CH714551B1 - Method of lubricating a watch mechanism. - Google Patents

Abstract

The invention relates to a method of lubricating a watch mechanism comprising a step of applying a grease comprising PTFE particles dispersed in a base oil, the grease having a load of PTFE adjusted with respect to the specific surface of the particles. particles so as to obtain a grease having a grade between 3 and 1, preferably a grade 2 according to the NLGI scale (National Lubricating Grease Institute).

Description

Technical area

The present invention relates to the field of watchmaking, in particular mechanical or electromechanical watchmaking.

In the field of mechanical or electromechanical watches, the functioning mechanisms need to be lubricated to ensure good tribological conditions in the interactions between the different parts. Thus, the gear train, the escapement, the time-setting, manual or automatic winding, or even the various displays or complications require the use of lubricants.

[0003] The lubricants used must always meet the following criteria: chemical stability: so as not to decompose over time; retention in the contact areas: so as not to be dispersed in the event of an impact or during operation of the mechanism and contaminate the movement; maintenance of mechanical performance: the repetition of stresses must not have an impact (as little as possible) on the behavior of the lubricant.

These criteria are very difficult to meet. Faced with the variety of speed and pressure conditions present in the different functions, watchmakers use specific lubricants with their own qualities for the escapement (high contact speed), winding (high pressure), the gears of the gear train. , .... Those skilled in the art are particularly aware of efficiency difficulties and epilamage constraints, for the lubrication of the exhaust.

[0005] Traditionally, the paddles are made of ruby, while the escape wheel is made of steel. Optimization of the tribological conditions between the anchor vanes and the escape wheel results in lubricating the areas of contact between them.

This lubrication is delicate and complex, and is the subject of much research, know-how and innovation. Indeed, the relative displacement speeds between the vanes and the teeth of the escape wheel are high, of the order of 70mm / s during the impulse phase, and the lubricant used must therefore have a suitable viscosity to be effective at these speeds.

[0007] Lubricants meeting these specifications are generally quite fluid. To be effective, it is imperative to maintain the lubricant used in the contact area in sufficient quantity without hindering the movement of the moving components. It must also remain in place during operation of the escapement and in the event of shocks so as not to impoverish the contact and soil the components inside the movement. This is achieved by the application of an epilame which contributes to the general and overall complexity of the lubrication of an exhaust. Indeed, the epilame forms a film on the surface of the lipophobic type pallets. The exhaust should be run dry so that the contact of the teeth of the escape wheel is free of epilame, so as to form a trench, in which the oil will then be applied and contained. , by the lipophobic properties of epilame.

[0008] In order to constitute a lubricant reservoir making it possible to supply the contact and reduce the contact surfaces, the teeth constituting the escape wheel can be bevelled.

[0009] More recently, watchmakers have explored the use of Silicon to produce the anchor and the escape wheel, because this material offers, in addition to freedom in the production of complex geometry, reduced friction coefficients, in particular for Silicon-Silicon interactions. Quite quickly, the use of SiO2 obtained by thermal oxidation or diamond obtained by CVD deposition was essential to improve the mechanical resistance and the tribological properties. Watchmakers have long argued that the silicon components thus coated would make it possible to overcome the lubrication difficulties known until then. However, in practice, it is generally found that, in order to obtain the expected performance levels, recourse to lubrication with traditional oils used for steel / ruby exhausts is also necessary with a silicon escapement.

[0010] This is all the more restrictive as the parts produced in silicon are more fragile than the parts made of steel, and that the current industrial epilamage processes are not applicable to parts made of silicon. Indeed, the use of a bulk epilamage treatment would inevitably damage the silicon parts given the fragility of silicon. Part by part depilamation would be tedious, expensive and inefficient.

[0011] Likewise, the production of a bevel like steel parts to constitute a reservoir, makes the manufacturing costs of silicon parts more complex and increases.

Watchmakers have also explored the use of lithography techniques known under the name LIGA to produce the anchor and the escape wheel. These techniques make it possible to reproduce given shapes with great precision. The parts are made of nickel or a nickel alloy, in particular NiP, by growth in structures defined by lithography.

