Measurement of the precision of a timepiece comprising a continuous rotation electromechanical transducer in the analogue time display device thereof

Patent metadata

Field	Value
Publication number	US-11892807-B2
Application number	US-202016854041-A
Country	US
Kind code	B2
Filing date	Apr 21, 2020
Priority date	Jun 6, 2019
Publication date	Feb 6, 2024
Grant date	Feb 6, 2024

Abstract

A method for measuring the medium frequency of a digital signal derived from a reference periodic signal generated by an electronic oscillator (quartz oscillator) forming a timepiece (2) which includes an analogue time display device and a continuous rotation electromechanical transducer (generator or continuous rotation motor) which is kinematically linked to this display device and wherein the medium rotational speed is regulated by a regulation device. The medium frequency of the digital signal is determined by a measurement device (70) without galvanic contact with the movement of the timepiece. The measurement method makes it possible to determine the rate of the timepiece and the precision of the electronic oscillator based on regulation impulses detected by a magnetic sensor (72) and over a measurement period limited to the duration of an inhibition cycle of periods of the reference periodic signal.

First claim

The invention claimed is:

1. A method for controlling a timepiece ( 2 ) based on a medium frequency of a digital signal (SDP, SDI) which is derived from a reference periodic signal (SPR) generated by an oscillator ( 26 ) forming an electronic time base ( 25 ) of the timepiece ( 2 ), this timepiece comprising a movement ( 4 ) incorporating a mechanism formed by a kinematic chain ( 8 ) which is arranged between a motor device ( 6 ; 10 ) of the movement and an analogue time display device ( 12 ), the motor device being formed by or the kinematic chain comprising or the kinetic chain being kinematically linked to a continuous rotation electromechanical transducer ( 6 ) of which the medium rotational speed is regulated by a regulation device ( 50 ), associated with the electronic time base, according to a nominal rotational speed, this regulation device being arranged to successively supply to the electromechanical transducer regulation impulses (BPn) to regulate the medium rotational speed thereof, these regulation impulses defining respectively the same events (tf n) which are synchronised on the rising edges or on the falling edges of said digital signal and which are detectable, by a measurement device ( 70 ) without galvanic contact with the movement, at respective detection times having the same time phase-shift with said same events;
the method comprising the following steps:
A) successively supplying to the electromechanical transducer the regulation impulses (BPn) to regulate the medium rotational speed thereof, these regulation impulses defining respectively the same events (tf n) which are synchronised on the rising edges or on the falling edges of said digital signal;
B) measurement, without galvanic contact with the movement, of a plurality of successive time intervals (TI n ) each occurring between two detection times which are detected for two respective regulation impulses among said regulation impulses;
C) determination, for each time interval of the plurality of time intervals, of a corresponding whole number (M n (S DP ), M n (S DI )) which is equal to the rounded result (NR n (S DP ), NR n (S DI )), to the nearest integer, of the division of this time interval by the theoretical medium period (PT DP , PMT DI ) given by said digital signal;
D) summation of the whole numbers determined in step C) for the plurality of time intervals, to thus obtain a total number of periods of said digital signal;
E) summation of the measured time intervals of the plurality of time intervals, to thus obtain a total measurement duration (T Mes ) corresponding to said total number of periods; and
F) calculation of the medium frequency of said digital signal by dividing the total number of periods by said total measurement duration; and
G) controlling the timepiece to operate by correcting a number of inhibitions applied to the digital signal based determining that the calculated medium frequency is deviated from a predetermined value.

2. The method according to claim 1 , wherein the measurement of the plurality of successive time intervals in step B) is performed such that each is less than a maximum duration which is equal to the theoretical medium period for said digital signal divided by double the maximum relative error for the natural frequency (FNR) of the reference periodic signal relative to a theoretical reference frequency (FRT).

3. The method according to claim 1 , wherein said digital signal is a periodic digital signal (SDP) wherein the medium frequency is equal to the medium natural frequency, over said total measurement duration, of the reference periodic signal divided by a given whole number.

