Patent ID: 8641573

Claim:
A power transmission unit for a vehicle, the power transmission unit having: a first prime mover; a plurality of speed change gear pairs including a first speed change gear pair and a second speed change gear pair, each of the speed change gear pairs having a different gear ratio, and wherein a power outputted from the first prime mover is transmitted to one of the plurality of speed change gear pairs; an output member for outputting power transmitted from one of the plurality of speed change gear pairs; and a selective power transmission mechanism for allowing the transmitted power from the one of the plurality of speed change gear pairs to transmit to the output member by selecting one of the speed change gear pairs from said plurality of speed change gear pairs, comprising: a second prime mover; a differential mechanism, which has at least a first rotary element connected with the first prime mover, a second rotary element connected with the second prime mover, and a third rotary element, the differential mechanism being adapted to perform a differential action among at least the first, second, and third rotary elements of the differential mechanism; a first speed change gear pair system, which has at least one of said plurality of speed change gear pairs, the first speed change gear pair system being arranged between the first rotary element and the output member; a second speed change gear pair system, which has at least another of said plurality of speed change gear pairs, the second speed change gear pair system being arranged between the third rotary element and the output member; a locking mechanism, which locks the second prime mover selectively to halt a rotation of the second prime mover, wherein the output member comprises a first output shaft and a second output shaft, both of the first and second output shafts being arranged parallel to a rotation axis of the differential mechanism; an idler shaft is arranged parallel to the rotation axis of the differential mechanism; the first speed change gear pair system includes a first drive gear to which a torque is transmitted from the first rotary element, and a first driven gear arranged on the first output shaft, the first drive gear and the first driven gear being said one of said plurality of speed change gear pairs; and the second speed change gear pair system includes a second drive gear to which a torque is transmitted from the third rotary element, the second drive gear is arranged on the idler shaft, and a second driven gear is arranged on the second output shaft, the second drive gear and the second driven gear being said another of said plurality of speed change gear pairs.