Diaphragm manufacturing method, valve diaphragm, and diaphragm valve equipped with 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 valves used in various industries such as chemical plants, the semiconductor manufacturing field, the liquid crystal manufacturing field, and the food industry, and more specifically to a diaphragm that suppresses the generation of particles, a method for manufacturing the same, and a diaphragm valve equipped with such a diaphragm. [Background technology]

[0002] In a diaphragm valve, an inlet flow path and an outlet flow path are connected to a valve chamber provided in the center of the valve body, a diaphragm is sandwiched between the valve body and a drive unit housing attached to the top of the valve body to isolate the valve chamber from the internal space of the drive unit housing, and the diaphragm is connected to the lower end of a stem driven by a drive mechanism disposed in the internal space of the drive unit housing, so that the valve body supported by the diaphragm is pressed against and separated from a valve seat provided in the valve chamber to open and close the inlet flow path and the outlet flow path. In addition, in chemical plants, semiconductor manufacturing fields, liquid crystal manufacturing fields, food manufacturing fields, and the like, highly corrosive fluids and fluids that require prevention of contamination are handled, so fluororesin materials, which have excellent chemical resistance and contamination resistance, are widely used for parts of diaphragm that come into contact with fluids. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-138641 A [Patent Document 2] JP 2016-211618 A Summary of the Invention [Problem to be solved by the invention]

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

[0005] Representative fluororesins used for diaphragms include polytetrafluoroethylene (PTFE) and a copolymer of tetrafluoroethylene (TFE) and perfluoroalkylvinylether (PAVE), i.e., perfluoroalkoxyalkane (PFA). It is known that PFA is better at suppressing the generation of particles as described above than PTFE, and it is therefore preferable to form the diaphragm, especially the valve seat abutment portion where particles are likely to be generated, from PFA.

[0006] The flowability and mechanical properties of the molded body of PFA change depending on the molecular structure. As described above, the diaphragm used in the diaphragm valve includes a valve body that contacts and separates from the valve seat, and a membrane that extends outward from the valve body to support the valve body. The membrane is required to be flexible in order to withstand repeated bending when the valve body is repeatedly brought into and out of contact with the valve seat.

[0007] However, PFA, which has a molecular structure with high fluidity and is easy to use for molding, has low flexibility and poor resistance to repeated bending. For this reason, for example, Patent Document 1 discloses a fluid control valve having a valve mechanism including a valve part having a seal part that seals the valve seat part so that it can move forward and backward, and a diaphragm part formed on the opposite side of the seal part and installed in a valve chamber, in which a fluororesin is used for the valve seat part and the valve body part, and a member formed from PFA is heat-sealed to the valve seat part and the seal part of the valve part, and the part where particles are likely to be generated by contact and separation is formed from PFA, and the diaphragm part, i.e., the membrane part, which is required to have flexibility and resistance to repeated bending, is formed from fluororesin. However, when PTFE is used as the above-mentioned fluororesin, the fusion efficiency between PTFE and the PFA used for the valve seat part and the seal part of the valve part is poor, which causes concerns about durability. Furthermore, since the diaphragm part is made of PTFE, there is a concern that particles will be generated 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 a first PFA material that has low fluidity but high flexibility, and then a columnar portion is formed on the film portion by injection molding a second PFA material that has high fluidity, and the columnar portion and the film portion are directly bonded to each other. However, in order to produce such a diaphragm, both rolling equipment and injection molding equipment are required, which increases the cost.

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a valve diaphragm which overcomes the problems of the prior art and has high resistance to repeated bending and which is capable of suppressing the generation of particles. [Means for solving the problem]

[0009] In view of the above object, the present invention provides, as a first aspect, a method for manufacturing a diaphragm for a valve, comprising: a valve body portion having a seal 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: using perfluoroalkoxyalkane as a raw material, injecting the raw material into a die to form a semi-finished product by injection molding; and subjecting the semi-finished product to a cutting process so that at least a die transfer surface remains on the sealing surface, the raw material comprising: The melt flow rate measured under a load of 5 kg and a measurement temperature of 372±0.1°C is 3 g / 10 min or less. The present invention provides a method for manufacturing a diaphragm, which is selected so that the specific gravity of the diaphragm is less than 2.135 and the result of an opening and closing durability test of the diaphragm is 55,000 times or more.

[0010] In the above-mentioned diaphragm manufacturing method, perfluoroalkoxyalkane, i.e. PFA, selected so that the specific gravity is less than 2.135 and the result of the opening and closing durability test of the diaphragm is 55000 or more is used as the raw material of the diaphragm. Therefore, the entire diaphragm is formed from PFA, and the generation of particles can be suppressed compared to the case where the diaphragm is formed from polytetrafluoroethylene (PTFE), which is commonly used. In addition, the lower the crystallinity of PFA and the higher the molecular weight, the higher the repeated bending resistance, which is the durability against repeated bending. Since the specific gravity is low when the molecular weight is high, the inventor found that the opening and closing durability test result is rapidly improved when the specific gravity is less than 2.135, and that when the specific gravity is less than 2.135 and the result of the opening and closing durability test is 55000 or more, it can withstand use as a diaphragm for a diaphragm valve. In the above-mentioned diaphragm manufacturing method, the diaphragm is manufactured using PFA having a specific gravity of less than 2.135 and an opening / closing durability test result of 55,000 or more. Therefore, the use of PFA makes it possible to suppress the generation of particles while ensuring high resistance to repeated bending that can withstand use in a diaphragm valve. Furthermore, if PFA can be injection molded, mass production at low cost becomes possible. Also, since the mold transfer surface formed by injection molding has a small surface roughness, by leaving the mold transfer surface on the sealing surface of the valve part without cutting, it is possible to prevent the deterioration of the surface roughness of the sealing surface caused by cutting, and further suppress the generation of particles due to contact between the sealing surface and the valve seat.

