Hybrid Powertrain with an Engine-Disconnecting Clutch 2002-01-0930

Several types of hybrid-electric vehicles have been developed at Ford Research Laboratory. Among the parallel hybrid systems with a single electric motor, two types were studied. In the first type, the electric motor was attached directly to the crankshaft (mild hybrid) [1], to enable the engine start-stop and regeneration functions. In the second type (full hybrid) the electric motor was connected to the engine through the use of a clutch to allow electric launch of the vehicle and pure electric driving at low speeds. The full hybrid powertrain described in this paper uses a more powerful electric motor for enhanced regenerative braking and engine power assist. An engine-disconnecting clutch saves energy during both the electric propulsion and during vehicle braking. When the clutch is disengaged the engine is shut-off, which eliminates the energy otherwise spent on motoring the engine during electric propulsion. Similarly, during the vehicle braking the energy, that otherwise is wasted on motoring the engine, is collected in the battery.

The design analysis includes a dynamic analysis of bearing loads for the crankshaft, starter-alternator, and transmission input shaft. The rotor radial deflections, amplified by a “flywheel whirl” effect, as well as clutch thermal loading, have also been accounted for. In addition, other aspects discussed here include stator and rotor alignment, clutch design, slave cylinder and clutch actuator, and other details.