JPH0241666B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shock absorber that automatically and variably controls damping force in accordance with the load amount of a vehicle.

The damping characteristics of a shock absorber required for a vehicle change depending on driving conditions.For example, in a truck, etc., the damping characteristics are required to be hard when loaded and soft when empty.

In order to cope with these problems, a load-sensitive shock absorber has been proposed by the present applicant in Japanese Patent Laid-Open No. 55-27547.

To explain this with reference to Fig. 1, 1 is a cylinder connected to the axle side, 2 is a piston, and 3 is a piston rod connected to the vehicle body. It is clearly defined.

The piston 2 is provided with a compression side damping valve 6 that opens during compression side operation and generates a damping force in the hydraulic oil flowing from the lower oil chamber 5 to the upper oil chamber 4, and a piston nut 7 is coupled to the lower part of the piston 2. A passage 8 is formed through the piston nut 7, the piston 2, and the piston rod 3 to communicate the upper and lower oil chambers 4, 5, and two damping valves 10, 11 are installed in series in this passage 8. Placed.

The damping valves 10 and 11 open during expansion-side operation, allowing hydraulic oil to flow from the upper oil chamber 4 to the lower oil chamber 5 while imparting resistance.

A side passage 12 is formed in the peripheral wall of the piston nut 7 to short-circuit the passage between the first damping valve 10 and the second damping valve 11 to the lower oil chamber 5. Spool 1 to open and close
3 is fitted on its outer periphery so that it can slide freely.

The spool 13 has one end of a spring 14 for detecting the stroke position of the piston 2 at a flange portion 15.
When the average stroke position (neutral position) of the piston 2 is upward, such as when the vehicle is empty, the acting force of the return spring 17 is smaller than that of the position detection spring 14, as shown on the right side of the figure. However, when the piston 2 moves relatively downward during loading, the spool 13 is opened by the position detection spring 14 with increased deflection force, as shown on the left side of the figure. is pushed up and closes the side passage 12.

Therefore, during the expansion side operation when the vehicle is empty, the hydraulic fluid is
After passing through the first damping valve 10 and the side passage 12, the oil flows out into the lower oil chamber 5 through the side passage 12, so that the generated damping force becomes weaker as shown in FIG. On the other hand, since the side passage 12 is closed when the vehicle is loaded, the fluid must pass through the second damping valve 11 after passing through the first damping valve 10, which increases fluid resistance and increases the generated damping force. be.

In this way, during the expansion side operation, the hydraulic oil selectively flows through the two damping valves 10 and 11 arranged in series, so that the damping force can be greatly changed between when the vehicle is empty and when the vehicle is loaded.

However, regarding the damping force generated during compression side operation,
The square groove 18 formed on the upper surface of the flange portion 15 of the spool 13 functions as a variable orifice, and when the vehicle is empty, the upstream passage 19 of the compression side damping valve 6 is wide open, and when the vehicle is loaded, the spool 13 moves upward to increase the effective area of the passage 19. It is designed to be restricted by a square groove 18. Therefore, in this case, only the variation range of the damping force depending on the presence or absence of the orifice is obtained, and in the piston operation region where the effect of the orifice is particularly low, that is, the piston low speed region, the damping force changes as shown in Fig. 2. There was a tendency that there was almost no change between when the car was empty and when it was loaded.

Therefore, when the vehicle is loaded and traveling at high speed, low frequency vibrations may cause the vehicle body to shake significantly and become unstable.

The present invention was proposed to solve such problems, and includes a first extension side installed in parallel with the piston,
a second expansion side parallel to each other with respect to the compression side damping valve;
Compression side damping valves are further arranged in parallel, and the above-mentioned first damping valve is arranged in parallel in response to the piston stroke position detection spring.
Alternatively, by providing a switching valve that opens and closes the passage connecting the second damping valve and the oil chamber, the damping characteristics when empty and loaded can be changed significantly from the low piston speed range on the compression side as well as on the rebound side. The object of the present invention is to provide a load-sensitive shock absorber.

Hereinafter, the present invention will be explained based on examples thereof.

In FIG. 3, the piston 2 is provided with a first expansion damping valve 21 and a compression damping valve 22 in parallel.

In a parallel relationship, a second rebound damping valve 23 and a compression damping valve 24 are arranged in parallel inside the piston nut 7 fitted under the piston 2. 23,2
4 is communicated with the upper oil chamber 4 via an internal passage 8 of the piston rod 3 and an internal passage (space) 26 of the piston nut 7.

A side passage 28 communicating the lower space 25 of the second valves 23, 24 with the lower oil chamber 5 is formed through the peripheral wall of the piston nut 7, and a spool 29 is slidably fitted onto the outer periphery of the side passage 28. , constitutes a switching valve 30 that opens and closes the side passage 28. Note that the lower opening of the piston nut 7 is closed by a cover plate 32.

The spool 29 can freely come into contact with and separate from the upper end of the piston position detection spring 14 installed in the lower oil chamber 5, and is pushed downward by the return spring 31 except when the piston 2 moves relatively downward. Side road 28 is open.

The aforementioned first expansion side and compression side damping valves 21 and 22
Leaf valves 34 are arranged on both sides of the piston 2 to open and close the through holes 33A and 33B provided in the piston 2.
A, 34B, and an outer through hole 33 on the pressure side.
Hydraulic oil flows by pushing up the upper leaf valve 34A from A, and flows by pushing down the lower leaf valve 34B from the inner through hole 33B on the growth side.

