relationship between the gripping portion and the head in each step of the transporting method. Next, the transporting method of the transporting belt  23  in the unidirectional printing of the liquid ejecting device  100  will be described with reference to  FIGS. 7 to 12 . Note that step S 201  to step S 204  are the same as step S 101  to step S 104  of the transporting method in the above-described bidirectional printing, and thus the description will be omitted. 
     Step S 205  is a second gripping step of gripping the transporting belt  23  by the second gripping portion  80   b . As illustrated in  FIG. 9 , when the head  42  is positioned outside the transporting belt  23  with respect to the first end portion  23   a  in the width direction, the control unit  1  generates the magnetic force in the second switching unit  74   b , and brings the second gripping portion  80   b  in the non-gripping state into the gripping state of gripping the second end portion  23   b  of the transporting belt  23 . At this time, a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the second end portion  23   b.    
     Note that, in step S 205 , the control unit  1  controls the carriage moving unit  45 , and the carriage  43  starts to move from the first end portion  23   a  side to the second end portion  23   b  side of the transporting belt  23 . 
     Step S 206  is a second movement step of moving the second gripping portion  80   b  in the gripping state in the transport direction. As illustrated in  FIG. 12 , the control unit  1  drives the second movement mechanism  77   b , and moves the second gripping portion  80   b  in the gripping state of gripping the transporting belt  23  from upstream to downstream in the transport direction to a predetermined position. The transporting belt  23  is transported in the transport direction together with the second gripping portion  80   b , and the medium P on the transporting belt  23  is transported to a predetermined position based on the print data. 
     Step S 207  is a second release step of releasing the gripped second gripping portion  80   b . The control unit  1  demagnetizes the magnetic force of the second switching unit  74   b , and brings the second gripping portion  80   b  in the gripping state into the non-gripping state in which the transporting belt  23  is not gripped. At this time, a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the second end portion  23   b.    
     Note that, as illustrated in  FIG. 12 , the control unit  1  completes the execution of step S 206  and step S 207  before the head  42  mounted on the carriage  43  reaches the second end portion  23   b  side that is the printing start position of the image forming operation performed in step S 208 , that is, when the head  42  is positioned away from the second end portion  23   b.    
     Further, step S 205  to step S 207  are a second operation step of performing the second operation in which the second gripping portion  80   b  grips the transporting belt  23  and moves to the predetermined position, and releases the gripped transporting belt  23 . 
     Step S 208  is a second return step of moving the second gripping portion  80   b  in the non-gripping state in the direction opposite to the transport direction. As illustrated in  FIG. 7 , the control unit  1  drives the second movement mechanism  77   b , and moves the second gripping portion  80   b  in the non-gripping state from the downstream to the upstream in the transport direction to the original position. 
     Note that, in step S 208 , the control unit  1  terminates the movement of the carriage  43  toward the second end portion  23   b  side, and causes the head  42  to be positioned at the printing start position. Then, the control unit  1  controls the head  42  and the carriage moving unit  45  based on the print data, and performs the image forming operation of causing the head  42  to eject the liquid while moving the carriage  43  from the second end portion  23   b  side to the first end portion  23   a  side of the transporting belt  23 . Furthermore, the control unit  1  controls the carriage moving unit  45 , moves the carriage  43  from the first end portion  23   a  side of the transporting belt  23  illustrated in  FIG. 9  to the second end portion  23   b  side illustrated in  FIG. 7 , and returns the head  42  to the printing start position of the next image forming operation. 
     As illustrated in  FIG. 12 , the micro vibration generated in step S 205  and step S 207  is excited at the second end portion  23   b  when the head  42  is located at the position away from the second end portion  23   b  that is the printing start position of the image forming operation. The micro vibration propagating through the transporting belt  23  is attenuated until the head  42  reaches the printing start position and starts to print. 
     Step S 201  to step S 208  are repeatedly performed, and the first operation by the first gripping portion  80   a  and the second operation by the second gripping portion  80   b  are alternately performed, and thus the transporting belt  23  is sequentially transported in the transport direction. The control unit  1  sequentially performs the image forming operation by the unidirectional printing on the medium P transported by the transporting belt  23 , and thus a desired image is formed on the medium P. 
