JPH07238979A - Variable damping force type hydraulic shock absorber - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to satisfy both the requirements for vehicle driving stability in the damping force variable stroke region and the requirements for vehicle riding comfort and steering stability in the damping force non-variable stroke region. Provide a variable damping force type hydraulic shock absorber. [Structure] The expansion side damping valve is a first-stage disc valve abutting on the inner seat surface 2d and 6, and a second-stage disc valve 7 and a third-stage disc valve 8 are abutting on the outer seat surface 2e.
And a washer 4b, 4c that forms a gap between the disc valves, and an intermediate chamber C is formed between the first-stage disc valve 6 and the second-stage disc valve 7. A constant orifice 6a is formed in the third-stage disc valve 6, and the reaction force of the damping force variable spring 12 is applied to the third-stage disc valve 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping force variable hydraulic shock absorber of the type in which the damping force is changed depending on the stroke position.

[0002]

2. Description of the Related Art As a damping force variable type hydraulic shock absorber of the type described above, for example, the one described in JP-A-61-88034 is known.

In this conventional damping force variable type hydraulic shock absorber, the reaction force of the spring is applied from a predetermined stroke region to the expansion side disc valve provided on the bottom surface side of the piston so that the piston speed is increased. In a constant state, the damping force is changed according to the reaction force of the spring that changes depending on the stroke position in the initial stage of the stroke of the hydraulic shock absorber (the variable stroke range of the damping force), and the hydraulic shock absorber extends from the middle. The damping force was kept constant until the cut state (a non-variable stroke region of the damping force).

[0004]

However, in such a conventional hydraulic shock absorber, since the extension side disk valve that receives the reaction force of the spring has only one stage, the ride comfort is emphasized. If the damping force in the variable stroke region is set low, it becomes impossible to generate a high damping force to obtain sufficient damping in the variable stroke region of the damping force. There is a problem that a high damping force cannot be generated in the medium / high piston velocity range, which is effective for stability. In addition, if damping force is set to a high value in the non-variable stroke region with emphasis on damping, in the non-variable stroke region and the variable stroke region of the damping force,
Both of them will worsen the riding comfort.

Further, if a constant orifice that bypasses the expansion side disk valve is installed in parallel to solve the above problems, another problem arises in that the damping force cannot be varied in the low piston speed range.

The present invention has been made by paying attention to the conventional problems as described above. In the variable stroke range of the damping force, a sufficiently high damping force is generated from the low piston speed range to control the steering stability. In the non-variable stroke range, a sufficiently low damping force proportional to the piston speed is generated in the low piston speed range, and a high damping force is generated in the medium / high piston speed range, so that the variable stroke of the damping force is increased. To provide a damping force variable hydraulic shock absorber capable of satisfying both the requirements for vehicle steering stability in the region and the requirements for vehicle comfort and steering stability in the non-variable stroke range of damping force. It is intended.

[0007]

In order to achieve the above-mentioned object, in the damping force variable type hydraulic shock absorber of the present invention, it is provided in a piston which defines two chambers inside a cylinder and slides. , An expansion side damping valve that generates a damping force by restricting the fluid flow in the communication passage that communicates between the two chambers during the expansion stroke, and a reaction force that corresponds to the stroke position from the predetermined stroke range A damping force variable spring that changes the generated damping force by acting on the valve, wherein the extension side damping valve is a first stage disc valve and a second stage disc valve and a third stage disc valve having a diameter larger than that of the first stage disc valve. A disc washer and a disc valve are provided, and a washer is provided in the inner peripheral portion between the disc valves to determine the deflection starting point of each disc valve and to form a gap that allows a predetermined amount of deflection. The end face of the piston lube is provided, and an inner seat surface for closing the communication passage by the first stage disc valve abuts, 2 in the outer periphery of the inner sheet surface
By contacting the first-stage disc valve, an outer seat surface forming an intermediate chamber is formed between the first-stage disc valve and the second-stage disc valve, and bypasses the first-stage disc valve to form a communication passage. A constant orifice that always communicates with the intermediate chamber is formed, and the reaction force of the damping force variable spring acts on the third-stage disc valve.

