Micro-actuator with magnetically retracting solenoid

Abstract

A magnetic micro-actuator (100) comprising a coil (6; 61; 62) controlling the axial displacement of a slide (30) comprising at least one permanent magnet (2) joined or aligned with a ferromagnetic or magnetized rear shaft (42) and guiding the field lines of the magnetic field of revolution along the axial direction (D) through the coil (6; 61; 62) in which the slide (30) travels, to a rear end (43) of said rear shaft (42) which tends to cooperate by magnetic attraction with at least one 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) to a rear end position when no coil (6; 61; 62) is energized.

Description

Field of invention

[0001] 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 slide, which comprises said micro-actuator, in an axial direction in a first direction, up to a front end-of-stroke position corresponding to a stop support between a first bearing surface of said structure and a first stop surface of said slide in which front end-of-stroke position a front shaft, which comprises said slide, is projecting out of a front face of said structure, and, when none of said coils is powered said slide is movable in said axial direction in a second direction opposite to said first direction,and is recalled by purely magnetic means to a rear end position corresponding to a stop support between a second support surface of said structure and a second stop surface of said slide.

[0002] The invention further relates to a printed circuit board comprising at least one such micro-actuator.

[0003] The invention further relates to a watch comprising at least one such micro-actuator and / or at least one such printed circuit board.

[0004] 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 micromechanics, particularly watchmaking. They must meet the constraints of actuation and return times, as well as the very small dimensions required by applications, particularly watchmaking.

[0006] The use of return springs increases the size of the micro-actuator and does not guarantee optimal durability.

[0007] US 2002 / 153982 A1 discloses a magnetic micro-actuator incorporating a slider having a stroke of 1 mm. Summary of the invention

[0008] The aim is to develop a micro-actuator capable of applying a controlled mechanical braking force, in particular for micro-mechanical applications and notably watchmaking.

[0009] A particularly interesting application concerns braking, which, in micromechanics and especially in watchmaking, requires an extremely short reaction time, as well as an extremely short return time to the rest position.

[0010] The aim is therefore to perfect a classic solenoid actuator, in order to meet the constraints of actuation and return time, as well as the very small dimensions required by applications, particularly watchmaking.

[0011] For this purpose, the invention relates to a magnetic micro-actuator according to claim 1.

[0012] The invention also relates to a printed circuit according to claim 18 comprising at least one such micro-actuator.

[0013] The invention further relates to a watch according to claim 21 comprising at least one such micro-actuator and / or at least one such printed circuit board. Preferred embodiments are defined in dependent claims 2 to 17 and 19, 20. Summary description of the drawings