     As described above, according to the liquid ejecting device  100  and the transporting method of the transporting belt  23  in Exemplary Embodiment 1, the following effects can be obtained. 
     The liquid ejecting device  100  includes the first gripping portion  80   a  capable of gripping the first end portion  23   a  of the transporting belt  23 , and the second gripping portion  80   b  capable of gripping the second end portion  23   b  of the transporting belt  23 . When the head  42  is positioned outside the transporting belt  23  with respect to the second end portion  23   b , the first gripping portion  80   a  performs the first operation of gripping the first end portion  23   a  of the transporting belt  23  and moving the transporting belt  23  in the transport direction, and releasing the gripped transporting belt  23 . When the head  42  is positioned outside the transporting belt  23  with respect to the first end portion  23   a , the second gripping portion  80   b  performs the second operation of gripping the second end portion  23   b  of the transporting belt  23  and moving the transporting belt  23  in the transport direction, and releasing the gripped transporting belt  23 . In the first operation and the second operation, the first gripping portion  80   a  or the second gripping portion  80   b  grips the end portion away from the position of the head  42  and releases gripping. A micro vibration in the up-and-down direction generated when the first gripping portion  80   a  or the second gripping portion  80   b  grips the transporting belt  23  or releases gripping is excited at the end portion away from the position of the head  42 . As a result, the vibration propagating through the transporting belt  23  is attenuated before the printing start position is reached or before printing starts, and thus the quality of an image printed on the medium P improves. Therefore, the liquid ejecting device  100  that improves image quality can be provided. 
     The liquid ejecting device  100  transports the transporting belt  23 , based on a detection result of the first detection unit  85   a  configured to detect a displacement of the first gripping portion  80   a  and a detection result of the second detection unit  85   b  configured to detect a displacement of the second gripping portion  80   b . Specifically, the first movement mechanism  77   a  of the first gripping portion  80   a  configured to move the transporting belt  23  in the transport direction is subjected to feedback control based on a detection result of the first detection unit  85   a . The second movement mechanism  77   b  of the second gripping portion  80   b  configured to move the transporting belt  23  in the transport direction is subjected to feedback control based on a detection result of the second detection unit  85   b . As a result, the transport accuracy of the transporting belt  23  improves. 
     The liquid ejecting device  100  transports the transporting belt  23  in the transport direction by alternately performing the first operation by the first gripping portion  80   a  and the second operation by the second gripping portion  80   b . In this way, even when a length of the transporting belt  23  along the first end portion  23   a  of the  23  of the transporting belt  23  and a length of the transporting belt  23  along the second end portion  23   b  of the transporting belt  23  are slightly different, a difference between the displacement on the first end portion  23   a  side and the displacement on the second end portion  23   b  side is less likely to be generated. As a result, the transport accuracy of the transporting belt  23  improves. 
     The transporting method of the transporting belt  23  performs the first operation step in which, when the head  42  is positioned outside the transporting belt  23  with respect to the second end portion  23   b , the first gripping portion  80   a  grips the first end portion  23   a  of the transporting belt  23  and moves the transporting belt  23  in the transport direction, and releases the gripped transporting belt  23 . Further, the transporting method of the transporting belt  23  performs the second operation step in which, when the head  42  is positioned outside the transporting belt  23  with respect to the first end portion  23   a , the second gripping portion  80   b  grips the second end portion  23   b  of the transporting belt  23  and moves the transporting belt  23  in the transport direction, and releases the gripped transporting belt  23 . In the first operation step and the second operation step, the first gripping portion  80   a  or the second gripping portion  80   b  grips the end portion away from the position of the head  42  and releases gripping. Since a micro vibration in the up-and-down direction generated when the first gripping portion  80   a  or the second gripping portion  80   b  grips the transporting belt  23  or releases gripping is excited at the end portion on the opposite side away from the position of the head  42 , the vibration propagating through the transporting belt  23  is attenuated before the printing start position is reached or printing starts. Accordingly, the quality of an image printed on the medium P improves. Therefore, the transporting method of the transporting belt  23  that improves image quality can be provided. 
