Patent ID: 7243532

Claim:
A misfire detection apparatus for internal combustion engines, comprising: an individual cylinder air fuel ratio information acquisition means to acquire air fuel ratios of exhaust gases in individual cylinders of an internal combustion engine, or parameters variable according thereto, as individual cylinder air fuel ratio information, a misfire detection means to detect misfire by a cylinder based on the individual cylinder air fuel ratio information acquired by the individual cylinder air fuel ratio information acquisition means, and a misfire cause determination means to determine a cause for misfire for that cylinder, in which misfire is detected by the misfire detection means, based on at least one of a fuel injection quantity, an intake air quantity, and ignition timing; wherein the individual cylinder air fuel ratio information acquisition means estimates air fuel ratios, as individual cylinder air fuel ratios, of exhaust gases in individual cylinders based on a detection value of an air fuel ratio sensor mounted in an exhaust-collector, through which exhaust gases of the respective cylinders collect to flow; a detection value of the air fuel ratio sensor is modeled by adding a weighed history of the air fuel ratio and a weighted history of detection values of the air fuel ratio sensor, and the information acquisition means estimates the air fuel ratio with the use of the model.