Axial-flux electrical machine and corresponding mounting method

Abstract

The invention relates to an axial-flux electrical machine (1) comprising: - a rotor (5) comprising a plurality of magnetic poles (52) that are arranged around a rotor shaft (4), - at least one stator (3a, 3b) of which a plurality of stator coils, comprising stator windings (34), is arranged facing the plurality of magnetic poles (52), - a circular bus (7a, 7b) connected to ends (340) of the stator windings (34), - at least one casing (21, 22) housing the stator (3a, 3b), the stator coils being secured to a main face (210) of the casing (21, 22), the main face (210) comprising a through-orifice (215) for the rotor shaft (4), the circular bus (7a, 7b) being arranged on the side opposite the stator coils with respect to the main face (210) of the casing (21, 22).

Description

Description Title of the invention: Axial flux electric machine and corresponding mounting method

[0001] The present invention relates to the fields of electrical engineering and mechanics and more specifically concerns an axial flux electric machine.

[0002] 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.

[0003] To reduce the size of such a motor used for traction or propulsion of an electric vehicle, consideration is being given to using an axial flux electric machine 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.

[0004] Such a machine therefore comprises a generally cylindrical housing containing at least one stator with stator coils, and a rotor attached to a rotating shaft passing through the middle of the housing. The stator coils are fixed within the housing between an inner cylindrical wall, which forms a bearing support for the rotating shaft, and an outer cylindrical wall. These stator coils are arranged angularly around the inner cylindrical wall, opposite the magnetic poles of the rotor.

[0005] To electrically connect the stator coils to the machine's phase connections, which are intended to be connected to an inverter, the ends of one stator winding of each stator coil are first soldered to a circular busbar (for example, a three-phase busbar) positioned between the stator coils and one of the internal or external cylindrical walls of the housing. Electrical connections to the circular busbar are then routed from the housing, either through the external cylindrical wall or through a flat wall of the housing through which the rotating shaft emerges.

[0006] Assembling such an electrical machine is complex and expensive, particularly because access to the ends of the stator windings for connecting and then soldering them to the circular busbar is limited. The space available for accessing connection and soldering tools is further reduced when the stator coils are surrounded by a cooling system.

[0007] The present invention remedies, at least in part, the drawbacks of the prior art by providing an axial flux electric machine in which the bus The circular busbar is positioned on an external face of the electrical machine's casing. This makes connecting and soldering the ends of the stator windings to the circular busbar much simpler.

[0008] To this end, the invention proposes an axial flux electrical machine comprising: - a rotor shaft, - a rotor integral with the rotor shaft, comprising a plurality of magnetic poles arranged around the rotor shaft, - at least one stator comprising a plurality of stator coils having stator windings and arranged opposite the plurality of magnetic poles, - a circular bus connected to the ends of the stator windings, - at least one housing containing the stator, the stator coils being attached to a main face of the housing, the main face having an opening for the passage of the rotor shaft, the axial flux electric machine being characterized in that the circular bus is arranged on the opposite side to the stator coils with respect to the main face of the housing.

[0009] Circular bus means circular connection means, comprising several conducting rings (circular conducting bars) not necessarily closed, each conducting ring being capable of conducting a phase current associated with a part of the stator coils to which it is connected.

[0010] The axial flux electric machine according to the invention comprises, for example, two stators arranged on either side of the rotor, each stator being housed in a generally cylindrical casing open on the rotor side. The two casings are fixed to each other to protect the rotor and the stators from the external environment. Alternatively, the axial flux electric machine according to the invention comprises a single stator, the casing then being closed by fixing a cover onto a generally cylindrical outer wall of the casing enclosing the stator and the rotor.

[0011] The housing comprises a wall arranged orthogonally to the rotor shaft, called the main wall in this application, comprising the main face to which the stator coils are attached, therefore internal to the housing, and an opposite external face on which the circular bus is arranged or through which the circular bus protrudes, according to the embodiments of the invention.

