JPH09217779A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure rod sealing without sacrificing sliding characteristics of a piston rod. SOLUTION: A cylinder 11 into which oil liquid is to be filled is housed in a casing 13, a reservoir chamber 12 into which oil liquid and gas are to be filled is formed between them, the upper opening of the reservoir chamfer 12 is sealed by a rod guide 31 and a seal block 65, and an O-ring 66 for preventing gas leakage from the reservoir chamber 12, two staged seal members 67, 68 for sealing the sliding parts of a piston rod 30 extending from the piston in the cylinder 11 are supported on the seal block 65. The seal member 67 on the first stage is made of a polytetrafluoroethylene ring, the seal member 68 on the second stage is formed of a rubber oil seal, the smooth sliding movement of the piston rod 30 is ensured by the seal member made of polytetrafluoroethylene, and outward leakage of oil leaking from the seal member 67 is prevented by the oil seal 68. When the large quantity of oil leak from the seal member 67, it is released to the reservoir chamber 12 by opening a check valve 69 in a releasing passage 75.

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 mounted on a suspension device such as an automobile.

[0002]

2. Description of the Related Art As a hydraulic shock absorber of this type, a cylinder in which an oil liquid is sealed is divided into an upper chamber and a lower chamber by a piston having a damping force generating mechanism, and a piston rod is connected to the piston at one end. The other end is inserted through a rod guide attached to the upper end opening of the cylinder and extended to the outside of the cylinder, and a reservoir chamber is provided around the cylinder in cooperation with the casing in which oil liquid and gas are sealed. , Communicating the bottom of the reservoir chamber with the cylinder lower chamber, actuating the damping force generating mechanism in accordance with expansion and contraction of the piston rod,
In addition, there is a so-called gas-containing double cylinder type in which the increase / decrease of the oil liquid in the cylinder is compensated by the reservoir chamber.

By the way, in such a gas-filled multi-cylinder type hydraulic shock absorber, in addition to the seal (rod seal) of the sliding portion of the piston rod, a gas seal for preventing gas leakage from the reservoir chamber is required. In addition, since the internal pressure of the cylinder is increased due to the influence of gas pressure, there is a constraint that the rod seal must be secured. For this reason, conventionally, a rubber ring-shaped seal member has been generally caulked in the opening of the casing so that the seal member is commonly used as a rod seal and a gas seal.
However, in such a seal structure, since the seal member is strongly pressed by the piston rod, there is a problem that the sliding characteristics of the piston rod are deteriorated.
The seal structure as shown in was adopted.

In FIG. 8, 1 is a cylinder, 2 is a rod guide attached to the upper end opening of the cylinder, and 3 is the cylinder 1.
A piston rod 4 extending from an internal piston (not shown) through the rod guide 2 is a casing surrounding the cylinder 1, and a reservoir chamber R is formed between the cylinder 1 and the casing 4. The upper opening of the reservoir chamber R is closed by an annular seal block 5 fitted between the rod guide 2 and the casing 4, and the seal block 5 has a pair of rod seals on the inner peripheral side thereof as rod seals. The seal members 6a and 6b are arranged in two stages, and an O-ring 7 as a gas seal is supported on the outer peripheral side thereof. Seal members 6a, 6 as rod seals
b is formed of a polytetrafluoroethylene (fluororesin) ring with particular emphasis on sliding characteristics, and is pressed against the circumferential surface of the piston rod 3 by O-rings 8a and 8b arranged on the back side of each ring. ing. Reference numeral 9 is a check valve that restricts the flow of gas from the reservoir chamber R into the cylinder upper chamber S via the passage 10.

[0005]

However, according to the above-described seal structure, since the seal members 6a and 6b made of polytetrafluoroethylene are used as the rod seal, especially when the operating speed of the piston rod becomes high. For example, oil leakage easily occurs from the first-stage sealing member 6a located on the cylinder upper chamber S side (high-pressure side), and when the amount of oil leakage increases, high pressure also occurs between the first and second stages. The oil liquid may leak out of the cylinder 1 from the sealing member 6b of the stage.

