JPH10141415A - Friction setting mechanism of hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably generate constant friction when a piston speed is minute low speed. SOLUTION: A slide bush 10 formed by coating a low friction member on a Teflon or metallic surface thereof which generates friction when a piston rod 5 strokes at minute low speed through a coming-off prevention member 9 is provided in a recessed part 8 formed in a rod guide 4. This slide bush 10 is annular, and one section thereof is cut. By arranging a coil spring 11 on the outside of the slide bush 10, an inner peripheral face of the slide bush 10 comes into contact with an outer peripheral face of the piston rod 5 at constant pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction setting mechanism for a hydraulic shock absorber capable of generating a constant friction in a very low speed range of a piston.

[0002]

2. Description of the Related Art A general structure of a hydraulic shock absorber used as a part of a vehicle suspension is such that a piston rod is inserted into a cylinder through a rod guide, and a tip of the piston rod is attached to an inner peripheral surface of the cylinder. A piston is provided for sliding contact, and an oil seal is provided outside the rod guide at the end of the cylinder to scrape off oil adhering to the outer peripheral surface of the piston rod.

[0003]

In the conventional structure described above, since the oil seal slides on the outer peripheral surface of the piston rod, friction occurs at this portion.
When the piston speed is high, the friction generated at the sliding contact between the oil seal and the piston rod does not significantly affect the characteristics of the hydraulic shock absorber, but when the piston speed is very low so that no damping force is generated in the piston, Specifically, when the piston speed is 0.01 m / s or less, the friction generated at the sliding contact portion between the oil seal and the piston rod affects the riding comfort.

That is, when assembling the shock absorber, the characteristics of the hydraulic shock absorber are set in consideration of the friction generated at the sliding contact portion between the oil seal and the piston rod when the piston speed is very low. However, when the oil seal deteriorates over time, friction generated at the oil seal portion is almost eliminated. As a result, it becomes difficult to suppress a minute vibration of 1 to 2 mm or less, and a minute stroke (fluctuation) generated after a large vibration when traveling on a rough road does not stop forever, adversely affecting ride comfort.

Incidentally, a structure in which a bush that slides on the outer peripheral surface of a piston rod by an elastic body in addition to a normal bush provided on the inner diameter portion of the rod guide is disclosed in Japanese Patent Application Laid-Open No. 53-115476. However, the bush that slides on the outer peripheral surface of the piston rod disclosed in this prior art is for preventing the impact noise and vibration generated inside the cylinder from leaking to the outside or transmitting to the vehicle body. Does not give a constant friction in a very low speed range.

[0006]

In order to solve the above-mentioned problems, a friction setting mechanism for a hydraulic shock absorber according to a first aspect of the present invention comprises a piston rod having one end attached to a piston which is in sliding contact with an inner peripheral surface of a cylinder. In a hydraulic shock absorber led out through a rod guide and an oil seal provided on a cylinder side, a constant friction between the piston rod and the piston rod is generated when the piston speed is very low in a space between the rod guide and the oil seal. The generated bush was provided.

A friction setting mechanism for a hydraulic shock absorber according to a second aspect of the present invention includes a rod guide and an oil seal in which the other end of a piston rod having one end attached to a piston sliding on the inner peripheral surface of the cylinder is provided on the cylinder side. In the hydraulic shock absorber led to the outside through the above, a retainer is provided on the piston rod, and a bush that generates a constant friction with the inner peripheral surface of the cylinder when the piston speed is very low is provided in the retainer.

As a means for bringing the bush into contact with the outer peripheral surface of the piston rod or the inner peripheral surface of the cylinder with a constant pressing force, a spring member or a rubber member can be considered.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view of a hydraulic shock absorber to which a friction setting mechanism according to the first invention is applied, and FIG.
FIG. 2 is an enlarged sectional view of a main part of FIG. 1. The hydraulic shock absorber has an inner cylinder 2 disposed in an outer cylinder 1, a bottom valve 3 provided at the bottom of the outer cylinder 1 and the inner cylinder 2, and an outer cylinder 1 and an inner cylinder. A rod guide 4 is provided at the top of the cylinder 2, and a piston rod 5 is inserted into the inner cylinder 2 via the rod guide 4.

At the lower end of the piston rod 5 is mounted a piston 6 which is in sliding contact with the inner peripheral surface of the inner cylinder 2.
1 and a lower oil chamber S2. The lower oil chamber S2 communicates with the oil reservoir S3 between the outer cylinder 1 and the inner cylinder 2 via the bottom valve 3.

A guide bush 7 is attached to an inner peripheral portion of the rod guide 4, and a hole through which the piston rod 5 is inserted is formed inside the guide bush 7.

On the other hand, a concave portion 8 is formed in the rod guide 4, and the surface of a Teflon or a metal which generates friction when the piston rod 5 strokes at a very low speed via a retaining member 9 is formed in the concave portion 8. A sliding bush 10 formed by coating a friction member is provided.

The sliding bush 10 has an annular shape and is cut at one place. By disposing a coil spring 11 outside the sliding bush 10, the inner peripheral surface of the sliding bush 10 has a constant pressure and the outer peripheral surface of the piston rod 5. Contact

The core 13 of the oil seal 12 is located between the upper end of the rod guide 4 and the upper end of the outer cylinder 1.
Holding. The oil seal 12 contacts the outer peripheral surface of the piston rod 5 at two places, and a part 12a of the oil seal 12 contacts the upper surface of the retaining member 9.

When the piston rod 5 strokes, part of the oil adhering to the surface of the piston rod 5 is removed by the gap G, the groove 14 formed at the bottom of the concave portion 8, the hole 15 formed in the retaining member 9, the rod guide, and the like. 4 is returned into the oil reservoir S3 via a groove 16 formed on the upper end of the rod guide 4 and a groove 17 formed on the side surface of the rod guide 4.

