Abgasreinigungsvorrichtung für Brennkraftmaschine

摘要

In the exhaust gas purification device of the present invention, No. 1 cylinder of the engine is operated at a rich air-fuel ratio and other cylinders (No. 2 to No. 4) are operated at a lean air-fuel ratio. The exhaust gases from the No. 1 and No. 2 cylinders are mixed each other and form a lean air-fuel ratio exhaust gas mixture. Further, since the air-fuel ratio of the No. 2 cylinder is lean, the exhaust gas from the No. 2 cylinder contains a relatively large amount of NOX. Therefore, an exhaust gas mixture supplied to the three-way catalyst has a rich air-fuel ratio and contains a relatively large amount of NOX. Therefore, at the three-way catalyst, a part of NOX in the exhaust gas mixture is converted to NH3. The exhaust gas mixture flowing out from the three-way catalyst and the lean exhaust gas from the No. 3 and No. 4 flows into a common exhaust gas passage where they mix each other to form a lean exhaust gas containing NH3 from the three-way catalyst and NOX from the No. 3 and No. 4 cylinders. This lean exhaust gas flows into a denitrating catalyst disposed on the common exhaust gas passage. Therefore, NOX in the exhaust gas is reduced by NH3 at the denitrating catalyst.