CH713636A2 - Mechanical timepiece comprising a movement whose progress is improved by a correction device. - Google Patents

Abstract

The mechanical timepiece is provided with a movement which comprises a mechanism indicating at least one temporal data, a mechanical resonator (6) forming a slave oscillator which speeds the operation of the indicating mechanism, and a mechanical correction device ( 52) to prevent any temporal drift in the operation of the indicating mechanism. The mechanical correction device is formed by a master mechanical oscillator (54) and a mechanical device (56) for braking the mechanical resonator, this braking device being arranged to be able to periodically apply to said mechanical resonator mechanical braking pulses at a frequency of braking determined by the master mechanical oscillator. Then, the mechanical system, formed of said mechanical resonator and the braking device, is configured to allow the braking device to be able to start the braking pulses preferably at any position of said mechanical resonator. Preferably, the braking pulses have a duration less than a quarter of a set period.

Description

Description

TECHNICAL FIELD [0001] The present invention relates to a mechanical timepiece comprising a movement whose progress is improved by a device for correcting any temporal drift in the operation of the mechanical oscillator which speeds the movement.

In particular, the mechanical timepiece is formed, on the one hand, by a movement comprising: a mechanism indicating at least one temporal data; a mechanical resonator capable of oscillating along a general axis of oscillation around a neutral position corresponding to its state of minimum potential energy, - a maintenance device of the mechanical resonator forming with it a mechanical oscillator which is arranged to clock the operation of the indicator mechanism, each oscillation of this mechanical oscillator defining an oscillation period, and, secondly, by a device for correcting a possible time drift in the operation of the aforementioned mechanical oscillator. Such a time drift occurs especially when the average natural oscillation period of said mechanical oscillator is not equal to a set period. This set period is determined by an auxiliary oscillator which is incorporated in the correction device.

BACKGROUND [0003] Timepieces as defined in the field of the invention have been proposed in a few previous documents. Patent CH 597 636, published in 1977, proposes such a timepiece with reference to FIG. 3. The movement is equipped with a sprung balance resonator and a conventional maintenance device comprising an anchor and an escape wheel in kinematic connection with a spring-loaded barrel. This watch movement further comprises an electronic device for regulating the frequency of its mechanical oscillator. This control device comprises an electronic circuit and a magnetic assembly formed of a flat coil, arranged on a support under the beam shank, and two magnets mounted on the balance and arranged close to each other so as to both pass over the coil when the oscillator is on.

The electronic circuit comprises a time base comprising a quartz resonator and for generating a reference frequency signal FR, this reference frequency being compared with the frequency FG of the mechanical oscillator. The detection of the frequency FG of the oscillator is performed via the electrical signals generated in the coil by the pair of magnets. The control circuit is arranged to be able momentarily to generate a braking torque via a magnet-coil magnetic coupling and a switchable load connected to the coil.

The use of an electromagnetic magnet-coil type system for coupling the sprung balance with the electronic control device generates various problems. First, the arrangement of permanent magnets on the balance means that a magnetic flux is constantly present in the watch movement and that this magnetic flux spatially varies periodically. Such a magnetic flux can have a detrimental effect on various members or elements of the watch movement, in particular on magnetic material elements such as parts made of ferromagnetic material. This can have repercussions on the proper functioning of the watch movement and also increase the wear of pivotal elements. One can certainly think to shield to a certain extent the magnetic system in question, but a shielding requires particular elements that are carried by the pendulum. Such shielding tends to increase the bulk of the mechanical resonator and its weight. In addition, it limits the possibilities of aesthetic configurations for the sprung balance.

The skilled person also knows mechanical watch movements which are associated with a device for regulating the frequency of their sprung balance which is of the electromechanical type. More precisely, the regulation intervenes via a mechanical interaction between the sprung balance and the regulating device, the latter being arranged to act on the oscillating balance by a system consisting of an abutment arranged on the balance and an actuator provided with a movable finger which is actuated at a braking frequency in the direction of the stop, without however touching the beam of the balance. Such a timepiece is described in the document FR 2 162 404. According to the concept proposed in this document, it is intended to synchronize the frequency of the mechanical oscillator with that of a quartz oscillator by an interaction between the finger and the stop when the mechanical oscillator has a time drift relative to a set frequency, the finger being provided to be able to momentarily block the rocker which is then stopped in its movement during a certain time interval (the abutment bearing against the finger moved in its direction during a return of the beam towards its neutral position), or limit the amplitude of oscillation when the finger comes against the stop while the rocker rotates towards one of its two angular positions extremes (defining its amplitude), the finger then stopping the oscillation and the pendulum starting directly in the opposite direction.

Such a control system has many disadvantages and can seriously doubt that it can form a functional system. The periodic actuation of the finger relative to the oscillating movement of the abutment and also a potentially large initial phase shift, for the oscillation of the abutment with respect to the periodic movement of the finger in the direction of this abutment, pose several problems. It will be noted that the interaction between the finger and the stop is limited to a single angular position of the balance, this angular position being defined by the angular position of the actuator relative to the axis of the sprung balance and the angular position of the stop on the pendulum at rest (defining its neutral position). Indeed, the movement of the finger is provided to stop the balance by contact with the stop, but the finger is arranged not to come into contact with the balance beam. In addition, it will be noted that the instant of an interaction between the finger and the stop also depends on the amplitude of the oscillation of the sprung balance.

It will be noted that the desired synchronization seems unlikely. Indeed, in particular for a sprung balance whose frequency is greater than the reference frequency setting the back and forth of the finger and with a first interaction between the finger and the abutment which temporarily holds the pendulum returning from one of its two extreme angular positions (correction reducing the error), the second interaction, after many oscillations without the stop touching the finger during its reciprocating movement, will certainly be a stop of the pendulum by the finger with immediate inversion of its sense of oscillation, in that the stop abuts against the finger while the rocker rotates towards said extreme angular position (correction increasing the error). Thus, not only is there an uncorrected time drift during a time interval that may be long, for example several hundred oscillation periods, but certain interactions between the finger and the stopper increase the time drift instead of the reduce! It will also be noted that the phase shift of the oscillation of the abutment, and therefore of the sprung balance, during the above-mentioned second interaction can be significant according to the relative angular position between the finger and the abutment (balance in its neutral position).

It can thus be doubted that the desired synchronization is obtained. Moreover, in particular if the natural frequency of the sprung balance is close but not equal to the reference frequency, situations where the finger is blocked in its movement in the direction of the balance by the stop which is located at this time in front of the finger are predictable. Such parasitic interactions can damage the mechanical oscillator and / or the actuator. In addition, this virtually limits the tangential extent of the finger. Finally, the duration of maintaining the finger in the interaction position with the stop must be relatively short, thus limiting a correction generating a delay. In conclusion, the operation of the timepiece proposed in document FR 2 162 404 appears to the highly improbable person skilled in the art, and he turns away from such teaching. SUMMARY OF THE INVENTION [0010] An object of the present invention is to find a solution to the technical problems and disadvantages of the prior art mentioned in the technological background.

In the context of the present invention, it is generally sought to improve the accuracy of the running of a mechanical watch movement, that is to say, to reduce the daily time drift of this mechanical movement. In particular, the present invention seeks to achieve such a goal for a mechanical watch movement whose gait is initially set at best. Indeed, a general object of the invention is to find a device for correcting a time drift of a mechanical movement, namely a device for correcting its progress to increase its accuracy, without giving up what it is. it can operate autonomously with the best accuracy that it is possible to have through its own characteristics, that is to say, in the absence of the correction device or when the latter is inactive.

Another object of the present invention is to achieve the above goals without having to incorporate electrical and / or electronic devices in the timepiece according to the invention, that is to say using organs and systems specific to so-called mechanical watches, the latter being able to integrate, according to various developments in the field of mechanical watchmaking, magnetic elements such as magnets and ferromagnetic elements, but no devices requiring a power supply and therefore a source of electrical energy .

For this purpose, the present invention relates to a timepiece as defined above in the technical field, wherein the mentioned mechanical oscillator is a slave oscillator and the correction device is of the mechanical type, this mechanical device of correction being formed by a mechanical auxiliary oscillator, which defines a master oscillator, and by a mechanical braking device of the mechanical resonator of the slave oscillator. The mechanical braking device is arranged to be able to apply to the mechanical resonator of the slave oscillator a mechanical braking torque during periodic braking pulses which are generated at a braking frequency selected only as a function of a reference frequency for the slave oscillator and determined by the master oscillator. Then, the mechanical system formed of the mechanical resonator of the slave oscillator and the mechanical braking device is configured to allow the mechanical braking device to be able to start the periodic braking pulses at any position of said mechanical resonator in a position range, along the general axis of oscillation of this mechanical resonator, which extends at least a first of two sides of the neutral position of said mechanical resonator over at least a first range of amplitudes that the The slave oscillator is likely to have this first side for a useful operating range of this slave oscillator.

In a general variant, the mechanical system mentioned is configured so that said position range of the mechanical resonator of the slave oscillator, in which the periodic braking pulses can begin, also extends from the second of the two sides of the oscillator. the neutral position of said mechanical resonator over at least a second range of amplitudes that the slave oscillator is likely to have from this second side, along the general axis of oscillation, for the useful operating range of this mechanical oscillator .

In a preferred embodiment, each of the two parts of the range of mechanical resonator positions identified above, respectively incorporating the first and second ranges of the amplitudes that the slave oscillator is likely to have respectively on both sides of the neutral position of its mechanical resonator, has a certain extent on which it is continuous or almost continuous.

In a general variant, the mechanical braking device is arranged so that the periodic braking pulses each have essentially a duration less than one quarter of the corresponding reference period to the inverse of the target frequency. In a particular variant, the periodic braking pulses have a duration less than 1/10 of the reference period. In a preferred variant, the duration of the periodic braking pulses is essentially less than 1/40 of the reference period.

