JP5546018B2 - Flow control valve - Google Patents

Description

  The present invention relates to a flow control valve used mainly in a gas supply system of a semiconductor manufacturing apparatus, and more particularly to a flow control valve that keeps the Cv value of a valve stable from normal temperature to high temperature and has little flow fluctuation.

Conventionally, focusing on maintaining the maximum flow rate of the high-temperature gas valve, the metal diaphragm is heat treated to increase the hardness and suppress the deformation amount of the diaphragm at a high temperature (for example, about 250 ° C.). Such a technique is disclosed in Patent Document 1 shown below.
In Patent Document 1, when a metal diaphragm made of a cobalt alloy is subjected to age-hardening heat treatment and the Vickers hardness is set to Hv 500 or more, a decrease in reaction force and thermal expansion of the metal diaphragm can be suppressed even in a high temperature environment. It is described that the gap between the metal diaphragm and the valve seat can be kept constant, and the source gas can be stably supplied into the semiconductor manufacturing apparatus.

However, when the diaphragm valve has a large diameter, the fluid pressure receiving area also increases, and when used at high temperature and in a vacuum state, the diaphragm drops so that it is pulled largely in the valve seat direction due to the negative pressure load, reducing the flow rate. In addition, the valve could naturally occlude.
In order to cope with this problem, Patent Document 2 discloses a technique in which a diaphragm is welded to an elevating member (actuator stem) for bringing the diaphragm into and out of contact with a valve seat.

On the other hand, in a dome-shaped metal diaphragm with increased hardness, if the maximum bulge height of the dome shape is used as a stroke length and the number of valve opening / closing operations is repeated, cracks tend to occur and durability is reduced. For this purpose, it is preferable to reduce the strain and strain applied to the metal diaphragm during the valve opening / closing operation, and a technique in which a dimension (distance) of 55 to 70% of the maximum bulge height is used as a stroke length is disclosed in Patent Document 3. Has been.
Although the opening / closing durability of the metal diaphragm is improved by setting the dimension (distance) of 55 to 70% of the maximum bulge height as the stroke length, the graph 1 of the conventional product (100%) in FIG. As shown in the graph 5 of the reference product (66%), it has been found by experiments by the present inventors that the Cv value varies greatly between room temperature and high temperature. Here, the conventional product (100%) in FIG. 4 shows a stroke length that is 100% of the maximum bulge height of the metal diaphragm, and the reference product (66%) is a metal diaphragm. The dimension (distance) of 66% of the maximum bulge height is the stroke length. The Cv value was calculated based on the JIS standard (JIS B0100-1984). Measurement temperature is 23 degreeC (at the time of normal temperature), 100 degreeC, 150 degreeC, 200 degreeC, and 250 degreeC (at the time of high temperature).

In addition, due to variations in processing accuracy and assembly accuracy of components constituting the flow control valve, the flow characteristics vary among products of each flow control valve. In particular, in a semiconductor device manufacturing process manufactured under a high temperature environment, the difference in flow rate characteristics (for example, Cv value) has a large influence on the process.
Therefore, for example, in Patent Document 3, as a stroke length adjusting mechanism for a metal diaphragm, a support cylinder portion of an actuator is screwed into a bonnet that covers a valve body, and is fixed by a lock nut screwed to the support cylinder portion. Thus, a technique for adjusting the height of the actuator attached to the valve body is disclosed.

JP 2008-151270 A JP 2006-90386 A JP 2007-64333 A

In recent years, when the Cv value of a valve changes greatly with a change in temperature, the quality of the film forming process of a miniaturized and highly integrated semiconductor device is adversely affected. There is a need for a flow control valve.
However, when the temperature of the raw material gas and the usage environment changes from normal temperature (about 20 ° C) to high temperature (about 250 ° C), the strength of the diaphragm decreases, and the central part of the diaphragm falls downward when the valve is opened. It will be close to the seat. When used in a vacuum state, the downward pressure of the diaphragm is further increased due to the negative pressure.
That is, when the diaphragm softens at high temperatures and negative pressure as described above acts, the valve opening position of the diaphragm is lowered, and the Cv value of the flow control valve is reduced to about 40 to 60% at normal temperature. However, it has been proved by experiments by the present inventors. Then, in the initial stage, specifically, with the mounting state at room temperature (a state where no negative pressure is applied), the diaphragm height is regulated in advance to the valve opening position at a high temperature. When the Cv value of the flow rate control valve was measured, the Cv value at the high temperature was of course substantially the same, but the Cv value at the normal temperature was compared to when the Cv value was not regulated at all. It turned out to shrink to about half the change. In other words, when the diaphragm stroke length is regulated from the beginning to the valve open position corresponding to the Cv value at high temperature, the stroke length is not regulated between the normal temperature and the high temperature, and the stroke length is not regulated. It has been found that it can be reduced to about half compared to the case, and that the Cv value at high temperature is almost the same as when the stroke length is not regulated.

Since the stroke length of the diaphragm is regulated in advance, when the diaphragm is welded to the lifting member (stem) as in the structure disclosed in Patent Document 2, the diaphragm is integrated with the lifting member (stem). Therefore, it is not possible to remove only the elevating member (stem). For this reason, the stroke length of the diaphragm cannot be reliably and accurately adjusted for each product with a simple mechanism.
At that time, a structure in which the stem is vertically separated into a first stem and a second stem, the first stem is connected to an elevating member (actuator), and the second stem is welded to the diaphragm is also conceivable.
However, since the second stem is welded to the diaphragm alone, the second stem descends integrally with the diaphragm at a high temperature and becomes lower than the height when the valve is opened at a normal temperature.
Therefore, the second stem that is in contact with the first stem when the valve is opened at normal temperature may be separated from the first stem when the valve is opened at high temperature. If the first stem and the second stem are separated when the valve is opened, the stroke length of the diaphragm cannot be regulated to a constant value, so that the Cv value fluctuates and the flow rate control is not stable.

