Patent ID: 7707874

Claim:
An internal-combustion-engine misfire determination device for determining an occurrence of a misfire in an internal combustion engine having a plurality of cylinders, of which an output shaft is connected, through a torsion element, to a downstream shaft downstream of the torsion element, the misfire determination device comprising: an output-shaft rotational speed detection portion for detecting an output shaft rotational speed that is the rotational speed of the output shaft; a downstream shaft rotational speed detection portion for detecting a downstream shaft rotational speed that is the rotational speed of the downstream shaft; a resonance influence component calculation portion that is configured to acquire the detected output shaft rotational speed and the detected downstream shaft rotational speed, and that calculates a resonance influence component that is the component caused by an influence of resonance due to torsion of the torsion element on the output shaft rotational speed, based on the detected output shaft rotational speed and the detected downstream shaft rotational speed; and a misfire determination portion for determining the occurrence of the misfire in the internal combustion engine based on a rotational speed for determination that is obtained by subtracting the calculated resonance influence component from the detected output shaft rotational speed.