Apparatus and method for control of a hydraulic brake system

1. A brake system for actuating a pair of front wheel brakes and a pair of rear wheel brakes, the system comprising:

a reservoir;

a deceleration signal transmitter operable by actuation of a brake pedal connected to the deceleration signal transmitter to generate a brake actuating signal at a first output;

first and second power transmission units configured for selectively providing pressurized hydraulic fluid for actuating the pair of front wheel brakes and the pair of rear wheel brakes during a braking event, the first power transmission unit actuating a selected one of the front wheel brakes and a selected one of the rear wheel brakes, and the second power transmission unit actuating the other one of the front wheel brakes and the other one of the rear wheel brakes;

first and second electronic control units for controlling the first and second power transmission units, respectively; and

a pair of rear brake motors for selectively electrically actuating respective rear wheel brakes, each rear brake motor being controlled by a selected one of the first and second electronic control units other than the first or second electronic control unit that controls the rear wheel brake associated with the same respective rear wheel brake;

wherein control of each of the pair of front wheel brakes and the pair of rear wheel brakes is provided by an arrangement of first and second parallel valves for each wheel brake, with a chosen one of the first and second parallel valves receiving input from an output of the other one of the first and second parallel valves such that one of the first and second parallel valves opens when de-energized in response to a pressure differential across the first and second parallel valves, with the first and second parallel valves for the selected front and rear wheel brakes being actuated by the first power transmission unit and the first and second parallel valves for the other front and rear wheel brakes being actuated by the second power transmission unit.

2. The brake system of claim 1 , wherein the first and second parallel valves have the same arrangement with each other for each wheel brake.

3. The brake system of claim 1 , wherein the control selectively provides slip control to each wheel brake corresponding to a selected arrangement of first and second parallel valves.

4. The brake system of claim 1 , wherein the control of each chosen wheel brake is provided by the arrangement of first and second parallel valves, with a chosen one of the first and second parallel valves receiving input from a first or second power transmission unit corresponding to the chosen wheel brake and output to the chosen wheel brake, and the other of the first and second parallel valves receiving input from the chosen wheel brake and output to the first or second power transmission unit corresponding to the chosen wheel brake.

5. The brake system of claim 1 , wherein the brake pedal and deceleration signal transmitter are hydraulically isolated from at least the reservoir and first and second power transmission units, and the brake actuating signal is conveyed to at least one of the first and second power transmission units solely as an electronic signal from the first output.

6. The brake system of claim 1 , including a damping orifice providing hydraulic damping and hydraulically interposed between the deceleration signal transmitter and the reservoir without providing a manual push through feature.

7. The brake system of claim 1 , including first and second control valves, each control valve located hydraulically interposed between a corresponding first or second power transmission unit and the reservoir.

8. The brake system of claim 7 , wherein the first and second control valves each are selectively operable to substantially block fluid flow to and from the reservoir and the corresponding first or second power transmission unit to facilitate retraction of a caliper of at least one of the wheel brakes actuated by the corresponding first or second power transmission unit for diagnostic purposes.

9. The brake system of claim 1 , wherein at least one of the first and second electronic control units is integrated into a corresponding first or second power transmission units, the at least one power transmission unit including

a PTU housing,

an electric PTU motor located within and affixed to the PTU housing such that the PTU housing absorbs torque developed by a stator of the electric PTU motor,

a longitudinally extending spindle located within the PTU housing and being selectively rotationally driven by the electric PTU motor, the spindle having first and second spindle ends separated by a spindle body,

a ball nut surrounding the spindle body and being driven by rotation of the spindle for reciprocating longitudinal movement therealong, the ball nut urging a plunger adjacent the second spindle end for longitudinal reciprocation within the PTU housing, and

a printed ECU circuit board located within the PTU housing adjacent the first spindle end, the printed ECU circuit board including a Hall effect sensor for interaction with a magnet carried by the first spindle end to responsively determine a position of the first spindle end relative to the Hall effect sensor.

10. The brake system of claim 1 , wherein the first power transmission unit and the first control valve are packaged together, and spaced apart from, the second power transmission unit and the second control valve.

11. The brake system of claim 1 , wherein the chosen one of the first and second parallel valves receives input from the output of the other one of the first and second parallel valves through a passage fluidly isolated from the wheel brake.