A brake system for actuating a plurality of wheel brakes comprising at least first and second wheel brakes, the system comprising:
- a reservoir;
- a master cylinder in fluid communication with the reservoir and operable during a backup braking mode to generate pressurized hydraulic fluid at first and second MC outputs for hydraulically actuating the first and second wheel brakes, respectively;
- a plurality of single corner actuators, each single corner actuator being hydraulically interposed between a selected one of the first and second MC outputs and a corresponding one of the first and second wheel brakes, each single corner actuator including
- a secondary power transmission unit configured for selectively providing pressurized hydraulic fluid at an SCA output for actuating the respective wheel brake in at least one of a normal non-failure braking mode and a backup braking mode, the secondary power transmission unit including an electric PTU motor configured to selectively pressurize the hydraulic fluid by transmitting rotary motion to a plunger assembly of the secondary power transmission unit;
- at least one two-position three-way valve interposed hydraulically between the plunger assembly and the respective wheel brake for selectively controlling provision of hydraulic fluid to the respective wheel brake from at least one of the plunger assembly and the master cylinder;
- and
- a bleed valve including;
- an elongate bleed valve bore having a first bore end in fluid communication with an ambient space and a second bore end, longitudinally spaced from the first bore end, with a bore lumen extending between the first and second bore ends;
- a supply side hydraulic line in fluid communication with the bore lumen adjacent the second bore end, the supply side hydraulic line being configured to selectively place the bore lumen in fluid communication with a source of pressurized hydraulic fluid;
- a fill side hydraulic line in fluid communication with the bore lumen at a location longitudinally interposed between the first bore end and the supply side hydraulic line, the fill side hydraulic line being configured to selectively place the bore lumen in fluid communication with a destination for pressurized hydraulic fluid from the source of pressurized hydraulic fluid along a bleed valve fluid path extending through a portion of the bore lumen;
- and
- an elongate bleed valve shuttle extending partially through the bore lumen for selective reciprocal motion between the first and second bore ends, the bleed valve shuttle having longitudinally spaced first and second shuttle ends selectively located longitudinally adjacent the respective first and second bore ends;
- wherein the bleed valve shuttle shifts longitudinally toward the first bore end into an operational configuration responsive to presence of a predetermined hydraulic pressure level within the bore lumen along the bleed valve fluid path, shifting of the bleed valve shuttle into the operational configuration being operative to urge air from the bore lumen into the ambient space;
- wherein the selected one of the first and second MC outputs is the supply side hydraulic line and the fill side hydraulic line is in fluid communication with a plunger cavity of the plunger assembly, wherein the bleed valve shuttle is urged to the operational configuration during initial hydraulic fill of the single corner actuator and remains in the operational configuration throughout subsequent operation of the brake system;
- and
- an electronic control unit for controlling at least one of the secondary power transmission unit and the two-position three-way valve responsive to at least one brake pressure signal;
- wherein each single corner actuator is indirectly fluidly connected to the reservoir via the master cylinder.