Patent Publication Number: US-8113622-B2

Title: Liquid ejecting apparatus

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a liquid ejecting apparatus. 
     2. Description of the Related Art 
     A liquid ejecting apparatus having nozzles for ejecting liquid and a sealing unit for sealing the nozzles is already known. In such the liquid ejecting apparatus, for example, in order to perform a nozzle cleaning operation, when positioning the sealing unit at a sealing position at which the sealing unit seals the nozzles and allowing the nozzles to eject liquid after having ended the cleaning operation, the sealing unit is positioned at an off position apart from the nozzles. In other words, the sealing unit moves between the sealing position and the off position. 
     In order to move the sealing unit as described above, the liquid ejecting apparatus may be provided with a slide configured to guide the sealing unit to the sealing position by moving rectilinearly one direction from between two directions which are opposite from each other and intersecting the direction of movement, and guide the sealing unit to the off position by moving rectilinearly in the other direction (see JP-A-2007-185869). Also, some of the liquid ejecting apparatuses having the slider have a motor, a drive mechanism executing a first movement to cause the slider to move rectilinearly in the one direction and a second movement to cause the slider to move rectilinearly in the other direction by a drive force from the motor, and a drive force transmitting unit configured to transmit the drive force to the drive mechanism by rotating in a state of engaging the drive mechanism in association with the rotation of the motor. 
     In the liquid ejecting apparatuses, as described above, the operation to move the sealing unit to the sealing position to cause the sealing unit to seal the nozzles, and the operation to move the sealing unit away from the nozzle are performed as a series of operations. Such the series of operations is required to be performed quickly in order to improve the processing speed of the liquid ejecting apparatus, and hence switching between the respective operations in the series of operations is preferably achieved smoothly. Therefore, switching between the operation to cause the slider to move rectilinearly in the one direction and the operation to cause the slider to move rectilinearly in the other direction, that is, switching of the direction of the rectilinear movement of the slider is preferably performed smoothly. 
     SUMMARY 
     An advantage of some aspects of the invention is to make the slider switch the direction of a rectilinear movement thereof smoothly. 
     According to an aspect of the present invention, a liquid ejecting apparatus includes: a nozzle configured to eject liquid; a sealing unit configured to seal the nozzle, the sealing unit moving between a sealing position for sealing the nozzle in a direction of movement and an off position apart from the nozzle; a slider configured to guide the sealing unit to the sealing position by moving rectilinearly in one direction of two directions which are directions opposite from each other and intersecting the direction of movement and guide the sealing unit to the off position by moving rectilinearly in the other direction; a motor; a drive mechanism configured to perform a first movement for moving the slider rectilinearly in the one direction and a second movement for moving the slider rectilinearly in the other direction by a drive force from the motor; a drive force transmitting unit configured to transmit the drive force to the drive mechanism by rotating in a state of engaging the drive mechanism in association with the rotation of the motor, the drive force transmitting unit rotating in the same direction of rotation both in a case of transmitting the drive force to the drive mechanism when the drive mechanism performs the first movement and in a case of transmitting the drive force to the drive mechanism when the drive mechanism performs the second movement. 
     In this configuration, the drive force transmitting unit rotates in the same direction of rotation both in the case of transmitting the drive force to the drive mechanism when the drive mechanism performs the first movement and in the case of transmitting the drive force to the drive mechanism when the drive mechanism performs the second movement. In other words, in the liquid ejecting apparatus described above, when the slider switches the direction of rectilinear movement, an operation or time to switch the direction of rotation of the drive force transmitting unit is not required. Therefore, the direction of rectilinear movement of the slider may be switched smoothly. 
     Preferably, the sealing unit includes a side wall opposing the slider, the side wall includes a projecting portion projecting outward of the side wall, the slider includes a groove cam with which the projecting portion engages, the sealing unit is guided to the sealing position by moving the projecting portion to one end of the groove cam along the groove cam when moving rectilinearly in the one direction, and the sealing unit is guided to the off position by moving the projecting portion to the other end of the groove cam along the groove cam when moving rectilinearly in the other direction. In this configuration, the direction of rectilinear movement of the slider having the groove cam may be switched smoothly. 
     Preferably, the drive force transmitting unit includes a first cam configured to transmit the drive force to the drive mechanism by rotating in a state of engaging the drive mechanism when the drive mechanism performs the first movement; a second cam configured to transmit the drive force to the drive mechanism by rotating in a state of engaging the drive mechanism when the drive mechanism performs the second movement; and a cam shaft configured to support the first cam and the second cam and rotate integrally with the first cam and the second cam in association with the rotation of the motor, and the drive force transmitting unit rotates in the same direction of rotation both in a case of rotating in the state in which the first cam engages the drive mechanism and a case of rotating in the state in which the second cam engages the drive mechanism. In this configuration, the direction of rectilinear movement of the slider is switched by switching the cam to engage the drive mechanism, and a simple configuration for switching the direction is achieved. 
     Preferably, while one of the first cam and the second cam engages the drive mechanism, the other cam is positioned apart from the drive mechanism. In this configuration, when one of the cams engages the drive mechanism, the other cam does not interfere, so that the drive mechanism is allowed to perform the first movement and the second movement adequately. 
     Preferably, the drive mechanism includes: a first rack provided on the slider to be interlocked with the slider; a composite gear having a large gear which engages the first rack and a small gear, the composite gear rotating in a normal direction to cause the first rack to move rectilinearly in the one direction and rotating in a reverse direction to cause the first rack to move rectilinearly in the other direction; a pair of second racks engaging the small gear in a state of opposing to each other, the one second rack moving rectilinearly in the one direction to rotate the composite gear in the normal direction and the other second rack moving rectilinearly in the one direction to rotate the composite gear in the reverse direction, the first cam rotates in a state of engaging the one second rack to cause the one second rack to move rectilinearly in the one direction, and the second cam rotates in a state of engaging the other second rack to cause the other second rack to move rectilinearly in the one direction. When the drive mechanism includes the second racks which engage separately the first cam and the second cam as in this configuration, a configuration to switch the direction of the rectilinear movement of the slider by switching the cam which engages the drive mechanism is further simplified. 
     Preferably, a suction pump configured to suck the liquid from the nozzle by bringing a space formed between the sealing unit and the nozzle into a negative pressure state is provided when the sealing unit seals the nozzle and the motor is rotatable in both the normal direction and the reverse direction, the cam shaft rotates in association with the rotation of the motor in the normal direction, and the suction pump is activated in association with the rotation of the motor in the reverse direction. According to the embodiment of the invention, the direction of rectilinear movement of the slider is switched while the drive force transmitting unit rotates in a constant direction of rotation. Therefore, the motor for rotating the drive force transmitting unit may also be rotated continuously in the same direction before and after the switching of the direction of the rectilinear movement of the slider. Accordingly, the rotation of the motor in the direction opposite from the direction of rotation when rotating the drive force transmitting unit may be used for activating the suction pump. Consequently, saving of the components in the liquid ejecting apparatus is achieved. 
     Preferably, an atmosphere release valve configured to bring the space in the negative pressure state into an atmosphere release state, a third cam configured to open the atmosphere release valve by rotating in a state of engaging the atmosphere release valve are provided, and the third cam being supported by the cam shaft rotates integrally with the cam shaft and engages the atmosphere release valve wile the first cam and the second cam are apart from the drive mechanism. Since a timing when the first cam or the second cam rotate while engaging the drive member and a timing when the third cam rotates while engaging the atmosphere release valve are differentiated, a load applied to the cam shaft (torque load) may be reduced in comparison with a configuration in which the two timings are overlapped with each other. 
     Other features of the invention will be apparent by descriptions in the specification and the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, where like numbers reference like elements. 
         FIG. 1  is a block diagram showing a configuration of a printer  11 . 
         FIG. 2  is a drawing showing a general configuration of the printer  11  schematically. 
         FIG. 3  is a drawing showing an array of nozzles Nz in a nozzle surface  22 . 
         FIG. 4  is a drawing of a maintenance unit  24  when viewed from above. 
         FIG. 5  is a cross-sectional view taken along the line V-V in  FIG. 4 . 
         FIG. 6  is a cross-sectional view taken along the line VI-VI in  FIG. 4 . 
         FIG. 7  is a cross-sectional view taken along the line VII-VII in  FIG. 4 . 
         FIG. 8  is a cross-sectional view taken along the line VIII-VIII in  FIG. 4 . 
         FIG. 9  is a drawing showing a state in which a cap unit  30  is positioned at a sealing position. 
         FIG. 10  is a drawing showing a state in which an atmosphere release valve  80  is in an opened state. 
         FIG. 11  is a drawing showing a state in which an atmosphere release valve  81  is in an opened state. 
         FIG. 12  is a first explanatory drawing showing a configuration of a slider drive mechanism  100 . 
         FIG. 13  is a second explanatory drawing showing the configuration of the slider drive mechanism  100 . 
         FIG. 14  is a drawing showing a state in which an engaging portion  52   a  of a second cam  52  engages an engaged portion  140   a  of a lowering rack  140 . 
         FIG. 15  is a drawing showing a state in which an elevating rack  130  reaches a terminal end of a rectilinear movement in one direction. 
         FIG. 16  is a timing diagrammatic drawing relating to an operation of the maintenance unit  24 . 
         FIG. 17  is a drawing showing a state in which the maintenance unit  24  is ready for the cleaning operation. 
         FIG. 18A  is a drawing showing a state in which the two atmosphere release valves  80  and  81  are in a closed state. 
         FIG. 18B  is a drawing showing a state in which the one atmosphere release valve  81  is in the opened state. 
         FIG. 18C  is a drawing showing a state in which the other atmosphere release valve  80  is in the opened state. 
         FIG. 19  is a drawing showing a state in which the maintenance unit  24  is finished with a first movement. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Liquid Ejecting Apparatus 
     Hereinafter, an ink jet printer (hereinafter referred to as a printer  11 ) will be described as an example of a liquid ejecting apparatus in the invention. 