[0012] The circular bus is preferably three-phase, but alternatively, it may have more or fewer phases. It is preferably arranged around the rotor shaft opening at a central portion of the main wall, or alternatively, the circular bus is located at a peripheral portion of this main wall, distal to the rotor shaft opening. Arranging the circular bus at the central portion allows for a smaller circular bus. and therefore to save on materials, for example copper.

[0013] Furthermore, it should be noted that the circular bus is not necessarily closed; it can be open, for example, between two ends of one of the stator windings. The different phases of the circular bus can take the form of conductive bars arranged circularly and superimposed parallel to the machine axis, or conversely, nested one inside the other perpendicular to the machine axis, with a layer of air or insulating material between the different phases. The connection between the ends of the stator windings and the different phases is made, for example, using conductive forks welded to the ends of the windings. These forks allow them to be attached to the circular bus before being connected to it by welding, brazing, or crimping. It should be noted that, unless otherwise specified, in this application, a connection refers to an electrical connection.

[0014] Finally, the circular bus thus arranged on the outside of the casing may not include a neutral phase, for example if electrical access to it is not necessary or if the stator coils are connected in delta.

[0015] Thanks to the invention, the connections of the ends of the stator windings to the circular bus can be made without being hindered by the cylindrical walls of the electrical machine, which greatly simplifies the welding carried out for these connections.

[0016] According to one feature of the invention, the main face of the casing has at least one recess allowing at least one end of one of the stator windings to pass through.

[0017] When the circular busbar is fixed to the main wall of the housing, preferably several recesses are provided in this wall to allow passage of all the stator winding ends, except possibly those connected to a neutral phase of the machine. Having several recesses rather than a single one increases the rigidity of the main wall of the housing.

[0018] In one embodiment of the invention, the circular bus is overmolded, at least partially, onto the casing on the external side of the electric machine. This overmolding is made of electrically insulating material and provides mechanical protection for the circular bus while limiting electrical risks. Only phase connections protrude from the overmolding, allowing the electric machine to be electrically connected to an inverter.

[0019] In another embodiment of the invention, the electric machine comprises a discoid plate having a central hole, and the stator coils are fixed to the discoid plate itself attached to the main face of the casing, the discoid plate having around the central hole, a plurality of orifices allowing the ends of the stator windings to pass to the outside of the electric machine.

[0020] The discoid plate is flat at least at the point where the active parts are attached. The machine (i.e., the stator coils) is mounted directly onto this discoidal plate, which is made, for example, of steel. This makes contact between the active parts and the discoidal plate easier to ensure, especially since the steel discoidal plate offers greater rigidity than the housing, which is often made of aluminum or plastic. The active parts are attached to the discoidal plate, for example, by gluing, interlocking (if the plate has grooves or ribs that complement the stator coil cores), or screwing. In one alternative embodiment, the discoidal plate is a stator yoke made of magnetic steel sheets.

[0021] In this other embodiment, the stator preferably comprises a sealed envelope fixed to the discoid plate, the stator coils being housed between the discoid plate and the sealed envelope, the plurality of orifices opening into the sealed envelope.

[0022] This sealed casing allows a heat transfer fluid, such as oil, to be sent into a sealed chamber formed by the casing and the discoid plate, in order to cool the stator windings. The oil enters and exits the sealed chamber through openings provided for this purpose in the main wall of the casing and in the discoid plate. These openings may correspond to ports designed to allow the ends of the stator windings to pass through to the circular bus located on the other side of the discoid plate.

[0023] Furthermore, in this other embodiment of the invention, the circular bus is preferably attached to the discoid plate on the side opposite the stator coils, through the recess.

