US Patent 9821789 Vehicle drive and method with electromechanical variable transmission

A vehicle drive includes a gear set, a first motor/generator coupled to a sun gear of the gear set, a second motor/generator selectively coupled to at least one of (a) a planetary gear carrier of the gear set and (b) a ring gear of the gear set, an engine coupled to the ring gear of the gear set and selectively coupled to the second motor/generator, and a clutch configured to selectively engage the second motor/generator to the engine. The first motor/generator and the second motor/generator are electrically coupled without an energy storage device configured to at least one of (a) provide electrical energy to the first motor/generator or the second motor/generator to power the first motor/generator or the second motor/generator and (b) be charged by electrical energy from the first motor/generator or the second motor/generator.