| 摘要 |
The present invention pertains to an exhaust emission purification system which comprises an oxidation catalyst and an exhaust emission purification unit that includes both a filter and a catalyst for selective reduction of NOx. When a fuel component is supplied to an exhaust emission and where prescribed conditions under which a part of the fuel component supplied to the exhaust emission passes through the oxidation catalyst to the downstream side thereof are satisfied, in this system, an ammonia or an ammonia precursor is supplied in an increased amount in comparison with the amount thereof supplied in non-pass through times where the prescribed conditions are not satisfied, and the supply of ammonia or an ammonia precursor in such an increased amount and/or the supply of a fuel component are controlled so that ammonia which is useful for selective reduction of NOx and which results from the ammonia or ammonia precursor thus supplied can arrive at the exhaust emission purification unit before the fuel component passing through the oxidation catalyst arrives at the purification unit. Thus, the present invention can minimize, in an exhaust emission purification system which is for an internal combustion engine and which has both a filter and a catalyst for selective reduction of NOx, the influence of a fuel component supplied to an exhaust emission on the exhaust emission purification activity of the catalyst as completely as possible. |
