Patent ID: 7360516

Claim:
A variable valve timing apparatus for changing a timing of opening/closing at least one of an intake valve and an exhaust valve provided in an engine, comprising: an actuator operating said variable valve timing apparatus; a changing mechanism configured to change the opening/closing timing, by an amount of change in accordance with an operation amount of said actuator, and further configured such that the change in said opening/closing timing is mechanically limited at a reference timing, at least during reference position learning; phase detecting means for detecting an opening/closing timing detection value to be used for controlling said opening/closing timing, by smoothing the opening/closing timing calculated based on a sensor output along the direction of time axis; an actuator operation amount setting portion for setting the operation amount of said actuator based on a deviation between said opening/closing timing detection value detected by said phase detecting means and a target value, at the time of normal control; and reference position learning means for generating an actuator operation command so that said opening/closing timing is changed to said reference timing, and when said opening/closing timing reaches said reference timing, learning a reference value of said opening/closing timing detection value in response; wherein said reference position learning means includes detecting means for detecting, when an amount of change in said opening/closing timing detection value by said phase detecting means becomes approximately zero, that said opening/closing timing has reached said reference timing; and said phase detecting means includes switching means for setting degree of smoothing for smoothing said opening/closing timing along the direction of the time axis smaller at the time of said reference position learning than at said normal control.