Compensation for clock fluctuations

Abstract

One aspect of the invention relates to a method for compensating the operation of a timepiece (1) as a function of temperature, the timepiece (1) having a waterproof case (2) equipped with a movement (3) equipped with a regulating organ having an oscillator (4) and pivoting on a pivot (9) lubricated with a lubricant having a viscosity η, the properties of which and the law of variation of said viscosity η as a function of temperature being determined in the factory by measurements and / or calculations, so that the thermal coefficient Ct of the movement (3) varies as a function of temperature according to a predetermined law Ct=g(T), and the operation of the movement varies as a function of the temperature T of said thermal coefficient Ct, generating a variation of the operation of the movement (3) as a function of temperature, in contrast to the variation of the operation generated by the pressure P of the gas.

Description

[Technical Field]

[0001] The invention relates to a method for compensating the operation of a water-resistant watch as a function of temperature, the water-resistant watch case comprising a movement, itself comprising a regulating organ, the regulating organ comprising an oscillator and pivoting on a lubricated pivot, said case comprising, when leaving the factory after initial configuration in operating mode, an internal volume V occupied by n moles of gas with a constant R substantially in accordance with the equation of state of an ideal gas.

[0002] The invention also relates to a watch suitable for use with the method.

[0003] The present invention relates to the field of regulating the running of mechanical or electromechanical watches. [Background technology]

[0004] The operation of a watch is subject to several parameters, such as, but not limited to, the spatial position of the watch, lubrication, wear, the winding of the spring that constitutes the energy source, friction, and of course the physical parameters of the environment in which the watch is placed.

[0005] The variation of the run as a function of temperature is a constant challenge for timepiece designers and the like. The elastic return means of an oscillator are particularly sensitive to temperature variations. In the specific, non-limiting case in which the elastic return means comprise one or more balance springs, the thermal coefficient Ct of the regulating mechanism causes the run of the movement to vary as a function of the temperature. By way of example, and to simplify the calculations, it can be assumed that the run varies substantially linearly as a function of the thermal coefficient Ct.

[0006] For greater precision, the thermal coefficient of a movement is generally set at 0 seconds per day per Kelvin. With such parameters, temperature fluctuations should not affect the operation of the movement. The typical distribution of thermal coefficients for identical movement builds is a symmetrical curve that is closer to a triangular peak than a bell-shaped one.

[0007] In chronometry, it is common knowledge that the running of a movement varies depending on the pressure of the environment in which it is placed. There are several possible explanations, such as the variation of the inertia of the oscillator (the inertia of the balance and the trapped air), because the density of the trapped air varies, and therefore the inertia of the air. The balance and the air are a special case. More generally, it refers to the inertial mass and the gas or gas blend. Various experiments have been carried out, which show that as the pressure decreases, the running increases. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] European Patent Application Publication No. 21216225 Summary of the Invention [Problem to be solved by the invention]

[0009] The objective is therefore to compensate the running of the watch according to variations in physical parameters: ambient temperature, the body temperature of the wearer, the expansion or contraction of the watch case in response to temperature, local pressure, altitude and humidity. However, there is no easy regulation system that addresses these problems inherent in temperature and pressure variations. [Means for solving the problem]

[0010] The present invention relates to compensating for running variations in a watch based on temperature and pressure.

[0011] To this end, the invention relates to a method for compensating the running of a water-resistant watch as a function of temperature, as set forth in claim 1.

[0012] The invention also relates to a watch suitable for use with the method.

[0013] The objects, advantages and features of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0014] [Figure 1] Superimposition of three graphs showing the operation of three different mechanical movements, the operation of the mechanical movements being represented on the y-axis in seconds per day as a function of pressure, and the pressure being represented on the x-axis in hectopascals. [Figure 2] Superposition of two graphs showing on the y-axis the pressure in hectopascals inside a watch case in an environment of variable temperature as a function of time, while time is represented on the x-axis in days, the first solid line calculated using the ideal gas equation of state and the other measured. [Figure 3] Schematic diagram of a timepiece with a waterproof case, which houses a movement, the movement itself comprising an oscillator, which comprises compensation means, which comprise a waterproof volume measuring device correcting the internal volume of the case, a waterproof gas injection or extraction reed, and a thermal device allowing the control and instantaneous increase of the internal temperature of the case. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention relates to compensating for running variations in a watch based on temperature and pressure.

