A fuel injection control device for an internal combustion engine

摘要

An internal combustion engine (1) is provided with fuel injection valves (10a, 10b, 10c, 10d) which directly inject fuel into the respective cylinders of the engine. An electronic control unit (ECU) (30) controls the fuel injection valves to execute a main fuel injection and a subsidiary fuel injection prior to the main fuel injection. The ECU sets the timing for executing the subsidiary fuel injection in such a manner that the delay of the fuel injected by the subsidiary fuel injection before it ignites becomes the same as the delay of the fuel injected by the subsidiary fuel injection under a predetermined standard operating condition of the engine. Further, the ECU sets the amount of subsidiary fuel injection so that it becomes the maximum limit which allows all the fuel injected by the subsidiary fuel injection to completely burn before the main fuel injection starts. Thus, since the amount of fuel injected by the subsidiary fuel injection is increased and the state of combustion of the fuel injected by the main fuel injection is improved. Further, all the fuel injected by the subsidiary fuel injection burns before the main fuel injection starts and a worsening of the exhaust gas emission and the generation of the exhaust smoke do not occur.