Balance for timepiece and method for manufacturing such a balance

Abstract

The invention relates to a balance (1) for a timepiece comprising a felloe (2), a hub (4) and at least one arm (8) connecting the hub (4) to said felloe (2), at least one portion of the balance (1) being made of an at least partially amorphous metal alloy, characterised in that said at least partially amorphous metal alloy is based on an element chosen from the group that comprises platinum, zirconium and titanium, and has a thermal expansion coefficient of 7 ppm / °C to 12 ppm / °C. The present invention also relates to a method for manufacturing such a balance by moulding as well as to a resonator comprising such a balance and a monocrystalline quartz hairspring.

Description

Field of invention

[0001] The invention relates to a balance for a timepiece comprising a rim, a hub and at least one arm connecting the hub to said rim, at least part of the balance being made of a partially or totally amorphous metal alloy. The present invention also relates to a method of manufacturing such a balance as well as a resonator comprising such a balance. Background of the invention

[0002] Such a balance wheel made of an amorphous metal alloy is described, for example, in published application EP 2 466 396. In this application, the balance wheel is associated with a steel balance spring and an iron-based amorphous metal alloy is used for the balance wheel, for its ferromagnetic properties. The problem that the invention, the subject of application EP 2 466 396, seeks to solve therefore concerns the protection of the balance spring against external disturbing magnetic fields which are likely to affect the frequency stability of the resonator.

[0003] The present invention relates to another parameter likely to affect the frequency stability of the resonator, and not addressed in application EP 2 466 396, namely thermal variations. Such thermal variations vary the stiffness of the hairspring, as well as the geometries of the hairspring and the balance, which modifies the spring constant and the inertia, and therefore the oscillation frequency. Watchmakers have worked hard to have temperature-stable oscillators and several avenues have been explored / exploited, including one that earned Charles-Edouard Guillaume a Nobel Prize for the development of the Elinvar alloy, the modulus of elasticity of which increases with temperature and compensates for the increase in inertia of the balance. Subsequently, the development of oxidized silicon, therefore thermally compensated, surpassed the performance of Elinvar and has the advantage of being less sensitive to magnetic fields.Similarly, the monocrystalline quartz balance spring allows thermal compensation for the change in inertia of the balance wheel. But unlike oxidized silicon, whose oxide thickness can be varied depending on the balance material used, quartz is limited to materials with a thermal expansion coefficient of around 10 ppm / °C, which corresponds, for example, to titanium and platinum. The main problem with these materials is machinability and the control of fine structure and / or a perfect finish (mirror polish, for example). In the case of titanium, its relatively low density limits its use for large balance wheels, and in the case of platinum, its high price limits its use to prestige and luxury products.

[0004] Patent document EP2703909 discloses a resonator comprising a balance spring formed in a monocrystalline quartz crystal and cooperating with a balance in which the coefficient of expansion of the balance is between +6 ppm.°C -1< and +12 ppm.°C -1< and the cutting angle of the balance spring relative to the z axis of said monocrystalline quartz crystal is between -5° and +5° in order to pair the balance spring with the balance spring. The balance according to this document comprises titanium and / or durimphy and / or platinum. Summary of the invention

[0005] The present invention aims to overcome these drawbacks by proposing a balance wheel made from new materials allowing said balance wheel to be paired with a balance spring, preferably made of monocrystalline quartz, but also of silicon.

[0006] Another aim of the present invention is to propose a balance wheel made from new materials allowing simpler and more precise manufacturing, so as to reduce, for example, the dispersion of inertia and / or unbalance within the same production batch.

[0007] To this end, the invention relates firstly to balance wheels for timepieces as defined in independent claims 1 and 2.

[0008] The present invention relates to methods of manufacturing such balances, these methods being defined in independent claims 16 and 17.

[0009] The present invention also relates to a resonator comprising a balance wheel as defined above and a monocrystalline quartz hairspring.

[0010] Such an at least partially amorphous metal alloy based on platinum, titanium or zirconium makes it possible to produce a balance wheel that can be paired with a monocrystalline quartz balance spring.

