MISFIRE DETECTION DEVICE FOR INTERNAL COMBUSTION ENGINE

Provided is a misfire detection device for detecting the misfire of an internal combustion engine on the basis of a rotational speed parameter indicating the rotational speed of the engine. The average change amount during a first predetermined period of the rotational speed parameter and an inertial speed change component accompanying the rotation of the engine are calculated, the rotational speed parameter is corrected according to the average change amount and the inertial speed change component to calculate a first corrected rotational speed parameter. A first relative speed parameter is calculated according to a deviation between a first reference value that is the first corrected rotational speed parameter corresponding to the rotational speed parameter detected at a reference time when a piston of a cylinder to be subjected to misfire determination is located near a compression top dead center and the first corrected rotational speed parameter. A first determination parameter is calculated by integrating the first relative speed parameters over the integration period of a crank angle of 720/N (N is the number of cylinders of the engine) degrees, and the misfire is determined on the basis of the first determination parameter. The reference time and the start time of the integration period are set according to the ignition time of the engine.