| abstract |
A variable camshaft timing system (VCT system) for an internal combustion engine having a rotatable crankshaft (22) and a rotatable camshaft (26, 126). The camshaft (26, 126) is position variable relative to the crankshaft (22). A spool valve (192) including a spool (200) slidable within a cylindrical member (198) selectively controls the movement of hydraulic fluid for actuating the oscillation of the hydraulic operators (54, 56, 160a, 160b) within the housing recess (132a, 132b) as the housing oscillates with respect to the camshaft (26, 126). In accordance with various aspects of the present invention, the VCT system also includes a means for controlling the position of the spool (200), a means for removing air from the VCT system and seals (160h) for sealing the housing (130) outer periphery to prevent hydraulic fluid from draining out of the VCT system when the engine is shut down. |