Alternate closed loop control system for an air-fuel ratio controller

摘要

A closed loop control system is disclosed for controlling the air-fuel ratio of an internal combustion engine. An oxygen sensor is connected into the control loop after engine warm up when the temperature has reached its operating temperature to maintain the air-fuel ratio close to the stoichiometric value. An engine roughness detector is connected into the control loop before the oxygen sensor has reached its operating temperature to maintain the air-fuel ratio close to a predetermined lean limit. A temperature sensor and switching means controlled thereby are provided to alternately connect the roughness detector and the oxygen sensor in the control loop.