CAMSHAFT PHASER WITH A ROTARY VALVE SPOOL

A camshaft phaser (12, 212) includes a stator (18, 218); a rotor (20, 220) defining an advance chamber (42, 242) and a retard chamber (44, 244) with the stator (18, 218); a valve spool (28, 228) that is rotatable about an axis (16, 216) and defining a supply chamber (98, 298) and a vent chamber (100, 300) with the rotor (20, 220); an actuator (18, 118) which rotates the valve spool (28, 228) to change the position of the rotor (20, 220) relative to the stator (18, 218) by 1) supplying oil from the supply chamber (98, 298) to the advance chamber (42, 242) and venting oil from the retard chamber (44, 244) to the vent chamber (100, 300) and 2) supplying oil from the supply chamber (98, 298) to the retard chamber (44, 244) and venting oil from the advance chamber (42, 242) to the vent chamber (100, 300); and a check valve (78, 278) which is displaceable axially between an open position which allows oil to flow from the vent chamber (100, 300) to the supply chamber (98, 298) and a closed position which prevents oil from flowing from the supply chamber (98, 298) to the vent chamber (100, 300).