Rotor for axial flux motor

Abstract

Title of the invention: Rotor for axial flux motor The present invention relates to a rotor (3) for an axial flux motor (1) comprising a magnetic element (5), a metal hub (8) and a support (9) for the magnetic element (5) fixed on the hub (8), said support (9) being made of a material different from the hub (8), in which the hub (8) has orifices (24) with at least two diametrically opposed orifices (24), the support (9) being engaged with the hub (8) by coupling means (12) housed in the orifices (24). Figure for abstract: figure 3

Description

Title of the invention: Rotor for axial flux motor

[0001] The present invention relates to the field of motor vehicles, and more particularly to the electrical machines equipping these motor vehicles.

[0002] Electric or hybrid motor vehicles use 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 the stator are coaxial and arranged around each other, such that windings embedded on the stator, respectively the rotor and magnetic elements present on the rotor, respectively the stator, generate a magnetic flux in a radial direction relative to an axis of rotation of the electric machine.

[0003] In order to reduce the size of 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 electrical machine. In such a machine, the rotor and the stator are arranged successively next to each other 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.

[0004] The rotor of an axial flux electric machine is usually in the form of a disc, which is commonly made up of a central hub and a magnetic element support. The central hub is connected to the transmission shaft, thus allowing the rotor to rotate. The support radially extends the hub and is sized to accommodate magnetic elements. Conventionally, such a rotor is made entirely of metal, which makes it both heavy and expensive to produce. In certain situations, a more economical approach is to use both plastic and metal elements and more particularly to provide a metal hub capable of absorbing the forces at the junction with the transmission shaft.This combination allows for a reduction in weight and manufacturing costs, but it raises the question of the rotor's resistance to the forces exerted in rotation, the connection between the metal hub and the plastic support having to be sufficiently rigid so that the support does not give way, particularly when the rotor is subjected to high rotation speeds.

[0005] The present invention falls within this context by proposing a rotor for an axial flux motor comprising a magnetic element, a metal hub and a support for the magnetic element fixed to the hub, said support being made of a material different from the hub, characterized in that the hub comprises orifices with at least two diametrically opposed orifices, the support being engaged with the hub by coupling means housed in the orifices.

[0006] It should be understood that the support may be non-metallic or metallic. Thus, when the support is made of a metallic material it will be of a metallic material different from the metallic material used for the hub.

[0007] The production of orifices in the hub and the presence of coupling means housed in the orifices reinforce the rotational connection between the hub and the support and this characteristic ensures that the rotor has great resistance to centrifugal forces, thus improving the reliability of the rotor.

[0008] It should be understood that these orifices are in the form of closed-edge cavities, formed directly in the material of the hub. Each orifice is made to form a housing for a coupling means and metallic material surrounds the housing over its entire periphery. In this, it is distinguished from embodiments in which notches are formed on a peripheral edge of the hub, being radially open on the outside of the hub. Such a configuration, with a closed section of the orifices, in a plane perpendicular to the axis of rotation of the rotor, makes it possible to ensure that the coupling means carried by the magnetic element support are in contact with the metallic material of the hub over their entire periphery, apart from the surface roughness. The moments induced by the rotation at high speeds of the rotor can thus be absorbed more easily by the support and the overall resistance of the rotor to stress is improved.This configuration ensures a solid attachment of the hub to the support.

[0009] It should be noted that at least two orifices are diametrically opposed, which makes it possible to distribute the forces evenly and avoid local stresses on the support.

[0010] According to an optional feature of the invention, the support is made of a plastic or composite material. Preferably, the composite material is a soft magnetic composite (SMC). The combination of a metal hub with a plastic support makes it possible to significantly reduce the weight of the rotor by using a lightweight material, thus improving the energy efficiency of the motor. The use of a plastic material as the support material also makes it possible to reduce manufacturing costs thanks to less expensive materials.

[0011] According to an optional feature of the invention, the orifices extend in the hub parallel to the axis of rotation of the rotor. By providing orifices and not notches, that is to say by providing cavities fully delimited radially by material of the hub, and by arranging the orifices and the coupling means intended to fill them parallel to the axis of rotation of the rotor, the transmission of forces due to centrifugal force is improved, by increasing the contact surface between the hub and the coupling means in a plane comprising this force. centrifugal, perpendicular to the axis of rotation of the rotor. In this way, the support is not only held by the frictional force resulting from the support between the support and the hub.

[0012] According to an optional characteristic of the invention, the coupling means are of a shape and dimensions complementary to those of the orifices of the hub.

[0013] In other words, the coupling means carried by the magnetic element support are in contact with the metallic material of the hub over their entire periphery, apart from the surface roughness. According to the embodiments of the invention, this aim can be achieved by filling the cavity formed by the orifice within the hub with material from the support, in an injection overmolding process, or it is possible to provide for the magnetic element support and hub to be produced separately from each other, with manufacturing tolerances that are sufficiently small so that the coupling means of the support fit almost without play, or are force-fitted, into the orifices of the hub.

