Patent Publication Number: US-7896481-B2

Title: Ink jet printer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2006-182815, filed on Jun. 30, 2006, the contents of which are hereby incorporated by reference into the present application. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an ink jet printer that prints onto a print medium by discharging ink. In particular, the present invention relates to a serial type ink jet printer in which an ink jet head is mounted on a carriage and which moves while printing. Note that the word “printer” used in the present specification is to be interpreted in the broadest sense, and is a concept that includes a facsimile device, a copy machine, a multi-function device, and the like. 
     2. Description of the Related Art 
     Serial type ink jet printers are widely known. This type of ink jet printer comprises an ink jet head, and a carriage on which the ink jet head is mounted. The ink jet head has a passage unit, an actuator, and a control board. The passage unit has ink passages and nozzles that communicate therewith. The actuator applies energy to the ink inside the passage unit. In this way, the ink inside the nozzles is discharged. The control board controls the actuator. 
     There is also a type of ink jet printer in which the ink jet head as well as an ink tank is mounted on the carriage. Many times the ink tank is disposed above the ink jet head in this type of ink jet printer. In addition, the ink tank is disposed below the ink jet head in the ink jet printer disclosed in Japanese Patent Application Publication No. 2000-246918. 
     BRIEF SUMMARY OF THE INVENTION 
     When the ink tank is located above or below the ink jet head, the ink jet printer will become thicker (taller). The present specification discloses technology that will allow an ink jet printer to become thinner by adjusting the positions of the ink jet head and the ink tank. 
     In the ink jet printer disclosed by the present specification, an ink jet head (including a passage unit, an actuator, and a control board) and an ink tank are mounted on a carriage. The ink jet head and the ink tank are offset in the plan view of the ink jet printer. This means that the ink jet head and the ink tank do not completely overlap in the plan view of the ink jet printer. In addition, the ink jet head and the ink tank overlap in the height direction of the ink jet printer. This not only means that the ink jet head and the ink tank completely overlap, but is a concept that also includes the ink jet head and the ink tank being partially overlapped. 
     According to the aforementioned structure, the thickness of the ink jet head and the ink tank can be reduced because these two components overlap in the height direction. The result is that a reduction in the thickness of the ink jet printer can be achieved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an oblique view of a multi-function device. 
         FIG. 2  shows a simple cross-sectional view of the printer unit. 
         FIG. 3  shows an oblique view of the printer unit. 
         FIG. 4  shows an oblique view of the printer unit. 
         FIG. 5  shows a plan view of the printer unit. 
         FIG. 6  shows a plan view of the printer unit. 
         FIG. 7  is a view taken from the arrow VII direction of  FIG. 5 . 
         FIG. 8  shows the cross-sectional view of line VIII-VIII of  FIG. 5 . 
         FIG. 9  shows an oblique view of an image recording unit. 
         FIG. 10  shows the cross-sectional view of line X-X of  FIG. 9 . 
         FIG. 11  shows a nozzle surface of an ink jet head. 
         FIG. 12  shows a partial cross-sectional view of the ink jet head. 
         FIG. 13  shows a capping mechanism.  FIG. 13A  shows a state where a cap is away the nozzle surface.  FIG. 13B  shows a state where the cap makes contact with the nozzle surface. 
         FIG. 14  shows a simple cross-sectional view of an ink supply mechanism. 
         FIG. 15  shows the structure of a female joint and a male joint.  FIG. 15A  shows the female joint and the male joint prior to being linked together.  FIG. 15B  shows the female joint and the male joint after having been linked together.  FIG. 15C  shows a condition in which ink will move between the female joint and the male joint. 
         FIG. 16  shows a simplified structure of the ink supply mechanism.  FIG. 16A  shows a condition in which ink is supplied to a sub tank.  FIG. 16B  shows a condition immediately prior to the sub tank being pushed.  FIG. 16C  shows a condition after the sub tank was pushed.  FIG. 16D  shows a condition after the sub tank has recovered.  FIG. 16E  shows a condition after ink was supplied to the sub tank. 
         FIG. 17  shows a simple cross-sectional view of a maintenance mechanism. 
         FIG. 18  shows the structure of the maintenance mechanism.  FIG. 18A  shows a condition prior to maintenance being performed.  FIG. 18B  shows a condition after the sub tank was pushed.  FIG. 18C  shows the condition after the sub tank has recovered.  FIG. 18D  shows the condition in which a wiper is moved.  FIG. 18E  shows a condition in which flushing is performed. 
         FIG. 19  shows a simple cross-sectional view of a printer unit of a second embodiment. 
         FIG. 20  shows a simple cross-sectional view of a printer unit of a third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     An embodiment will be described with reference to the drawings. Note that the embodiment described below is simply one example of the present invention. The embodiment described below can be suitably changed within a scope that does not change the essence of the present invention. 
       FIG. 1  shows an oblique view of a multi-function device  1 . The multi-function device  1  comprises a printer unit  2  and a scanner unit  3 . The printer unit  2  is located above the scanner unit  3 . The multi-function device  1  has a print function, a scan function, a copy function, a facsimile function, and the like. The printer unit  2  is an ink jet type. 
     The multi-function device  1  may be connected to and used with an external information processing device such as a computer or the like. The multi-function device  1  can print images and text on a print medium (e.g., a printing sheet) based upon print data including image data and text data transmitted from a computer or the like. The multi-function device  1  may also be connected to and used with a digital camera or the like. The multi-function device  1  may also print image data output from a digital camera or the like onto a printing sheet. In addition, the multi-function device  1  can also print image data or the like stored in a storage medium such as a separately mounted memory card or the like onto a printing sheet. 
     The multi-function device  1  has a rectangular shape. The multi-function device  1  has a width that is larger than the height thereof, and a depth that is larger than the height thereof. The printer unit  2  has a casing  2 A. A port  6  is formed in the front surface of the casing  2 A. The printer unit  2  has a feeding tray  10  and a discharge tray  11 . The feeding tray  10  and the discharge tray  11  are arranged on the inner side of the port  6 . The discharge tray  11  is arranged above the feeding tray  11 . The feeding tray  10  can house various sizes of printing sheets, e.g., A4 size or smaller. 
     A door  7  is arranged on the right lower portion of the front of the casing  2 A. A cartridge mounting unit  9  (see  FIG. 3 ) is arranged on the inner side of the door  7 . When the door  7  is opened, the cartridge mounting portion  9  will be exposed on the front side. A user can replace an ink cartridge  38  (see  FIG. 3 ) that is mounted in the cartridge mounting unit  9 . The cartridge mounting unit  9  has storage chambers that correspond to each color of ink. In the present embodiment, five colors of ink are used (cyan (C), magenta (M), yellow (Y), photoblack (PBk), and black (Bk)). Thus, five storage chambers are arranged in the cartridge mounting unit  9 . Each storage chamber houses an ink cartridge  38 A to  38 E of each corresponding color. 
     The scanner unit  3  is a so-called flat bed scanner. The multi-function device  1  has a document cover  30 . A platen glass on which a document is to be mounted, an image sensor that will read the document, and the like are arranged below the document cover  30 . 
     An operation panel  4  for operating the printer unit  2  and the scanner unit  3  is arranged on the upper portion of the front of the multi-function device  1 . The operation panel  4  is comprised of various operation buttons and a liquid crystal display. The multi-function device  1  will operate based upon operational commands from the operation panel  4 . If the multi-function device  1  is connected to an external computer, the multi-function device  1  can also operate based upon commands transmitted from the computer via a printer driver or a scanner driver. A slot unit  5  is arranged in the left upper portion of the front of the multi-function device  1 . The slot unit  5  can house various types of memory cards. When a predetermined operation is added to the operation panel  4 , the multi-function device  1  will read out image data stored in the memory card housed in the slot unit  5 . That image data will be displayed on the liquid crystal display of the operation panel  4 . The user can print any image while viewing the display thereof. 
