Abstract:
A valve device comprises a flow passage, a storage chamber, a valve seat, a diaphragm, a valve-closing unit, and a first biasing member. A fluid passes through the flow passage. The storage chamber is disposed in the flow passage for storing the fluid. The storing chamber includes an opening. The valve seat includes a communicating hole for releasing the fluid in the storage chamber through the communicating hole to the outside. The diaphragm operates to cover the opening of the storage chamber and displaces relative to the valve seat. The valve-closing unit brings the diaphragm into contact with the valve seat so as to block the communicating hole. The first biasing member expands a clearance between the diaphragm and the valve seat to open the valve device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2006-035414, filed on Feb. 13, 2006, the entire content of which is incorporated herein by reference.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a valve device and a liquid ejection device.  
       BACKGROUND OF THE INVENTION  
       [0003]     As a liquid ejection device for ejecting liquid from a liquid ejection head onto a target, an ink-jet printer exists. In the printer, ink is supplied from a cartridge that stores ink as a liquid to a recording head that serves as a liquid ejection head and that is mounted on a carriage. Then, the recording head is driven so as to eject ink toward paper as a target. One example of the printers is a so-called off-carriage printer. In a printer of this type, in order to make the size of the device small and reduce the load on the carriage, a cartridge is disposed at a location other than the carriage.  
         [0004]     A printer of this type includes an ink supply mechanism for supplying ink from the cartridge to the recording head by way of an ink flow passage made of an item such as a tube. In order to supply ink to the recording head in the face of pressure loss and gravity within the flow passage, the ink supply mechanism pressurizes the ink stored in the cartridge into ink flow passage in order to send the ink to the recording head.  
         [0005]     As an ink supply mechanism as described above, an ink supply mechanism for pumping air into the cartridge including a case and an ink pack has been proposed. The air supply mechanism includes a pressurizing pump, an air flow passage for supplying air into the case of the cartridge, and a pressure regulating device. The ink pack is made of a flexible material and the pressure of the air that is charged into the case crushes the ink pack. As a result, ink that is charged in the ink pack is pushed into the ink flow passage.  
         [0006]     When the pressurized air supplied to the cartridge reaches a predetermined value or higher, the pressure regulating device releases the pressure to regulate the pressure applied to the cartridge so as to fall within a predetermined range. As an example of such pressure regulating device, Japanese Unexamined Patent Publication No. 2002-211002 discloses a pressure regulating valve equipped with a drive lever and a diaphragm valve. The diaphragm valve is a channel—like rubber molded article which is molded into a shape such that it does not block the air communicating hole when no external force is applied to the diaphragm valve. When the drive lever is moved downward, a supporting shaft interlocked with the drive lever presses the diaphragm valve toward the air communicating hole by a biasing force, and, in response to the pressing force, the diaphragm valve is elastically deformed. As a result, the air communicating hole is blocked and the valve is forcedly closed. At this point, if the pressure in the air chamber inside the pressure regulating valve increases excessively, the diaphragm valve, by virtue of the air pressure acting against the biasing force of the spring member, warps in a direction away from the air communicating hole so as to release the air in the air chamber to the outside. In contrast, when the drive lever is moved upward, the drive lever pulls up the supporting shaft, so that the diaphragm valve, by virtue of its elasticity, returns to its original shape so as to open the air communicating hole.  
         [0007]     Recently, because of the high costs of a rubber molded article, a diaphragm valve in the shape of a thin film made of synthetic resin has been increasingly employed. Unlike a diaphragm valve made of a rubber molded article, such film is cheap since steps of designing and injection molding are eliminated.  
         [0008]     However, a diaphragm valve made of film is inferior to a diaphragm valve made of a rubber molded article in terms of elasticity. For this reason, when pressure inside the air chamber reaches a predetermined value or higher, the film displaces in a direction of valve opening by the air pressure but the clearance between the diaphragm valve and the air communicating hole becomes very small. Accordingly, when the air in the air chamber flows through this minute clearance to the air communicating hole, the flow rate thereof increases, resulting in the occurrence of vibration and unusual sounds.  
       SUMMARY OF THE INVENTION  
       [0009]     An objective of the present invention is to provide a valve device and a liquid ejection device that are capable of preventing the occurrence of vibration or unusual sounds.  
