EP4386488A1 - Compensation of the variation in the running of a watch - Google Patents

Abstract

One aspect of the invention concerns a method for compensating the rate as a function of the temperature of a watch (1) whose waterproof case (2) contains a movement (3) comprising a regulating member with an oscillator (4) and pivoted on pivots (9) lubricated with a lubricant of viscosity η, where the nature of said lubricant and the rule of variation of said viscosity η as a function of temperature η = f (T) are determined in the factory by measurement and/or calculation , such that said thermal coefficient Ct of said movement (3) varies as a function of the temperature according to a predetermined law Ct = g (T), and such that the course of the movement varies as a function of the temperature T of said thermal coefficient Ct so as to generate variations in the rate of said movement (3) as a function of the temperature, in the opposite direction to the variations in rate generated by said pressure P of said gas.

Description

Technical field of the invention

The invention relates to a method for compensating the rate as a function of the temperature of a waterproof watch, the waterproof case of which contains a movement itself comprising a regulating member comprising an oscillator and pivoted on lubricated pivots, said box containing, leaving the factory after the initial operating setting, an internal volume V occupied by n moles of a gas of constant R substantially following the ideal gas law.

The invention also relates to a watch suitable for implementing this method.

The invention relates to the field of rate adjustment of mechanical or electro-mechanical watches.

Technology background

The operation of a watch is subject to numerous parameters, such as, but not limited to, the position of the watch in space, lubrication, wear, the winding of the springs constituting the sources of energy, friction, and of course the physical parameters of the environment in which the watch is placed.

The variation in rate depending on the temperature is a constant concern for watch manufacturers. The elastic return means of the oscillator are particularly sensitive to temperature variations. In the particular and non-limiting case where these elastic return means comprise a hairspring or several hairsprings, the thermal coefficient Ct of the regulating member causes the rate of movement to vary as a function of the temperature. We can consider, by way of example and to simplify the calculations, that the step varies significantly linearly as a function of the thermal coefficient Ct.

To have better movement precision, the thermal coefficient is generally targeted at 0 seconds per day per Kelvin. With such parameters, temperature variations should not have any influence on the operation of the movement. The typical distribution of the thermal coefficient for producing identical movements is a symmetrical curve, closer to a triangular peak than to a bell.

It is known in watchmaking that the rate of a movement varies depending on the pressure of the environment in which it is located. Several explanations can be put forward, such as for example the variation in the inertia of the oscillator (inertia of the balance wheel and the onboard air) because the density of the onboard air varies and therefore its inertia as well. The case of the pendulum and that of air are particular cases, more generally we will speak of inertial mass, and of gas or mixture of gases. The various experiments carried out show that if the pressure drops, the walking increases.

It is therefore a question of compensating the movement of the watch according to the variation in physical parameters: temperature of the environment, body temperature of the user, expansion or contraction of the watch case depending on the temperature, pressure of the place, altitude, humidity. However, there is no simple development to deal in particular with the problems inherent to variations in temperature and pressure.

Summary of the invention

The invention relates to compensating the rate variation of a watch, based on temperature and pressure.

To this end, the invention relates to a method for compensating the rate as a function of the temperature of a waterproof watch, according to claim 1.

The invention also relates to a watch suitable for implementing this method.

Brief description of the figures

• la figure 1 superpose trois graphes illustrant en ordonnée la marche, en seconde par jour, en fonction de la pression en abscisse, en hectopascal, pour trois mouvements mécaniques différents;
• la figure 2 superpose, deux graphes illustrant en ordonnée la pression en hectopascal dans une boîte de montre dans un environnement à température variable, en fonction du temps en abscisse, en jours, l'un en trait plein calculée avec la loi des gaz parfaits, l'autre mesurée;
• la figure 3 représente, de façon schématisée, une montre dont la boîte étanche contient un mouvement comportant lui-même un oscillateur, équipée de moyens de compensation qui comportent un dispositif volumétrique étanche pour modifier le volume interne de la boîte, un conduit étanche d'injection ou d'extraction de gaz, et un dispositif thermique permettant l'augmentation contrôlée et momentanée de sa température interne.