[0016] Experiments carried out in a pressurized tank have shown a relatively good linearity of the operating variation with respect to pressure varying from atmospheric pressure (970 hPa) to 200 hPa, where the operating variation is represented on the y-axis in seconds per day as a function of pressure, and pressure is represented on the x-axis in hectopascals, and measurements are made in a pressurized tank. Figure 1 shows the results of measurements taken while trialling and testing several conventional mechanical movements. The overall linear section of the daily operating variation with respect to pressure is fairly linear, with slopes of (-0.0206) seconds per hectopascal per day for the upper curve, (-0.0161) seconds for the middle curve and (-0.0145) seconds for the lower curve, all other conditions being equal.

[0017] Experiments on the clock shown in Figure 1, with various diameters and closed at various altitudes, highlighted a running variation of about 0.95 seconds per day over an altitude difference of about 570 m. The following altitude formula: p(h) = 1013.25 x (1 - (0.0065 x h / 288.15)) 5.255 Based on this, we can find that the operational variation with altitude for this diameter is about -0.03 seconds per hPa per day. We call this value the pressure coefficient: Cp.

[0018] With respect to pressure variation with temperature, we assume that the ideal gas equation of state (P x V = n x R x T) is sufficient to define the situation.

[0019] In a closed clock, we consider the amount of air available (assuming zero leakage) to be given and finite. We also assume that the pressure difference between the pressure inside the clock and the pressure outside the clock is insufficient to deform the clock, and that the available volume inside the clock does not vary and therefore remains constant.

[0020] Experience shows that these estimates are relatively accurate. In Figure 2, the measured pressure inside the watch is compared to the theoretical pressure based on the ideal gas equation of state: P = (n x R / V) x T. It can be seen that the measurement and theoretical estimate are relatively comparable. Furthermore, experience shows that water-resistant watches have relatively little leakage, even when there is a significant pressure difference between the watch's interior and the environment in which it is placed. Therefore, we will assume that the watch is completely water-resistant.

[0021] The first assumption was that leakage from the watch was considered to be zero, the watch case was not deformable, and the trapped gas remained the same. The parameters n, R, and V were therefore constant, and it could be assumed that the pressure varied linearly with temperature.

[0022] The present invention primarily deals with the compensation of temperature and pressure variations. By combining the two influences, the goal is to counteract the two effects and to cancel (or minimize) these effects each other. The main benefit to the user is greater accuracy when wearing the watch.

[0023] Humidity has less of an effect than temperature and pressure. The working hypothesis is that the humidity content varies little with temperature or pressure in the normal circumstances in which a watch is worn. One approximation consists of ignoring this variation.

[0024] The following assumptions are made to simplify the calculations: -The pressure of the clock varies substantially linearly with temperature: P = [(n × R) / V] × T, - The operation of the movement varies depending on the temperature and the thermal coefficient of the movement, which also depends on the temperature: m(T) = Ct × T. -The running of the movement varies linearly with the gas pressure: m(P) = Cp x P.

[0025] The present invention therefore relates to a method for compensating the operation of a water-resistant watch 1 as a function of temperature, comprising a water-resistant watch case 2 equipped with a movement 3, itself equipped with a regulating organ, which in turn is equipped with an oscillator 4, pivoted on a pivot 9, which is lubricated with a lubricant of viscosity η. Upon leaving the factory after setting up its first run, this case 2 contains an internal volume V occupied by n moles of gas, the gas having a constant R substantially in accordance with the equation of state of an ideal gas. The constant R (or Avogadro's number) is known. The constant R depends on the gas inside the watch (usually air in this case). The number of moles n depends on the conditions under which the watch is closed (for example, atmospheric pressure, temperature, or the closure and sealing of the back cover).

[0026] It will be appreciated that the pivot 9 may be the pivot of a balance or the pivot of an anchor or escape wheel.

