CLOCK EQUIPPED WITH A MECHANICAL CLOCKWORK AND A CORRECTION DEVICE FOR THE HOUR DISPLAY

Description

Technical field

[0001] In general, the present invention relates to a timepiece comprising a mechanical movement, a display of a real time which is driven by this mechanical movement, and a device for correcting this real time. Technological background

[0002] In the field of mechanical watches, the classic way of correcting the real time indicated by its display is to use the classic stem-crown which is generally arranged to be able to act, in the pulled-out position, on a wheel set for driving the hour indicator and the minute indicator, thanks to a friction provided in the kinematic chain between these indicators and the escape wheel. Thus, to set a mechanical watch to the real time, it is generally necessary for the user or a robot to pull the stem-crown and rotate it to bring the hour and minute indicators into the respective desired positions, in particular by a visual comparison with a reference clock, such as those found for example in train stations, or with a digital time given for example by a computer.

[0003] Document WO 2018 / 177779 A1 describes a timepiece comprising a mechanical movement and a mechanical braking device for the mechanical resonator of this mechanical movement. The mechanical braking device is arranged to be able to apply a mechanical braking torque to the mechanical resonator during periodic braking pulses which are generated at a frequency selected only as a function of a set frequency F0c, which corresponds to the nominal value provided for the mechanical resonator. Remarkably, the periodic mechanical braking pulses at the selected frequency impose an oscillation on the mechanical resonator whose average frequency is equal to the set frequency F0c, with a precision specific to an electronic time base. This method makes it possible to impose a correct and precise rate on the mechanical movement as long as the braking device is activated to generate the periodic braking pulses.Thus, the correction device is a device for regulating the frequency of the mechanical oscillator arranged to be able to prevent a potential time drift which would result from an imprecise natural frequency of the mechanical resonator, by imposing on the mechanical resonator a more precise average frequency, that is to say closer to the set value F0c because coming from an electronic time base, via periodic braking pulses applied continuously to the mechanical resonator, which thus impose on this mechanical resonator the set frequency. It is therefore in fact a device for controlling the mechanical oscillator to a secondary oscillator of the electronic type, in particular a quartz oscillator.The teaching of document WO 2018 / 177779 A1 therefore does not make it possible to correct any temporal error, in particular an error detected in an analogue time display, but to prevent a temporal drift as long as the correction device is activated.

[0004] Document EP 3339982 A1 discloses a timepiece which comprises a mechanical movement and a closed-loop type regulating device associated with the mechanical oscillator, more precisely with the resonator of this mechanical oscillator. The regulating device comprises a sensor which is arranged in the mechanical movement to be able to detect the passage of the mechanical resonator through a neutral position and thus to make it possible to detect, if necessary, a time drift of the mechanical oscillator while the sensor is active. The regulating device further comprises a resonator braking device arranged to be able to selectively generate at least one braking pulse which is applied to the resonator each time the time drift detected by the sensor reaches a given limit value, among a positive limit value and a negative limit value.This teaching only allows for the correction of a time error detected on the mechanical oscillator itself during a certain period of operation thereof, but in no way a time error in the actual time displayed by an analog display of the timepiece. More precisely, the disclosed regulating device is arranged to be able to maintain a time drift of the mechanical oscillator, from an initial instant of activation of this regulating device, between the negative limit value and the positive limit value.

[0005] Document EP 3309630 A1 relates to a timepiece comprising a mechanical movement and a device for resetting an analogue display of the actual time, this time-resetting device being associated with an external device, for example a mobile telephone. It is provided that the external device communicates to a receiver provided in the timepiece information relating to a time zone, a date, summer time or a difference between the time displayed by the timepiece and the current time coming from a specific external source. To move the hands of the analogue display, a mechanism is provided arranged to be able to automatically manipulate the hands and comprising for this purpose an electromechanical motor which can be coupled to these hands to drive them momentarily.The time-setting mechanism may further comprise means for disengaging the display members, making it possible to momentarily disengage the mechanical means for driving the analog display, associated with the mechanical oscillator of the watch movement, in order to then be able to drive the hands by the electromechanical motor and carry out the time-setting. Summary of the invention

[0006] It is therefore noted that in the field of timepieces equipped with a mechanical movement, in addition to ensuring precise operation of this mechanical movement, a real need exists for a system for effectively correcting the actual time displayed by these timepieces comprising a mechanical movement. In particular, the present invention aims to be able to precisely set the time of a timepiece comprising a mechanical movement which drives a display of the time, preferably substantially at the exact actual time which is given by an external system arranged to provide it (in particular a system connected to an atomic clock), without requiring a user or a robot to actuate a stem-crown or another external control member of the timepiece to set the display itself.Within the scope of the invention, it is provided that the accuracy of the actual time setting of a timepiece equipped with a mechanical movement does not depend on a visual assessment by the user who must estimate when the various indicators concerned are in the correct respective positions.

[0007] 'Real time' means the legal time of a given location, in which the timepiece and its user are generally located. The real time is generally displayed in hours, minutes and, where appropriate, seconds. The real time may be indicated with a certain amount of error by a timepiece, particularly of the mechanical type. To indicate the legal time given with great precision, in particular by / via a GPS system, a telephone network or a computer connected in particular to a server on the Internet network receiving the real time from a high-precision clock, the expression 'exact real time' will be used in this text. This expression also applies to the real time given correctly by an electronic clock or an electronic time base, incorporated in a device external to the timepiece, which can be regularly synchronized with a high-precision clock giving the legal time.In this text, real time will also be referred to simply as 'the time', particularly when referring to the real time displayed by a timepiece.

[0008] To meet the above-mentioned needs which have been present in the watchmaking field for many years, the present invention relates to a timepiece which comprises: a display of the actual time; a mechanical movement formed by a display drive mechanism and by a mechanical resonator which is coupled to the drive mechanism so that its oscillation sets the pace of this drive mechanism; a device for correcting the actual time which is indicated by the display; and wherein the device for correcting the actual time displayed, incorporated in the aforementioned timepiece, is formed by: - ​​a receiver of an external correction signal for the actual time displayed, this external correction signal comprising information relating to a correction of said actual time displayed, - an electronic control unit, and - a device for braking the mechanical resonator; the electronic control unit being arranged to be able to process the information contained in the external correction signal, so as to determine a correction required for the actual time displayed, and to control the braking device as a function of this required correction.Furthermore, the device for correcting the actual displayed time is arranged so that, when the external correction signal received by the timepiece requires a correction of the actual displayed time, the braking device can act on the mechanical resonator during a correction period, to vary the rate of the drive mechanism, so as to effect at least the major part of the correction required for the actual displayed time, preferably substantially the entirety of this required correction.

[0009] By 'braking device' is generally understood any device capable of braking and / or stopping an oscillating mechanical resonator and / or of momentarily holding at rest (i.e. blocking) such a resonator. The braking device may be formed by one or more braking units (one or more actuators). In the case where the braking device is formed by several braking units, in particular two braking units, each braking unit is selected to act on the mechanical resonator in a specific situation relating to the required correction, in particular a first braking unit for correcting a delay and a second braking unit for correcting an advance (the second braking unit being advantageously arranged to be able to momentarily stop and block the resonator).By 'timing the rate of a display drive mechanism', we mean the act of timing the movement of the wheels of this mechanism when it is operating, in particular determining the rotation speeds of these wheels and thus of at least one indicator of the display. In the rest of the text, when the term 'resonator' without a specific qualifier is used, it is to designate a mechanical resonator. We will speak of an oscillating resonator to indicate that we are considering a resonator in its activated state, in which it oscillates while being maintained, via an escapement, by a source of mechanical energy.

[0010] In a preferred embodiment, the braking device is formed by an electromechanical actuator, arranged to be able to apply braking pulses to the mechanical resonator, and the electronic control unit comprises a device generating at least one frequency which is arranged to be able to generate a first periodic digital signal at a frequency F SUP .The electronic control unit is arranged to provide the braking device, each time the external correction signal received via the receiving unit corresponds to a delay in the displayed time that is intended to be corrected, with a first control signal derived from the first periodic digital signal, during a first correction period, to activate the braking device so that this braking device generates a first series of periodic braking pulses which are applied to the mechanical resonator at said frequency F SUP , the number of periodic braking pulses in said first series and therefore the duration of the correction period being determined by the delay to be corrected.The frequency F SUP is provided and the braking device is arranged in such a way that said first series of periodic braking pulses at the frequency F SUP can generate, during the first correction period, a first synchronous phase in which the oscillation of the mechanical resonator is synchronized (on average) to a correction frequency FS Cor which is higher than a set frequency F0c provided for the mechanical resonator.

[0011] According to a preferred variant, in which the watch movement comprises an escapement associated with the resonator, the frequency F SUP and the duration of the braking pulses of the first series of periodic braking pulses are selected so that, during said first synchronous phase, the braking pulses of said first series each occur outside a coupling zone between the oscillating resonator and the escapement.

[0012] In a particular embodiment, the timepiece comprises a device for blocking the mechanical resonator. Then, the electronic control unit is arranged to be able to supply the blocking device, when the external correction signal received via the receiving unit corresponds to an advance in the displayed time that is intended to be corrected, a control signal which activates the blocking device so that it blocks the oscillation of the mechanical resonator during a correction period determined by the advance to be corrected, so as to stop the operation of the drive mechanism during this correction period. The correction / blocking period normally has a duration substantially equal to the corresponding advance to be corrected.

[0013] In general, the correction of the time displayed by the display is related to an error detected in this displayed time by an external electronic device arranged to be able to provide the timepiece with the external correction signal. In a specific case, the correction of the displayed time is related to a seasonal change of time, or even to a change of time zone.

[0014] The invention also relates to an assembly formed by a timepiece according to the invention and an external device comprising a transmitter of said external correction signal. The external device comprises: a photographic device comprising a photographic sensor formed from a matrix of photo-detectors, an image processing algorithm which is arranged to be able to determine the position of at least one determined hand of the display of the timepiece in an image taken by the photographic device, and a time base capable of providing the exact real time.

[0015] In a preferred embodiment, the external device further comprises an algorithm for calculating a time error between a first time datum, displayed by the display at a given instant and detected by the external device via its photographic sensor and its image processing algorithm, and a second time datum corresponding to the first time datum and provided substantially at said given instant by the time base. When it is intended to correct the calculated time error, the external correction signal provided by the external device to the timepiece comprises information relating to this time error. Brief description of the figures

[0016] The invention will be described below in more detail with the aid of the appended drawings, given as non-limiting examples, in which: There Figure 1shows, partly schematically, a first embodiment of an assembly according to the invention comprising a timepiece, according to a first embodiment, which is provided with a mechanical movement, a time display and a device for correcting the displayed time, as well as an external electronic device, according to a first embodiment, which is arranged to be able to communicate with the correction module; The Figure 2 schematically represents a variant of the correction device of the timepiece according to the first embodiment of the Figure 1 ; THE Figures 3 And 4show, during a correction carried out by a series of periodic braking pulses, the evolution of the oscillation frequency of a mechanical resonator during a period of correction of an advance, respectively of a period of correction of a delay in the time indicated by a display of the timepiece considered, and this for the case of a ratio between the correction frequency and the set frequency relatively close to the value '1'; The Figure 5 shows, in the case of a relatively high ratio between the correction frequency and the reference frequency, the oscillation of a mechanical resonator at the beginning of a period of correction of a delay by a series of periodic braking pulses, this correction period having an initial transient phase; The Figure 6shows, during a correction of a delay carried out by a series of periodic braking pulses, some periods of oscillation of a mechanical resonator during a synchronous phase for two different synchronization frequencies; The Figure 7A shows, for a braking frequency corresponding to a braking pulse by alternating the oscillation of a mechanical resonator, several curves of the maximum relative synchronization frequency as a function of the amplitude of the free oscillation of the resonator and its quality factor; The Figure 7B shows, for a braking frequency corresponding to one braking pulse per oscillation period of a mechanical resonator, several curves of the maximum relative synchronization frequency as a function of the amplitude of the free oscillation of the resonator and its quality factor; The Figure 8is a graph giving, for a given setpoint frequency, approximately possible correction frequency ranges, to correct a delay in the time display using short periodic braking pulses, as a function of several braking frequencies selected for the braking pulses; The Figure 9 is a graph giving, for a given setpoint frequency, approximately possible correction frequency ranges, for correcting an advance in the time display using short periodic braking pulses, as a function of several braking frequencies selected for the braking pulses; The Figure 10 partially shows a second embodiment of a timepiece according to the invention; The Figure 11 partially shows a third embodiment of a timepiece according to the invention; The Figure 12schematically represents a fourth embodiment of a timepiece according to the invention; The Figure 13 shows a second embodiment of an assembly according to the invention comprising a timepiece according to the invention and an external electronic device, according to a second embodiment, serving as a box and charging station for the timepiece; The Figure 14 schematically shows the arrangement of electronic elements and functional units in the external electronic device of the second embodiment; The Figure 15 schematically represents a fifth embodiment of a timepiece according to the invention, which can form the assembly according to the second embodiment; The Figure 16 shows, partly schematically, a sixth embodiment of a timepiece according to the invention; and The Figures 17 and 18show the oscillation of the mechanical resonator during a delay correction period respectively for two variants of the braking device of the timepiece of the Figure 16 . Detailed description of the invention

[0017] In reference to the Figures 1 And 2 , a first embodiment of a timepiece according to the invention will be described below, as well as a first embodiment of an assembly according to the invention comprising a timepiece according to the invention and an external electronic device formed by a mobile telephone.

[0018] The timepiece 2 comprises a mechanical movement 4, an analog time display 12, a mechanism 10 for driving this display and a device 6 for correcting the time indicated by the display. The mechanical movement comprises a barrel 8 forming a source of mechanical energy for the drive mechanism 10 which is formed by a gear train 11, kinematically linked to the display, a mechanical resonator 14, formed by a balance wheel 16 associated with a balance spring 15, and an escapement 18 coupling this resonator to the drive mechanism so that the oscillation of the resonator sets the rate of this drive mechanism. The analog display 12 is formed by a dial 32, comprising indexes 36 forming a graduation for displaying the real time, and by hands 34 comprising an hour hand, a minute hand and a second hand.The hands have different shapes, in particular different lengths and / or widths. Preferably, the indexes are arranged so that the '12H' position for a 12-hour hour circle (or '24H' for a 24-hour hour circle) can be visually determined. In the case shown, the angular position of '12H' is defined by two parallel and substantially radial bars, while the angular positions of the other hours are defined by a single bar.

[0019] Various variants may be provided to enable at least one angular position of the display to be determined corresponding to a given number of minutes and / or seconds on the graduation provided for the display of minutes and / or seconds. It will be noted that the graduation is not necessarily visible. Indeed, for example, it is sufficient to know that we are dealing with a 12-hour hour ring and that the angular position '12H' is provided on a given and identifiable axis of the timepiece, and to have a visible mark on the side of the display enabling the angular position 12H to be determined on this given axis, and therefore any other angular position corresponding to any hour, any minute and / or any second.For example, the dial may have a pattern making it possible to define an orientation of the dial or the dial may include an additional sign defining a specific angular reference corresponding to a particular position of the intended graduation. Such an additional sign may also be placed on a flange surrounding the dial or on the bezel of the watch case in which the mechanical movement 4 is incorporated. It should be noted that the angular reference may simply be given by the shape of the case defining a specific axis that can be visually identified or by the winding crown. It should be noted that the present invention is not limited to an analog display of the real time, but may also relate to other displays of the real time, for example a display with a 'jumping hour' and / or in particular a 'jumping minute'. The display is therefore not limited to a system with hands having a quasi-continuous advance.The invention can therefore also be applied in particular to a system with discs or rings and in particular to a display provided through at least one window provided in the dial.

