Intake- and/or exhaust-valve timing control system for internal combustion engine

Claim 1

An intake- and/or exhaust-valve timing control system for an internal combustion engine comprising: a gear mechanism disposed between a timing pulley and a camshaft for adjusting the phase angle between said pulley and said camshaft; a drive mechanism provided for drivingly controlling said gear mechanism via oil pressure depending upon the operating state of said engine; said drive mechanism including; a hydraulic circuit having an oil supply passage for supplying working fluid from an oil pressure source for pressurizing the working fluid to said gear mechanism and an oil exhaust passage for exhausting the working fluid from said gear mechanism to an oil pan of said engine; a flow control valve disposed in said hydraulic circuit at a location included in a stationary member of said engine for controlling the amount of working fluid flowing through said hydraulic circuit; said oil exhaust passage being communicated through said flow control valve with the oil pan in such a manner as to prevent working fluid exhausted therethrough from being mixed with blow-by fumes or other vapors in said engine; said oil supply passage and said oil exhaust passage are juxtaposed and said flow control valve is arranged in such a manner as to traverse both said oil supply and oil exhaust passages; means for monitoring the operating state of said engine, said monitoring means generating a control signal representative of the operating state of said engine; and an actuator for actuating said flow control valve in response to said control signal from said monitoring means.