Flow control valve seat and manufacturing method thereof

Abstract

To provide a valve seat for a flow rate control valve which prevents roughness and deformation of a contact surface from occurring even if it receives repeated impactive hits by a high-hardness diaphragm over a long period of time and which does not cause a leak even if used for a long period of time.SOLUTION: A valve seat 3 for a flow rate control valve A is formed of a pedestal portion 3a and a valve seat portion 3b. The pedestal portion 3a is made of a corrosion-resistance metal, and a joining hole 7a is formed in a joining face 3s1 between the valve seat portion 3b and the pedestal portion. The valve seat portion 3b is made of a fluorine resin, and a joining protrusion 7t filling the joining hole 7a is formed in a joining face 3s2 between the pedestal portion 3a and the valve seat portion. An inner diameter wi of an inlet 7i of the joining hole 7a is formed smaller than an inner diameter oi of a depth part 7o.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a valve seat for a flow control valve installed in a vaporizer used to vaporize a liquid source in, for example, a semiconductor manufacturing process, and to a method for manufacturing the same. [Background technology]

[0002] Flow control valves are used in many areas, one example being their application in controlling the supply of raw materials in the semiconductor manufacturing process. Taking the semiconductor manufacturing process as an example, in recent years, there has been a demand for flow control valves to control the mass flow rate of liquid raw materials in processes such as ALD (Atomic Layer Deposition). Such flow control valves are generally of the "normally closed" type. The valve opening and closing mechanism generally involves a diaphragm with spring properties that moves in and out of contact with a metal valve seat to open and close the valve seat.

[0003] Solenoids have generally been used as the actuator for opening and closing diaphragm valves, but in order to achieve more accurate mass flow control, there has been a recent demand for faster rise and fall times and for switching flow rates in a short time. For this reason, piezoelectric elements that expand and contract simultaneously with the on / off switching of voltage have been adopted as valve opening and closing actuators. As a result, flow control valves can now be opened and closed by pulse-shaped control signals. An example of a "normally closed" fluid control valve that uses a piezoelectric element is the control valve described in Patent Document 1.

[0004] In the "normally closed" fluid control valve described in Patent Document 1, a cylindrical member is fixed to the upper surface of the valve body, and a valve rod is provided within this cylindrical member. The valve rod is provided with a vertically long rectangular through hole that extends from one side to the other side. A bridge is provided at the bottom of this through hole that penetrates from one side to the other side, and a piezoelectric element is fitted between the bridge and the ceiling surface of the through hole. The valve rod rises and falls based on the bridge as the piezoelectric element expands and contracts. A pressure spring is interposed between the ceiling surface of the cylindrical member and the upper end step of the valve rod. This pressure spring presses the valve rod toward the valve seat via a diaphragm provided on the valve body, bringing the valve rod into a "closed state." The pressing force of the diaphragm against the metal valve seat is due to the elastic force of the pressure spring.

[0005] A piezoelectric element is provided in the space inside the valve stem. As described above, the upper surface of the element is in contact with the upper inner surface (ceiling surface) of the space inside the valve stem, and the lower surface of the element is in contact with a bridge that is fixed to the valve body and serves as a reference for the change in length of the piezoelectric element. By applying a voltage to the element, the valve stem is pushed upward, and the diaphragm is separated from the valve seat to enter the "open state."

[0006] When the flow control valve is a mass flow control valve used in a semiconductor manufacturing process and the raw material supplied is a liquid raw material whose mass flow rate is strictly controlled, it is required to open and close the valve quickly as described above, and at the same time, it is important that leakage of the liquid raw material does not occur for a long period of time when the valve is "closed." [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 1-55487 Summary of the Invention [Problem to be solved by the invention]

[0008] This valve uses a metal valve seat, and as mentioned above, the diaphragm is driven by turning the piezoelectric element on and off, going from the "normally closed state" to the "open state" when it is on, and from the "open state" to the "closed state" when it is off, but when going from the "open state" to the "closed state" when it is off, the elastic force of the compression spring bends the diaphragm, which has a large springiness, and presses it against the seating surface of the metal valve seat to the "closed state." In the case of a metal valve seat, the parallelism of the seating surface (valve seat surface) to the contact and separation surface of the diaphragm and the smoothness of the seating surface are important factors in preventing minute leaks in the "closed state." In addition, if the spring force of the pressure spring is weak, a small leak occurs in the "closed state", so the spring force of the pressure spring is made strong to prevent this small leak. As a result, the seating surface, which is softer than the diaphragm, gradually becomes rough due to repeated impacts over a long period of time caused by the strong spring force, which causes the small leak to occur in the "closed state".

[0009] Therefore, the inventors have made the valve seat of the normally closed flow control valve separate from the valve body and selected resin as the material for the valve seat instead of metal. The materials used for this purpose require high temperature, high mechanical strength, and chemical resistance. Polyimide resin is one of the resins that can withstand valve opening and closing at high temperatures, and has excellent heat resistance and high strength. However, since polyimide resin has poor resistance to moisture absorption, water, and chemicals, it was found that it cannot be used for the valve seats of flow control valves that handle liquid raw materials for semiconductor manufacturing processes that are highly reactive with water, contain water, or are highly corrosive (degradable).

[0010] Another material is fluororesin (for example, polytetrafluoroethylene (hereinafter referred to as PTFE) and copolymer of polytetrafluoroethylene and perfluoroalkoxyethylene (hereinafter referred to as PFA)). These have excellent resistance to water and chemicals and are softer than polyimide resin, so they adhere well to the diaphragm and provide excellent valve closing properties.

[0011] However, because fluororesin has a large coefficient of thermal expansion, it was found that if the entire valve seat was made of fluororesin, the volume of the valve seat would change significantly due to temperature, and if a piezoelectric element with a small driving force was used as the actuator, it would be easily affected by temperature changes.

