CH715049B1 - Timepiece comprising a tourbillon. - Google Patents

Abstract

The timepiece comprises a tourbillon comprising a cage (6) which carries a balance wheel (16), a hairspring (15) and a magnetic escapement device (18), the latter comprising an escapement wheel set (20), comprising at least one annular magnetic structure (26), and further at least one magnetic element (33) coupled with the magnetic structure and having an oscillating movement synchronous with the oscillation of the mechanical resonator (14). The magnetic escapement (18) is arranged so as to alternately present energy accumulation phases, originating from a conversion of mechanical energy supplied by the barrel into magnetic potential energy in the magnetic escapement (18), and energy transfer phases accumulated in the magnetic escapement (18) to the mechanical resonator (14). During the energy transfer phases, the magnetic element (33) undergoes a radial magnetic force, relative to the axis of rotation of the escapement wheel set (20), so that the magnetic escapement (18) converts then in mechanical energy of the magnetic potential energy accumulated in the preceding energy accumulation phase in order to be able to maintain the oscillation of the mechanical resonator (14). The invention makes it possible to increase the oscillation frequency of the mechanical resonator (14) and thus the operating precision.

Description

Technical area

The present invention relates to timepieces comprising a watch movement equipped with a tourbillon carrying in a cage a mechanical resonator, formed of a balance wheel and a hairspring, and an escapement device. By tourbillon, we also understand what a person skilled in the art sometimes calls a carousel. Furthermore, such a watch movement comprises a barrel arranged to accumulate mechanical energy and a gear train kinematically connecting the tourbillon carriage to the barrel.

Technology background

[0002] Watch movements fitted with a tourbillon have been known for a long time. Such a watch movement and even a watch equipped with such a watch movement is generally called a 'tourbillon'.

[0003] In a conventional tourbillon, the carriage operates like a second wheel set. It comprises a second pinion and it is driven via this second pinion by a middle wheel. The cage carries a classic escapement made up of an escapement wheel and an anchor, in particular a Swiss anchor. The force is transmitted to the escapement wheel set via its pinion which meshes, like a satellite, with a fixed second wheel attached to the plate.

[0004] The operation of a conventional Swiss lever escapement is well known to those skilled in the art. The escape wheel has a plurality of teeth which cooperate with two pallets carried by the anchor. Each pallet has an inclined plane at its free end. To generate a maintenance pulse for the balance-spring, one of the teeth of the escape wheel presses tangentially against the inclined plane of one of the two pallets, so as to exert a force couple on the anchor which is thus driven in rotation by the escapement wheel, the latter being driven in rotation by the rotation of the cage via the fixed second wheel. The sustain pulse ends when the pulse beak, which each tooth of the escape wheel has, is at the bottom of the inclined plane. Thus, to generate a sustaining pulse, the escapement wheel must be able to undergo rotation over an angular distance corresponding to the angular distance, relative to the axis of rotation of the escapement wheel set, from the inclined plane of the pallet with which it interacts. However, as indicated, the rotation of the escape wheel is intimately linked to that of the tourbillon cage, a kinematic link being provided between the escape wheel and the tourbillon cage. Consequently, in order to drive the escape wheel in rotation, the tourbillon, which has a relatively high inertia, must be set in rotation. The maintenance pulse transmitted to the balance wheel is therefore limited in intensity by the inertia of the tourbillon and also of the gear train kinematically connecting the tourbillon cage to the barrel. The inertia of the tourbillon cage is related to the escape wheel, which increases the inertia of the latter.

[0005] The tourbillon mechanism is known for averaging the vertical positions and therefore improving the rate of a horological movement in a wristwatch when it is worn. However, in a conventional movement, the tourbillon increases the inertia of the escapement device because the cage of the tourbillon is integral in rotation with the escape wheel. This limits the acceleration that the escape wheel can undergo. The impulse given to the balance wheel being dependent on the rotation of the escape wheel, it is not possible to increase the frequency above 5 Hz in a reliable way at the chronometric level. As a result, the possible oscillation frequency for the balance-spring of such a tourbillon mechanism is limited. Thus, the oscillation frequency of a conventional balance-spring in a tourbillon is generally less than five Hertz (5 Hz) and can in certain specific cases reach 5 Hz. It is usually, for example, three Hertz. It is understood that this limits the rate precision that can be obtained with a watch movement equipped with a conventional tourbillon.

[0006] Thus, the remarkable advantage of the tourbillon for the precision of operation when worn by a watch which incorporates it is impaired, because of the operation of the conventional escapement, by the great inertia generally exhibited by its cage.

Summary of the invention

[0007] The object of the present invention is to provide a solution to the problem of the classic tourbillon mentioned above, so as to make it possible to further increase the chronometric benefit of a tourbillon, in particular to increase the running precision of the movement. watchmaker equipped with a tourbillon according to the invention by arranging a mechanical resonator in the cage of the tourbillon, having an oscillation frequency Fo greater than conventional frequencies, preferably greater than five Hertz (Fo > 5Hz).

[0008] To this end, the invention relates to a timepiece comprising a watch movement equipped with a tourbillon, which comprises a cage arranged rotating around a main axis, a barrel, arranged to accumulate mechanical energy, and a gear train that kinematically connects the tourbillon carriage to the barrel. The tourbillon carries a mechanical resonator, made up of a balance wheel and a hairspring, and an escapement device. According to the invention, the escapement device is a magnetic escapement which comprises an escape wheel set formed of an escapement pinion and of a magnetic structure or magnetic structures having a generally annular shape which is centered on an axis of rotation of the escapement mobile. The magnetic escapement further comprising a magnetic element which, or a plurality of magnetic elements each of which is arranged to have an oscillating movement which is synchronous with the oscillation of the mechanical resonator and which has a non-zero radial component relative to said rotation axis. The magnetic element or each of the magnetic elements of the plurality of magnetic elements is coupled, at least momentarily in a periodic manner, with the magnetic structure or the magnetic structures so that the escapement wheel completes a rotation of an angular period predetermined at each period of oscillation of the balance. Then, according to the invention, the magnetic escapement has, in normal operation of the watch movement, alternately energy accumulation phases, originating from a conversion of mechanical energy supplied by the barrel into magnetic potential energy in the magnetic escapement, and phases of transfer of energy accumulated in the magnetic escapement to the magnetic resonator.

