Electromagnetic actuator and electrical switching unit comprising such an electromagnetic actuator

Abstract

To provide an electromagnetic actuator including an assembly of laminated ferromagnetic plates, which enables the implementation of a diagnostic method.SOLUTION: An electromagnetic actuator (2) includes: an armature (4) carrying at least one coil (6); a ferromagnetic yoke (10) configured to channel a magnetic flux generated by the coil; and a ferromagnetic moving part (8) that interacts with the yoke (10) to form a magnetic circuit that is formed at least in part by an assembly of laminated metal plates, the moving part (8) being configured to move in relation to the armature under the action of the magnetic field generated by the coil. The actuator further includes an auxiliary magnetic circuit (20) made of electrically conductive material, in order to permit the flow of currents induced in the auxiliary magnetic circuit when a magnetic field is generated by the coil.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic actuator.

[0002] The invention also relates to an electrical switching unit comprising an actuator of this kind. [Background technology]

[0003] An electromagnetic actuator generally comprises a fixed armature carrying at least one coil capable of generating a magnetic field, and a movable part that moves in translation under the action of the magnetic field generated by the coil, by means of a magnetic circuit that serves to transmit magnetic flux.

[0004] This type of actuator is often found in electrical switching units such as contactors, relays, or remotely operated switches. The moving part is generally mechanically coupled to electrical contacts or a switching mechanism to selectively open or close an electrical circuit.

[0005] As shown in patent application EP 2 584 575 B1, several diagnostic methods and devices have been developed to estimate the wear and operating state of this type of actuator.

[0006] Furthermore, to improve the performance and / or reduce manufacturing costs of such actuators, it may be desirable to replace the ferromagnetic material used with an assembly of laminated ferromagnetic plates.

[0007] One drawback is that in this case the electrical current induced by the magnetic field cannot flow in the direction of the stack of plates due to insufficient conductivity at the contact surfaces between the plates.

[0008] Therefore, the diagnostic methods outlined above become impractical. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] EP2584575B1 Summary of the Invention [Problem to be solved by the invention]

[0010] Therefore, there is a need for an electromagnetic actuator that can overcome the above-mentioned drawbacks. [Means for solving the problem]

[0011] To that end, one aspect of the invention relates to an electromagnetic actuator, in particular for an electrical switching unit, which electromagnetic actuator comprises: an armature carrying at least one coil; a ferromagnetic yoke configured to conduct magnetic flux generated by the coil; - a ferromagnetic moving part that interacts with the yoke to form a magnetic circuit, the magnetic circuit being formed at least in part by an assembly of laminated metal plates, the moving part being configured to move relative to the armature under the action of a magnetic field generated by a coil; and The actuator further comprises an auxiliary magnetic circuit made of a conductive material, which allows for an induced current flow in the auxiliary magnetic circuit when a magnetic field is generated by the coil.

[0012] In accordance with the present invention, when a magnetic field is generated, the auxiliary magnetic circuit allows induced currents to flow within the actuator, but these induced currents cannot flow through other parts of the actuator, such as the magnetic circuit formed by the assembly of laminated ferromagnetic plates.

[0013] The induced current causes a phase offset between the magnetic flux and the electrical control current used to power the coil, thereby generating an electromotive force that is perceived based on the voltage across the terminals of the coil.

[0014] This electromotive force can be used to implement diagnostic methods and / or methods for detecting the wear or operating condition of the actuator.

[0015] Nevertheless, the induced currents flowing in the auxiliary magnetic circuit are still low enough not to impair the performance of the actuator, and in particular not to lead to very high energy losses.

[0016] According to some advantageous but non-essential aspects, such an electromagnetic actuator may incorporate one or more of the following features, either alone or in any technically permissible combination:

[0017] The auxiliary magnetic circuit is made of metal and has a closed outer shape in a geometric plane perpendicular to the direction of flow of the magnetic flux generated by the coils in the magnetic circuit.

[0018] - The auxiliary circuit has a metal piece attached to the actuator armature and surrounding the flow direction of the magnetic flux generated by the coil in the magnetic circuit.

[0019] - The metal piece is made of a non-magnetic material.

[0020] The auxiliary circuit has a layer of conductive material formed on the surface of the actuator armature by a surface treatment method, and the auxiliary circuit has a closed outer shape that surrounds at least a part of the magnetic circuit.