In the variable damping force type hydraulic shock absorber according to the second aspect of the present invention, the second expansion-side disc valve 7 is composed of three stacked disc plates, and the first-stage disc valve 7 comes into contact with the outer seat surface. An orifice hole is formed in the disc plate, and a through hole communicating with the orifice hole is formed in the second-stage disc plate.

[0009]

Since the variable damping force type hydraulic shock absorber of the present invention is configured as described above, in the non-variable stroke region of the damping force, in the low piston speed range, the damping force due to the flow resistance of the constant orifice is exerted. And the damping force due to the valve opening resistance of the expansion side second stage disc valve itself act in series, whereby a sufficiently low damping force proportional to the piston speed is generated, and in the middle / high piston speed range. Then, the damping force due to the valve opening resistance of the first expansion stage disc valve and the damping force due to the resistance obtained by adding the reaction force of the third stage expansion disc valve to the valve opening resistance of the second expansion stage disc valve itself. These act in series, whereby a high damping force can be generated, and therefore, the ride comfort and steering stability of the vehicle in the non-variable stroke region of the damping force can be secured.

Further, in the variable stroke range of the damping force, the resistance force of the third side disc valve on the extension side increases in accordance with the stroke position, so that a sufficiently high damping force can be generated from the low piston speed range. You can and therefore
It is possible to ensure the steering stability of the vehicle in the variable stroke range of the damping force.

Further, in the damping force variable type hydraulic shock absorber according to the present invention, only the third stage disc plate of the second side disc valve of the expansion side is opened first, so that in the extremely low piston velocity range. Will be able to generate very low damping forces.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings. (First Embodiment) FIG. 1 is a sectional view showing a structure of a piston 2 portion in a damping force variable hydraulic shock absorber according to a first embodiment of the present invention. As shown in FIG. The inside of the cylinder 1 is slidably provided so as to define an upper chamber A and a lower chamber B, and the piston 2 is attached to the tip small diameter portion 3 a of the piston rod 3.

That is, with respect to the tip small diameter portion 3a of the piston rod 3, a washer 4a, a pressure side disc valve 5, a piston 2, an extension side first stage disc valve 6, and a washer 4 are provided.
b, the expansion side second stage disc valve 7, a washer 4c, the expansion side third stage disc valve 8 and a washer 4d are sequentially mounted, and finally assembled by fastening with a nut 9. In addition, the expansion side first stage disc valve 6, the expansion side second stage disc valve 7 and the extension side third stage disc valve 8
And constitute the extension side damping valve.

A spring seat 10 is axially slidably mounted on the outer circumference of the nut 9, and a locking flange portion 9a is formed on the outer circumference of the lower end of the nut 9 so as to project therefrom. Part 9a and spring seat 10
A spring 11 having a very small set load is interposed between the inner peripheral portion of the spring seat 10 and the outer peripheral edge upper end surface of the spring seat 10 by the set load, and the outer peripheral edge of the third side disc valve 8 on the extension side. It is biased so that it always contacts the lower surface.

Further, a damping force variable spring 12 is interposed between the outer peripheral portion of the lower surface of the spring seat 10 and a base (not shown) so that the set load is increased as the shock absorber strokes in the pressure stroke direction. As a result, the setting force for pressing the spring seat 10 upward is increased.

The piston 2 is formed with a plurality of pressure side communication holes 2a on the outer peripheral side thereof for ensuring the flow of fluid from the lower chamber B to the upper chamber A, and on the inner peripheral side thereof is the upper chamber A. A plurality of extension side communication holes (communication passages) 2b for ensuring fluid flow from the lower chamber to the lower chamber B are formed. On the upper surface side of the piston 2, an annular pressure side seat surface 2c, which communicates with each pressure side communication hole 2a, is formed in a protruding manner, and the pressure side disk valve 5 is arranged in a state of contacting the pressure side seat surface 2c. Has been done.

