EP3313227A1

EP3313227A1 - Ultrasonic driving method

Info

Publication number: EP3313227A1
Application number: EP16751005.6A
Authority: EP
Inventors: Csaba AZAU; Jacques Jacot
Original assignee: Ecole Polytechnique Federale de Lausanne EPFL
Current assignee: Ecole Polytechnique Federale de Lausanne EPFL
Priority date: 2015-06-25
Filing date: 2016-06-24
Publication date: 2018-05-02
Also published as: JP2018521867A; KR20180030056A; WO2016207851A1

Abstract

A method for driving a first component (11) into a second component (12) by superimposing a mechanical wave of ultrasonic frequency (18) onto the movement (17) of at least one of the components (11, 12). The method comprises a step of adjusting the parameters of the method in order to control the quantity of energy dissipated at the interface (13) between the two components (11, 12). In particular, the oscillatory displacement at ultrasonic frequency is measured optically at a frequency greater than the ultrasonic application frequency and the oscillation amplitude is therefore estimated in real time in order to be able to keep same constant during the driving operation as a result of adjusting the ultrasonic power injected into the system. In particular, the method consists of driving timepiece components such as a pin, a shaft, a tube, a pinion, a screw foot, a post, a tube, an hour wheel, a timepiece jewel, a bearing, a timepiece shock-absorber, an intermediate part in a plate, a bridge, a ring, an intermediate part, a timepiece wheel, a disc, a dial, a hand or a bracelet link.

Description

ULTRASONIC CHASSING PROCESS

Corresponding request

The present application claims the priority of the European application N ° EP 15173943.0 filed on June 25, 2015 in the name of the Ecole Polytechnique FÉDÉRALE DE LAUSANNE (EPFL), the content of this prior application being incorporated by reference in its entirety in the present application .

State of the art

The present invention relates to the method of ultrasound scavenging, more specifically to a technique of soldering and / or soldering at the interface between at least two components resulting from the controlled dissipation of the ultrasound energy superimposed on the movement of least one component.

Document JP0246675A, JP1024939A, DE9305285UU1 and DE102013209407A1 disclose similar hunting methods for which neither reduction of the driving force nor increase of the mechanical strength of the driven assemblies are reported. The mechanical strength of the assemblies driven with such processes is ensured by a friction at the interface between the components.

Such methods are used in particular for assembling components on electronic boards. For these particular applications, the high compression of the elastic part of the electronic connector necessary for its complete insertion makes ultrasonic superposition advantageous during this phase of the driving cycle.

Document DE 102012211327A1 discloses similar hunting methods without increasing the mechanical strength of the assemblies removed. The mechanical strength of the assemblies driven with such processes is ensured by a friction at the interface between the components. As will be seen in the detailed description, the experiment contradicts this statement in the case of ultrasonic driving.

Such a method is used in particular for assembling fuel injection valves. For these particular applications, the very thin wall thickness of the direct fuel injection valve solenoid valve sleeve makes it impossible to drive this part over the valve body without the superposition of ultrasound to the movement of the valve. hunting tool.

The publication by Csaba Laurenczy, Damien Berlie and Jacques Jacot entitled "Ultrasonic press-fitttng: a new technical assembly" and published in the proceedings of the IPAS conference that took place from 16 to 18 February 2014 in Chamonix, France introduces the difficulties associated with conventional hunting method and highlights the significant reduction in driving force. The hypothesis of a reduction of the coefficient of friction in the presence of ultrasound is advanced without demonstration. As will be seen in the detailed description, the experiment performed since this publication contradicts this assumption.

Hunting is a commonly known attachment technique practiced to assemble at least two components without external filler material and without additional parts during the entire lifetime of the components and with the possibility of at least one disassembly. According to the conventional hunting method, holding

Mechanical attachment of at least two components driven is ensured by the friction at the interface between these components. This friction is due to the difference in size between the first component and the second. This difference is often called interference or clamping. This interference causes a dilation of the external component and a compression of the internal component whose combination creates a pressure at their interface. This pressure is at the origin of the friction.

