Patent ID: 6932038

Claim:
A camshaft phaser system for controllably varying the timing of an engine valve actuable by a camshaft in an internal combustion engine, the phaser timing being controllably varied by cyclic torque oscillation of the camshaft, comprising: a) a camshaft phaser having a stator and a rotor and at least one advance chamber and at least one retard chamber disposed therebetween; b) check valve means in said phaser for controlling communication of a hydraulic fluid in first and second opposing directions between said advance chamber and said retard chamber; c) a piston means for controllably opening and closing said check valve means, said piston means including first and second ramps and a piston bore; and d) a flow path for said hydraulic fluid between said advance chamber and said retard chamber, wherein said check valve means includes first and second check valves disposed in opposite orientations in said flow path, wherein said first and second check valves extend into said piston bore for selective engagement by said first and second ramps, respectively, during actuation of said piston; and wherein said first and second ramps are spaced axially such that said first and second check valves may be closed simultaneously, effectively locking said rotor in holding position.