[0011] It is more preferable that the raw material is selected so that the specific gravity is 2.12 or less and the result of the opening and closing durability test of the valve diaphragm is 1,000,000 or more times, which further improves the durability of the diaphragm.

[0012] It is also preferable that the raw materials are selected so that the flex life value of the diaphragm is 19,000,000 cycles or more. In this case, it is also possible to further improve the durability of the diaphragm.

[0014] In addition, as a second aspect, the present invention provides a diaphragm for a valve including 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 valve body portion and the membrane portion being: The melt flow rate measured under a load of 5 kg and a measurement temperature of 372±0.1°C is 3 g / 10 min or less. The present invention provides a valve diaphragm which is formed by molding a raw material made of a perfluoroalkoxyalkane selected so that the specific gravity of the diaphragm is 2.135 or less and the result of an opening / closing durability test of the diaphragm is 55,000 times or more, and the sealing surface is a mold transfer surface which is formed by injecting the raw material into a mold and performing injection molding.

[0015] The valve diaphragm is entirely formed by molding using perfluoroalkoxyalkane, i.e. PFA, as a raw material selected so that the 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 valve diaphragm can suppress the generation of particles compared to the case where the diaphragm is formed from polytetrafluoroethylene (PTFE), which is generally used. In addition, the present inventors have found that when the specific gravity is less than 2.135, the opening and closing durability test result is rapidly improved, 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, the diaphragm can withstand use as a diaphragm for a diaphragm valve. The valve diaphragm is manufactured using PFA having a specific gravity of less than 2.135 and a result of the opening and closing durability test of 55,000 or more, so that it is possible to ensure high repeated bending resistance that can withstand use in a diaphragm valve while suppressing the generation of particles by using PFA.

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

[0017] It is further preferable that the valve diaphragm is formed from a material that provides the diaphragm with a flex life value of 19,000,000 cycles or more.

[0019] In one embodiment, the valve body includes a main body having the sealing surface and a small diameter portion smaller than the main body, and the small diameter portion is supported by the membrane portion.

[0020] In addition, the membrane portion may include an annular skirt portion extending from the 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 the outer periphery of the bent portion.

[0021] In this case, the length of the bent portion is preferably set to be 1.8 to 2.8 times the stroke of the valve body portion in the direction of moving the seal surface toward and away from the valve seat. Also, it is preferable that the outer peripheral edge portion of the bent portion extends toward the valve body portion at an angle of 20° to 40° with respect to the support portion in the direction away from the seal surface. Furthermore, it is preferable that a recess recessed toward the valve body portion is formed on the side of the connection portion between the bent portion and the support portion away from the seal surface.

[0022] Furthermore, the present invention provides, as a third aspect, a diaphragm valve including the above-mentioned valve diaphragm. Effect of the Invention

[0023] According to the present invention, the valve diaphragm is made of PFA, which can suppress particle generation compared to the case where the diaphragm is made of the commonly used PTFE. Also, the valve diaphragm is manufactured using PFA with a specific gravity of less than 2.135 and an opening / closing durability test result of 55,000 or more, so that the use of PFA can ensure high repeated bending resistance that can withstand use in a diaphragm valve while suppressing particle generation. [Brief description of the drawings]

[0024] [Figure 1] FIG. 2 is a cutaway perspective view showing a diaphragm according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of the diaphragm shown in FIG. [Diagram 3] 2 is a vertical cross-sectional view showing a diaphragm valve including the diaphragm shown in FIG. 1. [Figure 4] FIG. 4 is a longitudinal sectional view showing a diaphragm valve including a diaphragm according to a second embodiment of the present invention. [Diagram 5] FIG. 5 is a cross-sectional view of a diaphragm according to the second embodiment shown in FIG. [Figure 6]FIG. 5 is a cross-sectional view showing a variation of the diaphragm shown in FIG. 4. [Figure 7] 5 is an enlarged cross-sectional view showing a membrane portion of the second diaphragm shown in FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, an embodiment of a diaphragm for a valve according to the present invention will be described with reference to the drawings, but it goes without saying that the present invention is not limited to the embodiment shown in the drawings. In the following description, a diaphragm refers to a valve component having a membrane portion that supports a valve body portion, and a diaphragm valve refers to a valve in general that supports a valve body portion with a membrane portion.

[0026] 1 and 2 show a valve diaphragm 15 according to a first embodiment of the present invention, and FIG. 3 shows a diaphragm valve 11 equipped with the valve diaphragm 15. As shown in FIG.

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

[0028] The valve body 13 is formed with a valve chamber 19 at the center of the upper part, as well as with a first flow path and a second flow path communicating with the valve chamber 19, and in the valve chamber 19, an annular valve seat 21 with which the diaphragm 15 comes into contact is formed around the opening from the first flow path to the valve chamber 19. In the illustrated embodiment, an inlet passage 25 is formed as the first flow path, extending from an inlet 23 formed on one of the opposing side surfaces of the valve body 13 and opening at the center of the bottom of the valve chamber 19, and an outlet passage 29 is formed as the second flow path, extending from an outlet 27 formed on the other of the opposing side surfaces of the valve body 13 and opening at a side surface of the valve chamber 21, and a raised annular valve seat 21 is formed around the opening from the inlet passage 25 to the valve chamber 19.

