To provide an air-fuel ratio feedback controller capable of suppressing a slippage of an air-fuel ratio from occurring when a disturbance is removed by correcting the slippage of the air-fuel ratio caused by the disturbance such as the recirculation of exhaust gas to a target air-fuel ratio by an integral operation.
The start (input) or stop (release) of the recirculation of exhaust gas is discriminated depending on whether or not an air-fuel ratio changes when a target air-fuel ratio is constant and the recirculation rate of the exhaust gas at that time matches a variation in the air-fuel ratio (S1 to S8). When the recirculation of the exhaust gas is stopped, the integral value of an air-fuel ratio deviation is reset to 0 (S9), and the correction to reduce the amount of fuel required during the execution of the recirculation of the exhaust gas is avoided to be performed.
YOSHIZAWA HIDEKAZU
IWAKI HARUHIRO
IIZUKA ISAMU
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