JPH07233838A - Hydraulic type buffer device - Google Patents

Abstract

PURPOSE:To prevent the mixing of air into the liquid as pressurized fluid and realize the long stroke by setting the cracking pressure of an air pressure packing lower than that of a hydraulic packing. CONSTITUTION:For a piston 19 for restoration, a hydraulic packing 64 for the seal of the hydraulic pressure, air pressure packings 65 and 66 for the seal of the air pressure, and an air chamber connected between the hydraulic packing 64 and the air pressure packing 65 are installed, and each cracking pressure of the air pressure packings 65 and 66 is set lower than the cracking pressure of the hydraulic packing 64.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber which absorbs kinetic energy of a load by a liquid such as hydraulic pressure.

[0002]

2. Description of the Related Art Conventionally, a back pressure generated by the operation movement of a main piston in a pressure chamber filled with pressure oil exerts a cushioning effect, and a return piston pressed by air pressure applies pressure to the pressure oil. A hydraulic shock absorber configured to generate and return the main piston is known (Japanese Utility Model Publication No. 2-27699).

Further, a hydraulic shock absorber using a diaphragm instead of the return piston is also known (Japanese Patent Laid-Open No. Sho 6-62).
No. 1-282635).

[0004]

However, the one using the return piston has a drawback that the air pressure easily leaks to the pressure oil as the return piston moves. When the air pressure leaks, the air may mix with the pressure oil to form bubbles, which may deteriorate the buffering characteristics.

Further, in the case of using the diaphragm, there is very little risk of leakage like the return piston, but since it is not possible to freely give a long stroke unlike the return piston, a hydraulic shock absorber. There is a drawback that the stroke cannot be increased.

Further, in the conventional hydraulic shock absorber, when the main piston is operatively moved, air may be sucked from between the piston rod connected to the main piston and the main body or the bush, so that the pressurized oil may be absorbed. Air could be mixed in.

The present invention has been made in view of the above problems, and provides a hydraulic shock absorber capable of preventing air from being mixed into a liquid which is a pressurized fluid and capable of a long stroke. The purpose is to do.

[0008]

In order to solve the above-mentioned problems, the apparatus according to the invention of claim 1 provides a buffering action by the back pressure generated by the operation movement of the main piston in the pressure chamber filled with the liquid. A hydraulic shock absorber configured to exert a pressure on the liquid by a return piston that is pressed by air pressure to return the main piston, and the return piston includes:
A hydraulic packing for sealing hydraulic pressure, a pneumatic packing for sealing pneumatic pressure, and an air chamber connected between the hydraulic packing and the pneumatic packing are provided, and the cracking pressure of the pneumatic packing is the liquid. It is configured to be set lower than the cracking pressure of the pressure packing.

According to a second aspect of the present invention, the return piston has a hydraulic packing for sealing hydraulic pressure on its outer peripheral surface, and a first pneumatic packing for sealing pneumatic pressure on its outer peripheral surface. A recessed portion that is open to the air pressure side in the central portion thereof and that communicates between the hydraulic packing and the first pneumatic packing, a cover member that fits into the recessed portion, and between the cover member and the recessed portion. And a second pneumatic packing that seals the second packing, and the cracking pressure of the second pneumatic packing is set to be lower than the cracking pressure of the hydraulic packing.

According to a third aspect of the present invention, a device is provided with a third pneumatic packing for sealing the piston rod connected to the main piston from the outside air.

[0011]

When the minute air leaks from the pneumatic packing, the first pneumatic packing, or the second pneumatic packing, the air pressure in the air chamber gradually increases. However, since the cracking pressure of the hydraulic packing is relatively high, the air pressure in the air chamber will not exceed the cracking pressure and leak from the hydraulic packing into the air chamber. When the pressure in the air pressure side chamber decreases, the air pressure in the air chamber is exhausted and decreases due to the leakage of the pneumatic packing.

The third pneumatic packing prevents air from entering the pressure chamber through the piston rod.

[0013]

1 is a cross-sectional front view of a shock absorber 1 according to the present invention, and FIG. 2 is an enlarged cross-sectional view of an essential part of the shock absorber 1 of FIG.

In FIG. 1, a shock absorber 1 includes a reservoir tube 11, a pressure tube (inner tube) 12,
Bushings 13a to 13c, intermediate cover 14, piston 1
5, a piston rod 16, a return tube 17, a cover 18, a return piston 19, a cover member 20, and the like.

The reservoir tube 11 has a cylindrical shape,
The bushes 13a to 13c and the intermediate cover 14 hermetically seal the inside to form the entire container for storing the pressure oil HY. The piston 15 slides on the inner peripheral surface of the pressure tube 12 which is mounted concentrically with the reservoir tube 11. The inside of the pressure tube 12 is partitioned by the piston 15 into left and right chambers 43, 41. The pressure tube 12 has a plurality of holes 51, each forming a thin blade orifice.
51 are arranged and provided along the axial direction. A chamber 42 is provided between the pressure tube 12 and the reservoir tube 11.
The chamber 42 and the chamber 43 communicate with each other through the hole 52.