Recently, a self-pumping mechanism has been provided which controls the extension length of the piston rod within a predetermined range according to the vibration transmitted from the suspension device to the piston rod and maintains the vehicle height constant regardless of the load. There is a hydraulic shock absorber (see, for example, Japanese Patent Laid-Open No. 60-261713), and in such a hydraulic shock absorber, the internal pressure of the cylinder is further increased by the pumping action, so that there is a greater possibility of oil leakage to the outside. It will be further increased.

The present invention has been made in view of the above conventional problems, and an object thereof is to ensure oil leakage from the rod seal to the outside without sacrificing the sliding characteristics of the piston rod. To prevent it.

[0008]

In order to solve the above-mentioned problems, the present invention provides a first-stage seal member, which is located on the cylinder upper chamber side, of two-stage seal members as rod seals provided in a seal block. A second stage seal member located outside the cylinder is formed of an oil seal from a fluororesin ring, and further, in the seal block,
A relief passage is provided between the first-stage seal member and the second-stage seal member to allow the leaked oil to escape to the reservoir chamber, and the valve is opened when the pressure of the leaked oil in the relief passage exceeds a predetermined value. It is characterized in that the check valve is installed.

With this construction, the first-stage sealing member located on the high pressure side is made of fluororesin, so that the sliding characteristics of the piston rod are guaranteed. Even if the high-pressure side seal member leaks oil, the oil seal as the second stage seal member prevents the oil liquid from leaking out of the cylinder, and moreover, the oil leak from the first stage seal member. If the pressure between the first and second sealing members becomes large due to the increase in the amount of oil, the check valve in the relief passage opens and the oil liquid escapes to the reservoir chamber. Leakage is prevented.

In the present invention, it is desirable that an oil reservoir is provided between the first-stage sealing member and the second-stage sealing member, and the escape passage is opened in the oil reservoir.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 to 6 show a first embodiment of the present invention. The first embodiment has a structure including a self-pumping mechanism, and a casing 13 that surrounds the cylinder 11 and forms a reservoir chamber 12 with the cylinder 11 extends downward from the lower end of the cylinder 11. Has been done. The inside of the casing 13 is partitioned into two upper and lower chambers by a partition member 14 fitted in the middle of the casing 13, and the cylinder 11 is disposed in the upper chamber of the casing 13,
The lower end thereof is abutted against the partition member 14. The extension portion 13a of the casing 13 has a closed end, and an inner cylinder 16 forming an annular chamber 15 (FIG. 4) between the extension portion 13a and the casing 13 is disposed in the lower chamber of the casing 13 corresponding to the extension portion 13a. Has been done. A free piston 17 is slidably fitted in the inner cylinder 16, and an upper side of the free piston 17 is an oil chamber 18 filled with oil liquid.
The lower side is a gas chamber 19 filled with high-pressure gas.
Respectively configured as. The gas chamber 19 is
A passage 20 (FIG. 2) provided at the lower end of the inner cylinder 16 communicates with the annular chamber 15, and the annular chamber 15 is also filled with high-pressure gas.

At the lower end of the cylinder 11 is a base valve 2
1, the inside of the cylinder 11 and the reservoir chamber 12 are communicated with each other by an oil passage 22 provided in the base valve 21 as shown in FIG. The base valve 21 is connected to the cylinder 1 from the reservoir chamber 12 through an oil passage 22.
A check valve 23 that allows the flow of the oil liquid into the inside of the No. 1 and an orifice 24 that constantly connects the oil passage 22 are provided.

An annular piston 25 is provided in the cylinder 11.
Is slidably fitted, and the inside of the cylinder 11 is moved by the piston 25 into the cylinder upper chamber 26 and the cylinder lower chamber 2.
It is divided into seven. As shown in FIG. 3, a substantially cylindrical piston bolt 28 is inserted into the piston 25, and a piston nut 29 is screwed and fixed to the tip of the piston bolt 28. The threaded portion 28 on the base end side of the piston bolt 28
The lower end of a hollow piston rod 30 is screwed into a, and the upper end of the piston rod 30 is attached to the cylinder 11
Of the cylinder 11 and the casing 13 are inserted through a rod guide 31 attached to the upper end opening and a sealing device 32 described later that closes the upper opening of the reservoir chamber 12 and seals the piston rod 30. . The cylinder 11 is filled with oil liquid, and the reservoir chamber 12 is filled with oil liquid and high-pressure gas.

