Multipole magnet, method of producing, and sensor system comprising same

Patent metadata

Field	Value
Publication number	US-11276517-B2
Application number	US-201916435782-A
Country	US
Kind code	B2
Filing date	Jun 10, 2019
Priority date	Jun 12, 2018
Publication date	Mar 15, 2022
Grant date	Mar 15, 2022

Abstract

A permanent magnet in the form of a multi-pole magnet, comprising an isotropic magnetic material, having a central axis, magnetised such that the magnetic field, considered on a virtual circle lies substantially in a virtual plane tangential to the circle, and rotates inside that virtual plane, depending on the position on the circle. A method of producing a magnet comprising: a) providing a shaped body comprising an isotropic magnetic material; b) providing at least four electrical conductor segments; c) simultaneously make currents flow in each conductor segment. A magnet made in this way. Use of such a magnet for angular position sensing. An angular position sensor system comprising such a magnet.

First claim

The invention claimed is:

1. A sensor system comprising:
a permanent magnet in the form of a multi-pole magnet comprising an isotropic magnetic material, the permanent magnet having an axis, and being magnetized such that the magnet creates a remanent magnetic field which, for each point of an imaginary circle located in a plane perpendicular to said axis and having a centre substantially located on said axis, is located substantially in a virtual plane tangential to said virtual circle in point and parallel to said axis, which magnetic field furthermore defines an angle relative to the plane containing the circle, which angle rotates as a function of the position of the point on the imaginary circle,
the magnet configured such that the remanent magnetic field generates an effective magnetic gain on a first side of the magnet relative to an opposite second side of the magnet; and
a sensor device arranged at the first side of the magnet at an axial distance from said magnet, and adapted for determining at least one magnetic quantity or at least one derived quantity or at least one magnetic field gradient created by said magnet.

2. The sensor system according to claim 1 , wherein the sensor device comprises at least three magnetic sensor elements located in a plane perpendicular to the axis of the magnet at the first side of the magnet, the at least three magnetic sensor elements not being collinear.

3. The sensor system according to claim 1 , wherein the sensor system is an angular position sensor system.

4. The sensor system according to claim 3 , wherein the sensor device is adapted for determining one or more field gradients of the magnetic field created by the magnet, in a plane perpendicular to the axis, and is adapted for determining an angular position of the sensor device relative to the permanent magnet, based on said field gradients.

5. The sensor system according to claim 3 , wherein the angular position is calculated based on the following formula or an equivalent formula:

θ
m

=

arctan
⁢

⁢
2
⁢

(

δ
⁢

⁢

B
x

δ
⁢

⁢
y

+

δ
⁢

⁢

B
y

δ
⁢

⁢
x

δ
⁢

⁢

B
x

δ
⁢

⁢
x

-

δ
⁢

⁢

B
y

δ
⁢

⁢
y

)

/

(

N
/
2

)

where N is an even integer number of at least 4, θm is the calculated angular position of the sensor device relative to the magnet, and wherein dBx/dy, dBy/dx, dBx/dx and dBy/dy are in-plane field gradients.

6. The sensor system according to claim 1 , wherein the sensor device is adapted for determining four magnetic field gradients created by said magnet.

7. The sensor system according to claim 1 , wherein the magnet has an opening or a cut-out with a tubular shape; and
wherein the imaginary circle is defined as the cross section of the plane perpendicular to the axis, and said tubular shape.

8. The sensor system according to claim 7 , wherein the tubular opening or tubular cut-out is a cylindrical through-hole or a conical through-hole or a cylindrical cut-out or a conical cut-out.

9. The sensor system according to claim 1 , wherein said angle rotates monotonically as a function of the position of the point on the imaginary circle; or
wherein said angle rotates substantially linearly as a function of the position of the point on the imaginary circle.

10. The sensor system according to claim 1 , wherein the remanent magnetic field (Br) has magnetic field components (Brx, Bry, Brz) which, at points located on said circular cross section, can be expressed or approximated by the following set of formulas, or an equivalent set of formulas:

(

Br
x

Br
y

Br
z

Assignees

• Melexis Tech Sa

Inventors

• Bidaux Yves

Classifications

• H01F7/0205

  Magnetic circuits with PM in general · CPC title

• H01F7/0273 Primary

  Magnetic circuits with PM for magnetic field generation · CPC title

• H01F7/021

  Construction of PM (H01F7/0278 takes precedence; PM compositions H01F1/032) · CPC title

• G01D5/145 Primary

  influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06) · CPC title

• G01B7/30

  for measuring angles or tapers; for testing the alignment of axes · CPC title