EP0203330B1 - Electronic time piece with a detector of the end of the life span of the battery - Google Patents

Abstract

The timepiece comprises an oscillator (1), a frequency divider (2), a control circuit (3), a stepping motor (4), a seconds hand (5), a circuit (7) for detecting steps missed by the motor, an up-down counter (15) having a capacity N, and a flip-flop (16). At each missed step the detecting circuit (7) generates a tally pulse (S7) which increments the counter (15). The latter is also decremented by periodic pulses appearing on the B output of the frequency divider (2). When a cell supplying the timepiece is nearly exhausted, the number of steps missed per unit of time is high and the counter (15) is, on balance, incremented. When passing from state N-1 to state N the counter issues on its Qh output a pulse that causes the Q output of the flip-flop (16) to go high. The control circuit (3) produces, in response to this high state of the flip-flop, a signal warning of the imminent end of the cell's life in the form of an irregular motion of the seconds hand (5). Otherwise, when the cell is still good, the number of missed steps is low and the counter (15) is decremented. When passing from state 1 to state 0 the counter issues on its Qb output a pulse that causes the Q output of the flip-flop (16) to go low, thereby stopping the warning signal.

Description

The present invention relates to an electronic timepiece comprising means for producing driving pulses, a motor comprising a rotor and means for rotating the rotor by a determined angle in response to each driving pulse, an autonomous source for supplying electrical energy the means for producing the driving pulses, means for producing a signal for detection of the approaching end of life of the source, and means for producing a warning signal in response to the detection signal.

Electronic timepieces, particularly watches, clocks and analog alarm clocks, are well known and their operation is entirely reliable as long as the energy contained in the source of electrical energy is sufficient.

These small timepieces mainly use batteries as autonomous electrical energy sources. As the available energy of the battery decreases, some of its parameters change, in particular the voltage across the battery drops. In high energy density batteries, such as watchmaking batteries containing mercury, silver or lithium, this drop in voltage is very rapid when the battery runs out. However, sufficient battery voltage is an essential condition for the proper functioning of the part, in particular of the engine. When the voltage drops below a critical threshold, the part begins to present the first signs of failure, then, a few days later, it stops definitively. The first signs of failure are manifested in the form of erratic rotations of the motor rotor in response to the driving impulses, while other parts of the workpiece, such as electronic circuits, which are less sensitive to voltage, continue to operate normally until '' when the engine stops completely.

Uncertainty about the end of battery life is a major drawback, which has considerably slowed down the distribution of the first electronic timepieces.

To overcome this difficulty, it has been proposed to incorporate an electronic end-of-life detector into electronic timepieces. This detector, in known embodiments, is composed of an electronic circuit accurately measuring the battery voltage, and an electronic circuit producing the warning signal when the voltage reaches the critical threshold, to make the user attentive. of the next engine shutdown.

A voltage measurement circuit, usable in a watch, is for example described and represented in US Pat. No. 4,024,415 where the terminal X in FIGS. 8 and 9 changes logic state when the battery voltage, designated by V _DD , drops below the critical threshold.

This information is used to produce the warning signal. This signal can, for example, take the form of a periodic modification of the rate of advance of the second hand, causing a limping of this hand, without however causing the loss of the hour or an increase in the consumption of motor energy. Such a modification can be obtained by means of a circuit described, for example, in patent CH 607 603.

Since electronic circuits can operate safely when the battery voltage is no longer sufficient to run the engine, this type of detector would be satisfactory if the voltage measurement circuit did not present major difficulties in implementation.

Indeed, the voltage around the critical threshold must be measured with great precision, to within a few tens of millivolts. This precision must not be influenced by temperature or by the aging of the elements. However, these performances are very difficult to achieve, even with circuits specially developed for this purpose which often require external components to be individually adjusted, which complicates manufacture and increases the cost price.

On the other hand, such a detector can only function correctly with the type of battery for which it was designed, for example mercury, and if the battery is replaced by a silver battery having a different critical threshold, the detector will provide an incorrect indication. However, currently, the trend is to produce timepieces that can function indifferently with mercury, silver or lithium batteries. No known end-of-life detector can therefore be used in this type of timepiece.

The present invention proposes to overcome these drawbacks by producing a timepiece provided with a very reliable end-of-life detector and suitable for various types of batteries.

The invention therefore relates to an electronic timepiece comprising means for producing driving pulses, a motor comprising a rotor and means for rotating the rotor by a determined angle in response to each driving pulse, an autonomous source. for supplying electrical energy to the means for producing the driving pulses, means for producing a signal for detecting the near end of life of said source, and means for producing a warning signal in response to said detection signal, said means for producing the detection signal comprising means for producing a control signal each time the rotor does not rotate correctly in response to a driving pulse, and a counter directly incremented by said control signal, said counter producing, in response in a predetermined state, said detection signal, remarkable in that said counter is a front-back counter re which is directly incremented by said control signal and decremented by periodic signals.