[0029] A base plate 53 may further be attached to the bottom of the valve body 13 for ease of installation.

[0030] As shown in detail in FIG. 1 and FIG. 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 may have other shapes. In the illustrated embodiment, the membrane portion 15b is provided so as to extend radially outward from the outer periphery of the lower end of the valve body portion 15a, but may be provided so as to extend radially outward from the upper end or middle portion of the valve body portion 15a as long as it is connected to the outer periphery of the valve body portion 15a and can support the valve body portion 15a. Furthermore, 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 so that the seal surface 15c is disposed opposite the valve seat 21 by sandwiching the outer periphery of the membrane portion 15b between the valve body 13 and the drive portion 17.

[0031] The actuator 17 includes an actuator housing 31 that is attached to the top of the valve body 13 and has an internal space, a stem 35 that is connected to the diaphragm 15, and an actuator mechanism that is housed in the internal space and drives the stem 35. In this embodiment, a cylinder portion that opens toward the valve body 13 is formed as an internal space in the actuator housing 31, and the actuator mechanism is composed of a piston 37 that is slidably housed in the cylinder portion and a coil spring 39 that serves as a biasing member. In addition, a diaphragm holder 41 is fitted into the opening of the cylinder portion of the actuator housing 31 on the valve body 13 side, and when the actuator 17 is attached to the top of the valve body 13, the outer peripheral edge portion of the membrane portion 15b is sandwiched between the top surface of the surrounding area of ​​the upper opening of the valve chamber 19 of the valve body 13 and the bottom surface of the diaphragm holder 41, so that the diaphragm 15 can be supported by the valve body 13.

[0032] The outer peripheral surface of the piston 37 is in contact with the inner peripheral surface of the cylinder portion so as to be slidable in the vertical direction, and the internal space of the cylinder portion is divided 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). A stem 35 is connected to the piston 37 so as to extend downward from the piston 37. 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 the tip of the stem 35 is connected to the diaphragm 15 (more specifically, the valve body portion 15a).

[0033] In the diaphragm 15 of the first embodiment shown in Figures 1 to 3, a male thread is formed on the outer peripheral surface of the connection end 35a of the stem 35, and a female thread is formed on the inner peripheral surface of a connecting hole 51 provided in the upper center of the valve body portion 15a, and the valve body portion 15a is connected to the connection end 35a of the stem 35 by screwing the connection end 35a into the connecting 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, and for example, the connection end 35a may be provided with an enlarged diameter locking portion, and the connection end 35a may be press-fitted into the connecting hole provided in the upper center of the valve body portion 15a to connect the connection end 35a and the valve body portion 15a.

[0034] A first communication port 47 communicating with the ceiling surface of the cylinder section defining the upper space 43 is formed in the upper part of the drive housing 31, and a working fluid (e.g., compressed air) can be supplied to and discharged from the upper space 43 through the first communication port 47. A second communication port 49 communicating with the bottom of the cylinder section defining the lower space 45 is formed in the side of the drive housing 31, and a working fluid can be supplied to and discharged from the second communication port 49 to the lower space 45. Furthermore, a coil spring 39 is arranged in a compressed state between the upper part of the drive housing 31 (the ceiling surface of the cylinder section) and the upper surface of the piston 37.

[0035] With this configuration, during normal operation when the working fluid is not supplied to the first communication port 47 and the second communication port 49, the piston 37 is urged downward by the coil spring 39 toward the valve body 13, and 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. By supplying the working fluid (e.g., compressed air) to the upper space 43 of the cylinder portion through the first communication port 47 to apply a downward fluid pressure to the upper surface of the piston 37 in a direction to bring it closer to the valve body 13, the force applied from the piston 37 to the valve body portion 15a 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, the opening from the inflow passage 25 to the valve chamber 19 is closed, as shown in FIG. 3, 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 (e.g., compressed air) flows into the lower space 45 of the cylinder part, and an upward fluid pressure acts on the lower surface of the piston 37 in a direction away from the valve body 13, and the piston 37 is pushed up in a direction away from the valve body 13 against the biasing force of the coil spring 39 (in some cases, in addition to this, a downward fluid pressure that the working fluid in the upper space 43 exerts on the piston 37). At this time, the working fluid in the upper space 43 of the cylinder part is discharged to the outside from the first communication port 47. When the piston 37 moves upward in a direction away from the valve body 13, the valve body part 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 path 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 inlet passage 25 from the inlet port 23 of the diaphragm valve 11 passes through the valve chamber 19 and the outlet passage 29 and flows out from the outlet port 27 to the outside.

