HK1233335B - Mechanical timepiece movement provided with a feedback system for the movement - Google Patents

Description

Mechanical watch movement provided with a feedback system for the movement

Technical Field

The invention relates to a mechanical timepiece movement provided with a feedback system for the movement.

Background Art

Over the years, mechanical watch movements have undergone numerous improvements, particularly to regulate or adjust the oscillation frequency of the sprung balance, a resonator used as a local oscillator. Conventional mechanical watch movements, and in particular their Swiss lever escapements, are characterized by their robustness to shocks experienced by the watch. This means that the watch's condition is generally unaffected by a single shock. However, the efficiency of such escapements is not very high, at around 30%, for example. Furthermore, the Swiss lever escapement does not allow the use of resonators with high frequencies or low amplitudes.

WO Patent Application No. 2006/045824 A2 discloses a regulating member for returning an oscillating sprung balance to its equilibrium position. An escapement is also provided for maintaining the balance's oscillations about its equilibrium position. To achieve this, the balance is connected to at least one movable permanent magnet, while the regulating member comprises a fixed permanent magnet to generate a magnetic field that returns the balance to its equilibrium position. However, there is no description of a feedback system capable of adjusting the oscillation frequency of the sprung balance, which is a disadvantage.

To maintain the resonator of the local oscillator at a high frequency, the principle of the Swiss lever escapement must be adjusted. To achieve this, increasing the frequency of the adjustment member requires more energy to maintain the oscillator. To reduce this energy, the oscillator's mass or inertia can be reduced to reduce the oscillation amplitude, the oscillator's quality factor can be increased, or the energy transfer efficiency between the drive member and the adjustment member can be improved. Therefore, with a conventional Swiss lever escapement, excessive energy is consumed due to the multiple accelerations and stops per second. Even if the Swiss lever and its wheel were made as light as possible, this would not easily lead to a high-frequency oscillator.

The mechanical movement proposed by De Bethune features a magnetic escapement with continuous sinusoidal energy transmission. A mechanical drive member transmits torque to a reduction gear train. At the end of this gear train, a magnetic rotor transfers energy to a resonator of a local oscillator, to which a permanent magnet is attached. The gear train speed is synchronized with the natural resonator frequency. The resonator, acting as a regulating element, controls the measurement of time. The precise and regular division of time controls the speed of the time indicator hand.

This resonator can replace conventional sprung balances to better meet the requirements and constraints of high-frequency oscillations, thereby improving precision. No specific attachment points exist. The resonator is more rigid and allows the use of the first natural mode of vibration. The quality factor is higher than that of conventional oscillators, even at low amplitudes.

However, the aforementioned embodiment for the De Bethune movement lacks shock resistance. Under such conditions, the hands are prone to rapid forward movement following any shock. Furthermore, there is no description of a feedback system for simply and precisely adjusting the oscillation frequency of the sprung balance, as described in the present invention, which is a disadvantage.

The present invention seeks to find a device for using a resonator with a local oscillator having a high quality factor, a high frequency and/or a low amplitude. This is achieved without giving up the shock robustness of the Swiss lever escapement.

Summary of the Invention

One of the main objectives of the present invention is therefore to remedy the above-mentioned drawbacks by proposing a mechanical timepiece movement provided with a feedback system capable of precisely regulating the oscillation frequency of the resonator of the local oscillator of the mechanical movement.

To this end, the invention relates to a mechanical timepiece movement comprising at least one barrel, a transmission wheel set driven at one end by said barrel, an escapement having a local oscillator with a resonator in the form of a sprung balance, and a feedback system for said mechanical timepiece movement, said escapement being driven at the other end of said transmission wheel set, wherein said feedback system comprises at least one precise reference oscillator combined with a frequency comparator for comparing the frequencies of the two oscillators, and an adjustment mechanism for adjusting the resonator of the local oscillator, so as to slow down or speed up said resonator, on the basis of the comparison result in said frequency comparator.

Optionally, the reference oscillator of the feedback system is excited by magnetic interaction via a rotating excitation wheel connected to one of the wheels in the transmission wheel set.

Optionally, the excitation wheel is a toothed wheel made of ferromagnetic material, and the reference oscillator includes at least one permanent magnet arranged at a first end of an arm, the arm being fixed to the mobile frame of the frequency comparator via a base, the permanent magnet being arranged near the excitation wheel so as to be attracted when each tooth of the rotating excitation wheel passes by and to generate oscillations at the reference frequency of the reference oscillator.

