Rotor for electromagnetic motor with two-part magnet structures

Abstract

The invention relates to a rotor (1) of an electromagnetic motor having a body (25a, 25b) comprising a hub (2) concentric with a central axis (7). Branches (3) extend radially from the hub (2) towards a hoop (8) forming an external periphery of the rotor (1). Magnet structures (10), housed between two adjacent branches (3), are in the form of two internal and external sub-structures (11, 12) extending radially between the two branches. The internal sub-structure (11) has its innermost face in at least partial contact, when the rotor is not rotating, with the hub (2) and its lateral faces each facing one of the two adjacent branches while being in mechanical engagement (13, 14) against a portion of the branch facing them with axial stop and freedom of radial movement of the rotor. The external substructure (12) presents its outermost face to the rotor, resting against the hoop (8). Abstract figure: FIGURE 1

Description

Title of the invention: Rotor for electromagnetic motor with two-part magnet structures

[0001] The present invention relates to a rotor for an axial flux electromagnetic motor or generator having an advantageously enlarged hub from which branches extend with a two-part magnet structure between two adjacent branches.

[0002] The invention also relates to an electromagnetic motor or generator equipped with such a rotor.

[0003] The present invention finds an advantageous but non-limiting application for an electromagnetic motor delivering high power with a high rotor rotation speed, which is obtained by the specific characteristics of the rotor according to the present invention. Such a motor can be used, for example, as an electromagnetic motor in a fully electric or hybrid motor vehicle.

[0004] Advantageously but not limitatively, the electromagnetic motor or generator may comprise at least one rotor framed by two stators, these elements being able to be superimposed on each other while being separated by at least one air gap on the same shaft.

[0005] In high speed applications, it is necessary to have very good mechanical strength of the rotating part, i.e. the rotor, in order to improve the reliability of the system.

[0006] For an axial flux electromagnetic machine, the rotor comprises a body in the form of a discoidal support for magnets having two circular faces connected by a thickness, the disc being delimited between an external crown formed by a hoop and an internal periphery delimiting a recess for a rotation shaft.

[0007] The magnets are each held in the disc-shaped support by holding means, a gap being left between the magnets.

[0008] In an axial flux motor, the peripheral speeds of the rotor generate centrifugal forces at the magnets which can become significant and limit the maximum permissible speeds.

[0009] For a magnet structure or magnet pole, the forces are mainly absorbed by the peripheral hoop and also by glue on the contour of the magnet structure binding it to the branches.

[0010] Axial flux motors are often used as motors with higher torques than radial flux motors. They can therefore be used in low speed applications.

[0011] For high speed applications, the rotor design in a flux motor Axial is more delicate because the forces due to centrifugal effects cause quite significant mechanical stresses in the rotor. Furthermore, eddy current losses become preponderant both in the magnets and also in the rotor part when it is made with electrically conductive materials.

[0012] For a rotor that has to rotate at high rotational speeds, the main disadvantage of a high rotational speed motor is the high probability of detachment of the magnet or magnets from the rotor as well as at least partial breakage of the rotor. The rotor of such a motor must therefore be capable of withstanding high rotational speeds.

[0013] The state of the art encourages the person skilled in the art to stiffen the discoidal support of the magnet or magnets to combat centrifugal force. This requires a specific material for the discoidal support and an increase in its size by thickening it so that the discoidal support is more rigid.

[0014] This has not given complete satisfaction because the motor or generator thus equipped with a discoidal support has a higher weight as well as an increased manufacturing cost.

[0015] One solution may be to produce meshes of elongated unit magnets in fibrous and resinous structures, so as to reduce eddy currents and to use a composite material body for the rotor which does not conduct electricity, ideally a fiberglass rotor, with a hoop placed at the periphery of the rotor so as to maintain the forces due to centrifugal effects.

[0016] However, for applications where the speeds become very high, the mechanical constraints become such that it is necessary to reduce the mass of the magnet in order to achieve these rotational speeds. However, the torque that an electrical machine must provide is proportional to the surface area of ​​the magnets interacting with the magnetic fields produced by the stators. A reduction in the surface area of ​​the magnets therefore leads to a reduction in the torque and therefore in the power of the machine.

[0017] Document EP-A-0 353 042, representing the closest state of the art, describes a rotor of an electromagnetic motor or generator having a body comprising an internal hub concentric with a central axis of rotation of the rotor, branches extending radially with respect to the central axis of rotation from the internal hub towards a hoop forming a circular external periphery of the rotor, at least one magnet being housed in each space delimited between two adjacent branches, each branch having a width decreasing away from the internal hub to end with a sharp point against the hoop, each magnet having an increasing width away from the internal hub to end against the hoop surrounding the rotor.

[0018] This document does not allow for support of multiple permanent magnets which may, on the one hand, to maintain the permanent magnets that the rotor supports effectively by preventing the magnets from detaching from the rotor while compensating the centrifugal force effectively and, on the other hand, to present a mechanical resistance such that the rotor can rotate at very high speeds.

[0019] Document FR-A-1 475 501 does not describe a rotor but only a magnet structure comprising several unit magnets without specifying an application for this magnet structure and suggesting that the disadvantages of the two aforementioned documents can be eliminated by the use of such a magnet structure with several unit magnets, given that a use of such a magnet structure for a rotor is not mentioned in this document.

