CH713160A2 - Timepiece comprising a switching device of a watch mechanism, such as a chronograph mechanism. - Google Patents

Abstract

The timepiece comprises a clock mechanism, such as for example a chronograph mechanism with a clutch device (30) comprising a control member (34) and a switching member (36) which can be alternately switched between two stable positions (engaged state and disengaged state). This timepiece comprises a magnetic system formed of a first bipolar magnet (50) fixed to the switching member, a second bipolar magnet (52) fixed to the support of the switching device so as to present continuously a magnetic interaction with the first bipolar magnet, and at least one high magnetic permeability element (54) forming the control member and being able to move back and forth between two control positions. The switching device is arranged so that, when the high magnetic permeability element is in its first control position, the two magnets generate between them a magnetic repulsion force and so that, when the element with high magnetic permeability is in its second control position, the two magnets generate between them a magnetic attraction force.

Description

Description

Field of the Invention [0001] The present invention relates to a switching device of a clock mechanism between two functional states.

In general, the present invention relates to a timepiece comprising a mechanism that can switch between a first state and a second state, a switching device of this mechanism and an actuating device of this switching device. The switching device comprises a control member actuated by the actuating device and a switching member that can be placed on command from a first stable position, for which the mechanism is in its first state, to a second stable position, for which mechanism is in its second state, and vice versa.

More particularly, the invention relates to a clutch device of a mechanism of a mechanical watch movement.

BACKGROUND OF THE INVENTION [0004] Various clutch devices of a chronograph mechanism are known to those skilled in the art. Patent Application EP 2 897 003 describes a conventional clutch device for a chronograph mechanism. This clutch device comprises an intermediate wheel which, when the clutch is engaged (device in the engaged state), meshes simultaneously with a chronograph wheel and a driving wheel and which, when the clutch is tripped (device in disengaged state), is removed from at least one of these two wheels to break the kinematic chain between them. For this purpose, the clutch device comprises a clutch rocker which carries the intermediate wheel at the end of one of its two arms and which is associated with a first return spring so that the end of the second arm of this clutch rocker remains in support against a column wheel. The column wheel thus forms a kind of cam and the aforementioned end of the clutch rocker forms a cam follower. To actuate this column wheel which alternately controls the clutch and disengagement of the chronograph mechanism, there is provided a large rocker which carries at one end a pivoted ratchet and associated with a second return spring.

The conventional clutch mechanism described above is complex. It comprises several pivoted components including a column wheel which is a complex piece and therefore relatively expensive. The two aforementioned springs generate frictional forces in the areas of mechanical contact provided, which generate wear. In addition, such springs are fragile and may have an elasticity that varies with age. Finally, the various members must be precisely mounted in the timepiece to be functional, including the operating ratchet of the column wheel and the large rocker that causes the reciprocating movement of the pawl. SUMMARY OF THE INVENTION The object of the present invention is to propose a device for switching a watch mechanism of a type different from the aforementioned conventional device and which eliminates several disadvantages of such a conventional device.

For this purpose, the present invention relates to a timepiece comprising a mechanism that can switch between a first state and a second state, a switching device of this mechanism between its first and second states and an actuating device. this switching device. The switching device comprises a control member actuated by the actuating device and a switching member which can switch on command from a first stable position, for which the mechanism is in its first state, to a second stable position, for which mechanism is in its second state, and vice versa. This timepiece comprises: a first bipolar magnet which is fixed to the switching member so as to undergo, when this switching member passes from its first stable position to its second stable position, a movement along a switching path between a first switching position and a second switching position, and vice versa, - a second bipolar magnet which is fixed to the support of the switching device so as to have a continuous magnetic interaction with the first bipolar magnet between its first and second switching positions, - at least one first element with high magnetic permeability forming at least partially the control member.

