JPS595447B2 - Vehicle hydraulic shock absorber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in hydraulic shock absorbers for vehicles.

More specifically, in a hydraulic shock absorber for a vehicle, the tip of a piston rod of a piston that slides inside a cylinder filled with hydraulic oil communicates via an orifice with one of the chambers of an inner cylinder partitioned by the piston. By providing a small volume gas chamber hermetically partitioned with a metal elastic film such as a metal elastic bellows filled with gas, the damping force is varied depending on the stroke of the piston, thereby improving riding comfort. sex,
The present invention relates to a hydraulic shock absorber for a vehicle that realizes a suspension system for a vehicle with excellent maneuverability.

Hydraulic shock absorbers used in vehicle suspension systems moderately suppress spring T vibrations caused by the road surface, prevent resonance on the springs, and suppress rolling during steering and pitching during acceleration and deceleration. Therefore, it is necessary to increase the damping force to some extent.

On the other hand, when the damping force is set high, vibrations caused by the excessively rough road surface are transmitted to the vehicle body, resulting in disadvantages such as deterioration of ride comfort and increase in road noise. Normally, the damping force of a hydraulic shock absorber is set to satisfy both of these requirements, but it is necessary to suppress vibrations caused by rolling or bouncing, etc., which have a large stroke of the hydraulic shock absorber, and to suppress vibrations caused by road surfaces with a small stroke. It is difficult to sufficiently eliminate both of these problems.

By the way, it is also known that the damping force of a hydraulic shock absorber is made variable depending on the stroke.

This type of apparatus attempts to solve the above problem by connecting the orifice of the oil passage that generates the damping force in the hydraulic shock absorber to orifices of different diameters depending on the stroke of the piston. However, in this type of device, it is necessary to strictly control the accuracy of the diameter and position of the orifice, making it extremely difficult to manufacture and having problems in terms of practicality. The present inventors have created the present invention in order to effectively and simply solve the above-mentioned problems with hydraulic shock absorbers.

An object of the present invention is to provide an orifice to the tip of a piston rod of a piston that slides in an inner cylinder of a double inner and outer cylinder filled with hydraulic oil, into one of the chambers of the inner cylinder partitioned by the piston. To provide a hydraulic shock absorber for a vehicle, in which a small-volume gas chamber is provided which is hermetically divided by a metal elastic film such as a metal elastic bellows filled with gas.

Therefore, the present invention uses a gas chamber to obtain a low damping force (at the beginning of the piston stroke), and achieves both characteristics of the originally specified damping force range over a certain degree of piston stroke and the low damping force range of minute strokes. Both are fully satisfied, ride comfort,
It is possible to obtain a shock absorber with excellent handling stability,
Further, it has the advantage that it has a simple structure, can be manufactured easily and inexpensively, and can be mass-produced.

Further, since the present invention uses compressible gas, there is a smooth connection between the low damping region and the specified damping region, and the present invention has the advantage that stroke dependent characteristics can be freely adjusted by increasing or decreasing the orifice and the gas volume. Next, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 is a vertical cross-sectional view schematically showing the hydraulic shock absorber, and the device 1
Inside. Consisting of double outer cylinders 2 and 3, a piston 4 is slidably fitted into the inner cylinder 2, a piston rod 5 extends above the cylinder and is connected to the vehicle body, and the outer cylinder 3 The lower part is connected to the wheel side.

The piston 4 is provided with a valve, an orifice, etc., and a bottom valve 7 with an orifice is provided on the plug 6 provided at the bottom of the inner and outer cylinders 2 and 3.
The upper ends of the rod guides 8 are connected concentrically to each other, and 9
1 is an oil seal, and 10 is a spring receiver. A reservoir chamber 11 is formed between the inner and outer cylinders 2 and 3, and hydraulic chambers 12 and 13 partitioned by a piston 4 are formed inside the inner cylinder 2, and each chamber is filled with hydraulic oil. .

FIG. 2 shows an enlarged view of the main parts of the device 1.

