JPH0473440A - Damping device generating device for hydraulic buffer - Google Patents

Abstract

PURPOSE:To facilitate the fine tuning by installing a valve member which relatively shifts for a partitioning wall member in correspondence with the pressure difference at least between two liquid chambers and forming an inclined surface which inclines for the relative shift direction of the valve member at one part of either the partitioning wall member or the valve member. CONSTITUTION:When a shock absorber is compressed, a piston rod 41 relatively shifts, and the working fluid in a liquid chamber 53 is pressurized, and the working fluid in the liquid chamber 53 presses the undersurface 101 of a valve body 100. As the reaction force for the pressing force, a coil spring 97 presses the upper surface 102 of the valve body 100, and when the pressing force of the working liquid exceeds the reaction force of the coil spring, the valve body 100 slidingly moves on the peripheral surface of the hole 44 of a piston 44 according to the magnitude of the differential pressure. Through this sliding, the interval (area) between the circumference of the undersurface 101 of the valve body 100 as partitioning member and the inclined surface 93b of a valve body 90 is opened to the area corresponding to the differential pressure. Accordingly, working fluid flows to a liquid chamber 52 from the liquid chamber 53, and the pressure between the liquid chamber is balanced, and a damping force is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a damping valve for a hydraulic shock absorber, and more particularly to a damping force generating device for a hydraulic shock absorber in which arbitrary damping force characteristics can be set.

[Conventional technology]

It is preferable that the damping valve of the hydraulic shock absorber provides a damping force that can be set depending on the usage condition of the hydraulic shock absorber.

For example, in the case of a shock absorber used in a vehicle suspension, the damping valve generates damping depending on various driving conditions such as when the vehicle is traveling at high speeds, when traveling on rough roads, or when driving normally. Preferably, the force is differentiated into extremely high hard, extremely low soft, or moderately normal.

For example, when driving at high speed on a flat road such as a highway, in order to suppress the minute vibrations that are applied to the vehicle body through the tires,
When the piston speed is in an extremely low speed range on the extension side of the shock absorber, it is preferable that the damping force be larger.

Therefore, there is a known damping force generating device that has been designed to allow the damping force characteristics to be arbitrarily changed, for example, as disclosed in Japanese Utility Model Application Laid-Open No. 63-99046.

As shown in FIG. 11, in this conventional damping force generating device for a hydraulic shock absorber, a piston 12 is slidably inserted into a cylinder 11, and two upper and lower oil chambers 14.
It is divided into 5 sections.

The damping force generator mainly includes the lower part of the piston rod 13, the piston 12, the valve holder 22, and the expansion side leaf valve 18.
It is composed of a valve seat 24, an extension side sub-leaf valve 25, etc.

An extension port 16 is formed in the piston, and an extension side leaf valve 18 is provided on the oil chamber 15 side of the extension port 16.
It is installed so that it can be opened and closed freely.

The valve retainer 22 is provided with an extension port 16a that opens into the upper oil chamber 14, and is installed adjacent to the piston 12, and the extension port 16a communicates the extension port 16 and the oil chamber 14.

The piston rod 13 is formed with a bypass passage 20 that opens into the upper oil chamber 14 and through holes 20a and 20b.

The valve seat 24 is formed with a passage 20C, which is part of a bypass passage that communicates with the through hole 20b and the lower oil chamber 15.
At the lower mouth end of the passage 20C on the downstream side of the bypass, an extension side sub-leaf valve 25 constituting a sub-valve is provided so as to be openable and closable.

At the time of extension, oil in the upper oil chamber 14 or extension ports 16a, 1
6, the expansion side leaf valve 18 is bent and a part of the oil flows into the lower oil chamber 15, and a part of the oil flows from the bypass passage 20a, through the passage 20, through the through hole 20b, and from the passage 20c to the expansion side sub-leaf valve 25. The oil is bent and flows out into the lower oil chamber 15.

