Method for manufacturing a magnetic pole element

Abstract

The invention relates to a method for manufacturing a magnetic pole element (1) for the rotor of an axial flux electric machine, said magnetic pole element comprising an upper layer (11) and a lower layer (12) arranged to extend one above the other along an axis of rotation of the rotor. The method comprises the following steps: - manufacturing a plurality of unit magnets (10); - forming the upper layer by assembling at least two of the unit magnets; - forming the lower layer by assembling at least two other unit magnets; - superimposing the upper and lower layers and fixing the upper layer to the lower layer. Figure for the abstract: Fig. 9.

Description

Title of the invention: Method for manufacturing an element with magnetic poles Technical field of the invention

[0001] The present invention relates generally to the field of electrical machines.

[0002] It relates more particularly to a magnetic pole element for an electric machine rotor.

[0003] It also relates to a method of manufacturing such an element with magnetic poles.

[0004] The invention finds a particularly advantageous application in the production of electric motors for electric or hybrid motor vehicles (car, truck, bus, etc.). It also applies more generally to other motorized devices, such as, for example, elevators, cranes, etc. State of the art

[0005] An axial flux electric machine generally comprises a stator, a rotor and an air gap separating them. The rotor carries a series of large permanent magnets, while a series of coils is carried by the stator. When the coils are energized by an electric current, the rotor, which is secured to the output shaft of the motor, is subjected to a torque resulting from the magnetic field (the magnetic flux created being an axial flux for an axial flux electric machine).

[0006] To reduce eddy current energy losses in the rotor, and thus increase the performance of the electrical machine, the large permanent magnets can be replaced by “magnetic pole elements” each comprising a plurality of small unit magnets. Indeed, a large permanent magnet is subject to greater eddy current losses than its equivalent in small unit magnets.

[0007] The unit magnets are arranged tightly to maximize the volume of magnetic material relative to the volume of the corresponding magnetic pole element and thus improve the performance of the electrical machine.

[0008] For example, document FR3064422 discloses a structure comprising small unit magnets. These unit magnets form cylindrical rods of hexagonal section, which have the advantage of being able to form a tight network while presenting a strong magnetic field. These unit magnets are bonded together by means of a resin.

[0009] However, the need has arisen to further reduce the eddy currents, preferably by maintaining a high ratio between the volume of magnetic material and the volume of the magnetic pole element. Presentation of the invention

[0010] In this context, the invention proposes a method for manufacturing a magnetic pole element for an electric machine rotor, said magnetic pole element comprising an upper layer and a lower layer which are arranged to extend one above the other along an axis of rotation of the rotor, the method comprising the following steps: - manufacturing a plurality of unit magnets; - formation of the upper layer by assembling at least two of the unit magnets; - formation of the lower layer by assembling at least two other unit magnets; - superimposing the top layer and the bottom layer and fixing the top layer to the bottom layer.

[0011] Thus, thanks to the invention, the eddy currents are further reduced since the element with magnetic poles is also segmented along the axis of rotation, that is to say in thickness. By extending one above the other, the different layers in fact limit the circulation of the eddy currents along the axis of rotation.

[0012] Furthermore, it is more advantageous, in order to maximize the volume of magnetic material, to segment the element with magnetic poles in thickness, as proposed by the invention, than to seek to produce unitary magnets of ever smaller section as in the prior art (this in fact further increases the proportion of glue which is necessary to maintain them).

[0013] Although the manufacture of the magnetic pole element appears more complex, since it requires the formation of several layers, the rotor implementing the magnetic pole element manufactured according to the invention is much less sensitive to eddy current losses than the rotors of the prior art, so that this complexity is largely compensated for by the performance obtained.

[0014] Finally, other advantageous and non-limiting characteristics of the method according to the invention make it possible to manufacture the unit magnets and / or the layers in a simple and reproducible manner. The method according to the invention is therefore particularly suitable for the mass production of the element with magnetic poles.

