Abstract: An intake-air quantity estimation apparatus for an internal combustion engine, including 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.

Abstract: A throttle model M2 estimates the flow rate mt of air passing thorough a throttle in accordance with an expression obtained on the basis of the law of conservation of energy, the law of conservation of momentum, and the law of conservation of mass. An intake pipe model M3 estimates the pressure Pm and temperature Tm of air within an intake pipe in accordance with an expression obtained on the basis of the law of conservation of mass and the law of conservation of energy. An intake valve model M4 estimates the flow rate mc of air passing around an intake valve in accordance with an expression obtained on the basis of the law of conservation of energy, the law of conservation of momentum, the law of conservation of mass, the equation of state, and the like. A cylinder model M5 estimates the pressure Pc and air temperature Tc within a cylinder in accordance with an expression obtained on the basis of the law of conservation of energy regarding the cylinder.