Thanks to the characteristics of the invention, surprisingly, the mechanical oscillator slave is synchronized to the master mechanical oscillator in an efficient and fast manner, as will become clear later in the detailed description of the invention. The mechanical correction device constitutes a synchronization device of the mechanical oscillator slave on the master mechanical oscillator, and this without closed-loop servo and without measuring sensor of the movement of the mechanical oscillator. The mechanical correction device thus operates with an open loop and it makes it possible to correct both an advance and a delay in the natural course of the mechanical movement, as will be explained later. This result is quite remarkable. By "synchronization on a master oscillator", here comprises a servo (open loop, without feedback) of the mechanical oscillator slave to the master mechanical oscillator. The operation of the correction device is such that the braking frequency derived from the reference frequency of the master oscillator is imposed on the slave oscillator which speeds the operation of the indicating mechanism of a given time data. We are not in the situation of coupled mechanical oscillators, nor even in the standard case of a forced oscillator. In the present invention, the braking frequency of the mechanical braking pulses determines the average frequency of the slave oscillator.

It is understood by 'clocking the march of a mechanism' the rhythm of the movement of the moving elements of this mechanism when it operates, in particular to determine the rotational speeds of its wheels and so at least one indicator of a given time.

In a preferred embodiment, the mechanical system formed of the mechanical resonator and the mechanical braking device is configured to allow the mechanical braking device to start, in the useful operating range of the slave mechanical oscillator, a mechanical braking pulse substantially at any instant of the natural oscillation period of this slave mechanical oscillator. In other words, one of the periodic braking pulses can begin substantially at any position of the mechanical resonator of the slave mechanical oscillator along the general axis of oscillation of this mechanical resonator.

In general, the braking pulses have a dissipative nature because a portion of the energy of the oscillator is dissipated by 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 mechanical resonator which has a certain extent (non-point) along the axis of oscillation.

In a particular embodiment, the braking pulses exert a braking torque on the slave resonator whose value is intended not to momentarily block this slave resonator during periodic braking pulses. In this case, preferably, the mechanical system mentioned above is arranged to allow the mechanical braking torque generated by each of the braking pulses to be applied to the slave resonator during a continuous or quasi-continuous time interval (non-zero or one-time). but having a certain significant duration).

BRIEF DESCRIPTION OF THE FIGURES [0022] The invention will be described below in more detail with the aid of the accompanying drawings, given by way of non-limiting examples, in which:

Fig. 1 shows, in part schematically, a first embodiment of a timepiece according to the invention,

Figs. 2A to 2D show partially a second embodiment of a timepiece according to the invention and a sequence of its operation,

Fig. 3 partially shows a third embodiment of a timepiece according to the invention,

Fig. 4 schematically shows a first configuration of the general arrangement of a timepiece according to the invention,

Fig. 5 schematically shows a second configuration of the general arrangement of a timepiece according to the invention,

Fig. 6 shows the application of a first braking pulse to a mechanical resonator in a certain alternation of its oscillation before it passes through its neutral position, as well as the angular velocity of the balance of this mechanical resonator and its angular position in a time interval during which the first braking pulse occurs,

Fig. 7 is a figure similar to FIG. 6 but for the application of a second braking pulse in a certain alternation of the oscillation of a mechanical oscillator after it has passed through its neutral position,

Figs. 8A, 8B and 8C respectively show the angular position of a balance-spring during a period of oscillation, the variation of the movement of the watch movement obtained for a fixed-duration braking pulse, for three values of one constant braking torque, depending on the angular position of the balance spring, and the corresponding braking power,

Figs. 9, 10 and 11 respectively show three different situations that may occur in an initial phase following the engagement of the correction device in a timepiece according to the invention,

Fig. 12 is an explanatory graph of the physical process involved following the engagement of the correction device in the timepiece according to the invention and leading to the desired synchronization for the case where the natural frequency of the slave mechanical oscillator is greater than at the set frequency,

Fig. 13 represents, in the case of FIG. 12, an oscillation of the slave mechanical oscillator and the braking pulses in a stable synchronous phase for a variant where a braking pulse occurs in each alternation,

Fig. 14 is an explanatory graph of the physical process involved following the engagement of the correction device in the timepiece according to the invention and leading to the desired synchronization for the case where the natural frequency of the slave mechanical oscillator is lower than at the set frequency,

Fig. 15 represents, in the case of FIG. 14, an oscillation of the mechanical slave oscillator and the braking pulses in a stable synchronous phase for a variant where a braking pulse occurs in each alternation,

Figs. 16 and 17 give respectively for the two cases of fig. 12 and 14, the graph of the angular position of a mechanical oscillator and the corresponding oscillation periods for an operating mode of the correction device in which a braking pulse occurs every four periods of oscillation,

Figs. 18 and 19 are respectively partial enlargements of FIGS. 16 and 17,

Fig. 20 represents, in a similar manner to the two previous figures, a specific situation in which the frequency of a mechanical oscillator is equal to the braking frequency,

Fig. 21 shows, for a variant of a timepiece according to the invention, the evolution of the oscillation period of the slave mechanical oscillator and the evolution of the total time error,

Fig. 22 shows, for another variant of a timepiece according to the invention, the graph of the oscillation of the mechanical oscillator slave in an initial phase following the engagement of the correction device of a possible time drift,

Figs. 23A to 23C partially show a fourth embodiment of a timepiece according to the invention and a sequence of its operation, and

Figs. 24A to 24C partially show a fifth embodiment of a timepiece according to the invention and a sequence of its operation.

Detailed Description of the Invention [0023] In FIG. 1 is shown, in part schematically, a first embodiment of a mechanical timepiece 2 according to the present invention. It comprises a mechanical clock movement 4 which comprises a mechanism 12 indicating a time data. The mechanical movement further comprises a mechanical resonator 6, formed by a rocker 8 and a hairspring 10, and a main device for maintaining this mechanical resonator which is formed by a main escapement. This main exhaust 14 and the mechanical resonator 6 form a mechanical oscillator 18 which speeds the operation of the indicator mechanism. The main escapement 14 is formed for example by an anchor and an escape wheel which is kinematically connected to a main source of mechanical energy 16. The mechanical resonator is able to oscillate around a neutral position (position of rest / zero angular position) corresponding to its state of minimum potential energy, along a circular axis whose radius corresponds for example to the outer radius of the strut 9 of the balance. As the position of the balance is given by its angular position, it is understood that the radius of the circular axis here is unimportant. It defines a general axis of oscillation which indicates the nature of the motion of the mechanical resonator, which can be linear, for example, in another particular embodiment.

The timepiece 2 further comprises a mechanical device 20 for correcting a possible time drift in the operation of the mechanical oscillator 18, this mechanical correction device comprising for this purpose a mechanical braking device 24 and a master mechanical oscillator 22 (hereinafter also referred to as the master oscillator). The master oscillator is associated / coupled to the mechanical braking device to provide a reference frequency which controls its operation and determines the braking frequency of the mechanical braking pulses provided by the mechanical braking device. It will be noted that the master oscillator 22 is an auxiliary mechanical oscillator insofar as the main mechanical oscillator, which directly rates the march of the watch movement, is the mechanical oscillator 18, the latter thus being a slave oscillator. Generally, the auxiliary mechanical oscillator is by nature or by construction more accurate than the main mechanical oscillator. In an advantageous variant, the master oscillator 22 is associated with an equalization mechanism of the force exerted on it to maintain its oscillation. The master oscillator 22 comprises an auxiliary mechanical resonator 28, here conventionally formed by a rocker 30 and a hairspring, and an auxiliary maintenance device formed by an auxiliary exhaust 32, which comprises for example an anchor 33 and a wheel exhaust 34 which rotates in steps, a step being performed at each alternation of the master oscillator. Thus, the average rotational speed of the wheel 34 is determined by the reference frequency of the master oscillator 22. The braking device 24 comprises a control mechanism 48 and a braking pulse generator mechanism 50 (also called pulse generator 'thereafter) arranged to generate mechanical braking pulses at a braking frequency determined by the control mechanism. This control mechanism comprises a control wheel 37, which is integral with a mobile 36 or forming thereof. The mechanism for generating braking pulses comprises a braking member, formed by a pivoting member 40, and a spring 44 associated with the pivoting member.

The mobile 36 is kinematically connected to an auxiliary source of mechanical energy 26. This mobile 36 is a mobile for transmitting the mechanical energy of the auxiliary source 26, on the one hand, to the master oscillator 22 and on the other hand, to the braking pulse generator 50. This is an advantageous variant insofar as the mechanical correction device requires a single source of mechanical energy. As the exhaust 32 maintains the resonator 28 via the mobile 36 which meshes with a pinion of the escapement wheel 34, the latter communicates to the mobile 36 a rhythm and thus determines its average angular velocity (because advance step-by-step) which is a function of the reference frequency of the master oscillator.

The pivoting member 40 is mounted on an axis of rotation 43 and thus forms a rocker with two arms. The first end 41 of the rocker cooperates with the control wheel 37, which carries pins 38 arranged to successively come into contact with said first end to actuate the rocker so as to first arm the pulse generator by pressing laterally against this first end to thereby pivot the rocker by compressing the spring 44. The pulse generator is armed during the step-by-step advance of the control wheel to a trigger step of a pulse of braking when the pin in contact with the first end passes beyond this first end which is then released. The braking device will be adjusted so that this release occurs positively during a determined step of the control wheel. The latch 40 here forms a kind of hammer. To apply the mechanical braking pulses to the balance 8, the latch 40 has at its second end a relatively rigid leaf spring 42 which forms a braking pad. Following the triggering step of a braking pulse, the rocker is rotated, thanks to the pressure exerted by the spring 44 then compressed, in the direction of the shank 9 of the beam and the spring blade undergoes a substantially radial movement relatively to the axis of rotation of the pendulum as it approaches the serge. The pulse generator is configured so that the braking pad comes into contact with the lateral surface 46 of the serge 9 during the first swing of the rocker after its release and so that it exerts on the balance a certain amount of torque. force to stop him momentarily. The braking pulse generator is preferably configured so that the movement of the rocker is sufficiently damped so as to avoid rebounds which would generate a series of braking pulses instead of having a single braking pulse at the frequency of the braking pulse. braking. However, this damping is adjusted so that the brake shoe comes into contact with the rocker during the first swing of the rocker following its release.

