EP2936254B1 - Thermocompensated chronometer circuit - Google Patents

Description

TECHNICAL AREA

The present invention relates to an electronic watch comprising one or more electric motors for driving analog display means, a watch module comprising a time base supplying a clock signal connected to a divider circuit, said divider circuit supplying a reference signal sent to a control circuit arranged to control the electric motor (s).

TECHNOLOGICAL BACKGROUND

It is known in the prior art, visible at the figure 1 , a time base formed by a piezoelectric resonator, for example, such as a quartz resonator 1, or a silicon resonator of the MEMS type connected to the terminals of an oscillator 2 whose output is connected to a frequency divider circuit 3 for obtain the desired running frequency for the watch so as to indicate the exact time. The output of the frequency divider circuit 3 is connected to a control circuit 4 of an electric motor 5 making it possible to drive the cogs, not shown here, rotating the analog display means, such as needles serving to supply the gear. indication of the time, ie hours, minutes and possibly seconds. The resonator, the oscillator, the divider circuit and the control circuit are installed in the same box 6. The documents EP 1 890 204 A1 and EP 2 169 479 A1 represent examples of this type of prior art.

However, this configuration does not make it possible to have a circuit independent of temperature fluctuations since no thermal compensation circuit is provided.

Thermally compensated watch circuits are known. These circuits include a watch module connected to a quartz and also connected to a temperature measurement and correction circuit. This measurement and correction circuit is thus arranged to measure the temperature and to correct the operation of the watch circuit. The documents GB 1,581,917 A US 2009/160569 A1 represent examples of this type of prior art.

A drawback of these circuits is that they take up space, that is to say that their surface area is large and that the calibration is carried out at the level of the calibers mounted. This leads to an increase in the manufacturing cost of the correction of the temperature dependence on the gauges. In addition, this configuration is sensitive to moisture that can infiltrate into the case of the timepiece. This sensitivity to humidity leads to a degradation in the precision and reliability of the watch circuit.

Moreover, for a watch circuit having a chronograph function, the disadvantage of having an additional module and therefore the same problems of surfaces and of sensitivity to humidity is added.

We also know the document US 3,902,312 A . This document describes an electronic watch comprising an outer case in which are mounted at least one electric motor for driving analog display means and a watch module comprising a time base supplying a clock signal connected to a divider circuit, said circuit. divider supplying a reference signal sent to a control circuit arranged to control said electric motor. A thermal compensation circuit is arranged in the time base. Finally, this document reveals that the time base, the thermal compensation circuit, the divider circuit and the control circuit are arranged in the same internal resin case, to form said watch module.

SUMMARY OF THE INVENTION

The invention relates to an electronic watch which overcomes the aforementioned drawbacks of the prior art by providing a watch whose time display is reliable and precise and whose manufacturing cost is lower.

To this end, the invention relates to an electronic watch as defined in independent claim 1 as well as to a calibration method as defined in independent claim 8.

Preferred embodiments are defined in the dependent claims.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 est un schéma d'une montre électronique avec affichage analogique selon l'art antérieur;
• la figure 2 est un schéma d'une montre électronique avec affichage analogique ayant une partie des caractéristiques de l'invention;
• la figure 3 est un schéma d'une montre électronique avec affichage analogique selon l'invention;

Other characteristics and advantages of the watch according to the present invention will emerge more clearly on reading the detailed description. of embodiments of the invention given solely by way of non-limiting example and illustrated by the appended drawing where:

• the figure 1 is a diagram of an electronic watch with analog display according to the prior art;
• the figure 2 is a diagram of an electronic watch with analog display having some of the characteristics of the invention;
• the figure 3 is a diagram of an electronic watch with an analog display according to the invention;

DETAILED DESCRIPTION OF THE INVENTION

Part of the invention is shown in the figure 2 . In this figure we see an electronic timepiece comprising a watch circuit 10 provided with a watch module 12. This watch module 12 comprises a time base 14 formed by a resonator 14a, for example piezoelectric, such as a quartz resonator, or else a MEMS type silicon resonator connected to the terminals of an oscillator 14b. This oscillator 14b is used to supply a clock signal Sh at a clock frequency. This clock frequency is generally 32768 Hz, conventionally called 32kHz. In the rest of the description, it will be understood that the term 32kHz refers to this value of 32768 Hz.

