Abstract: In a case of switching the control mode between the reference timing control mode and the F/B control mode, when an engine speed is greater than or equal to a predetermined speed, and when target advanced amount of intake valve timing is lower than a switching threshold (vicinity of the most retarded timing), an intake VCT is switched into the reference timing control mode. And when engine speed is more than the predetermined rotating speed, and when the target retarded amount of exhaust valve timing is less than the switching threshold (vicinity of the most advanced timing), an exhaust VCT is switched to the reference timing control mode.

Abstract: When a target advance angle VTT1 of an intake valve is a threshold K1 or less and when a target retard angle VTT2 of an exhaust valve is a threshold K2 or less, an intake-side variable valve timing device and an exhaust-side variable valve timing device are turned into a base mode. When a target advance angle VTT1 of an intake valve exceed the threshold K1 or when the target retard angle VTT2 of an exhaust valve exceeds the threshold K2, both of the variable valve timing devices are turned into a feedback mode at the same time.

Abstract: When a target advance angle VTT1 of an intake valve is a threshold K1 or less and when a target retard angle VTT2 of an exhaust valve is a threshold K2 or less, an intake-side variable valve timing device and an exhaust-side variable valve timing device are turned into a base mode. When a target advance angle VTT1 of an intake valve exceed the threshold K1 or when the target retard angle VTT2 of an exhaust valve exceeds the threshold K2, both of the variable valve timing devices are turned into a feedback mode at the same time.