Patent Application
20200409311
This application claims priority to European Patent Application No. 19182712.0, filed on Jun. 26, 2019, the entire contents of which are incorporated herein by reference.
The invention relates to a horological resonator comprising at least one inertia mobile component for a horological resonator, arranged so as to oscillate about an axis of oscillation and comprising at least one magnetic area, which magnetic area comprises at least one magnet or at least one magnetised ferromagnetic area, and comprising return means for maintaining the oscillation of the at least one inertia mobile component.
The invention further relates to a horological movement comprising powering and/or energy storage means arranged so as to power at least one such resonator, comprised in the movement, and an escapement mechanism comprising at least one escape wheel set arranged so as to engage, with interaction, with the at least one inertia mobile component of the resonator.
The invention further relates to a timepiece, in particular a watch, comprising at least one such movement.
The invention relates to the field of horological mechanisms, and more specifically horological resonators, of the magnetic type, or at least one part of the running thereof is based on magnetic attraction and/or repulsion, and in particular comprising magnets.
Certain mechanical resonators used in horology bear magnets.
Examples include the Clifford-type mechanisms, known from the documents FR1113932, FR2132162 and U.S. Pat. No. 2,946,183, or the direct synchronisation resonators of the SWATCH GROUP, known from the documents EP2887156 and EP3316046. In these oscillators, the use of magnets on the resonator allows for direct synchronisation, without frictional contact, between the resonator and the escape wheel. The absence of any pallet-lever between the escape wheel and the resonator, in addition to the absence of frictional contact, procure the advantage of high efficiency.
However, the magnets carried by the balance can be affected by the presence of external magnetic fields. The perturbation resulting therefrom, although low, can result in a variation of daily rate.
The document EP3273309A1 filed by Montres Breguet discloses a horological oscillator comprising a sprung balance assembly comprising a balance with a felloe, which is returned by a balance spring, pivoted with respect to a structure, on a first side by a torsion wire, fixed by an anchoring element to the structure, and on a second side, opposite to the first side, by a contactless magnetic pivot, the balance comprising a first pole embedded with the balance and the torsion wire, this first pole having a symmetry with respect to the axis of the sprung balance assembly, and cooperating with a second pole comprised in the structure, for the magnetic suspension of the first pole, and to exert on the distal end of the torsion wire, opposite to this anchoring element, a magnetic force for tensioning the torsion wire.
Document EP2891930A2 filed by The Swatch Group Research & Development Ltd discloses a device for regulating the relative angular speed between a magnetic structure and a resonator magnetically coupled to each other and forming an oscillator which defines a magnetic escapement. The magnetic structure includes at least one annular path formed of a magnetic material of which one physical parameter is correlated to the magnetic potential energy of the oscillator, the magnetic material being arranged along the annular path so that this physical parameter varies angularly in a periodic manner. The annular path includes, in each angular period, an area of accumulation of magnetic potential energy in the oscillator, radially adjacent to an impulse area. The magnetic material, in each accumulation area, is arranged so that the physical parameter of this magnetic material gradually increases angularly or gradually decreases angularly.
Document EP3299907A1 filed by ETA Manufacture Horlogere Suisse discloses a mechanical horological movement comprising a resonator, an escapement linked to the resonator and a display of at least one piece of temporal information. The display is driven by a mechanical drive device via a counter gear train, the working rate thereof is set by the escapement. At least the resonator is housed in a chamber which is subjected to a pressure that is below atmospheric pressure. The escapement is a magnetic escapement comprising an escape wheel directly or indirectly coupled to the resonator via a contactless magnetic coupling system, wherein the magnetic coupling system is formed such that a non-magnetic wall of the chamber passes through the magnetic escapement such that a first part of the escapement is located inside the chamber whereas a second part of the escapement is located outside the chamber.
The purpose of the present invention is to make such resonators insensitive to external magnetic fields.
For this purpose, the invention relates to a resonator inertia mobile component according to claim 1.
The invention further relates to a resonator comprising such an inertia mobile component.
The invention further relates to a movement comprising such a resonator.
The invention further relates to a timepiece, in particular a watch, comprising such a movement.
The invention further relates to a method for reducing the sensitivity, to an external magnetic field, of a horological resonator comprising internal magnetic interaction means between at least one inertia mobile component of said resonator, mounted such that it pivots about an axis of oscillation and comprising magnetic elements, and an escape wheel set or a structural element that is magnetised and/or ferromagnetic, comprised in said resonator.