The inside of the piston 4 has an oil passage 4a, and the upper opening of the oil passage 4a is elastically supported by a spring 14 and has an orifice 15a.
A check valve 15 is provided, and the chambers 12 and 13 are communicated through the oil passage 4a. In the compression stroke, the piston 4 slides toward the bottom valve 7 of the chamber 13, and oil passes through the oil passage of the piston 4, and the oil amount from the orifice of the bottom valve 7 is removed by the amount of oil corresponding to the volume of the piston rod 5 entering the valve. Oil flows out to the chamber 11 side against the
Obtain damping force. A chamber 17 formed by a casing 16 is provided at the tip 5a of the piston rod, and the chamber 17 communicates with the chamber 13 through an orifice 16a formed on the lower surface of the casing 16.

Inside the chamber 17, a metal elastic coating 18 such as a metal bellows formed of phosphor bronze or the like is installed on a holder 16b provided on the upper wall of the casing 16 to form a gas chamber 1 that is hermetically separated from the surroundings.
form 9. The gas chamber 19 contains a gas 19 such as N2 gas.
In addition, in the illustrated example, oil 19b is sealed as a buffering liquid, and the pressure of the gas 19a is set to be approximately the same as the hydraulic oil pressure in the buffering device when it is stationary. Next, its effect,
To explain the effect in detail, the shock absorber 1 operates in a known manner in compression and extension (tension) strokes to obtain hydraulic damping force. By the way, during the compression stroke, oil corresponding to the volume of the rod 5 does not flow out from the bottom valve 7 due to the sliding entry of the piston 4, and the oil pressure in the lower chamber 13 rises, and as is known, the oil pressure in the lower chamber 13 rises at a certain point in the piston stroke. A defined damping force is obtained at the orifice of the valve, which pressure has previously been introduced into the chamber 17 via the orifice 16a and acts on the metal elastic coating 18.

The pressure in the gas chamber 19, which is hermetically divided by this 18, is set to approximately the same pressure as the working oil pressure in the shock absorber when the piston 4 is at rest. Therefore, the gas chamber 19 is compressed by the low oil pressure increase at the beginning of the piston 4's operation, and oil corresponding to the compressive deformation of the gas chamber 19 escapes into the chamber 17, resulting in low damping at the beginning of the piston stroke. Generate force and obtain damping force in the initial stroke. Therefore, hydraulic damping is performed at the beginning of the piston stroke and in the small stroke range, absorbing and damping small bumps in the road surface, and suppressing vibration transmission to the vehicle body. As the piston stroke progresses, when the combined pressure of the maximum pressure in the gas chamber 19 and the elastic force of the metal elastic membrane reaches the set pressure of the bottom valve 7, the bottom valve 7 starts operating, and the hydraulic oil flows through the passage 7a. The damping force flows through the reservoir chamber 11 to generate a specified damping force.

The liquid 19b sealed in the gas chamber 19 protects the film by buffering it when it collides with the surroundings when the film contracts. By the way, as for the volume of the gas chamber 19, it is sufficient that the volume is small enough to correspond to the volume of entry of the rod during the piston stroke corresponding to small bumps in the road surface.

The piston stroke is about 10 mm on a normal road surface, and about 15 mm on a bad road surface, and the piston stroke that requires a high damping force during rolling or bouncing is about 20 mm to 120 mm. Therefore, the volume V1 of the gas chamber, that is, the volume of the pure frame of gas 19a excluding the incompressible liquid 19b in the gas chamber, is given by the diameter of the piston rod being d, and the remaining volume upon compression being ZV-1/I.
Considering the fact that it is desirable to set the value to OV, the volume V can be determined by the following equation.

FIG. 3 shows a modified embodiment in which a low damping force at the beginning of the stroke can be obtained in the tension stroke.

