Timepiece movement with increased power reserve

Abstract

The present invention relates to a timepiece movement (1) comprising a drive member (2), an escapement (4) receiving mechanical energy of the drive member (2) by way of a gear train (3) and a balance wheel / hairspring resonator (5) cooperating with the escapement (4). The maximum oscillation amplitude of the balance wheel / hairspring resonator (5), in all the possible operating states of the timepiece movement (1) and whatever the position of the timepiece movement (1) in space, does not exceed 230°. The invention also relates to a method for increasing the power reserve of a timepiece movement, according to which the timepiece movement is modified to reduce the maximum oscillation amplitude of the balance wheel / hairspring resonator and steps are implemented to improve the chronometric precision.

Description

[0001] Watch movement with increased power reserve

[0002] The present invention relates to a watch movement comprising a driving member (typically a barrel), an escapement arranged to receive mechanical energy from the driving member via a gear train and a sprung balance resonator arranged to cooperate with the escapement.

[0003] The present invention relates more particularly to such a watch movement with an improved power reserve.

[0004] Traditionally, to increase the power reserve of a watch movement, the size of the barrel and its spiral spring is increased so that it can store more energy, or several barrels are used in series, or several spiral springs are used in series in the same barrel. All of these solutions increase the size.

[0005] Another solution is proposed in document EP 2701013 A1. It consists of adding a differential gear device that allows the operating mode of the watch movement to be manually changed between a normal operating mode, to be used when the watch is being worn, and an operating mode with extended power reserve, to be used only when the watch is not being worn. In the second operating mode, the gear ratio in the train is modified to reduce the amplitude of oscillation of the sprung balance and thus increase the power reserve at the expense of chronometric accuracy.

[0006] Another document, EP 2871537 A1, describes a self-winding watch movement comprising a capture device which reinjects energy taken from the finishing gear into the barrel in order to increase the power reserve. This capture device is only active when the self-winding mechanism is inactive, i.e. when the watch remains in a fixed position in space. The differential gear device and the capture device described in these documents EP 2701013 A1 and EP 2871537 A1 increase the complexity and bulk of the watch movement.

[0007] The present invention aims to enable an increase in the power reserve in a given size and without complicating the watch movement.

[0008] To this end, the watch movement according to the invention is characterized in that the maximum oscillation amplitude of the balance-spring resonator, in all possible operating states of the watch movement and whatever the position of the watch movement in space, does not exceed 230°, preferably 225°, preferably 220°.

[0009] Traditionally, the maximum oscillation amplitude of a sprung balance in a watch movement is between 270° and 315° (see the Illustrated Professional Dictionary of Watchmaking by G. -A. Berner) and is preferably well above 300° (see for example patent EP 1473604). It is indeed accepted that low oscillation amplitudes are incompatible with good chronometric precision.

[0010] The present invention goes against this traditional teaching by limiting the maximum oscillation amplitude to a low value, this in all possible operating states, that is to say whatever the degree of winding of the driving member, the operating mode of the watch movement, the number of active complications, the active or inactive state of an automatic winding mechanism, etc., and whatever the position of the watch movement in space, it being recalled that for a sprung balance the oscillation amplitude is maximum when it is in a horizontal position and minimum in a vertical position.

[0011] The present invention is based on the observation that, contrary to technical prejudices on the subject, it is entirely possible to obtain, with low oscillation amplitudes, good chronometric performances equivalent to those obtained with high amplitudes. The flat-pendu in amplitude, the rate delay due to the escapement and the rate difference between the vertical positions can be corrected or compensated for example by playing on the viscous friction (for the flat-pendu in amplitude), by using a balance spring having a shape adapted to low amplitudes (to compensate for the rate delay due to the escapement) and by compensating the rate due to the weight of the balance spring by the rate due to the balance wheel imbalance (to reduce the rate difference between the vertical positions).

[0012] In particular, with regard to the hairspring, the latter may comprise in the present invention a wound blade having a variable rigidity and / or a variable pitch chosen so that the rate due to the eccentric development of the hairspring in the horizontal position decreases throughout the range of oscillation amplitudes between 130° and 220°.

