JPH0439090Y2 - - Google Patents

Description

[Detailed description of the invention] a. Industrial application field The invention relates to a fluid actuator.
Specifically, the present invention relates to a seal structure for a fluid actuator using a piston.

b. Prior Art FIGS. 4 to 6 show a part of a master cylinder, which is a main part of a fluid actuator using a piston.

In this master cylinder, a piston guide 2 is disposed in a housing 1, and a hole 3 is bored in the piston guide 2. During non-operation, a passage 4 communicates with an oil reservoir (not shown) through the hole 3. is opened into the pressure chamber 5. Also,
A through hole 7 is formed in the peripheral wall of the piston 6,
As shown in FIG. 4, when the through hole 7 and the hole 3 of the piston guide 2 are aligned, an oil reservoir (not shown) and the pressure chamber 5 are communicated with each other. Therefore, when the oil in the pressure chamber 5 becomes insufficient, oil is supplied from the oil reservoir to the pressure chamber 5.

Furthermore, in this master cylinder, an annular seal 8 is attached to the end surface of the piston guide 2 on the pressure chamber 5 side (the left end surface in FIGS. 4 and 5). When the piston 6 is pushed into the pressure chamber 5 and the through hole 7 of the piston 6 passes through the annular seal 8, communication between the through hole 7 and the hole 3 of the piston guide 2 is cut off. Therefore, when the piston 6 is further pushed into the pressure chamber 5, the oil in the pressure chamber 5 becomes
It is fed under pressure to an actuated device such as a wheel cylinder (not shown).

c. Problems to be solved by the invention By the way, in such a master cylinder, there is a loss stroke, in other words, when the passage hole 7 of the piston 6 and the hole 3 of the piston guide 2 are completely blocked by the annular seal 8. However, it is preferable that each product be substantially the same.

In the annular seal 8 of the master cylinder, the fifth
As shown in Figure 5a, when the piston 6 is inserted through the annular seal 8, the pressure applied by the annular seal 8 to the piston 6 (indicated by the length of the arrow in Figure 5b) is applied to the piston slide. The inner diameter of the sliding surface 8b corresponding to the flange portion 8a is made larger than other parts so that it is uniform over almost the entire sliding surface.

However, when the through hole 7 of the piston 6 reaches the annular seal 8, the oil pressurized within the pressure chamber 5 acts to spread the piston sliding surface of the annular seal 8 through the through hole 7. Still, sliding surface 8
At locations other than b, the inner annular portion 8 of the annular seal 8
Since the pressure in the pressure chamber 5 acts on the outer periphery of c, it is prevented from flowing out from the through hole 7 to the piston sliding surface, but when the through hole 7 passes through the sliding surface 8b, the external pressure is Since the oil is not acting, the oil pressurized in the pressure chamber 5 expands the annular seal 8 as shown by the arrow in FIG. 6, and flows out into the hole 3 through the gap between the piston guide 2 and the piston 6. There is a risk. Therefore, in order to accurately set the loss stroke, it is necessary to reduce the thickness of the flange portion 8a of the annular seal 8, shorten the length of the sliding surface 8b, and reduce the area where the sealing effect is unstable. However, this may weaken the annular seal 8 and reduce the sealing effect.

An object of the present invention is to provide an actuator in which the timing at which the pressure chamber and the reservoir are shut off is accurate, that is, the loss stroke is constant, and there is no variation from product to product.

d Means for Solving the Problems The fluid actuator of the present invention communicates a pressure chamber with a reservoir through a through hole formed on the circumferential surface of a piston, moves the piston inward of the pressure chamber,
The communication between the pressure chamber and the reservoir is cut off by the passage of the passage hole of the piston through the annular seal, and the fluid in the pressure chamber is removed by moving the piston inwardly into the pressure chamber. The annular seal has an annular recess on one end surface, and the piston sliding surface of the inner annular wall forming the side wall of the recess, and the bottom of the recess. An annular protrusion protruding inward is formed at a portion corresponding to the thick part of the flange portion forming the wall, and the annular seal is disposed with the annular recess facing into the pressure chamber, and With the piston inserted through the annular seal, the annular protrusion applies a pressure force to the piston that is greater than that of other parts of the piston sliding surface.