     Next, the internal construction of the multi-function device  1  will be described.  FIG. 2  shows a simple cross-sectional view of the printer unit  2 . An inclined separation plate  22  is arranged on the right edge of the feeding tray  10 . The inclined separation plate  22  is inclined to the right. The inclined separation plate  22  is positioned on the right edge of the printing sheets mounted in the feeding tray  10 . The inclined separation plate  22  separates only the uppermost printing sheet from a plurality of printing sheets. A paper transport path  23  is arranged above the inclined separation plate  22 . Other than the portion where the image recoding unit  24  is disposed, the paper transport path  23  is comprised of an outer side guide surface and an inner side guide surface. The outer side guide surface and the inner side guide surface face each other across a predetermined gap. 
     The paper transport path  23  extends upward from the feeding tray  10  via the inclined separation plate  22 . The paper transport path  23  has a curved path  17  that is curved on the front side, and a straight path  18  that extends in a straight line from the end of the curved path  17  to the front side of the multi-function device  1 . The straight path  18  reaches the discharge tray  11  via the image recording unit  24 . Printing sheets housed in the feeding tray  10  are guided so as to perform a U-turn in the curved path  17 . Printing sheets that have performed a U-turn are transported along the straight path  18 . The printing sheets will be printed by the image recording unit  24  in the straight path  18 . After that, the printing sheets will be ejected to the discharge tray  11 . A roller not shown in the drawings is arranged in the curved path  17 . The roller surface of the roller is exposed in the paper transport path  23 . The rotation shaft of the roller extends in a direction perpendicular to the plane of  FIG. 2 . Due to the existence of the roller, the printing sheets will be smoothly transported in the curved path  17 . 
     A paper supply roller  25  is arranged above the feeding tray  10 . The paper supply roller  25  will send the printing sheets stacked in the feeding tray  10  to the paper transport path  23 . The paper supply roller  25  is supported by one end of an arm  26 . The arm  26  is capable of rotating around a base shaft  27  arranged on the other end thereof. The drive force of an LF motor  71  (see  FIG. 3 ) is transmitted to the paper supply roller  25 . The drive force of the LF motor  71  is transmitted to the paper supply roller  25  via a drive force transmission mechanism that is constructed by meshing a plurality of gears. 
     The arm  26  rotates with the base shaft  27  as a center. The arm  26  is urged toward the feeding tray  10 . This urging force may be applied to the arm  26  by a spring or the like. In addition, the arm  26  may be urged toward the feeding tray  10  by the weight of the arm  26  itself. In addition, the arm  26  is constructed so as to move upward when the feeding tray  10  is attached to and detached from the casing  2 A. Because the arm  26  is urged downward, the paper supply roller  25  will contact with the printing sheets in the feeding tray  10 . When the paper supply roller  25  rotates, the uppermost printing sheet will be sent toward the inclined separation plate  22  by means of the frictional force between the roller surface of the paper supply roller  25  and the printing sheet. The leading edge of the printing sheet will be placed into contact with the inclined separation plate  22 . There will be times in which a plurality of printing sheets will be sent toward the inclined separation plate  22  due to friction or static electricity. When this occurs, the inclined separation plate  22  will separate the uppermost printing sheet from the other printing sheets. Next, the printing sheets will be sent to the paper transport path  23 . 
     The image recording unit  24  is arranged adjacent to the straight path  18 . The image recording unit  24  will print (record) images on the printing sheets by discharging ink droplets based upon the ink jet method. The image recording unit  24  has an ink jet head  35  (hereinafter referred to as a “head”), sub tanks  37  ( 37 A to  37 E), a carriage  34 , and the like. The sub tanks  37  can temporarily store ink. Ink will be supplied from the sub tanks  37  to the head  35 . In the present embodiment, five sub tanks  37 A to  37 E are provided. The five sub tanks  37 A to  37 E can store different colors of ink. 
     A platen  28  is arranged below the image recording unit  24 . The platen  28  faces the image recording unit  24 . Printing sheets are transported above the platen  28 . The width of the platen  28  (the length in the direction perpendicular to the plane of  FIG. 2 ) is larger than the width of the biggest printing sheet capable of being printed by the multi-function device  1 . Thus, the printing sheets will not run off of the platen  28 . 
     The transport direction of the printing sheets will be hereinafter referred to simply as the “paper transport direction”. A pair of transport rollers  75  is arranged on the upstream side of the head  35  in the paper transport direction. The pair of transport rollers  75  has a transport roller  73  and a pinch roller  74 . The pinch roller  74  is arranged below the transport roller  73 . The transport roller  73  and the pinch roller  74  will grasp printing sheets that are transported via the curved path  17 , and transport the printing sheets toward the platen  28 . In addition, a pair of discharge rollers  78  is arranged on the downstream side of the head  35  in the paper transport direction. The pair of paper discharge rollers  78  has a paper discharge roller  76  and a pinch roller  77 . The pinch roller  77  is arranged above the paper discharge roller  76 . The paper discharge roller  76  and the pinch roller  77  grasp the printing sheets printed by the head  35 , and transport the printing sheets toward the discharge tray  11 . The drive force of the LF motor  71  (see  FIG. 3 ) will be transmitted to the transport roller  73  and the paper discharge roller  76  via a drive force transmission mechanism such as gears or the like. 
     The pair of transport rollers  75  is arranged on the immediate upstream side of the head  35 . The pair of paper discharge rollers  78  is arranged on the immediate downstream side of the head  35 . The head  35  is arranged between the pair of transport rollers  75  and the pair of paper discharge rollers  78  in the paper transport direction. Although the separation distance between the pair of transport rollers  75  and the pair of paper discharge rollers  78  is slightly longer than the length of the head  35  in the paper transport direction, the length is set to be substantially the same. By arranging the pair of transport rollers  75  and the pair of paper discharge rollers  78  near the head  35 , the separation distance between the pair of transport rollers  75  and the pair of discharge rollers  78  can be shortened. The result is that the ability of the printing sheets transported above the platen  28  to be held can be improved. Deflection of the printing sheets on the platen  28  can be reduced. The quality of images printed on the printing sheets will be improved. 
     The operation of the LF motor  71  (see  FIG. 3 ) is controlled by a controller that performs overall control of the multi-function device  1 . The drive force from the LF motor  71  is transmitted to the t rollers  73 ,  76 . The operation of the rollers  73 ,  76  is controlled by the aforementioned controller based upon pulse signals output from a rotary encoder linked to the rotation shaft of the transport roller  73 . Note that the controller has a circuit board equipped with various electronic devices such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an EEPROM (Electrically Erasable and Programmable ROM), an ASIC (Application Specific Integrated Circuit), a driver IC, and the like. 
     Spur shaped bumps are formed on the roller surface of the pinch roller  77 . Because of this, deterioration in the quality of images printed on the printing sheets can be prevented, even if the printing sheets are in contact with the pinch roller  77 . The pinch roller  77  is capable of sliding in a direction away from the paper discharge roller  76 . The pinch roller  77  is urged by a coil spring so as to be placed into contact with the paper discharge roller  76 . When the printing sheets advance in between the paper discharge roller  76  and the pinch roller  77 , the pinch roller  77  will resist the urging force and retract a distance equal to the thickness of the printing sheets, and the printing sheets will be pushed toward the paper discharge roller  76 . In this way, the rotational force of the paper discharge roller  76  will be reliably transmitted. The pinch roller  74  also has the same construction as the aforementioned pinch roller  77 . The pinch roller  74  pushes the printing sheets toward the transport roller  73 . 
       FIG. 3  and  FIG. 4  show an oblique view of the printer unit  2 .  FIG. 5  and  FIG. 6  show a plan view of the printer unit  2 .  FIG. 3  and  FIG. 5  show a state in which the image recording unit  24  is located in the ink supply position.  FIG. 4  and  FIG. 6  show a state in which the image recording unit  24  is located in the maintenance position. In addition,  FIG. 7  is a view taken along the arrow VII direction of  FIG. 5 .  FIG. 8  shows the cross-sectional view of line VIII-VIII of  FIG. 5 . Note that each of the aforementioned drawings shows a state in which a head cover that covers the upper surface of the carriage  34  has been removed. 
