Seal load adjustment valve

Abstract

To provide a seal load adjustment valve capable of suppressing deformation of a valve seat to prevent deterioration of sealability even in use under high-temperature environment.SOLUTION: A seal load adjustment valve 1 comprises a seal load adjustment mechanism 30 having a seal load adjustment member 31 which adjusts a seal load of a valve body 28 for a valve seat 24 by causing the valve body 28 to approach and separate from the valve seat 24 as a stem 19 moves up and down and to open and close the valve, and by causing at least a central part symmetrical about a central axis to bulge and come into contact with a surface 19b perpendicular to an axis of the stem 19 so as to increase a thrust in a direction opposite to a valve closing direction in an axial direction of the stem 19 as an operating temperature of the valve increases.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a valve for controlling the flow of a fluid, and more particularly to a valve for controlling the flow of a high-temperature fluid by opening and closing a valve body by moving a stem up and down to approach and separate from a valve seat. [Background technology]

[0002] In recent years, in semiconductor manufacturing processes and panel manufacturing processes, the gases used in semiconductor manufacturing equipment have become increasingly hot, with high temperatures of over 200° C. now being used. For this reason, there is a demand for valves that control the supply and exhaust of gas to such semiconductor manufacturing equipment to be able to withstand high temperatures, and various high-temperature resistant valves have been proposed.

[0003] For example, Patent Document 1 describes a flow control valve in which the stroke length of a diaphragm can be easily and accurately adjusted, and by regulating the stroke length, the difference in CV value between high temperature and normal temperature is kept within a predetermined value.

[0004] Furthermore, Patent Document 2 describes a valve seat structure for a gas control valve in which a second thickness, which is the height of the valve seat member, is formed to be 0.5 to 1.5 times the first thickness, which is the valve body contact-separation portion in the radial direction. The valve seat structure of this gas control valve ensures sufficient deformation allowance for the diaphragm valve body to penetrate deeper when the valve is closed, and the valve seat member and the diaphragm valve body are in close contact to ensure high sealing performance, thereby blocking the flow of fluids such as high-temperature gas toward the output port without leakage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-189165 A [Patent Document 2] JP 2012-92861 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the flow control valve described in Patent Document 1, the stroke length is equal at high temperature and at room temperature, so that the valve seat is subjected to a load similar to that at room temperature even at high temperature, and there is a risk that the valve seat, whose strength is reduced by high temperature, will be significantly deformed.

[0007] In addition, in the valve seat structure of the gas control valve described in Patent Document 2, the second thickness and the first thickness of the valve seat member are set to predetermined values ​​corresponding to the predetermined high temperature, so that deformation of the valve seat member in response to the thermal expansion and restoring force due to the predetermined high temperature can be expected. However, with regard to deformation of the valve seat member at a temperature different from the predetermined high temperature, the thermal expansion and restoring force change depending on the temperature, so it is unclear whether sealing performance similar to that at the predetermined high temperature can be obtained.

[0008] The present invention was developed to solve the problems of the related art, and its object is to provide a valve for adjusting seal load that can suppress deformation of the valve seat and prevent a decrease in sealing performance even when the control fluid is at a high temperature. [Means for solving the problem]

[0009] In order to achieve the above object, the invention of claim 1 is a sealing load adjusting valve equipped with a sealing load adjustment mechanism having a sealing load adjustment member that adjusts the sealing load of the valve body against the valve seat by raising and lowering the stem so that the valve body approaches and separates from the valve seat to open and close, and at least the central part symmetrical about the central axis bulges and abuts against a surface perpendicular to the axis of the stem so as to increase the thrust in the direction opposite to the valve closing direction in the axial direction of the stem as the operating temperature of the valve rises.

[0010] The invention of claim 2 is a valve for adjusting a sealing load, in which the sealing load adjustment member is a high thermal expansion member made of a spring material with a large thermal expansion coefficient, and the sealing load adjustment mechanism further includes a restricting support member made of a low thermal expansion member with a small thermal expansion coefficient that supports and restricts the sealing load adjustment member from expanding in a direction perpendicular to the axis of the stem.

[0011] The invention of claim 3 is a valve for adjusting a sealing load, in which a regulating support member is annular with a regulating wall portion standing along the circumferential direction, and a sealing load adjustment member is arranged inside the inner surface of the regulating wall portion so that the outer end of this sealing load adjustment member can freely abut against the inner surface.

[0012] The invention of claim 4 is a sealing load adjustment valve in which a small diameter shaft portion is formed at the lower end of the stem via a stepped surface, this stepped surface being a surface perpendicular to the axis of the stem, a sealing load adjustment member is arranged so that the small diameter shaft portion passes through an insertion hole formed in the center and the upper surface can freely abut against the stepped surface, and the valve body is a diaphragm, and the stem is raised and lowered via a diaphragm piece arranged between the small diameter shaft portion of the stem and the diaphragm to move the diaphragm toward and away from the valve seat to open and close the valve.

[0013] The invention according to claim 5 is a valve for adjusting a seal load, in which the restriction support member uses an Invar material.

