Patent ID: 8499916

Claim:
A rotational coupling device, comprising: a rotor configured for coupling to a shaft for rotation therewith and disposed about a rotational axis, said rotor defining a first clutch engagement surface; a field shell disposed about said rotational axis and fixed against rotation; an electrical conductor disposed within said field shell on a first side of said rotor; an armature disposed on a second side of said rotor opposite said conductor, said armature defining a second clutch engagement surface, said armature, said rotor, and said field shell comprising members of a magnetic circuit; a torque transmission member coupled to said armature for rotation therewith, said torque transmission member disposed about said axis and supported by a bearing disposed about said axis; and, a sleeve disposed about said axis radially inwardly of said bearing wherein said sleeve has a magnetic permeability that is lower than a magnetic permeability of said members of said magnetic circuit; and, a spacer disposed about said axis radially inwardly of said bearing, said spacer having a magnetic permeability that is lower than said magnetic permeability of said members of said magnetic circuit.