Tilting device in a clock

Description

[0001] The invention relates to a pivoting device according to the set of claims as annexed.

[0002] It is well known that the oil used to lubricate the pivoting mechanisms of watch oscillators and providing good quality factors is Synt-A-Lube (SAL) 9010 from the manufacturer Moebius. This oil is currently commonly used for lubricating watch oscillators. It has a viscosity of 1.2 St at 20°C, according to the manufacturer's website: http: / / www.moebius-lubricants.ch / fr / produits / huiles.

[0003] Conventional pivoting mechanisms in watch oscillators, particularly balance-spring oscillators, induce varying degrees of friction on the pivots depending on the oscillator's position. Generally, friction is higher in the watch's vertical position, especially in the "hanging" or "12 o'clock" position, than in the movement's horizontal position, particularly in the "flat" or "CH" position. This results in a lower "quality factor" for the oscillator in vertical positions compared to horizontal positions. A difference in quality factor translates into a difference in amplitude for a balance-spring oscillator and can, in particular, lead to a difference in the movement's rate. Therefore, minimizing the difference in quality factor between horizontal and vertical positions is crucial for the accuracy of the timepiece.

[0004] Throughout this document, "position CH", "position FH", "position 6H", "position 12H", we mean clock positions defined by ISO 3158.

[0005] Known solutions from the prior art involve proposing pivoting devices for an oscillator shaped to generate essentially constant forces on the pivots, regardless of the watch's position. However, these pivoting devices require significant adaptations to conventional pivoting devices, which nevertheless provide complete satisfaction in terms of manufacturability and shock resistance.

[0006] In conventional balance wheel pivoting mechanisms, friction varies in different positions because the contact configurations between the pivot and the pivot jewel change. In a horizontal watch position, the balance staff is vertical, and the end of the pivot rests against a jewel called the counter-pivot. This jewel is typically flat, and the end of the pivot is rounded, resulting in a low resistive torque. In a vertical watch position, the balance staff is horizontal and rubs against the edge of a hole, usually an olive-shaped hole (with rounded edges) in a jewel. The resistive torque is greater, and the balance wheel's oscillation amplitude is lower than in the horizontal position.

[0007] To address this issue, one solution is to increase friction in the watch's horizontal positions by modifying the conventional balance wheel pivoting mechanism. This solution reduces the friction differences between horizontal and vertical positions.

[0008] Several embodiments have been proposed in the prior art. Document CH239786 notably discloses a pivoting device combining a perforated, olive-shaped stone and a stop (counter-pivot) inclined relative to the axis. This allows for continuous friction of the cylindrical part of the axis against the olive-shaped stone in horizontal positions, thus increasing the frictional forces or resistive torques in horizontal positions.

[0009] Patent application US2654990 discloses a pivot with a flat end and slightly rounded edges that rubs against a counter-pivot equipped with a hemispherical depression. The aim here is also to increase friction in horizontal positions by maximizing the lever arm of the friction forces relative to the balance staff axis. Similarly, patent application CH704770 proposes a pivot ending in a chamfer to increase friction forces or resistive torques in horizontal positions. Finally, patent application US201503215 discloses a pivoting device for a balance staff pivot, this device being equipped with cavities to retain lubricant, thereby reducing friction between the pivot and its bearing.

[0010] While these various designs increase the resistive torque or friction in the watch's horizontal positions, they do not, in particular, reduce the resistive torque or friction in the watch's vertical positions. Furthermore, these alternative pivoting mechanisms can prove fragile or prone to premature wear, in addition to being complex to manufacture.

[0011] The object of the invention is to provide a watch pivoting device that overcomes the aforementioned drawbacks and improves upon devices known in the prior art. In particular, the invention proposes a pivoting device in which the difference in quality factor between the "flat" and "hanging" positions is minimized. The invention also proposes a method for implementing such a pivoting device.

[0012] The assembly method according to the invention is defined by claim 1. Different embodiments of the assembly method are defined by claims 2 to 5.

[0013] The pivoting device or the clockwork mechanism or the clockwork movement or the clockwork part according to the invention is defined by claim 6.

[0014] The pivoting device according to the invention is also defined by claim 7.

[0015] Different embodiments of the pivoting device are defined by claims 8 to 10.

[0016] The clockwork mechanism according to the invention is defined by claim 11.

[0017] The watch movement according to the invention is defined by claim 12.

[0018] The timepiece according to the invention is defined by claim 13.

