MAGNETIC ESCAPE ROTARY PART OF A CLOCK MOVEMENT

Description

Field of invention

[0001] The invention relates to an escape wheel for a magnetic timepiece escapement mechanism, comprising a first surface which is the largest surface of said wheel or one of the largest surfaces of said wheel when said wheel has several, said wheel comprising at least one magnetized track, with a succession of areas according to a running period according to which its magnetic characteristics are repeated, each said area comprising a magnetic ramp with increasing field followed by a magnetic field barrier with increasing field and the field gradient of which is greater than that of said ramp. The invention also relates to a magnetic timepiece escapement mechanism, comprising, subjected to a driving torque, such an escape wheel cooperating indirectly with a sprung balance resonator via a stop.

[0002] The invention also relates to a resonator mechanism, comprising an energy source arranged to drive said escape wheel of a said magnetic escapement mechanism through a gear train.

[0003] The invention also relates to a movement comprising at least one such resonator mechanism.

[0004] The invention also relates to a watch comprising at least one such movement.

[0005] The invention relates to the field of watch regulating mechanisms, and more particularly to field effect escapement mechanisms, without contact or with attenuated contact, of the magnetic or electrostatic type. Background of the invention

[0006] In a Swiss anchor escapement, the escape wheel interacts with the anchor using a mechanical contact force, which generates significant friction and reduces the efficiency of the escapement.

[0007] Patent application EP2887157 in the name of THE SWATCH GROUP RESEARCH & DEVELOPMENT Ltd describes the replacement of this mechanical interaction by contactless forces of magnetic or electrostatic origin, which makes it possible, among other things, to minimize friction losses.

[0008] The practical realization of a magnetic anchor escapement requires varying the interaction energy according to ramps and barriers as described in the document above.

[0009] With regard to the magnetic interaction between mobiles, the prior art mentions the use of discrete magnets interacting with other discrete magnets as for example in document US 3,183,426, or discrete magnets interacting with an iron structure as in documents FR 2,075,383 and GB 671,360. The use of iron is justified by its ease of machining, which makes it possible to produce small structures that are repeated regularly around the circumference of a wheel. However, magnet-magnet interaction is preferred when it comes to advancing the escape wheel in jerks, because the energy required to stop the wheel is greater than for continuous systems. On the other hand, the use of discrete magnets does not easily allow the energy to be varied continuously, smoothly and linearly, to optimally produce ramps such as those described in the document EP2887157 cited above. Summary of the invention

[0010] The invention proposes to design an escapement wheel geometry, in particular an escape wheel, which makes it possible to create a magnetic interaction potential composed of ramps and barriers. This wheel geometry must be achievable with current micromagnet manufacturing technologies.

[0011] To this end, the invention relates to an escapement wheel for a magnetic escapement mechanism of a clockwork, according to claim 1.

[0012] The invention also relates to a magnetic clockwork escapement mechanism, comprising, subjected to a driving torque, such an escape wheel cooperating indirectly with a sprung balance resonator via a stop.

[0013] The invention also relates to a resonator mechanism, comprising an energy source arranged to drive said escape wheel of a said magnetic escapement mechanism through a gear train.

[0014] The invention also relates to a movement comprising at least one such resonator mechanism.

[0015] The invention also relates to a watch comprising at least one such movement. Summary description of the drawings