[0013] Despite the complex shapes that LIGA makes it possible to obtain, favoring geometric optimization and greater theoretical performance, it is nevertheless still necessary to lubricate the surfaces of the contact members of the exhaust, with a depilamage step and the application of an oil of the prior art to obtain the expected performance and ensure reliability of the exhaust.

[0014] Beyond the applications to the escapement, the question of lubrication is a permanent subject for any watch mechanism.

Disclosure of the invention

The present invention aims to provide a particularly flexible and efficient lubrication method, capable of being implemented for various watch mechanisms. It allows to obtain significant improvements in terms of performance and durability.

More specifically, the invention relates to a lubrication method as proposed in the claims.

Brief description of the drawings

Other details of the invention will emerge more clearly on reading the following description, made with reference to the appended drawing, in which: FIG. 1 represents comparative performance tests for three movements of a first caliber, with different lubrication configurations, after 24 hours of running in, FIGS. 2a and 2b respectively show, in terms of amplitude and efficiency, measurements carried out for 10 movements of a second caliber and three lubricants, Figures 3a, 3b and 3c show amplitude comparisons, while Figures 4a, 4b and 4c show performance comparisons, for 3 lubricants, compared to a reference lubricant A; the measurements are carried out on sets of movements of a third caliber.

Embodiment of the invention

As explained in detail in the introduction to the present application, the question of the lubrication of the mechanisms is a subject of permanent research for watchmakers. For exhausts, the goals pursued are to improve: the efficiency of the exhausts, the lubricants' stability over time, both in terms of performance and in terms of composition (chemical stability), their implementation to facilitate the industrialization of the lubrication stage.

The Applicant has identified, after much research, particularly interesting effects in the use of specific lubricants, to lubricate an exhaust.

The invention applies in particular to a method of lubricating a horological escapement mechanism comprising a mobile intended to receive a driving force and a stop member intended to cooperate with the mobile to block or leave free its alternating rotation. The mobile and the stop member respectively have first and second contact members intended to cooperate with each other.

At least the first or the second contact members are made from silicon, or based on nickel or a nickel alloy (in particular NiP) by LIGA type technology.

Advantageously, the escape mechanism is a so-called Swiss lever mechanism. The mobile is an escape wheel intended to be pivotally mounted and the stop member is an anchor also intended to pivot on its axis. The anchor is provided with an input pallet and an output pallet, intended to cooperate with the teeth of the escape wheel. The paddles on the one hand, and the teeth of the escape wheel on the other hand, define contact members, since they are intended to interact with each other, during the successive stages of the escapement. This type of mechanism is well known and does not need to be described in detail.

Preferably, the anchor on the one hand, and the escape wheel on the other hand are made in one piece based on silicon, optionally covered by a surface layer, for example of oxide, natural or produced by an oxidation step. Those skilled in the art can also envision other coatings or surface treatments on the contact members.

One can also consider other configurations in which only one of the anchor or of the escape wheel is silicon-based, or then only the contact members are silicon-based.

As an alternative, the anchor on the one hand, and the escape wheel on the other hand, are made in one piece based on nickel or a nickel alloy, obtained by LIGA type technology. The nickel or the nickel alloy used may also contain additives of the doping or solid lubricant type (hBN, talc, etc.). Those skilled in the art can also envision other coatings or surface treatments on the contact members.

One can also consider other configurations in which only one of the anchor or the escape wheel is based on nickel or a nickel alloy, or then only the contact members are at nickel base or nickel alloy.

According to the invention, the lubrication of the exhaust is characterized in that it comprises a step of applying a grease comprising particles of PTFE (polytetrafluoroethylene) dispersed in a base oil, the filler of PTFE being adjusted with respect to the specific surface of the particles so as to obtain a grease having a grade of between 3 and 1, preferably a grade 2 according to the NLGI scale (National Lubricating Grease Institute).

Preferably, the base oil is PFPE (Perfluoropolyether). The application can be carried out without epilamage.

Figure 1 shows the amplitude measurements of the balance. These measurements were carried out on three watch movements of the same type, with standard geometry of the anchor and the escape wheel. The graph represents the average values of the amplitude readings in 6 positions, at Ohms running (barrel loaded to the maximum without the sliding flange) after running-in for 24 hours, measured for each movement. A line represents, for each lubricant, the average of the measurements of the three movements. Between each lubricant, the movements are dismantled and degreased, then lubricated with the following lubricant.

