HK1140552B

HK1140552B - Coupled resonator for timepiece

Info

Publication number: HK1140552B
Application number: HK10106464.2A
Authority: HK
Inventors: Hessler Thierry; Trumpy Kaspar; Helfer Jean-Luc; Conus Thierry
Original assignee: The Swatch Group Research And Development Ltd
Priority date: 2008-07-04
Filing date: 2010-07-02
Publication date: 2013-01-25

Description

Coupled resonator for a timepiece

Technical Field

The present invention relates to a resonator for a timepiece, obtained by coupling (coupling) a first low-frequency resonator and a second high-frequency resonator.

Background

EP patent No.1843227A1 discloses a resonator according to the above definition. In this document, the first low-frequency resonator is a balance spring and the second high-frequency resonator is a tuning fork. One branch of the tuning fork is directly connected to the outer coil of the balance spring to form the coupling between the two resonators. The purpose of this arrangement is to stabilize the operating frequency of the timepiece, to make it more independent of external stresses and, ultimately, to improve the operating accuracy of the timepiece. In the disclosed arrangement the natural frequency of the first resonator is of the order of a few hertz and the frequency of the second resonator is of the order of kilohertz. The idea is to subject a first resonator, which is very sensitive to external disturbances, to a second resonator, which is less sensitive to said disturbances due to the high operating frequency. Such a control leads to an improvement in the performance of the first resonator in terms of impact resistance, for example when said first resonator is fitted with a conventional escapement system.

However, the embodiments described above rely on two resonators that are very different from each other, and the coupling and adjustment of these two resonators can create difficulties that, although not insurmountable, are large enough to affect the operation of the first low frequency resonator given the low inertia of the high frequency resonator and its capacity.

Thus, if the operation of the first low-frequency resonator can be adjusted using the balance by means of the second high-frequency resonator, which also uses the balance, the operating frequency of the timepiece will be stabilized at a certain point by using a resonator that is not secret to the person skilled in the art.

In horology, the number of alternations per hour 18000, 21600 and 28800 corresponding to oscillation frequencies of 2.5, 3 and 4hz is commonly used for sprung balance resonators. However, watches are known which are equipped with a sprung balance resonator oscillating at a higher frequency, the ideal aim of which is to allow the watch to achieve better chronometric performance when worn.

As written by Charles Huguenin et al, the article "echappent et Moteurspas pas" (FET,1974, pages 137 to 148), the result of multiplying the frequency by 2 reduces the effect of the biasing fault on the daily clock operation by a factor of 4. The increase in the oscillation frequency of the balance therefore has the double advantage of increasing the adjustability of the resonator and of making the watch less sensitive to changes in position.

However, these advantages must be achieved by increasing the number of teeth of the escape wheel. A conventional escape wheel typically has 15 teeth for a sprung balance resonator with a frequency of 2.5 to 3 hertz. This number of teeth has long been accepted because of the manufacturing problems of the escape wheel, the proper distribution ratio and number of teeth, and the pinion of the watch going train. For high-frequency resonators between 4 and 10 hz, the transmission ratio becomes very high, but this drawback disappears if the number of teeth of the escape wheel increases. The 21 teeth are the number quoted for the 5hz oscillation frequency, however this change is accompanied by a reduction in reliability, such as stopwatch and dropouts, requiring special attention in winding. Furthermore, it is generally known that the output of a swiss lever escapement drops sharply above 4 or 5 hz.

Disclosure of Invention

Thus, in order to take advantage of the benefits of high frequency resonators, the high frequency resonators are coupled to low frequency resonators controlled by conventional escapements without increasing the number of teeth on the escape wheel and with a known level of reliability provided by the escapement.

This arrangement is illustrated in the block diagram of fig. 1. In this figure, the first low-frequency resonator 2, 41 is constituted by a balance driven by the escapement and a going train 70 driven by a barrel 74. A time display 72, for example realized with hands, is produced by the going train 70. The second higher frequency resonator is represented by element 3, 42. The coupling between the two resonators is represented by the double arrow elements 8, 46.

