EP1399938B1 - Magnetic actuator with reduced response time - Google Patents

Description

TECHNICAL AREA

The present invention relates to magnetic actuators whether they be miniature or larger size. We talk about micro-actuators when they are miniature. The realization of such actuators uses machining techniques from mechanical structures, micro-machining or techniques used in microelectronics.

These actuators are used in particular to make electrical, optical, power, high frequency, switches, but also to realize pumps, valves, engines. By switch is meant a device with several contacts that can be closed separately while the relay has only one or more close at the same time. These contacts can be in open or closed position.

Electromagnetic relays and switches, miniaturized or not, are widely employees in many applications such as telecommunications in transmission or reception, in optical telecommunications, in equipment of automatic tests, in automobile, in aeronautics and in consumer electronics.

Pumps, valves, motors can be used in broad areas of application and including microbiology, medicine, optics etc.

STATE OF THE PRIOR ART

Known types of actuators include a fixed magnetic part 1 and a magnetic part mobile 2 who cooperate. The fixed magnetic part 1 is magnetically connected to the moving magnetic part.

Referring to Figure 1 which shows a example of magnetic actuator of known type to a single gap.

The fixed magnetic part 1 and the part movable magnet 2 form a magnetic circuit 6 closed on itself able to guide a magnetic flux. The fixed magnetic part 1 and the moving magnetic part 2 are stacked on top of each other. The circuit magnetic 6 cooperates with means 7 to generate the magnetic flux. The fixed magnetic part and the part mobile magnet 2 each comprise a portion 12, 8 respectively, helping to delimit an air gap 9 so that a force can be exerted at the level of the portion 8 of the movable part 2 to move it under the effect of the magnetic field.

In the gap 9 the magnetic flux is established transversally to the portion 8. In this for example, the fixed magnetic part 1 comprises a base or breech 10 which is extended by a first stud 11 and a second magnetic stud 12. second magnetic stud 12 helps delimit the gap 9.

The cylinder head 10 is connected magnetically to the mobile magnetic part 2 via the first stud 11. It also has a role of mechanical maintenance of the part mobile magnetic 2 with respect to the magnetic part fixed 1. The fixed magnetic part 1 and the part mobile magnetic 2 extend one above the other, in substantially parallel planes when the actuator is in the open position.

The magnetic circuit 6 in closed loop follows each other in one of the direction of circulation of the magnetic flux: the yoke 20, the first magnetic stud 11, the mobile part 2, the gap 9 and the second magnetic pad 12. Sa reference 6 schematizes the path traveled by the flow magnetic when crossing the different elements who compose it.

The mobile magnetic part 2 is in the example shaped arm with a support end 13 connected to the first magnetic stud 11 and another free end that corresponds in the example to the portion 8 helping to delimit the gap 9.

In the electrical relays, the end free serves as an electrical contact that the arm is made of electrically conductive material or that the arm is equipped with an electrical contact. No contact electric was not shown.

Means 7 to generate the flow Magnetic may include one or more coils surrounding one or more pieces of the game fixed magnet 1 and / or mobile magnetic part 2 and / or possibly one or more magnets permanent. When an electric current flows in a coils a magnetic flux is produced. It is materialized by the closed loop with arrows.

In the example of Figure 1, a winding 7 was represented around the first magnetic pad 11. Several coils could be used, they could be around breech 10, around the second magnetic stud 12 or even around the part movable magnetic 2.

In such a magnetic circuit 6, it is necessary to find a compromise between the cross sections to the flow of its different parts: that of the party movable magnetic 2, that of the fixed magnetic part 1 and that of the gap 9.

We seek to obtain an induction value important at the air gap 9 so that the force that will be exerted on the magnetic part mobile 2, at the portion 8, is important. This requires that the available magnetic flux in the gap 9 is important. Magnetic flux available in the air gap 9 corresponds to the one that is guided by the magnetic circuit 6 on both sides of the air gap 9. The maximum magnetic flux that can be guided by a piece of magnetic material is function magnetic material and section of the workpiece.

In unsaturated state of the magnetic material, the larger the section, the greater the magnetic losses are weak and in saturated state of the magnetic material, all the magnetic flux generated can not be contained and the excess of magnetic flux corresponds to the losses, it can not be guided by the magnetic material and it contributes only very slightly to the force.

The section of the magnetic circuit 6 can be substantially homogeneous throughout its length. In this case the mechanical performance of the actuator is mediocre.

Generally, the section of the game mobile magnet 2 is lower than that of the part fixed magnet 5 for mechanical reasons. Indeed it is sought that the stiffness of the movable part 2 not too important for her to bend easily. One of the ways to reduce the stiffness of the moving part is to reduce its section. This reduction of the section of the moving part is done at detriment of the possibility of flow passage magnetic element in the moving magnetic part, which leads to a decrease in the force at the level of the air gap and an increased response time of the part mobile.

There are other types of actuators magnetic in which there are several gaps.

In these types of actuators, we will call main airgap that which is delimited by transversal surfaces in the sense of the movement of the mobile magnetic part. There is in these configurations at least one other gap that will be qualified auxiliary.

Figure 2 illustrates a micro-relay in view On top. This micro-relay is realized in form planar and no longer in stacked form. He was described in the article: "Fully Batch Fabricated Magnetic Microactuators Using A Two Layer LIGA Process "by B. ROGGE, J. SCHULZ, J. MOHR, A. THOMMES and W. MENZ in TRANDUSCERS '95 - EUROSENSORS IX pages 320 to 323.

It now has on a support common 3 the fixed magnetic part 1 and the part movable magnetic 2. The movable magnetic part 2 corresponds to a free end 17 of a mobile arm 5 whose other end 13 is a bearing end secured to the support 3. The arm 5 and the part Magnetic fixed 1 are located next to each other substantially in the same plane, parallel to the plane of the support 3. The movement is in the plane of the arm 5 and the fixed magnetic part 1.

The free end 17 ends with a mobile electrical contact 16 intended to come against a fixed electrical contact 15 carried by the support 3.

The fixed magnetic part 1 has in this example a cylinder head 10 secured to one side of a magnetic block 12 which contributes to delimit the gap principal 9 with the mobile magnetic part 2. From the other side, the bolt 10 is integral with a magnetic extension 14, in this example in the form of arm, which comes opposite the magnetic stud 12. This magnetic stud 12 and the magnetic extension 14 delimit an auxiliary air gap 18.

The magnetic circuit 6 then comprises the cylinder head 10, the first magnetic pad 12, the second air gap 18, magnetic extension 14 and bypass the gap 9 and the mobile magnetic part 2. The low rigidity of the arm 5 implies a restoring force weak which slows down the movement in repulsion of the arms.

We understand that the functioning of this micro-relay is not optimum, the force that is exercised on the mobile part is very limited.

As before, the magnetic circuit 6 cooperates with means 7 to generate the flow magnetic. They were represented by a winding around breech 10 and another around his extension 14.

We also know by the request of patent WO-97/39468 an electrical relay such as shown in Figures 3A and 3B. These two figures are not on the same scale.

Instead of being of planar construction, this relay is of stacked construction. We find the fixed magnetic part 1 and the moving magnetic part 2 who cooperate. The mobile magnetic part 2 is a portion of a larger moving part 5 but this last is only sketched in the figures. It's missing its connection to a fixed element which can be for example a support on which would rest the magnetic part 1. The reason for this absence is that the link to the fixed element plays no magnetic role.

The fixed magnetic part 1 comprises, in this example, a breech 10 which is prolonged, in a central zone, by a central magnetic block 12 helping to delineate with the magnetic part mobile 2 the main airgap 9. It is assumed that the mobile magnetic part 2 corresponds substantially to the hatched portion of Figure 3A and that it takes the shape of a plate. The cylinder head 10 is also integral, on either side of the central block 12, two magnetic extensions 14 that project to the movable magnetic part 2. These extensions 14 are end in opposite, near the party mobile magnet 2, they each contribute to delimit with the moving magnetic part 2 a auxiliary air gap 18.

The magnetic circuit 6 then comprises, at following each other, breech 10, one of the extensions 14, the auxiliary air gap 18, the part mobile magnet 2, the main air gap 9 and the stud magnetic 12 central. The extensions 14 allow only better guidance of the magnetic flux at vicinity of the moving magnetic part 2. This is the the only way of guiding the flow and creating a additional air gap. There is no direct way flow guidance.

The magnetic flux flowing in the magnetic circuit 6 follows two closed loops that get join in the central stud 12. These two loops are symmetrical if the magnetic circuit is symmetrical with respect to a median axis passing through the central stud 12 in the direction of movement.

In this example, the magnetic part mobile 2 is a conductor of electricity, it plays the role of an electrical contact that when it gets closer of the central stud 12 under the effect of the induced force comes close an electrical circuit. This circuit electrical ends with two fixed contacts 15 inserted between the central magnetic block 12 and the movable magnetic part 2. These electrical contacts fixtures increase the size of the gap.

As before, the magnetic circuit 6 cooperates with means 7 to generate the flow magnetic. They were represented by a winding surrounding the central magnetic block 12.

In this configuration, the flow magnetic in the main air gap 9 is not optimum, because when looking to close the actuator, the magnetic flux in the cylinder head 10 is well guided towards the extensions 14 but all this flow does not pass through the mobile magnetic part 2 towards the main air gap 9, leaks occur significant flow between the extensions 14 and the breech 10, through the central stud 12, without passing neither by the mobile magnetic part 2 nor by the gap principal 9.

STATEMENT OF THE INVENTION

The present invention aims to realize an electromagnetic actuator whose strength applying on the moving part and the speed are increased compared to conventional actuators and which avoids a damping of the magnetic part mobile. Such an actuator makes it possible to have a significant displacement force while retaining the moving part a reduced section so that it has compatible mechanical properties with the reduction of the mechanical response time.

To achieve this, the present invention proposes a magnetic actuator having a circuit closed magnet, able to guide a magnetic flux, this magnetic circuit having a magnetic part fixed with a cylinder head and a moving magnetic part magnetically connected to each other and moreover, at least a main air gap delimited by at least one portion of the moving magnetic part and by the breech and in which the magnetic flux closes in establishing itself substantially across the mobile magnetic. The fixed magnetic part comprises more ways of recovering flows that help to delineate with the magnetic part mobile, an auxiliary air gap in which the flow Magnetic is established laterally to the part mobile magnetic field, the magnetic flux being contained in either side of the main air gap on one side the breech and the other jointly by the party mobile magnetic and by means of recovery of flow via the portion contributing to delimit the gap principal, the auxiliary airgap having a dimension in the flow setting direction that is minimum at the level of at least one zone of the portion helping to delimit the main air gap.

At least a first magnetic stud allows to mechanically and magnetically connect the cylinder head to the moving magnetic part.

At least one second magnetic pad helps to delimit the main gap, this stud magnetic being from either the breech or the mobile magnetic part. Advantageously this stud magnet is made of a hysteresis material.

At least one other magnetic pad allows mechanically and magnetically connect the cylinder head to flow recovery means.

The actuator comprises means for generate the magnetic flux in the magnetic circuit closed, these means for generating the magnetic flux can be made by at least one winding.

To avoid lateral displacements no desired from the mobile magnetic part, it can overall take the form of at least one arm to a or several non-parallel branches, connected between they at the level of the portion contributing to delimit the main air gap.

The means of recovery of flow can overall take the form of at least one arm to a or more branches.

The moving magnetic part could take the form of a star with several branches.

To avoid the appearance of forces parasites on the helping portion to delineate the main air gap, it is better that the means flow recovery present, in the direction displacement of the moving magnetic part, a thicker than that presented by the party movable magnetic in the direction of movement, so that the auxiliary air gap is delimited by surfaces that remain opposite when the displacement.

To limit the direct leakage flow between flow recovery means and the others fixed parts of the closed magnetic circuit, it is preferable that, knowing that the main air gap is defined by two surfaces opposite, the first belonging to the portion of the moving magnetic part and the second belonging to the breech, the first surface area is greater than the second surface and exceeds around the second surface.

For depreciation to be avoided effectively, it is possible that the dimension of the auxiliary air gap, in the sense of establishing the magnetic flux, which is almost maximal near the portion helping to delimit the main air gap and that it decreases the more one moves away from it.

The mobile magnetic part may comprise at least one through opening, in the sense of a displacement, in the moving magnetic part of to further reduce the depreciation.

The actuator can be stacked type, the cylinder head forming a first level and the whole formed by the flow recovery means and by the part mobile magnetic a second level.

To limit flow leaks, it is preferable that at least one of the levels has a form oblong substantially rounded at both ends.

For the same purpose, it is preferable that two levels overlap. At least one of the levels may have at least one central opening therethrough.

The actuator can be substantially symmetrical with respect to a median plane passing through the substantially movable magnetic part perpendicular to the direction of movement.

The actuator can be used to close or open an electrical circuit. The portion contributing to delimit the main airgap may include at least an electrical contact for contacting at least one other electrical contact when the actuator is closed.

According to another embodiment, the mobile magnetic part can end with at least an electrical contact offset from the portion helping to delimit the main air gap, this electrical contact being intended to contact at least another electrical contact when the actuator is closed.

The electrical contact can be isolated electrically of the moving magnetic part.

The moving magnetic part can be in magnetic material conducive to electricity.

• gravure dans un substrat d'un caisson à remplir d'un matériau magnétique pour réaliser une culasse d'une partie magnétique fixe,
• dépôt d'une première couche diélectrique sur le substrat avec la culasse,
• gravure d'au moins un caisson pour délimiter des moyens de génération d'un flux magnétique, et dépôt desdits moyens,
• dépôt d'une seconde couche diélectrique sur la première couche,
• gravure de caissons à travers les deux couches atteignant la culasse pour délimiter au moins un premier plot magnétique et au moins un second plot magnétique, le second plot contribuant à délimiter au moins un entrefer principal,
• dépôt des premier et second plots magnétiques dans les caissons,
• dépôt d'une couche sacrificielle sur la seconde couche diélectrique et gravure de la couche sacrificielle pour dégager le premier plot magnétique et assurer une séparation entre une partie magnétique mobile et des moyens de récupération de flux de la partie magnétique fixe déposés ultérieurement,
• dépôt sur la couche sacrificielle de matériau magnétique pour réaliser la partie magnétique mobile et les moyens de récupération de flux, puis gravure du matériau magnétique pour les délimiter,
• élimination de la couche sacrificielle sous la partie magnétique mobile pour la libérer et réaliser l'entrefer principal.

