JPH11173366A - Shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the control of damping force so far impossible by a conventional shock absorber. SOLUTION: While a piston rod is elongated, hydraulic fluid in an upper chamber flows into a lower chamber through a soft valve bypass passage and a hard valve bypass passage to generate a damping force having a magnitude based on a flow passage area of the soft valve bypass passage. In this way, it becomes possible to control damping force when a relative travel speed of the piston rod for a cylinder main body before a soft valve is opened is very low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shock absorber provided with a damping force control device.

[0002]

2. Description of the Related Art Conventionally, various shock absorbers having a damping force control device have been known. As an example,
“Toyota Soarer New Car Manual”, August 2, 1996, published by Toyota Motor Corporation Service Division, Vol. 2, page 15, (a) Cylinder body and (b) Partitioning the inside of the cylinder body into two chambers. A piston for increasing or decreasing the volume of these two chambers in accordance with the operation of the shock absorber, and a piston rod fixed thereto;
A hard valve that allows the flow of hydraulic fluid from the high-pressure chamber to the low-pressure chamber in a state where the hydraulic pressure difference between the high-pressure chamber of the higher pressure chamber and the low-pressure chamber of the lower pressure is large;
A variable throttle device that controls the flow area of a hard valve bypass passage provided in parallel with the hard valve, and in series with the variable throttle device, provided in parallel with the hard valve, in a state where the hydraulic pressure difference is small, And a damping force control device including a soft valve that allows the flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber.

In the shock absorber described in this manual, the force acting on the shock absorber is small,
When the soft valve is not opened, the hydraulic fluid does not flow, and the relative movement of the piston and the piston rod with respect to the cylinder body is not allowed. When the soft valve is opened, the hydraulic fluid flows through the soft valve and the hard valve bypass passage, and the above-described relative movement is allowed. When the passage area of the hard valve bypass passage is large, the resistance applied to the hydraulic fluid is smaller than when the passage area is small, so that the damping force generated when the relative movement speed of the piston rod to the cylinder body is the same is small. When the force acting on the shock absorber is large and the hard valve is opened, a part of the hydraulic fluid flows through the hard valve. The damping force is controlled as represented by the solid line in FIG.

In the shock absorber described in the above-mentioned manual, the damping force is controlled in this manner. When the relative moving speed is extremely small, the damping force is controlled in a state where the hard valve is opened. It cannot be controlled or controlled without the soft and hard valves open. The control represented by the solid line in FIGS. 5B and 5C cannot be performed.

[0005]