[0020] The problem underlying the present invention is to design a rotor for supporting several permanent magnets provided with a hoop for an axial flux electromagnetic machine which can, on the one hand, hold the permanent magnets that the rotor supports effectively by preventing the magnets from detaching from the rotor while compensating the centrifugal force effectively and, on the other hand, have a mechanical resistance such that the rotor can rotate at very high speeds.

[0021] To this end, the present invention relates to a rotor of an electromagnetic motor or generator having a body comprising an internal hub concentric with a central axis of rotation of the rotor, branches extending radially with respect to the central axis of rotation from the internal hub towards a hoop forming a circular external periphery of the rotor, a magnet structure forming a magnet pole being housed in each space delimited between two adjacent branches associated with the magnet structure, characterized in that each magnet structure is in the form of two distinct sub-structures, respectively internal and external according to their position in the rotor, extending radially between the two associated adjacent branches, the sub-structure internal to the rotor having its innermost face in at least partial contact, when the rotor is not rotating,with the internal hub and its lateral faces each facing one of the two associated adjacent branches being in mechanical engagement against a portion facing them of the associated adjacent branch with abutment in an axial direction to the rotor and freedom of movement in a radial direction to the rotor, and the substructure external to the rotor having its outermost face to the rotor bearing against the hoop.

[0022] The mechanical engagement according to the present invention allows the internal substructures to be held in an axial direction to the rotor while allowing it a small radial displacement, which was not possible by lateral gluing of the magnet structures in a single part against the branches.

[0023] The inventive approach of the present invention is to modify the shape of each magnet structure housed between two adjacent branches by creating two parts separate or substructures. The forces exerted on the external substructure are taken up by the hoop and the forces exerted on the internal substructure are taken up by the portions of the branches adjacent to the rotor hub by mechanical recovery.

[0024] The present invention thus allows a recovery of centrifugal forces specifically adapted to the position of the substructure in the rotor by being different for an internal substructure than for an external substructure.

[0025] This allows the rotor to reach rotation speeds greater than 15,000 revolutions per minute for a rotor diameter of approximately 300 millimeters.

[0026] As previously mentioned, for the rotors of axial flux machines, the magnets are glued to the branches which makes it possible to transmit part of the centrifugal forces into the branches, a part which varies depending on the modulus of the glue and therefore its temperature.

[0027] In the case of the present invention, the glue, to distribute the load on the branches, becomes useless mainly for the internal substructures, and the part of the force which passes into the branches no longer depends on the temperature, but only on the mass distribution of the two substructures of the magnet structure.

[0028] Another advantage, in addition to being able to increase the rotational speed of the rotor, is being able to put more magnet mass at the outer radius of the rotor. This promotes the creation of torque, at iso magnet mass, compared to an axial flux machine rotor with magnet structures in a single magnet block, at iso speed.

[0029] Advantageously, the mechanical engagement of each lateral face of the internal substructure of each magnet structure against a portion facing it of the associated adjacent branch by a male part carried laterally by each internal substructure housed in a female part carried by a portion of the branches facing the internal substructure or vice versa for positioning the male and female parts.

[0030] These optional means make it possible to guarantee transmission of the centrifugal forces exerted on internal substructures in the branches while ensuring axial maintenance of the internal substructures in the rotor.

[0031] Advantageously, each internal substructure is embedded in a first layer of composite completely coating the internal substructure, the first layer of composite being configured to form the male parts, each being carried laterally on one side by each internal substructure.

[0032] Advantageously, the two internal and external sub-structures of each magnet structure between two adjacent branches are embedded in a second layer of composite completely coating the magnet structure, the rotor also being coated in a third layer of composite.

[0033] There may thus be a triple coating in the rotor, the composition of the coatings which may differ depending on their role. The first coating concerns the coating of the substructures. This coating can be more flexible to allow deformation of the substructures. The second coating is that of the magnet structure or magnet pole which can contain more fibers to be more rigid. Finally, the third coating concerns the rotor itself and is also advantageously reinforced.

[0034] Providing three complementary coatings ensures high mechanical resistance sought for a rotor rotating at high speeds, especially since the composition of each coating is specifically selected according to the positioning of the coating in the rotor and the element that the coating surrounds.

[0035] Advantageously, the branches have a cross-sectional shape of a diamond connected to the internal hub by a foot widening towards the hub, the two faces of the diamond that are the most internal to the rotor of two associated adjacent branches framing the internal substructure of each magnet structure and the two faces of the diamond that are the most external to the rotor of two associated adjacent branches framing the external substructure of each magnet structure, the internal substructure of each magnet structure completely filling in the space between the two associated adjacent branches a first housing delimited between the two faces of the diamond that are the most internal of the two associated branches and the external substructure of each magnet structure completely filling in the space between the two associated adjacent branches a second housing delimited between the two faces of the diamond that are the most external of the two associated branches.

[0036] Such a diamond configuration makes it possible to limit the radial displacement of the internal substructures while being able to place a greater mass of magnet towards the outside of the rotor near the hoop for the external substructures.

