JPH09291964A - Damping valve for hydraulic shock absorber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide compatibility between a riding confort as a vehicle and drive stability by a method wherein the damping force characteristics of a hydraulic shock absorber form two-stage linear characteristics having excellent rise performance and stability without using a two-stage valve structure and a constant orifice. SOLUTION: A damping valve for a hydraulic shock absorber comprises a pressure chamber 12 communicated with the downstream part of a port 8 and surrounded with inner and outer peripheral sheets 28 and 30, which have the same heights as each other, an intermediate support surface 29 disposed in a state to be divided into a plurality of intermediate support surfaces in the pressure chamber 12 at one and the same high level, a leaf valve 16 having a fixed inner periphery and making simultaneous contact with inner and outer peripheral seats 28 and 30 and the intermediate support surface 29 to close the pressure chamber 12, and a spring 26 to energize the leaf valve 16 in a direction in which the pressure chamber 12 is closed. The spring force of the spring 26 is exerted on a leaf valve 16 part positioned facing the intermediate support surface 29 and working oil bends the outer peripheral part of the leaf valve 16 during very low speed of the hydraulic shock absorber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a damping valve for a hydraulic shock absorber used in a vehicle such as an automobile. More specifically, it has a novel structure capable of achieving both riding comfort and steering stability as a vehicle. A damping valve provided.

[0002]

2. Description of the Related Art Conventionally, as a damping valve for a hydraulic shock absorber of this type, for example, the Japanese Patent Application Publication No. 93136 of 1990.
An expansion-side damping valve (piston valve) and a compression-side damping valve (base valve) such as those proposed in Japanese Patent Application Publication No. 195039 and Japanese Patent Application Publication No. 195039 are known.

In the former damping valve, of these damping valves, two sets of valve seat surfaces having different height levels are divided into two stages in series on the downstream side of the port, and the respective valve seat surfaces are constructed in series. A leaf valve is provided on the seat surface, the leaf valve being fixed on the inner circumference to open with the flow of hydraulic oil.

By forming a constant orifice on the surface of the valve seat of the second stage, only the leaf valve of the first stage resists the initial flexural rigidity in the very low speed range of the hydraulic shock absorber where the flow rate of the hydraulic oil is small. The hydraulic oil is made to flow through the second-stage constant orifice while being pushed open, and the rising portion of the damping force characteristic by the second-stage constant orifice is raised by the first-stage leaf valve.

Further, in the low and medium speed range after which the flow rate of the hydraulic oil is increased, the throttling action of the constant orifice reaches its limit and the pressure in the pressurizing chamber between the leaf valves of the first and second stages becomes two. The initial flexural rigidity of the leaf valve at the first stage is exceeded.

As a result, the hydraulic oil flows by pressing and opening the second-stage leaf valve together with the first-stage leaf valve,
A linear damping force characteristic that does not have an orifice characteristic is generated.

On the other hand, in the latter damping valve, the inner pressurizing chamber is formed on the downstream side of the port by being surrounded by the inner peripheral seat surface and the intermediate seat surface of the same height level, and the outer side of the inner pressurizing chamber is formed. Similarly, the outer pressurizing chamber is formed on the same plane as the inner pressurizing chamber while being surrounded by the outer peripheral seat surface and the intermediate seat surface having the same height level.

These inner and outer pressure chambers are closed by a leaf valve having a fixed inner circumference extending from the inner peripheral seat surface to the outer peripheral seat surface, and a spring force is applied to a portion of the leaf valve facing the intermediate seat surface. Is added to increase the initial flexural rigidity of the leaf valve.

The inner pressure chamber and the outer pressure chamber are communicated with each other by a constant orifice formed on the intermediate seat surface, so that the constant orifice is sufficiently throttled in a very low speed range of the hydraulic shock absorber with a small hydraulic oil flow rate. The inner pressure chamber and the outer pressure chamber are kept at the same pressure by utilizing the point of no effect.

