| 摘要 |
PROBLEM TO BE SOLVED: To provide sufficient nitrogen oxides reducing treatment performance when nitrogen oxides are released from a nitrogen oxides storage catalyst 4 in stoichiometric or rich running in the case where a three-way catalyst 3 is provided upstream of an exhaust passage 12 and a nitrogen oxides storage catalyst 4 downstream of the exhaust passage 2 respectively. SOLUTION: A bypass passage 5 bypassing a three-way catalyst 3, a switch valve 6 as a bypass control valve, which is switchable so that at least a part of exhaust emission flows on the side of the bypass passage 5, and a control device 8 for controlling the switch valve 6 are provided. This control device 8 opens the switch valve 6 in stoichiometric or rich running and when the temperature of engine cooling water is a specified value or higher.
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