CH717941A2 - Magnetic retraction solenoid micro-actuator. - Google Patents

Abstract

The invention relates to a magnetic micro-actuator (100) comprising a coil (6) controlling the axial displacement of a slider (30) comprising at least one permanent magnet (2) contiguous or aligned with a rear shaft (42) ferromagnetic or magnetized and guiding the field lines of the magnetic field of revolution in the axial direction (D) through the coil (6) in which the slider (30) circulates, as far as a rear end (43) of the said rear shaft (42 ) which tends to cooperate by magnetic attraction with at least a first ferromagnetic restoration element (8), located in the vicinity of a rear face (25) of the structure (20) of the micro-actuator (100), to return said slide (30) in a rear limit position when no coil (6) is energized. Such a micro-actuator can for example be integrated into a watch to provide various functionalities.

Description

Field of the invention

The invention relates to a magnetic micro-actuator comprising at least one structure containing at least one coil arranged to exert, in a powered position, an axial thrust force on a slider, which said micro-actuator comprises, in a direction axial in a first direction, up to a front end-of-travel position corresponding to an abutment bearing between a first bearing surface of said structure and a first abutment surface of said slider in which end-of-travel position before a shaft front, which said slider comprises, protrudes from a front face of said structure, and, when no said coil is energized, said slider is movable in said axial direction in a second direction opposite to said first direction, and is returned by purely magnetic means towards a rear limit position corresponding to an abutment bearing between a second bearing surface of said structure and a second surface stop of said slider.

The invention also relates to a printed circuit comprising at least one such micro-actuator.

The invention also relates to a watch comprising at least one such micro-actuator and/or at least one such printed circuit.

The invention relates to the field of micro-mechanical actuation systems, in particular for the field of watchmaking.

Background of the invention

[0005] Conventional solenoid actuators are often poorly suited to micro-mechanics, and in particular to watchmaking. Indeed, they must meet the constraints of actuation and return time, as well as the very small dimensions required by applications, in particular watchmaking.

[0006] The use of return springs penalizes the size of the micro-actuator, and does not guarantee optimum hold over time.

Summary of the invention

[0007] The aim is to develop a micro-actuator capable of applying a controlled mechanical braking force, in particular for micro-mechanical applications and in particular watchmaking.

[0008] A particularly interesting application relates to braking, which, in micro-mechanics and in particular in watchmaking, requires an extremely short reaction time, as well as an extremely short return time to the rest position.

[0009] It is therefore a question of perfecting a conventional solenoid actuator, so as to meet the constraints of actuation and return time, as well as the very small dimensions required by applications in particular watchmaking.

To this end, the invention relates to a magnetic micro-actuator according to claim 1.

The invention also relates to a printed circuit comprising at least one such micro-actuator.

The invention also relates to a watch comprising at least one such micro-actuator and/or at least one such printed circuit.