The control member is arranged so that, when it is actuated repeatedly by the actuating device, the first element with high magnetic permeability undergoes a back-and-forth movement (reciprocating movement) between a first control position and a second control position. The switching device is arranged in such a way that, when the first high magnetic permeability element is in its first control position, the first and second magnets generate between them a magnetic repulsion force over substantially the whole of the switching path and whereby, when the first high magnetic permeability element is in its second control position, the first and second magnets generate between them a magnetic attraction force on at least a part of the switching path, this part being located on the second bipolar magnet.

In a specific embodiment, which will not be described later, a spring of relatively low return force is provided in addition to the magnetic switching device to participate in the displacement of the switching member in one direction and / or to help maintain this switching member in one of its stable positions. In particular, when the switching path is relatively long, such a spring can act on the switching member for, when the first element with high magnetic permeability is in its second control position, move this switching member on a first part the switching path located on the side opposite the second bipolar magnet, until the magnetic attraction force intervenes to attract the switching member towards the second bipolar magnet.

In a preferred embodiment, the magnetic repulsion force has an intensity and a range that are sufficient so that it can actuate only the switching member between its first stable position and its second stable position and then maintain it. in this second stable position; while the magnetic attraction force has an intensity and a range that are sufficient for it to operate alone the switching member between its second stable position and its first stable position and then maintain it in this first stable position.

Thanks to the magnetic system of the invention and in particular to the control member which comprises at least one element with high magnetic permeability movable between two aforementioned control positions, the magnetic switching device defines a bistable system. In addition, in the preferred embodiment, mentioned above, this switching device does not require any return spring associated with the switching member.

In a preferred embodiment, the control member is formed by a rocker pivoted so that the high magnetic permeability element undergoes a rotational movement between two determined angular positions when the control rocker is actuated. Such a rocker is a simpler piece to achieve a column wheel. In particular, the control rocker is pivoted so that the first high magnetic permeability element is rotated between a first angular position and a second angular position respectively defining the first control position and the second control position. Then, when the first element with high magnetic permeability is in its second angular position, this first element is substantially located on an alignment axis defined by the magnetic axis of the second bipolar magnet so that it is substantially between the first and second and second bipolar magnets. By cons, in its first angular position, the first element with high magnetic permeability is spaced from the aforementioned alignment axis.

It will be noted that the actuation of the control rocker does not require a pawl pivoted and associated with a return spring. It will also be noted that the magnetic system makes it possible to avoid any contact between the control member and the switching member.

In an advantageous embodiment, the switching path of the first bipolar magnet is substantially coincident with the alignment axis defined by the magnetic axis of the second bipolar magnet and the first bipolar magnet is arranged with its magnetic axis substantially oriented according to this alignment axis, the first and second bipolar magnets being arranged with their opposite polarities.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described hereinafter in detail with the aid of the accompanying drawings, given by way of non-limiting examples, in which:

Fig. 1 schematically shows a magnetic system whose particular function is put to pro fit in the present invention;

Fig. 2 represents a graph of the magnetic force experienced by a moving magnet of the magnetic system of FIG. 1 as a function of its distance from a high magnetic permeability element forming part of this magnetic system;

Figs. 3 and 4 are plan views of an embodiment of the invention in which a chrono-graph mechanism is switched by a clutch device between an engaged state and a disengaged state;

Figs. 5A to 5D represent various successive phases of an actuation of a control rocker between its two angular control positions;

Figs. 6A to 6D show schematically the magnetic system of the invention in four particular situations with the respective magnetic forces which are exerted on a magnet carried by a clutch rocker; and

Fig. 7 give four torque curves as a function of the angular position of the control lever, these curves showing the torques respectively experienced by this control rocker and the clutch rocker when the latter is either in its engaged position or in its disengaged position.

DETAILED DESCRIPTION OF THE INVENTION [0016] The following will first be described with the aid of FIGS. 1 and 2 a magnetic system which advantageously takes advantage of the present invention to achieve a bistable switching device, without contact between the control member and the switching member and without the need for a return spring to bring and then maintain this body of switching in one and the other of its two stable positions.

