Patent Grant
11327440
This application claims priority to European Patent Application No. 18197282.9 filed on Sep. 27, 2018, the entire disclosure of which is hereby incorporated herein by reference.
The present invention concerns a timepiece comprising a mechanical oscillator whose mean frequency is synchronized at a set point frequency determined by an auxiliary electronic oscillator. To this end, the timepiece includes a control device capable of correcting a possible temporal drift in the operation of the mechanical oscillator, which paces the operation of the timepiece movement in which it is incorporated.
More particularly, the timepiece is provided with a mechanical movement which includes:
This timepiece is also provided with a control device arranged to control the mean frequency of the mechanical oscillator and including:
Timepieces of the aforementioned type in the field of the invention were recently disclosed in Pat. Nos. CH 713,306A2 and EP3339982A1.
The timepiece disclosed in Pat. No. CH713,306A2 includes a mechanical movement, provided with a mechanical oscillator, and an electromagnetic system formed of at least one magnet mounted on the balance of a mechanical oscillator and a coil carried by a balance support. The electromagnetic system forms part of a control device arranged to control the mean frequency of the mechanical oscillator both when the oscillator has a positive temporal drift relative to an auxiliary oscillator, for example a quartz oscillator, and when it has a negative temporal drift. After observing that a braking pulse, applied to the resonator forming the mechanical oscillator in one vibration of its oscillation, produces a negative phase shift when it occurs prior to passage of the resonator through its neutral position and a positive phase shift when it occurs after the passage of the resonator through its neutral position, this document proposes a solution wherein the temporal drift is measured and the oscillating motion of the resonator is observed so that the control device can selectively apply thereto one or more braking pulses, respectively via one or more coil short-circuits, in one or more first respective half-vibrations (prior to the passage of the resonator through its neutral position) when the measured temporal drift corresponds to at least a certain gain and in one or more second respective half-vibrations (after the passage of the resonator through its neutral position) when the temporal drift corresponds to at least a certain loss. To achieve this, the electronic circuit of the control device includes a time counter or timer making it possible to determine, by detecting induced voltage pulses in the coil, whether an induced voltage pulse occurs in a first half-vibration or in a second half-vibration in order to selectively apply the braking pulses as indicated above. The control method implemented in this document, although remarkable, requires a relatively complex electronic circuit which thus uses a certain amount of electrical energy which is taken from the mechanical oscillator, which tends to reduce its oscillation amplitude and therefore the normal operating time for a given amount of mechanical energy stored in a barrel of the mechanical movement.
The timepiece disclosed in EP Patent Application No. 3339982A1 is characterized in that the system is arranged to generate mechanical braking pulses applied to the balance of the mechanical oscillator. However, the control method is similar to that of the preceding document. There is provided a sensor arranged to detect the passage of the resonator through its neutral position. On the basis of knowing the set point period of the mechanical oscillator and detections performed by the sensor, a control logic circuit determines via a time counter the instants at which the braking pulses must be triggered so that they occur selectively prior to or after the passage of the mechanical resonator through its neutral position in corresponding vibrations, i.e. to apply mechanical braking pulses either in first half-vibrations or two second half-vibrations. In this case too, a relatively complex electronic circuit is required.
It is a main object of the present invention to simplify the electronic circuit of the device for controlling the mean frequency of a mechanical oscillator, by providing an alternative to the prior art control devices described in the background of the invention, which is easy to implement in a timepiece.
To this end the invention concerns a timepiece as defined above in the field of the invention and which is characterized in that the control circuit includes a device for generating at least one frequency which is arranged to be capable of generating a periodic digital signal at a frequency FSUP; and in that, when it determines a temporal drift corresponding to at least a certain loss in the operation of the timepiece, the control circuit is arranged to be capable of momentarily providing to the braking device a first control signal to activate, during a first correction period, this braking device such that the braking device generates a series of periodic braking pulses which are applied to the mechanical resonator at frequency FSUP. The frequency FSUP and the duration of the first correction period are provided and the braking device is arranged so that the series of periodic braking pulses at frequency FSUP is capable to generate, during the first correction period, a synchronous phase in which the mechanical oscillator is synchronized to a correction frequency which is greater than a set point frequency F0c provided for the mechanical oscillator.