[0027] The variation in viscosity of the lubricating contact between the pallet and the pallet wheel, and between the pallet and the oscillator, is also taken into account.

[0028] The available volume V depends on the shape of the case. The design of the external components can potentially be modified to influence this.

[0029] In accordance with the present invention, the factory uses measurements and / or calculations to determine: - the value Cp of the pressure coefficient of the movement 3, which defines a relatively linear operating variation of the movement 3 as a function of the pressure P of the gas (or gas blend, if applicable), according to the formula m(P) = Cp x P. The pressure coefficient Cp of a movement can be measured experimentally or calculated theoretically. The pressure coefficient Cp of a movement depends on the type of movement involved. the value Ch of the humidity coefficient of the movement 3, which defines the maximum relatively linear operating variation of the movement 3 as a function of the humidity H at the movement 3, according to the formula m(H) = Ch x H. In the absence of linear variation, the maximum value of the slope of the highest linear section on the operating / humidity graph is taken; -Law η=f(T) for varying viscosity η depending on the lubricant properties and temperature determining the thermal coefficient Ct of the movement 3, which varies as a function of the temperature according to a predetermined law Ct=g(T), and the running of the movement varies as a function of the temperature T and of the thermal coefficient Ct of said movement 3 according to the formula m(T)=Ct*T=g(T)*T, The movement 3 is designed to generate operational fluctuations depending on temperature, as opposed to the operational fluctuations being generated by the gas pressure P.

[0030] More specifically, this rule η=f(T) for varying the viscosity η as a function of temperature is determined so as to generate operating variations of the movement 3 as a function of temperature, in contrast to the operating variations generated by the gas pressure P.

[0031] In this example, the pressure coefficient Cp is assumed to be constant.

[0032] Regarding the temperature coefficient Ct, the temperature coefficient Ct follows a non-linear law as a function of temperature according to a given law Ct=g(T).

[0033] where the g(T) function is, for example, the formula:

[0034] TIFF2025541808000002.tif10170

[0035] TIFF2025541808000003.tif36170

[0036] TIFF2025541808000004.tif7170

[0037] is.

[0038] For example, the viscosity of a lubricant is determined experimentally using a viscometer.

[0039] The h(η) function can also be determined experimentally by measuring the same movement with several lubricants of different viscosities, so that the running of the movement is determined by the formula:

[0040] TIFF2025541808000005.tif10170

[0041] and the thermal coefficient Ct of the movement 3.

[0042] This theoretical model incorporates the humidity parameter, assuming that relative humidity varies with temperature and that the operation of the watch varies with humidity (via Ch). However, in moderate ranges, this parameter can be neglected, since humidity has a much smaller effect on operation than temperature. In a simplified calculation, the humidity coefficient Ch of the movement 3 is determined to be zero.

[0043] More specifically, the pressure P and / or the number of moles n are adjusted by modifying the pressure P and / or by varying the temperature T of the watch 1 when the case 2 is closed.

[0044] The thermal coefficient Ct of the regulating engine is related to the pressure coefficient Cp by the environment inside the watch case 2 of the watch 1 (the presence of a gas with a constant R, the volume V inside the watch, and the number of moles n inside the watch).

[0045] In particular, the thermal coefficient of oscillator 4 depends, inter alia, on its elastic return means and its stiffness. In the specific, non-limiting case where this oscillator 4 is a hairspring balance, when making a silicon and / or silicon oxide hairspring, the thermal coefficient Ct of the hairspring balance assembly can be adjusted, inter alia, depending on the thickness of the oxide layer covering this balance. Likewise, the design of the flexibly guided oscillator blades can modify the thermal coefficient Ct.

[0046] The running variation of the movement as a function of pressure is assumed to be: Cp = -0.015 seconds per hectopascal per day. Considering that the watch is housed in a universal casing, the (n x R) / V constant was found experimentally to be approximately 3.3 hPa / K. This was calculated from measurements of the pressure and temperature inside the watch cap using the ideal gas equation of state.

