EP3767397B1 - Clock movement comprising a rotary element provided with a magnetic structure having a periodic configuration - Google Patents

Description

Technical area

The invention relates to watch movements provided with at least one rotating element participating in at least one magnetic system of the watch movement, this rotating element being provided with an annular magnetized structure having an angular variation of at least one physical parameter which defines.

“Rotating element” means an element arranged in the watch movement so as to be able to undergo a certain rotation, in a given direction or in both directions. Thus, this expression applies for example as much to an escape wheel as to a balance wheel.

Technology background

Various watch movements comprising at least one magnetic system intervening in the operation of the watch movement are known from the prior art. In particular, watch movements equipped with a magnetic escapement formed by a magnetic system in which participate at least one magnet carried by an anchor and at least one magnet carried by an escape wheel are known. Such magnetic escapements are described in particular in the documents EP_2887157 , EP_3128379 , EP_3128379 , EP_3208667 , EP_3217227 and CH_712154 . Also known are watch movements having a magnetic escapement without a stopper, part of the magnetic system of which is carried by the mechanical resonator of the watch movement and the other part is carried by an escape wheel. Such watch movements are described in particular in the documents CH_709031 and CH_713070 .

Summary of the invention

When a rotating element supports an annular magnetized structure and when the latter exhibits an angular variation of at least one physical parameter which defines it, the inventors have observed that, in the presence of at least one ferromagnetic part located in particular at the periphery of the rotating element, not only does this ferromagnetic part exert a radial attraction on the annular magnetized structure, so that a parasitic friction force is generated in the bearings of the shaft of the rotating element, but in addition the element rotating is subjected to a parasitic magnetic torque varying according to the angular position of the rotating element. Such a parasitic magnetic torque disturbs the proper functioning of the magnetic system in which the rotating element participates, in particular in the case of a magnetic escapement having an escape wheel of the type of the aforementioned rotating element.

Having brought to light this additional technical problem, the inventors sought a technical solution. The first thought that comes to mind is to remove the magnetic elements (magnets and elements made of ferromagnetic materials) close to the rotating element or to move them far enough from the latter to make their interaction with the annular magnetized structure negligible. However, it is often not easy to change the materials selected for the various elements and components of the watch movement. Thus, although non-ferromagnetic materials are known for manufacturing axes / shafts of rotating elements, it is sometimes preferable for other technical reasons or for questions of manufacturing costs to keep steel in particular for such axes. / trees. Then, it is often not possible to remove the magnetic elements in the environment of the rotating element in question without modifying the design of the watch movement. For example, an anchor magnet having a steel axis must remain at the periphery of the magnetic escape wheel to which this magnetic anchor is associated. Thus, the inventors have decided to seek a technical solution to solve the particular technical problem, namely the manifestation of a disturbing magnetic torque, which neither requires nor having to change the nature of magnetic elements in the environment of an element. revolving fitted with a magnetic structure presenting an angular variation of at least one physical parameter, nor having to modify the design of the watch movement, that is to say its various functional parts and their interactions.

To this end, the present invention relates to a watch movement comprising a mechanism formed by a rotating element, provided with an annular magnetic structure having an angular variation of at least one physical parameter which defines it, and by a first set of elements magnetic elements which consists of a functional magnetic element or of a plurality of functional magnetic elements, this first set of magnetic elements not being integral in rotation with the rotating element and having with the annular magnetized structure generally a first magnetic interaction which generates on the rotating element a first parasitic magnetic torque. The watch movement further comprises a second set of magnetic elements which consists of a magnetic compensation element or of a plurality of magnetic compensation elements not belonging to any mechanism of the watch movement, this second set of magnetic being not integral in rotation with the rotating element and having with the globally annular magnetized structure a second magnetic interaction which generates on the rotating element a second parasitic magnetic torque. The second set of magnetic elements is arranged relative to the first set of magnetic elements so that the maximum absolute value of the torque resulting from the addition of the first parasitic magnetic torque with the second parasitic magnetic torque is less than the maximum absolute value of the first parasitic magnetic couple.

According to a main embodiment, the first parasitic magnetic torque as a function of the angular position of the rotating element defines a first curve of the sinusoidal type having an angular period equal to 360°/N with N being an integer greater than one ( N > 1). In addition, the second set of magnetic elements is arranged relative to the first set of magnetic elements so that the second parasitic magnetic torque as a function of the angular position of the rotating element defines a second curve of the sinusoidal type also having said period angular, and so that the first and second parasitic magnetic couples have between them an angular phase shift substantially equal to 180°.

