JP2698502B2 - Metal diaphragm valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal diaphragm valve, and more particularly to an all-metal metal diaphragm valve for directly seating or releasing a metal diaphragm from a metal valve seat.

[0002]

2. Description of the Related Art Conventionally, as an on-off valve used in a piping system of a semiconductor manufacturing apparatus or the like, a valve free of a sliding portion that generates fine particles due to wear in a valve internal flow path and having no dead space is required. Was. In order to solve this problem, for example, there are metal diaphragm valves disclosed in JP-A-63-285373 and JP-A-2-29361. This metal diaphragm valve has a metal diaphragm made of metal and a resin valve seat whose central part bulges upward.The metal diaphragm is deformed within the elastic deformation range, and is directly seated on or separated from the valve seat. The valve was then opened and closed. However, recently, as the concentration of impurities in the source gas falls below the ppb level due to higher integration of semiconductors,
Requirement to be at t level.
One solution to this requirement is to minimize the amount of moisture and impurities adsorbed on and released from the material forming the valve internal flow path. However, the metal diaphragm valve using the above-mentioned conventional resin valve seat has the following problems. A) Since the resin material is inherently hygroscopic, it is difficult to completely release and remove the moisture and impurities adsorbed and absorbed by the resin valve seat. B) There is a limit to baking at high temperatures. C) It is highly corrosive and there is concern about the corrosion resistance to various types of source gases.

In view of the above, recently, a metal diaphragm valve having the following configuration has been considered to be optimal. a) The valve seat is a metal valve seat formed integrally with the valve box. b) All surfaces in contact with the fluid should be mirror-finished. c) In addition, it has a resin valve seat equal to or more sealing properties (about ^{1 × 10- 7 ~10- 9 atmcc /} sec). Therefore, there is a demand for a seal characteristic equal to or higher than that of the conventional one, even though the metal diaphragm and the metal valve seat are in contact with each other.

[0004]

However, in the case of metal-to-metal contact, the factor that enhances the sealing characteristics largely depends on the surface condition of the contact surface between the metal diaphragm and the metal valve seat, that is, the surface roughness. is there. The surface roughness of this contact surface can be generally up to about Rmax 0.1 μm, but in order to achieve the required sealing performance, it must be finished to an order of magnitude higher than this. Therefore, extremely high precision mirror finishing is required, and there is a problem in terms of equipment and cost.

As another means for improving the sealing properties, it has been considered to coat a soft metal on one of the contact surfaces (see Japanese Patent Application Laid-Open No. 2-266171). However, soft metals are inferior in durability, and thus have problems such as peeling in a short time, or generation of fine particles due to abrasion. The present invention has been made in order to solve the above problems, and has an object to provide a metal diaphragm valve having low cost, durability, and good sealing characteristics while being in contact with metals. And

[0006]

SUMMARY OF THE INVENTION According to the present invention, a metal valve box, a metal valve seat formed integrally with or separately from the valve box, and a peripheral portion thereof are hermetically clamped to the valve box. A metal diaphragm having a central portion directly opposed to and detachable from the valve seat; and a load means for displacing the central portion of the metal diaphragm in the valve seat direction, wherein the metal diaphragm and the valve seat When the hardness of each opposing surface is expressed by Vickers hardness, the difference between the hardness of the two is set to Hv50 to 400, and the difference in hardness is the hardness of the metal diaphragm Hv300 to 500, the valve seat Hv100 hardness
It is obtained by selecting each from the range of ~ 400.

[0007]

According to the present invention, since the contact surfaces of the metal diaphragm and the metal valve seat have an appropriate hardness difference as described above, when the metal diaphragm and the valve seat are pressed against each other when the valve is closed, the contact surface is hard. The surface of the soft member is finely deformed in accordance with the surface condition of the other member, and then the surface conditions of the soft member are brought into close contact with each other, so that the so-called conformability is exhibited and the sealing performance is improved. Further, generation of particles is suppressed.

Regarding the difference in hardness, it is effective to make the contact surface of the metal diaphragm harder than the valve seat side, and if the difference in hardness is Hv50 or less, minute deformation along one surface may occur. And the amount of leakage does not decrease because there is no conforming effect. Further, if it is Hv400 or more, the soft contact surface is deformed more than necessary with a relatively small number of times of opening and closing, and the leakage amount becomes large again, and there is a problem in durability. A preferable range is about Hv100 to 200.

Further, the hardness of the metal diaphragm is set to Hv300 or less.
The reason for choosing from the range of 500 is that if it is below Hv300, excessive deformation of the diaphragm will occur when pressed, and the sealing performance may be impaired, and the spring constant of the diaphragm will decrease, and the metal diaphragm itself will open when the valve is opened. This is because elastic recovery may not be possible. On the other hand, if it is Hv500 or more, on the contrary, the force for pushing the metal diaphragm when the valve is closed becomes too large, and if it exceeds the above range, the elastic characteristic of the metal diaphragm itself changes, which is not preferable. On the other hand, the reason for setting the hardness of the valve seat to Hv100 to 400 is that Hv100 or lower is too soft and deforms severely.
In addition, Hv400 is a naturally occurring hardness due to work hardening when a valve seat surface is machined, and further hardening requires additional means, which is inconvenient in terms of cost. Also,
As another means, a method may be used in which a thin film is formed on a metal diaphragm to give an apparent hardness difference. The material of the thin film may be Au, which is relatively soft and stable.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a fully closed state of a manually opened / closed type metal diaphragm valve. Reference numeral 1 denotes a metal diaphragm valve box made of corrosion-resistant stainless steel. An inflow channel 2 is formed on the left side, and an outflow channel 3 is formed on the right side in a substantially L-shape, and these channels communicate with each other through an upper opening. A convex annular valve seat 4 protruding upward is formed integrally with the valve box 1 at the upper end of the inflow passage 2. A step surface is formed on the periphery of the upper opening of the valve box 1, a peripheral portion of a metal diaphragm 5 described later is placed thereon, and a lid 7 is screwed to the valve box 1 via a diaphragm retainer 6. As a result, the periphery of the metal diaphragm 5 is hermetically clamped to the valve box 1. Thus, a sealed fluid chamber 11 is formed.

