HK1009530B - Electronic timepiece comprising a generator driven by a spring barrel - Google Patents

Description

Electronic timepiece with generator driven by barrel

The invention concerns an electronic timepiece whose power supply is constituted by a barrel, which can be wound manually or automatically, coupled to an alternator for supplying power to the electronic circuits of the electronic timepiece via a rectifier.

Such a timepiece is disclosed in swiss patent 686332. This patent document relates in particular to a control circuit which can control the rotation speed of the generator to a predetermined rotation speed corresponding to the normal operation of the timepiece, provided that the energy of the barrel is sufficient to maintain the required rotation speed value.

Timepieces equipped with a reserve power indicator in order to inform the owner of the timepiece when the barrel is exhausted of energy have long been known. Such an indicator is disclosed in european patent application EP0762243 in the name of the applicant of the present invention.

Such indicators generally operate as follows. During normal operation, the generator is directly coupled to the barrel and attempts to rotate too fast, so that the frequency of the voltage supplied is higher than the frequency value required by the frequency standard operating on the clock quartz. Therefore, the rotational speed of the generator must be reduced by periodically shorting the coils of the generator. The number of decelerations required to maintain the generator operating at the rated speed is large when the spring begins to relax, and gradually decreases as the energy stored in the spring is depleted.

This number of decelerations can then be used to determine when the energy of the spring is no longer sufficient to maintain the clock in proper operation. According to the principles disclosed in the above-mentioned patent application, the number of decelerations in a series is counted in successive time periods of a certain duration, during which time periods the number of decelerations is less than a predetermined value, a display may be activated to alert the user: the power reserve is quickly exhausted. In addition, the number of hours that the power reserve is still sufficient to display the correct time may also be displayed.

The timepiece of the prior art should therefore be equipped with another device, for example a window, followed by an indicator, in addition to the hands, which must be actuated in a particular manner as a function of the consumption state of the power reserve.

Furthermore, some battery-operated electronic timepieces are equipped with a battery consumption indicator which operates by means of a specific movement of one of the hands, in particular the second hand. Such electronic clocks and watches are also well known. Typically, these indicators operate by: the second hand has an interrupted action when the battery voltage drops below a predetermined minimum value, for example, taking a two second stroke on the dial every two seconds, instead of one pulse per second.

The invention provides an electronic timepiece in which a generator is driven by a barrel, and therefore a dedicated power reserve consumption indicator is not required, but power consumption can be indicated by a specific operation of a second hand, as in the case of a general motor-driven, battery-powered quartz timepiece.

Accordingly, an electronic timepiece of the present invention includes:

an alternating voltage generator connected to the electronic circuit of the electronic timepiece;

a barrel coupled to the generator to drive the generator;

a set of time hands also driven by said barrel;

the electronic circuit includes:

a time base for providing a standard frequency signal;

comparing means for comparing the frequency of said time base with the frequency of said alternating voltage, thereby generating an error signal;

the verifying device is connected with the comparing device and is used for verifying whether the error signal exceeds a first preset threshold value or not;

a speed reduction device controlled by the verification device to electrically reduce the rotational speed of the generator when the error signal exceeds the first predetermined threshold;

the timepiece is characterized in that:

said verification means also being adapted to verify whether said error signal exceeds a second predetermined threshold greater than said first predetermined threshold and to verify the degree of consumption of said barrel power reserve, said reduction means also being controlled when said second threshold is exceeded;

said verifying means is also configured to make it verify whether, after said error signal crosses said second predetermined threshold, said error signal becomes at least equal to a third predetermined threshold during a predetermined time for controlling said decelerating means at the expiration of said period of time;

such that each time the error signal reaches or exceeds the predetermined third threshold value, the respective hand is rotated at a speed higher than the corresponding speed indicating the correct time to indicate the consumption state.

Owing to these features, the exceeding of the second and third threshold values allows the electrical deceleration process of the generator to be controlled so as to rotate the second hand at regular intervals and instantaneously for an angle corresponding to several seconds from the moment when the barrel power reserve is consumed to a certain extent, causing the wearer to wind the barrel. This makes it possible to dispense with an auxiliary display which is dedicated to displaying the power reserve consumption.

