EP0082821A1 - Electronic watch provided with detection means for the passage across a reference position - Google Patents

Abstract

For performing a very precise detection of the position of at least one hand, the watch is provided with an electro-optical detection device. The detection device comprises a wheel 8 carrying a mirror 26. The wheel 8 is intermittently driven by the driving member 6 for defining n angular positions of the mirror 26. The member 6 is meshing with the gear train 12 of the watch. It further comprises a light emitter 30 and a light receiver 32 which receives a light beam when the mirror 26 is in an angular position corresponding to the reference position of the hand. The number n is inferior to the number of steps performed by the hand during a complete revolution of said hand.

Description

The present invention relates to an electronic watch provided with means for detecting the passage of a needle through a reference position.

More precisely, the invention relates to an electronic watch with hands which comprises electro-optical means for locating in time the passage of a hand or of several hands through a reference position.

In conventional electronic watches with display by hands, a time base delivers hourly pulses which are used to control a motor, which drives the hands via a gear train. The constant duration of the driving pulses is adjusted to a value such that, taking into account the voltage delivered by the battery, the electric energy supplied to the motor at each pulse is sufficient to advance the hands by one step even in the phases drive a date disc, if the watch has one. At least this is true as long as the battery voltage remains above a given threshold. Therefore, if the battery is in good working order, with each time pulse delivered by the time base, the time display members progress by a corresponding amount.

However, whatever the precautions taken to calculate and build the engine, there is of course no mechanical link between the stator of the motor whose coil receives the driving impulses and the rotor which is mechanically connected to the gear train and therefore to the time display members. So, if a large shock is applied to the entire watch, the rotor can turn one or more steps in one direction or the other without a driving impulse being applied to the coil. Or, if a shock occurs during the application of a driving impulse, this shock can prevent rotation of the motor or cause rotation in an unwanted direction. In summary, in all these cases the position of the hands no longer corresponds to the internal time of the watch, that is to say to the motor pulses delivered by the time base. To remedy this malfunction, it is therefore necessary to be able to periodically compare the actual position of one or more hands with the position they should have in view of the internal time of the watch.

In other electronic watches, at least one of the hands used to display the time can be used to display other information such as the date, the day of the week, etc. In this case, the motor is supplied on demand by motor pulses. particular which allow to bring one or more hands in front of graduations of the dial in order to display one of the non-hourly information. These motor pulses which no longer have anything to do with time pulses are counted in motor pulse counters. In order to keep the hourly information during these non-hourly information display phases, the hourly pulses are stored in counters associated with the time base. To return the hands to their position corresponding to the display of the current time, after one of the phases display indicators mentioned above, comparators compare the hourly information and the information contained in the motor pulse counters. Motor pulses are sent to the motor until there is identity between the contents of the hourly pulse and motor pulse counters. The hands then display the time information again. The same problem arises if the analog watch has an alarm function (display of the alarm time) or a stopwatch function. In all these cases it is necessary to have absolute reference information for the position of the hands. This is for example a signal which is delivered by a detector each time one or more needles pass through a determined position.

In certain analog watches, the normal duration of the driving pulses is determined in such a way that the energy contained in each pulse is sufficient to advance the hands by a corresponding number of steps, but insufficient when the torque which the motor must supply increases, for example when training the date disc. Of course, the duration of the motor pulses must be increased when this torque increases. This solution is interesting because it makes it possible to adapt the electrical energy supplied to the motor to the mechanical energy which the latter must supply. To detect that the electrical energy supplied was not sufficient to run the motor, a first solution consists in detecting during or immediately after each driving pulse whether the rotor has actually rotated. This detection is done directly or indirectly by a measurement of the induced voltage of the motor. Another detection method consists in periodically checking whether a needle, for example the needle of the seconds, passes well through a reference position, at the instant of appearance of the driving impulse associated with the time information corresponding to this position. In the latter case, it is therefore necessary to be able to locate ^- _I position of a hand at these precise times provided by the time base of the watch.

It can therefore be seen that there are numerous configurations of watches in which it is necessary to be able to identify the position of one or more hands. This is why we already use hand position detectors in watches.

A first type of detector used is constituted by a cam which rotates in synchronism with one or more needles thanks to a mechanical connection between these members.

The cam, for a precise angular position, closes an electrical contact which in turn controls the emission of an electrical pulse. The advantage of such a detector is that it is simple, but it is imprecise and unreliable. Furthermore, it can only be used with a unidirectional motor and it increases the energy which the motor must supply.

Another known detector is of the electro-optical type. Such a detector is described in Japanese patent application 74834/80 published on December 2, 1980. The watch includes a light-emitting diode which emits a light beam passing through a window on the dial. The needle carries on its inner face a mirror. When the needle is in the reference position, the mirror reflects the light beam towards a photo-transistor which thus detects the passage of the needle through the reference position. However, the resolution of such a system is poor and its implementation unattractive.