On the lower surface side of the piston 2, an annular expansion-side inner seat surface 2d which communicates with each expansion-side communication hole 2b is formed.
Is formed so as to project, and the first expansion-side disc valve 6 is arranged in a state of contacting the second expansion-side inner seat surface 2d, and the lower surface side of the piston 2 has the second expansion-side inner seat surface 2d. On the outer periphery of the ring-shaped extension-side outer seat surface 2 d, the ring-shaped extension-side outer seat surface 2
e is formed, and the second expansion-side disc valve 7 is arranged in contact with the second expansion-side outer seat surface 2e. That is, the intermediate chamber C is formed between the first expansion-side disc valve 6 and the second expansion-side disc valve 7.

The respective washers 4b, 4c and 4d determine the deflection fulcrum of the expansion side first stage disc valve 6, the expansion side second stage disc valve 7 and the extension side third stage disc valve 8. The clearance amount that allows the bending of the first expansion-side disc valve 6 and the second expansion-side disc valve 7 is determined.

The first expansion-side disc valve 6 is composed of three stacked disc plates, and the outer peripheral edge of the uppermost disc plate abutting the inner expansion-side seat surface 2d has a constant notch. The orifice 6a is formed.

The second expansion-side disc valve 7 is composed of two stacked disc plates, and the upper disc plate abuts the extension-side outer seat surface 2e, but the extension-side inner seat surface 2d is extended. By giving the step of the outer side seat surface 2e a little (about 0.1 mm) larger than the total plate pressure of the expansion side first stage disc valve 6 and the washer 4b, an initial deflection is given to the expansion side second stage disc valve 7. It is in a state of That is, by changing the plate thickness of the washer 4b, it is possible to change the initial deflection amount of the second expansion side disc valve.

The expansion side third stage disc valve 8 is composed of three stacked disc plates, and a spring seat 10 is provided on the lower surface of the outer peripheral edge of the lowermost disc plate.
The upper surface of the outer peripheral edge is in contact with.

Next, the operation of this embodiment will be described with reference to FIGS. (A) During the pressure stroke of the shock absorber (rebound direction) In the pressure stroke of the shock absorber, as shown in FIG. 1, the fluid on the lower chamber B side passes through the pressure side communication hole 2a and the pressure side seat surface 2c.
At this position, the pressure side disc valve 5 is opened and flows into the upper chamber A side. At this time, the flow of the fluid is restricted by the valve opening resistance of the pressure side disc valve 5 to generate a pressure side damping force.

(B) During the stroke of the shock absorber (bounding direction) In the stroke of the shock absorber, the fluid in the upper chamber A passes through the expansion side communication hole 2b and passes through the constant orifice 6a or the first stage of the expansion side. Open the disc valve 6 to open the intermediate chamber C
To the lower chamber B side by opening the second expansion side disc valve 7 from that position to the lower chamber B side. At this time, the flow of the fluid is the flow resistance of the constant orifice 6a or the first expansion side disc. The expansion side damping force is generated by being restricted by the valve opening resistance of the valve 6 and the valve opening resistance of the second expansion side disc valve 7. Hereinafter, the generation state of the damping force in the extension stroke will be described in detail according to the piston speed and the stroke position.

(A) Low piston speed range In the low piston speed range where the fluid flow rate is small,
As shown in FIG. 5, the fluid on the upper chamber A side flows into the intermediate chamber C from the extension side communication hole 2b through the constant orifice 6a, and from that position, the extension side second stage disc valve 7 is further opened to open the lower portion. It flows into the chamber B side. At this time, in the state of FIG. 2, since the reaction force of the damping force variable spring 12 is at the stroke position where it does not act on the third expansion stage disc valve 8, the second expansion disc valve 7 and the third expansion stage disc valve 7 are located. A sufficient clearance is secured between the second expansion disc valve 8 and the second expansion disc valve 7, and when the second expansion disc valve 7 is opened, the third expansion disc valve 8 is brought into contact with the third expansion disc valve 8 to restrict the opening. Never.

