| 摘要 |
<p>PROBLEM TO BE SOLVED: To quickly warm up an exhaust emission control catalyst during cold start of an internal combustion engine; and to suppress pressure loss of the internal combustion engine as much as possible.SOLUTION: A first pre-stage catalyst 8 and an exhaust emission control catalyst 10 are provided in exhaust passages 5 and 6 of an internal combustion engine 1. Both ends of an auxiliary exhaust passage 30 are connected to the exhaust passages 5 and 6 on the upstream side of the first pre-stage catalyst 8, and a second pre-stage catalyst 31 is disposed in the auxiliary exhaust passage 30. The auxiliary exhaust passage 30 is opened only when a temperature of the first pre-stage catalyst 8 is lower than a first predetermined temperature and a temperature of the exhaust emission control catalyst 10 is lower than a second predetermined temperature before completion of warm-up of the internal combustion engine 1.</p> |