In addition, second expansion side and compression side damping valves 23 and 24
In this example, through holes 36A and 36B are formed in a valve plate 35 fitted inside a piston nut 7, and these are opened and closed by leaf valves 37A and 37B arranged on the upper and lower surfaces of the through holes 36A and 36B, respectively.

Note that the through hole 36A has a seat portion 38A formed on the upper surface, but the through hole 36B has a sheet portion 38B formed on the lower surface.
are formed, and each opposite side has a leaf valve 3.
7A and 37B, and therefore, on the compression side, the hydraulic oil that passed through the right passage hole 36A pushed up the leaf valve 37A and flowed, and on the rebound side, the hydraulic oil passed through the left passage hole 36B. The hydraulic oil pushes down the leaf valve 37B and flows.

Note that a plurality of through holes 36A and 36B are actually provided on the circumference (two or more), and the through holes 36A and 36B are actually provided on the circumference.
8A and 38B are formed in the shape of a strip around the opening.

Next, the operation will be explained. First, when the vehicle is empty, the average stroke position of the piston 2 is upward, so the spool 29 of the switching valve 30 is not pushed by the piston position detection spring 14, or even if it is pushed, it is weak, and therefore the return spring 31, the switching valve 30 fully opens the side passage 28.

In this state, for example, when operating on the rebound side, the hydraulic oil in the upper oil chamber 4 passes through the first rebound damping valve 21 and flows into the lower oil chamber 5, and the hydraulic oil flows from the passage 8 into the second rebound damping valve 23. The oil then flows out from the side passage 28 to the lower oil chamber 5, thus forming two oil passages parallel to each other, and because a large flow rate flows, the generated damping force is relatively weak.

On the other hand, during pressure side operation, the hydraulic oil in the lower oil chamber 5 similarly flows into the internal space 25 from the side passage 28, and the second
One flows from the pressure side damping valve 24 to the upper oil chamber 4 via the passage 8, and the other flows from the lower oil chamber 5 to the upper oil chamber 4 via the first pressure side damping valve 22, and similarly weak damping force is generated. occurs.

On the other hand, when the average stroke position of the piston 2 falls during loading and the spool 29 is pushed up by the position detection spring 14, the switching valve 30 closes the side passage 28.

In this state, when either the expansion side or the compression side is operated, the passage of the second expansion side and compression side damping valves 23 and 24 is blocked, and the hydraulic fluid flows only through the first expansion and compression side damping valves 21 and 22. I will pass.

Therefore, even if the piston 2 moves at a low speed, for example, during pressure side operation, all the hydraulic oil passes through the first pressure side damping valve 22 and flows into the lower oil chamber 5, and in this way, a large flow rate is achieved. Because of this flow, a large damping force is reliably generated, unlike with conventional orifices.

However, the first damping valves 21 and 22 are set in advance so as to generate a high damping force when the vehicle is loaded.

Next, the embodiment shown in FIG. 4 will be explained. In this embodiment, a piston position detection spring 14 is installed in the upper oil chamber 4, and accordingly, a return spring 31 urges the spool 29 upward. The position detection spring 14 pushes down the spool 27 and opens the side passage 28 when the piston 2 is idle and the average stroke position moves upward.

Note that the first and second damping valves are reversed upside down from FIG. 3, and the piston nut 7 is also
also reverse and conclude.

Therefore, in this embodiment, as in the first embodiment, the damping force can be changed from the piston low speed range on both the extension side and the compression side between when the vehicle is empty and when the vehicle is loaded.

As described above, according to the present invention, it is possible to significantly change the damping force on both the rebound and compression sides from the low piston speed to the high speed range when the car is empty and when the car is loaded. This has the effect of improving high-speed maneuverability while reliably preventing bottoming out due to its hard damping characteristics when the vehicle is loaded.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a conventional device, and FIG. 2 is an explanatory diagram showing its damping characteristics. FIG. 3 is a sectional view of the main part of the first embodiment of the present invention, and FIG. 4 is a sectional view of the main part of the second embodiment. DESCRIPTION OF SYMBOLS 1... Cylinder, 2... Piston, 3... Piston rod, 4, 5... Oil chamber, 7... Piston nut, 14... Position detection spring, 21... First expansion side damping valve, 22... First compression damping valve, 23...Second rebound damping valve, 24...
Second pressure side damping valve, 26... internal passage, 29
...Spool, 28...Sideway, 30...Switching valve,
31...Return spring.

Claims (1)

[Claims] 1. A piston that is slidably inserted into a cylinder and defines upper and lower oil chambers, a first expansion side damping valve and a first compression side damping valve that are provided in parallel with each other on this piston, and a first damping valve that is provided on a piston rod connected to the piston and that A passage that bypasses the first expansion side and compression side damping valves and communicates the upper and lower oil chambers, a second expansion side and compression side damping valve that is provided in parallel with this passage, and a second expansion side and compression side damping valve that is supported by the piston and extends in the axial direction. a switching valve that opens and closes the passage as it moves; a return spring that biases the switching valve in one direction relative to the piston; and a return spring that biases the switching valve in a direction opposite to the return spring. a piston position detection spring interposed in the oil chamber, and the switching valve is moved to a position where the passage is closed based on the balance between the return spring and the piston position detection spring in a state where the switching valve is compressed by a predetermined amount. A load-sensitive shock absorber characterized by the following: