WO2021250509A1

WO2021250509A1 - Magnet pole with a plurality of unit magnets coated in a composite layer

Info

Publication number: WO2021250509A1
Application number: PCT/IB2021/054826
Authority: WO
Inventors: Jeremy MECH; Jeremy CARLES
Original assignee: Whylot
Priority date: 2020-06-09
Filing date: 2021-06-02
Publication date: 2021-12-16
Also published as: FR3111244A1

Abstract

The present invention relates to a magnet pole (10) formed of a plurality of elongate unit magnets, longitudinally oriented magnetically and extending in parallel, being secured to one another in a wafer connecting a front face and a rear face of the magnetic pole (10). The magnet pole (10) is entirely encapsulated in at least one fibre-reinforced composite layer (6), said at least one composite layer (6) defining an outer contour of the magnet pole (10).

Description

DESCRIPTION

TITLE: Magnet pole with several unit magnets coated in a layer of composite

Technical Field of the Invention The present invention relates to a magnet pole with several unit magnets, this magnet pole being embedded in a layer of composite. This or these magnet poles are advantageously intended to be housed in an electromagnetic machine with axial flow. The present invention finds an advantageous but non-limiting application for an electromagnetic motor delivering a high power with a high rotational speed of the rotor, which is obtained by specific characteristics of the rotor and of the magnets which it houses. Such a motor can be used, for example, as an electromagnetic motor by being able to rotate at high speeds. Prior art

In high speed applications, it is necessary to have very good mechanical strength of the rotating part of the electromagnetic machine, that is to say the rotor, in order to improve its reliability.

For an electromagnetic machine with axial flow, the rotor comprises a body in the form of a discordai support for magnets, the rotor having two circular faces connected by a thickness, the disc being frequently delimited between an outer ring formed by a hoop and a ring. internal periphery defining a recess for a rotation shaft.

The magnets are each held in the discordai support by retaining means, a gap being left between the magnets.

For high speed applications, the design of the rotor in an axial flow motor is tricky because the forces due to centrifugal effects cause quite large mechanical stresses in the rotor. In addition, the eddy current losses become predominant both in the magnets and also in the rotor part when it is made with electrically conductive materials.

For a rotor which must rotate at high rotational speeds, the main disadvantage of a high rotational speed motor is the high probability of detachment of the magnet or magnets from the rotor as well as at least partial rotor failure. . The rotor of such a motor must therefore be able to withstand high rotational speeds.

One solution may be to make meshes of unit magnets elongated in fibrous and resinous structures, so as to reduce eddy currents and to use a composite material body for the rotor which does not conduct electricity, ideally a fiberglass rotor, with a hoop placed at the periphery of the rotor so as to maintain the forces due to centrifugal effects.

Document FR-A-3064420 describes a three-dimensional magnet pole made up of a plurality of unit magnets. The magnet pole incorporates at least one mesh having meshes each delimiting a housing for a respective unit magnet, each housing having internal dimensions just sufficient to allow introduction of a unit magnet into its interior while leaving a space between the magnet pole. housing and the unitary magnet filled with a fiber-reinforced resin, the meshes being of fiber-reinforced insulating material.

It is also possible to glue the unit magnets together directly without the interposition of a mesh as shown in document FR-A-3064 419, this in particular by gluing the magnets together.

From these two documents, it follows that the unit magnets must be shaped to occupy as much space as possible inside the magnet pole, leaving only the space necessary for the glue or the mesh to ensure the maintenance of the magnets. units in the magnet pole.

In fact, the torque that an electromagnetic machine must provide is proportional to the area of the magnets in interaction with the magnetic fields produced by the one (s). machine stators. A reduction in the area of the magnets therefore leads to a reduction in the torque and therefore in the power of the machine.

It follows that these two patent applications propose a magnet pole made up of several unit magnets in the form of studs joined together by gluing and / or meshing. It is necessary to use covering skins making it possible both to stiffen the rotor on which these magnet poles are fixed and to prevent, for each magnet pole, the separation of the unit magnets from each other. . The covering skins are advantageously made of composite and bonded to the rotor.

