Position sensor using a compound magnetic flux source

• US 6,909,281 B2
• Filed: 07/03/2002
• Issued: 06/21/2005
• Est. Priority Date: 07/03/2002
• Status: Active Grant

• Current Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Original Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Inventors: Gassman, George Wayne, Hurd, Ronald Francis, Scafferi, Carl Gene
• Primary Examiner(s): Patidar, Jay
• Assistant Examiner(s): Aurora, Reena
• Application Number:
  US10/189,945
• Publication Number:
  US 20040004473A1
• Time in Patent Office: 1,084 Days
• Field of Search: 324/207.24, 324/207.15, 324/208, 324/202, 324/207, 324/251, 324/164, 324/174, 324/117.4, 324/225, 324/207.21, 324/207.26, 324/207.2, 324/235, 324/228, 324/262, 324/207.25, 324/207.22, 338/32.H, 338/32.R
• 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 non-contacting position sensor detects relative displacement between two objects. A magnetic flux source is provided by a plurality of discrete magnets selectively determined to produce a highly configurable flux source that is easily adapted to rotary or rectilinear displacement. The interaction of the individual flux fields generated by the discrete magnets is controlled to produce both linear and non-linear relationships with respect to changes in displacement. A flux-gathering pole piece is dimensionally optimized to integrate the plurality of individual flux fields directed to a magnetic sensor.

Claims

1. A position sensor for a valve assembly, wherein the position sensor comprises:

a magnetic flux source for generating a predefined magnetic field, the magnetic flux source consisting of a magnet array comprised of a plurality of discrete magnets providing a plurality of discrete magnetic fields, the plurality of discrete magnets being consecutively positioned relative to a centrally located magnet wherein the centrally located magnet essentially provides a magnetic null and each discrete magnetic field is a function of the relative position of each discrete magnet with respect to the centrally located magnet, and

a sensor placed proximate to the magnetic flux source to detect variations in the predefined magnetic field as a result of a relative displacement between the magnetic flux source and the sensor.

2. The position sensor of claim 1, wherein variations in the predefined magnetic field result from the plurality of discrete magnetic fields designed to interact and create a compound magnetic field that yields a predefined output signal from the sensor.

3. The position sensor of claim 2, wherein the sensor comprises:

a magnetic sensor;

a flux-gathering pole piece, the flux-gathering pole piece being geometrically formed to accumulate and direct the individual magnetic fields through the magnetic sensor; and

a processing means connected to the magnetic sensor to provide a signal representative of the displacement between the sensor and the magnetic flux source.

4. The apparatus of claim 3, wherein the interaction of the plurality of individual magnetic fields is determined by an angular rotation of the plurality of discrete magnets relative to the centrally located magnet and about an axis through the geometric center of the plurality of discrete magnets.

5. The apparatus of claim 2, wherein the interactions between the plurality of individual magnetic fields is determined by the induction of the plurality of discrete magnets relative to the centrally located magnet.

6. The position sensor of claim 2, wherein the relative displacement of the sensor with respect to the plurality of discrete magnets is rectilinear.

7. The position sensor of claim 6, wherein the variations in the magnetic field are substantially linear with respect to displacement.

8. The position sensor of claim 2, wherein the relative displacement of the sensor with respect to the plurality of discrete magnets is rotary.

9. The position sensor of claim 8, wherein the plurality of discrete magnets are positioned on a constant radius about the axis of rotation, the plurality of discrete magnets being positioned with a uniform angular distribution about the axis of rotation.

10. The position sensor of claim 9, wherein the variations in the magnetic field are substantially linear with respect to displacement.

11. The position sensor of claim 2, wherein the magnetic sensor is a Hall effect sensor, a magneto-resistor, a giant magneto-resistive bridge, or a flux gate.

12. A position sensor, wherein the position sensor comprises:

a magnetic flux source for generating a magnetic field, the magnetic flux source being comprised of a plurality of discrete magnets providing a plurality of adjacent magnetic fields, the plurality of discrete magnets being consecutively positioned relative to a centrally located magnet wherein the centrally located magnet essentially provides a magnetic null and each adjacent magnetic field is a function of the relative position of each discrete magnet with respect to the centrally located magnet wherein adjacent magnetic fields from the discrete magnets cooperatively interact to create the magnetic field;

a magnetic sensor; and

,

a processing means connected to the magnetic sensor to provide a signal representative of the displacement between the magnetic sensor and the magnetic flux source.

13. The apparatus of claim 12, wherein the interaction of the plurality of individual magnetic fields is determined by the angular rotation of the plurality of discrete magnets relatives to the centrally located magnet and about an axis through the geometric center of each of the plurality of discrete magnets.

14. The position sensor of claim 12, wherein the magnetic sensor comprises an electronic device responsive to a magnetic field and a flux-gathering pole piece, wherein the flux gathering pole piece is adapted to accumulate and direct the interacting magnetic fields through the magnetic sensor.

15. The position sensor of claim 14, wherein the electronic device is a Hall-effect device, magneto-resistor, a giant magneto-resistive bridge, or a flux gate.

16. The position sensor claim 12, wherein the interactions between the individual magnetic fields generate changes in the signal representative of the displacement in a substantially linear manner.