[0009] Finally, the magnetic escapement is arranged so that: during each energy accumulation phase, the magnetic element or the set of magnetic elements, which among the plurality of magnetic elements are then coupled to the magnetic structure or to the magnetic structures, undergoes a torque of magnetic force , relative to said axis of rotation, having a direction opposite to that of a driving torque, applied by the barrel via the tourbillon cage to the escapement wheel set, and an intensity lower than that of this driving force torque , so that the escapement wheel set is capable of rotating through a certain angle to allow the accumulation of a certain magnetic potential energy in the magnetic escapement; during each energy transfer phase, the magnetic element or each element of the set of magnetic elements, which of the plurality of magnetic elements is coupled to the magnetic structure or magnetic structures during a phase of accumulation of energy, undergoes a radial magnetic force (which is preferably principal), relative to said axis of rotation, during an alternation of its oscillating movement and in the direction of the radial component of this oscillating movement during this alternation, so that the magnetic escapement converts into mechanical energy magnetic potential energy accumulated (preferably the major part) in the preceding energy accumulation phase in order to be able to sustain the oscillation of the mechanical resonator.

[0010] Thanks to the characteristics of the timepiece according to the invention, in particular to the type of magnetic escapement selected to equip the tourbillon, the energy pulses transmitted to the mechanical resonator to maintain it are no longer limited in intensity. by the inertia of the tourbillon cage. In fact, even the inertia of the gear train no longer influences the generation of these energy pulses. Indeed, only the inertia of the anchor (in the case where a retainer is provided) influences the dynamics of the sustaining pulses supplied by the magnetic escapement to the mechanical resonator. It will be noted that the anchor here forms a magneto-mechanical converter. Thus, these maintenance pulses can be shorter, that is to say intervene in very limited time intervals which no longer depend on the inertia of the tourbillon. These remarkable characteristics make it possible to improve the precision of the rate of the watch movement and in particular to improve the isochronism of the mechanical resonators formed by a balance-spring. In addition, they make it possible to arrange in the tourbillon mechanical resonators having a high quality factor, in particular a balance-spring having a natural frequency of oscillation much higher than that of a balance-spring usual for a conventional tourbillon , in particular a natural frequency above 5 Hz.

The magnetic escapement according to the present invention therefore makes it possible to temporally dissociate the periodic transmission of a certain quantity of energy from the barrel to the magnetic escapement, which is arranged to accumulate it momentarily, and the transmission of this energy accumulated from the magnetic escapement to the mechanical resonator.

Thus, thanks to the magnetic escapement as selected in the context of the invention to equip a tourbillon, the sustaining pulses supplied by the magnetic escapement to the mechanical resonator can be generated mainly without rotation of the wheel. exhaust and substantially independently of such rotation. Thus, the inertia of the gear train and the inertia of the tourbillon cage no longer hinder the generation of sustain pulses. What is important is the radial character of the force which intervenes mainly to generate each maintenance pulse after a phase of accumulation of magnetic potential energy in the magnetic escapement, so that the fact that the cage rotates or not or only at a small angle is substantially without consequence on the generation of sustain pulses. Therefore, the tourbillon mechanism equipped with a magnetic escapement according to the invention can deliver maintenance pulses of short duration and of relatively high intensity.

[0013] In an advantageous embodiment, the mechanical resonator comprises a balance wheel which is magnetically pivoted in the tourbillon cage, which for this purpose comprises two magnetic bearings. This particular variant makes it possible, in addition to the various advantages procured by the selected magnetic escapement, to greatly limit the rate differences of the mechanical resonator between the horizontal positions and the vertical positions (the latter being averaged thanks to the tourbillon). It is therefore understood that it thus becomes possible to obtain a tourbillon watch having a very high rate precision.

Brief description of figures

The invention will be described below in more detail using the accompanying drawings, given by way of non-limiting examples, in which: Figure 1 is a partial perspective view of a first embodiment of a timepiece according to the invention, which is formed by a movement equipped with a tourbillon; Figure 2 is a partial top view of the watch movement of Figure 1 with some elements removed to facilitate the view of important elements for the invention; Figure 3 is a sectional view of the watch movement of Figure 1, according to section line III-III indicated in Figure 2; Figure 4 is a sectional view of the watch movement of Figure 1, according to section line IV-IV indicated in Figure 2; Figure 5 gives the two curves of the magnetic potential energy in the magnetic escapement of Figure 2, as a function of the angular position of the escapement mobile, for the retainer positioned respectively in one and the other of its two resting positions; Figures 6 to 9 partially represent the mechanical resonator and the magnetic escapement, incorporated in the tourbillon of the first embodiment, in four different positions during an alternation of the mechanical resonator; Figure 10 is a partial section, similar to that of Figure 3, of a second embodiment of the invention; Figure 11 is a partial schematic representation of a first variant of the first or second embodiment, in which only the balance wheel and the magnetic escapement incorporated in the tourbillon have been represented; Figure 12 shows a second alternative embodiment of the first or second embodiment of the invention; Figure 13 shows the mechanical resonator and the magnetic escapement, carried by the cage of a tourbillon, of a third embodiment of the invention; and Figure 14 shows, for the magnetic escapement of Figure 13, magnetic potential energy curves defined by the magnetic structure and alternately two magnetic elements fixed to the balance wheel and interacting with the magnetic structure.

Detailed description of the invention

With the aid of Figures 1 to 11, a first embodiment of the invention will be described below and in particular the specific operation of the magnetic escapement incorporated in the tourbillon of the invention.

[0016] The timepiece comprises a timepiece movement 2 equipped with a tourbillon 4 comprising a cage 6 arranged to rotate about a main axis 8, a barrel 10 arranged to accumulate mechanical energy and a gear train 11 kinematically connecting the tourbillon cage to the barrel. The tourbillon carries a mechanical resonator 14, formed by a balance wheel 16 and a hairspring 15, and an escapement device 18. The tourbillon is pivoted between a plate 3 and a bridge 9. The escapement device consists of a magnetic escapement which comprises an escapement wheel set 20 formed of an escapement pinion 24 and a first escapement wheel 22, the latter comprising a first magnetic structure 26 having a generally annular shape and centered on an axis of rotation 28 of the exhaust mobile.

[0017] The magnetic escapement comprises a retainer 30 which couples momentarily, in each alternation of the oscillation of the mechanical resonator 14, this mechanical resonator to the escapement wheel set 20. This retainer and the escape wheel set are pivoted between a part of the cage 6 and an exhaust bridge 19 carried by this cage. The retainer undergoes, when the mechanical resonator oscillates, a back and forth movement interspersed with phases of rest where the retainer is stopped alternately in two rest positions where it is respectively in abutment against two pins 36 and 37.