[0015] These advantageous and non-limiting characteristics of the method according to the invention, taken individually or in all technically possible combinations, are as follows: - said manufacturing step comprises: the manufacturing of intermediate magnets by cracking a magnet block, in a first segmentation direction, each intermediate magnet extending in length in the first segmentation direction, the manufacturing of the unit magnets by cracking the intermediate magnets in a second segmentation direction distinct from the first segmentation direction in which the intermediate magnets extend; - the method comprises, before the manufacture of the unit magnets and after the manufacture of the intermediate magnets (30) by cracking, bonding the intermediate magnets to each other; - the intermediate magnets are bonded together by complementary faces generated by the cracking of the magnet block or by original faces each coming from a face of the magnet block; - forming the upper layer or the lower layer comprises: bonding at least two of the unit magnets to each other so as to form an intermediate plate, segmenting the intermediate plate into two halves, rearranging and bonding the two halves to each other; - the method comprises a step of cutting the upper layer and the lower layer so as to give the magnetic pole element a predetermined shape; - forming the upper layer and the lower layer comprises gluing at least two of the unit magnets to each other or gluing at least two of the unit magnets to an adhesive sheet; - the step of manufacturing the upper layer or the lower layer comprises: bonding at least two of the unit magnets so as to form a first subgroup, bonding at least two other of the unit magnets so as to form a second subgroup, and bonding the first subgroup and the second subgroup so as to form the upper layer or the lower layer.

[0016] The invention also provides a magnetic pole element for an electric machine rotor, comprising an upper layer and a lower layer which are arranged to extend one above the other along an axis of rotation of the rotor, the upper layer comprising at least two unit magnets and the lower layer comprising at least two other unit magnets.

[0017] According to an optional characteristic of the invention, the upper layer and the lower layer each extend in a plane and in which each unit magnet has a length, parallel to the plane of its layer, and a thickness, perpendicular to the plane of its layer, the thickness of each unit magnet being less than the length of said unit magnet.

[0018] According to an optional characteristic of the invention at least one of the unit magnets of the upper layer has a larger dimension in an upper direction and at least one of the unit magnets of the lower layer has a larger dimension in a lower direction distinct from the upper direction.

[0019] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. Detailed description of the invention

[0020] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0021] In the attached drawings:

[0022] [Fig. 1] is a schematic perspective view of a first exemplary embodiment of a magnetic pole element according to the invention;

[0023] [Fig.2] is a schematic top view of a second exemplary embodiment of a magnetic pole element according to the invention;

[0024] [Fig.3] is a schematic perspective view of steps in manufacturing unit magnets for the manufacture of a third exemplary embodiment of an element with magnetic poles according to the invention;

[0025] [Fig.4] is a schematic perspective view of assembly steps of the unit magnets of [Fig.3] to manufacture the third embodiment of an element with magnetic poles;

[0026] [Fig.5] is a schematic perspective view of an alternative embodiment of the assembly steps of the unit magnets of [Fig.3] for manufacturing the third example embodiment of an element with magnetic poles;

[0027] [Fig.6] is a schematic perspective view of manufacturing steps of a fourth embodiment of a magnetic pole element according to the invention;

[0028] [Fig.7] is a schematic perspective view of a fifth example of embodiment of a magnetic pole element according to the invention placed in the body of a rotor;

[0029] [Fig.8] is a schematic perspective view of manufacturing steps of a sixth embodiment of a magnetic pole element according to the invention;

[0030] [Fig.9] is a schematic perspective view of manufacturing steps of a seventh embodiment of a magnetic pole element according to the invention;

[0031] [Fig.10] is a schematic perspective view of manufacturing steps of an eighth embodiment of a magnetic pole element according to the invention;

[0032] [Fig. 11] is a schematic top view of a ninth embodiment of a magnetic pole element according to the invention;

[0033] [Fig. 12] is a schematic top view of a second example of embodiment of a tenth with magnetic poles according to the invention;

[0034] [Fig. 13] is a schematic top view of manufacturing steps of an eleventh embodiment of a magnetic pole element according to the invention.