To remedy these drawbacks, a first object of the invention is to provide an electronic watch with hands comprising an electro-optical detector of the passage of a needle through a reference position which makes it possible to obtain an improved resolution and a high reliability.

A second object of the invention is to provide such a watch which moreover comprises means for comparing the instant of the passage of the needle by the reference position with the instant when this passage must take place in view of a information internal to the watch, preferably the internal time of the watch, and to compensate for the advance or possible delay of the hands relative to the internal time of the watch, or the internal information.

These objects are achieved by the invention by means of the claimed means.

• - la figure 1 est une coupe en élévation d'une partie d'une montre selon l'invention montrant le dispositif de détection du passage de l'aiguille par la position de référence, cette figure illustrant plus particulièrement la partie mécanique et la partie optique du détecteur;
• - la figure 2 est une vue de dessus des éléments mobiles du détecteur représenté sur la figure 1;
• - les figures 3a et 3b sont des schémas simplifiés illustrant deux variantes possibles de réalisation de la partie optique du détecteur représenté sur la figure 1;
• - la figure 4 est un schéma simplifié de la partie du circuit de la montre permettant de corriger éventuellement la position de l'aiguille en fonction des indications données par le détecteur de position;
• - la figure 5 est un schéma plus détaillé de l'ensemble logique de commande du circuit représenté sur la figure 4;
• - la figure 6 montre un organigramme expliquant le fonctionnement du circuit selon l'invention pour corriger la position des aiguilles et éventuellement pour initialiser la position des aiguilles;
• - les figures 7a et 7b sont des diagrammes de temps expliquant la façon dont on définit les instants de détection; et
• - les figures 8a et 8b montrent deux variantes de réalisation du dispositif de détection pour détecter le passage de deux aiguilles par une position de référence.

The invention will be better understood on reading the following description of several embodiments of the invention given by way of non-limiting examples. The description refers to the appended figures in which:

• - Figure 1 is a sectional elevation of a part of a watch according to the invention showing the device for detecting the passage of the needle through the reference position, this figure illustrating more particularly the mechanical part and the optical part the detector;
• - Figure 2 is a top view of the movable elements of the detector shown in Figure 1;
• - Figures 3a and 3b are simplified diagrams illustrating two possible alternative embodiments of the optical part of the detector shown in Figure 1;
• - Figure 4 is a simplified diagram of the part of the watch circuit for possibly correcting the position of the hand according to the indications given by the position detector;
• - Figure 5 is a more detailed diagram of the logic control assembly of the circuit shown in Figure 4;
• - Figure 6 shows a flowchart explaining the operation of the circuit according to the invention to correct the position of the needles and possibly to initialize the position of the needles;
• - Figures 7a and 7b are time diagrams explaining the way in which the instants of detection are defined; and
• - Figures 8a and 8b show two alternative embodiments of the detection device for detecting the passage of two needles through a reference position.

The part of the watch concerned by the invention essentially comprises an optico-mechanical detection assembly which makes it possible to detect the passage of a hand through a reference position and a circuit associated with the normal circuit of the watch which makes it possible to operate the information supplied by the detector to possibly correct the position of the hand in the event of desynchronization between the position of the hand and the internal time of the watch given by the time base or other internal information.

Furthermore, the invention can be applied to watches whose hands are driven by a single motor, or to watches whose hands are driven by two motors, each motor driving for example a hand. In the particular example considered, only the detection of the position of the minute hand of a watch that does not have a second hand. It is however clear that the invention could equally well apply to the case of the hour or second hand.

Referring to Figures 1 and 2 we will first describe the actual position detector.

There is shown in Figure 1 a part of the frame 2 of the watch movement, the line 4 symbolizing the dial. The detector comprises a movable part constituted by the mobiles 6 and 8. The mobile 6 is integral in rotation with an axis 10 pivotally mounted in the frame and which further carries a toothed pinion 12 meshing with the rest of the gear train driving the needles. The driving mobile 6 has a first part 6a in the form of a disc which is provided on its periphery with a driving finger 14. The driving mobile has a second part 6b also in the form of a disc whose diameter is smaller to that of portion 6a. The portion 6b is provided on its periphery with a notch 16 admitting as an axis of symmetry a radius which is at the same time the axis of symmetry of the finger 14. The detection mobile 8 also comprises a first portion 8a provided over its entire periphery n teeth 18 which can cooperate with the finger 14. The mobile 8 also comprises a second portion 8b also having the shape of a disc whose diameter is greater than that of the portion 8a. The entire periphery of the portion 8b is provided with n portions of concave cylindrical surfaces 20 separated from one another by edges 22. Each concave portion has the same plane of symmetry as the tooth 18 which is associated with it. Finally, the mobile 8 comprises a single orifice 24 in which a mirror 26 is driven out, the reflecting face 26a of which is a spherical cap or preferably a cap slightly oval spherical. As shown in FIG. 2, the center of the mirror is arranged on a radius constituting an axis of symmetry for one of the teeth 18. The assembly of the mobile 8 is secured to an axis 28 pivotally mounted in the frame 2.

