JPH08291836A - Hydraulic damping device - Google Patents

Abstract

PURPOSE: To improve riding comfort and operational stability and simplify assembling work by constituting a liquid damping device so as to obtain damping force characteristics according to piston speed. CONSTITUTION: The damping force generating mechanism of a liquid damping device comprises an upper valve mechanism 30 and lower valve mechanism 31, which are provided in a piston body 24. The disk valve 23 of the upper valve mechanism 30 has a hole 23a, which is communicated with a second communication hole 34 and is energized in the direction to clog a first communication hole 34 by a leaf spring 19. The disk valve 23 opens when the pressure in the lower liquid chamber 7 increases together with the sliding operation of a piston 4. A sub-disk valve 21 is provided spacially above the disk valve 23, and when piston speed becomes higher than a specified speed, deforms toward the disk valve 23 to partially clogs each hole 23a of the disk valve 23, increasing damping force.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber, and more particularly to a hydraulic shock absorber having a structure in which the damping force can be varied by changing the opening area of a plurality of holes provided in a disc valve.

[0002]

2. Description of the Related Art Conventionally, there has been known a hydraulic shock absorber as a shock absorber for automobiles, which buffers a shock by a fluid resistance of hydraulic fluid generated by the operation of a piston sliding in a cylinder. This type of hydraulic shock absorber has a structure in which a piston slides in a cylinder due to an increase in load applied to wheels, and an upper part in the cylinder is opened by opening and closing a communication passage provided in the piston that slides in the cylinder. The hydraulic fluid filled in the liquid chamber or the lower liquid chamber moves in the direction opposite to the sliding direction of the piston.

A first communicating passage provided on the outer side in the radial direction and a second communicating passage provided on the inner side of the first communicating passage penetrate through the piston. A disc valve having a leaf valve structure that opens and closes the first communication passage is provided, and a disc valve biased by a coil spring is provided below the piston.

In the hydraulic shock absorber having the above-mentioned structure, when the piston moves at a very low speed when the piston moves in the contraction direction, the minute gap formed between the disc valve and the communication passage serves as an orifice. The damping fluid is generated by the working fluid in the lower liquid chamber passing through the minute gap and the first communication passage and moving to the upper liquid chamber. And
When the piston speed is low, the disc valve opens and the flow rate of the hydraulic fluid passing through the first communication passage increases.

Further, as the piston speed increases,
The damping force will increase at a constant rate. When the piston slides in the extension direction, the valve provided in the lower portion of the piston operates in the opening direction, and the working fluid in the upper liquid chamber moves to the lower liquid chamber through the second communication passage.

In the above hydraulic shock absorber, the damping force can be reduced and the riding comfort can be improved by increasing the flow passage area of the communication passage in order to enhance the riding comfort. However, there arises a problem that steering stability is deteriorated. Therefore, in order to improve the riding comfort and steering stability of the vehicle, it is important to generate a damping force having a magnitude corresponding to the bound / rebound operation of the wheels.

For that reason, in the low speed region where the piston speed is low, the damping force generated is kept small,
In the medium speed range in which the piston speed further increases and moves, the damping force generated is set to increase at a constant rate with respect to the piston speed. When a large load is input and the piston speed increases, the damping force is set to increase rapidly with respect to the piston speed.

By doing so, when the bouncing / rebounding operation of the wheel is slow, the load applied to the piston is relatively small, so the damping force can be reduced and the riding comfort can be improved. Further, when the wheel bouncing / rebounding is fast, a large load acts on the piston, so that the damping force can be increased and the steering stability can be improved.

As a hydraulic shock absorber having such a damping force characteristic, there is one disclosed in, for example, Japanese Utility Model Laid-Open No. 1-176242. In the hydraulic shock absorber disclosed in the publication, a valve mechanism that changes the flow passage area of the second communication passage according to the sliding speed of the piston is provided.

This valve mechanism is composed of a conical valve body inserted into the second communication passage from the upper part of the piston, and a coil spring for urging the valve body in the direction of separating from the second communication passage. A plurality of second communication passages are provided, and the valve mechanism is provided in each of the communication passages.