[0035] A magnetic pole element 1 according to the invention is shown in [Fig.l].

[0036] The magnetic pole element 1 is here intended to be mounted within a rotor 2, as partially schematized in [Fig.7], for an electric machine. The invention is here more particularly described in the context of a magnetic pole element 1 for an axial flux electric machine. The invention can however also be implemented for a radial flux electric machine. The rotor 2 is itself intended to be part of an axial flux electric machine which further comprises a stator, or preferably two stators located on either side of the rotor 2.

[0037] Conventionally, the rotor 2 has a disc shape centered around an axis of rotation A1 also corresponding to the axis of the output shaft of the electrical machine. The rotor 2 comprises a body 3 provided with a plurality of housings 4, each housing 4 being designed to receive a magnetic pole element 1. As shown in [Fig.7], each housing 4 here has an overall shape of an isosceles trapezoid. The same is true for the magnetic pole element 1 since the latter has a shape complementary to that of its housing 4 to be inserted therein.

[0038] The stators (not shown) have the shape of flattened rings and are equipped, on their faces located on the side of the rotor 2, with teeth around which are wound windings of electrically conductive wires. When these windings are supplied with electric current, they generate a rotating magnetic field driving the magnetic pole elements 1, which sets the rotor 2 in motion around the axis of rotation AL

[0039] As shown in [Fig.l], the magnetic pole element 1 comprises a plurality of unit magnets 10, here several tens of unit magnets 10. Here, the term “unit” means that the unit magnets 10 are the smallest single-piece magnetic components contained by the magnetic pole element 1. The unit magnets 10 of the magnetic pole element 1 are mechanically bonded to each other, for example by means of an adhesive material such as a glue or a resin. The unit magnets 10 have, for example, a parallelepiped shape as illustrated in [Fig.l] or 7. The unit magnets 10 located at the periphery of the magnetic pole element 1, that is to say those facing the body 3, may however have other shapes to adapt to the overall shape of the housing 4.

[0040] As shown in [Fig.l], the unit magnets 10 of the magnetic pole element 1 are distributed in several layers 11, 12. This number of layers is equal to two in the embodiments shown, but it could be greater. The unit magnets 10 here form an upper layer 11 and a lower layer 12. The terms “upper” and “lower” are interchangeable here; they simply reflect the notion of stacking. Indeed, the upper layer 11 and the lower layer 12 extend one above the other along the axis of rotation A1 of the rotor 2. The arrangement of the upper layer 11 and the lower layer 12 is thus defined relative to their final position once the magnetic pole element 1 is integrated into the rotor 2.Once the rotor 2 is assembled, the upper layer 11 and the lower layer 12 each extend substantially orthogonally to the axis of rotation AL. The upper layer 11 and the lower layer 12 are each substantially planar.

[0041] The upper layer 11 and the lower layer 12 each comprise several unit magnets 10. For example, the upper layer 11 and the lower layer 12 illustrated in [Fig. 4] each comprise the same number of unit magnets 10, namely forty-two unit magnets 10. They may also contain different numbers of unit magnets 10, as illustrated in [Fig. 10].

[0042] Here, each unit magnet 10 has, orthogonally to the axis of rotation Al, a larger dimension which is called length and, parallel to the axis of rotation Al, a dimension called thickness which is constant. For example, when the unit magnets 10 have a square section parallel to the axis of rotation Al, as in [Fig.4], the length corresponds to a diagonal of said section.

[0043] The thickness of the unit magnets 10 is here strictly less than their length (this could alternatively be different). The thickness of each layer 11, 12 is therefore relatively small compared to its dimensions along a plane orthogonal to the axis of rotation AL. This makes it possible to stack several layers, for example three or four layers, for a given volume of the element with magnetic poles and therefore to further reduce the eddy currents.

[0044] Within each layer 11, 12, the unit magnets 10 are arranged side by side. More particularly, here they have lateral faces 13 substantially parallel to the axis of rotation A1 and which extend opposite each other. They also have an upper face 14 and a lower face 15 orthogonal to the axis of rotation A1 and which are connected by the lateral faces 13 and whose surfaces are larger than those of the lateral faces 13.