[0037] Advantageously, the bases of two adjacent branches associated in abutment against the internal hub are separated by an intermediate portion of the internal hub, the intermediate portion being in at least partial contact with a face most internal to the rotor of the internal substructure.

[0038] Advantageously, the internal and external substructures of each magnet structure are separated by a gap.

[0039] An operating clearance is desirable to prevent the internal substructure comes into contact with the associated external substructure. Each internal substructure would then, consequently, not be in contact with the walls of the branches facing it, and therefore all centrifugal forces would be taken up by the hoop and not by the facing portions of the branches of the rotor body.

[0040] The operating clearance can be filled with a flexible resin or glue, more flexible than the branches of the body, so as not to transmit the centrifugal load of each internal substructure onto the hoop.

[0041] Advantageously, at least one of the substructures of each magnet structure consists of a plurality of unit magnets secured by a fiber-reinforced insulating material.

[0042] Another synergy provided by the present invention is that the rotor can have between each branch unitary magnets grouped in an internal or external substructure.

[0043] This makes it possible to have a substructure having many unit magnets. It has been found that a substructure with such a plurality of unit magnets has a great power of not being sensitive to space or current harmonics generated by the stator windings. Consequently, the losses generated in the substructures are very low, and the efficiencies, particularly at high speed, are very high.

[0044] One of the optional measures of the present invention is to decompose an internal or external substructure which may be a whole magnet or a magnetic pole according to the state of the art into a plurality of small or micro-magnets.

[0045] A large magnet is subject to greater eddy current losses than its equivalent in small or micro-magnets. The use of small magnets or micromagnets therefore makes it possible to reduce these losses which are detrimental to the operation of the electromagnetic actuator.

[0046] The applicant has discovered that a plurality of unit magnets in a magnet structure gives a magnet structure having a much greater mechanical strength while retaining magnetic properties almost similar to those of a single magnet having a surface area equal to n times the elementary surface area of ​​the n unit magnets when n unit magnets are present.

[0047] Advantageously, each unit magnet is of elongated shape extending in the axial direction of the rotor, each unit magnet being of polygonal shape or each unit magnet having an at least partially ovoid contour, the ovoid shape or contour comprising a first portion forming the body of the unit magnet having a larger section and extending over a greater length of the unit magnet than at least a second longitudinal end portion pointing towards an associated longitudinal end of the unit magnet while decreasing in section as it approaches the longitudinal end.

[0048] It is known that, to obtain a magnetic field of optimal intensity, the ideal volume of a magnet must approach a cube or a cylinder whose length is equal to the diameter. It is common knowledge that increasing the length of a magnet beyond this does not bring any increase in the magnetic field.

[0049] In an optional embodiment, however, the approach of the present invention goes against this prejudice for the use of unitary magnets of elongated shape.

[0050] The length of a unit magnet is significantly increased relative to the diameter or a diagonal of its flat longitudinal face, contrary to what is widely practiced.

[0051] As regards ovoid magnets, these can have facets. This gives us, as unitary magnets, "crystals" associated with each other which are not linked over the entire surface of facets or longitudinal faces but layers of resin and glue come to construct a mesh network at the ends of the poly-facetted pads with limited contact zones between magnets.

[0052] Alternatively, for unit magnets of perfect ovoid shape with a first rounded portion, the contact between two adjacent unit magnets is more reduced by being able to be only punctual and corresponds substantially to an arc of a circle of reduced dimension between the two unit magnets.

[0053] A groove can be hollowed out to the dimension of the arc of the contact circle between two adjacent unit magnets to receive glue, advantageously in the form of resin.

[0054] Advantageously, each unit magnet is in the form of a slice whose thickness is at least less than ten times its length, the slices forming unit magnets being separated in said at least one of the substructures of each magnet structure by cutouts in an ortho-radial plane in the rotor.

[0055] Advantageously, said at least one of the sub-structures of each magnet structure consisting of a plurality of unitary magnets incorporates at least one mesh having meshes each delimiting a housing for a respective unitary magnet, each housing having internal dimensions allowing an introduction of a unitary magnet into its interior while leaving a space between the housing and the unitary magnet filled with a fiber-reinforced insulating material, the meshes being made of fiber-reinforced insulating material.

[0056] The mesh remains in place and can also be coated in a layer of composite. Such a mesh makes it possible to maintain individual magnets during the manufacture of the substructure and has the advantage of representing an additional solidification element of the substructure, the mesh being able to also contain reinforcing fibers.

[0057] For example, a honeycomb mesh is known to enhance the strength of an element, in this case a substructure. The individual magnets are inserted into hexagonal housings that hold them in place. The walls of the housings serve as electrical insulation and the density of the housings in the substructure can be significantly increased. The honeycomb mesh may be made of a fiber-reinforced insulating composite material.

[0058] Advantageously, the hub and the branches are made of glass fibers cast in resin.

[0059] These glass or reinforcing fibers contribute to increasing the resistance of the rotor, in particular the bending rigidity and buckling.

[0060] Advantageously, the rotor has circular faces delimiting it axially, a covering disc being arranged on at least one circular face of the rotor.