[Problem to be invented or solved]

However, because the structure generates damping force by bending the circumference of the annular leaf valve to form a gap in the port, the spring constant of the leaf valve is affected by the damping force generator of each shock absorber. Due to manufacturing errors, variations occur in the amount of deflection (stroke amount) of the leaf valve.

That is, due to variations in the amount of deflection (stroke amount), the error between the obtained damping force and the desired damping force increases, making it difficult to perform fine tuning.

In view of the above-mentioned problems, the present invention makes it possible to change the area of the gap caused by the relative displacement of the valve member and the partition member due to pressure transmission from the working fluid from one point. The objective is to suppress the rate of change in damping force according to the amount of relative displacement to a relatively small value, and to facilitate fine tuning.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a partition member within the cylinder, the partition member partitions two liquid chambers within the cylinder, and the two liquid chambers are connected through ports provided in the partition member. In the hydraulic shock absorber which communicates with each other and is provided with a damping force generating device at a port, the damping force generating device has a valve member that is displaced relative to the partition member according to a pressure difference between at least two liquid chambers, The present invention is characterized in that at least one of the valve members is formed with an inclined surface that is inclined with respect to the direction of relative displacement of the valve members.

[Effect]

According to the above means, since the inclined surface that is inclined with respect to the relative displacement direction of the valve member is formed on a part of at least one of the partition member and the valve member, the valve member can be connected to the partition wall member by pressure transmission from the working fluid. A change in the area of the gap caused by relative displacement occurs. As a result, the rate of change of the damping force according to the amount of relative displacement per unit length becomes a relatively small value.

That is, even if an error occurs in the amount of relative displacement between the valve body and the partition member, the error in the damping force caused by the error can be suppressed to a comparatively small value.

〔Example〕

Hereinafter, the present invention will be described in detail by taking a shock absorber as an example.

FIG. 2 is a diagram schematically showing the overall structure of the shock absorber.

The shock absorber 1 is fixed at the lower end of an external cylinder 50 to a suspension lower arm (not shown) via an axle side member (not shown), and at the upper end of a rod 41 fitted into the external cylinder. It is fixed together with a coil spring to a vehicle body (not shown) via a bearing 31 and a vibration isolating rubber 32.

A piston 40 connected to the lower end of a piston rod 41 is disposed inside the outer cylinder 50 so as to be slidable within the inner cylinder 51 .

A sealing material 42 is interposed on the outer peripheral surface of the piston 40. Therefore, the internal cylinder 51 is divided into a first liquid chamber 52 and a second liquid chamber 53 by the piston 40.

An oil reservoir chamber 60 is formed between the outer cylinder 50 and the inner cylinder 51. This oil reservoir chamber 60 allows oil to flow in and out of the second liquid chamber 53 because the volume of the second liquid chamber 53 changes when the piston 40 slides along the inner peripheral surface of the internal cylinder 51. A flow path 71 is provided between the second liquid chamber 53 and the oil reservoir chamber 60 as an inflow/outflow means.

FIG. 1 is an enlarged sectional view of a main part of a damping force generating device installed on a piston in a shock absorber.

At the center of the piston 40, concentric cylindrical holes 4 of four different diameters, first to fourth, are formed continuously in the sliding direction of the piston.
2.43.44.45 and a tapered portion 46 are formed.

The first hole 42 has the largest diameter, has a threaded groove 47 formed on its circumferential surface, and is threadedly engaged with a thread formed on the lower end circumferential surface of the piston rod 41 .

The second hole 43 is continuous with the first hole 42, has a polished peripheral surface, and is similar to the flat plate portion 9 of the first valve body 90, which will be described later.
The peripheral surface of 1 is slidable.

The third hole 44 has a smaller diameter than the second hole 43, is continuous with the second hole 43, and is capable of sliding on the outer peripheral surface of the second valve body 100 formed in a hollow cylindrical shape. .

The fourth hole 45 has the smallest diameter, and its lower end is the second hole.
The taper portion 46 communicates with the liquid chamber.

The tapered portion 46 is formed of an inclined surface whose diameter becomes larger as it extends toward the second liquid chamber.

