Torque sensor system including an elliptically magnetized shaft

• US 20070113683A1
• Filed: 11/09/2005
• Published: 05/24/2007
• Est. Priority Date: 10/21/2005
• Status: Active Grant

• Current Assignee: Stoneridge Control Devices, Inc. (Stoneridge Incorporated)
• Original Assignee: Stoneridge Control Devices, Inc. (Stoneridge Incorporated)
• Inventors: Hedayat, Kayvan, Poirier, Norman
• Granted Patent: US 7,363,827 B2
• Time in Patent Office: Days
• US Class Current: 73/862.331
• CPC Class Codes: G01L 3/102 involving magnetostrictive means magnetostrictive sensors H10N35/101

Abstract

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.

Claims

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.

2. The torque sensor of claim 1, wherein said elliptical magnetization has a nonzero axial component directed along a center line axis of said shaft at zero torque applied to said shaft, and wherein said magnetic sensor is configured to sense said nonzero axial component at zero torque.

3. The torque sensor of claim 1, 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.

4. The torque sensor of claim 1, wherein said elliptical magnetization has a nonzero axial component along a center line axis of said shaft at zero torque, and wherein nonzero axial component changes as said torque is applied to said shaft.

5. 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.

6. The torque sensor of claim 5, wherein a frequency of said sinusoidal signal is representative of a speed of said shaft.

7. A method of monitoring a torque applied to a shaft comprising:

magnetizing an active region of said shaft to have an elliptical magnetization; and

monitoring a magnetic field about said shaft, said magnetic field being representative of said torque applied to said shaft.

8. The method of claim 7, wherein said elliptical magnetization has a nonzero axial component directed along a center line axis of said shaft at zero torque.

9. The method of claim 7, wherein said magnetizing comprises:

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.

10. The method of claim 9, wherein said oblique angle is between about 10 degrees and 80 degrees.

11. The method of claim 7, 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.

12. The method of claim 7, 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.

13. The method of claim 12, wherein a frequency of said sinusoidal signal is representative of a speed of said shaft.

14. A torque sensor comprising:

a shaft having first and second active regions, each of first and second active regions having an elliptical magnetization;

a first fluxgate coil positioned about said shaft and coupled to a first magnetometer, said first magnetometer configured to provide a first sinusoidal signal as said shaft is rotated;

a second fluxgate coil positioned about said shaft and coupled to a second magnetometer, said second magnetometer configured to provide a second sinusoidal signal as said shaft is rotated, said second sinusoidal signal being ninety degrees out of phase with said first sinusoidal signal; and

torque circuitry configured to accept said first and second sinusoidal signals and provide an output signal representative of torque applied to said shaft.

15. The torque sensor of claim 14, wherein said torque circuitry is configured to calculate a square root of a sum of said first sinusoidal signal squared and said second sinusoidal signal squared to provide said output signal representative of torque applied to said shaft.

16. The torque sensor of claim 14, further comprising shaft speed circuitry configured to accept at least one of said first and said second sinusoidal signals and to provide an output signal representative of a speed of said shaft, wherein a frequency of said at least one of said first and second sinusoidal signals is representative of said speed of said shaft.

17. The torque sensor of claim 14, further comprising positioning circuitry to calculate an arc tangent of a ratio of said second sinusoidal signal to said first sinusoidal signal, wherein a result of said arc tangent operation is representative of a position of said shaft.