[0061] This applies mainly but not only to substructures of the magnet structure comprising a plurality of unit magnets. The large magnets used for the rotor according to the prior art dissipated a large amount of heat. This dissipation prevented the use of axial holding means in the form of composite covering discs and the heat dissipation could have consequences on the strength of the coating with accelerated aging of this coating as well as of the magnets.

[0062] Composite covering discs were therefore not frequently used in the state of the art because they did not resist the heat dissipation generated by the magnets.

[0063] As the present invention preferably uses a multitude of unit magnets replacing a compact magnet of the state of the art, heat dissipation is less and composite covering discs can be used as axial holding means, these discs advantageously replacing axial holding means between magnets and rotor body, possibly requiring modifications to the magnets or their coating to produce complementary fixing means with fixing means carried by the rotor.

[0064] Advantageously, a distal end of each branch bears against the hoop and the body of the rotor is formed from two equivalent body parts aligned axially in the rotor.

[0065] This makes it possible to achieve part of the mechanical engagement between associated branches and internal substructure by creating between the two body parts a female part, for example in the form of a groove, receiving a male part carried by each internal substructure.

[0066] The invention also relates to a method of manufacturing such a rotor, which method comprises the following steps: - Introduction of internal substructures between each pair of two adjacent associated branches of one of the two body parts, - Solidarity of the two body parts, - Introduction of external substructures between each pair of two associated adjacent branches of the body, each external substructure being in the radial extension of an internal substructure, - Positioning the hoop against the distal end of each branch and gluing the external substructures against the hoop.

[0067] Ease of manufacture is thus obtained by using a rotor in two parts glued together while being able to leave between them a gap providing part of the mechanical engagement between each internal substructure and its associated branches in the form of a female part able to house one or more male parts of each internal substructure. When the magnet structures are coated as a whole, the method can be modified by replacing the first step with an introduction of the magnet structures and their internal and external substructures between each pair of two associated adjacent branches of one of the two body parts and by eliminating the third step.

[0068] The invention relates to an axial flux electromagnetic motor or generator characterized in that it comprises at least one rotor as previously described, the electromagnetic motor or generator comprising at least one stator carrying at least one winding, the electromagnetic motor or generator comprising one or more air gaps between said at least one rotor and said at least one stator.

[0069] Advantageously, the electromagnetic motor or generator comprises at least one rotor associated with two stators.

[0070] The attached drawings illustrate the invention:

[0071] [Fig.l] represents an exploded view of an embodiment of a rotor according to the present invention,

[0072] [Fig.2] represents a very schematic view in axial section of an embodiment of a magnet structure forming part of a rotor according to the present invention, elements being shown separated from each other for greater visibility,

[0073] [Fig.3] represents a front perspective view of an embodiment of a internal substructure of a magnet structure forming part of a rotor according to the present invention,

[0074] [Fig.4] represents a radial sectional view of an embodiment of a structure magnet forming part of a rotor according to the present invention,

[0075] [Fig.5] represents a perspective view of an embodiment of a body composed of a hub and branches forming part of a rotor according to the present invention,

[0076] [Fig.6] represents an enlarged perspective view of a branch of the body shown in [Fig.5],

[0077] [Fig.7] represents a first optional embodiment of unitary magnets contained in a substructure of a magnet structure forming part of a rotor according to the present invention,

[0078] [Fig.8] represents a second optional embodiment of unit magnets contained in a substructure of a magnet structure forming part of a rotor according to the present invention,

[0079] [Fig.9] represents a third optional embodiment of unit magnets contained in a substructure of a magnet structure forming part of a rotor according to the present invention,

[0080] [Fig. 10] shows a fourth optional embodiment of a unitary magnet taken individually and contained in a substructure of a magnet structure forming part of a rotor according to the present invention.

[0081] The figures are given as examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. In particular the dimensions of the different parts are not representative of reality.

[0082] For brevity, magnet is not repeated after substructure since the structure containing the two substructures is a magnet structure and this is the case for all internal and external substructures.

[0083] In the following, where applicable, only one adjacent branch 3, one magnet structure 10, one internal substructure 11 and one external substructure 12 are referenced. The same applies to a single unit magnet in Figures 2 and 7 to 10, as well as a single layer of glue between unit magnets and, where applicable, a single mesh.

[0084] Everything stated for one of these referenced elements applies, however, to all similar non-referenced elements.

[0085] Referring to all the figures and more particularly to figures 1 to 6 and in particular to figures 1, 2 and 5, these figures show a rotor 1 with two branches 3 interposing between them a magnet structure shown divided and composed of an internal substructure 11 and an external substructure 12.

[0086] Such a rotor 1 is used in an electromagnetic motor or generator, advantageously with axial flux. The rotor 1, advantageously substantially circular, has a body 25a, 25b comprising an internal hub 2 concentric with a central axis 7 of rotation of the rotor 1 or longitudinal median axis of the rotor 1.

[0087] Branches 3 extend radially in the rotor 1 relative to the central axis 7 of rotation from the internal hub 2 towards a hoop 8 forming a circular external periphery of the rotor 1.

[0088] At least one magnet structure, referenced in [Fig.10], is housed in each space delimited between two adjacent branches 3 by its internal 11 and external 12 substructures.

