Diaphragm valve

Abstract

[Problem] To provide a diaphragm valve that can avoid an excessive decrease in Cv value when the diaphragm valve is used in a high-temperature environment. [Solution] A diaphragm valve 1 comprises an annular valve seat 20 and a support member 3 provided with an annular seat installation groove 8 for installing the valve seat 20, the support member 3 having an inner-circumferential-side crimping section 7A and an outer-circumferential-side crimping section 7B that face each other to form the seat installation groove 8, wherein the valve seat 20 has a tapered surface 20e, which is inclined according to an inclined portion 7Bb occurring to the outer circumferential side crimping section 7B due to plastic deformation and engages with the inclined portion 7Bb.

Description

diaphragm valve

[0001] The present invention relates to a diaphragm valve used in, for example, a semiconductor manufacturing process.

[0002] Diaphragm valves are known as one type of fluid control device for controlling the flow of various process gases in semiconductor manufacturing processes, etc. A diaphragm valve has a valve seat made of a material such as a fluororesin, which is fixed by caulking to a seat mounting groove in a valve body, and a diaphragm that is attached to the valve body so that it can come into contact with and separate from the valve seat, thereby opening and closing a flow path (see, for example, Patent Document 1).

[0003] JP 2017-089837 A JP 2019-100525 A

[0004] It is known that when the above-mentioned diaphragm valve is used in a high-temperature atmosphere of around 150°C to 200°C, the valve seat thermally expands, reducing the gap between the diaphragm and the valve seat, thereby reducing the Cv value. However, when the diaphragm valve is used in a high-temperature atmosphere, the Cv value decreases excessively, exceeding the decrease in Cv value due to the thermal expansion of the valve seat itself, resulting in a problem of gas flow becoming difficult.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a diaphragm valve that can suppress an excessive decrease in Cv value when used in a high-temperature atmosphere, and a method for manufacturing such a diaphragm valve.

[0006] The diaphragm valve of the present invention comprises an annular valve seat and a support member having an annular seat mounting groove for mounting the valve seat, wherein the support member has an inner circumferential crimped portion and an outer circumferential crimped portion that face each other and form the seat mounting groove, and the valve seat is inclined to match the inclined portion generated by plastic deformation in the outer circumferential crimped portion, and has a tapered surface that engages with the inclined portion.

[0007] Preferably, the valve seat has an annular upper surface as a sealing surface, an annular flat lower surface opposite the upper surface, an innermost surface perpendicular to the lower surface and engaging with the inner crimped portion, and an outermost surface perpendicular to the lower surface and engaging with the outer crimped portion, and the tapered surface is formed adjacent to the outermost surface.

[0008] More preferably, a configuration can be adopted in which a groove extending in the circumferential direction is formed in the bottom surface of the seat mounting groove of the support member, forming a gap between the support member and the valve seat.

[0009] Alternatively, a configuration can be employed in which a groove extending in the circumferential direction is formed on the lower surface of the valve seat, forming a gap between the support member and the valve seat.

[0010] Alternatively, a configuration can be adopted in which a second tapered surface is formed between the lower surface and the outermost peripheral surface of the valve seat, or between the lower surface and the inner peripheral surface of the valve seat, to form a gap between the support member and the valve seat.

[0011] According to the present invention, a diaphragm valve can be obtained that can prevent an excessive decrease in Cv value when used in a high-temperature atmosphere.