The conventional driving method suffers from several disadvantages such as, but not limited to, relatively high driving forces compared to the mechanical strengths obtained. These high driving forces add additional technical functions to the components that are often expensive to produce. These functions serve, for example, to increase the elastic limit of the material of at least one component or to increase at least one of the critical dimensions of at least one component in order to lower the corresponding mechanical stress and thus prevent plastic deformations. of these components.

Document EP1445670A1, EP1708045A2 and EP1850193A1 disclose constructions of the second component comprising elastic parts which make it possible to avoid permanent plastic deformations and / or breakages during driving. The role of this elastic part is all the more important when the component is made of a fragile material.

Such constructions are in particular used for the assembly of watch wheels made of a fragile material such as silicon. The aim is to reduce the driving forces and therefore the mechanical stresses. The use of ultrasound hunting makes it possible to achieve this same objective without modifying the construction or the material of the components by reducing the intrinsic driving force of the object of the invention. The high hunting forces typical of conventional hunting sometimes require the addition of expensive additional operations to the operating range. For example, the use of particular oils or greases, applied to at least one component, makes it possible in certain cases to reduce the driving forces. These lubricants may have a negative impact on subsequent manufacturing operations or require additional washing operations.

High driving forces can damage or break at least one component. Fragile components, especially ceramic watch stones or silicon watch wheels, are particularly vulnerable to this risk. In case of damage or breakage of at least one component, the functions provided by it can be eliminated and / or the mechanical strength decreased. In such a case, at least this component must be replaced. This operation is often very expensive.

The first European application EP 15173943.0, the present application of which claims priority, also discusses in detail the hunting technique, its principles and its models (see in particular chapters 2, 3 and 4 of the description of this prior application) and it is made reference to this discussion by reference in the present description.

On the other hand, the use of ultrasound as a vector of energy is known, as described in the first European application EP15173943.0 of which the present application claims priority, and reference is made to this discussion by reference in the present description. (see in particular Chapter 5 of the description of this earlier application).

Brief description of the invention

An object of the invention is to provide an improved method compared to the state of the art.

More specifically, an object of the invention and to propose a hunting method more efficient than those known, which has a better performance, requires a reduced driving force while achieving a better mechanical resistance of the parts assembled by this method.

According to the invention, the ultrasonic driving method is a technique of attachment between a first component and at least one other component by soldering and / or welding at the interface between these components.

The technical invention resides in particular in an original and inventive application of ultrasonic charging microtechnic components, that is to say, components of which at least one functional dimension is less than or equal to about three millimeters, as a non-limiting example. For this, the control of the energy dissipation of the ultrasound, for example by adjusting the acoustic impedance of the interface between the components, is necessary. The gains and good properties related to the subject of the invention are obtained only for a restricted energy range, for example between 100 mJ, and dependent on each application case. This very precise control is difficult to achieve for microtechnical dimensions. In particular, solder and / or solder points mainly responsible for the mechanical strength of such an assembly are obtained, without any dimensional change and / or aesthetic degradation of the components, by locally increasing the temperature at the contact points of the assembly. interface between components through controlled dissipation of ultrasound energy.

In one embodiment the invention relates to a method of driving at least a first component in a second component by superimposing a mechanical wave of ultrasonic frequency to the movement of at least one of the components. Preferably, at least one functional dimension is less than or equal to about three millimeters and a method of adjusting the process parameters allows control of the amount of energy dissipated at the interface between the two components.

In one embodiment, the ultrasound propagation directions are composed of at least one selected vibratory mode, one of whose directions is for example, but not only, parallel to the movement of the driving tool, perpendicular to the movement of the hunting tool and / or tangential to the latter. In such a case, the ultrasound is defined as a longitudinal mechanical wave, respectively radial and / or torsion.

In one embodiment, the ultrasound energy is dissipated in a controlled manner to the asperities of the interface in contact between the components. Preferably, this control is achieved through the adjustment of the acoustic impedance at the contact points of the interface.

In one embodiment, the dissipated energy of the ultrasound very locally raises the temperature of these contact points until at least the degradation of the mechanical properties of these points of contact or their fusion.