The present invention introduces two embodiments, the second embodiment being a special case of the first embodiment.

In addition to fulfilling the statements of the first paragraph of the present description, the first embodiment is characterized in that the first resonator has a first inertial mass associated with the first balance spring, the second resonator comprises a second inertial mass associated with the second balance spring, and a third balance spring is arranged between the first and second inertial masses to couple said first and second resonators.

In addition to fulfilling the statements of the first paragraph of the present description, a second embodiment is characterized in that the first resonator comprises a first inertial mass associated with the first balance spring, the second resonator comprises a second inertial mass associated with the second balance spring, and said second balance spring connects said first and second inertial masses to couple said first and second resonators.

Drawings

The invention will be explained in detail with the aid of the accompanying drawings which illustrate two embodiments described above, which are given by way of non-limiting example, wherein:

figure 1 is a block diagram illustrating a resonator of the invention and its associated parts in a timepiece;

figure 2 is a similar diagram showing how two resonators are arranged and coupled according to the first embodiment of the invention;

figure 3 is a plan view of a first embodiment of a resonator formed by coupling resonators each constituted by a balance;

FIG. 4 is a cross-sectional view along section line IV-IV in FIG. 3;

figures 5 and 6 are perspective views of the resonator shown in plan and cross-section in figures 3 and 4;

figure 7 is a graph showing the natural oscillation frequency of each resonator when the torque of the balance spring connecting the two resonators varies;

figure 8 is a graph showing the stabilizing effect on the disturbance generated by coupling the first and the second resonator when the torque of the balance spring connecting the two resonators varies, said disturbance affecting the torque of the balance spring of the first resonator, or affecting the inertial mass of the balance of said first resonator,

figure 9 is a similar diagram showing how two resonators are arranged and coupled according to a second embodiment of the invention;

figure 10 is a plan view of a second embodiment of a resonator produced by coupling resonators each constituted by a balance;

FIG. 11 is a cross-sectional view taken along section line XI-XI in FIG. 10;

figures 12 and 13 are perspective views of the resonator shown in plan and cross-section in figures 10 and 11;

figure 14 is a graph showing the natural oscillation frequency of each resonator when the torque of the balance spring of the first resonator varies, an

Figure 15 is a graph showing the stabilizing effect on the disturbance generated by coupling the first and second resonators when the torque of the balance spring of said first resonator varies, said disturbance affecting the balance spring of the first resonator, or affecting the inertial mass of the balance of said first resonator.

Detailed Description

First embodiment of the invention

A resonator 1 made according to the first embodiment of the present invention can be referred to the equivalent diagram in fig. 2. The resonator 1 is created by coupling a first resonator 2 and a second resonator 3. The first resonator 2 comprises a first inertial mass 4 (here depicted as a square mass), the first inertial mass 4 being associated with a first balance spring 5 (here depicted as a helical spring, one end of which is connected to the square mass and the other end of which is connected to a fixed part 73 of the timepiece, for example to the plate). The second resonator 3 comprises a second inertial mass 6 (here depicted as a square mass), the second inertial mass 6 being associated with a second balance spring 7 (here depicted as a helical spring, one end of which is connected to the square mass and the other end of which is connected to a fixed part 74 of the timepiece, for example a bridge). A third balance spring 8 (represented here by a helical spring) is arranged between the first inertial mass 4 and the second inertial mass 6 to couple said first resonator 2 and the second resonator 3.

Fig. 3 to 6 illustrate a practical configuration of the first embodiment of the present invention. Here, the first and second inertial masses are constituted by a first and a second balance 4 and 6, respectively, and the first, second and third balance springs are a first, second and third balance spring 5, 7 and 8, respectively.

It can be seen that according to a preferred embodiment of the invention, the first and second resonators 2 and 3 are arranged coaxially between the plate 11 and the plate 17 inside the timepiece. However, the invention is not limited to this arrangement, for example two resonators may be arranged side by side in a timepiece.