In a principal embodiment, the frequency FSUP is comprised in a first range of values extending from (M+1)/M to (M+2)/M inclusive, multiplied by a frequency FZ(N) which is equal to twice a set point frequency F0c, for the mechanical oscillator, divided by a positive integer number N, that is to say FZ (N)=2·F0c/N and [(M+1)/M]·FZ (N)<FSUP=<[(M+2)/M]·FZ (N), M being equal to one hundred times two to the power of K where K is equal to a positive integer number greater than zero and less than thirteen, that is to say 0<K<13 and M=100·2K, and N being less than M divided by thirty, that is to say N<M/30.
In the event that the control circuit determines a temporal drift corresponding to at least a certain gain in the operation of the timepiece, two general embodiments are provided. In the first general embodiment, the control circuit is arranged to be capable, after having detected said at least a certain gain, of stopping the mechanical oscillator and then momentarily locking the mechanical resonator in order to at least partially correct said at least a certain detected gain.
In the second general embodiment, the device for generating at least one frequency is a frequency generator device arranged also to be capable of generating a periodic digital signal at a frequency FINF. When the control circuit determines a temporal drift corresponding to at least a certain gain in the operation of the timepiece, the control circuit is arranged to be capable of momentarily providing to the braking device a second control signal to activate said braking device such that the braking device generates, during a second correction period, a series of periodic braking pulses which are applied to the mechanical resonator at frequency FINF. The frequency FINF and the duration of the second correction period are provided and the braking device is arranged so that the series of periodic braking pulses at frequency FINF is capable to generate, during the second correction period, a synchronous phase in which the mechanical oscillator is synchronized to a correction frequency which is less than the set point frequency F0c.
The frequency FINF is advantageously comprised in a second range of values extending from (M−2)/M to (M−1)/M inclusive multiplied by said frequency FZ (N), that is to say [(M−2)/M]·FZ (N)=<FINF<[(M−1)/M]·FZ (N).
In a main variant of the second general embodiment, each time the measuring circuit determines that the temporal drift corresponds to at least a certain gain or to at least a certain loss, the control circuit is arranged to be capable of momentarily providing to the braking device a control signal which is selectively formed by:
In particular, the duration of the braking pulses is less than a quarter of a set point period T0c, that is to say TP<T0c/4, T0c being by definition the inverse of set point frequency F0c.
In a preferred variant, positive integer number K is greater than two and less than ten, that is to say 2<K<10, and the number N is less than the number M divided by a hundred (N<M/100).
In a specific variant, the control circuit is arranged such that the control signal is provided to the braking device, each time the control circuit determines that the temporal drift corresponds to said at least a certain gain or to said at least a certain loss, during a correction period in which the frequency of the mechanical oscillator is synchronized respectively at a first correction frequency Fcor1 which is in said second range of values, computed with Fz (N=2)=F0c, or at a second correction frequency Fcor2 which is in said first range of values computed with Fz (N=2)=F0c.
In a preferred variant, the duration of the synchronous phase is arranged to be considerably greater than a maximum duration of a transitory phase that generally occurs at the start of the correction periods prior to the synchronous phase.
The invention will be described in more detail below with reference to the annexed drawings, given by way of non-limiting example, in which:
Timepiece 2 includes a mechanical timepiece movement 4 which incorporates a mechanism 6 arranged to indicate at least one time data item, a mechanical resonator 14, formed by a balance 16 pivotally mounted on the plate 5 and a balance spring 18, and a device for maintaining the oscillation of the mechanism resonator which, with said mechanical resonator, forms a mechanical oscillator which paces the running of the time data indicator mechanism. The oscillation maintaining device includes an escapement 12 formed by a pallet lever and an escape wheel which is kinematically connected to the barrel 8 via the gear train 10. The mechanical resonator is able to oscillate along an axis of oscillation, which is a circular geometric axis here, around a neutral position corresponding to a state of minimum potential energy. Each oscillation of the mechanical resonator defines one oscillation period and two vibrations.
