JP2000179607A - Hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize pistons while securing sealing performance between the mutual pistons in a two piston type. SOLUTION: A piston part 20 is composed of a lower piston 28 and an upper piston 56. The upper piston 56 is pressed in a recessed part 30 of the lower piston 28. Thus, sealing performance between mutual pistons is secured, and since a seal member such as an O ring can be abolished, the pistong part 20 can be miniaturized in the shaft direction and the radial direction. Since an outside diameter of a peripheral wall part 28B of the lower piston 28 changes by press-in, a band 78 is installed in an outer peripheral part of a main body part 28A uninfluenced by the press-in.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a two-piston type hydraulic shock absorber.

[0002]

2. Description of the Related Art Conventionally, hydraulic shock absorbers have been used in various technical fields to attenuate impact. For example, in the automotive field, a shock absorber is used as one component of a suspension. There are various types of shock absorbers of this type, and among them, those having two pistons for obtaining desired damping force characteristics (hereinafter, referred to as "two-piston type"). There is. An example of the disclosure is disclosed in US Pat. No. 5,706,91.
There is Japanese Patent Publication No. 9 and the shock absorber disclosed in this publication will be briefly described below.

FIG. 3 shows a shock absorber 100 disclosed in the above publication. As shown in the figure, a piston rod 104 is disposed in a cylinder 102 of a shock absorber 100 so as to be movable in an axial direction, and a lower piston 106 having a bottomed cylindrical shape is provided at a tip end thereof.
Are fixed with nuts 108. This lower piston 1
06, a substantially disc-shaped upper piston 1
10 are fitted. A port 112 is formed at the bottom of the lower piston 106, and a leaf valve 114 is provided corresponding to the port 112. Similarly,
Port 11 is also provided at the radially intermediate portion of upper piston 110.
6 are formed, and a leaf valve 118 is provided corresponding to the port 116.

[0004] A resin band 120 is fitted around the outer periphery of the lower piston 106 described above. The band 120 seals between the outer periphery of the lower piston 106 and the inner periphery of the cylinder 102. Further, an O-ring 122 made of rubber is fitted around the outer periphery of the upper piston 110. The outer periphery of the upper piston 110 and the lower piston 10
6 is sealed with the inner peripheral portion.

[0005]

However, the above-described shock absorber 100 having the piston structure has the following problems.

That is, since the O-ring 122 is fitted to secure the sealing performance between the outer peripheral portion of the upper piston 110 and the inner peripheral portion of the lower piston 106, only the sealing allowance by the O-ring 122 is provided. The size of the upper piston 110 increases in the axial direction. Further, since the O-ring 122 must be fitted in consideration of the position and diameter of the port 116, the size of the upper piston 110 increases in the radial direction. Therefore, according to the above configuration, there is a problem that the size of the upper piston 110 increases in both the axial direction and the radial direction, and accordingly, the size of the lower piston 106 also increases in the axial direction and the radial direction.

The present invention has been made in consideration of the above-described circumstances, and has as its object to obtain a hydraulic shock absorber capable of reducing the size of a piston in a two-piston type while ensuring sealability between the pistons.

[0008]

According to the present invention, there is provided a cylinder filled with a fluid, a piston rod inserted in the cylinder so as to be movable in an axial direction, and fixed to the piston rod. And a first piston having a port serving as a fluid flow path and having a concave portion at an end, and a first piston fitted into the concave portion of the first piston, And a valve that opens and closes each port of the first piston and the second piston in response to a pressure change associated with an expansion and contraction step, The two pistons are fixed by press-fitting into the recesses of the first piston.

According to a second aspect of the present invention, in the hydraulic shock absorber according to the first aspect of the present invention, the outer periphery of the first piston is located at a position where the outer periphery of the first piston does not overlap the second piston press-fitting portion. A seal member for sealing between the portion and the inner peripheral portion of the cylinder is mounted.

The operation of the present invention described in claim 1 is as follows.

