Linkage-type constant-pressure valve

Abstract

A constant-pressure valve (11) comprises: a valve main body (13) in which are formed a first valve chamber (23) and a second valve chamber (31) that are in communication via a communication path (37); a valve mechanism (15) which includes a first diaphragm (41) that supports a valve body part (41a) in a first valve chamber in a manner enabling contact / separation with / from a valve seat (39) formed in the communication path, and a second diaphragm (43) that faces the second valve chamber; a first force-applying mechanism (17); and a second force-applying mechanism (19). The first force-applying mechanism is provided with a first moving body (51) that is biased by a biasing member (53) and joined to the valve body part via a stem (55). The second force-applying mechanism is provided with a second moving body (67) to which a force is applied by an applied force adjustment mechanism (69) and to which is transmitted fluid pressure in the second valve chamber that acts on the second diaphragm. A link member (77) that extends to the outside of a liquid contact region links the two moving bodies.

Description

Interlocking constant pressure valve

[0001] The present invention relates to a constant pressure valve equipped with a diaphragm, which is used to suppress changes in fluid pressure when transferring various fluids in various industrial fields such as semiconductor manufacturing, chemical plants, and food processing.

[0002] Conventionally, in semiconductor manufacturing and the like, constant pressure valves equipped with two diaphragms, such as that disclosed in Patent Document 1, have often been used to achieve high-precision stability in controlling fluid pressure.

[0003] A conventional fluid control valve 300 shown in FIG. 9, which is an example of such a constant pressure valve, comprises a body 306 having a first valve chamber 301 and a second valve chamber 302, a communication hole 303 having a smaller diameter than the first valve chamber 301 and the second valve chamber 302 for communicating the two valve chambers, an outlet flow path 304 communicating with the first valve chamber 301, and an inlet flow path 305 communicating with the second valve chamber 302, a bonnet 310 having a cavity 309 therein accommodating a piston 307 and a spring 308, and a first valve chamber 309 connected below the piston 307. The valve chamber 301 is provided with a first valve mechanism 312 having a first diaphragm 311 that covers the valve chamber 301, a second valve mechanism 315 that is connected to the first valve mechanism 312 and has a valve element 314 with a second diaphragm 313 at its lower end, and a base plate 316 that is located below the main body 306 and holds the second diaphragm 313 between itself and the main body 306, and the valve element 314 moves toward and away from a valve seat 317 formed on the upper surface of the second valve chamber 302 to open and close the communication hole 303. Compressed air is supplied to the gap 309 through an intake hole 318, and the valve element 314 of the second valve mechanism 315 is pushed upward by the repulsive force of the spring 308 sandwiched between the flange 319 of the piston 307 and the spring retainer 320 and by the pressure of the fluid in the first valve chamber 301 acting on the lower surface of the first diaphragm 311 of the first valve mechanism 312, while being pushed downward by the pressure of the compressed air in the gap 309 acting on the upper surface of the first diaphragm 311. Furthermore, the lower surface of the valve element 314 and the upper surface of the second diaphragm 313 of the second valve mechanism 315 are subjected to fluid pressure, but because their pressure-receiving areas are approximately equal, the forces are approximately canceled out. Therefore, the valve element 314 comes to rest in a position where the three forces mentioned above are balanced.

[0004] For this reason, when the pressure in the downstream first valve chamber 301 increases, the force that the lower surface of the first diaphragm 311 receives from the fluid becomes greater than the force that the upper surface of the first diaphragm 311 receives from the compressed air, causing the first diaphragm 311 to move upward. Accordingly, the position of the valve disc 314 also moves upward, reducing the opening area between the valve disc 314 and the valve seat 317 and reducing the pressure in the first valve chamber 301. The valve disc 314 stops when it moves to a position where the three forces mentioned above are balanced. Unless the biasing force of the spring 308 changes significantly, the pressure inside the gap 309, i.e., the force that the upper surface of the first diaphragm 311 receives, remains unchanged, and the pressure in the first valve chamber 301 remains the same as before the change. On the other hand, when the pressure in the downstream first valve chamber 301 decreases, the force acting on the upper surface of the first diaphragm 311 from the compressed air becomes smaller than the force acting on the lower surface of the first diaphragm 311 from the fluid, causing the first diaphragm 311 to move downward. Accordingly, the position of the valve disc 314 also moves downward, increasing the opening area between the valve disc 314 and the valve seat 317 and increasing the pressure in the first valve chamber 301. The valve disc 314 stops moving when it moves to a position where the three forces mentioned above are balanced. As a result, just as when the pressure in the first valve chamber 301 increases, the fluid pressure in the first valve chamber 301 returns to the same pressure as before the change. In this way, fluctuations in the downstream fluid pressure are suppressed.

[0005] Japanese Patent Application Laid-Open No. 2004-38571

[0006] 9 , in order to enable the first diaphragm 311, the second diaphragm 313, and the valve element 314 to move in conjunction with each other, the shafts extending from the first diaphragm 311 and the second diaphragm 313 are generally connected to the valve element 314. However, since the valve element 314 is larger than the communication hole 303 that extends from the valve seat 317 and connects the first valve chamber 301 and the second valve chamber 302, for ease of assembly, the shaft of one of the first diaphragm 311 and the second diaphragm 313 and the valve element 314 are often formed integrally, while the shaft of the other of the first diaphragm 311 and the second diaphragm 313 and the valve element 314 are often connected by screwing. As a result, the threaded portion 321 is positioned within the liquid contact area through which the fluid flows, and particles generated at the threaded portion 321 during assembly or when the valve body 314 is driven may be mixed into the fluid, potentially contaminating the fluid.

[0007] Therefore, the object of the present invention is to solve the problems present in the prior art and to suppress the generation of particles in a constant pressure valve that suppresses pressure changes by linking two diaphragms, without providing a mechanism for linking the two diaphragms in the liquid contact area.

[0008] In view of the above object, the present invention provides a valve mechanism including a valve body in which a first valve chamber communicating with an inlet flow path, a second valve chamber communicating with an outlet flow path, and a communication passage that communicates the first valve chamber with the second valve chamber, a valve seat formed in the communication passage, a first diaphragm attached to the valve body facing the first valve chamber and supporting a valve element portion so as to be movable relative to the valve seat in a moving axial direction, and a second diaphragm attached to the valve body facing the second valve chamber, and a valve mechanism in which a valve seat is attached to the valve body and supports the valve element portion in a moving axial direction. a first force applying mechanism that applies a force to the first diaphragm in a direction that moves the first diaphragm toward the valve seat; and a second force applying mechanism that is attached to the valve body and applies a predetermined force to the second diaphragm in a direction that moves the second diaphragm toward the communication passage, and the interlocking constant pressure valve moves the valve body portion relative to the valve seat in accordance with the pressure of the fluid in the second valve chamber, wherein the first force applying mechanism comprises a first mechanism housing formed therein, and a first diaphragm housed in the first mechanism housing and movable in the movement axis direction. a spring member provided in the first mechanism housing chamber and configured to spring the first movable body in a direction to approach the communication passage; and a stem extending from the first movable body through the first mechanism housing and connected to the valve body portion of the first diaphragm, wherein the second force applying mechanism includes a second mechanism housing having a second mechanism housing formed therein, a second movable body accommodated in the second mechanism housing and movable in the movement axis direction, and a predetermined spring member adjustable to the second movable body in a direction to approach the communication passage. and a force transmission section extending from the second movable body through the second mechanism housing to transmit force between the second movable body and the second diaphragm, wherein a rod-shaped link member is provided between the first movable body and the second movable body and extends outside the first valve chamber and second valve chamber through the valve body in the direction of the movement axis, so that the first movable body and the second movable body are linked via the link member.

