JPH01220735A - Hydraulic shock absorber - Google Patents

Abstract

PURPOSE:To enable automatic regulation of damping force by arranging a pump circuit responsive to the excitation frequency of a hydraulic shock absorber mechanism in an independent closed circuit of working oil and regulating the throttle opening area of a damping valve with the output pressure from the pump circuit being employed as a pilot pressure. CONSTITUTION:A plunger 25 is displaced through one cycle excitation of a hydraulic shock absorber to cause pumping function thus feeding constant working oil continuously into a small chamber 21, where the response of the plunger 25 is maintained in wide variation range of exciting speed. Consequently, average working oil flow to be fed into the small chamber in unit time is proportional to the frequency of excitation. Oil pressure fed out from the small chamber 21 through an output path, i.e. the pilot pressure, is determined by the quantity of working oil fed from the small chamber 21 and the circulation flow through an orifice 24. The shape of a spool 15 is set such that the throttle opening of the spool valve 14 for receiving the pilot pressure is regulated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hydraulic shock absorber, and more particularly to a frequency-sensitive hydraulic shock absorber suitable for use in a four-vehicle suspension mechanism.

(Prior Art) As is well known, the form of vibration in the axle suspension of a vehicle is a two-degree-of-freedom vibration system, and therefore, due to the J1M dynamic input from the road surface while driving, the vibration frequency of the system is affected in a specific range. Resonant operation occurs.

When the peak time of such resonance operation is defined as a resonance point, there are a primary resonance point that occurs in a relatively low frequency region and a secondary resonance point that occurs in a relatively high frequency region a.

If such common ft operation is allowed to remain as it is.

-The vibration of spring 1 in the frequency range of the next resonance point increases,
The riding comfort during driving will be impaired, and the unsprung vibration will increase in the frequency range of the secondary resonance point, causing the wheels to have poor ground contact, resulting in poor clip performance and poor steering stability.

In order to prevent such a situation, it is desirable to employ an excitation frequency response type damping force adjustable hydraulic shock absorber that changes the vibration damping force in the suspension mechanism in the frequency range near the E resonance point.

Several types of such damping force adjustable hydraulic shock absorbers have already been proposed.

(A8 to be solved by the invention) By the way, among the previously proposed damping force adjustable hydraulic shock absorbers, the means for switching and changing the damping coefficient of the damping valve according to the vibration frequency uses a single frequency plate detection mechanism, an actuator a structure, etc. With the addition of ! The structure of the shock absorber becomes complicated, and there is a disadvantage that the number of assembly steps increases, resulting in decreased productivity and high cost.

In addition, with the method of changing the deflection rigidity of a damping valve consisting of an annular leaf valve, the width of the damping valve is repeatedly deflected with different magnitudes, which can lead to valve breakage and damage due to metal fatigue of the material. This has the disadvantage that it tends to occur easily and lacks stability.

Therefore, in view of the circumstances of the conventional means mentioned above, the unreleased 11J automatically reduces the generated damping force in response to the vibration frequency, which solves all the disadvantages of the conventional means in terms of mechanism and function. ni l! The purpose of the present invention is to provide a hydraulic shock absorber that can be changed in four positions.

(Means for Solving Problem A) According to the present invention, in a cylinder type hydraulic shock absorbing mechanism equipped with a damping valve, the excitation frequency I&← A responsive pump circuit is provided, and the output circuit pressure of the pump circuit is used as a pilot pressure to control the throttle opening of the damping valve [! Change the IO product by 6 Jl'g
! This is achieved by a hydraulic shock absorber configured to do so.

(Function) In other words, the pump circuit that responds to the excitation frequency includes, for example, a plunger that operates in response to the working pressure of the extension side oil chamber or the pressure side oil chamber divided by the piston of the hydraulic cylinder mechanism, and the plunger. It is composed of non-return checks placed in the supply and discharge circuits of the hydraulic oil that moves during operation, and has an excitation frequency that causes the plunger to reciprocate in response to changes in the oil pressure in the oil chamber (viston stroke operation). A predetermined amount of hydraulic fluid is delivered to its output circuit every cycle.

Therefore, even if the hydraulic pressure in the oil chamber changes due to piston movement caused by external vibration of the mechanism, the closed circuit in which the flow path system is independent from the hydraulic circuit of the hydraulic shock absorbing mechanism directly absorbs the effect. The wave path system of the closed circuit, which circulates with a predetermined wave path resistance without being affected by the bacteria, is kept stable. The circuit oil pressure of the output circuit, which receives acid hydraulic oil fed in accordance with the frequency, changes depending on the excitation frequency.

When MWing a damping valve such as a spool valve using this circuit oil pressure as pilot pressure, the spool shape is set so as to change the opening area of the narrow passage in the pilot pressure corresponding movement range of the spool. In the present invention, the hydraulic shock absorbing mechanism consisting of the means indicated by L has an excitation frequency-sensitive damping force that reduces the damping force in a plurality of regions of an arbitrary excitation frequency, and increases the damping force in other areas. Used as an adjustable hydraulic shock absorber (2).