In the valve mechanism before the piston operates, only the tip portion of the conical valve body is inserted into the second communication passage. However, when the piston speed is high, when the piston rapidly slides in the extension direction and the pressure in the upper liquid chamber increases, the pressure in the upper liquid chamber becomes larger than the spring force of the coil spring, so the conical valve body Moves into the second communication passage.
As a result, the flow passage area formed between the second communication passage and the valve body is reduced, and the damping force is increased.

Further, when the piston speed is low, the pressure in the upper liquid chamber does not suddenly increase, and the conical valve body does not move. As described above, in the hydraulic shock absorber of the above publication, the conical valve element is displaced to adjust the damping force so as to change the flow passage area of the second communication passage according to the sliding speed of the piston. Has become.

[0013]

However, in the above-mentioned conventional hydraulic shock absorber, the flow passage areas of the plurality of communication passages provided in the piston are changed by the valve mechanism including the conical valve body and the coil spring. Therefore, since the damping force is generated according to the piston speed, the number of parts is increased by that much, and the conical valve element and the coil spring must be attached to each of the plurality of communication passages. There is a problem that it takes too much time to work.

Moreover, one piston usually has 4 to 8
Since the individual communication passages are provided, the adjustment work for making the operation timing (operating pressure) of the valve mechanism provided in each communication passage constant is complicated, and extra time is required for the adjustment. . Therefore, there is a problem that the work efficiency in the assembly process is low and the manufacturing cost is high.

The present invention has been made in view of the above points, and by providing a sub disk valve for reducing the opening area of a plurality of holes of the disk valve by the operation of the piston, the damping force characteristic according to the traveling speed is provided. It is an object of the present invention to provide a hydraulic shock absorber in which the above-mentioned advantages are obtained and the assembling work is simplified.

[0016]

In order to solve the above problems, the present invention is characterized by taking the following means. According to the first aspect of the invention, the piston that slides in the cylinder filled with the liquid, the first communication passage that is provided so as to penetrate the piston, and the piston is located inside the first communication passage. A second communication passage provided on the piston, a disc valve for restricting the flow in one direction by opening or closing the first communication passage according to the sliding operation direction of the piston, and the disc valve provided on the disc valve. A hydraulic shock absorber having a plurality of holes communicating with the second communication passage and allowing a flow in the other direction, the opening area of the plurality of holes of the disc valve is reduced by the sliding motion of the piston. The sub disk valve to be operated is arranged at a position separated from the hole of the disk valve by a predetermined distance.

The invention of claim 2 is characterized in that, in the hydraulic shock absorber of claim 1, the damping force characteristic is changed by changing the outer diameter of the sub-disk valve.

Furthermore, the invention of claim 3 is characterized in that, in the hydraulic shock absorber according to claim 1, the damping force characteristic is varied by changing the distance between the sub-disk valve and the disk valve. It is a thing.

[0019]

The above-mentioned means operate as follows. According to the first aspect of the present invention, the sub disk valve, which reduces the opening area of the plurality of holes of the disk valve by the sliding movement of the piston, is provided at a position separated from the holes of the disk valve by a predetermined distance, and thus relatively The damping force can be adjusted with a simple structure, and the riding comfort and steering stability of the vehicle can be improved.

According to the second aspect of the invention, the damping force characteristic is varied by changing the outer diameter of the sub-disc valve, so that the rate of increase of the damping force with respect to the piston speed when the piston speed is high is large. The height can be adjusted. According to the third aspect of the invention, the position of the breaking point of the damping force characteristic with respect to the piston speed can be adjusted by varying the damping force characteristic by changing the distance between the sub disk valve and the disk valve. it can.

[0021]

Embodiments of the present invention will now be described with reference to the drawings. 1 and 2 show a hydraulic shock absorber 1 which is an embodiment of the present invention. In this embodiment, the hydraulic shock absorber 1
As an example, a shock absorber in an automobile suspension mechanism is cited as an example. Incidentally, FIG. 1 shows a hydraulic shock absorber 1.
2 is a vertical cross-sectional view showing the entire structure of FIG. 2, and FIG. 2 is an enlarged vertical cross-sectional view showing the vicinity of the piston 4.

