Patent ID: 8002057

Claim:
A hybrid drive system comprising: an input member connected to an engine; an output member connected to a wheel; a first rotating electric machine; a second rotating electric machine; a differential gearing; a controller that controls the first rotating electric machine and the second rotating electric machine; and an electric power supplier that supplies the first rotating electric machine and the second rotating electric machine with electric power, wherein: the differential gearing includes a first rotating element, a second rotating element, and a third rotating element, the first rotating electric machine is connected to the first rotating element, the input member is connected to the second rotating element, and at least one of the output member and the second rotating electric machine is connected to the third rotating element; the controller performs a fluctuation offset control that controls an output torque of the second rotating electric machine so as to offset torque fluctuations of the output member caused by fluctuations in an output torque of the first rotating electric machine; and the controller performs a torque limiting control that limits the output torque of the first rotating electric machine in a positive direction while limiting the output torque of the second rotating electric machine when the electric power supplier runs into a predetermined low voltage state.