[0011] Thanks to the properties of amorphous metals, a balance wheel made of an at least partially amorphous metal alloy based on platinum, zirconium or titanium can be produced using a simplified manufacturing process such as a casting process or a hot forming process. In addition, the at least partially amorphous metal alloy based on platinum, zirconium or titanium has the property of having a much larger elastic range than its crystalline equivalent, thanks to the absence of dislocation. This property makes it possible to overmould or integrate into the balance wheel elements making it possible to improve the centering as well as to adjust the inertia and / or the unbalance. Summary description of the drawings

[0012] Other features and advantages will become clear from the description given below, for informational purposes only and in no way limiting, with reference to the attached drawings, in which: there Figure 1 is a perspective view of a balance wheel according to the invention; Figure 2 is a partial top view of an alternative embodiment of a balance according to the invention; Figure 3 is a partial top view of another alternative embodiment of a balance according to the invention; Figure 4 is a sectional view along axis AA of the Figure 3 ; and the figures 5 to 10 are partial top views of other alternative embodiments of a balance according to the invention. Detailed Description of Preferred Embodiments

[0013] In reference to the Figure 1, a balance wheel 1 for a timepiece is shown. Such a balance wheel 1 traditionally comprises a rim 2, continuous or not, defining the external diameter of the balance wheel 1, a hub 4, forming its central part and provided with a hole 6 intended to receive a shaft (not shown) defining the pivot axis of the balance wheel 1. The hub 4 is securely connected to the rim 2 by arms 8. The arms 8 are here four in number and are arranged at 90°. Balance wheels with two or three arms are also usually found, arranged at 180° or 120° respectively.

[0014] At least a portion of the balance 1 is made of a partially or totally amorphous metal alloy. At least partially amorphous material will be understood to mean that the material is capable of being plastically deformed when heated to a temperature between its glass transition temperature and its crystallization temperature and capable of solidifying in an at least partially amorphous phase.

[0015] According to the invention, said at least partially amorphous metal alloy is based on an element chosen from the group consisting of platinum, zirconium and titanium, and has a coefficient of thermal expansion of between 7 ppm / °C and 12 ppm / °C.

[0016] In the present description, the expression "based on an element" means that said metal alloy contains at least 50% by weight of said element.

[0017] Said at least partially amorphous metal alloy used in the present invention may be based on platinum and has a coefficient of thermal expansion of between 8 ppm / °C and 12 ppm / °C.

[0018] Such an at least partially amorphous platinum-based metal alloy may consist, in atomic % values, of a platinum base whose content constitutes the balance, 13 to 17% copper 3 to 7% nickel 20 to 25% phosphorus.

[0019] The at least partially amorphous metal alloy used in the present invention may also be based on zirconium and has a coefficient of thermal expansion of between 8 ppm / °C and 11 ppm / °C.

[0020] Such an at least partially amorphous zirconium-based metal alloy may consist, in atomic % values, of a zirconium base whose content constitutes the balance, 14 to 20% copper 12 to 13% nickel 9 to 11% aluminum 2 to 4% niobium.

[0021] The at least partially amorphous metal alloy used in the present invention may also be titanium-based and has a coefficient of thermal expansion of between 8 ppm / °C and 11 ppm / °C.

[0022] Such an at least partially amorphous titanium-based metal alloy may consist, in atomic % values, of a titanium base, the content of which constitutes the balance, 5 to 45% of Cu 2 to 25% of Ni 2 to 30% of Zr 2 to 15% of Sn 0 to 5% of Si 0 to 5% of Hf.

[0023] Ideally, the alloys used in the invention do not contain any impurities. However, they may include traces of impurities which may result, often unavoidably, from the production of said alloys.

[0024] These platinum, titanium and zirconium-based alloys used in the present invention have the advantage of having a coefficient of thermal expansion of less than 12 ppm / °C and greater than 7 ppm / °C. They can therefore be used to produce at least part of a balance wheel which will be paired with a monocrystalline quartz balance spring.

[0025] More preferably, said at least partially amorphous metal alloy used in the present invention based on platinum is made up, in atomic % values, of: 57.5% Pt, 14.7% Cu, 5.3% Ni, 22.5% P

[0026] Such an alloy has a coefficient of thermal expansion between 11 and 12 ppm / °C.

[0027] More preferably, said at least partially amorphous metal alloy used in the present invention based on zirconium is made up, in atomic % values, of: 58.5% Zr, 15.6% Cu, 12.8% Ni, 10.3% Al, 2.8% Nb

[0028] Such an alloy has a coefficient of thermal expansion between 10.5 and 11 ppm / °C.

