Rotary or linear position sensor having a variable magnet profile

• US 8,373,410 B2
• Filed: 11/26/2007
• Issued: 02/12/2013
• Est. Priority Date: 11/28/2006
• Status: Active Grant

• Current Assignee: Moving Magnet Technologies
• Original Assignee: Moving Magnet Technologies
• Inventors: Frachon, Didier
• Primary Examiner(s): PATIDAR, JAY M
• Application Number:
  US12/516,107
• Publication Number:
  US 20100045275A1
• Time in Patent Office: 1,905 Days
• Field of Search: 3242072-20725
• US Class Current: 324/207.25
• CPC Class Codes: G01D 2205/77 Specific profiles
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

The invention relates to a magnetic angular or linear sensor including at least one permanent magnet defined in a cylindrical (r, Q & z) or Cartesian (x, y & z) coordinate system and at least two magneto-sensitive elements, in which the magnet can move in relation to said two magneto-sensitive elements. The invention is characterized in that at least one dimension of the magnet varies as a non-constant function and in that the magnetization of the magnets is oriented in a single direction, i.e. x, y or z in the case of a magnet defined in a Cartesian coordinate system or r, Q or z in the case of a magnet defined in a cylindrical coordinate system.

Claims

1. A magnetic angular or linear position sensor including:

at least one permanent magnet defined in a cylindrical (r, Q &

z) or Cartesian (x, y &

z) coordinate system and

at least two magneto-sensitive elements, wherein the magnet moves in relation to said two magneto-sensitive elements,

wherein the at least one magnet has at least a dimension which varies as a non constant function and in that the magnetization of said at least one magnet is oriented in a single direction x, y or z in the case of a magnet defined in a Cartesian coordinate system or r, Q or z in the case of a magnet defined in a cylindrical coordinate system, and wherein the at least two magneto-sensitive elements measure a magnetic flux angle, the magnetic flux angle being the angular direction of the magnetic flux.

2. A magnetic angular or linear position sensor according to claim 1, characterised in that said dimension varies according to a non constant and continuous law.

3. A magnetic angular or linear position sensor according to claim 2, characterised in that said dimension varies according to a non constant and periodical law.

4. An angular or linear magnetic position sensor according to claim 3, characterised in that at least one of the dimensions of said at least one magnet varies substantially as a sinusoidal function.

5. A magnetic linear or angular position sensor according to claim 1, characterised in that the magneto-sensitive elements measure two components of the magnetic field substantially at the same spot.

6. A magnetic linear or angular position sensor according claim 1, characterised in that a calculation of the position is made by calculating a ratio of two components of the magnetic field or by calculating an arctangent of the same ratio.

7. A magnetic linear or angular position sensor according to claim 1, characterised in that a calculation of the position is made by calculating the arctangent of a ratio of two components of the magnetic field after having applied a multiplying coefficient to the ratio of the two components of the magnetic field considered.

8. A magnetic linear or angular position sensor according to claim 6 characterised in that at least one of the calculation of the ratio of the two components in the magnetic field and the calculation of the arctangent of this ratio is made by a dedicated electronic component.

9. A magnetic linear or angular position sensor according to claim 6, characterised in that at least one of the calculation of the ratio of the two components of the magnetic field and the calculation of the arctangent of this ratio is integrated with the magneto-sensitive elements in a single component.

10. A magnetic linear or angular position sensor according claim 1, characterised in that the at least one permanent magnet is magnetized according to the width thereof, the width being oriented in the direction y of a magnet defined in a Cartesian coordinate system or in the direction r of a magnet defined in a cylindrical coordinates system.

11. A magnetic linear or angular position sensor according to claim 1, characterised in that the at least one permanent magnet is magnetized according to the thickness thereof, the thickness being oriented in the direction z of a magnet defined in a Cartesian coordinate system or in the direction z of a magnet defined in a cylindrical coordinates system.

12. A magnetic linear or angular position sensor according to claim 1, characterised in that the at least one permanent magnet is magnetized according to the length thereof, the length being oriented in the direction x of a magnet defined in a Cartesian coordinate system or in the direction Q of a magnet defined in a cylindrical coordinates system.

13. A magnetic linear or angular position sensor according to claim 1, characterised in that the at least one magnet is at least one of mounted and embedded on a ferromagnetic yoke.

14. An angular position sensor for a travel of less than 360°

according to claim 1,

characterised in that the at least one magnet is magnetized according to the thickness thereof, and in that a calculation of the position is obtained by measuring substantially at the same spot of the tangential Bt and, radial Br or axial Bz components and by an arctangent(GAIN Bt/Br−

Offset)), wherein Offset is the offset on the radial component Br, or arctangent(GAIN Bt/Bz−

Offset)) calculation, wherein Offset is the offset on the axial component Bz.

15. An angular position sensor for a travel of less than 360°

according to claim 1,

characterised in that the at least one magnet is magnetized according to the thickness thereof, the thickness being oriented in the direction x of a magnet defined in a Cartesian coordinate system or in the direction Q of a magnet defined in a cylindrical coordinates system, or radially or tangentially, and in that a calculation of the position is obtained by measuring the same tangential Bt, or radial Br, or axial Bz component, at three spots offset by θ

₁ and θ

₂ and by calculating the angular position obtained by the resolution of the equation system;

B1=Amplitude*Cos(Angle)+Offset

B2=Amplitude*Cos(Angle+θ

₁)+Offset

B3=Amplitude*Cos(Angle+θ

₂)+Offset.

16. An angular position sensor for a travel of less than 360°

according to claim 1, characterised in that two magneto-sensitive elements measure two components of the magnetic flux density substantially at the same spot located halfway between two magnets axially stacked and having a thickness substantially varying as a sinusoidal function.

17. An angular position sensor for a travel close to 360°

according to claim 16, characterised in that the two magnets are angularly shifted with respect to each another.

18. A magnetic position sensor according to claim 1, characterised in that the magnetic position sensor incorporates an outer magnetic field armoring device comprising a ferromagnetic material positioned close to the position sensor.

19. A magnetic position sensor according to claim 1, wherein the at least two magneto-sensitive elements are located at the same point relative to at least one direction of the coordinate system.