         [0010]     According to an aspect of the invention, a valve device is provided. The valve device comprises a flow passage, a storage chamber, a valve seat, a diaphragm, a valve-closing unit, and a first biasing member. The fluid passes through the flow passage. The storage chamber is disposed in the flow passage for storing the fluid. The storing chamber includes an opening. The valve seat includes a communicating hole for releasing the fluid in the storage chamber through the communicating hole to the outside. The diaphragm operates to cover the opening of the storage chamber and that displaces relative to the valve seat. The valve-closing unit brings the diaphragm into contact with the valve seat so as to block the communicating hole. The first biasing member expands a clearance between the diaphragm and the valve seat to open the valve device.  
         [0011]     According to another aspect of the invention, a valve device for regulating a pressure of the fluid passing through a flow passage is provided. The valve device comprises a housing, a storage chamber, a valve seat, a diaphragm, a valve-closing unit, and a first biasing member. The housing is disposed in the flow passage. The housing has an inlet hole and an outlet hole. The storage chamber is disposed in the housing for storing the fluid. The storing chamber includes an opening. The fluid is introduced into the storage chamber through the inlet hole and discharged from the storage chamber through the outlet hole. The valve seat extends into the storage chamber. The valve seat includes a communicating hole for releasing the fluid in the storage chamber through the communicating hole to the outside. The diaphragm operates to cover the opening of the storage chamber and that displaces relative to the valve seat. The valve-closing unit brings the diaphragm into contact with the valve seat so as to block the communicating hole. The first biasing member is disposed on the inside of the valve seat. The first biasing member biases the diaphragm for expanding a clearance between the diaphragm and the valve seat to open the valve device.  
         [0012]     According to yet another aspect of the invention, a liquid ejection device including the valve device as described above is also provided.  
         [0013]     Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The invention, together with the objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments in combination with the accompanying drawings in which:  
         [0015]      FIG. 1  is a plan view of a printer of an embodiment of the present invention.  
         [0016]      FIG. 2  is a partially enlarged cross-sectional view of a cartridge.  
         [0017]      FIG. 3  is a perspective view of a pressurizing unit.  
         [0018]      FIG. 4  is a perspective view of a pressure regulating valve.  
         [0019]      FIG. 5  is a cross-sectional view of the pressure regulating valve in an open state.  
         [0020]      FIG. 6  is a cross-sectional view of the pressure regulating valve in a closed state.  
         [0021]      FIG. 7  is a partially enlarged cross-sectional view of the pressure regulating valve in a closed state.  
         [0022]      FIG. 8  is a partially enlarged cross-sectional view of the pressure regulating valve in a state in which it is opened to atmospheric air. 
     
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0023]     Hereinafter, an embodiment of the present invention will be described with reference to FIGS.  1  to  8 .  
         [0024]      FIG. 1  is a plan view illustrating a schematic structure of an ink-jet printer serving as a liquid ejection device. As shown in  FIG. 1 , the printer  1  includes a frame  2  and a platen  3  is mounted on the frame  2 . Papers are fed onto the platen  3 , by a paper-conveying mechanism that has a paper-conveying motor (not shown). Further, a bar-like guide  4  is mounted on the frame  2  so as to extend in parallel with the longitudinal direction of the platen  3 . A carriage  5  is penetrated and supported by the guide  4  so as to be reciprocally movable in an axial direction of the guide  4 . The carriage  5  is connected to a carriage motor  7  by means of a timing belt  6  that stretches between the pulleys  6   a ,  6   b  so that the carriage  5  is driven by the carriage motor  7 . Thus, the carriage  5  is driven by the carriage motor  7  so as to move reciprocally along the guide  4 .  
         [0025]     A recording head  10  that serves as a liquid ejection head is mounted on the surface of the carriage  5  opposite to the platen  3 . The valve units  11  for supplying fluid or liquid ink to the recording head  10  are mounted on the carriage  5 . In this embodiment, four valve units  11  are provided, each corresponding to the color, or to the kind, of ink to be used in the printer  1 . On the lower surface of the recording head  10 , nozzles are provided (not shown). Ink droplets are ejected through ejecting ports of the nozzles onto the paper which is conveyed over the platen  3 .  
         [0026]     A cartridge holder  12  is provided on the right end of the frame  2 . Four cartridges  13 , serving as liquid containers, are detachably mounted in the cartridge holder  12 , As shown in  FIG. 2 , each cartridge  13  includes a case  14 , the interior of which is airtight, and an ink pack  15  provided in the case  14 . The ink pack  15  serves as a liquid-containing portion. Each ink pack  15  includes a flexible film that is formed into the shape of bag, and an ink supply port  15   a  that is made of synthetic resin. The ink packs  15  may be filled with a variety of inks. An inner space  17  is created between the case  14  and the ink pack  15 .  
