Circularly magnetized non-contact torque sensor and method for measuring torque using same

Abstract

A torque sensor for providing an output signal indicative of the torque applied to a rotating torqued member comprises a magnetoelastically active element for producing a magnetic field varying with the applied torque and a field modulating means for modulating the magnetic field in a periodic manner which is indicative of the speed of member rotation. A magnetic field vector sensor, such as a Hall effect sensor, senses the amplitude of the modulated field for providing an output signal which is linearly indicative of the torque applied to the rotating member. The field modulating means preferably comprises at least one ring having some uniformly spaced salient feature, such as gear-like teeth, around the periphery thereof. In one embodiment, the magnetoelastically active element comprises a ring of material endowed with an effective uniaxial magnetic anisotropy such that the circumferential direction is the easy axis, and magnetically polarized in a substantially circumferential direction. The ring is attached to the torqued member, such as a rotating shaft, so that application of a torque to the shaft is transmitted to the ring. In another embodiment, the magnetoelastically active portion includes two or more axially distinct, magnetically contiguous, oppositely polarized circumferential regions.

Dependencies are inferred from the claim text.