| CPC B60T 13/58 (2013.01) [B60T 7/042 (2013.01); B60T 13/148 (2013.01); B60T 13/686 (2013.01); B60T 13/746 (2013.01); H02K 7/06 (2013.01); H02K 7/116 (2013.01); B60T 2220/04 (2013.01); B60T 2270/402 (2013.01); B60T 2270/404 (2013.01); B60T 2270/82 (2013.01); F16D 2121/02 (2013.01); F16D 2121/24 (2013.01); F16D 2125/08 (2013.01); F16D 2125/24 (2013.01); F16D 2125/40 (2013.01); F16D 2125/50 (2013.01)] | 15 Claims |
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1. A brake system for selectively actuating at least one of a right rear wheel brake, a left front wheel brake, a left rear wheel brake, and a right front wheel brake, the system comprising:
a reservoir;
a power transmission unit configured for selectively providing pressurized hydraulic fluid for actuating at least a selected one of the wheel brakes during a braking event;
first and second rear brake motors for selectively electrically actuating respective left and right rear wheel parking brakes;
a first electronic control unit for at least partially controlling at least one of the power transmission unit and the first rear brake motor;
a second electronic control unit for at least partially controlling at least one of the power transmission unit and the second rear brake motor;
first and second SAP valves located hydraulically between the power transmission unit and at least two selected wheel brakes; and
an isolation valve and a dump valve associated with each wheel brake, the isolation valve being located hydraulically between a respective wheel brake and at least a corresponding one of the first and second SAP valves, and the dump valve being located hydraulically between a respective wheel brake and the reservoir, the SAP valves, the isolation valves, and the dump valves collectively defining first and second pressure circuits associated with respective first and second pairs of the wheel brakes and controllable by the respective first and second electronic control units;
wherein the power transmission unit is a stepped single acting plunger type power transmission unit, including
a ball screw,
a ball nut selectively driven by the ball screw,
a plunger piston operatively coupled to the ball nut, the plunger piston including longitudinally adjacent first and second piston segments, the first piston segment having a first cross-sectional footprint, and the second piston segment having a second cross-sectional footprint which is larger than the first cross-sectional footprint,
a housing at least partially enclosing the plunger piston, the ball screw, and the ball nut, and
a plunger chamber at least partially defined by the housing and at least one of the first and second cross-sectional footprints of the plunger piston, the plunger chamber being configured to contain hydraulic fluid and selectively pressurized by reciprocal motion of the plunger piston with respect to the housing, the plunger chamber including first and second chamber segments configured to receive the first and second piston segments, respectively, for reciprocal motion within the plunger chamber, wherein the first chamber segment has a first bore cross-sectional area, and the second chamber segment has a second bore cross-sectional area which is larger than the first bore cross-sectional area,
a first output channel in fluid communication between the first chamber segment and at least one SAP valve associated with a selected wheel brake,
a second output channel in fluid communication between the second chamber segment and at least one SAP valve associated with an other wheel brake, the first and second output channels being fluidically separated from one another by structures of the power transmission unit, and
an electric motor for selectively driving the ball screw of the single acting plunger assembly type power transmission unit to responsively reciprocate the plunger piston within the plunger housing.
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