Linkage position sensor having a magnet with two ramped sections for providing variable magnetic field

• US 5,955,881 A
• Filed: 12/17/1996
• Issued: 09/21/1999
• Est. Priority Date: 10/18/1994
• Status: Expired due to Term

• Current Assignee: CTS Corporation
• Original Assignee: CTS Corporation
• Inventors: White, James E., Campbell, Robert J., Jarrard, Craig A., McCurley, Jeffrey L., Zdanys, John Jr.
• Primary Examiner(s): O'Shea, Sandra L.
• Assistant Examiner(s): Patidar, Jay M.
• Application Number:
  US08/767,828
• Time in Patent Office: 1,008 Days
• Field of Search: 324/207.2, 324/207.21-207.24, 324/207.26, 324/173, 324/174, 324/207.25, 338/32 R, 338/32 H
• US Class Current: 324/207.2
• CPC Class Codes: G01B 7/02 for measuring length, width or thickness G01B7/004, G01B7/12 take precedence
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

An extremely reliable and effective position sensor is provided at low cost for determining the relative position of a mechanical linkage with respect to a reference point. The position sensor includes a rotor or bracket which is mechanically coupled to the linkage and contains at least two magnets on opposite walls adjacent a channel opening. The opposing magnets are formed with first and second sloped or ramped sections which produce produce variable magnetic fields as determined by the geometric profile of the magnets. One or more detectors are positioned in the air gap between the opposing magnets. As the linkage is moved, the rotor or bracket moves with respect to the detector causing a change in the strength of the magnetic field detected by the detector, whereby the detector determines the position of the movable linkage.

Claims

1. A sensor for detecting the position of a mechanical linkage relative to a reference point, comprising:

a pair of magnets, each magnet having a surface including at least a first and a second ramp section;

a magnetically permeable bracket interconnecting said pair of magnets in spaced-apart relationship and opposite each other to define a longitudinally extending air gap therebetween with said magnets facing each other across said air gap and with said magnets aligned in a manner such that the surface including the first and second ramp sections of one of the magnets faces the surface including the first and second ramp sections of the other of the magnets so that the first ends of said magnets are positioned opposite each other and the second ends of said magnets are positioned opposite each other and so that said air gap between said magnets varies in dimension longitudinally over a distance corresponding to at least a portion of the surface of the first and second ramp sections of the magnets;

said pair of magnets and said magnetically permeable bracket being mounted relative to a mechanical linkage in a manner such that movement of said mechanical linkage causes movement of said magnets and said bracket;

said pair of magnets and said magnetically permeable bracket forming a continuous magnetic circuit and producing a magnetic field coupled between said pair of magnets, said magnetic field having linearly varying strength lengthwise of said longitudinally extending air gap over the distance corresponding to at least a portion of the surface of the first and second ramp sections of the magnets; and

at least one detector fixedly mounted within said air gap intermediate said pair of magnets and positioned to detect said strength of said magnetic field between said magnets and to generate an output representative of the strength of said magnetic field.

2. The sensor as defined in claim 1, wherein said at least one detector includes at least one of an analog output circuit and a digital output circuit.

3. The sensor as defined in claim 1, wherein said magnets move linearly with respect to said at least one detector.

4. The sensor as defined in claim 1, wherein each magnet includes a prism-shaped longitudinal profile.

5. The sensor as defined in claim 1, wherein said air gap converges from one end of said magnets toward an opposite end of said magnets.

6. The sensor as defined in claim 1, wherein the bracket is attached to the mechanical linkage, said bracket having a pair of opposite sidewalls interconnected by a bottom wall, and each magnet is attached to and covers an interior surface of each sidewall.

7. The sensor as defined in claim 6, wherein said bracket is disposed at one end of a linkage rod and said bracket is movable between first and second positions by movement of the linkage.

8. The sensor as defined in claim 6, wherein said bracket is attached to at least one of a screw drive and a worm.

9. The sensor as defined in claim 6, wherein at least one of said opposite sidewalls is disposed at an angle with respect to a translational axis of said linkage.

10. The sensor as defined in claim 1, wherein said bracket has a C-shaped cross-sectional profile defining parallel first and second outwardly extending walls interconnected to each other at one end by a magnetically permeable pole piece with one of said pair of magnets being attached to said first outwardly extending wall and a second of said pair of magnets being attached to said second outwardly extending wall.