[0029] More preferably, said at least partially amorphous metal alloy used in the present invention based on titanium is made up, in atomic % values, of: 42.5% Ti, 7.5% Zr, 40% Cu, 5% Ni, 5% Sn

[0030] Such an alloy has a coefficient of thermal expansion between 8 and 11 ppm / °C.

[0031] According to a first embodiment of the invention, the rim 2, the hub 4 and the arms 8 are made of the same at least partially amorphous metal alloy based on platinum, zirconium or titanium as defined above. Advantageously, the balance wheel 1 is a single-piece, i.e. made from a single piece.

[0032] The balance 1 may for example be made entirely from the platinum-based alloy as defined above. Since platinum has a high density (21000 kg / m 3< ), the at least partially amorphous platinum-based alloy used in the invention also has a high density (15.5 g / cm 3< ), so that the addition of elements made of dense material to increase the inertia of the balance will not necessarily be necessary.

[0033] The balance 1 can also be made entirely from the at least partially amorphous zirconium or titanium-based alloy as defined above. Since zirconium or titanium has a lower density, the at least partially amorphous zirconium or titanium-based alloy used in the invention also has a lower density (6.5 g / cm 3< for zirconium and 5.5 g / cm 3< for titanium), so that the addition of elements made of denser material to increase the inertia of the balance is recommended, particularly if it is desired to produce a small balance for small movements. These elements make it possible to increase the inertia of the balance while maintaining an aesthetic rim geometry and with good aerodynamic properties.

[0034] Thus, according to a first variant represented on the Figure 2, the serge 2 may comprise first overmolded inertia adjustment elements 10, said first inertia adjustment elements 10 being made of a material having a density greater than the density of said at least partially amorphous metal alloy. These first inertia adjustment elements 10 may for example be made of tungsten or tungsten carbide, and are obtained by overmolding.

[0035] According to a second variant shown on the Figure 3, the rim 2 may comprise housings 12 intended to receive second inertia and / or unbalance adjustment elements 14, 15. These housings 12 may advantageously be provided during the manufacture of the balance 1 by molding, as will be seen below. The second inertia and / or unbalance adjustment elements 14, 15 may be, for example, weights, split weights, pins 14, split pins, or pins with unbalance 15, which act as weights. These elements are driven or clipped into the corresponding housings 12. On the Figure 3 a pin 14 inserted in its housing 12 are shown, as well as a pin with unbalance 15 inserted in its housing 12. The Figure 4 shows a sectional view along line AA of the Figure 3 representing the pin with unbalance 15 inserted in the housing 12 provided in the rim 2.

[0036] It is obvious that these elements for increasing the inertia of the balance are preferably used with a rim based on zirconium or titanium which is at least partially amorphous but can also be used with a rim in another material in a balance according to the invention.

[0037] To increase the inertia of the balance wheel, it is also possible to provide a thicker or wider rim, particularly in the case of larger balance wheels.

[0038] The 12 dwellings shown on the Figure 3 may also constitute housings intended to receive decorative and / or luminescent elements, such as tritium tubes (not shown).

[0039] According to another variant of the invention, the hub 4 may comprise integrated flexible centering elements, which allow self-centering of the balancer when it is mounted on an axle thanks to the elastic deformation of said flexible centering elements.

[0040] According to the Figure 5 , said integrated flexible centering elements 16 are elastic blades provided on the inner periphery of the hub 4 so as to be positioned in the hole 6. According to the Figure 6 , said integrated flexible centering elements 17 are provided on the surface of the hub 4 and are distributed around the hole 6. The flexible centering elements 16 and 17 can advantageously be put in place during the manufacture of the balance 1 by molding, as will be seen below.

[0041] According to another variant of the invention, at least one of the arms 8 carries third integrated flexible inertia adjustment elements.

[0042] According to the Figure 7 , the end of the arm 8 on the side of the rim 2 ends in two branches 8a, 8b forming between them a housing 18 in which is integrated a third flexible bistable “V” inertia adjustment element 19 for adjusting the frequency.

