Method for assembling a clock oscillator

Abstract

A method for assembling a clock oscillator, comprising at least the steps of: - (S1) manufacturing a plurality of elastic return springs (20) in a reference plate (100), - (S2) measuring at least one stiffness of at least one elastic return spring (20) and at least one stiffness of at most a predetermined quantity of the elastic return springs (20) manufactured in the reference plate (100), - (S3) deducing a stiffness of at least some of the unmeasured elastic return springs (20) from the reference plate (100), - (S4) performing a stiffness ranking of the manufactured unmeasured elastic return springs (20) and / or providing a pairing of the unmeasured elastic return springs (20) with an inertial element (10) of suitable inertia, to allow each manufactured elastic return spring (20) to be assembled with an inertial element (10).

Description

Technical field of the invention

[0001] The present invention relates generally to the manufacture of watch oscillators. Watch oscillators typically comprise an inertial element (for example, a balance wheel) and an elastic restoring element (for example, a balance spring), and in particular, the present invention relates to a method of assembling a watch oscillator in which a stiffness of the elastic restoring element is predicted or deduced. State of the art

[0002] It is known in the prior art that the frequency F of the oscillator depends on the inertia I of the inertial element and the stiffness R of the elastic restoring element, as defined by the formula: F = 1 2 π R I

[0003] Consequently, as is well known to watchmakers, it is necessary to measure the stiffness R of the elastic return elements to ensure that a watch oscillator will present the desired frequency (2.5 Hz, 3 Hz, 4 Hz for example). Description of the invention

[0004] One object of the present invention is to address the disadvantages of the prior art mentioned above and in particular, first of all, to propose a method of assembling a watch oscillator that is simpler than known methods, in particular a method of assembly that is faster and / or less expensive and / or whose stiffness measurements are simpler, and / or faster, and / or more reliable.

[0005] To this end, a first aspect of the invention concerns a method for assembling a clockwork oscillator arranged to exhibit oscillations of a predetermined frequency, the oscillator comprising at least: an inertial element, having an inertia, an elastic restoring element coupled to the inertial element and having a stiffness chosen according to said inertia to obtain oscillations at the predetermined frequency, the assembly method comprising at least the steps of: manufacturing a plurality of elastic restoring elements in a reference wafer with at least one lithography step to form a pattern on the reference wafer and at least one machining step (including for example an engraving step) according to at least a part of the pattern, measuring at least a stiffness of at least one elastic restoring element and at least a stiffness of at most a predetermined quantity of the elastic restoring elements manufactured in the reference wafer, deducing a stiffness of at least a part of the unmeasured elastic restoring elements of the reference wafer,to perform a stiffness classification of the manufactured, unmeasured elastic return elements and / or to provide for the pairing of the unmeasured elastic return elements with an inertial element of suitable inertia, to allow each manufactured elastic return element to be assembled with an inertial element to obtain a clockwork oscillator arranged to exhibit oscillations at the predetermined frequency.

[0006] According to the implementation described above, the stiffness measurement performed on only some of the elastic restoring elements is used to deduce or predict the stiffness of the unmeasured elastic restoring elements. These unmeasured elastic restoring elements can then be classified, matched, or coupled with inertial elements without verifying their stiffness.Indeed, following in-depth studies, the applicant discovered that manufacturing elastic return springs on a reference plate with at least one lithography step to form a pattern on the reference plate and / or at least one machining step (including, for example, an engraving step) on at least part of the pattern is sufficiently robust, reproducible, or reliable to guarantee the stiffness of unmeasured elastic return springs by measuring only a portion of the elastic return springs (or even a single elastic return spring) manufactured on the reference plate. In particular, deducing or predicting the stiffness of unmeasured elastic return springs can lead to a reliable stiffness classification within one class.In other words, by measuring only a limited sample of the elastic return elements manufactured on a plate, the method allows the stiffness of the other elastic return elements manufactured on that plate to be deduced or predicted, for stiffness ranking, matching, or coupling with a particular inertial element to be performed. According to the implementation described above, at most a predetermined quantity of the elastic return elements manufactured in the reference plate is measured; that is, a portion of the elastic return elements manufactured in the plate are not measured. One can choose to measure at most two elastic return elements, at most five elastic return elements, at most ten elastic return elements, or even at most 10% or 20% of the elastic return elements on the reference plate, and none of the other elastic return elements will be measured.

