| 摘要 |
PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine, capable of reliably mixing a reducing agent and exhaust gas.SOLUTION: An exhaust pressure control valve is fully closed (S10). When an upstream pressure being a pressure in a bypass passage upstream of a bypass valve becomes equal to or more than a first predetermined pressure, the bypass valve is fully opened (S12, S14). When a differential pressure between an upstream-side pressure and a downstream-side pressure becomes equal to or less than a first predetermined differential pressure, the bypass valve is fully closed (S16, S18). When the upstream pressure becomes equal to or more than a second predetermined pressure (S20), when NH3 concentration in exhaust gas downstream of a selective reduction catalyst is equal to or lower than a first predetermined concentration Pg1 (S22), and when the concentration obtained by adding ammonia and nitrogen oxide in the exhaust gas downstream of the selective reduction catalyst is equal to or less than a second predetermined concentration Pg2, the exhaust pressure control valve is fully opened (S24, S26). |
