EP3336613A1 - Timepiece resonator with two balances arranged to oscillate in a single plane - Google Patents

Abstract

The resonator for a timepiece comprises a support structure (2, 4) intended to allow the mounting of the resonator in a timepiece, a first and a second pendulum (6, 8) arranged to oscillate in the same plane, at least one first elastic element arranged to connect the first rocker (6) to the support structure, at least one second elastic element arranged to connect the second rocker (8) to the support structure, the configuration of the elastic elements determining two axes parallel (X ', X ") elastic pivoting for the two rockers, and the elastic elements forming elastic return means arranged to angularly return each of the rockers to a rest position.The resonator further comprises a shoulder strap (116, 118 ) arranged to couple the first and the second pendulum (6, 8), the strap being attached to the first and the second pendulum.The junction points of the respective shoulder strap with the first and the second pendulum are located in the same plane parallel to the oscillation plane of the pendulums. When the rockers are in their rest position, these junction points are symmetrical with respect to a center of symmetry (O) located midway between the two pivot axes (X ', X ").

Description

FIELD OF THE INVENTION

The present invention relates to a resonator for a timepiece comprising a support structure intended to allow the mounting of the resonator in a timepiece, two rockers arranged to oscillate in the same plane, and a plurality of elastic elements arranged to connect the two rockers to the support structure, the configuration of the plurality of elastic elements determining two parallel axes of elastic pivoting for the two rockers, and the plurality of elastic elements also forming elastic return means arranged to angularly return each of two rockers to a rest position.

PRIOR ART

Known mechanical watches usually use as a regulating member a sprung balance. The latter is composed of three main parts: a rocker in the form of a flywheel, an axis that carries the balance and which is terminated by two pivots for mounting the balance in a timepiece frame, and finally, a spiral spring which produces a return torque proportional to the size of the angle between the balance of its equilibrium position. As is well known, the sprung balance is the almost exclusive time base of mechanical watches for more than 300 years.

The use of a sprung balance as a time base gives the possibility of having robust watches and showing a chronometric accuracy of the order of 15 seconds per day. We can therefore say that spiral balance is a reliable and accurate resonator. The fact remains that the accuracy of quartz watches is still much higher than that of mechanical watches equipped with a sprung balance. This difference in precision is due in part to the fact that a quartz tuning fork has a quality factor considerably higher than that of a sprung balance.

The amplitude of the oscillations of a spiral balance is considerable. It usually varies between 180 ° and 315 ° depending on the degree of winding of the mainspring and according to the rather horizontal or rather vertical position of the watch. Under these conditions, the two bearings in which the axis of the balance wheel rotates are very stressed, which causes the dissipation of a fraction of the energy of the balance by friction. It will be understood that this friction contributes to lowering the quality factor of the sprung balance. Great efforts have been made to provide balance bearings with optimized tribological properties. Nevertheless, the negative effect of friction on the quality factor has not yet been eliminated.

In order to remedy the problems which have just been described, it has been proposed to replace the traditional pivots of the rockers by a flexible pivoting. The patent document CH 709 291 A2 , in particular, discloses a timepiece resonator comprising a support element, intended to allow the mounting of the resonator in a timepiece, a balance wheel in the form of a flywheel, and finally two elastic blades that connect the pendulum support member while crossing. The configuration of the two elastic blades is chosen so as to define a geometric pivot axis concentric with the balance. In addition, the two blades are arranged to exert a restoring torque on the balance. With this construction, when the resonator oscillates, the two blades deform playing both the role of spiral spring and flexible pivoting. It will be understood from the above that the solution proposed in this prior document eliminates one of the main causes of friction, since it removes the bearings of the balance to replace them with a flexible pivoting. According to the document CH 709 291 A2 , the proposed oscillator has a quality factor about 10 times higher than that of a sprung balance.