[0007] In other words, the invention may relate to a classification method or a matching prediction method.

[0008] In particular, one aspect of the present invention relates to a method for classifying an elastic return element, or to a method for predicting the pairing of an elastic return element, said elastic return element being intended for a clockwork oscillator arranged to exhibit oscillations of a predetermined frequency, the oscillator comprising at least: an inertial element, having an inertia, said elastic return element coupled to the inertial element and having a stiffness chosen according to said inertia to obtain oscillations at the predetermined frequency, the matching classification or prediction method comprising at least the steps of: obtaining a plurality of elastic return elements manufactured in a reference plate with at least one lithography step to form a pattern on the reference plate and at least one machining step according to at least a part of the pattern, measuring at least one stiffness of at least one elastic return element and at most a predetermined quantity of the elastic return elements manufactured in the reference plate,deduce a stiffness value for at least some of the unmeasured elastic return springs from the reference plate, classify the stiffness of the manufactured unmeasured elastic return springs, and / or provide for the pairing of the unmeasured elastic return springs with an inertial element of suitable inertia, to allow each manufactured elastic return spring to be assembled with an inertial element to obtain a clockwork oscillator arranged to oscillate at the predetermined frequency.

[0009] The process may have the following characteristics, taken alone or in combination.

[0010] According to one embodiment, the step of deducing the stiffness is preceded by a step of performing a conformity test of at least one measured stiffness.

[0011] In one embodiment, the conformity test includes: A comparison of at least one measured stiffness with a predetermined range of stiffnesses, and / or a statistical calculation, such as a variability calculation, if the stiffness of several elastic return elements is measured, and / or a mapping comparison of at least one measured stiffness with an expected stiffness map on the reference plate, and / or a comparison of a difference in stiffnesses of at least two measured elastic return elements with an expected difference based on the position of said at least two measured elastic return elements. According to this implementation, it can be verified that the measured stiffness is within a manufacturing tolerance range.The applicant observed that on several reference plates manufactured using the same process and / or on the same machine, variations in stiffness could be seen between specific areas or positions on the plate, and that these variations between areas or positions were the same from one plate to another. It is therefore possible to verify that two elastic return elements occupying specific positions do indeed exhibit the expected difference in stiffness.

[0012] According to one embodiment: If the conformity test yields a compliant result, then the process proceeds to the stiffness deduction step. If the conformity test yields a result that needs confirmation, then the process returns to the stiffness measurement step. If the conformity test yields a non-compliant result, then at least some of the manufactured elastic return elements are reworked or discarded. A step can also be included to send an alert message or prompt an inspection of the machine or the manufacturing process of the elastic return elements (if there is a conformity result that needs confirmation, or a non-compliant result).

[0013] In one embodiment, the stiffness measurement is performed on at least one elastic return element selected based on its position on the reference plate. According to this implementation, one or more elastic return elements can be sampled based on their position. For example, the stiffness of one or more elastic return elements manufactured in areas or at positions on the reference plate where extreme, maximum, minimum, or even average stiffness values ​​are expected can be measured. It is possible to deliberately choose to measure parts in areas or at positions on the reference plate where the parts are most likely to be non-conforming.

[0014] According to one embodiment, the stiffness measurement is performed on at least one elastic return element, preferably alone, still attached to the reference plate, preferably by applying vibratory excitation. For this purpose, the testing method described in published application EP4278234A1 may be used.

[0015] According to one embodiment, the stiffness measurement is carried out on at least one elastic restoring element by coupling it with a reference or standard inertial element, and then measuring an oscillation frequency.

[0016] According to one embodiment, the stiffness measurement is carried out by imposing a rotational torque on the elastic restoring element.