[0012] 1A and 1B are cross-sectional views of a main portion of a diaphragm valve according to an embodiment of the present invention. (a) is a cross-sectional view of a valve body, (b) is a top view of the valve body, and (c) is an enlarged cross-sectional view of a support portion in which a seat mounting groove is formed. (b) is an enlarged cross-sectional view of a valve seat. (a) is a cross-sectional view of a crimping jig, and (b) is an enlarged cross-sectional view of circle A in (a). (c) are cross-sectional views for explaining the crimping process. (a) is a cross-sectional view of a valve seat according to a first embodiment inserted into a seat mounting groove before plastic deformation, and (b) is a cross-sectional view showing the valve seat according to the first embodiment fixed in the seat mounting groove after plastic deformation. (a) is a cross-sectional view of a valve seat according to a second embodiment inserted into a seat mounting groove before plastic deformation, and (b) is a cross-sectional view showing the valve seat according to the second embodiment fixed in the seat mounting groove after plastic deformation. (a) is a cross-sectional view of a valve seat according to a third embodiment inserted into a seat mounting groove before plastic deformation, and (b) is a cross-sectional view showing the valve seat according to the third embodiment fixed in the seat mounting groove after plastic deformation. 1A is a cross-sectional view showing the state in which the valve seat according to the fourth embodiment is inserted into the seat mounting groove before plastic deformation, and FIG. 1B is a cross-sectional view showing the state in which the valve seat according to the fourth embodiment is fixed in the seat mounting groove after plastic deformation. 1A is a cross-sectional view showing the state in which the valve seat according to the comparative example is inserted into the seat mounting groove before plastic deformation, and FIG. 1B is a cross-sectional view showing the state in which the valve seat according to the comparative example is fixed in the seat mounting groove after plastic deformation.

[0013] First Embodiment In Fig. 1, a diaphragm valve 1 includes a metal valve body 3 as a support member, an annular valve seat 20, a diaphragm 30, a retainer adapter 32, a stem 34, a diaphragm retainer 36, and a bonnet 38. As shown in Fig. 2, the valve body 3 defines flow paths 4, 5, and 6 for a fluid such as a gas. As shown in Fig. 2(b), an annular seat mounting groove 8 is formed at the tip of a cylindrical support portion 7 formed in the valve body 3, and a valve seat 20 is mounted in this seat mounting groove 8. A metal bonnet 38 connected to an actuator (not shown) is threaded onto the inner periphery of a cylindrical portion 10 formed at the top of the valve body 3, and the lower end of the bonnet 38 presses against the outer periphery of the retainer adapter 32, thereby fixing the diaphragm 30 to the valve body 3. As shown in Figure 2 (c), before plastic deformation, the tip of the support portion 7 has a cylindrical inner circumferential crimped portion 7A and a cylindrical outer circumferential crimped portion 7B that face each other radially, defining a seat mounting groove 8.

[0014] 1, the diaphragm 30 is supported by the valve body 3 so as to be able to contact and separate from the valve seat 20. A stem 34, which holds a diaphragm retainer 36 at its lower end, is supported so as to be able to move in an upward direction A1 and a downward direction A2, is constantly biased in the downward direction A2 by a coil spring (not shown), and is driven upward by an actuator (not shown). The diaphragm valve 1 is a so-called normally closed valve.

[0015] The diaphragm 30 has a diameter larger than the valve seat 20 and is formed into an elastically deformable spherical shell shape from a metal such as stainless steel or a NiCo-based alloy. The diaphragm 30 defines a flow path connecting the flow path 4, which opens at the center of the valve body 3, to the annular flow path 6, which is arranged around the opening of the flow path 4. The flow path 6 and the flow path 5 are also in communication with each other. The diaphragm 30 is pressed by the diaphragm retainer 36, causing it to elastically deform and come into contact with the valve seat 20, thereby blocking the flow path. When the diaphragm retainer 36 is raised in the upward direction A1, the diaphragm 30 separates from the valve seat 20, and the flow path 4 and the flow path 6 communicate with each other through the gap between the diaphragm 30 and the valve seat 20.

