CH710914A1 - A method of manufacturing a micromechanical component anisotropic. - Google Patents

Abstract

A method of manufacturing by molding a micromechanical component (4B, 4E, 4A) made of an anisotropic composite material, composed of at least two immiscible components, including at least one reinforcing fiber and a binder matrix, the reinforcing fiber being embedded in the binder matrix, comprises a first step of stacking, in a mold, successive layers of reinforcing fibers, impregnated with matrix, hereinafter folds (2). Each fold (2) consists of a unidirectional sheet, or folds (2) woven, or multidirectional web. Each fold (2) has a given thickness ranging from 0.010 mm to 0.6 mm, and the stack of folds (2) forms a blank (1), the external dimensions of which are up to 50 or even 60 mm in length and up to 50 or 60mm wide. The blank (1) comprises at least one so-called final zone (11) corresponding to a portion of the micromechanical component (4B, 4E, 4A) and at least one so-called sacrificial zone (10) intended for machining operations. A second step consists in the application of a mechanical compression on the stack of folds (2) forming the blank (1) to ensure the compression of the materials, said mechanical compression being associated with a temperature cycle, or even the where appropriate, an air vacuum cycle for the purpose of extracting gases accumulated between the reinforcing fibers. A third step consists of machining the sacrificial zone or zones (10) of the blank (1), so as to lead to the micromechanical component (4B, 4E, 4A). The blank (1) formed in the first step has a specific anisotropic character, according to the orientations of the fibers and the thickness of each fold (2), this specific anisotropic character of the blank (1) being chosen according to the characteristics of the micromechanical component to be produced. The nature, shape and aesthetic appearance of the micromechanical component (4B, 4E, 4A) come from the shape of the mold, the type of stack and the machining operations taking into account the specific anisotropic nature of the blank (1). ), which specific anisotropic character is taken up in the micromechanical component (4B, 4E, 4A) produced. The invention also relates to a balance (4B) with variable moment of inertia for a timepiece, and an upper and / or lower element (4) of a tourbillon cage for a timepiece.

Description

The present invention relates to a method of manufacturing by molding a micromechanical component made from a composite material.

In general, the most frequently used micromechanical components are machined in a metallic material, such as iron, nickel silver, copper, brass, or other, and this by bar turning in the end of a bar, or by cutting a profile, or by stamping or punching a plate, or by milling a raw form. Some components may also be molded of thermosetting or thermoplastic synthetic material as long as their geometry is suitable for the production of a mold. The essential advantage of these techniques is their low cost of producing series of components.

The current trend is that the components are stronger, lighter, and more aesthetic. Composite materials, in the sense of reinforcing fiber and binder matrix, meet these criteria. Areas such as aeronautics, nautical, rail or automobile have taken advantage of the advantages of such materials and have developed a set of implementation processes adapted to their needs, generally summarized as follows: large, durable and lightweight parts with more or less lefts.

However, for micromechanical components, the conventional methods of implementation of composite materials have significant disadvantages that makes it difficult to achieve micromechanical components. The commonly used methods of implementation are generally unsuited to the particular constraints of small components. Therefore, a commonly used practice is to implement processes adapted to the size of the components to be produced but which, not taking into account the specificities of the composite materials, especially in terms of anisotropy, do not necessarily allow, because too random , to make the most of these materials. For example, the mass machining of a fibrous composite material resulting in a massive cut of the fibers removes the mechanical advantage of the use of such fibers.

Thus, to benefit from the exploitation of composite materials, the anisotropy must be taken into account at all stages of design and manufacture of the micromechanical component.

The choice of the fiber / matrix pair, the determination of the orientation of the fibers at each point of the micromechanical component and the taking into account of the operations necessary for the manufacture of the component, for example a machining operation, which have the subject of a theoretical study are complicated to implement, from a practical point of view. Indeed, the process respecting this succession of operations allowing the conformity of the theoretical choices throughout the production until the micromechanical component is difficult to implement.

For example, in the case of materials commonly used for producing watchmaking or micromechanical components, it is sufficient to know the nature of the material and the possible treatments it may have undergone to accurately predict the final behavior. component. The designer will choose, according to his needs, from a table of materials with well-known properties.

In the case of the use of a composite material, the knowledge of the fiber / matrix pair is not sufficient to allow the designer to predict the final behavior of the component to be made, as the behavior of the latter may vary. , for the same fiber / matrix pair chosen, depending on the position and orientation of these fibers.

