Magnetic position sensor having shaped pole pieces to provide a magnetic field having a varying magnetic flux density field strength

• US 6,653,830 B2
• Filed: 02/19/2002
• Issued: 11/25/2003
• 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): Le, N.
• Assistant Examiner(s): KINDER, DARRELL D
• Application Number:
  US10/079,694
• Publication Number:
  US 20030112006A1
• Time in Patent Office: 644 Days
• Field of Search: 324/207.2, 324/207.21, 324/207.24, 324/207.25, 310/156, 310/48
• US Class Current: 324/207.21
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A magnetic sensor is provided which includes a pair of magnets and a pair of shaped pole pieces positioned adjacent respective ones of the magnets and spaced apart to define an air gap therebetween. The magnets and the shaped pole pieces cooperate to provide a magnetic field having a magnetic flux density that varies along a length of the air gap. A magnetic flux sensor is positioned within the magnetic field to sense varying magnitudes of magnetic flux density along the length of the air gap and to generate an output signal representative of a position of the magnetic flux sensor relative to the magnetic field. In one embodiment, the air gap defines a varying width to provide varying magnitudes of magnetic flux density along the length. In another embodiment, the shaped pole pieces include portions of varying thickness to provide varying magnitudes of magnetic flux density along the length.

Claims

1. A magnetic sensor, comprising:

first and second magnets separated by a space;

first and second shaped pole pieces at least partially disposed within said space and positioned adjacent respective ones of said first and second magnets, said shaped pole pieces being spaced apart to define an air gap having a varying width along a length thereof, said magnets and said shaped pole pieces cooperating to provide a magnetic field having a magnetic flux density that varies along said length of said air gap; and

a magnetic flux sensor positioned within said magnetic field and operable to sense a varying magnitude of said magnetic flux density along said length of said air gap and to generate an output signal representative of a position of said magnetic flux sensor relative to said magnetic field.

2. The magnetic sensor of claim 1, wherein at least one of said first and second shaped pole pieces defines a tapered surface oriented at an acute angle relative to an axis extending along said length of said air gap, said tapered surface defining at least a portion of said varying width of said air gap.

3. The magnetic sensor of claim 2, wherein at least a portion of said tapered surface is a planar surface.

4. The magnetic sensor of claim 2, wherein at least a portion of said tapered surface is a curved surface.

5. The magnetic sensor of claim 2, wherein each of said first and second shaped pole pieces defines a tapered surface oriented at an acute angle relative to said axis, said tapered surfaces being arranged generally opposite one another and substantially symmetrical relative to said axis to define said varying width of said air gap.

6. The magnetic sensor of claim 1, wherein each of said first and second shaped pole pieces includes a portion of varying thickness extending along said length of said air gap, said portions of varying thickness being arranged generally opposite one another to define said varying width of said air gap.

7. The magnetic sensor of claim 1, wherein said magnetic flux sensor is a magnetoresistive sensor.

8. The magnetic sensor of claim 7, wherein said magnetoresistive sensor includes:

a first magnetoresistive element positioned within said magnetic field to sense said varying magnitude of said magnetic flux density; and

a second magnetoresistive element positioned within an auxiliary magnetic field having a substantially uniform magnetic flux density.

9. The magnetic sensor of claim 8, wherein said auxiliary magnetic field is generated by a third magnet positioned adjacent said second magnetoresistive element.

10. The magnetic sensor of claim 8, further comprising an electrical circuit connecting said first and second magnetoresistive elements in series and applying an electric potential across said first and second magnetoresistive elements to generate said output signal at a junction between said first and second magnetoresistive elements.

11. The magnetic sensor of claim 10, wherein said substantially uniform magnetic flux density of said auxiliary magnetic field has a magnitude substantially equal to an average magnitude of said varying magnitude of said magnetic flux density along said length of said air gap.

12. The magnetic sensor of claim 1, wherein each of said first and second magnets has a substantially rectangular configuration.

13. The magnetic sensor of claim 1, wherein each of said first and second magnets are polarized in the same direction.

14. The magnetic sensor of claim 1, further comprising a loop pole piece extending about said first and second magnets and said first and second shaped pole pieces to provide a closed magnetic circuit.

15. A magnetic sensor, comprising:

first and second magnets separated by a space;

first and second shaped pole pieces at least partially disposed within said space and positioned adjacent respective ones of said first and second magnets, said shaped pole pieces being spaced apart to define an air gap, at least one of said shaped pole pieces including a portion of varying thickness, said magnets and said shaped pole pieces cooperating to provide a magnetic field having a magnetic flux density that varies along a length of said air gap adjacent said portion of varying thickness; and

a magnetic flux sensor positioned within said magnetic field and operable to sense a varying magnitude of said magnetic flux density along said length of said air gap and to generate an output signal representative of a position of said magnetic flux sensor relative to said magnetic field.

16. The magnetic sensor of claim 15, wherein each of said first and second shaped pole pieces includes a portion of varying thickness extending along said length of said air gap.

17. The magnetic sensor of claim 16, wherein said portions of varying thickness are arranged generally opposite one another and are symmetrical relative to an axis extending along said length of said air gap.