     As shown in each of the drawings, a pair of flat guide rails  43 ,  44  is arranged above the straight path  18  of the paper transport path  23  (see  FIG. 2 ). Each guide rail  43 ,  44  extends in a direction (the horizontal direction of  FIG. 5 ) orthogonal to the paper transport direction (the downward direction of  FIG. 5 ). The guide rails  43 ,  44  are arranged across a predetermined distance in the paper transport direction (the downward direction of  FIG. 5 ). The guide rail  43  is arranged on the upstream side in the paper transport direction, and the guide rail  44  is arranged on the downstream side in the paper transport direction. Although the guide rail  43  and the guide rail  44  have a slight step in the vertical direction, they are arranged in substantially the same plane. The upper surface of each guide rail  43 ,  44  is set so as to be parallel with the printing sheets being transported. Because the printing sheets are horizontally transported above the platen  28 , the guide rails  43 ,  44  are also set to be horizontal with the upper surface. 
     The guide rails  43 ,  44  are arranged inside the casing  2 A, and function as a frame that supports each structural element that forms the printer unit  2 . The guide rails  43 ,  44  support the carriage  34 . The carriage  34  is capable of moving along the guide rails  43 ,  44  in a direction orthogonal to the paper transport direction (the direction in which the guide rails  43 ,  44  extend). More specifically, the end of the carriage  34  on the upstream side in the paper transport direction is supported by the guide rail  43  via a POM (polyacetyl resin) slide member or the like. In addition, the portion of the carriage  34  on the downstream side in the paper transport direction is supported by the guide rail  44  via the aforementioned slide member. The carriage  34  is mounted on the guide rails  43 ,  44  so as to span the guide rail  43  and the guide rail  44 . By arranging the guide rails  43 ,  44  across the paper transport direction, and horizontally aligning the guide rails  43 ,  44  in substantially the same plane, the height of the printer unit  2  can be reduced. The result is that a reduction in the thickness of the printer unit  2  can be achieved. 
     As shown from  FIG. 3  to  FIG. 6 , the length of the guide rails  43 ,  44  in the horizontal direction is longer than the length of the platen  28  in the horizontal direction. Friction tape or grease is applied to the guide rail  43 ,  44 . In this way, the sliding friction between the guide rails  43 ,  44  and the carriage  34  will be reduced. 
     The edge  45  of the guide rail  44  on the upstream side in the paper transport direction is curved upward (upward of the multi-function device  1 ) at an approximate right angle. The carriage  34  has a grasping portion  58  that grasps the edge  45  (see  FIG. 8  and  FIG. 10 ). In this way, the carriage  34  will be positioned on the guide rail  44 . The carriage  34  can be accurately moved (slid) in a direction (the horizontal direction of  FIG. 5 ) orthogonal to the paper transport direction. In other words, the carriage  34  will move reciprocally in a direction orthogonal to the paper transport direction, using the edge  45  of the guide rail  44  as a reference. 
     As shown in  FIG. 7 , the carriage  34  has an adjustment mechanism  59 . The adjustment mechanism  59  adjusts the vertical posture of the carriage  34  with respect to the vertical plane of the edge  45 . The adjustment mechanism  59  is arranged on one side surface of the carriage  34 . The adjustment mechanism  59  has a block unit  60  and a dial type movement mechanism  61 . The block unit  60  is capable of moving in the paper transport direction (the horizontal direction of  FIG. 7 ) while grasping the edge  45 . The block unit  60  will move in the paper transport direction when the movement mechanism  61  is operated. For example, when the dial  62  of the movement mechanism  61  is operated, an eccentric cam (not shown in the drawings) linked to the rotation shaft of the dial  62  will be driven. This results in the block unit  60  moving in the paper transport direction. Because the adjustment mechanism  59  is provided, the vertical posture of the carriage  34  with respect to the vertical plane of the edge  45  can be freely adjusted. 
     As shown in  FIG. 3  to  FIG. 6 , a head drive mechanism  46  is arranged on the upper surface of the guide rail  44 . The head drive mechanism  46  has a drive pulley  47 , a driven pulley  48 , and a timing belt  49 . The drive pulley  47  is connected to the right end of the guide rail  44 . The driven pulley  48  is connected to the left end of the guide rail  44 . The timing belt  49  extends around the pulleys  47 ,  48 . Gear teeth are arranged around the inner circumferential surface of the timing belt  49 . The timing belt  49  is an endless ring. Note that the timing belt  49  may also be a belt having ends. In this case, both ends of the belt are fixed to the carriage  34 . A CR motor (carriage motor)  72  is linked to the shaft of the drive pulley  47 . The drive force of the CR motor  72  is transmitted to the drive pulley  47 . In this way, the drive pulley  47  will rotate, and the timing belt  49  will circulate between the drive pulley  47  and the driven pulley  48 . 
     The bottom surface of the carriage  34  is fixed to the timing belt  49 . Thus, the carriage  34  will reciprocally move on the guide rails  43 ,  44  based upon the circulation of the timing belt  49 . The head  35  is mounted on the carriage  34 . Because of this, the head  35  will reciprocally move in the width direction of the paper transport path  23  (the direction orthogonal to the paper transport direction) as the primary scanning direction. 
     An encoder strip  42  is arranged on the guide rail  44 . The encoder strip  42  is a belt-shaped object comprised of a transparent resin. Both ends of the encoder strip  42  are supported by both ends in the width direction of the guide rail  44  (the reciprocating direction of the carriage  34 ). 
     A transparent portion that allows light to pass therethrough and a light blocking portion that blocks light are alternately arranged at a predetermined pitch on the encoder strip  42 . A transmission type optical sensor  41  (see  FIG. 8 ) is provided on the carriage  34 . The optical sensor  41  detects the pattern of the encoder strip  42  during the reciprocal movement of the carriage  34 . The head  35  mounted on the carriage  34  has a head control board  36  (described below). The head control board  36  outputs pulse signals in response to the detection signals of the optical sensor  41 . After receiving the pulse signals, the controller of the multi-function device  1  will determine the position and speed of the carriage  34 , and control the reciprocating movement of the carriage  34 . 
       FIG. 9  shows an enlarged oblique view of the image recording unit  24 . In addition,  FIG. 10  shows the cross-sectional view of line X-X of  FIG. 9 . Note that the line X-X of  FIG. 9  passes through the center of the sub tank  37 D. As noted above, the image recording unit  24  has the carriage  34 , the head  35 , the sub tanks  37 , and the like. The construction of the image recording unit  24  will be described in detail below. 
     As shown in  FIG. 10 , the carriage  34  has a rectangular shape that is long in the front to rear direction of the multi-function device  1 . A tank storage chamber  50  that serves to house the sub tanks  37  is provided on the downstream side of the central portion of the carriage  34  (the left side in  FIG. 10 ) in the paper transport direction. In the present embodiment, five sub tanks  37  ( 37 A to  37 E) corresponding to the five colors of ink used in the printer unit  2  are housed in the tank storage chamber  50 . The five sub tanks  37  ( 37 A to  37 E) are aligned in the width direction of the carriage  34  (the direction in which the guide rails  43 ,  44  extend). Each sub tank  37  has a rectangular shape that is long in the lengthwise direction of the carriage  34  (the horizontal direction of  FIG. 10 ). Side walls  66  that extend upward from the bottom surface of the tank storage chamber  50  are provided on both sides in the width direction of the tank storage chamber  50 . The side walls  66  prevent the sub tanks  37  from falling over. Note that the construction of one sub tank  37  and the periphery thereof will be described in detail below. 
     As noted above, the pair of paper discharge rollers  78  are arranged on the immediate downstream side of the head  35  (see  FIG. 2 ,  FIG. 7  and  FIG. 8 ). Thus, if the sub tanks  37  are to be temporarily placed above the pair of paper discharge rollers  78 , the sub tanks  37  must be placed significantly above the pair of paper discharge rollers  78  so as to not interfere with them. In this case, the thickness of the image recording unit  24  will increase. Because of this, in the present embodiment, as shown in  FIG. 8 , the sub tanks  37  are arranged on the downstream side of the pair of paper discharge rollers  78  in the paper transport direction. In this way, the sub tanks  37  will not interfere with the paper discharge rollers  78 . The sub tanks  37  and the pair of paper discharge rollers  78  overlap in the height direction of the multi-function device  1 . In this way, the thickness of the image recording unit  24  can be reduced. 