Nevertheless, always at high speeds of rotation and under high temperatures, for example above 120 ° C, it is difficult to obtain adhesives which at the same time have high mechanical strengths at high temperatures while ensuring a certain flexibility of the glue between the covering skins of the rotor and the structure of the rotor, for example the branches of the rotor, the hub of the rotor and the various magnet poles that the rotor carries between the branches.

Thus, at high rotational speeds, there may be detachment of the covering skins due to the loss in performance of the adhesive used to bond the covering skins to the rotor, hence reduced retention of the magnet poles. with their unit magnets in the rotor and weakened mechanical strength of the rotor.

Document FR-A-3014255 describes a discord rotor comprising a plurality of magnet poles arranged on the peripheral part of the rotor around a shaft or hub element. These magnet poles are integrated into a support or cage made of insulating and rigid material in order to ensure the mechanical strength of the assembly.

The composite support only coats the magnet poles on their lateral surface and only coats the hub at the periphery of this hub.

In this document, magnet poles are used which cannot be assimilated to unit magnets of a magnet pole. the Composite carrier must have a stepped shape to retain the magnet poles, which decreases the area available for the magnets.

In addition, the magnet poles extend longitudinally substantially in a plane parallel to the faces of the rotor and not in the thickness of the rotor. The magnet poles can have different lengths, this to adapt to the internal configuration defined by the composite support.

Document EA-B-009858, also published as WO-A1- 2008/145144 describes a magnet pole formed from several plates of elongated unit magnets, therefore not comparable to small unit magnets in the sense of the present invention. request. These plates are magnetically oriented longitudinally and extend in parallel by being secured to each other in a section connecting a front face and a rear face of the magnet pole. The magnet pole is not entirely covered with a strip or fabric of fibers incorporating reinforcing fibers and partially delimiting an outer contour of the magnet pole wrapped around the plates.

In this document, the covering of the magnet pole by a layer of composite is not complete, since a frame completes the covering of the magnet pole by the layer which does not cover the frame itself. At a high speed of rotation of the magnet pole, for example in a rotor, there is a high risk of rupture of the frame connection with the layer of composite.

Document US-A-2011/031431 describes a magnetic fiber carrying a plurality of magnet particles, which is different from a magnet pole encapsulated in a layer of fiber reinforced composite. The magnetic fiber comprises several magnet particles, each acting as a magnet pole. This document is therefore not intended for a magnet pole made up of several unit magnets. Document FR-A-3086 465 describes the characteristics of the preamble of claim 1 of the present application. This document discloses a rotor having a body consisting of several superimposed layers of composite containing fibers bonded by a resin, the fibers of each layer being oriented in a different predetermined direction for two superimposed layers. However, the layers described in this document do not offer sufficient mechanical strength. The document JP-A-S61 207 162 describes large magnets which can be considered as magnet poles but not being divided into smaller unit magnets secured together therefore not anticipating a magnet pole which is the subject of the present application. . The problem at the basis of the invention is essentially to stiffen a magnet pole made up of several unit magnets so that this magnet pole forms a single-piece structure with increased mechanical strength.

Summary of the invention To this end, the present invention relates to a magnet pole formed from several elongated unit magnets, oriented magnetically longitudinally and extending in parallel, being secured to each other in a wafer connecting a front face and a rear face of the pole. magnet, the magnet pole being entirely encapsulated in at least one composite layer delimiting an outer contour of the magnet pole, characterized in that said at least one composite layer is reinforced with fibers and is formed by a winding around the unit magnets of bands integrating the reinforcing fibers or of a fabric integrating reinforcing fibers. A coated magnet pole is thus obtained having, on the one hand, an attachment of the unit magnets to each other, as provided for in the closest state of the art and, on the other hand, an external stiffening by at least one fiber reinforced composite layer. In particular, if the documents FR-A-3064419, FR-A-3064420 and FR-A-3 086 465 provided for the unitary magnets to be joined together in a magnet pole, these documents neither described nor suggested that in addition to this securing, the three-dimensional magnet pole is coated on the outside with a layer of fiber-reinforced composite.

This contributes to reinforcing the mechanical resistance of a magnet pole by combining two modes of securing, namely a first securing of the unit magnets to each other and a second securing of all of the unit magnets forming a magnet pole, which allows such a magnet pole to withstand high rotational speeds.

A magnet pole is thus obtained individually coated in a layer of composite, which reduces eddy current losses.

