WO2019111195A1

WO2019111195A1 - Micro-mechanical horology component

Info

Publication number: WO2019111195A1
Application number: PCT/IB2018/059706
Authority: WO
Inventors: Julien PERRET
Original assignee: Patek Philippe Sa Geneve
Priority date: 2017-12-06
Filing date: 2018-12-06
Publication date: 2019-06-13
Also published as: EP3721298A1

Abstract

The micro-mechanical horology component comprises contact surfaces designed to slide against corresponding contact zones of another micro-mechanical component in a timepiece; – the micro-mechanical component being manufactured from a fragile material; – the said contact surfaces of the micro-mechanical component being grooved, the grooves being rectilinear and parallel to the direction of sliding; – the said grooves being separated by solid lands of a width of between 0.5 and 50 microns; and – the surface area occupied by the solid lands, referred to as the effective contact area, being comprised between 2 and 70% of the total area of the contact surface.

Description

Watchmaking micromechanical piece

A first embodiment of the present invention relates to a watchmaking micromechanical component arranged to interact mechanically with another micromechanical component in a timepiece, the two micromechanical parts comprising respective contact zones that are arranged to slide against each other. other during the mechanical interactions between the micromechanical watchmaking piece and the other micromechanical part. A second embodiment of the present invention concerns a mechanical timepiece which comprises a first and a second micromechanical component which are arranged to interact mechanically, the first and second micromechanical components comprising respective contact zones arranged to slide against each other. the other during the mechanical interactions between the first and the second micromechanical component, and at least the first micromechanical component being constituted by a watchmaking micromechanical component according to the first embodiment of the invention. The invention relates in particular to a micromechanical watchmaking piece which conforms to the above definition and which forms part of an anchor escapement. In this regard, it will be recalled that the exhaust is the mechanism that provides the interface between the wheel and the regulating member (the pendulum or pendulum) of a timepiece. The exhaust has particular function to maintain the oscillations of the regulating member.

PRIOR ART

The known escape mechanisms are diverse and numerous. However, at present, the exhaust mechanisms that equip the vast majority of mechanical watches are of the type Swiss lever escapement. Escapes of this type include an anchor whose two arms each end with a pallet. The anchor is arranged to pivot alternately in one direction and the other so that the pallets come one after another block and release, one of the teeth of the escape wheel. When one of the pallets releases a tooth that it hitherto blocked, the escape wheel turns a short time before a next tooth falls against the other pallet. The escapement wheel therefore advances in jerks, and we can note that it is the successive falls of the teeth of this wheel (once on two against the outside of the entry pallet, the other time against the inside the exit pallet) that are responsible for the ticking of the watch. It will be understood from the above that the pallets are continuously subjected to shocks and friction. This is the reason why pallets are most often made in rubies.

The movement of the escapement during each half-period of the pendulum can be broken down into three phases. These three phases are the disengagement phase during which the anchor pivots to disengage one of its vanes from the tooth of the escapement wheel with which it was engaged. When the anchor pivots, the pallet is released by sliding against the front flank of the tooth, so that it deviates a little from the escape wheel. Once the pallet released from the front flank of the tooth, the escape wheel is no longer completely blocked, and then we move to the impulse phase during which it is the pulse plane of the tooth that grows in bias against the pulse plane of the pallet. As the force exerted by the tooth on the pallet is oriented obliquely, the tangential component of this force causes the pulse plane of the tooth to slide against that of the pallet, and simultaneously, the normal component of this force propels the anchor , rotating it so as to briefly drive the pendulum. The anchor pivots until the pallet is finally outside the path of the tooth, ending the impulse phase. The escape wheel is then completely free to rotate until a next tooth falls on the other pallet, causing a new stop of the escape wheel. This third phase is called the fall phase. The sliding of the vanes against the teeth of the escape wheel necessarily generates friction forces. Thus, during the disengagement phase, a friction force opposes the sliding of the rest plane of the pallet against the leading edge of the tooth of the escape wheel. The anchor must provide some work to overcome this force. Similarly, during the following pulse phase, a friction force opposes the sliding of the pulse plane of the pallet against the pulse plane of the tooth. The escape wheel must provide some work to overcome this force. The existence of these relatively intense friction forces between the pallets of the anchor and the teeth of the escape wheel causes a decrease in both the precision and the life of the watch movement. In particular, the energy lost by the balance in the form of friction during the disengagement phase must then be compensated for by the escapement during the pulse phase. In addition, the escapement must also compensate for lost energy in the form of friction during the impulse phase itself, and the amount of energy spent for this purpose reduces the amount of energy that the exhaust can actually provide the pendulum. Yet another problem is that friction accelerates wear at the contact surfaces between the exhaust parts. Parts eventually become deformed and need to be replaced more often.

