Smart sealing for magnetorheological fluid actuators

In automotive and industrial environments, magnetorheological fluid–based applications such as clutches and brakes are gaining continuously more attention. However, one of the serious challenges for their application are drag losses at high shear rates. While viscous losses of the magnetorheological fluid can be eliminated by a magnetorheological fluid movement control based on partially filled shear gaps, commonly utilized sealings also cause drag losses based on dry friction. To overcome these challenges, in this contribution, a novel design of sealings for magnetorheological fluid–based actuators is introduced eliminating the adverse drag losses. The intended sealing is based on the magnetorheological fluid itself, positioned in a sealing gap and exposed to a well-defined magnetic stray field of a permanent magnet to prevent any leakage. To eliminate drag torques, a superimposed functional principle with the magnetorheological fluid movement control is utilized. An analytical and a simulation-based modeling approach is proposed describing the torque behavior of the magnetorheological fluid sealing. In experimental investigations, the drag torque-free operation is proven by showing a lossless operation above a defined rotational speed.