[0014] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, with reference to the attached drawings, where: there figure 1represents, schematically and in perspective, a micro-actuator according to the invention, comprising a block structure, here composed but not limited to a front housing and a rear housing, which surrounds a coil forming a stator, in which a slide is movable, which includes a permanent magnet and a shaft; the micro-actuator further comprises a first ferromagnetic restoration element, here in the particular form of a soft ferromagnetic ring, fixed to the rear of the rear housing, on the side opposite the front housing, which has an opening through which the slide can protrude; the figure 2 represents, schematically and in exploded perspective, the micro-actuator of the figure 1 ; there figure 3 represents, schematically and in cross-section along plane P passing through axis AA of the figure 1 , the micro-actuator of the figure 1, in a first variant where the slider comprises a front shaft and a rear shaft which are non-magnetic or soft ferromagnetic, and is in the actuated position; the figure 4 represents, in a similar way to the figure 3 , a second variant where the slider comprises a single-piece shaft made of permanent magnet, and is in the retracted position; the Figure 5 is a field diagram from a finite element simulation of the magnetic field for the micro-actuator of the figure 3; the field lines of the permanent magnet are guided through the front shaft and the rear shaft of the slider; the current-supplied coil 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 switched off, the ferromagnetic restoring element, namely the soft ferromagnetic ring, produces a force in the opposite direction, which acts on the slider and returns it to its initial position; the travel stroke is indicated by broken lines; the figure 6 is a diagram illustrating, for the micro-actuator of the figure 3, the variation of the force, represented on the ordinate, acting on the slide when it is moved along the Z axis, in the AA direction, as a function of the displacement D represented on the abscissa; the continuous line illustrates the variation of the positive force exerted by the coil when a current flows through it; the broken line illustrates the variation of the restoring force imposed by the ferromagnetic restoration element; the figure 7 is a diagram illustrating, for the micro-actuator of the figure 3 , and for the force profile illustrated by the figure 6 On the one hand, the variation of the slider's displacement along the Z-axis, in the AA direction, as a function of time t represented on the x-axis, is shown as a dashed line, and on the other hand, the variation of the slider's velocity as a function of time t is shown as a solid line; figure 8 is another diagram illustrating, for the micro-actuator of the figure 3 , and for the force profile illustrated by the figure 6 On the one hand, the variation of the slider's displacement along the Z-axis, in the AA direction, as a function of time t represented on the x-axis, is shown as a dashed line, and on the other hand, the variation of the force as a function of time t is shown as a solid line; figure 9 is, similarly to the Figure 5 , a field diagram from a finite element simulation of the magnetic field generated by a permanent toroidal magnet integral with the shaft, which has permanent magnet extensions at its ends; this finite element simulation concerns the slide alone, and does not include the coil or the rear ferromagnetic ring; the figure 10 represents, schematically, partially, and in cross-section through the axis of the slider, a slider surrounded by two coils, which, depending on their current supply, allow the establishment of magnetic fields of opposite or the same direction around the slider; figure 11represents, in a schematic, partial way, and in section passing through the axis of the slide, a slide on one side of which two coils are arranged, in an instantaneous situation of current supply where these two coils create magnetic fields of complementary effect, and of the same direction; the figure 12 represents, schematically, partially, and in cross-section passing through the axis of the slider, in a manner analogous to the figure 3 , a micro-actuator comprising a second ferromagnetic restoration element, in the front part of the structure, opposite the first ferromagnetic restoration element, and which is arranged to cooperate with the front end of the front shaft for its return; the figure 13 represents, in a manner analogous to the figure 12 , a micro-actuator of substantially symmetrical construction, comprising a coil on each side of the permanent magnet carried by the slider; the figure 14is 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; the 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; the figure 16 represents, schematically and in perspective, a micro-actuator according to the invention, comprising a juxtaposition of structures each containing a slide and the associated coil(s), in an arrangement where the projection of different slides corresponds to a matrix coding; the figure 17is 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 board, and whose slide is arranged to actuate a component of another mechanism such as a watch movement, and a second micro-actuator according to the invention whose slide is arranged to stimulate the epidermis of a user by protruding out of the casing of this micro-mechanism. Detailed Description of Preferred Embodiments

[0015] 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 herein as the slider. The aim is to create a miniature mechanical braking element with as few parts as possible and without a mechanical spring element.

[0016] Solenoid actuators are well-known in general mechanics, particularly for controlling mechanisms. Most incorporate a return spring for the slide, which limits their performance, especially regarding the duration of an operating cycle. They are difficult to miniaturize and are not used for personal protective equipment.

[0017] The aim is to develop a micro-actuator capable of applying a controlled mechanical braking force, in particular for micro-mechanical applications and notably watchmaking.

[0018] A particularly interesting application concerns braking, which, in micromechanics and especially in watchmaking, requires an extremely short reaction time, as well as an extremely short return time to the rest position.

[0019] The aim is therefore to perfect a classic solenoid actuator, in order to meet the constraints of actuation and return time, as well as the very small dimensions required by applications, particularly watchmaking.

