Patent Publication Number: US-2022212477-A1

Title: Printing apparatus and non-transitory computer-readable storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of International Application No. PCT/JP2020/034862 filed on Sep. 15, 2020 which claims the benefit of priority from Japanese patent application No.  2019 -180162 filed on Sep. 30, 2019. The entire contents of the earlier applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     An inkjet printing apparatus configured to perform a circulation of sedimentary ink at predetermined time intervals is suggested. When the ink is circulated, an ink concentration is uniformly restored. However, during the circulation of ink, a meniscus of the ink nozzle of an inkjet head is affected by a pressure variation and the like, and there is a concern that normal ink ejection cannot be performed. For this reason, a cleaning operation for the inkjet head is performed after the circulation. 
     In the above printing apparatus, when the circulation operation of ink that is performed at predetermined time intervals is stopped, a purging of discharging the ink in the inkjet head from the ink nozzle is performed, and then, a nozzle surface of the inkjet head is cleaned. Since the cleaning operation such as purging is always performed after the circulation operation of ink, there is a problem that ink consumption resulting from the cleaning operation increases. 
     SUMMARY 
     An object of the present disclosure is to provide a printing apparatus and a non-transitory computer-readable storage medium storing a computer program, which enable to reduce ink consumption resulting from a cleaning operation in the printing apparatus performing a circulation of ink and the cleaning operation for an inkjet head. 
     A first aspect of the present disclosure is a printing apparatus including a reservoir, an inkjet head and a controller. The reservoir is configured to store ink. The inkjet head is connected to the reservoir via a flow path. The controller is configured to perform circulation timing determination processing, print timing determination processing and circulation processing. In the circulation timing determination processing, the controller determines whether or not to arrive at a circulation timing for performing a circulation of the ink via at least one of the flow path or the inkjet head. In the print timing determination processing, the controller determines whether or not to arrive at a print timing, in a case where it is determined that the circulation timing comes to be arrived. In the circulation processing, the controller causes the printing apparatus to perform the circulation and a subsequent cleaning operation for the inkjet head in a case where it is determined that the print timing comes to be arrived, and to perform the circulation and not perform the subsequent cleaning operation in a case where it is not determined that the print timing comes to be arrived. 
     In the printing apparatus, in the case where the controller does not determine that the print timing comes to be arrived, the controller performs the circulation and does not perform the subsequent cleaning operation. Therefore, the ink consumption resulting from the cleaning operation is reduced. 
     A second aspect of the present disclosure is a non-transitory computer-readable storage medium storing a computer program. The computer program is executed by a processor of a printing apparatus including a reservoir, an inkjet head and a processor. The reservoir is configured to store ink. The inkjet head is connected to the reservoir via a flow path. The computer program causes the processor to perform circulation timing determination processing, print timing determination processing and circulation processing. In the circulation timing determination processing, the processor determines whether or not to arrive at a circulation timing for performing a circulation of the ink via at least one of the flow path or the inkjet head. In the print timing determination processing, the processor determines whether or not to arrive at a print timing, in a case where it is determined that the circulation timing comes to be arrived. In the circulation processing, the processor causes the printing apparatus to perform the circulation and a subsequent cleaning operation for the inkjet head in a case where it is determined that the print timing comes to be arrived, and to perform the circulation and not to perform the subsequent cleaning operation in a case where it is not determined that the print timing comes to be arrived. 
     In the case where the processor does not determine that the print timing comes to be arrived, the processor performs the circulation and does not perform the subsequent cleaning operation. Therefore, the ink consumption resulting from the cleaning operation is reduced. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a printing apparatus  1 . 
         FIG. 2  is a plan view of an inside of the printing apparatus  1 . 
         FIG. 3  shows an ink supply unit  700  of white ink of the printing apparatus  1 . 
         FIG. 4  is a block diagram showing an electrical configuration of the printing apparatus  1 . 
         FIG. 5  is a flowchart of circulation processing. 
         FIG. 6  is a flowchart of print processing. 
     
    
    
     DETAILED DESCRIPTION 
     A schematic configuration of a printing apparatus  1  will be described with reference to  FIGS. 1 to 3 . 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 printing apparatus  1 , respectively. 
     As shown in  FIG. 1 , the printing apparatus  1  is an inkjet printer configured to perform printing by ejecting liquid ink onto a printing medium (not shown) such as paper and fabric such as a T-shirt. The printing apparatus  1  is configured to print a color image on the printing medium by ejecting, for example, five types of inks (white (W), black (K), yellow (Y), cyan (C), and magenta (M)) having different colors downward. 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 collectively referred to as color ink. Further, when collectively referring to white ink and color ink or when any one is not specified, they are simply referred to as ink. 