[0019] The attached figures represent, by way of example, an embodiment of a timepiece according to the invention. THE figures 1 et 2 These are schematic views of how a timepiece is manufactured, with the timepiece in its "flat" position and its "hanging" position, respectively. figure 3 is a graph representing the changes in the quality factor of a timepiece as a function of its position for different lubricants used in the pivoting mechanisms of the oscillators. figure 4 is a graph representing the differences between the average quality factors of positions CH and FH and the quality factor in position 6H of the timepiece for the different lubricants, these differences being noted on the figure 3 . There figure 5 is a graph representing the changes in the quality factor of a timepiece as a function of its position for different lubricants used in the pivoting mechanisms of the oscillators. figure 6 is a graph representing the differences between the average quality factors of positions CH and FH and the quality factor in position 6H of the timepiece for the different lubricants, these differences being noted on the figure 5 . There figure 7 is a graph representing the differences between the average quality factors of the CH and FH positions and the quality factor in the 6H position of the timepiece as a function of the viscosity of the lubricants used in the oscillator pivoting devices. figure 8 is a graph representing the evolution of the quality factor of a watch part in its 6H position as a function of the viscosity of the lubricants used at the level of the pivoting devices of the oscillators.

[0020] An embodiment of a 400 timepiece is described below with reference to figures 1 et 2 The timepiece is, for example, a watch, in particular a wristwatch. The timepiece includes a mechanical watch movement. The watch movement includes a mechanism, specifically a balance-spring type oscillator.

[0021] The mechanism or oscillator includes at least one, in particular two, pivoting devices 100. These pivoting devices allow the balance wheel 10 to be pivoted on a frame 20 of the mechanism or movement around an axis A.

[0022] The balance wheel includes a shaft 11 itself comprising at least one pivot 1, in particular two pivots each located at one end of the shaft.

[0023] The mechanism 200 or the movement 300 comprises the frame 20. The frame 20 is equipped with at least one bearing 2 intended to cooperate with a pivot or to receive a pivot. Preferably, the frame comprises two bearings 2, each bearing cooperating with or receiving a pivot. A first bearing is, for example, mounted on a plate of the frame and a second bearing is, for example, mounted on a bridge of the frame.

[0024] The bearing 2 or each bearing advantageously comprises a pivot stone 21 and a counter-pivot stone 22. The bearing or each bearing advantageously forms part of a damper.

[0025] The pivot comprises an end surface 101, in particular a convex or hemispherical surface 101, and a lateral surface 102, in particular a cylindrical surface 102. The pivot may be made of material from the balance shaft 11.

[0026] The tier 2 includes a pivot stone 21 having a surface 211 in the form of the side of a circular hole, in particular an olive-shaped surface, and a counter-pivot stone 22 having a surface 221, in particular a flat surface.

[0027] Surfaces 101 and 221 are intended to cooperate by contact to guide the oscillator in pivoting, particularly in a "flat" position of the timepiece.

[0028] Surfaces 102 and 211 are intended to cooperate by contact to guide the oscillator in pivoting, particularly in a "hanging" position of the timepiece.

[0029] The watch pivoting device 100 comprises the pivot 1 and a bearing 2.

[0030] At least one surface of the pivot 101, 102 and / or one surface of the bearing 211, 221 is coated with a lubricant whose kinematic viscosity at a temperature of 20°C is greater than or equal to 1.5 St.

[0031] Preferably, all surfaces 101, 102, 211 and 221 involved in guiding the oscillator are coated with a lubricant whose kinematic viscosity at a temperature of 20°C is greater than or equal to 1.5 St.

[0032] The lubricant is preferably an oil or grease.

[0033] Furthermore, the lubricant may or may not contain additives.

[0034] According to the invention, the kinematic viscosity at a temperature of 20°C of the lubricant is advantageously greater than or equal to 3 St.

[0035] According to the invention, the kinematic viscosity of the lubricant at a temperature of 20°C is advantageously less than or equal to 50 St

[0036] According to the invention, the pivot is a balance shaft pivot of a balance-spring type oscillator having an oscillation frequency greater than or equal to 3 Hz, or even greater than or equal to 4 Hz.

[0037] As seen previously, the tier advantageously includes one or more stones, in particular one or more ruby ​​stones.

[0038] Preferably, the pivot is a pivot of an element, in particular of the pendulum, whose mass is greater than 5×10 -2< g or whose moment of inertia is greater than 5×10 -10< kg.m 2< .