Other features and advantages of the invention will be better understood upon reading the following detailed description given with reference to the accompanying drawings, in which:
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The invention relates to the production of a horological mechanism that is insensitive to the external magnetic field, and more specifically a horological resonator of the magnetic type, or at least one part of the running thereof is based on magnetic attraction and/or repulsion, and in particular comprising magnets, which is insensitive to the external magnetic field.
The invention relates to a horological resonator 100.
This horological resonator 100 comprises at least one inertia mobile component 1 arranged such that it oscillates about an axis of oscillation D1, and return means for maintaining the oscillation of this at least one inertia mobile component 1.
This at least one inertia mobile component 1 comprises at least one magnetic area 10, which is arranged so as to engage with an escape wheel set 2. This magnetic area 10 comprises at least one magnet or at least one magnetised ferromagnetic area.
Additionally, the total resultant magnetic moment of all of these magnetic areas 10 is aligned in the direction of the axis of oscillation D1.
According to the invention, from among all of said magnetic areas 10, a first set of magnetic areas 11, 12, 13, 14 is arranged for this magnetic interaction with the escape wheel set 2 or a structural element 3 of the resonator 100, such as a detent pin or similar element, and a second set of magnetic areas is arranged so as to compensate for the resultant of the magnetic moments of all of the magnetic areas of the first set, such that this resultant has a zero component in any plane perpendicular to the axis of oscillation D1.
Additionally, this second set comprises at least one magnetised area or at least one balancing magnet 6, the direction of the magnetic moment thereof crosses the axis of oscillation D1 in order to obtain magnetic balancing of this at least one inertia mobile component 1.
More particularly, the inertia mobile component 1 bears at least one magnetic compensating element 4, the magnetisation component thereof in a direction perpendicular to the axis of oscillation D1 can be adjusted in order to obtain a total resultant magnetic moment that is aligned in the direction of the axis of oscillation D1.
More particularly, the magnetic centre of mass of the inertia mobile component 1 is located on the axis of oscillation D1. This magnetic centre of mass is defined by the moments of order 1: xB, yB, zB of the component of the magnetic moment in the direction of the axis of oscillation D1.
In these formulae, the sum is calculated for all infinitesimal elements of magnetic moment μi and only the component μiz along the axis of oscillation D1 is considered.
More particularly, all of the magnetic areas 10 comprised in this inertia mobile component 1 have permanent magnetisation.
Even more particularly, all of the magnetic areas 10 comprised in the inertia mobile component 1 only comprise permanent magnets, and are devoid of ferromagnetic components and of ferromagnetic areas, like the entirety of the inertia mobile component 1 is also devoid thereof.
The invention further relates to a horological resonator 100 comprising at least one such inertia mobile component 1, and comprising return means for maintaining the oscillation of the at least one inertia mobile component 1.
According to the invention, the resultant of the magnetic moments of all of the magnetic areas 10 borne by the at least one inertia mobile component 1 has a zero component in any plane perpendicular to the axis of oscillation D1.
More particularly, the resultant of the magnetic moments of all of the magnetic areas 10 borne by all of the inertia mobile components 1 of the same axis of oscillation D1, comprised in the resonator 100, has a zero component in any plane perpendicular to the axis of oscillation D1.
More particularly, all of the areas comprised in the resonator 100 in the immediate vicinity of the at least one inertia mobile component 1 have a zero magnetic moment, and are devoid of any ferromagnetic components, ferromagnetic areas and magnets.
More particularly, all of the areas comprised in the resonator 100 in the immediate vicinity of each inertia mobile component 1 of the same axis of oscillation D1, comprised in the resonator 100, have a zero magnetic moment, and are devoid of any ferromagnetic components, ferromagnetic areas and magnets.
The invention further relates to a horological movement 1000, comprising such a resonator 100, powering and/or energy storage means 300 arranged so as to power at least one such resonator 100, comprised in the movement 1000, and an escapement mechanism 200 comprising at least one escape wheel set 2 arranged so as to engage, with interaction, with the at least one inertia mobile component 1 of the resonator 100.
According to the invention, the at least one inertia mobile component 1 and the at least one escape wheel set 2 with which it engages, on the one hand comprise magnets which are permanent magnets, and on the other hand are devoid of ferromagnetic components and of ferromagnetic areas, like the entirety of the resonator 100 and the components of the escapement mechanism 200, other than the at least one escape wheel set 2 which comprises escapement magnets 299, which are also devoid thereof.
More particularly, the at least one inertia mobile component 1 is arranged such that it engages, with magnetic interaction, in a plane perpendicular to the axis of oscillation D1 or oblique relative to the axis of oscillation D1, with the at least one escape wheel set 2 and/or a structural element 3, that is magnetised and/or ferromagnetic, comprised in the movement 1000.