     The white ink is mainly ejected to an entire or partial printing area, as a base in printing, when a color of the printing medium is a deep color. The color ink is mainly used for printing after the white ink is ejected. The white ink is a liquid containing a component having a higher sedimentation property than a component contained in the color ink. The component having a high sedimentation property is, for example, titanium oxide. Titanium oxide is an inorganic pigment with a relatively high specific gravity. Pigment particles tend to settle in the white ink containing a component having a high sedimentation property For this reason, when performing printing by the white ink, it is necessary to maintain favorable flowability in a flow path of the white ink of the white ink by keeping the white ink in a sufficiently agitated state. 
     As shown in  FIGS. 1 and 2 , the printing apparatus  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 mounting frame unit  4 , and maintenance units  141  and  142  in a non-printing area  140 , which will be described later. 
     An operation panel  5  for operating the printing apparatus  1  is provided at a position on the right front side of the housing  2 . The operation panel  5  includes a display  50  and an operation button  52 . The operation button  52  is operated when an operator inputs instructions regarding various operations of the printing apparatus  1 . 
     The frame body  10  has a substantially rectangular frame shape, as seen from above, and is installed on an upper part of the housing  2 . The frame body  10  is configured to support the guide shaft  9  (refer to  FIG. 2 ) on the front side and the rail  7  on the 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  and extends in the right and left direction. 
     The carriage  20  is supported so as to be able to be conveyed in the right and left direction along the guide shaft  9 . As shown in FIGs. 1  and  2 , 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 . As shown in FIGs. 1  to  3 , the head units  100  and  200  have a housing  30 , respectively. As shown in  FIG. 3 , the housing  30  of the head unit  100  is configured to support a head part  110  capable of ejecting ink toward a printing medium at a lower part. A lower part of the head unit  200  is also configured in a similar manner to the head unit  100 . 
     The head part  110  includes a nozzle surface (not shown) that is a surface having a plurality of fine nozzles (not shown) capable of ejecting ink downward. The nozzle surface is a flat surface extending in the right and left and front and rear directions, and forms a bottom surface of each of the head units  100  and  200 . 
     As shown in  FIG. 1 , the drive belt  101  is bridged along the right and left direction inside the frame body  10 . The drive motor  19  is connected to the carriage  20  via a drive belt  101 . When the drive motor  19  drives the drive belt  101 , the carriage  20  is reciprocally moved in the right and left direction along the guide shaft  9 . 
     The platen drive mechanism  6  includes a pair of guide rails (not shown) and a platen (not shown). 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 so as to be movable in the front and rear direction along the pair of guide rails. The platen has a substantially rectangular plate shape where a longitudinal direction is the front and rear direction, as seen from above, and is provided below the frame body  10 . The platen is configured to hold the printing medium at an upper part. The platen drive mechanism  6  is configured to convey the printing medium in the front and rear direction (sub-scanning direction) by moving the platen in the front and rear direction by using a motor (not shown) provided at a rear end portion of the printing apparatus  1  as a drive source. Printing is performed on the printing medium by ejecting ink from the head part  110  that reciprocally moves in the right and left direction (main scanning direction). A human detecting sensor  23  configured to detect a human is provided at a front end portion of the platen drive mechanism  6 . 
     As shown in  FIG. 1 , the mounting frame unit  4  is provided on a right side of the housing  2 . The mounting frame unit  4  is supported by a substantially cuboid housing  81  where a longitudinal direction is the front and rear direction. Cartridges  311  and  312  configured to accommodate the white ink and cartridges  321  to  324  configured to accommodate the color ink can be mounted to the mounting frame unit  4 . 
     As shown in  FIGS. 1 and 2 , an area where printing by the head units  100  and  200  is performed on movement paths of the head units  100  and  200  is referred to as a printing area  130 . An area other than the printing area  130  on the movement paths of the head units  100  and  200  is referred to as a non-printing area  140 . The non-printing area  140  is an area at a left end portion of the printing apparatus  1 . The printing area  130  is an area ranging from a right side of the non-printing area  140  to a right end portion of the printing apparatus  1 . The platen is provided below the movement paths of the head units  100  and  200 , in the printing area  130 . 
     As shown in  FIG. 2 , the maintenance units  141  and  142  are provided below the movement paths of the head units  100  and  200 , respectively, in the non-printing area  140 . In the maintenance units  141  and  142 , a head cleaning such as purging is performed so as to restore ink ejection performance of the head units  100  and  200  and to ensure a printing quality of the printing apparatus  1 . The purging is an operation where the head units  100  and  200  discharge inks containing foreign matters, air bubbles or the like from the head part  110  and the like. 
