Patent Publication Number: US-9895895-B2

Title: Head washing device and inkjet printer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a 371 of international application of PCT application serial no. PCT/JP2015/069173, filed on Jul. 2, 2015, which claims the priority benefit of Japan application no. JP 2014-138137, filed on Jul. 3, 2014. The entirety of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification. 
     TECHNICAL FIELD 
     The present invention relates to a head washing device and an inkjet printer. 
     BACKGROUND ART 
     An inkjet printer has a plurality of nozzles for ejecting ink. To an ejection surface having those nozzles, contaminations such as ink may attach. It is known an inkjet printer configured to remove contaminations of such an ejection surface by a wiping member such as a wiper. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP-A-2009-132007 
     SUMMARY 
     Technical Problem 
     Contaminations of the wiper can be removed, for example, by another member. However, it is feared that contaminations such as ink with increased viscosity may remain on the wiper. 
     An example of tasks to be achieved by the present invention is to provide a head washing device and an inkjet printer capable of effectively washing a wiping member. 
     Solution to Problem 
     A head washing device according to one embodiment of the present invention is characterized by including a storage tank, a wiping unit, and a washing unit. In the storage tank, washing solution for washing the wiping unit is stored. The wiping unit has a wiping member for wiping an ejection surface. The washing unit washes the wiping member in the washing solution of the storage tank. 
     The washing unit washes the wiping member for wiping the ejection surface of an inkjet head, using the washing solution of the storage tank. Contaminations attached to the wiping member are mixed in a large amount of washing solution contained in the storage tank. In this way, the wiping member is effectively washed, whereby it is possible to suppress contaminations remaining on the wiping member from adhering to the ejection surface of the inkjet head. 
     In the above-described head washing device, it is preferable that the washing unit include a washing member whose at least a portion is immersed in the washing solution of the storage tank and which comes into contact with the ejection surface of the inkjet head and the wiping member and washes the ejection surface and the wiping member. 
     The washing member washes the ejection surface of the inkjet head and the wiping member. In this way, the ejection surface and the wiping member are washed more effectively. If the ejection surface is wiped by the wiping member (for example, a wiper) in a state where contaminations such as ink have attached to the ejection surface, the contaminations may be jammed into some nozzles existing in the ejection surface, thereby causing nozzle clogging. For this reason, if the ejection surface of the inkjet head is washed by the washing member, it is possible to suppress contaminations such as ink from entering nozzles, thereby suppressing nozzle clogging from occurring. Further, since one washing member washes the ejection surface and the wiping member, the number of components of the head washing device is reduced, and the space of the head washing device is saved. 
     In the above-described head washing device, it is preferable that the wiping member have a contact portion which is in contact with the ejection surface of the inkjet head, and the contact portion be exposed from the washing solution of the storage tank when the wiping member wipes the ejection surface, and be immersed in the washing solution of the storage tank when the washing unit washes the wiping member. 
     When the wiping unit washes the wiping member, the contact portion of the wiping member is immersed in the washing solution of the storage tank. Therefore, contaminations attached to the wiping member are mixed in the large amount of washing solution contained in the storage tank, whereby the wiping member is more effectively washed. Further, when the wiping member wipes the ejection surface of the inkjet head, the contact portion of the wiping member is exposed from the washing solution. If the wiping member from which these contaminations have been washed away wipes the ejection surface, the washing solution remaining on the ejection surface washed by the washing unit is wiped off, and the corresponding ejection surface becomes likely to dry. As a result, workability of washing of the ejection surface improves. 
     In the above-described head washing device, it is preferable that the head washing device further include an automatic level adjustment mechanism capable of changing the position of the solution level of the washing solution of the storage tank. 
     By changing the position of the solution level of the washing solution of the storage tank by the automatic level adjustment mechanism, it is possible to immerse the contact position of the ejection surface and the washing member in the washing solution in a case of washing the ejection surface by the washing member. Therefore, it is possible to perform washing on the ejection surface in the washing solution, and it is possible to improve the washing efficiency. Also, in a case of wiping the ejection surface by the wiping member, if the solution level of the washing solution is positioned below the ejection surface, it is possible to surely wipe the ejection surface. Like these, by changing the position of the solution level of the washing solution of the storage tank by the automatic level adjustment mechanism, it is possible to more surely perform washing in a case of washing the ejection surface of the inkjet head using the washing member and the wiping member. 
     In the above-described head washing device, it is preferable that the wiping unit have a first drive mechanism for moving the wiping member between a first position where the contact portion is exposed from the washing solution of the storage tank and a second position where the contact portion is immersed in the washing solution of the storage tank. 
     The first drive mechanism moves the wiping member between the first position where the contact portion is exposed from the washing solution of the storage tank and the second position where the contact portion is immersed in the washing solution of the storage tank. Therefore, the contact portion of the wiping member can be immersed in the washing solution without controlling the solution level of the washing solution. Further, since the contact portion can be moved to the second position by the first drive mechanism, it is possible to suppress the contact portion from unexpectedly coming into contact with the ejection surface before it is washed by the washing member, thereby suppressing contaminations remaining on the contact portion from adhering to the ejection surface of the inkjet head. 
     In the above-described head washing device, it is preferable that the head washing device include a control unit for controlling the wiping unit such that the wiping unit wipes the ejection surface, after the washing member washes the ejection surface. 
     Since the washing solution and contaminations remaining on the ejection surface are wiped off by wiping the ejection surface by the wiping unit after the ejection surface is washed by the washing member, it is possible to make the ejection surface likely to dry while improving the washing efficiency of the ejection surface. 
     In the above-described head washing device, it is preferable that the washing unit include a second drive mechanism for rotating or vibrating the washing member. 
