Classifications

• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/32—Component parts or constructional details, e.g. collet, stud, virole or piton
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/04—Oscillators acting by spring tension
  • G04B17/045—Oscillators acting by spring tension with oscillating blade springs
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/02—Elements
  • C30B29/06—Silicon
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
  • C30B29/60—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape characterised by shape
  • C30B29/66—Crystals of complex geometrical shape, e.g. tubes, cylinders
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F1/00—Springs
  • F16F1/02—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant
  • F16F1/025—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant characterised by having a particular shape
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/04—Oscillators acting by spring tension
  • G04B17/06—Oscillators with hairsprings, e.g. balance
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B17/00—Mechanisms for stabilising frequency
  • G04B17/32—Component parts or constructional details, e.g. collet, stud, virole or piton
  • G04B17/34—Component parts or constructional details, e.g. collet, stud, virole or piton for fastening the hairspring onto the balance
  • G04B17/345—Details of the spiral roll
• • C—CHEMISTRY; METALLURGY
  • C30—CRYSTAL GROWTH
  • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
  • C30B33/00—After-treatment of single crystals or homogeneous polycrystalline material with defined structure
  • C30B33/08—Etching
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F2224/00—Materials; Material properties
  • F16F2224/02—Materials; Material properties solids
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F2226/00—Manufacturing; Treatments
  • F16F2226/04—Assembly or fixing methods; methods to form or fashion parts
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
  • F16F2230/00—Purpose; Design features
  • F16F2230/24—Detecting or preventing malfunction, e.g. fail safe
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B11/00—Click devices; Stop clicks; Clutches
• • G—PHYSICS
  • G04—HOROLOGY
  • G04B—MECHANICALLY-DRIVEN CLOCKS OR WATCHES; MECHANICAL PARTS OF CLOCKS OR WATCHES IN GENERAL; TIME PIECES USING THE POSITION OF THE SUN, MOON OR STARS
  • G04B21/00—Indicating the time by acoustic means
  • G04B21/02—Regular striking mechanisms giving the full hour, half hour or quarter hour
  • G04B21/06—Details of striking mechanisms, e.g. hammer, fan governor
• • G—PHYSICS
  • G04—HOROLOGY
  • G04F—TIME-INTERVAL MEASURING
  • G04F7/00—Apparatus for measuring unknown time intervals by non-electric means
  • G04F7/04—Apparatus for measuring unknown time intervals by non-electric means using a mechanical oscillator
  • G04F7/08—Watches or clocks with stop devices, e.g. chronograph
  • G04F7/0804—Watches or clocks with stop devices, e.g. chronograph with reset mechanisms