[0021] The magnetic yoke has a spreader made of solid magnetic material, and the auxiliary magnetic circuit is formed by the spreader.

[0022] The moving part consists of a solid magnetic material, the magnetic yoke is completely formed by an assembly of laminated metal sheets, and the auxiliary magnetic circuit is formed by the moving part.

[0023] The auxiliary circuit has at least one metal piece surrounding an arm formed at the end of the movable part.

[0024] - The auxiliary circuit has a metal piece surrounding each of the end arms of the moving part.

[0025] According to another aspect, the electrical switching unit comprises an electromagnetic actuator as defined hereinbefore.

[0026] The invention will be better understood and other advantages of the invention will appear more clearly in the light of the following description of one embodiment of an electromagnetic actuator, given by way of example only and in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic perspective view of an electromagnetic actuator according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic exploded view of the electromagnetic actuator of FIG. 1. [Figure 3] FIG. 5 is a schematic perspective view of a portion of an electromagnetic actuator according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] 1 and 2 show an electromagnetic actuator 2 according to some embodiments.

[0029] As can be seen in more detail in FIG. 2, the actuator 2 has an armature 4 carrying at least one coil 6, a moving part 8, and a ferromagnetic yoke 10 configured to transmit the magnetic flux generated by the coil 6.

[0030] The at least one coil 6 is configured to generate a magnetic field along a longitudinal axis X2, which here corresponds to the direction of movement of the movable part 8.

[0031] In the example shown, two coils 6 are mounted adjacent to each other on the armature 4 and are controlled together. In practice, several coils 6 may be used together to generate a magnetic field. However, in a variant, only one coil 6 may be used.

[0032] Here, the coils 6 each have a cylindrical shape with axis X2 as the central axis.

[0033] The one or more coils 6 are arranged to be powered by a control circuit, which is not shown and may be external to the actuator 2 .

[0034] According to some exemplary implementations, the armature 4 is made of a polymeric material, an electrically insulating material such as polyamide, or any suitable material.

[0035] The movable part 8 is designed to move relative to the armature 4 under the action of a magnetic field generated by one or more coils 6 .

[0036] The movable part 8 is in particular configured for reversible and selective translational movement relative to the armature 4 between a retracted position and an extended position. In the example shown, this movement is performed by translation in the direction X2.

[0037] The movable part 8 interacts with a yoke 10 to form a magnetic circuit capable of conducting the magnetic flux generated by the coil or coils 6 .

[0038] For example, both the movable part 8 and the yoke 10 are made of a magnetic material, preferably a ferromagnetic material.

[0039] The yoke 10 is in particular formed at least partially or entirely from an assembly of laminated metal plates, and the movable part 8 is preferably also formed at least partially or entirely from an assembly of laminated metal plates.

[0040] For example, as illustrated in Figures 1 and 2, the metal plates or sheets are stacked in an assembly along a direction perpendicular to the axis X2.

[0041] Furthermore, the movable part 8 and the yoke 10 have complementary shapes, which allow loopback of the magnetic flux generated by the coil(s) 6 .

[0042] For example, the movable part 8 has a "T" shape and comprises a rod-shaped elongated central part 12 extending along the axis X2. Here, the central part 12 has a rectangular cross section, which is defined in a transverse plane perpendicular to the axis X2.

[0043] The movable part 8 also comprises an arm 14 , for example two arms 14 , arranged at the distal end of the central part 12 and extending perpendicularly thereto.

[0044] The armature 4 here comprises a central orifice 16 extending along the axis X2 and surrounded by one or more coils 6. Thus, when a magnetic field is generated by the one or more coils 6, a corresponding magnetic flux flows along the central portion 12.

[0045] The central portion 12 is received within a central orifice 16 and slides along the central orifice 16 as the movable part 8 translates.

[0046] The yoke 10 has a closed shape with a C-shaped profile, and its upper and lower faces are parallel to the axis X2 here. The yoke 10 defines a central cavity in which the armature 4 is housed.

[0047] The distal ends of the upper and lower surfaces of the yoke 10 here have spreaders 18, which are in the form of folded edges of the upper and lower surfaces of the yoke 10.

