Fuel injection system of an internal combustion engine

A fuel injection system of an internal combustion engine (M2) for determining a fuel injecting amount q of a fuel injection valve (M4) based on a physical model describing a behavior of fuel coming into a cylinder (M3) of the engine (M2) utilizing an amount fw of fuel adhering to an inner wall of an intake pipe (M1) and an amount fv of vapor fuel in the intake pipe (M1) as state variables, the system comprising:

• an operating state detection means (M5) for detecting a rotating speed .omega. of the engine (M2), an evaporating amount Vf of the fuel adhering to the inner wall of the intake pipe (M1), a fuel/air ratio .lambda. of a mixture coming into the cylinder (M3), and an amount m of air coming into the cylinder (M3);
• a dividing means (M6) for dividing the evaporating amount Vf by the engine speed .omega.;
• an estimation means (M7) for calculating estimation values fw and fv of the adhering fuel amount fw and the vapor fuel amount fv, based on a product .lambda..multidot.m of the detected fuel/air ratio .lambda. and the detected air amount m, said division Vf/.omega. at the dividing means (M6) and the injecting amount q, utilizing a first equation determined from the physical model;
• a summing means (M8) for summing up a difference m.multidot.(.lambda.-.lambda.r) between the product .lambda..multidot.m and a product .lambda.r.multidot.m of a preset target fuel/air ratio .lambda.r and the air amount m;
• and
• a fuel injecting amount calculation means (M9) for calculating the fuel injecting amount q, based on the division Vf/.omega., the estimated values fw and fv, the product .lambda.r.multidot.m, and the difference summed up at the summing means (M8), utilizing a second equation determined from the physical model.