| 摘要 |
PROBLEM TO BE SOLVED: To keep the sulfur component storage capacity of an exhaust emission control device low.SOLUTION: An internal combustion engine includes an exhaust emission control catalyst 20, and temperature detecting means 46 for detecting or estimating the temperature of the exhaust emission control catalyst. A control device performs feedback control so that the air-fuel ratio of exhaust gas flowing into the exhaust emission control catalyst becomes a target air-fuel ratio, and performs setting control of the target air-fuel ratio to set the target air-fuel ratio to be a rich set air-fuel ratio and a lean set air-fuel ratio, alternately. In addition, when the temperature of the exhaust emission control catalyst detected or estimated by the temperature detecting means is a predetermined upper limit temperature or lower, the control device makes a variation difference obtained by subtracting a rich degree of the rich set air-fuel ratio from a lean degree of the lean set air-fuel ratio, greater than when the temperature is higher than the upper limit temperature. |
