Intake air amount-estimating apparatus for internal combustion engines

Abstract

An intake air amount-estimating apparatus for an internal combustion engine estimates an amount Gc of intake air actually drawn into a combustion chamber, based on a model formulated on an intake passage in which a portion of the intake passage extending from a throttle valve to each of the combustion chamber is regarded as a chamber. A value Gc' of the intake air amount in a steady operating condition is determined at least based on engine rotational speed and pressure within the chamber. An effective opening area A of the throttle valve is determined at least based on throttle valve opening and the pressure within the chamber. A first-order delay value ADELAY of the effective opening area of the throttle valve is determined. The intake air amount value Gc' is corrected to calculate the amount Gc by an equation of Gc=Gc'.times.(A/ADELAY). The ADELAY value is calculated by the use of a correction value for use in calculating the ADELAY value, which is set in a manner depending on a detected change in the amount of air charged in the chamber.