The present invention also relates to a method for producing a magnetic actuator. It comprises the following steps:

• etching in a substrate of a box to be filled with a magnetic material to make a cylinder head of a fixed magnetic part,
• depositing a first dielectric layer on the substrate with the cylinder head,
• etching at least one box to define means for generating a magnetic flux, and depositing said means,
• depositing a second dielectric layer on the first layer,
• etching of boxes through the two layers reaching the cylinder head to delimit at least a first magnetic pad and at least a second magnetic pad, the second stud helping to define at least one main gap,
• deposition of the first and second magnetic studs in the boxes,
• depositing a sacrificial layer on the second dielectric layer and etching the sacrificial layer to disengage the first magnetic pad and provide separation between a movable magnetic part and flux recovery means of the fixed magnetic part subsequently deposited,
• depositing on the sacrificial layer of magnetic material to produce the mobile magnetic part and the flux recovery means, then etching the magnetic material to delimit them,
• removing the sacrificial layer under the moving magnetic part to release it and realize the main air gap.

The present invention also relates to a relay having a magnetic actuator as well defined.

The present invention also relates to a switch having at least one actuator magnetic so defined to present several main air gaps.

The present invention also relates to a pump comprising a magnetic actuator thus defined, in which the mobile magnetic part is secured of a membrane helping to delimit a cavity for circulate a fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

La figure 1 (déjà décrite) représente une coupe longitudinale d'un actionneur magnétique connu.

La figure 2 (déjà décrite) représente une vue de dessus d'un autre actionneur magnétique connu.

Les figures 3A et 3B (déjà décrites) montrent respectivement en coupe longitudinale et en vue de dessus un troisième actionneur magnétique connu.

Les figures 4A à 4D montrent respectivement en vue de dessus, en coupe longitudinale selon l'axe BB, en coupe longitudinale selon l'axe CC, en vue de dessous, un actionneur magnétique selon l'invention.

Les figures 5A à 5D montrent en vue de dessus des actionneurs magnétiques selon l'invention, équipés de moyens pour éviter un amortissement de la partie magnétique mobile lors de son déplacement.

Les figures 6A et 6B montrent respectivement en vue de dessus et en vue de dessous, un actionneur magnétique selon l'invention, à flux de fuite limité.

Les figures 7A et 7B montrent un actionneur magnétique massif, la figure 7C un actionneur magnétique symétrique par rapport à un plan médian de la partie magnétique mobile, sensiblement perpendiculaire à la direction du mouvement et la figure 7D un actionneur magnétique réalisé en micro-technologies.

Les figures 8A à 8D montrent une coupe longitudinale et des vues de dessus d'un actionneur magnétique à grande stabilité mécanique en torsion.

Les figures 9A et 9B montrent respectivement en vue de dessus et en coupe longitudinale, un relais électrique selon l'invention.

Les figures 10A à 10C montrent différentes variantes du contact électrique d'un actionneur selon l'invention.

Les figures 11A et 11B sont respectivement une vue de dessus et une vue en coupe d'un commutateur électrique selon l'invention.

Les figures 12A et 12B sont respectivement une vue de dessus et une vue en coupe d'une pompe selon l'invention.

Les figures 13A à 13F représentent différentes étapes de fabrication d'un actionneur similaire à celui de la figure 8A.

Other features and advantages of the invention will appear on reading the description which follows, illustrated by the attached figures.

Figure 1 (already described) shows a longitudinal section of a known magnetic actuator.

Figure 2 (already described) shows a top view of another known magnetic actuator.

Figures 3A and 3B (already described) respectively show in longitudinal section and in top view a third known magnetic actuator.

FIGS. 4A to 4D respectively show a top view, in longitudinal section along the axis BB, in longitudinal section along the axis CC, seen from below, a magnetic actuator according to the invention.

FIGS. 5A to 5D show, in plan view, magnetic actuators according to the invention, equipped with means for preventing a damping of the mobile magnetic part during its displacement.

Figures 6A and 6B respectively show in top view and in view from below, a magnetic actuator according to the invention, limited leakage flow.

FIGS. 7A and 7B show a massive magnetic actuator, FIG. 7C a magnetic actuator symmetrical with respect to a median plane of the moving magnetic part, substantially perpendicular to the direction of movement and FIG. 7D a magnetic actuator made of micro-technologies.

Figures 8A to 8D show a longitudinal section and top views of a magnetic actuator with high mechanical torsional stability.

Figures 9A and 9B respectively show in top view and in longitudinal section, an electrical relay according to the invention.

FIGS. 10A to 10C show different variants of the electrical contact of an actuator according to the invention.

Figures 11A and 11B are respectively a top view and a sectional view of an electrical switch according to the invention.

Figures 12A and 12B are respectively a top view and a sectional view of a pump according to the invention.

FIGS. 13A to 13F represent different manufacturing steps of an actuator similar to that of FIG. 8A.

DETAILED PRESENTATION OF PARTICULAR EMBODIMENTS

Figures 4A to 4D respectively show in top view, in cross section along the axis BB, in cross section along the axis CC, in view from below a magnetic actuator according to the invention. Such an actuator may for example be a micro-relay used in particular in devices portable telephones. It is feasible in micro-technology with stacked layers.

In this configuration the circuit magnetic closed 26, able to guide a magnetic flux, is shown schematically by the bold arrows. It has a fixed magnetic part 21 and a magnetic part mobile 22 magnetically connected to each other.

The fixed magnetic part 21 has a substantially flat cylinder head or base 30 which extends on one side by a first magnetic stud 31 for magnetically connect the fixed magnetic part 21 and the moving magnetic part 22. It is extended by the other side by a second magnetic pad 32 which helps delineate a main air gap 29 between the fixed magnetic portion 21 and a portion 28 of the movable magnetic part 22. It furthermore comprises 40 stream recovery means that will be detailed thereafter.

The moving magnetic part 22 is shaped substantially plane arm having an end 33 of solidarity support of the first magnetic stud 31 and ending with a free end. In this example the free end corresponds to the portion 28 that helps to delimit the main air gap 29. This portion 28 has a maximum amplitude during a displacement of the mobile magnetic part 22. This portion 28 is opposite the second stud magnetic 32, it is on this portion that applies the force generated during the actuation.

The first magnetic pad 31 also has a role of mechanical anchoring of the magnetic part mobile 22 to the fixed magnetic part 21. This anchoring can be done by embedding or by articulation. The first magnetic block can be realized in totality in magnetic material or only in part.

