Sensor System Including A Magnetized Shaft

• US 20110265581A1
• Filed: 07/12/2011
• Published: 11/03/2011
• 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 8,191,431 B2
• Time in Patent Office: Days
• US Class Current: 73/862.333
• 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 and an anti-aging 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/or shaft rotational position. The anti-aging magnetic sensor may be positioned adjacent the active region to provide a reference signal output that is substantially independent of torque applied to said shaft.

Claims

1. A sensor comprising:

a shaft formed from a magnetorestrictive material and having at least one magnetized active region disposed between first and second passive regions in an axial extent of said shaft, said at least one active region having at least partially opposing magnetic polarizations in a radial cross-section taken in said axial extent;

at least one magnetic sensor positioned adjacent said active region and configured to sense each of said opposing magnetic polarizations and provide an output in response to said opposing magnetic polarizations, said output varying with the rotational angle and being representative of a torque applied to said shaft; and

at least one an anti-aging magnetic sensor positioned adjacent said active region and configured to sense said opposing magnetic polarizations and provide a reference signal output that is substantially independent of torque applied to said shaft.

2. The sensor of claim 1, wherein said anti-aging magnetic sensor comprises a fluxgate sensor.

3. The sensor of claim 1, wherein said anti-aging magnetic sensor comprises a coil that is axially oriented relative to said shaft.

4. The sensor of claim 1, wherein a peak-to-peak amplitude of said output is representative of said torque applied to said shaft.

5. The sensor of claim 1, wherein said magnetic sensor comprises a flux gate sensor.

6. The sensor of claim 5, wherein said fluxgate sensor comprises a coil that is radially oriented relative to said shaft.

7. The sensor of claim 5, wherein said fluxgate sensor comprises a coil that is tangentially oriented relative to said shaft.

8. The sensor of claim 1, wherein said shaft is a tubular shaft.

9. A method of compensating for aging effects in a torque sensor for determining torque applied to a shaft, said method comprising:

establishing at least one magnetized active region disposed between first and second passive regions in an axial extent of said shaft, said at least one active region having at least partially opposing magnetic polarizations in a radial cross-section taken in said axial extent;

positioning at least one magnetic sensor adjacent said active region and configured to sense each of said opposing magnetic polarizations and provide an output in response to said opposing magnetic polarizations, said output varying with the rotational angle of said shaft and being representative of a torque applied to said shaft;

positioning an anti-aging magnetic sensor adjacent said active region for sensing said opposing magnetic polarizations and providing a reference signal output that is substantially independent of torque applied to said shaft; and

adjusting said output in response to said reference signal.

10. The method of claim 9, wherein said anti-aging magnetic sensor comprises a fluxgate sensor.

11. The method of claim 9, wherein said anti-aging magnetic sensor comprises a coil that is axially oriented relative to said shaft.

12. The method of claim 9, wherein said adjusting comprises maintaining a constant ratio of an amplitude of said output to said reference signal.

13. The method of claim 9, wherein a peak-to-peak amplitude of said output is representative of said torque applied to said shaft.

14. The method of claim 9, wherein said at least one magnetic sensor comprises a flux gate sensor.

15. The method of claim 14, wherein said fluxgate sensor comprises a coil that is radially oriented relative to said shaft.

16. The method of claim 14, wherein said fluxgate sensor comprises a coil that is tangentially oriented relative to said shaft.

17. A method of compensating for aging effects in a torque sensor for determining torque applied to a shaft, said method comprising:

establishing at least one magnetized active region in said shaft;

positioning at least one magnetic sensor adjacent said active region and configured to sense a magnetic polarization of said magnetized active region and provide an output representative of a torque applied to said shaft; and

positioning an anti-aging magnetic sensor adjacent said active region for sensing said magnetic polarization and providing a reference signal output that is substantially independent of torque applied to said shaft; and

adjusting said output in response to said reference signal.

18. The method of claim 17, wherein said anti-aging magnetic sensor comprises a fluxgate sensor.

19. The method of claim 17, wherein said anti-aging magnetic sensor comprises a coil that is axially oriented relative to said shaft.

20. The method of claim 17, wherein said adjusting comprises maintaining a constant ratio of an amplitude of said torque output to said reference signal.