Patent ID: 8573708

Claim:
A hydraulic braking system for use in a vehicle employing both hydraulic and regenerative braking, comprising: a master cylinder having an outlet port, said cylinder responsive to vehicle operator applied brake pedal pressure to provide pilot pressure at the outlet port; a hydraulic pedal simulator; a two position spool valve operable in a first position to directly hydraulically couple the cylinder outlet port with the pedal simulator and in a second position to apply pilot pressure directly to a vehicle wheel brake actuator and to block the pilot pressure from the pedal simulator; a first source and a second source each providing hydraulic proportional pressure proportional to regenerative braking torque; and a control valve for providing boost hydraulic pressure from a boost pressure source to the vehicle wheel brake actuator in proportion to a pressure differential between the pilot pressure and the hydraulic proportional pressure, wherein there are two hydraulic braking circuits, one for supplying boost pressure to vehicle front wheels and the other for supplying boost pressure to vehicle rear wheels, two regenerative braking circuits, one for braking vehicle front wheels and the other for braking vehicle rear wheels, the first source and the second source providing front and rear proportional hydraulic pressures proportional to respective front and rear regenerative braking torque, and wherein the control valve includes a first control valve and a second control valve, the first control valve providing boost hydraulic pressure from the boost pressure source to a respective one of the two hydraulic braking circuits in proportion to the pressure differential between the pilot pressure and one of the front and rear proportional hydraulic pressures, and the second control valve providing boost hydraulic pressure from the boost pressure source to the other of the two hydraulic braking circuits in proportion to the pressure differential between a mechanical force equivalent to the pilot pressure and the other of the front and rear respective proportional hydraulic pressures.