Optionally, the reference oscillator comprises two arms attached to the base, the first end of each arm respectively carrying a permanent magnet to form a tuning fork, and the first and second permanent magnets are attracted towards the rotating excitation wheel as each tooth passes.

Optionally, two permanent magnets are arranged near the exciting wheel and at diametrically opposite positions, wherein the exciting wheel is located between the two permanent magnets.

Optionally, the excitation wheel includes an odd number N of teeth.

Optionally, the number N of teeth of the excitation wheel is at least equal to 9.

Optionally, the mobile frame of the frequency comparator is mounted on the plate of the mechanical timepiece movement while being held in a defined position via at least one return spring so as to be displaced linearly or angularly according to the frequency difference of the two oscillators.

Optionally, the moving frame is a hollow wheel arranged coaxially with the excitation wheel, the hollow wheel is mounted to rotate freely on the base plate by means of roller bearings, pin bearings or ball bearings, and the moving frame is held in a defined position via two return springs connected to the moving frame at diametrically opposite positions.

Optionally, according to the rotational speed V _ext of the excitation wheel and the number N of teeth of the excitation wheel, which define an excitation frequency ω _ext equal to N·V _ext , the mobile frame of the frequency comparator is set to be angularly displaced in proportion to the difference between the oscillation frequency ω ₀ of the reference oscillator and the excitation frequency ω _ext , so as to control the adjustment mechanism and adjust the oscillation frequency of the balance with hairspring.

Optionally, the adjustment mechanism comprises at least one adjustment member connected to the frequency comparator, the mobile adjustment member being arranged to be displaced linearly or angularly to adjust the oscillation frequency of the sprung balance.

Alternatively, the regulating member mounted to rotate on the plate comprises a beak portion and a base portion driven at the output of the frequency comparator, the beak portion being able to move closer to or further away from the last coil of the balance spring depending on the angle of rotation of the beak portion, according to the frequency comparison in the feedback system.

Optionally, the regulating member, mounted in rotation on the plate, comprises a base portion driven at the output of the frequency comparator and an arcuate portion of a shape complementary to the outer surface of the balance, so as to vary the friction induced by the air on the balance as a function of the frequency comparison in the feedback system.

Optionally, the excitation wheel comprises at least portions made of ferromagnetic material, which portions are regularly spaced apart from one another and are arranged over the entire circumference of the excitation wheel to magnetically interact with at least one permanent magnet of the reference oscillator.

Optionally, the toothed excitation wheel comprises ferromagnetic portions at least on or within the teeth to magnetically interact with at least one permanent magnet of the reference oscillator.

Optionally, the toothed excitation wheel comprises a continuously deposited layer of ferromagnetic material on peripheral teeth of said excitation wheel to magnetically interact with at least one permanent magnet of said reference oscillator.

Optionally, the excitation wheel comprises regularly spaced permanent magnets arranged on its periphery to magnetically interact with at least one arm of the reference oscillator made of ferromagnetic material in order to cause the reference oscillator to oscillate at a determined reference frequency.

Optionally, the excitation wheel is arranged to excite a reference oscillator in the form of a cross-stripe resonator by magnetic interaction.

Optionally, the resonator comprises an arcuate segment or a circular flywheel having a magnetized portion or at least one permanent magnet facing the excitation wheel at a close distance, or having portions made of ferromagnetic material regularly spaced apart from each other and arranged at the periphery, the arcuate segment or the circular flywheel being connected to a first substrate via two first cross-flexible strips extending at a distance from each other in two parallel planes, the first cross-flexible strips extending at a distance from each other, the mobile first substrate being fixed to a mobile second substrate, the second substrate being connected to a fixed plate via two second cross-flexible strips, the fixed plate being fixedly mounted on the plate of the mechanical watch movement, the second cross-flexible strips extending at a distance from each other in two parallel planes, the two parallel planes of the second cross-flexible strips also being parallel to the two planes of the first cross-flexible strips.

Optionally, the first substrate and the second substrate of the frequency comparator are angularly displaced according to the frequency comparison of the two oscillators to control the adjustment mechanism.

Optionally, the adjustment mechanism comprises an adjustment beak attached to the first and second baseplates, the adjustment beak being movable closer to or further away from the last coil of the balance spring depending on a comparison of the oscillator frequencies in the feedback system.

Optionally, the adjustment beak comprises, above an aluminium plate arranged on a plate of the mechanical timepiece movement, a braking permanent magnet in order to dampen vibrations of the adjustment beak.

