| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve control accuracy of air/fuel ratio, in a system with an oxygen sensor or a linear A/F sensor respectively installed in the upstream and the downstream of a catalyst. SOLUTION: Air/fuel ratio (fuel injection amount) is feedback controlled so that air/fuel ratio of exhaust gas in the upstream of a catalyst is conformed to target air/fuel ratio based on an output of an air/fuel ratio sensor in the upstream, also sub-feedback control for correcting the target air/fuel ratio in the upstream of the catalyst is performed to be based on an output of an oxygen sensor in the downstream. Here, in the case that a deviation between the air/fuel ratio in the upstream of the catalyst and theoretical air/fuel ratio is in a prescribed range, a parameter (rich integration itemλIR, lean integration itemλIL, rich skip itemλSKR, lean skip itemλSKL) of the sub-feedback control is enlarged as this deviation of the air/fuel ratio increases, while in the case that this deviation of the air/fuel ratio is out of the prescribed range, this parameter is fixed to a prescribed value smaller than a maximum value of this parameter in the above prescribed range.</p> |