Brief description of the drawings

Other characteristics and advantages of the invention will appear on reading the detailed description which follows, with reference to the appended drawings, where: FIG. 1 represents, schematically and in perspective, a micro-actuator according to the invention, comprising a block structure, here composed without limitation of a front casing and a rear casing, which surrounds a coil forming a stator, in which a slider is movable, which comprises a permanent magnet and a shaft, the micro-actuator also comprises a first ferromagnetic restoration element, here in the particular form of a soft ferromagnetic ring, fixed to the rear of the rear case, on the side opposite the front casing which has an opening through which the slider can protrude; FIG. 2 represents, schematically and in exploded perspective, the micro-actuator of FIG. 1; FIG. 3 represents, schematically and in section along the plane P passing through the axis AA of FIG. 1, the micro-actuator of FIG. 1, in a first variant where the slider comprises a front shaft and a rear shaft non-magnetic or soft ferromagnetic, and is in the actuated position; FIG. 4 represents, similarly to FIG. 3, a second variant where the slider comprises a one-piece permanent magnet shaft, and is in the retracted position; FIG. 5 is a field diagram resulting from a finite element simulation of the magnetic field for the micro-actuator of FIG. 3; the field lines of the permanent magnet are guided through the front shaft and the rear shaft of the slider; the coil supplied with current drives the slider, comprising the front shaft, the rear shaft, and the magnet, in a positive Z direction; when the current in the coil is cut off, the ferromagnetic restoration element, in particular the soft ferromagnetic ring, produces a force in the opposite direction, which acts on the slider and brings it back to its initial position; the displacement stroke is indicated by dashed lines; FIG. 6 is a diagram illustrating, for the micro-actuator of FIG. 3, the variation in the force, represented on the ordinate, acting on the slider when it is moved along the Z axis, in the direction AA, as a function of the displacement D shown on the abscissa; the continuous line illustrates the variation of the positive force exerted by the coil when a current passes through it; the broken line illustrates the variation in the restoring force imposed by the ferromagnetic restorative element; FIG. 7 is a diagram illustrating, for the micro-actuator of FIG. 3, and for the force profile illustrated by FIG. 6, on the one hand in broken line the variation of the displacement of the slider, along the axis Z, in the direction AA, as a function of time t represented on the abscissa, and on the other hand in continuous line the variation of the speed of the slider as a function of time t; FIG. 8 is another diagram illustrating, for the micro-actuator of FIG. 3, and for the force profile illustrated by FIG. 6, on the one hand in broken line the variation of the displacement of the slider, along the axis Z, along the direction AA, as a function of time t represented on the abscissa, and on the other hand in continuous line the variation of the force as a function of time t; Figure 9 is, similarly to Figure 5, a field diagram resulting from a finite element simulation, of the magnetic field generated by a permanent toroidal magnet integral with the shaft, which has extensions at its ends d permanent magnet; this finite element simulation relates to the slide only, and does not include the coil or the rear ferromagnetic ring; FIG. 10 represents, schematically, partially, and in section passing through the axis of the slider, a slider surrounded by two coils, which, according to their current supply, make it possible to establish around the slider magnetic fields in opposite directions or of the same meaning; FIG. 11 shows, schematically, partially, and in section passing through the axis of the slider, a slider on a single side of which are arranged two coils, in an instantaneous current supply situation where these two coils create fields magnets of complementary effect, and of the same direction; FIG. 12 represents, schematically, partially, and in section passing through the axis of the slider, similarly to FIG. 3, a micro-actuator comprising a second ferromagnetic restoration element, in the front part of the structure, at opposite the first ferromagnetic restoration element, and which is arranged to cooperate with the front end of the front shaft for its return; FIG. 13 represents, analogously to FIG. 12, a micro-actuator of substantially symmetrical construction, comprising a coil on each side of the permanent magnet carried by the slider; Figure 14 is a detail of the rear part of a micro-actuator according to the invention, in which the first ferromagnetic restoration element is a solid element; Figure 15 is a detail of the rear part of another micro-actuator according to the invention, in which the first ferromagnetic restoration element comprises two ferromagnetic rings of different diameters and substantially coplanar; FIG. 16 represents, schematically and in perspective, a micro-actuator according to the invention, comprising a juxtaposition of structures each containing a slider and the associated coil or coils, in an arrangement where the projection of different sliders corresponds to a matrix coding; FIG. 17 is a block diagram representing a micro-mechanism, in particular a watch, comprising a first micro-actuator according to the invention, forming part of a printed circuit, and whose slider is arranged to actuate a component of a another mechanism such as a clockwork, and a second micro-actuator according to the invention, the slider of which is arranged to stimulate the epidermis of a user by projecting out of the case of this micro-mechanism.

Detailed Description of Preferred Embodiments

The present invention describes a linear solenoid electromagnetic micro-actuator, or plunger micro-actuator, which uses a magnetic element to retract the armature, also called the plunger core, and referred to here as the slider. The aim is to make a miniature mechanical braking element with as few parts as possible and without a mechanical spring element.

[0015] Solenoid actuators are well known in the field of general mechanics, in particular for controlling mechanisms. Most have a slider return spring, which limits their performance, particularly when it comes to the duration of an operating cycle. They are difficult to miniaturize, and are not used for personal equipment.