[0013] In the state of the art, variations in the stiffness and / or pitch of a balance spring are generally used to make the development of the balance spring concentric, see for example patent EP 1473604 of the present applicant and patent EP 2299336 in the name of Rolex SA. These variable stiffnesses and / or pitches do not, however, change, or only very little, the shape of the rate curves for small amplitudes. However, the average rate of known balance springs (average of the rates in their different horizontal and vertical positions) - whether they have the classic shape of an Archimedes spiral, with or without a Breguet terminal curve, or whether they have a variable stiffness and / or a variable pitch along their blade - is not monotonous at small amplitudes and has a local maximum / minimum around 150°, which prevents known balance springs from compensating for the rate delay due to the escapement for small oscillation amplitudes.The present applicant has discovered that variations in rigidity and / or pitch along the blade forming the balance spring can be found which allow the rate due to the eccentric development of the balance spring in the horizontal position (corresponding to the average rate) to decrease throughout the range of oscillation amplitudes between 130° and 220° and thus partially or totally compensate for the rate due to the escapement throughout this range. The oscillator (assembly formed by the resonator and the escapement) can therefore be operated at small amplitudes without degrading its isochronism.

[0014] The present invention also provides a watch, in particular a wristwatch, comprising a watch movement as defined above.

[0015] The present invention further proposes a method for increasing the power reserve of a watch movement comprising a driving member, an escapement arranged to receive mechanical energy from the driving member via a gear train and a balance-spring resonator arranged to cooperate with the escapement, characterized in that the watch movement is modified to reduce the maximum oscillation amplitude of the balance-spring resonator, and in that steps are implemented to improve chronometric precision.

[0016] Like the watch movement defined above, the method according to the invention goes against traditional teaching which considers that the oscillation amplitude must be high. Contrary to technical prejudices, good chronometric performances, equivalent to those encountered with large amplitudes, can be obtained after implementing steps to correct or compensate for defects.

[0017] The present invention will be better understood from the following detailed description given with reference to the accompanying drawings in which:

[0018] - Figure 1 is an isochronism diagram (step), obtained by analytical modeling, of a traditional spiral in the form of an Archimedean spiral positioned horizontally;

[0019] - figures 2 and 3 are reproductions of figures 4 and 8 of patent EP 2299336, which represent isochronism curves of hairsprings whose thickness and pitch vary in a non-monotonous manner to make the development of the hairspring substantially concentric;

[0020] - figure 4 is a plan view of a hairspring used in a first embodiment of the invention; the numbers 3, 6, 9 and 12 around the hairspring indicate the angular position of the hairspring relative to the dial of the timepiece that it is intended to equip;

[0021] - Figure 5 is a diagram of the thickness of the blade of the hairspring of Figure 4 as a function of the number of turns measured from the inner end of the hairspring;

[0022] - Figure 6 is a diagram of the pitch of the hairspring of Figure 4 as a function of the number of turns measured from the inner end of the hairspring;

[0023] - figure 7 is a diagram, obtained by numerical simulation, showing the rate due to the eccentric development of the balance spring of figure 4 in the horizontal position in the oscillation range of 130° to 220°;

[0024] - figure 8 is a diagram, obtained by numerical simulation, of the steps due to the weight of the balance spring of figure 4 in the four vertical reference positions 3H, 6H, 9H and 12H;

[0025] - figure 9 is a plan view of a hairspring used in a second exemplary embodiment of the invention;

[0026] - Figure 10 is a diagram of the thickness of the blade of the hairspring of Figure 9 as a function of the number of turns measured from the inner end of the hairspring;

[0027] - Figure 11 is a diagram of the pitch of the hairspring of Figure 9 as a function of the number of turns measured from the inner end of the hairspring;

[0028] - figure 12 is a diagram, obtained by numerical simulation, showing the rate due to the eccentric development of the balance spring of figure 9 in the horizontal position in the oscillation range from 70° to 220°;

[0029] - figure 13 is a diagram, obtained by numerical simulation, of the steps due to the weight of the balance spring of figure 9 in the four vertical reference positions 3H, 6H, 9H and 12H;

[0030] - Figure 14 is a plan view of a hairspring used in a third embodiment of the invention; - Figure 15 is a diagram of the thickness of the blade of the hairspring of Figure 14 as a function of the number of turns measured from the inner end of the hairspring;

[0031] - Figure 16 is a diagram of the pitch of the hairspring of Figure 14 as a function of the number of turns measured from the inner end of the hairspring;

[0032] - figure 17 is a diagram, obtained by numerical simulation, showing the rate due to the eccentric development of the balance spring of figure 14 in the horizontal position in the oscillation range from 70° to 220°;

[0033] - Figure 18 is a block diagram showing the main elements of a watch movement.

