| 摘要 |
<p>PURPOSE:To prevent the discharge of the noxious constituent into the atmosphere by surely converging the air-fuel ratio near the theoretical air-fuel ratio. CONSTITUTION:A CPU 32 judges the inversion direction of the output of a downstream O2 sensor 27, skippingly corrects the target air-fuel ratio XTG by a skip quantity on the opposite side to the inversion direction, and calculates the fuel injection quantity for each 360 deg. crank angle (CA) of the rotation of an engine l based on the difference between the corrected target air-fuel ratio ATG and the air-fuel ratio lambda detected by an upstream O2 sensor 26. Since the target fuel injection quantity is immediately reflected to the fuel injection quantity at the updating speed for each 360 deg. CA, the fuel injection quantity is controlled with very good responsiveness against the disturbance of the air-fuel ratio. The upper/lower limit guard for the target air-fuel ratio lambdaTG is set based on the stuck material quantity of a catalyst 13 after the state of the downstream O2 sensor 27 is learnt, the air-fuel ratio in the downstream of the catalyst 13 is suppressed with a large disturbance, and the air-fuel ratio is surely controlled near the theoretical air-fuel ratio.</p> |
