JPS6227295B2 - - 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.

This invention was proposed in order to solve this problem, and uses a so-called back-throttle type damping force generation system that can simultaneously adjust the damping force characteristics on the rebound side and the compression side when the car is empty and when the car is loaded. It is an object of the present invention to provide a shock absorber having means.

In order to achieve the above object, the present invention provides the piston with first and second rebound damping valves in parallel that allow flow only from the upper chamber to the lower chamber during the rebound operation, and the first rebound damping valve and the second rebound damping valve are set differently, and the first port communicates the upper chamber and the lower chamber via the first rebound damping valve with the upper chamber via the second rebound damping valve. A second port that communicates with the lower chamber is installed in parallel with the piston, and a pressure side damping valve that only allows flow from the lower chamber to the upper chamber during pressure side operation is interposed between the base valve side and the piston. The piston is provided with a sleeve that is displaced according to a change in the relative position of the piston by a spring, and the sleeve has an extension side valve section that selectively opens and closes the first and second ports in response to the displacement, and a pressure side valve section that selectively opens and closes the first and second ports in response to the displacement. The area of the oil passage on the upstream side of the damping valve is also formed with a compression side valve part that increases or decreases with displacement, and the area is adjusted based on the displacement of the sleeve corresponding to the expansion side position when the car is empty and the compression side position when the car is loaded. The generated damping force can be changed.

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. The upper chamber 6 is connected to the upper chamber 6 through the first port 10 that allows the flow to flow toward the
A second port 11 through which oil flows toward the lower chamber 7 is arranged in isolation, and the first port 10 and the second port 11 are selectively connected in accordance with changes in the relative position of the piston 4. A sleeve 12 that opens and closes is slidably inserted.

The second expansion damping valve 9 is an annular leaf valve disposed outside the first expansion damping valve 8, and its outer periphery is fixed by a guide 41. 1st
The expansion damping valve 8 is an annular leaf valve whose set load is set smaller than that of the second expansion damping valve 9, and its inner periphery is fixed by a guide 41. An annular valve seat 10 for the first port 10 and the second port 11 is provided on the back surface of each of these damping valves 8 and 9.
a, 11a are arranged, but the valve seat surfaces on the inner circumferential side of the valve seat 11a and the outer circumferential side of the valve seat 10a are common, and a common constant orifice 13 is formed on this common seat surface. .

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 a compression side (compression side) damping valve 18 and a constant orifice 19 are provided on the outer peripheral wall of the sleeve 12. A contraction side oil passage 20 through which oil in the lower chamber 7 flows toward the upper chamber 6, and a flange-like 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.
Extension side valve part 23 that selectively opens and closes b and 11b
and the outer circumferential wall of the guide 17.
A flange portion 25 for forming a flange portion 25 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, so the tip of the position detection spring 15 separates from the sleeve 12 and becomes a free length, as shown in FIG. , the sleeve 12 is pushed down by the biasing force of the other spring 16 until it lands on the stepped portion of the guide 17. As a result, the inlet 10b of the first port 10
Inlet 11b of second port 11 opened lower
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
The oil 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 very slow (for example, 0.1 m/sec or less). In a region where the speed is high (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 side damping valves 8 to match the required damping characteristic b during the extension stroke when the vehicle is empty as shown in FIG. 4, the required characteristic b 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 orifice 13. For the extension stroke in the high speed region,
At the same time, the oil in the upper chamber 6 is transferred from the second port 11 to the second
It is pushed open against the elasticity of the expansion side damping valve 9 and flows into the lower chamber 7. Therefore, the damping force generated at this time is determined by the set load (spring rigidity) of the second damping valve 9. Therefore, by setting the set load of the second damping valve 9 to match the required damping characteristic a during the extension stroke when loading a vehicle as shown in FIG. This provides damping characteristics.

Of course, these damping characteristics during the extension stroke can be freely set by appropriately selecting the area of the constant orifice 13 and the set loads of the first and second damping valves 8, 9. On the other hand, 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 achieved much closer. especially,
At low speeds (for example, 0.3 m/sec or less), the damping force on the extension side when the vehicle is empty and when the vehicle is loaded can be varied widely and arbitrarily, and the damping characteristics can be significantly improved.

