EP1346264B1 - Analog electronic watch having a time reset device following power shortage - Google Patents

Abstract

The invention concerns an electronic watch comprising analog display means (1) consisting of at least a hand (2) driven by at least a motor (3), a time base (4) for controlling the means powering (8) the motor, a rechargeable power source (9), and means for stopping (14) the motor, which act in particular on the powering means and time counting means (18) synchronously with the display means for adequate power supply. When a power shortage is detected by the stop means, the display means are stopped, the corresponding value of the counting means is stored in storage means and the counting means continue to operate. When sufficient power is restored, means computing time difference (20) send signals representing the time difference (21) between the stored value and the value of the time counting means to the powering means for time reset of the analog display means.

Description

The present invention relates to an electronic watch which comprises analogue display means consisting of at least one needle driven by at least one motor, a time base for controlling drive means of said motor, a rechargeable power source, motor stopping means acting in particular on said drive means and time counting means in synchronism with said analog display means for a sufficient supply voltage of the source.

A watch comprising means for detecting insufficient power supply to the motor is known in particular from the document WO 98/33098 . This document presents an electronic watch comprising electrically driven and electronically controlled needles containing time data, a power source and means for detecting the insufficiency of this source. In case of insufficient power the needles are brought and maintained on reference positions programmed in advance in the electronic means.

This watch has some disadvantages. Indeed, the hands of the watch are the reflection of the value of a counter of the electronic means. This is why it is necessary to bring the needles into a reference position, during a power failure, to force the value of this counter to a programmed reference value before the watch is switched on. Thus, this clock synchronized needles can no longer be used as a timer. It is therefore necessary to have a second counter that counts the time during a power failure. On the other hand, during normal operation of the watch, which represents the majority of the operating time, the two counters contain the same values. These two counters unnecessarily complicate the electronic means of the watch.

The document EP-A-1 014 227 discloses an electronic watch according to the preamble of claim 1.

The main purpose of the invention is therefore to overcome the drawbacks of the abovementioned prior art by providing an electronic watch which comprises simplified electronic means that do not require the programming of a reference value for the time-release following an insufficiency of time. 'food.

For this purpose, the subject of the invention is an electronic watch of the type mentioned in the introduction, which is characterized in that, when a lack of power is detected by said stop means, said display means are stopped and the corresponding value of said counting means is stored in means of storage, said counting means continuing to operate, and in that time difference calculation means send, as soon as the supply is again sufficient, time difference signals between the stored value and the value of the means of counting said training means for the time setting of said analog display means.

Advantageously, said motor stopping means are actuated for a first threshold voltage corresponding to the detection of a power failure of the motor and they are kept actuated as long as a second voltage, of threshold greater than the first voltage of threshold has not been reached by the power source, which avoids problems related to the variation of supply voltage due to load variations when stopping elements such as the engine.

This second threshold voltage corresponds to a determined load level of the power source.

Indeed, when stopping one of the energy-consuming elements such as the motor, it is common that rechargeable power sources of the battery or accumulator type have their voltage level which varies somewhat. This variation of the supply voltage is a phenomenon known to those skilled in the art. When the load of the power source becomes insufficient to supply the current necessary for the operation of the watch, stopping a power-consuming element, such as the motor, causes a large drop in load and power requirements, which causes a variation of the supply voltage. This discontinuity in the discharge of the power source creates, as shown in Figure 3, a transient period (t1, t1 + dt), during which the engine is stopped and restarted several times in succession until the voltage level is insufficient to operate the motor again. This transitional period prematurely wears the parts of the watch which are thus actuated and then stopped. In addition, the user may think of a malfunction of his watch by seeing the needles stop, move to a reference position and restart several times in a row.

According to a variant of the invention, it is possible, during the detection of a power failure, to provide a sufficient period of time for maintaining the stop means activated in order to avoid the effects of the variation of the charging load. the power source between t1 and t1 + dt described above.

The storage means may be composed in particular of a non-volatile memory.

