Patent Publication Number: US-2022212476-A1

Title: Inkjet printer and non-transitory computer-readable storage medium storing computer-readable instructions

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of International Application No. PCT/JP2021/011908 filed on Mar. 23, 2021 which claims the benefit of priority from Japanese patent application No. 2020-065198 filed on Mar. 31, 2020. The entire contents of the earlier applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     Known is an inkjet printer configured to circulate ink for purposes of removing air bubbles and eliminating sedimentation of ink components in a head or in a flow path from an ink storage unit to the head. For example, an inkjet printer includes a plurality of pressure generating chambers, a supply liquid chamber, a plurality of supply passages, a circulating liquid chamber, a plurality of circulation passages, and a circulation tank. The pressure generating chambers are configured to individually communicate with a plurality of nozzles and to apply a pressure to ink. The supply liquid chamber is configured to accommodate ink that is supplied to the pressure generating chambers. The supply passages are configured to supply the ink from the supply liquid chamber to the pressure generating chambers. The circulation passages are configured to communicate the pressure generating chambers and the circulating liquid chamber, and to cause the ink in the pressure generating chambers to be accommodated in the circulating liquid chamber. The ink in the circulating liquid chamber is sent to the circulation tank. Therefore, the ink is collected from the circulating liquid chamber to the circulation tank via the circulation passages, together with air bubbles. In addition, the ink circulation eliminates sedimentation of ink components. 
     In the inkjet printer, when a circulation speed of the ink is increased so as to further remove air bubbles and eliminate sedimentation of ink components, meniscus of the nozzles may be destroyed. In this case, the air bubbles may be drawn into the head from the nozzles. Therefore, it is considered to circulate the ink in a circulation flow path in a state where a cap is filled with the ink or a cleaning liquid. However, a positive pressure may be generated from the nozzles into the cap, in which case the cap separates from a nozzle surface. This may cause the ink to flow to an outside of the cap. 
     SUMMARY 
     An object of the present disclosure is to provide an inkjet printer and a non-transitory computer-readable storage medium storing computer-readable instructions, which enable to reduce a positive pressure that is generated in a cap and reducing a possibility that ink will flow to an outside of the cap. 
     A first aspect of the present disclosure is an inkjet printer including a nozzle surface, a plurality of manifolds, supply flow paths, circulation flow paths, a cap and a controller. The nozzle surface is provided on a head and has a plurality of nozzle rows each having a plurality of nozzles. The plurality of manifolds are configured to supply ink to the nozzles provided in each nozzle row. The supply flow paths are connected to at least one of the manifolds and are configured to supply the ink to the manifold connected to the supply flow paths. The circulation flow paths are connected to at least one of the manifolds and are configured to circulate the ink from the manifold to which the ink is supplied through the supply flow path. The cap is provided to be in contact with the nozzle surface on an outside of the nozzles respectively provided in at least two of the nozzle rows. The controller is configured to execute first circulation processing where head circulation of circulating the ink through one of the supply flow paths, one of the manifolds and one of the circulation flow paths is performed, and head circulation of circulating the ink through another of the supply flow paths, another of the manifolds and another of the circulation flow paths is not performed, in a liquid-contact state where the ink or a cleaning liquid supplied in the cap is contacted with the nozzle surface. 
     A second aspect of the present disclosure is a non-transitory computer-readable medium storing computer-readable instructions, when executed by a computer of an inkjet printer. The inkjet printer includes a nozzle surface, a plurality of manifolds, supply flow paths, circulation flow paths, a cap and the computer. The nozzle surface is provided on a head configured to eject ink and has a plurality of nozzle rows each having a plurality of nozzles configured to eject the ink. The plurality of manifolds are configured to supply the ink to the nozzles provided in each nozzle row. The supply flow paths are connected to at least one of the manifolds and are configured to supply the ink to the manifold connected to the supply flow paths. The circulation flow paths are connected to at least one of the manifolds and are configured to circulate the ink from the manifold to which the ink is supplied through the supply flow path. The cap is provided to be in contact with the nozzle surface on an outside of the nozzles respectively provided in at least two of the nozzle rows. The computer-readable instructions cause the computer to perform first circulation processing where head circulation of circulating the ink through one of the supply flow paths, one of the manifolds and one of the circulation flow paths is performed, and head circulation of circulating the ink through another of the supply flow paths, another of the manifolds and another of the circulation flow paths is not performed, in a liquid-contact state where the ink or a cleaning liquid supplied in the cap is contacted with the nozzle surface. 
     Due to the first circulation processing where the head circulation through one of the supply flow paths, one of the manifolds and one of the circulation flow paths is performed and the head circulation through another of the supply flow paths, another of the manifolds and another of the circulation flow paths is not performed, a positive pressure that is generated in the cap can be reduced, as compared to a case where the head circulation of circulating the ink through the one of the supply flow paths, the one of the manifolds and the one of the circulation flow paths is performed and the head circulation of circulating the ink through the another of the supply flow paths, the another of the manifolds and another of the circulation flow paths is also performed. Therefore, it is possible to reduce a possibility that the cap will separate from the nozzle surface and the ink will flow to an outside of the cap. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of an internal structure of a printer  1 . 
         FIG. 2  is a longitudinal sectional view of the internal structure of the printer  1 . 
         FIG. 3  is a perspective view of a head unit  100 . 
         FIG. 4  is a partially cross-sectional area of the head unit  100 . 
         FIG. 5  is a partially cross-sectional view showing nozzles  111  and manifolds  170 A and  180 A of a head part  110 . 
         FIG. 6  shows a flow path configuration of ink  68  of the printer  1 . 
         FIG. 7  is a flow path diagram of a cleaning liquid  76 A and the ink  68 . 
         FIG. 8  is a block diagram showing an electrical configuration of the printer  1 . 
         FIG. 9  is a flowchart of liquid-contact circulation processing. 
         FIG. 10  is a sub-routine of a circulation operation A. 
         FIG. 11  is a flow path diagram showing a liquid-contact state. 
     
    
    
     DETAILED DESCRIPTION 
     A schematic configuration of a printer  1  will be described with reference to  FIGS. 1 and 2 . The upper, lower, left lower, right upper, right lower and left upper in  FIG. 1  are the upper, lower, front, rear, right and left of the printer  1 , respectively. 
     As shown in  FIG. 1 , the printer  1  is configured to perform printing by ejecting ink onto a printing medium (not shown) such as a paper and cloth such as a T-shirt. In the present embodiment, the printer  1  is configured to print a color image on the printing medium by ejecting downward five types of inks (white (W), black (K), yellow (Y), cyan (C), and magenta (M)) different from each other. In descriptions below, white ink of the five types of inks is referred to as white ink, and inks of four colors of black, cyan, yellow and magenta are referred to as color ink when they are collectively referred to. Further, when collectively referring to white ink and color ink or when any one is not specified, they are simply referred to as ink. By including a resin component in the ink, the adhesion of the ink to the printing medium is improved. The white ink also contains an emulsion and contains titanium oxide as a pigment. Titanium oxide has a relatively high specific gravity, and pigment particles tend to precipitate. Therefore, when printing of the white ink is not performed for a long time, it is preferable to perform the printing by the white ink after eliminating the precipitation of the white ink. 
     As shown in  FIG. 1 , the printer  1  includes a housing  2 , a frame body  10 , a guide shaft  9 , a rail  7 , a carriage  20 , head units  100  and  200 , a drive belt  101 , a drive motor  19 , a platen drive mechanism  6 , a platen  5 , and the like. The housing  2  is provided with an operation unit (not shown). The operation unit includes a display  45  (refer to  FIG. 8 ) and an operation button  46  (refer to  FIG. 8 ). The operation button  46  is operated when an operator inputs instructions concerning various operations of the printer  1 . 
