US Patent 9428042 Electromechanical variable transmission

A drive train for a vehicle includes an engine having an output shaft, a first gear set, a second gear set, a first motor/generator coupled to the first gear set, a second motor/generator coupled to the second gear set and electrically coupled to the first motor/generator, a first clutch, and a second clutch. Planetary gears of both sets are rotatably supported by respective planetary gear carriers that are coupled to each other. The first clutch selectively engages the output shaft of the engine with the second motor/generator, and the second clutch and a third gear set operate to selectively engage at least one of the sun gear and the ring gear of the second gear set with the planetary gear carriers of the first and second gear sets.