Patent Publication Number: US-11047503-B2

Title: Actuator, valve device, and fluid supply system

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a bypass continuation application of International Application No. PCT/JP2018/023882, filed Jun. 22, 2018, which claims priority to Japanese Patent Application No. 2017-131484, filed Jul. 4, 2017. The contents of these applications are incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to an actuator, a valve device and a fluid supply system. 
     BACKGROUND 
     Conventionally, it has been required to open/close, at a constant speed, a valve device to be opened/closed using a driving fluid (see, e.g., Japanese Patent Application Publication No. 2015-068438). In the valve device disclosed in Japanese Patent Application Publication No. 2015-068438, two needle valves and two check valves are provided in an air drive portion to reduce fluctuations in an operating speed of an actuator and reduce fluctuations in a speed of opening/closing the valve device. 
     SUMMARY 
     However, since the valve device disclosed in Japanese Patent Application Publication No. 2015-068438 has the two needle valves and the two check valves in the air drive portion, a configuration of an entire system thereof is complicated. 
     It is therefore an object of the present disclosure to provide an actuator, a valve device, and a fluid supply system which can reduce fluctuations in operating speed using a simple configuration. 
     An actuator in accordance with one or more embodiments includes: a casing; a pressure reducing valve provided in the casing to reduce a pressure of a driving fluid supplied from an outside of the casing to a predetermined level; and a piston provided in the casing to form a pressure chamber together with the casing and driven by the driving fluid that has been pressure-reduced to the predetermined level. 
     A valve device in accordance with one or more embodiments includes: a body in which a fluid passage is formed; a valve body which opens and closes the fluid passage; a stem which moves closer to and away from the body to cause the valve body to open and close the fluid passage; a casing; a pressure reducing valve provided in the casing to reduce a pressure of a driving fluid supplied from an outside of the casing to a predetermined level; and a drive portion provided in the casing to drive the stem using the driving fluid that has been pressure-reduced to the predetermined level resulting from the pressure reduction by the pressure reducing valve. 
     A fluid supply system in accordance with one or more embodiments includes a supply source which supplies a driving fluid; a valve device to be driven using the driving fluid supplied from the supply source, the valve device including a body in which a fluid passage is formed, a valve body which opens and closes the fluid passage, a stem which moves closer to and away from the body to cause the valve body to open and close the fluid passage, and an actuator having therein a pressure reducing valve which reduces a pressure of the driving fluid to a predetermined level and a drive portion which drives the stem using the driving fluid that has been pressure-reduced to the predetermined level; and a switching member which switches between a flow of the driving fluid supplied from the supply source to the valve device and a flow of the driving fluid discharged from the drive portion of the valve device to an outside thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a front view of a valve device according to an embodiment; 
         FIG. 2  is a top view of the valve device according to the present embodiment; 
         FIG. 3  is a cross-sectional view of the valve device illustrated in  FIG. 2  along a line III-III; 
         FIG. 4  is a cross-sectional view in which the vicinity of a partition disc is illustrated in enlarged relation; 
         FIG. 5  is a cross-sectional view of the valve device illustrated in  FIG. 1  along a line V-V; 
         FIG. 6  is a configuration diagram of a fluid supply system according to the present embodiment; 
         FIG. 7A - FIG. 7D  is illustrative view of an operation of a pressure reducing valve device during opening/closing of the valve device; 
         FIG. 8  illustrates a semiconductor production apparatus including the valve device and the fluid supply system each according to the present embodiment; 
         FIG. 9  is a view illustrating a mode in which a check valve is added to an intermediate casing; and 
         FIG. 10  is a view illustrating a state where a poppet plug, a spring retainer, and a check valve are fixed to the intermediate casing using setscrews. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings, a description will be given of a valve device according to an embodiment of the present disclosure. 
       FIG. 1  is a front view of a valve device  1  according to the present embodiment.  FIG. 2  is a top view of the valve device  1  according to the present embodiment.  FIG. 3  is a cross-sectional view of the valve device  1  illustrated in  FIG. 2  along a line  FIG. 4  is a cross-sectional view in which the vicinity of a partition disc  22  is illustrated in enlarged relation.  FIG. 5  is a cross-sectional view of the valve device  1  illustrated in  FIG. 1  along a line V-V. Note that the valve device  1  according to the present embodiment is a diaphragm valve. 
     As illustrated in  FIG. 1 , the valve device  1  includes a body  10  and an actuator  20 . Note that the following description will be given on the assumption that an actuator  20  side of the valve device  1  is an upper side, while a body  10  side of the valve device  1  is a lower side. 
     [Body  10 ] 
     As illustrated in  FIG. 3 , the body  10  includes a body main body  11 , a sheet  12 , a bonnet  13 , a retaining ring  14 , a diaphragm  15 , a retaining adapter  16 , and a diaphragm retainer  17 . 
     In the body main body  11 , a valve chamber  11   a , and a fluid inflow path  11   b  and a fluid outflow path  11   c  each communicating with the valve chamber  11   a  are formed. The sheet  12  has an annular shape and is provided around a peripheral edge of a portion in which the valve chamber  11   a  and the fluid inflow path  11   b  communicate with each other. 
     The bonnet  13  has a generally cylindrical shape and has an external thread portion provided around an outer periphery of a lower end portion thereof screwed into an internal thread portion provided in the body main body  11  to be fixed to the body main body  11  so as to cover the valve chamber  11   a . The retaining ring  14  is attached to an outer periphery of an upper end portion of the bonnet  13  so as to fix the actuator  20  to the body  10 . 