[0016] The aim is to develop a micro-actuator capable of applying a controlled mechanical braking force, in particular for micro-mechanical applications and in particular watchmaking.

[0017] A particularly interesting application concerns braking, which, in micro-mechanics and in particular in watchmaking, requires an extremely short reaction time, as well as an extremely short return time to the rest position.

[0018] It is therefore a question of perfecting a conventional solenoid actuator, so as to meet the constraints of actuation and return time, as well as the very small dimensions required by applications in particular watchmaking.

The micro-actuator device 100 according to the invention is illustrated by Figures 1 and 2. It forms a block structure, here not limited to a front housing 10 and a rear housing 12. This rear housing 12 surrounds a coil 6, which forms the stator, and a slider, which comprises at least one permanent magnet 2 and a shaft 4. This shaft 4 can be in one piece, or divided into several aligned parts, for example a front shaft 41 and a rear shaft 42 on either side of the permanent magnet 2 as seen in Figure 3. A first ferromagnetic restoration element 8, including but not limited to a soft ferromagnetic ring, is attached to the rear of the rear housing 12 , on the side opposite the front casing 10. The micro-actuator device assembly 100 is here held assembled, in a non-limiting manner, by two pins 14.

[0020] The micro-actuator 100 operates similarly to a solenoid actuator. When an electric current is applied to the coil 6, a force is generated which pushes the magnet 2 back and pushes the shaft 4 forward, in a positive Z direction, towards the front housing 10. The maximum displacement is determined at the end of travel by a limit stop, for example the contact of the magnet 2 with the front housing 10. If the current is reversed, the slider is retracted to the initial position defined by the point of contact between the slider and the stator (coil 6).

In some applications, it is advantageous to apply a current in one direction only (unipolar drive). In this case, two options for the return of the slider can be envisaged: for the general case where the micro-actuator 100 is intended to operate in several orientations, as in the case of a watch, one can use at least one first ferromagnetic element 8, represented by a ring in figures 1 to 4; this ferromagnetic element 8 can also be a block or a disk. In a very particular case, in particular static, where the micro-actuator 100 is positioned such that the slider 30 always moves upwards in a vertical direction, the necessary restoring force can be provided by the weight of the slider 30 which is pulled down by the gravity field. This arrangement can only be used for static installations, such as clocks. In the general case, a return force must be generated to ensure the recoil of the slider towards a rest position.

Figures 3 and 4 are cross sections of such micro-actuators 100 of different construction, Figure 3 illustrates the deployed (actuated) state of a slider 30 comprising a front shaft 41 and a rear shaft 42 both ferromagnetic, and FIG. 4 illustrates the retracted position (stop) of a slider 30 with a single one-piece shaft 4 uniting the front shaft 41 and the rear shaft 42 and forming a permanent magnet.

In a variant such as Figure 3 with a front shaft 41 and a rear shaft 42, it is essential that the rear shaft 42 is ferromagnetic in order to guarantee the necessary actuation and retraction forces. The front shaft 41 can itself be ferromagnetic or non-magnetic. The front shaft 41 is more particularly intended to establish physical contact with a target object, generally placed at less than 0.5 mm from the micro-actuator 100.

[0024] This target object may consist of an element of a mechanism, in particular a display mechanism, or an oscillator, for example a pendulum, or else the epidermis of a user for a device haptic feedback, or whatever.

[0025] The range of movement, and therefore the position of the target, can of course be adjusted according to the application. It must be ensured that even with a longer stroke the actuating and restoring forces are correctly adjusted.

In a variant like that of Figure 4, the shaft 4 and the magnet 2 constitute a one-piece element. Here again, the front part forming the front shaft 41 of the shaft 4 can be non-magnetic, but it is advantageous for the rear part forming the rear shaft 42 of the shaft 4 to be made of magnetized material.

