Method for manufacturing diaphragm, diaphragm for valve, and diaphragm comprising the same

Abstract

To provide a diaphragm for a valve, which has high resistance against repeated bending and can suppress occurrence of particles.SOLUTION: A diaphragm 15 for a valve comprises a valve body part 15a having a sealing surface 15c for contacting and sealing a valve seat, and a membrane part 15b extending outward from the valve body part 15a and supporting the valve body part 15a. A method for manufacturing the diaphragm 15 for a valve comprises molding a semi-finished product using perfluoroalkoxyalkane as a raw material, and cutting the semi-finished product, wherein the raw material is selected so that the specific gravity is less than 2.135 and the opening / closing durability test result of the diaphragm 15 is 55000 times or more.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a diaphragm suitable for a valve used in various industries such as chemical factories, semiconductor manufacturing fields, liquid crystal manufacturing fields, and food fields. More specifically, the present invention relates to a diaphragm that suppresses the generation of particles, a method for manufacturing the same, and a diaphragm valve including such a diaphragm.

Background Art

[0002] In a diaphragm valve, an inflow-side flow path and an outflow-side flow path communicate with a valve chamber provided in the central portion of a valve body. A diaphragm that isolates the valve chamber and the internal space of a drive unit housing is sandwiched between the valve body and a drive unit housing attached to the upper portion of the valve body. By connecting the diaphragm to the lower end portion of a stem driven by a drive mechanism disposed in the internal space of the drive unit housing, a valve body supported by the diaphragm is brought into pressure contact with and separated from a valve seat provided in the valve chamber, and the space between the inflow-side flow path and the outflow-side flow path is generally opened and closed. Further, in chemical factories, semiconductor manufacturing fields, liquid crystal manufacturing fields, food fields, etc., since fluids with strong corrosiveness or fluids requiring contamination prevention are handled, fluororesin materials excellent in chemical resistance and contamination resistance are widely used for components in contact with fluids in diaphragm valves.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In fields where high cleanliness is required, particles generated within a diaphragm valve can be a problem. For example, in the manufacturing process of semiconductor wafers, contaminants such as particles, various metals, and polymer compounds are generated. If these remain or adhere to the semiconductor wafer, it can have a significant impact on quality. Therefore, in the manufacturing process of semiconductor wafers, the semiconductor wafers are cleaned using a cleaning liquid. However, if particles are generated within the diaphragm valve used on the piping for supplying the cleaning liquid, and the cleaning liquid containing such particles is discharged from the diaphragm valve and used for cleaning the semiconductor wafer, sufficient cleaning cannot be performed, resulting in a problem of reduced cleanliness of the semiconductor wafer. Therefore, it is desirable to suppress the generation of particles in the diaphragm valve, particularly the generation of particles from the diaphragm which is in contact with the liquid and is also a movable part.

[0005] Typical fluororesins used for diaphragms include polytetrafluoroethylene (PTFE) and a copolymer of tetrafluoroethylene (TFE) and perfluoroalkyl vinyl ether (PAVE), namely perfluoroalkoxy alkane (PFA). It is known that PFA is more likely to suppress the generation of particles as described above than PTFE. It is preferable that the diaphragm, particularly the valve seat contact part where particles are likely to be generated, is formed from PFA.

[0006] By the way, due to its molecular structure, the fluidity and mechanical properties of the molded body of PFA change. Also, as described above, the diaphragm used in a diaphragm valve includes a valve body part that comes into contact with and separates from the valve seat, and a membrane part that extends outward from this valve body part and supports the valve body part. In order to withstand repeated bending when repeatedly bringing the valve body part into contact with and separating from the valve seat, flexibility is required for the membrane part.

[0007] However, PFA with a molecular structure that has high fluidity and is easy to use in molding processes has low flexibility and poor resistance to repeated bending. For this reason, for example, Patent Document 1 discloses a valve mechanism unit including a valve unit having a seal unit that seals the valve seat portion in a freely advancing and retracting manner, and a diaphragm unit formed on the side opposite to the seal unit and mounted in the valve chamber. A fluid control valve is disclosed in which a fluororesin is used for the valve seat portion and the valve body portion, and a member formed of PFA is heat-sealed to the valve seat portion and the seal portion of the valve unit. The portion where particles are likely to be generated due to contact and separation is formed of PFA, and the diaphragm unit, that is, the film portion, which requires flexibility and resistance to repeated bending, is formed of a fluororesin. However, when PTFE is used as the above-described fluororesin, the fusion efficiency between PTFE and the PFA used for the valve seat portion and the seal portion of the valve unit is not good, so there is a concern about durability. Furthermore, since the diaphragm unit is made of PTFE, there is a concern about the generation of particles due to repeated bending. Patent Document 2 discloses a diaphragm in which a thin film portion that is difficult to form by injection molding is formed by rolling from a first type of PFA material that has low fluidity but high flexibility, and then a columnar portion is formed by injection molding on the film portion from a second type of PFA material that has high fluidity, and the columnar portion and the film portion are directly joined. However, in order to produce such a diaphragm, both rolling equipment and injection molding equipment are required, which increases the cost.

[0008] Therefore, an object of the present invention is to provide a valve diaphragm that solves the problems existing in the prior art and has high resistance to repeated bending and can suppress the generation of particles.

Means for Solving the Problems

[0009] In view of the above object, the present invention provides, as a first aspect, a method for manufacturing a diaphragm for a valve, the diaphragm having a valve body portion with a sealing surface for abutting and sealing against a valve seat and a film portion extending outward from the valve body portion and supporting the valve body portion, the method including a step of forming a semi-finished product using perfluoroalkoxy alkane as a raw material and a step of performing a cutting process on the semi-finished product, wherein the raw material has a specific gravity of less than 2.135 and is selected such that the opening and closing durability test result of the diaphragm is 55,000 times or more.

[0010] In the above method for manufacturing a diaphragm, perfluoroalkoxy alkane (PFA), which has a specific gravity of less than 2.135 and is selected such that the opening and closing durability test result of the diaphragm is 55,000 or more, is used as the raw material of the diaphragm. Therefore, the entire diaphragm is formed from PFA, and generation of particles can be suppressed as compared with the case of forming a diaphragm from generally used polytetrafluoroethylene (PTFE). Further, the lower the crystallinity of PFA and the higher the molecular weight, the higher the resistance to repeated bending, which is the durability against repeated bending. When the molecular weight is high, the specific gravity is low. Thus, the inventor has found that when the specific gravity is less than 2.135, the opening and closing durability test result improves rapidly, and when the specific gravity is less than 2.135 and the opening and closing durability test result is 55,000 or more, it can withstand use as a diaphragm for a diaphragm valve. In the above method for manufacturing a diaphragm, since a diaphragm is manufactured using PFA having a specific gravity of less than 2.135 and an opening and closing durability test result of 55,000 or more, it is possible to ensure high resistance to repeated bending that can withstand use in a diaphragm valve while suppressing generation of particles due to the use of PFA.