The piston 15 has a rightward direction (arrow M in FIG. 1).
A check valve CV is provided which is closed when moving in one direction) and opens when moving in the opposite direction. Piston 1
5, a piston rod 16 is connected, and the piston rod 16 penetrates through the bushes 13a to 13c and projects to the outside. A hydraulic packing 61, a pneumatic packing 62, and a dust wiper 63 are attached to the bushes 13a to 13c.

The intermediate cover 14 includes the reservoir tube 11
And at the right end of the pressure tube 12 so that there is no leakage between them. The return tube 17 has a cylindrical shape, the inside is sealed by the intermediate cover 14 and the cover 18, and is partitioned by the return piston 19 into left and right chambers 44 and 45. The intermediate cover 14 is provided with a refueling port 59.

The chamber 44 communicates with the chamber 42 through a hole 53 provided in the pressure tube 12 and a hole 54 provided in the intermediate cover 14. A port 55 provided on the cover 18 communicates with the chamber 45.

On the outer peripheral surface of the return piston 19,
A hydraulic packing 64 and a pneumatic packing 65 are mounted, and an annular groove 56 is formed between the hydraulic packing 64 and the pneumatic packing 65. The return piston 19 is provided with a recess 57 that opens toward the chamber 45 at the center in the radial direction. In the recess 57,
The cover member 20 is fitted therein, and a gap between them is sealed by a pneumatic packing 66. The chamber 46 provided in the recess 57 communicates with the groove 56 by the hole 58.

Hydraulic packing 64, pneumatic packing 65,
The pneumatic packing 66 and the pneumatic packing 66 are both packings that exert a sealing effect only in one direction, such as a U packing. The pressure at which leakage starts when pressure is applied from those non-pressurized sides (opposite side of the lip in the case of U packing), that is, the respective cracking pressures P64 and P6.
5 and P66 are set in the following relationship with each other.

P64>P65> P66 (1) or P64≈P65> P66 (2) That is, the cracking pressure P64 of the hydraulic packing 64.
Is greater than or substantially equal to the cracking pressure P65 of the pneumatic packing 65, and the cracking pressure P66 of the pneumatic packing 66 is less than any other cracking pressure P64, P65. This is the hydraulic packing 6
4 and the pneumatic packing 65 are for moving, while the pneumatic packing 66 is for fixing, it is possible to easily design the cracking pressure P66 of the pneumatic packing 66 to be low by reducing the rigidity of the lip, for example. In addition,
Formula (2) corresponds to the case where the hydraulic packing 64 and the pneumatic packing 65 are the same, for example.

Next, the operation of the shock absorber 1 will be described. An air pressure source having an appropriate pressure is connected to the port 55 via a pressure regulating valve, a pressure gauge, a solenoid valve for switching connection and exhaust.

With the piston rod 16 returning to the position shown in FIG.
When colliding with the tip of 6, the piston rod 16 moves in the right direction (direction of arrow M1) while absorbing the kinetic energy of the object. In the process, since the check valve CV is closed, the pressure oil HY in the chamber 41 is jetted from the hole 51 to the chamber 42, and a back pressure is generated in the pressure oil HY in the chamber 41 due to its resistance. A part of the pressure oil HY ejected into the chamber 42 flows into the chamber 43 from the hole 52, and the rest flows into the chamber 44 from the holes 53 and 54 to press the return piston 19 to the right to move it. . The amount of the pressure oil HY flowing into the chamber 44 is equal to the product of the sectional area of the piston rod 16 and the moving stroke.

During this time, the pneumatic packing 62 prevents air from entering the chamber 41 from the piston rod 16. Now, the return piston 19 is pressed by the air pressure source connected to the port 55, and pressure is generated in the pressure oil HY in the chamber 44. This pressure is
It is also transmitted to the pressure oil HY in 2, 43 and acts on the piston 15 and the piston rod 16. The piston rod 16 is pressed to the left by a force equal to the product of the pressure of the pressure oil HY and the cross-sectional area of the piston rod 16.

Therefore, when the object colliding with the piston rod 16 is stopped or removed and the pressing force of the pressure oil HY overcomes the resistance force such as the frictional force acting on the piston rod 16, the piston rod 16 moves to the left. Move and return to the original position.

While the piston rod 16 is moving to the left, the check valve CV is opened and the chamber 4 is opened through the hole 53.
A part of the pressure oil HY that has flowed into 2 flows into the chamber 41 through the hole 51, and the rest rapidly flows into the chamber 41 from the open check valve CV through the hole 52 and the chamber 43. Therefore, the piston rod 16 returns promptly. After the piston rod 16 returns, the solenoid valve is switched to connect the port 55 to the atmosphere and exhaust the air in the chamber 45.

