JP7645536B2 - Valve actuator and valve using same - Google Patents

Description

This invention relates to a valve actuator equipped with a stroke increase mechanism that increases the stroke of the valve body of a valve that opens and closes the flow of fluid, and a valve that uses the same.

In semiconductor manufacturing equipment and chemical plants, various types of valves are used to control the flow rate of material gases, etching gases, etc. Sometimes it is necessary to control the opening and closing of a valve in short cycles of about milliseconds, and in such cases, this is achieved by using piezoelectric elements such as piezo elements to open and close the valve.

The valve described in Patent Document 1 adjusts the force that the output end of the piezoelectric element exerts on the lower support by expanding and contracting the piezoelectric element, causing the diaphragm and valve seat to come into contact with and separate from each other, opening and closing the flow of fluid.

International Publication No. WO2019/159959 International Publication No. WO2018/123852

To increase the flow rate of a valve, the Cv value must be increased, which requires a larger stroke for the valve disc. It is possible to increase the Cv value with air-driven or motor-driven valves, but when short-period opening and closing on the order of milliseconds is required, it is common to use a valve equipped with a piezoelectric actuator.

However, depending on whether short-period responsiveness or fluid flow rate is more important, piezoelectric element drive, air drive, or motor drive are used alternatively depending on the situation in which the valve is used, and it is difficult to realize a valve actuator that satisfies both responsiveness and Cv value.

Semiconductor manufacturing equipment and chemical plants require valves that can control the flow of fluid gases at high speed and adjust various changing flow rates, and it is becoming increasingly difficult to meet these demands by simply choosing between responsiveness and Cv value, as has been the case up until now.

The present invention has been made in consideration of these points, and its purpose is to provide a valve actuator equipped with a stroke increase mechanism that can increase the movement stroke of the valve body.

The actuator for a valve with a stroke increase mechanism according to the present invention (1), which has been made to solve the above problems, is used for a valve having a valve body that opens and closes the flow of fluid by coming into contact with and separating from a valve seat arranged in a fluid flow path formed in a valve body, and is an actuator for a valve having a stroke increase mechanism that increases the stroke of the valve body, the stroke increase mechanism being arranged between the output end of the actuator and the valve body, the output end being abutted against and pressed by a plurality of balls, and a ball accommodating space for accommodating the balls being provided on the output end side, the ball accommodating space being a ball retaining member connected to the valve body having a conical support tapered surface that widens outward and upward, and a stem that penetrates a through hole formed in the center of the ball retaining member, one end of the valve body side having a valve body pressing portion that presses the valve body, and the other end of the output end side having a stem tapered surface with a tapered tip that abuts against the balls.

By using such a stroke increase mechanism, even if the stroke of the actuator that moves the valve body is small, it is possible to increase that small stroke by several times, thereby increasing the Cv value.

The present invention (2) is an actuator for a valve according to the present invention (1), in which the output end is moved by the expansion and contraction of a piezoelectric element, and the valve body holding portion is moved by the movement of the output end.

Piezoelectric actuators have the disadvantage of good time response but a small stroke, so by providing such a stroke increase mechanism, even a piezoelectric actuator can have good time response and the stroke of the valve disc can be increased, making it possible to increase the Cv value of the valve.

The present invention (3) is an actuator for a valve according to either the present invention (1) or the present invention (2), in which the valve element is a diaphragm.

Flow control devices are used in film formation and etching equipment for semiconductor manufacturing. Metal diaphragm valves are widely used in flow control devices because of their high corrosion resistance, low dust generation, good gas replacement, good responsiveness, and the ability to quickly and reliably close the fluid passage when the valve is closed. Piezoelectric element drive devices (piezo actuators) are widely used as drive mechanisms for opening and closing metal diaphragms, and are often used in flow control valves that require high accuracy because they can operate at high speed and have relatively small hysteresis in their operating characteristics. Piezoelectric element drive actuators have the disadvantage that the stroke of the valve body press that presses the valve body (diaphragm) is small, but even valves that use such piezoelectric element drive actuators have a stroke increase mechanism, so the Cv value can be increased.

The present invention (4) is a valve equipped with a valve actuator according to any one of the present inventions (1) to (3). By using such a valve, it is possible to obtain a valve with good time response and a high Cv value.

The present invention provides a valve actuator that can increase the stroke of the valve body.

1A shows a diaphragm valve equipped with a valve actuator according to an embodiment of the present invention, in which (A) shows a closed state and (B) shows an open state. 5A to 5C are schematic diagrams illustrating the operation of a stroke increasing mechanism of the valve actuator according to the embodiment of the present invention.

