Patent Publication Number: US-2013235128-A1

Title: Ink Jet Printer

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of prior U.S. application Ser. No. 12/474,993, filed May 29, 2009, the entire contents of which are incorporated herein by reference thereto. 
    
    
     BACKGROUND 
     1. Field 
     In the present specification, an ink jet printer comprising an ink jet head is taught. In particular, in the present specification, a new mechanism for opening and closing an exhaust valve of the ink jet head is taught. 
     2. Description of the Related Art 
     Ink jet printers are taught in U.S. Pat. No. 7,258,420, US Patent Application Publication No. 2005/195246 (Published Patent Application of U.S. Pat. No. 7,452,065), etc. These ink jet printers comprise an ink jet head provided with an exhaust valve, a cam member provided with a cam groove, and a guide member that is guided along the cam groove in the case where the cam member rotates. In the case where the guide member is present in a predetermined position within the cam groove, the guide member makes contact with the exhaust valve, and the exhaust valve is in an opened state. In this state, gas within the ink jet head (for example, bubbles within the ink) can be discharged. 
     BRIEF SUMMARY 
     One of the features taught in the present specification is an ink jet printer. This ink jet printer may comprise an ink jet head, a cam member, a cam follower, and a valve operation mechanism. The ink jet head may comprise an ink chamber, an exhaust passage communicating with the ink chamber, and an exhaust valve disposed at the exhaust passage. The cam member may comprise a cam groove. The cam member may be configured to rotate. The cam groove may comprise a first groove, a second groove, and a third groove. The second groove and the third groove may branch from one end of the first groove. The cam follower may be configured to be guided along the cam groove. The valve operation mechanism may be coupled to the cam follower. In a state where the cam follower is present in a predetermined position in the third groove, the valve operation mechanism may make contact with the exhaust valve, and the exhaust valve may be in an opened state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic configuration of an ink jet printer. 
         FIG. 2  shows a part of an interior of the ink jet printer. 
         FIG. 3  shows a schematic configuration of each element related to maintenance. 
         FIG. 4  shows a state where a cap has risen from the state of  FIG. 3 . 
         FIG. 5  shows a state where a slider has moved toward the left from the state of  FIG. 4 . 
         FIG. 6  shows a plan view of a cam member. 
         FIG. 7  shows a plan view of a rotation member. 
         FIG. 8  shows a block diagram of a controller and each element connected thereto. 
         FIG. 9  shows how the state of the cam member, etc. changes in the case where the cam member makes one revolution in a state where a stopper is present in an upper position. 
         FIG. 10  shows how the state of the cam member, etc. changes in the case where the cam member makes one revolution in a state where the stopper is present in a lower position. 
         FIG. 11  shows a flowchart of processes executed by the controller. 
         FIG. 12  shows a continuation of the flowchart of  FIG. 11 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An ink jet printer of the present embodiment will be described with reference to the figures. Moreover, in the present embodiment, a part of the description of the configuration of the ink jet printer will be omitted. A more detailed description of the configuration of ink jet printers is taught in, for example, U.S. Pat. No. 7,258,420, US Patent Application Publication No. 2005/195246 (Published Patent Application of U.S. Pat. No. 7,452,065), US Patent Application Publication No. 2007/296754, etc. The contents of these documents are incorporated by reference into the present specification. 
     (Overall Configuration of Ink Jet Printer) 
       FIG. 1  shows an ink jet printer  2  of the present embodiment. The ink jet printer  2  comprises a casing  4 , a first tray  6 , a second tray  26 , and a feed path  12 . The casing  4  houses the elements  6 ,  12 ,  26 , etc. The first tray  6  houses a print medium  8  that is yet to be printed. The print medium  8  is fed along the feed path  12  to the second tray  26 . An image is formed (printed) on the print medium  8  during the feeding process. The second tray  26  houses a print medium  28  that has been printed. 
     The ink jet printer  2  further comprises a feed roller  10 , a pair of rollers  14  and  16 , and a pair of rollers  22  and  24 . The feed roller  10  sends the print medium  8  within the first tray  6  toward the pair of rollers  14  and  16  (toward the upper right in  FIG. 1 ). The print medium  8  thereby enters between the pair of rollers  14  and  16 . The pair of rollers  14  and  16  feed the print medium  8  toward the pair of rollers  22  and  24  (toward the left in  FIG. 1 ). As a result, the print medium  8  enters between the pair of rollers  22  and  24 . An image is formed on the print medium  8  between the pair of rollers  14  and  16  and the pair of rollers  22  and  24 , thus forming the printed print medium  28 . The pair of rollers  22  and  24  feed the printed print medium  28  to the second tray  26 . 
     The ink jet printer  2  further comprises a platen  20  and an ink jet head  30 . The platen  20  and the ink jet head  30  are disposed between the pair of rollers  14  and  16  and the pair of rollers  22  and  24 . The platen  20  is disposed below the ink jet head  30 . The print medium  8  passes between the platen  20  and the ink jet head  30 . At this juncture, the ink jet head  30  forms an image on the print medium  8 . Note that the configuration of the ink jet head  30  will be described later in detail. 
     The ink jet printer  2  further comprises a cartridge housing part  46  and an ink fetching path  44 . The cartridge housing part  46  houses an ink cartridge  50 . The ink cartridge  50  houses ink. The ink cartridge  50  is connected with one end of the ink fetching path  44 . The other end of the ink fetching path  44  communicates with the ink jet head  30 . The ink within the ink cartridge  50  is sent to the ink jet head  30  via the ink fetching path  44 . Moreover, although only one ink cartridge  50  is shown in  FIG. 1 , the ink jet printer  2  may be provided with a plurality of ink cartridges (that is, a plurality of colors of ink may be utilized). 
     Moreover, the ink jet printer  2  further comprises a cartridge sensor  48  and a controller  60 . The cartridge sensor  48  is connected to the controller  60 . In a state where the ink cartridge  50  is housed in the cartridge housing part  46 , the cartridge sensor  48  sends a first signal (for example, a high signal) to the controller  60 . Alternatively, in a state where the ink cartridge  50  is not housed in the cartridge housing part  46 , the cartridge sensor  48  sends a second signal (for example, a low signal) to the controller  60 . 
