One proposed structure of an engine misfire detection apparatus detects a misfire of an engine in a power output apparatus, based on an output torque command value of a first motor generator (see, for example, Patent Document 1). The power output apparatus includes the engine, a planetary gear mechanism having a carrier and a ring gear respectively linked with a crankshaft of the engine and with an axle, a first motor generator linked with a sun gear of the planetary gear mechanism, and the second motor generator linked with the axle. In the power output apparatus, the output torque of the first motor generator is varied in synchronism with the explosive combustion timing of the engine, in order to control the potential vibrations due to the torque pulsation of the engine. The occurrence of an engine misfire is detected in response to a significant fall of the output torque command value from a previous value. In another proposed structure of the power output apparatus, the second motor generator is linked with the axle via a transmission (see, for example, Patent Document 2).    Patent Document 1: Japanese Patent Laid-Open Gazette No. 2000-240501    Patent Document 2: Japanese Patent Laid-Open Gazette No. 2005-170317
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