     As shown in  FIG. 2 , the maintenance unit  141  includes a cap  67  and the like. The cap  67  is provided on a left side of the maintenance unit  141 , is made of a synthetic resin such as silicon rubber, and has a bottom wall  671  and a peripheral wall  672 . The cap  67  is arranged inside a cap support part  69  configured to support the cap  67 . The cap support part  69  is configured to move in an upper and lower direction by drive of a motor, a gear and the like (not shown). A cap lip  676  of the peripheral wall  672  of the cap  67  having moved upward is in close contact with the periphery of a nozzle arrangement area of a first nozzle row W 1  (refer to  FIG. 3 ), a second nozzle row W 2  (refer to  FIG. 3 ), a third nozzle row (not shown) and a fourth nozzle row (not shown) in the head unit  100  having moved to the non-printing area  140 . Thereby, the first nozzle row W 1  to the fourth nozzle row are covered. In descriptions below, positions of the cap  67  and the cap support part  69  at the time when the cap  67  is in close contact with the periphery of the nozzle arrangement area are referred to as a covering position. In addition, positions of the cap  67  and the cap support part  69  at the time when the cap  67  is not in close contact with the periphery of the nozzle arrangement area are referred to as a cap separation position. The cap  67  is connected to a suction pump  199  (refer to  FIG. 4 ) by a tube (not shown). When the suction pump  199  is driven, an inside of the cap  67  surrounded by the bottom wall  671  and the peripheral wall  672  becomes a negative pressure. When the cap  67  and the cap support part  69  are at the covering position, the suction pump  199  makes the inside of the cap  67  a negative pressure, so that the purging is performed. Further, the maintenance units  141  and  142  are provided with wiper blades  35  and  35 . The wiper blade  35  is used for a wipe, which will be described later. 
     Ink Supply Unit  700   
     In the below, an ink supply unit  700  configured to supply the white ink to the head unit  100  is described with reference to  FIG. 3 . The ink supply unit  700  is configured to supply the white ink to the head part  110 , and is a part where the white ink circulates. The ink supply unit  700  includes a first supply flow path  711 , a second supply flow path  712 , a third supply flow path  713 , a fourth supply flow path  714 , a fifth supply flow path  715 , a first circulation flow path  721 , and a first bypass flow path  801 , a second bypass flow path  802 A, a second bypass flow path  802 B, a sub-pouch  8 , a pump  752 , opening/closing valves  31 ,  763  and  766 , and filters  771 ,  772  and  773 . In the below, the entire second bypass flow path  802 A and second bypass flow path  802 B are ‘second bypass flow path  802 ’. 
     The head part  110  includes a first nozzle row W 1  and a second nozzle row W 2  for ejecting white ink, and a flow path  670 . The flow path  670  has one end connected to the fourth supply flow path  714 , and the other end connected to the fifth supply flow path  715 . In addition, the flow path  670  is configured to connect the first nozzle row W 1  and the second nozzle row W 2 . The head unit  100  includes another head part having a third nozzle row and a fourth nozzle row (not shown) having a similar configuration to that described above. A flow path for supplying white ink to the third nozzle row and the fourth nozzle row has a similar configuration to the flow path for supplying white ink to the first nozzle row W 1  and the second nozzle row W 2 . Therefore, in descriptions below, the head part  110  including the first nozzle row W 1  and the second nozzle row W 2  is described, and the descriptions of the head part including the third nozzle row and the fourth nozzle row are omitted. 
     As an example, the sub-pouch  8  has a flexible bag shape and is configured to accommodate the white ink supplied from the white ink cartridges  311  and  312 . In addition, the sub-pouch  8  is configured to supply the white ink to the head part  110 . The head part  110  is configured to eject the white ink supplied from the sub-pouch  8  to perform printing on a printing target. 
     The first bypass flow path  801 , the second bypass flow path  802 , the first supply flow path  711 , the second supply flow path  712 , the third supply flow path  713 , the fourth supply flow path  714 , the fifth supply flow path  715 , and the first circulation flow path  721  are formed by, for example, hollow tubes. The first supply flow path  711  is a flow path connected to the white ink cartridges  311  and  312  (refer to  FIG. 1 ) and the sub-pouch  8  and configured to supply the white ink from the white ink cartridges  311  and  312  to the sub-pouch  8  via a degassing module (not shown). 
     The second supply flow path  712  is connected to the sub- pouch  8 , the fourth supply flow path  714  and the fifth supply flow path  715 . The second supply flow path  712  is a flow path configured to supply the white ink from the sub-pouch  8  to the head part  110  via the fourth supply flow path  714  and the fifth supply flow path  715 . The third supply flow path  713  is a flow path connected to the sub-pouch  8  and configured to supply the white ink from the sub-pouch  8  to the head part including the third nozzle row and the fourth nozzle row (not shown). The fourth supply flow path  714  is a flow path connected to the second supply flow path  712  and the first nozzle row W 1  of the head part  110  and configured to supply the white ink to the first nozzle row W 1 . The fifth supply flow path  715  is a flow path connected to the second supply flow path  712  and the second nozzle row W 2  of the head part  110  and configured to supply the white ink to the second nozzle row W 2 . 