     (Configuration of Ink Jet Head) 
     The ink jet head  30  comprises an ink chamber  32 , an exhaust passage  34 , an ink passage  36 , a nozzle surface  40 , etc. The ink chamber  32  communicates with the ink fetching path  44 . Ink within the ink cartridge  50  is sent to the ink chamber  32  via the ink fetching path  44 . One end of the exhaust passage  34  communicates with the ink chamber  32 . The other end side of the exhaust passage  34  is not shown in  FIG. 1 . The configuration of the other end side of the exhaust passage  34  will be described in detail later. One end of the ink passage  36  communicates with the ink chamber  32 . A nozzle  42  (not shown in  FIG. 1 , but shown in  FIG. 3 ) is formed at the other end of the ink passage  36 . A plurality of nozzles  42  is formed in the nozzle surface  40 . 
     (Configuration of Carriage) 
       FIG. 2  shows the configuration of the interior of the ink jet printer  2 . The ink jet printer  2  further comprises a carriage  70 , a belt  72 , a pair of pulleys  74  and  76 , and a carriage motor  78 . The ink jet head  30  is mounted on the carriage  70 . The carriage  70  is connected to the belt  72 . The belt  72  is suspended between the pair of pulleys  74  and  76 . The carriage motor  78  is connected to the pulley  76 . 
     When the carriage motor  78  is driven, the pulley  76  rotates. When the pulley  76  rotates, the belt  72  and the pulley  74  rotate. The carriage  70  connected to the belt  72  thereby moves. The carriage  70  moves in the direction in which the belt  72  is suspended between the pair of pulleys  74  and  76  (a direction perpendicular to the plane of the paper in  FIG. 1 ). The movement of the carriage  70  moves the ink jet head  30 . The range shown by the arrow P 2  is the range in which the platen  20  is present. That is, the range shown by the arrow P 2  is the range through which the print medium  8  passes. In a state where the carriage  70  is present in the range shown by the arrow P 2 , the ink jet head  30  is facing the print medium  8  (see  FIG. 1 ). In this state, the ink jet head  30  discharges ink from the nozzles  42 , and is capable of forming an image on the print medium  8 . By contrast, the range shown by the arrow P 1  is a range through which the print medium  8  does not pass. In a state where the carriage  70  is present in the range shown by the arrow P 1 , maintenance as described later is executed on the ink jet head  30 . Below, the range shown by the arrow P 1  is termed a waiting position, and the range shown by the arrow P 2  is termed a printing position. 
     (Configuration related to Maintenance) 
       FIG. 3  shows a schematic configuration of the ink jet head  30  and elements for executing maintenance (e.g., a purge process, an exhaust process, etc.; described later) on the ink jet head  30 . As described above, the ink jet head  30  comprises the exhaust passage  34  that communicates with the ink chamber  32 . The ink jet head  30  further comprises an exhaust opening  80 , an exhaust valve  82 , and a spring  84 . The exhaust opening  80  opens to the exterior of the ink jet head  30 . The exhaust passage  34  communicates with the exhaust opening  80 . The exhaust valve  82  is inserted into the exhaust opening  80 . The spring  84  applies force in a direction for closing the exhaust valve  82  (downward force in the present embodiment) to the exhaust valve  82 . More specifically, the spring  84  applies force to the exhaust valve  82  in a direction for closing the exhaust opening  80  (that is, a direction for closing the exhaust passage  34 ) such that the exhaust valve  82  enters the exhaust opening  80 . As a result, the exhaust valve  82  assumes a closed state in the case where external force other than from the spring  84  is applied to the exhaust valve  82 . That is, the exhaust passage  34  assumes a closed state. 
     The ink jet printer  2  further comprises various elements  100 ,  110 ,  120 ,  150 ,  170 , etc. related to maintenance of the ink jet head  30 . These elements  100 ,  110 ,  120 ,  150 ,  170 , etc. are present below the ink jet head  30  that is present in the waiting position P 1  (see  FIG. 2 ). 
     (Configuration of Cap) 
     The ink jet printer  2  comprises a nozzle cap  100  and an exhaust cap  110 . The nozzle cap  100  and the exhaust cap  110  are configured integrally. However, the nozzle cap  100  and the exhaust cap  110  may be configured separately in another embodiment. The nozzle cap  100  and the exhaust cap  110  can be moved between an upper position and a lower position.  FIG. 3  shows a state where the caps  100  and  110  are present in the lower position.  FIG. 4  shows a state where the caps  100  and  110  are present in the upper position. 
     In a state where the nozzle cap  100  is present in the lower position (the state of  FIG. 3 ), the nozzle cap  100  does not make contact with the nozzle surface  40  of the ink jet head  30 . In a state where the nozzle cap  100  is present in the upper position (the state of  FIG. 4 ), the nozzle cap  100  makes contact with the nozzle surface  40  in which the nozzles  42  are formed. That is, in the state where the nozzle cap  100  is present in the upper position, the nozzle cap  100  caps the nozzle surface  40 . Further, in other words, in the state where the nozzle cap  100  is present in the upper position, the nozzle cap  100  caps the nozzles  42 . The nozzle cap  100  comprises an opening  104 . The opening  104  communicates with one end of a first passage  180 . A space  102  within the nozzle cap  100  communicates with the first passage  180  via the opening  104 . The other end of the first passage  180  is capable of communicating with a gas passage  172   a  of a rotation member  170  described later (see  FIG. 7 ). 
     In a state where the exhaust cap  110  is present in the lower position (the state of  FIG. 3 ), the exhaust cap  110  does not make contact with a lower surface  85  (see  FIG. 3 ) onto which the exhaust opening  80  of the ink jet head  30  opens. In a state where the exhaust cap  110  is present in the upper position (the state of  FIG. 4 ), the exhaust cap  110  makes contact with the lower surface  85 . That is, in the state where the exhaust cap  110  is present in the upper position, the exhaust cap  110  caps the lower surface  85 . Further, in other words, in the state where the exhaust cap  110  is present in the upper position, the exhaust cap  110  caps the exhaust opening  80 . Further, in other words, in the state where the exhaust cap  110  is present in the upper position, the exhaust cap  110  caps the exhaust valve  82 . The exhaust cap  110  comprises an opening  114 . The opening  114  communicates with one end of a second passage  190 . Space  112  within the exhaust cap  110  communicates with the second passage  190  via the opening  114 . The other end of the second passage  190  is capable of communicating with the gas passage  172   a  of the rotation member  170  described later (see  FIG. 7 ). 