• la fig. 1 représente le schéma d'une forme de réalisation du circuit de la pièce d'horlogerie selon l'invention; et
• la fig. 2 représente le schéma d'une autre forme de réalisation du circuit de la même pièce d'horlogerie.

Other properties and advantages of the timepiece according to the present invention will emerge from the description which follows, given with reference to the appended drawing and giving by way of explanation but in no way limiting, examples of embodiment of such a piece of watchmaking. In this drawing, where the same references relate to similar elements:

• fig. 1 represents the diagram of a form of realization of the timepiece circuit according to the invention; and
• fig. 2 shows the diagram of another embodiment of the circuit of the same timepiece.

The circuit shown in fig. 1 comprises an oscillator 1, for example quartz, a frequency divider 2, a control circuit 3, a stepping motor 4 comprising a rotor which drives, by means of a gear train not shown, display of the hour and in particular an aperture 5 indicating the seconds, a circuit for detecting missed steps giving a signal each time the motor has not rotated in response to a driving impulse from the control circuit, a counter 8 , two AND gates 9 and 10 with two inputs, an OR gate 11 with two inputs and an inverter 12. A battery, not shown, supplies energy to all the circuits and the motor 4.

The output S of oscillator 1 provides a reference signal which is applied to the input E of the frequency divider 2. On the main output S of this divider 2 appears a time signal, for example of 1 Hz, which is applied at the input E of the control circuit 3. The divider 2 also supplies, on a multiple output A, logic signals of various frequencies, on an output B a signal formed by one pulse per minute and on an output C a signal formed by one pulse per hour. All these signals are derived in a known manner from the oscillator signal and the frequencies of the last two signals can, of course, be different from those indicated.

The control circuit 3 receives on a multiple input B the signals coming from the output A of the frequency divider 2 and it elaborates, in a manner known per se, using combinational logic circuits and from these signals and the signal schedule applied to its input E, a control signal S ₃ which appears on its output S. The signal S ₃ is formed by a series of driving pulses following each other at one second intervals. This signal is applied to the stepping motor 4 and, in response to each driving pulse, the rotor turns by a given angle so as to advance the second hand 5 by one second.

Circuit 3 also includes an input A whose logic state influences the position of the driving pulses relative to each other, without changing their number, and, consequently, modifies the movement of the motor 4. When input A is at the low logic level, the pulses, which can be separated into even and odd pulses, are regularly distributed over time and the motor thus advances by one step every second, causing the second hand to move at the same rate 5. On the other hand, when the input A is brought to the high logic level, the even pulses are offset with respect to the odd pulses so, for example, that an even pulse is immediately followed by an odd pulse. The engine then advances two close steps every two seconds. The seconds hand 5 then advances irregularly, giving the impression of limping, while continuing to indicate the exact time. This clearly perceptible limp constitutes the warning signal, informing the user of an imminent breakdown of the part. An example of a circuit making it possible to obtain the irregular advancement of the second hand is shown in FIG. 1 of the patent CH 607 603 already cited. References P and S visible in this figure correspond respectively to the input A of the control circuit 3 and to the motor 4 of Figures 1 and 2 of this case. The circuit 3 can also include an input C, the function of which will be explained below.

The control signal S ₃ is also applied to the input E of the missed step detector circuit 7. This circuit delivers on its output S a control signal S ₇ indicating the non-rotation of the rotor of the motor 4 in response to a driving pulse. of the signal S ₃ , the malfunction of the engine being able to result from several effects, in particular from the exhaustion of the battery supplying the timepiece.

Various embodiments of missed step detector circuits are known, in particular that represented in the diagram of FIG. 12 of patent CH 628 201. In this circuit the signal applied to the motor contains, between two driving pulses, a short test pulse of duration insufficient to cause the rotor to rotate. This test pulse creates in the motor a current which crosses a measurement resistor, referenced 117, and causes at its terminals a voltage which is compared with a reference voltage thanks to a differential amplifier 110 at the output of which appears a logic signal H The signal H corresponds to the control signal S ₇ of the circuits of the present case. This signal remains at low logic level as long as the motor rotor turns normally in response to each drive pulse. On the other hand, if the rotor does not rotate during a driving pulse, this missed step is signaled by a brief passage to the high logic level of the signal H before the next driving pulse.

The pulse of the signal H which appears when the rotor has not turned triggers, in the circuit of the last document cited, a driving correction pulse intended to make up for the lost step.