[0009] Furthermore, the conventional methods consisting of an overlay of plies implemented in an open mold are not compatible with the level of precision required for a micromechanical component. They can nevertheless allow the realization of a component with a surplus of material. This surplus will then be removed by a material removal process. Given the non-isotropic nature of the consolidated composite material, depending on the nature of the geometry of the removal of material, the latter can be quite detrimental to the mechanical integrity of the component. Indeed, the machining in the mass, whatever the process, without taking into account very fine of the internal constitution, in the sense of the precise knowledge of the nature, the thickness, the constitution, the position and orientation of each fold is therefore highly hazardous as to the quality of the component thus produced.

The closed mold molding processes, compression molding in particular, allow the realization of more complex components, for example, may limit the need for recourse to subsequent operations of removal of material. However, in this case, obtaining complex shapes is made possible in particular by the application of high pressure on the composite material during implementation. This high pressure will allow creep of the matrix in the viscous state and inevitably causes a displacement of the fibers, without precise knowledge of the position of each fold at the end of the process. This type of process is no longer suitable since it is desired a fixed position of each fold from the beginning to the end of the implementation process, whether for mechanical or aesthetic reasons in particular.

The present invention relates to a method of manufacturing by molding a micromechanical component made of a composite material respecting the anisotropy of said composite material.

According to the invention, a method of manufacturing by molding a micromechanical component made of an anisotropic composite material composed of at least two immiscible components, including at least one reinforcing fiber and a binder matrix , the reinforcing fiber being embedded in the binder matrix, comprises a first step consisting in stacking, in a mold, successive layers of reinforcing fibers, impregnated with matrix, hereinafter folds, each fold consisting of unidirectional sheet in wherein the reinforcing fibers are arranged parallel to each other, or woven plies, wherein the reinforcing fibers are woven in two directions, or multidirectional web, wherein the reinforcing fibers are arranged without preferred orientation. Each fold can have a given thickness ranging from 0.010 mm to 0.6 mm, the stack of plies forming a blank, the external dimensions of which are up to 50 or even 60 mm in length and up to 50 or even 60 mm in width. The blank comprises at least one so-called final zone corresponding to a part of the micromechanical component and at least one so-called sacrificial zone intended for machining operations. A second step is to apply a mechanical compression on the stack of plies forming the blank to ensure the compression of materials, said mechanical compression being associated with a temperature cycle. Optionally this second step can be completed by the application of an air vacuum cycle in order to extract gases accumulated between the reinforcing fibers. Finally, a third step is to remove material on the sacrificial zone or zones of the blank, so as to lead to the micromechanical component. The blank formed in the first step has a specific anisotropic character, according to the fiber orientations and the thickness of each fold, this specific anisotropic character of the blank being chosen as a function of the characteristics of the micromechanical component to be produced. The nature, shape and aesthetic appearance of the micromechanical component come from the shape of the mold, the type of stack and the material removal operations taking into account the specific anisotropic nature of the blank, which specific anisotropic character is taken over. in the micromechanical component produced.

In a first embodiment, the reinforcing fiber is a dry or pre-impregnated fiber and the binder matrix is a liquid or semi-liquid matrix.

The removal operation may consist for example of a bore, a cutting, tapping, drilling, milling, threading, grinding and / or grinding, grinding, cutting water jet, laser cutting and engraving, laser / water jet combination.

In another embodiment, the blank is of thickness close to the desired final thickness, slightly greater or to an integer near fold, so as to be set to a desired thickness and flatness by a grinding or milling operation.

In order not to weaken the micromechanical component, the realization of tapping or a driving operation in a local area of said micromechanical component, can be done only if the fibers are disposed in said local area, in different directions, so as to locally create a quasi isotropic behavior.

According to another aspect of the invention, a manufacturing method by molding a rocker is made from a blank in which the rocker comprises a serge in which at least two spaced apart link arms are connected to said serge by one of their ends, said connecting arms being interconnected by their other end by an annular element in the center of said serge. The blank comprises at least one reinforcing fiber with a high Young's modulus of between 100 and 900 GPa.

According to this other aspect of the invention, the blank comprises a stack of successive layers of reinforcing fibers, impregnated with matrix, in a flat or near-plane mold, the reinforcing fibers taking the form of the mold. The stack of successive layers of reinforcement fibers, hereinafter plies, comprises one or more so-called final zones corresponding to a portion of the balance, the link arms of the balance being composed of fibers oriented radially and the central annular portion being composed of fibers whose orientation is varied.

Preferably, the blank is made from a carbon fiber and an epoxy resin, the carbon fiber being embedded in the epoxy resin.

