Land vehicles – Wheeled – Running gear
Patent
1995-10-20
1997-10-21
Dickson, Paul N.
Land vehicles
Wheeled
Running gear
280714, B60G 1126
Patent
active
056788460
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle suspension device.
The present invention relates particularly to a vehicle suspension device for use in a vehicle suspension system wherein actuators are used between the wheel and hub assemblies of the vehicle to control the relative position of the wheel and hub assemblies with respect to the vehicle body. The actuators generally comprise hydraulic piston and cylinder arrangements. An example of such a vehicle suspension system is disclosed in European patent EP 0114757.
When hydraulically powered actuators are used in a vehicle suspension system, the power used by the actuators is generally provided by the engine of the vehicle. Any power taken from the engine of the vehicle detracts from the engine performance and economy. Therefore it is important that the actuator should use as little power as possible during operation. This is especially important when the vehicle is passing over very rough ground and the actuators are required to make many rapid movements. In fact, if the actuators require too much power, the pressure of the fluid within the system may fall since the source of pressurized fluid within the system may not be able to provide sufficient fluid to meet the demand of the actuator. In such circumstances, the active suspension system ceases to function properly, being not able to adequately control the motion of each actuator.
SUMMARY OF THE INVENTION
The present invention provides a vehicle suspension device comprising: an actuator having a piston and a plurality of chambers, a source of pressurized fluid, an exhaust for pressurized fluid, first sensor means for sensing the force applied to the actuator, second sensor means for sensing the pressure of the fluid supplied by the source of pressurized fluid, and control means for controlling the extension of the actuator by controlling flow of fluid to and from at least one of the chambers, which control means receives signals from the first and the second sensor means and controls the actuator accordingly, wherein;
the control means connects the said chamber to the source of pressurized fluid when the control means determines that the force applied to the actuator is;
greater than the force that can be applied to the piston by the greatest achievable difference in pressures acting on the surfaces thereof,
acting to expel fluid from the said chamber, and
acting to assist a piston in attaining a velocity required by the control means.
Preferably the control means locks the actuator by preventing fluid from flowing into or out of the said first chamber when the control means determines that force applied to the actuator is;
greater than the force that can be applied to the piston by the greatest achievable difference in pressures on the surfaces thereof, and
acting to force the piston in a direction opposite to the direction of the velocity required of the piston by the control means.
The control means connects the said chamber to the exhaust for pressurised fluid when the control means determines that the force applied to the actuator is;
greater than the force that can be applied to the piston by the greatest achievable difference in pressure on the surfaces thereof,
acting to induce fluid into the said first chamber, and
acting to aid the piston in obtaining the velocity required by the control means.
Preferably the control device comprises a processor and a valve means controlled by the processor, the valve means being connected to the said chamber, the source of pressurized fluid and the exhaust for pressurized fluid, and the valve means metering the flow of fluid to and from the first chamber.
Preferably the valve means comprises a spool member movable within a housing to open and close apertures defined in the housing, the movement of the spool member being controlled by the processor.
In one preferred embodiment the actuator comprises a first and a second chamber, the surface of the piston acting in the first chamber is larger than the surface of the piston actin
REFERENCES:
patent: 5082308 (1992-01-01), Jones
patent: 5102161 (1992-04-01), Williams
patent: 5290048 (1994-03-01), Takahashi et al.
patent: 5348338 (1994-09-01), Kuriki et al.
Dickson Paul N.
Lotus Cars Limited
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