EP2979139B1 - Pivoting train arbor of a timepiece - Google Patents

Description

Field of the invention

The invention relates to a mobile rotating watch-making shaft, said shaft being made in one or more aligned parts.

The invention also relates to a rotating clock watch comprising such a shaft.

The invention also relates to a clockwork mechanism comprising such a shaft and / or such a mobile, including an escape mechanism.

The invention also relates to a watch movement comprising such a shaft and / or such a mobile and / or such a mechanism.

The invention also relates to a timepiece, including a watch, including such a shaft and / or such a mobile, and / or such a mechanism, and / or such a movement.

The invention relates to the field of watch mechanisms, in particular the field of regulating members, in particular for mechanical watches.

Background of the invention

The regulating organ of a mechanical watch is constituted by a harmonic oscillator, the sprung balance, whose oscillation natural frequency depends mainly on the inertia of the balance and the elastic rigidity of the spiral.

The oscillations of the sprung balance, otherwise damped, are maintained by the pulses provided by an escapement generally composed of one or two pivoting mobiles. In the case of the Swiss lever escapement, these pivoting mobiles are the anchor and the escape wheel. The march of the watch is determined by the frequency of the sprung balance and by the disturbance generated by the impulse of the escapement, which generally slows down the natural oscillation of the sprung balance and thus causes a delay in running.

The march of the watch is therefore disturbed by all the phenomena that can alter the natural frequency of the sprung balance and / or the time dependence of the impulse provided by the escapement.

In particular, following the transient exposure of a mechanical watch to a magnetic field, gait defects (related to the residual effect of the field) are generally observed. The origin of these defects is the permanent magnetization of the fixed ferromagnetic components of the movement or the cladding and the permanent or transient magnetization of the moving magnetic components forming part of the regulating organ (sprung balance) and / or the exhaust .

After exposure to the field, magnetically or magnetically permeable mobile components (balance, hairspring, exhaust) are subjected to magnetostatic torque and / or magnetostatic forces. In principle, these interactions modify the apparent rigidity of the sprung balance, the dynamics of the escape mobiles and the friction. These modifications produce a fault that can range from a few tens to a few hundred seconds a day.

The interaction of the watch movement with the external field, during the exhibition, can also lead to the stop of the movement. In principle, the arrest in the field and the residual run-out are not correlated, because the arrest in field depends on the transient magnetization, sub-field, of the components (and therefore of the permeability and the saturation field). components), while the residual run fault depends on the residual magnetization (and therefore, mainly, the coercive field of the components) which can be low even in the presence of a significant magnetic permeability.

After the introduction of spirals made of very weakly paramagnetic materials (for example, silicon), the spiral is no longer responsible for the lack of running watches. The magnetic disturbances still observable for magnetization fields below 1.5 Tesla are therefore due to the magnetization of the balance shaft and to the magnetization of the escapement wheels.

The anchor body and the escape wheel can be made of very low paramagnetic materials, without their mechanical performance being affected. On the contrary, the shafts of the mobiles require very good mechanical performances (good tribology, low fatigue) to allow an optimal and constant pivoting in the time, and it is therefore preferable to manufacture them in hardened steel (typically carbon steel type 20AP or the like). However, such steels are materials that are sensitive to magnetic fields because they have a high saturation field combined with a high coercive field. The balance, anchor and escape wheel shafts are currently the most critical components in the face of the magnetic disturbances of the watch.

Document D1 WO 2004/008258 A2 DETARPATEK PHILIPPE describes a rotor-stator system consisting of a wheel consisting of a pre-magnetized permanent magnet in a fixed diametral direction, as well as an oscillator maintenance solution. This document discloses a production shaft of an electromagnetic torque on which are mounted a rotor and a second pinion, which are not parts of the shaft but are mounted on the shaft, this shaft being a standard shaft without any property specific magnetic.

Document D2 US 3,683,616 A STEINEMANN (STRAUMANN Institute), describes an escapement mechanism where all the parts mounted on the balance shaft, and on the anchor, the escape wheel, as well as at least the main part of the balance shaft are manufactured from a very weakly paramagnetic material, having a magnetic permeability μ less than 1.01. One variant relates to the application of a layer at least at the points of support of the balance shaft. In particular variants, some of the components of the exhaust are formed solely from such a very weakly paramagnetic material. The hairspring can, for its part, be made of such a very weakly paramagnetic material, or an anti-ferromagnetic metal having a magnetic permeability μ less than 1.01. In still another variant, parts mounted on the balance shaft are formed from a material selected from the group consisting of monel, silver, nickel, copper, a beryllium alloy, and a copper-manganese alloy or a nickel alloy. In yet another variant, the anchor and the escape wheel are formed of a material selected from the group consisting of silver, nickel, a copper-beryllium alloy, and a nickel alloy. or manganese-copper.
More particularly, the balance shaft comprises trunnions, and, with the exception of the bearing pins, is integrally formed from a material having a magnetic permeability μ less than 1.01. In another variant, the assembly of the balance shaft is formed of a material having a magnetic permeability μ less than or equal to 1.01. The balance shaft may, again, be made of a hardenable bronze.

Document D3 CH 705 655 A2 ROLEX describes the minimization of the residual effect, that is to say, the difference in the running of a watch subjected to variations in external magnetic fields. This minimization is correlated as a surprising effect, with the geometry of the axis of the balance. More particularly, this document describes an oscillator comprising a spiral made of paramagnetic or diamagnetic material, and an assembled balance wheel comprising a shaft on which are mounted a balance, a plate, a shell integral with the spiral, and where, or the maximum diameter of the shaft is less than 3.5 / 2.5 / 2.0 times the minimum diameter of the shaft on which one of the other elements is mounted, or the maximum diameter of the shaft is less than 1.6 / 1.3 times the maximum diameter of the shaft on which is mounted one of the other elements. This document discloses a tree having homogeneous intrinsic magnetic properties, in this case a strongly ferromagnetic tree. However, the plateau is not an integral part of the tree. The document DE 11 74 518 B discloses a monobloc alloy shaft based on the elements Fe, Ni, Co, Cr, Mo, W in combination with Be, Ti, Nb, Ta and C. These alloys have low magnetic properties with good mechanical properties.