Therefore, when such a hydraulic shock absorber is used in a vehicle suspension system, the hydraulic pressure damper *S has a large M capability in both conventional resonance point frequency ranges to suppress resonance operation in the suspension system.

Also, it lowers the damping force in other frequency ranges to give soft spring performance to the wire system.

(Embodiments) Next, preferred embodiments of the present invention will be described with reference to the attached drawings.

FIG. 1 is a vertical side view of a hydraulic shock absorber showing an embodiment of the present invention, in which a piston 3 supported by a piston rod 2 is fitted into a cylinder 1 so as to be movable, and the piston 3 and the cylinder A free piston 4 is disposed between the piston 5 and the piston 5 to constitute a cylinder-type hydraulic shock absorber a4m.

The inside of the cylinder i is divided by the piston 3 into an expansion side chamber 6 filled with hydraulic oil and an overwhelm chamber 7, and a damping valve mechanism disposed in the piston 3 connects these two chambers 6 and 7. It is connected by 8.

, on the other hand, the piston rod 2 is composed of a hollow shaft body,
An oil chamber 9 and an air chamber I are located in the hollow part closed to the outer end plugging T.
O is formed.

The oil chamber 9 functions as a reservoir chamber in a hydraulic oil circuit for controlling the throttle opening in the damping valve mechanism 8, and a slight volume change in the oil chamber 9 during operation, which will be described later, is reduced to the air weight 0. The pressure in the reservoir chamber is always kept almost constant by absorbing it through compression and expansion.
It is.

Further, the free piston 4 has a pressurized air chamber 11 after its ff, and the change in internal volume of the cylinder due to the movement of the piston rod 2 into and out of the cylinder during the stroke operation of the piston 3 is absorbed by the compression*i of the air chamber 11. There is nothing like that.

The hydraulic fluid circuit having the oil chamber 9 has a flow path system configured as a closed circuit independent of the expansion side chamber 6 and the pressure side chamber 7.

Both chambers 6 and 7 and the hydraulic oil in the closed circuit are placed under high pressure to prevent cavitation from occurring in each flow path during operation.

Next, the specific structure of the damping valve mechanism 8 will be explained with reference to FIG. 2 which shows the damping valve mechanism 8 in an enlarged manner.

In the piston 3, the main boat 12 that opens on the side of the compression side of the piston 3 and the main boat 12 that opens on the side of the compression side of the piston 3 are closed via a spool valve 14, and the spool 15 of the valve 14 is closed. An operating pressure of J[9 is applied to one end face by a passage 17 communicating with the oil chamber 9 together with a weak pressure expansion spring 16 acting in the valve closing direction, and a pilot pressure (described later) is applied to the other end face by a passage 18. There is no way for it to work.

The closed circuit, which is connected to the spool valve 14 by 12t, is from the #oil storage chamber 9 through the passage 19, passes through the small chamber 21 while being prevented from backflow by the check valve 20, and is then connected to another check valve 2.
The other end of the brunge R-25, which has one end facing the small passenger compartment 21, is connected to the expansion side compartment. arranged to receive a room pressure of 9, and
A return spring 26 is attached to the spool 25 in a direction that opposes the chamber pressure.

A pressure holding chamber 28 containing a ring-shaped elastic body 27 made of a porous material is attached to the output passage 23.

With such a configuration, the previous passage 18 and the output passage 28
are in a connected state, and the spool valve i4 operates using the circuit pressure of the output passage 28 as the pay port/seat pressure.

According to the embodiment L, the vibration applied to the hydraulic fII impactor body causes the piston 3 to first shift in the middle direction due to the relative movement between the cylinder l and the piston 3.
At the beginning of M, the chamber pressure of the expansion side chamber 6 increases, and as a result, the plunger 25 receiving this chamber pressure moves to the 211th
．． It descends against the expansion force of the spring 26 and moves to the bottom dead center position.

By this movement, the hydraulic oil in the path of travel at the tip of the plunger 25 is pushed out into the small chamber 21, so the hydraulic oil in the chamber 21 is pressurized, pushing open the check valve z2 and directing it toward the two output passages. sent out.

At this time, the other check valve 2G is closed due to the pressure in the small chamber 2I.

On the other hand, when the piston 3 starts displacing in the forward direction, the pressure in the expansion side chamber 6 decreases, so that the plunger 2S increases the expansion force of the spring 26 and the hydraulic pressure of the closed circuit that acts on it. to move to top dead center.

As a result, the pressure in the small chamber 21 decreases, and the check valve 20
opens to replenish the hydraulic oil in the oil chamber 9 into the small compartment 21. At this time, the passage pressure of the output passage 23 is maintained by the elastic body 2) of the pressure holding chamber 28 attached thereto, so one check valve 22 is closed.