The aims, advantages and characteristics of the invention will appear better on reading the detailed description which follows, with reference to the appended drawings, where:

• there figure 1 superimposes three graphs illustrating on the ordinate the walking, in seconds per day, as a function of the pressure on the abscissa, in hectopascal, for three different mechanical movements;
• there figure 2 superimposes, two graphs illustrating on the ordinate the pressure in hectopascal in a watch case in an environment with variable temperature, as a function of time on the abscissa, in days, one in solid line calculated with the ideal gas law, the other measured;
• there Figure 3 represents, schematically, a watch whose waterproof case contains a movement itself comprising an oscillator, equipped with compensation means which comprise a waterproof volumetric device for modifying the internal volume of the case, a waterproof injection conduit or gas extraction, and a thermal device allowing the controlled and momentary increase of its internal temperature.

Detailed description of the invention

The invention relates to compensating the rate variation of a watch, based on temperature and pressure.

The experiment carried out in a tank under pressure shows relatively good linearity of the operating variations for a pressure varying from atmospheric pressure (970 hPa) up to a pressure of 200hPa, the variation of operation in seconds per day on the ordinate, as a function of the pressure in hectopascal on the abscissa, the measurement being carried out in a pressure tank. There figure 1 presents the results of measurements carried out on various well-tested classic mechanical movements. We note the very linear general appearance of the daily rate as a function of pressure, all things being equal, with slopes, in seconds per day per hectopascal, respectively of (-0.0206) for the upper curve, of ( -0.0161) for the middle curve, (- 0.0145) for the low curve.

• p(h)=1013.25*(1-(0.0065*h/288.15))^^5.255, on peut trouver que la variation de marche en fonction de l'altitude pour ce calibre est de l'ordre de -0.03 seconde par jour par hPa. Nous appellerons cette valeur le coefficient de pression: Cp.

An experiment on watches equipped with another caliber and closed at different altitudes than those of the figure 1 highlights a variation in walking of the order of 0.95 seconds per day, for an altitude difference of approximately 570m. Based on the following altitude formula:

• p(h)=1013.25*(1-(0.0065*h/288.15))^ ^5.255 , we can find that the variation in rate as a function of altitude for this caliber is of the order of -0.03 seconds per day per hPa. We will call this value the pressure coefficient: Cp.

Concerning the variation of pressure as a function of temperature, we will assume that the ideal gas law (P*V=n*R*T) is sufficient to define the situation.

In a closed watch, the volume of air available is considered given and finite (assuming that leaks are zero). We will also make the assumption that the pressure difference between the pressure inside the watch and outside the watch is not enough to deform the watch; the volume available in the watch does not vary and therefore remains constant.

Experience shows us that these approximations are relatively correct. On the figure 2 , the pressure measured in a watch is compared to a theoretical pressure based on the ideal gas law: P=(n*R/V)*T. We see that the measurements and the theoretical approximation are relatively comparable. In addition, experience has shown us that leaks are relatively low for a waterproof watch even with a large pressure difference between the inside of the watch and the environment in which it is located. We will therefore assume that the watch is perfectly waterproof.

Initial assumptions showed that leaks from the watch are considered zero, the watch case is undeformable and the enclosed gas remains the same. It is therefore possible to conclude that the parameters n, R and V are constants; the pressure therefore varies linearly as a function of the temperature.

The invention proposes to mainly deal with compensation for variations in temperature and pressure. A combination of the two effects aims to oppose them so that their effects cancel each other out (or are minimized). The main advantage for the user is better precision of the watch when worn.

The influence of humidity is weaker than those of temperature and pressure. In the working hypothesis, the humidity level changes little depending on the temperature or pressure, in the usual areas of wearing a watch. An approximate calculation consists of neglecting this variation.

• la pression dans la montre varie sensiblement linéairement en fonction de la température : P = [(n*R)/V] * T;
• la marche du mouvement varie en fonction de la température, et en fonction du coefficient thermique Ct du mouvement, qui dépend lui aussi de la température,: m(T )= Ct * T;
• la marche du mouvement varie linéairement selon la pression des gaz: m(P) = Cp * P.

The following assumptions are made to simplify the calculations:

• the pressure in the watch varies substantially linearly as a function of the temperature: P = [(n*R)/V] * T;
• the rate of movement varies as a function of the temperature, and as a function of the thermal coefficient Ct of the movement, which also depends on the temperature: m(T)= Ct * T;
• the rate of movement varies linearly according to the gas pressure: m(P) = Cp * P.

