Brake-by-wire braking system with hydraulic fail-safe

Abstract

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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of one aspect of the disclosed brake-by-wire braking system having a hydraulic fail-safe;

FIG. 2 is a partial schematic and partial sectional view of an electro-hydraulic brake actuator of the system of FIG. 1;

FIG. 3 is a front elevational view, in section, of an electro-mechanical brake caliper of the system of FIG. 1;

FIG. 4 is a front elevational view, in section, of a pedal feel emulator of the system of FIG. 1;

FIG. 5 is a perspective view of a master cylinder assembly of the system of FIG. 1 including the pedal feel emulator of FIG. 4; and

FIG. 6 is a front elevational view, in section of the master cylinder and pedal feel emulator assembly of FIG. 5.

Claims

1. A brake-by-wire braking system comprising: a braking unit;an electro-hydraulic actuator in fluid communication with said braking unit by way of a first fluid path;a master cylinder in fluid communication with said braking unit by way of a second fluid path;a normally open solenoid valve operatively associated with said second fluid path; anda control unit adapted to actuate said normally open solenoid valve, wherein actuation of said normally open solenoid valve generally fluidly isolates said master cylinder from said braking unit.

2. The system of claim 1 wherein said braking unit is a brake caliper.

3. 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.

4. The system of claim 3 wherein said displaced hydraulic fluid pressurizes said first fluid path.

5. The system of claim 1 wherein said electro-hydraulic actuator is in communication with said control unit and said control unit is adapted to actuate said electro-hydraulic actuator when said normally open solenoid valve is actuated.

6. The system of claim 1 wherein said master cylinder is connected to a brake pedal.

7. The system of claim 1 wherein said master cylinder is in selective fluid communication with a brake pedal feel emulator.

8. The system of claim 7 wherein, when said normally open solenoid valve is actuated, hydraulic fluid displaced from said master cylinder is transferred to said brake pedal feel emulator.

9. The system of claim 7 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.

10. The system of claim 7 further comprising a hydraulically actuated bypass valve operatively positioned between said master cylinder and said brake pedal feel emulator.

11. The system of claim 1 wherein said braking unit is associated with a wheel of a vehicle.

12. 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 at least two 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 at least two 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; anda 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.

13. The system of claim 12 wherein said hydraulically actuated braking unit is a brake caliper.

14. The system of claim 12 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.

15. The system of claim 14 wherein said displaced hydraulic fluid pressurizes said first fluid path.

16. The system of claim 12 wherein said master cylinder is connected to a brake pedal.

17. The system of claim 12 wherein said master cylinder is in selective fluid communication with a brake pedal feel emulator.

18. The system of claim 17 wherein, when said normally open solenoid valve is actuated, hydraulic fluid displaced from said master cylinder is transferred to said brake pedal feel emulator.

19. The system of claim 17 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.

20. The system of claim 17 further comprising a hydraulically actuated bypass valve operatively positioned between said master cylinder and said brake pedal feel emulator.

21. The system of claim 12 wherein said electro-hydraulic actuator includes a motor having a motor shaft and a motor shaft brake adapted to selectively lock said motor shaft.

22. The system of claim 12 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.