Patent ID: 6216457
Filing Date: 2001-04-17
Classification: B60T

Abstract:
A vehicle hydraulic system comprising:a hydraulic fluid reservoir;a first fluid conduit in fluid communication with said reservoir and a second fluid conduit;a pressure source supplying pressurized hydraulic fluid to said first fluid conduit and to said second fluid conduit;a vehicle braking system having a hydraulically operated boost piston assembly for supplementing a force exerted by a vehicle operator to operate brakes of a vehicle braking system, wherein said second fluid conduit is in fluid communication with said boost piston assembly;a back pressure valve operative in said first fluid conduit to maintain a desired pressure in said second fluid conduit when the vehicle operator is not operating said vehicle brakes;a boost pressure control valve operative in said second fluid conduit for directing pressurized hydraulic fluid therethrough to said boost piston assembly only when said vehicle brakes are operated and for allowing substantially no fluid flow to said boost piston assembly when said vehicle brakes are not operated;a third fluid conduit providing fluid communication from said second fluid conduit, at a point between said boost pressure control valve and said boost piston assembly, to said back pressure valve to control the back pressure generated by said back pressure control valve; andmeans disposed in said third fluid conduit to limit a pressure reduction rate in said third fluid conduit.