Patent ID: 7293780

Claim:
A vehicle roll control system for a vehicle having a pair of wheels each rotatable on an axle, comprising a torsion bar; a first arm attached to the torsion bar at one end of the first arm and being connectable to one of the axles at the other end of the first arm; a hydraulic actuator attached to the torsion bar; and control means connected to the hydraulic actuator and controlling the operation thereof on detection of a predetermined vehicle condition; wherein the hydraulic actuator comprises a housing, a piston making a sealing sliding fit inside the housing to define a first fluid chamber and a second fluid chamber, and a piston rod connected to the piston and extending through the second fluid chamber and out of the housing; wherein the control means acts on detection of the predetermined vehicle condition either to apply fluid pressure to the first and second fluid chambers with a substantially fixed pressure differential when the piston tends to move in a first direction to extend the hydraulic actuator, or to apply a fluid pressure to the second fluid chamber above the fluid pressure in the first fluid chamber whilst maintaining the fluid pressure in the first fluid chamber substantially constant when the piston tends to move in a second direction to compress the hydraulic actuator; and wherein the control means comprises a source of fluid pressure, a fluid reservoir, first and second pressure control valves fluidly connected in series between the pressure source and the reservoir, and a directional valve fluidly connected between the pressure control valves and the hydraulic actuator, wherein the pressure control valves are actuated to control the fluid pressure in the first and second fluid chambers.