One advantage of the mechanical timepiece movement according to the invention lies in the fact that it is possible to optimize the accuracy of the reference oscillator without having to worry about its shock resistance and therefore the shock resistance of the local oscillator without having to worry about its accuracy.

Another advantage is that it is possible to provide a product that complies with the aesthetic codes of watchmaking thanks to the presence of the sprung balance as local oscillator, while improving precision through the use of a reference oscillator that can be at high frequency.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, advantages and characteristics of a mechanical timepiece movement provided with a feedback system for the mechanical movement will appear more clearly in the following non-limiting description made with reference to the accompanying drawings, in which:

- FIG1 is a schematic diagram showing various components of a conventional mechanical watch movement in conjunction with a movement feedback system according to the present invention,

- FIG. 2 shows in more detail the elements making up a conventional mechanical movement in conjunction with the feedback system according to the invention,

- FIG3 shows a simplified view of the components of a feedback system according to a first embodiment and primarily of the combination of a reference oscillator and a frequency comparator according to the invention,

FIG4 shows a graph of the interaction torque between the excitation wheel and the tuning fork of the reference oscillator having a permanent magnet as a function of the rotational speed of the wheel in the feedback system according to the first embodiment of FIG3 ,

- FIG5 shows a first embodiment of the adjustment mechanism of the feedback system for adjusting the oscillation frequency of a resonator of a local oscillator according to the invention,

- FIG6 shows a second embodiment of the adjustment mechanism of the feedback system for adjusting the oscillation frequency of the resonator of the local oscillator according to the invention, and

- Figure 7 shows a simplified view of the components of a feedback system according to a second embodiment with an input excitation wheel for comparing the speeds of a local oscillator and a reference oscillator of the feedback system according to the invention.

DETAILED DESCRIPTION

In the following description, all those components of a mechanical timepiece movement that are well known to a person skilled in the art will be described only in a simplified manner.

As can be seen schematically in Figure 1, a mechanical timepiece movement 1 is shown provided with a feedback system 2 for precisely regulating the speed or operation of a conventional mechanical movement 1'. The conventional mechanical movement 1' comprises a mechanical energy source 11, which is at least one barrel, a transmission assembly 12 and a local oscillator 13.

The transmission assembly 12 comprises a gear wheel set 12 driven by the barrel 11 at a first end wheel. The wheels of the gear wheel set 12 are preferably toothed wheels. The last drive wheel of the gear wheel set 12 drives the escapement of a local oscillator 13. This local oscillator 13 also includes a resonator in the form of a balance with a hairspring.

Feedback system 2 can be connected to the input of local oscillator 13 in order to control in particular the oscillation frequency of the resonator of the local oscillator. The connection between conventional mechanical movement 1 ' and feedback system 2 can be achieved via the last wheel of transmission wheel set 12.

Feedback system 2 first includes a reference oscillator 21, which is accurate, i.e., at least more accurate than the resonator of local oscillator 13. Feedback system 2 also includes a frequency comparator 22 and an adjustment mechanism 23. Frequency comparator 22 is connected to or combined with reference oscillator or resonator 21 to compare the speeds of the two oscillators 21, 13. Adjustment mechanism 23 can adjust the oscillation frequency of the resonator of local oscillator 13 based on the comparison result of frequency comparator 22. The frequency of a resonator, such as the balance of hairspring of local oscillator 13, can thus be adjusted by the adjustment mechanism, which will be described below, to slow down or speed up the resonator of the local oscillator.

It should be noted that the “speed” or frequency of a local oscillator or a reference oscillator refers to the rotational speed or oscillation frequency of a wheel to which the local oscillator and/or the reference oscillator is connected.

FIG2 shows in more detail the various elements of a conventional mechanical movement of mechanical timepiece movement 1. This conventional mechanical movement thus comprises a barrel 11 having an outer toothing intended to mesh with a central pinion 121′ of a first wheel 121 of a transmission wheel train 12. This multiplication of the rotational speed of first wheel 121 relative to that of the barrel outer toothing is thus achieved.

Transmission wheel set 12 may also include a second wheel 122, whose central pinion 122′ is driven by the outer toothed ring of first wheel 121. This also multiplies the rotational speed of second wheel 122, which rotates faster than first wheel 121. A third wheel 123 may also be provided and driven by the outer toothed ring of second wheel 122 via central pinion 123′. This also multiplies the rotational speed of third wheel 123, which rotates faster than second wheel 122. This third wheel 123 may be the last wheel of transmission wheel set 12, used to drive one or more time indicator hands of a mechanical watch.

