Axial flux electric machine and corresponding mounting method

Abstract

Axial Flux Electric Machine and Corresponding Mounting Method The invention relates to an axial flux electric machine (1) comprising: - a rotor (5) having a plurality of magnetic poles (52) arranged around a rotor shaft (4), - at least one stator (3a, 3b) of which a plurality of stator coils having stator windings (34) are 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 housing (21, 22) housing the stator (3a, 3b), the stator coils being fixed to a main face (210) of the housing (21, 22), the main face (210) having a passage (215) for the rotor shaft (4), the circular bus (7a, 7b) being arranged on the side opposite the stator coils relative to the main face (210) of the housing (21, 22). (Figure 1)

Description

Title of the invention: Axial flux electric machine and corresponding assembly 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, that is to say 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] In order to reduce the size of such a motor used for the traction or propulsion of an electric vehicle, it is envisaged to use, instead of a radial flux electric machine, an axial flux electric machine. This type of machine is in fact generally more compact at least in one axial direction corresponding to the axis of rotation of the machine, which gives it a discoid appearance.

[0004] Such a machine therefore comprises a casing of overall cylindrical shape housing at least one stator comprising stator coils, and a rotor fixed to a rotating shaft passing through the casing in its middle. The stator coils are fixed in the casing between an internal cylindrical wall delimiting a bearing support for the rotating shaft, and an external cylindrical wall. These stator coils are arranged angularly all around the internal cylindrical wall, opposite the magnetic poles of the rotor.

[0005] To electrically connect the stator coils to phase connections of the machine, intended to be connected to an inverter, the ends of a stator winding of each stator coil are first welded to a circular bus, for example three-phase, arranged between the stator coils on the one hand and one of the internal or external cylindrical walls of the casing on the other hand. Then electrical connections to the circular bus are made to exit from the casing, either through the external cylindrical wall or through a flat wall of the casing through which the rotating shaft exits.

[0006] The assembly of such an electrical machine is complex and expensive, in particular because accessibility to the ends of the stator windings for connecting them and then soldering them to the circular bus is reduced. The space available for approaching the connection and soldering tools is even more reduced when the stator coils are surrounded by a cooling system.

[0007] The present invention at least partially overcomes the drawbacks of the prior art by providing an axial flux electric machine in which the bus circular is arranged on an external face of the casing of the electric machine. Thus the connection and soldering of the ends of the stator windings to the circular bus is much simpler.

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

[0009] By circular bus is meant here circular connection means, comprising several conductive rings (circular conductive bars) not necessarily closed, each conductive 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 electrical machine according to the invention comprises, for example, two stators arranged on either side of the rotor, each stator being housed in a casing of generally cylindrical shape open on the rotor side, the two casings being fixed to each other to protect the rotor and the stators from the external environment. Alternatively, the axial flux electrical machine according to the invention comprises a single stator, the casing then closing by fixing a cover to a generally cylindrical external wall of the casing enclosing the stator and the rotor.

[0011] The casing 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 secured, therefore internal to the casing, and an opposite external face on which the circular bus is arranged or through which the circular bus projects, depending on the embodiments of the invention.

[0012] The circular bus is preferably three-phase but in variants comprises more or fewer phases. It is preferably arranged around the passage orifice of the rotor shaft at a central portion of the main wall, or in a variant the circular bus is arranged at a peripheral portion of this main wall, distal to the passage orifice of the rotor shaft. The arrangement of the circular bus at the central portion makes it possible to have a circular bus of smaller dimensions. and therefore save its material, 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 take for example the form of conductive bars arranged circularly and superimposed parallel to the axis of the machine, or on the contrary nested within each other orthogonally to the axis of the machine, 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 allowing 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 stated, 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 a 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 a characteristic of the invention, the main face of the casing comprises at least one recess allowing at least one end of one of the stator windings to pass through.

[0017] When the circular bus is fixed on the main wall of the casing, preferably several recesses are provided on this wall of the casing, to allow all the ends of the stator windings to pass through, except possibly those connected to a neutral phase of the machine. Having several recesses rather than just one reinforces the rigidity of the main wall of the casing.

