EP2406806B1 - Electromagnetic actuator with shunt flux circuit - Google Patents

Description

The present invention relates to a permanent magnet electromagnetic actuator conventionally comprising a magnetic armature, a movable pallet, a generally spring-loaded return mechanism and electrical means comprising at least one conductor whose current makes it possible to vary the flux in the magnetic circuit. to change the balance between the magnetic force and that of the spring. Such an actuator may for example be used as a relay, the aforementioned conductor then taking the form of a coil. The document EP0301935 discloses an electromagnetic trigger comprising an open armature, a movable pallet and a permanent magnet. It further comprises a return spring and a coil wound around one of the arms of the frame. The magnet generates a magnetic flux in the armature and the pallet, keeping the latter in the closed position. When a current flows through the coil, the flow thus created cancels or reduces that of the magnet, and the pallet then opens under the action of the spring.

The object of the invention is to provide an actuator with very high sensitivity, that is to say operating with a minimum value of ampere-turns generating, however, at at least one gap a flow variation sufficient to counterbalance the mechanical force and cause the pallet to move. In terms of relays, the goal is to control the impedance of the coil, which in fact depends on the value of the reluctant circuit seen by the coil.

For this purpose, the actuator of the invention, more precisely comprising a permanent magnet, a ferromagnetic armature forming a closed loop, a pallet creating two air gaps with the armature and movable between an open position and a closed position, mechanical means for returning the pallet to the open position and at least one electrical conductor capable of generating a magnetic flux in the actuator, is essential in that the magnet, the armature and the pallet are arranged so that the magnet generates fluxes in two magnetic circuits in parallel having a portion of the armature which is saturated for at least one of the parallel circuits, a common branch comprising the magnet and a fraction of the separate pallet by an air gap of said reinforcing portion, and in that the conductor or conductors are capable of generating, in a magnetic loop comprising the unsaturated portion of the armature, the air gaps and the pallet, a flow that adds to the flow created by the magnet in one of the air gaps and one of the fractions of the pallet, and there subtracted in the other air gap and the other fraction of the pallet.

The principle of the structure of the invention consists in generating a strong flow variation on the pallet with a minimum of ampere-turns in a portion of the overall magnetic circuit, by opposing the flux generated by the magnet. In the case of the invention applied to an inductive coil relay, the reluctance seen by the coil depends on the reluctances of the saturated portions, the unsaturated part of the armature and, to a lesser extent, the gap reluctances. .

Given the configuration of the magnetic circuit of the invention, if the reluctances of the saturated portions are small compared with those of the air gaps, the reluctance seen by the coil will be substantially equal to the sum of the reluctances of the saturated portions and the reluctance of the remainder of the the armature, which are known, hence the desired control of the impedance of the relay coil.

According to a possible configuration, the pallet may be U-shaped whose legs are placed on either side of the magnet, their free ends forming two air gaps with a part of the closed loop of the frame containing the two portions. saturated each leading to the common branch with the permanent magnet.

According to the invention, the closed magnetic loop may either comprise a coil wound around a portion of the closed loop of the armature separate from the parallel magnetic circuits, or surround at least two power supply conductors of an electrical circuit.

The closed loop of the frame can obviously take various forms, for example rectangular, circular shape, etc.

According to one possibility, the permanent magnet can be secured to the ferromagnetic armature.

In addition, the saturated portions may consist of zones of the reinforcement of reduced section relative to the rest of the reinforcement.

The configuration of the invention leads to a structure that is magnetically unpolarized, since it allows a trigger the direction of the current in the conductor (s) of the electrical means.

• La figure 1 représente schématiquement une première forme possible d'actionneur pour l'invention ;
• La figure 2 montre le schéma électromagnétique équivalent à la structure de la figure 1 ; et
• La figure 3 montre une variante de la figure 1.

The invention will now be described in more detail, with reference to examples illustrated by the appended figures, for which:

• The figure 1 schematically represents a first possible form of actuator for the invention;
• The figure 2 shows the electromagnetic pattern equivalent to the structure of the figure 1 ; and
• The figure 3 shows a variant of the figure 1 .

With reference to the figure 1 , the armature (1) forms a closed loop surmounted by a pallet (2) with two lateral branches (3, 4) in the middle of which is a permanent magnet (5). The armature (1) is traversed by two conductors (8, 9). It also comprises at least one saturated zone (6, 7) or plug area located at or near the magnet (5). Two air gaps (10, 11) are formed between the pallet (2) and the armature (1).

Magnetic operation is explained in figure 2 . Without electrical fault, the magnet (5) globally sees two branches of magnetic reluctance in parallel, corresponding to two fractions of pallets respectively traversed by the flows phi1 and phi2.