FIG. 3 (a) is a sectional view similar to FIG. 2 showing another embodiment, and FIG. 3 (b) is a sectional view taken along the line bb in FIG. 3 (a). In this embodiment, the sliding bush 10 is contracted inward by the elastic force of the coil spring 11 so as to generate a constant friction. In this embodiment, however, a rubber member 19 is interposed in the case 18. The sliding bush 10 is baked. The inner diameter of the sliding bush 10 is set to be smaller than the outer diameter of the piston rod 5 in a state where no external force is applied. The cut portion 10a spreads against the rubber member 19, and the inner peripheral surface of the sliding bush 10 comes into contact with the outer peripheral surface of the piston rod 5 at a constant pressure.

Incidentally, a slit 20 is formed in the rubber member 19 in the axial direction in advance, and when the piston rod 5 is inserted, the slit 20 also expands to become an oil passage.

FIGS. 4 (a) to 4 (d) are views showing still another embodiment, and the embodiment shown in FIG.
4 are provided, two elastic rings 21 are provided.
In the embodiment shown in (b), the cross-sectional shape of the elastic ring 21 is not a circle but a flat ellipse. FIG.
The embodiment shown in (c) is a combination of the sliding bush 10 and a clip 22 for reducing the sliding bush 10 from the outer periphery. When the sliding bush 10 itself is made of an elastic body, the clip 22 is unnecessary. Further, FIG.
The embodiment shown in FIG. 1 comprises a combination of a sliding bush 10 and a leaf spring 23 for reducing the sliding bush 10 from the outer periphery.

FIG. 5 is a longitudinal sectional view of a hydraulic shock absorber to which the friction setting mechanism according to the second invention is applied, and FIG. 6 is an enlarged sectional view of a main part of FIG. A retainer 24 is attached, and a sliding bush 25 is provided on the outer periphery of the retainer 24. The sliding bush 25 is slidably contacted with the inner peripheral surface of the cylinder by a spring member or a rubber member 26 at a constant pressure.

[0020]

As described above, the friction setting mechanism of the hydraulic shock absorber according to the first invention of the present application is provided with the other end of the piston rod having one end on which the piston slidingly contacting the inner peripheral surface of the cylinder is provided on the cylinder side. In the hydraulic shock absorber led out through a rod guide and an oil seal,
A bush is provided in the space between the rod guide and the oil seal to generate a constant friction with the piston rod when the piston speed is very low, and the friction setting mechanism of the hydraulic shock absorber according to the second invention of the present application is Since the piston rod is provided with a retainer, and the retainer is provided with a bush that generates a constant friction with the inner peripheral surface of the cylinder when the piston speed is very low, for example, the piston speed is less than 0.01 m / s. A constant friction can be imparted in a low speed range, so that the fine vibration of the shock absorber does not continue forever, and stable riding comfort can be secured.

Further, when a metal spring member is used as a means for bringing the bush into contact with the outer peripheral surface of the piston rod or the inner peripheral surface of the cylinder with a constant pressing force, the spring member is not deteriorated by oil. It is possible to generate stable friction.

On the other hand, when an elastic rubber member is used instead of the metal spring member, the assembling becomes simple and the cost becomes advantageous.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a hydraulic shock absorber to which a friction setting mechanism according to a first invention is applied.

FIG. 2 is an enlarged sectional view of a main part of FIG. 1;

FIG. 3A is a sectional view similar to FIG. 2 showing another embodiment,
(B) is a sectional view taken along line bb of (a).

FIGS. 4A to 4D are diagrams showing another embodiment.

FIG. 5 is a longitudinal sectional view of a hydraulic shock absorber to which a friction setting mechanism according to a second invention is applied.

FIG. 6 is an enlarged sectional view of a main part of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Outer cylinder, 2 ... Inner cylinder, 4 ... Rod guide, 5 ... Piston rod, 6 ... Piston, 7 ...
Guide bush, 8 recess, 9 retaining member, 10,
25 ... sliding bush, 11 ... coil spring, 12 ...
Oil seal, 19: rubber member, 21: elastic ring,
22: clip, 23: leaf spring, 24: retainer.

Claims (4)

[Claims] 1. A hydraulic shock absorber wherein the other end of a piston rod having a piston attached to one end thereof in sliding contact with an inner peripheral surface of a cylinder is led out through a rod guide provided on the cylinder side and an oil seal. A friction setting mechanism for a hydraulic shock absorber, wherein a bush that generates a constant friction with a piston rod when a piston speed is very low is provided in a space between the oil seal and the oil seal. 2. A hydraulic shock absorber in which the other end of a piston rod having a piston that is in sliding contact with the inner peripheral surface of the cylinder at one end is led out through a rod guide provided on the cylinder side and an oil seal. A friction setting mechanism for a hydraulic shock absorber, wherein a retainer is provided, and a bush that generates a constant friction with an inner peripheral surface of the cylinder when a piston speed is very low is provided in the retainer. 3. The friction setting mechanism for a hydraulic shock absorber according to claim 1, wherein the bush is brought into contact with the outer peripheral surface of the piston rod or the inner peripheral surface of the cylinder with a constant pressing force by a metal spring member. A friction setting mechanism for a hydraulic shock absorber. 4. The friction setting mechanism for a hydraulic shock absorber according to claim 1, wherein the bush is brought into contact with an outer peripheral surface of the piston rod or an inner peripheral surface of the cylinder with a constant pressing force by an elastic rubber member. A friction setting mechanism for a hydraulic shock absorber.