     2. Exemplary Embodiment 2 
       FIG. 13  is a block diagram illustrating electrical coupling of a liquid ejecting device according to Exemplary Embodiment 2. Note that the same component as in Exemplary Embodiment 1 is given the same number, and the redundant description of the component will be omitted. Exemplary Embodiment 1 exemplifies the liquid ejecting device  100  having the configuration in which the first and second gripping portions  80   a  and  80   b  that grip the transporting belt  23  transport the transporting belt  23  in the transport direction, thereby transporting the medium P. In a liquid ejecting device  200  in the present exemplary embodiment, the second roller  25  rotates and is driven, and the transporting belt  23  rotates, thereby transporting the medium P in the transport direction. 
     2-1. Configuration of Liquid Ejecting Device 
     The liquid ejecting device  200  includes the transport unit  20  and the printing unit  40 . Each of the units of the liquid ejecting device  200  is attached to the frame  10 . 
     The first roller  24  in the present exemplary embodiment is a belt driven roller provided upstream of the printing unit  40 . The second roller  25  is a belt driving roller provided downstream of the printing unit  40 . The second roller  25  is provided with a transport motor  25   b  that rotates and drives the second roller  25 . The transport motor  25   b  is driven, and the transporting belt  23  rotates and moves with the rotation of the second roller  25 , and thus the first roller  24  is driven and rotates. In this way, the medium P supported by the transporting belt  23  is transported in the transport direction. 
     The first and second gripping portions  80   a  and  80   b  in the gripping state of gripping the transporting belt  23  move in the transport direction together with the transporting belt  23  that rotates and moves by a driving force of the transport motor  25   b . The first gripping portion  80   a  in the non-gripping state moves in the direction opposite to the transport direction by the first movement mechanism  77   a , and the second gripping portion  80   b  in the non-gripping state moves in the direction opposite to the transport direction by the second movement mechanism  77   b.    
     As illustrated in  FIG. 13 , the liquid ejecting device  200  includes a control unit  201  that controls each component included in the liquid ejecting device  200 . The control unit  201  is configured to include the I/F unit  2 , the CPU  3 , the control circuit  4 , the storage unit  5 , and the like. The CPU  3  is coupled to each component via a bus. 
     The control circuit  4  is a circuit coupled to the transport motor  25   b , and configured to generate a control signal for controlling the driving of the transport motor  25   b , based on the print data and the arithmetic result of the CPU  3 . 
     The control unit  201  generates a first current control signal for controlling a driving portion that generates a magnetic force in the first switching unit  74   a . The first switching unit  74   a  switches the first gripping portion  80   a  between the gripping state and the non-gripping state, based on the first current control signal. 
     The control unit  201  generates a transport motor control signal for controlling the transport motor  25   b , based on the calculated displacement of the first gripping portion  80   a , and performs feedback control of the transport motor  25   b . In other words, the transporting belt  23  is transported based on a detection result of the first detection unit  85   a . For example, the control unit  201  performs a first operation in which the first gripping portion  80   a  grips the transporting belt  23  and moves with the transporting belt  23  to a predetermined position in the transport direction, and releases the gripped transporting belt  23  by the control of the first switching unit  74   a  by the first current control signal and the control of the transport motor  25   b  by the transport motor control signal. 
     The control unit  201  generates a second current control signal for controlling a driving portion that generates a magnetic force in the second switching unit  74   b . The second switching unit  74   b  switches the second gripping portion  80   b  between the gripping state and the non-gripping state, based on the second current control signal. 
     The control unit  201  generates a transport motor control signal for controlling the transport motor  25   b , based on the calculated displacement of the second gripping portion  80   b , and performs feedback control of the transport motor  25   b . In other words, the transporting belt  23  is transported based on a detection result of the second detection unit  85   b . For example, the control unit  201  performs a second operation in which the second gripping portion  80   b  grips the transporting belt  23  and moves with the transporting belt  23  to a predetermined position in the transport direction, and releases the gripped transporting belt  23  by the control of the second switching unit  74   b  by the second current control signal and the control of the transport motor  25   b  by the transport motor control signal. 