     The frame body  10  has a substantially rectangular frame shape, in plan view, and is installed on an upper part of the housing  2 . The frame body  10  is configured to support the guide shaft  9  on a front side and the rail  7  on a rear side, respectively. The guide shaft  9  extends in a right and left direction inside the frame body  10 . The rail  7  is arranged to face the guide shaft  9  extending in the right and left direction. The carriage  20  is supported to be conveyable in the right and left direction along the guide shaft  9 . As shown in  FIG. 1 , the head units  100  and  200  are arranged in a front and rear direction and mounted on the carriage  20 . The head unit  100  is located behind the head unit  200 . 
     The drive belt  101  is bridged along the right and left direction inside the frame body  10 . The drive motor  19  is provided on a right front part inside the frame body  10 . The drive motor  19  is connected to the carriage  20  via the drive belt  101 . When the drive motor  19  drives the drive belt  101 , the carriage  20  reciprocally moves in the right and left direction (scanning direction). This causes the head units  100  and  200  to reciprocally move in the right and left direction. 
     The platen drive mechanism  6  includes a pair of guide rails (not shown) and the platen  5 . The pair of guide rails extends in the front and rear direction inside the platen drive mechanism  6  and is configured to support the platen  5  so as to be movable in the front and rear direction. The platen  5  has a plate shape and is provided below the frame body  10 . The platen  5  is configured to hold the printing medium at the top. The platen drive mechanism  6  is configured to be driven by a sub-scanning drive unit  16  (refer to  FIG. 8 ), which will be described later, thereby moving the platen  5  in the front and rear direction along the pair of guide rails. Printing is performed on the printing medium by ejecting the ink from a head part  110  configured to reciprocally move in the right and left direction while the platen  5  conveys the printing medium in the front and rear direction (sub-scanning direction). 
     As shown in  FIG. 2 , a maintenance unit  141  of the printer  1  includes a cap  91  and a cap support part  92 . The cap  91  is supported by the cap support part  92 , and is provided to be in contact with a nozzle surface  112 , which will be described later, on an outside of a first nozzle row W 1 , a second nozzle row W 2 , a third nozzle row W 3 , and a fourth nozzle row W 4  (which will be described later) by a cap drive unit  18  (refer to  FIG. 8 ). 
     &lt;Head Unit  100 &gt; 
     A detailed configuration of the head unit  100  will be described with reference to  FIGS. 3 and 4 . As shown in  FIG. 3 , the head unit  100  includes a housing  30 , a head part  110 , a buffer tank  60 , and the like. The housing  30  has a substantial box shape and is configured to support the head part  110  configured to eject ink at a lower part. An inside of the head part  110  is divided into, for example, four ink chambers (not shown) configured to supply white ink to manifolds  170 A,  180 A,  170 B and  180 B. The head part  110  has a planar nozzle surface  112 . The nozzle surface  112  is provided with a plurality of nozzles  111  for ejecting white ink. The plurality of nozzles  111  is aligned in a row rearward from the front side of the nozzle surface  112  along the front and rear direction, and is aligned in a plurality of rows along the right and left direction. As shown in  FIG. 3 , the plurality of nozzles  111  is divided into four sets of a first nozzle row W 1 , a second nozzle row W 2 , a third nozzle row W 3 , and a fourth nozzle row W 4  from the left. The plurality of nozzles  111  corresponds to a plurality of ejection channels (not shown) provided in the head part  110 . A plurality of piezoelectric elements (not shown) provided in the head part  110  is driven, so that the plurality of ejection channels can eject downward white ink from the plurality of nozzles  111  corresponding to the plurality of ejection channels. The head unit  100  is placed on the carriage  20  with the nozzle surface  112  facing downward. 
     As shown in  FIGS. 3 and 4 , the buffer tank  60  has a hollow cuboid shape and is formed to extend in parallel to the nozzle surface  112  at an upper part of the head unit  100 . The buffer tank  60  is configured to temporarily store ink therein to absorb a pressure fluctuation of the ink supplied to the head part  110 , and then to supply the ink to the head part  110 . As shown in  FIG. 4 , the buffer tank  60  includes four storage chambers  61  configured to store ink on the front side, and each storage chamber  61  is connected to each of flow paths  62 A,  62 B,  62 C and  62 D facing downward. The flow paths  62 A,  62 B,  62 C and  62 D have filters  75 E,  75 F,  75 G and  75 H provided at a lower part, respectively. The flow paths  62 A to  62 D are respectively connected to the manifolds  170 A,  180 A,  170 B and  180 B, which will be described later, via the filters  75 E to  75 H, respectively. 
     &lt;Structures of Manifolds of First Nozzle Row W 1  and Second Nozzle Row W 2 &gt; 
     Structures of manifolds of the first nozzle row W 1  and the second nozzle row W 2  are described with reference to  FIG. 5 .  FIG. 5  is a partial cross-sectional view showing structures of manifolds in the head part  110  shown in  FIG. 4 . In  FIG. 5 , structures of manifolds of the first nozzle row W 1  and the second nozzle row W 2  are shown, and the third nozzle row W 3  and the fourth nozzle row W 4  on the right side of the second nozzle row W 2  are omitted. As shown in  FIG. 5 , the head part  110  has the first nozzle row W 1  and the second nozzle row W 2 . The first nozzle row W 1  has a plurality of manifolds  171  to  174  and a plurality of nozzle rows L 1  to L 6 . The second nozzle row W 2  has a plurality of manifolds  181  to  183  and a plurality of nozzle rows L 7  to L 12 . The manifold  171  of the first nozzle row W 1  is configured to communicate with the nozzles  111  included in the nozzle row L 1 . The manifold  172  is configured to communicate with the nozzles  111  included in the nozzle rows L 2  and L 3 . The manifold  173  is configured to communicate with the nozzles  111  included in the nozzle rows L 4  and L 5 . The manifold  174  is configured to communicate with the nozzles  111  included in the nozzle rows L 6 . Respective front end portions of the manifolds  171  to  174  are provided with supply ports  131 ,  132 ,  133  and  134 , respectively. The supply ports  131  to  134  are connected to the flow path  62 A via the filter  75 E (refer to  FIG. 4 ), and therefore, can supply the ink  68  to the manifolds  171  to  174 , respectively. Hereinafter, the manifolds  171  to  174  are also referred to as ‘manifold  170 A’. 
     In addition, the manifold  181  of the second nozzle row W 2  is configured to communicate with the nozzles  111  included in the nozzle rows L 7  and L 8 . The manifold  182  is configured to communicate with the nozzles  111  included in the nozzle rows L 9  and L 10 . The manifold  183  is configured to communicate with the nozzles  111  included in the nozzle rows L 11  and L 12 . Respective front end portions of the manifolds  181  to  183  are provided with supply ports  135 ,  136  and  137 , respectively. The supply ports  135  to  137  are connected to the flow path  62 B via the filter  75 F (refer to  FIG. 4 ), and therefore, can supply the ink  68  to the manifolds  181  to  183 , respectively. Hereinafter, the manifolds  181  to  183  are also referred to as ‘manifold  180 A’. Respective rear end portions of the manifolds  181  to  183  are connected to a left end-side of a communication passage  150 A. In addition, respective rear end portions of the manifolds  171  to  174  are connected to a right end-side of the communication passage  150 A. 
     When performing printing on a printing medium, the ink  68  is supplied from the supply ports  131  to  137  to the manifolds  171  to  174  and  181  to  183 , respectively, and is ejected from the nozzle rows L 1  to L 12 , as described above. In addition, during head circulation of the ink  68 , which will be described later, the ink  68  flows from one side to the other side of the first nozzle row W 1  and the second nozzle row W 2 . For example, the ink  68  flows from the supply ports  131  to  134  to the manifolds  171  to  174 , respectively, and the ink  68  flows to the manifolds  181  to  183  via the communication passage  150 A and returns to the supply ports  135  to  137 . Therefore, during the head circulation of the ink  68 , the manifolds  171  to  174 , the communication passage  150 A, and the manifolds  181  to  183  form a circulation flow path of the ink  68  in the head part  110 . The flow paths  62 A to  62 D, the manifolds  171  to  174  and  181  to  183  and the communication passage  150 A in the head part  110  are narrower and more complicated in structure than flow paths  714 C,  715 C and  802  (refer to  FIG. 6 ) outside the head part  110 , which will be described later. Therefore, a flow path resistance inside the head part  110  is greater than a flow path resistance outside the head part  110 . Note that, the structure is similar to the flow path for supplying the ink  68  to the third nozzle row W 3  and the fourth nozzle row W 4 . 
