Shock absorber for a suspension element of a heavy vehicle

Details Shock absorber for a suspension element of a heavy vehicle Shock absorber for a suspension element of a heavy vehicle

1987-02-06

1988-09-06

Butler, Douglas C.

Brakes

Internal-resistance motion retarder

Having a thrust member with a variable volume chamber

18832214, 267 6411, 280705, F16F 950

Patent

active

047686286

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a shock absorber for a suspension element of a heavy vehicle.
This suspension element is of the type of those described in French patent applications No. 85 05 064, now French patent No. 2579936, and No. 85 05 067 now French patent No. 2579935 filed on Apr. 3, 1985 by the Applicant.
These patent applications describe a suspension element comprising an arm through which extends a wheel stub-axle of the vehicle, and rotatively articulated on a fixed part connected to the chassis of the vehicle, with interposition of rolling means between this fixed part and the rotary arm. A hydraulic chamber is provided in the arm and contains a slidable piston on which is articulated a link whose end opposed to the piston is articulated to the fixed part, the latter having an interior volume concentric with the axis of the fixed part connected to the chassis of the vehicle. More particularly, patent application No. 85 05 064 describes a ground clearance corrector adapted to be placed in the aforementioned interior volume so as to constantly control the ground clearance of the chassis of the vehicle at a pre-set value, irrespective of the profile of the ground over which the vehicle travels.
This suspension element comprises a shock absorber communicating on one hand with a hydraulic chamber of the piston and on the other hand with hydraulic chambers separated from gas chambers by two freely slidable pistons.
It is therefore to this shock absorber that the present invention relates.
According to the invention, the shock absorber comprises a hollow slide slidably mounted in a fixed member disposed in a sleeve inside the body, separated from the latter by an annular gap and having an opening which communicates with a conduit opening into the hydraulic chamber, the fixed member is mounted with clearance in the sleeve and provided with radial ports communicating with the interior of the slide, which is biased against said fixed member by an elastic return member bearing on the body, the slide being arranged in such manner as to be capable of occupying alternately a first position in which it closes any communication between said annular gap and the interior of the slide when the suspension element is subjected to a low frequency oscillation, less than .sqroot.2 times its frequency of resonance, and a second position in which it establishes a communication between its interior volume and the annular gap between the sleeve and the body when the suspension element is subjected to an oscillation frequency greater than its frequency of resonance.
Under these conditions, when the frequency of oscillation or excitation of the wheel associated with this suspension element is low, the slide remains closed, the force and the displacement transmitted to the suspension element are large, and the shock absorption is high.
On the other hand, when the oscillation frequency of the wheel is sufficiently high and the forces transmitted to the suspension are sufficiently large, the slide is opened and remains open so that the shock absorption obtained is low. In other words, the vehicle then does not undergo large vertical displacements.
Further features and advantages of the invention will be apparent from the following description with reference to the accompanying drawings which illustrate an embodiment by way of a non-limiting example:
FIG. 1 is a longitudinal sectional view with a partial elevational view of an embodiment of the suspension element in which the shock absorber to which the invention relates may be mounted;
FIG. 2 is an axial sectional view of an embodiment of the shock absorber according to the invention, the slide being closed;
FIG. 3 is a view similar to FIG. 2 showing the shock absorber with its slide open;
FIG. 4 is a diagram illustrating the variation of the shock absorption as a function of the frequency of oscillation transmitted to the suspension element and to its shock absorber.
FIG. 1 shows a suspension element for a heavy vehicle similar to that described in the aforementioned Frenc

REFERENCES:
patent: 3459439 (1969-08-01), Sinclair et al.
patent: 3614125 (1971-10-01), Sinclair
patent: 4153237 (1979-05-01), Supalla
patent: 4156536 (1979-05-01), Brandstadter
patent: 4552344 (1985-11-01), Johnson

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