GMR sensor with flux concentrators

• US 20050280411A1
• Filed: 06/16/2004
• Published: 12/22/2005
• Est. Priority Date: 06/16/2004
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Bicking, Robert E.
• Granted Patent: US 7,112,957 B2
• Time in Patent Office: Days
• US Class Current: 324/207.21
• CPC Class Codes: G01B 7/14 for measuring distance or clearance between spaced objects or spaced apertures G01B7/30 takes precedence
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

A proximity sensor that is capable of producing a relatively larger output signal than past proximity sensors, and in some cases, an output signal that is relatively independent of the speed at which a target passes the sensor. In one illustrative embodiment, the proximity sensor includes a first magnetoresistive resistor and a second magnetoresistive resistor connected in a bridge configuration. The first magnetoresistive resistor is spaced from the second magnetoresistive resistor along the path of a moving ferrous target. A bias magnet source is positioned behind the proximity sensor, and the ferrous target passes in front of the proximity sensor. The ferrous target alters the direction of the bias magnetic field in the vicinity of the first and second magnetoresistive resistors as the ferrous target passes by the proximity sensor. Flux concentrators are positioned proximate to each of the first and second magnetoresistive resistors. The flux concentrators may help redirect or shunt the magnetic field component produced by the bias magnet source that is perpendicular to the direction of motion of the target through the first and second magnetoresistive resistors in a direction that is parallel to the direction of motion of the target.

Claims

1. A proximity sensor comprising:

a first magnetoresistive resistor;

a second magnetoresistive resistor spaced from the first magnetoresistive resistor;

a first flux concentrator positioned proximate the first magnetoresistive resistor; and

a second flux concentrator positioned proximate the second magnetoresistive resistor;

wherein, the first magnetoresistive resistor and the second magnetoresistive resistor are electrically coupled in a bridge configuration.

2. The proximity sensor according to claim 1, wherein at least one of the first magnetoresistive resistor and the second magnetoresistive resistor is a giant magneto resistance resistor having an in-plane first axis direction and an orthogonal in-plane second axis direction.

3. The proximity sensor according to claim 2, wherein the first flux concentrator and second flux concentrator each include a pair of ferrous material regions.

4. The proximity sensor according to claim 1, wherein the first flux concentrator and second flux concentrator include a permalloy material.

5. The proximity sensor according to claim 3, wherein the first magnetoresistive resistor is disposed between the first flux concentrator pair of ferrous material regions.

6. The proximity sensor according to claim 5, wherein the second magnetoresistive resistor is disposed between the second flux concentrator pair of ferrous material regions.

7. The proximity sensor according to claim 2, wherein the first flux concentrator redirects a magnetic field component along the first axis direction through the first magnetoresistive resistor along the second axis direction.

8. The proximity sensor according to claim 7, wherein the second flux concentrator redirects a magnetic field component along the first axis direction through the second magnetoresistive resistor along the second axis direction.

9. The proximity sensor according to claim 2, wherein the first and second flux concentrators direct magnetic flux across the first and second magnetoresistive resistors along the second axis direction.

10. The proximity sensor according to claim 5, wherein the first flux concentrator pair of ferrous material regions each include an inner face proximate the first magnetoresistive resistor and an opposing outer face, wherein each inner face is planar or substantially planar and parallel to the first axis.

11. The proximity sensor according to claim 6, wherein the second flux concentrator pair of ferrous material regions each include an inner face proximate the second magnetoresistive resistor and an opposing outer face, wherein each inner face is planar or substantially planar and parallel to the first axis.

12. The proximity sensor according to claim 10, wherein at least a portion of the first flux concentrator pair of ferrous material regions opposing outer face is non-planar.

13. The proximity sensor according to claim 11, wherein at least a portion of the second flux concentrator pair of ferrous material regions opposing outer face is non-planar.

14. A proximity sensor comprising:

a first pair of magnetoresistive resistors;

a second pair of magnetoresistive resistors;

a first flux concentrator positioned proximate the first pair of magnetoresistive resistors; and

a second flux concentrator positioned proximate the second pair of magnetoresistive resistors;

wherein the first pair of magnetoresistive resistors and the second pair of magnetoresistive resistors are electrically coupled in a bridge configuration.

15. The proximity sensor according to claim 14, wherein the first pair of magnetoresistive resistors and second pair of magnetoresistive resistors are giant magneto resistance resistors and each giant magneto resistance resistor has an in-plane standard axis direction and an orthogonal in-plane cross-axis direction.

16. The proximity sensor according to claim 15, wherein the first flux concentrator and second flux concentrator are each formed from a pair of ferrous material regions.

17. The proximity sensor according to claim 14, wherein the first flux concentrator and second flux concentrator are formed from permalloy material.

