Patent ID: 7278394
Filing Date: 2007-10-09
Classification: F02D

Abstract:
1. An air-fuel-ratio control apparatus applied to an internal combustion engine including: a catalyst unit disposed in an exhaust passage of the internal combustion engine; upstream air-fuel-ratio sensor disposed in the exhaust passage to be located upstream of the catalyst unit; and fuel injecting means for injecting fuel according to an instruction, the air-fuel-ratio control apparatus comprising: target air-fuel ratio determining means that determines a target air-fuel ratio that changes in accordance with an operation state of the internal combustion engine; base fuel injection quantity acquiring means that acquires a base fuel injection quantity that is a quantity of fuel for obtaining the determined target air-fuel ratio; first delay processing means that acquires a value corresponding to the target air-fuel ratio which has been determined at the point a dead time before the present point in time, the dead time being defined as a period from a time when the instruction for injecting fuel is issued to a time when exhaust gas generated based upon a combustion of the fuel reaches the upstream air-fuel-ratio sensor; second delay processing means that acquires a value obtained by performing a low-pass filter process to the value acquired by the first delay processing means; upstream-side feedback correction value calculation means that calculates an upstream-side feedback correction value, which is a feedback correction value for feedback-controlling an air-fuel ratio of gas mixture supplied to the internal combustion engine, on the basis of the value acquired by the second delay processing means and the output value from the upstream air-fuel-ratio sensor; fuel injection quantity calculation means that calculates a fuel injection quantity on the basis of the acquired base fuel injection quantity and the calculated upstream-side feedback correction value; and air-fuel-ratio control means that feedback-controls the air-fuel ratio of gas mixture, which is supplied to the internal combustion engine, by giving the instruction for injecting the fuel in the calculated fuel injection quantity to the fuel injecting means.