| 摘要 |
PROBLEM TO BE SOLVED: To provide a misfire detection device of an internal combustion engine for improving accuracy of misfire-detection and accuracy of misfire-cause determination. SOLUTION: When a misfire is caused, unburned gas is discharged from a cylinder in which a misfire has been caused and the air/fuel ratio of exhaust gas is suddenly changed. Taking note of the behavior of the air/fuel ratio, an air/fuel ratio (air/fuel ratio in each cylinder) of exhaust gas of each cylinder is estimated on the basis of a detection value of an air/fuel ratio sensor placed at an exhaust-gas confluent part to which exhaust gas of each cylinder gathers. Determination of a normal combustion or misfire is made on the basis whether an air/fuel ratio of each cylinder is in a normal combustion range (a range from the rich-side criterion C1 to the lean-side criterion C2) or not. Whether the cause of the misfire is in the fuel system or not is determined on the basis of difference between an actual injection quantity in the misfired cylinder and a mean actual injection quantity of all the cylinders. Further, whether the cause of the misfire is in the air system or not is determined on the basis of difference between an estimated air-volume in the misfired cylinder and a mean actual air-volume of all the cylinders. Further, whether the cause of the misfire is in the ignition system or not is determined by comparing an advance-angle side criterion C7 with a retard-angle side criterion C8 with respect to the ignition timing in the misfired cylinder. COPYRIGHT: (C)2005,JPO&NCIPI
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