Patent ID: 8490762

Claim:
A magnetorheological (MR) damper assembly containing MR fluid comprising; a cylinder defining a central longitudinal axis, a first MR piston end plate, a second MR piston end plate, a MR piston core coaxially aligned with said central longitudinal axis and disposed longitudinally between and attached to said first MR piston end plate and said second MR piston end plate, a piston ring attached to said first and second MR piston end plates and including a first longitudinal end adjacent said first MR piston end plate and a second longitudinal end adjacent said second MR piston end plate and said piston ring being disposed radially outwardly from said MR piston core to define a primary MR passageway therebetween, a surface portion of said piston ring in sliding engagement with said cylinder defining at least one surface groove having a narrow circumferential extent and extending between said first and second longitudinal ends of said piston ring and being open to said first and second longitudinal ends of said piston ring and being substantially straight and tilted with respect to a line drawn on said surface portion parallel to said central longitudinal axis when said surface portion is viewed as being longitudinally cut and laid flat to provide a secondary MR passageway for receiving MR fluid and providing lubrication between said surface portion of said piston ring and said cylinder.