In the variant shown, the retainer is formed by an anchor which carries two magnetic elements 32 and 33 each arranged so as to present an oscillating movement which is synchronous with the oscillation of the mechanical resonator and which is oriented mainly according to a radial direction relative to the axis of rotation 28 of the anchor. The two magnetic elements are similar and located on the same side of the escapement wheel 22. They are both coupled simultaneously in a similar manner to the first magnetic structure, which is arranged so that these two magnetic elements are coupled with it. continuously (or quasi-continuously) and so that their respective magnetic couplings add up. The operation of this magnetic escapement will be described in more detail below.

In the variant shown, the escapement wheel set 20 comprises a second wheel 38 comprising a second magnetic structure 40 which has planar symmetry with the first magnetic structure 26 and which is located at a distance from the latter so as to allow two magnetic elements 32 and 33 to be located, when they oscillate, at least momentarily between the first and second magnetic structures. The two magnetic elements 32 and 33 interact, in a similar way, simultaneously with the first and second magnetic structures, so that the effects are additive. The two magnetic elements are coupled with the first and second magnetic structures so that the escapement wheel rotates through a predetermined angular period at each period of oscillation of the balance 16. The first and second magnetic structures and are formed respectively a first permanent magnet and a second permanent magnet which each have an axial magnetization and the same polarity. The two magnetic elements of the anchor are each formed by a permanent magnet having an axial magnetization and an inverted polarity relative to the first and second magnets, so as to undergo a magnetic repulsion force with each of the two magnetic structures.

Preferably, the first and second wheels 22 and 38 respectively carry a first ferromagnetic structure 44 and a second ferromagnetic structure 46 which respectively cover the first and second magnetic structures on the two outer sides of the assembly consisting of these first and second magnetic structures, so as to form in association with some fixing pins (see Figure 3) rising from each of the two ferromagnetic structures, a certain shielding of the first and second magnetic structures and of each magnetic element located between them and thus magnetically coupled with them. The two ferromagnetic structures respectively form two supports for the two magnetic structures. In the variant shown, since the two magnetic elements are continuously coupled with the first and second magnetic structures and therefore remain located between the two ferromagnetic structures, the magnetic escapement is partially shielded. In addition, the magnetic fields of the magnetic structures and the magnetic elements are confined by the first and second ferromagnetic structures.

[0021] In general, the magnetic escapement is arranged so as to present, in normal operation of the watch movement, alternately energy accumulation phases, originating from a conversion of mechanical energy supplied by the barrel into energy magnetic potential in the magnetic escapement, and phases of energy transfer accumulated in the magnetic escapement to the magnetic resonator. Each energy accumulation phase and the energy transfer phase which follows it occur during a time interval equal to half of an oscillation period of the mechanical resonator.

In the context of the first embodiment, the arrangement of the magnetic escapement mentioned in the previous paragraph and the operation of this magnetic escapement will be described below using Figures 5 to 9. Figure 5 shows two magnetic potential energy curves 66 and 68, respectively for the two rest positions of anchor 30 where the latter rests respectively against stops 36 and 37, which each correspond to the magnetic potential energy EPM in the escapement magnetic as a function of the angle θ giving the angular position of the escape wheel set 20 and therefore of the magnetic structures 26 and 40 (it will be noted that this angle θ is measured according to the direction of rotation of the escape wheel set, namely the direction schedule in the example shown in Figures 6 to 9). A magnetic escapement of the type selected for the first embodiment of the invention is disclosed in patent application EP 3 208 667 A1. Its operation and the specific characteristics of this operation which are used in the context of the present invention will be described below. Figures 6 to 9 show four successive instants of an alternation of the balance 16 and an alternation of the lever 30 which is momentarily coupled to this balance.

Firstly, the two magnetic structures 26 and 40 together define, in each of the two rest positions of the anchor 30, increasing portions of magnetic potential energy PC1, respectively PC2 for the magnetic elements 32 and 33 of the anchor 30 which are both coupled, here continuously, to the two magnetic structures. In the variant described, these increasing portions are substantially defined by a magnetic track 58 that each of the two magnetic structures 26 and 40 comprises, this magnetic track having a particular layout, alternately entering and exiting relative to a median geometric circle. During normal operation of the watch movement, this particular layout is adapted to an accumulation of magnetic potential energy during rotation of the escapement wheel set over a certain angular distance, while the lever is alternately in its two positions. rest. Each magnetic track 58 is formed by the permanent magnet which constitutes the corresponding magnetic structure, this permanent magnet being arranged in magnetic repulsion with the permanent magnets which constitute the two magnetic elements 32 and 33, as already described.

The increasing portions PC1 and PC2 thus define angular ramps for the accumulation of magnetic potential energy in the magnetic escapement. During each energy accumulation phase, the two magnetic structures 26, 40 and therefore the escapement wheel are subjected to a couple of magnetic forces (schematized in Figures 8 and 9 by two tangential arrows FT) having a direction opposite to the direction of rotation of the escapement wheel (given in these figures by a circular arrow), i.e. opposite to a driving torque applied by the barrel via the tourbillon carriage to the escapement wheel, and a intensity lower than that of this driving torque, so that the escapement wheel rotates through a certain angle to allow the accumulation of a certain magnetic potential energy in the magnetic escapement. It will be noted that the two magnetic elements 32 and 33 are each subjected, in reaction, to a magnetic force FM1, respectively FM2 having, on the one hand, a non-zero tangential component relative to the axis of rotation of the escapement wheel set (c' that is to say a tangent component at all points to a geometric circle centered on the axis of rotation 28). On the other hand, these magnetic forces FM1 and FM2 are oriented so that the anchor also undergoes a torque of magnetic force, which keeps the fork 52 bearing against the stop pin 36, respectively 37 depending on whether the anchor is in one or the other of its two rest positions in the considered energy accumulation phase. In Figure 8, which shows a situation of the magnetic escapement substantially at the start of an energy accumulation phase, the magnetic forces FM1 and FM2 are oriented so that the torque of magnetic force applied to the anchor is greater than the torque of magnetic force applied to this anchor at the end of an energy accumulation phase (situation corresponding to that of Figure 6, but already visible in Figure 9 showing an intermediate situation of the magnetic escapement during an energy accumulation phase).

During each energy accumulation phase, it can be said that the two magnetic elements 32 and 33 of the anchor, which are coupled to the two magnetic structures 26 and 40, together climb one of the angular accumulation ramps of magnetic potential energy PC1 or PC2, by a certain rotation of the escapement wheel set, while the anchor 30 is in a phase of rest. However, it will be noted that it is a magnetic interaction energy so that it is the set of 'magnetic structures and magnetic elements' which climbs the angular ramps of accumulation of magnetic potential energy. In the case of a coordinate system linked to the watch movement, it is in fact rather the escapement wheel which climbs the increasing portions PC1 and PC2 of the potential energy curves 66 and 68, since it rotates while the magnetic elements are stationary. Nevertheless, if we consider a coordinate reference associated with the escapement mobile and fixed relative to the latter, then it is indeed the two magnetic elements which climb the increasing portions. It is therefore understood that this is equivalent.

In Figure 5, we see that the magnetic escapement is arranged so that the increasing portions PC1 of the first magnetic potential energy curve 66 are respectively shifted by an angular half-period P/2 relative to the portions increasing PC2 of the second magnetic potential energy curve 68. Next, the two magnetic structures define for the two magnetic elements 32 and 33, in each of the two rest positions of the anchor, magnetic barriers BM1, respectively BM2 which succeed to increasing portions PC1, respectively PC2. The magnetic barriers BM1 and BM2 of a magnetic potential energy curve 66, 68 are formed respectively by magnetic pads 60 and 62 which are located alternately on either side of the magnetic track 58. Each magnetic barrier BM1 is thus located angularly between two successive magnetic barriers BM2 (and therefore vice versa).

More specifically, in the variant described, two successive magnetic barriers BM1 or BM2 are angularly offset by an angular period P. The two magnetic elements of the anchor are angularly offset, relative to the axis of rotation 28, substantially of an angle equal to 3P/2 (generally of an odd number of half-periods P/2). In each of the two rest positions of the anchor, when one of the two magnetic elements is coupled with an outgoing part of the track 58, the other is coupled with a reentrant part of this track. Then, when the first magnetic element is in front of an external magnetic pad 60, the second is in front of an internal magnetic pad 62, and vice versa.

[0028] During normal operation of the watch movement, the magnetic barriers are arranged so as to generate, on the two magnetic elements having climbed a previous angular ramp, a relatively large magnetic force torque which is opposed to the drive torque applied by the barrel to the escapement wheel set, in order to be able to stop the angular advance of the escapement wheel set. For a given torque of mechanical force, the escapement wheel finally stops at a substantially determined angular position (situation corresponding to Figure 6), corresponding in Figure 5 to the stable points E1, E3, E2N+1. with N>0, alternately on curves 66 and 68. It will be noted that slight rebounds can take place so that the escapement mobile undergoes a certain oscillation around these stable points, which is damped quite quickly under the action usual rubbing on horological mobiles. In a preferred variant, the watch movement 2 comprises a rocket 12 for equalizing the force torque supplied by the barrel 10 to the tourbillon carriage 6, so that the escapement wheel set is subjected to a substantially constant torque in the range useful functioning of the timepiece. Thus, throughout this operating range, the aforementioned stable points correspond to a potential magnetic energy of the same value.

Then, during each energy transfer phase, the two magnetic elements 32 and 33 each undergo a radial magnetic force FR1 and FR2 (situation corresponding to Figure 7), relative to the axis of rotation 28 of the escapement mobile, during an alternation of its oscillating movement and in the direction of this oscillating movement during this alternation. It will be noted that this radial magnetic force is generally a radial component of the total magnetic force exerted on each of the magnetic elements. It will be noted that the oscillating movement of each of the magnetic elements is, in the preferred variant which is represented, substantially radial relative to the axis of rotation 28 of the escapement wheel set and therefore of the magnetic structures 26 and 40 which are generally centered on this rotation axis. The axis of rotation of the anchor is positioned for this purpose in the watch movement. The magnetic forces, acting respectively on the magnetic elements of the anchor, which supply mechanical energy to this anchor, in the form of the work of a couple of magnetic forces, are therefore here substantially the radial components FR1, FR2, named also radial magnetic forces, respective total magnetic forces.

As in a conventional mechanical Swiss lever escapement, each alternation of the lever 30 is started by an initial drive of this lever by the balance via a pin 50 (pin having a truncated disc profile) which is placed between the two horns of the fork 52 of the anchor. This initial phase allows the magnetic elements 32 and 33 to each undergo an initial radial displacement before they undergo, in a following phase of the considered alternation of their oscillating movement, a drop in magnetic potential energy so that the magnetic escapement generally undergoes a reduction in magnetic potential energy, referenced D1 and D2 in FIG. such an alternation, the anchor passes from one position of rest to another so that the magnetic potential energy in the magnetic escapement varies passing from a situation described by the curve 66 to a situation described by the curve 68 or vice versa, depending on whether the anchor is initially in one or the other of its two rest positions at the beginning of the considered alternation.

The arrangement of the magnetic escapement described above, from which follows the profile of each of the two curves 66 and 68, therefore allows this magnetic escapement to convert into mechanical energy the magnetic potential energy accumulated in the phase of accumulation of previous energy to supply it to the anchor in the form of a force torque which works as the anchor turns. Thus, the lever becomes a driver and provides an energy pulse to the balance via its fork 50, as in a conventional mechanical escapement, to maintain the oscillation of the balance-spring. What is remarkable in the magnetic escapement selected in the context of the invention is that the transfer of energy can take place without any rotation of the escapement wheel set, as represented in FIG. 5 for the particular variant where the escapement mobile remains at the same angular position during each alternation of the anchor, the magnetic potential energy at the end of the alternation corresponding to the points E2, E4, E2N with N>0, alternately on the curves 68 and 66. note that depending on the driving torque of the barrel, the inertia of the tourbillon carriage and the specific arrangement of the magnetic structures, the escapement wheel set may undergo a slight rotation during the lever alternations, particularly in their phase terminal. Such a variant is also represented in Figure 5 where the magnetic escapement is at the end of the alternation at the points E2*, E4*, E2N* with N > 0. The important thing for the type of magnetic escapement selected, this is not that the escape wheel rotates or does not rotate during the transmission of an energy pulse to the mechanical resonator, but it is that a certain angular displacement of the latter is not necessary to trigger this energy impulse, once the balance wheel is mechanically coupled to the lever via its fork, and to generate it entirely, so that its intensity does not depend on the inertia of the elements between the barrel and the escapement wheel set , in particular not from the inertia of the tourbillon cage.

