Torque Bias Coupling for AWD Applications

The penetration of AWD technologies in the passenger car and crossover SUV market segments is increasing significantly. New market niches are created by changes in the customer priorities from emphasis on traction enhancements to safety, handling and fun-to-drive. This paper introduces a new Torque Bias Coupling concept, which addresses one of the major issues of the current designs: controllability. Essentially consisting of a magnetic particles clutch, mounted in a quasi-static torque split arrangement within a planetary gear set, the coupling offers simultaneously a good power and torque density, which makes it suitable in particular for front wheel drive based vehicle platforms converted to all wheel drive configurations. An important advantage consists of a torque transfer characteristic independent of the input-output relative speed. Also, the coupling actuation does not rely on a differential speed, allowing a high flexibility for the control algorithms. The paper presents different phases of the coupling development process, including various design solutions, performance validation based on test results and vehicle integration aspects.