     The first circulation flow path  721  is a flow path connected to the first supply flow path  711  or the white ink cartridges  311  and  312  and the sub-pouch  8  and configured to circulate the white ink from the sub-pouch  8  to the first supply flow path  711  or the white ink cartridges  311  and  312 . The fourth supply flow path  714  has the opening/closing valve  763  and the filter  771 . The opening/closing valve  763  is controlled by the CPU  11  to open/close the fourth supply flow path  714 . The filter  773  is configured to remove foreign matters contained in the white ink flowing through the fourth supply flow path  714 . The fifth supply flow path  715  has the opening/closing valve  766  and the filter  773 . The opening/closing valve  766  is controlled by the CPU  11  to open/close the fifth supply flow path  715 . The filter  773  is configured to remove foreign matters contained in the white ink flowing through the fifth supply flow path  715 . 
     In the ink supply unit  700  shown in  FIG. 3 , the first bypass flow path  801  is configured to connect the fourth supply flow path  714  and the fifth supply flow path  715 . The fourth supply flow path  714  has a first connection portion  795  between the filter  771  and the first nozzle row W 1 . The first connection portion  795  is configured to connect the fourth supply flow path  714  and the first bypass flow path  801 . In addition, the fifth supply flow path  715  has a second connection portion  796  between the filter  773  and the second nozzle row W 2 . The second connection portion  796  is configured to connect the fifth supply flow path  715  and the first bypass flow path  801 . Further, the first bypass flow path  801  includes the filter  772  and the pump  752  from the first connection portion  795  toward the second connection portion  796 . The filter  772  is configured to remove foreign matters contained in the white ink flowing through the first bypass flow path  801 . Note that, a flow path of the fourth supply flow path  714  between the first connection portion  795  and the head part  110  is referred to as a fourth supply flow path  714 A. In addition, a flow path of the fifth supply flow path  715  between the second connection portion  796  and the head part  110  is referred to as a fifth supply flow path  715 A. The fifth supply flow path  715 A is configured to function as a reflux flow path for the white ink during circulation processing of the white ink, which will be described later. 
     In the printing apparatus  1  shown in  FIG. 3 , on the head part  110 -side, the fourth supply flow path  714 A and the fifth supply flow path  715 A are connected via the second bypass flow path  802 . The second bypass flow path  802  includes an opening/closing valve  31 . A flow path of the second bypass flow path  802  between the opening/closing valve  31  and the fourth supply flow path  714 A is the second bypass flow path  802 A. A flow path between the opening/closing valve  31  and the fifth supply flow path  715 A is the second bypass flow path  802 B. Note that, the description of an ink supply unit configured to supply the color ink to the head unit  200  is omitted. The ink supply unit configured to supply the color ink to the head unit  200  may have a similar structure to the ink supply unit  700 , or may not have the first bypass flow path  801  and the second bypass flow path  802  and may not have a structure where the color ink circulates. 
     Electrical Configuration of Printing Apparatus  1   
     As shown in  FIG. 4 , the printing apparatus  1  includes the CPU  11  responsible for control of the printing apparatus  1 . The CPU  11  electrically connects a ROM  12 , a RAM  13 , a head drive unit  14 , a main scanning drive unit  15 , a sub-scanning drive unit  16 , a cap drive unit  18 , an operation panel  5 , a pump drive unit  900 , a valve drive unit  780 , a human detecting sensor  23 , a cartridge sensor, a clock  26  and a storage device  27  via a bus  55 . 
     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 printing apparatus  1 . The RAM  13  is configured to temporarily store a variety of data, a previous circulation time, a previous printing time, print data, a flag and the like, which are used in the control program. The head drive unit  14  is electrically connected to the head units  100  and  200  configured to eject inks, and is configured to drive a piezoelectric element provided in each ejection channel of the head units  100  and  200  (refer to  FIG. 1 ), thereby ejecting inks from the first nozzle row W 1  (refer to  FIG. 3 ), the second nozzle row W 2  (refer to  FIG. 3 ), the third nozzle row (not shown), the fourth nozzle row, and the like. 
     The main scanning drive unit  15  includes a drive motor  19  (refer to  FIG. 1 ) 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 (not shown) 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  69  in the upper and lower direction, thereby moving the cap  67  in the upper and lower direction. Driving the cap drive unit  18  moves the cap support part  69  of the maintenance unit  141  and the cap support part  69  of the maintenance unit  142  in the upper and lower direction at the same time. The pump drive unit  21  is configured to drive the pump  752  and the suction pump  199 . The operation panel  5  includes a display  50  and an operation button  52 . An input from the operation button  52  is input to the CPU  11 . 
     The human detecting sensor  23  is configured to detect a human, for example. An output from the human detecting sensor  23  is input to the CPU  11 , and the CPU  11  is configured to determine whether or not a human is present in front of the printing apparatus  1 , based on the input from the human detecting sensor  23 . The cartridge sensors  24  are each provided in the mounting frame unit  4 , and configured to detect the mounting of the cartridges  311  to  324 . The valve drive unit  780  is configured to control the opening/closing valves  766 ,  763  and  31 , which are opening/closing valves. The clock  26  is configured to generate a clock signal for measuring a time. The storage device  27  is a writable non-volatile storage device such as an HDD or a flash memory. 