Therefore, the damping force due to the flow resistance of the constant orifice 6a and the damping force due to the valve opening resistance of the second expansion side disc valve 7 itself act in series, whereby, as shown in FIG. It produces a low damping force that is linear with piston speed.

Further, as shown in FIG. 3, at the stroke position where the damping force variable spring 12 is in contact with the spring seat 10, the reaction force of the damping force variable spring 12 acts on the third side disc valve 8 on the extension side. However, since the expansion side third stage disc valve 8 is bent upward, the expansion side second stage disc valve 7 and the extension side third stage disc valve 8 are provided.
The clearance between the second expansion stage side disc valve 8 is reduced when the second expansion stage side disc valve 7 is opened.
After that, the opening of the valve is regulated by abutting against, and thereby a high damping force is generated in proportion to the reaction force of the damping force variable spring 12. The reaction force of the damping force variable spring 12 increases in proportion to the stroke position. As shown in FIG. 7, the generated damping force increases in the bounding direction when the piston speed is constant.

(B) Medium / High Piston Velocity Region In the medium / high piston velocity region where the fluid flow rate is large, as shown in FIG. 4, the fluid on the upper chamber A side passes through the extension side communicating hole 2b, The expansion side first stage disc valve 6 is opened to flow into the intermediate chamber C, and from that position, the expansion side second stage disc valve 7 is further opened to flow into the lower chamber B side.
At this time, in the state of FIG. 4, the reaction force of the damping force variable spring 12 is at the stroke position where it does not act on the third expansion stage disc valve 8, but since the flow amount of the fluid increases, the second expansion stage The eye disc valve 7 is largely bent and abuts on the third side disc valve 8 on the extension side.

Therefore, the damping force due to the valve opening resistance of the first expansion side disc valve 6 and the valve opening resistance of the second expansion side disc valve 7 itself are added with the reaction force of the third expansion side disc valve 8. The damping force due to resistance acts in series,
Thereby, as shown in FIG. 6, a high damping force is generated.

Further, as shown in FIG. 5, at the stroke position where the damping force variable spring 12 is in contact with the spring seat 10, the reaction force of the damping force variable spring 12 acts on the extension side third stage disc valve 8. However, since the expansion side third stage disc valve 8 is bent upward, the expansion side second stage disc valve 7 and the extension side third stage disc valve 8 are provided.
The clearance between the second expansion stage side disc valve 8 is reduced when the second expansion stage side disc valve 7 is opened.
The valve opening control is started by making an early contact with, and thereby a high damping force is generated in proportion to the reaction force of the damping force variable spring 12. Then, the reaction force of the damping force variable spring 12 increases in proportion to the stroke position, and as shown in FIG. 7, the generated damping force increases in the bounding direction when the piston speed is constant.

As described above, the damping force variable hydraulic shock absorber of the first embodiment has the following effects. In the low piston velocity range, a sufficiently low damping force can be generated linearly with respect to the piston velocity,
This makes it possible to improve the riding comfort of the vehicle.

Even in the non-variable stroke region of the damping force in which the damping force variable spring does not come into contact with the spring seat, a high damping force can be generated in the medium / high-speed piston velocity range, thereby improving the steering stability of the vehicle. You will be able to improve.

In the variable stroke range of the damping force in which the damping force variable spring is in contact with the spring seat, a high damping force can be generated from the low piston speed range, thereby improving the steering stability. Will be able to.