     In the upper end portion of the bonnet  13 , a recessed portion  13   a  is formed and, in the recessed portion  13   a , a first O-ring  13 B having a circular cross section is provided. The first O-ring  13 B guides vertical movement (movement to be closer to and away from the diaphragm  15 ) of a stem  26 , and prevents the driving fluid from leaking from a first pressure chamber S 1  described later to an outside thereof. 
     The diaphragm  15  as a valve body has an outer peripheral edge portion thereof pressed and held between the retaining adapter  16  disposed at a lower end of the bonnet  13  and a bottom surface of the body main body  11  forming the valve chamber  11   a . The diaphragm  15  is in the form of a spherical shell and has an upwardly protruding arc shape in a natural state. The diaphragm  15  moves away from and comes into contact with the sheet  12  to open/close a fluid passage. For example, the diaphragm  15  is formed of a metal thin plate cut out into a circular shape which is then formed into the spherical shell shape having an upwardly protruding center portion. 
     The diaphragm retainer  17  is provided over the diaphragm  15  and configured to be able to press the center portion of the diaphragm  15 . 
     [Actuator  20 ] 
     The actuator  20  has a generally cylindrical overall shape, and is configured to include a lower casing  21 , the partition disc  22 , a support disc  23 , an intermediate casing  24 , an upper casing  25 , the stem  26 , compression coil springs  27 , second to sixth O-rings  28 A to  28 E each having a circular cross section, four bolts  29  (see  FIG. 2 ), a drive portion  30 , a pressure reducing valve  40 , and a lift amount adjustment mechanism  50 . Note that the lower casing  21 , the partition disc  22 , the support disc  23 , the intermediate casing  24 , and the upper casing  25  form a casing of the actuator  20 . 
     The lower casing  21  has a generally cylindrical shape and is formed with a bonnet through hole  21   a  through which the bonnet  13  extends and a drive portion containing hole  21   b  in which the drive portion  30  is contained. 
     Through the bonnet through hole  21   a , an upper portion of the bonnet  13  extends, and an upper end of the bonnet  13  is fixed by the retaining ring  14  to the lower casing  21 . In an inner peripheral surface  21 C in which the drive portion containing hole  21   b  is formed, a first stepped portion  21 D and a second stepped portion  21 E are formed. In addition, between the lower casing  21  and the bonnet  13 , the second O-ring  28 A is interposed to prevent the driving fluid from leaking from the first pressure chamber S 1  described later to the outside thereof and prevent dust or the like from entering the actuator  20  from an outside thereof. 
     The partition disc  22  is provided in the lower casing  21  and has a first disc portion  22 A, an upwardly protruding portion  22 B, and a first downwardly protruding portion  22 C. The first disc portion  22 A has a generally disc shape having, at a center thereof, a first stem through hole  22   d  formed therein to allow the stem  26  to extend therethrough, while having, in an inner periphery and an outer periphery thereof, first and second O-ring containing grooves  22   e  and  22   f  formed to extend around the inner and outer peripheries and have annular shapes. In the first and second O-ring containing grooves  22   e  and  22   f , the third and fourth O-rings  28 B and  28 C are contained. The third O-ring  28 B guides the vertical movement of the stem  26  to prevent the driving fluid from leaking out of a second pressure chamber S 2  described later. 
     The upwardly protruding portion  22 B has an annular shape and protrudes upward from an outer peripheral edge of an upper surface of the first disc portion  22 A. The first downwardly protruding portion  22 C has an annular shape and protrudes downward from an outer peripheral edge of a lower surface of the first disc portion  22 A. The first downwardly protruding portion  22 C has a lower end thereof in contact with the second stepped portion  21 E of the lower casing  21 , and the first downwardly protruding portion  22 C and the first stepped portion  21 D of the lower casing  21  form an annular first outer peripheral portion containing groove  22   g . The first outer peripheral portion containing groove  22   g  corresponds to a first annular groove formed in an inner periphery of the casing. 
     The support disc  23  is located over the partition disc  22 , and has an external thread portion provided in an outer periphery thereof screwed into an internal thread portion provided in an inner periphery of an upper end portion of the lower casing  21  to be fixed to the lower casing  21  so as to close the drive portion containing hole  21   b.    
     The support disc  23  has a second disc portion  23 A, a second downwardly protruding portion  23 B, and a third downwardly protruding portion  23 C. The second disc portion  23 A has a generally disc shape having, at a center thereof, a second stem through hole  23   d  formed therein to allow the stem  26  to extend therethrough. In the second disc portion  23 A, fourth bolt screwing holes  23   e  (of which only two are illustrated in  FIG. 4 ) are further formed. 
     The second downwardly protruding portion  23 B has an annular shape and protrudes downward from an outer peripheral edge of a lower surface of the second disc portion  23 A. The third downwardly protruding portion  23 C has an annular shape and protrudes downward from an outer peripheral edge of a lower surface of the second downwardly protruding portion  23 B. The third downwardly protruding portion  23 C is configured to have a radial thickness smaller than a radial thickness of the second downwardly protruding portion  23 B. Due to the thickness difference therebetween, a third stepped portion  23 F is formed. 
     The third downwardly protruding portion  23 C has a lower end thereof in contact with the upwardly protruding portion  22 B of the partition disc  22 , and the third stepped portion  23 F and the upwardly protruding portion  22 B form an annular second outer peripheral portion containing groove  23   g . Note that first stepped portion  21 D, the second stepped portion  21 E, the upwardly protruding portion  22 B and the first downwardly protruding portion  22 C of the partition disc  22 , and the second downwardly protruding portion  23 B and the third downwardly protruding portion  23 C of the support disc  23  form an inner peripheral portion of the casing. The second outer peripheral portion containing groove  23   g  corresponds to a first annular groove formed in the inner peripheral portion of the casing. 
