Concept of a start-up clutch with nickel-titanium shape memory alloys

Abstract

The ability of Shape Memory Alloys (SMA) to remind two different macroscopic shapes and to alter between these shapes by changing their temperature, leads to innovative approaches within drive technology. Especially Nickel-Titanium (NiTi) Shape Memory Alloys offer high actuating forces and adjustment travel in combination with high cycle stability. The shape memory effect is based on the transformation between martensitic and austenitic microstructure depending on the temperature of the actuators. The transformation temperatures in the range of 20°C to 100°C make NiTi SMA attractive for engineering applications. This paper investigates the technical use of NiTi SMA as actuators within a start-up clutch. The start-up of a drive train demands a higher torque, caused by the acceleration of the masses, than during the nominal speed. This demand can be realized with NiTi-Shape Memory Alloys (NiTi-SMA) without increasing the nominal size of the clutch appreciable.