Patent ID: 12248276

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention relates to a horological resonator mechanism, which constitutes an alternative to the resonators described in the Swiss patent application No. 00518/18, or in the European patent application No. 18168765.8 filed by ETA Manufacture Horlogère Suisse, or in the Swiss patent application No. 715526 or in the European patent application No. 3561607 filed by ETA Manufacture Horlogère Suisse incorporated herein by reference, a person skilled in the art knowing how to combine the features thereof with those specific to the present invention.

The invention is based on the observation that silicon (or silicon and/or a silicon oxide) is the most suitable material for the flexure pivot, but not for the shock protection. More specifically, in order to fulfil its shock protection role, the structure must be capable of large deformations with high resilience. Some metallic materials are more suitable than silicon for this function. For example, NiP is more suitable than silicon. More specifically, the Young's modulus is 90 GPa for NiP compared to 150 GPa for Si, and the maximum stress is 1,700 MPa for NiP compared to 1,000 MPa for Si. This means that the maximum allowable deformation is three times greater for NiP than for Si.

The invention thus consists of making the pivot out of a first material, in particular silicon or an equivalent, and making the shock protection out of a second material, in particular nickel-phosphorus NiP or an equivalent, this second material having very different physical properties to the first material.

The difficulty lies in assembling the two parts without adding too great a mass at the point of assembly. In order to achieve this, we propose using an elastic assembly system, with or without adhesive. One practical example embodiment is shown inFIGS.2and3.

This horological resonator mechanism100comprises, as seen inFIG.1, a structure1and an anchor unit30, from which is suspended at least one inertial element2which is arranged to oscillate with a first degree of rotational freedom RZ about a pivot axis D extending in a first direction Z. This inertial element2is subjected to return forces exerted by a flexure pivot200comprising a plurality of substantially longitudinal elastic strips3, each fixed at a first end to the anchor unit30, and at a second end to the inertial element2. Each elastic strip3is deformable essentially in a plane XY perpendicular to the first direction Z.

The anchor unit30is suspended from the structure1by a flexible suspension300, which is arranged to allow the anchor unit30to move in five flexible degrees of freedom of the suspension which are:a first degree of translational freedom in the first direction Z,a second degree of translational freedom in a second direction X orthogonal to the first direction Z,a third degree of translational freedom in a third direction Y orthogonal to the second direction X and to the first direction Z,a second degree of rotational freedom RX about an axis extending in the second direction X,and a third degree of rotational freedom RY about an axis extending in the third direction Y.

According to the invention, the resonator mechanism100is a composite assembly made of at least two different materials, and which comprises, on the one hand, the flexure pivot200, which is made of a first material characterised by a first Young's modulus E1 and by a first yield strength Sigma 1 and by a first modulus of rigidity G1, and, on the other hand, the flexible suspension300, which is made of a second material characterised by a second Young's modulus E2 and by a second yield strength Sigma 2 and by a second modulus of rigidity G2.

The modulus of rigidity is defined here as the rigidity G=K1c{circumflex over ( )}2/E, where K1c is the fracture toughness and E is the Young's modulus. A high rigidity modulus G means that the part is capable of storing more elastic energy before breaking.

More particularly, the value of the second modulus of rigidity G2 is greater than ten times the value of the first modulus of rigidity G1. Also more particularly, the value of the second modulus of rigidity G2 is greater than eighty times the value of the first modulus of rigidity G1. This is the case when the first material is silicon and/or a silicon oxide, and when the second material is NiP, the G2/G1 ratio being close to 100;

More particularly, the ratio Sigma 2/E2 is at least twice the ratio Sigma 1/E1.

More particularly, the value of the first Young's modulus E1 is greater than or equal to 1.5 times the value of the second Young's modulus E2.

More particularly, the value of the second yield strength Sigma 2 is greater than or equal to 1.5 times the value of the first yield strength Sigma 1.

More particularly, at least one inertial element2is integral with the flexure pivot200.

More particularly, the flexible suspension300is integral with the structure1.

More particularly, the flexure pivot200is capable of being removed from the flexible suspension300.

More particularly, the flexible suspension300comprises clamping elements, in particular jaws939, to immobilise the flexure pivot200. Advantageously, these jaws939constitute the gripping elements of an elastic clamp930.FIG.3shows the resting position of this clamp denoted by the reference numeral938.

More particularly, the flexible suspension300comprises at least one pocket933which is capable of receiving adhesive to immobilise the flexure pivot200.

More particularly, the junction between the flexible suspension300and the flexure pivot200is made on the anchor unit30, which preferably comprises reliefs309, the shape whereof is complementary to the profile of the elements939.

In a specific manner, the clamp930is suspended from an intermediate mass305, which in turn is suspended from the structure1or from another intermediate mass303.