According to a well known relation, the friction force that must be overcome for a solid to slide on a constant speed surface is given by the following formula:

Fd ⁼ A FN

where F _d is the dynamic friction force;

m is the coefficient of dynamic friction;

F _N is the normal component of the application force. In most practical situations, the force of application and its normal component F _{N are more} similar to data of the problem than to parameters on which it would be possible to play. Thus, in order to reduce friction, it has rather sought to decrease the coefficient of friction m. It is known that this coefficient depends on several factors such as the pairing of the materials in contact, the roughness of the contact surfaces, the surface treatments, the lubrication, etc. In particular, the use of oil as a lubricant is widespread in watchmaking. The use of lubrication, however, has a number of problems. In particular, it requires regular services to be given to the watch, so as to be able to put oil back in or clean the wheels. It would therefore be advantageous to have watch micromechanical parts that comply with the definition given in the preamble and that do not require the use of a lubricant. BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to overcome the disadvantages of the prior art which have just been explained. The present invention achieves this and other objects by providing, on the one hand, a watchmaking micromechanical component according to the appended claim 1, and by providing, on the other hand, a mechanical timepiece according to the claim 8 annexed.

It will be understood that the term "contact zone" can designate both a plane contact zone (in other words a contact surface) and a linear contact zone (in other words an edge formed by the meeting of two surfaces).

According to the invention, the contact surfaces of the micromechanical part have rectilinear and parallel ridges. A first effect of the presence of ridges formed in a contact surface is to reduce the area of the portion of the contact surface, which is effectively in friction when the contact surface slides against a contact area of another room . In this regard, it can be noticed that the area of contact does not appear in the formula of the dynamic friction force (given above). Indeed, it is generally accepted that the friction force is independent of the contact area. However, the tests carried out by the Applicant show that the presence of streaks on the contact surface leads to a reduction in the friction forces even in the case of a relatively large contact surface (130 micron component height).

According to the invention, the micromechanical watchmaking piece is made of a fragile material. It will be understood that in the present text, the term "fragile material" refers to materials which, in the context of a use in watchmaking micromechanics, are characterized by a brittle fracture, that is to say a break without plastic deformation. beforehand, during an elastic loading, as soon as the stress reaches the critical threshold locally. A fragile material is therefore by definition a material that easily breaks by its very nature. A brittle material may show some elasticity. However, when subjected to constraints of a certain intensity, it breaks without prior plastic deformations. Examples of fragile materials that can be used with the invention are glasses, ceramics, silicon, polymers, in particular quartz, sapphire and mono- or polycrystalline silicon, as well as amorphous quartz. Examples of glasses include vitreous silica, soda-lime glasses, borosilicates, non-alkaline glasses, vitreous silica, alumino-silicates and fluorinated glasses. Three families of ceramics can also be identified: oxides, non-oxides and composites. These three families of ceramics include: silicon oxide, zirconium oxide, alumina, silicon carbides or nitrides, silinvar® for composites. Finally, among the polymers, there may be mentioned, for example, polymers with high mechanical performance, such as PEEK or polyamides.

In general, the resistance of fragile materials in case of shocks is not very high either. This is probably the reason why, to the knowledge of the plaintiff, it has never been proposed until now to realize components for an escape mechanism in the form of monolithic parts each made from a single piece of glass. The person skilled in the art knows, indeed, that the lenses intended to withstand shocks are usually laminated glasses. That is to say laminated glasses which consist of a plurality of glass sheets bonded to each other by interlayer films whose behavior is plastic.