     The curved path  17  is arranged on the upstream side of the head  35  in the paper transport direction. Because of this, it is difficult to arrange the sub tanks  37  on the upstream side in the paper transport direction. Thus, the sub tanks  37  are arranged on the downstream side of the head  35  in the paper transport direction. In this case, the path between the ink cartridges  38  arranged on the front side of the multi-function device  1  and the sub tanks  37  can also be shortened. Note that in the present embodiment, the sub tanks  37  are arranged on the downstream side of the head  35  in the paper transport direction, but the sub tanks  37  may also be arranged on the upstream side of the head  35  in the paper transport direction (the upstream side of the pair of transport rollers  75  in the paper transport direction). In addition, regardless of whether the sub tanks  37  are on the upstream side or the downstream side of the head  35 , the sub tanks  37  may also be arranged on the sides of the head  35  (the sides in the reciprocating direction of the carriage  34 ). 
     As shown in  FIG. 10 , the sub tanks  37  are arranged above the guide rail  44 . The sub tanks  37  and the guide rail  44  overlap in the plan view of the multi-function device  1 . The load of the sub tanks  37  is received by the guide rails  44  via the bottom surface  53  of the sub tank  37  and the support portion of the carriage  34 . The result is that shifting (deforming) of the position of the carriage  34  caused by the load of the sub tanks  37  can be prevented. Smooth movement of the carriage  34  and optimal printing can be achieved. 
     The sub tanks  37  temporarily store ink that is supplied from the ink cartridges  38  (see  FIG. 3 ). The sub tanks  37  are arranged further upstream of an ink supply passage  51  than the head  35 . In other words, the sub tanks  37  are arranged above the discharge tray  11 . From the plan view of the multi-function device  1 , the discharge tray  11  and the sub tanks  37  overlap. Ink inside the sub tanks  37  is supplied to the head  35  via the ink supply passage  51  described below. Supply of the ink from the ink cartridges  38  to the sub tanks  37  is performed by the ink supply mechanism described below. When ink supply is performed by the ink supply mechanism  80 , air bubbles will be generated in the passage between the ink cartridge  38  and the sub tank  37 . The air bubbles are captured by the sub tanks  37 . Because of this, the air bubbles can be prevented from entering the head  35  (the cavities  115  and the manifolds  116  described below). 
     The sub tanks  37  each have an upper surface  52 , a bottom surface  53 , and side surfaces  54 . The upper surface  52  and the bottom surface  53  are each flat. The side surfaces  54  have a bellows shape along the entire circumference thereof. The sub tanks  37  are comprised of synthetic resin. For example, each of the aforementioned portions can be formed by means of blow molding. Because the side surfaces  54  are formed in a bellows shape, the side surfaces  54  are capable of expanding and contracting in the vertical direction. If an external force is applied in the vertical direction with respect to the sub tanks  37 , the side surfaces  54  will contract or expand from their original shape. When the external force is eliminated, the side surfaces  54  will return to their original shape. In other words, the sub tanks  37  are capable of elastic deformation. For example, when the sub tanks  37  are pushed downward, the side surfaces  54  will contract. When the pushing force is eliminated, the side surfaces  54  will return from the contracted state to their original shape. Note that a plate  55  that covers the upper surface  52  of each sub tank  37  is provided on the upper side of the upper surface  52 . The plate  55  is comprised of a metal plate or a thick resin plate. The upper surface  52  of each sub tank  37  is protected by the plate  55 . In the present embodiment, the side surfaces  54  are formed into a bellows shape as a means of achieving the elastic deformation of the sub tanks  37 . However, for example, the side surfaces  54  may also be formed from an elastic material such as rubber or the like. 
     The sub tanks  37  can store the average amount of ink consumed in one print process. In the present embodiment, the volume of each sub tank  37  is set so as to store about 0.5 to 1.0 (ml). Because of this, the load on the carriage  34  can be lessened, and the burden on the CR motor  72  that reciprocally moves the carriage  34  can be reduced. Note that the volume of the sub tanks  37  may be changed in accordance with need. The sub tanks  37  may also store more or less than the aforementioned amount of ink. 
     As shown in  FIG. 10 , the sub tanks  37  each have two through holes  56 ,  57 . One of the through holes  56  is provided in the front end (the left end of  FIG. 10 ) of the upper surface  52  of each sub tank  37 . The other through hole  57  is provided in the rear end (the right end of  FIG. 10 ) of the bottom surface  53 . In addition, a female joint  63  is provided on the left side of each sub tank  37 . The female joints  63  are arranged on the front end of the tank storage chamber  50 . The female joints  63  are linked with the ink cartridges  38  (see  FIG. 3 ). Note that because there are five sub tanks  37 , there are five female joints  63 . A coupling  64  is connected to each female joint  63 . The couplings  64  and the through holes  56  are connected by flexible tubes  65 . Ink passages are formed between the female joints  63  and the sub tanks  37 . 
     In contrast, each through hole  57  is connected to one end of the ink supply passage  51  that supplies ink to the head  35 . Each ink supply passage  51  has a first portion that extends horizontally rightward from each through hole  57 , and a second portion that extends downward from the right end of the first portion. The lower end of the second portion extends to the bottom surface of a head storage chamber  110  described below. The lower end of the second portion is linked to the head  35 . For example, each ink supply passage  51  can be constructed by covering a groove formed in a synthetic resin plate member with a thin film. In addition, each ink supply passage  51  can also be constructed by means of a flexible tube. 
     Arms  100  that receive an external force and push each aforementioned plate  55  downward are provided above the tank storage chamber  50 . A shaft hole  102  is formed in the approximate central portion of each arm  100 . A shaft  101  that extends between the aforementioned pair of side walls  66  is inserted into the shaft holes  102 . The arms  100  are pivotably supported by the shaft  101 . Because there are five sub tanks  37  ( 37 A to  37 E) in the present embodiment, there are 5 arms  100  ( 100 A to  100 E). 
     Each arm  100  has a rearward arm  103  and a forward arm  104 . The rearward arm  103  extends horizontally rearward from the shaft hole  102  (rightward in  FIG. 10 ). The forward arm  104  extends horizontally forward from the shaft hole  102  (leftward in  FIG. 10 ). The forward arm  104  extends forward past the front end of the carriage  34  (the left end of  FIG. 10 ). A pressing portion  105  is on the tip of the rearward arm  103 . Each pressing portion  105  comes into contact with each plate  55 . Each pressing portion  105  transmits the drive force of each arm  100  to each plate  55 . Each pressing portion  105  is formed to have a spherical surface. In this way, force can always be applied in the vertical direction with respect to each plate  55 . In addition, an input portion  106  that receives external force from a push rod  83  described below (see  FIG. 4 ) is provided on the front end of each forward arm  104 . The contact surface of each input portion  106  is also formed to have a spherical surface. When an external force is applied to each input portion  106  from below, each arm  100  will pivot clockwise around the shaft  101 . In this way, the rearward arms  103  will be pushed downward, and the pressing portions  105  will come into contact with the plates  55 . The pressing force will be applied to the plates  55 , and the side surfaces  54  of each sub tank  37  will contract. 
     A head storage chamber  110  for housing the head  35  is provided on the upstream side of the sub tanks  37  in the paper transport direction (further upstream in the paper transport direction than the central portion of the carriage  34 ; the right side of  FIG. 10 ). The sub tanks  37  and the head storage chamber  110  are aligned in the paper transport direction. In other words, the sub tanks  37  and the head storage chamber  110  overlap in the height direction of the multi-function device  1 . The sub tanks  37  and the head storage chamber  110  are completely offset in the plan view of the multi-function device  1 . A concave portion  111  provided in the carriage  34  defines the head storage chamber  110 . The concave portion  111  extends downward from the same surface as the bottom surface of the tank storage chamber  50 . The head  35  is arranged on the bottom portion of the concave portion  111 . The lower surface (the nozzle surface) of the head  35  is below the sub tanks  37 . Because of this, the fluid levels of the ink stored in the sub tanks  37  are always located higher than the nozzle surface of the head  35 . 