[0034] With reference to Figure 18, a watch movement 1 according to the invention comprises, in a conventional manner, a driving member 2, a gear train 3 driven by the driving member 1, an escapement 4 driven by the gear train 3 and a balance-spring resonator 5 whose oscillations are maintained by the escapement 4. The escapement 4 and the resonator 5 together form an oscillator. The balance spring of the resonator 5 is mounted on the balance staff and serves as a return spring for the balance. The driving member 2 typically comprises one or more barrels.

[0035] According to the invention, the maximum force of the driving member 2 and the gear ratios in the gear train 3 are chosen so that the maximum oscillation amplitude of the resonator 5, in all possible operating states of the watch movement 1 and whatever the position of the watch movement 1 in space, does not exceed 230°, preferably 225°, preferably 220°. In practice, the maximum oscillation amplitude is the oscillation amplitude of the resonator 5 when the driving member 2 is fully wound, the resonator 5 is in a horizontal position and any complications integrated or associated with the watch movement 1 (for example a chronograph mechanism) are in the state where they draw the least energy from the driving member 2.Thanks to the low oscillation amplitude of the resonator 5, the power reserve of the watch movement 1 can be high, typically greater than 65 h, without having to increase the size of the driving member 2 or add a special device.

[0036] The power P dissipated in a balance-spring resonator can be expressed by the following formula: where f is the oscillation frequency of the balance, 0o is the oscillation amplitude of the balance, lo is the moment of inertia of the balance and Q is the quality factor of the resonator 5. The quality factor Q depends in theory on the oscillation amplitude and dry and viscous friction. However, it can be approximated by the following formula: where T is the viscous friction torque (considered constant), which leads to the following formula:

[0037] P = 2n 2 f 2 d^r

[0038] An important aspect of chronometric accuracy is the amplitude of the hanging plate, i.e. the difference A9o between the average of the oscillation amplitudes in the horizontal positions of the resonator and the average of the oscillation amplitudes in the vertical positions of the resonator. The amplitude of the hanging plate is given by the following formula: and can therefore be approximated as follows: where f v is the dry friction coefficient in the vertical position of the resonator.

[0039] We therefore see that by reducing the oscillation amplitude 0o we reduce the power dissipated in the resonator 5 - therefore we increase the power reserve - and that by increasing the viscous friction r we reduce the flat-pendu in amplitude - therefore we improve the chronometric precision. As the oscillation amplitude 0o is squared in the formula for power P, and not the viscous friction torque T, we can both reduce the oscillation amplitude 0o and increase the viscous friction torque T to improve the power reserve and the flat-pendu in amplitude. The viscous friction torque can be increased by reducing the space between the balance wheel and the parts of the watch movement frame that surround it, in particular by reducing the radial space between the balance wheel and the frame, for example by replacing the balance bridge with a balance bridge with a different cutout.A hanging plate with an amplitude not exceeding 40°, or even 35°, or even 30° can be obtained quite easily in this way, for example with a moment of inertia lo between 3 and 12 mg.cm. 2 , preferably between 3 and 10 mg.cm 2 , preferably between 5 and 10 mg.cm 2 , an oscillation frequency f between 3 and 5 Hz, preferably between 3 and 4 Hz, and a viscous friction torque T greater than 4.10' 11 Nms / rad, preferably greater than 5.10' 11 Nms / rad, and typically between 4.10' 11 and 1 O' 10 Nms / rad, preferably between 5.10' 11 and 8.10' 11 Nms / rad.