[0016] Other characteristics and advantages of the invention will appear on reading the detailed description which follows, with reference to the appended drawings, where: there figure 1 represents, schematically and in plan, a magnetic escapement mechanism described in patent application EP2887157, comprising an escape wheel with magnetized tracks, internal and external, cooperating with a polar mass of a magnetic anchor; the figure 2 is a graph relating to the mechanism of the figure 1 , which shows the variation in magnetic interaction energy between the escape wheel and the polar mass of the magnetic anchor included in this mechanism; figure 3 represents, schematically and in plan, a magnetic escape wheel according to the invention, in cooperation with a magnetic anchor cooperating with a balance wheel; the figure 4 represents, schematically and in plan, the arrangement of this escape wheel with a magnetic layer according to the invention; the figures 5, 7, 9 , illustrate the representation in polar coordinates of the magnetic layer relative to the axis of the escape wheel, with respect respectively to the potential ramp, the potential barrier, and the accumulation of the two; the figures 6, 8, 10 respectively illustrate the corresponding associated ramp and barrier shapes; figure 11represents, schematically and in section, a wheel made up of two magnetized layers in order to cancel the axial forces by compensation, both in repulsion with the anchor magnet; the figure 12 represents, schematically and in plan, an advantageous variant where the anchor comprises two polar masses arranged angularly to work alternately, in the extreme angular positions of the anchor, one with the inner track, the other with the outer track; the figure 13 represents, schematically and in plan, narrowings of the magnetized track to optimize the linearity of the ramps of the magnetic interaction potential; the figure 14 represents, schematically and in plan, a zone of mechanical consolidation of the wheel, which comprises a central ring connected by stiffening spokes to some of the barrier pads of the magnetic layer; the figure 15 represents, in a similar way to the figure 11, the use of a ferromagnetic layer, in particular iron, as a magnetic circuit or shield for the wheel; figures 16, 17, 18 , represent, in a similar way to the Figures 5, 7 and 9 , the modification of the profile by the integration of non-linearities, in the form of cusps, so as to compensate for the non-linearities of the magnetic interaction, and the figure 19 represents, schematically and in plan, the corresponding wheel; the figure 20 represents, schematically and in plan, a detail of an anti-shock device produced by mechanical stops on the wheel and on the anchor; the figure 21 represents, schematically and in perspective, the whole of a resonator mechanism, comprising, from a barrel, to the sprung balance resonator, a gear train, and such a magnetic escapement mechanism with magnetic anchor; the figure 22is a block diagram representing a watch comprising a movement equipped with a resonator mechanism with such a magnetic anchor escapement mechanism; the figures 23 and 24 represent, in plan and perspective view, a watch comprising such a magnetic escapement. Detailed Description of Preferred Embodiments

[0017] The invention relates to an escapement wheel 1 for a magnetic escapement mechanism 100 of a watch.

[0018] This mobile 1 comprises a first surface S which is the largest surface of the mobile 1 or one of the largest surfaces of the mobile 1; for example when the mobile 1 is a disk, the first surface S can be its upper face or its lower face.

[0019] This escapement wheel 1 comprises at least one magnetized track 10, with a succession of areas defining a running period PD according to which its magnetic characteristics are repeated, each area comprising a magnetic ramp with increasing field followed by a magnetic field barrier with increasing field and whose field gradient is greater than that of the ramp which precedes it.

[0020] According to one aspect of the invention as claimed, the magnetized track 10 comprises a continuous and closed magnetic layer 4 around the axis of the escapement wheel. More particularly, this magnetic track is closed around the entire periphery of the escapement wheel.

[0021] According to the invention as claimed, this magnetic track is of constant thickness and variable width.

[0022] More particularly, this magnetic track extends over the first surface S of the escapement wheel 1, and has a geometry in projection onto this first surface S which defines the magnetic ramps and magnetic field barriers.

[0023] It is understood that the magnetic field variations can be angular variations of the field, and that the variation of the field gradient between the ramp part and the barriers can also be a variation of the angular component of the field.

[0024] In a particular embodiment, and as illustrated by the figures, the escape wheel 1 is an escape wheel, and comprises at least one ring or one disc or one hollow disc (generally called 'disc') one face of which carries the magnetized track 10, and, in a particular and non-limiting manner, constitutes the first surface S of the wheel 1. In this case, the width of the magnetic layer 4 extends in the radial direction relative to the axis A1 of this disc.

[0025] More particularly, the magnetized track 10 comprises, connected on either side of a boundary F, an internal track 11 and an external track 12 comprising magnetic field barriers staggered with respect to the boundary F, alternating by half a period. In the case of an escape wheel, this boundary F is a circle C, concentric with the two tracks 11 and 12.

[0026] More particularly, the magnetic escapement mechanism 100 for a timepiece comprises, subjected to a driving torque, such an escapement wheel set 1 cooperating indirectly with a sprung balance resonator via a stop 2, which is a pivoting magnetic stop comprising at least one polar mass 20 arranged to cooperate alternately with the internal track 11 and the external track 12 of such a magnetic layer 4.

