Patent ID: 6526930
Filing Date: 2003-03-04
Classification: F01L

Abstract:
A valve timing control system for an internal combustion engine, comprising:sensor means for detecting engine operation states of an internal combustion engine; intake or exhaust cam shafts for driving intake or exhaust valves, respectively, of said internal combustion engine in synchronism with a rotation of a crank shaft of said internal combustion engine; at least one actuator operatively connected to at least one of cam shafts for driving said intake or exhaust valves, respectively; a hydraulic pressure supply unit for feeding a hydraulic pressure to drive said actuator; and control means for controlling the hydraulic pressure fed from said hydraulic pressure supply unit to said actuator in dependence on said operating states of said internal combustion engine while changing a relative phase of said cam shaft relative to said crank shaft, wherein said actuator includes a retarding hydraulic chamber and an advancing hydraulic chamber for setting an adjustable range of said relative phase; a locking mechanism for setting said relative phase to a lock-up position within said adjustable range; and an unlocking mechanism for releasing said locking mechanism in response to a predetermined level of hydraulic pressure fed from said hydraulic pressure supply unit, and wherein, when driving said locking mechanism to control said relative phase to be within a predetermined range of said lock-up position, said control means reduces a limit of a control range.