FIG. 5 illustrates the appearance of the magnetic field lines for the variant with a soft ferromagnetic front shaft 41 and rear shaft 42 of the micro-actuator 100 of FIG. 3, with a cylindrical magnet 2 and a first element of annular ferromagnetic restoration 8. This figure 5 is the result of a finite element simulation with radial symmetry. The rear shaft 42 guides the field lines from the magnet 2 to the coil 6 and to the first restoration element 8. The field lines from the permanent magnet 2 are guided through the front shaft 41 and the rear shaft 42. Coil 6 drives slider 30 in the positive Z direction. If the current in the coil is interrupted, the first ferromagnetic restoration element 8, in particular a soft ferromagnetic ring, produces a force in the opposite direction, which acts on the slider 30 and brings it back to its initial position. The travel distance δ is indicated by dashed lines; in this example the displacement stroke is 0.5 mm.

The finite element simulation is used to obtain the force as a function of the displacement for the cases of coil 6 de-energized (0 V) and coil 6 energized (2.5 V). The calculated forces are illustrated in the graph of FIG. 6. This FIG. 6 illustrates, for the micro-actuator of FIG. 3, the variation of the force, represented on the ordinate, acting on the slider 30 when it is moved along of the axis Z, in the direction AA, as a function of the displacement D shown on the abscissa; the continuous line illustrates the variation of the positive force exerted by coil 6 when a current passes through it; the broken line illustrates the variation of the restoring force imposed by the ferromagnetic ring 8.

When the current is off, according to the curve in broken lines, the force is negative (retraction) and decreases when the slider 30 moves forward. It is important to note that even at maximum extension, the force remains both sufficient to restore and retract slider 30, and in this configuration is on the order of minus 0.1 mN. The force required is defined by the static friction between the slider 30 and the stator, defined by the points of contact between the shafts and the casing as described in detail below, and the force of gravity. The force profile for the walking state, according to the solid line curve, is positive, close to 0.5 mN. The starting force remains high and even increases by more than 20% when the slider 30 slides forward. This is the result of the presence, at the rear, of the soft ferromagnetic rear shaft 42, which ensures that a large field and a large field gradient, generated by the magnet 2, combine with the coil 6 .

To obtain the dynamics from the calculated forces, the differential equation of such a system is integrated on the desired time scale. The results are shown in Figures 7 and 8.

The plots are generated for a slider 30 with a mass of 0.015 g and an actuation pulse of 2.5 V for 4 ms, and correspond to the force profile illustrated by FIG. 6 commented on above. The maximum displacement is fixed at 0.3 mm. This corresponds to an impact with an object by the front shaft 41, since the device itself has a maximum possible displacement of δ=0.5 mm. As seen in figure 7, during the impact, there is a rebound after a small indentation. The graphs indicate that shaft 4 reaches its target after about 5 ms at a speed of 120 mm/s. The impact velocity and the mass of the mobile define the contact force, and the rebound defines a momentum. When the supply to coil 6 is stopped, even before impact, slider 30 returns to the rest position in 5 ms. The return is ensured by the ferromagnetic ring 8, but also by the rebound, which can occur during contact. The rebound is beneficial because it avoids static friction, which could prevent slider 30 from returning.

[0032] Figure 8 illustrates displacement and force as a function of time. It is clearly visible that once the actuating current of the coil 6 is cut off, the slider 30 begins to slow down because the force is negative. However, the point of impact is still reached. Since there is a restoring force, the slider 30 returns to its starting position and possibly bounces several times depending on the damping at the point of contact. It is important that once stopped, the slider 30 is still firmly held in place by the holding force exerted between the first ferromagnetic restoration element 8 and the slider 30. In this example, the holding force is d 'about 0.5 mN, which is sufficient to maintain a stable rest position even in the event of small vibrations and shocks.

Figure 9 illustrates the magnetic field generated by a slider 30 made entirely of a permanent magnet, which has permanent magnet extensions at both ends of the shaft. In this configuration, the shafts and the magnet are one piece. The shading illustrates the Bzpositive (white) and negative (gray) areas. The field lines are very similar to those obtained with the composite magnet-ferromagnetic shaft slider.