[0014] According to an optional characteristic of the invention, the hub comprises a cylindrical sleeve, the axis of which defines an axis of rotation of the rotor, and a plate extending in radial extension of the sleeve, substantially perpendicular to the axis of rotation, the orifices being formed in the thickness of the plate of the hub. More precisely, the sleeve is located in the center of the hub, to ensure the connection with a transmission shaft, while the plate radially extends the sleeve by surrounding the sleeve concentrically, so that the plate interacts with the support.

[0015] According to an optional characteristic of the invention, the orifices are positioned circumferentially on the plate around the axis of rotation of the rotor.

[0016] According to an optional characteristic of the invention, the orifices are positioned at regular intervals relative to each other.

[0017] According to an optional characteristic of the invention, the support comprises an internal crown and an external crown extending circularly around the hub and extending radially around the magnetic element, said internal crown comprising the coupling means.

[0018] According to an optional characteristic of the invention, the internal crown and the external crown are connected by radial branches participating in forming housings intended to receive the magnetic elements.

[0019] According to an optional feature of the invention, the internal crown extends opposite a single face of the hub, the coupling means forming ribs extending projecting from the face of the internal crown which is opposite the hub. These ribs are designed to fit into the holes in the hub. Their shapes and dimensions are carefully adapted to correspond to those of the holes, which ensures a strong grip of the bracket on the hub.

[0020] According to an optional characteristic of the invention, the internal crown extends opposite two opposite faces of the hub, the coupling means forming a stud connecting two parts of the internal crown arranged on either side of the hub. The internal crown rests on each of the axial faces of the hub, that is to say each of the opposing axial faces, so that a first part of the internal crown and a second part of the internal crown axially enclose the hub, being linked by studs forming the coupling means. In this embodiment, it is understood that the support, and therefore the internal crown, is produced by injection of material during an operation of overmolding the support on the hub.

[0021] According to an optional feature of the invention, the support and the hub are irreversibly connected to each other. The support and the hub are connected together, for example, by overmolding the support onto the hub, which guarantees a solid connection between these elements.

[0022] According to an optional characteristic of the invention, the rotor comprises a means for reversibly fixing the support to the hub. In particular, the support can be produced in an injection process without the metal hub and then these two elements can be assembled against each other, by engaging the support in the hub via the coupling elements, and finally ensuring the position of one relative to the other using the reversible fixing means.

[0023] According to an optional feature of the invention, the support is segmented. In this configuration, each individual segment comprises at least one coupling means, thus giving each segment the ability to be independently fixed to the hub. The complete support is formed by fixing each of the segments to the hub.

[0024] According to an optional feature of the invention, at least one of the orifices is a through orifice. And according to another optional feature of the invention, at least one of the orifices is a blind orifice. In other words, the orifices of the hub can be of different natures as long as they cooperate with the coupling means and allow good transmission of forces during rotation of the rotor. In this context, all or part of the orifices can be blind, that is to say be non-through and have a bottom, or all or part of the orifices can pass right through the hub.

[0025] According to an optional feature of the invention, the sleeve is configured to cooperate with a transmission shaft comprising a threaded part, the rotor comprising a self-locking nut intended to be screwed onto said threaded part. This self-locking nut offers protection against any risk of unwanted loosening, in particular in the presence of vibrations, which thus reinforces the stability of the entire rotor.

[0026] According to an optional feature of the invention, the internal crown has an internal edge facing the self-locking nut, the distance between the internal edge and the self-locking nut being reduced to a minimum to ensure perfect contact between the nut and the metal hub without interference from the material of the support. The use of a self-locking nut in this context makes it possible to mount the self-locking nut on the transmission shaft with a tool pushing axially on the self-locking nut, so that it is not necessary to provide a clearance zone between the internal crown and the self-locking nut for the passage of a tightening key. It is thus possible to increase the covering surface of the hub by the material of the internal crown and ensure better grip between the material of the internal crown and the metal material of the hub.

[0027] According to an optional feature of the invention, the sleeve has an internal surface and an annular band forming a projection from said internal surface and locally reducing the internal diameter of the sleeve. This feature allows a force fit with the transmission shaft.

[0028] According to an optional feature of the invention, the transmission shaft comprises a centering part and a clamping part whose external diameters are different, the external diameter of the centering part being substantially identical to the internal diameter of the internal surface of the sleeve, and the external diameter of the clamping part being larger than the internal diameter of the annular band forming a projection. These features make it possible, during the assembly of the transmission shaft and the hub, to guarantee the coaxiality of these two parts and the rigid assembly by fitting.

[0029] According to an optional feature of the invention, the clamping portion of the transmission shaft is knurled. The knurling thus improves the connection between the transmission shaft and the projection of the rotor hub and contributes to more efficient torque transmission, thereby improving the overall performance of the rotor.