Summary of the invention

The invention proposes to limit the magnetic interaction on the shafts of a watch mechanism, within a movement incorporated into a timepiece, in particular a watch.

To this end, the invention relates to a mobile rotating watchmaking tree, said shaft being made in one or more aligned parts, characterized in that said shaft is magnetically inhomogeneous.

According to one characteristic of the invention, said shaft is magnetically inhomogeneous with a variation of the intrinsic magnetic properties of said shaft radially with respect to said pivot axis.

According to one characteristic of the invention, said shaft is magnetically inhomogeneous with a variation of the intrinsic magnetic properties of said shaft radially with a symmetry of revolution with respect to said pivot axis.

The invention also relates to a rotating clock watch comprising such a shaft.

The invention also relates to a clockwork mechanism comprising such a shaft and / or such a mobile, including an escape mechanism.

The invention also relates to a watch movement comprising such a shaft and / or such a mobile and / or such a mechanism.

The invention also relates to a timepiece, including a watch, including such a shaft and / or such a mobile, and / or such a mechanism, and / or such a movement.

Brief description of the drawings

• la figure 1 représente, sous forme d'un schéma tridimensionnel, une première variante d'arbre de mobile selon l'invention, comportant une zone centrale de propriétés magnétiques intrinsèques différentes de celles de la zone périphérique qui entoure cette zone centrale axée sur l'axe de pivotement du mobile ;
• la figure 2 représente, de façon schématisée, en vue en coupe et avec une coloration grisée d'autant plus intense que le champ rémanent est élevé, un arbre homogène de l'art antérieur après son exposition à un champ magnétique ;
• la figure 3 représente, de façon schématisée et similaire à la figure 2, l'arbre de la figure 1, avec un champ rémanent concentré sur sa zone centrale et axiale ;
• la figure 4 illustre, sous forme d'un graphe, la comparaison des couples magnétiques exercés sur ces deux modèles d'arbres de balancier de la figure 2 et de la figure 3, le graphe G2 correspondant à l'arbre homogène de la figure 2 est représenté en trait interrompu, et le graphe G3 correspondant à l'arbre inhomogène selon l'invention est représenté en trait continu. En abscisse figure l'angle en degrés, et en ordonnée le couple exercé sur le balancier, en mN.mm ;
• la figure 5 illustre, sous forme d'un graphe, la comparaison des couples magnétiques exercés sur ces deux modèles d'arbres de balancier de la figure 2 et de la figure 3, comparés au couple de rappel du spiral et au couple appliqué au balancier par l'ancre. Le graphe G2 correspondant à l'arbre homogène de la figure 2 est représenté en trait interrompu, et le graphe G3 correspondant à l'arbre inhomogène selon l'invention est représenté en trait continu. Le trait mixte interrompu G4 représente le couple de rappel exercé par le spiral. Le couple d'entretien, appliqué au balancier par l'ancre, est représenté sous la forme d'une horizontale G5 en trait pointillé.
• la figure 6 représente, de façon similaire à la figure 1, une deuxième variante d'arbre de mobile selon l'invention, comportant une partie médiane de propriétés magnétiques intrinsèques différentes de celles de deux zones d'extrémité qui entourent cette partie médiane, de part et d'autre selon la direction de l'axe de pivotement du mobile ;
• la figure 7 représente, de façon analogue à la figure 3, la répartition du champ rémanent sur l'arbre de la figure 6, avec un champ rémanent concentré sur ses deux zones d'extrémité axiales ;
• la figure 8 représente, sous forme d'un schéma-blocs, une pièce d'horlogerie, comportant un mouvement comportant un mécanisme comportant un mobile équipé d'un arbre selon l'invention.

Other features and advantages of the invention will appear on reading the detailed description which follows, with reference to the appended drawings, in which:

• the figure 1 represents, in the form of a three-dimensional diagram, a first variant of a mobile tree according to the invention, comprising a central zone of intrinsic magnetic properties different from those of the peripheral zone which surrounds this central zone centered on the pivot axis mobile
• the figure 2 represents schematically, in sectional view and with a greyish color all the more intense as the remnant field is high, a homogeneous tree of the prior art after exposure to a magnetic field;
• the figure 3 represents, schematically and similar to the figure 2 , the tree of the figure 1 , with a remnant field concentrated on its central and axial zone;
• the figure 4 illustrates, in the form of a graph, the comparison of the magnetic couples exerted on these two models of balance figure 2 and some figure 3 , the graph G2 corresponding to the homogeneous tree of the figure 2 is shown in broken lines, and the graph G3 corresponding to the inhomogeneous tree according to the invention is shown in solid lines. On the abscissa is the angle in degrees, and in ordinate the torque exerted on the balance, in mN.mm;
• the figure 5 illustrates, in the form of a graph, the comparison of the magnetic couples exerted on these two models of balance figure 2 and some figure 3 , compared to the return moment of the hairspring and the torque applied to the balance by the anchor. The graph G2 corresponding to the homogeneous tree of the figure 2 is shown in broken lines, and the graph G3 corresponding to the inhomogeneous tree according to the invention is shown in solid lines. The interrupted mixed line G4 represents the return torque exerted by the spiral. The couple of maintenance, applied to the pendulum by the anchor, is represented in the form of a horizontal G5 dashed line.
• the figure 6 represents, similarly to the figure 1 a second variant of a mobile shaft according to the invention, comprising a median part of intrinsic magnetic properties different from those of two end zones which surround this median part, on either side according to the direction of the axis pivoting the mobile;
• the figure 7 represents, in a similar way to figure 3 , the distribution of the remnant field on the tree of the figure 6 , with a remnant field focused on its two axial end zones;
• the figure 8 represents, in the form of a block diagram, a timepiece, comprising a movement comprising a mechanism comprising a mobile equipped with a shaft according to the invention.

