Position sensor using a compound magnetic flux source

• US 7,005,847 B2
• Filed: 06/16/2005
• Issued: 02/28/2006
• Est. Priority Date: 07/03/2002
• Status: Expired due to Term

• Current Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Original Assignee: Fisher Controls International LLC (Emerson Electric Company)
• Inventors: Hurd, Ronald Francis, Scafferi, Carl Gene, Gassman, George Wayne
• Primary Examiner(s): Ledynh, Bot
• Assistant Examiner(s): Aurora, Reena
• Application Number:
  US11/153,937
• Publication Number:
  US 20060012362A1
• Time in Patent Office: 257 Days
• Field of Search: 324/207.24, 324/207.15, 324/251, 324/174, 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: 324/207.25
• 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, wherein the position sensor comprises:

a sensor, the sensor including an electronic device being responsive to magnetic fields and a flux-gathering pole piece for collecting and directing magnetic flux to the sensor, the flux-gathering pole piece being constructed by the symmetric placement of a first and a second L-shaped section of magnetically permeable material forming a U-shape with a bifurcated base, the bifurcated base of the U-shaped pole piece having a gap separating the first and second L-shaped sections wherein the gap is sized to provide intimate contact with the electronic device, and

a magnetic flux source for generating a magnetic field that varies in a substantially linear manner, the magnetic flux source being cylindrically shaped and having a length essentially two-thirds of the internal width of the flux-gathering pole piece such that when rotated between the first and second L-shaped sections of the flux-gathering pole piece the magnetic flux source generates a signal representative of the displacement between the sensor and the magnetic flux source.

2. The apparatus of claim 1, wherein the magnetic flux source is comprised of a single bar magnet.

3. The apparatus of claim 1, wherein the magnetic flux source is comprised of a plurality of discrete magnets placed in intimate contact with polar attraction.

4. The apparatus of claim 1, wherein the representative signal is produced through about 110 degrees of rotation, the rotation being symmetrically distributed about a plane bisecting the first and second L-shaped sections of the flux-gathering pole piece, the bisecting plane being orthogonal to the sensing plane of the magnetic sensor.