     The head  35  has a passage unit  33 , a head control board  36 , and the like. A plurality of nozzles  39  is formed in the passage unit  37 . Each nozzle  39  selectively discharges ink droplets toward the printing sheets transported through the straight path  18  (see  FIG. 2 ). The discharge amount and discharge timing of the ink is controlled by the head control board  36 . The head control board  36  has a variety of electronic components (condensers and the like)  36 A. When the multi-function device  1  is seen in plan view, the sub tanks  37  and the head  35  are completely offset (i.e., do not overlap at all). In addition, the sub tanks  37  and the head  35  overlap in the height direction of the multi-function device  1 . Note that in the present embodiment, the type of head  35  used is one which will discharge ink due to the deformation of piezoelectric elements  114  (see  FIG. 12 ). However, for example, a type of head can also be used that will discharge ink by heating the ink to produce bubbles. 
       FIG. 11  shows the nozzle surface of the head  35 . Five rows of nozzles aligned in the horizontal direction are formed in the nozzle surface. Each row of nozzles is formed by aligning a plurality of nozzles in the paper transport direction. Each row of nozzles can discharge a different color of ink. Note that the horizontal direction of  FIG. 11  is the reciprocating direction of the carriage  34 . Note also that the pitch and number of the nozzles  39  in the transport direction is set in consideration of the resolution of the images and the like. In addition, the number of rows of nozzles can also be increased or decreased in response to the type and number of color inks. 
       FIG. 12  shows the internal construction of the passage unit  33  in simplified form. The head  35  has piezoelectric elements  114 . The piezoelectric elements  114  deform when a predetermined voltage is applied by the head control board  36 . The passage unit  33  has a cavity  115 . The cavity  115  communicates with the nozzle  39 . When the piezoelectric element  114  deforms, the volume of the cavity  115  will change. In this way, energy will be applied to the ink inside the cavity  115 , and the ink will be discharged from the nozzle  39 . 
     One set comprising the cavity  115  and the piezoelectric element  114  is provided for each nozzle  39 . In other words, the number of the aforementioned sets is equal to the number of nozzles. The passage unit  33  has a manifold  116 . A plurality of cavities  115  communicate with the manifold  116 . In the present embodiment, there are five manifolds  116  because five colors of ink are used. The passage unit  33  has an ink supply port  117 . The ink supply port  117  communicates with the manifold  116 . An ink supply passage  51  (see  FIG. 10 ) is connected to the ink supply port  117 . Thus, ink sent into the ink supply passage  51  is supplied to the manifold  116  from the ink supply port  117 . Ink supplied from the ink supply port  117  to the manifold  116  is distributed to each cavity  115 . 
     As shown in  FIG. 3  to  FIG. 6 , an ink supply mechanism  80 , a capping mechanism  120  (see  FIG. 4  and  FIG. 6 ), and a maintenance mechanism  140  are provided in an area in which printing sheets do not pass (outside the printing range of the head  35 ). 
     First, the construction of the capping mechanism  120  will be described. The capping mechanism  120  is arranged adjacent to the right end of the range of movement of the head  35 .  FIG. 13  shows an enlarged view of the capping mechanism  120 .  FIG. 13A  shows an uncovered state in which the nozzles  39  are not covered by a cap  121 .  FIG. 13B  shows a covered state in which the nozzles  39  are covered by the cap  121 . The capping mechanism  120  has the cap  121 , a cap support portion  94 , and a movement mechanism  122 . The cap  121  is capable of covering the nozzles  39  of the head  35 . The cap support portion  94  supports the cap  121 . The movement mechanism  122  causes the cap support portion  94  to move and the cap  121  to come into contact with the nozzle surface of the head  35 . 
     The movement mechanism  122  has a slide cam  123 , a rack gear  124 , a pinion gear  125 , and a drive transmission mechanism  126 . The slide cam  123  is arranged below the cap  121 . The rack gear  124  causes the slide cam  123  to move in the front to rear direction of the multi-function device  1  (the horizontal direction of  FIG. 13A  and  FIG. 13B ). The pinion gear  125  meshes with the rack gear  124 . The drive transmission mechanism  126  transmits the drive force of the LF motor  71  to the pinion gear  125 . The pinion gear  125  is capable of moving in a direction perpendicular to the plane of  FIG. 13 . The movement of the pinion gear  125  is controlled by a drive means such as a solenoid (not shown in the drawings) or the like. The pinion gear  125  moves between a position in which it is meshed with the rack gear  124  and a position in which it is not meshed with the rack gear  124 . The drive force of the LF motor  71  is transmitted to the rack gear  124  via the pinion gear  125  when the pinion gear  125  is meshed with the rack gear  124 . In this way, the rack gear  124  will move in the front to rear direction of the multi-function device  1 . Note that the rotational direction of the pinion gear  125  can be switched by using a planetary gear or the like and switching the gear arrangement of the drive transmission mechanism  126 . In other words, the movement direction of the rack gear  124  can be switched between the front direction (the leftward direction of  FIG. 13 ) and the rear direction (the rightward direction of  FIG. 13 ). The slide cam  123  is linked to the rack gear  124 . When the rack gear  124  moves, the slide cam  123  will also move. A groove  131  is formed in the slide cam  123 . The groove  131  has an inclined surface  127  that inclines downward from front to rear, an upper flat portion  130  that extends leftward from the right end of the inclined surface  127 , and a lower flat portion  129  that extends rightward from the lower end of the inclined surface  127 . 
     The cap support portion  94  has a spring receptor  96 , a coil spring  97 , and a cap holder  95 . The spring receptor  96  is supported by the frame or the like of the printer unit  2 . The spring receptor  96  is capable of sliding in the vertical direction of  FIG. 13 . In other words, the spring receptor  96  can slide in a direction toward the nozzles  39  and in a direction away from the nozzles  39 . A through hole  98  is formed in the spring receptor  96 . The through hole  98  passes through the spring receptor  96  in the thickness direction (the vertical direction). A shaft  99  of the cap holder  95  is inserted into the through hole  98 . A link bar  128  that extends downward is connected to the bottom of the spring receptor  96 . A pin member  132  is connected to the lower end of the link bar  128 . The pin member  132  is fitted into the groove  131 . There is some looseness between the pin member  132  and the groove  131 . The pin member  132  is capable of sliding between the lower flat portion  129  and the upper flat portion  130  of the groove  131 . Note that the through hole  98  and the link bar  128  are shown to be overlapped in  FIG. 13A  and  FIG. 13B . However, these are offset in the direction perpendicular to the plane of  FIG. 13  in plan view. 
     The cap holder  95  holds the cap  121 . The cap  121  is installed on the upper surface of the cap holder  95 . The cap  121  is, for example, comprised of synthetic resin having flexibility. A cross-section of the cap  121  is U-shaped. The cap  121  has a tray shape. The bottom surface of the cap  121  is mounted on the upper surface of the cap holder  95 . The cap holder  95  has the shaft  99  that extends downward from the approximate center of the bottom surface. The shaft  99  is inserted from above into the through hole  98  of the spring receptor  96 . 
     There are coil springs  97  between the spring receptor  96  and the cap holder  95 . The direction in which the coil springs  97  contract and expand is the vertical direction of  FIG. 13 . The cap holder  95  is supported by the coil springs  97 . Note that in  FIG. 13 , only two coil springs  97  are shown. However, there are another two coil springs  97 . In the present embodiment, there is a total of four coil springs. Because of this, the support of the cap holder  95  will be stable. Note that the arrangement and number of coil springs  97  can be changed. 