     Circulation Processing of Ink 
     Circulation processing of ink includes ‘ink circulation processing without passing through the head part  110 ’ and ‘ink circulation processing passing through the head part  110 ’. First, the ‘ink circulation processing without passing through the head part  110 ’ is described with reference to  FIG. 3 . The CPU  11  closes the opening/closing valve  766  and the opening/closing valve  763  and opens the opening/closing valve  31 . The CPU  11  then drives the pump  752 . The ink flows from the pump  752  in a direction of an arrow  401 , and flows through the fourth supply flow path  714 A in a direction of an arrow  403 . 
     The flow path  670  of the head part  110  has a narrower flow path than the second bypass flow paths  802 A and  802 B, has a complicated structure, and makes it difficult for ink to flow. Therefore, a flow path resistance of the flow path  670  is larger than the second bypass flow paths  802 A and  802 B. Therefore, the ink flows through the second bypass flow path  802 A in a direction of an arrow  404  rather than through the flow path  670 . Subsequently, the ink passes through the opening/closing valve  31  in a direction of an arrow  405  and flows through the second bypass flow path  802 B in a direction of an arrow  406 . The ink then flows back through the fifth supply flow path  715 A in a direction of an arrow  407 , and flows into the first bypass flow path  801 . The ink flowing into the first bypass flow path  801  flows from the pump  752  in the direction of the arrow  401  and circulates in a similar manner to that described above. The CPU  11  stops the pump  752  after performing the circulation processing of ink for a first predetermined time, which will be described later. When printing print data, the CPU  11  closes the opening/closing valve  31  and opens the opening/closing valve  766  and the opening/closing valve  763 . 
     Ink Circulation Processing Passing Through Head Part  110   
     Next, the circulation processing passing through the head part  110  is described. First, the CPU  11  closes the opening/closing valve  31 , the opening/closing valve  766 , and the opening/closing valve  763 . The CPU  11  then drives the pump  752 . 
     The ink flows from the pump  752  in the direction of the arrow  401 , and flows through the fourth supply flow path  714 A in the direction of the arrow  403 . Since the opening/closing valve  31  is closed, the ink flows through the flow path  670  of the head part  110  in the directions of the arrows  411 ,  412  and  413 . The ink then flows back through the fifth supply flow path  715 A in the direction of the arrow  407 , and flows into the first bypass flow path  801 . The ink flowing into the first bypass flow path  801  flows from the pump  752  in the direction of the arrow  401  and circulates in a similar manner to that described above. The CPU  11  stops the pump  752  after performing the ink circulation processing for the first predetermined time. 
     Details of Control on Circulation Processing of Ink 
     The details of control on the circulation processing by the CPU  11  of the printing apparatus  1  are described with reference to  FIG. 5 . In descriptions below, the circulation processing of ink is also simply referred to as ‘circulation’. The circulation was performed previously and a time at which the circulation ended is referred to as ‘previous circulation time’. As an example, when the circulation ends, the CPU  11  acquires a time at that time point from the built-in clock  26 . The CPU  11  stores the acquired time in the storage device  27 , as the previous circulation time. In addition, the printing was performed previously and a time at which the printing ended is referred to as ‘previous printing time’. When the printing ends, the CPU  11  acquires a time at that time point from the built-in clock  26 . The CPU  11  stores the acquired time in the storage device  27 , as the previous printing time. 
     The CPU  11  operates based on the control program stored in the ROM  12 , thereby controlling the printing apparatus  1  to perform circulation processing shown in  FIG. 5 . First, the CPU  11  acquires the previous circulation time from the RAM  13  ( 51 ). Next, the CPU  11  acquires a current time from the clock  26  (hereinafter referred to as ‘current time’) (S 2 ). Next, the CPU  11  determines whether or not to arrive at a circulation timing for performing circulation (S 3 ). As an example, the CPU  11  compares the previous circulation time acquired in the processing of Si and the current time acquired in the processing of S 2 , and when the current time exceeds a second predetermined time from the previous circulation time, the CPU  11  determines that the circulation timing has been arrived (S 3 : YES). An example of the second predetermined time is 7 hours. In the case where it is not determined that the circulation timing has been arrived (S 3 : NO), the CPU  11  returns the processing to S 1 . 
     In the case where it is determined that the circulation timing has been arrived (S 3 : YES), the CPU  11  performs a circulation of the ink. The CPU  11  performs at least one of ‘ink circulation processing without passing through the head part  110 ’ and ‘ink circulation processing passing through the head part  110 ’. The CPU  11  may also perform both the processing. After performing the circulation, the CPU  11  determines whether the circulation is completed (S 5 ). In the case where it is not determined that the circulation is completed (S 5 : NO), the CPU  11  returns the processing to S 5 . In the case where the circulation of ink is performed for the first predetermined time, for example,  10  minutes, and the circulation is over, the CPU  11  determines that the circulation is completed (S 5 : YES). Next, the CPU  11  acquires a current time from the clock  26  (S 6 ). The current time acquired in the processing of S 6  is a time at which this circulation is completed. Next, the CPU  11  stores the current time acquired in the processing of S 6  in the storage device  27 , as the previous circulation time (S 7 ). 
