This paper describes the development of a safety-clutch by using magnetorheological fluids (MRF) to switch the
transmission torque between a motor and a generator in a bus-like vehicle. The clutch is based on a new design
combining an axial MRF-actuator and a ball coupling mechanism. This so called "MRF-ball-clutch" avoids the
disadvantages of traditional bell- or disc-MRF-clutch designs where the torque is transmitted by the MRF which leads to
a self-heating due to the shearing forces in the fluid and a more or less significant drag torque caused by limitations of
the relation between minimal and maximal transmittable torque. The safety clutch based on the new MRF-clutch design
requires a minimum of power consumption and allows switching high torsional moments in a very compact, lightweight
and robust design.
The work was done within the Fraunhofer System Research for Electromobility FSEM, founded by the German Federal
Ministry of Research and Technology.