[0012] The present invention has been made in consideration of the problems of the conventional examples described above, and a first object of the present invention is to provide a valve seat for a flow control valve which will not become rough or deform on the contact surface even if it is subjected to repeated impacts from a hard diaphragm for a long period of time, and which will not cause minute leaks even with long-term use, and a second object of the present invention is to provide a method for manufacturing such a valve seat. [Means for solving the problem]

[0013] Claim 1: a valve seat 3 of a flow control valve A, which is provided in a valve chamber 4 through which a liquid source L passes, and which is provided with a supply hole 3j opening into a seating surface 3z with which a diaphragm 5 comes into contact and separates, and which controls the amount of the liquid source L passing through by the diaphragm 5 coming into contact and separating from the seating surface 3z, The valve seat 3 is composed of a seat portion 3a provided in the valve chamber 4 and a valve seat portion 3b joined to a joining surface 3s1 of the seat portion 3a and with which the diaphragm 5 comes into contact and separates, The base portion 3a is made of a corrosion-resistant metal, and a joint hole 7a is formed in a joint surface 3s1 with the valve seat portion 3b. The valve seat portion 3b is made of fluororesin, and a joining protrusion 7t is formed on a joining surface 3s2 with the base portion 3a to fill the joining hole 7a. The connecting hole 7a is characterized in that the inner diameter wi of the entrance 7i is smaller than the inner diameter oi of the inner portion 7o.

[0014] Claim 2 provides the valve seat 3 of the flow control valve A described in claim 1, The fluororesin of the valve seat portion 3b is characterized by being tetrafluoroethylene or a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene.

[0015] Claim 3 provides the valve seat 3 of the flow control valve A described in claim 1, The valve seat 3 is characterized by being composed of a base portion 3a that protrudes integrally from the valve chamber 4, and a valve seat portion 3b that is joined to a joining surface 3s1 of the base portion 3a and with which the diaphragm 5 comes into contact and separates.

[0016] Claim 4 provides the valve seat 3 of the flow control valve A described in claim 1, The valve seat 3 is characterized in that it is composed of a base portion 3a attached to a valve seat accommodation hole 4s formed in the valve chamber 4, and a valve seat portion 3b joined to a joining surface 3s1 of the base portion 3a and with which the diaphragm 5 comes into contact and separates.

[0017] Claim 5 is a method for manufacturing the valve seat 3 of the flow control valve A according to any one of claims 1 to 4, The base portion 3a is formed using a corrosion-resistant metal; The joining surface 3s1 of the base portion 3a is irradiated with a laser to form the joining hole 7a in the joining surface 3s1, A fluororesin sheet that will become the valve seat processing layer 3b1 is placed on the joining surface 3s1, The valve seat processing layer 3b1, which is a fluororesin sheet, is heated and compressed toward the joining surface 3s1 of the base portion 3a, so that a part of the fluororesin sheet is pressed into the joining hole 7a, and a valve seat portion 3b having the joining protrusion 7t filled in the joining hole 7a is formed on the joining surface 3s1.

[0018] Claim 6 is a manufacturing method of the valve seat 3 of the flow control valve A according to claim 5, The valve seat processing layer 3b1 is compressed to form a compressed layer 3b2, which is then polished to form a valve seat portion 3b on the joining surface 3s1 of the seat portion 3a. Effect of the Invention

[0019] The valve seat 3 according to the present invention is a hybrid type in which the base portion 3a is made of a corrosion-resistant metal and the valve seat portion 3b is made of a fluororesin. The valve seat portion 3b, which has excellent adhesion to the diaphragm 5 and excellent chemical resistance to the liquid raw material L but poor mechanical strength, is reinforced by the base portion 3a made of a corrosion-resistant metal. This makes it possible to realize a valve seat 3 whose contact surface does not become rough or deformed even when it is subjected to repeated impacts from the hard diaphragm 5 for a long period of time, and which does not cause micro-leaks even when used for a long period of time.

[0020] Moreover, over the entire joint surfaces 3s1 and 3s2 of the two, the joint protrusions 7t that fill the joint holes 7a are formed on the valve seat portion 3b, and the shape of this joint hole 7a is such that the inner diameter wi of the entrance 7i of the joint hole 7a is smaller than the inner diameter oi of the innermost portion 7o, so that the joint protrusions 7t are in a fixed fit. As a result, the valve seat portion 3b will not come off the base portion 3a even if subjected to repeated impacts over a long period of time as described above.

[0021] If the valve seat portion 3b is made of tetrafluoroethylene or a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene, the above-mentioned effects can be maximized. [Brief description of the drawings]

[0022] [Figure 1] 1A is a vertical cross-sectional view of an example of a valve to which a valve seat according to a first embodiment of the present invention is applied when no voltage is applied, and FIG. 1B is a vertical cross-sectional view of the same valve when a voltage is applied. [Diagram 2] FIG. 2 is a vertical cross-sectional view of an embodiment of a valve to which the valve seat shown in FIG. 1 is applied, in an initial assembled state in which an elastic member is unloaded. [Diagram 3] 1(b), (b) is a view taken along the line XX in FIG. 1(b), (c) is a view taken along the line YY in FIG. 1(b), and (d) is a view taken along the line ZZ in FIG. [Figure 4] 2(a) is a partial enlarged cross-sectional view of the valve chest when the diaphragm in FIG. 1 closes the valve seat, and FIG. 2(b) is a partial enlarged cross-sectional view of the valve chest when the diaphragm opens the valve seat. [Diagram 5] 1(a) to (e) are cross-sectional views showing a first manufacturing procedure of the valve seat of the present invention, (b-2) is a plan view of (b), and (c-2) is a cross-sectional view without polishing. [Figure 6] 1A to 1E are cross-sectional views showing a second manufacturing procedure for the valve seat of the present invention, (c-2) is a cross-sectional view in the case without polishing, and (d-2) is a cross-sectional view in the case where holes are drilled after compression processing. [Figure 7] 11 is a cross-sectional view showing a seat portion used in a third manufacturing procedure of the valve seat of the present invention. FIG. [Figure 8] FIG. 5(e) is a partially enlarged view of the bonding surface portion of FIG. [Figure 9] FIG. 6 is a partially enlarged cross-sectional view of a valve chest to which a valve seat according to a second embodiment of the present invention is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in detail below with reference to the illustrated embodiments. A flow control valve A of a liquid source vaporizer, which is an example to which the valve seat 3 of the present invention is applied, comprises a base block 1 and a valve opening / closing mechanism 10. In this embodiment, the base block 1 is made up of two blocks: a lower base block 1a and an upper base block 1b. The base block lower part 1a is made up of a first lower part 1a1 and a second lower part 1a2 attached thereto.