Timepiece 2 further includes a device for controlling the mean frequency of the mechanical oscillator, this control device 20 including an electronic control circuit 22 which is associated with a reference time base formed by an auxiliary oscillator 26. This auxiliary oscillator is formed by a quartz resonator 23 and a clock circuit 38 which maintains the oscillation of the quartz resonator and receives therefrom a reference frequency signal that the clock circuit outputs in the form of a periodic digital reference signal SQ. It will be noted that other types of auxiliary oscillators can be provided, particularly an oscillator fully integrated in the control circuit. By definition, the auxiliary oscillator is more accurate than the mechanical oscillator. Control device 20 also includes a sensor 24 for detecting at least one angular position of the balance when it is oscillating, making it possible to detect, for a useful operating range of the mechanical oscillator, a number of vibrations or periods in the oscillation of the mechanical resonator. The control device also includes a mechanical braking device 26 arranged to be capable of momentarily applying a braking force to mechanical resonator 14, in particular mechanical braking pulses to its balance. Finally, the timepiece assembly includes an energy source 32 associated with a storage device 34 for the electrical energy produced by the energy source. The energy source is, for example, formed by a photovoltaic cell or by a thermoelectric element, but these examples are non-limiting. In the case of a battery, the energy source and the storage device together form a single same electric component.
Generally, control device 20 also includes a measuring device arranged to measure, on the basis of position signals provided by the sensor, a temporal drift DT of the mechanical oscillator relative to the auxiliary oscillator (reference time base 36). It is clear that this measurement is easy, given that there is provided a sensor capable of detecting the passage of the mechanical resonator through a certain angular position, particularly through its neutral position. Such an event occurs in every vibration (oscillation half-period) of the mechanical oscillator. The measuring circuit will be described in more detail hereinafter.
Sensor 24 is arranged to be capable of detecting the passage of at least one reference point of balance 16 through a certain given angular position relative to a support of said mechanical resonator. In an advantageous variant, the sensor is arranged to detect the passage of the mechanical resonator through its neutral position. It will be noted that, in this variant, the sensor can be associated with the escapement lever to detect the tilting of the lever during oscillation maintenance pulses which are essentially provided when the mechanical resonator passes through its neutral position.
In a particular variant, sensor 24 is an optical sensor, of the photoelectric type, which includes a light source, arranged to be capable of sending a light beam towards the balance, and a light detector, arranged to receive in return a light signal whose intensity periodically varies as a function of the position of the balance. For example, the beam is sent over side surface 15 of balance rim 17, this surface having a limited area of different reflectivity from the two adjacent areas, such that the sensor can detect the passage of this limited area and provide a position signal to the control device when this event occurs. It will be clear that the circular surface that has variable reflection for the light beam can be located elsewhere on the balance. The variation can, in a particular case, be produced by a hole in the reflective surface. The sensor can also detect the passage of a specific part of the balance, for example an arm, the neutral position corresponding for example to the middle of a signal reflected by the arm. It is thus clear that modulation of the light signal makes it possible to detect in various ways at least one angular position of the balance, by a negative or positive variation in the light captured. In other variants, the position sensor may be of the capacitive or inductive type and thus be arranged to be capable of detecting a variation in capacitance, respectively inductance, as a function of the position of the balance. The sensor includes means for converting the analogue light signal into a digital signal SC. It may also include a flip-flop for dividing by two the light signal when the latter occurs once per vibration, so that signal SC corresponds to the oscillation frequency F0 of the mechanical oscillator. Those skilled in the art know of many sensors which could easily be incorporated in the timepiece assembly according to the invention.