As shown in FIG. 1, the hydraulic shock absorber 1 is roughly composed of an outer cylinder 2, a cylinder 3 as an inner cylinder 3, a piston 4, a piston rod 5, a base valve 10 and the like. The outer cylinder 2 has a cylindrical shape, and a cylindrical cylinder 3 filled with a working fluid (working oil) having a predetermined viscosity is disposed inside the outer cylinder 2. A piston 4 is slidably inserted in the cylinder 3 in the vertical direction (A1 and A2 directions) in the figure. A piston rod 5 extending in the longitudinal direction of the cylinder 3 is connected to the piston 4.

The cylinder 3 is divided into an upper liquid chamber 6 and a lower liquid chamber 7 by inserting the piston 4. Further, the outer diameter of the cylinder 3 is set to be smaller than the inner diameter of the outer cylinder 2, so that an annular space (hereinafter referred to as the reservoir chamber 13) is formed between the outer cylinder 2 and the cylinder 3. The piston 4 is provided with a damping force generating mechanism that generates a damping force. This damping force generating mechanism will be described later for convenience of description.

On the other hand, a lower cap 9 is fixed to the lower end opening 2a of the outer cylinder 2 by welding or the like, and the cylinder 3
A base valve 10 is disposed at the lower end opening of the. In addition, about half of the reservoir chamber 13 is filled with hydraulic fluid, and about half of the reservoir chamber 13 is filled with a gas having a predetermined pressure (for example, nitrogen gas). Further, a rod guide 11 is arranged in the upper opening of the cylinder 3, and a through hole 12 through which the piston rod 5 slidably passes is formed in the center thereof.

A ring nut 14 is provided at the upper end opening of the outer cylinder 2 and is screwed to the screw. The ring nut 14 contacts the upper surface of the rod guide 11 to hold the rod guide 11 and the cylinder 3. Further, an oil seal 15 that seals the outer circumference of the piston rod 5 is interposed between the ring nut 14 and the rod guide 11.

The piston 4 is arranged in a small diameter portion 5a provided at the lower end of the piston rod 5 (in the figure, only the small diameter portion 5a of the piston rod 5 is shown in cross section). Specifically, a screw 5b is formed at the lower end of the small diameter portion 5a, and the washer 18, the leaf spring 19, the spacer 20, the sub disk valve 21, the spacer 22, the disk valve 23, and the small diameter portion 5a are formed. The piston body 24, the disc valve 25, the guide collar 26, and the coil spring 27 are sequentially inserted and finally tightened by a tightening nut 28.

A concave portion is formed on the outer wall of the piston 4, and an annular seal member 29 is arranged in the concave portion. The seal member 29 is configured to be in liquid-tight sliding contact with the inner wall of the cylinder 3, so that the piston 4 is configured to be liquid-tightly slidable in the vertical direction in the cylinder 3.

Next, the structure of the damping force generating mechanism provided on the piston 4 will be described. The damping force generating mechanism is roughly composed of an upper valve mechanism 30 provided at an upper portion of the piston body 24 and a lower valve mechanism 31 provided at a lower portion of the piston body 24. Upper valve mechanism 30
Is composed of the washer 18, the leaf spring 19, the spacer 20, the sub disk valve 21, the spacer 22 and the disk valve 23, and the lower valve mechanism 31 is composed of the disk valve 25, the guide collar 26 and the coil spring 27.

In the piston body 24, a large-diameter mounting hole 32 is formed in the central portion of the piston body 24, and a first communication passage 33 and a second communication passage 34 which are also axially penetrated are formed. In this embodiment, six first communication passages 33 and six second communication passages 34 are provided at equal intervals.

The cross-sectional area of the second communication passage 34 is set larger than that of the first communication passage 33. An annular groove 35 communicating with the first communication passage 33 is provided at the upper end of the piston body 24, and the annular groove 35 is opened and closed by the disc valve 23.