[0039] An embodiment of a method for mounting a watch pivoting device 100 as described above or a mechanism 200 as described above or a movement 300 as described above or a watch part 400 as described above is disclosed below.

[0040] The process includes the following steps: supply the pivot 1; supply the bearing 2; apply, on at least one surface (101, 102, 211, 221) of the pivot and / or the bearing, a lubricant whose kinematic viscosity at a temperature of 20° C is greater than 3St and less than 50St; place the pivot in the bearing.

[0041] The order of the last two steps is irrelevant. The lubricant can be applied before or after the pivot is installed in the bearing.

[0042] The process can be implemented in a production phase of a movement or a watch part.

[0043] Alternatively, the process can also be implemented during a maintenance phase of the movement or timepiece, particularly during service operations or during overhaul operations.

[0044] The applicant's studies have shown that it is surprisingly possible to homogenize the friction coefficients of the pivoting devices described above through appropriate lubrication. More specifically, the studies demonstrate that using a lubricant with a kinematic viscosity (more simply referred to as "viscosity" hereafter) within a given range significantly reduces the difference in quality factor between the horizontal ("flat") and vertical ("hanging") positions of the movement.

[0045] In horizontal positions (CH, FH) of the movement, while the more viscous the lubricant, the higher the resistive or frictional torque within the oscillator's pivoting mechanism, experiments show that this is not the case for inclined positions of the movement, particularly vertical ones. Indeed, the coefficient of friction depends not only on the viscosity of the lubricant used, but also, notably, on the oscillator's speed and the load applied against the oscillator's bearing, and therefore, in particular, on the mass, especially the oscillator's inertia.It is therefore possible, particularly for a given oscillator speed and inertia, to define an advantageous viscosity range for a lubricant, which allows for the most appropriate possible harmonization of the friction torque of the oscillator's pivoting mechanism according to the different positions the watch may occupy while being worn. This viscosity range extends from 3 St to 50 St at 20°C.

[0046] These conclusions are based on experimental measurements conducted in two distinct phases. In the first phase, five non-additized oils from the same chemical family, differing only in viscosity, were considered. For each oil, quality factors were measured for different positions of a movement whose oscillator pivot mechanism had been previously broken in. In the second phase, four additive-containing oils, differing in viscosity, were considered. For each oil, quality factors were measured for different positions of a movement whose oscillator pivot mechanism had been previously broken in. In each phase, an additive-containing lubricant known as SAL 9010 (9010) from the Moebius company served as the reference. The movement considered was a Rolex type 3130 with a 4 Hz oscillator and a balance wheel with an inertia of 14 × 10⁻¹⁰ kg·m².In each phase, ten samples of a Rolex 3130 type movement were measured.

[0047] The measurements are performed without an escapement, using an automated device that obtains quality factor (QF) values ​​for an oscillator over a given oscillation range and for a given range of movement positions. The movement thus sweeps through different horological positions, from the FH position (reference position at 0° inclination, balance staff vertical) to the CH position (180° rotation, balance staff vertical), passing through the 6H position (90° rotation, balance staff horizontal), in 10° increments. A strict cleaning protocol for the oscillator pivoting mechanism is followed between lubrication applications to thoroughly remove all traces of previous lubricants, particularly additives, ensuring that only the effect of the oil in question is measured, without the influence of others.After ultrasonic cleaning, the pivoting mechanism is immersed successively in different baths. Only after this cleaning protocol is the new lubricant applied.

[0048] In the first phase, the five non-additive lubricants considered (excluding the reference lubricant) are synthetic base oils of the PAO (PolyAlphaOlefin) type which have different viscosities: A first oil A has a viscosity of 1.3 St at 20°C; A second oil B has a viscosity of 7.1 St at 20°C; A third oil C has a viscosity of 12.9 St at 20°C; A fourth oil D has a viscosity of 21.4 St at 20°C; A fifth oil E has a viscosity of 44 St at 20°C.

[0049] The viscosity of the reference 9010 oil used is 1.2 St at 20°C.

[0050] There figure 3 For each lubricant, the graph presents curves showing the evolution of the quality factor (QF) for a reference oscillator amplitude of 280°, as a function of different movement positions (P). This reference amplitude is considered representative of a load-bearing motion and representative of the effects of the lubricants on the oscillator's pivoting mechanism. For each movement position, the quality factor values ​​are averages obtained from measurements taken on each of the 3130 type movement samples.