Additional elements can be integrated in the blank before undergoing mechanical compression.

According to a completely different aspect of the invention, a method of manufacturing by molding a top and / or bottom member of a vortex cage made from a blank, wherein said upper member and / or The bottom of a vortex cage has at least two arms. Each arm has two ends, said arms being distributed around an end by which said arms are connected, the reinforcing fibers being oriented, longitudinally, in a number of orientations at least equal to the number of arms.

According to this other aspect of the invention, the blank is made from a carbon fiber and an epoxy resin, the carbon fiber being embedded in the epoxy resin.

The characteristics of the invention will appear more clearly on reading the description of several embodiments given solely by way of example, in no way limiting with reference to the schematic figures, in which: <tb> Fig. 1 <SEP> represents a perspective view of a stack of plies of composite materials constituting a type of blank; <tb> Fig. 2 <SEP> represents an exploded perspective view of a stack of plies of composite materials, folds having unidirectional fibers in precise and varied orientations; <tb> Fig. 3 <SEP> represents an exploded perspective view of a stack of plies of composite materials, plies having different thicknesses, unidirectional fibers and woven fibers; <tb> Fig. 4 <SEP> is an exploded perspective view of a stack of plies of composite materials and two metal sheets disposed at each end to sandwich pleats having unidirectional fibers and woven fibers; <tb> Fig. 5 <SEP> represents a partial schematic view of the production of a balance from a stack of plies of composite materials comprising fibers in four orientations, the folds being then compressed to form a blank from which the pendulum is extracted ; <tb> Fig. 6 <SEP> is a partial schematic view of the realization of a vortex cage element from a stack of plies of composite materials comprising fibers in three orientations, the plies then being compressed to form a blank from where is extracted the element of tourbillon cage; and <tb> Fig. 7 <SEP> represents a blank from which three indicator hands are extracted.

The following description relates to horological applications and more particularly to a manufacturing process by molding a balance 4B, a tourbillon cage element 4E and 4A needles from a blank 1.

The machining of watch components (for example 4B, Fig. 5, 4E, Fig. 6, 4A, Fig. 7) is done via the use of blanks 1. These blanks 1 have a standard external shape for which the manufacturers of components equip their machining centers with adapted positions, allowing easy positioning and location, as well as sometimes, an appropriate gripping mode for palletizing for serial work. The components 4 can then be machined and taken from this blank 1.

The production of a blank 1 whose constitution is precisely known (nature of the fiber / matrix pair, but also the position and orientation of the fibers) makes it possible to predict the final mechanical behavior according to the selected blank 1 and whose external dimensions are known to allow the machinist in micromechanics to work in a conventional manner according to the rules of the art of his field.

It is here admitted that the fibers are grouped in the form of folds 2 that is to say having two dimensions and a half (a plane and a thickness) and that these fibers are pre-impregnated with a binder matrix. We will now speak of folds 2. As illustrated in FIG. 1, the blank 1 consists of a stack of plies 2 of composite materials.

The blank 1 therefore advantageously combines a strict compliance with the orientations and positions of the fibers, decided according to the type of component 4B, 4E, 4A to be produced from the blank 1, and a precision component 4B, 4E, 4A then taken from the blank 1 known according to the capability of the machine used. In the example illustrated in FIG. 2, the blank 1 is made from a stack of plies 2 of composite materials, the plies 2 having unidirectional fibers in various orientations, for example according to the arrangement illustrated in FIG. 2 (0 / -45 / 45/0/0/0/45 / -45 / 0).

In another example illustrated in FIG. 3, the blank 1 is made from a stack of plies 2 of composite materials, the plies 2 having different thicknesses, unidirectional fibers 2U and 2T woven fibers, or in this example three plies 2U arranged between two plies 2T.

In another example illustrated in FIG. 4, the blank 1 is made from a stack of plies 2 of composite materials and two metal sheets 3 arranged at each end to sandwich pleats 2 having unidirectional fibers 2U and the center of the woven fibers 2T.

This blank 1, for example of FIG. 3 or FIG. 4, once consolidated, can be machined on a machining center with known accuracy capabilities to achieve a micromechanical component with the desired benefits of composite materials constituting it and with great repeatability from one manufacture to another.