[0009] In the above-described interlocking constant pressure valve, a first movable body of a first force applying mechanism movable in the direction of its movement axis is biased by a biasing member in a direction approaching the communicating passage, and a predetermined force is applied to a second movable body of a second force applying mechanism movable in the direction of its movement axis by a force adjustment mechanism in a direction approaching the communicating passage. Furthermore, a link member extending in the direction of the movement axis outside the first valve chamber and the second valve chamber is provided between the first movable body and the second movable body. Because the first movable body and the valve body portion of the first diaphragm are connected via a stem, a force is constantly applied by the biasing member to the valve body portion supported by the first diaphragm in a direction approaching a valve seat formed in the communicating passage. The first force applying mechanism and the second force applying mechanism are attached to the valve body so as to apply force to the first diaphragm and the second diaphragm facing the first valve chamber and the second valve chamber, respectively, which are located on opposite sides of the communicating passage, and a force is applied to the first movable body of the first force applying mechanism and the second movable body of the second force applying mechanism by the biasing member and the applied force adjustment mechanism, respectively, in a direction that brings them closer to the communicating passage. That is, the first movable body and the second movable body receive forces in directions that bring them closer to each other in the direction of the movement axis, and the link member is sandwiched between the first movable body and the second movable body, and the first movable body and the second movable body are linked via the link member in the same direction and at the same interval in the direction of the movement axis. Because the force transmission part extending from the second movable body transmits force between the second movable body and the second diaphragm, in addition to the force applied by the force adjustment mechanism, the pressure of the fluid in the second valve chamber acting on the second diaphragm is applied to the second movable body of the second force application mechanism via the force transmission part in a direction that offsets the force applied by the force adjustment mechanism (i.e., a direction that moves the second movable body away from the communicating passage). Therefore, the first movable body and the second movable body, which are linked via the link member, stop at a position where three forces, namely, the biasing force applied to the first movable body by the biasing member, the force applied to the second movable body by the force adjustment mechanism, and the fluid pressure applied by the fluid in the second valve chamber to the second movable body via the second diaphragm and the force transmission part, are balanced.Therefore, when the force applied to the second movable body by the force adjustment mechanism, which is one of the two forces acting on the second movable body, is adjusted and changed, the position of the first movable body changes, and the position of the valve body relative to the valve seat via the stem changes. As a result, the opening area between the valve body and the valve seat is adjusted, the flow rate from the first valve chamber to the second valve chamber changes, and the fluid pressure can be adjusted to a desired level. Furthermore, under conditions where the force applied to the second movable body by the force adjustment mechanism is constant, when the pressure of the fluid in the second valve chamber increases, the pressure of the fluid in the second valve chamber increases in a direction that offsets the force applied by the force adjustment mechanism, and the second movable body moves away from the communicating passage. On the other hand, when the pressure of the fluid in the second valve chamber decreases, the pressure of the fluid in the second valve chamber decreases in a direction that offsets the force applied by the force adjustment mechanism, and the second movable body moves toward the communicating passage. Accordingly, the valve element connected via the stem to the first movable element, which is linked to the second movable element via the link member, moves toward the valve seat when the pressure of the fluid in the second valve chamber increases, thereby reducing the opening area between the valve seat and the valve element, and moves away from the valve seat when the pressure in the second valve chamber decreases, thereby increasing the opening area between the valve seat and the valve element. As a result, changes in the pressure of the downstream fluid can be suppressed and the pressure can be kept approximately constant. Furthermore, the link member linking the first movable element and the second movable element can be disposed outside the first valve chamber and the second valve chamber, and the threaded portion for linking the first diaphragm and the second diaphragm can be arranged not in the liquid-contact area.

[0010] In the above-mentioned interlocking constant pressure valve, it is preferable that the applied force adjustment mechanism is configured to apply a force to the second movable body that is greater than or equal to the pressure that the fluid in the second valve chamber exerts on the second diaphragm.

[0011] In the interlocking constant pressure valve, it is preferable that a plurality of link members extend between the first movable body and the second movable body.

[0012] In one embodiment, the force transmission portion can be configured to abut against the second diaphragm and transmit force between the second movable body and the second diaphragm.

[0013] In this case, the applied force adjustment mechanism may include a pressurized fluid chamber and a pressurized diaphragm provided adjacent to the pressurized fluid chamber, and may be configured to apply the pressure of pressurized fluid adjustably supplied into the pressurized fluid chamber to the second movable body via the pressurized diaphragm. Applying the pressure of the pressurized fluid to the second movable body via the pressurized diaphragm eliminates the need to provide a seal member for sealing between the outer circumferential surface of the second movable body and the inner circumferential surface of the second mechanism housing chamber, thereby reducing friction between the outer circumferential surface of the second movable body and the inner circumferential surface of the second mechanism housing chamber and improving pressure responsiveness.

[0014] Preferably, the pressurized fluid is compressed air.

[0015] In another embodiment, the force transfer portion may be coupled to the second diaphragm.

[0016] In this case, the applied force adjustment mechanism may include a recess provided on a surface of the second mechanism housing facing the second diaphragm, and when the second force application mechanism is attached to the valve body, the second diaphragm covers the recess to form a pressurized fluid chamber, and by adjustably supplying pressurized fluid into the pressurized fluid chamber, fluid pressure acting on the second diaphragm is applied to the second movable body via the force transmission unit. Because the second diaphragm and the force transmission unit are connected, the pressure applied to the second diaphragm by the fluid in the pressurized fluid chamber is transmitted to the second movable body via the force transmission unit, and a force in a direction moving the second movable body toward the first movable body can be applied to the second movable body. Furthermore, because the force adjusted by the applied force adjustment mechanism is applied directly to the second diaphragm, pressure responsiveness is improved.

[0017] Preferably, the pressurized fluid is compressed air.

[0018] In the above-described interlocking constant pressure valve, the biasing member may be, for example, a coil spring.