[0020] The micro-actuator device 100 according to the invention is illustrated by the figures 1 and 2 It forms a block structure, here but 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 slide, which includes at least one permanent magnet 2 and a shaft 4. This shaft 4 can be a single 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 the figure 3. A first ferromagnetic restoration element 8, in particular but not limited to a soft ferromagnetic ring, is fixed to the rear of the rear housing 12, on the side opposite the front housing 10. The entire micro-actuator device assembly 100 is here held assembled, in a non-limiting manner, by two pins 14.

[0021] The micro-actuator 100 operates similarly to a solenoid actuator. When an electric current is applied to the coil 6, a force is generated that repels the magnet 2 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 the stroke by an end 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 contact point between the slider and the stator (coil 6).

[0022] In some applications, it is advantageous to apply a current in only one direction (unipolar drive). In this case, two options for the return of the slider can be considered: for the general case where the micro-actuator 100 is intended to operate in several orientations, as in the case of a watch, at least one first ferromagnetic element 8, represented by a ring on the figures 1 to 4This ferromagnetic element 8 can also be a block or a disc. In a very specific case, particularly a static one, where the micro-actuator 100 is positioned so 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 downwards by gravity. This arrangement is hardly usable except for static installations, such as clocks. In the general case, a restoring force must be generated to ensure the slider retracts to a rest position.

[0023] THE Figures 3 and 4 are cross-sections of such micro-actuators, 100 of different construction, the figure 3 illustrates the deployed (actuated) state of a slide 30 comprising a front shaft 41 and a rear shaft 42, both ferromagnetic, and the figure 4illustrates the retracted (stopped) position of a slide 30 with a single one-piece shaft 4 uniting the front shaft 41 and the rear shaft 42 and forming a permanent magnet.

[0024] In a variant such as the figure 3 With a front shaft 41 and a rear shaft 42, it is essential that the rear shaft 42 be ferromagnetic to ensure the necessary actuation and retraction forces. The front shaft 41 can be either ferromagnetic or non-magnetic. The front shaft 41 is specifically designed to establish physical contact with a target object, generally located less than 0.5 mm from the micro-actuator 100.

[0025] This target object may consist of an element of a mechanism, in particular a display mechanism, or an oscillator, for example a pendulum, or the epidermis of a user for a haptic feedback device, or other.

[0026] The range of movement, and therefore the target position, can naturally be adjusted according to the application. Care must be taken to ensure that, even with a longer stroke, the actuation and return forces are correctly adjusted.

[0027] In a variant like that of the figure 4 The shaft 4 and the magnet 2 form a single unit. 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 the magnetized material.

[0028] There Figure 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 the figure 3 , with a cylindrical magnet 2 and a first annular ferromagnetic restoration element 8. This Figure 5This is the result of a radially symmetric finite element simulation. The rear shaft 42 guides the magnetic field lines of the magnet 2 to the coil 6 and to the first restoration element 8. The field lines of the permanent magnet 2 are guided through the front shaft 41 and the rear shaft 42. The coil 6 drives the slide 30 in the positive Z direction. If the current in the coil is interrupted, the first ferromagnetic restoration element 8, specifically a soft ferromagnetic ring, produces a counter-force, which acts on the slide 30 and returns it to its initial position. The displacement stroke δ is indicated by dashed lines; in this example, the displacement stroke is 0.5 mm.

[0029] Finite element simulation is used to obtain the force as a function of 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 the figure 6 . This figure 6 illustrates, for the micro-actuator of the figure 3 , the variation of the force, represented in ordinate, acting on the slide 30 when it is moved along the Z axis, in the direction AA, as a function of the displacement D represented in abscissa; the solid line illustrates the variation of the positive force exerted by the coil 6 when it is traversed by a current; the dashed line illustrates the variation of the restoring force imposed by the ferromagnetic ring 8.

[0030] When the current is switched off, as shown by the dashed line, the force is negative (retraction) and decreases as the slide 30 moves forward. It is important to note that even at maximum extension, the force remains sufficient to both restore and retract the slide 30, and in this configuration is on the order of -0.1 mN. The required force is determined by the static friction between the slide 30 and the stator, defined by the contact points between the shafts and the casing as described in detail below, and the gravitational force. The force profile for the running state, as shown by the solid line, is positive, close to 0.5 mN. The starting force remains high and even increases by more than 20% as the slide 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.