[0020] The correction device 6 comprises a receiver 30 of an external correction signal S Ext for the time displayed by the display 12 and an electronic unit 28 for controlling the displayed time which is arranged to be able to process the information contained in the external correction signal S Ext and generate in response at least one internal correction signal relating to a correction of the displayed time, which is determined by the external correction signal S Ext, that is to say by the information contained in this external correction signal. The timepiece is arranged so as to allow a correction of the time indicated by its display as a function of the external correction signal S Ext which it receives. To carry out a correction of the displayed time, the correction device generally comprises a device for braking the mechanical resonator.In a main variant, the braking device is formed by an electromechanical actuator, for example an actuator of the piezoelectric type 22A. Then, the braking device is controlled by an electronic control unit 28 which transmits to it a control signal S Cmd to control its power supply circuit so as to temporally manage the application of a mechanical braking force on the mechanical resonator 14. In general, the correction device is arranged so that the braking device can act, each time that the external correction signal S Ext received by the timepiece requires a correction of the displayed time, on the mechanical resonator 14 during a correction period to vary the rate of the drive mechanism 10 so as to correct at least the majority of the displayed time.

[0021] In the variant shown, the actuator 22A comprises a braking member which is formed by a flexible blade 24, which has on two opposite surfaces (perpendicular to the plane of the Figure 1) respectively two piezoelectric layers which are each coated with a metal layer forming an electrode. The piezoelectric actuator comprises a power supply circuit 26 for applying a certain voltage between the two electrodes so as to apply an electric field through the two piezoelectric layers, which are arranged so as to bend the blade 24 towards the felloe 20 of the balance 14, when a voltage is applied between the two electrodes, so that the end portion of the blade, forming a movable braking pad, can press against the external circular surface of the felloe and thus exert a mechanical braking force on the mechanical resonator. It will be noted that the voltage can be variable, to vary the mechanical braking force and therefore the mechanical braking torque applied to the balance.Concerning the braking device, reference may be made to document WO 2018 / 177779 for various variants of arrangement of such a braking device in a mechanical watch movement. In a particular variant, the braking device is formed by a blade actuated by a magnet-coil system. In another particular variant, the balance comprises a central shaft which defines or carries a part other than the rim of the balance, for example a disc, defining a circular braking surface. In the latter case, a pad of the braking member is arranged so as to exert pressure against this circular braking surface during the momentary application of a mechanical braking force.

[0022] The receiving unit 30 is preferably a contactless receiver, for example a sensor of optical signals coded according to a given communication protocol, a 'Bluetooth' receiver (preferably 'Bluetooth Low Energy': BLE) or a receiver for short-distance wireless communication known by the acronym NFC. Note that in these last two cases, these are in practice communication units for receiving and sending signals according to a predefined standard. The receiving unit 30 is arranged to be able to demodulate the external correction signal S Ext and provide the electronic control unit 28 with a digital correction signal S Cor corresponding to the demodulated signal S Ext.

[0023] A preferred variant of a first embodiment of an assembly according to the invention comprises a timepiece according to the invention and a mobile telephone 40 in which at least one time correction application is installed for implementing the present invention, in particular for detecting an error in the time indicated by the display of the timepiece and providing an external correction signal S Ext corresponding to this timepiece. The mobile telephone comprises its own resources which are used by the time correction application, in particular a power source 42, a time base 48 giving the exact real time, and a photographic device comprising a photographic sensor formed by a matrix of photo-detectors. The time base can be formed by an electronic clock which is regularly synchronized to an exact real time provided by the telephone network or by WIFI and / or by a GPS receiver.Thus, the time base provides a reference time that can be very precise, synchronized for example with an atomic clock giving the exact real time of the location of the mobile phone and its user. The photographic device 44 has a sensor formed by a matrix of pixels allowing a precise image to be taken of the analog display 12.

[0024] The time correction application installed in the mobile phone comprises an image processing algorithm 46 or the application is arranged to be able to exploit such an algorithm which is the subject of a specific image processing application installed in the mobile phone or in a server to which the mobile phone has access in particular via the Internet. The image processing algorithm is arranged to be able to determine the position of at least one determined hand of the analog display 12 in an image taken by the photographic device 44, that is to say the position of this hand relative to a graduation provided for its display, this graduation being able to be reduced to a single visual reference making it possible to determine a particular position of a virtual graduation, as indicated previously.In a two-hand display (hours and minutes), at least the angular position of the minute hand relative to a dial marker 32 or another part of the timepiece visible on the display side will be determined, making it possible to determine the minute displayed relative to the minute scale (visible or not). In a three-hand display (hours, minutes and seconds), at least the angular position of the minute hand and that of the second hand will be determined. Reference will also be made to the preceding passage relating to various variants which may be provided for determining at least one angular position of the display.

[0025] Then, the time correction application comprises an algorithm for calculating a time error between a first time datum, indicated by the display at a given instant and detected by the external device, in particular the mobile telephone 40, via its photographic sensor and its image processing algorithm, and a second time datum corresponding to the first time datum and provided at said given instant by the time base 48. As indicated above, the first time datum can be the minute displayed, the minute and second displayed or the actual time displayed (hours, minutes and seconds).

[0026] Finally, the mobile phone 40 comprises a transmission unit (a transmitter) of the external correction signal S Ext . The transmission unit is of the same type as the reception unit (of the receiver) of the timepiece, in particular of the optical type (photodiode) or of the radio type (for example a BLE or NFC communication unit). The time correction application comprises a function for encoding the result provided by the algorithm for calculating a time error in a format specific to the transmission unit 52 for sending the external correction signal S Ext . Thus, when it is intended to correct the detected time error, the external correction signal provided by the external device to the timepiece comprises information relating to this time error. Preferably, the information transmitted is the detected time error in the most precise unit that the time display allows, generally the second or the tenth of a second.It will be noted that the decision whether or not to correct the display can be made by the application in the portable device or by the electronic control unit in the timepiece. If the detected error is zero, it is obvious that no correction is required. If the detected error is non-zero but small, for example less than five seconds, it is possible in a variant to decide that this error does not require any correction. In other words, at least in a given operating mode, it is possible to define a range of values ​​for the detected time error for which no correction of the display is provided.

[0027] In another variant, it is provided that the algorithm for calculating a time error described above is incorporated into the timepiece. In this case, the external correction signal S Ext contains the first time data and the second time data which are then processed by the algorithm for calculating a time error which is integrated into the electronic control unit located in the timepiece. In an embodiment where the timepiece comprises an internal electronic clock, in particular for an electronic module of the 'Fitness' type, the time from the time base of the mobile phone can also be transmitted, as additional information, to the timepiece.Indeed, the second time data relates to the time of image capture and does not correspond exactly to the time of transmission of the external correction signal, so that additional data relating to a third time data is advantageous if it is desired to provide, for an additional function, an exact time to an internal electronic clock of the timepiece.

[0028] To the Figure 2The correction device of the timepiece is shown according to the first embodiment. The receiving unit 30A is formed by a sensor of an optical signal. This optical sensor comprises at least one element of the phototransistor type. In one variant, it is part of or consists of a solar cell forming an energy harvester 54 and used to power an electricity accumulator 56. In another variant, the optical sensor 30A is an element separate from the energy harvester 56 which serves as an energy source for a power supply circuit 58 of the correction device. The energy harvester can be formed by various types of devices known to those skilled in the art, for example a magnetic, light or heat energy harvester. In one variant, the magnetic energy harvester is arranged to receive energy from an external magnetic source making it possible to recharge the electricity accumulator without electrical contact.In another advantageous variant, the energy harvester is formed by a magnet-coil system making it possible to recover a little energy from the oscillation of the mechanical resonator of the timepiece and therefore from the barrel maintaining this oscillation. In this latter variant, at least one magnet is arranged on the oscillating element of the resonator or on the support of the resonator and at least one coil respectively on said support or on said oscillating element, so that the majority of the magnetic flux generated by the magnet passes through the coil when the resonator oscillates in its useful operating range. Preferably, the magnet-coil coupling is provided around the neutral position (rest position) of the resonator. In another variant, in which the mechanical movement is an automatic movement, the oscillating mass is used to drive a micro-generator producing electricity which is stored in the accumulator.Note that the energy harvester can also be hybrid, i.e. made up of several different units, notably of the wireless / contactless type, which are designed to recover various energies from various energy sources and transform these various energies into electrical energy.

[0029] The electronic control unit 28A controls a braking device 22 of the resonator 14, in particular an electromechanical actuator 22A shown schematically in Figure 1. Other types of actuators for momentarily applying a braking force to the mechanical resonator may be provided. Optionally, the electronic control unit includes a circuit 68 for detecting the level of available electrical energy, this detection circuit providing a signal S NE to a control logic circuit 60 to give it information relating to the level of electrical energy available, so that this logic circuit can know whether the correction module has sufficient energy before launching an operation for correcting the displayed time. If this is not the case, the following various options are possible: 1) The timepiece has a transmitter for directly indicating to the user that the accumulator must be recharged to enable a complete correction of the displayed time, for example via an optical or acoustic signal generated by the transmitter. The timepiece does not make any correction until the electrical energy level is sufficient for a complete correction. 2) The timepiece has a transmitter, in particular a BLE or NFC communication unit or an optical transmitter formed of at least one light-emitting diode, for indicating to the mobile phone 40 that the accumulator must be recharged to enable a complete correction of the displayed time. The mobile phone can then indicate this information to the user on its electronic display.In one variant, the timepiece does not make any correction until the electrical energy level is sufficient for a complete correction. In an advantageous variant, the mobile phone directly activates a function for recharging the electricity accumulator 56 via the energy harvester 54 or another energy harvesting device suitable for energy transfer from the mobile phone, for example by magnetic induction. 3) The timepiece only makes a partial correction of the displayed time using the energy available in the accumulator 56 and, preferably, informs the mobile phone, via a transmitter arranged in the timepiece, of the fact that the correction made will only be partial and possibly the remaining error that the logic circuit 60 can calculate. 4) The timepiece does not make any correction and does not transmit any information (simple variant with 'mute' timepiece).

[0030] In the absence of electrical energy management as indicated above, the timepiece can begin a required correction operation if the available electrical voltage is sufficient and carry out this correction operation as long as the electrical voltage supplied by the power supply circuit 58 is sufficient. In an advantageous variant, provision is made to put the correction device into a standby mode when no correction operation of the displayed time is planned, so as to save the electrical energy available in the accumulator 56. Various parts of the correction module can be activated, as required, only during different periods. We will return later in the context of another embodiment to the management of the electrical power supply of the correction device according to the invention.

[0031] The electronic control unit 28A, incorporated in the first embodiment of the timepiece 2, comprises a control logic circuit 60, which receives the digital correction signal Scor supplied by the receiver 30A of the external correction signal S Ext , and a generator device 62 of a periodic digital signal having a given frequency F SUP (the generator device 62 is also called 'frequency generator' or simply 'generator' at the frequency F SUP ). Depending on whether the time error T Err to be corrected corresponds to a delay or an advance in the time display, the control logic circuit 60 generates respectively either two control signals S1 R and S2 R , which it supplies respectively to the frequency generator 62 and to a time counter 63 ('timer'), or a control signal SA which it supplies to a time counter 70.The time counters 63 and 70 are programmable and are used to measure an intended correction period, respectively a period PR Cor for the correction of a delay and a period PA Cor for the correction of an advance. By definition, an advance corresponds to a positive error and a delay corresponds to a negative error. As indicated previously, the logic circuit receives either the time error T Err to be corrected (preferred variant), or a time displayed by the timepiece at a given instant and the corresponding exact real time provided by a time base of the external electronic device. In the second case, it calculates the time error T Err itself.

[0032] The arrangement of the electronic control unit 28A for correcting a detected delay in the time display will first be explained, and only subsequently the arrangement of this unit for correcting an advance.

[0033] In the case of a negative error corresponding to a delay, it is provided, according to a first mode of correction of a delay, to generate a series of periodic braking pulses at a frequency F SUP , these periodic braking pulses being applied by the braking device 22, in particular by the actuator 22A to the oscillating resonator. To do this, the logic control circuit 60 activates the frequency generator 62 via the signal S1 R and the time counter 63 which counts up or down a time interval corresponding to a correction period PR Cor whose duration (the value) is determined by the logic circuit (by definition, the expression 'time counter' includes a time counter at a given time interval and also a time downcounter to zero from this given time interval which is initially introduced into this time downcounter).

[0034] In the variant shown, when the frequency generator is activated, it provides a periodic digital signal S FS , at the frequency F SUP , to another time counter 64 (timer at a value Tp corresponding to a duration selected for the periodic braking pulses). The outputs of the timers 63 and 64 are supplied to an 'AND' logic gate 65 which provides as output a periodic activation signal S C1 to periodically activate the braking device 22, during the intended correction period PR Cor, via an 'OR' logic gate 66 or any other switching circuit making it possible to transmit the periodic activation signal S C1 to the braking device. The periodic activation signal S C1 forms the control signal S Cmd in the case of a correction of a delay detected in the time displayed by the timepiece.Thus, the braking device applies periodic braking pulses to the mechanical resonator at the frequency F SUP during a correction period PR Cor whose duration (value) depends on the delay to be corrected. Generally, the braking pulses have a dissipative character because part of the energy of the oscillating resonator is dissipated during these braking pulses. In a main embodiment, the mechanical braking torque is applied substantially by friction, in particular by means of a mechanical braking member exerting a certain pressure on a braking surface of the resonator, preferably a circular braking surface, as explained previously during the description of the timepiece 2 with reference to the . Figure 1 .

[0035] Preferably, as for the variant shown in Figure 1, the system formed by the mechanical resonator and the braking device of this resonator is configured so as to allow the braking device to start, within the useful operating range of the oscillating resonator, a mechanical braking pulse substantially at any instant of the natural oscillation period of the oscillating resonator. In other words, one of the periodic braking pulses can start substantially at any angular position of the oscillating resonator, in particular the first braking pulse occurring during a correction period.

[0036] According to the teaching given by document WO 2018 / 177779 already cited above, it is possible to precisely regulate the average frequency of an oscillating resonator by continuously applying periodic braking pulses to it at a braking frequency F FR advantageously corresponding to twice the set frequency F0c divided by a positive integer N, i.e. F FR = 2·F0c / N. The braking frequency F FR is proportional to the set frequency F0c for the mechanical resonator and depends only on this set frequency as soon as the positive integer N is given.It is learned from document WO 2018 / 177779 that, after a transient phase occurring at the start of the activation of the braking device applying the periodic braking pulses at the braking frequency F FR , a synchronous phase is established during which the oscillation of the mechanical resonator is synchronized, on average, on the set frequency F0c, provided that the braking torque applied by the braking pulses and the duration of these braking pulses are selected so that the braking pulses occur, during the synchronous phase, when the mechanical resonator passes through extreme positions of its oscillation, that is to say that the reversal of the direction of the oscillation movement occurs during each braking pulse or at the end of each braking pulse.The latter situation occurs in the advantageous, notably safer, case where the mechanical resonator is stopped by each braking pulse and then remains blocked by the braking device until the end of this braking pulse.

[0037] Although of little interest, document WO 2018 / 177779 indicates that synchronization can also be obtained for a braking frequency F FR greater than twice the set frequency (2F0), in particular for a value equal to M·F0 with M being an integer greater than two (M > 2). In a variant with F FR = 4·F0, there is just an energy loss in the system without effect during the synchronous phase, because one pulse out of two occurs at the neutral point of the resonator; which is disadvantageous. For a higher braking frequency F FR, the pulses in the synchronous phase that do not occur at the extreme positions cancel out their effects two by two. It is therefore understood that these are theoretical cases without much practical interest.It should be noted that other braking frequencies can lead to synchronization of the resonator on the set frequency, but the conditions for implementing the regulation process are much more delicate and difficult to implement.

