# US 2019/0378639 A1 · Multipole magnet, method of producing, and sensor system comprising same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0378639 A1 - Document ID: US20190378639A1 - Status: Published application - Kind: A1 - Application number: 16/435,782 - Filed: 2019-06-10 - Published: 2019-12-12 - Earliest claimed: 2018-06-12 - Assignees: Melexis Technologies SA - Applicants: Melexis Technologies SA - Inventors: Yves BIDAUX - Web page: https://patentgrep.com/patent/US20190378639A1 ## CPC - H01F 7/0273: {Magnetic circuits with PM for magnetic field generation} - G01B 7/30: for measuring angles or tapers; for testing the alignment of axes - G01D 5/145: {influenced by the relative movement between the Hall device and magnetic fields (see G01R33/06)} - H01F 7/0205: {Magnetic circuits with PM in general} - H01F 7/021: {Construction of PM (H01F7/0278 takes precedence; PM compositions H01F1/032)} - H01F 13/003: {Methods and devices for magnetising permanent magnets (permanent magnets H01F7/02)} - H01F 41/0273: {Imparting anisotropy (methods and devices for magnetising permanent magnets H01F13/003)} - H01F 41/028: {Radial anisotropy (for rotor or stator bodies H02K15/02)} - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS - G01D: MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR ## 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. ## Claims ### Claim 1 A permanent magnet in the form of a multi-pole magnet wherein the magnet comprises an isotropic magnetic material; the magnet has an axis; the magnet is 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. ### Claim 2 (depends on 1) The permanent magnet of 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. ### Claim 3 (depends on 2) The permanent magnet of claim 2, 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. ### Claim 4 (depends on 1) The permanent magnet 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. ### Claim 5 (depends on 1) The permanent magnet 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 ) = Br isotropic  ( sin  ( θ )  cos  ( N   θ / 2 ) - cos  ( θ )  cos  ( N   θ / 2 ) sin  ( N   θ / 2 ) ) where N is an integer value of at least 4, Brx, Bry and Brz is an x, y and z-component respectively of the remanent magnetic field, Brisotropic is a magnitude of the remanent magnetic field, and θ is an angle about the axis. ### Claim 6 (depends on 1) The permanent magnet according to claim 1, wherein an outer surface of the permanent magnet has a circular or a regular polygonal cross section with the plane that contains the virtual circle, for example a square or a hexagon or an octagon. ### Claim 7 A method of producing a permanent magnet in the form of a multi-pole magnet having an axis, the multi-pole magnet having a plurality of at least four poles as seen from a point on said axis; the method comprising the following steps: a) providing a shaped body comprising or consisting of an isotropic magnetic material, the shaped body having an axis and a centre; b) providing a number of at least four electrical conductor segments arranged in a plane perpendicular to said axis, the conductor segments being oriented radially with respect to said axis, and being angularly spaced by an angle of 360° divided by said number; c) simultaneously applying or inducing or otherwise make currents flow through each of said number of conductor segments, the currents in the even numbered conductor segments flowing towards the axis, the currents in the odd numbered conductor segments flowing away from said axis. ### Claim 8 (depends on 7) The method of claim 7, wherein the shaped body provided in step a) furthermore comprises a plurality of radially oriented grooves for accommodating said electrical conductor segments; and wherein step b) further comprises: at least partially inserting the plurality of electrical conductor segments inside said grooves. ### Claim 9 (depends on 1) A sensor system comprising: a permanent magnet according to claim 1; a sensor device arranged at an axial distance from said magnet, and at a radial offset from said axis, 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. ### Claim 10 (depends on 9) A sensor system according to claim 9, wherein the sensor device comprises at least three magnetic sensor elements located in a plane perpendicular to the axis of the magnet, the at least three magnetic sensor elements not being collinear. ### Claim 11 (depends on 9) A sensor system according to claim 9, wherein the sensor system is an angular position sensor system. ### Claim 12 (depends on 11) A sensor system according to claim 11, 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. ### Claim 13 (depends on 11) A sensor system according to claim 11, 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. ### Claim 14 (depends on 11) A sensor system according to claim 11, wherein the permanent magnet further comprises two vertically magnetized dipoles arranged on opposite sides of the isotropic magnet body for allowing determination of an angular position within a 360° range.