EGR rate determination method and control device for internal combustion engine

摘要

The present invention makes it possible to accurately determine an EGR rate from an in-cylinder pressure. An EGR rate determination method for an internal combustion engine according to the present invention, a combustion period is calculated by using in-cylinder pressure data measured by an in-cylinder pressure sensor. An in-cylinder flame velocity is then calculated from the combustion period. Next, in accordance with prepared data indicative of the influence of an engine speed on the flame velocity, a portion of the flame velocity calculated from the combustion period that is affected by the engine speed is eliminated. Eventually, a current EGR rate is determined from the flame velocity from which the portion affected by the engine speed is eliminated.