CN101377255B

CN101377255B - Vacuum opening/closing valve

Info

Publication number: CN101377255B
Application number: CN2008102149212A
Authority: CN
Inventors: 渡边雅之; 宫原诚; 梅泽俊祐
Original assignee: CKD Corp
Current assignee: CKD Corp
Priority date: 2007-08-29
Filing date: 2008-08-29
Publication date: 2010-06-23
Anticipated expiration: 2028-08-29
Also published as: CN101377255A; KR100987466B1; JP2009074681A; KR20090023146A

Abstract

A durable vacuum opening/closing valve connectable with a vacuum chamber and a vacuum pump is arranged to control vacuum pressure in the vacuum chamber by changing an opening degree of an O ring serving as a valve element relative to a valve seat. A predetermined clearance between an outer peripheral surface of a piston and an inner peripheral surface of a cylinder is sealed by a bellofram which changes its shape in association with movement of the piston moved to open or close the valve. The bellofram includes an inclined surface with a predetermined inclination angle and the outer periphery of the piston includes an inclined surface with a predetermined inclination angle, so that an inner diameter of the bellofram in contact with the piston and the outer diameter of the piston are equal when the valve element is in contact with the valve seat.

Description

Vacuum on/off valve

Technical Field

The present invention relates to a vacuum opening/closing valve. Specifically, the vacuum on/off valve can be connected between the vacuum container and the vacuum pump for controlling the vacuum pressure of the gas in the vacuum container by changing the valve opening degree.

Background

Heretofore, for example, in a semiconductor manufacturing process, such a vacuum pressure control system has been proposed that alternately fills and discharges a process gas and a purge gas in a vacuum chamber in which a wafer is placed. In such a vacuum pressure control system, a vacuum on/off valve is provided so as to be connectable between a vacuum chamber and a vacuum pump. The vacuum opening/closing valve is provided to control the vacuum pressure of the process gas to be supplied into the vacuum chamber by changing the opening degree of the hollow opening/closing valve (see japanese unexamined patent publication No. 09(1997) -072458).

The conventional vacuum opening/closing valve will be explained with reference to fig. 11 to 16. Fig. 11 is a sectional view of a vacuum on/off valve 100 provided in the vacuum pressure control system disclosed in JP 09-072458A. Fig. 12 is an enlarged view of portion R of fig. 11, showing the bellofram 150 in a valve closed state. FIG. 13 is a cross-sectional view of a conventional bellofram. Fig. 14 is an explanatory diagram showing the texture of the base cloth 151B of the bellofram 150.

In the vacuum opening/closing valve 100, driving air is supplied into the air chamber AS to move the piston 140 upward (in fig. 11), and accordingly, the poppet valve element 176 connected to the piston 140 through the piston rod 147 is moved upward in the stroke direction of the piston 140 so that the poppet valve element 176 is separated from the valve seat 173, thereby opening the valve. The piston 140 may move inside the single-acting cylinder 130 (hereinafter, referred to as "cylinder 130"), but the piston 140 does not contact the cylinder 130 to prevent the viscous sliding. The gap 145 between the piston 140 and the cylinder 130 is hermetically sealed by a bellofram 150 that can move according to the movement of the piston 140. Thus, the air chamber AS can ensure its airtightness.

As shown in fig. 13, the cross-section of the bellofram 150 is trapezoidal when viewed from the liner direction (or radial direction) of the piston 140. The bellofram 150 is formed of rubber in which a base cloth 151B such as polyester is embedded by insert molding. As shown in fig. 14, the texture of the base cloth 151B is formed by weaving warp yarns and weft yarns in a plain weave by passing each warp yarn over and under each weft yarn in a lattice pattern. The bellofram includes a center portion 152 fixed to the pressure receiving surface 142 of the piston 140, and a flange portion 153 fixed by the flange holding portion 132 of the cylinder 130. In the bellofram 150, the peripheral single-tapered surface 154, which is deeply folded back from the flange portion 153 toward the central portion 152, is a single inclined surface having a single tapered angle θ p with an imaginary line N parallel to the axis AX.

Further, the reason why the conventional bellofram 150 is designed to be trapezoidal is as follows:

(a) in the vacuum opening/closing valve 100 provided with the bellofram 150, the outer diameter dp of the outer circumferential surface of the piston 140 is smaller than the inner diameter of the cylinder 130 by the predetermined gap 145, and the single tapered surface 154 of the bellofram 150 may be stretched to the top dead center of the piston 140 according to the movement of the piston 140.

(b) In the vacuum opening/closing valve 100, the center portion 152 and the flange portion 153 of the bellofram 150 are located almost on the same level in the valve-closed state. As shown in fig. 11 and 12, the single tapered surface 154 is folded inside the gap 145 between the piston 140 and the cylinder 130 in a mountain-folded shape.

This is because the single tapered surface 154 is formed to have a single inclined surface forming a predetermined single tapered angle θ p with respect to the axis AX, i.e., the imaginary line N, so that the bellofram 150 can be easily extended and retracted in accordance with the opening/closing action of the vacuum opening/closing valve 100.

Further, vacuum opening/closing valves operated using a bellows seal are disclosed in FIG. 1 of Japanese unexamined patent application publication No. 2002-132354 and FIGS. 2, 5 and 6 of Japanese unexamined patent application publication No. 07(1995) -150623. Further, the technique in which the bellofram is provided with the inclined surfaces having different angles is disclosed in fig. 1 and 4 of japanese unexamined patent application publication No. 56(1981) -049462, fig. 3 of japanese unexamined utility model application publication No. 61(1986) -140296, and fig. 2 and 5 of japanese unexamined utility model application publication No. 61(1986) -172230.

Further, a bellows seal member made by insert molding rubber around a tricot fabric base cloth is disclosed in Japanese unexamined patent application publication No. 10(1998) -317262 and Japanese unexamined patent application publication No. 10(1998) -132077.

However, the above-described vacuum opening/closing valve 100 has the following problems:

(1) fig. 11 and 12 show a closed state of the vacuum opening/closing valve 100. In this state, when the driving air is supplied into the air chamber AS, the pressure of the driving air is applied to the center portion 152 of the bellofram 150 and the single-cone surface 154 folded back inside the gap 145 between the piston 140 and the single-acting cylinder 130, thereby moving the piston 140 upward.