[0027] There figure 1 illustrates the principle of a magnetic escapement mechanism 100, comprising an escape wheel 1 with magnetized tracks 10, 11 internal and 12 external, separated by a circle C, cooperating with a polar mass 20 of a stop, in particular of a magnetic anchor 2, as described in the document EP2887157 cited above.

[0028] The magnetic interaction energy between the wheel 1 and the polar mass 20 of the anchor 2, in particular comprising at least one magnet, varies as indicated on the graph of the figure 2 showing the PD period on each of the two tracks. The potential barriers 131, 132, indicated ++ on the Figures 1 and 2 , have the effect of stopping the advance of the wheel 1. The energy ramps which extend, on each of the inner tracks 11 and 12 outer, from a region - - to a region + +, and which are seen by the polar mass 20 of the anchor 2 during the rotation of the escape wheel 1, have the effect of accumulating the energy, which is transmitted to a pin 30 of a balance 3 during the tilting of the anchor 2.

[0029] The invention is described here in a particular, non-limiting mode, which is that of a magnetic escapement. It can be implemented in an electrostatic mode, with reference to the document EP2887157 cited above.

[0030] To constitute the ramps and the potential barriers, a first known solution consists of varying the thickness, or the magnetization intensity, of magnets arranged on each of the tracks 11 and 12, to vary the interaction energy with the polar mass 20 of the anchor 2.

[0031] The variation in thickness of the added magnets induces a variation in the air gap between the anchor 2 and the tracks 10, unless these magnets are embedded in the escape wheel 1, so as to present a surface of the same level facing the polar mass 20 of the anchor 2. The development therefore requires combining control of the gradient of the field generated by the magnets of the tracks 11 and 12, and control of the interaction between the polar mass 20 and these magnets in the air gap, which is delicate due to the discontinuities.

[0032] Another alternative which is not part of the invention as claimed, consists of varying the magnetization intensity of the magnets, or of the tracks themselves, which proves difficult to control well.

[0033] In short, these methods are suitable for laboratory tests, but are difficult to adapt for mass production.

[0034] The invention also proposes a solution for industrial implementation that is easier than varying the thickness of the magnets or their magnetization intensity, which consists of using a magnetized layer 4 of constant thickness and magnetization, arranged in the plane of the wheel 1 in a particular surface distribution, and whose geometry is designed so as to produce the desired energy variations composed of ramps and barriers.

[0035] There figure 3presents an example of such a geometry: a magnetized layer 4 is arranged on the escape wheel 1, and constitutes a magnetized track 10, which interacts in a repulsive manner with the polar mass 20 of the anchor 2 which is arranged above the wheel 1. The geometry of the layer 4 is chosen so that the interaction with the polar mass 20 or the magnets of the anchor 2 produces the ramps and barriers necessary for the proper functioning of the magnetic anchor escapement.

[0036] As seen on the figures 3 And 4, this magnetized track 10 formed by the magnetized layer 4 extends, partly at the level of the inner track 11, and partly at the level of the outer track 12, which correspond to the two extreme positions of the polar mass 20 of the anchor 2 (support against the anchors). The inner track 11 has a radial width R1, the outer track 12 has a radial width R2. R0 is the radius of the circle C which separates the inner track 11 and the outer track 12.

[0037] To fully understand the method for designing the geometry of the magnetic layer 4, the figures 5 to 10 illustrate its representation in polar coordinates relative to the axis of the escape wheel 1 in Figures 5, 7, and 9 , with the relative eccentricity of the surfaces as a function of the angle at the center related to the period PD, and respectively the figures 6, 8 and 10 illustrate the corresponding associated ramp shapes and barriers.