The piston 25 has oil passages 33 and 34 for communicating the cylinder upper chamber 26 and the cylinder lower chamber 27.
And a normally closed disc valve 35 (damping force generating mechanism) that bends by a predetermined pressure on the cylinder upper chamber 26 side and opens to allow the oil liquid in one of the oil passages 33 to flow to generate a damping force. It is provided. A notch 36 that forms an orifice passage (a damping force generating mechanism) is provided in the valve seat portion of the disc valve 35, and the notch 36 allows the upper and lower chambers 26 and 27 of the cylinder to communicate with each other at all times. Further, the piston 25 is a normally closed disc valve 37 (a damping force is generated) which bends by a predetermined pressure on the cylinder lower chamber 27 side and opens to allow the oil liquid to flow in the compression side passage 34 to generate a damping force. Mechanism) is provided.

Inside the piston rod 30, the hollow portion 3 is formed.
A stepped pump tube 38 having a large diameter portion 38a and a small diameter portion 38b having a diameter slightly smaller than 0a is inserted. The upper end of the piston rod 30 is closed, and the end of the pump tube 38 on the side of the small diameter portion 38b is pressed by the holding spring 39 near the closed end of the piston rod 30 (FIG. 6), so that the large diameter portion 38a. Piston bolt 28
It is fixed in position by abutting against (FIG. 3). An annular oil passage 40 is formed between the inner surface of the piston rod 30 and the pump tube 38, and communicates with the cylinder upper chamber 26 via a passage 41 (FIG. 3) provided in the side wall of the piston rod 30. There is.

A base end of a tubular pump rod 43 is connected to the partition member 14 and the base valve 21 via a retainer 42 as shown in FIG. The coupling portion between the pump rod 43 and the retainer 42 is formed in a spherical shape and can be slidably contacted with each other, so that the inclination of the pump rod 43 due to the operation of the hydraulic shock absorber can be allowed and the positional deviation can be absorbed. ing. The tip end side of the pump rod 43 is extended along the axis of the cylinder 11, and the piston bolt 28 is inserted therethrough to allow the large diameter portion 38 of the pump tube 38 to pass.
It is loosely inserted in a and is slidably fitted in the small diameter portion 38b. A pump chamber 44 is formed on the upper side of the small diameter portion 38b of the pump tube 38 by the tip of the pump rod 43. The pump chamber 44 includes a passage 43a in the pump rod 43 and a passage 42a in the retainer 42. Is connected to the oil chamber 18 by an oil passage 45 (see FIG. 4).

At the upper end of the small diameter portion 38b of the pump tube 38, there is provided a check valve 46 which allows only the flow of the oil liquid from the pump chamber 44 to the oil passage 40, and the tip of the pump rod 43. The part is provided with a check valve 47 that allows only the flow of the oil liquid from the oil chamber 18 to the pump chamber 44 through the oil passage 45. As shown in FIG. 6, the check valve 46 is attached to the open end of the small diameter portion 38b by a valve spring 49 whose one end is locked to a substantially U-shaped retainer 48 fixed to the tip of the small diameter portion 38b of the pump tube 38. It is provided with the pressed valve body 50, and by the pressure on the pump chamber 44 side,
The valve body 50 is pushed up from the opening end of the small diameter portion 38b against the elastic force of the valve spring 49 to open the valve. In the figure, 51 is a stopper that restricts the movement of the valve body 50. On the other hand, the check valve 47 at the tip of the pump rod 43 is
As shown in FIG. 5, a valve spring 5 having one end locked to a substantially U-shaped retainer 52 fixed to the tip of the pump rod 43.
The valve body 5 pressed against the open end of the pump rod 43 by
4, and an oil passage 45 communicating with the oil chamber 18
By the pressure on the side, the valve body 54 is pushed up from the open end of the pump rod 43 against the elastic force of the valve spring 53 to open the valve.

