| 摘要 |
PROBLEM TO BE SOLVED: To provide an air-fuel ratio control method for an internal combustion engine capable of positively shifting an air-fuel ratio of mixture to be supplied to the internal combustion engine to be lean or rich by a desired value. SOLUTION: When an air-fuel ratio is shifted to a lean side, a value for a control constantλis turned to be reduced right after the output voltage of an oxygen sensor is turned to be increased at the D point. When the output voltage of the oxygen sensor is reversed at the E point in increase/decrease, without crossing a slice level V02 , and moved to a lean side as the value for the control constantλis turned to be reduced, the value for the control constantλis turned to be increased from the D point after a preset time T1 passed. The internal of a preset time T1 is controlled to positively shift an air-fuel ratio of mixture to be supplied to an internal combustion engine from a theoretical air-fuel ratio by a desired shift amount.
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