[0043] According to the figure 8 , a third flexible buckling inertia adjustment element 20 is provided in the housing 18 for adjusting the frequency. For this purpose, the third inertia adjustment element 20 is made of a material having expansion properties different from the at least partially amorphous metal alloy based on platinum, zirconium or titanium of the balance of the invention, such as silicon or silicon oxide.

[0044] According to the Figure 9 , the end of the arm 8 on the side of the serge 2 ends in three branches 8a, 8b, 8c forming between them two housings 18a, 18b in which are integrated third flexible multi-stable ratchet inertia adjustment elements 22a, 22b for adjusting the frequency.

[0045] These third flexible inertia adjustment elements 19, 20, 22a, 22b for frequency adjustment can advantageously be put in place during the manufacture of the balance 1 by molding, as will be seen below.

[0046] These third flexible inertia adjustment elements 19, 20, 22a, 22b for frequency adjustment can be used both when the entire balance is made of an at least partially amorphous metal alloy based on zirconium, titanium or platinum according to the invention and when the arms are made of an at least partially amorphous metal alloy based on zirconium, titanium or platinum according to the invention, the rest of the balance, and in particular the rim, being made of another material.

[0047] According to another variant of the invention, one of the arm 8, the rim 2 and the hub 4 has a structured surface condition. Only one of the elements may have a structured surface condition or all the elements of the balance may have a structured surface condition, this structured surface condition being able to be identical or different. Figure 10represents a balance wheel of the invention for which the serge 2 has a structured surface state different from the structured surface state presented by the arm 8. This structured surface state can be a polished, satin, sandblasted, pearled, sun-polished state, etc. It is also possible to provide in the mold for the manufacture of the balance wheel microstructures forming a photonic network in order to replicate these microstructures on the surface of the balance wheel. These microstructures can make it possible to create a photonic crystal giving the part a certain color, a hologram, or a diffraction network which can constitute an anti-counterfeiting element. The structures are directly introduced into the mold, and are replicated during the manufacture of the balance wheels by hot forming, which no longer requires finishing operations.

[0048] According to a second embodiment of the invention, the arms and the hub of the balance wheel are made from the at least partially amorphous metal alloy based on zirconium, titanium or platinum defined above, the rim being made from a material having a density greater than the density of said at least partially amorphous metal alloy used for the arms and the hub. This material may itself be the at least partially amorphous metal alloy based on platinum as defined above or another material.For example, the arms and the hub of the balance wheel are made from the at least partially amorphous metal alloy based on zirconium or titanium as defined above to enable the balance wheel to be paired with a single-crystal quartz balance spring, and the rim is made from another material having a density greater than the density of the at least partially amorphous metal alloy based on zirconium or titanium used for the arms and the hub in order to improve the inertia of the balance wheel.

[0049] It is obvious that in this second embodiment of the invention, the rim may comprise the same first inertia adjustment elements or the same housings for receiving the second inertia and / or unbalance adjustment elements or decorative and / or luminescent elements as those described above for the first embodiment of the invention. Similarly, the hub may comprise the same integrated flexible centering elements as those described above for the first embodiment of the invention. Similarly, the arm may comprise the same integrated flexible third inertia adjustment elements as those described above for the first embodiment of the invention. Similarly, the elements of the balance may have structured surface conditions as described above for the first embodiment of the invention.

[0050] The present invention also relates to a method of manufacturing a balance wheel 1 for which the rim 2, the hub 4 and the arms 8 are made from said partially or totally amorphous metal alloy based on platinum, zirconium or titanium as defined above, comprising the following steps: a) producing a mold having the negative shape of the balance, possibly providing microstructures forming a decoration or a surface photonic network b) introducing into the mold said at least partially amorphous metal alloy based on an element chosen from the group consisting of platinum, zirconium and titanium, the metal alloy being heated to a temperature between its glass transition temperature and its crystallization temperature to be hot formed in the balance mold c) cooling said metal alloy at a cooling rate chosen to obtain a balance in said partially or totally amorphous metal alloy based on an element chosen from the group consisting of platinum, zirconium and titanium d) releasing the balance obtained in step c) from its mold.

[0051] Additionally, as indicated in claim 16, the first inertia adjustment elements (10) are overmolded into the rim.

