Patent ID: 7818113

Claim:
A valve timing control apparatus for a valve timing adjustment mechanism that adjusts timing of opening and closing one of an intake valve and an exhaust valve of an internal combustion engine having an output shaft and a camshaft, the valve timing control apparatus comprising: an output-side rotor that is rotatable synchronously with the output shaft; a cam-side rotor that is rotatable synchronously with the camshaft that opens and closes the one of the intake valve and the exhaust valve; a hydraulic pump that is configured to supply hydraulic oil such that one of the output-side and cam-side rotors rotates relative to the other one of the rotors; a control device that outputs a drive command signal associated with rotation of the one of the rotors relative to the other one of the rotors; a control valve that controls the speed of the rotation of the one of the rotors relative to the other one of the rotors by controlling supply of the hydraulic oil in accordance with the drive command signal outputted by the control device; a storage device that prestores standard data indicating a predetermined relation for a reference product of the valve timing adjustment mechanism between a dead zone width and a parameter correlated with the dead zone width for each hydraulic oil temperature, wherein: the dead zone width corresponds to a change amount of the drive command signal that is changed from a first value to a second value; when the drive command signal is the first value, the rotors are in a hold state, where the speed of the rotation of the one of the rotors relative to the other one of the rotors is substantially zero such that a rotational position of the one of the rotors relative to the other one of the rotors is substantially maintained; and when the drive command signal is changed from the first value and becomes the second value, the speed of the rotation of the one of the rotors relative to the other one of the rotors starts changing sharply; and learning means for detecting and learning a value of the parameter of the dead zone width of the valve timing adjustment mechanism during the hold state by changing the drive command signal, wherein: the control device computes the drive command signal based on the value learned by the learning means, the standard data, and hydraulic oil temperature.