JPH112281A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a free piston from interfering with a piston by arranging a communication passage in a cylinder, which communicates with a gas chamber and a hydraulic oil chamber when the free piston is moved toward the piston side by a fixed distance. SOLUTION: In long-term use of a strut damper 1, hydraulic oil inside upper and lower hydraulic oil chambers S1, S2 is gradually reduced, and a gas chamber G communicates with the upper hydraulic oil chamber S1 via a communication groove 7b when a free piston 8 is moved to the communication groove 7b. In this case, in an extension stroke in which a piston 18 and an outer cylinder 2 are lowered as against an inner cylinder 7, for example, sealed gas inside the gas chamber G flows into the upper hydraulic oil chamber S1 via the communication groove 7b. In a shrinkage stroke in which the piston 18 and the outer cylinder 2 are lifted as against the inner cylinder 7, actuating oil inside the upper hydraulic oil chamber S1 flows into the gas chamber G via the communication groove 7b. Therefore, the free piston 8 is stopped in the communication groove 7b part so as not to move toward the piston 18 side anymore, so that the free piston 8 is prevented from interfering with the upper end of a rod 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an improvement of a hydraulic shock absorber.

[0002]

2. Description of the Related Art In a shock absorber provided with a free piston, when the shock absorber is used for a long period of time, for example, slight damage occurs to an oil seal and a piston rod, and hydraulic oil leaks to the outside little by little. Therefore, the free piston may interfere with the piston. As a countermeasure against this, as for a shock absorber in which the free piston is restricted from moving more than necessary, see, for example, Japanese Utility Model Laid-Open Publication No. Sho 53-72085, “Gas pressurized shock absorber” and Japanese Utility Model Publication No. Hei 5-164424, “Spring of shock absorber”. A load adjusting mechanism "and JP-A-55-17714," Hydraulic shock absorber "are known.

[0003] The above-mentioned arrangement is designed to prevent the piston or hydraulic oil from jumping out when disassembled, and to prevent the free piston from hitting the tip of the piston rod. 1 and this cylinder 1
A free piston 14 is slidably inserted therein, and a stopper 17 is provided in which the wall of the cylinder 1 between the free piston 14 and the piston 7 is annularly recessed radially inward.

The above description relates to a spring load adjusting mechanism that adjusts the load of a suspension spring by moving a spring receiver provided on the outer periphery of a cylinder of a shock absorber in the axial direction of the cylinder, and is shown in FIG. As described above, the free piston provided in the cylinder 2 and the free piston inserted into the cylinder 2 in order to regulate the movement of the free piston toward the piston 8,
And a regulating member fixed to the cylinder 2 by recessing the cylinder 2 inward.

It is an object of the present invention to provide a hydraulic shock absorber provided with a safety mechanism for breaking a free piston when the free piston moves abnormally and quickly connecting the gas chamber and the oil chamber. As shown in FIGS. 2 and 5 of the publication, a cylinder 1, a piston 3 and a free piston 2 inserted vertically into the cylinder 1,
A needle member 10 and a needle-like projection 3c are provided at the lower end of the piston 3 for opening a through hole in the free piston 2 when the free piston 2 rises abnormally.

[0006]

In each of the above, since the cylinder has a depression on the outer periphery, the shock absorber having the outer surface of the cylinder as a sliding surface is provided with a free piston having the depression on the outer periphery. The second regulatory structure cannot be adopted. In the above description, when the free piston 2 collides with the needle member 10 or the needle-like projection 3c, it is only necessary to open a through hole in the free piston 2. However, the piston 3 and the free piston 2 are integrated, and Up and down movement may not be performed smoothly.

Accordingly, an object of the present invention is to prevent the free piston from interfering with the piston, to make the outer surface of the cylinder a sliding surface, and to have the free piston affect the movement of the piston. There is not to provide a hydraulic shock absorber.