     Next, the CPU  11  acquires the previous printing time from the storage device  27  (S 8 ). The previous printing time is a time at which printing is completed in print processing, which will be described later, and is a time stored in the storage device  27  as the previous printing time. 
     Next, the CPU  11  determines whether or not to arrive at a print timing (S 9 ). Whether or not to arrive at the print timing is determined based on whether a possibility that printing will be performed from now on is high. As an example, the CPU  11  determines that the print timing has been arrived, in the case where the previous printing time acquired in S 8  is within a preset third predetermined time from the previous circulation time stored in S 7 . That is, in the case where printing has been performed within the third predetermined time from the time at which the circulation (S 4 ) is completed, it is determined that the print timing has been arrived. An example of the third predetermined time is 30 minutes. This is because in the case where the printing has been performed within 30 minutes, a possibility that next printing will be performed is high. 
     Next, in the case where it is determined that the print timing has been arrived (S 9 : YES), the CPU  11  performs head cleaning (S 10 ). An example of the head cleaning is purging. In the case where the CPU  11  determines that the print timing has been arrived, a possibility that next printing will be performed is high. Therefore, menisci of the first nozzle row W 1  (refer to  FIG. 3 ), the second nozzle row W 2  (refer to  FIG. 3 ), the third nozzle row (not shown), and the fourth nozzle row (not shown) are aligned by the head cleaning, so that it is possible to increase a possibility that normal ink ejection from the nozzles will be performed during printing. In the case where the head cleaning is performed, the CPU  11  stores an ON status of a head cleaning execution flag in the storage device  27  ( 511 ). 
     In the case where the CPU  11  does not determine that the print timing has been arrived (S 9 : NO), the CPU  11  does not perform head cleaning, and the CPU  11  stores an OFF status of the head cleaning execution flag in the storage device  27  (S 12 ) and proceeds to the processing to S 1 . Since a possibility that next printing will be performed is not high, the head cleaning is not performed. Therefore, the ink consumption resulting from the head cleaning is reduced. 
     Subsequently, details of the print processing by the CPU  11  of the printing apparatus  1  are described with reference to refer to 6. The CPU  11  operates based on the control program stored in the ROM  12 , thereby controlling the printing apparatus  1  to perform print processing. First, the CPU  11  determines whether a print instruction is received (S 21 ). As an example, in the case where an input of a print instruction is received from the operation panel  5 , or in the case where an input of a print instruction is received from a terminal device such as a personal computer (not shown) connected to the printing apparatus  1 , the CPU  11  determines that the print instruction is received (S 21 : YES). In the case where it is not determined that the print instruction is received (S 21 : NO), the CPU  11  returns the processing to S 1 . 
     In the case where it is determined that the print instruction is received (S 21 : YES), the CPU  11  determines whether the head cleaning has been performed from the precious circulation to the present time (S 22 ). As an example, the CPU  11  does not determine that the head cleaning has been performed from the previous circulation to the present time, in the case where the OFF status of the head cleaning execution flag is stored in the storage device  27  (S 22 : NO). In the case where the CPU  11  does not determine that the head cleaning has been performed from the previous circulation to the present time (S 22 : NO), the CPU performs the head cleaning (S 23 ). The menisci of the first nozzle row W 1  to the fourth nozzle row (not shown) are aligned by the head cleaning, so that a possibility that normal ink ejection from the first nozzle row W 1  to the fourth nozzle row (not shown) will be performed during next printing increases. 
     Next, the CPU  11  performs printing (S 24 ), and acquires a current time at which printing is completed from the clock  26  (S 25 ). Next, The CPU  11  stores the current time acquired in S 25  in the storage device  27 , as the previous printing time (S 26 ). Note that, in the case where the ON status of the head cleaning execution flag is stored in the storage device  27 , the CPU  11  determines that the head cleaning has been performed from the previous circulation to the present time (S 22 : YES), performs printing (S 24 ) without performing the head cleaning (S 23 ), and performs processing of S 25  and S 26 . After the processing of S 26 , the CPU  11  returns the processing to S 21 . 