The reference measurement is a standard exhaust, with a steel escape wheel (with bevelled teeth) and ruby anchor vanes, epilamated and lubricated according to the methods of the state of the art. The following 7 measurements relate to silicon exhausts, with identical geometries to the standard reference escapement but without bevel on the teeth of the escape wheel. The 1st measurement corresponds to dry running, without lubrication. Measurement A corresponds to lubrication according to the state of the art, that is to say with epilamage and lubrication as in the reference exhaust.

Measurement B relates to the fat used according to the method of the invention. Measurements C to F relate to different types of lubricants tested, with or without epilame, depending on the consistency and flow of the grease.

It is observed that the fat B makes it possible to obtain higher yields than the other solutions, with a significant improvement of 24 ° compared to the reference, and of at least 22 ° compared to the alternatives tested. In addition, this level of performance is obtained without the application of epilame and with a simplified geometry of the teeth of the escape wheel (without bevel), which represents an industrial advantage.

In Figure 2, the performance of other lubricants were studied on an escapement with an anchor and an anchor wheel made of NiP, the teeth of which are not bevelled. 10 movements of a second caliber (different from that used in FIG. 1) were used for the measurements. The graph represents the average values of the amplitude readings (fig. 2a) in 6 positions, at 0 hours of operation (barrel loaded to the maximum without the sliding flange) after running in for 24 hours, and the efficiency (fig. 2b) measured for each movement, in low horizontal position. A line represents, for each lubricant, the average of the measurements of the different movements. Between each lubricant, the movements are dismantled and degreased, then lubricated with the following lubricant. The lubricant A is a reference lubricant of the state of the art, B is the lubricant according to the invention and C is another lubricant tested.

There is an amplitude gain of 25 ° and a gain of 9 performance points in the low horizontal position, for the grease according to the invention compared to the reference.

In Figure 3, other lubricants have been studied on an escapement with an anchor and an anchor wheel made of NiP, the teeth of which are not bevelled, on series of movements of the same caliber of a second type. The graph represents the average values of the amplitude readings in 6 positions, at Ohms running (barrel loaded to the maximum without sliding flange) after a 24 hour break-in. A line represents, for each lubricant, the average of the measurements of the different movements. For each comparison, the measurements are carried out on different batches, which is why the results are presented 2 to 2 and not all on the same graph. Lubricant A is a reference lubricant of the state of the art recognized for its performance, B is the lubricant according to the invention and G and H are other lubricants tested.

An amplitude gain of 16 ° was observed for the fat according to the invention compared to the reference, which is a significant improvement compared to the amplitudes obtained with G and H.

In Figure 4, the corresponding yields have been shown at the amplitudes measured in Figure 3.

A yield gain of 6 points is observed, ie 13.9% for the fat according to the invention compared to the reference, which is a significant improvement compared to the yields obtained with G and H.

The improvements obtained are considerable (between 6 and 9 performance points) compared to the weak optimizations generally observed, which are of the order of those obtained with the other lubricants tested (between 0 frequently and 3 points for a single lubricant ).

In terms of composition, different fats of the above family were tested, with comparable results. Thus, the base oil (PFPE) can have a viscosity measured at 40 ° C., between 15 and 330 cSt, preferably between 18 and 310 cSt. The PTFE particles dispersed in the base oil are submicron and the density can be adjusted by a person skilled in the art, so as to obtain a grease which, in the end, has a grade between 3 and 1, preferably a grade. 2. In practice, the PTFE load is adjusted with respect to the specific surface area of the particles as a function of the target grade. Typically, the particles have a size of between 20nm and 1.2µm. Advantageously, the size is between 50 nm and 1 μm.

This grade corresponds to a fairly viscous grease, qualified according to the NLGI table (National Lubricating Grease Institute) below.

NLGI consistency numbers

[0042] 000 445-475 fluid cooking oil 00 400-430 semi-fluid apple sauce 0 355-385 very soft brown mustard 1 310-340 soft tomato paste 2 265-295 „normal“ grease peanut butter 3 220-250 firm vegetable shortening 4 175-205 very firm frozen yogurt 5 130-160 hard smooth pate 6 85-115 very hard cheddar cheese

This type of grease can be deposited using an oil spike, usually used, or using other equipment or dispensers allowing at least partial automation of the dispensing of the lubricant on the functional surfaces. contact organs.