The invention thus relates to a method of compensating the rate as a function of the temperature of a waterproof watch 1, the waterproof case 2 of which contains a movement 3 comprising a regulating member itself comprising an oscillator 4 and which is pivoted on pivots 9 lubricated with a lubricant of viscosity η. This box 2 contains, leaving the factory after the initial operating adjustment, an internal volume V occupied by n moles of a gas of constant R substantially following the ideal gas law. The constant R (or Avogadro's number) is known. It depends on the gas that is in the watch (in our case generally air). The number of moles n will depend on the conditions for closing the watch (atmospheric pressure, temperature or closure and blocking of the caseback for example).

We understand that the pivots 9 can be the pivots of a balance, as well as those of an anchor, or even of an escape wheel.

We also consider the viscosity variation of the lubricated anchor-anchor wheel and anchor-oscillator contact.

The available volume V depends on the geometry of the box. It is possibly possible to modify the construction of the cladding to influence this point.

• une valeur du coefficient de pression Cp du mouvement 3, définissant la variation relativement linéaire de la marche du mouvement 3 en fonction de la pression P du gaz (ou du mélange de gaz le cas échéant) selon l'équation m(P) = Cp * P. Le coefficient de pression du mouvement Cp peut être mesuré expérimentalement ou calculé théoriquement. Il dépend de chaque typologie de mouvement,
• une valeur du coefficient d'humidité Ch dudit mouvement 3, définissant la variation relativement linéaire maximale de la marche dudit mouvement 3 en fonction de l'humidité H dans ledit mouvement 3 selon l'équation m(H) = Ch * H. A défaut de variation linéaire on considère la valeur maximale de pente de la plus haute tangente au graphe marche/humidité,
• la nature du lubrifiant et la règle de variation de la viscosité η en fonction de la température η = f (T), telle que le coefficient thermique Ct du mouvement 3 varie en fonction de la température selon une loi Ct = g (T) prédéterminée, et telle que la marche du mouvement varie en fonction de la température T et en fonction du coefficient thermique Ct dudit mouvement 3 selon l'équation m(T)= Ct * T = g (T)* T,

de façon à générer des variations de marche du mouvement 3 en fonction de la température, en sens inverse des variations de marche générées par la pression P du gaz.According to the invention, the following is determined in the factory by measurement and/or calculation:

• a value of the pressure coefficient Cp of movement 3, defining the relatively linear variation of the progress of movement 3 as a function of the pressure P of the gas (or of the gas mixture if applicable) according to the equation m(P) = Cp * P. The pressure coefficient of movement Cp can be measured experimentally or calculated theoretically. It depends on each type of movement,
• a value of the humidity coefficient Ch of said movement 3, defining the maximum relatively linear variation of the step of said movement 3 as a function of the humidity H in said movement 3 according to the equation m(H) = Ch * H. Otherwise of linear variation we consider the maximum slope value of the highest tangent to the walking/humidity graph,
• the nature of the lubricant and the rule of variation of viscosity η as a function of temperature η = f (T), such that the thermal coefficient Ct of movement 3 varies as a function of temperature according to a predetermined law Ct = g (T) , and such that the course of the movement varies as a function of the temperature T and as a function of the thermal coefficient Ct of said movement 3 according to the equation m(T)= Ct * T = g (T)* T,

so as to generate variations in the rate of movement 3 as a function of the temperature, in the opposite direction to the variations in rate generated by the pressure P of the gas.

More particularly, we determine this rule of variation of the viscosity η as a function of the temperature η = f (T), so as to generate variations in the movement of the movement 3 as a function of the temperature which are inverse to the variations in the movement generated by the pressure. P gas.

In the present example, it was considered that the pressure coefficient Cp is constant.

The temperature coefficient Ct follows a non-linear law depending on the temperature.

Given that the relative humidity will vary according to the temperature and that the rate of the watch will vary according to variations in humidity (via the Ch), this theoretical model integrates the humidity parameter. However, this parameter can, in temperate regions, be neglected because the influence of humidity on walking is much less than that of the temperature. In a simplified calculation, we determine the humidity coefficient Ch of movement 3 to be zero.

More particularly, 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 at the time of closing the box 2.

The thermal coefficient Ct of the regulating organ is linked to the pressure coefficient Cp by the environment in box 2 of watch 1 (the gas of constant R present, the volume V inside the watch and the quantity of moles n in the watch).

