AIR-QUANTITY ESTIMATION DEVICE FOR INTERNAL COMBUSTION ENGINE WITH SUPERCHARGER

The present invention provides, in an internal combustion engine having a supercharger, an air amount estimating apparatus capable of estimating an amount of air drawn into a cylinder with high accuracy without involving an increased calculation load. The air amount estimating apparatus estimates a cylinder air amount through calculation that incorporates a physical model representing behavior of air flowing through an intake path. When, at this time, a ratio of a throttle downstream pressure to a throttle upstream pressure as calculated with the physical model is smaller than a reference ratio, a throttle flow rate is calculated using an equation of throttle based on the throttle upstream pressure, the throttle downstream pressure, and an opening of a throttle. When the ratio of the throttle downstream pressure to the throttle upstream pressure is greater than the reference ratio, the throttle flow rate is calculated using an equation of linear interpolation based on a compressor flow rate and an intake valve flow rate.