     (Configuration of Valve Operation Mechanism) 
     The ink jet printer  2  comprises a valve operation mechanism  120 . The valve operation mechanism  120  comprises a spring support member  122 , a spring  124 , a slider  126 , a shaft  130 , and a stopper  132 . The spring support member  122  is fixed to a side of the casing  4  (see  FIG. 1 ), and thus does not move. The spring support member  122  supports one end of the spring  124 . The other end of the spring  124  is connected to the slider  126 . That is, the spring  124  is disposed between the spring support member  122  and the slider  126 . The spring  124  applies force (in the present embodiment, force in the leftward direction of  FIG. 3 ) to the slider  126  such that the slider  126  approaches a rotation center  152  of a cam member  150  described later. 
     The slider  126  comprises a guide groove  128  and a protrusion  129 . The guide groove  128  is a cross-sectionally U-shaped groove that has a guide surface for guiding a lower end  130   a  of the shaft  130  described later. Moreover, the guide groove  128  may equally well be a slit (a through hole) that has a guide surface for guiding the lower end  130   a  of the shaft  130  described later. A portion at one side of the guide groove  128  in a horizontal direction (in the present embodiment, the portion at the right side in  FIG. 3 ) is formed in a higher position than the other side of the guide groove  128  in the horizontal direction (in the present embodiment, the portion at the left side in  FIG. 3 ). The protrusion  129  protrudes upward more than the remaining portion of the slider  126 . 
     As described above, the slider  126  receives force from the spring  124  (force in the leftward direction of  FIG. 3 ) such that the slider  126  approaches the rotation center  152  described later. The slider  126  is capable of moving from the position of  FIG. 4  toward the rotation center  152  described later (leftward in  FIG. 4 ) in accordance with the state of the cam member  150  described later.  FIG. 5  shows the slider  126  having moved from the position of  FIG. 4  toward the rotation center  152  described later (leftward in  FIG. 4 ). That is, the slider  126  is capable of moving between a right position (the position of  FIG. 4 ) and a left position (the position of  FIG. 5 ). 
     In a state where the ink jet head  30  is present in the waiting position P 1 , the shaft  130  is present in a position corresponding to the exhaust opening  80  and the exhaust valve  82 . That is, from a plan view of the ink jet printer  2 , the shaft  130  overlaps with the exhaust opening  80  and the exhaust valve  82 . The shaft  130  extends in a vertical direction. The shaft  130  is coupled to the slider  126 . More specifically, the lower end  130   a  of the shaft  130  fits into the guide groove  128 . In the case where the slider  126  moves in the horizontal direction, the shaft  130  is guided along the guide groove  128 . Moreover, even if the slider  126  moves in the horizontal direction, the absolute position of the shaft  130  in the horizontal direction does not change. In a state where the slider  126  is present in the right position (the position of  FIG. 4 ), the lower end  130   a  of the shaft  130  is present at the left end (the lower end) of the guide groove  128 . In a state where the slider  126  is present in the left position (the position of  FIG. 5 ), the lower end  130   a  of the shaft  130  is present at the right end (the upper end) of the guide groove  128 . 
     An opening  116  is formed in a lower surface of the exhaust cap  110 . The shaft  130  passes through the opening  116 . An upper end  130   b  of the shaft  130  is present in the space  112  within the exhaust cap  110 . Moreover, the shaft  130  is not fixed to the exhaust cap  110 . That is, even if the exhaust cap  110  moves in a vertical direction, the shaft  130  does not move with the exhaust cap  110 . 
     The stopper  132  is fixed to a lower surface of the nozzle cap  100 . In a state where the nozzle cap  100  is present in the lower position (the state of  FIG. 3 ), the stopper  132  makes contact with a side (the left side in  FIG. 3 ) of the protrusion  129  of the slider  126 , the side being closer to the rotation center  152  described later. The stopper  132  makes contact with the protrusion  129  from a side that is closer to the rotation center  152  described later than the protrusion  129 . By contrast, in a state where the nozzle cap  100  is present in the upper position (the state of  FIG. 4 ), the stopper  132  does not make contact with the protrusion  129  of the slider  126 . In this state, the stopper  132  allows the leftward movement of the slider  126  that is receiving force in a leftward direction from the spring  124 . That is, in a state where the stopper  132  is present in the lower position (the state of  FIG. 3 ), the protrusion  129  makes contact with the stopper  132 , and consequently the slider  126  cannot move from the position of  FIG. 3  toward the rotation center  152  described later (leftward in  FIG. 3 ). In a state where the stopper  132  is present in the upper position (the state of  FIG. 4 ), the slider  126  is capable of moving to the position of  FIG. 5  toward the rotation center  152  described later (leftward in  FIG. 4 ) in accordance with the state of the cam member  150  described later. 
     (Configuration relating to Cam) 
     The ink jet printer  2  comprises a cam follower  140 , the cam member  150 , and a cam motor  240  (see  FIG. 8 ). The cam follower  140  extends in a vertical direction. One end of the cam follower  140  is fixed to a lower surface of the slider  126 . The other end of the cam follower  140  is coupled to the cam member  150 . More specifically, the other end of the cam follower  140  fits into a cam groove  160  formed in the cam member  150 . In the case where the cam member  150  rotates, the cam follower  140  is guided along the cam groove  160 . 
     The cam member  150  is connected to the cam motor  240  (see  FIG. 8 ). The cam member  150  has a rotation axis  152  as its center, and is capable of rotating.  FIG. 6  shows a plan view of the cam member  150  (a view along the direction of the arrow D 1  in  FIG. 3 ). The cam member  150  is capable of rotating in the direction of the arrow D 2  (clockwise). Moreover, in the present embodiment, the cam member  150  does not rotate in the anti-clockwise direction. The cam member  150  comprises a cam main body  154  and three protruding parts  220 ,  222 , and  224 . The cam main body  154  is substantially disc shaped. The cam groove  160  is formed in an upper surface of the cam main body  154  (a surface at the upper side in  FIG. 3 ). The cam groove  160  is a cross-sectionally U-shaped groove that comprises a guide surface for guiding the cam follower  140 . 
