JP2000240708A - Hydraulic buffer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To generate the predetermined stabilized damping force with a damping valve while eliminating a danger of contamination of the oil with air by communicating a piston side oil chamber with a reservoir arranged in the periphery of a cylinder, and forming the reservoir with a gas chamber separated from the oil chamber communicated with the piston side oil chamber by a diaphragm. SOLUTION: A piston side oil chamber R4 partitioned by a piston 3 in a cylinder 1 is communicated with a reservoir arranged in the periphery of the cylinder 1 through a damping valve 1a arranged inside of the cylinder 1 at a lower end thereof. This reservoir has a diaphragm D in a space formed between the cylinder 1 and an outer cylinder 6 arranged in the periphery of the cylinder 6. In this space, a gas chamber G is partitioned from an oil chamber R, which is communicated with the piston side oil chamber R4 through the damping valve 1a, by the diaphragm D. With this structure, even if the oil is transferred between the piston side oil chamber R4 and the oil chamber R, generation of wave in an oil surface is restricted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber, and more particularly to an improvement of a multi-stage hydraulic shock absorber.

[0002]

2. Description of the Related Art A multi-stage hydraulic shock absorber can have a smaller installation length than a standard hydraulic shock absorber. There is an advantage that the upper end of the shock absorber does not protrude from the rear floor inside the vehicle, that is, the rear floor inside the vehicle can be flattened in the left-right direction and widened.

By the way, in principle, as shown in FIG. 3, a multi-stage type hydraulic shock absorber has a first-stage piston rod 2 which is a second-stage cylinder in a first-stage cylinder 1 as shown in FIG. The second stage piston rod 4 is inserted into the first stage piston rod 2 so that the second stage piston rod 4
Are inserted so as to be able to protrude and retract under the intervention of the piston 5.

[0004] Further, an upper oil chamber R1 and a lower oil chamber R2, which are partitioned by a piston 5 and can communicate with each other via a damping valve 5a disposed in the piston 5, are provided in the first stage piston rod 2. In addition, the cylinder 1 has a rod-side oil chamber R3 and a piston-side oil chamber R4 partitioned by a piston 3.

[0005] The lower oil chamber R2 is
And communicates with the rod-side oil chamber R3 through a passage 2a formed in
It is assumed that the piston-side oil chamber R4 communicates with a reservoir (not shown) disposed on the outer peripheral side of the cylinder 1 through a damping valve 1a disposed inside the lower end of the cylinder 1.

Incidentally, in this conventional example, the reservoir is assumed to be formed in the form of a so-called reservoir chamber, and the cylinder 1 has an outer cylinder 6 on the outer peripheral side thereof, and a gap is formed therebetween. (Not shown), an oil chamber R communicating with the piston side oil chamber R4 via the damping valve 1a in this gap and an oil surface O above the oil chamber. And a gas chamber G provided as a so-called reservoir chamber.

In this conventional example, the upper oil chamber R1, the lower oil chamber R2, and the rod-side oil chamber R3 are cut off from the piston-side oil chamber R4 by the arrangement of the piston 3 so as to form a closed oil chamber space. On the other hand, the cross-sectional area of the piston rod 4 and the cross-sectional area of the rod-side oil chamber R3 are set to be substantially the same.

Therefore, in this hydraulic shock absorber, when the piston rod 4 is protruded and retracted with respect to the piston rod 2 which is a second-stage cylinder, a predetermined damping valve 5a disposed on the piston 5 is used. While the damping force is generated, the inflow and outflow of an amount of oil corresponding to the invading volume integral and the retreating volume integral of the piston rod 4 is expressed in the rod side oil chamber R3.

As a result, the piston rod 2 is
Therefore, a predetermined damping force is also generated by the damping valve 1a disposed between the piston-side oil chamber R4 and the oil chamber R forming the reservoir.

As described above, in the conventional hydraulic shock absorber, when the piston rod 4 is extended and retracted with respect to the piston rod 2, the piston rod 2 is also extended and retracted with respect to the cylinder 1. Therefore, each damping valve 5 is operated under a so-called smooth expansion and contraction operation.
According to a and 1a, a damping force as set can be generated.

[0011]

However, in this type of multi-stage hydraulic shock absorber, including the case of the above-described conventional example, the oil corresponding to the invading volume of the first-stage piston rod 2 during the compression operation. Has a reservoir to secure a place of access, but this reservoir, as described above,
When a so-called reservoir chamber is used, the volume of the gas chamber G is set as large as possible so as not to increase the compression ratio in the gas chamber G.

