EP1058278A2 - Wound magnetic circuit - Google Patents

Abstract

The magnetic circuit manufacture technique has a magnetic center section (3) inside an outer coil (2) formed by winding a conductor wire on a slightly conical shaped mandril. The magnetic center is spiral in shape with one end (16) shaped away from the mandril tube axis.

Description

The present invention relates to a wound magnetic circuit and a method of manufacture of such a circuit.

Wound magnetic circuits are used in many fields among which are current sensors and transformers. In applications such as current sensors, accuracy is closely related to the magnetic properties of the materials used and the precision of manufacturing. Achieving desired precision is often against the need reduce the manufacturing cost and reduce the size of the components.

A method of manufacturing a winding on a toroidal magnetic circuit is described in European patent EP 668 596. The process described in this patent, who tries to meet the criteria mentioned above, understands the steps to wind a conductive wire coated with a thermo-adhesive around a mandrel cylindrical to form a coil, to open a magnetic circuit by spreading the lips of the air gap, thread the coil onto the magnetic circuit and then close the magnetic circuit.

There are several drawbacks to this conventional process. First, it is very difficult to remove the spool from the cylindrical mandrel and then thread it onto the core. Second, the opening and closing of the magnetic circuit, like all plastic deformation, deteriorates the magnetic properties of circuit.

In view of these drawbacks, the object of the present invention is to provide a wound magnetic circuit having electrical and magnetic behavior precise and can be manufactured industrially economically.

Objects of the invention are achieved by the method of manufacturing a circuit magnetic winding according to claim 1, the magnetic winding circuit of the claim 5, and the device for manufacturing a magnetic circuit The wound wire of claim 8.

In the present invention, a method of manufacturing a magnetic circuit wound with an electric coil and a magnetic core with the stages of making the coil by winding a conducting wire on a mandrel having a slightly conical outer surface, and thread the spool on a core magnetic in the form of an open coil, this coil being first formed before establishing the specified magnetic properties of the magnetic material of the turn. After the coil has been threaded onto the magnetic core, we distorts the ends of the core in a direction essentially orthogonal to the plane of the magnetic circuit to bring them closer. Advantageously, by this process, the magnetic material is deformed minimum so as not to degrade these magnetic properties.

The coil can be threaded onto the magnetic core during removal of the mandrel, which reduces the time and costs of manufacturing the magnetic circuit coil. For this purpose, it is advantageous that one end of the magnetic core is inserted into a cavity at one end of the mandrel to facilitate threading the coil on the magnetic core.

The wound magnetic circuit may further include a flange and a connector, the flange and the connector being each arranged at one end respective of the coil, the coil being mounted on the magnetic core formed a toroidal magnetic wire. The flange facilitates threading of the spool on the nucleus by its shape and its dimensions, on the one hand, and by the reduction of the coefficient of friction, on the other hand. For this purpose, the flange can advantageously have a chamfered interior surface to facilitate its followed by the curvature of the nucleus. The flange also avoids damage to the insulation of the electric wire by friction on the toroid.

The mandrel of the device for manufacturing a wound magnetic circuit, around which the coil is formed, may have an outer surface of shape slightly conical. This facilitates removal of the spool from the mandrel.

The angle α of the cone can be very small and have, for example, a value tan α between 0.001 and 0.01. The difference in coil diameter between the ends is thus negligible.

The mandrel can also have a cavity at its end to allow the insertion of the end of the magnetic core into the cavity, and thus facilitate the assembly of these components.

la Fig. 1 est une vue en perspective d'un mandrin et d'une bobine formée sur le mandrin et prête à être insérée sur un noyau magnétique, selon l'invention;

la Fig. 2 est une coupe longitudinale de l'ensemble montré à la Fig. 1;

la Fig. 3 est une vue d'un fil magnétique continu utilisé pour former le noyau magnétique;

la Fig. 4 est une vue d'un noyau magnétique découpé du fil magnétique continu; et

les Figures 5 à 7 sont des vues en perspective montrant divers étapes dans la fabrication de la bobine.

