Method of fuel injection control in engine

In an engine control apparatus in which a quantity of fuel injected by fuel injection means is controlled to maintain a desired air-fuel ratio wherein said engine control apparatus operates in response to an output from an air-fuel ratio sensor sensing the air-fuel ratio between quantities of air and fuel to be supplied to a cylinder of an engine, and an output from an engine rotation speed sensor, the method comprising the steps of:

• identifying unknown parameters in a transfer function of the fuel supply system in which the dynamic characteristic of the fuel supply system and the retarded flow of exhaust gases are factors, said unknown parameters being based on the fuel deposition rate and the time constant of fuel vaporization wherein said transfer function defines a model of the fuel supply system in accordance with a sensed air-fuel ratio, the quantity of the suction air, intake manifold pressure, engine rotational speed and the quantity of fuel injected;
• estimating the quantity of fuel supplied to the cylinder on the basis of the unknown parameters obtained from said identifying step and the delay of time representing the time elapsed between the time at which a quantity of fuel is injected into the cylinder of said engine and the time at which said sensed air-fuel ratio is detected by said air-fuel ratio sensor due to a retarded flow of exhaust gases;
• and
• controlling the quantity of fuel to be injected by said fuel injection means so that the air-fuel ratio between the estimated quantity of air to be supplied to the cylinder and the estimated quantity of fuel supplied to the cylinder attains a desired air-fuel ratio.