     The cam groove  160  comprises a first groove  162 , a second groove  164 , and a third groove  166 . The first groove  162  has an arc shape with the rotation center  152  of the cam member  150  as its center. The first groove  162  extends clockwise from one end  162   a  to the other end  162   b.  The second groove  164  and the third groove  166  branch from the one end  162   a  of the first groove  162 . Further, the second groove  164  and the third groove  166  branch from the other end  162   b  of the first groove  162 . The second groove  164  has an arc shape with the rotation center  152  of the cam member  150  as its center. The second groove  164  extends in an anti-clockwise direction from the one end  162   a  of the first groove  162  to the other end  162   b  of the first groove  162 . The first groove  162  and the second groove  164  form a circular loop. The third groove  166  comprises a linear shaped groove  168  extending from the one end  162   a  of the first groove  162  to an inner circumferential side and a linear shaped groove  169  extending from the other end  162   b  of the first groove  162  to the inner circumferential side. An end part at an innermost circumferential side of the groove  168  and an end part at an innermost circumferential side of the groove  169  are connected. Moreover, below, the position where the groove  168  and the groove  169  are connected is termed an intermediate position. 
     As described above, the first groove  162  and the second groove  164  form a circular loop. Further, the third groove  166  extends towards the inner circumferential side from the one end  162   a  and the other end  162   b  of the first groove  162 . As a result, a distance R 2  between the rotation center  152  and the third groove  166  is smaller than a distance R 1  between the rotation center  152  and the first groove  162  (that is, the distance R 1  between the rotation center  152  and the second groove  164 ). The distance between the rotation center  152  and any position in the third groove  166  is smaller than the distance R 1 . 
     When the cam member  150  rotates in the direction of the arrow D 2 , the cam follower  140  is guided along the cam groove  160 . That is, there is a change in the relative position of the cam follower  140  with respect to the cam groove  160 . In the present embodiment, the second groove  164  and the third groove  166  branch from the one end  162   a  of the first groove  162 . As a result, a state in which the cam follower  140  is guided along the first groove  162  and the second groove  164  and also a state in which the cam follower  140  is guided along the first groove  162  and the third groove  166  exist. This feature will be described later in detail. 
     The three protruding parts  220 ,  222  and  224  are fixed to an outer circumferential face (a side face) of the cam main body  154 . Along the circumferential direction of the cam main body  154 , the protruding part  220  has the shortest length, the protruding part  222  has a medium length and the protruding part  224  has the longest length. 
     The ink jet printer  2  further comprises a cam sensor  230 . The cam sensor  230  is disposed in the vicinity of the cam member  150 . The cam sensor  230  is connected to the controller  60  (see  FIG. 8 ). In a state where the cam sensor  230  is facing the protruding parts  220 ,  222  and  224 , a first signal (for example, a high signal) is sent to the controller  60 . In a state where the cam sensor  230  is not facing the protruding parts  220 ,  222  and  224 , a second signal (for example, a low signal) is sent to the controller  60 . As described above, the protruding parts  220 ,  222  and  224  have differing lengths. As a result, in the case where the cam member  150  rotates at the constant speed, the periods during which the cam sensor  230  is facing the protruding parts  220 ,  222  and  224  respectively differ. For example, the period for which the cam sensor  230  is facing the protruding part  220  is short, while the period for which the cam sensor  230  is facing the protruding part  224  is long. As a result, the period at which the cam sensor  230  begins and finishes sending the first signal (hereinbelow termed a period of the first signal) changes in accordance with which of the protruding parts  220 ,  222  and  224  is facing the cam sensor  230 . 
     (Configuration of Rotation Member) 
     As shown in  FIG. 3 , the ink jet printer  2  further comprises the rotation member  170 .  FIG. 7  shows a plan view of the rotation member  170  (a view in the direction of the arrow D 1  of  FIG. 3 ). The rotation member  170  comprises a main body member  172  and a ring member  174 . The main body member  172  is substantially disc shaped. As shown in  FIG. 3 , the main body member  172  is coupled to the cam member  150  below this cam member  150 . As a result, the main body member  172  rotates following the rotation of the cam member  150 . The main body member  172  also rotates in the direction of the arrow D 2  (clockwise) of  FIG. 6 . The gas passage  172   a  is formed within the main body member  172 . One end  172   b  and the other end  172   c  of the gas passage  172   a  open onto an outer circumferential face (a side face) of the main body member  172 . 
     The ring member  174  has a ring shape. The main body member  172  is fitted into the interior of the ring member  174 . The ring member  174  is fixed to the side of the casing  4  (see  FIG. 1 ), and does not rotate. Three through holes  174   a,    174   b  and  174   c  are formed in the ring member  174 . The through hole  174   a  communicates with the first passage  180 . That is, as shown in  FIG. 3 , the through hole  174   a  communicates with the space  102  within the nozzle cap  100  via the first passage  180 . The through hole  174   b  communicates with a pump passage  200 . The ink jet printer  2  further comprises a pump  210 . The pump passage  200  is connected to the pump  210 . The through hole  174   c  communicates with the second passage  190 . That is, as shown in  FIG. 3 , the through hole  174   c  communicates with the space  112  within the exhaust cap  110  via the second passage  190 . 
     When the cam member  150  rotates, the main body member  172  rotates with respect to the ring member  174 . In accordance with the phase of the cam member  150  (the phase of the main body member  172 ), the gas passage  172   a  of the main body member  172  assumes a communicating state with the through holes  174   a,    174   b,  and  174   c  of the ring member  174 . For example, when the main body member  172  rotates clockwise by 180 degrees from the state of  FIG. 7 , the one end  172   b  of the gas passage  172   a  communicates with the through hole  174   a,  and the other end  172   c  of the gas passage  172   a  communicates with the through hole  174   b.  In this state, the space  102  within the nozzle cap  100  communicates with the pump  210  via the first passage  180 , the through hole  174   a,  the gas passage  172   a,  the through hole  174   b,  and the pump passage  200 . Further, for example, when the main body member  172  rotates clockwise by 270 degrees from the state of  FIG. 7 , the one end  172   b  of the gas passage  172   a  communicates with the through hole  174   b,  and the other end  172   c  of the gas passage  172   a  communicates with the through hole  174   c.  In this state, the space  112  within the exhaust cap  110  communicates with the pump  210  via the second passage  190 , the through hole  174   c,  the gas passage  172   a,  the through hole  174   b,  and the pump passage  200 . 