Other objects and advantageous aspects of the invention will emerge from the description and claims below, and from the appended drawings, in which

Fig. 1 is a perspective view of a mandrel and a coil formed on the mandrel and ready to be inserted on a magnetic core, according to the invention;

Fig. 2 is a longitudinal section of the assembly shown in FIG. 1;

Fig. 3 is a view of a continuous magnetic wire used to form the magnetic core;

Fig. 4 is a view of a magnetic core cut from the continuous magnetic wire; and

Figures 5 to 7 are perspective views showing various stages in the manufacture of the coil.

A wound magnetic circuit 1 comprises a coil 2 and a core magnetic 3. The coil 2 has a flange 4 at an anterior end 19, a connector 5 at the other end (10), and a coiled conductive wire 6 around a central cavity 7 and extending between the connector 5 and the flange 4. The conducting wire 6 can be, for example, a conventional copper wire provided with an insulating and adherent layer to form the coil. The wire can also be only insulating, the application of an adherent being done during the reel formation.

Connector 5 has terminals 8 for circuit connection magnetic wound to electronics or other device. Terminals 8 are housed in a housing 9 of the connector which also serves as a support for a end 10 of the coil and the end of the conductor wires of the coil which are electrically connected to terminals 8. The connection of the conductive wires to an external device is therefore made easier by integrating the connector 5 into the coil during the manufacture of the coil, and at the same time allows protect and ensure a good connection between the conductors of the coil and external electronics.

The flange 4, at the other end of the coil 2, serves as a support for the end reel insertion and provides an inner guide surface 11 for protect the wire at the threading end of the spool against abrasion during threading on the core 3 which can cause short circuits between turns. In addition, the guidance of the end of the coil by the flange 4 during the deformation of the coil during its threading on the O-ring, is markedly improved. Indeed, the flange 4 makes it possible to define the shape well and the dimensions of the guide surface 11 and reduce the coefficient of friction between the coil and the magnetic core 3. In particular, the flange has a chamfer 18 to follow the curvature of the magnetic core 3.

After the connector 8 and the flange 4 have been threaded onto a mandrel 12, such as shown in Fig. 5, one end of the conductive wire is connected to a connector terminal 8a and the coil 2 is then wound on the mandrel 12 as shown in Fig. 6. At the end of the winding, the other end of the wire conductor is connected to one of terminals 8b. The connection between the wire and the terminals 8a, 8b, can be done by coiled connection or by other means conventional. The coil can have one or more windings additional connected to one or more additional terminals, such than 8c.

The mandrel 12 extends along an axis of rotation A to an end 13. The mandrel has a conical outer surface 14 to facilitate removal of the reel of the mandrel and its threading on the magnetic core 3. The angle α of the cone can be very small, for example tan a can have a value between 0.001 and 0.01, so that the influence of the cone on the variation in diameter of the coil is negligible while retaining the advantage of facilitating the removal of the coil of the mandrel. It should be noted that this advantage is all the more important as the wires are coated with an adhesive product to maintain the shape of the coil.

The mandrel has a positioning part 17 for positioning and block the relative rotation of connector 5 on the mandrel. The chuck further includes a recess 15 at its end for the insertion of one end 16 of the magnetic core 3 during the step of threading the coil 2 onto the core, as shown in Figures 1, 2 and 7. After forming the coil on the mandrel 12, the coil 2 can therefore be easily and directly threaded onto the magnetic core 3, as shown in FIG. 7, by the action of a pusher 20 engaging the connecting end 5 (see Fig. 1). The pusher has the shape of a fork which is placed astride the connector behind flanges 21 of the connector after the winding operation. The pusher moves, in the direction (P) parallel to the axis (A) of the mandrel, so as to position the coil 2 precisely on the magnetic core 3. In the case of the use of a wire provided with a thermo-adhesive layer, the coil can be heated, or kept hot, to allow its deformation during threading on the core 3.