The aforementioned resonator, however, has certain disadvantages. Indeed, according to this document the amplitude of oscillations of the pendulum is typically 20 °. Under these conditions, the effect of a possible collinearity defect between, on the one hand, the kinetic momentum of the balance, and on the other hand, its geometric pivot axis, can not be simply neutralized by the rotation. Moreover, it is feared that a flexible pivot pin as described above is more sensitive to shocks than a sprung balance. In order to remedy these last two problems, the patent document EP 3,035,127 A1 proposes to couple two resonators with flexible pivot, so as to achieve a form of tuning fork. According to this proposal, the coupling between the two resonators is provided by a movable connecting element to which the elastic blades of the two resonators are fixed by one end. The other end of each pair of blades is connected to one of the two rockers as before. It will be understood that according to this second prior document, the connecting element carries the two rockers, while being itself resiliently fixed on a support member rigidly mounted in the timepiece. With such an arrangement, the geometric axes of pivoting of the two rockers each occupy a fixed position relative to the connecting element, while being movable collectively relative to the frame of the timepiece.

As the title of the document indicates EP 3,035,127 A1 , the oscillator he describes is a form of tuning fork. In this respect, it is known that a benefit related to the symmetry of tuning forks is that it favors some well-defined oscillation modes having a high quality factor. Among these modes of oscillation, the two most fundamental modes are the symmetrical mode and the antisymmetric mode. As far as horological applications are concerned, the antisymmetrical mode (the tuning fork legs move at the same time in opposite directions) is the most advantageous because of its lower sensitivity to external phenomena; in particular shocks. With a tuning fork intended for a horological application, it is therefore important that the symmetrical oscillation mode (the tuning fork branches move at the same time in the same direction) is always effectively damped. In this context, the document EP 3,035,127 A1 teaches to couple the oscillations of the two rockers by using a connecting element suspended elastically on a fixed element. A peculiarity of the antisymmetric resonance mode is that the center of mass of the system remains at rest, the forces acting on the link element of the tuning fork mutually neutralizing each other. Under these conditions, to favor the antisymmetric resonance mode, the suspension of the connecting element must be adjusted so that the vibrations of this element are strongly damped, while ensuring that the connecting element remains free of transmitting to the second balance the excitation pulses received on the first balance. In view of the above, it is feared that it is very difficult to adjust the suspension of the connecting element satisfactorily.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a resonator with a high quality factor, and which comprises two rockers mechanically coupled, the coupling between the rockers being designed to promote the antisymmetric oscillation mode. The invention achieves this goal by providing a resonator according to the appended claim 1.

In the present patent application, the term "support structure" does not necessarily mean a single support piece. Indeed, according to the invention, the support structure may for example comprise two separate support members, one of the support members for mounting the first beam and the other support member for mounting the second beam.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 est une vue en plan de dessus d'un résonateur pour pièce d'horlogerie conforme à un premier mode de réalisation particulier de l'invention ;
• les figures 2A et 2B sont des vues partielles de dessus montrant en détail la paire de lames élastiques qui relie un des balanciers à la structure de support du résonateur, conformément respectivement à une deuxième et à une troisième variante du premier mode de réalisation illustré dans la figure 1 ;
• les figures 3 et 4 sont des vues en perspectives d'un résonateur pour pièce d'horlogerie conforme à un deuxième mode de réalisation particulier de l'invention.

Other features and advantages of the present invention will appear on reading the following description, given solely by way of non-limiting example, and with reference to the appended drawings in which:

• the figure 1 is a top plan view of a timepiece resonator according to a first particular embodiment of the invention;
• the Figures 2A and 2B are partial top views showing in detail the pair of resilient blades which connects one of the rockers to the support structure of the resonator, respectively in accordance with a second and a third variant of the first embodiment illustrated in FIG. figure 1 ;
• the Figures 3 and 4 are perspective views of a resonator for a timepiece according to a second particular embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The figure 1 is a top plan view of a timepiece resonator, which is in accordance with a particular embodiment of the invention. According to the invention, the illustrated resonator comprises a support structure intended to allow its mounting on a frame (not shown) of a mechanical watch. In the present example, the support structure consists of two flanges respectively referenced 2 and 4. The resonator further comprises two generally referenced balances 6 and 8 which, in the illustrated example, generally have the shape of an ellipse with a large central notch. When the rockers are in their rest position as shown, the two notches open opposite one another. It can be seen further that the two flanges 2, 4 of the support structure are each arranged inside one of the notches. Each beam further comprises a serge 10 provided to give it greater inertia. The serge extends along the periphery of the pendulum. The first and second pendulums preferably have the same mass and the same dimensions so that it is easy to oscillate at the same frequency.