     Basic Configuration of Printer  11   
     Referring now to  FIGS. 1 to 3 , the basic configuration of the printer  11  according to the embodiment will be described.  FIG. 1  is a block diagram showing a configuration of the printer  11 .  FIG. 2  is a drawing schematically showing a general configuration of the printer  11  and, in the drawing, a vertical direction of the printer  11 , a direction of transport of a recording medium P, and a direction of movement of a carriage  16  are shown by arrows.  FIG. 3  is a drawing showing an array of nozzles Nz in a nozzle surface  22  and, in the drawing, the direction of transport of the recording medium P and the direction of movement of the carriage  16  are shown by arrows. 
     The printer  11  is a printing apparatus configured to print an image on the recording medium P by receiving print data from a host computer HC and ejecting ink as liquid on the recording medium P on the basis of the print data. In the embodiment, the printer  11  includes a transporting roller  13 , the carriage  16 , a head  21 , a maintenance unit  24 , and a printer controller  25  as main components as shown in  FIG. 1  and  FIG. 2 . 
     The transporting roller  13  is a roller which rotates about a revolving shaft along the direction of movement of the carriage  16  inside a frame  12  of the printer  11 . The transporting roller  13  is rotated by a drive force of a transporting motor  14  in sliding contact with the recording medium P with an outer peripheral surface thereof and transports the recording medium P in the direction of transport. 
     The carriage  16  reciprocates along a guide shaft  15  which supports the carriage  16  in the frame  12  to transfer the head  21  mounted on the carriage  16  in the direction of movement of the carriage  16 . As shown in  FIG. 2 , in order to move the carriage  16 , a drive pulley  17 , a driven pulley  18 , a drive motor  19  configured to drive the drive pulley  17 , and a timing belt  20  extended between the two pulleys are provided. The timing belt  20  is fixedly supported by the carriage  16 , and the carriage  16  moves in the direction of movement thereof by the rotation of the timing belt  20 . 
     The head  21  includes a plurality of the nozzles Nz formed on a lower surface (that is, the nozzle surface  22 ) and is configured to eject ink from the nozzles Nz toward the recording medium P. As shown in  FIG. 3 , on the nozzle surface  22 , the plurality of nozzles Nz are arranged at a regular pitch along the direction of transport and form nozzle rows. The printer  11  in this embodiment is a color ink jet printer ejecting ink in five colors, and the nozzle rows are formed for the respective colors of the ink. The nozzles Nz each include an ink chamber and a piezoelectric element, not shown, and drops of ink are ejected from the nozzle Nz by the ink chamber contracting and expanding by the operation of the piezoelectric element. 
     A plurality of (for five colors in this embodiment) ink cartridges  23  for supplying ink to the head  21  are provided and, in this embodiment, the respective ink cartridges  23  are demountably mounted on the carriage  16  as shown in  FIG. 2 . However, the configuration in which the ink cartridges  23  are mounted on the carriage  16  is not limited, and a configuration in which the ink cartridges  23  are mounted outside the carriage  16  is also applicable. 
     The maintenance unit  24  performs a cleaning operation for the nozzles Nz for maintaining ejection of ink from the nozzles Nz in a good condition. The cleaning operation is an operation to restrain clogging of the nozzles Nz caused by ink increased in viscosity near openings of the nozzles Nz, and discharge ink in the nozzles Nz for removing dusts or air bubbles mixed in the ink. When the cleaning operation is performed, the head  21  is positioned at a position (home position) at an end portion within a range of movement (in  FIG. 2 , the other end portion in the direction of movement of the carriage  16 ) where the recording medium P is not placed. The maintenance unit  24  described above is arranged so as to be positioned below the head  21  when the head  21  is positioned at the home position within the frame  12 , and collects ink (waste ink) discharged from the nozzles Nz by the cleaning operation or a flushing operation, described later. A configuration of the maintenance unit  24  will be described later in detail. 
     The printer controller  25  is configured to control the respective components (that is, the transporting roller  13 , the carriage  16 , the head  21 , and the maintenance unit  24 ) via a control circuit on the basis of the print data transmitted from the host computer HC. The state in the printer  11  is monitored by a detector group  26 , and the detector group  26  outputs signals according to the result of detection to the printer controller  25 . 
     Configuration of Maintenance Unit  24   
     Subsequently, referring to  FIG. 4  to  FIG. 8 , a configuration of the maintenance unit  24  will be described.  FIG. 4  is a drawing of the maintenance unit  24  when viewed from above and, in the drawing, a direction corresponding to the direction of movement of the carriage  16  (the direction of movement of the carriage in the drawing) and a direction corresponding to the direction of transport of the recording medium P (direction of transport in the drawing) are shown by arrows.  FIG. 5  to  FIG. 8  are cross-sectional views of  FIG. 4 .  FIG. 5  is a cross-sectional view taken along the line V-V,  FIG. 6  is a cross-sectional view taken along the line VI-VI,  FIG. 7  is a cross-sectional view taken along the line VII-VII, and  FIG. 8  is a cross section taken along the line VIII-VIII, respectively. In the respective drawings from  FIG. 5  to  FIG. 8 , the vertical direction and directions corresponding to the direction of transport of the recording medium P (direction of transport in the drawings) are indicated by arrows. 
     As shown in  FIG. 4  to  FIG. 7 , the maintenance unit  24  includes a cap unit  30  as a sealing unit, a cap elevating unit  40 , a cam unit  50  as a drive force transmitting unit, suction pumps  60 , a drive motor  70 , and two atmosphere release valves  80  and  81 . 
     The cap unit  30  is configured to come into contact with the nozzle surface  22  of the head  21  in a state of being positioned at the home position to close the nozzles Nz (more specifically, the openings of the nozzles Nz) when performing the cleaning operation described above. The cap unit  30  is stored in a cap unit chamber  91  formed in a casing  90  of the maintenance unit  24  as shown in  FIG. 4 . 
     The cap unit  30  includes substantially box-shaped cap members  31  each formed with a square opening on top surface, and a cap holder  32  for storing the cap members  31  as shown in  FIGS. 4 and 5 . The cap holder  32  accommodates a plurality of (five in this embodiment) the cap members  31  so as to correspond to the plurality of nozzle rows formed on the nozzle surface  22  respectively. The plurality of cap members  31  are arranged along the longitudinal direction (that is, the direction corresponding to the direction of movement of the carriage  16 ) of the cap holder  32  as shown in  FIG. 4 . 
     As shown in  FIG. 4  and  FIG. 5 , the cap members  31  each include a rubber-made seal member  31   a  which surrounds the opening formed on top surface thereof. Then, the cap unit  30  seals the nozzles Nz by bringing the seal members  31   a  of the respective cap members  31  into tight contact with the nozzle surface  22  so as to surround the nozzle rows corresponding to the respective cap members  31 . When the seal members  31   a  come into tight contact with the nozzle surface  22 , recessed-shaped spaces are formed between the nozzles Nz and the cap unit  30 . In other words, when the seal members  31   a  come into tight contact with the nozzle surface  22 , spaces surrounded by the nozzle surface  22  and the cap members  31  are formed immediately below the openings of the nozzles Nz. The spaces serve as spaces for receiving waste ink ejected from the nozzles Nz by the cleaning operation and, are referred to as waste ink receiving spaces. Forming the waste ink receiving spaces to bring the cap unit  30  into a state in which the cleaning operation (that is, sucking action of waste ink) is performable, or into a state in which evaporation of ink from the nozzles Nz is restrained is referred to as “sealing”. 
     What is essential is to bring the state of the cap unit  30  in the above-described state (that is, a state in which the nozzles Nz are sealed) and, for example, a state in which the cap unit  30  seals the nozzles Nz in a state in which the seal members  31   a  are in tight contact with portion other than the nozzle surface  22  is also applicable. Also, in the state in which the cap unit  30  seals the nozzles Nz, the waste ink receiving spaces may be closed spaces by being partitioned by the nozzle surface  22  and the cap members  31  (that is, airtight spaces), or may not be the closed spaces. 
     The cap unit  30  is able to reciprocate in the vertical direction in the cap unit chamber  91  by the cap elevating unit  40 . In other words, the vertical direction corresponds to the direction of movement of the cap unit  30  in this embodiment. In a stroke of movement where the cap unit  30  moves in the vertical direction, when the cap unit  30  reaches an upper end (that is, a top dead center), the cap unit  30  comes into contact with the nozzle surface  22  of the head  21  at the home position and seals the nozzles Nz. The upper end of the stroke of movement corresponds to a sealing position. In contrast, in the stroke of movement as described above, when the cap unit  30  reaches a lower end (that is, a bottom dead center), the cap unit  30  is apart from the nozzles Nz, and is positioned at a farthest position from the nozzles Nz. The lower end of the stroke of movement corresponds to an off position. In a state in which the cap unit  30  is positioned at the off position, the head  21  is movable in the direction of movement (the direction of movement of the carriage  16 ) without being interfered by the cap unit  30 . 
     The cap elevating unit  40  is configured to make the cap unit  30  reciprocate in the vertical direction, and includes a slider  41  and a slider drive mechanism  100  shown in  FIG. 6 . 
     The slider  41  is a substantially H-shaped resin mold member having a pair of rectangular plate-shaped vertical portions  41   a  being upright substantially vertically outsides both ends of the cap holder  32  in the longitudinal direction (see  FIG. 6 ), and a horizontal portion  41   b  arranged between the vertical portions  41   a  at a position slightly above lower ends of the respective vertical portions  41   a  (see  FIG. 12 ). The slider  41  is stored in the cap unit chamber  91  in a state in which the horizontal portion  41   b  is positioned below the cap holder  32 . Then, the slider  41  is rectilinearly reciprocated in a direction intersecting the vertical direction (a horizontal direction in this embodiment, more specifically, the direction corresponding to the direction of transport of the recording medium P). By the rectilinear movement of the slider  41 , the cap unit  30  reciprocates between the sealing position and the off position in the vertical direction. 