[0030] According to an optional characteristic of the invention, a resin is arranged to cover the magnetic element, on at least one face of the support. This resin may for example be composed of epoxy polymer. This resin has various advantages such as that of reinforcing the overall structure of the rotor or that of increasing the lifespan of the rotor by providing protection from the external environment.

[0031] According to an optional characteristic of the invention, the support has at least one through notch for the passage of the resin on each of the faces of the support. This characteristic makes it possible to facilitate the process of obtaining the rotor comprising the resin.

[0032] According to an optional characteristic of the invention, the notch(s) are formed in the edges of the housings.

[0033] According to an optional characteristic of the invention, the notch(s) are formed in at least one corner of the housings.

[0034] According to an optional characteristic of the invention, the plastic material of the support is loaded with metal fibers.

[0035] According to an optional feature of the invention, the hub and the transmission shaft form a single-piece assembly. The use of a single-piece assembly eliminates potential mechanical clearances that could occur between the transmission shaft and the hub in configurations composed of separate parts. In addition, this single-piece assembly ensures efficient and reliable power transmission, reduces the risk of mechanical failure and simplifies the assembly process.

[0036] Other characteristics, details and advantages of the invention will emerge more clearly on reading the description which follows on the one hand, and examples of embodiment given for informational and non-limiting purposes with reference to the appended drawings on the other hand, in which:

[0037] [Fig. 1] is a general representation of an axial flux motor, with a rotor which is the subject of the invention and two stators arranged axially on either side of the rotor;

[0038] [Fig.2] illustrates, schematically, a first embodiment of a rotor for an axial flux motor, this rotor comprising a hub and a magnetic element support;

[0039] [Fig.3] illustrates, schematically, a sectional view of the rotor according to the first embodiment, which notably makes visible the fact that the hub and the magnetic element support form a single-piece assembly, obtained for example by overmolding the support on the hub;

[0040] [Fig.4] illustrates, schematically, an exploded view of the rotor according to the first embodiment;

[0041] [Fig.5] illustrates, schematically, a second embodiment of the rotor for an axial flux motor, this rotor comprising a hub and a magnetic element support;

[0042] [Fig.6] illustrates, schematically, a sectional view of the rotor according to the second embodiment, which makes visible in particular the fact that the hub and the magnetic element support are made integral in rotation with respect to each other by the presence of coupling means similar to ribs on the support, housed in orifices of the hub;

[0043] [Fig.7] illustrates a front view of the magnetic element support, making the construction in several segments particularly visible;

[0044] [Fig.8] illustrates, schematically, an exploded view of the rotor according to the second embodiment;

[0045] [Fig.9] illustrates, schematically, the interaction between the hub and the shaft of rotor transmission for axial flux motor according to the invention.

[0046] The features, variants and the different embodiments of the invention may be combined with each other, in various combinations, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be imagined comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0047] In the figures, the elements common to several figures retain the same reference.

[0048] In the detailed description which follows, the terms "axial" and "radial", used to specify the orientation of the rotor for axial flux motor according to the invention as well as its components, relate to the axis of rotation of the rotor, that is to say the axis around which the rotor of the axial flux motor rotates. This axis of rotation of the rotor is represented in the figures by a chain-dotted axis A. The term "radial" corresponds to a direction perpendicular to the axis of rotation of the rotor and passing through this axis of rotation.

[0049] [Fig.l] thus schematically illustrates an axial flux motor 1 according to the invention, intended to equip an electric or hybrid motor vehicle. The axial flux motor 1 comprises a casing 2 which contains a rotor 3 and at least one stator 4. As shown here, the axial flux motor 1 comprises a first stator 4A and a second stator 4B. The stators 4 and the rotor 3 are stacked so that the first stator 4A and the second stator 4B are arranged on either side of the rotor in the direction of the axis of rotation of the rotor 3. The rotor 3 and the stators 4 are respectively in the form of discs, a center of which is inscribed in the axis of rotation of the rotor 3.

[0050] A magnetic element 5 of the rotor 3 is arranged opposite a winding 6 of each of the stators 4, considering the direction of the axis of rotation of the rotor 3. The magnetic element 5 and the windings 6 are thus configured to allow the creation of a magnetic field passing axially from the rotor to the stators.

[0051] The casing 2 is crossed, in the direction of the axis of rotation of the rotor 3, by a transmission shaft 7 of the axial flux motor 1 which is parallel to the axis of rotation of the rotor 3.

[0052] The rotor 3 comprises a hub 8 which ensures the connection with the transmission shaft 7.

[0053] The rotor 3 according to the invention will now be described in detail in relation to the Figures 2 to 9. A first embodiment will be described in the detailed description of Figures 2 to 4 and [Fig.9], while a second embodiment will be detailed in the description of Figures 5 to 8 and [Fig.9].