The second magnetic pad 32 which contributes to delimit the main air gap 29 may have a role of electrical contact in the application of a relay electric.

It is possible to realize the second plot magnetic in a hysteresis material for example it can be achieved by electrolytic deposition of a cobalt alloy. This realization mode makes it possible to obtain a stable state of the actuator.

The two magnetic studs 31, 32 are located at both ends of the bolt 30.

In the main air gap 29 the flow magnetic closes by establishing itself transversely in the plane of the moving magnetic part 22.

According to one characteristic of the invention, the fixed magnetic part 21 comprises means for flux recovery 40, magnetically connected with the cylinder head 30 which delimit with the magnetic part mobile 22 at least one auxiliary air gap 38 lateral wherein the magnetic flux settles laterally to the moving part 22. In this example, the connection between the cylinder head 30 and the means of stream recovery 40 is done through the first magnetic stud 31.

The means to generate the magnetic flux 27 can be made by one or more windings placed around the magnetic circuit 26 closed. One or several permanent magnets can be provided in supplement or instead of coils.

In FIGS. 4, the means for generating the magnetic flux are not represented, in a for the sake of clarity, but they are visible in the figures 5 described later. They can be placed around of the breech, magnetic studs, means of flux recovery or even the magnetic part mobile, if they do not interfere with the movement.

In the example of FIGS. 4, the means of stream recovery 40 are represented such an arm to two branches 41, substantially flat with one end 40.1 magnetically unrelated and a support end 40.2 connected magnetically and mechanically to the cylinder head 30 via the first magnetic stud 31. 40 flow recovery means are located substantially in the same plane as the magnetic part mobile 22.

The two branches 41 are joined to two ends of the arm 40. The two branches delimit a space in which the part takes place In this example, the magnetic mobile magnetic part 22 and the means of 40 flux recovery are integral to the same first magnetic stud 31, but several studs could to be present. The means of recovery of flows 40 surround the fixed magnetic part 22 and the gap lateral auxiliary 38, which they help to delimit, borders the mobile magnetic part 22 since its flush mounting end 33 up to portion 28 helping to delimit the main air gap 29.

The means of recovery of flows 40 cooperate with the moving magnetic part 22. They recover some of the magnetic flux established in the main air gap 29 which, when the part magnetic magnet 22 is in a saturated state, can not be guided by it. This may be the case when the main air gap 29 is low, when the relay is being closed for example, especially for deposited thin-film materials electrolytic for example, for which the value of the saturation induction is weak.

In FIGS. 4 flow circulation magnetic has been shown. The magnetic flux that settles in the auxiliary gap 38 is directed substantially transversely to that which is established in the main gap 29 and therefore substantially transversely to the movement.

By making an analogy with a circuit electric, the closed magnetic circuit 26 as well realized includes a section comprising the means of flux recovery 40 and the moving magnetic part 22 mounted in parallel, this section being in series with another section including the first magnetic block 31, the cylinder head 30, the second magnetic pad 32 and the main air gap 29 mounted in series.

The means of recovery of flows 40 allow to increase the section of the magnetic circuit in the part corresponding to the magnetic part mobile and therefore to guide a more magnetic flux important that the one that could be guided in the lack of recovery means. These means of 40 stream recovery are used before, during, and after the movement of the moving magnetic part 22.

It is then possible to give the game magnetic mobile 22 a section adapted to mechanical constraints desired without fearing that she saturates, because saturation is no longer synonymous with reduced force acting on the contributing portion 28 to delimit the main air gap 29 and time of long answer.

Thanks to the presence of the means of flux recovery 40, for a low air gap principal, the magnetic flux that is established therein to be increased and the force that is exerted also. There is less magnetic flux that can not be guided because saturation.

For a larger main air gap, the reluctance of the magnetic circuit 26 is decreased by the magnetic elements put in place and the gain of Magnetic flux and force are appreciable. We recalls that the reluctance of a magnetic circuit is the equivalent of the resistance of an electrical circuit.

In any case, the strength gain magnetic drive causes a decrease in the time of mechanical switching.

The distance between the magnetic part mobile 22 and the flow recovery means 40 characterizes the auxiliary airgap 38. It can be substantially constant as shown in Figure 4A. However, it is best to adjust to adjust the passage of the flow and optimize the force exerted on the maximum amplitude portion 28 and avoid depreciation. It is better that the dimension D1 of the auxiliary air gap 38, in the direction the magnetic flux, which is minimal at level of at least one area of the contributing portion 28 to delimit the main air gap.

Always with the aim of optimizing the value the force exerted on the magnetic part mobile 22, it is preferable to limit the appearance of parasitic forces between the recovery means of flow 40 and the moving magnetic part 22.

When establishing a flow magnetic in two magnetic elements, forces reluctant effects tend to align the two magnetic elements in the direction of induction magnetic. If the flow recovery means 40 and the mobile magnetic part 22 have the same dimension in the direction of movement, when actuating, it occurs a gap between them, this shift can lead to that the surfaces delimiting the gap auxiliary 38 are no longer opposite. The part mobile magnetic 22 then undergoes a Lorentz force who opposes his move and who can disrupt the operation of the actuator.

To avoid this phenomenon, it is preferable that the flow recovery means 40 have, in the direction of movement, a thickness E1 greater than that E2 of the mobile magnetic part 22 so that the surfaces delimiting the air gap auxiliary 38 remain in opposite.

It is also better to limit the flow of direct leakage between the recovery means of stream 40 and the other fixed parts of the circuit closed magnet 26, in particular the second stud magnetic 32.

The main air gap 29 is delimited by the portion 28 of the moving magnetic portion 22 which has a surface S1 and the second stud magnetic 32 of the cylinder head 30 which has a surface S2 facing the surface S1. To limit the flow leakage, it is possible that the surface S1 is more large than the S2 surface and that it exceeds around the surface S2. The surface S1 exceeds a distance P1 the surface S2.

The magnetic flux contained in the means recovery 40 then goes more willingly into the portion 28 of the moving magnetic portion 22 that in the second stud 32.

We are now interested in Figures 5A and 5B which are two variants, seen from above, of a magnetic actuator according to the invention. These figures are comparable to Figure 4A with respect to the overall shape of the mobile magnetic part 22 and the magnetic flux recovery means 40.

FIG. 5A shows the means to generate the magnetic flux 27 in the form of one or several windings 27.1 to 27.3. There are a large number of possibilities to dispose of them and to realize them. In this example, we find a 27.1 winding around each of the studs 31, 32, a winding 27.2 around the arm forming the movable magnetic part 22 and a winding 27.3 around each of the branches 41 of the flow recovery means 40.

It is assumed that the associated windings 27.1 the studs 31, 32 are spiral windings. This guy winding, compatible with micro-technologies, is easy to achieve. Windings 27.2, 27.3 around arm and branches were represented as type solenoid. One or more windings 27.4 of the latter type for example, can be associated with the breech 30 as shown in Figure 6B.

To further reduce the response time of the actuator according to the invention, it is preferable to provide means to avoid amortization of the mobile magnetic part 22 during its movement. These means promote an escape of air found in the main air gap 29 when the displacement of the movable magnetic part 22 has for effect of reducing the main air gap 29.

