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

Abstract

Method for manufacturing a timepiece mobile, in which a substrate is produced with a first material comprising at least nickel and phosphorus, the substrate is shaped to the geometry of the mobile, and the substrate is galvanically or chemically coated, on at least one surface of the mobile substrate, with at least one second material which constitutes the peripheral layer of the mobile on the at least one surface of the mobile substrate, and which comprises at least nickel and which has less phosphorus than the first material, or which comprises nickel and lacks 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, can prove sensitive in certain climatic conditions, which are likely to lead to a degradation of performance, particularly in terms of amplitude regularity, stops, or even aging, especially when the two antagonistic components of the friction couple are made of similar LIGA materials.

[0006] Document WO 2008 / 052 378 A2 discloses the example of a watch part made of a material containing nickel and phosphorus, and coated on the surface with another material. Summary of the invention

[0007] 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.

[0008] For this purpose, the invention relates to a method for manufacturing watch movements according to claim 1. Detailed description of preferred embodiments

[0009] The invention relates to the field of micromechanical components, and more particularly to watch movements.

[0010] 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.

[0011] In Swiss lever escapement mechanisms, the contact between the ruby ​​lever of the anchor and the tooth of the escape wheel is particularly sensitive, as is the contact between the fork and the pallet fork pin or between the fork and the anchor stops.

[0012] This is particularly important to ensure the presence of lubricant on the contact surfaces between the escape wheel and the anchor, and to reduce the aging of the escape wheel and the anchor.

[0013] 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.

[0014] The stability of the lubrication at the contact between the anchor levers and the escape wheel must ensure the consistency of the amplitude.

[0015] To this end, the addition of a coating in the form of a layer of galvanic nickel (Ni) preferably, or of chemical nickel (for example NiP6-9), or even of nickel-boron deposited by chemical means, on a LIGA NiP12 escape wheel greatly improves the performance of the movements.

[0016] Indeed, various tests have demonstrated that this significant improvement is linked to better adhesion of the epilame under predetermined climatic conditions, for example at 50° Celsius and a humidity level of 90%. The inventors observed better adhesion of the epilame to the material when the amount of phosphorus on the surface is reduced; consequently, the lubricant's performance is all the better when the amount of phosphorus is low.

[0017] In one variant, the galvanic nickel coating can be an alloy, for example Ni-Fe, or Ni-W, or other.

[0018] 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 low thickness, less than 10 micrometers, which constitutes a peripheral layer of the movement at the level of this at least one surface of the substrate of the movement, and which comprises only nickel and boron.

[0019] More specifically, this first non-magnetic material is chosen.

[0020] More specifically, this second non-magnetic material is chosen. More precisely, it exhibits a non-magnetic character.

[0021] 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 gives the part its non-magnetic character.

[0022] In a particular embodiment, the substrate is a nickel-phosphorus of NiPx formulation, with x between 1% and 15% by mass, or more particularly with x between 10% and 15% by mass, the latter range making it possible to guarantee the non-magnetic character of the coating.

[0023] The coating covering the substrate is low in phosphorus, and its thickness is not limited to between 0.2 micrometers and 10.0 micrometers, and, more particularly, between 0.2 micrometers and 2.0 micrometers.

[0024] Preferably, the coating has a thickness of 0.5 micrometers.

[0025] The coating treatment with a low-phosphorus coating, according to the invention, can be carried out by galvanic means.

[0026] 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.

[0027] 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.

[0028] Alternatively, the recoating treatment with a low or zero phosphorus coating can be done chemically, according to a chemical nickel application process, 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, according to the invention, a nickel-boron NiB.

[0029] Adding a layer of nickel, or NiP6-9, or NiB, increases the stability of the epilame in all climatic conditions, the grip of the epilame and therefore the resistance of any common watch lubricant.

[0030] More specifically, the epilame used is a fluoride-based formulation.

[0031] 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.

[0032] 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 pallet fork pin and the stops, are rounded, which allows for a point of contact instead of a line of contact.

[0033] 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.

[0034] 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.

[0035] 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 a 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.

[0036] 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 a second material, which constitutes a 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.

[0037] More specifically, the substrate is shaped to the geometry of the mobile.

[0038] More specifically, this substrate coating is carried out by galvanic and / or chemical and / or PVD and / or CVD means.

[0039] In one variation, this substrate coating is applied to surfaces of the moving part other than the surfaces that guide the moving part for pivoting or for 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.

[0040] In another variant, the substrate coating is carried out on the surfaces of the mobile including these mobile guidance surfaces.

[0041] In yet another variation, this coating is applied to at least one surface 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.

[0042] 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.

[0043] In one variant, the substrate coating is applied to all surfaces of the mobile.

[0044] More specifically, the first material containing phosphorus with a mass proportion between 1% and 15% is chosen.

[0045] More specifically, the first material consisting solely of nickel and phosphorus is chosen.

[0046] More specifically, the first non-magnetic material is chosen with a proportion by mass of phosphorus between 10% and 15%.

[0047] More specifically, the first non-magnetic material is chosen.

