Patent ID: 7677223
Filing Date: 2010-03-16
Classification: F01N,F02D,Y02A,Y02T

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; downstream air-fuel-ratio sensor disposed in the exhaust passage to be located downstream of the catalyst unit; and fuel injecting means for injecting fuel according to an instruction, the air-fuel-ratio control apparatus comprising: base fuel injection quantity acquiring means that acquires a base fuel injection quantity, which is a quantity of fuel for obtaining a target air-fuel ratio, on the basis of the operation state of the internal combustion engine; downstream-side feedback correction value calculation means that calculates a downstream-side feedback correction value, which is a feedback correction value for feedback-controlling an air-fuel ratio of an gas mixture supplied to the internal combustion engine, on the basis of the output value from the downstream air-fuel-ratio sensor; control-use base fuel injection quantity acquiring means that acquires a control-use base fuel injection quantity, which is a fuel-injection quantity for feedback-controlling the air-fuel ratio of the gas mixture supplied to the internal combustion engine, on the basis of the acquired base fuel injection quantity and the calculated downstream-side feedback correction value; composite air-fuel ratio acquiring means that acquires a value corresponding to composite air-fuel ratio, which corresponds to an air-fuel ratio for feedback-controlling the air-fuel ratio of the gas mixture supplied to the internal combustion engine, on the basis of the output value from the upstream air-fuel-ratio sensor and the calculated downstream-side feedback correction value; upstream-side feedback correction value calculation means that calculates an upstream-side feedback correction value, which is a feedback correction value for feedback-controlling the air-fuel ratio of the gas mixture supplied to the internal combustion engine, on the basis of the acquired value corresponding to composite air-fuel ratio; fuel injection quantity calculation means that calculates the fuel injection quantity on the basis of the acquired control-use 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 the gas mixture 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.