Patent ID: 7418857

Claim:
An air quantity estimation apparatus for an internal combustion engine having an intake passage for introducing air taken from outside of the engine into a cylinder; a throttle valve which is disposed in said intake passage and whose opening is adjustable for changing quantity of air passing through the intake passage; a supercharger including a compressor disposed in said intake passage at a position upstream of said throttle valve for compressing the air in said intake passage; and an intercooler disposed in said intake passage between said throttle valve and said supercharger for cooling air in said intake passage, the air quantity estimation apparatus comprising: an intercooler-internal air condition estimation means for estimating pressure and temperature of the air in the intercooler as pressure and temperature of throttle valve upstream air which is air at a position upstream of said throttle valve in said intake passage, respectively, by use of an intercooler model configured on the basis of an energy conversation law with respect to the air in the intercooler, the intercooler model being designed in consideration of a first energy imparted by said supercharger to air supplied into said intercooler, and a second energy exchanged between a wall of the intercooler and the air in the intercooler; and a cylinder intake-air quantity estimation means for estimating, on the basis of the estimated pressure of the throttle valve upstream air and the estimated temperature of the throttle valve upstream air, cylinder intake-air quantity which is quantity of air introduced into said cylinder.