[0014] The invention according to claim 6 is a valve for adjusting a seal load, in which the stem is raised and lowered using an actuator as a drive source or using a manual handle as a drive source.

[0015] According to the invention of claim 1, the valve is provided with a sealing load adjustment mechanism having a sealing load adjustment member that adjusts the sealing load of the valve body against the valve seat by causing at least the central portion, which is symmetrical about the central axis, to bulge and come into contact with a surface perpendicular to the stem axis so as to increase the thrust in the direction opposite to the valve closing direction in the axial direction of the stem as the operating temperature of the valve rises. As a result, as the operating temperature rises, the central portion of the seal load adjustment member bulges symmetrically about the central axis and abuts against a surface perpendicular to the axis of the stem, increasing the force pushing the stem back in the direction opposite to the valve closing direction. As a result, a substantially constant load is applied to the stem in the valve closing direction, and as the temperature rises, the force pushing the stem back in the opposite direction by the seal load adjustment member increases, and as the temperature rises, the load applied through the stem to the valve seat which has softened, is reduced. In any high temperature range, a load of an appropriate magnitude according to the strength of the valve seat at that temperature is applied to the valve seat through the stem. As a result, deformation of the valve seat can be suppressed and a decrease in sealing performance can be prevented even when used in a high temperature environment.

[0016] According to the invention of claim 2, the seal load adjustment member is a high thermal expansion member made of a spring material with a large thermal expansion coefficient, and the seal load adjustment mechanism further includes a restricting support member made of a low thermal expansion material with a small thermal expansion coefficient that supports and restricts the seal load adjustment member from expanding in a direction perpendicular to the axis of the stem. As a result, the sealing load adjustment member, which expands as the operating temperature rises, is prevented from expanding in a direction perpendicular to the axis of the stem by the regulating support member with a low thermal expansion coefficient, and expansion in the axial direction of the stem in the opposite direction to the valve closing direction is promoted, thereby increasing the force with which the sealing load adjustment member abuts against a surface perpendicular to the stem axis as the operating temperature rises, pushing the stem back in the opposite direction to the valve closing direction. As a result, the stem is subjected to a substantially constant load in the valve closing direction, and the force pushing the stem back in the opposite direction is effectively increased by the high thermal expansion member which expands as the temperature rises, and the load acting through the stem on the valve seat which softens as the temperature rises is reduced. In any high temperature range, a load of an appropriate magnitude according to the strength of the valve seat at that temperature is acted on the valve seat through the stem. As a result, deformation of the valve seat can be suppressed and a decrease in sealing performance can be prevented even when used in a high temperature environment.

[0017] According to the invention of claim 3, the regulating support member is annular in shape having a regulating wall portion standing upright in the circumferential direction, and a sealing load adjustment member is arranged inside the inner surface of the regulating wall portion so that the outer peripheral end of this sealing load adjustment member can freely abut against the inner surface. As a result, the sealing load adjustment member is prevented from expanding in a direction perpendicular to the axis of the stem by the regulating wall portion that rises along the circumferential direction of the regulating support member, which is a low thermal expansion member, and the force pushing the stem back in the reverse direction by the sealing load adjustment member is evenly distributed around the circumferential direction of the stem centered on the stem axis and applied to the stem, so that the pushing back force corresponding to the temperature rise can be applied to the stem more effectively by the sealing load adjustment member.

[0018] According to the invention of claim 4, a small diameter shaft portion is formed at the lower end of the stem via a stepped surface, and this stepped surface is a surface perpendicular to the axis of the stem, and the seal load adjustment member is arranged so that the small diameter shaft portion passes through an insertion hole formed in the center so that the upper surface can freely abut against the stepped surface, and the valve body is a diaphragm, and the diaphragm is opened and closed by moving the stem up and down via a diaphragm piece arranged between the small diameter shaft portion of the stem and the diaphragm. As a result, the force pushing the stem in the opposite direction by the seal load adjustment member is transmitted via the step surface, while the load in the valve closing direction is transmitted to the diaphragm from the small diameter shaft portion via the diaphragm piece in a manner suitable for the diaphragm. Therefore, even when the diaphragm valve is used in a high temperature environment, deformation of the valve seat can be suppressed and deterioration of the sealing performance can be prevented.

[0019] According to the invention of claim 5, since the regulating support member is made of Invar material, it hardly expands even when used in a high temperature environment. Therefore, the force pushing the stem back in the reverse direction can be adjusted by taking into account only the expansion rate of the seal load adjustment member, which expands as the operating temperature rises. As a result, the force pushing the stem back in the reverse direction can be easily adjusted.