     (Control Configuration) 
     Next, the control configuration of the ink jet printer  2  will be described. Moreover, a brief description will also be given herein of the configuration for moving the nozzle cap  100  and the exhaust cap  110  (see  FIG. 3 ) in the vertical direction (which may also be referred to as the configuration for moving the stopper  132  in the vertical direction).  FIG. 8  shows a schematic view of the control configuration of the ink jet printer  2 . The controller  60  sends control signals to the ink jet head  30  (see  FIG. 1 ), the carriage motor  78  (see  FIG. 2 ), the cam motor  240 , and the pump  210  (see  FIG. 3  and  FIG. 7 ). The elements  30 ,  78 ,  240  and  210  are thereby controlled. Further, the cartridge sensor  48  (see  FIG. 1 ) and the cam sensor  230  (see  FIG. 6 ) send the first signal (e.g., the high signal) and the second signal (e.g., the low signal) to the controller  60 . The controller  60  is capable of detecting whether the ink cartridge  50  is housed in the cartridge housing part  46  based on the signals from the cartridge sensor  48 . Further, the controller  60  is capable of detecting the phase of the cam member  150  based on the signals from the cam sensor  230 . 
     Moreover, the ink jet printer  2  further comprises a gear mechanism  250  connected to the cam motor  240 . The cam member  150  and the caps  100  and  110  are connected to the cam motor  240  via the gear mechanism  250 . When the cam motor  240  rotates in a positive direction, the gear mechanism  250  transmits the driving force of the cam motor  240  to the caps  100  and  110 . In this case, the driving force of the cam motor  240  is not transmitted to the cam member  150 . When the cam motor  240  rotates in the positive direction, the caps  100  and  110  move in the vertical direction. For example, in a state where the caps  100  and  110  are present in the lower position (the state of  FIG. 3 ), the caps  100  and  110  move to the upper position (the state of  FIG. 4 ) when the cam motor  240  rotates by a first angle in the positive direction. Further, for example, in a state where the caps  100  and  110  are present in the upper position in (the state of  FIG. 4 ), the caps  100  and  110  move to the lower position (the state of  FIG. 3 ) when the cam motor  240  rotates by a second angle in the positive direction. By contrast, when the cam motor  240  rotates in a reversed direction, the gear mechanism  250  transmits the driving force of the cam motor  240  to the cam member  150 . In this case, the driving force of the cam motor  240  is not transmitted to the caps  100  and  110 . Moreover, this type of method for changing the object to which the driving force is transmitted in accordance with the direction of rotation of the motor is taught in, for example, U.S. Pat. No. 6,883,896. The contents of this document are incorporated by reference into the present specification. 
     (Operation of the Other Elements accompanying the Rotation of the Cam Member) 
     Next, the operation of the other elements accompanying the rotation of the cam member  150  will be described. First, with reference to  FIG. 9 , the case in which the cam member  150  rotates in a state where the stopper  132  is present in the upper position (the position of  FIG. 4  and  FIG. 5 ) will be described. In the present embodiment, in a state where the cam member  150  is present in the phase shown in  FIG. 6 , the phase of the cam member  150  is zero. Moreover, the state shown in  FIG. 6  is a state in which a downstream end surface  224   a,  in the direction of rotation, of the longest protruding part  224  of the cam member  150  is facing the cam sensor  230  (a state of having being detected by the cam sensor  230 ). The state of the phase of the cam member  150  being zero can be termed, in other words, an initial position of the cam member  150 . 
     In the state where the phase of the cam member  150  is zero, the cam follower  140  is present in the first groove  162 , the slider  126  is present in the right position (the position of  FIG. 4 ), and the lower end  130   a  of the shaft  130  is present in the lower end (the left end) of the guide groove  128  of the slider  126 . In this state, the upper end  130   b  of the shaft  130  does not make contact with the exhaust valve  82 , and the exhaust valve  82  is in the closed state. Further, in the state where the phase of the cam member  150  is zero, the gas passage  172   a  within the rotation member  170  communicates only with the through hole  174   c  of the ring member  174 . 
     When the cam member  150  rotates in the direction of the arrow D 2  (clockwise) from the state where the phase is zero to a state where the phase is θ 1 , the cam follower  140  is guided along the first groove  162 . The cam follower  140  is still present within the first groove  162 . As a result, the slider  126  is present in the right position (the position of  FIG. 4 ), and the lower end  130   a  of the shaft  130  is present in the lower end (the left end) of the guide groove  128  of the slider  126 . The exhaust valve  82  is still in the closed state. In the state where the phase of the cam member  150  is θ 1 , the gas passage  172   a  within the rotation member  170  communicates with the through hole  174   a  and the through hole  174   b  of the ring member  174 . That is, the space  102  within the nozzle cap  100  communicates with the pump  210  via the gas passage  172   a.  Since the nozzle cap  100  is present in the upper position, the space  102  within the nozzle cap  100  is in a sealed state. In this state, if the pump  210  is driven, negative pressure is applied to the space  102  within the nozzle cap  100 . As a result, ink is discharged from the nozzles  42 . That is, a purge process can be executed. 
     When the cam member  150  rotates in the direction of the arrow D 2  from the state where the phase is θ 1  to a state where the phase is θ 2 , the cam follower  140  is guided along the first groove  162 . The cam follower  140  reaches the one end  162   a  of the first groove  162 . Since the stopper  132  is present in the upper position, the protrusion  129  does not make contact with the stopper  132  in the slider  126  that is receiving force from the spring  124  toward the rotation center  152  (leftward in  FIG. 4 ). That is, the slider  126  is allowed to move toward the rotation center  152  of the cam member  150 . As a result, when the cam member  150  rotates further in the direction of the arrow D 2  from the state where the phase is θ 2 , the cam follower  140  is guided along the third groove  166  (more specifically the groove  168  (see  FIG. 6 )) that extends from the one end  162   a  of the first groove  162  toward the rotation center  152  of the cam member  150  and, as a result, the slider  126  also moves toward the rotation center  152  of the cam member  150  (leftward in  FIG. 4 ). 