[0032] It will be noted that the magnetic escapement selected in the context of the first embodiment is substantially at constant force; that is to say that the reductions in magnetic potential energy in the phases of energy transmission to the balance remain substantially constant in the useful operating range of the timepiece. It is a property of the magnetic system of the selected magnetic escapement (see Figure 5). Indeed, even in the absence of a device for equalizing the force torque applied to the escapement wheel set by the barrel, the sustaining pulses supplied to the mechanical resonator in said useful operating range (force torques applied by the barrel to the escape wheel varying within a range of given values) correspond respectively to quantities of energy having close values. The rocket 12 for equalizing the force couple provided by the barrel to the tourbillon carriage/to the escapement wheel set therefore serves here to improve the efficiency of the entire system (watch movement).

[0033] In general, in the context of the first embodiment, the selected magnetic escapement comprises a retainer which couples momentarily, in each alternation of the oscillation of the mechanical resonator, this mechanical resonator to the escapement mobile, the stopper carrying a magnetic element or a plurality of magnetic elements and undergoing, when the mechanical resonator oscillates, a back and forth movement interspersed with phases of rest where the stopper is stopped alternately in two rest positions. A magnetic structure or several magnetic structures respectively define in the two rest positions of the retainer a first curve of magnetic potential energy and a second curve of magnetic potential energy, both as a function of the angle of the escapement mobile and presenting each: increasing portions for the magnetic interaction between the magnetic structure or magnetic structures and said magnetic element or the set of magnetic elements which, among the plurality of magnetic elements, are coupled to the magnetic structure, respectively to the magnetic structures in the position corresponding rest of the stopper, these increasing portions being configured so as to be able to be climbed cyclically and periodically, during normal operation of the watch movement, by this magnetic element or by this set of magnetic elements, and magnetic barriers which respectively follow the increasing portions in the corresponding rest position of the stopper, these magnetic barriers being arranged so as to be able to stop an angular advance of the escapement wheel set while the stopper is in this corresponding rest position .

Then, the increasing portions of the first magnetic potential energy curve are respectively angularly shifted relative to the increasing portions of the second magnetic potential energy curve, each magnetic barrier of one of the first and second potential energy curves magnetic being located angularly between two successive magnetic barriers on the other of these first and second magnetic potential energy curves.

[0035] In addition, the magnetic escapement is arranged so that: the energy accumulation phases occur mainly and respectively in the successive rest phases of the retainer, during each energy accumulation phase, said magnetic element or the set of magnetic elements, which among the plurality of magnetic elements is then coupled to the magnetic structure or to the magnetic structures, is capable of at least partially climbing a increasing portions during a certain rotation of the escapement wheel set, the increasing portions of the first and second magnetic potential energy curves can, during normal operation of the watch movement, be respectively and alternately climbed at least partially during successive energy accumulation phases.

Finally, the magnetic escapement is also arranged so that: the energy transfer phases occur respectively in the successive alternations of the to-and-fro movement of the retainer, this magnetic escapement undergoes, during normal operation of the watch movement, an overall reduction in magnetic potential energy during each of the successive alternations of the to-and-fro movement of the retainer, and the reduction in magnetic potential energy in the magnetic escapement results mainly from a work of the radial magnetic force exerted on said magnetic element or on each magnetic element of the set of magnetic elements which, among the plurality of magnetic elements, were coupled to the magnetic structure or to the magnetic structures during a previous rest phase, this work of the radial magnetic force thus being supplied to the retainer which is arranged to transmit it for the most part to the mechanical resonator, so that this mechanical resonator can receive a pulse of mechanical energy in each alternation of the to-and-fro movement of this retainer.

The variant of the first embodiment represented comprises six external magnetic pads 60 forming as many magnetic stops for momentarily stopping the escape wheel and also six internal magnetic pads 62 also forming as many magnetic stops. It will be noted that the number of external/internal magnetic pads can be different and preferably greater. Thus in another variant, the number of external/internal magnetic pads is equal to ten or twelve. It will also be noted that, in another variant, provision is made to have only internal magnetic pads or, preferably, only external magnetic pads.

In an advantageous variant, shown in Figures 2 and 6 to 9, a mechanical safety device is provided in the event of shocks or other strong accelerations that the magnetic escapement may undergo. It is obtained by the teeth 70 integral with the escapement wheel set arranged at the level of the arms 54 and 55 of the anchor which respectively carry the two magnets 32 and 33, these teeth being capable of cooperating with two fingers located respectively at the ends of the two arms. In each lever rest position, if the magnetic barrier described above does not exert sufficient stopping torque to prevent the escapement wheel set from passing through it, one of the two fingers then comes into abutment against one of the teeth 70.

[0039] As the invention makes it possible to increase the oscillation frequency of the sprung balance, even by a great deal, it is provided for this purpose, in particular to maintain the angular speed of the tourbillon cage at one revolution per minute, that the tourbillon carries an intermediate wheel set 74 whose intermediate wheel 76 meshes with the escapement pinion 24 and whose intermediate pinion 78 meshes with the fixed seconds wheel 80 which the watch movement comprises. The intermediate wheel is a wheel reducing the rotational frequency of the escapement wheel and is here arranged so that the tourbillon carriage performs one revolution on itself per minute. In an advantageous variant, the oscillation frequency Fo of the mechanical resonator is greater than five Hertz (Fo>5 Hz). In a preferred variant, this frequency is substantially equal to or greater than 6 Hz (Fo >= 6Hz) and, in a specific variant, the oscillation frequency of the mechanical resonator has a value between, including, eight Hertz and twelve Hertz ( 8Hz =< Fo =< 12Hz). It will be noted that an intermediate wheel set is already useful for lower oscillation frequencies of the balance-spring, for example for three Hertz (Fo = 3 Hz), because the escape wheel set completes one revolution in the example shown for six periods of oscillation of the balance-spring, which corresponds to a rotation frequency much higher than that of a conventional toothed escapement wheel.

[0040] The rotation frequency FRot of the escape wheel is determined by the frequency of the mechanical resonator Fo and by the number of external magnetic pads 60, respectively the number of internal magnetic pads 62. In a general variant, the rotation frequency FRot (number of revolutions per second) of the escapement mobile is between, inclusive, a quarter and a sixteenth of the oscillation frequency Fo of the mechanical resonator (Fo/16=<FRot=<Fo/4). This amounts to saying that the number NPA of magnetic pads/of external 60 or internal 62 magnetic stops is between four and sixteen (4<=NPA<=16), because FRot=Fo/NPA. In a first example with an oscillating mechanical resonator at three Hertz (Fo = 3 Hz) and the toothing of the fixed wheel (80) comprising 108 teeth, the intermediate pinion comprises 14 teeth and the intermediate wheel comprises 70 teeth, whereas the pinion exhaust (24) has 18 teeth. In a second example with an oscillating mechanical resonator at six Hertz (Fo = 6 Hz) and the toothing of the fixed wheel comprising 120 teeth, the intermediate pinion comprises 12 teeth and the intermediate wheel comprises 72 teeth, whereas the escapement pinion includes 12 teeth.

