Patent ID: 8041502

Claim:
An engine misfire detection method of detecting a misfire of an internal combustion engine in a power output apparatus that includes the internal combustion engine having an output shaft linked to a driveshaft and a motor enabling input and output of power from and to the output shaft of the internal combustion engine and ensures output of at least part of output power of the internal combustion engine to the driveshaft under vibration control of controlling the motor to reduce a vibration caused by operation of the internal combustion engine, the engine misfire detection method comprising: (a) computing a unit angle rotation time required for rotation of the output shaft of the internal combustion engine by every predetermined unit rotation angle according to a rotational position of the output shaft of the internal combustion engine; (b) making tentative detection on occurrence or non-occurrence of a misfire in the internal combustion engine based on the computed unit angle rotation time; (c) in response to the tentative detection of a misfire in the internal combustion engine in the step (b), making final detection on the occurrence or the non-occurrence of a misfire in the internal combustion engine based on the computed unit angle rotation time; and (d) in the event of no final detection of a misfire in the internal combustion engine in the step (c), outputting prohibition of execution of the vibration control and, after the prohibition of execution of the vibration control, making final detection on the occurrence or the non-occurrence of a misfire in the internal combustion engine based on the computed unit angle rotation time.