[0089] Thus, according to the present invention, each magnet structure 10 is in the form of two distinct substructures 11, 12 respectively internal and external according to their position in the rotor 1. Each pair of two distinct substructures 11, 12 respectively internal and external has its external substructure 12 extending its internal substructure 11 radially between the two associated adjacent branches 3.

[0090] Each internal substructure 11 of the rotor 1 has its innermost face opposite the internal hub 2, without being secured to the internal hub 2, bearing at least partially against the internal hub 2 at least when the rotor 1 is not rotating and the centrifugal forces are not pushing each internal substructure 11 towards the periphery of the rotor 1.

[0091] The lateral faces of each internal substructure 11 of the rotor 1 are each opposite one of the two associated adjacent branches 3 being in mechanical engagement 13, 14 against a portion facing them of the associated adjacent branch.

[0092] This mechanical engagement 13, 14 guarantees a stop in an axial direction to the rotor 1 and a limited freedom of movement in a radial direction to the rotor 1, away from the internal hub 2 towards the hoop 8.

[0093] To avoid unwanted radial displacements during rotation of the rotor 1, for example oscillations, it is advantageous to provide limited friction in the mechanical engagement 13, 14, this in a radial direction, between the branches 3 associated with each internal substructure 11. A coefficient of friction can be selected taking into account a desired rotational speed of the rotor 1 and the magnitude of the centrifugal forces then applied to the internal substructures 11.

[0094] Each external substructure 12 to the rotor 1 has its outermost face to the rotor 1 bearing against the hoop 8.

[0095] As can be seen in particular in Figures 3, 5 and 6, the mechanical engagement 13, 14 of each lateral face of the internal substructure 11 of each magnet structure against a portion facing it of the associated adjacent branch can be carried out by a male part 13 carried laterally by each internal substructure 11 housed in a female part 14 carried by a portion of the branches 3 facing the internal substructure 11.

[0096] The reverse can also be possible by providing the internal substructure 11 with female parts and the branches with male parts.

[0097] For example, a rail as a male part 13 carried laterally by each internal substructure 11 can be inserted into a groove as a female part 14 carried by a portion of the branches 3 facing the internal substructure 11. It is also possible to use tenons as male parts 13 penetrating into mortises or recesses carried by the branches 3. The reverse is also possible.

[0098] Any mechanical connection can also be used provided that this connection provides a stop in an axial direction for the rotor 1 and limited freedom of movement in a radial direction to rotor 1.

[0099] Referring in particular to figures 2 and 3, each internal 11 or external 12 substructure can be embedded in a first layer 15 of composite completely coating the internal 11 or external 12 substructure.

[0100] In the case of an internal substructure 11, the first layer 15 of composite can be configured to form the male parts 13, each being carried laterally on one side by each internal substructure 11.

[0101] Referring in particular to [Fig.2], the two internal and external sub-structures 11, 12 of each magnet structure 10 between two adjacent branches 3 can be embedded in a second layer 16 of composite completely coating the magnet structure 10.

[0102] In this case, when present, the second layer 16 of composite can be shaped to carry a male part 14 on each of its lateral sides.

[0103] In addition, the rotor 1 can also be coated in a third layer 17 of composite, this third layer 17 also being able to coat at least one covering disc 27.

[0104] A portion of the third layer 17 is shown in this [Fig.2] spaced from the second layer 16 and the covering disc 27 to be visible while in reality this third layer is adjacent to the second layer, interposing or not between them a covering disc 27.

[0105] The composite layers may contain reinforcing fibers. The fiber content may differ between the layers. Thus, without this being limiting, the first layer 15 of the internal substructure 11 may be less loaded with fibers and be a little more deformable than the second or third layers 16, 17 so that the internal substructure 11 can move slightly closer to the external substructure 12, the rotor being in rotation.

[0106] The magnet volume of each outer substructure 12 may be larger than the magnet volume of each inner substructure 11. This can be seen in [Fig.4], the outer substructure being able to be of truncated conical shape by being open towards the hoop 8.

[0107] Placing each external magnet substructure 12 with its largest opening oriented towards the external periphery of the rotor 1, i.e. the hoop 8, makes it possible to increase the magnet parts placed at the periphery of the rotor 1 and therefore to increase the total magnetization surface.

[0108] As can best be seen in [Fig.5] for a single branch, bases of two adjacent branches 3 may be separated by an intermediate portion 9 of the inner hub 2.

[0109] The hub 2 and the branches 3 can be made of glass fibers cast in resin. Strong plastic fibers can also be used to increase the strength of the rotor 1, including bending and buckling rigidity.

[0110] To solidify the rotor 1, the rotor body 25a, 25b and the branches 3 may be in one piece. The branches 3 may or may not be secured to the hoop 8 by their tapered end 3b.

[0111] As can be seen in particular in figures 1, 2, 5 and 6 taken in combination, [Fig.6] being an enlarged view of a portion of branch surrounded and referenced A in [Fig.5], the branches 3 may have in section a diamond shape 19 connected to the internal hub 2 by a foot 18 widening towards the outside of the diamond 19 towards the hub 2.

[0112] The two faces of the rhombus 19 in section the most internal to the rotor 1 of two associated adjacent branches 3 can frame the internal substructure 11 of each magnet structure 10. The two faces of the rhombus 19 in section the most external to the rotor 1 of two associated adjacent branches 3 can frame the external substructure 12 of each magnet structure 10.