Detailed Description of the Preferred Embodiments

The object of the invention is to protect an oscillator from any magnetic disturbance.

The invention aims in particular at limiting the magnetic interaction on the shafts 1 of the moving parts 10 of a watch mechanism 20, within a movement 30 incorporated in a timepiece 40, in particular a watch, and in particular for the maintenance (exhaust) and control (sprung balance) components which constitute a preferred application on the balance wheel, anchor and escape wheel shafts.

The invention is described here for this application only to the maintenance (exhaust) and regulating (balance spring) components. The skilled person, watchmaker, will extrapolate it to other mechanisms.

The invention can allow watches with spiral, anchor body and nonmagnetic escape wheel to withstand, without stopping, magnetic fields of the order of a Tesla, and without the mechanical performance (chronometry and mobile aging) are affected.

The invention makes it possible to reduce the residual effect of watches with spiral, anchor body and non-magnetic escape wheel to less than one second per day.

The geometry of the shaft of a pendulum is generally more complex than the geometry of the anchor rod, and that of the shaft of the escape wheel. Two alternative variants, non-limiting, using the same principle are illustrated for the case of a balance shaft. Their generalization in the case of the anchor rod and the escape wheel, or other mobiles, will be obvious to the skilled person.

By convention, the term "axis" refers to a virtual geometric element such as a pivot axis, and "shaft" to a real mechanical element, made in one or more parts. For example, a pair of pivots 2A and 2B aligned and reported on either side of a median portion 6 of a mobile 10, to guide it in pivoting is also called "tree".

In the remainder of the description, "magnetically permeable" materials are defined as materials having a relative permeability of between 10 and 10,000, such as steels, which have a relative permeability close to 100 for balance shafts for example. or around 4000 for steels commonly used in electrical circuits, or other alloys whose relative permeability reaches values of 8000 to 10000.

"Magnetic" materials, for example in the case of polar masses, will be called materials capable of being magnetized so as to have a residual field of between 0.1 and 1.5 Tesla, such as for example the "Neodymium Iron Boron". a magnetic energy density Em close to 512 kJ / m ³ and giving a residual field of 0.5 to 1.3 Tesla. A lower residual field level, towards the lower part of the range can be used when combining, in a magnetization couple, such a magnetic material with a magnetically permeable antagonist component of high permeability, closer to 10000, in the range of 100 to 10,000.

Ferromagnetic materials are materials whose characteristics are: saturation field Bs> 0 at temperature T = 23 ° C, coercive field Hc> 0 at temperature T = 23 ° C, maximum magnetic permeability μ _R > 2 at the temperature T = 23 ° C, Curie temperature Tc> 60 ° C. More particularly, those whose characteristics are: saturation field Bs <0.5 T at temperature T = 23 ° C, coercive field Hc <1000 kA / m at temperature T = 23, will be described as "weakly ferromagnetic". ° C, maximum magnetic permeability μ _R <10 at temperature T = 23 ° C, Curie temperature Tc> 60 ° C.

The possibility of using ferromagnetic materials with specific characteristics makes it possible simultaneously to satisfy the demand for mechanical strength, magnetic resistance, and manufacturability of the components.

More particularly, those whose characteristics are: saturation field Bs> 1 T at temperature T = 23 ° C, coercive field Hc> 3,000 kA / m at temperature T = 23 ° C, will be described as "strongly ferromagnetic". , maximum magnetic permeability μ _R > 50 at temperature T = 23 ° C, Curie temperature Tc> 60 ° C

"Paramagnetic" materials will be referred to as materials having a relative magnetic permeability of between 1.0001 and 100, for example for spacers interposed between a magnetic material and a magnetically permeable antagonist component, or alternatively between two magnetic materials, for example a spacer between a component and a polar mass. Low paramagnetic materials, having magnetic permeability of between 1.01 and 2, can be used for the implementation of the invention. Materials such as CoCr20Ni16 Mo7, known especially under the name "Phynox®" or nickel-phosphorus NiP (either with a concentration of 12% phosphorus but hardened, or with a concentration of phosphorus of less than 12%) are weakly paramagnetic, therefore usable for the implementation of the invention.

The use of non-magnetic materials (magnetic permeability less than 1.01) is very limiting, because these materials are either difficult to machine or mechanically unsuitable for the requested functions (and therefore require a coating or a hardening procedure making them ferromagnetic). which explains why the first watch resistant to 15'000 Gauss was presented only in 2013. For example, non-magnetic materials are: aluminum, gold, brass or similar.

"Diamagnetic" materials will be referred to as materials of relative magnetic permeability less than 1 (negative magnetic susceptibility, less than or equal to -10 ^-5 ), such as graphite or graphene.

Finally, we will call "soft magnetic" materials, not to say non-magnetic, especially for shielding, materials with high permeability but high saturation, because we do not want them to be permanently magnetized: they must drive the best possible the field, so as to reduce the field to their outside. Such components can then also protect a magnetic system from external fields. These materials are preferably chosen to have a relative magnetic permeability of between 50 and 200, and with a saturation field greater than 500 A / m.

Materials described as "non-magnetic" have a relative magnetic permeability very slightly greater than 1, and less than 1.0001, as typically silicon, diamond, palladium and the like. These materials can generally be obtained by MEMS technologies or by the "LIGA" process.

Thus, the one-piece shaft 1 of a rotating mobile watch 10 is made of one or more parts 2, which are then aligned on a pivot axis D.

It should be noted that this shaft 1 is a pivoting axial element, which serves as a support for other components: plate, flange, collar, balance, but which is not constituted by these other components, which are driven, glued, welded, brazed , or supported on the tree, or maintained by other methods. The characteristics presented below concern this single tree 1.

According to the invention, this one-piece shaft 1 is magnetically inhomogeneous.