     More specifically, the cap holder  32  includes side walls  32   a  opposing the slider  41  (more specifically, the vertical portions  41   a  of the slider  41 ) at the both end portions in the longitudinal direction. The side walls  32   a  each include column-shaped projecting portions  33  projecting outwardly of the respective side walls  32   a  as shown in  FIG. 5 . In contrast, the vertical portions  41   a  of the slider  41  are each formed with groove cams  42  to which the projecting portions  33  engage as shown in  FIG. 6 . The groove cams  42  each include a portion inclined with respect to the horizontal direction. The groove cam  42  is formed in such a manner that one groove cam end  42   e  (an end positioned on the other end side in the direction corresponding to the direction of transport of the recording medium P) is positioned above the other groove cam end  42   f  (an end positioned on one end side in the direction corresponding to the direction of transport of the recording medium P) and the distance between the one groove cam end  42   e  and the other groove cam end  42   f  in the vertical direction is equal to the distance between the sealing position and the off position in the vertical direction. By the engagement (more specifically, fitted engagement) of the projecting portions  33  with the groove cams  42 , the slider  41  supports the cap unit  30  in such a manner that the projecting portions  33  are slidable in the groove cams  42 . 
     The pair of vertical portions  41   a  of the slider  41  in this embodiment are each formed with the two groove cams  42  having the same shape as shown in  FIG. 6 , and a positional relationship between the two groove cams  42  is a relationship achieved by being translated in the longitudinal direction (a direction along the direction corresponding to the direction of transport of the recording medium P) of the vertical portions  41   a  of the slider  41 . The side walls  32   a  of the cap holder  32  have two each of projecting portions  33  and the projecting portions  33  engage the corresponding groove cams  42 . 
     When the slider  41  having the groove cams  42  as described above moves rectilinearly in the direction from the other end to one end in the direction corresponding to the direction of transport of the recording medium P (in  FIG. 6 , the direction indicated by an arrow X and is referred to as one direction, hereinafter), the projecting portions  33  slide in the groove cams  42  along the groove cams  42  toward the one groove cam ends  42   e . At this time, since the projecting portions  33  are pushed upward by the bottom portions of the groove cams  42 , the entire cap unit  30  including the cap holder  32  moves upward. Then, when the slider  41  continues to move rectilinearly and moves the projecting portions  33  finally to the one groove cam ends  42   e , the cap unit  30  reaches the sealing position as shown in  FIG. 9 .  FIG. 9  is a drawing showing a state in which the cap unit  30  is positioned at the sealing position.  FIG. 6  and  FIG. 9  correspond to each other, and  FIG. 6  shows a state in which the cap unit  30  is positioned at the off position. 
     In the same manner, when the slider  41  moves rectilinearly in the direction from the one end to the other end in the direction corresponding to the direction of transport of the recording medium P (in  FIG. 6 , the direction indicated by an arrow Y and is referred to as the other direction, hereinafter), the projecting portions  33  are caused to move to the other groove cam ends  42   f  along the groove cams  42 . At this time, the projecting portions  33  slide in the groove cams  42  as if they drop down along the groove cams  42 , and hence the entire cap unit  30  moves downward. As shown in  FIG. 7  and  FIG. 8 , substantially cylindrical shaped tube supporting portions  82   b  and  83   b  are formed on the opposite side of the lip portions  82   a  and  83   a  with the intermediary of the inner walls of the valve seat forming members  82  and  83 . Then, when the projecting portions  33  move to the other groove cam ends  42   f , as shown in  FIG. 6 , the cap unit  30  reaches the off position. 
     As described above, the slider  41  guides the cap unit  30  to the sealing position by moving rectilinearly in the one direction, and guides the cap unit  30  to the off position by moving rectilinearly in the other direction. Here, the one direction and the other direction are opposite directions from each other, and are two directions intersecting the vertical direction, which is the direction of movement of the cap unit  30 . 
     The groove cams  42  according to the embodiment will be described in further detail. As shown in  FIG. 6 , upper horizontal grooves  42   a , gently inclined grooves  42   b , steeply inclined grooves  42   c , and lower horizontal grooves  42   d  are arranged in sequence from the one groove cam ends  42   e  to the other groove cam ends  42   f . The upper horizontal grooves  42   a  are portions for holding the cap unit  30  in the sealing position. The lower horizontal grooves  42   d  are portions for holding the cap unit  30  in the off position. The gently inclined grooves  42   b  and the steeply inclined grooves  42   c  are both inclined with respect to the horizontal direction, and are portions to move the cap unit  30  in the vertical direction by sliding the projecting portions  33  of the cap holder  32  in the interiors thereof. 
     Then, the angle of inclination of the gently inclined grooves  42   b  positioned on the sides of the one groove cam ends  42   e  is smaller than the angle of inclination of the steeply inclined grooves  42   c . It is for reducing a load applied to equipment (for example, the slider  41  or the slider drive mechanism  100 ) for elevating the cap unit  30  when bringing the cap unit  30  into contact with the nozzle surface  22  by elevating the cap unit  30  to the sealing position (more specifically, when bringing the seal members  31   a  into tight contact with the nozzle surface  22 ). More specifically, the load is inevitably generated when securing a contact pressure between the cap unit  30  and the nozzle surface  22 , and is increased with increase in speed to bring the cap unit  30  into contact with the nozzle surface  22  (elevating speed). Therefore, in this embodiment, the load is alleviated by moving the cap unit  30  gently by designing the angle of inclination of the groove cams  42  where the projecting portions  33  pass to be gentle immediately before the cap unit  30  comes into contact with the nozzle surface  22 . 
     The slider drive mechanism  100  is a drive mechanism for rectilinearly moving the slider  41  and performs a first movement for moving the slider  41  rectilinearly in the one direction and a second movement for moving the slider  41  rectilinearly in the other direction by a drive force transmitted from the drive motor  70 . The detailed description of the slider drive mechanism  100  will be given later. 
     The cam unit  50  is configured to transmit the drive force from the drive motor  70  to the slider drive mechanism  100  by rotating in a state of engaging the slider drive mechanism  100  in association with the rotation of the drive motor  70 . The cam unit  50  in this embodiment has a function to open the atmosphere release valves  80  and  81  by rotating in a state of engaging the atmosphere release valves  80  and  81 . Then, the cam unit  50  includes a first cam  51 , a second cam  52 , two third cams  53  and  54 , and a cam shaft  55  for supporting these cams as shown in  FIG. 5  to  FIG. 8 . The axial direction of the cam shaft  55  extends along the direction corresponding to the direction of movement of the carriage  16  and, the one third cam  53 , the other third cam  54 , the second cam  52 , and the first cam  51  are arranged in sequence from an axially one end (one end of the direction corresponding to the direction of movement of the carriage  16 ) of the cam shaft  55  in the axial direction. 
     As shown in  FIG. 5  or  FIG. 6 , the first cam  51  and the second cam  52  are cams having engaging portions  51   a  and  52   a  projecting in a hook shape. The first cam  51  transmits the drive force from the drive motor  70  to the slider drive mechanism  100  by rotating in a state of engaging the slider drive mechanism  100  (more specifically, an engaged portion  130   a  of an elevating rack  130 , described later) when the slider drive mechanism  100  performs the first movement. In other words, the first cam  51  is a cam for causing the slider drive mechanism  100  to perform the first movement. The second cam  52  transmits the drive force from the drive motor  70  to the slider drive mechanism  100  by rotating in a state of engaging the slider drive mechanism  100  (more specifically, an engaged portion  140   a  of a lowering rack  140 , described later) when the slider drive mechanism  100  performs the second movement. In other words, the second cam  52  is a cam for causing the slider drive mechanism  100  to perform the second movement. 
     The two third cams  53  and  54  are cams having the engaging portions  53   a  and  54   a  projecting in a projecting shape as shown in  FIG. 7  and  FIG. 8  respectively. The third cams  53  and  54  open the corresponding atmosphere release valves  80  and  81  by rotating in a state of engaging the corresponding atmosphere release valves  80  and  81  (more specifically, the engaged portions  80   a  and  81   a  of the atmosphere release valves  80  and  81 ). 
     The cam shaft  55  rotates integrally with the first cam  51 , the second cam  52 , and the two third cams  53  and  54  when the drive motor  70  rotates (more specifically, when the drive motor  70  rotates in the normal direction as described above). Then, the cam shaft  55  according to the embodiment rotates always in a constant direction of rotation when rotating (the direction indicated by an arrow R in  FIG. 5 ). Therefore, the direction of rotation of the entire cam unit  50  including the cam shaft  55  is always the constant direction. 
     The suction pumps are devices configured to suck ink from the nozzles Nz during the cleaning operation (that is, the ink in the nozzles Nz is forcedly discharged from the nozzles Nz). The suction pumps  60  in this embodiment are tube pumps each including a revolving shaft, not shown, and performing a sucking action by the rotating revolving shaft. 
     The suction pumps  60  suck air in internal spaces in the interiors of the cap members  31  through connecting tubes connected to the internal spaces of the cap members  31 . In other words, when the cap unit  30  comes into contact with the nozzle surface  22  of the head  21  and the waste ink receiving spaces are formed between the nozzles Nz and the cap unit  30 , the suction pumps  60  suck air in the waste ink receiving spaces. Accordingly, the waste ink receiving spaces assume a negative pressure state. Consequently, the suction pumps  60  suck ink in the nozzles Nz from the nozzles (in other words, the waste ink receiving spaces receive the waste ink). Also, when the waste ink receiving spaces are brought from the negative pressure state to an atmosphere release state during the operation of the suction pumps  60 , the suction pumps  60  suck air in the waste ink receiving spaces but does not suck ink in the nozzles Nz (so-called opened suction). At this time, when the waste ink is stored in the waste ink receiving spaces, the suction pumps  60  suck waste ink from the waste ink receiving spaces and deliver the waste ink to a waste ink tank, not shown. 
     In this embodiment, there are provided two such suction pumps  60  (only one of the suction pumps  60  is shown in  FIG. 5  or  FIG. 6  for the convenience of representation in the drawings). One of the two suction pumps  60  corresponds to the cap member  31  positioned closest to the one end of the cap holder  32  in the longitudinal direction (hereinafter, referred to as the cap member  31  at one end) and the other suction pump  60  corresponds to the remaining cap members  31 . In other words, one of the suction pumps  60  sucks air in the internal space of the cap member  31  at the one end and the other suction pump  60  sucks air in the internal spaces of the remaining cap members  31  respectively. 