According to the second embodiment of the invention, the mechanical timepiece comprises a first and a second micromechanical component which comprise respective contact zones arranged to slide against each other during the mechanical interactions between the first and the second component. second micromechanical component. The first micromechanical component, at least, is constituted by a watch micromechanical component according to the first embodiment of the invention.

According to a particular embodiment of the second embodiment of the invention, only the first component is in accordance with the first embodiment of the invention; the rectilinear and parallel ridges of the contact zones of the second component being inclined or perpendicular to the direction of sliding. An advantage of this embodiment is to reduce the risk that the respective contact areas will cling to each other.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the present invention will appear on reading the following description, given solely by way of non-limiting example, and with reference to the appended drawings in which:

Figure 1 is a schematic plan view showing a Swiss lever escapement of the prior art;

Figure 2 is a schematic perspective view of an escape wheel corresponding to a first exemplary embodiment of the micromechanical component of the invention; Figure 3A is a schematic plan view showing the pulse plane of one of the teeth of the escape wheel of Figure 2;

Figure 3B is a sectional view along B-B of Figure 3A; Figure 4 is a perspective view of an anchor corresponding to a second exemplary embodiment of the micromechanical component of the invention;

Fig. 5 is a close-up showing in more detail the pulse plan of the entry pallet of the anchor of Fig. 4;

FIG. 6 is a diagrammatic plan view showing a pulse plane which may belong to one of the pallets of an anchor according to a third embodiment of the invention, or alternatively belong to one of the teeth of FIG. an escape wheel according to a fourth embodiment of the invention;

FIG. 7 is a schematic plan view of an embodiment of a contact zone of the second micromechanical component of a timepiece, said contact zone being arranged to slide against a contact zone of the first micromechanical component. of the timepiece, and the first component being constituted by a micromechanical watchmaking piece according to one embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

The invention will be described hereinafter in the context of a Swiss lever escapement. It will be understood, however, that the invention is not limited to this restricted field of application, but rather concerns all exhaust mechanisms, and more generally, all the micromechanical watchmaking devices in which two components are brought to bear. rub against each other.

Figure 1 is a schematic plan view showing a Swiss lever escapement of the prior art. The mechanism represented comprises in particular an escape wheel 3, an anchor 5 and a large plate 7 by the center of which the axis of the balance 9 passes. The two arms of the anchor each end with a pallet 11, 13. The pallets are arranged to cooperate with the teeth 15 of the escape wheel 3. In a conventional manner, the escape wheel is connected to the barrel (not shown) via a gear train (not shown) which engages with the gear wheel. exhaust (referenced 17). The escape wheel is thus urged continuously forward (that is, clockwise as shown in Figure 1). It will be noted that at the instant shown, one of the teeth 15 of the escape wheel 3 is immobilized against the rest plane of the entry pallet 11 of the anchor 5. Driven by the balance, the anchor 5 starts a pivoting movement around the axis 19 in the clockwise direction. Pivoting the anchor clockwise causes the entry pallet to slide upward (in the drawing) against the leading edge of tooth 15. This release phase will end when the rest of the pallet will have ceased to hinder the advance of the front flank of the tooth. Then, it is the flattened top of the tooth 15 (called the tooth impulse plane) which will slide against the underside of the pallet 11 (the impulse plane of the pallet). The angled contact between the two pulse planes will also have the effect of pushing the input pallet 11 upwards, so that the pivoting movement of the anchor 5 in the clockwise direction will be accentuated. This pulse phase will end when the input pallet 11 has been pushed far enough to provide a completely clear passage to the tooth 15. The two successive phases which have just been described during which a tooth 15 of the wheel of exhaust 3 slides against the surfaces of one of the pallets 11, 13 of the anchor 5, each generate considerable friction.