         [0027]     As shown in  FIG. 1 , the ink supply port  15   a  of each ink pack  15  is connected to each of the valve units  11  provided on the carriage  5  by an ink supply passage  16  that serves as a liquid flow passage. Each ink supply passage  16  is comprised of a tube made of a flexible material or a flow passage that is formed by cutting a hard resin material.  
         [0028]     A pressurizing unit  20  is mounted on the end portion of frame  2 . The pressurizing unit  20  is a device for conveying air in a pressurized state as a fluid to the cartridges  13  by way of an air-supplying passage  21  that serves as a flow passage for fluid. The air-supplying passage  21  branches into plural passages (4 passages in this embodiment) at a distributor  26  that is located downstream in the pressurizing unit  20  and the branched passages  21  are connected to the respective cartridges  13 .  
         [0029]     As described above, an inner space  17  is provided between the case  14  and the ink pack  15  in each cartridge  13 . In each case  14 , a non-illustrated air-communicating hole which communicates with an inner space  17  is formed. Each of the air-supplying passages  21  (see  FIG. 1 ) is connected to each air-communicating hole. Thus, air, conveyed as a fluid from the pressurizing unit  20  in a pressurized state, is introduced into each individual inner space  17  in the cartridge  13  via each air-supplying passage  21 . When an inner space  17  is filled with air in a high pressure state, the ink pack  15  is crushed by the air pressure. This results in ink being pushed out of the ink pack  15  into the ink supply passage  16 , so that ink is supplied to the valve unit  11 .  
         [0030]     Next, the pressurizing unit  20  will be described with reference to  FIG. 3 . As illustrated in  FIG. 3 , the pressurizing unit  20  includes a drive motor  22 , a pressurizing pump  23 , a pressure sensor  24 , and a pressure regulating valve  30  that serves as a valve device. The drive motor  22  is, for example, a stepping motor the drive shaft of which is connected to the pressurizing pump  23 . When the drive motor  22  rotates normally, the pressurizing pump  23  conveys the pressurized air as a pressurized fluid to the cartridge  13 . When the drive motor  22  rotates in a reverse direction, the pressurizing pump  23  does not convey the pressurized air to the cartridge  13 .  
         [0031]     A transmission mechanism  25  having tooth wheels is connected to the drive motor  22  to transmit the rotational force of the drive motor  22  to the pressure regulating valve  30 . By virtue of the rotational force transmitted by the transmission mechanism  25 , the pressure regulating valve  30  selectively opens and closes a part of the air flow passage that extends from the pressurizing pump  23  to the cartridge  13 . Further, the pressure sensor  24  is located adjacent to the pressure regulating valve  30 . The pressure sensor  24  detects the pressure of air conveyed by the pressurizing pump  23  and outputs the result of such detection to an external unit. When the pressure sensor  24  detects that the pressure of the pressurized air has decreased to a predetermined value or lower, it controls the drive motor  22  by means of the external unit to drive the pressurizing pump  23 .  
         [0032]     First, when the drive motor  22  rotates normally, the pressurizing pump  23  normally rotates to convey pressurized air to the pressure regulating valve  30  by the pressure sensor  24 . When the pressure regulating valve  30  supplies ink in the cartridge  13  to the recording head  10 , the valve  30  is closed so that the pressurized air is conveyed toward the cartridge  13 . When the main power supply of the printer  1  is turned off, the valve  30  opens the air flow passage to the atmospheric air so as to release the air pressure applied to the ink pack  15 , thereby preventing leakage of ink from the recording head  10 . In contrast, when the pressure regulating valve  30  detects that the pressure of the pressurized air supplied to the cartridge  13  has increased to a predetermined value or higher, it automatically opens the air flow passage to the atmospheric air so as to release the pressurized air, and thus adjust the air pressure in the cartridge  13  so that it falls within a predetermined pressure range.  