[0019] In one embodiment, the link member may be sandwiched between the first movable body and the second movable body so as to be movable toward or away from the first movable body, and in another embodiment, both ends of the link member may be fixed to the first movable body and the second movable body, respectively.

[0020] According to the interlocking constant pressure valve of the present invention, the first movable body is applied with a resultant force of two forces acting on the second movable body via the link member, and with a biasing force from the biasing member acting in a direction away from the communicating passage via the first movable body and the link member, so that the first movable body stops at a position where these three forces are balanced. Therefore, when the force applied to the second diaphragm, which is one of the two forces acting on the second movable body, is adjusted by the force adjustment mechanism, the position of the first movable body changes, and the position of the valve body relative to the valve seat changes via the stem. As a result, the opening between the valve body and the valve seat is adjusted, allowing the fluid to be regulated to a desired pressure. Furthermore, even if the pressure of the fluid in the second valve chamber increases or decreases, the resultant force of the two forces acting on the second movable body changes, changing the balanced position of the first movable body, suppressing changes in the pressure of the downstream fluid and maintaining a substantially constant pressure. Furthermore, the link member that links the first movable body and the second movable body is disposed outside the first valve chamber and the second valve chamber, and the threaded portion for linking the first diaphragm and the second diaphragm is not provided in the liquid-contacting area, so that threading work in the liquid-contacting area is not required. Therefore, assembly can be performed without worrying about contamination of parts located in the liquid-contacting area, making assembly easier and suppressing the generation of particles in the liquid-contacting area.

[0021] FIG. 1 is a plan view of a linked constant pressure valve according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of the linked constant pressure valve taken along line A-A in FIG. 1. FIG. 3 is a cross-sectional view of the linked constant pressure valve taken along line B-B in FIG. 1. FIG. 4 is a cross-sectional view of the linked constant pressure valve taken along line C-C in FIG. 1. FIG. 5 is a cross-sectional view of the linked constant pressure valve taken along line D-D in FIG. 1, showing a state in which the valve body portion is in a closed position. FIG. 6 is a cross-sectional view of the linked constant pressure valve taken along line D-D in FIG. 1, showing a state in which the valve body portion is in an open position. FIG. 7 is a cross-sectional view of the linked constant pressure valve taken along line D-D in FIG. 1, showing a state in which the valve body portion is in an intermediate position. FIG. 8 is a cross-sectional view of a linked constant pressure valve according to another embodiment of the present invention. FIG. 9 is a cross-sectional view showing the overall configuration of a linked constant pressure valve of the prior art.

[0022] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a linked constant pressure valve according to the present invention will now be described with reference to the drawings.

[0023] 1 to 7 show the overall configuration of a linked constant pressure valve 11 according to one embodiment of the present invention. Referring to Fig. 1 to 7, the linked constant pressure valve 11 comprises a valve body 13, a valve mechanism 15 provided within the valve body 13, a first force applying mechanism 17 attached to the upper part of the valve body 13, and a second force applying mechanism 19 attached to the lower part of the valve body 13, and the valve mechanism 15 opens and closes the constant pressure valve 11 and controls the pressure of the fluid by adjusting the valve opening degree.

[0024] In this embodiment, the valve body 13 is made of polytetrafluoroethylene (PTFE). However, the valve body 13 may also be made of other suitable materials, such as perfluoroalkoxyalkane (PFA). The valve body 13 may also be made from a resin bonded body formed by bonding a PFA molded body made of PFA and a PTFE molded body made of PTFE by baking or other methods. In this case, to prevent particle generation when the valve body portion 41a (described later) contacts the valve seat 39, it is preferable to make the portion including the valve seat 39 from a PFA molded body and the remaining portion from a PTFE molded body. A lower recess 21, which has a circular planar shape, and a first valve chamber 23, which is located above the center of the lower recess 21 and has a smaller diameter than the lower recess 21, are formed in the lower center of the valve body 13, and are continuous with each other. An inlet flow path 25 is provided in communication with the first valve chamber 23. However, the reason why the first valve chamber 23 has a smaller diameter than the lower recess 21 is to facilitate the fixation of a first diaphragm 41, which will be described later, to the lower recess 21, and the first valve chamber 23 does not need to have a smaller diameter than the lower recess 21 as long as it does not interfere with the fixation of the first diaphragm 41. Furthermore, an annular stepped portion 27 is formed on the bottom surface of the valve body 13 so as to surround the lower recess 21. Meanwhile, an upper recess 29 having a circular shape in plan view is formed in the center of the top of the valve body 13, and a second valve chamber 31 is formed continuously with the upper recess 29. The second valve chamber 31 is located below the center of the upper recess 29 and has a smaller diameter than the upper recess 29, and an outlet-side flow path 33 is provided in communication with the second valve chamber 31. However, the reason why the second valve chamber 31 has a smaller diameter than the upper recess 29 is to facilitate the fixation of a second diaphragm 43, which will be described later, to the upper recess 29, and the second valve chamber 31 does not have to have a smaller diameter than the upper recess 29 as long as it does not interfere with the fixation of the second diaphragm 43. In addition, an annular stepped portion 35 is formed on the top surface of the valve body 13 so as to surround the upper recess 29. Furthermore, a communication passage 37 that communicates between the first valve chamber 23 and the second valve chamber 31 is formed in the valve body 13, and a valve seat 39 is formed around the opening of the communication passage 37 to the first valve chamber 23.

[0025] The valve mechanism 15 is composed of a first diaphragm 41 and a second diaphragm 43. In the illustrated embodiment, the first diaphragm 41 is made of PTFE and includes a valve body portion 41 a, a membrane portion 41 b extending outward from the outer periphery of the lower end of the valve body portion 41 a, a cylindrical vertical support portion 41 c provided on the outer periphery of the membrane portion 41 b and extending in the vertical direction in the drawing, and an annular horizontal support portion 41 d extending horizontally from the end (the lower end in the drawing) of the vertical support portion 41 c. The first diaphragm 41 is attached to the lower part of the valve body 13 by inserting the vertical support part 41c along the inner circumferential surface of the lower recess 21 with the valve body part 41a disposed within the first valve chamber 23 and fitting the horizontal support part 41d into the annular step part 27 of the valve body 13, thereby separating the first valve chamber 23 from the outside and supporting the valve body part 41a disposed within the first valve chamber 23. The second diaphragm 43 is made of PTFE and includes a force application part 43a, a membrane part 43b extending outward from the outer periphery of the force application part 43a, a cylindrical vertical support part 43c provided on the outer periphery of the membrane part 43b and extending in the vertical direction, and an annular horizontal support part 43d extending horizontally from an end (the upper end in the figure) of the vertical support part 43c. The second diaphragm 43 is attached to the upper part of the valve body 13 by inserting the vertical support part 43c along the peripheral wall of the upper recess 29 with the force application part 43a positioned within the second valve chamber 31 and having the horizontal support part 43d received in the annular step part 35 of the valve body 13, thereby separating the second valve chamber 31 from the outside and supporting the force application part 43a positioned within the second valve chamber 31.