[0008]

In order to achieve the above object, a first aspect of the present invention is to provide a piston in which a gas chamber and a hydraulic oil chamber in a cylinder are divided by a free piston, and a piston is provided on a tip side. In a hydraulic shock absorber of a type in which a change in volume due to a rod is compensated in a gas chamber, a communication passage for communicating the gas chamber with the hydraulic oil chamber when the free piston moves a predetermined distance toward the piston is provided in the cylinder.

The gas chamber and the hydraulic oil chamber can communicate with each other, the free piston does not move to the piston side beyond a certain distance, and the free piston does not interfere with the tip of the piston rod or the piston. It does not affect the movement of the piston rod or piston.
Also, by providing the communication passage in the cylinder, the outer surface of the cylinder can be used as a sliding surface.

According to a second aspect of the present invention, the communication path is a longitudinal groove formed in the cylinder wall so as to be long in the axial direction. The communication groove can be easily formed, and the gas chamber and the hydraulic oil chamber can be smoothly communicated via the gas or the hydraulic oil.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a cross-sectional view of a strut damper according to the present invention when it is fully extended. A strut damper 1 serving as a hydraulic shock absorber includes an outer cylinder 2, an upper oil seal 3 provided at an upper end portion of an inner surface of the outer cylinder 2, and The upper bearing 4 thereunder, the lower bearing 5 provided in the middle part of the outer cylinder 2 and the lower oil seal 6 thereunder, and the upper and lower oil seals 3, 6 and the upper and lower bearings 4, 5 are vertically moved. An inner cylinder 7 as a cylinder inserted as much as possible, and a free piston 8 inserted in the inner cylinder 7 to separate the upper gas chamber G and the oil chamber.

The strut damper 1 includes a mount joint 12 fixed to the upper end of the inner cylinder 7, a joint bolt 12a formed on the mount joint 12, and a dust into which the joint bolt 12a is inserted. A cover 13 and an upper spring seat 14,
A bump stopper rubber 15 fitted to the outer surface of the upper inner cylinder 7 in the dust cover 13, a rod 17 as a piston rod extending upward from a bottom lid 16 attached to the bottom of the outer cylinder 2, and an upper end of the rod 17 And a piston 18 which partitions the oil chamber in the inner cylinder 7 into an upper oil chamber S1 and a lower oil chamber S2. In addition, the mount joint part 12
Mount portion 11 for reducing the impact transmitted from strut damper 1 to the vehicle body when strut damper 1 is attached to the vehicle body
Is a member interposed between the vehicle body and the vehicle body.

Further, the strut damper 1 includes a shaft sealing device 21 mounted on a lower portion of the inner cylinder 7 to support the rod 17, and a lower spring seat 22 mounted on an outer surface of an intermediate portion of the outer cylinder 2.
A suspension spring 23 disposed between the lower spring seat 22 and the upper spring seat 14;
And a mounting portion 24 provided for mounting to a knuckle (not shown) on the wheel side at a lower portion of the vehicle. 2a is a step for positioning the lower side of the lower bearing 5 and the lower oil seal 6; 8a is an O-ring attached to the free piston 8;
Reference numeral denotes a distance collar inserted into the inner surface of the outer cylinder 2 for positioning the upper oil seal 3 and the upper bearing 4 with respect to the lower bearing 5 and the lower oil seal 6.

FIG. 2 is an enlarged sectional view of a piston and a shaft sealing device of the strut damper according to the present invention. The piston 18 includes a washer 31, a compression valve 32, a piston body 33, and an extension valve 34. , And a washer 35 are sequentially inserted into a small-diameter portion 17a formed at the upper end of the rod 17, and fixed with a nut N1. Piston body 3
Reference numeral 3 denotes extension-side oil passages 33a and 33 through which hydraulic oil passes during the extension stroke.
a, contraction side oil passages 33b, 33 through which hydraulic oil passes during the contraction stroke.
b. Reference numeral 36 denotes a stopper rubber.

