Method for manufacturing a micromechanical component, in particular of a timepiece mobile, with optimised contact surface

Abstract

A method for manufacturing a watch movement, in which a substrate is made with a first material comprising at least nickel and phosphorus, the substrate is shaped to the geometry of the movement, and the substrate is coated, by galvanic and / or chemical means, at the level of at least one surface of the substrate of the movement, with at least a second material, which constitutes the peripheral layer of the movement at the level of at least one surface of the substrate of the movement, and which comprises at least nickel and is poorer in phosphorus than the first material, or which comprises nickel and is devoid of phosphorus.

Description

Scope of the invention

[0001] The invention relates to a method for manufacturing a micromechanical component, in particular a watch movement.

[0002] The invention relates to the field of watchmaking mechanisms, and more particularly to escapement mechanisms comprising at least one escape wheel and at least one anchor, of which at least one is non-magnetic. Background of the invention

[0003] In Swiss lever escapement mechanisms, the Swiss lever escapement wheels are historically made of nickel-plated steel, and are sensitive to magnetic fields.

[0004] We know of alternatives with materials such as nickel-phosphorus NiP12 implemented by the "LIGA" process (Lithography and Electro-Galvanizing), which have a non-magnetic behavior.

[0005] However, the use of such materials, nickel-phosphorus or similar compounds, can be problematic under certain climatic conditions, which may lead to performance degradation, particularly in terms of amplitude regularity, stopping, or aging, especially when the two opposing components of the friction torque are made of similar LIGA materials. While the deposition of a superficial gold layer may help stabilize amplitude, it does not solve the overall problem, may even exacerbate aging, and can affect running stability. Document CH 514 873 A shows a nickel-plated brass or steel substrate. Summary of the invention

[0006] The invention aims to solve the technical problem of the holding of the usual watch lubricant, and more particularly to guarantee an epilame effect, under usual climatic conditions, on components made of LIGA NiP12, or similar, non-ferromagnetic, in particular on anchors and Swiss lever escape wheels.

[0007] For this purpose, the invention relates to a method for manufacturing watch movements according to claim 1. Detailed description of preferred embodiments

[0008] The invention relates to the field of micromechanical components, and more particularly to watch movements.

[0009] The invention aims to solve in particular the technical problem of the holding of the usual watch lubricant, under usual climatic conditions, on components made of LIGA NiP12, or similar, non-ferromagnetic, in particular on wheels of a Swiss lever escapement mechanism.

[0010] The contact between the ruby ​​lever of the anchor and the tooth of the escape wheel is particularly sensitive.

[0011] This is particularly about preventing any contamination of the anchor, especially the anchor fork, and ensuring the presence of lubricant on the contact surfaces of the escape wheel and the anchor, and reducing the aging of the escape wheel and the anchor.

[0012] The main problem is the loss of epilame effect on the exhaust wheel board, which causes oil to spread and loss of lubrication at the contact between the wheel tooth and the ruby ​​lift.

[0013] The stability of the lubrication at the contact between the anchor levers and the escape wheel must ensure the consistency of the amplitude.

[0014] To this end, adding a layer of galvanic nickel (Ni), chemical nickel (e.g., NiP6-9), or chemically deposited nickel-boron to a LIGA NiP12 escape wheel significantly improves movement performance. Various tests have demonstrated that this notable improvement is linked to better resistance of the epilame under climatic conditions, particularly temperature and humidity, better adhesion of the epilame to the material when the amount of phosphorus on the surface is reduced, and improved lubricant performance when the phosphorus content is lower. Specifically, the tribological behavior of a pure nickel surface layer is superior to that of a NiP6-9 layer, which itself is superior to that of a NiP12 or NiP13 layer.

[0015] In one variant, the galvanic nickel coating can be an alloy, for example Ni-Fe, or Ni-W, or other.

