Suspension system for vehicle

Abstract

A suspension system for a vehicle which has a hydraulic cylinder that extends and retracts in accordance with a change in the distance between a vehicle body and an axle to vary the volumetric capacity of a working chamber defined therein, an accumulator connected to the working chamber in the hydraulic cylinder, a control valve controlling the flow rate of oil charged into and discharged from the accumulator and the hydraulic cylinder, and a vehicle level sensor detecting a change in the above-described distance. The suspension system further has a control unit that controls the control valve, on the basis of a flow control signal obtained by multiplying the detected signal from the vehicle level sensor by an amplification factor, so as to restore the vehicle to a neutral state. The control unit is arranged to increase the amplification factor when the amount of the extension or retraction of the hydraulic cylinder is close to the extent of the full stroke thereof. When the vehicle is running on a normal road surface, the suspension system absorbs any changes in the road surface, thereby stably maintaining the attitude of the vehicle body, and in the case of large irregularities, it is possible to prevent full rebound or full bump which would otherwise occur when the hydraulic cylinder performs a full-stroke operation.