The braking pulse generator is arranged so that the periodic braking pulses can have a certain duration, mainly by a dynamic dry friction. In this respect the stiffness and the mass of the leaf spring 42 can be selected appropriately. The leaf spring 42 dampens the shock during the impact thereof on the beam while extending the contact time and generating frictional braking between the leaf spring and the braking surface provided on the balance. We will also choose adequate stiffness for the spring 44 and determine the position of the latch relative to the braking surface when the spring is at rest (position 'not deformed'). Finally, it will be noted that other parameters of the pulse generator will advantageously be adjusted, in particular the length of each of its two arms and the position of the anchoring of the spring on one of its two arms.

In an advantageous variant, the balance of the master resonator is mounted on flexible blades. Similarly, the anchor of the exhaust may be formed of flexible blades defining a bistable system and do not have a rotated shaft. In another specific variant, the coupling between the anchor and the escape wheel is magnetic. In this case, we have a magnetic escapement with stop. Any high precision mechanical oscillator can therefore be incorporated into a timepiece according to the invention. For example, the master oscillator 22 oscillates at a natural frequency of 10 Hz and has an intrinsic accuracy greater than the slave oscillator 18 whose reference frequency is equal to 3 Hz. The escape wheel 34 comprises twenty teeth and so it performs a half-turn per second (1/2 turn / s). In the variant shown, the control wheel carries five pins 38 regularly spaced on its serge. The reduction ratio between the pinion of the escape wheel and the control wheel being provided here at 7.5 (6-tooth pinion and 45-toothed wheel), the control wheel 37 performs 1/15 turn per second (1). / 15 revolution / s) and the pulse generator is thus armed and released every third of a second, thus generating braking pulses at a frequency of 1/3 Hz (called 'braking frequency'). As the reference frequency for the main oscillator 18 is 3 Hz, the mechanical correction device 20 generates a mechanical braking pulse every nine set periods, which corresponds substantially to one pulse per nine periods of oscillation. main oscillator whose natural frequency is best adjusted to the set frequency. The synchronization obtained by the mechanical correction device according to the invention will be described in detail later.

In a variant, it is provided that the control wheel carries only one pin so as to generate a single braking pulse per revolution. In this case, the braking frequency is equal to 1/15 Hz and a braking pulse occurs every forty-five periods. In another variant also functional, as will be apparent from the description of the synchronization phenomenon obtained by the invention, the control wheel has two pins diametrically opposite. In this case, the braking frequency is equal to 2/15 Hz and a braking pulse occurs every twenty-two and a half periods, that is to say only every forty-five alternations (odd number) of the main oscillator slave 18.

In general, the mechanical braking device 24 is arranged to periodically apply to the mechanical resonator 6 braking pulses at a braking frequency selected only as a function of the reference frequency for the slave main oscillator and determined by the master auxiliary oscillator 22. The mechanical braking device comprises a braking member capable of momentarily coming into contact with a braking surface of the slave mechanical resonator 6. For this purpose, the braking member is movable and has a movement of reciprocating device which is controlled by a mechanical control device which periodically actuates it at a braking frequency, so that the braking member periodically comes into contact with the braking surface of the slave mechanical resonator in order to apply to it braking pulses.

Next, the mechanical system, formed of the slave mechanical resonator 6 and the mechanical braking device 24, is configured to allow the mechanical braking device to be able to start the periodic braking pulses at any position of the resonator. mechanical slave at least in a certain continuous or quasi-continuous range of positions by which this slave mechanical resonator is likely to pass along its general axis of oscillation. The variant shown in FIG. 1 corresponds to a preferred variant in which the mechanical system is configured to allow the mechanical braking device to apply a mechanical braking pulse to the slave mechanical resonator at any instant of an oscillation period in the useful operating range of the slave oscillator. Indeed, the outer lateral surface 46 of the serge 30 defines a continuous and circular braking surface, so that the pad 42 of the braking member 40 can exert a mechanical braking torque at any angular position of the sprung balance. Thus, a braking pulse can begin at any angular position of the slave mechanical resonator between the two extreme angular positions (the two amplitudes of the slave oscillator respectively on both sides of the neutral position of its mechanical resonator). is likely to reach when the slave oscillator is functional.

It will be noted that the braking surface may be other than the outer lateral surface of the balance beam. In a variant not shown, it is the central shaft of the balance which defines a circular braking surface. In this case, a pad of the braking member is arranged to exert a pressure against this surface of the central shaft during the application of the mechanical braking pulses.

In a general operating mode, the mechanical braking device 24 is arranged so that the periodic braking pulses each have substantially less than a quarter of the set period for the oscillation of the slave mechanical oscillator 18.

By way of nonlimiting examples, for a main clock resonator formed by a sprung balance, whose spiral constant k = 5.75 E-7 Nm / rad and the inertia I = 9.1 E-10 kg m2, and a set frequency FOc equal to 4 Hz, we can consider a first variant for a watch movement whose unsynchronized operation is not very precise, with a daily error of about five minutes, and a second variant for another watch movement of which Unsynchronized operation is more accurate with a daily error of about thirty seconds. In the first variant, the range of values for the average braking torque is between 0.2 pNm and 10 pNm, the range of values for the duration of the braking pulses is between 5 ms and 20 ms and the range of values relative to the braking period for the application of the periodic braking pulses is between 0.5 s and 3 s. In the second variant, the range of values for the average braking torque is between 0.1 pNm and 5 pNm, the range of values for the duration of the periodic braking pulses is between 1 ms and 10 ms and the range of values for the braking period is between 3 s and 60 s, ie at least once a minute.

Note that the main slave oscillator is not limited to a version comprising a sprung balance and an escapement with a stop, including the Swiss anchor type. Other mechanical oscillators may be provided, in particular with a flexible leaf rocker. The exhaust may include a stop or be of continuous rotation type. This is also true for the auxiliary mechanical oscillator forming the master oscillator. As the master oscillator is the one that finally gives the high precision required for the march of the mechanical movement, we will try to select for him a mechanical oscillator that is as accurate as possible, knowing that this oscillator does not have to train the mechanism or mechanisms of the watch movement, including a mechanism indicating the time. This is illustrated by the second embodiment of the invention described hereinafter.

In FIG. 2A is shown a second embodiment of a timepiece according to the invention. To avoid overloading the drawing, only the main resonator slave 6 and the mechanical correction device 52 have been represented. The correction device is formed by a master mechanical oscillator 54 and a mechanical braking device 56 which comprises a braking pulse generating mechanism 50 similar to that presented in the context of the first embodiment. The resonator 6, similar to that of FIG. 1, and the pulse generator 50 will not be described here again in detail.

The master oscillator 54 is of the magnetic escaping type. It comprises a resonator 60 formed of a rocker 62 and a hairspring 66 (shown schematically). In a variant, the balance is mounted on flexible blades. This balance has two arms which are located on two sides of its pivot axis and which carry at their respective ends two magnets 63 and 64. These two magnets are used to couple the resonator 60 to an escape wheel 68. This wheel of exhaust and the magnets 63 and 64 form the magnetic escapement of the master oscillator 54. The escape wheel comprises a magnetic structure formed of two annular tracks 70 and 72. Each of the two annular tracks has an alternation of annular sectors 74 and 76, a sector 74 and an adjacent sector 76 together defining an angular period of the magnetic structure. Both tracks are angularly out of phase by half a period. In general, a sector 74 has at least one physical characteristic or defines at least one physical parameter, relative to the magnets carried by the pendulum, which is different from a similar physical characteristic of a sector 76 or a similar physical parameter. defined by a sector 76. In other words, the magnetic potential for any of the two magnets passing over a sector 74 is different from the magnetic potential that it has when passing over a sector 76. In particular, it is expected that a minimum magnetic potential appears in one of the two sectors while a maximum magnetic potential appears in the other of these two sectors. Thus, if the escape wheel rotates, it causes the resonator 60 to swing to its own oscillation frequency (natural frequency) which then imposes a continuous rotational speed on the escape wheel according to the value of this frequency of oscillation, here called 'reference frequency'. The escape wheel advances an angular period of the magnetic structure per oscillation period of the balance 62. It will be noted that if the resonator is directly excited and oscillates at its resonant frequency (natural frequency ), then the escape wheel is rotated at the above-mentioned continuous rotational speed. By continuous rotation speed, it is understood here that the wheel rotates without stopping; but there may be a periodic variation in speed.

Several variants are possible for the magnetic structure of the escape wheel 68. In a first variant, the sectors 74 are formed of a ferromagnetic material while the sectors 76 are formed of a non-magnetic material. In a second variant, the sectors 74 are formed of a magnetic material while the sectors 76 are formed of a non-magnetic material. In a third variant, the sectors 74 are formed of a material magnetized in a first direction while the sectors 76 are formed of a magnetized material in a second direction opposite to the first direction (opposite polarities). In the latter case, each of the two magnets 63 and 64 undergoes a magnetic repulsion force above one of the two sectors and a magnetic attraction force above the other sector. Other improved variants are described in the patent application EP 2 891 930. Reference can be made to this document to understand in greater depth the operation of the master oscillator 54.

The escape wheel carries at its periphery a finger 58 arranged to be able to actuate the pulse generator 50 at each turn made by the escape wheel. This finger belongs to the braking device 56 and its role is similar to a pin 38 of the first embodiment. Thus, the escape wheel and the actuating finger 58 together form a control mechanism of the pulse generator 50. A sequence of the operation of the correction device of the second embodiment is given in FIGS. 2A to 2D.

In FIG. 2A, the pulse generator 50 is at rest and the actuating finger 58 turns progressively in its direction. In fig. 2B, the actuating finger has come into contact with the end 41 of the latch 40 and the latch 40 has begun to rotate in a clockwise direction. The pulse generator is thus armed. Continuing to rotate, the finger slides along the end 41 until it loses contact with this end, which releases the rocker and then triggers the generation of a braking pulse, an event which is represented in FIG. fig. 2C. The spring 44 compressed in advance causes, during a first swing, the rocker in a counterclockwise direction and the spring blade 42, defining a braking pad, press against the braking surface 46 of the balance rod during a certain time interval. Following the braking pulse, the rocker turns clockwise again during a second swing and then it oscillates around the rest position of the pulse generator by undergoing damping, as shown in FIG. 2D. Finally, the rocker stabilizes until the actuating finger has completed a new turn.