In one embodiment, the degradation of the mechanical properties and / or the melting of the contact points between the components significantly reduces the driving force compared to a conventional driving method, that is to say without overlapping ultrasound.

In one embodiment, the increase of the temperature at the interface contact points accelerates the local diffusion between the components until solder points and / or solder points without dimensional change or aesthetic degradation of the components. components, but with a significant increase in the mechanical strength of the ultrasonically driven assembly compared to a conventional driving method, that is to say without ultrasonic superposition.

In one embodiment, increasing the temperature at the contact points of the interface increases the actual contact area between the components. The increase of the real contact surface is all the more important that one of the materials wets, in the sense of the capillarity, or envelope, for example but not only by elastic or plastic deformation, the second, the increase of the mechanical strength being proportional to this increase in the actual contact area.

In one embodiment, increasing the actual contact area between the components can create at least one mechanical shape clamping possibly having the same dimensions as the asperities of the interface between the components.

In one embodiment, the invention relates to the use of a method as described in the present application, for driving a first component in a second component.

The first component may be for example, but not only, a pin, an axis, a pinion, a screw-foot, a tenon, a tube, a barrel, a watch-stone, a bearing, a horological shock absorber, an intermediate piece and / or another piece of dressing and / or movement of a watch.

The second component may be for example, but not only, a plate, a bridge, a ring, an intermediate piece, a watch wheel, a board, a dial, a needle, a bracelet mesh and / or another piece dressing and / or movement of a watch.

In one embodiment, the invention relates to the use of a method as described in the present application, for hunting around a first component of a second component.

The first component may be for example, but not only, a pin, an axis, a pinion, a screw-foot, a tenon, a tube, a barrel, a clock stone, a horological shock absorber and / or a bearing.

In one embodiment, the invention relates to an assembly of parts by the method of the invention. The assembled parts may be, for example, those mentioned above, in the context of watchmaking, but without limitation in this field, other assemblies of parts that can make use of the method according to the invention.

Detailed description of the invention

The dissipation of the ultrasound energy at the asperities of the interface of the components causes at least one of the effects described below: i. the very local increase in temperature which leads to a degradation of the mechanical properties of the asperities of the interface between the components that can go as far as the fusion of at least one of the materials

ii. the reduction of the stress in the dimension orthogonal to the driving direction due to the contraction of the material perpendicular to the direction of application of the driving force (Poisson effect)

or. the stochastic positioning of at least one of the components in a minimum energy configuration during all or part of the hunting cycle

Of the three phenomena, the effect that seems to be the most important is that of the very local increase in temperature, since it makes it possible simultaneously to obtain a significant reduction in the driving force (Fig.1.2) and an increase in the mechanical strength (Fig. 1. 3).

By analogy with electrical circuits, the dissipation of acoustic energy occurs at points of high acoustic impedance. In this case, these are the contact points of the hole-component interface. At these locations, two changes in waveguide properties dissipate energy:

(i) material change: from platinum brass pin bearing steel to

(ii) reducing the section of the waveguide: from the diameter of the component driven to that of each roughness of the bore-component interface.

On the basis of this simple model, it is possible to dissipate acoustic energy in a controlled manner at the contact points of the hole-component interface. To identify the

quantity of acoustic energy transmitted to the contact points and compare it with the work of the driving force, an energy balance of the driving process is

ultrasound (Tab.6.2).

Typical energy balances of the ultrasonic driving process, we draw an important observation: the acoustic energy input of ultrasound is higher, in some

At least an order of magnitude, when working with the driving force, see Fig. 1.1

which illustrates the measurement of the acoustic power Pa (-) and the acoustic energy Ea (- -) during an ultrasonic driving cycle. Ultrasonic assisted expression is the

more frequently used to describe a machining or assembly process to which a mechanical wave is superimposed. This idea of ultrasonic assistance to the hunting process was also at the origin of the research work carried out. Because the role of ultrasound goes beyond the meaning of the word assistance, the term ultrasonic hunting is used to identify this new attachment technique.