This elastic assembly has the advantage of minimising the added mass.

More particularly, the ratio Sigma 2/E2 is at least three times the ratio Sigma 1/E1.

More particularly, the first material is silicon and/or a silicon oxide.

More particularly, the second material is nickel-phosphorus NiP.

In particular, the modulus of rigidity of silicon is almost 100 times lower than that of all nickel alloys. A combination of the first material, which is silicon and/or a silicon oxide, and the second material, which is nickel-phosphorus NiP, is particularly advantageous for the desired shock protection application and the dissipation (losses) of NiP is greater than that of silicon, which is an additional advantage.

It goes without saying that alloys other than nickel-phosphorus NiP can have a sigma yield strength to Young's modulus E ratio that is sufficiently high to satisfy the conditions of the invention. In this case, the nickel-phosphorus NiP has the major advantage of being able to be precisely shaped using the “LIGA” (Lithography Galvano-Abformung) method, with a perfect geometry and narrow tolerances that are perfectly compatible with horological requirements. For the specific application shown in the figures, the flexible suspension300is advantageously, but in a non-limiting manner, made of a nickel-phosphorus NiP plate with a thickness of between 180 and 420 micrometres.

FIG.3describes the assembly of the flexure pivot200with the flexible suspension300, and shows the assembly area in detail, and also describes the assembly procedure. The assembly takes place in three stages: firstly, the elastic clamp930(in particular made of NiP) is opened so that the anchor unit30(in particular made of silicon) can be inserted into the jaws939; then the clamp930is released such that the jaws939thereof grip and block the reliefs309of the anchor unit30; finally, only if necessary, adhesive is inserted into at least one pocket933between the clamp930and the anchor unit30.

The elastic clamp930is designed to provide a high clamping force. It is thus important to ensure that the Hertzian pressure does not exceed the maximum stress at the contact between the jaw939and the relief309of the silicon anchor unit30. For this reason, the shape of the jaw939closely fits that of the relief309, so that the difference in the radius of curvature is as small as possible. Giving the jaw939some flexibility allows it to deform slightly to accommodate any geometric errors between the clamp930and the anchor unit30.

The pocket933provided for the adhesive consists, on the one hand, of at least one wide area where the adhesive can be easily inserted, and on the other hand, of at least one narrower area which helps to distribute the adhesive by capillary action.

The use of the torsional flexibility of a translation stage allows the torsional stiffnesses of the suspension to be better managed. This is achieved by orienting the strips of the XY stages so that the direction of greatest torsional flexibility is towards the axis of rotation of the resonator. The torsional flexibility thereof is managed by moving the strips closer together.

Thus, the flexible suspension300advantageously comprises, between the anchor unit30and a first intermediate mass303, which is attached to the structure1directly or by means of a plate301that is flexible in the first direction Z, a transverse translation stage32with flexure bearing, and which comprises transverse strips320or transverse flexible rods1320, which are rectilinear and extend in the second direction X and symmetrically about a transverse axis D2intersecting the pivot axis D.

In one particular non-limiting embodiment, and as illustrated by the figures, the flexible suspension300further comprises, between the anchor unit30and a second intermediate mass305, a longitudinal translation stage31with flexure bearing, and which comprises longitudinal strips310or longitudinal flexible rods, which are rectilinear and extend in the third direction Y and symmetrically about a longitudinal axis D1intersecting the pivot axis D. Moreover, between the second intermediate mass305and the first intermediate mass303, the transverse translation stage32with flexure bearing comprises transverse strips320or transverse flexible rods, which are rectilinear and extend in the second direction X and symmetrically about the transverse axis D2intersecting the pivot axis D.

More particularly, the longitudinal axis D1intersects the transverse axis D2, and in particular the longitudinal axis D1, the transverse axis D2, and the pivot axis D are concurrent.

In a more particular manner, the longitudinal translation stage31and the transverse translation stage32each comprise at least two flexible strips or rods, each strip or rod being characterised by its thickness in the second direction X when the strip or rod extends in the third direction Y or conversely, by its height in the first direction Z and by its length in the direction in which the strip or rod extends, the length being at least five times greater than the height, the height being at least as great as the thickness, and more particularly at least five times greater than this thickness, and even more particularly at least seven times greater than this thickness.

More particularly, the transverse translation stage32comprises at least two transverse flexible strips or rods, parallel to one another and of the same length.FIGS.1and4show a non-limiting alternative embodiment with four parallel transverse strips, and, more particularly, each consisting of two half-strips arranged on two superimposed levels, and extending in the continuation of one another in the first direction Z. These half-strips can either be completely free from one another, or made integral with one another by bonding or the like, or by SiO2growth in the case of a silicon construction, or the like. Naturally, the longitudinal translation stage31, where present since it is optional, can follow the same construction principle.FIG.6shows an alternative embodiment with flexible rods, grouped into two levels of two rods, with a substantially square cross-section; another alternative embodiment comprises circular flexible rods. The number, disposition, and cross-section of these strips or rods can vary without departing from the scope of the present invention.