[0054] [Fig. 2] schematically represents a first embodiment of the rotor 3 intended to be integrated into the axial flux motor 1. In this embodiment, the rotor 3 is made up of magnetic elements 5, a hub 8 and a support 9 for the magnetic elements 5. The rotor 3 also comprises a transmission shaft 7 and a self-locking nut 10.

[0055] According to the invention, the hub 8 is metallic and the support 9 is designed in a material different from the hub. The material of the support 9, whether non-metallic or metallic, must therefore be different from that of the hub.

[0056] The hub 8 and the support 9 are linked in mutual rotation by coupling means 12 described later in Figures 3 and 4. The hub does not appear in this illustration because it is masked by the support 9, here overmolded on the hub 8, and by the self-locking nut 10. It will be described in more detail with reference to Figures 3 and 4.

[0057] The transmission shaft 7 is located in the center of the rotor 3 and allows it to be driven in rotation by cooperating with the hub 8. Its visibility is also limited in this figure so that additional details will be provided below with reference in particular to figures 4 and 9.

[0058] The self-locking nut 10, for its part, has an annular shape. It guarantees the prevention of any involuntary movement between the shaft 7 and the hub 8. It is provided with perforations 11 arranged allowing it to be screwed onto the transmission shaft 7 by means of a suitable mechanical device.

[0059] The support 9 may be made of a plastic material, such as thermoplastics. When the support 9 is made of plastic, it may also comprise fillers such as fibers.

[0060] The support 9 may also be made of a composite material. The composite material is preferably a soft magnetic composite (SMC). SMC materials consist of iron powder particles coated with an electrically insulating layer and can be shaped into complex shapes by means of powder metallurgy, thus enabling the design of three-dimensional magnetic circuits.

[0061] Commercial references of thermoplastics and SMC such as PEEK GF50, PA6.6 GF50 or SMC Somaloy 700HR 5P are particularly suitable for its use.

[0062] The support 9 comprises an internal crown 13 and an external crown 14 which are arranged concentrically around the axis of rotation. These crowns extend radially on either side of the magnetic element 5, the support further comprising radial branches 15 which connect the two crowns together. Housings 16 are thus formed in these crowns and the radial branches to accommodate portions of the magnetic element 5.

[0063] The internal crown 13 is the part of the support 9 positioned closest to the axis of rotation of the rotor 3. This internal crown has two distinct radial end edges including an internal edge 17, oriented opposite the axis of rotation of the rotor 3, and an external edge 18 which faces the external crown 14 and helps to delimit the housings for the magnetic element 5.

[0064] The outer ring 14 is the part of the support 9 furthest from the axis of rotation of the rotor 3. The outer ring 14 has two distinct radial end edges, including an inner edge 19, oriented towards the inner ring 13 and participating in delimiting the housings for the magnetic element 5, and an outer edge 20 which constitutes the portion of the outer ring 14 furthest from the axis of rotation of the rotor 3.

[0065] Between the two crowns, and specifically between the inner edge 19 of the outer crown 14 and the outer border 18 of the inner crown 13, an interval of non-zero distance is intersected by the radial branches 15 extending linearly in a radial manner and connecting the inner crown 13 to the outer crown 14. The particular configuration of the elements of the support 9 therefore creates empty spaces delimited by the inner edge 19 of the outer crown 14, the outer border 18 of the inner crown 13 and the radial branches 15 and forming said housings 16, sized to receive the parts of the magnetic element 5.

[0066] The two crowns comprise holes 21 distributed along their surface, and here arranged circumferentially relative to the axis of rotation of the rotor 3. These holes 21, without any specific technical function for the assembled rotor 3, result from the manufacturing process thereof as will be detailed below.

[0067] [Fig. 3] schematically illustrates the rotor of the first embodiment in a sectional view with a sectional plane comprising the axis of rotation of the rotor 3. This figure makes it possible in particular to highlight technical characteristics not visible in [Fig. 2], and in particular the hub 8.

[0068] The hub 8 comprises in particular a sleeve 22 and a plate 23. The sleeve 22 is cylindrical and its axis of revolution coincides with the axis of rotation of the rotor 3. The plate 23 extends in radial extension of the sleeve 22 and is therefore positioned substantially perpendicular to the axis of rotation of the rotor 3.

[0069] Orifices 24 are arranged in the thickness of the hub 8, more specifically on the plate 23. The orifices 24 extend in the hub 8 parallel to the axis of rotation of the rotor 3. These orifices 24 have the shape of circular cavities with closed edges which may have a bottom or which may pass right through the hub 8. In this embodiment, in which the support is overmolded onto the hub, it is preferable for the orifices 24 to pass right through the hub.

[0070] It is understood that the orifices open only axially, being delimited radially by the metallic material of the hub and in particular of the plate 23, over all the perimeter of the housing formed by the orifice 24. It is thus notable that these orifices do not open radially onto the periphery of the plate.