Inside the lower end of the piston rod 41, a flow path 48 consisting of a hole having a substantially T-shaped cross section is formed, and when the piston rod 41 is screwed into the piston 40, it faces the second hole and is connected to the first liquid chamber. There are openings in two places in the cross-sectional view.

A flow path 48 facing the second hole 43 of the piston 40
The diameter of the hole is smaller than that of the second hole, and the outer circumferential surface of the flow path at that position is formed by a stopper portion 49 that restricts the sliding of the flat plate portion of the first valve body, which will be described later, or by a piston rod 41. has been done.

Note that the flow path 48 is sufficiently wider than a set orifice of a valve body, which will be described later, and has a cross-sectional area that does not affect the damping force generated by the pulp.

Therefore, the lower end of the flow path 48 has an enlarged diameter so as not to affect the working fluid flowing through the hole provided in the stopper member.

The first valve body 90 is integrally formed with a cylindrical support portion 92 having a smaller diameter than the fourth hole 45, a disk-like flat plate portion 91 on the upper portion thereof, and a valve portion 93 on the lower portion.

The flat plate part 91 has a polished peripheral surface, a port 94 is provided on the flat surface, and is placed inside the second hole 43 so as to be able to slide on the peripheral surface of the second hole 43. second hole 4
The stopper portion 4 of the piston rod 41 is pressed by a coil spring 96 supported at the interface between the third hole 44 and the third hole 44.
I am facing 9.

Further, the flat plate part 9 serves as a support part and supports the third hole 44 and the fourth hole 45 of the second valve body 100 placed in the third hole 44.
A coil spring 97 presses against the boundary surface.

The lower valve portion 93 has a cylinder 93a having a diameter that is in close contact with the hole of the second valve body 100 formed in a hollow cylindrical shape and protrudes from the lower surface of the second valve body 100 into the second liquid chamber 53. , the upper part thereof is an inclined surface 93b such that the cross-sectional area gradually decreases as it extends from the lower surface to the upper surface of the second valve body 100.
is formed.

Next, the action of the shock absorber according to the present invention will be explained using FIGS. 3 and 4.

When a vehicle runs over a convex part while driving, the piston rod is displaced relative to the shock absorber when it is compressed.
The working fluid in the second liquid chamber 53 is pressurized.

Therefore, the pressure in the first liquid chamber 52 becomes lower than the pressure in the second liquid chamber 53.

The working fluid in the second liquid chamber 53 is then transferred to the second valve body 100.
Press the lower surface 101 of.

The coil spring 97 presses the upper surface 102 of the second valve body 100 as a reaction force of the pressing force, and when the pressing force of the working fluid exceeds the reaction force of the coil spring, that is, depending on the magnitude of the differential pressure, The second valve body 100 slides on the circumferential surface of the third hole 44 of the piston 4o.

20 By sliding, a gap (area) between the inner circle of the lower surface 101 of the second valve body 100 serving as a partition wall member and the inclined surface 93b of the first valve body 9o opens to an area corresponding to the differential pressure.

By forming this gap, the working fluid flows from the second liquid chamber 53 to the first liquid chamber 52, the pressure between the liquid chambers becomes balanced, and a damping force is generated at this time (FIG. 3).

During this time, as the piston rod 41 enters into the internal cylinder 51, the sum of the volumes of the first liquid chamber 52 and the second liquid chamber 53 decreases.

Therefore, almost at the same time as the gap is formed, pressure fluctuations caused by the volume reduction in the liquid chamber cause the working fluid to leak into the flow path 7.
1, the fluid is transferred to the oil reservoir chamber 60.

As a result of the above, the pressures in each chamber during compression of the shock absorber 1 become balanced.

Next, when the vehicle gets into or out of a recess while the vehicle is running, that is, when the shock absorber 1 expands or contracts, the piston rod 41 of the shock absorber 1 is displaced relative to the internal cylinder 51. The working fluid in the liquid chamber 52 is pressurized.

Therefore, the pressure in the second liquid chamber 53 is lower than the pressure in the first liquid chamber 52.