The shaft sealing device 21 includes a rod guide 42 positioned by a ring 41 fixed to the inner cylinder 7, a bush 43 provided on the rod guide 42 for sliding the rod 17, and a rod guide 42. And a lip seal fixing member 45 to which the lip seal 44 is baked and fixed. The lip seal 44 is pressed into the inner surface of the inner cylinder 7 by applying the lip seal 44 to the lip seal fixing member 45. And a press-fitting fixing member 46 which is bent and fastened by crimping or the like.

The operation of the piston 18 during the extension stroke described above will be described below. In the extension stroke in which the piston 18 and the outer cylinder 2 are lowered with respect to the inner cylinder 7, the hydraulic oil in the lower oil chamber S2 passes through the extension oil passages 33a, 33a as indicated by the arrows, and passes through the extension valve 34. To open the upper oil chamber S1. At this time, an extension-side damping force is generated.

FIG. 3 is a cross-sectional view of the strut damper according to the present invention at the time of maximum compression, and shows a state in which the upper end of the outer cylinder 2 collides with the bump stopper rubber 15 to reduce the impact at the time of maximum compression.

FIG. 4 is an enlarged sectional view of the piston portion of the strut damper according to the present invention, and the operation of the piston in the contraction stroke will be described with reference to FIG. In the contraction stroke in which the piston 18 and the outer cylinder 2 rise with respect to the inner cylinder 7, the upper oil chamber S
As shown by the arrow, the hydraulic oil in the compression oil passage 1
The compression valve 32 is pushed open through b and 33b to reach the lower oil chamber S2. At this time, a damping force on the contraction side is generated.

5 (a) to 5 (c) are explanatory views of the communication groove of the inner cylinder according to the present invention, FIG. 5 (a) is an enlarged sectional view of a main part of the communication groove portion of the strut damper, and FIG. FIG. 4A is a cross-sectional view taken along the line bb, and FIG. In (a), a communication groove 7b as a communication passage for communicating the gas chamber G with the upper oil chamber S1 is provided on the inner surface 7 of the inner cylinder 7.
a is formed at a plurality of positions in the axial direction, and the axial length L satisfies L> B, where B is the width (length in the axial direction) of the free piston 8.

The axial positions of the communication grooves 7b do not interfere with the free piston 8 when the strut damper 1 (see FIG. 1) is in the maximum extension state.
(See FIG. 3).
1 and 3 is a position that does not interfere with the upper end of FIG.

In FIG. 5B, the cross-sectional shape of the communication grooves 7b is U-shaped. As a processing method, for example,
A disc-shaped cutter is inserted into the inner cylinder 7, fed to the inner surface 7a side by a predetermined depth to start cutting, and then the cutter is fed in the axial direction by a predetermined length to obtain an axial length L (FIG. )) Is a method of cutting.

The operation of the communication groove 7b described above will now be described. In (c), when the strut damper 1 is used for a long time, the hydraulic oil in the upper and lower oil chambers S1 and S2 gradually decreases and the free piston 8 moves to the communication groove 7b. The upper oil chamber S1 communicates with the communication groove 7b.
Connect with. Here, for example, in the extension stroke in which the piston 18 and the outer cylinder 2 are lowered with respect to the inner cylinder 7, the gas sealed in the gas chamber G flows into the upper oil chamber S1 through the communication grooves 7b. .

In the contraction stroke in which the piston 18 and the outer cylinder 2 rise relative to the inner cylinder 7, the hydraulic oil in the upper oil chamber S1 flows into the gas chamber G through the communication grooves 7b. Accordingly, the free piston 8 is stopped at the communication groove 7b..., Does not move further to the piston 18 side, and the free piston 8 does not interfere with the upper end of the rod 17.

The O-ring 8a of the free piston 8 is in line contact with the inner surface 7a of the inner cylinder 7 and has a clearance between the outer surface and the inner surface 7a of the free piston 8. Therefore, the axial length L of the communication grooves 7b (see FIG. 5 (a) is slightly larger than the axially sealed portion of the inner surface 7a by the O-ring 8a, the gas chamber G communicates with the upper oil chamber S1.