[0051] These curves each exhibit a parabolic shape. They decrease for a movement from position FH (0°) to position 6H (90°), and then increase for a movement from position 6H (90°) to position CH (180°). In horizontal positions (FH and CH) and for small angles of inclination, it is observed that the more viscous the lubricant, the lower the quality factors. In these movement configurations, oils 9010 and A provide the best quality factor values ​​(327 and 334 respectively in positions FH and CH for oil 9010, and 330 and 338 respectively in positions FH and CH for oil A). Next come oil B (respectively 303 and 312 in positions FH and CH), oil C (respectively 289 and 297 in positions FH and CH), oil D (respectively 268 and 275) and finally oil E (respectively 220 and 224 in positions FH and CH).For greater angles of movement, it is noted that the quality factor values ​​become significantly closer between the different lubricants, particularly between lubricant 9010, lubricant A, and lubricants B and C. In the 6H position specifically, while oils 9010 and A give quality factor values ​​of 253 and 256 respectively, oil B gives a quality factor value of 249 and oil C gives a quality factor value of 243. A direct consequence of these observations concerns the flat-hanging quality factor (PP-FQ), that is, the difference between the average of the quality factors of the CH and FH positions and the quality factor in the 6H position. At the reference amplitude of 280°, the flat-hanging values ​​of quality factor of oils B, C, and D, between 40 and 60, are significantly less important than the flat-hanging values ​​of quality factor of oils 9010 and A which tend towards 80 (. Figure 4 ). The PP-FQ quality factor flat-hanging of oil E is, meanwhile, even smaller with a value of around 30.

[0052] In general, the oscillator's quality factor is observed to be less sensitive to movement positions with lubricants B, C, and D than with lubricants A and 9010, while remaining sufficiently high, in the range of 230 to 320, to allow for good chronometric and / or energy performance of the oscillator. Oil C gives particularly good results with a flat-hanging quality factor value of around 50, and quality factor values ​​between 242 and 297. In other words, the friction torque within the pivoting mechanism lubricated by oil C is low enough to obtain satisfactory quality factors and varies little enough to obtain consistent quality factors regardless of movement positions, and therefore a low PP-FQ.

[0053] In the second phase, the four lubricants considered (excluding the reference lubricant) are HP type additive oils, which have different viscosities: A sixth oil Synt-HP500 (HP500) from the manufacturer Moebius, with a viscosity of 5 St at 20°C; A seventh oil Synt-HP750 (HP750) from the manufacturer Moebius, with a viscosity of 7.5 St at 20°C; An eighth oil Synt-HP1000 (HP1000) from the manufacturer Moebius, with a viscosity of 10 St at 20°C; A ninth oil Synt-HP1300 (HP1300) from the manufacturer Moebius, with a viscosity of 13 St at 20°C.

[0054] The viscosity of the reference SAL 9010 oil used is 1.2 St at 20°C.

[0055] There figure 5 For each of these lubricants, the graph presents curves showing the evolution of the quality factor (QF), for a reference oscillator amplitude of 280°, as a function of different motion positions (P). For each motion position, the quality factor values ​​are averages obtained from measurements taken on each of the 3130 type motion samples.

[0056] As previously observed, these curves each exhibit a parabolic shape. They decrease for a movement from position FH (0°) to position 6H (90°), and then increase for a movement from position 6H (90°) to position CH (180°). In horizontal positions (FH and CH) and for small angles of inclination, it is also observed that the more viscous the lubricant, the lower the quality factors. In these movement configurations, oil 9010 provides the best quality factor values ​​(327 and 334 respectively in positions FH and CH). Next come the HP500 oil (306 and 312 respectively in positions FH and CH), the HP750 oil (301 and 305 respectively in positions FH and CH), the HP1000 oil (291 and 299 respectively in positions FH and CH) and finally the HP1300 oil (282 and 287 respectively in positions FH and CH).For greater inclinations of movement, it is noted that the values ​​of quality factors become closer between the different lubricants, in particular they become significantly closer between the different HP type lubricants.

[0057] In position 6H in particular, the quality factor values ​​of HP type oils are between 235 and 238. At the reference amplitude of 280°, the PP-FQ quality factor values ​​of HP type oils, between 50 and 70, are lower than that of oil 9010, which tends towards 80 ( Figure 6 ).

[0058] In general, it is observed that the oscillator quality factor is less sensitive to movement positions with HP-type lubricants, while remaining sufficiently high, in the range of 230 to 315, to allow for good chronometric and / or energy performance of the oscillator. In other words, the frictional torques within pivoting devices lubricated by HP-type oils are low enough to obtain satisfactory quality factors and vary little enough to achieve consistent quality factors regardless of movement positions, and therefore a low PP-FQ quality factor.