     The drive motor  70  is a motor as a common drive source for the cam unit  50  and the suction pumps  60 . The drive motor  70  and a drive shaft  71  connected directly to the drive motor  70  are stored in a motor box  92 , and the motor box  92  is arranged in parallel with the casing  90  on one end side in a direction corresponding to the direction of transport of the recording medium P as shown in  FIG. 4 . The drive motor  70  and the drive shaft  71  in this embodiment are rotatable both in the normal direction and the reverse direction. 
     The drive shaft  71  is interlocked with the above-described cam shaft  55  via a gear train (not shown) stored in a gear box  93  shown in  FIG. 4 . In this embodiment, a one-way clutch is formed at a final stage of the gear train. In this embodiment, with the one-way clutch, when the drive motor  70  rotates in the normal direction, the cam unit  50  including the cam shaft  55  rotating in association with the rotation of the drive motor  70 . In contrast, when the drive motor  70  rotates in the reverse direction, the cam unit  50  does not rotate. The drive shaft  71  is interlocked also with the revolving shafts of the respective suction pumps  60 , and one-way clutches are formed at final stages of transmission mechanisms (not shown) provided between the drive shaft  71  and the revolving shafts of the respective suction pumps  60 . With the one-way clutches, in this embodiment, when the drive motor  70  rotates in the reverse direction, the drive force of the drive motor  70  is transmitted to the suction pumps  60  via the drive shaft  71  and the revolving shafts of the suction pumps  60 , so that the suction pumps  60  are activated. In contrast, when the drive motor  70  rotates in the normal direction, the suction pumps  60  are not driven. In this embodiment, when the drive motor  70  rotates in the reverse direction, both of the two suction pumps  60  are activated simultaneously. 
     In this manner, in this embodiment, the drive source of the cam unit  50  and the drive source of the suction pumps  60  are common, so that the simplification of devices in the printer  11  (more specifically, the maintenance unit  24  of the printer  11 ) is achieved. 
     The two atmosphere release valves  80  and  81  are valves to communicate the internal spaces of the cap members  31  with the atmosphere when released. In other words, the atmosphere release valves  80  and  81  restore the waste ink receiving spaces described above to the atmosphere release state by releasing the above-described waste ink receiving spaces in the negative pressure state. In this embodiment, the atmosphere release valve  80 , which is one of the two atmosphere release valves  80  and  81 , corresponds to the cap member  31  at the one end, and the other atmosphere release valve  81  corresponds to the remaining cap members  31 . 
     The atmosphere release valves  80  and  81  are members of an elongated lever shape as shown in  FIG. 7  and  FIG. 8 . At one end portions of the respective atmosphere release valves  80  and  81  in the longitudinal direction, the hook-shaped engaged portions  80   a  and  81   a  are formed as shown in  FIG. 7  and  FIG. 8 . The engaged portions  80   a  and  81   a  engage the corresponding third cams  53  and  54 . In association with the fact that one of the two atmosphere release valves  80  and  81  corresponds to the cap member  31  at the one end and the other one corresponds to the remaining cap members  31  as described above, the one third cam  53  of the two third cams  53  and  54  corresponds to the cap member  31  at the one end, and the other third cam  54  corresponds to the remaining cap members  31 . The other end portions  80   b  and  81   b  in the longitudinal direction of the respective atmosphere release valves  80  and  81  have valve element supporting portions  80   c  and  81   c  projecting upward as shown in  FIG. 7  and  FIG. 8 . Respective valve elements  80   d  and  81   d  are supported by the respective valve element supporting portions  80   c  and  81   c  in a state of covering over the valve element supporting portions  80   c  and  81   c.    
     Valve seats with respect to the valve elements  80   d  and  81   d  are lip portions  82   a  and  83   a  provided on valve seat forming members  82  and  83  as shown in  FIG. 7  and  FIG. 8 . The lip portions  82   a  and  83   a  are substantially cylindrical portions projecting toward the one end side of the direction corresponding to the direction of transport of the recording medium P as shown in  FIG. 7  and  FIG. 8 , and come into contact with the valve elements  80   d  and  81   d  at distal end portions  82   c  and  83   c  thereof. The tube supporting portions  82   b  and  83   b  support terminal ends of the connecting tubes (not shown) connected to the cap members  31  by fitting the terminal ends of the connecting tubes. In this embodiment, the one tube supporting portion  82   b  supports the terminal end of the connecting tube connected to the cap member  31  at the one end. The other the other tube supporting portion  83   b  supports the terminal end of the connecting tube which is a unified portion of the connecting tube which is branched at a distal end and connected to the respective cap members  31 . 
     As shown in  FIG. 7  and  FIG. 8 , internal spaces of the lip portions  82   a  and  83   a  and internal spaces of the tube supporting portions  82   b  and  83   b  are communicated via communication holes  82   d  and  83   d . Therefore, the internal spaces of the lip portions  82   a  and  83   a  are in communication with the internal spaces of the cap members  31  via the connecting tubes supported by the tube supporting portions  82   b  and  83   b . Then, when the valve elements  80   d  and  81   d  and the distal end portions  82   c  and  83   c  of the lip portions  82   a  and  83   a  come into contact with each other, distal end openings of the lip portions  82   a  and  83   a  are closed, and hence terminal end openings of the connecting tubes are closed. In contrast, when the valve elements  80   d  and  81   d  move away from the distal end portions  82   c  and  83   c  of the lip portions  82   a  and  83   a , the distal end openings of the lip portions  82   a  and  83   a  are released, and hence the internal spaces of the connecting tubes communicate with the atmosphere. 
     The respective atmosphere release valves  80  and  81  are supported so as to be pivotable about pivotal shafts  80   e  and  81   e . Also, the atmosphere release valves  80  and  81  are urged in the direction in which the valve elements  80   d  and  81   d  pivot to come into contact with the distal end portions  82   c  and  83   c  of the lip portions  82   a  and  83   a  by an urging member, not shown. 
     Subsequently, opening and closing of the atmosphere release valves  80  and  81  configured as described above will be described. While the engaged portions  80   a  and  81   a  of the atmosphere release valves  80  and  81  are not in engagement with the engaging portions  53   a  and  54   a  of the corresponding third cams  53  and  54 , since the atmosphere release valves  80  and  81  are urged by the urging member as described above, the valve elements  80   d  and  81   d  of the atmosphere release valves  80  and  81  are continuously in contact with the distal end portions  82   c  and  83   c  of the lip portions  82   a  and  83   a  as shown in  FIG. 7  and  FIG. 8 . In other words, at this time, the respective atmosphere release valves  80  and  81  are in a closed sate. In contrast, when the corresponding third cams  53  and  54  rotate in a state in which the engaged portions  80   a  and  81   a  of the atmosphere release valves  80  and  81  and the engaging portions  53   a  and  54   a  of the corresponding third cams  53  and  54  are in engagement, the atmosphere release valves  80  and  81  pivot in such a manner that the valve elements  80   d  and  81   d  moves away from the distal end portions  82   c  and  83   c  of the lip portions  82   a  and  83   a  about the pivotal shafts  80   e  and  81   e . In other words, the engaging portions  53   a  and  54   a  of the third cams  53  and  54  press the engaged portions  80   a  and  81   a  of the corresponding atmosphere release valves  80  and  81  in the direction of rotation of the third cams  53  and  54  against an urging force of the urging member acting on the corresponding atmosphere release valves  80  and  81 . Accordingly, as shown in  FIG. 10  and  FIG. 11 , the valve elements  80   d  and  81   d  of the atmosphere release valves  80  and  81  move away from the distal end portions  82   c  and  83   c  of the lip portions  82   a  and  83   a , and the atmosphere release valves  80  and  81  are brought into an opened sate.  FIG. 10  and  FIG. 11  show a state in which the atmosphere release valves  80  and  81  are respectively brought into the opened state, and correspond respectively to  FIG. 7  and  FIG. 8 . 
     Then, when the cap members  31  are in contact with the nozzle surface  22 , if the atmosphere release valves  80  and  81  corresponding to the cap members  31  are in the closed state, the terminal end openings of the connecting tubes connected to the cap members  31  are closed, so that the internal spaces (waste ink receiving spaces) of the cap members  31  are isolated from the atmosphere. In contrast, when the cap members  31  are in contact with the nozzle surface  22 , if the atmosphere release valves  80  and  81  corresponding to the cap members  31  are in the opened state, the internal spaces of the connecting tubes connected to the cap members  31  are brought into communication with the atmosphere, so that the internal spaces of the cap members  31  are brought into the atmosphere release state. 
     With the maintenance unit  24  in the configuration as described above, the cleaning operation and operations in association with the cleaning operation are performed. As described above, the plurality of cap members  31  are provided corresponding respectively to the plurality of nozzle rows formed on the nozzle surface  22  of the head  21  in this embodiment. Also, the suction pumps  60  and the atmosphere release valves  80  and  81  are separated into the one corresponding to the cap member  31  at the one end and the one corresponding to the remaining cap members  31 . Furthermore, in this embodiment, a timing to open the atmosphere release valves  80  and  81  while the suction pumps  60  are in operation is changed between the atmosphere release valves  80  and  81 . 
     More specifically, the atmosphere release valve  80  corresponding to the cap member  31  at the one end is closed and the atmosphere release valve  81  corresponding to the remaining cap members  31  is opened at a certain period while the two respective suction pumps  60  are in operation in a state in which the cap unit  30  is positioned at the sealing position. Therefore, in the above-described certain period, the suction pump  60  corresponding to the cap member  31  at the one end brings the internal space (that is, the waste ink receiving space) of the cap member  31  at the one end into the negative pressure state, and performs an operation to suck ink in the respective nozzles Nz sealed by the cap member  31  at the one end (closed suction). In contrast, in the certain period as described above, since the internal spaces of the remaining cap members  31  are in the atmosphere release state, the suction pump  60  corresponding to the remaining cap members  31  performs an opened suction. 