The following describes in detail the embodiments of the present invention with reference to the drawings. Note that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses.

Figure 1 shows a diaphragm valve equipped with a valve actuator according to an embodiment of the present invention, with (A) showing the closed state and (B) showing the open state. An inlet flow path 11 and an outlet flow path 12 are formed inside the valve body 10 of the valve 1, and a valve seat 13 is disposed at the internal open end of the inlet flow path 11. A valve element (diaphragm) 14, which opens and closes the flow of fluid by coming into contact with and separating from the valve seat 13, is fixed to the valve body 10 by a pressure adapter 15. In this embodiment, a diaphragm is used as this valve element 14, but it may also be, for example, an inverted cone-shaped needle-shaped element formed at the tip of the stem 20.

The upper part of the valve body 10 protrudes upward, and a recess is formed inside to accommodate the diaphragm 14 and the presser adapter 15, with a female thread on the inside of the recess. A ball retaining member 30, which functions as a bonnet and has a male thread that screws into the female thread, is fixed to the valve body 10 by screwing. The diaphragm 14 is formed, for example, from a thin plate of nickel-chromium alloy steel, and is formed into an inverted dish shape with the center part slightly bulging upward. The shape of the diaphragm 14 may be flat, and the material may be stainless steel, Inconel alloy, or other alloy steel. The diaphragm 14 may be formed from a single diaphragm, or may be formed by stacking two or three diaphragms.

A through hole 31 is provided in the center of the ball retaining member 30, through which the stem 20 passes. A valve body pressing portion 21 that presses against the diaphragm 14 is formed at the lower end of the stem 20, and a stem tapered surface 22 is formed at the upper end. The upper portion of the ball retaining member 30 protrudes upward, and is internally threaded to screw into the guide member 48, and the outer surface of the lower end of the guide member 48 is threaded for screwing.

The ball holding member 30 has a recess in the upper part into which the guide member 48 is screwed. A further recess is formed below this recess to become the ball receiving space 33, and the bottom surface of this ball receiving space 33 is a cone-shaped support tapered surface 32 that widens outward and upward.

A through hole is provided in the guide member 48 in the vertical direction, and a support cylinder 41 is disposed through the through hole and containing a piezoelectric element 40 inside. The support cylinder 41 has a large diameter portion on the upper side and a small diameter portion on the lower side, each of which has a recess, and the large diameter portion recess is provided with a piezoelectric element 40. The small diameter portion recess is abutted by a lower support 42 that is pressed downward by the piezoelectric element 40, and a split base 43 is disposed below it. The split base 43 is formed by assembling half-split base pieces in an opposing relationship, and the guide member 48, the split base 43, and the ball holding member 30 are integrally held and fixed by the guide member 48. Before assembling the split base 43, an elastic member 44 is inserted into the recess inside the small diameter portion. The piezoelectric element 40 can be a metal-sealed laminated piezoelectric actuator in which a piezo stack in which piezoelectric elements are stacked is sealed in a metal container.

The lower part of the lower narrow diameter part of the support cylinder 41 forms the output end 45 of the valve actuator 2, and the bottom surface of this output end 45 forms the output end lower surface 46. The output end lower surface 46 abuts against the upper surface of the ball 34, which also contacts the support tapered surface 32 and the stem tapered surface 34. . When there are three balls, they are arranged at 120 degree intervals, and when there are four balls, they are arranged at 90 degree intervals. If there are too many balls, the actuator will become large, so when making a compact actuator, it is preferable to have three to four balls.

A lock nut 51 and a cap nut 50 are arranged on the top of the support cylinder 41 to position and fix the piezoelectric element 40 inside the support cylinder 41. Wiring 52 for applying voltage to the piezoelectric element 40 extends from the top of the cap nut 50.

In FIG. 1A, the positioning of the piezoelectric element 40 is performed so that the valve body pressing portion 21 presses the diaphragm 14 to close the valve 1. When a voltage is applied to the piezoelectric element 40 from this state through the wiring 52, the piezoelectric element 40 expands slightly. When the piezoelectric element 40 expands, a downward pressing force acts on the lower support 42, but the lower support 42 is in contact with the center of the split base 43 and its position does not change. Therefore, a pushing force corresponding to the expansion of the piezoelectric element 40 acts on the support cylinder 41, and the support cylinder 41 rises against the elastic force of the elastic member 44 while the axis is held by the guide member 48. As a result, the pressing force from the valve body pressing portion 21 to the diaphragm 14 decreases, and the diaphragm 14 is lifted off the valve seat 13 by its own elastic force, opening the valve. Note that the elastic member 44 may be, for example, a stack of disc springs.