[0071] The orifices 24 are filled with material from the support, during the overmolding by injection of material which is the manufacturing method of this first embodiment. This filling of the orifices with material from the support forms the coupling means 12 previously mentioned, these coupling means thus being in contact with the metal hub around the entire periphery of the coupling means.

[0072] These coupling means 12 take the form of studs integral with the internal crown 13 obtained simultaneously by injection by an appropriate shape of the injection mold. In the illustrated embodiment, the studs forming the coupling means open axially on either side of the hub, so that the internal crown 13 has a junction portion with the hub which extends on either side of this hub 8 in the direction of the axis of rotation of the rotor 3. In other words, a first part of the internal crown 13 is in contact with a first axial face of the hub, and more particularly with a first axial face of the plate 23, and a second part of the internal crown 13 is in contact with a second axial face of the hub, and more particularly with a second axial face of the plate 23, and the studs forming the coupling means 12 connect each of these two parts of the internal crown 13, engaged within the material of the support 9.

[0073] In a variant of this first embodiment, the injection mold is configured such that the rotor resulting from the manufacturing method comprises an internal crown extending against only one axial face of the hub. In this variant, the orifices formed in the thickness of the hub and filled with the material of the support during injection may be blind holes. In this variant, the advantage of having studs, forming the coupling means 12, which extend into the orifices 24 in a direction parallel to the axis of rotation of the rotor 3, being in contact with the metal surface of the hub around the entire periphery of these studs is retained.

[0074] In order to obtain a balanced distribution of forces during rotation of the rotor 3, the orifices 24 are arranged in a diametrically opposite manner. Other technical characteristics of these orifices 24 will be described in the detailed description of [Fig.4].

[0075] [Fig.4] shows a schematic illustration of the first embodiment of the rotor 3, this time illustrated by an exploded view. This figure makes it possible to visualize each component of the rotor 3 and to understand how these components are arranged together. It is important to understand that this exploded view is a schematic view to aid understanding and not a realistic view. Indeed, as shown in the figure, the support 9 appears to be a structure that can be mounted with the rest of the elements of the rotor 3. However, the support 9 is in this embodiment formed by molding after placing other elements of the rotor 3 and in particular the hub 8 in an injection mold. For a better understanding, the manufacturing process of the first embodiment of the rotor 3 will be detailed in the rest of the description.

[0076] The hub 8, as mentioned above, consists of a plate 23 and a sleeve 22. The sleeve 22 has on its inner surface an annular band forming a projection 25, thus reducing the diameter of the inner surface of the sleeve 22 at this specific location. The plate 23 radially extends the sleeve at an axial end thereof and is therefore arranged perpendicular to the axis of rotation of the rotor 3. The orifices 24 on the plate 23 are arranged circumferentially and arranged diametrically opposite each other two by two. In addition, the orifices 24 are positioned at regular intervals from each other.

[0077] It is notable here that the orifices 24 are formed in the thickness of the material and do not protrude radially over the peripheral edge of the hub 8. They are delimited over their entire periphery by material of the hub 8. This is particularly of interest insofar as it is possible to transmit forces effectively between the hub and the support via the coupling means 12 that the support 9 comprises.

[0078] This illustration also provides a detailed view of the transmission shaft 7. The shaft is divided into three distinct parts: a centering part 26, a clamping part 27 and a threaded part 28. Each part of the transmission shaft 7 has a different external diameter, with the centering part 26 having the largest external diameter and the threaded part 28 having the smallest external diameter.

[0079] It is notable that the parts are arranged axially one after the other so that the external diameter decreases as one moves along the axis of rotation, this arrangement allowing the progressive insertion of each of the parts of the transmission shaft into the hub.

[0080] Additional information on the hub 8 and the transmission shaft 7 is visible in [Fig.9], thus allowing a better understanding of the interaction between the transmission shaft 7 and the sleeve 22 of the hub 8.

[0081] A method for obtaining the rotor 3 of the first embodiment according to the invention will now be detailed. This method of obtaining comprises a placement step during which the hub 8 and the magnetic elements 5 are placed within an injection mold of the rotor 3. The precise position of the magnetic element 5 within the injection mold relative to the hub 8 is ensured by placement pins.

[0082] Once the hub 8 and the magnetic elements 5 are suitably arranged within the injection mold, the production process comprises an overmolding step in which the support 9 is injected into the mold. The material chosen to form the support 9 propagates in the mold with a portion which covers at least one face of the hub, at the level of the plate 23, and with a portion which penetrates into each of the orifices 24. The injection of material is carried out so that the orifices are filled by the material of the support. This portion of the material of the support which fills the orifices 24 forms the coupling means 12, which are advantageously engaged with the metal hub over their entire periphery. The material of the support also extends throughout the mold and includes the magnetic elements 5, which forms the support 9.