More specifically and clearly as shown in fig. 4, first resonator 2 substantially comprises a first balance 4 associated with a first balance spring 5. The first resonator 2 is mounted on a first spindle 9, the first spindle 9 rotating at a first end in a bearing 10 fixed to a machine plate 11 and at a second end in a bearing 12 fixed to an intermediate clamp 13. The outer and inner coils of first balance spring 5 are fixed to balance spring stud 23, which is loaded on machine plate 11, and to inner attachment point 28 of first mandrel 9, respectively.

Second resonator 3 substantially comprises a second balance 6 associated with a second balance spring 7. The second resonator 3 is mounted on a second spindle 14, the first end of which spindle 14 rotates in a bearing 15 fixed to the intermediate clamp 13 and the second end of which rotates in a bearing 16 fixed to a clamp 17. The outer and inner coils of second balance spring 7 are fixed to a balance spring stud 25 carried on plate 17 and to an inner attachment point 26 of second arbour 14, respectively.

Examining fig. 3 to 6, it is illustrated that the first resonator 2 comprises balance 4, the diameter of balance 4 being greater than the diameter of balance 6 of resonator 3, indicating that the frequency of the first resonator is lower than that of the second resonator, assuming, of course, that the torque produced by each balance spring is approximately the same. Under these conditions, it is clear that the escapement must be connected to the first resonator, which will be controlled by the second resonator to improve its immunity to interference. Fig. 4 shows that the first arbour 9 to which the first resonator 2 is connected is loaded with a roller 18 and a striker pin 19, the striker pin 19 cooperating, for example, with a pallet, which in turn cooperates with an escape wheel.

The coupling that exists between the resonators 2 and 3 will now be described. This coupling is achieved by a third balance spring 8. Fig. 4 and 5 illustrate that balance spring 8 comprises two windings 20 and 21 arranged in series and mounted on either side of intermediate bridge 13. Thus, the inner coils of the first winding 20 are fixed to the inner connection points 27 fixed to the second mandrel 14, while the inner coils of the second winding 21 are fixed to the inner connection points 22 fixed to the first mandrel 9, the outer coils of said windings being interconnected by means of the strips 75.

The invention is not limited to the above description. The third balance spring may in fact have only one winding. In this case, it is not necessary to show in the figures that the inner coil of the single winding is fixed to the connection point 27 fixed to the second arbour 14, while the outer coil is fixed to the balance spring stud carried by the first balance 4.

The advantages of coupling two resonators, one oscillating at a low frequency and the other oscillating at a higher frequency, are briefly described below, making the resonators more stable when oscillating at a low frequency.

Mechanical resonator consisting of a mass and a balance spring, characterized in that its mass m and its balance spring constant k, expressed in milligrams (mg) and micro-newtons per meter (μ N/m), respectively, according to the horological manufacturing-related orders in the equivalent diagram of fig. 2. In this example, mass m is a balance wheel characterized by milligrams per square centimeter (mg cm)²) The represented inertial mass, and the constant k, are related to the balance spring, which is characterized by a unit torque represented in terms of μ N · m/rad. Thus, the frequency of the resonator is expressed as follows:

taking a clock movement number commonly available on the market as an example, k is 1.10^-6Nm/rad and m is 16.10^-10kg·m²Thus, the frequency f is 4 Hz.

The central question is to know whether the second, higher frequency resonator stabilizes the frequency of the first, low frequency resonator. This effect is considered by a stability factor S, defined as:

in this relationship, ω₁Is the normal angular frequency, W, of the first resonator alone_1pIs the disturbance angular frequency, Ω, of the first resonator alone₁Is the normal angular frequency, omega, of the coupled system_1pIs the perturbation angular frequency of the coupled system. It is clear that if the stability factor S is equal to 2, the precision of the timepiece with coupled resonator system is twice that of a timepiece with only the first resonator. For example, a clock that walks 10 seconds per day will only walk 5 seconds faster during the same period.

