Search Results

The development of a transducer for sensing the torque on the output shaft of a four speed rear wheel drive automatic transmission is described. Magnetoelastic polarized ring technology was selected based on its independence from shaft properties and its non-contact mode of sensing. The ring and several intermediate sleeves were attached by press fits onto an experimental shaft. The magnetic field arising from the ring with the application of torque was sensed by flux gate sensing elements. Ability to accurately measure the output torque of an engine driven transmission over its full range of torque and speed was demonstrated by dynamometer tests.

The benefits of a magnetoelastic torque sensing system and its application on Formula 1 and CHAMP Car racing driveshafts are identified. In particular, the use of circumferential remanent magnetic bands on the shaft itself has enabled a design that satisfies the application's demanding packaging requirements. The criteria used to determine the suitability of a given shaft material for optimal magnetoelastic characteristics and concurrent mechanical strength are illustrated. Shaft material and geometry are shown to have significant effects on sensor performance. Design considerations for the magnetic field sensor layout and signal conditioning circuit are also presented. The racing driveshaft application is shown to add particular challenges in terms of temperature, packaging, and kinematic tracking. Magnetization and calibration processes associated with field operation of the sensor are discussed.