AIR-FUEL RATIO CONTROL DEVICE FOR SUPERCHARGE LEAN-BURN GASOLINE INTERNAL COMBUSTION ENGINE

摘要

PURPOSE:To control an air-fuel ratio to a lean side without deteriorating operability in a device wherein a lean combustion is performed under a supercharge condition by changing the shifting speed to a lean air-fuel ratio according to an acceleration degree in an intermediate range from a theoretical air-fuel ratio to the lean air-fuel ratio. CONSTITUTION:A supercharge condition detecting means B detects a condition where supercharging is substantially carried out by a supercharger A. When a non-supercharge condition is judged by the supercharge condition detecting means B, a rich air-fuel ratio is set by a rich air-fuel ratio setting means D. Under the supercharge condition, a target lean air-fuel ratio is set by a lean air-fuel ratio setting means D through an intermediate air-fuel ratio which is inclined to the lean side a little compared to the rich air-fuel ratio. When an acceleration condition of an engine is detected by an acceleration detecting means E, the changing speed of the air-fuel ratio is adjusted so as to accelerate the shifting to the target lean air-fuel ratio by means of an air-fuel ratio changing speed adjusting means G.