EGR rate estimation system for internal combustion engine

摘要

A system for estimating an exhaust gas recirculation rate for an internal combustion engine. In the system, the EGR rate when its operation is steady is first determined to a desired value with respect to the engine operating conditions at least including the engine speed and the engine load, then the EGR rate is estimated as; EGR rate=(steady-state EGR rate)x{(gas flow rate QACT determined by the actual valve lifting amount and the ratio between the upstream pressure and the downstream pressure of valve)/(gas flow rate QCMD determined by a command value and the ratio between the upstream pressure and the downstream pressure of valve)} A delay time until the recycled gas enters the combustion chamber is determined and one from among the EGR rates or a fuel injection correction coefficients calculated therefrom consecutively is selected.