[0034] Friction is a limiting factor. Friction is a concern and the design must ensure that the shaft slip is effective. Friction should be minimized with a front shaft 41 and a rear shaft 42 perfectly aligned, held in position by the guide openings made in the housings 10 and 12. The friction between the materials making up the shaft and the casing must be minimized by matching low friction materials or adding lubricating coatings. Another more expensive solution, in keeping with watchmaking traditions, is to match stones (rubies) with a metal or ceramic shaft. Sufficient clearance between the outside diameter of the shaft and the inside diameter of the coil ensures that no contact is made between the shaft and the coil. The same is true with regard to the clearance between the shaft and the structure 20 of the micro-actuator, and between the outer diameter of the magnet 2 and the cavity of the structure 20, so that the magnet 2 does not not touch this structure 20. Naturally the calculation of each gap takes into account the total operating temperature range of the device.

The communication of information to a user generally uses the senses of sight and hearing. The other classic senses, smell, taste, and touch, on the other hand, are little used. Haptic feedback is currently an active area of research, with many variations.

[0036] Thus such a micro-actuator can be used for other applications, in particular in the field of feedback haptics such as a Braille display, for tact reading. Text coding for the use of the blind by characters in raised or reentrant relief were developed from the 14th century, by Zayn Ud Dîn AI Alidî, then in the 15th century by Francesco Lana de Terzi, and in the 18th century by Valentin Haüy , founder of the first school for the blind. The reading codes were perfected in the 19th century by Charles Barbier de la Serre, for a military application of writing or night reading, then by Louis Braille, whose code became universal. Abraham-Louis Breguet made, also in the 18th century, tact watches, with protruding pins, to allow the time to be read in the dark.

[0037] The use of the sense of touch is currently an active area of research with many variations. In particular, we tend to distinguish cutaneous perception at the level of the epidermis, and so-called haptic perception, which is concerned with the combination of information provided by the nervous and muscular system of the individual with information specific to this local cutaneous perception. , and which makes it possible to more broadly define an object, its movements, or its deformations. This haptic perception can also be combined with information provided by other senses of the individual, such as the perception of temperature for example.

The micro-actuator according to the invention facilitates tact reading, due to its small dimensions. It allows, in particular, to repeat the same signal with a particular frequency, indeed certain frequencies increase the stimulation for tactile applications, which also makes it possible to reduce the force of impact necessary.

This micro-actuator can still be used in portable electronics, in particular for personal equipment, as a mechanical signaling system, for example to exert pressure or percussion on a limb to indicate a notification, an alarm , a telephone call or the arrival of a message, the crossing of a particular threshold of a physical quantity such as a level of radioactivity, or other.

More particularly, and as illustrated by the figures, the invention thus relates to a magnetic micro-actuator 100 comprising at least one structure 20 containing at least one coil 6, 61, 62.

This coil 6, 61, 62, is arranged to exert, in a powered position, an axial thrust force on a slider 30, which includes the micro-actuator 100, in an axial direction D in a first direction, until at a forward limit position corresponding to an abutment bearing between a first bearing surface 21 of the structure 20 and a first abutment surface 31 of the slider 30.

[0042] In this front end position, a front shaft 41, which the slider 30 comprises, projects out of a front face 24 of the structure 20.

And, when no coil 6, 61, 62 is energized, the slider 30 is movable in the axial direction D in a second direction opposite to the first direction, and is returned by purely magnetic means to an end position. rear stroke corresponding to an abutment support between a second bearing surface 22 of the structure 20 and a second abutment surface 32 of the slider 30.

According to the invention, the slider 30 comprises at least one permanent magnet 2 contiguous with a rear shaft 42 aligned with the front shaft 41, or constituting at least a part of the rear shaft 42. This at least one magnet permanent 2 generates a magnetic field of revolution around the axial direction D.

The rear shaft 42 is ferromagnetic or magnetized, and is arranged to guide the field lines of the magnetic field of revolution substantially in the axial direction D through this at least one coil 6, 61, 62, in which circulates the slider 30, as far as a rear end 43 of the rear shaft 42 which tends to cooperate by magnetic attraction with at least one first ferromagnetic restoration element 8.