[0040] Another important aspect of chronometric precision is isochronism, that is, the variation of the rate as a function of the oscillation amplitude of the resonator. Figure 1 shows the theoretical isochronism curve of a traditional hairspring in the shape of an Archimedean spiral and with a constant blade thickness, in a horizontal position. It can be seen that between an amplitude of 100°, or even 130°, and an amplitude of 220° the rate is not monotonous but increases then decreases. This prevents the delay caused by the escapement, which is monotonous (increasing rate), from being correctly compensated.

[0041] The aforementioned isochronism curve is the rate curve due to the eccentric development of the balance spring in the horizontal position, that is to say the rate curve due to the reactions of the balance staff pivots to the decentering of the balance spring. Indeed, the non-concentric development of a balance spring during the oscillation of the balance with which it is associated generates lateral forces from the pivots on the bearings in which they rotate, lateral forces which vary according to the oscillation amplitude and decrease or increase the frequency of the balance-spring resonator. This disturbance is the same in all horizontal or vertical positions of the resonator. It can be expressed by a rate pi, in seconds per day (s / d), as a function of the amplitude 0o of the balance:

[0042] 2TT

[0043] 86400 f dX ,

[0044] Al(^o) — □ n 2 — ^{(p^e^dq) 2TT0Q J Lit /

[0045] 0 where: 0 is the elongation of the pendulum relative to its equilibrium position: 0(cp) = 0o cos cp and: X(0) = ^ | (0)| 2 o being the radius of gyration of the balance spring and A(0) being the displacement of the geometric center of the balance spring (located on the axis of rotation of the balance) during contractions and expansions of the balance spring in a theoretical situation where this geometric center is free, the axis of the balance spring not being held by any bearing, the outer end of the balance spring being taken as a fixed reference point. To this disturbance due to the reactions of the pivots is added, in vertical positions, a disturbance due to the weight of the balance spring, linked to the displacements of the center of mass of the balance spring caused by the eccentric development of the latter. This additional disturbance can be expressed by a rate p2, in seconds per day (s / d), as a function of the amplitude 0o of the balance: where Ms is the mass of the hairspring, L is the length of the hairspring, E is the Young's modulus of the hairspring, I is the quadratic moment of the hairspring, g is the constant of gravity, 0 is the elongation of the balance wheel relative to its equilibrium position (0 = 0o cos <p) et y g is the ordinate of the center of mass of the hairspring in a frame (O, x, y) where O is the geometric center of the hairspring and the y axis is opposite to the force of gravity.

[0046] For further explanations on the two above-mentioned disturbances, please refer to the work "Traité de construction horlogère" by M. Vermot, P. Bovay, D. Prongué and S. Dordor, published in 2011 by Presses polytechniques et universitaires romandes.

[0047] As already indicated, the rate pi is identical in all positions, horizontal and vertical, of the oscillator. The same is true of the rate due to the escapement. On the other hand, the rate p2 due to the weight of the balance spring differs according to the vertical position. The average of the rates p2 for the four vertical reference positions (3H, 6H, 9H and 12H) spaced 90° apart is zero. We can therefore consider the rate pi as representing the average of the rates of the balance spring in all positions of said balance spring.

[0048] Figures 2 and 3 are reproductions of Figures 4 and 8 of patent EP 2299336. The FH curve of each of these figures corresponds to the rate pi described above, namely the rate due to the eccentric development of the balance spring in the horizontal position or rate due to the reactions of the pivots. If we draw the average curve of the rates in the four vertical positions (average of the 3H, 6H, 9H and 12H curves), we see that it is confused with the FH curve, which is consistent with the above statement. The CH curve of each of Figures 2 and 3 does not only represent the rate due to the reactions of the pivots. An additional disturbance, not indicated in the text of patent EP 2299336, has clearly been added.

[0049] The balance springs according to patent EP 2299336 are formed of a blade of variable thickness (more generally of variable rigidity) wound according to a pitch which also varies. The variations in thickness and pitch are chosen so that the development of the balance spring is substantially concentric and so that the radial forces of the pivots in their bearings are substantially zero. The FH curve shows that the rate due to the reactions of the pivots only decreases from an amplitude of approximately 200° (figure 2) or even does not decrease (figure 3), which makes it impossible to compensate for the rate delay due to the escapement for small amplitudes.

