Brake-by-wire braking system with hydraulic fail-safe
View Patent ↗A brake-by-wire braking system including a braking unit, an electro-hydraulic actuator in fluid communication with the braking unit by way of a first fluid path, a master cylinder in fluid communication with the braking unit by way of a second fluid path, a normally open solenoid valve operatively associated with the second fluid path, and a control unit adapted to actuate the normally open solenoid valve, wherein actuation of the normally open solenoid valve generally fluidly isolates the master cylinder from the braking unit.
1. A brake-by-wire braking system for a vehicle having at least two wheels comprising:
a control unit;
an electro-mechanical brake caliper associated with a first one of said wheels, said electro-mechanical brake caliper being in communication with and actuateable by said control unit;
a hydraulically actuated braking unit associated with a second one of said wheels;
an electro-hydraulic actuator in fluid communication with said hydraulically actuated braking unit by way of a first fluid path, said electro-hydraulic actuator being in communication with and actuateable by said control unit;
a master cylinder in fluid communication with said hydraulically actuated braking unit by way of a second fluid path, wherein said master cylinder is in selective fluid communication with a brake pedal feel emulator;
a hydraulically actuated bypass valve operatively positioned between said master cylinder and said brake pedal feel emulator; and
a normally open solenoid valve operatively associated with said second fluid path, said normally open solenoid valve being in communication with and actuateable by said control unit,
wherein, when said electro-hydraulic actuator is actuated, said normally open solenoid valve is actuated.
2. The system of claim 1 wherein said electro-hydraulic actuator includes a hydraulic fluid chamber and an electric motor connected to a piston, said piston being moveable through said hydraulic fluid chamber in response to actuation of said electric motor, to displace a hydraulic fluid from said hydraulic fluid chamber.
3. The system of claim 2 wherein said displaced hydraulic fluid pressurizes said first fluid path.
4. The system of claim 1 wherein said hydraulically actuated braking unit is a brake caliper.
5. The system of claim 1 wherein said master cylinder is connected to a brake pedal.
6. The system of claim 1 wherein, when said normally open solenoid valve is actuated, hydraulic fluid displaced from said master cylinder is transferred to said brake pedal feel emulator.
7. The system of claim 1 wherein said brake pedal feel emulator includes a piston closely and slideably received within a bore, said piston being spring biased to resist introduction of hydraulic fluid into said bore.
8. The system of claim 1 wherein said electro-hydraulic actuator includes a motor having a motor shaft and a motor shaft brake adapted to selectively lock said motor shaft.
9. The system of claim 1 wherein said electro-mechanical brake caliper includes a motor, a ball screw assembly and a latching mechanism adapted to prohibit said motor and said ball screw assembly from back-driving.