Accordingly, the shape of the single tapered surface 154 changes from the mountain-folded shape in fig. 12 to another shape partially bulging toward both the outer circumferential surface of the piston 140 and the inner surface of the cylinder 130 due to the driving air supplied to the air chamber AS (see fig. 15).

The trapezoidal bellows seal 150 is provided with a single tapered surface 154 located outside the outer peripheral surface of the piston 140 with respect to the axial direction AX. At a certain position in the axial direction AX, the conical surface diameter Dp of the conical surface of the bellofram 150 that is in contact with the piston 140 is larger than the outer diameter Dp of the piston 140, as shown by the two-dot chain line in fig. 16. The bellows seal 150 includes a conical surface and the piston is cylindrical. Therefore, the shortest diameter of the bellofram 150 must be determined according to the diameter of the piston 140, resulting in a large difference between π Dp and π Dp at the position shown in FIG. 12.

In other words, the circumferential length (the circumference of the single tapered surface) of the single tapered surface 154, pi Dp, is greater than the circumferential length pi Dp (the circumference of the piston) on the outer circumferential surface of the piston 140. Therefore, the portion of the bellofram 150 that is not in contact with the outer circumferential surface of the piston 140 is likely to form the pleated portion 159.

As the difference between the circumferential length of the single tapered surface and the outer circumferential length of the piston, pi Dp, becomes larger, the pleat 159 also becomes larger. Further, the pressure applied to the outer circumferential surface of the piston 140 along the single tapered surface 154 of the bellofram 150 is greater than the pressure in the inner space of the pleating portion 159 between the single tapered surface 154 and the outer circumferential surface of the piston 140.

Accordingly, when pressure is applied to the pleating part 159 along the single tapered surface 154, portions of the single tapered surface 154 are pressed to contact or come closer to each other and extend radially outward from the outer circumferential surface of the piston 140. Accordingly, each extension is folded largely at the bent portion 159B located on the outermost side in the radial direction. When the single tapered surface 154 extends partially radially outward, the portion of the single tapered surface 154 having the bent portion 159B of the pleated portion 159 tends to fold sharply, possibly resulting in excessive bending stress being formed on the bent portion 159B.

In a state where the bent portion 159B is formed as shown in fig. 16, when the piston 140 in fig. 15 moves upward, the bent portion 159B changes from contact with the piston 140 side to contact with the inner wall side of the cylinder 130. In other words, the direction of the curved portion 159B is turned 180 degrees (in the radial direction). When contacting the inner wall side of the cylinder 130, since the diameter of the inner wall is large enough to stretch the bent portion 159B, the bent portion 159B becomes smooth. However, when the bent portion 159B is turned 180 degrees, stress is concentrated on the bent portion 159B. The stress concentration is repeated every time the vacuum opening/closing valve is operated, thereby causing vertical cracks to occur in the bellofram 150.

Although the applicant has provided the above-described vacuum on/off valve all over the world, it is difficult for the applicant to find a cause of the problem regarding the durability of the bellofram 150. Finally, the applicant has now successfully identified this cause by trial and error as described above.

(2) Second, since the base cloth of the bellofram 150 is formed into a plain weave texture as shown in fig. 14, the bellofram 150 has less flexibility and is difficult to freely bend. Therefore, when the driving air is supplied, the pleating portion 159 locally appears as a considerable wrinkle in the circumferential direction of the single tapered surface 154 (see fig. 16). Subsequently, during the valve closing process, some portions of the base fabric of the single tapered surface 154, which form mountain folds at the pleats 159, rub against each other. This may cause the cracks generated in the top (folds) 158 to become larger over time so as to reach the pleats 159, thereby abrading or destroying the base fabric of the bellofram 150.

Due to the problems mentioned in (1) and (2), there is a possibility that the gas supplied into the air chamber AS may leak through the bellofram 150, and the valve opening degree of the vacuum opening/closing valve 100 cannot be controlled. As a result, the bellofram 150 must be replaced frequently and a more durable vacuum on/off valve is required.

Disclosure of Invention

The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a durable vacuum opening/closing valve in which a gap between an outer circumferential surface of a piston and an inner circumferential surface of a cylinder is hermetically sealed by a bellows seal that can move according to the movement of the piston, and the piston opens or closes the vacuum opening/closing valve by fluid movement.

(1) To achieve the object of the present invention, a vacuum opening/closing valve is provided that can be connected between a vacuum container and a vacuum pump. The valve comprises: a valve seat formed with a port connectable with one of a vacuum vessel and a vacuum pump, a valve element movable into and out of contact with the valve seat, a piston movable by a fluid to move the valve element, a cylinder in which the piston is accommodated, and a bellofram arranged to tightly seal a predetermined gap between an outer circumferential surface of the piston and an inner circumferential surface of the cylinder and to change in shape according to movement of the piston. The vacuum on/off valve is provided to control the vacuum pressure in the vacuum container by changing the opening degree of the valve element with respect to the valve seat. In the vacuum opening/closing valve, the bellofram includes a peripheral surface formed at a predetermined inclination angle and disposed to be in contact with an outer peripheral surface of the piston, the outer peripheral surface of the piston includes an inclined surface formed at a predetermined inclination angle, the bellofram and the piston are designed such that when the valve element is in contact with the valve seat, an inner diameter of the peripheral surface of the bellofram at a portion contacting the piston is equal to an outer diameter of the piston contacting the peripheral surface of the bellofram, an inclination angle of the bellofram is equal to the inclination angle of the piston, the peripheral surface of the bellofram includes first and second inclined surfaces having different inclination angles with respect to an axis of a stroke direction of the piston along a central axis of the bellofram in cross section, and the inclination angle of the bellofram is smaller one of the inclination angles of the first and second inclined surfaces And (4) respectively. The vacuum opening/closing valve further comprises a rod connecting the valve element and the piston, wherein the bellofram further comprises a through-hole through which the rod extends, and the bellofram is fitted on the outer periphery of the rod through the through-hole and positioned at a proper position.