[0031] To obtain the dynamics from the calculated forces, the differential equation of such a system is integrated over the desired time scale. The results are illustrated in figures 7 and 8 .

[0032] The traces are generated for a 30 slider of mass 0.015 g and an actuation pulse of 2.5 V lasting 4 ms, and correspond to the force profile illustrated by the figure 6 commented above. The maximum displacement is set at 0.3 mm. This corresponds to an impact with an object by the front shaft 41, because the device itself has a maximum possible displacement of δ=0.5 mm. As seen on the figure 7Upon impact, there is a rebound after a slight indentation. The graphs indicate that the shaft 4 reaches its target after approximately 5 ms at a speed of 120 mm / s. The impact speed and the mass of the moving part define the contact force, and the rebound defines the momentum. When the power supply to the coil 6 is stopped, even before impact, the slide 30 returns to its rest position in 5 ms. This return is ensured by the ferromagnetic ring 8, but also by the rebound, which can occur upon contact. The rebound is beneficial because it avoids static friction, which could prevent the return of the slide 30.

[0033] There figure 8This illustrates displacement and force as a function of time. It is clearly visible that once the actuation current of coil 6 is switched off, slider 30 begins to slow down because the force is negative. However, the point of impact is still reached. Because there is a restoring force, slider 30 returns to its starting position and may bounce several times depending on the damping at the point of contact. It is important that once stopped, slider 30 is still held firmly in place by the holding force exerted between the first ferromagnetic restoration element 8 and slider 30. In this example, the holding force is approximately 0.5 mN, which is sufficient to maintain a stable resting position even under minor vibrations and shocks.

[0034] There figure 9illustrates 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 magnet are a single piece. The shading illustrates the positive (white) and negative (gray) B z areas. The field lines are very similar to those obtained with the composite magnet-ferromagnetic shaft slider 30.

[0035] Friction is a limiting factor. Friction is a concern, and the design must ensure efficient shaft movement. It is advisable to minimize friction with a perfectly aligned front shaft 41 and rear shaft 42, held in position by guide openings in the housings 10 and 12. Friction between the materials composing the shaft and the casing must be minimized by matching materials with a low coefficient of friction or by adding lubricating coatings. Another, more expensive solution, in keeping with watchmaking traditions, is to match jewels (rubies) with a metal or ceramic shaft. Sufficient clearance between the outer diameter of the shaft and the inner diameter of the coil ensures that no contact is established between the shaft and the coil.The same applies 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 touch this structure 20. Naturally the calculation of each clearance takes into account the total range of operating temperatures of the device.

[0036] Communicating information to a user typically relies on sight and hearing. The other traditional senses—smell, taste, and touch—are rarely used. Haptic feedback is currently an active area of ​​research, with numerous variations.

[0037] Thus, such a micro-actuator can be used for other applications, particularly in the field of feedback haptics such as a Braille display, for tactile reading. Text encodings for the blind using raised or recessed characters were developed in the 14th century by Zayn Ud Dîn Al Alidî, then in the 18th century by Francesco Lana de Terzi, and in the 18th century by Valentin Haüy, founder of the first school for the blind. Reading codes were perfected in the 19th century by Charles Barbier de la Serre, for a military application of writing or reading at night, then by Louis Braille, whose code became universal. Abraham-Louis Breguet also produced tactile watches in the 18th century, with protruding pins, to allow reading the time in the dark.

[0038] The use of the sense of touch is currently an active area of ​​research with many variations. In particular, a distinction is made between cutaneous perception at the level of the epidermis and so-called haptic perception, which focuses on the combination of information provided by the individual's nervous and muscular systems with information specific to this local cutaneous perception. This allows for a broader definition of an object, its movements, or its deformations. This haptic perception can also be combined with information provided by other senses, such as the perception of temperature.