[0048] 1, when the actuator 2 is in an assembled configuration, the spreader 18 is positioned facing the arms 14 of the moving part 8. The spreader 18 facilitates folding of the magnetic flux between the yoke 10 and the moving part 8.

[0049] Depending on whether the mobile part 8 is in its retracted or deployed position, the arms 14 are in contact with the spreader 18 or, conversely, spaced apart from the spreader 18, respectively.

[0050] Even if the spreader 18 is omitted, the arm 14 facilitates folding back the magnetic flux between the movable part 8 and the yoke 10 in the magnetic circuit.

[0051] The operation of such electromagnetic actuators is known and will not be described in further detail.

[0052] In general, the actuator 2 can be used in an electrical switching unit such as a contactor, or a relay, or a remotely operated switch, or an electrical protection unit.

[0053] For example, an electrical switching unit may have one or more separable electrical contacts that can be moved between an open state and a closed state to selectively interrupt or allow the flow of electrical current.

[0054] In this case, the actuator 2 may be coupled to a moving contact, for example to directly move the moving contact of the switching unit, or may be coupled to a switching mechanism associated with the switching unit and configured to move the contact when triggered by the actuator.

[0055] For example, the movable part 8 is coupled to a lever for actuating a switching mechanism.

[0056] As a variant, a different type of electric unit may include an actuator 2 of this kind.

[0057] Advantageously, a diagnostic method, such as that described in patent application EP 2 584 575 B1, and / or a method for estimating the wear state or operating state of the actuator, is implemented by a diagnostic device associated with such an electric unit or actuator 2. As a variant, other diagnostic and / or monitoring methods may also be used.

[0058] According to many embodiments of the present invention, the actuator 2 further comprises an auxiliary magnetic circuit 20 made of an electrically conductive material.

[0059] The auxiliary magnetic circuit 20 is configured to allow an induced current flow therein when a magnetic field is generated by the coil 6 .

[0060] The induced current is, for example, an eddy current.

[0061] In many examples, the auxiliary circuit 20 has the shape of a ring, or more generally a closed contour, that surrounds at least a portion of the magnetic flux generated by the one or more coils 6 and flowing in the magnetic circuit formed by the combination of the movable part 8 and the yoke 10.

[0062] Therefore, in practice, the auxiliary circuit 20 is arranged to surround at least a part of the magnetic circuit formed by the combination of the movable part 8 and the yoke 10. For example, the auxiliary circuit 20 surrounds a cross section of at least a part of the magnetic circuit.

[0063] For example, the auxiliary circuit 20 may directly surround the central portion 12 of the moving part 8 or may surround the central orifice 16 of the armature 4 (indeed, it may at least partially surround the central portion 12).

[0064] For example, "ring-shaped" herein means the closed outline defined by auxiliary circuit 20, which when disposed around the magnetic flux generated by one or more coils 6, can have a circular, or essentially circular, or elliptical, or square, or rectangular, or polygonal, or any suitable shape that allows for the flow of current induced and the folding of loops when a magnetic field is generated by one or more coils 6.

[0065] For example, the auxiliary circuit 20 defines a closed contour in a geometric plane perpendicular or essentially perpendicular to the axis X2, and more generally in a geometric plane perpendicular or essentially perpendicular to the direction of the magnetic flux flowing in the magnetic circuit formed by the movable part 8 and the yoke 10.

[0066] According to a preferred embodiment, one exemplary implementation of which is illustrated in FIGS. 1 and 2, the auxiliary circuit 20 comprises a piece of metal, such as a hollow metal plate, mounted on the armature 4, for example on the front face 22 of the armature 4.

[0067] The hollow plate therefore has the shape of a ring. As a variant, the metal piece can be a folded electrical conductor, such as a wire, or a folded metal strip, or a short-circuited coil. In other words, the metal piece is separated from the magnetic circuit formed by the combination of the movable part 8 and the yoke 10 .

[0068] Nevertheless, other locations are also possible for fastening said metal piece to the armature 4, for example on the rear surface or around the centre of the armature 4. In this last case, the metal piece may also be placed in the part of the armature 4 separating the two coils 6 or inside the armature 4 below one of the coils 6, in which case an electrical insulating element can be inserted between the coil 6 and said metal piece.

[0069] In the example shown, the metal plate forming the auxiliary circuit 20 comprises a central orifice 24 intended to be aligned with the central orifice 16 of the armature 4 .