[0038] There Figure 5represents two angular periods of the inner 11 and outer 12 tracks with a magnetic layer 4 which follows a continuous periodic path in alternation which is substantially symmetrical, in particular and not limited to triangular, in order to produce the potential ramps. The variation in interaction energy with the polar mass 20 of the anchor 2 is represented in the figure 6 in solid line when the polar mass 20 is on the outer track 12 (position 1) and in broken line when the polar mass 20 is on the inner track 11 (position 2). The interaction energy increases when the superposition of the magnetic track 4 of the wheel 1 and the polar mass 20 of the anchor 2 increases. The profile of the periodic path can, again, be substantially sinusoidal, or other, depending on the desired ramp profiles. The linear profile of this example is advantageous for lowering the minimum maintenance torque CE allowing the escapement to operate.

[0039] In the same way, the figure 7 represents two angular periods of the tracks, inner 11 and outer 12, with a magnetic layer 4 which is composed of discrete barrier pads 41, here made up of rectangular areas, in order to produce the potential barriers. The corresponding interaction energy variation is represented in the figure 8 in solid line when the polar mass 20 is on the outer track 12 (position 1) and in broken line when the polar mass 20 is on the inner track 11 (position 2).

[0040] Finally, the figure 9 represents two angular periods of the inner 11 and outer 12 tracks with a magnetic layer 4 which is the sum of the ramps of the Figure 5 and barriers of the figure 7 . The corresponding interaction energy variation is represented in the figure 10in solid line when the polar mass 20 is on the outer track 12 (position 1) and in broken line when the polar mass 20 is on the inner track 11 (position 2). We see that we obtain what is desired, that is to say ramps followed by potential barriers, which alternate successively on the two tracks 11 and 12.

[0041] Naturally, the discrete barrier pads 41 are rectangular here for ease of modeling. They can also adopt other similar shapes, as long as these shapes remain compatible with the desired magnetic potential distribution.

[0042] When we transform the geometry of the figure 10 in Cartesian coordinates, we obtain the geometry of the magnetic layer represented in the figures 3 And 4 , provided of course that the pattern is repeated as many times as necessary to fill the entire wheel 1. For the non-limiting example of wheel 1 of the figures 3 And 4 we have chosen N = 6 steps per revolution, so that the angular period is PD = 2 Pi / 6. Of course we can choose another value for the number N of steps per revolution. In practice it is advantageous to choose N as large as possible, the upper limit being fixed by the technology used as well as by the air gap between the polar mass 20 of the anchor 2 and the wheel 1.

[0043] It is understood that the geometry of the magnetic layer 4 depends on that of the wheel 1. In particular, if the latter is of small diameter and if N is low, it may be advantageous to have R1 larger than R2, so as to compensate for the curvature, and to obtain identical ramp and barrier profile characteristics on the two tracks 11 and 12. The example in the figures corresponds to the particular case where R1 and R2 are equal.

[0044] Different variants, which can generally be combined, make it possible to further improve the proper functioning of the system. Some allow, in particular, the use of a plurality of very thin magnetic layers 4, which can then be produced by processes other than mechanical, in particular electrochemical, by plasma deposition, or others.

[0045] According to a characteristic of the invention, the magnetic layer 4 extends alternately over the internal track 11 and the external track 12.

[0046] More particularly, the magnetic layer 4 comprises, at each half-period, a barrier pad 41 constituting a magnetic field barrier, extending on one side of the boundary F, and alternately on the internal track 11 and on the external track 12.

[0047] More particularly still, these barrier posts 41 are connected, one after the other, by a strip 40 of width less than the smallest width of the barrier posts 41.

[0048] More particularly, the strip 40 changes concavity on either side of each barrier pad 41, and remains on the same side of the boundary F between two successive barrier pads 41.

[0049] In particular, the strip 40 comprises a narrowing 42 next to each barrier pad 41.

[0050] In particular, the strip 40 includes a turning point 46 between two successive barrier posts 41.

[0051] For the compensation of axial forces at the escape wheel 1, it is advantageous to use a variant of wheel 1 comprising two magnetic layers 4, upper 4S and lower 41, between which the polar mass 20 of the anchor 2 is sandwiched, as shown in the figure 11. Let us recall that the polar mass 20 of the anchor 2 acts in repulsion with the magnetized layers 4S and 4I of the wheel 1. We can naturally design an escape wheel 1 with an even greater number of levels, and an anchor 2 comprising as many polar masses as spaces delimited two by two by the different magnetic layers 4 of the different levels to combine the effects, within the limit of the vertical size authorized by the movement in which the escapement mechanism 100 is integrated.