Other features and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, by way of example only. In the drawings:

fig. 1 is a graph of the winding/unwinding of a barrel as a function of the number of revolutions of said barrel, showing the variation of the torque available to the spring, and in particular the consumption of the reserve of power;

FIG. 2 is a schematic diagram of a timepiece control circuit according to the invention;

FIG. 3 is a graph of the count value of the up-down counter used in the control circuit of FIG. 2 as a function of time to illustrate the operation of the control circuit;

fig. 4 shows another embodiment of this type of motor by means of a schematic diagram of a timepiece generator according to the invention.

Fig. 1 shows an example of the variation of the torque produced by a barrel that can be used in an electronic timepiece with a generator according to the invention. The figure shows the variation of the torque value of the barrel in grams of millimetres as a function of the number of revolutions thereof during winding and unwinding of the barrel. One winding of the barrel usually corresponds to about 8 hours of operation of the timepiece. Of course, all of these values and those given later are merely examples.

Curve a corresponds to the upper curve. Curve a starts from point a1, where the spring is completely relaxed, and ends at a maximum winding point a2 after the winding process of 7 barrel turns, the barrel potential torque at point a2 being about 1200 gmi.

Curve B is the unwinding curve of the spring barrel, during which the barrel supplies energy to the timepiece. The curve starts at point B1, at a torque value of about 1050 gms (this torque value is reduced from the torque value at point a2 because of unavoidable mechanical losses), and ends at point B2, at which the balance spring is fully relaxed, the point B2 of course coinciding with point a 1.

It should be noted that if the timepiece is self-winding, these curves will vary as a function of the actions added to the timepiece, both winding and unwinding operations varying with the environment and being closely coincident.

The critical torque value (C) is also indicated by the broken line T_{Critical point of}). As long as the barrel can provide a rotation greater than this thresholdThe rotor of the generator will always reach the rated speed required by the clock to keep correct timing. This threshold value may correspond, for example, to an output voltage frequency of the generator equal to 21.3 hz.

Beyond the point of change C of the curve B and the dotted line T_CTimepieces are generally considered to enter an "energy depleted" state, which is commonly referred to by watchmakers as "EOL", which is derived from the term "End of life", which is derived from simulating the End of battery life in a typical quartz watch. In this example, C_CThe point is located at a position of the spring corresponding to a degree of loosening of the spring of about 5.3 turns thereof. The EOL condition extends throughout the first phase PFI during which the generator is decelerated intermittently for a longer time, thus informing the user of the condition of a loose spring through a particular movement of the second hand of the timepiece, in particular the movement of the second hand in jumping.

The PFI phase takes the amplitude of about 0.75 turns of the barrel, as shown in the example of fig. 1, the following phase being the phase called "significant deceleration" of the generator. During this phase, the rotation speed of the generator is maintained at a value at which the rotation of the hands actually reaches a rotation number that is imperceptible to the wearer. This phase continues until the energy accumulated in the spring is almost completely exhausted (in the example after the seventh revolution).

However, the clock is free of wheels and is wound automatically or manually, and can still be started easily as long as sufficient winding is performed again. It will be seen later that the PFP stage may be immediately after the PFI stage, or separated from the PFI stage by a period of time I, the latter being the case in fig. 1, depending on certain parameters chosen at the time of circuit design.

Furthermore, according to another embodiment of the invention, which will be described in more detail later with reference to fig. 4, it is also possible to take the measure of reducing the rotational speed of the generator rotor by magnetic deceleration at the end of the PFP phase, for example by applying a slight magnetic positioning torque, preferably by means of at least one stationary magnet arranged at a suitably chosen distance near the rotor. This arrangement allows the barrel to be temporarily stopped from rotating while waiting for the spring to be wound again, either automatically or manually.

Referring now to fig. 2, there is shown a simplified diagram of a timepiece according to the invention.