18. The magnetic sensor of claim 16, wherein said portions of varying thickness cooperate to define a varying width of said air gap along said length.

19. The magnetic sensor of claim 18, wherein each of said first and second shaped pole pieces defines a tapered surface oriented at an acute angle relative to an axis extending along said length of said air gap, said tapered surfaces being arranged generally opposite one another to define said varying width of said air gap.

20. The magnetic sensor of claim 19, wherein at least a portion of each of said tapered surfaces is a planar surface.

21. The magnetic sensor of claim 19, wherein at least a portion of each of said tapered surfaces is a curved surface.

22. The magnetic sensor of claim 15, wherein said magnetic flux sensor is a magnetoresistive sensor.

23. The magnetic sensor of claim 22, wherein said magnetoresistive sensor includes:

a first magnetoresistive element positioned within said magnetic field to sense said varying magnitudes of said magnetic flux density; and

a second magnetoresistive element positioned within an auxiliary magnetic field having a substantially uniform magnetic flux density.

24. The magnetic sensor of claim 23, further comprising an electrical circuit connecting said first and second magnetoresistive elements in series and applying an electric potential across said first and second magnetoresistive elements to generate said output signal at a junction between said first and second magnetoresistive elements.

25. A magnetic sensor, comprising:

at least two magnets;

at least two shaped pole pieces positioned adjacent respective ones of said magnets, said at least two shaped pole pieces being spaced apart to define a first air gap and a second air gap, said at least two magnets and said at least two shaped pole pieces cooperating to provide a first magnetic field having a magnetic flux density that varies along a length of said first air gap and to provide a second magnetic field having a magnetic flux density that varies along a length of said second air gap; and

a magnetic flux sensor, including;

a first magnetic flux sensor element positioned within said first magnetic field and operable to sense a varying magnitude of said magnetic flux density along said length of said first air gap; and

a second magnetic flux sensor element positioned within said second magnetic field and operable to sense a varying magnitude of said magnetic flux density along said length of said second air gap; and

wherein said first and second magnetic flux sensor elements cooperate to generate an output signal representative of a position of said magnetic flux sensor relative to said first and second magnetic fields.

26. The magnetic sensor of claim 25, wherein said first and second magnetic flux sensor elements are magnetoresistive elements.

27. The magnetic sensor of claim 26, further comprising an electrical circuit connecting said first and second magnetoresistive elements in series and applying an electric potential across said first and second magnetoresistive elements to generate said output signal at a junction between said first and second magnetoresistive elements.

28. The magnetic sensor of claim 25, wherein said varying magnitude of said magnetic flux density along said length of said first air gap is inversely proportional to said varying magnitude of said magnetic flux density along said length of said second air gap.

29. The magnetic sensor of claim 25, wherein said first air gap has a varying width to provide said varying magnitude of said magnetic flux density along said length of said first air gap, said second air gap having a varying width to provide said varying magnitude of said magnetic flux density along said length of said second air gap.

30. The magnetic sensor of claim 29, wherein said varying width of said first air gap converges, and wherein said varying width of said second air gap diverges.

31. The magnetic sensor of claim 25, wherein said at least two shaped pole pieces include portions of varying thickness to provide said varying magnitude of said magnetic flux density along said length of said first air gap and along said length of said second air gap.

32. The magnetic sensor of claim 25, wherein said first and second air gaps extend along a common longitudinal axis.

33. The magnetic sensor of claim 32, wherein said first and second air gaps are substantially symmetrical relative to a transverse axis arranged substantially perpendicular to said longitudinal axis.

34. The magnetic sensor of claim 25, wherein said first air gap extends along a first axis, said second air gap extending along a second axis offset from said first axis.

35. The magnetic sensor of claim 34, wherein said first axis and said second axis are substantially parallel.

36. A magnetic sensor, comprising:

first and second magnets;

first and second shaped pole pieces positioned adjacent respective ones of said first and second magnets and spaced apart to define an air gap, said magnets and said shaped pole pieces cooperating to provide a magnetic field having a magnetic flux density that varies along a length of said air gap; and

a first magnetoresistive element positioned within said magnetic field to sense a varying magnitude of said magnetic flux density along said length of said air gap; and

a second magnetoresistive element positioned within an auxiliary magnetic field having a substantially uniform magnetic flux density; and

wherein said first and second magnetoresistive elements cooperate to generate an output signal representative of a position of said first magnetoresistive element relative to said magnetic field.

37. The magnetic sensor of claim 36, wherein said auxiliary magnetic field is generated by a third magnet positioned adjacent said second magnetoresistive element.

38. The magnetic sensor of claim 36, further comprising an electrical circuit connecting said first and second magnetoresistive elements in series and applying an electric potential across said first and second magnetoresistive elements to generate said output signal at a junction between said first and second magnetoresistive elements.

39. The magnetic sensor of claim 36, wherein said substantially uniform magnetic flux density of said auxiliary magnetic field has a magnitude substantially equal to an average magnitude of said varying magnitude of said magnetic flux density along said length of said air gap.

40. The magnetic sensor of claim 36, wherein said second magnetoresistive element is operable to generate an electronic signal representative of an ambient temperature adjacent the magnetic sensor.