[0011] More preferably, the raw material is selected such that the specific gravity is 2.12 or less and the opening and closing durability test result of the diaphragm for the valve is 1,000,000 times or more. In this case, it is further possible to improve the durability of the diaphragm.

[0012] Further, it is preferable that the raw material is selected such that the flex life value of the diaphragm is 1,900,000 times or more. Also in this case, it is possible to further improve the durability of the diaphragm.

[0013] The step of molding the semi-finished product is preferably a step of injecting the raw material into a mold and producing the semi-finished product by injection molding. The step of performing the cutting process is more preferably a step of performing cutting on the semi-finished product such that at least a mold transfer surface remains on the seal surface. If PFA can be injection molded, mass production can be carried out at low cost. Further, since the mold transfer surface formed by injection molding has a small surface roughness, by leaving the mold transfer surface on the seal surface of the valve portion without performing cutting, a decrease in the surface roughness of the seal surface due to cutting is prevented, and generation of particles due to contact between the seal surface and the valve seat is further suppressed.

[0014] Further, as a second aspect, the present invention provides a valve diaphragm including a valve body portion having a seal surface for abutting against and sealing a valve seat and a film portion extending outward from the valve body portion and supporting the valve body portion, wherein the valve body portion and the film portion are formed by molding using a perfluoroalkoxy alkane selected such that the specific gravity is 2.135 or less and the result of the opening and closing durability test of the diaphragm is 55,000 times or more as a raw material.

[0015] The diaphragm for the valve is entirely formed by molding using perfluoroalkoxy alkane, i.e., PFA, which is selected such that its specific gravity is less than 2.135 and the result of the opening and closing durability test of the diaphragm is 55,000 or more. Therefore, the diaphragm for the valve can suppress the generation of particles as compared with the case of forming a diaphragm from generally used polytetrafluoroethylene (PTFE). Further, the inventor has found that when the specific gravity is less than 2.135, the result of the opening and closing durability test improves rapidly, and when the specific gravity is less than 2.135 and the result of the opening and closing durability test is 55,000 or more, it can withstand use as a diaphragm for a diaphragm valve. Since the diaphragm for the valve is manufactured using PFA with a specific gravity less than 2.135 and an opening and closing durability test result of 55,000 or more, it is possible to ensure high repeated bend resistance that can withstand use in a diaphragm valve while suppressing the generation of particles due to the use of PFA.

[0016] Preferably, the diaphragm for the valve is formed from the raw material having a specific gravity of 2.12 or less and the result of the opening and closing durability test of the diaphragm being 1,000,000 times or more.

[0017] Furthermore, more preferably, the diaphragm for the valve is formed from the raw material having a flex life value of the diaphragm of 19,000,000 times or more.

[0018] Furthermore, preferably, the seal surface is a mold transfer surface formed by injecting the raw material into a mold.

[0019] In one embodiment, the valve body portion includes a main body portion having the seal surface and a reduced-diameter portion thinner than the main body portion, and the reduced-diameter portion is supported by the film portion.

[0020] Further, the film portion may include an annular skirt portion extending in a direction away from the main body portion from the outer peripheral portion of the tip end portion of the small-diameter portion, a bent portion convexly curved in a direction away from the main body portion radially outward from the skirt portion, and a support portion extending planar radially outward from the outer peripheral edge portion of the bent portion.

[0021] In this case, it is preferable that the length of the bent portion is determined to be 1.8 times to 2.8 times the stroke of the valve body portion in the direction of contacting and separating the seal surface with respect to the valve seat. Further, it is preferable that the outer peripheral edge portion of the bent portion extends inclined so as to form an angle in the range of 20° to 40° in a direction away from the seal surface with respect to the support portion toward the valve body portion. Furthermore, it is preferable that a concave portion recessed toward the valve body portion side is formed on the side far from the seal surface at the connection portion between the bent portion and the support portion.

[0022] Furthermore, as a third aspect, the present invention provides a diaphragm valve including the above-described diaphragm for a valve.

Effects of the Invention

[0023] According to the present invention, since the diaphragm for a valve is formed of PFA, generation of particles can be suppressed as compared with the case of forming a diaphragm from generally used PTFE. Further, since the diaphragm for a valve is manufactured using PFA having a specific gravity of less than 2.135 and an opening / closing durability test result of 55000 or more, it is possible to secure high repetitive bend resistance that can withstand use in a diaphragm valve while suppressing generation of particles due to the use of PFA.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0025] Hereinafter, embodiments of the diaphragm for a valve according to the present invention will be described with reference to the drawings. However, it goes without saying that the present invention is not limited to the illustrated embodiments. Further, in the following description, the diaphragm means a valve member including a film portion that supports the valve body portion, and the diaphragm valve means the entire valve that supports the valve body portion by the film portion.

[0026] FIGS. 1 and 2 show the diaphragm 15 for a valve according to the first embodiment of the present invention, and FIG. 3 shows the diaphragm valve 11 including the diaphragm 15 for a valve.

[0027] First, referring to FIG. 3, the overall configuration of the diaphragm valve 11 will be described. The diaphragm valve 11 includes a valve body 13, a diaphragm 15, and a drive unit 17 that drives the diaphragm 15, and the drive unit 17 is attached to the upper part of the valve body 13.

[0028] In the valve body 13, a valve chamber 19 is formed at the upper center, and a first flow path and a second flow path communicating with the valve chamber 19 are formed. In the valve chamber 19, an annular valve seat 21 with which the diaphragm 15 comes into contact and separates is formed around the opening from the first flow path to the valve chamber 19. In the illustrated embodiment, as the first flow path, an inflow path 25 is formed which extends from an inlet 23 formed on one of the opposing side surfaces of the valve body 13 and opens at the center of the bottom of the valve chamber 19. As the second flow path, an outflow path 29 is formed which extends from an outlet 27 formed on the other of the opposing side surfaces of the valve body 13 and opens on the side surface of the valve chamber 21. An annular valve seat 21 that bulges around the opening from the inflow path 25 to the valve chamber 19 is formed.

[0029] A base plate 53 can be further attached to the lower part of the valve body 13 to facilitate installation.

[0030] As shown in detail in FIGS. 1 and 2, the diaphragm 15 includes a valve body portion 15a and a membrane portion 15b extending outward from the valve body portion 15a. In the illustrated embodiment, the valve body portion 15a has a generally cylindrical shape, but it may have other shapes. Also, in the illustrated embodiment, the membrane portion 15b is provided so as to extend radially outward from the outer peripheral portion of the lower end portion of the valve body portion 15a. However, as long as it is connected to the outer peripheral portion of the valve body portion 15a and can support the valve body portion 15a, it may be provided so as to extend radially outward from the upper end portion or the intermediate portion of the valve body portion 15a. Further, a seal surface 15c is formed at the bottom of the valve body portion 15a, and the diaphragm 15 is supported by the valve body 13 such that the seal surface 15c is disposed to face the valve seat 21 by sandwiching the outer peripheral edge portion of the membrane portion 15b between the valve body 13 and the drive unit 17.