     Then, in this embodiment, only the cap member  31  at the one end and the suction pump  60  corresponding to the cap member  31  at the one end perform the closed suction for the cleaning operation. In other words, only one nozzle row closed by the cap member  31  at the one end from among the plurality of nozzle rows formed on the nozzle surface  22  of the head  21  corresponds to the object of the cleaning operation. That is, when performing the cleaning operation, the one nozzle row as the object of the cleaning operation is positioned above the cap member  31  at the one end in the direction of movement of the head  21 . On the other hand, when performing the flushing operation, described later, the plurality of nozzle rows formed on the nozzle surface  22  are respectively positioned above the corresponding cap members  31  (in other words, the respective nozzle rows and the respective cap members  31  are positioned in pairs). An operation of the maintenance unit  24  will be described again in detail later. 
     Slider Drive Mechanism  100   
     Referring now to  FIG. 5  and  FIG. 6 , which are already described above, and  FIG. 12  and  FIG. 13 , a configuration of the slider drive mechanism  100  will be described.  FIG. 12  and  FIG. 13  are explanatory drawings showing the configuration of the slider drive mechanism  100 .  FIG. 12  is a cross section taken along the line XII-XII in  FIG. 6 , and  FIG. 13  is a cross section taken along the line XIII-XIII in  FIG. 6 , respectively. In  FIG. 12  and  FIG. 13 , a direction corresponding to the direction of movement of the carriage  16  and a direction corresponding to the direction of transport of the recording medium P are shown by arrows, respectively. For the convenience of representation in the drawing, the cross section taken along the line XIII-XIII in  FIG. 13  includes cross sections at different positions in the vertical direction between the cross sections on the one end side and the other end side in the direction corresponding to the direction of transport (see  FIG. 6 ). 
     The slider drive mechanism  100  performs the first movement for moving the slider  41  rectilinearly in the one direction and the second movement for moving the slider  41  rectilinearly in the other direction by the drive force from the drive motor  70  transmitted by the cam unit  50  as described above. In other words, the slider drive mechanism  100  is configured to transform the rotational movement of the drive motor  70  in the normal direction (more specifically, the rotational movement of the drive shaft  71 ) to the rectilinear movement of the slider  41  in cooperation with the cam unit  50 . 
     The slider drive mechanism  100  includes a slider rack  110  as a first rack, a composite gear  120 , and the elevating rack  130  and the lowering rack  140  as a pair of second racks as shown in  FIG. 5 ,  FIG. 6 ,  FIG. 12 , and  FIG. 13 . 
     The slider rack  110  is a rack projecting from an inner wall surface of the vertical portion  41   a  (the vertical portion  41   a  at the other end side in the direction corresponding to the direction of movement of the carriage  16 ) of the slider  41  as shown in  FIG. 12 . The slider rack  110  is integrally molded with the slider  41 , and is fixed to the slider  41 . Therefore, the slider rack  110  is interlocked with the slider  41 . In other words, when the slider rack  110  is moved, the slider  41  is moved integrally with the slider rack  110  in the direction of movement of the slider rack  110 . Respective teeth of the slider rack  110  are arranged in the direction corresponding to the direction of transport of the recording medium P, that is, along the direction of the rectilinear movement of the slider  41 . 
     The composite gear  120  is positioned below the horizontal portion  41   b  of the slider  41  in the interior of the casing  90 , and includes a large gear  121  shown in  FIG. 12  and a small gear  122  shown in  FIG. 13 . The composite gear  120  is mounted in the cap unit chamber  91  in a state in which the large gear  121  is positioned above the small gear  122 , and a revolving shaft extend along the vertical direction, and is able to rotate about the revolving shaft in the normal direction and the reverse direction. The position of arrangement of the composite gear  120  in the cap unit chamber  91  is a position at which the large gear  121  engages the slider rack  110 . 
     Then, the composite gear  120  moves the slider rack  110  rectilinearly in the one direction when the large gear  121  rotates in the normal direction in a state of engaging the slider rack  110 . Consequently, the slider  41  to which the slider rack  110  is fixed moves rectilinearly in the one direction. In contrast, the composite gear  120  moves the slider rack  110  rectilinearly in the other direction when the large gear  121  rotates in the reverse direction in the state of engaging the slider rack  110 . Consequently, the slider  41  moves rectilinearly in the other direction. In other words, in this embodiment, a pinion-rack mechanism is employed as a mechanism to move the slider  41  rectilinearly. 
     The elevating rack  130  and the lowering rack  140  are both formed of plate-shaped members, and are racks being positioned on a bottom surface of the cap unit chamber  91  and engaging the small gear  122  in an opposed state, and the lowering rack  140  is arranged on one end side and the elevating rack  130  is arranged on the other end side in the direction corresponding to the direction of movement of the carriage  16 . The elevating rack  130  and the lowering rack  140  are each formed with teeth for engaging the small gear  122  on the other end portion in a direction corresponding to the direction of transport of the recording medium P as shown in  FIG. 13 . The elevating rack  130  and the lowering rack  140  are both attached in the interior of the cap unit chamber  91  so as to be movable rectilinearly in the direction corresponding to the direction of transport (that is, in the direction of rectilinear movement of the slider  41 ). 
     Then, when the elevating rack  130  is moved rectilinearly in the one direction (the direction from the other end to the one end in the direction corresponding to the direction of transport of the recording medium P, and is the direction indicated by a sign T in  FIG. 13 ) in a state of engaging the small gear  122 , the composite gear  120  including the small gear  122  rotates in the normal direction. At this time, the lowering rack  140  engaging the small gear  122  at a position opposing the elevating rack  130  moves rectilinearly in the other direction (the direction opposite from the direction of rectilinear movement of the elevating rack  130 ). In the same manner, when the lowering rack  140  is moved rectilinearly in the one direction in a state of engaging the small gear  122 , the composite gear  120  including the small gear  122  rotates in the reverse direction, so that the elevating rack  130  is moved rectilinearly in the other direction (the direction opposite from the direction of the rectilinear movement of the lowering rack  140 ). 
     Provided at one end portion of the elevating rack  130  in the direction corresponding to the direction of transport is the engaged portion  130   a  which engages the engaging portion  51   a  of the first cam  51  in a state of being projected from an upper surface of the elevating rack  130  substantially in the vertical direction. Then, when the first cam  51  rotates in a state in which the engaging portion  51   a  of the first cam  51  engages the engaged portion  130   a  of the elevating rack  130 , as shown in  FIG. 13 , a pressing force F 1  that the engaging portion  51   a  of the first cam  51  presses the elevating rack  130  in the one direction is generated. The elevating rack  130  is moved rectilinearly in the one direction by the pressing force F 1 . 
     In the same manner, provided at one end portion of the lowering rack  140  in the direction corresponding to the direction of transport is the engaged portion  140   a  which engages the engaging portion  52   a  of the second cam  52  in a state of being projected from an upper end surface of the lowering rack  140  substantially in the vertical direction. Then, when the second cam  52  rotates in a state in which the engaging portion  52   a  thereof engages the engaged portion  140   a  of the lowering rack  140 , as shown in  FIG. 14 , a pressing force F 2  that the engaging portion  52   a  of the second cam  52  presses the lowering rack  140  in the one direction is generated. The lowering rack  140  is moved rectilinearly in the one direction by the pressing force F 2 .  FIG. 14  is a drawing showing the state in which the engaging portion  52   a  of the second cam  52  engages the engaged portion  140   a  of the lowering rack  140 , and corresponds to  FIG. 13 . 
     The slider drive mechanism  100  having the configuration as described above receives the drive force from the drive motor  70  via the cam unit  50 , which rotates in the direction indicated by the arrow R in  FIG. 5  in association with the rotation of the drive motor  70  in the normal direction, and performs the first movement and the second movement as described above by the drive force. 
     More specifically, when the first cam  51  reaches a position where the engaging portion  51   a  of the first cam  51  engages the engaged portion  130   a  of the elevating rack  130  in the direction of rotation by the rotation of the cam unit  50 , and then the cam unit  50  further continues to rotate, the first cam  51  rotates in the state in which the engaging portion  51   a  of the first cam  51  engages the engaged portion  130   a  of the elevating rack  130 , so that the elevating rack  130  is moved rectilinearly in the one direction. Accordingly, the composite gear  120  rotates in the normal direction. The composite gear  120  rotates in the normal direction and moves the lowering rack  140  which engages the small gear  122  on the opposite side from the elevating rack  130  rectilinearly in the other direction, and moves the slider rack  110  which engages the large gear  121  rectilinearly in the one direction integrally with the slider  41 . A series of operations as described above corresponds to the first movement of the slider drive mechanism  100 . Then, at a time point when the elevating rack  130  reaches the terminal end of the rectilinear movement in the one direction (the position of the elevating rack  130  shown in  FIG. 15 ), the first movement is completed, and the elevation of the cap unit  30  by the slider  41  is also ended (brought into the state in which the cap unit  30  is positioned at the sealing position).  FIG. 15  is a drawing showing a state in which the elevating rack  130  reaches the terminal end of the rectilinear movement in the one direction, which corresponds to  FIG. 12 . 
     In contrast, when the second cam  52  reaches a position where the engaging portion  52   a  of the second cam  52  engages the engaged portion  140   a  of the lowering rack  140  in the direction of rotation thereof by the rotation of the cam unit  50 , and then the cam unit  50  further continues to rotate, the second cam  52  rotates in the state in which the engaging portion  52   a  of the second cam  52  engages the engaged portion  140   a  of the lowering rack  140 , so that the lowering rack  140  is moved rectilinearly in the one direction. Accordingly, the composite gear  120  rotates in the reverse direction. The composite gear  120  rotates in the reverse direction and moves the elevating rack  130  which engages the small gear  122  on the opposite side from the lowering rack  140  rectilinearly in the other direction, and moves the slider rack  110  which engages the large gear  121  rectilinearly in the other direction integrally with the slider  41 . The series of operations as described above corresponds to the second movement of the slider drive mechanism  100 . Then, at a time point when the lowering rack  140  reaches the terminal end of the rectilinear movement in the one direction (the position of the lowering rack  140  shown in  FIG. 12 ), the second movement is completed, and the lowering of the cap unit  30  by the slider  41  is also ended (brought into the state in which the cap unit  30  is positioned at the off position). 