[0024] In other words, unlike the previous embodiment where the circular bus is fixed to the housing, in this other embodiment of the invention, the circular bus is preferably fixed to the discoid plate. This fixing to the discoid plate helps to limit variations between, on the one hand, any forks present on the ends of the windings or on the circular bus, and on the other hand, respectively, the circular bus or the ends of the windings, since the manufacturing tolerances of the circular plate are more easily controlled than those of the housing. The recess is therefore of dimensions substantially identical to those of the circular bus. If the bus is closed, the main wall of the housing is then made in two parts, these two parts being joined together by means of the discoid plate.

[0025] In both embodiments, the circular bus is of course not directly in contact with the housing or the discoid plate, an insulating layer of air or electrically insulating material being interposed between the circular bus and the housing or the discoid plate.

[0026] In the other embodiment of the invention, the circular bus is, for example The circular bus is overmolded, at least partially, onto the disc-shaped plate. This overmolding provides mechanical protection for the bus, contributes to electrical safety, and creates a sealed chamber for the stator windings, which are immersed in a heat transfer fluid. These stator windings are enclosed by the sealed casing on one side and the disc-shaped plate, which contains multiple openings, on the other. The overmolding prevents the heat transfer fluid from leaking through these openings, unless they are specifically designed as inlets or outlets for supplying or removing the fluid from the sealed chamber.

[0027] Furthermore, this alternative embodiment allows the active parts of the machine and its sealed enclosure to be assembled together as a module, which is then installed within the electrical machine's housing. This enables testing of the active parts' functionality and the sealed chamber's integrity before final assembly, eliminating the need to first assemble the entire machine and then disassemble it if the test is unsuccessful. Finally, this module can be used on various axial flux electrical machines.

[0028] Of course, other embodiments are possible, particularly in the embodiment where the circular bus is fixed to the housing. It is also preferable to provide a sealed enclosure around the active parts of the stator, which allows it to be cooled without generating friction losses at the rotor. In all these embodiments, the construction of such a sealed enclosure encumbers the central part of the stator and hinders the integration of a circular bus. The axial flux machine according to the invention overcomes this drawback.

[0029] The invention also relates to a method for assembling an axial flux electrical machine according to the invention, comprising the following steps: - fixing the stator coils to the discoid plate, the ends of the stator windings being inserted through the plurality of holes, - fixing the waterproof casing onto the discoid plate, - connection of the circular bus to the ends of the stator windings, and - fixing the discoid plate onto the main face of the housing.

[0030] The ends of the stator windings inserted through the plurality of orifices are of course those intended to be connected to the circular bus, and therefore do not necessarily include the ends of the stator windings intended to be connected to a neutral phase of the machine.

[0031] The steps of the assembly process according to the invention are preferably carried out in the order indicated above, which allows the module "active parts-discoid plate-circular bus-sealed enclosure" to be assembled independently of the rest of the electrical machine.

[0032] This allows, in particular, the step of fixing the discoid plate onto the face The main casing should be preceded by a step to verify the proper electrical operation of the stator by supplying power to the circular bus.

[0033] In this case, preferably, the step of fixing the discoid plate to the main face of the housing is preceded, in the following order: - a circular bus overmolding step, implemented after the step of verifying the proper electrical operation of the stator, - a step of connecting an oil circuit to the discoid plate using openings provided for this purpose in the discoid plate, and - a step of verifying the tightness of a sealed chamber formed by the discoid plate and the sealed envelope.

[0034] The invention finally relates to a motor vehicle comprising an electric motor-propulsion unit comprising an axial flux electric machine according to the invention.

[0035] The assembly method according to the invention and the vehicle according to the invention have advantages similar to those of the axial flux electric machine according to the invention.