The solution proposed by the present invention is to achieve a total fiber covering of each magnet pole taken individually with directions making it possible to ensure mechanical strengths in the three directions of the space of the magnet pole.

It is then possible to manufacture both the magnet pole and its unit magnets by providing a composite layup with reinforced fibers having given preferential directions around the magnet pole. The external coating of each magnet pole also makes it possible to give it an external dimension specifically adapted to its housing in a cavity of the rotor, hence ease of mechanical insertion of each magnet pole into the rotor during its installation. manufacturing. Advantageously, the reinforcing fibers of said at least one composite layer are fibers of glass, carbon, aramid or an equivalent material bonded or resinated with a thermosetting or thermoplastic material. Advantageously, said at least one composite layer comprises multiaxial fabrics. Advantageously, the unit magnets are secured to form a set of magnets by interposing at least locally an adhesive or a resin between them or the unit magnets are housed in a mesh having cavities corresponding to the sections of the unit magnets being or not stuck in the mesh. The glue or resin may or may not contain fibers.

A mesh has the advantage of allowing a prior maintenance of the unit magnets in the magnet pole and of reinforcing their final maintenance while having the disadvantage of slightly reducing the area of unit magnets available in the magnet pole.

Bonding the unit magnets together, possibly less resistant than bonding associated with a mesh, however offers a certain freedom, given that this bonding between unit magnets can only be partial, which presents unexpected effects. This can be very advantageous for unitary longitudinal poly-faceted magnets.

In this case, it is not desirable to glue the unit magnets face to face but only locally on the recessed shapes hollowed out in each unit magnet and then containing glue, advantageously in the form of resin.

These contact zones can be point, linear or in an arc of a circle depending on the outer contour of the unit magnets. It is the glue contained in these recessed shapes which provides the adhesion of two adjacent unit magnets.

As unit magnets are thus obtained "crystals" associated with one another which are not linked over the entire surface of facets or of longitudinal faces. On the contrary, layers of resin and glue come to replace, for example, at least one longitudinal end in order to build a mesh network at the ends of the poly-faceted pads as unit magnets with limited contact zones between magnets. Advantageously, the bands overlap at least partially, each forming a portion of the front and rear faces and of the edge of the magnet pole. Advantageously, the bands form at least two superimposed layers, the bands of at least one second layer crossing with the bands of a first layer.

This makes it possible to strengthen the magnet pole in several directions simultaneously. The reinforcing fibers ensure the maintenance of the magnet pole in the radial, ortho-radial and axial directions.

Advantageously, at least one auxiliary band of fibers extends along the edge of the magnet pole.

Advantageously, the magnet pole has an outer shape with front and rear faces of trapezoidal, rectangular, triangular or circular section.

The external shape of the magnet pole is mainly defined for its insertion in a rotor, frequently in a cavity intended for it.

Advantageously, when the magnet pole has a section with two opposite parallel sides, the bands extend perpendicularly or diagonally to the two parallel opposite sides.

Advantageously, the unit magnets are ovoid in shape or the sections of the unit magnets are rectangular, square, triangular, circular, trapezoidal or polygonal. Regarding an ovoid magnet, considering a unitary magnet as an elementary element in the form of a pad, the ideal shape of this pad is an ellipsoid of symmetrical revolution also called an ovoid shape, approximately a flattened sphere which, by virtue of its topology, is difficult to demagnetize because its magnetic field relative to the magnetization is shapeless. There is in fact no rotating field in the corners of the unit magnets.

The invention also relates to a method of manufacturing at least one such magnet pole comprising a step of forming a set of unit magnets secured directly or indirectly to each other by bonding or application of a resin and a step of encapsulating the assembly of unit magnets in at least one composite layer reinforced with fibers delimiting an outer contour of the magnet pole.

Advantageously, said at least one layer of fiber reinforced composite is formed at least by a winding of flexible bands or fabrics integrating the reinforcing fibers around all of the unit magnets.