The blank 1 will advantageously have a high accuracy of thickness and flatness, compatible with the tolerances required according to these criteria on the component 4B, 4E, 4A finished. In fact, the machining will generally take place in two operations, the work being carried out on the face from above, then from below. The intervention on the underside will require a flipping of the component 4B, 4E, 4A, following which the precise knowledge of thickness and flatness of the blank 1 allow a respect of the same tolerances on the component 4B, 4E, 4A. This respect of tolerance of thickness and flatness will be guaranteed by the phase of implementation and consolidation of the blank 1 (stacking of a known number of folds 2 of a known thickness of folds) and the pressure conditions. / temperature to ensure a final thickness of the blank 1.

Depending on the case of desired final thickness, it may be that the pitch of the folds 2 does not allow an exact compliance with this thickness (the final thickness corresponds to an integer number of folds that can, for their part, be different thicknesses). In such a case, it is advisable to produce a blank 1 of approximate thickness of the final thickness, in slight excess, to an integer close to fold 2. Then, a thickness setting operation must be performed to guarantee the tolerance of thickness and flatness. This operation can be carried out on a platen machine (single-sided or double-sided), for example by grinding or milling.

The first step in the development of the present invention is to define its constitution, in terms of choice of the nature, type, number and orientation of each ply 2 of pre-impregnated. This choice will be different according to the purpose of the component 4B, 4E, 4A which will be machined in the present invention, whether the purpose is mechanical, aesthetic or otherwise.

In general, a rocker with variable moment of inertia comprises a wheel-shaped part comprising a serge, connection elements between the serge and the axis of the balance and a certain arrangement of screws nuts or flyweights fixed on the balancing serge that allow by adjusting their positions to change the imbalance and the moment of inertia of the pendulum.

The accuracy of a watch equipped with a sprung balance depends essentially on the frequency stability of its sprung balance. Different parameters affect the frequency stability of a sprung balance whose amplitude variations of the pendulum oscillations. These amplitude variations are notably related to the positions of the watch, to the loss of the moment of force, to the friction, in particular with the pivots of the balance shaft and the unbalance of the latter. This has the effect of causing a lack of isochronism of the sprung balance, this isochronism defect having an impact on the precision of the timepiece.

Moreover, among the other important criteria for a pendulum we can mention in particular the mass, the resistance, the coefficient of friction, the coefficient of thermal expansion, the non-magnetism, the hardness, ... It is extremely rare and unlikely that a single material alone can meet all the expected characteristics. The present invention aims to select and combine different materials that best meet each function of the balance.

In a clockwork, the axis of rotation must have specific features to reduce friction, it will usually be made of brass. The weights must have a high density, that is to say a concentrated mass for a small volume, more precisely a minimized outer surface to limit the friction of the air to which the pendulum will be subjected during oscillations. These masses can be made for example platinum. Thus, the characteristics of the axis and flyweights being defined, it is expected that the part mechanically connecting them to be the most transparent in terms of mass, deformation, elongation. The use of a composite material based on carbon fibers and epoxy resin has these advantages, with a very high strength / mass ratio.

This very high ratio is made possible by the intrinsic characteristics of the composite material, but also its non-isotropic use, that is to say with a fiber orientation in a specific direction, depending on the forces exerted by the weights on the hub, namely their mass and the centrifugal force in motion. This precise determination of the forces makes it possible to choose a fiber with a high Young's modulus, between 100 and 900 GPa, a binding matrix making it possible to transit the forces in the fiber, and a precise orientation of the fibers, this resulting in a mechanical joining. between weights and hub for a minimized mass. This mass gain makes it possible, with a given inertia, to produce a complete balance wheel of reduced mass, or of equal mass, to be able to increase its inertia by allocating the mass gained to the flyweights.

This orientation will be predominantly radial, in order to limit the boom to stop due to the mass of the weights and exerting a bending of the arms, and limit elongation during oscillations, due to the centrifugal force traction exerted by the weights. This radial distribution is made possible by the use of unidirectional sheets or son.

The conventional assembly of hunting to assemble materials of different nature will be made possible by the local orientation of the particular fibers. Indeed, we have seen that the mechanical considerations led to a preferred fiber orientation along radial axes. These orientations of fibers on such small thicknesses do not allow the driving, the driven axis exerting a uniformly distributed pressure in all directions of the plane, which leads to delamination, separation of the fibers. By arranging fibers in different directions in the area near the hunting, the fibers will be allowed to counter this pressure exerted by the driven axis. This method of assembly can be used to fix the weights on the joining part made of composite materials.

The high ratio of resistance / mass associated with a judicious orientation of the fibers makes it possible to limit the overall mass of the pendulum. Thus, according to another approach, inertia and balance mass defined with a "standard" balance, it is possible to achieve a balance using these composite materials, with equal performance, but with a larger size. Thus, if the available volume authorizes it, the present invention makes it possible to design a visually larger balance and to provide a sensible differentiation.

