| 摘要 |
PURPOSE:To prevent emission, drivability and fuel consumption from getting worse, by altering a rich/lean judging level of air-fuel ratio control according to a degree of deterioration in an air-fuel ratio sensor detected. CONSTITUTION:A control circuit 90 finds a fundamental fuel injection quantity from suction air quantity data Q by a suction quantity sensor 4 and engine speed data N by an air-fuel ratio sensor 8, then performs the closed-loop control of an air-fujel ratio so as to become a theoretical air-fuel ratio on the basis of an air- fuel ratio sensor 6, and compensates the fundamental fuel injection quantity. And, when the counting value of a sample counter exceeds a range of 400, it performas statistical processing operation as to 400 data of an output voltage value of the air-fuel ratio sensor 8, and finds a standard deviation value VS. And, when VS<=0.2 is the case, it is judged that there is some deterioration in the air-fuel ratio sensor 8 whereby a rich/lean judging level RL is altered with an equation of RL=0.45+(0.2-VS)/2 like this. With this constitution, the air-fuel ratio is always controllable within the specified range. |