These means 42.1 may consist in providing along the moving magnetic part 22 one or several first zones Z1 at which the 40 magnetic flux recovery means are more only in one or more Z2 zones.

To optimize the force exerted on the portion 28 which delimits the main air gap 29 and avoid damping of the moving magnetic part 22, the auxiliary air gap 38 has a dimension in the direction of establishment of the magnetic flux that is minimum in at least one area of the 28th helping to delimit the main air gap. is therefore larger in at least one area outside of said portion 28.

In the example of FIGS. 5A and 5B, the mobile magnetic part 22 is an arm that ends 28, the latter being enlarged by relative to the width of the arm. The distance D2 between the flow recovery means 40 and the part magnetic magnet 22 is near maximum in the vicinity of the 28th portion and it decreases more away from it. At level of the portion 28 the distance D1 is minimal as we saw earlier. In FIGS. 5A, 5B, the minimum dimension D1 exists all around the portion 28.

If the size of the auxiliary airgap is substantially constant, air is likely to remain trapped at the moving magnetic part 22, which dampens his movement.

These means to promote the exhaust may also consist of providing the magnetic part mobile 22 through apertures 42.2 in the direction of the movement. This configuration is illustrated in Figure 5B in combination with adjusting the distance between the magnetic part mobile 22 and the flux recovery means 40. find a series of openings 42.2 along the arm from the bearing end 33 to the portion 28 and two sets of openings along the portion 28.

Figures 5C and 5D show two more configurations of the auxiliary air gap 38, they are derived from Figures 5A and 5B.

We notice that the magnetic part mobile 22 may move sideways in the plan of the auxiliary airgap 38 to come to contact the flow recovery means 40, because of a mechanical instability due to magnetic forces between the mobile magnetic part 22 and the flux recovery means 40. The magnetic part mobile 22 may come crashing against the means 40. This generates a disfunction and wear of the actuator.

It is possible, to avoid this disadvantage of increasing the dimension D3 of the gap auxiliary 38, on both sides of the mobile magnet 22 at the portion 28 helping to delimit the main air gap. against, at the end of the moving magnetic part 22, at the end of the arm, the dimension D4 of the gap auxiliary, in the flow direction magnetic, remains minimal.

In these figures 5, it is assumed that the first magnetic pad 31 and the second magnetic pad 32 are derived from the moving magnetic part 22 instead from the fixed magnetic part 21. The 40 stream recovery means are always connected magnetically and mechanically at the breech 30 by the first magnetic stud 31. The second magnetic stud 32 is then part of portion 28 of the game movable magnet 22. The main air gap is delimited by the second magnetic pad 32 and by the portion of the breech that is opposite with this second stud magnetic.

Always in the optics of optimizing force exerted on the portion 28, we try to limit flow leaks in the magnetic circuit 26 especially between its stacked levels. The flow leaks are due to the length of the circuit magnetic field, the magnetic material section and the shape effects of the circuit. In materials in thin layers, leaks are more important than in massive materials.

It is possible, however, to limit the effect of form, to give the breech 30 (which corresponds to a first level of the actuator) and / or the assembly formed by the mobile magnetic part 22 and the flow recovery means 40 (which corresponds to a second level of the actuator) an oblong shape substantially rounded at both ends. The Figures 6A and 6B are top and bottom views respectively an actuator according to the invention.

It is also possible, always in the same purpose, to overlap the two levels. In the example of FIG. 6, the bolt 30 exceeds the entire mobile magnetic part 22-means of stream recovery 40 on much of his periphery. It can also provide at least one through opening on at least one of the levels for reduce the areas facing each other. In the example, the breech 30 is provided with a large opening 43 substantially central. This configuration is not others are possible.

We will now see another example of relay according to the invention. It is assumed that the relay has been made by conventional technologies assembly and machining of mechanical structures by opposition to micro-technologies. Such a relay relatively massive is particularly suitable for the high powers.

This relay is shown in top view in Figure 7A and in section in Figure 7B. We finds the fixed magnetic part 21 with the bolt 30 magnetically and electrically connected to the part mobile magnet 22 via the first holding stud 31. The second stud 32 which contributes to delimit the main air gap 29 is massive. The means for generating the magnetic flux 27 are made by a winding arranged around the second stud 32. The mobile magnetic part 22 is an arm with a bearing end 33 connected to the first stud 31 and a free end forming the portion 28 which comes into opposite the second stud 32 to delimit the gap principal 29.

The flow recovery means 40 are made by a massive arm mechanically connected and magnetically by one of its ends 35 at the cylinder head 30 via a third stud 34. Like the other two studs, this third stud 34 is a protuberance with respect to the breech 30. On could consider that this third stud 34 is issued 40 flow recovery means instead of doing part of the breech.

The other end 36 of the arm is not connected magnetically, she comes close to the mobile magnetic part 22 and contributes with this the last to delimit the auxiliary airgap 38. In the previous configurations, the mobile magnetic part and the flow recovery means were directed substantially in the same direction while in this configuration their directions are substantially perpendicular. Their magnetic binding points with the breech are distinct.

It is assumed that in this configuration the mobile magnetic part 22 and the second stud magnetic 32 are electrically conductive and make part of an electrical circuit that is open when the actuator is open and that is closed when the actuator is closed.

We can symmetrize the actuator according to the invention with respect to a median plane P passing through the mobile magnetic part 22 substantially perpendicular to the direction of movement (materialized by a double-pointed arrow). We can thus achieve a switch. Figure 7C illustrates this configuration. The magnetic part mobile 22 is now connected by its end 33 supporting a breech with two branches 30.1, 30.2 substantially parallel and this connection is made by first two studs 31.1, 31.2 in the extension one of the other. It is the same for the means of 40 flux recovery. They are magnetically connected each to a branch 30.1, 30.2 of the bolt 30 via two third studs that are not visible on the Figure 7C but which are in the extension one of the other.

There is also a pair of seconds pads 32.1, 32.2 in the extension of one another, facing each other, each of them contributing to delimit a main air gap 29.1, 29.2 with the mobile magnetic part 22. These air gaps are arranged in the extension of one another, and other of the mobile magnetic part 22. The portion 28 of the movable magnetic portion 22 is the seat of a force exercising one way or the other, so as to move the magnetic part mobile 22 to one of the second pads 32.1 or to the other 32.2. We have represented the means to generate the magnetic flux in the form of two coils 27.1, 27.1, one 27.1 allowing the flow to settle in one 28.1 of the main gaps and the other 27.2 allowing the flow to settle in the other gap principal 28.2. The windings 27.1, 27.2 encircle each one of the second pads 32.1, 32.2.

If the second magnetic studs 32.1, 32.2 are made of a hysteresis material, one can obtain two stable states of the actuator.