The problem to be solved by the present invention, the means for solving the problem, the function and the effect of the present invention are to provide a damping force control which cannot be performed by a conventional shock absorber. That is. This problem is solved by providing the shock absorber with the following structures. In addition, each mode is divided into items, item numbers are assigned, and if necessary, the numbers of other items are cited and described in the same format as the claims. This is to clarify the possibility of adopting the features described in each section in combination. (1) a cylinder body, a piston for partitioning the interior of the cylinder body into two chambers, and increasing and decreasing the volume of these two chambers with the operation of the shock absorber, and a piston rod fixed thereto; A hard valve that allows a flow of hydraulic fluid from the high-pressure chamber to the low-pressure chamber in a state where the hydraulic pressure difference between the high-pressure chamber having a higher pressure and the low-pressure chamber having a lower pressure is large; And a damping force control device including a soft valve that allows a flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber in a state where the hydraulic pressure difference is small,
The shock absorber according to claim 1, wherein the damping force control device includes a variable throttle device that controls a flow passage area of a liquid passage provided in parallel with the soft valve. In the shock absorber described in this section, for example, when the soft valve and the hard valve are arranged in series, and the hard valve bypass passage parallel to the hard valve is not provided, the hard valve is not opened. In this state, the hydraulic fluid does not flow, and relative movement of the piston and the piston rod with respect to the cylinder body is not allowed. When the hard valve is opened, the hydraulic fluid is caused to flow through the soft valve or a liquid passage provided in parallel with the soft valve (hereinafter, referred to as a soft valve bypass passage) and the hard valve, and relative movement is allowed. You. The ratio between the flow rate of the working fluid passing through the soft valve bypass passage and the flow rate of the working fluid passing through the soft valve is determined according to the flow passage area of the soft valve bypass passage, and the damping force is represented by a solid line in FIG. Is controlled to be As described above, in the shock absorber described in this section, the damping force can be controlled in a state where the hard valve is opened when the relative moving speed is extremely low, and the conventional shock absorber is not suitable. It is possible to perform the control that was possible. (2) The shock absorber according to (1), wherein the hard valve and the soft valve are provided in series with each other. (3) The shock absorber according to (2), wherein the damping force control device further includes a hard valve bypass passage having a throttle function provided in parallel with the hard valve.
In the shock absorber described in this section, since both the soft valve bypass passage and the hard valve bypass passage are provided, even before the soft valve and the hard valve are opened, the hydraulic fluid is supplied to the soft valve bypass passage and the hard valve bypass passage. It can be made to flow through a valve bypass passage. Further, the damping force generated in this state can be controlled by controlling the flow path area of the soft valve bypass passage as shown by the solid line in FIG. The force acting on the shock absorber is small, and the damping force can be controlled even when the soft valve and the hard valve are not opened. The hard valve bypass passage may be provided with a variable throttle device capable of controlling the flow passage area thereof. (4) At least one of the hard valve and the soft valve allows the flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber during both extension and contraction of the piston rod. Features (1) or
The shock absorber according to any one of the above aspects (3) (Claim 2). In the shock absorber described in the above-mentioned manual, the hard valve and the soft valve allow the flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber when the piston rod is being extended or contracted. However, it was not acceptable in the other state.
Therefore, the hard valve and the soft valve both include a valve for extension when allowing the flow of hydraulic fluid during extension and a valve for contraction that allows during the contraction. Could not avoid becoming complicated. On the other hand, in the shock absorber described in this section, at least one of the hard valve and the soft valve allows the flow of the hydraulic fluid both during the extension and the contraction of the piston rod. It is not necessary to include both the use and the use at the time of contraction, and accordingly, the structure of the piston can be simplified. (5) Both the hard valve and the soft valve are in the state where the piston rod is both extended and contracted,
The hard valve and the soft valve allow the flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber, and the hard valve and the soft valve respectively include a portion on one side of the two chambers of the piston and the other chamber. (1)
The shock absorber according to any one of paragraphs (4) to (4). Since the hard valve and the soft valve are respectively provided on both sides of the piston, the size of the piston can be reduced. (6) At least one of the hard valve and the soft valve has a generally annular plate shape, and one surface is
A leaf valve disposed so as to face one of the two chambers, and the opposite surface faces an intermediate liquid passage between the hard valve and the soft valve, and an inner peripheral side of the leaf valve. And a chamber-side seat member that supports one edge of the outer peripheral side from the one chamber side, and the other edge of the inner peripheral side and the outer peripheral side of the leaf valve from the intermediate liquid passage side. (1) including the supporting intermediate sheet member
(5) The shock absorber according to any one of the above (5). A force corresponding to the fluid pressure in one of the high-pressure chamber and the low-pressure chamber acts on one surface of the leaf valve, and a force corresponding to the fluid pressure in the intermediate fluid passage acts on the other surface. When the fluid pressure in the intermediate fluid passage is larger than the fluid pressure in one chamber by a set pressure or more, the edge on one side of the inner peripheral side and the outer peripheral side is pressed against the chamber side sheet member, and the other side portion is pressed. Is bent, and the flow of the hydraulic fluid from the intermediate fluid passage to the one chamber is allowed. Conversely, when the fluid pressure in one of the high-pressure chamber and the low-pressure chamber is larger than the fluid pressure in the intermediate fluid passage by a set pressure or more, the edge on the other side between the inner peripheral side and the outer peripheral side is the intermediate sheet. It is pressed against the member, and the portion on one side is bent to allow the flow of the hydraulic fluid from one chamber to the intermediate fluid passage. Here, since the leaf valve is formed in the shape of an annular plate, the outer peripheral portion bends at the inner peripheral edge as a fulcrum, and the inner peripheral portion flexes at the outer peripheral edge as a fulcrum. In some cases, the outer peripheral side of the former flexes more easily than the inner peripheral side of the latter flexes. Therefore, the easiness of opening the hard valve and the soft valve differs during extension and contraction. Normally, it is desirable to generate a larger damping force during elongation than during contraction. Therefore, it is desirable that the inner peripheral side bend during elongation. Here, the number of leaf valves included in the leaf valve may be one or more, and a plurality of leaf valves may be overlapped in the axial direction. (7) Both the soft valve and the hard valve include a generally annular leaf valve, and the leaf valve of the soft valve is more flexible than the leaf valve of the hard valve. Or the shock absorber according to any one of the above items (6). The leaf valve of the soft valve may have a shape that is more flexible than the leaf valve of the hard valve, or may be made of a material that is more flexible. For example, if the ratio or difference of the outer diameter to the inner diameter of the leaf valve is increased or the thickness is reduced, the leaf valve is easily bent. (8) a cylinder body, a piston for partitioning the interior of the cylinder body into two chambers, and increasing and decreasing the volumes of the two chambers with the operation of the shock absorber, and a piston rod fixed thereto; A hard valve that allows a flow of hydraulic fluid from the high-pressure chamber to the low-pressure chamber in a state where the hydraulic pressure difference between the high-pressure chamber having a higher pressure and the low-pressure chamber having a lower pressure is large; And a damping force control device including a soft valve that allows a flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber in a state where the hydraulic pressure difference is small,
At least one of the hard valve and the soft valve allows the flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber during both extension and contraction of the piston rod, and the damping A force control device for controlling a soft valve bypass passage provided in parallel with the soft valve and a flow path area of the soft valve bypass passage; and a hard valve bypass provided in parallel with the hard valve. A shock absorber comprising at least one of a passage and a high-speed variable throttle device for controlling a passage area of a hard valve bypass passage.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A shock absorber according to an embodiment of the present invention will be described in detail with reference to the drawings.
The shock absorber is one of the components of the suspension. As shown in FIG. 4, the cylinder body 10 of the shock absorber is attached to the wheel member 12 via a bracket, and the piston rod 14 is attached to the vehicle body member 16.
Attached to. Further, a spring 18 is provided between the lower seat 20 attached to the cylinder body 10 and the upper seat 22.