[0024] The valve chamber 4 is a space that is circular in plan view and is provided between the first lower part 1a1 and the second lower part 1a2. The valve chamber 4 is divided into upper and lower parts in a liquid-tight manner by a diaphragm 5 described below, with the lower part on the first lower part 1a1 side of the diaphragm 5 being the lower valve chamber 4a and the upper part on the second lower part 1a2 side being the upper valve chamber 4b. Because it is divided into upper and lower parts in a liquid-tight manner as described above, the liquid raw material L does not leak from the lower valve chamber 4a to the upper valve chamber 4b.

[0025] A liquid raw material introduction passage 6 through which the liquid raw material L sent from a storage tank (not shown) passes is formed in the first lower portion 1a1. The first lower portion 1a1 may be a block body integrally formed with the valve seat 3 (first embodiment, FIG. 4) or may be a separate body (second embodiment, FIG. 9). The valve seat 3 will be described first in the first embodiment, and then in the second embodiment. The first lower portion 1a1 of the first embodiment is integrally formed with the valve seat 3 as described later. The liquid raw material introduction passage 6 of the first lower portion 1a1 communicates with a supply hole 3j of the valve seat 3. The inner diameter of the supply hole 3j is smaller than the inner diameter of the liquid raw material introduction passage 6. The valve seat 3 will be described later.

[0026] In this embodiment, as described above, the liquid raw material introduction passage 6 communicates with the supply hole 3j of the valve seat 3, and the opening / closing port 3k of the valve seat 3 opens into the valve chest lower part 4a. The liquid raw material supply passage 9 opens into the bottom of the valve chest lower part 4a. Liquid raw material supply path 9 is drilled from the bottom of valve chamber lower portion 4a toward the side surface of first lower portion 1a1. Liquid raw material L flows into valve chamber lower portion 4a of valve chamber 4 through valve seat 3. Then, this liquid raw material L passes through liquid raw material supply path 9 and is supplied to vaporization chamber 100 of a vaporizer (not shown) to which this flow control valve A is connected. Although not shown, conversely, the passage opening to the bottom of valve chest lower portion 4a may be used as the liquid raw material inlet passage, and the passage communicating with valve seat 3 may be used as the liquid raw material supply passage, connected to the vaporization chamber.

[0027] The second lower portion 1a2 is provided with an upper valve chamber 4b. A plunger guide hole 4h is formed in the ceiling of the upper valve chamber 4b, and a plunger 51 constituting the valve opening / closing mechanism 10 is guided to slide up and down.

[0028] Next, the valve seat 3 of the first embodiment will be described. The valve chamber lower part 4a is circularly recessed into the upper surface (contact surface with the second lower part 1a2) of the block-shaped first lower part 1a1. The valve seat 3 is integrally provided in a cylindrical shape protruding from the center of the bottom of the valve chamber lower part 4a, and a supply hole 3j is drilled in the center (FIG. 4). The valve seat 3 is composed of a pedestal part 3a and a valve seat part 3b. The part rising from the bottom of the valve chamber lower part 4a is the pedestal part 3a, and the part joined to the joining surface 3s1, which is the upper surface of the pedestal part 3a, and the part with which the diaphragm 5 comes into contact and separates is the valve seat part 3b (FIG. 5(e)). The seat surface 3z of the valve seat 3 is slightly lower than the upper surface of the first lower part 1a1, and in this embodiment, the difference between the seat surface 3z and the upper surface of the first lower part 1a1 is the deflection allowance of the diaphragm 5.

[0029] The first lower portion 1a1 including the main components of the valve A and the seat portion 3a is made of a corrosion-resistant metal (stainless steel), and as described above, the valve seat portion 3b made of a fluororesin is laminated on the joint surface 3s1 of the joint portion 3a2 of the seat portion 3a. And, at the center of the valve seat 3, a supply hole 3j is provided that extends from the liquid raw material introduction passage 6 to the upper surface of the valve seat portion 3b as described above. The portion of the supply hole 3j that opens to the upper surface of the valve seat portion 3b is the opening / closing port 3k. Furthermore, the fluororesin that is the material of the valve seat portion 3b is preferably tetrafluoroethylene or a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene in terms of water resistance, chemical resistance, heat resistance, and valve closing ability (i.e., adhesion to the diaphragm 5).

[0030] The base portion 3a and the valve seat portion 3b are firmly joined at their joining surfaces 3s1 and 3s2. That is, a large number of joining holes 7a are formed in the joining surface 3s1 of the base portion 3a, and joining protrusions 7t that fit snugly into the joining holes 7a on the fluororesin joining surface 3s2 as shown below and fill the joining holes 7a.

[0031] The inner diameter wi of the inlet 7i of the connection hole 7a is smaller than the inner diameter oi of the innermost portion 7o (FIG. 8). The connection protrusion 7t that has entered the connection hole 7a is in a fixed fit, and the valve seat portion 3b will not peel off from the connection surface 3s1 of the seat portion 3a unless the connection protrusion 7t is cut off from its base.

[0032] There are several methods for joining the valve seat portion 3b. (1) There are three cases: a hole 3j1 that serves as a reference for the supply hole 3j in the base portion 3a is pre-formed (Figure 5); a hole 3j1 is not formed and is formed at the end of the process (Figure 6); and a semi-machined hole 3j2 that serves as a reference for the supply hole 3j is pre-formed (Figure 7). (2) The valve seat portion 3b may be subjected to only hot compression (Fig. 5(c-2), Fig. 6(c-2)), or may be subjected to hot compression and then polishing (Fig. 5(a)-(e), Fig. 6(a)-(e)).