         [0033]     Next, the structure of the pressure regulating valve  30  will be described with reference to FIGS.  4  to  7 .  FIG. 4  is a perspective view of the pressure regulating valve  30 .  FIG. 5  is a cross-sectional view of the pressure regulating valve  30 .  FIGS. 6 and 7  are partially enlarged cross-sectional views of the pressure regulating valve  30 . As shown in  FIG. 4 , the pressure regulating valve  30  includes a first cover  31  that is substantially in a plate-like shape and mounted integrally with the pressurizing pump  23  and the pressure sensor  24 , and a second cover  32  that is mounted onto the first cover  31  from above. The first cover  31  and the second cover  32  are made of a synthetic resin such as polypropylene.  
         [0034]     As shown in  FIG. 5 , the first cover  31  has a first housing  33  in the shape of a bottomed cylinder that extends in a longitudinal direction of the pressure regulating valve  30 . An air introducing hole  34  and an air discharging hole  35  are respectively formed through the first cover  31  to be connected to the inside of the first housing  33 . The air introducing hole  34  and the air discharging hole  35  together constitute an air flow passage that extends from the pressurizing pump  23  to the cartridge  13 . The air introducing hole  34  is connected with the air flow passage of the pressurizing pump  23 , whereas the air discharging hole  35  is connected with the air flow passage of the cartridge  13 .  
         [0035]     Further, a communicating portion  36  in the generally cylindrical shape is formed to protrude from the inner bottom surface of the first housing  33 . An air communicating hole  37  that serves as a communicating hole is provided inside the communicating portion  36  and extends through the first housing  33 . The air communicating hole  37  establishes a connection between the inside of the first housing  33  and the outside of the first housing  33 , or of the first cover  31 , in other words, the atmospheric air. A cylindrical sealing member  38  is provided around the communicating portion  36  to surround the communicating portion  36 . The sealing member  38  is made of rubber or a synthetic resin, and its height (i.e. the height in the x direction in  FIG. 5 ) is greater than the height of the communicating portion  36 . The base end of the sealing member  38  is formed into a flat plate-like shape, and the top end thereof is formed into a tapered shape. The communicating portion  36  and the sealing member  38  together constitute a valve seat  39  to which a diaphragm  40  is brought into contact.  
         [0036]     An opening  33   a  of the first housing  33  is covered with the diaphragm  40  which is displaceable in the x direction and the direction opposite to the x direction, as illustrated in  FIG. 5 . The diaphragm  40  includes a film  41  and a pressure receiving plate  42 . The plate  42  serves as a contact member and is thicker than the film  41 . The film  41  is made of a synthetic resin such as polyethylene which is weldable onto the first cover  31 . The peripheral edge of the film  41  is welded onto the upper surface  31   a  of the first cover  31 , so that the film  41  and the inner surface of the first housing  33  together constitute an air chamber  44  that serves as a storage chamber.  
         [0037]     The pressure receiving plate  42  is made of a plate-like rubber or a synthetic resin, and is formed into the shape of a disc that is of a size sufficient to block the inlet of the air communicating hole  37  and the inlet of the sealing member  38 . The pressure receiving plate  42  is pasted or welded onto substantially the central part of the film  41 . In the valve closing state, the diaphragm  40 , made up of the film  41  and the pressure-receiving plate  42 , is applied the external force, with the result that the pressure-receiving plate  42  and the sealing member  38  make contact with each other, and thus block the air communicating hole  37 . In the valve opening state, as the film  41  receives the pressure within the air chamber  44 , the film  41  is displaced in a direction away from the valve seat  39 , that is, in the x direction, and thus the air communicating hole  37  is opened. A “valve opening state” of the diaphragm  40  means not only a state where the pressure-receiving plate  42  is completely separated from the sealing member  38 , but also a state where a clearance is formed between the pressure-receiving plate  42  and the sealing member  38 . In other words, the valve opening state also includes a state where a part of the pressure-receiving plate  42  is separated from the sealing member  38  while, at the same time, another part thereof remains in contact with the sealing member  38 .  
         [0038]     A biasing spring  45 , which is made of a coil spring that serves as a biasing member, is provided in the air communicating hole  37  of the communicating portion  36 . In the valve opened state, the biasing spring  45  biases the pressure receiving plate  42  so as to expand the clearance between the pressure receiving plate  42  and the sealing member  38 . As a result, when the diaphragm  40  moves away from the air communicating hole  37 , the clearance between the sealing member  38  (i.e. an inlet of the air communicating hole  37 ) and the pressure receiving plate  42  is expanded.  