[0020] According to the invention of claim 6, the stem can be raised and lowered using an actuator as a drive source or by operating a manual handle as a drive source, making it applicable to both automatic and manual valves. [Brief description of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of a seal load adjusting valve according to a first embodiment in a valve open state. [Diagram 2] 1 is a cross-sectional view showing a schematic configuration of a seal load adjusting valve according to a first embodiment in a valve closed state. [Diagram 3] 6 is a graph showing the relationship between temperature and the force (reaction force) with which the seal load adjusting member pushes back the stem in the opposite direction. [Figure 4] FIG. 6 is a cross-sectional view showing a schematic configuration of a seal load adjusting valve according to a second embodiment in an open state. [Diagram 5] 11 is a diagram for explaining how a seal load adjustment member of a seal load adjustment valve increases a thrust force in a direction opposite to the valve closing direction in the axial direction of the stem as the temperature rises. FIG. [Figure 6] FIG. 13 is a diagram for explaining a modified example of the stem.

[0022] A first embodiment of a seal load adjusting valve according to the present invention will be described in detail with reference to Figs. The present disclosure is not limited to the embodiments shown below. It should be noted that the drawings are schematic, and the dimensional relationships and ratios of each element may differ from the reality. Furthermore, the drawings may include parts with different dimensional relationships and ratios. Fig. 1 is a cross-sectional view showing a schematic configuration of a seal load adjustment valve 1 according to embodiment 1 in a valve open state. Fig. 2 is a cross-sectional view showing a schematic configuration of a seal load adjustment valve 1 according to embodiment 1 in a valve closed state.

[0023] The seal load adjustment valve 1 according to the first embodiment of the present invention has a drive mechanism section 10, a valve body section 20, and a base section 40 that connects the drive mechanism section 10 and the valve body section 20 together.

[0024] <Regarding the driving mechanism 10> The drive mechanism 10 has pistons 12, 13 provided in two spaces, upper and lower, inside a casing 11 partitioned by a sub-base 11a, and air chambers 14, 15 formed between the upper piston 12 and the sub-base 11a, and between the lower piston 13 and the inner wall of the base 40, respectively. This drive mechanism 10 constitutes an air-driven actuator in which two pistons 12, 13 in two stages, one above the other, move up and down by supplying and discharging air to the two air chambers 14, 15, and a stem 19 moves up and down in conjunction with the up and down movement of the two pistons 12, 13.

[0025] An air connection portion 16 is provided on the upper surface of the casing 11 of the drive mechanism portion 10 for introducing air supplied from an air supply source (not shown) into the casing 11. Inside the casing 11, an air flow path 17 that connects the air connection portion 16 to the two air chambers 14, 15 is provided.

[0026] In addition, a spring 18 is disposed between the upper piston 12 and the casing 11, and this spring 18 exerts a downward biasing force on the upper piston 12, and this downward biasing force is also exerted on the lower piston 13 which abuts against the upper piston 12 at its lower side. The lower piston 13 is capable of freely coming into contact with a stem 19 disposed below the lower piston 13. The stem 19 receives a downward urging force from a spring 18 via the upper and lower pistons 12, 13.

[0027] <Regarding the stem 19 of the drive mechanism 10> The majority of the stem 19 is inserted into the stem guide hole 41 in the base portion 40 and is guided by the stem guide hole 41 so as to be able to move up and down freely, with its upper end protruding into the casing 11 so as to be able to abut against the piston 13 on the lower stage, and its lower end protruding into the body 21 so as to be able to abut against the diaphragm piece 27. This stem 19 has a small diameter shaft portion 19a formed via a stepped surface 19b at its lower end which abuts against the diaphragm piece 27, and this stepped surface 19b is a surface perpendicular to the axis of the stem 19 which abuts against the upper surface 31b of the seal load adjustment member 31 described later.

[0028] <Regarding the valve body 20> The valve main body 20 has an inlet side flow passage 22 which serves as a gas inlet and an outlet side flow passage 23 which serves as a gas outlet inside a body 21, and a valve seat 24 is provided between the inlet side flow passage 22 and the outlet side flow passage 23.

[0029] The body 21 has an outer hull that is generally rectangular parallelepiped in shape, and a threaded portion that can be screwed into the casing 11 is formed on the upper inner circumferential surface, and a portion into which the bonnet 25 is fitted is formed on the inner side thereof. Inside the body 21 , a diaphragm 28 is fixed with its outer periphery sandwiched between a step of the body 21 and the bonnet 25 in a state in which it can freely come into contact with the valve seat 24 . An inlet side passage 22 is drilled in the body 21 from the bottom surface to the valve chamber 26 along the axial center position of the stem 19, and a valve seat 24 is fixed to the peripheral portion of the opening where the inlet side passage 22 connects to the valve chamber 26.

[0030] The valve seat 24 is ring-shaped and made of a fluororesin such as PFA (perfluoroalkoxyalkane). The material of the valve seat 24 is not limited to fluororesin, and other materials may be used as long as they have heat resistance and chemical resistance.

[0031] The bonnet 25 has a generally flat cylindrical shape, and supports a diaphragm piece 27 inside the cylinder so that the diaphragm piece 27 can slide up and down. The diaphragm piece 27 is adapted to come into contact with the small diameter shaft portion 19 a of the stem 19 which protrudes into the body 21 through the base portion 40 .