[0026] In the illustrated embodiment, the first diaphragm 41 is made entirely of PTFE, but this is not limiting. For example, the first diaphragm 41 may be made from a resin bonded body obtained by bonding a PFA molded body made of PFA and a PTFE molded body made of PTFE by baking or the like. In this case, in order to suppress the generation of particles when the valve body 41 a abuts against the valve seat 39, it is preferable to make the portion of the valve body 41 a of the first diaphragm 41 that abuts against the valve seat 39 (the tip) from a PFA molded body and the remaining portion from a PTFE molded body.

[0027] The first force applying mechanism 17 is attached to the lower part of the valve body 13 and functions to apply force to the first diaphragm 41 in a direction that moves the valve body portion 41 a of the first diaphragm 41 attached to the first valve chamber 23 side of the valve body 13 closer to the valve seat 39. The first force applying mechanism 17 includes a first mechanism housing main body 45 in which a recess is formed, a first cover member 49 that closes the upper opening of the recess of the first mechanism housing main body 45 and forms a first mechanism accommodating chamber 47 therein, a first movable body 51 that moves within the first mechanism accommodating chamber 47 along the movement axis in a direction approaching and moving away from the communicating passage 37, a biasing member 53 that is provided within the first mechanism accommodating chamber 47 and biases the first movable body 51 in a direction that causes the first movable body 51 to approach the communicating passage 37 in the movement axis direction, and a stem 55 that extends from the first movable body 51 through the first cover member 49 so as to protrude to the outside from the first force applying mechanism 17, and the valve body portion 41 a of the first diaphragm 41 arranged in the first valve chamber 23 is connected to the tip end of the stem 55. In the illustrated embodiment, the stem 55 and the valve body 41 a are connected by screwing, but other methods such as press-fitting may also be used. The first mechanism housing main body 45 and the first cover member 49 constitute the first mechanism housing. The first mechanism housing main body 45 is provided with a vent hole 57 that communicates with the first mechanism housing chamber 47, allowing air to enter and exit the first mechanism housing chamber 47 through the vent hole 57. The first movable body 51 is biased by the biasing member 53 in a direction that moves the first movable body 51 toward the communication passage 37. Therefore, as the biasing force of the biasing member 53 causes the first movable body 51 to move within the first mechanism housing chamber 47 along the inner circumferential surface of the first mechanism housing chamber 47 in the direction of the movement axis, a force is constantly applied to the valve body 41 a of the first diaphragm 41 connected to the tip of the stem 55 of the first movable body 51 in a direction that presses the valve body 41 a against the valve seat 39.

[0028] In the illustrated embodiment, the first movable body 51 has a generally disk shape, and its outer peripheral surface slides against the inner peripheral surface of the first mechanism housing chamber 47, guiding the first movable body 51 to move in the direction of the movement axis. In the illustrated embodiment, a coil spring is used as the biasing member 53, and the coil spring is arranged to be sandwiched between a concave spring seat 51 a formed on the bottom surface of the first movable body 51 and a concave spring seat 45 a formed on the bottom surface of the recess in the first mechanism housing main body 45 (i.e., the bottom surface of the first mechanism housing chamber). In the illustrated embodiment, the ventilation port 57 is provided on the bottom surface of the first mechanism housing main body 45. However, the configuration of the interlocking constant pressure valve 11 is not limited to the configuration of the illustrated embodiment, and the first movable body 51 may have a shape other than a circular plate, for example, a polygonal plate shape or an elliptical plate shape, the biasing member may also be composed of other materials such as an elastic body, and the breathing port 57 may also be provided at a position other than the bottom surface, such as on the side of the recess of the first mechanism housing main body 45.

[0029] The first cover member 49 is formed with a protrusion 49a that extends toward the valve body 13. When the first force applying mechanism 17 is attached to the valve body 13, the protrusion 49a of the first cover member 49 is inserted into the lower recess 21 of the valve body 13, so that the vertical support portion 41c of the first diaphragm 41 attached to the lower recess 21 of the valve body 13 is sandwiched between the inner circumferential surface of the lower recess 21 and the outer circumferential surface of the protrusion 49a of the first cover member 49, and the horizontal support portion 41d of the first diaphragm 41 is sandwiched between the step portion 27 of the valve body 13 and the top surface of the first cover member 49 around the protrusion 49a. In this state, as shown in FIG. 4 , the first force applying mechanism 17 is fixed to the valve body 13 using a fastener 59, whereby the first diaphragm 41 is fixed to the valve body 13 and the valve body portion 41 a is supported within the first valve chamber 23.

[0030] The second force applying mechanism 19 is attached to the top of the valve body 13 and functions to apply an adjustable predetermined force to the second diaphragm 43 attached to the second valve chamber 31 side of the valve body 13 in a direction that moves the force acting portion 43a of the second diaphragm 43 closer to the communicating passage 37. The second force applying mechanism 19 includes a second mechanism housing main body 61 in which a recess is formed, a second cover member 65 that closes the lower opening of the recess of the second mechanism housing main body 61 to form a second mechanism accommodating chamber 63 inside, a second movable body 67 that moves within the second mechanism accommodating chamber 63 along the movement axis in a direction approaching and moving away from the communicating passage 37, an application force adjustment mechanism 69 that applies a predetermined force to the second movable body 67 that can be adjusted in a direction to move the second movable body 67 toward the communicating passage 37 in the movement axis direction, and a force transmission part 71 that extends from the second movable body 67 through the second cover member 65 so as to protrude to the outside from the second force applying mechanism 19. In this embodiment, the force transmission portion 71 and the force application portion 43a are not connected, and the tip of the force transmission portion 71 abuts against the force application portion 43a of the second diaphragm 43, pressurizing the force application portion 43a in a direction that moves the force application portion 43a closer to the communicating passage 37, thereby applying force to the second diaphragm 43 (more specifically, its force application portion 43a). In this embodiment, the force transmission portion 71 is integrally formed with the second movable body 67, but it may be formed as a separate body and connected by screwing or the like. The second mechanism housing main body 61 and the second cover member 65 constitute a second mechanism housing. The second mechanism housing main body 61 is provided with a ventilation port 73 (see FIG. 2 ) that communicates with the second mechanism housing chamber 63, allowing air to enter and exit the second mechanism housing chamber 63 through the ventilation port 73. The second diaphragm 43 is in contact with the fluid in the second valve chamber 31 and is in contact with a force transmission part 71 extending from the second movable body 67. As a result, fluid pressure acting on the second diaphragm 43 from the fluid in the second valve chamber 31 is applied to the second movable body 67 via the force transmission part 71 in a direction that moves the second movable body 67 away from the second valve chamber 31, i.e., in a direction that pulls the second movable body 67 away from the communicating passage 37, and an adjustable constant force is applied by the applied force adjustment mechanism 69 in a direction that moves the second movable body 67 closer to the communicating passage 37.The force applied to the second movable body 67 from the force adjustment mechanism 69 is adjusted to be greater than the fluid pressure applied to the second movable body 67 from the fluid in the second valve chamber 31 via the second diaphragm 43 and the force transmission part 71, and a resultant force acts on the second movable body 67 in a direction that brings it closer to the connecting passage 37.