[0039] The micro-actuator according to the invention makes it easier to read by touch, due to its small dimensions. In particular, it allows the same signal to be repeated with a particular frequency; in fact, certain frequencies increase the stimulation for tactile applications, which also makes it possible to reduce the necessary impact force.

[0040] This micro-actuator can still be used in portable electronics, particularly 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 phone call or the arrival of a message, the crossing of a particular threshold of a physical quantity such as a radioactivity level, or other.

[0041] More specifically, and as illustrated by the figures, the invention relates to a magnetic micro-actuator 100 comprising at least one structure 20 containing at least one coil 6, 61, 62.

[0042] This coil 6, 61, 62, is arranged to exert, in a powered position, an axial thrust force on a slide 30, which comprises the micro-actuator 100, along an axial direction D in a first direction, up to a forward end-of-stroke position corresponding to a stop support between a first support surface 21 of the structure 20 and a first stop surface 31 of the slide 30.

[0043] In this front end-of-travel position, a front shaft 41, which the slider 30 comprises, projects from a front face 24 of the structure 20.

[0044] And, when no coil 6, 61, 62 is supplied, the slide 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 a rear end-of-travel position corresponding to a stop support between a second support surface 22 of the structure 20 and a second stop surface 32 of the slide 30.

[0045] According to the invention, the slide 30 comprises at least one permanent magnet 2 joined 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 permanent magnet 2 generates a magnetic field of revolution around the axial direction D.

[0046] 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 the slide 30 circulates, to 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.

[0047] 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 return the slide 30 to its rear end position when no coil 6, 61, 62, is energized.

[0048] More specifically, 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.

[0049] In particular, this at least one permanent magnet 2 is monobloc with the front shaft 41 and / or with the rear shaft 42.

[0050] More particularly, this at least one permanent magnet 2 comprises the first stop surface 31 of the slide 30 and / or the second stop surface 32 of the slide 30. More particularly still, this at least one permanent magnet 2 is radially salient with respect to the front shaft 41 and / or the rear shaft 42, and forms a collar carrying the first stop surface 31 and / or the second stop surface 32 of the slide 30.

[0051] More particularly, 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 during its recoil to the rear end-of-travel position.

[0052] More specifically, at least one first ferromagnetic restoration element 8 is of revolution about the axial direction D, and includes a front stop surface, which is arranged to cooperate in stop support with the rear shaft 42 during its recoil to the rear end position.

[0053] More particularly, at least one permanent magnet 2 is joined 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 to 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 slide 30 to its rear end position when no coil 6, 61, 62, is energized.

[0054] More specifically, structure 20 includes at least one coil 6, 61, 62, connected to a bidirectional power supply.

[0055] 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 to create magnetic fields of opposite directions. It is therefore the polarization of the power supply which determines the operating mode.

[0056] More specifically, at least two coils 6, 61, 62, are on either side of this at least one permanent magnet 2 of the slide 30.

[0057] More specifically, at least two coils 6, 61, 62 are on either side of all the permanent magnets 2 that comprise the slide 30.

[0058] More particularly, the micro-actuator 100 comprises a plurality of structures 20, which are joined by lateral 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.

[0059] The stroke of the slider 30 obviously depends on the sizing of the micro-actuator 100. For watchmaking applications, a stroke on the order of a millimeter, in particular less than or equal to 1.0 mm, or even a fraction of a millimeter, is compatible with many applications.

[0060] More particularly, in a non-limiting embodiment, 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 impulse to another component that comprises a resonator, or an escapement mechanism, or a display mechanism, of a watch. Among the advantageous watchmaking applications, mention may be made of stop-seconds, the triggering or stopping of a chronograph, the adjustment of the time setting, the adjustment of the calendar, the striking of a gong or a gong in a striking mechanism, or other.

[0061] More particularly, 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 pulse per touch to give a warning signal to a user, and / or to transmit to the user a series of coded pulses.