[0052] To produce a balance wheel from a partially or totally amorphous metal alloy based on platinum, zirconium or titanium, it is advantageous to use the properties of the metal in an at least partially amorphous state to shape it.

[0053] Indeed, the at least partially amorphous metal allows great ease in shaping, allowing the manufacture of parts with complicated shapes with greater precision. This is due to the particular characteristics of the amorphous metal which can soften while remaining at least partially amorphous for a certain time in a given temperature range [Tg - Tx] specific to each alloy (for example for the Zr-based alloy: Tg=440°C and Tx=520°C). It is thus possible to shape it under relatively low stress and at a low temperature, thus allowing the use of a simplified process such as hot forming. The use of such a material also makes it possible to reproduce fine geometries very precisely because the viscosity of the alloy decreases sharply as a function of temperature in the temperature range [Tg - Tx] and the alloy thus matches all the details of the negative.For example, for a platinum-based material as defined above, shaping is done at around 300°C for a viscosity reaching 10 3< Pa.s for a stress of 1 MPa, instead of a viscosity of 10 12< Pa.s at temperature Tg. The use of dies has the advantage of creating high-precision three-dimensional parts, which cutting or stamping cannot achieve.

[0054] One process used is the hot forming of an amorphous preform. This preform is obtained by melting the metallic elements intended to constitute the partially or totally amorphous metallic alloy based on platinum, zirconium or titanium in a furnace. This melting is done in a controlled atmosphere with the aim of obtaining the lowest possible oxygen contamination of the alloy. Once these elements are melted, they are cast in the form of a semi-finished product, then cooled rapidly in order to maintain the partially or totally amorphous state. Once the preform is produced, hot forming is carried out in order to obtain a final part. This hot forming is carried out by pressing in a temperature range between the glass transition temperature Tg and the crystallization temperature Tx of the metallic alloy for a given time to maintain an at least partially amorphous structure.This is done in order to retain the elastic properties characteristic of amorphous metals.

[0055] Typically for the Zr-based alloy and for a temperature of 440°C, the pressing time should not exceed approximately 120 seconds. Thus, hot forming makes it possible to preserve the initial at least partially amorphous state of the preform. The different stages of final shaping of the single-piece balance according to the invention are then: 1) heating the dies having the negative shape of the balance to a chosen temperature 2) introducing the at least partially amorphous metal preform between the hot dies, 3) applying a closing force to the dies in order to replicate the geometry of the latter on the at least partially amorphous metal preform, 4) waiting for a chosen maximum time, 5) opening the dies, 6) rapid cooling of the balance below Tg so that the material retains its at least partially amorphous state, and 7) removing the balance from the dies.

[0056] Of course, the balance can be made by casting or injection. This process consists of casting or injecting the metal alloy heated to a temperature between its glass transition temperature and its crystallization temperature to be at least partially amorphous into a mold having the shape of the final part. Once the mold is filled, it is cooled rapidly to a temperature below T g in order to avoid crystallization of the alloy and thus obtain a balance made of at least partially amorphous metal as defined above.

[0057] The mold can be reused or dissolved to release the parts. The molding process has the advantage of perfectly replicating the geometry of the balance, including any decorations or surface structuring. This results in less dispersion of inertia and better centering on a production batch of balances. The molding process makes it possible to obtain a balance with aesthetic geometry, with sharp interior angles, a rounded rim and / or arm profile, and a perfect finish. It is also possible to provide a non-continuous rim. For maximum quality, the mold will be made in silicon using a DRIE process. It is obvious that the mold can also be made by milling, laser, EDM or any other type of machining.

[0058] The elastic properties characteristic of at least partially amorphous metals are used to overmould or integrate functional and / or decorative elements in the rim and / or at the arms and / or at the hub, for example by means of corresponding inserts placed in the mould before the introduction of the metal alloy heated between its glass transition temperature and its crystallisation temperature to be at least partially amorphous.

[0059] More particularly, the method of the invention may comprise a step of overmolding the first inertia adjustment elements 10 in the felloe 2, by means of inserts placed in the mold before the introduction of the metal alloy heated between its glass transition temperature and its crystallization temperature to be at least partially amorphous and overmolded.

[0060] The method of the invention may also comprise a step of overmolding the flexible centering elements 16, 17 on the hub 4, on its inner periphery or on its surface.