The magnetic system 2 comprises a first fixed magnet 4, a high magnetic permeability element 6 and a second magnet 8 which is movable, along an axis of displacement here confused with the alignment axis 10 of these three magnetic elements. , relative to the assembly formed by the first magnet 4 and the element 6. This element 6 is arranged between the first magnet and the second magnet, close to the first magnet and in a specific position relative thereto. In a particular variant, the distance between the element 6 and the magnet 4 is less than or substantially equal to one-tenth of the length of this magnet along its axis of magnetization. Element 6 is made up of, for example, carbon steel, tungsten carbide, nickel, FeSi or FeNi, or other alloys with cobalt such as Vacozet® (CoFeNi) or Vacoflux® (CoFe). In an advantageous variant, this element with high magnetic permeability consists of a metal glass based on iron or cobalt. Element 6 is characterized by a saturation field Bs and a permeability μ. The magnets 4 and 8 are for example ferrite, FeCo or PtCo, rare earths such as NdFeB or SmCo. These magnets are characterized by their remanent field Br1 and Br2.

The element with high magnetic permeability 6 has a central axis which is preferably substantially coincident with the magnetization axis of the first magnet 4 and also with the magnetization axis of the second magnet 8, this central axis being here coincides with the alignment axis 10. The respective magnetization directions of the magnets 4 and 8 are opposite. These first and second magnets therefore have opposite polarities and they are likely to undergo relative movement between them over a certain relative distance. The distance D between the element 6 and the movable magnet 8 is indicated in FIGS. 1 and 2. Note that the axis 10 is provided here linear, but this is a non-limiting variant. The axis of displacement can also be curved, as in the embodiment which will be described later. In the latter case, the central axis of the element 6 is preferably approximately tangent to the axis of curved displacement and thus the behavior of such a magnetic system is, in a first approximation, similar to that of the magnetic system described here. . This is all the more true that the radius of curvature is large relative to the maximum possible distance between the element 6 and the movable magnet 8. In a preferred variant, as shown in FIG. 1, the element 6 has dimensions in a plane orthogonal to the central axis 10 which are greater than those of the first magnet 4 and those of the second magnets in projection in this orthogonal plane. Note that, in the case where the second movable magnet abuts end of stroke against the high magnetic permeability element, the second magnet advantageously comprises a cured surface or a thin layer of hard material on its surface.

The two magnets 4 and 8 are arranged in magnetic repulsion so that, in the absence of the element with high magnetic permeability 6, a magnetic repulsion force tends to move these two magnets away from each other . Surprisingly, however, the arrangement between these two magnets of the element 6 reverses the direction of the magnetic force exerted on the moving magnet when the distance between this movable magnet and the element 6 is sufficiently small, so that the moving magnet then undergoes a magnetic attraction force. Curve 12 of FIG. 2 represents the magnetic force exerted on the moving magnet 8 by the magnetic system 2 as a function of the distance D between the movable magnet and the element with high magnetic permeability 6. It is noted that the moving magnet undergoes, on a first D1 range of the distance D, overall a magnetic attraction force which tends to maintain the magnet 8 against the element 6 or to bring it back to it in case of removal, this overall attraction force resulting from the presence of the element with high magnetic permeability (especially ferromagnetic) which allows a reversal of the magnetic force between two magnets arranged in magnetic repulsion. Then, the element 6 and the two magnets are arranged so that the second magnet 8 undergoes, on a second range D2 of the distance D, globally a magnetic repulsion force. This second range corresponds to distances between the element 6 and the magnet 8 which are greater than the distances corresponding to the first range of the distance D. The second range is limited by a maximum distance Dmax which is generally defined by a limit stop the removal of the moving magnet.