     When the slider  126  moves toward the rotation center  152  (leftward in  FIG. 4 ), the lower end  130   a  of the shaft  130  is guided upward along the guide groove  128  of the slider  126 . The shaft  130  thereby moves from the lower position (the position of  FIG. 4 ) to the upper position (the position of  FIG. 5 ). When the phase of the cam member  150  becomes θ 3 , the lower end  130   a  of the shaft  130  reaches the right end of the guide groove  128  of the slider  126 , and the shaft  130  reaches the upper position (the position of  FIG. 5 ). In this state, the upper end  130   b  of the shaft  130  makes contact with the exhaust valve  82 , and since the upper end  130   b  of the shaft  130  pushes the exhaust valve  82  upwards, the exhaust valve  82  assumes the opened state. Moreover, in the state where the phase of the cam member  150  is θ 3 , the cam follower  140  is present in the intermediate position of the third groove  166  (the position closest to the rotation center  152  of the cam member  150 ). 
     In the state where the phase of the cam member  150  is θ 3 , the gas passage  172   a  within the rotation member  170  communicates with the through hole  174   b  and the through hole  174   c  of the ring member  174 . That is, the space  112  within the exhaust cap  110  communicates with the pump  210  via the gas passage  172   a.  Since the exhaust cap  110  is present in the upper position, the space  112  within the exhaust cap  110  is in a sealed state. In this state, when the pump  210  is driven, negative pressure is applied to the space  112  within the exhaust cap  110 . As a result, gas (air, etc.) within the ink chamber  32  is discharged via the exhaust passage  34  and the exhaust opening  80 . That is, an exhaust process can be executed. If gas is present within the ink chamber  32 , it is possible that this gas blocks the ink passage  36  (see  FIG. 1 ), leading to unsatisfactory printing because ink cannot be discharged from the ink passage  36 . In the present embodiment, since the exhaust process can be executed, such unsatisfactory printing can be restricted. 
     When the cam member  150  rotates in the direction of the arrow D 2  from the state where the phase is θ 3  to a state where the phase is θ 4 , the cam follower  140  is guided along the third groove  166  from the intermediate position of the third groove  166  (more specifically, is guided along the groove  169  (see  FIG. 6 )). That is, the cam follower  140  is guided away from the rotation center  152  of the cam member  150  and, as a result, the slider  126  also moves away from the rotation center  152  of the cam member  150  (the rightward direction of  FIG. 5 ). The cam follower  140  reaches the other end  162   b  of the first groove  162 . When the slider  126  moves in the rightward direction of  FIG. 5 , the lower end  130   a  of the shaft  130  is guided downward along the guide groove  128  of the slider  126 . The shaft  130  thereby moves from the upper position (the position of  FIG. 5 ) to the lower position (the position of  FIG. 4 ). When the phase of the cam member  150  becomes  04 , the shaft  130  reaches the left end (the lower end) of the guide groove  128  of the slider  126 , and reaches the lower position (the position of  FIG. 4 ). 
     When the cam member  150  rotates further in the direction of the arrow D 2  from the state where the phase is θ 4 , the cam member  150  returns to the initial position in which the phase is zero. As is clear from the above description, in the state where the stopper  132  is present in the upper position (the position of  FIG. 4 ), the cam follower  140  is guided along the first groove  162  and the third groove  166 , and is not guided along the second groove  164 . In the state where the cam follower  140  is present in the first groove  162 , the exhaust valve  82  is in the opened state, and in the state where the cam follower  140  is present in the intermediate position of the third groove  166 , the exhaust valve  82  is in the closed state. The exhaust valve  82  can be switched between the closed state and the opened state by performing one revolution of the cam member  150 . 
     Next, with reference to  FIG. 10 , the case in which the cam member  150  rotates in the state where the stopper  132  is present in the lower position (the position of  FIG. 3 ) will be described. The case in which the cam member  150  rotates in the direction of the arrow D 2  from the state where the phase is zero to the state where the phase is θ 2  is the same as in the case of  FIG. 9 . Since the stopper  132  is present in the lower position (the position of  FIG. 3 ), the stopper  132  makes contact with the protrusion  129  from the side closer to the rotation center  152 . As a result, the slider  126  cannot move in the leftward direction of  FIG. 3  even if the slider  126  receives force from the spring  124  to move the slider  126  toward the rotation center  152  (force in the leftward direction of  FIG. 3 ). As a result, when the cam member  150  rotates further in the direction of the arrow D 2  from the state where the phase is θ 2 , the cam follower  140  is guided along the second groove  164 . In this case, since the slider  126  does not move, the exhaust valve  82  maintains the closed state without the shaft  130  also moving upward. 
     When the cam member  150  rotates in the direction of the arrow D 2  from the state where the phase is θ 2  to the state where the phase is θ 4 , the cam follower  140  reaches the other end  162   b  of the first groove  162 . When the cam member  150  rotates further in the direction of the arrow D 2  from the state where the phase is θ 4 , the cam member  150  returns to the initial position where the phase is zero. As is clear from the above description, in the state where the stopper  132  is present in the lower position (the position of  FIG. 3 ), the cam follower  140  is guided along the first groove  162  and the second groove  164 , and is not guided along the third groove  166 . The exhaust valve  82  is in the closed state regardless of whether the cam follower  140  is present in either the first groove  162  or the second groove  164 . As a result, the exhaust valve  82  can maintain the closed state even if the cam member  150  undergoes one revolution. Utilizing this, the ink jet printer  2  executes a process (described later) for returning to an original position that stops the cam member  150  in the initial position. 
     (Processes Executed by Controller) 
     Next, processes executed by the controller  60  will be described.  FIG. 11  and  FIG. 12  show a flowchart of the processes executed by the controller  60 . In an initial state in which the ink jet printer  2  is manufactured and shipped, the carriage  70  is present in the waiting position P 1  (see  FIG. 2 ), and the caps  100  and  110  are present in the upper position (the position of  FIG. 4 ). Turning on a power source of the ink jet printer  2  in this initial state is a trigger for starting the flowchart of  FIG. 11  and  FIG. 12 . 
     The controller  60  executes positive rotation of the cam motor  240  (see  FIG. 8 ) by a first predetermined angle (S 10 ). The caps  100  and  110  thereby move from the upper position (the position of  FIG. 4 ) to the lower position (the position of  FIG. 3 ). The stopper  132  that is fixed to the nozzle cap  100  also moves from the upper position to the lower position. The slider  126  is thereby prevented from moving in the leftward direction of  FIG. 3 . 