  In the structure in which the height of the actuator attached to the bonnet that covers the valve body of the actuator is adjusted by the screwing amount as in the structure disclosed in Patent Document 3, the height of the actuator attached to the bonnet is determined by the screw thread and the screw groove. It is difficult to adjust the stroke length of the diaphragm with high accuracy and certainty due to subtle changes due to variations in machining accuracy.

  Furthermore, the negative pressure acting on the diaphragm due to the fluid flowing in the valve chamber from the input port toward the output port tends to become stronger on the output port side. And if a diaphragm softens at the time of high temperature, the elastic force which restores upwards at the time of valve opening will fall. Therefore, when the temperature is high, the influence of the negative pressure becomes relatively high, and a change in the restoring posture of the diaphragm is likely to occur. This is one of the factors that cause the Cv value to vary between normal temperature and high temperature.

  The present invention has been made in view of the circumstances as described above, and its main purpose is to maintain a stable Cv value fluctuation between normal and high temperatures even when used at high temperatures and in vacuum. Therefore, it is an object of the present invention to provide a flow rate control valve that can easily and accurately adjust the stroke length of a diaphragm in order to ensure a sufficient flow rate and reduce variations in Cv values between products.

In order to achieve the above object, a flow control valve according to the present invention has the following configuration. (1) A valve body provided with a valve seat on the bottom surface of the valve chamber communicating with the input port and the output port, and disposed above the valve seat so as to come into contact with and separate from the valve seat, and a central portion thereof bulges upward. The metal diaphragm, a stem that moves the central portion of the metal diaphragm up and down, an actuator that drives the stem, and the metal diaphragm disposed above the outer peripheral edge of the metal diaphragm and the bottom surface of the valve chamber. In the flow control valve provided with a holder part to which the actuator is connected at the upper part while holding the diaphragm in an airtight manner,
The stem is vertically divided into a first stem connected to the actuator and a second stem pressed against the upper surface of the central portion of the metal diaphragm, and can be contacted and separated from each other;
In the valve opening position of the metal diaphragm, the stroke length of the metal diaphragm is reduced from the full stroke length of the metal diaphragm by restricting the rise of the second stem by the first stem .
By limiting the stroke length of the metal diaphragm to 20 to 49% of the full stroke length of the metal diaphragm, the difference in Cv value between high temperature (250 ° C.) and normal temperature is within 0.19. Features.

( 2 ) In the flow control valve described in ( 1 ),
The actuator has an air cylinder part and a spring part,
The use stroke length of the metal diaphragm is made within the range of the regulation value by sandwiching a shim between the air cylinder part and the spring part.
( 3 ) In the flow control valve described in (1) or (2) ,
The actuator includes an air cylinder having a piston in a case,
A through hole for measuring the stroke length of the metal diaphragm is provided in the case of the air cylinder.
( 4 ) In the flow control valve described in any one of (1) to ( 3 ),
The second stem moves up and down in sliding contact with a communication hole formed in the center of the holder portion.

The flow control valve of the present invention having such characteristics has the following operational effects.
The invention described in (1) includes a valve body provided with a valve seat on the bottom surface of a valve chamber communicating with an input port and an output port, and a central portion of the valve body disposed above and adjacent to the valve seat. Between the metal diaphragm that bulges upward, the stem that moves the center of the metal diaphragm up and down, the actuator that drives the stem, and the bottom of the valve chamber that is disposed above the outer peripheral edge of the metal diaphragm In a flow control valve that includes a holder portion to which an actuator is connected at an upper portion thereof while air-tightly holding a diaphragm, the stem is pressed against the first stem connected to the actuator and the upper surface of the central portion of the metal diaphragm. The second stem is divided into upper and lower parts, can be contacted and separated from each other, and the first stem regulates the rise of the second stem at the valve opening position of the metal diaphragm. The Rukoto, since the use stroke length of the metal diaphragm is characterized in that reduced than the full stroke length of the metal diaphragm, functions and effects described below.

In the invention of (1), since the first stem regulates the rise of the second stem at the valve opening position of the metal diaphragm, the strength of the metal diaphragm is high at room temperature. The second stem pressed against the upper surface of the central portion of the metal diaphragm tends to move upward from the valve opening position at a high temperature, but the second stem is in contact with the first stem connected to the actuator. , Upward movement is restricted. Therefore, the rising position of the second stem when the valve is open can be made substantially constant from the normal temperature to the high temperature, and the use stroke length of the metal diaphragm can be controlled to be substantially constant from the normal temperature to the high temperature. As a result, a stable flow rate can be ensured with little variation in the Cv value between normal temperature and high temperature.

  In addition, the stem is divided vertically into a first stem connected to the actuator and a second stem pressed against the upper surface of the central portion of the metal diaphragm, and can be brought into contact with and separated from each other. When adjusting the operating stroke length of the diaphragm by adjusting the raised end position of the stem, with the actuator and the first stem assembled together, remove the actuator from the holder and adjust the mounting position of the first stem. In addition, the use stroke length of the diaphragm can be easily and accurately adjusted by connecting to the holder portion. As a result, the Cv value can be easily and accurately adjusted.

