Theoretical and experimental investigation of axial shear gap arrangements for the enhancement of the torque capacity of energy efficient MR-actuators

In this contribution a design for the enhancement of the torque capacity of energy efficient MRF-based coupling elements will be presented. Magnetorheological fluids (MRF) are smart fluids, consisting of fine magnetic particles in an oil based carrier fluid, with the particular characteristics of changing their apparent viscosity significantly under the influence of a magnetic field. This property allows the design of mechanical devices for torque transmission, such as brakes and clutches, with a continuously adjustable torque generation. Applying the MR-fluid movement control viscous induced drag torques can be eliminated. In combination with a smart MRF-based sealing also losses due to the sealing can be significantly reduced above a well-defined rotational speed increasing the energy efficiency considerably. In addition, the serpentine flux guidance offers an attractive design saving space, weight and feeding energy. For a further enhancement of the torque density certain different possibilities arise. Beside a strengthening due to a combined squeeze and shear mode a design based on multiple axial shear gaps was shown before. Here the most appropriate design will be investigated in more detail. Simulations based on a multiphysic-FEA will be performed and a detailed investigation of the torque enhancement compared to a MRF-based coupling elements with a single shear gap and same outer dimensions will evaluate the degree of torque enhancement.