For example, the reference frequency of the master oscillator 54 is equal to 12 Hz and the magnetic structure of the escape wheel has magnetic periods of 30 °, or 12 periods in total. The brake pulse generating mechanism is therefore actuated at a braking frequency of 1 Hz because the escape wheel performs one revolution per second. In another variant, the number of magnetic periods is equal to 24 so that the braking frequency is then equal to 2 Hz.

FIG. 3 shows a third embodiment of a timepiece according to the invention. The timepiece 80 (shown in part) differs from that of FIG. 1 by only a few features of the slave main resonator 6A and the braking pulse generating mechanism 50A. The resonator 6A comprises a serge 9A having cavities 84 (in the general plane of the balance) in which are housed screws 82 for balancing the balance. Thus, the outer lateral surface 46A of the beam no longer defines a continuous circular surface, but a discontinuous circular surface with four continuous angular sectors. It will be noted that the leaf spring 42 has a contact surface with an extent such that braking pulses remain possible for any angular position of the beam 8A, even when a cavity is opposite the leaf spring, as shown. in fig. 3. Then, the flip-flop 40A of the pulse generator 50A is held in a central part by two elastic strips 86A and 86B which respectively extend on both sides of the rocker, which can thus pivot about a fictitious axis defined by the two elastic blades. The two resilient blades are fixed to two studs each having a slot in which is rigidly inserted a blade end. Finally, a damper 88 is associated with the flip-flop 40A so as to sufficiently damp the oscillation of this flip-flop, after the generation of a first braking pulse, in order to prevent other significant braking pulses from being applied to the resonator 6A in a braking period following this first braking pulse.

In figs. 4 and 5 are schematically represented two alternative configurations for the general arrangement of a timepiece according to the invention. Fig. 4 relates to a preferred arrangement that has been implemented in the previously described embodiments. On the one hand, there is the watchmaking movement with a main part in which a main source of mechanical energy, formed by a main cylinder, transmits its energy, via a main transmission, to a slave oscillator 92 and to a mechanical mechanism. indication of the time whose operation is clocked by this slave oscillator. According to the invention, a braking device is arranged to brake the slave resonator, the intensity of this braking periodically varying at a braking frequency, as already exposed. This braking device is part of a mechanical correction device independent of the elements of the main part of the mechanical movement. The mechanical correction device comprises an auxiliary source of mechanical energy formed by an auxiliary barrel which is distinct from the main barrel. This auxiliary barrel supplies its energy, via an auxiliary transmission, on the one hand to the master oscillator 94 and on the other hand to the braking device. In the first embodiment, the energy is supplied to the braking device through the auxiliary transmission (version V1), a mobile of this auxiliary transmission forming a control mechanism of the pulse generator which not only determines the instants of triggering the braking pulses but in addition transmits the energy necessary to arm this pulse generator. In the second embodiment, it is the escape wheel which performs directly with the actuating finger these two functions (version V2). This arrangement has the advantage of completely separating mobiles in connection with the slave oscillator of mobiles in connection with the master oscillator. This makes it possible to avoid any coupling between the two oscillators which could possibly influence the operation and accuracy of the master oscillator. The only interaction expected between the slave oscillator and the master oscillator is constituted by the braking pulses.

FIG. 5 shows an alternative general arrangement that can be envisaged. It is characterized in that the main part of the watch movement and the correction device have in common a single source of energy, namely a barrel supplying its energy, via a possible common transmission, to a differential mechanism which distributes this energy on the one hand to the slave oscillator 92 and the time indicating mechanism and, on the other hand, to the master oscillator 94 and the braking device. It should be noted that this alternative does not prevent having several barrels in series or in parallel supplying energy to the differential mechanism.

Before presenting other particular embodiments, the following will be described in detail the remarkable operation of a timepiece according to the invention and how the synchronization of the main oscillator slave on the oscillator auxiliary master is obtained.

We will describe below, with reference to FIGS. 6 and 7, a remarkable physical phenomenon highlighted in the context of developments that led to the present invention and involved in the synchronization method implemented in the timepiece according to the invention. The understanding of this phenomenon will better understand the timing obtained by the correction device regulating the gait of the mechanical movement, a result which will be described later in detail.

In figs. 6 and 7, the first graph indicates the instant tP1 at which a braking pulse P1, respectively P2 is applied to the mechanical resonator considered to perform a correction of the operation of the mechanism which is clocked by the mechanical oscillator formed by this resonator. The last two graphs respectively show the angular velocity (values in radians per second: [rad / s]) and the angular position (values in radian: [rad]) of the oscillating organ (later also 'the pendulum') of the mechanical resonator over time. The curves 90 and 92 respectively correspond to the angular speed and to the angular position of the freely oscillating rocker (oscillation at its natural frequency) before the intervention of a braking pulse. After the braking pulse are represented the speed curves 90a and 90b corresponding to the behavior of the resonator respectively in the case disturbed by the braking pulse and the undisturbed case. Similarly, the position curves 92a and 92b correspond to the behavior of the resonator respectively in the case disturbed by the braking pulse and the undisturbed case. In the figures, the instants tp-1 and tp2 in which the braking pulses P1 and P2 are involved correspond to the time positions of the medium of these pulses. However, the beginning of the braking pulse and its duration are considered as the two parameters which define a braking pulse temporally.

It will be noted that the pulses P1 and P2 are represented in FIGS. 6 and 7 by binary signals. However, in the following explanations, mechanical braking pulses applied to the mechanical resonator and not control pulses are considered. Thus, it will be noted that, in certain embodiments, in particular with mechanical correction devices having a mechanical control device, the control pulse can intervene at least in part before the application of a mechanical braking pulse. In such a case, in the following explanations, the braking pulses P1, P2 correspond to the mechanical braking pulses applied to the resonator and not to previous control pulses.

It will also be noted that the braking pulses may be applied with a constant force torque or a non-constant force torque (for example substantially Gaussian or sinusoidal curve). By braking pulse, it is understood the momentary application of a force torque to the mechanical resonator which brakes its oscillating member (balance), that is to say, which opposes the oscillating movement of this oscillating member. In the case of a non-zero torque that is variable, the duration of the pulse is generally defined as the portion of this pulse that has a significant torque force to brake the mechanical resonator. It will be noted that a braking pulse can have a large variation. It can even be chopped and form a succession of shorter pulses. In the case of a constant torque, the duration of each pulse is expected to be less than half a set period and preferably less than one quarter of a set period. It should be noted that each braking pulse can either brake the mechanical resonator without stopping it, as in FIGS. 6 and 7, either stop it during the braking pulse and stop it momentarily during the rest of this braking pulse.

Each free oscillation period TO of the mechanical oscillator defines a first alternation AO1 followed by a second alternation AO2 intervening each between two extreme positions defining the oscillation amplitude of this mechanical oscillator, each alternation having a duration identical TO / 2 and having a passage of the mechanical resonator by its zero position at a median time. The two successive alternations of an oscillation define two half-periods during which the rocker is respectively subjected to an oscillation movement in one direction and then an oscillation movement in the other direction. In other words, an alternation here corresponds to a rocking of the balance in one direction or the other direction between its two extreme positions defining the amplitude of oscillation. In general, there is a variation of the oscillation period during which a braking pulse occurs and thus a point variation of the frequency of the mechanical oscillator. In fact, the temporal variation relates to the only alternation during which the braking pulse intervenes. By 'median moment', we understand a moment intervening substantially in the middle of the alternations. This is precisely the case when the mechanical oscillator oscillates freely. On the other hand, for the alternations in which regulation pulses occur, this median instant no longer corresponds exactly to the middle of the duration of each of these alternations due to the disturbance of the mechanical oscillator generated by the regulating device.

We will first describe the behavior of the mechanical oscillator in a first case of correction of its oscillation frequency, which corresponds to that shown in FIG. 6. After a first period TO then begins a new period T1, respectively a new alternation A1 during which a braking pulse P1 occurs. At initial time tP1 starts alternating A1, the resonator 14 occupying a maximum positive angular position corresponding to an extreme position. Then comes the braking pulse P1 at time tP1 which is located before the median time tNi at which the resonator passes through its neutral position and therefore also before the corresponding median time tN0 of the undisturbed oscillation. Finally the alternation A1 ends at the final time tF1. The braking pulse is triggered after a time interval TA1 following the instant TD1 marking the beginning of the alternation A1. The duration TA1 is less than half-alternation TO / 4 less the duration of the braking pulse P1. In the example given, the duration of this braking pulse is much less than a half-alternation TO / 4.

In this first case, the braking pulse is generated between the beginning of an alternation and the passage of the resonator by its neutral position in this alternation. The angular speed in absolute value decreases at the moment of the braking pulse P1. Such a braking pulse induces a negative time phase shift TCi in the oscillation of the resonator, as shown in FIG. 6 the two curves 90a and 90b of the angular velocity and also the two curves 92a and 92b of the angular position, that is to say a delay relative to the undisturbed theoretical signal (shown in broken lines). Thus, the duration of the alternation A1 is increased by a time interval TCi. The oscillation period T1, comprising the alternation A1, is therefore extended relative to the value TO. This causes a specific decrease in the frequency of the mechanical oscillator and a momentary slowing of the associated mechanism whose operation is clocked by this mechanical oscillator.

[0054] Referring to FIG. 7, will be described below the behavior of the mechanical oscillator in a second case of correction of its oscillation frequency. After a first period TO then begins a new oscillation period T2, respectively an alternation A2 during which a braking pulse P2 occurs. At the initial moment tD2 begins the alternation A2, the mechanical resonator then being in an extreme position (maximum negative angular position). After a quarter period TO / 4 corresponding to a half-wave, the resonator reaches its neutral position at the median time tN2. Then comes the braking pulse P2 at time tP2 which is located in alternation A2 after the median time tN2 at which the resonator passes through its neutral position. Finally, after the braking pulse P2, this alternation A2 ends at the final instant tj = 2 at which the resonator again occupies an extreme position (maximum positive angular position in the period T2) and therefore also before the corresponding final instant tFo of undisturbed oscillation. The braking pulse is triggered after a time interval Ta2 following the initial time TD2 of the alternation A2. The duration Ta2 is greater than a half-alternation TO / 4 and less than an alternation TO / 2 less the duration of the braking pulse P2. In the example given, the duration of this braking pulse is much less than half a half cycle.