     In this embodiment, as shown in  FIG. 13  and  FIG. 14 , a coil spring  132  is arranged in the interior of the cap unit chamber  91 . The coil spring  132  urges the elevating rack  130  in the one end side of the direction corresponding to the direction of transport of the recording medium P in a state in which one end portion thereof is in contact with the other end of the same direction. Therefore, in the second movement in which the elevating rack  130  is moved rectilinearly in the other direction (in other words, the lowering rack  140  is moved rectilinearly in the one direction), the elevating rack  130  moves rectilinearly in the other direction against the urging force. When the cap unit  30  is moved downward by the slider drive mechanism  100  causing the slider  41  to move in the other direction by the urging force of the coil spring  132 , abrupt lowering of the cap unit  30  is prevented. Accordingly, an impact applied to the cap unit  30  when the cap unit  30  is lowered to the off position may be alleviated. 
     Operation of Maintenance Unit  24   
     Referring now to  FIG. 16 , the operation of the maintenance unit  24  such as the vertical movement of the cap unit  30  or an opening and closing operation of the respective atmosphere release valves  80  and  81  will be described.  FIG. 16  is a timing diagrammatic drawing relating to the operation of the maintenance unit  24 . The lateral axis of the same diagrammatic drawing indicates the amount of rotation of the cam unit  50  from a reference time point (angle of rotation), and in the following description, a time point when the first cam  51  starts to engage the elevating rack  130  is defined as the reference time point (that is, a time point when the angle of rotation is 0 degree). 
     When the maintenance unit  24  performs the cleaning operation as described above, first of all, the head  21  moves to the home position in association with the movement of the carriage  16 . At this time, the maintenance unit  24  is a state shown in  FIG. 17  when viewed from above, and in this state, the cap unit  30  is positioned at the off position in the vertical direction.  FIG. 17  is a drawing showing a state in which the maintenance unit  24  is ready for the cleaning operation. At this time, as shown in  FIG. 18A , the two atmosphere release valves  80  and  81  are both in the closed state.  FIG. 18A  is a drawing when the two atmosphere release valves  80  and  81  are in the closed sate, and is an enlarged drawing showing the periphery of the atmosphere release valves  80  and  81  in  FIG. 4 . 
     When the head  21  reaches the home position, the respective nozzle rows formed on the nozzle surface  22  are positioned right above the opening of the corresponding cap members  31  (for example, the nozzle row positioned at the extremity at one end side in the direction of movement of the head  21  is positioned right above the opening of the cap member  31  at the one end). In this state, the drive motor  70  rotates in the normal direction, and the cam unit  50  rotates in association with the rotation of the drive motor  70 . At a time point when the cam unit  50  starts to rotate (more specifically, it is a time point when the cam unit  50  starts to rotate firstly after the head  21  is positioned at the home position, and corresponds to the reference time point described above), the engaging portion  51   a  of the first cam  51  engages the engaged portion  130   a  of the elevating rack  130 . 
     By the rotation of the cam unit  50 , the first cam  51  rotates in the state in which the engaging portion  51   a  thereof engages the engaged portion  130   a  of the elevating rack  130 . Accordingly, the pressing force F 1  that the engaging portion  51   a  of the first cam  51  presses the elevating rack  130  in the one direction is generated. Consequently, the slider drive mechanism  100  performs the first movement, and the slider  41  moves rectilinearly in the one direction by this first movement. Consequently, the cap unit  30  moves upward toward the sealing position as shown in  FIG. 16 . 
     In this embodiment, while the engaging portion  51   a  of the first cam  51  rotates while engaging the engaged portion  130   a  of the elevating rack  130 , the engaging state between the engaging portion  52   a  of the second cam  52  and the engaged portion  140   a  of the lowering rack  140  is released. In other words, while the first cam  51  engages the elevating rack  130 , the second cam  52  is positioned at a position away from the lowering rack  140  in the direction of rotation. In this configuration, when the first cam  51  rotates in the state of engaging the elevating rack  130 , that is, when the slider drive mechanism  100  performs the first movement, the slider drive mechanism  100  performs the first movement adequately without being interfered with the second cam  52 . The configuration as described above, may be realized by adjusting the shapes of the first cam  51  and the second cam  52  (more specifically, the shapes of the engaging portions  51   a  and  52   a ), the relative positional relationship between the position of the first cam  51  and the position of the second cam  52  viewed from the cam shaft  55 , and the shapes or the position of the engaged portions  130   a  and  140   a  of the elevating rack  130  and the lowering rack  140 . 
     Then, when the cam unit  50  rotates by about 40 degrees from the reference time point, as shown in  FIG. 16 , an operation to forcedly eject ink from the nozzles Nz of the head  21 , that is, the flushing operation is performed. The flushing operation is an operation to drive the piezoelectric elements provided for the respective nozzles to forcedly eject ink in the nozzles Nz from the nozzles Nz. The flushing operation is performed in association with the above-described cleaning operation for the purpose of discharging ink increased in viscosity in the vicinity of the openings of the nozzles Nz and putting meniscuses formed at the openings of the nozzles Nz in order. The waste ink generated by the flushing operation is received in the internal spaces of the cap members  31  corresponding to the nozzles Nz from which the waste ink is ejected (the cap members  31  positioned right below the respective nozzles Nz). Since the cap unit  30  is in the course of elevating when the flashing operation is performed, the respective cap members  31  receive the waste ink generated by the flushing operation in the internal spaces thereof while elevating. 
     By the further rotation of the cam unit  50 , the first cam  51  further rotates in the state in which the engaging portion  51   a  thereof engages the engaged portion  130   a  of the elevating rack  130 , the slider drive mechanism  100  continues to perform the first movement and the slider  41  continues to move further rectilinearly in the one direction. Accordingly, the cap unit  30  is continued to elevate further toward the sealing position. During this period, the above-described flushing operation is ended, and the head  21  is moved to a position where one of the nozzle rows which is an object of the cleaning operation is positioned right above the cap member  31  at the one end. 
     Then, at a time point when the cam unit  50  rotates by about 60 degrees from the reference time point, as shown in  FIG. 16 , the cap unit  30  reaches the sealing position and the first movement by the slider drive mechanism  100  is ended (that is, the rectilinear operation of the slider  41  in the one direction is ended), and the maintenance unit  24  assumes a state shown in  FIG. 19  when viewed from above.  FIG. 19  is a drawing showing a state of the maintenance unit  24  after the first movement is ended. 
     As a result of reaching of the cap unit  30  to the sealing position, the cap member  31  at the one end (more specifically, the seal member  31   a  of the cap member  31  at the one end) comes into contact with the nozzle surface  22  so as to surround one of the nozzle rows as the object of the cleaning operation. Then, the cap unit  50  rotates until the engaging state between the engaging portion  51   a  of the first cam  51  and the engaged portion  130   a  of the elevating rack  130  is released. More specifically, the cam unit  50  rotates until both the engaging state between the engaging portion  51   a  of the first cam  51  and the engaged portion  130   a  of the elevating rack  130  and the engaging state between the engaging portion  52   a  of the second cam  52  and the engaged portion  140   a  of the lowering rack  140  are brought into a released state. 
     When the cam unit  50  rotates by about 75 degrees from the reference time point, as shown in  FIG. 16 , the engaged portion  81   a  of the one atmosphere release valve  81  (atmosphere release valve B in  FIG. 16 ) of the two atmosphere release valves  80  and  81  and the engaging portion  54   a  of the third cam  54  corresponding to the one atmosphere release valve  81  of the two third cams  53  and  54  engage. Here, the one atmosphere release valve  81  corresponds to the cap members  31  other than the cap member  31  at the one end (that is, the remaining cap members  31 ). In other words, the one atmosphere release valve  81  corresponds to the cap members  31  which seal the nozzle rows other than the nozzle row as the object of the cleaning operation. 
     By the further rotation of the cam unit  50 , the third cam  54  corresponding to the one atmosphere release valve  81  rotates in a state in which the engaging portion  54   a  engages the engaged portion  81   a  of the one atmosphere release valve  81 , so that the one atmosphere release valve  81  gradually opens. Then, as shown in  FIG. 16 , at a time point when the cam unit  50  rotates by about 80 degrees from the reference time point, the one atmosphere release valve  81  assumes a completely opened state. In contrast, at this time, the other atmosphere release valve  80  (that is, the atmosphere release valve  80  corresponding to the cap member  31  at the one end) is still in the closed state as shown in  FIG. 18B . In other words, while the engaging portion  54   a  of the third cam  54  corresponding to the one atmosphere release valve  81  engages the engaged portion  81   a  of the atmosphere release valve  81 , an engaging state between the engaging portion  53   a  of the third cam  53  corresponding to the other atmosphere release valve  80  and the engaged portion  80   a  of the atmosphere release valve  80  is released. In other words, in this embodiment, the atmosphere release valve  81  corresponding to the remaining cap members  31  is opened prior to the atmosphere release valve  80  corresponding to the cap member  31  at the one end.  FIG. 18B  is a drawing showing a state in which the one atmosphere release valve  81  is brought into the opened state, and a state in which the one atmosphere release valve  81  is in the opened state while the other atmosphere release valve  80  is in the closed state. 
