Valve timing control system for internal combustion engine

摘要

A valve timing control system for an internal combustion engine for preventing hitching of a lock pin of an actuator at the time of changing a cam angle is provided. The valve timing control system is provided with actuators 15 and 16 connected to cam shafts 15C and 16C, hydraulic pressure supply units 19 and 20 for driving the actuators, and a controller 21A for controlling a hydraulic pressure for the actuators in dependence on engine operation states while changing a relative phase of the cam shafts relative to crank shafts. The actuator includes a locking mechanism for setting the relative phase to a lock-up position, and an unlocking mechanism for releasing the locking mechanism in response to a predetermined hydraulic pressure. The controller executes a releasing operation of the locking mechanism if the lock-up position in the locking mechanism changes from inside a predetermined range to outside the predetermined range.