Hydraulic circuit system for a vehicle height control device

Abstract

A hydraulic circuit system for a vehicle height control device is provided comprising actuators for increasing and decreasing vehicle heights as respective results of the supply and the discharge of working fluid to and from their working fluid chambers, a supply passage means and a discharge passage means for supplying and discharging working fluid to and from the chambers, respectively, control valve means for controlling the supply and the discharge of working fluid, cut-off valve means provided in the supply and discharge passage means and adapted to remain in their closed position so long as the pressure within the supply passage means is not more than a predetermined value. The system further comprises a bypass valve means for selectively communicating the supply and the discharge passage means with each other so that the pressure within the supply passage means may be controlled. The opening and closing of the cut-off valve means can be performed by solely controlling the bypass valve means, thereby reducing the electric power required to operate the system. Undesired decrease in vehicle height can positively be prevented by the cut-off valve means even in the event where the control valve means is shifted for supplying the working fluid to the chambers under the condition where the pressure within the supply passage means is relatively low.