Further, by limiting the stroke length of the metal diaphragm to 20 to 49% of the full stroke length of the metal diaphragm, the difference in Cv value between high temperature (250 ° C.) and normal temperature is within 0.19. Therefore, even when used at a high temperature and in a vacuum state, a stable flow rate can be ensured with little variation in the Cv value between normal temperature and high temperature.
Here, the reason why the lower limit of the stroke length of the diaphragm is 20% of the full stroke length is that the Cv value (250 ° C) at a high temperature (250 ° C) at that time is 0.12, and the Cv value is smaller than this. This is because it is practically equivalent to a diaphragm whose outer diameter is reduced by one rank, and therefore there is no meaning of a large size. In addition, the upper limit of the diaphragm stroke length is 49% of the full stroke length because the difference in Cv value between high temperature (250 ° C) and normal temperature is 0.19. This is because the flow rate control system becomes practically complicated and it becomes difficult to perform stable flow rate control.
That is, at a high temperature (250 ° C.), the softened diaphragm is subjected to negative pressure, and the gap with the valve seat is reduced, and accordingly, the Cv value is reduced to about 40 to 60% as compared with the normal temperature. Under the idea that the Cv value is limited to be smaller than the reduced Cv value, the diaphragm stroke is limited to 20 to 49% of the full stroke length of the diaphragm in the initial state. The difference between the Cv value (normal temperature) and the Cv value (250 ° C.) at high temperature (250 ° C.) is within the range of 0.19. A stable flow rate can be ensured with little change in Cv value between normal and high temperatures without dropping one rank and without complicating the flow control system.

The invention described in ( 2 ) is the flow control valve described in ( 1 ), wherein the actuator has an air cylinder part and a spring part, and a shim is sandwiched between the air cylinder part and the spring part. Therefore, if you have multiple shims that fit between the air cylinder part and the spring part, the use stroke length of the metal diaphragm can be set to the desired stroke length. Easy and reliable adjustment. For this reason, even when the stroke length of the metal diaphragm is slightly different for each product, the adjustment within the range of the regulation value can be performed with high accuracy and reliability. Also, because it is shim adjustment, unlike the structure where the actuator is adjusted by the screwing amount, it does not change slightly due to variations in the processing accuracy of the thread and groove, so the diaphragm stroke length can be adjusted accurately and reliably. Is easy.
Therefore, the use stroke length of the diaphragm for each product can be adjusted more easily and accurately, and the variation in the Cv value between products can be further reduced.

In the invention described in ( 3 ), in the flow control valve described in (1) or (2) , the actuator includes an air cylinder having a piston in the case, and the through hole for measuring the stroke length of the metal diaphragm Is provided in the case of the air cylinder, and with the air cylinder attached to the valve body, the measuring rod is inserted into the through hole provided in the case of the air cylinder and brought into contact with the piston, The stroke length of the metal diaphragm can be measured. The piston is connected to the first stem via a piston rod, and the first stem regulates the upward movement of the second stem pressed against the upper surface of the central portion of the metal diaphragm. This is because it moves up and down in conjunction with.
Thereby, the stroke length of the diaphragm for each product can be easily confirmed, so that the adjustment can be performed more easily and accurately, and the variation in the Cv value between products can be further reduced.

The invention described in ( 4 ) is the flow rate control valve described in any one of (1) to ( 3 ), wherein the second stem is slidably contacted with a communication hole formed in the center of the holder portion. Since the metal diaphragm strength is lowered at high temperatures and the recovery posture of the metal diaphragm is likely to change, the central portion of the metal diaphragm is not moved by the pressed second stem. While moving up and down with the second stem while being held in a shape substantially along the lower end surface, the correct stroke trajectory can be accurately reproduced.
As a result, the fluctuation of the Cv value can be further reduced between normal temperature and high temperature (250 ° C.).

1 is an overall cross-sectional view of a fluid control valve 1 according to a first embodiment of the present invention, showing a valve open state of a metal diaphragm. It is an upper part sectional view of fluid control valve 1 concerning a 1st embodiment of the present invention, and shows attachment state S of a cylinder part when it removes from an upper holder. It is a lower fragmentary sectional view of fluid control valve 1 concerning a 1st embodiment of the present invention, and shows the valve closed state of a metal diaphragm. It is the graph which calculated | required the relationship between valve temperature and Cv value using the fluid control valve 1 which concerns on 1st Embodiment of this invention. FIG. 2 is an upper partial cross-sectional view of the fluid control valve 1 according to the first embodiment of the present invention, showing a state in which a measuring rod is inserted into a through hole in order to measure the stroke length of the metal diaphragm. It is sectional drawing of the cylinder case of the flow control valve 2 which concerns on 2nd Embodiment of this invention, Comprising: The adjustment knob which adjusts the raising end position of a piston rod is shown.