[0031] The drive unit 17 includes a drive unit housing 31 attached to the upper part of the valve body 13 and having an internal space formed therein, a stem 35 connected to the diaphragm 15, and a drive mechanism housed in the internal space and driving the stem 35. In the present embodiment, a cylinder portion that opens toward the valve body 13 is formed as an internal space within the drive unit housing 31, and the drive mechanism is constituted by a piston 37 slidably housed within the cylinder portion and a coil spring 39 as a biasing member. Further, a diaphragm retainer 41 is fitted into the opening on the valve body 13 side of the cylinder portion of the drive unit housing 31. When the drive unit 17 is attached to the upper part of the valve body 13, the outer peripheral edge portion of the film portion 15b is sandwiched between the upper surface of the peripheral region around the upper opening of the valve chamber 19 of the valve body 13 and the bottom surface of the diaphragm retainer 41, enabling the diaphragm 15 to be supported by the valve body 13.

[0032] The outer peripheral surface of the piston 37 is in slidable contact with the inner peripheral surface of the cylinder portion in the vertical direction, partitioning the internal space of the cylinder portion into an upper space 43 surrounded by the upper surface of the piston 37, the inner peripheral wall of the cylinder portion, and the ceiling surface of the cylinder portion, and a lower space 45 surrounded by the lower surface of the piston 37, the inner peripheral wall of the cylinder portion, and the bottom surface of the cylinder portion (i.e., the upper surface of the diaphragm retainer 41). Further, the stem 35 is connected to the piston 37 so as to extend downward therefrom. The stem 35 is slidably inserted into a through-hole provided through the diaphragm retainer 41 and extends to the valve chamber 19, and a connection end 35a located at its tip is connected to the diaphragm 15 (specifically, the valve body portion 15a).

[0033] In the diaphragm 15 of the first embodiment shown in FIGS. 1 to 3, a male screw portion is formed on the outer peripheral surface of the connection end 35a of the stem 35, and a female screw portion is formed on the inner peripheral surface of the connection hole 51 provided at the upper center of the valve body portion 15a. The valve body portion 15a is connected to the connection end 35a of the stem 35 by screwing the connection end 35a and the connection hole 53. However, the connection between the connection end 35a of the stem 35 and the valve body portion 15a is not limited to screwing. For example, a locking portion with an enlarged diameter is provided at the connection end 35a of the stem 35, and the connection end 35a is press-fitted into the connection hole provided at the upper center of the valve body portion 15a, so that the connection end 35a and the valve body portion 15a may be connected.

[0034] At the upper part of the drive unit housing 31, a first communication port 47 communicating with the ceiling surface of the cylinder part partitioning the upper space 43 is formed, and it is possible to supply and discharge the working fluid (for example, compressed air) to and from the upper space 43 through the first communication port 47. Further, at the side part of the drive unit housing 31, a second communication port 49 communicating with the bottom of the cylinder part partitioning the lower space 45 is formed, and it is possible to supply and discharge the working fluid to and from the lower space 45 through the second communication port 49. Furthermore, a coil spring 39 is disposed in a compressed state between the upper part of the drive unit housing 31 (ceiling surface of the cylinder part) and the upper surface of the piston 37.

[0035] With such a configuration, when the working fluid is not supplied to the first communication port 47 and the second communication port 49, normally, the piston 37 is biased downward toward the valve body 13 by the coil spring 39 and pushed down. Along with this, the valve body portion 15a of the diaphragm 15 connected to the piston 37 via the stem 35 is moved downward and pressed against the valve seat 21. In addition, by supplying the working fluid (for example, compressed air) to the upper space 43 of the cylinder portion through the first communication port 47 and applying a downward fluid pressure in the direction approaching the valve body 13 to the upper surface of the piston 37, the force acting on the valve body portion 15a from the piston 37 via the stem 35 can be changed, and the force pressing the valve body portion 15a against the valve seat 21 can be adjusted. As a result of the valve body portion 15a being pressed against the valve seat 21, as shown in FIG. 3, the opening from the inflow passage 25 to the valve chamber 19 is closed, and the diaphragm valve 11 is in a closed state. When the working fluid is supplied to the second communication port 49 from this state, the working fluid (for example, compressed air) flows into the lower space 45 of the cylinder portion, and an upward fluid pressure in the direction away from the valve body 13 acts on the lower surface of the piston 37. The piston 37 is pushed upward in the direction away from the valve body 13 against the biasing force of the coil spring 39 (in some cases, in addition to this, the downward fluid pressure exerted by the working fluid in the upper space 43 on the piston 37). At this time, the working fluid in the upper space 43 of the cylinder portion is discharged to the outside through the first communication port 47. When the piston 37 moves upward in the direction away from the valve body 13, the valve body portion 15a of the diaphragm 15 connected to the piston 37 via the stem 35 moves upward and separates from the valve seat 21. As a result, the opening from the inflow passage 25 to the valve chamber 19 is opened, and the diaphragm valve 11 is in an open state. In the open state, the fluid that has flowed into the inflow passage 25 from the inlet 23 of the diaphragm valve 11 flows out to the outside through the valve chamber 19, the outflow passage 29, and the outlet 27.

[0036] With the approach and separation of the valve body portion 15a of the diaphragm 15 from the valve seat 21 accompanying the opening and closing of the diaphragm valve 11 as described above, the bending of the film portion 15b that supports the valve body portion 15a is repeatedly performed. For this reason, the film portion 15b of the diaphragm 15 is required to have resistance to repeated bending.

[0037] The diaphragm 15 according to the first embodiment of the present invention is entirely formed of perfluoroalkoxy alkane (PFA). PFA has a molecular structure that is less likely to generate particles when used as a material for the diaphragm, as compared with polytetrafluoroethylene (PTFE), which is generally used as a material for the diaphragm. Therefore, the generation of particles can be suppressed by forming the diaphragm 15 from PFA. On the other hand, PFA generally has the characteristic of low flexibility. The diaphragm 15, particularly the film portion 15b, repeatedly bends as described above. For this reason, if the diaphragm 15 is formed from a type of PFA with low flexibility, it is likely to be damaged and its durability decreases. However, in recent years, for example, as described in Japanese Patent Application Laid-Open No. 2017-119750, PFA with a high-flexibility molecular structure has been developed and is now in circulation. PFA has a lower crystallinity, and the higher the molecular weight, the higher the resistance to repeated bending, which is the durability against repeated bending, and when the molecular weight is high, the specific gravity is low. From this, the inventor has found that when the specific gravity is less than 2.135, the result of the opening and closing durability test improves rapidly, and when the specific gravity is less than 2.135 and the result of the opening and closing durability test is 55,000 times or more, it can withstand use as a diaphragm for a diaphragm valve. Therefore, as the PFA used for the diaphragm 15, those with a specific gravity less than 2.135 and an opening and closing durability test result of 55,000 or more are selected. Alternatively, as the PFA used for the diaphragm 15, those with a specific gravity less than 2.135 and a flex life value of 180,000 times or more may be selected. Preferably, the diaphragm 15 is formed from PFA with a specific gravity of 2.12 or less and an opening and closing durability test result of 1,000,000 times or more, or PFA with a specific gravity of 2.12 or less and a flex life value of 19,000,000 times or more.

