JPH023054B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic shock absorber whose damping force can be freely adjusted.

The damping characteristics required for a vehicle vary widely depending on driving conditions.

For example, Japanese Utility Model Application Publication No. 54-117486 discloses a mechanism that can freely adjust such damping characteristics, which will be explained with reference to FIG.

A piston 2 is slidably housed inside the cylinder 1, and oil chambers A and B are defined above and below the piston 2, and a free piston 3 is housed below the piston 2.
defines a gas chamber C.

The piston 2 is provided with expansion side and compression side damping valves 4 and 5 in parallel, and when the piston rod 6 is pulled out during the expansion side operation, the piston 2 resists the hydraulic oil flowing from the contracting oil chamber A to the expanding oil chamber B through the expansion side damping valve 4. On the other hand, during pressure side operation when the piston rod 6 enters, the pressure side damping valve 5 provides resistance to the hydraulic oil flowing from the oil chamber B to the oil chamber A, thereby generating a damping force.

The gas chamber C delimited by the free piston 3 compensates for the inflow and outflow of oil corresponding to the volume of entry of the piston rod 6 on the pressure side.

The piston rod 6 is provided with a rotary valve 8 having a small hole 9 at the tip of an operating rod 7 passing through it, and a through hole 11 of a passage 10 bypassing the piston section from oil chamber A to B. The hole 9 forms a variable orifice that communicates the oil chambers A and B.

A rotary solenoid 13 provided at the protruding end of the operating rod 7 is driven to rotate the rod 7, causing the rotary valve 8 to close the through hole 11 and open the through hole 11 by reversing the rotary valve 8.

Therefore, when a soft damping characteristic is desired, such as when driving in a city, by opening the rotary valve 8, the oil chambers A and B are opened by adding the expansion side and compression side damping valves 4 and 5 and the passage 10 having an orifice. Since they are in communication, the flow resistance of hydraulic oil is reduced and the damping force is reduced.

On the other hand, if you want to obtain hard damping characteristics to ensure maneuverability in high-speed vehicle ranges, by closing the rotary valve 8, you can close the rebound and compression damping valves 4 and 5.
A relatively high damping force is generated only by

In this way, the damping force can be switched, but as shown in Figure 2, simply opening and closing the orifice of the rotary valve 8 will greatly affect the damping characteristics in the low piston speed range, where the orifice flow rate is large. Even if the orifice is changed, in the medium and high speed range where the effectiveness of the orifice is constant, the damping characteristics exist almost only in the expansion side and compression side damping valves 4 and 5, and there is a drawback that a large change cannot be obtained.

An object of the present invention is to provide a hydraulic shock absorber whose damping characteristics can be adjusted over a wide range from a low piston speed range to a high speed range.

The present invention provides a second compression damping valve in series with the first rebound and compression damping valves.
The oil passage between the first and second damping valves is selectively short-circuited to the oil chamber by a switching valve, and when the switching valve is open, the first damping valve is A relatively low damping characteristic is obtained by the damping valve, and when the switching valve is closed, a high damping characteristic is obtained by the second expansion side damping valve and the compression side damping valve in series with the first damping valve.

Embodiments of the present invention will be described below based on the drawings.

In FIGS. 3 and 4, the piston 2 has a first
The expansion-side and compression-side damping valves 4 and 5 shown in the figure are arranged side by side in the same manner as in the prior art.

However, in this embodiment, the expansion side and compression side damping valves 4 and 5 are both flexible leaf valves 4A and 5A, and open and close ports 4B and 5B, respectively. Note that the seat portion of the outer port 5B is raised in an annular shape around the port opening, so that the inner port 4B is in communication with the oil chamber A even when the leaf valve 5A is present.

A switching valve 16 and second expansion-side and compression-side damping valves 17 and 18 are disposed inside the piston nut 15 that is fitted into the piston 2.

The switching valve 16 selectively short-circuits the oil passage 19 between the first damping valves 4 and 5 and the second damping valves 17 and 18 with the oil chamber B by opening and closing the bypass port 20. , is attached to an operating rod 7 passing through the piston rod 6.

The bypass port 20 is provided at a position opposite to the cylindrical portion 22 of the piston nut 15, and the valve portion 23 of the switching valve 16 is in sliding contact with the inner periphery of the cylindrical portion 22.

As shown in FIGS. 4A and 4B, the switching valve 16 is a cylindrical body with a symmetrical cutout.
two valve parts 23 and a support arm 24 connecting the valve parts 23
and a long hole 25 provided in the center of the support arm 24.
The slit leg portion 26 (formed by cutting off both sides) of the hollow shaft 27 that locks onto the tip of the operating rod 7 is inserted, and as the rod 7 rotates, the switching valve 16 opens.
is starting to rotate.