[0036] 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:

[0037] [Fig. 1] schematically represents in axial section a quarter of an axial flux electrical machine according to the invention, in one embodiment of the invention,

[0038] [Fig.2] schematically represents in axial section a quarter of a pre-assembled module made up of active parts, a circular bus, a sealed enclosure and a discoid plate of the axial flux electric machine of [Fig.1],

[0039] [Fig.3] schematically represents in ortho-radial section the module of [Fig.2] fixed inside a housing of the axial flux electric machine of [Fig.1],

[0040] [Fig.4] schematically represents an external face of a main wall of the casing of [Fig.3],

[0041] [Fig. 5] is a flowchart representing steps in a method for assembling the axial flux electric machine of [Fig. 1], in one embodiment of the invention, and

[0042] [Fig.6] is a schematic representation of the first steps in the assembly process of [Fig.5],

[0043] According to an embodiment of the invention shown in [Fig. 1], an axial flux electric machine 1 according to the invention comprises a housing or casing 2 formed of two casings 21 and 22. Each of the casings 21, 22 comprises an outer cylindrical wall and an inner cylindrical wall, the latter providing a space 215 for the passage of a rotor shaft 4 of the electric machine 1. The rotor shaft 4 is intended to rotate around an axis of rotation X. It is guided in its rotation by ball bearings 6 attached on one side to the casing 2 and on the other side to the rotor shaft 4.

[0044] In this request, an "axial" orientation therefore refers to an orientation along the X axis of the electric machine 1, while an ortho-radial orientation refers to an orientation orthogonal to the X axis of the electric machine 1. The section of [Fig.1] is therefore made in a plane containing the X axis of the electric machine 1. Only the part above the rotor shaft 4 is represented schematically.

[0045] Each of the housings 21, 22 also includes a substantially flat wall connecting these two cylindrical walls and orthogonal to the X axis of the electrical machine, this wall being called the main wall of the housing 21, 22.

[0046] The housing 2 accommodates a rotor 5, which is fixed to the rotor shaft 4 and has a plurality of magnetic poles 52 arranged around the rotor shaft 4. More precisely, the rotor 5 is in the form of a disc with a hole in its center to allow the passage of the rotor shaft 4. The rotor shaft has a shoulder against which a rotor hub is pressed, a ring being screwed, by means of bolts 80, on the other side of the rotor into the shoulder to clamp the hub and thus secure the rotor 5 to the rotor shaft 4.

[0047] The hub, for example, is part of a star structure 51 formed of composite material based on polymer and glass or carbon fibers, branches of this star structure 51 extending from the hub to house magnetic poles 52 between them. Each magnetic pole housed between two branches is, for example, segmented, that is to say, formed of small permanent magnets glued together and glued to the hub by means of a resin 54. Finally, a ring 53 around the star structure 51 and the magnetic poles 52 makes it possible to keep them in the star structure 51 despite the centrifugal force when the electrical machine 1 is operating.

[0048] In this embodiment of the invention, the electrical machine 1 comprises two stators 3a, 3b, each having active parts or stator coils. The stators 3a, 3b each have a circular bus 7a, 7b to which their respective stator coils are electrically connected. These circular buses 7a, 7b allow the electrical connection of the electrical machine 1 to one or more inverters. Since the two stators 3a, 3b are structurally identical, only stator 3a is described herein.

[0049] The stator 3a comprises a plurality of stator coils regularly distributed around the X axis of rotation and arranged opposite the magnetic poles 52, that is to say that the stator coils are arranged orthogonally to the X axis of rotation, so that each stator coil can be opposite a magnetic pole 52 for a predetermined angle of rotation of the rotor.

[0050] Each stator coil has a magnetic core 30 formed for example of a stack of magnetic steel sheets, a winding support 36 and a stator winding 34 of a copper wire. Each winding has two ends at the two ends of the copper wire, each end being connected to a different phase of the electrical machine 1, here a three-phase electrical machine.

[0051] The magnetic cores 30 are fixed by gluing to a discoid plate 32, in the shape of a flat disc having a central hole 320, allowing the discoid plate 32 to be inserted between the two cylindrical walls of the housing 21. Indeed, in this embodiment of the invention, the stator coils are not directly fixed to the housing 21 to allow an assembly of the stator coils and the circular buses of the electric machine 1 independently of the other parts of the electric machine 1.