The present invention also relates to a rotor for an electromagnetic machine with axial flow, characterized in that it houses at least one magnet pole described above, the unit magnets extending axially to the rotor in a thickness of the rotor, the rotor being in the form of a disc with the front face of said at least one magnet pole opening onto one face of the disc and the rear face of said at least one magnet pole opening onto the opposite face of the disc. Due to the covering of each magnet pole taken individually by a layer of fiber-reinforced composite, each magnet pole is easily adapted to the cavity provided to house it in the rotor. The magnet poles thus encapsulated were encapsulated in three dimensions. The covering skins covering each face of the rotor are no longer necessary, which reduces, on the one hand, the manufacturing cost of the rotor by eliminating a step of gluing the covering skins and, on the other hand, the material cost per the removal of these covering skins. The cover skins performed their holding action on all magnet poles taken as a group while the composite layer of a magnet pole performs specific holding of its associated magnet pole, which provides improved hold. because individual of all magnet poles in the rotor.

Advantageously, a periphery of the rotor is formed by a layer of coating composite which may or may not be reinforced with fibers.

In this case, three forms of coating or bonding can be associated. A first bonding ensures the joining of the unit magnets to each other. A second coating relates to a magnet pole taken as an entity and a third coating, advantageously with reinforcing fibers, relates to the rotor carrying the magnet pole or poles.

Such a rotor is therefore mechanically strong and can withstand high rotational speeds while having an optimum magnetized surface.

Brief description of the figures

Other characteristics, aims and advantages of the present invention will become apparent on reading the detailed description which follows and with regard to the appended drawings given by way of non-limiting examples and in which:

[Fig. 1] - figure 1 is a schematic representation of a front view of a rotor intended for an electromagnetic machine with axial flow according to the present invention, the rotor carrying magnet poles made up of several unit magnets, the poles d 'magnet being individually encapsulated in a layer of fiber reinforced composite,

[Fig. 2] - figure 2 shows a magnet pole with several unit magnets in the course of manufacture and not yet encapsulated in a layer of composite, in accordance with a first embodiment of the present invention,

[Fig. 3] - figure 3 shows a magnet pole with several unit magnets during manufacture and identical to that shown in figure 2, the magnet pole being additionally coated with a binder but not yet encapsulated in a layer of composite, this during a step of forming a magnet pole in accordance with a first embodiment of the present invention,

[Fig. 4] - Figure 4 shows a magnet pole with several unit magnets during manufacture and identical to that shown in Figure 2, a band of reinforcing fibers being applied to the magnet pole during a step of forming a magnet pole in accordance with a second embodiment of the present invention,

[Fig. 5] - figure 5 shows a magnet pole with several unit magnets identical to that shown in figure 2 but completely coated with at least one layer of composite, the magnet pole thus produced conforming to the first or the second embodiment of the present invention according to whether the binder is applied beforehand on the assembly of unit magnets or on the bands of reinforcing fibers,

[Fig. 6] - figure 6 shows a magnet pole with several unit magnets being manufactured by being coated with two series of diagonally crossed composite strips, in accordance with a third embodiment of the present invention,

[Fig. 7] - figure 7 shows a magnet pole with several unit magnets, the magnet pole being complete by being coated with a fabric layer of reinforcing fibers with the fibers oriented at 0 and 90 ° in accordance with a fourth embodiment of the present invention,

[Fig. 8] - Figure 8 shows a magnet pole with several unit magnets in the course of manufacture, the magnet pole receiving an auxiliary strip of composite on its wafer in accordance with a fifth embodiment of the present invention.

All the figures are to be taken in combination and reference may be made when describing a figure to references found in one of the other figures.

A single unitary magnet of a first or of a second group is referenced in the figures but what is stated for this unitary magnet is valid for all the unitary magnets of the same group. The same is true for a single magnet pole referenced in FIG. 1 or a single band of reinforcing fibers for a series of bands.

Detailed description of the invention

Referring to Figure 1, this Figure 1 shows a rotor 1 according to the present invention. The rotor 1 may have branches 3 interposing between two adjacent forms a magnet pole 10 made up of several polygonal unit magnets, but such branches 3 are not compulsory in the context of the present invention.

Such a rotor 1 can be used in an electromagnetic motor or generator, advantageously with axial flow. The rotor 1, advantageously substantially circular in the form of a ring, has a body comprising an internal hub 2 concentric with a central axis 7 of rotation of the rotor 1 or longitudinal median axis of the rotor 1. The branches 3 extend radially in the rotor 1 relative to the central axis 7 of rotation from the internal hub 2 towards a hoop 8 forming a circular external periphery of the rotor 1.