[0038] In the context of the development which led to the present invention, it has been highlighted that the remarkable phenomenon highlighted in document WO 2018 / 177779 can be used not only to continuously synchronize a resonator to its set frequency, but also to vary in a determined manner the oscillation frequency of a resonator in two frequency ranges located respectively below and above its set frequency; that is to say that it is possible to impose a determined average frequency on a mechanical resonator which is different from its set frequency, higher or lower,by applying periodic braking pulses which can synchronize this resonator on a frequency different from the set frequency but sufficiently close to the latter to allow the establishment of a synchronous phase between the oscillating resonator and the braking device generating the braking pulses at a frequency selected for this purpose, while maintaining the oscillating resonator in a functional regime to regulate the running of the timepiece. The present invention proposes to use this remarkable discovery to carry out a correction of the time displayed by a timepiece by varying the running of the mechanical watch movement considered, that is to say by varying the frequency of the resonator which regulates the running of the mechanism driving the display of the timepiece in question during a given correction period.,

[0039] In particular, in the first embodiment of the electronic control unit described here, provision is made to correct a detected delay in the displayed time according to a first delay correction mode in which, during a correction period PR Cor , the oscillating resonator is synchronized to a correction frequency FS Cor which is higher than the set frequency F0c. It has been demonstrated in the context of the development leading to the present invention that, similarly to the case of synchronization to the set frequency, the best results are obtained, for a correction frequency higher or lower than the set frequency, when the braking frequency F Bra is selected, for a given correction frequency F Cor, so as to satisfy the following mathematical relationship: F Bra = 2 ⋅ F Cor / N , where N is a positive integer.

[0040] Thus, the periodic braking pulses are applied to the mechanical resonator at a braking frequency F Bra advantageously corresponding to twice the correction frequency F Cor divided by a positive integer N, preferably low. This relationship is valid for a correction frequency F Cor = FScor which is higher than the set frequency and also for a correction frequency F Cor = FI Cor which is lower than the set frequency (first mode of correction of an advance which will subsequently occur in another embodiment of a timepiece according to the invention). The braking frequency F Bra is therefore proportional to the intended correction frequency F Cor and depends only on this correction frequency as soon as the positive integer N is selected. By 'synchronization on a given frequency' is meant an average synchronization on this given frequency.This definition is important for a number N greater than two. For example, in the case N = 6, we have only one oscillation period out of three which undergoes a variation in its duration, relative to the set period T0c = 1 / F0c (in fact relative to the natural / free oscillation period T0 = 1 / F0), via a time shift generated by each braking pulse in the oscillation of the resonator.

[0041] It will be noted that, as in the case of synchronization on the set frequency, other braking frequencies can make it possible to obtain, under certain conditions, synchronization on a desired correction frequency, but the selection of a braking frequency F Bra = 2·F Cor / N makes it possible to obtain synchronization on the frequency F Cor more efficiently and with greater stability. In general, the mathematical relationship between the braking frequency and the correction frequency is F Bra = (p / q)·F Cor with p and q two positive integers and the number q advantageously greater than the number p. The person skilled in the art can experimentally establish a list of the fractional numbers p / q which are appropriate and under which conditions (in particular for which braking torque).

[0042] It should be noted that braking pulses can be applied with a constant torque or a non-constant torque (for example, substantially in a Gaussian or sinusoidal curve). By 'braking pulse' is meant the momentary application of a torque to the resonator which brakes its oscillating member (balance), i.e. which opposes the oscillating movement of this oscillating member. In the case of a variable torque, the duration of the pulse is generally defined as the part of this pulse which presents a significant torque to brake the resonator, in particular the part for which the torque is greater than half the maximum value. It should be noted that a braking pulse can present a strong variation. It can even be chopped and form a succession of shorter pulses.Generally, the duration of each braking pulse is expected to be less than half of a setpoint period T0c for the resonator, but it is advantageously less than a quarter of a setpoint period and preferably less than T0c / 8.

[0043] To Figures 3 And 4 are represented, for a mechanical resonator having a set frequency F0c = 4 Hz and exhibiting an oscillation 72, respectively a first series of periodic braking pulses 74 applied to the resonator at a frequency F INF = 2·FI Cor with FI Cor = 0.99975·F0c = 3.999 Hz, for the case of a natural frequency F0 = 4.0005 Hz, and a second series of periodic braking pulses 76 applied to the resonator at a frequency F SUP = 2·FS Cor with FS Cor = 1.00025·F0c = 4.001 Hz, for the case of a natural frequency F0 = 3.9995 Hz. The graphs below the Figures 3 , 4show the evolution of the oscillation frequency of the resonator during a correction period, which is defined as the period during which the braking pulses at the frequency F INF or F SUP are applied to the resonator. Curve 78 shows the evolution of the oscillation frequency of the mechanical resonator during the application of the first series of periodic braking pulses 74 for a correction of an advance detected in the displayed time, the braking frequency F INF leading to a correction frequency FI Cor , given by the synchronization frequency, which is lower than the set frequency F0c (first mode of correction of an advance).Curve 80 shows the evolution of the oscillation frequency of the mechanical resonator during the application of the second series of periodic braking pulses 76 for a correction of a delay detected in the displayed time, the braking frequency F SUP leading to a correction frequency FS Cor, given by the synchronization frequency, higher than the set frequency (first mode of correction of a delay).

[0044] The very short correction period at Figures 3 And 4 was taken to be able to show a complete correction period while having a representation of the oscillation of the resonator and the periodic braking pulses which is clearly visible on the graph giving the angular position of the resonator as a function of time. Indeed, in a few seconds, the possible correction is relatively small, in practice less than one second. For the correction frequencies chosen at Figures 3 And4 , the correction is therefore very small. Thus, if the natural frequencies (natural / free frequencies) of the oscillating resonator are here within the norm for a mechanical watch, since they correspond to a daily error of approximately 10 seconds per day (advance, respectively retardation), the correction frequencies are given purely as examples and are much closer to the set frequency than the correction frequencies which are generally provided for the implementation of the first mode of correction of an advance or retardation. In conclusion, the Figures 3 And 4are given only schematically to generally explain the behavior of the oscillating resonator when subjected to a series of periodic braking pulses at a correction frequency close to, but different from, the set frequency, and in the case of a natural frequency leading to a classical time drift. More detailed and precise considerations regarding possible correction frequencies will be explained later.

[0045] In the two graphs showing the frequency curves 78 and 80, at the beginning of the correction period, a transient phase PH Tr is observed during which the frequency varies before stabilizing at the frequency FI Cor, respectively FS Cor during a synchronous phase PH Syn which follows the transient phase. In both cases shown, the transient phase PH Tr is relatively short (less than 2 seconds) and the frequency changes in the direction of the desired correction frequency. In both cases shown, the average correction per unit of time during the transient phase is approximately equal to that which occurs during the synchronous phase. However, it should be noted that the transient phase can be longer, for example from 3 to 10 seconds, and the frequency changes during the transient phase vary from case to case so that the average correction is variable and not determined, but it remains practically small.We can refer to the . figures 9 to 11 of document WO 2018 / 177779 where the transient phases to synchronize the resonator on the set frequency F0c, from a close but different natural frequency, are longer. It will be noted that at the figure 10 of this document, while the set frequency is higher than the natural frequency of the resonator, the oscillation frequency begins to decrease at the beginning of the transient phase before increasing to finally exceed the natural frequency and stabilize at the set frequency.

[0046] The duration of the transient phase and the evolution of the frequency during this transient phase depend on various factors, in particular the braking torque, the duration of the pulses, the initial amplitude of the oscillation, and the instant at which the first braking pulse occurs in an oscillation period. It is therefore difficult to control the time difference resulting from a transient phase relative to the set frequency. For example, if F Cor = 1.05 F0c = 4.2 Hz and the transition phase lasts a maximum of 10 seconds, and if we assume that the average frequency during this transition phase is equal to F0c, then the absolute time difference with respect to F Cor is at most equal to half a second. This uncertainty therefore causes a small error in the correction generated during a correction period, but it is not negligible. We will see later a solution to avoid such an error.In the first embodiment of the electronic control unit, there is therefore a small possible error in the correction obtained if the correction period PR Cor is determined (the duration of) only on the basis of the time error T Err to be corrected, by defining this correction period as the period during which a series of periodic braking pulses at the intended braking frequency are applied to the resonator, and by assuming that the oscillation frequency during the correction period is that of the synchronization frequency.

[0047] The synchronization frequency determines the correction frequency. By definition, the correction frequency F Cor is equal to the synchronization frequency. It should be noted that, in the synchronous phase of the correction period, the duration of the braking pulses must be sufficient for the braking torque applied to the resonator to allow it to stop (passing through an extreme angular position, defining its instantaneous amplitude) during or at the end of each braking pulse. In the case of a synchronization frequency higher than the set frequency to correct a delay, the time interval during which the resonator remains stopped during a braking pulse reduces the possible correction per unit of time, so that it is preferable to limit this time interval, taking into account a certain safety margin, to have a shorter correction period thanks to a higher synchronization frequency.It should be noted that the frequency of the braking pulses, the maintenance energy supplied to the resonator at each alternation of its oscillation and the value of the braking torque are involved in the time interval necessary to stop the oscillating resonator. For a given braking frequency and the resulting correction frequency, the person skilled in the art will be able to determine, in particular experimentally or by simulations, a braking torque and a duration for the braking pulses so as to optimize the braking system. For set frequencies between 2 Hz and 10 Hz, braking torques between 0.5 µNm and 50 µNm and braking pulse durations between 2 ms and 10 ms generally prove appropriate for the correction frequencies that are practically advantageous to use (these ranges of values ​​being given as examples and are in no way limiting).

[0048] Based on the assumption mentioned above, namely that the synchronization frequency occurs over the entire correction period PR Cor , we can determine the value of the correction period to be provided on the basis of the time error T Err to be corrected, the set frequency F0c and the correction frequency F Cor ; and since the synchronization frequency determines the correction frequency which is equal to it, we can also determine the value of the correction period to be provided on the basis of the time error T Err to be corrected, the set frequency F0c and the braking frequency F Bra . By definition, an advance in the time display corresponds to a positive error while a delay corresponds to a negative error. We obtain the following mathematical relationships to determine the value of the correction period: P Cor = T Err ⋅ F 0 c / F 0 c − F Cor = 2 T Err ⋅ F 0 c / 2 F 0 c − N ⋅ F Bra

[0049] In the first mode of correction of a delay (negative error), the correction frequency F Cor = FS Cor is greater than F0c, so that P Cor is positive. In this case the braking frequency F Bra = F SUP . We then have the relationship: PR Cor = T Err ⋅ F 0 c / F 0 c − FS Cor = 2 T Err ⋅ F 0 c / 2 F 0 c − N ⋅ F SUP

[0050] In the first mode of correction of an advance (positive error), the correction frequency F Cor = Fl Cor is less than F0c, so that P Cor is positive. In this case the braking frequency F Bra = F INF . We then have the relationship: PA Cor = T Err ⋅ F 0 c / F 0 c − Fl Cor = 2 T Err ⋅ F 0 c / 2 F 0 c − N ⋅ F INF

[0051] In an alternative embodiment, the external electronic device (mobile phone 40) has in memory or receives from the timepiece in question the set frequency for the mechanical resonator of this timepiece and the higher frequency intended to correct a delay (possibly according to value ranges for this delay). Thus, in this alternative, the time correction application which is implemented in the external electronic device can determine the value of the correction period PR Cor and communicate this information to the timepiece via the external correction signal S Ext . In this alternative, the electronic control unit of the timepiece does not need resources to calculate the value of the correction period on the basis of the time error T Err to be corrected.

[0052] Following the general presentation relating to a correction of the rate of a mechanical timepiece obtained by a series of periodic braking pulses applied to its resonator, we can return to the first embodiment of the timepiece according to the invention. The electronic control unit 28A ( Figure 2) is arranged to provide the braking device, each time the external correction signal S Ext received by the receiving unit of the timepiece 2 corresponds to a delay in the displayed time that is intended to be corrected, with a control signal S C1 derived from the periodic digital signal S FS provided by the frequency generator 62, during a correction period PR Cor , to activate the braking device 22 so that this braking device generates a series of periodic braking pulses which are applied to the resonator at the frequency F SUP . Since (the duration of) the correction period is determined by the delay to be corrected, the number of periodic braking pulses in the series of periodic braking pulses is therefore also determined by the delay to be corrected.The frequency F SUP is provided and the braking device is arranged in such a way that each series of periodic braking pulses at the frequency F SUP can generate, during the corresponding correction period, a first synchronous phase in which the oscillation of the resonator is synchronized (by definition 'average synchronized') on a correction frequency FScor which is higher than the set frequency F0c provided for the mechanical resonator.

[0053] In reference to the Figures 5 to 10 ,some observations relating to the braking pulses will be set out below, in particular concerning the braking frequencies F Bra and the corresponding correction frequencies F Cor which are advantageously envisaged in a preferred variant of the first mode of correction of a delay, and also in a preferred variant of a first mode of correction of an advance (which will be implemented in an embodiment described subsequently), in which it is provided to correct an advance detected in the time displayed by a series of braking pulses at a frequency F INF , already defined previously, resulting in a correction frequency FI Cor , also defined previously, which is lower than the set frequency F0c.

[0054] There Figure 5shows a first part of a correction period with a relatively high ratio between the correction frequency FS Cor = 3.5 Hz and the set frequency F0c = 3.0 Hz (substantially equal to the natural frequency of the resonator when it is freely oscillating, represented by the oscillation 82), namely a ratio RS = FS Cor / F0c = 3.5 / 3.0 = 1.167. When braking pulses 84 are applied to the mechanical resonator with a braking frequency F Bra = F SUP = 2 FS Cor = 7.0 Hz (case N = 1) and a sufficient braking force torque, allowing in the transient phase PH Tr to sufficiently reduce the amplitude of the oscillation 86 of the oscillating resonator to finally stop it during each braking pulse, the corresponding correction frequency, i.e. FS Cor = 3.5 Hz, can be imposed on this resonator relatively quickly.It will be noted that in the example given, the desired synchronization is already obtained after one second, but a PHst phase of stabilization of the oscillation occurs at the beginning of the synchronous phase PH Syn. In the case shown, the amplitude increases again during the stabilization phase to finally stabilize at an amplitude corresponding to approximately one third of the initial amplitude of the free resonator.

[0055] A demonstrator (a prototype of the timepiece according to the invention) was produced for the case presented in the Figure 5. By applying periodic braking pulses at the frequency F SUP = 7.0 Hz to the mechanical resonator, a 7-hour advance on the timepiece display was obtained for a 6-hour correction period, and this in a very precise manner. This 'gained' precisely 1 hour in 6 hours of real time. Such a result opens up prospects for corrections to the time indicated by the display which are other than corrections of a time drift of this display due solely to the inaccuracy of the freely operating resonator (i.e. in the absence of braking pulses). Thus, as will be seen in another embodiment described later, the present invention makes it possible to correct the 1-hour jump which occurs at a seasonal change of time (in particular for the transition from winter time to summer time where the legal time is advanced).We can even think about correcting a change of time zone that may occur during a trip.

[0056] There Figure 6shows the free oscillation 82A of a mechanical resonator, a first oscillation 86A of this resonator in a synchronous phase of a correction period where the ratio RS between the correction frequency FS Cor and the set frequency F0c is relatively low (i.e. relatively close to '1'), and a second oscillation 86B of this resonator in a synchronous phase of a correction period where the ratio RS between the correction frequency FScor and the set frequency F0c is relatively high (i.e. relatively far from '1'). The first oscillation 86A results from a series of periodic braking pulses 84A of relatively low intensity and occurring once per oscillation period (which corresponds to the case N = 2 with F SUP = FScor).On the other hand, the second oscillation 86B results from a series of periodic braking pulses 84B of relatively high intensity and occurring once per alternation of the oscillation (which corresponds to the case N = 1, i.e. F SUP = 2·FScor).

