Patent ID: 6247766
Filing Date: 2001-06-19
Classification: B60T,F16K

Abstract:
A brake control system for providing a variable pressure to selectively apply at least one vehicle wheel brake of the driven wheels of a vehicle comprising:an operator controlled master cylinder having a reservoir;a first passage for delivering fluid from said reservoir through said master cylinder to a plurality of valves including a prime valve and a plurality of brake apply valves, each of said brake apply valves being effective to control the distribution of fluid to respective vehicle wheel brakes;a fluid pump for distributing fluid from said reservoir to at least one brake apply valve, said prime valve being disposed between said reservoir and said pump for selectively controlling inlet fluid to said pump;an isolation valve having an inlet port connected between an outlet of said pump and the brake apply valve and an outlet port connected to release to said reservoir a portion of the fluid output of said pump in response to an electric signal, said isolation valve including a valve spool slidably disposed in a stepped diameter valve bore, electromagnetically responsive to an electric signal to exert a pressure against fluid flowing from said inlet port to said outlet port, and cooperating therewith to form a fluid dampening mechanism including a flow restriction formed between a cylindrical wall of a valve land on said spool and a cylindrical wall of a first portion of said stepped diameter valve bore and an expansible chamber in fluid communication with said flow restriction; anda pulsed electric signal generator connected to provide said electric signal to said isolation valve to continuously and linearly establish a maximum pressure during each self apply operation wherein said maximum pressure for each self-apply operation is not greater than the maximum pressure necessary to provide the braking effort required by at least one of the vehicle wheel brakes.