Next, an embodiment of a flow control valve according to the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is an overall cross-sectional view of a flow control valve 1 according to a first embodiment of the present invention, showing a valve open state. FIG. 2 is an upper partial sectional view of the fluid control valve 1 according to the first embodiment of the present invention, and shows an assembled state S of the cylinder part when it is removed from the upper holder. FIG. 3 is a partial cross-sectional view of the lower part of the fluid control valve 1 according to the first embodiment of the present invention, and shows a closed state of the metal diaphragm. FIG. 4 is a graph showing the relationship between the valve temperature and the Cv value using the fluid control valve 1 according to the first embodiment of the present invention. FIG. 5 is an upper partial sectional view of the fluid control valve 1 according to the first embodiment of the present invention, and shows a state in which a measuring rod is inserted into a through hole in order to measure the stroke length of the metal diaphragm.
The flow control valve 1 of 1st Embodiment is assembled | attached to the gas supply system of a semiconductor manufacturing apparatus similarly to a prior art, and controls supply of high temperature gas. The flow control valve 1 is a normally closed type air operated on-off valve. The flow control valve 1 includes an actuator portion 3 disposed above, a valve portion 4 disposed below and having a metal diaphragm, and a holder portion 5 that connects the two. In the actuator part 3, the air cylinder part 6 and the spring part 7 are connected via a thin plate (shim) 52.

As shown in FIG. 1, the air cylinder unit 6 includes a cylinder base 31, a cylinder case 32, a piston 33, an intermediate plate 34, a piston rod 35, an O-ring 36, and a pressurizing chamber 37. The spring portion 7 includes a spring retainer 61, a compression spring 62, a rod guide 63, a presser nut 64, and a first stem 71.
An upper flange 31A projects from the upper end side of the cylinder base 31, and a cylindrical cylinder guide 31B projects from the outer peripheral edge thereof. A cylindrical cylinder case 32 whose upper end is closed is screwed onto the cylinder guide 31B from above. An upper piston 33A and a lower piston 33B are slidably fitted in the cylinder case 32 and the cylinder guide 31B, respectively. An intermediate plate 34 is disposed between the upper and lower pistons 33A and 33B. A guide hole 34A for guiding the vertical movement of the piston rod 35 connected to the upper and lower pistons 33A and 33B is formed in the middle plate 34 at the center. The outer peripheral end of the intermediate plate 34 is fitted into a stepped portion 32 </ b> D formed downward on the inner wall surface of the cylinder case 32. The upper end lower surface of the cylinder case 32 and the stepped portion 35B formed on the piston rod 35 are in contact with each other when the valve is opened, thereby restricting the cylinder stroke length.

  In the center of the upper end of the cylinder case 32, a pilot port 32A and a guide hole 32B for guiding the vertical movement of the piston rod 35 are formed to penetrate vertically. The piston rod 35 is supplied with operating air (compressed air) supplied from the pilot port 32A between the upper piston 33A and the intermediate plate 34 and between the lower piston 33B and the cylinder base 31. A supply hole 35 </ b> A for supplying the pressure chambers 37, 37 is formed. Therefore, when operating air is supplied to the pilot port 32A, the upper and lower pistons 33A, 33B and the piston rod 35 are driven upward (in the valve opening direction). The upper and lower pistons 33A and 33B and the piston rod 35 to be driven are fitted with O-rings 36 at positions where they are in sliding contact with the cylinder case 32, the intermediate plate 34, and the cylinder guide 31B.

  As shown in FIG. 5, a through hole 32 </ b> C for measuring the stroke length of the metal diaphragm 43 is formed on the outer peripheral side of the upper end of the cylinder case 32. The stroke length of the metal diaphragm 43 can be measured by inserting the measuring rod R into the through hole 32C and coming into contact with the upper piston 33A. The upper piston 33A is connected to the first stem 71 via the piston rod 35, and the first stem 71 regulates the rise of the second stem 72 pressed against the upper surface of the central portion of the metal diaphragm 43. This is because the diaphragm 43 moves up and down in conjunction with the vertical movement of the center portion of the diaphragm 43.

As shown in FIG. 1, a lower flange 31 </ b> C is formed at the lower end of the cylinder base 31. The lower flange 31 </ b> C is in contact with an upper surface 61 </ b> A of a spring retainer 61 that holds a compression spring 62 that urges downward (in the valve closing direction) through a thin plate (shim) 52.
The thin plate (shim) 52 is formed in a substantially C shape. The thin plate (shim) 52 has an outer diameter substantially equal to the outer diameter of the lower flange 31C and is appropriately selected from a plurality of sheets. The material of the thin plate (shim) 52 is, for example, SUS304, and the thickness is about 0.05 mm. The thin plate (shim) 52 is preferably prepared with a plurality of shims having different thicknesses and shims having the same thickness. It is because it can be adjusted to an optimal dimension by combining.
A male screw is provided at the center of the lower end of the lower flange 31C and is screwed into a female screw provided on the boss portion 61B of the spring retainer 61. The thin plate (shim) 52 is clamped between the upper surface 61A of the spring retainer 61 and the lower flange 31C of the cylinder base 31 by tightening the screw.
Therefore, the thin plate (shim) 52 can be easily replaced by loosening the screw at the lower center portion of the lower flange 31C and removing it from the spring retainer 61.
A through hole 31D through which the piston rod 35 penetrates is formed at the center of the lower flange 31C.

At the lower end of the boss portion 61B of the spring retainer 61, a rod guide 63 through which the piston rod 35 passes is provided. The rod guide 63 has a role of holding the spring 62B.
Further, a male screw is provided at the lower end portion of the penetrating piston rod 35 and is screwed into a female screw provided at the upper end central portion 71 </ b> A of the first stem 71. Therefore, the upward driving force of the piston rod 35 is transmitted to the first stem 71. The lower end of the compression spring 62 is in contact with the upper outer peripheral portion 71B of the first stem 71 with which the piston rod 35 is screwed. Therefore, the elastic force of the compression spring 62 presses the first stem 71 downward. In this embodiment, two types of compression springs 62A and 62B having different outer diameters and wire diameters are provided. The reason for this is to provide the necessary thrust and save space in the vertical direction.
A cylindrical spring guide 61C is suspended from the outer peripheral edge of the spring retainer 61, and a flange 61D having a predetermined thickness is formed outwardly at the lower end thereof.