[0057] By appropriately selecting the braking torque and the braking frequency, it is observed that the correction frequency can vary continuously between the set frequency F0c and a certain upper frequency FSC max , for the correction of a delay in the displayed time, and continuously between the set frequency F0c and a certain lower frequency FIC max , for the correction of an advance in the displayed time. The upper frequency FSC max and the lower frequency FIC max are not values ​​that can be easily calculated theoretically. They must be determined practically for each timepiece. It will be noted that although this information is interesting, it is not necessary.What is important is that the braking frequencies are selected and the braking torques available are suitable to generate during each correction period, preferably fairly quickly, a synchronous phase during which the mechanical resonator can oscillate at the correction frequency provided by the mathematical relationship given above, without being stopped in its oscillation (i.e. it is necessary to avoid stopping the resonator so that it can no longer start from the stopped position, which would lead to a stoppage of the display drive mechanism).

[0058] On the Figure 6a safety angle θ Sec is indicated below which, in absolute value, stopping the mechanical resonator will be avoided (i.e. between -θ Sec and θ Sec ), and therefore above which the amplitude, in absolute value, must practically remain during the synchronous phase, at least after the stabilization phase. Advantageously for the operation of the mechanical resonator, the angle θ Sec is provided equal to or, preferably, greater than an angle θ ZI (see Figure 10) which corresponds to the coupling angle between the resonator and the escapement associated with it, on one side and the other side of the neutral position of the resonator defined by the angular position of the coupling pin carried by the balance wheel plate when this resonator is at or passes through its rest position. We thus declare 'forbidden zone', to stop the mechanical resonator during a braking impulse, the angular coupling zone (-θ ZI to θ ZI ) between the mechanical resonator and the escapement (we will note that it is possible to brake in this forbidden zone during the transient phase, but we will avoid stopping the resonator in this forbidden zone). We will note that, in the useful operating range of the resonator, it may be necessary, to maintain correct operation of the escapement and in particular to ensure the release phase, for the safety angle θ Sec to be greater than the coupling angle θ ZI .The person skilled in the art will be able to determine a value for the safety angle θ Sec for each mechanical movement associated with a correction device according to the first embodiment. The coupling angle θ ZI may vary from one mechanical movement to another, in particular between 22° and 28°.

[0059] The condition of non-blocking of the resonator in the safety angular zone during the period of correction of a delay is important because a counting of the passage of time via the escapement (i.e. the timing of the running of the mechanism driving the time display) must continue during this period of correction of a delay. Thus, very advantageously, said frequency F SUP and the duration of the periodic braking pulses are selected so that, during said synchronous phase of a correction period within the framework of the first mode of correction of a delay, the periodic braking pulses each occur outside a coupling zone between the oscillating mechanical resonator and the escapement, preferably outside a safety zone defined for the mechanical movement.The same applies to the selection of the said frequency F INF and the duration of the periodic braking pulses in the first mode of correction of an advance.

[0060] To guide the person skilled in the art in the choice of correction frequencies and corresponding braking frequencies, a mathematical model has been established based on the equation of motion of a mechanical oscillator. To determine a maximum correction, positive or negative, the resonator is considered in a synchronous and stable phase. Then, a simplification is introduced for the sustaining force applied to the resonator by the energy source via the escapement, considering it to be of the cos(ωt) type. It will be noted that this simplification is prudent in that it reduces the maximum value relative to the real case where the entire energy supplied to the resonator occurs in the forbidden zone θ ZI defined previously.Finally, we consider the duration of the braking pulses to be very small, in fact punctual, by defining the braking frequency F Bra as the inverse of the time value T Sec at which the resonator reaches, in the equation of motion given below, the safety angle θ Sec in the half-wave corresponding to the number N selected in the relation F Cor = N·F Bra / 2.

[0061] To find the maximum correction and thus the minimum or maximum period depending on whether the time error to be corrected is negative (delay) or positive (advance), the time t=0 is given by a braking pulse during which the oscillator is stopped at the safety angle θ Sec . Then, in the stable synchronous phase, the resonator must stop at the next braking pulse at the earliest, respectively at the latest also at the safety angle (-1 N< )·θ Sec in a time range given by the value of N and by the fact that the correction frequency is planned higher or lower than the set frequency F0c to correct the delay or the advance.

[0062] In this case, the equation of motion is given by: θ t = θ 0 + θ Sec − θ 0 e − t τ × cos 2 πf 0 t where τ = Q·T0 / π , T0 is the free oscillation period (considered equal to T0c = 1 / F0c for calculations) and θ 0 is the amplitude of free oscillation.

[0063] We therefore observe that the quality factor Q of the mechanical resonator intervenes in the equation of motion.

[0064] To obtain a correction frequency FS Cor higher than the set frequency F0c, T Sec must intervene in an alternation after the resonator has passed through its neutral / rest position. We therefore have for a given N: θ T Sec = − 1 N θ Sec avec T Sec ∈ 2 N − 1 4 T 0 , N 2 T 0

[0065] The maximum braking frequency FSB max (N) = 1 / T Sec and the maximum correction frequency FSC max (N) = N·FSB max / 2.

[0066] To obtain a correction frequency FI Cor lower than the set frequency F0c, T Sec must intervene in an alternation before the resonator passes through its neutral / rest position. We therefore have for a given N: θ T Sec = − 1 N θ Sec avec T Sec ∈ N 2 T 0 , 2 N + 1 4 T 0

[0067] The minimum braking frequency FIB min (N) = 1 / T Sec and the minimum correction frequency FIC min = N·FIB min / 2.

[0068] THE Figures 7A and 7Brepresent respectively the curves of RS max (N=1) = FSC max (N=1) / F0c and of RS max (N=2) = FSC max (N=2) / F0c as a function of the amplitude θ 0 of the free oscillation of the mechanical resonator for various quality factors Q of this mechanical resonator. It is observed that the smaller the quality factor, the larger the ratio RS max (N).

[0069] There Figure 8 gives, for a resonator having a quality factor Q = 100, a free amplitude θ 0 = 300° and a safety angle θ Sec = 25°, the upper correction frequency ranges, for a set frequency F0c and various respective values ​​of N, which are possible within the framework of the first mode of correction of a delay, by representing the ratio RS = FS Cor / F0c which extends between the value '1' and RS max (N).

[0070] There Figure 9gives, for a resonator having a quality factor Q = 100, a free amplitude θ 0 = 300° and a safety angle θ Sec = 25°, the lower correction frequency ranges, for a set frequency F0c and various respective values ​​of N, which are possible within the framework of the first mode of correction of an advance, by representing the ratio RI = FI Cor / F0c which extends between RI max (N) and the value '1'.

[0071] As previously stated, the ranges given to the Figures 8 and 9 derive from a simplified theoretical model. We see that the maximum and minimum correction frequencies depend on several parameters. These figures give a good indication of reality for a mechanical movement with fairly standard properties. However, for each given mechanical movement, it will be necessary to define the limit values ​​if we wish to approach them in order to make large corrections in relatively short correction periods.

[0072] After having explained in detail the arrangement of the electronic control unit and the operation of the correction device of the first embodiment of the timepiece according to the invention for correcting a delay in the time displayed by the timepiece, the arrangement of the electronic control unit according to this first embodiment will be explained below for correcting an advance in the time displayed according to a second mode of correction of an advance.

[0073] To enable the implementation of the second mode of correction of an advance, the timepiece comprises a device for blocking the mechanical resonator. Generally, in the context of the second mode of correction of an advance, the electronic control unit is arranged to be able to provide the blocking device, when the external correction signal received by the receiving unit corresponds to an advance in the displayed time that is intended to be corrected, a control signal which activates the blocking device so that this blocking device blocks the oscillation of the mechanical resonator during a correction period determined by the advance to be corrected, so as to stop the operation of said drive mechanism during this correction period.

[0074] In the first embodiment described with reference to the Figures 1 And 2, the timepiece 2 comprises a blocking device which is constituted by the braking device 22, in particular by the piezoelectric actuator 22A, which also serves to implement the first mode of correction of a delay. When the external correction signal S Ext received by the reception unit 30 corresponds to an advance in the displayed time which is intended to be corrected, the logic circuit 60 of the electronic control unit 28A ( Figure 2) provides a control signal SA to the time counter 70 (timer) which is programmable. This timer 70 then generates a signal S C2 for activating the braking device 22, via the 'OR' gate 66 or another switch, for a correction period PA Cor whose duration is substantially equal to the corresponding advance T Err to be corrected. The periodic activation signal S C2 then forms the control signal S Cmd . It will be noted that the activation signal S C2 controls the braking device 22 in a mode of blocking the mechanical resonator for a relatively long duration, namely for substantially the entire correction period PA Cor = T Err . For this purpose, the voltage then supplied by the power supply circuit 26 between the two electrodes of the piezoelectric blade 24 may differ from that intended to generate the periodic braking pulses to correct a delay.This voltage is selected so that the braking force applied to the mechanical resonator can stop it, preferably fairly quickly, and then block it until the end of the correction period.

[0075] In a variant, the electrical voltage applied to the piezoelectric blade 24 is provided to be variable during the correction period. For example, it is possible to provide a higher voltage at the start of the correction period, which is selected to quickly stop the resonator, in particular during the alternation of the oscillation of this resonator in which the start of the correction period occurs, and then to reduce the voltage to a lower value but sufficient to keep the resonator stopped. Advantageously, the electrical voltage will be selected so that the resulting braking force cannot stop the mechanical resonator in the forbidden angular zone (-θ ZI to θ ZI ) defined previously.For this purpose, the braking torque is selected large enough to be able to stop the resonator and lock it in the angular stopping position, whatever it may be, and small enough so that this braking torque cannot stop the resonator in the forbidden angular zone. Preferably, stopping the resonator in the safety angular zone (-θ Sec to θ Sec ), described previously, will be avoided. This last condition is important when the resonator is not self-starting. Generally speaking, it is sufficient to ensure that the resonator can restart at the end of the correction period.

[0076] According to a specific variant making it possible to ensure a rapid stopping of the resonator outside the aforementioned safety angular zone, a preliminary phase is provided occurring before the correction period where the resonator is blocked (i.e. where it remains stopped following its stopping occurring quickly or immediately at the start of the correction period). During the preliminary phase, it is provided to use the first mode of correction of a delay available in the first embodiment. It can be seen that in the synchronous phase of the first correction mode described above, the passage through an extreme angular position occurs during each braking pulse. Thus, the braking pulses are in phase with passages of the mechanical resonator through one of its two extreme angular positions, each of these passages defining the start of an alternation.Advantage is taken of this fact by activating the frequency generator 62 during the preliminary phase, which is planned to be relatively short in duration but nevertheless of sufficient duration to establish a synchronous phase where the resonator is synchronized to the frequency FS Cor . The preliminary phase ends for example during a last braking pulse which is immediately followed by the correction period with an activation of the braking device in the blocking mode. Thus, it is known that the resonator is blocked outside the safety angular zone. The braking torque for the preliminary phase can be planned different from that used for the correction of a delay explained previously.

[0077] Since the frequency behavior during the transient phase at the beginning of a series of periodic braking pulses can vary from case to case, it is hardly possible to determine the error generated by the preliminary phase. However, it is possible to estimate a maximum error. For example, if the frequency F SUP = 1.05·F0c (correction of 30 seconds in 10 minutes) and the preliminary phase is planned with a duration of 10 seconds (selected duration greater than those of transient phases that may occur), the maximum error can be estimated at 0.5 seconds (half a second). For a mechanical movement, while such an error is not negligible, it is relatively small since a conventional mechanical movement has a daily error generally between 0 and 5 to 10 seconds.

[0078] In reference to the Figure 10 ,a second embodiment of a timepiece according to the invention will be described which is distinguished from the first embodiment by the arrangement of the blocking device making it possible to advantageously implement the second mode of correction of an advance in the time display associated with the mechanical movement of the timepiece. This mechanical movement 92 comprises a conventional escapement 94 formed by an anchor wheel 95 and an anchor 96 which can oscillate between two pins 95. The anchor comprises a fork 97 between the horns of which is conventionally inserted at each alternation the pin 98 also forming the escapement and carried by a plate 100 which is integral with the shaft 102 of the balance 104 (partially shown) of the mechanical resonator or made of the same material as this shaft (that is to say that the shaft is machined with a longitudinal profile defining the plate).The plate 100 is circular and centered on the central axis of the shaft 102 which defines the axis of rotation of the balance wheel 104.

[0079] The timepiece includes a locking device 106 which is separate from the braking device 22A ( Figure 1 ) used for the correction of a delay. This blocking device is therefore dedicated to the implementation of the second mode of correction of an advance. The blocking device is formed by an electromechanical actuator, in particular by a piezoelectric actuator of the same type described in connection with the Figure 1. According to the variant shown, the actuator comprises a flexible piezoelectric blade 24A and its two electrodes are supplied with voltage by a power supply circuit 26A. The blade 24A has at its free end a projecting part 107, forming a stud, which is located on the side of the plate 100. The blade extends in a direction parallel to a tangent of the circumference of the plate, at a short distance from this circular circumference. The plate has a through hollow 108, which opens radially on the periphery of the plate and whose profile in the general plane of the plate is provided to allow the stud 107 to be housed there when it is located angularly opposite this hollow and the piezoelectric actuator 106 is activated.According to the variant shown, the hollow 108 is diametrically opposite the pin 98 and the stud is located angularly at the zero position of the pin (i.e. at the angular position of this pin when the resonator is at rest, respectively passes through its neutral position). Note that this zero angular position of the pin normally defines the zero angular position of the balance 104, and therefore of the mechanical resonator, in an angular reference frame fixed relative to the mechanical movement 92 and centered on the axis of rotation of the balance.

[0080] In an equivalent variant, the hollow may be arranged at another angle relative to the pin, for example at 90°, and the actuator 106 is then positioned at the periphery of the plate so that the stud 107 is diametrically opposite the hollow when the resonator is at rest. Thus, whatever the alternation and the angular position when the piezoelectric actuator is activated, the stud will enter the hollow when the resonator is in an equal angular position, in absolute value, substantially at 180° (this being exactly the case if the balance is set to the reference mark, that is to say that the pin is aligned with the respective centers of rotation of the balance and the anchor when the resonator is at rest).This value of 180° is clearly outside the safety zone (it is greater than the safety angle defined previously) and it is generally lower than the range of amplitudes of the mechanical resonator corresponding to its useful operating range.

[0081] Then, according to the advantageous variant represented in the Figure 10, the side walls of the hollow 108 are parallel to the radius passing through its center and the axis of rotation of the balance. In an equivalent variant, these side walls are provided radial. Similarly, the stud 107 has two side walls, perpendicular to the general plane of the plate, which are parallel to the radius passing through its center and the axis of rotation of the balance or which are, in the equivalent variant, substantially radial relative to the axis of rotation. Thanks to this arrangement, when the stud 107 is introduced into the hollow 108 which then serves as its housing, this stud blocks the rotation of the plate 100 and therefore of the balance 104 by a substantially tangential force whose direction is substantially parallel to the general longitudinal direction of the piezoelectric blade 24A.When the actuator 106 is activated, the end of the blade carrying the stud 107 undergoes a substantially radial displacement, relative to the axis of rotation of the balance, and the stud can then, depending on the angular position of the balance at that moment, either exert an essentially radial force on the circular lateral surface of the plate 100, or enter at least partially into the hollow 108. The actuator only needs to be arranged so that the stud can undergo, when this actuator is activated, a sufficient displacement to enter the hollow when the latter is located in an angular position corresponding substantially to that of the stud (in a fixed angular reference frame relative to the stud).