In Figure 10 is shown, in cross section similar to that of Figure 3, a second embodiment of the invention. Only the distinctive elements of this second embodiment will be described below. It will be noted that the magnetic escapement is identical to that of the first embodiment and that all the variants which have been described for this first embodiment also apply to the second embodiment, which is distinguished by the arrangement of the mechanical resonator 14A which comprises a balance wheel 16A pivoted magnetically in the cage 6A of the tourbillon 4A. The cage comprises for this purpose two magnetic bearings 84 and 86 which are formed respectively by two magnets 88 and 90, the shaft 92 of the balance 16A being provided in ferromagnetic material to ensure its alignment between the two magnets. For the operation of such magnetic pivoting and various possible variants, reference may be made to documents EP 2 450 758, EP 3 109 712 and EP 3 106 933. What is remarkable with such a magnetic system for pivoting the balance in a tourbillon is the fact that it makes it possible to greatly reduce the differences in rate between the horizontal positions and the vertical positions of the movement, whereas the tourbillon makes it possible to average the differences in rate between the various vertical positions.

Two variants of the first and second embodiments will be described below. The first variant is shown in Figure 11, in a simplified manner. The escapement device 18B comprises an anchor 30B and an escape wheel set 20B, formed of a single wheel 22 similar to that of the variants described above and therefore carrying a magnetic structure 26 which will not be described here again. In this Figure 11, there is shown the median geometric circle 96 around which substantially each energy pulse supplied to the anchor 30B which transmits it to the mechanical resonator 14B (of which only the pendulum 16A has been shown schematically). This median geometric circle 96 separates the re-entrant portions from the incoming portions of the magnetic track 58 and also the outer stop pads 60 from the inner stop pads 62, which form the magnetic barriers described previously. More generally, this circle 96 separates two annular and contiguous magnetic tracks 98 and 100 facing which the single magnetic element 32B of the anchor is located respectively in the two rest positions of this anchor and therefore alternately during the accumulation phases of successive magnetic potential energy in the magnetic escapement. The operation of this magnetic escapement is similar to that already described. The major distinction of this variant resides in the anchor 30B which is provided with a single magnet 32B, arranged in repulsion of the magnetized magnetic structure 26, and in the escapement wheel set which comprises only a single magnetic structure arranged a level lower/higher than that in which the magnet oscillates when the watch movement is in operation.

The variant of Figure 12 is distinguished by the material arrangement of various parts forming the magnetic escapement 18C. On the other hand, the operation is similar to that already described, the magnetic structure 26C having in plan substantially the same design as the structure 26. The escapement wheel set 20C and its wheel 22C, carrying the magnetic structure 26C, respectively differ from the wheel set 20B and its wheel 22 of the previous figure in that the structure 26C extends laterally to a core 23, at its periphery, while the structure 26 is arranged on a support disc (with high magnetic permeability or not depending on the variant) . The anchor 30C is, depending on the variant, similar to the anchor 30 or 30B, with the exception of the arrangement of the magnetic elements. More precisely, the anchor 30C comprises at least one pair of similar magnetic elements 32C and 33C (two identical magnets in the example shown) which are located respectively above and below the magnetic structure 26C and which are both coupled in a similar manner. to this magnetic structure and so that their respective magnetic couplings are added. Preferably, each pair of magnets is carried by a support 31 made of a material with high magnetic permeability (notably ferromagnetic) having a general 'C' shape.

With reference to Figures 13 and 14, there will be described below a third embodiment of the invention which is characterized by a magnetic escapement 118 without stopper, the escapement mobile 120 being directly magnetically coupled to the mechanical resonator 114 (shown schematically) whose balance wheel 116 carries the magnetic elements 102 and 103. The balance wheel is associated with a hairspring 115. The cage 106 of the tourbillon is schematized by a block to which is fixed one end of the hairspring and which carries the pendulum 116 and mobile 120, which are arranged to pivot in cage 106, respectively around two axes of rotation 8 and 28 as in the two previous embodiments. The escape wheel 120 rotates continuously and synchronously with the oscillation of the mechanical resonator (that is to say the escape wheel rotates by a predetermined angular period during each period of oscillation of the balance wheel 116) . It will be noted that the angular speed of the escape wheel set may exhibit a certain variation during each period of oscillation, in particular depending on whether one is in an energy accumulation phase or an energy transfer phase. .

The magnetic structure 126 is annular and alternately formed of annular sectors 128, in which are arranged magnets in magnetic repulsion with the magnets 102 and 103 when they are presented alternately opposite these annular sectors, and annular sectors 130 made of a non-magnetic material, such as brass or aluminum. Each pair of adjacent annular sectors defines an angular period of the magnetic structure. Preferably, the magnets of the magnetic structure 126 have an angularly increasing thickness in the opposite direction to the direction of rotation provided for the escapement wheel set, so as to have an air gap which decreases between each of them and the magnet 102, 103 which passes above (when the escapement mobile rotates) and also a magnetic flux which intensifies. For such an advantageous variant, Figure 14 shows level curves 134 for the magnetic potential energy in the magnetic escapement (consisting here of the magnetic structure 126 and the two magnets 102 and 103 integral with the balance wheel) as a function of the position relative angle of one or the other of the two magnets 102 and 103. When the mechanical resonator 114 oscillates, these two magnets oscillate with a phase shift of 180°, each according to a path represented by the curve 140 in a reference frame of polar coordinates linked to the escape mobile. Each annular sector 128 defines a set 128A of level curves, two successive sets 128A being separated by a sector 126A of zero magnetic potential energy defined by an annular sector 126. The level curves 134 increase towards the interior of those- ci, that is to say that the outer curve has less potential energy than the following curve located inside the latter, and so on. For other variant embodiments, reference will be made to document EP 2 891 930 which describes magnetic escapements of the type selected in the context of the third embodiment.

When the mechanical resonator is in its neutral position (minimum mechanical energy position shown in Figure 13), the two magnets 102, 103 are located on a circle 132 of zero position. When the mechanical resonator oscillates, these two magnets penetrate alternately above the magnetic structure so that the pendulum is constantly magnetically coupled to this magnetic structure. For these two magnets to alternately experience the same coupling with the magnetic structure, they have an angular offset of an odd number of angular half-periods of the magnetic structure. Thus, the escapement wheel performs a rotation of a determined angular period at each period of oscillation of the balance wheel. Moreover, similarly to the previous embodiments, the two magnets 102 and 103 mainly undergo a radial movement, relative to the axis of rotation 28 of the escapement wheel set, when the balance wheel oscillates. Preferably, their movement is radially oriented when they cross the zero position circle 132 (corresponding to the outer circle of the magnetic structure). As mentioned, in the variant proposed here, the two magnets 102 and 103 are alternately coupled to the magnetic structure so that they successively undergo a magnetic coupling with one of the magnetized annular sectors 128. Thus, the overall magnetic potential energy in the Magnetic escapement 118 is given by contour lines 134 in Figure 14.