     &lt;Ink Supply Units  700 A and  700 B&gt; 
     As shown in  FIG. 6 , ink supply units  700 A and  700 B are parts where the ink  68  is supplied from a sub-pouch  8  to the head part  110  and the ink  68  circulates. As an example, the sub-pouch  8  has a flexible bag shape and is configured to accommodate the ink  68  supplied from a main tank (not shown) of white ink. In addition, the sub-pouch  8  is connected to the main tank (not shown) of white ink by a first flow path  711 . The ink  68  in the sub-pouch  8  is circulated to the main tank by a circulation flow path  721 . The sub-pouch  8  is connected to the ink supply unit  700 A via a second flow path  712 , and is connected to the ink supply unit  700 B via a third flow path  713 . 
     The ink supply unit  700 A includes a fourth flow path  714 A, a fifth flow path  715 A, a first bypass flow path  801 A, a second bypass flow path  802 A, a second bypass flow path  802 B, a pump  752 A, and electromagnetic valves  31 A,  763 A and  766 A, and filters  75 A,  75 B and  772 A. Hereinafter, the second bypass flow path  802 A and the second bypass flow path  802 B are collectively referred to as ‘second bypass flow path  802 ’ unless there is need to make a distinction. As shown in  FIG. 6 , one end of the manifold  170 A of the head part  110  is connected to the flow path  62 A shown in  FIG. 4 , and the other end is connected to the communication passage  150 A. One end of the manifold  180 A is connected to the flow path  62 B shown in  FIG. 4 , and the other end is connected to the communication passage  150 A. Since a flow path of the fourth flow path  714 A( 714 C), which is in the head part  110 , is the flow path  62 A, the fourth flow path  714 A( 714 C) is connected to the manifold  170 A and supplies the ink  68  to the manifold  170 A. Since a flow path of the fifth flow path  715 A( 715 C), which is in the head part  110 , is the flow path  62 B, the fifth flow path  715 A( 715 C) is connected to the manifold  180 A and supplies the ink  68  to the manifold  180 A. A relationship between the manifolds  170 B and  180 B and the fourth flow path  714 B and fifth flow path  715 B is similar to a relationship between the manifolds  170 A and  180 A and the fourth flow path  714 A and fifth flow path  715 A. 
     As shown in  FIG. 6 , the second flow path  712  is connected to the sub-pouch  8 , the fourth flow path  714 A and the fifth flow path  715 A, and is configured to supply the ink  68  from the sub-pouch  8  to the fourth flow path  714 A and the fifth flow path  715 A. The third flow path  713  is connected to the sub-pouch  8 , the fourth flow path  714 B and the fifth flow path  715 B, and is configured to supply the ink  68  from the sub-pouch  8  to the fourth flow path  714 B and the fifth flow path  715 B. The fourth flow path  714 A has the electromagnetic valve  763 A and the filter  75 A. The electromagnetic valve  763 A is configured to be controlled by a CPU  11  (refer to  FIG. 8 ), thereby opening and closing the fourth flow path  714 A. The fifth flow path  715 B has the electromagnetic valve  766 A and the filter  75 B. The electromagnetic valve  766 A is configured to be controlled by the CPU  11 , thereby opening and closing the fifth flow path  715 A. 
     The first bypass flow path  801 A is configured to connect the fourth flow path  714 A and the fifth flow path  715 A each other outside the head part  110 . For example, the first bypass flow path  801 A is configured to connect the fourth flow path  714 A and the fifth flow path  715 A each other downstream of the filters  75 A and  75 B. The bypass flow path  801 A has the filter  772 A and the pump  752 A. The filter  772 A is provided on the fourth flow path  714 A-side with respect to the pump  752 A. Note that, a side, which is downstream of a connection place with the first bypass flow path  801 A, of the fourth flow path  714 A is referred to as a fourth flow path  714 C. In addition, a side, which is downstream of the connection place with the first bypass flow path  801 A, of the fifth flow path  715 A is referred to as a fifth flow path  715 C. The fifth flow path  715 C functions as a circulation flow path of the ink  68  during circulation processing of ink, which will be described later. 
     On the head part  110 -side with respect to the first bypass flow path  801 A, the fourth flow path  714 A and the fifth flow path  715 A are connected via the second bypass flow path  802 . The second bypass flow path  802  has the electromagnetic valve  31 A. The electromagnetic valve  31 A is configured to be controlled by the CPU  11 , thereby opening and closing the second bypass flow path  802 . A flow path, which is between the electromagnetic valve  31 A and the fourth flow path  714 C, of the second bypass flow path  802  is referred to as ‘second bypass flow path  802 A’, and a flow path, which is between the electromagnetic valve  31 A and the fifth flow path  715 C, of the second bypass flow path  802  is referred to as ‘second bypass flow path  802 B’. 
     The ink supply unit  700 B has a configuration similar to the ink supply unit  700 A, and includes a fourth flow path  714 B, a fifth flow path  715 B, a first bypass flow path  801 B, a second bypass flow path  902 A, a second bypass flow path  902 B, a pump  752 B, and electromagnetic valves  31 B,  763 B and  766 B, and filters  75 C,  75 D and  772 B. Hereinafter, the second bypass flow path  902 A and the second bypass flow path  902 B are collectively referred to as ‘second bypass flow path  902 ’ unless there is need to make a distinction. The head part  110  further includes a third nozzle row W 3  and a fourth nozzle row W 4  for ejecting white ink, a communication passage  150 B, a manifold  170 B and a manifold  180 B. One end of the manifold  170 B is connected to the flow path  62 C, and the other end is connected to the communication passage  150 B. One end of the manifold  180 B is connected to the flow path  62 D, and the other end is connected to the communication passage  150 B. 
     The fourth flow path  714 B is connected to the third flow path  713  and the manifold  170 B, and is configured to supply the ink  68  to the manifold  170 B. The manifold  170 B is configured to supply the ink  68  to the nozzles  111  (refer to  FIG. 3 ) of the third nozzle row W 3 . The fifth flow path  715 B is connected to the third flow path  713  and the manifold  180 B, and is configured to supply the ink  68  to the manifold  180 B. The manifold  180 B is configured to supply the ink  68  to the nozzles  111  (refer to  FIG. 4 ) of the fourth nozzle row W 4 . 
     The fourth flow path  714 B has the electromagnetic valve  763 B and the filter  75 C. The electromagnetic valve  763 B is configured to be controlled by the CPU  11 , thereby opening and closing the fourth flow path  714 B. The fifth flow path  715 B has the electromagnetic valve  766 B and the filter  75 D. The electromagnetic valve  766 B is configured to be controlled by the CPU  11 , thereby opening and closing the fifth flow path  715 B. 
     The first bypass flow path  801 B is configured to connect the fourth flow path  714 B and the fifth flow path  715 B each other. For example, the first bypass flow path  801 B is configured to connect the fourth flow path  714 B and the fifth flow path  715 B each other, downstream of the filters  75 C and  75 D. The bypass flow path  801 B has the filter  772 B and the pump  752 B. The filter  772 B is provided on the fourth flow path  714 B-side with respect to the pump  752 B. Note that, a side, which is downstream of a connection place with the first bypass flow path  801 B, of the fourth flow path  714 B is referred to as a fourth flow path  714 D. In addition, a side, which is downstream of the connection place with the first bypass flow path  801 B, of the fifth flow path  715 B is referred to as a fifth flow path  715 D. The fifth flow path  715 D functions as a circulation flow path of the ink  68  during circulation processing of ink, which will be described later. 
