Sensor assembly using differential sensing elements for detecting direction of motion of a rotating object

• US 20030205998A1
• Filed: 06/03/2003
• Published: 11/06/2003
• Est. Priority Date: 02/06/2001
• Status: Active Grant

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Omekanda, Avoki M., Heremans, Joseph Pierre, Schroeder, Thaddeus, Lequesne, Bruno P. B.
• Granted Patent: US 7,009,384 B2
• Time in Patent Office: Days
• US Class Current: 324/165
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other
• CPC Class Codes: G01P 13/04 Indicating positive or negative direction of a linear movement or clockwise or anti-clockwise direction of a rotational movement
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors

Abstract

A target wheel sensor assembly includes a target wheel, a magnet, and two or more sensing elements placed therebetween. The magnet and the sensing elements are configured so that as the target wheel rotates each of the sensing elements outputs a respective asymmetric signal relative to the direction of rotation of the target wheel or an object mechanically connected to the wheel. Each of these asymmetric signals is differentially combined with one another to determine the direction of motion of the target wheel, and, if optionally desired, the position of the target wheel.

Claims

1. A sensor assembly for detecting direction of rotation of an object, comprising:

a magnet having opposite poles and defining a center substantially midway between the poles, the center of the magnet being positioned along a central axis of the sensor assembly;

a target wheel mechanically connected to the object; and

at least two sensing elements placed between the target wheel and the magnet, the magnet and sensing elements being configured so that as the target wheel rotates it causes each sensing element to output respective asymmetric signals relative to the direction of rotation of the object in response to sensing structure on the target wheel, each of said asymmetric signals being differentially combined to generate a combined signal indicative of the direction of rotation of the object.

2. The sensor assembly of claim 1, wherein the magnet and the sensing elements are oriented perpendicular to the central axis, and wherein the magnet generates a magnetic field that is oriented at an angle relative to the central axis.

3. The sensor assembly of claim 2, wherein the angle comprises a range of about twenty degrees to about seventy degrees.

4. The sensor assembly of claim 1, wherein the magnet is oriented perpendicular to the central axis, the magnet further generating a magnetic field that is oriented parallel to the central axis, and wherein each of the sensing elements is oriented at an angle relative to the central axis.

5. The sensor assembly of claim 4, wherein the angle comprises a range of about zero degrees to about seventy degrees.

6. The sensor assembly of claim 1, wherein the magnet and the sensing elements are oriented perpendicular to the central axis, the magnet further generating a magnetic field that is oriented parallel to the central axis, and wherein one of the sensing elements is placed at a distance from the central axis that is different than the distance from the central axis for the other sensing element.

7. The sensor assembly of claim 6, wherein the magnet defines a length and the distance for any of the sensing elements relative to the central axis comprises a range of about forty percent to one hundred percent of one-half of the length.

8. The sensor assembly of claim 1, wherein the magnet further defines a longitudinal axis and generates a magnetic field that is oriented perpendicular to the longitudinal axis, each of the sensing elements being oriented parallel to the longitudinal axis of the magnet, and wherein the magnet and each of the sensing elements is oriented at an angle relative to the central axis.

9. The sensor assembly of claim 8, wherein the angle comprises a range from about one degree to about forty degrees.

10. The sensor assembly of claim 1, further comprising:

a magnetic piece placed near the magnet, the magnetic piece being configured so that as the target wheel rotates it causes each sensing element to enhance the asymmetry in each output signal relative to the direction of rotation of the object.

11. The sensor assembly of claim 10, wherein the magnetic piece is placed adjacent to one side of the magnet.

12. The sensor assembly of claim 10, wherein the magnet defines a top, the magnetic piece includes an upper portion and a lateral portion extending therefrom, and wherein the magnetic piece is placed so that the upper portion is adjacent to the top of the magnet and the lateral portion is adjacent to one side of the magnet.

13. The sensor assembly of claim 12, wherein the upper portion of the magnetic piece is tapered.

14. The sensor assembly of claim 1, wherein the magnet defines a lower surface that is oriented perpendicular to the central axis and an upper surface that is oriented at an angle relative to the central axis.

15. The sensor assembly of claim 1, wherein the magnet comprises first and second segments for generating a first magnetic field and a second magnetic field.

16. The sensor assembly of claim 15, wherein the first magnetic field and the second magnetic field have different field strengths.

17. The sensor assembly of claim 1, wherein the magnet comprises first and second discrete magnets for generating a first magnetic field and a second magnetic field.

18. The sensor assembly of claim 17, wherein the first magnetic field and the second magnetic field have different field strengths.

19. The sensor assembly of claim 17, wherein the first and second magnetic fields have a mutually orthogonal direction relative to one another.

20. A target wheel sensor assembly for sensing at least direction of rotation of a target wheel, the sensor assembly defining a central axis and comprising:

a target wheel defining a center, the center of the target wheel being located along the central axis;

a magnet placed near the target wheel, the magnet defining a center intermediate opposite poles of the magnet, the center of the magnet being located along the central axis; and

at least two sensing elements placed between the target wheel and the magnet, each of the sensing elements producing a respective asymmetric output signal relative to the direction of rotation of the target wheel in response to sensing structure on the target wheel as the wheel rotates, each output signal being differentially combined with one another to supply a combined output signal indicative of a direction of rotation of the target wheel and a position of the target wheel.

21. The sensor assembly of claim 20, wherein the magnet and each of the sensing elements are oriented perpendicular to the central axis, and wherein the magnet generates a magnetic field that is oriented at an angle with the central axis.

22. The sensor assembly of claim 20, wherein the magnet is oriented perpendicular to the central axis, the magnet further generating a magnetic field that is oriented parallel to the central axis, and wherein each of the sensing elements is oriented at an angle with the central axis.

23. The sensor assembly of claim 20, wherein the magnet and the sensing element are oriented perpendicular to the central axis, the magnet further generating a magnetic field that is oriented parallel to the central axis, and wherein one of the sensing elements is placed at a distance from the central axis that is different than the distance from the central axis for the other sensing element.

24. The sensor assembly of claim 20, wherein the magnet defines a longitudinal axis and generates a magnetic field that is oriented perpendicular to the longitudinal axis, each of the sensing elements being oriented parallel to the longitudinal axis of the magnet, and wherein the magnet and each of the sensing elements is oriented at an angle with the central axis.

25. The sensor assembly of claim 20, further comprising:

a magnetic piece placed near the magnet, the magnetic piece being configured so that as the target wheel rotates it causes each of the sensing elements to enhance the asymmetry in each output signal relative to the direction of rotation of the target wheel.

26. The sensor assembly of claim 20, wherein the magnet defines a lower surface that is oriented perpendicular to the central axis and wherein an upper surface that is oriented at an angle with the central axis.

27. The sensor assembly of claim 20, wherein the magnet generates at least a first magnetic field and at least a second magnetic field.

28. A target wheel sensor assembly for sensing at least direction of rotation of a target wheel, the sensor assembly defining a central axis and comprising:

a target wheel defining a center, the center of the target wheel being located along the central axis;

a magnet having opposite poles and defining a center substantially midway between the poles, the center of the magnet being located along the central axis;

at least two sensing elements placed between the target wheel and the magnet, the sensing elements defining a center, the center of the sensing elements being offset from the central axis, each of the sensing elements outputting an asymmetric signal in response to sensing structure on the target wheel as the target wheel rotates, each output signal being differentially combined with one another to supply a combined output signal indicative of the direction of rotation of the target wheel; and

a processor for determining the direction of rotation of the target wheel based on the combined asymmetric signal from the at least two sensing elements.