The generator of the timepiece, represented by the box 1, is composed of a magnetized rotor 2 and at least one coil 3. The rotor is mechanically coupled, for example via a gear train 4, shown in dotted lines, to a barrel 5 in which a spring 6 is housed. The spring may be wound by a manual or automatic winding machine, which is well known and not shown. The gear train 4 is also coupled to a set of chronograph hands consisting of an hour hand 7, a minute hand 8 and a second hand 9. The hands are coupled to each other in a usual manner with a suitable gear ratio and are rigidly coupled to the rotor of the generator 1, so that they rotate as soon as the rotor 2 rotates.

The generator 1 supplies an alternating voltage at its terminals 1a and 1b, for example, with a frequency of 21.3 hz (64/3 hz) and a maximum value of 1.2 volts. The generator 1 is connected to a rectifier, for example a double alternating rectifier (double alternating rectifier)10, the output of which is connected to an integrated circuit 11, some components of the integrated circuit 11 forming a rotational speed control circuit for the generator 1. Input voltage V of integrated circuit 11_DDAnd V_SSIs constant. It should be noted that fig. 2 only shows those elements of the integrated circuit 11 which are essential for implementing the principles of the present invention.

The quartz 12 controls an oscillator forming part of the integrated circuit 11, which sends a pulsed signal with a frequency of 32768 hz to the frequency divider 13, the time base being formed by these elements.

The signal supplied by the terminal 14 of the frequency divider 13 has a frequency corresponding to the nominal frequency which the generator 1 must supply to enable the correct timing of the respective hands 7, 8, 9. In the above example, the nominal frequency is 21.3 Hz (64/3 Hz). The output 14 is connected to the count-up input 15 of the up-down counter 16.

The generator 1 has a terminal 1a connected to one input of a comparator 17, the other input of the comparator 17 being connected to a reference voltage source 18, for example to ground. The output of comparator 17 is connected to the down count input 19 of up-down counter 16.

As soon as the voltage at the generator terminal 1a slightly exceeds ground potential, the comparator 17 provides an output pulse to the up-down counter 16. Thus, in this example, assuming that the generator 1 is rotating completely at the nominal rotational speed corresponding to a frequency of 21.3 hz, the count value of the up-down counter 16 must be 0 at the end of each alternation of the generator output voltage.

The output of the up-down counter 16 is connected to a decision logic circuit 20. The decision logic 20 produces an output signal at terminal 21 as a function of some predetermined criterion, which we will talk back later, which is the data supplied through the wiring of a certain number of basic gates that make up the decision logic. Such decision logic circuits are made by those skilled in the art familiar with these criteria after studying this specification and will not be described in detail herein.

The signal present at the output 21 is applied to the control pole of a switching element 22 which selectively controls the deceleration of the generator 1. This switching element 22 may be a MOS transistor, the source/drain path of which is connected between the terminals 1a and 1b of the generator 1.

The control circuit of the present invention also employs a circuit 23 called a "start-up" circuit, commonly referred to as a POR (power on reset) circuit. It is known to those skilled in the art that such POR circuits are provided in particular in most integrated circuits, and in particular in those used in electronic clocks and watches, for setting the elements of the integrated circuit in a certain logic state, so that when a voltage is applied to the logic circuit, these elements can operate in the appropriate logic state.

In the arrangement of the invention the start-up circuit 23 has two complementary outputs 23a and 23b which change logic levels when the voltage applied to the integrated circuit 11 exceeds a predetermined value in one direction or the other, respectively. In the example, this value may be about 0.7 volts, ignoring any hysteresis that the signal may experience.

In particular, in the case of the present invention, the output 23a of the start-up circuit 23 is connected to the up-down counter 16, and the level of the up-down counter 16 takes "1" when its logic level goes from "0" to "1".

The output terminal 23b is connected to the substantial deceleration switching element 24. The switching element 24 may consist of a PMOS transistor, the drain/source path of which is connected in series with a resistor 25, the two elements together constituting the power supply terminal V of the parallel integrated circuit 11_DDAnd V_SSIs split. When the logic level at the output 23 of the start-up circuit 23 goes from "1" to "0", the switching element is turned on.

The timepiece of the invention operates as follows.

After winding of the barrel 6 has been completed and the timepiece is operating normally, the control circuit of the invention is responsible for the task of limiting the speed of rotation of the generator 1, since if it is not limited, it may overspeed until the energy accumulated in the spring is exhausted, driving the hands at high speed.