The tree 1 according to the invention has intrinsic magnetic properties (permeability, saturation field, coercive field, Curie temperature, dependent hysteresis curve) which are non-uniform in its volume.

Remember that magnetization is not part of these intrinsic magnetic properties. The magnetization profile of such a tree after magnetization does not depend solely on the intrinsic magnetic properties, but depends in particular on the magnetic field source that magnetized it and the shape and size of said tree. For example, the tree may have non-uniform magnetization even if the intrinsic magnetic properties are uniform

Recall also that a component can not become, for example, ferromagnetic after being subjected to a magnetic field: a material is either ferromagnetic, or paramagnetic, antiferromagnetic or diamagnetic. The temperature can modify this characteristic but it can not be modified by an external field. It is important to differentiate the magnetization from the intrinsic magnetic properties of the material.

The invention proposes, in a particular case, to use, in a case where the tree is bi-material, either paramagnetic materials or ferromagnetic materials having well-defined intrinsic properties.

In particular, this one-piece shaft 1 is magnetically inhomogeneous, with a variation of the intrinsic magnetic properties of this one-piece shaft 1, either in the axial direction of the pivot axis D of the one-piece shaft 1, or radially with a symmetry of revolution relative to this pivot axis D, both in the axial direction of the pivot axis D and radially with a symmetry of revolution relative to this pivot axis D.

In a particular variant, the one-piece shaft 1 is magnetically inhomogeneous with a variation of the intrinsic magnetic properties radially with respect to the pivot axis D.

In a preferred embodiment, this variation of the intrinsic magnetic properties of the one-piece shaft 1 is made radially with a symmetry of revolution with respect to the pivot axis D.

By "inhomogeneous tree in the radial direction" is meant here that the magnetic properties of the shaft vary in the radial direction from the center of the shaft to the periphery (while the shaft may or may not be magnetically homogeneous in the axial direction).

Only the material located in the heart of the tree, in an area hereinafter called central zone 3, that is to say in the vicinity of the pivot axis D, has a high saturation field (Bs> 1 T ), a magnetic permeability μ _R maximum greater than 50, and a coercive field Hc greater than 3 kA / m (all these properties are typical of 20AP steel preferably used for pivoting shafts because of good mechanical performance). Naturally, if other materials are used, these threshold values must be adapted by routine tests.

While the material at the periphery of the shaft, in a zone hereinafter referred to as the peripheral zone 4, is either weakly paramagnetic or ferromagnetic with a low saturation field (Bs <0.5 T), a low maximum magnetic permeability μ _R <10, and a weak coercive field.

A diagram of this solution is shown in figure 1 which is a three-dimensional diagram of the first variant. The one-piece balance shaft 1 is composed of a strongly ferromagnetic central zone 3 (grayed out) and a paramagnetic or weakly ferromagnetic peripheral zone 4 (in white).

In this case, the two regions (strongly ferromagnetic in central zone 3 and weakly paramagnetic in peripheral zone 4 are precisely separated by a steep interface zone 7: the interface between the two regions 3 and 4 may however have a finite width, in correspondence with a regular gradient of the magnetic properties, without the results being affected, the strongly ferromagnetic region in the central zone 3 at the heart of the monobloc shaft 1 is preferably contained in a cylinder with a radius less than 100 micrometers (and centered on the pivot axis D) to achieve the desired performance.

In practice, the magnetic inhomogeneity described here can be obtained by combining two different materials (by brazing, welding or depositing one material on the other), or, in the case where an alloy is used (for example, steel carbon), by heat treatment or under electric or magnetic field of all or part of the finished component. More particularly, thermal and electromagnetic treatments are well suited for a well-defined treatment in space.

• en grisé foncé les zones avec un champ rémanent de 0,6T ;
• en grisé moyen les zones avec un champ rémanent de l'ordre de 0,2 à 0,4T ;
• et en gris très clair ou en blanc les zones avec un champ rémanent inférieur à 0,2T.

L'aimantation est supérieure en correspondance du rayon maximum de l'arbre.The figure 2 shows the prior art, in the form of a monobloc shaft 1 of conventional balance beam, homogeneous, made of steel AP. This figure illustrates the remanent field, after magnetization at 0.2 T. During this magnetization, this shaft is subjected to an external field of 0.2 T oriented in the direction orthogonal to the pivot axis, the shaft is magnetized throughout its volume, its residual field being between 0.3 T and 0.6 T, as shown in FIG. figure 2 which shows:

• in dark gray areas with a remnant field of 0.6T;
• in medium shaded areas with a remnant field of the order of 0.2 to 0.4T;
• and in very light gray or white areas with a remnant field less than 0.2T.

The magnetization is greater in correspondence of the maximum radius of the tree.

The figure 3 shows the remanent field of a monobloc shaft 1 radially inhomogeneous balance according to the first embodiment of the invention. This monoblock tree 1 has the same geometry as that of the figure 2 , but only the heart, in central zone 3, is made of steel AP, while its periphery, in peripheral zone 4, is weakly paramagnetic. The shaft is subjected to an external field of 0.2 T oriented in the direction orthogonal to the pivot axis D. The remanent field is about 0.4 T and concentrated in the core in central zone 3.

When the timepiece is subjected to the action of an external magnetic field, during the oscillation of the sprung balance, the magnetic shaft of the balance is subjected to a magnetic torque which tends to orient it in the direction of the external field. The moment of this pair may be high enough to stop the movement of this balance-spring.

Because of the highly differentiated magnetization, the homogeneous tree of the figure 2 is subjected to a magnetic torque, whose moment is more than 10 times higher than that which is applied to the inhomogeneous tree of the figure 3 . Indeed, the one-piece shaft 1 according to the invention comprises a remanent field field on a very small radius, whereas in the prior art the high remanent field areas are precisely in the areas of larger radius.