A spacer 22 is interposed between the sub disk valve 21 and the disk valve 23, and the sub disk valve 21 is provided at a position separated from the disk valve 23 by the thickness of the spacer 22. The sub-disc valve 21 is deformed toward the disc valve 23 when the piston speed exceeds a predetermined value.

The disc valve 23 has a leaf valve structure, and is biased by the leaf spring 19 in a direction to close the first communication passage 33. Therefore, the disc valve 23
The valve opening operation is performed when the pressure in the lower liquid chamber 7 increases as the piston 4 slides, and the pressure difference between the upper liquid chamber 6 and the lower liquid chamber 7 becomes a predetermined value or more. In this way, the first communication passage 3
3 is configured to allow only the working fluid to flow from the lower liquid chamber 7 to the upper liquid chamber 6 by the action of the disc valve 23. In addition, the leaf spring 19 is the small diameter portion 5 of the piston rod 5.
It is composed of an annular portion fitted to a and an abutting portion that radially projects from the annular portion and abuts on the disc valve 23.

FIG. 3 is an enlarged plan view showing the disc valve 23 and the sub-disc valve 21. The sub-disc valve 21 has a smaller diameter than the disc valve 23. Further, since the disc valve 23 is provided so as to open and close the first communication passage 33, the second communication passage is provided in a portion facing the second communication passage 34 provided inside the first communication passage 33. A plurality of holes 23 a communicating with 34 are provided.

The holes 23a, together with the second communication passage 34, form a passage for the working fluid in the upper liquid chamber 6 to move to the lower liquid chamber 7, and the same number as the second communication passage 34 (6 in this embodiment). ) It is provided. The outer diameter of the sub disk valve 21 is
Dimension d that does not cover approximately half of the opening area of the hole 23a
Formed in ₁ .

The sub disk valve 21 includes a spacer 22.
Since they are separated from each other by a predetermined distance, when the piston speed is relatively slow, they are separated from the plurality of holes 23a.
When the piston speed is relatively high, the disc valve 2 bends in the direction in which it comes into contact with the disc valve 23, as will be described later.
A part of each hole 23a of No. 3 is closed to restrict the flow of the hydraulic fluid.
In the hydraulic shock absorber 1, since the sub-disk valve 21 is provided, the six holes 23a can be simultaneously switched to the semi-closed state to increase the damping force, so that the number of parts is smaller than that of the conventional structure. It can be used less and the manufacturing cost can be reduced.

The second communication passage 3 of the piston body 24
An annular groove 36 is provided at a lower position where 4 is formed. The annular groove 36 is opened and closed by the disc valve 25 of the lower valve mechanism 31. The disc valve 25 has a leaf valve structure, and is biased by a coil spring 27 in a direction of closing the second communication passage 34.
Therefore, the disc valve 25 opens when the pressure in the upper liquid chamber 6 increases as the piston 4 slides and the pressure difference between the upper liquid chamber 6 and the lower liquid chamber 7 becomes a predetermined value or more. . In this way, the second communication passage 34 is connected to the disc valve 25.
By the action of, the working fluid is allowed to flow only from the upper liquid chamber 6 to the lower liquid chamber 7.

Subsequently, the hydraulic buffer device 1 having the above-mentioned configuration.
The operation in the contraction stroke (stroke in which the piston 4 moves in the A1 direction) will be described with reference to FIG. FIG. 4 is a vertical cross-sectional view showing an operating state when the load applied to the wheel when passing through the step increases and the piston 4 slides in the A1 direction.

When the piston 4 slides in the A1 direction, the disc valve 23 of the upper valve mechanism 30 flexes and opens in a direction away from the annular groove 35 as the pressure of the lower liquid chamber 7 increases. Therefore, the hydraulic fluid in the lower liquid chamber 7 passes through the first communication passage 33 and moves to the upper liquid chamber 6. As a result, a damping force with respect to the contraction process is generated.