Next, as shown in FIG. 3, the holder unit 5 includes an adapter 51 and a holder 53.
The adapter 51 is formed with a cylindrical hollow portion 51 </ b> B at the top and bottom, and a compression spring 62 and a first stem 71 connected to the piston rod 35 are inserted therein.
A first male screw is provided on the upper outer peripheral surface of the adapter 51, and is screwed with a female screw provided on the inner peripheral surface of the presser nut 64. An engaging portion 64 </ b> A projects inwardly at the inner peripheral edge of the upper end of the presser nut 64 and engages with the flange portion 61 </ b> D of the spring retainer 61. The adapter 51 is connected to the spring retainer 61 by fastening the screw of the presser nut 64.

A second male screw is provided on the lower outer peripheral surface of the adapter 51, and is screwed into a female screw provided on the inner peripheral surface of the cylinder portion 41 </ b> A protruding from the upper portion of the valve body 41 constituting the valve portion 4. Yes.
The upper end of the holder 53 is in contact with the lower end of the adapter 51. The contact portion 53 </ b> B of the holder 53 is formed in a bowl shape and regulates the radial direction and the vertical direction of the adapter 51. The holder 53 is disposed above the outer peripheral edge 43 </ b> B of the metal diaphragm 43, and holds the metal diaphragm 43 in an airtight manner between the bottom surface of the valve chamber 44.
A communication hole 53A that is in sliding contact with the outer peripheral edge 72A of the second stem 72 when the valve is opened and closed is formed in the center of the holder 53.

Next, as shown in FIG. 3, the valve unit 4 includes a valve body 41, a valve seat 42, a metal diaphragm 43, and a second stem 72.
A valve chamber 44 communicating with the input port 41B and the output port 41C is formed on the inner surface of the cylinder portion 41A protruding from the upper portion of the valve body 41. On the bottom surface of the valve chamber 44, a valve seat 42 is provided at a location communicating with the input port 41B. The material of the valve seat 42 is PI (polyimide) or PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) having excellent heat resistance. The valve seat 42 is caulked to the valve body 41. Above the valve seat 42, a metal diaphragm 43 that is in contact with and away from the valve seat 42 and whose central portion 43A bulges upward is disposed. The metal diaphragm 43 is formed by laminating a plurality of thin films made of nickel / cobalt alloy and press-bonded into a sheet shape. The metal diaphragm 43 is manufactured by laminating three thin films each having a thickness of 0.1 mm, and the bulging amount of the central portion 43A is 0.9 mm in a free state. Moreover, since the metal diaphragm 43 is heat-treated in order to increase the strength, the hardness has a Vickers hardness Hv500 or more.
The lower end 72B of the second stem 72 is pressed against the upper surface of the central portion 43A of the metal diaphragm 43.
The second stem 72 has a substantially cylindrical shape, and a lower end 72B of the second stem 72 is formed in a curved shape that gently bulges downward. At the stage of attaching to the valve body 41 (initial stage), the central portion 43A of the metal diaphragm 43 is restricted to a shape substantially along the curved surface of the lower end 72B of the second stem 72. Even when the valve is open, the central portion 43A of the metal diaphragm 43 is held in a shape substantially along the curved surface of the lower end 72B of the pressed second stem 72.

In this embodiment, by restricting the stroke length T of the metal diaphragm 43 to 20 to 49% of the full stroke length of the metal diaphragm 43, the difference in Cv value between the high temperature (250 ° C.) and the normal temperature is zero. 19 or less.
Hereinafter, the basis of the above numerical limitation will be described with reference to FIG. FIG. 4 is a graph showing the relationship between the valve temperature and the Cv value using the fluid control valve 1 according to the first embodiment of the present invention.
First, the lower limit of the stroke length T used for the metal diaphragm 43 is set to 20% of the full stroke length. The Cv value (250 ° C.) at a high temperature (250 ° C.) at that time becomes 0.12. This is because, if it becomes smaller, it becomes practically equivalent to the metal diaphragm 43 with the outer diameter reduced by one rank, so there is no meaning of a large size. The upper limit of the stroke length of the metal diaphragm 43 is 49% of the full stroke length because the difference between the Cv value at the high temperature (250 ° C.) and the normal temperature is 0.19. This is because if the difference is large, the flow rate control system becomes practically complicated and it becomes difficult to perform stable flow rate control.

In the present embodiment, the optimum value of the used stroke length T of the metal diaphragm 43 is 0.4 mm. In this case, the use stroke length of the metal diaphragm 43 is regulated to 44% with respect to the full stroke length (height 0.9 mm in the free state).
According to the experiments by the present inventors, when the use stroke length T of the metal diaphragm 43 is restricted to 44% of the full stroke length, the Cv value at high temperature (250 ° C.) is 0.39, and at normal temperature (23 ° C.). The Cv value at 0.5 was 0.57. Therefore, the difference in Cv value in that case is 0.18. On the other hand, when the use stroke length of the metal diaphragm 43 was not regulated, the Cv value at high temperature (250 ° C.) was 0.43, and the Cv value at normal temperature (23 ° C.) was 0.79. Therefore, the difference in Cv value in that case is 0.36.
Thus, by restricting the stroke length of the metal diaphragm 43 to 44% of the full stroke length, the Cv value at high temperature (250 ° C.) is not significantly reduced (−0.04), and at high temperature (250 ° C. ) To Cv value fluctuation amount (0.18) at normal temperature (23 ° C.) can be reduced to about half of Cv value fluctuation amount (0.36) when not regulated. .
The Cv value was calculated based on the JIS standard (JIS B0100-1984). Measurement temperature is 23 degreeC (at the time of normal temperature), 100 degreeC, 150 degreeC, 200 degreeC, and 250 degreeC (at the time of high temperature).