As shown in FIG. 1, the shock absorber includes a piston 28, a damping force control device 30, and the like in addition to the cylinder body 10 and the piston rod 14. The piston rod 14 penetrates through the piston 28, and is fixed at its end by a nut, so that the piston 28 and the piston rod 14 can be integrally moved. The piston 28 is liquid-tight and slidable with respect to the cylinder body 10, and the interior of the cylinder body 10 is partitioned into a lower chamber 34 and an upper chamber 36 by the piston 28.

The damping force control device 30 includes a hard valve 4
0, a soft valve 42, a variable throttle device 44, and the like. A hard valve 40 is provided on the lower chamber side of the piston 28, a soft valve 42 is provided on the upper chamber side, and an intermediate liquid passage 46 is provided between the hard valve 40 and the soft valve 42. Also, the piston rod 14
Is provided with an axial hole 48 extending in the axial direction and having an opening in the lower chamber 34, and a control rod 50 is disposed in the axial hole 48 so as to be relatively rotatable. A plurality of radial holes 52, 54 (see FIG. 2) extending in the radial direction are formed in a portion of the piston rod 14 facing the intermediate liquid passage 46 and a portion corresponding to the upper chamber 36, respectively. An annular groove 55 is formed at a portion where the radial hole 52 intersects. Since the groove 55 has an annular shape, the opening area is kept substantially the same regardless of the relative phase of the control rod 50 to the piston rod 14. A plug 56 having a throttling function is attached to the opening on the lower chamber 34 side of the axial hole 48.

Similarly to the piston rod 14, the control rod 50 is formed with an axial hole 57 extending in the axial direction. The axial hole 57 has a stepped shape with an upper portion having a small diameter portion. Control rod 50
Radial holes 58 and 60 are formed at positions corresponding to the radial holes 52 and 54 of the piston rod 14 to communicate with the axial holes 57, respectively. As shown in FIG. 2, a protrusion 62 is formed on the outer periphery of the upper part of the control rod 50.
0 based on the relative phase to the piston rod 14,
The overlapping state of the protrusion 62 and the radial hole 54 is controlled.