     The control unit  201  performs an image forming operation of generating a head control signal for controlling the driving portion of the head  42  and a carriage control signal for controlling the driving portion of the carriage moving unit  45 , and ejecting the liquid droplet to the medium P by causing the head  42  moved by the carriage  43  to eject the liquid. 
     The control unit  201  causes the movement of the transporting belt  23  in the transport direction and the image forming operation to be alternately performed, and thus an image based on the image data is printed on the medium P. 
     2-2. Transporting Method in Bidirectional Printing 
       FIG. 14  is a flowchart diagram illustrating the transporting method of the transporting belt in the bidirectional printing. The transporting method of the transporting belt  23  in the bidirectional printing of the liquid ejecting device  200  will be described. 
     Step S 301  is the same as step S 101  described in Exemplary Embodiment 1, except that step  301  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. In step S 301 , a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the first end portion  23   a  gripped by the first gripping portion  80   a.    
     Step S 302  is a first movement step of moving the first gripping portion  80   a  in the gripping state in the transport direction. The control unit  201  drives the transport motor  25   b , and moves the transporting belt  23  in the transport direction. In this way, as illustrated in  FIG. 8 , the first gripping portion  80   a  in the gripping state of gripping the transporting belt  23  moves from upstream to downstream in the transport direction. The transporting belt  23  is transported in the transport direction based on a detection result of the first detection unit  85   a , and the medium P on the transporting belt  23  is transported to a predetermined position based on print data. 
     Step S 303  is the same as step S 103  described in Exemplary Embodiment 1, except that step S 303  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. In step S 303 , a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the first end portion  23   a  that has been gripped by the first gripping portion  80   a.    
     Note that step S 301  to step S 303  are a first operation step of performing the first operation in which the first gripping portion  80   a  grips the transporting belt  23  and moves to the predetermined position, and releases the gripped transporting belt  23 . 
     Step S 304  is the same as step S 104  described in Exemplary Embodiment 1, except that step S 304  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. 
     Note that, in step S 304 , the control unit  201  controls the head  42  and the carriage moving unit  45  based on the print data, and performs the image forming operation of causing the head  42  to eject the liquid while moving the carriage  43  from the second end portion  23   b  side to the first end portion  23   a  side of the transporting belt  23 . The image forming operation may start simultaneously with step S 303  or may start between step S 304  and step S 305 . As illustrated in  FIG. 8 , the micro vibration generated in step S 301  and step S 303  is excited at the first end portion  23   a  away from the head  42  positioned on the second end portion  23   b  side that is the printing start position of the image forming operation. The micro vibration propagating through the transporting belt  23  is attenuated before reaching the printing start position. 
     Step S 305  is the same as step S 105  described in Exemplary Embodiment 1, except that step S 305  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. In step S 305 , a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the second end portion  23   b  gripped by the second gripping portion  80   b.    
     Step S 306  is a second movement step of moving the second gripping portion  80   b  in the gripping state in the transport direction. The control unit  201  drives the transport motor  25   b , and moves the transporting belt  23  in the transport direction. In this way, as illustrated in  FIG. 10 , the second gripping portion  80   b  in the gripping state of gripping the transporting belt  23  moves from upstream to downstream in the transport direction. The transporting belt  23  is transported in the transport direction based on a detection result of the second detection unit  85   b , and the medium P on the transporting belt  23  is transported to a predetermined position based on the print data. 
     Step S 307  is the same as step S 107  described in Exemplary Embodiment 1, except that step S 307  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. 
     Note that step S 305  to step S 307  are a second operation step of performing the second operation in which the second gripping portion  80   b  grips the transporting belt  23  and moves to the predetermined position, and releases the gripped transporting belt  23 . 
     Step S 308  is the same as step S 108  described in Exemplary Embodiment 1, except that step S 308  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. 
     Note that, in step S 308 , the control unit  201  controls the head  42  and the carriage moving unit  45  based on the print data, and performs the image forming operation of causing the head  42  to eject the liquid while moving the carriage  43  from the first end portion  23   a  side to the second end portion  23   b  side of the transporting belt  23 . The image forming operation may start simultaneously with step S 307  or may start between step S 308  and step S 301  when step S 301  to step S 308  are repeatedly performed. As illustrated in  FIG. 9 , the micro vibration generated in step S 305  and step S 307  is excited at the second end portion  23   b  away from the head  42  positioned on the first end portion  23   a  side that is the printing start position of the image forming operation. The micro vibration propagating through the transporting belt  23  is attenuated before reaching the printing start position. 
