An infinitely variable camshaft timing device (phaser) has a control valve
located in the rotor. Since the control valve is in the rotor, the
camshaft need only provide a single passage for supplying engine oil or
hydraulic fluid, and does not need multiple passageways for controlling
the phaser, as in the prior art. Two check valves, an advance chamber
check valve and a retard chamber check valve, are also located in the
rotor. The check valves are located in the control passages for each
chamber. The main advantage of putting the check valves in the advance and
retard chambers instead of having a single check valve in the supply is to
reduce leakage. This design also eliminates high pressure oil flow across
the spool valve and improves the response time of the check valve to the
torque reversals due to a shorter oil path. In addition, the phaser of the
present invention outperforms an oil pressure actuated device and consumes
less oil.