The speed limiting process is controlled by the presence of the speed reduction control transistor 22, which upon receipt of a corresponding signal from the decision logic 20, shorts the terminals 1a and 1b of the generator, thereby electrically reducing the speed of the generator. The decision logic circuit 20 continuously analyses the count value of the up-down counter 16 and provides a control signal to the transistor 22 as soon as the count value of the counter 16 equals "-1". It is in these cases. The generator frequency is higher than the frequency provided by the frequency divider 13 and the hands 7, 8, 9 will necessarily rotate too fast. The transistor 22 is now rendered conductive, so that the rotational speed of the generator is restored to the corresponding nominal rotational speed with correct timing.

Therefore, in order to maintain the rated speed of the generator 1, the control circuit constantly compares the standard frequency supplied by the frequency divider 13 with the frequency of the voltage supplied to the terminal 1a of the generator 1 and analyzed by the comparator 17.

In the example described, this operating condition lasts for about 5.3 revolutions of the spring plate 5 (a little longer than about 40 hours), provided of course that the spring 6 is not in the condition of manual or automatic rewinding. As this period of time elapses, the frequency of successive decelerations gradually decreases. It should be noted that in this operating state, the repeated short-circuiting of the generator 11 by the transistor 22 does not interfere with the operation of the integrated circuit 11, and the provision of two capacitors (not shown) with a relatively large capacitance in the rectifier 10 makes it possible to permanently supply the voltage required for this purpose.

When the torque value generated by barrel 5 falls to C_{Critical value}(C in FIG. 1)_CPoint) the generator has reached such a speed that its frequency is no longer sufficient to make the pulses processed by comparator 17 compensate the pulses of up-down counter 16 originating from frequency divider 13, but the voltage supplied by the generator to integrated circuit 11 is still sufficient to make it work. The count value of the counter is therefore increased to a predetermined threshold value corresponding, for example, to its total positive capacity (counter gain value), which in the present example may be equal to 512, which corresponds to about 24 seconds, considering the frequency with which the signal at terminal 15 of counter 16 causes it to continue to operate, the connection of decision logic 20 also being made to detect this predetermined threshold value.

Therefore, once this value is reached, the determination logic circuit 20 turns on the reduction transistor 22 to reduce the number of revolutions of the generator 1. The generator 1 rotates during the counting of the up/down counter 16 at a speed lower than the nominal speed, each hand 7, 8, 9 being slower than the corresponding speed at the correct time, with a lag equal to the counting time (24 seconds in this example) of said counter.

The generator 1 is in a condition of deceleration and the voltage supplied to the integrated circuit 11 drops to a low value which, once the various charged capacitors of the rectifier 10 have been sufficiently discharged, becomes less than the voltage at which the integrated circuit 11 can still operate correctly (typically 0.7 volts). This renders the reduction transistor 22 non-conductive, which no longer receives a control signal from the decision logic circuit 20, among other effects. Furthermore, the logic levels of the signals at the output terminals 23a and 23b are inverted as the voltage at the terminals of the integrated circuit drops below the value of the voltage to which the start-up circuit 23 is applied.

Thereafter, the generator 1 can be rotated faster and the voltage supplied to the integrated circuit 11 can rise until the start-up circuit 23 is again active and causes the logic levels of the terminals 23a and 23b to change state in the opposite direction, at which point the integrated circuit 11 starts to operate again.

These operations, just mentioned, are carried out at the very beginning of the PFI phase, which can last for several hours if the spring 6 is not wound, when the quartz watch is motor-driven, and then it is transferred to the "EOL" type intermittent advance condition. The rest of the operation of the timepiece at this stage is shown in fig. 3. A) in fig. 3 shows the change of the logic level at the output 23a of the start-up circuit 23 at this stage of operation. Section b) of fig. 3 shows how the count value N (curve C) in the up-down counter 16 can change from the moment the POR signals of the terminals 23a and 23b change state in the opposite direction as just mentioned. This time is represented by t in fig. 3b)₀And (4) showing.