The damping force is invariable only by changing the plate thickness of the washer 4c that determines the bending fulcrum of the second expansion stage disc valve 7 or by changing the rigidity of the third expansion stage disc valve 8. It is possible to easily change the stroke position that changes from the variable state to the variable state and the variable magnification of the damping force.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the description of this embodiment, the same components as those in the first embodiment will be designated by the same reference numerals and the description thereof will be omitted, and only the differences will be described.

That is, in the variable damping force type hydraulic shock absorber of this embodiment, as shown in FIGS. 8 to 15, the disc plates 7a, 7b, 7 in which the second expansion-side disc valve 7 is stacked three sheets.
As shown in the plan view in FIG. 9, four orifice holes a are formed in the first-stage disc plate 7a that abuts on the extension side outer seat surface 2e, and the second-stage disc plate 7b is formed. Is formed with four through holes b which communicate with the orifice holes a, respectively, and the expansion side first stage disc valve 6 is composed of two stacked disc plates, and the expansion side third stage disc valve 8 is formed. It is different from the first embodiment in that it is composed of four stacked disc plates. The through hole b may be continuously formed as shown in the modification of FIG. 10. In this case, the outer peripheral annular portion of the second-stage disc plate 7b is located on the first-stage disc plate 7a side. It is necessary to join them together.

Next, among the actions of this embodiment, the generation state of the damping force in the extension stroke will be described according to the piston speed and the stroke position.

(A) Non-variable stroke region (a) Low piston velocity region In the extremely low piston velocity region where the fluid flow rate is small, as shown in FIG. 11, the fluid on the upper chamber A side is in the extension side communicating hole 2
Although it flows into the intermediate chamber C from b through the constant orifice 6a, the first-stage disc plate 7
It passes through the orifice hole a formed in a and flows into the through hole b formed in the intermediate disc plate 7b, and from that position, only the third stage disc plate 7c is opened to flow into the lower chamber B side. . At this time, since the reaction force of the damping force variable spring 12 is in the non-variable stroke region where it does not act on the extension side third stage disc valve 8, the third stage disc plate 7c and the extension side third stage disc valve 8 are separated from each other. A sufficient clearance is secured between them, and when the expansion-side second-stage disc valve 7 is opened, the expansion-side third-stage disc valve 8 does not come into contact with the extension-side third-stage disc valve 8 and its opening is not restricted.

Therefore, the damping force due to the flow resistance of the constant orifice 6a and the orifice hole a and the third-stage disc plate 7c of the second-stage disc valve 7 on the expansion side.
A low damping force due to only the valve opening resistance acts in series, and as a result, as shown in FIG. 16, a very low damping force linear to the piston speed is generated.

Further, in the low piston velocity range, which is a little higher than the extremely low piston velocity, the third stage disc plate 7c largely bends as shown in FIG. Abut on the third stage disc valve 8.

Therefore, the resistance due to the reaction force of the expansion side third stage disc valve 8 is added to the valve opening resistance of the third stage disc plate 7c itself, and as a result, as shown in FIG. Generate.

(B) Medium Piston Velocity Range In the medium piston velocity range in which the speed is further increased from the low piston velocity, as shown in FIG. 13, in addition to the third stage disc plate 7c, the fluid flow rate increases. , Extension side 1
The fluid is circulated by opening the stage disc valve 6 and the first and second stage disc plates 7a and 7b. Therefore, the first and second stage disc plates 7a, 7b
The valve opening resistance of is also added, and a higher damping force is generated.

(C) High Piston Velocity Range In the medium piston velocity range, which is higher than the low piston velocity, the fluid flow rate increases, and as shown in FIG. 14, the first and second stage disc plates 7a,
The deflection amount of 7b increases and the third stage disc plate 7c
The three disc plates 7a, 7b, 7c
(Increase side second stage disc valve 7) integrated to extend side 3
Abut on the stepped disc valve 8. Therefore, the valve opening resistance of the second expansion-side disc valve 7 due to the reaction force of the third expansion-side disc valve 8 is further increased to generate a higher damping force.