     By repeatedly performing from step S 301  to step S 308 , the transporting belt  23  is sequentially transported in the transport direction, and the first operation by the first gripping portion  80   a  and the second movement by the second gripping portion  80   b  are alternately performed. The control unit  201  sequentially performs the image forming operation by the bidirectional printing on the medium P transported by the transporting belt  23 , and thus a desired image is formed on the medium P. 
     2-3. Transporting Method in Unidirectional Printing 
       FIG. 15  is a flowchart diagram illustrating the transporting method of the transporting belt in the unidirectional printing. The transporting method of the transporting belt  23  in the unidirectional printing of the liquid ejecting device  200  will be described. Note that step S 401  to step S 404  are the same as step S 301  to step S 304  of the transporting method in the above-described bidirectional printing, and thus the description will be omitted. 
     Step S 405  is the same as step S 205  described in Exemplary Embodiment 1, except that step S 405  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. In step S 405 , a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the second end portion  23   b.    
     Note that, in step S 405 , the control unit  201  controls the carriage moving unit  45 , and the carriage  43  starts to move from the first end portion  23   a  side to the second end portion  23   b  side of the transporting belt  23 . 
     Step S 406  is a second movement step of moving the second gripping portion  80   b  in the gripping state in the transport direction. The control unit  201  drives the transport motor  25   b , and moves the transporting belt  23  in the transport direction. In this way, as illustrated in  FIG. 12 , the second gripping portion  80   b  in the gripping state of gripping the transporting belt  23  moves from upstream to downstream in the transport direction. The transporting belt  23  is transported in the transport direction based on a detection result of the second detection unit  85   b , and the medium P on the transporting belt  23  is transported to a predetermined position based on the print data. 
     Step S 407  is the same as step S 207  described in Exemplary Embodiment 1, except that step S 407  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. In step S 407 , a micro vibration in the up-and-down direction is excited on the transporting belt  23  from the second end portion  23   b.    
     Note that, as illustrated in  FIG. 12 , the control unit  201  completes the execution of step S 406  and step S 407  before the head  42  mounted on the carriage  43  reaches the second end portion  23   b  side that is the printing start position of the image forming operation performed in step S 408 , that is, when the head  42  is positioned away from the second end portion  23   b.    
     Further, step S 405  to step S 407  are a second operation step of performing the second operation in which the second gripping portion  80   b  grips the transporting belt  23  and moves to the predetermined position, and releases the gripped transporting belt  23 . 
     Step S 408  is the same as step S 208  described in Exemplary Embodiment 1, except that step S 408  is performed by the control unit  201  instead of the control unit  1 , and thus the description will be omitted. 
     Note that, in step S 408 , the control unit  201  terminates the movement of the carriage  43  toward the second end portion  23   b  side, and causes the head  42  to be positioned at the printing start position. Then, the control unit  201  controls the head  42  and the carriage moving unit  45  based on the print data, and performs the image forming operation of causing the head  42  to eject the liquid while moving the carriage  43  from the second end portion  23   b  side to the first end portion  23   a  side of the transporting belt  23 . Furthermore, the control unit  201  controls the carriage moving unit  45 , moves the carriage  43  from the first end portion  23   a  side of the transporting belt  23  illustrated in  FIG. 9  to the second end portion  23   b  side illustrated in  FIG. 7 , and returns the head  42  to the printing start position of the next image forming operation. 
     As illustrated in  FIG. 12 , the micro vibration generated in step S 405  and step S 407  is excited at the second end portion  23   b  when the head  42  is located at the position away from the second end portion  23   b  that is the printing start position of the image forming operation. The micro vibration propagating through the transporting belt  23  is attenuated until the head  42  reaches the printing start position and starts to print. 