The magnetic force exerted on the moving magnet is a continuous function of the distance D and therefore has a zero value at the distance D \ m for which there is inversion of this magnetic force. This is a remarkable operation of the magnetic system 2 which is implemented in the switching device according to the invention. The inversion distance Dinv is determined by the geometry of the three magnetic parts forming the magnetic system and by their magnetic properties. This inversion distance can therefore be selected, to a certain extent, by the physical parameters of the three magnetic elements of the magnetic system 2 and by the distance separating the fixed magnet from the ferromagnetic element. It is the same for the evolution of the slope of the curve 12, the variation of this slope and in particular the intensity of the attractive force when the moving magnet approaches the ferromagnetic element can thus be adjusted .

With reference to FIGS. 3 to 7, an embodiment of the invention will be described below.

The watch movement 22 comprises a chronograph mechanism 24 partially represented by the chronograph wheel 26. In a conventional manner, this chronograph mechanism can switch between a first disengaged state, that is to say at a standstill, and a second engaged state in which the chronograph wheel 26 is kinematically coupled to the driving wheel 28 of the watch movement. For this purpose, there is provided a switching device of the chronograph mechanism, forming a clutch device 30 of this mechanism, and an actuating device 32 of this clutch device. The clutch device 30 comprises a control member, formed by a control rocker 34 actuated by the actuating device, and a switching member 36 which comprises a clutch rocker 38 mounted on a plate 23, a bridge of flip-flop 40 and a clutch wheel 42 rotated between this rocker and this bridge. The switching member 36 is capable of placing a first stable position on command (FIG 3), in which an arm of the lever 38 bears against the stop 44 and the clutch wheel in an unengaged position. with the chronograph wheel, at a second stable position (FIG 4), wherein the aforementioned arm of the rocker 38 is in abutment against the stop 45 and the clutch wheel in a position meshing with the chronograph wheel; and vice versa.

For this purpose, a first bipolar magnet 50 is attached to a first end of the latch 38 which is pivoted about an axis 46 at its second end. When this switching member moves from its first stable position to its second stable position, the magnet 50 is moved along a switching path defined by the arc of circle traversed by this magnet between its first switching position and its second switching position, respectively corresponding to the first and second stable positions of the switching member. Magnet 50 follows the same path in opposite direction as it moves from its second switching position to its first switching position.

Next, the timepiece 22 comprises a second bipolar magnet 52 which is fixed to the plate 23 so as to present continuously a magnetic interaction with the first bipolar magnet 50 between its first and second switching positions.

According to the invention, the control lever 34 comprises a first element with high magnetic permeability 54 and is arranged so that, when it is actuated repeatedly by the actuating device, the first element at high magnetic permeability is reciprocated between a first control position and a second control position. The control rocker is pivoted so that the first element 54 is rotated between a first angular position (FIG 3) and a second angular position (FIG 4) respectively defining the first control position and the second control position. When the first element 54 is in its second angular position, it is located substantially between the first and second bipolar magnets, so as to form with these two bipolar magnets a magnetic system of the type described above in FIGS. 1 and 2.

Preferably, in its second angular position, the first element 54 is located on an alignment axis 56 defined by the magnetic axis of the magnet 52 so that it is substantially between the first and second magnets bipolar; while, in its first angular position, the first element 54 is spaced from the alignment axis 56. Preferably, as is the case in the embodiment described, the switching path of the bipolar magnet 50 is substantially coincident with the alignment axis 56, so that the two bipolar magnets are substantially aligned along this alignment axis for any position of the magnet 50 along the switching path. Then, the magnet 50 is arranged with its magnetic axis substantially oriented along the alignment axis and so that the first and second bipolar magnets 50 and 52 have their polarities opposite.

