AIR-FUEL RATIO CONTROLLER FOR INTERNAL COMBUSTION ENGINE

摘要

PURPOSE:To set an effective oxygen accumulative quantity and to improve an exhaust emission characteristic by calculating an oxygen accumulative quantity and the maximum oxygen accumulative quantity stored in a catalyst converter, controlling the air-fuel ratio of an air-fuel mixture and changing a prescribed range based on an operating state. CONSTITUTION:An oxygen accumulative quantity stored in a catalyst converter 14 disposed in the exhaust system of an internal combustion engine 1 is calculated by an oxygen accumulative quantity calculating means 5. The maximum oxygen accumulative quantity stored in the catalyst converter 14 is calculated by a maximum oxygen accumulative quantity calculating means 5. The air-fuel ratio of an air-fuel mixture fed to the internal combustion engine 1 is controlled by an air-fuel ratio control means 5 so that the calculated oxygen accumulative quantity is limited within a prescribed range in the calculated maximum oxygen accumulative quantity. The prescribed range is changed by a changing means based on the operating state of the internal combustion engine 1. Thus, the oxygen accumulative quantity of the catalyst converter 14 can be set within the prescribed range in the maximum oxygen accumulative quantity meeting an effective oxygen accumulative quantity and a purification efficiency is prevented from being lowered.