Magnetic position sensor having shaped pole pieces for improved output linearity

• US 6,586,929 B1
• Filed: 02/19/2002
• Issued: 07/01/2003
• Est. Priority Date: 12/14/2001
• Status: Expired due to Fees

• Current Assignee: Wabash Technologies Incorporated (Sensata Technologies Holding Plc)
• Original Assignee: Wabash Technologies Incorporated (Sensata Technologies Holding Plc)
• Inventors: Luetzow, Robert H.
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US10/079,369
• Publication Number:
  US 20030112004A1
• Time in Patent Office: 497 Days
• Field of Search: 324/207.12, 324/207.13, 324/207.2, 324/207.21, 324/207.22, 324/207-3-2, 324/251, 324/261, 324/262, 338/32.R, 338/32.H
• US Class Current: 324/207.24
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A magnetic position sensor including a pair of magnets of opposite polarity which are spaced apart to define an air gap extending along an axis, and a pair of shaped pole pieces at least partially disposed within the air gap and positioned adjacent respective ones of the magnets. The pole pieces are formed of a composite material comprising a non-magnetic material and a magnetizable material. The pole pieces cooperate with the magnets to generate a magnetic field that is substantially symmetrical relative to the axis and which has a magnetic flux density that linearly varies along the axis. A magnetic flux sensor is positioned within the magnetic field to sense varying magnitudes of magnetic flux density along the axis through a sensing plane oriented substantially perpendicular to the axis. The magnetic flux sensor generates an output signal uniquely representative of a sensed magnitude of the magnetic flux density.

Claims

1. A magnetic sensor, comprising:

a magnet extending along an axis;

a pole piece positioned adjacent said magnet and being at least partially formed of a non-magnetic material, said magnet and said pole piece cooperating to generate a magnetic field having a magnetic flux density that linearly varies along said axis; and

a magnetic flux sensor positioned within said magnetic field and operable to sense varying magnitudes of said magnetic flux density along said axis and to generate an output signal representative of a sensed magnitude of said magnetic flux density.

2. The magnetic sensor of claim 1, wherein said non-magnetic material comprises a plastic material.

3. The magnetic sensor of claim 2, wherein said plastic material comprises a nylon material.

4. The magnetic sensor of claim 1, wherein said pole piece is formed of a composite material comprising said non-magnetic material and a magnetizable filler material.

5. The magnetic sensor of claim 4, wherein said composite material is Nylon 6/6.

6. The magnetic sensor of claim 4, wherein said composite material has a magnetic reluctance less than a magnetic reluctance of steel.

7. The magnetic sensor of claim 1, wherein said magnetic flux sensor defines a magnetic flux sensing plane oriented substantially perpendicular to said axis.

8. The magnetic sensor of claim 1, wherein said magnet has a rectangular configuration and wherein said pole piece includes a tapered surface facing away from said magnet and oriented at an oblique angle relative to said axis.

9. The magnetic sensor of claim 8, wherein said tapered surface is a planar surface.

10. A magnetic sensor, comprising:

a first magnet spaced apart from a second magnet to define an air gap extending along an axis;

first and second pole pieces at least partially disposed within said air gap and positioned adjacent respective ones of said first and second magnets, said first and second pole pieces being at least partially formed of a non-magnetic material and cooperating with said magnets to generate a magnetic field having a magnetic flux density that linearly varies along said axis; and

a magnetic flux sensor positioned within said magnetic field and operable to sense varying magnitudes of said magnetic flux density along said axis and to generate an output signal representative of a sensed magnitude of said magnetic flux density.

11. The magnetic sensor of claim 10, wherein said first and second pole pieces are formed of a composite material comprising said non-magnetic material and a magnetizable filler material.

12. The magnetic sensor of claim 11, wherein said composite material is Nylon 6/6.

13. The magnetic sensor of claim 11, wherein said composite material has a magnetic reluctance less than a magnetic reluctance of steel.

14. The magnetic sensor of claim 10, wherein said magnetic flux sensor defines a magnetic flux sensing plane oriented substantially perpendicular to said axis.

15. The magnetic position sensor of claim 10, wherein said magnetic field is substantially symmetrical relative to said axis.

16. The magnetic sensor of claim 10, wherein first magnet is polarized in a first direction relative to said axis, said second magnet being polarized in a second direction relative to said axis, said first direction being generally opposite said second direction.

17. The magnetic sensor of claim 10, wherein said first and second pole pieces define opposing tapered surfaces oriented at an oblique angle relative to said axis.