As shown in FIGS. 1 and 3, when the valve is opened and closed, the outer peripheral edge 72A of the second stem 72 is guided in sliding contact with the communication hole 53A of the holder 53. Therefore, the posture of the second stem 72 is always Held constant. Therefore, the posture of the central portion 43A of the metal diaphragm 43 pressed against the lower end of the second stem 72 is also maintained in a substantially constant form without being inclined when moving up and down as the valve opens and closes. More specifically, even if the strength of the metal diaphragm 43 decreases at a high temperature and the restoration posture of the metal diaphragm 43 easily changes, the central portion of the second diaphragm 72 pressed against the central portion of the metal diaphragm 43 While moving up and down with the second stem 72 while being held in a shape substantially along the lower end surface, the correct stroke trajectory can be accurately reproduced.
As shown in FIG. 1, the outer diameter Q of the second stem 72 is at least larger than the outer diameter P of the valve seat 42. Therefore, the central portion 43 </ b> A of the metal diaphragm 43 that is held in a shape substantially along the lower end surface of the second stem 72 is held in substantially the same shape at least in the range where it contacts the valve seat 42.
This means that the gap between the metal diaphragm 43 and the valve seat 42 when the valve is opened is more easily maintained even when the temperature changes from room temperature to high temperature (250 ° C.).

The upper end of the second stem 72 can be in contact with or separated from the lower end of the first stem 71. Therefore, the first stem 71 is in a state S (state shown in FIG. 2) in which the cylinder base 31, the cylinder case 32, the piston 33, the piston rod 35, the spring retainer 61, and the compression spring 62 constituting the air cylinder unit 6 are assembled together. ) Can be separated from the second stem 72.
Also, as shown in FIG. 3, a concave seat surface 72C is formed at the upper center portion of the second stem 72, and a convex seat surface having a conical or arcuate tip at the lower center portion of the first stem 71. Is formed downward. Therefore, even if the first stem 71 is slightly tilted, the contact position with the second stem 72 is unlikely to change, so that the stroke length of the metal diaphragm 43 can be more accurately regulated.

<Description of operation>
As shown in FIG. 1, when the operation air is supplied to the pilot port 32A, the flow control valve 1 supplies the operation air to the pressurizing chambers 37, 37, and moves the upper and lower pistons 33A, 33B and the piston rod 35 upward (valve Drive in the opening direction). Since the first stem 71 is connected to the piston rod 35, the first stem 71 rises to the rising end position against the elastic force of the compression spring 62. The second stem 72, whose rise is restricted by the first stem 71, rises due to the restoring force of the metal diaphragm 43. The central portion 43A of the metal diaphragm 43 is separated from the valve seat 42 and is in a valve open state. Since the first stem regulates the rise of the second stem at the valve open position of the metal diaphragm 43, the use stroke length T of the metal diaphragm is smaller than the full stroke length. When the metal diaphragm 43 is opened, the source gas is supplied from the input port 41B through the valve chamber 44 to the output port 41C. When the temperature of the source gas or the environmental temperature of the place where the flow control valve is installed becomes high (about 250 ° C.), the strength of the metal diaphragm 43 decreases, and the negative pressure of the source gas acts in a vacuum state. The valve opening position of the metal diaphragm 43 at (about 250 ° C.) is lower than the valve opening position at normal temperature.
However, since the first stem 71 regulates the rise of the second stem 72 even at a high temperature (about 250 ° C.), the stroke length T of the metal diaphragm 43 is changed from room temperature to a high temperature (about 250 ° C.). Even if changes, it is held substantially constant.
On the other hand, when the flow control valve 1 stops supplying the operating air to the pilot port 32A, the first stem 71 is driven downward (in the valve closing direction) by the elastic force of the compression spring 62. The first stem 71 descends together with the second stem 72 while restricting the rise of the second stem 72. As shown in FIG. 3, as the second stem 72 descends, the metal diaphragm 43 comes into contact with the valve seat 42 at the central portion 43 </ b> A, and the valve diaphragm is closed. When the metal diaphragm 43 is closed, the supply of the source gas to the output port 41B is stopped.

<Effect>
Since the first stem 71 restricts the rise of the second stem 72 at the valve opening position of the metal diaphragm 43, the metal diaphragm 43 has a high restoring force when the valve is opened at room temperature, The second stem 72 tries to move upward from the valve opening position at the time of high temperature by the restoring operation of the metal diaphragm 43, but the second stem 72 comes into contact with the first stem 71 connected to the piston rod 35 and moves upward. Movement to is regulated. Therefore, the rising end position of the second stem 72 when the valve is open can be made substantially constant from the normal temperature to the high temperature, and the use stroke length T of the metal diaphragm 43 can be controlled to be substantially constant from the normal temperature to the high temperature. As a result, a stable flow rate can be ensured with little variation in the Cv value between normal temperature and high temperature.