As a result, while suppressing the deflection of the leaf valve portion from the inner peripheral seat surface to the intermediate seat surface by the spring force, the working oil is flowed while deflecting only the outer peripheral portion of the leaf valve through the constant orifice, and the orifice characteristic The rising portion is lifted according to the valve characteristics of the leaf valve.

Further, in the low and medium speed range after which the flow rate of the hydraulic oil is increased, the hydraulic oil pressure in the inner pressurizing chamber is increased by the flow resistance of the constant orifice to resist the spring force and bend the entire leaf valve. A linear damping force characteristic is generated by opening the intermediate seat surface as well as the outer peripheral seat surface to flow the hydraulic oil.

Thus, both damping valves set the damping force characteristic of the hydraulic shock absorber over the entire speed range to a damping force characteristic with a good start-up characteristic to achieve both riding comfort and steering stability of the vehicle. It will be.

[0013]

However, even so, in the former damping valve, the first-stage leaf valve and the second-stage leaf valve are arranged in series with each other, and in the very low speed region, the first-stage leaf valve is used. While opening the first leaf valve against the initial flexural rigidity, hydraulic oil is made to flow through the second-stage constant orifice, and in the low and middle speed range, the first- and second-stage leaf valves are separated. It is configured to push open against the initial flexural rigidity to allow hydraulic oil to flow.

Therefore, the damping force characteristics in the very low speed range and the damping force characteristics in the low and middle speed range and thereafter are both affected by the initial flexural rigidity of the leaf valve of the first stage. It is not possible to independently set the damping force characteristics in the low and middle speed range, and to keep the inclination of the damping force characteristics in the low and middle speed range low while raising the damping force characteristics in the very low speed range. This is a very difficult technique.

As a result, if an attempt is made to raise the damping force characteristics in the very low speed range with an emphasis on steering stability, the inclination of the damping force characteristics after the low and middle speed range becomes large, and the riding comfort will be somewhat small. On the other hand, if the inclination of the damping force characteristics in the low and middle speed range is reduced with emphasis on riding comfort, the rising characteristics of the damping force in the very low speed range will decline, and conversely the steering stability will be sacrificed. It has the inconvenience of becoming

Further, in order to prevent the disturbance of the damping force characteristics by smoothing the flow of hydraulic oil through the damping valve having a two-stage structure, the leaf valve of the first stage is compared with the leaf valve of the second stage. It is inevitable to use a valve having a small plate thickness so as to have a small diameter and a small rigidity.

Therefore, the stress on the first-stage leaf valve becomes large, which is disadvantageous in terms of strength, and there is also a disadvantage that the first-stage leaf valve is cracked after a short period of use.

Further, since a step is required between the first-stage leaf valve and the second-stage leaf valve, it is necessary to change the plate thickness of these leaf valves to change the specifications of damping force characteristics. There is also a problem in that it is necessary to change the plate thickness of the spacer or the like sandwiched between the first-stage leaf valve and the second-stage leaf valve to perform step management.

On the other hand, according to the latter damping valve, since the same damping force characteristic is obtained by using a single leaf valve, the above-mentioned problems of the former damping valve are solved. You can

On the other hand, however, in this device, the switching of the damping force characteristics between the very low speed range and the low and middle speed range is performed depending on the throttling resistance of the constant orifice provided on the intermediate seat surface. .

The throttling resistance of the constant orifice at this switching point is such that when the entire leaf valve bends and begins to separate from the intermediate seat surface, an annular gap is created between the leaf valve and the intermediate seat surface, and the throttling resistance rapidly increases. Fall to.

This means that before and after the switching point,
This means that the throttling resistance of the constant orifice changes abruptly and largely, and the hydraulic oil pressures in the inner pressure chamber and the outer pressure chamber fluctuate accordingly.

As a result, there is a problem in that the damping force characteristics near the switching point are disturbed, which not only seriously impairs the steering stability but also deteriorates the riding comfort.

