CETANE NUMBER ESTIMATION DEVICE

In order to estimate the cetane number of a fuel, fuel injection is executed by controlling the driving of a fuel injection valve by a prescribed amount. The amount of change in the rotation of a diesel engine generated in response to the fuel injection is detected, and the cetane number of the fuel is estimated on the basis of this amount of change in the rotation. The actual amount of fuel injected from the fuel injection valve is detected, and when the difference between the amount actually detected and the prescribed amount is equal to or greater than a threshold value, the execution of the fuel cetane number estimation process is restricted.