Intelligent Field Shaping for Magnetic Speed Sensors

• US 20140103915A1
• Filed: 10/17/2012
• Published: 04/17/2014
• Est. Priority Date: 10/17/2012
• Status: Active Grant

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Satz, Armin
• Granted Patent: US 9,316,663 B2
• Time in Patent Office: Days
• US Class Current: 324/207.25
• CPC Class Codes: G01D 11/245 Housings for sensors
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01P 3/487 delivered by rotating magnets
• CPC Class Codes: G01P 3/488 delivered by variable reluctance detectors
• 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 33/09 Magnetoresistive devices
• CPC Class Codes: G01R 33/091 Constructional adaptation of the sensor to specific applications

Abstract

The present disclosure provides for techniques to improve the sensitivity of magnetic sensor systems. One embodiment of a magnetic sensor system includes a magnetic biasing body comprised of a hard magnetic material and including a recess therein. The recess corresponds to a magnetic flux guidance surface of the magnetic biasing body. The magnetic sensor system also includes a magnetic sensing element arranged in or proximate to the recess. A magnetic flux concentrator, which is made of a soft magnetic material, is disposed in the recess between the magnetic flux guidance surface and the magnetic sensing element. Other techniques are also described.

Claims

1. A magnetic sensor system, comprising

a magnetic biasing body comprised of a hard magnetic material and including a recess therein, wherein the recess corresponds to a magnetic flux guidance surface of the magnetic biasing body;

a magnetic sensing element arranged in or proximate to the recess; and

a soft magnetic material disposed in the recess between the magnetic flux guidance surface and the magnetic sensing element.

2. The sensor system of claim 1, wherein the soft magnetic material is arranged to concentrate a magnetic field from the magnetic biasing body to the magnetic sensing element.

3. The sensor system of claim 1, wherein the soft magnetic material is spaced apart from the magnetic sensing element.

4. The sensor system of claim 1, wherein the flux guidance surface has an inverted pyramidal shape.

5. The sensor system of claim 1, wherein the flux guidance surface comprises three or more inclined planar surfaces that intersect at a junction region.

6. The sensor system of claim 1, wherein the flux guidance surface is conical in shape.

7. The sensor system of claim 1, wherein the flux guidance surface is defined between a first circular or rounded opening having a first area and a second circular or rounded opening having a second, different area, wherein a tapered sidewall connects the first circular or rounded opening and the second circular or rounded opening.

8. The sensor system of claim 1, wherein the hard magnetic material comprises a ferrite material.

9. The sensor system of claim 1, wherein the soft magnetic material comprises a ferrite material.

10. The sensor system of claim 1, wherein the hard magnetic material comprises a rare earth material.

11. The sensor system of claim 1, wherein the soft magnetic material is conformally disposed over the flux guidance surface.

12. The sensor system of claim 1, wherein the soft magnetic material is disposed over less than all of the flux guidance surface.

13. The sensor system of claim 1, wherein the magnetic biasing body comprises protrusions extending therfrom, wherein the protrusions have respective upper surfaces that lie along a plane.

14. The sensor system of claim 13, wherein the magnetic sensing element is arranged on a support structure bridging the recess and coupled to the upper surfaces.

15. The sensor system of claim 14, wherein the magnetic sensing element is positioned on or adjacent to the plane.

16. The sensor system of claim 15, wherein the magnetic sensing element is positioned on or adjacent to the plane to correspond to a zero-magnetic field location relative to the magnetic biasing body.

17. An apparatus, comprising:

a rotary element including a plurality of magnets arranged about an outer circumference thereof;

a magnetic biasing body spaced apart from the rotary element and including a recess therein, wherein the recess corresponds to a magnetic flux guidance surface of the magnetic biasing body;

a magnetic sensing element arranged between the rotary element and the magnetic biasing body and arranged in or proximate to the recess; and

a magnetic flux compressor disposed in the recess between the magnetic flux guidance surface and the magnetic sensing element.

18. The apparatus of claim 17, wherein the magnetic biasing body comprises protrusions extending from a base region of the magnetic biasing body towards the rotary element, wherein the protrusions have respective upper surfaces that lie along a plane.

19. The apparatus of claim 18, wherein the magnetic sensing element is arranged on or adjacent to the plane and changes its resistance commensurate with changes in a magnetic field component in the plane, but is insensitive to changes in a magnetic field component perpendicular to the plane.

20. The apparatus of claim 18, wherein the magnetic sensing body comprises magnetic material having a magnetic hardness that is greater than that of the magnetic flux compressor.