| 摘要 |
In an exhaust gas purification apparatus for an internal combustion engine ( 1 ) equipped with independent exhaust passages ( 2 a, 2 b) provided one for each cylinder group ( 1 a, 1 b) with a catalyst ( 3 a, 3 b) having a NOx trapping ability being arranged in each exhaust passage, the present invention is intended to provide a technique that can independently control the flow rates of exhaust gases flowing into the respective catalysts. To this end, the exhaust gas purification apparatus according to the present invention provides a communication passage ( 4 ) connecting mutually portions of said exhaust passages ( 2 a, 2 b) at upstream of said catalysts ( 3 a, 3 b), an upstream side switching valve ( 5 ) openning and closing said upstream side communication passage ( 4 ), a plurality of flow rate regulation valves ( 6 a, 6 b) being arranged at downstream of connecting portions of said exhaust passages with said upstream side communication passage, respectively, and a control section ( 9 ) controlling said upstream side switching valve ( 5 ) and said respective flow rate regulation valves ( 6 a, 6 b) in accordance with the states of said respective catalysts ( 3 a, 3 b). When the NOx trapping ability of one of the plurality of catalysts ( 3 a, 3 b) is regenerated, the control section ( 9 ) opens the upstream side switching valve ( 5 ), fully closes one flow rate regulation valve ( 6 a, 6 b) in one of the exhaust passages ( 2 a, 2 b) in which the one catalyst ( 3 a, 3 b) is arranged, and operates a reducing agent addition valve ( 7 a, 7 b) in such a manner that the reducing agent arrives at the one catalyst ( 3 a, 3 b) when the actual degree of opening of the one flow rate regulation valve ( 6 a, 6 b) becomes fully closed.
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