Torque sensor system including an elliptically magnetized shaft
A torque sensor includes a shaft and a magnetic sensor. The shaft may have at least one active region having an elliptical magnetization. The magnetic sensor may be configured to sense a magnetic field about the shaft, where the magnetic field is representative of a torque applied to the shaft. The elliptical magnetization may have a nonzero axial component directed along a center line axis of said shaft at zero torque.
1. A torque sensor comprising:
a shaft having at least one active region, said at least one active region having an elliptical magnetization; and
a magnetic sensor configured to sense a magnetic field about said shaft, said magnetic field being representative of a torque applied to said shaft,
wherein said elliptical magnetization is induced by current driven between a pair of magnetizing clamps, said pair of magnetizing clamps oriented in parallel with each other and further oriented at an oblique angle with respect to a center line axis of said shaft, wherein said elliptical magnetization has a nonzero axial component along a center line axis of said shaft at zero torque, and wherein said nonzero axial component at zero torque is at least partially dependent on a value of said oblique angle.
2. The torque sensor of claim 1 , wherein said magnetic sensor is configured to sense said nonzero axial component at zero torque.
3. The torque sensor of claim 1 , wherein nonzero axial component changes as said torque is applied to said shaft.
4. The torque sensor of claim 1 , wherein said magnetic field sensed by said magnetic sensor comprises alternating magnetic polarities as said shaft is rotated and said magnetic sensor provides a sinusoidal signal having an amplitude representative of said torque applied to said shaft.
5. The torque sensor of claim 4 , wherein a frequency of said sinusoidal signal is representative of a speed of said shaft.
6. A method of monitoring a torque applied to a shaft comprising:
magnetizing an active region of said shaft to have an elliptical magnetization, said magnetizing comprising:
orientating a pair of magnetizing clamps about said shaft, said pair of magnetizing clamps oriented in parallel with each other and at an oblique angle with respect to a center line axis of said shaft, and
driving a current between said pair of magnetizing clamps; and
monitoring a magnetic field about said shaft, said magnetic field being representative of said torque applied to said shaft.
7. The method of claim 6 , wherein said elliptical magnetization has a nonzero axial component directed along a center line axis of said shaft at zero torque.
8. The method of claim 6 , wherein said oblique angle is between about 10 degrees and 80 degrees.
9. The method of claim 6 , wherein said elliptical magnetization has an axial component along a center line axis of said shaft at zero torque, and wherein said axial component changes as said torque is applied to said shaft.
10. The method of claim 6 , wherein said monitored magnetic field comprises alternating magnetic polarities as said shaft is rotated and wherein said method further comprises providing a sinusoidal signal having an amplitude representative of said torque applied to said shaft.
11. The method of claim 10 , wherein a frequency of said sinusoidal signal is representative of a speed of said shaft.