[0031] In this embodiment, the second movable body 67 has a generally circular disk shape, and its outer peripheral surface slides against the inner peripheral surface of the second mechanism housing chamber 63, guiding the second movable body 67 to move in the direction of the movement axis. In this embodiment, the applied force adjustment mechanism 69 includes a pressurized fluid chamber 69a provided contiguous with the second mechanism housing chamber 63 and a pressurized diaphragm 69b disposed adjacent to the pressurized fluid chamber 69a so as to separate the pressurized fluid chamber 69a from the second mechanism housing chamber 63. Pressurized fluid is supplied to the pressurized fluid chamber 69a through a pressurized fluid supply port 69c, and the pressure of the pressurized fluid in the pressurized fluid chamber 69a acts on the second movable body 67 in a direction to move it closer to the communicating passage 37 via the pressurized diaphragm 69b disposed in contact with the second movable body 67. The pressure applied to the second movable body 67 can be adjusted by adjusting the amount of pressurized fluid supplied. However, the force adjustment mechanism 69 is not limited to the configuration of the illustrated embodiment as long as it can apply an adjustable constant force to the second movable body 67. For example, the force adjustment mechanism 69 may be configured by a cylinder mechanism that directly presses the second movable body 67. Furthermore, as long as the force adjustment mechanism 69 can apply a force to the second movable body 67, it does not need to apply a force directly to the second movable body 67, and the force adjustment mechanism 69 may be configured to apply a force indirectly to the second movable body 67.

[0032] The second cover member 65 is formed with a protrusion 65a that extends toward the valve body 13. When the second force applying mechanism 19 is attached to the valve body 13, the protrusion 65a of the second cover member 65 is inserted into the upper recess 29 of the valve body 13, so that the vertical support portion 43c of the second diaphragm 43 attached to the upper recess 29 of the valve body 13 is sandwiched between the inner circumferential surface of the upper recess 29 and the outer circumferential surface of the protrusion 65a of the second cover member 65, and the horizontal support portion 43d of the second diaphragm 43 is sandwiched between the step portion 35 of the valve body 13 and the bottom surface of the second cover member 65 around the protrusion 65a. In this state, as shown in FIG. 4 , the second force applying mechanism 19 is fixed to the valve body 13 using a fastener 75, whereby the second diaphragm 43 is fixed to the valve body 13 and the force application portion 43 a is supported within the second valve chamber 31.

[0033] 5 , for example, a link member 77 is provided between the first movable body 51 and the second movable body 67. The link member 77 extends through the valve body 13, outside the first valve chamber 23, the communicating passage 37, and the second valve chamber 31, and is movable in the direction of the movement axis. In the illustrated embodiment, one end of the link member 77 abuts against the upper surface of the first movable body 51, and the other end abuts against the second movable body 67 in a manner that allows them to approach or separate from each other. The first movable body 51 and the second movable body 67 are disposed on opposite sides of the communicating passage 37, and as described above, the first movable body 51 is biased by the biasing force of the biasing member 53 in a direction approaching the communicating passage 37, and the second movable body 67 is applied with a force in a direction approaching the communicating passage 37 by a resultant force of the fluid pressure acting from the fluid in the second valve chamber 31 via the second diaphragm 43 and the force transmission part 71 and the predetermined force applied by the applied force adjustment mechanism 69. That is, a force is applied to the first movable body 51 and the second movable body 67 in a direction that moves them toward each other. Therefore, the link member 77 is sandwiched between the first movable body 51 and the second movable body 67, and force can be transmitted between the first movable body 51 and the second movable body 67 via the link member 77. In the illustrated embodiment, four link members 77 are provided between the first movable body 51 and the second movable body 67. However, as long as force can be transmitted between the first movable body 51 and the second movable body 67, only one link member 77 or multiple link members 77 may be provided. In order to transmit force between the first movable body 51 and the second movable body 67 in a balanced manner, it is preferable to provide multiple link members 77 between the first movable body 51 and the second movable body 67.

[0034] As described above, the first movable body 51 and the second movable body 67 transmit forces to each other via the link member 77. As a result, the second movable body 67 stops at a position where three forces, namely, the adjustable constant pressure force applied to the second movable body 67 from the force adjustment mechanism 69, the fluid pressure acting on the second diaphragm 43 from the fluid in the second valve chamber 31 and applied to the second movable body 67 via the force transmission unit 71, and the biasing force acting on the first movable body 51 by the biasing member 53 and applied to the second movable body 67 via the link member 77, are balanced; once the position of the second movable body 67 is determined, the position of the first movable body 51 is determined via the link member 77, and the position of the valve body portion 41 a connected to the first movable body 51 via the stem 55 is also determined.

[0035] Therefore, by adjusting the predetermined force applied to the second movable body 67 by the force adjustment mechanism 69, it is possible to change the balance position of the three forces acting on the second movable body 67, and to move the first movable body 51 in conjunction with the movement of the second movable body 67. As a result, the gap (i.e., opening area) between the valve body portion 41a connected to the first movable body 51 via the stem 55 and the valve seat 39 can be changed, and the valve opening degree can be adjusted.

[0036] Furthermore, when the pressure of the fluid in the second valve chamber 31 changes, the balance position of the three forces acting on the second movable body 67 changes, and the first movable body 51 moves in conjunction with the movement of the second movable body 67. As a result, the gap between the valve body portion 41 a and the valve seat 39 changes, and as will be described later, the flow rate of the fluid flowing from the first valve chamber 23 through the communicating passage 37 into the second valve chamber 31 changes so as to cancel out the change in fluid pressure.

