Axial flux electric machine and method for manufacturing such a machine
Patent Information
- Application Number
- PCT/EP2026/058469
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-25
- Filing Date
- 2026-03-25
- Publication Date
- 2026-10-01
Smart Images
Figure EP2026058469_01102026_PF_FP_ABST
Abstract
Description
[0001] DESCRIPTION
[0002] Title of the invention: Axial flux electric machine and method for manufacturing such a machine
[0003] The present invention relates to the fields of mechanics and electrotechnics, and more specifically concerns an axial flux electric machine and its manufacture.
[0004] Currently, electric or hybrid electric vehicles use electric traction or propulsion motors, which are often radial flux electric machines, meaning that the stator windings of such a machine generate a magnetic flux in a radial direction relative to an axial direction corresponding to the axis of rotation of the machine.
[0005] It should be noted that in this application, an axial direction is parallel to the axis of rotation of a rotor of the electrical machine under consideration, a radial direction is orthogonal to the axial direction while passing through the axis of rotation of the rotor, and an ortho-radial or angular direction is orthogonal to the axial direction and to a radial direction.
[0006] To reduce the size of a traction or propulsion motor in an electric or hybrid electric vehicle, the use of an axial flux electric machine is being considered instead of a radial flux electric machine. This type of machine is generally more compact, at least in one axial direction corresponding to the machine's axis of rotation, giving it a disc-like shape.
[0007] Figure 1 is an example of an embodiment of an axial flux electric machine according to the prior art. This electric machine comprises a casing 4a composed of two half-casings 42a and 44a held together to form a chamber housing a rotor 12a and two stators 2a, each composed of a plurality of stator teeth 18a, each equipped with a winding 8a and projecting from an annular magnetic yoke 10a. Each half-casing 42a, 44a houses a separate stator 2a.
[0008] The stator teeth 18a of each stator 2a are fixed to a wall of one of the half-cases 42a, 44a by means of the magnetic yoke 10a of the stator 2a, this magnetic yoke 10a being, for example, cast and the corresponding overmolding 7a being screwed to the wall of the half-case 42a, 44a. The stator teeth 18a are arranged circularly around the central openings of the half-cases 42, 44, central openings through which a rotor shaft 14a passes.
[0009] The rotor shaft 14a is movably mounted between the central openings of each half-casing 42a, 44a by bearings 16a. The rotor 12a typically consists of a non-magnetic composite structure 122a having housings arranged angularly on the rotor 12a around a central portion of the composite structure 122a. This central portion has a hole for the rotor shaft 14a to pass through and is screwed to a hub fixed to the rotor shaft 14a. The housings of the composite structure 122a contain permanent magnets 124a, each capable of receiving the magnetic flux generated by one of the windings 8a, which drives the rotor 12a to rotate about the axis of rotation 142a. A circular pre-stressed flange 126a retains the permanent magnets 124a in the housings of the composite structure 122a.
[0010] The distance between the rotor 12a and each of the stators 2a must be controlled and minimized to improve the performance of the electric machine. Not only must it be non-zero, in order to create an air gap between the permanent magnets 124a of the rotor 12a and the teeth 18a of each stator 2a, thus allowing the rotor to rotate relative to the stator without contact, but it must also be sufficiently small, for example on the order of a millimeter, so as not to negatively impact the magnetic performance of the electric machine. Furthermore, the air gap must be symmetrical on both sides of the rotor 12a.
[0011] This distance between the rotor 12a and each of the stators 2a depends on the connections that position each element. In the dimension chain used to calculate this distance, the more links and tolerance intervals there are that define these links, the larger the nominal space between each stator 2a and the rotor 12a must be to avoid any contact between these elements, which negatively impacts the magnetic performance of the electric machine.
[0012] There is therefore a need for an assembly of an axial flux electric machine that allows for better control of the distance between each rotor and each stator of this axial flux electric machine. The present invention aims to remedy at least partially the aforementioned drawbacks by providing an axial flux electric machine in which the magnetic yoke of a stator is directly fixed to a housing of the electric machine, which makes it possible to eliminate a dimension and a tolerance range in the chain of dimensions used to calculate the distance between the rotor and the stator.
[0013] To this end, the invention proposes an axial flux electrical machine, comprising at least:
[0014] - a rotor attached to a rotating shaft,
[0015] - a stator comprising a magnetic yoke, teeth that project axially from the magnetic yoke towards the rotor, and windings arranged around the teeth, - a housing for the electrical machine, comprising a mounting bracket for the magnetic yoke,
[0016] the electric machine being characterized in that the magnetic cylinder head has a fixing surface on one side opposite the teeth with respect to the magnetic cylinder head, the fixing surface being in contact with bearing portions of the fixing support, the latter having at least one recess located between the bearing portions and filled with a volume of glue retaining the magnetic cylinder head against the fixing support.
[0017] The housing may comprise several walls, the mounting support being one of these walls, for example, forming a cover or half of a housing, or a wall attached to a cover. The housing has at least one central hole for the passage of the rotating shaft. Of course, the electrical machine according to the invention may have more than one rotor and more than one stator, for example, two stators with a rotor positioned between them, as in the example described in relation to the prior art.
[0018] Furthermore, in this application, the magnetic yoke and teeth are formed as a single unit by winding a magnetic sheet metal strip into crenellations, with the winding layers stacked radially. This design eliminates the need for a dimensional chain link between the yoke and the teeth. However, in an alternative embodiment, the teeth are attached to the magnetic yoke, for example, by a system of grooves on the yoke or teeth, and complementary ribs on the teeth or yoke respectively, with the ribs being inserted into the grooves. Other embodiments are of course possible; for example, the teeth can be bonded to the yoke. The teeth and / or the yoke can, for example, be made of sintered soft magnetic material.
[0019] Thanks to the invention, the magnetic cylinder head's mounting surface is in direct contact with the bearing portions of the mounting bracket, meaning there is no glue or other fastening material between the magnetic cylinder head and these bearing portions. This eliminates the distance between the magnetic cylinder head and its mounting bracket, thus removing a dimensional chain link and allowing for better control of the distance between the rotor and the stator.
[0020] It should be noted that if the glue were located between the bearing portions and the magnetic cylinder head, rather than in the recess, the thickness of glue would constitute an additional link in the chain of dimensions, and given that glue is a deformable material, the tolerance range associated with this thickness would be significant compared to this thickness.
[0021] The bearing portions of the fixing support are preferably flat and in direct contact with the fixing surface, which is also flat.
[0022] In one embodiment of the invention, the mounting support has a central hole for the passage of the rotating shaft, the bearing portions of the mounting support having a first ring of material and a second ring of material, which surround the central hole, at least one recess being located between the first ring of material and the second ring of material.
[0023] It is understood that the annular magnetic cylinder head rests on the first ring of material and the second ring of material, the space between the first ring of material and the second ring of material being able to be entirely or partially filled with glue, retaining the magnetic cylinder head against the mounting support.
[0024] The fixing support includes, for example, several recesses located between the first ring of material and the second ring of material, the bearing portions having bridges of material connecting the first ring of material and the second ring of material by separating the recesses from each other.
[0025] The material bridges are oriented radially along their length, with the recesses defined on one side by the material rings and on the other by the material bridges. The recesses are structurally identical. Each one is rectangular with rounded corners, and its longer sides are curved to follow the curvature of the first and second material rings. The rounded corners allow the adhesive to spread evenly across the entire surface of the recess.
[0026] It is understood that the shape of the recess(es) depends on the characteristics of the adhesive used, and in particular its viscosity at the temperature at which it is applied and then spread within the recess by pressing the magnetic cylinder head against the mounting surface. For example, a bead of adhesive is placed in each recess, with a volume equal to or nearly equal to that of the recess, and the adhesive must spread throughout most of the recess without running onto the contact areas of the mounting surface. The number and shape of the recesses are therefore highly variable depending on the size of the adhesive bead and thus its viscosity. As an alternative, for example, the recesses are round and form several staggered rings of recesses between the first and second rings of material.
[0027] Furthermore, the recess(s) should preferably extend over at least 50% of the magnetic breechblock's mounting surface. More precisely, the recesses should extend over 50 to 90% of this mounting surface. This feature ensures a sufficiently robust attachment of the magnetic breechblock to the mounting bracket.
[0028] The magnetic breechblock mounting surface should be understood here as the flat annular surface of the axial end face of the magnetic breechblock opposite the axial end face of the magnetic breechblock attached to the teeth. The edges of the recesses must therefore encompass at least 50% of this mounting surface, and preferably between 50% and 90% of it.
[0029] The at least one recess is, for example, between 0.5 and 3 millimeters deep. Preferably, the at least one recess is between 1 and 2 millimeters deep. This depth is measured in the axial direction. It is constant throughout the entire depth of the recess. It is determined based on the viscosity of the adhesive. A bubble of adhesive applied in the recess, with a volume equal to that of the recess, must form a dome with a height greater than the depth of the recess. In one embodiment of the invention, the at least one recess includes at least one drainage hole. This drainage hole is deeper than the depth of the recess. It may pass through the mounting surface and serves to drain excess adhesive and / or air.
[0030] The drain hole is preferably located in a corner of the recess.
[0031] In other words, the drainage hole is located further from the center of the recess than from the recess's edges, in a plane perpendicular to the axial direction. This positioning of the drainage hole allows the adhesive to spread over a large portion of the recess before any excess adhesive and / or air escapes through the drainage hole. Ideally, the adhesive should fill at least 90% of the recess.
[0032] The invention also relates to a method for manufacturing an axial flux electrical machine according to the invention, comprising the steps of:
[0033] - positioning within the recess, of a volume of glue with a volume at least equal to 90% of that of the recess,
[0034] - magnetic cylinder head pressed against the mounting bracket,
[0035] - solidification of the glue.
[0036] The positioning step is, for example, preceded by bringing the glue volume to room temperature. This volume of glue is deposited in the center of the recess, in the form of a glue bubble.
[0037] The invention also relates to an electric or hybrid vehicle comprising an axial flux electric machine according to the invention.
[0038] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples of embodiments given with reference to the attached schematic drawings on the other hand, in which:
[0039] [fig 1] already discussed in relation to the prior art, is a cross-sectional view along a plane extending axially and radially, of an axial flux electrical machine according to the prior art,
[0040] [Fig. 2] is a cross-sectional view along a plane extending axially and radially, of an axial flux electric machine according to the invention, in one embodiment of the invention; [Fig. 3] is a perspective view of a portion of a housing of the electric machine of Figure 2, serving as a mounting support for a stator of the electric machine; and
[0041] [fig 4] represents steps in a manufacturing process for an electrical machine according to the invention, in the embodiment of figures 2 and 3.
[0042] According to an embodiment of the invention illustrated in figure 2, an axial flux electric machine 1 according to the invention comprises a rotor 12 attached to a rotating shaft 14, two stators 2 arranged on either side of the rotor 12, and a housing 4 for closing the electric machine 1, housing the rotor 12 and the stators 2.
[0043] The housing 4 is formed here of a cylindrical wall 46 and two walls extending primarily in a plane orthogonal to an axis of rotation 142 of the rotor 12, each of the two walls comprising a bearing housing for a bearing 16 mounted around the rotating shaft 14. These two walls extending orthogonally to the axis of rotation 142 of the rotor 12 each correspond, in this embodiment of the invention, to a mounting support 42, 44 for a separate stator 2. The cylindrical wall 46 is fixed to the external radial ends of each of these walls.
[0044] The housing 4 is preferably metallic, for example steel or aluminum, but alternatively it can be made of synthetic polymer (plastic).
[0045] Each stator 2 comprises a magnetic yoke 10, teeth 18 projecting axially from the magnetic yoke 10 towards the rotor 12, and windings 8 arranged around the teeth 18. In this embodiment of the invention, the windings 8 are housed in winding supports 7 that are fitted around the teeth 18. The teeth 18 have a trapezoidal shape, and the magnetic yoke 10 has an annular shape. The magnetic yoke 10 and the teeth 18 are formed as a single unit by winding a magnetic sheet metal strip in a crenellated pattern, with the winding layers stacked radially. The magnetic sheet metal strip is, for example, made of grain-oriented or grain-unoriented electrical steel.
[0046] The stator teeth 18 of each stator 2 are fixed to one of the mounting brackets 42, 44 by means of the magnetic yoke 10 of the stator 2, the latter being bonded to the mounting bracket 42, 44, as described below. Each mounting bracket 42, 44 has an overall discoidal shape, with a central hole 3 for the passage of the rotating shaft 14, formed by the bearing arranged in the mounting bracket 42, 44 and receiving the bearing 16. In this embodiment of the invention, the rotor 12 is composed of a non-magnetic composite structure 122 having housings arranged angularly on the rotor 12 around a central part of the composite structure 122, this central part having a passage hole for the rotor shaft 14 and being fixed by screws to a hub integral with the rotor shaft 14.The housings of the composite structure 122 include permanent magnets 124, each capable of receiving the magnetic flux generated by one of the windings 8, which causes the rotor 12 to rotate around the axis of rotation 142. A circular pre-stressed collar 126 retains the permanent magnets 124 in the housings of the composite structure 122.
[0047] The magnetic yoke 10 of each stator 2 has a mounting surface 11 for one of the mounting supports 42, 44. This mounting surface 11 is annular and located at an axial end of the magnetic yoke 10, opposite the axial end of the magnetic yoke 10 which is fixed to the teeth 18. The mounting surface 11 is flat, neglecting the relief formed by the stacking of winding layers of the sheet metal strip forming the yoke 10 and the teeth 18.
[0048] Each fixing support 42, 44 has at least one recess 5 filled with glue 9, the glue being in contact with the fixing surface 11, except at the level of areas of the fixing surface 11 which are directly in contact with the fixing support 42, 44, i.e. at the level of bearing portions 6 of the fixing support 42, 44, visible in figure 3. The glue 9 adheres all the better to the fixing surface 11 thanks to the relief formed by the stacking of sheet metal layers mentioned above.
[0049] As can be seen in figure 3, the bearing portions 6 of each fixing support 42, 44 are flat.
[0050] More specifically, the support portions 6 comprise a first ring of material 62 disposed around the bearing of the fixing support 42, 44, a second ring of material 64 disposed around the first ring of material 62, and bridges of material 60 connecting the first ring of material 62 and the second ring of material 64. The first ring of material 62 is a flat portion located at an internal radial periphery of the fixing support 42, 44 and the second ring of material 64 is a flat portion located at an external radial periphery of the fixing support 42, 44.
[0051] Several recesses 5, here six recesses, are arranged between the first ring of matter 62 and the second ring of matter 64, and separated from each other by the bridges of matter 60. The first ring of matter 62, the second ring of matter 64 and the bridges of matter 60 delimit the recesses 5, which here each have a rectangular shape with rounded corners and whose long sides are curved so as to follow the shape of the first and second rings of matter 62, 64.
[0052] Each recess 5 is one to two millimeters deep. All the recesses 5 cover at least 50% of the mounting surface 11 of the magnetic head 10. In addition, each recess 5 has a drainage hole 50 for excess glue and / or air, located in a corner of the recess 5. This drainage hole 50 may be through-hole, but not necessarily. Of course, the presence of these drainage holes 50 is optional; it compensates for the inability to precisely control the amount of glue to be applied to the available volume.
[0053] We now describe, in relation to Figure 4, steps of a manufacturing process 100 of the axial flux electric machine 1. It is assumed prior to these steps that the yoke 10 and the teeth have already been assembled by winding a magnetic sheet metal strip, itself cut from a sheet of electrical steel with oriented or non-oriented grains.
