| 摘要 |
PROBLEM TO BE SOLVED: To improve the estimation accuracy of an exhaust oxygen concentration by providing a means which feedback-controls the opening of an EGR valve so as to match an estimation value of the exhaust oxygen concentration to a target value.SOLUTION: A normative value of an EGR amount is preliminarily stored for each engine operating range. In the case of stable control in which an error between a corrected estimation value CEX_s of the exhaust oxygen concentration and a detection value CEX_sensor is within a predetermined range, and an error between the corrected estimation value CEX_s and a target value CEX_trg is within a predetermined range, a divergence amount &Dgr;MEGR between a normative value MEGR_norm corresponding to the operating range of the moment and the corrected estimation value CEX_s is calculated (S25). Based on the divergence amount &Dgr;MEGR, a consumed oxygen amount correction coefficient K1f (combustion parameter) showing a combustion state is corrected and learnt in association with the operating range of the moment (S30). The exhaust oxygen concentration is estimated using the learnt consumed oxygen amount correction coefficient K1f. |