According to the invention, the rockers are connected to the support structure by a plurality of elastic elements. More specifically, in the illustrated embodiment, each rocker 6, 8 is connected to one of the two flanges 2, 4 by a pair of resilient blades (referenced respectively 12a, 12b and 14a, 14b). As shown in the figure, one end of each blade is attached to the rocker by the bottom of the notch, while the other end is secured to the flange in the same notch, so that each pair of resilient blades is arranged inside the notch of the pendulum to which it is attached. It can also be seen that the two elastic blades of the same pair intersect so as to form a X which extends in the plane of the pendulum inside the notch. Those skilled in the art will understand from the foregoing that the configuration of the pair of blades connecting one of the rockers to the support structure determines an axis of elastic pivoting X ', X "for this rocker. perpendicular to the plane of the pendulum and it passes through the point of intersection of the two blades of the X. This point of intersection moves very slightly during the movement of the pendulums.For reasons which will appear more clearly later, the formed X by the resilient blades is preferably positioned in the notch so that the intersection of the geometric axis of pivoting with the plane of the balance coincides with the center of mass of the balance.

The figure 1 shows again that the two elastic blades 12a, 12b or 14a, 14b which form the X have their junction point halfway between their two ends. Simulations show that the configuration in which the two blades of the X-shaped structure intersect in the middle, provides a clean and frictionless rotation around the geometric axis of pivoting. In addition, such a flexible X pivot has the advantageous characteristic of producing a return torque proportional to the magnitude of the angle between the balance of its equilibrium position, and that in one direction as in the other. Note further that the term "clean rotation" used above refers to a rotation that minimizes the displacement of the pivot axis.

We will admit for the rest of this description that the height of the blades corresponds to their extension perpendicular to the plane of the balance, while their thickness corresponds to their extension in the plane of the balance, perpendicular to their length. The thickness of the blades is preferably reduced so as to give the elastic blades sufficient flexibility in the plane of the beam. The height blades is determined so as to give them sufficient rigidity to contain oscillations of the balance in the same determined plane. The two pairs of blades are preferably made of the same material. In addition, as shown in the figures, the two flexible X pivots preferably have identical dimensions so that the first and the second pendulum have the same fundamental frequency of resonance when they have the same mass and the same moment. inertia.

The Figures 2A and 2B are enlarged partial views showing a second and third configuration variant of the pair of resilient blades connecting one of the rockers to the support structure of the resonator of the invention. Comparing the Figures 1, 2A and 2B it can be observed in particular that these figures are distinguished by the value of the angle between the two resilient strips coming from one of the flanges 4, 4 'or 4 ". figure 1 , this angle is substantially equal to 90 °, in the Figure 2A , it is substantially less than 90 °, and finally in the Figure 2B it is substantially larger than 90 °. The angle at which the blades intersect has an impact on the excitability of some out-of-plane oscillation modes of the pendulums. These higher modes are undesirable for most horological applications of the resonator of the invention. In practice we will choose the angle between the elastic blades according to the shape of the rockers and the desired stiffnesses according to the different plans.

According to the invention, the resonator further comprises a flexible blade 16 which constitutes a strap arranged to couple the first and the second beam 6 and 8. The flexible blade is attached to the first and second pendulums, the junctions, respectively 16a and 16b, of the flexible blade with the first and the second balance are located in the same plane parallel to the plane of oscillation of the two rockers and are symmetrical to each other with respect to the point central figure (referenced O). Referring always to the figure 1 it can be seen that between the two junction points 16a and 16b, the shape of the blade 16 has a central symmetry about the central point O. It will be understood however that this characteristic is only present when the rockers 6, 8 are in their position. rest position. As can be seen in the figure, the center of symmetry O is located halfway between the geometric pivot axes of the two rockers.

The figure 1 still shows a line d which passes through the center O and through the junctions 16a, 16b of the flexible blade 16 with the two rockers 6, 8. In exemplary embodiments, the line d is at an angle α of at least 30 ° , or at least 45 °, with the plane containing the first and the second geometric axis of pivoting.