[0038] Here, the opening and closing durability test was conducted by attaching a diaphragm to a diaphragm valve with a diameter of the opening from the inflow passage 25 to the valve chamber 19 (i.e., orifice diameter) of 1 / 8 inch, with the fluid temperature at room temperature, constantly applying a fluid pressure of 0.5 MPa, an opening and closing operation pressure of 0.5 Mpa, and an opening and closing stroke (the moving distance of the valve body portion 15a relative to the valve seat 19 during opening and closing) of 1.1 mm. While repeatedly switching the environmental temperature between 5°C for 6 hours and 100°C for 6 hours, the opening and closing were repeated with an opening time of 1.2 seconds and a closing time of 0.8 seconds, and the number of times until the diaphragm was damaged was measured. Also, the flex life value was measured in accordance with JIS P 8115.

[0039] Furthermore, in order to be able to produce the diaphragm 15 by injection molding, it is preferable that the PFA has a melt flow rate (MFR) measured in accordance with ASTM D1238 at a load of 5 kg and a measurement temperature of 372 ± 0.1°C of 3 g / 10 minutes or less. When forming the diaphragm 15 from PFA by injection molding, for example, after producing a semi-finished product by injection molding of the above-mentioned type of PFA, a part that is difficult to form by injection molding due to factors such as being thin like the film portion 35b can be formed by cutting, and thus the diaphragm 15 can be produced. By producing the diaphragm 15 by injection molding, the contact surface with the mold surface in the molded product becomes the mold transfer surface, so the surface roughness is smaller and the smoothness is higher than that of the surface by cutting. Therefore, by subjecting the semi-finished product produced by injection molding to cutting so as to leave a metal transfer surface on the liquid contact surface, the diaphragm 15 can be produced, and the smoothness of the liquid contact surface can be increased and the generation of particles can be suppressed. In particular, by subjecting the semi-finished product produced by injection molding to cutting so as to leave a metal transfer surface on the seal surface 15c of the valve body portion 15a that repeatedly contacts and separates from the valve seat 21, the diaphragm 15 can be produced, preventing a decrease in the surface roughness of the seal surface 15c by cutting and increasing the smoothness of the seal surface 15c, so that the friction with the valve seat 21 can be reduced and the generation of particles can be suppressed.

[0040] Note that the valve body 13, the drive housing 31 of the drive unit 17, the stem 35, and the piston 37 are preferably formed of a fluororesin material in order to prevent corrosion by fluids. As the fluororesin material, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), or polychlorotrifluoroethylene (PCTFE) can be used.

[0041] Next, the operation of the diaphragm valve 11 shown in FIG. 3 will be described.

[0042] In a normal state where no operating fluid (e.g., compressed air) is supplied to the drive unit 17 from the first communication port 47 and the second communication port 49, the piston 37 of the drive unit 17 is biased downward in a direction approaching the valve body 13 by the coil spring 39 and is moved, that is, pushed down. Along with this, the valve body portion 15b is also moved downward via the stem 35 together with the piston 37. As a result, the sealing surface 15c of the valve body portion 15a is pressed against the valve seat 21, and the diaphragm valve 11 is in a closed state as shown in FIG. 3. When it is desired to increase the sealing thrust, an operating fluid is supplied to the upper space 43 of the cylinder portion through the first communication port 47, and in addition to the biasing force by the coil spring 39, the fluid pressure of the operating fluid flowing into the upper space 43 is made to act downward on the upper surface of the piston 37, thereby changing the force, that is, the pressing force, for pressing the sealing surface 15c of the valve body portion 15a against the valve seat 21 via the stem 35, and the force for pressing the valve body 15 against the valve seat 21 can also be adjusted.

[0043] From this state, when the working fluid is supplied to the second communication port 49 of the drive unit 17 in a state where the supply of the working fluid from the first communication port 47 is stopped (for example, compressed air), the fluid pressure of the working fluid flowing into the lower space 45 of the cylinder part through the second communication port 49 acts upward on the piston 37 (that is, in a direction away from the valve body 13), and the piston 37 is moved upward in a direction away from the valve body 13 against the biasing force of the coil spring 39 and the fluid pressure of the working fluid in the upper space 43, that is, pushed up. At this time, the working fluid in the upper space 43 is discharged to the outside through the first communication port 47. When the piston 37 is pushed up, the valve body part 15a is also moved upward via the stem 35, and the sealing surface 15c of the valve body part 15a is separated from the valve seat 21, and the diaphragm valve 11 is in an open state.

[0044] When the supply of the working fluid to the second communication port 49 is stopped, due to the biasing force of the coil spring 39, the piston 37 is biased downward again and pushed down, the sealing surface 15c of the valve body part 15a is pressed against the valve seat 21, and it becomes a closed state again.

[0045] Thus, as the diaphragm 15 moves up and down at the valve body portion 15a of the diaphragm 15 (i.e., approaches and separates from the valve seat 21) with the opening and closing of the diaphragm valve 11, the film portion 15 that supports the valve body portion 15a repeats bending. Also, the lower the crystallinity and the higher the molecular weight of PFA, the higher the resistance to repeated bending, which is the durability against repeated bending, and the specific gravity decreases as the molecular weight increases. The diaphragm 15 is made of PFA with a specific gravity less than 2.135 and an opening and closing durability test result of 55,000 or more, or PFA with a specific gravity less than 2.135 and a flex life value of 180,000 or more. Preferably, it is made of PFA with a specific gravity of 2.12 or less and an opening and closing durability test result of 1,000,000 or more, or PFA with a specific gravity of 2.12 or less and a flex life value of 19,000,000 or more. Therefore, the diaphragm 15 has sufficient resistance to repeated bending and can ensure sufficient durability. Also, when the diaphragm valve 11 opens and closes, the valve body portion 15a is pressed against or separated from the valve seat 21 as the film portion 15b moves or bends. Therefore, due to the impact and friction when the valve body portion 15a contacts the valve seat 21 and the repeated bending of the film portion 15b, particles are likely to be generated from the diaphragm 15. However, the diaphragm 15 is made of PFA with a molecular structure that is less likely to generate particles. Therefore, the diaphragm 15 has an effect of suppressing the generation of particles compared to the case of using other fluororesin materials such as PTFE. That is, the diaphragm 15 can suppress particles by using PFA and can ensure high resistance to repeated bending that can withstand use in a diaphragm valve.

[0046] The present invention is not limited to the configuration of the diaphragm 15 of the first embodiment. FIG. 4 shows a diaphragm 111 including a valve diaphragm 115 according to a second embodiment of the present invention.

[0047] First, referring to FIG. 4, the overall configuration of the diaphragm valve 111 will be described. Similar to the diaphragm valve 11, the diaphragm valve 111 includes a valve body 113, a diaphragm 115, and a driving unit 117 that drives the diaphragm 115, and the driving unit 117 is attached to the upper part of the valve body 113.