     In addition, on the head part  110 -side, the fourth flow path  714 B and the fifth flow path  715 B are connected via the second bypass flow path  902 . The second bypass flow path  902  has the electromagnetic valve  31 B. The electromagnetic valve  31  is configured to be controlled by the CPU  11 , thereby opening and closing the second bypass flow path  902 . A flow path, which is between the electromagnetic valve  31 B and the fourth flow path  714 D, of the second bypass flow path  902  is referred to as ‘second bypass flow path  902 A’, and a flow path, which is between the electromagnetic valve  31 B and the fifth flow path  715 D, of the second bypass flow path  902  is referred to as ‘second bypass flow path  902 B’. Note that, although the flow paths  62 A to  62 D and the filters  75 E to  75 H shown in  FIG. 4  are not shown in  FIG. 6 , the positions where they are provided are parts of the fourth flow paths  714 A and  714 B and the fifth flow paths  715 A and  715 B connected to the manifolds  170 A,  180 A,  170 B and  180 B, in the head part  110 . 
     &lt;Cleaning Liquid Supply Unit  120 &gt; 
     A cleaning liquid supply unit  120  shown in  FIG. 7  is provided in the printer  1 , and includes a cleaning liquid bottle  76 , a cleaning liquid flow path  121 , a drainage flow path  122 , a suction pump  190 , and a drainage tank  77 . The cleaning liquid bottle  76  is configured to accommodate the cleaning liquid  76 A. The cleaning liquid flow path  121  is configured to connect the cleaning liquid bottle  76  and a supply hole  661  of the cap  91  and to supply the cleaning liquid  76 A to an inside  663  of the cap  91 . In addition, the cleaning liquid flow path  121  has an atmospheric opening port  123 , an electromagnetic valve  781 , and an electromagnetic valve  782 . The electromagnetic valve  782  is configured to open and close the atmosphere opening port  123 . The electromagnetic valve  781  is configured to open and close the cleaning liquid flow path  121 . The drainage flow path  122  is configured to connect an exhaust hole  662  of the cap  91  and the drainage tank  77 . In addition, the drainage flow path  122  has an electromagnetic valve  783  and the suction pump  190 . The electromagnetic valve  783  is configured to open and close the drainage flow path  122 . The suction pump  190  is configured to suck the air, ink  68  and cleaning liquid  76 A in the drainage flow path  122  and the cap  91  and to discharge the same to the drainage tank  77 . 
     &lt;Electrical Configuration of Printer  1 &gt; 
     As shown in  FIG. 8 , the printer  1  includes the CPU  11  responsible for control of the printer  1 . The CPU  11  is electrically connected to a ROM  12 , a RAM  13 , a head drive unit  14 , a main scanning drive unit  15 , a sub-scanning drive unit  16 , an EEPROM  17 , a cap drive unit  18 , a display  45 , an operation button  46 , a pump drive unit  21  and a valve drive unit  780  via a bus  22 . 
     The ROM  12  is configured to store a control program, initial values, and the like for the CPU  11  to control an operation of the printer  1 . The RAM  82  is configured to temporarily store a variety of data that are used for the control program. The EEPROM  17  is a non-volatile memory, and is configured to store a time at which printing processing (S 1 ), which will be described later, ends, and the like. The head drive unit  83 A is electrically connected to the head part  110  configured to eject ink, and is configured to drive a piezoelectric element provided in each ejection channel of the head part  110  (refer to  FIGS. 3 and 4 ) to eject ink from the nozzles  111 . 
     The main scanning drive unit  15  is connected to the drive motor  19  and is configured to move the carriage  20  in the right and left direction (main scanning direction). The sub-scanning drive unit  16  includes a motor, a gear, and the like (not shown), and is configured to drive the platen drive mechanism  6  (refer to  FIG. 1 ) to move the platen  5  in the front and rear direction (sub-scanning direction). 
     The cap drive unit  18  includes a cap drive motor (not shown), a gear, and the like, and is configured to move the cap support part  92  shown in  FIG. 2  in the upper and lower direction to move the cap  91  in the upper and lower direction. The display  45  is configured to display a variety of information. An input from the operation button  46  is input to the CPU  11 . The pump drive unit  21  is configured to drive and control the suction pump  190 , the pump  752 A and the pump  752 B. The valve drive unit  780  is configured to drive and control the electromagnetic valves  781 ,  782 ,  783 ,  784 ,  31 A,  31 B,  763 A,  766 A,  763 B and  766 B. 
     &lt;Liquid-Contact Circulation Processing&gt; 
     Liquid-contact circulation processing is described with reference to  FIGS. 6 to 11 . In the printer  1 , circulation of the ink  68  is performed at regular intervals for purposes of removing air bubbles in the ink  68  and eliminating sedimentation of ink components such as pigment in the flow path of the ink  68 . In this case, in order to further remove air bubbles and eliminate sedimentation of ink components, when a circulation speed of the ink  68  is increased and circulation of the ink  68  is performed, a meniscus of the nozzle  111  may be destroyed. When the meniscus is destroyed, a malfunction such as introduction of air bubbles into the head part  110  from the nozzle  111  or outflow of the ink  68  from the nozzle  111  may occur. Therefore, it is considered to perform liquid-contact circulation so as to increase the circulation speed of the ink  68  and to perform circulation of the ink  68  while reducing the possibility of occurrence of the malfunction. In the liquid-contact circulation, the ink  68  is circulated, for example, in the first bypass flow path  801 A, the fourth flow path  714 C, the manifold  170 A, the communication passage  150 A, the manifold  180 A and the fifth flow path  715 C, in a state where the cap  91  is closely contacted with the nozzle surface  112  so as to cover the nozzles  111  and the cap  91  is filled with the cleaning liquid  76 A. When a positive pressure is generated from the nozzles  111  into the cap  91 , the cap  91  may separate from the nozzle surface  112 , and the ink  68  may flow to an outside of the cap  91 . In this case, the ink  68  may adhere to a component of the printer  1 . For example, when the ink adheres to the cap support part  92  and a spring (not shown) for pressing the cap  91 , the pigment and resin components of the ink  68  remain on the cap support part  92  and the spring, resulting in poor capping of the cap  91  to the nozzle surface  112 . Further, if the ink  68  leaking from the cap  91  adheres to a sensor (not shown), a detection failure may be caused. In addition to this, if the leaked ink  68  adheres to other driving components, a driving failure may be caused. The liquid-contact circulation processing of the present embodiment aims to reduce the positive pressure that is generated in the cap  91 . 
     For example, when a power supply of the printer  1  becomes on, the CPU  11  reads out a program of main processing (not shown) for performing main control such as a printing operation of the printer  1 , a program of liquid-contact circulation processing (refer to  FIG. 9 ), and the like from the ROM  12 , and develops the programs onto the RAM  13 . The CPU  11  executes the main processing and the liquid-contact circulation processing according to the programs. 
     As shown in  FIG. 9 , when printing processing (S 1 ) ends, the CPU  11  raises the cap  91  by the cap drive unit  18  and brings the cap  91  in contact with the nozzle surface  112  of the head part  110  so as to prevent the nozzles  111  from drying. Then, the CPU  11  stores an end time in the EEPROM  17  (S 1 ). Next, the CPU  11  determines whether a first predetermined time has elapsed from the end time of the latest printing processing (S 1 ) stored in the EEPROM  17  (S 2 ). The first predetermined time is, for example,  6  hours. When it is not determined that the first predetermined time has elapsed (S 2 : NO), the CPU  11  continues the determination of S 2 . When it is determined that the first predetermined time has elapsed (S 2 : YES), the CPU  11  performs end-job maintenance. 