According to the invention, the first and the second pendulum have the same fundamental resonance frequency. Because of the presence of the shoulder strap 16, when one of the rockers deviates from its equilibrium position by pulling the strap after him, the other rocker is forced to follow the movement away from its position. balance in the other direction. In particular, referring to the figure 1 it can be understood that if the first rocker 6 pivots in the clockwise direction, it exerts traction on the shoulder strap 16. The inertia of the shoulder strap being very small compared to that of the rockers, the tension at which the shoulder strap is subjected is echoes on the second balance 8 at the junction 16b. The second pendulum thus undergoes a torque that tends to rotate it counterclockwise. By moving away from their rest position, the two balances deform the elastic blades X 12a, 12b, 14a, 14b which connect them to the support structure (the flanges 2 and 4). The deformation of the two pairs of elastic blades generates two return couples which are exerted respectively on the first and the second beam. It can be understood from the foregoing that the presence of the strap 16 has the effect of synchronizing the oscillations of the two rockers. It may also be noted in passing that the oscillations of the two rockers coupled to the resonance frequency are said to be antisynchronous, and not simply synchronous, when the oscillations occur in an antisymmetric mode in accordance with what has just been described.

The Figures 3 and 4 are perspective views of a resonator for a timepiece according to a second particular embodiment of the invention. As can be seen, the resonator illustrated in the Figures 3 and 4 is very similar to the resonator of the figure 1 . However, according to the second particular embodiment of the invention which is the subject of the present example, the resonator comprises a pair of straps 116, 118 attached to each other at mid-length by a rigid coupling element 120. The straps 116, 118 are also each attached to the first and second pendulums 6 and 8. On the figure 3 one half of the shoulder strap 116, which extends between the first beam 6 and the coupling element 120, is designated 116 ', and the other half of the shoulder strap 116, which is extends between the coupling element and the second rocker 8, by the reference 116. Likewise, one half of the shoulder strap 118, located between the first rocker and the coupling element, has been designated by the reference 118 ', and the other half by the reference 118 ".

We can observe on the figure 3 in particular that, when the rockers are in their rest position as illustrated, the shoulder straps 116, 118 are symmetrical to each other relatively, on the one hand, to the plane containing the first and second pivot axes X ' and X ", and on the other hand, with respect to a parallel and equidistant mediating plane of the two pivotal geometrical axes (the trace of the mediator plane in the plane of the pendulums is represented in FIG. figure 3 by a broken line designated by the reference m).

Referring again to Figures 3 and 4 it can be observed that the pair of shoulder straps 116, 118 is mainly constituted by a first flexible blade attached to the first rocker 6 by its two ends, and by a second flexible blade attached to the second rocker 8 by its two ends. It can be seen that the two flexible blades are further connected to one another via the coupling element 120. The two flexible blades are connected to the coupling element in their middle, and it will be understood that that in the construction shown, the two halves of the first flexible blade respectively constitute the half 116 'of the shoulder strap 116 and the half 118' of the shoulder strap 118. Similarly, the two halves of the second flexible blade respectively constitute the other half 116 "of the ramp 116 and the other half 118" of the ramp 118.

According to the illustrated embodiment, the coupling element 120 is rigid and is arranged to connect rigidly a central portion of the first flexible blade and a central portion of the second flexible blade, so that these two central portions are kept spaced and parallel to each other. An advantage of the second embodiment which has just been described is its highly symmetrical character which gives even more stability to the antisymmetric oscillation mode of the resonator. Another advantage is that the vibrations of the balance at resonance translate into a back and forth movement of the rigid coupling element 120 along a rectilinear path in the plane of symmetry of the resonator (the mediating plane m already mentioned). . The fact of having a part performing a back and forth along a rectilinear trajectory could in particular be used to associate an exhaust with the resonator.

In the example shown in Figures 3 and 4 , the serge 10 of each beam 6, 8 is located on the underside of the balance. She can however, alternatively, be located on the upper side or both sides of the balance.

The resonator according to the invention can be made in one piece of silicon and / or silicon oxide, diamond, quartz or metal, for example. For this purpose, techniques of the DRIE or LIGA type may be employed. The resonator according to the invention can also be obtained by an assembly of parts.