FIG. 1B shows a state in which the piezoelectric element 40 is expanded by applying a voltage to the piezoelectric element 40 from the wiring 52. The expansion of the piezoelectric element 40 causes the support cylinder 41 to move upward by L _1. As the support cylinder 41 moves upward, the output end lower surface 46 also moves upward by L ₁ , the stem 20 moves upward, and the ball 34 moves laterally outward, and stops when the support cylinder 41, the ball 34, and the stem 20 are balanced. FIG. 1B shows the state after stopping. Since the stem 20 moves upward by L ₂ , the valve body holding portion 21 also moves upward by L ₂ , and the diaphragm 14 can also deform upward by L _2. Since L ₂ is greater than L ₁ , the stroke is enlarged. The amount of increase in the stroke is determined by the angle of the tapered surface 32 and the stem tapered surface 22. When the divergence angle of the tapered surface 32 is 110° and the angle of the tip of the stem tapered surface 22 is 30°, _L2 can be increased to about 8 times _L1 , or about 10 times depending on the angle.

FIG. 2 shows a schematic diagram of the mechanism by which the stroke is enlarged. The output end lower surface 46 in the valve closed state is shown by a horizontal dotted line. When the valve changes from the closed state to the open state, the output end lower surface 46' is shown by a solid line drawn above the dotted line of the output end lower surface 46. The vertical distance between these two straight lines is L _1. The support tapered surface 34 is fixed to the valve body 10 and does not move. The ball 34 in the valve closed state is shown by a dotted circle. When the output end lower surface 46 moves upward by L ₁ , the ball 34 becomes the solid circle of the ball 34', and the ball 34 moves laterally outward. The stem tapered surface 22 (dotted line) moves to the stem tapered surface 22' (solid line), and the upward movement distance is L ₂ .

It is clear that _L2 is larger than _L1 , and the stroke is enlarged. As is clear from Figure 2, the principle of the stroke enlargement mechanism is based on a structure in which the ball 34 is disposed surrounded by the output end lower end surface 46, the support tapered surface 32, and the stem tapered surface 22, and is supported at three points. In the embodiment shown in Figure 2, when _L1 is 58 μm, _L2 is 478 μm, which is about eight times that.

In Figure 2, the stem taper surface 22' (solid line) abuts against the output end lower surface 46' (solid line), but in Figure 1, a recess is provided in the center of the output end lower surface 46, so there is no abutment. This recess is omitted in Figure 2.

As explained above, the valve actuator of the present invention can be used effectively in valves because it can increase the stroke even when the stroke is small, such as in the case of piezoelectric element drive.

REFERENCE SIGNS LIST 1 valve 2 valve actuator 10 valve body 11 inlet flow passage 12 outlet flow passage 13 valve seat 14 valve body (diaphragm)
15 Holding adapter 20 Stem 21 Valve body holding portion 22, 22' Stem tapered surface 30 Ball holding member 31 Through hole 32 Support tapered surface 33 Ball accommodating space 34, 34' Ball 40 Piezoelectric element 41 Support cylinder 42 Lower support 43 Split base 44 Elastic member 45 Output end 46, 46' Output end lower surface 48 Guide member 50 Cap nut 51 Lock nut 52 Wiring

Claims (3)

1. A valve actuator for use in a valve having a valve body that opens and closes a flow of a fluid by coming into contact with and separating from a valve seat disposed in a fluid flow path formed in a valve body, the valve actuator comprising: a stroke increasing mechanism that increases the stroke of the valve body,
the stroke increasing mechanism is disposed between the output end of the actuator and the valve body,
A plurality of balls that are pressed against the output end by contacting the balls;
a ball accommodating space for accommodating the ball is provided on the output end side, and the ball accommodating space is connected to the valve body having a conical support tapered surface that widens outward and upward;
a stem that passes through a through hole formed in the center of the ball retaining member, the stem having a valve body pressing portion at one end on the valve body side that presses the valve body, and a stem tapered surface having a tapered tip that abuts against the ball at the other end on the output end side;
The valve actuator, wherein the valve body is a diaphragm that moves away from the valve seat by its own elastic force . The valve actuator according to claim 1, wherein the output end is moved by the expansion and contraction of a piezoelectric element, and the valve body holder is moved by the movement of the output end. A valve comprising the valve actuator according to any one of claims 1 to 2 .

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