A hard valve bypass is provided by a portion of the axial hole 48 provided in the piston rod 14 and an axial hole 57 provided in the control rod 50 between the intermediate liquid passage 46 and the lower chamber 34, the plug 56 and the like. A passage 64 is configured. In the hard valve bypass passage 64, an orifice is formed by the stopper 56. A portion between the intermediate liquid passage 46 of the axial holes 48 and 57 and the upper chamber 36, the radial holes 60 and 54, and the like form a soft valve bypass passage 66. The flow passage area of the soft valve bypass passage 66 is determined by the radial hole 54 of the piston rod 14 and the protrusion 6 provided on the control rod 50.
2 is controlled based on the overlapping state.

The variable throttle device 44 includes the control rod 50 and a rotating device (not shown) for rotating the control rod 50 relative to the piston rod 14. The rotating device includes an electric motor 68, and the phase of the control rod 50 relative to the piston rod 14 is controlled by the control of the electric motor 68, thereby controlling the flow passage area. The electric motor 68 is controlled by the control device 70.

As shown in FIG. 1, the hard valve 40 includes a valve seat 80 as a chamber-side seat provided below the piston 28, a leaf valve 82 having a generally annular thin plate shape, and a leaf valve 82. And an intermediate seat member 86 provided above an inner peripheral edge of the leaf valve 82. The intermediate side sheet member 86 is brought into contact with the piston 28 via a spacer 88 so as to receive a force applied from the lower chamber 34 to the leaf valve 82 in the direction toward the intermediate liquid passage 46. An annular groove 90 is formed in the piston 28, and the groove 90 is provided with a plurality of liquid passages 91 communicating with the lower chamber 34. The outer peripheral edge of the groove 90 is a valve seat 80. The leaf valve 82 is supported in a state where it is elastically deformed by the valve seat 80 and the intermediate side seat member 86 with its upper surface 92 facing the intermediate liquid passage 46 and its lower surface 94 facing the lower chamber 34. Will be done. The leaf valve 82 is deflected when the pressure difference between the intermediate liquid passage 46 and the lower chamber 34 exceeds a set pressure, and the hard valve 40 is opened.

When the liquid pressure in the lower chamber 34 is higher than the liquid pressure in the intermediate liquid passage 46 by a predetermined pressure or more, the inner peripheral edge of the leaf valve 82 is pressed against the intermediate sheet member 86 and the intermediate sheet member 86 is pressed. The outer peripheral side portion is bent upward with the fulcrum 86 as a fulcrum. When the fluid pressure in the intermediate fluid passage 46 is higher than the fluid pressure in the lower chamber 34 by a set pressure or more, the outer peripheral edge is pressed against the valve seat 80, and the inner peripheral side is bent downward about the valve seat 80 as a fulcrum. Can be Here, the leaf valve 82 is harder to bend at the inner circumferential side than at the outer circumferential side, so that the hard valve 40 is harder to open during extension of the piston rod 14 than during contraction. Desirably, the damping force generated in the shock absorber is greater during extension than during contraction.

The soft valve 42 is similar to the hard valve 40, and includes a valve seat 100, a leaf valve 102,
It includes a positioning member 104, a chamber-side sheet member 106, and the like. The chamber-side sheet member 106 is brought into contact with the piston rod 14 fixed to the piston 28 via the spacer 108. In the present embodiment, the leaf valve 10
2 is larger in the outer circumferential direction than the leaf valve 82 (the ratio of the outer diameter to the inner diameter is larger), and the corresponding groove 110 formed in the piston 28 is
It is larger in the outer circumferential direction. This makes the soft valve 42 easier to open than the hard valve 40. The leaf valve 102 is a leaf valve 8
Even if the difference between the hydraulic pressures acting on both surfaces is small, it can be bent.