[0059] Regardless of the phase considered, it appears that the oscillator's quality factor (QF) depends primarily on the viscosity of the lubricant used. Whether the lubricant contains additives or not, it is possible to vary the oscillator's QF by changing the viscosity of the lubricant.

[0060] More specifically, it is possible to vary, and in particular to reduce, the oscillator's quality factor flatness by varying the viscosity of a polyalphaolefin (PAO)-based lubricant. "Polyalphaolefin-based lubricant" preferably means a lubricant whose main constituents are polyalphaolephins or a lubricant containing more than 60% polyalphaolephins by mass.

[0061] Additionally, such a lubricant may or may not contain friction-modifying additives, antioxidants, and / or anti-wear additives to meet predefined performance and reliability objectives, particularly time-based performance and reliability. This list is not exhaustive.

[0062] Compared to the reference lubricant (oil A or Synt-A-Lube (SAL) 9010 from the manufacturer Moebius), it is noted that a lubricant with a viscosity of at least 5 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 10%.

[0063] Compared to the reference lubricant (oil A) and based on the parabolic regression curve ( figure 7 ) relating to polyalphaolephine-based lubricants, it is noted that a polyalphaolephine-based lubricant having a viscosity of at least 1.8 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 7%.

[0064] Compared to the reference lubricant (oil A) and based on the parabolic regression curve ( figure 7 ) relating to polyalphaolephine-based lubricants, it is noted that a polyalphaolephine-based lubricant having a viscosity of at least 2.2 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 8%.

[0065] Compared to the reference lubricant (oil A) and based on the parabolic regression curve ( figure 7 ) relating to polyalphaolephin-based lubricants, it is noted that a polyalphaolephin-based lubricant having a viscosity of at least 3 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 10%.

[0066] Compared to the reference lubricant (oil A) and based on the parabolic regression curve ( figure 7 ) relating to polyalphaolephine-based lubricants, it is noted that a polyalphaolephine-based lubricant having a viscosity of at least 5 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 15%.

[0067] Compared to the reference lubricant (oil A) and based on the parabolic regression curve ( figure 7 ) relating to polyalphaolephine-based lubricants, it is noted that a polyalphaolephine-based lubricant having a viscosity of at least 6 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 20%.

[0068] Compared to the reference lubricant (oil A) and based on an interpolation line passing through points A and B of the figure 7 , it is noted that a polyalphaolephine-based lubricant with a viscosity of at least 1.5 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 1%.

[0069] Compared to the reference lubricant (oil A) and based on an interpolation line passing through points A and B of the figure 7 , it is noted that a polyalphaolephine-based lubricant with a viscosity of at least 1.6 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 2%.

[0070] Compared to the reference lubricant (oil A) and based on an interpolation line passing through points A and B of the figure 7 , it is noted that a polyalphaolephine-based lubricant with a viscosity of at least 1.8 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 3%.

[0071] Compared to the reference lubricant (oil A) and based on an interpolation line passing through points A and B of the figure 7 , it is noted that a polyalphaolephine-based lubricant with a viscosity of at least 2 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 4%.

[0072] Compared to the reference lubricant (oil A) and based on an interpolation line passing through points A and B of the figure 7 , it is noted that a polyalphaolephine-based lubricant with a viscosity of at least 2.2 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 5%.

[0073] Compared to the reference lubricant (oil A) and based on an interpolation line passing through points A and B of the figure 7 , it is noted that a polyalphaolephine-based lubricant with a viscosity of at least 3 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 8%.

[0074] Compared to the reference lubricant (oil A) and based on an interpolation line passing through points A and B of the figure 7 , it is noted that a polyalphaolephin-based lubricant with a viscosity of at least 5 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 15%.

[0075] Compared to the reference lubricant (oil A) and based on an interpolation line passing through points A and B of the figure 7 , it is noted that a polyalphaolephin-based lubricant with a viscosity of at least 6 St at 20°C allows the hanging flat to be reduced by a quality factor of at least 20%.

[0076] Compared to the reference lubricant (Synt-A-Lube (SAL) 9010 oil from the manufacturer Moebius) and based on the curves of the figure 8 , it is noted that a lubricant with a viscosity of less than 14 St at 20°C does not allow the quality factor to decrease by more than 20%.