. Cette rotation est possible grâce au fait que, pendant la phase d'entraînement, une arête 22 peut temporairement pénétrer dans l'encoche 16. Au contraire, en dehors des phases d'entraînement, la coopération de la surface latérale de la portion 6b du mobile 6 avec une portion cylindrique 20 du mobile 8 verrouille en rotation le mobile 8 tout en permettant une libre rotation du mobile 6.In a vertical plane, the portions 6a and 8a are arranged at the same level. The same goes for portions 8b and 6b. The radius of the portion 6b of the mobile 6 is substantially equal to that of the cylinder defining the portions of cylindrical surfaces 20 of the mobile 8. It is easily understood that, during the meshing phases, the finger 14 acts on one of the teeth 18 and drives the rotation of the mobile 8 by an angle which is worth

. This rotation is possible thanks to the fact that, during the drive phase, an edge 22 can temporarily penetrate into the notch 16. On the contrary, outside the drive phases, the cooperation of the lateral surface of the portion 6b of the mobile 6 with a cylindrical portion 20 of mobile 8 rotatably locks mobile 8 while allowing free rotation of mobile 6.

The detection assembly further comprises a light source 30 preferably constituted by a light emitting diode in the infrared and a light sensor 32 constituted for example by a photo-transistor. These components are fixed on a support 34 and electrically connected by electrical connections symbolized by 36 to a printed circuit 38 fixed on the support 34. The printed circuit 38 is connected to the integrated circuit of the watch by any suitable means. The link 36 represents the supply conductors of the light-emitting diode 30, the polarization conductors of the photo-transistor 32 (or of the photodiode) and the conductors for collecting the signal delivered by the light detector (photo-transistor) in response to the light beam applied to it. The detection assembly 30, 32 is for example placed in a housing 40 closed by the transparent plate 42. A window 44 is provided in the frame 2 to allow the passage of incident and reflected light beams. It clearly appears that the light detector 32 receives a light signal only if the light-emitting diode 30 is energized and the mirror is placed opposite the light emitter 30 so that it returns to the detector 32 a significant part of the incident light beam.

For example, the mobile 8 has an outside diameter of 4 mm, which does not occupy an important place in the watch. The reflecting surface 26a of the mirror 26 which is a spherical cap has a diameter of 1 mm. The mobile 8 has 15 teeth 18. (n = 15). The mobile takes 15 steps per turn.

Despite these reduced dimensions, there is only a slight overlap between the different positions successively occupied by the mirror. This result, combined with the concavity of the mirror, means that the light signal received by the light detector 32 is only significant for a single position of the mirror.

In the example considered, the motor driving the minute and hour hands makes 120 steps per hour, that is to say per dial turn of the minute hand. The mobile 8 making 15 steps per revolution, that is to say per hour, the mobile 6 must make one revolution every four minutes, that is to say one revolution for eight steps of the engine. The mobile 6 must be mounted in the gear train in such a way that it effectively has this speed of rotation. The mirror 26 is therefore moved every four minutes, ie every eight steps from the engine. The duration of the meshing phase between the mobiles 6 and 8 corresponds to two steps of the engine in the example considered. Of course in other embodiments, the engagement time could be equal to one step of the motor.

The fact that the mobile 8 takes only 15 steps instead of 120 per revolution of the needle represents a very important advantage for the resolution of the system, while making it possible to limit the diameter of the mobile 8. In fact, for a diameter of the reflecting surface 26a of the mirror it is possible to reduce the diameter 0 of the circle on which the mirror is centered, since by reducing the number of steps made by the mobile 8 per revolution, the angle at the center between two successive positions is increased from the center of the mirror. The assembly constituted by the mobiles 6 and 8 therefore behaves like a mechanical amplifier of rotation with respect to the devices of the prior art. This improves the resolution of the needle position detection without increasing the size of the mechanical part of the detection device.

This value n = 15 corresponds to a good compromise between the resolution for given dimensions of the mobiles and the torque which it is necessary to have to drive the mobile 8 in rotation. Furthermore, it is possible to drive the mobile. 8 motor steps per revolution. However, it would be possible to envisage other reports. From a general point of view we have the relation: = kxn; in which p is the number of steps of the needle to make a revolution of the dial, and k is the number of steps of the motor necessary for the mobile 6 to make a revolution. Of course, n must be strictly greater than or equal to two for there to be detection. In fact it must be significantly greater than two for the lock between the mobile 6 and 8 is technologically possible. Likewise, n must be less than p for there to be an amplification effect. In fact, for there to be an improvement in the resolution, the number n must be significantly less than p.

