Patent ID: 7032374
Filing Date: 2006-04-25
Classification: F01N,F02D,Y02T

Abstract:
1. An exhaust purification apparatus for an internal combustion engine equipped with fuel injection means for injecting fuel in a quantity changed in accordance with operating condition of the engine, comprising: a catalyst unit disposed in an exhaust passage of the engine; an upstream air-fuel-ratio sensor disposed in the exhaust passage to be located upstream of the catalyst unit; a downstream air-fuel-ratio sensor disposed in the exhaust passage to be located downstream of the catalyst unit; main-feedback control means for calculating a main-feedback control quantity on the basis of an output value of the upstream air-fuel-ratio sensor and a predetennined upstream-side target value, and correcting, on the basis of the main-feedback control quantity, the quantity of fuel injected by the fuel injection means, to thereby feedback-control the air-fuel ratio of the engine; and sub-feedback control means for calculating a sub-feedback control quantity on the basis of an output value of the downstream air-fuel-ratio sensor and a predetermined downstream-side target value, and correcting, on the basis of the sub-feedback control quantity, the quantity of fuel injected by the fuel injection means, independently of the correction of the fuel injection quantity by the main-feedback control means, to thereby feedback-control the air-fuel ratio of the engine.