JP2001349444A - Seal structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seal structure capable of outputting motion of a small stroke stably with favorable precision, and miniaturizing an actuator. SOLUTION: This seal structure comprising a piston member 7 fixed to a slide rod 4 inserted into cylinders 2 and 3 for keeping gas tightness between the axially slidable piston member 7 and the cylinder 3 is provided with a seal member 8 comprising an inner circumferential fixture part 11 and an outer circumferential fixture part 12, circularly formed, and connected to each other by a film-like flexible part 13, and a pressure receiving surface formed at the outer circumferential fixture part 12 for diametrically receiving fluid pressure. The inner circumferential fixture part 11 is fixed to the piston member 7, and the outer circumferential fixture part 12 is engaged with an installation part formed on an inner wall of the cylinder 3, where a seal member 8 is installed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seal structure such as an actuator which outputs a reciprocating linear motion by being displaced by a fluid pressure, and more particularly to a seal capable of outputting a stable and accurate small stroke motion. Regarding the structure.

[0002]

2. Description of the Related Art An actuator that outputs a linear reciprocating motion is used, for example, in an operate valve in which a valve is connected to an output shaft to open and close the valve. There are various types of actuators used for such valves.For example, when working in a specific atmosphere, air is used to perform drive control using air pressure rather than a solenoid valve for safety reasons. Operate valves are used. Further, there are various types of actuators constituting the air operated valve, such as a diaphragm type or a piston packing type. In such a situation, the development of an air-operated actuator for outputting a small stroke motion was a problem this time.

Conventionally, an air operated actuator (hereinafter simply referred to as “actuator”) has a diaphragm type shown in FIG. 6 or a type shown in FIG. 7 as a seal structure for maintaining airtightness between a drive unit and a cylinder. There is a piston packing type as shown. Further, there is a case using a bellows flam, but the description is omitted here. Therefore, the structure of these illustrated actuators will be briefly described.

In a diaphragm type actuator 50 shown in FIG. 6, an output rod 51 is slidably supported by penetrating a body 52.
3 are integrally formed. That is, the diaphragm 53
Is clamped between clamping plates 54A and 54B and is fixed to an output rod 51 penetrating the center hole thereof with a tightening nut 55. The diaphragm 53 has a curved flexible portion continuing from a central portion formed in a plane, and a peripheral portion thereof is pressed and fixed between the diaphragm 53 and the body 52 by a cylindrical pressing member 56. Then, the cylinder cover 57 presses down the pressing member 56 fitted inside, and
Threaded.

The actuator 50 is urged by a spring 58 from above with the output rod 51 via a holding plate 54A. On the other hand, in order to apply air pressure against the urging force, a lower pressurized diaphragm 53 is used. Room 59
Is formed in the output rod 51. Therefore, according to this actuator 50,
The diaphragm 53 is raised by the air pressure of the compressed air supplied to the pressurizing chamber 59 through the pilot hole 60, and is lowered by the urging force of the spring 58 when the air is exhausted. The actuator 50 outputs a reciprocating linear motion from the output rod 51 by the vertical movement of the diaphragm 53.

Next, a piston packing type actuator 70 shown in FIG.
Is slidably mounted in the cylinder cover 73 and urged by a spring 74 from above. An output rod 75 penetrating the center is fitted to the piston 72, and a pilot hole 77 formed in the output rod 75 communicates with a lower pressurizing chamber 76 partitioned by the piston 72. Therefore, this actuator 70
According to the above, the piston 72 rises by the air pressure of the air supplied to the pressurizing chamber 76 through the pilot hole 77,
Conversely, when the air is exhausted, the spring 74 is lowered by the urging force of the spring 74. The actuator 70 has the piston 7
The reciprocating linear motion is output from the output rod 75 by the up and down movement of 2.