In particular, the thermal coefficient of oscillator 4 depends, among other things, on the elastic return means of the oscillator, and on their rigidity. In the particular and non-limiting case where this oscillator 4 is a balance-spring, when producing a balance-spring in silicon and/or silicon oxide, the thermal coefficient Ct of the balance-spring assembly can be adjusted in particular by function of the thickness of the oxide layer which covers this hairspring. Similarly, the production of the blades of a flexible guided oscillator can modify the thermal coefficient Ct.

Consider that the variation in rate of a movement as a function of pressure varies as follows: Cp = -0.015 seconds per day per hectopascal. By considering a watch case with a generic casing, we obtain experimentally that the constant (n*R)/V is worth approximately 3.3 hPa/K. It was calculated based on measurements of pressure and temperature in the watch head using the ideal gas law.

In order for the watch to be least sensitive to temperature variations, it would be appropriate to target a thermal coefficient of the regulating organ at 0.05 seconds per day per Kelvin. This value is calculated based on the equation Ct = - [Cp * (n * R) / V]: (0.015*3.3=0.05).

By targeting the thermal coefficient of the spiral balance at a value different from 0 seconds per day per Kelvin, the chronometric measurements in movement will be disrupted. For example, when passing certification as a chronometer with phases at 8°C and 38°C, there would be a difference in operation of around 1.5 seconds per day generated by the thermal coefficient of the movement between hot and cold phases. However, if we fit this movement into the watch of the previous example (Cp=-0.015, (n*R)/V=3.3), the rate becomes practically insensitive to the temperature variation.

It is therefore necessary to ensure that the law of variation of the viscosity η = f (T) of the pivot lubricant (in the case of a sprung balance) is compatible with these limits.

More particularly, the elastic return means of the oscillator 4 are produced in silicon and/or silicon oxide, and, during factory preparation, the thermal coefficient of these elastic return means is modified by modification of the thickness. of silicon oxide layer.

More particularly, the elastic return means of the oscillator 4 are produced in the form of thin elastic blades by a “LIGA” process, and, during preparation in the factory, the thermal coefficient of these elastic return means which comprises the oscillator 4 by application of a coating and/or by local ablation and/or by playing on the shape ratios.

More particularly, the elastic return means of the oscillator 4 are produced in the form of thin elastic strips by a wire drawing or rolling process, and, during preparation in the factory, the thermal coefficient of these elastic return means is modified. that oscillator 4 comprises by application of a coating and/or by local ablation and/or by playing on the shape ratios.

A variant embodiment consists of working on the geometry of the interior of the watch, by modifying the interior volume of the case by a stroke imparted to a movable member such as a piston or the like.

Thus, in a variant designed in particular for an after-sales application, the compensation means 10 comprise a sealed volumetric device 5 allowing a technician to modify the internal volume of the box 2, which comprises at least one movable piston in the box 2, under the action of an external micrometric control screwable and lockable in position by a special tool not supplied to the user.

As readable in the document EP21216225A1 , it is also possible to combine several effects simultaneously (variation of Ct, Cp, casing conditions or volume in the watch) in order to achieve the desired objective.

From a general point of view, it appears that Ct dispersion must be minimized in order to minimize the effect of temperature on a watch.

The invention also relates to a watch 1 suitable for implementing this method. This waterproof watch 1 comprises a waterproof box 2, which contains a movement 3 itself comprising an oscillator 4, which is pivoted on pivots 9 lubricated with a lubricant of viscosity η variable with the temperature according to a law η = f (T) determined according to this method.

Claims (18)