     As illustrated in  FIG. 3 , the intermediate casing  24  has a generally cylindrical shape, and is provided over the lower casing  21  and the support disc  23 . The intermediate casing  24  has, at a center thereof, a third stem through hole  24   a  formed to extend therethrough along a vertical direction. In an inner periphery of the intermediate casing  24 , third and fourth O-ring containing grooves  24   b  and  24   c  are formed to extend around the inner periphery and have annular shapes. In the third and fourth O-ring containing grooves  24   b  and  24   c , fifth and sixth O-rings  28 D and  28 E are contained. The fifth and sixth O-rings  28 D and  28 E guide the vertical movement of the stem  26  to prevent the driving fluid from leaking to an outside of the actuator  20 . 
     Also, as illustrated in  FIG. 5 , the intermediate casing  24  has generally cylindrical first and second insertion holes  24   e  and  24   f  formed to inwardly extend from an out peripheral surface  24 D thereof. The first and second insertion holes  24   e  and  24   f  are coaxially formed to communicate with each other. The first insertion hole  24   e  also communicate with the third stem through hole  24   a . The intermediate casing  24  also has a driving fluid passage hole  24   g  (see also  FIG. 3 ) formed therein. The driving fluid passage hole  24   g  extends from an upper surface of the intermediate casing  24  to the second insertion hole  24   f  The intermediate casing  24  also has four bolt insertion holes  24   h  formed therein. 
     As illustrated in  FIG. 3 , the upper casing  25  has a generally cylindrical shape, and is provided over the intermediate casing  24 . The upper casing  25  is provided with a protruding portion  25 F having, at a center thereof, an adjustment mechanism attachment hole  25   a  formed to extend therethrough along the vertical direction. The adjustment mechanism attachment hole  25   a  has a bolt screwing hole  25   b  and a top insertion hole  25   c  having a hexagonal transverse section. 
     The upper casing  25  also has a driving fluid inlet port  25   d  and four bolt insertion holes  25   e  (of which only two are shown) each formed therein. The driving fluid inlet port  25   d  is formed at a position located above the second insertion hole  24   f  of the intermediate casing  24  to have an upper end portion thereof connected to a pipe joint not shown and a lower end portion thereof communicating with the driving fluid passage hole  24   g.    
     The stem  26  has a generally cylindrical shape and is provided to be movable in the vertical direction and extend from the diaphragm retainer  17  to the upper casing  25  through the bonnet  13 , the lower casing  21 , and the intermediate casing  24 . Depending on an adjusted amount of the lift amount, an upper end of the stem  26  is caused to enter or exit the top insertion hole  25   c  by vertical movement of the stem  26 . The stem  26  has a driving fluid inflow path  26   a  formed in an upper half portion thereof to extend in the vertical direction, and further has first to third driving fluid outlet ports  26   b  to  26   d  each formed to traverse the driving fluid inflow path  26   a.    
     The driving fluid inflow path  26   a  has an upper end thereof closed by a ball  26 E. The first driving fluid outlet port  26   b  communicates with the first insertion hole  24   e . The second driving fluid outlet port  26   c  is located below the first driving fluid outlet port  26   b  to communicate with the second pressure chamber S 2  described later. The third driving fluid outlet port  26   d  is located below the second driving fluid outlet port  26   c  to communicate with the first pressure chamber S 1  described later. 
     In the bonnet  13 , the compression coil springs  27  are provided around an outer periphery of a lower half portion of the stem  26  to constantly bias the stem  26  in a downward direction. 
     The individual bolts  29  are inserted into the bolt insertion holes  25   e  of the upper casing  25  and into the bolt insertion holes  24   h  of the intermediate casing  24  to be screwed into the bolt screwing holes  23   e  of the support disc  23  and thus integrate together the lower casing  21 , the intermediate casing  24 , and the upper casing  25 . 
     [Drive Portion  30 ] 
     The drive portion  30  includes a first piston  31 , a seventh O-ring  32 , a first seal member  33 , a second piston  34 , an eighth O-ring  35 , a second seal member  36 , and retaining rings  37  and  38 . 
     The first piston  31  has a generally disc shape having, at a center thereof, a fourth stem through hole  31   a  formed therein to allow the stem  26  to extend therethrough. In an inner periphery of the first piston  31 , a fifth O-ring containing groove  31   b  is formed to continuously extend around the inner periphery and have an annular shape while, in an outer periphery of the first piston  31 , a first inner peripheral portion containing groove  31   c  is formed. The first inner peripheral portion containing groove  31   c  corresponds to a second annular groove formed in an outer peripheral portion of a piston. 
     The seventh O-ring  32  having a circular cross section is contained in the fifth O-ring containing groove  31   b  to prevent the driving fluid from leaking out of the first pressure chamber S 1  described later. 
     The first seal member  33  is an annular member made of a resin, and includes a first inner peripheral portion  33 A, a first outer peripheral portion  33 B, and a first intermediate portion  33 C. The first inner peripheral portion  33 A has a generally ellipsoidal cross section and is fitted in the first inner peripheral portion containing groove  31   c . The first inner peripheral portion  33 A corresponds to a first fitting portion. The first outer peripheral portion  33 B has a generally ellipsoidal cross section and is fitted in the first outer peripheral portion containing groove  22   g . The first outer peripheral portion  33 B corresponds to a second fitting portion. 
     The first intermediate portion  33 C is located between the first inner peripheral portion  33 A and the first outer peripheral portion  33 B and configured to have a thickness smaller than that of each of the first inner peripheral portion  33 A and the first outer peripheral portion  33 B to connect a vertical middle portion of the first inner peripheral portion  33 A and a vertical middle portion of the first outer peripheral portion  33 B. A maximum distance along an axial direction of the first seal member  33  over which the first inner peripheral portion  33 A can move relative to the first outer peripheral portion  33 B is limited to a predetermined distance which is not more than half a thickness of the first seal member  33 . 