[0033] 5(a) to 5(e) show a case where holes 3j1 serving as references for supply holes 3j are formed in advance in pedestal portion 3a, and after heat compression, polishing is performed to form valve seat portion 3b. A hole 3j1 is formed in the center of the prepared base portion 3a. The base portion 3a is integrally formed with the first lower portion 1a1. First, a joining hole 7a is formed in the joining surface 3s1 of the base portion 3a. While blowing air or inert gas, the entire surface of the joint surface 3s1 of the base portion 3a is scanned with a pulsed laser, for example, to blow away the metal melted by the laser irradiation, forming numerous joint holes 7a in the joint surface 3s1. As described above, the inner diameter wi of the inlet 7i of the formed joint holes 7a is smaller than the inner diameter oi of the inner part 7o.

[0034] After the formation of the joining holes 7a has been completed, a fluororesin sheet formed to fit the joining surface 3s1 of the base portion 3a is placed on the joining surface 3s1 of the base portion 3a. This fluororesin sheet is dense and does not contain any air bubbles inside, and is ring-shaped with a hole drilled therein to match the hole 3j1 of the base portion 3a, and serves as the valve seat processing layer 3b1. The thickness of this valve seat machining layer 3b1 is selected depending on the machining method to include both the compression allowance Q and the grinding allowance K, or to include only the compression allowance Q without grinding. The compression is performed on the valve seat processing layer 3b1 made of a fluororesin layer as in the above, but for ease of understanding, the compression allowance Q is shown diagrammatically.

[0035] After the valve seat processing layer 3b1 is placed, the valve seat processing layer 3b1 is pressed against the joining surface 3s1 with a press member (not shown) while being heated. A part of the pressed, softened valve seat processing layer 3b1 penetrates into every corner of the joining hole 7a. When polishing is performed, compression is performed so that a polishing allowance K is left.

[0036] When the compression is completed, the surface of the compressed layer 3b2 is polished to a predetermined height as a final finishing step, as described above. If polishing is not performed, the compression is completed after the predetermined height. If a hole 3j1 is previously formed in the center of the base portion 3a, a round bar (not shown) is inserted into the hole 3j1 to block it so that the fluororesin does not enter the hole 3j1 due to heat compression.

[0037] As shown in Fig. 6, if the prepared seat portion 3a does not have a hole 3j1, a joining hole 7a is formed in the same manner as above, and then a fluororesin sheet formed to fit the joining surface 3s1 of the seat portion 3a is placed on the joining surface 3s1 of the seat portion 3a. This fluororesin sheet becomes the valve seat processing layer 3b1, and in this case is a circular plate with no holes.

[0038] In this case, too, a thickness including the compression allowance Q and the polishing allowance K, or a thickness including only the compression allowance Q without polishing, is selected, and the valve seat machining layer 3b1 is heated and compressed in the same manner as above. In this case, since the hole 3j1 is not drilled, an appropriate method can be adopted, such as (a) drilling the supply hole 3j from the base portion 3a to the valve seat portion 3b after the heating and compression to complete the formation of the valve seat 3, (b) further polishing is performed after the drilling of the supply hole 3j, or (c) polishing is performed and then the supply hole 3j is finally drilled.

[0039] As shown in Figure 7, when a half-machined hole 3j2 is drilled in a prepared base portion 3a to a depth that leaves a laser processing range, as in Figure 6, (a) after heating and compressing, a supply hole 3j is drilled from the base portion 3a to the valve seat portion 3b based on the half-machined hole 3j2 to complete the formation of the valve seat 3, (b) after drilling the supply hole 3j, further polishing is performed, or (c) or after polishing, the supply hole 3j is finally drilled. An appropriate method can be used.

[0040] The diaphragm 5 is formed of a disk-shaped elastic thin plate with concentric ridges, and the central part is a flat valve part 5a that comes into contact with and separates from the valve seat 3, and its outer periphery is sandwiched liquid-tight between the first lower part 1a1 and the second lower part 1a2. When no pressing force is applied to the valve part 5a, the central valve part 5a is separated from the opening 3k of the valve seat 3 by the tension of the diaphragm 5 as shown in FIG. 4(b), and is assembled in this state. As described later, when the valve part 5a is pressed by the valve operating part 50, which is a part of the valve opening and closing mechanism part 10, it comes into contact with the opening 3k of the valve seat 3 as shown in FIG. 4(a) and closes the opening 3k of the valve seat 3. The pressing force F during closing is adjusted by the amount of deflection of the elastic member 60 arranged in the part depending on the amount of screwing of the upper bearing part 21 into the lower bearing part 25 of the slide bearing part 20, as described later.

[0041] As described above, the valve seat 3 is composed of the base portion 3a and the valve seat portion 3b made of fluororesin, so that when the valve portion 5a of the diaphragm 5 comes into contact with the seating surface 3z of the valve seat portion 3b by the pressing force F of the elastic member 60, its entire surface deforms to fit the valve portion 5a and fits tightly, ensuring reliable closure. Note that, because the valve seat portion 3b is backed up by the base portion 3a, the deformation remains in the vicinity of the seating surface 3z, and the valve seat portion 3b does not deform even after repeated opening and closing operations (repeated contact and separation operations of the valve portion 5a with the seating surface 3z) over a long period of time.

[0042] The valve seat 3 is unblocked when the piezoelectric element 45 expands (voltage application) eliminating the pressing force F from the plunger 51, causing the central valve portion 5a of the diaphragm 5 to move away from the seat surface 3z of the valve seat 3 due to its return tension, opening the opening / closing port 3k.

[0043] The valve opening / closing mechanism 10 is composed of a slide bearing portion 20, a support portion 30, a piezoelectric actuator portion 40 having a piezoelectric element 45, a valve operating portion 50, and a resilient member 60. The valve opening / closing mechanism 10 has a role of accurately and quickly transmitting the expansion and contraction of the piezoelectric element 45 to accurately and quickly open and close the diaphragm 5, so the valve opening / closing mechanism 10 of the flow control valve A of the present invention is structured to suppress the occurrence of errors due to thermal effects as much as possible. That is, in the present invention, in combination with the above-mentioned heat-insulating structure, the support 31 with a low linear expansion coefficient is used and the expansion and contraction of the piezoelectric element 45 is directly transmitted to the diaphragm 5, thereby enabling accurate and quick valve opening and closing.