• les balanciers 6, 8 pourraient avoir une autre forme allongée que la forme d'une ellipse et pourraient aussi avoir une forme ronde, carrée, en aile de papillon ou autre. Les formes allongées sont toutefois préférées car elles permettent d'éloigner les points d'attache des bretelles 16, 116, 118 sur les balanciers 6, 8, ce qui facilite l'ajustement du couplage élastique entre lesdits balanciers ;
• au lieu de s'ouvrir en regard l'une de l'autre, les encoches des balanciers 6, 8 dans lesquelles se trouvent les brides 2, 4 et les lames élastiques 12a, 12b, 14a, 14b pourraient s'ouvrir vers l'extérieur des balanciers 6, 8 ou pourraient même être fermées ;
• l'orientation des brides 2, 4 et des lames élastiques 12a, 12b, 14a, 14b dans les encoches pourrait être différente de celle représentée. Par exemple l'une des brides 2, 4 ou les deux pourraient être tournées de plus ou moins 90° par rapport à leur position illustrée à la figure 1. Les orientations respectives des brides 2, 4 peuvent être identiques ou opposées ;
• au lieu d'être coplanaires et de se croiser physiquement comme dans les modes de réalisation illustrés, les lames élastiques 12a, 12b, 14a, 14b de chaque paire pourraient s'étendre dans deux plans parallèles différents pour former un pivot flexible de type « Wittrick ». Par rapport à un pivot flexible de type « Wittrick » le pivot flexible en X utilisé dans les modes de réalisation illustrés présente le désavantage d'un mouvement parasite plus important de l'axe géométrique de pivotement X', X" lors de la flexion, et de lames plus courtes dans lesquelles les concentrations de contraintes sont plus élevées. Par contre, la rigidité transversale des lames est bien plus élevée ce qui améliore la stabilité des balanciers 6, 8 dans leur plan de rotation et leur résistance aux chocs hors de leur plan de rotation ;
• d'autres types de pivot flexible qu'un pivot en X ou qu'un pivot « Wittrick » pourraient être utilisés pour relier chaque balancier 6, 8 à la structure de support 2, 4. De plus, le nombre de lames ou d'éléments élastiques formant chaque pivot flexible peut être supérieur à deux ou même égal à un.

It will be further understood that various modifications and / or improvements obvious to those skilled in the art can be made to the embodiments which are the subject of the present description without departing from the scope of the present invention defined by the appended claims. In particular :

• the pendulums 6, 8 could have another elongated shape that the shape of an ellipse and could also have a round shape, square, butterfly wing or other. The elongate shapes are however preferred because they allow to move the attachment points of the straps 16, 116, 118 on the rockers 6, 8, which facilitates the adjustment of the elastic coupling between said rockers;
• instead of opening facing each other, the notches of the rockers 6, 8 in which are the flanges 2, 4 and the elastic blades 12a, 12b, 14a, 14b could open towards the outside the rockers 6, 8 or could even be closed;
• the orientation of the flanges 2, 4 and elastic strips 12a, 12b, 14a, 14b in the notches may be different from that shown. For example one of the flanges 2, 4 or both could be rotated more or less 90 ° from their position illustrated in FIG. figure 1 . The respective orientations of the flanges 2, 4 may be identical or opposite;
• instead of being coplanar and physically crossing as in the illustrated embodiments, the resilient blades 12a, 12b, 14a, 14b of each pair could extend in two different parallel planes to form a "Wittrick" type flexible pivot ". With respect to a "Wittrick" type flexible pivot, the flexible X-pivot used in the illustrated embodiments has the disadvantage of a greater parasitic movement of the geometric pivot axis X ', X "during bending, and shorter blades in which the stress concentrations are higher, however, the transverse rigidity of the blades is much higher which improves the stability of the rockers 6, 8 in their plane of rotation and their impact resistance out of their range. rotation plan;
• other types of flexible pivot than an X pivot or a "Wittrick" pivot could be used to connect each balance 6, 8 to the support structure 2, 4. In addition, the number of blades or resilient members forming each flexible pivot may be greater than two or even one.