As a general operation, the two pistons are assembled (integrated) by fitting the second piston into a recess formed at the end of the first piston. That is, a two-piston type hydraulic shock absorber is configured. Ports are respectively formed in the first piston and the second piston, and when a pressure change occurs in the chamber separated by the first piston due to the expansion and contraction process, each port is opened or closed by the valve. I do. Therefore, the damping force characteristic can be made to be a desired characteristic by adjusting the setting method of each port of the first piston and the second piston and the setting method of the valve provided therewith.

Here, in the present invention, the second piston is connected to the first piston.
Since the piston is fixed in the recess by press-fitting, the seal between the outer periphery of the second piston and the inner periphery of the recess of the first piston is ensured by the press-fitting configuration. For this reason, there is no need to fit a seal member such as an O-ring to the outer peripheral portion of the second piston as in the related art, and the seal member can be eliminated.

According to the present invention, a seal is provided between the outer peripheral portion of the first piston and the inner peripheral portion of the cylinder at a position where the outer peripheral portion of the first piston does not overlap with the press-fit portion of the second piston. In other words, since the second piston press-fit portion of the first piston and the seal member mounting portion are in separate and independent positional relations, the influence of the press-fit affects the sealability of the seal member. Disappears.

That is, when the second piston is pressed into the recess of the first piston, the outer diameter of the recess (that is, the second piston press-fit portion of the first piston) changes. Therefore, if the seal member is attached to the outer peripheral portion of the second piston press-fit portion of the first piston, a change in the outer diameter of the second piston press-fit portion affects the sealability of the seal member. However, in the present invention, since the second piston press-fit portion and the seal member mounting portion are not wrapped, the influence of the press-fit does not affect the sealing property of the seal member.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A shock absorber 10 as a "hydraulic shock absorber" according to an embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 2, the shock absorber 10 is a twin tube type having an outer tube 12 and an inner tube 14 as a "cylinder", each of which has a cylindrical shape and is arranged concentrically. ing. Although not shown, a dish-shaped lower cap is welded to the lower end of the outer tube 12, and a ring nut is screwed to the upper end of the outer tube 12. On the other hand, a base valve is provided at the lower end of the inner tube 14, and a rod guide is fitted to the upper end of the inner tube 14. An oil seal is provided on the shaft core of the ring nut, and a square seal ring is interposed between the ring nut and the rod guide.

A piston rod 16 is inserted into the shaft core of the inner tube 14 so as to be movable in the axial direction. A small diameter portion 18 is formed at a lower end portion of the piston rod 16, and a piston portion 20 is disposed on the small diameter portion 18. It should be noted that the interior of the inner tube 14 is divided into the upper chamber 22 and the lower chamber 24
And is segregated. The upper chamber 22 and the lower chamber 24 are filled with oil as “fluid”. Further, a gas such as oil and nitrogen gas is sealed in a reservoir chamber 26 formed between the outer tube 12 and the inner tube 14 in a separated state.

Next, the detailed structure of the piston section 20 will be described.

As shown in FIG. 1 on an enlarged scale, a small-diameter portion 18 at the lower end of the piston rod 16 has a piston mounting portion 18A having a smooth peripheral surface, and a nut having an external thread formed on the peripheral surface. A mounting portion 18B is formed.

The piston mounting portion 18A of the small diameter portion 18 has
Lower piston 2 as "first piston" having a substantially cylindrical shape
8 has been inserted. A concave portion 30 is formed on the upper end side of the lower piston 28, and the lower piston 28 has a thick body portion 2 formed by the concave portion 30.
8A and a thin peripheral wall portion 28B are formed. A lower first annular groove 32 and a lower second annular groove 34 are formed concentrically on the upper end surface of the main body 28A.
A lower third annular groove 36 is formed on the lower end surface of the lower ring. The lower first annular groove 32 and the lower third annular groove 36 formed at positions opposing each other are connected to the lower first port 3 penetrating in the axial direction.
8 and the lower second annular groove 3
The lower chamber 24 and the lower chamber 24 are communicated with each other by a lower second port 40 penetrating in the axial direction.