[0061] The method of the invention may also comprise a step of overmolding the third flexible inertia adjustment elements 19, 20, 22a, 22b in the arm 8.

[0062] The molding process also allows for the provision of a mold that has microstructures forming a decoration or a photonic network so as to obtain the structured surface states on the arms and / or the hub and / or the rim as described above. It is also possible to add a logo to the mold.

[0063] The present invention also relates to a method of manufacturing a balance wheel for which the hub and at least one arm are made from the at least partially amorphous metal alloy based on zirconium, titanium or platinum defined above, the rim being made from a material having a density greater than the density of said at least partially amorphous metal alloy used for the arms and the hub, said method comprising the following steps: a) producing a mold having the negative shape of the balance a') inserting into the mold a serge or serge elements made of a material having a density greater than the density of the at least partially amorphous metal alloy based on platinum, zirconium or titanium used for the arms and the hub b) introducing into the mold said at least partially amorphous metal alloy based on an element chosen from the group consisting of platinum, zirconium and titanium, this metal alloy being heated to a temperature between its glass transition temperature and its crystallization temperature to be hot formed in the balance mold c) cooling said metal alloy at a cooling rate chosen to obtain a balance made of at least partially amorphous metal alloy based on an element chosen from the group consisting of platinum,zirconium and titanium d) release the balance obtained in step c) from its mold.

[0064] The present invention also relates to a resonator comprising a balance wheel as defined above and a monocrystalline quartz hairspring.

[0065] Thus, the balance wheel according to the invention is made of a material allowing the use of a simple manufacturing process while having a coefficient of thermal expansion allowing it to be paired with a monocrystalline quartz balance spring. The balance wheel according to the invention also allows at least arms having a coefficient of thermal expansion allowing it to be paired with a monocrystalline quartz balance spring, while having a high inertia while maintaining a compact and aesthetic rim geometry, of small volume, using a suitable rim, either comprising elements made of a material of greater density, or being itself made of a material of greater density.

[0066] It is also possible to carry out a heat treatment to adjust the coefficient of expansion of the partially amorphous material in its final form by relaxation of the amorphous structure (without crystallization).

[0067] It is also possible to adjust the coefficient of expansion by partial and controlled crystallization of the partially amorphous material in its final form.

Claims

1. A balance (1) for timepieces comprising a felloe (2), a hub (4) and at least one arm (8) connecting the hub (4) to said felloe (2), at least one part of the balance (1) being made of an at least partially amorphous metal alloy, said at least partially amorphous metal alloy being based on an element chosen among the group consisting of platinum, zirconium and titanium, and having a coefficient of thermal expansion comprised between 7 ppm / °C and 12 ppm / °C, in which balance the hub (4) and the arm (8) are made of said at least partially amorphous metal alloy, the felloe (2) being made of a first material with a density greater than the density of said at least partially amorphous metal alloy in which the hub (4) and the arm (8) are made.

2. A balance (1) for timepieces comprising a felloe (2), a hub (4) and at least one arm (8) connecting the hub (4) to said felloe (2), at least one part of the balance (1) being made of an at least partially amorphous metal alloy, said at least partially amorphous metal alloy being based on an element chosen among the group consisting of platinum, zirconium and titanium, and having a coefficient of thermal expansion comprised between 7 ppm / °C and 12 ppm / °C, in which balance the felloe (2), the hub (4) and the arm (8) are made of said at least partially amorphous metal alloy and the felloe (2) comprises overmoulded first inertia setting elements (10), said first inertia setting elements (10) being made of a second material with a density greater than the density of said at least partially amorphous metal alloy.

3. The balance (1) according to claim 1, characterised in that the felloe (2) comprises overmoulded first inertia setting elements (10), said first inertia setting elements (10) being made of a second material with a higher density than the density of said at least partially amorphous metal alloy.

4. The balance (1) according to any of the preceding claims, characterised in that the felloe (2) comprises beds (12) for second inertia and / or unbalance setting elements (14, 15).

5. The balance (1) according to any of the preceding claims, characterised in that the felloe (2) comprises beds (12) for decorative and / or luminescent elements.

6. The balance (1) according to any of the preceding claims, characterised in that the hub (4) comprises integrated resilient centring elements (16, 17).

