Patent ID: 7383118

Claim:
A control apparatus for an internal combustion engine which includes an EGR passage for connecting an exhaust passage and an intake passage of the engine and an EGR control valve disposed in the EGR passage and adapted to control a flow rate of EGR gas flowing from the exhaust passage to the intake passage, the control apparatus comprising: operating-condition obtainment means for obtaining operating conditions of the engine; EGR-ratio-obtainment-value obtainment means for obtaining, as an EGR ratio obtainment value, an EGR ration on the basis of the obtained operating conditions, the EGR ratio being a ratio of a flow rate of EGR gas taken in a cylinder of the engine to a flow rate of gas taken in the cylinder of the engine; relation obtainment means for obtaining, on the basis of the obtained operating conditions, a relation between NOx generation amount and PM generation amount in the obtained operating conditions; generation ratio determination means for determining a ratio between the NOx generation amount and the PM generation amount; EGR-ratio-target-value determination means for determining a target value of the EGR ratio from the obtained relation and the determined ratio; and EGR-control-valve control means for controlling the opening of the EGR control valve such that the EGR ratio obtainment value coincides with the EGR ratio target value.