[0044] The slide bearing portion 20 is composed of an upper bearing portion 21 and a lower bearing portion 25 . The lower bearing portion 25 is a cylindrical member with an open top and a closed bottom, with a female screw formed on the inner peripheral surface of the upper portion and a through hole 25h formed in the center of the bottom portion. The lower bearing portion 25 is mounted on the upper portion 1b of the base block.

[0045] The upper bearing 21 is a cylindrical block with an element storage hole 22 that is open on the top surface drilled in the center and multiple (three in this embodiment) post holding holes 23 that penetrate vertically around it. In this embodiment, the post holding holes 23 are formed at equiangular positions on the same circumference and a bearing 24 is set inside. A post 31 is inserted into this bearing 24. A male screw is engraved on the lower outer periphery of the upper bearing 21 and is screwed into the lower bearing 25 so that it can be screwed forward and backward, allowing the insertion allowance into the lower bearing 25 to be adjusted.

[0046] A steel ball fixing hole 21k is drilled at the bottom of the element storage hole 22 of this upper bearing 21, into which a second steel ball P2 fits. The second steel ball P2 makes point contact with the bottom of the piezoelectric element 45 (described later) and serves as a reference for the expansion and contraction of the piezoelectric element 45. An upper spring retaining hole 21h is recessed on the opposite side (lower surface) of the bottom of the element storage hole 22.

[0047] The support section 30 is composed of multiple support columns 31 (three in this embodiment), an upper end support member 33 attached to the upper part of the support columns 31, and a lower end support member 37 attached to the lower part. The support pillar 31 is a columnar member made of a metal with a linear expansion coefficient close to zero (for example, an iron-nickel alloy: Invar). The support pillar 31 is inserted into the bearing 24 of the slide bearing portion 20, and slides smoothly in the vertical direction.

[0048] The upper end support member 33 is composed of a disk-shaped upper end support plate 34 and an auxiliary pillar 35 suspended from the underside of the upper end support plate 34 in line with the support pillar 31, and the upper end of the support pillar 31 is screwed to the lower end of the auxiliary pillar 35. A female screw hole 34h for a fixing screw 36 is threadedly formed in the center of the upper end support plate 34. The length of the support pillar 31 is considerably longer than the auxiliary pillar 35, so that thermal expansion of the auxiliary pillar 35 in the longitudinal direction can be ignored. (Note that, although not shown, the auxiliary pillar 35 may be omitted and the support pillar 31 may be screwed directly to the upper end support plate 34.)

[0049] The lower end support member 37 is a disk-shaped member, and like the upper end support plate 34, a mounting hole is drilled to match the support 31, and the lower end of the support 31 is screwed into this mounting hole. A protrusion 37t that presses the plunger 51 is protruded from the center of the lower surface of the lower end support member 37. This protrusion 37t is inserted into the through hole 25h of the lower bearing part 25. In addition, a lower spring part holding hole 37h is recessed in the center of the upper surface of the lower end support member 37 in correspondence with the upper spring part holding hole 21h of the upper bearing part 21. A resilient member 60 is disposed between the upper spring part holding hole 21h and the lower spring part holding hole 37h, and the screwing allowance of the upper bearing part 21 relative to the lower bearing part 25 is adjusted to provide a predetermined resilient force. This resilient force is related to the valve seat closing force (pressing force F) of the diaphragm 5, as described later. (The above-mentioned spring upper part holding hole 21h and spring lower part holding hole 37h are for determining the position of the resilient member 60, but may be omitted.)

[0050] The piezoelectric actuator section 40 is composed of a piezoelectric element 45 and a ball guide 41 attached to the upper end of the piezoelectric element 45 . The length of the piezoelectric element 45 changes instantaneously according to the magnitude of the applied voltage, and when the applied voltage is zero, the extension length is zero, and the larger the applied voltage, the longer the extension length becomes. The length when the voltage applied to the piezoelectric element 45 is zero is defined as T, and the extension of the piezoelectric element 45 when a voltage is applied is defined as Δt. Here, the reference plane M for measuring the extension of the piezoelectric element 45 is defined as the bottom surface of the piezoelectric element 45.

[0051] As described below, the position of the reference plane M of the piezoelectric element 45 is adjusted so that when the extension length Δt of the piezoelectric element 45 is zero (i.e., the applied voltage is zero), the elastic member 60 presses the diaphragm 5 with an optimal elastic force, whereby the valve portion 5a of the diaphragm 5 contacts the entire surface of the seating surface 3z of the valve seat 3 with an appropriate pressing force F, and the opening / closing port 3k of the valve seat 3 can be reliably closed.

[0052] In addition, the piezoelectric element 45 has a very fast response speed to the applied voltage, and even if the voltage applied to the piezoelectric element 45 is set to a pulsed state at very short time intervals, the extension length Δt can be changed instantaneously in response to the applied voltage. Therefore, when the voltage applied to the piezoelectric element 45 is set to zero, the piezoelectric element 45 also instantaneously returns to its original length, and in response, the elastic member 60 instantaneously extends and pushes down the diaphragm 5 via the plunger 51. At this time, the valve portion 5a of the diaphragm 5 comes into impact contact with the seat surface 3z of the valve seat 3, which will be described later.

[0053] A second steel ball P2 for point contact between the lower end surface (reference surface M) of this piezoelectric element 45 and the bottom surface of the element housing hole 22 of the bearing upper portion 21 is disposed in a state of being fitted into the steel ball fixing hole 21k.

[0054] The ball guide 41 is a cylindrical member attached to the upper end of the piezoelectric element 45, and has a positioning hole 42 in its center, into which the first steel ball P1 fits. A fixing screw 36 is screwed into a female screw hole 34h in the center of the upper end support plate 34. The first steel ball P1 attached to the lower end of the fixing screw 36 is located directly above the positioning hole 42, and the fixing screw 36 is screwed into the female screw hole 34h in the center of the upper end support plate 34 with a clearance G larger than the screwing amount of the upper bearing part 21 described later. The clearance G is represented by the distance between the contact points of the first steel ball P1 and the positioning hole 42. The attached resilient member 60 has a free length, which is represented as S1 (FIG. 2).