Definitions

• the present invention relates to a watch spring made of monocrystalline material, in particular of monocrystalline silicon. It also relates to a method for producing such a watch spring.
• spring is meant any elastically deformable element to receive energy and / or produce force or movement.
• Monocrystalline silicon is a material highly valued in mechanical watchmaking for its advantageous properties, in particular its low density, its high resistance to corrosion, its non-magnetic nature and its ability to be machined by micro-manufacturing techniques. It is thus used to manufacture spiral springs, balances, flexibly guided oscillators, escapement anchors and escapement wheels.
• this material has the disadvantage of low mechanical strength. It can break easily, without prior plastic deformation, under the effect of external stresses.
• the present invention aims to provide a new approach for increasing the mechanical strength of a watch spring in monocrystalline silicon, which may or may not be combined with that consisting in coating the silicon oxide silicon or any other processing method aimed at improving mechanical strength.
• the present invention aims to provide a new approach for increasing the mechanical strength of a watch spring made of monocrystalline material.
• a method of making a watch spring in monocrystalline material comprising the following steps: a) drawing the spring, b) identifying one or more areas of weakness of the spring by which or by at least one of which the spring will rupture in the event of excessive deformation, c) fabricate the spring from a plate of monocrystalline material extending in a determined plane, orienting the spring in the plate such that the direction of the macroscopic stresses in the or each zone of weakness when the spring is deformed is substantially parallel to a plane of cleavage of the material secant to the determined plane.
• the present invention also provides a watch spring made of monocrystalline material elastically deformable in a determined plane and comprising one or more areas of weakness through which or through at least one of which the spring breaks in the event of excessive deformation, characterized in that the direction of the stresses macroscopic in the or each zone of weakness when the spring is deformed is substantially parallel to a plane of cleavage of the material secant to the determined plane.
• the present invention further provides a watch movement and a timepiece comprising such a spring.
• FIG. 1 is a top view of an example of a watch spring can be produced by the method according to the invention, the spring being shown in a deformed state, more precisely in its state of maximum deformation in normal operation, and the tensile stresses which it undergoes being represented by shades of gray;
• FIG. 2 is a perspective view of part of the watch spring illustrated in Figure 1, with the tensile stresses represented by shades of gray;
• FIG. 3 is a diagram showing the different steps of the process according to the invention.
• Figure 4 shows schematically in top view ( Figure 4 (a)) and in profile view ( Figure 4 (b)) a single crystal silicon wafer (100) with a flat [110];
• Figure 5 shows schematically in top view ( Figure 5 (a)) and in side view ( Figure 5 (b)) a single crystal silicon wafer (110) with a flat [100];
• FIG. 6 shows schematically in top view ( Figure 6 (a)) and in profile view ( Figure 6 (b)) a single crystal silicon wafer (111) with a flat [112]
• Figures 1 and 2 show a watch spring, in this case a rocker spring, comprising a rigid base 1 and an elastic arm 2.
• the rigid base 1 is intended to be fixed to a fixed or movable frame of a watch movement. , typically on the movement plate.
• the elastic arm 2 extends from the rigid base 1 and performs the spring function. In use, the elastic arm 2 works in flexion and acts on the rocker via its free end 3 to return it to a determined angular position.
• the present invention proposes, according to a particular embodiment, the method illustrated in FIG. 3 and described below, with its steps E1 to E3.
• the spring is first drawn by computer-aided design (step E1) taking into account the function that it is intended to perform and the location that it is intended to occupy in the movement.
• step E2 We then calculate by the finite element method (step E2) the intensity and direction of the macroscopic stresses undergone by the spring when it is subjected to bending under its normal conditions of use.
• the calculation takes into account the dimensions of the spring and the elastic characteristics (modulus of elasticity and Poisson's ratio) of the material.
• modulus of elasticity and Poisson's ratio In the case of an anisotropic monocrystalline silicon, we can at this stage rely on an average modulus of elasticity and Poisson's ratio.
• the silicon being much less resistant in traction than in compression, the simulation can be limited to the side of the elastic arm 2 which works in traction during bending, namely the right side in FIG. 1.
• Zone 4 of the spring where the stresses of traction have the greatest intensity constitutes the zone of weakness by which the spring will break from a certain force applied to its free end.
• the calculation in this step E2 can be performed for the state of maximum deformation of the spring during its normal operation in motion.
• the spring is then manufactured by etching, for example deep reactive ionic etching called DRIE or laser etching, of a wafer of monocrystalline silicon (step E3).
• the etching is carried out so that the spring has a particular orientation in the wafer, namely an orientation such that the direction D of the stresses in the zone of weakness 4 is parallel to a cleavage plane of the monocrystalline silicon secant to the mean plane P ( see Figures 4 to 6) in which the plate extends and in which the spring will deform in use.
• Single crystal silicon has a diamond-like cubic crystal structure with an atom (i) at the eight vertices of the cube, (ii) at the center of each faces of the cube, (iii) in four of the eight tetrahedral sites of the cube, ie at the center of the tetrahedron formed by a corner of the cube and the three atoms at the center of the three adjacent faces of this corner.
• the most atom-dense crystallographic planes are cleavage planes, in other words weak planes along which the material fractures when it is subjected to too great a force. In the case of monocrystalline silicon, the cleavage planes are the planes of the ⁇ 111 ⁇ family.