Method of compensating the rate as a function of the temperature of a waterproof watch (1), the waterproof case (2) of which contains a movement (3) itself comprising a regulating member comprising an oscillator (4) and pivoted on pivots (9) lubricated with a lubricant of viscosity η, said box (2) containing, leaving the factory after the initial operating adjustment, an internal volume V occupied by n moles of a gas of constant R substantially following the law ideal gases, characterized in that we determine in the factory by measurement and/or calculation: - a value of the pressure coefficient Cp of said movement (3), defining the relatively linear variation of the progress of said movement (3) as a function of the pressure P, at constant temperature, of said gas according to the equation m(P) = Cp *P, - a value of the humidity coefficient Ch of said movement (3), defining the maximum relatively linear variation of the gait of said movement (3) as a function of the humidity H in said movement (3) according to the equation m(H) = Ch * H, - the nature of said lubricant and the rule of variation of said viscosity η as a function of the temperature η = f (T), such that said thermal coefficient Ct of said movement (3) varies as a function of the temperature according to a law Ct = g ( T) predetermined, and such that the course of the movement varies as a function of the temperature T and as a function of said thermal coefficient Ct of said movement (3) according to the equation m(T)= Ct * T = g (T)* T, so as to generate variations in the rate of said movement (3) as a function of the temperature, in the opposite direction to the variations in rate generated by said pressure P of said gas. Method according to claim 1, characterized in that said rule of variation of said viscosity η is determined as a function of the temperature η = f (T), so as to generate variations in the rate of said movement (3) as a function of the temperature inverse to the variations in rate generated by said pressure P of said gas. Method according to claim 1 or 2, characterized in that 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 said watch (1) before closing said box (2). Method according to one of claims 1 to 3, characterized in that the humidity coefficient Ch of said movement (3) is determined to be zero. Method according to one of claims 1 to 4, characterized in that , for an after-sales application, said box (2) is equipped with a sealed volumetric device (5) allowing an after-sales technician to modify the internal volume of said box (2), and/or at least one sealed gas injection or extraction conduit (6), and/or a thermal device (7) allowing the controlled and momentary increase of its internal temperature . Method according to claim 5, characterized in that said volumetric device (5) comprises at least one piston movable in said box (2) and under the action of an external micrometric control screwable and lockable in position by a special tool not supplied to the user. Method according to claim 5, characterized in that said sealed gas injection or extraction conduit (6) can be locked in position by a special tool not supplied to the user. Method according to claim 5, characterized in that said thermal device (7) comprises light energy conversion means and/or energy storage means. Method according to one of claims 1 to 8, characterized in that said elastic return means of said oscillator (4) are produced in silicon and/or silicon oxide, and in that , during preparation in the factory, the thermal coefficient of said elastic return means is modified by modification of the thickness of the silicon oxide layer. Method according to one of claims 1 to 8, characterized in that said elastic return means of said oscillator (4) are produced in the form of thin elastic blades by a “LIGA” process, and in that during the preparation in factory, the thermal coefficient of said elastic return means which comprises said oscillator (4) is modified by application of a coating and/or by local ablation and/or by playing on the shape ratios. Method according to one of claims 1 to 8, characterized in that said elastic return means of said oscillator (4) are produced in the form of thin elastic strips by a drawing or rolling process, and in that during the factory preparation, the thermal coefficient of said elastic return means which comprises said oscillator (4) is modified by application of a coating and/or by local ablation and/or by playing on the shape ratios. Method according to one of claims 1 to 11, characterized in that during the preparation in the factory, the number of moles of gas in said watch is modified, or by closing said box (2) with a pressure defined by calculation to make the running of the watch insensitive to temperature, or by closing said box (2) with a temperature defined by calculation to make the running of the watch insensitive to temperature, and by slowly cooling said box (2) after its closure. Method according to one of claims 1 to 12, characterized in that during the preparation in the factory, the nature of the gas contained in the watch is modified, by total or partial exchange of said gas with a new gas or mixture of gases having a other value of said constant R, adapted for the adequate adjustment of said thermal coefficient Ct to make the operation of the watch insensitive to temperature. Method according to claim 13, characterized in that said box (2) is sealed after said gas exchange, to prevent any action by the user in the absence of a special tool. Method according to one of claims 1 to 14, characterized in that during preparation in the factory, the internal volume of said box (2) is modified by adjusting the stroke of at least one piston, under the action of a micrometric control that can be screwed and locked in position using a special tool not provided to the user. Method according to one of claims 1 to 15, characterized in that during preparation in the factory, the gas or gas mixture contained in said box (2) is dried to reduce the humidity H. Method according to one of claims 1 to 16, characterized in that during preparation in the factory, a desiccator is inserted into said box, to fix the residual humidity H. Waterproof watch (1), the waterproof case (2) of which contains a movement (3) itself comprising an oscillator (4), characterized in that said oscillator (4) is pivoted on pivots (9) lubricated with a lubricant of viscosity η variable with the temperature according to a law η = f (T) determined according to one of claims 1 to 17.

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