Figure 7D illustrates a relay having substantially the same structure but realized in micro-technology. We start from a substrate 70 for example in silicon. An opening 71 is etched in the substrate to realize the means to generate the flow magnetic 27 in the form of a spiral winding. We have it fills with conductive material. We put on one of faces of the substrate 70 an electrically insulating layer 72 at the spiral winding. We pierce at least one pair of holes 73 through the substrate 70, they are fills with conductive material to make two electrical contacts 75 to be connected electrically when the magnetic actuator is closed.

Other holes 74 are drilled through the substrate 70 and the insulating layer 72 to achieve the studs 31, 32, 34. They are filled with material magnetic. We took care to place the second stud 32 which helps to delineate the main air gap 29 in the central area of the winding. The third pad 34 is not visible but it is comparable to that of the Figure 7A.

We also deposit, on the face bearing the insulating layer 72 the yoke 30 connected to the pads 31, 32, 34. On the other side of the substrate 70, a sacrificial layer, made of silicon oxide for example, it is engraved at the level of magnetic bonding pads 31, 34. A resin is deposited photolithographically at through a mask and developed to create a box in which we will deposit the moving magnetic part 22 and the flux recovery means 40. The layer sacrificial is then released under the party mobile magnetic to give him his freedom to movement. The sacrificial layer is not shown in Figure 7D but its location is found between the substrate 70 and the magnetic part 22. The latter masks the means of stream recovery.

The moving magnetic part 22 is prolonged beyond the main air gap 29 to come into screws of the two electrical contacts 75 carried by the 70. When the actuator is closed, both electrical contacts 75 are electrically connected via the free end of the movable magnetic part 22. On assume that in this example the magnetic part mobile or at least its free end is carried out in magnetic material conducive to electricity.

We will now describe another variant of a magnetic actuator according to the invention, this last having a high mechanical stability in torsion. Referring to Figs. 8A-8C.

We find the breech 30 which is supported by a support 80 which can be glass, ceramic or in silicon for example.

In Figure 8B, it has a first single stud 31 which ensures both its connection magnetic with the mobile magnetic part 22 and with the flow recovery means 40 and a second plot 32 which helps to delimit the main air gap 29.

In Figure 8C, it has a pair of first pads 31.1, 31.2 which ensures both its magnetic connection with the moving magnetic part 22 and with the flow recovery means 40 and a second stud 32 which helps to delimit the main air gap 29.

In FIG. 8D, the auxiliary air gap has a dimension in the direction of establishment of the flow which is minimal at the level of at least one zone of the portion helping to delimit the gap main.

The mobile magnetic part 22 is always in the form of substantially plane arms but instead of being massive arm consists of two branches 22.1, 22.2 not parallel. On one side branches 22.1, 22.2 are magnetically and mechanically connected to either the first single stud 31, at one of the studs 31.1, 31.2 of the pair and on the other they come together to form the portion 28 which helps to delimit the gap principal 29.

The flow recovery means 40, in this example, are shaped like a substantially plane arm which is housed between the two branches 22.1, 22.2 of the mobile magnetic part 22 substantially in the same plan.

The branches 22.1, 22.2 are substantially symmetrical with respect to a longitudinal axis of the arm flow recovery means 40. This arm is magnetically and mechanically connected to one side, either to the first single pad 31, or to the pair of first pads 31.1, 31.2, and on the other side is free. he is approaching the portion 28. It delimits with the movable magnet 22 the auxiliary air gap 38. The means 27 to generate the flow take the form of a or several windings. In Figure 8B, we have represented a single winding 27 around the first stud 31 single while in Figure 8C is shown a winding 27.1, 27.2 around each of the pads 31.1, 31.2 of the pair. We could have added a winding around the second stud 32.

The realization of a micro-technology actuator similar to that of Figure 8A can be do as follows with reference to Figs. 13A to 13F.

On the substrate 80, we will realize the cylinder head 30. One layer of resin is deposited, then performs a lithography step. We are serious about substrate 80 or in a layer deposited on the substrate a box 130. A conductive underlayer is deposited 131 at the bottom of the box 130 (Figure 13A).

The cylinder head is electrolytically deposited. The depot is then planarized to keep the breech 30 only in the box 130 (Figure 13B).

A dielectric layer is then deposited 81, for example, silicon oxide, and is etched at least one box 132 to delimit the means 27 for generate the flux in the form of winding with their studs electrical control. This engraving is preceded a lithography step. It does not reach the the cylinder head 30. The conductive tracks of the coils 27, for example copper, are deposited by electrolysis, this step is preceded by the deposition of an underlayer driver and is followed by a planarization step (Figure 13C).

A new dielectric layer is deposited 82. The two dielectric layers 81, 82 are etched caissons 133 for delimiting the studs 31, 32. This engraving is preceded by a step of lithography. The boxes 133 reach the breech 30. The magnetic studs 31, 32 are deposited electrolysis, this step is preceded by the deposit of a conductive underlayer and is followed by a step planarization (Figure 13D).

A sacrificial layer is then deposited 83 for example in silicon oxide, and it is serious to clear the first magnetic stud 31 and ensure a separation between the moving magnetic part and the fixed magnetic part with recovery means flows that will be deposited (Figure 13E).

A layer of material is then deposited magnetic to achieve the fixed magnetic part with the flow recovery means 40 and the part movable magnet 22 and by a lithography step and engraving they are delimited. Finally, the layer sacrificial 83 is removed, for example by etching chemical, under the moving magnetic part 22 for the free (Figure 13F).

The electric control pads coils 27 are exposed (not shown). The actuator can be covered with a cover of protection (not shown).

We will now see examples of relays and electrical switches by detailing more particularly their electrical contacts.

In Figure 9A, we see in top view an electric relay comparable to that of the figure 4A. The yoke 30 is supported by a substrate 90. 40 flow recovery means are visible they take the form of an arm with two branches. The part movable magnet 22 protrudes beyond the second stud magnetic 32 and its end ends with a mobile electrical contact 91 offset from the main air gap 29. The substrate 90 on which rests the cylinder head 30 has a conductive track 92 discontinuous. The discontinuity 93 is at the level of movable electrical contact 91. When the actuator is in the closed state, the movable electrical contact 91 comes contact the conductive track 92 on either side of the discontinuity 93 so as to restore continuity. It is assumed that, on each side of the discontinuity 93, the track 92 has a contact zone 94 of material different from that of the track. This material can be in gold, for example, to improve the quality of contact. The conductive track 92 can be a simple conductive line or a microstrip line by example. It's this last configuration that is represented.

Portion 28 on which the force and the movable electrical contact 91 were staggered relative to each other along the portion mobile magnetic 22, but they stay in the same plan. They can be made by the same step technology. We can thus keep a gap 29 as low as possible, in relation to the case where the distance between the electrical contacts is included in the main air gap when the actuator is in the open state and a distance between the contact mobile electric 91 and the largest runway 92 possible. The movable electrical contact 91 can be disposed at any part of the game mobile magnet and it is dimensioned independently dimensions of it. We have space to adjust the level of the track 91 on the substrate 90. It is an advantageous construction to increase the closing force of the relay.

We can consider making contact at the main air gap 29. This is this variant shown in Figures 10A, 10B, 10C.