[0036] As described above, the membrane portion 15b supporting the valve body portion 15a is repeatedly bent as the valve body portion 15a of the diaphragm 15 approaches and separates from the valve seat 21 in response to the opening and closing of the diaphragm valve 11. For this reason, the membrane 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 made of perfluoroalkoxyalkane (PFA). Compared with polytetrafluoroethylene (PTFE), which is generally used as a material for diaphragms, PFA has a molecular structure that is less likely to generate particles when used as a material for diaphragms. Therefore, if the diaphragm 15 is formed from PFA, the generation of particles can be suppressed. On the other hand, PFA generally has a characteristic of being low in flexibility. As described above, the diaphragm 15, particularly the membrane portion 15b, is repeatedly bent. For this reason, if the diaphragm 15 is formed from a type of PFA with low flexibility, it becomes more likely to break and its durability decreases. However, in recent years, as described in, for example, JP 2017-119750 A, PFA with a molecular structure with high flexibility has been developed and has become available. The lower the crystallinity of PFA and the higher the molecular weight, the higher the repeated bending resistance, which is the durability against repeated bending, and when the molecular weight is high, the specific gravity is low. From this, the inventors found that when the specific gravity is less than 2.135, the results of the open / close durability test are improved drastically, and when the specific gravity is less than 2.135 and the results of the open / close durability test are 55,000 times or more, the PFA can withstand use as a diaphragm for a diaphragm valve. Therefore, the PFA used for the diaphragm 15 is selected to have a specific gravity of less than 2.135 and a result of the open / close durability test of 55,000 times or more. Alternatively, the PFA used for the diaphragm 15 may be selected to have a specific gravity of less than 2.135 and a flex life value of 180,000 times or more. Preferably, the diaphragm 15 is formed from a PFA having a specific gravity of 2.12 or less and a result of the open / close durability test of 1,000,000 times or more, or a PFA having a specific gravity of 2.12 or less and a flex life value of 19,000,000 times or more.

[0038] The opening and closing durability test was performed by attaching a diaphragm to a diaphragm valve with an opening diameter (i.e., orifice diameter) of 1 / 8 inch from the inlet passage 25 to the valve chamber 19, and repeatedly opening and closing with an open time of 1.2 seconds and a close time of 0.8 seconds while repeatedly switching between an environmental temperature of 5°C for 6 hours and a temperature of 100°C for 6 hours, under conditions of a fluid temperature of room temperature, a constant load of fluid pressure of 0.5 MPa, an opening and closing pressure of 0.5 MPa, and an opening and closing stroke (the distance traveled by the valve body 15a relative to the valve seat 19 when opening and closing) of 1.1 mm, and measuring the number of times the diaphragm was broken. The flex life value was measured in accordance with JIS P 8115.

[0039] Furthermore, in order to make the diaphragm 15 by injection molding, it is preferable that the melt flow rate (MFR) of the PFA is 3 g / 10 min or less, measured at a load of 5 kg and a measurement temperature of 372 ± 0.1 ° C. according to ASTM D1238. When forming the diaphragm 15 from PFA by injection molding, for example, after a semi-finished product is produced by injection molding of the above-mentioned type of PFA, the diaphragm 15 may be produced by forming a portion such as the film portion 35b, which is difficult to form by injection molding due to factors such as its thinness, by cutting. By producing the diaphragm 15 by injection molding, the contact surface with the mold surface of the molded product becomes the mold transfer surface, so that the surface roughness is smaller than that of the surface produced by cutting, and the smoothness is increased. Therefore, by producing the diaphragm 15 by performing cutting on the semi-finished product produced by injection molding so as to leave a metal transfer surface on the liquid contact surface, the smoothness of the liquid contact surface is increased, making it possible to suppress the generation of particles. In particular, by manufacturing the diaphragm 15 by subjecting a semi-finished product produced by injection molding to cutting so as to leave a metal transfer surface on the sealing surface 15c of the valve body portion 15a, which repeatedly comes into and out of contact with the valve seat 21, the deterioration of the surface roughness of the sealing surface 15c due to the cutting process is prevented and the smoothness of the sealing surface 15c is increased, thereby reducing friction with the valve seat 21 and suppressing the generation of particles.

[0040] In order to prevent corrosion caused by fluid, the valve body 13, the drive unit housing 31 of the drive unit 17, the stem 35, and the piston 37 are preferably made of a fluororesin material. Examples of the fluororesin material that can be used include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polychlorotrifluoroethylene (PCTFE).

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

[0042] In normal operation when no working fluid (e.g., compressed air) is supplied to the actuator 17 from the first communication port 47 and the second communication port 49, the piston 37 of the actuator 17 is urged downward by the coil spring 39 in a direction approaching the valve body 13, that is, pushed down. Accordingly, the valve body 15b is also moved downward together with the piston 37 via the stem 35. As a result, the seal surface 15c of the valve body 15a is pressed against the valve seat 21, and the diaphragm valve 11 is in a closed state as shown in FIG. If it is desired to increase the sealing thrust, the working fluid can be supplied to the upper space 43 of the cylinder portion through the first communication port 47, and in addition to the biasing force of the coil spring 39, the fluid pressure of the working fluid that has flowed into the upper space 43 can be caused to act downward on the upper surface of the piston 37, thereby changing the force that presses the sealing surface 15c of the valve body portion 15a against the valve seat 21 via the stem 35, i.e., the pressing force, and thereby adjusting the force that presses the valve body 15 against the valve seat 21.

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

[0044] When the supply of working fluid to the second communication port 49 is stopped, the piston 37 is again urged downward by the force of the coil spring 39, and the sealing surface 15c of the valve body portion 15a is pressed against the valve seat 21, thereby returning to the closed state.