[0083] The obtaining method comprises a removal step in which the support-hub-magnetic element assembly is removed from the injection mold. For this, the placement pins are removed, which forms the holes 21 within the support 9.

[0084] The transmission shaft 7 is then fitted into the sleeve 22 during an assembly step. The self-locking nut 10 is then screwed onto the threaded portion 28 of the transmission shaft 7 in order to secure the assembly of the rotor 3. It is notable, for example in [Fig. 3], that the self-locking nut 10 takes a final position in which the internal edge of the internal crown 13 is directly opposite the self-locking nut, the distance between the internal edge and the self-locking nut being reduced to a minimum. The self-locking nut is mounted by pushing axially on it via the axial perforations 11, so that it is not necessary to provide tooling that engages around it and it is therefore not necessary to provide sufficient clearance to leave room for this tooling.It is thus possible to have a large quantity of support material covering the metallic hub material, and having this large covering surface makes it possible to make the mechanical connection between the two components of the rotor according to the invention, namely the hub and the support, more robust, while limiting the radial size of the rotor.

[0085] As may have been mentioned previously, the transmission shaft 7 and the hub may be pre-assembled or made in one piece, so that the transmission shaft is already present in the mold when the material forming the support is injected.

[0086] We will now describe a second embodiment of the rotor 3 designed to be integrated into the axial flux motor 1, with reference to [Fig.5] in particular.

[0087] In this configuration, the rotor 3 comprises identical components having similar functions to those observed in the first embodiment. It is notably composed of magnetic elements 5, a metal hub 8, a support 9 for the magnetic elements 5, a transmission shaft 7 and a self-locking nut 10, it being understood that as mentioned previously the transmission shaft and the hub could be made in one piece and that it is thus not necessary to have a self-locking nut.

[0088] Here again, the hub 8 and the support 9 are linked in mutual rotation by coupling means 12 described later in Figures 6 and 8. In this representation of [Fig.5], the hub 8 is not visible and its specificities will be discussed in [Fig.8]. Concerning the transmission shaft 7 and where appropriate the self-locking nut 10 of this second embodiment, they are identical in all aspects to those of the first embodiment.

[0089] The support 9 is made of a metallic or non-metallic material, preferably of a composite material such as SMC. Certain thermoplastics can also be used.

[0090] Similar to the first embodiment, the support 9 is composed of an inner ring 13, with an inner edge 17 and an outer edge 18, and an outer ring 14, provided with an inner edge 19 and an outer edge 20. The rotor comprises an epoxy polymer resin 29 associated with the support to cover and protect the magnetic elements. This resin 29 extends radially between the outer edge 18 of the inner ring 13 and the inner edge 19 of the outer ring 14. Although not shown in this illustration, the resin 29 is arranged on two faces of the support 9. It should be noted that this resin 29 can also be provided in the rotor of the first embodiment.

[0091] Other characteristics of the support 9 will be detailed in [Fig.8].

[0092] In the second embodiment, the rotor 3 is also equipped with a reversible fixing means 30, consisting of a fixing ring 31 and screws 32. This device aims to ensure the fixing of the hub 8 and the support 9 between them, thus minimizing any potential play within the rotor 3, in a context different from the first embodiment in that the support is not overmolded on the hub but produced elsewhere and then attached to it. The fixing ring 31, of annular shape, has round holes 33 to receive the screws 32. The reversible fixing means will be described in more detail with reference to Figures 7 and 8.

[0093] [Fig.6] schematically shows a sectional view of the rotor 3 according to the second embodiment.

[0094] The hub 8 comprises, in a manner similar to the first embodiment, a sleeve 22 and a plate 23. In a similar manner, the plate 23 comprises orifices 24 arranged in a diametrically opposite manner. These orifices 24 are here through, but can also be blind, provided that they are formed in the material of the metal hub and that they do not open radially onto a peripheral edge of this hub.

[0095] It should however be noted that the plate 23 differs here from what was described in the first embodiment in that it has a stepped configuration, with a first portion directly extending the sleeve and a second portion carrying the orifices 24n, this first portion and this second portion being axially offset from each other, so as to form a step between them.

[0096] The internal crown 13 here extends only opposite one of the faces of the hub 8 and it carries the coupling means 12 only on one face. The coupling means 12 form ribs and extend projecting from the face of the internal crown 13 opposite the hub 8. These coupling means 12 are designed to be inserted into the orifices 24 and are dimensioned so that the points of contact between the edges delimiting an orifice and the material of the coupling means are as numerous as possible, where appropriate requiring a force fitting of the coupling means into the orifices. In this way, the forces are transmitted as efficiently as possible and make it possible to ensure the joint rotational connection of the hub 8 and the support 9. In accordance with what was mentioned previously in the first embodiment, the coupling means 12 extend in the orifices 24 in a direction parallel to the axis of rotation of the rotor 3.