It is observed in Figure 14 that the magnetic escapement is arranged so as to present, during normal operation of the watch movement, alternately energy accumulation phases, coming from a conversion of mechanical energy provided by the barrel in magnetic potential energy in the magnetic escapement, and phases of transfer of energy accumulated in the magnetic escapement to the magnetic resonator. The magnetic escapement defines rising angular ramps 136 for the accumulation of magnetic potential energy which, during the continuous rotation of the magnetic structure, alternately undergo the magnets 102 and 103 during successive energy accumulation phases during which they successively and partially climb these ascending angular ramps. Since the magnetic interaction force between the magnets 102, 103 and the magnetic structure is oriented perpendicular to the level lines 134, these magnets then experience a magnetic force which is essentially perpendicular to the radius it forms with the axis of rotation 28 Thus, the magnetic structure 126 (and therefore the escapement wheel) undergoes, during each energy accumulation phase, a torque of magnetic force, relative to its axis of rotation, having a direction opposite to that of driving torque, applied by the barrel via the tourbillon carriage to the escapement wheel set. It will be noted that the arrangement of the magnets 102, 103 and the magnetic annular sectors 128 is provided so that, in normal operating mode, the intensity of the magnetic force torque is lower than that of the driving torque, so that the escapement wheel set can continue its rotation and rotate through a certain angle, thus allowing an accumulation of potential energy in the magnetic escapement.

The magnetic escapement also defines downward radial ramps 138 of magnetic potential energy down which the two magnets 102 and 103 alternately descend after having respectively climbed the upward angular ramps 136. Like the magnetic force which is exerted on each magnet 102 , 103, descending a downward radial ramp, is oriented perpendicular to the level lines 134, it then undergoes, during energy transfer phases, mainly a radial magnetic force, relative to the axis of rotation 28, during each alternation of the oscillation movement of the mechanical resonator and in the direction of this oscillation movement during this alternation, so that the magnetic escapement then converts into mechanical energy magnetic potential energy accumulated in the accumulation phase of previous energy to be able to maintain the oscillation of the mechanical resonator. The reduction in magnetic potential energy in the magnetic escapement therefore mainly results from a work of the radial magnetic force exerted alternately on each of the two magnetic elements, this work of the radial magnetic force being transmitted directly to the mechanical resonator, so that this mechanical resonator receives a pulse of mechanical energy in each alternation of its oscillating movement.

The descending radial ramps 138 extend over a certain angular distance so that the continuous movement of the escape wheel has no effect on the particular characteristics sought in the context of the present invention. Indeed, the important thing is that the main radial force which is exerted alternately on each of the two magnets fixed to the balance does not depend almost on any rotation of the escapement wheel set. Indeed, it is observed in Figure 14 that the arrangement of the magnetic structure makes it possible to generate the energy pulses for the balance wheel without rotation of the escapement wheel set. If the latter were to stop at the end of the energy accumulation phase, then the balance wheel would nevertheless receive in the form of an impulse the same quantity of energy as that which it receives by undergoing during the energy transfer phases a some rotational motion. Moreover, it is observed that this quantity of energy remains almost constant, whether the angular speed of the balance wheel is small or relatively large, provided that the magnetic escapement is arranged in such a way that, in normal operation, it does not reach the top of the rising angular ramps 136 at the end of the energy accumulation phases. This condition is provided for in the magnetic escapement according to this third embodiment.

[0050] Finally, it will be noted that a fusee (similar to the fusee 12 shown in the context of the first embodiment) incorporated into the watch movement makes it possible to equalize the force couple supplied by the barrel to the tourbillon cage, so that the escape wheel is subjected to a constant torque during the normal operation of the watch movement. In the context of the third embodiment, such a fuse makes it possible to obtain a stationary operating phase over the entire useful operating range of the watch movement, with the oscillation amplitude of the balance which remains constant and maintenance pulses which supply the balance wheel with the same quantity of mechanical energy. All the benefit procured by a fuse for equalizing the torque of force in a conventional mechanical watch movement is brought to the timepiece according to this third embodiment.

Claims (12)

