Patent ID: 6533369
Filing Date: 2003-03-18
Classification: B60T

Abstract:
A brake system for providing secondary hydraulic braking in a de-energized operational mode, said system comprising:a wheel brake assembly including a brake application device; a master cylinder in fluid communication with said wheel brake assembly for operation of said brake application device when said brake system is in the de-energized operational mode; a first valve disposed between said master cylinder and said wheel brake assembly to decouple said master cylinder from said wheel brake assembly in an energized operational mode such that said master cylinder is prevented from operating said brake application device in the energized operational mode, and to couple said master cylinder with said wheel brake assembly in the de-energized operational mode such that said master cylinder can operate said brake application device in the de-energized operational mode to provide the secondary hydraulic braking through said master cylinder; an actuator assembly in fluid communication with said wheel brake assembly for operation of said brake application device independent of said master cylinder when said brake system is in the energized operational mode, said actuator assembly comprising a motor, a screw device, and a piston wherein, upon activation, said motor rotates said screw device to advance said piston and increase hydraulic pressure to said brake application device; a controller operatively connected to said motor for activating said screw device and said piston to operate said brake application device independent of said master cylinder when said brake system is in the energized operational mode; and a second valve disposed between said actuator assembly and said wheel brake assembly, said second valve being normally-closed such that said second valve is open in the energized operational mode to couple said actuator assembly with said wheel brake assembly in the energized operation mode to allow said screw device and said piston to operate said brake application device, and is closed in the de-energized operational mode to isolate said wheel brake assembly from said screw device and said piston in the de-energized operational mode such that the secondary hydraulic braking is provided through said master cylinder.