[0050] In the watch movement 1 according to the invention, the hairspring is advantageously designed with a variable blade thickness and / or a variable pitch so as to obtain a decreasing pi rate in a range of amplitudes including small amplitudes. In all that follows, the thickness of the hairspring blade and the pitch of the hairspring are measured radially relative to the geometric center of the hairspring. In addition, the pitch, i.e. the distance between two consecutive turns, is measured between the neutral fibers of the turns.

[0051] Examples of hairsprings that can be used in the invention are illustrated in Figures 4, 9 and 14. These hairsprings are made of a silicon-based material, more precisely silicon covered with a thermal compensation layer of silicon oxide, and have a coil height of 120 μm, a distance between their inner end and their geometric center (distance measured between the neutral fiber and the geometric center) of 0.565 mm, a distance between their outer end and their geometric center (distance measured between the neutral fiber and the geometric center) of 2.35 mm and a number of turns that varies from one hairspring to another, namely respectively 9.62 turns, 8.44 turns and 7.37 turns for the hairsprings of Figures 4, 9 and 14.

[0052] As can be seen in Figures 5, 10 and 15, the thickness of the blade forming the hairspring decreases continuously and over more than one revolution from the inner end of the hairspring (abscissa 0 on the diagram) until it reaches a minimum. Then, from this minimum, the thickness of the blade increases continuously and over more than one revolution to the outer end of the hairspring.

[0053] The pitch of these example hairsprings is shown in Figures 6, 11 and 16. It increases continuously over more than half its length, in number of turns, and may increase continuously from the inner end to the outer end.

[0054] More generally, it is advantageous in the present invention for the thickness of the blade forming the balance spring to decrease continuously and over more than one revolution in the direction of winding of the blade from a first point located on the inner coil and to decrease continuously and over more than one revolution in the direction opposite to the direction of winding of the blade from a second point located upstream of the first point in said direction opposite to the direction of winding of the blade. Preferably, the second point is located on the outer coil or on the coil which immediately follows the outer coil in said direction opposite to the direction of winding of the blade. The first point may be the inner end of the balance spring or a point distinct from the inner end. The second point may be the outer end of the balance spring or a point distinct from the outer end.Preferably, in the direction of winding of the blade, the thickness of the blade decreases continuously from the first point until it reaches a minimum (which may be the thickness of a single point of the hairspring or a portion of the hairspring), then increases continuously from this minimum to the second point. Preferably, the point or portion of minimum thickness is closer to the first point than to the second point in number of turns. Preferably, the thickness at the first point is greater, and even greater by a factor greater than 2, than the thickness at the second point.

[0055] Figures 7, 12 and 17 show the rate pi due to the eccentric development of the balance spring in the horizontal position for the balance springs of figures 4, 9 and 14 respectively. It can be seen that, in the entire range of amplitudes from 130° to 220°, or even from 120° to 220°, or even from 110° to 220°, or even from 100° to 220°, or even from 90° to 220°, or even from 80° to 220°, or even from 70° to 220°, the rate pi is decreasing, which makes it possible to compensate for these small amplitudes the increasing rate of an escapement, in particular a Swiss lever escapement. The balance springs of figures 4, 9 and 14 produce a rate deviation pi between the amplitudes of 130° and 220° greater than 1.2 s / d, 1.5 s / d and 5 s / d respectively, making it possible to compensate for a corresponding rate delay due to the escapement in this amplitude range.Generally, the balance springs used in the invention preferably produce a rate deviation pi between the amplitudes of 130° and 220° of at least 1 s / d, or even at least 1.5 s / d, or even at least 2 s / d, or even at least 3 s / d, or even at least 4 s / d.

[0056] These examples of spirals are further designed so that the minimum distance between the turns, at the most unfavorable point in contraction, distance measured between the two facing faces, is 25 pm.

[0057] Other combinations of variations in the thickness and pitch of the balance springs than those described above can be found. It is also possible to vary only the thickness or only the pitch. Furthermore, an alternative to varying the thickness would be to vary the stiffness of the blade in another way, for example by heat treatment or doping the silicon. Materials other than silicon, in particular metallic materials, can be used for these balance springs. Finally, other means than a variation in stiffness and / or pitch could be considered.

