Rotor for axial flux rotating electric machine

Abstract

Rotor for axial flux rotating electrical machine The present invention relates to a rotor for an axial flux rotating electrical machine (1), comprising a circular structure (9) centered around an axis of rotation (5), a magnetic element (10) divided into a plurality of angular sectors (11) and an overmolded resin body (12) mechanically holding the magnetic element (10) within the circular structure (9), the circular structure (9) comprising a plurality of housings each receiving one of the angular sectors (11) of the magnetic element (10), each angular sector (11) extending between an inner radial end edge and an outer radial end edge, each angular sector (11) comprising a first lateral edge and a second lateral edge, each edge delimiting a first face and a second face of the angular sector,characterized in that at least a portion of one of the edges is oriented obliquely with respect to one of the faces (23, 24) of said angular sector. (figure 2),

Description

Title of the invention: Rotor for axial flux rotating electrical machine

[0001] The present invention relates to the field of axial flux rotating electrical machines equipping vehicles, and relates more particularly to a rotor adapted for such rotating electrical machines.

[0002] Electric or hybrid motor vehicles use rotating electrical machines, in particular electric motors with at least one stator and one rotor, which are often radial flux machines. In such machines, the rotor and stator are coaxial and arranged around each other, such that windings on either the rotor or the stator generate a magnetic flux in a radial direction with respect to an axis of rotation of the rotating electrical machine.

[0003] In order to reduce the size of rotating electrical machines in motor vehicles, it is known to use, instead of a radial flux machine, an axial flux machine, which is more compact at least in a direction parallel to the axis of rotation of the rotating electrical machine. In such a machine, the rotor and at least one stator are arranged successively side by side along the axis of rotation of the electrical machine, and the magnetic flux is then generated parallel to the axis of rotation of the electrical machine. The efficiency of the rotating electrical machine is particularly affected by the effective axial flux passage area between the rotor and the stator. In this context, it is advantageous to have an axial flux machine with one rotor and two stators arranged on either side of the rotor along the axial direction.

[0004] The rotor of an axial flux electric machine, in the form of a disk, comprises at least one support and a magnetic element, in particular in the form of a permanent magnet, housed and secured to the support. This magnetic element must be mechanically held securely in the axial direction so as to resist axial forces resulting from the magnetic flux generated by each wound stator, which tend to axially attract the rotor towards the stator. More specifically, in the context of a two-stator axial flux machine, each angular sector of the rotor is alternately attracted and repelled axially by the magnetic field circulating between the rotor and the first stator, and simultaneously attracted and repelled axially by the magnetic field circulating between the rotor and the second stator. Retaining means must be provided to prevent axial displacement and detachment of the magnetic element from the rotor support.

[0005] To this end, the magnetic element is fixed to the rotor structure, notably by means of an injected resin. One objective for improving such a rotor is to increase its mechanical strength by securing the position of the magnetic element within the rotor. However, it is necessary to provide means of improvement that do not degrade the efficiency of the rotating electrical machine, that is to say, the effective axial magnetic flux passage area between the rotor and either of the stators.

[0006] The present invention falls within this context and, as such, proposes a rotor for a rotating electrical machine with axial flux, comprising a circular structure centered around an axis of rotation, a magnetic element divided into a plurality of angular sectors extending regularly around the axis of rotation, and a resin-overmolded body mechanically holding the magnetic element within the circular structure. The circular structure comprises a plurality of housings, each receiving one of the angular sectors of the magnetic element. Each angular sector extends mainly radially between an internal radial end edge and an external radial end edge. Each angular sector comprises a first lateral edge and a second lateral edge connecting the internal radial end edge to the external radial end edge. Each edge delimits a first radial face and a second radial face of the angular sector.each of said radial faces being perpendicular or substantially perpendicular to the axis of rotation of the rotor, characterized in that at least a portion of at least one of the edges of each angular sector is oriented obliquely with respect to one of the radial faces of said angular sector.

[0007] The magnetic element of the rotor can in particular be a permanent magnet, partitioned into equal parts forming respectively an angular sector and distributed regularly angularly around the axis of rotation of the rotor.

[0008] The circular structure of the rotor forms a support for this magnetic element and constitutes the central part of the rotor insofar as it is also connected to a hub attached to a transmission shaft, in order to transmit the rotation from the shaft to the rotor or vice versa. Slots are defined within it so that each angular sector of the magnetic element can be inserted and secured, one angular sector per slot. Advantageously, the slots are complementary in shape to the angular sectors. Both the circular structure and the arrangement of angular sectors are centered on the axis of rotation to ensure balanced rotation, the regular arrangement of the angular sectors also contributing to the balancing of the rotor.