[0045] Each layer 11, 12 thus has a thickness substantially equal to the thickness of the unit magnets 10 that it comprises.

[0046] The unit magnets 10 may be arranged in a similar manner from one layer 11, 12 to the next, for example as shown in [Fig.l].

[0047] However, the orientation of the unit magnets 10 may differ between the upper layer 11 and the lower layer 12. The unit magnets 10 of the upper layer 11 may have a larger dimension in an upper direction and the unit magnets 10 of the lower layer 12 may have a larger dimension in a lower direction distinct from the upper direction. This arrangement makes it possible to limit the eddy current loops that may circulate within the magnetic pole element 1. Remarkably, this arrangement also gives the magnetic pole element 1 great resistance to the mechanical stresses linked to the operation of the electrical machine.

[0048] Such an arrangement is well illustrated in the exemplary embodiment of [Fig. 9]. The unit magnets 10 of the upper layer 11 extend here rectilinearly in a first direction DI and the unit magnets 10 of the lower layer 12 extend rectilinearly in a second direction D2 which here forms an obtuse angle α of approximately 110 degrees with the first direction DI. Thus, in this exemplary embodiment, the upper direction and the lower direction, which are substantially coincident with the first direction and the second direction respectively, also form an angle of approximately 110 degrees.

[0049] As another example, in the embodiment of [Fig. 2], the unit magnets 10 have a rectangular section and their large sides are oriented: radially (from top to bottom in [Fig. 2]) when they belong to the lower layer 12 (these are then represented in transparency by dotted lines), radially meaning here parallel to a direction perpendicular to the axis of rotation A1 and passing through the plane of symmetry of the magnetic pole element 1; and orthoradially (from left to right in [Fig. 2]) when they belong to the upper layer 11, orthoradially meaning here perpendicular to the aforementioned direction and to the axis of rotation A1

[0050] In the embodiment of [Fig.2], the unit magnets 10 can advantageously be manufactured in the same way, whether they belong to the upper layer 11 or the lower layer 12, only their orientation differs.

[0051] The magnetic pole element 1 according to the invention is manufactured by implementing a method comprising the following main steps:

[0052] - a step E1 of manufacturing the unit magnets 10; - a step E2 of forming the upper layer 11 by assembling certain unit magnets 10 and of forming the lower layer 12 by assembling other unit magnets 10; - a step E3 of superimposing the upper layer 11 and the lower layer 12 and fixing the upper layer 11 to the lower layer 12.

[0053] Step E1 begins here with a sub-step E1 1 of providing one or more magnet blocks 20 from which the unit magnets 10 necessary for the manufacture of the magnetic pole element 1 are manufactured. As shown in [Fig. 3], the magnet blocks 20 have dimensions greater than those of the unit magnets 10. Here they have the shape of a rectangular parallelepiped. The magnet blocks 20 are made of a ferromagnetic material such as neodymium-iron-boron or samarium-cobalt alloys or ferrites.

[0054] Generally, the unit magnets 10 are obtained by segmenting the magnet blocks 20 by cracking or by cutting. The cutting can be carried out by means of a laser, a water jet or even a saw. The method according to the invention is described here in the context of segmentation by cracking, however segmentation by cutting can be implemented. Cracking is defined here as the separation into several parts by breaking or shattering under the action of an impact or pressure. The cracking of a magnet block 20 is for example carried out by a repetition of cantilevering one end of the magnet block 20 and by pressing on the latter. Preferably, the cracking of a magnet block 20 is carried out by applying pressure, until breaking, between two curved surfaces.

[0055] Preferably, before each cracking, one or more rectilinear grooves are made in the magnet block 20 (or in intermediate elements described below), for example by laser, so as to choose the cracking lines of the magnet block 20 when the latter is put under pressure. Such grooves have, for example, a width and a depth of between 0.4 and 1 mm, for example 0.5 mm.