That is, a constant amount of hydraulic oil is always sent into the small compartment 2K due to the pumping action caused by the displacement of the plunger 25 in response to the vibration of the hydraulic shock absorber body for one cycle. The responsiveness of the plunger 25 is maintained over a wide variation range of the excitation speed (excitation frequency variation range), as shown in FIGS. 3(a) and (11).

Therefore, the flow rate of hydraulic oil sent into the small chamber 21 is proportional to the excitation frequency on average per unit time.

On the other hand, the hydraulic oil sent from the small chamber 2I to the two output passages is retained in the pressure holding chamber 28 under compression by the elastic body 27, and the orifice of the through hole is moderately narrowed. The oil is gradually returned to the oil chamber 9 through the oil chamber 24.

As a result, the working oil pressure of the two output passages, that is, the bar f lot pressure in the communication passage 18, is constantly increased by the hydraulic oil sending noise from the small chamber 21 and the jcltIl passing through the orifice 24.
It is uniquely determined by t & shi, and is low in the low excitation speed region (low frequency region) where the amount of delivery per unit time is small, and increases as the excitation speed increases (see (8) in Figure 2). The state will be as shown.

Then, the spool 15 of the spool valve 14 that receives this pilot pressure is displaced as shown in FIG. By using the spool 15 with a shape set in multiple stages, the spool displacement state in the low frequency range (No. 411A) shown in Figure 11),
Displacement shape 8 in the same intermediate frequency range (shown in FIG. 4 (B)), displacement shape 8 in the same high frequency range (shown in FIG. 4 (C) U4), and aa
For each displacement of the displacement shape wB (shown in FIG. 4 (0)) in one frequency range, the aperture aperture area in the melting 29 is calculated as shown in the third diagram (
It can be changed as shown in the book).

Therefore, the main boat 1
As a result of the resistance of the hydraulic oil flow path between the expansion side chamber 6 and the overwhelming chamber 7, which are communicated by the expansion side chamber 6 and the overwhelming chamber 7, which are communicated by the expansion side chamber 6 and the overwhelming chamber 7, being regulated by the aforesaid throttle opening area, the damping force against the movement of the piston 3 of the vibrating knife is 3[' As shown in 4(f), it changes depending on the excitation frequency.

(Effect of IJI) As described above, according to the hydraulic shock absorber of the present invention, the hydraulic shock absorber responds to the excitation frequency to the main body during the closed circuit of the hydraulic oil in which the flow path system is independent from the main body of the loose ##. A pump circuit is provided, and the output circuit pressure of the pump circuit is used as a pilot pressure to variably adjust the aperture area of the damping valve. Therefore, an excitation frequency-sensitive hydraulic system in which the damping force changes depending on the excitation frequency is realized. A shock absorber can be obtained, and by changing the diaphragm aperture area in multiple stages, the damping force can be reduced in a plurality of regions of an arbitrary excitation frequency, and the damping force can be increased in other regions. Since it is also possible to measure the -f function, this can be used in the -vehicle suspension to maintain a large damping force in both conventional resonance point frequency ranges, suppressing the resonance operation in the suspension system, and, By lowering the damping force in other frequency ranges, it is possible to create a shock absorber that exhibits a soft spring effect on the line system.
The structure of the #1 device itself is relatively simple, and it can be constructed with a small number of parts.In addition, the damping force is generated by using the pump circuit output oil pressure, which is driven by the variable angle oil pressure in the cylinder, as pilot pressure. The hydraulic #ll shock absorber of the present invention is extremely useful in practical use, as it can be used without being affected by the orientation of the shock absorber body because it controls M4.

4. rfJ#iI Explanation of Drawings Section tUA shows an embodiment of the hydraulic shock absorber according to the present invention.
Ijfr11 side view, FIG. 2 is a vertical cross-sectional side view showing an enlarged view of the damping valve mechanism portion in the first illustrated embodiment, and FIG. IIJ characteristic diagram,
FIG. 4 is a diagram showing the operating state of the main parts of the mechanism in the hydraulic shock absorber of the present invention.

1 =-・Cylinder 2・Viston rod 3・Piston 4・Free piston 6・
... Rebound side chamber 7 ... Compression side chamber 8 ... Damping valve mechanism 9 ... Oil chamber 10 - ... Air chamber 1
2.13...Main port 14-...Spurb?
15-...Spool 20, 22...Check valve 25-...Plunger-°-Mi representative jf Physician Amano Izumi 1''-21-- Figure 4 (A) <C> CB) CD)

Claims (1)

[Claims] In a cylindrical hydraulic shock absorber with a damping valve,
A pump circuit responsive to the excitation frequency applied to the mechanism is provided in an independent hydraulic oil closed circuit, and the aperture opening area of the damping valve is variably adjusted using the output circuit pressure of the pump circuit as a pilot pressure. A hydraulic shock absorber characterized by