[0016] The valve seat 20 is made of a resin such as PFA or PTFE and is elastically deformable. As shown in Fig. 3, the valve seat 20 has an annular upper surface 20a as a sealing surface that contacts the diaphragm 30 to seal the flow path, an annular flat lower surface 20b opposite the upper surface 20a, an innermost surface 20c perpendicular to the lower surface 20b, an inner tapered surface 20g adjacent to the innermost surface 20c and inclined at an angle γ with respect to the innermost surface 20c, an upper tapered surface 20f formed between the inner tapered surface 20g and the upper surface 20a and inclined at an angle α with respect to the innermost surface 20c, and an outermost surface 20d perpendicular to the lower surface 20b. The upper surface 20a is a tapered surface inclined at an angle β with respect to the lower surface 20b. The tapered surface 20e of the present invention is formed adjacent to the outermost peripheral surface 20d and is a tapered surface inclined at an angle θ with respect to the outermost peripheral surface 20d. The angle θ of the tapered surface 20e is an inclination angle that matches the inclined portion generated by plastic deformation due to crimping at the outer peripheral crimped portion 7B. In this embodiment, the angle α is approximately 60 degrees, the angle β is approximately 5 degrees, the angle γ is approximately 2 degrees, and the angle θ is approximately 25 degrees. Note that these angles are not limited to these values, and in particular, the angle θ of the tapered surface 20e can be changed in various ways as long as it is within a range that does not cause fluid leakage and does not shift during crimping.

[0017] FIG. 4 shows the structure of the crimping jig 100. As shown in FIG. 4A, the crimping jig 100 has an annular crimping groove 101 formed in the lower end surface of a cylindrical body 102. The crimping groove 101 has an engagement surface 101a that engages with the outer crimped portion 7B of the valve body 3 and an engagement surface 101b that engages with the inner crimped portion 7A. The engagement surface 101a that engages with the outer crimped portion 7B is a tapered surface inclined at the angle θ described above. The inclination of this engagement surface 101a determines the inclination of the inclined portion 7Bb of the outer crimped portion 7B, which will be described later. The engagement surface 101b acts to tilt the inner crimped portion 7A from near its base, while the engagement surface 101a acts to tilt only the tip end side of the outer crimped portion 7B, preventing tilting of the base side.

[0018] As shown in Figure 5, when the valve seat 20 is inserted into the seat mounting groove 8 and the crimping jig 100 arranged above the valve body 3 is lowered, the engaging surfaces 101a and 101b of the crimping groove 101 engage with the inner crimping portion 7A and the outer crimping portion 7B, respectively, and the inner crimping portion 7A and the outer crimping portion 7B tilt toward the valve seat 20, thereby fixing the valve seat 20 to the valve body 3.

[0019] As shown in Figure 6(a), when the valve seat 20 is inserted into the seat mounting groove 8 before plastic deformation, a relatively large gap is formed between the tapered surface 20e of the valve seat 20 and the outer crimped portion 7B. When the inner crimped portion 7A and the outer crimped portion 7B are plastically deformed using a crimping jig 100 from this state, the inner crimped portion 7A tilts from its base, compressing and engaging the innermost surface 20c and inner tapered surface 20g of the valve seat 20, as shown in Figure 6(b). The inclined portion 7Bb at the tip of the outer crimped portion 7B engages with the tapered surface 20e of the valve seat 20, and the base portion 7Bc of the outer crimped portion 7B engages with the outermost surface 20d of the valve seat 20. At the same time, the lower surface 20b of the valve seat 20 engages with the bottom surface 7C of the seat mounting groove 8. Here, because the valve seat 20 is formed with a tapered surface 20e inclined at an angle θ, the inclined portion 7Bb of the outer circumferential crimped portion 7B, which is inclined in the same manner as the tapered surface 20e, does not bite into the tapered surface 20e to significantly compress the tapered surface 20e. Specifically, because the tapered surface 20e is inclined to match the inclination of the inclined portion 7Bb of the outer circumferential crimped portion 7B, the inclination of the inner circumferential crimped portion 7A presses the tapered surface 20e and the outermost peripheral surface 20d toward the wall surface of the outer circumferential crimped portion 7B, but the presence of the tapered surface 20e distributes the compression of the tapered surface 20e and the outermost peripheral surface 20d, keeping the compression to a minimum and preventing partial excessive compression.

