MAGNETIC MULTI-TURN ABSOLUTE POSITION DETECTION DEVICE

• US 20130169270A1
• Filed: 08/12/2011
• Published: 07/04/2013
• Est. Priority Date: 08/24/2010
• Status: Active Grant

• Current Assignee: Moving Magnet Technologies
• Original Assignee: Moving Magnet Technologies
• Inventors: Biwersi, Stphane, Delbaere, Michal, Masson, Grald, Ronnat, Yannick
• Granted Patent: US 9,316,482 B2
• Time in Patent Office: Days
• US Class Current: 324/207.25
• CPC Class Codes: G01B 7/30 for measuring angles or tapers; for testing the alignment of axes
• CPC Class Codes: G01D 2205/26 Details of encoders or position sensors specially adapted to detect rotation beyond a full turn of 360°, e.g. multi-rotation
• CPC Class Codes: G01D 2205/80 Manufacturing details of magnetic targets for magnetic encoders
• CPC Class Codes: G01D 5/24409 Interpolation using memories
• CPC Class Codes: G01D 5/2458 with incremental and absolute tracks on separate encoders
• CPC Class Codes: G01L 3/104 involving permanent magnets

Abstract

The disclosure relates to a magnetic device for detecting the absolute position of an input shaft capable of rotating more than 360°, the device including a main magnetic sensor, a motion reducer, and a secondary magnetic sensor, wherein the main magnetic sensor is connected to a rotor, measures the rotation of the shaft for ranges of angles of less than 360°, and includes a main magnet, the motion reducer converts the rotation of the shaft into a reduced rotation, the maximum amplitude of which is equal to no more than 360°, and the secondary magnetic sensor measures the reduced rotation and includes a secondary magnet. According to the disclosure, the secondary magnet is arranged between the upper and lower planes of the main rotor, and the main magnet has P pairs of poles, where P is greater than 1.

Claims

1. A magnetic device for detecting the absolute position of a rotating input shaft, the device comprising:

a main rotor comprising a main magnet secured to the input shaft effecting a travel of n times 360°

, n being greater than 1, and a driving member of a motion converter;

at least one first magnetosensitive probe delivering, over a magnetic angle of 360°

, a signal proportional to a direction of a magnetic field generated by the main magnet to derive a measurement of absolute position of the input shaft;

a secondary magnet having two magnetic poles and effecting a travel of around 360°

under effect of the rotation of the input shaft via a motion converter;

at least one second magnetosensitive probe delivering, over a magnetic angle of around 360°

, a signal proportional to the direction of a magnetic field generated by the secondary magnet and able to derive therefrom a measurement of absolute position of the secondary magnet;

the second probe and the secondary magnet constituting a position sensor of epsilon precision, expressed as a percentage;

the secondary magnet being substantially positioned within a height H defined by upper and lower planes of the main rotor; and

the main magnet being multipole and having P pairs of poles, where P is greater than 1.

2. A magnetic device for detecting the absolute position according to claim 1, wherein P is less than an integer part of 360/T, with

3. A magnetic device for detecting the absolute position according to claim 1, wherein the main magnet inscribes in an inner volume of the driving member.

4. A magnetic device for detecting the absolute position according to claim 1, wherein the P poles are sinusoidally-magnetised.

5. A magnetic device for detecting the absolute position according to claim 1, wherein the P poles are radially magnetised.

6. A magnetic device for detecting the absolute position according to claim 1, wherein the P poles are gradually saturatedly magnetised.

7. A magnetic device for detecting the absolute position according to claim 1, further comprising electronics which, by signals from the two magnetosensitive probes, makes it possible to logically derive an absolute position of the input shaft.

8. A magnetic device for detecting the absolute position according to claim 1, wherein the main magnet is associated with at least two magnetosensitive probes.

9. A magnetic device for detecting the absolute position according to claim 8, wherein the two magnetosensitive probes are offset angularly by an angle equal to 360.i/P−

F90/P degrees where i is a natural integer that may be zero.

10. A magnetic device for detecting the absolute position according to claim 1, wherein the first and second magnetosensitive probes are of the Hall effect type each being capable of reading two distinct signals representing 2 of the 3 magnetic components generated by either one of the main and secondary magnets.

11. A magnetic device for detecting the absolute position according to claim 1, wherein the probes calculate an electrical angle β

after multiplying one of 2 signals B1 and B2 by a gain G such that

12. A magnetic device for detecting the absolute position according to claim 1, wherein at least one of the magnetosensitive probes is of the magnetoresistive type.

13. A magnetic device for detecting the absolute position according to claim 1, wherein at least one of the magnetosensitive probes is associated with a flux concentrator.

14. A system comprising at least one magnetic device detecting an absolute position and a steering column, the magnetic device detecting the torsion of the steering column;

the at least one magnetic device operably detecting the relative angular position of coaxial input and output shafts connected by a torsion bar in order to derive therefrom the torsion torque exerted on the bar, including a first rotor magnetic structure comprising a plurality of magnets, and a second stator structure in the vicinity of which at least one magnetosensitive probe is placed;

a main rotor comprising a main magnet secured to the input shaft effecting a travel greater than 360°

, and a driving member of a motion converter;

at least a first magnetosensitive probe delivering, over a magnetic angle of 360°

, a signal proportional to a direction of a magnetic field generated by the main magnet and deriving therefrom a measurement of absolute position of the input shaft;

a secondary magnet having two magnetic poles and effecting a travel of around 360°

under effect of the rotation of the input shaft via a motion converter;

at least a second magnetosensitive probe delivering, over a magnetic angle of around 360°

, a signal proportional to the direction of a magnetic field generated by the secondary magnet and deriving therefrom a measurement of absolute position of the secondary magnet;

the second probe and the secondary magnet constituting a position sensor;

the secondary magnet being substantially positioned within a height defined by upper and lower planes of the main rotor; and

the main magnet having multiple pairs of poles;

the main magnet being substantially concentric with the stator structure;

at least one of the magnetosensitive probes of the relative angular position detection device and the first and second probes being substantially positioned within the height defined by the upper and lower planes of the main rotor.

15. A magnetic device for detecting the absolute position according to claim 14, further comprising a ferromagnetic ring interposed between the multipole main magnet of the position sensor and the second stator structure of the device for detecting the relative angular position.

16. A magnetic device for detecting the absolute position according to claim 14, wherein the second stator structure of the device for detecting the relative angular position includes a plastic support and a ferromagnetic part, the multipole main magnet and the driving member of the motion converter being integrated in the plastic support.

17. A magnetic device for detecting the absolute position according to claim 16, wherein the driving member of the motion converter and a plastic support are the same piece.

18. A magnetic device for detecting the absolute position according to claim 17, wherein the plastic support is moulded onto the multipole main magnet.

19. A magnetic device for detecting the absolute position according to claim 14, wherein a the number P′

of pairs of magnetic poles in the plurality of magnets is equal to k times a number P of pairs of magnetic poles of the main magnet, k being an integer.

20. A magnetic device for detecting the absolute position according to claim 14, wherein a number P of pairs of magnetic poles of the main magnet is equal to k times the number P′

of pairs of magnetic poles in the plurality of magnets, k being an integer.