     The second drive mechanism rotates or vibrates the washing member. Therefore, the ejection surface of the inkjet head and the wiping member are more effectively washed. Further, since the washing member whose at least a portion has been immersed in the washing solution of the storage tank rotates or vibrates, contaminations having transferred from the ejection surface and the wiping member onto the washing member are mixed in the washing solution, whereby the washing member is washed. 
     In the above-described head washing device, it is preferable that the second drive mechanism be magnetically coupled with the washing member with a wall of the storage tank interposed therebetween, and rotate or vibrate the washing member. 
     The second drive mechanism is magnetically coupled with the washing member with the wall of the storage tank, and rotates or vibrates the washing member. Therefore, it is possible to rotate or vibrate the washing member without providing the second drive mechanism inside the storage tank or providing a member passing through the wall of the storage tank. Therefore, it is possible to downsize the storage tank, and the washing solution is suppressed from leaking from the storage tank. 
     An inkjet printer according to one embodiment of the present invention is characterized by including an inkjet head and the above-described head washing device. 
     In the above-described inkjet printer, it is preferable that the inkjet printer further include a supporting member configured to support the inkjet head and extend along a scan direction, and the inkjet head be movable along the supporting member, in a scan part for performing ink ejection and an extension part deviated from the scan part, and the head washing device wash the ejection surface of the inkjet head positioned in the extension part. 
     The head washing device washes the ejection surface of the inkjet head positioned in the extension part deviated from the scan part for performing ink ejection. Therefore, empty spaces of the inkjet printer can be effectively used, and the inkjet printer can be downsized. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to effectively wash the wiping member. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating the configuration of an inkjet printer according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view illustrating an inkjet head and a washing station. 
         FIG. 3  is a cross-sectional view illustrating the inkjet head and the washing station as seen from a direction different from that of  FIG. 2 . 
         FIG. 4  is a block diagram illustrating an example of the configuration of a controller. 
         FIG. 5  is a flow chart illustrating an example of an operation of the inkjet printer. 
         FIG. 6  is a cross-sectional view illustrating the inkjet head and the washing station in a brush washing process. 
         FIG. 7  is a bottom view illustrating a carriage and a brush. 
         FIG. 8  is a cross-sectional view illustrating the inkjet head and the washing station in a wiping process. 
         FIG. 9  is a cross-sectional view illustrating an inkjet head and a washing station according to a second embodiment of the present invention. 
         FIG. 10  is an explanatory view of an operation of a modification of the first embodiment when an ejection surface is washed by a brush. 
         FIG. 11  is an explanatory view of an operation of a modification of the first embodiment when an ejection surface is wiped by wipers. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     Hereinafter, a first embodiment will be described with reference to  FIG. 1  to  FIG. 8 . Also, with respect to each of some constituent elements according to embodiments and a description of the corresponding constituent element, a plurality of expressions will be used together. With respect to the corresponding constituent element and the description, it is not hindered to use other unused expressions. Also, with respect to each of constituent elements for which a plurality of expressions is not used and a description thereof, it is not hindered to use other expressions. 
       FIG. 1  is a view illustrating the configuration of an inkjet printer  10  according to a first embodiment of the invention. As shown in  FIG. 1 , the inkjet printer  10  includes an inkjet head  11 , a carriage  12 , a bar  13 , a table  14 , a maintenance station  15 , a washing station  16 , and a controller  19 . The bar  13  is an example of a supporting member. The washing station  16  is an example of a head washing device. 
     The inkjet head  11  has an ejection surface  26  having a plurality of nozzles, and the individual nozzles eject corresponding ink, respectively. For example, the inkjet printer  10  includes the inkjet head  11  having a plurality of nozzles corresponding to cyan (C), magenta (M), yellow (Y), black (K), white, and other colors, respectively. However, one or more inkjet heads  11  may be provided. 
     The carriage  12  holds the inkjet head  11 . The bar  13  extends along a main scan direction, and moves in a sub scan direction by a drive mechanism using a motor or the like. On the bar  13 , the carriage  12  is attached so as to be movable. In other words, the bar  13  supports the inkjet head  11  held by the carriage  12 . The carriage  12  holding the inkjet head  11  moves along the bar  13  (along the main scan direction). 
     As shown in the drawings, in this specification, an X axis, a Y axis, and a Z axis are defined. The X axis, the Y axis, and the Z axis are perpendicular to one another. The X axis is parallel to the sub scan direction. The Y axis is parallel to the main scan direction. The Z axis is parallel to, for example, a vertical direction. 
     On the table  14 , media M can be mounted. Media M is not limited to paper, and may be various materials such as plates, fabrics, and structures. The thickness of each medium M (the dimension in a direction parallel to the Z axis) depends on the corresponding medium M. Each medium M is positioned and fixed on the table  14 , for example, by suction, pins, or the like. However, the present invention is not limited to the table  14 , and each medium M may be supported on any other member such as a platen. 
     The bar  13  is disposed over the table  14  with a predetermined gap. Along the bar  13 , the carriage  12  moves in a scan part (a scan path) A 1  over a medium M mounted on the table  14 , and two extension parts A 2  and A 3  (overrun sections) deviated from the scan part A 1 . 
     The inkjet head  11  ejects ink onto the medium M mounted on the table  14  when the carriage  12  is positioned in the scan part A 1 . The extension parts A 2  and A 3  are positioned at both end portions of the bar  13 . In other words, between the two extension parts A 2  and A 3 , the scan part A 1  is positioned. 
     The maintenance station  15  moves in the sub scan direction together with the bar  13 . The maintenance station  15  is disposed so as to face the inkjet head  11  of the carriage  12  positioned on one extension part A 2 . 
     The washing station  16  moves in the sub scan direction together with the bar  13 . The washing station  16  is disposed so as to face the inkjet head  11  of the carriage  12  positioned on the other extension part A 3 . 
