Engine Misfire Detection Apparatus, Hybrid Vehicle Equipped With the Same, and Engine Misfire Detection Method

An engine misfire detection apparatus for detection of a misfire in a multi-cylinder internal combustion engine included in a power output apparatus, where the power output apparatus includes the multi-cylinder internal combustion engine having a crankshaft mechanically linked with a driveshaft, a motor that outputs power to the driveshaft, and a transmission mechanism that transmits power between a rotating shaft of the motor and the driveshaft with a change in gear position,

• the engine misfire detection apparatus comprising:
• a rotational position detection unit that detects a rotational position of the crankshaft of the internal combustion engine;
• a unit angle rotation time computation module that computes a unit angle rotation time required for rotation of an output shaft of the internal combustion engine by every predetermined unit rotation angle according to the detected rotational position;
• a threshold value setting module that sets a first threshold value and a second threshold value to be used for detection of an engine misfire according to a gear position of the transmission mechanism;
• and
• an engine misfire detection module that performs an engine misfire detection, the engine misfire detection making a tentative decision on an engine misfire when any of the computed unit angle rotation times is greater than the first threshold value,
• after the tentative decision on the engine misfire, the engine misfire detection specifying an object unit angle rotation time that is greater than the first threshold value among the computed unit angle rotation times and making a final decision on the engine misfire when a ratio of a unit angle rotation time of a different cylinder, which is different from a target cylinder corresponding to the specified object unit angle rotation time, to the specified object unit angle rotation time is in a range defined by the second threshold value.