[0016] Thus the invention relates to a method of manufacturing a micromechanical component, in particular a watch movement, according to which a substrate is made with a first material comprising at least nickel and phosphorus, this substrate is shaped to the geometry of the movement, and the substrate is coated, by galvanic and / or chemical means, at the level of at least one surface of the substrate of the movement, with at least a second material of thin thickness, less than 10 micrometers, which constitutes the peripheral layer of the movement at the level of this at least one surface of the substrate of the movement, and which comprises at least nickel and is poorer in phosphorus than the first material, or which comprises nickel and is devoid of phosphorus.

[0017] More specifically, this first non-magnetic material is chosen.

[0018] More specifically, this second non-magnetic material is chosen.

[0019] It is noted that nickel is not non-magnetic, and that NiP6-9% is not necessarily so; it is the thinness of the deposit that preserves the non-magnetic nature of the part.

[0020] According to the invention, the substrate is a nickel-phosphorus of NiPx formulation, with x between 1% and 15% by mass, inclusive of terminals, or more particularly with x between 10% and 15% by mass, inclusive of terminals, the latter range making it possible to guarantee the non-magnetic character of the coating.

[0021] This substrate is covered with a low-phosphorus coating, according to the invention, the thickness of which is more particularly and not limited to between 0.2 micrometers and 5.0 micrometers inclusive, and, more particularly still, between 0.2 micrometers and 2.0 micrometers inclusive.

[0022] The coating treatment with a low-phosphorus coating, according to the invention, can be carried out by galvanic means.

[0023] It is possible to apply a heat treatment to the substrate before the deposition operation, in particular galvanic, or to apply a heat treatment to the assembly formed by the substrate and its coating after the deposition operation, in particular galvanic.

[0024] It is also possible to apply a chemical treatment to the substrate to modify its surface characteristics in order to facilitate the adhesion of the coating, in particular by galvanic means.

[0025] Alternatively, the coating treatment with a low-phosphorus coating, according to the invention, can be carried out chemically, according to a process of applying chemical nickel, which can be pure nickel, or a low-phosphorus nickel-phosphorus, for example NiP6-9, with 6% to 9% by mass of phosphorus, or even a nickel-boron NiB.

[0026] Adding a layer of nickel, or NiP6-9, or NiB, increases the stability of the epilame in climatic conditions, the grip of the epilame and therefore the resistance of any common watch lubricant.

[0027] More specifically, the epilame used is a fluoride-based formulation.

[0028] The lubricant can also be deposited on an exhaust valve with a supplement in the form of a paste based on molybdenum disulfide MoS2, which acts as a lubricant and lubricant sponge.

[0029] Advantageously, the escapement mechanism in question has a geometry that minimizes the contact surfaces; for example, preference is given to using a cradled anchor, which is an anchor whose active faces of the fork, intended to come into contact with the ellipse and the stops, are rounded, which allows for a point of contact instead of a line of contact.

[0030] An innovative design of an escapement mechanism includes an anchor made of LIGA, or an anchor whose pallets are at least made of LIGA. In such a case, the LIGA parts of the anchor are subject to the same problem, and the same solution is applicable.

[0031] The invention makes it possible to guarantee normal aging conditions, a constant amplitude, and the absence of stopping, particularly in the presence of cradled LIGA nickel-phosphorus anchors, which provide better shock resistance than silicon anchors, for example.

[0032] Thus, a preferred method is implemented for manufacturing a clockwork mechanism, according to which: a substrate is manufactured with a first material comprising at least nickel and phosphorus, and a coating is made on this substrate, at the level of at least one surface of the mobile substrate, with at least a second material which constitutes the peripheral layer of the mobile at the level of this at least one surface of the substrate; this at least a second material comprises at least nickel, and is poorer in phosphorus than the first material, or this at least a second material comprises nickel and is devoid of phosphorus.

[0033] More specifically, this coating of the substrate is applied, at least at one surface adjacent to a friction surface of the moving part, with at least one second material, which constitutes the peripheral layer of the moving part at the level of this at least one surface adjacent to a friction surface. By "adjacent" we mean that the two surfaces are contiguous, or at least tangent; their intersection is not empty, even if it is limited to an isthmus of very small cross-section.

[0034] More specifically, the substrate is shaped to the geometry of the mobile.

[0035] More specifically, this substrate coating is carried out by galvanic and / or chemical and / or PVD and / or CVD means.