         [0039]     As shown in  FIGS. 4 and 5 , the second cover  32  includes a plate-like attachment portion  46  and a second housing  47  that assumes the shape of a cylinder having a lid. A through hole  48  is formed through the cover portion  47   a  of the second housing  47 . A switching member  50 , which is comprised of a valve-closing unit, is passed through the through hole  48 . The switching member  50  includes a plate-like engagement portion  50   a  and a penetrating portion  50   b  that extends downward from the engagement portion  50   a  and that penetrates through the second housing  47 . A spherical contact portion  50   c  is formed on the lower end of the penetrating portion  50   b . In the vicinity of the contact portion  50   c , an annular protruding portion  50   d  is formed in a circumferential direction of the penetrating portion  50   b.    
         [0040]     Further, an annular spring receiving portion  51  is fitted with the annular protruding portion  50   d  of the switching member  50 . An annular stepwise portion  51   a  is formed so as to protrude from the lower peripheral portion of the spring receiving portion  51 . A coil spring  52  that serves as a biasing member is placed between the stepwise portion  51   a  of the spring receiving portion  51  and the cover portion  47   a  of the second housing  47 . The coil spring  52  applies a biasing force onto the spring receiving portion  51  and the switching member  50  in the direction along which they are pressed against the diaphragm  40 . The coil spring  52  is comprised of the valve-closing unit.  
         [0041]     Further, an engagement piece  60  which constitutes a cam mechanism  55  that serves as a moving mechanism comes into contact with the lower surface  50   e  of the engagement portion  50   a  of the switching member  50 . The cam mechanism  55  is comprised of the valve-closing unit. As shown in  FIG. 4 , the cam mechanism  55  is equipped with a pair of supporting portions  57  that have been formed so as to extend from the cover portion  47   a  of the second housing  47 .  
         [0042]     A rotational shaft  59  is rotatably supported by the supporting portions  57  and a drive lever  58  is connected to one end of the rotational shaft  59 . The drive lever  58  is configured in such a way that, as it is driven by the transmission mechanism  25 , as described above, it rotates only at a predetermined angle. Thus, the rotational shaft  59  rotates in accordance with the rotation of the drive lever  58 .  
         [0043]     As shown in  FIG. 5 , the rotational shaft  59  supports the engagement piece  60 . The engagement piece  60  is formed into the shape of deformed polygon and has at least five sides. In this embodiment, the engagement piece  60  includes first to fifth sides  60   a  to  60   e . The distances from the rotational shaft  59 , which forms a center of rotation, to the first to fifth sides  60   a  to  60   e  differ from each other. For example, the distance between the second side  60   b  and the rotational shaft  59  is the longest. In contrast, the distance between the third side  60   c  and the rotational shaft  59  is relatively short.  
         [0044]     For example, as shown in  FIG. 5 , in a state where the second side  60   b  of the engagement piece  60  is in contact with the lower surface  50   e  of the engagement portion  50   a  of the switching member  50 , the engagement piece  60  pushes the switching member  50  upward in the x direction against the biasing force of the coil spring  52 . At this point, the contact portion  50   c  of the switching member  50  is in a state in which it is separated from the diaphragm  40 . Then, by virtue of the biasing force of the biasing spring  45  provided in the air communicating hole  37 , the pressure-receiving plate  42  of the diaphragm  40  is pushed upward in a direction away from the valve seat  39 , that is, in the x direction. As a result, a clearance is created between the pressure receiving plate  42  and the sealing member  38 . The air chamber  44  is released to the atmospheric air, and in turn, the air flow passage that extends from the pressurizing pump  23  to the cartridge  13  is released to the atmospheric air.  
         [0045]     When the rotational shaft  59  rotates in the direction R 1 , as shown in  FIG. 5 , that is, in a counterclockwise direction as the drive lever  58  rotates, the engagement piece  60  shifts from a state in which its second side  60   b  is in contact with the engagement portion  50   a  into the state in which its third side  60   c  is brought into contact with the engagement portion  50   a . The distance between the rotational shaft  59  that acts as a center of rotation and the third side  60   c  that is in contact with the engagement portion  50   a  is reduced, and the switching member  50  is thereby depressed downward in the direction opposite to the x direction by the biasing force of the coil spring  52 . The biasing force of the coil spring  52  is set to be larger than the biasing force of the biasing spring  45 .  