  In addition, the stem is vertically divided into a first stem 71 connected to the piston rod 35 and a second stem 72 pressed against the upper surface of the central portion of the metal diaphragm 43, so that the stem can be brought into contact with and separated from each other. When adjusting the rising end position of the first stem 71 at the time of opening and adjusting the use stroke length T of the metal diaphragm 43, the state S in which the actuator portion 3 including the first stem 71 is assembled integrally (the state shown in FIG. 2) ), The actuator portion 3 is removed from the holder portion 5, the attachment position of the first stem 71 is adjusted, and the connection to the holder portion 5 makes it easy to adjust the stroke length T of the metal diaphragm 43. And can be done accurately. As a result, the Cv value can be easily and accurately adjusted.

In particular, by limiting the stroke length T of the metal diaphragm 43 to 20 to 49% of the full stroke length of the metal diaphragm 43, the difference in Cv value is within 0.19. However, it is possible to secure a stable flow rate with little variation in the Cv value between normal temperature and high temperature.
Here, the reason why the lower limit of the stroke length T used for the metal diaphragm 43 is 20% of the full stroke length is that the Cv value (250 ° C.) at a high temperature (250 ° C.) at that time is 0.12. This is because, when the value is small, it is practically equivalent to the metal diaphragm 43 with the outer diameter reduced by one rank. In addition, the upper limit of the stroke length T used for the metal diaphragm 43 is set to 49% of the full stroke length because the difference in Cv value between the high temperature (250 ° C.) and the normal temperature is 0.19. This is because if the difference between the values becomes large, the flow control system becomes practically complicated and it becomes difficult to perform stable flow control.
That is, at a high temperature (250 ° C.), the softened metal diaphragm 43 is subjected to negative pressure and the gap with the valve seat is reduced, and accordingly, the Cv value is reduced to about 40 to 60% compared with that at normal temperature. To do. In the initial state, the stroke length T of the metal diaphragm 43 is restricted to 20 to 49% of the full stroke length of the metal diaphragm 43 under the concept of limiting the Cv value to be smaller than the decreased Cv value. Therefore, since the difference between the Cv value (250 ° C.) at high temperature (250 ° C.) and the Cv value (normal temperature) at normal temperature is within the range of 0.19, even if it is used in a high temperature and vacuum state, Without changing the outer diameter of the metal diaphragm 43 by one rank and without complicating the flow rate control system, the Cv value varies little between normal temperature and high temperature, and a stable flow rate can be secured.

By using a thin plate (shim) 52 between the air cylinder part 6 and the spring part 7, the use stroke length T of the metal diaphragm 43 is within the range of the regulation value. If a plurality of thin plates (shim) 52 are prepared in between, the use stroke length T to be set can be easily and reliably adjusted. Therefore, even when the stroke length T of the metal diaphragm 43 is slightly different for each product, the adjustment within the range of the regulation value can be performed with high accuracy and reliability. In addition, since the shim adjustment is used, the stroke length T of the metal diaphragm 43 is highly accurate and reliable because it does not change subtly due to variations in the machining accuracy of the threads and screw grooves, unlike the structure in which the actuator is adjusted by the screwing amount. Easy to adjust to.
Therefore, the use stroke length T of the metal diaphragm 43 for each product can be adjusted more easily and accurately, and the variation in the Cv value between products can be further reduced.
By setting the thickness of the thin plate (shim) 52 to 0.05 mm, the Cv value variation between products at high temperature (250 ° C.) is ± 8.6%, and the temperature variation is ± 1.0% per 5 ° C. 3%, and the total could be suppressed to about ± 10%.

Further, since the through hole 32C for measuring the stroke length T of the metal diaphragm 43 is provided on the outer peripheral side of the upper end of the cylinder case 32, the through hole provided in the cylinder case 32 with the air cylinder portion 6 attached to the valve body 41. The stroke length T of the metal diaphragm 43 can be measured by inserting the measuring rod R into the hole 32C and contacting the upper piston 33A. The upper piston 33A is connected to the first stem 71 via the piston rod 35, and the first stem 71 regulates the rise of the second stem 72 pressed against the upper surface of the central portion of the metal diaphragm 43. This is because the diaphragm 43 moves up and down in conjunction with the vertical movement of the center portion of the diaphragm 43.
As a result, the stroke length T of the metal diaphragm 43 for each product can be easily confirmed for the flow rate control valve 1 used in the manufacturing apparatus. Therefore, the adjustment is performed more easily and accurately, and the Cv value varies between products. Can be further reduced. Moreover, since it is not necessary to remove the flow control valve 1 from a manufacturing apparatus when measuring, a line stop etc. can be suppressed to the minimum.

Further, since the second stem 72 moves up and down in sliding contact with the communication hole 53A formed in the center of the holder 53, the strength of the metal diaphragm 43 decreases at a high temperature, and the restoring posture of the metal diaphragm 43 changes. Even if it becomes easy, the central portion 43A of the metal diaphragm 43 moves up and down together with the second stem 72 while being held in a shape substantially along the curved surface of the lower end 72B of the pressed second stem 72, and the correct stroke locus Can be accurately reproduced.
As a result, the fluctuation of the Cv value can be further reduced between normal temperature and high temperature (250 ° C.).