[0056] The assembly of the unit magnets 10, during the formation of the upper layer 11 and the lower layer 12, may comprise the bonding of the unit magnets 10 together, as shown in [Fig. 4], for example by means of an epoxy resin, thermosetting adhesives or two-component glues, or the bonding of the unit magnets 10 to an adhesive sheet 60 as shown in [Fig. 6]. The unit magnets 10 may also be bonded by means of a fiber adhesive tape, which subsequently makes it possible to impregnate the unit magnets 10 in an adhesive penetrating between the fibers to reinforce their cohesion.

[0057] In a first embodiment shown in Figures 3 to 5, the manufacturing method is characterized by the manufacturing of intermediate magnets 30 whose size is between that of the magnet block 20 and that of the unit magnets 10.

[0058] As shown in [Fig.3], in this first embodiment, the manufacture of the unit magnets 10 more specifically comprises a sub-step E12 of manufacturing the intermediate magnets 30 by cracking the magnet block 20. The cracking is carried out according to a first segmentation direction SI. Each intermediate magnet 30 then extends in length according to this first segmentation direction SI.

[0059] Step E12 continues with sub-step E13 of bonding the intermediate magnets 30 to each other. Remarkably, the intermediate magnets 30 are here bonded to each other by complementary faces 31 generated during the cracking of the magnet block 20. Two faces are here said to be “complementary” when they come from the same cracking line.

[0060] Thus, although the cracking does not generate perfectly flat faces, effective interlocking of the intermediate magnets 30 is ensured by the fact that the complementary faces 31 have reliefs of complementary shape. Such bonding makes it possible to limit the quantity of glue and therefore to increase the volume of magnetic material in proportion to the volume of the element with magnetic poles 1.

[0061] Here, as schematized by steps E1 1 to E13 of [Fig. 3], the intermediate magnets 30 are bonded according to their original configuration directly resulting from the cracking. Once bonded, they then have a shape similar to that of the magnet block 20. Alternatively, the intermediate magnets can be rearranged before their bonding. Preferably, it is then provided that they are bonded together either by complementary faces or by original faces each resulting from a face of the magnet block 20 (here again in order to increase the volume of magnetic material in proportion to the volume of the element with magnetic poles 1).

[0062] As shown in [Fig. 3], step E1 finally comprises a sub-step E14 of cracking the intermediate magnets 30 so as to form groups 35 of unit magnets 10. Each intermediate magnet 30 thus makes it possible to manufacture several groups 35, each group 35 being formed of several unit magnets 10.

[0063] The intermediate magnets 30 are more particularly cracked according to a second segmentation direction S2 distinct from the first segmentation direction SL. In the exemplary embodiment of [Fig. 3], the second segmentation direction S2 is orthogonal to the first segmentation direction SL. The groups 35 and the unit magnets 10 formed are thus generally rectangular parallelepipeds.

[0064] At the end of sub-step E14, the unit magnets 20 of each group 35 are therefore glued to each other, as shown in [Fig. 3]. They are in particular glued to each other along the second segmentation direction S2. Generally, in the figures, when two unit magnets 10 or two intermediate magnets 30 are shown adjoining, this schematizes that they are glued to each other, otherwise, they are shown at a distance from each other.

[0065] In this first embodiment of the manufacturing method, step E2 is characterized by the assembly of intermediate plates 50 and their separation into two halves 51. Two variants of carrying out this step are illustrated in Figures 4 and 5. In these two variants, this step E2 is composed of three sub-steps.

[0066] During a sub-step E21, several groups 35 of unit magnets 10 are glued to each other to form an intermediate plate 50. In the variants of FIGS. 4 and 5, the unit magnets 10 from two magnet blocks 20 are glued to form the intermediate plate 50. The intermediate plate 50 is here generally rectangular.

[0067] Step E2 then comprises sub-step E22 of segmenting, by cracking or by cutting, the intermediate plate 50 into two halves 51. The two halves 51 are here substantially identical.