The first ultrasonic driving experiments confirm the possibility of transporting energy to the links responsible for the mechanical resistance of the components removed. However, there is a lack of a signature that makes it possible to compare the performance of conventional hunting with that of ultrasound hunting. Therefore, we define a new signature of the hunting process: hunting force - mechanical strength and a new attribute: the efficiency η (without unit).

To characterize the hunting performance, a new signature is introduced by placing the experiments in the plane defined by the maximum driving force on the abscissa and the axial axial strength on the y-axis (Fig.1.2). In this plane and for each test, the coordinate ratio η = Ta / Fm defines this new indicator η of the efficiency of the driving processes. This indicator is valid for both conventional and ultrasonic hunting.

Figure 1.2 illustrates the signature {driving force, mechanical strength}. The slope of the linear regression line of the experimental points defines the efficiency η of a hunting process.

The parameters were validated on 150 tests with an interference of 0.010 mm, a

advance of 20 mm s ^" 'for brass plate (CuZn39Pb2) a contact length

ranging from 1.0 mm to 2.9 mm with holes diameter 1.002 mm, drilled-bored

with Sphinx tool 55652 and for Ac ClOOCro steel pin, with a length of

10 mm having a roughness Ra of 0.0001 mm.

This indicator η of the efficiency of the hunting processes is equal to the slope of the line of linear regression of the experimental points. If this slope is less than 1, so η <l, the axial resistance of the drive is internal to the theoretical value predicted by the Lamé-Clapeyron-Coulomb model. In practice, this is always the case for conventional hunting (Fig.7).

By comparing this indicator between conventional hunting and ultrasonic hunting, it is observed that ultrasound hunting has two remarkable advantages discussed below:

(i) a drastic reduction of the driving force

(ii) a significant increase in the mechanical strength.

In addition to the two guiding questions related to microtechnology hunting, a new issue is gradually becoming important for the watch industry: How to reduce the cost of non-quality related to hunting watchmaking?

This cost of non-quality is related on the one hand to the great variability of the mechanical strength and on the other hand to the breakage of synthetic stones. In particular, the high driving forces which are typical of the microtechnical driving damage or breakage of synthetic stones and silicon watch wheels. Each damaged part must be untied and replaced manually. This cost of non-quality amounts to tens of thousands of francs per year for the watch industry. Ultrasonic hunting can provide a solution to this old watchmaking problem.

Figure 7 illustrates the reduction of driving force in the presence of ultrasound

The parameters have been validated for at least 9 tests with interference of 0.010 mm, an advance of 10 mm s ^"1 for brass plates (CuZn39Pb2) a contact length of 1.0 mm containing holes of diameter 1.002 mm, perforated bored with Sphinx tool 55652 and for Ac ClOOCrô steel pin, 10 mm long with Ra roughness of 0.0001 mm.

Ultrasonic hunting is a tested solution to this problem universally found in manufacturing. The reduction of the driving force, in certain cases, by at least an order of magnitude (FIG. 7) makes it possible to reduce the mechanical stress exerted on the component, which can be fragile, and thus to avoid its breakage. This gain clearly surpasses the gains of a few percent obtained by the continuous improvement actions carried out by the manufacturers today.

Two simultaneous mechanisms lead to this drastic reduction of the driving force. The first mechanism is a break in the points of contact between the wall of the bore and the component p. ex. but not only due to an oligocyclic fatigue. The driven component can be seen as an ultrasonic frequency jackhammer bringing the links to the bore-component interface until they break through a cyclic fatigue phenomenon. The second mechanism is a degradation of the mechanical properties of the materials forming the hole-component interface. This acoustic attenuation of the interface is due to a local increase in temperature (Ham and Broom, 1957, 1962, Dugdale, 1959). This sharp rise in temperature, located only on the few square micrometers of the actual contact area of each point of contact, is caused by the dissipation of the acoustic energy of the ultrasound at the point of highest acoustic impedance. These two mechanisms are responsible for the significant decrease in the resistance to deformation of the weaker material, often the platinum or bridge brass; and therefore responsible for the decrease of the driving force.