Such a band 8 can be inserted, in a known manner, around the rotor 1 in order to maintain the centrifugal forces of the rotor 1.

The hub 2 and the branches 3 can be of the same piece and form a rotor body 2, 3. At least one magnet pole 10 comprising a plurality of unit magnets of small size is housed in each space delimited between two. adjacent branches 3, the unit magnets not being visible in Figure 1 because coated with a composite layer 6 made of bands 6a of reinforcing fibers, but these unit magnets are visible for example in Figures 2, 4 and 8.

With reference to all the figures, the present invention relates to a magnet pole 10 formed of several unitary magnets 4 elongated, oriented magnetically longitudinally and extending in parallel, being integral with one another. This joining takes place in a thickness of the magnet pole 10, that is to say through a slice 10a presented by the magnet pole 10 and connecting a front face and a rear face of the magnet pole 10.

The front and rear faces are intended to be carried by a respective face of a rotor 1 in the form of a disc, the unit magnets 4 extending lengthwise in the thickness of the rotor 1.

One or more large magnets can thus be broken down into a plurality of small or micro-magnets. A magnet of large dimensions is subject to eddy current losses greater than its equivalent in small or micro-magnets. The use of small magnets or micro-magnets therefore makes it possible to reduce these losses which are detrimental to the operation of the rotor 1. This was known from the closest state of the art. In accordance with an essential feature of the present invention, the magnet pole 10 is fully encapsulated in at least one layer of fiber reinforced composite 6.

The composite layer or layers 6 thus delimit an outer contour of the magnet pole 10.

A magnet pole 10 consists of multiple unit magnets 4, advantageously in the form of pads joined together by a binder. Under high axial loads or during high rotational speeds, the binder securing the unit magnets 4 may not be sufficient and the magnet pole 10 may disintegrate.

It is therefore necessary, to achieve high speeds, to ensure that each magnet pole 10 housed in a rotor 1 of an electromagnetic motor remains compact so that neither the unit magnets 4 nor the binder are ejected from the rotor. 1.

The present invention provides for the individual encapsulation of a magnet pole 10 by a layer of composite 6 which is mechanically resistant and not current conducting.

This implies that this composite layer 6, for the purpose of mechanical reinforcement and binder of a magnet pole 10, must remain in place under stresses which would cause the magnet pole 10 to break without such reinforcement.

The reinforcing fibers of the composite layer (s) 6 may be fibers of glass, carbon, aramid or an equivalent material bonded or resinated with a thermosetting or thermoplastic material.

It is also possible that the layer or layers of composite 6 comprise multiaxial fabrics 6b with fibers oriented in different directions, therefore one or more layers of composite 6 with textile reinforcement.

The term fabric 6b is to be taken in its broad sense as meaning a widened textile strip which can be woven or non-woven.

In each magnet pole 10, according to a first configuration, the unit magnets 4 can be joined together to form a set of magnets by interposing at least locally an adhesive or a resin between them.

In a second configuration, the unit magnets 4 are housed in a mesh having cavities corresponding to the sections of the unit magnets 4, whether or not they are glued into the mesh.

FIG. 2 shows a magnet pole 10 in preparation with a set of unit magnets 4 secured together, which corresponds to a magnet pole 10 in accordance with the state of the art but also to a magnet pole 10 unfinished according to the present invention.

Figure 3 shows the same magnet pole 10 in somewhat more advanced preparation with a set of unit magnets 4 coated or coated with at least one binder layer 9, for example two crossed binder layers.

It is however not necessary to go during the manufacture of a magnet pole 10 through this coating step, the binder 9 being able to be applied directly to a strip 6a, 6d or a fabric 6b of reinforcing fibers forming the fiber-reinforced composite layer (s) 6, as will be seen in Figures 4 and 6.

Thus, in FIG. 4 a strip 6a of reinforcing fibers is directly bonded to all of the unit magnets 4 without prior coating of all of the unit magnets 4, the strip 6a carrying the binder on its face facing the assembly. individual magnets 4.

Figure 5 shows a magnet pole 10 completed according to the embodiments of Figures 3 or 4 with bands 6a of fibers extending substantially perpendicular to two opposite parallel sides of the magnet pole 10, which is not obligatory.

