| 摘要 |
PROBLEM TO BE SOLVED: To suppress discharge of NOx, in an air-fuel ratio control device for an internal combustion engine having air-fuel ratio sensors disposed in respective positions situated upper stream and downstream from a catalyst converter. SOLUTION: In this control device, it is predicted that an air-fuel ratio detected by an O2 sensor on the downstream side is turned over from rich to lean when the current detecting value VOS of the output voltage of the O2 sensor on the downstream side is higher than a given thresholdα(, for example, 0.55 V) and a decrease amount DVOS (=VOSP-VOS) by which a preceding detecting value VOSP detected a given time (, for example, 8 ms) before is decreased to a current detecting value VOS is higher than a given amountβ(, for example, 0.1 V), and a constant RSR participating in air-fuel ratio feedback control is switched to a direction in which it points to rich. This early switching suppresses a deviation of an engine air-fuel ratio to the lean side and reduces a discharge amount of NOx.
|