[0009] The shape of the angular sectors is determined in particular by each of its edges. The radial end edges are curved so as to conform to the circular shape of the rotor, while the lateral edges are radial to substantially follow the arrangement of a radius of the rotor and facilitate the arrangement of two adjacent angular sectors. The radial faces are delimited by each of the edges and extend perpendicularly to the axis of rotation. The radial faces are thus arranged so as to be opposite one of the stators of the rotating electrical machine once the latter is fully assembled.

[0010] The resin-overmolded body is injected once all the angular sectors of the magnetic element have been positioned. The resin thus maintains all the angular sectors within the circular structure, particularly with respect to the axial direction, i.e. parallel to the axis of rotation, preventing the magnetic elements from being pulled away under the effect of a magnetic flux attracting the angular sector, i.e. a permanent magnet, towards one of the stators.

[0011] Where appropriate, each angular sector has a means of fixing within its own housing, for example by complementarity of shapes with the housing, and the resin complements this means of fixing to prevent axial detachment of the angular sector under the effect of the magnetic flux.

[0012] It is understood that the quantity of material, in this case the resin, covering the angular sector defines the pull-out resistance of this angular sector. More specifically, it is the thickness of resin interposed between the angular sector and a stator that defines the pull-out resistance of the angular sector towards this stator under the effect of the magnetic field circulating between this stator and the rotor; and the greater the axial thickness of the layer, the better the pull-out resistance.

[0013] As mentioned, according to the invention, at least a portion of an edge contributing to the delimitation of the angular sector of the magnetic element, here a permanent magnet, is configured so as to extend obliquely with respect to the radial face it prolongs. In other words, the at least one edge prolongs, in all or part of its radial dimension, a radial face of the angular sector, facing one of the stators, by presenting an inclination with respect to the normal to this radial face, so as to form a ramp whose surface is turned towards said stator.

[0014] By means of this, at least a portion of at least one oblique edge is covered, the amount of resin capable of axially supporting the angular sector is increased, thereby improving the mechanical strength of the magnetic element. More specifically, the axial thickness of resin interposed between the angular sector and a given stator is increased by generating this ramp shape on which the resin rests. The end of the ramp furthest from this given stator is thus covered with an axial thickness of resin significantly greater than the axial thickness of resin covering the radial face of the angular sector.

[0015] The obliquity of at least part of one of the edges of an angular sector allows for modification of the arrangement of the contact surfaces between said angular sector and the resin of the overmolded body, which are opposite one of the two stators. It is understood that here, with respect to edges of the angular sector that are conventionally perpendicular to the radial faces, the edges delimiting the angular sectors are made to contribute to the pull-out resistance force, by generating at these edges a contact surface suitable for being covered by an axial thickness of resin.

[0016] By oblique arrangement of a portion of an edge of the angular sector, the aim here is to specify that this portion of the edge is not perpendicular to the radial face, and that in this area, the inclination of the edge with respect to a plane perpendicular to this radial face exceeds the few degrees that can be found on magnetic parts due to manufacturing tolerances. Here, by way of non-limiting example, the angle of inclination between the radial face of the angular sector and the portion of the edge that extends it obliquely is between 100° and 140°.

[0017] In this part of the edge, the edge forms an angle with a first radial face of a first angle value, different from 90°, and this same edge forms an angle with the second radial face of a second angle value, the first angle value and the second angle value being additional angle values.

[0018] It should be noted that this configuration may result in a reduction in the surface area of ​​at least one radial face of the angular sector if the obliquity of the edges is generated by removing material from the corresponding angular sector, but this reduction is negligible and has no impact on the efficiency of the rotating electrical machine. Preferably, the obliquity of the edges is configured so that the radial faces of an angular sector remain of equal or substantially equal surface area in order to maintain a balance in terms of the magnetic flux circulating between the rotor and each of the stators arranged on either side of the rotor once the rotating electrical machine is in operation.

[0019] Configuring an angular sector with a plurality of oblique edges makes it possible to increase in several areas the axial thickness of the resin layer and thus to further strengthen the mechanical support of this angular sector within the circular structure.

[0020] According to a feature of the invention, at least one of the edges is oblique to a radial face equally along the entire radial dimension of said edge. In other words, the angle of inclination between the edge and the radial face of the angular sector is constant, or substantially constant considering manufacturing tolerances, from the inner radial end edge to the outer radial end edge.

[0021] According to one feature of the invention, the angular sector is formed from a plurality of radially juxtaposed segments, at least two adjacent segments having lateral walls participating in forming the same lateral edge of the angular sector, said lateral walls being oblique with respect to the same radial face of the angular sector with different angles of inclination from each other.

[0022] In other words, the angular sector is not made in one piece but in at least two parts forming radially juxtaposed segments. These segments form partially annular, concentric portions, and the lateral walls of these segments extend radially from one another to form the lateral edges of the angular sector. Each lateral wall of a segment has its own oblique orientation, so that two adjacent segments may have different orientations. Of course, by different angles of inclination, we mean here that the difference in the angle of inclination is significant, on the order of several degrees, so as to be distinguished from a difference due to manufacturing tolerances.As mentioned previously, the oblicity of a lateral edge allows for a local increase in the amount of resin, and this difference in the oblique orientation from one part of an angular sector to another allows for the distribution, for a given lateral edge of an angular sector, of the areas where the resin is in excess thickness.