A stepped flanged nut 42 is screwed into the nut mounting portion 18B of the small diameter portion 18. Flanged nut 42
A spring seat 44 is fitted to the step portion 42A so as to be slidable in the axial direction. This spring seat 4
A compression coil spring 46 (which is an element grasped as an urging means in a broad sense) is wound between the flange 4 and the flange 42B of the flanged nut 42. The compression coil spring 46 constantly urges the spring seat 44 toward the lower piston 28. A lower first port 38 is provided between the spring seat 44 and the lower end surface of the lower piston 28.
The lower first leaf valve 48 that opens and closes is interposed. In the present embodiment, the lower first leaf valve 48 is constituted by two leaf springs. However, the thickness and the number of leaf springs are appropriately changed in accordance with the setting of the damping force characteristic.

A thin disk-shaped lower second leaf valve 49 for opening and closing the lower second port 40 is provided on the upper end surface side of the lower piston 28 (on the bottom side of the concave portion 30). The lower first leaf valve 49 has a lower first leaf valve 49.
At a position facing the port 38, a circular hole 5 for oil distribution is provided.
1 is formed.

Further, on the upper surface side of the lower second leaf valve 49, a thin stopper plate 52 having a plurality of circular holes 50 formed at a radially intermediate portion is disposed. In addition,
A pair of spacers 54 are arranged above and below the axis of the stopper plate 52.

An upper piston 56 as a thin "second piston" is mounted in the recess 30 formed in the lower piston 28 described above. An upper first annular groove 58 is formed on the upper end surface of the upper piston 56, and an upper second annular groove 60 and an upper third annular groove 62 are formed concentrically on the lower end surface of the upper piston 56. I have. The upper first annular groove 58 and the upper third annular groove 62 formed at positions facing each other are communicated with each other by an upper first port 64 penetrating in the axial direction, and the upper second annular groove 60 and the upper chamber. 22 are mutually connected by an upper second port 66 penetrating in the axial direction.

The piston mounting portion 18A of the small diameter portion 18 of the piston rod 16 has a stopper plate 6 having a predetermined thickness at a position separated from the upper piston 56 by a predetermined distance.
8 is attached. A leaf sheet 72 is provided between the stopper plate 68 and the upper end surface of the upper piston 56.
The upper first leaf valve 70 is disposed with a space therebetween. The upper first leaf valve 70 is
This is a valve provided corresponding to the port 64. In addition,
In the present embodiment, the upper first leaf valve 70 is constituted by three leaf springs, but the thickness and the number of leaf springs are appropriately changed according to the setting of the damping force characteristic.

An upper second leaf valve 74 is disposed between the lower end surface of the upper piston 56 and the stopper plate 52 (more precisely, the spacer 54 disposed above the stopper plate 52). . A circular hole 76 for oil circulation is formed at a position of the upper second leaf valve 74 facing the upper first port 64.
The upper second leaf valve 74 is a valve provided corresponding to the upper second port 66.

Here, in the present embodiment, the upper piston 56 is fixed to the lower piston 28 by press-fitting the upper piston 56 into the recess 30 of the lower piston 28. Therefore, the outer peripheral portion of the upper piston 56 and the inner peripheral portion of the peripheral wall portion 28B of the lower piston 28 are in close contact with each other, and a predetermined sealing performance is ensured. Further, in the present embodiment, a resin band 78 as a “seal member” is attached to the outer periphery of the main body 28A of the lower piston 28. That is, in the present embodiment, the upper piston press-fit portion and the band mounting portion of the lower piston 28 are set to have a positional relationship (independent positional relationship) such that they do not overlap with each other.

Next, the operation and effect of this embodiment will be described.

First, the general flow of oil during the elongation step and the contraction step will be briefly described.

In the elongation step, the inner tube 1
4, the pressure in the upper chamber 22 is higher than the pressure in the lower chamber 24. Therefore, the oil in the upper chamber 22 is supplied to the upper piston 5
After passing through the upper second port 66 of FIG. 6, the upper second leaf valve 74 is elastically deformed and flows into the recess 30 of the lower piston 28. Since the amount of elastic deformation of the upper second leaf valve 74 is regulated by the stopper plate 52, the upper second leaf valve 74 is elastically deformed within the range. The oil that has flowed into the recess 30 flows into the lower first port 38 of the lower piston 28 from the circular hole 51 of the lower second leaf valve 49 on the lower piston 28 side. The oil that has flowed into the lower first port 38 pushes down the spring seat 44 against the urging force of the compression coil spring 46 according to the piston speed, and flows into the lower chamber 24 through a gap with the lower first leaf valve 48. I will do it. In the above process, a damping force in the elongation step is obtained.