In the second case considered, the braking pulse is generated, in an alternation, between the median instant at which the resonator passes through its neutral position (zero position) and the final instant at which this alternation ends. The angular speed in absolute value decreases at the moment of the braking pulse P2. Remarkably, the braking pulse here induces a positive phase shift TC2 in the oscillation of the resonator, as shown in FIG. 4 the two curves 90b and 90c of the angular velocity and also the curves 92b and 92c of the angular position, that is an advance relative to the undisturbed theoretical signal (shown in broken lines). Thus, the duration of the alternation A2 is reduced by the time interval TC2. The oscillation period T2 comprising the alternation A2 is therefore shorter than the value TO. This consequently generates a point increase in the frequency of the mechanical oscillator and a momentary acceleration of the associated mechanism whose operation is clocked by this mechanical oscillator. This phenomenon is surprising and unintuitive, which is why the skilled person ignored it in the past. Indeed, getting an acceleration of the mechanism by a braking pulse is a priori surprising, but such is the case when this step is clocked by a mechanical oscillator and the braking pulse is applied to its resonator.

The aforementioned physical phenomenon for mechanical oscillators is involved in the synchronization method implemented in a timepiece according to the invention. Unlike general education in the horological field, it is possible not only to reduce the frequency of a mechanical oscillator by braking pulses, but it is also possible to increase the frequency of such a mechanical oscillator also by braking pulses. The person skilled in the art expects to be able to practically only reduce the frequency of a mechanical oscillator by braking pulses and, as a corollary, to be able only to increase the frequency of such a mechanical oscillator by the application of driving pulses. during a supply of energy to this oscillator. Such intuition, which has imposed itself in the field of watchmaking and therefore comes first on board in the mind of a person skilled in the art, proves false for a mechanical oscillator. Thus, as will be explained later in detail, it is possible to synchronize, via an auxiliary oscillator defining a master oscillator, a mechanical oscillator which is otherwise very precise, that it momentarily has a frequency that is slightly too high or too low. It is therefore possible to correct a frequency that is too high or a frequency that is too low only by means of braking pulses. In summary, the application of a braking torque during an alternation of the oscillation of a sprung balance causes a negative or positive phase shift in the oscillation of this sprung balance depending on whether this braking torque is applied respectively before or after the sprung balance has passed through its neutral position.

The synchronization method resulting from the correction device incorporated in a timepiece according to the invention is described below. In fig. 8A is shown the angular position (in degrees) of a clockwise mechanical resonator oscillating with an amplitude of 300 ° during an oscillation period of 250 ms. In fig. 8B is shown the daily error generated by braking pulses of one millisecond (1 ms) applied in successive oscillation periods of the mechanical resonator according to the instant of their application within these periods and therefore depending on the angular position of the mechanical resonator. Here, we start from the fact that the mechanical oscillator operates freely at a natural frequency of 4 Hz (undisturbed case). Three curves are given respectively for three pairs of forces (100 nNm, 300 nNm and 500 nNm) applied by each braking pulse. The result confirms the physical phenomenon explained above, namely that a braking pulse occurring in the first quarter period or the third quarter period generates a delay resulting from a decrease in the frequency of the mechanical oscillator, while a braking pulse occurring in the second quarter period or the fourth quarter period generates an advance from an increase in the frequency of the mechanical oscillator. Then, it is observed that, for a given torque force, the daily error is equal to zero for a braking pulse occurring at the neutral position of the resonator, this daily error increasing (in absolute value) as one s' approach to an extreme position of the oscillation. At this extreme position where the speed of the resonator passes through zero and the direction of motion changes, there is a sudden inversion of the sign of the daily error. Finally, in fig. 8C is given the braking power consumed for the three aforementioned force torque values as a function of the moment of application of the braking pulse during a period of oscillation. As the speed decreases when approaching the extreme positions of the resonator, braking power also decreases. Thus, while the generated daily error increases when approaching the extreme positions, the necessary braking power (and therefore the energy lost by the oscillator) decreases significantly.

The error generated in FIG. 8B may correspond to a correction in the case where the mechanical oscillator has a natural frequency that does not correspond to a set frequency. Thus, if the oscillator has a low internal frequency, braking pulses occurring in the second or fourth quarter of the oscillation period can allow correction of the delay taken by the free oscillation (undisturbed), this correction being more or less strong depending on the moment of the braking pulses within the oscillation period. On the other hand, if the oscillator has a high natural frequency, braking pulses occurring in the first or third quarter of the oscillation period can allow a correction of the advance taken by the free oscillation, this correction being more or less strong depending on the moment of the braking pulses in the oscillation period.

The teaching given above makes it possible to understand the remarkable phenomenon of the synchronization of a main mechanical oscillator (slave oscillator) on an auxiliary mechanical oscillator, forming a master oscillator, by the only periodic application of braking pulses on the slave mechanical resonator at a braking frequency Ffr advantageously corresponding to twice the reference frequency FOc divided by a positive integer N, ie FFr = 2F0c / N. The braking frequency is thus proportional to the reference frequency for the master oscillator and depends only on this setpoint frequency as soon as the positive integer number N is given. As the reference frequency is provided equal to a fractional number multiplied by the reference frequency, the braking frequency is therefore proportional to the reference frequency and determined by this reference frequency, which is provided by the auxiliary mechanical oscillator which is by nature or by construction more accurate than the main mechanical oscillator.

The aforementioned synchronization obtained by the correction device incorporated in the timepiece of the invention will now be described in more detail with the aid of FIGS. 9 to 22.

In FIG. 9 is represented on the top graph the angular position of the slave mechanical resonator, including the spring balance of a clock resonator, freely oscillating (curve 100) and oscillating with braking (curve 102). The frequency of the free oscillation is greater than the reference frequency FOc = 4 Hz. The first mechanical braking pulses 104 (hereinafter also called pulses') occur here once per oscillation period in a half-cycle between the passage through an extreme position and the passage through zero. This choice is arbitrary because the planned system does not detect the angular position of the mechanical resonator; it is therefore just one possible hypothesis among others that will be analyzed later. We are here in the case of a slowing down of the mechanical oscillator. The braking torque for the first braking pulse is provided here greater than a minimum braking torque to compensate for the advance that takes the free oscillator over a period of oscillation. This has the consequence that the second braking pulse takes place a little before the first inside the quarter period where these pulses occur. Curve 106, which gives the instantaneous frequency of the mechanical oscillator, in fact indicates that the instantaneous frequency decreases below the reference frequency at the first pulse. Thus, the second braking pulse is closer to the foregoing extreme position, so that the effect of braking increases and so on with subsequent pulses. In a transient phase, the instantaneous frequency of the oscillator thus gradually decreases and the pulses are gradually approaching an extreme position of the oscillation. After a certain time, the braking pulses include the passage through the extreme position where the speed of the mechanical resonator changes direction and the instantaneous frequency then begins to increase.

The braking has this particular that it opposes the movement of the resonator regardless of the direction of its movement. Thus, when the resonator goes through an inversion of the direction of its oscillation during a braking pulse, the braking torque automatically changes sign at the moment of this inversion. There are then braking pulses 104a which have, for the braking torque, a first part with a first sign and a second part with a second sign opposite to the first sign. In this situation, there is therefore the first part of the signal which intervenes before the extreme position and which opposes the effect of the second part which intervenes after this extreme position. If the second part decreases the instantaneous frequency of the mechanical oscillator, the first part increases it.

The correction then decreases to stabilize finally and relatively quickly to a value for which the instantaneous frequency of the oscillator is equal to the reference frequency (corresponding here to the braking frequency). Thus, in the transient phase follows a stable phase, also called synchronous phase, where the oscillation frequency is substantially equal to the target frequency and where the first and second portions of the braking pulses has a substantially constant and defined ratio.

The graphs of FIG. 10 are similar to those of FIG. 9. The major difference is the value of the natural frequency of the free mechanical oscillator which is lower than the reference frequency FOc = 4 Hz. The first pulses 104 occur in the same half-wave as in FIG. 9. It is observed as expected a decrease in the instantaneous frequency given by the curve 110. The oscillation with braking 108 therefore takes momentarily more delay in the transient phase, until the pulses 104b begins to encompass the passage of the resonator by an extreme position. From this moment, the instantaneous frequency begins to increase until reaching the target frequency, because the first part of the pulses occurring before the extreme position increases the instantaneous frequency. This phenomenon is automatic. Indeed, as long as the duration of the oscillation periods is greater than the duration of the setpoint period TOc, the first part of the pulse increases while the second part decreases and consequently the instantaneous frequency continues to increase until a stable situation where the set period is substantially equal to the oscillation period. So we have the desired synchronization.

The graphs of FIG. 11 are analogous to those in fig. 10. The major difference comes from the fact that the first braking pulses 114 occur in another half-wave alternation in FIG. 10, namely in a half-wave between the zero crossing and the passage through an extreme position. According to what has been explained above, an increase in the instantaneous frequency given by the curve 112 is observed here in a transient phase. The braking torque for the first braking pulse is here provided greater than a minimum braking torque to compensate for the delay that takes the free mechanical oscillator on a period of oscillation. This has the consequence that the second braking pulse takes place a little after the first inside the quarter period where these pulses occur. The curve 112 indicates that the instantaneous frequency of the oscillator increases above the setpoint frequency at the first pulse. Thus, the second braking pulse is closer to the end position that follows, so that the effect of braking increases and so on with subsequent pulses. In the transient phase, the instantaneous frequency of the oscillation with braking 114 thus increases and the braking pulses are gradually approaching an extreme position of the oscillation. After a certain time, the braking pulses include the passage through the extreme position where the speed of the mechanical resonator changes direction. From that moment, we have a phenomenon similar to that explained above. The braking pulses 114a then have two parts and the second part decreases the instantaneous frequency. This decrease in the instantaneous frequency continues until it has a value equal to the reference value for the same reasons as given with reference to FIGS. 9 and 10. The frequency decrease stops automatically when the instantaneous frequency is substantially equal to the set frequency. This results in a stabilization of the frequency of the mechanical oscillator at the reference frequency in a synchronous phase.