[0055] 2, the initial state of the flow control valve A configured as described above is a state in which the length of the resilient member 60 is a free length S1, and in this state, it is disposed between the spring upper portion retaining hole 21h of the upper bearing portion 21 and the spring lower portion retaining hole 37h of the lower end support member 37. At this point, the upper bearing portion 21 is screwed into the lower bearing portion 25 as described above. Meanwhile, the diaphragm 5 is not deformed, and is separated from the seat surface 3z of the valve seat 3 by its tension, and the opening / closing port 3k is in the "open state."

[0056] The valve operating portion 50 comes into contact with the diaphragm 5 to open and close it, and in this embodiment, this corresponds to the plunger 51, the third steel ball P3, and the protective plate 52. The third steel ball P3 is fixed to the lower end of the plunger 51 and is in contact with the protective plate 52.

[0057] The protective plate 52 is a circular metal plate with a hemispherical recess formed in the center of its upper surface into which the lower part of the third steel ball P3 fits, and its flat lower surface is disposed so as to come into surface contact with the valve portion 5a in the center of the diaphragm 5. The depth of the recess is smaller than the radius of the third steel ball P3, and there is a gap between the lower surface of the plunger 51 and the upper surface of the protective plate 52, so that the pressing force F applied to the plunger 51 is applied vertically to the protective plate 52 via the third steel ball P3. Note that since the lower surface of the protective plate 52 is flat and comes into surface contact with the valve portion 5a in the center of the diaphragm 5, the surface pressure is low, and the valve portion 5a is protected by the protective plate 52 and does not deform. The upper end of the plunger 51 abuts against the projection 37t of the lower end support member 37, and moves up and down in accordance with the vertical movement of the projection 37t. The plunger 51 is inserted through the through hole 8h of the cooling fin 8 and the plunger guide hole 4h of the second lower portion 1a2.

[0058] In this embodiment, a compression coil spring is used as the resilient member 60. However, other spring members can also be used.

[0059] From this initial state, the resilient member 60 is deflected to obtain an appropriate valve closing force (pressing force F) from the diaphragm 5. That is, when the upper bearing 21 is screwed from this initial state (FIG. 2) to screw downward inside the lower bearing 25, the lower end support member 37 is pushed down via the resilient member 60, and the protrusion 37t of the lower end support member 37 pushes down the plunger 51. Since the plunger 51 is in contact with the diaphragm 5 in the "open state" via the third steel ball P3 and the protective plate 52, the diaphragm 5 is pushed in and the diaphragm 5 is deflected towards the valve seat 3.

[0060] If the upper bearing 21 is screwed further, the diaphragm 5 will eventually bend until it comes into contact with the valve seat 3, and the bending of the diaphragm 5 will stop in this state. At this point, the diaphragm 5 is simply in contact with the valve seat 3, so liquid leakage will occur when pressure is applied from the liquid raw material introduction passage 6. Therefore, the upper bearing 21 will continue to be screwed further from this state. If the upper bearing 21 is screwed further, only the elastic member 60 will bend, and the pressing force F of the diaphragm 5 pressing the valve seat 3 will gradually increase. Then, when the diaphragm 5 is closed with the pressing force F that can prevent liquid leakage from the valve seat 3, the screwing of the upper bearing 21 will stop, and the double nut or the threaded part will be fixed, for example, with an adhesive. As a result, the upper bearing 21 and the lower bearing 25 will become one body, and the setting of the bending amount of the elastic member 60 will be completed. The length of the elastic member 60 at this time is represented by S2 (FIG. 1(a)). This integrates the upper bearing 21 and the lower bearing 25, completing the setting of the amount of deflection of the resilient member 60. The length of the resilient member 60 at this time is represented by S2 (FIG. 1(a)).

[0061] During the screwing of the upper bearing 21 into the lower bearing 25, the first steel ball P1 of the fixing screw 36 is spaced apart from the positioning hole 42 of the ball guide 41 with a sufficient clearance G, so that it does not come into contact with the ball even when the deflection amount of the resilient member 60 has been set. After setting this amount of deflection, the fixing screw 36 is tightened until the first steel ball P1 comes into contact with the ball guide 41. At this time, if the amount of deflection of the resilient member 60 is changed by tightening too much, liquid leakage will occur, so the amount of tightening is limited to just bringing the ball into contact. This allows the flow control valve A to function as a "normally closed type." That is, the diaphragm 5 is deflected by the elastic force (pressing force F) of the elastic member 60, and the valve seat 3 is normally closed.

[0062] Next, the operation of the flow control valve A will be described. The flow control valve A is incorporated into a known system, such as a semiconductor manufacturing system, for use. The flow control valve A is connected to a storage tank (not shown) and receives a supply of liquid source L from the storage tank. The supplied liquid source L passes through a liquid source inlet path 6 and reaches the valve seat 3.

[0063] 1(a) is closed by the diaphragm 5, and the liquid source L is stopped at the opening 3k. The valve seat portion 3b of the valve seat 3 is made of resin, so it adheres very well to the diaphragm 5, can withstand long-term use and does not cause micro-leaks. When the vaporization of the liquid raw material L begins, a voltage is applied to the piezoelectric element 45. In response to the applied voltage, the piezoelectric element 45 instantly extends upward from the reference plane M, and the upper end support plate 34 is pushed upward by the amount of extension via the fixing screw 36. This extension is defined as Δt. As a result, the support column 31 and the lower end support member 37 attached to its lower end instantly move upward by that amount (extension Δt), and as described above, they are pressed against the upper bearing 21 fixed to the lower bearing 25, compressing the resilient member 60 by (extension Δt). The length of the compressed resilient member 60 is defined as S3 (FIG. 1(b)).