[0077] Compared to the reference lubricant (Synt-A-Lube (SAL) 9010 oil from the manufacturer Moebius) and based on the curves of the figure 8 , it is noted that a lubricant with a viscosity of less than 5 St at 20°C does not allow the quality factor to decrease by more than 15%.

[0078] Compared to the reference lubricant (Synt-A-Lube (SAL) 9010 oil from the manufacturer Moebius) and based on the parabolic regression curve relating to polyalphaolephin-based lubricants ( figure 8 ), it is noted that a polyalphaolephine-based lubricant with a viscosity of less than 12 St at 20°C does not allow the quality factor to decrease by more than 10%.

[0079] Compared to the reference lubricant (Synt-A-Lube (SAL) 9010 oil from the manufacturer Moebius) and based on the parabolic regression curve relating to polyalphaolephin-based lubricants ( figure 8 ), it is noted that a polyalphaolephine-based lubricant with a viscosity of less than 5 St at 20°C does not reduce the quality factor.

[0080] Compared to the reference lubricant (Synt-A-Lube (SAL) 9010 oil from the manufacturer Moebius) and based on the parabolic regression curve relating to polyalphaolephin-based lubricants ( figure 8 ), it is noted that a polyalphaolephine-based lubricant with a viscosity of less than 8 St at 20°C does not allow the quality factor to decrease by more than 5%.

[0081] The invention can also be applied to another type of pivoting device or to a pivoting device capable of pivoting a different element of a balance wheel.

Claims

1. A method of assembly of a watch pivot device (100) or a watch mechanism (200) or a watch movement (300) or a timepiece (400), the watch pivot device (100) or the watch mechanism (200) or the watch movement (300) or the timepiece (400) comprising: - a balance staff pivot (1) of an oscillator of the balance wheel and hairspring type, notably of an oscillator of the balance wheel and hairspring type having a frequency of oscillation greater than or equal to 3 Hz, or greater than or equal to 4 Hz, and - a bearing (2), the method comprising the following stages: - supplying the pivot (1); - supplying the bearing (2); - applying, to at least one surface (101, 102, 211, 221) of the pivot and / or of the bearing, a lubricant of which the kinematic viscosity at a temperature of 20°C is greater than 3 St and lower than 50 St; - positioning the pivot in the bearing.

2. The method as claimed in the preceding claim, wherein the lubricant is a polyalphaolefin-based lubricant.

3. The method as claimed in one of the preceding claims, wherein the kinematic viscosity of the lubricant at a temperature of 20°C is greater than 4 St or 5 St or 6 St and / or wherein the kinematic viscosity of the lubricant at a temperature of 20°C is lower than 40 St or 35 St or 30 St.

4. The method as claimed in one of the preceding claims, wherein the bearing comprises at least one jewel, more particularly a ruby.

5. The method as claimed in one of the preceding claims, wherein the pivot is a pivot of an element of which the mass is greater than 5 × 10-2 g and / or of which the moment of inertia is greater than 5 × 10-10 kg.m2.

6. A watch pivot device (100) comprising a balance staff pivot (1) of an oscillator of the balance wheel and hairspring type having a frequency of oscillation greater than or equal to 3 Hz, or greater than or equal to 4 Hz and a bearing (2), at least one surface (101, 102, 211, 221) of the pivot and / or of the bearing being coated with a lubricant of which the kinematic viscosity at a temperature of 20°C is greater than 3 St and lower than 50 St.

7. The device as claimed in claim 6, wherein the lubricant is a polyalphaolefin-based lubricant.

8. The device as claimed in one of claims 6 or 7, wherein the kinematic viscosity of the lubricant at a temperature of 20°C is greater than 4 St or 5 St or 6 St and / or wherein the kinematic viscosity of the lubricant at a temperature of 20°C is lower than 40 St or 35 St or 30 St.

9. The device as claimed in one of claims 6 to 8, wherein the bearing comprises at least one jewel, more particularly a ruby.

10. The device as claimed in one of claims 6 to 9, wherein the pivot is a pivot of an element of which the mass is greater than 5 × 10-2 g and / or of which the moment of inertia is greater than 5 × 10-10 kg.m2.

11. A watch mechanism (200) comprising a device as claimed in one of claims 6 to 10.

12. A watch movement (300) comprising a device as claimed in one of claims 6 to 10 or a mechanism as claimed in the preceding claim.

13. A timepiece (400), more particularly a wristwatch, comprising a movement as claimed in the preceding claim or a mechanism as claimed in claim 11 or a device as claimed in one of claims 6 to 10.