Patent ID: 6161376
Filing Date: 2000-12-19
Classification: F02D

Abstract:
A method for controlling an air-fuel ratio in an internal combustion engine, comprising the steps of:disposing, at an upstream side of an exhaust gas purification catalytic converter, a wide range air-fuel ratio sensor which detects an air-fuel ratio over a wide range in response to a concentration of a specific component in exhaust gas;disposing, at a downstream side of said exhaust gas purification catalytic converter, a downstream side air-fuel ratio sensor which detects an air-fuel ratio in response to a concentration of a specific component in exhaust gas;learning a deviation of the detected result of said downstream side air-fuel ratio sensor from a target air-fuel ratio;correcting said target air-fuel ratio, based on the learning result of said step of learning, to thereby set a corrected target air-fuel ratio;oscillating said corrected target air-fuel ratio set by said step of correcting the target air-fuel ratio at a predetermined period with a predetermined amplitude; andcontrolling the air-fuel ratio of an engine intake mixture to be said oscillated corrected target air-fuel ratio, based on the detected result of said wide range air-fuel ratio sensor.