Next, regarding the operation of the hydraulic shock absorber 1 in the extension stroke (the stroke in which the piston 4 moves in the A2 direction),
This will be described with reference to FIG. FIG. 5 is a longitudinal sectional view showing an operating state when the piston 4 slides in the A2 direction. When the piston 4 slides in the A2 direction, the disc valve 25 of the lower valve mechanism 31 flexes and opens in a direction away from the annular groove 36 as the pressure of the upper liquid chamber 6 increases. For example, when the piston velocity when the piston 4 slides in the A2 direction is very low, the disc valve 25 slightly opens to form a minute gap around the annular groove 36.

A small amount of hydraulic fluid passes through a plurality of holes 23a provided in the disc valve 23 of the upper valve mechanism 30 and the second communication passage 34 through the minute gap, and then from the upper liquid chamber 6 to the lower liquid chamber 7. Moving. When this piston speed is low, it has a state of having orifice characteristics, and is hereinafter referred to as a "low speed region".

When the piston speed is increased, the disc valve 25 is largely bent as shown in FIG. 5, and the working fluid moving from the upper liquid chamber 6 to the lower liquid chamber 7 is increased. As a result, the damping force is suppressed to a low level and the riding comfort is improved. In this state, the load applied to the wheels does not increase so much, the piston speed becomes medium speed, and is hereinafter referred to as "medium speed region".

Further, when a large load is input, the piston speed further increases and the pressure difference between the upper liquid chamber 6 and the lower liquid chamber 7 increases. Therefore, the sub-disk valve 21 of the upper valve mechanism 30 bends so that the peripheral edge thereof comes into contact with the disk valve 23 due to the flow of the hydraulic fluid caused by the pressure difference.

Since the sub disk valve 21 is formed to have a size that covers approximately half the opening area of each hole 23a of the disk valve 23 as shown in the plan view of FIG. When is deformed toward the disc valve 23, almost half of the opening area of the six holes 23a provided in the disc valve 23 are simultaneously closed. This significantly reduces the flow passage area through which the hydraulic fluid can pass.

As described above, only by providing the sub-disc valve 21 above the disc valve 23, all the holes 23a provided in the disc valve 23 can be switched to the semi-closed state as the piston speed increases. As a result, the upper liquid chamber 6 passes through the hole 23a and the second communication passage 34.
The flow velocity (flow rate) of the hydraulic fluid moving from the lower liquid chamber 7 to the lower liquid chamber 7 is narrowed. That is, when the movement amount of the hydraulic fluid is reduced by the action of the sub-disk valve 21, the damping force increases,
The steering stability of the vehicle can be improved. When the sub-disk valve 21 throttles each hole 23a of the disk valve 23 in the semi-closed state in this way, the piston speed is higher, which is hereinafter referred to as a "high speed region".

FIG. 6 shows damping force characteristics when the hydraulic shock absorber 1 according to this embodiment operates in the extending direction. In the figure, the horizontal axis represents the piston speed, and the vertical axis represents the generated damping force. Further, a change point at which the orifice characteristic is switched to the valve characteristic is indicated by v ₁ in the figure, and a break point at which the piston speed is changed from the medium speed region to the high speed region is indicated by v ₂ in the drawing.

In the hydraulic shock absorber 1 according to this embodiment, the piston speed is very low as described above, and the disc valve 25 is slightly opened to form the minute gap around the annular groove 36. In, the damping force characteristic shows the orifice characteristic. Further, in the medium speed range where the disc valve 25 is opened, the hydraulic shock absorber 1 exhibits a valve characteristic as a damping force characteristic, so that the damping force exhibits a 2/3 power characteristic with respect to the piston speed. Further, even in a high speed region where the sub-disk valve 21 is deformed to halve the opening area of each hole 23a of the disk valve 23, the hydraulic shock absorber 1 exhibits a port characteristic as a damping force characteristic, and the damping force varies with the piston speed. In contrast, a quadratic curve is shown.

