Design and experimental evaluation of energy-efficient MRF-coupling elements with multiple shear gaps for enhancement of torque capacity

In this contribution a novel design for the enhancement of the torque capacity resp. torque-to-mass ratio of energy-efficient coupling elements based on magnetorheological fluids (MRF) will be presented. Applying the MR-fluid movement control and the smart MR-fluid seal, viscous induced drag torques can be eliminated increasing the energy efficiency significantly. In addition, the serpentine flux guidance offers a suitable design saving space, weight and feeding energy. However, the torque-to-mass ratio of these very energy-efficient coupling elements is still lower, compared to conventional MRF-coupling elements or to wet running multiple-disc clutches. For a further enhancement of the torque-to-mass ratio certain arrangements of multiple shear gaps are discussed. By the most promising design, based on two axial shear gaps in the outer region of the coupling element, an increased torque-to-mass ratio of 40% can be achieved. For the experimental evaluation of the torque enhancement, the manufactured design of a test-actuator is presented and investigated focusing on the torque transmission and the almost loss-free operation at certain rotational speeds.