[0023] According to one feature of the invention, at least two adjacent segments have lateral walls forming the same lateral edge of the angular sector which are oblique with respect to the same radial face of the angular sector with angles of inclination one greater than 90° and the other less than 90°.

[0024] In this way, it is ensured that, for a given angular sector and for a lateral edge of this angular sector, there are areas where the excess resin is arranged mainly between the lateral edge and one of the two stators, and areas where the excess resin is arranged mainly between the lateral edge and the other of the two stators. This improves the distribution of the resin and ensures that the forces required to hold the angular sector in position are distributed homogeneously to maintain said angular sector both with respect to a stator located on one side of the rotor and with respect to the stator located on the other side of the rotor.

[0025] According to one feature of the invention, the segments of an angular sector are divided into first segments whose lateral wall, participating in forming a first lateral edge of the angular sector, is oblique to a radial face of the angular sector at an angle of inclination greater than 90°, and second segments whose lateral wall, participating in forming a first lateral edge of the angular sector, is oblique to said radial face of the angular sector at an angle of inclination less than 90°, the first and second segments being arranged alternately from one radial end edge to the other. In other words, along the radial dimension from one radial end edge to the other, a first segment is surrounded by two second segments and / or a second segment is surrounded by two first segments.

[0026] According to a feature of the invention, at least two opposite edges of an angular sector among the radial end edges or the lateral edges are oblique with respect to at least one of the radial faces of said angular sector.

[0027] According to a feature of the invention, the radial end edges of an angular sector are oblique with respect to at least one of the radial faces of said angular sector.

[0028] According to another feature of the invention, the lateral edges of an angular sector are oblique with respect to at least one of the radial faces of said angular sector.

[0029] Having oblique edges opposite each other, that is to say arranged on either side of the angular sector in the radial or orthoradial direction, makes it possible to generate pull-out resistance forces which are distributed in a balanced way on each side of an angular sector and thus improve the resistance to stress of the angular sector.

[0030] According to a feature of the invention, one of the two opposite oblique edges forms a first ramp whose surface is opposite one of the stators and the opposite oblique edge forms a ramp whose surface is opposite the other of the stators.

[0031] In this way, for the same angular sector, a first zone of axial resin thickness is generated, arranged between one edge of the angular sector and the first stator, and thus intended to improve the pull-out resistance of the angular sector towards this first stator, and a second zone of axial resin thickness is arranged between the opposite edge of the angular sector and the second stator, and thus intended to improve the pull-out resistance of the angular sector towards this second stator. The presence of these two zones of axial thickness, each arranged axially on one side of the angular sector, ensures that the angular sector is held securely in both directions of the axial direction.

[0032] According to one feature of the invention, an angle of inclination of one edge with respect to one of the radial faces is equal to an angle of inclination of the opposite edge with respect to the other radial face. The ramp formed by one edge and the ramp formed by the opposite edge are parallel. This results in two axially thickened areas, each arranged axially on one side of the angular sector, which are substantially dimensioned in the same way, so that the retention of the angular sector is optimal. This is particularly relevant when the angular sector comprises radially juxtaposed segments forming said angular sector and the lateral walls of two adjacent segments have different angles of inclination. On the other hand, we understand that an angle of inclination of a wall of a first segment with respect to one of the radial faces is equal to an angle of inclination of the opposite wall of the first segment with respect to the other of the radial faces.

[0033] According to one feature of the invention, the circular structure comprises an inner annular section, an outer annular section, and a plurality of radial branches connecting the inner annular section to the outer annular section and defining the housings, the radial branches separating two adjacent housings. Once the angular sectors are positioned, each inner radial end edge is opposite the inner annular section, each outer radial end edge is opposite the outer annular section, while each lateral edge is opposite one of the radial branches.

[0034] According to one feature of the invention, the inner annular section, the outer annular section, and the radial arms each comprise at least one inner surface that helps to define at least one of the recesses. The circular structure comprises at least one rib that projects radially from at least one of the inner surfaces and extends partially into the corresponding recess. The inner surface corresponds to an area of ​​the inner annular section, the outer annular section, and the radial arms whose thickness is equal to or substantially greater than the thickness of the angular sectors. The rib projects from at least one of the inner surfaces, thus forming a finger intended to be embedded in the resin. This increases the adhesion of the resin of the overmolded body to the circular structure and therefore enhances the stability of the angular sectors within the circular structure via this resin.Furthermore, the presence of this rib ensures that the angular sector is not pressed against the entire axial dimension of the internal surface and that a space is created between the internal surface and the angular sector. This space can then be filled with resin, which solidifies around the rib, reinforcing the mechanical retention of the angular sector in its housing. The rib can be formed, in particular, in the middle, considering the axial direction, of the internal surface from which it protrudes, so that the finger-like effect of increasing resin adhesion has the same effect on the resin covering one radial face of an angular sector as on the other radial face.

