JPS6216339B2 - - 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 upper chamber to the lower chamber, and a sleeve (spool) that changes the effective area of the port according to changes in the relative position of the piston. ), so that the port resistance can be made variable and the damping force on the rebound side when the vehicle is loaded can be increased.There was a shock absorber with a so-called variable rear aperture structure.

However, since such conventional shock absorbers use a single rebound-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. Area where target is slow (e.g. 0.3m/sec or less)
The disadvantage is that it is not possible to increase the rate of change in the damping force on the rebound side when the car is empty and when the car is loaded.
As a result, there was a problem that the required damping characteristics could not be sufficiently achieved.

The present invention was proposed to solve this problem, and provides a shock absorber in which the damping characteristics on the extension 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 a cylinder outer cylinder, 2 is a cylinder inner cylinder, 3 is a base valve, 4 is a piston, and 5 is a piston rod. partition into.

As shown in FIGS. 2 and 3, the disk portion 4' of the piston 4 is provided with oil from the upper chamber 6 to the lower chamber 7 via the first rebound damping valve 8 during the rebound stroke of the shock absorber. A first port 10 that allows the oil to flow toward the lower chamber 7 and a second port 11 that allows the oil in the upper chamber 6 to flow toward the lower chamber 7 via the first expansion damping valve 8 and the second expansion damping valve 9 are arranged in isolation. has been established,
A sleeve 12 that selectively opens and closes the first port 10 and the second port 11 according to changes in the relative position of the piston 4 is freely slidably interposed.

The first and second rebound damping valves 8 and 9 are tandem leaf valves integrally constructed by coaxially stacking plate springs with different outer diameters, and are the rear surface of the first rebound damping valve 8 having a large diameter. An annular valve seat 10a of the first port 10 is arranged on the back side, and an annular valve seat 11a of the second port 11 is arranged on the back side of the small-diameter second expansion-side damping valve 9,
Groove-shaped constant orifices 13 and 14 are formed by cutting out a portion of the outer periphery of both valve seats 10a and 11a to smooth the start-up characteristics.

The relative position of the piston 4 is detected and the sleeve 1 is
A position detection spring (control spring) 15 for driving the valve 2 is disposed in the lower chamber 7, and its rear end is fixed to the base valve 3. Further, a spring 16 that opposes the biasing force of the position detection spring 15 is interposed between the upper outer circumferential wall of the sleeve 12 and the ceiling of the piston 4.

The sleeve 12 is inserted into an annular groove formed by the piston 4 and the guide (piston nut) 17, and the outer peripheral wall of the sleeve 12 is provided with a compression side (compression side) damping valve 18 and a constant orifice 19. A contraction side oil passage 20 through which oil in the lower chamber 7 flows toward the upper chamber 6, and a flange-shaped valve portion 21 that makes the effective area of the oil passage 20 variable are provided. Further, inlets 10 for first and second ports 10 and 11, which penetrate through the piston 4 and open in series on the outer circumferential wall of the guide 17, are provided on the inner circumferential wall of the sleeve 12.
A valve portion 23 for selectively opening and closing the valves b and 11b and a flange portion 25 for forming an extension side oil passage 24 between the outer circumferential wall of the guide 17 are provided in a protruding manner.

When the vehicle is empty and the loaded weight is small, the piston 4 strokes at the upper part of the inner cylinder 2, so the tip of the position detection spring 15 separates from the sleeve 12 and becomes a free length, as shown in FIG. 12 is pushed down by the biasing force of another spring 16 until it lands on the stepped portion of the guide 17. As a 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 extension side valve portion 23 of the sleeve 12, and the inlet 10b of the first port 10 is opened.

Therefore, during the rebound stroke of the shock absorber when the vehicle is empty, as the piston 4 rises, the oil in the upper chamber 6 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, disk part 4' and guide 17
0, is introduced into the first port 10 through the extension side oil passage 24, and flows into the lower chamber 7 through the constant orifice 13 in a region where the speed of the piston 4 is extremely slow (for example, 0.1 m/sec or less), but the speed of the piston 4 In a region where the flow is fast (for example, 0.1 m/sec or more), the first expansion damping valve 8 is simultaneously pushed open and the flow flows into the lower chamber 7. Moreover, this first damping valve 8
Since all of the oil passing through flows into the lower chamber 7 without pushing the second damping valve 9 open, the damping force generated at this time is determined by the set load (spring rigidity) of the first damping valve 8. Therefore, by setting the set load of these first compression damping valves 8 to match the required damping characteristic d during the extension stroke when the vehicle is empty as shown in FIG. 4, the required characteristic d can be met. It is possible to exhibit excellent damping characteristics.