The O-ring 3 is made of a magnetically permeable material conventional, such as iron-nickel and it can have any suitable form (wire, flat, sheet metal, or assembly of such elements). Typically, to have good magnetic properties, the material used is annealed after its deformation in the form of an open torus, because plastic deformations important degrades the magnetic properties. However, it is no longer possible to anneal the torus once the coil is mounted on it.

In the present invention, the plastic deformations of the magnetic material are reduced to a minimum to reduce the influence of deformations on the magnetic properties. For this purpose, the magnetic material has, for example, the shape of a wire 3 'in the form of a helical turn, as shown in FIG. 3, and then cut along the dotted lines e1 and e2. We thus form several individual turns, as shown in Fig. 4, the turns being ready for assembly of the coil, as described above, the only plastic deformation individual turns being carried out after the assembly of the coil for bring the ends 16, 16 'closer to the magnetic core 3. The ends 16, 16 'are deformed by rotation in an essentially orthogonal direction (O) on the plane of the magnetic circuit and form an air gap of a length specified, depending on the application.

During the formation of the helical turn, the pitch (P) can be adjusted to correspond to the necessary spacing, in the orthogonal direction (O) to circuit plane, between the ends 16, 16 'so as to allow the insertion of the coil on the core. The thickness (E) of the longitudinal cut of the coil to form the individual turns can be adjusted so that after the rotational deformation of the ends 16, 16 'of the magnetic circuit in the direction essentially orthogonal (O) to the circuit plane, the ends are separated by the specified gap length. In this case, the thickness (E) of the cutout is substantially equal to the length of the air gap.

The magnetic material can therefore be annealed after the formation of the coil, or after cutting the individual turns, so that the only deformation that undergoes the magnetic core after being annealed, is due to the approximation of ends 16, 16 'of the magnetic circuit.

Claims (12)

Method of manufacturing a wound magnetic circuit (1) having a electric coil (2) and a magnetic core (3) comprising the steps of make the coil (2) by winding a conductive wire (6) on a mandrel (12) having a slightly conical outer surface (14), threading the spool (2) on a magnetic core (3) in the form of an open coil having ends (16, 16 '), this turn being first formed before the establishment of the properties specified magnetic material of the coil, and to deform the ends (16, 16 ') of the magnetic core in a direction essentially orthogonal (O) to the plane of the wound magnetic circuit to bring them closer. Method according to claim 1, characterized in that the coil (2) is threaded onto the magnetic core (3) during removal of the mandrel (12). Method according to claim 2, characterized in that one end (16) of the magnetic core (3) is inserted into a cavity (15) at one end (13) of the mandrel (12) to facilitate threading of the coil (2) on the core magnetic (3). Method according to one of the preceding claims, characterized in that, before or during the winding operation, there is a flange (4) on the mandrel (12) to form a front end (19) of the coil (2), this end being intended to be threaded first on the magnetic core (3). Coiled magnetic circuit (1) comprising an electric coil (2) and a magnetic core (3), the coil (2) comprising a conductive wire (6), a flange (4) and a connector (5), the flange (4) and the connector (5) being each arranged at a respective end of the coil (2), the coil being mounted on the magnetic core (3) formed of a shaped magnetic wire toric. Coiled magnetic circuit according to the preceding claim, characterized in that the inner cavity (7) of the coil (2) has a slightly shaped conical. Coiled magnetic circuit according to one of claims 5 or 6, characterized in that it is manufactured by one of the methods according to one of claims 1 to 4. Device for manufacturing a wound magnetic circuit comprising a coil (2) mounted on a magnetic core (3) of toroidal shape, the device comprising a mandrel (12) around which the coil is formed, the mandrel having an outer surface (14) of slightly conical shape. Device according to the preceding claim, characterized in that the angle a of the cone to a value tan α lying between 0.001 and 0.01. Device according to claim 8 or 9, characterized in that the mandrel (14) has a cavity (15) at its end (13) to allow the insertion of the end (16) of the magnetic core (3) in the cavity. Device according to one of claims 8 to 10, characterized in that it has a pusher (20) having sufficient travel to push the spool (2) out of the mandrel (12). Device according to claim 12, characterized in that the pusher (20) has the shape of a fork.

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