[0058] Yet another important aspect of chronometric accuracy is the rate deviation in the different vertical positions of the resonator. Figures 8 and 13 show the rate p2 due to the weight of the balance spring for the balance springs of Figures 4 and 9 respectively. Rate 2 is shown for the four vertical reference positions 3H, 6H, 9H and 12H spaced 90° apart. It can be seen that for each of these four vertical positions, the rate p2 vanishes at an oscillation amplitude between 200° and 240°, or even between 210° and 230°.This passage of the curves through zero at approximately 220°, rather than at amplitudes of 163.5° and 330.5° as in the case of an Archimedean spiral, makes it possible to apply the teachings of patent EP 3433680 and patent application EP 3913441 of the present applicant, that is to say in particular to compensate the rate p2 due to the weight of the balance spring by the rate due to the balance wheel imbalance, the balance wheel imbalance (unbalance and angular position of the center of gravity) being chosen for this purpose. In this way, the rate differences between the different vertical positions are minimized.

[0059] It is therefore possible in the present invention to optimize both the isochronism of the oscillator, by minimizing the variations in the rate or frequency as a function of the oscillation amplitude, and the rates at the positions, and this while the balance springs have an eccentric, or even very eccentric, development. It is also possible, as has been explained, to minimize the flat-hanging in amplitude. All these optimizations are applicable to low oscillation amplitudes.

[0060] The present invention therefore relates to a watch movement 1 whose maximum oscillation amplitude of the resonator 5 does not exceed 230°, preferably 225°, preferably 220°, since it has been demonstrated that such a movement with increased power reserve can have good chronometric precision despite its low oscillation amplitude.

[0061] The present invention also relates to a method for increasing the power reserve of a watch movement, according to which the watch movement is modified to reduce the maximum oscillation amplitude of the balance-spring resonator and steps are implemented to improve chronometric precision, namely for example:

[0062] - a step consisting of correcting the amplitude of the flat-hanging balance-spring resonator by increasing the viscous friction to which the balance is subjected,

[0063] - and / or a step consisting of compensating for the running delay of the watch movement due to the escapement by replacing the hairspring of the balance-spring resonator with a hairspring comprising a wound blade having variable rigidity and / or a variable pitch, the variation in rigidity and / or pitch being such that the running due to the eccentric development of the hairspring in the horizontal position decreases throughout the range of oscillation amplitudes between 130° and 220°,

[0064] - and / or a step consisting of replacing the balance spring of the balance-spring resonator with a balance spring comprising a wound blade having a variable rigidity and / or a variable pitch, the variation in rigidity and / or pitch being such that each of the respective steps due to the weight of the balance spring in four vertical positions spaced 90° apart cancel each other out at an oscillation amplitude of between 200° and 240°, preferably between 210° and 230°, and creating a balance defect making it possible to at least partially compensate for the step due to the weight of the balance spring in each of these vertical positions.

[0065] In the method according to the invention, the watch movement can be in the form of a physical object or in the form of a virtual object (computer-aided design digital data) from which a physical watch movement will then be manufactured.

[0066] To further improve the chronometric performance of the watch movement, the moment of inertia of the balance wheel and / or the oscillation frequency can be increased in order to increase the denominator in the general formula for the rate as a function of the disturbing torque Cb representing all disturbances such as manufacturing and assembly tolerances and external disturbances (temperature, humidity, magnetism, shocks, etc.): where S = Qo.lo.f 2 is called "chronometric sensitivity". Certainly, increasing the moment of inertia lo or the frequency f increases the hanging plane in amplitude A0o and increasing the frequency f increases the power P dissipated in the resonator and therefore reduces the power reserve. But it is possible to find a good balance between the viscous friction T, the chronometric sensitivity S and the power P. To do this, we can for example implement the following steps in the method according to the invention:

[0067] - choose a certain percentage of decrease in the oscillation amplitude,

[0068] - compensate for the reduction in the oscillation amplitude by increasing the moment of inertia of the balance and / or the oscillation frequency in order to obtain a chronometric sensitivity deemed sufficient (for example at least equal to that of the initial watch movement),

[0069] - increase the viscous friction torque in order to reduce the hanging plane in amplitude (this step can correspond to the step mentioned above consisting of correcting the hanging plane in amplitude),

[0070] - verify that the modification of the oscillation amplitude, the moment of inertia and / or the oscillation frequency, and the viscous friction torque does indeed lead to a reduction in the power dissipated in the resonator, and therefore to an increase in the power reserve.