In the case of use of a beam, a major feature is its dimensional stability in time and depending on external conditions, particularly the impact of temperature, to ensure a constant isochronism. The present invention makes it possible to ensure a very high dimensional stability thanks to a lower coefficient of thermal expansion than the conventionally used materials. For this, it will be appropriate to choose a particular carbon fiber, having this specificity of thermal expansion almost zero, while retaining its mechanical characteristics, specifically in terms of Young's modulus, particularly important in this case of use. Moreover, the arrangement of the fibers will be extremely important for the respect of the criterion of thermal elongation. Indeed, if the appropriately selected fiber can have a coefficient of thermal expansion almost zero, this is not the case of the binder matrix of the family of polymers. Thus, the consolidated composite material will have an almost zero elongation in the longitudinal direction of the fibers, while it will be non-negligible in the transverse direction. Therefore, the radial orientation favored by the mechanical aspects is also suitable for thermal aspects. Virtually zero elongation ensures constant inertia as a function of temperature. Elongation, which we can not avoid, in the transverse direction of the fibers, will have no impact on the inertia of the balance.

The accuracy of the calibres depends on the quality of their regulating organ, and obtaining very high oscillation frequencies, for example 10 Hz, to be compared to the usual frequencies of 2.5 to 4 Hz, can not be used. obtained only with the design of suitable regulating members, in particular with regard to the pendulum.

In the case of using a pendulum subjected to high frequency oscillations, for example 10 Hz, the aerodynamic aspects have a significant impact on the performance, which can be seen in particular through the value of the factor. quality. The fundamental parameter qualifying any resonator is its Q quality factor. It is a dimensionless number that can be interpreted in two different but closely related ways. We can first consider Q as the ratio between the internal energy W of the resonator and the energy dissipation AW due to Joule losses during an oscillation cycle. A high quality factor resonator will thus require less energy for its maintenance than an identical resonator but with a low quality factor. Another interpretation of the quality factor, a little more abstract but important to understand, says that the stability of a resonator is proportional to its quality factor. The stability of a time base is therefore directly related to the quality factor of its resonator: the higher it is, the more the resonator is insensitive to its maintenance mechanism. In order to maximize the latter, it is necessary to reduce the friction on the moving parts. An aerodynamic study of the pendulum in motion shows that it is necessary to limit the wet surface and to minimize the coefficient of drag. One solution is to minimize the front surface and give the arms a shape with leading and trailing edges with a suitable profile. At the scale considered, it is not obvious to produce such shapes by conventional machining methods. The present invention proposes to use advantageously the molding capacity of the fibers by producing this profile in a molding tool which will in turn move the fibers during their implementation and ensure compliance with this aerodynamic profile, guaranteeing a better aerodynamic efficiency than a rectangular section.

The composite material selected for the present invention also has advantageous non-magnetic characteristics in the case of use of a balance, thus limiting its influence to external magnetic disturbances and ensuring consistency of the isochronism. The composite material selected for the present invention also has a high corrosion resistance.

In the example illustrated in FIG. 5, a beam 4B is made from a blank 1 consisting of a stack of seven plies 2 of composite materials comprising fibers in four orientations. The folds 2 are compressed to form a blank 1 from which the balance 4B is extracted after a machining operation.

In this example, the balance 4B taken includes a serge 5, discontinuous, wherein four connecting arms 6 spaced from each other are connected to said serge 5 by one end of said arms 6. The connecting arms 6 are connected between them by their other end by an annular element 7 in the center of said serge 5. The four connecting arms 6 and the serge 5 are made of a composite material based on carbon fibers and epoxy resin having a very high resistance / mass ratio. The fibers are oriented radially with respect to an axis of rotation around the annular element 7 and whose orientation of the fibers in the annular element is achieved by arranging the reinforcing fibers in different directions. The stack of folds 2 is made with unidirectional fibers according to the illustrated arrangement comprising four different orientations, a first orientation at 0 °, a second orientation at 90 °, a third and a fourth orientation determined by the arrangement of the connecting arms 6, the value 0 ° corresponding to fibers oriented along the bisector of an angle between two successive arms 6 connected by a serge portion 5. In this example illustrated the angle & is the bisector of the angle between the two arms 6 successive. In other words, the angle between said successive arms 6 connected by a serge portion 5 is 2 ° B. In this example the angle Q> can take a value between 10 ° and 90 ° for example.