     Effects of Embodiment 
     In the present embodiment, the CPU  11  of the printing apparatus  1  performs the circulation timing determination step (S 3 ) of determining whether or not to arrive at the circulation timing for performing at least of the circulation of ink without passing through the head part or the circulation of the ink passing through the head part. In the case where it is determined that the circulation timing has been arrived (S 3 : YES), the CPU  11  performs circulation (S 4 ). Next, the CPU  11  performs the print timing determination step (S 9 ), and in the case where it is determined that the print timing has been arrived (S 9 : YES), the CPU  11  performs cleaning for the head part (S 10 ). In the case where it is not determined that the print timing has been arrived (S 9 : NO), the CPU  11  does not perform the head cleaning. Therefore, in the case where it is not determined that the print timing has been arrived (S 9 : NO), the CPU  11  does not perform the head cleaning after the circulation (S 4 ). Therefore, the ink consumption resulting from the head cleaning is reduced. That is, in the case where it is determined in the determination processing of S 21  that the print instruction has been received (S 21 : YES), and in the case where it is determined in the determination processing of S 22  that the head cleaning has been performed (S 22 : YES), the CPU  11  can start printing (S 24 ) without performing the head cleaning (S 23 ). Therefore, printing can be started without waiting for the head cleaning (S 23 ). 
     The CPU  11  performs the print instruction determination step (S 21 ) of determining whether or not to arrive at the print instruction, and the print step (S 24 ) of performing the head cleaning (S 23 ) and performing printing in the case where it is determined that the print instruction has been received (S 21 : YES). Therefore, even though the head cleaning is not performed after the circulation, the CPU  11  performs the head cleaning (S 23 ) in the case where it is determined that the print instruction has been received (S 21 : YES). Therefore, a possibility that normal ink ejection from the head part will be performed during printing increases. 
     In the print processing, in the case where the head cleaning has not been performed from the previous circulation to the present time (S 22 : NO), the CPU  11  performs the head cleaning (S 23 ) and performs printing (S 24 ). Therefore, even though the head cleaning has not been performed from the previous circulation of the ink to the present time (S 22 : NO), the CPU  11  performs the head cleaning (S 23 ) and then performs printing (S 24 ). Therefore, a possibility that normal ink ejection from the head part will be performed during printing increases. 
     In the print timing determination step (S 9 ), in the case where printing has been performed within the third predetermined time, the CPU  11  determines that the print timing has been arrived (S 29 : YES) because there is a high possibility that printing will be performed again. Therefore, the CPU  11  can more accurately determine the print timing, based on a time at which printing has been performed. 
     The present disclosure is not limited to the above embodiment, and can be variously changed. For example, the CPU  11  of the printing apparatus  1  may determine that the print timing has been arrived (S 9 : YES) in the print timing determination step (S 9 ), in the case where an operation is received on the operation panel  5  within a preset fourth predetermined time. In the case where the operation is received on the operation panel  5  within the fourth predetermined time, there is a high possibility that printing will be performed, so that the CPU  11  determines that the print timing has been arrived. Therefore, the CPU  11  can more accurately determine the print timing, based on a time at which the operation is received on the operation panel  5 . Therefore, in the case where the operation is received on the operation panel  5  before the fourth predetermined time, the CPU  11  performs the head cleaning (S 10 ) after the circulation (S 4 ). The CPU  11  performs only the circulation (S 4 ), in the case where the operation is not received on the operation panel  5  before the fourth predetermined time. 
     In the case where the storage device  27  stores an operation schedule for operating the printing apparatus  1  registered by the operator, the CPU  11  may determine in the print timing determination step (S 9 ) that the print timing has been arrived (S 9 : YES), in the case where it is determined that it is within a period of the operation schedule. An example of the operation schedule is circulation execution at 7:30 am, printing start at 8:00 am, circulation execution at 12:00 am, printing end at 6:00 pm, and the like. Therefore, in the case of this operation schedule, the CPU  11  determines that 7:30 am to 6:00 pm is within the operation schedule. In this case, the CPU  11  can more accurately determine the print timing, based on the operation schedule. Therefore, the CPU  11  performs the head cleaning (S 10 ) after the circulation (S 4 ), in the case where it is determined that it is within the period of the operation schedule (S 10 ). The CPU  11  performs only the circulation (S 4 ), in the case where it is not determined that it is within the period of the operation schedule. 
     In the print timing determination step (S 9 ), the CPU  11  may determine that the print timing has been arrived, in the case where received print data has not been processed. The case where the print data has not been processed is, for example, a case where the printing data stored in the RAM  13  is not printed by a number of print instructions instructed from the operation panel  5  or the terminal device connected to the printing apparatus  1 . In this case, the CPU  11  may determine that the print timing has been arrived (S 9 : YES). In the case where the print data has not been processed, there is a high possibility that printing will be performed. Therefore, the CPU  11  can more accurately determine the print timing, based on a processing status of the print data. Therefore, the CPU  11  performs the head cleaning (S 10 ) after the circulation (S 4 ), in the case where it is determined that the received print data has not been processed. In the case where it is determined that the print data has been printed by the number or more of print instructions, the CPU  11  only performs the circulation (S 4 ). 