[0071] These steps can be repeated to gain even more power reserve.

[0072] These steps can of course be complementary to those consisting of replacing the hairspring and creating a balance wheel imbalance. Furthermore, the steps consisting of choosing a certain percentage reduction in the oscillation amplitude, increasing the balance wheel's moment of inertia and / or the oscillation frequency and increasing the viscous friction torque, possibly supplemented by the steps consisting of replacing the hairspring and creating a balance wheel imbalance, could be implemented to increase chronometric sensitivity without necessarily improving the power reserve compared to the initial watch movement, for example to increase chronometric sensitivity while maintaining a power reserve deemed sufficient, for example equal to or slightly lower than that of the initial movement.A watch movement with increased chronometric sensitivity has the advantage of being less sensitive to disturbances and being easier to adjust (adjustment of the average rate by rotating the balance weights or by milling the balance, for example).

Claims

CLAIMS Clock movement (1) comprising a power unit (2), an escapement (4) arranged to receive mechanical energy from the power unit (2) via a gear train (3) and a balance-spring resonator (5) arranged to cooperate with the escapement (4), characterized in that the maximum amplitude of oscillation of the balance-spring resonator (5), in all possible operating states of the clock movement (1) and regardless of the position of the clock movement (1) in space, does not exceed 230°, preferably 225°, preferably 220°. Watch movement according to claim 1, characterized in that the balance spring (5) is arranged so that the rate due to the eccentric development of the spring in horizontal position decreases throughout the range of oscillation amplitudes between 130°, preferably 120°, preferably 110°, preferably 100°, preferably 90°, preferably 80°, preferably 70°, and 220°.A watch movement according to claim 1, characterized in that the balance spring (5) comprises a coiled blade having variable stiffness and / or variable pitch, and in that the variation in stiffness and / or pitch is such that the rate due to the eccentric development of the spring in the horizontal position decreases throughout the range of oscillation amplitudes between 130°, preferably 120°, preferably 110°, preferably 100°, preferably 90°, preferably 80°, preferably 70°, and 220°. A watch movement according to claim 3, characterized in that the stiffness of the blade decreases continuously over more than one turn in the direction of the blade's winding from a first point located on the inner coil of the balance spring, and decreases continuously over more than one turn in the opposite direction to the blade's winding from a second point located upstream of the first point in said opposite direction to the blade's winding. A watch movement according to claim 4, characterized in that the second point is located on the outer coil of the balance spring or on the coil immediately following the outer coil in said opposite direction to the blade's winding. A watch movement according to claim 4 or 5, characterized in that the first point is the inner end of the balance spring and / or the second point is the outer end of the balance spring.A watch movement according to any one of claims 4 to 6, characterized in that, in the direction of the blade's winding, the blade's stiffness decreases continuously from the first point to a minimum, and then increases continuously from that minimum to the second point. A watch movement according to any one of claims 4 to 7, characterized in that the blade's stiffness at the first point is greater than the blade's stiffness at the second point. A watch movement according to any one of claims 3 to 8, characterized in that the rigidity of the blade at the inner end of the balance spring is greater than the rigidity of the blade at the outer end of the balance spring. A watch movement according to any one of claims 3 to 9, characterized in that the blade pitch increases continuously over more than half the blade length, in number of turns. A watch movement according to any one of claims 1 to 10, characterized in that the balance spring of the balance-spring resonator (5) is arranged so that each of the respective steps due to the weight of the balance spring in four vertical positions spaced 90° apart cancels out at an oscillation amplitude between 200° and 240°, preferably between 210° and 230°.A watch movement according to any one of claims 3 to 10, characterized in that the variation in rigidity and / or pitch of the blade is such that each of the respective rates due to the weight of the balance spring in four vertical positions spaced 90° apart cancels out at an oscillation amplitude between 200° and 240°, preferably between 210° and 230°. A watch movement according to claim 11 or 12, characterized in that the balance wheel of the balance-spring resonator (5) has an imbalance defect enabling it to at least partially compensate for the rate due to the weight of the balance spring in each of said four vertical positions. A watch movement