     An example of the end-job maintenance is described with reference to  FIGS. 7 and 11 . The CPU  11  closes the electromagnetic valve  781  and opens the electromagnetic valve  783  in a state where the cap  91  is in contact with the nozzle surface  112  of the head part  110 . Next, the CPU  11  drives the suction pump  190  for a certain time. The insides of the drainage flow path  122  and the cap  91  become a negative pressure, and the CPU  11  executes a purge in which ink is sucked from the nozzles  111  of the head part  110 , as shown in  FIG. 7 . Next, the CPU  11  opens the electromagnetic valve  781  and closes the electromagnetic valve  782 . The electromagnetic valve  783  remains open. Next, the CPU  11  drives the suction pump  190 . The insides of the drainage flow path  122 , the cap  91 , and the cleaning liquid flow path  121  become a negative pressure, and as shown in  FIG. 11 , the cleaning liquid  76 A flows from the cleaning liquid bottle  76  to the cleaning liquid flow path  121 , the electromagnetic valve  781 , and the cap  91 . Thereafter, the CPU  11  stops the suction pump  190  and closes the electromagnetic valve  781  and the electromagnetic valve  783 . Therefore, the inside of the cap  91  is filled with the cleaning liquid, and the state in which the cleaning liquid  76 A is in contact with the nozzle surface  112  is maintained. 
     &lt;Circulation Operation A&gt; 
     Next, the CPU  11  executes a circulation operation A (S 4 ). As the circulation operation A, in first circulation processing, the CPU  11  performs head circulation, which will be described later, for the first nozzle row W 1  and the second nozzle row W 2 , and does not perform the head circulation for the third nozzle row W 3  and the fourth nozzle row W 4 . Since the filter  772 A is provided on a downstream side with respect to a direction in which the pump  752 A delivers the ink  68 , a zero point of a pressure at which the positive pressure due to the delivery of the ink  68  from the pump  752 A and the negative pressure due to the suction of the ink  68  of the pump  752 A are balanced is moved to the manifold  170 A-side of the first nozzle row W 1  with respect to a center of the communication passage  150 A. As a result, a negative pressure is generated in the nozzles  111  of the first nozzle row W 1  and the second nozzle row W 2 . However, actually, a suction capability of the pump  752 A to suck the ink  68  cannot create an absolute vacuum due to the structure of the pump  752 A, and is specified to a predetermined value. In contrast, a delivery capability of the pump  752 A to deliver the ink  68  can be made higher than the suction capability by increasing a number of rotations of the pump  752 A. Therefore, in the head circulation, when the number of rotations of the pump  752 A is increased, the flow path resistances of the manifold  170 A, the communication passage  150 A, and the manifold  180 A of the head part  110  are large, so that the suction capability of the pump  752 A cannot catch up with the delivery capability, the zero point of the pressure is moved to the manifold  180 A-side and the positive pressure may be thus generated in the nozzles  111  of the first nozzle row W 1  and the second nozzle row W 2 . 
     In head-outside circulation such as bypass circulation and filter circulation (which will be described later) in which the ink  68  does not circulate in the head part  110  having a large flow path resistance but circulates in a flow path outside the head part  110 , the flow path resistance of the flow path through which the ink  68  passes is much smaller, as compared to the head circulation. Therefore, a load that is applied to the pump  752 B is reduced, and the suction capability of the pump  752 B is not reduced. Further, in the head-outside circulation, the ink  68  can be circulated through the second bypass flow paths  802  and  902 , the fourth flow path  714 A, and the fifth flow path  715 A, which are further apart from the nozzles  111 , as compared to the head circulation. Therefore, the zero point of the pressure is on the manifold  170 A-side, and a negative pressure is applied to the nozzles  111 . That is, in the head-outside circulation, the positive pressure that is applied to the nozzles  111  is reduced, as compared to the head circulation. The same applies to the third nozzle row W 3 -side and the fourth nozzle row W 4 -side. In the present embodiment, the CPU  11  reduces the positive pressure, which is generated in the cap  91 , by executing, in the ink supply units  700 A and  700 B, the head circulation on one side and executing the head-outside circulation or not executing circulation on the other side, without executing the head circulation at the same time. Hereinafter, the circulation operation A is described with reference to a sub-routine shown in  FIG. 10 . First, the CPU  11  resets a counter n configured to count numbers of execution times of first circulation processing (S 42 ) and second circulation processing (S 43 ), as ‘n=0’ (S 41 ). 
     &lt;First Circulation Processing&gt; 
     Next, the CPU  11  executes first circulation processing (S 42 ). As the first circulation processing, the CPU  11  performs head circulation, which will be described later, for the first nozzle row W 1  and the second nozzle row W 2  for a predetermined time. In addition, as the first circulation processing, the CPU  11  performs bypass circulation, which will be described later, for the third nozzle row W 3  and the fourth nozzle row W 4  for a predetermined time. 
     &lt;Head Circulation of First Nozzle Row W 1  and Second Nozzle Row W 2  In First Circulation Processing&gt; 
     The head circulation of the first nozzle row W 1  and the second nozzle row W 2  in the first circulation processing is described with reference to  FIG. 6 . The CPU  11  closes the electromagnetic valve  763 A, the electromagnetic valve  766 A, and the electromagnetic valve  31 A of the ink supply unit  700 A. Next, the CPU  11  drives the pump  752 A at a predetermined rotation speed for a predetermined time. Therefore, the ink  68  flows from the pump  752 A through the first bypass flow path  801 A in a direction of an arrow  401 A and through the fourth flow path  714 C in a direction of an arrow  403 A. Since the electromagnetic valve  31 A is closed, the ink  68  flows through the manifold  170 A, the communication passage  150 A, and the manifold  180 A of the head part  110  in directions of arrows  411 A,  412 A and  413 A. Next, the ink  68  flows through the fifth flow path  715 C in a direction of an arrow  407 A and flows into the first bypass flow path  801 A. The ink  68  flowing into the first bypass flow path  801 A flows from the pump  752 A in the direction of the arrow  401 A and circulates in a similar manner to described above. The CPU  11  stops the pump  752 A after performing the head circulation of the ink  68  for a predetermined time. 
     &lt;Circulation Other Than Head Circulation of Third Nozzle Row W 3  and Fourth Nozzle Row W 4  In First Circulation Processing&gt; 
     Circulation other than the head circulation of the third nozzle row W 3  and the fourth nozzle row W 4  is described with reference to  FIG. 6 . An example of the circulation other than the head circulation is the head-outside circulation. The circulation other than the head circulation of the third nozzle row W 3  and the fourth nozzle row W 4  is circulation in which the ink  68  does not circulate through the fourth flow path  714 D, the manifold  170 B, the communication passage  150 B, the manifold  180 B, and the fifth flow path  715 D. For example, the CPU  11  closes the electromagnetic valves  763 B and  766 B of the ink supply unit  700 B and opens the electromagnetic valves  31 B. Next, the CPU  11  drives the pump  752 B at a predetermined number of rotations for a predetermined time. The ink  68  flows from the pump  752 B through the first bypass flow path  801 A in a direction of an arrow  401 B and through the fourth flow path  714 D in a direction of an arrow  403 B. As described above, the flow path resistances of the manifold  170 B, the communication passage  150 B and the manifold  180 B are greater than those of the second bypass flow paths  902 A and  902 B. Therefore, the ink  68  flows through the second bypass flow path  902 A in a direction of an arrow  404 B. Next, the ink  68  flows through the electromagnetic valve  31 B in a direction of an arrow  405 B, through the second bypass flow path  902 B in a direction of an arrow  406 B and through the fifth flow path  715 D in a direction of an arrow  407 B, and flows into the first bypass flow path  801 B. The ink  68  flowing into the first bypass flow path  801 B flows from the pump  752 B in the direction of the arrow  401 B and circulates in a similar manner to described above. This circulation is called bypass circulation. The CPU  11  stops the pump  752 B after performing the bypass circulation of the ink  68  for a predetermined time. In the first circulation processing, the CPU  11  simultaneously executes, for example, the head circulation and the bypass circulation. For example, the CPU  11  may start the rotation of the pump  752 A in the head circulation and the rotation of the pump  752 B in the bypass circulation at the same time, rotate the pumps at the same rotation speed for a predetermined time, and end the rotations at the same time. In addition, the CPU  11  may make the rotation speed of the pump  752 A slower than the rotation speed of the pump  752 B, and make the circulation speed of the ink  68  in the head circulation slower than the circulation speed of the ink  68  in the bypass circulation. Further, the CPU  11  may cause the pump  752 A to perform intermittent driving that repeats drive for a predetermined time and stop for a predetermined time. Further, the CPU  11  may start the head circulation later than the bypass circulation by driving the pump  752 A for performing the head circulation after driving the pump  752 B for performing the bypass circulation. Further, the CPU  11  may end the head circulation earlier than the circulation other than the head circulation, such as the bypass circulation, by stopping the drive of the pump  752 A for performing the head circulation earlier than stopping the drive of the pump  752 B for performing the bypass circulation. 
