CONTROL APPARATUS FOR INTERNAL COMBUSTION ENGINE

An electronic control unit calculates a rotation variation amount ΣΔNE as a cetane number index value of the fuel supplied to an internal combustion engine and executes fuel injection control in a first execution mode corresponding to the rotation variation amount ΣΔNE (S S). In a mixing period in which the cetane number of the fuel supplied to the internal combustion engine is changed due to the fuel feed into the fuel tank (S: YES), the fuel injection control is executed in a second execution mode such that, compared with the first execution mode, stable operation of the internal combustion engine is given more importance (SYES, S). When calculation of the rotation variation amount ΣΔNE is executed during the mixing period (S: YES), fuel injection control is executed while limiting the reflection of the rotation variation amount ΣΔNE (S S).