On the other hand, during the contraction step, the pressure in the lower chamber 24 of the inner tube 14 is higher than the pressure in the upper chamber 22. For this reason, after the oil in the lower chamber 24 passes through the lower second port 40 of the lower piston 28, the lower second leaf valve 49 is elastically deformed and flows into the recess 30 of the lower piston 28. Since the amount of elastic deformation of the lower second leaf valve 49 is regulated by the stopper plate 52, the lower second leaf valve 49 is elastically deformed within the range. The oil that has flowed into the recess 30 flows into the upper first port 64 of the upper piston 56 from the circular hole 76 of the upper second leaf valve 74 on the upper piston 56 side. The oil flowing into the upper first port 64 elastically deforms the upper first leaf valve 70 according to the piston speed and flows into the upper chamber 22. In the above process, a damping force at the time of the shrinking step is obtained.

Since the shock absorber 10 according to the present embodiment is of the two-piston type, the damping force characteristics at the time of the elongation step and the damping force characteristic at the time of the contraction step are based on the design specifications of the lower piston 28 (the port By adjusting and combining the diameter, the leaf valve thickness and number of sheets, the spring constant of the compression coil spring, etc.) and the design specifications (port diameter, leaf valve thickness and number of leaf valves, etc.) on the upper piston 56 side, The desired characteristics are set.

Here, in the shock absorber 10 according to the present embodiment, the upper piston 56 is fixed to the recess 30 of the lower piston 28 by press-fitting the upper piston 56 into the recess 30 of the lower piston 28. . Therefore, the sealing property between the outer peripheral portion of the upper piston 56 and the inner peripheral portion of the peripheral wall portion 28B of the lower piston 28 is as follows.
It is secured by the configuration of press fitting. Therefore, there is no need to fit a seal member such as an O-ring to the outer peripheral portion of the upper piston 56 unlike the related art, and the seal member can be eliminated.

Therefore, the size of the upper piston 56 can be reduced in the axial direction and the radial direction. Further, since the size of the upper piston 56 can be reduced in the axial direction and the radial direction, the size of the concave portion 30 of the lower piston 28 can also be reduced. Therefore, not only the upper piston 56 but also the lower piston 28 can be reduced in axial and radial directions. As a result, according to the present embodiment, in the two-piston type, the upper piston 56
The size of the entire piston section 20 can be reduced while ensuring the sealing performance between the piston section 20 and the lower piston 28.

Since the sealing member such as the O-ring can be eliminated and the size of the entire piston portion 20 can be reduced, a cost reduction effect can be obtained.

Further, according to the present embodiment, the upper piston 56 is press-fitted into the peripheral wall portion 28B of the lower piston 28, and the band 78 is attached to the outer peripheral portion of the main body 28A of the lower piston 28. Then, since the press-fit portion of the upper piston 56 in the lower piston 28 and the mounting portion of the band 78 are in a separate and independent positional relationship, the influence of the press-fit does not affect the sealing property of the band 78.

That is, when the upper piston 56 is pressed into the concave portion 30 of the lower piston 28, the concave portion 30
The outer diameter of the peripheral wall 28B of the lower piston 28 changes. Therefore, if the band 78 is attached to the outer peripheral portion of the peripheral wall portion 28B of the lower piston 28,
The change in the outer diameter of B affects the sealing performance of the band 78. However, in the present embodiment, since the press-fit portion of the upper piston 56 in the lower piston 28 and the mounting portion of the band 78 are not overlapped, the influence of the press-fit does not affect the sealing property of the band 78. as a result,
According to the present embodiment, the sealing performance between the outer peripheral portion of the lower piston 28 and the inner peripheral portion of the inner tube 14 can be improved.