Stopping movement occurs if the torque acting on the shaft is greater than the restoring moment exerted by the hairspring for angles lower than the lifting angle, and the maintenance torque applied by the anchor to the balance. These two pairs, obtained for typical parameters, are compared with the magnetic torque acting on the homogeneous tree and on the inhomogeneous tree, on the graph of the figure 5 .

The figure 4 illustrates the comparison of the magnetic couples exerted on these two models of balance shafts: the graph G2 corresponding to the homogeneous tree of the figure 2 is shown in broken lines, and the graph G3 corresponding to the inhomogeneous monobloc shaft 1 according to the invention (first variant of the figure 3 , or second variant of the figure 7 explained later) is shown in solid lines. On the abscissa is the angle in degrees, and in ordinate the torque exerted on the balance, in mN.mm. In both cases, the torque varies sinusoidally with the rotation angle of the balance spring (here zero is fixed arbitrarily).

The homogeneous tree of the figure 2 is subjected to a magnetic torque much greater than the pair of the spiral and the maintenance torque. In this case, the sprung balance will be stopped for a field smaller than 0.2 T.

The inhomogeneous monobloc shaft 1 according to the first variant of the invention is subjected to a torque less than the torque exerted by the spiral in the angle of lift (<30 °) and the maintenance torque. In this case, the sprung balance will not be stopped under a field of 0.2 T.

The figure 5 illustrates the comparison of the magnetic pairs on a balance shaft, homogeneous according to the prior art, and inhomogeneous according to the invention (first variant, or second variant exposed later), imposed by an external field of 0.2 T, compared to torque of the spiral and the torque applied to the balance by the anchor. In the same way as figure 4 , the figure 5 illustrates the comparison, on a small angular amplitude, of the magnetic couples exerted on these two models of balance shafts: the graph G2 corresponding to the homogeneous tree is shown in broken lines, and the graph G3 corresponding to the inhomogeneous tree is shown in solid line. The interrupted mixed line G4 represents the return torque exerted by the spiral. The maintenance torque, applied to the balance by the anchor, is represented in the form of a horizontal G5 dotted line.

As a result of the magnetization of the watch, the one-piece shaft 1 of the balance 10 is immersed in the magnetic field created by the fixed ferromagnetic components of the movement 30, or / and the timepiece 40, of which it is part. The one-piece shaft 1 is then subjected to a torque similar to that shown in FIG. figure 4 but from a weaker moment. This disturbance torque is responsible for the residual running error. A movement equipped with an inhomogeneous monobloc shaft 1 according to the first variant of the invention is therefore affected by a walking defect which is between 3 and 10 times less than that which affects a movement equipped with a traditional homogeneous tree.

The second variant of the invention relates to a shaft which is inhomogeneous in the axial direction, parallel to the axis of pivoting of the shaft.

The inhomogeneity of the magnetic properties is this time realized in the axial direction. The ends 2 of the monobloc shaft 1, constituted by the pivots 2A and 2B, which must have optimum mechanical properties, are generally made of magnetic materials, while the middle part 6 of the monobloc shaft 1 is made of weakly paramagnetic material.

The length (in the axial direction) accumulated of the magnetic parts of the one-piece shaft 1 is advantageously less than one third of the total length of the one-piece shaft 1.

The difference in length between the magnetic parts is advantageously kept below 10%.

This second variant is schematized on the figure 6 , on which preferably only the pivots 2A and 2B are made of ferromagnetic material.

The monobloc shaft 1 of the figure 6 comprises, in the direction of the pivot axis D, a median portion 6 surrounded on both sides by two end zones 8. And only these end zones 8, preferably made of pivoted steel, have a high saturation field of Bs greater than 1 T, a maximum magnetic permeability μ _R greater than 50, and a coercive field Hc greater than 3 kA / m. While the material in the middle part 6 is either weakly paramagnetic or ferromagnetic with a low saturation field Bs of less than 0.5 T, a low maximum magnetic permeability μR less than 10, and a low coercive field.

• une partie médiane paramagnétique avec 2>µ>1.01 ;
• une partie médiane amagnétique (tel que défini plus haut) ;
• une partie médiane paramagnétique avec µ<1.01, et dont le volume est inférieur au volume de la partie ferromagnétique, pourvu que le volume de la partie ferromagnétique soit inférieur à une valeur $$\mathrm{X}={\mathrm{\delta }}_{\mathrm{m}}\left({\mathrm{C}}_{\mathrm{ech}}+k{\mathrm{\theta }}_{\mathrm{l}}\right)/\left(b{\mathrm{\mu }}_0{B}_{\mathrm{s}}H{\mathrm{\theta }}_{\mathrm{l}}\right)$$
  

où, pour un arbre 1 qui est un arbre de balancier d'un ensemble balancier-spiral de mouvement de montre, X est fonction du défaut de marche relatif maximal souhaité δ_m, (généralement δ_m = 10^-4) de la rigidité du spiral k, du couple d'entretien maximal du balancier C_ech, de l'angle de levée θ_l, de la perméabilité du vide µ₀, du champ de saturation B_s de la partie ferromagnétique de l'arbre et du champ d'aimantation maximal H que la montre est censée supporter sans dépasser le défaut relatif δ_m. Le coefficient b est un facteur, de l'ordre de l'unité si les autres quantités sont exprimées dans le système internationale, et qui dépend de la forme géométrique de l'arbre X est typiquement compris entre 0.1 mm³ et 1 mm³. Comme pour la première variante, le champ rémanent est inférieur (et plus localisé) que dans le cas d'un arbre homogène selon la figure 2, comme le montre la figure 7.More particularly, in this type of execution of the figure 6 we can have advantageous choices:

• a paramagnetic median part with 2>μ>1.01;
• a non-magnetic medial portion (as defined above);
• a paramagnetic median part with μ <1.01, and whose volume is smaller than the volume of the ferromagnetic part, provided that the volume of the ferromagnetic part is less than a value $$\mathrm{X}={\mathrm{\delta }}_{\mathrm{m}}\left({\mathrm{VS}}_{\mathrm{ech}}+k{\mathrm{\theta }}_{\mathrm{l}}\right)/\left(b{\mathrm{\mu }}_0{B}_{\mathrm{s}}H{\mathrm{\theta }}_{\mathrm{l}}\right)$$
  

where, for a shaft 1 which is a balance shaft of a pendulum balance-spring assembly, X is a function of the desired maximum relative running defect δ _m , (generally δ _m = 10 ^-4 ) of the rigidity of the spiral k, the maximum maintenance torque of the balance C _ech , the lifting angle θ _l , the vacuum permeability μ ₀ , the saturation field B _s of the ferromagnetic part of the shaft and the field of maximum magnetization H that the watch is supposed to support without exceeding the relative defect δ _m . The coefficient b is a factor, of the order of one unit if the other quantities are expressed in the international system, and which depends on the geometric shape of the X-tree is typically between 0.1 mm ³ and 1 mm ³ . As for the first variant, the remanent field is smaller (and more localized) than in the case of a homogeneous tree according to the figure 2 as shown in figure 7 .

This figure 7 represents the remanent field, after magnetization at 0.2 T, of a one-piece integral shaft 1 of inhomogeneous balance according to the second variant of the invention. The pivots are made of 20 AP steel. The middle part 6 is weakly paramagnetic.

The torque acting on the one-piece shaft 1 in this case is equivalent to that obtained for the first variant ( Figure 4 and Figure 5 ).

In practice, as for the first variant, the desired magnetic inhomogeneity can be obtained by combining two different materials (by brazing, welding or depositing one material on the other) or, in the case where an alloy is used (by carbon steel), by heat treatment or under electric or magnetic field of all or part of the finished component.

It is still possible to mix the first and second variants, the monobloc shaft 1 is then magnetically inhomogeneous with a variation of its intrinsic magnetic properties both in the axial direction of the pivot axis D and radially relative to to this pivot axis D.

In one or the other of these variants, the invention is easy to implement and inexpensive, since, in practice, a simple two-material embodiment makes it possible to obtain the desired result. For example, an embodiment according to the first variant with a balance rod constituting the peripheral zone 4 which is produced, according to the desired inertia, of aluminum, gold, brass or the like, while the central zone 3 is made in the form of a 20AP steel bar or similar: a low inertia beam is obtained with a light alloy serge, in particular of aluminum, easy to machine and to drill through, and a core of drawn or drawn steel, or cleavage, with a diameter less than 100 micrometers. Similarly, a rocker according to the second variant and with very low inertia has a machined middle portion 6 of aluminum alloy and having at its axial ends two housings for driving pivots 2A and 2B pivoted steel.

• cas fortement ferromagnétique / faiblement ferromagnétique ;
• cas fortement ferromagnétique / faiblement paramagnétique avec 2>µ>1.01, malgré un préjugé considérant un tel matériau comme inutilisable pour ce type de construction. Notamment le « Phynox » rentre dans cette gamme de matériaux ;
• cas où la portion (masse) paramagnétique de l'arbre n'est pas la portion (masse) principale. Des solutions où la portion ferromagnétique est dominante sont efficaces et inclues dans la présente demande : les dimensions maximales (absolues) de la portion fortement ferromagnétique sont déterminées uniquement par la rigidité du spiral et le couple d'entretien (voir équation (1)).

The following bi-material achievements give good results, despite contrary teachings of the literature:

• strongly ferromagnetic / weakly ferromagnetic case;
• strongly ferromagnetic / weakly paramagnetic case with 2>μ> 1.01, despite a prejudice considering such a material as unusable for this type of construction. In particular, the "Phynox" is part of this range of materials;
• case where the paramagnetic portion (mass) of the tree is not the main portion (mass). Solutions where the ferromagnetic portion is dominant are effective and included in the present application: the maximum (absolute) dimensions of the highly ferromagnetic portion are determined solely by the stiffness of the hairspring and the maintenance torque (see equation (1)).

In a particular embodiment, the shaft 1 comprises at least one projecting part of larger radius about its pivot axis D, and at least said projecting part is delimited, on either side of said pivot axis D, by two surfaces symmetrical with respect to said pivot axis D and which define, in projection on a plane perpendicular to said pivot axis D, a profile inscribed in a rectangle whose ratio of the length to the width defines a shape ratio which is greater than or equal to at 2, the direction of said length defining a main axis DP.

The invention also relates to a pivoting watchmaking wheel 10 comprising a one-piece shaft 1 according to the invention.

The invention also relates to a watchmaking mechanism comprising such a monobloc shaft 1 and / or such a mobile 10, in particular an escape mechanism.

In the particular embodiment set out above and where the shaft 1 comprises at least one such particular projecting part, this clockwork mechanism 20 comprises such a mobile 10 oscillating around a rest position defined by a rest plane passing through a pivot axis D, said mobile 10 being biased towards a rest position by elastic return means. And this mobile 10 comprises such a shaft 1 which comprises at least one such particular projecting part, this shaft 1 being made of steel, and said main axis DP of said shaft 1, in the plane orthogonal to said shaft, occupies a determined angular position relative to said plane of rest in said rest position of said mobile 10, said mechanism 20 having a preferred magnetization direction DA which is substantially orthogonal to said main axis DP of said shaft 1 in said rest position.

The invention also relates to a horological movement comprising such a monobloc shaft 1 and / or such a mobile 10 and / or such a mechanism 20.

The invention also relates to a timepiece 40, in particular a watch, comprising such a one-piece shaft 1 and / or such a mobile 10, and / or such a mechanism 20, and / or such a movement 30.

In short, the invention requires no pre-magnetized permanent magnet or magnetic wheel, but only magnetically passive (paramagnetic or ferromagnetic) shafts.

The object of the invention is not to provide a maintenance solution of the oscillator, but to protect the oscillator from any magnetic disturbance.