An annular passage 55 communicating with the cylinder lower chamber 27 is formed between the piston rod 28 and the large diameter portion 38a of the pump tube 38 and the pump rod 43 (FIG. 3). Further, the pump rod 43 is formed with a notch 56 extending axially from a tip end fitted to the pump tube 38 to a predetermined portion, and the pump rod 43 and the small diameter portion 38 of the pump tube 38 are formed by the notch 56.
A liquid passage 57 is formed between it and b. The notch 56 is
When the extension length of the piston rod 30 is shorter than a predetermined standard range (when it is shorter than the first predetermined position which is the lower limit of the standard range), only the small diameter portion 38b of the pump tube 38 overlaps and the large diameter portion 38a overlaps. Liquid passage 5
The communication between 7 and the annular passage 55 is cut off. In addition, when the piston rod 30 extends to a predetermined standard range (when it extends to a first predetermined position that is the lower limit of the standard range), the pump tube 38 moves together with the piston rod 30 and the large diameter portion 38 a becomes the notch 56. By overlapping, the liquid passage 57 communicates with the annular passage 55 and communicates with the cylinder upper and lower chambers 26 and 27.

Further, on the side wall of the pump rod 43, there is provided an orifice passage 58 penetrating from the oil passage 45 to the wall surface (FIG. 3). The orifice passage 58 has a cutout 5
6 is arranged at a portion closer to the pump chamber 44 with respect to the lower end of 6, and is located at a position overlapping the small diameter portion 38b of the pump tube 38 when the extension length of the piston rod 30 is within a predetermined standard range, and the orifice Passage 58 and ring passage 55
Communication with is interrupted. Also, the piston rod 30
When the extension length of the cylinder exceeds a predetermined standard range, the orifice passage 58 overlaps with the large diameter portion 38a of the pump tube 38, the orifice passage 58 communicates with the annular passage 55, and the upper and lower chambers 26, 27 of the cylinder are communicated. It is designed to communicate with. Reference numeral 59 is a rebound stopper that is mounted on the piston rod 30.

The present hydraulic shock absorber serves as a vehicle suspension device by connecting the upper end of the piston rod 30 to the vehicle body side (not shown) and the lower end of the casing 13 to the wheel side (not shown). A mounting bracket 60 for mounting on the wheel side is fixed to the lower end of the casing 13, and a spring bearing 61 for receiving a suspension spring (not shown) is fixed to the upper end of the casing 13.

Here, the sealing device 32 includes a sealing block 65 composed of first, second and third ring bodies 62, 63 and 64 which are sequentially stacked from the rod guide 31 toward the upper end opening side of the casing 13. An O-ring 66 for gas sealing, which is supported on the outer peripheral side of the seal block 65, and first and second seal members 67 and 68 for rod sealing, which are supported in two stages on the inner peripheral side of the seal block 65, It is roughly configured by a check valve 69 for releasing oil, which is arranged in the middle of the seal block 65. Seal block 6
Each ring body constituting 5 is fastened and fixed to the rod guide 31 by screwing the third ring body 64 into the threaded portion 70 provided at the open end of the casing 13. A bearing sleeve 71 for slidably guiding the piston rod 30 is fitted on the inner circumference of the rod guide 31.

Of the ring bodies 62, 63, 64 forming the seal block 65, the first ring body 62 located on the rod guide 31 side has a recess 62a for receiving the annular projection 31a formed on the rod guide 31. It is provided on the inner peripheral side of the lower surface, and the tip of the outer diameter portion around the recess 62 is brought into contact with the upper surface of the rod guide 31 to be fixed in position. Further, the first ring body 62 has an annular protrusion 62b at the center of the upper surface thereof, and the inner recess of the annular protrusion 62b is provided as a storage portion for accommodating the rod seal first seal member 67. The outer peripheral surface of the annular protrusion 62b is provided as a fitting surface on which the check valve 69 is mounted (fitted). The concave portion inside the annular protrusion 62b is arranged outside the first seal member 67 and presses and biases the first seal member 67 toward the piston rod 30.
The ring 72 is also arranged. Also, the rod guide 31
The annular projection 31a has a check valve 73 that operates using the inner circumference of the recess 62a of the first ring body 62 as a sealing surface.
The check valve 73 serves to prevent the gas in the reservoir chamber 12 from entering the cylinder upper chamber 26.

