Variable valve timing controller for internal combustion engine

A variable valve timing controller adjusting a valve timing of an intake valve and/or an exhaust valve by varying a speed of an electric motor relative to a rotational speed of a camshaft in such a manner as to vary a camshaft phase representing a rotational phase of the camshaft relative to a crankshaft of an internal combustion engine, the variable valve timing controller comprising:

• a target motor speed computing means for computing a target motor speed based on a rotation speed of the internal combustion engine and a deviation between a target camshaft phase and an actual camshaft phase;
• a motor drive control means for feedback controlling a motor current representing a driving current of the motor in such a manner as to decrease a deviation between the target motor speed and an actual motor speed;
• a motor current estimating means for estimating the motor current;
• a motor current restricting means for restricting the motor current when the motor current estimated by the motor current estimating means exceeds a predetermined value;
• and
• an abnormality-diagnosis means for determining whether an abnormality exists based on a deviation between the target camshaft phase and the actual camshaft phase in consideration of a deterioration of responsivity of the variable valve timing control due to a restriction of the motor current by the motor current restricting means.