| 摘要 |
PURPOSE:To improve NOX purifying rate and prevent deterioration of NOX catalyst by making a bypass operation range small to the high speed load side, and expanding it to the low speed load side, according to alcohol concentration of alcohol/gasoline mixed fuel. CONSTITUTION:At an exhaust system of an internal combustion engine 1 using mixed fuel of alcohol and gasoline, a bypass valve 4 is provided which changes over the flow of exhaust gas to lean NOX catalyst 2 and a bypass passage 3. An operation condition of the internal combustion engine 1 is detected, and alcohol concentration of mixed fuel is detected by a means 6. A bypass operation range is set by a means 7 based on the detected concentration, and the operation range of the engine 1 is judged by a means 8 whether it is in the bypass operation range or not. When it is in the bypass operation range, the exhaust gas is flowed to the bypass passage 3. When it is not in the bypass operation range, the bypass valve 4 is controlled by a means 9 so that the exhaust gas is flowed to the NOX catalyst 2. |