[0062] More particularly, the micro-actuator 100 comprises a plurality of sliders 30 arranged to transmit to the user a series of pulses geometrically distant from each other.

[0063] The invention further relates to a printed circuit board 400 comprising at least one such micro-actuator 100, in the form of an SMD component brazed onto the plate of the printed circuit board 400.

[0064] More specifically, the printed circuit board 400 includes at least one power supply circuit for a coil 6, 61, 62, of a micro-actuator 100. More specifically still, the printed circuit board 400 includes a power supply circuit for each coil 6, 61, 62, which is included in each micro-actuator 100 which is carried by the printed circuit board 400.

[0065] The invention further relates to a watch 1000 comprising at least one such micro-actuator 100, and / or at least one such printed circuit board 400, and at least one power source 600 for supplying current to at least one coil 6, 61, 62, of a micro-actuator 100, and / or at least a movement 500 comprising at least one power source 600 for supplying current to at least one coil 6, 61, 62, of a micro-actuator 100.

[0066] In summary, the invention describes an electromagnetic actuator that can be used to apply a braking force or haptic feedback. It can be set in motion by a unipolar voltage source since the restoring force is provided by a first ferromagnetic restoring element 8, such as, in particular, a ring made of soft ferromagnetic material.

[0067] The micro-actuator according to the invention thus presents several advantages.

[0068] When not activated, 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.

[0069] The invention is advantageous in any configuration requiring an extremely rapid return of the plunger slide.

[0070] No force needs to be applied to maintain the retracted position.

[0071] The proposed geometry is also inherently shock-resistant because the slider 30 is highly constrained with only one dimension of freedom.

[0072] The proposed device is very compact and has only one moving component. No spring is required.

[0073] The 100 micro-actuator can be manufactured as an SMD component for easy integration onto a standard printed circuit board, ensuring ease of implementation and moderate cost.

Claims

1. Magnetic microactuator (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 sliding block (30), comprised in said microactuator (100), in an axial direction (D) in a first direction, up to a front end-of-travel position, corresponding to an abutment bearing between a first bearing surface (21) of said structure (20) and a first abutment surface (31) of said sliding block (30), and wherein in the front end-of-travel position, a front arbor (41), comprised in said sliding block (30), is protruding from a front face (24) of said structure (20), and, when no said coil (6; 61; 62) is powered said sliding block (30) is moveable in said axial direction (D) in a second direction opposite to the first direction, and is brought back by purely magnetic means to a rear end-of-travel position corresponding to an abutment bearing between a second bearing surface (22) of said structure (20) and a second abutment surface (32) of said sliding block (30), characterised in that the travel of the sliding block (30) is lower or egal to 1 mm, said sliding block (30) comprising at least one permanent magnet (2) joined with a rear arbor (42) aligned with said front arbor (41), or consisting of at least one portion of said rear arbor (42), said at least one permanent magnet (2) generating a magnetic field of revolution around said axial direction (D), which rear arbor (42) is ferromagnetic or magnetised 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) wherein circulates said sliding block (30), up to a rear end (43) of said rear arbor (42) that tends to cooperate by magnetic attraction with at least one first ferromagnetic restoration element (8), located in the vicinity of a rear face (25) of said structure (20), opposite said front face (24), in order to bring said sliding block (30) back into its said rear end-of-travel position when no said coil (6; 61; 62) is powered.

2. Microactuator (100) according to claim 1, characterised in that said at least one permanent magnet (2) is inserted between said front arbor (41) and a rear arbor (42) aligned with said front arbor (41).

3. Microactuator (100) according to claim 1 or 2, characterised in that said at least one permanent magnet (2) is integral with said front arbor (41) and / or with said rear arbor (42).

4. Microactuator (100) according to one of claims 1 to 3, characterised in that said at least one permanent magnet (2) comprises said first abutment surface (31) of said sliding block (30) and / or said second abutment surface (32) of said sliding block (30).