According to an improved embodiment, the second set of magnetic elements consists of K magnetic compensation elements or K groups of magnetic compensation elements having substantially the same configuration, K being an integer greater than one (K>1) . The K magnetic compensation elements or groups of magnetic compensation elements are arranged in such a way that K parasitic magnetic couples, generated on the rotating element respectively by these K magnetic compensation elements or groups of magnetic compensation elements, present relative to the first parasitic magnetic torque respectively K angular phase shifts which are respectively equal to substantially J 360°/(K+1) with J being an integer ranging from one to K, i.e. J = 1, ..., K.

Thanks to the characteristics of the object of the invention, the overall parasitic magnetic torque is therefore reduced, which is exerted by at least one functional magnetic element on the rotating element provided with an annular magnetic structure, by adding in the surrounding space of this rotating element at least one magnetic compensation element.

In an advantageous embodiment where the integer K is provided equal to two (K = 2), the annular magnetized structure is configured and the compensation magnetic element is arranged so that the maximum absolute value of said resulting torque is less than 15% of the maximum value of the first parasitic magnetic torque. Claim 1 defines a horological movement according to the present invention. Preferred embodiments are defined in claims 2-14.

Brief description of figures

• La Figure 1 est un vue partielle et simplifiée d'un mouvement horloger mécanique muni d'un échappement magnétique divulgué dans le document EP_3208667 ,
• La Figure 2 est une coupe transversale d'un échappement magnétique du type divulgué dans le document EP_3208667 ,
• La Figure 3 est une vue partielle, en coupe horizontale, de l'échappement magnétique de la Figure 2,
• La Figure 4 montre la courbe d'un couple perturbateur engendré par l'axe magnétique de l'ancre sur la roue d'échappement en fonction de la position angulaire de cette dernière avec l'échappement magnétique des Figures 2 et 3,
• La Figure 5 montre partiellement un premier mode de réalisation d'un mouvement mécanique selon l'invention,
• La Figure 6 montre une courbe d'un couple perturbateur restant qui s'exerce sur la roue d'échappement en fonction de sa position angulaire dans le premier mode de réalisation,
• La Figure 7 montre partiellement un deuxième mode de réalisation d'un mouvement mécanique selon l'invention,
• Les Figures 8A et 8B montrent respectivement les deux courbes de couples perturbateurs engendrés, en fonction de la position angulaire de la roue d'échappement, individuellement par l'axe de l'ancre et l'axe d'un mobile intermédiaire sur la roue d'échappement dans le deuxième mode de réalisation,
• La Figure 8C montre un couple perturbateur exercé globalement par les éléments magnétiques fonctionnels que sont l'axe de l'ancre et l'axe du mobile intermédiaire sur la roue d'échappement dans le deuxième mode de réalisation,
• La Figure 8D montre le couple perturbateur restant qui s'exerce sur la roue d'échappement en fonction de sa position angulaire dans le deuxième mode de réalisation,
• La Figure 9 montre partiellement un troisième mode de réalisation d'un mouvement mécanique selon l'invention,
• La Figure 10 montre le couple perturbateur restant qui s'exerce sur la roue d'échappement en fonction de sa position angulaire dans le troisième mode de réalisation.
• La Figure 11 montre partiellement un quatrième mode de réalisation d'un mouvement mécanique selon l'invention, et
• La Figure 12 montre le couple perturbateur résiduel qui s'exerce sur la roue d'échappement en fonction de sa position angulaire dans le quatrième mode de réalisation.

The invention will be described below in more detail using the accompanying drawings, given by way of non-limiting examples, in which:

• The Figure 1 is a partial and simplified view of a mechanical watch movement provided with a magnetic escapement disclosed in the document EP_3208667 ,
• The Figure 2 is a cross-section of a magnetic escapement of the type disclosed in the document EP_3208667 ,
• The Figure 3 is a partial view, in horizontal section, of the magnetic escapement of the Figure 2 ,
• The Figure 4 shows the curve of a disturbing torque generated by the magnetic axis of the pallet on the escapement wheel as a function of the angular position of the latter with the magnetic escapement of the Figure 2 and 3 ,
• The Figure 5 partially shows a first embodiment of a mechanical movement according to the invention,
• The Figure 6 shows a curve of a remaining disturbing torque which is exerted on the escape wheel as a function of its angular position in the first embodiment,
• The Picture 7 partially shows a second embodiment of a mechanical movement according to the invention,
• The Figures 8A and 8B show respectively the two curves of disturbing torques generated, as a function of the angular position of the escape wheel, individually by the axis of the lever and the axis of a mobile intermediate on the escape wheel in the second embodiment,
• The Figure 8C shows a disturbing torque exerted overall by the functional magnetic elements which are the axis of the lever and the axis of the intermediate wheel set on the escape wheel in the second embodiment,
• The Figure 8D shows the remaining disturbing torque which is exerted on the escape wheel as a function of its angular position in the second embodiment,
• The Figure 9 partially shows a third embodiment of a mechanical movement according to the invention,
• The Picture 10 shows the remaining disturbing torque exerted on the escape wheel as a function of its angular position in the third embodiment.
• The Picture 11 partially shows a fourth embodiment of a mechanical movement according to the invention, and
• The Picture 12 shows the residual disturbing torque exerted on the escape wheel as a function of its angular position in the fourth embodiment.