4. The method according to claim 3 , wherein the precision of said oscillator is determined by calculating a relative error given by the result of the division of the difference between said medium frequency of the periodic digital signal obtained in step F) and a theoretical medium frequency, equal to the reciprocal of said theoretical medium period (PT DP ), by this theoretical medium frequency.

5. The method according to claim 1 , wherein said digital signal is an inhibited digital signal (SDI) which has periods (PDI, PDI*) of variable durations according to an inhibition of a certain number of periods of the reference periodic signal during successive inhibition cycles.

6. The method according to claim 5 , wherein the precision of the analogue time display device is determined by calculating a relative error given by the result of the division of the difference between the medium frequency of the inhibited digital signal, obtained in step F), and a theoretical medium frequency, equal to the reciprocal of said theoretical medium period (PMTDI), by this theoretical medium frequency.

7. The method according to claim 6 , wherein the rate of the timepiece is obtained by multiplying said relative error by the number of seconds in one day.

8. The method according to claim 5 , wherein said inhibition is performed according to a process which distributes the inhibition of the certain number of periods of the reference periodic signal using each inhibition cycle; and in that the plurality of successive time intervals is envisaged such that the increase of the duration of any time interval among this plurality, resulting from the inhibition of one or more period(s) of the reference periodic signal during this time interval, is at most equal to half of one/said theoretical medium period of the inhibited digital signal.

9. The method according to claim 1 , wherein said electromechanical transducer is a generator ( 6 ) formed by a rotor ( 18 ) equipped with permanent magnets and a stator ( 16 ) comprising at least one coil ( 22 A, 22 B, 22 C) through which a variable magnetic flux, which is generated by the magnets of the rotor when the latter is rotating, passes; and in that said regulation impulses are braking impulses of the rotor each generated by a momentary short-circuit of said at least one coil.

10. The method according to claim 1 , wherein said electromechanical transducer is a continuous rotation motor formed by a rotor equipped with permanent magnets and a stator comprising at least one coil through which a variable magnetic flux, which is generated by the magnets of the rotor when the latter is rotating, passes, the continuous rotation motor forming said motor device; and in that said regulation impulses are motor electrical impulses which are each generated by a momentary electrical power supply of said at least one coil.

11. The method according to claim 9 , wherein said regulation device is arranged to generate regulation impulses in such a way that, in normal operation, any two successive regulation impulses have between the respective starts (td n ) thereof the same positive whole number of alternations of an induced voltage signal generated by said variable magnetic flux in said at least one coil when the rotor is rotating; and in that the regulation of the medium rotational speed of the rotor is obtained by a variation of the duration of the regulation impulses.

12. The method according to claim 9 , wherein said regulation device is arranged to generate regulation impulses in such a way that, in normal operation, any two successive regulation impulses have between the respective starts (td n ) thereof the same positive whole number of alternations of an induced voltage signal generated by said variable magnetic flux in said at least one coil when the rotor is rotating; in that the regulation impulses have, at least over a certain regulation period, substantially the same duration; and in that the regulation of the medium rotational speed of the rotor during said regulation period is

Assignees

• Swatch Group Res & Dev Ltd

Inventors

• Born Jean-Jacques
• Nagy Laurent

Classifications

• G04C3/16 Primary

  incorporating an electro-dynamic continuously rotating motor (G04C3/02 - G04C3/12 take precedence) · CPC title

• G04C10/00

  Arrangements of electric power supplies in time-pieces {(Mounting, assembling of components G04C3/008)} · CPC title

• G04F5/10

  using electric or electronic resonators (G04F5/14 takes precedence) · CPC title

• G04C3/00 Primary

  Electromechanical clocks or watches independent of other time-pieces and in which the movement is maintained by electric means (clocks driven by synchronous motors G04C15/00) · CPC title

• G04C11/00

  Synchronisation of independently-driven clocks · CPC title