A movable electrical contact 97 is attached to the mobile magnetic part 22 at the level of the portion 28 seat of the force generated by the magnetic flux. This mobile electrical contact 97 is electrically isolated of the mobile magnetic part 22 by a layer insulation 95. This insulating layer 95 can be removed if the mobile magnetic part 22 is electrically conductive and that this property is used. In this case, we can electrically isolate the part movable magnetic 22 of the rest of the actuator magnetic. It can thus serve itself to the transmission of an electrical signal, contact mobile electric coming to close an electric circuit integrating the mobile magnetic part.

We can consider that the electrical contact be realized by the magnetic material itself as illustrate it in figures 11.

A discontinuous conducting track 96 is represented next to the mobile contact 97. It is found between the second magnetic pad 32 and the contact In this configuration, we do not have represented from contact areas on the runway for improve the quality of the contact. With such configuration, the main air gap 29 is increased the more we add electrically conductive layers or insulation between the moving magnetic part 22 and the second magnetic pad 32, while the spacing between the electrical contacts is substantially constant. Despite the increase in the air gap, the process to realize the actuator can be more simple.

It can be considered for the actuator can function as a switch, that the mobile magnetic part 22 is equipped with two movable electrical contacts 97.1, 97.2. These contacts are placed substantially symmetrically with respect to a median plane of the moving magnetic part 22 substantially perpendicular to the direction of the movement. They are each intended to come close a electrical circuit, schematized by a contact zone 96.1, 96.2, these circuits being arranged on the else of the mobile magnetic part 22. By generating a magnetic flux in the main air gap 29 in a direction or in the other, the mobile magnetic part 22 is move in one direction or in the opposite direction and one of the mobile electrical contacts 97.1 or 97.2 just shut down one of the electrical circuits.

As in FIG. 10A, the contact zone fixed 96.1 is located between the second magnetic pad 32 and the movable electrical contact 97.1. In this representation the insulating layer between the part movable magnet 22 and the electrical contacts mobiles 97.1, 97.2 is omitted.

To make a switch, it is also possible to place the anchor of the party mobile magnet 22 in its central part instead of place it at one of its ends. Figures 11A and 11B illustrate this variant. Now the part movable magnet 22 is in balance with two free ends 37.1, 37.2. It has two portions 28.1, 28.2 which help to delimit each a main air gap 29.1, 29.2 and these portions find on the side of its two free ends 37.1, 37.2.

The breech 30 is now equipped with a first central magnetic anchor pad 31 and a pair of second pads 32.1, 32.2 which contribute each to delimit one of the main air gaps 29.1, 29.2. It is made of a magnetic material electrically conductive. It is assumed that in this example the first central magnetic pad 31 serves also to magnetically connect the means of recovery of flux 40 at the cylinder head 30. The means of stream recovery 40 are comparable to those represented in FIGS. 6. The means for generating the magnetic flux 27 take the form of a pair of windings 27.1, 27.2, each of them surrounding one of the second pads. References 100.1 and 100.2 represent the electrical terminals for the power supply windings. The terminals 100.1 are electrically connected directly to one end of the driver of a winding 27.1, 27.2 while terminals 100.2 are connected via a 100.3 conductor and via one of the seconds magnetic studs 32.1, 32.2 at the other end of the conductor of a winding 27.1, 27.2.

The windings 27.1, 27.2 are isolated electrically of the cylinder head 30 by a layer dielectric 101 which also extends between the first magnetic stud 31 and the cylinder head.

The mobile magnetic part 22 comprises at level of its free ends 37.1, 37.2 a zone 28.1, 28.2 on which the force is exerted during the actuation of the switch. This area 28.1, 28.2 is located opposite each of the second pads 32.1, 32.2, it helps to delimit the main air gap 29.1, 29.2.

The two free ends 37.1, 37.2 are terminate with a contact area, electrical 102.1, 102.1 mobile. It is assumed that the magnetic part mobile 22 is conducting electricity as well as the first magnetic stud 31. The latter is connected to a input conductor E for routing a signal electrical to the mobile magnetic part 22. In screw with respect to each of the electrical contact zones 102.1, 102.2 is a fixed electrical contact 104.1, 104.2 electrically isolated from the second magnetic pad 32.1, 32.2 by a dielectric layer 101. This contact electrical supply is extended by an output conductor S1, S2. The mobile magnetic part comes to contact one fixed electrical contacts 104.1, 104.2, the signal electrical power can be collected on any of the output conductors S1 or S2. The windings 27.1, 27.2 are also electrically isolated from output conductors S1, S2.

The passage of electrical signals and the passage of the magnetic flux are schematized on the right part of Figure 11B. In this example the electrical signal goes through the moving magnetic part but neither by the second magnetic pad nor by the cylinder head. We could have imagined that he goes through these parts of the magnetic circuit.

The windings can be independent or be electrically connected in series, for example opposite windings can be in series in the case use of materials with remanent magnetization or of hysteresis materials.

Figures 12A, 12B illustrate now an actuator according to the invention in an application of pump and more particularly micro-pump.

We find the mobile magnetic part 22 formed of several branches 22.1, 22.2, 22.3 in star. The center 28 of the star helps to delineate the main air gap 29. It may take the form of a magnetic block bearing the same reference 28. The ends of branches 22.1, 22.2, 22.3 are support ends connected magnetically and mechanically at the single breech 30. The breech can for example in the form of a disc. The breech is with a series of first pads 31.1, 31.2, 31.3 to connect it to the mobile magnetic part 22. It also comprises a second central stud 32 which helps delineate the main air gap 29 and a series of third pads 34.1, 34.2, 34.3 for the magnetically and mechanically connect to the means of stream recovery 40.1, 40.2, 40.3. These means of stream recovery help to delineate a auxiliary airgap 38.1, 38.2, 38.3 with the part 22. They occupy the space between two contiguous branches remaining spaced branches.

In this pump configuration, one suppose the first studs and the third studs are joined in their upper part so as to form a peripheral ring at the bolt 30 on which is fixed a membrane 120. This membrane 120 is also attached to the mobile magnetic part 22 and the pad 28 but not the means of recovery of flow 40. This membrane moves at the rate of displacements of the mobile magnetic part 22. It serves to actuate the circulation of a fluid. She can have a compressive, suction or ejection on the fluid. It is performed in a material compatible with the fluid to be pumped or is protected by a surface treatment.

In the example of FIG. 12, the membrane 120 helps delimit on one side with the breech 30 a first cavity 121. The auxiliary air gaps 38.1, 38.2, 38.3 may serve as contributing orifices to the circulation of the fluid, for its ejection of or its suction in an actuating cavity 122 included between the other side of the membrane 120 and the means of flux recovery 40. At least one other orifice 44 also contributing to fluid circulation could cross the crown and lead into the actuating cavity 122. A valve system (no represented) would be used for the fluid to circulate appropriately.

The means to generate the magnetic flux are represented in the form of coils 27 encircling the first magnetic studs 31.1, 31.2, 31.3 and the second magnetic pad 32. A layer seal 123 coats the coils 27 between the cylinder head 30 and the magnetic studs 31.1, 31.2, 31.3, 32, 34.1, 34.2, 34.3 so as to isolate them from the cavity 121.