The final wheel 123 of the transmission wheel train 12 drives the escapement of the local oscillator 13. This escapement may include an escape wheel 16, whose central pinion 16' is driven by the final wheel 123, and a Swiss lever 15 meshing with the escape wheel and cooperating in a conventional manner with a sprung balance 14. Sprung balance 14 has a hairspring 14', which is attached at one end to the balance staff and at the other end to a hairspring stud, which is typically attached to the watch plate. The oscillation frequency of the sprung balance is controlled and regulated by a feedback system 2.

A first embodiment of a feedback system 2 is shown in FIG3 . This feedback system includes a frequency discriminator. Because the local oscillator of a conventional mechanical movement is imprecise but shock-resistant, the movement excites a more accurate reference oscillator or resonator 32, 32′, 33, 33′ of the feedback system. The speed or frequency of the reference resonator is then compared with the speed or frequency of the resonator of the local oscillator by means of a frequency comparator 35, 36, 36′. The output of the frequency comparator controls the elements of a regulating mechanism to adjust the speed of the resonator of the local oscillator.

It should be noted that the reference resonator is combined with a frequency comparator. There is a magnetic interaction with a rotating wheel connected to a conventional mechanical movement to excite the reference resonator and compare the speed or frequency of the oscillator.

Excitation wheel 31 can be directly connected to a wheel in the transmission wheel set of a conventional mechanical movement. Alternatively, the excitation wheel can be a wheel in the transmission wheel set, or a multiplier or division arrangement can be provided between the excitation wheel 31 and a wheel in the transmission wheel set. Excitation wheel 31 thus rotates at a rotational speed V _ext that is proportional to the angular excitation frequency or pulse of the local oscillator. Excitation wheel 31 has a number N of peripheral teeth. The number N can be an odd number; for example, the excitation wheel can have nine teeth.

The reference oscillator or resonator of the feedback system has at least one permanent magnet 33 arranged at the free end of an arm 32 of the resonator, attached via a base 34 to a movable frame 35 mounted on the plate of the watch movement. This permanent magnet 33 is arranged near the exciting wheel 31 and preferably the magnetic polarization of the magnet is oriented towards the center of the exciting wheel 31.

The permanent magnet 33 is attracted to the excitation wheel 31 when there is a tooth near the magnet, and is less attracted to the excitation wheel when the magnet faces the empty space between two teeth of the excitation wheel. Since the excitation wheel rotates at a certain speed _Vext , the magnet 33 will oscillate at the second frequency _ω0 due to the magnetic interaction with the excitation wheel 31.

During the rotation of excitation wheel 31 and according to its outer peripheral number of teeth, N, an excitation frequency, ω _ext , is determined based on the wheel's natural rotational speed, V _ext . The excitation frequency ω _ext is therefore equal to N·V _ext , where N is the number of teeth on the excitation wheel. The number of teeth, N, can be an odd number; for example, the excitation wheel can have nine teeth. This excitation frequency ω _ext can then be compared with the oscillation frequency ω ₀ of a reference oscillator to compare the speeds of the two oscillators.

Preferably, two arms 32, 32' are provided, each having a permanent magnet 33, 33' mounted at its first end to define a tuning fork. The second ends of the two arms 32, 32' are joined and attached to a frame 35 via a base 34. The two permanent magnets 33, 33' are arranged near the excitation wheel 31 and at diametrically opposed positions, wherein the excitation wheel 31 is located between the two permanent magnets 33, 33'.

The moving frame 35 is preferably a hollow wheel arranged coaxially with the excitation wheel 31. This hollow wheel 35 is held in free rotation on the base plate by roller bearings, pin bearings, or ball bearings 38 that contact the inner surface of the hollow wheel 35. The number of roller bearings, pin bearings, or ball bearings 38 must be at least three to enable the frame or hollow wheel to rotate about the same axis of rotation as the excitation wheel. However, the frame or hollow wheel 35 is held in a defined position by at least one return spring 36 or two return springs 36, 36' attached to one side of the base plate. Preferably, the return springs 36, 36' are connected to the hollow wheel at diametrically opposed positions.

