Combustion state diagnosis apparatus for an internal combustion engine

In common-rail diesel engine, the vaporized reaction of the fuel injected into the cylinder, the low-temperature oxidation, thermal decomposition reaction, for each reaction forms high temperature oxidation reaction, as a starting point the reaction initiation temperature, the gradient of the oblique side reaction rate, reaction area the amount, reaction time to create the ideal heat generation rate waveform model consisting of isosceles triangle having a length of the base, the ideal heat generation rate waveform of each reaction mode and facilitated by filtering the ideal heat generation rate waveform model to create a. And the ideal heat generation rate waveform for each reaction, compared with the actual heat release rate waveform of each actual reaction forms obtained from the detected cylinder pressure, when the deviation exists reaction mode is not less than a predetermined amount the diagnoses an abnormality has occurred in the reaction form.