US Patent 9970515 Multi-mode electromechanical variable transmission

A drive system includes a first gear set and a second gear set, each including a sun gear, a ring gear, a plurality of planetary gears coupling the sun gear to the ring gear, and a carrier rotationally supporting the plurality of planetary gears, a first electrical machine directly coupled to the sun gear of the first gear set, a second electrical machine directly coupled to the sun gear of the second gear set, a connecting shaft directly coupling an engine to the ring gear of the first gear set, a driveshaft configured to transport power from the first electrical machine, the second electrical machine, and the engine to a tractive element of the vehicle, and a clutch selectively rotationally coupling the first carrier and the second carrier to the driveshaft when engaged.