Magnetoelastic torque transducer

Abstract

A torque transducer comprises a sleeve of magnetic material, which is attached concentrically and rigidly to an axle, and at least two stationary windings for excitation of the axle and two windings for sensing the torque transmitted by the axle, as well as a magnetic housing concentrically surrounding the windings. The sleeve is formed with two parallel, annular zones, which are provided with slits having a substantially regular pitch and making an angle of .+-.45.degree. with a generatrix of the envelope surface of the sleeve. The excitation windings are series-connected and generate a magnetic flux in the axle surface. The measuring windings are connected in opposition, whereby the measuring signal is approximately zero in case of zero torque in the axle. When the axle is subjected to a torque, the bars between the slits in the annular zones will be subjected to tensile stress and compressive stress, respectively, in the direction of the flux. This leads to a polarized magnetic unbalance, which results in a difference voltage from the measuring windings which, after phase-sensitive detection, gives a measure of the magnitude and sign of the torque.