[0032] The bonnet 25 has an upright wall portion 25a that stands along the circumferential direction on the outer circumferential edge portion, and the restricting support member 32 is fitted inside this upright wall portion 25a.

[0033] The diaphragm 28 is generally disk-shaped, and in this embodiment, a plurality of diaphragms made of a nickel-cobalt alloy are stacked on top of each other. The diaphragm 28 has its outer peripheral edge sandwiched and fixed between a step of the body 21 and the bonnet 25 to form an outer peripheral seal portion of the valve chamber 26 .

[0034] <Regarding the seal load adjustment mechanism 30 provided in the valve body 20> The seal load adjustment mechanism 30 will be described in detail below. The sealing load adjustment mechanism 30 comprises a sealing load adjustment member 31 with a large thermal expansion coefficient that is freely abutted against the step surface 19b, which is a surface perpendicular to the axis of the stem 19, and a restricting support member 32 with a small thermal expansion coefficient that supports and restricts the expansion of the sealing load adjustment member 31 in a direction perpendicular to the axis so that the sealing load adjustment member 31 increases the thrust in the axial direction of the stem 19 opposite the valve closing direction as the operating temperature of the valve increases.

[0035] <Regarding the seal load adjusting member 31> The seal load adjusting member 31 is a spring material that bulges symmetrically about a central axis and has a large coefficient of thermal expansion, and is made of, for example, stainless steel. The seal load adjusting member 31 has an end face with a bulging dome-like outer shape, and has an insertion hole 31a formed in the center, through which the small diameter shaft portion 19a of the stem 19 is inserted. The insertion hole 31 a has a diameter slightly larger than the diameter of the small diameter shaft portion 19 a of the stem 19 . In addition, as long as the seal load adjustment member 31 has a shape in which at least the central portion is bulged symmetrically about the central axis, it may have, for example, a dome-shaped central portion and an outer peripheral end edge surface that protrudes radially outward like a brim.

[0036] The seal load adjusting member 31 is disposed inside the body 21 such that the small diameter shaft portion 19a passes through an insertion hole 31a formed in the center thereof and an upper surface 31b can freely come into contact with the step surface 19b of the stem 19. More specifically, the seal load adjusting member 31 is disposed inside the body 21 with the small diameter shaft portion 19a of the stem 19 inserted through an insertion hole 31a and supported by a restriction support member 32. When this sealing load adjustment member 31 is in an elastically neutral state, its upper surface 31b is just in contact with the step surface 19b of the stem 19, or is slightly spaced from the step surface 19b, i.e., there is some play between the upper surface 31b of the sealing load adjustment member 31 and the step surface 19b of the stem 19. In other words, when the valve is in a fully open state, the reaction force of the seal load adjusting member 31 does not act on the stem 19 .

[0037] In addition, when a play is provided between the upper surface 31b of the seal load adjusting member 31 and the step surface 19b of the stem 19 when the seal load adjusting member 31 is in an elastically neutral state, the amount of the play is set to be smaller than the stroke of the stem 19. For example, if the stroke of the stem 19 required to fully open the valve is 0.6 mm, and when the valve is closed the stem 19 is pressed downward 0.2 mm from the no-load position against the seal load adjustment member 31, and the reaction force is applied to the stem 19, the amount of play should be set to 0.4 mm. The amount of play between the upper surface 31b of the seal load adjusting member 31 and the step surface 19b of the stem 19 may be adjusted appropriately according to the reaction force that is to be applied to the stem 19 by the seal load adjusting member 31.

[0038] <Regarding the Regulating Support Member 32> The restriction support member 32 has an annular shape and is made of, for example, an Invar alloy. This regulating support member 32 has a circular mounting surface 32a on which the seal load adjustment member 31 is placed, and a regulating wall portion 32b that stands up circumferentially on the outer circumferential edge portion of the mounting surface 32a so as to be able to freely abut against the outer circumferential end portion 31c of the seal load adjustment member 31 placed on the mounting surface 32a.

[0039] The outer diameter of the mounting surface 32a is set to be substantially equal to the diameter of the outer circumferential end portion 31c of the seal load adjusting member 31 in an elastically neutral state.

[0040] The height of the restricting wall portion 32b is set to be higher than the height of the outer circumferential end portion 31c of the sealing load adjusting member 31 placed on the placement surface 32a. The height of the restriction wall portion 32b is set to be lower than the height of the upright wall portion 25a of the bonnet 25.

[0041] <Materials of the sealing load adjusting member 31 and the restricting support member 32> In this embodiment 1, the seal load adjustment member 31 is made of a material having a thermal expansion coefficient that generates a reaction force that reduces the load on the valve seat 24 when the valve seat 24 softens with an increase in temperature, to a degree that does not affect the sealing performance. Moreover, the regulating support member 32 is made of a material that hardly expands even at high temperatures exceeding 200°C. Therefore, the sealing load adjusting member 31 and the restricting support member 32 may be made of materials other than those shown in the first embodiment, so long as the materials satisfy these properties. In addition, in consideration of heat resistance, it is more preferable that the seal load adjusting member 31 and the restricting support member 32 are made of a metal material.