[0048] More specifically, the second material is chosen, consisting only of pure nickel, or only of nickel and phosphorus.

[0049] More specifically, the second material is chosen with a proportion by mass of phosphorus less than or equal to 15%.

[0050] More specifically, the second non-magnetic material is chosen with a proportion by mass of phosphorus between 10% and 15%.

[0051] As an alternative, the second material is chosen with a proportion by mass of phosphorus between 6% and 12%.

[0052] In another alternative, the second material is chosen with a proportion by mass of phosphorus between 1% and 6%.

[0053] In yet another alternative, the second material is chosen with a proportion by mass of phosphorus less than or equal to 1%.

[0054] More specifically, the second material containing boron is chosen.

[0055] More specifically, the second material, consisting solely of nickel and boron, is chosen.

[0056] In one variant, the second material is applied galvanically.

[0057] In another variant, the second material is applied chemically.

[0058] More specifically, the coating is applied with a thickness of less than 10 micrometers.

[0059] More specifically, the coating is applied with a thickness between 0.2 micrometers and 5.0 micrometers. More specifically, the coating is applied with a thickness between 0.2 micrometers and 2.0 micrometers.

[0060] In yet another variant, the coating is applied with a thickness of less than 0.2 micrometers, specifically in the vicinity of 0.1 micrometers.

[0061] 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.

[0062] In particular, the substrate is produced by a "LIGA" process (lithography-galvanization-forming, from the German "Röntgenlithographie, Galvanoformung, Abformung").

[0063] More specifically, a galvanic and / or chemical coating is applied to all surfaces of the substrate with such a second material.

[0064] More specifically, this process is applied to the manufacture of an escapement mechanism formed for example by an escape wheel or an anchor.

[0065] 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.

[0066] 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.

[0067] This process allows the production of a micromechanical component, in particular a watch movement, and more specifically an escapement mechanism movement, whose surface area is optimized.

[0068] The resulting moving part can advantageously receive a lubricating substance on its friction surfaces, for example, a synthetic oil or grease suitable for precision microtechnical applications, familiar to watchmakers. Such a lubricating substance can be combined with a paste based on molybdenum disulfide (MoS2).

[0069] The mobile can also advantageously receive a layer of epilame on at least one surface of the coating other than its friction surfaces in order to allow better adhesion of the lubricating substance.

Claims

1. Method for manufacturing a timepiece wheel, by which a substrate is manufactured with a first material including at least nickel and phosphorus, and a coating of said substrate is performed, on at least one surface of the substrate of said wheel, with at least one second material that constitutes a peripheral layer of said wheel at said at least one surface of the substrate of said wheel, characterised in that said second material only consisting of nickel and boron.

2. Method according to claim 1, characterised in that said coating of said substrate is performed, on at least one surface adjoining a friction surface of said wheel, with said at least one second material that constitutes the peripheral layer of said wheel at said at least one surface adjoining a friction surface of said wheel.

3. Method according to claim 1 or 2, characterised in that said substrate is shaped to the geometry of said wheel.

4. Method according to one of claims 1 to 3, characterised in that said coating of said substrate is performed galvanically and / or chemically and / or by PVD and / or CVD.

5. Method according to one of claims 1 to 4, characterised in that said first material only consisting of nickel and phosphorus is selected.

6. Method according to one of claims 1 to 5, characterised in that said first material with a proportion by weight of phosphorus between 1% and 15% is selected.

7. Method according to one of claims 1 to 6, characterised in that said first non-magnetic material with a proportion by weight of phosphorus between 10% and 15% is selected.

8. Method according to one of claims 1 to 7, characterised in that said second material with a thickness less than 10 micrometres is applied.

9. Method according to claim 8, characterised in that said second material with a thickness less than 5 micrometres is applied.

10. Method according to claim 9, characterised in that said second material with a thickness between 0.2 micrometres and 5.0 micrometres is applied.

11. Method according to claim 10, characterised in that said second material with a thickness between 0.2 micrometres and 2.0 micrometres is applied.

12. Method according to one of claims 1 to 11, characterised in that a heat treatment is applied to the assembly formed by said substrate and its said coating, at a temperature between 100°C and 500°C, for 1 to 8 hours.

13. Method according to claim 12, characterised in that said heat treatment is performed after the coating operation.

14. Method according to claim 12, characterised in that said heat treatment is performed before the coating operation.

15. Method according to one of claims 1 to 14, characterised in that said second substrate is produced by a "LIGA" method.

16. Method according to one of claims 1 to 15, characterised in that said method is applied to the manufacturing of an escapement wheel that is an escape wheel or a pallet.

17. Method according to claim 2 and one of claims 1 to 16, characterised in that the thickness of said second material that constitutes the peripheral layer of said wheel at said at least one surface adjoining a friction surface is limited to less than 10 micrometres.

18. Method according to claim 16, characterised in that the thickness of said second material that constitutes the peripheral layer of said wheel at said at least one surface adjoining a friction surface is limited to less than 5 micrometres.