[0045] In this way, the membrane portion 15 supporting the valve body portion 15a of the diaphragm 15 repeatedly bends due to the up and down movement of the valve body portion 15a of the diaphragm 15 accompanying the opening and closing of the diaphragm valve 11 (i.e., the approach and separation of the valve body portion 15a from the valve seat 21). In addition, the lower the crystallinity and the higher the molecular weight of PFA, the higher the repeated bending resistance, which is the durability against repeated bending, and the higher the molecular weight, the lower the specific gravity. The diaphragm 15 is formed from PFA having a low specific gravity of less than 2.135 and an opening and closing durability test result of 55,000 or more, or PFA having a low specific gravity of less than 2.135 and a flex life value of 180,000 times or more, preferably PFA having 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 having a specific gravity of 2.12 or less and a flex life value of 19,000,000 times or more. Therefore, the diaphragm 15 has sufficient repeated bending resistance and can ensure sufficient durability. In addition, when the diaphragm valve 11 is opened or closed, the membrane portion 15b of the diaphragm 15 moves or bends, so that the valve body portion 15a is pressed against or separated from the valve seat 21. Therefore, particles are likely to be generated from the diaphragm 15 due to the impact and friction when the valve body portion 15a contacts the valve seat 21 and the repeated bending of the membrane portion 15b. However, the diaphragm 15 is made of PFA, which has a molecular structure that makes it difficult for particles to be generated. Therefore, the diaphragm 15 has an effect of suppressing particle generation compared to the use of other fluororesin materials such as PTFE. In other words, the diaphragm 15 can suppress particles by using PFA, while ensuring 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 in the first embodiment. FIG. 4 shows a diaphragm 111 comprising a valve diaphragm 115 according to a second embodiment of the invention.

[0047] First, the overall configuration of the diaphragm valve 111 will be described with reference to Fig. 4. Like the diaphragm valve 11, the diaphragm valve 111 comprises a valve body 113, a diaphragm 115, and a drive unit 117 that drives the diaphragm 115. The drive unit 117 is attached to the upper part of the valve body 113.

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

[0049] As shown in detail in Fig. 5, the diaphragm 115 includes a valve body portion 115a and a membrane portion 115b extending 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 thin diameter portion 157 that is thinner than the main body portion 155. The thin diameter portion 157 preferably has a tapered shape that becomes thinner toward the end portion (tip) on the drive portion 117 side. In addition, the membrane portion 115b is formed so as to extend outward from the outer periphery of the tip (end portion on the drive portion 117 side) of the thin diameter portion 157 of the valve body portion 115a. In detail, the membrane portion 115b includes an annular skirt portion 159 extending upward toward the drive portion 117 from the outer periphery of the tip portion (the end portion on the drive portion 117 side) of the thin-diameter portion 157 of the valve body portion 115a, a bent portion 161 extending radially outward from the upper end portion of the skirt portion 159 in a convex curve in a direction away from the valve body portion 115a, and a support portion 163 extending radially outward from the outer periphery 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 valve body portion 115a to move up and down to approach and separate from the valve seat 112 when the diaphragm valve 111 is opened and closed. The longer the bent portion 161 is, the gentler the degree of bending with respect to the stroke (movement distance) of the valve body portion 115a when the diaphragm valve 111 is opened and closed, so that the stress generated when the valve body portion 115a moves up and down is smaller, and the generation of particles is less likely to occur. On the other hand, the longer the bent portion 161 is, the more easily the membrane portion 115b of the diaphragm 115 receives a force from the fluid in the form of fluid pressure in a direction that pulls the valve body portion 115a away from the valve seat 121. As a result, it becomes necessary to increase the seal thrust, which is the force that presses the valve body portion 115a against the valve seat 121 by the drive portion 117, by the amount that resists the fluid pressure received by the membrane portion 115b, and particles are more likely to be generated. Furthermore, as the length of the bent portion 161 increases, the valve chamber 119 must also be made larger, which is a disadvantage in that the overall size of the diaphragm valve 111 also increases. Therefore, in order to suppress the increase in size of the diaphragm valve 111 while suppressing the generation of particles, the length of the bent portion 161 is 1.8 to 2.8 times the movement distance, i.e., the stroke, of the valve body portion 115a when the diaphragm valve 111 is opened or closed, and preferably 2.1 to 2.4 times the stroke. If the length of the bent portion 161 is set to 2.1 times or more the stroke of the valve body portion 115a when the diaphragm valve 111 is opened or closed, the stress generated in the film portion 115b of the diaphragm 115 is reduced, and if the length of the bent portion 161 is set to 2.4 times or less the stroke of the valve body portion 115a when the diaphragm valve 111 is opened or closed, the force that the film portion 115b of the diaphragm valve 115 receives from the fluid pressure in the direction of pulling the valve body portion 115a away from the valve seat 121 is reduced, and the seal 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 is opened or closed, the effect of suppressing the generation of particles while suppressing an increase in the size of the diaphragm valve 111 is particularly enhanced.

[0051] Furthermore, because the valve body portion 115a has a poppet shape, even if the valve body portion 115a is placed inside a valve chamber 119 of the same size, the gap between the inner surface of the valve chamber 119 and the outer surface of the upper part of the thin-diameter portion 157 of the valve body portion 115a is wider, making it easier to ensure the length of the bent portion 161.

[0052] As shown in detail in Fig. 5 and Fig. 7, the support portion 163 of the diaphragm 115 is composed of an annular first horizontal support portion 163a extending horizontally (parallel to the seal surface 115c) from the outer peripheral edge portion of the bent portion 161 in the radial direction outward, a cylindrical vertical support portion 163b located outside the first horizontal support portion and extending in the up-down direction (vertical direction), and an annular second horizontal support portion 163c located outside the vertical support portion and extending 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 extends inclined from the first horizontal support portion 163a toward the valve body portion 115a so as to form an angle θ with respect to the first horizontal support portion 163a in the direction away from the seal surface 115c. 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 set to 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 improved. Furthermore, if the angle θ is set to 35° or less, the angle between both sides of the recess 165 described later becomes an obtuse angle, which makes processing easier and reduces the defective rate. Furthermore, a step portion is provided at the upper opening of the valve chamber 119 of the valve body 113, and when a protruding portion 131a protruding and extending from the center of the bottom of a drive unit housing 131 of a 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 step portion of the upper opening of the valve chamber 119 of the valve body 113, and the outside of the protruding portion 131a of the drive unit housing 131 is inserted. A vertical support portion 163b is sandwiched between the peripheral surface and the vertical surface of the step portion of the upper opening of the valve chamber 119 of the valve body 113, and a second horizontal support portion 163c is sandwiched between the bottom surface of the drive unit housing 131, which is positioned outward from the protrusion 131a, and the upper surface of the surrounding area of ​​the upper opening of the valve chamber 119 of the valve body 113.This makes it possible to fix and support the diaphragm 115 to the valve body 113 so that the sealing surface 115c is positioned opposite the valve seat 121.