In the advantageous variant described with the help of the Figures, see in particular FIGS. 4 and 5D, it will be noted that when, on the one hand, the control lever 34 is in its second control position and the first element 54 is then opposite the second magnet 52 and, on the other hand, the switch 36 is in its second stable position in which the first magnet 50 experiences a magnetic attraction force, this first magnet, the second magnet 52 and the high permeability element 54 are all aligned on the alignment axis 56 that is to say that the respective magnetic axes of these two magnets and the longitudinal axis of the element 54 are parallel and located on the same line. The fact that the alignment axis intercepts the axis of rotation 58 represents an advantageous case, but not necessary.

The control lever 34 further comprises a second element with high magnetic permeability 60 arranged to be substantially aligned with the first and second bipolar magnets 50 and 52 when the first element with high magnetic permeability 54 is in its first position. control (Fig. 3). It will be noted from the outset that this second element 60 is not essential to the invention. Thus, in a particular variant, the control rocker comprises only one element with high magnetic permeability, namely the element 54. However, the second element 60 is advantageous because it serves in particular to partially channel the flow of the second magnet. 52 along the alignment axis 56 when the control rocker is in its first control position and thus to promote its interaction with the first magnet 50 without the element 54 deviates to a large extent magnetic flux magnets in its transverse direction relative to the alignment axis. In addition, this element 60 serves to adjust the magnetic repulsion force and in particular to limit this force. In an advantageous variant, the second element with high magnetic permeability is arranged to be located closer to one or the other of the first and second bipolar magnets irrespective of the position of the first bipolar magnet along the switching path. , so as to have a magnetic repulsion force on the integer of this switching path.

The control rocker comprises a positioning device 62 formed by a pin 66 associated with a positioning spring 64. This spring has two positioning recesses which respectively define the first and second angular positions of the rocker when the pin is housed. successively in these two hollows. The control rocker further comprises an opening 68, between its pivot axis 58 and the first high magnetic permeability element 54, in which the second magnet 52 is arranged, this opening having a contour provided so that the control rocker can freely rotate between its first and second angular positions. In the variant shown, the opening 68 has the shape of an annular sector and the elements 54 and 60 are located opposite this opening relative to the pivot axis, on either side of an axis of symmetry. of the annular opening.

The actuating device 32 comprises a shuttle 72 guided in translation in a translation direction. For this purpose, the shuttle comprises two oblong holes 74 and 75 in which are respectively arranged two rollers 76 and 77 mounted rotating on two shafts fixed to the plate 23. To actuate alternately the lever 34 in the two directions of rotation between its two positions angularly stable, this shuttle comprises, at one end facing a rear portion of the rocker, a leaf spring 78 terminated by an actuating head 80 and extending, in its undeformed position (rest position), along a thrust axis 70 parallel to the direction of translation and advantageously intercepting the pivot axis 58 of the control lever. Then, the rear part of the rocker is located on a side opposite to the first element 54 relative to the pivot axis 58, this rear part having a symmetrical profile with two actuating recesses 85 and 86 respectively located on the left and right sides. other of an axis of symmetry 88, intercepting the pivot axis 58, and whose respective profiles are provided to receive the actuating head 80. The rear portion of the rocker further has a projection 82 which is arranged between the two actuating recesses and which has two symmetrical flanks 83 and 84 respectively leading into the two actuating recesses. The axis of symmetry 88 of the aforementioned rear part passes substantially through the top of the projecting portion 82.

[0031] Remarkably, as shown in FIGS. 5A to 5D, the shuttle 72 and the control lever 34 are arranged so that, when the lever 34 is in any of its two control positions and the shuttle is pushed in the direction of the rocker by means of a 90, the actuating head 80 firstly abuts against one (in Fig. 5A, the flank 84) of the two sides of the projecting portion facing it (see Fig. 5A) and then slides along it. flank, elastically deforming the leaf spring 78, until it is housed in the actuating recess at the bottom of the hollow in question (see Fig. 5B). Then, continuing to push the shuttle along its direction of translation, the actuating head generates a thrust force F1 which produces a moment of force on the rocker to drive it in rotation at least beyond a median angular position between said first and second angular positions (see Fig. 5C), so as to allow the tilting of the control rocker in the other of its two canceled positions (see Fig. 5D). By repeating this operating operation of the rocker, the actuating device of the control rocker allows the tilting of this control rocker alternately between its first and second stable angular positions corresponding to the two control positions of the control rocker.

