METHOD FOR ESTIMATING ACTUAL EGR RATE IN EGR SYSTEM, AND EGR SYSTEM

A controller, in shifting the state of the EGR system from the EGR operating state to the EGR non-operating state at the time of performing the deceleration of the vehicle, calculates a provisional EGR ratio that is a provisional value of the current EGR ratio, estimates the provisional EGR ratio as the actual EGR ratio when a fore-and-aft differential pressure of the EGR valve is equal to or more than a predetermined value, performs correction to make the provisional EGR ratio smaller, and estimates the corrected provisional EGR ratio as the actual EGR ratio when the fore-and-aft differential pressure of the EGR valve is less than the predetermined value.