And the resultant of the magnetic moments of all of the magnetic areas 10 borne by the at least one inertia mobile component 1 has a zero component in any plane perpendicular to the axis of oscillation D1.
More particularly, the resultant of the magnetic moments of all of the magnetic areas 10 borne by all of the inertia mobile components 1 of the same axis of oscillation D1, comprised in the resonator 100, has a zero component in any plane perpendicular to the axis of oscillation D1.
More particularly, from among all of the magnetic areas 10 comprised in the at least one inertia mobile component 1, a first set of magnetic areas is arranged for the magnetic interaction with at least one escape wheel set 2 or a structural element 3, and a second set of magnetic areas is arranged so as to compensate for the resultant of the magnetic moments of all of the magnetic areas of the first set such that the resultant has a zero component in any plane perpendicular to the axis of oscillation D1, and the second set of magnetic areas is further arranged such that the magnetic interaction efforts of the constituents thereof with any escape wheel set 2 or any structural element 3 of the resonator 100 are less than one tenth of the magnetic interaction efforts of the constituents of the first set of magnetic areas with any escape wheel set 2 or any structural element 3 of the resonator 100.
More particularly, at least one escape wheel set 2 or at least one structural element 3 that is magnetised and/or ferromagnetic, comprised in the movement 1000, and which is arranged so as to engage, with magnetic interaction, with at least one inertia mobile component 1, has a resultant of the magnetic moments of all of the magnetised areas and of all of the magnets comprised therein having a zero component in any plane perpendicular to the axis of oscillation D1 or in any plane perpendicular to its own axis of oscillation if rotatably mounted.
More particularly, each escape wheel set 2 or structural element 3 that is magnetised and/or ferromagnetic, comprised in the movement 1000, and which is arranged so as to engage, with magnetic interaction, with at least one inertia mobile component 1, has a resultant of the magnetic moments of all of the magnetised areas and of all of the magnets comprised therein having a zero component in any plane perpendicular to the axis of oscillation D1 or in any plane perpendicular to its own axis of oscillation if rotatably mounted.
More particularly, the second set comprises at least one magnetised balancing area and/or a balancing magnet 6, the position of the magnetic centre of mass thereof, as defined hereinabove, is not located on the axis of oscillation D1, and is adjusted by calculation in order to obtain magnetic balancing of the at least one inertia mobile component 1.
More particularly, each magnetised area or magnet comprised in the second set has a magnetic moment, the position of the magnetic centre of mass thereof is not located on the axis of oscillation D1.
More particularly, the first set comprises at least one magnetised balancing area or a balancing magnet 6, the position of the magnetic centre of mass thereof is not located on the axis of oscillation D1 in order to obtain magnetic balancing of the at least one inertia mobile component 1.
More particularly, each magnetised area or magnet comprised in the first set has a magnetic moment, the position of the magnetic centre of mass thereof is not located on the axis of oscillation D1.
More particularly, the second set comprises at least one magnetised balancing area and/or a balancing magnet 6, the direction of the magnetic moment thereof crosses the axis of oscillation D1 in order to obtain magnetic balancing of the at least one inertia mobile component 1.
More particularly, each magnetised area or magnet comprised in the second set has a magnetic moment, the direction thereof crosses the axis of oscillation D1.
More particularly, the first set comprises at least one magnetised balancing area or a balancing magnet 6, the direction of the magnetic moment thereof crosses the axis of oscillation D1 in order to obtain magnetic balancing of the at least one inertia mobile component 1.
More particularly, the second set comprises at least one magnetised area or a balancing magnet 6, the position of the magnetic centre of mass thereof is located, relative to the axis of oscillation D1, opposite the magnetic centre of mass of the other magnets carried by the inertia mobile component, in order to obtain magnetic balancing of the at least one inertia mobile component 1.
More particularly, each magnetised area or magnet comprised in the first set has a magnetic moment, the direction of the magnetic moment thereof crosses the axis of oscillation D1.
More particularly, all of the magnetised areas and all of the magnets borne by each inertia mobile component 1 have permanent magnetisation.
More particularly, all of the magnetised areas and all of the magnets borne by at least one escape wheel set 2 or structural element 3, comprised in the movement 1000, have permanent magnetisation.
More particularly, all of the magnetised areas and all of the magnets borne by each escape wheel set 2 or structural element 3, comprised in the movement 1000, have permanent magnetisation.
More particularly, all of the magnetic areas 10, and each at least one magnetised area or each at least one balancing magnet 6, comprised in the inertia mobile component 1, have permanent magnetisation.