     The first piston  31 , the lower casing  21 , and the bonnet  13  form the first pressure chamber S 1 . The first pressure chamber S 1  is sealed by the first O-ring  13 B, the second O-ring  28 A, the seventh O-ring  32 , and the first seal member  33 . The first pressure chamber S 1  communicates with each of the driving fluid inflow path  26   a  and the third driving fluid outlet port  26   d  which are formed in the stem  26 . 
     The first piston  31  has an upper surface thereof provided with the retaining ring  37  which is attached to the stem  26 . Consequently, when the first piston  31  moves upward, the stem  26  moves upward together with the retaining ring  37 . 
     The second piston  34  has a generally disc shape having, at a center thereof, a fifth stem through hole  34   a  formed therein to allow the stem  26  to extend therethrough. In an inner periphery of the second piston  34 , a sixth O-ring containing groove  34   b  is formed to continuously extend around the inner periphery and have an annular shape while, in an outer periphery of the second piston  34 , a second inner peripheral portion containing groove  34   c  is formed. The second inner peripheral portion containing groove  34   c  corresponds to a second annular groove formed in an outer peripheral portion of the piston. 
     The eighth O-ring  35  having a circular cross section is contained in the sixth O-ring containing groove  34   b  to prevent the driving fluid from leaking out of the second pressure chamber S 2  described later. 
     The second seal member  36  is an O-ring made of a resin, and includes a second inner peripheral portion  36 A, a second outer peripheral portion  36 B, and a second intermediate portion  36 C. The second inner peripheral portion  36 A has a generally ellipsoidal cross section and is fitted in the second inner peripheral portion containing groove  34   c . The second inner peripheral portion  36 A corresponds to the first fitting portion. The second outer peripheral portion  36 B has a generally ellipsoidal cross section and is fitted in the second outer peripheral portion containing groove  23   g . The second outer peripheral portion  36 B corresponds to the second fitting portion. 
     The second intermediate portion  36 C is located between the second inner peripheral portion  36 A and the second outer peripheral portion  36 B and configured to have a thickness smaller than that of each of the second inner peripheral portion  36 A and the second outer peripheral portion  36 B to connect a vertical middle portion of the second inner peripheral portion  36 A and a vertical middle portion of the second outer peripheral portion  36 B. A maximum distance along an axial direction of the second seal member  36  over which the second inner peripheral portion  36 A can move relative to the second outer peripheral portion  36 B is limited to a predetermined distance which is not more than half a thickness of the second seal member  36 . 
     The second piston  34  and the partition disc  22  form the second pressure chamber S 2 . The second pressure chamber S 2  is sealed by the third O-ring  28 B, the eighth O-ring  35 , and the second seal member  36 . The second pressure chamber S 2  communicates with each of the driving fluid inflow path  26   a  and the second driving fluid outlet port  26   c  which are formed in the stem  26 . 
     The second piston  34  has an upper surface thereof provided with the retaining ring  38  which is attached to the stem  26 . Consequently, when the second piston  34  moves upward, the stem  26  moves upward together with the retaining ring  38 . 
     [Pressure Reducing Valve  40 ] 
     The pressure reducing valve  40  is provided in the intermediate casing  24  and includes a poppet portion  41  and a pressure reducing portion  42 . 
     The poppet portion  41  is provided in the second insertion hole  24   f , and includes a poppet plug  43 , a poppet  44 , and a poppet spring  45 . The poppet plug  43  is fitted into the second insertion hole  24   f  and fixed to the intermediate casing  24 , and has a first poppet O-ring  43 A. The first poppet O-ring  43 A prevents the driving fluid in an inflow chamber R 1  described later from leaking to an outside thereof. A space in the second insertion hole  24   f  which is inner than the poppet plug  43  forms the inflow chamber R 1  into which the driving fluid flows. The inflow chamber R 1  communicates with the driving fluid passage hole  24   g.    
     The poppet  44  has a poppet main body  44 A and a rod  44 B. The poppet main body  44 A is located in the inflow chamber R 1 , and has a second poppet O-ring  44 C. The second poppet O-ring  44 C is configured to move away from and come into contact with a peripheral edge portion  241  of a portion of the intermediate casing  24  in which the first insertion hole  24   e  and the second insertion hole  24   f  communicate with each other to provide or cut off communication between the inflow chamber R 1  and a decompression chamber R 2  described later. 
     The rod  44 B extends from an end portion of the poppet main body  44 A closer to the first insertion hole  24   e  toward the first insertion hole  24   e  to be located in the decompression chamber R 2  described later. The poppet spring  45  is provided between the poppet plug  43  and the poppet  44  to bias the poppet  44  toward the pressure reducing portion  42 . 
     The pressure reducing portion  42  is provided in the first insertion hole  24   e , and includes a spring retainer  46 , a pressure reducing piston  47 , and a pressure reducing spring  48 . 
     The spring retainer  46  is pressed or screwed in the first insertion hole  24   e  to be fixed to the intermediate casing  24 . The pressure reducing piston  47  is provided to be movable in a space in the first insertion hole  24   e  which is inner than the spring retainer  46 , and has a piston O-ring  47 A. A space in the first insertion hole  24   e  which is inner than the pressure reducing piston  47  forms the decompression chamber R 2  into which the driving fluid flows. The decompression chamber R 2  communicates with each of the first driving fluid outlet port  26   b  and the driving fluid inflow path  26   a  via the third stem through hole  24   a . The piston O-ring  47 A prevents the driving fluid in the decompression chamber R 2  from leaking to an outside thereof. 