This first ferromagnetic restoration element 8 is located in the vicinity of a rear face 25 of the structure 20, opposite the front face 24, and is arranged to cooperate with the magnetic field created by the permanent magnet. 2, to recall the slider 30 to its rear limit position when no coil 6, 61, 62 is energized.

More particularly, this at least one permanent magnet 2 is interposed between the front shaft 41 and a rear shaft 42 aligned with the front shaft 41.

More particularly, this at least one permanent magnet 2 is integral with the front shaft 41 and/or with the rear shaft 42.

More particularly, this at least one permanent magnet 2 comprises the first abutment surface 31 of the slider 30 and/or the second abutment surface 32 of the slider 30. Even more particularly, this at least one permanent magnet 2 projects radially relative to the front shaft 41 and/or the rear shaft 42, and forms a collar carrying the first abutment surface 31 and/or the second abutment surface 32 of the slider 30.

[0050] More specifically, at least one first ferromagnetic restoration element 8 is of revolution around the axial direction D, and arranged to surround the rear shaft 42 without contact when it moves back into the rear end-of-travel position.

[0051] More particularly, at least one first ferromagnetic restoration element 8 is of revolution around the axial direction D, and comprises a front abutment surface, which is arranged to cooperate in abutment support with the rear shaft 42 during its recoil in the rear limit position.

More particularly, at least one permanent magnet 2 is contiguous with the front shaft 41, or constitutes at least a part of the front shaft 41, this at least one permanent magnet 2 generating a magnetic field of revolution around the axial direction D; this front shaft 41 is ferromagnetic or magnetized, and is arranged to guide the field lines of the magnetic field of revolution substantially along the axial direction D as far as a front end 45 of the front shaft 41, which tends to cooperate by magnetic attraction with at least one second ferromagnetic restoration element 9, located in the vicinity of the front face 24 of the structure 20, to return the slider 30 to its rear limit position when no coil 6, 61, 62 is supplied .

More particularly, the structure 20 comprises at least one coil 6, 61, 62, connected to a bidirectional current supply.

More particularly, the structure 20 contains a plurality of coils 6, 61, 62. The current supply mode of these coils can make it possible to create magnetic fields of the same direction in the axial direction D, or else to create opposite magnetic fields. It is therefore the polarization of the power supply which determines the mode of operation.

More particularly, at least two coils 6, 61, 62 are on either side of this at least one permanent magnet 2 of the slider 30.

More particularly, at least two coils 6, 61, 62 are on either side of all the permanent magnets 2 that the slider 30 has.

More specifically, the micro-actuator 100 comprises a plurality of structures 20, which are joined by side faces and together form a block 200 with a matrix of sliders 30 arranged to project from at least a first side of the block 200 .

The stroke of the slider 30 obviously depends on the sizing of the micro-actuator 100. For watchmaking applications, a stroke of the order of a millimeter, in particular less than or equal to 1.0 mm, or even a fraction of a with many applications.

More particularly, in a non-limiting execution, corresponding to an embodiment illustrated by the diagrams of the figures, the micro-actuator 100 is a watch component and comprises at least one slider 30 with a stroke less than or equal to 0.5 mm, and which is arranged to give a stop or adjustment pulse to another component comprising a resonator, or an escapement mechanism, or a display mechanism, of a watch. Among the advantageous horological applications, mention may be made of the stop-seconds, the triggering or stopping of a chronograph, the setting of the time, the adjustment of the calendar, the percussion of a gong or a gong in a striking mechanism, or the like.

[0060] More specifically, the micro-actuator 100 is a component of a portable device in contact with the skin of a user, and comprises at least one slider 30 which is arranged to give at least one impulse per touch to give a warning signal to a user, and/or to transmit a series of coded pulses to the user.

More specifically, the micro-actuator 100 comprises a plurality of sliders 30 arranged to transmit to the user a series of pulses geometrically spaced from each other.

The invention also relates to a printed circuit 400 comprising at least one such micro-actuator 100, in the form of an SMD component soldered to the plate of the printed circuit 400.

[0063] More particularly, the printed circuit 400 comprises at least one supply circuit for a coil 6, 61, 62, of a micro-actuator 100. More particularly still, the printed circuit 400 comprises a supply circuit for each coil 6, 61, 62, which each micro-actuator 100 carries on the printed circuit 400.