[0097] It is notable in [Fig.6] that the step formed in the plate, between the two portions of this plate, forms a radial stop surface for the positioning of the internal crown 13.

[0098] This step also forms a radial stop for the positioning of the fixing ring 31 of the reversible fixing means 30. In this position, with the fixing ring 31 bearing on the internal crown 13, it is notable that the annular ring axially covers the coupling means 12.

[0099] [Fig.7] is a view from below of the support 9 according to the second method of rea lization, making visible different characteristics of the support 9.

[0100] The coupling means 12, here four in number, respectively have the shape of an oblong rib. These coupling means 12 are arranged in a circumferential and regular arrangement.

[0101] Near each rib, a round hole 34 is arranged to allow the fixing of a screw 32 of the reversible fixing means 30 to the support.

[0102] This [Fig.7] makes more particularly visible a characteristic, which can also be applied in the first embodiment, relating to the presence of notches 35 located on the edges of the radial branches 15, the internal edge 19 of the external crown 14 and the external border 18 of the internal crown 13. These notches 35 are thus formed in the edges and corners of the housings 16. The latter allow the resin 29 to spread effectively on each face of the rotor during the injection of the resin 29 in the manufacturing process of the rotor 3.

[0103] [Fig.7] makes it particularly visible that the support 9 is designed in this second embodiment in a segmented manner. Here, it is divided into four identical segments. Each segment integrates a portion of the internal 13 and external 14 crowns, radial branches 15, at least one coupling means 12, and at least one round hole 34, and the juxtaposition of the segments next to each other makes it possible to form the support 9 as a whole. The segments are held in place relative to each other by the reversible fixing means. The presence of at least one coupling means 12 and one round hole 34 per segment makes it possible to guarantee the solid assembly of each segment to the hub 8 and ensure cohesion in rotation.

[0104] The segmentation of the support 9 makes it easier to produce and handle the support 9, which in this second embodiment must be produced prior to assembly. However, it should be noted that this segment can be produced in one piece, particularly in application cases where the rotor has a diameter small enough to produce the entire support in an injection mold.

[0105] [Fig.8] shows a schematic illustration of the second embodiment of the rotor 3, this time illustrated by an exploded view. This [Fig.8] makes it possible to visualize each component of the rotor 3 and to understand how these components are arranged together. However, this exploded view is a schematic view and not a realistic view. Indeed, as shown in the figure, the resin 29 appears to be a structure that can be mounted with the rest of the elements of the rotor 3. However, the resin 29 is in this embodiment formed by injection on each face of the support 9. For a better understanding, we will therefore return to the manufacturing method of the second embodiment of the rotor 3 in the rest of the detailed description.

[0106] As indicated previously, the hub 8 consists of a plate 23 and a sleeve 22. More specifically, the sleeve 22 incorporates a projection 25, and the plate 23 has orifices 24 diametrically opposed two by two and arranged in an annular manner. However, a notable distinction lies in the oblong shape of the orifices 24 of this embodiment, designed to adapt perfectly to the coupling means 12. In addition, the plate 23 also has round holes 36 similar to those present on the support 9 and on the fixing ring 31. These round holes 36 are arranged close to the orifices 24 and make it possible to accommodate the screws 32.

[0107] Concerning the transmission shaft 7, it is also similar to the version of the first embodiment, being divided into three parts: the centering part 26, the clamping part 27 and the threaded part 28.

[0108] [Fig. 9] schematically illustrates the cooperation between the transmission shaft 7 and the hub 8. This figure is applicable to each of the embodiments. The transmission shaft 7 comprises three parts. The centering part 26 has an external diameter which is substantially identical to the internal diameter of the sleeve 22. This characteristic makes it possible to obtain optimal centering of the transmission shaft 7 in the hub 8. The clamping part 27 has an external diameter which is less than that of the internal diameter of the sleeve 22, but greater than that of the internal diameter of the projection 25. In this way, it is possible to insert the clamping part 27 into the sleeve 22 until it reaches the projection 25. It is then necessary to force-fit the transmission shaft 7.

[0109] In each of the embodiments, the clamping portion 27 is knurled, thus allowing plastic deformation of the knurling during fitting. This deformation of the knurling improves the adhesion between the transmission shaft 7 and the projection 25 of the hub 8, thus contributing to efficient torque transmission.

[0110] The threaded portion 28 has a smaller diameter than the projection 25, however, it is sized so as to correspond substantially to the internal diameter of the self-locking nut 10. This portion is thus specifically designed to be screwed with the self-locking nut 10. When mounting the transmission shaft on the hub, the transmission shaft is inserted into the sleeve of the hub by first passing the threaded portion, the small diameter of which allows the projection 25 to pass without interference. The axial dimension of the sleeve and the parts of the transmission shaft causes the centering portion 26 to come into contact with the internal surface of the sleeve before the clamping portion 27 comes into contact with the projection 25.The interaction between the centering part 26 and the sleeve thus makes it possible to recenter the transmission shaft to ensure that the force-fitting part, when the clamping part 27 meets the projection 25, is done with homogeneous forces around the entire circumference of the clamping part.

