Patent ID: 7421991

Claim:
A camshaft phaser for selectively varying the valve timing of an internal combustion engine by varying the phase relationship between an engine crankshaft and an engine camshaft, comprising: a) a stator drivable by said engine crankshaft and having a plurality of angularly spaced-apart radial lobes extending inwardly; b) a first rotor disposed within said stator, attachable to said camshaft, and having a plurality of angularly spaced-apart first radial vanes extending outwardly of a first hub interspersed with said spaced-apart radial lobes; c) a second rotor disposed within said stator adjacent said first rotor having a plurality of angularly spaced-apart second radial vanes extending outwardly of a second hub interspersed with said spaced-apart radial lobes, wherein said interspersion of said first radial vanes and said second radial vanes with said spaced-apart lobes defines a plurality of phase advance chambers and a plurality of phase retard chambers; and d) a working fluid disposed in said phase advance chambers and phase retard chambers; wherein rotation of said second rotor with respect to said stator in a first direction causes rotation of said first rotor with respect to said stator in a second and opposite direction.