[0052] Thus, more particularly, the escape wheel 1 comprises a plurality of parallel discs, the faces of which facing each other each carry a magnetized track 10 in symmetry with respect to each other with respect to a median plane perpendicular to the common axis of the discs, and the width of each magnetic layer 4 extends in the radial direction with respect to the axis of the disc. More particularly, the two end discs of this plurality of discs each comprise, on the side opposite the plurality of discs, a ferromagnetic layer constituting a magnetic shield protecting the wheel from external magnetic fields.

[0053] More particularly still, the magnetic escapement mechanism 100 comprises such an escapement wheel 1, and the stop 2 comprises at least one polar mass 20 in each air gap where the parallel discs whose faces face each other each carry a magnetized track 10.

[0054] It is thus possible to have a configuration with several stages of anchor magnets, each anchor magnet working between two specific stages of the escape wheel.

[0055] There figure 12illustrates an advantageous variant where the anchor 2 comprises two polar masses 201 and 202 arranged angularly to work alternately, in the extreme angular positions of the anchor 2, one with the inner track 11, the other with the outer track 12, thus the forces are added. This configuration has many advantages. First of all, the difference in torque due to the difference in radius between the inner track 11 and the outer track 12 is compensated since there is always one of the polar masses of the anchor 2 which is on the inner track 11 while the other is on the outer track 12. Then, the manufacturing irregularities of the wheel 1, from one angular period to the next, are averaged since the polar masses of the anchor do not see the same defects. Finally, the torques transmitted at each alternation are doubled.

[0056] To lower the minimum operating torque CE of the escapement, it is important that the magnetic potential ramp is as linear as possible. For this purpose, small adjustments to the geometry of the magnetic layer 4 can be made. For example, it is advantageous to make a small narrowing 42 of the magnetic layer 4, when the pole mass of the anchor passes in the vicinity of a barrier which is on the adjacent track as shown in the figure 13 These narrowings 42 of the magnetized track make it possible to optimize the linearity of the ramps of the magnetic interaction potential.

[0057] Production is also important in mass production.

[0058] An advantageous method for producing the magnetic layer(s) 4 of the escape wheel 1 consists of using a substrate that provides mechanical strength, and on which the magnetized layer 4 is deposited, which is typically NdFeB or SmCo or Pt and Co alloys. Indeed, as thin layers of rare earth magnets are fragile, it is advantageous to solidify them with a substrate. The layer can be deposited by CVD or PVD type methods or by galvanic growth. The desired geometry can be obtained by placing a removable mask on the substrate before carrying out the deposition, a mask that can be removed subsequently. The layer can also be deposited uniformly on the substrate (CVD, PVD, or glued) and then chemically etched on the unwanted areas. In all these situations, the geometries presented so far can be used because the mechanical strength is provided by the substrate.We understand the interest of multi-level escapement wheels in the case of this method of development.

[0059] Another variant of development concerns the manufacture of the magnetic layer 4 by machining the desired geometry in a thin magnet plate, whether by traditional methods, by laser cutting, by electro-erosion or by chemical attack, it is then advantageous to complete the magnetic layer 4 by stiffeners 44 extending in the central zone of the escape wheel 1, outside the surfaces swept by the anchor 2, in order to ensure the mechanical solidity of the manufactured component. An example is visible in figure 14, where the mechanical consolidation zone, which extends towards the axis A1 of the wheel 1, and essentially outside the inner track 11, comprises a central ring 43 connected by stiffening spokes 44 to some of the barrier pads 41 of the magnetic layer 4. More precisely, the stiffening spokes 44 are connected to the barrier pads 41 of the inner track 11 because these are the parts which are the least sensitive to a disturbing field. The mechanical consolidation zone thus produced makes it possible to ensure mechanical solidity, without significantly changing the potential for magnetic interaction between the anchor 2 and the wheel 1.