[0017] According to one embodiment, the stiffness measurement is performed: on a single elastic return element if the manufacture was carried out with a lithography mask or a lithography machine having a validated manufacturing history or deemed sufficiently compliant, or on a plurality of elastic return elements if the manufacture was carried out with a lithography mask or a lithography machine having a manufacturing history not validated or deemed insufficiently compliant.

[0018] In one embodiment, the assembly process includes at least one step consisting of recognizing or maintaining an orientation of the reference plate. In another embodiment, the orientation of the reference plate is recognized or restored by measuring the stiffness of at least two elastic return elements and comparing the measurement result with a predetermined expected stiffness map.

[0019] In one embodiment, the assembly process includes a preliminary phase comprising a step of establishing a stiffness map during preliminary fabrications of elastic return elements on reference plates. According to this implementation, a statistical study is conducted on these preliminary fabrications to determine the stiffness variations and the areas in which these variations recur on the same reference plate. This allows for the construction of a topographic model of the expected stiffnesses in subsequent fabrications. This model can then be used in the step of deducing the stiffness of the unmeasured elastic return elements.

[0020] According to one embodiment, the mapping is established: on at least 30 reference plates, preferably at least 40 reference plates, preferably at least 50 reference plates if new manufacturing equipment is used, such as a new lithography mask or a new lithography machine, on at most 20 reference plates, at most 10 reference plates, At most, 5 reference plates are used if known manufacturing equipment is employed, such as a known lithography mask or a known lithography machine. In other words, the preliminary mapping phase is adjusted based on knowledge and / or mastery of the manufacturing process for the elastic return springs.

[0021] According to one embodiment, the assembly process includes a step consisting of: Applying dimensional adjustments to at least one elastic return element to correct its stiffness, and / or applying a thermal compensation treatment to at least one elastic return element. In one embodiment, the dimensional adjustment and / or thermal compensation treatment is performed after measuring the stiffness of a sample of elastic return elements from the reference plate. In one embodiment, the dimensional adjustment may consist of adding or removing material from elastic return elements. In another embodiment, the dimensional adjustment may consist of smoothing at least one flank of the elastic return elements.

[0022] In one embodiment, the reference wafer comprises at least one silicon layer for manufacturing the elastic return elements. In another embodiment, the manufacturing of the elastic return elements may include a deep reactive ion etching step. In one embodiment, the elastic return elements are balance springs or spiral springs used in watchmaking. In another embodiment, the elastic return elements are silicon components coated with a layer of silicon oxide.

[0023] According to one embodiment, the assembly process includes a final step consisting of mechanically coupling at least one unmeasured elastic restoring element with an inertial element.

[0024] According to one embodiment, the inertial element is a balance wheel, or includes at least one balance wheel rim. Description of the figures

[0025] Other features and advantages of the present invention will become more apparent upon reading the following detailed description of embodiment(s) of the invention given by way of non-limiting example(s) and illustrated by the accompanying drawings, in which: [ fig. 1 ] represents the two essential components of an oscillator, namely an inertial element (here a balance wheel), and an elastic restoring element (here a balance spring) to be coupled together; fig. 2 ] represents a schematic view of a reference plate in which several elastic return elements have been manufactured; [ fig. 3 [ ] represents a schematic view of the stiffness measurement of an elastic return element still attached to the reference plate of the figure 1 ; fig. 4 ] represents the main steps in the manufacturing process of a watch oscillator. Detailed description of implementation method(s)

[0026] There figure 1 represents an inertial element 10 and an elastic return element 20 to be coupled together to form a clockwork oscillator. In this particular example, the inertial element 10 is a balance wheel and the elastic return element 20 is a balance spring. To be functional, the clockwork oscillator obviously includes other components besides those of the figure 1 , such as a balance axle, a balance plate, a pin... which the skilled craftsman knows without needing to describe them in detail.