[0007]

However, such a conventional actuator has the following problems. First, in the case of the diaphragm-type actuator 50, if the same thrust is generated under the same air pressure as the piston 72, the diameter of the diaphragm 53 becomes large, and the structure of the actuator 50 becomes complicated. The score increases. As shown in FIG. 6, the diaphragm 53 needs to sandwich its peripheral edge with a certain width, so that the pressing member 56 and the like are required, and the diameter of the cylinder cover 57 increases accordingly. Such an increase in the size of the actuator 50 leads to an increase in the size of a device to which the actuator 50 is attached, for example, an air operated valve, and cannot meet the needs of a semiconductor manufacturing facility that is becoming more compact and integrated. .

In the case of the piston-cylinder type actuator 70, the diameter does not increase as in the case of the diaphragm type, but when output, the ring packing 71 always receives sliding resistance, so that the hysteresis is large and the stroke is small. There was a problem that output accuracy was not stable. Therefore, as the structure for outputting a stable movement of the small-stroke actuator, the former diaphragm type which does not receive sliding resistance is preferable, while the diaphragm type has a problem of enlargement as described above. It has been a reality that there has been no small actuator that outputs a small stroke motion.

In view of the above, an object of the present invention is to provide a seal structure capable of stably outputting a small-stroke motion with high accuracy and capable of reducing the size of an actuator.

[0010]

According to the present invention, a piston member is fixed to a sliding rod inserted into a cylinder, and a seal for maintaining airtightness between the piston member sliding in the axial direction and the cylinder. The inner fixed portion and the outer fixed portion formed in a ring are connected by a film-shaped flexible portion, and a pressure receiving surface for radially receiving fluid pressure is formed on the outer fixed portion. A seal member is provided, wherein the inner peripheral fixing portion is fixed to the piston member, and the outer peripheral fixing portion is fitted to a mounting portion formed on an inner wall of the cylinder to mount the seal member.

Further, the present invention is a seal structure in which a piston member is fixed to a sliding rod inserted into a cylinder, and airtightness is maintained between the piston member and the cylinder sliding in the axial direction. A ring-shaped inner peripheral fixed portion and an outer peripheral fixed portion are connected by a film-shaped flexible portion, and a pressure receiving surface for radially receiving fluid pressure is formed on the inner peripheral fixed portion and the outer peripheral fixed portion. The inner peripheral fixing portion is fitted to a mounting portion formed on the outer peripheral portion of the piston member, and the outer peripheral fixing portion is fitted to a mounting portion formed on the inner wall of the cylinder. It is characterized by attaching a seal member.

Further, according to the present invention, in the sealing structure, the piston member and the mounting portion formed on the inner wall of the cylinder are annular grooves formed in an annular shape, and the inner peripheral fixing portion and the outer peripheral fixing portion are It is characterized in that it has a shape that fits tightly into the annular groove.

Therefore, according to the seal structure of the present invention, each pressure-receiving surface is pressurized in the radial direction by the fluid pressure pressurized in the cylinder without fixing the peripheral portion and the inner peripheral portion like a diaphragm. As a result, the fitting portion is pressed against the inner wall of the cylinder and the piston member to maintain airtightness. Therefore, there is no sliding resistance as in the case of the diaphragm, so that a small stroke movement can be output stably and accurately, and a structure for fixing the peripheral portion is not required. By reducing the size, the size of the actuator can be reduced.

[0014]

Next, an embodiment of a seal structure according to the present invention will be described with reference to the drawings. 1 and 2 are cross-sectional views of an actuator having the seal structure of the present embodiment, and show different output forms. This actuator 1 is of an air operated type like the above-mentioned conventional example, and has a cylinder cover 3 screwed to the body 2.
An airtight space (pressurizing chamber) is formed in the inside. A through hole 21 is formed at the center of the body 2, and a sliding rod 4 slidably inserted therein protrudes outward from inside the cylinder cover 3. That is, a cylindrical male screw portion 22 for connecting to a driven side (for example, a valve) is formed in the body 2, and the sliding rod 4 protrudes therein.