When the excitation wheel 31 rotates at a certain rotation speed V _ext , the tuning fork reference oscillator will be excited at an oscillation frequency ω _0. The excitation of the reference oscillator is obtained due to the rotation of the excitation wheel 31, and the excitation wheel 31 is made of ferromagnetic material to magnetically interact with one or more permanent magnets 33, 33' carried at the first end of the arm 32, 32'. The excitation wheel 31 can also be provided with a ferromagnetic portion on or in the teeth for magnetically interacting with the permanent magnets 33, 33'. The ferromagnetic material can also be continuously deposited on the outer peripheral teeth of the excitation wheel 31. Therefore, a magnetic interaction torque or locking torque is also generated. Since the excitation wheel rotates in the counterclockwise direction, the frame 35 will also tend to move in the counterclockwise direction while being held by the return springs 36, 36'.

The rotational speed of the excitation wheel 31 can be gradually increased and then, in principle, stabilized near the reference rotational frequency ω _0. As mentioned above, in this case, there is a locking torque. However, if the interaction torque increases further, the system unlocks and the speed of the excitation wheel 31 is then limited only by friction. Therefore, it is sought to synchronize the speeds of the two oscillators via a feedback system.

As also shown in FIG4 , due to the interaction torque about the angular excitation frequency, a locking torque occurs when the angular excitation frequency ω _ext approaches the locking frequency. The mobile frame 35 will then be in a position that balances this locking torque and the torque of the return springs 36, 36 ′. The frame also includes a toothed portion for meshing with, for example, an output wheel 37. The angular position of the output wheel 37 thus proportionally represents the difference in angular frequency or rotational frequency ω _ext −ω _0, allowing the local oscillator to be adjusted via the output wheel 37, which constitutes one of the elements of the adjustment mechanism.

It should also be noted that the frame 35 and the return springs 36, 36' can be combined into a single-piece component. Furthermore, the reference oscillator can be in a different form than a tuning fork. A permanent magnet can also be arranged on the excitation wheel, with the tuning fork having ferromagnetic arms 32, 32'. The ends of each arm face the excitation wheel so as to be excited by the rotation of the excitation wheel 31.

Figure 5 shows a simplified view of a first embodiment of a feedback system adjustment mechanism for adjusting the speed or frequency of a local oscillator according to the difference determined in the frequency comparator of the feedback system. The local oscillator is represented in Figure 5 only by the balance wheel 14 and the hairspring 14'.

The adjustment mechanism is represented by the output wheel 37 of the feedback system, which meshes with a toothed base, for example in the form of a circular arc, of a mobile adjustment member 137. The adjustment member is mounted on the watch plate for rotation about an axis parallel to the axis of rotation of the balance wheel, but external to the balance-sprung 14. The adjustment member thus includes a beak at the end of the arm opposite the toothed portion. The adjustment beak can be moved closer to or further away from the last coil of the balance-sprung 14', depending on the angle of rotation θ of the beak, which is determined by the frequency comparison in the feedback system.

The moving beak of adjusting member 137 acts on the effective length _L0 of the hairspring at a given rate of extension. The oscillation period of the balance with hairspring depends on the effective length of hairspring 14'. During oscillation, the hairspring alternately retracts and extends. If an obstacle, such as a rigid beak, is placed in the extension path of the last wheel of the hairspring, the effective length of the hairspring is momentarily altered during oscillation. This results in a reduction in the average effective length and, consequently, a shortening of the oscillation period.

Obviously, it is conceivable not to use the output wheel 37 , but to allow the toothed portion of the frame to mesh directly with the toothed portion of the adjustment member 137 .

FIG6 shows a simplified view of a second embodiment of a feedback system adjustment mechanism for adjusting the speed or frequency of a local oscillator according to the difference determined in the frequency comparator of the feedback system. As in FIG5 , the local oscillator is represented in FIG6 only by the balance wheel 14 and the hairspring 14 ′.

In this second embodiment of the adjustment mechanism, adjustment member 137 includes a toothed base, for example in the form of a circular arc, that directly engages with the toothed portion of the frequency comparator frame. The adjustment member is mounted on the watch plate for rotation about an axis parallel to the balance's axis of rotation but external to the balance-sprung 14. The adjustment member also includes an arcuate portion, shaped complementary to the outer surface of the balance 14, to modify the friction induced by the air on the balance. This arcuate portion is arranged on opposite sides of the toothed portion relative to the adjustment member's axis of rotation. Depending on the difference in rotational frequency, ω _ext -ω ₀ , the arcuate portion can be moved closer to or further away from the outer surface of the balance to adjust the speed or frequency of the local oscillator. Thus, by carefully selecting the isochronism curve of the balance-sprung used, the frequency of the balance decreases as the friction induced by the arcuate portion of adjustment member 137 closer to the balance increases, and vice versa.