Optionally, the balance 4B may comprise additional elements, for example flyweights, which are directly integrated during the production phase of the blank 1.

Thus, in the case of the embodiment of a balance 4B, the blank 1 is made of an anisotropic composite material composed of carbon fibers and epoxy resin having a very high strength to mass ratio. The method comprises a first operation consisting in stacking, in a mold, successive layers of carbon fibers, impregnated with epoxy resin, hereinafter plies 2, each ply 2 consisting of a unidirectional layer in which the carbon fibers are arranged. parallel to each other, each ply 2 having a given thickness ranging from 0.010mm to 0.6mm, the stack of plies 2 forming a blank 1, the external dimensions of which are up to 60mm in length and up to 60mm in width .

The blank 1 comprises a so-called final zone 11 corresponding to the shape of the balance 4B and a so-called sacrificial zone 10 intended for machining operations.

Then, the application of a mechanical compression on the stack of folds 2 forming the blank 1 ensures the compression of materials, said mechanical compression being associated with a temperature cycle.

Finally, a machining operation of the sacrificial zone 10 of the blank 1 can extract the balance 4B.

The balance 4B with variable moment of inertia comprises a serge 5, discontinuous, in which four spaced apart connecting arms 6 are connected to said serge 6 by one end of said arms 6, said connecting arms 6 are connected by one of their end to a central ring 7 and at their other end, two by two, to a serge portion 5. The link arms 6 and the serge 5 are made from a composite material using a carbon fiber, the module high Young, between 100 and 900 GPa, whose fibers are oriented radially relative to an axis of rotation around the annular element 7 and whose orientation of the fibers in the annular element 7 is made by arranging the fibers reinforcement in different directions.

According to another aspect of the invention, the method is implemented to manufacture another watchmaking component 4, such as an upper or lower element of tourbillon cage 4E for clockwork, illustrated in FIG. 6, made of composite materials.

The vortex, if it improves the performance of a mechanical movement in terms of isochronism, nevertheless has an impact on the operation of said movement by its energy consumption, direct impact on the power reserve and potentially on isochronism according to its mass.

As any moving element of a mechanical movement, the tourbillon cage has any interest in having a minimized total mass. The use of a low density material is therefore preferred. Nevertheless, because of their geometric shape, the upper and lower cages generally have slender arms. This slenderness, which imposes a weak section, therefore requires a high resistance. It is a material with a high ratio of rigidity / mass that will be suitable. A composite material in the reinforcing fiber sense, such as a carbon fiber and a binder matrix such as an epoxy resin, has intrinsic mechanical properties superior to the materials conventionally used for producing tourbillon cages, particularly in terms of specific Young's modulus. that is, the module brought back to the ground.

In a fibrous material, which is not isotropic in nature, the value of the modulus varies very substantially depending on the orientation of the fibers. It is therefore necessary, to ensure the desired rigidity, to precisely orient the fibers in certain strategic places of the tourbillon cage.

For the realization of the arms, a study of resistance of non-isotropic materials will highlight the need to have a maximum of fibers in the longitudinal direction of the arms.

In the case of use of a tourbillon cage, a major feature of the latter is its dimensional stability over time and depending on external conditions, particularly the impact of temperature, to ensure isochronism constant. The present invention makes it possible to ensure a very high dimensional stability thanks to a lower coefficient of thermal expansion than the conventionally used materials. For this, it will be necessary to choose a particular carbon fiber, having a thermal expansion specificity of almost zero, while retaining its mechanical characteristics, specifically in terms of Young's modulus, particularly important in this case of use. Moreover, the arrangement of the fibers will be extremely important for meeting this criterion of thermal elongation. Indeed, if the appropriately selected fiber can have a coefficient of thermal expansion almost zero, this is not the case of the binder matrix of the family of polymers. Thus, the consolidated composite material will have an almost zero elongation in the longitudinal direction of the fibers, while it will be non-negligible in the transverse direction. Therefore, the radial orientation favored by the mechanical aspects is also suitable for thermal aspects. Virtually zero elongation ensures constant inertia as a function of temperature. Elongation, which can not be avoided, in the transverse direction of the fibers, will have no impact on the inertia of the cage.

The composite material selected for the present invention also has advantageous non-magnetic characteristics in the case of use of a tourbillon cage, thus limiting its influence to external magnetic disturbances and ensuring consistency of the isochronism.

The composite material selected for the present invention also has a high corrosion resistance.