       FIG. 2  is a schematic diagram for explaining washing of the inkjet head  11 , and is a cross-sectional view illustrating the inkjet head  11  and the washing station  16 . As shown in  FIG. 2 , the inkjet head  11  includes a main body  21 , a plurality of pressure chambers  22 , a plurality of nozzles  23 , a plurality of drive elements  24 , and ink supply passages  25 . Each of the ink supply passages  25  has a supply part  25   a  and a common part  25   b , and is an example of a passage. 
     The main body  21  is formed substantially in a cuboid shape. However, the shape of the main body  21  is not limited thereto. The main body  21  has the ejection surface  26  substantially flat. The ejection surface  26  faces downward, and faces the table  14  and each medium M. 
     The plurality of pressure chambers  22  is provided inside the main body  21 . The pressure chambers  22  are disposed side by side in a direction parallel to the X axis. The plurality of pressure chambers  22  connects the common parts  25   b  of the ink supply passages  25  and the plurality of nozzles  23 . 
     The plurality of nozzles  23  is holes for ejecting the ink, and is formed in the ejection surface  26  of the main body  21 . In other words, the ink is ejected from the ejection surface  26 . The ink is an example of a first liquid. The nozzles  23  are connected to the common parts  25   b  of the ink supply passages  25  through corresponding pressure chambers  22 . The nozzles  23  are disposed side by side in a direction parallel to the X axis. 
     The plurality of drive elements  24  is formed at parts of corresponding pressure chambers  22 . The drive elements  24  are piezoelectric elements, and deform, thereby changing the internal ink pressures of the pressure chambers  22 , if a voltage is applied. The drive elements  24  deform, thereby increasing or decreasing the internal ink pressures of the pressure chambers  22 , thereby ejecting ink drops from the nozzles  23 . Also, the drive elements  24  are not limited to those shown in  FIG. 2 , and can be applied to every drive method of the related art classifiable as a piezo manner. For example, the drive elements  24  may be elements laminated on diaphragm films constituting the pressure chambers  22 . Also, the drive elements may be elements of a thermal type called thermal jet or bubble jet (registered as a trade mark). 
     The ink supply passages  25  are connected to the individual pressure chambers  22  by the common parts  25   b , and are passages for supplying the ink from the supply parts  25   a  into the individual pressure chambers  22  through the common parts  25   b . The ink supply passages  25  are connected to ink tanks corresponding to the nozzles  23  through an ink supply unit  27 . The ink supply units  27  are examples of a liquid supply unit. The ink supply units  27  supply the ink of the ink tanks into the pressure chambers  22  and the nozzle  23  through the ink supply passages  25 . 
     The ink supply units  27  have dampers  31 . The dampers  31  are provided on passages provided between the ink tanks and the inkjet head  11 . The dampers  31  mitigate change in ink pressure when the ink enters or exits from the inkjet head  11 . 
     The maintenance station  15  shown in  FIG. 1  regularly washes the inkjet head  11  at relatively short intervals, thereby maintaining the quality of printing using the inkjet head  11 . In other words, the maintenance station  15  suppresses the ejection surface  26  from being contaminated, and keeps the viscosity of the ink of the nozzles  23  low, thereby stabilizing ink ejection of the inkjet head  11 . The maintenance station  15  has a cap and wipers. 
     The cap of the maintenance station  15  covers the ejection surface  26  of the inkjet head  11  from below, thereby suppressing the ink of the nozzles  23  from drying. The inkjet head  11  performs flushing, that is, ejecting the ink into washing solution contained in the cap. The wipers wipe the ejection surface  26 . However, in the present invention, the configuration of the maintenance station is not limited thereto as long as it has a maintenance function for the inkjet head  11 . 
     The washing station  16  regularly washes the inkjet head  11  at relatively long intervals, such as once every day, or once every predetermined number of days, or once every week, thereby maintaining the quality of printing using the inkjet head  11 . However, the washing station  16  may wash the inkjet head  11  only in a predetermined case, not regularly. The washing station  16  removes ink of a range from low viscosity to high viscosity from the ejection surface  26  and the nozzles  23 , thereby returning the inkjet head  11  to its initial state. 
     As shown in  FIG. 2 , the washing station  16  includes a storage tank  41 , a washing unit  42 , a brush drive mechanism  43 , an automatic level adjustment mechanism  44 , and an actuator  45 . The brush drive mechanism  43  is an example of a second drive mechanism. 
     The storage tank  41  is formed in a box shape with the upper end portion opened. However, the shape of the storage tank  41  is not limited thereto. In the storage tank  41 , a washing solution L is stored. The washing solution L is an example of a second liquid, and is, for example, a solvent. 
     The storage tank  41  has a bottom wall  46  and a plurality of side walls  47 . The plurality of side walls  47  stands up from the edges of the bottom wall  46 , respectively. The bottom wall  46  and the side walls  47  are made of a non-magnetic material such as austenitic stainless steel (for example, SUS304) or a synthetic resin. 
     The washing unit  42  includes a brush  51  and two supporting walls  52 . The brush  51  is an example of a washing member. The brush  51  is dipped in the washing solution L of the storage tank  41 . The brush  51  has a rotary shaft  54 , a plurality of hairs  55 , and a first magnet  56 . 
     If the inkjet head  11  reaches a washing position of the washing station  16 , the actuator  45  moves the storage tank  41  toward the inkjet head  11 , and holds the storage tank  41  at a position for a washing operation. 
     The rotary shaft  54  extends in a direction parallel to the X axis. The rotary shaft  54  is supported on the supporting walls  52  provided inside the storage tank  41 , so as to be rotatable. The hairs  55  are disposed in the circumferential direction on the rotary shaft  54 , and protrude in the radial direction from the rotary shaft  54 . Therefore, the hairs  55  form a substantially cylindrical shape. The hairs  55  are made of a synthetic resin resistant to the solvent, such as polypropylene, nylon, and polycarbon. The first magnet  56  is attached to one end portion of the rotary shaft  54 . The first magnet  56  faces a side wall  47  of the storage tank  41 . The brush  51  is partially exposed from the washing solution L. However, the whole of the brush  51  may be immersed in the washing solution L. 