7. The balance (1) according to the preceding claim, characterised in that said integrated resilient centring elements (16) are provided on the inner circumference of the hub (4).

8. The balance (1) according to any of the preceding claims, characterised in that the arm (8) carries third integrated resilient inertia setting elements (19, 20, 22a, 22b).

9. The balance (1) according to any of the preceding claims, characterised in that either the arm (8), the felloe (2) or the hub (4) has a structured surface condition.

10. The balance (1) according to any of the preceding claims, characterised in that said at least partially amorphous metal alloy is platinum-based and has a coefficient of thermal expansion comprised between 8 ppm / °C and 12 ppm / °C.

11. The balance (1) according to claim 10, characterised in that the at least partially amorphous platinum-based metal alloy is composed, in atomic % values, of: - a platinum base, the content of which constitutes the remainder, - 13 to 17% of copper - 3 to 7% of nickel - 20 to 25% of phosphorus.

12. The balance (1) according to any of claims 1 to 9, characterised in that said at least partially amorphous metal alloy is zirconium-based and has a coefficient of thermal expansion comprised between 8 ppm / °C and 11 ppm / °C.

13. The balance (1) according to claim 12, characterised in that the at least partially amorphous zirconium-based metal alloy is composed, in atomic % values, of: - a zirconium base, the content of which constitutes the remainder, - 14 to 20% of copper - 12 to 13% of nickel - 9 to 11% of aluminium - 2 to 4 % of niobium.

14. The balance (1) according to any of claims 1 to 9, characterised in that said at least partially amorphous metal alloy is titanium-based and has a coefficient of thermal expansion comprised between 8 ppm / °C and 11 ppm / °C.

15. The balance (1) according to claim 14, characterised in that the at least partially amorphous titanium-based metal alloy is composed, in atomic % values, of: - a titanium base, the content of which constitutes the remainder, - 5 to 45% of Cu - 2 to 25% of Ni - 2 to 30% of Zr - 2 to 15% of Sn - 0 to 5% of Si - 0 to 5% of Hf.

16. A method for manufacturing a balance (1) comprising a felloe (2), a hub (4) and at least one arm (8) made of an at least partially amorphous metal alloy based on an element chosen among the group consisting of platinum, zirconium and titanium according to claim 2, comprising the following steps: a) making a mould having the negative form of the balance (1) b) introducing into the mould said at least partially amorphous metal alloy based on an element chosen among the group consisting of platinum, zirconium and titanium, said metal alloy being heated to a temperature comprised between its glass transition temperature and its cristallisation temperature in order to be hot-formed c) cooling said metal alloy at a cooling rate chosen to obtain a balance (1) made of said at least partially amorphous metal alloy based on an element chosen among the group consisting of platinum, zirconium and titanium d) releasing the balance (1) obtained in step c) from its mould, the method further comprising a step of overmoulding first inertia setting elements (10) in the felloe (2).

17. A method for manufacturing a balance comprising a hub and at least one arm made of an at least partially amorphous metal alloy based on an element chosen among the group consisting of platinum, zirconium and titanium according to claim 1, comprising the following steps: a) making a mould having the negative form of the balance a') inserting into the mould a felloe or felloe elements made of a material with a higher density than the density of said at least partially amorphous metal alloy based on an element chosen among the group consisting of platinum, zirconium and titanium b) introducing into the mould said at least partially amorphous metal alloy based on an element chosen among the group consisting of platinum, zirconium and titanium, said metal alloy being heated to a temperature comprised between its glass transition temperature and its cristallisation temperature in order to be hot-formed c) cooling said metal alloy at a cooling rate selected to obtain a balance made of said at least partially amorphous metal alloy based on an element chosen among the group consisting of zirconium and titanium d) releasing the balance obtained in step c) from its mould18. The method according to any of claims 16 or 17, characterised in that it comprises a step of overmoulding resilient centring elements (16, 17) on the hub (4).

19. The method according to any of claims 16 to 18, characterised in that the method comprises a step of overmoulding third resilient inertia setting elements (19, 20, 22a, 22b) in the arm (8).

20. The method according to any of claims 16 to 19, characterised in that the mould has microstructures forming a decoration or a photonic grating.

21. A resonator comprising a balance according to any of claims 1 to 15 and a monocrystalline quartz balance spring.

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