JP7653780B2 - Diaphragm manufacturing method, valve diaphragm, and diaphragm valve equipped with the same - Google Patents

Description

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 particle generation, a method for manufacturing the same, and a diaphragm valve equipped with such a diaphragm.

In a diaphragm valve, the inlet and outlet flow paths communicate with a valve chamber provided in the center of the valve body, and 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. The diaphragm is connected to the lower end of a stem driven by a drive mechanism located in the internal space of the drive unit housing, and the valve body supported by the diaphragm is pressed against and separated from a valve seat provided in the valve chamber, opening and closing the inlet and outlet flow paths. In addition, in chemical plants, semiconductor manufacturing fields, liquid crystal manufacturing fields, food manufacturing fields, and other fields, 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.

JP 2016-138641 A JP 2016-211618 A

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 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 diaphragm valves, and in particular to suppress the generation of particles from the diaphragm, which is in contact with the liquid and is also a moving part.

Typical fluororesins used for diaphragms include polytetrafluoroethylene (PTFE) and a copolymer of tetrafluoroethylene (TFE) and perfluoroalkylvinylether (PAVE), i.e., perfluoroalkoxyalkane (PFA). However, 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 contact portion where particles are likely to be generated, from PFA.

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 portion that contacts and separates from the valve seat, and a membrane portion that extends outward from the valve body portion and supports the valve body portion. The membrane portion must be flexible in order to withstand repeated bending when the valve body portion is repeatedly brought into and out of contact with the valve seat.

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 back and forth, and a diaphragm part formed on the opposite side of the seal part and installed in the 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 due to 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 in the seal part of the valve part and the valve part is not good, 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 also discloses a diaphragm in which a thin membrane 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 membrane by injection molding a second PFA material that has high fluidity, and the columnar portion and the membrane portion are directly bonded. However, to produce such a diaphragm, both rolling equipment and injection molding equipment are required, which increases costs.

The object of the present invention is therefore to provide a valve diaphragm that is highly resistant to repeated bending and can suppress particle generation by eliminating the problems present in the prior art.

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

In the above-mentioned diaphragm manufacturing method, perfluoroalkoxyalkane, i.e. PFA, selected so that the specific gravity is less than 2.135 and the opening and closing durability test result 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 compared with the case where the diaphragm is formed from the commonly used polytetrafluoroethylene (PTFE), the generation of particles can be suppressed. 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 opening and closing durability test result 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 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 suppress the generation of particles while ensuring high repeated bending resistance that can withstand use in a diaphragm valve. Furthermore, if PFA can be injection molded, mass production can be performed at low cost. In addition, 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 performing cutting processing, the decrease in surface roughness of the sealing surface due to cutting processing is prevented, and the generation of particles due to contact between the sealing surface and the valve seat is further suppressed.

It is further preferable that the raw materials are selected so that the specific gravity is 2.12 or less and the opening and closing durability test result of the valve diaphragm is 1,000,000 or more times. In this case, it is possible to further improve the durability of the diaphragm.

The raw materials are preferably 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.

In addition, the present invention provides, as a second aspect, a valve diaphragm 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, wherein the valve body portion and the membrane portion are formed by molding using as a 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 2.135 or less, and the result of an opening and closing durability test of the diaphragm is 55,000 times or more, and the sealing surface is a mold transfer surface formed by injection molding by injecting the raw material into a mold.

The valve diaphragm is entirely formed by molding using perfluoroalkoxyalkane, i.e. PFA, selected so that the specific gravity is less than 2.135 and the diaphragm's opening and closing durability test result is 55,000 or more as a raw material. Therefore, the valve diaphragm can suppress particle generation compared to when the diaphragm is formed from commonly used polytetrafluoroethylene (PTFE). The inventor also 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 opening and closing durability test result is 55,000 or more, the diaphragm can withstand use as a diaphragm for a diaphragm valve. The valve diaphragm is manufactured using PFA with a specific gravity of less than 2.135 and an opening and closing durability test result of 55,000 or more, so that the use of PFA can suppress particle generation while ensuring high repeated bending resistance that can withstand use in a diaphragm valve.

It is preferable that the valve diaphragm is formed from a 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.