     The brush drive mechanism  43  includes a first motor  61 , a driver circuit  62 , and a second magnet  63 . The first motor  61  is driven by the driver circuit  62 . The second magnet  63  is attached to an output shaft  61   a  of the first motor  61 . The second magnet  63  faces the first magnet  56  with the side wall  47  of the storage tank  41  interposed therebetween. 
     By the first magnet  56  and the second magnet  63 , the brush drive mechanism  43  is magnetically coupled with the brush  51  with the side wall  47  of the storage tank  41  interposed therebetween. If the first motor  61  is driven, the second magnet  63  attached to the output shaft  61   a  rotates. As a result, the rotary shaft  54  having the first magnet  56  attached thereon also rotates. In other words, the brush drive mechanism  43  rotates the brush  51 . By this method, it is possible to completely prevent leakage of the solution from the storage tank  41  along the rotary shaft. However, the rotary shaft  54  may pass through the side wall  47  of the storage tank  41  and be directly rotated by the first motor  61 . In the case where the rotary shaft  54  is directly rotated by the first motor  61 , the bottom wall  46  and the side walls  47  may not be made of a non-magnetic material, and may be made of, for example, a magnetic metal material. 
     The automatic level adjustment mechanism  44  includes an adjustment tank  67  and a supply tank  68 . The adjustment tank  67  is connected to the storage tank  41  such that liquid can flow, and stores the washing solution L. The supply tank  68  is disposed above the adjustment tank  67 , and stores the washing solution L. 
     In the adjustment tank  67 , a connection hole  67   a  for connection with atmosphere is formed. From the bottom surface of the supply tank  68 , a pipe  68   a  extends downward. The leading end of the pipe  68   a  is immersed under the solution level of the washing solution L stored in the adjustment tank  67 . 
     The automatic level adjustment mechanism  44  can automatically supply the washing solution L into the storage tank  41 , and keeps the solution level of the washing solution L of the storage tank  41  constant. The height of the solution level of the washing solution L in the adjustment tank  67  becomes equal to the height of the solution level of the washing solution L of the storage tank  41 . 
     If the washing solution L is supplied into the storage tank  41 , whereby the solution level of the washing solution L of the adjustment tank  67  lowers, the leading end of the pipe  68   a  of the supply tank  68  is exposed from the corresponding solution level. As a result, air enters the supply tank  68  from the leading end of the pipe  68   a , whereby the pressure of the supply tank  68  rises, whereby the washing solution L of the supply tank  68  is supplied into the adjustment tank  67 . 
     If the solution level of the washing solution L of the adjustment tank  67  rises, the leading end of the pipe  68   a  of the supply tank  68  soaks under the corresponding solution level. As a result, the inflow of air from the leading end of the pipe  68   a  is blocked, whereby the supply of the washing solution L from the supply tank  68  stops. Therefore, the solution level of the washing solution L of the adjustment tank  67  is kept in the vicinity of the leading end of the pipe  68   a.    
     In the storage tank  41 , an outlet  71  and a discharge valve  72  are provided. The outlet  71  is formed in the bottom wall  46  of the storage tank  41 . The washing solution L stored in the storage tank  41  is discharged from the outlet  71 . The discharge valve  72  is, for example, an electromagnetic valve. The discharge valve  72  blocks leakage of the washing solution L from the outlet  71 . 
     The storage tank  41  can be moved along a direction parallel to the Z axis by the actuator  45 . The actuator  45  moves the storage tank  41  in the direction of the Z axis, thereby preventing collision with the inkjet head  11  moving, and holds the position of the storage tank  41 . 
       FIG. 3  is a cross-sectional view illustrating the inkjet head  11  and the washing station  16  as seen from a direction different from that of  FIG. 2 . As shown in  FIG. 3 , the washing station  16  further includes a wiping unit  81 . The wiping unit  81  includes two wipers  83  and a wiper drive mechanism  84 . The wipers  83  are examples of a wiping member. The wiper drive mechanism  84  is an example of a first drive mechanism. 
     The wipers  83  are made of an elastic material such as synthetic rubber. Each wiper  83  includes a base portion  83   a , and a leading-end portion  83   b  thinner than the base portion  83   a . The leading-end portion  83   b  is an example of a contact portion, and is more likely to bend than the base portion  83   a  is. 
     The wiper drive mechanism  84  includes two support shafts  87  and two second motors  88 . The support shafts  87  are immersed in the washing solution L of the storage tank  41 , and are supported so as to be rotatable. The second motors  88  are disposed outside the storage tank  41 , and rotate the support shafts  87 . The second motors  88  may be directly joined with the support shafts  87 , or may be magnetically coupled with them. 
     The base portions  83   a  of the wipers  83  are attached to the support shafts  87 . The wipers  83  may be attached to the support shafts  87  so as to be removable, and be exchangeable. The second motors  88  rotate the support shafts  87 , whereby the wipers  83  are swung between exposure positions P 1  and dip positions P 2 . The exposure positions P 1  are examples of a first position. The dip positions P 2  are examples of a second position. In  FIG. 3 , the wipers  83  which are at the exposure positions P 1  are shown by alternate long and two short dashes lines. 
     At the exposure positions P 1 , the wipers  83  extend, for example, in a direction parallel to the Z axis. However, the wipers  83  which are at the exposure positions P 1  are not limited thereto, and may be inclined with respect to the Z axis. The leading-end portions  83   b  of the wipers  83  can be protruded and exposed from the solution level of the washing solution L of the storage tank  41 . The base portions  83   a  of the wipers  83  may be immersed in the washing solution L, or may be exposed from the washing solution L, for example, partially. 