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

[0054] The driving unit 117 includes a driving unit housing 131 attached to the top of the valve body 113 and having an internal space formed therein, a cover member 133 attached to the top of the driving unit housing 131, a stem 135 connected to the diaphragm 115, and a driving mechanism housed in the internal space and driving the stem 135. The internal space of the driving unit housing 131 is formed as a cylinder portion that opens upward, and the driving mechanism is composed of a piston 137 slidably housed in the cylinder portion and a coil spring 139 as a biasing member. In addition, a protrusion 131a is formed protruding from the center of the bottom of the driving unit housing 131, and when the driving unit 117 is attached to the top of the valve body 113, the protrusion 131a of the driving unit housing 131 is inserted into the upper opening of the valve chamber 119 of the valve body 113. As a result, the outer peripheral edge of the membrane portion 115b of the diaphragm 115 is clamped between the tip surface (bottom surface) of the protrusion 131a of the drive unit housing 131 and the horizontal surface of the step portion of the upper opening of the valve chamber 119 of the valve body 113, between the outer peripheral surface of the protrusion 131a of the drive unit housing 131 and the vertical surface of the step 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 surrounding area of ​​the upper opening of the valve chamber 119 of the valve body 113, and the diaphragm 115 is fixed and supported to the valve body 113 so that the sealing surface 115c is positioned opposite the valve seat 121.

[0055] A guide shaft 167 is connected to the piston 137 so as to extend upward, and a stem 135 is connected to the piston 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 the tip of the stem 135 is connected to the diaphragm 115 (more specifically, the valve body portion 115a). The outer peripheral surface of the piston 137 is in contact with the inner peripheral surface of the cylinder portion so as to be slidable in the up-down 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 cover 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 cover member 133 and is adapted to guide the up and down movement of the piston 137 (i.e., the movement of the piston 137 in the direction in which the sealing surface 115c of the valve body portion 115a connected to the stem 135 extending from the piston 137 moves toward and away from the valve seat 121).

[0056] A first communication port 147 communicating with the ceiling surface of the cylinder section defining the upper space 143 is formed in the cover member 133, and a working fluid (e.g., compressed air) can be supplied to and discharged from the upper space 143 through the first communication port 147. A second communication port 149 communicating with the bottom of the cylinder section defining the lower space 145 is formed in the side of the drive unit housing 131, and a working fluid can be supplied to and discharged from the second communication port 149 to the lower space 145. Furthermore, a coil spring 139 is arranged in a compressed state between the lower surface of the cover member 133 (the ceiling surface of the cylinder section) and the upper surface of the piston 137.

[0057] 5, the diaphragm 115 of the second embodiment is provided with an enlarged diameter locking portion at the connection end 135a of the stem 135, and the connection end 135a of the stem 135 and the valve body portion 115a are connected by press-fitting the connection end 135a (locking portion) 135a of the stem 135 into a connecting hole 151 provided in the upper center of the valve body portion 115a (specifically, its thin diameter portion 157). However, the connection between the connection 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 thread may be formed on the inner circumferential surface of a connecting hole 151' provided in the connecting end 135a' of the stem 135, and a male thread may be formed on the outer circumferential surface of a protrusion 169 provided protruding from the upper center of the valve body portion 115a (more specifically, the thin 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' into the protrusion 169 of the valve body portion 115a.

[0058] In addition, if the thin-diameter portion 157 is narrowed, it becomes easier to ensure the length of the bent portion 161, but since it is necessary to form the connecting hole 151 in the thin-diameter portion 157 of the valve body portion 115a when the connecting end 135a of the stem 135 is press-fitted into the connecting hole 151 provided in the valve body portion 115a as shown in Fig. 5, the diameter of the thinnest part of the thin-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, the connecting end 135a is thickened to increase its strength, making it less likely to deform, and stable sealing can be achieved even if the seal thrust is reduced. Furthermore, if the poppet diameter is made 2.3 times or less the orifice diameter, as described below, the force acting on the surfaces or step surfaces of the main body portion 155 and the narrow diameter portion 157 to press the valve body portion 115a of the diaphragm 115 against the valve seat 121, caused by the fluid pressure acting on the membrane portion 115b (more specifically, the bent portion 161) extending from the upper end of the narrow diameter portion 157, can be offset, and the effect of reducing the seal thrust can be strengthened. Furthermore, as shown in Fig. 6, when the connecting hole 151' provided in the connection end 135a' of the stem 135 is screwed into the protrusion 169 protruding from the valve body portion 115a, the poppet diameter can be made smaller than that shown in Fig. 5, but due to restrictions on the screw size, the poppet diameter is 0.8 to 1.5 times the orifice diameter, and preferably 1.0 to 1.3 times. If the poppet diameter is made 1.0 times or more the orifice diameter, the connection end 135a' or the protrusion 169 is made thicker to increase its strength, making it less likely for the connection end 135a' or the protrusion 169 to deform, and stable sealing can be achieved even if the seal thrust is reduced.Furthermore, by making the poppet diameter 1.3 times or less the orifice diameter, as described below, the force acting on the surfaces or step surfaces of the main body portion 155 and the narrow diameter portion 157 to press the valve body portion 115a of the diaphragm 115 against the valve seat 121, caused by the fluid pressure acting on the membrane portion 115b (more specifically, the bent portion 161) extending from the upper end of the narrow diameter portion 157, can be offset, thereby enhancing the effect of reducing the seal thrust.

