JPH0579525A - Hydraulic buffer - Google Patents

Abstract

PURPOSE:To prevent self-excited vibration of a disc valve at opening the disc valve and generation of abnormal sound by making the contact area between a valve seat formed on a piston and a disc valve into line contact. CONSTITUTION:Annular valve seats 22, 23 having circular arc-like section are formed on both side end parts of a piston 21 by which oil chambers A and B are defined in a cylinder 1. Disc valves 8, 9 to be separated and seated are arranged on the respective valve seats 22, 23. Hereby, contact parts between the respective valve seats 22, 23 and the respective disc valves 8, 9 are formed into line contact so as to reduce contact area.

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 is preferably used for damping the vibration of a vehicle.

[0002]

2. Description of the Related Art Here, FIGS. 4 and 5 show a conventional hydraulic shock absorber.

In the figure, 1 is a cylinder, 2 is a piston rod provided so as to project into the cylinder 1, and 3 is fixed to a small diameter portion 2A of the piston rod 2, and is slidably inserted into the cylinder 1. The piston shown is shown. The piston 3 defines the inside of the cylinder 1 into two oil chambers A and B. When the piston 3 is displaced toward the contraction side or the expansion side, the oil liquid flowing from one oil chamber to the other oil chamber. A damping force is generated in the shock absorber to dampen the vibration.

Next, the aforementioned damping force generating mechanism will be described.

Valve seats 4, 5 are annularly located near the outer peripheral portions of both ends of the piston 3 and have a trapezoidal cross section.
Reference numeral 7 denotes a protrusion provided on the inner peripheral portions of both ends of the piston 3, and the valve seats 4 and 5 are in a state of slightly protruding in the axial direction from the protrusions 6 and 7.

Reference numerals 8 and 9 are fitted to the small diameter portion 2A of the piston rod 2, and the inner peripheral edge portions of the piston rods 2 are in contact with the projections 6 and 7, respectively, and the outer peripheral edge portions are seated on and off the valve seats 4 and 5, respectively. The extension side disc valve is shown, and each disc valve 8,
9 is formed to have a diameter larger than the outer diameter of each of the valve seats 4 and 5, the reduction-side disc valve 8 is configured by stacking three discs 8A, and the extension-side disc valve 9 includes four discs. It is configured by stacking the disks 9A.

Numerals 10 and 11 are spacers for elastically deforming the disk valves 8 and 9 in directions away from the valve seats 4 and 5, respectively, and numerals 12 and 13 are valve opening of the disk valves 8 and 9. 4 shows a restricting member (retainer) that restricts the degree via the washers 14, 14, and the disc valve 8, the spacer 10, and the restricting member 12 are sandwiched between the piston 3 and the step portion 2B formed on the piston rod 2, and The disc valve 9, the spacer 11, and the regulating member 13 are sandwiched between the piston 3 and a lock nut 15 screwed to the tip side of the small diameter portion 2A of the piston rod 2. And
The disk valves 8 and 9 come into contact with the projections 6 and 7 and the valve seats 4 and 5, respectively, so that the disk valves 8 and
9 and the end faces of the piston 3 between the annular oil chambers 16 and 17
Is defined. Further, reference numerals 18 and 19 denote reduction-side and extension-side communication passages provided in the piston 3, respectively. The reduction-side communication passage 18 communicates the oil chamber A and the annular oil chamber 16 with each other, and the extension-side communication passage 19 is provided. Is for communicating the oil chamber B with the annular oil chamber 16, and a plurality of communication passages 18 and 19 are provided so as to be inclined with respect to the axis of the piston 3.

Reference numeral 20 denotes a piston ring mounted on the outer peripheral surface of the piston 3.

The hydraulic shock absorber according to the prior art has the above-mentioned structure, and its operation will be described below.

It is now assumed that the piston 3 is displaced together with the piston rod 2 in the arrow X direction (reduction side) in the drawing. As a result, the pressure inside the oil chamber A becomes high, and the pressure inside the oil chamber A rises. This pressure is guided into the annular oil chamber 16 and acts on the disk valve 8 on the reduction side. When the pressure acting on the disc valve 8 becomes larger than the spring force of the disc valve 8, the outer peripheral edge portion thereof is elastically deformed, and the valve seat 4
Move away from. As a result, the flow passage area from the annular oil chamber 16 to the oil chamber B increases, and the damping force characteristic changes.

On the other hand, the piston 3 is opposite to the above-mentioned arrow Y.
When it is displaced in the direction (extension side), the same operation as described above is performed. However, the disk 9 of the disk valve 9 on the extension side
Since four A are used and the number of disks 8A of the disk valve 8 on the reduction side is three, the valve opening pressure of the disk valve 9 is higher than that of the disk valve 8, so that the piston 3 is extended so as to be displaced in the Y direction. The stroke exhibits higher damping force characteristics than the reduction stroke in which the stroke is displaced in the X direction.

[0012]

By the way, in the above-mentioned prior art, due to the formation of the piston 3, the front end faces of the valve seats 4 and 5 are formed in a trapezoidal shape with a predetermined width, and Since the tip surfaces of the valve seats 4 and 5 are completely covered by the disk valves 8 and 9, the disk valves 8 and 9 and the valve seats 4 and 5 are in surface contact with each other with a certain contact area. ing. Due to this surface contact, the oil having the valve opening pressure is suddenly applied to the disc valves 8 and 9 at the moment when the disc valves 8 and 9 are opened when the piston rod 2 is contracted and extended. The disc valves 8 and 9 cause self-excited vibration between the valve seats 4 and 5,
There is a problem that abnormal noise is generated by this vibration.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention prevents self-excited vibration between the piston rod and each valve seat of each disc valve when the piston rod is contracted and extended, and the An object of the present invention is to provide a hydraulic shock absorber capable of preventing the generation of sound.

