Land vehicles – Wheeled – Running gear
Patent
1985-06-04
1989-05-16
Marmor, Charles A.
Land vehicles
Wheeled
Running gear
267 6426, B60G 1126, B60G 1700
Patent
active
048303984
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The invention relates to vehicle suspension arrangements.
In U.S. Pat. No. 4,625,993 and in International Patent Application PCT/GB84/00014, both of which claim priority from UK Patent Application No. 83 01 741, there is disclosed a vehicle suspension system comprising wheel suspension devices the displacement of which can be varied, and means responsive to the loading of the suspension devices to feed back to the devices electric signals effecting a predetermined displacement.
Such a vehicle suspension system permits control of the ride of the vehicle and its attitude to be achieved substantially independently. The system can be rendered capable of keeping the vehicle substantially stable in all planes of movement, irrespective of external forces.
The present invention is concerned with the provisions of an improved wheel suspension device for use in such a system or in other systems serving a similar purpose.
The present invention accordingly provides a wheel suspension device comprising an hydraulic actuator of which the piston position is adjustable in response to forces acting thereon and/or to a selected control input, and a load bearing strut responsive to the actuator piston experience to minimise the load carried by the actuator.
The present invention thus also provides a wheel suspension device comprising a double acting hydraulic actuator and a strut of which the pre-load and load deflection characteristics are adjustable, the actuator and the strut being arranged to share the suspension load, and means for adjusting the pre-load and load deflection characteristics of the strut in response to the pressure differential experience by the piston of the hydraulic actuator so as to minimise the share of the suspension load carried by the actuator.
The present invention also provides a vehicle wheel suspension device comprising an inner end member slidable into and out of an outer end member, the members enclosing between them a fluid body of which the volume is selectively adjustable, the inner end member also having a piston portion slidably engaging the outer member interior, the ends of the piston portion being exposed to respective fluid pressures to effect the relative sliding movement of the end members. The fluid body can comprise a body of a suitable hydraulic fluid, but can instead comprise a body of air or other gas of which the volume is adjustable by alteration of the volume of a body of liquid in contact with the body of gas either directly or by way of a free piston, so as to vary the spring rate of the strut.
Typically, the double acting hydraulic actuator is substantially irreversible within a range of load determined by its cross-sectional area and fluid differential supply pressure. Thus, a demand load will effect a displacement, which can remain unaltered in spite of a change in load. The actuator can incorporate sensing means responsive to at least one of piston position, piston velocity and piston acceleration, for supplying signals to electrical control circuitry included in the system in which the suspension device of the invention is incorporated, which circuitry provides outputs controlling the device.
The pre-load and load deflection characteristics of the load bearing strut are conveniently adjustable by variation of the hydraulic fluid quantity present in the strut by way of a servo-valve. The movement of the hydraulic fluid can be employed to damp the movement of the actuator.
Although it is convenient to incorporate the wheel suspension device of the invention to an electric system, when transducers measuring load, pressure, velocity and/or displacement can be included, the device can be controlled mechanically, as by way of a mechanical linkage between the device and the vehicle. Although primarily applicable to road vehicles, the usefulness of the device of the invention is not so limited.
The invention, which can be embodied in a variety of ways, will be understood to provide a wheel suspension device for an active suspension system in which the load on t
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Williams David A.
Wright Peter G.
Diederiks, Jr. Everett G.
Group Lotus Public Limited Company
Marmor Charles A.
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