[0052] It is therefore the discoid plate 32 which is fixed directly on a main face 210 of the main wall of the casing 21, this main face being internal to the electrical machine 1. The fixing of the discoid plate 32 to the casing 21 uses threaded studs 82 passing through the main wall of the casing through holes 212 provided for this purpose, and nuts screwed onto these threaded studs 82, the nuts pressing the discoid plate 32 against the main face 210.

[0053] The ends 340 of the stator windings 34 project radially from the stator coils and each has a portion curved in the axial direction, passing through an orifice 326 (orifices 326 are referenced in Figures 2 and 3) in the discoid plate 32. The curved portions of the ends 340 of the stator windings 34 protruding from the discoid plate 32 are welded to the circular bus 7a. This bus is fixed to the discoid plate 32 on the side opposite the stator coils by an overmolding, passing through a recess 218 in the main wall of the housing 21.

[0054] The circular bus 7a is therefore located on the other side of the main face 210 relative to the stator coils.

[0055] A sealed casing 38, enclosing the stator coils over the discoid plate 32, is fixed to the discoid plate 32 by screws 84, 86 (referenced [Fig. 2]). Together with the discoid plate 32, it forms a sealed chamber 9 in which a heat transfer fluid, such as oil, can circulate to cool the stator coils of the stator 3a.

[0056] The sealed chamber 9 here takes the form of a right prism with a flat, crown-shaped base. The sealed casing 38 comprises, around the base of the sealed chamber 9, a first circular ledge distal to the X-axis of rotation of the electrical machine 1, and a second circular ledge proximal to the X-axis of rotation of the electrical machine 1. The screws 84 and 86 pass through these ledges, as does the discoidal plate 32. Openings 214 and 216 allow the heads of the respective screws 84 and 86 to protrude. of the discoidal plate 32 towards the outside of the electrical machine 1, without preventing the discoidal plate 32 from coming into contact with the main face 210 of the housing 21. Of course, other methods of attaching the sealed enclosure 38 are conceivable, and the sealed enclosure 38 can take slightly different forms from that shown in this embodiment of the invention. It is also possible to provide several sealed enclosures, each enclosing separate stator coils of the same stator.

[0057] Figure 2 now describes a module 37 comprising the stator coils of stator 3a, the circular bus 7a, the discoid plate 32 and the sealed enclosure 38, this module 37 being assembled independently of the rest of the electrical machine 1.

[0058] Of course, this [Fig. 2] is schematic; it shows a cross-section along an axial plane (passing through the axis of rotation X) of a stator coil within the sealed enclosure 38, fixed to the discoid plate 32, to which the bus 7a is also attached. Four winding ends are shown to illustrate the connection of the winding ends to the circular bus, but it is quite clear that each stator coil has only two winding ends.

[0059] In Figure 2, it is more clearly visible that the sealed casing 38 comprises an external cylindrical partition 380, distal to the central hole 320 of the discoid plate 32, an internal cylindrical partition 382, ​​proximal to the central hole 320 of the discoid plate 32, and a membrane 384 connecting the two external cylindrical partitions 380 and internal cylindrical partitions 382 over the stator coils. The sealed casing 38 is made of a synthetic material (plastic), for example, a polymer, the membrane 384 being thinner than the external cylindrical partitions 380 and internal cylindrical partitions 382 to limit the size of the air gap between the stator 3a and the rotor 5.

[0060] In order to ensure the sealing of the sealed chamber 9 formed by the discoid plate 32 and the sealed envelope 38, an annular sealing gasket 388 is axially pressed between the external cylindrical partition 380 and the discoid plate 32, and an annular sealing gasket 386 is axially pressed between the internal cylindrical partition 382 and the discoid plate 32.