[0064] When the protrusion 37t of the lower end support member 37, which had been pressing the plunger 51, rises in accordance with the extension of the piezoelectric element 45, the diaphragm 5 is deformed in the return direction in accordance with this rise, pushing up the plunger 51 and opening the opening / closing port 3k of the valve seat 3. At this time, since the lower end of the elastic member 60 is held by the lower end support member 37, its elastic force is applied to the extended piezoelectric element 45 via the support 31, but not to the diaphragm 5. Therefore, the diaphragm 5 returns by its own tension in the return direction and moves away from the valve seat 3. Therefore, the distance of the separation is equal to the above Δt. Then, the liquid raw material L flows into the valve chamber lower part 4a from the opened opening / closing port 3k, and flows into the vaporization chamber 100 of the vaporizer through the liquid raw material supply passage 9 that opens at the bottom of the opening / closing port.

[0065] To close the valve seat 3 from this state, the voltage applied to the piezoelectric element 45 is set to zero. When the applied voltage becomes zero, the piezoelectric element 45 instantly returns to its original length T. Following this contraction, the lower end support member 37 of the support section 30 moves downward, pushing down the diaphragm 5 via the plunger 51. The diaphragm 5 is pushed down by the pressing force F of the elastic member 60 as described above, closing the valve seat 3. As a result, the liquid raw material L is sent to the vaporization chamber 100 at the commanded flow rate accurately without any time lag.

[0066] At the time of closing, the valve opening and closing operation uses the instantaneous piezoelectric element 45 and the resilient member (coil spring) that operates in response to the instantaneous piezoelectric element 45, so that the valve portion 5a of the diaphragm 5 comes into contact with the seating surface 3z of the valve seat 3 by the spring force, but since the valve seat portion 3b that constitutes the seating surface 3z is made of fluororesin, the contact is soft and the seating surface 3z is not damaged. At the same time, the valve seat portion 3b deforms slightly along the valve portion 5a of the diaphragm 5, so that the valve portion 5a comes into close contact with the entire surface of the seating surface 3z. In addition, even if the seating surface 3z is not a mirror surface, in other words, even if the seating surface 3z has slight irregularities, the convex parts of the seating surface 3z are deformed and concave, realizing no leakage from this contact portion.

[0067] The valve opening and closing by the piezoelectric element 45 is performed by a pulse signal from the control unit, and is repeated in a short time. The valve seat portion 3b is made of fluororesin as described above, and is soft, so it has excellent closing properties against the violent closing and separating movements of the hard diaphragm 5. Moreover, the valve seat portion 3b made of fluororesin is backed up by the base portion 3a made of corrosion-resistant metal, so it does not lose its shape even if it is subjected to violent opening and closing movements over a long period of time. If the valve seat portion 3b is made thin enough so as not to interfere with the opening and closing drive, no difference in thermal expansion that would affect the expansion and contraction of the piezoelectric element 45 will occur even if there is a difference in the temperature at which the liquid raw material L is heated.

[0068] Furthermore, in the flow control valve A of the present invention, the base block lower part 1a and the valve opening / closing mechanism part 10 are separated by the base block upper part 1b, and the cooling space R and the cooling fins 8 are provided in the base block upper part 1b, so that heat transferred from the base block lower part 1a side is dissipated to the cooling fins 8 and at the same time the base block upper part 1b is air-cooled in the cooling space R, and the valve opening / closing mechanism part 10 is not affected by the heat of the base block lower part 1a which comprises the valve chamber 4. Furthermore, because the base block upper part 1b is composed of multiple column members with thin cross sections, heat conduction from the base block lower part 1a is suppressed.

[0069] In addition, since the linear expansion coefficient of the piezoelectric element 45 on the valve opening / closing mechanism 10 side is close to zero and is almost the same as the linear expansion coefficient of the alloy used in the support 31, the dimensional change Δt of the piezoelectric element 45 is transmitted to the diaphragm 5 accurately and instantly.

[0070] Note that, as an example of the flow control valve A to which the valve seat 3 of the present invention is applied, one installed in a vaporizer used to vaporize liquid raw materials in the semiconductor manufacturing process has been given, but flow control valves are used in many fields and are not limited to the above embodiment. In addition, in this embodiment, the plunger 51 and the third steel ball P3 are used as the valve actuation part 50, but the protrusion 37t of the lower end support member 37 may be extended to replace the plunger 51, and the protrusion 37t and the third steel ball P3 may be used as the valve actuation part 50.

[0071] Next, a second embodiment of the valve seat 3 will be described (FIG. 7). In the second embodiment, differences from the first embodiment will be mainly described, and the description of the first embodiment will be used for the same configurations and effects. In the second embodiment, the valve seat 3 is separate and independent from the first lower part 1a1. Therefore, in order to attach the valve seat 3 to the first lower part 1a1, the first lower part 1a1 is divided into upper and lower parts and is composed of a first lower body 1a3 and a first lower valve seat mounting member 1a4.

[0072] The valve seat 3 is composed of a base portion 3a fixed to the first lower valve seat mounting member 1a4, and a valve seat portion 3b joined to a joining surface 3s1 of the base portion 3a and with which the diaphragm 5 comes into contact and separates (Figure 9).

[0073] The base portion 3a is made of a corrosion-resistant metal (stainless steel) and is composed of a flange portion 3a1 formed with a large diameter, a stepped portion 3a3 which is narrower than the flange portion 3a1 and provided at the center of the flange portion 3a1, and a joint portion 3a2 which is narrower than the stepped portion 3a3 and protrudes from the center of the stepped portion 3a3, and a valve seat portion 3b made of fluororesin is similarly laminated on a joint surface 3s1 of the joint portion 3a2. A supply hole 3j is provided in the center of the valve seat 3, which extends from the surface 3e on the supply side of the liquid raw material L to the upper surface of the valve seat portion 3b. The portion of the supply hole 3j which opens to the upper surface of the valve seat portion 3b is an opening / closing port 3k. The fluororesin used as the material for the valve seat portion 3b, the state of bonding between the base portion 3a and the valve seat portion 3b, the case in which the holes 3j1 and the semi-machined holes 3j2 serving as reference holes for the supply holes 3j are provided in advance, or the case in which these are not provided and the supply holes 3j are provided later, and the case in which polishing is performed or not, are the same as in the first embodiment. The first lower valve seat mounting member 1a4 is provided with a valve seat receiving hole 4s formed in accordance with the valve seat 3 so as to open to the center of the bottom surface of the valve chest lower part 4a.