(Second Embodiment)
FIG. 6 is a cross-sectional view of the cylinder case 32 of the flow control valve 2 according to the second embodiment, and shows an adjustment knob 38 that adjusts the rising end position of the piston rod 35.
The second embodiment is different from the first embodiment in that an adjustment knob 38 that adjusts the rising end position of the piston rod 53 is provided at the center of the upper end of the cylinder case 32, and the other points are common to the first embodiment. doing. Here, it demonstrates centering on a different point from 1st Embodiment, The same code | symbol as 1st Embodiment is attached | subjected to drawing in the location which is common in 1st Embodiment, and the description is abbreviate | omitted suitably.

As shown in FIG. 6, the adjustment knob 38 includes a head portion 38 </ b> A disposed at the center of the upper end of the cylinder case 32 and leg portions 38 </ b> B that extend to the lower end of the cylinder case 32 and are screwed into the cylinder case 32. The head 38 </ b> A is a knob that is outside the cylinder case 32 and adjusts the rising end position of the piston rod 35. Within the cylinder case 32, the lower end of the leg portion 38 </ b> B is in contact with the upper end of the piston rod 35. Therefore, when the head portion 38A is turned, the screwing depth of the leg portion 38B changes, and the rising end position of the piston rod 35 also changes in conjunction with it.
On the other hand, the adjustment knob 38 is formed with a pilot port 32A at the center of the upper end of the head 38A. The adjustment knob 38 is formed with a second feed hole 38C communicating with the feed hole 35A of the piston rod 35 from the pilot port 32A at the upper end of the head portion 38A to the lower end of the leg portion 38B. . Therefore, the operating air supplied from the pilot port 32A is supplied to the upper and lower pressurizing chambers 37, 37 via the second supply hole 38C and the supply hole 35A of the piston rod 35.
A through hole 32 </ b> C for measuring the stroke length T of the metal diaphragm 43 is formed on the outer periphery of the upper end of the cylinder case 32. The measuring rod R is inserted into the through-hole 32C and brought into contact with the upper piston 33A, so that the stroke length T of the metal diaphragm 43 is measured and the adjustment knob 38 is rotated, whereby the rising end position of the piston rod 35 is measured. Can be adjusted. The stroke length T of the metal diaphragm 43 can be adjusted more easily.

In addition, this invention is not limited to the said embodiment, Various application is possible.
(1) For example, in the said embodiment, although the fluid control valve 1 was used for the semiconductor manufacturing apparatus, it cannot be overemphasized that a use application is not limited to this.
(2) For example, in the above embodiment, the fluid control valve 1 is a normally closed type air operated on / off valve, but may be a normally open type air operated on / off valve. The fluid control valve 1 may be a flow rate adjustment valve, a manual valve, a solenoid valve, or the like.
(3) For example, in the above embodiment, the air cylinder portion 6 and the spring portion 7 are connected via the thin plate (shim) 52, but the spring portion 7 and the holder portion 5 are connected via the thin plate (shim) 52. May be connected. In that case, a thin plate (shim) 52 is sandwiched between the lower end of the flange 61D of the spring retainer 61 and the upper end of the adapter 51. You can adjust.
(4) Moreover, the thin plate (shim) 52 is not limited to a substantially C shape, and may be a substantially U shape or a substantially donut shape.

DESCRIPTION OF SYMBOLS 1, 2 Flow control valve 3 Actuator part 4 Valve part 5 Holder part 6 Air cylinder part 7 Spring part 31 Cylinder base 32 Cylinder case 32C Through-hole 33 Piston 34 Intermediate | middle plate 35 Piston rod 36 O-ring 37 Pressurization chamber 38 Adjustment knob 41 Valve body 42 Valve seat 43 Metal diaphragm 44 Valve chamber 51 Adapter 52 Thin plate (Shim)
53 Holder 61 Spring retainer 62 Compression spring 63 Rod guide 64 Presser nut 71 First stem 72 Second stem P Valve seat outer diameter Q Second stem outer diameter S Actuator assembly state T Stroke length of metal diaphragm

Claims (4)

A valve body provided with a valve seat on the bottom surface of the valve chamber communicating with the input port and the output port, and a metal diaphragm disposed above the valve seat so as to come into contact with and separate from the valve seat, and a central portion thereof bulges upward. And the stem that moves the central portion of the metal diaphragm up and down, the actuator that drives the stem, and the bottom of the valve chamber that is disposed above the outer peripheral edge of the metal diaphragm. In the flow control valve provided with a holder portion to which the actuator is coupled at the upper portion thereof,
The stem is vertically divided into a first stem connected to the actuator and a second stem pressed against the upper surface of the central portion of the metal diaphragm, and can be contacted and separated from each other;
In the valve opening position of the metal diaphragm, the stroke length of the metal diaphragm is reduced from the full stroke length of the metal diaphragm by restricting the rise of the second stem by the first stem .
By limiting the stroke length of the metal diaphragm to 20 to 49% of the full stroke length of the metal diaphragm, the difference in Cv value between high temperature (250 ° C.) and normal temperature is within 0.19. Characteristic flow control valve. The flow control valve according to claim 1 ,
The actuator has an air cylinder part and a spring part,
A flow rate control valve characterized in that a use stroke length of the metal diaphragm is set within a range of the regulation value by sandwiching a shim between the air cylinder part and the spring part. In the flow control valve according to claim 1 or 2 ,
The actuator includes an air cylinder having a piston in a case,
A flow rate control valve, wherein a through hole for measuring a stroke length of the metal diaphragm is provided in a case of the air cylinder. In the flow control valve according to any one of claims 1 to 3 ,
The flow control valve according to claim 1, wherein the second stem moves up and down in sliding contact with a communication hole formed in the center of the holder portion.

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