JPH023059B2 - - 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, piston 2, and piston rod 3 to communicate the upper and lower oil chambers 4, 5, and two damping valves 10, 11 are arranged in series in this passage 8. be done.

The damping valves 10 and 11 open during push-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 13 to open and close
is slidably fitted around its outer periphery.

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, it flows out into the lower oil chamber 5 through the side passage 12, so the generated damping force becomes weaker, as also 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 the fluid resistance and increases the raw damping force. It is.

In this way, during the expansion side operation, the hydraulic oil selectively flows through the two damping valves 10 and 11 arranged in series. The damping force can be changed significantly between when the car is empty and when it 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 arranged in series, and the first and second damping valves are arranged in series in response to a piston stroke position detection spring.
By installing a switching valve that opens and closes a side path that short-circuits the oil chamber between the damping valves, 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.

A second expansion damping valve 23 and a compression damping valve 24 are arranged in parallel inside the piston nut 7 that is fitted on the lower side.
The valves 21, 22 and 23, 24 are communicated through an internal passage (space) 26 of the piston nut 7.

A side passage 28 communicating between the internal passage 26 and the oil chamber 5 is formed through the side passage 28, and a spool 29 is slidably fitted to the outer periphery of the side passage 28, thereby forming a switching valve 30 that opens and closes the side passage 28. .

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.
From A, the upper leaf valve 34A is pushed up and hydraulic oil flows, and on the extension side, the lower leaf valve 34B is pushed down from the inner through hole 33B, and the same hydraulic oil flows.

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

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, during expansion-side operation, the hydraulic oil in the upper oil chamber 4 passes through the first expansion-side damping valve 21, reaches the internal passage 26, and flows out from there to the lower oil chamber 5 via the side passage 28.

In this case, unless the outflow resistance in the side passage 28 becomes greater than the set pressure of the second rebound damping valve 23, this second valve 23 will not open, and therefore the damping force will be exclusively the same as that of the first damping valve 23. Generated by valve 21.

On the other hand, during pressure side operation, the hydraulic oil in the lower oil chamber 5 similarly flows into the internal passage 26 from the side passage 28, and the first
Flows to the upper oil chamber 4 through the pressure side damping valve 22,
This first valve 22 generates a weak damping force.

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, the first and second damping valves are arranged in series during either expansion side or compression side operation, and the hydraulic fluid always passes through the first and second damping valves.

Therefore, even if the piston 2 moves at a low speed, for example, during pressure side operation, the hydraulic fluid that has passed through the first pressure side damping valve 22 will necessarily flow to the second pressure side damping valve 24.
The oil flows through the oil chamber 5 to the lower oil chamber 5, and therefore, unlike a conventional orifice, a large damping force is reliably generated.

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 29 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 expansion 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, 2... Second compression damping valve, 26... Internal passage, 29...
... Spool, 28 ... Side channel, 30 ... Switching valve, 3
1...Return spring.

Claims (1)

[Claims] 1. A piston is slidably inserted into a cylinder to define upper and lower oil chambers, and the piston is provided with first expansion and compression damping valves in parallel, and second expansion and compression damping valves that are parallel to each other. A valve is provided in series with the first damping valve, a side path is formed between the first and second damping valves to short-circuit to the oil chamber, and this side path is responsive to a piston position detection spring installed in the oil chamber. A load-sensitive shock absorber characterized by being equipped with a switching valve that opens and closes when the load changes.