Mechanical braking device 26 is arranged to be capable of applying to balance 16 mechanical braking pulses in order to control the frequency of the mechanical oscillator when a certain temporal drift DT is observed in this mechanical oscillator. In an advantageous variant, a braking torque applied to the mechanical resonator by any mechanical braking pulse is less than a locking torque of the mechanical oscillator and the braking pulse duration is arranged to take at most a certain energy from the mechanical resonator, so that the oscillation amplitude remains higher than a given minimum value. In other words, the braking torque is less than the torque exerted by the balance spring at the minimum amplitude provided and the pulse duration is such that this minimum amplitude is respected for a predefined minimum torque force which is exerted by the barrel (note that the mechanical oscillator is maintained by the barrel via the escapement), in order not to momentarily lock the oscillating motion of the mechanical resonator during the braking pulses and to keep the mechanical oscillator within its useful operating range as soon as the barrel exerts a torque force higher than the minimum torque force. In another more general variant, it is possible to apply a braking torque greater than the torque exerted by the balance spring at the minimum amplitude provided, but the pulse duration is determined while considering maintenance of oscillation of the mechanical oscillator, such that this minimum amplitude is maintained for the minimum torque force of the barrel, from which the timepiece is intended to be functional, and for any angular position of the mechanical resonator during application of a braking pulse. It will be noted that the energy taken from the mechanical resonator is maximum when the braking pulse occurs during the passage of the resonator through its neutral position.
In
Actuator 26 includes a piezoelectric element powered by control circuit 30 which applies thereto an electrical activation voltage as a function of control signal SF supplied by control circuit 22. When the piezoelectric element is momentarily subjected to voltage, the braking member moves into contact with a braking surface of the balance in order to brake it. In the example represented in
In a particular variant (not represented), the balance includes a central staff which forms or which carries a part other than the balance rim forming a circular braking surface. In such case, a pad of the braking member is arranged to come and exert pressure against this circular braking surface during the application of mechanical braking pulses.
A circular braking surface, for an oscillating member that is pivoted (balance), associated with at least one brake pad, carried by the braking device of the control device, forms a mechanical braking system which has decisive advantages. Indeed, as a result of this system, braking pulses can be applied to the mechanical resonator at any time during oscillations, independently of the oscillation amplitude of the balance. It will also be noted that the pad of the braking member can also have a circular contact surface, of the same radius as the braking surface, but a flat surface has the advantage of leaving some margin in the positioning of the braking member relative to the balance, which allows for greater manufacturing tolerances and tolerances for assembling the braking device inside the timepiece movement or at its periphery.
Advantageously, the various elements of control device 20 form an independent module of the timepiece movement. Thus, this module can be assembled or associated with mechanical movement 4 simply when they are placed inside a watch case. In particular, such a module can be fixed to a casing ring which surrounds the timepiece movement. It is understood that the electronic control unit can thus advantageously be associated with the timepiece movement once the latter has been fully assembled and timed, since the assembly and disassembly of this module can occur without having to act on the actual mechanical movement.
Generally, control circuit 22 is arranged to be capable of determining whether a temporal drift, which is measured by the measuring device on the basis of signals that it receives from sensor 24 and from reference time base 36, corresponds to at least a certain gain or at least to a certain loss and if so, to be capable of generating a control signal which selectively actuates the braking device, to generate periodic braking pulses which are applied to the mechanical resonator with a braking frequency that is a function of the measured temporal drift, in order to at least partially correct this temporal drift.
In a main variant, control circuit 22 includes a frequency generator device arranged to be capable of generating a first periodic digital signal SFI at a first frequency FINF (first braking frequency) and a second periodic digital signal SFS at a second frequency FSUP (second braking frequency).