On the other hand, during the contraction side stroke, the sleeve 12 is relatively pushed down and the contraction side valve portion 21 is pressed against the piston 4 in the state shown in FIG. 2 when the vehicle is empty.
Since it separates from the lower end 32 and opens the contraction side oil passage 20, the oil in the lower chamber 7 passes through the oil passage 20 and the constant orifice 19 when the piston 4 is at a low speed, and flows into the area where the piston 4 is at a high speed. At the same time, the expansion side damping valve (relief valve) 18 is pushed open and flows into the upper chamber 6, and at the same time oil corresponding to the volume of entry of the piston rod 5 flows from the lower chamber 7 through the base valve 3 into the chamber 40. For this reason, the areas of the constant orifice 19 and oil passage 20 and the set loads of the damping valve 18 and base valve 3 are set in accordance with the required damping characteristic d 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 matches the required damping characteristic d. Moreover, when the vehicle is loaded as shown in FIG. 3, the sleeve 12 relatively rises to bring 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 flows from the oil passage 20 reduced by the contraction side valve part 21 to the upper chamber 6 through the constant orifice 19 or by pushing open the damping valve 18, so that the area of this oil passage 20 is reduced. This reduces the oil passage area and increases port resistance. From this, the damping characteristics at that time are determined by the area of the constant orifice 19 and the oil passage 20,
It is determined by the set load of the damping valve 18 and the base valve 3, and therefore the area of the constant orifice 19 and the oil passage 22, the set load of the damping valve 18, etc. are determined by the setting load of the damping valve 18 and the base valve 3 during the contraction side stroke during loading as shown in Fig. 4. By designing according to the required attenuation characteristic c, it becomes possible to obtain a relatively high attenuation characteristic that meets the required attenuation characteristic c.

As described above, according to the present invention, there is provided a first port exclusively for use when the car is empty, which allows oil in the upper chamber to flow toward the lower chamber via the first rebound damping valve, and a port that also allows oil to flow through the second rebound damping valve. A second port is installed in parallel, and the first
Since the port and the second port are selectively opened and closed via a sleeve that responds to changes in the relative position of the piston, damping characteristics can be arbitrarily applied depending on the requirements when the vehicle is empty or when the vehicle is loaded. In particular, since the rate of change in the rebound damping force when the vehicle is empty and when the vehicle is loaded can be made large and arbitrary, the characteristics in the low piston speed range are significantly improved. Furthermore, in the present invention, the opening area of the oil passage through which oil flows from the lower chamber to the upper chamber via the compression side damping valve during compression operation is
By increasing and decreasing the damping force as the sleeve is displaced, it is possible to appropriately adjust the compression side damping force characteristics depending on the state of empty and loaded cars. , an even better buffering function can be obtained.

Furthermore, in the present invention, the variable damping force generating means consisting of the oil passages, ports, sleeves, etc. described above is concentrated in the piston, and it is not necessary to perform complicated machining on other parts such as the piston rod. Since there is no material, it is easy to process, reducing production costs, and the simple structure means that it can be expected to have excellent durability. Furthermore, it is possible to use a compact leaf valve type damping valve on both the rebound side pressure side, which 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...Constant orifice, 15...Position detection spring, 16 ...Spring, 17...Guide.

Claims (1)

[Claims] 1. First and second rebound damping valves that allow flow only from the upper chamber to the lower chamber when operating on the rebound side are provided in parallel on the piston, and the set load of the first rebound damping valve and the second rebound damping valve is are set differently, and the first
A first port that communicates between the upper chamber and the lower chamber via the expansion side damping valve and a second port that communicates the upper chamber and the lower chamber via the second expansion side damping valve are arranged in parallel on the piston, while, The piston is equipped with a pressure side damping valve that only allows flow from the lower chamber to the upper chamber during pressure side operation, and a sleeve that is displaced according to changes in the relative position of the piston by a spring interposed between the base valve side and the piston. , and this sleeve includes an expansion side valve portion that selectively opens and closes the first and second ports in accordance with the displacement, and a contraction side valve portion that increases or decreases the area of the upstream oil passage of the compression side damping valve in accordance with the displacement. A shock absorber characterized by forming a valve part.