• la figure 1 représente une vue d'ensemble du dispositif de mise à l'heure selon un mode de réalisation préféré de l'invention ;
• la figure 2 représente l'état du moteur en fonction de la tension délivrée par la source d'alimentation ;
• la figure 3 représente une période de décharge / recharge de la source d'alimentation dans un dispositif de l'art antérieur, et
• la figure 4 représente une période de décharge / recharge de la source d'alimentation dans un dispositif selon l'invention.

Other features and advantages of the present invention will become apparent from the following description, given by way of example and with reference to the accompanying drawings, in which:

• Figure 1 shows an overview of the time setting device according to a preferred embodiment of the invention;
• FIG. 2 represents the state of the motor as a function of the voltage delivered by the power source;
• FIG. 3 represents a discharge / recharge period of the power source in a device of the prior art, and
• FIG. 4 represents a discharge / recharge period of the power source in a device according to the invention.

Figure 1 shows the elements of the watch necessary for the understanding of the invention. The electronic watch comprises analog display means 1 generally consisting of at least two hands 2. One serves to indicate the hours and the other the minutes. It is possible to provide a third needle for indicating, for example, seconds.

The needles 2 are driven by at least one motor 3. Preferably, the hour hand and the minute hand are driven by a stepping motor and that of the seconds is driven by another stepper motor. Indeed, for the sake of saving energy, the motor driving the seconds hand can be stopped earlier.

The arrangement of motors and cogs for driving the needles will not be described here. Indeed, there are already known watch movements comprising several motors for actuating, for example, individually needles.

A time base 4 makes it possible to define for each motor 3 the pitch for the advance of the needle 2 associated with said motor. The time base 4, generally used, consists in particular of a crystal oscillator, referenced 5 and 6, and different frequency divider stages 7 of the oscillator 6 to drive each motor 3 with the desired pitch. Drive means 8 or motors 3 are provided for this purpose.

The motor 3 is powered by a rechargeable power source 9 of the accumulator or battery type. This power source 9 can be recharged in various ways, including the use of photovoltaic cells, oscillating weight, or by electrical contacts. The latter method will be used preferably to satisfy a need for fast and complete recharging.

Voltage comparators 11 and 12 are placed at the output of the supply source 9. They receive as input a fraction of the supply voltage obtained by a voltage divider, for example a resistive bridge, and a voltage V ' _S1 , respectively V ' _S2 . These voltages are a reflection of the threshold voltages V _S1 and V _S2 (see FIGS. 2 to 4).

V _S1 corresponds to a voltage sufficient to ensure synchronization between the time indication of the analog display 1 and the pulses supplied by the time base 4 to the drive means of the motor 8. Typically, the value of this voltage is chosen with a safety factor in relation to the minimum voltage necessary for the correct operation of the motor 3.

V _S2 corresponds to a determined load level for which the load is deemed sufficient to restart the engine. The latter could still function properly below this voltage. This second threshold voltage also makes it possible to avoid the effects as discussed with reference to FIG.

Obtaining reflective voltages V ' _S1 and V' _S2 is achieved by means of a conventional circuit known to those skilled in the art. This circuit, not shown, comprises means for supplying a reference voltage to which a resistive voltage divider bridge is applied, defining the two voltages V ' _S1 and V' _S2 . These two voltages are therefore lower than the threshold voltages V _S1 and V _S2 .

The comparator 11, respectively 12, compares the fractional supply voltage with the reflection voltage V ' _S1 , respectively V' _S2 . These comparison means 11 and 12 are operational as long as the supply voltage is greater than a minimum voltage V _OUT (see FIG. 4).

Advantageously, there is provided switching means, not shown, leaving only the comparator 11 active when discharging the power source 9, and conversely leaving the comparator 12 active when charging the power source 9.

Stop means 14 of the engine retrieve the results of the comparisons. These means make it possible, in particular, to detect an insufficiency of supply of the source 9. According to the state of the power supply and according to the preceding state of the motor provided by a signal 13, these stop means 14 will send to the means of power supply. drive 8 a motor status control signal 15, which will be either an engine stop signal or a start signal of the engine. The evolution of these engine states as a function of the comparisons made by the comparators 11 and 12 will be studied in detail in FIG. 2.

The means for stopping the engine are in particular connected to a reset circuit 17. This time reset circuit 17 is composed of at least one counter 18 for counting the time according to the pulses, received by the time base 4, storage means composed of at least one memory 19 for storing the contents of the counter 18 and means for calculating the time difference 20 allowing to obtain the offset 24 between the position of the hands 2 and the exact time.