     The rod  44 B has a leading end thereof in contact with the pressure reducing piston  47 . The pressure reducing spring  48  is provided between the spring retainer  46  and the pressure reducing piston  47  to bias the pressure reducing piston  47  toward the poppet portion  41 . The poppet spring  45  and the pressure reducing spring  48  have respective biasing forces which are set such that, in a state where the driving fluid has not flown into either the inflow chamber R 1  or the decompression chamber R 2  or where a pressure increase in the decompression chamber R 2  due to inflow of the driving fluid is not sufficient, the second poppet O-ring  44 C of the poppet main body  44 A moves away from the peripheral edge portion  241  to provide communication between the inflow chamber R 1  and the decompression chamber R 2 . 
     [Lift Amount Adjustment Mechanism  50 ] 
     As illustrated in  FIG. 3 , the lift amount adjustment mechanism  50  includes a locknut  51 , an adjustment screw  52 , and an adjustment top  53 . 
     The locknut  51  is attached to an upper end of the protruding portion  25 F of the upper casing  25 . The adjustment screw  52  has different pitches in an upper portion  52 A and a lower portion  52 B. The lower portion  52 B is configured to have the pitch lower than that of the upper portion  52 A. The upper portion  52 A of the adjustment screw  52  is screwed into the bolt screwing hole  25   b . The adjustment top  53  has a hexagonal transverse section, has a screwing recessed portion  53   a  formed therein, and is inserted into the top insertion hole  25   c  to be vertically movable therein. Into the screwing recessed portion  53   a , the lower portion  52 B of the adjustment screw  52  is screwed. 
     By rotating the adjustment screw  52 , the adjustment top  53  is vertically moved. This adjusts a distance over which the stem  26  vertically moves and adjusts a lift amount of the diaphragm  15 . Note that a state where an upper end of the stem  26  is in contact with a lower end of the adjustment top  53  corresponds to a state where the stem  26  is located at an upper dead point. 
     [Fluid Supply System  2 ] 
     Next, referring to  FIG. 6 , a description will be given of a fluid supply system  2  according to the present embodiment. 
       FIG. 6  is a configuration diagram of the fluid supply system  2 . 
     As illustrated in  FIG. 6 , the fluid supply system  2  includes an accumulator  3 , a three-way valve  4  as an electromagnetic valve, and the valve device  1  described above. The accumulator  3  is a supply source which supplies the driving fluid which is, e.g., operating air. The three-way valve  4  is switching unit which switches between a flow of the driving fluid supplied from the accumulator  3  to the valve device  1  and a flow of the driving fluid discharged from the drive portion  30  (first and second pressure chambers S 1  and S 2 ) of the valve device  1  to an outside thereof 
     [Opening/Closing Operation of Valve  1 ] 
     Next, referring to  FIG. 3 ,  FIG. 4 ,  FIG. 6 , and  FIG. 7A  to  FIG. 7D , a description will be given of an opening/closing operation of the valve device  1  in the fluid supply system  2  according to the present embodiment. As pressure conditions in the present embodiment, a pressure of the driving fluid to be supplied from the accumulator  3  to the valve device  1  is set to 0.5 MPa, while a pressure of the driving fluid to be supplied to the first and second pressure chambers S 1  and S 2  through the decompression chamber R 2  is set to 0.35 MPa. 
       FIG. 7A - FIG. 7D  is illustrative view of an operation of the pressure reducing valve  40  during opening/closing of the valve device  1 . In  FIG. 7A - FIG. 7D , the flows of the driving fluid are shown by hollow arrows. 
     As illustrated in  FIG. 3 , in the valve device  1  of the present embodiment, in the state where the driving fluid has not flown into the first and second pressure chambers S 1  and S 2 , the stem  26  under the biasing forces of the compression coil springs  27  is at a lower dead point (close to the body main body  11 ), while the diaphragm  15  is pressed by the diaphragm retainer  17 , and therefore the valve device  1  is in a closed state. In other words, in a normal state (state where the driving fluid is not supplied), the valve device  1  is in the closed state. 
     Then, the three-way valve  4  illustrated in  FIG. 6  is brought into a state where the driving fluid flows from the accumulator  3  to the valve device  1 . As a result, the driving fluid is supplied from the accumulator  3  to the valve device  1 . The driving fluid passes from the driving fluid inlet port  25   d  through the driving fluid passage hole  24   g  via an air tube and a pipe joint which are not shown to flow into the inflow chamber R 1 , as illustrated in  FIG. 7A . The pressure of the driving fluid flows flowing into the inflow chamber R 1  is 0.5 MPa. 
     Since the inflow chamber R 1  and the decompression chamber R 2  communicate with each other, as illustrated in  FIG. 7B , the driving fluid flows into the decompression chamber R 2  to increase a pressure in the decompression chamber R 2 . When the pressure in the decompression chamber R 2  increases, the pressure reducing piston  47  moves toward the spring retainer  46  against the biasing force of the pressure reducing spring  48 . Then, when the pressure in the decompression chamber R 2  reaches 0.35 MPa as a predetermined pressure (drive pressure), as illustrated in  FIG. 7C , the second poppet O-ring  44 C of the poppet  44  comes into contact with the peripheral edge portion  241  to cut off the communication between the inflow chamber R 1  and the decompression chamber R 2 . 