The invention also relates to a watch 1000 comprising at least one such micro-actuator 100, and/or at least one such printed circuit 400, and at least one energy source 600 to supply current to at least one coil 6 , 61, 62, of a micro-actuator 100, and/or at least one movement 500 comprising at least one energy source 600 to supply current to at least one coil 6, 61, 62, of a micro-actuator 100.

In sum, the invention describes an electromagnetic actuator which can be used to apply a braking force or a haptic feedback. It can be set in motion by a unipolar voltage source since the restoring force is provided by a first ferromagnetic restoration element 8, such as in particular a ring of soft ferromagnetic material.

The micro-actuator according to the invention thus has several advantages.

In the absence of actuation, the retracted position is stable and well defined. This ensures that braking is only applied during the „on“ state, even in the event of mechanical disturbances such as vibrations or shocks.

The invention is advantageous in any configuration requiring extremely rapid return of the plunger slide.

[0069] It is not necessary to apply power to maintain the retracted position.

[0070] The proposed geometry is also intrinsically resistant to shocks because the slider 30 is strongly constrained with a single dimension of freedom.

The proposed device is very compact and comprises only one mobile component. No spring is needed.

The micro-actuator 100 can be manufactured as an SMD component for easy integration on a standard printed circuit, which guarantees great ease of installation and a moderate cost.

Claims (21)

