| 摘要 |
PURPOSE:To enable a high accurate lean air-fuel ratio control to be performed over a long period, by comparing a sensor output change amount with a predetermined reference value and correcting a target lean air-fuel ratio value to a rich side, when the output change amount is larger than the reference value, while to a lean side when the output change amount is smaller than the reference value. CONSTITUTION:In the case of an engine in which a feedback control of a fuel injection amount from a fuel injection valve 3 is performed by an ECU13 being based on the deviation of an actual air-fuel ratio value, detected by an air-fuel ratio sensor 9, from a target lean air-fuel ratio value, a sensor output change amount in a certain sensor output point is detected and compared with a reference value. And when the output change amount is larger than the reference value, the target lean air-fuel ratio value is decreased smaller by the amount of a correction value in proportion to a degree of change of the output change amount, being corrected to a rich side. On the contrary, when the output change amount is smaller than the reference value, the target lean air-fuel ratio value is increased larger by the amount of the correction value in proportion to the degree of change of the output change amount so as to be corrected to a lean side.
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