     At the dip positions P 2 , the wipers  83  extend, for example, in a direction parallel to the Y axis. However, the wipers  83  which are at the dip positions P 2  are not limited thereto. The base portions  83   a  and leading-end portions  83   b  of the wipers  83  can be immersed in the washing solution L of the storage tank  41 . 
     At the dip positions P 2 , the leading-end portions  83   b  of the wipers  83  are in contact with the hairs  55  of the brush  51 . Therefore, if the brush  51  is rotated by the brush drive mechanism  43 , in the washing solution L, the hairs  55  of the brush  51  brush and wash the leading-end portions  83   b.    
       FIG. 4  is a block diagram illustrating an example of the configuration of the controller  19 . The controller  19  controls operations of the inkjet printer  10 . The controller  19  includes a head position control unit  101 , an ejection control unit  102 , a maintenance control unit  103 , a wiper control unit  104 , a brush control unit  105 , and a storage tank position control unit  107 . 
     The head position control unit  101  controls a moving mechanism  112  through a driver circuit  111 . The moving mechanism  112  includes, for example, a motor, gears, and a belt, and moves the carriage  12  along the bar  13 . In other words, the head position control unit  101  controls the positions of the inkjet head  11  and the carriage  12  in a Y direction. 
     The ejection control unit  102  controls the drive elements  24  of the inkjet head  11  through a driver circuit  116 . In other words, the ejection control unit  102  controls the driver circuit  116 , thereby supplying a drive voltage from the driver circuit  116  to the drive elements  24 . 
     The ejection control unit  102  can selectively drive the plurality of drive elements  24 . In other words, the ejection control unit  102  can drive at least one drive element  24 , such that at least one nozzle  23  corresponding to the corresponding drive element  24  performs ejection of liquid such as ink. In other words, the ejection control unit  102 , the driver circuit  116 , and the drive elements  24  constitute an example of a first control mechanism. 
     The maintenance control unit  103  controls the maintenance station  15 . The maintenance control unit  103  controls the motor and the electromagnetic valve included in the maintenance station  15 , for example, through a driver circuit, thereby exchanging the washing solution stored in the cap, or wiping the ejection surface  26  of the inkjet head  11  with the wipers. 
     The wiper control unit  104  controls the second motors  88  of the wiping unit  81  through a driver circuit  118 . In other words, the wiper control unit  104  makes the driver circuit  118  drive the second motors  88 , such that the wipers  83  are swung between the exposure positions P 1  and the dip positions P 2 . 
     The brush control unit  105  controls the first motor  61  through the driver circuit  62 . The brush control unit  105  makes the driver circuit  62  drive the first motor  61 , thereby rotating the brush  51  as described above. 
     The storage tank position control unit  107  controls the actuator  45  through a driver circuit  114 . The actuator  45  moves the storage tank  41  in a direction parallel to the Z axis. In other words, the storage tank position control unit  107  controls the position of the storage tank  41  in a Z direction. 
     The controller  19 , and the head position control unit  101 , the ejection control unit  102 , the maintenance control unit  103 , the wiper control unit  104 , the brush control unit  105 , and the storage tank position control unit  107  included in the controller, and the like are composed of hardware such as an arithmetic device and a memory, and programs for implementing predetermined functions of them. 
     Now, an operation of the inkjet printer  10  described above will be described.  FIG. 5  is a flow chart illustrating an example of the operation of the inkjet printer  10 . The operation of the inkjet printer  10  to be described below is performed, for example, by a predetermined program. 
     The inkjet printer  10  performs printing on a medium M, for example, in response to a print command from an external personal computer or an operation unit provided on the inkjet printer  10 . In other words, on the basis of the corresponding print command, the inkjet printer  10  moves the carriage  12  and the bar  13  in the sub scan direction and the main scan direction. The inkjet head  11  ejects the ink from the nozzles  23  onto the medium M, whereby an image is forming on the medium M. 
     During the printing, the carriage  12  moves in the scan part A 1  and the extension parts A 2  and A 3  along the bar  13 . The carriage  12  moves from one extension part A 2  to the other extension part A 3  through the scan part A 1 . The carriage  12  having reached the other extension part A 3  returns to the initial extension part A 2  (a standby position). In other words, the carriage  12  performs movement direction reversal in the extension parts A 2  and A 3 . 
     Each of the maintenance station  15  and the washing station  16  faces the inkjet head  11  positioned in an empty space (the extension part A 2  or A 3 ) necessary for reversal of the carriage  12 . Therefore, downsizing of the inkjet printer  10  is possible. 
     While the inkjet printer  10  is operating like during the printing described above, the controller  19  determines whether it is a timing to perform washing on the inkjet head  11  (STEP S 11 ). For example, in a case where time is counted by a timer, and the counted time reaches a predetermined period, the controller  19  determines that it is a timing to perform washing on the inkjet head  11  (“Yes” in STEP S 11 ). The corresponding period is, for example, half a day or a time required for deposition or condensation of the ink to occur. In a case where it is determined that it is a timing to perform washing on the inkjet head  11 , the time count of the timer is reset. 
     For example, when the operation of the inkjet printer  10  finishes (during a long idle period), or when it is estimated that the viscosity of the ink contained in the inkjet head  11  is about 20 millipascals or higher, the controller  19  may determine that it is a timing to perform washing on the inkjet head  11 . However, a criterion for determining that it is a timing to perform washing on the inkjet head  11  is not limited thereto. 
     If it is determined that it is a timing to perform washing on the inkjet head  11 , the head position control unit  101  of the controller  19  controls the moving mechanism  112 , thereby moving the carriage  12  to the extension part A 3 . In other words, the carriage  12  is moved over the washing station  16  (STEP S 12 ). 
     Subsequently, the storage tank position control unit  107  controls the actuator  45 , thereby raising the storage tank  41 . As a result, as shown in  FIG. 3 , the ejection surface  26  of the inkjet head  11  comes into contact with the hairs  55  of the brush  51  (STEP S 13 ). 