(2) In the above vacuum opening/closing valve (1), it is preferable that the bellofram includes a fixing portion at a radial periphery, the bellofram is fixed to the cylinder by the fixing portion, and the bellofram further includes a curved portion connecting the inclined surfaces of the first and second, the curved portion being disposed closer to the fixing portion than a center portion of the bellofram in the axis direction.

(3) In the above vacuum opening/closing valve (1), preferably, the bellofram is made of a rubber molded member formed of a base cloth insert-molded with rubber, and the base cloth is a flexible woven texture along the surface of the bellofram.

(4) In the above vacuum opening/closing valve (3), preferably, the texture of the base fabric is a tricot fabric.

The vacuum opening/closing valve according to (1) can be connected between the vacuum chamber and the vacuum pump for controlling the vacuum pressure in the vacuum chamber by changing the opening degree of the valve element with respect to the valve seat. The vacuum opening/closing valve is further configured such that a predetermined gap between an outer circumferential surface of the piston and an inner circumferential surface of the cylinder is hermetically sealed by a bellows seal that moves according to a movement of the piston moved by the fluid to open or close the valve. An inner circumferential surface of the bellofram in contact with the piston is formed to be inclined at a predetermined inclination angle, and an outer circumferential surface of the piston is inclined at a predetermined inclination angle. When the valve element is in contact with the valve seat, the inner peripheral diameter of the bellofram contacting the piston is equal to the outer peripheral diameter of the piston. Therefore, in a state where the vacuum opening/closing valve is closed, when driving air is supplied into the cylinder to apply air pressure to the bellofram, the inner diameter of the bellofram and the outer diameter of the piston are equal, so that the bellofram will not be bent or pleated.

Conventionally, the piston has a right circular cylindrical shape. Therefore, the inner diameter of the bellofram contacting the end face of the piston must be larger than the outer diameter of the piston. In the present embodiment, the outer periphery of the piston includes a tapered surface, and therefore, in the state where the valve is closed, the inner diameter of the bellofram and the outer diameter of the piston can be determined to be equal to each other.

Further, in the vacuum opening/closing valve according to (1), the taper angle of the bellofram is equal to the taper angle of the piston. Therefore, even when the piston moves a certain distance, the inner diameter of the bellofram is equal to the outer diameter of the piston, so that the bellofram is not easily bent or pleated. The applicant has determined that even if the angle of taper of the bellofram is slightly greater than that of the piston, the durability of the bellofram can be significantly improved as long as the inner diameter of the bellofram and the outer diameter of the piston are equal when the valve element contacts the valve seat. The applicant has also fully realized that if the taper angle of the bellofram and the taper angle of the piston are made equal, the durability can be further improved.

In the vacuum opening/closing valve according to (1), the bellofram is formed with at least two tapered surfaces having different inclination angles from each other with respect to an axis in a stroke direction of the piston when viewed in a cross section in a cylinder liner direction of the piston. When the bellofram is formed with two tapered surfaces, for example, the first taper angle θ 1 is determined to be larger than the single taper angle θ p (θ p < θ 1) of the conventional bellofram, the second single taper angle θ 2 may be smaller than the single taper angle θ p (θ 2< θ p).

In this case, the bellofram is designed such that a first single tapered surface having a first single taper angle θ 1 with respect to the axis is closer to the inner peripheral surface of the cylinder, and a second tapered surface having a second tapered angle θ 2 with respect to the axis is closer to the outer peripheral surface of the piston. Accordingly, the taper angle of the second tapered surface of the bellofram may be equal to the taper angle of the outer circumferential surface of the piston.

Accordingly, the bellofram is formed with at least two tapered surfaces having different inclination angles from each other so that the bellofram can be kept stretchable in accordance with the opening/closing movement of the vacuum opening/closing valve. The bellows seal also prevents short term damage from cracking caused by the pleating of the bellows seal.

In the vacuum opening/closing valve according to (1), the bellofram is fitted on the outer periphery of the rod connecting the piston and the valve element, and the bellofram is further formed with a through hole for positioning the bellofram.

Thus, the bellofram can be accurately positioned relative to the piston by the stem.

To open or close the vacuum opening/closing valve, the tapered surface is moved and stretched to the top dead center or the bottom dead center according to the movement of the piston. At this time, the tapered surface approaches the intermediate position in a mountain-folded form in the stroke direction.

In the vacuum opening/closing valve according to (2), the curved portion connecting the respective tapered surfaces is disposed closer to the fixing portion than the center portion of the bellofram in the axial direction. Thus, the conical surface of the bellofram folds over, but not at the bend.

Even when the vacuum opening/closing valve is repeatedly opened or closed, the tapered surface is not folded at a bent portion where stress concentration occurs more easily than other portions of the tapered surface of the bellofram. Therefore, the bellofram can prevent damage (fatigue of the material constituting the bellofram) due to repeated folding of the tapered surface at the bent portion.

As a result, any damage of the bellofram at an early stage can be prevented.

Further, in the vacuum opening/closing valve according to (3), the bellofram is made of a rubber molded member including rubber and a base cloth having a flexible texture along a surface of the bellofram.

Thereby, the bellofram can be made airtight by the rubber, and can be made strong against the pressure of the fluid by the base cloth. Therefore, the bellofram can be freely bent along the shape of the outer circumferential surface of the piston in accordance with the movement of the piston.

In the vacuum opening/closing valve of the present invention according to (4), the base fabric of the bellofram is a tricot fabric, so that the bellofram is easily bent according to the movement or the peripheral shape of the piston when pressure is applied by the fluid.

In particular, when the tapered surface of the bellofram bulges along the outer peripheral surface of the piston and pressure is applied by the fluid, the bellofram tends to flex to align itself with the outer peripheral surface of the piston.

Therefore, in the vacuum opening/closing valve of the present invention, at a certain position of the piston in the stroke direction, the slit between the periphery of the tapered surface and the periphery of the outer peripheral surface of the piston causes the tapered surface of the bellofram to pleat, which can be smaller than that in the conventional vacuum opening/closing valve. Furthermore, the wrinkles can be kept small and spread over the tapered surface, unlike the local presence of considerable wrinkles on the single tapered surface of the bellow seal of conventional on/off valves. Therefore, when the vacuum opening/closing valve is opened or closed, any contact between the mountain-folded tapered surfaces of the pleating parts can be avoided, thereby preventing the base cloths from rubbing against each other.