[0035] According to one feature of the invention, an edge formed at the junction of an oblique edge and a radial face extends radially between the free end of a first rib and the internal surface bearing this first rib, along a first axial side of the first rib, and an edge formed at the junction of the opposite oblique edge and the other radial face extends radially between the free end of a second rib and the internal surface bearing this second rib, along a second axial side of the second rib that is axially opposite to said first axial side. Thus, one can Ensure that the surface area of ​​the radial faces is as large as if the edges had been straight and positioned between the ribs, with a portion of each radial face positioned axially opposite the rib. Such an angular sector is inserted into its housing at an angle that allows the first edge to pass to one side of the rib, and is then tilted to assume a position perpendicular to the rotor's axis of rotation.

[0036] According to one feature of the invention, the rotor comprises a hub fixed for rotation to a drive shaft, the internal annular section cooperating with said hub. As a reminder, the rotor is part of a rotating electrical machine, which is used in a motor vehicle. For example, the rotating electrical machine could be a starter-alternator. When driven in rotation by the action of a rotating magnetic field, the rotor drives the drive shaft via the hub, which contributes to the propulsion of the vehicle, or to some of the vehicle's functions other than propulsion.

[0037] According to one feature of the invention, the overmolded body at least partially covers a radial face of an angular sector, and the portion of the overmolded body covering the radial face has a thickness of less than 10% of the thickness of the angular sector. The thicknesses are measured along the axial direction defined by the axis of rotation of the rotor.

[0038] The resin also takes the form of a layer covering the radial faces, and as mentioned, the presence of this resin increases the mechanical resistance of the angular sectors to axial pull-out via magnetic flux. The presence of axial resin overthicknesses opposite the oblique edges and the resulting improvement in holding performance makes it possible to reduce the thickness of the resin layer applied to the radial faces. This, in turn, reduces the air gap, i.e., the axial distance between the rotor and one of the stators, and thus improves the performance of the rotating electrical machine.

[0039] According to one feature of the invention, at least one edge of the angular sectors comprises a first portion extending obliquely from the first radial face and a second portion extending obliquely from the second radial face, the two oblique portions meeting at a projecting edge. This is a variant of a rotor according to the invention, in which the oblique edge is characterized by the presence of two ramps whose surfaces are oriented in opposite directions. The first portion extending obliquely from the first radial face forms a ramp facing this first radial face, and the second portion extending obliquely from the second radial face forms a ramp facing this second radial face. Thus, as before, there are two ramps, with one ramp facing each of the radial faces, which increases the performance of Mechanical strength is maintained in both axial directions, but it is noteworthy here that these two ramps are formed on the same edge. If necessary, these two opposing ramps can be formed on opposite edges. The protruding edge is positioned as close as possible to the corresponding internal surface, leaving a gap to allow resin injection on either side of the edge.

[0040] The invention also covers a rotating axial flux electric machine for a vehicle, comprising a rotor as described above, a first stator and a second stator arranged on either side of the rotor along an axial direction, and a housing delimiting an internal volume containing the rotor and the two stators. As described above, the rotor according to the invention is integrated within a rotating axial flux electric machine, that is to say, in which the magnetic flux is generated in the direction parallel to the axis of rotation of the rotor, such a rotating axial flux electric machine being particularly useful for reasons of compactness.

[0041] The invention also covers a method of mounting a rotor as described above, in which: - The angular sectors of the magnetic element are placed within the housings of the circular structure, - once the angular sectors are in place, the overmolded body is formed by injecting resin into the housings and covering the radial faces.

[0042] More specifically, this method allows the angular sectors of the magnetic element to be positioned and fixed within the circular structure. The injection of resin to form the overmolded body serves as a means of fixing the angular sectors within the recesses of the circular structure.

[0043] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0044] [Fig. 1] is a cross-sectional view of a rotating axial flux electrical machine,

[0045] [Fig.2] is a general view of a rotor according to the invention, equipping a machine electrical as illustrated in [Fig.1],

[0046] [Fig.3] is an exploded view of the rotor of [Fig.2], making visible a body overmolded with resin, angular sectors, a circular structure attached to a hub, and a drive shaft cooperating with the hub,

[0047] [Fig.4] is a cross-sectional view of a portion of the rotor according to section IV-IV illustrated on the [Fig.2],

[0048] [Fig.5] is a representation similar to that of [Fig.4], illustrating a structure alternative rotor, notably distinct from that illustrated in [Fig.4] by the shape of the edges of the angular sector;

[0049] [Fig.6] illustrates, in perspective, an angular sector according to an alternative embodiment of the invention.

