Patent ID: 7918470

Claim:
A hydraulic suspension system comprising: a suspension base supporting wheels; a hydraulic cylinder for displaceably suspending said suspension base from a vehicle body; an oil passage connected to said hydraulic cylinder; an accumulator incorporated within said oil passage; a flow control valve incorporated at an oil passage portion between said hydraulic cylinder and said accumulator for controlling an amount of work oil flowing therebetween; a pressure sensor for detecting a cylinder oil passage pressure effective on said hydraulic cylinder; and a control unit for controlling operation of said flow control valve, based upon a detection value from said pressure sensor; and wherein said control unit includes: a threshold setting section for setting a threshold for said cylinder oil passage pressure; a determining section operable to detect a first state in which said cylinder oil passage pressure is below a set threshold and a second state in which said cylinder oil passage pressure is greater than the set threshold; and valve controlling section operable to control said flow control valve in such a manner that in said first state communication is established between said hydraulic cylinder and said accumulator through an orifice having a large flow passage cross section area, and that in said second state communication is established between said hydraulic cylinder and said accumulator through an orifice having a small flow passage cross section area.