[0059] 1, in the diaphragm valve 111 shown in FIG. 4, in the normal state in which the working fluid is not supplied to the first communication port 147 and the second communication port 149, the piston 137 is urged downward toward the valve body 113 by the coil spring 139 and pushed down, and accordingly, 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. In addition, by supplying the working fluid (e.g., compressed air) to the upper space 143 of the cylinder portion through the first communication port 147 to apply a downward fluid pressure to the upper surface of the piston 137 in a direction to bring it closer to the valve body 113, the force acting on the valve body portion 115a from the piston 137 via the stem 135 can be changed, and the force with which the valve body portion 115a is pressed against the valve seat 121 can be adjusted. As a result of the valve body portion 115a being pressed against the valve seat 121, the opening from the inflow passage 125 to the valve chamber 119 is closed, and the diaphragm valve 111 is in a closed state, as shown in Fig. 4. 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 acts on the lower surface of the piston 137 in a direction away from the valve body 113, so that the piston 137 is pushed up in a direction away from the valve body 113 against the biasing force of the coil spring 139 (and, in some cases, the downward fluid pressure acting 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 from the first communication port 147. When the piston 137 moves upward in a 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 opened. In the open state, the fluid that has flowed into the inflow passage 125 from the inlet 123 of the diaphragm valve 111 flows through the valve chamber 119 and the outlet passage 129 and flows out from the outlet 127 to the outside.

[0060] The diaphragm 115 according to the second embodiment is formed from PFA having a specific gravity of less than 2.135 and a result of an opening and closing durability test of 55,000 or more, or alternatively, PFA having a specific gravity of less than 2.135 and a flex life value of 180,000 or more. Preferably, the diaphragm 115 is formed from PFA having a specific gravity of 2.12 or less and a result of an opening and closing durability test 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] The results of the open / close durability test are measured according to the open / close durability test described above, and the flex life value is measured in accordance with JIS P 8115.

[0062] Furthermore, in order to make the diaphragm 115 by injection molding, it is preferable that the PFA 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 a semi-finished product is produced by injection molding the above-mentioned type of PFA, a portion such as the film portion 135b that is difficult to form by injection molding may be formed by cutting to produce the diaphragm 115. By producing the diaphragm 115 by injection molding, the contact surface with the mold surface becomes the mold transfer surface, so that the surface roughness is smaller than that of the surface produced by cutting, and the smoothness is increased. Therefore, by producing the diaphragm 115 by performing cutting on the semi-finished product produced by injection molding so as to leave a metal transfer surface on the liquid contact surface, the smoothness of the liquid contact surface is increased, making it possible to suppress the generation of particles. In particular, by producing a diaphragm by subjecting a semi-finished product produced by injection molding to cutting so as to leave a metal transfer surface on the sealing surface 115c of the valve body portion 115a, which repeatedly comes into and out of contact with the valve seat 121, the deterioration of the surface roughness of the sealing surface 115c due to the cutting process is prevented and the smoothness of the sealing surface 115c is increased, thereby reducing friction with the valve seat 121 and suppressing the generation of particles.

[0063] In order to prevent corrosion caused by fluid, the valve body 113, the drive unit housing 131 of the drive unit 117, the cover member 133, the stem 135, and the piston 137 are preferably made of a fluororesin material. Examples of the fluororesin material that can be used include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polychlorotrifluoroethylene (PCTFE).

[0064] The operation and manufacturing method of the diaphragm valve 111 using the diaphragm 115 having such a configuration are similar to those of the diaphragm valve 11, and therefore a description thereof will be omitted.