The gain observed by a factor of two to ten is much greater than the ratio between the coefficients of static friction μ and kinetic μ ₀ . The generally accepted value of this ratio is between 1 and 3 for microtechnical hunting. Contrary to the conclusion of many publications, the reduction of the driving force is therefore not due to a decrease in the coefficient of friction. In particular, the microtechnical dimensions, where the very definition of these coefficients and the values of these are called into question (Chap.4.2 of the priority request). If the reduction of the force of hunting can seem surprising a priori, the increase of mechanical strength is a more awaited result. Indeed, it has been justified the use of ultrasound as energy vector in order to increase the mechanical strength of the assemblies hunted. How does ultrasound hunting make it possible to multiply by ten the mechanical strength of the assemblages driven?

The mechanical strength of ultrasonically driven assemblies is multiplied by the creation of solder and / or solder points between the wall of the hole and the component by dissipation of the acoustic energy of the ultrasound at the contact points of the interface.

The dissipation of the ultrasonic energy at the contact points of the hole-component interface is at the origin of the increase in the mechanical strength of the assemblies driven by ultrasound. The very localized increase in temperature caused by this dissipation of acoustic energy promotes the growth of the actual contact surface between the wall of the hole and the component. This surface increase is explained by a drastically increased plasticization. This advanced plasticization is itself due to a resistance to radial stress decreased by the degradation of the mechanical properties of the weakest material at this temperature. For the metal components such as but not only the pins, feet-screws, tenons, tubes, needles, bracelet stitches and other parts of the cladding, a second simultaneous mechanism increases the mechanical strength of assemblies expelled ultrasonically. The intermetallic diffusion is very clearly favored by the increase of temperature. The creation of brazing points and / or welding is thus catalyzed.

Figure 13 shows boxes with whiskers illustrating the effect of the type of component on the efficiency η of the hunt

The parameters were validated on 96 tests with an interference of 0.010 mm, an advance of 2 mm s ^" for brass platinum (CuZn39Pb2) a contact length ranging from 1.0 mm to 2.9 mm containing holes with a diameter of 1.002 mm, drilled-bored with Sphinx tool 55652 and for Ac C100Cr6 steel pin, 10 mm long with Ra roughness of 0.0001 mm.

For tests of principle, without optimization of the parameters of the ultrasonic driving process, the indicator η takes the value η = 0.6 for the conventional driving and η = 2.4 for the ultrasonic driving (Fig.1.2). So with identical components, process parameters and driving force, the ultrasound-driven components have a mechanical strength four times higher than those of a conventional drive.

By its two remarkable advantages, the ultrasound hunting process offers several unique opportunities for innovation and improvement.

With the significant decrease in driving force, ultrasonic driving makes it possible to drive longer pins without increasing their diameter and without risking their buckling. Because the driving force is reduced, the residual stresses introduced into the deck or deck are also reduced. It can also be used to drive thin boards over gables and / or to sew on them without damaging them or deforming them plastically. With a reduction of the driving force by a factor of two to ten, ultrasonic hunting also makes it possible to obtain appropriate mechanical properties without breaking the synthetic stones and thus to significantly reduce the cost of non-quality.

With an increase in mechanical strength, ultrasonic driving makes it possible, for example, to drive shorter pins for the same mechanical strength. The miniaturization of watches is thus facilitated. With a mechanical strength up to five times higher than that of conventional hunting, ultrasound hunting p. ex. but not only pins becomes a production method economically and technically concurrent with rivet e, screwing and / or laser welding p. e x. for assembling the links of the bracelet and / or other assemblies of the movement or the cladding of a watch.

Ultrasonic hunting also reduces interference without reducing the mechanical strength of synthetic stones. This reduction in interference provides a solution to the systematic breakage of these fragile components and significantly reduces the cost of non-quality. Reference is also made to Chapter 6 of priority application EP 15173943.0 of which this application claims priority, and this chapter 6 is incorporated by reference in the present description.