avec phi1 +phi2 = flux généré par l'aimant (aux fuites magnétiques près). Dans cette hypothèse, l'aimant équilibre la valeur des flux pour équilibrer la valeur des réluctances.It then generates in each branch a magnetic flux such as: $$\begin{array}{l}\mathit{RPAL}\mathit{1}\left(\mathit{phi}\mathit{1}\right)\mathit{x}\mathit{phi}\mathit{1}\mathit{+}\mathit{Rent}\mathit{1}\left(\mathit{phi}\mathit{1}\right)\mathit{x}\mathit{phi}\mathit{1}\mathit{+}\mathit{Rmat\_haut}\left(\mathit{phi}\mathit{1}\mathit{+}\mathit{phi}\mathit{2}\right)\mathit{x}\left(\mathit{phi}\mathit{1}\mathit{+}\mathit{phi}\mathit{2}\right)\\ \mathit{+}\mathit{Rmat\_bas}\left(\mathit{phi}\mathit{1}\mathit{+}\mathit{phi}\mathit{2}\right)\mathit{x}\left(\mathit{phi}\mathit{1}\mathit{+}\mathit{phi}\mathit{2}\right)\mathit{+}\mathit{R}\mathit{1}\left(\mathit{phi}\mathit{1}\right)\mathit{x}\mathit{phi}\mathit{1}\mathit{=}\\ \mathit{RPAL}\mathit{2}\left(\mathit{phi}\mathit{2}\right)\mathit{x}\mathit{phi}\mathit{2}\mathit{+}\mathit{Rent}\mathit{2}\left(\mathit{phi}\mathit{2}\right)\mathit{x}\mathit{phi}\mathit{2}\mathit{+}\mathit{Rmat\_haut}<figure-callout\; id="1"\; label="\; phi\; "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\; </figure-callout>\left(\mathit{phi}\right)\left(\mathit{1}\mathit{+}\mathit{phi}\mathit{2}\right)\mathit{x}\\ \left(\mathit{<figure-callout\; id="1"\; label="phi\; "\; filenames="imgf0001.png"\; state="\{\{state\}\}">phi\; </figure-callout>}\mathit{1}\mathit{+}\mathit{<figure-callout\; id="2"\; label="phi\; "\; filenames="imgf0001.png"\; state="\{\{state\}\}">phi\; </figure-callout>}\mathit{2}\right)\mathit{+}\mathit{Rmat\_bas}<figure-callout\; id="1"\; label="\; phi\; "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\; </figure-callout>\left(\mathit{phi}\right)\left(\mathit{1}\mathit{+}\mathit{phi}\mathit{2}\right)\mathit{x}\left(\mathit{<figure-callout\; id="1"\; label="phi\; "\; filenames="imgf0001.png"\; state="\{\{state\}\}">phi\; </figure-callout>}\mathit{1}\mathit{+}\mathit{<figure-callout\; id="2"\; label="phi\; "\; filenames="imgf0001.png"\; state="\{\{state\}\}">phi\; </figure-callout>}\mathit{2}\right)\mathit{+}\mathit{R}\mathit{2}\left(\mathit{phi}\mathit{2}\right)\mathit{x}\mathit{<figure-callout\; id="2"\; label="phi\; "\; filenames="imgf0001.png"\; state="\{\{state\}\}">phi\; </figure-callout>}\mathit{2}\end{array}$$

with phi1 + phi2 = flux generated by the magnet (near magnetic leakage). In this case, the magnet balances the value of the fluxes to balance the value of the reluctances.

Material reluctances such as Rpal, R1 and R2 are nonlinear and saturable. The Rmat_haut and Rmat_bas reluctances may represent a gap and / or a saturable magnetic material.

The Rent1 and Rent2 reluctances represent the equivalent gap between the pallet and the armature. R1 and R2 are saturated.

When an electrical fault appears, the conductors or the coil (as shown) generate a magnetic flux Phi_bob in the Rbas branch, which flows through the maximized loop containing the air gaps (10, 11) and the pallet (2).

In this case, the magnetic flux generated by the conductors will oppose that of the magnet (5) on one of the polar surfaces and will be added to the flux of the magnet for the other polar surface, as shown by the arrows appearing on the figure 2 .

The figure 3 shows a variant to the figure 1 , of different shape and in which the magnet is not integral with the armature (1), which comprises a coil (8 ') exciter. The operation is however identical.

Many other configurations are possible, the illustrated examples not being considered exhaustive of the invention.

Claims (4)

1. Electromagnetic flux bypass actuator having a permanent magnet (5), a ferromagnetic armature (1) forming a closed loop, a keeper (2) creating two air gaps (10, 11) with the armature (1) and mobile between an open position and a closed position, a mechanical means of returning the keeper to the open position and at least one electrical conductor (8, 8', 9) able to generate a magnetic flux in the actuator, where the magnet (5), the armature (1) and the keeper (2) are arranged so that the magnet (5) generates lines of flux in two magnetic circuits in parallel having a section of the armature (6, 7) which is saturated for at least one of the parallel circuits, a common branch including the magnet (5) and a part of the keeper separated by an air gap (10, 11) from the said section of the armature (6, 7), and where the conductor or conductors (8, 8', 9) are able to generate, in a magnetic loop containing the non-saturated part of the armature (1), the air gaps (10, 11) and the keeper (2), a flux that is added to the flux created by the magnet (5) in one of the air gaps (10, 11) and one part of the keeper (2), and is subtracted from it in the other air gap (11, 10) and the other part of the keeper (2).
2. Electromagnetic actuator according to the preceding claim, characterized in that the keeper (2) is in the form of a U of which the legs (3, 4) are placed on either side of the magnet (5), their free ends forming two air gaps (10, 11) with a part of the armature (1) closed loop containing two saturated sections (6, 7), each one leading to the common branch with the permanent magnet (5).
3. Electromagnetic actuator according to the preceding claim, characterized in that the permanent magnet (5) is fixed to the ferromagnetic armature (1).
4. Electromagnetic actuator according to one of claims 1 to 3, characterized in that the saturated sections (6, 7) are made up of areas of the armature (1) with a reduced cross-section compared to the rest of the armature (1).

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