[0047] To ensure that the clock is as insensitive as possible to temperature fluctuations, the thermal coefficient of the regulating mechanism should be set to 0.05 seconds per day per Kelvin. This value is calculated using the formula Ct = -[Cp × (n × R) / V]:(0.015 × 3.3 = 0.05).

[0048] Setting the thermal coefficient of the hairspring balance to a value other than 0 seconds per Kelvin per day disrupts running chronometer measurements. For example, in a chronometer certification test involving temperature steps of 8°C and 38°C, there is a running difference of approximately 1.5 seconds per day, generated by the thermal coefficient of the movement between the hot and cold steps. However, if the movement of this watch is adapted from the previous example (Cp = -0.015, (n x R) / V = 3.3), the running becomes almost insensitive to temperature fluctuations.

[0049] It is therefore important to ensure that the viscosity variation model η=f(T) of the lubricant at the pivoting body (in the case of a hairspring balance) complies with these limits.

[0050] More particularly, the elastic return means on the oscillator 4 are made from silicon and / or silicon oxide, and during factory preparation the thermal coefficient of these elastic return means is changed by modifying the thickness of the silicon oxide layer.

[0051] More specifically, the elastic return means on the oscillator 4 are made in the form of thin elastic blades using the "LIGA" process, and during factory preparation the thermal coefficient of these elastic return means on the oscillator 4 is modified by plating and / or by local ablation and / or by adjusting the form ratio.

[0052] More specifically, the elastic return means on the oscillator 4 are made in the form of thin elastic blades using a drawing or rolling process, and during preparation in the factory the thermal coefficient of these elastic return means on the oscillator 4 is modified by plating and / or by local ablation and / or by adjusting the form ratio.

[0053] A variant embodiment consists in acting on the internal geometry of the watch and modifying the internal volume of the watch case by imparting a stroke to a movable organ such as a piston.

[0054] Thus, in one variant specifically designed for after-sales use, the compensation means 10 comprises a waterproof volume measuring device 5 that allows an engineer to change the internal volume of the case 2, the waterproof volume measuring device 5 comprising at least one piston movable within the case 2, which is actuated by an external micrometric control and which can be screwed and locked into position by a special tool not supplied to the user.

[0055] As can be seen from patent document 1, several influences (variations in Ct, Cp, conditions of the casing or volume within the watch) can be combined simultaneously to achieve the desired objective.

[0056] From an overall perspective, it appears that to minimize the effect of temperature on the clock, the loss of Ct must be minimized.

[0057] The invention also relates to a timepiece 1 suitable for use with the method, said timepiece 1 comprising a water-resistant case 2 housing a movement 3, itself comprising an oscillator 4 pivoted on a pivot 9, said pivot 9 being lubricated with a lubricant of viscosity η, which varies with temperature according to the model η=f(T) determined by the method.

Claims

1. A method for compensating the operation of a water-resistant watch (1) depending on the temperature, the water-resistant case (2) of said watch (1) comprising a movement (3) itself comprising a regulating mechanism, the regulating mechanism comprising an oscillator (4) pivoting on a pivot (9) lubricated with a lubricant of viscosity η, said case (2) containing, when leaving the factory after initial setting in operating mode, an internal volume V occupied by n moles of gas having a constant R substantially in accordance with the equation of state of an ideal gas, The method includes, at a factory: the value Cp of the pressure coefficient of the movement (3), which defines the relatively linear operational variation of the movement (3) as a function of the pressure P of the gas at constant temperature, according to the formula m(P) = Cp x P; the value Ch of the pressure coefficient of the movement (3), which defines the relatively linear maximum operating variation of the movement (3) as a function of the humidity H at the movement (3), according to the formula m(H) = Ch x H; - the rule η=f(T) that the viscosity η varies depending on the properties of the lubricant and the temperature is determined by measuring and / or calculating the thermal coefficient Ct of the movement (3), so that the thermal coefficient Ct of the movement (3) varies as a function of the temperature according to a predetermined law Ct = g(T), and the running of the movement varies as a function of the temperature T and the thermal coefficient Ct of the movement (3) according to the formula m(T) = Ct x T = g(T) x T, 10. A method, characterized in that the movement (3) generates running variations as a function of the temperature, as opposed to being generated by the pressure P of the gas.