[0060] Another variant concerns the use of a ferromagnetic layer 5, in particular iron, as a magnetic circuit or shield for the wheel 1. This layer can also be used as a substrate for the magnetized layer 4 and therefore ensure mechanical strength. figure 15 shows a similar arrangement to that of the figure 11 , where the wheel 1 comprises an outer upper ferromagnetic layer 5S, and an outer lower ferromagnetic layer 5I, each of them carrying respectively the upper 4S and lower 4I magnetized layer. This arrangement makes it possible to best separate the magnetic fields external to the wheel 1 and whose effects on the escapement are to be stopped, from the fields internal to the magnetic escapement mechanism 100, which are necessary for the operation of the escapement.

[0061] It may be necessary to adapt the shape of the ramps of the magnetic layer 4 according to the constitution of the wheel 1, with or without ferromagnetic material, iron in particular. Indeed, the presence of such a shielding in ferromagnetic material introduces non-linearities in the magnetic interaction between the anchor and the wheel. These non-linearities must be compensated to obtain potential ramps that are as linear as possible. As above, variations in the width of the magnetic layer 4 can be introduced by narrowings 42. Another method consists of slightly modifying the shape of the triangular profile visible in the Figure 5 which is used to produce the ramps. For example in the figure 16 this profile is modified by the integration of non-linearities 45, in particular in the form of cusps 46, so as to compensate for the non-linearities of the magnetic interaction. This profile is then combined with the barrier pads 41 of the figure 17to obtain the geometry of the figure 18 in polar coordinates. Finally the geometry is transformed into Cartesian coordinates and we obtain the figure 19 which is an alternative to the geometry of the figure 13 .

[0062] There figure 20 shows a variant with mechanical stops 19 on wheel 1 and additional mechanical stops 29 on anchor 2, to ensure that the system does not unhook in the event of an impact. These stops must be arranged to block the advance of wheel 1 when the polar mass of the anchor crosses a magnetic barrier following an impact.

[0063] In one variant, the anti-detachment stops are of the magnetic type. An advantageous variant thus comprises a small magnet on each point of the anti-detachment star, and a ferromagnetic part on the anchor stop: in this case, during the first rebound, the magnetic attraction makes it possible to dissipate almost all of the impact energy by suddenly stopping the rebounds. The correct pulling position is then resumed thanks to the main magnetic potential (wheel-magnet pallet). In a second variant, the magnets located on each point of the star work in repulsion with magnets located on the anchor anti-detachment stops: in this case, any risk of collision (destroying the stops) is excluded, while leaving more freedom in the design of the magnetic wheel and in the indexing of the star.

[0064] There figure 21shows the whole of a resonator mechanism 200, comprising, from an energy source here comprising a barrel 7, to the balance-spring resonator, with the balance 3 and the balance spring 6, a gear train 8, and such a magnetic escapement mechanism 100 with magnetic anchor 2.

[0065] Naturally, if the examples described concern an escapement wheel consisting of a wheel, the teachings of the invention are applicable to a wheel of any shape, for example the variants of document EP2887157 where the escapement wheel is a cylinder, or a continuous strip, in which case the profile of magnetic layer 4 can be directly that of the figures 9 Or 18 , or even a left escapement mobile, for example and not limited to with fins at the level of the ramps and / or potential barriers.

[0066] The invention also relates to a movement 300 comprising at least one such resonator mechanism 200.

[0067] The invention also relates to a watch 400 comprising at least one such movement 300.