     Subsequently, the head position control unit  101  controls the moving mechanism  112 , thereby moving the inkjet head  11  in a direction parallel to the Y axis.  FIG. 6  is a cross-sectional view illustrating the inkjet head  11  and the washing station  16  in a brush washing process. As shown in  FIG. 6 , the hairs  55  of the brush  51  come into contact with the ejection surface  26  of the inkjet head  11  moving. 
     While the inkjet head  11  is moved, the brush control unit  105  controls the brush drive mechanism  43  such that the brush  51  is rotated. The brush  51  may be rotated only in a normal rotation direction, or may be rotated in the normal and reverse rotation directions by reversing the rotation direction at predetermined intervals. 
     The hairs  55  of the rotating brush  51  remove contaminations attached to the ejection surface  26  of the inkjet head  11  (STEP S 14 ). A portion of the brush  51  exposed from the washing solution L brushes and washes the ejection surface  26  of the inkjet head  11 . The brush  51  draws up the washing solution L by rotating. As a result, the washing solution L is dashed on the ejection surface  26 , whereby the ejection surface  26  is washed. Further, since a portion of the brush  51  is dipped in the washing solution L, a number of hairs  55  of the brush  51  get wet with the washing solution L. The hairs  55  of the brush  51  wet with the washing solution L brush the ejection surface  26  of the inkjet head  11 , whereby the ejection surface  26  is effectively washed. 
     However, prior to STEP S 14 , the ejection surface  26  may be immersed in the washing solution L, and if the ejection surface  26  is immersed in the washing solution L, the concentration of the ink attached to the ejection surface  26  decreases. Further, if the brush  51  brushes the ejection surface  26  in the state where the ejection surface is under the washing solution L, contaminations of the ejection surface  26  are effectively removed. 
     Meanwhile, the wipers  83  are disposed basically at the dip positions P 2 . Therefore, the hairs  55  of the brush  51  rotating brush the leading-end portions  83   b  of the wipers  83  under the washing solution L, thereby removing contaminations attached to the leading-end portions  83   b . Contaminations of the other portions of the wipers  83  can also be removed by the washing solution L. Also, the wipers  83  do not come into contact with the inkjet head  11  moving. As described above, when the brush  51  washes the wipers  83 , the wipers  83  are immersed in the washing solution L of the storage tank  41 . 
     The contaminations of the ejection surface  26  of the inkjet head  11  and the contaminations of the leading-end portions  83   b  of the wipers  83  removed by the brush  51  are mixed in the washing solution L. In other words, even if the contaminations adhere to the hairs  55  of the brush  51 , since the brush  51  rotates in the washing solution L, the contaminations of the hairs  55  are removed by the washing solution L. 
       FIG. 7  is a bottom view illustrating the carriage  12  and the brush  51 . If the length of the brush  51  (the dimension along the X axis) is set to be longer than the length of the inkjet head  11  as shown in  FIG. 7 , it is possible to wash the whole of the ejection surface  26 . Meanwhile, the width of the brush  51  (the diameter, that is, the dimension along the Y axis) may be narrower than the width of the inkjet head  11 , and thus downsizing is possible. Also, if the lengths of the wipers  83  (the dimension along the X axis) are set to be longer than the length of the inkjet head  11 , it is possible to wipe the whole of the ejection surface  26 . The widths of the wipers  83  (the dimensions along the Y axis) may be set to be narrower than the width of the inkjet head  11 , and thus downsizing is possible. 
       FIG. 8  is a cross-sectional view illustrating the inkjet head  11  and the washing station  16  in a wiping process. After the washing of the inkjet head  11 , as shown in  FIG. 8 , the wiper control unit  104  controls the second motors  88 , thereby moving the wipers  83  to the exposure positions P 1 . As a result, the leading-end portions  83   b  of the wipers  83  are exposed from the solution level of the washing solution L. 
     If the washing on the ejection surface  26  by the brush  51  (STEP S 14 ) finishes, the head position control unit  101  controls the moving mechanism  112 , thereby moving the inkjet head  11  in a direction parallel to the Y axis. The leading-end portions  83   b  of the wipers  83  come into contact with the ejection surface  26  of the moving inkjet head  11 . 
     The leading-end portions  83   b  of the wipers  83  wipe the ejection surface  26  of the moving inkjet head  11 , whereby the washing solution L and contaminations remaining on the ejection surface  26  are removed (STEP S 16 ). In this way, the ejection surface  26  becomes likely to dry while being washed. 
     As described above, if the washing on the ejection surface  26  by the brush control unit  105  (STEP S 14 ) finishes, the controller  19  controls the head position control unit  101  and the wiper control unit  104 , thereby performing control to perform wiping on the ejection surface  26  by the wipers  83  (STEP S 16 ). The controller  19  is an example of a control unit. 
     Subsequently, the head position control unit  101  controls the moving mechanism  112 , thereby moving the carriage  12  to the extension part A 2  (the standby position) (STEP S 17 ). By the above-described operation, the washing on the inkjet head  11  by the washing station  16  is completed. 
     Also, in a case where it is determined that it is not a timing to perform washing on the inkjet head  11  (“No” in STEP S 11 ), the controller  19  determines whether t is a timing to perform maintenance of the inkjet head  11  (STEP S 18 ). For example, in a case where time is counted by another timer, and the counted time reaches a predetermined period, the controller  19  determines that it is a timing to perform maintenance of the inkjet head  11  (“Yes” in STEP S 18 ). The corresponding period is shorter than a period for determining a timing to perform washing on the inkjet head  11 . In a case where it is determined that it is a timing to perform maintenance on the inkjet head  11 , the time count of the corresponding timer is reset. 