Another possibility for the resolution to be improved without increasing the dimensions of the mobile 8 is to provide that the mobile 8 makes several turns per dial turn of the needle. If g is the number of turns of mobile 8 per revolution of the dial, n 'the number of steps of mobile 8, we have:

Of course, in this case, the passage of the mirror 26 in front of the optical detector corresponds to q different positions of the needle. Such a detector therefore does not allow the position of the needle to be initialized.

It is also possible to provide other optical systems for carrying out the detection. Figures 3a and 3b illustrate two variants of the optical system of Figure 1. In the case of Figure 3a the mirror 26 is replaced by a diaphragm 26 'formed in the mobile 8. The transmitter and receiver 30 and 32 are arranged on either side of the mobile 8 and are coaxial. In the case of FIG. 3b, the detector 32 and the transmitter 30 are arranged side by side and on the same side with respect to the mobile 8. The mobile 8 is pierced with a diaphragm 26 'and an identical concave mirror 26 " to the mirror 26 of FIGS. 1 and 2 is placed facing the emitter and the detector, the mirror 26 "and the detection - emitter assembly being arranged on either side of the mobile 8. These two solutions present the disadvantage of increasing the overall thickness of the device.

In all cases the transmitter and the receiver are fixed and an optical device constituted by a mirror or a diaphragm is secured to the mobile 8, this device allowing the light beam to reach the detector only if it occupies a corresponding angular position. when the needle passes through the or through a reference position.

The operation of the actual detector is obvious from the preceding description. While the light-emitting diode 30 is supplied, it emits a light beam towards the mobile 8. As long as the mirror 26 is not opposite the emitter 30, the photo-transistor receives no light or at least no significant light level . It therefore does not deliver any detection signal. On the contrary if the mirror is in front of the transmitter 30, the receiver 32 receives a reflected light beam of significant level and it delivers a detection signal.

FIGS. 8a and 8b illustrate alternative embodiments of the detector in the case where the detection is carried out when two watch hands occupy a determined position, for example when the hour hand and the minute hand both occupy the 12 o'clock position on the dial.

According to the variants of Figures 8a and 8b we find the mobile 8 which is rotated by the mobile 6 which rotates at the same time as the minute hand for example. The detector comprises a second mobile 8 ′ having the same axis of rotation as the mobile 8 and which is kinematically linked to the movement of the hour hand. In other words the mobile 8 makes one revolution per revolution of the minute hand while the mobile 8 'makes one revolution or half a revolution per revolution of the hour hand. Depending on the case detection will be done each time the two hands are in the 12 o'clock position or for two needles passing through the 12 o'clock position. In the second case, of course, a distinction is made between noon and midnight.

More generally, the mobile 8 ′ makes a turn when the needle associated with it makes m turns (m <3).

According to the embodiment of FIG. 8a, the mobile 8 has a mirror 27, the active face 27a of which is concave and faces the mobile 8 '. The mobile 8 'is provided with a hole 29, the center of which is located at the same distance from the axis of rotation as that of the mirror 27. The light source 30 and the light detector 32 are found, which are fixed relative to the watch case. The mobile 8 'is mounted between the mobile 8 and the transmitter-receiver assembly 30-32. It is easily understood that, as long as the mobile 8 ′ is not in the reference position, the mobile 8 receives no light. When the orifice 29 is at least partially vis-à-vis the transmitter, the mobile 8 receives light, but this is not reflected. It is only when the two needles are in the reference position that the mirror 27 and the hole 29 are superimposed and arranged with respect to the light emitter. In order to prevent the reflection of light from the lower face 8'a of the mobile 8 'from inadvertently triggering the receiver 32, the portion of the face 8'a which passes in front of the transmitter 30 is provided with ridges 31 which return the light emitted by the emitter 30 out of the sensitive face of the receiver.

Figure 8b shows another embodiment of the optical system. The mobile 8 has on its periphery a support 33 for a concave mirror 35 corresponding to a reduced sector of the mobile 8. The mobile 8 ′ carries on a reduced sector of its periphery a second concave mirror 37. When the two needles are in the reference position the two mirrors 35 and 37 face each other. Their optical parameters are such that, in this configuration, and in this configuration alone, the beam emitted by the light source 30 is returned to the receiver 32.

In other words, there is detection when there is a given optical relationship between the positions of the optical devices mounted on the two detection mobiles.

Of course, the detection could also be done from the position of the minute hand and that of the seconds.

