AIR-FUEL RATIO CONTROLLER OF ENGINE

PURPOSE:To enable the fuel injection amount from a fuel injection valve to be sufficiently throttled, so as to enable the air-fuel ratio to be kept as the target air-fuel ratio by providing a means for extending the output capable range of control output in the air-fuel feedback control within the specific low loading range in the feedback region. CONSTITUTION:A control unit C is a synthetic controller of an engine CE, and it performs various kinds of control of the engine CE by taking the O2 concentration (air-fuel ratio) in exhaust gas to be detected by an O2 sensor 9 as the control information. And the feedback correction value is calculated according to the deviation of the air-fuel ratio found by this O2 concentration in relation to the target air-fuel ratio to be set according to the driving state. The upper limit and the lower limit are set in this feedback correction value, so as to perform the feedback guard. The changing speed of the air-fuel ratio is enhanced by extending the output capable range of control output within the feedback guard extending range. Thereby stability and control precision of the air-fuel ratio control are improved.