The output of the oscillator is connected to a frequency divider circuit 16 to obtain the desired running frequency for the watch so as to indicate the exact time. For example, the divider circuit 16 will output a frequency of 1 Hz so that the second hand can move one step per second. The output of the frequency divider circuit 16 is connected to a control circuit 18. This control circuit 18 is used in order to manage the clock module 12, that is to say to adjust the running of the timepiece and manage functions such as low battery mode. It will be understood that the control circuit 18, the time base 14 and the frequency divider circuit 16 can be in the form of the same component.

The watch circuit 10 is also provided with an electric motor M1 making it possible to drive the cogs, not shown here, rotating the analog display means, such as hands 22 serving to provide the time indication, ie hours, minutes and possibly seconds. The electric motor is connected to the control circuit 18 which controls the operation of said electric motor M1.

Advantageously according to the invention, the control circuit 18, the time base 14 and the frequency divider circuit 16 are arranged in the same housing 13 and the clock circuit further comprises a measurement and correction circuit 26 allowing a thermo. compensation. This measurement and correction circuit 26 is placed between the oscillator circuit 14b and the frequency divider circuit 16. This measurement and correction circuit 26 is used to thermally compensate the watch module 12, that is to say that in depending on the temperature, it will act on the signal leaving oscillator 14b, that is to say the clock signal Sh. The measuring and correction circuit 26 acts so that the signal leaving said measuring circuit and correction 26 is accurate on average over a defined period. For this, the measurement and correction circuit 26 inhibits pulses on the clock signal Sh. Therefore, the assembly formed of the time base 14 and of the measurement and correction circuit 26 supplies a signal Si, of which the frequency is lower than the frequency of the clock signal Sh. This is due to the fact that the measurement and correction circuit 26 inhibits pulses, that is to say that it suppresses pulses. For example, for a 32 kHz clock signal, an 8192Hz frequency signal conventionally called 8 kHz thermo-compensated, that is to say precise and reliable, will be supplied by this assembly formed of the time base 14 and of the control circuit. measurement and correction 26.

To improve the reliability of the watch module 12, the case 13 in which it is arranged is made of ceramic and is hermetically sealed before calibration. The housing 13 is placed under vacuum and then closed. This ensures that humidity will not be able to infiltrate said case 13. Consequently, humidity will have no influence on the precision of the watch module 12.

Indeed, one aspect of the invention consists in providing a calibration method making it possible to obtain a timepiece circuit 10 that is reliable over time.

For this, the method consists in assembling the control circuit 18, the time base 14, the frequency divider circuit 16 and the measurement and correction circuit 26 in the same housing 13 in order to form the clock module 12. Then, the calibration is done in batch, that is to say in parallel. It will then be understood that a plurality of watchmaking modules 12 are calibrated at the same time. This calibration then consists in measuring the characteristics of the resonator 14a as well as of the measuring circuit 26 as a function of the temperature and then in determining the correction parameters.

These correction parameters are stored in the measurement and correction circuit 26. Thus, the correction parameters of each resonator 14a of a plurality of clock modules 12 are determined simultaneously.

This method then has the advantage of allowing the calibration of a large number of watchmaking modules 12 simultaneously and therefore of reducing the costs associated with this calibration.

Advantageously according to the invention, this configuration makes it possible to simply produce a thermo-compensated chronograph watchmaking module 30 as visible at the bottom. figure 3 .

Indeed, the present invention provides for using the clock signal of the watch module 12 to clock a chronograph module 30. This chronograph module 30 comprises a control circuit and circuits making it possible to operate the hands of the chronograph function. For example, the control circuit of the chronograph module 30 is arranged to operate two motors M2 and M3. In this case, it is conceivable that there is no motor M1 connected to the clock module 12.

According to the invention, the chronograph module 30 is clocked with the thermo-compensated signal, that is to say the signal Si exiting from the measurement and correction circuit 26 of the watch module 12. In the example cited above, for a clock signal Sh having a frequency of 32 kHz, a thermo-compensated signal Si of frequency 8 kHz is obtained.

Therefore, the chronograph module 30 is a module which does not have its own time base, which reduces its cost.

This thermo-compensated signal Si supplied by the watchmaking module 12 is used to reconstruct signals useful for the chronograph module 30. For example, the thermo-compensated signal can be used to reconstruct a signal at a higher frequency to clock a control circuit. of the chronograph module. As a result, the chronograph module control circuit can operate the motors M2, M3 associated with this chronograph function.