Note that there is a spring 92 which exerts a restoring force on the shuttle 72. This spring can be replaced by a spring incorporated in a push button associated with the pusher 90 if the latter is integral in translation of the pushbutton. As will be seen later, the switching device according to the invention requires a low thrust force on the pusher so that one can essentially determine the force that a user must apply to change the state of the device. Chronograph mechanism by selecting the return force of the spring associated with the shuttle.

Here are some observations in connection with the preferred embodiment shown in the figures: - The fact that the pin 66 is located on the axis of symmetry 88 is only a symmetrical variant advantageous for the positioning device 62; - The fact that the leaf spring 78 is arranged at rest (in its undeformed state) on the thrust axis 70 of the shuttle is an advantageous variant but not mandatory (indeed, a certain angle between them is possible); - The fact that the axis of thrust, on which is located the leaf spring rest, intercepts the pivot axis 58 and the axis of symmetry 88 has an identical angular offset (in absolute value) with this axis of pushing in the two control positions of the rocker is a preferred variant; - The fact that the alignment axis 56 is parallel to the translation direction of the shuttle is a special case not mandatory; and the fact that the thrust axis 70 coincides with the alignment axis 56 defines an advantageous but not mandatory case.

Referring more particularly to FIGS. 6A to 6D and 7 and in the light of the operation of the magnetic system described above with the aid of FIGS. 1 and 2, will be described below the operation of the clutch device 30. In FIG. 7 are shown four torque curves as a function of the angular position of the control rocker 34, respectively the angular position of the first element with high magnetic permeability 54 between the two stable positions of the control rocker respectively between the two positions of control of the element 54. For the embodiment described with reference to the figures, the 0 ° position corresponds to the second control position of the element 54 while the 20 ° position corresponds to the first control position of this element 54. In the 0 ° angular position of the rocker, the clutch device is engaged or brought into this engaged state. In the angular position 20 ° of the rocker, the clutch device is disengaged or brought into this disengaged state. These four curves represent the torques exerted, on the one hand, on the chronograph rocker 38 and thus on the switching member 36 (curves 100 and 102) and, on the other hand, on the control rocker (curves 104 and 106) when the switching member is held (forcibly) either in its first first stable position (curves 100 and 104), or in its second stable position (curves 102 and 106).

Whatever the position of the switching member, we see that the torque produced by the magnetic force generated by the magnetic system, consisting of two magnets 50 and 52 and two high magnetic permeability elements 54 and 60, passes a negative torque corresponding to a magnetic attraction force when the latch of

Claims (11)

