Hydraulic control device for active suspension system

A hydraulic control device for an active suspension system employing a pressure source, and a linear hydraulic cylinder including a system connected in parallel with a spring between a wheel and a vehicle body, said piston having two pressure receiving surfaces of different areas facing two chambers separated by said piston in said cylinder, said hydraulic control device comprising:

• conduit means for supplying output pressure from said pressure source substantially continuously and directly to one of said two chambers corresponding to a smaller one of said pressure receiving surfaces of said piston during normal operation of the pressure source;
• a control valve connected between said pressure source and the other of said two chambers for controlling the pressure in said other chamber to allow said hydraulic cylinder to operate as a powered actuator for said active suspension system;
• means for reducing the pressures of said two chambers to a level near the atmospheric pressure when operation of the pressure source becomes abnormal;
• switch valve means provided in a bypass passage between said two chambers for selectively communicating said two chambers with each other;
• flow restricting means provided between one of said chambers and said switch valve means;
• and
• an accumulator connected to said bypass passage capable of accommodating a change in the capacity of one of said chambers due to a piston rod extending from said piston out of said cylinder when the pressures of said two chambers are at said level near the atmospheric pressure.

A hydraulic control device for an active suspension system employing a pressure source, and a linear hydraulic cylinder including a piston connected in parallel with a spring between a wheel and a vehicle body, said piston having two pressure receiving surfaces of different areas facing two chambers separated by said piston in said cylinder, said hydraulic control device comprising:

• conduit means for supplying output pressure from said pressure source substantially continuously and directly to one of said two chambers corresponding to a smaller one of said pressure receiving surfaces of said piston during normal operation of the pressure source;
• a control valve connected between said pressure source and the other of said two chambers for controlling the pressure in said other chamber to allow the hydraulic cylinder to operate as a powered actuator for said active suspension system;
• means for reducing the pressures of said two chambers to a level near the atmospheric pressure when operation of the pressure source becomes abnormal;
• switch valve means provided in a bypass passage between said two chambers for selectively communicating said two chambers with each other;
• flow restricting means provided between one of said chambers and said switch valve means;
• and
• fluid accommodating means connected to said bypass passage for accommodating a change in the capacity of at least one of said chambers when the pressures of said chambers are at said level near the atmospheric pressure.

A hydraulic control device for an active suspension system employing a pressure source, a linear hydraulic cylinder including a piston connected in parallel with a spring between a wheel and a vehicle body, said piston having two pressure receiving surfaces of different areas facing two chambers separated by said piston in said cylinder, conduit means for supplying output pressure from said pressure source substantially directly to one of said two chambers corresponding to a smaller one of said pressure receiving surfaces of said piston, and a control valve connected between said pressure source and the other of said two chambers for controlling the pressure in said other chamber to allow said hydraulic cylinder to operate as a powered actuator for said active suspension system, said hydraulic control device comprising:

• means for reducing the pressures of said two chambers to a level near the atmospheric pressure;
• switch valve means provided in a bypass passage between said two chambers for selectively communicating said two chambers with each other;
• flow restricting means provided in said bypass passage;
• a storage container connected to said bypass passage capable of accommodating an amount of actuating oil corresponding to a capacity of said cylinder;
• and
• said pressure reducing means being adapted to gradually open at least one of said two chambers to the atmosphere.