     By repeatedly performing from step S 401  to step S 408 , the transporting belt  23  is sequentially transported in the transport direction, and the first operation by the first gripping portion  80   a  and the second movement by the second gripping portion  80   b  are alternately performed. The control unit  201  sequentially performs the image forming operation by the unidirectional printing on the medium P transported by the transporting belt  23 , and thus a desired image is formed on the medium P. 
     As described above, according to the liquid ejecting device  200  and the transporting method of the transporting belt  23  in Exemplary Embodiment 2, the following effects can be obtained. 
     The liquid ejecting device  200  includes the first gripping portion  80   a  capable of gripping the first end portion  23   a  of the transporting belt  23 , and the second gripping portion  80   b  capable of gripping the second end portion  23   b  of the transporting belt  23 . When the head  42  is positioned outside the transporting belt  23  with respect to the second end portion  23   b , the first gripping portion  80   a  performs the first operation of gripping the first end portion  23   a  of the transporting belt  23  and moving with the transporting belt  23  in the transport direction, and releasing the gripped transporting belt  23 . When the head  42  is positioned outside the transporting belt  23  with respect to the first end portion  23   a , the second gripping portion  80   b  performs the second operation of gripping the second end portion  23   b  of the transporting belt  23  and moving with the transporting belt  23  in the transport direction, and releasing the gripped transporting belt  23 . In the first operation and the second operation, the first gripping portion  80   a  or the second gripping portion  80   b  grips the end portion away from the position of the head  42  and releases gripping. A micro vibration in the up-and-down direction generated when the first gripping portion  80   a  or the second gripping portion  80   b  grips the transporting belt  23  or releases gripping is excited at the end portion away from the position of the head  42 . As a result, the vibration propagating through the transporting belt  23  is attenuated before the printing start position is reached or before printing starts, and thus the quality of an image printed on the medium P improves. Therefore, the liquid ejecting device  200  that improves image quality can be provided. 
     The liquid ejecting device  200  transports the transporting belt  23 , based on a detection result of the first detection unit  85   a  configured to detect a displacement of the first gripping portion  80   a  and a detection result of the second detection unit  85   b  configured to detect a displacement of the second gripping portion  80   b . Specifically, the transport motor  25   b  that moves the transporting belt  23  in the transport direction is subjected to feedback control based on a detection result of the first detection unit  85   a  or the second detection unit  85   b , and thus the transport accuracy of the transporting belt  23  improves. 
     The liquid ejecting device  200  alternately performs the first operation by the first gripping portion  80   a  and the second operation by the second gripping portion  80   b  on the transporting belt  23  transported in the transport direction. In this way, even when a length of the transporting belt  23  along the first end portion  23   a  of the  23  of the transporting belt  23  and a length of the transporting belt  23  along the second end portion  23   b  of the transporting belt  23  are slightly different, a difference between the displacement on the first end portion  23   a  side and the displacement on the second end portion  23   b  side is less likely to be generated. As a result, the transport accuracy of the transporting belt  23  improves. 
     The transporting method of the transporting belt  23  performs the first operation step in which, when the head  42  is positioned outside the transporting belt  23  with respect to the second end portion  23   b , the first gripping portion  80   a  grips the first end portion  23   a  of the transporting belt  23  and moves with the transporting belt  23 , and releases the gripped transporting belt  23 . Further, the transporting method of the transporting belt  23  performs the second operation step in which, when the head  42  is positioned outside the transporting belt  23  with respect to the first end portion  23   a , the second gripping portion  80   b  grips the second end portion  23   b  of the transporting belt  23  and moves with the transporting belt  23 , and releases the gripped transporting belt  23 . In the first operation step and the second operation step, the first gripping portion  80   a  or the second gripping portion  80   b  grips the end portion away from the position of the head  42  and releases gripping. Since a micro vibration in the up-and-down direction generated when the first gripping portion  80   a  or the second gripping portion  80   b  grips the transporting belt  23  or releases gripping is excited at the end portion on the opposite side away from the position of the head  42 , the vibration propagating through the transporting belt  23  is attenuated before the printing start position is reached or printing starts. Accordingly, the quality of an image printed on the medium P improves. Therefore, the transporting method of the transporting belt  23  that improves image quality can be provided. 
     Contents derived from the exemplary embodiments will be described below. 