     &lt;Second Circulation Processing&gt; 
     Next, the CPU  11  executes second circulation processing (S 43 ). As the second circulation processing, the CPU  11  performs the bypass circulation as an example of the circulation other than the head circulation for the first nozzle row W 1  and the second nozzle row W 2  for a predetermined time, and performs the head circulation for the third nozzle row W 3  and the fourth nozzle row W 4  for a predetermined time. 
     &lt;Bypass Circulation of Ink Supply Unit  700 A in Second Circulation Processing&gt; 
     The circulation other than the head circulation of the first nozzle row W 1  and the second nozzle row W 2  is circulation where the ink  68  does not circulate through the fourth flow path  714 C, the manifold  170 A, the communication passage  150 A, the manifold  180 A, and the fifth flow path  715 C, and is, for example, the above-described bypass circulation. The CPU  11  executes bypass circulation in the ink supply unit  700 A. Since the bypass circulation in the ink supply unit  700 A is similar to the bypass circulation in the ink supply unit  700 B described above, the description thereof is omitted. 
     &lt;Head Circulation of Third Nozzle Row W 3  and Fourth Nozzle Row W 4  In Second Circulation Processing&gt; 
     The head circulation of the third nozzle row W 3  and the fourth nozzle row W 4  in the second circulation processing is described. The CPU  11  executes head circulation in the ink supply unit  700 B. Since the head circulation in the ink supply unit  700 B is similar to the head circulation in the ink supply unit  700 A described above, the description thereof is omitted. 
     Next, the CPU  11  sets the counter n=n+1 (S 44 ). Therefore, n=1. The CPU  11  determines whether n≥3 (S 45 ), and when the CPU  11  does not determine n≥3 (S 45 : NO), the CPU advances the processing to S 42 , and repeats the processing of S 42  to S 45  in a similar manner to described above. When three sets of the first circulation processing and the second circulation processing are executed, n=3, and therefore, the CPU  11  determines n≥3 (S 45 : YES). Next, the CPU  11  performs three sets of filter circulation processing in the ink supply units  700 A and  700 B (S 46 ). 
     &lt;Filter Circulation&gt; 
     The filter circulation in the ink supply unit  700 A is described with reference to  FIG. 6 . The CPU  11  opens the electromagnetic valve  763 A and the electromagnetic valve  766 A and closes the electromagnetic valve  31 A of the ink supply unit  700 A. Next, the CPU drives the pump  752 A for a predetermined time. The ink  68  flows from the pump  752 A through the first bypass flow path  801 A in the direction of the arrow  401 A. The flow path resistances of the manifold  170 A, the communication passage  150 A and the manifold  180 A are greater than those of the fourth flow path  714 A and the fifth flow path  715 A. Therefore, the ink  68  flows through the fourth flow path  714 A in a direction of an arrow  414 A, rather than in the direction of the manifold  170 A, the communication passage  150 A and the manifold  180 A. Therefore, the ink  68  flows through the filter  75 A and the electromagnetic valve  763 A in the direction of the arrow  414 A, flows through the fifth flow path  715 A in a direction of an arrow  416 A, flows through the electromagnetic valve  766 A and the filter  75 B, and flows into the first bypass flow path  801 A. The ink  68  flowing into the first bypass flow path  801 A flows from the pump  752 A in the direction of the arrow  401 A and circulates in a similar manner to described above. The CPU  11  stops the pump  752 B after performing the filter circulation of the ink  68  for a predetermined time. Since the filter circulation in the ink supply unit  700 B is similar to the filter circulation in the ink supply unit  700 A, the description thereof is omitted. 
     After executing three sets of the above-described filter circulation, the CPU  11  returns the processing to the liquid-contact circulation processing of  FIG. 9 , and determines whether the processing is returned from the liquid-contact state (S 5 ). The CPU  11  determines as returning, when a printing instruction is input from the operation button  46  (refer to  FIG. 8 ) or when a printing instruction is input from a terminal apparatus (not shown) such as a computer connected to the printer  1  (S 5 : YES). When the CPU  11  determines as returning (S 5 : YES), the CPU  11  performs a return operation A as follows (S 6 ). As shown in  FIG. 11 , the CPU  11  opens the electromagnetic valves  781 ,  782  and  783  in a state where the cap  91  is in contact with the nozzle surface  112  of the head part  110 . Next, the CPU  11  drives the suction pump  190  for a certain time to discharge the cleaning liquid  76 A of the cap  91  to the drainage tank  77 . Next, as shown in  FIG. 7 , the CPU  11  closes the electromagnetic valve  781 , opens the electromagnetic valve  783 , and drives the suction pump  190  for a certain time to perform the above-described purge processing. Next, the CPU  11  controls the cap drive unit  18  (refer to  FIG. 8 ) to separate the cap  91  from the nozzle surface  112 . Next, the CPU performs a nozzle surface wiping operation of wiping off excess ink and the like remaining on the surface of the nozzle surface  112  of the head part  110  by a wiper  36  (refer to  FIG. 2 ). Next, the CPU  11  executes printing processing (S 1 ). Thereafter, the CPU performs the processing of S 2  to S 5 , as described above. 
     When the CPU  11  does not determine as returning (S 5 : NO), the CPU determines whether a second predetermined time has elapsed from the circulation operation A (S 7 ). An example of the second predetermined time is  6  hours. When YES is not determined in the determination of S 6 , the CPU  11  advances the processing to S 5 . When YES is determined in the determination of S 6 , the CPU  11  advances the processing to S 4  and performs the circulation operation A. Thereafter, the CPU performs the determinations of S 5  to S 7 , in a similar manner to described above. 
     &lt;Operational Effects of Embodiment&gt; 
     As described above, in the liquid-contact state where the cleaning liquid  76 A supplied in the cap  91  is contacted with the nozzle surface  112 , the CPU  11  of the printer  1  executes the first circulation processing (S 42 ) where the head circulation of circulating the ink  68  through the fourth flow path  714 C, the manifold  170 A, the communication path  150 A, the manifold  180 A and the fifth flow path  715 C is performed on the ink supply unit  700 A-side and the head circulation of circulating the ink  68  through the fourth flow path  714 C, the manifold  170 A, the communication passage  150 A, the manifold  180 A and the fifth flow path  715 C is not performed on the ink supply unit  700 B-side. Therefore, as compared to a case where the head circulation is performed on the ink supply unit  700 A-side and the head circulation is performed on the ink supply unit  700 B-side, the head circulation where a positive pressure is generated in the nozzles  111  is not performed at the same time, so that the positive pressure that is generated in the cap can be reduced. Therefore, a possibility that the cap  91  will separate from the nozzle surface  112  and the ink  68  will flow to an outside of the cap can be reduced. If the ink  68  flows to the outside of the cap, the content and resin included in the ink  68  remain on the spring (not shown) for moving the cap  91  and the cap support part  92 , resulting in poor capping of the cap  91  to the nozzle surface  112 . Further, if the ink  68  adheres to a sensor (not shown), a detection failure of the sensor occurs, and if the ink  68  adheres to other drive components, a drive failure occurs. In the present embodiment, since the possibility that the cap  91  will separate from the nozzle surface  112  and the ink  68  will flow to the outside of the cap is reduced, the above-described problems can be solved. 