In other words, in the fluid actuator of the present invention, the pressure of the sliding surface of the annular seal against the piston corresponding to the flange portion is made stronger than the pressure of other sliding surfaces, and the through hole of the piston During the passage, fluid in the pressure chamber is prevented from escaping into the reservoir, thereby eliminating unstable areas of sealing effectiveness.

f Example Fig. 1 shows a master cylinder as an actuator according to the present invention, Fig. 2 shows a part of its annular seal, and Fig. 3 shows the sealing action.

The cylinder housing 11 of the master cylinder 10 is composed of a body body 12 and a cap 13 screwed onto the body body 12. Inside the cylinder housing 11, ring-shaped piston guides 14 and 15 are arranged. Pistons 16 and 17 are inserted through these piston guides 14 and 15, respectively. The piston guide 15 and the piston 17 create two pressure chambers 1 inside the cylinder housing 11.
8 and 19. the piston 16,
17 is a sleeve 20 disposed within the pressure chamber 18
They are also guided by. This sleeve 20 has an inner circumferential surface formed in a spline shape in order to secure a space for the pressure chamber 18, and the pistons 16, 17 are guided by the protruding ridges 20a. Further, the pistons 16 and 17 are arranged between the pistons 16 and 17 and between the pistons 16 and 17
The spring 2 arranged between the and the body main body 12
1 and 22, it is biased to the right in FIG. These pistons 16 and 17 have recesses opening at their tips, and through holes 23 and 24 are formed in the peripheral walls forming the recesses, respectively. The piston guides 14 and 15 have holes 25 and 26 bored in the radial direction, one end of which opens into the sliding surface of the pistons 16 and 17, and the other end of which opens into the sliding surface of the cylinder housing. It communicates with passages 27 and 28 formed in 11. Pressure chambers 18, 1 of these piston guides 14, 15
Annular seals 29 and 30 are attached to the end face on the 9 side. As shown enlarged in FIG. 2, these annular seals 29, 30 have annular recesses 29a, 30a on one end surface, and the inner annular walls 29b, 30b forming the recesses is inclined toward the axis, and the inner circumferential surfaces (piston sliding surfaces) of the inner annular walls 29b, 30b corresponding to the thick parts of the flange portions 29c, 30c forming the bottom walls of the recesses 29a, 30a are Annular protrusions 29d and 30d are formed. And this annular seal 29,3
0, as shown in FIG.
a, 30a toward the pressure chambers 18, 19, and the flange portions 29c, 30c toward the piston guides 14, 15.
It is attached to the cylinder housing 11 in contact with the cylinder housing 11.

FIG. 2b is an enlarged view of a state in which the annular seal 29 is attached to the cylinder housing 112 and the piston 16 is inserted through the annular seal 29. In this state, the entire inner circumferential surface of the annular seal 29 is in contact with the piston 16, but the pressing force is different at various locations as shown by the length of the arrow. The pressure contact force is particularly large at the annular protrusion 29d because the inner annular wall 29d can be deformed so as to escape radially outward, whereas the annular protrusion 29d has a flange radially outward. Since the portion 29c exists, it cannot escape and only compressive deformation is allowed, which requires a larger force for deformation.In other words, a large repulsive force is generated for the same amount of deformation. In addition,
Although not shown, the same is true for the annular seal 30.

In addition, in FIG. 1, the reference numeral 31 indicates an oil reservoir, and the oil reservoir 31 is
Passages 32 and 33 fixedly installed in the cylinder housing 11 and bored at the bottom of the oil reservoir 31 communicate with the passages 27 and 28 of the cylinder housing 11, respectively. In addition, codes 34 and 35 are
These holes are bored in the cylinder housing 11, and the pressure chambers 18 and 19 communicate with an actuated device (not shown), such as a wheel cylinder, through these holes 34 and 35.

The operation of the master cylinder 10 described above will be explained below with reference to FIG. However, in FIG. 3, one piston 16, the piston guide 14,
Although only the annular seal 29 and the like are shown, the other piston 17, piston guide 15, annular seal 30, etc. perform the same function, so their explanation will be omitted here.