[0048] In the valve body 113, similar to the case of the diaphragm valve 11, a valve chamber 119 is formed at the upper center, and a first flow path and a second flow path communicating with the valve chamber 119 are formed. In the valve chamber 119, a raised valve seat 121 with which the diaphragm 115 comes into contact and separates is formed around the opening from the first flow path to the valve chamber 119. In the embodiment shown in FIG. 4, as the first flow path, an inflow path 125 is formed that extends from an inlet 123 formed on one of the opposing side surfaces of the valve body 113 and opens at the center of the bottom of the valve chamber 119. As the second flow path, an outflow path 129 is formed that extends from an outlet 127 formed on the other of the opposing side surfaces of the valve body 113 and opens on the side surface of the valve chamber 121. An annular valve seat 121 that bulges around the opening from the inflow path 125 to the valve chamber 119 is formed.

[0049] As shown in detail in FIG. 5, the diaphragm 115 includes a valve body portion 115a and a film portion 115b that extends outward from the valve body portion 115a. The valve body portion 115a has a so-called poppet shape including a main body portion 155 and a reduced-diameter portion 157 that is thinner than the main body portion 155. The reduced-diameter portion 157 preferably has a tapered shape that becomes thinner toward the end (tip) on the driving unit 117 side. Further, the film portion 115b is formed to extend outward from the outer peripheral portion of the tip (the end on the driving unit 117 side) of the reduced-diameter portion 157 of the valve body portion 115a. Specifically, the film portion 115b includes an annular skirt portion 159 that extends upward from the outer peripheral portion of the tip (the end on the driving unit 117 side) of the reduced-diameter portion 157 of the valve body portion 115a toward the driving unit 117, a bent portion 161 that extends convexly in a direction away from the valve body portion 115a in the radial direction outward from the upper end portion of the skirt portion 159, and a support portion 163 that extends in the radial direction outward from the outer peripheral edge portion of the bent portion 161.

[0050] The bent portion 161 is a portion that supports the valve body portion 115a so as to allow the up and down movement of the valve body portion 115a for approaching and separating from the valve seat 112 when the diaphragm valve 111 opens and closes. The longer the length of the bent portion 161, the gentler the degree of bending with respect to the stroke (moving distance) of the valve body portion 115a when the diaphragm valve 111 opens and closes. Therefore, the stress generated during the up and down movement of the valve body portion 115a becomes smaller, and the generation of particles is less likely to occur. On the other hand, the longer the length of the bent portion 161, the easier it is for the film portion 115b of the diaphragm 115 to receive, as fluid pressure, the force in the direction of pulling the valve body portion 115a away from the valve seat 121 from the fluid. As a result, it is necessary to increase the sealing thrust, which is the force for pressing the valve body portion 115a against the valve seat 121 by the driving portion 117, by an amount corresponding to the fluid pressure received by the film portion 115b, and particles are likely to be generated. Also, as the length of the bent portion 161 increases, it is necessary to increase the valve chamber 119, resulting in the demerit that the overall size of the diaphragm valve 111 also increases. Therefore, in order to achieve the effect of suppressing the generation of particles while suppressing an increase in the size of the diaphragm valve 111, the length of the bent portion 161 is 1.8 to 2.8 times the moving distance, that is, the stroke, of the valve body portion 115a when the diaphragm valve 111 opens and closes, and it is preferably 2.1 to 2.4 times the stroke. If the length of the bent portion 161 is 2.1 times or more the stroke of the valve body portion 115a when the diaphragm valve 111 opens and closes, the stress generated in the film portion 115b of the diaphragm 115 becomes low. If the length of the bent portion 161 is 2.4 times or less the stroke of the valve body portion 115a when the diaphragm valve 111 opens and closes, the force in the direction of pulling the valve body portion 115a away from the valve seat 121 received by the film portion 115b of the diaphragm valve 115 due to the fluid pressure decreases, and the sealing thrust can be reduced. Therefore, if the length of the bent portion 161 is in the range of 2.1 to 2.4 times the stroke of the valve body portion 115a when the diaphragm valve 111 opens and closes, the effect of suppressing the generation of particles while suppressing an increase in the size of the diaphragm valve 111 is particularly enhanced.

[0051] In addition, since the valve body portion 115a has a poppet shape, even if the valve body portion 115a is arranged in the valve chamber 119 of the same width, the gap between the inner peripheral surface of the valve chamber 119 and the outer peripheral surface of the upper portion of the small-diameter portion 157 of the valve body portion 115a becomes wider, and it becomes easier to secure the length of the bent portion 161.

[0052] As shown in detail in FIGS. 5 and 7, the support portion 163 of the diaphragm 115 includes an annular first horizontal support portion 163a that extends horizontally (parallel to the seal surface 115c) radially outward from the outer peripheral edge of the bent portion 161, a cylindrical vertical support portion 163b that is located outside the first horizontal support portion and extends in the vertical direction (vertical direction), and an annular second horizontal support portion 163c that is located outside the vertical support portion and extends in the horizontal direction. As shown in FIG. 7, the outer peripheral edge portion of the bent portion 161 on the first horizontal support portion 163a side is inclined and extends from the first horizontal support portion 163a so as to form an angle θ with respect to the first horizontal support portion 163a in a direction away from the seal surface 115c toward the valve body portion 115a. The angle θ is in the range of 20° to 40°, and preferably in the range of 25° to 35°. If the angle θ is 25° or more, the stress generated in the film portion 115b of the diaphragm 115 can be reduced, and the effect of suppressing the generation of particles from the diaphragm 115 can be further enhanced. Also, if the angle θ is 35° or less, the angle formed by both side surfaces of the recess 165 described later becomes an obtuse angle, making processing easier and reducing the defect rate. Further, a stepped portion is provided at the upper opening of the valve chamber 119 of the valve body 113. When a protruding portion 131a that protrudes and extends from the center of the bottom of the drive unit housing 131 of the drive unit 117 described later is inserted into the upper opening of the valve chamber 119 of the valve body 113, the first horizontal support portion 163a is sandwiched between the tip surface (bottom surface) of the protruding portion 131a of the drive unit housing 131 and the horizontal surface of the stepped portion of the upper opening of the valve chamber 119 of the valve body 113, and the vertical support portion 163b is sandwiched between the outer peripheral surface of the protruding portion 131a of the drive unit housing 131 and the vertical surface of the stepped portion of the upper opening of the valve chamber 119 of the valve body 113. Furthermore, by sandwiching the second horizontal support portion 163c between the bottom surface of the drive unit housing 131 located outside the protruding portion 131a and the upper surface of the peripheral region of the upper opening of the valve chamber 119 of the valve body 113, the diaphragm 115 can be fixed and supported to the valve body 113 so that the seal surface 115c is disposed to face the valve seat 121.

[0053] Furthermore, as shown in FIG. 5, a recess 165 that is recessed toward the valve body portion 115a is formed on the side far from the seal surface 115c at the connection portion between the bent portion 161 and the first horizontal support portion 163a.

