To simplify determination process while keeping determination accuracy good and enable accurate misfire detection without overlooking misfire in relation to a misfire detection device for an internal combustion engine for detecting misfire and specifying misfire cylinder.
Crank angle time Tn for each cylinder right after ignition or firing each explosion cycle is acquired as engine rotation speed information. Crank angle time Tn of a present explosion cylinder is defined as x coordinate value and crank angle time Tn-1 of a previous explosion cylinder is defined as y coordinate value and a present plot point Pn is plotted on an xy plane. Determination vector Pn-1Pn from a previous plot point Pn-1 toward present plot point Pn is calculated. If the determination vector Pn-1Pn has same direction as a predetermined determination reference vector and length of the determination reference vector or greater, it is determined that misfire occurred in a previous explosion cylinder.
Mamoru Takada
Atsushi Hirayama
Hidekazu Onishi
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