• intensité du champ d'arrêt sous-champ augmentée pour les montres avec spiral, corps d'ancre et roue d'échappement amagnétique ; ceci signifie qu'une montre devrait être soumise à des champs magnétiques beaucoup plus élevés que ceux que peut rencontrer l'utilisateur dans sa vie normale, avant de risquer une perturbation risquant de mener à l'arrêt du mouvement ;
• effet résiduel réduit pour les montres avec spiral, corps d'ancre et roue d'échappement amagnétique ;
• performances mécaniques identiques aux montres de l'état actuel de la technique, puisque les surfaces de contact tribologiques continuent à être réalisées dans des matériaux validés pour ces applications.

The invention, in one or the other of its variants, has important advantages:

• increased subfield field arrest strength for watches with hairspring, anchor body and non-magnetic escape wheel; this means that a watch should be subjected to magnetic fields much higher than those which the user may encounter in his normal life, before risking a disturbance likely to lead to the cessation of movement;
• reduced residual effect for watches with spiral, anchor body and non-magnetic escape wheel;
• mechanical performance identical to the watches of the current state of the art, since the tribological contact surfaces continue to be made in materials validated for these applications.

Claims (34)

1. One-piece arbor (1) of a pivoting timepiece wheel set (10), said one-piece arbor(1) being made in one or more aligned parts (2), characterized in that said one-piece arbor (1) is magnetically inhomogeneous and has intrinsic magnetic properties, which are: permeability, saturation field, coercive field, Curie temperature and the dependent hysteresis curve, which are not uniform throughout the volume of the arbor.
2. One-piece arbor (1) according to claim 1, characterized in that said arbor (1) is magnetically inhomogeneous, with a variation in the intrinsic magnetic properties of said one-piece arbor (1) either in the axial direction of the pivot axis (D) of said one-piece arbor (1), or radially with respect to said pivot axis (D), or both in the axial direction of the pivot axis (D) of said one-piece arbor (1) and radially with rotational symmetry with respect to said pivot axis (D).
3. One-piece arbor (1) according to claim 1, characterized in that said arbor (1) is magnetically inhomogeneous with a variation in the intrinsic magnetic properties of said one-piece arbor (1) radially with respect to said pivot axis (D).
4. One-piece arbor (1) according to claim 3, characterized in that said arbor (1) is magnetically inhomogeneous with a variation in the intrinsic magnetic properties of said one-piece arbor (1) radially with rotational symmetry with respect to said pivot axis (D).
5. One-piece arbor (1) according to claim 1, characterized in that said arbor (1) is magnetically inhomogeneous with a variation in the intrinsic magnetic properties of said one-piece arbor (1) in the axial direction of the pivot axis (D) of said one-piece arbor (1).
6. One-piece arbor (1) according to claim 1, characterized in that said arbor (1) is magnetically inhomogeneous with a variation in said intrinsic magnetic properties of said one-piece arbor (1) both in the axial direction of the pivot axis (D) of said one-piece arbor (1) and radially with rotational symmetry with respect to said pivot axis (D).
7. One-piece arbor (1) according to any of the preceding claims, characterized in that the arbor includes at least either a paramagnetic portion with a magnetic permeability (µ) comprised between 1.01 and 2, or a ferromagnetic portion.
8. One-piece arbor (1) according to the preceding claim, characterized in that the arbor includes at least one paramagnetic portion with a magnetic permeability (µ) comprised between 1.01 and 2.
9. One-piece arbor (1) according to the preceding claim, characterized in that the arbor includes at least one median paramagnetic portion with a magnetic permeability (µ) comprised between 1.01 and 2.
10. One-piece arbor (1) according to any of claims 7 to 9, characterized in that the arbor includes at least one weakly ferromagnetic portion, with a saturation field Bs < 0.5 T at temperature T = 23°C, a coercive field Hc < 1,000 kA/m at temperature T = 23°C, a maximum magnetic permeability µ_R < 10 at temperature T = 23°C, and a Curie temperature Tc > 60°C.
11. One-piece arbor (1) according to any of claims 7 to 10, characterized in that the arbor includes at least one paramagnetic portion, with a a magnetic permeability (µ) comprised between 1.01 and 2 and at least one weakly ferromagnetic portion, with a saturation field Bs < 0.5 T at temperature T = 23°C, a coercive field Hc < 1,000 kA/m at temperature T = 23°C, a maximum magnetic permeability µ_R < 10 at temperature T = 23°C, and a Curie temperature Tc > 60°C.
12. One-piece arbor (1) according to any of the preceding claims, characterized in that the arbor includes at least one portion made of CoCr20Ni16 Mo7.
13. One-piece arbor (1) according to any of the preceding claims, characterized in that the arbor includes at least one portion made of NiP.
14. One-piece arbor (1) according to any of the preceding claims, characterized in that the arbor is an at least bimaterial arbor and includes at least one portion made of highly ferromagnetic material and at least one portion made of weakly ferromagnetic material.
15. One-piece arbor (1) according to any of the preceding claims, characterized in that the arbor is an at least bimaterial arbor and includes at least one portion made of highly ferromagnetic material and at least one portion made of weakly paramagnetic material with a magnetic permeability (µ) comprised between 1.01 and 2.
16. One-piece arbor (1) according to any of the preceding claims, characterized in that the arbor is an at least bimaterial arbor and includes one portion made of paramagnetic material whose mass is lower than that of another portion made of ferromagnetic material.
17. One-piece arbor (1) according to the preceding claim, characterized in that the arbor is a balance staff of a sprung balance assembly of a watch movement, and in that the volume of said other portion made of ferromagnetic material is less than a value X = δ_m (C_ech + k θ_l) / (b µ₀ B_s H θ_l)
    where:

    - δ_m is the desired maximum relative rate defect close to 10^-4,

    - k is the stiffiness of the balance spring,

    - C_ech is the maximum torque for maintaining oscillation of the balance,

    - θ_l is the lift angle,

    - µ₀ is vacuum permeability,

    - B_s is the saturation field of the ferromagnetic portion of said arbor (1),

    - H is the maximum magnetization field that said watch is intended to withstand without exceeding said relative rate defect δ_m,