     In the print timing determination step (S 9 ), the CPU  11  may determine that the print timing has been arrived, in the case where the human detector configured to detect a human detects a human. For example, in the case where a human detecting signal is input from the human detecting sensor  23 , it is determined that the print timing has been arrived (S 9 : YES). In the case where a human who operates the printing apparatus  1  is present, there is a high possibility that printing will be performed. Therefore, the CPU  11  can more accurately determine the print timing, based on a detection result of the human detecting sensor  23 . Note that, in the case where the human detector such as a camera of the terminal device connected to the printing apparatus  1  detects a human, the CPU  11  may receive a human detecting signal from the terminal device and determine that the print timing has been arrived. Therefore, in the case where the human detector detects a human (S 9 : YES), the CPU  11  performs the head cleaning (S 10 ) after the circulation (S 4 ). The CPU  11  performs only the circulation (S 4 ) in the case where the human detector does not detect a human (S 9 : NO). Note that, a position where the human detecting sensor  23  is provided is not limited to the front part of the printing apparatus  1 , and may be the upper surface of the operation panel  5 , the upper surface or the side surface of the housing  2 , or the like. 
     Further, the CPU  11  may store a printing execution history of the printing apparatus  1  in the storage device  27 , analyze the printing execution history by using an AI or the like, and estimate an operation pattern of a standard printing of the printing apparatus  1 . As an example, the CPU  11  estimates that printing is performed only from 8:00 am to 8:00 pm, printing is not performed on Sunday, and the like. The CPU  11  determines that the print timing has been arrived (S 9 : YES) when it is within a time zone during which printing is performed. In addition, the CPU  11  does not determine that the print timing has been arrived (S 9 : NO) when it is outside the time zone during which printing is performed. Therefore, the CPU  11  performs the head cleaning (S 10 ) after the circulation (S 4 ), in the case where it is determined that it is within the time zone during which printing is performed. The CPU  11  performs only the circulation (S 4 ), in the case where it is determined that it is outside the time zone during which printing is performed. 
     Further, the CPU  11  may determine that the print timing has been arrived (S 9 : YES), even in the case where the operation button  52  of the operation panel  5  is operated within the first predetermined time before the previous circulation time stored in the processing of S 7  and an operation including a print instruction is performed after the circulation (S 4 ) is over. A time at which the operation including a print instruction is performed is stored in the storage device  27 . This is because in the case where the operation button  52  of the operation panel  5  is operated within the first predetermined time before the previous circulation time and the operation including the print instruction is performed, there is a high possibility that printing will be performed again. An example of the first predetermined time is 30 minutes. 
     Note that, the head cleaning is not limited to purging, and may be wiping of the nozzle surfaces (not shown) of the first nozzle row W 1  (refer to  FIG. 3 ) and the second nozzle row W 2  (refer to  FIG. 3 ) by the wiper blade  35  (refer to  FIG. 2 ), flushing of ink from the first nozzle row W 1  and the second nozzle row W 2 , or the like. Further, as the ink circulation processing without passing through the head part  110 , the CPU  11  may perform the circulation of ink in the sub-pouch  8 , the first circulation flow path  721 , the first supply flow path  711 , and the bypass flow path (not shown). Note that, the example of the second predetermined time in the case where it is determined that the circulation timing has been arrived is not limited to 7 hours. For example, it may be set by the operator, such as 6 hours. In addition, the example of the third predetermined time in the case where it is determined whether or not to arrive at the print timing (S 9 ) is not limited to 30 minutes. A means for changing the third predetermined time may be provided. As an example, the CPU  11  may change the predetermined time from 30 minutes by an input of a time from the operation panel  5 . Further, in the determination processing of S 9 , the CPU  11  may determine that the print timing has been arrived (S 9 : YES), in the case where it is detected that a maintenance at the start of an operation has been performed within a fifth predetermined time before the execution of the circulation. An example of the fifth predetermined time is 30 minutes. An example of the maintenance at the start of an operation is detachment/attachment of the cartridge for stirring, purging with a large suction force, and the like. This is because there is a high possibility that printing will be performed, after the maintenance at the start of an operation. The detection of the maintenance at the start of an operation may be performed in such a manner that the CPU  11  detects an input of completion of the maintenance at the start of an operation from the operation panel  5 . The CPU  11  acquires a time at that time from the clock  26  and stores the same in the storage device  27 . 
     Further, the previous circulation time, the previous printing time, the head cleaning execution flag, and the like may be stored in the RAM  13  in the case where a power supply of the printing apparatus  1  is not turned off. Note that, in the determination of S 3  shown in  FIG. 5 , a circulation time may be set in advance, and the CPU  11  may determine that the circulation timing has been arrived, when the current time acquired in S 2  reaches the circulation time. Further, the reservoir of ink is not limited to the cartridge, and may be an ink tank or the like. 
     Further, the ink circulation processing passing through the head part  110  may be performed inside the head part  110 . That is, a circulation flow path having a drive unit such as a pump or an actuator is provided in the head part  110 . The CPU  11  may perform an ink circulation processing passing through the circulation flow path inside the head part  110 .