     A liquid ejecting device includes a transporting belt configured to transport a medium in a transport direction, a head configured to move between a first end portion and a second end portion of the transporting belt in a width direction that intersects the transport direction, and eject a liquid onto the medium, a first gripping portion configured to grip the first end portion of the transporting belt, and move in the transport direction, and a second gripping portion configured to grip the second end portion of the transporting belt, and move in the transport direction, where, when the head is positioned outside the transporting belt with respect to the second end portion in the width direction, the first gripping portion performs a first operation of gripping the transporting belt and moving to a predetermined position, and releasing the gripped transporting belt, and, when the head is positioned outside the transporting belt with respect to the first end portion in the width direction, the second gripping portion performs a second operation of gripping the transporting belt and moving to a predetermined position, and releasing the gripped transporting belt. 
     According to the configuration, when the head is positioned outside the transporting belt with respect to the second end portion, the first gripping portion that grips the first end portion of the transporting belt performs the first operation. When the head is positioned outside the transporting belt with respect to the first end portion, the second gripping portion that grips the second end portion of the transporting belt performs the second operation. In the first operation and the second operation, a micro vibration generated when the first gripping portion or the second gripping portion grips the transporting belt or releases gripping is excited at the end portion away from the position of the head. As a result, the vibration propagating through the transporting belt is attenuated before the head reaches a position at which ejection of the liquid starts or before the head starts to eject the liquid, and thus the quality of an image printed on the medium improves. Therefore, the liquid ejecting device that improves image quality can be provided. 
     The liquid ejecting device described above may further include a first detection unit configured to detect a displacement of the first gripping portion, and a second detection unit configured to detect a displacement of the second gripping portion, where the first gripping portion may perform the first operation, based on a detection result of the first detection unit, and the transporting belt may be transported based on a detection result of the first detection unit or the second detection unit. 
     According to the configuration, the transporting belt is moved in the transport direction, based on a detection result of the first detection unit configured to detect a displacement of the first gripping portion that grips the transporting belt or the second detection unit configured to detect a displacement of the second gripping portion that grips the transporting belt. As a result, the transport accuracy of the transporting belt improves. 
     In the liquid ejecting device described above, the first operation and the second operation may be alternately performed. 
     According to the configuration, the transporting belt is alternately transported by the first gripping portion and the second gripping portion. As a result, a difference between the displacement on the first end portion side of the transporting belt and the displacement on the second end portion side of the transporting belt is less likely to be generated, and thus the transport accuracy of the transporting belt improves. 
     A transporting method of a transporting belt is a transporting method of a transporting belt of a liquid ejecting device including the transporting belt configured to transport a medium in a transport direction, a head configured to move between a first end portion and a second end portion of the transporting belt in a width direction that intersects the transport direction, and eject a liquid onto the medium supported by the transporting belt, a first gripping portion configured to grip the first end portion of the transporting belt, and move in the transport direction, and a second gripping portion configured to grip the second end portion of the transporting belt, and move in the transport direction, and includes a first operation step in which, when the head is positioned outside the transporting belt with respect to the second end portion in the width direction, the first gripping portion grips the transporting belt and moves to a predetermined position, and releases the gripped transporting belt, and a second operation step in which, when the head is positioned outside the transporting belt with respect to the first end portion in the width direction, the second gripping portion grips the transporting belt and moves to a predetermined position, and releases the gripped transporting belt. 
     According to the method, when the head is positioned outside the transporting belt with respect to the second end portion, the first operation step is performed, and the first gripping portion that grips the first end portion of the transporting belt transports the transporting belt in the transport direction. When the head is positioned outside the transporting belt with respect to the first end portion, the second operation step is performed, and the second gripping portion that grips the second end portion of the transporting belt transports the transporting belt in the transport direction. In the first operation step and the second operation step, a micro vibration generated when the first gripping portion or the second gripping portion grips the transporting belt or releases gripping is excited at the end portion away from the position of the head. As a result, the vibration propagating through the transporting belt is attenuated before the head reaches a position at which ejection of the liquid starts or before the head starts to eject the liquid, and thus the quality of an image printed on the medium improves. Therefore, the transporting method of the transporting belt that improves image quality can be provided.