| 摘要 |
PROBLEM TO BE SOLVED: To cool exhaust gas returned to an intake pipe so as to effectively lower generation of NOx, in addition to purification of exhaust gas by injecting auxiliary fuel into an exhaust circulation path, in a device with an auxiliary fuel injection means which performs auxiliary fuel injection after fuel injection by a main fuel injection means. SOLUTION: In a cylinder injection type internal combustion engine, main fuel injection as fuel injection essential for operating an engine is carried out for providing a stratified combustion state and a homogeneous combustion state. An EGR pipe 11, diverted from an exhaust pipe 5 on the downstream side of a NOx catalyst 6 for returning a part of exhaust gas to an intake pipe 2, is arranged, and in the middle of the EGR pipe 11, an EGR inlet temperature sensor 12 is arranged, while an auxiliary fuel injection valve 13 is arranged. During the operation of the internal combustion engine, an amount of NOx generated by the operation is estimated from the number of engine revolutions, the fuel injection amount, engine water temperature, EGR gas temperature and the like by means of an ECU 8, and according to the estimated NOx generated amount, an auxiliary injection amount is computed for performing auxiliary fuel injection inside the EGR pipe 11. |