Figure 2 is a schematic perspective view of an escape wheel 53 corresponding to a first particular embodiment of the invention. The escape wheel of this example is a monolithic piece made from a single piece of glass. However, it will be understood that other variants of the invention, the escape wheel may not be glass, but be made of another fragile material. In addition, the escape wheel may not be monolithic, but may consist of several assembled parts. FIGS. 3A and 3B are diagrammatic views respectively in plan and in section of the pulse plane 67 of one of the teeth 65 of FIG. In accordance with the invention, the escape wheel 53 is distinguished from the exhaust wheels of the prior art in that the impulse planes 67 of each of the teeth 65 bear streaks (or crenellations) rectilinear and parallel to the sliding direction. Referring more particularly to FIGS. 3A and 3B, it can be seen that the surface of each of the pulse planes 67 comprises seven parallel ribs (or merlons) (each represented by a thick white line), and that each rib is separated from each other. its neighbors by a streak (represented by a thick black line). In the example illustrated, the ribs and ridges are each 10 microns wide, so that the total width of the pulse plane 67 is 130 microns. It will be noted in passing that the escape wheel 53 is of constant thickness and that its thickness is equal to the width of the pulse planes; that is to say 130 microns. It can also be calculated that the effective contact area during the pulse phase is reduced by 46.2% with respect to an escape wheel of the same size having smooth pulse planes. As already mentioned, the applicant has carried out tests which show that the use of a streaked escape wheel such as that of the present example can lead to a significant reduction in the proportion of the energy which is dissipated because of the friction forces. . Moreover, the particular angular shape of the crenellations and merlons is simple to produce by laser. This makes it possible to obtain a very precise line and to control the depth of the slots thanks to an easy tool to parameterize. This shape also makes it possible to easily control the degree of wear of the watchmaking micromechanical component. As a witness of wear, the shape in merlons and slots allows to know at a glance if, yes or no, the friction has altered the mechanical properties of the micromechanical part by deteriorating the shape of the contact zone.

Figure 4 is a perspective view of an anchor 105 which corresponds to a second particular embodiment of the invention. FIG. 5, for its part, is a close-up showing in more detail the pulse plane 121 of the entry pallet 1 1 1 of the anchor 105. The anchor shown is a monolithic piece manufactured from a single piece of glass. However, it will be understood that according to other variants of the invention, the anchor may not be made of glass, but be made of another fragile material. In addition, the anchor could not be monolithic, but be formed of several pieces assembled. According to the invention, the anchor 105 is distinguished from the anchors of the prior art because the pulse planes 121, 123 of its two pallets 1 1 1, 1 13 have rectilinear striations and are parallel to the direction of rotation. sliding. Referring more particularly to Figure 5, it can be seen that the surface of the pulse plane 121 has seven merlons (or ribs) parallel, and each coast is separated from its neighbors by a slot (or streak). In the illustrated example, the merlons have a width of 12 microns, while the slots have a width of 8 microns, so that the total width of the pulse plane 121 is 132 microns. Similar to what was already the case with the escape wheel of the previous example, the illustrated anchor is of constant thickness. Its thickness is therefore substantially equal to 132 microns. It can also be calculated that the effective contact area during the impulse phase is reduced by 36.4% with respect to an anchor of the same dimension having smooth impulse planes.

Figure 6 is a schematic plan view similar to Figure 3A. The impulse plane that it represents may be that of one of the pallets of an anchor according to a third embodiment of the invention, or alternatively, that of one of the teeth of an escape wheel according to a fourth embodiment of the invention. In the example shown, the pulse plane comprises five parallel rows of eleven lugs each. It will be understood that these five rows are separated from each other by four first grooves which are oriented parallel to the sliding direction. It can further be seen that the pulse plane also has two lateral striations (or shoulders) which are parallel to the first striations, and ten second striations which separate the eleven pins from each row from each other. The second grooves are oriented perpendicular to the direction of sliding, so that they cut the first four ridges and the two lateral striations at right angles and form with them a rectangular network. In the illustrated example, the ridges all have a width of 13 microns, and the lugs have the shape of squares of 10 microns on one side, so that the total width of the pulse plane is equal to 128 microns is that its length is slightly greater than 240 microns.