2. 2. The method according to claim 1, characterized in that the law η=f(T) for varying the viscosity η as a function of the temperature is determined so as to generate operational variations of the movement (3) as a function of the temperature, opposite to the operational variations generated by the pressure P of the gas.

3. 3. The method according to claim 1 or 2, characterized in that the pressure P and / or the number of moles n are adjusted by changing the pressure P and / or varying the temperature T of the watch (1) before closing the case (2).

4. 4. Method according to any one of claims 1 to 3, characterized in that the humidity coefficient Ch of the movement (3) is determined to be zero.

5. 5. The method according to any one of claims 1 to 4, characterized in that for after-sales use, the case (2) is provided with a waterproof volume measuring device (5) that allows an after-sales technician to correct the internal volume of the case (2), and / or at least one waterproof gas injection or extraction lead (6), and / or a thermal device (7) that controls and allows the internal temperature of the case (2) to be increased instantaneously.

6. 6. The method according to claim 5, characterized in that the volume measuring device (5) comprises at least one piston, which is movable in the case (2) and which can be screwed and locked into position by means of a special tool not supplied to the user, under the action of an external micrometric control.

7. 6. A method according to claim 5, characterized in that the waterproof gas injection or extraction lead (6) can be locked in place by means of a special tool not supplied to the user.

8. 6. The method according to claim 5, characterized in that the thermal device (7) comprises light energy conversion means and / or energy storage means.

9. 9. The method according to any one of claims 1 to 8, characterized in that the elastic return means on the oscillator (4) are made from silicon and / or silicon oxide, and that during preparation in the factory the thermal coefficient of the elastic return means is changed by modifying the thickness of a silicon oxide layer.

10. 9. A method according to any one of claims 1 to 8, characterized in that the elastic return means on the oscillator (4) are made in the form of thin elastic blades using the "LIGA" process, and that during preparation in the factory the thermal coefficient of the elastic return means on the oscillator (4) is modified by plating and / or by local ablation and / or by adjusting the morphology ratio.

11. 9. A method according to any one of claims 1 to 8, characterized in that the elastic return means on the oscillator (4) are made in the form of thin elastic blades using a drawing or rolling process, and that during factory preparation the thermal coefficient of the elastic return means on the oscillator (4) is modified by plating and / or by local ablation and / or by adjusting the form ratio.

12. 12. A method according to any one of claims 1 to 11, characterized in that during preparation in the factory, the number of moles of gas in the watch is changed by closing the case (2) at a pressure calculated to make the operation of the watch insensitive to temperature, or by closing the case (2) at a temperature calculated to make the operation of the watch insensitive to temperature and slowly cooling the case (2) after closing it.

13. 13. A method according to any one of claims 1 to 12, characterized in that during preparation in the factory, the properties of the gas contained in the watch are modified by total or partial replacement of said gas with a new gas or gas blend suitable for adjusting said thermal coefficient Ct sufficiently so that the operation of the watch becomes insensitive to temperature, said new gas or gas blend having a different value of said constant R.

14. 14. Method according to claim 13, characterized in that the case (2) is sealed after the gas exchange to prevent any manipulation by users without special tools.

15. 15. A method according to any one of claims 1 to 14, characterized in that during preparation in the factory, the internal volume of the watch case (2) is corrected by setting the stroke of at least one piston actuated by micrometric control, said at least one piston being able to be screwed and locked in place by means of a special tool not supplied to the user.

16. 16. A method according to any one of the preceding claims, characterized in that during preparation in the factory, the gas or gas blend contained in the case (2) is dried so as to reduce its moisture content H.

17. 17. Method according to any one of the preceding claims, characterized in that during preparation in the factory a desiccant is inserted into the case in order to fix the residual humidity H in the case.

18. A water-resistant watch (1) having a water-resistant case (2) housing a movement (3), said movement (3) itself comprising an oscillator (4), characterized in that said oscillator (4) is pivoted on a pivot (9), said pivot (9) being lubricated with a lubricant of viscosity η, said viscosity η varying with temperature according to a model η=f(T) determined according to any one of claims 1 to 17.

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