| 摘要 |
PURPOSE:To improve an engine internal temperature reduction effect without damaging the improving effect of fuel consumption occasioned by bringing an air-fuel ratio into a lean region by effecting EGR control by performing reflux of exhaust gas to an air intake system when the running state of an engine is a supercharge region where supercharge capacity is exhibited. CONSTITUTION:Signals from sensors 43, 80-82 are inputted to a control unit U to output the signals to injectors 56 and 57 and first and second EGR valves 67 and 73 to perform control of an EGR and control of an air-fuel ratio. In all of a middle load and high rotation region, reflux of comparatively high temperature EGR gas is carried out on the comparatively low load side by a first EGR valve 67. Meanwhile, a second EGR valve 73 is used on the comparatively high load side to effect reflux of low temperature EGR gas. A target air-fuel ratio is brought into a more lean state than a theoretical air-fuel ratio and set to A/F=16. This constitution produces an more eminent temperature reduction effect than reduction of an engine internal temperature only by bringing an air-fuel ratio into a lean region while the improvement effect of a fuel consumption factor is ensured. |