More particularly, the transverse strips or rods of the transverse translation stage32have a first plane of symmetry, which is parallel to the transverse axis D2, and which passes through the pivot axis D.

More particularly, the transverse strips or rods of the transverse translation stage32have a second plane of symmetry, which is parallel to the transverse axis D2, and orthogonal to the pivot axis D.

More particularly, the transverse strips or rods of the transverse translation stage32have a third plane of symmetry, which is perpendicular to the transverse axis D2, and parallel to the pivot axis D.

More particularly, the transverse strips or rods of the transverse translation stage32extend over at least two levels parallel to one another, each level being perpendicular to the pivot axis D.

More particularly, the arrangement of the transverse strips or rods of the transverse translation stage32is identical on each level.

More particularly, the rectilinear flexible rods or transverse strips320are flat strips whose height is at least five times greater than their thickness.

More particularly, the rectilinear flexible rods or transverse strips320are rods with a square or circular cross-section, whose height is equal to their thickness.

More particularly, the longitudinal translation stage31comprises at least two longitudinal flexible strips or rods, parallel to one another and of the same length.

More particularly, the longitudinal strips or rods of the longitudinal translation stage31have a first plane of symmetry, which is parallel to the longitudinal axis D1, and which passes through the pivot axis D.

More particularly, the longitudinal strips or rods of the longitudinal translation stage31have a second plane of symmetry, which is parallel to the longitudinal axis D1, and orthogonal to the pivot axis D.

More particularly, the longitudinal strips or rods of the longitudinal translation stage31have a third plane of symmetry, which is perpendicular to the longitudinal axis D1, and parallel to the pivot axis D.

More particularly, the transverse strips or rods of the longitudinal translation stage31extend over at least two levels parallel to one another, each level being perpendicular to the pivot axis D.

More particularly, the arrangement of the transverse strips or rods of the longitudinal translation stage31is identical on each level.

More particularly, the rectilinear flexible rods or longitudinal strips310are flat strips whose height is at least five times greater than their thickness.

More particularly, the rectilinear flexible rods or longitudinal strips310are rods with a square or circular cross-section, whose height is equal to their thickness.

In particular, the resonator mechanism100comprises axial stop means comprising at least a first upper axial stop and a second lower axial stop to limit the translational travel of the inertial element2at least in the first direction Z, the axial stop means being arranged to cooperate in abutment with the inertial element2for protecting the longitudinal strips3at least from axial impacts in the first direction Z, and the second plane of symmetry is substantially at an equal distance from the first axial stop7and from the second axial stop8.

In one specific alternative embodiment, the resonator mechanism100comprises a plate attached to or in one piece with the structure1, comprising at least one flexible strip302extending in a plane perpendicular to the pivot axis D and attached to the first intermediate mass303, and which is arranged to allow the first intermediate mass303to move in the first direction Z. More particularly, the plate301comprises at least two such coplanar flexible strips. However, such a plate301is optional if the height of the strips of the XY translation stages is small compared to the height of the flexible strips3, in particular less than one third of the height of the flexible strips3, and in particular if these translation stages comprise flexible rods as shown inFIG.6.

As explained hereinabove, the technology used in the manufacturing process allows two separate strips to be obtained in the height of a silicon wafer, which enhances the torsional flexibility of the stage without making it more flexible for translation. Furthermore, the resonator mechanism100can thus advantageously comprise at least two superimposed elementary assemblies, which each group together one level of the anchor unit30, and/or of a base of the at least one inertial element2, and of the flexure pivot200or of the flexible suspension300, which always form a composite assembly, and/or of the first intermediate mass303, and/or of the transverse translation stage32, and/or of a breakable element used only during the assembly and destroyed before the oscillator is commissioned; each elementary assembly can be assembled with at least one other elementary assembly by bonding or the like, by mechanical assembly, or by SiO2growth in the case of a silicon construction, or the like.

More particularly, such an elementary assembly further comprises at least one level of the second intermediate mass305and/or of the longitudinal translation stage31.

The invention further relates to a horological oscillator mechanism500comprising such a horological resonator mechanism100, and an escapement mechanism400, arranged to cooperate with one another.

The invention further relates to a horological movement1000comprising at least one such oscillator mechanism500and/or at least one resonator mechanism100.

The invention further relates to a watch2000comprising at least one such movement1000and/or at least one oscillator mechanism500and/or comprising at least one such resonator mechanism100.