according to any one of claims 2 to 13, characterized in that the deviation of said rate due to the eccentric development of the balance spring in the horizontal position between the amplitude of 130° and the amplitude of 220° is at least 1 second per day, preferably at least 1 second per day. minus 1.5 seconds per day, preferably at least 2 seconds per day, preferably at least 3 seconds per day, preferably at least 4 seconds per day. A watch movement according to any one of claims 2 to 14, characterized in that said rate due to the eccentric development of the balance spring in a horizontal position partially compensates for at least one rate delay due to the escapement (4) throughout the entire range of oscillation amplitudes between 130°, preferably 120°, preferably 110°, preferably 100°, preferably 90°, preferably 80°, preferably 70°, and 220°. A watch movement according to any one of claims 1 to 15, characterized in that the amplitude of the balance spring resonator does not exceed 40°, preferably 35°, preferably 30°.Watch movement according to any one of claims 1 to 16, characterized in that the viscous friction torque to which the balance wheel of the balance-spring resonator is subjected is greater than 4.10'. 11 Nms / rad, preferably greater than 5.10' 11 Nms / rad. Watch movement according to any one of claims 1 to 17, characterized in that the escapement (4) is a Swiss lever escapement. Watch comprising a watch movement (1) according to any one of claims 1 to 18. Method for increasing the power reserve of a watch movement comprising a power unit, an escapement arranged to receive mechanical energy from the power unit via a gear train, and a A balance-spring resonator arranged to cooperate with the escapement, characterized in that the watch movement is modified to decrease the maximum oscillation amplitude of the balance-spring resonator, and in that steps for improving chronometric accuracy are implemented. A method according to claim 20, characterized in that the modification of the watch movement is implemented such that the maximum oscillation amplitude of the balance-spring resonator, in all possible operating states of the watch movement and regardless of the position of the watch movement in space, does not exceed 230°, preferably 225°, preferably 220°. A method according to claim 20 or 21, characterized in that the steps for improving chronometric accuracy comprise at least one of the following steps: - correct the flat-hanging in amplitude of the balance-spiral resonator; - to compensate for the time lag in the watch movement due to the escapement; - reduce the rate difference between the different vertical positions of the balance wheel-hairspring resonator. Method according to any one of claims 20 to 22, characterized in that the steps for improving chronometric precision include a step consisting of correcting the amplitude of the balance wheel-hairspring resonator by increasing the viscous friction to which the balance wheel is subjected. A method according to any one of claims 20 to 23, characterized in that the steps for improving chronometric accuracy include a step of compensating for the rate loss of the watch movement due to the escapement by replacing the balance spring resonator with a balance spring arranged so that the rate due to the eccentric development of the balance spring in the horizontal position decreases throughout the entire range of oscillation amplitudes between 130° and 220°. A method according to any one of claims 20 to 24, characterized in that the steps for improving chronometric accuracy include a step of replacing the balance spring resonator with a balance spring arranged so that each of the respective rates due to the weight of the balance spring in four vertical positions spaced 90° apart cancels out at an oscillation amplitude between 200° and 240°, preferably between 210° and 230°.A method according to claim 25, characterized in that the steps for improving chronometric accuracy include a step consisting of creating a balance wheel imbalance to compensate at least partially for the rate of movement due to the weight of the balance spring in each of said four vertical positions. A method according to any one of claims 20 to 26, characterized in that the steps for improving chronometric accuracy include the following steps: - increase the moment of inertia and / or the oscillation frequency of the balance wheel of the balance-spring resonator, - to increase the viscous friction to which the balance wheel is subjected. A method for making a clock movement less sensitive to disturbances, the clock movement comprising a driving element, an escapement arranged to receive mechanical energy from the driving element via a gear train and a balance-spring resonator arranged to cooperate with the escapement, characterized in that the clock movement is modified to decrease the maximum amplitude of oscillation of the balance-spring resonator, in that the moment of inertia and / or the frequency of the balance wheel of the balance-spring resonator is increased and in that the viscous friction to which the balance wheel is subjected is increased.

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