     For example, when it is determined that the viscosity of the ink contained in the inkjet head  11  is predetermined viscosity of about 20 millipascal-second (mPa·s) or lower, the controller  19  may determine that it is a timing to perform maintenance on the inkjet head  11 . However, a criterion for determining that it is a timing to perform maintenance of the inkjet head  11  is not limited thereto. 
     If it is determined that it is a timing to perform maintenance on the inkjet head  11 , in a state where the carriage  12  is in the extension part A 2  (the standby position), the ejection control unit  102  of the controller  19  controls the drive elements  24 , thereby micro-vibrating the drive elements  24  (STEP S 19 ). Although the drive elements  24  increase or decrease the ink pressures of the pressure chambers  22 , the corresponding ink is not ejected from the nozzles  23 . By the corresponding micro-vibration, the ink meniscuses of the nozzles  23  vibrate, whereby drying and viscosity increasing of the ink in the vicinities of the nozzles  23  are suppressed. However, micro-vibration of the drive elements  24  is not limited to a maintenance period, and may be always performed during the operation of the inkjet printer  10 . 
     Subsequently, the ejection control unit  102  controls the drive elements  24 , thereby performing flushing, that is, ejecting the ink from the nozzles  23  (STEP S 20 ). The ink is ejected from the nozzles  23  into the washing solution of the cap of the maintenance station  15 . In this way, for example, the ink having higher viscosity due to drying in the vicinities of the nozzles  23  is discharged, whereby clogging of the nozzles  23  and flight curves of ink drops are suppressed. 
     Subsequently, the maintenance control unit  103  wipes the ejection surface  26  of the inkjet head  11  by the wipers of the maintenance station  15  (STEP S 21 ). As a result, contaminations such as the ink and dust attached to the ejection surface  26  are removed. 
     By the above-described operation, maintenance on the inkjet head  11  by the maintenance station  15  is completed. However, the maintenance station  15  may select and perform at least one of micro-vibrating (STEP S 19 ), flushing (STEP S 20 ), and wiping (STEP S 21 ). 
     Further, the maintenance station  15  may suck the washing solution of the cap from the nozzles  23  of the ejection surface  26  of the inkjet head  11  covered by the cap. In this way, the ink and contaminations with higher viscosity contained in the inkjet head  11  can be removed. 
     The controller  19  repeats washing (STEPS S 11  to S 17 ) and maintenance (STEPS S 18  to S 21 ) of the inkjet head  11  described above, until the operation of the inkjet printer  10  finishes (STEP S 22 ). In this way, the inkjet head  11  is kept clean, and the quality of printing is maintained. 
     In the inkjet printer  10 , precipitation of pigments of the ink in ink tubes (ink passages between the ink tanks and the inkjet head  11 ) can be suppressed by providing annular passages between the dampers  31  and the ink tanks and performing ink circulation. Generation of contaminations on the dampers  31  is suppressed by flushing (STEP S 20 ) of the maintenance station  15 . 
     Generation of contaminations on the ejection surface  26  of the inkjet head  11  is suppressed by brush washing (STEP S 14 ) of the washing station  16 . Thickening of the ink meniscuses of the nozzles  23  is suppressed by flushing (STEP S 20 ) of the maintenance station  15 . 
     As described above, generation of contaminations and the like which can cause a failure of printing of the inkjet head  11  is suppressed by the maintenance station  15  and the washing station  16 . In other words, by combining the maintenance station  15  and the washing station  16 , the inkjet head  11  is effectively maintained. 
     According to the inkjet printer  10  related to the first embodiment, the washing unit  42  washes the wipers  83  for wiping the ejection surface  26  of the inkjet head  11 , using the washing solution L of the storage tank  41 . Contaminations attached to the wipers  83  are mixed in the large amount of washing solution L of the storage tank  41 . In this way, the wipers  83  are effectively washed, and contaminations remaining on the wipers  83  are suppressed from adhering to the ejection surface  26  of the inkjet head  11 . 
     In the above-described first embodiment, the brush  51  may be vibrated by the brush drive mechanism  43 . The brush  51  brushes and washes the ejection surface  26  of the inkjet head  11  by vibrating. 
     The method of performing washing by bringing the brush  51  into contact with the ejection surface  26  like in the first embodiment described above is efficient particularly in a case of ejecting any one of emulsion ink and ultraviolet curing type ink as ink from the ejection surface  26 . If emulsion ink and ultraviolet curing type ink harden once, since weatherability is high, it is difficult for them to be removed by subsequent washing. In other words, in a case where washing of the ejection surface of the inkjet head is insufficient, if such ink hardens on the ejection surface, it is difficult to remove it from the ejection surface by subsequent washing. Therefore, washing of the ejection surface of the inkjet head needs to be properly performed at appropriate timings. Also, the type of the solvent of the washing solution L may be appropriately selected according to the type of ink. 
     Second Embodiment 
     Hereinafter, a second embodiment will be described with reference to  FIG. 9 . Also, in the following embodiment description, constituent elements having the same functions as those of constituent elements having been already described are denoted by the same reference symbols, and may not be described. Also, a plurality of constituent elements denoted by the same reference symbol is not limited to a case where every function and every property are common, and may have different functions and different properties according to individual embodiments. 
       FIG. 9  is a cross-sectional view illustrating an inkjet head  11  and a washing station  16  according to the second embodiment. As shown in  FIG. 9 , the washing unit  42  of the second embodiment includes an ultrasonic washing device  121 , in place of the brush  51 . 
     The ultrasonic washing device  121  is attached to the storage tank  41 , and makes ultrasonic waves propagate in the washing solution L stored in the storage tank  41 . The corresponding ultrasonic waves wash the ejection surface  26  of the inkjet head  11  immersed in the washing solution L, and the wipers  83 . 
     Like the ultrasonic washing device  121  of the second embodiment, the washing unit  42  may wash the ejection surface  26  of the inkjet head  11  and the wipers  83 , without contacts. Also, the washing unit  42  may include both of the brush  51  of the first embodiment and the ultrasonic washing device  121  of the second embodiment. 