It can be seen that a signal POR (output 23) is applied to the counter 16. Therefore, when the signal is at time t₀Turning to 1, the count value on counter 16 turns to + 1. Furthermore, the decision logic 20 is connected to the frequency divider 13 and receives from the frequency divider 13 a time signal determining that the predetermined time limit DP of 4 seconds is chosen in this example. The decision logic 20 can also determine that the count value of the counter 16 reaches a certain threshold value (N ═ N) when the predetermined time period DP ends_{Critical point of}) Or passes this value to provide a control signal to transistor 22.

Although in the PFI phase the generator 1 always rotates at a speed lower than the nominal one, it drives the hands at a speed sufficiently fast for the nominal speed of the correct time, as for the second hand, the travel angle is sufficient to create a phenomenon (which is typically a few seconds at a time) that makes the owner of the timepiece not aware of and to drive him to rewind.

However, when the generator 1 is rotating during the PFI phase, the pulses supplied to the counter 16 via the comparator 17 are always at a lower frequency than the frequency supplied by the divide frequency 13. The counter 16 then counts up. The criterion adopted by the decision logic circuit 20 is therefore aimed at the predetermination of the counter value of the counter at the frequency divider 13Reaching or exceeding N before expiration of period DP_{Critical point of}The value controls the deceleration transistor 22. Fig. 3 illustrates this process by curves C and D. Curve C corresponds to reaching N just at the expiration of the predetermined time period_{Critical point of}The case of a value. The curve D shows a case where the count value N2 of the counter 16 is much larger than the threshold value at the expiration of the predetermined period DP. Then, when the determination logic circuit 20 controls the deceleration transistor 22 at the end of the period DP, the generator 1 enters the deceleration state, the voltage supplied to the circuit 11 sharply drops to the extent that the circuit 11 stops operating, the deceleration transistor 22 again enters the non-conductive state, the generator is restarted again, and the second hand is driven in an intermittent manner. This process can be repeated as long as one of the following two conditions does not occur.

The first case is where the user transfers the movement of the spring to the spring by manually rewinding it or by starting to wear the watch. In this case, the accumulated value in the counter 16 will drop, because the generator 1 will quickly return to the nominal speed, pulsing the counter 16 at the same rhythm as the frequency divider 13. This situation is represented by curve E in fig. 3.

Another situation is where the consumption of power reserves is more significant. In this case, when the generator is restarted, the voltage it supplies is no longer sufficient to supply the integrated circuit 11. Recall also that in the above example, this corresponding value is 0.9 volts. The process then enters an intermediate period indicated at I in figure 1. During this period, the hands always rotate at a very slow speed and the transistor 22 cannot slow down the generator.

As the generator speed drops further, the starter circuit 23 will function when, for example, the voltage supplied to the integrated circuit 11 exceeds 0.7 volts in the direction of the drop. When this occurs, the signal at terminal 23b goes to "1", thereby turning on transistor 24. This causes the shunt formed by the transistor 24 and the resistor 25 to be connected at the supply terminal V_DDAnd V_SSIn the meantime. The value of the shunt is chosen so that the current formed in this shunt absorbs a certain amount of energy, so that barrel 5 is no longer able to absorb the energy at the rate perceived by wearing watch 2The hands are driven. This very slow rate is established throughout the significant deceleration phase PFP until the power reserve is almost fully depleted.

The period of marked deceleration PFP, although optional, can inform the wearer of the complete stop of the watch (when the second hand is rotating slowly to such an extent that it is not perceptible to the wearer). Without this phase, the wearer might inadvertently think that the timepiece is still running, the hands still moving forward despite the slow rotation speed, and the wearer still perceives this, especially during a certain period of time immediately following the intermittent deceleration phase PFI. Furthermore, for the same reason, the duration of the period I (during which the hands have rotated relatively slowly, but still smoothly) is also as short as possible, which can be achieved by choosing a value very close to the minimum voltage at which the integrated circuit can still operate and the voltage at which the output signal of the start-up circuit 23 changes level.

It should also be noted that the value of resistor 25 must be chosen so that the shunt it forms with transistor 24 is such as not to hinder the restart process when the wearer rewinds spring 5 from the phase PFP of significant deceleration.