     In this embodiment, while the engaging portion  54   a  of the third cam  54  corresponding to the one atmosphere release valve  81  engages the engaged portion  81   a  of the one atmosphere release valve  81 , the engaging state between the engaging portion  51   a  of the first cam  51  and the engaged portion  130   a  of the elevating rack  130 , and the engaging state between the engaging portion  52   a  of the second cam  52  and the engaged portion  140   a  of the lowering rack  140  are both released. In other words, while the first cam  51  is positioned at a position apart from the elevating rack  130  in the direction of rotation thereof and the second cam  52  is positioned at the position apart from the lowering rack  140  in the direction of rotation thereof, the third cam  54  corresponding to the one atmosphere release valve  81  engages the one atmosphere release valve  81 . In this configuration, a timing when the third cam  54  corresponding to the one atmosphere release valve  81  rotates while engaging the one atmosphere release valve  81  is different from a timing when the first cam  51  rotates while engaging the elevating rack  130  and a timing when the second cam  52  rotates while engaging the lowering rack  140 . Consequently, a load (torque load) applied to the cam shaft  55  is reduced in comparison with a case in which these timings are overlapped with each other. 
     The configuration in which the respective timings are shifted from each other is realized by adjusting the shapes of the first cam  51 , the second cam  52 , and the third cam  54  corresponding to the one atmosphere release valve  81 , the relative positional relationship among the respective cams when viewed from the cam shaft  55 , and the shapes or the positions of the engaged portions which engage the engaging portions  51 a,  52   a , and  54   a  (that is, the respective engaged portions  130   a ,  140   a , and  81   a  of the elevating rack  130 , the lowering rack  140 , and the one atmosphere release valve  81 ). 
     Then, at a time point when the cam unit  50  further rotates in a state in which the cap unit  30  is in the sealing position and the one atmosphere release valve  81  is opened, and the angle of rotation from the reference time point reaches about 95 degrees, the drive motor  70  switches the direction of rotation from the normal direction to the reverse direction. Consequently, while the rotation of the cam unit  50  is interrupted, the both of the two suction pumps  60  are activated as shown in  FIG. 16 . At this time, since the atmosphere release valve  80  corresponding to the cap member  31  at the one end is in the closed state, the internal space of the cap member  31  at the one end (that is, the waste ink receiving space partitioned by the cap member  31  at the one end and the nozzle surface  22 ) is isolated from the atmosphere. As a result of activation of the two suction pumps  60  in such a state, the suction pump  60  corresponding to the cap member  31  at the one end performs the closed suction. In other words, the internal space of the cap member  31  at the one end is brought into the negative pressure state, and ink is ejected from the respective nozzles Nz sealed by the cap member  31  at the one end. 
     In contrast, since the respective internal spaces of the remaining cap members  31  are in the atmosphere release state because the atmosphere release valve  81  corresponding to the respective remaining cap members  31  is in the opened state. Therefore, the suction pump  60  corresponding to the remaining cap members  31  performs the opened suction. With this opened suction, the waste ink generated by the above-described flushing operation and accumulated in the respective internal spaces of the remaining cap members  31  is sucked by the suction pump  60  corresponding to the remaining cap members  31 . 
     After having operated the respective suction pumps  60  for a predetermined period, the drive motor  70  switches the direction of rotation again from the reverse direction to the normal direction. Accordingly, the suction pumps  60  are stopped and the cam unit  50  rotates again. Then, at a time point when the cam unit  50  rotates by about 105 degrees from the reference time point, the engaged portion  80   a  of the other atmosphere release valve  80  which is still in the closed state (that is, the atmosphere release valve  80  corresponding to the cap member  31  at the one end, and is indicated by an atmosphere release valve A in  FIG. 16 ) engages the engaging portion  53   a  of the third cam  53  corresponding to the other atmosphere release valve  80  as shown in  FIG. 16 . 
     Then, by the rotation of the cam unit  50 , the third cam  53  corresponding to the other atmosphere release valve  81  rotates in the state in which the engaging portion  53   a  engages the engaged portion  80   a  of the other atmosphere release valve  80 , so that the other atmosphere release valve  80  gradually opens. Then, as shown in  FIG. 16 , at a time point when the cam unit  50  rotates by about 110 degrees from the reference time point, the other atmosphere release valve  80  assumes a completely opened state. Accordingly, the internal space of the cap member  31  at the one end which used to be the negative pressure state (that is, the waste ink receiving space) is brought into the atmosphere release state. As shown in  FIG. 18C , the one atmosphere release valve  81  is still in the opened state at a time point when the other atmosphere release valve  80  is brought into the opened state. Subsequently, the two atmosphere release valves  80  and  81  are both maintained in the opened state for a while.  FIG. 18C  is a drawing showing a state in which the other atmosphere release valve  80  is brought into the opened state, and a state in which the two atmosphere release valves  80  and  81  are both in the opened state. 
     In this embodiment, when the engaging portion  53   a  of the third cam  53  corresponding to the other atmosphere release valve  80  engages the engaged portion  80   a  of the other atmosphere release valve  80 , the first cam  51  is positioned at the position apart from the elevating rack  130  in the direction of rotation thereof, and the second cam  52  is positioned at the position apart from the lowering rack  140  in the direction of rotation thereof. In this configuration, a timing when the third cam  53  corresponding to the other atmosphere release valve  80  rotates while engaging the other atmosphere release valve  80  is different from the timing when the first cam  51  rotates while engaging the elevating rack  130  and the timing when the second cam  52  rotates while engaging the lowering rack  140 . Consequently, as described above, the load applied to the cam shaft  55  may be alleviated. As described above, the configuration in which the respective timings are shifted from each other is realized by adjusting the shapes of the first cam  51 , the second cam  52 , and the third cam  53  corresponding to the other atmosphere release valve  80 , the relative positional relationship among the respective cams when viewed from the cam shaft  55 , and the shapes or the positions of the respective engaged portions  130   a ,  140   a , and  80   a  of the elevating rack  130 , the lowering rack  140 , and the other atmosphere release valves  80 . 
     Then, at a time point when the cam unit  50  further rotates in the state in which the two atmosphere release valves  80  and  81  are opened and the angle of rotation from the reference time point reaches about 125 degrees, the direction of rotation of the drive motor  70  is switched again from the normal direction to the reverse direction. Accordingly, the rotation of the cam unit  50  is interrupted again, and the two suction pumps  60  are activated. At this time, since the both of the two atmosphere release valves  80  and  81  are in the opened state, the internal space of the cap member  31  at the one end and the internal spaces of the remaining cap members  31  are both in the atmosphere release state. Therefore, the two suction pumps  60  each perform the opened suction. Therefore, the waste ink generated by the cleaning operation and received in the internal space of the cap member  31  at the one end is sucked by the suction pump  60  corresponding to the cap member  31  at the one end. In contrast, the suction pump  60  corresponding to the remaining cap members  31  sucks continuously the waste ink accumulated in the respective internal spaces of the remaining cap members  31 . 
     Subsequently, after having operated the suction pumps  60  for the predetermined period, the drive motor  70  switches the direction of rotation again from the reverse direction to the normal direction. In association with it, the suction pumps  60  are stopped, while the cam unit  50  rotates again. When the cam unit  50  rotates by about 145 degrees from the reference time point, the engaging state between the engaging portions  53   a  and  54   a  of the respective third cams  53  and  54  and the engaged portions  80   a  and  81   a  of the respective atmosphere release valves  80  and  81  are started to be released, and the two atmosphere release valves  80  and  81  are started to be closed substantially at the same time. Then, as shown in  FIG. 16 , at a time point when the cam unit  50  rotates by about 150 degrees from the reference time point, the two atmosphere release valves  80  and  81  assume a completely closed state. 
     At the time point when the cam unit  50  rotates by about 150 degrees from the reference time point, the second cam  52  reaches the position in which the engaging portion  52   a  of the second cam  52  engages the engaged portion  140   a  of the lowering rack  140  in the direction of rotation thereof. Subsequently, as a result of rotation of the second cam  52  in the state in which the engaging portion  52   a  engages the engaged portion  140   a  of the lowering rack  140  by the further rotation of the cam unit  50 , the pressing force F 2  that the second cam  52  presses the lowering rack  140  in the one direction is generated. Consequently, the slider drive mechanism  100  starts to perform the second movement, and the slider  41  moves rectilinearly in the other direction, and the cap unit  30  positioned at the sealing position starts to move downward toward the off position. 
     As described above, when the engaging portion  51   a  of the first cam  51  rotates while engaging the engaged portion  130   a  of the elevating rack  130 , the engaging state between the engaging portion  52   a  of the second cam  52  and the engaged portion  140   a  of the lowering rack  140  is released. In other words, when the second cam  52  engages the lowering rack  140 , and the first cam  51  is positioned at the position apart from the elevating rack  130  in the direction of rotation. Accordingly, when the slider drive mechanism  100  performs the second movement, the slider drive mechanism  100  performs the second movement adequately without being interfered with the first cam  51 . 
     Then, while the cap unit  30  is lowered, the head  21  moves in the direction of movement of the head  21  so that the respective nozzle rows of the nozzle surface  22  are positioned right above the openings of the corresponding cap members  31 . Subsequently, as shown in  FIG. 16 , at a time point when the cam unit  50  rotates by about 170 degrees from the reference time point, the above-described flushing operation is performed again, and the ink is forcedly ejected from the respective nozzles Nz. The flushing operation performed after the cleaning operation (post-cleaning flushing) is an operation for putting the meniscuses formed at the openings of the respective nozzles in order. Then, the waste ink generated by the post-cleaning flushing is received in the internal spaces of the cap members  31  corresponding to the respective nozzles Nz from which the waste ink is ejected (the cap members  31  positioned right below the respective nozzles Nz) as in a case of the flushing operation performed before the cleaning operation (pre-cleaning flushing). When the post-cleaning flushing is being performed, since the cap unit  30  is in the course of lowering, the cap members  31  receive the waste ink generated by the post-cleaning flushing in the internal spaces thereof while lowering. 
     While the cam unit  50  further rotates, the post-cleaning flushing is ended, while the second cam  52  continues to rotate in the state in which the engaging portion  52   a  thereof engages the engaged portion  140   a  of the lowering rack  140 . Consequently, the slider drive mechanism  100  continuously moves the slider  41  rectilinearly in the other direction by the second movement, and the cap unit  30  moves further downward. Then, as shown in  FIG. 16 , the cap unit  30  reaches the off position in the vertical direction and the second movement by the slider drive mechanism  100  is ended at a time point when the cam unit  50  rotates by about 210 degrees from the reference time point (in other words, the rectilinear movement of the slider  41  in the other direction is ended). 