Then, the upper surface of the flat plate portion 91 of the first valve body 9o is pressed.

As a reaction force of the pressing force, the coil springs 96 and 97 press the lower surface of the flat plate part 91 of the first valve body 9o, and when the pressing force of the working fluid exceeds the reaction force of the coil spring, that is, a difference occurs. When pressure is generated, the first valve body 9
o slides on the circumferential surface of the second hole 43 of the piston 4°.

By this sliding, the gap (area) between the inner circle of the lower surface of the second valve body 100 and the inclined surface 93b of the first valve body 9o serving as the partition wall member opens to an area corresponding to the differential pressure.

By forming this gap, the working fluid flows from the first liquid chamber 52 to the second liquid chamber 53, and the pressures between the liquid chambers become balanced (FIG. 4).

During this time, as the piston rod 41 advances from inside the internal cylinder 51, the sum of the volumes of the first liquid chamber 52 and the second liquid chamber 53 increases.

Therefore, almost at the same time as the gap is formed, the working fluid flows from the oil reservoir chamber 60 through the flow passage 71 due to the pressure fluctuation caused by the increase in the volume of the liquid chamber, and flows into the second liquid chamber 5.
Move to 3.

From the above, the pressure in each chamber is balanced when the shock absorber is extended.

During expansion and compression, the size of the gap is related to the above-mentioned relationship with the piston speed. Any characteristic can be set depending on the shape of the first valve body, etc.

To explain this using an example when the piston of this embodiment is extended, if the first valve body 90 moves in the direction of the second liquid chamber 53 for a predetermined time due to the pressure of the working fluid, the movement of the valve body 90 Due to the distance ΔL, an open area S is created between the inner circle of the lower surface 101 of the second valve body 100, and the characteristic 1 of the damping force characteristic diagram in FIG. 5 is obtained.

This embodiment is a damping force generation mechanism configured so that the area S between the valves in the middle speed range of a curve that roughly divides the piston speed into a low speed range a, a middle speed range b, and a high speed range C is maximized. Since the increase rate of the area S with respect to the valve stroke is set small, the low speed region a has a sharp rise.

Further, as the vehicle approaches the medium speed range, the slope of the curve tends to decrease upward, and the curve becomes a smooth slope.

After that, due to the gap between the cylindrical support part 92 of the first valve body 90 and the inner circle of the lower surface 101 of the second valve body 100, the damping force becomes a fixed orifice characteristic, so the slope of the curve or the upward direction. It becomes a quadratic curve with an increasing trend.

Note that by forming an arbitrary inclined surface on the first valve body 90, it is possible to obtain curves with various characteristics. for example,
In another embodiment, as shown in FIG. 6 or FIG.
It is also possible to form the inclined surface 93b of the valve body 90 into a curved shape.

In the second embodiment, the first valve body 90c in FIG.
Since the damping force is curved in a concave manner, the characteristic 2 in the damping force characteristic diagram in FIG. 5 can be obtained.

Further, in the third embodiment, the first valve body 90e in FIG. 7 is arranged inside the shock absorber 1 of the first embodiment instead of the first valve body 90, and the inclined surface 93f is Since it is curved in a convex shape, the damping force characteristic shown in FIG. 3 in FIG. 5 can be obtained.

In the above embodiments, the fixed orifice characteristics in the high speed region C were obtained by the fixed orifice between the valve bodies, but other fixed orifices may be provided.

Further, the inner circle of the second valve body is not limited to a circle (for example,
It may have various shapes such as an elliptical shape, but preferably has a shape that matches the circumferential surface of the valve portion having the inclined surface of the first valve body.

In addition, in this embodiment, whether the flow path 71 is used or
If the spring constant of the coil spring 97 that biases the second valve body is made small, a base valve as disclosed in FIG. 1 of Japanese Utility Model Application Publication No. 59-191446, for example, may be used.

Next, FIG. 8 shows a fourth embodiment, and is an enlarged cross-sectional view of the main part of a damping force generating mechanism provided in a base valve in a shock absorber.