     Through the operation from the state illustrated in  FIG. 7A  to the state illustrated in  FIG. 7B , the driving fluid having the predetermined pressure flows from the decompression chamber R 2  into the first and second pressure chambers S 1  and S 2  via the first driving fluid outlet port  26   b , the driving fluid inflow path  26   a , the second driving fluid outlet port  26   c , and the third driving fluid outlet port  26   d . The fluid supply system  2  is configured such that the driving fluid at 0.5 MPa is supplied from the accumulator  3  into the inflow chamber R 1  to maintain the state of the pressure reducing valve  40  illustrated in  FIG. 7C . 
     When the driving fluid flows into the first and second pressure chambers S 1  and S 2 , the first and second pistons  31  and  34  rise against the biasing forces of the compression coil springs  27 . As a result, the stem  26  moves to the upper dead point (moves away from the body main body  11 ), the diaphragm retainer  17  is moved upward by each of a resilient force of the diaphragm  15  and the pressure of the fluid (gas), and the valve device  1  is brought into an open state. 
     As a result of the rising of the first piston  31 , in the first seal member  33 , the first inner peripheral portion  33 A rises with the first piston  31 , while the first outer peripheral portion  33 B does not rise, and the first intermediate portion  33 C is deformed with the rising of the first inner peripheral portion  33 A. Likewise, as a result of the rising of the second piston  34 , in the second seal member  36 , the second inner peripheral portion  36 A rises with the second piston  34 , while the second outer peripheral portion  36 B does not rise, and the second intermediate portion  36 C is deformed with the rising of the second inner peripheral portion  36 A. 
     To shift the valve device  1  from the opening state to the closed state, the three-way valve  4  is switched to the flow of the driving fluid discharged from the drive portion  30  (first and second pressure chambers S 1  and S 2 ) of the valve device  1  to the outside. This reduces the pressure in the inflow chamber R 1 , and as illustrated in  FIG. 7D , brings the second poppet O-ring  44 C of the poppet  44  away from the peripheral edge portion  241 , and provides communication between the inflow chamber R 1  and the decompression chamber R 2 . As a result, the driving fluid in the first and second pressure chambers S 1  and S 2  flows into each of the decompression chamber R 2  and the inflow chamber R 1  via the second driving fluid outlet port  26   c , the third driving fluid outlet port  26   d , the driving fluid inflow path  26   a , and the first driving fluid outlet port  26   b  to be discharged to the outside via the driving fluid passage hole  24   g  and the driving fluid inlet port  25   d.    
     As a result of lowering of the first piston  31  and the second piston  34 , the first inner peripheral portion  33 A of the first seal member  33  and the second inner peripheral portion  36 A of the second seal member  36  also lower to bring each of the first seal member  33  and the second seal member  36  into an original state. The stem  26  is returned by the biasing forces of the compression coil springs  27  to the lower dead point, and the diaphragm  15  is pressed by the diaphragm retainer  17  to bring the valve device  1  into the closed state. 
     [Semiconductor Production Apparatus  100 ] 
     Next, a description will be given of a semiconductor production apparatus  100  in which the valve device  1  and the fluid supply system  2  each described above are used. 
       FIG. 8  illustrates the semiconductor production apparatus  100  including the valve device  1  and the fluid supply system  2  each according to the present embodiment. 
     As illustrated in  FIG. 8 , the semiconductor production apparatus  100  is, e.g., a CVD device which includes the fluid supply system  2 , a gas supply portion  60 , a vacuum chamber  70 , and an exhaust portion  80  and forms a passivation film (oxide film) over a wafer. 
     The gas supply portion  60  includes a gas supply source  61  and a fluid control device  62 . The vacuum chamber  70  includes a mounting table  71  for mounting thereon a water  72  and an electrode  73  for forming a thin film over the wafer  72 . The vacuum chamber  70  is connected to a commercial power source  101 . The exhaust portion  80  includes an exhaust pipe  81 , an opening/closing valve  82 , and a dust collector  83 . 
     When a thin film is formed over the wafer  72 , by the opening/closing of the valve device  1  in the fluid supply system  2 , a supply of gas to the vacuum chamber  70  is controlled. When powder and granules generated as by-products when the thin film is formed over the wafer  72  are to be removed, the opening/closing valve  82  is brought into an open state, and the powder and granules are removed by the dust collector  83  via the exhaust pipe  81 . 
     As described above, the actuator  20  of the present embodiment includes the pressure reducing valve  40  which reduces the pressure of the driving fluid supplied from the outside to the predetermined level and the first and second pistons  31  and  34  provided in the casing to form the first and second pressure chambers S 1  and S 2  together with the casing and driven by the driving fluid that has been pressure-reduced to the predetermined level resulting from the pressure reduction by the pressure reducing valve  40 . 
     Even when the pressure of the driving fluid from the accumulator  3  varies, such a configuration allows the pressure reducing valve  40  to supply the driving fluid having the predetermined pressure into the first and second pressure chambers S 1  and S 2 . Thus, it is possible to maintain an operating speed of the actuator  20  constant using a simple configuration and reduce fluctuations in respective operations of the first and second pistons  31  and  34 . 
     By applying the actuator  20  to the valve device  1  and applying the valve device  1  to the fluid supply system  2  including the accumulator  3  which supplies the driving fluid and the three-way valve  4  which switches between the flows of the driving fluid, it is possible to maintain an opening/closing speed of the valve device  1  constant. Consequently, in the semiconductor production apparatus  100  including the valve device  1  or the fluid supply system  2 , it is possible to supply a predetermined amount of the gas to the vacuum chamber  70  and thus form a film having an intended film thickness over the wafer. 