The realization of such a component will be made possible by the preliminary development of a blank 1, the constituent folds will be epoxy carbon prepreg, and whose grammages and orientations will depend on the geometry of the cage bridges. In the widespread case of a vortex cage element 4E with three arms 8, it will be necessary to arrange the fibers in each direction of the arms 8, so that the element of the cage 4E has a homogeneous mechanical behavior.

As illustrated in FIG. 6, the upper and / or lower element of a tourbillon cage 4E for a timepiece is obtained from a blank 1. The element 4E comprises three arms 8 distributed around an end 9 through which the arm 8 are connected, the arms 8 being made of a composite material using a reinforcing fiber, the fibers of which are oriented longitudinally in three orientations. The stack of folds 2 is made with unidirectional fibers having an orientation of 60 ° relative to each other. The stack of folds 2 is made with unidirectional fibers according to the following arrangement: (0 / 607-60 / 0/60 / -60 / 0/60 / -60). In theory, a mirror symmetry should be respected in the stack, but in the present case, an identical distribution of the orientations in each arm 8 is favored in order to have a homogeneous mechanical behavior from one arm 8 to the other.

In another example, illustrated in FIG. 7, needles 4A of a watch are made from a blank 1, consisting of a stack of folds 2 whose reinforcing fibers are oriented, longitudinally, in at least two orientations. In this example, there are three folds 2.

In the field of watchmaking, taking into account the mechanical and / or aesthetic constraints, other watch components can be manufactured according to the method described, such as a stamp / hammer, a cog, a whirlwind, a spring / jumper, a mass support, a watch case without ice, a watch bezel and many other components

Furthermore, the coloring of the material is not described, but it is possible in an additional step of the process.

The present invention aims to ensure, in each location of a micromechanical component produced, an optimum arrangement of the constituent fibers, according to the considerations required by the need, whether mechanical or aesthetic, for example.

The examples described above highlight the advantages of the method and its application for watch components. However, the present invention also allows the manufacture of a micromechanical component for other fields such as medical, automotive, mobile telephony, aviation, space, robotics, jewelery or leather goods.

Claims (22)