The second expansion side and compression side damping valves 17 and 18 are
Similarly to damping valves 4 and 5, ports 17B and 18B
It is composed of leaf valves 17A and 18A that open and close, and the port 1 of each damping valve 17 and 18 is
The inlets of 7B and 18B are leaf valves 18A and 17
A is formed so that the flow of oil into each other is not obstructed.

Next, the effect will be explained.

By turning the operating rod 7, the switching valve 16
When the bypass port 20 is opened, the oil passage 19 communicates with the oil chamber B (see FIG. 4A).

Therefore, during pressure side operation, the hydraulic oil in oil chamber B is
From the bypass port 20, which has much less resistance than the second compression damping valve 18, it flows through the oil passage 19 to the oil chamber A while pushing the first compression damping valve 5 open, and similarly when the rebound side is operated, it flows into the oil chamber A. The hydraulic oil A expands the first expansion damping valve 4, flows into the oil passage 19, and further flows out from the bypass port 20 to the oil chamber B.

Therefore, the second damping valves 17 and 18 do not work at all, and the damping force is generated solely by the first expansion and compression damping valves 4 and 5, resulting in relatively soft (normal) damping characteristics. It will be done.

On the other hand, when the switching valve 16 is rotated by the operation rod 7 to close the bypass port 20, the oil passage 19 between the first damping valves 4, 5 and the second damping valves 17, 18 is connected to the oil chamber B. communication is cut off (Fig. 4B).

As a result, for example, during pressure-side operation, the hydraulic oil in the oil chamber B first pushes the second pressure-side damping valve 18 wide and flows into the oil passage 19, and then spreads the first pressure-side damping valve 5 and flows into the oil chamber A. In this way, by passing through the two damping valves 18, it encounters a large resistance and generates a high damping force.

At this time, by changing the setting value of the damping force of the second compression side damping valve 18, the adjustment range of the damping characteristic can be changed greatly.

During the expansion-side operation, the hydraulic oil in the oil chamber A passes through the first expansion-side damping valve 4 and the second expansion-side damping valve 17 that are in series with each other, thereby obtaining a large damping force in the same manner as described above.

These relationships are shown in Figure 5. In this way, the first and second damping valves, which have a large flow rate control width, are selectively connected in series, so unlike conventional variable orifices, it is possible to The damping force can be adjusted over a wide range up to high speeds.

FIG. 6 shows another embodiment of the present invention, but the difference from FIG. 3 is that the first pressure side damping valve 5'
The annular valve 30 is configured to be biased in the valve closing direction by a cone spring 31 in that it is a non-return valve.

Therefore, in this case, since the first compression damping valve 5' is easy to open, the damping force on the compression side when the switching valve 16 is opened is lower than that on the expansion side.

As described above, in the present invention, the soft damping characteristic by the first damping valve and the hard damping characteristic by the series connection of the first and second damping valves can be freely selected. This has the effect of making it possible to greatly change the range of force adjustment, thereby satisfying both the conditions of vehicle ride comfort and handling stability.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional device, and FIG. 2 is a diagram showing its damping characteristics. FIG. 3 is a sectional view of the main part showing an embodiment of the present invention, FIGS. 4A and B are sectional views taken along the line -- in FIG. 3 showing the operating state of the switching valve, and FIG. 5 is a damping characteristic diagram of the present invention , FIG. 6 is a sectional view of a main part of another embodiment. 1...Cylinder, 2...Piston, 4...First
Rebound side damping valve, 5... First compression side damping valve, 6...
Piston rod, 7... Operating rod, 15... Piston nut, 16... Switching valve, 17... Second rebound damping valve, 18... Second compression damping valve, 1
9... Oil road, 20... Bypass port.

Claims (1)

[Scope of Claims] 1. A hydraulic shock absorber in which a piston connected to a piston rod is housed in a cylinder to form upper and lower oil chambers, and expansion side and compression side damping valves are arranged in parallel on the piston, A switching valve in which a second expansion-side and compression-side damping valve is arranged in series with the first expansion-side and compression-side damping valve, and selectively short-circuits an oil passage between the first and second damping valves to an oil chamber. A damping force adjustable hydraulic shock absorber. 2. The damping force adjustable hydraulic shock absorber according to claim 1, wherein the switching valve is rotatably driven from the outside via an operating rod that passes through the piston rod.