JPH11173306A - Negative pressure type actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the action of atmosphereic pressure on the whole diaphragm though a gap between the diaphragm and a nipping plate, by providing a ringlike sealing member having elastic resiliency toward a nipping member, on close to an outer peripheral end between the contact surfaces of the nipping member on an atmospheric pressure chamber side and the diaphragm. SOLUTION: The action of atmospheric pressure in an atmospheric pressure chamber, on the lower surface center of a diaphragm 3 through a gap 14, can be eliminated because a compressed ringlike sealing part 15 is elastically repelled to be pressure-contacted to the upper surface of a nipping plate 7, even a driving tube 6 is bent upward at the time of the action of an actuator to form the gap 14 between the diaphragm 3 and the plate 7. Consequently the pressure receiving area of the diaphragm 3 can be increased to prevent applying excess pressing force to a driving tube 6, thereby eliminating the more expansion of the gap 14. Resultantly the holding force of the diaphragm 3 can be reduced to eliminate pulling the whole outward also the possibility for concentrating high stress in the vicinity of a center through hole.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative pressure actuator used for driving, for example, an exhaust brake valve of an automobile.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional negative pressure type actuator for driving an exhaust brake valve. A lower flange of a lower cup-shaped upper casing (1) has an upward cup. Flange at the upper end of the lower casing (2)
(2a) is clamped, and a peripheral portion of a rubber diaphragm (3) is clamped between the flanges (1a) and (2a). The inside of both casings (1) and (2) is partitioned by a diaphragm (3) into a negative pressure chamber (4) and a normal pressure chamber (5).

The central portion of the diaphragm (3) has a driving cylinder (6) having a smaller diameter and a bottomed cylinder than the casings (1) and (2) and also serving as a clamping member, and a clamping plate (7) having the same diameter as the driving cylinder. By screwing a nut (9) to the upper end of a driving rod (8) penetrating through the center of the diaphragm
(3) The drive cylinder (6) and the holding plate (7) are fixed to the drive rod (8).

[0004] The diaphragm (3) has a rolling shape having an inverted U-shaped bent portion (3a) on the outer peripheral portion, and the bent portion (3a) and the inner cylindrical portion (3b) are vertically arranged. casing
It is located in a gap between the inner peripheral surface of (1) and (2) and the outer peripheral surface of the drive cylinder (6).

A drive rod (8) penetrates a communication hole (10) formed in the center of the lower casing (2), and has a lower end for opening and closing an exhaust brake valve (not shown) provided in an exhaust pipe. Connected to lever.

The upper casing (1) in the negative pressure chamber (4)
A compression coil spring is provided between the upper surface of the
(11) is concentrically contracted, whereby the drive cylinder
(6) is constantly biased downward.

A suction pipe (12) connected to a negative pressure source is fixedly connected to the negative pressure chamber (4) at an appropriate position on the upper surface of the upper casing (1).

The upper end of the upper part of the drive rod (8) is in contact with the center of the upper surface in the upper casing (1), thereby stopping the upper end of the drive cylinder (6). 13) is fixed.

In the above-described negative pressure type actuator,
When the negative pressure chamber (4) is communicated with a negative pressure source by operating a switching valve provided in the middle of the suction pipe (12), the pressure in the negative pressure chamber (4) is reduced, so that the driving cylinder (6) is a compression coil spring (1
4 is moved to the position of the imaginary line in FIG. 4 while compressing 1), and the upper end of the upward projecting portion (8a) of the driving rod (8) is
Stop in contact with. As a result, the drive rod (8) is raised, the exhaust brake valve is fully closed, and the vehicle is braked.

[0010]

The above-described actuator for driving the exhaust brake valve needs to operate the valve body against a relatively large exhaust pressure (back pressure) in the exhaust pipe. The pressure in the chamber (4) is greatly reduced to increase the pressure difference between the normal pressure chamber (5) and the driving cylinder (6) so as to be pulled up by a large force.