[0068] In the first variant of sub-step E22 illustrated in [Fig.4], the intermediate plate 50 is segmented along the contours of the unit magnets 10. Each unit magnet 10 of the plate layer 50 therefore remains whole. In the second variant of sub-step E22 illustrated in [Fig.5], the intermediate plate 50 is segmented along a straight line separating certain unit magnets 10 into two parts.

[0069] Here, whatever the variant of sub-step E22, each half 51 generally has the shape of a right-angled trapezoid, which allows them to be rearranged subsequently into an isosceles trapezoid.

[0070] This rearrangement takes place, during a sub-step E23, by turning over one of the halves 51 and then fixing the two halves 51 to each other so as to form the upper layer 11 or the lower layer 12.

[0071] It is clear from Figures 3 to 5 that the two halves 51 are here bonded by faces which were originally faces of the magnet block 20, that is to say which are not the result of cracking steps. These bonding faces are therefore particularly flat, which makes it possible to obtain effective and compact bonding of the two halves 51.

[0072] The two halves 51 are more specifically arranged so as to give each layer 11, 12, and therefore the magnetic pole element 1, a predetermined shape corresponding to that of the housing 4. It is noted here that in steps E21 of FIGS. 4 and 5, one half of the unit magnets 10 of the intermediate plate 50 is offset relative to the other by a distance less than the length of a unit magnet 10. This makes it possible to give, after rearrangement, a slight curvature to each edge of the layers 11, 12 which is intended to be located at the periphery of the rotor 2.

[0073] The upper layer 11 and the lower layer 12 are then superimposed and bonded during step E3.

[0074] In this first embodiment, the magnetic pole element 1 is manufactured from several identical magnet blocks 20 (four in the embodiment illustrated in FIGS. 3 to 5) and all segmented in the same way. Similarly, all the layers 11, 12 are produced in the same way (according to the steps of [Fig. 4] or 5). The manufacturing process of the magnetic pole element 1 is therefore easily industrializable.

[0075] A second embodiment of the method for manufacturing the magnetic pole element 1 is shown in [Fig.6]. The idea of ​​this second embodiment is to reduce the number of cracking and bonding steps leading to the assembly of each layer 11, 12.

[0076] Thus, as shown in [Fig.6], the magnet block 20 is divided into a plurality of unit magnets 10 separated from each other.

[0077] For this, step E1 may comprise a manufacture of intermediate magnets 30, as in the first embodiment, with the difference that they are not glued to each other.

[0078] Step E1 can also comprise cracking along the two segmentation directions S1, S2 in a single step, for example by putting the magnet block 20 under pressure between two surfaces forming spherical caps.

[0079] In this second embodiment, step E2 of assembling each layer 11, 12, comprises the arrangement, and therefore the fixing, of the unitary magnets on adhesive sheets 60.

[0080] As shown in [Fig.6], each layer 11, 12 comprises an adhesive sheet 60 whose shape corresponds to the shape of the housing 4 and therefore to the shape of the magnetic pole element 1 and on which the unit magnets 10 are fixed. The unit magnets 10 are then directly arranged so as to form the upper layer 11 or the lower layer 12. Unlike the first embodiment, this second embodiment does not include the assembly of intermediate plates, which limits the number of steps of the method.

[0081] The layers 11, 12 are then fixed by fixing the individual magnets 10 of the upper layer 11 to the adhesive sheet 60 of the lower layer 12, or vice versa.

[0082] [Fig. 7] illustrates another variant of this second embodiment. As shown in [Fig. 7], an adhesive sheet 60, preferably rigid, is installed in the housing 4 provided to receive the magnetic pole element 1. The upper layer 11 and the lower layer 12 are then assembled, superimposed and fixed by gluing the unit magnets 10 directly onto the adhesive sheet 60 which is held in the housing 4.

[0083] In a third embodiment shown in [Fig.8], the manufacturing method comprises, after fixing the upper layer 11 to the lower layer 12, a subsequent step E4 of cutting the upper layer 11 and the lower layer 12. In this third embodiment, the upper layer 11 and the lower layer 12 are cut once glued so as to limit the risk of breakage.