To improve the efficiency of the correction pulse and to prevent the timepiece from losing the time, the duration of this pulse is chosen to be greater than that of the normal driving pulses provided for operating the engine with minimum energy.

The catching up of lost steps can also be used in the timepiece according to the present invention, but it is not necessary to produce the warning signal of the end of life of the battery. The control circuit 3 includes for this purpose the input C which can be connected to the output S of the circuit 7. In response to any pulse on the signal S ₇ , the circuit 3 then produces a driving pulse of correction on the signal S ₃ .

The output S of the circuit 7 is connected to an input of the AND gate 9, the output of which is connected to the counting input C of the counter 8 which delivers on its output Q a logic detection signal Q ₈ of missed steps. This counter has a capacity N and it will be assumed that on power-up it goes into the state N = 0. Its output Q then remains at the low logic level as long as it has counted less than N pulses. This output goes to logic level high at the Nth pulse to fall back to logic level low at the pulse next session. The output Q is connected to the input A of the circuit 3 to cause the limping of the needle 5 indicating the end of life of the battery. The output Q is finally connected to the input of the inverter 12, the output of which is connected to the other input of the AND gate 9 and to an input of the AND gate 10. The output of the latter gate is connected to a input of the OR gate 11, the output of which is connected to the reset input R of the counter 8. The other input of the AND gate 10 and the other input of the OR gate 11 are respectively connected to the outputs B and C of divider 2.

The operation of the circuit shown in Figure 1 is as follows. When the circuit is powered up using a new battery, the Q output of counter 8 goes to logic low. The input A of the control circuit 3 being at the same logic level, the output S of this circuit produces, in response to the signals from the oscillator 1 and the frequency divider 2, a control signal S ₃ which advances the regu - firstly the second hand 5. The low logic level of the output Q causes a high logic level on the inputs of the AND gates 9 and ET 10 which are connected to the output of the inverter 12. These two doors therefore allow passage the signals present on their other inputs.

As the battery becomes depleted, its voltage drops and from a certain critical threshold the motor 4 begins to miss steps. At each failed step there appears on the output S of the detector 7 a pulse which passes through the AND gate 9 to increment the counter 8 by one unit. Furthermore, the signal supplied by the divider 2 on its output B passes through the AND gate 10 and OR gate 11 to reset the counter to zero once per minute. It follows that, if the number of steps missed by the motor during each minute is less than N, the counter 9 will never be completely filled and its output Q, delivering the detection signal Q ₈ , will be permanently at the logic level low. On the other hand, as soon as the number of missed steps per minute reaches or exceeds N, at the Nth step not missed the output Q of the counter 8 goes to the high logic level as well as the detection signal Qs. This causes a low logic level at the output of the inverter 12, blocking the AND gates 9 and 10. The signal corresponding to (N + 1) 1 "not missed therefore does not reach the counter 8, any more than the pulses of minutes present on the output B of the divider 2. The output Q of the counter 8 therefore remains permanently at the high logic level, causing the appearance of the warning signal by the hand 5.

Of course, if the missed steps are caught, the timepiece continues to indicate the exact time, without the operation of the circuit which has just been described being modified.

The number N is arbitrary and marks the boundary between the number of failed steps per acceptable time unit, resulting from transient causes such as shock or the influence of an intense magnetic field, and the number of failed steps indicating failure next permanent part, mainly due to exhaustion of the battery.

Whatever the value of N chosen, situations can always occur in which the warning signal indicates by error the next end of life of the battery, the timepiece having simply been subjected, for example, to a field magnetic which stopped this motor for a sufficiently long time. Once removed from this field, the part naturally resumes normal operation.

To avoid such erroneous information, the counter 8 is periodically reset to zero, for example once per hour, by the signal appearing on the output C of the frequency divider 2, transmitted on the input R of the counter 8 through the door OR 11. The warning signal then indicates that the battery is exhausted only if it persists for at least one hour.

The diagram of another embodiment of the circuit of the part according to the invention is shown in FIG. 2. We recognize in this figure the elements referenced 1 to 7 already described in connection with the first embodiment of the circuit and arranged in the same manner as in FIG. 1.