At this time, if the diameter of the outer cylinder 6 is set to be large while keeping the diameter of the cylinder 1 as it is, a gas chamber G having a large capacity can be secured. Setting a large diameter cannot be said to be a preferable measure.

Therefore, in order to increase the volume of the gas chamber G, the position of the oil surface O is set to a position shown by a solid line in the figure which is lower than the position shown by the broken line in the figure. Will be set.

As a result, the position of the oil surface O is lowered, so to speak, for example, when the oil surface O undulates between the piston side oil chamber R4 and the oil chamber R due to the expansion and contraction operation. In addition, when the hydraulic shock absorber is tilted during so-called transportation or the like and air flows into the piston-side oil chamber R4, the phenomenon of air being mixed into oil tends to occur.

Then, the oil mixed with air is supplied to the damping valve 1.
When passing through a, the generation of a predetermined stable damping force cannot be expected, and the air separated from the oil accumulates in the piston side oil chamber R4, thereby causing the adiabatic compression phenomenon during the compression operation. There is concern.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to eliminate the possibility of mixing air into oil and to prevent the adiabatic compression phenomenon from occurring. Another object of the present invention is to provide a multi-stage hydraulic shock absorber that enables a predetermined stable damping force to be generated by a damping valve and is optimally used as, for example, a rear shock absorber in a four-wheeled vehicle.

[0017]

In order to achieve the above-mentioned object, the structure of the hydraulic shock absorber according to the present invention is basically changed to a first-stage cylinder in which a second-stage cylinder is provided in a first-stage cylinder. The piston rod is inserted so as to be able to protrude and retract under the intervention of the piston, and the second-stage piston rod is inserted so as to be able to protrude and retract under the intervention of the piston inside the first-stage piston rod. An upper oil chamber and a lower oil chamber are defined by a piston connected to the second-stage piston rod and can communicate with each other via a damping valve disposed on the piston. It has a rod-side oil chamber and a piston-side oil chamber defined by a piston connected to the piston rod,
The piston-side oil chamber communicates with a reservoir disposed on the outer peripheral side of the cylinder, and the reservoir has an oil chamber that communicates with the piston-side oil chamber, and a gas chamber separated from the oil chamber by a diaphragm or a free piston. Let's say

More specifically, in the above configuration, more specifically, the closed oil chamber space in which the upper oil chamber, the lower oil chamber, and the rod-side oil chamber are isolated from the piston-side oil chamber by the arrangement of the piston. On the other hand, it is preferable that the cross-sectional area of the second-stage piston rod and the cross-sectional area of the rod-side oil chamber are set to be substantially the same.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the drawings. In the embodiment shown in FIG. 1, however, the principle shown in FIG. Is configured in the same manner as the hydraulic shock absorber.

Therefore, in the illustrated embodiment,
Except where necessary, parts having the same configuration as the hydraulic shock absorber shown in FIG. 3 are denoted by the same reference numerals in the drawing, and detailed description thereof will be omitted.
The following description focuses on features of the present invention.

That is, in the hydraulic shock absorber according to the present invention, as shown in FIG.
The piston-side oil chamber R4 defined by the cylinder 1 communicates with a reservoir disposed on the outer peripheral side of the cylinder 1 via a damping valve 1a disposed inside the lower end of the cylinder 1.

In the embodiment shown in the drawings, the reservoir has a diaphragm D in a gap formed between the cylinder 1 and an outer cylinder 6 disposed on the outer peripheral side thereof.
In the arrangement of the diaphragm D, an oil chamber R communicating with the piston-side oil chamber R4 via the damping valve 1a in the gap is defined as a gas chamber G separated from the oil chamber R.

Incidentally, in the illustrated embodiment,
The upper end of the diaphragm D is held in a liquid-tight state between the outer periphery of the upper end of the cylinder 1 and the inner periphery of the lower end annular portion 7a of the cap 7 that seals the upper ends of the cylinder 1 and the outer cylinder 6. And

The lower end of the diaphragm D is held in a liquid-tight manner between the lower end and the inner periphery of the outer cylinder 7 while being held on the outer periphery of a flange portion 1b connected to the outer periphery of the lower end of the cylinder 1. It is going to be.

Therefore, in the hydraulic shock absorber configured as described above, there is no oil level (see reference numeral O in FIG. 3).
Therefore, for example, even if oil flows between the piston-side oil chamber R4 and the oil chamber R due to the expansion / contraction operation, there is no waviness of the oil surface, and the hydraulic shock absorber is tilted during so-called transportation. Also, the air, that is, the gas in the gas chamber G does not flow into the piston side oil chamber R4, so that the phenomenon of so-called air mixing into the oil does not occur.