Figure 6 shows an unfinished magnet pole 10 comprising at least two composite layers 6 made by the interweaving of a first series of strips 6a with a second series of strips 6d extending at a different angle a from the first series. In this figure, the two series of bands 6a and 6d are not crossed at right angles but towards 45 °, which is not obligatory, another crossing angle being able to be used. Figure 7 shows a magnet pole 10 completed by being encapsulated in a fabric layer 6b of reinforced fibers or bed of reinforced fibers with two different orientations of the fibers including a basic orientation at 0 ° and an orientation at 90 ° relative to at the basic orientation, which is not obligatory, another angle of crossing of the fibers or threads in the fabric 6b which can be selected.

It follows that the bands 6a, 6d of reinforcing fibers of figure 6 can directly be replaced by a fabric 6b of figure 7 which, in the same way, can be glued over the set of unit magnets 4 during the manufacture of the magnet pole 10.

Thus, the fiber-reinforced composite layer (s) 6 can be formed at least by a winding of flexible bands 6a, 6d or of fabrics 6c integrating the reinforcing fibers around all of the unit magnets 4.

Fig. 8 shows an embodiment to be combined with other embodiments to achieve a complete encapsulation of the unitary magnet assembly 4 to provide a magnet pole 10.

In this embodiment shown in Figure 8, at least one auxiliary strip 6c of fibers may extend along the edge 10a of the magnet pole 10.

The longitudinal edges of the auxiliary fiber strip 6c can be folded over the front and rear faces of the magnet pole 10 in order to cover the ridges of the magnet pole 10. This is for example shown in Figures 5 and 6.

For all embodiments, the fabric layer (s) 6b or bed of reinforcing fibers or bands 6a, 6d of reinforcing fibers serve, in addition to encapsulating the magnet pole 10 individually as a whole, to maintain the unit magnets 4 to each other, in addition to their prior joining during the formation of a set of unit magnets 4. The fibers can be placed in different orientations, wound up seamlessly, or manually placed piece by piece.

The fibers can be pre-coated, fixed on the magnet pole 10, for example during the curing of the resin.

The fibers can be glued, preferably with the same glue or a glue compatible with the glue securing the unit magnets 4. This can be done directly in a mold during the manufacturing process of the magnet pole 10.

The fibers can go around the magnet pole 10, in several directions and the different layers or series of bands 6a, 6d of fibers can cross each other to create a multiaxial weave.

The composite layer (s) 6 may be formed by winding around the set of tape magnets 6a, 6d incorporating the reinforcing fibers or a fabric 6b incorporating the reinforcing fibers.

The bands 6a, 6d of reinforcing fibers may overlap at least partially, each forming a portion of the front and rear faces and of the slice 10a of the magnet pole 10.

For example, the bands 6a, 6d of reinforcing fibers can form at least two superimposed layers, the bands 6d of at least one second layer crossing with the bands 6a of a first layer.

This can for example be seen in Figure 6 where the bands 6d of the second layer make an angle α with the bands 6a of the first layer.

The magnet pole 10 may have an exterior shape with front and rear faces of trapezoidal, rectangular, triangular or circular section. This essentially depends on its use, for example for its adaptation in a specific cavity made in a rotor 1 for the or each magnet pole 10.

When the magnet pole 10 has a section with two opposite sides parallel, the bands 6a, 6d may extend perpendicular or diagonally to the two opposite parallel sides. This is shown in particular in Figure 6.

The unit magnets 4 can be ovoid in shape or the sections of the unit magnets 4 can be rectangular, square, triangular, circular, trapezoidal or polygonal, advantageously hexagonal.

The invention also relates to a method of manufacturing at least one such magnet pole 10 as described above.

The method according to the invention comprises a step of forming a set of unit magnets 4 attached directly or indirectly to one another by bonding or application of a resin.

The application of the resin can be done by impregnation, casting, injection or the like.

This step of forming a set of unit magnets 4 is followed by a step of encapsulating the assembly of unit magnets 4 in at least one layer of fiber-reinforced composite 6 delimiting an outer contour of the pole of magnet 10. Referring more particularly to FIG. 1, the present invention also relates to a rotor 1 for an electromagnetic machine with axial flow, the rotor 1 housing at least one magnet pole 10 previously described, the unit magnets 4 s' extending axially to the rotor 1 in a thickness of the rotor 1. The rotor 1 is in the form of a disc with the front face of said at least one magnet pole 10 opening onto one face of the disc and the rear face of said at least one magnet pole 10 opening onto the opposite face of the disc.