Detailed description of the invention

With reference to Figures 1 to 4 , a mechanical watch movement 2 of the prior art will be described below in order to better highlight the technical problem posed by such a watch movement which is provided with a balance wheel 4 and a magnetic escapement formed by a magnetic lever 8 and an escape wheel referenced 6 in the variant of the Figure 1 , respectively 6A in the variant of Figure 2 and 3 . The magnetic anchor is provided with two magnetic pallets 9, 10 arranged at the free ends of two arms.

In the variant of Figure 1 , the escapement wheel 6 comprises a non-magnetic support 11 on which is arranged a structured magnetic layer 12 which alone forms an annular magnetic structure of the escapement wheel. This structured magnetic layer has a magnetic track 14 which surrounds the shaft 20 of the escape wheel along a generally circular path but with convex portions 14a, that is to say outgoing, and concave portions 14b, i.e. incoming. In addition, the structured magnetic layer 12 has external magnetic pads 16 and internal magnetic pads 17 which are located respectively on both sides of the magnetic track 14 and which define magnetic barriers for the magnetic pallets of the anchor 8. Operation of such a magnetic escapement is described in the documents cited above in the technological background, so that reference will be made to these documents to know it.

In the variant of Figure 2 and 3 , the escapement wheel 6A comprises two structured magnetic layers 12A and 12B which are each identical to the layer 12 of the Figure 1 and which are arranged axially opposite each other with the pads 16 and 17 of the layer 12A superimposed on the corresponding pads of the layer 12B. The two layers 12A and 12B are arranged on two respective supports 11A and 11B, made of non-magnetic material, which are fixedly mounted on the shaft 20, which comprises a pinion 22 for driving the escape wheel 6A. The two structured magnetic layers are located on the side of an intermediate space defined by the two supports 11A, 11B and into which the two respective ends of the two arms of the anchor 8 penetrate, so as to allow magnetic interaction of the magnetic pallets of the anchor with the two layers 12A and 12B. The two structured magnetized layers 12A, 12B together form an annular magnetized structure of the magnetic escape wheel 6A. The two layers 12A, 12B each have a constant thickness, so that the annular magnetized structure also has a constant thickness axially.

As indicated in the summary of the invention, for various reasons, the axis 18 of the anchor is provided here in ferromagnetic material. In general, within the scope of the invention, a watch movement is considered comprising a mechanism formed by a rotating element, provided with an annular magnetized structure having an angular variation of at least one physical parameter defining this annular magnetized structure, and by a first set of magnetic elements which consists of at least one functional magnetic element, this first set of magnetic elements not being integral in rotation with the rotating element and generally having a first magnetic interaction with the annular magnetized structure . In the examples considered in the detailed description of the invention, the rotating element is a magnetic escape wheel. However, the rotating element can be another component, in particular a pendulum. Next, in the examples considered, the first set of magnetic elements consists of at least one axis made of ferromagnetic material, in particular the axis of the lever associated with the escape wheel and/or the axis an intermediate mobile located close to this wheel and forming a gear train which transmits the torque from a barrel to the escapement wheel. It will be understood that the invention is not limited solely to axes made of ferromagnetic materials, but that it applies to any other magnetic element capable of being arranged at the immediate periphery of the rotating element in question, in particular to a magnetic escape wheel, and to present a significant magnetic interaction with its annular magnetized structure. By 'magnetic element' is meant a magnet, a ferromagnetic element or a combination of both.

Note that in the variant considered in Figure 2 and 3 , essentially two physical parameters of the annular magnetized structure exhibit an angular variation, namely the radial width of each structured magnetized layer 12A, 12B and the average distance of each structured magnetized layer from the axis of rotation 21 of the escape wheel 6A. The angular variations of the radial width and the average distance to the axis of rotation of the two layers 12A, 12B, and therefore of the annular magnetized structure, are periodic so that the annular magnetized structure has an angular period equal to 360°/N with N being an integer greater than one (N > 1). In particular, in the variant considered, the annular magnetized structure has an angular period PA equal to 360°/N with N=6, ie an angular period of 60° or π/3 [rad].

The ferromagnetic axis 18 forms a body of revolution so that the volume of magnetic material that it defines remains invariant whatever the angular position of the anchor 8. Thus, the first magnetic interaction between the magnetic axis 18 and the annular magnetic structure 12A-12B of wheel 6A generates on this wheel, because it comprises a periodic annular magnetic structure, a first parasitic magnetic torque which depends substantially only on the angular position of wheel 6A and which varies periodically in function of the angular position of the wheel 6A by having, in the variant considered, the same angular period PA, here 60° or π/3 [rad], as the annular magnetized structure 12A-12B. A portion of the curve 30 of the first parasitic magnetic torque is given at the Figure 4 .