[0042] Such a sealing load adjustment mechanism 30 can be easily assembled to the valve body 20 by fitting the regulating support member 32 to the bonnet 25 and positioning the sealing load adjustment member 31 so that the outer peripheral end portion 31c is positioned inside the inner peripheral surface 32c of the regulating wall portion 32b of the regulating support member 32 with the small diameter shaft portion 19a of the stem 19 passing through the insertion hole 31a.

[0043] <Regarding the base portion 40> The base portion 40 connects the casing 11 of the drive mechanism portion 10 and the body 21 of the valve main body portion 20, and has a stem guide hole 41 formed therein through which the stem 19 passes so as to be able to move up and down freely. The upper and lower parts of the base part 40 have, for example, a screw structure, so that the upper part is screwed into a screw part provided on the casing 11 and the lower part is screwed into a screw part provided on the body 21 . This base portion 40 has a reduced outer diameter compared to the casing 11 and the body 21 so that heat from the valve main body portion 20 is less likely to be conducted to the drive mechanism portion 10, and connects between the casing 11 and the body 21 with an overall narrowed shape.

[0044] <Relationship between temperature and the force (reaction force) that the seal load adjusting member 31 pushes back the stem in the opposite direction> Here, the results of an analysis conducted by the present inventors on the relationship between the force (reaction force) with which the seal load adjusting member 31 pushes back the stem 19 in the opposite direction and temperature will be described with reference to FIG. FIG. 3 is a graph showing the relationship between the force (reaction force) with which the seal load adjusting member 31 pushes the stem 19 back in the opposite direction and temperature. Here, in the graph shown in FIG. 3, the horizontal axis indicates the change in temperature, and the vertical axis indicates the force (reaction force) with which the seal load adjusting member 31 pushes back the stem 19 in the opposite direction.

[0045] In this analysis, SUS631 is assumed as the seal load adjusting material, and its physical property data (coefficient of thermal expansion) is used. In addition, the Invar material FN36 is assumed as the regulating support member, and its physical property data (coefficient of thermal expansion) is used. In this analysis, as an example, as described above, the stem 19 is pressed downwardly against the seal load adjusting member 31 by 0.2 mm from the no-load position, and a reaction force is applied to the stem 19. As shown in FIG. 3, it can be seen that the force (reaction force) of the seal load adjusting member 31 pushing the stem 19 back in the opposite direction increases as the temperature increases. From the results of this analysis, the inventors found that by using a seal load adjustment mechanism 30 having a seal load adjustment member 31 and a regulating support member 32 to apply a reaction force to the stem 19 in response to the rise in temperature, the load applied through the stem 19 is reduced, and a load of an appropriate magnitude in accordance with the strength of the valve seat 24 is applied to the valve seat 24 through the stem 19 at any high temperature range, for the valve seat 24 softened at that temperature.

[0046] <Opening and closing operation of seal load adjustment valve 1> Next, the opening and closing operation of the seal load adjustment valve 1 will be described. When the seal load adjustment valve 1 changes from a valve closed state to a valve open state (see FIG. 1), the stem is moved to the upper end position of the stroke by the drive mechanism 10, and the diaphragm 28 is moved to the valve open position. More specifically, air is introduced into air flow path 17 from an air supply source (not shown) through air connection portion 16, and air is supplied to two air chambers 14, 15 through air flow path 17.

[0047] When air is supplied to the two air chambers 14, 15, the upper piston 12 is moved upward against the biasing force of the spring 18 by the pressure of the air filled in the upper air chamber 14, and the lower piston 13 is also moved upward to follow the upward movement of the upper piston 12 by the pressure of the air filled in the lower air chamber 15. Then, the stem 19, which had been pushed downward by the pistons 12, 13, is released from the load of the pistons 12, 13 and is moved upward together with the diaphragm piece 27 by the elastic restoring force of the diaphragm 28, so that the diaphragm 28 is separated from the valve seat 24, resulting in an open valve state.

[0048] As the stem 19 moves upward, the seal load adjusting member 31, which had been pushed downward by the stem 19, is elastically restored to a neutral state. For example, as described above, if the stroke of the stem 19 required to fully open the valve is 0.6 mm and the amount of play between the upper surface 31b of the seal load adjustment member 31 and the step surface 19b of the stem 19 is 0.4 mm, the diaphragm 28 will elastically restore, causing the stem 19 to be raised to a position where the upper surface 31b of the seal load adjustment member 31 and the step surface 19b of the stem 19 are separated by that amount of play.

[0049] On the other hand, when the seal load adjustment valve 1 changes from an open state to a closed state (see Figure 2), as air is discharged from the two air chambers 14, 15, the air pressure that was moving the two pistons 12, 13 upward decreases, and the upper piston 12 is pushed downward by the force of the spring 18, which in turn pushes the lower piston 13 downward. Then, the stem 19 is pressed downward by the lower piston 13, and the diaphragm 28 is pressed downward via the diaphragm piece 27, so that the diaphragm 28 comes into contact with the valve seat 24 and the valve is closed.

