AIR-FUEL RATIO CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

摘要

PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device for an internal combustion engine more accurately estimating alcohol concentration by calculating alcohol concentration from an integrated quantity calculated from actual measurement value and target value calculated by at least one of an A/F sensor and a sub-oxygen sensor after completion of fuel cut. SOLUTION: This air-fuel ratio control device for an internal combustion engine is provided with the A/F sensor 60 or the sub-O2sensor 61 in an exhaust gas passage. Difference between the actual measurement value and the target value of A/F sensor value or sub-O2sensor value output by the A/F sensor 60 or the sub-O2sensor 61 during predetermined period of time is integrated after fuel cut recovery judgment. Alcohol concentration can be accurately learned by renewing ethanol concentration learning value according to the integrated value when the integrated value is not less than a predetermined value at a time of ethanol concentration learning calculated beforehand, or is less than the predetermined value. Consequently, accuracy of alcohol concentration learning value is improved. COPYRIGHT: (C)2009,JPO&INPIT