[0111] Concerning this second embodiment, a method for obtaining this rotor 3 will now be detailed. This method comprises a molding step during which the material of the support is injected into an injection mold. This step allows the formation of the support 9. Depending on the type of injection mold used, the support 9 can be obtained either in the form of an assembly or in the form of several support segments 9. At the end of this step, the support 9 or the segments of the support 9 are removed from the injection mold.

[0112] The method for obtaining the rotor 3 comprises a coupling step during which the coupling means 12 of the support 9 are placed in the orifices 24 of the hub 8, thus making the support 9 integral in rotation with the hub 8. In the case where the support 9 is formed of several segments, the segments can be placed one by one on the hub 8 thanks to the coupling means 12. During this step, the reversible fixing means 30 is then fixed to the hub 8 and to the support 9. For this, the fixing ring 31 is placed on the face of the support 9 opposite that which is opposite the hub 8. The fixing ring 31 is then fixed using the screws 32 screwed into the round holes present on the fixing ring 31, the support 9 and on the hub 8.

[0113] The method for obtaining the rotor 3 also has a covering step in which the assembly formed by the support 9, the hub 8 and the fixing means 30 is placed in a mold. The resin 29 is then injected into the mold. During this covering step, the resin 29, which may be an epoxy polymer, penetrates into the notches 35 and then covers two faces of the support 9. The resin 29 then extends from the internal crown 13 to the external crown 14 on two faces of the support 9. It should be noted that, as mentioned previously, this resin injection step can also be carried out in the first embodiment.

[0114] During an assembly step, the transmission shaft 7 is then fitted into the sleeve 22. The self-locking nut 10 is then screwed, by means of the perforations 11 and a suitable mechanical device, onto the threaded part 28 of the transmission shaft 7 in order to complete the assembly of the rotor 3. As mentioned previously, the transmission shaft 7 and the hub can be pre-assembled or made in one piece, so that the transmission shaft is already present in the mold when the material forming the support is injected.

[0115] As just described, the present invention achieves the aims it has set itself by proposing a rotor for an axial flux motor offering guarantees on the mechanical strength of the assembly at high rotation speeds. The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any equivalent means and configuration as well as to any technically operative combination of such means.

Claims

Claims

1. Rotor (3) for axial flux motor (1) comprising a magnetic element (5), a metal hub (8) and a support (9) for the magnetic element (5) fixed on the hub (8), said support (9) being made of a material different from the hub (8), characterized in that the hub (8) comprises orifices (24) with at least two diametrically opposed orifices (24), the support (9) being engaged with the hub (8) by coupling means (12) housed in the orifices (24).

2. Rotor (3) according to claim 1, wherein the orifices (24) extend in the hub parallel to the axis of rotation of the rotor (3).

3. Rotor (3) according to one of claims 1 or 2, in which the hub (8) comprises a cylindrical sleeve (22), the axis of which defines an axis of rotation of the rotor, and a plate (23) extending in radial extension of the sleeve (22), substantially perpendicular to the axis of rotation, the orifices (24) being formed in the thickness of the plate (23) of the hub (8).

4. Rotor (3) according to any one of claims 1 to 3, wherein the support (9) comprises an internal crown (13) and an external crown (14) extending circularly around the hub (8) and extending radially around the magnetic element (5), said internal crown (13) carrying the coupling means (12).

5. Rotor (3) according to any one of claims 1 to 4, in which the internal crown (13) extends opposite a single face of the hub, the coupling means (12) forming ribs extending in projection from the face of the internal crown (13) opposite the hub.

6. Rotor (3) according to any one of claims 1 to 4, in which the internal crown (13) extends opposite two opposite faces of the hub, the coupling means (12) forming a pad connecting two parts of the internal crown (13) arranged on either side of the hub.

7. Rotor (3) according to any one of claims 1 to 6, in which the support (9) and the hub (8) are linked together irreversibly.

8. Rotor (3) according to any one of claims 1 to 6, in which the rotor (3) comprises a reversible fixing means (30) of the support (9) on the hub (8).

9. Rotor (3) according to any one of claims 1 to 8, wherein at least one of the orifices (24) is a through orifice.

10. Rotor (3) according to any one of claims 1 to 9 in com- combination with claim 3, wherein the sleeve (22) is configured to cooperate with a transmission shaft (7) comprising a threaded part (28), said rotor (3) comprising a self-locking nut (10) intended to be screwed onto said threaded part (28).

11. Rotor (3) according to claim 10, in which the hub (8) and the transmission shaft (7) form a single-piece assembly.

12. Rotor (3) according to any one of the preceding claims, wherein the support (9) is made of a plastic or composite material such as a soft magnetic composite material.

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