     The actuator  20  according to the present embodiment also includes the casing having the first and second outer peripheral portion containing grooves  22   g  and  23   g  formed in the inner peripheral portion thereof, the first and second pistons  31  and  34  having the first and second inner peripheral portion containing grooves  31   c  and  34   c  formed in the outer peripheral portion thereof, forming the first and second pressure chambers S 1  and S 2  together with the casing, and driven by the driving fluid from the outside, and the annular first and second seal members  33  and  36  having the first and second inner peripheral portions  33 A and  36 A to be fitted into the first and second outer peripheral portion containing grooves  22   g  and  23   g , having the first and second outer peripheral portions  33 B and  36 B to be fitted into the first and second inner peripheral portion containing grooves  31   c  and  34   c , and sealing the first and second pressure chambers S 1  and S 2 . 
     In such a configuration, when the first and second pistons  31  and  34  move, only the first and second inner peripheral portions  33 A and  36 A of the first and second seal members  33  and  36  move together with the first and second pistons  31  and  34 . This can inhibit the first and second seal members  33  and  36  from slidably moving along an inner peripheral surface of the casing and prevent abrasion of the first and second seal members  33  and  36 . Consequently, even when the number of times the actuator  20  is used increases, the first and second pistons  31  and  34  are not abraded, and it is possible to reduce fluctuations in the operations of the first and second pistons  31  and  34 . 
     By also applying the actuator  20  to the valve device  1 , it is possible to maintain the opening/closing speed of the valve device  1  constant. As a result, in the semiconductor production apparatus  100  including the valve device  1 , it is possible to supply a predetermined amount of gas to the vacuum chamber  70  and thereby form a film having an intended film thickness over the wafer. 
     The maximum distance along the axial direction of each of the first and second seal members  33  and  36  over which each of the first and second inner peripheral portions  33 A and  36 A can move relative to each of the first and second outer peripheral portions  33 B and  36 B is limited to a predetermined distance not more than half the thickness of each of the first and second seal members  33  and  36 . This can inhibit the first and second seal members  33  and  36  from slidably moving along the inner peripheral surface of the casing and prevent abrasion of the first and second seal members  33  and  36 . 
     The first and second seal members  33  and  36  also have the first and second intermediate portions  33 C and  36 C located between the first and second inner peripheral portions  33 A and  36 A and the first and second outer peripheral portions  33 B and  36 B and configured to have thicknesses smaller than those of the first and second inner peripheral portions  33 A and  36 A and the first and second outer peripheral portions  33 B and  36 B. 
     Such a configuration allows the first and second seal members  33  and  36  to follow the movement of the first and second pistons  31  and  34  only through deformation of the first and second intermediate portions  33 C and  36 C. Therefore, it is possible to prevent the first and second seal members  33  and  36  from slidably moving along the inner peripheral surface of the casing and prevent abrasion of the first and second seal members  33  and  36 . 
     Note that the present disclosure is not limited to the embodiment described above. Those skilled in the art will appreciate that various additions, modifications, and the like are possible without departing from the scope of the present disclosure. 
     For example, in the embodiment described above, as illustrated in  FIG. 9 , in addition to the pressure reducing valve  40 , a check valve  49  may also be provided in the intermediate casing  24 . In this case, in the intermediate casing  24 , a third insertion hole  24   j  is formed, and a first communication hole  24   k  providing communication between the first insertion hole  24   e  and the third insertion hole  24   j  and a second communication hole  24   m  providing communication between the second insertion hole  24   f  and the third insertion hole  24   j  are formed. The second communication hole  24   m  has an end portion closed by a ball  24 N. The driving fluid passage hole  24   g  of the intermediate casing  24  is formed to be located immediately above the check valve  49  and communicate with the third insertion hole  24   j . The driving fluid inlet port  25   d  is formed at a position in the upper casing  25  located above the third insertion hole  24   j  of the intermediate casing  24  to have a lower end portion thereof communicating with the driving fluid passage hole  24   g . Each of the driving fluid passage hole  24   g  and the driving fluid inlet port  25   d  corresponds to a driving fluid passage. 
     The check valve  49  is fitted in the third insertion hole  24   j  to be fixed to the intermediate casing  24 , and has a check valve O-ring  49 A and a valve body  49 B made of a resin. A space in the third insertion hole  24   j  which is inner than the check valve  49  forms a check chamber R 3 . The check valve O-ring  49 A prevents the driving fluid in the check chamber R 3  from leaking to the outside thereof. The valve body  49 B is displaceable depending on a pressure in the check chamber R 3  and, by displacement of the valve body  49 B, the check valve  49  is brought into a closed state or an open state. When the check valve  49  is in the closed state, communication between the check chamber R 3  and the first communication hole  24   k  is cut off. When the check valve  49  is in the open state, communication is provided between the check chamber R 3  and the first communication hole  24   k.    
     When the driving fluid flows from the driving fluid passage hole  24   g  of the intermediate casing  24  into the check chamber R 3 , the check valve  49  is brought into the closed state, and the driving fluid flows into the inflow chamber R 1  via the second communication hole  24   m . Since the inflow chamber R 1  and the decompression chamber R 2  communicate with each other, the driving fluid that has flown into the inflow chamber R 1  flows into the decompression chamber R 2  to increase the pressure in the decompression chamber R 2 . When the pressure in the decompression chamber R 2  increases, the pressure reducing piston  47  moves toward the spring retainer  46  against the biasing force of the pressure reducing spring  48 . Then, when the pressure in the decompression chamber R 2  reaches a predetermined level, the second poppet O-ring  44 C of the poppet  44  comes into contact with the peripheral edge portion  241  to cut off the communication between the inflow chamber R 1  and the decompression chamber R 2 . 
     As a result, the driving fluid having a predetermined pressure flows from the decompression chamber R 2  into the first and second pressure chambers S 1  and S 2  via the first driving fluid outlet port  26   b , the driving fluid inflow path  26   a , the second driving fluid outlet port  26   c , and the third driving fluid outlet port  26   d . Consequently, the valve device  1  is brought into the open state. 
