Abstract: In an internal combustion engine provided with a variable valve mechanism that variably controls at least an operating characteristic (valve lift amount and the like) of an intake valve, a valve opening area AWm at a valve overlap time is calculated based on a valve lift amount (VCS-ANGL) and opening timing IVO of the intake valve, and a spit-back gas amount Wm at the valve overlap time is calculated based on the valve opening area AWm. On the other hand, a volume flow ratio (basic actual engine volume flow ratio) RQH0VEL1 in the intake valve, equivalent to an actual intake air amount of the engine, is calculated based on the valve lift amount and closing timing of the intake valve, and a basic residual gas amount Wcyl is calculated based on the basic actual engine volume flow ratio RQH0VEL1. Then, a resultant obtained by adding the spit-back gas amount Wm and the basic residual gas amount Wcyl, is set as a total residual gas amount of the engine.

Abstract: In a variable valve event and lift mechanism that rotates a control shaft by a motor to successively vary a valve event and a valve lift amount of engine valves, a VEL control unit integrally provided with an angle sensor that detects a rotation angle of the control shaft, is disposed and a signal of a target rotation angle of the control shaft is output to the VEL control unit from an engine control unit, so that the VEL control unit feedback controls the motor.