[0054] The drive unit 117 includes a drive unit housing 131 that is attached to the upper part of the valve body 113 and has an internal space formed therein, a lid member 133 that is attached to the upper part of the drive unit housing 131, a stem 135 that is connected to the diaphragm 115, and a drive mechanism that is housed in the internal space and drives the stem 135. The internal space of the drive unit housing 131 is formed as a cylinder portion that opens upward, and the drive mechanism is composed of a piston 137 that is slidably housed in the cylinder portion and a coil spring 139 as a biasing member. Further, a protruding portion 131a protrudes from the center of the bottom surface of the drive unit housing 131, and when the drive unit 117 is attached to the upper part of the valve body 113, the protruding portion 131a of the drive unit housing 131 is inserted into the upper opening of the valve chamber 119 of the valve body 113. Thereby, between the tip surface (bottom surface) of the protruding portion 131a of the drive unit housing 131 and the horizontal surface of the stepped portion of the upper opening of the valve chamber 119 of the valve body 113, between the outer peripheral surface of the protruding portion 131a of the drive unit housing 131 and the vertical surface of the stepped portion of the upper opening of the valve chamber 119 of the valve body 113, and between the bottom surface of the drive unit housing 131 and the peripheral region of the upper opening of the valve chamber 119 of the valve body 113, the outer peripheral edge portion of the film portion 115b of the diaphragm 115 is clamped, and the diaphragm 115 is fixed and supported to the valve body 113 so that the seal surface 115c is disposed to face the valve seat 121.

[0055] The piston 137 is connected to a guide shaft 167 so as to extend upward, and is connected to a stem 137 so as to extend downward (i.e., toward the valve body 113). The stem 135 is slidably inserted into a through hole provided through the bottom of the drive unit housing 131, and a connection end 135a located at its tip is connected to the diaphragm 115 (specifically, its valve body portion 115a). The outer peripheral surface of the piston 137 is in slidable contact with the inner peripheral surface of the cylinder portion in the vertical direction, and the internal space of the cylinder portion is divided into an upper space 143 surrounded by the upper surface of the piston 137, the inner peripheral wall of the cylinder portion, and the ceiling surface of the cylinder portion (i.e., the lower surface of the lid member 133), and a lower space 145 surrounded by the lower surface of the piston 137, the inner peripheral wall of the cylinder portion, and the bottom surface of the cylinder portion (i.e., the bottom of the drive unit housing 131). The guide shaft 167 is slidably inserted into a through hole provided through the lid member 133, and guides the vertical movement of the piston 137 (i.e., the movement of the piston 137 in the direction of separating and approaching the sealing surface 115c of the valve body portion 115a connected to the stem 135 extending from the piston 137 with respect to the valve seat 121).

[0056] The lid member 133 is formed with a first communication port 147 that communicates with the ceiling surface of the cylinder portion partitioning the upper space 143, and it is possible to supply and discharge the working fluid (e.g., compressed air) to and from the upper space 143 through the first communication port 147. Further, a second communication port 149 that communicates with the bottom of the cylinder portion partitioning the lower space 145 is formed on the side portion of the drive unit housing 131, and it is possible to supply and discharge the working fluid to and from the lower space 145 through the second communication port 149. Furthermore, a coil spring 139 is disposed in a compressed state between the lower surface of the lid member 133 (ceiling surface of the cylinder portion) and the upper surface of the piston 137.

[0057] In the diaphragm 115 of the second embodiment, as shown in detail in FIG. 5, a locking portion having an enlarged diameter is provided at the connecting end 135a of the stem 135, and the connecting end (locking portion) 135a of the stem 135 is press-fitted into a connecting hole 151 provided at the upper center of the valve body portion 115a (specifically, its reduced-diameter portion 157), whereby the connecting end 135a of the stem 135 and the valve body portion 115a are connected. However, the connection between the connecting end 135a of the stem 135 and the valve body portion 115a is not limited to press-fitting. For example, as shown in FIG. 6, a female screw portion is formed on the inner peripheral surface of a connecting hole 151' provided at the connecting end 135a' of the stem 135, and a male screw portion is formed on the outer peripheral surface of a protruding portion 169 provided so as to protrude from the upper center of the valve body portion 115a (specifically, the reduced-diameter portion 157), and the connecting end 135a' of the stem 135 and the valve body portion 115a may be connected by screwing the connecting hole 151' of the connecting end 135a' and the protruding portion 169 of the valve body portion 115a together.

[0058] Incidentally, if the diameter of the narrow-diameter portion 157 is reduced, it becomes easier to secure the length of the bent portion 161. However, as shown in FIG. 5, when the connection end 135a of the stem 135 is press-fitted into the connection hole 151 provided in the valve body portion 115a, since it is necessary to form the connection hole 151 in the narrow-diameter portion 157 of the valve body portion 115a, the diameter of the narrowest part of the narrow-diameter portion 157 (hereinafter referred to as the poppet diameter) is 1.8 to 2.5 times the diameter of the opening from the inflow passage 125 to the valve chamber 119 (hereinafter referred to as the orifice diameter), and it is preferably 2.0 to 2.3 times. If the poppet diameter is 2.0 times or more the orifice diameter, by thickening the connection end 135a to increase the strength, the connection end 135a becomes less likely to deform, and even if the seal thrust is reduced, it can be stably sealed. Also, if the poppet diameter is 2.3 times or less the orifice diameter, as will be described later, due to the fluid pressure acting on the surface or the stepped surface of the main body portion 155 and the narrow-diameter portion 157, the force in the direction of pressing the valve body portion 115a of the diaphragm 115 against the valve seat 121, and due to the fluid pressure acting on the film portion 115b (specifically, the bent portion 161) extending from the upper end of the narrow-diameter portion 157, the force in the direction of pulling the film portion 115b of the diaphragm 115 away from the valve seat 121 are offset, and the effect of reducing the seal thrust can be enhanced. Further, as shown in FIG. 6, when the connection hole 151' provided in the connection end 135a' of the stem 135 is screwed with the protrusion 169 protruding from the valve body portion 115a, the poppet diameter can be made smaller than the case shown in FIG. 5, but due to the screw size constraints, the poppet diameter is 0.8 to 1.5 times the orifice diameter, and it is preferably 1.0 to 1.3 times. If the poppet diameter is 1.0 times or more the orifice diameter, by thickening the connection end 135a' or the protrusion 169 to increase the strength, the connection end 135a' or the protrusion 169 becomes less likely to deform, and even if the seal thrust is reduced, it can be stably sealed.Also, if the poppet diameter is made 1.3 times or less the orifice diameter, as will be described later, the force in the direction of pressing the valve body portion 115a of the diaphragm 115 against the valve seat 121 due to the fluid pressure acting on the surface or the step surface of the main body portion 155 and the small-diameter portion 157, and the force in the direction of separating the membrane portion 115b (specifically, the bent portion 161) of the diaphragm 115 from the valve seat 121 due to the fluid pressure acting on the membrane portion 115b extending from the upper end of the small-diameter portion 157 can be offset, enhancing the effect of reducing the seal thrust.

