Magnetic position sensor having shaped pole pieces at least partially formed of a non-magnetic material for producing a magnetic field having varying magnetic flux density along an axis

• US 6,798,195 B2
• Filed: 12/19/2002
• Issued: 09/28/2004
• 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:
  US10/325,531
• Publication Number:
  US 20030122641A1
• Time in Patent Office: 649 Days
• Field of Search: 324/207.22, 324/207.12, 324/207.13, 324/207.26, 324/251, 324/261, 324/262, 324/207.2, 324/207.21, 324/207.24, 324/207.25, 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 magnetic circuit including;

first and second magnets spaced apart to define an air gap extending along an axis; and

first and second shaped pole pieces at least partially formed of a non-magnetic material and at least partially disposed within said air gap adjacent respective ones of said first and second magnets to produce a magnetic field having varying magnetic flux density along said axis; and

a magnetic flux sensor disposed within said magnetic field and operable to sense said varying magnetic flux density along said axis.

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 first and second pole pieces are 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 steel.

7. The magnetic sensor of claim 1, wherein said magnetic circuit includes a magnetically permeable bracket extending peripherally about said first and second magnets and said first and second pole pieces, said magnetically permeable bracket being peripherally interrupted in at least one location.

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

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

10. The magnetic sensor of claim 1, wherein first magnet is polarized in a first direction, said second magnet being polarized in a second direction generally opposite said first direction.

11. The magnetic sensor of claim 10, wherein said magnetic flux sensor defines a magnetic flux sensing plane generally aligned with said first and second directions of polarization.

12. The magnetic sensor of claim 1, wherein each of said first and second shaped pole pieces includes a pair of ramp-shaped portions and a rectangular-shaped portion extending between said pair of ramp-shaped portions.

13. The magnetic sensor of claim 12, wherein said pair of ramp-shaped portions are symmetrical relative to a central axis passing transversely through said rectangular-shaped portion.

14. The magnetic sensor of claim 1, wherein said magnetic flux density varies in a substantially linear manner along said axis.

15. A magnetic sensor, comprising:

a magnetic circuit including;

first and second magnets spaced apart to define an air gap extending along an axis;

first and second shaped pole pieces at least partially formed of a non-magnetic material and at least partially disposed within said air gap adjacent respective ones of said first and second magnets; and

a magnetically permeable bracket extending peripherally about said first and second magnets and said first and second pole pieces and being peripherally interrupted by at least one opening;

wherein said magnetic circuit produces a magnetic field having varying magnetic flux density along said axis; and

a magnetic flux sensor disposed within said magnetic field and operable to sense said varying magnetic flux density along said axis.

16. The magnetic sensor of claim 15, wherein said magnetically permeable bracket is peripherally interrupted by a pair of openings to divide said magnetically permeable bracket into two portions.

17. The magnetic sensor of claim 16, wherein said pair of openings are arranged generally opposite one another to divide said magnetically permeable bracket into two substantially symmetrical portions.

18. The magnetic sensor of claim 17, wherein said substantially symmetrical portions of said magnetically permeable bracket are U-shaped.

19. The magnetic sensor of claim 15, wherein said at least one opening is positioned along said axis in communication with said air gap.

20. The magnetic sensor of claim 19, wherein said at least one opening is sized to permit said magnetic flux sensor to pass therethrough during relative displacement between said magnetic circuit and said magnetic flux sensor.

21. The magnetic sensor of claim 15, wherein said first and second pole pieces are formed of a composite material comprising said non-magnetic material and a magnetizable filler material, said composite material having a magnetic reluctance less than steel.

22. The magnetic sensor of claim 15, wherein first magnet is polarized in a first direction, said second magnet being polarized in a second direction generally opposite said first direction, said magnetic flux sensor defining a magnetic flux sensing plane generally aligned with said first and second directions of polarization.

23. A magnetic sensor, comprising:

a magnetic circuit including;

first and second magnets spaced apart to define an air gap extending along an axis; and

first and second shaped pole pieces at least partially formed of a non-magnetic material and at least partially disposed within said air gap adjacent respective ones of said first and second magnets, each of said first and second shaped pole pieces including at least one ramp-shaped portion;

wherein said magnetic circuit produces a magnetic field having varying magnetic flux density along said axis; and

a magnetic flux sensor disposed within said magnetic field and operable to sense said varying magnetic flux density along said axis.

24. The magnetic sensor of claim 23, wherein said at least one ramp-shaped portion includes a tapered surface arranged at an oblique angle relative to said axis.

25. The magnetic sensor of claim 23, wherein said at least one ramp-shaped portion includes an axial surface arranged substantially parallel to said axis and extending contiguously from said tapered surface.

26. The magnetic sensor of claim 23, wherein each of said first and second shaped pole pieces includes a pair of said at least one ramp-shaped portion.

27. The magnetic sensor of claim 26, wherein each of said first and second shaped pole pieces includes a rectangular-shaped portion extending generally along said axis between said pair of ramp-shaped portions.

28. The magnetic sensor of claim 27, wherein said pair of ramp-shaped portions are symmetrical relative to a central axis passing transversely through said rectangular-shaped portion.

29. The magnetic sensor of claim 23, wherein said first and second pole pieces are formed of a composite material comprising said non-magnetic material and a magnetizable filler material, said composite material having a magnetic reluctance less than steel.

30. The magnetic sensor of claim 23, wherein first magnet is polarized in a first direction, said second magnet being polarized in a second direction generally opposite said first direction, said magnetic flux sensor defining a magnetic flux sensing plane generally aligned with said first and second directions of polarization.