Not only that, the flow resistance (throttle resistance) when the hydraulic oil originally flows through the constant orifice is extremely sensitive to the instantaneous flow rate change of the hydraulic oil and the viscosity change due to the high and low temperature of the hydraulic oil. Fluctuates.

Therefore, not only the switching point of the damping force characteristics after the low speed range and the low and medium speed range, which are switched by the throttle resistance of the constant orifice, easily fluctuate, but especially in the low speed range where the hydraulic oil flows through the constant orifice. There is also a disadvantage that the damping force characteristics are greatly disturbed, and the riding comfort or the steering stability of the vehicle is impaired by the disturbance of the damping force characteristics.

Therefore, an object of the present invention is to provide a stable two-stage linear valve characteristic having a stable rising characteristic without using two sets of leaf valves and a constant orifice for the low speed region and for the low and medium speed regions. It is an object of the present invention to provide a damping valve of a hydraulic shock absorber capable of ensuring both riding comfort and steering stability of a vehicle as damping force characteristics.

[0027]

SUMMARY OF THE INVENTION As described below, the above-mentioned object is to reduce the amount of hydraulic oil in a port communicating between two oil chambers partitioned by the relative expansion and contraction of a cylinder and a piston. In a hydraulic shock absorber equipped with a damping valve that restricts a flow to generate a damping force, the damping valve is connected to a downstream side of a port and is surrounded by an inner peripheral seat surface and an outer peripheral seat surface having the same height level. The pressurizing chamber formed in step 1, the intermediate support surface disposed in the pressurizing chamber at the same height level as the inner and outer peripheral seat surfaces, and the inner and outer peripheral seat surface and the intermediate support surface are simultaneously contacted to form the pressurizing chamber. A leaf valve with a fixed inner circumference arranged so as to close it, and a spring force that assists the initial flexural rigidity of the leaf valve is applied to the portion of the leaf valve facing the intermediate support surface to close the pressurizing chamber. Constructed with a biasing spring It is achieved by.

Further, the purpose is to reduce the flow of the working oil in the port communicating between the two oil chambers divided by the relative expansion and contraction of the cylinder and the piston to generate a damping force. In a hydraulic shock absorber provided with a valve, the damping valve communicates with the downstream side of the port and is formed by being surrounded by an outer peripheral seat surface and an intermediate seat surface having the same height level, and an intermediate seat surface. The inner pressurizing chamber, which is formed by being surrounded by the intermediate seating surface and the inner peripheral seating surface at the same height level inside the outer pressurizing chamber, is in contact with the inner and outer peripheral seating surfaces and the intermediate seating surface at the same time. The leaf valve with a fixed inner circumference arranged to block both the inner and outer pressure chambers and the outer portion of the leaf valve facing the intermediate seat surface by applying a spring force to assist the initial flexural rigidity of the leaf valve. Pressure chamber and inner pressure chamber Also achieved by constructing in the spring for biasing the leaf valve in a direction to close together while isolating.

That is, with the above-mentioned structure, the hydraulic oil flowing into the pressurizing chamber or the outer pressurizing chamber through the port as the hydraulic shock absorber expands and contracts is operated in the pressurizing chamber or the outer pressurizing chamber. To bend the leaf valve to generate a damping force and try to flow between the two oil chambers.

In this case, when the hydraulic shock absorber expands and contracts in a very low speed range and has a small flow rate of hydraulic oil, the hydraulic oil pressure applied to the pressurizing chamber or the outer pressurizing chamber due to the deflection resistance of the leaf valve is It is relatively low, and with the hydraulic fluid pressure, the leaf valve cannot be pushed open all the way against the spring force.

As a result, the hydraulic oil flowing into the pressurizing chamber or the outer pressurizing chamber flows by deflecting only the outer peripheral portion without deflecting the entire leaf valve, pushing the leaf valve in a state where the spring constant is high. It flows while opening.

As a result, the damping force generated in the very low speed range is
It is a linear damping force characteristic with a stable valve characteristic having a good rising characteristic.