Observe the operation of the detector. It concerns the electrical consumption of the detector. It is obvious that in a watch it is necessary to reduce as much as possible the electric consumption to increase the lifespan of the battery supplying the watch. However, a photodiode represents a high consumption on the scale of the watch. It is therefore advantageous to limit the supply time of the diode 30. In the particular case described the engagement time between the mobiles 6 and 8 corresponds to two steps of the motor. Between these two steps, the position of the mobile 8 is uncertain. More generally, the engagement time T is x. t, x being an integer and t the time taken by the needle to cross a step. In the particular case described x is equal to 2. On the other hand the motor makes 120 steps per hour for the minute hand. Motor impulses are alternately positive and negative. It is very possible to foresee that an even driving impulse (positive impulse) brings the minute hand on a scale of the minutes and that a negative driving impulse brings the hand of the minutes in an intermediate position between two minute graduations. Likewise, it is very possible to predict that the end of an engagement phase of the mobiles 6 and 8 coincides with a positive driving impulse. Of course the reference position is chosen to coincide with a scale of the minutes, for example the zero scale. Consequently, it suffices to supply the transmitter 30 with a time t ₀ after each positive driving pulse.

Figures 7a and 7b illustrate the control of the transmitter 30, I _o and Il representing two respectively positive and negative driving pulses. In normal operation they are offset by 30 seconds. Their duration is for example of the order of 5 ms. J represents the supply pulse of the diode. This pulse lasts for example 1 ms, and the offset t is worth 12 ms. Thus the number of times that the diode is supplied is reduced, and the duration of each supply period is short. In the following description, the signal delivered by the detector 32 will be given the value 1 when the mirror 26 is opposite the transmitter 30 and the value zero otherwise.

Before describing in detail the circuits which make it possible to verify that the position of the minute hand corresponds to the internal time of the watch, we will briefly describe the principle. Detection is carried out at each normal revolution of the minute hand. The emitting diode 30 is supplied at the instants 59 minutes and 60 minutes defined by the time base of the watch, the reference position being the zero graduation. This gives a number of two binary digits, the one on the right giving the value of the detection signal at the 60th minute and the one on the left the value of the signal at the 59th minute. Detection takes place on the 59th and 60th minute because the engagement time corresponds to two motor steps (x = 2), i.e. one minute. If the mechanism was provided for the engagement to last only one motor step, detection would take place at the 60th minute and 59 minutes 30 seconds. If the number is 01 it means that the needle has actually passed through the reference position at the 60th minute. The hand is therefore in synchronism with the time base.

If the number is 00, the hand is late or advances at least 5 minutes. Indeed, the mirror only rotates every eight motor steps, that is to say every four minutes.

If the number is 11, the needle is one, two or three minutes early. The fact that there are three possible values is due to the fact that the mobile 8 only moves every four minutes.

If the number is 10, the needle is also ahead. This advance is then exactly four minutes.

In all cases where the number is other than 01, high frequency alternating driving pulses are applied to the motor, for example at 64 Hz. Detection is carried out after each positive driving pulse. When the number 01 is obtained, it means that the minute hand passes through the reference position. The minute hand and the time base are synchronized. The missing motor pulses are sent if necessary. If for an accidental reason, after 60 positive driving impulses the number 01 is not obtained, the application of the rapid impulses is stopped in order to avoid discharging the watch battery. FIG. 4 shows the general organization of the part of the circuit of the watch which makes it possible to readjust the position of the hand minutes on the internal time given by the time base of the watch.

There is the oscillator 40 of the watch which conventionally delivers a periodic signal, for example, at 32,768 Hz. This signal is introduced into a frequency generator 42 which can deliver at least one periodic signal. In the example considered, this signal has a frequency of 1/30 Hz or 64 Hz. The periodic signal is applied to the input of the forming circuit 44 or "driver" which applies to the stepper motor 46 alternating driving pulses to said frequency. The motor 46 drives one or two hands 48, 48 ′ which serve, for example, to display the minute and the hour, by means of a gear train symbolized by 50. As has already been explained, the gear train 50 also drives the transmission mobile 6. This advances the detection mobile 8 which carries the mirror by one step every four minutes. Associated with mobile 8, there is the light emitter 30 and the light receiver 32. As already explained the transmitter 30 is controlled by a supply circuit 52 which determines the moment of excitation of the transmitter 30 and the duration and the shape of the excitation pulse (for example 1 ms). The current or voltage delivered by the detector 32 is shaped in the circuit 54 to deliver a logic signal S. As has already been explained, the signal S has the value 1 if the mirror is opposite the transmitter assembly -receiver and the value 0 otherwise. A logic circuit bearing the general reference 56 controls the implementation of the method for synchronizing the position of the minute hand with the internal time of the watch given by the frequency generator 42.