The micromechanical watchmaking component of the invention may be manufactured using any method that the skilled person deems appropriate. However, advantageously, the part can be made by 3D machining of a piece of silica glass (amorphous quartz). Preferably, the part is manufactured from a piece of transparent silica glass by a femtosecond laser machining process. This method consists in providing a laser producing pulses whose duration is of the order of the femtosecond; focusing the laser beam so as to selectively expose in a desired pattern the volume of a piece of transparent glass; and finally etch the exposed piece of glass with fluoridic acid.

It has been seen that a second embodiment of the invention concerns a mechanical timepiece which comprises a first and a second micromechanical component which are arranged to interact mechanically, the first and second micromechanical components comprising respective contact zones arranged to sliding against each other during the mechanical interactions between the first and the second micromechanical component, and at least the first micromechanical component being constituted by a watch micromechanical component according to the first embodiment of the invention. According to a mode exemplary embodiment of this second embodiment of the invention, only the first component is in accordance with the first embodiment of the invention. As for the second component, it comprises contact zones whose rectilinear and parallel ridges are inclined or perpendicular to the direction of sliding.

FIG. 7 is a schematic plan view of an exemplary embodiment of a contact zone of the second micromechanical component of a timepiece, said contact zone being arranged to slide against a contact zone of the first component micromechanical timepiece, and the first component being constituted by a watch micromechanical part according to an embodiment of the invention. It can be seen that the contact zone represented in FIG. 7 is very similar to that of FIG. 6. However, it can be seen that the rows of pins of the contact zone of the second micromechanical component are inclined by 30 ° relative to the sliding direction. The inclination can vary from 10 ° to 45 °, this advantageously allows a reduction in friction.

It will be further understood that various modifications and / or improvements obvious to those skilled in the art can be made to the embodiments which are the subject of the present description without departing from the scope of the present invention defined by the appended claims. In particular, although the invention has been described in connection with an escapement wheel and an anchor, it is clear that the invention does not only concern the components of the exhausts, but that it relates in a very general way all the watch micromechanical parts.

Claims

1. Watchmaking micromechanical part comprising contact surfaces designed to slide against corresponding contact areas of another micromechanical part in a timepiece, characterized in that

the micromechanical part is made from a fragile material;

said contact surfaces of the micromechanical part are striated, the striations being rectilinear and parallel to the direction of sliding;

the streaks are separated by solid intervals whose width is between 0.5 and 50 microns; preferably between 0.5 and 25 microns;

the area occupied by the full intervals, known as the effective contact area, is between 2 and 70% of the total surface area of the contact surface.

2. Watch micromechanical part according to claim 1, characterized in that, in cross section, the rectilinear and parallel striations have a slot shape, and the full intervals have a merlon shape.

3. micromechanical watchmaking piece according to claim 1 or 2, characterized in that it is a monolithic piece made from a single piece of a fragile material.

4. Horological micromechanical component according to claim 3, characterized in that the fragile material is selected from glasses, silicon, ceramics and polymers.

5. Horological micromechanical component according to claim 3, characterized in that the fragile material is silica glass.

6. micromechanical watchmaking part according to any one of the preceding claims, characterized in that said contact surfaces of the micromechanical part have first grooves parallel to the direction of sliding, and second striations orientation different from those first striations, the first and second streaks together forming a network.

7. Horological micromechanical component according to claim 6, characterized in that the second grooves are oriented perpendicularly to the direction of sliding.

8. Mechanical timepiece comprising a first and a second micromechanical component arranged to interact mechanically, the first and second micromechanical component comprising respective contact zones arranged to slide against each other during the mechanical interactions between the first and the second micromechanical component; characterized in that

at least the first micromechanical component is made from a fragile material;

the contact zones of the first micromechanical component are striated surfaces, the striations being rectilinear and parallel to the direction of sliding.

said streaks are separated by solid intervals whose width is between 0.5 and 50 microns; preferably between 0.5 and 25 microns;

Mechanical timepiece according to claim 8, characterized in that, in cross-section, the rectilinear and parallel striations of the contact zones of the first mechanical component have a slot shape, the intervals between the striations having a shape of merlon.

Mechanical timepiece according to claim 8 or 9, characterized in that the contact zones of the second micromechanical component are striated, the striations being rectilinear and at an angle to the direction of sliding.