• FIG. 4 shows a single crystal silicon wafer 5 cut in the plane (100) with a flat ("fiat wafer") 6 oriented in the direction [110]
• the dotted lines 7 represent the intersections between the plane (100) and planes of the ⁇ 111 ⁇ family.
• FIG. 5 shows a single crystal silicon wafer 8 cut in the plane (110) with a flat 9 oriented in the direction [100].
• the dotted lines 10 represent the intersections between the plane (110) and planes of the ⁇ 111 ⁇ family.
• FIG. 6 shows a single crystal silicon wafer 11 cut in the plane (111) with a flat 12 oriented in the direction [112]
• the dotted lines 13 represent the intersections between the plane (111) and other planes of the family ⁇ 111 ⁇ . Said intersections 7, 10 and 13 between the plane in which the wafer is cut and the planes of the ⁇ 111 ⁇ family constitute cleavage directions.
• step E3 of the method according to the invention provision is made to orient the spring in the plate such that the direction D of the stresses in the zone of weakness 4 is parallel to one of the directions of cleavage 7 if the spring is made of silicon (100) with a flat [110], to one of the cleavage directions 10 if the spring is made of silicon (110) with a flat [100] and to one of the cleavage directions 10 if the spring is made of silicon (110) with a flat [100] 'one of the cleavage directions 13 if the spring is made in silicon (111) with a flat [112]
• the spring illustrated in Figures 1 and 2 comprises a single area of weakness.
• the spring may include several areas of weakness where the tensile stresses are greatest and the direction of the stresses differs from one area of weakness to another. If such configuration is observed in step E2, the spring is oriented in the silicon wafer so that the direction of the stresses of each zone of weakness is parallel to one of the cleavage planes. If this is not possible given the crystallographic directions of the wafer, the spring is redrawn (step E1) then the stresses are recalculated (step E2) until a shape of the spring comprising a single zone of weakness or zones is found. weakness in which the respective directions of the stresses can each be parallel to one of the cleavage planes. To change the position of the areas of weakness and therefore the direction of the stresses, we can vary the thickness of the elastic blade 2. Instead of changing the shape of the spring or in addition to this change, we can choose a silicon wafer. monocrystalline cut along another crystallographic plane.
• the method according to the invention can comprise intermediate steps EU and EI2 consisting respectively of recalculating the stresses in the spring on the basis of the exact elastic characteristics taking into account the anisotropy of the material and the chosen orientation. for the spring in the plate, and to modify the dimensions and / or the shape of the spring to obtain a desired stiffness and / or a desired breaking stress. If the modification of the spring is likely to change the direction of the maximum stresses, and therefore the choice of the orientation of the spring in the plate, these intermediate steps can be implemented iteratively to refine the characteristics of the spring.
• the mechanical resistance of watch springs produced according to the invention is significantly increased compared to springs whose direction of maximum stresses is not parallel to any cleavage plane.
• tests carried out on two batches of nearly thirty specimens each, the specimens being made of silicon (100) covered with silicon oxide and being subjected to bending have shown that the median value of the breaking stress is d ' around 4.7 GPa when the stresses of the weak area are directed following a cleavage plane, against about 3.4 GPa when the stresses of the zone of weakness are directed at 45 ° with respect to a cleavage plane. This difference is much greater than the improvement which the difference in modulus of elasticity can bring between the two orientations of the test piece.
• the springs monocrystalline silicon produced according to the invention can be covered with a reinforcing layer of silicon oxide.
• the thickness of such a layer is typically at least 0.5 ⁇ m and for example between 0.5 ⁇ m and 5 ⁇ m.
• Other types of reinforcing layers and / or other treatments aimed at further increasing the mechanical strength can be envisaged, such as, for example, a treatment for smoothing the surfaces of the springs.
• the improvement in mechanical strength obtained by the invention can be used to reduce the dimensions of the spring for a given force exerted in current operation and thus to reduce its bulk in the watch movement.
• the invention can be applied to various types of watch spring, in particular to rocker springs, hammer springs, lever springs, jumpers, flexible guides (for example parallel blades guiding in translation or pivots flexible, in particular flexible oscillator pivots) or elastic parts of watch components (such as toothed wheels or ferrules) serving for mounting these components on support members such as axles.
• the invention can be applied in particular to the elastic arms of the hairspring shell illustrated in FIG. 10B of patent application EP 2175328.
• the monocrystalline material of the springs produced according to the invention is not necessarily silicon. In variants of the invention, it can be diamond, aluminum oxide (for example sapphire or ruby) or silicon carbide.
• the springs produced according to the invention can be used in the movement of a wristwatch, a pocket watch or a clock, for example.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Crystallography & Structural Chemistry (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• General Physics & Mathematics (AREA)
• General Engineering & Computer Science (AREA)
• Geometry (AREA)
• Mechanical Engineering (AREA)
• Micromachines (AREA)
• Springs (AREA)
• Crystals, And After-Treatments Of Crystals (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=67998269

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Family Applications Before (1)

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Family Cites Families (11)

• 2019
  • 2019-09-20 EP EP19198559.7A patent/EP3795855A1/de not_active Withdrawn
• 2020
  • 2020-09-08 WO PCT/IB2020/058319 patent/WO2021053454A1/fr unknown
  • 2020-09-08 EP EP20768412.7A patent/EP4031778A1/de active Pending
  • 2020-09-08 US US17/761,976 patent/US20220326657A1/en active Pending
  • 2020-09-08 JP JP2021572566A patent/JP2022548446A/ja active Pending
  • 2020-09-08 CN CN202080034581.4A patent/CN113826049B/zh active Active

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