As a result, even if any crack is generated on the mountain fold in the tapered surface, the bellofram can be prevented from being damaged by friction due to crack propagation of the base cloth having the mountain-folded tapered surface.

Further, the tricot fabric is, for example, similar to a knitted fabric, a rib fabric formed in a ridge-shaped pattern having mountain portions and valley portions alternately continuous in a predetermined direction, or the like. This technique, including tricot fabrics, can provide flexible, elastic and stretchable fibers.

Further, in the above vacuum opening/closing valve, the bellofram includes a radially central portion formed with a projection projecting outward in a thickness direction of the bellofram, and the piston includes a pressure receiving surface formed with a groove in a cylinder liner direction. The bellows seal and the piston are coaxially disposed and secured by the engagement of the protrusion and the groove.

Therefore, the radially central portion of the bellofram can be prevented from being relatively displaced with respect to the pressure receiving surface of the piston. Therefore, the tapered surface of the bellofram can be equally curved and extended in the circumferential direction of the tapered surface in accordance with the movement of the piston, so that the piston can be appropriately moved.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the advantages and principles of the invention. In the drawings, there is shown in the drawings,

fig. 1 is a sectional view of a bellofram provided in an on/off valve in the present embodiment;

FIG. 2 is an explanatory enlarged view of a portion X in FIG. 1, showing a rubber molded member constituting a bellofram;

FIG. 3 is an explanatory diagram showing the texture of the base cloth of the bellofram;

fig. 4 is an explanatory view showing the structure of the vacuum opening/closing valve in the valve-closed state;

fig. 5 is an explanatory view showing the structure of the vacuum opening/closing valve in the valve-open state;

fig. 6 is an enlarged view of a portion P shown in fig. 4;

fig. 7 is an explanatory enlarged view of a portion Q in fig. 6, showing a gap between an outer peripheral surface of the piston and an inner peripheral surface of the cylinder;

FIG. 8 is a cross-sectional view of the piston;

FIG. 9 is an illustrative cross-sectional view taken along line A-A of FIG. 6 showing a pressurized bellows seal;

fig. 10 is an explanatory diagram showing the configuration of a vacuum pressure control system including the vacuum on/off valve in the present embodiment;

fig. 11 is an explanatory view showing the structure of a conventional vacuum opening/closing valve;

fig. 12 is an enlarged view of a portion R in fig. 11;

FIG. 13 is a cross-sectional view of a conventional bellofram;

FIG. 14 is an explanatory view showing the texture of the base cloth of the conventional bellofram;

FIG. 15 is a cross-sectional view of a conventional bellowed seal under pressure; and

fig. 16 is a cross-sectional view taken along line B-B in fig. 15.

Detailed Description

A detailed description will now be given of preferred embodiments of a vacuum on/off valve embodying the present invention with reference to the accompanying drawings. Fig. 10 is an explanatory diagram showing the configuration of the vacuum pressure control system 1 including the vacuum opening/closing valve 10.

The vacuum pressure control system 1 is a system for performing surface treatment on a wafer 8 by alternately filling or discharging a process gas and a purge gas into or from a vacuum chamber 2 in which the wafer 8 is placed during semiconductor manufacturing. As shown in fig. 10, the vacuum pressure control system 1 mainly includes a vacuum chamber 2 (vacuum container), a vacuum pump 5, an air supply source 6 for supplying driving air AR, a vacuum open/close valve 10, a servo valve (not shown) for controlling the opening degree of the vacuum open/close valve 10, and a vacuum pressure controller 7 electrically connected to the vacuum open/close valve 10 and the like.

The gas supply port 2a of the vacuum chamber 2 is connected in parallel to the process gas supply source and the nitrogen gas supply source. The process gas is used for surface treatment of the wafer 8 disposed in the vacuum chamber 2, and the nitrogen gas is used for purging of the process gas from the vacuum chamber 2.

On the other hand, the gas discharge port 2b of the vacuum chamber 2 is connected in parallel with the vacuum opening/closing valve 10 and the pressure sensor 3 for the chamber through the closing valve 4. The pressure sensor 3 is electrically connected to a vacuum pressure controller 7 to measure the vacuum pressure of the process gas or the like in the vacuum chamber 2. Further, the vacuum opening/closing valve 10 is connected to the vacuum pump 5.

The vacuum opening/closing valve 10 will now be described with reference to fig. 1 to 6.

Fig. 1 is an explanatory sectional view of a bellofram 50 provided in the vacuum opening/closing valve 10 of the present embodiment, when viewed from the cylinder liner direction (radial direction) BR of the piston 40. Fig. 2 is an explanatory enlarged sectional view of a portion X in fig. 1, showing a rubber molded member 51 constituting the bellofram 50. Fig. 3 is an explanatory view showing the texture of the base cloth 51B of the rubber molded member 51 in fig. 2. Fig. 4 is an explanatory diagram showing the structure of the vacuum opening/closing valve 10 in the valve-closed state. Fig. 5 is an explanatory diagram showing the structure of the vacuum opening/closing valve 10 in the valve-open state. Fig. 6 is an enlarged view of a portion P shown in fig. 4.

The vacuum on/off valve 10 of the present embodiment is used to control the vacuum pressure of the process gas or the like in the vacuum chamber 2 by changing the valve opening VL by the drive air AR supplied from the air supply source 6 into the air chamber AS through a servo valve, not shown.

The vacuum opening/closing valve 10 includes a pilot cylinder portion 20 and a bellows type lift valve portion 70. In the direction of the axis AX, or in the valve displacement direction (the vertical direction in fig. 4 and 5) in which the poppet valve element 76 is opened or closed, the pilot cylinder portion 20 is located on the valve opening side (the upper side in fig. 4 and 5), and the bellows type poppet valve portion 70 is located on the valve closing side (the lower side in fig. 4 and 5).

The pilot cylinder portion 20 includes: single-acting cylinder 30, flange retainer 32, cavity AS, piston 40, return spring 47, bellows seal 50, etc.