For this, the logic circuit 56 receives on its inputs 56a and 56b the logic signal S and the periodic signal delivered by the frequency generator 42. It delivers on its output 56 ′ a signal for controlling the frequency delivered by the generator 42 and on its output 56'b a control signal from the supply circuit 52.

Figure 5 shows in more detail the organization of logic circuit 56 and the various associated circuits.

The frequency generator 42 is constituted by several division stages 60. They deliver on their output 60a a signal of frequency 1/30 Hz used for the normal control of the motor and on their output 60b a signal of frequency 64 Hz allowing to drive the engine at high speed. The outputs 60a and 60b are connected to the forming circuit 44 by a controllable switch 62. It goes without saying that the switch 62 is in fact produced by semiconductor elements, for example complementary MOS transistors.

The logic circuit 56 comprises a counter by 120 referenced 64 which receives on its clock input 64a the frequency signal 1/30 Hz. The counter 64 delivers on its output 64a a pulse each time it has counted 120 applied pulses at its clock input. The counter 64 is associated with a comparator 66 which constantly compares the state of the counter 64 with the value 118. The comparator delivers a signal on its output 66'a when the content of the counter 64 changes to 118. It is easily understood that the comparator 66 delivers a signal for each 59th minute, and that the counter 64 delivers a pulse for each 60th minute. The outputs 64'a and 66'a are connected to two inputs of an OR gate 68. The output of the gate 68 drives a circuit 70 for controlling the supply circuit 52 of the transmitter 30.

The circuit 56 also includes a shift register 72. The register 72 is supplied by the output of the shaping circuit 54 of the signal delivered by the receiver 32 through the delay circuit 73 whose time constant is of the order 1 ms. It also includes a reset input 72a. There is also a zero comparator 71 which receives the signal delivered by the circuit 73. The comparator 71 is activated only when the signal delivered by the comparator 66 appears. Its purpose is therefore only to compare the value of the signal S resulting from detection at the 59th minute. It delivers a signal on its output 71a if its input is zero. The register 72 is associated with a digital comparison circuit 74 which compares the state of the register 72 with the number 01 at the times when the transmitter is supplied. If the content of register 72 is equal to 01, circuit 74 delivers a signal on its output 74a, and if not, it delivers a signal on its output 74b. It is clear that the purpose of register 72 is to store the last two values of the detection signal 5. The output 74b of the comparator 74 is connected to an input of an OR gate 76 via the blocking circuit 78. The purpose of this circuit is to allow only one pulse applied to its input 78a to pass unblocking pulse is not applied to its control input 78b. This control input 78b is connected to the output 66'a of the comparator 66. The OR gate 76 receives on its second input the signal delivered by the comparator 71, and the output of the gate 76 is connected to the reset input at zero 72a of register 72.

The switch 62 is controlled by a circuit 80. The circuit 80 delivers a level 0 signal which brings the switch 62 into the position 0 if a signal is applied to its input N. It delivers a level 1 signal which brings the switch 62 to position 1 if a signal is applied to its input R. In other words, if the input N of the circuit 80 is supplied, the trainer circuit 44 receives pulses of high frequency 64 Hz. The logic circuit 56 also includes a parity detector 82 which is connected to the output 60b of the divider 60. It does not allow the pulse applied to its input only if it is of even rank, that is to say if it controls the application to the motor of a positive driving impulse. The output of the detector 82 is connected on the one hand to an input of the OR gate referenced 68 and on the other hand to the clock input 84a of a counter by 60 referenced 84. In addition the counter 84 has an input reset 84b. The input 84b is connected to the output of the control circuit 80 so that the counter 84 is kept at zero as long as the circuit 80 maintains the switch 62 in the position 0. In other words the counter 84 does not count the even pulses of the signal at 64 Hz only when these are applied to the forming circuit. The output 84c of the counter 84, which delivers a pulse each time 60 even pulses have been counted, is connected to an input of an OR gate referenced 86 whose output is connected to the input N of the control circuit 80. This output is also connected to the power supply control circuit 70 of the transmitter to then prohibit the supply of power to the transmitter. The other input of gate 86 is connected to the output 74a of the comparator 74 via the calculation circuit 88. Finally, the output 74b of the comparison circuit 74 is connected to the input R of the control circuit 80 of the switch 62.

The operation of the circuit in FIG. 5 will be explained using the flow diagram in FIG. 6. The normal pulses at 1 / 30th of Hz counted by the counter 64 are compared to the value 118 by the test referenced 100 ( comparator 66). If the rank of the pulse is different from 118, it is compared to 120 by test 102 (counter 64). If the rank is also different from 120, we return to the entry for test 100. This means that the 59th minute has not yet been reached. If the rank of the pulse is equal to 118, at 104 the register 72 is set to zero (the content of which is called SR in the flowchart) and the transmitter 30 is supplied. The value of the signal S delivered by the detector 32 is loaded into the register 72 at 106. At 108 we test the value of the signal S. If S = 0 we return to the input of the test 100. If S is different from 0, we go to step 110. In fact in this case we are sure that the binary value will not be 01. At 110 register 72 is reset to zero (0 + SR).

