US Patent 8475311 Hybrid power driving system and gear position operation method thereof

A hybrid power driving system for a vehicle comprises an internal-combustion engine, a first electric motor, a second electric motor, a planetary coupling mechanism, a speed-reduction mechanism and a differential mechanism. An output shaft of the internal-combustion engine is connected with an input shaft of the first electric motor, and an output shaft of the first electric motor is connected with an output shaft of the second electric motor via a first clutch. The output shaft of the second electric motor is connected with one of a sun gear and a ring gear of the planetary coupling mechanism at a position of the output shaft along its axial direction. And the output shaft of the second electric motor is connected with the other one of a sun gear and a ring gear at another position of the output shaft along the axial direction via a second clutch.