The curve 30, although not defining exactly a function F(θ)=A·sinθ, is of the sinusoidal type. By 'curve of the sinusoidal type', we understand a curve that is alternately positive and negative, with positive extreme values which are close, normally identical but which may differ slightly, and negative extreme values which are close, normally identical but which may differ slightly . Then, the positive extreme values and the negative values are, in absolute values, close to each other, preferably almost identical but they can differ to a certain extent, for example by 10% to 20%. A periodic character can be recognized in such a curve with the period as the angular distance between two positive extreme values or, equivalently, two negative extreme values. Finally, the two half-periods forming the period of such a curve can have different values, as is the case of curve 30 at the Figure 4 , although it is advantageous for the two half-periods to have substantially the same value.

In a first embodiment of the invention shown in Figure 5 , the watch movement is similar to that of the prior art described above as regards the mechanism(s) which compose it and it further comprises a magnetic compensation element 32 which is similar in shape to the magnetic axis 18 or, more generally, configured to generate on the annular magnetized structure, in particular on the structured magnetic layer 12A which forms it, a torque having substantially the same intensity as that of the torque generated by the axis 18 ( Figure 4 ). This magnetic compensation element 32 is here formed by a magnetic pin, arranged at the periphery of the magnetic escape wheel and formed by a ferromagnetic material, and it is arranged so as to present an angular offset relative to the magnetic axis, related to an angular period of the periodic structured magnetized layer 12A and therefore to the angular period of the periodic annular magnetized structure. A second parasitic magnetic torque generated by the magnetic pin 32 defines a curve similar to the curve 30 of the Figure 4 , but the first and second parasitic magnetic couples have between them a phase shift of about 180°, preferably 180°. This 180° phase shift corresponds to an angular shift between the magnetic axis 18 and the magnetic pin 32 which is equal to [(2M-1)/N] 180°, with N being the number of angular periods of the magnetized structure ring, or N=6 in the example shown, and M being a positive integer which is less than or equal to N.

Preferably, the magnetic pin 32 is arranged on the side diametrically opposite to the functional magnetic axis 18 to also compensate for the major part of the magnetic attraction force exerted by this axis 18 on escape wheel 6A. The torque resulting from the addition of the first and second parasitic magnetic torques is shown in Figure 6 . It is first observed that the maximum absolute value V2 of this resulting torque is lower than the maximum absolute value V1 of the first parasitic magnetic torque represented in Figure 4 . In the example treated here, the maximum absolute value V2 of the resulting torque is slightly less than half the maximum absolute value V1 of the first parasitic magnetic torque. Then, it is further observed that the curve 34 of the resulting torque has a period equal to half the angular period PA of the structured magnetized layer 12A and therefore of the annular magnetized structure. This is easily understood from the fact that the arrangement of a compensation axis out of phase by 180° generates magnetic configurations which are identical for a rotation of a half-period PA/2 of the escapement wheel 6A. If we decompose curve 30 into a Fourier series, the addition of two such curves out of phase by 180° cancels the harmonic of order n = 1 (also called the fundamental), but we double the harmonic of order n=2 which has a period equal to half the period of the fundamental, this last period being equal to the period PA of the curve 30 of the first parasitic magnetic couple.

In general, the watch movement comprises a second set of magnetic elements which consists of a magnetic compensation element or a plurality of magnetic compensation elements not belonging to any mechanism of the watch movement, this second set of magnetic elements being non-rotatably connected to the rotating element and having with the globally annular magnetized structure a second magnetic interaction which generates on the rotating element a second parasitic magnetic torque. According to the invention, the second set of magnetic elements is arranged relative to the first set of magnetic elements so that the maximum absolute value of the torque resulting from the addition of the first and second parasitic magnetic torque is less than the maximum absolute value of the first parasitic magnetic torque.

In a main embodiment, to which the first embodiment described before corresponds, the first parasitic magnetic torque as a function of the angular position of the rotating element defines a first curve of the sinusoidal type having an angular period equal to 360°/N , with N being an integer greater than one (N > 1). Then, the second set of magnetic elements is arranged relative to the first set of magnetic elements so that the second parasitic magnetic torque as a function of the angular position of said rotating element defines a second curve of the sinusoidal type also exhibiting said angular period, and so that the first and second parasitic magnetic couples have between them an angular phase shift substantially equal to 180°.

