A control device of an internal combustion engine provided with throttle air passage calculating means for calculating an amount of throttle air passage through a throttle valve, excess air calculating means for calculating an amount of excess air to a cylinder corresponding to drop in air pressure in intake pipe due to an intake valve for that cylinder opening, cylinder air charge estimating means for estimating a cylinder air charge amount for each cylinder based on the amount of throttle air passage detected by the throttle air passage detecting means and an amount of excess air calculated by the excess air calculating means, and engine control means for controlling the internal combustion engine based on the cylinder air charge amount for each cylinder estimated by the cylinder air charge estimating means.
An air quantity estimation apparatus for an internal combustion engine estimates intake pipe section pressure, which is pressure of air within an intake pipe section. When throttle valve opening is smaller than a threshold value, the apparatus estimates the intake pipe section pressure by use of an intercooler model constructed on the basis of conservation laws for air within the intercooler section and an intake pipe model constructed based on conservation laws for air within the intake pipe section. Meanwhile, when the throttle valve opening is greater than the threshold value, the apparatus estimates the intake pipe section pressure by use of an intercooler-intake pipe combined model constructed based on conservation laws for air within a combined section formed by combining the intercooler section and the intake pipe section. The apparatus estimates cylinder air quantity on the basis of the estimated intake pipe section pressure.
A control system of an internal combustion engine provided with a throttle valve passage air flow calculation equation by which the throttle valve passage air flow mt is expressed as a function of the downstream side intake pipe pressure at the downstream side of the throttle valve and a cylinder intake air flow calculation equation by which the cylinder intake air flow mc is expressed as a function of the downstream side intake pipe pressure, where said downstream side intake pipe pressure Pm and cylinder intake air flow mc when the throttle valve passage air flow mt found from said throttle valve passage air flow calculation equation and the cylinder intake air flow mc found from said cylinder intake air flow calculation equation match are calculated as the downstream side intake pipe pressure Pmta and cylinder intake air flow mcta at the time of steady operation under the operating conditions at that time is provided.
The present invention embodies an engine intake air flow meter measuring a mass flow rate based on measured pressures in an intake pipe, such as a pressure difference between two points and a pressure at a point. Calculations for integration and double integration of the pressure difference are performed, and both values of integration and double integration are corrected at a moment when an air flow rate is detected to be a zero based on a value of a time derivative of the pressure. Then a mass flow rate and an amount of air are calculated by the value of integration and the value of double integration respectively.
A cylinder air filling amount is divided into a first amount of air and a second amount of air, the first amount of air and the second amount of air are calculated, and the first amount of air and the second amount of air are totaled to calculate a cylinder air filling amount. The first amount of air is the excess of the cylinder air filling amount with respect to the throttle valve air passage amount occurring due to an intake stroke being performed. The drop in intake pressure occurring due to an intake stroke being performed is detected for each cylinder and the total value of the intake pressure drop in a 720.degree. crank angle range is calculated. The first amount of air is calculated based on an intake pressure drop and the intake pressure drop total value. Due to this, it is possible to simply and accurately calculate a cylinder air filling amount.
Calculation models (22, 24) for an in-cylinder air charge amount determine an estimated intake air pressure (Pe) based on an intake air flow rate (Ms), and then determine an air charge amount (Mc) from the estimated intake air pressure (Pe). A correction execution module (26) corrects, while a vehicle is traveling, the calculation model based on the relationship between the estimated intake air pressure (Pe) and a measured intake air pressure (Ps).