[0050] In this way, when the stem 19 is moved downward to the valve closed state, the step surface 19b of the stem 19 abuts against the upper surface 31b of the seal load adjustment member 31, and the stem 19 presses the seal load adjustment member 31 downward. When the stem 19 presses the seal load adjustment member 31 downward, a force (reaction force) that pushes the seal load adjustment member 31 back in the opposite direction acts on the stem 19 due to the elastic repulsive force of the seal load adjustment member 31. More specifically, when the seal load adjustment member 31 is pushed downward by the stem 19, the portion that bulges toward the central axis of the stem 19 elastically deforms so that it is recessed, and the elastic restoring force acts on the stem 19 as a force that pushes the stem 19 back upward. In addition, when the sealing load adjustment member 31 deforms to concave the bulging portion, it elastically deforms so as to expand in a direction perpendicular to the axis of the stem and also thermally expands, but the outer peripheral end portion 31c of the sealing load adjustment member 31 abuts against the regulating wall portion 32b of the regulating support member 32, preventing this deformation, and the force pushing the stem 19 back upward is applied to the stem 19 more efficiently.

[0051] Furthermore, as is clear from the above-mentioned analysis results, the reaction force of the seal load adjustment member 31 increases as the temperature rises, so that in a high temperature environment, a reaction force of a magnitude corresponding to the high temperature is exerted on the stem 19. In other words, a substantially constant load is applied to the stem 19 in the valve closing direction by the drive mechanism 10, and as the temperature rises, the force pushing the stem 19 back in the opposite direction by the seal load adjustment member 31 increases, and as the temperature rises, the load applied through the stem 19 to the valve seat 24 which has softened as the temperature rises is reduced, so that at any temperature range over high temperatures, a load of an appropriate magnitude according to the strength of the valve seat 24 at that temperature is applied to the valve seat 24 through the stem 19.

[0052] <Effects of the First Embodiment> As described above, the sealing load adjustment valve 1 of embodiment 1 is equipped with a sealing load adjustment mechanism 30 having a sealing load adjustment member 31 that adjusts the sealing load of the valve body 28 against the valve seat 24 by having a central portion symmetrical about the central axis bulge and abut against a step surface 19b perpendicular to the axis of the stem 19 so as to increase the thrust in the direction opposite to the valve closing direction in the axial direction of the stem 19 as the operating temperature of the valve rises. As a result, as the operating temperature rises, the central portion of the seal load adjustment member 31 bulges symmetrically about the central axis and abuts against a surface perpendicular to the axis of the stem 19, thereby increasing the force pushing the stem 19 back in the direction opposite to the valve closing direction. As a result, with respect to the stem 19 which is subjected to a substantially constant load in the valve closing direction, the force pushing the stem 19 back in the opposite direction by the seal load adjustment member 31 increases as the temperature rises, and the load applied through the stem 19 to the valve seat 24 which softens as the temperature rises is reduced, so that at any high temperature range, a load of an appropriate magnitude according to the strength of the valve seat 24 at that temperature is applied to the valve seat 24 through the stem 19. As a result, deformation of the valve seat 24 can be suppressed and a decrease in sealing performance can be prevented even when used in a high temperature environment.

[0053] Furthermore, in the seal load adjustment valve 1 of embodiment 1, the seal load adjustment member 31 is a high thermal expansion member made of a spring material with a large thermal expansion coefficient, and the seal load adjustment mechanism 30 further includes a restricting support member 32 made of a low thermal expansion member with a small thermal expansion coefficient that supports and restricts the seal load adjustment member 31 from expanding in a direction perpendicular to the axis of the stem 19. As a result, the sealing load adjusting member 31, which expands as the operating temperature rises, is prevented from expanding in a direction perpendicular to the axis of the stem 19 by the regulating support member 32, which has a low thermal expansion coefficient, and expansion in the axial direction of the stem 19 in the opposite direction to the valve closing direction is promoted, so that as the operating temperature rises, the sealing load adjusting member 31 abuts against a surface perpendicular to the axis of the stem 19, increasing the force pushing the stem 19 back in the opposite direction to the valve closing direction. As a result, the force pushing the stem 19 back in the opposite direction is effectively increased by the seal load adjustment member 31, which expands as the temperature rises, against the stem 19, which is subjected to a substantially constant load in the valve closing direction, and the load applied through the stem 19 to the valve seat 24, which softens as the temperature rises, is reduced. In any high temperature range, a load of an appropriate magnitude according to the strength of the valve seat 24 at that temperature is applied to the valve seat 24 through the stem 19. As a result, deformation of the valve seat 24 can be suppressed and a decrease in sealing performance can be prevented even when used in a high temperature environment.

