Patent ID: 6418896
Filing Date: 2002-07-16
Classification: F01L,Y10T

Abstract:
A variable valve timing system for advancing and retarding a valve timing of intake and exhaust valves of a combustion engine, the system being programmed to control a hydraulic pressure control condition of a hydraulic pressure circuit in the system to shift from an initial hydraulic pressure control condition in which a rotor is maintained at an initial volume and locked by a lock mechanism to a volume shiftable hydraulic pressure control condition in which a volume of an advanced angle chamber is varied to reach a target advanced angle value via a transitional hydraulic pressure condition in which the rotor is maintained at the initial volume and the lock mechanism is released,wherein the hydraulic pressure supplied to the lock mechanism and in the advanced angle chamber is controlled to be gradually increased while the hydraulic pressure in a retarded angle chamber is maintained at high level during the transitional hydraulic pressure control condition.