The reconstructed higher frequency signal can be used for a function of determining the position of the cogs.

This possibility of clocking a chronograph module 30 with a thermo-compensated signal from a watchmaking module has advantages.

Firstly, it makes it possible to produce a simple thermo-compensated chronograph watch module. In fact, known chronograph watch modules directly use the signal at the output of the 32KHz resonator to operate. However, by using the signal directly at the output of the resonator, the latter cannot be thermo-compensated. As a result, the operation of the chronograph watch module becomes random. Likewise, by using an existing thermo-compensated signal, we avoids having to produce a chronograph module 30 comprising its own time base and its own measurement and correction circuit.

On the contrary, with the present invention, it is possible to obtain a watch circuit 10 with an entirely thermo-compensated chronograph function and at lower cost. Indeed, the present invention uses the single watch module 12 and its thermo-compensated signal Si of 8 kHz frequency to thermo-compensate the chronograph module 30 by ensuring that the thermo-compensated signal is used by said chronograph module. As a result, it is easy to switch from a watch module to a chronograph watch module.

In addition, this configuration makes it possible to have a chronograph watch module that is more economical in electrical energy. In fact, the chronograph module uses a thermo-compensated clock signal with a frequency lower than the frequency of the time base 14. However, the higher the frequency, the greater the losses linked to the interconnection capacities. Indeed, the transport of a signal of a certain frequency on a printed circuit is subjected to the capacitive effects, inductive and to the effects of skin which can take place. These effects are all related to frequency implying an increase in losses related to these effects as a function of frequency. Therefore, to compensate for the losses, it is necessary to provide more electrical power.

With the configuration according to the invention, a lower frequency is used to clock the chronograph module and therefore the losses linked to overconsumption are lower.

It will be understood that various modifications and / or improvements and / or combinations obvious to a person skilled in the art can be made to the various embodiments of the invention described above without departing from the scope of the invention defined by the appended claims.

Claims (10)

1. Electronic watch comprising an outer case wherein is arranged at least one electric motor (M1) for driving analogue display means, a clock module (12) comprising a time base (14) delivering a clock signal (Sh) connected to a divider circuit (16), said divider circuit delivering a reference signal sent to a control circuit (18) arranged to control said electric motor, and wherein the clock module (12) further comprises a measuring and correction circuit (26) arranged between the time base and the divider circuit and delivering an intermediate thermocompensated signal (Si), the time base, the measuring and correction circuit, the divider circuit and the control circuit being arranged in the same inner case (13) to form said clock module, and said watch further comprising a chronograph module (30) connected to the clock module (12), said chronograph module being directly clocked by the intermediate thermocompensated signal (Si) from the clock module.
2. Electronic watch according to claim 1, characterised in that the time base comprises a resonator (14a) and an oscillator circuit (14b).
3. Electronic watch according to claim 1, characterised in that the time base (14) delivers a 32 kHz clock signal.
4. Electronic watch according to claim 1, characterised in that the chronograph module (30) is arranged to control at least one electric motor (M2, M3).
5. Electronic watch according to any of the preceding claims, characterised in that the case (13) of the clock module is hermetically sealed.
6. Electronic watch according to any of the preceding claims, characterised in that the case (13) of the clock module (12) is an integrated circuit in which the time base is incorporated.
7. Electronic watch according to any of the preceding claims, characterised in that the case (13) of the clock module is made of ceramic.
8. Method of calibrating at least one clock module (12) comprising a time base (14) delivering a clock signal (Sh) connected to a divider circuit (16), said divider circuit delivering a reference signal sent to a control circuit (18) arranged to control said electric motor, the clock module further comprising a measuring and correction circuit (26) arranged between the time base and the divider circuit and delivering an intermediate thermocompensated signal (Si), the method including the following steps:

   - assembling the module (12) by assembling the time base, the divider circuit, the control circuit and the measuring and correction circuit (26) in an inner case (13), then by closing this case (13);

   - measuring the characteristics of the time base (14) as a function of temperature;

   - determining correction parameters;

   - storing the correction parameters in the measuring and correction circuit (26);

   - connecting a chronograph module (30) to the clock module (12),

   - clocking said chronograph module (30) by the intermediate signal (Si) compensated from the clock module.
9. Calibration method according to claim 8, characterised in that the case (13) is hermetically vacuum sealed.
10. Calibration method according to claim 8, characterised in that a plurality of clock modules (12) are simultaneously calibrated.

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