On the other hand, the hydraulic oil pressure applied to the pressurizing chamber or the external pressurizing chamber is generated when the outer peripheral portion of the leaf valve is deflected as the hydraulic oil flow rate increases due to the increase in the expansion / contraction speed of the hydraulic shock absorber. It rises as the flow resistance increases.

Therefore, when the expansion / contraction speed of the hydraulic shock absorber increases and enters from the low speed region to the low / medium speed region and thereafter, the leaf valve is initially deflected by the increased hydraulic oil pressure in the pressurizing chamber or the outer pressurizing chamber. And will be pushed open against the spring force for assisting.

Therefore, the leaf valve starts to flex as a whole with the outer peripheral edge of the inner peripheral seat surface, which is the fixed portion, as a fulcrum, or at the same time, the leaf valve is opened between the intermediate seat surface and the inside of the outer pressurizing chamber. The hydraulic oil pressure is transmitted to the inner pressure chamber, and the entire pressure receiving surface of the leaf valve is enlarged and flexed.

In this way, the leaf valve bends over the whole and begins to flow the hydraulic oil, so that the damping force generated at low and medium speeds is a linear damping force characteristic with a stable valve characteristic with a small inclination.

As described above, unlike the above-mentioned conventional example, without using two sets of leaf valves and constant orifices for the very low speed region and for the low and middle speed regions, a stable rising characteristic is obtained in the very low speed region. As a linear damping force characteristic of the valve characteristic and a stable linear valve damping characteristic of the valve characteristic with a small inclination in the low and middle speed range, the riding comfort and the steering stability of the vehicle are improved together.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. The present invention is also applicable to a piston valve of a single-cylinder type hydraulic shock absorber, and is similar to the conventional example described above. In addition, it can be directly applied to the piston valve and the base valve of the double cylinder type hydraulic shock absorber.

Therefore, here, only the case where it is applied to the piston valve used as the expansion side damping valve in various types of hydraulic shock absorbers will be described, and the other description will be omitted.

FIG. 1 is a vertical cross-sectional view showing only the piston portion of the hydraulic shock absorber.
Inside of the, the piston 3 attached to the piston rod 2
Is slidably fitted through a piston ring 4 provided on the outer circumference, and the interior of the cylinder 1 is partitioned by the piston 3 into an upper oil chamber 5 and a lower oil chamber 6.

The piston 3 is formed with a plurality of pressure side ports 7 and a plurality of expansion side ports 8 respectively.
The compression side port 7 and the extension side port 8 extend in the vertical direction along the axis of the piston 3.

The upper end of the pressure side port 7 is opened to the annular pressure side pressurizing chamber 9 formed on the upper surface of the piston 3, and the lower end is a gap formed by reducing the diameter of the lower outer peripheral surface of the piston 3. The oil passage 10 leads to the lower oil chamber 6.

On the other hand, the upper end of the expansion side port 8 is also separated from the pressure side pressurizing chamber 9 on the upper surface of the piston 3 and is arranged inwardly concentrically with the expansion side annular groove 1 formed therein.
1, and the lower end communicates with the expansion side pressurizing chamber 12 formed by partially recessing the lower surface of the piston 3.

In this way, the upper oil chamber 5 and the lower oil chamber 6 in the cylinder 1 defined by the piston 3 are communicated with each other by the pressure side port 7 and the extension side port 8, respectively.

On the other hand, on the upper surface of the piston 3, the compression side damping valve 13 is covered so as to cover the compression side pressurizing chamber 9 and the expansion side annular groove 11.
And a leaf valve 16 that covers the expansion side pressurizing chamber 12 and constitutes an expansion side damping valve 15 is provided on the lower surface side.

The leaf valves 14 and 16 are fitted together with the piston 3 into the spigot portion 2a of the piston rod 2, and fixed by a piston nut 17 screwed to the lower end of the spigot portion 2a.

In the above, the upper surface of the leaf valve 14 and the step portion 2 of the piston rod 2 in the compression side damping valve 13 are arranged.
A spacer 19, a leaf spring 20 and a valve stopper 21 are sandwiched between the b and b.