18. The magnetic sensor of claim 17, wherein said first and second pole pieces define opposing non-tapered surfaces contiguous with said opposing tapered surfaces and arranged parallel to said axis.

19. The magnetic sensor of claim 10, further comprising magnetically permeable bracket extending about said first and second magnets and said first and second pole pieces.

20. The magnetic sensor of claim 19, wherein each of said first and second magnets includes:

a first substantially flat surface adjoined to a corresponding surface of said magnetically permeable bracket; and

a second substantially flat surface adjoined to a corresponding surface of a respective one of said first and second pole pieces.

21. The magnetic sensor of claim 10, wherein end portions of said first and second pole pieces overhang respective ends of said first and second magnets.

22. The magnetic sensor of claim 10, further comprising third and fourth pole pieces at least partially disposed within said air gap and positioned adjacent respective ones of said first and second magnets, said third and fourth pole pieces being at least partially formed of said non-magnetic material and cooperating with said magnets to generate a magnetic field having a magnetic flux density that linearly varies along said axis.

23. The magnetic sensor of claim 22, wherein said magnetic fields are substantially symmetrical relative to a transverse axis extending across said air gap.

24. The magnetic sensor of claim 10, wherein each of said first and second magnets has a rectangular configuration.

25. A magnetic sensor, comprising:

a magnet extending along an axis;

a shaped pole piece positioned adjacent said magnet and cooperating with said magnet to generate a magnetic field having a magnetic flux density that linearly varies along said axis; and

a magnetic flux sensor positioned within said magnetic field and operable to sense varying magnitudes of said magnetic flux density along said axis through a sensing plane oriented substantially perpendicular to said axis and to generate an output signal representative of a sensed magnitude of said magnetic flux density.

26. The magnetic sensor of claim 25, wherein said shaped pole piece is formed of a composite material comprising a non-magnetic material and a magnetizable filler material.

27. The magnetic sensor of claim 25, wherein said shaped pole piece defines a tapered surface oriented at an oblique angle relative to said axis.

28. The magnetic sensor of claim 27, wherein said shaped pole piece defines a non-tapered surface contiguous with said tapered surface and arranged parallel to said axis.

29. The magnetic sensor of claim 27, wherein said tapered surface is a planar surface.

30. A magnetic sensor, comprising:

a first magnet spaced apart from a second magnet to define an air gap extending along an axis;

first and second shaped pole pieces at least partially disposed within said air gap and positioned adjacent respective ones of said first and second magnets, said first and second shaped pole pieces cooperating with said magnets to generate a magnetic field having a magnetic flux density that linearly varies along said axis; and

a magnetic flux sensor positioned within said magnetic field and operable to sense varying magnitudes of said magnetic flux density along said axis through a sensing plane oriented substantially perpendicular to said axis and to generate an output signal representative of a sensed magnitude of said magnetic flux density.

31. The magnetic sensor of claim 30, wherein said first and second shaped pole piece are formed of a composite material comprising a non-magnetic material and a magnetizable filler material.

32. The magnetic position sensor of claim 30, wherein said magnetic field is substantially symmetrical relative to said axis.

33. The magnetic sensor of claim 30, wherein first magnet is polarized in a first direction relative to said axis, said second magnet being polarized in a second direction relative to said axis, said first direction being generally opposite said second direction.

34. The magnetic sensor of claim 30, wherein said first and second pole shaped pieces define opposing tapered surfaces oriented at an oblique angle relative to said axis.

35. The magnetic sensor of claim 34, wherein said first and second shaped pole pieces define opposing non-tapered surfaces contiguous with said opposing tapered surfaces and arranged parallel to said axis.

36. The magnetic sensor of claim 30, further comprising a magnetically permeable bracket extending about said first and second magnets and said first and second shaped pole pieces.

37. The magnetic sensor of claim 30, wherein end portions of said first and second shaped pole pieces overhang respective ends of said first and second magnets.

38. The magnetic sensor of claim 30, further comprising third and fourth shaped pole pieces at least partially disposed within said air gap and positioned adjacent respective ones of said first and second magnets, said third and fourth shaped pole pieces cooperating with said magnets to generate a magnetic field having a magnetic flux density that linearly varies along said axis.

39. The magnetic sensor of claim 38, wherein said magnetic fields are substantially symmetrical relative to a transverse axis extending across said air gap.

40. The magnetic sensor of claim 30, wherein each of said first and second magnets has a rectangular shape and wherein each of said first and second shaped pole pieces has a wedge shape.