EGR CONTROL SYSTEM OF INTERNAL COMBUSTION ENGINE, INTERNAL COMBUSTION ENGINE, AND EGR CONTROL METHOD OF INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To provide an EGR (Exhaust Gas Recirculation) control system which, when the opening of an EGR valve provided in an EGR passage is controlled using an excess air ratio corresponding to the operational state of an internal combustion engine comprising an EGR system having the EGR valve in the EGR passage, can perform EGR while avoiding increase in a NOx discharge quantity when the operational state of the internal engine is in a transient state.SOLUTION: A control device 30 is constituted to calculate a target excess air ratio λt and an in-cylinder oxygen concentration target value Dt on the basis of the operational state of an internal combustion engine 10, and to change the target excess air ratio λt in such a manner that the value of the in-cylinder oxygen concentration target value Dt can be kept when the running state of the internal combustion engine 10 is in an acceleration state during an EGR control.SELECTED DRAWING: Figure 2 【課題】ＥＧＲ通路にＥＧＲバルブを有して構成されるＥＧＲシステムを備えた内燃機関で、内燃機関の運転状態に応じた空気過剰率を使用してＥＧＲバルブの開度を制御する場合に、エンジンの運転状態が過渡状態でのＮＯｘ排出量の増加を回避してＥＧＲをすることができる内燃機関のＥＧＲ制御システム、内燃機関及び内燃機関のＥＧＲ制御方法を提供する。【解決手段】制御装置３０が、内燃機関１０の運転状態に基づいて目標空気過剰率λｔとシリンダ内酸素濃度目標値Ｄｔを算出し、ＥＧＲ制御中で内燃機関１０の運転状態が加速状態にあるときは、シリンダ内酸素濃度目標値Ｄｔの値を維持するように目標空気過剰率λｔを変更するように構成される。【選択図】図２