[0050] Figure 1 is a representation of a rotating electrical machine 1 with axial flux that can be integrated within a motor vehicle. Such a rotating electrical machine 1 comprises a rotor 2 according to the invention, a first stator 3 and a second stator 4, all centered around an axis of rotation 5. The stators 3, 4 are further arranged on either side of the rotor 2 in an axial direction parallel to the axis of rotation 5. The rotor is equipped with magnetic elements and each of the stators 3, 4 is equipped with coils 6. The rotating electrical machine 1 also comprises a drive shaft 7 and a housing 8, which is shown here in the form of two half-housings 8a, 8b and which houses the rotor 2, the stators 3, 4 and partially the drive shaft 7.

[0051] When the rotating electrical machine 1 is started, for example when the vehicle is starting, the coils 6 of the stators 3, 4 are supplied with electrical energy and generate a magnetic flux. The control of this flux, by appropriate electronic means, allows the rotor 2, equipped with these magnetic elements, to rotate. In particular, the electrical supply to the coils 6 is controlled to generate a rotating electric field within which the magnetic elements, and therefore the rotor 2, are made to rotate. The air gap between the stator and the magnetic elements of the rotor, through which the magnetic flux passes from the rotor to the stator and vice versa, is arranged axially so that the magnetic flux can be considered to be implemented in the axial direction.

[0052] The rotor 2 is therefore driven in rotation and drives with it the drive shaft 7 which in turn initiates a movement of one or more elements not shown, for example in order to participate in the starting of the vehicle.

[0053] Figures 2 and 3 are detailed views of the rotor 2 according to the invention. More specifically, they are respectively a general view and an exploded view of the rotor 2.

[0054] In addition to the drive shaft 7 mentioned previously, the rotor 2 comprises a circular structure 9, a magnetic element 10 divided into a plurality of angular sectors 11 respectively supported by the circular structure 9, and an overmolded resin body 12 which covers at least partially the angular sectors, in particular to ensure their retention within the circular structure 9.

[0055] The circular structure 9 comprises an internal annular section 13 forming a central zone of the rotor 2, an external annular section 14 forming a periphery of the rotor 2, and a plurality of radial branches 15 regularly spaced from each other and connecting the internal annular section 13 to the external annular section 14. The internal annular section 13 and the external annular section 14 are both centered on the axis of rotation 5 of the rotor 2. The internal annular section 13 is rotationally fixed to the drive shaft 7 by means of a hub 16.

[0056] The internal annular section 13, the external annular section 14, and the radial branches 15 define a plurality of housings 17 distributed evenly around the axis of rotation 5. Each of these housings 17 is designed to accommodate one of the angular sectors 11 of the magnetic element 10. The housings 17 thus have a shape similar to the shape of the angular sectors 11. The radial branches 15 also allow two adjacent angular sectors 11 to be separated. Each housing 17 is delimited by an internal surface 18 of the internal annular section 13, the external annular section 14, and the radial branches 15 corresponding to said housing 17.

[0057] Each angular sector 11 of the magnetic element 10 naturally possesses magnetic properties to ensure the rotation of the rotor 2. By way of example, each angular sector is a magnet capable of moving around the axis of rotation 5 in a rotating magnetic field. Each angular sector 11 is defined by an internal radial end edge 19 and an external radial end edge 20, as well as by a first lateral edge 21 and a second lateral edge 22, both of which connect the internal radial end edge 19 to the external radial end edge 20.

[0058] Each angular sector 11 has a radial face opposite each of the stators arranged on either side of the rotor. More specifically, each angular sector has a first radial face 23 and a second radial face 24, each of these radial faces being perpendicular or substantially perpendicular to the axis of rotation 5 of the rotor. As mentioned, once the rotating electrical machine is assembled, each of the radial faces 23, 24 is opposite one of the stators of said rotating electrical machine. The electromagnetic efficiency of the rotating electrical machine is notably dependent on the surface area of ​​the angular sector opposite the stator, and therefore on the radial, or lateral, dimension of this radial face.

[0059] The overmolded body 12 provides mechanical support for the angular sectors 11 of the magnetic element 10 within the circular structure 9. In [Fig. 3], the overmolded body 12 is shown as a single piece in an exploded view, in its final form, but it should be noted that it is formed by resin injection during a rotor 2 assembly process according to the invention. The resin injection to form the overmolded body 12 is carried out once all the angular sectors 11 are positioned in the recesses 17 of the circular structure 9. The resin is injected in particular so as to mechanically hold the angular sectors 11 within the recesses 17. The resin used to form the overmolded body 12 extends between the edges 19, 20, 21, 22 of the angular sectors 11 and the internal surface 18 of the internal annular section 13, of the external annular section 14 and of the radial branches 15. Furthermore, the surmounted body 12 covers at least partially the radial faces 23, 24 of the angular sectors 11 of the magnetic element 10.