[0084] As shown in [Fig. 8], before being cut, the upper layer 11 and the lower layer 12 have a generally rectangular shape. They are cut along the straight lines shown in thick lines, so as to give the magnetic pole element 1 a shape adapted to that of the housing 4.

[0085] Advantageously, this third embodiment makes it possible to manufacture large layers, to superimpose them and to fix them, then to cut out from this assembly several elements with magnetic poles 1 (which also limits the cutting residues).

[0086] This third embodiment of the method makes it possible to simply manufacture the magnetic pole element 1 according to the embodiment example of [Fig.2]. For this, one of the large layers is reoriented, here by a 90 degree rotation, before it is bonded to the other large layer. Once the magnetic pole element 1 has been cut, the unit magnets 10 are generally rectangular and those of the upper layer 11 have large sides orthogonal to the large sides of those of the lower layer 12 (shown in dotted lines).

[0087] A fourth embodiment is shown in [Fig.9]. In this fourth embodiment also, the upper layer 11 and the lower layer 12 are cut to give shape to the magnetic pole element 1. However, the cutting is here carried out before the superposition of the layers 11, 12. Thus, the upper layer 11 is cut during a step E4A and the lower layer 12 is cut during a step E4B, the steps E4A and E4B both preceding the step E3.

[0088] In the exemplary embodiment illustrating this fourth embodiment, the unit magnets 10 extend rectilinearly from one edge to another of the layer 11, 12. They are obtained here by cracking the magnet block 20 in a single segmentation direction.

[0089] As shown in [Fig.9], once they have been assembled and cut, the upper layer 11 and the lower layer 12 are identical. Before their fixing, one of the layers 11, 12 is turned over, which allows, as explained above, that the unit magnets 10 of the upper layer 11 and those of the lower layer 12 have distinct orientations.

[0090] [Fig. 10] illustrates a fifth embodiment of the method for manufacturing the magnetic pole element 1. As clearly appears in [Fig. 10], this fifth embodiment is characterized by the fact that the upper layer 11 and the lower layer 12 have different sizes.

[0091] Here, the upper layer 11 and the lower layer 12 more particularly comprise identical unit magnets 10 but in different numbers. Thus, in [Fig. 10], the upper layer 11 assembled in step E2A comprises less of unit magnets 10 than the lower layer 12 assembled in step E2B. The layers 11, 12, however, have similar shapes.

[0092] In addition, the unit magnets 10 of the upper layer 11 are offset relative to those of the lower layer 11 in the sense that the lower faces 15 of the unit magnets 10 of the upper layer 11 extend opposite several upper faces 14 of unit magnets of the lower layer 12.

[0093] Preferably, in this fifth embodiment, a third layer, identical to the upper layer 11, is fixed against the lower layer 12 opposite the upper layer 11. The lower layer 12 is thus sandwiched between two identical and smaller layers.

[0094] This fifth embodiment can also be implemented for a magnetic pole element 1 having rectilinear lateral edges 17 as shown in [Fig.11].

[0095] Remarkably, the wider lower layer 12 can then fit into grooves, generally radial, provided in the housing 4. This makes it possible to improve the retention of the magnetic pole element 1, in particular along the axis of rotation AL. The insertion into the housing 4 is then preferably radial, the housing 4 being open towards the periphery of the rotor 2. The magnetic pole elements 1 are then, for example, retained by a hoop.

[0096] It is also possible, as shown in [Fig. 12], for the lower layer 12 which is sandwiched to protrude from the side of one of the lateral edges 17 and to be set back from the side of the other lateral edge 17 so as to form a rib. The housing 4 then has a groove and a rib.

[0097] Advantageously, the magnetic pole element 1 formed according to this fifth embodiment is particularly robust, it also makes it possible to save magnetic material while maintaining an efficiency (for the electric machine) similar to that of the other embodiments. This particular structure also makes it possible to reduce vibrations within the magnetic pole element 1 when the electric machine is in operation.