As a result, the leaf valve 14 is constructed as a leaf valve structure in which the inner circumference is fixed, and is pressed against the upper surface of the piston 3 by the spring force of the leaf spring 20 to pressurize the downstream side of the pressure side port 7. The chamber 9 will be closed.

However, depending on the above, the leaf valve 14 of the compression side damping valve 13 also closes the annular groove 11 on the upstream side of the expansion side port 8.

Therefore, in order to prevent this, an oil hole 22 is formed in the portion of the leaf valve 14 facing the annular groove 11, and the annular groove 11 is formed by the oil hole 22 and the oil hole 23 formed in the valve stopper 21. It is prevented from being blocked by 14.

On the lower surface of the leaf valve 16 which is the expansion side damping valve 15, the piston nut 17 is sandwiched with the main valve 24 guided by the outer peripheral surface of the piston nut 17.
A coil spring 26 is interposed between the lower end flange portion 18 and the lower end flange portion 18.

Also in this leaf valve 16, the spacer 27 for adjusting the spring force (initial set load) of the coil spring 26 is sandwiched between the leaf valve 16 and the piston nut 17, and the spacer 2
The inner peripheral portion is tightened and fixed by a piston nut 17 through 7.

Thus, the leaf valve 16 is also constructed as a leaf valve structure of which the inner circumference is fixed, and by pressing the leaf valve 16 against the lower surface of the piston 3, the pressurizing chamber downstream of the expansion side port 8 is pressed. Blocking 12

Moreover, in the above, the pressurizing chamber 12 on the downstream side of the expansion side port 8 has an annular inner peripheral seat surface 28 and the inner peripheral seat, as can be seen from FIG. 2 which is a bottom view of the piston 3. An internal gear type recess surrounded by an intermediate support surface 29 extending radially from the surface 28 in the outer peripheral direction at the same height level and an outer peripheral seat surface 30 at the same height level outside thereof. It is formed as.

Then, as shown in FIG. 1, the main valve 24
Coil spring 2 applied to the leaf valve 16 through
The pressing surface 25 of the main valve 24 is arranged so as to face the intermediate support surface 29 on the piston 3 side so that the spring force of 6 acts on the intermediate support surface 29 on the piston 3 side.

As a result, the coil spring 2 described above is
The spring force of 6 presses the leaf valve 16 against the intermediate support surface 29 through the main valve 24, and the spring force assists and increases the initial flexural rigidity of the leaf valve 16.

In this embodiment, the pressurizing chamber 12 is formed as an internal gear type recess by the intermediate support surface 29 extending radially from the inner peripheral seat surface 28. It may be provided separately from the seat surface 28.

As described above, the intermediate support surface 29 is formed in the pressurizing chamber 12 which is the downstream side of the expansion side port 8, and the spring force is applied to the leaf valve 16 so as to face the intermediate support surface 29. The point is extremely important in constructing the present invention, as will be understood from the description of the operation described below.

That is, if the cylinder 1 and the piston 3 are relatively displaced in the direction of compressing the upper oil chamber 5 as the hydraulic shock absorber extends, the hydraulic oil pressure in the upper oil chamber 5 rises and at that time. The hydraulic fluid flows toward the expanding lower oil chamber 6.

The hydraulic fluid which has started to flow is first passed through the oil hole 23 of the valve stopper 21 and the compression side damping valve 13
Is applied to the upper surface of the leaf valve 14 in
The leaf valve 14 is held closed without opening.

As a result, the working oil flows from the oil hole 22 of the leaf valve 14 into the pressurizing chamber 12 on the lower surface through the expansion side port 8 of the piston 3 to increase the hydraulic oil pressure in the pressurizing chamber 12. Leaf valve 16 of extension side damping valve 15
Is bent to open the outer peripheral seat surface 30 and try to flow to the lower oil chamber 6 on the downstream side.

