Patent ID: 7706958

Claim:
An EGR control apparatus for an internal combustion engine which has an external EGR device for changing the amount of exhaust gases discharged from a cylinder to an exhaust passage and recirculated into the cylinder as an external EGR amount, and an internal EGR device for changing the amount of previously burnt gases generated in the cylinder which is left within the cylinder as a gas at a higher temperature than the exhaust gases as an internal EGR amount, and is operated in a combustion mode which is switched among a plurality of combustion modes including a stratified self ignition combustion mode for burning a stratified air-fuel mixture with self ignition, a stratified flame propagation combustion mode for burning the stratified air-fuel mixture with a spark ignition, and a homogeneous flame propagation combustion mode for burning a homogeneous air-fuel mixture with a spark ignition, said EGR control apparatus comprising: combustion mode selecting means for selecting one of the plurality of combustion modes; total target EGR amount calculating means for calculating a total target EGR amount which is a target for the sum total of the internal EGR amount and the external EGR amount in accordance with the selected combustion mode; target in-cylinder gas temperature setting means for setting a target temperature of an unburnt gas within the cylinder as a target in-cylinder gas temperature in accordance with the selected combustion mode; target internal EGR amount calculating means for calculating a target internal EGR amount which is a target of the internal EGR amount in accordance with the set target in-cylinder gas temperature; target external EGR amount calculating means for calculating a target external EGR amount which is a target of the external EGR amount by subtracting the calculated target internal EGR amount from the calculated total target EGR amount; and EGR control means for controlling the internal EGR amount and the external EGR amount, respectively, so as to reach the target internal EGR amount and the target external EGR amount by driving said internal EGR device and said external EGR device.