JPS624575B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shock absorber whose damping characteristics can be automatically changed in accordance with the loaded weight of a vehicle.

For shock absorbers used in vehicles including two-wheeled vehicles and four-wheeled vehicles, especially vehicles with large body load fluctuations such as light vans and trucks,
It is required that the damping force changes depending on the loading condition of the vehicle.

For this reason, conventionally, for example, the piston has a port equipped with a damping valve that allows flow only from the lower chamber to the upper chamber, and a sleeve (spool) that changes the effective area of the port according to changes in the relative position of the piston. ), the port resistance was made variable to increase the damping force on the compression side (compression side) when the vehicle was loaded, and there was a shock absorber with a so-called variable rear aperture structure.

However, since such conventional shock absorbers use a single compression-side damping valve, the pressure itself when the damping valve starts to open does not change even if the loading status of the vehicle changes. The disadvantage is that it is not possible to increase the rate of change in the damping force on the compression side when the vehicle is empty and when it is loaded in the slow range (for example, 0.3 m/sec or less), and as a result, there is the problem that the required damping characteristics cannot be sufficiently achieved. Ta.

The present invention was proposed in order to solve this problem, and provides a shock absorber in which damping characteristics on the compression side can be freely set when the vehicle is empty and when the vehicle is loaded.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4 of the accompanying drawings.

First, to explain the structure, in the figure, 1 is an outer cylinder, 2 is an inner cylinder, 3 is a base valve, 4 is a piston, and 5 is a piston rod. The piston 4 divides the inside of the inner cylinder 2 into an upper chamber 6 and a lower chamber 7. do.

As shown in FIGS. 2 and 3, the piston 4 has a first valve that allows oil in the lower chamber 7 to flow toward the upper chamber 6 via a first compression damping valve 8 during the contraction stroke of the shock absorber. A port 10 and a second port 11 that allows oil in the lower chamber 7 to flow toward the upper chamber 6 via the first compression damping valve 8 and the second compression damping valve 9 are arranged in parallel in isolation. 1st port 10
A sleeve 12 that selectively opens and closes the second port 11 and the second port 11 in response to changes in the relative position of the piston 4 is freely slidably interposed.

The first and second compression damping valves 8 and 9 are tandem leaf valves integrally constructed by coaxially stacking annular leaf springs with different outer diameters, and the first compression damping valve 8 has a large diameter. 1st port 1 on the back (back side) of
The annular valve seat 10a of the second port 11 is arranged on the back surface of the small-diameter second compression side damping valve 9, and a part of the outer periphery of both valve seats 10a, 11a is cut out. Groove-shaped constant orifice 13,
14 to make the rise characteristics smooth.

The relative position of the piston 4 is detected and the sleeve 1 is
A position detection spring (control spring) 15 for driving the position detection spring 2 is disposed in the upper chamber 6, and its rear end is fixed to the sleeve 12. Further, a spring 16 that opposes the biasing force of the position detection spring 15 is interposed between the lower outer circumferential wall of the sleeve 12 and the bottom of the piston 4.

The sleeve 12 is inserted into an annular groove formed by the piston 4 and the guide 17, and an extension damping valve 18 is provided on the outer peripheral wall of the sleeve 12.
and the upper chamber 6 through the constant orifice 19.
an extension side oil passage 20 that allows the oil to flow toward the lower chamber 7;
A flange-like valve portion 21 that makes the effective area of the oil passage 20 variable is provided, and a port 22 that passes through the valve portion 21 and communicates between the upper chamber 6 and the expansion-side damping valve 18. Moreover, on the inner peripheral wall of the sleeve 12,
a valve portion 23 that selectively opens and closes the inlets 10b and 11b of the first and second ports 10 and 11 that penetrate through the piston 4 and open in series on the outer peripheral wall of the guide 17;
A flange portion 25 for forming a contraction side oil passage 24 with the outer peripheral wall of the guide 17 is provided in a protruding manner.

When the vehicle is empty and the loaded weight is small, the piston 4 strokes at the top of the inner cylinder 2. Therefore, as shown in FIG. It is pressed against the bearing 26 and pushes down the sleeve 12 against the urging force of other springs 16 until it lands on the bottom of the piston 4. the result,
The inlet 11b of the second port 11, which is open below the inlet 10b of the first port 10, is closed by the contraction side valve portion 23 of the sleeve 12, and the inlet 10b of the first port 10 is opened.

Therefore, during the contraction side stroke of the shock absorber when the vehicle is empty, as the piston 4 descends, the oil in the lower chamber 7 flows through the piston rod passage 27 and inside the piston, as shown by the thick solid arrow A in FIG. Through passage 3 of chamber 28, stopper 29 and guide 17
0, the oil is introduced into the first port 10 through the oil passage 31 passing through the compression side oil passage 24 and the contraction side valve part 23, and is introduced into the first port 10 through the oil passage 31 that passes through the compression side oil passage 24 and the contraction side valve part 23, and is
0.1m/sec or less), it flows into the upper chamber 6 through the constant orifice 13, but the piston 4
In a region where the speed of piston rod 5 is high (for example, 0.1 m/sec or more), the first compression damping valve 8 is simultaneously pushed open and flows into the upper chamber 6, and at the same time oil corresponding to the entering volume of the piston rod 5 flows from the lower chamber 7 into the base valve. 3 into chamber 40. Moreover, the oil that has passed through the first damping valve 8 flows into the upper chamber 6 without pushing open the second damping valve 9, so that the damping force generated at this time is reduced to the first compression damping valve 8. Therefore, the set load of these first compression side damping valves 8 is set to match the required damping characteristic b during the contraction side stroke when the vehicle is empty as shown in FIG. By doing so, it is possible to exhibit a damping characteristic that meets the required characteristic b.