At this time, when the extension speed of the hydraulic shock absorber is in a very low speed range, the working oil flow flowing from the upper oil chamber 5 to the lower oil chamber 6 is small, so that the pressurizing chamber 12 on the extending side is provided. The applied hydraulic pressure is relatively low.

Therefore, with the hydraulic oil pressure applied to the pressurizing chamber 12, the leaf valve 16 assisted by the coil spring 26 through the main valve 24 cannot be flexed as a whole.

Therefore, the hydraulic oil flowing into the expansion side pressurizing chamber 12 is deflected only to the outer peripheral portion of the leaf valve 16 with the outer peripheral edge of the main valve 24 as a fulcrum, and then to the lower oil chamber 6 on the downstream side. Flow.

Thus, since the hydraulic oil flows while pushing open the leaf valve 16 in a state where the spring constant is high, the damping force generated during that time is a linear damping force characteristic of stable valve characteristic with a good rising characteristic.

On the other hand, the hydraulic oil pressure generated in the pressurizing chamber 12 on the expansion side is pushed open while bending the outer peripheral portion of the leaf valve 16 as the hydraulic oil flow rate increases due to the increase in the expansion speed of the hydraulic shock absorber. It rises as the flow resistance when flowing increases.

As a result, when the extension speed of the hydraulic shock absorber exceeds the very low speed range and enters the low and middle speed range higher than that, the leaf valve 16 is caused by the hydraulic oil pressure in the pressurizing chamber 12 on the expansion side. Is pushed down against the spring force of the coil spring 26 together with the main valve 24.

As a result, this time, the leaf valve 16 bends all over with the outer peripheral edge of the inner peripheral seat surface 28 which is the fixed portion as a fulcrum to start flowing the hydraulic oil, and the damping force characteristic after low and medium speed is The linear damping force characteristic is a stable valve characteristic with a smaller inclination than the damping force characteristic in the very low speed range.

Thus, without using two sets of leaf valves and constant orifices for the very low speed range and for the low and middle speed range and thereafter, the damping force characteristics are raised in two linear stages of stable valve characteristics with good rising characteristics. Keep the force characteristics,
The riding comfort and the steering stability as a vehicle are improved.

During the compression operation of the hydraulic shock absorber, the working oil in the lower oil chamber 6 is pressurized on the pressure side from the clearance oil passage 10 between the cylinder 1 and the piston 3 through the pressure side port 7 of the piston 3. It flows into the chamber 9.

The hydraulic oil flowing into the pressurizing chamber 9 pushes open the leaf valve 14 of the compression side damping valve 13 against the flexural rigidity and the spring force of the leaf spring 20, and opens the upper oil chamber 5. The flow resistance of the hydraulic oil at that time generates a compression side damping force based on a predetermined damping force characteristic.

Although not shown in the drawing, the lower oil chamber 6 or the lower oil chamber 6 is communicated with respect to the volume change of the cylinder 1 caused by the withdrawal and intrusion of the piston rod 2 accompanying the expansion and contraction operation of the hydraulic shock absorber. This is dealt with by providing a pressure gas chamber defined by a free piston in a part or forming a reservoir chamber.

Next, another embodiment of the present invention will be described with reference to FIG.
And it demonstrates based on FIG.

In this embodiment, the piston 3a
As can be seen from FIG. 4, which is a bottom view of FIG.
8 and the outer peripheral seat surface 30, instead of the intermediate support surface 29 in the previous embodiment, an annular intermediate seat surface 29a having the same height level between the inner peripheral surface and the outer peripheral seat surfaces 28, 30. Is formed.

The intermediate seat surface 29a cooperates with the inner and outer seat surfaces 28 and 30 to form a concentric annular recess between them, and the piston 3a is formed by these recesses.
The outer side pressurizing chamber 12a and the inner side pressurizing chamber 12b, which are separated from each other on the lower surface, are formed.

The annular groove 11 on the upper surface side of the piston 3a is communicated with the outer pressurizing chamber 12a through the expansion side port 8, and the pressing surface 25 of the main valve 24 is arranged so as to face the intermediate seat surface 29a. ing.