     The wiping unit  81  of the second embodiment includes one wiper  83 . The number of wipers  83  may be two like in the first embodiment, or may be one like in the second embodiment, or may be any other number. 
     Also, the automatic level adjustment mechanism  44  may change the position of the solution level of the washing solution L of the storage tank  41 , if necessary. In other words, since the height of the solution level of the washing solution L of the storage tank  41  becomes equal to the height of the solution level of the washing solution L of the adjustment tank  67  of the automatic level adjustment mechanism  44 , the height of the solution level of the washing solution L of the storage tank  41  may be adjusted by adjusting the height of the solution level of the washing solution L of the adjustment tank  67 . In order to implement this, for example, the automatic level adjustment mechanism  44  may be configured such that the supply tank  68  is movable in a vertical direction. 
     In a case where the supply tank  68  of the automatic level adjustment mechanism  44  is configured so as to be movable in a vertical direction, if the height of the solution level of the washing solution L of the storage tank  41  is raised, the supply tank  68  is raised, whereby the leading end of the pipe  68   a  is exposed from the solution level of the washing solution L, whereby air enters the supply tank  68  from the leading end of the pipe  68   a . In the case where air enters the supply tank  68 , since the internal pressure of the supply tank  68  increases, due to this pressure change, it is possible to supply the washing solution L of the supply tank  68  into the adjustment tank  67 , and it is possible to raise the solution level of the washing solution L of the adjustment tank  67 . As a result, it is possible to raise the solution level of the washing solution L of the storage tank  41 . 
     Also, in a case of lowering the height of the washing solution L of the storage tank  41 , the height of the leading end of the pipe  68   a  is lowered by lowering the supply tank  68 , and the discharge valve  72  of the storage tank  41  is opened, whereby a portion of the washing solution L stored in the storage tank  41  is discharged from the outlet  71 . In this way, it is possible to lower the solution level of the washing solution L of the storage tank  41  together with the solution level of the washing solution L of the adjustment tank  67 . 
     Like these, in a case where the automatic level adjustment mechanism  44  is configured so as to be able to change the height of the solution level of the washing solution L of the storage tank  41 , the height of the solution level may be changed according to steps during washing of the inkjet head  11 . Specifically, in a case where washing of the inkjet head  11  is performed by the washing station  16 , between during brush washing using the brush  51  and during wiping using the wipers  83 , the height of the solution level of the washing solution L may be changed by the automatic level adjustment mechanism  44 . 
       FIG. 10  is an explanatory view of an operation of a modification of the first embodiment during washing of the ejection surface  26  by the brush  51 . For example, in a case of washing the ejection surface  26  of the inkjet head  11  by the brush  51 , the solution level of the washing solution L of the storage tank  41  may be adjusted by the automatic level adjustment mechanism  44  such that the height of the solution level of the washing solution L becomes a height equal to or higher than a contact position of the ejection surface  26  and the brush  51 . In the case of performing washing of the ejection surface  26  by the brush  51 , it is possible to perform washing on the ejection surface  26  by the brush  51  in the washing solution L by making the height of the solution level of the washing solution L of the storage tank  41  such a height that the contact position of the ejection surface  26  and the brush  51  is immersed. In this case, it is possible to improve the washing efficiency. 
       FIG. 11  is an explanatory view of an operation of a modification of the first embodiment during wiping on the ejection surface  26  by the wipers  83 . Also, in a case of wiping the ejection surface  26  of the inkjet head  11  by the wipers  83 , the solution level of the washing solution L of the storage tank  41  may be lowered such that the height of the solution level is positioned below the leading-end portions  83   b  of the wipers  83 . In other words, the height of the solution level of the washing solution L of the storage tank  41  may be adjusted by the automatic level adjustment mechanism  44  such that the position of the solution level of the washing solution L is set below the ejection surface  26 . Since wiping on the ejection surface  26  by the wipers  83  is performed by wiping off the washing solution L attached to the ejection surface  26  of the inkjet head  11 , if the solution level of the washing solution L is positioned below the ejection surface  26 , it is possible to surely wipe the ejection surface  26 . Like these, if the position of the solution level of the washing solution L of the storage tank  41  is changed by the automatic level adjustment mechanism  44 , it is possible to more surely perform washing in a case of washing the ejection surface  26  of the inkjet head  11  using the brush  51  and the wipers  83 . 
     However, the height of the solution level of the washing solution L by the automatic level adjustment mechanism  44  may be adjusted by a method other than the method of moving the supply tank  68  in the vertical direction. For example, a means for supplying the washing solution L, such as a pump, may be provided in the automatic level adjustment mechanism  44  such that the washing solution L is supplied from the supply means into the adjustment tank  67  directly or through the supply tank  68 . Like this, by providing a means for supplying the washing solution L so as to supply the washing solution L into the adjustment tank  67 , it is possible to adjust the height of the solution level of the washing solution L of the adjustment tank  67 , and it is possible to adjust the height of the solution level of the washing solution L of the storage tank  41 . 
     The embodiments of the present invention described above are not intended to restrict the scope of the invention, and are just examples included in the scope of the invention. Also, the schematic diagrams do not show the structure of an actual inkjet head, and the ink passages, the ink drive elements, and the like are different from their actual shapes. Some embodiments of the present invention may be obtained by making changes, omissions, and additions on the above-described embodiments, for example, with respect to at least some of specific uses, structures, shapes, functions, and effects, without departing from the gist of the invention. 
     For example, a portion of the brush  51  of the washing unit  42  may be protruded from a side wall  47  of the storage tank  41 . If a portion of the brush  51  is provided so as to protrude from the storage tank  41  and be in contact with the ejection surface  26  of the inkjet head  11 , position control on the storage tank  41  by the actuator  45  may not be performed.