control occupies the 0 ° angular position at a positive torque corresponding to a magnetic repulsion force when this rocker occupies the angular position 20 °. Thus, for the 0 ° angular position of the control rocker, the torque range TR1 exerted on the clutch member is entirely negative, whereas for the angular position 20 ° of this rocker, the torque range TR2 exerting itself on the clutch member is entirely positive. In conclusion, as revealed by the torque curves of FIG. 7, the clutch device is arranged so that, when the first element 54 is in its second control position (FIG 4 and FIG 6A), the first and second magnets 50 and 52 generate between them a force of magnetic attraction (magnetic force in attraction) over the whole of the switching path of the first magnet, and so that, when this first element 54 is in its first control position (FIG 3 and FIG 6C), the first and second second magnets generate between them a magnetic repulsion force (repulsion magnetic force) over the entire switching path. In addition, the magnetic repulsion force is provided with an intensity and a range that are sufficient for it to operate only the switching member 36 between its first stable position and its second stable position, and then that it maintain it in this second stable position; while the magnetic attraction force has an intensity and a range which are sufficient for it to actuate only this switching member between its second stable position and its first stable position, and then it maintains it in this first stable position . Thus, no return spring associated with the switching member is necessary in this preferred embodiment. FIG. 7 shows another advantage of the switching device according to the invention. It is observed that the torque that must be exerted on the control lever is much lower than the torque exerted on the switching member (clutch lever 38). Thus, a user must provide a lower force on the pusher to trigger the clutch function, respectively the disengagement function, in comparison with a conventional mechanical device. It will be noted that, in another variant, the disengaged state and the engaged state are reversed so that the chronograph mechanism is driven when the control member is in one of its two control positions generating a force magnetic repulsion, while it is stopped when this control member is in the other of its two control positions generating a magnetic attraction force. Figs. 6A to 6D are given to show the variation of the magnetic force acting on the magnet 50 integral with the clutch lever 38 as a function of the angular position of the control lever 34. FIG. 6A partially shows the clutch device 30 in its engaged state with the control rocker in its stable clutch position. The magnetic force FM1 is a magnetic attraction force towards the fixed magnet 52, this force being oriented substantially along the alignment axis 56 and has a relatively high intensity because the moving magnet 50 is located the element having a high magnetic permeability 54 (the longer of the two elements 54 and 60) and a short distance thereof, this element 54 also being a short distance from the fixed magnet 52. FIG. 6B shows the transition to a disengaged state of the clutch device by the tilting of the control lever in the clockwise direction. The magnetic force FM2 changes orientation when the flip-flop 34 is pi voted during this passage and becomes a magnetic repulsion force for the movable magnet 50, respectively for the clutch rocker 38 carrying this magnet. Fig. 6G shows the control rocker in its stable disengagement position with the high magnetic permeability element 60 (the shorter of the two elements 54 and 60) substantially aligned with the alignment axis 56. The distance between the element 60 and the movable magnet 50 is relatively large and the magnetic repulsion force FM3 is substantially oriented along the alignment axis Finally, Fig. 6D shows the passage of the clutch device from an engaged state to a disengaged state when the rocker 34 is pivoted counterclockwise, the magnetic force FM4 changes orientation again during this passage to become a magnetic attraction force when the movable magnet 50 approaches the element 54 At the end of pivoting of the control lever, it is again in the configuration of Fig. 6A Thus, a complete cycle of the clutch device according to the invention is completed. A timepiece comprising a mechanism (24) which can switch between a first state and a second state, a device (30) for switching this mechanism between its first and second states and a device (32) for actuating this state. switching device; the switching device comprising a control member (34) actuated by said actuating device and a switching member (36), said switching device being arranged so that the switching member is capable of placing on command of a first stable position, for which the mechanism is in its first state, at a second stable position, for which the mechanism is in its second state, and vice versa; this timepiece being characterized in that it comprises: - a first bipolar magnet (50) which is fixed to said switching member so as to undergo, when this switching member passes from its first stable position to its second stable position a movement along a switching path between a first switching position and a second switching position, and vice versa; - a second bipolar magnet (52) which is fixed to a support of the switching device so as to present continuously a magnetic interaction with the first bipolar magnet between its first and second switching positions, - at least one first element with high magnetic permeability (54) at least partially forming said control member; in that said control member is arranged such that, when actuated repeatedly by the actuating device, the first high magnetic permeability element (54) is reciprocated between a first control position and a second control position; and in that the switching device is