The operation of the shock absorber configured as described above will be described with reference to FIG. When the distance between the wheel-side member 12 and the vehicle body-side member 16 increases, an upward force acts on the piston 28 (a force for extending the piston rod 14 acts), and the hydraulic pressure in the upper chamber 36 decreases. It becomes higher than the hydraulic pressure of the lower chamber 34. The hydraulic fluid in the upper chamber 36 flows through the soft valve bypass passage 66 and the hard valve bypass passage 64 to the lower chamber 34.

When the fluid pressure in the upper chamber 36 is higher than the fluid pressure in the intermediate fluid passage 46 by the opening pressure of the soft valve 42, the soft valve 42 is opened, and a part of the hydraulic fluid is supplied to the soft valve 4.
2. It is made to flow through the hard valve bypass passage 64. If the fluid pressure in the intermediate fluid passage 46 becomes higher than the fluid pressure in the lower chamber 34 by the opening pressure of the hard valve 40, the hard valve 40
Is opened. As a result, the hydraulic fluid is supplied to the soft valve 42 or the soft valve bypass passage 66 and the hard valve 40.
Alternatively, it can be made to flow into the lower chamber 34 via the hard valve bypass passage 64. In the soft valve 42, the outer peripheral edge of the leaf valve 102 is pressed against the valve seat 100, and the inner peripheral side is bent about the valve seat 100 as a fulcrum. Is pressed against the valve seat 80,
The inner peripheral side portion is bent with the valve seat 80 as a fulcrum.

In the shock absorber according to the present embodiment, the damping force is controlled by controlling the flow area of the soft valve bypass passage 66 as shown by the solid line in FIG. 5 (c). The operating force acting on the shock absorber is very small, and the damping force can be controlled in a state where neither the soft valve 42 nor the hard valve 40 is opened. As a result, gentle shaking of the vehicle body can be satisfactorily suppressed, and transient posture changes can be suppressed. Control of the damping force is often required when the relative moving speed is very low.

When the distance between the wheel side member 12 and the vehicle body side member 16 becomes small and a downward force acts on the piston 28 (when a force for contracting the piston rod 14 acts), the hydraulic pressure of the lower chamber 34 is reduced. Becomes higher than the hydraulic pressure of the upper chamber 36. The hydraulic fluid in the lower chamber 34 is supplied to the hard valve bypass passage 6.
4 or through the hard valve 40, the soft valve bypass passage 66 or the soft valve 42. In the soft valve 42, the leaf valve 1
02 is bent about the chamber-side seat member 106 as a fulcrum, and similarly in the hard valve 40, the outer circumference of the leaf valve 82 is bent about the intermediate seat member 86 as a fulcrum. The damping force is controlled as during elongation. As described above, the leaf valve 82 and the leaf valve 1
In each of Nos. 02, the case where the inner peripheral side portion is bent and the case where the outer peripheral side portion is bent are less likely to bend in the former case. Therefore, when the relative movement speed of the piston rod 14 with respect to the cylinder body 10 is the same, the resistance applied to the hydraulic fluid during extension is greater than during contraction, and the generated damping force is greater.

As described above, in the shock absorber according to the present embodiment, the soft valve bypass passage 66 is provided.
By controlling the flow passage area, damping force control, which was impossible in a conventional shock absorber, becomes possible. This enables control in a state where the relative movement speed before the soft valve 42 is opened is very small.
Further, the hard valve 40 and the soft valve 42 allow the piston rod 14 to extend and contract during both extension and contraction.
The hard valve 40 and the soft valve 42 are provided on both sides of the piston 28, respectively. As a result, the structure of the piston 28 can be simplified, and the size can be reduced.

In the above embodiment, the flow area of the hard valve bypass passage 64 is fixed, but may be variable. In that case, a control rod that can be relatively rotated may be provided on both the control rod 50 and the piston rod 14, or a spool that can be relatively moved may be provided. When the passage area of the hard valve bypass passage 64 is constant, the control rod can be shortened in the axial direction as shown in FIG. Further, the hard valve bypass passage 64 is not essential. When the hard valve bypass passage 64 is not provided, the damping force is controlled as indicated by a solid line in FIG. The damping force can be controlled in a state where the relative movement speed of the piston rod 14 with respect to the cylinder body 10 is very small and the hard valve 40 is opened. When the hard valve bypass passage 64 is unnecessary,
It may be plugged in either the axial hole 48 of the piston rod 14 or the axial hole 57 of the control rod 50 to close the opening to the lower chamber 34. Further, as shown in FIG. 5D, a shock absorber in which a soft valve and a variable throttle device are provided in parallel, a circuit in which a fixed throttle is provided in series with these, and a shock absorber in which a hard valve is provided in parallel are also used.
The present invention can be applied. In that case, as shown by the solid line in the figure, the damping force can be controlled in a state where the relative movement speed of the piston rod with respect to the cylinder body is very low.

