Targets for coil actuated position sensors

• US 10,641,842 B2
• Filed: 05/26/2017
• Issued: 05/05/2020
• Est. Priority Date: 05/26/2017
• Status: Active Grant

• Current Assignee: Commissariat a L'Energie Atomique (AES Corporation), Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: Latham, Alexander, Fermon, Claude, Monreal, Gerardo A., Milesi, Alejandro Gabriel
• Primary Examiner(s): Shah, Neel D
• Application Number:
  US15/606,352
• Publication Number:
  US 20180340988A1
• Time in Patent Office: 1,075 Days
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01D 5/2013 by a movable ferromagnetic element, e.g. a core G01D5/2033 takes precedence
• CPC Class Codes: G01R 33/0005 Geometrical arrangement of magnetic sensor elements; Apparatus combining different magnetic sensor types G01R33/0206 takes precedence
• CPC Class Codes: G01R 33/0011 comprising means, e.g. flux concentrators, flux guides, for guiding or concentrating the magnetic flux, e.g. to the magnetic sensor
• CPC Class Codes: G01R 33/0017 Means for compensating offset magnetic fields or the magnetic flux to be measured; Means for generating calibration magnetic fields
• CPC Class Codes: G01R 33/0094 Sensor arrays
• CPC Class Codes: G01R 33/025 Compensating stray fields G01R33/0017 takes precedence
• CPC Class Codes: H01F 5/04 Arrangements of electric connections to coils, e.g. leads

Abstract

An apparatus comprises a conductive material having varying thickness along its length, the varying thickness providing varying response along a length of the conductive material to a magnetic field having a non-zero frequency; wherein the magnetic field produces an eddy current in the conductive material which generates a reflected magnetic field, wherein the varying response causes the reflected magnetic field to vary in strength along the length of the conductive material. The apparatus may include one or more reference portions of conductive material.

Claims

1. An apparatus comprising:

a cylinder comprising a conductive material having a varying thickness around a circumference of the cylinder, wherein the thickness varies as a function of an angle of the cylinder, the varying thickness providing a varying response of the conductive material to a magnetic field having a non-zero frequency;

wherein the magnetic field produces an eddy current in the conductive material which generates a reflected magnetic field, wherein the varying response causes the reflected magnetic field to vary in strength around the circumference of the conductive material to permit detection of the angle of the cylinder.

2. The apparatus of claim 1 further comprising a low-conductivity material physically coupled to the conductive material.

3. The apparatus of claim 1 wherein the varying response is based at least in part on the thickness of the conductive material.

4. The apparatus of claim 1 wherein the varying response is due to a distance between the conductive material and a source of the magnetic field.

5. The apparatus of claim 1 wherein the thickness of the conductive material varies in a radial dimension of the cylinder.

6. The apparatus of claim 1 wherein the thickness of the conductive material varies in an axial dimension of the cylinder.

7. An apparatus comprising:

a cylinder comprising first material having a first conductivity and a plurality of wells positioned around a circumference of the cylinder, the plurality of wells comprising a second material having a second conductivity higher than the first conductivity and providing a response to a magnetic field having a non-zero frequency,

wherein the magnetic field produces an eddy current in the second material which generates a reflected magnetic field, and

wherein the response of the second material causes the reflected magnetic field to vary in strength around the cylinder circumference to permit detection of the angle of the cylinder.

8. The apparatus of claim 7 wherein the plurality of wells comprises two or more circular rows of wells each arranged in a circle around the cylinder.

9. A system comprising:

one or more magnetic field sensing elements;

a coil configured to produce a magnetic field having a non-zero frequency; and

a cylinder comprising;

a conductive material having a thickness that varies around a circumference of the cylinder and as a function of an angle of the cylinder, wherein the varying thickness provides a varying response of the conductive material to the magnetic field;

wherein the magnetic field produces one or more eddy currents in the conductive material which generate a reflected magnetic field that varies in strength around the circumference of the conductive material to permit detection of the rotational angle of the cylinder.

10. The system of claim 9 wherein the cylinder comprises a low-conductivity material physically coupled to the conductive material.

11. The system of claim 9 wherein the varying response is based at least in part on the thickness of the conductive material.

12. The system of claim 9 wherein the varying response is due to a distance between the conductive material and a source of the magnetic field.

13. The system of claim 9 wherein the one or more magnetic field sensing elements are positioned outside the cylinder.

14. The system of claim 9 wherein the one or more magnetic field sensors are arranged in a grid.

15. The system of claim 9 wherein the cylinder comprises a reference portion of conductive material.

16. The system of claim 9 wherein the coil is configured to produce a second magnetic field having a second non-zero frequency.

17. An apparatus comprising:

a rod comprising conductive material having a thickness that varies substantially linearly along a length of the rod, the varying thickness providing varying response along a length of the conductive material to a magnetic field having a non-zero frequency;

wherein the magnetic field produces an eddy current in the conductive material which generates a reflected magnetic field, wherein the varying response causes the reflected magnetic field to vary in strength along the length of the conductive material.

18. The apparatus of claim 17 further comprising:

one or more magnetic field sensing elements proximate to the rod; and

a coil configured to produce the magnetic field having a non-zero frequency.

19. An apparatus comprising:

a rod comprising a first material having a first conductivity and a plurality of wells positioned along a length of the rod, the plurality of wells comprising a second material having a second conductivity greater than the first conductivity and responsive to a magnetic field having a non-zero frequency,

wherein the magnetic field produces an eddy current in the second material which generates a reflected magnetic field, and

wherein the response of the second material causes the reflected magnetic field to vary in strength along the length of the rod.