Magnetoelastic torque sensor with ambient field rejection
AssigneeMethode Electronics, Inc.
InventorSeong-Jae LEE
Life of this patent
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Abstract
The present invention involves a method and apparatus for canceling the effects of magnetic field noise in a torque sensor by placing three sets of magnetic field sensors around a shaft, the first set of field sensors being placed in the central region of the shaft and the second and third sets of field sensors being placed on the right side and left side of the field sensors placed at the central region, respectively. A torque-induced magnetic field is not cancelled with this arrangement of field sensors but a magnetic near field from a near field source is cancelled.
Claims47
1-50. (canceled)
A method for reducing the noise in a signal from a torque sensor caused by near magnetic field sources, the method comprising the steps of:
- providing a torque sensor comprising:
- a longitudinally extending member;
- a magnetoelastically active region directly or indirectly attached to or forming a part of the surface of the member in such a manner that torque applied to the member is proportionally transmitted to the active region, the active region comprising at least one region magnetically polarized such that the magnetized polarity becomes increasingly helically shaped as the applied torque increases;
- at least one primary magnetic field sensors arranged proximate the at least one region for outputting a first signal corresponding to a torque-dependent magnetic flux emanating from the active region;
- at least one secondary magnetic field sensor axially spaced in a first direction by a pre-determined first distance from the plurality of primary magnetic field sensors for outputting a second signal corresponding to an ambient magnetic flux emanating from the near magnetic field source;
- at least one secondary magnetic field sensor axially spaced in a second direction opposite the first direction a pre-determined second distance from the plurality of primary magnetic field sensors for outputting a third signal corresponding to the ambient magnetic flux emanating from the near magnetic field source;
- receiving the first signal upon the application of the torque;
- receiving the second and third signals;
- and
- adjusting the first signal using the second and third signals thereby compensating for the effects of the near magnetic field source.
A torque sensor comprising:
- a longitudinally extending member;
- a magnetoelastically active region directly or indirectly attached to or forming a part of the surface of the member in such a manner that torque applied to the member is proportionally transmitted to the active region, the active region comprising at least one region magnetically polarized such that the magnetized polarity becomes increasingly helically shaped as the applied torque increases;
- a plurality of primary magnetic field sensors arranged proximate the at least one region for outputting a first signal corresponding to a torque-dependent magnetic flux emanating from the active region;
- at least one secondary magnetic field sensor axially spaced in a first direction by a pre-determined first distance from the plurality of primary magnetic field sensors for outputting a second signal corresponding to an ambient magnetic flux emanating from a near magnetic field source;
- at least one secondary magnetic field sensor axially spaced in a second direction opposite the first direction by a pre-determined second distance from the plurality of primary magnetic field sensors for outputting a third signal corresponding to the ambient magnetic flux emanating from the near magnetic field source;
- means for adjusting the first signal using the second and third signals thereby compensating for the effects of the near magnetic field source.
Dependencies are inferred from the claim text.