Patent ID: 6253542
Filing Date: 2001-07-03
Classification: F02D

Abstract:
A method of controlling the air-fuel ratio of an internal combustion engine having an exhaust passage including a catalytic converter, the method comprising the steps of:providing a first air-fuel ratio sensor for characterizing at least one constituent of an exhaust gas stream from the engine, the first air-fuel ratio sensor being positioned upstream of the catalytic converter;providing a second air-fuel ratio sensor for characterizing at least one constituent of the exhaust gas stream from the engine, the second air-fuel ratio sensor being positioned downstream of the catalytic converter;detecting an output value of the second air-fuel ratio sensor wherein the output value is indicative of a rich or lean exhaust gas air-fuel ratio and, in response;monitoring the engine mass airflow; andmodifying the air-fuel ratio of the engine by setting a proportional gain term of a feedback loop as a function of the output value and the engine speed and load, and reducing the proportional gain term as a function of the engine mass airflow.