1. Magnetic micro-actuator (100) comprising at least one structure (20) containing at least one coil (6; 61; 62) arranged to exert, in a powered position, an axial thrust force on a slider (30), that said micro-actuator (100) comprises, in an axial direction (D) in a first direction, up to a front end-of-travel position corresponding to abutment bearing between a first bearing surface (21) of said structure (20) and a first abutment surface (31) of said slider (30) in which front limit position a front shaft (41), which said slider (30) comprises, projects out of a front face ( 24) of said structure (20), and, when no said coil (6; 61; 62) is energized, said slider (30) is movable in said axial direction (D) in a second direction opposite to said first direction, and is returned by purely magnetic means towards a rear end-of-travel position corresponding to a stop press between a second bearing surface (22) of said structure (20) and a second abutment surface (32) of said slider (30), characterized in that said slider (30) comprises at least one permanent magnet (2) contiguous with a rear shaft (42) aligned with said front shaft (41), or constituting at least a part of said rear shaft (42), said at least one permanent magnet (2) generating a magnetic field of revolution around said axial direction (D) , which rear shaft (42) is ferromagnetic or magnetized and is arranged to guide the field lines of said magnetic field of revolution substantially in said axial direction (D) through said at least one coil (6; 61; 62) in which said slider (30) circulates, as far as a rear end (43) of said rear shaft (42) which tends to cooperate by magnetic attraction with at least a first ferromagnetic restoration element (8), located in the vicinity of a rear face (25) of said structure (20), opposite said front face (24), to return said slider (30) to its said rear limit position when no said coil (6; 61 ; 62) is powered. 2. Micro-actuator (100) according to claim 1, characterized in that said at least one permanent magnet (2) is interposed between said front shaft (41) and a rear shaft (42) aligned with said front shaft (41) . 3. Micro-actuator (100) according to claim 1 or 2, characterized in that said at least one permanent magnet (2) is integral with said front shaft (41) and/or with said rear shaft (42). 4. Micro-actuator (100) according to one of claims 1 to 3, characterized in that said at least one permanent magnet (2) comprises said first abutment surface (31) of said slider (30) and/or said second abutment surface (32) of said slider (30). 5. Micro-actuator (100) according to one of claims 1 to 4, characterized in that said at least one permanent magnet (2) projects radially with respect to said front shaft (41) and/or said rear shaft (42 ), and forms a collar carrying said first abutment surface (31) and/or said second abutment surface (32) of said slider (30). 6. Micro-actuator (100) according to one of claims 1 to 5, characterized in that at least one first ferromagnetic restoration element (8) is of revolution around said axial direction (D), and arranged to surround without contact with said rear shaft (42) when it moves back into the rear limit position. 7. Micro-actuator (100) according to one of claims 1 to 5, characterized in that at least a first ferromagnetic restoration element (8) is of revolution around said axial direction (D), and comprises a surface of front stop arranged to cooperate in stop support with said rear shaft (42) when it moves back into the rear end-of-travel position. 8. Micro-actuator (100) according to one of claims 1 to 7, characterized in that at least one said permanent magnet (2) is contiguous with said front shaft (41), or constitutes at least a part of said front shaft (41), said at least one permanent magnet (2) generating a magnetic field of revolution around said axial direction (D), which front shaft (41) is ferromagnetic or magnetized and is arranged to guide the field lines of said magnetic field of revolution substantially in said axial direction (D) up to a front end (45) of said front shaft (41), which tends to cooperate by magnetic attraction with at least one second ferromagnetic restoration element (9), located in the vicinity of said front face (24) of said structure (20), to return said slider (30) to its said rear limit position when no said coil (6; 61; 62) is energized. 9. Micro-actuator (100) according to one of claims 1 to 8, characterized in that said structure (20) comprises at least one said coil (6; 61; 62) connected to a bidirectional current supply. 10. Micro-actuator (100) according to one of claims 1 to 9, characterized in that said structure (20) contains a plurality of said coils (6; 61; 62) arranged to create magnetic fields of the same direction according to the axial direction (D). 11. Micro-actuator (100) according to one of claims 1 to 9, characterized in that said structure (20) contains a plurality of said coils (6; 61; 62) of which at least two are arranged to create fields magnets in opposite directions along the axial direction (D). 12. Micro-actuator (100) according to claim 10 or 11, characterized in that at least two said coils (6; 61; 62) are on either side of said at least one permanent magnet (2) of said slider ( 30). 13. Micro-actuator (100) according to claim 12, characterized in that at least two said coils (6; 61; 62) are on either side of all said permanent magnets (2) that said slider ( 30). 14. Micro-actuator (100) according to one of claims 1 to 13, characterized in that said micro-actuator (100) comprises a plurality of said structures (20) contiguous by lateral faces and together forming a block (200 ) with a matrix of said sliders (30) arranged to project from at least a first side of said block (200). 15. Micro-actuator (100) according to one of claims 1 to 14, characterized in that said micro-actuator (100) is a watch component and comprises at least one said slider (30) with a stroke less than or equal to to 1.0 mm, arranged to give a stop or adjustment pulse to another component that comprises a resonator, or an escapement mechanism, or a display mechanism, of said watch. 16. Micro-actuator (100) according to one of claims 1 to 14, characterized in that said micro-actuator (100) is a component of a portable device in contact with the skin of a user and comprises at least a said slider (30) arranged to give at least one pulse per touch to give a warning signal to a user, and/or to transmit to said user a series of coded pulses. 17. Micro-actuator (100) according to claims 14 and 16, characterized in that said micro-actuator (100) comprises a plurality of said slides (30) arranged to transmit to said user a series of pulses geometrically distant from each other. others. 18. Printed circuit (400) comprising at least one said micro-actuator (100) according to one of claims 1 to 17, in the form of a SMD component soldered to the plate of said printed circuit (400). 19. Printed circuit (400) according to claim 18, characterized in that said printed circuit (400) comprises at least one circuit for supplying a said coil (6; 61; 62) of a said micro-actuator ( 100). 20. Printed circuit (400) according to claim 19, characterized in that said printed circuit (400) includes a power supply circuit for each said coil (6; 61; 62) that includes each said micro-actuator (100) that carries said printed circuit (400). 21. Watch (1000) comprising at least one said micro-actuator (100) according to one of claims 1 to 15 and/or at least one printed circuit (400) according to one of claims 18 to 20, and at least one source of energy (600) to supply current to at least one said coil (6; 61; 62) of a said micro-actuator (100), and/or at least one movement (500) comprising at least one source of energy (600) to supply current to at least one said coil (6; 61; 62) of a said micro-actuator (100).