Electromechanical apparatus comprising a capacitive device for detection of the angular position of a wheel set, and method for detection of the angular position of a wheel set

Patent metadata

Field	Value
Publication number	US-2016178402-A1
Application number	US-201514978452-A
Country	US
Kind code	A1
Filing date	Dec 22, 2015
Priority date	Dec 23, 2014
Publication date	Jun 23, 2016
Grant date	—

Abstract

Electromechanical apparatus comprising a wheel set and an analogue indicator member ( 14 ) which are integral in rotation, a stepping motor, and a capacitive device for detection of the angular position of the wheel set, comprising a rotor ( 4: 10 ), a stator ( 18 a , 18 b , 20 a , 20 b , 22, 24, 26 a , 26 b , 26 c ) and an electronic measuring circuit ( 28 ), the stator comprising a first pair of electrodes ( 18 a , 18 b ) having a first capacitance (C 1 ) and a second pair of electrodes ( 20 a , 20 b ) having a second capacitance (C 2 ), the rotor being adapted such that the values of the two capacitances depend on the angular position of the rotor, and an electronic measuring circuit ( 28 ) being provided for generating an output signal representative of a difference between the respective values of the first (C 1 ) and of the second (C 2 ) capacitance.

First claim

What is claimed is:

1 . An electromechanical apparatus comprising a wheel set and an analogue indicator member which are integral in rotation, a stepping motor, an electronic control circuit arranged to control the stepping motor, a drive train connecting the stepping motor to the wheel set and to the analogue indicator member, and a capacitive detection device, the drive train having a ratio such that the stepping motor causes the wheel set to make exactly one complete revolution in a determined integer number of motor steps, so that the motor steps subdivide one complete revolution of the wheel set into said integer number of mutually equidistant angular positions, and the capacitive detection device comprising a rotor integral in rotation with the wheel set, a stator and an electronic measuring circuit, the stator comprising a first pair of electrodes having a first capacitance, the rotor being adapted such that the value of the first capacitance depends on the angular position of said rotor, and the electronic measuring circuit being arranged to generate and to provide to the electronic control circuit a signal dependent on the value of the first capacitance;
wherein the stator includes a second pair of electrodes having a second capacitance, the value of the second capacitance depending on the angular position of said rotor, wherein the pairs of electrodes and the electronic measuring circuit are configured such that the signal is representative of a difference between the respective values of the first and of the second capacitance, and wherein the electronic control means contain a stored correspondence table which contains reference values for the signal as a function of the angular position of the rotor for said mutually equidistant angular positions of the wheel set.

2 . The electromechanical apparatus according to claim 1 , wherein the electronic control circuit includes a circuit for counting the control impulses of the stepping motor, in order to count the steps made by the stepping motor.

3 . The electromechanical apparatus according to claim 2 , wherein the stepping motor is a bipolar motor arranged to be powered by current impulses whose flow direction must be inverted at each step in order to operate the motor in a determined direction, and wherein the correspondence table which is stored in the electronic control circuit contains, in addition to the reference values for the signal as a function of the angular position of said rotor, an indication of parity (even or odd) for each angular position of said rotor, depending on whether an even motor step or an odd motor step is required to reach the angular position in question.

4 . The electromechanical apparatus according to claim 1 , wherein the rotor of the capacitive detection device comprises a wheel made of a conductive material and whose plate is pierced with an opening of determined shape and dimensions, the capacitive detection device being arranged so that one electrode of the first pair and one electrode of the second pair are at least partially opposite said opening respectively in a first and a second angular position of said rotor.

5 . The electromechanical apparatus according to claim 1 , wherein the electrodes of the first and of the second pair extend in the same plane perpendicular to the axis of said rotor.

6 . The electromechanical apparatus according to claim 5 , wherein the two pairs of electrodes are isometric to each other, and superposable by rotating one of the two pairs about the axis.

7 . The electromechanical apparatus according to claim 1 , wherein the stator of the capacitive detection device comprises a conductor that connects one of the electrodes of the first pair to one of the electrodes of the second pair.

8 . The electromechanical apparatus according to claim 1 , wherein the analogue indicator member is a hand.

9 . The electromechanical apparatus according to claim 8 , wherein the hand is integral with the rotor, the hand pointing in the direction of the centre of the opening so that the unbalance caused by the presence of the opening can at least partially compensate for the torque caused by the weight of the hand.

10 . The electromechanical apparatus according to claim 1 , wherein the correspondence table which contains the reference values for the signal as a function of the angular position of said rotor is stored in a non-volatile memory of the electronic control circuit.

11 . The electromechanical apparatus according to claim 9 , wherein the reference values for the signal define a function of the angular position of said rotor, the function being a piecewise linear function.

12 . A method for determination of the angular position of a wheel set integral in rotation with an analogue indicator of an electromechanical apparatus according to claim 1 , the method including the steps of:
I. controlling the stepping motor so as to cause a rotor integral with said wheel set to make one complete step-by-step revolution, and to store signal values provided by the electronic measuring circuit for at least one in two of said mutually equidistant angular positions of said wheel set; II. drawing, from the stored table matching at least one part of the integer number of mutually equidistant angular positions of the wheel set to as many reference values of the signal, a plurality of sequences of reference values respectively corresponding to the various possible circular permutations of said at least one in two angular positions of said mutually equidistant angular positions, and calculating a correlation between the succession of stored values of the signal provided and each of the sequences of reference values; III. determining the angular position of said analogue indicator by identifying among the correlations calculated for the various sequences of reference values, the correlation whose value is maximum.

13 . The method for determination of the angular position of a wheel set according to claim 12 , wherein in step (I), the values of the signal provided by the electronic measuring circuit are stored for all said mutually equidistant angular positions of the wheel set, and wherein, in step (II), the number of reference value sequences is equal to said determined number, the sequences respectively corresponding to the various circular permutations of all said equidistant angular positions.

14 . The method for determination of the angular position of a wheel set according to claim 12 , wherein the stepping motor of the electromechanical apparatus is a bipolar motor arranged to be powered by current impulses whose direction of flow must be inverted at each step in order to operate the motor in a determined direction, the method wherein said determined number is an even number, wherein in step (I), the values of the signal provided by the electronic measuring circuit are stored for one in two of the mutually equidistant angular positions of the wheel set, and wherein, in step (II), the number of reference value sequences is equal to half of said determined number, the sequences respectively corresponding to the various circular permutations of said one in two of the mutually equidistant angular positions.

15 . The method for determination of the position of a wheel set according to claim 12 , comprising a preliminary step of creating a correspondence table, said creation step including a generation of a theoretical curve and an adjustment of the parameters of said theoretical curve over an empirical curve provided by the capacitive detection device.

16 . The method for determination of the pos

Assignees

• Eta Sa Mft Horlogere Suisse

Inventors

• Klopfenstein Francois
• Lagorgette Pascal
• Schmutz Damien
• Haenni Raphael
• Tardivon Matthieu

Classifications

• G04C3/146

  incorporating two or more stepping motors or rotors · CPC title

• G04C3/14 Primary

  incorporating a stepping motor (G04C3/02 - G04C3/12 take precedence {; generating commutating pulses in primary clocks G04C13/0463}) · CPC title

• G01R27/26

  Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants {; Measuring impedance or related variables} · CPC title

• G04C3/002

  Position, e.g. inclination dependent switches · CPC title

• G04D7/1207

  only for measuring · CPC title