More particularly, this at least one inertia mobile component 1 and this at least one escape wheel set 2 with which it engages, respectively comprise magnetic areas 10 and at least one magnetised area or a balancing magnet 6, and escapement magnets, all of which are formed by permanent magnets, and are, with the exception of the magnetic areas 10 of the at least one magnetised area or of the at least one balancing magnet 6, and of the escapement magnets 299, devoid of ferromagnetic components and of ferromagnetic areas, like the entirety of the resonator 100 and the components of the escapement mechanism 200 other than the at least one escape wheel set 2 and the inertia mobile component 1.
More particularly, the inertia mobile component 1 is devoid of any ferromagnetic components and ferromagnetic areas other than the magnetic areas 10 and than the at least one magnetised area or the at least one balancing magnet 6, which are all formed by permanent magnets.
More particularly, all of the magnetic areas 10, and each at least one magnetised area or balancing magnet 6, and each at least one magnetic compensating element 4, comprised in the inertia mobile component 1, have permanent magnetisation.
More particularly, the inertia mobile component 1 is devoid of any ferromagnetic components and ferromagnetic areas other than the magnetic areas 10, the at least one magnetised area or the at least one balancing magnet 6, and the at least one magnetic compensating element 4, which are all formed by permanent magnets.
More particularly, at least one inertia mobile component 1 is a balance, and at least one escape wheel set 2 is an escape wheel.
More particularly, the movement 1000 comprises at least one structural element 3, which is arranged so as to engage, with magnetic interaction, with the at least one inertia mobile component 1 at a magnetic area 13, 14 thereof, and this structural element 3 is in particular a detent pin 33 or a banking limiting the travel of the at least one inertia mobile component 1, or a similar element.
The invention further relates to a timepiece 2000, in particular a watch, comprising at least one such movement 1000 and/or one such resonator 100.
More particularly, this watch 2000 comprises a case with a magnetic shield in order to enclose each resonator 100 comprised in the watch 2000.
The invention allows for the implementation of a method for reducing the sensitivity, to an external magnetic field, of a horological resonator 100 comprising internal magnetic interaction means between, on the one hand, at least one inertia mobile component 1 of the resonator 100, mounted such that it pivots about an axis of oscillation D1 and comprising magnetic elements 10, and, on the other hand, an escape wheel set 2 or a structural element 3 that is magnetised and/or ferromagnetic, comprised in the resonator 100, for which resonator 100 two reference axes OX and OY orthogonal to one another and to the axis of oscillation D1 are defined.
According to the invention:
The figures more particularly show, in a non-limiting manner, the application of the invention to a resonator 100 with an inertia mobile component 1 which is a balance.
Let's consider a balance 1, mounted such that it pivots about an axis of oscillation D1, and which bears magnets 11 and 12 intended to interact with an escape wheel 2, pivoting about an escapement axis D2, as shown in
Each magnet 11, 12 has a magnetic moment, which is an extensive vector quantity calculated as being the integral of the magnetisation over the entire volume of the magnet. The magnetic moment can be shown as the needle of a compass, which is subject to a torque when immersed in an external magnetic field.
In order to minimise the perturbation effect of an external magnetic field on the resonator 100, the total magnetic moment of the magnets 11, 12, borne by the balance 1, must be aligned in the direction of the axis of oscillation D1 of the balance 1, in this case denoted as the Z axis.
Ideally, the magnetic moment should solely be formed of the component p, that is aligned with the Z axis. The component of this moment which is perpendicular to the Z axis, i.e. μxy, represents an error that should ideally be corrected.
More specifically, let's suppose that the total resultant magnetic moment is not aligned with the Z axis, and thus that a component of the magnetic moment exists that is perpendicular to the axis of oscillation in
In the presence of an external magnetic field Bext, it is subjected to a torque which tends to align same with this external field, and the intensity thereof depends on the angular position of the balance 3, as shown in
In theory, the magnetisation of the magnets 11, 12, borne by the balance 1, can still be assumed to be aligned in the direction of the axis of oscillation. However, in practice, it is known that there are always imperfections, resulting from the assembly, magnetisation, or other cause, and thus a small alignment error is unavoidable, and thus so is the presence of this small perturbation component μxy.
More specifically, an alignment error produces such a small component μxy in the plane perpendicular to the axis of oscillation, which acts as a needle of a compass. Thus, an external magnetic field Bext produces a perturbation torque which depends on the position of the balance, and thus a variation of daily rate. More specifically, such a perturbation torque, which varies in a non-linear manner with the angle of the balance 1, is known to affect the running of the resonator 100.