[0082] A relatively low friction force can be expected when the stud comes to bear against the circular lateral surface of the plate at the start of a correction period, i.e. following activation of the actuator, in the case where the hollow is not opposite the stud when its proximal surface reaches the level of the circular circumference of the plate. Thus, it can be ensured that the amplitude of the resonator decreases little during the initial braking effected by the stud exerting a radial force against this circular lateral surface. Then, when the stud is inserted into the hollow while the latter is opposite the stud, the radial force exerted by the piezoelectric blade on the plate can be very low, or even zero. The electrical energy required to block the resonator during the correction period can therefore be relatively small, much smaller than in the case of the first embodiment.

[0083] When the correction device of the timepiece receives an external correction signal corresponding to the correction of an advance detected in the time display, its logic control circuit, in a manner similar to the operation of the first embodiment, activates the blocking device 106, by providing it with a control signal S C2 similar to that described previously in the context of the first embodiment, for a period substantially equal to the time error to be corrected.By means of the arrangement of a hollow in a circular plate centered on the axis of rotation of the resonator and an actuator having a corresponding part, but preferably less wide than the hollow, which is arranged to be able to undergo a substantially radial movement between a non-interaction position, corresponding to a non-powered state of the actuator, and a state of interaction with the balance of the resonator, corresponding to a powered state of the actuator in the variant described here, the start of the activation of the blocking device 106 can take place at any time, whatever the angular position of the resonator and whatever the direction of the oscillation movement (therefore independently of the alternation in progress among the two alternations forming each oscillation period). This is very advantageous.

[0084] Finally, in connection with the second embodiment, the electromechanical actuator may be of a type other than that shown in Figure 10. For example, in one variant, the actuator may comprise a ferromagnetic or magnetized core which can be moved under the action of a magnetic field generated by a coil. In particular, this core is collinear with the coil and it comprises an end portion emerging from the coil at least when the actuator is activated, this end portion forming a finger which is configured to be able to be introduced into the hollow of the plate, this finger having in particular an end portion with the shape of the pad 107. In a preferred variant, the actuator is a bistable actuator. The power supply to the actuator is advantageously maintained, during its activation to move from the non-interaction position to the interaction position, until the pad has entered at least partially into the hollow 108.Such a variant is particularly interesting because the actuator does not have to exert any blocking force by applying radial pressure to an element of the resonator balance in its two stable positions corresponding respectively to the intended non-interaction position and the interaction position. In this preferred variant, the energy consumption can be very low, regardless of the duration of the correction period, which is very advantageous.

[0085] In reference to the Figure 11 , a third embodiment of a timepiece according to the invention will be described, which is essentially distinguished from the first embodiment by the arrangement of the blocking device making it possible to advantageously implement the second mode of correcting an advance in the time display associated with the mechanical movement of the timepiece. The references already described in relation to the Figures 1 And2will not be described here again in detail. As in the second embodiment, the timepiece 112 according to the third embodiment comprises a blocking device 114 which is distinct from the braking device 22B used for correcting a delay. The braking device 22B is similar to the braking device 22A already described and its operation is similar, that is to say that it is adapted for the implementation of the first mode of correcting a delay explained in detail previously. This braking device 22B comprises a power supply 26B which is partially common to that of the blocking device 114 and which receives the control signal S C1 .Then, it comprises a piezoelectric blade 24B in the shape of a square, this shape being provided here as a possible variant and to make it easier to arrange the piezoelectric blade 24B and the piezoelectric blade 25, forming the blocking device, on the same surface of a support containing the common power supply 26B. However, other variants can be provided, in particular a braking device identical to that of the . Figure 1 with a power supply circuit entirely separate from that of the blocking device.

[0086] The locking device 114 is remarkable for at least two reasons. First, it acts on a conventional mechanical resonator 14 requiring no modification, in particular no specific machining unlike the second embodiment. Then, the locking device is a bistable device, that is to say that a locking element has two stable positions, namely here the lever 115. The locking device is arranged in such a way that a first of the two stable positions of the lever corresponds to a position of non-interaction with the balance 16 while the second of these two stable positions corresponds to a position of locking of the resonator via a radial force exerted by a blade 116, forming the lever 115, on the rim 20 of the balance.The blade 116 is pivoted around an axis arranged in the mechanical movement 4A (in another variant, the lever is arranged so that its pivot axis is arranged on a support separate from the mechanical movement and belonging to a correction module). In one variant, this axis is formed by a fixed pin around which an annular end portion of the blade 116 is mounted. This blade is rigid or semi-rigid, a slight flexibility being able to be advantageous.

[0087] The blade 116 is associated with a particular magnetic system making it possible to generate the bistable character of the lever 115 and consequently of the blocking device 114. The magnetic system comprises a first magnet 118, carried by the blade and therefore integral in rotation with this blade, a second magnet 119 arranged fixedly in the mechanical movement, or relative to the latter, and a ferromagnetic plate 120 arranged between the first magnet and the second magnet, at a small fixed distance from the second magnet 119 or against it (for example the plate is glued against this magnet, only a layer of glue then separating the magnet from the plate).

[0088] The first and second magnets 118, 119 have magnetic polarities that are opposite and their respective magnetic axes are substantially aligned. Thus, in the absence of the ferromagnetic plate, these two magnets would constantly exert a repulsive force on each other and the rocker would always remain or return, in the absence of forces external to the magnetic system, to a position where the blade is in abutment against a pin 124 limiting its rotation. However, thanks to the arrangement of the ferromagnetic plate, there is an inversion of the magnetic force that is exerted between the two magnets. More precisely, when the movable magnet 118 is approached from its remote position (shown in Figure 11), the repulsive force decreases until it is cancelled and finally reverses when the moving magnet comes close to the ferromagnetic plate. Thus, when the moving magnet 118 is located very close to or against the ferromagnetic plate 120, this moving magnet experiences a magnetic force of attraction. This astonishing physical phenomenon is explained in detail in patent application CH 711 889, which also contains some watchmaking applications.

[0089] The lever 114 is arranged so as to have two stable positions in the absence of forces external to the magnetic system of the locking device. The first stable position is a non-interaction position in which the blade 116 is in abutment against the pin 124, the moving magnet 118 then undergoing a magnetic repulsion force which holds the lever against this pin. The second stable position is an interaction position in which the blade 116 is in abutment against the rim 20 of the balance 16, the moving magnet 118 then undergoing a magnetic attraction force which holds the lever against this rim. The ferromagnetic plate 120 is arranged so that the blade exerts a radial force for locking the balance 16, and therefore the resonator 14, when the lever is in its second stable position.In order for the blade to be able to exert a locking force against the outer lateral surface of the felloe 20, the surface of the plate 120 located opposite the moving magnet 118 must be slightly set back relative to the proximal surface of this moving magnet when the blade 116 comes into contact with the felloe. If the blade is semi-rigid and therefore has a certain flexibility, it is possible that the moving magnet will finally come into abutment against the proximal surface of the ferromagnetic plate, but then the blade is in flexion.

[0090] To move the flip-flop 115 between its two stable positions, in both directions, the blocking device comprises a device for actuating this flip-flop. This actuating device 126 is controlled by the logic circuit of the electronic control unit via its power supply circuit which receives the control signal S C2 . What is remarkable is the fact that the blocking force exerted by the blocking device does not come from an electrical supply of this blocking device but from the magnetic system which forms it. Thus, the blocking device requires electrical power only at the beginning and at the end of the blocking period occurring in the second mode of correction of an advance, when switching the flip-flop between its two stable states.

[0091] By way of example only, the actuating device 126 is formed by a piezoelectric device comprising a piezoelectric blade 25 which can be flexed in both directions from its rest position (non-activated position), by the application of an electrical voltage, supplied by the power supply circuit 26B, between its two electrodes respectively with a positive and negative electrical polarity. The flip-flop 115 comprises a fork 122 defining a cavity inside which the free end of the piezoelectric blade 25 is housed. The width of the cavity is preferably provided to be greater than the width of the free end of the blade 25 and this blade is arranged so that it is against a first side wall of the cavity when the flip-flop is in its first stable position and against the second side wall of this cavity when the flip-flop is in its second stable position.By adjusting the width of the cavity, the piezoelectric blade 25 can be made substantially straight, i.e. without bending, in the two stable positions of the rocker. However, a slight residual bending as shown, in the absence of voltage applied by the power supply, can be expected and be advantageous given the path to be taken by the end of the piezoelectric blade.

[0092] In an advantageous variant, the device for actuating the rocker is formed by an electromagnetic magnet-coil system, the magnet being in particular fixed to the rocker and the coil is fixed to the support of the rocker in a manner substantially aligned with the magnet. Depending on the polarity of the electrical voltage applied to the coil, the rocker undergoes a force of magnetic attraction or repulsion, thus making it possible to easily move the rocker from one of its two stable positions to the other in both directions.

[0093] In another variant leading to the same physical phenomenon and therefore to the same desired effect, the ferromagnetic plate 120 is arranged against the moving magnet 118, to which it is integral. Finally, in another variant, it is planned to combine the second and third embodiments. To do this, the blade of the rocker comprises, in the region of contact with the felloe 20, a stud which projects towards this felloe, which has a hollow along its generally circular circumference.The person skilled in the art will know how to arrange the locking device so that its first stable position is a non-interaction position and its second stable position is an interaction position in which the stud is at least partially inserted into the hollow, this stud generally initially exerting dynamic dry friction against the outer lateral surface of the rim, when the lever is actuated by the actuating device to move from its first stable position to its second stable position at the start of a period of correction of an advance, before entering the hollow when the latter is presented opposite the stud during the oscillation of the balance.

[0094] In reference to the Figures 1 And 12 ,A fourth embodiment of a timepiece will be described below. This fourth embodiment is a preferred embodiment which differs from the first embodiment substantially by the method of correcting an advance and by some improvements and by variants relating to certain units of the correction device 132.

[0095] First, the receiving unit 30B of the correction device is a BLE unit (acronym for 'Bluetooth Low Energy'). Then, the power supply 130 of the correction device is more advanced than in the variant shown for the first embodiment ( Figure 2). The energy harvester is a solar cell 54A, in particular arranged at the level of the dial or the bezel carrying the glass protecting the dial. This dial generally forms a part of the time display. In addition, a photodiode 136 is provided to receive a light signal for activating the correction device provided by the external electronic device, in particular from the mobile phone 40, to trigger / start in the timepiece a cycle for correcting the displayed time on the basis of an external correction signal S Ext then provided by the external electronic device (in other words to start the method for correcting the displayed time which is implemented in the correction device 132).

[0096] The power supply 130 comprises a circuit 134 for managing the power supply of the correction device 132. This circuit is capable of receiving various information from the electricity accumulator 56 and it receives from the photodiode 136 a wake-up signal S W-UP when this photodiode receives a specific light signal from the mobile telephone 40. Various measures known to those skilled in the art can be taken to prevent the photodiode from sending unwanted wake-up signals to the correction device. In particular, a specific narrow frequency band can be selected. In addition, the light signal can be coded, in particular by a modulation of its light intensity and the photodiode 136 or the management circuit 134 is then arranged to be able to determine whether the logic code corresponding to this modulation indeed concerns an expected wake-up signal.Once the management circuit 134 has received a valid wake-up signal, it detects the energy level available in the accumulator 56. As in the first embodiment, if the energy level is insufficient to complete the correction process, the management circuit can react in various ways. In particular, it can wake up the BLE unit and send a message to the mobile phone via this BLE unit so that this external device gives this information to the user via its electronic display. Then, it can either remain in standby mode for an electrical energy supply via its solar cell or another energy recovery means provided in addition, or start, as far as possible, a correction cycle while knowing that it risks not being able to complete it correctly due to a lack of available energy.

[0097] When the available energy level is sufficient for a correction cycle, the management circuit 134 activates, in a first variant, firstly the BLE unit while waiting for an external correction signal S Ext . The BLE unit generally has the resources to check whether an external signal received at the correct frequency has the standard format, but it may be that the control logic circuit 60A must be activated for the analysis of a signal received by the BLE unit if this signal is received at the correct frequency and has the correct format. In the latter case, it is the analysis of the digital correction signal S Cor which will indicate, if necessary, that the received signal is not appropriate or incomplete. Thus, in a second variant, the management circuit directly activates the BLE unit and the control logic circuit, but preferably not the other elements of the correction device.If no correction signal is received or received correctly, the management circuit 134 can, in one variant, inform the mobile phone (directly or via the control logic circuit 60A, the latter then having to be activated to do so), and either wait for a new external correction signal within an additional time, or return to a 'Standby' mode while waiting for a new wake-up signal. In another variant where the timepiece comprises an electronic or electromechanical means for giving a visible signal to the user, the management circuit 134 can then use this means to indicate itself to the user that he is not able to make a correction, because he is not receiving or is not receiving correctly the external correction signal.

[0098] In the first variant mentioned above, when the BLE unit receives an external correction signal S Ext at the right frequency and in the right format, it activates at least the control logic circuit 60A to which it supplies the digital correction signal for analysis and continuation of a correction cycle. If the digital signal S Cor includes the expected time information, in particular the time error T Err to be corrected and its mathematical sign '+ / -' indicating whether it is a delay or an advance to be corrected (this latter information being binary, a single bit can be provided for this purpose), the management circuit 134 then activates the entire correction device and the power supply circuit 26C of the braking device.

[0099] As the fourth embodiment is characterized by an implementation of the first mode of correction of a delay, as in the first embodiment, and of the first mode of correction of an advance already described previously but not implemented in the first embodiment, any planned correction is carried out by a series of periodic braking pulses during a correction period. In a main variant, all the braking pulses are planned with the same duration Tp. Thus, only one and the same timer 64 is necessary to determine the duration of the braking pulses and this timer is arranged, in the variant shown in Figure 12 , in the power supply circuit 26C. This timer provides an activation / actuation signal S Act to a switch 138 placed between a voltage source 140 and the braking member 24C acting on the balance. The braking member 24C is for example similar to the piezoelectric blade ( Figure 1) of the variant shown for the first embodiment. Thus, the switch 138 controls the power supply to the actuator forming the braking device. The timer 64 receives a first control signal S1 Cmd from a switching device 66A which is controlled by the logic circuit 60A so that the first control signal is selectively formed by a periodic digital signal from among three periodic digital signals provided S FS , S FI and S F0c which respectively have three different frequencies F SUP , F INF and F0c. The periodic digital signal periodically resets the timer to the selected frequency and, in response, this timer periodically activates the actuator for a duration Tp, by momentarily making the switch 138 conductive, to generate a series of periodic braking pulses at this selected frequency.

[0100] When the digital correction signal indicates that a time error corresponds to a delay to be corrected or that the control logic circuit has itself determined such a time error to be corrected on the basis of the information contained in the external correction signal, the logic circuit 60A determines, as a function of the selected frequency F SUP, a corresponding correction period PR Cor or a number of periodic braking pulses to be generated at the frequency F SUP during the current correction cycle. To do this, it uses the formula relating to this calculation which was established previously.To apply the series of braking pulses at the frequency F SUP leading to a correction frequency FS Cor higher than the set frequency, it uses the frequency generator 62, already described, which supplies a periodic digital signal S FS at the frequency F SUP to the timer 64 via the switch 66A, which is controlled for this purpose by the control logic circuit.

[0101] When the digital correction signal indicates that a time error corresponds to an advance to be corrected or that the control logic circuit has itself determined such a time error to be corrected on the basis of the information contained in the external correction signal, the logic circuit 60A determines, as a function of the selected frequency F INF , a corresponding correction period PA Cor or a number of periodic braking pulses to be generated at a frequency F INF , previously defined, during the current correction cycle. To do this, it uses the formula relating to this calculation which was established previously.To apply the series of braking pulses at the frequency F INF leading to a correction frequency FI Cor lower than the set frequency, it uses the frequency generator 142 which supplies a periodic digital signal S FI at the frequency F INF to the timer 64 via the switch 66A, which is controlled for this purpose by the control logic circuit.