[0036] In one variation, this substrate coating is applied to surfaces of the moving part other than the surfaces that guide the moving part for its pivoting or for its guidance along a single degree of freedom. More specifically, this substrate coating is applied to all surfaces of the moving part other than these guiding surfaces.

[0037] In another variant, the substrate coating is carried out on the surfaces of the mobile including these mobile guidance surfaces.

[0038] In yet another variation, this substrate coating is applied to surfaces adjacent to a friction surface of the moving part, other than the surfaces that guide the moving part for its pivoting or for its guidance along a single degree of freedom. More specifically, this substrate coating is applied to all surfaces of the moving part other than the surfaces that guide the moving part for its pivoting or for its guidance along a single degree of freedom.

[0039] In yet another variant, the substrate coating is carried out on surfaces adjacent to a frictional surface of the mobile, including the guiding surfaces of the mobile for its pivoting or for its guidance according to a single degree of freedom.

[0040] In one variant, the substrate coating is applied to all surfaces of the mobile.

[0041] More specifically, the first material containing phosphorus is chosen with a mass proportion between 1% and 15% inclusive.

[0042] More specifically, the first material consisting solely of nickel and phosphorus is chosen.

[0043] More specifically, the first non-magnetic material is chosen with a proportion by mass of phosphorus between 10% and 15% inclusive.

[0044] More specifically, the first non-magnetic material is chosen.

[0045] More specifically, the second material is chosen, consisting only of pure nickel, or only of nickel and phosphorus.

[0046] More specifically, the second material is chosen with a proportion by mass of phosphorus less than or equal to 15%.

[0047] More specifically, the second non-magnetic material is chosen with a proportion by mass of phosphorus between 10% and 15% inclusive.

[0048] As an alternative, the second material is chosen with a proportion by mass of phosphorus between 6% and 12% inclusive.

[0049] In another alternative, the second material is chosen with a proportion by mass of phosphorus between 1% and 6%, excluding limits.

[0050] In yet another alternative, the second material is chosen with a proportion by mass of phosphorus between 0% and 1% inclusive.

[0051] More specifically, the second material containing boron is chosen.

[0052] More specifically, the second material, consisting solely of nickel and boron, is chosen.

[0053] In one variant, the second material is applied galvanically.

[0054] In another variant, the second material is applied chemically.

[0055] More specifically, the second material is applied with a thickness of less than 10 micrometers.

[0056] More specifically, the second material is applied with a thickness between 0.2 micrometers and 5.0 micrometers, inclusive. More specifically still, the second material is applied with a thickness between 0.2 micrometers and 2.0 micrometers, inclusive.

[0057] In yet another variant, the second material is applied with a thickness between zero and 0.2 micrometers, excluding limits, particularly in the vicinity of 0.1 micrometers.

[0058] Specifically, the substrate and its coating assembly undergo a heat treatment at a temperature between 100°C and 500°C for 1 to 8 hours. Alternatively, this heat treatment is performed after the coating operation. In another alternative, it is performed before the coating operation.

[0059] In particular, the substrate is produced by a "LIGA" process (lithography-galvanization-forming, from the German "Röntgenlithographie, Galvanoformung, Abformung").

[0060] More specifically, a galvanic and / or chemical coating is applied to all surfaces of the substrate with such a second material.

[0061] More specifically, this process is applied to the manufacture of an escapement mechanism, which is an escape wheel or an anchor.

[0062] In one variant, the thickness of the second material constituting the peripheral layer of the mobile is limited at least at one surface adjacent to a friction surface to less than 10 micrometers. More specifically, the thickness of the second material constituting the peripheral layer of the mobile is limited at least at one surface adjacent to a friction surface to less than 5 micrometers.

[0063] In one variant, the thickness of the second material constituting the peripheral layer of the mobile is limited to less than 10 micrometers at at least one surface of the substrate. More specifically, the thickness of the second material constituting the peripheral layer of the mobile is limited to less than 5 micrometers at at least one surface of the substrate.