[0054] The first step 102 of the manufacturing process 100 is bringing the adhesive 9 to room temperature, for example to 20°C (degrees Celsius). This adhesive 9 is, for example, a two-component epoxy adhesive or a cyanoacrylate adhesive. This first step 102 brings the adhesive 9 to the desired viscosity.
[0055] A second step 104 of the manufacturing process 100 is then the positioning in each recess 5 of each fixing support 42, 44, of a volume of glue 9 substantially equal to the volume of the recess 5. More precisely this volume of glue 9 is placed in the center of the recess 5. This volume of glue 9 takes the form of a bubble of glue 9 forming a dome once centered in the recess 5, and whose apex protrudes from the recess 5.
[0056] A third step 106 of the manufacturing process 100 is then the plating of the magnetic breech 10 of each stator 2 onto a separate mounting support 42, 44, so that the mounting surface 11 of the magnetic breech 10 is in contact with the bearing portions 6 of the mounting support 42, 44.
[0057] Finally, a fourth step 108 of the manufacturing process 100 is the solidification of the glue 9, by allowing a drying time for the glue 9. Of course, the invention is not limited to the examples just described, and numerous modifications can be made to these examples without departing from the scope of the invention. In particular, the characteristics of the different embodiments and variants mentioned in this application can be combined to carry out the invention, provided that these embodiments and variants are not incompatible with each other.
Claims
DEMANDS 1- Axial flux electrical machine (1), comprising at least: - a rotor (12) fixed to a rotating shaft (14), - a stator (2) comprising a magnetic yoke (10), teeth (18) which project axially from the magnetic yoke (10) towards the rotor (12), and windings (8) arranged around the teeth (18), - a housing (4) for closing the electric machine (1), comprising a mounting support (42, 44) for the magnetic cylinder head (10), the electric machine (1) being characterized in that the magnetic cylinder head (10) has a fixing surface (11) on a side opposite the teeth (18) with respect to the magnetic cylinder head (10), the fixing surface (11) being in contact with bearing portions (6) of the fixing support (42, 44), the latter having at least one recess (5) located between the bearing portions (6) and filled with a volume of glue (9) retaining the magnetic cylinder head (10) against the fixing support (42). 2- Axial flux electric machine (1) according to claim 1, wherein said support portions (6) of the fixing support (42, 44) are flat and in direct contact with the fixing surface (11), which is also flat. 3- Axial flux electric machine (1) according to claim 1 or 2, in which the mounting support (42, 44) has a central hole (3) for the passage of the rotating shaft (14), the bearing portions (6) of the mounting support (42, 44) having a first ring of material (62) and a second ring of material (64), which surround the central hole (3), at least one recess (5) being located between the first ring of material (62) and the second ring of material (64). 4- Axial flux electric machine (1) according to claim 3, in which the mounting support (42, 44) has several recesses (5) located between the first ring of material (62) and the second ring of material (64), said support portions (6) having material bridges (60) connecting the first ring of material (62) and the second ring of material (64) by separating the recesses (5) from each other. 5- An axial flux electric machine (1) according to any one of claims 1 to 4, wherein the recess(s) (5) extend over at least 50% of the mounting surface (11) of the magnetic yoke (10). 6- An axial flux electric machine (1) according to any one of claims 1 to 5, wherein at least one recess (5) has a depth of between 0.5 and 3 millimeters. 7- Axial flux electric machine (1) according to any one of claims 1 to 6, wherein at least one recess (5) has at least one discharge hole (50). 8- Axial flux electric machine (1) according to claim 7, in which the discharge hole (50) is located in a corner of the recess (5). 9- Axial flow electric machine (1) according to any one of claims 1 to 8, in which the volume of glue (9) fills at least 90% of the recess (5). 10- A method for manufacturing (100) an axial flux electrical machine (1) according to any one of claims 1 to 9, comprising the steps of: - positioning (104) in the recess (5), of a volume of glue (9) with a volume at least equal to 90% of that of the recess (5), - plating (106) of the magnetic cylinder head (10) against the mounting support (42, 44), - solidification (108) of the glue (9).