[0113] The internal substructure 11 of each magnet structure 10 can completely fill in the space between the two associated adjacent branches 3 a first housing 20 delimited between the two innermost faces of the diamond 19 in section of the two associated branches 3.

[0114] The internal substructure 11 of each magnet structure 10 may leave a lateral cavity opposite the foot 18. This lateral cavity may be less than five percent of the surface area filled by the internal substructure 11.

[0115] The external substructure 12 of each magnet structure 10 can completely fill in the space between the two associated adjacent branches 3 a second housing 21 delimited between the two outermost faces of the diamond 19 in section of the two associated branches 3.

[0116] Bases of two adjacent branches 3 associated in abutment against the internal hub 2 may be separated by an intermediate portion 9 of the internal hub 2. The intermediate portion 9 of the internal hub 2 may be in at least partial contact with a face most internal to the rotor 1 of the internal substructure 11.

[0117] The internal and external substructures 11, 12 of each magnet structure 10 may be separated by a clearance 22.

[0118] The clearance 22 may be of rounded shape, the succession of clearances 22 in the magnet structures of the rotor 1 forming a circle centered on the center of the rotor 1 through which the central axis 7 of rotation passes.

[0119] The operating clearance 22 can be filled with a flexible resin or glue, more flexible than the branches 3 of the rotor 1, so as not to transmit the centrifugal load of the internal substructure 11 onto the hoop 8.

[0120] Alternatively, this game 22 can also remain empty.

[0121] While it is possible for at least one internal or external substructure 11 or 12 to contain only one magnet, with reference to Figures 7 to 10 while referring to the other figures for the references missing from these figures, at least one of the substructures 11, 12 of each magnet structure 10 may also consist of a plurality of unit magnets 4, 4c, 4d secured by a fiber-reinforced insulating material 23.

[0122] As shown in [Fig.7], each unit magnet 4, 4c, 4d may be of elongated shape extending in the axial direction of the rotor 1. The unit magnets 4, only one of which is referenced in this [Fig.7], are not to be confused with the magnet structures 10 or with large magnets not shown in the figures.

[0123] It follows that each magnet structure 10 may be three-dimensional and made up of a plurality of unit magnets 4, 4c, 4d.

[0124] Thus in [Fig.7], each unit magnet 4 of the plurality of unit magnets is of polygonal shape, preferably parallelepiped.

[0125] In [Fig.9], four parallelepiped unit magnets 4 are shown, which are larger than the unit magnets 4 of [Fig.7] and therefore less numerous, in this [Fig.9], there are four.

[0126] In [Fig. 10], each unit magnet 4c may have an at least partially ovoid outline.

[0127] This ovoid unitary magnet 4c may comprise a first portion 4a forming the body of the unitary magnet 4c having a larger section and extending over a greater length of the unitary magnet 4c than at least a second longitudinal end portion 4b pointing towards an associated longitudinal end of the unitary magnet 4c, decreasing in section as it approaches the longitudinal end.

[0128] For any type of unit magnets, the unit magnets may be directly adjacent to each other while being partially in contact. The unit magnets 4 may be bonded by depositing glue. The plurality of unit magnets 4, 4c, 4d creates a mesh of magnets without the interposition of holding elements between them other than the glue, the unit magnets 4, 4c, 4d being in direct contact between adjacent magnets.

[0129] It is possible to have a magnet structure 10 having internal and external substructures 11, 12 each comprising different unit magnets.

[0130] In [Fig.2] in a substructure 11 of the magnet structure 10, the unit magnets 4 are glued against each other without meshing between them while in the other substructure 12 the unit magnets are glued together with the interposition of a mesh 24.

[0131] Thus at least one of the substructures 11, 12 of each magnet structure 10 consisting of a plurality of unit magnets can integrate at least one mesh 24 having meshes each delimiting a housing for a respective unit magnet 4.

[0132] Each housing may have internal dimensions just sufficient to allow the introduction of a unit magnet 4 into its interior while leaving a space between the housing and the unit magnet 4 filled with a fiber-reinforced insulating material, the meshes being made of fiber-reinforced insulating material.

[0133] In [Fig.2], reference 23 shows an insulating material filling a gap between two unit magnets 4.

[0134] It is also possible to design a magnet structure 10 without meshing in its internal and external substructures 11, 12.

[0135] Thus, the unit magnets may be pixelated magnets having square, rectangular or any other shape. Resin or glue 23 may be injected between the magnets to form a blank of both internal and external substructure.

[0136] The pixels can be made in directions inclined relative to the axis of symmetry of the internal 11 or external 12 substructure comprising them at any angle.

[0137] It is possible to provide different unit magnets of a substructure 11 or 12 compared to those of a substructure 12 or 11 associated in the same magnet structure 10.

[0138] In another embodiment, as shown in [Fig. 8] each unit magnet may be in the form of a 4d slice having a thickness at least less than ten times its length. In this [Fig. 8], there are shown six 4d unit magnets, each in the form of a slice.