The counter 18 operates continuously as long as the power source 9 delivers a minimum voltage V _OUT sufficient to supply the time base 4 and operate said counter 18. Below this voltage V _OUT , no function is ensured. to work properly. In general, this voltage V _OUT is substantially lower than the first threshold voltage V _S1 , which leaves the user with a sufficient amount of time, for example, a minimum of several hours, to be aware of the insufficiency of feeding, the needles 2 being stopped. The user can then recharge the battery or battery 9 while keeping accurate time information.

During a power failure, the motor 3 is stopped as well as the needles 2. The stop means 14 then send the information signal 16a concerning the stopping of the motor to a memory 19. The value then contained in the counter 18 is stored in the memory 19. Preferably, a nonvolatile memory 19 is used.

When the motor 3 is restarted, an information signal 16b is sent to the difference calculation means 20. Thus, these means 20 perform the subtraction between the current value 22 of the counter 18 and the stored value 23 in the memory 19 The result obtained is in the form of time difference signals 21 which are sent to the driving means of the motor 8 in order to reset the hands 2 to the time. Needles 2 are brought on time by the shortest path. Depending on the value of the difference, the drive means 8 control the rotation of the motor 3 in one direction or the other.

1. 1. 0 heure ≤ (heure actuelle - heure mémorisée) < 6 heures rotation : sens des aiguilles d'une montre ;
2. 2. 6 heures ≤ (heure actuelle - heure mémorisée) < 12 heures rotation : sens inverse des aiguilles d'une montre ;
3. 3. -12 heures < (heure actuelle - heure mémorisée) ≤ -6 heures rotation : sens des aiguilles d'une montre ;
4. 4. -6 heures < (heure actuelle - heure mémorisée) < 0 heure rotation : sens inverse des aiguilles d'une montre ;

An example of realization could be the following one:

1. 1. 0 hour ≤ (current time - stored time) <6 hours rotation: clockwise;
2. 2. 6 hours ≤ (current time - stored time) <12 hours rotation: counterclockwise;
3. 3. -12 hours <(current time - stored time) ≤ -6 hours rotation: clockwise;
4. 4. -6 hours <(current time - stored time) <0 hour rotation: counterclockwise;

Other embodiments for bringing the needles to the hour by the shortest path can also be envisaged.

FIG. 2 represents the operation of the motor stopping means 14 as a function of the comparisons made by the comparators 11 and 12 and as a function of the state of the motor 15, seen in FIG. 1.

On the abscissa, is represented the supply voltage delivered by the source 9. This voltage can vary between 0 and V _MAX . The zero voltage corresponds to the voltage delivered when the battery or the accumulator 9 is totally discharged. The voltage V _MAX corresponds to the maximum voltage delivered when the battery or accumulator is fully charged. The voltage V _OUT , defined earlier, corresponds to the minimum voltage for which the data of the counter 18 is accurate. The voltages V _S1 and V _S2 correspond to the two threshold voltages whose associated reflective voltages V ' _S1 and V' _S2 make it possible to control the state of the motor.

In ordinate, is represented the state in which is the motor. If the state corresponds to A, the motor is stopped. If the state is M, the motor is running.

Starting from a state of maximum load of the power source 9, the voltage delivered is V _MAX . At this supply voltage, the energy supplied is sufficient, the motor is therefore running, that is to say in the M state.

With time and the use of the time functions of the watch, the battery or the accumulator 9 discharges. When the supply voltage becomes lower than the threshold voltage V _S1 , the energy supplied by the source is no longer sufficient to ensure synchronization between the time base 4 and the hourly indication of the hands 2. The means stopping of the motor 14 are actuated and the motor 3 is stopped via the drive means of the motor 8. The motor 3 goes to the state A.

Once the engine 3 stopped, the hands 2 are also stopped. The value of the time counter 18 is stored, the counter continues to operate. The majority of the energy consumed by the device is the energy consumed by the engine. The latter stopped, consumption becomes very low. Therefore, the watch can still calculate the time during the entire period of time during which the supply voltage is less than V _S1 but greater than V _OUT .