On the other hand, a cylindrical guide portion 31 is protruded inside the cylinder cover 3, and a sliding rod 4 is further slidably inserted into the guide portion 31. Therefore, the sliding rod 4 is vertically supported by the body 2 and the cylinder cover 3 and can move linearly along its axis. Actuator 1 has
Such a sliding rod 4 is provided with a seal structure which is a feature of the present embodiment, whereby a pressurizing chamber 5 is formed below a cylinder cover 3 divided into upper and lower chambers, and a spring 6 is loaded above the cylinder cover 3. Have been.

In the seal structure of the present embodiment, the piston member 7 is fitted through the sliding rod 4 and the diaphragm packing 8 is mounted to keep the piston member 7 and the cylinder cover 3 airtight. Have been. Here, FIG.
Is an enlarged sectional view showing the diaphragm packing 8, and FIG. 4 is an enlarged sectional view showing the mounted state of the diaphragm packing 8. Diaphragm packing 8
A small-diameter inner peripheral fixing portion 11 and a large-diameter outer peripheral fixing portion 12 which are both formed in an annular shape are coaxially arranged, and one continuous sealing member like a diaphragm is formed by a curved film-like flexible portion 13. Make up.

The inner and outer fixing portions 11 and 12 are both formed to be thick, and the outer fixing portion 12 has a trapezoidal cross section as shown in the figure. In particular, the outer peripheral fixing portion 12 has a lip packing shape in which the inner peripheral side forms a vertical pressure receiving surface 12A, and the outer peripheral side forms a pressing surface 12B that is inclined so as to expand toward the bottom. Further, the inner peripheral side root portion P1 of the flexible portion 13 protrudes from the middle position of the inner peripheral fixing portion 11, and the convex portion of the flexible portion 13 that becomes an acute angle has an R. On the other hand, in the outer peripheral side root portion P2 of the flexible portion 13, the flexible portion 13 protrudes upward from the upper end surface of the outer peripheral fixing portion 12, and the pressure receiving surface 1
2A is continuous with the concave side of the flexible portion 13.

Then, such a diaphragm packing 8
To assemble the actuator 1 with the piston member 7
The cylinder cover 3 is provided with a mounting portion. That is, the piston member 7 has an annular mounting groove 7A formed on its outer peripheral surface, and the cylinder cover 3 has an annular mounting groove 3A formed on its inner peripheral surface. The side surface of the mounting groove 3A of the cylinder cover 3 is formed vertically, and does not match the shape of the outer peripheral fixing portion 12 fitted therein. This is to improve the adhesion between the pressure receiving surface 12A and the mounting groove 3A by the elastic deformation of the outer peripheral fixing portion 12.

Then, the inner peripheral fixing portion 11 is inserted into the mounting groove 7A.
The outer peripheral fixing portions 12 are respectively fitted into the mounting grooves 3A, and the diaphragm packing 8 is mounted as shown in FIG.
Specifically, the inner peripheral fixing portion 11 of the diaphragm packing 8 is
Is strongly pushed into the mounting groove 7A of the piston member 7, and is firmly mounted by a stress due to its own elasticity. On the other hand, the outer peripheral fixing portion 12 of the diaphragm packing 8
The pressing surface 12 having the shape shown in FIG. 3 is fitted into the mounting groove 3A of the cylinder cover 3 and inclined outward.
B is pushed back inward by the reaction force, and as shown in FIG. 4, the pressing surface 12A is deformed so as to be inclined inward. At this time, the pressing surface 12 comes into air-tight contact with the side surface of the mounting groove 3 </ b> A due to the elastic force due to the elastic deformation of the outer peripheral fixing portion 12.

The interior of the cylinder cover 3 is divided into upper and lower chambers by such a sealing structure, and the actuator 1 has a port through a sealed lower pressurizing chamber 5 and a pilot hole 4A formed in the sliding rod 4. 32 is in communication.
On the other hand, the spring 6 is loaded on the upper part partitioned by the seal structure as described above, and the piston member 7 is urged downward. The cylinder cover 3 is provided with breathing holes 33 at its upper end.