18. The proximity sensor according to claim 16, wherein the first pair of magnetoresistive resistors is disposed between the first flux concentrator pair of ferrous material regions.

19. The proximity sensor according to claim 18, wherein the second pair of magnetoresistive resistors is disposed between the second flux concentrator pair of ferrous material regions.

20. The proximity sensor according to claim 14, wherein the first flux concentrator redirects a magnetic field component along the standard axis through the first pair of magnetoresistive resistors in the cross-axis direction.

21. The proximity sensor according to claim 20, wherein the second flux concentrator redirects a magnetic field component along the standard axis direction through the second pair of magnetoresistive resistors in the cross-axis direction.

22. The proximity sensor according to claim 14, wherein the first and second flux concentrators direct magnetic flux across the first and second pair of magnetoresistive resistors in the cross-axis direction.

23. The proximity sensor according to claim 16, wherein the first flux concentrator pair of ferrous material regions each include an inner face proximate the first pair of magnetoresistive resistors and an opposing outer face, wherein each inner face is planar and parallel to the standard axis.

24. The proximity sensor according to claim 23, wherein the second flux concentrator pair of ferrous material regions each include an inner face proximate the second pair of magnetoresistive resistors and an opposing outer face, wherein each inner face is planar and parallel to the standard axis.

25. The proximity sensor according to claim 23, wherein at least a portion of the first flux concentrator pair of ferrous material regions opposing outer face is non-planar.

26. The proximity sensor according to claim 24, wherein at least a portion of the second flux concentrator pair of ferrous material regions opposing outer face is non-planar.

27. A proximity transducer for detecting a position of a ferromagnetic target, comprising:

a magnetic field biasing source having an end and an axis, the magnetic field biasing source producing a radial magnetic field component in a direction perpendicular to the axis at the end; and

a proximity sensor lying in a plane perpendicular or substantially perpendicular to the axis of the magnetic field biasing source and disposed between the end of the magnetic field biasing source and a ferromagnetic target, the proximity sensor comprising;

a first pair of magnetoresistive resistors;

a second pair of magnetoresistive resistors;

a first flux concentrator positioned proximate the first pair of magnetoresistive resistors; and

a second flux concentrator positioned proximate the second pair of magnetoresistive resistors;

wherein, the first pair of magnetoresistive resistors and the second pair of magnetoresistive resistors are electrically coupled in a bridge configuration.

28. The proximity transducer according to claim 27, wherein the first pair of magnetoresistive resistors and second pair of magnetoresistive resistors are giant magneto resistance resistors, and each giant magneto resistance resistor has an in-plane standard axis direction and an orthogonal in-plane cross-axis direction.

29. The proximity transducer according to claim 28, wherein the first flux concentrator and second flux concentrator are each formed from a pair of ferrous material regions.

30. The proximity transducer according to claim 29, wherein the first flux concentrator and second flux concentrator are formed from permalloy material.

31. The proximity transducer according to claim 29, wherein the first pair of magnetoresistive resistors is disposed between the first flux concentrator pair of ferrous material regions.

32. The proximity transducer according to claim 31, wherein the second pair of magnetoresistive resistors is disposed between the second flux concentrator pair of ferrous material regions.

33. The proximity transducer according to claim 32, wherein the first flux concentrator redirects a magnetic field component of the magnetic field biasing source that extends along the standard axis though the first pair of magnetoresistive resistors in the cross-axis direction.

34. The proximity transducer according to claim 33, wherein the second flux concentrator redirects a magnetic field component of the magnetic field biasing source that extends along the standard axis though the second pair of magnetoresistive resistors in the cross-axis direction.

35. The proximity transducer according to claim 34, wherein the ferromagnetic target is a gear tooth.

36. The proximity transducer according to claim 35, wherein the ferromagnetic target is configured for movement in a direction parallel to the cross-axis direction.

37. The proximity transducer according to claim 27, wherein the first and second flux concentrators are configured to redirect magnetic flux across the first and second pair of magnetoresistive resistors in the cross-axis direction.

38. The proximity transducer according to claim 36, wherein the first flux concentrator pair of ferrous material regions each include an inner face proximate the first pair of magnetoresistive resistors and an opposing outer face, wherein the each inner face is planar and parallel to the standard axis.

39. The proximity transducer according to claim 38, wherein the second flux concentrator pair of ferrous material regions each include an inner face proximate the second pair of magnetoresistive resistors and an opposing outer face, wherein the each inner face is planar and parallel to the standard axis.

40. The proximity transducer according to claim 39, wherein at least a portion of the first flux concentrator pair of ferrous material regions opposing outer face is non-planar.

41. The proximity transducer according to claim 40, wherein at least a portion of the second flux concentrator pair of ferrous material regions opposing outer face is non-planar.