Engine misfire identification device for internal combustion engine and engine misfire identification method

Abstract

A rotational fluctuation is given as a variation in rotation speed of a crankshaft at every specific crank angle, that is, at every 120 degrees, corresponding to an ignition timing in each cylinder of a six-cylinder engine. The engine misfire identification technique of the invention calculates a difference between a specific rotational fluctuation at a specific crank angle and a previous rotational fluctuation at a crank angle of 360 degrees before the specific crank angle as a rotational fluctuation difference, and sums up the specific rotational fluctuation at the specific crank angle and the previous rotational fluctuation at the crank angle of 360 degrees before the specific crank angle to give a total rotational fluctuation. The engine misfire identification technique successively adopts a single misfire judgment logic, a consecutive misfire judgment logic, and an intermittent misfire judgment logic to discriminate among a single misfire pattern, a consecutive misfire pattern, and an intermittent misfire pattern and distinctly and accurately identify misfires in the engine, based on the calculated rotational fluctuation, rotational fluctuation difference, and total rotational fluctuation.