[0037] Furthermore, the first movable body 51 and the second movable body 67 are linked via a link member 77 that extends through the valve body 13, the first valve chamber 23, the communicating passage 37, and the outside of the second valve chamber 31, the second diaphragm 43 is linked to the second movable body 67 via the force transmission part 71, and the valve body part 41a is linked to the first movable body 51 via the stem 55, so that the position of the valve body part 41a relative to the valve seat 39 changes in response to changes in the pressure of the fluid in the second valve chamber 31. In addition, the connecting part between the stem 55 and the valve body part 41a is located on the opposite side of the liquid-contacting area. Therefore, while the first diaphragm 41 and first movable body 51 and the second diaphragm 43 and second movable body 67 are linked, there is no need to provide a connecting part within the liquid-contacting area for linking them. This eliminates the need for connecting operations such as screwing in the liquid-contacting area, allowing assembly to be performed without worrying about contamination of the parts located in the liquid-contacting area, facilitating assembly and preventing the generation of particles in the liquid-contacting area due to the connecting parts. Furthermore, since there is no need to provide a connecting member for interlocking the second diaphragm 43 and the valve body portion 41a by passing it through the communicating passage 37, the fluid in the liquid-contacting area can more easily flow through the communicating passage 37. As a result, fluid is less likely to stagnate, which can have the effect of improving the accuracy of flow rate control.

[0038] In addition, as described above, the link member 77 is sandwiched between the first movable body 51 and the second movable body 67, and if force can be transmitted between the first movable body 51 and the second movable body 67 via the link member 77, there is no need to fix both ends of the link member 77 to the first movable body 51 and the second movable body 67. Therefore, the first force applying mechanism 17 and the second force applying mechanism 19 can be modularized as independent separate units, and the link member 77 can be sandwiched between the first movable body 51 and the second movable body 67 simply by later attaching the first force applying mechanism 17 and the second force applying mechanism 19 to the top and bottom of the valve body 13 through which the link member 77 passes, thereby making it possible to easily assemble the interlocking constant pressure valve 11.

[0039] In this embodiment, the pressure diaphragm 69b of the force adjustment mechanism 69, the first mechanism housing body 45, first cover member 49, and first movable body 51 of the first force applying mechanism 17, and the second mechanism housing body 61, second cover member 65, and second movable body 67 of the second force applying mechanism 19 are made of PTFE, and the link member 77 is made of polyvinylidene fluoride (hereinafter referred to as PVDF). However, these, along with the other components of the interlocked constant pressure valve 11 described above, may be made of other appropriate materials and are not particularly limited. For example, the link member 77 may be made of a metal material.

[0040] Next, the operation of the interlocking constant pressure valve 11 will be described. In the interlocking constant pressure valve 11, when no force is applied to the second movable body 67 by the applied force adjustment mechanism 69, the second movable body 67 receives a force in a direction moving the second movable body 67 away from the communicating passage 37 due to the fluid pressure applied from the fluid in the second valve chamber 31 via the second diaphragm 43 and the force transmission part 71, and the biasing force applied to the first movable body 51 by the biasing member 53 and transmitted via the link member 77, causing the second movable body 67 to move along the movement axis in a direction away from the communicating passage 37. Accordingly, the first movable body 51 also moves along the movement axis in the same direction via the link member 77, and the valve body part 41 a of the first diaphragm 41 is pushed upward via the stem 55 and pressed against the valve seat 39. At this time, the communication passage 37 is closed by the valve body portion 41a, so that the fluid does not flow from the first valve chamber 23 to the second valve chamber 31, and the valve is in a closed state.

[0041] From this state, when a predetermined force is applied to the second movable body 67 by the force adjustment mechanism 69, the second movable body 67 is pushed by the applied force in a direction approaching the communicating passage 37 along the movement axis, and overcomes the biasing force of the biasing member 53 that acts on the first movable body 51 and is transmitted to the second movable body 67 via the link member 77, so the second movable body 67 moves along the movement axis in a direction approaching the communicating passage 37, i.e., toward the first movable body 51. Because the link member 77 is disposed between the first movable body 51 and the second movable body 67, when the second movable body 67 attempts to approach the first movable body 51 along the movement axis, the first movable body 51 is moved along the movement axis in a direction away from the communicating passage 37 with the link member 77 interposed between it and the second movable body 67. As a result, the valve body portion 41a of the first diaphragm 41, which is connected to the first movable body 51 via the stem 55, moves away from the valve seat 39, allowing fluid to flow into the connecting passage 37 through the gap between the valve body portion 41a and the valve seat 39, and fluid begins to flow from the first valve chamber 23 to the second valve chamber 31.

[0042] When the fluid flows into the second valve chamber 31, the fluid pressure acting on the second diaphragm 43 in a direction away from the communicating passage 37 in the movement axis direction by the fluid in the second valve chamber 31 is applied to the second movable body 67 via the force transmission part 71. In the illustrated embodiment, the pressure acting on the second diaphragm 43 in a direction away from the communicating passage 37 in the movement axis direction by the fluid in the second valve chamber 31 is transmitted to the second movable body 67 via the force transmission part 71 abutting against the second diaphragm 43. If the force applied by the force adjustment mechanism 69 to the second movable body 67 in a direction along the movement axis to bring the second movable body 67 closer to the communicating passage 37 is adjusted to be greater than the fluid pressure applied to the second movable body 67 from the fluid in the second valve chamber 31 via the second diaphragm 43 and the force transmission part 71 in a direction along the movement axis away from the communicating passage 37, then the resultant force of the two forces applied to the second movable body 67 by the force adjustment mechanism 69 and the fluid in the second valve chamber 31, i.e., the resultant force of the force applied by the force adjustment mechanism 69 and the fluid pressure of the fluid in the second valve chamber 31, will act in a direction to bring the second movable body 67 closer to the communicating passage 37 along the movement axis, i.e., in a direction to bring the second movable body 67 closer to the first movable body 51 along the movement axis. On the other hand, the first movable body 51 is constantly biased by the biasing member 53 in a direction that moves the first movable body 51 toward the communication passage 37 along the axis of movement, i.e., in a direction that moves the first movable body 51 toward the second movable body 67 along the axis of movement. Therefore, a force acts on the first movable body 51 and the second movable body 67 via the link member 77 in a direction that moves them toward each other, and the link member 77 is sandwiched between the first movable body 51 and the second movable body 67, so that they move together as if they were connected via the link member 77. As a result, the first movable body 51 and the second movable body 67 stop at a position where the resultant force of two forces acting in opposite directions on the second movable body 67, i.e., the resultant force of the force acting on the second movable body 67 by the force adjustment mechanism 69 in a direction to move it closer to the communicating passage 37 and the fluid pressure acting on the second movable body 67 from the fluid in the second valve chamber 31 via the second diaphragm 43 and the force transmission part 71 in a direction to move it away from the communicating passage 37, is balanced with the biasing force acting on the first movable body 51 from the biasing member 53.