The present embodiment is characterized by the above-mentioned points, and in this respect, it is different from the previous embodiment as well as the latter conventional example described at the beginning.

Moreover, even in this case, the hydraulic oil flowing from the upper oil chamber 5 to the lower oil chamber 6 during the extension operation of the hydraulic shock absorber closes the leaf valve 14 of the compression side damping valve 13. While maintaining the above condition, it flows into the outer pressurizing chamber 12a on the lower surface through the expansion side port 8 of the piston 3a.

At this time, while the extension speed of the hydraulic shock absorber is in a very low speed range, the operation oil flow flowing from the upper oil chamber 5 to the lower oil chamber 6 is a small flow rate, and hence the operation is added to the outer pressurizing chamber 12a. Oil pressure is relatively low.

Therefore, the working oil flowing into the outer pressurizing chamber 12a does not bend the leaf valve 16 as a whole while compressing the coil spring 26 through the main valve 24, but the outer peripheral edge of the main valve 24. Is used as a fulcrum to bend the outer peripheral portion of the leaf valve 16 and flow into the lower oil chamber 6.

As a result, the hydraulic oil flows while pushing open the leaf valve 16 in the state where the leaf valve 16 has a high spring constant, and the damping force generated during that time is a linear damping force characteristic of stable valve characteristic with a good rising characteristic.

On the other hand, when the expansion speed of the hydraulic shock absorber increases and enters the low to middle speed range and thereafter, the leaf valve 16 is increased due to the increase of the hydraulic oil pressure in the outer pressurizing chamber 12a accompanying the increase of the expansion speed. Are pushed down against the spring force of the coil spring 26 in the main valve 24.

As a result, the leaf valve 16 begins to flex around the outer peripheral edge of the inner peripheral seat surface 28 as a fulcrum, and the working oil flows out to the lower oil chamber 6 while keeping the flexural rigidity of the leaf valve 16 small. .

At the same time, together with this, the leaf valve 16
Is separated from the intermediate seat surface 29a of the piston 3a,
As a result, the hydraulic oil pressure acting on the outer pressurizing chamber 12a also flows into the inner pressurizing chamber 12b, so that the pressure receiving area is increased and the leaf valve 16 is more easily bent.

In this way, the slope of the damping force characteristic after low and medium speeds is smaller than the slope of the damping force characteristic after low and medium speeds in the above-described embodiment, and the linear damping force characteristic of stable valve characteristics is obtained. I am trying to become.

Therefore, even with this configuration, the damping force characteristic can be made into a stable linear two-stage with a good rising characteristic without using two sets of leaf valves and a constant orifice for the low speed region and for the low and middle speed regions. It is possible to improve the riding comfort and the steering stability of the vehicle while maintaining the damping force characteristics.

The operation of the hydraulic shock absorber in the compression operation in this embodiment and the measure for the change in the volume of the cylinder 1 due to the expansion / contraction operation are the same as in the case of the previous embodiment, and the description thereof will be omitted. Omit it.

In each of the embodiments of the present invention described above, the main valve 24 and the coil spring 26 are used to apply the spring force to the leaf valve 16 of the extension side damping valve 15.

However, instead of the main valve 24 and the coil spring 26, a leaf spring whose inner circumference is fixed is arranged on the lower surface side of the leaf valve 16, and the pressing portion of the leaf spring and the intermediate support surface 29 of the piston 3 or Needless to say, the same applies when the leaf valve 16 is sandwiched between the pressing portion of the leaf spring and the intermediate seat surface 29a of the piston 3a.

Further, as described at the beginning, the expansion side damping valve 15 as the piston valve in each of the above-described embodiments is the pressure side damping valve of the double-cylinder type hydraulic shock absorber based on the description so far. Obviously, it can be directly applied to the base valve.