By the way, when the hydraulic shock absorber expands and contracts,
Needless to say, the diaphragm D expands and contracts to allow expansion and contraction of the oil chamber R and the gas chamber G.

In the above description, the reservoir is the cylinder 1
However, from the point of view of the present invention, the reservoir may be of an external type as shown in FIG.

That is, as shown in FIG. 2A, it is assumed that the cylinder 1 is formed in a single cylinder type, while the piston side oil chamber R4 in the cylinder 1 is provided outside the accumulator Q as a reservoir. Through a pipe line L.

The accumulator Q has a diaphragm D inside, and the diaphragm D separates the oil chamber R from the oil chamber R communicating with the piston side oil chamber R4 via the pipe line L. And a gas chamber G to be divided.

It is assumed that a damping valve V which functions in the same manner as the damping valve 1a shown in FIG.

Therefore, in the case of this embodiment, the so-called hydraulic shock absorber main body having the accumulator Q at the outside is smaller in the radial direction than the hydraulic shock absorber shown in FIG. This is advantageous in that it can be easily mounted on a vehicle.

In the case of this embodiment, if the pipe L is constructed so as to have flexibility while having a so-called pressure-resistant structure, the accumulator is located at an arbitrary position away from the hydraulic shock absorber main body. Since it becomes possible to arrange Q, it is advantageous in that the above-described deterioration in mountability to a vehicle is not caused.

According to the above description, the accumulator Q constituting the reservoir may be of a type having a free piston F instead of the diaphragm D as shown in FIG. 2B, for example.

That is, the accumulator Q has a free piston F inside, and the free piston F allows the oil chamber R to communicate with the piston side oil chamber R4 via the pipe L, and the oil chamber R And a gas chamber G to be separated.

It is assumed that a damping valve V is disposed in the pipe L. The damping valve V is not shown, including the case shown in FIG. Of course, it may be arranged in the housing forming the accumulator Q.

[0036]

As described above, according to the present invention, the piston-side oil chamber defined in the first cylinder communicates with the reservoir disposed on the outer peripheral side of the cylinder.
Since the reservoir has an oil chamber communicating with the piston-side oil chamber, and this oil chamber and a gas chamber separated by a diaphragm or a free piston, for example, the piston-side oil chamber and the reservoir are Even if there is oil coming between the oil chamber that constitutes, there is no ripple of the oil level,
Even if the hydraulic shock absorber is tilted during so-called transportation or the like, the air, that is, the gas in the gas chamber constituting the reservoir does not flow into the piston-side oil chamber, and the phenomenon of so-called air mixing into the oil does not occur.

As a result, according to the present invention, there is no fear that air is mixed into the oil, so that the adiabatic compression phenomenon is not caused, and it is possible to generate a predetermined stable damping force by the damping valve. For example, it is most suitable for use as a rear shock absorber in a four-wheeled vehicle.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a principle of a hydraulic shock absorber according to the present invention.

FIG. 2A is a schematic longitudinal sectional view showing a hydraulic shock absorber according to another embodiment in principle. (B) It is a figure which shows the reservoir by another embodiment in principle.

FIG. 3 is a view showing a hydraulic shock absorber as a conventional example, similarly to FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder 1a, 6a, V Damping valve 1b Flange part 2 First-stage piston rod used as a second-stage cylinder 2a Passage 3,5 Piston 4 Second-stage piston rod 6 Outer cylinder 7 Cap 7a Lower-end annular part D Diaphragm G Gas chamber L Pipe Q Accumulator R Oil chamber R1 Upper oil chamber R2 Lower oil chamber R3 Rod side oil chamber R4 Piston side oil chamber

Claims (1)

[Claims] A first-stage piston rod, which is a second-stage cylinder, is inserted into a first-stage cylinder so as to be able to protrude and retract under the intervention of a piston, and a second-stage piston is inserted into the first-stage piston rod. The rod is inserted so as to be able to protrude and retract under the intervention of the piston, and is separated into the first-stage piston rod by a piston connected to the second-stage piston rod, and mutually separated via a damping valve arranged on this piston. The piston has an upper oil chamber and a lower oil chamber that can communicate with each other, and has a rod-side oil chamber and a piston-side oil chamber defined by a piston connected to a first-stage piston rod in a cylinder. The side oil chamber communicates with the reservoir located on the outer periphery of the cylinder, and the reservoir is separated from the oil chamber that communicates with the piston side oil chamber by a diaphragm or free piston. Hydraulic shock absorber characterized by having a closed gas chamber