On the other hand, when loading a vehicle with a large load, as shown in FIG. 3, the piston 4 strokes at the bottom of the inner cylinder 2, so the position detection spring 15 is disengaged from the thrust bearing 26, etc., and has a free length. Therefore, the sleeve 12 is connected to the other spring 1.
6, the contraction side valve portion 23 is pushed up until it comes into contact with the upper step portion 17a formed on the guide 17. As a result, the first port 10 is closed by the contraction side valve portion 23, and the second port 11 is opened.

Therefore, the loaded weight increases and the sleeve 12
When the first port 10 is closed as shown in Fig. 3, as shown by the thick solid line arrow A' in Fig. 3,
During the contraction side stroke when the speed of the piston 4 is slow, the oil in the lower chamber 7 flows into the constant orifice 14,1.
3 into the upper chamber 6, and the piston 4
During the contraction side stroke in the region where the speed of and flows into the upper chamber 6. Therefore, the damping force generated at this time is determined by the sum of the set loads (spring rigidities) of the first damping valve 8 and the second damping valve 9. Therefore, the combined set load of the second damping valve 9 and the first damping valve 8 should be set to match the required damping characteristic a during the contraction side stroke during loading as shown in FIG. As a result, a large damping characteristic meeting the required characteristic a can be obtained.

Of course, these damping characteristics during the contraction side stroke can be freely set by appropriately selecting the areas of the constant orifices 13 and 14 and the set loads of the first and second damping valves 8 and 9. ,
In this respect, compared to the conventional method in which the characteristics are relatively changed by changing the constant orifice and port area, the required characteristics can be brought closer. In particular, at low speeds (for example, 0.3 m/sec or less), the damping force on the compression side can be varied widely and arbitrarily when the vehicle is empty and when the vehicle is loaded, and the damping characteristics can be significantly improved.

Although not directly related to the gist of this invention,
During the extension stroke, in the state shown in FIG.
Because it is separated more and the extension side oil passage 20 is opened,
As shown by the thin arrow B in FIG. 2, the oil in the upper chamber 6 passes through the oil passage 20 and the port 22 provided in the valve part 21, and when the piston 4 is at a low speed, it passes through the constant orifice 19, so that the speed of the piston 4 increases. In the fast region, the rebound damping valve (relief valve) 18
is pushed open and flows into the lower chamber 7. Therefore, the areas of the constant orifice 19, oil passage 20 and port 22, and the set load of the damping valve 18 are
By setting it in accordance with the required damping characteristic d during the extension stroke when the car is empty as shown in Fig. 4,
It is possible to exhibit a damping characteristic that matches this required damping characteristic d.

Moreover, when loading the vehicle as shown in FIG.
is brought into contact with the inner wall stepped portion 32 of the piston 4, and the extension side oil passage 20 is reduced. As a result, as shown by the thin line arrow B' in FIG. This oil passage 20
The oil passage area becomes smaller and the port resistance increases due to the decrease in the oil passage area. From this, the damping characteristics at that time are constant orifice 19 and port 22.
The area of the constant orifice 19 and the port 22 and the set load of the damping valve 18 are determined by the area of the constant orifice 19 and the port 22 and the set load of the damping valve 18 as shown in FIG. By designing in accordance with C, it becomes possible to obtain a relatively high attenuation characteristic that meets the required characteristic C.

As described above, according to the present invention, the structure includes a first port that allows oil in the lower chamber to flow toward the upper chamber via the first compression-side damping valve that communicates in only one direction;
A second port is provided in parallel to allow oil in the lower chamber to flow toward the upper chamber via the compression side damping valve and the second compression side damping valve,
A sleeve 12 that selectively opens and closes its first and second ports in response to changes in the relative position of the piston.
, it is possible to provide damping characteristics according to the requirements for both when the vehicle is empty and when the vehicle is loaded. In particular, since the rate of change in the damping force on the compression side when the vehicle is empty and when the vehicle is loaded can be made large and arbitrary, the characteristics at low piston speeds are significantly improved.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view of the shock absorber of the present invention, Fig. 2 is an enlarged sectional view of the piston portion of Fig. 1 when the vehicle is empty, and Fig. 3 is an enlarged sectional view of the piston portion when the vehicle is loaded. The cross-sectional view shown in FIG. 4 is a graph showing the attenuation characteristics of the present invention. 1...Outer cylinder, 2...Inner cylinder, 3...Base valve, 4...
Piston, 5... Piston rod, 6... Upper chamber, 7
...Lower chamber, 8...First compression damping valve, 9...Second compression damping valve, 10...First port, 11...Second port, 12...Sleeve, 13, 14...Constant orifice, 15...Position detection spring , 16...
Spring, 17...Guide.

Claims (1)

[Claims] 1 Leaf valves with different effective diameters are stacked coaxially on the piston, and first and second damping valves are provided in tandem, and oil in the lower chamber is transferred to the upper chamber through the first damping valve only during the contraction side stroke. A first port through which the oil flows toward the piston, and a second port through which the oil in the lower chamber flows toward the upper chamber through both the first and second damping valves are arranged in parallel to the piston, and the first port A shock absorber comprising a sleeve that selectively opens and closes the second port and the second port in response to changes in the relative positions of the pistons.