In addition, according to the present embodiment, the change in the outer diameter due to the press-fitting of the upper piston 56 is limited to only the peripheral wall portion 28B of the lower piston 28, and the band 7
Since it does not reach the body part 28A, which is the mounting part of 8,
The roundness of the main body 28A with the band 78 attached is also as designed. Furthermore, when the piston portion 20 is inserted into the inner tube 14, the only portion that slides on the inner tube 14 is the portion (one portion) where the band 78 is mounted, and the band 78 is made of resin. ,
Low frictional resistance. In combination with these actions, according to the present embodiment, an effect that the assemblability of the piston portion 20 to the inner tube 14 can be improved can also be obtained.

In the present embodiment, the present invention is applied to the so-called twin-tube type shock absorber 10, but the present invention is not limited to this, and may be applied to the so-called single-tube type shock absorber. Good.

In this embodiment, the band 78 is used as the seal member.
Any sealing member can be used as long as it can seal between the outer peripheral portion of the inner tube 8A and the inner peripheral portion of the inner tube 14. For example, a plurality of sealing members such as O-rings are attached at predetermined intervals to the main body 28A of the lower piston 28. A configuration of fitting to the outer peripheral portion may be adopted.

Further, in this embodiment, the lower piston 2
The band 78 is attached to the outer peripheral portion of the main body portion 28A of the lower piston 28. In the relationship with the present invention described in claim 1, the sealing member such as the band 78 is attached to the peripheral wall portion 2
8B or the main body 28
A configuration in which the seal member is attached across the outer peripheral portion of A and the peripheral wall portion 28B is also included.

Further, in the present embodiment, the present invention is applied to the shock absorber 10 constituting a part of the suspension of the automobile. However, the application of the hydraulic shock absorber according to the present invention is not limited to this, and various objects may be applied. Applicable to devices in the technical field.

[0043]

As described above, in the hydraulic shock absorber according to the first aspect of the present invention, the second piston is fixed in the recessed portion of the first piston by press-fitting. The sealing member such as the O-ring can be eliminated, and the second piston can be reduced in size in the axial direction and the radial direction. Further, since the second piston can be reduced in size in the axial direction and the radial direction, the size of the concave portion of the first piston can also be reduced. Therefore, not only the second piston but also the first piston can be downsized in the axial and radial directions. As a result, according to the present invention, in the two-piston type, there is obtained an excellent effect that the size of the piston can be reduced while ensuring the sealing performance between the pistons.

According to a second aspect of the present invention, in the hydraulic shock absorber according to the first aspect of the present invention, a seal member is mounted at a position where the outer peripheral portion of the first piston does not overlap with the second piston press-fitting portion. Therefore, it is possible to prevent the influence of the press-fitting from affecting the sealing property of the sealing member, and as a result, there is an excellent effect that the sealing property between the piston and the cylinder can be improved.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a two-piston type piston portion in a shock absorber according to the present embodiment.

FIG. 2 is a partial cross-sectional view of the shock absorber, showing a state where the piston portion shown in FIG. 1 is inserted into an inner tube.

FIG. 3 is an enlarged cross-sectional view of a two-piston type piston portion in a conventional shock absorber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Shock absorber (hydraulic shock absorber) 14 Inner tube (cylinder) 16 Piston rod 22 Upper chamber 24 Lower chamber 28 Lower piston (first piston) 30 Recessed part 38 Lower first port 40 Lower second port 48 Lower first leaf valve 49 Lower second leaf valve 56 Upper piston (second piston) 64 Upper first port 66 Upper second port 70 Upper first leaf valve 74 Upper second leaf valve 78 Band (seal member)

Claims (2)

[Claims] 1. A cylinder filled with a fluid, a piston rod axially movably inserted into the cylinder, a cylinder fixed to the piston rod and separating a chamber of the cylinder from the fluid. A first piston having a port serving as a path and having a concave portion at an end; a second piston fitted into the concave portion of the first piston and having a port serving as a fluid flow path; And a valve that opens and closes each port of the second piston in response to a pressure change caused by a step of expanding and contracting, wherein the second piston is press-fitted into a recess of the first piston. A hydraulic shock absorber characterized by being fixed by: 2. An outer peripheral portion of the first piston includes a second piston.
The hydraulic shock absorber according to claim 1, wherein a seal member that seals between an outer peripheral portion of the first piston and an inner peripheral portion of the cylinder is mounted at a position not overlapping with the piston press-fitting portion.