         [0046]     The switching member  50 , depressed downward in the direction opposite to the x direction by the biasing force of the coil spring  52 , causes its contact portion  50   c  to press the diaphragm  40  against the sealing member  38 . As a result, the pressure-receiving plate  42  crushes the top end of the sealing member  38  so as to create a valve closed state in which the air communicating hole  37  is blocked. Thus, the air flow passage that extends from the pressurizing pump  23  to the cartridge  13  comes into an air-tight state without being released to the atmospheric air. The pressurized air supplied from the pressurizing pump  23  is conveyed into the inner space  17  of the cartridge  13  in a pressurized state.  
         [0047]     Next, operation of the pressurizing unit  20  will be described. When the main power supply of the printer  1  is in an off state, the pressure regulating valve  30  is open, as shown in  FIG. 5 . If the pressure regulating valve  30  is in a closed state when the power supply is off, the air filling the cartridge  13  may pressurize the ink pack  15  to cause the ink to leak out of an ink supply port (not shown) that is formed on the cartridge  13 , or out of the recording head  10 . Further, the pressurized air in the cartridge  13  may press the cartridge  13  against the cartridge holder  12  so as to make it difficult to remove the cartridge  13  from the cartridge holder  12 . To avoid these problems, even after the main power supply of the printer  1  has turned off, the supply of electric power to the power supply circuit is continued for a predetermined time period by use of a delay circuit or the like, and during this period, the drive motor  22  is rotated reversely. Reverse rotation of the drive motor  22  causes the pressure regulating valve  30  to open by means of the transmission mechanism  25 .  
         [0048]     When the main power supply of the printer  1  is turned on and printing is started, the drive motor  22  rotates normally. The rotational force of the drive motor  22  is transmitted to the cam mechanism  55  by means of the transmission mechanism  25  to drive the drive lever  58  of the cam mechanism  55  to rotate normally. As the drive lever  58  rotates normally, the rotational shaft  59  rotates in the direction of R 1 , in other words, in the counterclockwise direction illustrated in  FIG. 5 . As a result, the engagement piece  60  moves out of a state where its second side  60   b , which is separated a long distance away from the center of rotation, is in contact with the lower surface of the engagement portion  50   a , into a state illustrated in  FIG. 6  where its third side  60   c , which is separated by a relatively short distance from the center of rotation, is brought into contact with the lower surface of the engagement portion  50   a . As a result, the switching member  50  shifts from a state where it is pushed upward by the engagement piece  60  into the state where, by virtue of the biasing force of the coil spring  52 , it approaches the diaphragm  40 , in other words, it is depressed downward in the direction opposite to the x direction. At the same time, as shown in  FIG. 6 , the contact portion  50   c  of the switching member  50  pushes the diaphragm  40  against the sealing member  38 , and in consequence, the pressure-receiving plate  42  is pressed against the sealing member  38  so as to make contact with the sealing member  38  in the face of the biasing force of the biasing spring  45  disposed in the air communicating hole  37 , as shown in  FIG. 7 . As a result, the air communicating hole  37  is blocked, and in consequence, the pressure regulating valve  30  is closed.  
         [0049]     As described above, the drive lever  58  is configured to rotate only at a predetermined angle by, for example, means of a restricting member provided on the transmission mechanism. Thus, even if the drive motor  22  further rotates normally, further rotational force to be transmitted to the pressure regulating valve  30  is prevented.  
         [0050]     As the drive motor  22  further rotates normally, the pressurizing pump  23  conveys the pressurized air toward the cartridge. The air supplied from the pressurizing pump  23  is sent to the pressure sensor  24  through the air flow passage. The pressure sensor  24  detects the air pressure in the passage between the pressurizing pump  23  and the cartridge  13 . If the pressure detected exceeds a predetermined upper limit value P 1 , the pressure sensor  24  outputs the detection signal of the upper limit value P 1  to a non-illustrated control circuit that is provided in the printer  1 .  
         [0051]     The pressurized air supplied from the pressure sensor  24  flows through the air introducing hole  34  of the pressure regulating valve  30  into the air chamber  44 . If the air pressure in the air chamber  44  is at a predetermined value or lower, the air in the air chamber  44  is discharged through the air discharging hole  35  and sent to the cartridge  13  by way of the air passage. The pressurized air charged into the inner space  17  of the cartridge  13  crushes the ink pack  15 , and the ink in the ink pack  15  is in turn pushed into the ink supply passage  16 . The ink supplied to the ink supply passage  16  is then supplied to the recording head  10 , from which ink is ejected toward paper by driving a piezoelectric element (not shown).  