[0020] For comparison, a case where a valve seat 200 without a tapered surface 20e is fixed to a seat mounting groove 8 will be described with reference to FIG. 10 . Note that the same reference numerals are used in FIG. 10 for the same components as those described above. As shown in FIG. 10( a), when the valve seat 200 is inserted into the seat mounting groove 8 before plastic deformation, almost no gap is formed between the outermost peripheral surface 20d of the valve seat 200 and the outer crimped portion 7B. When the inner crimped portion 7A and the outer crimped portion 7B are plastically deformed using the crimping jig 100 from this state, as shown in FIG. 10( b), the inner crimped portion 7A tilts from near its base, compressing and engaging the innermost peripheral surface 20c and inner tapered surface 20g of the valve seat 200, while the inclined portion 7Bb at the tip end of the outer crimped portion 7B significantly bites into the outermost peripheral surface 20d of the valve seat 20, excessively compressing the valve seat 200. At the same time, the root portion 7Bc of the outer circumferential crimped portion 7B engages with the outermost peripheral surface 20d of the valve seat 20. At the same time, the lower surface 20b of the valve seat 20 engages with the bottom surface 7C of the seat mounting groove 8. In this way, the inclined portion 7Bb of the outer circumferential crimped portion 7B significantly compresses the valve seat 200, which is thought to result in excessively large compressive stress remaining in the valve seat 200 compared to the case shown in FIG. 6 . When the diaphragm valve 1 is used in a high-temperature atmosphere with the valve seat 200 remaining in a large compressive stress state, the valve seat 200 is heated to a high temperature and expands. This not only causes thermal expansion, but also expansion due to the release of compressive stress within the valve seat 200, which is thought to reduce the gap between the upper surface 20a (as a sealing surface) and the diaphragm 30. This is thought to be the reason why the Cv value of the diaphragm valve 1 decreases excessively when used in a high-temperature atmosphere, making it difficult for gas to flow.

[0021] In this embodiment, the shape of the valve seat 20 is optimized in advance by forming a tapered surface 20e on the valve seat 20 that is inclined to match the inclined portion 7Bb generated by plastic deformation in the outer circumferential crimped portion 7B, so that excessive compressive stress due to crimping is not generated in the valve seat 20. This prevents excessive compressive stress from remaining in the valve seat 20 after plastic deformation of the inner circumferential crimped portion 7A and the outer circumferential crimped portion 7B. As a result, the compressive stress inside the valve seat 200 is released in a high-temperature atmosphere, bringing the diaphragm 30 of the diaphragm valve 1 and the upper surface 20a, which serves as the sealing surface of the valve seat 20, closer together, preventing an excessive decrease in the Cv value.

[0022] Second Embodiment A second embodiment of the present invention will be described with reference to FIG. 7 . Note that the same reference numerals are used in FIG. 7 for the same components as in the first embodiment. The valve seat 20A shown in FIG. 7 has a groove 21 formed circumferentially on its underside 20b, with the remaining configuration being the same as the valve seat 20. When the valve seat 20A undergoes plastic deformation from the state shown in FIG. 7(a) to the state shown in FIG. 7(b), the tapered surface 20e acts to prevent excessive compressive stress from remaining in the valve seat 20A due to the crimping. In addition, after plastic deformation is complete, a gap is formed between the support portion 7 of the valve body 3 and the valve seat 20A. In a high-temperature atmosphere, the groove 21 accommodates a portion of the expansion of the valve seat 20A due to thermal expansion and the release of compressive stress, thereby further preventing the sealing surface 20a of the valve seat 20A from approaching the diaphragm 30. This further reduces the decrease in Cv value in a high-temperature atmosphere compared to the first embodiment.

[0023] Third Embodiment A third embodiment of the present invention will be described with reference to Figure 8. Note that the same reference numerals are used in Figure 8 for the same parts as in the first embodiment. A circumferentially extending groove 9 is formed in the bottom surface 7C of the seat mounting groove 8 formed in the support portion 7 shown in Figure 8. When the state shown in Figure 8(a) changes to the state shown in Figure 8(b) through plastic deformation, a gap is formed between the valve seat 20 and the support portion 7 of the valve body 3. This configuration, similar to the second embodiment, can further suppress the decrease in Cv value in a high-temperature atmosphere compared to the first embodiment.