[0054] Furthermore, in the sealing load adjustment valve 1 of embodiment 1, the regulating support member 32 is annular in shape having a regulating wall portion 32b standing upright in the circumferential direction, and the sealing load adjustment member 31 is arranged inside the inner surface 32c of the regulating wall portion 32b such that the outer peripheral end portion 31c of this sealing load adjustment member 31 can freely abut against the inner surface 32c. As a result, the sealing load adjustment member 31 is prevented from expanding in a direction perpendicular to the axis of the stem 19 by the regulating wall portion 32b that stands along the circumferential direction of the regulating support member 32, which is a low thermal expansion member, and the force pushing the stem 19 back in the opposite direction by the sealing load adjustment member 31 is evenly distributed around the circumferential direction of the stem 19 centered on the axis of the stem 19 and applied to the stem 19, so that the pushing back force corresponding to the temperature rise can be applied to the stem 19 more effectively by the sealing load adjustment member 31.

[0055] Furthermore, in the seal load adjustment valve 1 of embodiment 1, the stem 19 has a small diameter shaft portion 19a formed at its lower end via a stepped surface 19b, and this stepped surface 19b is a surface perpendicular to the axis of the stem 19. The seal load adjustment member 31 is arranged so that the small diameter shaft portion 19a passes through an insertion hole 31a formed in the center so that the upper surface 31b can freely abut against the stepped surface 19b. The valve body 28 is a diaphragm, and the diaphragm 28 is moved toward and away from the valve seat 24 by the rising and falling movement of the stem 19 via a diaphragm piece 27 arranged between the small diameter shaft portion 19a of the stem 19 and the diaphragm which is the valve body 28, thereby opening and closing the valve body 28. As a result, the force of the seal load adjustment member 31 pushing the stem 19 in the opposite direction is transmitted via the step surface 19b, while the load in the valve closing direction is transmitted from the small diameter shaft portion 19a to the diaphragm 28 via the diaphragm piece 27 in a manner suitable for the diaphragm 28. Therefore, even when the diaphragm valve is used in a high temperature environment, deformation of the valve seat 24 can be suppressed and deterioration of the sealing performance can be prevented.

[0056] Furthermore, in the seal load adjustment valve 1 of embodiment 1, the regulating support member 32 is made of Invar material, and therefore hardly expands even when used in a high temperature environment. Therefore, the force pushing the stem 19 back in the reverse direction can be adjusted by taking into consideration only the expansion rate of the seal load adjustment member 31, which expands as the operating temperature increases. As a result, the force pushing the stem 19 back in the reverse direction can be easily adjusted.

[0057] <Embodiment 2> Next, a seal load adjusting valve 2 according to a second embodiment will be described with reference to FIGS. Fig. 4 is a cross-sectional view showing a schematic configuration of the seal load adjustment valve 2 in an open state according to embodiment 2. Fig. 5 is a view for explaining that the seal load adjustment member 131 of the seal load adjustment valve 2 increases the thrust in the direction opposite to the valve closing direction in the axial direction of the stem 19 as the temperature increases. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and redundant explanations will be omitted. The seal load adjustment valve 2 of the second embodiment differs from the seal load adjustment valve 1 of the first embodiment in that a bimetal is used as a seal load adjustment member 131 of a seal load adjustment mechanism 130 and in that no restriction support member 32 is provided.

[0058] <Regarding the seal load adjustment member 131 of the seal load adjustment valve 2> The seal load adjustment member 131 of the seal load adjustment valve 2 uses a disk-shaped bimetal in which two or more types of metals or alloys with different thermal expansion coefficients are bonded together in the thickness direction. The seal load adjusting member 131 has an insertion hole 131a formed in the center thereof, through which the small diameter shaft portion 19a of the stem 19 is inserted. The insertion hole 131 a has a diameter slightly larger than the diameter of the small diameter shaft portion 19 a of the stem 19 .

[0059] The seal load adjusting member 131 is disposed inside the body 21 such that the small diameter shaft portion 19a passes through an insertion hole 131a formed in the center thereof and an upper surface 131b can freely come into contact with the step surface 19b of the stem 19. More specifically, the seal load adjusting member 131 is disposed inside the body 21 with the small diameter shaft portion 19a of the stem 19 inserted through the insertion hole 131a and placed on the upper surface of the bonnet 25.

[0060] As shown in FIG. 5(a), this seal load adjusting member 131 is in a flat plate state in a room temperature environment. On the other hand, when the seal load adjusting member 131 is changed from a room temperature environment to a high temperature environment, the seal load adjusting member 131 is thermally deformed so that the center portion bulges upward as shown in FIG. 5(b). Therefore, in a high temperature environment, a force (reaction force) pushing back the stem 19 in the opposite direction is applied by the repulsive force of the seal load adjusting member 131. The seal load adjustment member 131 using such a bimetal does not expand in a direction perpendicular to the axis of the stem 19, unlike the one using the high thermal expansion member shown in embodiment 1, and therefore does not need to be supported by the regulating support member 32 of embodiment 1.