With the aid of FIGS. 12 to 15, the behavior of the mechanical oscillator in the transition phase will be explained for any moment in which a first braking pulse occurs during a period of oscillation, as well as the final situation corresponding to the phase synchronous where the oscillation frequency is stabilized on the set frequency. Fig. 12 represents a period of oscillation with the curve S1 of the positions of a mechanical resonator. In the case considered here, the natural oscillation frequency FO of the free mechanical oscillator (without braking pulses) is greater than the reference frequency FOc (FO> FOc). The oscillation period conventionally comprises a first alternation A1 followed by a second alternation A2, each between two extreme positions (tm-- !, Am ^; tm, Am; tm + 1, Am + 1) corresponding to the amplitude oscillation. Then, in the first half-cycle, an impulse pulse "Imp1" is represented, the middle time position of which occurs at a time t-ι and, in the second alternation, another braking pulse 'lmp2' whose middle time position intervenes at a time t2. The pulses Imp1 and Imp2 have a phase shift of TO / 2, and they are particular because they correspond, for a given profile of the braking torque, to corrections generating two unstable equilibriums of the system. Since these pulses occur respectively in the first and third quarter of the oscillation period, they therefore slow down the mechanical oscillator to an extent that makes it possible to correct the natural frequency that is too high for the free mechanical oscillator (with the frequency of braking selected for application of braking pulses). It will be noted that the pulses Imp1 and Imp2 are both first pulses, each being considered for itself in the absence of the other. It will be noted that the effects of pulses Imp1 and Imp2 are identical.

If a first pulse occurs at time t-ι or t2, then we will theoretically have a repetition of this situation during the next oscillation periods and an oscillation frequency equal to the reference frequency. Two things are to be noted for such a case. First, the probability that a first pulse will occur exactly at time L or t2 is relatively small, although possible. Secondly, in the event that such a particular situation arises, it can not last long. Indeed, the instantaneous frequency of a sprung balance in a timepiece varies a little over time for various reasons (amplitude of oscillation, temperature, change of spatial orientation, etc.). Although these reasons are disruptions that we generally seek to minimize in luxury watchmaking, the fact remains that in practice such an unstable equilibrium will not last very long. Note that the higher the braking torque, the longer the time! and t2 are close to the two times of passage of the mechanical resonator by its neutral position which follow respectively. It will also be noted that the smaller the difference between the natural oscillation frequency FO and the reference frequency FOc, the more the times L and t2 are also close to the two passage times of the mechanical resonator by its neutral position which respectively follows them.

Now consider what happens as soon as one deviates a little time positions ti or t2 during the application of the pulses. According to the teaching given with reference to FIG. 8B, if a pulse intervenes on the left (previous time position) of the pulse Imp1 in the zone Z1a, the correction increases so that during the following periods, the previous extreme position ΑΠ.Ί will progressively approach the braking pulse. On the other hand, if a pulse intervenes on the right (posterior temporal position) of the pulse Imp1, to the left of the zero position, the correction decreases so that during the following periods the pulses drift towards this zero position where the correction becomes nothing. Then, the effect of the pulse changes and an increase in the instantaneous frequency occurs. As the natural frequency is already too high, the pulse will quickly drift to the extreme position Am. Thus, if a pulse occurs to the right of the pulse Imp1 in the zone Z1b, the following pulses will progressively approach the extreme position following Am One observes the same behavior in the second alternation A2. If a pulse occurs to the left of pulse Imp2 in zone Z2a, the following pulses will progressively approach the previous extreme position. On the other hand, if a pulse occurs to the right of pulse Imp2 in zone Z2b, the following pulses will progressively approach the next extreme position Am + 1. It will be noted that this formulation is relative because in reality the frequency of application of the braking pulses is imposed by the master oscillator (braking frequency given), so that it is the periods of oscillation which vary and in fact is the end position in question which is close to the moment of application of a braking pulse. In conclusion, if a pulse occurs in the first alternation A1 at a time other than h, the instantaneous oscillation frequency evolves in a transient phase during the following oscillation periods so that one of the two extreme positions of this first alternation (positions of reversal of the direction of movement of the mechanical resonator) progressively approaches the braking pulses. The same goes for the second alternation A2.

FIG. 13 shows the synchronous phase corresponding to a final stable situation occurring after the transitional phase described above. As already stated, as soon as the passage through an extreme position occurs during a braking pulse, this extreme position will be stalled on the braking pulses provided that these braking pulses are configured (the torque and the duration) to be able to sufficiently correct the time drift of the free mechanical oscillator at least by a braking pulse occurring entirely, as the case may be, just before or just after an extreme position. Thus, in the synchronous phase, if a first pulse occurs in the first alternation A1, the extreme position Am_i of the oscillation is locked on the impulses Impla, or the extreme position Am of the oscillation is locked on the pulses Imp1 b . In the case of a substantially constant torque, the impulse pulses Imp1 and Impib each have a first portion whose duration is shorter than that of their second part, so as to correct exactly the difference between the natural frequency too high of the main oscillator slave and the set frequency imposed by the master auxiliary oscillator. Similarly, in the synchronous phase, if a first pulse occurs in the second alternation A2, the extreme position Am of the oscillation is locked to the pulse Imp2a, or the extreme position Am + 1 of the oscillation is set on the Imp2b pulses.

It will be noted that the impulses Impla, respectively Impib, Imp2a and Imp2b occupy stable relative temporal positions. Indeed, a slight deviation to the left or right of one of these pulses, due to an external disturbance, will have the effect of reducing a next pulse to the initial relative time position. Then, if the time drift of the mechanical oscillator varies during the synchronous phase, the oscillation will automatically undergo a slight phase shift so that the ratio between the first part and the second part of the Impla pulses, respectively Impib, Imp2a and Imp2b varies. in a measure that adapts the correction generated by the braking pulses to the new frequency difference. Such behavior of the timepiece according to the present invention is truly remarkable.

Figs. 14 and 15 are similar to FIGS. 12 and 13, but for a situation where the natural frequency of the oscillator is lower than the set frequency. Consequently, the pulses Imp3 and Imp4, corresponding to an unstable equilibrium situation in the correction provided by the braking pulses, are located respectively in the second and fourth quarter of periods (times t3 and t4) where the pulses generate a increase of oscillation frequency. The explanations in detail will not be repeated here because the behavior of the system follows from the preceding considerations. In the transient phase (Fig. 14), if a pulse occurs in alternating A3 to the left of pulse Imp3 in zone Z3a, the previous extreme position (tm, Am) will progressively approach the next pulses. On the other hand, if a pulse occurs to the right of pulse Imp3 in zone Z3b, the next extreme position (tm, Am) will progressively approach the next pulses. Similarly, if a pulse occurs in the alternation A4 to the left of the pulse Imp4 in the zone Z4a, the previous extreme position (tm, Am) will progressively approach the next pulses. Finally, if a pulse occurs to the right of the pulse Imp4 in the zone Z4b, the next extreme position (tm + 1, Am + 1) will progressively approach the next pulses during the transition phase.

In the synchronous phase (FIG 15), if a first pulse occurs in the first alternation A3, the extreme position Am_i of the oscillation is keyed on the pulses Imp3a, or the extreme position Am of the oscillation is impaled on imp3b pulses. In the case of a substantially constant torque, the pulses Imp3a and Imp3b each have a first portion whose duration is longer than that of their second part, so as to correct exactly the difference between the natural frequency too low of the oscillator main slave and the set frequency imposed by the master auxiliary oscillator. Similarly, in the synchronous phase, if a first pulse occurs in the second alternation A4, the extreme position Am of the oscillation is keyed on the pulse Imp4a, or the extreme position Am + i of the oscillation is set on the Imp4b pulses. The other considerations made in the context of the case described above with reference to FIGS. 12 and 13 apply by analogy to the case of fig. 14 and 15. In conclusion, that the natural frequency of the free mechanical oscillator is too high or too low and whatever the moment of the application of a first braking pulse within a period of oscillation, the correction device of the invention is effective and quickly synchronizes the frequency of the mechanical oscillator, timing the movement of the mechanical movement, on the reference frequency which is determined by the reference frequency of the master auxiliary oscillator , which controls the braking frequency at which the braking pulses are applied to the resonator of the mechanical oscillator. This remains true if the natural frequency of the mechanical oscillator varies and even if it is, in certain periods of time, greater than the reference frequency, while in other periods of time it is lower than this reference frequency.

The teaching given above and the synchronization obtained thanks to the characteristics of the timepiece according to the invention also apply to the case where the braking frequency for the application of the braking pulses is not equal to the set frequency. In the case of the application of a pulse per oscillation period, the pulses occurring at the unstable positions (t-ι, Imp1, t2, Imp2, t3, Imp3, t4, Imp4) correspond to corrections to compensate the temporal drift during a single oscillation period. On the other hand, if the predicted braking pulses have a sufficient effect to correct a time drift during several oscillation periods, it is then possible to apply a single pulse per time interval equal to these several oscillation periods. We will then observe the same behavior as for the case where a pulse is generated by oscillation period. Considering the oscillation periods in which the pulses occur, we have the same transient phases and the same synchronous phases as in the case described above. In addition, these considerations are also correct if there is an integer number of alternations between each braking pulse. In the case of an odd number of alternations, alternate alternately, alternatively A1 or A3 alternately A2 or A4 alternately in FIGS. As the effect of two shifted pulses of an alternation is identical, it is understood that the synchronization is performed as for an even number of alternations between two successive braking pulses. In conclusion, as already indicated, the behavior of the system described with reference to FIGS. 12 to 15 is observed as soon as the braking frequency FFr is equal to 2F0c / N, FOc being the reference frequency for the oscillation frequency and N a positive integer.

Although not very interesting, it will be noted that the synchronization is also obtained for a braking frequency Ffr greater than twice the reference frequency (2F0), namely for a value equal to N times FO with N> 2. a variant with Ffr = 4F0, there is just a loss of energy in the system without effect in the synchronous phase, because a pulse on two occurs at the neutral point of the mechanical resonator. For a braking frequency Ffr higher than 2F0, the pulses in the synchronous phase that do not intervene at the extreme positions cancel their effects two by two. We therefore understand that these are theoretical cases without much practical meaning.