A first valve case 40 with a thread 401 formed on its circumferential surface
Inside the center of the piston 0, concentric cylindrical holes having three different diameters, first to third, and a tapered portion 405 are formed continuously in the sliding direction of the piston (not shown).

The circumferential surface of the first hole 402 is polished so that it can slide on the circumferential surface of a flat plate portion 91 of a first valve 90, which will be described later.

The second hole 403 has a smaller diameter than the first hole, is continuous with the first hole, and is capable of sliding on the outer peripheral surface of the second valve body 100 formed in a hollow cylindrical shape.

The third hole 404 has the smallest diameter, and its lower end is connected to a tapered portion 405 that communicates with the oil reservoir chamber 600.

The tapered portion 405 is formed of a slope whose diameter increases as it extends in the direction of the oil reservoir chamber 600.

The second valve case 480 is similar to the first valve case 400.
A color flow path 481 consisting of a concentric hole is formed inside, and a thread 482 is formed on the outer peripheral surface.

The flow path 481 of the second valve case 480
When the threads of the valve case fit into the thread grooves 511 of the inner cylinder 510, they communicate with the first hole 402.

Further, the diameter of the flow path 481 communicating with the first hole 402 of the first valve case 400 is smaller than that of the first hole 402, and the outer circumferential surface of the flow path at that position is Stopper portion 483 that restricts sliding of flat plate portion 91 of body 90
is formed from the second valve case 480.

The first valve body 90 includes a cylindrical support portion 92 having a smaller diameter than the third hole 404, and a disk-like flat plate portion 91 on the top thereof.
A valve portion 93 is integrally formed at the bottom.

The flat plate part 91 has a polished peripheral surface, a port is formed on the flat surface, and is placed inside the first hole 402 so as to be able to slide on the peripheral surface of the first hole 402. Well, the first
The second pulp case 48 is pressed by a coil spring 96 supported at the interface between the hole 402 and the second hole 403.
It is in contact with the stopper part 483 of 0.

Further, the flat plate portion 91 serves as a support surface and the second hole 403
A coil spring 97 presses the second valve body 100 placed on the boundary surface between the second hole and the third hole.

In the lower valve part 93, a cylinder 93a having a diameter that is in close contact with the hole of the second valve element 100 formed in a hollow cylindrical shape protrudes from the lower surface of the second valve element 100 into the oil reservoir chamber 600. An inclined surface 93b is formed in the upper part so that the cross-sectional area gradually decreases as it extends from the lower surface to the upper surface of the second valve body 100.

The shock absorber of this embodiment is a dual-tube type absorber in which a fixed orifice is formed in the piston to communicate between the liquid chambers of the cylinder, and the area of the fixed orifice is determined by the area set between the valve bodies. This is larger than the orifice surface area.

With the above configuration, the operation of the shock absorber will be explained.

When the vehicle runs over a convex portion while running, that is, when the shock absorber is compressed, the piston rod of the shock absorber is relatively displaced to pressurize the working fluid in the second fluid chamber (not shown).

Therefore, the pressure in the first liquid chamber is lower than the pressure in the second liquid chamber.

As a result, the working fluid flows from the second liquid chamber to the first liquid chamber, and the pressure between the liquid chambers becomes balanced.

During this time, as the piston rod penetrates further into the internal cylinder 510, the sum of the volumes of the first liquid chamber and the second liquid chamber decreases.

Therefore, due to the pressure fluctuation caused by the volume reduction of the internal cylinder liquid chamber, the working fluid is pushed upwardly by the coil springs 97 and 96 into the first valve body 9.
0 downward to move the fluid to the oil reservoir chamber 600 (FIG. 9).

From the above, the pressure in each chamber is balanced when the shock absorber is compressed.

When the vehicle gets into or out of a recess while the vehicle is running, the shock absorber piston rod is relatively displaced to pressurize the working fluid in the first fluid chamber (
(not shown).

Therefore, the pressure in the second liquid chamber is lower than the pressure in the first liquid chamber (
Become.