In the vacuum opening/closing valve 10, when the driving air AR is supplied into the air chamber AS, the piston 40 moves upward inside the cylinder 30 in the stroke direction ST parallel to the axis AX without contacting the inner peripheral surface 31 of the cylinder 30. The outer diameter dp of the outer peripheral surface 41 of the piston 40 is designed to be smaller than the diameter of the inner peripheral surface 31 of the cylinder 30 by a predetermined value. The piston 40 includes a pressure receiving surface 43 provided with an annular recess 44 recessed in the stroke direction ST. Further, a predetermined gap 45 is provided between the outer peripheral surface 41 of the piston 40 and the inner peripheral surface 31 of the cylinder 30. AS will be described hereinafter, the gap 45 is hermetically sealed by the bellofram 50 in fig. 1 to ensure the air tightness of the air chamber AS.

Further, the piston 40 moves without contacting the inner circumferential surface 31 of the cylinder 30, thereby preventing the viscous sliding of the piston 40. Therefore, the piston 40 can move inside the cylinder 30 with high sensitivity and accurate positioning.

The piston 40 is urged toward the valve-closing side in the valve-displacement direction by the return spring 47. When the driving air AR is not supplied into the air chamber AS, the piston 40 is placed at the bottom dead center by the urging force of the return spring 47 (see fig. 4). In contrast, when the drive air AR is supplied into the air chamber AS, the piston 40 moves toward the valve-opening side in the valve-displacement direction against the urging force of the return spring 47 (see fig. 5).

Further, in the vacuum opening/closing valve 10, a displacement sensor 81 is provided to measure the amount of displacement of the piston 40 in the valve displacement direction from the bottom dead center to the top dead center (see fig. 4 and 5). The displacement amount indicates the valve opening degree of the vacuum opening/closing valve 10. The displacement sensor 81 is not in contact with the piston 40, but is electrically connected to the vacuum pressure controller 7.

The bellofram 50 is formed from a rubber moulded member 51. The rubber molded member 51 is formed by insert molding of a base fabric 51B having a tricot texture and rubber 51A (see fig. 1 and 2). The tricot fabric shown in fig. 3 is, for example, similar to a knitted fabric, a rib fabric formed in a ridge-shaped pattern having mountain portions and valley portions alternately continuous in a predetermined direction, or the like. This technique, including tricot fabrics, can provide flexible, elastic, and stretchable fibers.

The bellofram 50 is stretchable to keep the effective pressure receiving area of the pressure receiving surface 43 of the piston 40 constant when the driving air AR is supplied into the air chamber AS. The bellofram 50 is constituted by a rubber molded member 51, and the rubber molded member 51 is made of a base cloth 51B having a sufficient strength against the pressure of the driving air AR supplied to the air chamber AS and a rubber 51A having a sufficient airtightness. The rubber 51A of the rubber molded member 51 may include natural rubber and synthetic rubber such as acrylonitrile-butadiene rubber, styrene-butadiene rubber, isoprene rubber, propylene-butadiene rubber, acrylonitrile-isoprene rubber, chloroprene rubber, isobutylene-isoprene rubber (butyl rubber), ethylene propylene rubber, acrylic rubber, fluorocarbon rubber, ether-thioether rubber, polysulfide rubber, urethane rubber, silicone rubber, and the like. As for the material of the base cloth 51B, for example, a thread such as polyamide (nylon 6, nylon 66, etc.), aramid, polyester, or cotton may be selected, and woven so as to have flexibility along the

respective surfaces

51a, 51B of the bellofram 50 (rubber molded member 51).

As shown in fig. 1, in the present embodiment, the bellofram 50 is formed with a first tapered surface 55A and a second tapered surface 55B, the first tapered surface 55A and the second tapered surface 55B having different inclination angles from each other with respect to an axis AX in a stroke direction ST (vertical direction in fig. 4 and 5) of the piston 40 when viewed in a section in a liner direction BR (in a lateral direction in fig. 4 and 5) of the piston 40. The bellofram 50 further comprises: a peripheral flange 54 (fixed portion) that is peripheral in the radial direction (the cylinder direction BR of the piston 40), and a central portion 52 (radially central portion) that is located at the center in the radial direction so as to be continuous with the flange 54 via first and second tapered surfaces 55A and 55B interposed between the central portion 52 and the flange 54.

The first taper surface 55A is turned up (in the drawing) from the flange 54 at a taper start point 54S on the radially inner side of the flange 54. The first tapered surface 55A is an annular inclined surface having a first taper angle θ 1(0< θ 1<90 °) with respect to an imaginary line M parallel to the axis AX. Similarly, the second tapered surface 55B is an annular inclined surface having a second tapered angle θ 2(0< θ 2< θ 1) with respect to the imaginary line M. First and second tapered surfaces 55A and 55B are continuous at bend 56. In the form shown in fig. 1, the bent portion 56 is closer to the flange 54 than the center of the bellofram 50 in the direction of the axis AX. The reason why the bent portion 56 is positioned at such a position is as follows: when the vacuum opening/closing valve 10 is closed, the second tapered surface 55B of the bellofram 50 moves and is stretched to the top dead center of the piston 40 according to the movement of the piston 40. At this time, the second tapered surface is mountain-folded in the vicinity of the center position in the stroke direction ST.

Further, the central portion 52 is continuous with the second tapered surface 55B in the cylinder liner direction BR (lateral direction in fig. 4 and 5) of the piston 40. The center portion 52 is formed with a through hole 57 passing through the piston rod 48 and a protrusion 53 circumferentially disposed around the through hole 57 and protruding in the thickness direction (vertical direction in fig. 1) of the center portion 52. The through hole 57 is precisely sized to fit tightly over the outer circumference of the piston rod 48.

As shown in fig. 6, the projection 53 fits in the recess 44 of the piston 40, thereby positioning the bellofram 50 relative to the piston 40. When the center portion 52 of the bellofram 50 is in contact with the pressure contact surface 43 of the piston 40, the center portion 52 is interposed between the piston 40 and the plate-like fixing member 46, so that the bellofram 50 is fixed by the threaded connection of the piston 40 and the fixing member 46.

Further, the flange 54 of the bellofram 50 is held and firmly fixed between the cylinder 30 and the flange holding portion 32.