The ultrasonic driving method of the present invention makes it possible to reduce the driving force by means of one of the physical phenomena described above or a combination thereof. The experiment shows a decrease in the driving force of at least an order of magnitude in the presence of ultrasound (Figure 7). This gain of a factor of 5 or more is much greater than the ratio between the coefficients of static and kinetic friction. The generally accepted value of this ratio is between 1 and 3 for the cases of application of this invention. The reduction of the driving force is therefore not due to a decrease in the coefficient of friction, in particular microtechnical dimensions or the definition of this coefficient itself and the values thereof are challenged.

The reduction of the driving force during ultrasonic driving makes it possible to reduce the elastic deformation due to the elasticity of at least one component. The hysteresis effect is thus smaller which allows a relative positioning between the components more accurate and more repeatable. For the reasons described above, these precision gloves are not due to a decrease in the coefficient of friction.

The reduction of the driving force obtained by applying ultrasonic driving makes it possible to eliminate the use of lubricants or surface coatings intended to obtain the same effect.

The term "ultrasonically assisted" is most often used to describe a machining or assembly process to which a mechanical wave is superimposed. This idea of ultrasonic assistance to the hunting process was also at the origin of the research and development that led to the invention. However the energy supply of the ultrasounds is superior to the work of the driving force. In some cases of application of the method described by this patent, the ultrasound energy is greater than the work of the driving force of at least one magnitude. Because the role of ultrasound goes beyond the meaning of the word assistance, the term hunting claw is used to identify the method described in this patent.

To obtain solder or solder, the components should preferably, but not necessarily, be metallic. The bonds created between the components by the local increase of the temperature caused by the dissipation of the ultrasound energy at the contact point of the interface is made possible even between metals deemed non-weldable.

The frequency of the mechanical waves superimposed on the movement of the driving tool is for example, but not only, higher than the human hearing limit usually defined as 18 kHz. Frequencies of 20 kHz, 30 kHz, 35 kHz and 40 kHz are usually used as working frequencies in ultrasonic welding machines for plastics. Higher frequencies are also usable for the ultrasonic driving process.

The control of the advance of the ultrasonic driving tool can be for example, but not only, performed through a position control loop, force control or energy control. A combination of these three solutions according to the needs of the component assembly is possible. This advance can be in a range between 0.1 mm / s and 300 mm / s depending on the application case.

A particular, but not unique, embodiment of the solution of the invention is explained in more detail with reference to the schematic drawings hereinafter.

Figure 3 illustrates a first step of the method of the invention for driving a first component (11) into a second component (12). The components (11, 12) are positioned relative to each other by the action of the driving tool (15) and / or under the action of at least one setting portion (16). The components (11, 12) are mainly held together by a solder (20) and / or a solder (21) created by the dissipation of the ultrasound energy (18). This energy is transmitted by the driving tool (15) which serves as a waveguide and / or at least a part of the setting (16) which can also serve as a waveguide.

Figure 4 illustrates the dissipation of ultrasound energy (18) is very local. This energy is dissipated at the asperities (14) of the interface (13) between the components (11, 12) and which are in contact. The dimensions of the asperities and the acoustic properties of the materials are notably used to calculate the acoustic impedance used for the controlled adjustment of the dissipation of the ultrasound energy.

Figure 5 illustrates the forces and moments of force acting between a first component (10) and a second component (20) at the hole-component interface (30) according to the Lamé-Clapeyron-Coulomb model.

Figure 6 illustrates the hole-component interface (30), y. vs. the asperities (50) between a first component (10) and a second component (20) at the hole-component interface (30).

Figure 7 illustrates (bottom curves) the reduction of the driving force in the presence of ultrasound for the following validated parameters: an interference of 0.010 mm, an advance of 10 mm s ^-1 for brass platinum (CuZn39Pb2) a contact length of 1.0 mm containing 1.002 mm diameter holes, drilled-bore with Sphinx tool 55652 and for AcC100Cr6 steel pins, length 10 mm with Rade roughness 0.0001 mm. Figure 8 illustrates box plots illustrating the effect of component type on hunting performance and ultrasonic driving gains for the following validated parameters: interference of 0.010 mm, advance of 2 mm s ^-1 for brass plate (CuZn39Pb2) a contact length of 1.0 mm containing 1.002 mm diameter holes, drilled-bore with Sphinx tool 55652 and for ClOOCr6 steel pins, 10 mm long with roughness Ra of 0.0001 mm.

