| 摘要 |
PROBLEM TO BE SOLVED: To improve a purifying factor of NOx in exhaust by increasing produced amount of NH3 , in the case of reducing NOx in exhaust by using this NH3 , by converting NOx in exhaust of rich air-fuel ratio to NH3 . SOLUTION: In a lean burn internal combustion engine provided with a cylinder #1 operated by rich air-fuel ratio and cylinders #2, #3, #4 operated by lean air-fuel ratio, exhaust of rich air-fuel ratio formed by mixing exhaust of the cylinders #1, #2 is supplied to a catalytic converter rhodium 5, NOx in mixed exhaust gas is converted in NH3 by the catalytic converter rhodium. Exhaust containing this NH3 is made to join and mix with lean air-fuel ratio exhaust from the cylinders #3, #4 in a common exhaust passage 4, to be made to flow in a NOx removal catalyst 9 in the downstream side of the exhaust passage 4. In the NOx removed catalyst, by NH3 in exhaust, NOx contained in lean air-fuel ratio exhaust is purified. Exhaust in the cylinder #2, because of lean air-fuel ratio combustion, contains a large amount of NOx . Consequently, mixed exhaust, though it is in rich air-fuel ratio, comes to contain a large amount of NOx as a material of NH3 , in the catalytic converter rhodium, a sufficient amount of NH3 for purifying NOx in the NOx removal catalyst is produced. |