[0027] There figure 2 represents a schematic view of a reference wafer 100 in which several elastic return elements 20 have been manufactured and on which the elastic return elements 20 are still attached by a bridge to the rest of the reference wafer 100. In particular, the reference wafer 100 is a silicon wafer, in particular of the SOI type (with a Si working layer, a Si support layer separated by a buried SiO2 layer), and the elastic return elements 20 have been manufactured by a manufacturing process including in particular a photolithography step (deposition of a photosensitive resin layer and formation of a pattern in the photosensitive resin) and a deep reactive ion etching (DRIE) step.

[0028] We can note figure 2 that the reference plate 100 includes a straight edge 110 which allows the reference plate 100 to be oriented, and we can then, with an orthonormal coordinate system x, yz, define or find a position of each elastic return element on the reference plate 100. For example, we can define an x, y position for each part: The elastic return element at the bottom left can have the coordinates (1; 1) for "1st piece from the left, located on the 1st line from the bottom", the elastic return element at the bottom right can have the coordinates (8; 1) for "8th piece from the left, located on the 1st line from the bottom", the elastic return element at the top left can have the coordinates (1; 13) for "1st piece from the left, located on the 13th line from the bottom", the elastic return element at the top right can have the coordinates (10; 13) for "10th piece from the left, located on the 13th line from the bottom".

[0029] The elastic return elements 20 are still attached by a bridge to the rest of the reference plate 100, and it is therefore possible to measure their stiffness by imposing a vibratory excitation as shown in the figure 3 Indeed, a vibrational excitation source 200 can be placed opposite an elastic return element (here, the one with coordinates (5, 1) for the 5th position from the left and the 1st row from the bottom), and a laser vibrometer 300 can be positioned on the other side of the elastic return element to be measured. Thus, a predetermined vibrational excitation applied to the elastic return element with coordinates (5, 1) will cause a vibrational response that can be measured by the laser vibrometer 300. Within this vibrational response, resonance peaks can be identified, which can be used to measure the stiffness of the elastic return element with coordinates (5, 1). All the details of this control method can be found, for example, in the published international patent WO2022152857A1.Of course, other known methods exist to measure the stiffness of an elastic return element 20 of the reference plate 100 (application of a torque and measurement of an angular displacement, coupling with a reference rocker arm and measurement of the frequency...).

[0030] During the numerous manufacturing processes of reference plates and the subsequent stiffness measurements, the applicant observed that the components of the same reference plate exhibit variability in stiffness. In particular, it was found that not all the elastic return elements of the same plate could be grouped or classified into the same stiffness class. However, the applicant also observed that, for the same manufacturing process of the same reference part, the variations from plate to plate are reproducible depending on the position or location of the part on the reference plate 100 relative to a datum, such as an XY coordinate system.In other words, to give a concrete example, the part with coordinates (1; 1) will have the same difference in stiffness as the part with coordinates (1; 13) on two different reference plates but manufactured using the same process (typically with the same steps and equipment, for lithography and for engraving).

[0031] Thus, by conducting a preliminary statistical study, it is possible to create a stiffness map on a reference plate manufactured using a given process. Then, for a newly manufactured reference plate, it is possible to measure the stiffness of only a sample of the manufactured parts to deduce or predict the stiffness of the unmeasured parts.

[0032] As shown by figure 4 The assembly method or process steps include at least the following steps: Step S1: manufacture a plurality of elastic return elements 20 in a reference plate 100 with at least one lithography step to form a pattern on the reference plate and at least one machining step (an engraving step) according to the pattern; Step S2: measure at least one stiffness of at least one elastic return element 20 for at most a predetermined quantity of elastic return elements 20 manufactured in the reference plate 100; Step S3: deduce a stiffness of at least some of the unmeasured elastic return elements 20 from the reference plate 100; Step S4: perform a stiffness ranking of the manufactured unmeasured elastic return elements 20 and / or provide for a pairing of the unmeasured elastic return elements 20 with an inertial element of suitable inertia.to allow the assembly of each elastic return element manufactured with an inertial element to obtain a clockwork oscillator arranged to exhibit oscillations at the predetermined frequency.

[0033] Of course, we can foresee a step of assembly or manufacture of the clock oscillator with the coupling of at least one of the elastic return organs 20 not measured with an inertial element of an adapted or given inertia.