(B) Variable stroke region As shown in FIG. 15, in the variable stroke region where the damping force variable spring 12 is in contact with the spring seat 10, the reaction force of the damping force variable spring 12 is the third step on the extension side. Since it acts on the disc valve 8 and bends the third-stage disc valve 8 upward, the clearance between the third-stage disc plate 7c and the extension-side third-stage disc valve 8 is reduced. The amount of clearance reduction changes depending on the stroke position.
The timing at which the third-stage disc plate 7c bends and comes into contact with the third side disc valve 8 on the extension side is advanced according to the stroke position. As shown in FIG. The generated damping force changes in the increasing direction.

Therefore, in the damping force variable type hydraulic shock absorber of the second embodiment, the same effects as those of the first embodiment can be obtained and the following effects can be obtained. Since only the third-stage disc plate 7c of the second side disc valve 7 on the expansion side is opened first, a very low damping force can be generated in the extremely low piston velocity range.

The damping force characteristics in the low piston speed range can be easily changed by simply changing the diameter of the orifice hole a formed in the first-stage disc plate 7a.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and there are design changes and the like within the scope not departing from the gist of the present invention. Also included in the present invention.

For example, in the embodiment, the constant orifice is formed by notch in the first expansion side disc valve 6, but it may be a through hole, and the inner seat surface 2
It can also be formed by a hole that communicates with the extension side communication hole 2b that is formed at any position of the piston 2 on the d side or between the inner seat surface 2d and the outer seat surface 2e.

The number of disc valves for each stage is not limited to that in the embodiment, and can be arbitrarily selected according to the damping force characteristics.

[0049]

As described above, in the variable damping force type hydraulic shock absorber of the present invention, the expansion side damping valve is the first stage disc valve and the second stage disc valve having a diameter larger than that of the first stage disc valve. And a third-stage disc valve, and a washer is provided on the inner peripheral portion between the disc valves to determine a deflection starting point of each disc valve and to form a clearance allowing a predetermined amount of deflection. At the end face of the piston where the damping valve is provided, the first-stage disc valve closes to close the communication passage, and the second-stage disc valve abuts on the outer periphery of the inner seat face to make the first-stage disc. An outer seat surface that forms an intermediate chamber is formed between the valve and the second-stage disc valve, and the first-stage disc valve is bypassed to provide a continuous space between the communication passage and the intermediate chamber. Constant orifice is formed which communicates, by a reaction force of the variable damping force spring and so as to act on the third stage disk valve,
In the variable stroke range of damping force, it is possible to generate a sufficiently high damping force from the low piston speed range, which makes it possible to ensure steering stability and, in the non-variable stroke range, in the low piston speed range. It can generate a sufficiently low damping force proportional to the piston speed and a high damping force in the medium / high piston speed range. The effect that it becomes possible to satisfy both the stability requirement and the stability requirement is obtained.

Further, in the variable damping force type hydraulic shock absorber according to the present invention, the second-stage expansion side disc valve is composed of three stacked disc plates, and the first-stage disc abutting against the outer seat surface. The plate has an orifice hole, and the second-stage disc plate has a through hole communicating with the orifice hole, so only the third-stage disc plate is opened in the extremely low piston speed range. Therefore, it is possible to generate an even lower damping force.

[Brief description of drawings]

FIG. 1 is a sectional view showing a piston portion of a damping force variable hydraulic shock absorber according to a first embodiment of the present invention.

FIG. 2 is a half cross-sectional view of an essential part for explaining the action of the damping force in the shock absorber in the first embodiment in the non-variable stroke region and the low piston velocity region.

FIG. 3 is a half cross-sectional view of an essential part for explaining the action of the damping force in the variable stroke region and the low piston velocity region in the shock absorber of the first embodiment.

FIG. 4 is a half cross-sectional view of an essential part for explaining the action of the damping force in the shock absorber in the first embodiment in the non-variable stroke region and the high piston velocity region.