     Next, the controller  60  starts reverse rotation of the cam motor  240  (S 12 ). The cam member  150  starts to rotate in the direction of D 2  of  FIG. 6 . Since the stopper  132  is present in the lower position (the position of  FIG. 3 ), the cam follower  140  is guided along the first groove  162  and the second groove  164 , and is not guided along the third groove  166 , even if the cam member  150  rotates. As a result, the exhaust valve  82  is maintained in the closed state (see  FIG. 10 ). 
     In the state where the cam member  150  is rotating, the controller  60  monitors a signal sent from the cam sensor  230  (see  FIG. 6 ) (S 14 ). As described above, in the process of the cam member  150  performing one revolution, there is a change in the period that the cam sensor  230  sends the first signal (e.g., the high signal) to the controller  60 . In S 14 , the controller  60  first carries out at least one revolution of the cam member  150 , and monitors the change in the period of the first signal across three stages. Since the protruding parts  220 ,  222  and  224  face the cam sensor  230  in sequence, the period of the first signal changes in sequence from a shortest state, to a medium state and then to a longest state. The controller  60  further rotates the cam member  150 . The controller  60  detects in sequence that the period of the first signal is in the shortest state and the medium state, and then determines YES in S 14  when there is a change from the second signal to the first signal (that is, when the starting point of the longest period of the first signal is detected). The timing at which YES is determined in S 14  is the timing at which the cam sensor  230  is facing the surface  224   a  of the protruding part  224  (see  FIG. 6 ). In the case of YES in S 14 , the controller  60  stops the cam motor  240  (S 16 ). The cam member  150  thereby stops in the initial position (the position of  FIG. 6 ). That is, the process for returning the cam member  150  to the original position is completed. 
     If the process for returning the cam member  150  to the original position is executed, it is possible to stop the cam member  150  in the initial position (the state where the phase is zero). In the case where the cam member  150  is present in the initial position, when the cam member  150  is rotated in a later process, the cam member  150  can be stopped in a desired phase by adjusting the angle of rotation of the cam motor  240  (for example, see a third predetermined angle of S 24 , a fourth predetermined angle of S 28  and a fifth predetermined angle of S 32 , all of  FIG. 12 ). For example, even in the case where the cam member  150  cannot be stopped in a desired phase based on the signal sent from the cam sensor  230  (the case where it is desirable to stop the cam member  150  in a phase in which the protruding parts  220 ,  222  and  224  are not facing the cam sensor  230 ), it is possible to stop the cam member  150  in the desired phase based on the angle of rotation of the cam motor  240 . 
     Moreover, if the cam member  150  is adjusted to the initial position in the initial state in which the ink jet printer  2  is manufactured and shipped, it is unlikely that the process for returning the cam member  150  to the original position will be required. However, there is a possibility that external force will be applied to the cam member  150  during the transportation of the ink jet printer  2 , and that the cam member  150  consequently may rotate. That is, there is a possibility that the cam member  150  becomes misaligned from the initial position even though the cam member  150  had been adjusted to the initial position. In the present embodiment, in order to resolve this type of problem, the process for returning the cam member  150  to the original position is executed in the process of  FIG. 11  when the power source is turned on for the first time after manufacturing and shipping. Further, as will be described later, the process for returning the cam member  150  to the original position is executed in cases where other conditions are fulfilled. This is because it is not possible to eliminate the possibility of the cam member  150  becoming misaligned from the initial position during the utilization of the ink jet printer  2 . 
     Next, the controller  60  confirms the state of the signal sent from the cartridge sensor  48  (see  FIG. 1 ) (S 18 ). As described above, in a state where the ink cartridge  50  is present in the cartridge housing part  46 , the cartridge sensor  48  sends the first signal (e.g., the high signal). In the case where the first signal sent from the cartridge sensor  48  has been received, the controller  60  determines YES in S 18 . In this case, the process proceeds to S 22  of  FIG. 12 . 
     By contrast, in the case where the second signal sent from the cartridge sensor  48  has been received, the controller  60  determines NO in S 18 . In this case, the controller  60  executes positive rotation of the cam motor  240  (see  FIG. 8 ) by a second predetermined angle (S 20 ). The caps  100  and  110  thereby move from the lower position (the position of  FIG. 3 ) to the upper position (the position of  FIG. 4 ). When S 20  ends, the controller  60  ends the process of  FIG. 11  and  FIG. 12 , and shifts into the waiting state. 
     In S 22  of  FIG. 12 , the controller  60  executes a positive rotation of the cam motor  240  by the second predetermined angle. The process of S 22  is the same as the process of S 20  of  FIG. 11 . The caps  100  and  110  thereby move from the lower position (the position of  FIG. 3 ) to the upper position (the position of  FIG. 4 ). Further, the stopper  132  fixed to the nozzle cap  100  also moves from the lower position to the upper position. 
     Next, the controller  60  executes reverse rotation of the cam motor  240  by a third predetermined angle (S 24 ). The cam member  150  is thereby rotated from the initial position in which the phase is zero to the state where the phase is θ 1  (see  FIG. 9 ). As described above, in the state where the phase of the cam member  150  is θ 1 , the space  102  within the nozzle cap  100  communicates with the pump  210  via the gas passage  172   a.  Next, the controller  60  drives the pump  210  (S 26 ). Ink is thereby discharged from the nozzles  42 . The purge process is thereby completed. 
     Next, the controller  60  executes reverse rotation of the cam motor  240  by a fourth predetermined angle (S 28 ). The cam member  150  is thereby rotated from the state where the phase is θ 1  to the state where the phase is θ 3  (see  FIG. 9 ). As described above, in the state where the phase of the cam member  150  is θ 3 , the space  112  within the exhaust cap  110  communicates with the pump  210  via the gas passage  172   a.  Moreover, the exhaust valve  82  is in the opened state. Next, the controller  60  drives the pump  210  (S 30 ). Gas within the ink chamber  32  is thereby discharged via the exhaust passage  34  and the exhaust opening  80 . The exhaust process is thereby completed. When the exhaust process is completed, the interior of the ink chamber  32  is filled with ink. 
     Finally, the controller  60  executes reverse rotation of the cam motor  240  by a fifth predetermined angle (S 32 ). The cam member  150  is thereby rotated from the state where the phase is θ 3  to a state where the phase is 360 degrees (that is, the initial position). The exhaust valve  82  assumes the closed state during this process. When S 32  ends, the process of  FIG. 11  and  FIG. 12  ends. 
