| 摘要 |
PURPOSE:To enable to execute proper feedback control on the air-fuel ratio for both of operative cylinders and inoperative cylinders of an engine capable of changing the number of cylinders to be operated, by separating the exhaust passage for operative cylinders and that for inoperative cylinders from each other to a position just before a catalyst, and providing an air-fuel ratio sensor in each of the exhaust passages. CONSTITUTION:In low-load operation of an engine, fuel injection valves (a)-(c) stop fuel supply to cylinders #1-#3 that are to be rendered inoperative. At the same time, a fresh-air supply valve 10 is opened by the instruction of a control circuit 12, and an intake passage 2 for the cylinders #1-#3 is closed by a fresh-air stop valve 11, so that the cylinders #1-#3 are rendered inoperative. Further, an exhaust passage 5 for the inoperative cylinders #1-#3 and an exhaust passage 6 for operative cylinders #4-#6 are separated from each other to a position just before a catalyst 15, and air-fuel ratio sensors 13, 14 are provided respectively in the exhaust passages 5, 6. The output signals of the two air-fuel ratio sensors 13, 14 are furnished to the control circuit 12 and used for feedback control of the air-fuel ratio for the inoperative cylinders #1-#3 and operative cylinders #4-#6. |