The flow path area of the soft valve bypass passage 66 does not need to be continuously controllable, but may be stepwise controllable or may be switchable between fully open and fully closed. Further, a spool valve may be used instead of the rotary valve. In that case, a motion conversion mechanism that converts the rotation of the electric motor into a linear movement in the axial direction is required.

Further, the shock absorber may have a structure shown in FIGS. In the present embodiment, the flow path area of the soft valve bypass passage 66 is controlled not by controlling the area of the opening with respect to the upper chamber 36 but by controlling the area of the opening with respect to the intermediate liquid passage 46. Can be. In this case, the groove 55 becomes unnecessary, and the groove 140 is formed in the piston rod 14. Also, the piston rod 14 can be attached to the wheel side member, and the cylinder body 10 can be attached to the vehicle body side member. In this case, the hydraulic pressure in the lower chamber becomes higher than the hydraulic pressure in the upper chamber during extension of the piston rod, During contraction, the hydraulic pressure in the upper chamber becomes higher than the hydraulic pressure in the lower chamber. Further, in the above embodiment, the leaf valve 1 of the soft valve 42
02 is made larger in the outer circumferential direction than the leaf valve 82 of the hard valve 40 so that the soft valve 4
2, the leaf valve 102 can be easily opened. However, the leaf valve 102 can be made thinner than the leaf valve 82 or made of a material that is easily bent.
2 can be more easily bent than the leaf valve 82. Further, the hard valve bypass passage 64 may include the groove 55, the radial hole 52, and the like in addition to the axial hole 48, the axial hole 57, and the plug 56.

Although not specifically exemplified, the present invention can be carried out in various modified and improved forms based on the knowledge of those skilled in the art without departing from the scope of the claims.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the vicinity of a piston of a shock absorber according to an embodiment of the present invention.

FIG. 2 is a sectional view of the shock absorber taken along the line II.

FIG. 3 is a diagram showing an operation state of the shock absorber.

FIG. 4 is an external view of the entire shock absorber.

FIG. 5 is a diagram showing damping force characteristics of damping force generated in various shock absorbers.

FIG. 6 is a sectional view showing the vicinity of a piston of a shock absorber according to another embodiment of the present invention.

FIG. 7 is a sectional view showing the vicinity of a piston of a shock absorber according to still another embodiment of the present invention.

FIG. 8 is a sectional view taken along the line II-II of the shock absorber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Cylinder main body 14 Piston rod 28 Piston 30 Damping force control device 40 Hard valve 42 Soft valve 44 Variable throttle device 46 Intermediate liquid passage 50 Control rod 64 Hard valve bypass passage 66 Soft valve bypass passage 80, 100 Valve seat 82, 102 Leaf valve 86,106 sheet member

Claims (2)

[Claims] Claims: 1. A cylinder body, and the interior of the cylinder body is partitioned into two chambers.
A piston for increasing or decreasing the volume of the two chambers and a piston rod fixed thereto, with the operation of the shock absorber, and a high-pressure chamber having a higher pressure and a low-pressure chamber having a lower pressure among the two chambers. A hard valve that allows the flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber in a state where the hydraulic pressure difference is large, and a flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber when the hydraulic pressure difference is small. A damping force control device including an allowable soft valve, wherein the damping force control device includes a variable throttle device that controls a flow passage area of a liquid passage provided in parallel with the soft valve. Shock absorber characterized by the above-mentioned. 2. The system according to claim 1, wherein at least one of the hard valve and the soft valve permits a flow of the hydraulic fluid from the high-pressure chamber to the low-pressure chamber during both extension and contraction of the piston rod. 2. The method according to claim 1, wherein
The shock absorber according to the above.