| 摘要 |
PROBLEM TO BE SOLVED: To solve the following problems: if an air-fuel ratio is a theoretical air-fuel ratio or is made slightly rich when a catalyst is exposed to comparatively low-temperature exhaust gas in an idling condition and is gradually cooled, oxygen occluded inside of the catalyst is consumed, thereby lowering a CO or HC conversion efficiency. SOLUTION: This air-fuel ratio control method for an internal combustion engine controls the air-fuel ratio by using an air-fuel ratio correction constant set based on the output of an oxygen sensor after detecting that the oxygen sensor is activated, in the internal combustion engine including the catalyst provided in an exhaust passage and the oxygen sensor provided upstream of the catalyst. The operating condition of the internal combustion engine is determined after detecting activation of the oxygen sensor. When the determined operating condition is an idling condition and a flow rate of exhaust gas passing through the catalyst exceeds a predetermined value, it is estimated that the temperature of the catalyst is lowered, and the air-fuel ratio correction constant is selected so that the air-fuel ratio is made lean. COPYRIGHT: (C)2010,JPO&INPIT |