Figs. 16 and 17 show the synchronous phase for a variant with a braking frequency Ffr equal to one quarter of the target frequency, a braking pulse therefore occurring every four periods of oscillation. Figs. 18 and 19 are partial enlargements respectively of FIGS. 16 and 17. FIG. 16 relates to a case where the natural frequency of the main oscillator is greater than the reference frequency FOc = 4 Hz, while FIG. 17 relates to a case where the natural frequency of the main oscillator is greater than this reference frequency. It is observed that only the periods of oscillation T1 * and 12 *, in which Impib or Imp2a braking pulses Imp3b or Imp4a, respectively, have a variation relative to the natural period TO *. The braking pulses generate a phase shift only in the corresponding periods. Thus, the instantaneous periods oscillate here around an average value which is equal to that of the set period. It will be noted that in FIGS. 16 to 19, the instantaneous periods are measured from a zero crossing on a rising edge of the oscillation signal to such a next pass. Thus, the synchronous pulses that occur at the extreme positions are fully encompassed in periods of oscillation. To be complete, fig. 20 shows the specific case where the natural frequency is equal to the target frequency. In this case, the oscillation periods TO * remain all equal, the impulse pulses Imp5 occurring exactly at extreme positions of the free oscillation with first and second parts of these pulses which have identical durations (case of a constant braking torque), so that the effect of the first part is canceled by the opposite effect of the second part.

FIG. 21 shows the variation of the oscillation periods for a set frequency FOc = 3 Hz and an appropriate braking pulse occurring every three periods of oscillation of the mechanical oscillator which clock the operation of a time-indicating mechanism with a daily error of 550 seconds a day, or about 9 minutes a day. This error is very important, but the braking device is configured to correct such an error. The effect of the braking must be relatively large here, there is a large variation of the instantaneous period but the average period is substantially equal to the set period after the engagement of the correction device in the timepiece according to the invention. and a short transitional phase. When the correction device is inactive, it is observed, as expected, that the total temporal error increases linearly as a function of time, whereas this error stabilizes rapidly after the activation of the correction device. Thus, if a time setting is performed after such engagement of the correction device and the transient phase, the total error (also called 'cumulative error') remains low, so that the timepiece indicates by the following an hour with a precision corresponding to that of the master oscillator incorporated in this timepiece and associated with the braking device.

FIG. 22 shows the evolution of the amplitude of the slave mechanical oscillator after the activation of the correction device according to the invention. In the transient phase, there is a relatively marked decrease in amplitude in a case where the first pulse is near the zero position (neutral position). The various braking pulses occurring in particular in a first part of this transient phase generate relatively high energy losses, which follows from the graph of FIG. 8C. Subsequently, the energy losses decrease rather quickly and finally become minimal for a given correction in the synchronous phase. Therefore, it is observed that the amplitude increases again as soon as the pulses include the passage through an extreme position of the mechanical resonator and continues to increase at the beginning of the synchronous phase although the dissipated braking energy then stabilizes at its minimum, given a relatively large time constant for the amplitude variation of the mechanical oscillator. Thus, the part according to the invention also has the benefit of stabilizing in a synchronous phase for which the energy dissipated by the oscillator, due to the braking pulses provided, is minimal. Indeed, the oscillator has after stabilization of its amplitude the smallest possible amplitude decrease for the braking pulses provided. This is an advantage because when the mainspring servicing the main oscillator relaxes, the minimum oscillation amplitude to ensure the operation of the mechanical movement is reached as late as possible while ensuring accurate walking. The device for correcting the gait of a mechanical movement that generates the synchronization according to the invention therefore has a minimized influence for the power reserve.

In order to minimize the disturbances caused by the braking pulses and in particular the energy losses for the watch movement, short pulse durations or even very short pulse durations will preferably be selected. Thus, in a particular variant, the braking pulses each have a duration less than 1/10 of the set period. In a preferred variant, the braking pulses each have a duration between 1/250 and 1/40 of said set period. In the latter case, for a reference frequency equal to 4 Hz, the duration of the pulses is between 1 ms and 5 ms.

With reference to FIGS. 1 to 3, there are described timepieces with mechanical resonators having a circular braking surface enabling the braking device to apply a mechanical braking pulse to the slave mechanical resonator substantially at any instant of a period of oscillation in the useful operating range of the slave oscillator. This is a preferred embodiment variant. Since the watch movements generally have pendulums having a circular serge with an advantageously continuous external surface, the preferred variant indicated above can easily be implemented in such movements without requiring modifications of their mechanical oscillator. It will be understood that this preferred variant makes it possible to minimize the duration of the transition phase and to ensure the desired synchronization in the best time.

However, the stable synchronization can already be obtained, after a certain period of time, with a mechanical system, formed of the slave mechanical resonator and the mechanical braking device, which is configured to allow the mechanical braking device to it is possible to initiate the periodic braking pulses at any position of the slave mechanical resonator only in a continuous or quasi-continuous range of positions of this defined resonator, of a first of two sides of the neutral position of the slave mechanical resonator, by the amplitude range of the slave oscillator for its useful operating range. Advantageously, this range of positions is increased, on the minimum amplitude side, at least by an angular distance corresponding to the duration of a braking pulse, so as to allow for a minimum amplitude a braking pulse by a dry friction dynamic. So that the mechanical system can act in all the alternations and not only in all periods of oscillation, it is then necessary for this mechanical system to be configured so as to allow the mechanical braking device to also be able to start the periodic braking pulses. at any position of the mechanical resonator of the second of two sides of said neutral position, in the amplitude range of the slave mechanical oscillator for its useful operating range. Advantageously, the range of positions is also increased, on the minimum amplitude side, at least by an angular distance substantially corresponding to the duration of a braking pulse.

Thus, in a first general variant, the above-mentioned continuous or quasi-continuous range of positions of the slave mechanical resonator extends, from a first of two sides of its neutral position, at least over the amplitude range that the The slave oscillator is capable of having this first side for a useful operating range of this slave oscillator and advantageously moreover, on the side of a minimum amplitude of the amplitudes range, at least over an angular distance substantially corresponding to the duration. braking pulses. In a second general variant, in addition to the continuous or quasi-continuous range defined above in the first general variant, which is a first continuous or quasi-continuous range, the aforementioned mechanical system is configured to allow the mechanical braking device it is also possible to start the periodic braking pulses at any position of the slave mechanical resonator, the second of the two sides of its neutral position, at least in a second continuous or quasi-continuous range of positions of this slave mechanical resonator extending over the range of amplitudes that the slave oscillator is likely to have this second side for said useful operating range and advantageously additionally, on the side of a minimum amplitude of the latter range of amplitudes, at least on said first distance angular.

Finally, in the context of the present invention, two categories of periodic braking pulses can be distinguished in relation to the intensity of the mechanical force torque applied to the slave mechanical resonator and the duration of the periodic braking pulses. Concerning the first category, the braking torque and the duration of the braking pulses are provided, for the useful operating range of the slave oscillator, so as not to momentarily block the mechanical resonator slave during periodic braking pulses at the same time. less in most of the possible transitional phase that has been described previously. In this case, the system is arranged so that the mechanical braking torque can be applied to the slave mechanical resonator, at least in the major part of the possible transient phase, during each braking pulse.

In an advantageous variant, the oscillating member and the braking member are arranged in such a way that the periodic braking pulses can be applied, at least in the major part of the possible transient phase, mainly by dynamic dry friction. between the braking member and a braking surface of the oscillating member. Concerning the second category, for the useful operating range of the slave oscillator and in the synchronous phase that has been described above, the mechanical braking torque and the duration of the periodic braking pulses are provided so as to block the mechanical resonator during periodic braking pulses at least in their terminal part.

In a particular variant, a momentary blocking of the slave mechanical resonator by the periodic braking pulses is provided in the synchronous phase whereas, in an initial part of the eventual transient phase, where the periodic braking pulses occur out of the positions. extremes of the slave mechanical resonator, the latter is not blocked by these periodic braking pulses.

In figs. 23A to 23C is shown a sequence of the operation of a correction device in a fourth embodiment of a timepiece according to the invention. Only the slave main resonator 6 and the mechanical correction device 52A have been represented. The correction device is formed by a master auxiliary oscillator 96 and by a braking device 56A, similar to that presented in the context of the first embodiment, which comprises a braking pulse generating mechanism 50A. The master oscillator 96 is related to the oscillator 54 of the second embodiment. Its operation is analogous and will not be described here again. It is distinguished by its resonator 98 formed by a tuning fork which carries at the free ends of its two vibrating branches respectively two magnets 99 and 100 which have an axial magnetization. These magnets serve to couple the resonator 98 to an escape wheel 68. The escape wheel and the two magnets form the magnetic escapement of the master oscillator 96. Since the tuning fork has a fundamental resonance mode with its two branches oscillating in phase opposition and that the two magnets 99 and 100 that it carries are arranged at rest diametrically opposite to the axis of rotation of the escape wheel, the number of magnetic periods of the magnetic structure of the escape wheel is planned pair. The tuning fork may have a relatively high natural frequency, so that it is envisaged in a variant to arrange the actuating finger 58 on a mobile of an auxiliary transmission train with the mechanical energy necessary for the operation of the device. correction 52A, this mobile rotating at a lower speed than the escape wheel 68.

The operation of the correction device differs from that of the preceding embodiments in that the control mechanism formed by the escape wheel 68 and the actuating finger 58 acts inversely on the generating mechanism. braking pulses 50A. As in fig. 2A, when the finger 58 rotates towards the end 41 of the latch 40, the latter is at rest and the leaf spring 42 is at a distance from the braking surface 46 of the beam 8 (Figure 23A). On the other hand, as soon as the finger comes into contact with the end 41 of the rocker, the latter starts to rotate in the clockwise direction and the leaf spring rotates progressively in the direction of the braking surface 46 until it touches it. while the finger 58 is still bearing against said end 41 (FIG 23B showing the rocker when it has just come into contact with the balance). Then, as the finger continues its continuous advance, the leaf spring presses more and more against the beam to brake until the contact between the finger and said end is lost and the rocker is then released (Fig. 23C), which terminates the braking pulse because the latch is then pulled back by the spring 44A which has relaxed in the previous phase.