Claims (10)

Resonator for a timepiece comprising a support structure (2, 4) intended to allow the mounting of the resonator in a timepiece, a first and a second balance (6, 8) arranged to oscillate in the same plane, to at least one first elastic element (12a, 12b) arranged to connect the first rocker (6) to the support structure, at least one second elastic element (14a, 14b; 14a ', 14b'; 14a ', 14b') arranged for connecting the second rocker (8) to the support structure, the configuration of the elastic elements determining two parallel geometric axes (X ', X ") of elastic pivoting for the two rockers, and the elastic elements forming elastic return means arranged to angularly recall each of the rockers to a rest position, characterized - in that it further comprises a strap (16; 116, 118) arranged to couple the first and the second pendulum (6, 8), the strap being attached to the first and the second pendulum, in that the points of junction (16a, 16b) of the shoulder strap respectively with the first and the second balance are situated in the same plane parallel to the oscillation plane of the rockers, and in that, when the rockers are in their rest position, said rocking points are junction are symmetrical with respect to a center of symmetry (O) located midway between the two axes of pivoting geometry. Resonator according to claim 1, characterized in that , when the rockers are in their rest position, the shape of the strap is symmetrical with respect to said center of symmetry (O). Resonator according to claim 1 or 2, characterized in that , when the rockers are in their rest position, a radius connecting the center of symmetry (O) to the junction point (16a, 16b) with the first or the second pendulum, parallel to the plane of oscillation, makes an angle (α) of at least 30 °, preferably at least 45 °, with the plane containing the first and the second pivoting geometrical axis (X ', X "). Resonator according to any one of the preceding claims, characterized in that it comprises a pair of straps (116, 118) attached to each other at mid-length and each attached to the first and second pendulums (6 8), the pair of straps comprising said sling, and - in that , when the rockers (6, 8) are in their rest position, the two shoulder straps (116, 118) of the pair of shoulder straps are symmetrical to one another relative, on the one hand, to the plane containing the first and second pivotal geometric axis (X ', X "), and secondly, relative to a median plane (m) parallel and equidistant from the two pivotal geometric axes. Resonator according to claim 4, characterized in that the pair of shoulder straps (116, 118) comprises a first flexible blade attached to the first rocker (6) at its two ends, a second flexible blade attached to the second rocker (8) by its two ends, and a coupling element (120) arranged to rigidly connect a central portion of the first flexible blade and a central portion of the second flexible blade, so that the central portions of the two flexible blades are kept spaced and parallel one to the other. Resonator according to any one of claims 1 to 5, characterized in that the first and the second balance (6, 8) have an elongated shape. Resonator according to claim 6, characterized in that the distance between the geometric axis of pivoting (X ', X ") of a balance and the edge of the same beam is at least 1.5 times, of preferably at least twice, greater in a direction perpendicular to the plane containing the two axes of pivoting geometry (X ', X ") than in a direction parallel to this plane. Resonator according to any one of the preceding claims, characterized in that the at least one first elastic element (12a, 12b) comprises a first pair of elastic blades which are parallel to the plane of pivoting of the rockers (6, 8), the blades of the first pair (12a, 12b) being attached to the support structure (2, 4) at one end and to the first beam (6) at the other end, and in that the at least one second element elastic member (14a, 14b; 14a ', 14b'; 14a '', 14b '') comprises a second pair of resilient blades which are parallel to the pivoting plane of the rockers (6, 8), the blades of the second pair (14a, 14b 14a ', 14b'; 14a ", 14b") being attached to the support structure (2, 4) at one end and to the second beam (8) at the other end, the two pivot axes (X ' , X ") of the two balances each perpendicularly crossing the two elastic blades of one of the pairs. Resonator according to claim 8, characterized in that the pair of elastic blades (12a, 12b, 14a, 14b) perpendicularly crossing one and the same pivoting geometrical axis (X ', X ") are contained in the same plane parallel to the plane of rotation. pivoting of the rockers, so that the two elastic blades of the same pair intersect at the point of their intersection with the geometric axis of pivoting. Resonator according to claim 9, characterized in that the two elastic blades (12a, 12b, 14a, 14b) of the same pair intersect in their middle.

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