It is further preferable that the valve diaphragm is formed from the raw material that gives the diaphragm a flex life value of 19,000,000 cycles or more.

In one embodiment, the valve body includes a main body having the sealing surface and a narrow diameter portion that is narrower than the main body, and the narrow diameter portion is supported by the membrane portion.

The membrane portion may also include an annular skirt portion extending from the outer periphery of the tip of the narrow diameter portion in a direction away from the main body portion, a bent portion curved convexly from the skirt portion in a direction away from the main body portion in the radial direction, and a support portion extending in a flat shape radially outward from the outer periphery of the bent portion.

In this case, it is preferable that the length of the bent portion is 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. It is also preferable that the outer peripheral edge portion of the bent portion extends toward the valve body portion at an angle of 20° to 40° relative to the support portion in the direction away from the seal surface. Furthermore, it is preferable that a recess is formed on the side of the connection portion between the bent portion and the support portion that is recessed toward the valve body portion, away from the seal surface.

Furthermore, as a third aspect, the present invention provides a diaphragm valve equipped with the above-mentioned valve diaphragm.

According to the present invention, the valve diaphragm is formed from PFA, which can suppress particle generation compared to when the diaphragm is formed from the commonly used PTFE. In addition, 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 the use of PFA can suppress particle generation while ensuring high resistance to repeated bending that can withstand use in a diaphragm valve.

FIG. 2 is a cutaway perspective view of a diaphragm according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view of the diaphragm shown in FIG. 1 . FIG. 2 is a vertical cross-sectional view showing a diaphragm valve including the diaphragm shown in FIG. 1 . FIG. 4 is a longitudinal sectional view showing a diaphragm valve including a diaphragm according to a second embodiment of the present invention. 5 is a cross-sectional view of a diaphragm according to the second embodiment shown in FIG. 4. FIG. 5 is a cross-sectional view showing a variation of the diaphragm shown in FIG. 4 . 5 is an enlarged cross-sectional view showing a membrane portion of the second diaphragm shown in FIG. 4 . FIG.

Below, an embodiment of a valve diaphragm 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 addition, 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.

Figures 1 and 2 show a valve diaphragm 15 according to a first embodiment of the present invention, and Figure 3 shows a diaphragm valve 11 equipped with a valve diaphragm 15.

First, the overall configuration of the diaphragm valve 11 will be described with reference to Figure 3. The diaphragm valve 11 comprises 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 top of the valve body 13.

The valve body 13 has a valve chamber 19 formed in the center of the upper part, and a first flow path and a second flow path communicating with the valve chamber 19. In the valve chamber 19, an annular valve seat 21 is formed around the opening from the first flow path to the valve chamber 19, to which the diaphragm 15 moves. In the illustrated embodiment, the first flow path is an inlet 25 that 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, and the second flow path is an outlet 29 that extends from an outlet 27 formed on the other opposing side surface of the valve body 13 and opens at the side surface of the valve chamber 21. A raised annular valve seat 21 is formed around the opening from the inlet 25 to the valve chamber 19.

A base plate 53 can further be attached to the bottom of the valve body 13 to facilitate installation.

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 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 positioned 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.

The drive unit 17 includes a drive unit 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 a drive 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 drive unit housing 31, and the drive mechanism is composed of a piston 37 that is slidably housed in the cylinder portion and a coil spring 39 as a biasing member. In addition, a diaphragm holder 41 is fitted into the opening of the cylinder portion of the drive unit housing 31 on the valve body 13 side, and when the drive unit 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.

The outer peripheral surface of the piston 37 is in vertically slidable contact with the inner peripheral surface of the cylinder section, and divides the internal space of the cylinder section into an upper space 43 surrounded by the upper surface of the piston 37, the inner peripheral wall of the cylinder section, and the ceiling surface of the cylinder section, and a lower space 45 surrounded by the lower surface of the piston 37, the inner peripheral wall of the cylinder section, and the bottom surface of the cylinder section (i.e., the upper surface of the diaphragm retainer 41). In addition, 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 is connected to the diaphragm 15 (more specifically, the valve body portion 15a).

In the first embodiment of the diaphragm 15 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 connection 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 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, and for example, the connection end 35a may be connected to the valve body portion 15a by providing an enlarged diameter locking portion on the connection end 35a of the stem 35 and pressing the connection end 35a into the connection hole provided in the upper center of the valve body portion 15a.