For this reason, as shown in FIG. 5, a strong differential pressure acts in the direction of the arrow on the curved portion (3a) of the diaphragm (3), and the central portion of the diaphragm (3) is pressed from above by this pressure. An upward bending load is applied to the drive cylinder (6) that is connected to the drive rod (8). Then, as shown in the enlarged view of FIG.
(6) is warped upward, and a gap (14) is formed between the diaphragm (3) and the holding plate (7). When such a gap (14) is formed, the atmospheric pressure in the normal pressure chamber (5) acts on the lower surface of the central portion of the diaphragm (3) through the gap (14), and the diaphragm (3) The pressure receiving area becomes large, and a force acts to bend the drive cylinder (6) further upward. As a result, the gap (14)
Becomes larger, the holding force of the diaphragm (3) becomes smaller, and the whole is pulled outward, so that stress concentrates in the vicinity of the through hole for the drive rod (8) inserted in the center. And may damage that part.

In order to solve this problem, the drive cylinder (6)
It is conceivable to increase the rigidity by increasing the thickness of the actuator, but this is not preferable because not only the size and weight of the actuator cannot be reduced, but also the response becomes slow.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and prevents atmospheric pressure from acting on the entire diaphragm through a gap between the diaphragm and a holding plate.
It is an object of the present invention to provide a negative pressure type actuator capable of greatly improving the durability of a diaphragm.

[0014]

According to the present invention, the above-mentioned problem is solved as follows. (1) The space in the casing is divided into a negative pressure chamber and a normal pressure chamber by a diaphragm, and both surfaces of the central portion of the diaphragm are held by a holding member connected to a driving rod to act on the outer peripheral end of the diaphragm. Due to the differential pressure,
In the negative pressure type actuator for operating the driving rod, an annular seal member having an elastic repulsive force toward the holding member is provided near an outer peripheral end between a contact surface of the holding member and the diaphragm on the normal pressure chamber side. Provide.

(2) In the above item (1), the sealing member is provided between the contact surface between the holding member on the negative pressure chamber side and the diaphragm so as to face the sealing member on the normal pressure chamber side.

(3) In the above item (1) or (2), a plurality of seal members are provided at a predetermined distance in the radial direction.

(4) In any one of the above items (1) to (3), the seal member is formed integrally with the diaphragm.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. The actuator itself is
Since the configuration is the same as that of the conventional one, the entire view is omitted and only the main part is shown. The same members as those of the conventional one are denoted by the same reference numerals, and detailed description thereof is omitted. I do.

FIG. 1 shows a first embodiment of the present invention, in which a driving cylinder (6) and a holding plate (7) in a diaphragm (3) are shown.
On both sides near the outer edge of the clamping part (3c) located between
A plurality (two in this embodiment) of annular seal portions (15) swelling in the thickness direction before being pressed by the drive cylinder (6) and the holding plate (7).
(15) are integrally formed close to each other.

The annular seal portion (15) includes a diaphragm
At the time of mounting (3), it is elastically compressed by the driving cylinder (6) and the holding plate (7). If such an annular seal portion (15) is provided, as shown in an enlarged view in FIG. 2, the drive cylinder (6) warps upward when the actuator is operated, and the diaphragm
Even if a gap (14) is formed between (3) and the holding plate (7), the compressed annular seal portion (15) rebounds resiliently, so that the upper surface of the holding plate (7) is resilient. To press, as in the past,
The atmospheric pressure in the normal pressure chamber (not shown) does not act on the center of the lower surface of the diaphragm (3) through the gap (14).

As a result, the pressure receiving area of the diaphragm (3) becomes large, so that an excessive pressing force is prevented from being applied to the driving cylinder (6), and the gap (14) does not further expand. Therefore, the holding force of the diaphragm (3) is reduced, so that the whole is not pulled outward, and there is no possibility that a large stress is concentrated near the center through hole.

The annular seal portion (15) may be provided only on the lower surface of the diaphragm (3). However, the annular seal portion (15) is provided on the upper surface as well, because the elastic repulsive force of that portion is increased.
This is to increase the pressure contact force to (7) and further enhance the sealing effect of the gap (14). The reason why a plurality of annular seal portions (15) are used is to improve the sealing performance.