In FIG. 1, a rotor 1 with branches 3 and surrounded by a band 8 is described, but these characteristics are only optional. This also applies to the shape of the hub 2.

Advantageously but not in a limiting manner, a periphery of the rotor 1 can be formed by a layer of coating composite which may or may not be reinforced with fibers.

The rotor 1 can be part of an electromagnetic machine with axial flow, associated with one or more stators. There can also be several rotors 1 in the electromagnetic machine. The invention is in no way limited to the embodiments described and illustrated which have been given only by way of examples.

Claims

1. Magnet pole (10) formed of several unit magnets (4) elongated, oriented magnetically longitudinally and extending in parallel by being secured to each other in a slice (10a) connecting a front face and a rear face of the pole. magnet (10), the magnet pole (10) being fully encapsulated in at least one composite layer (6) delimiting an outer contour of the magnet pole (10), characterized in that said at least one layer is reinforced of fibers and is formed by a winding around the unit magnets (4) of bands (6a, 6d) integrating the reinforcing fibers or of a fabric (6b) integrating the reinforcing fibers.

2. Magnet pole (10) according to the preceding claim, wherein the reinforcing fibers of said at least one composite layer (6) are fibers of glass, carbon, aramid or an equivalent bonded material. or resinated with a thermosetting or thermoplastic material.

Magnet pole (10) according to any preceding claim, wherein said at least one composite layer (6) comprises multiaxial fabrics (6b).

4. Magnet pole (10) according to any one of the preceding claims, wherein the unit magnets (4) are secured to form a set of magnets by interposing at least locally an adhesive or a resin between they or the unit magnets (4) are housed in a mesh having cavities corresponding to the sections of the unit magnets (4) by being glued or not in the mesh.

5. A magnet pole (10) according to any preceding claim, wherein the bands (6a, 6d) overlap at least partially, each forming a portion of the. front and rear faces and edge (10a) of the magnet pole

(10).

6. Magnet pole (10) according to the preceding claim, wherein the bands (6a, 6d) form at least two superimposed layers, the bands (6d) of at least a second layer intersecting with the bands (6a). of a first layer.

7. Magnet pole (10) according to any one of the two preceding claims, wherein at least one auxiliary strip (6c) of fibers extends along the edge (10a) of the magnet pole (10). .

8. A magnet pole (10) according to any one of the three preceding claims, which has an outer shape with front and rear faces of trapezoidal, rectangular, triangular or circular section.

9. Magnet pole (10) according to the preceding claim, wherein, when the magnet pole (10) has a section with two opposite sides parallel, the bands (6a, 6d) extend perpendicular or diagonally to the two. opposite sides parallel.

10. A magnet pole (10) according to any preceding claim, wherein the unit magnets (4) are ovoid in shape or the sections of the unit magnets (4) are rectangular, square, triangular, circular, trapezoidal or polygonal.

11. A method of manufacturing at least one magnet pole (10) according to any one of the preceding claims, the method comprising a step of forming a set of unit magnets (4) joined directly or indirectly to one another. to others by gluing or applying a resin and a step of encapsulating the assembly of unit magnets (4) in at least one layer of composite (6) reinforced with fibers delimiting an outer contour of the magnet pole ( 10).

12. Method according to the preceding claim, wherein said at least one layer of composite (6) reinforced with fibers is formed at least by a winding of strips (6a, 6d) flexible or of fabrics (6c) integrating the reinforcing fibers around of all the unit magnets (4).

13. Rotor (1) for an electromagnetic machine with axial flow, characterized in that it houses at least one magnet pole (10) according to any one of claims 1 to 10, the unit magnets (4) s' extending axially to the rotor (1) in a thickness of the rotor (1), the rotor (1) being in the form of a disc with the front face of said at least one magnet pole (10) opening onto one face of the disc and the rear face of said at least one magnet pole (10) opening onto the opposite face of the disc.

14. Rotor (1) according to the preceding claim, wherein a periphery of the rotor (1) is formed by a coating composite layer reinforced or not with fibers.