[0070] Said metal piece may be fixed to the armature 4 by dedicated fixing elements, or by gluing, or by welding, or by any suitable means.

[0071] For example, openings 26 are formed in the metal strip at multiple locations. Each opening 26 is configured to interact with a corresponding anchor pad 28 formed on the armature.

[0072] Optionally, as in the example seen in FIG. 2, the front face 22 of the armature 4 may have a recess or groove forming a receptacle for receiving a metal piece forming the auxiliary circuit 20, in which a fixing pad 28 is formed.

[0073] In accordance with the present invention, the auxiliary magnetic circuit 20 allows induced currents to flow within the actuator when a magnetic field is generated by the coil 6, but these induced currents cannot flow through other parts of the actuator, such as the magnetic circuit formed by the assembly of laminated ferromagnetic plates.

[0074] The induced current results in a phase offset between the magnetic flux generated by coil 6 and the electrical control current used to power coil 6, thereby generating an electromotive force that is perceived based on the voltage across the terminals of coil 6.

[0075] This electromotive force may be used to implement diagnostic methods and / or methods for detecting the wear or operating state of the actuator, such as for example those described in patent application EP2584575B1, or in combination with other methods which may be used as variants.

[0076] Nevertheless, the induced currents flowing in the auxiliary magnetic circuit 20 are still low enough not to impair the performance of the actuator 2, and in particular not to lead to very high energy losses.

[0077] The invention therefore makes it possible to obtain an electromagnetic actuator that is robust and inexpensive to manufacture, which is compatible with diagnostic and / or monitoring and / or condition sensing methods.

[0078] Advantageously, the material forming the auxiliary circuit 20 is a non-magnetic metal such as copper or aluminum, or any suitable material or alloy, preferably a metal with low resistivity.

[0079] For example, the thermal fluctuation rate of electrical resistance is 0.005K. -1 Preferably, metals are selected that are:

[0080] The use of non-magnetic materials makes it possible to reduce variations in skin thickness when induced currents are generated and flow through the auxiliary circuit 20, which ultimately makes it possible to reduce or even eliminate variations in the equivalent resistance of the auxiliary circuit 20.

[0081] Therefore, in the case of diagnostic or monitoring or condition detection methods based on measuring the electromotive force generated across the terminals of the coil 6 by such induced currents, such as those outlined above, the component of this electromotive force associated with the equivalent resistance of the auxiliary circuit 20 will be constant over the time period considered, facilitating the interpretation of the results.

[0082] Such diagnostic and / or monitoring and / or condition sensing methods are therefore easier to implement and give more reliable results than when induced currents flow in solid magnetic materials.

[0083] However, as a variant, the conductive material forming the auxiliary circuit 20 may also be a magnetic metal, such as a ferromagnetic metal.

[0084] Many other embodiments are possible, some of which are described below.

[0085] Each of the embodiments described below may differ from the previously described embodiments relating to actuator 2 in terms of how the auxiliary magnetic circuit 20 is implemented, but it will be understood that the role and general operation of the auxiliary magnetic circuit 20, as well as the nature of the materials used to form the auxiliary magnetic circuit 20, are similar to those previously described with reference to actuator 2.

[0086] Thus, according to some alternative embodiments not shown, the auxiliary circuit 20 may be located somewhere other than the armature 4, but still be located so as to surround at least a portion of the magnetic flux generated by the coil 6.

[0087] The auxiliary magnetic circuit 20 may also be made by other than attached magnetic pieces.

[0088] According to a first example, illustrated in particular with reference to Figure 3, an electromagnetic actuator 2' is similar in operation to the actuator 2 described so far, but comprises an auxiliary magnetic circuit 20' having a layer of conductive material formed on the surface of the armature by a surface treatment method such as autocatalytic or electrochemical deposition of a metal such as nickel or tin. For example, this layer is formed here on face 22.

[0089] As mentioned above, the auxiliary circuit 20 ′ has a closed contour that encloses the magnetic flux generated by the coil 6 .

[0090] According to a second example, not shown, the auxiliary circuit 20 comprises at least one metal piece surrounding one of the end arms 14 of the mobile part 8. This metal part is, for example, as described above in connection with the actuator 2.