The first frequency FINF is comprised in a range of values extending from (M−2)/M to (M−1)/M inclusive multiplied by a frequency FZ(N) which is equal to twice a set point frequency F0c, for the mechanical oscillator, divided by a positive integer number N, that is to say FZ(N)=2·F0c/N and [(M−2)/M]·FZ (N)=<FINF<[(M−1)/M]·FZ (N), M being equal to one hundred times two to the power of K where K is equal to a positive integer number greater than zero and less than thirteen, that is to say 0<K<13 and M=100·2K, and N is less than M divided by thirty, that is to say N<M/30. The second frequency FSUP is comprised in a range of values extending from (M+1)/M to (M+2)/M inclusive, multiplied by frequency FZ (N), that is to say [(M+1)/M]·FZ (N)<FSUP=<[(M+2)/M]·FZ (N), where M and N are defined as above. The operator ‘=<’ means ‘equal to or less than’, the limit in question being comprised within the range of values.
Control circuit 22 is arranged to momentarily provide, each time that it determines that temporal drift DT of the mechanical oscillator corresponds to at least a certain gain or at least a certain loss, to braking device 26 a control signal SF during a correction period, this control signal SF being selectively formed by:
In a preferred variant, positive integer number K is greater than two and less than ten, that is to say 2<K<10, and the number N is less than the number M divided by a hundred (N<M/100).
The duration TP of the braking pulses is less than half a set point period T0c, that is to say TP<T0c/2, T0c being by definition the inverse of set point frequency F0c for the mechanical oscillator formed of resonator 14 and escapement 12. Preferably, in this first embodiment, the braking pulses have a duration TP which is less than a quarter of the set point period T0c, that is to say TP<T0c/4.
If the digital signal SC provided by sensor 24 has a period corresponding to a vibration of the mechanical oscillator, a flip-flop can be arranged in control circuit 22 upstream of counter CB in order to divide by two the periodic pulses of signal SC and to provide to the input of counter CB a single pulse per oscillation period T0.
Braking device control circuit 30 includes a supply voltage source VACT which powers the braking member to activate it via a switch 50, which is controlled by periodic signal SP provided by a timer 48 incorporated in the control circuit to control the braking pulse duration. The timer selectively receives, via control signal SF, the first periodic digital signal SFI and the second periodic digital signal SFS which periodically activate the timer during a correction period as a function of detection of a certain gain or a certain loss in the operation of the mechanical oscillator and therefore in the operation of the timepiece, and this is repeated throughout successive distinct correction periods when a temporal drift persists. Thus, timer 48 periodically makes switch 50 conductive during each correction period to generate, as appropriate, either a first series of braking pulses 60, or a second series of braking pulses 61 (see
In a preferred variant, the braking surface of balance 16 is configured to allow the braking device to start, in a useful operating range of the mechanical oscillator, a braking pulse of each first series of braking pulses and a braking pulse of each second series of braking pulses in any angular position of mechanical resonator 14 between the two extreme angular positions that it can occupy when it oscillates in the useful operating range of the timepiece. Since the amplitude of oscillation of the balance/balance spring is generally greater than 180° (+/−180° in a conventional mechanical movement, the aforementioned condition means, in the variant represented in
In each sequence of the first control mode, logic circuit 40 first determines whether the value of counter CB is greater than a positive integer number N1H (corresponds to a gain of the mechanical oscillator) or less than a negative integer number−N2H (corresponding to a loss of the mechanical oscillator). If CB>N1H (the first case considered), the logic circuit activates frequency generator 42 via a control signal SA and this frequency generator starts to supply first periodic digital signal SFI, at first frequency FINF defined above, to control circuit 30 of the braking device via logic gate 46. As a result, the braking device then starts to periodically generate a first series of braking pulses 60 at first frequency FINF. This situation is represented in
It will be noted that, in order to provide a visible representation of the angular position of the mechanical resonator and of the braking pulses,
During the activation phase of frequency generator 42, logic circuit 40 waits until the value of counter CB becomes equal to or less than an integer number N1L, which is less than number N1H and preferably less in absolute value than N1H. In the example represented in
In
It will be noted that, in absolute value, the difference between FINF (N=2) and F0c is preferably greater than a typical difference between F0 and F0c. Thus, the braking device is generally actuated less than half the time, i.e. less than 12 hours per day. In the example given here, assuming that natural frequency F0 remains stable over time, the braking device will have to be actuated for around 8 hours per day.