[0139] The slices 4d forming unit magnets can be separated in said at least one of the substructures 11, 12 of each magnet structure 10 by cutouts in an ortho-radial plane in the rotor 1. The empty spaces between two slices 4d can be filled with resin or glue as insulating material 23.

[0140] The hub 2 and the branches 3 may be made of fiberglass cast in resin, whether or not they are in one piece.

[0141] The hoop 8 of the rotor 1 may be made of glass fibers or carbon fibers. The hoop 8 may circumferentially surround the magnet structures 10 at an outer periphery of the rotor 1.

[0142] The hoop 8 contributes, if necessary, to the radial maintenance of the magnet structures 10 in addition to the mechanical engagement of the internal substructure 11 with the branches 3. The distal ends of the branches 3 may or may not be secured to the hoop 8 but are in abutment against the hoop 8. The hoop 8 is visible in particular at Figures 1 and 4.

[0143] The rotor 1 may have circular faces delimiting it axially, a covering disc 27, visible in [Fig.2], being arranged on at least one circular face of the rotor 1, advantageously a covering disc 27 for each circular face of the rotor 1.

[0144] This makes it possible to prevent axial movement of the magnet structures 10 between two branches 3. A covering disc 27 is shown very schematically in [Fig.2] being spaced from the magnet structure 10 to be better visible.

[0145] As can be seen in particular in [Fig.l], the body of the rotor 1 can be in two equivalent body parts 25a, 25b aligned axially in the rotor 1, preferably two concentric discs glued against each other.

[0146] A gap made between the two discs can make it possible to produce locally in the branches 3 for portions facing the internal substructures 11, 12 the female parts 14, visible in particular in figures 5 and 6, useful for producing the mechanical engagement 13, 14 of each lateral face of the internal substructure 11 of each magnet structure 10 against a portion facing it of the associated adjacent branch by cooperating with a respective male part 13 carried laterally on both sides of each internal substructure 11.

[0147] As can be seen in particular in figures 5 and 6 for a single part of the body 25a represented but this is also valid for the other part 25b, in a preferred embodiment, each part of the body 25a, 25b, comprises an internal contour 26a which is of smaller dimension while being diamond-shaped like the external contour of each part of the body 25a.

[0148] Referring to Figures 1, 5 and 6 taken in combination, when the two body parts 25a, 25b are pressed against each other, their internal contour 26a facing each other, a groove 13 forming a female part is produced delimited inside the two body parts 25a, 25b pressed against each other.

[0149] As an alternative to a two-part body, it is also possible to design a single-part body with a groove on the lateral sides of the branches as a female part.

[0150] The invention also relates to a method for manufacturing a rotor 1 in two portions as previously mentioned. The first step of the method is an introduction of internal substructures 11 previously shaped and each forming a closed entity, each internal substructure 11 being housed between a pair of two adjacent branches 3 associated with one of the two body parts 25a, 25b of rotor 1.

[0151] The second step consists of joining the two body parts 25a, 25b together, for example by gluing.

[0152] The third step is an introduction of external substructures 12 between each pair of two adjacent associated branches 3 of the body 25a, 25b.

[0153] Each external substructure 12 is in the radial extension of an internal substructure 11.

[0154] The fourth step consists of positioning the hoop 8 against the distal end of each branch followed by gluing the external substructures 12 against the hoop 8.

[0155] It is recalled that the internal substructures 11 are neither glued against the branches 3 nor against the hub 2.

[0156] Alternatively, it is possible to produce complete magnet structures individually forming a whole, each containing an internal substructure 11 and an external substructure 12 secured to each other, the first step of the alternative method being an introduction of the magnet structures 10 previously shaped and each forming a closed entity between each pair of two adjacent branches 3 associated with one of the two body parts 25a, 25b of rotor 1.

[0157] The third step of the method previously mentioned is then deleted in this alternative variant.

[0158] The invention finally relates to an axial flux electromagnetic motor or generator comprising at least one such rotor 1, the electromagnetic motor or generator comprising at least one stator carrying at least one winding, the electromagnetic motor or generator comprising one or more air gaps between said at least one rotor 1 and said at least one stator.

[0159] The electromagnetic motor or generator may preferably comprise at least one rotor 1 associated with two stators.

Claims

Claims

1. Rotor (1) of an electromagnetic motor or generator having a body (25a, 25b) comprising an internal hub (2) concentric with a central axis (7) of rotation of the rotor (1), branches (3) extending radially with respect to the central axis (7) of rotation from the internal hub (2) towards a hoop (8) forming a circular external periphery of the rotor (1), a magnet structure (10) forming a magnet pole being housed in each space delimited between two adjacent branches (3) associated with the magnet structure (10), each magnet structure (10) being in the form of two distinct sub-structures (11, 12) respectively internal and external according to their position in the rotor (1) by extending radially between the two adjacent branches (3) associated, the internal sub-structure (11) to the rotor (1) having its innermost face in contact at least partial, when the rotor (1) is not rotating,with the internal hub (2) and its lateral faces each facing one of the two associated adjacent branches (3) being in mechanical engagement (13, 14) against a portion facing them of the associated adjacent branch with abutment in an axial direction to the rotor (1) and the external substructure (12) to the rotor (1) having its outermost face to the rotor (1) bearing against the hoop (8), characterized in that the internal substructure (11) to the rotor (1) has freedom of movement in a radial direction to the rotor (1), the internal and external substructures (11, 12) of each magnet structure (10) being separated by a clearance (22).,

2. Rotor (1) according to claim 1, in which the mechanical engagement (13, 14) of each lateral face of the internal substructure (11) of each magnet structure (10) against a portion facing it of the associated adjacent branch is done by a male part (13) carried laterally on both sides of each internal substructure (11) housed in a female part (14) carried by a portion of the branches (3) facing the internal substructure (11) or vice versa for positioning the male (13) and female (14) parts.