[0091] In this second example, the closed contour of the auxiliary circuit does not extend around the axis X2, since in this case the arm 14 (and therefore the magnetic flux carried by the magnetic circuit) is perpendicular to the axis X2.

[0092] Preferably, in this second example, two such metal pieces are used, each one surrounding one of the two arms 14 of the mobile part 8, so as to form two auxiliary circuits.

[0093] Specifically, the magnetic flux is split in two at the arms 14, with half of the magnetic flux going to each of the two arms 14. Nevertheless, by placing an auxiliary circuit around each arm 14, a phase offset is obtained across the actuator 2, similar to if a single auxiliary circuit were placed around the central portion 12.

[0094] Other embodiments may be implemented when at least part of the yoke 10 or the movable part 8 is not formed entirely by an assembly of laminated metal plates, for example when at least one or the other of them consists at least partially of solid ferromagnetic material.

[0095] In one example not shown, the moving part 8 is made of solid magnetic material and the yoke 10 is formed entirely by an assembly of laminated metal plates. In that case, the auxiliary magnetic circuit is formed by the moving part 8, which is made of solid ferromagnetic material and through which induced currents can flow freely.

[0096] According to another example not shown, the yoke 10 is made of solid magnetic material and the movable part 8 is formed entirely by an assembly of laminated metal plates. In that case, the auxiliary magnetic circuit is formed by the yoke 10, which is made of solid ferromagnetic material, and the induced currents can flow freely within the yoke 10.

[0097] According to yet another example, the spreader 18 of the yoke 10 is made of a solid magnetic material, with the remainder of the yoke 10 being formed by an assembly of laminated metal plates.

[0098] In that case, the auxiliary magnetic circuit is formed by the spreader 18, and since the spreader 18 consists of a solid ferromagnetic material, the induced currents can flow freely within the spreader 18.

[0099] Any feature of one of the previously described embodiments or variations may be implemented in other described embodiments and variations. [Explanation of symbols]

[0100] 2 Actuators 4 Armature 6 coils 8 Moving parts 10 Ferromagnetic yoke, yoke 12 Central part 14 Arm, end arm 16 Central Orifice 18 Spreader 20 Auxiliary magnetic circuit, auxiliary circuit 22 Front, side 24 Central Orifice 26 Opening 28 Fixation Pad X2 Longitudinal axis, axis 2' Electromagnetic actuator 20' Auxiliary magnetic circuit, auxiliary circuit

Claims

1. An electromagnetic actuator (2; 2'), in particular for an electrical switching unit, comprising: an armature (4) carrying at least one coil (6); a ferromagnetic yoke (10) configured to transmit the magnetic flux generated by the coil; a ferromagnetic moving part (8) that interacts with the ferromagnetic yoke (10) to form a magnetic circuit, the magnetic circuit being formed at least in part by an assembly of laminated metal plates, the ferromagnetic moving part (8) being configured to move relative to the armature (4) under the action of the magnetic flux generated by the coil (6); the electromagnetic actuator (2; 2') further comprises an auxiliary magnetic circuit (20; 20') made of a conductive material, allowing an induced current flow in the auxiliary magnetic circuit (20; 20') when a magnetic field is generated by the coil; The electromagnetic actuator (2; 2'), characterized in that the auxiliary magnetic circuit (20') has a layer of conductive material formed on the surface of the armature (4) of the electromagnetic actuator (2') by a surface treatment method, and the auxiliary magnetic circuit (20') has a closed outer shape that surrounds at least a part of the magnetic circuit.

2. 2. The electromagnetic actuator according to claim 1, wherein the auxiliary magnetic circuit is made of metal and has a closed outer shape in a geometric plane perpendicular to a flow direction of the magnetic flux generated by the coil in the magnetic circuit.

3. 3. The electromagnetic actuator according to claim 1, wherein the ferromagnetic yoke has a spreader (18) made of a solid magnetic material, and the spreader (18) facilitates folding back magnetic flux between the ferromagnetic yoke (10) and the ferromagnetic moving part (8).

4. 3. An electromagnetic actuator according to claim 1 or 2, wherein the ferromagnetic moving part (8) is made of a solid magnetic material and the ferromagnetic yoke (10) is completely formed by an assembly of laminated metal sheets.

5. An electrical switching unit, characterized in that it comprises an electromagnetic actuator (2; 2') according to any one of claims 1 to 4.

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