In each control mode sequence, if CB<−N2H (the second case considered), logic circuit 40 activates frequency generator 44 via a control signal SR and this frequency generator starts to supply second periodic digital signal SFS, at second frequency FINF defined above, to control circuit 30 of the braking device via logic gate 46. As a result, the braking device then starts to periodically generate a second series of braking pulses 61 at second frequency FSUP. This situation is represented in
It will be noted that, in order to provide a visible representation of the angular position of the mechanical resonator and of the braking pulses,
During the activation phase of frequency generator 44, logic circuit 40 waits until the value of counter CB becomes equal to or greater than an integer number N2L, which is greater than number N2H and preferably less in absolute value than N2H. In the example represented in
In
The control circuit is arranged such that each correction period has sufficient duration to establish the synchronous phase in which the frequency of the mechanical oscillator is synchronized, as a function of a detected positive or negative drift, respectively at a first correction frequency Fcor1 which is equal to FINF calculated with Fz (N=2)=F0c or at a second correction frequency Fcor2 which is equal to FSUP calculated with Fz (N=2)=F0c.
In a preferred variant, the duration of the synchronous phase is considerably greater than the maximum duration of the transitory phase, notably at least ten times greater.
The timepiece is characterized in that a temporal drift, detected by the control circuit in association with a sensor, is corrected by periodically generating a series of braking series at a selected frequency close to but different from a frequency FZ (N)=2·F0c/N, N being a positive integer number, which makes it possible to control the mean frequency of the mechanical oscillator so that it is equal to a set point frequency F0c without having to manage the braking pulse trigger times relative to the angular position of the mechanical oscillator as in the prior art. The instant of a first braking pulse of each series of pulses could be determined relative to the angular position of the mechanical oscillator to ensure a relatively short transitory phase prior to the stable synchronization phase, but such a variant is not necessary.
Referring to
‘Electromagnetic braking’ means the braking of the mechanical resonator caused by an electromagnetic interaction between at least one permanent magnet, carried by the mechanical resonator or a support of said mechanical resonator, and at least one coil respectively carried by the support or the mechanical resonator and associated with an electronic circuit wherein it is possible to generate an induced current in the coil via the permanent magnet.
In a general variant (not represented), the electromagnetic braking device is formed by an electromagnetic system which includes a coil 78 carried by a support 5 of mechanical resonator 14A and at least one permanent magnet carried by a balance of the mechanical resonator, this electromagnetic system being arranged such that an induced voltage is generated between the two coil terminals 78A & 78B in each vibration during oscillation of the mechanical resonator for a useful operating range of the mechanical oscillator. The control device is arranged to allow the control circuit to momentarily reduce the impedance between the two coil terminals, during distinct time intervals TP, to generate pulses for electromagnetic braking of the mechanical resonator. In the advantageous variant of the second embodiment described with reference to
In the particular variant represented in
In an advantageous variant represented in
Preferably, control device 72 includes a power supply circuit formed by a storage capacitor CAL and a rectifier circuit (signal SB) for voltage induced in coil 78 by a second pair of bipolar magnets 66 & 67 carried by balance 16A for this purpose. In
The power supply circuit is connected, on the one hand, to a coil terminal, and, on the other hand, to a reference potential (earth) of the control device at least periodically during the passage of the mechanical resonator through its neutral position, but preferably constantly. The second pair of magnets generates induced voltage pulses 90A and 90B during passages of balance 8B through the zero angular position; these pulses have greater amplitude than the induced voltage pulses generated by the first pair of magnets 64 & 65 and are used for powering the storage capacitor whose voltage is represented by curve 94 in
Control circuit 74 of an advantageous variant of the second embodiment, which implements a second control mode of the invention, is represented in
As shown in
By analogy with the first embodiment described above, comparator 52 can also be considered as part of the sensor and not of the measuring device. It will be noted that, generally, an additional pair of magnets is advantageous but not indispensable, since in another variant, pulses 88A and 88B can also be used for electrically powering the control device and also for detecting the number of vibrations or oscillation periods of the mechanical resonator. Generally, the reference voltage is selected such that, in a useful operating range of the mechanical oscillator, comparator 52 supplies to a first input of counter CB a predetermined number of pulses per oscillation period of the mechanical resonator, and clock signal SH is set so that it delivers the same number of pulses per set point period T0c (inverse of set point frequency F0c) to a second input of counter CB. As in the first embodiment, this counter CB outputs a signal corresponding to its state and which gives a measurement of temporal drift DT of the mechanical oscillator relative to auxiliary oscillator 36.