With reference to Figure 7 and 8A at 8D, a second embodiment also corresponding to the aforementioned main embodiment will be described. The watch movement, shown partially on the Picture 7 , comprises a magnetic escape wheel 36 provided with an annular magnetized structure formed, as in Figure 2 , of two structured magnetic layers of which only the lower layer 38A appears at the Picture 7 . The escape wheel comprises a shaft 20 and a non-magnetic support 40 carrying the lower magnetic layer 38A. This escape wheel is arranged to rotate around an axis of rotation 21. It is associated with a magnetic anchor 8A, which is formed by a magnetic axis 18A and two non-magnetic arms, shown in broken lines, which carry at their ends free respectively two magnetic pallets 9, 10. The structured magnetic layer 38A and the annular magnetic structure formed by this structured magnetic layer differ from the layer 12 A and from the annular magnetic structure of the Figure 5 by a new configuration.

The annular magnetized structure formed of the structured magnetized layer 38A or of two such superimposed layers, as shown in Figure 2 , defines magnetic barriers 17A for the magnetic anchor which are angularly offset by the angular period PA. It will be noted that only internal magnetic pads 17A have been provided in the advantageous variant considered. Layer 38A has a constant thickness and defines a magnetic track 14A with variable radial width. Preferably, the annular magnetized structure is configured so that its outer profile is substantially circular and continuous, as in the case of the advantageous variant of the Picture 7 . By 'circular external profile', in the case of a structure having two structured magnetic layers, it is understood that each layer has an external profile which is substantially circular. In this case, preferably, the diameters of the two structured magnetic layers are equal, so that the external profiles of these two layers define a cylindrical geometric surface. Such an arrangement of the annular magnetized structure makes it possible, on the one hand, to reduce the first parasitic magnetic torque generated by the functional magnetic element or elements at the periphery of the escape wheel 36 and, on the other hand, to reduce the ratio between the maximum absolute value of the resulting torque (from the addition of the first parasitic magnetic torque and the parasitic magnetic torque generated by the compensation pin) and that of the first parasitic magnetic torque.

The second embodiment is distinguished from the first again by the fact that two functional magnetic elements at the direct periphery of the escape wheel are considered here, namely the magnetic axis 18A of the lever 8A and the magnetic axis 42 an intermediate mobile forming a cog between the escapement wheel and a barrel of the watch movement and meshing with the pinion of the escapement wheel. To the Figures 8A and 8B are represented the individual magnetic couples which are generated respectively by the two magnetic axes 18A and 42 (at least partly in ferromagnetic material). To the Figure 8C is represented the curve 44 of the first parasitic magnetic torque generated globally by the functional magnetic elements, other than the magnetic pallets of the anchor, which are close to the annular magnetized structure of the escape wheel 36. It is noted that the individual magnetic pairs exhibit periodic curves with the angular period PA of the annular magnetized structure, this angular period PA being equal to 30°, i.e. 360°/N with N=12 corresponding to the number of angular periods of the annular magnetized structure of the Picture 7 . Then, we see that the individual magnetic torque generated by the axis 42 is predominant. Finally, given that the two axes 18A and 42 have between them a relatively small angular offset with respect to the angular period PA of the structured magnetic layer 38A, the first parasitic magnetic torque ( Figure 8C ) has a curve 44 close to that of the Figure 8B , also with a period PA, these two curves having a certain phase difference between them.

Preferably, the magnetic compensation pin 32A is arranged so that the individual magnetic torque, constituting the second parasitic magnetic torque, which it exerts on the escape wheel has an angular phase shift of 180° with the first magnetic torque. parasitic, and not with the individual magnetic torque of the ferromagnetic axis 42 ( Figure 8B ), although the latter is largely predominant. Then, given that the first set of magnetic elements, which consists of functional magnetic elements, comprises two functional magnetic elements, the pin 32A is dimensioned so as to optimize the compensation that it produces, in particular its diameter and/or its distance from the axis of rotation 21 is/are adjusted so that the maximum absolute value of the second parasitic magnetic torque, generated by the compensation pin 32A, best compensates for the first parasitic magnetic torque and that the resulting torque, whose curve 46 is given at the Figure 8D , from the addition of first and second parasitic magnetic couples thus have the smallest possible amplitude, that is to say the smallest possible maximum absolute value.

Thanks to the configuration of the structured magnetic layer 38A, therefore of the annular magnetic structure that it forms, and to the arrangement of the magnetic compensation pin 32A, the maximum absolute value V4 of the torque resulting from the addition of the first and second aforementioned parasitic magnetic torques is less than 30% of the maximum absolute value V3 of the first parasitic magnetic torque. Indeed, in the example described, it is observed that the ratio between the maximum absolute value V4 of the curve 46 and the maximum absolute value V3 of the curve 44 gives approximately 1/5.