[0065] In the diaphragm valve 111, as in the diaphragm valve 11, the membrane portion 115 supporting the valve body portion 115a is repeatedly bent by the up and down movement of the valve body portion 115a of the diaphragm 115 (i.e., the approach and separation of the valve body portion 115a from the valve seat 121). In addition, the lower the crystallinity and the higher the molecular weight of PFA, the higher the repeated bending resistance, which is the durability against repeated bending, and the higher the molecular weight, the lower the specific gravity. The diaphragm 115 is formed from PFA having a specific gravity of less than 2.135 and an opening and 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 times or more, preferably PFA having 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 having a specific gravity of 2.12 or less and a flex life value of 19,000,000 times or more. Therefore, the diaphragm 115 has sufficient resistance to repeated bending, and sufficient durability can be ensured. In addition, when the diaphragm valve 111 is opened or closed, the membrane portion 115b moves or bends, so that the valve body portion 115a of the diaphragm 115 is pressed against or separated from the valve seat 121. Therefore, particles are likely to be generated from the diaphragm 115 due to impact and friction when the valve body portion 115a contacts the valve seat 121, and repeated bending of the membrane portion 115b. However, the diaphragm 115 is formed of PFA, which has a molecular structure that makes it difficult for particles to be generated. Therefore, the diaphragm 115 has an effect of suppressing particle generation compared to when other fluororesin materials such as PTFE are used. That is, the diaphragm 115 can suppress particles by using PFA, while ensuring 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 thin 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. This cancels out a force in a direction that presses the valve body portion 115a of the diaphragm 115 against the valve seat 121 caused by the pressure of the fluid acting on the surface or step surface of the main body portion 155 and the thin diameter portion 157, and a force in a direction that pulls the membrane portion 115b of the diaphragm 115 away from the valve seat 121 caused by the pressure of the fluid acting on the membrane portion 115b (more specifically, the bent portion 161) extending from the upper end of the thin diameter portion 157. Therefore, the force in the direction that pulls the diaphragm 115 away from the valve seat 121 that is generated by the fluid pressure acting on the diaphragm 115 can be reduced. As a result, it is possible to reduce the seal thrust for pressing the valve body portion 115a of the diaphragm against the valve seat 121, thereby reducing the stress generated by pressing the valve body portion 115a against the valve seat 121 when the valve is closed, and thus suppressing the generation of particles. In particular, as described above, if the poppet diameter is set to 2.3 times or less the orifice diameter when the connecting hole 151 of the valve body portion 115a and the connecting end 135a are connected by a press-fit method, or if the poppet diameter is set to 1.3 times or less the orifice diameter when the protrusion portion 169 of the valve body portion 115a and the connecting hole 151' of the connecting end 135a' are connected by a screw-fit method, the effect of reducing the seal thrust can be strengthened by canceling out the force in the direction pressing the valve body portion 115a of the diaphragm 115 against the valve seat 121 and the force in the direction pulling the membrane portion 115b of the diaphragm 115 away from the valve seat 121, and the effect of suppressing the generation of particles can be improved.

[0067] In addition, a recess 165 is provided on the side farther from the sealing surface 115c at the connection between the bent portion 161 and the support portion 163 (more specifically, the first horizontal support portion 163a), and the outer peripheral edge portion of the bent portion 161 on the first horizontal support portion 163a side extends at an angle of 30° from the first horizontal support portion 163a in the direction away from the sealing surface 115c toward the valve body portion 115a. As a result, the bent portion 161 becomes easier to bend relative to the first horizontal support portion 163a which is clamped between the tip surface (bottom surface) of the protrusion 131a of the drive unit housing 131 and the horizontal surface of the step portion of the upper opening of the valve chamber 119 of the valve body 113, and the valve body portion 115a becomes easier to move up and down. As a result, the seal thrust is reduced, and the stress generated by pressing the seal surface 115c of the valve body portion 115a against the valve seat 121 when the valve is closed is reduced, thereby further enhancing the effect of suppressing the generation of particles.

[0068] Although the present invention has been described above with reference to the illustrated embodiment, the present invention is not limited to the illustrated embodiment. For example, in the diaphragm 115 according to the second embodiment, a male thread portion may be formed on the outer periphery of the connecting end 135a of the stem 135, and a female thread portion may be formed on the inner periphery of the connecting hole 151 provided in the valve body portion 115a, so that the connecting end 135a of the stem 135 and the valve end portion 115a are connected by screwing. In addition, the present invention can be applied to a suckback valve having a suckback function for preventing dripping, a needle valve having a flow rate adjustment function, a constant flow rate valve, a constant pressure valve or a back pressure valve for adjusting pressure, etc., as long as the valve supports the valve body portion to the valve body by the membrane portion, regardless of the use or function. [Explanation of symbols]

[0069] 11 Diaphragm valve 15 Diaphragm 15a Valve body 15b Membrane part 15c Sealing surface 111 Diaphragm valve 115 Diaphragm 115a Valve body 115b Membrane part 115c sealing surface 155 Main body 157 Reduced diameter part 159 Skirt Club 161 Bend 163 Support part 163a First horizontal support 163b Vertical support 163c Second horizontal support 165 Recess

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 using perfluoroalkoxyalkane as a raw material and injecting the raw material into a mold to form a semi-finished product by injection molding; A step of subjecting the semi-finished product to a cutting process so that at least a die transfer surface remains on a sealing surface; wherein the raw materials are selected so that the melt flow rate measured under a load of 5 kg and a measurement temperature of 372±0.1° C. is 3 g / 10 min or less, the specific gravity is less than 2.135, and the diaphragm can be opened and closed at a durability test result of 55,000 times 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. 3. The method for manufacturing a diaphragm according to claim 1, wherein the raw materials are selected so that the flex life value of the diaphragm is 19,000,000 cycles or more.

4. 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, The valve body portion and the membrane portion are formed by molding using as raw material a perfluoroalkoxyalkane selected so that the melt flow rate measured under a load of 5 kg and a measurement temperature of 372±0.1°C is 3 g / 10 min or less, the specific gravity is less than 2.135, and the diaphragm can be opened and closed more than 55,000 times in a durability test, and the sealing surface is a mold transfer surface formed by injection molding by injecting the raw material into a mold.

5. 5. The valve diaphragm according to claim 4, 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.

6. 6. The valve diaphragm according to claim 4, wherein the valve diaphragm is formed from a material having a flex life value of the diaphragm of 19,000,000 cycles or more.

7. 7. The diaphragm for a valve according to claim 4, 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.

8. 8. The diaphragm for a valve as described in claim 7, 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.

9. 9. The diaphragm for a valve according to claim 8, 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.

10. 10. The diaphragm for a valve according to claim 8 or claim 9, 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.

11. 11. The valve diaphragm according to claim 8, 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.

12. A diaphragm valve having a valve diaphragm described in any one of claims 4 to 11.

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