[0061] <Effects of the second embodiment> As described above, the sealing load adjustment valve 2 of embodiment 2 is provided with a sealing load adjustment mechanism 130 having a sealing load adjustment member 131 that adjusts the sealing load of the valve body 28 against the valve seat 24 by having a central portion symmetrical about the central axis bulge and abut against a step surface 19b perpendicular to the axis of the stem 19 so as to increase the thrust in the direction opposite to the valve closing direction in the axial direction of the stem 19 as the operating temperature of the valve rises. As a result, as the operating temperature rises, the central portion of the seal load adjustment member 131 bulges symmetrically about the central axis and abuts against the step surface 19b perpendicular to the axis of the stem 19, thereby increasing the force pushing the stem 19 back in the direction opposite to the valve closing direction. As a result, with respect to the stem 19 which is subjected to a substantially constant load in the valve closing direction, the force pushing the stem 19 back in the opposite direction by the seal load adjustment member 131 increases as the temperature rises, and the load applied through the stem 19 to the valve seat 24 which softens as the temperature rises is reduced, so that in any high temperature range, a load of an appropriate magnitude according to the strength of the valve seat 24 at that temperature is applied to the valve seat 24 through the stem 19. As a result, as with the seal load adjusting valve 1 of embodiment 1, deformation of the valve seat 24 can be suppressed and a decrease in sealing performance can be prevented even when used in a high temperature environment.

[0062] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present disclosure.

[0063] For example, in the above embodiment, the stem 19 is raised and lowered using the drive mechanism 10 as a drive source, i.e., an actuator as a drive source, but the stem 19 may also be raised and lowered using a manual handle as a drive source.

[0064] Also, for example, in the above-mentioned embodiment 1, the upper surface 31b of the sealing load adjustment member 31 abuts against the step surface 19b of the stem 19, but other configurations are possible as long as the upper surface 31b of the sealing load adjustment member 31 is provided so as to be able to abut against a surface perpendicular to the axis of the stem 19. For example, as shown in Fig. 6, an expanded diameter portion 19c may be provided in a part of the stem 19, and the upper surface 31b of the sealing load adjustment member 31 may abut against a lower surface 19d of this expanded diameter portion 19c as a surface perpendicular to the axis of the stem 19.

[0065] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0066] 1, 2 Seal load adjustment valve 10 Drive mechanism 11 Casing 11a Sub-bass 12 Piston (upper piston) 13 Piston (lower piston) 14, 15 Air chamber 16 Air connection 17 Air flow path 18 Spring 19 Stem 19a Small diameter shaft part 19b Step surface (surface perpendicular to the stem axis) 19c Expanded diameter part 19d Bottom 20 Valve body 21 Body 22 Inlet side flow path 23 Outlet side flow path 24 Valve seat 25 Bonnet 25a Standing wall section 26 Valve chamber 27 Diaphragm piece 28 Diaphragm (valve body) 30, 130 Seal load adjustment mechanism 31, 131 Seal load adjustment member 31a, 131a Insertion hole 31b, 131b top surface 31c, 131c outer edge 32 Regulatory support member 32a Placement surface 32b Restriction wall 32c Inner surface 40 Base 41 Stem guide hole

Claims

1. A valve in which the valve body moves toward and away from the valve seat by the up and down movement of the stem, a valve for adjusting a sealing load comprising a sealing load adjustment mechanism having a sealing load adjustment member which adjusts the sealing load of the valve body against the valve seat by expanding at least a central portion symmetrical about a central axis and abutting against a surface perpendicular to the axis of the stem so as to increase a thrust force in a direction opposite to the valve closing direction in the axial direction of the stem as the operating temperature of the valve increases.

2. The seal load adjustment member is a high thermal expansion member made of a spring material having a large thermal expansion coefficient, 2. The valve for adjusting a seal load as described in claim 1, wherein the seal load adjustment mechanism further includes a restricting support member made of a low thermal expansion material having a small thermal expansion coefficient that supports and restricts the seal load adjustment member from expanding in a direction perpendicular to the axis of the stem.

3. 3. A valve for adjusting a sealing load as described in claim 2, wherein the regulating support member is annular with a regulating wall portion standing up along a circumferential direction, and the sealing load adjustment member is arranged inside the inner surface of the regulating wall portion so that the outer peripheral end of the sealing load adjustment member can freely abut against the inner surface.

4. The stem has a small diameter shaft portion formed at a lower end thereof via a stepped surface, the stepped surface being a surface perpendicular to the axis of the stem, The seal load adjusting member is disposed so that the small diameter shaft portion passes through an insertion hole formed in a central portion thereof and an upper surface of the seal load adjusting member can freely abut against the step surface, The valve body is a diaphragm, 2. A valve for adjusting a seal load according to claim 1, wherein the diaphragm is opened and closed by moving the stem up and down via a diaphragm piece disposed between the small diameter shaft portion of the stem and the diaphragm, thereby moving the diaphragm toward and away from the valve seat.

5. 3. The seal load adjusting valve according to claim 2, wherein the restriction support member is made of an Invar material.

6. 2. The valve for adjusting a seal load according to claim 1, wherein the stem is raised and lowered by using an actuator as a drive source or by operation of a manual handle as a drive source.

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