Patent ID: 7680585

Claim:
An internal EGR control device for an internal combustion engine for controlling internal EGR which causes burned gases to remain in a cylinder, comprising: a variable valve mechanism that controls an internal EGR amount by changing a valve-closing timing of an exhaust valve of the engine; operating condition-detecting means for detecting operating conditions of the engine; target internal EGR amount-setting means for setting a target internal EGR amount which serves as a target to which the internal EGR amount is controlled, according to the detected operating conditions of the engine; exhaust gas temperature-obtaining means for obtaining a temperature of exhaust gases exhausted from the engine; exhaust gas pressure-obtaining means for obtaining a pressure of the exhaust gases; air-fuel ratio parameter-detecting means for detecting an air-fuel ratio parameter representative of an air-fuel ratio of an air-fuel mixture supplied to the engine; gas constant-calculating means for calculating a gas constant of burned gases according to the detected air-fuel ratio parameter; target internal EGR amount-correcting means for correcting the target internal EGR amount based on a gas state equation, using the obtained temperature and pressure of exhaust gases, and the calculated gas constant; valve-closing timing-calculating means for calculating the valve-closing timing of the exhaust valve according to the corrected target internal EGR amount; and control means for controlling said variable valve mechanism based on the calculated valve-closing timing of the exhaust valve.