     In addition, in the liquid-contact state where the cleaning liquid  76 A supplied in the cap  91  is contacted with the nozzle surface  112 , the CPU  11  executes the second circulation processing (S 43 ) where the head circulation of circulating the ink  68  through the fourth flow path  714 D, the manifold  170 B, the communication path  150 B, the manifold  180 B and the fifth flow path  715 D is performed on the ink supply unit  700 B-side and the head circulation of circulating the ink  68  through the fourth flow path  714 C, the manifold  170 A, the communication passage  150 A, the manifold  180 A and the fifth flow path  715 C is not performed on the ink supply unit  700 A-side. Therefore, as compared to a case where the head circulation is performed on the ink supply unit  700 A-side and the head circulation is performed on the ink supply unit  700 B-side, the head circulation where the positive pressure is generated is not performed at the same time, so that removal of air bubbles and elimination of sedimentation of ink components can be made even in the fourth flow path  714 D, the manifold  170 B, the communication passage  150 B, the manifold  180 B and the fifth flow path  715 D while reducing the positive pressure that is generated in the cap  91 . 
     Further, the CPU  11  executes the first circulation processing (S 42 ) of performing the bypass circulation of circulating the ink  68  in the fourth flow path  714 D, the second bypass flow path  902 , the fifth flow path  715 D and the first bypass flow path  801 A. Therefore, in the bypass circulation, the ink  68  is circulated through the second bypass flow path  902 , which is further apart from the nozzles  111  than the manifolds  170 B and  180 B. As described above, a negative pressure is generated in the nozzles  111  in the bypass circulation. Therefore, the positive pressure that is generated in the cap  91  can be reduced by performing the bypass circulation together with the head circulation, as the first circulation processing (S 42 ). Further, in the bypass circulation, since the flow path resistance of the flow path through which the ink  68  passes is smaller than the case of the head circulation, the ink circulates more through the flow path, and the sedimentation of components of the ink  68  can be eliminated. 
     Further, the CPU  11  executes the second circulation processing (S 43 ) of performing the bypass circulation of circulating the ink  68  in the fourth flow path  714 C, the second bypass flow path  802  and the fifth flow path  715 C. Therefore, in the bypass circulation, the ink  68  is circulated through the second bypass flow path  802  whose flow path resistance is smaller than those of the manifolds  170 A and  180 A. Therefore, as the second circulation processing (S 43 ), by performing the bypass circulation through the fourth flow path  714 C, the second bypass flow path  802  and the fifth flow path  715 C, together with the head circulation through the fourth flow path  714 D, the manifold  170 B, the communication passage  150 B and the manifold  180 B, the possibility that the positive pressure will be generated in the cap can be reduced. 
     The nozzle surface  112  of the printer  1  has the nozzles  111  provided as the first nozzle row W 1 , the second nozzle row W 2 , the third nozzle row W 3 , and the fourth nozzle row W 4 . In addition, the printer  1  has the manifold  170 A configured to supply the ink  68  to the nozzles  111  provided in the first nozzle row W 1 , the manifold  180 A configured to supply the ink  68  to the nozzles  111  provided in the second nozzle row W 2 , the manifold  170 B configured to supply the ink  68  to the nozzles  111  provided in the third nozzle row W 3  and the manifold  180 B configured to supply the ink  68  to the nozzles  111  provided in the fourth nozzle row W 4 . Further, the printer  1  has the fourth flow path  714 C connected to one of the manifold  170 A and the manifold  180 A and configured to supply the ink  68 , and the fourth flow path  714 D connected to one of the manifold  170 B and the manifold  180 B and configured to supply the ink  68 . Further, the printer  1  has the fifth flow path  715 C connected to one of the manifold  170 A and the manifold  180 A and configured to circulate the ink  68 , and the fifth flow path  715 D connected to one of the manifold  170 B and the manifold  180 B and configured to circulate the ink  68 . The cap  91  is provided to be in contact with the nozzle surface  112  on an outside of the nozzles  111  respectively provided in the first nozzle row W 1 , the second nozzle row W 2 , the third nozzle row W 3 , and the fourth nozzle row W 4 . The CPU  11  executes the first circulation processing (S 42 ) where the head circulation of circulating the ink  68  is performed in the fourth flow path  714 C, the manifold  170 A, the manifold  180 A and the fifth flow path  715 C and the head circulation of circulating the ink  68  is not performed in the fourth flow path  714 D, the manifold  170 B, the manifold  180 B and the fifth flow path  715 C, in the liquid-contact state. 
     Therefore, in the liquid-contact state, by the first circulation processing (S 42 ) where the head circulation of circulating the ink  68  is performed in the fourth flow path  714 C, the manifold  170 A, the manifold  180 A and the fifth flow path  715 C and the head circulation of circulating the ink  68  is not performed in the fourth flow path  714 D, the manifold  170 B, the manifold  180 B and the fifth flow path  715 C, the positive pressure that is generated in the cap  91  can be reduced. Therefore, the possibility that the cap  91  will separate from the nozzle surface  112  and the ink  68  will flow to an outside of the cap can be reduced. 
     The CPU  11  executes the second circulation processing (S 43 ) where the head circulation of circulating the ink  68  is performed in the fourth flow path  714 D, the manifold  170 B, the manifold  180 B and the fifth flow path  715 D and the head circulation of circulating the ink  68  is not performed in the fourth flow path  714 C, the manifold  170 A, the manifold  180 A and the fifth flow path  715 C, in the liquid-contact state. Therefore, while reducing the positive pressure that is generated in the cap  91 , the removal of air bubbles and the elimination of sedimentation of ink components are improved even in the fourth flow path  714 D, the manifold  170 B, the manifold  180 B and the fifth flow path  715 D. 
     The printer  1  includes the second bypass flow path  902  configured to connect the fourth flow path  714 D and the fifth flow path  715 D, and the CPU  11  executes the first circulation processing (S 42 ) where the bypass circulation of circulating the ink  68  is performed in the second bypass flow path  902 , which connects the fourth flow path  714 D and the fifth flow path  715 D. Therefore, the positive pressure that is generated in the cap  91  can be reduced by performing the bypass circulation together with the head circulation, as the first circulation processing (S 42 ). In addition, the printer  1  includes the second bypass flow path  802  configured to connect the fourth flow path  714 C and the fifth flow path  715 C, and the CPU  11  executes the second circulation processing (S 43 ) where the bypass circulation of circulating the ink  68  is performed in the fourth flow path  714 C, the fifth flow path  715 C and the second bypass flow path  802 . Therefore, the positive pressure that is generated in the cap  91  can be reduced by performing the bypass circulation together with the head circulation, as the second circulation processing (S 43 ). 
     In the first circulation processing (S 42 ) or the second circulation processing (S 43 ), the CPU  11  may cause the rotation speed of the pump  752 A and the rotation speed of the pump  752 B to differ from each other, thereby causing the circulation speed of the ink  68  in the head circulation and the circulation speed of the ink  68  in the circulation such as the bypass circulation other than the head circulation to differ from each other. For example, in the first circulation processing (S 42 ), the CPU  11  makes the rotation speed of the pump  752 A slower than the rotation speed of the pump  752 B, and in the second circulation processing (S 43 ), the CPU  11  makes the rotation speed of the pump  752 B slower than the rotation speed of the pump  752 A and makes the circulation speed of the ink  68  in the head circulation slower than the circulation speed of the ink  68  in the circulation such as bypass circulation other than the head circulation. In this case, as compared to a case where the circulation speed of the ink  68  in the head circulation and the circulation speed of the ink  68  in the circulation such as the bypass circulation other than the head circulation are the same, the load that is applied to the pumps  752 A and  752 B is reduced due to the slower circulation speed of the ink  68  in the head circulation, and therefore, the suction capability is not lowered. Therefore, the positive pressure that is applied to the ink  68  in the nozzles  111  is reduced, and therefore, the positive pressure that is generated in the cap  91  during the head circulation can be reduced. 