It should be noted that, for both embodiments described with reference to FIGS. 5 and 6 , adjustment member 137 is linearly movable in order to adjust the oscillation frequency of sprung balance 14 .

The oscillation frequency of balance 14 can be adjusted, in addition to the friction caused by the air, by means of a magnetic coupling between adjustment member 137 and said balance.

Regarding the feedback system and according to another embodiment, different arrangements of reference oscillators can be provided to magnetically interact with the excitation wheel, thereby determining the speed or frequency of the two oscillators. The excitation wheel can include magnetic tracks arranged annularly on a surface and regularly spaced apart from one another. These annular magnetic tracks are centered on the axis of rotation of the excitation wheel. When the excitation wheel rotates, at least one magnetic coupling element, which serves as a permanent magnet of the reference oscillator, is excited by the rotating magnetic tracks of the excitation wheel. This permanent magnet is elastically held on a moving frame that can be moved angularly or linearly to compare the frequencies of the two oscillators and enable the adjustment mechanism to adjust the oscillation frequency of the balance with hairspring.

Figure 7 shows a second embodiment of the feedback system. In this second embodiment, a reference oscillator is integrated with a frequency comparator to control the adjustment mechanism. There is also a magnetic interaction with a rotating wheel connected to a conventional mechanical movement to excite the reference resonator and compare the speed or frequency of the oscillator.

As described in detail with reference to FIG3 , the excitation wheel 41 of this second embodiment can be directly connected to a wheel in the transmission wheel train of a conventional mechanical movement. Thus, the excitation wheel 41 can be the last wheel in the transmission wheel train or a wheel connected to the transmission wheel train in a transmission wheel assembly. The excitation wheel 41 rotates at a rotational speed V _ext that represents the frequency of a local oscillator (i.e., proportional to the oscillation frequency of the balance-sprung 14). The excitation wheel 41 can excite a reference oscillator, which in this case is a cross-stripe resonator.

The reference oscillator or resonator is a resonator having crossed strips 44, 45, 48, and 49. It includes at least one permanent magnet 43 on an arcuate segment 42, located close to a toothed excitation wheel 41. This rigid arcuate segment, which can be made of a metallic material, is connected to a first base plate 46 via two first, cross-flexible strips 44 and 45. These first, cross-flexible strips 44 and 45 extend at a distance from one another in two parallel planes. These two parallel planes are also parallel to the plane of the excitation wheel 41 and to the watch plate, on which the various elements of the mechanical movement and feedback system are mounted.

The first base plate 46 is also fixed to a second plate 47, the complementary part of the cross-strip resonator. This second plate 47 is connected to a fixed plate 50, which is fixedly mounted on the watch plate, via two second cross-flexible strips 48, 49. These second cross-flexible strips 48, 49 extend at a distance from one another in two parallel planes, also parallel to the two planes of the first elastic strips 44, 45. These second cross-flexible strips 48, 49 are located between the first elastic strips 44, 45 and the watch plate.

The first and second base plates 46, 47 are movable and angularly shifted according to the locking torque between the resonator and the wheel. Although shown as arcuate, the first and second base plates 46, 47 may have another general shape, such as a rectangular parallelepiped, and may be formed as a single unitary body. During rotation of the excitation wheel 41, which is preferably made of a ferromagnetic material, the arcuate segments 42, together with their permanent magnets 43, oscillate at a frequency _ω0 in the plane of the excitation wheel. A magnetic interaction occurs, and depending on the rotational speed of the excitation wheel, a defined locking torque causes angular displacement of the plates 46, 47.

In this second embodiment, the adjustment mechanism is formed by an adjustment beak 53, attached, for example, to the second base plate 47. A second permanent magnet 52 is arranged on the adjustment beak 53, which cooperates, for example, with an aluminum plate 51 arranged below the beak and on the watch plate. This aluminum plate 51 damps vibrations of the beak 53 following the oscillations of the arcuate segment 42, which acts like a Foucault brake.

Plates 46 and 47 are displaced relative to their equilibrium positions according to the comparison of the rotational frequencies ω _ext −ω ₀ . This angular displacement of plates 46 , 47 causes beak 53 to move in the direction of balance spring 14 ′ of balance 14 in order to adjust the oscillation frequency of the local oscillator, as described with reference to FIG5 . If sprung balance 14 oscillates at a frequency that is too low, beak 53 advances towards the last coil of balance spring 14 ′ in order to reduce the effective length of said balance spring, and vice versa if the oscillation frequency is too high.

