| 摘要 |
PURPOSE:To set amounts of NOx and unburnt HC and Co which are discharged to the atmosphere to be at zero(0) level. CONSTITUTION:Catalytic converter rhodium 17, catalytic oxidation 20, and NOx absorbers 23, 24 for absorbing NOx when the air-fuel ratio of exhaust gas which flows in is in lean condition, are arranged in an engine exhaust passage. Rich air mixture is burnt in an engine combustion chamber, and also secondary air is supplied upstream of the catalytic converter rhodium 17, and the air-fuel ratio of exhaust gas flowing in the catalytic converter rhodium 17 is set to be in an air-fuel ratio richer than the air-fuel ratio of air mixture which is burnt in a combustion chamber. The secondary air is supplied toward the upstream side of the catalytic oxidation 20, and the air-fuel ratio of exhaust gas which flows in the catalytic oxidation 20 and the NOx absorbers 23, 24 is set to be in such condition as slightly leaner than a theoretical air-fuel ratio. |