However, since the clearance is set small so as not to tilt when the free piston 8 moves, when the free piston 8 moves to the position of the communication groove 7b, the gas chamber G and the upper oil chamber S1 are moved. , That is, the flow of gas from the gas chamber G to the upper oil chamber S1 or the upper oil chamber S1
In some cases, the flow of the hydraulic oil from 1 to the gas chamber G is not performed smoothly.

Therefore, the axial length L of the communication grooves 7b is
When L> B (see FIG. 5A), when the free piston 8 moves to the position of the communication groove 7b, the communication between the gas chamber G and the upper oil chamber S1 is made smooth, so that the free piston 8 The free piston 8 is prevented from moving again without exerting a vertical force.

As described above, when the free piston 8 moves to the piston 18 side by a predetermined distance, the communication groove 7b for communicating the gas chamber G with the upper oil chamber S1 is provided in the inner cylinder 7, The gas chamber G and the upper oil chamber S1 can be communicated with each other.
Does not affect the movement of the rod 17 and the piston 18.

Also, by providing the communication grooves 7b in the inner cylinder 7, the outer surface of the inner cylinder 7 can be used as a sliding surface. Further, the communication grooves 7b are formed as longitudinal grooves formed in the inner surface 7a of the inner cylinder 7 in the axial direction so that the communication grooves 7b can be easily formed, and the gas chamber G and the upper oil chamber are formed. It is possible to smoothly communicate with S1 via gas or hydraulic oil. .

In the present embodiment, the communication groove 7b of the present invention has a U-shaped cross section. However, the present invention is not limited to this. The U-shaped, V-shaped, semi-circular, and circular shapes may be used. The shape may be a part. In addition, the number of the communication grooves 7b is four, but the number is not limited to this, and any other number may be used as long as the function as the communication grooves 7b and the necessary strength of the inner cylinder 7 can be secured.

[0030]

According to the present invention, the following effects are exhibited by the above configuration. In the hydraulic shock absorber according to the first aspect, when the free piston moves to the piston side by a predetermined distance, the communication passage for communicating the gas chamber and the hydraulic oil chamber is provided in the cylinder. The free piston does not move more than a certain distance to the piston side, does not interfere with the tip of the piston rod or the free piston, and the free piston affects the movement of the piston rod and piston Not even. Also, by providing the communication passage in the cylinder, the outer surface of the cylinder can be used as a sliding surface.

In the shock absorber according to the second aspect of the present invention, since the communication path is a longitudinal groove formed in the cylinder wall so as to be long in the axial direction, the communication groove can be easily formed. Can be smoothly communicated via gas or hydraulic oil.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a strut damper according to the present invention at the maximum extension.

FIG. 2 is an enlarged sectional view of a piston and a shaft sealing device of the strut damper according to the present invention.

FIG. 3 is a cross-sectional view of the strut damper according to the present invention at the time of maximum compression.

FIG. 4 is an enlarged sectional view of a piston portion of the strut damper according to the present invention.

FIG. 5 is an explanatory view of a communication groove of the inner cylinder according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Hydraulic shock absorber (strut damper), 7 ... Cylinder (inner cylinder), 7b ... Communication path (communication groove), 8 ... Free piston, 17 ... Piston rod (rod), 18 ... Piston, G ... Gas chamber, S1 , S2 ... Hydraulic oil chamber (upper / lower oil chamber).

Claims (2)

[Claims] 1. A hydraulic shock absorber of the type in which a gas chamber and a hydraulic oil chamber in a cylinder are separated by a free piston, and a change in volume caused by a piston rod having a piston disposed on the tip side is compensated by the gas chamber. A hydraulic shock absorber characterized in that a communication passage for communicating a gas chamber and a hydraulic oil chamber is provided in the cylinder when the piston moves a predetermined distance toward the piston. 2. The hydraulic shock absorber according to claim 1, wherein the communication passage is a longitudinal groove formed in the cylinder wall so as to be long in the axial direction.