[0102] Generally, to enable the implementation of the first mode of correction of an advance, the electronic control unit 28B is arranged to be able to supply to the braking device, when the external correction signal received by the reception unit corresponds to an advance in the displayed time which it is intended to correct, a control signal derived from a periodic digital signal supplied by a frequency generator at a frequency F INF , during a correction period, to activate the braking device so that it generates a series of periodic braking pulses applied to the mechanical resonator at the frequency F INF .This frequency F INF is provided and the braking device is arranged in such a way that the series of periodic braking pulses at the frequency F INF can generate, during the correction period, a synchronous phase in which the oscillation of the mechanical resonator is synchronized to a correction frequency FI Cor which is lower than the set frequency F0c provided for the mechanical resonator. The (duration of the) correction period and therefore the number of periodic braking pulses in said series of periodic braking pulses are determined by the advance to be corrected.

[0103] The correction device of the fourth embodiment comprises an improvement to increase the precision of the correction carried out and also to allow the application of relatively high braking torques, in particular for corrections at frequencies relatively far from the set frequency, without risking the mechanical resonator being permanently stopped by a stop, during a braking pulse at the start of the correction period, in the angular coupling zone between the resonator and the escapement or more generally in the safety angular zone described above.According to this improvement, the timepiece comprises a device for determining the passage of the oscillating mechanical resonator through at least one specific position, this device for determining a specific position of the mechanical resonator allowing the electronic control unit to determine a specific instant at which the oscillating mechanical resonator is in said specific position, and therefore to determine the phase of the resonator. Then, the electronic control unit is arranged so that a first activation of the braking device occurring at the start of the correction period, to generate a first interaction between this braking device and the mechanical resonator, is triggered as a function of said specific instant.

[0104] According to an advantageous variant of the improvement set out above and with reference to the Figure 12 ,the correction device further comprises a frequency generator 144 which is arranged to be able to generate a periodic digital signal S F0c at the set frequency F0c provided for the resonator. The electronic control unit 28B is arranged to be able to supply the braking device with a control signal derived from the periodic digital signal S F0c , during a preliminary period directly preceding the correction period, to activate the braking device in such a way that this braking device generates a preliminary series of periodic braking pulses which are applied to the mechanical resonator at the set frequency F0c. To do this, the control logic circuit 60A supplies the generator 144 with a control signal S PP .The duration Tp of the periodic braking pulses and the braking force applied to the oscillating resonator, during the preliminary series of periodic braking pulses, are provided in such a way that none of these braking pulses can stop the oscillating resonator in the coupling zone of this oscillating resonator with the escapement associated with it (between - θ ZI and θ ZI ) or, preferably, in a predefined safety zone (between -θ Sec and θ Sec ) encompassing the coupling zone (these zones have been explained previously).

[0105] Then, the duration of the preliminary period and the braking force applied to the oscillating resonator, during the preliminary series of periodic braking pulses, are provided so as to generate at least at the end of the preliminary period a preliminary synchronous phase in which the oscillation of the mechanical resonator is synchronized (on average) on the set frequency F0c. In the variant shown, the electrical voltage source 140 is variable and controlled by the logic circuit 60A which provides it with a control signal S2 Cmd , so that the voltage level applied to the braking member 24C can be varied to vary the braking force. It is thus possible to provide a lower braking force during the preliminary period than during a correction period which follows it. It is also possible to vary the braking force during the preliminary period and / or the correction period.

[0106] The correction period, intended to correct an advance or a delay, directly follows the preliminary period. More precisely, the triggering of a first braking pulse at the frequency F INF or F SUP , at the start of a correction period of the displayed time, occurs after a time interval determined relative to an instant at which the last braking pulse of the preliminary period is triggered, so that this first braking pulse occurs outside a predefined safety zone encompassing the aforementioned coupling zone. This condition is easily fulfilled by the fact that the resonator is in a synchronous phase at least at the end of the preliminary period; which has the consequence that the resonator stops during the last braking pulse of this preliminary period.Thus, a reversal of the direction of rotation occurs during said last braking pulse, so that the start of a new alternation of the oscillation of the resonator occurs during this last braking pulse. The correction device can thus know, with an accuracy of Tp / 2 (for example an accuracy of 3 ms), the phase of the oscillation. Consequently, the electronic control unit can be arranged so that the control logic circuit can determine an initial time for triggering the first braking pulse which meets the above-mentioned condition, by activating the frequency generator 62 or 142, depending on the correction required, after a determined time interval since said last braking pulse which ensures that the first braking pulse is outside the predefined safety zone.

[0107] Furthermore, the instant of triggering of said first braking pulse and the braking force applied to the oscillating resonator, during this first pulse and then during the periodic braking pulses which follow during the correction period, are provided in such a way that the synchronous phase at the correction frequency FI Cor or FS Cor preferably begins from the first braking pulse, or from a second braking pulse if the first braking pulse serves to reduce the amplitude of the oscillation without managing to stop the resonator, and that this synchronous phase remains throughout the correction period. In a particular variant, the first braking pulse of the correction period occurs after a time interval corresponding to the inverse of the frequency F SUP or F INF , depending on the correction required, following the instant at which the last braking pulse of the preliminary period occurs.In another particular variant, said time interval is selected equal to the inverse of twice the correction frequency FS Cor or FI Cor , depending on the correction required, or to the inverse of this frequency FS Cor or FI Cor . The improvement described above is remarkable because it uses available resources, in particular the braking device provided to carry out the required correction, to determine the phase of the oscillation of the resonator. No sensor specific to the determination of this phase is necessary. In addition, no significant time drift is induced by the preliminary period (generally at most T0c / 4). It will be noted that the generators at the various frequencies have been represented separately in the . Figure 12 , but only one programmable frequency generating device can be used.

[0108] In reference to the Figures 13 to 15 ,A second embodiment of an assembly 150 according to the invention will be described below, which comprises a timepiece 154 according to a fifth embodiment and an external device 152 according to a second embodiment of an assembly according to the invention. The timepiece is a wristwatch (hereinafter the watch) and the external device forms a case comprising a housing for receiving the watch in a given position. The case 152 is provided with a photographic device 156 arranged in the cover of the case so as to be able to take an image of the entire display of the timepiece when the cover is closed with the timepiece 154 correctly placed in the housing.

[0109] Box 152 is equipped with various electronic units and circuits. This box includes: a photographic device comprising a photographic sensor formed from a matrix of photo-detectors, an image processing algorithm which is arranged to be able to determine the position of at least one determined hand of the display of the timepiece in an image taken by the photographic device (note that this algorithm can be processed in an external server in communication with the box), a time base capable of providing the exact real time, an algorithm for calculating a time error between a first time datum, indicated by the display at a given instant and detected by the external device via its photographic sensor and its image processing algorithm, and a second time datum corresponding to the first time datum and provided substantially at said given instant by the time base, a transmitter of an external correction signal comprising information relating to said time error,this transmitter being formed by a BLE unit in the variant shown.

[0110] The box 152 further comprises an electronic display 153, a central control unit and, in order to be able to receive the exact real time regularly or on demand, a communication unit (RF unit) capable of receiving the exact real time via an antenna provided for this purpose (radio synchronization), or a WIFI unit for receiving the exact real time via the Internet, or a GPS unit. The box also comprises a power supply capable of being powered or recharged via a USB or other type socket. Finally, the box comprises a wireless charging unit, by magnetic induction, for the watch 154 which notably comprises a Fitness module. This wireless charging unit is preferably arranged in a support introduced into the housing of the box so as to be close to the watch and under it when it is placed in the box, in particular to allow its battery 56A to be recharged.

[0111] The watch 154 comprises various electronic elements and circuits. The references already described previously will not be described again here in detail. This watch comprises a BLE unit 30B for receiving various signals, including in particular a signal for correcting the time displayed by the watch, as well as a braking device 22C, the constituent elements of which have already been described previously, which receives an activation signal S Act from the electronic control unit which will be described later. Then, the watch 154 comprises a rechargeable battery 56A, preferably by magnetic induction (by contactless means), and a power management circuit 134A, similar to that already described in relation to the watch of the Figure 12. Optionally, the watch further comprises a Fitness module 156 and an electronic display 158 associated in particular with the Fitness module, which can use the BLE unit to communicate with electronic devices external to the watch, in particular with the box 152, a mobile phone or any other suitable electronic device, for example a computer.

[0112] The electronic control unit 28C of the watch 154 is arranged to allow the implementation of the first mode of correction of a delay, according to an improved variant, and to correct an advance according to the first mode of correction or the second mode of correction already described. Thus, this electronic control unit comprises a logic control circuit 60B which controls a switching device 66B in parallel with a frequency generator device at the frequencies F0c, F INF and F1 SUP and F2 SUP. F1 SUP and F2 SUP are two different values ​​selected for the frequency F SUP defined previously.This frequency generating device is composed of a generator 144 at the frequency F0c, for the implementation of a preliminary period already described in the context of the fourth embodiment of a timepiece according to the invention, of a generator 142 at the frequency F INF also described in the context of the fourth embodiment, and of two generators 62A and 62B respectively providing two periodic digital signals S FS1 and S FS2 having respective frequencies F1 SUP and F2 SUP . In other words, the frequency generating device is arranged so as to be able to generate, to correct a delay in the displayed time, a periodic digital signal selectively at the frequency F1 SUP and at the frequency F2 SUP to control the braking device.The frequencies F1 SUP and F2 SUP are provided so that the correction frequency FS Cor , to correct a delay according to the first correction mode, can take two different values ​​F1 Cor and F2 Cor , respectively for the two frequencies F1 SUP and F2 SUP , with the correction frequency F2 Cor higher than the correction frequency F1 Cor .

[0113] It is advantageously provided that the selection of the frequency F1 SUP is carried out when the delay to be corrected, in absolute value, is less than a given value while the selection of the frequency F2 SUP is carried out when this delay is equal to or greater than this given value. The frequency F SUP can therefore take, depending on the value of the delay to be corrected, at least two different values ​​F1 SUP and F2 SUP . Depending on the activated generator, the control signal S1 Cmd is formed by one of the periodic digital signals S F0c , S FI , S FS1 and S FS2 . This signal S1 Cmd itself directly forms the activation signal S Act . It should be noted that no timer is provided to determine the duration of the braking pulses, because in this variant it is provided that the periodic digital signals S F0c , S FI , S FS1 and S FS2 define this duration by their cyclic ratio determined between their high logic state ('1') and their low logic state ('0').Thus, for example, the duration of the high logic state determines the duration of each braking pulse, the switch 138 then being closed (transistor on) at the rising edges of the periodic digital signal supplied and being open (transistor off) at the falling edges of this periodic digital signal.

[0114] In addition, the electronic control unit 28C includes a timer 70, similar to that described with reference to the Figure 2 , to enable the implementation of the second correction mode already described in the first embodiment of a watch according to the invention. This timer 70 provides a control signal S3 Cmd to activate the braking device via a logic gate 'OR' ('OR') 166 also receiving the control signal S1 Cmd (it will be noted that the switching operated by the logic gate can be incorporated in the switch 66B, making this logic gate introduced in the diagram of the Figure 15to differentiate the first correction mode from the second correction mode). Thus, it is possible to select either the first correction mode or the second correction mode to correct a lead.

[0115] It is advantageous to select the first correction mode when the advance to be corrected is less than a given value while the second correction mode is selected when the advance to be corrected is equal to or greater than this given value. As the first mode of correction of an advance makes it possible to consume less electrical energy than the second mode of correction with a braking device of the electromechanical actuator type having a single stable position in the absence of power supply (for example the piezoelectric actuator 22A at the Figure 1), the selection between the first and second correction modes may also depend on the level of the rechargeable battery 56A. Similarly, since the first mode of correction of a delay requires a priori a stronger braking torque in the case of a relatively high ratio between the correction frequency and the set frequency, the selection between the generator 62A and the generator 62B may also depend on the level of the rechargeable battery.

[0116] The fifth embodiment of a timepiece comprises means for being able to correct not only an error in the displayed time, resulting from a time drift of the oscillating resonator or from an imprecise manual time setting, but also to allow the displayed time to be changed at the appropriate time during a seasonal time change (change from winter time to summer time and vice versa). To do this, the watch 154 comprises an internal clock circuit 162 and a programmable time counter 160. The application installed in an external device (box 152 or a mobile phone 40 of the Figure 1), to be able to communicate with the watch and activate its correction device, includes the 'seasonal time change' function to program the watch 154 so that it moves forward by one hour or backward by one hour (or half an hour, if applicable) on the night scheduled for the time change. For this purpose, the external device is arranged to be able to send to the watch, via its transmitter intended to communicate with this watch, a correction signal relating to the seasonal time change. This correction signal includes the planned time jump and its direction (+ / - 1 hour), as well as an indication relating to the period of time remaining until the night and time scheduled for the time change (for example a period of 15 days, 8 hours and 20 minutes). Thus, the external device includes the resources necessary to know not only the exact real time but also the date.Based on the date when the 'seasonal time change' function is activated, the application easily calculates the aforementioned remaining time period.

[0117] When the watch 154 receives the external correction signal with the indication that this signal relates to an upcoming time change, the control logic circuit 60B programs the time counter 160 so that the latter measures the remaining period of time, from a reset signal received from the logic circuit, until the time scheduled for the time change. Alternatively, the start of the time measurement takes place as soon as the clock circuit 162 is activated by the logic circuit after the time counter has been programmed, this activation occurring quickly after the reception of the external correction signal. To carry out the seasonal time change on the scheduled night, the watch 154 can take advantage of the fact that it can be recharged by the recharging unit of the box 152.Indeed, as the time change is generally scheduled at night, after midnight, the user can put the watch in the case on the night in question and activate the recharging of the watch battery (unless this is done automatically). Thus, the watch has enough energy to carry out the relatively long time correction. For such a correction, the watch will select, as appropriate, either the second mode of correction of an advance by activating the timer 70, after having provided it with the duration of the correction period PA Cor, or the generator F2 SUP by activating it for a correction period PR Cor calculated for a delay corresponding to the jump of '1 hour'. For example, the ratio RS = F2Cor / F0c is planned to be greater than 1.10 and preferably greater than 1.15. As indicated previously, the first mode of correction of a delay makes it possible to correct, for example, 1 hour during a correction period of 6 hours.We can even consider correcting 1 hour into 5 hours.

[0118] It will be noted that the braking device may be formed by an actuator of a type other than that described previously, in particular by an actuator of the electromagnetic type comprising a magnet-coil coupling system provided for directly braking the mechanical resonator, at least one magnet being fixed to the balance of the resonator or to its support and at least one coil being respectively carried by this support or the balance of the resonator.

[0119] In reference to the Figures 16 to 18 , A sixth embodiment of a timepiece according to the invention will be described below. This sixth embodiment is arranged to allow the implementation of the second mode of correction of an advance, already described in previous embodiments, and a second mode of correction of a delay which will be described here in detail.

[0120] The timepiece 170 according to the sixth embodiment is partially shown in Figure 16 , where only the mechanical resonator 14A of the mechanical movement is shown. Apart from the device for correcting the displayed time, the other elements of the timepiece are similar to those shown in the Figure 1 . The mechanical resonator comprises a balance 16A associated with a balance spring 15. The balance comprises a rim 20A which has a projecting portion 190 rising radially at its periphery. No other element of the balance rises to the radial position of the end portion of the projecting portion 190.

[0121] The balance wheel comprises a mark 191 formed by a non-symmetrical succession of bars having different reflection coefficients of the light coming from an optical sensor 192 or simply a different reflection of this light, in particular a succession of at least two black bars of different widths and separated by a white bar, the width of one of the two black bars being equal to the sum of the widths of the other black bar with the white bar. It is understood that the bars thus form a sort of code with a transition in the middle of the mark 191. Instead of black bars and a white bar, other colors can be used. In a variant, the black bars correspond to matte areas of the serge, while the white bar corresponds to a polished area of ​​this serge. The black bars can also correspond to notches in the serge which have an inclined plane.Several variants are therefore possible. It will be noted that the mark 191 has been shown on the top of the rim for its description, but in the variant shown it is located on the outer lateral surface of the rim since the optical sensor is arranged in the general plane of the balance 16A. In another variant, the mark is located as shown, on the upper or lower surface of the rim, and the sensor is then rotated 90° to be able to illuminate this mark.

