Patent ID: 7196430

Claim:
A hybrid drive system for driving a load, comprising: an internal combustion engine, the engine being operable in a plurality of rotation speed ranges, including a high-efficiency range; a first electrical unit having a rotary component that is coupled to a rotary power output component of the engine; a second electrical unit having a rotary component that is coupled to the load; a clutch coupled to the rotary components of the first and second electrical units for connecting the rotary power output component of the engine and the rotary component of second electrical unit to transmit rotary power or interrupt transmission of rotary power; and control means for engaging the clutch to couple the rotary power output component of the engine to the load when the load is being driven in a high-power range, for disengaging the clutch to isolate the rotary power output component of the engine from the load when the load is being driven in a reduced power range, for operating the engine in its high-efficiency range when the load is being driven in the reduced power range, and for operating the second electrical unit as a motor and the first electrical unit as a generator that supplies electricity to the second electrical unit when the load is being driven in the reduced power range.