Position sensor and method for determining a position of a timepiece setting stem

Patent metadata

Field	Value
Publication number	US-10267653-B2
Application number	US-201515514729-A
Country	US
Kind code	B2
Filing date	Sep 22, 2015
Priority date	Oct 20, 2014
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

A position sensor and method for determining an axial and/or an angular position of a setting stem of a timepiece. A magnet is provided on the setting stem, and at least one magnetic field sensor is configured to detect changes in magnetic field strength along at least a first axis and a second axis as the rotatable element rotates; the second axis is not parallel to the first axis. The changing magnetic field sensed by the magnetic sensor is converted into a characteristic signature path which may then be mapped onto a circular signature path in two dimensions to derive the angular position of the setting stem.

First claim

The invention claimed is:

1. A position sensor for determining an axial and/or an angular position of a rotatable element of a timepiece, the position sensor comprising:
a permanent magnet configured to rotate with the rotatable element about a rotation axis of the rotatable element;
a magnetic field sensor, static with respect to the timepiece and configured to measure a magnitude and an orientation of an incident magnetic field along at least a first axis and a second axis, and detect changes in the magnetic field magnitude and orientation, due to rotation of the magnetic field of the permanent magnet, along the first axis and the second axis as the rotatable element rotates, the second axis being not parallel to the first axis;
means for deducing angular orientation from the measured magnitude and orientation of the magnetic field.

2. The position sensor according to claim 1 , wherein the permanent magnet is arranged in a distal axial region of the rotatable element.

3. The position sensor according to claim 1 , wherein the permanent magnet is arranged in a circumferential region of the rotatable element.

4. The position sensor according to claim 1 , wherein the magnetic field sensor comprises at least three mutually non-parallel measurement axes.

5. The position sensor according to claim 1 , further comprising a transform unit to perform a mapping transform between a first frame of reference to a second frame of reference.

6. The position sensor according to claim 5 , wherein the second frame of reference comprises a circular signature path in two dimensions.

7. The position sensor according to claim 5 , wherein the first frame of reference comprises an elliptical signature path in three dimensions.

8. The position sensor or method according to claim 1 , wherein the permanent magnet is configured to move axially with the rotatable element during an axial movement of the rotatable element.

9. The position sensor according to claim 8 , wherein the rotatable element has at least a first and a second predetermined axial position, wherein a rotation of the rotatable element in the first predetermined axial position is associated with a first timepiece function, and a rotation of the rotatable element in the second predetermined axial position is associated with a second timepiece function or no timepiece function.

10. The position sensor according to claim 8 , wherein the magnetic sensor comprises a first sensing mode, in which the magnetic sensor is configured to detect the axial movement of the rotatable element, and a second sensing mode, in which the magnetic sensor is configured to detect the rotation of the rotatable element.

11. The position sensor according to claim 10 , wherein the magnetic sensor is configured to perform sensing at a first resolution and/or at a first sampling rate when the position sensor is in the first sensing mode, and to perform sensing at a second resolution and/or at a second sampling rate when the position sensor is in the second sensing mode, wherein the first resolution is lower than the second resolution and/or the first sampling rate is lower than the second sampling rate.

12. The position sensor according to claim 1 , further comprising a shielding arranged around the position sensor to shield components of the timepiece from the magnetic field of the permanent magnet.

13. The position sensor or method according to claim 1 , wherein the rotatable element is assembled to, or unitary with, a setting stem of the timepiece.

14. A method of determining a position of a rotatable element of a timepiece, the method comprising:
arranging a permanent magnet to rotate with the rotatable element about a rotation axis of the rotatable element;
using a magnetic field sensor to measure a magnitude and an orientation of an incident magnetic field along at least a first axis and a second axis and detect changes in the magnetic field magnitude and orientation, due to rotation of the magnetic field of the permanent magnet, along the first axis and second axis as the rotatable element rotates, the second axis being not parallel to the first axis;
deducing the angular orientation from the measured magnitude and orientation of the magnetic field.

15. The method according to claim 14 , further comprising performing a mapping transform between a first frame of reference to a second frame of reference.

16. The method according to claim 14 , wherein the second frame of reference comprises a circular signature path in two dimensions.

17. The method according to claim 14 , wherein the first frame of reference comprises an elliptical signature path in three dimensions.

Assignees

• Swatch Group Res & Dev Ltd

Inventors

• Ferri Yvan
• Hoover David
• Born Jean-Jacques

Classifications

• G04C3/004

  Magnetically controlled · CPC title

• G01S5/22

  Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements (G01S5/28 takes precedence) · CPC title

• G01S5/18

  using ultrasonic, sonic or infrasonic waves · CPC title

• G01S5/0081 Primary

  Transmission between base stations · CPC title

• G01D5/14 Primary

  influencing the magnitude of a current or voltage · CPC title