     When the pin member  132  is located in the lower flat portion  129  of the groove  131 , the cap  121  is separated from the nozzle surface of the head  35  as shown in  FIG. 13A . In other words, an uncovered state in which the nozzles  39  are not covered with the cap  121  will be achieved. When the rack gear  124  moves from the uncovered state to the rear of the multi-function device  1  (the right direction of  FIG. 13 ), the pin member  132  will move from the lower flat portion  129  to the upper flat portion  130 . In this way, the link bar  128  and the spring receptor  96  will rise, and the cap  121  will also rise. The cap  121  will come into contact with the nozzle surface of the head  35 . When the spring receptor  96  moves further upward after the cap  121  is placed in contact with the nozzle surface, the coil spring  97  will be compressed. In this way, as shown in  FIG. 13B , an urging force that strongly presses the nozzle surface of the head  35  is applied to the cap  121 , and the cap  121  and the nozzle surface are attached to each other with no gap therebetween. In other words, the covered state in which the nozzles  39  are not covered with the cap  121  will be achieved. At this point, the space inside the cap  121  will be in a positive pressure state due to the cap  121  flexing by means of the aforementioned urging force. Because of this, the leakage of ink from the nozzles  39  can be prevented. In addition, when the rack gear  124  moves from the covered state of  FIG. 13B  in the forward direction of the multi-function device  1  (the left direction of  FIG. 13 ), the spring receptor  96  will descend. Simultaneously with this, the coil springs  97  will gradually extend. When the spring receptor  96  descends further, the cap  121  will be separated from the nozzle surface of the head  35 . When the decent of the spring receptor  96  is complete, the uncovered state shown in  FIG. 13A  will be achieved. 
     Next, the construction of the ink supply mechanism  80  will be described. As shown in  FIG. 4  and  FIG. 6 , the ink supply mechanism  80  is arranged adjacent to the right end of the range of reciprocal motion of the carriage  34 . The carriage  34  can move to the right end of the guide rails  43 ,  44  (the ink supply position). In this state, the ink supply mechanism  80  will supply ink from the ink cartridges  38  to the sub tanks  37 . During ink supply, the nozzles  39  will be covered by the cap  121  by means of the capping mechanism  120 . The ink supply mechanism  80  has a push rod  83 , male joints  84 , and a drive mechanism  82  (see  FIG. 14 ). 
     The male joints  84  are linked with the female joints  63 . In the present embodiment, there are five male joints  84  because there are 5 female joints. Each male joint  84  is connected to an ink tube that extends from each ink cartridge  38 . Each male joint  84  is supported by a support block  81 . Each male joint  84  is capable of sliding in a direction that approaches the female joint  63  (upward) and a direction away from the female joint (downward). 
     The push rod  83  applies force in the upward direction to the input portion  106  of the arms  100 . The push rod  83  extends from the arm  100 A to the arm  100 E so as to be capable of applying force simultaneously upward to the five arms  100  ( 100 A to  100 E). The push rod  83  is arranged on the forward side of the male joints  84 . The pushrod  83  is capable of sliding in the vertical direction. 
       FIG. 14  shows a simple cross-sectional view of the ink supply mechanism  80 . The drive mechanism  82  has a slide cam  85 , a pinion gear  86 , and a coil spring  87 . The slide cam  85  is arranged below the guide rail  44  (see  FIG. 3 ). A rack gear  88  that meshes with the pinion gear  86  is formed on the bottom surface of the slide cam  85 . The pinion gear  86  causes the slide cam  85  to slide in the forward and backward direction of the multi-function device  1  (the horizontal direction of  FIG. 14 ). The pinion gear  86  is capable of moving in a direction perpendicular to the plane of  FIG. 14 . The movement of the pinion gear  86  is achieved by a solenoid or the like (not shown in the drawings). The pinion gear  86  is capable of moving between a position in which the rack gear  88  is meshed and a position in which the rack gear  88  is not meshed. The drive force of the LF motor  71  is transmitted to the pinion gear  86  when the pinion gear  86  is meshed with the rack gear  88 . That drive force is transmitted to the slide cam  85  via the rack gear  88 . In this way, the slide cam  85  will move in the forward direction of the multi-function device  1  (the left direction of  FIG. 14 ). One end of the coil spring  87  is linked to the slide cam  85 . The other end of the coil spring  87  is linked to the casing  2 A or the like. The coil spring  87  will extend when the slide cam  85  moves forward. In other words, the coil spring  87  will urge the slide cam  85  rightward when the slide cam  85  has moved leftward. 
     The slide cam  85  has an inclined surface  90  that inclines forward from the rear, an upper flat portion  92  that extends rightward from the upper end of the inclined surface  90 , and a lower flat portion  91  that extends leftward from the lower end of the inclined surface  90 . The slide cam  85  is capable of moving between a position in which the slide cam  85  supports the support block  81  and the push rod  83  with the lower flat portion  91 , and a position in which the slide cam  85  supports these with the upper flat portion  92 . The push rod  83  is arranged to the left of the male joints  84 . Thus, when the slide cam  85  moves from the state shown in  FIG. 14 , the male joints  84  will first come into contact with the inclined surface  90 . In this way, the male joints  84  will rise, and the male joints  84  will be linked with the female joints  63 . The result is that the ink passages will be formed between the ink cartridges  38  and the sub tanks  37 . When the slide cam  85  moves further to the left, the pushrod  83  will come into contact with the inclined surface  90 . In this way, the pushrod  83  will rise, and the pushrod  83  will push the input portions  106  upward. 
     Next, the construction of the female joints  63  and the male joints  84  will be described in detail with reference to  FIG. 15 . Note that a portion of the female joints  63  and the male joints  84  is omitted in  FIG. 15 . Each female joint  63  has a joint main body  150 , a plug member  151 , and a coil spring  152 . The joint main body  150  is formed into a tubular shape. The plug member  151  is capable of moving in the axial direction in the interior of the joint main body  150 . The lower half of the plug member  151  has a ball shape. The coil spring  152  urges the plug member  151  downward. An interior space  154  of the joint main body  150  is an ink flow passage. Each interior space  154  communicates with the sub tank  37  via the coupling  64 , the tube  65 , and the through hole  56 . A hole  153  in which the rod  161  of the male joint  84  is to be inserted is formed in the joint main body  150 . The hole  153  is formed in a linking surface  155  that will link with the male joint  84 . The hole  153  is closed by the plug member  151 . The plug member  151  is capable of moving between a position in which the hole  153  is open and a position in which the hole  153  is closed. The coil spring  152  urges the plug member  151  toward the hole  153 . The state in which the hole  153  is closed by the plug member  151  is maintained by the coil spring  152  (see  FIG. 15A ). 
     A seal member  156  is arranged on the linking surface  155  of the joint main body  150 . The seal member  156  is formed so as to completely surround the hole  153 . The seal member  156  will prevent ink from leaking to the outside when the female joint  63  and the male joint  84  are linked. The seal member  156  is constructed of, for example, nitrile rubber (NBR), silicone rubber (VMQ), or the like. The seal member  156  has flexibility, and will flex by means of a pressing force from the male joint  84 . 
     The spring force of the coil spring  152  is set as follows. In other words, when the pressure inside the sub tank  37  is smaller than a predetermined negative pressure (back pressure) that is lower than atmospheric pressure, the coil spring  152  will not withstand the force that pushes the plug member  151  into the joint main body  150  and thus will be compressed. When the pressure inside the sub tank  37  has recovered to the aforementioned negative pressure or higher, the coil spring  152  will withstand the force that pushes the plug member  151  inside the joint main body  150  and thus will extend. When ink is discharged from the head  35 , the barometric pressure inside the sub tank  37  will gradually decrease. In this case, when the barometric pressure inside sub tank  37  is less than the aforementioned predetermined negative pressure, the hole  153  will be opened and atmospheric air will flow into the sub tank  37  from the hole  153 . When the barometric pressure inside the sub tank  37  recovers to the aforementioned negative pressure or higher, the hole  153  will be closed by means of the plug member  151 . The pressure inside the sub tank  37  can be prevented from reaching the predetermined negative pressure or lower. In addition, if the temperature inside the sub tank  37  increases, the barometric pressure inside the sub tank  37  will increase. When the barometric pressure inside the sub tank  37  becomes higher than a predetermined value, air will leak to the outside from a slight gap between the plug member  151  and the joint main body  150  (the hole  153 ). This will be achieved because the plug member  151  is formed into the ball shape. The result is that the barometric pressure inside the sub tank  37  will be prohibited from becoming higher than the aforementioned predetermined value. In the present embodiment, the barometric pressure inside the sub tank  37  will be maintained within a predetermined range. The result is that the meniscuses of the nozzles  39  will always be maintained in an optimal state. 