The force of the spring 44A can here be very small, but preferably sufficient damping is provided to prevent oscillation of the rocker, following its release, generating a second parasitic braking pulse during the braking period following the first impulse. The duration of the braking pulses is determined by the angular distance on which the actuating finger remains in contact with the end of the rocker following the moment when the leaf spring touches the braking surface. This angular distance can be adjusted to a given value by adjusting in particular the length of the actuating finger. It will be noted that the braking torque increases here during the braking pulse and then decreases almost instantaneously as soon as the rocker is released. This force torque can be adjusted to a given value in particular according to the rigidity of the leaf spring and the length ratio between the two arms of the rocker.

In figs. 24A to 24C is shown a sequence of the operation of a correction device in a fifth embodiment of a timepiece according to the invention. Only the main slave resonator 6 and a part of the mechanical correction device have been represented. The correction device is formed by a master auxiliary oscillator 22A, of which only the escape wheel 34A has been shown (its resonator and the anchor being similar to those shown in Fig. 1), and by a braking device 56A . Thus, as in the first embodiment, the escape wheel rotates step by step with an angular velocity determined by the reference frequency of the master resonator. The braking device comprises a braking pulse generating mechanism 50A similar to that presented above in the context of the fourth embodiment. This pulse generator operates in the same manner as that of the fourth embodiment. The control mechanism 48A of the braking device is formed here by the escape wheel and by two pins 38 fixed on this wheel diametrically opposite.

Unlike the previous embodiment, the control mechanism advances by step. The generation of a braking pulse is provided during a step of the escape wheel (Figure 24B). This wheel has for example 15 teeth and the master oscillator 22A operates at a reference frequency of 7.5 Hz. The escape wheel performs 1/2 turn per second so that the braking pulses are made at a frequency of 1 Hz braking. At each period of the master oscillator the wheel 34A takes two steps and advances by an angular distance equal to 24 °, so that at least one of the two steps corresponds to a rotation of at least 12 °. The end 41 of the flip-flop 40 is configured and positioned relative to the circle described by the pins 38 in rotation so as to allow the braking pulse to be completely effected at a given pitch of the control wheel. Note that it is advantageous that the rocker is already rotated during a step of the control wheel preceding that which occurs to generate a braking pulse. In this case, care should be taken to arrange the braking device so that the leaf spring 42 rotates towards the braking surface 46 of the beam during said preceding step without touching this braking surface, but stopping at a short distance from this one (Fig. 24A).

Figs. 24A to 24C show three configurations of the braking device operating over a reference period during which the escape wheel performs two successive steps. Fig. 24A represents a first state of the braking device at the end of a determined pitch of the wheel 34A. Fig. 24B represents a second state of the braking device during a first step following said determined step (application of a braking pulse to the balance 8). Fig. 24C corresponds to a third state where the wheel 34A has completed the first step represented in FIG. 24B, before intervening a second step following directly said first step. Since during a step, the wheel 34A rotates very quickly (free rotation), the duration of the braking pulses can be thus relatively short.

Claims (23)

claims 1. Timepiece (2, 80) comprising a mechanical movement (4) which comprises: - a mechanism (12) indicating at least one temporal data, - a mechanical resonator (6, 6) capable of oscillating the along a general axis of oscillation around a neutral position (0) corresponding to its state of minimum potential energy, - a device (14) for the maintenance of the mechanical resonator forming with this mechanical resonator a mechanical oscillator (18 ) which is arranged to clock the march of the indicator mechanism; the timepiece further comprising a device for correcting a possible time drift in the operation of said mechanical oscillator; characterized in that said correction device (20, 52, 52A) is of the mechanical type, said mechanical correction device being formed by a mechanical auxiliary oscillator (22, 22A, 54, 96), which defines a master oscillator, and by a mechanical device (24, 56, 56A) for braking said mechanical resonator; in that the mechanical braking device is arranged to be able to apply to said mechanical resonator (6, 6A) a mechanical braking torque during periodic braking pulses which are generated at a selected braking frequency only as a function of a target frequency for said mechanical oscillator, which defines a slave oscillator, and determined by said master oscillator, the mechanical system formed of said mechanical resonator and the mechanical braking device being configured to allow the mechanical braking device (24, 56, 56A) to ability to initiate said periodic braking pulses at any position of said mechanical resonator in a range of positions along said general axis of oscillation, which extends at least a first of both sides of the neutral position of said resonator mechanics over at least a range of amplitudes that said oscillator e sclave is likely to have this first side for a useful operating range of this slave oscillator. 2. Timepiece according to claim 1, characterized in that a first portion of said range of mechanical resonator positions, incorporating said range of amplitudes that the mechanical oscillator is likely to have said first side of the neutral position said mechanical resonator, has a certain extent on which it is continuous or almost continuous. Timepiece according to claim 1 or 2, characterized in that said mechanical system is configured such that said position range of the mechanical resonator, in which said periodic braking pulses can begin, also extends from the second of the two sides of the neutral position of said mechanical resonator over at least a range of amplitudes that said mechanical oscillator is likely to have this second side for said useful operating range of this mechanical oscillator. 4. Timepiece according to claim 3, characterized in that a second part of said range of positions of the mechanical resonator, incorporating said range of amplitudes that the mechanical oscillator is likely to have said second side of the position neutral of said mechanical resonator, has a certain extent on which it is continuous or almost continuous. 5. Timepiece according to any one of the preceding claims, characterized in that said braking frequency is provided equal to twice said reference frequency divided by a positive integer N, ie Ffr = 2 FOc / N where Ffr is the braking frequency and FOc is the set frequency. 6. Timepiece according to any one of the preceding claims, characterized in that said mechanical braking device (24, 56, 56A) is arranged in such a way that the periodic braking pulses each have essentially a duration less than a quarter of the period. setpoint corresponding to the inverse of the setpoint frequency. 7. Timepiece according to any one of claims 1 to 5, characterized in that the mechanical braking device (24,56,56A) is arranged so that the periodic braking pulses each have essentially a duration less than 1 / 10 of the corresponding setpoint period in inverse of the setpoint frequency. 8. Timepiece according to any one of claims 1 to 5, characterized in that the mechanical braking device (24,56,56A) is arranged in such a way that the periodic braking pulses each have essentially a duration of less than 1 / 40 of the corresponding setpoint period in inverse of the setpoint frequency. 9. Timepiece according to any one of the preceding claims, characterized in that said mechanical system is configured to allow the mechanical braking device (24,56,56A) to begin, in said useful operating range of said slave oscillator one of said periodic braking pulses at any position of said mechanical resonator along said general axis of oscillation. 10. Timepiece according to any one of the preceding claims, characterized in that said master oscillator (22, 22A) comprises a master resonator (28) which is formed by a sprung balance or a rocker mounted on flexible blades. 11. Timepiece according to any one of the preceding claims, characterized in that said master oscillator (22, 22A) comprises an exhaust provided with a stop (33) and thus operating in a step-by-step mode. 12. Timepiece according to any one of claims 1 to 9, characterized in that said master oscillator (96) comprises a master resonator which is formed by a tuning fork (98). Timepiece according to any one of claims 1 to 10 and 12, characterized in that said master oscillator (54, 96) comprises a continuously rotating escapement of the magnetic type, with a magnetic coupling between a master resonator (60, 98) forming this master oscillator and an escape wheel (68) forming the continuously rotating escapement. 14. Timepiece according to any one of the preceding claims, characterized in that said master oscillator is associated with a mechanism of equalization of the force exerted on its master resonator to maintain its oscillation. Timepiece according to any one of the preceding claims, characterized in that the mechanical braking device (24, 56, 56A) comprises a control mechanism (48, 48A, 58 & 68) and a mechanism (50, 50A) brake pulse generator which is arranged to be actuated by the control mechanism at said braking frequency, so as to exert on an oscillating member (8, 8A) of the mechanical resonator (6, 6A) of said slave oscillator said mechanical braking torque during said periodic braking pulses. 16. Timepiece according to claim 14, characterized in that said braking pulse generating mechanism comprises a rocker (40, 40A) associated with a spring (44, 44A) or a flexible element and provided with an organ braking device (42) arranged to come into contact with a braking surface (46) of said oscillating member during said periodic braking pulses. Timepiece according to claim 15, characterized in that said control mechanism comprises an actuating finger (58) or an actuating pin (38) arranged / arranged on a control wheel (68, 37, 34A) so as to be able to actuate at each turn of said control wheel said latch to generate one of said periodic braking pulses; and in that the control wheel is rotated at an average speed which is determined by said master oscillator. 18. Timepiece according to claim 17, characterized in that said control wheel is integral with an escape wheel (34A) of said master oscillator. 19. Timepiece according to claim 17, characterized in that said canceled wheel is secured to a mobile (36) for transmitting the energy of a mechanical barrel (26) to said master oscillator, said transmission wheel being kinematically connected to an escape wheel of the master oscillator. Timepiece according to any one of claims 17 to 19, characterized in that said mechanical braking device (24, 56) is arranged in such a way that the actuating finger (58) or the actuating pin (38) ) comes, at each turn of the control wheel, momentarily in contact with said rocker (40) to first drive it in rotation thereby arming the braking pulse generating mechanism and then triggering one of said periodic braking pulses then that the contact between the actuating finger or the actuating pin and said generating mechanism is interrupted. 21. Timepiece according to any one of the preceding claims, characterized in that it comprises an auxiliary barrel provided to supply energy said master oscillator and not said slave oscillator, the latter being supplied in energy by a main barrel. 22. Timepiece according to any one of the preceding claims, characterized in that said periodic braking pulses have a torque and a duration which are provided for said useful operating range of the slave oscillator, so as not to not momentarily blocking said mechanical resonator during the periodic braking pulses for at least a major part of a possible transient phase in the operation of the timepiece, this transient phase possibly being able to take place, following an engagement of the mechanical correction device before a synchronous phase where the slave oscillator is synchronized with said periodic braking pulses; and in that said mechanical system is arranged such that said mechanical braking torque can be applied to said mechanical resonator, at least in said major part of said eventual transient phase, during said duration of each of the periodic braking pulses. 23. Timepiece according to any one of the preceding claims, characterized in that, for said useful operating range of said slave oscillator and in a synchronous phase of the operation of the timepiece where this slave oscillator is synchronized with said pulses of periodic braking, these periodic braking pulses have a force torque and a duration that are provided so as to momentarily block said mechanical resonator during periodic braking pulses at least in their end portion.