A first communication port 47 is formed in the upper part of the drive housing 31, which communicates with the ceiling surface of the cylinder section that defines the upper space 43, 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 is formed in the side of the drive housing 31, which communicates with the bottom of the cylinder section that defines the lower space 45, 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.

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 toward the valve body 13 by the coil spring 39 and pushed down, 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. In addition, by supplying the working fluid (e.g., compressed air) to the upper space 43 of the cylinder part through the first communication port 47 and applying a downward fluid pressure to the upper surface of the piston 37 in a direction approaching the valve body 13, 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, 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 acting on the piston 37 by the working fluid in the upper space 43). 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 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 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 flows into the inlet 25 from the inlet 23 of the diaphragm valve 11 flows through the valve chamber 19 and the outlet 29 and flows out to the outside from the outlet 27.

As the valve body portion 15a of the diaphragm 15 approaches and separates from the valve seat 21 due to the opening and closing of the diaphragm valve 11 as described above, the membrane portion 15b supporting the valve body portion 15a is repeatedly bent. For this reason, the membrane portion 15b of the diaphragm 15 is required to be resistant to repeated bending.

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 diaphragm material, PFA has a molecular structure that is less likely to generate particles when used as a diaphragm material. Therefore, forming the diaphragm 15 from PFA can suppress the generation of particles. On the other hand, PFA generally has the 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 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. From this, the inventor found that when the specific gravity is less than 2.135, the results of the opening and closing durability test are rapidly improved, and when the specific gravity is less than 2.135 and the results of the opening and closing durability test are 55,000 times or more, the diaphragm 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 opening and closing 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 opening and closing 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.

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 measuring the number of times the diaphragm was broken by repeatedly opening and closing with an opening time of 1.2 seconds and a closing 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 the conditions of room temperature, constant load of 0.5 MPa fluid pressure, 0.5 MPa opening and closing pressure, and 1.1 mm opening and closing stroke (the distance traveled by the valve body 15a relative to the valve seat 19 during opening and closing). The flex life value was measured in accordance with JIS P 8115.

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. in accordance with ASTM D1238. When forming the diaphragm 15 from the PFA by injection molding, for example, after making a semi-finished product by injection molding of the above-mentioned type of PFA, the diaphragm 15 may be made by forming a part that is difficult to form by injection molding due to factors such as thinness, such as the membrane part 35b, by cutting. By making the diaphragm 15 by injection molding, the contact surface with the mold surface in the molded product becomes the mold transfer surface, so that the surface roughness is smaller than that of the surface by cutting processing and the smoothness is increased. Therefore, by making the diaphragm 15 by cutting the semi-finished product made 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 and the generation of particles can be suppressed. In particular, by producing the diaphragm 15 by machining a semi-finished product made by injection molding so that a metal transfer surface remains on the seal surface 15c of the valve body portion 15a, which repeatedly comes into and out of contact with the valve seat 21, the surface roughness of the seal surface 15c is prevented from decreasing due to machining, and the smoothness of the seal surface 15c is increased, reducing friction with the valve seat 21 and suppressing the generation of particles.

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 to prevent corrosion by the fluid. Examples of fluororesin materials that can be used include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polychlorotrifluoroethylene (PCTFE).

Next, the operation of the diaphragm valve 11 shown in Figure 3 will be described.

During normal operation when no working 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 urged downward by the coil spring 39 in a direction approaching the valve body 13, i.e., 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 you want to increase the sealing thrust, you can supply the working fluid to the upper space 43 of the cylinder 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 acts downward on the upper surface of the piston 37, changing the force that presses the seal surface 15c of the valve body portion 15a against the valve seat 21 via the stem 35, i.e., the pressing force, and adjusting the force that presses the valve body 15 against the valve seat 21.

When the working fluid (e.g., compressed air) is supplied to the second communication port 49 of the drive unit 17 from this state 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 through the second communication port 49 acts upward (i.e., in the direction away from the valve body 13) on the piston 37, and the piston 37 is moved upward in the direction away from the valve body 13, i.e., 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.

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, returning to the closed state.