On the other hand, when a vehicle is loaded 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 comes into contact with the flange of the sleeve 12 and 12 is pushed up until it comes into contact with the piston 4. As a result, the first port 10 is closed by the extension side valve portion 23, and the second port 11 is opened. Note that the set load of the spring 16 is set lower than that of the position detection spring 15.

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 extension stroke when the speed of the piston 4 is slow, oil in the upper chamber 6 enters the second port 11 through the oil passage 31 penetrating the valve portion 23 and flows into the lower chamber 7 through the constant orifices 14 and 13.
During the extension stroke in the region where the speed of the piston 4 is high, the oil in the upper chamber 6 simultaneously flows from the second port 11 against the combined elasticity of the first extension damping valve 8 and the second extension damping valve 9. The liquid is pushed open and flows into the lower chamber 7. Therefore, the damping force generated at this time is the first damping valve 8.
and the set load (spring rigidity) of 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 c during the extension stroke when loading a vehicle as shown in FIG. This makes it possible to obtain a large damping characteristic that meets the required characteristic c.

Of course, these damping characteristics during the extension 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, the required characteristics can be brought closer to the required characteristics than the conventional method in which the characteristics are relatively changed by changing the constant orifice and port area. In particular, at low speeds (for example, 0.3 m/sec or less), the damping force on the extension 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 contraction side stroke, in the state shown in FIG. 2 when the vehicle is empty, the sleeve 12 is pushed down relatively and its contraction side valve portion 21 separates from the lower end portion 32 of the piston 4, opening the contraction side oil passage 20 to a large extent. Therefore, the oil in the lower chamber 7 passes through the oil passage 20 to the piston 4.
When the speed of the piston 4 is low, oil passes through the constant orifice 19, and when the speed of the piston 4 is high, the expansion side damping valve (relief valve) 18 is simultaneously pushed open and flows into the upper chamber 6. At the same time, oil corresponding to the entering volume of the piston rod 5 flows into the lower chamber. 7 to base valve 3
through which it flows into chamber 40. For this reason, the areas of the constant orifice 19 and the oil passage 20 and the set loads of the damping valve 18 and the base valve 3 are set in accordance with the required damping characteristic b during the contraction side stroke when the vehicle is empty, as shown in Fig. 4. By doing so, it is possible to exhibit a damping characteristic that matches this required damping characteristic b. Moreover, when the vehicle is loaded as shown in FIG. 3, the sleeve 12 rises relatively and brings the contraction side valve part 21 into contact with the lower end part 32 of the piston 4, reducing the area of the contraction side oil passage 20. let As a result, the oil in the lower chamber 7 is transferred from the oil passage 20 reduced by the contraction side valve part 21 to the constant orifice 19.
through the upper chamber 6 or by pushing open the damping valve 18.
As the area of the oil passage 20 decreases, the oil passage area becomes smaller and the port resistance increases. From this, the damping characteristics at that time are determined by the areas of the constant orifice 19 and the oil passage 20, and the set loads of the damping valve 18 and the base valve 3, and therefore, the constant orifice 19
By designing the area of the oil passage 20 and the set load of the damping valve 18 in accordance with the required damping characteristic a during the contraction side stroke during loading as shown in FIG. This makes it possible to obtain high attenuation characteristics.

As described above, according to the present invention, the structure includes a first port that allows oil in the upper chamber to flow toward the lower chamber via the first expansion-side damping valve that communicates in only one direction;
A second port is installed in parallel to allow oil in the upper chamber to flow toward the lower chamber via the expansion side damping valve and the second expansion 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 when the vehicle is empty and when the vehicle is loaded. In particular, since the rate of change in the damping force on the extension side when the vehicle is empty and when the vehicle is loaded can be set to a large value as desired, the characteristics at low piston speeds are significantly improved. In addition, since the damping valve is a leaf valve type, it can be made compact and has the advantage that the basic length of the shock absorber can be shortened.

[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 extension damping valve, 9...Second extension damping valve, 10...First port, 11...Second port, 12...Sleeve,
13, 14...Constant orifice, 15...
...Position detection spring, 16...Spring, 1
7...Guide.

Claims (1)

[Claims] 1 First and second damping valves are provided in tandem by stacking leaf valves with different effective diameters on the same axis of the piston, and oil in the upper chamber is transferred to the lower chamber only during the extension stroke via the first damping valve. A first port through which the oil flows toward the piston, and a second port through which the oil in the upper chamber flows toward the lower 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.