[0061] The sidewalks bordering the external cylindrical partitions 380 and internal partitions 382 each have several holes 322, 324 in which are integrated inserts for screwing the screws 84, 86 respectively into these inserts through the discoid plate 32.

[0062] The ends 340 of the stator windings visible here include, in particular:

[0063] - a winding end 348, electrically connected to a circular conductor bar 78 of the circular bus 7a. This circular conductor bar 78 is, for example, intended to form a neutral phase of the electrical machine 1.

[0064] - one end 346 of the winding, electrically connected to a conductive bar circular 76 of the circular bus 7a. This circular conductor bar 76 is, for example, intended to form a first phase of the electrical machine 1.

[0065] - a winding end 344, electrically connected to a circular conductive bar 74 of the circular bus 7a. This circular conductive bar 74 is, for example, intended to form a second phase of the electrical machine 1.

[0066] - and a winding end 342, electrically connected to a circular conductive bar 72 of the circular bus 7a. This circular conductive bar 72 is, for example, intended to form a third phase of the electrical machine 1.

[0067] The winding ends 348, 346, 344, 342 each pass through a separate orifice 326 in the discoid plate 32 to connect to the respective circular conductive bar 78, 76, 74 or 72. Each of these winding ends has, for example, a metal fork welded to one end of the copper wire of the corresponding winding, the fork clipping onto the circular conductive bar to which the winding end is to be electrically connected, and then the electrical connection is made by a weld.

[0068] Alternatively, the circular conductor bars themselves have such forks, regularly spaced along the conductor bars, to clip onto the ends of the windings. This variant, however, requires adjusting the position of the forks relative to the holes 326. An example of such forks integrated into a circular bus is illustrated [Fig. 2] in patent application number FR2213114.

[0069] Figure 3 now shows, in ortho-radial section just below the membrane 384, the stator coils fixed to the discoid plate 32, itself fixed to the housing 21. In this Figure 3, the stator coils are not fully drawn to simplify the figure. Only three stator coils are fully drawn, for which are visible their winding supports 36, their magnetic cores 30 drawn with dashed lines, as well as the ends of the windings 342, 344, 346, 348 protruding from the winding supports 36.

[0070] The plurality of orifices 326 through which the ends of the windings 340 pass is regularly distributed on the stator plate 32 and in the sealed chamber 9, around the axis of rotation X of the electric machine 1. Each orifice 326 is dedicated to one end of winding, but alternatively wider orifices can be provided allowing, for example, both ends of the same stator winding to pass through at the same time.

[0071] Furthermore, in this embodiment of the invention, the circular conductive bars 72, 74, 76, 78 are nested within each other in that order. Consequently, the openings 326 through which the winding ends 348 pass are further from the X axis of rotation than the openings 326 through which the winding ends 346 pass. These latter orifices 326 are themselves further from the X-axis of rotation than the orifices 326 through which the winding ends 344 pass, and these other latter orifices 326 are themselves further from the X-axis of rotation than the orifices 326 through which the winding ends 342 pass. This facilitates the connection of the end forks 340 to the circular bus 7a.

[0072] Alternatively, especially if the forks are carried by the circular bus, the conductive bars of the latter are for example superimposed and the orifices 326 are all at the same distance from the X axis of rotation.

[0073] Two openings, 92 and 94, located between stator coils, are provided on the discoidal plate 32 in the sealed chamber 9. Opening 92 corresponds to a heat transfer fluid inlet and opening 94 to a heat transfer fluid outlet. These two openings are almost diametrically opposed to ensure even distribution of the heat transfer fluid. Of course, more than two openings can be provided if more than one heat transfer fluid inlet or outlet is required, and depending on the configuration of the sealed casing 38, which can, for example, be closed between two stator coils. In other variations, these two openings, 92 and 94, are located between the external cylindrical partition 380 and the stator coils.