     Meanwhile, the three-way valve  4  is switched to the flow of the driving fluid discharged from the drive portion  30  (first and second pressure chambers S 1  and S 2 ) of the valve device  1  to the outside thereof to reduce the pressure in the check chamber R 3  and bring the check valve  49  into the open state. This provides communication between the check chamber R 3  and the first communication hole  24   k  to allow the driving fluid in the first and second pressure chambers S 1  and S 2  to be discharged from the first communication hole  24   k  and the check chamber R 3  to the outside via the driving fluid inflow path  26   a  and the first driving fluid outlet port  26   b . This also allows the driving fluid in the inflow chamber R 1 , the decompression chamber R 2 , and the second communication hole  24   m  to be discharged from the check chamber R 3  to the outside thereof. 
     Thus, the actuator  20  includes the check valve  49  which is brought into the closed state when the driving fluid is introduced into the first and second pressure chambers S 1  and S 2  to allow the driving fluid to flow to the pressure reducing valve  40  and which is brought into the open state when the driving fluid is discharged from the first and second pressure chambers S 1  and S 2  to the outside thereof to allow the driving fluid to be discharged from the first and second pressure chambers S 1  and S 2  to the outside thereof. 
     In such a configuration, when the driving fluid is discharged from the first and second pressure chambers S 1  and S 2  to the outside thereof, the driving fluid is discharged to the outside without passing through the pressure reducing valve  40 . This can enlarge a flow path from each of the first and second pressure chambers S 1  and S 2  to the check valve  49  to increase a discharged amount of the driving fluid, and thereby reduce the time required by the driving fluid to be discharged. As a result, it is also possible to reduce the time required by the valve device  1  to shift from the open state to the closed state. Note that, when only the pressure reducing valve  40  is provided, it is necessary to produce a pressure difference between spaces before and after the poppet main body  44 A, and consequently an area of a gap (orifice portion) between the poppet main body  44 A and the peripheral edge portion  241  cannot easily be increased. Accordingly, the discharged amount of the driving fluid cannot be increased. 
     In the embodiment described above, the actuator  20  is applied to the valve device  1 , but may also be applied to another device. Also, in the embodiment described above, the switching member which switches between the flow of the driving fluid from the accumulator  3  to the valve device  1  and the flow of the driving fluid discharged from the drive portion  30  of the valve device  1  to the outside thereof is the three-way valve  4 , but may also be another member. 
     The shape of each of the first and second seal members  33  and  36  is not limited to that shown in the embodiment described above. For example, each of the first and second seal members  33  and  36  may also have a circular, X-shaped, or U-shaped cross section. Each of the first and second pressure chambers S 1  and S 2  may also be configured to have a changeable internal volume. 
     In the embodiment described above, a case in which the semiconductor production apparatus  100  is a CVD device is described, but the semiconductor production apparatus  100  may also be a sputtering device or an etching device. Also in the embodiment described above, an embodiment in which the valve device  1  is disposed with the actuator  20  facing upward and the body  10  facing downward is described, but the direction in which the valve device  1  is disposed is not limited thereto. The valve device  1  may also be disposed in a horizontal direction or in an upside down direction. 
       FIG. 10  illustrates a state where the poppet plug  43 , the spring retainer  46 , and the check valve  49  are fixed to the intermediate casing  24  using the setscrews  41 A,  42 A and  49 C. 
     In the embodiment described above, the poppet plug  43 , the spring retainer  46 , and the check valve  49  are respectively fitted in the second insertion hole  24   f , the first insertion hole  24   e , and the third insertion hole  24   j  and fixed to the intermediate casing  24 . However, as illustrated in  FIG. 10 , it may also be possible to respectively form internal thread portions  24 P,  24 Q, and  24 R on sides of respective openings of the second insertion hole  24   f , the first insertion hole  24   e , and the third insertion hole  24   j  and respectively insert the poppet plug  43 , the spring retainer  46 , and the check valve  49  into the second insertion hole  24   f , the first insertion hole  24   e , and the third insertion hole  24   j  such that the poppet plug  43 , the spring retainer  46 , and the check valve  49  are slidably movable therein. Then, the setscrews  41 A,  42 A, and  49 C having the respective external threshold portions are screwed into the respective internal thread portions  24 P,  24 Q, and  24 R. As a result, the poppet plug  43  is supported with respect to the intermediate casing  24 , while being interposed between the poppet spring  45  and the setscrew  41 A. The spring retainer  46  is supported with respect to the intermediate casing  24 , while being interposed between the pressure reducing spring  48  and the setscrew  42 A. 
     The setscrews  41 A,  42 A, and  49 C are setscrews with negative grooves. The poppet plug  43 , the spring retainer  46 , the poppet spring  45 , the pressure reducing spring  48 , the setscrew  41 A, and the setscrew  42 A respectively correspond to a first spring retainer, a second spring retainer, a first spring, a second spring, a first setscrew, and a second setscrew. The setscrew  41 A forms a portion of the poppet portion  41 . The setscrew  42 A forms a portion of the pressure reducing portion  42 . 
     In such a configuration, an amount of screwing in of each of the setscrews  41 A and  42 A is adjusted to move the poppet plug  43  and the spring retainer  46  and thus allow the respective biasing forces of the poppet spring  45  and the pressure reducing spring  48  to be adjusted. Thus, it is possible to adjust a drive pressure (predetermined pressure) for the pressure reducing valve  40  and adjust the opening/closing speed of the valve device  1 . As a result, it is possible to uniformize the opening/closing speed of each of the valves  1  and uniformize respective speeds of the opening operation and the closing operation of the valve device  1 .