[0091]

As described above, according to the invention of claim 1, in the very low speed range when the hydraulic shock absorber expands and contracts, only the outer peripheral portion of the leaf valve flexes without compressing the spring, and the damping force. In the low and middle speed range, the leaf valve is flexed as a whole while compressing the spring to generate the damping force.Therefore, two different sets for the low and middle speed ranges are used. Of the vehicle, the linear damping force characteristics of stable valve characteristics with good start-up characteristics are set without using the leaf valves in series and without using a fluid resistance element such as a constant orifice. It is possible to secure both the steering stability and the steering stability.

Further, according to the invention of claim 2, in addition to the above effect, when the hydraulic shock absorber exceeds the very low speed range and enters the low and middle speed range and thereafter, the pressure receiving area of the leaf valve is automatically changed from small to large. The initial setting load of the spring that applies the spring force to the leaf valve can be reduced, and the inclination of the damping force characteristics in the low and middle speed range can be further reduced to further improve the riding comfort of the vehicle. Will be possible.

[Brief description of drawings]

FIG. 1 is a partial vertical front view showing an embodiment in which a damping valve of a hydraulic shock absorber according to the present invention is applied to a piston valve which is an extension side damping valve.

FIG. 2 is a bottom view showing the piston in the same embodiment as seen from the lower surface side.

FIG. 3 is also a partial vertical sectional front view showing another embodiment in which the damping valve of the hydraulic shock absorber according to the present invention is applied to a piston valve which is an expansion side damping valve.

FIG. 4 is a bottom view showing the piston in the same embodiment as seen from the lower surface side.

[Explanation of symbols]

 1 Cylinder 2 Piston Rod 3 Piston 5 Upper Oil Chamber 6 Lower Oil Chamber 7 Pressure Side Port 8 Expansion Side Port 9 Pressure Side Pressure Chamber 12 Expansion Side Pressure Chamber 13 Pressure Side Damping Valve 14 Pressure Side Leaf Valve 15 Expansion Side Damping Valve 16 Expansion-side leaf valve 24 Main valve 25 Main valve pressing surface 26 Coil spring 28 Inner peripheral seat surface 29 Intermediate support surface 29a Intermediate seat surface 30 Outer peripheral seat surface

Claims (2)

[Claims] 1. A damping valve is provided for restricting a flow of hydraulic oil in a port communicating between two oil chambers divided by a relative expansion and contraction of a cylinder and a piston to generate a damping force. In the hydraulic shock absorber, the damping valve communicates with the downstream side of the port and is formed by being surrounded by an inner peripheral seat surface and an outer peripheral seat surface having the same height level, and an inner peripheral surface and an outer peripheral seat surface. An intermediate support surface arranged in the pressure chamber at the same height level, a leaf valve having a fixed inner circumference arranged to simultaneously contact the inner and outer peripheral seat surfaces and the intermediate support surface to block the pressure chamber, and an intermediate support. A hydraulic buffer characterized in that it is constituted by a spring for biasing the leaf valve in a direction of closing the pressurizing chamber by applying a spring force for assisting the initial flexural rigidity of the leaf valve to the portion of the leaf valve facing the surface. Damping valve. 2. A damping valve for restricting a flow of hydraulic oil in a port communicating between two oil chambers, which is defined by relative expansion and contraction of a cylinder and a piston, to generate a damping force. In the hydraulic shock absorber, the damping valve is connected to the downstream side of the port and is separated from the outer pressure chamber formed by being surrounded by the outer peripheral seat surface and the intermediate seat surface having the same height level and the intermediate seat surface. An inner pressure chamber formed by being surrounded by the intermediate seat surface and an inner peripheral seat surface having the same height level inside the outer pressure chamber, and the inner and outer seat surfaces simultaneously contacting the inner and outer peripheral seat surfaces and the intermediate seat surface. A leaf valve having a fixed inner circumference arranged so as to block the pressurizing chamber, and a spring force for assisting the initial flexural rigidity of the leaf valve is applied to the portion of the leaf valve facing the intermediate seat surface to form the outer pressurizing chamber. Together with separating the inner pressure chamber A damping valve for a hydraulic shock absorber, comprising a spring for urging a leaf valve in a closing direction.