     Each male joint  84  has a joint main body  160 , a rod  161 , and a coil spring  162 . The joint main body  160  is formed into a tubular shape. The rod  161  is capable of moving in the axial direction in the interior of the joint main body  160 . The coil spring  162  urges the rod  161  upward. An interior space  164  of the joint main body  160  is an ink flow passage. The interior space  164  communicates with the ink cartridge  38  via a tube not shown in the drawings. A hole  163  is formed in the joint main body  160 . The hole  163  is formed in a linking surface  166  that will be linked with the male joint  63 . The rod  161  is inserted into the hole  163 . The rod  161  projects upward beyond the hole  163 . The outer diameter of the rod  161  is set to be smaller than the inner diameter of the hole  163 . Ink is capable of moving through the hole  163  even in a state in which the rod  161  is inserted into the hole  163 . 
     A blocking member  165  that closes the hole  163  from the inside is connected to one end of the rod  161 . The rod  161  is capable of moving between a position in which the hole  163  is closed with the blocking member  165  and a position in which the hole  163  is open. The coil spring  162  urges the blocking member  165  toward the hole  163 . In this way, the hole  163  will be closed with the blocking member  165 , and the rod  161  will be maintained in a state in which it projects out of the hole  163 . 
     The spring force of the coil spring  162  is set as follows. In other words, the spring force of the coil spring  162  is set to be stronger than the coil spring  152  of the female joint  84 . The spring force of the coil spring  162  is set such that when the rod  161  is in contact with the plug member  151  as shown in  FIG. 15B , the coil spring  152  is compressed but the coil spring  162  is not compressed. In addition, the spring force of the coil spring  162  is set such that when the link surface  166  of the male joint  84  has come into contact with the seal member  156 , the force relationship between the spring force of the coil spring  152  and the spring force of the coil spring  162  will be opposite. In other words, when the male joint  84  rises further upward from the state in which the link surface  166  of the male joint  84  is in contact with the seal member  156  (see  FIG. 15B ), the coil spring  162  will be compressed only the corresponding amount of flexibility in the seal member  156 . In this way, the hole  163  in the male joint  84  will be opened. In other words, when the male joint  84  rises up, the hole  153  in the female joint  63  will be opened first. Next, the link surface  166  of the male joint  84  will be placed into contact with the seal member  156 . Finally, the hole  163  in the male joint  84  will be opened. 
     Next, the ink supply operation performed by the ink supply mechanism  80  will be described.  FIG. 16  is a drawing that serves to describe the ink supply operation. Note that in  FIG. 16 , the pinion gear  86  is omitted. In the present embodiment, the ink supply operation will be executed when the remaining quantity of ink inside the sub tank  37  is less than a predetermined quantity. The following construction may also be adopted in order to detect the remaining quantity of ink inside the sub tank  37 . For example, when the sub tank  37  is transparent, an optical sensor such as a photointerrupter or the like will be arranged on the carriage  34 . The controller can determine whether or not there is less than the predetermined quantity based upon the output of the optical sensor. In addition, the quantity of ink discharged may also be counted by a dot counter, and the remaining quantity of ink determined from that count value. The controller will cause the carriage  34  to move to the ink supply position (the position shown in  FIG. 3  and  FIG. 5 ) when the remaining quantity of ink is less than a predetermined quantity. In this case, the stop position of the carriage  34  will be controlled (see  FIG. 16A ) such that the nozzles  39  of the head  35  are located directly above the cap  121 . 
     Next, the controller will drive the movement mechanism  122  (see  FIG. 13 ), and will cause the cap  121  to rise. In this way, the cap  121  is attached to the lower surface of the head  35  (see  FIG. 16B ). Ink will not leak from the nozzles  39  during ink supply because the nozzles  39  are blocked. The controller will drive the drive mechanism  82  at the same time it causes the cap  121  to move. The controller will cause the pinion gear  86  (see  FIG. 14 ) and the rack gear  88  of the slide cam  85  to mesh, and then apply the drive force of the LF motor to the slide cam  85 . In this way, the slide cam  85  will move forward (the left direction of  FIG. 16 ). The male joint  84  will be raised up by the inclined surface  90  of the slide cam  85 . The male joint  84  will link with the female joint  63  (see  FIG. 16B ). In this way, ink passages will be formed between the ink cartridges  38  and the sub tanks  37 . 
     The controller will cause the slide cam  85  to move further forward. The push rod  83  will be raised up by the inclined surface  90 . At this point, a force that pushes the forward arm  104  upward to the input portion  106  of the arm  100  will be applied. The arm  100  will pivot due to this force. In this way, the pressing portion  105  of the rearward arm  103  will push the plate  55  of the sub tank  37  downward. The result is that, as shown in  FIG. 16C , the sub tank  37  will be compressed, and the ink, air, etc. inside the sub tank  37  will move from the through hole  56  to the ink cartridge  38 . Note that the ink will flow smoothly into the ink cartridge  38  due to the provision of an air ventilation hole in the ink cartridge  38 . 
     When the ink inside the sub tank  37  has been almost completely exhausted, the controller will cause the slide cam  85  to move rearward (rightward in  FIG. 16 ). The controller will release the meshing between the pinion gear  86  and the rack gear  88 . In this way, the spring force of the coil spring  87  will be applied to the slide cam  85 . The push rod  83  will descend along the inclined surface  90  of the slide cam  85 . In this way, the pressing force applied to the sub tank  37  will be released at the same time that the push rod  83  moves away from the input portion  106  of the forward arm  104 . The sub tank  37  will return to its original shape. At this point, as shown in  FIG. 16D , the ink inside the ink cartridge  38  will move into the sub tank  37 . 
     When the slide cam  85  moves further rearward, the male joint  84  will descend (see FIG.  16 E). In this way, the link between the male joint  84  and the female joint  63  will be released. At this point, a small quantity of air will come into the interior from the hole  153  of the female joint  63 , and the sub tank  37  will expand. In this way, ink stored in the ink passage from the female joint  63  up to the through hole  56  will flow inside the sub tank  37 . The ink inside the ink cartridge  38  will be supplied into the sub tank  37  in accordance with each of the aforementioned operations. 
     Next, the construction of the maintenance mechanism  140  will be described. As shown in  FIG. 3  to  FIG. 6 , the maintenance mechanism  140  is arranged adjacent to the left end of the reciprocating range of the carriage  34 . The carriage  34  can move to the left end of the guide rails  43 ,  44  (the maintenance position). In this state, maintenance on the head  35  will be performed (air discharge of ink such as positive pressure purge, flushing, or the like) by means of the maintenance mechanism  140 . Sludge and air bubbles in the nozzles  39  of the head  35  and in the ink passages from the sub tanks  37  up to the nozzles  39  can be removed (purged) by performing maintenance. As shown in  FIG. 3 , the maintenance mechanism  140  has a wiper  146 , an ink tray  141 , a push rod  142 , and a drive mechanism  143  that pushes the pushrod  142  upward. 
     The ink tray  141  is in the same plane as the upper surface of the platen  28 . The ink tray  141  is arranged inside the reciprocating range of the carriage  34  and outside the printing range. Note that liquid adsorbent material such as felt or the like is arranged inside the ink tray  141 . Ink that has been discharged will be adsorbed by the liquid adsorbent material. The wiper  146  that wipes off the nozzle surface of the head  35  is connected to the ink tray  141 . A drive mechanism not shown in the drawings will cause the wiper  146  to slide in the front to rear direction when the wiper  146  has been pushed onto the head  35 . In this way, ink adhered to the nozzle surface will be wiped off. 
     The push rod  142  pushes the input portion  106  of the arm  100  upward. The push rod  142  can push the input portion of one arm  100  selected from the five arms  100  ( 100 A to  100 E). The width of the push rod  142  is the same as the width of the input portion  106 . The push rod  142  is capable of sliding in the vertical direction below the input portion  106 . 