[0059] With the above-described configuration, similar to the diaphragm valve 11 shown in FIG. 1, even in the diaphragm valve 111 shown in FIG. 4, when the working fluid is not supplied to the first communication port 147 and the second communication port 149 during normal times, the piston 137 is biased downward toward the valve body 113 by the coil spring 139 and pushed down. Along with this, the valve body portion 115a of the diaphragm 115 connected to the piston 137 via the stem 135 is moved downward and pressed against the valve seat 121. By supplying the working fluid (for example, compressed air) to the upper space 143 of the cylinder portion through the first communication port 147 and applying a downward fluid pressure in the direction approaching the valve body 113 to the upper surface of the piston 137, the force acting on the valve body portion 115a from the piston 137 via the stem 135 can be changed, and the force pressing the valve body portion 115a against the valve seat 121 can be adjusted. As a result of the valve body portion 115a being pressed against the valve seat 121, as shown in FIG. 4, the opening from the inflow passage 125 to the valve chamber 119 is closed, and the diaphragm valve 111 is in a closed state. When the working fluid is supplied to the second communication port 149 from this state, the working fluid flows into the lower space 145 of the cylinder portion, and an upward fluid pressure in the direction away from the valve body 113 acts on the lower surface of the piston 137, and the piston 137 is pushed upward in the direction away from the valve body 113 against the biasing force of the coil spring 139 (in some cases, in addition to this, the downward fluid pressure exerted on the piston 137 by the working fluid in the upper space 143). At this time, the working fluid in the upper space 143 of the cylinder portion is discharged to the outside through the first communication port 147. When the piston 137 moves upward in the direction away from the valve body 113, the valve body portion 115a of the diaphragm 115 connected to the piston 137 via the stem 135 moves upward and separates from the valve seat 121. As a result, the opening from the inflow passage 125 to the valve chamber 119 is opened, and the diaphragm valve 111 is in an open state. In the open state, the fluid that has flowed into the inflow passage 125 from the inlet 123 of the diaphragm valve 111 flows out to the outside through the valve chamber 119, the outflow passage 129, and the outlet 127.

[0060] The diaphragm 115 according to the second embodiment is formed of PFA having a specific gravity of less than 2.135 and an opening / closing durability test result of 55,000 or more, or PFA having a specific gravity of less than 2.135 and a flex life value of 180,000 or more, similar to the diaphragm 15 according to the first embodiment. Preferably, the diaphragm 115 is formed of PFA having a specific gravity of 2.12 or less and an opening / closing durability test result of 1,000,000 or more, or PFA having a specific gravity of 2.12 or less and a flex life value of 19,000,000 or more.

[0061] Note that the opening / closing durability test result is measured according to the above-described opening / closing durability test. Also, the flex life value is measured according to JIS P 8115.

[0062] Furthermore, in order to be able to produce the diaphragm 115 by injection molding, the PFA preferably has a melt flow rate (MFR) of 3 g / 10 min or less measured at a load of 5 kg and a measurement temperature of 372 ± 0.1°C in accordance with ASTM D1238. When forming the diaphragm 115 from PFA by injection molding, for example, after producing a semi-finished product by injection molding of the above-described type of PFA, the diaphragm 115 may be produced by forming a portion that is difficult to form by injection molding, such as the film portion 135b, by cutting. By producing the diaphragm 115 by injection molding, the contact surface with the mold surface becomes the mold transfer surface, so the surface roughness is smaller and the smoothness is higher than that of the surface by cutting. Therefore, by subjecting the semi-finished product produced by injection molding to cutting so as to leave a metal transfer surface on the liquid contact surface, the diaphragm 115 is produced, thereby increasing the smoothness of the liquid contact surface and suppressing the generation of particles. In particular, by subjecting the semi-finished product produced by injection molding to cutting so as to leave a metal transfer surface on the seal surface 115c of the valve body portion 115a that repeatedly contacts and separates from the valve seat 121, the diaphragm is produced, thereby preventing a decrease in the surface roughness of the seal surface 115c due to cutting and increasing the smoothness of the seal surface 115c, so that the friction with the valve seat 121 is reduced and the generation of particles can be suppressed.

[0063] Note that the valve body 113, the drive housing 131 of the drive unit 117, the lid member 133, the stem 135, and the piston 137 are preferably formed of a fluororesin material in order to prevent corrosion by a fluid. As the fluororesin material, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), or polychlorotrifluoroethylene (PCTFE) can be used.

[0064] The operation and manufacturing method of the diaphragm valve 111 using the diaphragm 115 having such a configuration are the same as those of the diaphragm valve 11, and thus the description thereof is omitted.

[0065] In the diaphragm valve 111, similar to the diaphragm valve 11, the bending of the film portion 115 that supports the valve body portion 115a is repeated due to the vertical movement of the valve body portion 115a of the diaphragm 115 (i.e., the approach and separation of the valve body portion 115a with respect to the valve seat 121). Also, the lower the crystallinity and the higher the molecular weight of PFA, the higher the resistance to repeated bending, which is the durability to repeated bending, and the specific gravity decreases as the molecular weight increases. The diaphragm 115 is made of PFA with a specific gravity of less than 2.135 and an opening / closing durability test result of 55,000 or more, or PFA with a specific gravity of less than 2.135 and a flex life value of 180,000 or more. Preferably, it is made of PFA with a specific gravity of 2.12 or less and an opening / closing durability test result of 1,000,000 or more, or PFA with a specific gravity of 2.12 or less and a flex life value of 19,000,000 or more. Therefore, the diaphragm 115 has sufficient resistance to repeated bending and can ensure sufficient durability. Also, when the diaphragm valve 111 opens and closes, the valve body portion 115a is pressed against or separated from the valve seat 121 as the film portion 115b moves or bends. Therefore, due to the impact and friction when the valve body portion 115a contacts the valve seat 121 and the repeated bending of the film portion 115b, particles are likely to be generated from the diaphragm 115. However, the diaphragm 115 is made of PFA with a molecular structure in which particles are less likely to be generated. Therefore, the diaphragm 115 has the effect of suppressing the generation of particles compared to the case where other fluororesin materials such as PTFE are used. That is, the diaphragm 115 can suppress particles by using PFA and can ensure high resistance to repeated bending that can withstand use in a diaphragm valve.

