Patent ID: 7000580

Claim:
A variable cam timing phaser for an internal combustion engine having at least one camshaft comprising: a housing having an outer circumference for accepting drive force; a rotor for connection to a camshaft coaxially located within the housing, the housing and the rotor defining at least one vane separating a chamber in the housing into an advance chamber and a retard chamber, the vane being capable of rotation to shift the relative angular position of the housing and the rotor; a spool valve comprising a spool having at least two lands separated by a central spindle, slidably mounted within a sleeve received by a bore, and a plurality of check valves; and a passage from the advance chamber to a port in the spool valve and a passage from the retard chamber to a port in the spool valve, such that when the spool is in the first position, fluid from the advance chamber flows through the passage and the port to the bore surrounding the central spindle of the spool valve and through a first check valve within the spool valve and port to the passage to the retard chamber and when the spool is in the second position, fluid from the retard chamber flows through the passage and the port to the bore surrounding the central spindle of the spool valve and through a second check valve within the spool valve and port to the passage to the advance chamber; wherein when the spool is in the third position, the passage from the advance chamber to the port in the spool is blocked by the second check valve within the spool valve and the passage from the retard chamber to the port in the spool valve is blocked by the first check valve within the spool valve.