An improvement is proposed in the described variant of the second embodiment in that the compensation pin 32A is arranged so that its position relative to the axis of rotation 21 can be adjusted to adjust the angular phase shift and/or the value maximum absolute value of the second parasitic magnetic torque (curve 44) and thus optimize the curve of the resulting torque (curve 46), in particular the maximum absolute value V4 of this resulting torque, that is to say reduce this maximum absolute value at the smallest possible value. More specifically, the pin 32A forms an eccentric that the watchmaker can turn using a tool to adjust its distance from the axis of rotation and therefore from the annular magnetic structure. If it is desired not to vary the angular position of the compensation pin, it is possible in a variant to arrange the compensation pin in a kind of radial slide. A person skilled in the art will know how to provide the means necessary for adjusting the radial and/or angular position of this compensation pin.

With reference to Figures 9 and 10 , a third embodiment of the invention will be described below. This third embodiment differs from the first embodiment only in that the single pin of compensation of the second embodiment is replaced by two compensation pins 50, 52 similar to the magnetic axis 18 which here constitutes all the functional magnetic elements considered (this magnetic axis considered can be either the axis of the anchor, or the axis of an intermediate mobile meshing with the escapement wheel 6A). The two compensation pins are arranged so that the two individual magnetic torques which they respectively exert on the escape wheel are out of phase respectively by 120° and 240° (equivalent to -120°) relative to the first parasitic magnetic torque generated by the magnetic axis 18. In other words, in the present case, the two magnetic compensation elements 50, 52 have relative to each other an angular offset whose remainder of the integer division by the angular period PA is equal to 360°/(3·N) where N is the number of angular periods of the annular magnetized structure, ie N=6 in the example considered. Then, as here only a functional magnetic element 18 is considered, the two compensating magnetic elements are arranged so as to present, relative to the functional magnetic element, two angular offsets including the two remainders of the integer division of each of them by the angular period PA are respectively equal to 360°/3·N and 720°/3·N, i.e. 20° and 40° (note that PA = 60°). In addition, the two magnetic compensation pins 50 and 52 are arranged so as to distribute these two compensation pins and the magnetic axis 18 as evenly as possible around the axis of rotation to minimize friction in the bearings of the wheel. exhaust due to the magnetic attraction exerted by each of them on the annular magnetized structure of this wheel.

To the Picture 10 is given the curve 54 of the resultant torque exerted overall by the two compensating pins and the functional magnetic element of the Figure 9 . First, it is observed that the maximum absolute value V5 of curve 54 is relatively low. It is less than 20% of the maximum absolute value V1 of the first parasitic magnetic torque (see Figure 4 ). Then the curve 54 is periodic and has a period angular period equal to one third of the angular period PA of the annular magnetized structure, ie an angular period equal to PA/3. It is thus realized that the arrangement of two compensation pins, with the aforementioned angular offsets relative to the magnetic axis 18, generates a second parasitic magnetic torque which makes it possible to compensate for the two first harmonics (n=1, 2) of the decomposition in Fourier series of the first parasitic magnetic torque generated by the functional magnetic axis. On the other hand, the third harmonic is reinforced, which is why a periodic curve 54 is obtained with a period equal to PA/3. As the third harmonic (n=3) has a relatively low amplitude, the resulting torque curve has a maximum absolute value V5 which is much lower than the corresponding values V2 and V4 of the two preceding embodiments. By taking the escapement wheel 36 of the second embodiment, it is possible to further reduce this maximum absolute value, as appears at Picture 12 .

With reference to Figures 11 and 12 , a fourth embodiment will be described. This fourth embodiment differs from the second embodiment in that the single magnetic compensation pin of the second embodiment is replaced here by two magnetic compensation pins 32B and 32C which are arranged in an equivalent manner to the third embodiment . We are therefore in a case where the first set of magnetic elements comprises a plurality of functional magnetic elements, i.e. two magnetic axes in the variant described, and the second set of magnetic elements comprises a plurality of magnetic compensation elements, i.e. two pins in this variant. The two compensation pins are arranged so that the two individual magnetic torques which they respectively exert on the escape wheel are out of phase respectively by 120° and 240° relative to the first parasitic magnetic torque generated globally by the two magnetic axes 18A and 42. In other words, the two magnetic compensating elements present here relative to each other an angular offset whose remainder of the integer division by the angular period PA is equal to 360°/(3·N) where N is the number of angular periods of the annular magnetized structure, or N=12 in the example considered. This remainder is therefore equal to 10° so that the angle DA5 between the two pins 32B and 32C is equal to 40° in the example shown in Picture 11 , or at an angular period (equal to 30°) to which the remainder of 10° is added. It will be noted that since the effect of the axis 18A of the anchor is taken into account, the angle DA6 between the axis 42 and the pin 32B does not correspond to an integer period PA to which one adds or subtracts 10°, although this angle DA6 approaches it due to the fact that the axis 42 is predominant in the first parasitic magnetic torque generated by the two functional magnetic elements on the escape wheel.

