| 摘要 |
PURPOSE:To maintain nitrogen oxide in exhaust gas at a low level, by a method wherein a cylinder group is divided into 2 groups of a rich air-fuel ratio and a lean air-fuel ratio to detect oxygen concentration in exhaust gas, and based on the results, fuel injection is controlled. CONSTITUTION:In an internal combustion engine provided with an electronic fuel injection controller 10, a cylinder group is divided into 2 groups of at least one cylinder I and remaining cylinders II-VI, and the fuel flow rate characteristics of their respective fuel injection valves 7a and 7b are set so that the air-fuel ratio of the one cylinder I becomes more rich than a theoretical air- fuel ratio having a larger amount of NO, and the air-fuel ratios of the other cylinders II-VI become more lean than a theoretical air-fuel ratio. An exhaust pipe 5a, corresponding to a group consisting of one cylinder I , and exaust pipe 5b, corresponding to at least one cylinder II of a group consisting of the remaining cylinders, are gathered together, and based on an output detected by a sensor 8 for oxygen concenteration in exhaust gas present in the vicinity of a gathering part 5c, a valve opening time ratio between the fuel injection valves 7a and 7b of all cylinders is controlled. |