[0122] The optical sensor 192 is arranged to detect the passages of the oscillating resonator through its neutral position (corresponding to the angular position '0' for the projecting part 190) and to make it possible to determine the direction of movement of the balance during each passage through this neutral position. This optical sensor comprises an emitter 193 of a light beam in the direction of the rim 20A, this emitter being arranged so that it illuminates the mark 191 when the resonator passes through its neutral position, and a light receiver 194 arranged to receive at least a portion of the light beam which is reflected by the rim at the mark.The optical sensor thus forms a device for detecting a specific angular position of the balance, enabling the electronic control unit to determine a specific instant at which the oscillating mechanical resonator is in the specific angular position, and also a device for determining the direction of movement of the balance when the oscillating resonator passes through the specific angular position. Other types of detector for the position and direction of movement of the resonator may be provided in other variants, in particular capacitive or inductive detectors.

[0123] Then, the timepiece 170 comprises a resonator braking device which is formed by an electromechanical device 174 with a bistable movable stop. An alternative embodiment, by way of non-limiting example, is shown in Figure 16. The electromechanical device 174 comprises an electromechanical motor 176, of the small clockwork stepper motor type, which is powered by a power supply circuit 178, which comprises a control circuit arranged to generate, when it receives a control signal S4 Cmd, a series of three electrical pulses which are supplied to the coil of the motor so that its rotor 177 advances by one step with each electrical pulse, i.e. by half a rotational revolution. The series of three electrical pulses is intended to drive the rotor rapidly, continuously or almost continuously. The rotor pinion meshes with an intermediate wheel 180 which meshes with a wheel having a diameter equal to three times that of the rotor pinion and fixedly carrying a first bipolar permanent magnet 182. Given the diameter ratio between said pinion and the wheel carrying the magnet 182, the latter rotates half a turn during a series of three electrical pulses.Thus the first magnet has a first rest position and a second rest position in which the first magnet has a magnetic polarity opposite to that of the first rest position (by 'rest position' is meant a position in which the magnet 182 is located after the motor 176 has carried out on command a series of three electrical pulses and its rotor has then stopped rotating).

[0124] In addition, the actuator 174 comprises a bistable rocker 184 pivoted about an axis 185 fixed to the mechanical movement and limited in its rotation by two pins 188 and 189. The bistable rocker comprises at its free end, forming the head of this rocker, a second bipolar permanent magnet 186 which is movable and substantially aligned with the first magnet 182, the magnetic axes of these two magnets being provided to be substantially collinear when the first magnet is in one or the other of its two rest positions. Thus, the first rest position of the first magnet corresponds, relative to the second magnet 186, to a position of magnetic attraction, and its second rest position corresponds to a position of magnetic repulsion.Each time the control signal S4 Cmd activates the power supply circuit to carry out a series of three electrical pulses, the first magnet rotates half a turn and the rocker alternately passes from a stable position of non-interaction with the balance of the resonator to a stable position of interaction with this balance in which the rocker 184 then forms a stop for the projecting part 190, which abuts against the head of this rocker when the resonator oscillates and the projecting part reaches the level of this head, regardless of the direction of rotation of the balance during the shock.

[0125] In the non-interaction position, the movable rocker is outside a space swept by the projecting part 190 when the resonator oscillates with an amplitude in its useful operating range. On the other hand, in the interaction position, the movable rocker is located partially in this space swept by the projecting part and thus forms a stop for the resonator. By 'stable position' is meant a position in which the rocker remains in the absence of a power supply to the motor 176 which is used to actuate the rocker between its two stable positions, in both directions. The rocker thus forms a bistable movable stop for the resonator. This rocker therefore forms a retractable stop member for the resonator. The actuator 174 is arranged so that the rocker can remain in the non-interaction position and in the interaction position without maintaining a power supply to the motor 176.

[0126] The stop member in its interaction position and the projecting part define a first angular stop position θ B for the balance of the oscillating resonator which is different from its neutral position, the projecting part abutting against the stop member at this first angular stop position when it arrives from its angular position '0', corresponding to the neutral position of the resonator, during a second half-alternation of a first determined alternation among the two alternations of each oscillation period of the resonator. Then, the angle θ B is provided less than a minimum amplitude of the oscillating mechanical resonator in its useful operating range. In addition, the angle θ B is provided so that the oscillating resonator is stopped by the stop member outside the coupling zone of the oscillating resonator with the escapement of the mechanical movement, which has already been described.The stop member in its interaction position and the projecting portion also define a second angular stop position, close to the first but greater than it, for the balance of the oscillating resonator when the projecting portion arrives from an extreme angular position of the resonator during a first half-alternation of the second alternation among the two alternations of each oscillation period. This second angular stop position is also provided to be less than a minimum amplitude of the oscillating mechanical resonator in its useful operating range.

[0127] It will be noted that the projecting portion 190 may, in another variant, rise axially from the felloe or from one of the arms of the balance and the bistable electromechanical device 174 is then arranged so that the bistable lever exhibits a movement in a plane parallel to the axis of rotation of the balance. In this other variant, the respective magnetization axes of the two magnets 182 and 186 are axial and remain substantially collinear, the magnet 182 then being arranged under the head of the lever. It will be noted that such an arrangement of the bistable electromechanical device may also be provided within the framework of the variant shown with a projecting portion rising radially from the felloe. It will be noted that the projecting part of the resonator can, in another variant, be arranged around the balance shaft, in particular on the periphery of a plate carried by this shaft or made of the same material as the shaft.In one variation, such a plate is the plate carrying the escapement pin.

[0128] Finally, the timepiece 170 comprises an electronic control unit 196 which is associated with the optical sensor 192 and arranged to control the power supply circuit 178 of the electromechanical device, to which the unit 196 supplies the control signal S4 Cmd. The electronic control unit comprises a control logic circuit 198, a bidirectional time counter 200 and a clock circuit 202. This control unit and the receiver 204 of the external correction signal S Ext are associated with the electromechanical device 174 to allow the implementation of the second mode of correction of an advance and also of the second mode of correction of a delay in the time indicated by the display of the timepiece, explained below.By 'advance' and 'delay' in the displayed time is understood both an error detected by an external device, comprising a specific application to the present invention, and a jump forward or backward in the displayed time which is required via an external correction signal S Ext supplied to the timepiece by an external device, whether in particular for a seasonal time change as explained previously or even to effect a change of time zone in the case where the user of the timepiece moves from one time zone to another.

[0129] To implement the second correction mode implemented in this sixth embodiment, the electronic control unit 196 is arranged to control the electromechanical device (also called 'actuator' or 'electromechanical actuator') so that it can selectively actuate the stop member (the bistable lever 184), depending on whether it is intended to correct a delay or an advance in the time displayed by the timepiece, so that this stop member is moved from its non-interaction position to its interaction position respectively before the projecting portion 190 reaches said first angular stop position θ B during said second half-alternation of said first alternation of an oscillation period and before the projecting portion 190 reaches said second angular stop position during said first half-alternation of said second alternation of an oscillation period.

[0130] Generally, to correct at least in part an advance (positive time error), the electromechanical device is arranged in such a way that, when the stop member is actuated to stop the mechanical resonator in a first half-wave, the stop member momentarily prevents, after the projecting part has abutted against this stop member, the mechanical resonator from continuing the natural oscillation movement specific to this first half-wave, so that this natural oscillation movement during the first half-wave is momentarily interrupted before it is continued, after a certain blocking time which ends with the withdrawal of the stop member.Preferably, in the case of a bistable electromechanical device as described above, provision is made to correct substantially the integer of a positive time error, determined by an external correction signal supplied to the timepiece according to the invention, during a continuous blocking period defining a correction period, which is provided to be substantially equal to the advance to be corrected.To do this, in the variant described, following the instant of passage of the resonator through its neutral position during a said second alternation of an oscillation period (alternation where the projecting part 190 arrives at the level of the head of the rocker 184 before the passage of the resonator through its neutral position), this second alternation being detected by the optical sensor 192 thanks to the arrangement provided for detecting the direction of the oscillation movement during the detection of the passages of the resonator through its neutral position, the electronic control unit waits until a delay of T0c / 4 is reached to activate the actuator so that it drives, via its motor, the rocker 184 between its stable non-interaction position to its stable interaction position where the head of the rocker forms a stop for the projecting part.Depending on the value of the stop angular position, for example between 90° and 120°, it is possible to provide a shorter time than T0c / 4, for example T0c / 5, to trigger a series of three electrical pulses to drive the motor 176 so that its rotor rotates quickly by one and a half revolutions, the time interval to allow the rocker to pivot between its two stable positions, by reversing the direction of the magnetic flux generated by the magnet 182, being thus lengthened. In the latter case, it must be ensured that the projecting part has indeed exceeded the stop angular position in the alternation preceding the first half-alternation during which it is intended to block the resonator during a correction period.

[0131] Generally, to correct at least in part a delay (negative time error), the electromechanical device is arranged so that, when the stop member is actuated to stop the mechanical resonator in a second half-alternation of at least one said first alternation of an oscillation period (alternation during which the projecting part 190 arrives at the level of the head of the rocker 184 after the resonator has passed through its neutral position), it thus prematurely ends this second half-alternation without blocking the resonator but by reversing the direction of the oscillation movement of this resonator, so that the mechanical resonator begins, following an instantaneous or almost instantaneous stop caused by the collision of the projecting part with the stop member, directly a following alternation.Thus, in the context of the second mode of correcting a delay, the position and direction of movement detector of the resonator and the electronic control unit are arranged so as to be able to activate the actuator, each time that the external correction signal received by the receiving unit corresponds to a delay in the displayed time, so that this actuator actuates its stop member so that the projecting part of the oscillating resonator abuts against this stop member in a plurality of half-alternations of the oscillation of the mechanical resonator which each follow its passage through the neutral position, so as to prematurely put an end to each of these half-alternations without blocking the mechanical resonator. The number of half-alternations of said plurality of half-alternations is determined by the delay to be corrected.

[0132] In a preferred variant shown in Figures 17 and 18, the electronic control unit and the actuator are arranged in such a way that, to correct at least in part a delay, the rocker is maintained in its interaction position, following an actuation of this rocker from its non-interaction position to its interaction position while the oscillating resonator is angularly located on the side of its neutral position relative to the angular stop position, until the end of the correction period during which the projecting part of the oscillating mechanical resonator periodically abuts several times against the head of the rocker, the duration of the correction period during which the rocker is maintained in its interaction position being determined by the delay to be corrected.The pivoting of the rocker from its non-interaction position to its interaction position can occur either in a so-called first alternation (the one where the impact with the projecting part is expected, this first alternation being detected by detecting the direction of rotation of the balance) preferably directly after detecting the passage through the neutral position so that the rocker is placed in its interaction position before the projecting part reaches the stop angle θ B, or in a so-called second alternation (also detected by detecting the direction of rotation of the balance) directly after detecting the passage through the neutral position, this second variant leaving more time to actuate the rocker and allow it to be placed stably in its interaction position (the stop angle is by definition less than or equal to 180°).For example, if θ B = 120° and the amplitude of the free oscillation of the resonator θ L = 270°, then in the second variant we have a time interval corresponding to a rotation between the angle '0' and a little less than 240° (360°-120°), or approximately 230° if the angle θ T to the axis of rotation defined by the head of the rocker is approximately 10°, to carry out the pivoting of the rocker (so as not to block the balance by exceeding the position of the projecting part in the second alternation); whereas in the first variant we only have a time interval corresponding to a rotation between the angle '0' and 120°. It will be noted that if θ L < 360°- θ B - θ T , then we have much more time in the second variant to carry out the pivoting of the rocker.

[0133] Generally, to determine the duration of a delay correction period, the electronic control unit comprises a measuring circuit associated with the optical sensor, this measuring circuit comprising a clock circuit, providing a clock signal at a determined frequency, and a comparator circuit making it possible to measure a time drift of the oscillating resonator relative to its set frequency, the measuring circuit being arranged to be able to measure a time interval corresponding to a time drift of the mechanical resonator since the start of the correction period. The electronic control unit is arranged to end the correction period as soon as said time interval is equal to or slightly greater than a time error which is provided by the external correction signal.

[0134] In the variant described in Figure 16 ,the measuring circuit comprises a clock circuit 202, providing a periodic digital signal at the frequency F0c / 2, and a bidirectional counter 200 (reversible counter). This bidirectional counter receives at its '-' input the periodic signal from the clock circuit (generating a decrement of this counter by two units for each setpoint period T0c = 1 / F0c) and at its '+' input a digital signal from the optical sensor 192 which comprises a pulse or a change of logic state at each passage of the resonator 14A through its neutral position '0'. As such a passage occurs in each alternation of the oscillating resonator, the counter 200 is incremented by two units at each oscillation period. Thus the state of the counter (integer number M Cb ) is representative of a time drift of the mechanical resonator relative to the setpoint frequency which is determined by the clock circuit having the precision of a quartz oscillator.The integer M Cb corresponds to the number of additional alternations carried out by the resonator, from an initial instant when the reversible counter is reset, relative to a case of an oscillation at the set frequency.

[0135] The control logic circuit 198 receives from the optical sensor 192 a digital signal allowing this logic circuit to determine the passages of the resonator through its neutral position and the direction of the oscillation movement at each of these passages. To correct a given delay, following detection of a passage of the resonator through its neutral position as described above, the control logic circuit, on the one hand, activates the actuator 174 so that it actuates the flip-flop to its interaction position and, on the other hand, resets (performs a 'reset') the clock circuit 202 and the bidirectional counter 200, which defines the start of a correction period. It will be noted that this reset can, in a variant, take place before the actuator 174 is powered to effect the pivoting of the flip-flop, but after the electronic control unit 196 and the optical sensor 192 are activated. In one variant, resetting of the clock circuit is not provided.In other variants, the optical sensor is replaced by another type of sensor, for example of the magnetic or capacitive type. In a specific variant, the detector of the passage of the mechanical resonator through its neutral position is formed by a miniaturized sound sensor (MEMS type microphone) capable of detecting the sound pulses generated by the impacts between the balance pin and the anchor fork forming the escapement of the mechanical movement.

[0136] The number of alternations at the set frequency F0c in a negative time error T Err (given delay) is equal to -T Err 2 F0c. Thus, as soon as the number M Cb of the bidirectional counter reaches this value or slightly exceeds it (because this value is not in all cases an integer), the given delay is made up and the time display is again correct (it then gives the real time accurately, in particular with an accuracy of one second). The logic control circuit is therefore arranged to be able to compare the state of the counter with the value -T Err 2 F0c, and to end the correction period as soon as it detects that the number M Cb is equal to or greater than this value, by controlling the power supply circuit 178 of the actuator so that the latter actuates the flip-flop from its stable interaction position to its stable non-interaction position.

[0137] To Figures 17 and 18the oscillations of the resonator 14A are represented, respectively in two particular extreme cases of the preferred variant set out previously, at the start of a correction period of a given delay. Figure 17concerns the case where the kinematic energy of the resonator is entirely absorbed during each impact between the projecting part of the balance and the head of the stop. The free oscillation 210 has in particular a second free alternation A2 L before a detection of a time t 0 at the passage of the resonator through its neutral position (position '0' of the projecting part 190) in the first alternation which follows, the time t 0 marking the start of a correction period of a given delay. The rocker is moved into its interaction position directly after the time t 0 . Following the first impact between the projecting part and the rocker, a relatively large positive phase shift DP1 is obtained between the fictitious free oscillation 211 and the oscillation 212.Then a stable phase is established where the oscillation 212 is shortened, relative to a fictitious free oscillation 213 since the previous stopping of the resonator by the stop member, in the second half-alternation of the first alternation A1 of each oscillation period; which then results in a positive phase shift DP2 smaller than DP1. The second alternation A2 of the oscillation 212 is not disturbed by the rocker.