The curve 60 of the torque resulting from the addition of the first parasitic magnetic torque, globally generated by the first set of magnetic elements, with the second parasitic magnetic torque, globally generated by the second set of magnetic elements, is shown in Picture 12 . In other words, the resulting torque is the result of the addition of all the individual parasitic magnetic torques that are considered. The annular magnetized structure of the fourth embodiment is configured and the two magnetic compensation elements are arranged so that the maximum absolute value V6 of the resulting torque is less than 15%, or even 12% of the maximum absolute value V3 (see Figure 8C ) of the first parasitic magnetic couple. A person skilled in the art can optimize the system by specifically configuring the two compensation pins which are preferably identical, in particular their respective diameters and their respective distances from the axis of rotation. It will be noted in particular that the two pins 32B and 32C are not here respectively identical, in their respective configurations and their relative arrangement on the periphery of the escapement wheel 36, to the two axes 18A and 42. If such were the case, one would in fact be in a variant of the second embodiment in which the two pins would together form a group of magnetic elements to be considered as an inseparable whole and not individually, that is to say not as two distinct compensation elements whose individual parasitic magnetic couples could present different phase shifts relative to the first magnetic couple parasite and selected as described above. Indeed, in the context of the fourth embodiment, to obtain the desired effect, namely to best compensate the first two harmonics of the curve of the first parasitic magnetic torque (see Figure 8C ) and thus minimize the amplitude of the disturbing torque on the escape wheel, it is preferably necessary for the two compensation pins to be in their respective configurations, in particular their dimensions and the material from which they are made, and their respective arrangements relative to the axis of rotation, in particular the distance to this axis of rotation, substantially identical to the compensation pin 32A of the second embodiment which optimizes the result of this second embodiment or that they have the same effect as this compensation pin 32A on the annular magnetic structure.

Generally, in the context of the third and fourth embodiments, the second set of magnetic elements consists of K magnetic compensation elements or K groups of magnetic compensation elements having substantially the same configuration, K being an integer greater than one (K>1). The K magnetic compensation elements or groups of magnetic compensation elements are arranged so that K parasitic magnetic couples, generated on the rotating element provided with the annular magnetized structure respectively by these K magnetic compensation elements or groups of magnetic elements compensation, have relative to the first parasitic magnetic torque, generated by functional magnetic elements, respectively K phase shifts angles which are respectively equal to substantially J 360°/(K+1) with J being an integer ranging from one to K, i.e. J = 1, ..., K.

In a preferred mode, the integer K is equal to two (K=2) and the two magnetic compensation elements or groups of magnetic compensation elements are similar to each other, one of the two magnetic compensation elements or groups of elements compensation magnets having relative to each other an angular offset whose remainder of the integer division by said angular period is equal to 360°/(3·N), N being the number of periods in a range of 360° of the curve of the first parasitic magnetic couple.

In other embodiments, in which the integer K is greater than two (K>2), the K compensating magnetic elements or groups of compensating magnetic elements are similar to each other and a certain compensating magnetic element or group of magnetic compensation elements, among said K magnetic compensation elements or groups of magnetic compensation elements, has relative to the other magnetic compensation elements or groups of magnetic compensation elements K-1 angular offsets whose K-1 remainders of the integer division of each of them by the angular period are respectively equal to J 360°/[(K+1) N] with J being an integer ranging from one to K-1, i.e. J = 1 , ..., K-1.

Finally, in a particular embodiment in which the first set of magnetic elements considered consists of a single functional magnetic element, the positive integer N is thus equal to a number of angular periods that the annular magnetized structure and the K compensating magnetic elements are arranged in such a way as to present, relative to the single functional magnetic element, K angular offsets whose K remainders of the integer division of each of them by the angular period are respectively equal to J 360°/[( K+1) N] with J being an integer ranging from one to K, i.e. J = 1, ..., K.

Claims (14)

