Patent ID: 8215467

Claim:
A magnetorheological fluid (MRF) clutch selectively connecting a rotatable first member with a rotatable second member, the MRF clutch comprising: a drum portion containing a magnetically-permeable stator and a magnetic core, said drum portion being operatively connected to one of the rotatable first member and the rotatable second member; a rotor operatively connected to the other of the rotatable first member and the rotatable second member, said rotor having a magnetically-permeable member extending axially into said drum portion, with said magnetically-permeable member at least partially defining an outer working gap in conjunction with said magnetically-permeable stator and an inner working gap in conjunction with said magnetic core; magnetorheological (MR) fluid substantially filling each of said inner working gap and said outer working gap; and a magnetic field generator positioned radially inward of the magnetically-permeable member, embedded in said magnetic core, and operable for generating a magnetic field suitable for changing an apparent viscosity of said MR fluid, wherein the inner working gap is radially inward of the outer working gap relative to the magnetic field generator; wherein a ratio of a thickness of said outer working gap to a thickness of said inner working gap equals a ratio of magnetic flux in the outer working gap to magnetic flux in the inner working gap, such that slip power dissipated per unit volume in said inner working gap is equal to slip power dissipated per unit volume in said outer working gap.