In the vacuum opening/closing valve 10, when the piston 40 is positioned at the bottom dead center, more specifically, when the driving air AR is not supplied into the air chamber AS, the flange 54 and the center portion 52 of the bellofram 50 are positioned on almost the same level in the stroke direction ST (see fig. 4). Thus, in the gap 45 between the piston 40 and the cylinder 30, the second tapered surface 55B is mountain-folded at the top 58, as shown in fig. 4, 6, and 7.

On the other hand, when the driving air AR is supplied into the air chamber AS, the second tapered surface 55B mountain-folded at the top 58 AS shown in fig. 6 and 7 bulges along the inner peripheral surface 31 of the cylinder 30 and the outer peripheral surface 41 of the piston 40 AS shown by the two-dot chain line in fig. 7 while protruding toward the top dead center (upper side in fig. 6 and 7) in the stroke direction ST of the piston 40 AS shown in fig. 5.

As described above, the flange 54 of the bellofram 50 is fixed by the flange holding portion 32, and the center portion 52 of the bellofram 50 is fixed by the pressure receiving surface 43 of the piston 40, respectively. In this case, the first and second tapered surfaces 55A and 55B are provided in the gap 45 between the piston 40 and the cylinder 30 to hermetically seal the gap 45, so that the tapered surfaces 55A and 55B are folded inward or outward according to the movement of the piston 40.

Fig. 6 is an enlarged view of a portion P in fig. 4 in a valve-closed state where the O-ring 79 is in full contact with the valve seat 73. In other words, fig. 6 shows the bellofram 50 in a valve closed state.

In the valve closed state when the O-ring 79 is sufficiently in contact with the valve seat 73, when the drive air AR is supplied into the valve 10, the bellofram 50 changes its shape as indicated by the two-dot chain line in fig. 7. In other words, the contact portion of the bellofram 50 with respect to the piston 40 slightly varies. In the present embodiment, the inner diameter of the bellofram 50 at the position where the bellofram 50 contacts the piston 40 is defined as W2 (specifically, the upper end indicated by the height L, or the upper end of the bellofram 50 contacting the piston 40 as indicated by the two-dot chain line in fig. 7).

Fig. 8 is a sectional view of the piston 40. The piston 40 includes an end having a tapered surface 40a that tapers at an angle θ. The angle θ is determined to be equal to the second taper angle θ 2 of the bellofram 50. The piston conical surface 40a is disposed at about the lower half of the piston 40. This is because the upper half does not need to be tapered since it is not in contact with the bellofram 50.

In the valve-closed state when the O-ring 97 is sufficiently in contact with the valve seat 73, when the driving air AR is supplied, the outer diameter of the upper contact point of the outer periphery of the piston 40 in contact with the bellofram 50 is W1.

On the other hand, in the valve-closed state when the O-ring 79 is in contact with the valve seat 73, the inner diameter of the upper contact point of the bellofram 50 in contact with the piston 40 when the drive air AR is supplied is W2.

As shown in fig. 7, the outer diameter of the piston 40 at a position distant from the bottom end of the piston 40 by a distance L is defined as W1. The distance L1 from the bottom end of the piston 40 is as high as the upper contact limit of the bellofram 50 contacting the piston 40.

Here, in the valve closed state shown in fig. 4, W2 of the bellofram 50 and W1 of the piston 40 are equal in length.

The bellows type poppet valve portion 70 will be described below.

The bellows type poppet valve portion 70 is constituted by a valve main body 71, a bellows 75, a poppet valve member 76, an O-ring retainer 77, an O-ring 79, and the like.

The piston rod 48 is disposed through a diametrically central portion of the piston 40 and is connected to the piston 40 by an O-ring 79 interposed between the piston rod 48 and the piston 40. The piston rod 48 extends down to the bellows type poppet valve portion 70 and is connected at one end of the piston rod 48 to a poppet valve member 76 on the valve opening side. The poppet valve member 76 may move in the valve displacement direction in accordance with the movement of the piston 40 in the stroke direction ST. One end (upper end in fig. 4 and 5) of the bellows 75 is fixed to the valve body 70 or the like in the axis AX direction, and the other end of the bellows 75 is fixed to the poppet valve element 76. In this way, the bellows 75 is mounted to surround the radially outer periphery of the piston rod 48 in a stretchable manner in accordance with the movement of the poppet valve element 76 in the valve displacement direction.

On the valve-closing side (lower side in fig. 4 and 5) of poppet valve member 76, poppet valve member 76 is fixed with O-ring retainer 77, thereby forming annular O-ring mounting portion 78 defined by poppet valve member 76 and O-ring retainer 77. An O-ring 79 is provided in the O-ring mounting portion 78 to come into contact with the valve seat 73 of the valve main body 71. The valve body 71 is provided with a first port 72 connected to the vacuum pump 5 and a second port 74 connected to the gas discharge port 2b of the vacuum chamber 2.

In the vacuum opening/closing valve 10, when the driving air AR is not supplied into the air chamber AS, the piston 40 is positioned at the bottom dead center by the urging force of the return spring 47. The poppet valve 76 connected to the piston 40 is thus pressed against the valve seat 73 by the O-ring 79. As a result, the first port 72 is blocked by the poppet valve element 76, thereby closing the vacuum opening/closing valve 10 (valve opening VL equal to 0).

On the other hand, when the driving air AR is supplied into the air chamber AS, the piston 40 is moved to the valve-opening side in the valve-displacement direction against the urging force of the return spring 47. Therefore, the poppet valve member 76 and the O-ring 79 are simultaneously moved to the valve opening side, separated from the valve seat 73. Accordingly, the vacuum opening/closing valve 10 is opened (valve opening VL >0), allowing the first and

second ports

72 and 74 to communicate with each other. After the vacuum opening/closing valve 10 is opened, the vacuum pump 5 can suck the process gas or nitrogen gas from the vacuum chamber 2.

In the vacuum opening/closing valve 10 of the present embodiment, the bellofram 50 includes a first tapered surface 55A having a first taper angle θ 1 and a second tapered surface 55B having a second taper angle θ 2 with respect to the axis AX when viewed from a cross section in the liner direction BR of the piston 40.