Therefore, the actuator 1 having the seal structure composed of the diaphragm packing 8 outputs a reciprocating linear motion by the following operation. Actuator 1 is
Normally, the piston member 7 is pushed down under the urging force of the spring 6, and the sliding rod 4 is at the position shown in FIG. When the compressed air is sealed from the port 32, the compressed air is supplied to the pressurizing chamber 5 through the pilot hole 4A. Therefore, the pressure in the pressurizing chamber 5 increases, and the piston member 7 and the diaphragm packing 8 are pressurized from below,
The piston member 7 moves up to the position shown in FIG.

On the other hand, if the compressed air in the pressurizing chamber 5 is exhausted, it is pushed down by the spring 6 as the pressure decreases. The upper limit of the stroke of the sliding rod 4 is determined at a position where the piston member 7 contacts the lower end of the guide portion 31. One lower limit is not set in the actuator 1, and for example, in an assembled valve, It is determined by the position where the valve body contacts the valve seat.

The actuator 1 can output a motion by adjusting the air pressure in the pressurizing chamber 5, but the diaphragm packing 8 naturally has the
It functions as a seal member to prevent air leakage inside. That is, air leakage at the time of pressurization to raise the sliding rod 4 is prevented. Therefore, this diaphragm packing 8
The function will be described in more detail. When the compressed air is supplied to the pressurizing chamber 5, the pressure in the pressurizing chamber 5 increases, and the pressure directly acts on the diaphragm packing 8 on the surface on the pressurizing chamber 5 side. Therefore, the flexible portion 13 and the piston member 7
Receives air pressure from the pressurizing chamber 5 side, and a thrust for raising the sliding rod 4 acts.

At this time, the diaphragm packing 8 is provided not only on the flexible portion 13 but also on the pressure receiving surface 12A of the outer peripheral fixed portion 12 facing the pressurizing chamber 5 in the radial direction (on the cylinder cover 3 side).
The air pressure. Therefore, the outer peripheral fixing portion 12
Means that the pressing surface 12B has its own elasticity so that the mounting groove 3A
And pressurized by air pressure to be further airtightly pressed. Further, at this time, the outer peripheral fixing portion 12 is compressed by the radial pressing force and deforms in the axial direction (vertical direction in the drawing), and the upper and lower end surfaces thereof are strongly pressed against the groove surface of the mounting groove 3A. That is, when the diaphragm packing 8 is driven, the tightness of the outer peripheral fixing portion 12 is improved by the air pressure compared with the non-driven state where no air pressure is applied, and the sealing performance is increased.

On the other hand, the inner peripheral fixing portion 11 is already airtightly fitted by its own elasticity, and has a sufficient sealing property. In addition, the diaphragm packing 8 has the outer peripheral side root portion P2 of the flexible portion 13 pulled upward by the rise of the piston member 7, but the outer peripheral fixing portion 12 catches itself on the mounting groove 3A and the pressure receiving surface described above. 12A
The sealing state can be maintained without shifting in the mounting groove 3A due to the air pressure received at the step S1.

Therefore, the actuator 1 constituted by such a seal structure does not receive the sliding resistance unlike the piston packing, so that there is no hysteresis. There is no need to make it big. Therefore, a small stroke motion can be output stably and accurately, and the actuator 1 can be downsized.

By the way, the seal structure of the present embodiment can be variously modified in addition to the above-mentioned one, and can be applied to all diaphragm valves. For example, the diaphragm packing 8 is configured such that the inner peripheral fixing portion 11 is firmly sandwiched between the piston members 7, but a wide pressure receiving surface such as the outer peripheral fixing portion 12 is provided on the inner peripheral side to increase the sealing performance by air pressure. You may do so.