[0066] Furthermore, the valve body portion 115a of the diaphragm 115 has a poppet shape in which a reduced-diameter portion 157 that is thinner than the main body portion 155 is formed between the membrane portion 115b and the main body portion 155 of the valve body portion 115a. As a result, the force in the direction of pressing the valve body portion 115a of the diaphragm 115 against the valve seat 121 due to the fluid pressure acting on the surface or the stepped surface of the main body portion 155 and the reduced-diameter portion 157, and the force in the direction of pulling the membrane portion 115b of the diaphragm 115 away from the valve seat 121 due to the fluid pressure acting on the membrane portion 115b (specifically, the bent portion 161) extending from the upper end of the reduced-diameter portion 157 are offset. Therefore, the force in the direction of pulling the diaphragm 115 away from the valve seat 121, which is generated when the fluid pressure acts on the diaphragm 115, can be reduced. As a result, since it becomes possible to reduce the seal thrust for pressing the valve body portion 115a of the diaphragm against the valve seat 121, the stress generated when the valve body portion 115a is pressed against the valve seat 121 during valve closure is reduced, and the effect of suppressing the generation of particles is achieved. In particular, as described above, when connecting the connection hole 151 of the valve body portion 115a and the connection end 135a by press fitting, the poppet diameter is set to 2.3 times or less the orifice diameter, or when connecting the protrusion 169 of the valve body portion 115a and the connection hole 151' of the connection end 135a' by screwing, if the poppet diameter is set to 1.3 times or less the orifice diameter, the effect of reducing the seal thrust by offsetting the force in the direction of pressing the valve body portion 115a of the diaphragm 115 against the valve seat 121 and the force in the direction of pulling the membrane portion 115b of the diaphragm 115 away from the valve seat 121 can be enhanced, and the effect of suppressing the generation of particles can be improved.

[0067] Further, at the connection portion between the bent portion 161 and the support portion 163 (specifically, the first horizontal support portion 163a), a concave portion 165 is provided on the side far from the seal surface 115c, and the outer peripheral edge portion of the bent portion 161 on the first horizontal support portion 163a side is inclined and extends from the first horizontal support portion 163a so as to form an angle of 30° with respect to the first horizontal support portion 163a in a direction away from the seal surface 115c toward the valve body portion 115a. As a result, the bent portion 161 is more likely to bend with respect to the first horizontal support portion 163a sandwiched between the tip surface (bottom surface) of the protruding portion 131a of the drive unit housing 131 and the horizontal plane of the step portion of the upper opening of the valve chamber 119 of the valve body 113, and the valve body portion 115a is more likely to move up and down. As a result, the seal thrust is reduced, the stress generated by pressing the seal surface 115c of the valve body portion 115a against the valve seat 121 at the time of valve closing is reduced, and the effect of suppressing the generation of particles can be further enhanced.

[0068] As described above, the present invention has been described with reference to the illustrated embodiments, but the present invention is not limited to the illustrated embodiments. For example, in the diaphragm 115 according to the second embodiment, a male screw portion is formed on the outer periphery of the connection end 135a of the stem 135, and a female screw portion is formed on the inner peripheral surface of the connection hole 151 provided in the valve body portion 115a, and the connection end 135a of the stem 135 and the valve end portion 115a may be connected by screwing. Further, the present invention can be applied to a sack-back valve having a sack-back function for preventing liquid leakage, a needle valve having a flow rate adjustment function, a constant flow rate valve, a constant pressure valve for adjusting pressure, a back pressure valve, etc., as long as it is a valve that supports the valve body portion by a film portion regardless of the application, function, etc.

Explanation of reference numerals

[0069] 11 Diaphragm valve 15 Diaphragm 15a Valve body portion 15b Film portion 15c Seal surface 111 Diaphragm valve 115 Diaphragm 115a Valve body portion 115b Membrane part 115c Sealing surface 155 Body part 157 Reduced diameter part 159 Skirt part 161 Bending part 163 Support part 163a First horizontal support part 163b Vertical support part 163c Second horizontal support part 165 Concave part

Claims

1. A method for manufacturing a diaphragm for a valve, the method comprising the steps of: manufacturing a diaphragm for a valve having a valve body portion having a sealing surface for contacting and sealing against a valve seat; and a membrane portion extending outward from the valve body portion and supporting the valve body portion, the method comprising the steps of: A step of forming a semi-finished product using a perfluoroalkoxyalkane as a raw material; A step of subjecting the semi-finished product to a cutting process; wherein the raw materials are selected so that the specific gravity of the raw materials is less than 2.135 and the result of an opening and closing durability test of the diaphragm is 55,000 or more.

2. 2. The method for manufacturing a diaphragm according to claim 1, wherein the raw material is selected so that the specific gravity of the raw material is 2.12 or less and the result of an opening and closing durability test of the valve diaphragm is 1,000,000 or more times.

3. The method for manufacturing a diaphragm according to claim 1 or 2, wherein the raw materials are selected so that the flex life value of the diaphragm is 19,000,000 cycles or more.

4. The method for manufacturing a diaphragm according to claim 1 , wherein the step of molding the semi-finished product is a step of injecting the raw material into a mold to produce the semi-finished product by injection molding.

5. The method for manufacturing a diaphragm according to claim 4, wherein the cutting step is a step of cutting the semi-finished product so that at least a mold transfer surface remains on the sealing surface.

6. A diaphragm for a valve comprising a valve body portion having a sealing surface for contacting and sealing against a valve seat, and a membrane portion extending outward from the valve body portion and supporting the valve body portion, A diaphragm for a valve, characterized in that the valve body portion and the membrane portion are formed by molding using as raw material a perfluoroalkoxyalkane selected so as to have a specific gravity of less than 2.135 and such that the diaphragm can be subjected to an opening and closing durability test of 55,000 times or more.

7. 7. The valve diaphragm according to claim 6, wherein the valve diaphragm is formed from a raw material having a specific gravity of 2.12 or less and a result of an opening / closing durability test of the diaphragm being 1,000,000 or more times.

8. 8. The valve diaphragm according to claim 6, wherein the valve diaphragm is formed from a material having a flex life value of the diaphragm of 19,000,000 cycles or more.

9. 9. The valve diaphragm according to claim 6, wherein the sealing surface is a mold transfer surface formed by injecting the raw material into a mold and performing injection molding.

10. 10. The diaphragm for a valve according to claim 6, wherein the valve body portion includes a main body portion having the sealing surface and a thin diameter portion narrower than the main body portion, and the thin diameter portion is supported by the membrane portion.

11. 11. The diaphragm for a valve as described in claim 10, wherein the membrane portion includes an annular skirt portion extending from an outer periphery of the tip of the thin diameter portion in a direction away from the main body portion, a bent portion convexly curved radially outward from the skirt portion in a direction away from the main body portion, and a support portion extending flatly radially outward from an outer periphery of the bent portion.

12. 12. The diaphragm for a valve according to claim 11, wherein a length of the bent portion is determined to be 1.8 to 2.8 times a stroke of the valve body portion in a direction in which the seal surface approaches and moves away from the valve seat.

13. 13. The diaphragm for a valve according to claim 11 or 12, wherein the outer peripheral edge portion of the bent portion extends toward the valve body portion at an angle in the range of 20° to 40° relative to the support portion in a direction away from the seal surface.

14. 14. The valve diaphragm according to claim 11, wherein a recess is formed on a side of a connection between the bent portion and the support portion, the recess being recessed toward the valve body portion, the side being away from the seal surface.

15. A diaphragm valve comprising the valve diaphragm according to any one of claims 6 to 14.

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