[0034] The applicant observed that this method allows for a precise classification (for example, to within one stiffness class, i.e., to a class width value between approximately 1.10⁻⁹ Nm / rad and 3.10⁻¹⁰ Nm / rad, with, for example, a first class width of 4.5.10⁻¹⁰ Nm / rad, a second class width of 6.5.10⁻¹⁰ Nm / rad, and a third class width of 8.5.10⁻¹⁰ Nm / rad, depending on the inertia of the rocker arm to be coupled to the elastic return element) of the unmeasured elastic return elements. In particular, these results were obtained with the method of the figure 3 by vibratory excitation and measurement of a vibratory response for the measured elastic return elements 20. In other words, the sample of measured elastic return elements 20 underwent a stiffness measurement without contact or coupling; the prediction or deduction of the stiffness for the unmeasured elastic return elements 20 is made from a stiffness map established during a preliminary study and measurement phase; and the stiffness classification is accurate to within one stiffness class. This method has several advantages: measurement time is saved, the non-contact measurement by vibrometry is fast, safe, and does not contaminate the parts, and the final classification or coupling is reliable, i.e., the clockwork oscillator exhibits the correct oscillation frequency...

[0035] During the preliminary phase carried out to establish the stiffness map, it is obviously possible to measure the stiffness using the non-contact vibrometry method briefly described. figure 3 . We can also perform checks or calibrations using another method of measuring stiffness.

[0036] Both the preliminary phase and the measurement phase of the sample of a newly manufactured reference plate 100 can be adapted according to the following points: If the manufacturing process is fully known on a known reference, the number of reference plates to be measured during the preliminary mapping phase can be reduced (one can choose to measure a maximum of ten plates, a maximum of five plates), as can the sample size of a newly manufactured reference plate (one can choose to measure a maximum of ten elastic return elements, a maximum of five elastic return elements, a maximum of two elastic return elements, or even a single elastic return element). If the manufacturing process is not fully known or not fully stable on a known reference, the number of reference plates to be measured during the preliminary mapping phase can be increased (one can choose to measure on at least 30 reference plates, preferably at least 40 reference plates, preferably at least 50 reference plates).just like the sample size of a newly manufactured reference plate 100 (one can choose to measure at least two elastic return elements, at least five elastic return elements, at least ten elastic return elements, or even 10% or 20% of the elastic return elements of the reference plate).

[0037] Therefore, a control step can be implemented before proceeding to deduce or predict the stiffness of unmeasured elastic return elements. Indeed, the applicant observed that stiffness differences were reproducible between specific positions of the parts, from one plate to another. It may be beneficial to verify the stiffness differences between parts at specific positions on the same plate. If the difference conforms to expectations, then the newly manufactured reference plate can be declared compliant. Otherwise, further conformity tests can be performed (on other parts of the reference plate, or using other calculations, such as variability or standard deviation), or even all or part of the parts can be rejected.

[0038] It can also be noted that the stiffness measurement on a portion of parts of a newly manufactured reference plate and the deduction or prediction of the stiffness of the other parts of the newly manufactured reference plate is carried out taking into account the timing of these steps, in particular, if this is carried out: before or after oxidation - deoxidation to smooth the sides of the parts, before or after a step of providing thermal compensation to the parts.

[0039] In other words, the method can be implemented immediately after the engraving stage and any necessary structure release steps. In this case, the measured stiffness is obviously not the final stiffness of the elastic restoring elements, but it has been found that the deduction or prediction (taking into account subsequent manufacturing steps) is perfectly valid. Therefore, it can be noted that the same stiffness measurement of some of the elastic restoring elements 20 (or even a single elastic restoring element 20) can be used to: define subsequent manufacturing operations for the silicon parts (smoothing, thermal compensation), and deduce or predict the final stiffness of all the elastic restoring elements manufactured. Industrial application

[0040] An assembly method according to the present invention, and its manufacture, are capable of industrial application.

[0041] It will be understood that various modifications and / or improvements obvious to a person skilled in the art can be made to the different embodiments of the invention described in this description without departing from the scope of the invention.