[0064] This process allows the production of a micromechanical component, in particular a watch movement, and more specifically an escapement mechanism movement, with an optimized contact surface.

Claims

1. A method for manufacturing a horology mobile, in which a substrate is manufactured with a first material comprising at least nickel and phosphorus, with a proportion by mass of phosphorus comprised between 1% and 15%, limits included, and in which said substrate is plated on at least one surface of the substrate of said mobile, with at least one second material that constitutes the peripheral layer of said mobile on said at least one surface of the substrate of said mobile, and which comprises at least nickel and which is lower in phosphorus than said first material, or which comprises nickel and is phosphorus-free.

2. The method according to claim 1, characterised in that said substrate is plated, on at least one surface adjoining a friction surface of said mobile, with said at least one second material that constitutes the peripheral layer of said mobile on said at least one surface adjoining a friction surface of said mobile.

3. The method according to claim 1 or 2, characterised in that said substrate is shaped to the geometry of said mobile.

4. The method according to any of claims 1 to 3, characterised in that said substrate is plated using a galvanic and / or chemical and / or PVD and / or CVD method.

5. The method according to any of claims 1 to 4, characterised in that said first material consisting only of nickel and of phosphorus is chosen.

6. The method according to any of claims 1 to 5, characterised in that said first non-magnetic material with a proportion by mass of phosphorus comprised between 10% and 15%, limits included, is chosen.

7. The method according to any of claims 1 to 6, characterised in that said second material comprising only pure nickel, or only nickel and phosphorus, is chosen.

8. The method according to any of claims 1 to 6, characterised in that said second material with a proportion by mass of phosphorus less than or equal to 15% is chosen.

9. The method according to claim 8, characterised in that said second material with a proportion by mass of phosphorus comprised between 6% and 12%, limits included, is chosen.

10. The method according to claim 8, characterised in that said second material with a proportion by mass of phosphorus comprised between 1% and 6%, limits excluded, is chosen.

11. The method according to claim 8, characterised in that said second material with a proportion by mass of phosphorus comprised between 0% and 1%, limits included, is chosen.

12. The method according to any of claims 1 to 6, characterised in that said second material comprising boron is chosen.

13. The method according to any of claims 1 to 6, characterised in that said second material consisting only of nickel and of boron is chosen.

14. The method according to any of claims 1 to 6, characterised in that said second non-magnetic material with a proportion by mass of phosphorus comprised between 10% and 15%, limits included, is chosen.

15. The method according to any of claims 1 to 14, characterised in that said second material is applied using a galvanic method.

16. The method according to any of claims 1 to 14, characterised in that said second material is applied using a chemical method.

17. The method according to any of claims 1 to 16, characterised in that said second material is applied with a thickness of less than 10 micrometres.

18. The method according to claim 17, characterised in that said second material is applied with a thickness of less than 5 micrometres.

19. The method according to claim 18, characterised in that said second material is applied with a thickness comprised between 0.2 micrometres and 5.0 micrometres, limits included.

20. The method according to claim 19, characterised in that said second material is applied with a thickness comprised between 0.2 micrometres and 2.0 micrometres, limits included.

21. The method according to any of claims 1 to 20, characterised in that a thermal treatment is applied to the assembly formed by said substrate and its said plating, at a temperature comprised between 100°C and 500°C, for 1 to 8 hours.

22. The method according to claim 21, characterised in that said thermal treatment is carried out after the plating operation.

23. The method according to claim 21, characterised in that said thermal treatment is carried out before the plating operation.

24. The method according to any of claims 1 to 23, characterised in that said substrate is produced using a "LIGA" method.

25. The method according to any of claims 1 to 24, characterised in that said method is applied to the manufacture of an escapement mobile which is an escapement wheel or a pallet.

26. The method according to claim 2 and any of claims 1 to 25, characterised in that the thickness of said second material which consists of the peripheral layer of said mobile on said at least one surface adjoining a friction surface is limited to less than 10 micrometres.

27. The method according to claim 25, characterised in that the thickness of said second material which consists of the peripheral layer of said mobile on said at least one surface adjoining a friction surface is limited to less than 5 micrometres.