On the other hand, of the ring bodies 62, 63, 64 constituting the seal block 65, the intermediate second ring body 63 has a cup shape, and the tip of the cup wall 63a has the first ring body 62. The position is fixed by abutting on the upper surface of the. Then, in this fixed state, the cup bottom 63b of the second ring body 63 functions as a stopper that holds down the movement of the first seal member 67 and the O-ring 72 in the axial direction. Further, the inner peripheral surface of the cup wall 63a of the second ring body 63 is provided as a sealing surface of the oil-releasing check valve 69, and the cup bottom 63b thereof is provided with the third ring body 64. An escape passage 75 is provided which leads from the oil sump portion 74 on the inner diameter side to the check valve 69. The escape passage 75 communicates with the reservoir chamber 12 via a sub escape passage 75 a formed on the outer peripheral surface of the first ring body 62 and a sub escape passage 76 also formed on the outer peripheral surface of the rod guide 31. Further, the upper corner of the second ring body 63 is chamfered obliquely, and the O-ring 66 for gas sealing is arranged in this chamfered portion and prevented from coming off by the third ring body 64. . on the other hand,
The second seal member 68 as a rod seal is fitted to the inner surface of the third ring body 64 and is prevented from coming off by a step 64 a provided on the inner surface of the third ring body 64.

The first seal member (first stage seal member) 67 as the rod seal is made of a polytetrafluoroethylene ring, and the second seal member (second stage seal member) 68 is made of rubber. Each is formed from an oil seal. The second seal member 68 has two upper and lower lip portions 30 a, 3 that come into contact with the piston rod 30.
0b, and a spring 77 for pressing and urging each lip portion 30a, 30b against the piston rod 30.

The operation of the first embodiment having the above arrangement will be described below.

During the extension stroke of the piston rod 30, the oil liquid on the cylinder upper chamber 26 side is pressurized as the piston 25 moves, and this pressure oil flows through the oil passage 33 to the cylinder lower chamber 27 side, and the notch 36 is formed. The damping force is generated by the orifice formed by. At this time, the oil liquid that the piston rod 30 has withdrawn from the cylinder 11 passes through the oil passage 22 of the base valve 21 from the reservoir chamber 12 by the expansion of the gas, opens the check valve 23, and is replenished to the cylinder lower chamber 27. . Also, the piston speed increases, and the cylinder upper chamber 26
When the hydraulic pressure on the side reaches a predetermined pressure, the disc valve 35 opens to suppress an excessive increase in the damping force.

During the compression stroke of the piston rod 30, the oil liquid in the cylinder lower chamber 27 side is pressurized as the piston 25 moves, and this pressure oil flows through the oil passage 33 to the cylinder upper chamber 26 side, and the notch 36 The damping force is generated by the orifice formed by. At this time, the oil that has penetrated the piston rod 30 into the cylinder 11 is absorbed by the base valve 21.
Through the orifice 24 and the oil passage 22 into the reservoir chamber 12 to compress the gas. Further, when the piston speed increases and the hydraulic pressure in the cylinder lower chamber 27 reaches a predetermined pressure, the disc valve 37 opens to allow the oil liquid to flow through the contraction side passage 34, thereby suppressing an excessive increase in the damping force.

Next, the vehicle height adjusting function of the hydraulic shock absorber 1 will be described. When the vehicle is empty (at a standard vehicle height), the gas chamber 19 and the reservoir chamber 12 on the bottom side have the same pressure, and the extension length of the piston rod 30 is within a predetermined standard range. In this state, the notch 56 of the pump rod 43 overlaps with the large diameter portion 38a of the pump tube 38, and the pump chamber 44 communicates with the cylinder upper and lower chambers 26 and 27 through the liquid passage 57 and the annular passage 55. There is no pumping action.