Now, the first and second taper angles θ 1 and θ 2 between the imaginary line M parallel to the axis AX and the first and second tapered surfaces 55A and 55B will be verified below by comparison with the bellofram 50 of the vacuum opening/closing valve 10 and the bellofram 150 of the conventional vacuum opening/closing valve 100.

As described above, in the vacuum opening/closing valve 10, the angle of the tapered surface 55A with respect to the axis AX (imaginary line M) is the first taper angle θ 1(0< θ 1<90 °). Similarly, the angle of the second tapered surface 55B with respect to the axis AX (imaginary line M) is a second taper angle θ 2(0< θ 2< θ 1). Accordingly, the diameter of the second tapered surface 55B at a certain position in the direction of the axis AX is defined as a second tapered surface diameter D2. Further, the circumferential length at this position is defined as a second tapered surface circumference π D2.

On the other hand, in the conventional vacuum opening/closing valve 100, the bellofram 150 has only a single tapered surface 154. Specifically, the angle of the single tapered surface 154 with respect to an imaginary line N parallel to the axis AX of the bellofram 150 is a single taper angle θ p (0< θ p <90 °) (see fig. 13). Therefore, the diameter of the single tapered surface 154 at a certain position in the piston stroke direction is defined as a single tapered surface Dp. Further, the circumferential length at the position is defined as a single tapered surface circumferential length pi Dp (see fig. 16).

In the vacuum opening/closing valve 10 of the present embodiment, the first taper angle θ 1 is determined to be larger than the single taper angle θ p (θ p < θ 1), and therefore the second taper angle θ 2 can be smaller than the single taper angle θ p (θ 2< θ p). In other words, the relational expression of the first taper angle θ 1, the second taper angle θ 2, and the single taper angle θ p is expressed as θ 2< θ p < θ 1 (1). Based on the relation (1), the bellofram 50 of the vacuum opening/closing valve 10 is designed such that a first tapered surface 55A having a first taper angle θ 1 with respect to the axis AX is located closer to the inner peripheral surface 31 of the cylinder 30, and a second tapered surface 55B having a second taper angle θ 2 with respect to the axis AX is located closer to the outer peripheral surface 41 of the piston 40.

On the other hand, the tapered surface 40a of the piston 40 is angled at the same angle as the second tapered surface 55B of the bellofram 50. In the valve closed state when the O-ring 79 is sufficiently in contact with the valve seat 73, the bellofram 50 is deformed or changes its position as shown by the two-dot chain line in fig. 7 when the drive air AR is supplied. At this time, as described above, at the upper limit where the bellofram 50 and the piston 40 contact each other, the inner diameter W2 of the bellofram 50 is equal to the outer diameter W1 of the piston 40. Therefore, as shown in fig. 9, when the driving air AR is supplied, the bellofram 50 and the piston 40 are brought into close contact with each other, causing no bending or pleating at all.

Thereafter, the contact position of the bellofram 50 with the piston 40 is changed. However, the tapered surface 40a of the piston 40 has an equal taper angle to the second tapered surface 55B of the bellofram 50 so that the bellofram 50 and the piston 40 still continue to remain in close contacting relationship.

Such wrinkles are no longer generated in the bellofram 50, and thus stress concentration is not generated when the piston 40 moves, as compared to the pleated portion 159 generated in the conventional bellofram 150. Therefore, even when the piston 40 is repeatedly moved, the occurrence of cracks moving in the direction of the piston 40 can be prevented. The applicant of the present application has repeatedly tested and determined that cracks are not generated even if the test is repeated several tens of times as much as the test performed in the conventional valve.

As explained above, according to the present embodiment, a vacuum on/off valve may be connected between the vacuum container 2 and the vacuum pump 5 for controlling the vacuum pressure in the vacuum chamber 2 by changing the opening degree of the O-ring 79 serving as a valve element with respect to the valve seat 73. The vacuum opening/closing valve 10 is also configured such that a predetermined gap between the outer circumferential surface of the piston 40 and the inner circumferential surface 31 of the cylinder 30 is hermetically sealed by the bellofram 50 that moves according to the movement of the piston 40 moved by the fluid to open or close the vacuum opening/closing valve 10. The bellofram 50 is formed at a predetermined taper angle θ 2, and the outer circumference of the piston 40 is inclined at the predetermined taper angle θ. When the valve element is in contact with the valve seat 73, the inner peripheral diameter of the bellofram 50 in contact with the piston 40 is equal to the outer peripheral diameter of the piston 40. Therefore, in the state where the vacuum opening/closing valve 10 is closed, when the driving air AR is supplied into the cylinder 30 to apply pressure to the bellofram 50, since the inner diameter of the bellofram 50 and the outer diameter of the piston 40 are equal, the bellofram 50 is not bent or pleated.

Conventionally, the piston has a right circular cylindrical shape. Therefore, the inner diameter of the bellofram contacting the end face of the piston must be larger than the outer diameter of the piston. In the present embodiment, the outer periphery of the piston includes a tapered surface, and therefore, in the valve-closed state, the inner diameter of the bellofram and the outer diameter of the piston can be determined to be equal to each other.

Further, the second taper angle θ 2 of the inner peripheral surface of the bellofram 50 in contact with the piston 40 is equal to the first taper angle θ 1 of the piston 40. Therefore, even when the piston 40 moves a certain distance, the inner diameter of the bellofram 50 contacting the piston 40 is equal to the outer diameter of the piston 40, so that the bellofram 50 is not easily bent or pleated.

The applicant has sufficiently confirmed that even if the second taper angle θ 2 of the bellofram 50 is slightly larger than the taper angle θ of the piston 40, the durability of the bellofram 50 can be significantly enhanced as long as the inner diameter of the bellofram 50 is equal to the outer diameter of the piston 40 when the O-ring 79 as the valve element is in contact with the valve seat 73. The applicant has also fully recognized that durability can be further enhanced if the second taper angle θ 2 of the bellofram 50 and the taper angle θ of the piston 40 are determined to be equal.

Further, the bellofram 50 is formed with the first and second tapered surfaces 55A and 55B, so that the bellofram 50 can be kept stretchable in accordance with the opening/closing movement of the vacuum opening/closing valve 10. The bellofram 50 also prevents short term damage due to cracking caused by the pleating of the bellofram 50.