1. Timepiece movement comprising a mechanism consisting of a rotating element (6A; 36), provided with an annular magnetized structure (12A-12B; 38A) exhibiting an angular variation of at least one physical parameter defining said annular magnetized structure, and of a first set of magnetic elements which is formed of one functional magnetic element (18) or of a plurality of functional magnetic elements (18A, 42), this first set of magnetic elements not being integral in rotation with said rotating element and having overall with the annular magnetized structure a first magnetic interaction which generates on said rotating element a first magnetic disturbance torque (30; 44); characterized in that the timepiece movement further comprises a second set of magnetic elements which consists of a magnetic compensation element (32; 32A) or of a plurality of magnetic compensation elements (32B,32C; 50,52) not forming part of any timepiece movement mechanism, this second set of magnetic elements not being integral in rotation with said rotating element and having overall with the annular magnetized structure a second magnetic interaction which generates on said rotating element a second magnetic disturbance torque; and in that the second set of magnetic elements is arranged relative to the first set of magnetic elements such that the maximum absolute torque value (34; 46) resulting from the addition of the first and second magnetic disturbance torques is lower than the maximum absolute value of the first magnetic disturbance torque.
2. Timepiece movement according to claim 1, characterized in that the first magnetic disturbance torque (30; 44) as a function of the angular position of said rotating element (6; 6A, 36) defines a first sinusoidal type curve having an angular period (PA) equal to 360°/N, with N being an integer number greater than one (N > 1); and in that the second set of magnetic elements is arranged relative to the first set of magnetic elements such that the second magnetic disturbance torque as a function of the angular position of said rotating element defines a second sinusoidal type curve also having said angular period, and such that the first and second magnetic disturbance torques exhibit therebetween an angular phase shift substantially equal to 180°.
3. Timepiece movement according to claim 2, characterized in that the second set of magnetic elements consists only of said magnetic compensation element (32A); and in that the annular magnetized structure (38A) is configured and said magnetic compensation element is arranged such that the maximum absolute value of said resultant torque is less than 30% of the maximum absolute value of the first magnetic disturbance torque.
4. Timepiece movement according to claim 2, characterized in that the second set of magnetic elements consists of K magnetic compensation elements (32B, 32C; 50, 52) or K groups of magnetic compensation elements substantially having the same configuration, K being an integer number greater than one (K > 1); and in that said K magnetic compensation elements or groups of magnetic compensation elements are arranged such that K individual magnetic disturbance torques generated on the rotating element respectively by said K magnetic compensation elements or groups of magnetic compensation elements, exhibit relative to said first magnetic disturbance torque respectively K angular phase shifts which are respectively equal to substantially J·360°/(K+1) with J being an integer number ranging from one to K, i.e. J = 1, ..., K.
5. Timepiece movement according to claim 4, wherein the integer number K is equal to two (K = 2), characterized in that the two magnetic compensation elements (32B, 32C; 50, 52) or groups of magnetic compensation elements are similar to each other, one of the two magnetic compensation elements or groups of magnetic compensation elements exhibiting relative to the other an angular offset whereby the remainder of the integer division by said angular period is equal to 360°/(3·N).
6. Timepiece movement according to claim 5, characterized in that the annular magnetized structure (38A) is configured and the two magnetic compensation elements are arranged such that the maximum absolute value of said resultant torque is less than 15% of the maximum absolute value of the first magnetic disturbance torque.
7. Timepiece movement according to claim 4, wherein the integer number K is greater than two (K > 2), characterized in that said K magnetic compensation elements or groups of magnetic compensation elements are similar to each other, a certain magnetic compensation element or group of magnetic compensation elements among said K magnetic compensation elements or groups of magnetic compensation elements exhibiting relative to the other magnetic compensation elements or groups of magnetic compensation elements K-1 angular offsets whereby the K-1 remainders of the integer division of each by the angular period are respectively equal to J·360°l[(K+1)·N] where J is an integer number ranging from one K-1, i.e. J = 1, ..., K-1.
8. Timepiece movement according to any of claims 4 to 7, wherein the first set of magnetic elements considered consists only of said functional magnetic element (18), the positive integer number N thus being equal to a number of angular periods exhibited by the annular magnetized structure; characterized in that said K magnetic compensation elements (50, 52) are arranged to exhibit relative to said functional magnetic element K angular offsets whereby the K remainders of the integer division of each by said angular period are respectively equal to J·360°/[(K+1)·N] where J is an integer number ranging from one to K, namely J = 1, ..., K.
9. Timepiece movement according to any of the preceding claims, characterized in that said rotating element is a magnetic escape wheel (6A, 36) forming a magnetic escapement.
10. Timepiece movement according to claim 9, characterized in that said functional magnetic element is a shaft (18; 18A) of a magnetic pallet fork (8; 8A) also forming said magnetic escapement, said shaft being formed by a ferromagnetic material; and in that the annular magnetized structure defines magnetic barriers (16, 17; 17A) for the magnetic pallet fork which are angularly offset by said angular period (PA).
11. Timepiece movement according to claim 9 or 10, characterized in that said magnetic compensation element is a pin arranged at the periphery of the magnetic escape wheel and formed by a ferromagnetic material.
12. Timepiece movement according to any of claims 9 to 11, characterized in that the annular magnetized structure has a constant thickness, said angularly variable physical parameter being the radial width of said annular magnetized structure.
13. Timepiece movement according to any of claims 9 to 12, characterized in that the annular magnetized structure (38A) is configured such that the external profile thereof is circular and continuous.
14. Timepiece movement according to any of the preceding claims, characterized in that said magnetic compensation element (32A) is arranged such that the position thereof relative to said rotating element can be adjusted to regulate said angular phase shift and to optimise said maximum intensity of said resultant torque.

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