The following is a practical example, which gives the first and second resonators the following characteristics:

the resonator 1: m is₁＝21mg·cm²，k₁1 μ N · m/rad, so f₁＝3.47Hz

And 2, the resonator: m is₂＝21mg·cm²，k₂1.5 μ N · m/rad, so f₂These resonators pass through a constant k of 7.75Hz_cIs coupled to the mainspring.

Referring to fig. 2 and 4, reference numeral 2 denotes a low frequency resonator 1, m₁Indicating balance 4, k₁Representing the constant of balance spring 5. Reference numeral 3 denotes a resonator 2, m having a higher frequency₂Indicating balance 6, k₂Representing the constant of balance spring 7. It is to be noted that in this example the balance has the same dimensions, unlike the case of the balance in fig. 4, in which the second resonator has a higher natural frequency due to its higher spring constant.

Graphs such as those of fig. 7 and 8 are calculated based on the above-described actual data analysis.

FIG. 7 is a graph illustrating the natural frequency f of a coupled resonator system₁And f₂Constant k as balance spring coupling two resonators_cA graph of the function of (a).

Fig. 8 is a diagram illustrating the stability factor S as a constant k of balance spring 8 coupling two resonators_cA graph of the function of (a).

Curve S_mShows when constant k_cThe effect of stabilizing the disturbance generated by coupling the first and second resonators on the inertial mass of the balance wheel affecting the first low-frequency resonator when varied. This effect is not very significant and is relatively unimportant, since the inertial mass of the balance is not affected by external disturbances.

Curve S_kThe stabilizing effect of the disturbance generated by coupling the first and second resonators on the torque affecting the balance spring of the first resonator (i.e. the resonator driven by the escapement system) is shown. It can be seen that for k_cThe value is 1 μ Nm/rad, the stability factor is close to 2 and positive, since among other things disturbances due to the position of the balance spring, vibrations and temperature variations affect the balance spring first.

Second embodiment of the invention

A resonator 40 made according to a second embodiment of the invention can be referred to the equivalent diagram in fig. 9. The resonator 40 is created by coupling a first resonator 41 and a second resonator 42. The first resonator 41 comprises a first inertial mass 43 (here depicted as a square mass), the first inertial mass 43 being associated with a first balance spring 44 (here depicted as a helical spring, one end of which is connected to the square mass and the other end of which is connected to a fixed part 73 of the timepiece, for example a plate). The second resonator 42 comprises a second inertial mass 45 (here depicted as a square mass), the second inertial mass 45 being associated with a second balance spring 46 (here depicted as a helical spring, one end of which is connected to the square mass 43 and the other end of which is connected to the square mass 45). Second balance spring 46 therefore connects first inertial mass 43 and second inertial mass 45 to couple said first resonator 41 and second resonator 42. In fact, balance spring 46 has a double function: which constitutes the second resonator 42 and couples the first resonator 41 and the second resonator 42.

The second embodiment can be considered as a special case of the first embodiment. In fact, if the third balance spring 7 of the first embodiment shown in fig. 2 and its connection to the fixing point 74 are removed, an equivalent diagram illustrating the second embodiment is obtained in fig. 9, which is described in detail below with reference to fig. 10 to 13.

Fig. 10 to 13 illustrate a practical configuration of the second embodiment of the present invention. Here, as already stated with reference to the first embodiment according to the invention, the first and second inertial masses are constituted by a first and a second balance wheel 43 and 45, respectively, and the first and second balance springs are a first and a second balance spring 44 and 46, respectively.

It can be seen that first balance 43 has a circular case surrounding a second, higher frequency resonator 42, said circular case 43 constituting a first, low frequency resonator 41 with a first balance spring 44.