[0074] The valve seat 3 thus formed is inserted into the valve seat housing hole 4s from below, and its flange portion 3a1 is screwed to the first lower valve seat mounting member 1a4. An O-ring 4o is fitted between the stepped portion 3a3 of the valve seat 3 and the corresponding stepped portion of the valve seat housing hole 4s so as to surround the joint portion 3a2, thereby preventing leakage of the liquid raw material L that has flowed into the valve chamber lower portion 4a from the valve chamber lower portion 4a.

[0075] The first lower body 1a3 is attached to the lower surface of the first lower valve seat mounting member 1a4 to form the first lower part 1a1. An O-ring 6o is provided at the joint between the lower surface of the first lower valve seat mounting member 1a4 and the upper surface of the first lower body 1a3 so as to surround the liquid raw material introduction passage 6, ensuring the connection between the liquid raw material introduction passage 6 and the supply hole 3j and preventing liquid leakage from this joint. The operation of the second embodiment is the same as that of the first embodiment, and therefore the description thereof will be cited.

[0076] As described above, the valve seat 3 according to the present invention does not have a contact surface that becomes rough or deformed even when it is subjected to repeated impacts from the hard diaphragm 5 for a long period of time, and therefore no micro-leaks occur even after long-term use, and the valve seat portion 3b does not separate from the base portion 3a. [Explanation of symbols]

[0077] A: flow control valve, F: pressing force, G: clearance, K: grinding allowance, L: liquid material, M: reference surface, P1-P3: 1st-3rd steel balls, oi: inner diameter of the inner part of the connecting hole, Q: compression allowance, R: cooling space, S: length of the elastic member, T: initial length of the piezoelectric element, Δt: elongation, wi: inner diameter of the entrance of the connecting hole 1: base block, 1a: base block lower part, 1a1: first lower part, 1a2: second lower part, 1a3: first lower body, 1a4: first lower valve seat mounting member, 1b: base block upper part, 3: valve seat, 3a: pedestal part, 3a1: flange part, 3a2: joint part, 3a3: step part, 3b: valve seat part, 3b1: valve seat machined layer, 3b2: compression layer, 3e: supply side surface, 3j: supply hole, 3j1: hole, 3j2: semi-machined hole, 3s1·3s2: joint surface, 3k: opening and closing port, 3z: seat surface, 4: valve chamber, 4a: valve chamber lower part, 4b: valve chamber upper part, 4h: plunger guide hole, 4o: O-ring, 4s: valve seat storage hole, 5: diaphragm, 5a: valve part, 6: liquid raw material introduction passage, 6o: O-ring, 7a: joint hole, 7i: inlet, 7o: inner part, 7t: joint projection, 8: cooling fin, 8h: through hole, 9: liquid raw material supply passage, 10: valve opening / closing mechanism, 20: slide bearing, 21: upper part of bearing, 21h: upper part of spring holding hole, 21k: steel ball fixing hole, 22: element storage hole, 23: support post holding hole, 24: bearing, 25: lower part of bearing, 25h: through hole, 30: support post, 31: support, 33: upper end support member, 34: upper end support plate, 34h: female thread hole, 35: auxiliary post, 36: fixing screw, 37: lower end support member, 37h: lower part of spring holding hole, 37t: projection, 40: piezo actuator, 41: ball guide, 42: positioning hole, 45: piezo element, 50: valve operating part, 51: plunger, 52: protective plate, 60: elastic member, 100: vaporization chamber

Claims

1. A valve seat of a flow control valve, which is provided in a valve chamber through which a liquid raw material passes, and which is provided with a supply hole opening to a seat surface with which a diaphragm comes into contact and separates, and which controls an amount of the liquid raw material passing through the valve seat by the diaphragm coming into contact and separating from the seat surface, the valve seat includes a base portion provided in the valve chamber and a valve seat portion joined to a joining surface of the base portion and with which the diaphragm comes into contact and separates, The base portion is made of a corrosion-resistant metal, and a joining hole is formed on a joining surface with the valve seat portion, The valve seat portion is made of fluororesin, and a joining protrusion that fills the joining hole is formed on the joining surface with the base portion, 1. A valve seat for a flow control valve, wherein the inner diameter of the inlet of the connecting hole is smaller than the inner diameter of the inner hole at the back.

2. 2. The valve seat of a flow control valve according to claim 1, wherein the fluororesin of the valve seat portion is tetrafluoroethylene or a copolymer of tetrafluoroethylene and perfluoroalkoxyethylene.

3. 2. The valve seat of a flow control valve according to claim 1, wherein the valve seat is composed of a base portion protruding integrally from the valve chamber, and a valve seat portion joined to a joining surface of the base portion and with which the diaphragm comes into contact and separates.

4. 2. The valve seat of a flow control valve according to claim 1, wherein the valve seat is composed of a base portion attached to a valve seat receiving hole formed in the valve chamber, and a valve seat portion joined to a joining surface of the base portion and with which the diaphragm comes into contact and separates.

5. forming the base portion using a corrosion-resistant metal; The joining surface of the base portion is irradiated with a laser to form the joining hole in the joining surface; A fluororesin sheet that will become a valve seat processing layer is placed on the joining surface, 5. The method for manufacturing a valve seat for a flow control valve according to any one of claims 1 to 4, characterized in that a fluororesin sheet which is the valve seat processing layer is heated and compressed toward a joining surface of the base portion, and a part of the fluororesin sheet is pressed into the joining hole, thereby forming a valve seat portion on the joining surface having the joining protrusion filled in the joining hole.

6. 6. The method for manufacturing a valve seat of a flow control valve according to claim 5, further comprising polishing a compressed layer formed by compressing the valve seat processing layer to form a valve seat portion on a joining surface of a base portion.

Images