When the vehicle load increases and the vehicle height becomes lower than the standard vehicle height, and the extension length of the piston rod 30 becomes shorter than the standard range, the notch 56 of the pump rod 43 becomes a small diameter portion of the pump tube 38. 38b and is closed. In this state, when the piston rod 30 expands and contracts due to the vibration of the suspension device during traveling, the pump rod 43 in the small diameter portion 38b of the pump tube 38 retracts during the extension stroke, and the pressure in the pump chamber 44 decreases. The check valve 47 opens and the oil liquid in the oil chamber 18 is introduced into the pump chamber 44 through the oil passage 45. Further, during the compression stroke, the pump rod 43 advances to pressurize the inside of the pump chamber 44, and thus the check valve. The valve 46 is opened and the oil liquid in the pump chamber 44 is supplied to the cylinder upper chamber 26 through the oil passages 40 and 41, and the cylinder upper and lower chambers 26 and 27 and the reservoir chamber 1
2 is pressurized to extend the piston rod 30. In this way, the vehicle height is increased by repeating the pumping operation by utilizing the vibration during traveling. When the vehicle height reaches the standard vehicle height and the extension length of the piston rod falls within the standard range, the notch 56 of the pump rod 43 overlaps with the large diameter portion 38a of the pump tube 38, and the pump chamber 44 becomes the cylinder upper and lower chambers. The pumping operation is released by communicating with 26 and 27.

Further, when the vehicle load becomes smaller and the vehicle height becomes higher than the standard vehicle height and the extension length of the piston rod 30 becomes longer than the standard range, the notch 56 of the pump rod 43 and the orifice passage 58 are formed. The pump chamber 44 overlaps with the large-diameter portion 38a of the pump tube 38, the pump chamber 44 communicates with the cylinder upper and lower chambers 26 and 27 to release the pumping operation, and the cylinder upper and lower chambers 26 and 27 pass through the annular passage 55 and the orifice passage 58. Is connected to the oil passage 45,
The pressure oil in the cylinder upper and lower chambers 26 and 27 is returned to the oil chamber 18, and the cylinder upper and lower chambers 26 and 27 and the reservoir chamber 1
2 is decompressed and the vehicle height drops. When the vehicle height falls to the standard vehicle height and the extension length of the piston rod 30 falls within the standard range, the orifice passage 58 of the pump rod 43 overlaps with the small diameter portion 38b of the pump tube 38 and is closed, so that the cylinder upper and lower chambers 26 and 27 are closed. The return operation of the pressure oil inside stops.

As described above, the vehicle height can be adjusted to be constant regardless of the load by repeating the pumping action and the returning action by utilizing the vibration of the suspension system during traveling.

By the way, when the piston rod 30 extends and pumps, the hydraulic pressure in the cylinder upper chamber 26 rises, and the oil liquid tends to leak from the first seal member 67 as a rod seal. Leakage is prevented by the first seal member 67 at the first stage (high pressure side). However, when the piston rod 30 expands relatively rapidly, or when the number of pumping operations is large, the pressure in the upper chamber 26 of the cylinder becomes even higher, and the first polytetrafluoroethylene made of polytetrafluoroethylene with emphasis on sliding characteristics. A small amount of oil leaks from the seal member 67. The leaked oil liquid is prevented from leaking to the outside by the second stage (low pressure side) second seal member 68 made of a rubber oil seal and is stored in the oil sump 74, but the amount of leakage gradually increases. When the oil pressure in the oil sump portion 74 rises to a predetermined pressure, the check valve 69 in the escape passage 75 opens, and the oil liquid in the oil sump portion 74 passes through the escape passage 75 and the sub escape passages 75a and 76. Inflow to the reservoir chamber 12 and thus outflow of oil liquid to the outside is completely prevented. Moreover, the oil pressure in the oil sump portion 74 does not exceed the predetermined pressure due to the escape of the oil liquid, and the sealability of the oil seal (second seal member) is permanently maintained. Particularly in the first embodiment, the oil seal 6
Since the back surfaces of the lips 30a and 30b of No. 8 are urged to the rod guide 30 by the spring 77, even if a high lateral load such as a strut is applied, the oil seal 68 follows and the sealing performance is secured.

FIG. 7 shows a second embodiment of the present invention. The feature of the second embodiment is that the oil relief check valve 69 in the first embodiment is used.
(FIG. 1) is omitted, and the check valve portion 80 is integrally provided on the second seal member 68, and the first and second ring bodies 62 and 63 forming the seal block 65 are integrated as a ring body 81. In this structure, the ring body 81 is provided with a seal surface 82 against which the escape passage 75 and the tip of the check valve portion 80 abut. The operation of the second embodiment is the same as that of the first embodiment, but the number of parts is reduced as compared with the first embodiment, so that cost reduction can be achieved.

