Motor vehicle braking system and method

摘要

A motor vehicle (12) has a chassis (16) with wheels (26, 34) on which the motor vehicle travels, a powertrain having an engine (20) coupled to at least one of the wheels, a primary brake system (38) for braking the motor vehicle via foundation brakes at the wheels, and a secondary brake system for braking the vehicle via at least one powertrain brake mechanism (57) that can apply brake torque to at least one of the wheels to which the powertrain is coupled. The primary brake system has a mechanical operator (40) that when operated by a driver causes pressure to be created in the primary brake system for operating the foundation brakes to apply brake torque correlated with magnitude of the pressure. A device (42) signals a controller (44) that the foundation brakes are being applied. A selector (58) available to the driver signals the controller for selectively enabling use of the secondary brake system in conjunction with the primary brake system.