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 the 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 with a specific gravity of less than 2.135 and an opening and 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 times or more, preferably 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. Therefore, the diaphragm 15 has sufficient resistance to repeated bending 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 formed from PFA, which has a molecular structure that makes it difficult for particles to be generated. Therefore, the diaphragm 15 has an effect of suppressing the generation of particles compared to the use of other fluororesin materials such as PTFE. In other words, the diaphragm 15 can ensure high resistance to repeated bending that can withstand use in a diaphragm valve while suppressing particles by using PFA.

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 present invention.

First, the overall configuration of the diaphragm valve 111 will be described with reference to Figure 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, and the drive unit 117 is attached to the top of the valve body 113.

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 a raised valve seat 121 is formed around the opening from the first flow path to the valve chamber 119 in the valve chamber 119, where the diaphragm 115 comes into contact with and separates from the valve chamber 119. In the embodiment shown in FIG. 4, the first flow path is an inlet 125 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, and the second flow path is an outlet 129 that extends from an outlet 127 formed on the other of the opposing side surfaces of the valve body 113 and opens at the side of the valve chamber 121, and a raised annular valve seat 121 is formed around the opening from the inlet 125 to the valve chamber 119.

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 narrows toward the end (tip) on the drive unit 117 side. In addition, the membrane portion 115b is formed so as to extend outward from the outer periphery of the tip (end on the drive unit 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 that extends upward 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 toward the drive portion 117, a bent portion 161 that extends radially outward from the upper end of the skirt portion 159 in a convex curve in a direction away from the valve body portion 115a, and a support portion 163 that extends radially outward from the outer periphery of the bent portion 161.

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 relative to the stroke (movement distance) of the valve body portion 115a when the diaphragm valve 111 is opened and closed, so the stress generated when the valve body portion 115a moves up and down is smaller, and particles are less likely to be generated. 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 the direction of pulling 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 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 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 membrane 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 membrane 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.

In addition, because the valve body portion 115a has a poppet shape, even if the valve body portion 115a is placed in 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 narrow diameter portion 157 of the valve body portion 115a is wider, making it easier to ensure the length of the bent portion 161.

As shown in detail in Figures 5 and 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 Figure 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 membrane 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 the two side surfaces 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 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 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 into the upper opening of the valve chamber 119 of the valve body 113. 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 located outboard of 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 allows the diaphragm 115 to be fixed and supported to the valve body 113 so that the seal surface 115c is positioned opposite the valve seat 121.

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

The drive unit 117 includes a drive unit housing 131 that is attached to the top of the valve body 113 and has an internal space formed therein, a cover member 133 that is attached to the top 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 that opens upward, and the drive mechanism is composed of a piston 137 that is slidably housed in the cylinder, 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 drive unit housing 131, and when the drive unit 117 is attached to the top of the valve body 113, the protrusion 131a of the drive 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 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, between the outer peripheral surface of the protruding portion 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.

The piston 137 is connected to the guide shaft 167 so as to extend upward, and to the 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 the connection end 135a located at the tip of the stem 135 is connected to the diaphragm 115 (more specifically, its 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 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 that penetrates the cover member 133, and guides the up and down movement of the piston 137 (i.e., the movement of the piston 137 in the direction in which the seal 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).

A first communication port 147 is formed in the cover member 133, which communicates with the ceiling surface of the cylinder section that defines the upper space 143, 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 is formed in the side of the drive unit housing 131, which communicates with the bottom of the cylinder section that defines the lower space 145, 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 disposed 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.

In the diaphragm 115 of the second embodiment, as shown in detail in Figure 5, an enlarged diameter locking portion is provided 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 (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 the 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 (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' and the protrusion 169 of the valve body portion 115a.

If the thin-diameter portion 157 is narrowed, it becomes easier to ensure the length of the bent portion 161. However, as shown in FIG. 5, when the connecting end 135a of the stem 135 is press-fitted into the connecting hole 151 provided in the valve body portion 115a, it is necessary to form the connecting hole 151 in the thin-diameter portion 157 of the valve body portion 115a. Therefore, 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 inlet passage 125 to the valve chamber 119 (hereinafter referred to as the orifice diameter), and it is preferable to make it 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 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, if the poppet diameter is set to 1.3 times the orifice diameter or less, as described below, the force acting on the surfaces or step surfaces of the main body 155 and the narrow diameter portion 157 to press the valve body portion 115a of the diaphragm 115 against the valve seat 121 due to 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 will cancel out, and the effect of reducing the seal thrust can be strengthened.