5. Microactuator (100) according to one of claims 1 to 4, characterised in that said at least one permanent magnet (2) is protruding radially in relation to said front arbor (41) and / or to said rear arbor (42), and forms a flange supporting said first abutment surface (31) and / or said second abutment surface (32) of said sliding block (30).

6. Microactuator (100) according to one of claims 1 to 5, characterised in that at least one first ferromagnetic restoration element (8) is of revolution around said axial direction (D), and arranged to surround without contact said rear arbor (42) during its recoil to rear end-of-travel position.

7. Microactuator (100) according to one of claims 1 to 5, characterised in that at least one first ferromagnetic restoration element (8) is of revolution around the axial direction (D), and comprises a frontal abutment surface arranged to cooperate in abutment bearing with said rear arbor (42) during its recoil to rear end-of-travel position.

8. Microactuator (100) according to one of claims 1 to 7, characterised in that at least one said permanent magnet (2) is joined with said front arbor (41), or constitutes at least one portion of said front arbor (41), said at least one permanent magnet (2) generating a magnetic field of revolution around said axial direction (D), which front arbor (41) is ferromagnetic or magnetised 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 arbor (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), in order to bring back said sliding block (30) into its rear end-of-travel position when no said coil (6; 61; 62) is powered.

9. Microactuator (100) according to one of claims 1 to 8, characterised in that said structure (20) comprises at least one said coil (6; 61; 62) connected to a two-way power supply.

10. Microactuator (100) according to one of claims 1 to 9, characterised in that said structure (20) contains a plurality of said coils (6; 61; 62) arranged to create magnetic fields of the same direction in the axial direction (D).

11. Microactuator (100) according to one of claims 1 to 9, characterised in that said structure (20) contains a plurality of said coils (6; 61; 62) of which at least two are arranged to create magnetic fields of opposite direction in the axial direction (D).

12. Microactuator (100) according to claim 10 or 11, characterised in that at least two said coils (6; 61; 62) are on either side of said at least one permanent magnet (2) of said sliding block (30).

13. Microactuator (100) according to claim 12, characterised in that at least two said coils (6; 61; 62) are on either side of all of the said permanent magnets (2) comprised in said sliding block (30).

14. Microactuator (100) according to one of claims 1 to 13, characterised in that said microactuator (100) comprises a plurality of said structures (20) joined by lateral faces and together forming a block (200) with a matrix of said sliding blocks (30) arranged to protrude from at least one first side of said block (200).

15. Microactuator (100) according to one of claims 1 to 14, characterised in that said microactuator (100) is a watch component and comprises at least one said sliding block (30) with a travel less than or equal to 1.0 mm, arranged to give a stop or adjustment impulse to another component comprised in a resonator, or an escapement mechanism, or a display mechanism, of one said watch.

16. Microactuator (100) according to one of claims 1 to 14, characterised in that said microactuator (100) is a component of a portable device in contact with the skin of a user and comprises at least one said sliding block (30) arranged to give at least one impulse per touch to give a warning signal to a user, and / or to transmit to said user a series of coded impulses.

17. Microactuator (100) according to claims 14 and 16, characterised in that said microactuator (100) comprises a plurality of said sliding blocks (30) arranged to transmit to said user a series of impulses geometrically apart from one another.

18. Printed circuit (400) comprising at least one said microactuator (100) according to one of claims 1 to 17, in the form of CMS component soldered on the plate of said printed circuit (400).

19. Printed circuit (400) according to claim 18, characterised in that said printed circuit (400) comprises at least one circuit for powering a said coil (6; 61; 62) of a said microactuator (100).

20. Printed circuit (400) according to claim 19, characterised in that said printed circuit (400) comprises a power supply circuit for each said coil (6; 61; 62) comprised in each said microactuator (100) that said printed circuit (400) supports.

21. Watch (1000) comprising at least one said microactuator (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 energy source (600) for powering at least one said coil (6; 61; 62) of a said microactuator (100), and / or at least one movement (500) comprising at least one energy source (600) for powering at least one said coil (6; 61; 62) of a said microactuator (100).

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