As a result, the working fluid flows from the first liquid chamber to the second liquid chamber, and the pressure between the liquid chambers becomes balanced.

During this time, the piston rod moves further outward from the internal cylinder 510, so that the sum of the volumes of the first liquid chamber and the second liquid chamber increases.

Therefore, due to the pressure fluctuation caused by the increase in the volume of the internal cylinder liquid chamber, the working fluid opens the second valve body 100, which is negatively biased downward by the coil spring 97, upward, and the fluid is transferred from the oil reservoir chamber 600 to the second valve body 100. Move to the liquid chamber and stir (Figure 10).

As a result of the above, the pressures in each chamber during compression of the shock absorber become balanced.

In this series of actions, by setting the orifice area of the base valve to a smaller value than the area of the fixed orifice of the piston, the damping force characteristic curve is set to be smaller than the increase ratio of the surface WS with respect to the valve stroke. There is a sudden rise in the low speed range.

〔Effect of the invention〕

According to the present invention, since the rate of change in damping force according to the amount of relative displacement per unit length is suppressed to a relatively small value, even if an error occurs in the amount of relative displacement between the valve body and the partition member, the It becomes possible to suppress the error in the damping force caused by this to a relatively small value, and it becomes possible to perform fine tuning easily.

Furthermore, by forming the inclined surface of the valve body according to the required damping force characteristic curve, a simple damping force generating device can be installed in the piston or base valve.

Furthermore, in the conventional means of obtaining damping force characteristics by opening and closing two valves with different spring constants using valve opening pressure,
During mass production, there was a problem in which the maximum value of the variation in damping force characteristics, that is, the absolute value width, caused by manufacturing errors in the spring constants of two valves became large.The present invention solves this problem, and even in mass production, it is possible to achieve uniform damping force characteristics. It is possible to maintain performance.

Furthermore, by arbitrarily setting the orifice area using a valve body with a slope, it is possible to freely set the damping force characteristics over the entire piston speed range without requiring parts such as rotary valves as in the past. It becomes possible.

[Brief explanation of drawings]

1 to 4 show a first embodiment of the present invention,
FIG. 2 is a sectional view schematically showing the overall structure of the shock absorber. FIG. 1 is a sectional view showing a damping force generating device, which is a main part of the invention, and is installed in a piston in a shock absorber. FIG. 3 is an operational diagram of FIG. 1 when the shock absorber is compressed. FIG. 4 is an operational diagram of FIG. 1 when the shock absorber is extended. FIG. 5 shows the damping force characteristics. FIG. 6 shows an application example (second embodiment) of the inclined surface of the valve body. FIG. 7 shows another application example (third embodiment) of the inclined surface of the valve body. FIG. 8 is a sectional view showing a damping force generating device (third embodiment) which is a main part of the invention and is installed in a base valve. FIG. 9 is an operational diagram of FIG. 8 when the shock absorber is compressed. FIG. 10 is an operational diagram of FIG. 8 when the shock absorber is compressed. FIG. 11 shows the prior art. Description of symbols Piston 40 Piston rod 41 First hole 42, 402, second hole 43.403 Third hole 44, 404, fourth hole 45 Taper part 46.405 Channel 48, 48L Stopper part 49, 483, internal cylinders 51, 510, first liquid chamber 52, second liquid chamber 53, first valve body 90, 90c, 90e. Flat plate part 91, strut part 92, valve parts 93, 93c, 93e. Cylinder 93a1 Inclined surfaces 93b, 93d, 93f. Port 94, coil spring 96.97,

Claims (1)

[Claims] A partition member is provided in the cylinder, the partition member partitions two liquid chambers in the cylinder, the two liquid chambers communicate through a port provided in the partition member, and a damping force generator is provided in the port. In the pressure shock absorber, the damping force generating device includes a valve member that is displaced relative to the partition member depending on the pressure difference between at least two liquid chambers, and a valve is provided in a portion of at least one of the partition member and the valve member. A damping force generating device for a hydraulic shock absorber, characterized in that an inclined surface is formed that is inclined with respect to a direction of relative displacement of members.