In the hydraulic shock absorber 1 according to the above embodiment, when the piston speed changes from the medium speed range to the high speed range,
The sub disk valve 21 has each hole 2 of the disk valve 23.
Since 3a is narrowed to the semi-closed state, the damping force increases more rapidly than in the medium speed range. As a result, when the load applied to the wheels increases, the piston speed increases and the damping force also increases rapidly, so that the steering stability of the vehicle is improved.

As described above, the point at which the rate of increase of the damping force with respect to the piston speed changes abruptly, that is, the break point at which the piston speed switches from the medium speed region to the high speed region (v _{2 in the} figure).
The steering stability of the vehicle can be improved by increasing the rate of increase of the damping force from the point indicated by.

Next, a modified example of the present invention will be described below. In addition, in the following description of each modified example, FIGS.
The same components as those of the hydraulic shock absorber 1 according to the embodiment described with reference to FIGS. FIG. 7 is an enlarged view of the damping force generating mechanism of the hydraulic shock absorber according to the modification.

In the above embodiment, the sub disk valve 21 has an outer diameter of d ₁ so as to cover an opening area of about half of each hole 23a of the disk valve 23. Here, by changing the outer diameter of the sub disk valve 21 from d ₁ to d ₂ , the sub disk valve 21 can cover most of the holes 23a of the disk valve 23 as shown by the alternate long and short dash line in FIG. . This significantly reduces the flow passage area through which the hydraulic fluid can pass.

When the outer diameter of the sub disk valve 21 is changed from d ₁ to d ₂ as described above, the flow passage area of each hole 23a is decreased and the rate of increase of the damping force is increased in the high speed region described above. That is, in FIG. 6, it is possible to change the damping force increase rate after the break point v ₂ from the solid line I 2 to the broken line II to change the hydraulic shock absorber to a desired damping force characteristic.

As described above, by changing the outer diameter dimension of the sub-disc valve 21, the damping force characteristics in the high speed region can be easily changed, and a plurality of types of sub-disc valves 21 having different outer diameter dimensions are prepared in advance. Since the sub-disk valve 21 having an arbitrary outer diameter is selected and incorporated into the piston 4 by manufacturing, the manufacturing cost can be kept low.

FIG. 8 is an enlarged view showing only the damping force generating mechanism of another modification of the present invention. Sub disk valve 21
A spacer 22 is interposed between the disk valve 23 and the disk valve 23, and the sub disk valve 21 is provided at a position separated from the disk valve 23 by the thickness of the spacer 22. The sub disk valve 21 is a disk valve 23.
Since the hole 23a is deformed to the side and the flow passage area of the hole 23a is narrowed, the timing of partially closing each hole 23a of the disk valve 23 varies depending on the thickness t of the spacer 22.

That is, when the separation distance of the sub disk valve 21 from the disk valve 23 is small, the bending point v ₂ shown in FIG. 6 moves to the medium speed region side, and the disk valve 23
If the distance between the sub disk valve 21 and the sub disk valve 21 is large, the bending point v ₂ moves to the high speed region side. Therefore, by changing the thickness t of the spacer 22, the separation distance between the disc valve 23 and the sub-disc valve 21 can be set to an arbitrary distance. For example, as shown in FIG. 8, the spacer 22 is thickened. As a result, the break point v ₂ can be moved to the high speed region side. Therefore,
By preparing in advance a plurality of types of spacers 22 having different thicknesses t, the break point v _{2 at} which the medium speed region is switched to the high speed region can be set at an arbitrary position.

Alternatively, the distance between the disc valve 23 and the sub disc valve 21 may be changed by changing the number of spacers 22 interposed between the disc valve 23 and the sub disc valve 21. Further, in the above embodiment, the sub disk valve 21 formed in the annular shape is described as an example. However, for example, a small hole facing the hole 23a of the disk valve 23 is provided in the sub disk valve 21, and the hole diameter of this small hole is set. The flow rate of the hydraulic fluid flowing through the communication passage 34 may be adjusted by means of.

Further, in the above embodiment, the sub disk valve 21 is deformed so as to reduce the opening areas of all the six holes 23a provided in the disk valve 23 in the high speed region where the piston speed is high. Not limited to this, for example, a notch facing the hole 23a may be provided on the outer circumference of the sub-disk valve 21 to reduce the opening area of 1 to 3 of the 6 holes 23a.