As is clearly shown in cross section in fig. 11, the circular housing 43, which constitutes the first balance, mounts a first cheek 47 carrying a first trunnion 48, the first trunnion 48 rotating in a bearing 49 fixed to a plate 50. This first trunnion 48 carries a roller 51 and an impulse pin 52, and the impulse pin 52 cooperates, for example, with a pallet fork, which in turn cooperates with an escape wheel. The circular housing 43 also mounts a second cheek 53 carrying a second trunnion 54, the second trunnion 54 rotating in a bearing 55 fixed to a clamp plate 56. A balance spring stud 57 is attached to the bridge 56, the outer coil of the first balance spring 44 is fixed to the balance spring stud 57, and the inner coil of the first balance spring 44 is fixed to an inner connection point 58 fixed to the second trunnion 54. The circular housing or balance 43 and balance spring 44 constitute a first low-frequency resonator 41, the performance of which is improved.

Fig. 11 also shows that a second balance 45 and balance spring 46, which constitute a second resonator 42 (which is surrounded by a circular housing 43), are carried on arbour 59, the first end of which rotates in bearing 60 fixed to first cheek 47 of housing 43 and the second end of which rotates in bearing 61 fixed to second cheek 53 of the housing. Further, the outer and inner coils of second balance spring 46 are fixed to balance spring stud 62 mounted on second cheek 53 of case 43 and to inner attachment point 63 of arbour 59, respectively.

Examining fig. 10 to 12, it is illustrated that first resonator 41 comprises a balance or a housing 43 with a larger diameter than balance 45 of second resonator 42, indicating that the frequency of the first resonator is lower than that of the second resonator, and that the torques produced by the balance springs respectively are equal. It is therefore clear that the escapement will be connected to a first resonator, which must be controlled by a second resonator, in order to improve the immunity to interference.

The advantage of coupling two resonators, one oscillating at a low frequency and the other oscillating at a higher frequency, to improve the performance of the resonator oscillating at a low frequency has been explained in the discussion of the first embodiment. Therefore, the explanation will not be returned to the theory that is also applicable to the second embodiment as described above.

However, as a practical example, namely:

the resonator 1: m is₁＝20mg·cm²，k₁Variable ═ variable

And 2, the resonator: m is₂＝6.4mg·cm²，k_c＝0.4μN·m/rad，k₂＝0

Referring to fig. 9 and 11, reference numeral 41 denotes a low frequency resonator 1, m₁Indicating balance or casing 43, k₁Representing the constant of balance spring 44, reference 42 representing the higher frequency resonator 2, m₂Indicating balance 45, k_cConstant, k, representing balance spring 46_cAlso shown is a balance spring coupling the two resonators.

The curves of FIGS. 14 and 15 were established by analytical calculations based on the actual data described aboveFigure (a). The variable chosen is no longer k in the first embodiment_cBut rather the most decisive parameter k₁。

FIG. 14 is a graph showing the natural frequency f of a coupled resonator system₁And f₂A graph that varies as a function of the constant k1 of balance spring 44 that constitutes first resonator 41.

Fig. 15 shows a stability factor (which is defined with reference to the first embodiment) as a constant k affecting the mainspring 44 of the first resonator 41₁A graph of the function of (a).

Curve S_mShowing the constant k as balance spring 44₁The stabilizing effect of the disturbance generated by coupling the first and second resonators 41 and 42 on the inertial mass of the balance wheel affecting the first low-frequency resonator 41, varies. This effect is much more pronounced than that observed in the first embodiment.

Curve S_kThe stabilizing effect of the disturbance generated by coupling first and second resonators 41 and 42 on the torque of first balance spring 44 affecting first resonator 41 is shown. It can be seen that for k₁The value 2. mu.N.m/rad, the stability factor S is about 2.5.

Conclusion

The two embodiments described demonstrate that the performance of a first low-frequency resonator (balance resonator with a frequency of the order of 2 to 6 hz) can be improved if it is coupled to a second higher-frequency resonator (balance resonator with a frequency of the order of 10 hz). The first low frequency resonator is more sensitive to some interference than the second higher frequency resonator due to, for example, wear or vibration. It is envisaged that the second resonator counteracts any thermal variations and/or isochronous defects of the first resonator. Furthermore, the first resonator is easily compatible with a usual escapement system, which is different from the second resonator. It is therefore reasonable to: the two resonators involved in the coupling thus benefit from a good adaptability between the first resonator and the escapement and a high insensitivity of the second resonator to the aforementioned disturbances.

