Patent ID: 8646424
Filing Date: 2014-02-11
Classification: F01L

Abstract:
1. A variable valve timing device for adjusting a valve timing of a valve being opened/closed by a camshaft which is driven by a torque transmitted from a crankshaft of an internal combustion engine, the variable valve timing device comprising: a housing defining a hydraulic chamber therein; a vane rotor disposed to define an advancing chamber and a retarding chamber by dividing the hydraulic chamber in a rotational direction, the vane rotor being rotatable to change a rotational phase relative to the housing in response to hydraulic fluid introduced into one of the advancing chamber and the retarding chamber; a control valve having a sleeve and a spool disposed in the sleeve in a reciprocally movable manner, the control valve being adapted to control in-flow and out-flow of the hydraulic fluid with respect to both the advancing chamber and the retarding chamber by adjusting a spool position in an axial direction; a driving source which changes the spool position by generating a driving force of the spool in response to an instruction value; and a biasing device which generates and adjusts a biasing force biasing the spool against the driving force, wherein the control valve provides a first region and a second region arranged along the axial direction in a region where the spool is movable, and wherein the biasing device includes: a movable member which is capable of being engaged with the spool in the first region to move together with the spool, and is capable of resting on the sleeve in the second region to enable the spool to move relative to the movable member; a first resilient member which generates a first restoring force for pushing the spool in the axial direction when the spool is in both the first region and the second region; and a second resilient member which generates a second restoring force for pushing the movable member in the axial direction when the spool is in both the first region and the second region, wherein the movable member engages with the spool in the first region to enable the second restoring force to act on the spool, and rests on the sleeve in the second region to disable the second restoring force to act on the spool, and wherein the movable member is supported by the spool in a manner that the movable member is apart from the sleeve in a radial direction.