The state of counter CB is provided to two comparators 82 and 84. The first comparator 82 compares the state of counter CB to a first integer number N1 greater than zero, to determine whether or not the measured temporal drift is greater than this first number N1, and thus detects whether at least a certain gain has occurred in the operation of the mechanical oscillator. The second comparator 84 compares this state to a second negative integer number−N2, N2 being greater than zero, to determine whether or not the measured temporal drift is less than this second number−N2, and thus detects whether at least a certain loss has occurred in the operation of the mechanical oscillator. The output of first comparator 82 is provided to a first frequency generator 42A arranged to generate a first periodic digital signal SFI at first frequency FINF during a correction period each time that this output indicates that the state of counter CB is greater than number N1. More particularly, first generator 42A of frequency FINF includes means arranged for activating and then deactivating said generator, the signal provided by the first comparator being provided to a ‘start’ input of the first generator to activate it as soon as this first comparator indicates that the state of counter CB is greater than number N1. Similarly, the output of second comparator 84 is provided to a second frequency generator 44A arranged to generate a second periodic digital signal SFS at second frequency FSUP during a correction period each time that this output indicates that the state of counter CB is less than number−N2. More particularly, second generator 44A of frequency FSUP includes means arranged for activating and then deactivating said generator, the signal provided by the second comparator being provided to a ‘start’ input of the second generator to activate it as soon as the second comparator indicates that the state of counter CB is less than number−N2. The first and second periodic digital signals and frequencies have already been described in the context of the first embodiment and have the same characteristics in the second embodiment as in the first embodiment, so these signals and frequencies will not be described again here. Control signal SF is similar to that described in the first embodiment; it is formed of signal SFI when the first frequency generator is activated and of signal SFS when the second frequency generator is activated.
It is understood that the two frequency generators are never simultaneously activated. Electrical connection point 86 corresponds in practice to an electronic element, for example an ‘OR’ logic gate, or to an electronic circuit, for example a multiplexer with two or three input positions and only one output (it is thus a switch with two or three inputs here). In the case of three input positions, there is advantageously a neutral position in which the switch is not connected to either of the two frequency generators. As in the first embodiment, control signal SF is provided to a timer 48 which outputs the periodic signal SP described above. For each elementary pulse of signal SFI or of signal SFS, corresponding to a period of the respective frequency, the timer generates a pulse to activate switch 50, which is a short circuit switch for coil 78 here. Thus, in each period of signal SFI and of signal SFS a short circuit pulse is generated during a distinct time interval of duration TP.
An N counter (referenced CN) also receives control signal SF and it counts the number of elementary pulses (number of periods) in this control signal SF from the start of each correction period. It is thus reset to zero at the start of any correction period, simultaneously with the activation, as appropriate, of the first or second frequency generator. This N counter stops the frequency generator which was activated in the correction period concerned as soon as it has counted N elementary pulses (i.e. N periods) via an input ‘Stop’ comprised in each of the two frequency generators, N being an integer number greater than one (N>1). In an advantageous variant, the N counter is then deactivated until the start of the next correction period. Preferably, the number N is considerably greater than ‘1’, this number N being, for example, comprised between 100 and 10,000. In each correction period N short circuit pulses are thus generated for coil 78 during N respective distinct time intervals each having a duration TP.