Claims

1. A resonator (1) for a timepiece, constituted by coupling a first low-frequency resonator (2) and a second higher-frequency resonator (3), wherein the first resonator (2) has a first inertial mass (4) associated with a first balance spring (5), the second resonator (3) has a second inertial mass (6) associated with a second balance spring (7), a third balance spring (8) is arranged between the first inertial mass (4) and the second inertial mass (6) to couple said first resonator (2) and the second resonator (3), the first and second inertial masses being constituted respectively by a first balance (4) and a second balance (6), the first, second and third balance springs being respectively a first balance spring (5), a second balance spring (7) and a third balance spring (8);

the method is characterized in that: the first resonator (2) and the second resonator (3) are arranged coaxially inside the timepiece.

2. The resonator of claim 1, further characterized by: a first resonator (2) is mounted on a first arbour (9), the first end of which (9) rotates in a bearing (10) fixed to a plate (11) and the second end of which rotates in a bearing (12) fixed to an intermediate plate (13), the outer and inner coils of a first balance spring (5) of said first resonator (2) being fixed to a balance spring stud (23) mounted on the plate (11) and to an inner attachment point (28) of said first arbour (9), respectively, a second resonator (3) is mounted on a second arbour (14), the first end of the second arbour (14) rotating in a bearing (15) fixed to said intermediate plate (13) and the second end of which rotates in a bearing (16) fixed to the plate (17), the outer and inner coils of a second balance spring of said second resonator (3) being fixed to a balance spring stud (25) mounted on the plate (17) and to a fixed to a balance spring stud (25) and to the plate (17), respectively Is fixed on the inner connecting point (26) of the second mandrel (14).

3. The resonator of claim 2, wherein: the first arbour (9) is equipped with a roller (9) and an impulse pin (19) cooperating with the escapement.

4. The resonator of claim 2, wherein: the third balance spring (8) comprises two windings (20, 21) arranged in series and mounted on either side of an intermediate bridge (13), the inner coil of the first winding (20) being fixed to an inner connection point (27) fixed to the second arbour (14), and the inner coil of the second winding (21) being fixed to an inner connection point (22) fixed to the first arbour (9).

5. A resonator (40) for a timepiece, constituted by coupling a first low-frequency resonator (41) and a second higher-frequency resonator (42), wherein the first resonator (41) has a first inertial mass (43) associated with a first balance spring (44), the second resonator (42) has a second inertial mass (45) associated with a second balance spring (46) connecting said first and second inertial masses to couple said first resonator (41) and said second resonator (42), the first and second inertial masses being constituted respectively by a first balance (43) and by a second balance (45), the first and second balance springs being respectively a first balance spring (44) and a second balance spring (46), the first balance (43) having a circular case (43) surrounding the second higher-frequency resonator (42), said circular case (43) and first balance spring (44) constituting the first low-frequency resonator (41), the method is characterized in that: the circular case (43) is fitted with a first cheek (47) with a first trunnion (48) rotating in a bearing (49) fixed to the plate (50) and fitted with a roller (51) and with an impulse pin (52) cooperating with the escapement, the circular case (43) is fitted with a second cheek (53) fitted with a second trunnion (54) rotating in a bearing (55) fixed to the plate (56) and having a balance spring stud (57) fixing the outer coil of the first balance spring (44) whose inner coil is fixed to an inner connection point (58) fixed to the second trunnion (54), the second balance spring (45) and balance spring (46) constituting the second resonator (42) being fitted on an arbour (59) whose first end rotates in a bearing (60) fixed to the first cheek (47) of the case (43), the second end rotates in a bearing (61) fixed to a second cheek (53) of the housing (43), and the outer and inner coils of the second balance spring (46) are fixed to a balance spring stud (62) mounted on the second cheek (53) of the housing (43) and to an inner connection point (63) of the arbor (59), respectively.