[0024] Fourth Embodiment A fourth embodiment of the present invention will be described with reference to FIG. 9 . Note that the same reference numerals are used in FIG. 9 for the same components as in the first embodiment. The valve seat 20B shown in FIG. 9 further includes a tapered surface 20k formed between the lower surface 20b of the valve seat 20B and the outermost peripheral surface 20d, and a tapered surface 20j formed between the lower surface 20b of the valve seat 20B and the innermost peripheral surface 20c. The tapered surfaces 20k and 20j are second tapered surfaces of the present invention. When the state shown in FIG. 9(a) changes to the state shown in FIG. 9(b), gaps SP are formed between the support portion 7 and the tapered surfaces 20k and 20j, respectively. In a high-temperature atmosphere, the gaps SP accommodate a portion of the expansion of the valve seat 20B due to thermal expansion and the release of compressive stress, thereby further preventing the upper surface 20a (as the sealing surface) of the valve seat 20B from approaching the diaphragm 30. This further reduces the decrease in Cv value in a high-temperature atmosphere compared to the first embodiment. In this embodiment, the valve seat 20B is formed with the tapered surface 20k and the tapered surface 20j, but it may be formed with only one of them.

[0025] While the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific examples, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. For example, in the above embodiments, the valve body 3 is used as an example of the support member of the present invention, but the present invention is not limited to this, and can also be applied to a case in which a valve mounting groove and two crimping portions are formed in a member called an inner disk that is independent of the valve body 3, and the valve seat 20 is fixed thereto.

[0026] 1: Diaphragm valve 3: Valve body 4, 5, 6: Flow path 7: Support portion 7A: Inner circumferential crimped portion 7B: Outer circumferential crimped portion 7Bb: Inclined portion 7Bc: Base portion 7C: Bottom surface 8: Seat mounting groove 9: Groove portion 10: Cylindrical portion 20: Valve seat 20A: Valve seat 20B: Valve seat 20a: Upper surface (sealing surface) 20b: Lower surface 20c: Innermost circumferential surface 20d: Outermost circumferential surface 20e: Tapered surface 20f: Upper tapered surface 20g: Inner circumferential tapered surface 20j: Tapered surface 20k: Tapered surface 21: Groove portion 30: Diaphragm 32: Pressing adapter 34: Stem 36 : Diaphragm holder 38 : Bonnet 100 : Crimping jig 101 : Crimping groove 102 : Body 101a, 101b : Engagement surface 200 : Valve seat A1 : Upward direction A2 : Downward direction SP : Gap

Claims

1. A diaphragm valve comprising: an annular valve seat; and a support member having an annular seat mounting groove for mounting the valve seat, wherein the support member has an inner circumferential crimped portion and an outer circumferential crimped portion which face each other and form the seat mounting groove, and the valve seat is inclined to match an inclined portion generated by plastic deformation in the outer circumferential crimped portion, and has a tapered surface which engages with the inclined portion.

2. A diaphragm valve as described in claim 1, wherein the valve seat has an annular upper surface as a sealing surface, an annular and flat lower surface opposite the upper surface, an innermost surface perpendicular to the lower surface and engaging with the inner crimped portion, and an outermost surface perpendicular to the lower surface and engaging with the outer crimped portion, and the tapered surface is formed adjacent to the outermost surface.

3. A diaphragm valve as set forth in claim 2, wherein a circumferentially extending groove portion is formed in the bottom surface of the seat mounting groove of said support member, forming a gap between said support member and said valve seat.

4. A diaphragm valve as set forth in claim 2, wherein a circumferentially extending groove is formed on the lower surface of said valve seat, forming a gap between said support member and said valve seat.

5. A diaphragm valve as described in claim 2, wherein a second tapered surface is formed between the lower surface and the outermost peripheral surface of the valve seat, or between the lower surface and the inner peripheral surface of the valve seat, for forming a gap between the support member and the valve seat.

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