During this time, if the pneumatic packing 6
When a small amount of air leaks from 5, 66, the air pressure in the chamber 46 gradually increases. However, since the pneumatic packing 66 is for fixing, the amount of leakage is smaller than that of the pneumatic packing 65. Although the air pressure in the chamber 46 gradually increases, the cracking pressure P64 of the hydraulic packing 64 is relatively high, so that the air pressure in the chamber 46 exceeds the cracking pressure P64 and air leaks from the hydraulic packing 64 into the chamber 44. However, when the port 55 is connected to the exhaust side, the air is discharged into the chamber 45 due to the leakage of the pneumatic packing 66 or the pneumatic packing 65 (cracking pressure P66, P65).
The air pressure in the chamber 46 drops.

Therefore, air is not mixed into the pressure oil HY, and the shock absorbing performance of the shock absorber 1 does not deteriorate. Moreover, since the stroke of the return piston 19 can be arbitrarily lengthened, it can be easily applied to the shock absorber 1 having a long stroke.

FIG. 3 shows a return piston 19a of another embodiment.
FIG. In FIG. 3, the return piston 1
The cover member 20a is screwed into the concave portion 57 of 9a in a state in which the sealing tape is wound. This makes room 4
6 is sealed. The cracking pressure P64 of the hydraulic packing 64 is set higher than the cracking pressure P65 of the pneumatic packing 65. In this case, the structure of the return piston 19a becomes simple.

When a small amount of air leaks from the pneumatic packing 65, the air pressure in the chamber 46 gradually increases, but the air pressure in the chamber 46 does not exceed the cracking pressure P64 and leaks from the hydraulic packing 64 into the chamber 44. When the port 55 is connected to the exhaust side, air is exhausted into the chamber 45 due to leakage of the pneumatic packing 65. The return piston 1
9a without providing the concave portion 57 and the cover member 20a,
The groove 56 may be deepened or widened to increase the volume.

In the above-described embodiment, the structure for generating the back pressure in the chamber 41 can be modified in various ways other than the above. Instead of the pressure oil HY, another liquid such as water can be used. Air contains nitrogen and other gases. In addition, the structure, shape, dimensions of the whole or each part of the shock absorber 1,
The material and the like can be variously changed in accordance with the gist of the present invention.

[0032]

According to the present invention, it is possible to provide a hydraulic shock absorber capable of preventing air from being mixed into a liquid which is a pressurized fluid as much as possible and having a long stroke.

According to the second aspect of the present invention, it becomes easy to set the cracking pressure of the second pneumatic packing low, and it is possible to more effectively prevent the air from being mixed into the liquid.

[Brief description of drawings]

FIG. 1 is a sectional front view of a shock absorber according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing a main part of the shock absorber of FIG.

FIG. 3 is a cross-sectional view showing a return piston of another embodiment.

[Explanation of symbols]

 1 shock absorber 15 piston (main piston) 19, 19a return piston 20, 20a cover member 41 chamber (pressure chamber) 46 chamber (air chamber) 57 recess 62 pneumatic packing (third pneumatic packing) 64 hydraulic packing (hydraulic pressure) Packing) 65 Pneumatic packing (first pneumatic packing) 66 Pneumatic packing (second pneumatic packing)

Claims (3)

[Claims] 1. A back pressure generated by operative movement of a main piston in a pressure chamber filled with a liquid exerts a cushioning action, and a return piston pressed by air pressure generates a pressure in the liquid, A hydraulic shock absorber configured to return-move the main piston, wherein the return piston has hydraulic packing for sealing hydraulic pressure, pneumatic packing for sealing air pressure,
And an air chamber connected between the hydraulic packing and the pneumatic packing, wherein the cracking pressure of the pneumatic packing is set lower than the cracking pressure of the hydraulic packing. Shock absorber. 2. A buffering effect is exerted by a back pressure generated by the operation movement of a main piston in a pressure chamber filled with a liquid, and a pressure is generated in the liquid by a return piston pressed by an air pressure. A hydraulic shock absorber configured to return the piston, wherein the return piston has a hydraulic packing for sealing hydraulic pressure on its outer peripheral surface and a pneumatic packing for sealing air pressure on its outer peripheral surface. First
Pneumatic packing, a recess opening in the central portion toward the pneumatic side and communicating between the hydraulic packing and the first pneumatic packing, a cover member fitted in the recess, the cover member and the recess A second pneumatic packing that seals between the second pneumatic packing and the second packing, and the cracking pressure of the second pneumatic packing is set lower than the cracking pressure of the hydraulic packing. apparatus. 3. A third pneumatic packing for sealing the piston rod connected to the main piston from the outside air, wherein the third pneumatic packing is provided.
The hydraulic shock absorber described.