To improve accuracy of estimation of an inside EGR amount, by estimating a valve clearance to correct valve timing based on the estimated valve clearance.
The valve timing is calculated based on an opening/closing timing change amount of a variable valve system solenoids 22, 23, and a cylinder gas amount is calculated based on a cylinder temperature, cylinder pressure, a gas constant, a cylinder capacity in closing an exhaust valve calculated based on the calculated valve timing. A split-back gas amount during overlapping of an intake valve opening period with an exhaust valve opening period is calculated, and then the inside EGR amount is calculated based the calculated values of the cylinder gas amount and the split-back gas amount. Where, in calculation of the valve timing, a valve clearance amount is estimated based on a valve temperature to correct the valve timing by the estimated valve clearance amount.
OSHIMI YOICHI
NAGAISHI HATSUO