Obtaining this level of performance for a grease of this viscosity is particularly surprising. Indeed, having regard to the relative displacement speeds of the contact members, the use of a grease is a priori not indicated, because its response to a shear stress, such as undergone during a contact with the exhaust, is not fast enough. However, it has been found that the mechanical strength of this type of grease drops suddenly when it is subjected to a shear stress, in other words, it becomes fluid rapidly during the friction undergone in operation. On the other hand, the flow threshold also quickly returning to its normal level after the end of the application of a mechanical stress, the grease advantageously remains in place on the contact members, despite the absence of epilame.

Even more surprisingly, it was found that this grease exhibits quite interesting properties and suitable for lubricating other watch mechanisms, without limitation to the escapement, and adapts to other interfaces of contact.

In addition, it exhibits aptitudes for aging and for maintaining the mechanical operating conditions of most watch mechanisms.

Thus, tests carried out on the aging of the notches of the winding stem, show that after 5000 tensile / pressure cycles, equivalent to 10 years + of aging, the lubricant according to the method of the invention meets the specifications fixed charges: torque variation ≤30%; no degradation of components; no degradation of function; pull-out test at 25N (the rod remains in place).

Other conventionally used lubricants do not pass the tests.

Tests were also carried out on several (5) movements, on the aging of the time-setting system, on 10,000 turns of the road, which is equivalent to 10 years + of aging. After the equivalent of 3 years, 5 years, 8 years and 10 years, the lubricant according to the invention meets the specifications set: torque variation ≤30%; no degradation of components; no degradation of function.

On other lubricants tested, it has already been observed after the 1st year of aging that 3 out of 4 movements no longer performed their function (seizure of the crown wheel and breakage of the teeth of the winding pinion). Some wear was observed under the crown wheel of the last movement.

For an automatic winding system, the lubricants conventionally used allow operation corresponding to 3 million revolutions of the oscillating weight. The parts in play are the winding pawls on the winding wheel (steel-copper metal) and the eccentric of the pawl (ruby-steel). With the lubricant according to the invention, it was possible to go beyond 10 million revolutions of the oscillating weight, which corresponds to the use of a sports wearer, for 10 years +.

It is thus noted that the lubricant identified and selected according to the invention has truly extraordinary capacities and can be applied, not only in a very interesting manner to the escapement, but also to other watch mechanisms, in particular mechanisms. manual winding using steel / steel contacts, or steel / copper metal contacts with or without galvanic coating, automatic winding mechanisms using ruby / steel or metal / metal contacts, date mechanisms or mechanisms setting the time. This list is not exhaustive.

Thus a method is proposed for lubricating a watch mechanism, adapting to several watch mechanisms, with improved properties in terms of performance, aging and industrial application.

Claims (9)

1. A method of lubricating a watch mechanism comprising a step of applying a grease comprising particles of PTFE dispersed in a base oil, said grease having a load of PTFE adjusted with respect to the specific surface of the particles in such a manner. to obtain a grease having a grade between 3 and 1, preferably a grade 2, according to the NLGI scale of the National Lubricating Grease Institute. 2. Lubrication method according to claim 1, characterized in that said base oil is PFPE. 3. Method according to one of claims 1 and 2, characterized in that said watch mechanism is a manual winding mechanism, implementing steel-steel contacts or steel-copper metal contacts, with or without galvanic coating. 4. Method according to one of claims 1 and 2, characterized in that said watch mechanism is an automatic winding mechanism, implementing ruby-steel contacts or metal-metal contacts. 5. Method according to one of claims 1 and 2, characterized in that said clockwork mechanism is a date mechanism. 6. Method according to one of claims 1 and 2, characterized in that said clock mechanism is a time setting mechanism. 7. Lubrication method according to one of claims 2 to 6, characterized in that said base oil has a viscosity measured at 40 ° C of between 15 and 330 cSt, preferably between 18 and 310 cSt. 8. Lubrication method according to one of claims 2 to 7, characterized in that the PTFE particles have a size between 30nm and 1.2 µm, preferably between 50nm and 1 µm. 9. Lubrication method according to one of the preceding claims, characterized in that the grease is applied using an oil spike or an automatic dispenser.