[0043] When the communicating passage 37 is in an open state and fluid is flowing into the second valve chamber 31, if the pressure of the upstream fluid, i.e., the pressure of the fluid in the first valve chamber 23, increases and the pressure of the fluid in the second valve chamber 31 increases, the fluid pressure acting on the second diaphragm 43 from the fluid in the second valve chamber 31, which is one of the forces acting on the second movable body 67, increases, and the resultant force on the second movable body 67, which is in the opposite direction to the biasing force applied to the first movable body 51 by the biasing member 53, decreases. As a result, the biasing force applied to the first movable body 51 by the biasing member 53 becomes greater than the resultant force applied to the second movable body 67, and the first movable body 51 moves in a direction approaching the communicating passage 37, and the valve body 41 a approaches the valve seat 39 via the stem 55. This reduces the gap (i.e., opening area) between the valve body 41 a and the valve seat 39, thereby reducing the valve opening. As a result, the flow rate of the fluid flowing from the first valve chamber 23 through the communication passage 37 into the second valve chamber 31 decreases, and the pressure in the second valve chamber 31 decreases.

[0044] Conversely, when the communicating passage 37 is in an open state and fluid is flowing into the second valve chamber 31, if the pressure of the upstream fluid, i.e., the pressure of the fluid in the first valve chamber 23, decreases and the pressure of the fluid in the second valve chamber 31 decreases, the fluid pressure acting on the second diaphragm 43 from the fluid in the second valve chamber 31 decreases, and the resultant force on the second movable body 67, which is in the opposite direction to the biasing force applied to the first movable body 51 by the biasing member 53, increases. As a result, the resultant force applied to the second movable body 67 overcomes the biasing force applied to the first movable body 51 by the biasing member 53, and the first movable body 51 moves in a direction away from the communicating passage 37, and the valve body 41 a is separated from the valve seat 39 via the stem 55. This increases the gap (i.e., opening area) between the valve body 41 a and the valve seat 39, increasing the valve opening. As a result, the flow rate of the fluid flowing from the first valve chamber 23 through the communication passage 37 into the second valve chamber 31 increases, and the pressure in the second valve chamber 31 increases.

[0045] In either case, the valve will eventually stop at a position where the resultant force of the two forces applied to the second movable body 67 by the force adjustment mechanism 69 and the fluid in the second valve chamber 31 balances with the biasing force acting from the biasing member 53 on the first movable body 51. If the force applied to the second movable body 67 by the force adjustment mechanism 69 does not change significantly, the force applied to the second diaphragm 43 by the force adjustment mechanism 69 via the force transmission unit 71 will remain unchanged, and the fluid pressure acting on the lower surface of the second diaphragm 43 from the fluid in the second valve chamber 31 will be approximately the same as the pressure before the upstream pressure increased or decreased. In the illustrated embodiment, unless the pressure of the pressurized fluid in the pressurized fluid chamber 69a of the force adjustment mechanism 69 changes significantly, the force applied by the force adjustment mechanism 69 to the upper surface of the second diaphragm 43 remains unchanged, and the fluid pressure acting on the lower surface of the second diaphragm 43 from the fluid in the second valve chamber 31 remains approximately the same as before the upstream pressure increased or decreased.

[0046] In this way, when the pressure of the upstream fluid changes and the pressure in the second valve chamber 31 increases or decreases, the resultant force of the two forces acting on the second movable body 67 changes, changing the positions of the first movable body 51 and the second movable body 67 so as to balance the force acting on the first movable body 51, and moving the valve body portion 41 a relative to the valve seat 39 in a direction that suppresses changes in the pressure of the fluid in the second movable body 67 located downstream. As a result, even if the pressure of the upstream fluid changes, the pressure of the fluid in the second valve chamber 31 can be kept approximately constant.

[0047] 1 to 7, a force is applied directly to the second movable body 67 via the pressure diaphragm 69b by the pressurized fluid supplied to the pressurized fluid chamber 69a, and the force acting on the second movable body 67 is applied to the second movable body 67 via the force transmission unit 71 that abuts against the force application unit 43a. However, as long as the force application adjustment mechanism 69 can apply a force to the second movable body 67 and the second force application mechanism 19 can apply a force to the second diaphragm 43, the configurations of the second force application mechanism 19 and the force application adjustment mechanism 69 are not limited to the embodiments shown in FIGS.

[0048] Figure 8 shows another embodiment of the interlocked constant pressure valve 11' equipped with a second force applying mechanism 119 having an applied force adjustment mechanism 169 configured differently from the interlocked constant pressure valve 11 of the embodiment shown in Figures 1 to 7. The embodiment shown in Figure 8 has the same configuration as the embodiment shown in Figures 1 to 7 except for the second force applying mechanism 119, and in Figure 8, the same reference numerals are used for the configuration that is common to Figures 1 to 7. The following will mainly describe the second force applying mechanism 119, and a description of the common configuration will be omitted.

[0049] In the interlocking constant pressure valve 11 according to the embodiment shown in Figures 1 to 7, the applied force adjustment mechanism 69 is composed of a pressurized fluid chamber 69a provided contiguous with the second mechanism accommodating chamber 63, and a pressurized diaphragm 69b arranged adjacent to the pressurized fluid chamber 69a so as to separate the pressurized fluid chamber 69a from the second mechanism accommodating chamber 63. Furthermore, the force transmission portion 71 presses the second diaphragm 43 simply by being in contact with the force application portion 43a of the second diaphragm 43, and the force applied to the second movable body 67 by the applied force adjustment mechanism 69 is transmitted to the second diaphragm 43 via the force transmission portion 71.

[0050] 8 , the applied force adjustment mechanism 169 is composed of a pressurized fluid chamber 169a provided on a surface of the second mechanism housing (more specifically, the second cover member 65) facing the second diaphragm 43, and a pressurized fluid supply port 169c provided in the second mechanism housing (more specifically, the second cover member 65) for supplying and discharging pressurized fluid to and from the pressurized fluid chamber 169a. More specifically, when the second force applying mechanism 119 is attached to the valve body 13, the pressurized fluid chamber 169a is formed by the second diaphragm 43 covering a recess provided on the surface of the second cover member 65 facing the second diaphragm 43. In addition, the force transmission part extending from the second movable body 67 is connected to the force application part 43a of the second diaphragm 43, so that the force application part 43a of the second diaphragm 43 and the second movable body 67 work together and force is transmitted between the second diaphragm 43 and the second movable body 67 via the force transmission part 71.

[0051] With this configuration, when the pressure of the pressurized fluid supplied to the pressurized fluid chamber 169a through the pressurized fluid supply port 169c acts on the surface of the second diaphragm 43 opposite to the second valve chamber 31, a force in a direction that moves the force application portion 43a of the second diaphragm 43 toward the communicating passage 37 in the movement axis direction is applied to the second movable body 67 via the force transmission portion 71. Therefore, by adjusting the amount of pressurized fluid supplied through the pressurized fluid supply port 169c, it is possible to adjust the force applied to the second movable body 67 in a direction that moves the force application portion 43a of the second diaphragm 43 toward the communicating passage 37 in the movement axis direction, and it is possible to fulfill the function of the applied force adjustment mechanism 169.