[0074] Furthermore, four screws 84 pass through the first ledge of the watertight casing 38 to fix it to the discoid plate 32, being regularly spaced along this first ledge. This ledge is radially delimited by the external cylindrical partition 380 on one side and by a first edge 327 of the watertight casing 38 on the other.

[0075] Similarly, four screws 86 pass through the second ledge of the watertight casing 38 to fix it to the discoid plate 32, being regularly spaced along this second ledge. This ledge is radially delimited by the internal cylindrical partition 382 on one side and by a second edge 325 of the watertight casing 38 on the other.

[0076] Figure 4 now shows the external face of the main wall of the housing 21, in which the module 37 is mounted. Since the circular bus 7a is overmolded onto the discoid plate 32, the overmolding 70a is visible in this figure 4, passing through the recess 218 of the housing 21. This recess 218 is essentially the same shape as the overmolding 70a. As the circular bus 7a is not closed, the main wall of the housing 21 is a single piece.

[0077] Phase connections 73 pass through the overmolding 70a and allow the phases of the electrical machine 1 to be connected to an inverter, and also allow access to the neutral phase of the electrical machine 1.

[0078] Finally, the casing 21 has openings 920 and 940 superimposed on the respective openings 92 and 94 for the inlet and outlet of the heat transfer fluid, in order to supply the sealed chamber 9 with heat transfer fluid, and to draw this heat transfer fluid from the sealed chamber 9.

[0079] A method for mounting 100 of the axial flux electric machine 1 is now described in relation to figures 5 and 6.

[0080] A first step 110 of the assembly process 100 is the attachment of the stator coils to the discoid plate 32 by inserting each end 340 of the stator windings 34 through the corresponding openings 326. The stator coils are attached by bonding the magnetic cores 30 to the discoid plate 32. Alternatively, other types of attachment are used, for example, by welding.

[0081] A second step 120 of the assembly process 100 is the fixing of the watertight envelope 38 onto the discoid plate 32. This step involves positioning the inserts of the sidewalks of the watertight envelope 38, opposite the openings 322, 324, and then screwing the screws 82, 84 into these inserts through the openings 322 and 324 respectively.

[0082] A third step 130 of the assembly process 100 is the connection of the circular bus 7a to the ends 340 of the stator windings 34. For this, the forks at the ends 340 of the stator windings are clipped onto their corresponding circular conductive bars, and then solder joints are made to secure these connections. At the end of the third step 130, the module 37 is obtained.

[0083] A fourth step 140 of the assembly process 100 is to verify the correct electrical operation of the stator 3a by supplying power to the circular bus 7a. If this electrical test confirms that the stator 3a is functioning correctly, then the next step 150 is to overmold the electrical bus 7a onto the discoid plate 32, which protects the mechanical structure of the circular bus 7a and its connections. The phase connections 73 protrude from the overmolding 70a obtained during this step 150.

[0084] The step following the overmolding step 150 is a leak-tight connection step 160 of an oil circuit to the sealed chamber 9 of the stator 3a using the openings 92, 94 in the discoid plate 32. This step 160 is followed by a leak-tightness check step 170 of the sealed chamber 9 formed by the discoid plate 32 and by the sealed envelope 38.

[0085] If this test carried out in step 170 concludes that the sealed chamber 9 is watertight, then the next step 180 is the fixing of the discoid plate 32 on the main face 210 of the housing 21.

[0086] Similar steps are carried out in parallel to mount the stator 3b in the housing 22. Then the housings 21 and 22 are mounted on either side of the rotor 5 fixed to the rotor shaft 4, and are fixed to each other.

[0087] Alternatively, the method for assembling the electrical machine omits step 140 and / or steps 160 and 170. In other variants, the order of the steps differs; for example, the circular bus 7a is attached to the winding ends 340 after the discoid plate 32 is fixed to the housing 21, or the sealing enclosure 38 is fixed to the discoid plate 32 takes place after the circular bus 7a is fixed to the winding ends 340, and / or after the discoid plate 32 is fixed to the housing 21.

