MAGNET WITH OPPOSING DIRECTIONS OF MAGNETIZATION FOR A MAGNETIC SENSOR

• US 20150022197A1
• Filed: 07/19/2013
• Published: 01/22/2015
• Est. Priority Date: 07/19/2013
• Status: Active Grant

• Current Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Original Assignee: Allegro Microsystems Incorporated (Sanken Electric Company Limited)
• Inventors: David, Paul, Taylor, William P.
• Granted Patent: US 10,408,892 B2
• Time in Patent Office: Days
• US Class Current: 324/251
• 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: G01R 33/02 Measuring direction or magnitude of magnetic fields or magnetic flux G01R33/20 takes precedence
• CPC Class Codes: G01R 33/07 Hall effect devices

Abstract

In one aspect, a magnetic field sensor is configured to detect a ferromagnetic object. The magnetic field sensor includes a magnet that includes two North regions and two South regions configured to generate opposing directions of magnetization to form a magnetic flux. The magnetic field sensor also includes a magnetic field sensing element configured to generate an is output signal responsive to changes in the magnetic flux caused by movement of the ferromagnetic object.

Claims

1. A magnetic field sensor configured to detect a ferromagnetic object comprising:

a magnet comprising two North regions and two South regions configured to generate opposing directions of magnetization to form a magnetic flux; and

magnetic field sensing element configured to generate an output signal responsive to changes in the magnetic flux caused by movement of the ferromagnetic object.

2. The sensor of claim 1 wherein the magnetic field sensing element is disposed in a location that detects the greatest change in magnetic flux when the ferromagnetic object is present versus when the ferromagnetic object is not present.

3. The sensor of claim 2 wherein the magnetic field sensing element is disposed between the magnet and a point where the ferromagnetic object moves closes to the magnet.

4. The sensor of claim 1 wherein the magnetic field sensing element detects changes in at least one of a magnitude or vector of the magnetic field.

5. The sensor of claim 1 wherein the magnet comprises at least one face having a North region and a South region.

6. The sensor of claim 1 wherein the magnet comprises at least a first face and a second face each having a North region and a South region,

wherein the first face is opposite the second face.

7. The sensor of claim 1 wherein the ferromagnetic object is one of a hard ferromagnetic material or a soft ferromagnetic material.

8. The sensor of claim 1 wherein the ferromagnetic object is a magnetic object.

9. The sensor of claim 1 wherein the ferromagnetic object is a tooth on a gear.

10. A magnetic field sensor configured to detect a tooth on a wheel comprising;

a magnet comprising at least two North regions and two South regions configured to generate opposing directions of magnetization to form a magnetic field, at least one face of the magnet having one of the two North regions and one of the two South regions; and

a magnetic field sensing element comprising a Hall element configured to sense magnetic flux changes not parallel to a surface of the magnetic field sensing element and configured to generate an output signal responsive to changes in the magnetic field caused by movement of the tooth comprising a ferrous material, the magnetic field sensing element being disposed between. the magnet and a point when the tooth moves closest to the magnet.

11. The sensor of claim 10 wherein the magnetic field sensing element detects changes in one of a magnitude or angle of the magnetic field.

12. The sensor of claim 10 wherein the tooth is magnetic.

13. The sensor of claim 10 wherein the at least one face of the magnet comprises at least a first face and a second face each having a North region and a South region,

wherein the first face is opposite the second face,

14. The sensor of claim 10 wherein the ferromagnetic object is one of a hard ferromagnetic material or a soft ferromagnetic material.