[0014]

A feature of the structure adopted by the present invention for solving the above-mentioned problems is that the valve seat is formed so as to make line contact with the disc valve at its tip.

[0015]

With the above structure, the oil having the valve opening pressure can be gradually added to the disc valve when the disc valve is opened.

[0016]

Embodiments of the present invention will be described below with reference to FIGS. In the embodiments, the same components as those of the above-described conventional technique are designated by the same reference numerals, and the description thereof will be omitted.

In the figure, 21 indicates a piston of this embodiment,
The piston 21 is constructed in substantially the same manner as the above-described conventional piston 3, and annular valve seats 22 and 23 having an arc-shaped cross section are formed on the outer peripheries of both end surfaces of the piston 21. Ring-shaped protrusions 24, 25 on the inner peripheral side
Is formed, the valve seats 22 and 23 and the protrusions 24 and 25 are formed.
There are annular oil chambers 26 and 27 between and. Also,
In the axial direction of the piston 21, a plurality of contraction-side and extension-side communication passages 28 and 29 that obliquely penetrate both end surfaces are formed.

Here, the valve seats 22 and 23 are always closed by the disc valves 8 and 9, and as shown in FIG. 2, the tips of the valve seats 22 and 23 and the disc valves 8 and 9 are connected. The contact portion comes to have an annular line contact.

The present embodiment has the above-mentioned structure, and its basic operation is not different from that of the prior art.

However, according to this embodiment, the piston 21
Since the valve seats 22 and 23 respectively formed on both end surfaces of the valve seat are formed to have an arcuate cross-section, the portions in contact with the disk valves 8 and 9 can be made into line contact, and the valve seats 22 and 23 can be made into line contact. The contact area between the disk valves 8 and 9 can be reliably reduced. And
When the piston rod 2 is contracted or extended, the oil having the valve opening pressure applied to the disc valves 8 and 9 is gradually added to the valve seat 2.
2,23, each disc valve 8,
It is possible to effectively prevent the self-excited vibration of the disk valves 8 and 9 at the moment when the valve seats 9 and 9 open from the valve seats 22 and 23, and reliably prevent the generation of abnormal noise.

That is, when the speed of the piston 21 increases to some extent during extension, the extension side disk valve 9 bends and begins to open. At this time, the oil liquid flows through the communication passage 29 of the piston 21 to gradually increase the pressure, and tends to flow out between the piston 21 and the disc valve 9. Then, it passes through the maximum pressure point (where the valve seat 23 and the disc valve 9 are in line contact) and gradually flows to the oil chamber A from the piston 21 while gradually lowering the pressure. The disk valve 8 and the valve seat 22 operate in the same manner even when contracted. Thus, after the disc valves 8 and 9 are opened, the time for which the maximum pressure of the oil liquid is applied is much shorter than that of the conventional one, and the pressure drop after the maximum pressure is the same as that of the conventional one. Since it is smoother than the above, the occurrence of self-excited vibration and abnormal noise can be reliably prevented.

In the above embodiment, the valve seats 22 and 2 are
However, the present invention is not limited to this, and may be formed as a valve seat 31 having a triangular cross section as shown in FIG. 3, and the contact portions with the disc valves 8 and 9 are linear. The cross-sectional shape of the valve seat may be such that it makes contact.

Although each disk valve 8 and 9 is composed of a plurality of disks, the present invention is not limited to this, and one disk may be used.

Further, in the above embodiment, the valve seats 22 and 23 are formed on both end faces of the piston 21, but the present invention is not limited to this, and the valve seats are formed on one end face to reduce or reduce the size. It is also possible to use it for a damping force generator for only one of the expansions.

[0025]

As described above in detail, in the hydraulic shock absorber according to the present invention, the shape of the valve seat is formed so as to make line contact with the disc valve, so that the contact area between the disc valve and the valve seat can be surely reduced. Therefore, it is possible to effectively prevent self-excited vibration of the disc valve at the moment when the disc valve is opened when the piston rod is contracted or extended, and it is possible to reliably prevent abnormal noise.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a main part of a hydraulic shock absorber showing an embodiment of the present invention.

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

FIG. 3 is an enlarged sectional view similar to FIG. 2 showing a modified example of the present invention.

FIG. 4 is a longitudinal sectional view of a main part of a hydraulic shock absorber according to a conventional technique.

5 is an enlarged cross-sectional view of a main part in FIG.

[Explanation of symbols]

 1 Cylinder 8,9 Disc valve 21 Piston 22,23,31 Valve seat A, B Oil chamber

Claims (1)

[Claims] 1. A cylinder, a piston slidably inserted into the cylinder and defining two oil chambers in the cylinder, and an annular valve seat disposed on an end surface of the piston. In a hydraulic shock absorber comprising a disc valve disposed on the end surface of the piston so as to be seated on and off each valve seat, the valve seat is formed so as to make line contact with the disc valve at its tip. And a hydraulic shock absorber.