     Further, the CPU  11  intermittently drives the pump  752 A configured to perform the head circulation, in the first circulation processing (S 42 ), and intermittently drives the pump  752 B configured to perform the head circulation, in the second circulation processing (S 43 ). By intermittently driving the pump for head circulation, the pressure is not continuously applied to the ink  68  in the nozzles  111 , and the positive pressure that is generated in the cap  91  during the head circulation can be reduced. 
     In addition, in the first circulation processing (S 42 ) or the second circulation processing (S 43 ), the CPU  11  drives the pump  752 A and drives the pump  752 B to perform the head circulation and the circulation such as the bypass circulation other than the head circulation. Further, the CPU  11  ends the head circulation earlier than the circulation such as the bypass circulation other than the head circulation. In this case, by ending the head circulation earlier than the circulation other than the head circulation, the head circulation can be ended in a state where a negative pressure is generated in the cap  91 , and a period for which the positive pressure that is generated in the cap  91  is generated can be shortened. 
     Further, in the first circulation processing (S 42 ), the CPU  11  drives the pump  752 A configured to perform the head circulation, later than the pump  752 B configured to perform the circulation such as the bypass circulation other than the head circulation, thereby causing the head circulation to start later than the circulation other than head circulation. Further, in the second circulation processing (S 43 ), the CPU  11  drives the pump  752 B configured to perform the head circulation, later than the pump  752 A configured to perform the circulation such as the bypass circulation other than the head circulation, thereby causing the head circulation to start later than the circulation other than head circulation. In this case, by causing the head circulation to start later than the circulation other than the head circulation, the negative pressure can be first generated in the cap  91  by the circulation other than the head circulation, and the period for which the positive pressure is generated in the cap  91  at the time of startup of the head circulation can be shortened. 
     Note that, in the above embodiment, the bypass circulation has been described as an example of the circulation other than the head circulation. However, the circulation other than the head circulation may also be the filter circulation described above. For example, the filter circulation may also be performed instead of the bypass circulation of the first circulation processing and the second circulation processing shown in S 42  and S 43 . In the filter circulation, the ink  68  passes through the filters  75 A and  75 B or the filters  75 C and  75 D, so that a flow rate of the ink  68  becomes slow. Therefore, the load that is applied to the pumps  752 A and  752 B is reduced, and therefore, the suction capability is not reduced, and the possibility that the positive pressure will be generated in the nozzles  111  can be reduced. In addition, the filter circulation can remove deposits of the filters  75 A to  75 D. On the other hand, since the bypass circulation is closer to the nozzles  111  of the head part  110  than the filter circulation, the negative pressure that is applied to the nozzles  111  is greater, as compared to the filter circulation. Therefore, in the first circulation processing and the second circulation processing, the positive pressure that is generated in the cap  91  can be reduced by setting the bypass circulation as the circulation that is executed at the same time as the head circulation. Further, the circulation other than the head circulation may also be processing in which nothing is circulated. For example, the circulation of the ink  68  may not be performed instead of the bypass circulation in the first circulation processing and the second circulation processing shown in  FIG. 12 . In this case, since the circulation of the ink  68  is not performed, the positive pressure associated with the circulation of the ink  68  is not generated. Therefore, the positive pressure that is generated in the cap  91  can be reduced. Further, in the liquid-contact circulation, the liquid that is filled in the cap  91  is not limited to the cleaning liquid  76 A, and may also be the ink  68  ejected from the nozzles  111  of the head part  110 . 
     In addition, the ‘first predetermined time’ in S 2  and the ‘second predetermined time’ in S 7  are not limited to 6 hours. The predetermined times may be determined as appropriate by a test and the like. In addition, the other predetermined times may also be determined as appropriate, based on a test and the like. Further, the circulation processing shown in  FIG. 9  may also be executed not immediately after the end-job maintenance (S 3 ) but after a predetermined time has elapsed. Further, the CPU  11  may perform the end-job maintenance (S 3 ) at a predetermined time. For example, the CPU  11  may perform the end-job maintenance at 8:00 p.m. In the ink supply unit  700 A, the bypass flow path may be provided other than the first bypass flow path  801 A and the second bypass flow path  802 . For example, a third bypass flow path configured to connect the fourth flow path  714 C and the fifth bypass flow path  715 C may be provided between the first bypass flow path  801 A and the second bypass flow path  802 . The bypass circulation may be performed via the first bypass flow path  801 A, the fourth flow path  714 C, the fifth flow path  715 C and the third bypass flow path. The same applies to the ink supply unit  700 B. Further, in the circulation operation A, the number of times that the first circulation processing (S 42 ) and the second circulation processing (S 43 ) are performed is not limited to three times. In addition, the number of times of the filter circulation processing is not limited to three sets. An appropriate number of times may be set by a test. 
     The head circulation is not limited to the circulation of the ink  68  between the manifold  170 A of the first nozzle row W 1  and the manifold  180 A of the second nozzle row W 2  and between the manifold  170 B of the third nozzle row W 3  and the manifold  180 B of the fourth nozzle row W 4 . For example, although the plurality of manifolds  171  to  174  is provided to the flow path  62 A, one manifold may also be provided. The supply ports may be provided at the front and rear ends of one or more manifolds. For example, the flow path  62 A shown in  FIG. 4  may be connected to the supply port at the front end of one manifold, and the flow path  62 B shown in  FIG. 4  may be connected to the supply port at the rear end of the one manifold. Similarly, the flow path  62 C shown in  FIG. 4  may be connected to the supply port at the front end of another manifold, and the flow path  62 D shown in  FIG. 4  may be connected to the supply port at the rear end of the another manifold. In this case, the cap may surround only the nozzles corresponding to the two manifolds. Therefore, in one of the first circulation processing and the second circulation processing shown in S 42  and S 43 , the CPU  11  may execute the circulation processing in the manifold connected to the flow paths  62 A and  62 B, and in the other of the first circulation processing and the second circulation processing, the CPU  11  may execute the circulation processing in the manifold connected to the flow paths  62 C and  62 D. Therefore, in the above embodiment, there are four nozzle rows, but in this modified embodiment, it is sufficient to provide at least two nozzle rows. Therefore, in the present disclosure, a plurality of nozzle rows may be provided. 
     During the bypass circulation of the first circulation processing and the second circulation processing shown in S 42  and S 43 , the CPU  11  closes the electromagnetic valve  763 A and the electromagnetic valve  763 B, but may open the same. When a temperature is low, a viscosity of the ink  68  increases. As a result, the resistance of the flow path through which the ink  68  flows increases. Therefore, the load of the pumps  752 A and  752 B increases. Thus, when the electromagnetic valves  763 A,  766 A,  763 B and  766 B are closed and the bypass circulation is executed, the positive pressure may be generated without the negative pressure by the bypass circulation. Therefore, the CPU  11  can reduce a value of the positive pressure by opening the electromagnetic valve  763 A and the electromagnetic valve  763 B. That is, in the first circulation processing and the second circulation processing shown in S 42  and S 43 , the CPU  11  determines whether the temperature is equal to or lower than a predetermined temperature, based on an output from a thermometer (not shown). When the temperature is equal to or lower than the predetermined temperature, the CPU  11  closes the electromagnetic valve  763 A and the electromagnetic valve  763 B. When the temperature is higher than the predetermined temperature, the CPU  11  opens the electromagnetic valve  763 A and the electromagnetic valve  763 B. Thereby, the positive pressure that is generated in the cap  91  can be reduced.