Other configurations are possible, especially the fluid could be in a tank included in the pump and there would be at least an orifice to eject it.

By removing the membrane such structure could be used as a relay.

Claims (24)

1. Magnetic actuator having a closed magnetic circuit (26) capable of guiding a magnetic flux, this magnetic circuit (26) comprising a fixed magnetic part (30, 31, 32) with a yoke (30) and a mobile magnetic part (22), magnetically connected to each other and also at least one main air gap (29), delimited by at least one portion (28) of the mobile magnetic part (22) and by the yoke (30), in which the magnetic flux is closed by being set up approximately transverse to the mobile magnetic part (22), in the movement direction of said part (22), characterized in that the fixed magnetic part (30, 31, 32) comprises flux recuperation means (40) that contribute with the mobile part (22) to delimiting an auxiliary air gap (38) in which the magnetic flux is set up laterally to the mobile part (22) and consequently substantially transversely to the movement of the mobile part (22), the magnetic flux being contained on each side of the main air gap (29), on one side by the yoke (30), and on the other side jointly by the mobile part (22) and the flux recuperation means (40) through a portion (28) of the mobile magnetic part (22) contributing to delimiting the main air gap (29), the dimension of the auxiliary air gap (38) in the direction in which magnetic flux is set up being a minimum in at least one area of the portion (28) contributing to delimiting the main air gap (29).
2. Magnetic actuator according to claim 1, characterized in that at least one first magnetic stud (31) is used to connect the yoke (30) mechanically and magnetically to the mobile magnetic part (22).
3. Magnetic actuator according to either of claims 1 or 2, characterised in that at least one second magnetic stud (32) contributes to delimiting the main air gap (29), and this magnetic stud (32) is made from a material with hysteresis.
4. Magnetic actuator according to one of claims 1 to 3, characterised in that at least one other magnetic stud (34) is used to mechanically and magnetically connect the yoke (30) to the flux recuperation means (40).
5. Magnetic actuator according to one of claims 1 to 4, characterised in that it comprises means (27) for generating the magnetic flux in the closed magnetic circuit (26), these means for generating the magnetic flux being made by at least one winding.
6. Magnetic actuator according to one of claims 1 to 5, characterised in that the mobile magnetic part (22) is globally in the form of at least one arm with one or several non-parallel branches connected to each other at the portion contributing to delimiting the main air gap (29).
7. Magnetic actuator according to one of claims 1 to 6, characterised in that the mobile magnetic part (22) is in the form of a star with several branches (22.1, 22.2, 22.3).
8. Magnetic actuator according to one of claims 1 to 7, characterised in that the thickness (E1) of the flux recuperation means (40) in the direction of movement of the mobile magnetic part (22) is more than the thickness (E2) of the mobile magnetic part (22) in the displacement direction, so that the auxiliary air gap (38) is delimited by surfaces that remain facing each other during the movement of the mobile magnetic part (22).
9. Magnetic actuator according to one of claims 1 to 8, characterised in that the main air gap (29) is defined by two facing surfaces (S1, S2), the first surface (S1) forming part of the portion (28) of the mobile magnetic part (22) and the second surface (S2) forming part of the yoke (30), the first surface (S1) being larger than the second surface (S2) and projecting all around the second surface (S2).
10. Magnetic actuator according to one of claims 1 to 9, characterised in that the dimension (D2) of the auxiliary air gap (38) in the direction in which the magnetic flux is set up is practically maximum close to the portion (28) contributing to delimiting the main air gap (29), and decreases as the distance from this portion increases.
11. Magnetic actuator according to one of claims 1 to 10, characterised in that the mobile magnetic part (22) comprises at least one through opening (42.2) in the direction of displacement.
12. Magnetic actuator according to one of claims 1 to 11, characterised in that the yoke (30) forms a first level of the actuator and the assembly formed by the flux recuperation means (4) and by the mobile magnetic part (22) forms a second level, the two levels being stacked.
13. Magnetic actuator according to claim 12, characterised in that at least one of the levels has an oblong shape approximately rounded at its two ends.
14. Magnetic actuator according to either of claims 12 or 13, characterised in that the two levels overlap.
15. Magnetic actuator according to one of claims 12 to 14, characterised in that at least one of the levels comprises a central through opening (43).
16. Magnetic actuator according to one of claims 1 to 15, characterised in that it is approximately symmetric about a median plane (P) passing through the mobile magnetic part (22) approximately perpendicular to the movement direction.
17. Magnetic actuator according to one of claims 1 to 16, characterised in that the portion (28) contributing to delimiting the main air gap (29) comprises at least one electrical contact (97) that will contact at least one other electrical contact (96) when the actuator is closed.
18. Magnetic actuator according to one of claims 1 to 16, characterised in that the mobile magnetic part (22) is terminated by at least one electrical contact (91) offset from the portion (28) contributing to delimiting the main air gap (29), this electrical contact being designed to contact at least one other electrical contact when the actuator is closed.
19. Magnetic actuator according to either of claims 17 or 18, characterised in that the electrical contact (97) is electrically isolated from the mobile magnetic part (22).
20. Magnetic actuator according to one of claims 17 to 19, characterised in that the mobile magnetic part (22) is made of an electrically conducting magnetic material and acts as an electrical contact.
21. Method for making a magnetic actuator according to one of claims 1 to 20, characterised in that it comprises the following steps:

    etch a caisson (130) in a substrate (80) to be filled with a magnetic material to make a yoke (30) from a fixed magnetic part (30, 31, 32),

    deposit a first dielectric layer (81) on the substrate (80) with the yoke (30),

    etch at least one caisson (132) to delimit the means (27) of generating a magnetic flux and deposit the said means (27),

    deposit a second dielectric layer (82) on the first layer (81),

    etch caissons (133) through the two layers (81, 82) reaching the yoke (30) to delimit at least one first magnetic stud (31) and at least one second magnetic stud (32), the second stud (32) contributing to delimiting at least one main air gap (29),

    deposit first and second magnetic studs (31, 32) in the caissons (133),

    deposit a sacrificial layer (83) on the second dielectric layer (82) and etch the sacrificial layer (83) to expose the first magnetic stud (31) and to make a separation between a mobile magnetic part (22) and flux recuperation means (40) of the fixed magnetic part, deposited later,

    deposit magnetic material on the sacrificial layer (83) to make the mobile magnetic part (22) and flux recuperation means (27), then etch the magnetic material to delimit them,

    eliminate the sacrificial layer (83) under the mobile magnetic part (22) to expose it and make the main air gap (29).
22. Relay characterised in that it comprises a magnetic actuator according to one of claims 1 to 20.
23. Selector switch characterised in that it comprises at least one magnetic actuator according to one of claims 1 to 20, so as to have several main air gaps (29.1, 29.2).
24. Pump characterised in that it comprises a magnetic actuator according to one of claims 1 to 16, in which the mobile magnetic part (22) is fixed to a membrane (120) that contributes to delimiting a cavity (122) in which a fluid can be circulated.

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