If, during step 102, the rank of the pulse at 1 / 30th of Hz is equal to 120 (60th minute), the sensor is supplied with 112 and the value of the signal S delivered by the detector 32 is entered in register 72 during step 114. In step 116 we compare the content SR of register 72 to 01, which is done by comparator 74. If SR is 01 we return to operation 100. Indeed, this means that the minute hand is in phase with the internal time of the watch. If on the contrary SR is different from the value 01, we go to operation 110 which consists in resetting the register 72 to zero. This operation is performed by the gate 76 and by the circuit 78 which is not blocked since it is the first time that a comparison is made. As SR is different from 01, a signal is applied to input R of the control circuit of the switch 62. These are therefore pulses at 64 Hz which are applied to the forming circuit 44. These operations are symbolized by the references 118 and 120 in FIG. 6. At 122 the parity of the fast pulse is tested (circuit 82). If the pulse is odd we return to operation 120. If the pulse is even, its rank is compared to 60 during operation 124. Concretely this comparison is made by the counter 84. If the rank is equal to 60 we return to the start operation 100. This means that the needle position error has not been corrected, but that the correction is nevertheless stopped so as not to drain the battery. This instruction results in the fact that the circuit 80 receives a signal on its input N. The pulses at 1/30 Hz are therefore again applied to the motor. If the rank of the even pulse is less than 60, the transmitter 30 is supplied (operation 126) and the value of the corresponding signal S is loaded into the register 72 at 128.

This new content is compared to the value 01 (operation 130). This is achieved by the comparator 74. If the content is different from 01 we return to operation 120, that is to say that a new fast pulse is processed. As this is not the first comparison, the circuit 78 is blocked and the register 72 is therefore not reset. On the other hand, it is always the fast pulses which are applied to the forming circuit 44 since it is on its input R that the control circuit 80 receives a pulse. If on the contrary the content of 72 is equal to 01, the circuit 80 receives a pulse on its input N. It is therefore again pulses of normal frequency which are applied to the forming circuit.

Circuit 88 calculates the number N of pulses to be applied to the motor to exactly put the hand in phase with the internal time of the watch (operation 132). In the case where the high frequency is equal to 64 Hz, the correction lasts a maximum of 2 seconds. During the duration of the generator correction 60 did not emit any time pulse. The minute hand must therefore remain on the graduation 60. The calculation circuit 88 is therefore not useful, and N is zero. In the case where the second hand has to be reset, the time signal can have a frequency of 2 Hz. If the high frequency signal has a frequency of 64 Hz, the correction may require 120 motor steps, this correction can take approximately 2 seconds. During this time, the generator 60 has delivered several time pulses, so the hand must no longer occupy position 0 but another position. The circuit 88 calculates the number N of hourly pulses delivered and sends N additional rapid pulses to the trainer circuit 44. It should be added that the optical detection is carried out every two periods of the signal delivered by the frequency generator 42, whether it act of the signal at 1 / 30th Hz or of the signal at 64 Hz. More generally if the engagement time of the two mobiles 6 and 8 corresponds to x pitch of the motor, detection will be carried out every x periods of the periodic signal actually applied to the motor (1 / 30th of Hz or 64 Hz).

In the correction mode described above, the control is done when the needle is driven at its normal speed, that is to say by pulses at 1 / 30th of Hz. However, it is known to use a needle or the hands to display information other than the present time. You can display a wake-up time, date, month, etc. For this, the watch includes memories which contain information representative of the position that the needle must occupy to display the selected information.

To drive the needle to this position, one solution is to apply rapid pulses to the motor, for example at 64 Hz. The number of pulses to be applied is determined from the content of the memory storing the position of the information to display and the content of the present time counters. During rapid movement, the needle can pass through the reference position. It is interesting to check the actual position of the needle with its theoretical position during this fast-running phase. It is easy to see that the problem has not changed significantly. The difference lies first in the fact that the correction signal to be applied if necessary and the motor control signal have the same frequency. It doesn't matter. Then the difference lies in the way in which the moments when the control must be carried out are elaborated. In fact, in this case, these times can no longer be determined from the counter 64 incremented by the time base pulses and from the comparator 66. It suffices to provide that the counter 64 is incremented by the time base pulses during normal operation and by pulses at 64 Hz during fast walking. Thus the circuits 66 and 64 will effectively supply detection pulses for the 118th motor control pulse and for the 120th. These times are then defined on the basis of internal information. When the hands returned to the present time display position, the rapid pulses continued were applied to the input of counter 64 until the hands occupied the desired position. Then the 1 / 30th Hertz time base pulses are again applied to counter 64.