11. The sensor as defined in claim 10, wherein said bracket moves in an arc with respect to said at least one detector.

12. The sensor as defined in claim 11, wherein said bracket is caused to move by a rotor interconnected therewith.

13. The sensor of claim 10, wherein each magnet has a flat surface bonded to said bracket.

14. The sensor as defined in claim 13, wherein each magnet has a length and a width substantially greater than a length and a width of said at least one detector.

15. The sensor of claim 1 wherein the first ramp sections on the magnets have corresponding slopes structured to provide a varying air gap dimension between the first ramp sections.

16. The sensor of claim 15 wherein the second ramp sections on the magnets have corresponding second slopes different from the first slopes.

17. The sensor of claim 16 wherein the second ramp sections on the magnets are structured to provide a constant air gap dimension between the second ramp sections.

26. The sensor of claim 15 wherein the second ramp sections on the first and second magnets are structured to provide a constant air gap dimension between the second ramp sections.

18. An automotive linkage position sensor, comprising in combination:

a mechanically actuated linkage member movable between first and second positions;

first and second magnets each having a surface including at least a first and a second ramp section, said first and second magnets being interconnected by a magnetically permeable bracket and being positioned opposite each other to define an air gap therebetween with said magnets facing each other across said air gap and with the surface including the first and second ramp sections of the first magnet being aligned to face the surface including the first and second ramp sections of the second magnet, said interconnected first and second magnets and said magnetically permeable bracket forming a continuous magnetic circuit and producing a magnetic field having linearly varying strength over a distance corresponding to at least a portion of the surface of the first and second ramp sections of the magnets;

said interconnected magnets being mounted relative to said mechanically actuated linkage member in a manner such that movement of said mechanical linkage member causes movement of said magnets; and

at least one detector received within said air gap substantially midway between said first and second magnets to detect said magnetic field, said at least one detector fixed with respect to said movable mechanically actuated linkage member.

19. The position sensor as defined in claim 18, wherein said linkage member moves in an arc with respect to said at least one detector.

20. The position sensor as defined in claim 18, wherein said linkage member moves linearly along an axis with respect to said at least one detector.

21. The position sensor as defined in claim 18, wherein at least a portion of each of said first and second magnets has a wedge-shaped longitudinal profile.

22. The position sensor as defined in claim 18, wherein at least one of the ramp sections of each magnet is inclined with respect to an axis of movement of said linkage member.

23. The position sensor as defined in claim 18, wherein the surface of each of said first and second magnets has a length and a width substantially greater than said at least one detector such that said detector is not exposed to any bulging magnetic fields produced at a periphery of said first and second magnets.

24. The sensor of claim 18 wherein the first ramp sections on the first and second magnets have corresponding slopes structured to provide a varying air gap dimension between the first ramp sections.

25. The sensor of claim 24 wherein the second ramp sections on the first and second magnets have corresponding second slopes different from the first slopes.

27. A sensor for detecting a position of a movable piece, comprising:

a) a bracket, coupled to the movable piece and being magnetically permeable, having a first and second parallel flange;

b) a first and second magnet coupled to the first and second flange respectively, the first and second magnets having;

1) opposing first ramp sections and opposing second ramp section;

2) the first ramp section of each magnet having a first slope that is relative to the first flange; and

3) the second ramp section of each magnet having a second slope that is relative to the first flange, wherein the second slope is different from the first slope;

c) a magnetic field coupled between the first and second magnets, having a linearly varying flux strength determined by varying distances between the opposing first and second magnets;

d) a continuous magnetic circuit formed from the bracket, the first and second magnets and the magnetic field; and

e) a detector positioned between the first and second magnets for determining the position of the moveable piece.

28. The sensor of claim 27 including a third flange for connecting the first and second flange.

29. The sensor of claim 27 wherein the second slope is parallel to the first flange.

30. The sensor of claim 27 wherein the second slope is positive.

31. The sensor of claim 27 wherein the detector is a Hall effect device.

32. The sensor of claim 27 wherein the first and second magnets move in an arcuate oath relative to the detector.

33. The sensor of claim 27 wherein the first and second magnets move linearly with respect to the detector.