Patent ID: 7200486

Claim:
An intake-air quantity estimation apparatus for an internal combustion engine, comprising: an intake-air quantity estimation device that includes a cylinder pressure estimation device that estimates pressure within a cylinder through calculation using a model of the cylinder obtained based on a law of conservation of energy, the intake-air quantity estimation device estimates a cylinder intake-air quantity based on the estimated pressure within the cylinder, the cylinder intake-air quantity representing the amount of air flowing into the cylinder, wherein the model of the cylinder to be used by the cylinder pressure estimation device is configured based on an expression dPc/dt=(κ·R·Tm/Vc)·mc−(κ·Pc/Vc)·(dVc/dt), where Pc is pressure within the cylinder, κ is the ratio of specific heat, R is a gas constant, Tm is a temperature of air flowing into the cylinder, Vc is a cylinder volume, and mc is a cylinder intake-air flow rate representing a flow rate of air flowing into the cylinder.