FIG. 3a shows the piston 16 in its inactive or standby state. In this state, the through hole 23 of the piston 16 is located at the center of the hole 25 of the piston guide 14, and the pressure chamber 18 is located at the center of the hole 25 of the piston guide 14.
3, oil reservoir 3 via hole 25 and passage 27
It is connected to 5. Therefore, in this state, no hydraulic pressure is acting on the actuated device (not shown).

Now, when the piston 16 is pushed into the pressure chamber 18, the through hole 23 also moves to the left in FIG.
However, until the through hole 23 reaches the sliding surface of the annular seal 29 with the piston 16, the pressure chamber 18 is communicated with the hole 25 through the gap between the inner peripheral surface of the piston guide 14 and the piston 16. . Therefore, the oil in the pressure chamber 18 is allowed to escape to the hole 25.

Furthermore, when the piston 16 is pushed into the pressure chamber 18, the through hole 23 reaches the sliding surface of the annular seal 31 with the piston 16, as shown in FIG. 3b. In such a state, the pressure within the pressure chamber 18 acts to expand the annular seal 31 through the through hole 23, but since the pressing force against the piston 16 by the annular protrusion 29d is large, the through hole 23 is occluded. Furthermore, even if the piston 16 is pushed into the pressure chamber 18 and the through hole 23 reaches the inner annular portion 31b, the pressure inside the pressure chamber 18 also acts on the outer peripheral surface of the inner annular portion 31b of the annular seal 31, so the through hole 23 is definitely closed.

In addition, although the master cylinder 10 was shown as an actuator in the said Example, this invention is not limited to a master cylinder. An actuator to which the present invention is applied communicates a pressure chamber with a reservoir through a through hole formed on the circumferential surface of a piston, moves the piston inward of the pressure chamber, and connects the through hole of the piston with an annular seal. A fluid actuator that cuts off communication between the pressure chamber and the reservoir by passing through the pressure chamber, and further moves the piston inward of the pressure chamber to forcefully feed the fluid in the pressure chamber to the actuated device. That's fine.

g Effect of the invention As described above, in the fluid actuator according to the invention, by forming the annular protrusion on the piston sliding surface corresponding to the flange of the annular seal,
The pressure force applied to the piston at this portion is greater than that at other portions to reliably close the passage hole of the piston.

Therefore, in the fluid actuator according to the present invention, when the passage hole of the piston reaches the annular seal, communication between the pressure chamber and the reservoir is reliably cut off, and a uniform loss stroke can be obtained between products. Moreover, although the pressure force against the piston is large at the annular protrusion,
Others may be small, and the sliding resistance to the piston will not increase much.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a master cylinder as a fluid actuator according to the present invention, Fig. 2 is an enlarged sectional view of a part of the annular seal of the master cylinder, and Fig. 3 is an operation of the master cylinder. 4 is a sectional view showing a seal portion of a conventional fluid actuator, FIG. 5 is an enlarged sectional view of a part of the annular seal, and FIG. FIG. 3 is a partially enlarged sectional view showing the operation of the master cylinder equipped with the annular seal. 10... Master cylinder, 11... Cylinder housing, 14, 15... Piston guide, 1
6, 17... Piston, 18, 19... Pressure chamber,
23, 24... through hole, 25, 26... hole, 27,
28... Passage, 29, 30... Annular seal, 29
a, 30a... annular recessed part, 29b, 30b... inner annular part, 29c, 30c... flange part, 29
d, 30d... annular protrusion, 31... oil reservoir, 32, 33... passage, 34, 35... hole.

Claims (1)

[Scope of utility model registration request] The pressure chamber is communicated with the reservoir through a through hole formed in the circumferential surface of the piston, the piston is moved inward of the pressure chamber, and the through hole of the piston passes through an annular seal, thereby reducing the pressure. In a fluid actuator that disconnects communication between a chamber and the reservoir and further moves the piston inward of the pressure chamber to forcefully transfer fluid in the pressure chamber to an actuated device, the annular seal has one end surface. has an annular recess in the recess, and protrudes inward at a portion of the piston sliding surface of the inner annular wall forming the side wall of the recess, which corresponds to the thick part of the flange forming the bottom wall of the recess. An annular protrusion is formed, and with the annular seal disposed with the annular recess facing into the pressure chamber and the piston inserted through the annular seal, the annular protrusion presses the piston. A fluid actuator characterized in that the force is greater than that of other parts of the piston sliding surface.