         [0052]     During time periods when the pressurized air is supplied from the pressurizing pump  23 , or the pressurized air supplied from the pressurizing pump  23  is stopped, the control circuit described above controls the pressurizing unit  20  based on the pressure detected by the pressure sensor  24 , in such a manner that the pressure of the air supplied to the cartridge  13  falls within an appropriate range that conforms with the state of the printer  1 .  
         [0053]     Specifically, when the pressure sensor  24  detects that the pressure exceeds the upper limit value P 1 , the pressure sensor  24  terminates rotation of the drive motor  22  to stop the pressurizing pump  23  and to prevent further application of pressure onto the interior of the cartridge  13 . The pressure regulating valve  30  is held in a closed state. Further, when the pressure sensor  24  detects that the pressure is below the lower limit value P 2  while the pressurizing pump  23  is stopped, the control circuit controls the drive motor  22  so as to rotate normally, and thus drive the pressurizing pump  23  to supply air in a pressurized state.  
         [0054]     The pressure regulating valve  30  also serves as an air release valve which, even when the pressure sensor  24  or the control circuit breaks down or makes an erroneous detection while the pressurizing pump  23  is supplying pressurized air, prevents excessive pressure from occurring in the air flow passage that extends from the pressurizing pump  23  to the cartridge  13 . As described above, the film  41  is provided so as to be displaceable both in a direction moving away from the valve seat  39 , or the x direction, and in a direction approaching toward the valve seat  39 , or the direction opposite to the x direction. Thus, if the pressure inside the air chamber  44  of the pressure regulating valve  30  exceeds the threshold value Pa that serves as a predetermined value, the sum of the pressing force resulting from the pressurized air from the air chamber  44  and the biasing force of the biasing spring  45  that is disposed in the air communicating hole  37  exceeds the biasing force applied by the coil spring  52 . As a result, as shown in  FIG. 8 , the film  41  is displaced in the x direction and a clearance S, which is expanded by the biasing spring  45 , is formed between the pressure receiving plate  42  and the sealing member  38  (an atmospheric air release state).  
         [0055]     The biasing force and the length of the biasing spring  45  are set to such values that enable the clearance S between the pressure-receiving plate  42  and the sealing member  38  to be a size that does not cause vibration or unusual sounds. As a result, when the air passes through the clearance S, the air in the air chamber  44  flows through the air communicating hole  37  without making the film  41  or the pressure receiving plate  42  vibrate and without generating turbulence of the kind that causes unusual sounds, and then, the pressure within the air chamber  44  and the air flow passage is decreased to the level of atmospheric pressure. Thus, any breakages of the cartridge  13  and the air supply passage  21  can be prevented.  
         [0056]     When the pressure regulating valve  30  is closed, the printer  1  terminates printing and the power supply is turned off, the supply of electric power to the power supply circuit may be maintained by use of a device such as a delay circuit. While this state is maintained, the drive motor  22  is rotated in a reverse direction. As described above, the drive lever  58  of the cam mechanism  55  then rotates in a reverse direction so as to bring the second side  60   b  of the engagement piece  60  into contact with the switching member  50  as shown in  FIG. 5 . Thus, the switching member  50  is pushed upward in a direction moving away from the sealing member  38  and, by virtue of the biasing force applied by the spring force  45 , the diaphragm  40  is brought into an valve opening state.  
         [0057]     The embodiment described above has the following advantages.  
         [0058]     The pressure regulating valve  30  includes a diaphragm  40  that is comprised of the film  41  and the pressure receiving plate  42  and an air chamber  44  that is comprised of a first housing  33  and a diaphragm  40 . Further, the pressure regulating valve  30  also includes a biasing spring  45  in the air communicating hole  37  of the communicating portion  36 . The biasing force of the biasing spring  45  is suppressed to a level where the clearance S that is formed between the pressure receiving plate  42  and the sealing member  38  when the valve is opened does not cause vibration or unusual sounds as a result of air flowing through the air communicating hole  37  to occur. Thus, even when the film  41  is used for the diaphragm  40 , occurrence of vibration or unusual sounds caused by the air flow in the valve opened state can be prevented. Further, since the diaphragm  40  is made of the film  41 , costs can be reduced more than a case where a rubber molded article is used.  
         [0059]     The biasing spring  45  is housed in the air communicating hole  37 . Thus, space can be reduced to a greater extent than in a case where the biasing spring  45  is disposed around the communicating portion  36 .  