The embodiments of the present invention are given by way of illustrative example and should not be considered as limiting. Variations are possible by using in particular equivalent means. The execution modes can also be combined with each other.

Claims

claims

A method of driving at least a first component (11) into a second component (12) by superimposing an ultrasonic frequency mechanical wave (18) on the movement (17) of at least one of the components (11, 12), said method being characterized by at least one functional dimension of less than or equal to about three millimeters and method of adjusting the process parameters for controlling the amount of energy dissipated at the interface (13) between the two components (11, 12).

2. Method according to claim 1, wherein the ultrasonic propagation direction (18) is composed of at least one selected vibratory mode, which may be for example, but not only, parallel to the movement (17) of the tool for driving (15), perpendicular to the movement (17) of the driving tool (15) and / or tangential to the latter (15).

3. Method according to one of the preceding claims, wherein the ultrasound energy (18) is dissipated in a controlled manner to the asperities (14) of the interface (13) in contact between the components (11, 12), said control being achieved through the adjustment of the acoustic impedance at the contact points (14) of the interface (13).

4. Method according to one of the preceding claims, wherein the dissipated energy of the ultrasound (18) very locally raises the temperature of these contact points (14) to at least the degradation of the mechanical properties of these points of contact. contact (14) otherwise their fusion.

5. Method according to one of the preceding claims, wherein the degradation of the mechanical properties and / or the melting of the contact points (14) between the components (11, 12) significantly reduces the driving force compared to a method of conventional hunting without superposition of ultrasound.

6. Method according to one of the preceding claims, wherein the increase in temperature at the contact points (14) of the interface (13) accelerates the local diffusion between the components (11, 12) to obtain brazing points (20) and / or soldering points (21) without dimensional change or aesthetic degradation of the components, but with a significant increase in the mechanical strength of the ultrasonically driven assembly compared to a conventional driving method without superposition of ultrasound.

7. Method according to one of the preceding claims, wherein increasing the temperature at the contact points (14) of the interface (13) increases the actual contact area between the components (11, 12), said increase the real contact surface being all the more important that one of the materials wets, in the sense of the capillarity, or envelope, by elastic or plastic deformation, the second, the increase of the mechanical strength being proportional to this increase of the actual contact area.

8. Method according to one of the preceding claims, wherein the increase of the actual contact surface between the components (11, 12) creates at least one mechanical clamping shape having optionally the same dimensions as the asperities (14) of the interface (13) between the components (11, 12).

9. Use of a method according to one of the preceding claims, for the driving of at least a first component (11) in a second component (12).

10. Use according to claim 9, wherein the first component is a pin, an axis, a pinion, a screw, a tenon, a tube, a barrel, a clock stone, a bearing, a shockproof watchmaker, a piece intermediate and / or another piece of dressing and / or movement of a watch.

11. Use according to claim 9 or 10, wherein the second component is a plate, a bridge, a ring, an intermediate piece, a watch wheel, a board, a dial, a needle, a bracelet mesh and / or another piece of dressing and / or movement of a watch.

12. Use of a method according to one of the preceding claims, for hunting around a first component (11) of a second component (12).

13. Use according to claim 12, wherein the first component is a pin, an axis, a tube, a pinion, a pinion, a screw, a tenon, a tube, a barrel, a clock stone, a bearing, a watchmaker's shockproof, an intermediate piece and / or another piece of dressing and / or movement of a watch.

14. Use according to claim 12 or 13, wherein the second component is a plate, a bridge, a ring, an intermediate piece, a watch wheel, a board, a dial, a needle, a bracelet mesh and / or another piece of dressing and / or movement of a watch.

15. Assembly of parts obtained by a process as defined in one of claims 1 to 8.