[0060] Since each angular sector 11 of the magnetic element 10 is subjected to a mechanical stress exerted by the axial magnetic flux generated within the rotating electrical machine 1 illustrated in [Fig. 1], the resin-covered body 12 must provide mechanical resistance to the angular sectors 11 against the magnetic flux, and in particular against the angular sector being pulled away from the rotor body. The greater the axial thickness of the resin body between the angular sector and one of the stators, the better the resistance to being pulled away in the direction of that stator. And in a context with two stators on either side of the rotor, it is important that the axial thickness of the resin-covered body be significant in both directions of the axial direction.

[0061] The particularity of the rotor 2 according to the invention is that at least one of the edges 19, 20, 21, 22 of an angular sector 11 of the magnetic element 10 is oriented obliquely with respect to one of the radial faces 23, 24 of said angular sector 11. And each angular sector 11 can be configured in this way.

[0062] Such an oblique orientation of an edge extending from a radial face makes it possible to generate a ramp whose inclined surface faces the radial face extended by this oblique edge. This provides an additional contact surface for the resin, which faces the stator and helps to resist the pull-out of the angular sector. The obliquity of the edge and the resulting inclination of the ramp mean that the axial thickness of resin covering this edge can be progressively increased, thus generating locally, at each oblique edge, a zone of axial resin excess that axially covers a portion of the angular sector, thereby increasing the axial retention mechanical performance of this resin.

[0063] Figure 4 is a cross-sectional view of a portion of the fully assembled rotor. The section is made along section plane IV-IV illustrated in Figure 2. Figure 4 allows observation, in particular, of the oblique orientation of the edges of the angular sector 11 and the resulting formation of areas of axial excess resin in axial contact with a portion of the angular sector.

[0064] The oblicity of an edge of the angular sector is measured by the value of the angle of inclination α of that edge with respect to the radial face of the angular sector that the edge extends away from the center of that angular sector. By way of example, the value of the angle of inclination α is between 100° and 140°.

[0065] In [Fig.4], the inner radial end edge 19 and the outer radial end edge 20 are oriented obliquely with respect to the first radial face 23 and the second radial face 24. Advantageously, two edges opposite each other are oriented obliquely with respect to at least one of the radial faces 23, 24. In a manner not illustrated, the two lateral edges 21, 22 can also be oriented obliquely with respect to the first radial face 23 and / or the second radial face 24, either alternatively or in addition to the fact that the two radial end edges are oriented obliquely as mentioned and illustrated here.

[0066] Advantageously, as illustrated in [Fig. 4], the two obliquely oriented opposite edges are oriented at the same angle of inclination α, that is, so as to each form a ramp facing its own stator, the ramps having the same slope. Each opposite edge extends its own radial face at the same angle of inclination α so that these opposite edges are parallel to each other. This makes it possible to generate equivalent mechanical resistance in both directions of the axial direction. In the configuration as illustrated in [Fig.4], a first axial overthickness zone 121 is implemented by positioning the resin along an oblique edge, this first axial overthickness zone 121 being formed between the angular sector and a first stator opposite the first radial face 23 and a second axial overthickness zone 122 is implemented by positioning the resin along an opposite oblique edge, this second axial overthickness zone 122 being formed between the angular sector and a second stator opposite the second radial face 24. .

[0067] In order to further enhance the mechanical strength achieved by the overmolded body 12, the main structure 9 may include a rib 25 projecting radially from at least one of the internal surfaces 18 of said main structure 9, so as to extend into the housing 17. As can be seen in [Fig. 4], the internal annular section 13 and the peripheral annular section 14 each include a rib 25, each of which may have various dimensions. The rib 25, when the resin forming the overmolded body 12 is injected, increases the resin's adhesion in order to further enhance the mechanical strength once the overmolded body 12 is formed.

[0068] As previously mentioned, the overmolded body 12 at least partially covers the radial faces 23, 24 in the form of a thin layer 120, as illustrated in [Fig. 4]. The increased mechanical strength at the edges of the angular sector, due in particular to the obliquity of the edges according to the invention, potentially allows for a reduction in the thickness of the resin layer covering the radial faces 23, 24.

[0069] The portion of the overmolded body covering the radial face has a thickness E. Preferably, the thickness E is the same from one radial face to the other. In particular, it can be less than 10% of the thickness of the angular sector, the thicknesses being measured along the axial direction defined by the axis of rotation 5 of the rotor. It is particularly advantageous to limit the thickness of these layers since this allows the stators to be brought closer to the rotor and reduces the air gap.