    - b is a coefficient depending on the geometric shape of the arbor and is close to 1.0 if the other quantities are expressed in the International System of Units, said value X being comprised between 0.1 mm³ and 1 mm³.
18. One-piece arbor (1) according to any of claims 1 to 13, characterized in that the arbor is made of only one material and is magnetically inhomogeneous as a result of the manufacturing process.
19. One-piece arbor (1) according to claim 3 or 4, characterized in that only the material located at the core of said one-piece arbor (1), in a central area (3) in proximity to the pivot axis (D) of said one-piece arbor (1), made of steel, has a high saturation field (Bs) having a value greater than 1 T, a maximum magnetic permeability (µ_R) greater than 50, and a coercive field (Hc) higher than 3 kA/m, whereas the material in a peripheral area (4) of said one-piece arbor (1) is weakly paramagnetic.
20. One-piece arbor (1) according to claim 3 or 4, characterized in that only the material located at the core of said one-piece arbor (1), in a central area (3) in proximity to the pivot axis (D) of said one-piece arbor (1) made of steel, has a high saturation field (Bs) having a value greater than 1 T, a maximum magnetic permeability (µ_R) greater than 50, and a coercive field (Hc) higher than 3 kA/m, whereas the material in a peripheral area (4) of said one-piece arbor (1) is ferromagnetic with a low saturation field (Bs) having a value of less than 0.5 T, a low maximum magnetic permeability (µ_R) of less than 10 and a low coercive field.
21. One-piece arbor (1) according to claim 20, characterized in that the material in a peripheral area (4) of said one-piece arbor (1) is weakly paramagnetic, with a low saturation field (Bs) having a value of less than 0.5 T, a low maximum magnetic permeability (µ_R) of less than 10 and a low coercive field.
22. One-piece arbor (1) according to claim 20, characterized in that the material in a peripheral area (4) of said one-piece arbor (1) is ferromagnetic, with a low saturation field (Bs) having a value of less than 0.5 T, a low maximum magnetic permeability (µ_R) of less than 10 and a low coercive field.
23. One-piece arbor (1) according to any of claims 20 to 22, characterized in that the highly ferromagnetic region of said central area (3) at the core of said one-piece arbor (1) is contained in a cylinder having a radius of less than 100 micrometres and centred on said pivot axis (D) of said one-piece arbor (1).
24. One-piece arbor (1) according to claim 5, characterized in that the arbor includes, in the direction of said pivot axis (D), a median portion (6) surrounded on either side by two end areas (8), and in that only said end areas (8), made of steel, have a high saturation field (Bs) having a value greater than 1 T, a maximum magnetic permeability (µ_R) greater than 50, and a coercive field (Hc) higher than 3 kA/m, whereas the material in said median portion (6) of said one-piece arbor (1) is weakly paramagnetic.
25. One-piece arbor (1) according to claim 5, characterized in that the arbor includes, in the direction of said pivot axis (D), a median portion (6) surrounded on either side by two end areas (8), and in that only said end areas (8), made of steel, have a high saturation field (Bs) having a value greater than 1 T, a maximum magnetic permeability (µ_R) greater than 50, and a coercive field (Hc) higher than 3 kA/m, whereas the material in said median portion (6) of said one-piece arbor (1) is ferromagnetic with a low saturation field (Bs) having a value of less than 0.5 T, a low maximum magnetic permeability (µ_R) of less than 10 and a low coercive field.
26. One-piece arbor (1) according to any of the preceding claims, characterized in that its magnetic inhomogeneity is obtained by combining two different materials by brazing, welding or depositing one material on the other.
27. One-piece arbor (1) according to any claims 1 to 25, characterized in that its magnetic inhomogeneity is obtained by using an alloy subjected to a heat treatment or to the action of an electric or magnetic field on all or part of said one-piece arbor (1) or of said wheel set (10).
28. One-piece arbor (1) according to any of the preceding claims, characterized in that the arbor is a balance staff.
29. One-piece arbor (1) according to any of the preceding claims, characterized in that said arbor (1) includes at least one protruding portion having a larger radius around the pivot axis (D), and at least said protruding portion is delimited, on either side of said pivot axis (D), by two surfaces, which are symmetrical with respect to said pivot axis (D), and which define, in projection on a plane perpendicular to said pivot axis (D), a profile inscribed in a rectangle, whose length to width ratio defines an aspect ratio which is greater than or equal to 2, the direction of said length defining a main axis (DP).
30. Pivoting timepiece wheel set (10) including at least one said one-piece arbor (1) according to any of the preceding claims.
31. Timepiece mechanism (20) including a said one-piece arbor (1) according to any of claims 1 to 29 and/or a said wheel set (10) according to the preceding claim, characterized in that said mechanism (20) is an escapement mechanism.
32. Timepiece mechanism (20) according to the preceding claim, including a said wheel set (10) according to claim 30 oscillating about a rest position defined by a rest plane passing through a pivot axis (D), said wheel set (10) being returned to a rest position by elastic return means, characterized in that said wheel set (10) includes a said arbor (1) according to claim 29, said arbor (1) being made of steel, and said main axis (DP) of said arbor (1), in the plane orthogonal to said arbor (1), occupies a determined angular position with respect to said rest plane in said rest position of said wheel set (10), said mechanism (20) having a preferred direction of magnetization (DA) which is substantially orthogonal to said main axis (DP) of said arbor (1) in said rest position.
33. Timepiece movement (30) including a said one-piece arbor (1) according to any of claims 1 to 29, and/or a said mechanism (20) according to the preceding claim.
34. Timepiece (40) or watch, including a said arbor (1) according to any of claims 1 to 29?, and/or a said mechanism (20) according to claim 32 and/or a said movement (30) according to the preceding claim.

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