The insensitivity of the resonator to external fields can be improved by several approaches.
The first improvement proposed thus consists of adding at least one compensating magnet 4 on the balance 1, as shown in
There are several ways of producing such a compensating magnet 4, for which the component perpendicular to the axis of oscillation can be adjusted, as shown in
Use of at least two diametrically-magnetised cylindrical magnets can be considered, the axis thereof is parallel to the axis of oscillation D1 of the resonator, having moments μc1 and μc2, which are rotated in order to adjust the resultant thereof, as shown in
A radially-magnetised cylindrical magnet can also be added, the resultant magnetisation thereof is zero. The adjustment thus takes place by removing a part of this magnet, as shown in
Micro-magnets (magnetic pixels) can also be considered in the directions ±X and ±Y that are removed as necessary, as shown in
A spherical magnet magnetised along the axis of oscillation can also be considered, which magnet is located in a spherical recess, as shown in
This list is non-exhaustive. For example, another solution would be to add a single cylindrical magnet, diametrically magnetised with the right intensity, equal to that of μxy, and which could be oriented in order to adjust the direction of μc. In order to adjust the intensity of this magnet, the field used for the magnetisation thereof can be varied.
It goes without saying that each of these solutions for creating an adjustable compensating magnet is, advantageously, carried by the balance 1, close to the axis of oscillation D1 thereof, as shown in
Regardless of the method used for the adjustment, the residual sensitivity of the resonator must be previously measured, and the desired compensation must be calculated. To achieve this, a uniform external magnetic field Bx0 is simply applied along +X and −X, and the rate difference Δmx resulting therefrom is measured. The same is carried out for a magnetic field along Y. The components of the compensating magnetic moment are calculated as follows: μx=k·Δmx/(86400 Bx0), and for the other component, simply replace x by y in this formula, where:
μx=magnetic moment in A·m−2
k=rotational stiffness of the return spring of the balance in N*m/rad=N*m. For example k=10−6 N·m/rad for a sprung balance.
Δmx=rate in seconds per day
Bx0=magnetic field in Tesla.
Let's now assume that this total magnetic moment alignment work has been carried out so that the component of the magnetic moment perpendicular to the axis of oscillation D1 has become negligible. The next perturbation effect that affects the running of the balance 1, when it is placed in an external field Bext is caused by the displacement, in an arc of a circle, of the magnetic moment in a non-homogeneous field Bz, as shown in
In order to cancel out this effect, it suffices to position the resultant magnetic moment on the axis of oscillation D1 (point O). However, the magnetic pallet-stones 11 and 12 that interact with the escape wheel 2 cannot be displaced to this point.
A second improvement proposed thus consists of adding a balancing magnet 6, as shown in
This balancing magnet 6 is magnetised in the direction of the axis of oscillation D1. It is positioned opposite the position of the magnetic centre of mass of the other magnets 11 and 12 carried by the balance 1, as shown in
In other words, the mass is replaced by μz in the definition of the centre of mass:
More specifically, in order to obtain magnetic balancing, the magnetic centre of mass of the total magnetisation of the resonator 100 is placed on the axis of oscillation D1.
This approach is applicable to the example shown in
A plurality of methods are available for adding this magnetic balancing magnet. It should be specified that the geometrical configuration and location of this balancing magnet can be calculated when designing the pallet-stone magnets 11, 12 and similar elements. Thus, the balancing magnet 6 can be manufactured with the same technology used to manufacture the pallet-stones: conventional machining, laser, thin film deposition, or other technology. Another solution can consist of subsequently adding same, for example, by spraying magnetic material onto the balance felloe, by additive manufacturing or jetting, or by any other suitable method, in order to balance it. It goes without saying that this list is not exhaustive.
To summarise, the invention proposes:
The invention allows high insensitivity to be obtained for a resonator incorporating magnetic functions into the external magnetic fields, without any noteworthy increase in the volume of the components thereof, and at a low cost.
The invention applies equally to new equipment as it does to mechanisms that have already been manufactured, which can be safely improved under reasonable economic conditions.
The invention is described herein with reference to the specific case of a resonator, which is the most sensitive member of a timepiece, for which any magnetic perturbation is capable of having direct repercussions by degrading the running thereof. The horologist will also know how to apply this to other less sensitive mechanisms of a watch, such as magnetic strike mechanisms or other mechanisms.
The invention has been described with reference to the preferred case of a magnetic interaction, however the principle remains applicable to an electrostatic interaction, or even to a combined magnetic and electrostatic interaction.
| Number | Date | Country | Kind |
|---|---|---|---|
| 19182712.0 | Jun 2019 | EP | regional |