[0138] There Figure 18concerns a particular case of a hard shock or elastic shock between the projecting part and the head of the rocker. In this case the kinetic energy of the resonator is conserved at each shock, given that there is no dissipation of kinetic energy during the shocks, but only a reversal of the direction of the oscillation movement. The amplitude of the oscillation 216 during the correction period thus remains identical to that of the free oscillation 210, and therefore of the fictitious free oscillation 217 for each oscillation period. Following time t 0 a stable phase is established with alternations A1* and A2* of duration T2 much less than T0 / 2, generating a relatively large positive phase shift DP3 at each oscillation period.To obtain an elastic shock, it is possible to provide that the rocker has a certain elasticity, in particular that the body of the rocker and / or its head are formed of an elastic material capable of undergoing a certain compression, so as to momentarily absorb the kinetic energy of the balance to restore it immediately after the reversal of the direction of the oscillation movement. In this case, the oscillation 216 will slightly exceed the stop angle θ B . In another more sophisticated variant, it is the projecting part which is mounted elastically on the rim of the balance. For example, the projecting part has a base forming a slide arranged in a circular slide machined in the rim and an elastic element, in particular a small coil spring is arranged in the slide at the rear of the slide, that is to say on the other side of the head of the rocker relative to the projecting part when it is in its angular position '0'.In practice, the shocks between the projecting part of the balance and the stop of the electromechanical device generally occur in a way which corresponds to a physical situation between the two extreme situations described in . Figures 17 and 18 .

[0139] Finally, in another embodiment, the electromechanical device is formed by a monostable electromechanical actuator which comprises a movable finger arranged in such a way that this movable finger can be moved alternately between a first radial position and a second radial position when this actuator is respectively not activated (not powered) and activated (i.e. it is powered). The first radial position of the finger corresponds to a position of non-interaction with the balance of the oscillating resonator and its second radial position corresponds to a position of interaction with the oscillating balance in which this finger then forms a stop for the projecting part of the oscillating balance, in a similar manner to the head of the rocker 184.

Claims

1. Timepiece (2; 112; 132; 154; 170) comprising: - a display displaying an actual time (12), - a mechanical movement (4; 4A; 92) comprising a mechanism (10) for driving the display and a mechanical resonator (14; 14A) which is coupled to the drive mechanism such that the oscillation thereof times the running of this drive mechanism, - a device for correcting the actual time indicated by the display ; the device for correcting the actual time displayed being formed by: - a receiver unit (30, 30A; 30B; 204) for receiving an external correction signal (SExt) for correcting the actual time displayed, this external correction signal comprising an information relative to a correction of said actual time displayed, - an electronic control unit (28, 28A; 28B; 196) arranged to be able to process said information contained in the external correction signal such as to determine a correction required for the actual time displayed ; characterised in that the device for correcting the actual time displayed comprises a braking device (22; 22A; 22A, 106; 22B, 114; 24C, 26C; 22C; 174) for braking the mechanical resonator ; in that the electronic control unit is arranged to be able to control the braking device as a function of at least the correction required ; and in that the device for correcting the actual time is arranged such that, when the external correction signal received by the timepiece requires the actual time displayed to be corrected, the braking device can act on the mechanical resonator during a correction period, to vary the running of the drive mechanism, so as to carry out at least the major part, preferably substantially all of the required correction.

2. Timepiece according to claim 1, characterised in that it comprises a device (144; 192) for determining the passage of the oscillating mechanical resonator through at least one specific position, the device for determining this specific position of the mechanical resonator allowing said electronic control unit to determine a specific moment at which the oscillating mechanical resonator is located in said specific position; and in that the electronic control unit is arranged such that a first activation of the braking device occurring at the start of the correction period, to produce a first interaction between this braking device and the mechanical resonator, is initiated as a function of said specific moment.

3. Timepiece according to claim 2, wherein the horological movement comprises an escapement associated with the mechanical resonator, characterised in that the braking device comprises an actuator (174) provided with a stop member (184) for stopping the oscillating mechanical resonator, the stop member being capable of being actuated between a position of non-interaction with the mechanical resonator and a position of interaction wherein this stop member forms an abutment for a projecting part (190) of the oscillating mechanical resonator, the projecting part being arranged to abut against the stop member when the latter is in the position of interaction thereof, the stop member in the position of interaction thereof and the projecting part defining a stop position (θB) for the oscillating mechanical resonator which is different from the neutral position thereof, corresponding to the minimum potential energy state of the mechanical resonator, and less than a minimum amplitude of the oscillating mechanical resonator in the usable operating range thereof; in that said stop position is further provided such that the oscillating mechanical resonator is brought to a halt by the stop member outside a coupling zone (θZI) of the escapement with the oscillating mechanical resonator; and in that the circuit for determining said specific position of the oscillating mechanical resonator and the electronic control unit are arranged such that they can activate the actuator, when the external correction signal (SExt) received by the receiver unit corresponds to a loss in the time displayed that is to be corrected, such that this actuator actuates the stop member thereof so that the projecting part (190) of the oscillating mechanical resonator comes to abut against this stop member (184) in a plurality of half-alternations of the oscillating mechanical resonator each of which follow the passage thereof through said neutral position, so as to prematurely end each of these half-alternations without blocking the mechanical resonator, the number of half-alternations of said plurality of half-alternations or a duration of the correction period during which the stop member is held in the position of interaction thereof being determined by said loss to be corrected.

4. Timepiece according to claim 3, characterised in that the device for determining said specific position of the oscillating mechanical resonator comprises a detector (192) for detecting the position and direction of motion of the mechanical resonator, this detector and the mechanical resonator being arranged to allow the passage of the oscillating mechanical resonator through said specific position ('0') in each period of the oscillation thereof to be detected and to allow the electronic control unit (196) to determine the direction of motion of the oscillating mechanical resonator in the alternation during which the passage of the oscillating mechanical resonator through said specific position is detected; and in that the electronic control unit is arranged such that it can at least partially correct said loss, such that this unit can control the actuator (174) so that this actuator actuates the stop member thereof from the position of non-interaction thereof into the position of interaction thereof when the oscillating mechanical resonator is situated on the neutral position side relative to said stop position, and so that the actuator subsequently holds the stop member in this position of interaction for a determined duration that is sufficient for the projecting part of the oscillating mechanical resonator to abut at least once against the stop member.

5. Timepiece according to claim 4, characterised in that said actuator (174) is of the bistable type and is arranged such that it can remain in the position of non-interaction and in the position of interaction without maintaining a power supply to this actuator; and in that the electronic control unit and the actuator are arranged such that, to at least partially correct said loss, the stop member (184) is maintained in the position of interaction thereof, after the stop member is actuated from the position of non-interaction thereof to the position of interaction thereof when the oscillating mechanical resonator is located on the neutral position side relative to said stop position, until the end of said correction period during which the projecting part (190) of the oscillating mechanical resonator periodically abuts several times against the stop member.

6. Timepiece according to claim 4 or 5, characterised in that the electronic control unit comprises a measuring circuit which is associated with said detector, this measuring circuit comprising a clock circuit (202), providing a clock signal at a determined frequency (F0c / 2), and a comparator circuit (200) allowing a time drift of the oscillating mechanical resonator relative to the setpoint frequency thereof to be measured, the measuring circuit being arranged such that it can measure a time interval corresponding to a time drift of the mechanical resonator from the start of the correction period, the electronic control unit being arranged to end the correction period as soon as said time interval is greater than or equal to a time error that is supplied by the external correction signal.

7. Timepiece according to claim 1 or 2, characterised in that the braking device is formed by an electromechanical actuator (22, 22A; 22B; 22C; 24C & 26C), which is arranged such that it can apply braking pulses to the mechanical resonator, and the electronic control unit comprises a device for generating at least one frequency (62, 62A, 62B) which is arranged such that it can generate a first periodic digital signal (SFS, SFS1, SFS2) at a frequency FSUP; in that the electronic control unit is arranged to provide the braking device, when the external correction signal received by the receiver unit corresponds to a displayed time loss that is to be corrected, with a first control signal (SC1, SAct(SFS), S1Cmd(SFS1,SFS2)) derived from the first periodic digital signal, during a first correction period, to activate the braking device such that this braking device generates a first series of periodic braking pulses that are applied to the mechanical resonator at said frequency FSUP, the duration of the first correction period and thus the number of periodic braking pulses in said first series being determined by said loss to be corrected; and in that the frequency FSUP is provided and the braking device is arranged such that said first series of periodic braking pulses at the frequency FSUP can, during said first correction period, result in a first synchronous phase wherein the oscillation of the mechanical resonator (14) is synchronised to a correction frequency FSCor which is greater than a setpoint frequency F0c provided for the mechanical resonator.

8. Timepiece according to claim 7, characterised in that said frequency FSUP can take at least two different values F1SUP and F2SUP as a function of said loss to be corrected; in that said device for generating at least one frequency is a frequency generator device which is arranged such that it can generate said first periodic digital signal selectively at the frequency F1SUP and at the frequency F2SUP; and in that the frequencies F1SUP and F2SUP are provided such that said correction frequency FSCor can take two different values F1Cor and F2Cor, respectively for the two frequencies F1SUP and F2SUP, where F2Cor is higher than F1Cor, the frequency F1SUP being selected when said loss is lower than a given value, whereas the frequency F2SUP is selected when said loss is greater than or equal to this given value.

9. Timepiece according to claim 7 or 8, characterised in that said device for generating at least one frequency is a frequency generator device (62, 142; 62A, 62B, 142) which is arranged such that it can further generate a second periodic digital signal (SFI) at a frequency FINF; in that the electronic control unit (28B; 28C) is arranged such that it can provide the braking device, when the external correction signal received by the receiver unit corresponds to a displayed time gain that is to be corrected, with a second control signal (SAct(SFI), S1Cmd(SFI)) derived from the second periodic digital signal, during a second correction period, to activate the braking device such that this braking device generates a second series of periodic braking pulses that are applied to the mechanical resonator at said frequency FINF, the duration of the second correction period and thus the number of periodic braking pulses in said second series being determined by said gain to be corrected; and in that the frequency FINF is provided and the braking device is arranged such that said second series of periodic braking pulses at the frequency FINF can, during said second correction period, result in a second synchronous phase wherein the oscillation of the mechanical resonator is synchronised to a correction frequency FICor which is less than the setpoint frequency F0c provided for the mechanical resonator.

10. Timepiece according to claims 7 or 8, wherein the horological movement comprises an escapement associated with the mechanical resonator, characterised in that said frequency FSUP and the duration of the braking pulses of the first series of periodic braking pulses are selected such that, during said first synchronous phase, each of the braking pulses of said first series occurs outside a coupling zone (θZI) of the oscillating mechanical resonator with the escapement.

11. Timepiece according to claim 9, wherein the horological movement comprises an escapement associated with the mechanical resonator, characterised in that said frequency FINF and the duration of the braking pulses of the second series of periodic braking pulses are selected such that, during said second synchronous phase, each of the braking pulses of said second series occurs outside a coupling zone (θZI) of the oscillating mechanical resonator with the escapement.

12. Timepiece according to any of claims 7 to 11, characterised in that the device for generating at least one frequency is a frequency generator device (62, 142, 144; 62A, 62B, 142, 144) which is arranged such that it can further generate a third periodic digital signal (SF0c) at the setpoint frequency F0c for the mechanical resonator; in that the electronic control unit is arranged such that it can provide the braking device with a third control signal (SAct(SF0c), S1Cmd(SF0c)) derived from the third periodic digital signal, during a preliminary period preceding the correction period, to activate the braking device such that this braking device generates a preliminary series of periodic braking pulses which are applied to the mechanical resonator at the setpoint frequency F0c, the duration of these braking pulses and the braking force applied to the oscillating mechanical resonator during the preliminary series of periodic braking pulses being provided such that none of these braking pulses can bring the oscillating mechanical resonator to a halt inside a coupling zone (θZI) of the oscillating mechanical resonator with the escapement; in that the electronic control unit is arranged such that the duration of the preliminary period and the braking force applied to the oscillating mechanical resonator during the preliminary series of periodic braking pulses allow, at least at the end of the preliminary period, a preliminary synchronous phase to be produced, wherein the oscillation of the mechanical resonator is synchronised to the setpoint frequency F0c; and in that the electronic control unit is arranged such that the initiation of a first braking pulse of the first series of periodic braking pulses, during said correction period, occurs after a time interval determined relative to a moment at which the last braking pulse of the preliminary period was initiated, the moment at which said first braking pulse is initiated and the braking force applied to the oscillating mechanical resonator during said first series of periodic braking pulses being provided such that said first synchronous phase at said correction frequency FSCor starts instantly at said first braking pulse or a second braking pulse.

13. Timepiece according to any of the preceding claims, characterised in that, it comprises a device (22; 106; 114; 174) for blocking the mechanical resonator; and in that the electronic control unit is arranged such that it can provide the blocking device, when the external correction signal received by the receiver unit corresponds to a displayed time gain that is to be corrected, with a fourth control signal which activates the blocking device such that this blocking device blocks said oscillation of the mechanical resonator during said correction period which is determined by said gain to be corrected, in order to stop the running of said drive mechanism during this correction period.

14. Timepiece according to claim 13, characterised in that said correction period has a duration that is substantially equal to said gain to be corrected.

15. Timepiece according to claim 13 or 14, characterised in that the blocking device is formed by a device (114) that is separate from said braking device and comprises a bistable lever (115), the first stable position of this bistable lever corresponding to a position of non-interaction with the mechanical resonator and the second stable position thereof corresponding to a position for halting and blocking the mechanical resonator.

16. Timepiece according to any of claims 13 to 15, characterised in that the blocking device (106) forms a lock for the mechanical resonator, a part (107) of this blocking device being inserted into a cavity (108), arranged in a circular element (100) of the balance forming the mechanical resonator, when the blocking device is activated to block this mechanical resonator during the period for correcting a given gain.

17. Timepiece according to any of the preceding claims, characterised in that, said correction of the displayed time is relative to a time error detected in the displayed time by an external device capable of supplying said external correction signal to the timepiece.

18. Timepiece according to any of claims 1 to 16, characterised in that said correction of the displayed time is relative to a time zone change or to a seasonal time change.

19. Timepiece according to claim 18, characterised in that it further comprises a measuring circuit, formed by a programmable counter and a clock circuit, for measuring a remaining time interval between a receipt of an external correction signal relative to a seasonal change and a scheduled date and time for making this seasonal change.

20. Assembly formed by a timepiece according to any of the preceding claims and by an external device (40; 152) comprising a transmitter (52) for transmitting said external correction signal; characterised in that the external device comprises: - a photographic device (44; 1156) comprising a photographic sensor formed by an array of photodetectors, - an image processing algorithm which is arranged to be able to determine the position of at least one determined hand of said display of the timepiece in an image captured by the photographic device, and - a time base (48) capable of supplying the precise actual time.

21. Assembly according to claim 20, characterised in that the external device (40; 152) further comprises an algorithm for calculating a time error between a first time datum, indicated by the display at a given moment in time and detected by the external device via the photographic sensor thereof and the image processing algorithm thereof, and a second time datum corresponding to the first time datum and supplied substantially at said given moment in time by said time base; and in that, when it is intended to correct said determined time error, the external correction signal supplied by the device external to the timepiece comprises information relating to this time error.

22. Assembly according to claim 20 or 21, characterised in that the external device is a mobile phone (40).

23. Assembly according to claim 20 or 21, characterised in that the external device is incorporated into a box (152) provided for the timepiece and comprising a recess for receiving the timepiece (154) in a given position.