arranged so that, when the first high magnetic permeability element is in its first control position, the first and second magnets generate between them a magnetic repulsion force over substantially the entire said path. and when the first high magnetic permeability element is in its second control position, the first and second magnets generate between them a magnetic attraction force on at least a part of the switching path, this part being located on the side of the second bipolar magnet. Timepiece according to Claim 1, characterized in that the magnetic repulsion force has an intensity and a range which are sufficient for it to be able to actuate only the switching element (36) between its first stable position and its second stable position and then maintain it in this second stable position, while the magnetic attraction force has an intensity and range that are sufficient for it to operate alone said switching member between its second stable position and its first stable position and then maintain it in this first stable position. Timepiece according to claim 1 or 2, characterized in that said control member (34) is formed by a control lever which is pivoted so that said first element with high magnetic permeability is rotated between a first angular position and a second angular position respectively defining the first control position and the second control position; in that, when the first high magnetic permeability element (54) is in the second angular position, this first element is substantially located on an alignment axis (56), defined by the magnetic axis of the second bipolar magnet, of way that it is substantially between the first and second bipolar magnets; whereas, in its first angular position, the first element with high magnetic permeability is spaced from said alignment axis. 4. Timepiece according to claim 3, characterized in that the switching path of the first bipolar magnet (50) is substantially coincident with said alignment axis and the first bipolar magnet is arranged with its magnetic axis substantially oriented according to this alignment axis, the first and second bipolar magnets being arranged with their polarities opposite. 5. Timepiece according to claim 3 or 4, characterized in that the control lever comprises an opening (68) between its pivot axis (58) and the first element with high magnetic permeability, said second magnet (52). being arranged in this opening at least when the control rocker is in its second angular position, this opening having a contour provided so that the control rocker can freely rotate between its first and second angular positions. 6. Timepiece according to any one of claims 3 to 5, characterized in that the control lever comprises a pin (66) associated with a positioning spring (64) which has two positioning recesses respectively defining the first and second angular positions of the rocker when the pin is housed successively in these two positioning recesses. 7. Timepiece according to any one of claims 3 to 6, characterized in that said actuating device comprises a shuttle (72) guided in translation in a given direction of translation, this shuttle comprising, at an end facing a rear portion of the rocker, a leaf spring (78) terminated by an actuating head (80) and extending, in its undeformed position, along a thrust axis (70) which is parallel to said translation direction and substantially intercepting the pivot axis of the control lever; in that said rear part of the rocker is situated on a side opposite to said first element with high magnetic permeability relative to said pivot axis, this rear part having a symmetrical profile with two actuating recesses (85, 86) located respectively from on either side of an axis of symmetry (88) substantially intercepting said pivot axis and whose respective profiles are provided to receive the actuating head, a projecting portion (82) being arranged between the two actuating recesses and having two symmetrical flanks (83, 84) respectively leading into the two actuating recesses, said axis of symmetry of the rear portion passing substantially through the apex of the projecting portion; and in that the shuttle and the control lever are arranged in such a way that, when the shuttle is pushed towards the control lever, the actuating head slides first along one of the two sides of the projecting part. facing, elastically deforming said leaf spring, until it is housed in the actuating recess at the bottom of this sidewall, and then this actuating head generates a moment of force on the rocker allowing it to be rotated. at least beyond a median angular position between said first and second angular positions, so as to allow the tilting of the control rocker alternately between its first and second angular positions. 8. Timepiece according to any one of the preceding claims, characterized in that said control member further comprises a second element with high magnetic permeability (60) arranged to be substantially aligned with said first and second bipolar magnets when the first element with high magnetic permeability is in its first control position. 9. Timepiece according to claim 8, characterized in that the second element with high magnetic permeability (60) is arranged to be located closer to one or the other of the first and second bipolar magnets whatever or the position of the first bipolar magnet along said switching path. 10. Timepiece according to any one of the preceding claims, characterized in that said switching member is formed by a clutch device (30) comprising a clutch rocker (38) to which is fixed the first magnet , the first and second stable positions of the clutch rocker being respectively defined by two stops (44, 45) between which pass an arm of this clutch rocker. 11. Timepiece according to claim 10, characterized in that said mechanism is a chronograph mechanism, the actuating device comprising a pusher (90) operable by a user of the timepiece.