Claims

1. Escape wheel set (1) for a magnetic timepiece escapement mechanism (100), comprising a first surface (S) which is the largest surface of said wheel set (1) or one of the largest surfaces of said wheel set (1) when said wheel set (1) comprises a plurality thereof, said wheel set (1) including at least one magnetized track (10), with a succession of ranges about a period of rotational travel (PD) in which the magnetic features thereof are repeated, each said range including a magnetic ramp followed by a magnetic field barrier jointly arranged to generate, with a pole piece (20) of a stop member (2), an interaction energy with an increasing field for the magnetic ramp and also with an increasing field for said barrier, the field gradient of said latter increasing field being higher than that of the increasing field of the magnetic ramp, said at least one magnetized track (10) being continuous and closed about an axis of said wheel set, extending over said first surface (S) of said escape wheel set (1), and whose geometry, when projected onto said first surface (S), defines said magnetic ramps and magnetic field barriers; characterized in that said magnetized track (10) includes a magnetic layer (4) of constant thickness and magnetization, and of variable width to define at least, on the one hand, the magnetic ramps and, on the other hand, said magnetic field barriers; in that said magnetized track (10) comprises, connected on either side of a boundary (F), an internal track (11) and an external track (12) including said magnetic field barriers staggered with respect to said boundary (F), in alternate half-periods; in that said magnetic layer (4) comprises, at each half-period, a barrier stud (41) forming a said magnetic field barrier, extending substantially on only one side of said boundary (F), the barrier studs being arranged alternately on said internal track (11) and on said external track (12); and in that said magnetic layer (4) extends alternately, essentially over said internal track and said external track between the successive barrier studs.

2. Escape wheel set (1) according to claim 1, characterized in that said magnetized track (10) includes a continuous, closed magnetic layer (4) over the entire periphery of said escape wheel set (1).

3. Escape wheel set (1) according to claim 1 or 2, characterized in that said escape wheel set (1) includes at least one disc of which one face forms said first surface (S) and carries said magnetized track (10), and in that said width of said magnetic layer (4) extends in the radial direction with respect to the axis of said disc which is coincident with said axis of the wheel set.

4. Escape wheel set (1) according to one of the preceding claims, characterized in that said barrier studs (41) are connected, one after the other, by a band (40), the width whereof between these barrier studs is smaller than the smallest width of the barrier studs (41).

5. Escape wheel set (1) according to claim 4, characterized in that said band (40) changes concavity on either side of each said barrier stud (41).

6. Escape wheel set (1) according to claim 5, characterized in that said band (40) comprises a cusp (46) between two successive said barrier studs (41).

7. Escape wheel set (1) according to one of the preceding claims, characterized in that said escape wheel set (1) includes at least one substrate ensuring mechanical strength which is coated with a magnetized layer of NdFeB or of SmCo or of Pt and Co alloys forming the magnetic layer (4).

8. Escape wheel set (1) according to one of the preceding claims, characterized in that said escape wheel set (1) comprises a plurality of parallel discs whose opposite faces each carry a said magnetized track (10) in symmetry relative to each other with respect to a median plane perpendicular to said axis of the wheel set.

9. Escape wheel set (1) according to claim 8, characterized in that the two end discs of said plurality of discs each include, on the side opposite to said plurality of discs, a ferromagnetic layer forming a magnetic shield protecting said wheel set from external magnetic fields.

10. Magnetic timepiece escapement mechanism (100) comprising, subjected to a drive torque, an escape wheel set (1) according to one of the preceding claims cooperating indirectly with a sprung balance resonator via a said stop member (2), characterized in that said stop member (2) is a pivoting magnetic stop member comprising at least said one pole piece (20) arranged to cooperate alternately with said internal track (11) and said external track (12), said magnetic layer (4) generating a said first increasing field for said pole piece along each said magnetic ramp, said barrier studs defining, for said pole piece, a said second increasing field, the field gradient whereof being higher than that of the magnetic ramps.

11. Magnetic escapement mechanism (100) according to claim 10, characterized in that said stop member (2) comprises two pole pieces (201; 202) angularly arranged to work alternately, in the extreme angular positions of said stop member (2), one with said internal track (11), and the other with said external track (12).

12. Magnetic escapement mechanism (100) according to claim 10 or 11, characterized in that said escape wheel (1) includes mechanical stops (19) and in that said stop member (2) includes complementary mechanical stops (29) for preventing any dislocation in the event of a shock.

13. Resonator mechanism (200) including an energy source (7) arranged to drive, via a gear train (8), said escape wheel (1) of a said magnetic escapement mechanism (100) according to any of claims 10 to 12.

14. Timepiece movement (300) including at least one resonator mechanism (200) according to claim 13.

15. Watch (400) including at least one movement (300) according to claim 14.