In the above two embodiments, the second stage seal member (second seal member) 68 is made of rubber, but the present invention is not limited to this material and may be made of plastic, for example. be able to.

[0036]

As described above in detail, according to the hydraulic shock absorber of the present invention, the sliding characteristic of the piston rod can be guaranteed by the first-stage sealing member formed of polytetrafluoroethitefron (fluorine resin). Not only that, the second-stage sealing member including an oil seal can prevent the oil liquid from leaking to the outside. Moreover, when the amount of oil leaking from the first-stage sealing member increases and the pressure between the first-stage and second-stage sealing members increases, the check valve in the relief passage opens and the oil liquid flows into the reservoir chamber. Can be reliably prevented from leaking to the outside of the cylinder. Furthermore, when an oil reservoir is provided between the first-stage seal member and the second-stage seal member and the relief passage is opened to the oil reservoir, by temporarily storing the oil liquid in the oil reservoir, The number of check valve operations is reduced as much as possible, and its life is extended.

[Brief description of drawings]

FIG. 1 is a sectional view showing a main structure of a hydraulic shock absorber according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the overall structure of the hydraulic shock absorber according to the first embodiment.

FIG. 3 is a cross-sectional view showing a piston portion of the hydraulic shock absorber shown in FIG. 2 and a structure around the piston portion.

FIG. 4 is a cross-sectional view showing a base valve of the hydraulic shock absorber shown in FIG. 2 and a structure around the base valve.

5 is a cross-sectional view showing a check valve of a pump rod of the hydraulic shock absorber shown in FIG. 2 and a structure around it.

FIG. 6 is a cross-sectional view showing a check valve of a pump tube of the hydraulic shock absorber shown in FIG. 2 and a structure around the check valve.

FIG. 7 is a sectional view showing a main structure of a hydraulic shock absorber according to a second embodiment of the present invention.

FIG. 8 is a sectional view showing a seal structure of a conventional hydraulic shock absorber.

[Explanation of symbols]

11 Cylinder 12 Reservoir Chamber 13 Casing 18 Oil Chamber 19 Gas Chamber 21 Base Valve 25 Piston 26 Cylinder Upper Chamber 27 Cylinder Lower Chamber 30 Piston Rod 31 Rod Guide 35 Disc Valve (Damping Force Generating Mechanism) 38 Pump Tube 43 Pump Rod 44 Pump Chamber 65 seal guide 66 O-ring for gas seal 67 1st seal member (ring made from polytetrafluoroethitefron) 68 2nd seal member (oil seal) 69 Check valve 75 Escape passage

Claims (2)

[Claims] 1. A cylinder in which an oil liquid is sealed is divided into upper and lower chambers by a piston having a damping force generating mechanism, and the other end of a piston rod whose one end is connected to the piston is opened at the upper end of the cylinder. A rod guide attached to the cylinder portion and extending to the outside of the cylinder, and a reservoir chamber in which oil and gas are sealed in cooperation with the casing is provided around the cylinder, and the bottom portion of the reservoir chamber is provided in the cylinder. A seal block, which communicates with the lower chamber and seals the piston rod, is provided with a seal member arranged in two stages in the axial direction, and the damping force generating mechanism is actuated in accordance with expansion and contraction of the piston rod. In the hydraulic shock absorber in which the increase / decrease in the reservoir chamber is compensated by the reservoir chamber, the first-stage seal member located on the cylinder chamber side in the axial direction of the seal members is made of fluororesin. A second-stage sealing member located above the first-stage sealing member is formed of an oil seal from a ring, and the first-stage sealing member and the second-stage sealing member are formed in the seal block. A hydraulic shock absorber characterized in that an escape passage for releasing the leaked oil to the reservoir chamber is provided, and a check valve that opens when the pressure of the leaked oil in the escape passage exceeds a predetermined value is interposed. . 2. The hydraulic pressure according to claim 1, wherein an oil sump portion is provided between the first-stage seal member and the second-stage seal member, and the escape passage is opened to the oil sump portion. Shock absorber.