The metal diaphragm 5 is made of an appropriate metal material that can be elastically deformed, and is used by stacking two or three sheets in such a manner that the central portion thereof swells upward. The central portion is disposed as described above so that the valve portion can directly open and close (seated or unseated) to open and close the valve seat. On the other hand, the loading means 10 is provided with a valve stem 8 fitted into a central through hole of the lid 7 and partially screwed together, and a handle 9 provided at an outer end of the valve stem 8. Here, the valve stem may be moved up and down by fluid pressure such as air pressure or magnetic force. Although the distal end surface of the valve stem 8 has an appropriate curved shape, a pressing member made of a soft material may be interposed between the curved end surface and the metal diaphragm 5.

When the handle 9 is rotated, the valve rod 8 moves up and down, so that the central portion of the metal diaphragm comes into contact with and separates from the valve seat to open and close the valve. That is, when the valve stem 8 is lowered, the lowermost surface of the curved surface presses the metal diaphragm 5, the metal diaphragm is elastically deformed, and the central portion moves downward, but the central portion moves within the range of the elastic deformation of the metal diaphragm. The distance between the metal diaphragm and the valve seat, that is, the lift is determined so that the portion is pressed against the valve seat 4 to close the valve. Then, when the valve stem 8 is raised thereafter, the metal diaphragm 5 rises following the valve stem 8 so as to elastically return to the original shape. That is, the valve is opened and closed by deforming the metal diaphragm within the elastic deformation range. The surface roughness of the contact surface between the valve seat 4 and the metal diaphragm 5 is approximately the same as that of Rmax 0.2 μm, and the other fluid contact surfaces are also appropriately mirror-finished. .

In the metal diaphragm valve configured as described above, a leakage test was performed with a helium leak detector on the examples in Table 1 below in which the hardness of the metal diaphragm and the valve seat were changed. The hardness of the test product was determined by measuring the hardness of each contact surface at three points using a micro Vickers tester, and the average was used. In addition, as a comparative example, the same test was performed for each of the samples having different hardness differences. The result is shown in FIG. The metal diaphragm was made of a Ni-Co alloy material, and was subjected to aging treatment (for example, by changing the rolling ratio) to obtain a desired hardness. Further, the valve seat was made of SUS 316L material, and a desired hardness was obtained by appropriately performing burnishing from a raw material state.

[0014]

[Table 1]

As shown in FIG. 2, it can be seen that Examples Nos. 1, 2 and 3 in which the difference in hardness is within the range of Hv50 to 400 are stable in the leak region equal to or higher than the conventional one. On the other hand, in the comparative example No. 4 (the difference in hardness is small), the leakage amount hardly changes even if the number of times of opening and closing is repeated. In addition, it is recognized that in No. 5 (the difference in hardness is large), the leakage tends to increase. As described above, the surface roughness of the contact surface is Rmax 0.
It can be seen that the leakage amount can be reduced by relating an appropriate difference in hardness to the contact surface even at about 2 μm. It was also found that the amount of generated particles was reduced as compared with the conventional example.

[0016]

According to the present invention, it is possible to provide a metal diaphragm valve which is low in cost and durable in spite of contact between metals, has little generation of particles, and has good sealing characteristics.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a metal diaphragm valve to which an embodiment of the present invention is applied.

FIG. 2 is a diagram showing the results of a leak test of an example and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Valve box 2 ... Inflow channel 3 ... Outflow channel 4 ... Valve seat 5 ... Metal diaphragm 6 ... Diaphragm holder 7 ... Lid 8 ... Valve rod 9 ... Handle 10 ... Load means 11 ... Fluid chamber

Claims (2)

(57) [Claims] 1. A metal valve box, a metal valve seat formed integrally with or separately from the valve box, a peripheral portion of which is hermetically sealed by the valve box, and a central portion of which is formed by the valve seat. In a metal diaphragm valve having a metal diaphragm which directly opposes and separates directly and a load means for displacing a central portion of the metal diaphragm in the direction of the valve seat, the hardness of each of the opposed surfaces of the metal diaphragm and the valve seat is determined. A metal diaphragm valve characterized by a difference in hardness between Hv50 and 400 when expressed in Vickers hardness. 2. The hardness difference according to claim 1, wherein the hardness of the metal diaphragm is Hv300 to 500, and the hardness of the valve seat is Hv100 to Hv100.
400. A metal diaphragm valve characterized by being obtained by selecting from the above ranges.