In the drawings, the same elements as in the embodiment described above are given the same reference numerals. Room 17
The gas chamber 19 inside is formed using the lower wall of the casing 116 as a holder, and the upper wall of the casing 116 has an orifice 116a formed therein. Further, since an oil passage 20 that opens into the chamber 12 and opens at the tip of the rod is formed in the rod 5, the chamber 17 communicates with the chamber 12 via the oil passage 20 of the orifice 116a1. In the tension stroke, hydraulic oil corresponding to the effective volume due to the tension of the piston rod 5 first enters the chamber 17 via the oil passage 20 in the same manner as described above, thereby generating a low damping force at the beginning of the stroke.

As is clear from the following description, according to the present invention, a chamber is provided at the tip of the piston rod of the shock absorber and communicates with one of the chambers in the inner cylinder partitioned by the piston, and a metal elastic coating is provided in this chamber. A sealed gas chamber is provided, and a gas of approximately the same pressure as the static hydraulic pressure in the shock absorber is sealed inside, so that the increase in hydraulic pressure at the beginning of the piston stroke is absorbed and attenuated by the compressive deformation of the gas chamber of the metal film, and the pressure is regulated. It is possible to cover the low damping force range before damping force generation.

Therefore, we have created a vehicle hydraulic system that fully satisfies both the characteristics of the low damping force range of the small stroke at the beginning of the piston stroke and the original specified damping force range, and that smoothly connects both characteristics, resulting in excellent ride comfort and handling. A shock absorbing device can be obtained. It is possible to effectively, quickly and reliably suppress vibrations caused by small road surface irregularities at the beginning of the piston stroke before the specified damping force range, which was difficult to solve in the past. By suppressing the vibrations that occur in this area, and combining it with the specified damping force, it is possible to obtain excellent damping performance in the entire area.

In addition, the structure is such that a gas chamber sealed with a metal elastic coating is provided at the tip of the piston rod, and hydraulic pressure is applied to this via an orifice, so it can be easily manufactured without changing the conventional structure of the shock absorber. Since it is made of metal bellows, etc., it has no gas permeability, and its function can be guaranteed over a long period of time.The mass of the moving part is small, and since it is an elastic body, it has good responsiveness, and the above effects are ensured. It has many advantages, such as the fact that it can be guaranteed, and even if gas escapes or the metal coating is damaged, there will be no effect on the original specified damping force, making it preferable to use fail-safe functional soil.

Furthermore, the low damping force at the beginning of the stroke can be freely adjusted by increasing or decreasing the volume of the gas in the gas chamber and the orifice that guides hydraulic pressure into the gas chamber, and by controlling the amount of oil in the gas chamber within an appropriate range, it is possible to Problems such as inflection points, hammering sounds, and shock vibrations can be avoided, and since the gas volume is small and the airtight type is closed, negative effects caused by temperature changes (changes in posture, changes in the rising characteristics of gas springs) are extremely small. Demonstrate.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a vertical sectional view schematically showing a hydraulic shock absorber, FIG. 2 is an enlarged view of the main parts, and FIG. 3 is a diagram of another embodiment. In the drawing, 2 is an inner cylinder, 3 is an outer cylinder, 4 is a piston, 5 is a piston rod, 7 is a bottom valve, 12 and 13 are working chambers, 16 and 116 are casings, 16a and 116a are orifices, and 17 is a chamber. , 18 is a metal elastic coating, 19 is a gas chamber, 19a is a gas, 19b is a liquid such as oil, and 20 is an oil passage.

Claims (1)

[Scope of Claims] 1. A hydraulic shock absorber for a vehicle comprising a piston supported by a piston rod that slides within a cylinder filled with hydraulic oil, and a valve that operates at a predetermined hydraulic pressure or higher during a compression stroke of the piston, A chamber is provided at the tip of the piston rod that communicates with one of the chambers of the inner cylinder divided by the piston through an orifice, and the chamber is hermetically divided with a metal coating such as a metal elastic bellows filled with gas. A hydraulic shock absorber for a vehicle characterized by having a small volume gas chamber. 2. The hydraulic shock absorber for a vehicle according to claim 1, wherein the gas chamber is sealed together with a liquid.