In the above-described configuration, in the diaphragm valve 11 shown in FIG. 1, in the diaphragm valve 111 shown in FIG. 4, during normal operation when 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 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 part through the first communication port 147 to apply a downward fluid pressure to the upper surface of the piston 137 in a direction approaching 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 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 part, 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 part is discharged to the outside from the first communication port 147. When the piston 137 moves upward away from the valve body 113, the valve body portion 115a of the diaphragm 115, which is 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 flows 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 to the outside from the outlet 127.

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

The results of the open/close durability test are measured according to the open/close durability test described above. The flex life value is measured according to JIS P 8115.

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 making a semi-finished product by injection molding of the above-mentioned type of PFA, the diaphragm 115 may be made by forming a portion that is difficult to form by injection molding, such as the membrane portion 135b, by cutting. By making 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 made by cutting, and the smoothness is increased. Therefore, by making the diaphragm 115 by cutting the semi-finished product made by injection molding so that the metal transfer surface remains 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 machining a semi-finished product produced by injection molding so that a metal transfer surface remains 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 surface roughness of the sealing surface 115c is prevented from decreasing due to machining, and the smoothness of the sealing surface 115c is increased, reducing friction with the valve seat 121 and making it possible to suppress the generation of particles.

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 to prevent corrosion by the fluid. Examples of fluororesin materials that can be used include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polychlorotrifluoroethylene (PCTFE).

The operation and manufacturing method of the diaphragm valve 111 using the diaphragm 115 configured in this manner is similar to that of the diaphragm valve 11, so a description will be omitted.

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 the 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 a PFA having a specific gravity of less than 2.135 and an opening and closing durability test result of 55,000 or more, or a PFA having a specific gravity of less than 2.135 and a flex life value of 180,000 times or more, preferably a 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 a 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 the impact and friction when the valve body portion 115a contacts the valve seat 121, and the repeated bending of the membrane portion 115b. However, the diaphragm 115 is formed from PFA, which has a molecular structure that makes it difficult for particles to be generated. Therefore, the diaphragm 115 has an effect of suppressing the generation of particles compared to the use of other fluororesin materials such as PTFE. In other words, the diaphragm 115 can ensure high resistance to repeated bending that can withstand use in a diaphragm valve while suppressing particles by using PFA.

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 the force in the direction of pressing the valve body portion 115a of the diaphragm 115 against the valve seat 121 caused by the fluid pressure acting on the surface or step surface of the main body portion 155 and the thin 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 caused by the fluid pressure 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 of pulling the diaphragm 115 away from the valve seat 121 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 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, and the effect of suppressing the generation of particles can be improved.

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 toward the valve body portion 115a in a direction away from the sealing surface 115c. This makes it easier for the bent portion 161 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 makes it easier for the valve body portion 115a to move up and down. As a result, the seal thrust is reduced, reducing 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, further enhancing the effect of suppressing particle generation.

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 may be connected by screwing. In addition, the present invention can be applied to a suckback valve having a suckback function to prevent 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.

REFERENCE SIGNS LIST 11 diaphragm valve 15 diaphragm 15a valve body portion 15b membrane portion 15c seal surface 111 diaphragm valve 115 diaphragm 115a valve body portion 115b membrane portion 115c seal surface 155 main body portion 157 reduced diameter portion 159 skirt portion 161 bent portion 163 support portion 163a first horizontal support portion 163b vertical support portion 163c second horizontal support portion 165 recess

Claims (12)

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 cutting the semi-finished product so that at least a mold transfer surface remains on the 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. The method for manufacturing a diaphragm according to claim 1, wherein the raw material is selected so that the specific gravity is 2.12 or less and the opening and closing durability test result of the valve diaphragm is 1,000,000 or more times. 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 times or more. 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 a perfluoroalkoxyalkane as a raw material 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. 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. 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. 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. 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. 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. 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. 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. A diaphragm valve comprising the valve diaphragm according to any one of claims 4 to 11 .

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