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Investigation of energy-efficient MRF-based clutches for hybrid powertrains

The requirements for transmission and coupling elements in hybrid powertrains are rising continuously. On this occasion a novel clutch-design is investigated and validated in this contribution. The transmission of power is based on magnetorheological fluids (MRF) including a fluid movement control for enabling a drag torque-free operation for an increased energy efficient operation. Drag losses in powertrains are a serious deficiency for an energy-efficient application. MRFs are highly qualified for the utilization in powertrains considering their particular characteristics of changing their apparent viscosity significantly under influence of a magnetic field by fast switching times and a smooth torque control. The proposed MRF-clutch with three different variations of the fluid movement control is designed based on a numerical model and validated by experimental measurements with a realized prototype. The main aspects during the investigation are focused on the coupling functions under the influence of high rotational speeds up to 6000 min-1 and also the safety behavior of the different variations by the fluid control in case of a system failure. The theoretical and experimental investigation demonstrates the suitability for an integration of clutches based on MRF in electrical or hybrid powertrains as an alternative to conventional coupling elements.