In addition to the method of mounting the inner peripheral fixing portion 11 and the outer peripheral fixing portion 12, the outer peripheral fixing portion (the same applies to the inner peripheral fixing portion) 41 as shown in FIG. A mounting groove 41A may be provided on the side, and a projection 42A that fits into the mounting groove 41A may be provided on the cylinder cover (same for the piston member) 42 side. Furthermore, such grooves and projections need not necessarily be annular. That is, the seal structure of the present invention uses a diaphragm-type seal member having fixed portions on the inner and outer circumferences of the film-shaped flexible portion,
Since the sealing property is ensured by the air pressure without forcibly inserting the fixing portion, any structure may be used as long as the fixing portion has a pressure receiving surface and can be sealed by the pressure received in the radial direction by the air pressure.

Furthermore, by adopting such a structure,
The effect of greatly improving the durability of the sealing member is also exerted. That is, the diaphragm used in the related art is broken due to a crack at the base portion due to the flexure of the flexible portion, but in the seal structure shown in the above embodiment, the diaphragm packing 8 is attached to the diaphragm packing 8. As described above, there is no stress concentration in the initial state because it is not firmly sandwiched by the fixed portion. Therefore, even when the flexible member 13 is bent by the vertical movement of the piston member 7, no crack is generated in the portion P3 shown in FIG. 4, and the strength is stabilized.

[0030]

According to the present invention, there is provided a pressure receiving surface for connecting an inner peripheral fixed portion and an outer peripheral fixed portion formed in an annular shape with a film-shaped flexible portion, and receiving a fluid pressure in the outer peripheral fixed portion in a radial direction. Since a seal structure is provided in which a seal member is formed, the inner peripheral fixed portion is fixed to the piston member, and the outer peripheral fixed portion is fitted to a mounting portion formed on the inner wall of the cylinder to mount the seal member. A small stroke motion can be output stably and accurately, and the actuator can be downsized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an actuator having a seal structure according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an actuator having a seal structure according to one embodiment of the present invention.

FIG. 3 is an enlarged sectional view showing the diaphragm packing 8;

FIG. 4 is an enlarged sectional view showing a state in which the diaphragm packing 8 is mounted.

FIG. 5 is an enlarged sectional view of a mounting portion showing a seal structure according to one embodiment of the present invention.

FIG. 6 is a sectional view of a diaphragm type actuator which is a conventional seal structure.

FIG. 7 is a cross-sectional view of a double piston packing type actuator having a conventional sealing structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Actuator 2 Body 3 Cylinder cover 4 Sliding rod 5 Pressurizing chamber 6 Spring 7 Piston member 8 Diaphragm packing 11 Inner circumference fixed part 12 Outer circumference fixed part 13 Flexible part 3A, 7A Mounting groove 12A Pressure receiving surface

Claims (3)

[Claims] 1. A seal structure in which a piston member is fixed to a sliding rod inserted into a cylinder and which keeps airtight between the piston member and the cylinder which slides in the axial direction. A sealing member having a pressure receiving surface for receiving a fluid pressure in a radial direction on the outer fixed portion, the inner fixed portion and the outer fixed portion being connected by a film-shaped flexible portion; A seal structure wherein a fixing portion is fixed to the piston member, and the outer peripheral fixing portion is fitted to a mounting portion formed on an inner wall of the cylinder, and the seal member is mounted. 2. A seal structure in which a piston member is fixed to a sliding rod inserted into a cylinder, and the airtightness between the piston member and the cylinder sliding in the axial direction is maintained. A sealing member in which the inner fixed portion and the outer fixed portion are connected by a film-shaped flexible portion, and a pressure receiving surface for radially receiving fluid pressure is formed on the inner fixed portion and the outer fixed portion. The seal member is attached by fitting the inner peripheral fixing portion to a mounting portion formed on an outer peripheral portion of the piston member, and fitting the outer peripheral fixing portion to a mounting portion formed on an inner wall of the cylinder. A seal structure characterized by performing. 3. The seal structure according to claim 1, wherein the piston member and the mounting portion formed on the inner wall of the cylinder are annular grooves formed in an annular shape, and the inner peripheral fixing portion and the outer periphery are provided. A seal structure for an actuator, wherein the fixing portion has a shape that fits tightly into the annular groove.