     In the ink jet printer  2  of the aforementioned embodiment, the cam member  150  comprises the second groove  164  and the third groove  166  that branch from the first groove  162 . In the state where the cam follower  140  is present in the first groove  162  or the second groove  164 , the exhaust valve  82  is maintained in the closed state. Further, in the state where the cam follower  140  is present in the intermediate position of the third groove  166  (the position where the phase of the cam member  150  is θ 3 ), the exhaust valve  82  assumes the opened state. The cam follower  140  can be switched between the state of being guided along the third groove  166  and the state of being guided along the second groove  164  by adjusting the position of the stopper  132 . In the former state, the exhaust valve  82  can be in the opened state, and consequently it is possible to execute the exhaust process in which gas within the ink chamber  32  is discharged. Further, in the latter state, it is possible to rotate the cam member  150  while the exhaust valve  82  is maintained in the closed state. The process for returning the cam member  150  to the original position can thereby be executed without opening the exhaust valve  82  (see S 14  and S 16  of  FIG. 11 ). It is possible to control the opening of the exhaust valve  82  in situations other than situations in which the exhaust process must be executed. 
     If a configuration is adopted in which the third groove  166  is not present and the exhaust valve  82  is opened when the process for returning the cam member  150  to the original position is executed (below, this is termed a specific configuration), the following problems occur. When the process for returning the cam member  150  to the original position is executed, air may enter the ink chamber  32  from the exhaust valve  82  since the exhaust valve  82  is open, and unsatisfactory printing may occur. Unsatisfactory printing caused by the presence of air in the ink chamber  32  might be rectified by executing the exhaust process. For example, in the processes of  FIG. 11  and  FIG. 12 , the exhaust process is executed after the process for returning the cam member  150  to the original position, and consequently unsatisfactory printing might not occur even if the exhaust valve  82  is opened when the process for returning the cam member  150  to the original position is executed. However, the process for returning the cam member to the original position is not executed only during the processes of  FIG. 11  and  FIG. 12 , but is also executed when other conditions have been fulfilled. For example, the process for returning the cam member  150  to the original position may be executed after a predetermined period has elapsed since the previous execution of the process for returning the cam member, or may be executed when the user executes a predetermined operation. Further, the process for returning the cam member  150  to the original position may be executed whenever, for example, the purge process (the process of S 26  of  FIG. 12 ) has been executed a predetermined number of times. That is, there are situations in which only the process for returning the cam member  150  to the original position needs to be executed, while it is not necessary to execute the exhaust process. In the ink jet printer  2  of the present embodiment, the process for returning the cam member to the original position can be executed without opening the exhaust valve  82 , and consequently, the exhaust process after the process for returning the cam member to the original position does not necessarily need to be executed. The exhaust process after the process for returning the cam member to the original position can be omitted. As a result, compared to the aforementioned specific configuration in which the exhaust process is required after the process for returning the cam member to the original position, it is possible to reduce the time required to execute the processes for returning the cam member to the original position. Moreover, this description does not exclude a configuration in which the exhaust process is executed after the process for returning the cam member to the original position. The exhaust process after the process for returning the cam member to the original position may be executed as required (see, for example, the flowchart of  FIG. 11  and  FIG. 12 ). 
     Moreover, even in the aforementioned specific configuration, the process for returning the cam member to the original position can be executed without opening the exhaust valve  82  if the process for returning the cam member  150  to the original position is executed after the carriage  70  has been moved from the waiting position P 1  to another position (for example, the printing position P 2 ). However, in this method, the process of moving the carriage  70  from the waiting position P 1  to another position is required when the process for returning the cam member to the original position is to be executed. As a result, there is an increase in the time required to execute the processes for returning the cam member to the original position. In the ink jet printer  2  of the present embodiment, the process for returning the cam member to the original position can be executed without opening the exhaust valve  82  in the state where the carriage  70  is present in the waiting position P 1  (that is, in the state where the shaft  130  is present in a position facing the exhaust valve  82 ). Since the process of moving the carriage  70  is not necessary when the process for returning the cam member to the original position is to be executed, the time required to execute the processes for returning the cam member to the original position can be made shorter than in the method described above. 
     Further, in the present embodiment, the gas passage  172   a  is formed in the rotation member  170  that rotates following the rotation of the cam member  150 . It is possible, by adjusting the phase of the cam member  150 , to switch between a state where the space  102  within the nozzle cap  100  communicates with the pump  210  via the gas passage  172   a,  and a state where the space  112  within the exhaust cap  110  communicates with the pump  210  via the gas passage  172   a.  As a result, the purge process and the exhaust process can be executed independently by the single pump  210 . 
     Variants of the above embodiment are set forth below. 
     (1) The other end  162   b  of the first groove  162  need not communicate with the second groove  164  and the third groove  166 . For example, the first groove  162  and the second groove  164  need not form a circular loop, and instead an arc shape may be formed by the first groove  162  and the second groove  164 . In this case, it is preferred that the cam member  150  is configured so as to be capable of rotating in both a clockwise and an anti-clockwise direction. Moreover, the cam groove  160  may further comprise the other groove. The other groove may communicate with at least one of the first groove  162 , the second groove  164 , and the third groove  166 , or may equally well not communicate with any of the grooves  162 ,  164 , and  166 . 
     (2) In the above embodiments, the exhaust valve  82  is opened and closed by the exhaust valve  82  moving in the vertical direction. However, the exhaust valve  82  may equally well move in another direction (for example, the horizontal direction). In this case, it is preferred that the direction of movement of the configurational elements  84 ,  120 ,  140 ,  150 , etc. is adjusted so that movement of the exhaust valve  82  in the other direction is realized. 
     (3) The stopper  132  may equally well not be fixed to the nozzle cap  100 . For example, the stopper  132  may move its posture (position). In a state where the stopper  132  is in a first posture (first position), the stopper  132  may allow the slider  126  to move leftward in  FIG. 3 . In a state where the stopper  132  is in a second posture (second position), the stopper  132  may prevent the slider  126  from moving leftward in  FIG. 3 . 
     (4) The motor that rotates the cam member  150  may be a different motor from the motor that rotates the rotation member  170 . Further, the motor that rotates the cam member  150  may be a different motor from the motor that moves the caps  100  and  110  in the vertical direction.