1. Timepiece comprising a watch movement (2) equipped with a tourbillon (4) comprising a cage (6,6A,106) arranged to rotate around a main axis, a barrel arranged to accumulate mechanical energy and a gear train kinematically connecting said tourbillon carriage to the barrel, the tourbillon carrying a mechanical resonator (14, 14B, 114), formed by a balance wheel (16, 16A, 116) and a hairspring, and a exhaust device; this timepiece being characterized in that the escapement device consists of a magnetic escapement (18) which comprises an escapement wheel set (20, 20B, 20C, 120) formed of an escapement pinion and at least one magnetic structure (26,40,26C, 126), which has a generally annular shape which is centered on an axis of rotation (28) of the escapement wheel set, this magnetic escapement further comprising a magnetic element or a plurality of magnetic elements (32,33,32B,32C,33C,102,103), this magnetic element or each magnetic element of the plurality of magnetic elements being arranged to have an oscillating movement which is synchronous with the oscillation of the mechanical resonator and which has a non-zero radial component relative to said axis of rotation, said magnetic element being coupled with said at least one magnetic structure or each magnetic element of said plurality of magnetic elements being coupled, at least simultaneously periodically, with said at least one magnetic structure so that the escapement wheel rotates through a determined angular period at each period of oscillation of the balance wheel; in that the magnetic escapement is arranged so as to present, during normal operation of the watch movement, alternately energy accumulation phases, originating from a conversion of mechanical energy supplied by the barrel into potential energy magnetic in the magnetic escapement, and energy transfer phases accumulated in the magnetic escapement to the magnetic resonator; and in that the magnetic escapement is arranged so that: – during each energy accumulation phase, said at least one magnetic structure undergoes a torque of magnetic force, relative to said axis of rotation, having a direction opposite to that of a driving torque, applied by the barrel via the tourbillon cage to the escapement wheel, and an intensity lower than that of this driving torque, so that the escapement wheel rotates through a certain angle to allow the accumulation of a certain magnetic potential energy in the magnetic escapement; – during each energy transfer phase, said magnetic element or each magnetic element of a set of magnetic elements, which among the plurality of magnetic elements was coupled to said at least one magnetic structure during a phase of accumulation of previous energy, undergoes a radial magnetic force, relative to said axis of rotation, during an alternation of its oscillating movement and in the direction of the radial component of this oscillating movement during this alternation, so that the The magnetic escapement then converts into mechanical energy magnetic potential energy accumulated in said preceding energy accumulation phase in order to be able to maintain the oscillation of the mechanical resonator. 2. Timepiece according to claim 1, characterized in that said magnetic escapement comprises a stopper (30, 30B, 30C) which couples momentarily, in each alternation of the oscillation of the mechanical resonator, this mechanical resonator to the mobile of escapement (20, 20B, 20C), the retainer bearing said magnetic element or said plurality of magnetic elements and undergoing, when the mechanical resonator (14, 14B) oscillates, a back and forth movement interspersed with phases of rest where the retainer is stopped alternately in two rest positions; in that said at least one magnetic structure defines in the two rest positions of the retainer respectively a first magnetic potential energy curve (66) and a second magnetic potential energy curve (68), both as a function of the angle of the escapement mobile and each having: – increasing portions (PC1, PC2) for the magnetic interaction between said at least one magnetic structure and said magnetic element or the set of magnetic elements which, among the plurality of magnetic elements, are coupled to said at least one structure magnet in the corresponding rest position of the retainer, these increasing portions being configured so as to be able to be climbed, during said normal operation, cyclically and periodically by this magnetic element or by this set of magnetic elements, and – magnetic barriers (BM1, BM2) which respectively follow the increasing portions, these magnetic barriers being arranged so as to be able to stop an angular advance of the escapement wheel set while the retainer is in the corresponding rest position; said increasing portions of the first magnetic potential energy curve being respectively shifted relative to the increasing portions of the second magnetic potential energy curve, each magnetic barrier of one of the first and second magnetic potential energy curves being located angularly between two successive magnetic barriers of the other of these first and second magnetic potential energy curves; the magnetic escapement being arranged so that: – the energy accumulation phases occur mainly and respectively in the successive rest phases of the retainer, – during each energy accumulation phase, said magnetic element or all of the magnetic elements, which among said plurality of magnetic elements are then coupled to said at least one magnetic structure, is capable of at least partially climbing a of said increasing portions during a certain rotation of the escapement wheel set, - the increasing portions of the first and second magnetic potential energy curves can, during said normal operation, be respectively and alternately climbed at least partially during successive energy accumulation phases; and in that the magnetic escapement is further arranged so that: – the energy transfer phases occur respectively in the successive alternations of the to-and-fro movement of the retainer, – this magnetic escapement undergoes, during said normal operation, an overall reduction in magnetic potential energy (D1, D2) during each of the successive alternations of the to-and-fro movement of the retainer, and – the reduction in magnetic potential energy in the magnetic escapement results mainly from a work of said radial magnetic force (FR1, FR2) exerted on said magnetic element or on each magnetic element of the set of magnetic elements which, among the plurality of magnetic elements, were coupled to said at least one magnetic structure during a previous rest phase, this work of the radial magnetic force thus being supplied to the retainer which is arranged to transmit it for the most part to the mechanical resonator , so that this mechanical resonator receives a pulse of mechanical energy in each alternation of the to-and-fro movement of this retainer. 3. Timepiece according to claim 1 or 2, characterized in that the tourbillon further carries an intermediate wheel set (74) whose intermediate wheel (76) meshes with the escapement pinion (24) and whose intermediate pinion (78) meshes with a fixed seconds wheel (80) that comprises the watch movement, the intermediate wheel being a wheel reducing the frequency of rotation of the escapement wheel and being arranged so that the said tourbillon carriage completes one revolution on itself per minute. 4. Timepiece according to one of the preceding claims, characterized in that the oscillation frequency Fo of the mechanical resonator is equal to or greater than six Hertz, ie Fo >= 6 Hz. 5. Timepiece according to claim 3, characterized in that the oscillation frequency Fo of the mechanical resonator has a value between, inclusive, eight Hertz and twelve Hertz, ie 8 Hz =< Fo =< 12 Hz. 6. Timepiece according to claim 3 or 5 or claims 4 and 3, characterized in that the rotation frequency FRotdu escapement mobile has a value between, including, a quarter and a sixteenth of the frequency d oscillation Fo of the mechanical resonator, ie Fo/4 <= FRot<= Fo/16. 7. Timepiece according to one of the preceding claims, characterized in that the magnetic escapement comprises at least two similar magnetic elements (32,33) which are located on the same side of said magnetic structure (26) and which are both coupled simultaneously to this magnetic structure so that their respective magnetic couplings add up. 8. Timepiece according to one of the preceding claims, characterized in that the magnetic escapement comprises at least one pair of similar magnetic elements (32C, 33C) which are located respectively above and below said magnetic structure (26C) and which are both coupled simultaneously to this magnetic structure so that their respective magnetic couplings add up. 9. Timepiece according to one of claims 1 to 7, wherein said magnetic structure is a first magnetic structure (26); characterized in that the escapement wheel set comprises a second magnetic structure (40) which has planar symmetry with the first magnetic structure and which is located at a distance from the latter so as to allow said magnetic element or each magnetic element of said plurality of magnetic elements (32,33) to be located, during said oscillating movement, at least momentarily between the first and second magnetic structures. 10. Timepiece according to claim 9, characterized in that the first magnetic structure and the second magnetic structure are respectively formed of a first permanent magnet and a second permanent magnet which each have an axial magnetization and the same polarity. ; and in that said magnetic element or each magnetic element of said plurality of magnetic elements (32,33) is formed by a permanent magnet having an axial magnetization and an inverted polarity relative to the first and second magnets, so as to undergo a force of magnetic repulsion upon magnetic coupling with each of the first and second magnetic structures. 11. Timepiece according to claim 10, characterized in that said escape wheel set (20) carries a first ferromagnetic structure (44) and a second ferromagnetic structure (46) which respectively cover the first and second magnetic structures (26 ,40) on the two outer sides of the assembly of these first and second magnetic structures, so as to thus form a shielding of the first and second magnetic structures and of each magnetic element when the latter is located between the latter and is thus coupled magnetically with them. 12. Timepiece according to one of the preceding claims, characterized in that the balance wheel (16A) is pivoted magnetically in the cage (6A) of the tourbillon which comprises for this purpose two magnetic bearings (84,86).