         [0060]     The pressure regulating valve  30  includes a switching member  50  that forces the diaphragm  40  to displace to a position where it is in contact with the sealing member  38 , and a cam mechanism  55  for driving the switching member  50 . Thus, the pressure regulating valve can also serve as a regulator for adjusting pressure inside the air flow passage.  
         [0061]     A drive motor  22  is provided which serves as both the driving source for the pressurizing pump  23  and the driving source for forcing the pressure regulating valve  30  to selectively open and close. Thus, the driving source of the pressurizing pump  23  can be effectively utilized and there is no need for a plurality of pumps for generating pressurized air.  
         [0062]     The pressure regulating valve  30  is mounted in the printer  1 . This structure is especially effective in that the vibration and unusual sounds can be suppressed in the printer  1  for which quietness there is required.  
         [0063]     The embodiment as described above may be varied as follows.  
         [0064]     The pressurizing unit  20  may further include a pressure detection device for detecting a pressure value. When a pressure value outputted from the pressure detection device exceeds a permitted air pressure, the control circuit may control the drive motor  22  so to rotate in a reverse direction and open the pressure regulating valve  30  to protect the cartridge  13 , the air supply passage  21 , or other parts from breakage. In such circumstances, the control circuit controls the drive motor  22  so as to rotate in a reverse direction. When the drive motor  22  rotates in a reverse direction, the drive lever  58  rotates in an opposite direction by means of the transmission mechanism  25 . In response to this, the rotational shaft  59  rotates in the direction R 2  in  FIG. 6  (in the clockwise direction in  FIG. 6 ) so as to cause the engagement piece  60  to move away from a state in which its third side  60   c  is in contact with the engagement portion  50   a  to a state in which its second side  60   b  is in contact with the engagement portion  50   a , as shown in  FIG. 5 . The engagement piece  60  pushes the switching member  50  upward against the biasing force of the coil spring  52 . Accordingly, the switching member  50  moves in an upward direction moving away from the sealing member  38  so as to bring the diaphragm  40  into a state in which it is separated from the sealing member  38 . Accordingly, by effectively utilizing the pressure regulating valve  30 , pressure inside the air flow passage can be controlled with greater precision.  
         [0065]     Instead of providing the drive motor  22 , the pressurizing pump  23 , the pressure sensor  24 , and the pressure regulating valve  30  in the pressurizing unit  20  integrally by the first and second covers  31 ,  32 , they may be separately provided.  
         [0066]     The engagement piece  60  may also assume any shape other than the shapes described above, such as a rectangular shape and a hexagonal shape.  
         [0067]     The sealing member  38  may be omitted.  
         [0068]     Instead of in the air communicating hole  37 , the biasing spring  45  may be provided, at other positions such as in the space between the bottom surface of the first housing  33  and the film  41 , or on the outside of the communicating portion  36 .  
         [0069]     The biasing spring  45  may be any other spring such as a stretching spring. Alternatively, the biasing member may be any other elastic member, other than a spring, such as a rubber member.  
         [0070]     The coil spring  52  may be provided so as to bias the switching member  50  toward the valve opening position. For example, the coil spring  52  may be interposed between the second housing  47  and the engagement portion  50   a  of the switching member  50 . Further, the cam mechanism  55  may be any other mechanism than the cam, as long as it is a mechanism that is capable of moving the switching member  50  to a valve closing position against the biasing force of the coil spring  52 .  
         [0071]     The switching member  50  for selectively opening and closing the diaphragm  40  may also be a plunger that is driven by the passage or breakage of electric current to the solenoid. This eliminates the cam mechanism  55  and control of the valve-opening operation and the valve closing operation is facilitated.  
         [0072]     The fluid that is sent from the pressurizing pump  23  to the cartridge  13  may be liquid.  
         [0073]     The printer  1  may also be any printer other than an ink-jet printer, such as a heat transfer printer.  
         [0074]     The pressure regulating valve  30  may be mounted in devices other than the printer  1  and the liquid ejection device.  
         [0075]     The liquid ejection device is not limited to the printer  1 . Alternatively, the liquid ejection device may be a device for manufacturing a color filter such as a liquid crystal display, a device for forming an electrode such as an organic EL display and a flat emitting display (FED), a jet device for jetting biological organic substances for manufacturing bio-chips, and a device for manufacturing precise pipettes.  
         [0076]     The present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.