Further, in the above-mentioned embodiment, the piston 4 is provided with the sub disk valve 21 for reducing the opening area of the hole 23a provided in the disk valve 23, but such a structure is also applied to other valve mechanisms. For example, the valve mechanism of the base valve 10 provided at the bottom of the cylinder 3 may be configured to have the sub-disk valve 21 similarly to the upper valve mechanism 30 of the above embodiment.

[0058]

As described above, according to the present invention, the following various effects can be realized. According to the first aspect of the present invention, the sub disk valve, which reduces the opening area of the plurality of holes of the disk valve by the sliding movement of the piston, is provided at a position separated from the holes of the disk valve by a predetermined distance. The number of parts is smaller than that of the one, and the damping force can be adjusted with a relatively simple configuration. Therefore, a troublesome adjustment work is not required in the assembly process, and the assembly can be efficiently performed, so that the manufacturing cost can be suppressed to be low. Further, by the action of the sub-disk valve, the damping force generated when the piston speed is low can be reduced, and the damping force can be increased when the piston speed at which a large load is input is high. The steering stability can be improved.

According to the second aspect of the invention, the damping force characteristic is varied by changing the outer diameter of the sub-disk valve, so that the rate of increase of the damping force with respect to the piston speed when the piston speed is high is large. The height can be adjusted, and the rate of increase of the damping force can be set to an arbitrary gradient.

According to the third aspect of the present invention, the damping force characteristic is changed by changing the distance between the sub-disc valve and the disc valve to adjust the position of the breaking point of the damping force characteristic with respect to the piston speed. It is possible to set the area after the break point where the rate of increase of the damping force rapidly increases to an arbitrary range.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing the overall configuration of a hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is an enlarged vertical cross-sectional view showing a portion near a piston of the hydraulic shock absorber of the present invention.

FIG. 3 is an enlarged plan view showing a disc valve and a sub-disc valve.

FIG. 4 is a vertical cross-sectional view showing an operating state when a load on a wheel increases when passing through a step and a piston slides in a direction A1.

FIG. 5 is a vertical cross-sectional view showing an operating state when the piston slides in the A2 direction.

FIG. 6 shows damping force characteristics when the hydraulic shock absorber operates in the extending direction.

FIG. 7 is an enlarged vertical sectional view showing a damping force generating mechanism of a hydraulic shock absorber according to a modification of the present invention.

FIG. 8 is a longitudinal sectional view showing, in an enlarged manner, only a damping force generating mechanism of another modification of the present invention.

[Explanation of symbols]

 1 Hydraulic Buffer 2 Outer Cylinder 3 Cylinder 4 Piston 5 Piston Rod 6 Upper Liquid Chamber 7 Lower Liquid Chamber 10 Base Case 21 Sub Disc Valve 22 Spacer 23 Disc Valve 24 Piston Body 25 Disc Valve 30 Upper Valve Mechanism 31 Lower Valve Mechanism 33 First communication passage 34 Second communication passage

Claims (3)

[Claims] 1. A piston that slides in a cylinder filled with a liquid, a first communication passage that penetrates through the piston, and the piston that is located inside the first communication passage. A second communication passage provided on the disk valve, a disc valve that opens or closes the first communication passage according to the sliding operation direction of the piston to restrict the flow in one direction, and the disc valve provided on the disc valve. In a hydraulic shock absorber having a plurality of holes communicating with the second communication passage and allowing a flow in the other direction, a sub-valve for reducing the opening area of the plurality of holes of the disc valve by the sliding operation of the piston. A hydraulic shock absorber, wherein the disc valve is arranged at a position separated from the hole of the disc valve by a predetermined distance. 2. The hydraulic shock absorber according to claim 1, wherein damping force characteristics are changed by changing an outer diameter of the sub-disk valve. 3. The hydraulic shock absorber according to claim 1, wherein damping force characteristics are changed by changing a distance between the sub disk valve and the disk valve.