It goes without saying that the circuit of FIG. 5 is only an example of embodiment using discrete logic circuits. The flow diagram of FIG. 6 shows that the circuit 56 could just as easily be produced using a microprocessor.

It follows from the above description that the actual detector, according to the invention, effectively solves the problem of locating the position of the hand in a watch. It has good resolution, that is to say that there is no risk of detection error between two successive angular positions. However, the whole detector has reduced dimensions which make it easily accommodatable in the movement of the watch.

Claims (7)

1. Electronic watch comprising a frequency generator for delivering at least one periodic signal, stepping motor means controlled by said signal, at least one hand for displaying the time making p steps per revolution, a gear train for transmitting the movement of the motor to the needle and of means for detecting the passage of said needle through at least one reference position, characterized in that the detection means comprise: - a mobile detection member (8) mounted pivoting about an axis (28) and provided with a first optical device (26, 26 '), - a mobile drive member (6) connected to said gear train (10, 12) and cooperating with said mobile detection member (8) to successively give said first optical device (26, 26 ') n angular positions separated by turn of said mobile detection member (8) with p> n ≥ 2 and p = kxn, n being an integer; - a second optical device which is fixed comprising means (30) for emitting a light beam towards the mobile detection member (8) and light detection means (32) for receiving at least a portion of said light beam only when said first optical device (26, 26 ') is in that or those of the n positions corresponding to the reference position or positions of said needle and for converting said light beam into an electrical signal; and - means (54, 56) for delivering a detection signal in response to said electrical signal. 2. Watch according to claim 1, characterized in that said second optical device consists of said light emitter (30) and said light detector (32) which are arranged on the same side of said detection mobile (8), and in that said first optical device consists of a mirror (26) mounted on the face of the mobile (8) facing towards said transmitter (30) and said detector (32), said mirror (26) only reflecting the light beam emitted by said transmitter to said detector (32) only for said angular position. 3. Watch according to any one of claims 1 and 2, characterized in that said drive mobile (6) comprises on its periphery a single drive finger (14), in that said detection mobile (8) comprises on its periphery n teeth (18) cooperating with said finger (16) so that said first optical device (26) progresses from an angular position at each revolution of said driving mobile (6), and in that said mobile ( 6, 8) further comprise on their peripheries means (6b, 20, 22) for allowing free rotation of said driving mobile (6) and for immobilizing said detection mobile (8) in rotation outside the phases of drive by said finger (14). 4. Watch according to any one of claims 1 to 3 characterized in that said frequency generator (40) delivers a first periodic signal to cause said hand (48) to make said p steps per revolution and a second periodic signal, in that said processing means comprises means (54) for assigning a first value to the signal delivered by said detector (32) when said mobile (8) occupies the position corresponding to the reference position and a second value in other cases, and means (72) for memorizing two successive values of said signal when said transmitter (30) is supplied, that the drive of said detection mobile (8) by said driving mobile (6) to pass from one angular position to the next requires x motor pitch (46), and in that it further comprises means (64, 66) for detecting, in response to the first periodic signal, a first instant when said needle must normally pass through said reference position and a second instant preceding said first instant of x periods of said first signal, means (70, 52) for supplying said transmitter (30) at said two instants, means (74) for comparing the two memorized values corresponding to said two instants with a pair of predetermined values corresponding to the effective passage of said needle through the position of reference, means (62, 80) for applying to said motor means said second periodic signal in place of said first periodic signal if said two stored values are different from said pair of predetermined values, means (70, 52) for supplying said transmitter ( 30) every x periods of said second periodic signal if said second periodic signal is applied to said motor means, and means (62, 80) for replenishing said motor means (46) with said first periodic signal when the last two stored values corresponding to times for supplying said transmitter (30) are identical to said pair of predetermined values. 5. Watch according to claim 4, characterized in that the two periodic signals have different frequencies, the frequency of said second signal being greater than that of the first signal. 6. Watch according to claim 1, comprising a first hand performing p steps per revolution and a second hand performing one revolution when said first hand has performed a plurality of revolutions, characterized in that said detection means further comprise a movable member additional detection (8 ') mounted pivoting about the same axis as said movable detection member (8) and cooperating with said gear train (10, 12) to make a turn when said second needle makes m turns (m <3 ), said additional detection member (8 ') comprising a third optical device (29 or 37) so that said light detection means (32) receive at least part of the light beam only when, at the same time, said first optical device (27, 35) is in that or those of the n positions corresponding to the passage of the first needle through the reference position or positions, and said third optical device (29 or 37) is d in a position corresponding to an optical relationship with said first optical device (27, 35). 7. Watch according to claim 6, characterized in that the first hand is the minute hand and the second hand that of the hours.

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