The circuit of fig. 2 further comprises a front-rear counter 15 having two inputs C and D and two outputs Q _h and Q _b . This counter 15 can count up to N + 1. It is therefore likely to be in N + 1 different states 0, 1, 2, ... N-1 or N. Its entry C makes it possible to count forward or, in other words, increment the counter 15, while its input D makes it possible to count back, or to decrease the counter. The output Q _h of this counter 15 is an upward overshoot output. This output delivers a pulse when the counter goes from state N-1 to state N in response to a pulse applied to input C. The output Q _b is, for its part, an output for going below . It delivers a pulse when the counter goes from state 1 to state 0 in response to a pulse applied to input D. The passage of counter 15 from state N to state 0, or from state 0 to state N, on the other hand, produces no signal on the outputs Q _h and Q _b . The input C of the counter 15 is connected to the output S of the missed step detector 7, while its input D is connected to the output B of the frequency divider 2. The output Q _h of the counter is connected to the input of setting to state S of a flip-flop RS 16, while the output Q _b is connected to the reset input R of this same flip-flop. Finally the flip-flop 16 has an output Q which is connected to the input A of the control circuit 3. A signal in the high logic state, applied to the input S of the flip-flop 16, also puts its output Q at the high logic state, while the same signal applied to its R input puts its Q output at the low logic level. On the other hand, a signal at the low logic level has no effect on the inputs of flip-flop 16.

The operation of the circuit shown in fig. 2 is as follows. Assuming that the battery supplying the timepiece still has a good reserve of energy, the number of missed steps will be low, for example less, on average, than one missed step per minute. The counter 15 will therefore receive on its input C, on average, a lower number of pulses than on its input D which, being connected to the output B of the frequency divider 2, receives one pulse per minute. The counter will thus be decremented on average and, when it goes from state 1 to state 0, the pulse generated by output Q _b will reset to zero the flip-flop 16 or will confirm this state, The output Q of the flip-flop being then at the low logic level, and consequently also the detection signal Q ₁₆ , the timepiece will not produce any warning signal at the end of battery life.

On the other hand, if the stack reaches exhaustion, the number of missed steps will be high, for example greater, on average, than one missed step per minute. The counter 15 will therefore be incremented on average and, when it passes from state N-1 to state N, the pulse generated by the output Q _h will bring the output Q of the flip-flop 16 to the logic high level, making pass the detection signal 0 ₁₆ in the same state. This high level of the signal 0 _{1 6 will} cause the warning signal of the next end of life of the battery, in the same way as in the case of FIG. 1.

Of course the frequency of the pulses arriving at the input D of the counter 15 may be different from that taken as an example and, if each missed step is caught up, this correction will in no way influence the operation of the circuit.

As a variant, the timepiece may comprise, in place of the display by hands, an electro-optical display provided with a sign indicating the end of the life of the battery, for example with liquid crystals or light emitting diodes, referenced 6 in figs. 1 and 2. The control input of this display is connected to the output Q of the counter 8 or to the output Q of the flip-flop 16. In response to a high logic level of the detection signal G ₈ or Q ₁₆ on these outputs , the end of life sign becomes apparent and constitutes the warning signal equivalent to that obtained above by the limping of the second hand 5.

The present invention also applies to timepieces using a control circuit which continuously adjusts, by discrete steps, the duration of the driving pulses, comprised between a minimum value and a maximum value, at the momentary load of the motor, so as to avoid the engine consuming unnecessarily high energy. This duration is chosen so that the number of missed steps per unit of time remains below a certain limit, each missed step being caught up to avoid losing the exact time. A timepiece provided with such an improvement is described in detail, for example, in US Pat. No. 4,326,278. The warning signal for the end of the battery life may then be produced, as has has been described above, only when the duration of the motor pulses has for some time reached its maximum duration.

It is understood that the timepieces which have just been described may undergo other modifications which are obvious to those skilled in the art, without departing from the scope of the present invention.

Claims (4)

1. An electronic timepiece comprising means (3) for producing drive pulses, a motor (4) having a rotor and means for turning the rotor through a set angle in response to each drive pulse, an autonomous source for supplying the drive pulse, producing means with electric energy, means (7, 8, 9; 7, 15, 16) for producing a detection signal (Q₈; Q₁₆) representative of the imminent end of the source's life and means (6) for producing a warning signal in response to the signal from the detecting means, the detecting means (7, 8, 9; 7, 15, 16) including means (7) for producing a tally signal (S₇) whenever the rotor does not turn correctly in response to a drive pulse, and a counter (8; 15) arranged to be incremented by said tally signal, with said counter producing, in response to a predetermined state, the detection signal characterized in that said counter (15) is an up-down counter which is directly incremented by the tally signal and decremented by periodic signals.

2. An electronic timepiece according to claim 1, characterized in that the detecting means include means (10, 11) for periodically resetting said counter (8) to zero.

3. An electronic timepiece according to any of the preceding claims, characterized in that the drive pulse producing means (3) include means enabling the rhythm of the drive pulses to be modified in response to said detection signal.

4. An electronic timepiece according to any of the preceding claims, characterized in that it further comprises electro-optic display means (6) that change the appearance of their display in response to said detection signal.

Images