The user seeing the needles 2 stopped then knows that the battery or the accumulator 9 must be recharged. When recharging the power source 9, the motor 3 is restarted only from a second threshold voltage V _S2 greater than V _S1 and corresponding to a determined minimum charge level. The stop means 14 remain actuated, during charging, for a value between V _S1 and V _S2 , because the state of the engine is A.

Figures 3 and 4 show a conventional discharge / recharge cycle of the power source 9 as a function of time, according to the prior art (Figure 3) and according to the invention (Figure 4).

As described in the introduction of this description, a device, according to Figure 3, leads to the creation of a transitional period that we want to avoid.

Indeed, during the discharge, when the supply voltage becomes lower than the threshold voltage V _S1 , t1, the motor is stopped. Now, the engine is the majority consumer of energy of the device. Therefore, when stopped, the battery charge drops sharply.

The supply voltage again becomes greater than V _s1 . At the same time, the result of the comparator 11 between the fraction of the supply voltage and the associated reflection voltage V ' _S1 , controlling not only the stop, but also the running of the motor, becomes again positive, thus, the engine is restarted immediately after shutdown. There is then a transitional period during which the motor and therefore the needles are stopped and restarted several times in a row. This period ceases, at t1 + dt, when the overvoltage is no longer sufficient to restart the engine.

In a device according to the invention, as in FIG. 4, two reflective voltages V ' _S1 and V' _S2 associated with the threshold voltages V _S1 and V _{S2 are used} to manage the means for stopping the motor 14, which makes it possible to avoid the disadvantage, mentioned above, current in the devices of the prior art provided with battery or accumulator 9.

For this, a second threshold voltage V _S2 greater than V _S1 is provided. The value of V _S2 is taken in such a way that it is greater than the voltage V _S1 to which is added the overvoltage due to the stopping of the main consumer, that is to say, when the motor stops. 3.

Thus, the disadvantages related to the variation of the supply voltage due to load variations are avoided. The power source 9 goes directly into a lower energy operating mode. Therefore, the discharge slope is much less pronounced between instants t1 and t2. The moment t2 represents the moment when the user realizes that the hands 2 of his watch are stopped and decides to recharge the battery or the accumulator 9. The recharge is represented between times t2 and t3.

According to a variant of the invention, it is also possible, during the detection of a power failure, to provide a sufficient period of time to avoid the effects of the variation of the load between t1 and t1 + dt, represented in Figure 3. This period of time may possibly be programmed according to the needs of a user.

Of course, other embodiments of an electronic watch according to the invention could still be described to the knowledge of a person skilled in the art without departing from the scope of the invention defined by the claims.

Claims (5)

1. Electronic watch including analogue display means (1) formed of at least one hand (2) driven by at least one motor (3), a time base (4) for controlling means (8) for driving said motor, a rechargeable power source (9), means (14) for stopping the motor (3) acting particularly on said drive means (8), time counting means (18) in synchronism with said analogue display means (1) for a sufficient supply voltage, characterized in that when said stopping means (14) detect a power shortage, said display means (1) are stopped and the corresponding value of said counting means (18) is stored in storage means (19), said counting means (18) continuing to operate, and in that, as soon as the power supply is sufficient again, time difference calculating means (20) send time difference signals (21) between the stored value and the value of the counting means to said drive means (8) in order to reset said analogue display means to the right time.
2. Electronic watch according to claim 1, characterized in that said motor stopping means (14) are activated for a first threshold voltage (V_S1) corresponding to detection of a power shortage for the motor (3) and in that they are kept activated as long as a second threshold voltage (V_S2) greater than the first threshold voltage (V_S1) has not been reached by the power source.
3. Electronic watch according to claim 2, characterized in that the second threshold voltage (V_S2) corresponds to a determined charge level of the power source (9).
4. Electronic watch according to claim 1, characterized in that said stopping means (14) are kept activated during a period of time sufficient to avoid the load change effects in the power source, upon detection of a power shortage.
5. Electronic watch according to any one of claims 1 to 4, characterized in that the display means (1) are reset to the right time, when the motor stopping means (14) are deactivated, by the shortest route.

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