[0052] The operation of the force adjustment mechanism 169 in the embodiment shown in Figure 8 is common to the operation of the force adjustment mechanism 69 in the embodiments shown in Figures 1 to 7 in that an adjustable predetermined force is applied to the second movable body 67 in a direction that moves the second movable body 67 closer to the communicating passage 37 in the direction of the movement axis. Therefore, the operation of the interlocked constant pressure valve 11' in the embodiment shown in Figure 8 is similar to that of the interlocked constant pressure valve 11 in the embodiments shown in Figures 1 to 7, and therefore a description thereof will be omitted here. On the other hand, the force adjustment mechanism 169 of the interlocked constant pressure valve 11' in the embodiment shown in Figure 8 can directly apply force to the second diaphragm 43, thereby achieving the effect of improving responsiveness to pressure changes of the fluid in the second valve chamber 31 compared to the interlocked constant pressure valve 11. Furthermore, since the force application portion 43a of the second diaphragm 43 and the second movable body 67 are connected via the force transmission portion 71, the responsiveness to pressure changes of the fluid in the second valve chamber 31 can be further improved.

[0053] Although the interlocking constant pressure valve according to the present invention has been described above with reference to the illustrated embodiment, the present invention is not limited to the illustrated embodiment. For example, in the illustrated embodiment, a coil spring is used as the biasing member 53 of the first force applying mechanism 17, but an elastic body, a working fluid, or a combination of a working fluid and a coil spring may also be used. Furthermore, while a working fluid is used to apply force to the second diaphragm 43 in the force applying mechanism 69 of the second force applying mechanism 19, an elastic body, a coil spring, or a combination of a working fluid and a coil spring may also be used instead of a working fluid. The biasing member 53 and the force applying mechanism 69 may be a combination of any of the mechanisms. Furthermore, both ends of the link member 77 may be fixed to the first movable body 51 and the second movable body 67, for example, by adhesive. However, when multiple link members 77 are provided between the first movable body 51 and the second movable body 67, it is preferable that both ends of the link members 77 abut against the first movable body 51 and the second movable body 67 so that they can be moved toward and away from each other, in order to allow for differences in length between the link members 77.

[0054] REFERENCE SIGNS LIST 11 Interlocking constant pressure valve 11' Interlocking constant pressure valve 13 Valve body 15 Valve mechanism 17 First force applying mechanism 19 Second force applying mechanism 23 First valve chamber 25 Inlet side flow path 31 Second valve chamber 33 Outlet side flow path 37 Communication passage 39 Valve seat 41 First diaphragm 41a Valve body portion 43 Second diaphragm 45 First mechanism housing body 47 First mechanism accommodating chamber 49 First cover member 51 First movable body 53 Urging member 55 Stem 61 Second mechanism housing body 63 Second mechanism accommodating chamber 65 Second cover member 67 Second movable body 69 Applied force adjustment mechanism 71 Force transmission portion 77 Link member 119 Second force applying mechanism 169 Applied force adjustment mechanism

Claims

1. A linked constant pressure valve comprising: a valve body having a first valve chamber communicating with an inlet flow path, a second valve chamber communicating with an outlet flow path, and a communicating passage connecting the first valve chamber and the second valve chamber; a valve seat formed in the communicating passage; a first diaphragm attached to the valve body facing the first valve chamber and supporting a valve element portion so as to be movable relative to the valve seat in the direction of its movement axis; and a valve mechanism including a second diaphragm attached to the valve body facing the second valve chamber; a first force applying mechanism attached to the valve body and applying a force to the first diaphragm in a direction that moves the valve element portion toward the valve seat; and a second force applying mechanism attached to the valve body and applying a predetermined force to the second diaphragm in a direction that moves the second diaphragm toward the communicating passage, wherein the valve mechanism moves the valve element portion relative to the valve seat in accordance with the pressure of a fluid in the second valve chamber, the first force applying mechanism comprises a first mechanism casing having a first mechanism accommodating chamber formed therein, a first movable body accommodated in the first mechanism accommodating chamber and movable in the direction of the movement axis, a biasing member provided in the first mechanism accommodating chamber and biasing the first movable body in a direction to approach the communicating passage, and a stem extending from the first movable body through the first mechanism casing and connected to the valve body portion of the first diaphragm; the second force applying mechanism comprises a second mechanism casing having a second mechanism accommodating chamber formed therein, a second movable body accommodated in the second mechanism accommodating chamber and movable in the direction of the movement axis, an applied force adjustment mechanism applying an adjustable predetermined force to the second movable body in a direction to approach the communicating passage, and a force transmission portion extending from the second movable body through the second mechanism casing and transmitting force between the second movable body and the second diaphragm; a rod-shaped link member is provided between the first movable body and the second movable body, and extends outside the first valve chamber and the second valve chamber, penetrating the valve body in the direction of the movement axis, and the first movable body and the second movable body are linked together via the link member.

2. The interlocking constant pressure valve according to claim 1, wherein the applied force adjustment mechanism is configured to apply a force to the second movable body that is greater than or equal to the pressure exerted on the second diaphragm by the fluid in the second valve chamber.

3. The interlocked constant pressure valve of claim 1, wherein a plurality of link members extend between said first movable body and said second movable body.

4. A linked constant pressure valve as described in any one of claims 1 to 3, wherein the force transmission portion is configured to abut against the second diaphragm and transmit force between the second movable body and the second diaphragm.

5. A linked constant pressure valve as described in claim 4, wherein the applied force adjustment mechanism includes a pressurized fluid chamber and a pressure diaphragm provided adjacent to the pressurized fluid chamber, and is configured to apply the pressure of pressurized fluid adjustably supplied into the pressurized fluid chamber to the second movable body via the pressure diaphragm.

6. The interlocked constant pressure valve of claim 5, wherein the pressurized fluid is compressed air.

7. A linked constant pressure valve according to any one of claims 1 to 3, wherein the force transmission part is connected to the second diaphragm.

8. A linked constant pressure valve as described in claim 7, wherein the applied force adjustment mechanism includes a recess provided on a surface of the second mechanism housing facing the second diaphragm, and when the second force application mechanism is attached to the valve body, the second diaphragm covers the recess to form a pressurized fluid chamber, and by adjustably supplying pressurized fluid into the pressurized fluid chamber, the fluid pressure acting on the second diaphragm is applied to the second movable body via the force transmission part.

9. The interlocked constant pressure valve of claim 8, wherein the pressurized fluid is compressed air.

10. A linked constant pressure valve according to any one of claims 1 to 3, wherein the biasing member is a coil spring.

11. A linked constant pressure valve as claimed in any one of claims 1 to 3, wherein the link member is sandwiched between the first movable body and the second movable body so as to be movable toward and away from each other.

12. A linked constant pressure valve as claimed in any one of claims 1 to 3, wherein both ends of the link member are fixed to the first movable body and the second movable body, respectively.