Magnetoelastic Torque Sensor and Method

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:
• an at least partially hollow longitudinally extending member;
• a magnetoelastically active region effective at the inner 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 set 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 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 magneto-elastically active region 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 four primary magnetic field sensors arranged approximate the at least one region and radially aligned with respect to the longitudinally extending member for outputting a first signal corresponding to a torque-dependent magnetic flux emanating from the active region;
• at least two secondary magnetic field sensors axially spaced in a first direction by a pre-determined first distance from the plurality of primary magnetic field sensors;
• at least two secondary magnetic field sensors axially spaced in a second direction opposite the first direction by a pre-determined second distance from the plurality of primary magnetic field sensors, wherein
• two primary magnetic field sensors and two secondary magnetic field sensors are mounted on a first side of a circuit board, and the other two primary and two secondary magnetic field sensors are mounted on a second, opposite side of the board.