     Then, the direction of rotation of the drive motor  70  is switched again from the normal direction to the reverse direction at a time point when the cap unit  30  reaches the off position, and the rotation of the cam unit  50  is interrupted, and the two suction pumps  60  are activated. At this time, since the respective cap members  31  are apart from the nozzle surface  22  of the head  21 , the openings of the cap members  31  face the atmosphere. In other words, at this time, the internal spaces of the respective cap members  31  are in the atmosphere release state. Therefore, the two suction pumps  60  each perform the opened suction, and suck the waste ink generated by the post-cleaning flushing and accumulated in the internal spaces of the respective cap members  31 . 
     After having operated the respective suction pumps  60  for the predetermined period, the drive motor  70  switches the direction of rotation from the reverse direction to the normal direction and, in association with it, the suction pumps  60  are stopped while the cam unit  50  starts to rotate. Subsequently, at a time point when the cam unit  50  rotates by 360 degrees (that is, one turn) from the reference time point, the drive motor  70  is stopped. Accordingly, the respective portions of the cam unit  50  return to positions in the direction of rotation where they are positioned at the reference time point. 
     At a time point when the above-described series of operations is completed, the operation of the maintenance unit  24  (the operation to perform the cleaning operation once) is ended. In contrast, the head  21  waits for the next ink ejecting operation (the ink ejecting operation as the operation for the image forming process) in a state of staying at the home position. In the above-described description, the flushing operation is performed respectively before and after the cleaning operation. However, the invention is not limited thereto and, for example, a configuration in which only one of the pre-cleaning flushing and the post-cleaning flushing is performed is also applicable. 
     Effectiveness of Printer  11  in the Embodiment 
     In the printer  11  provided with the maintenance unit  24  described above, the direction of the rectilinear movement of the slider  41  may be switched smoothly. Accordingly, the operation to move the cap unit  30  to the sealing position and causes the cap unit  30  to seal the nozzles Nz for the cleaning operation and the operation to move the cap unit  30  away from the nozzles Nz after the cleaning operation are performed smoothly as a series of operations. The effectiveness of the printer  11  in the embodiment will be described in further detail. 
     As described already in the paragraphs of BACKGROUND, a configuration in which the slider  41  is provided in the cap elevating unit  40  for moving the cap unit  30  in the vertical direction is already known. The slider  41  guides the cap unit  30  to the sealing position by moving rectilinearly in the one direction which is on the two directions opposite from each other and intersecting the vertical direction, and guides the cap unit  30  to the off position by moving rectilinearly in the other direction. 
     As in this embodiment, the slider  41  may have the groove cams  42  which engage the projecting portions  33  provided on the cap unit  30  (more specifically, the side walls  32   a  of the cap holder  32 ). The groove cams  42  each have the portion inclined with respect to the horizontal direction, and the slider  41  elevates the cap unit  30  to the sealing position by moving the projecting portions  33  to the one groove cam ends  42   e  along the groove cams  42  when moving rectilinearly in the one direction. In contrast, the slider  41  lowers the cap unit  30  to the off position by moving the projecting portions  33  to the other groove cam ends  42   f  along the groove cams  42  when moving rectilinearly in the other direction. 
     The slider  41  as described above is suitable as a member to move the cap unit  30  in the vertical direction. For example, the slider  41  in this embodiment is downsized as a came which realizes the vertical movement of the cap unit  30  in comparison with a cylindrical cam which moves the cap unit  30  in the vertical direction by rotating while coming into abutment with the lower surface of the cap unit  30  (more specifically, the cap holder  32 ). Furthermore, with the slider  41  in this embodiment, in a case where the contact surface area between the cap unit  30  and the nozzle surface  22  becomes relatively large, the contact pressure according to the contact surface area may be secured adequately. In other words, with the slider  41  in this embodiment, the load which is inevitably generated when securing the contact pressure may be reduced. 
     There is a case in which the printer  11  is provided with the drive motor  70 , the slider drive mechanism  100  configure to make the slider  41  to move rectilinearly by the drive force from the drive motor  70 , and a cam unit configured to transmit the drive force to the slider drive mechanism  100  by rotating in a state of engaging the slider drive mechanism  100  in association with the rotation of the drive motor  70  for moving the slider  41  rectilinearly. The slider drive mechanism  100  performs the first movement which moves the slider  41  rectilinearly in the one direction and the second movement which moves the slider  41  rectilinearly in the other direction. In contrast, in both in a case where the slider drive mechanism  100  performs the first movement and in a case where the slider drive mechanism  100  performs the second movement, the cam unit rotates while engaging the slider drive mechanism  100  for transmitting the drive force from the drive motor  70  to the slider drive mechanism  100 . 
     As the cam unit described above, for example, a cam unit which switches the direction of rotation for switching the operation of the slider drive mechanism  100  from the first movement to the second movement (or the second movement to the first movement) (which is different from the cam unit  50  in this embodiment and is referred to as the other cam unit) is contemplated. However, with the configuration in which the direction of rotation is switched to switch the operation of the slider drive mechanism  100  as the other cam unit, the switching operation of the direction of rotation is complicated, so that a significant time is required for the switching operation. In other words, smooth switching of the direction of the rectilinear movement of the slider  41  becomes difficult. Consequently, the operation to move the cap unit  30  to the sealing position when performing the cleaning operation and the operation to move the cap unit  30  away from the nozzles Nz after the cleaning operation are not performed smoothly as a series of operations, so that the processing speed of the printer  11  may be lowered. 
     In contrast, the cam unit  50  in this embodiment rotates in the same direction of rotation both in a case where the drive force from the drive motor  70  is transmitted to the slider drive mechanism  100  when the slider drive mechanism  100  performs the first movement, and in a case where the drive force is transmitted to the slider drive mechanism  100  when the slider drive mechanism  100  performs the second movement. More specifically, the cam unit  50  in this embodiment includes the first cam  51  having the engaging portion  51   a  which engages the engaged portion  130   a  of the elevating rack  130  and the second cam  52  having the engaging portion  52   a  which engages the engaged portion  140   a  of the lowering rack  140 . Then, the engaging state between the respective engaged portions  130   a  and  140   a  of the elevating rack  130  and the lowering rack  140  and the engaging portions  51   a  and  52   a  of the first cam  51  and the second cam  52  is switched while the cam unit  50  rotates in the predetermined direction of rotation. More specifically, when the cam unit  50  rotates in the predetermined direction of rotation, the combination of the rack and cam in the engaging state is switched. 
     In this manner, in this embodiment, when the slider  41  switches the direction of the rectilinear movement, it is not necessary to switch the direction of rotation of the cam unit  50 , and the time to switch the direction of rotation is not necessary as well. Accordingly, the direction of the rectilinear movement of the slider  41  may be switched smoothly. In other words, the operation to move the cap unit  30  to the sealing position when performing the cleaning operation and the operation to move the cap unit  30  away from the nozzles Nz after the cleaning operation are performed smoothly as the series of operations. 
     Also, in order to realize the cam unit  50  which does not need the switching of the direction of rotation when switching the direction of the rectilinear movement of the slider  41 , the configuration of this embodiment is such that the combination of the rack and cam in the engaging state is switched by the rotation of the cam unit  50  in the predetermined direction. More specifically, the cam which transmits the drive force from the drive motor  70  to the slider drive mechanism  100  by rotating while engaging the slider drive mechanism  100  is divided into the cam which rotates by engaging the slider drive mechanism  100  when causing the slider  41  to move rectilinearly in the one direction (that is, the first cam  51 ) and the cam which rotates by engaging the slider drive mechanism  100  when causing the slider  41  to move rectilinearly in the other direction (that is, the second come  52 ). In addition, in the slider drive mechanism  100 , the portions which engage the first cam  51  and the second cam  52  (that is, the engaged portions  130   a  and  140   a  of the elevating rack  130  and the lowering rack  140 ) are provided separately for the respective cams. Consequently, the direction in which the slider  41  moves rectilinearly may be switched smoothly with a relatively simple configuration in this embodiment. 
     Other Embodiment 
     Although the printer  11  as the liquid ejecting apparatus has mainly been described on the basis of the embodiment as described above, the embodiment of the present invention as described above is simply for facilitating the understanding of the invention, and is not intended to limit the invention. The invention may be modified or improved without departing the scope of the invention, and the invention includes equivalents as a matter of course. 
     Although the printer  11  is configured to eject the ink as an example of the liquid in the embodiment as describe above, the ink may be water based ink or may be solvent ink. Although the printer  11  which ejects ink has been described in the above-described embodiment, the invention is not limited thereto, and a liquid ejecting apparatus which ejects other types of liquid may be contemplated. In other words, the invention may be embodied in the liquid ejecting apparatus which ejects liquid other than the ink (including liquid type substances including particles of functional material dispersed or mixed therein, or fluid type substances such as gel other than the liquid). 
     For example, liquid ejecting apparatuses which eject liquid type substances containing electrode material or colorant in the form of dispersion or dissolution used for manufacturing liquid crystal displays, EL (electroluminescence) displays, or surface emission-type displays, liquid ejecting apparatuses which eject biological organic substance used for manufacturing biochips, or liquid ejecting apparatuses which are used as accurate pipettes and eject liquid as a sample may also be applicable. Furthermore, it may be liquid ejecting apparatuses which eject lubricant for pinpoint lubrication for precise machines such as watches or cameras, liquid ejecting apparatuses which eject transparent resin liquid such as UV-cured resin on a substrate for forming micro-semispherical lens (optical lens) or the like used for optical communication elements or the like, liquid ejecting apparatuses which eject etching liquid such as acid or alkali for etching the substrate or the like, or a fluid-like substance ejecting apparatus which eject gel. The invention may be applied to any one of the liquid ejecting apparatuses. 
     The entire disclosure of Japanese Patent Application No. 2008-151940, filed Jun. 10, 2008 is expressly incorporated by reference herein.