       FIG. 17  shows a simple cross-sectional view of the maintenance mechanism  140 . The drive mechanism  143  has a slide cam  144 , a pinion gear  145 , and a coil spring  147 . The slide cam  144  is arranged below the guide rail  44  (see  FIG. 3 ). The rack gear  148  that meshes with the pinion gear  145  is formed on the bottom surface of the slide cam  144 . The pinion gear  145  causes the slide cam  144  to slide in the forward and backward direction (the horizontal direction of  FIG. 17 ). The pinion gear  145  is capable of moving in the direction perpendicular to the plane of  FIG. 17 . This movement is achieved by a solenoid or the like (not shown in the drawings). The pinion gear  145  is capable of moving between a position in which the rack gear  148  is meshed and a position in which the pinion gear  145  is not meshed. The drive force of the LF motor  71  is transmitted to the pinion gear  145  when the pinion gear  145  is meshed with the rack gear  148 . This drive force is transmitted to the slide cam  144  via the rack gear  148 . In this way, the slide cam  144  will move rearward (the left direction of  FIG. 17 ). One end of the coil spring  147  is linked to the slide cam  144 . The other end of the coil spring  147  is linked to the casing  2 A or the like. The coil spring  147  will extend when the slide cam  144  moves forward. In other words, the coil spring  147  will urge the slide cam  144  in a direction that returns the slide cam  144  to its original position prior to movement. 
     The slide cam  144  has an inclined surface  135  that inclines upward from left to right, an upper flat portion  136  that extends rightward from the upper end of the inclined surface  135 , and a lower flat portion  137  that extends leftward from the lower end of the inclined surface  135 . The slide cam  144  is capable of sliding between a position in which the slide cam  144  supports the push rod  142  on the lower flat portion  137  and a position in which the slide cam  144  supports the pushrod  142  on the upper flat portion  136 . As noted above, the push rod  142  is capable of sliding in the vertical direction. When the slide cam  144  moves leftward from the state shown in  FIG. 17 , the push rod  142  will rise along the inclined surface  135 . In this way, the upper end of the push rod  142  will be in contact with the input portion  106 , and an upward force will be applied to the input portion  106 . 
     Next, the operation of the maintenance mechanism  140  will be described.  FIG. 18  is a drawing which serves to describe the operation of the maintenance mechanism  140 . Note that in  FIG. 18 , the pinion gear  145  is omitted. In the present embodiment, maintenance will be performed only when a sufficient quantity of ink to perform maintenance is remaining inside the sub tank  37 . Thus, in the event that a maintenance command is input when there is little ink remaining inside the sub tank  37 , maintenance will be performed after the ink supply operation noted above has been performed. 
     The controller will cause the carriage  34  to move to the maintenance position (the position shown in  FIG. 4  and  FIG. 6 ) when the controller determines that the quantity of ink remaining inside the sub tank  37  is at a predetermined value or greater based upon the output value of an optical sensor, the count value of a dot counter, or the like. In the event that the ink color on which maintenance is to be performed has been selected (e.g., a user can select the ink color; in another example, the controller can select the ink color in response to the previous print condition), the controller will cause the arm  100  and the push rod  142  corresponding to the requested ink color to move to a position that matches in plan view (see  FIG. 18A ). In this state, the nozzles  39  of the head  35  are directly above the ink tray  141 . 
     Next, the controller will drive the drive mechanism  143 , and will cause the slide cam  144  to move rearward (in the leftward direction of  FIG. 18 ). In other words, the controller will cause the pinion gear  145  (see  FIG. 17 ) and the rack gear  148  of the slide cam  144  to mesh. Then, the controller will apply the drive force of the LF motor  71  to the slide cam  144 . The push rod  142  will be raised up by the inclined surface  135  of the slide cam  144 . An upward force will be applied to the input portion  106  of the arm  100  corresponding to the selected ink color. The arm  100  will pivot in the counter clockwise direction due to this force. In this way, the pressing portion  105  of the rearward arm  103  will push the plate  55  of the sub tank  37  downward. The result is that, as shown in  FIG. 18B , the sub tank  37  will be compressed, and the ink, air, etc. inside the sub tank  37  will be discharged from the through hole  57 . Ink and air will be ejected from the nozzles  39  via the ink supply passage  51 . In this way, sludge and air bubbles in the ink passages from the sub tanks  37  to the nozzles  39  will be eliminated. This elimination process will be hereinafter referred to as a positive pressure purge. 
     When the positive pressure purge is complete, the controller will cause the slide cam  144  to move forward (the rightward direction of  FIG. 18 ). The controller will release the meshing between the pinion gear  145  and the rack gear  148 . In this way, the spring force of the coil spring  147  will be applied to the slide cam  144 . The push rod  142  will descend along the inclined surface  135  of the slide cam  144 . In this way, the pressing force applied to the sub tank  37  will be released and the push rod  142  will move away from the input portion  106  of the forward arm  104 . The sub tank  37  will expand, and will return to its original shape (see  FIG. 18C ). At this point, the pressure inside the sub tank  37  will be below the aforementioned predetermined negative pressure. The result is that the coil spring  152  of the female joint  63  will be compressed, and air will flow in from the hole  153 . Note that because the nozzles  39  are microscopic holes, air will not flow from the nozzles  39  even if air flows in from the hole  153 . 
     In addition, when the positive pressure purge is completed, the controller will drive the wiper  146 . In this way, ink adhered to the nozzle surface due to ink injection will be wiped off (see  FIG. 18D ). This operation will be hereinafter referred to as wiping. When wiping is performed, different colors of ink on the nozzle surface can be prevented from mixing. 
     When wiping is performed, other colors of ink may enter into the nozzles  39 . Because of this, a so-called flushing will be performed. In other words, the controller will control the piezoelectric elements (see  FIG. 12 ), and will cause minute quantities of ink to be discharged from the nozzles (see  FIG. 18E ). When the aforementioned maintenance is performed, the effect of cleaning the ink passages from the sub tanks  37  to the nozzles  39  will be obtained. In addition, the effect of eliminating air bubbles and sludge inside the head  35  will be obtained. In addition, the effect of eliminating mixed ink colors, preventing the nozzle surface from drying, etc. will also be obtained. In addition, in the present embodiment, because a positive pressure purge is possible with respect to only the passages corresponding to selected ink colors, the quantity of ink consumed during maintenance can be reduced compared to when all colors are purged. 
     In the aforementioned embodiment, the sub tanks  37  and the head  35  are offset in the plan view of the multi-function device  1 . Because of this, the sub tanks  37  and the head  35  can overlap in the height direction of the multi-function device  1 . Because the sub tanks  37  are not arranged above or below the head  35 , the image recording unit  24  can be made thinner. 
     Second Embodiment 
       FIG. 19  shows a simple cross-sectional view of a printer unit  2  of a second embodiment. In  FIG. 19 , the same reference numbers as the first embodiment will be used for the same elements as the first embodiment. In the present embodiment, the ink cartridges  138  and the sub tanks  137  are always connected when the ink cartridges  138  are mounted to the printer unit  2 . The ink cartridges  138  and the sub tanks  137  are connected by tubes  139  having elasticity. The ink cartridges  138  and the sub tanks  137  are also connected when the head  35  is printing on printing sheets. Thus, ink can be supplied from the ink cartridges  38  to the sub tanks  137  even when the head  35  is printing on printing sheets. The sub tanks  137  and the head  35  are offset in the plan view of the multi-function device  1 . In addition, the sub tanks  137  and the head  35  overlap in the height direction of the multi-function device  1 . Because the sub tanks  137  are not arranged above or below the head  35 , the image recording unit  24  can be made thinner. 
     Third Embodiment 
       FIG. 20  shows a simple cross-sectional view of a printer unit  3  of a third embodiment. In  FIG. 20 , the same reference numbers as the first embodiment will be used for the same elements as the first embodiment. In the present embodiment, the ink cartridges  238  are detachably mounted on the carriage  34 . When the carriage  34  moves in a state in which the ink cartridges  238  are mounted on the carriage  34 , the carriage  34  will move together with the ink cartridges  238 . The ink cartridges  238  and the head  35  are connected when the ink cartridges  238  are mounted on the carriage  34 . The ink cartridges  238  and the head  35  are offset in the plan view of the multi-function device  1 . In addition, the ink cartridges  238  and the head  35  overlap in the height direction of the multi-function device  1 . Because the ink cartridges  238  are not arranged above or below the head  35 , the image recording unit  24  can be made thinner.