Egr control apparatus and method for internal combustion engine

Abstract

An EGR control apparatus and method for an internal combustion engine which burns an air-fuel mixture with self ignition in addition to a flame propagation combustion, are provided for improving the combustion efficiency, engine output, drivability, and exhaust gas characteristics in an internal combustion engine which involves a self ignition combustion of an air-fuel mixture in addition to a flame propagation combustion. The EGR control apparatus comprises an ECU which selects one of a stratified self ignition mode, a stratified flame propagation combustion mode, and a homogeneous flame propagation combustion mode, sets a total target EGR amount and a target in-cylinder gas temperature in accordance with the selected combustion mode, calculates a target internal EGR amount in accordance with the value, calculates a target external EGR amount by subtracting the target internal EGR amount from the total target EGR amount, and controls the internal EGR amount and the external EGR amount to be the target internal EGR amount and the target external EGR amount, respectively, by driving three mechanisms.