Fig. 4 shows another embodiment of the invention that can be added to the above-described assembly as an aid to completely prevent the generator 1 from rotating at the end of the significant deceleration phase PFP. This embodiment consists in placing, close to the periphery of the rotor 2 of the generator 1, one or more magnets with a minimum of attraction force but capable of exerting a slight positioning torque on the rotor, which must be less than the torque that the barrel can provide when the power reserve is almost completely exhausted, so as not to hinder restarting.

In the exemplary embodiment illustrated in fig. 4, the rotor 2 shown in plan view consists of a plurality of magnets oriented perpendicular to the plane of the drawing. The magnets are arranged alternately along the circumference of the rotor with north and south poles alternating with one another. The magnets 26 are also positioned adjacent the rotor in the same orientation.

Claims (8)

1. An electronic timepiece comprising:

an alternating voltage generator (1) connected to a rectifier (10) for supplying power to an electronic circuit (11) of the timepiece;

a barrel (5, 6) coupled to the generator (1) for driving the generator (1);

a set of time hands (7, 8, 9) also driven by said barrel (5, 6);

the electronic circuit includes:

a time base (11, 12) for providing a standard frequency signal;

-comparing means (16, 17) for comparing the frequency of said time base (12, 13) with the frequency of said alternating voltage, thereby generating an error signal; and

-verification means (20) connected to said comparison means (16, 17) for verifying whether said error signal exceeds a first predetermined threshold; and

-deceleration means (22), controlled by said verification means (20), to electrically decelerate said generator (1) when said error signal crosses said first predetermined threshold,

the timepiece is characterized in that:

said verification means (20) being further configured so that it also verifies whether said error signal crosses a second predetermined threshold greater than said first predetermined threshold, said deceleration means (22) also being controlled when said second threshold is crossed, and verifies a predetermined depletion of the power reserve of said barrel (5, 6);

said verification means (20) are further configured to make it verify whether, after exceeding said second predetermined threshold, said error signal becomes at least equal to a third predetermined threshold during a predetermined time, in order to control said deceleration means when said period of time expires;

so that each time the error signal reaches or exceeds the third predetermined threshold value, the respective hands (7, 8, 9) rotate at a speed higher than the corresponding speed indicating the correct time, indicating the depletion state.

2. Timepiece according to claim 1, wherein said comparison means comprise an up-down counter (16) whose first input (15) receives said time-based signal and whose second input (19) receives a pulse signal having a frequency equal to the instantaneous frequency of the voltage supplied by said generator (1).

3. Timepiece according to claim 2, wherein the second input (19) of the up-down counter (16) is connected to the output of a comparator (17), the first input of the comparator (17) being connected to the output (1a) of the generator (1), the second input of the comparator (17) being connected to a reference voltage source (18).

4. Timepiece according to claim 2, wherein said verification means (20) is a wired logic circuit for analyzing the output of said up-down counter (16) selectively as a function of its three positions representing said first, second and third predetermined threshold values, respectively.

5. Timepiece according to claim 3, wherein said verification means (20) is a wired logic circuit for analyzing the output of said up-down counter (16) selectively as a function of its three positions representing said first, second and third predetermined threshold values, respectively.

6. Timepiece according to any one of claims 1 to 5, wherein said integrated circuit (11) has an enabling circuit (23) called POR circuit, said timepiece being characterized in that it further has a resistive shunt (24, 25) able to selectively connect the output of said rectifier (10) when said enabling circuit (23) detects that the voltage supplied by said rectifier (10) has dropped below a predetermined value.

7. Timepiece according to claim 6, wherein said resistive shunt consists of a resistor (25) connected in series with a switching element (24), the switching state of the switching element (24) being controlled by said starting circuit (23), said resistor being calibrated so that the timepiece can be restarted by re-winding of said barrel (5, 6) after the power reserve has been exhausted.

8. Timepiece according to claim 7, further comprising at least one magnet (27) arranged in proximity to said generator (1) and applying a detent torque to the rotor (2) of said generator, the magnitude of the torque being such that the timepiece can be restarted by rewinding said barrel after the power reserve has been completely exhausted.