Patent ID: 7703280

Claim:
A hydraulic ride control system for a working vehicle, said system comprising: a hydraulic cylinder, an actuator control valve for controlling a pressure in a pressure chamber of said hydraulic cylinder, an accumulator connected to a bottom side of said pressure chamber of said hydraulic cylinder via a first connection line, a reservoir connected to a rod side of said pressure chamber of said hydraulic cylinder via another, second connection line that is independent of said first connection line, a normally closed opening control valve having a pilot chamber for selectively communicating or cutting off said connection lines depending on a pressure in said pilot chamber, a load pressure detection means for detecting a load pressure on said hydraulic cylinder and outputting a signal corresponding to said load pressure, a vehicle speed detection means for detecting a vehicle speed of said working vehicle and outputting a signal corresponding to said vehicle speed, a selector means for selectively feeding a pressure to or draining a pressure from said pilot chamber, and a clock means for measuring time from a time point of an input of a signal from a speed sensor or a load pressure sensor into a controller, wherein, responsive to a signal outputted from at least one of said load pressure detection means and said vehicle speed detection means, said control means changes an opening of said opening control valve, and wherein a control signal holding the opening of the opening control valve small is outputted from the controller to the selector means during a predetermined time while a control signal increasing gradually the opening of the opening control valve is outputted from the controller to the selector means from a time point beyond said predetermined time.