According to a different variant embodiment, the arcuate section 42 can be replaced by a flywheel carrying at least one permanent magnet 43 or having a magnetized portion made in the metal material of the flywheel so as to be excited by the exciting wheel 41 when the exciting wheel 41 rotates. This flywheel can be connected to the first base plate 46 by two first cross-flexible strips 44, 45 that are remote from each other and cross on a virtual pivot axis parallel to the axis of rotation of the exciting wheel. The cross-stripe can be arranged at an angle α relative to the pivot axis, which angle α can be between 60° and 80°.

Two second cross flexible strips 48 , 49 are also remote from each other, but are arranged between the first cross strips 44 , 45 and the watch plate to which the fixing plate 50 of the combined reference oscillator and frequency comparator is fixed.

In light of the foregoing description, a person skilled in the art can devise numerous variant embodiments of a mechanical timepiece movement equipped with a feedback system for the movement without departing from the scope of the invention as defined by the appended claims. It is conceivable to provide the excitation wheel with at least one permanent magnet for interacting with a ferromagnetic metal portion of the reference resonator, thereby causing it to oscillate at a defined frequency. The excitation wheel can be a circular wheel without teeth but with ferromagnetic portions regularly spaced apart from one another and arranged over its entire circumference for magnetically interacting with the permanent magnets of the reference oscillator. When an arm or magnetized element of the reference oscillator is magnetically coupled to the excitation wheel to control the adjustment of the adjustment mechanism, the frequency comparator frame can be linearly displaced.

Claims (20)