[0088] 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 features of different embodiments can be combined to carry out the invention, provided that these embodiments are not incompatible with each other.

Claims

Claims

1. Axial flux electric machine (1) comprising: - a rotor shaft (4), - a rotor (5) secured to the rotor shaft (4), comprising a plurality of magnetic poles (52) arranged around the rotor shaft (4), - at least one stator (3 a, 3 b) comprising a plurality of stator coils comprising stator windings (34) and arranged opposite the plurality of magnetic poles (52), - a circular bus (7a, 7b) connected to ends (340) of the stator windings (34), - at least one casing (21, 22) housing the stator (3a, 3b), the stator coils being secured to a main face (210) of the casing (21, 22), the main face (210) comprising a passage orifice (215) for the rotor shaft (4), the axial flux electrical machine (1) being characterized in that the circular bus (7a, 7b) is arranged on the side opposite the stator coils relative to the main face (210) of the casing (21, 22).

2. An axial flux electrical machine (1) according to claim 1, wherein the main face (210) of the casing (21, 22) comprises at least one recess (214) allowing at least one end (342, 344, 346, 348) of one of the stator windings (34) to pass through.

3. An axial flux electrical machine (1) according to claim 1 or 2, wherein the circular bus (7a, 7b) is at least partly overmolded onto the casing (21, 22) on the external side of the electrical machine (1).

4. An axial flux electrical machine (1) according to claim 1 or 2, wherein the electrical machine (1) comprises a discoidal plate (32) comprising a central hole (320), and the stator coils are fixed to the discoidal plate (32) itself attached to the main face (210) of the casing (21, 22), the discoidal plate (32) comprising around the central hole (320), a plurality of orifices (326) allowing the ends (340) of the stator windings (34) to pass towards the outside of the electrical machine (1).

5. An axial flux electrical machine (1) according to claim 4, wherein the stator (3a, 3b) comprises a sealed casing (38) fixed to the discoid plate (32), the stator coils being housed between the discoid plate (32) and the sealed casing (38), the plurality of orifices (326) opening into the sealed casing (38).

6. An axial flux electrical machine (1) according to claim 5, wherein the circular bus (7a, 7b) is attached to the discoid plate (32) on the side opposite the stator coils, through the recess (214).

7. An axial flux electrical machine (1) according to claim 6 in which the circular bus (7a, 7b) is at least partially overmolded onto the discoid plate (32).

8. Method of mounting (100) an axial flux electric machine (1) according to claims 4 to 6, comprising steps of: - fixing (110) the stator coils on the discoid plate (32), the ends (340) of the stator windings (34) being inserted through the plurality of orifices (326), - fixing (120) of the waterproof envelope (38) on the discoid plate (32), - connection (130) of the circular bus (7a, 7b) to the ends (340) of the stator windings (34), and - fixing (180) of the discoid plate (32) on the main face (210) of the casing (21, 22).

9. Method of mounting (100) an axial flux electrical machine (1) according to claim 8, in which the step of fixing (180) the discoid plate (32) on the main face (210) of the casing (21, 22) is preceded by a step of verifying (140) the correct electrical operation of the stator (3 a, 3b) by electrically supplying the circular bus (7a, 7b).

10. Method of mounting (100) an axial flux electric machine (1) according to claim 9, in which the step of fixing (180) the discoid plate (32) on the main face (210) of the casing (21, 22) is preceded, in the following order: - a step of overmolding (150) the circular bus (7a, 7b), implemented after the step of verifying (140) the correct electrical operation of the stator (3a, 3b), - a step of connecting (160) an oil circuit to the discoid plate (32) using openings (92, 94) provided for this purpose in the discoid plate (32), and - a step of verifying (170) the sealing of a sealed chamber (9) formed by the discoid plate (32) and by the sealed envelope (38).

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