Claims

1. A method for assembling a clock oscillator arranged to exhibit oscillations of a predetermined frequency, the oscillator comprising at least: - an inertial element (10), having an inertia, - an elastic return element (20) coupled to the inertial element (10) and having a stiffness chosen according to said inertia to obtain oscillations at the predetermined frequency, the assembly method comprising at least the steps of: - (S1) manufacturing a plurality of elastic return elements (20) in a reference plate (100) with at least one lithography step to form a pattern on the reference plate (100) and at least one machining step along at least a part of the pattern, - (S2) measuring at least one stiffness of at least one elastic return element (20) and at least one stiffness of at most a predetermined quantity of the elastic return elements (20) manufactured in the reference plate (100)- (S3) deduce a stiffness of at least a portion of the unmeasured elastic return elements (20) from the reference plate (100), - (S4) perform a stiffness classification of the manufactured unmeasured elastic return elements (20) and / or provide for pairing the unmeasured elastic return elements (20) with an inertial element (10) of suitable inertia, to allow each manufactured elastic return element (20) to be assembled with an inertial element (10) to obtain a clockwork oscillator arranged to exhibit oscillations at the predetermined frequency.

2. Assembly method according to claim 1, wherein the step of deducing the stiffness is preceded by a step of performing a conformity test of at least one measured stiffness.

3. Assembly method according to claim 2, wherein the conformity test comprises: - a comparison of at least one measured stiffness with a predetermined range of stiffnesses, and / or - a statistical calculation, such as a variability calculation, if the stiffness of several elastic return members (20) is measured, and / or - a mapping comparison of at least one measured stiffness with an expected mapping of stiffnesses on the reference plate (100) and / or - a comparison of a difference in stiffnesses of at least two measured elastic return members (20) with an expected difference as a function of a position of said at least two measured elastic return members (20).

4. Assembly method according to claim 3, wherein: - if the conformity test gives a conforming result, then the process proceeds to the stiffness deduction step, - if the conformity test gives a conforming result to be confirmed, then the process returns to the stiffness measurement step, - if the conformity test gives a non-conforming result, then at least part of the manufactured elastic return elements (20) are reworked or discarded.

5. Assembly method according to any one of claims 1 to 4, wherein the stiffness measurement is carried out on at least one elastic return member (20) chosen according to its position on the reference plate (100).

6. Assembly method according to any one of claims 1 to 5, wherein the stiffness measurement is carried out on at least one elastic return member (20) still attached to the reference plate (100), preferably by applying a vibratory excitation.

7. Assembly method according to any one of claims 1 to 6, wherein the stiffness measurement is carried out: - on a single elastic return element (20) if the manufacture was carried out with a lithography mask or a lithography machine having a validated manufacturing history or deemed sufficiently compliant, or - on a plurality of elastic return elements (20) if the manufacture was carried out with a lithography mask or a lithography machine having a manufacturing history not validated or deemed insufficiently compliant.

8. Assembly method according to any one of claims 1 to 7, comprising a preliminary phase including a step of establishing a stiffness map during preliminary fabrications of elastic return elements (20) on reference plates.

9. Assembly method according to claim 8, wherein the mapping is established: - on at least 30 reference plates, preferably at least 40 reference plates, preferably at least 50 reference plates if new manufacturing equipment is used, such as for example a new lithography mask or a new lithography machine, - on at most 20 reference plates, at most 10 reference plates, at most 5 reference plates if known manufacturing equipment is used, such as for example a known lithography mask or a known lithography machine.

10. Assembly method according to any one of claims 1 to 9, comprising a step of: - applying a dimensional adjustment to at least one elastic return element (20) to correct its stiffness, and / or - applying a thermal compensation treatment to at least one elastic return element (20).

11. Assembly method according to any one of claims 1 to 10, wherein the reference plate (100) comprises at least one silicon layer for manufacturing the elastic return members (20).

12. Assembly method according to any one of claims 1 to 11, comprising a final step of mechanically coupling at least one unmeasured elastic return member (20) with an inertial element (10).

Images