Importance

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Abstract

A torque sensor comprises a magnetoelastically active element, and a magnetic sensor, such as a Hall effect sensor, responsive to the field of the magnetoelastically active portion. In one embodiment, the magnetoelastically active portion 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 therting. The torque on the ring reorients the circumferential magnetic orientation of the ring, producing a helical magnetic orientation having both circumferential and axial components. A magnetic field vector sensor is mounted in a fixed position relative to the ring and oriented so that it responds maximally only to the field due to the axial magnetization components of the ring. The output of the sensor is thus proportional to the change in orientation of the magnetization resulting from torque applied to the shaft and transmitted to the ring. In another embodiment, the magnetoelastically active portion includes two or more axially distinct, magnetically contiguous, oppositely polarized circumferential regions. The regions may comprise physically separate rings or may be formed onto a single ring.

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First Claim