Further, in the vacuum opening/closing valve 10, the curved portion 56 connecting the first and second tapered surfaces 55A and 55B is disposed closer to the flange 54 than the center portion of the bellofram 50 in the direction of the axis AX. Therefore, the second tapered surface 55B of the bellofram 50 is mountain-folded but is not folded at the bent portion 56.

Even when the vacuum opening/closing valve 10 is repeatedly opened and closed, the second tapered surface 55B is not folded at the bent portion 56 where stress concentration is more likely to occur than the first and second tapered surfaces 55A and 55B of the bellofram 50. Therefore, it is possible to prevent the bellows seal 50 from being damaged (material fatigue of the rubber molded member 51) due to the repeated folding of the second tapered surface 55B at the bend 56.

As a result, any damage of the bellofram 50 at an early stage can be prevented.

In the vacuum opening/closing valve 10 of the present embodiment, the bellofram 50 is fitted on the outer periphery of the piston rod 48 that connects the piston 40 with the poppet valve member 76 that holds the O-ring 79 as the valve member, and the bellofram 50 is also formed with the through-hole 57 for positioning the bellofram 50 with respect to the piston 40. Thus, the bellofram 50 can be easily and accurately positioned relative to the piston 40.

Further, in the vacuum opening/closing valve 10, the bellofram 50 is made of a rubber molded member 51, and the rubber molded member 51 includes a rubber 51A and a base cloth 51B having a flexible texture of tricot along a surface 51A of the bellofram 50. Specifically, the rubber molded member 51 is formed in such a manner that the base cloth 51B is embedded in the rubber 51A by insert molding. As a result, the bellofram 50 can obtain airtightness by the rubber 51A, and obtain strength against the pressure of the driving air AR by the base cloth 51B. Therefore, the bellofram 50 can freely bend or change shape along the outer circumferential surface shape of the piston 40 according to the movement of the piston 40.

Specifically, in the vacuum opening/closing valve 10 of the present embodiment, the base cloth 51B of the bellofram 50 is a tricot fabric. Therefore, when the second tapered surface 55B of the bellofram 50 is bulged along the outer peripheral surface 41 of the piston 40 during the supply of the driving air AR, the bellofram 50 is easily bent to align itself with the outer peripheral surface 41 of the piston 40.

In the vacuum opening/closing valve 10, the bellofram 50 and the piston 40 are coaxially disposed and fixed by fitting the protrusion 53 into the recess 44.

Therefore, the central portion 52 of the bellofram 50 can be prevented from being relatively misaligned with respect to the pressure receiving surface 43 of the piston 40. Therefore, the first and second tapered surfaces 55A and 55B of the bellofram 50 can be equally bent or extended in the circumferential direction of the tapered surfaces 55A and 55B in accordance with the movement of the piston 40. As a result, the piston 40 can be appropriately moved, so that the gap 45 between the outer peripheral surface 41 of the piston 40 and the inner peripheral surface 31 of the single-acting cylinder 30 can be tightly sealed by the bellofram 50 in an appropriate manner.

The present invention is not limited to the embodiment(s) described above, but may be embodied in other specific forms without departing from the essential characteristics thereof.

For example, in the above-described embodiment, the recess 44 of the piston 40 is annularly provided in the pressure receiving surface 43, and the protrusion 53 of the bellofram 50 is annularly provided on the central portion 52, respectively. Alternatively, such recesses and protrusions may be provided in any other form as long as the recesses and protrusions are positioned by engagement. The position and shape of the recess in the piston and the protrusion in the bellofram can be modified and changed as appropriate.

Further, in the bellofram 50 of the present embodiment, a first annular tapered surface 55A having a first inclination angle θ 1 defined with respect to the imaginary line M is located between the taper starting point 54S and the curved portion 56. Alternatively, the portion of the bellofram between the fixing portion and the tapered surface may form an arc shape in cross section when viewed from the cylinder liner direction (radial direction).

Claims

1. A vacuum on/off valve connectable between a vacuum vessel and a vacuum pump, the valve comprising:

a valve seat formed with a port connectable with one of the vacuum container and the vacuum pump;

a valve element movable into and out of contact with the valve seat;

a piston movable by fluid to move the valve element;

a cylinder in which the piston is received; and

a bellofram placed to hermetically seal a predetermined gap between an outer circumferential surface of the piston and an inner circumferential surface of the cylinder and to change in shape in association with movement of the piston;

the vacuum on/off valve is arranged to control the vacuum pressure in the vacuum container by changing the opening degree of the valve element with respect to the valve seat,

wherein,

the bellofram includes a peripheral surface formed with a predetermined inclination angle and arranged to be in contact with an outer peripheral surface of the piston,

the outer circumferential surface of the piston includes an inclined surface formed with a predetermined inclination angle,

the bellofram and the piston are designed such that when the valve element is in contact with the valve seat, the inner diameter of the peripheral surface of the bellofram at the portion in contact with the piston is equal to the outer diameter of the piston in contact with the peripheral surface of the bellofram,

the peripheral surface of the bellofram comprises a first inclined surface and a second inclined surface having different inclination angles with respect to an axis in the stroke direction of the piston in section along a central axis of the bellofram, and

the inclination angle of the bellofram is arranged such that the smaller one of the inclination angles of the first and second inclined surfaces is equal to the inclination angle of the piston,

the vacuum opening/closing valve further includes a rod connecting the valve element and the piston,

wherein,

the bellofram further comprises a through-hole through which the stem extends, an

The bellofram fits over the outer circumference of the stem through the through-hole and is positioned in place.

2. The vacuum on/off valve of claim 1,

the bellofram comprises a fixing portion at a radial periphery with which the bellofram is fixed to the cylinder,

the bellofram further includes a curved portion connecting the first inclined surface and the second inclined surface, the curved portion being disposed closer to the fixing portion than a center portion of the bellofram in the direction of the axis.

3. The vacuum on/off valve of claim 1,

the bellofram is made of a rubber molded member formed of a base cloth insert-molded with rubber,

the base fabric is a flexible woven texture along a surface of the bellofram.

4. The vacuum on/off valve of claim 3, wherein the texture of the base fabric is a tricot fabric.