1. A mechanical watch movement (1), comprising at least one mainspring barrel (11), a gear train (12) driven at one end by the mainspring barrel, an escapement mechanism having a local oscillator (13) in the form of a balance wheel and a hairspring, and a feedback system (2) for the mechanical watch movement, the escapement mechanism being driven at the other end of the gear train (12). The feedback system (2) is characterized in that it includes at least one precise reference oscillator (21), which is combined with a frequency comparator (22) for comparing the frequencies of two oscillators. The feedback system also includes an adjustment mechanism (23) for adjusting the resonator of the local oscillator based on the comparison result in the frequency comparator to slow down or speed up the resonator. The reference oscillator of the feedback system (2) is excited by magnetic interaction via a rotating excitation wheel connected to one of the wheels in the transmission wheel assembly (12). The excitation wheel (31) is a toothed wheel made of ferromagnetic material, and the reference oscillator (21) includes at least one permanent magnet (33) disposed at a first end of an arm (32), the arm being fixed to the moving frame (35) of the frequency comparator via a base (34), the permanent magnet (33) being disposed near the excitation wheel (31) so as to be attracted as each tooth of the rotating excitation wheel passes and to generate oscillation at the reference frequency of the reference oscillator. 2. The mechanical watch movement (1) according to claim 1, characterized in that the reference oscillator (21) includes two arms (32, 32') attached to the base (34), each arm having a first end bearing a permanent magnet (33, 33') to form a tuning fork, and the first and second permanent magnets (33, 33') being attracted to the rotating excitation wheel as each tooth passes. 3. The mechanical watch movement (1) according to claim 2, characterized in that two permanent magnets (33, 33') are arranged near the excitation wheel (31) and at opposite positions along the diameter, wherein the excitation wheel (31) is located between the two permanent magnets (33, 33'). 4. The mechanical watch movement (1) according to claim 2, characterized in that the excitation wheel (31) comprises an odd number of N teeth. 5. The mechanical watch movement (1) according to claim 4, characterized in that the number of teeth N of the excitation wheel is at least equal to 9. 6. The mechanical watch movement (1) according to claim 1, characterized in that the moving frame (35) of the frequency comparator (22) is mounted on the plate of the mechanical watch movement and is held in a defined position by at least one return spring (36) so as to be linearly or angularly displaced according to the frequency difference between the two oscillators. 7. The mechanical watch movement (1) according to claim 6, characterized in that the moving frame (35) is a hollow wheel arranged coaxially with the excitation wheel (31), the hollow wheel being mounted on the movement plate by means of roller bearings, pin bearings or ball bearings to rotate freely, and the moving frame (35) is held in a defined position by means of two return springs (36, 36') connected to the moving frame at diametrically opposite positions. 8. The mechanical watch movement (1) according to claim 6, characterized in that, according to the rotational speed _Vext of the excitation wheel (31) which is defined as an excitation frequency ωext equal to N _{· Vext} and the number of teeth N of the excitation wheel, the moving frame (35) of the frequency comparator (22) is configured to be angularly displaced to the ground in proportion to the difference between the oscillation frequency _ω0 of the reference oscillator and the excitation frequency _ωext , so as to control the adjustment mechanism (23) and adjust the oscillation frequency of the balance wheel. 9. The mechanical watch movement (1) according to claim 1, characterized in that the adjustment mechanism (23) includes at least one adjustment member (137) connected to the frequency comparator (22), the movable adjustment member being configured to shift linearly or angularly to adjust the oscillation frequency of the balance wheel. 10. The mechanical watch movement (1) according to claim 9, characterized in that the adjusting member (137) mounted to rotate on the movement plate includes a beak portion and a base portion driven at the output of the frequency comparator (22), wherein the beak portion is capable of moving closer to or further away from the last coil of the hairspring (14') according to the rotation angle of the beak portion based on the frequency comparison in the feedback system. 11. The mechanical watch movement (1) according to claim 9, characterized in that the adjusting member (137) mounted to rotate on the plate includes a base portion driven at the output of the frequency comparator (22) and an arcuate portion whose shape is complementary to the outer surface of the balance wheel (14) for changing the friction caused by air on the balance wheel according to the frequency comparison in the feedback system. 12. The mechanical watch movement (1) according to claim 1, characterized in that the excitation wheel (31) includes at least portions made of ferromagnetic material, these portions being regularly spaced apart from each other and arranged on the entire periphery of the excitation wheel to magnetically interact with at least one permanent magnet (33) of the reference oscillator. 13. The mechanical watch movement (1) according to claim 1, characterized in that the toothed excitation wheel (31) includes a ferromagnetic portion at least on or within the teeth to magnetically interact with at least one permanent magnet (33) of the reference oscillator. 14. The mechanical watch movement (1) according to claim 1, characterized in that the toothed excitation wheel (31) includes a continuously deposited ferromagnetic material layer on the outer peripheral teeth of the excitation wheel (31) to magnetically interact with at least one permanent magnet (33) of the reference oscillator. 15. The mechanical watch movement (1) according to claim 1, characterized in that the excitation wheel (31) includes regularly spaced permanent magnets arranged on the periphery of the excitation wheel to magnetically interact with at least one arm (32) of the reference oscillator made of ferromagnetic material so as to cause the reference oscillator to oscillate at a defined reference frequency. 16. The mechanical watch movement (1) according to claim 1, characterized in that the excitation wheel (41) is configured to excite a reference oscillator in the form of a cross-strip resonator (44, 45, 48, 49) through magnetic interaction. 17. The mechanical watch movement (1) according to claim 16, characterized in that the resonator comprises an arc-shaped section (42) or a circular flywheel, the arc-shaped section or the circular flywheel having a magnetized portion or at least one permanent magnet (43) facing the excitation wheel (41) at close range, or having portions made of ferromagnetic material regularly spaced apart from each other and arranged around the periphery, the arc-shaped section (42) or the circular flywheel being connected to a first substrate (46) by two first cross flexible strips (44, 45), the first cross flexible strips being in Two parallel planes extend at a certain distance from each other. The movable first substrate (46) is fixed on the movable second substrate (47). The second substrate (47) is connected to the fixed plate (50) by two second cross flexible strips (48, 49). The fixed plate is fixedly installed on the main plate of the mechanical watch movement. The second cross flexible strips (48, 49) extend at a certain distance from each other in two parallel planes. The two parallel planes of the second cross flexible strips are also parallel to the two planes of the first cross flexible strips (44, 45). 18. The mechanical watch movement (1) according to claim 17, characterized in that the first substrate (46) and the second substrate (47) of the frequency comparator are shifted to the ground according to the frequency comparison angle of the two oscillators to control the adjustment mechanism (23). 19. The mechanical watch movement (1) according to claim 18, characterized in that the adjustment mechanism (23) includes an adjustment beak (53) attached to the first substrate (46) and the second substrate (47), the adjustment beak being movable to the last coil of the hairspring (14') according to the comparison of the oscillator frequency in the feedback system. 20. The mechanical watch movement (1) according to claim 19, characterized in that the adjusting beak (53) includes a braking permanent magnet (52) above an aluminum plate (51) arranged on the main plate of the mechanical watch movement to attenuate the vibration of the adjusting beak.