FIG. 3 shows a second embodiment of the present invention. In this embodiment, two annular concave grooves (16) formed on the upper surface of the outer peripheral end of the holding plate (7) are provided under elastic rubber O-ring-shaped sealing members (17) and (17), respectively. The gap (14) is sealed by fitting the end faces and pressing the upper end face against the lower face of the diaphragm (3). In this embodiment, the same operation and effect as described above can be obtained. In addition,
Such a sealing member (17) may be provided between the contact surfaces of the drive cylinder (6) and the diaphragm (3).

As described above, in the present invention,
Even if a gap (14) is formed between the diaphragm (3) and the holding plate (7), the gap (14) is sealed by the elastic repulsive force of the annular seal portion (15) or the sealing member (17). Since atmospheric pressure is prevented from acting on the lower surface of the diaphragm (3),
It is not necessary to increase the rigidity of the drive cylinder (6), for example, by making it thicker, so that the entire actuator can be reduced in size and weight.

According to the present invention, there is provided an actuator which supplies compressed air into the normal pressure chamber (5) (see FIG. 4) in addition to the negative pressure type actuator to operate the driving rod (8). Also, the present invention can be applied to an actuator having a normal diaphragm having no folded portion (3a).

[0026]

According to the present invention, the following effects can be obtained. (a) Even if a gap is formed between the diaphragm and the holding plate, the gap is blocked by a seal member, thereby preventing atmospheric pressure from acting on the entire diaphragm. Therefore,
The gap is excessive, and the holding force of the diaphragm is reduced, thereby preventing the diaphragm from being damaged.

(B) According to the second aspect, the pressing force of the sealing member against the holding member on the normal pressure chamber side is increased, and the sealing effect can be enhanced.

(C) According to the third aspect, the contact area of the sealing member with the holding plate is substantially increased, so that the sealing effect is further enhanced.

(D) According to the fourth aspect, the number of parts is reduced, and the cost required for manufacturing and assembling is reduced, so that it can be implemented at a low cost.

[Brief description of the drawings]

FIG. 1 is a front view of a central longitudinal section of a main part showing a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional front view of a main part showing a state where a seal portion closes a gap when the actuator is operated.

FIG. 3 is an enlarged vertical sectional front view of a main part showing a state in which a gap is closed by a seal member according to a second embodiment of the present invention.

FIG. 4 is a central longitudinal sectional front view of a conventional negative pressure type actuator.

FIG. 5 is also a longitudinal front view of a central portion of the main part when the actuator is operated.

FIG. 6 is a front view of the main part in FIG.

[Description of sign]

 (1) Upper casing (2) Lower casing (3) Diaphragm (3a) Curved section (3c) Clamping section (4) Negative pressure chamber (5) Normal pressure chamber (6) Drive cylinder (clamping member) (7) Clamping Plate (clamping member) (8) Drive rod (9) Nut (10) Communication hole (11) Compression coil spring (12) Suction tube (13) Stopper (14) Clearance (15) Seal (16) Annular groove ( 17) Seal member

Claims (4)

[Claims] 1. A space in a casing is partitioned into a negative pressure chamber and a normal pressure chamber by a diaphragm, and both surfaces of a central portion of the diaphragm are held by a holding member connected to a driving rod. In a negative pressure actuator in which the driving rod is actuated by the applied differential pressure, an elastic repulsive force is applied toward the holding member toward an outer peripheral end between a contact surface of the holding member and the diaphragm on the normal pressure chamber side. A negative pressure type actuator provided with an annular seal member having the same. 2. The negative pressure actuator according to claim 1, wherein the sealing member is provided between the holding member on the negative pressure chamber side and the contact surface of the diaphragm so as to face the sealing member on the normal pressure chamber side. 3. The negative pressure actuator according to claim 1, wherein a plurality of seal members are provided at a predetermined distance in the radial direction. 4. The negative pressure actuator according to claim 1, wherein the seal member is formed integrally with the diaphragm.