It will be noted that it is possible to know approximately which temporal drift DT (absolute time error) is corrected by a certain number N of short circuit pulses generated in one correction period, so that it is easy to select a number N which corresponds to the detected temporal DT. In a preferred variant where the two frequency differences between set point frequency F0c and respectively the first frequency FINF and the second frequency FSUP are set at the same value and where the number N1 is equal to the number N2, the number N is chosen so that a negative or positive detected temporal drift is substantially corrected during a correction period that follows the detection thereof. The same result can be obtained with a number N1 different from the number N2 if the two aforementioned frequency differences are not set at the same value.
Generally, on the basis of the teaching given in Pat. No. CH 713306, it is understood that, on the one hand, if short circuit pulses 84 for coil 78 occur at least partially during pulses 88A, these induced voltage pulses 88A generate distinct electromagnetic braking pulses which produce negative phase shifts in the oscillation of mechanical resonator 14A, so that they can generate a loss in the operation of the timepiece to correct a gain. On the other hand, if short circuit pulses 84 for coil 78 occur at least partially during pulses 88B, these induced voltage pulses 88B generate distinct electromagnetic braking pulses which produce positive phase shifts in the oscillation of mechanical resonator, so that they can generate a gain in the operation of the timepiece to correct a loss. It will be noted that an angular offset of 180° has the advantage of great efficiency for generating braking pulses via short circuit pulses 84, which efficiently corrects a gain or a loss in the operation of the timepiece.
As in the first embodiment, during a correction period in which there is generated either a first series of braking pulses via a corresponding first series of coil short circuit pulses, or a second series of braking pulses via a corresponding second series of coil short circuit pulses, a transitory phase is observed in a first part of the correction period (of varying length depending on the case and in particular depending on the time at which the first short circuit pulse of the N short circuit pulses generated in each correction period occurs) during which the instantaneous frequency of the mechanical oscillator changes from the frequency that it had prior to the correction period in question to the selected correction frequency, namely either frequency FINF (N=2) or frequency FSUP (N=2) depending on the detected temporal drift that is being corrected. Following the transitory phase there is a stable phase/synchronous phase in a second part of the correction period. During the synchronous phase, the oscillator frequency is synchronized at the selected correction frequency, namely at the first correction frequency Fcor1 or at the second correction frequency Fccor2. It is thus observed that, provided that the natural temporal drift of the timepiece remains in a nominal range for which the electromagnetic braking device has been designed, in each correction period there is a synchronous phase where the mechanical oscillator exhibits the correction frequency selected by selecting braking frequency FINF or FSUP, regardless of the angular position of balance 16A during a first short circuit pulse in any correction period. In the synchronous phase, if there is no particular external disturbance (for example a shock or a certain acceleration of the balance due to an abrupt movement), each short circuit pulse generates an electromagnetic braking pulse, which is not always the case in the transitory phase.
In the synchronous phase, it is observed in
It will be noted that, in the definition of the present invention in the specification and claims, the braking pulses in the second embodiment respectively correspond to the short circuit pulses that they produce, so that each braking pulse of a first series of braking pulses and of a second series of braking pulses encompasses all the distinct braking pulses that may occur during time interval TP of the corresponding short circuit pulse. It will also be noted that, in the transitory phase, if time intervals T are less than time portions with no voltage induced in the coil, it is possible for no braking pulses to appear in the initial short circuit pulses. In the synchronous phase of a correction period, a braking pulse may contain only one distinct braking pulse, which is the case when time interval TP has a duration less than that of the time portions with no induced voltage situated around the extreme angular positions. In the advantageous variant represented in
In the situation where the timepieces naturally runs fast, the inverse is observed, namely that, in the synchronous phase of the correction period, the aforementioned second distinct braking pulse is stronger than the first distinct braking pulse during each short circuit pulse, such that a small correction of the detected gain occurs during each short circuit pulse.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18197282 | Sep 2018 | EP | regional |
| Number | Name | Date | Kind |
|---|---|---|---|
| 7016265 | Born | Mar 2006 | B2 |
| 7306364 | Born | Dec 2007 | B2 |
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