[0070] As can be seen in [Fig. 4], the dimensioning of the angular sector can be adjusted so as not to penalize the electromagnetic performance of the rotating electrical machine, and in particular by ensuring that the surface area of ​​the radial face facing the stator remains the same as if there were a radial face extended by straight edges. An edge of an oblique edge, at the end of the ramp, is thus arranged radially beyond the rib facing said oblique edge, that is to say that the distance between the axis of rotation of the rotor and this edge is greater than the value of the distance between the axis of rotation of the rotor and the rib, as illustrated in [Fig. 4] by the distance dl.

[0071] In a preferred embodiment, an edge at the junction of an oblique edge and the first radial face is disposed radially beyond the end face of the corresponding rib, being located further outside the rotor than the end face of the rib, and an edge at the junction of the opposite oblique edge and the second radial face is disposed radially beyond the end face of the corresponding rib, being located further inside the rotor than the end face of the rib, these two edges being arranged axially, one between the first stator and the corresponding rib and the other between the second stator and the corresponding rib. Of course, this description applies here to the illustration in [Fig.4] in which the oblique edges are the radial end edges, but it could be applied to the lateral edges, the edges then extending beyond the end face of the corresponding rib in an orthoradial direction.

[0072] Fig. 5 is an illustration of the same cross-sectional view as in Fig. 4 but with an alternative structure of the angular sector 11. Apart from this alternative structure, all structural and functional elements are equivalent to what has been described in Fig. 4 and reference will therefore be made to the description of that figure for the elements common to the two corresponding rotor variants.

[0073] This alternative structure of the angular sector 11 differs from what has been previously described in that the radial end edges both comprise a first oblique portion 26 with respect to the first radial face 23 and a second oblique portion 27 with respect to the second radial face 24. Moreover, for each of the radial end edges of the angular sector 11, the two oblique portions 26 and 27 meet at a projecting edge 28. This alternative structure again allows for the formation of areas of axial thickness opposite an oblique edge, thus improving the pull-out resistance of the angular sector. Advantageously, here, an axial thickness of resin is interposed between each edge of the angular sector and each of the stators. The amount of axial material between an edge and a given stator is less than in the embodiment of [Fig. 4], but it is better distributed along each edge.

[0074] Of course, as with the embodiment described above, the same configuration could be implemented, alternatively and cumulatively, with the lateral edges of the angular sector.

[0075] Figure 6 illustrates an alternative embodiment of the invention, which differs from this which was previously described in the structure of the angular sectors. The rest of the description, relating to the arrangement of the angular sectors with respect to the stator or relating to the presence of resin forming the overmolded body with local overthicknesses due to the oblicity of at least one edge of the opposite sector, can be applied to this embodiment variant.

[0076] In this embodiment, the angular sector differs in that it is formed of a plurality of radially juxtaposed segments 100. These segments 100 can form partially annular portions, all concentric. Alternatively, the segments can comprise an internal radial end segment 110, one edge of which forms the curved internal radial end edge 19, an external radial end segment 111, one edge of which forms the curved external radial end edge 20, and a plurality of intermediate segments 101, 102, whose opposing edges form planar edges, that is, edges extending mainly in a flat, uncurved surface, each of these two opposing planar edges being in contact with a planar edge of an adjacent segment. The [Fig.6] illustrates contact surfaces 103 between two plane edges of adjacent segments 100, these adjacent segments being able to be made independently and then brought together, but it may be provided that the angular sector is made in one piece and that the segments are identified by the specific shape of their lateral walls which participate in forming the lateral edge of the angular sector of these segments.

[0077] In this variant, when considering the lateral walls 104, 105 of at least two adjacent segments 101, 102 participating in forming the same lateral edge 21, 22 of the angular sector 11, said lateral walls 104, 105 are oblique with respect to the same radial face 23, 24 of the angular sector with different angles of inclination from each other.

[0078] Two adjacent segments 101, 102 can thus be identified in that, even though their lateral walls extend in a radial continuity from one another to participate in forming one of the lateral edges 21, 22 of the angular sector, they have a different inclination with respect to the same radial face 23, 24.

[0079] In the illustrated example, the difference in inclination of two lateral walls of adjacent segments is such that the angles of inclination of these two lateral walls, with respect to the same radial face, are one greater than 90° and the other less than 90°.

[0080] This difference in inclination of the two lateral walls of adjacent segments can be reproduced from one radial end edge of the angular sector to the other radial end edge, thus forming an alternation in the arrangement of segments of a first type, with a lateral wall whose angle of inclination with respect to a radial face is greater than 90° and of segments of a second type, with a lateral wall whose angle of inclination with respect to this radial face is less than 90°.

[0081] As mentioned previously, the obliquity of a lateral edge allows for a local increase in the amount of resin, and this difference in the oblique orientation from one part of an angular sector to another makes it possible to distribute, for a given lateral edge of an angular sector, the areas where the resin is in excess. In this context, the alternation of segment types as just described allows for a homogeneous distribution of the forces holding the angular sector together, generated by the excess resin.

