Apparatus for estimating exhaust gas recirculation quantity

An apparatus for estimating a quantity of recirculated exhaust gas flowing into a cylinder of an internal combustion engine, the apparatus comprising:

• an EGR valve controlling a quantity of an exhaust gas recirculated from an exhaust passage into an intake passage through an EGR passage;
• a measuring means for measuring a quantity of an intake air flowing through the intake passage;
• a first means for computing a quantity of a total gas flowing into a cylinder by means of an intake valve model which simulates a behavior of gas flowing through the intake passage toward a cylinder;
• a second means for computing a quantity of the exhaust gas passing through the EGR valve by means of an EGR valve model which simulates a behavior of the recirculated exhaust gas passing through the EGR valve;
• a third means for computing a temporal quantity of the exhaust gas flowing into the cylinder based on the quantity of the exhaust gas passing through the EGR valve by means of an EGR diffusion model which simulates a behavior of the exhaust gas flowing through the intake passage toward an intake port of the internal combustion engine;
• a fourth means for obtaining the quantity of the intake air flowing into the cylinder by subtracting the temporal quantity of the exhaust gas flowing into the cylinder from the total quantity of the gas flowing into the cylinder;
• a fifth means for correcting the quantity of the intake air flowing into the cylinder by means of the intake air quantity measured by the measuring means;
• a sixth means for computing an intake air pressure based on the quantity of the intake air corrected by the fifth means, and
• a seventh means for computing a quantity of the recirculated exhaust gas flowing into the cylinder based on at least the intake air pressure.