Patent ID: 7223191

Claim:
A power transmission system for vehicles including a first pair of drive wheels and a second pair of drive wheels, the system comprising: a main power transmission system configured to drive the first pair of wheels via a first train of torque transmitters; and an auxiliary power transmission system configured to transmit drive power from an electric motor to the second pair of drive wheels via an interruptive second train of torque transmitters including: a differential; a speed-reducing mechanism for reducing a rotational speed of the electric motor; a two-way clutch disposed between the electric motor and the differential, wherein rotation of the electric motor before rotation of the differential operates the two-way clutch to connect the second train of torque transmitters and wherein rotation of the differential before rotation of the electric motor operates the two-way clutch to disconnect the second train of torque transmitters; and a controller capable of changing a rotation of the electric motor so as to encourage disengagement of the clutch.