[0098] Whatever the embodiment, once the magnetic pole element 1 has been manufactured, the latter is magnetized. The magnetization step can be carried out before or after the installation of the magnetic pole element 1 in the housing 4 of the rotor 2. The magnetic pole element 1 is for example fixed in its housing 4 by means of a thermosetting resin injected between the magnetic pole element 1 and the body 2.

[0099] [Fig. 13] illustrates a sixth embodiment. As shown in [Fig. 13], this sixth embodiment is distinguished from the previous embodiments by the use of a magnet block 20 whose shape is complementary to that of the housing 4. Here, for example, the magnet block 20 provided in sub-step El 1 is of generally trapezoidal shape (like the housing 4, which is for example shown in [Fig.7]). In step El, the unit magnets 10 are manufactured by cracking in two directions, here perpendicular. Then, during a sub-step E2C, the unit magnets 10 are bonded so as to form sub-groups 36. During a step E2D, the sub-groups 36 are bonded together to form the layer 11, 12.

[0100] As illustrated in [Fig. 13], the unit magnets 10, in particular those at the periphery of the magnetic pole element 1, can then have particular shapes, for example non-parallel piped such as triangular shapes. This embodiment therefore makes it possible to obtain more varied shapes of unit magnets 10 and thus to fill the volume of the housing 4 more efficiently with magnetic material.

[0101] The present invention is in no way limited to the embodiments described and shown, but those skilled in the art will be able to provide any variant in accordance with the invention. For example, within the same element with magnetic poles, a layer may comprise unit magnets of a size and / or shape different from those of the unit magnets of another layer.

Claims

Claims

1. A method of manufacturing a magnetic pole element (1) for a rotor (2) of an electric machine, characterized in that, said magnetic pole element (1) comprising an upper layer (11) and a lower layer (12) which are arranged to extend one above the other along an axis of rotation (A1) of the rotor (2), the method comprises the following steps: - manufacturing intermediate magnets (30) by cracking a magnet block (20), along a first segmentation direction (SI), each intermediate magnet (30) extending in length along the first segmentation direction (SI); - manufacturing a plurality of unit magnets (10) by cracking the intermediate magnets (30) along a second segmentation direction (S2) distinct from the first segmentation direction (SI) along which the intermediate magnets (30) extend; - formation of the upper layer (11) by assembling at least two of the unit magnets (10);- forming the lower layer (12) by assembling at least two other of the unit magnets (10); - superimposing the upper layer (11) and the lower layer (12) and fixing the upper layer (11) to the lower layer (12), and in that the method comprises, before the manufacture of the unit magnets (10) and after the manufacture of the intermediate magnets (30) by cracking, bonding the intermediate magnets (30) to each other.;

2. Method according to claim 1, in which the intermediate magnets (30) are bonded together by complementary faces generated by the cracking of the magnet block (20) or by original faces each originating from a face of the magnet block (20).

3. A method according to one of claims 1 to 2, wherein the formation of the upper layer (11) or the lower layer (12) comprises: - bonding at least two of the unit magnets (10) to each other so as to form an intermediate plate (50); - segmenting the intermediate plate (50) into two halves (51); - rearranging and gluing the two halves (51) to each other.

4. A method according to claim 1, wherein the step of manufacturing the upper layer (11) or the lower layer (12) comprises: - bonding at least two of the unit magnets (10) so as to form a first subgroup (36); - bonding at least two more of the unit magnets (10) so as to form a second subgroup (36); and - bonding the first subgroup (36) and the second subgroup (36) so as to form the upper layer (11) or the lower layer (12).

5. Method according to one of claims 1 to 4, comprising a step of cutting the upper layer (11) and the lower layer (12) so as to give the magnetic pole element (1) a predetermined shape.

6. A method according to one of claims 1 to 5, wherein forming the upper layer (11) and the lower layer (12) comprises bonding at least two of the unit magnets (10) to each other or bonding at least two of the unit magnets (10) to an adhesive sheet (60).

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