1. Method of manufacturing by molding a micromechanical component (4B, 4E, 4A) made based on an anisotropic composite material composed of at least two immiscible components, including at least one reinforcing fiber and a binder matrix, the reinforcing fiber being embedded in the binder matrix, the method comprising the following operations: a) Stacking, in a mold, successive layers of matrix-impregnated reinforcing fibers, hereinafter folds (2), each fold (2) consisting of a unidirectional sheet in which the reinforcing fibers are arranged parallel to each other; other, or wrinkles (2) woven, wherein the reinforcing fibers are woven in two directions, or multidirectional web, wherein the reinforcing fibers are arranged without preferred orientation, each fold (2) having a given thickness ranging from 0.010mm to 0.6mm, the stack of folds (2) forming a blank (1), whose external dimensions are up to 50 or even 60mm in length and up to 50 or even 60mm in width, said blank (1) comprising at least one so-called final zone (11) corresponding to a portion of the micromechanical component (4B, 4E, 4A) and at least one so-called sacrificial zone (10) intended for machining operations, b) applying a mechanical compression on the stack of folds (2) forming the blank (1) to compress the materials, said mechanical compression being associated with a temperature cycle, c) Where appropriate, apply an air vacuum cycle for the purpose of extracting gases accumulated between the reinforcing fibers, and d) machining the sacrificial zone or zones (10) of the blank (1), so as to lead to the micromechanical component (4B, 4E, 4A), characterized in that the blank (1) formed in step a) has a specific anisotropic character, according to the orientations of the fibers and the thickness of each fold (2), this specific anisotropic character of the blank (1) being chosen according to characteristics of the micromechanical component (4B, 4E, 4A) to be produced, and the nature, shape and aesthetic appearance of the micromechanical component (4B, 4E, 4A) comes from the shape of the mold, the type of stack and the machining operations taking into account the specific anisotropic nature of the blank (1 ), which specific anisotropic character is taken up in the micromechanical component (4B, 4E, 4A) produced. 2. The method of claim 1, wherein the reinforcing fiber is a dry or pre-impregnated fiber and the binder matrix is a liquid or semi-liquid matrix. 3. The method of claim 1 or 2, wherein the machining operation comprises a bore, cutting, tapping, drilling, milling, threading, grinding and / or grinding. 4. Method according to one of the preceding claims, wherein the blank (1) is of thickness close to the desired final thickness, slightly greater or an integer near folds (2) and the blank is put at a desired thickness and flatness by a grinding or milling operation. 5. Method according to one of the preceding claims, wherein the fibers are arranged in a local area of the micromechanical component (4B, 4E, 4A), in different directions, so as to locally create a quasi-isotropic behavior, for the performing tapping or a driving operation. 6. Method according to one of the preceding claims for manufacturing by molding a pendulum (4B) of a watch mechanism from a blank (1), the balance (4B) comprising a serge (5) in which at at least two spaced connecting arms (6) are connected to said serge (5) by one of their ends, said connecting arms (6) being interconnected at their other end by an annular element (7) in the center of said serge , the blank (1) comprising at least one reinforcing fiber with a high Young's modulus of between 50 and 900 GPa. 7. Method according to claim 6, wherein the blank (1) comprises a stack, in a mold, of successive layers of reinforcing fibers, planar or quasi-planar, impregnated with matrix, the said so-called final zones (11). ) corresponding to a portion of the beam (4B), the link arm (6) of the beam (4B) being composed of radially oriented fibers and the central annular portion (7) being composed of fibers whose orientation is varied. 8. The method of claim 6 or 7, wherein the blank (1) is made of a carbon fiber and an epoxy resin by embedding the carbon fiber in the epoxy resin. 9. Method according to one of claims 6, 7 or 8, wherein additional elements are integrated in the blank (1) before undergoing mechanical compression. 10. Method according to one of claims 1 to 5 of manufacturing by molding of an upper element and / or lower (4E) of a vortex cage made from a blank (1), said upper element and / or lower (4E) a vortex cage having at least two arms (8), each arm (8) having two ends, said arms (8) being distributed around an end by which said arms (8) are connected , the reinforcing fibers being oriented longitudinally in a number of orientations at least equal to the number of arms (8). 11. The method of claim 10, wherein the blank (1) is made based on a carbon fiber and an epoxy resin by flooding the carbon fiber in the epoxy resin. 12. Method according to one of claims 1 to 9 for manufacturing a watch component, medical, automotive, mobile telephony, aviation, space, robotics, jewelery or leather goods. 13. Pendulum (4B) with a variable moment of inertia for a timepiece obtainable according to the method of one of claims 1 to 9, comprising a serge (5) in which at least two spaced connecting arms (6) are connected to said serge (5) by one end of said arms (6), said connecting arms (6) being interconnected by their other end by an annular element (7) in the center of said serge (5), characterized in that that the connecting arms (6) and the serge (5) are made of a composite material using a high Young's modulus reinforcing fiber, between 50 and 900 GPa, whose fibers are oriented radially relative to an axis of rotation around the annular element (7) and whose orientation of the fibers in the annular element (7) is achieved by arranging the reinforcing fibers in different directions. 14. Pendulum (4B) according to claim 13, wherein the serge (5) is discontinuous. 15. Pendulum (4B) according to one of claims 13 or 14, comprising four connecting arms (6), the connecting arms (6) being connected by one end to a central ring (7) and their other end, two by two, to a portion of serge (5). 16. Pendulum (4B) according to one of claims 13 to 15, wherein an axis of the beam (4B) is driven into the annular element (7) in the center of said serge (5). 17. Pendulum (4B) according to one of claims 13 to 16, wherein additional elements, for example flyweights, are integrated. 18. Pendulum (4B) according to one of claims 13 to 17, wherein weights are arranged on the connecting arms (6) and / or on the serge (5). 19. Pendulum (4B) according to one of claims 13 to 18, wherein the stack of folds (2) is made with unidirectional fibers in an arrangement comprising four different orientations, a first orientation at 0 °, a second orientation at 90 °, a third and a fourth orientation determined by the arrangement of the link arms (6), the value 0 ° corresponding to fibers oriented along the bisector of an angle between two successive arms (6) connected by a portion of serge (5). 20. Upper and / or lower element (4E) of a tourbillon cage for a timepiece obtainable according to the method of one of claims 10 or 11, the element (4E) comprising at least two arms (8). distributed around an end by which said arms (8) are connected, the arms (8) being made of a composite material using a reinforcing fiber, the fibers of which are oriented, longitudinally, according to a number of orientations at least equal to the number of arms (8). 21. Element (4E) according to claim 20, said element (4E) having three arms (8) evenly distributed, the stack of folds (2) being made with unidirectional fibers having an orientation of 60 ° relative to the other. 22. Element (4E) according to claim 20 or 21, said element (4E) having three arms (8) regularly distributed, the stack of folds (2) being made with unidirectional fibers according to the following arrangement: (0 / 60 / -60 / 0/60 / -60 / 0/60 / -60).