| 摘要 |
PROBLEM TO BE SOLVED: To improve learning convergence while avoiding generation of convergence variation by increasing learning gain for correction if deviation more than a prescribed one is between a learned value and calculated value, in learning air-fuel ratio correction amount based on the detected output of an oxygen sensor on the downstream side of a catalyst. SOLUTION: According to the output of the first oxygen sensor on the upstream side, the first air-fuel ratio correction amount, or air-fuel ratio feedback correction coefficientαis set by proportional integral control. The second air-fuel ratio correction amount, or correction value PHOS is set according to the output of the second oxygen sensor on the downstream side. Learning gain is increased for correction by a prescribed period if deviation more than a prescribed value is between the learning value PHOSA and correction value PHOS.
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