Hydraulic control device for active suspension system

Abstract

A hydraulic control device for an active suspension system employing a linear hydraulic cylinder including a piston connected in parallel with a spring between a wheel and a vehicle body, the piston having two pressure receiving surfaces of different areas facing two chambers separated by the piston in the cylinder, comprising a balancing valve for reducing the pressures of the two chambers to a level near the atmospheric pressure, a switch valve provided in a bypass passage between the two chambers for selectively communicating the two chambers with each other, a flow restricting orifice provided in the bypass passage; and an accumulator connected to the bypass passage capable of accommodating a change in the capacity of one of the chambers due to a piston rod extending from the piston out of the cylinder when the pressures of the two chambers are at the level near the atmospheric pressure. Alternatively, the accumulator could be replaced with a storage container connected to the bypass passage capable of accommodating an amount of actuating oil corresponding to a capacity of the cylinder. Thus, the active suspension system can serve as a workable passive suspension system when the supply of hydraulic oil is interrupted for any reason, and the reliability of the system can be improved.