3. Rotor (1) according to the preceding claim, in which each internal substructure (11) is embedded in a first layer (15) of composite entirely coating the internal substructure (11), the first layer (15) of composite being configured to form the male parts (13) each being carried laterally on one side by each internal substructure (11).

4. Rotor (1) according to the preceding claim, in which the two internal and external sub-structures (11, 12) of each magnet structure (10) between two adjacent branches (3) are embedded in a second layer (16) of composite entirely coating the magnet structure (10), the rotor (1) also being coated in a third layer (17) of composite.

5. Rotor (1) according to any one of the three preceding claims, in which the branches (3) have in section a diamond shape (19) connected to the internal hub (2) by a foot (18) widening towards the hub (2), the two faces of the diamond (19) in section most internal to the rotor (1) of two associated adjacent branches (3) framing the internal substructure (11) of each magnet structure (10) and the two faces of the diamond (19) in section most external to the rotor (1) of two associated adjacent branches (3) framing the external substructure (12) of each magnet structure (10),the internal substructure (11) of each magnet structure (10) entirely filling in the space between the two associated adjacent branches (3) a first housing (20) delimited between the two innermost faces of the rhombus (19) in section of the two associated branches (3) and the external substructure (12) of each magnet structure (10) entirely filling in the space between the two associated adjacent branches (3) a second housing (21) delimited between the two outermost faces of the rhombus (19) in section of the two associated branches (3).,

6. Rotor (1) according to any one of the preceding claims, wherein at least one of the substructures (11, 12) of each magnet structure (10) consists of a plurality of unit magnets (4, 4c, 4d) secured by a fiber-reinforced insulating material (23).

7. Rotor (1) according to claim 6, wherein each unit magnet (4, 4c) is of elongate shape extending in the axial direction of the rotor (1), each unit magnet (4) being of polygonal shape or each unit magnet (4c) having an at least partially ovoid outline, the ovoid shape or outline comprising a first portion (4a) forming the body of the unit magnet (4c) having a larger section and extending over a greater length of the unit magnet (4c) than at least one second longitudinal end portion (4b) pointing towards an associated longitudinal end of the unit magnet (4c) while decreasing in section as it approaches the longitudinal end tudinal.

8. Rotor (1) according to claim 6, wherein each unit magnet (4, 4c, 4d) is in the form of a slice (4d) having a thickness at least less than ten times its length, the slices (4d) forming unit magnets being separated in said at least one of the substructures (11, 12) of each magnet structure (10) by cutouts in an ortho-radial plane in the rotor (1).

9. Rotor (1) according to any one of the three preceding claims, wherein said at least one of the substructures (11, 12) of each magnet structure (10) consisting of a plurality of unit magnets (4, 4c, 4d) incorporates at least one mesh (24) having meshes each delimiting a housing for a respective unit magnet (4, 4c, 4d), each housing having internal dimensions allowing an introduction of a unit magnet (4, 4c, 4d) therein while leaving a space between the housing and the unit magnet (4, 4c, 4d) filled with a fiber-reinforced insulating material (23), the meshes being made of fiber-reinforced insulating material.

10. Rotor (1) according to any one of the preceding claims, in which the inner hub (2) and the branches (3) are made of glass fibers cast in resin.

11. Rotor (1) according to any one of the preceding claims, in which the rotor (1) has circular faces delimiting it axially, a covering disc (27) being arranged on at least one circular face of the rotor (1).

12. Rotor (1) according to any one of the preceding claims, in which a distal end of each branch (3) bears against the hoop (8) and the body (25a, 25b) of the rotor (1) is formed of two equivalent body parts (25a, 25b) aligned axially in the rotor (1).

13. Method for manufacturing a rotor (1) according to the preceding claim, which method comprises the following steps: - Introduction of internal substructures (11) between each pair of two associated adjacent branches (3) of one of the two body parts (25a, 25b), - Joining the two body parts (25a, 25b), - Introduction of external substructures (12) between each pair of two associated adjacent branches (3) of the body (25a, 25b), each external substructure (12) being in the pro- radial lengthening of an internal substructure (11), - Positioning of the hoop (8) against the distal end of each branch (3) and bonding of the external substructures (12) against the hoop (8), the internal and external substructures (11, 12) of each magnet structure (10) being separated by a clearance (22).

14. Axial flux electromagnetic motor or generator characterized in that it comprises at least one rotor (1) according to any one of claims 1 to 12, the electromagnetic motor or generator comprising at least one stator carrying at least one winding, the electromagnetic motor or generator comprising one or more air gaps between said at least one rotor (1) and said at least one stator.

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