FIG. 5 is a half sectional view of an essential part for explaining the action of the damping force in the variable stroke region and the high piston velocity region in the shock absorber of the first embodiment.

FIG. 6 is a characteristic diagram of damping force with respect to piston speed in the shock absorber of the first embodiment.

FIG. 7 is a damping force characteristic diagram with respect to a stroke position in the shock absorber of the first embodiment.

FIG. 8 is a sectional view showing a main part of a damping force variable hydraulic shock absorber according to a second embodiment of the present invention.

FIG. 9 is a plan view showing an expansion side second stage disc valve in the shock absorber of the second embodiment.

FIG. 10 is a plan view showing a modified example of the second expansion-side disc valve in the shock absorber of the second embodiment.

FIG. 11 is a half cross-sectional view of an essential part for explaining the action of the damping force in the shock absorber in the second embodiment in the non-variable stroke region and in the extremely low piston velocity region.

FIG. 12 is a half cross-sectional view of an essential part for explaining the action of the damping force in the second embodiment shock absorber in the non-variable stroke region and the low piston velocity region.

FIG. 13 is a half cross-sectional view of an essential part for explaining the action of the damping force in the shock absorber in the second embodiment in the non-variable stroke region and the medium piston velocity region.

FIG. 14 is a half cross-sectional view of the main part for explaining the action of the damping force in the non-variable stroke region and the high piston velocity region in the shock absorber of the second embodiment.

FIG. 15 is a half cross-sectional view of an essential part for explaining the action of the damping force in the variable stroke region in the shock absorber of the second embodiment.

FIG. 16 is a characteristic diagram of damping force with respect to piston speed in the shock absorber of the second embodiment.

FIG. 17 is a damping force characteristic diagram with respect to a stroke position in the shock absorber of the second embodiment.

[Explanation of symbols]

 A Upper chamber B Lower chamber C Intermediate chamber 1 Cylinder 2 Piston 2b Extension side communication hole (communication passage) 2d Extension side inner seat surface 2e Extension side outer seat surface 4b Washer 4c Washer 4d Extension side first stage disc valve (extension Side damping valve) 6a Constant orifice 7 Second expansion side disc valve (Extension side damping valve) 8 Third extension side disc valve (Extension side damping valve) 12 Damping force variable spring 7a First stage disc plate 7b Second stage Disc plate 7c Third stage disc plate a Orifice hole b Through hole

Claims (2)

[Claims] Claim: What is claimed is: 1. A damping force is generated by restricting fluid flow in a communication passage, which is provided in a piston that defines two chambers inside a cylinder and slides, and communicates between the two chambers during an extension stroke. An extension side damping valve and a damping force variable spring that changes a generated damping force by causing a reaction force corresponding to a stroke position from a predetermined stroke region to act on the extension side damping valve are provided. Second-stage disc valve with a larger diameter than the first-stage disc valve and the first-stage disc valve and 3
The damping valve includes a stepped disc valve, and a washer that determines a deflection starting point of each disc valve and forms a gap that allows a predetermined amount of deflection in the inner peripheral portion between the disc valves. The inner seat surface that closes the communication passage when the first-stage disc valve comes into contact with the end surface of the piston provided with is the first-stage disc valve that comes into contact with the second-stage disc valve at the outer periphery of the inner seat surface. An outer seat surface that forms an intermediate chamber is formed between the second stage disc valve and a constant orifice that bypasses the first stage disc valve and always communicates between the communication passage and the intermediate chamber, A damping force variable type hydraulic shock absorber, wherein a reaction force of the damping force variable spring is made to act on the third stage disc valve. 2. An expansion-side second-stage disc valve is constituted by three stacked disc plates, and an orifice hole is formed in the first-stage disc plate that abuts the outer seat surface, and the second-stage disc plate is formed. The through hole is formed so as to communicate with the orifice hole.
Variable damping force type hydraulic shock absorber described.