[0082] In the illustrated example, it is noteworthy that the segments may have opposite lateral walls which are parallel to each other, so that a lateral wall of a segment has an angle of inclination with respect to a radial face which is greater than 90° and that the opposite lateral wall of this same segment has an angle of inclination with respect to this radial face which is less than 90°.

[0083] The invention, as described above, achieves its intended purpose and makes it possible to propose a rotor comprising a magnetic element divided into angular sectors whose retention within a circular rotor structure is reinforced by means of resin, by simple means that are easy to implement and do not negatively impact the electromagnetic performance of the electrical machine equipped with such a rotor. These simple means consist in particular of a specific configuration of at least one of the edges of said angular sectors. Variations not described here could be implemented without departing from the scope of the invention, provided that, in accordance with the invention, they comprise a rotor conforming to the invention with an angular sector edge oriented obliquely with respect to the radial face of the angular sector intended to be opposite a stator.

Claims

Demands

1. Rotor (2) for an axial flux rotating electrical machine (1), comprising a circular structure (9) centered about an axis of rotation (5), a magnetic element (10) divided into a plurality of angular sectors (11) extending regularly about the axis of rotation (5), and an overmolded resin body (12) mechanically retaining the magnetic element (10) within the circular structure (9), the circular structure (9) comprising a plurality of housings (17), each receiving one of the angular sectors (11) of the magnetic element (10), each angular sector (11) extending principally radially between an inner radial end edge (19) and an outer radial end edge (20), each angular sector (11) comprising a first lateral edge (21) and a second lateral edge (22) connecting the inner radial end edge (19) to the outer radial end edge (20), each edge (19, 20, 21,22) delimiting a first radial face (23) and a second radial face (24) of the angular sector (11), each of said radial faces (23, 24) being perpendicular or substantially perpendicular to the axis of rotation (5) of the rotor (2), characterized in that at least a part of one of the edges (19, 20, 21, 22) of an angular sector (11) is oriented obliquely with respect to one of the radial faces (23, 24) of said angular sector (11).

2. Rotor (2) according to claim 1, wherein said at least one of the edges (19, 20, 21, 22) is oblique with respect to a radial face (23, 24) equally over the entire radial dimension of said edge.

3. Rotor (2) according to claim 1, wherein said angular sector is formed of a plurality of radially juxtaposed segments (100, 101, 102), at least two adjacent segments (101, 102) having lateral walls (104, 105) participating in forming the same lateral edge (21, 22) of the angular sector, said lateral walls (104, 105) being oblique with respect to the same radial face (23, 24) of the angular sector with different angles of inclination from each other.

4. Rotor (2) according to any one of claims 1 to 3, wherein at least two opposite edges (19, 20, 21, 22) of an angular sector (11) among the radial end edges (19, 20) or the lateral edges (21, 22) are oblique with respect to at least one of the radial faces (23, 24) of said angular sector.

5. Rotor (2) according to any one of the preceding claims, wherein an angle of inclination of one of the edges (19, 20, 21, 22) with respect to one of the radial faces (23, 24) is equal to an angle of inclination of the opposite edge (19, 20, 21, 22) with respect to the other of the radial faces (23, 24).

6. Rotor (2) according to any one of the preceding claims, wherein the circular structure (9) comprises an internal annular section (13), an external annular section (14) and a plurality of radial branches (15) connecting the internal annular section (13) to the external annular section (14) and delimiting the housings (17), the radial branches (15) separating two adjacent housings (17), and wherein the internal annular section (13), the external annular section (14) and the radial branches (15) comprise at least one internal surface (18) participating in delimiting at least one of the housings (17), the circular structure (9) comprising at least one rib (25) radially projecting from at least one of the internal surfaces (18) to extend partially into the interior of the corresponding housing (17).

7. Rotor (2) according to any one of the preceding claims, wherein the overmolded body (12) at least partially covers the radial faces (23, 24).

8. Rotor (2) according to any one of the preceding claims, wherein at least one edge (19, 20, 21, 22) of the angular sectors (11) comprises a first portion (26) obliquely extending the first face (23) and a second portion (27) obliquely extending the second face (24), the two oblique portions (26, 27) joining in a salient edge (28).

9. Axial flux rotating electric machine (1) for vehicle, comprising a rotor (2) according to any one of the preceding claims, a first stator (3) and a second stator (4) arranged on either side of the rotor (2) in an axial direction, and a housing (8) delimiting an internal volume containing the rotor (2) and the two stators (3, 4).

10. A method for mounting a rotor (2) according to any one of claims 1 to 8, wherein: The angular sectors (11) of the magnetic element (10) are placed within the housings (17) of the circular structure (9), once the angular sectors (11) are placed, the overmolded body (12) is formed by injecting resin into the housings (17) and covering the radial faces (23, 24).

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