Sensor System Including A Magnetized Shaft

• US 20070089539A1
• Filed: 10/23/2006
• Published: 04/26/2007
• 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 7,469,604 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
• CPC Class Codes: G01L 3/104 involving permanent magnets

Abstract

A sensor includes a shaft and a magnetic sensor. The shaft may have at least one magnetized active region. The magnetic sensor may be configured to sense a magnetic field about the shaft, and may provide an output representative of torque applied to the shaft, shaft rotational speed and shaft rotational position.

Claims

1. A sensor comprising:

a shaft having at least one magnetized active region, said at least one active region having at least partially opposing magnetic polarizations; and

a magnetic sensor positioned adjacent said active region and configured to provide a sinusoidal output in response to said opposing magnetic polarizations as said shaft rotates, said sinusoidal output being representative of a torque applied to said shaft.

2. The sensor of claim 1, wherein an amplitude of said sinusoidal signal is representative of a rotational position of said shaft.

3. The sensor of claim 1, wherein a frequency of said sinusoidal signal is representative of a speed of said shaft.

4. The sensor of claim 1, wherein said shaft comprises magnetized saturation zones on opposing sides of said active region.

5. A method of inducing a magnetization in a magnetorestrictive shaft used in a sensor system for monitoring torque applied to the shaft comprising, said method comprising:

directing a current through an axial extent of the shaft in a direction that is not a single axial direction.

6. The method of claim 5, said method comprising directing current through said shaft at an oblique angle to an axis of the shaft.

7. The method of claim 6, wherein said oblique angle is between about 10 degrees and 80 degrees.

8. The method of claim 5, said method comprising directing first and second currents through said axial extent of said shaft in at least partially opposing directions.

9. The method of claim 5, said method comprising directing first and second currents through said axial extent in at least partially opposing circumferential directions.

10. The method of claim 5, said method comprising directing first and second currents through said axial extent in at least partially opposing axial directions.

11. A 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.

12. The sensor of claim 11, 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.

13. The sensor of claim 11, wherein said elliptical magnetization is induced by current driven between a pair of electrode clamps, said pair of electrode 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.

14. The sensor of claim 11, 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.

15. The sensor of claim 11, 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.

16. The sensor of claim 15, wherein a frequency of said sinusoidal signal is representative of a speed of said shaft.

17. A sensor comprising:

a shaft having at least one magnetized active region;

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

a second fluxgate coil positioned about said shaft 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.

18. The sensor of claim 17, 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.

19. The sensor of claim 17, 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.

20. The sensor of claim 17, 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.