[0018] In one embodiment of the invention, the circular bus is overmolded at least in part onto the casing on the external side of the electrical machine. This overmolding is made of electrically insulating material, and makes it possible to mechanically protect the circular bus while limiting electrical risks. Only phase connections emerge from the overmolding, to allow the electrical machine to be electrically connected to an inverter.

[0019] In another embodiment of the invention, the electrical machine comprises a discoid plate comprising 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 comprising around the central hole, a plurality of orifices allowing the ends of the stator windings to pass towards the outside of the electrical machine.

[0020] The discoid plate is flat at least at the level of the attachment of the active parts of the machine (i.e. the stator coils) directly onto this discoid plate, which is for example made of steel. Contact between the active parts and the discoid plate is thus easier to ensure, especially since the discoid plate, when made of steel, has better rigidity than the casing which is often made of aluminum or plastic. The active parts are fixed onto the discoid plate for example by gluing, fitting (if the plate has grooves or ribs complementary to the cores of the stator coils) or screwing. In an alternative embodiment, the discoid plate is a stator yoke formed from 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 envelope makes it possible to send a heat transfer liquid, for example oil, into a sealed chamber formed by the sealed envelope and the discoid plate, in order to cool the stator windings. The oil enters the sealed chamber and leaves it, through openings provided for this purpose in the main wall of the casing and in the discoid plate. These openings may correspond to orifices provided to allow passage from the ends of the stator windings to the circular bus arranged 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 casing, in this other embodiment of the invention, the circular bus is preferentially fixed to the discoid plate. This fixing to the discoid plate makes it possible to limit the dispersions 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, because the manufacturing tolerances of the circular plate are more easily controlled than those of the casing. The recess is therefore of dimensions substantially identical to those of the circular bus. If the latter is closed, the main wall of the casing is then made in two parts, the joining of these two parts being carried out by means of the discoid plate.

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

[0026] In the other embodiment of the invention, the circular bus is for example overmolded at least in part on the discoid plate. The overmolding of the circular bus mechanically protects the circular bus, contributes to electrical safety and makes it possible to form a sealed chamber for the stator windings intended to be immersed in a heat transfer fluid. Indeed, these stator windings are surrounded by the sealed envelope on the one hand and the discoid plate comprising the plurality of orifices on the other hand. The overmolding of the circular bus makes it possible to prevent the heat transfer fluid from leaking through these orifices, when these do not form an inlet or an outlet intended to bring or withdraw the heat transfer fluid from the sealed chamber.

[0027] In addition, this other embodiment makes it possible to assemble together the active parts of the machine as well as its sealed casing, in the form of a module to be subsequently assembled in the casing of the electric machine. This makes it possible, before this last assembly, to test the correct operation of the active parts as well as the sealing of the sealed chamber, without having to first assemble the entire machine and then disassemble it in the event of an inconclusive test. Finally, this module can be assembled on different axial flux electric machines.

[0028] Of course, other embodiments are conceivable, in particular in the embodiment in which the circular bus is fixed to the casing, it is also preferable to provide a sealed envelope around the active parts of the stator, which makes it possible to cool it without generating friction losses at the rotor. In all these embodiments, the production of such a sealed envelope clutters the central part of the stator and hinders the integration of a circular bus there. The axial flux machine according to the invention makes it possible to overcome this drawback.

[0029] The invention also relates to a method of mounting an axial flux electric machine according to the invention, comprising steps of: - fixing the stator coils on the discoid plate, the ends of the stator windings being inserted through the plurality of orifices, - fixing the waterproof envelope on the discoid plate, - connection of the circular bus to the ends of the stator windings, and - fixing the discoid plate on the main face of the casing.

[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 method according to the invention are preferably carried out in the order indicated above, which makes it possible to assemble the “active parts-disco plate-circular bus-sealed casing” module independently of the rest of the electrical machine.

[0032] This allows in particular that the step of fixing the discoid plate on the face main casing is preceded by a step of checking the correct electrical operation of the stator by electrical supply of the circular bus.

[0033] In this case, preferably, the step of fixing the discoid plate on the main face of the casing is preceded, in the following order: - a step of overmolding the circular bus, implemented after the step of verifying the correct electrical functioning 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 discoidal plate and by the sealed envelope.

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

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

[0036] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several exemplary embodiments given for informational and non-limiting purposes with reference to the appended schematic drawings on the other hand, in which:

[0037] [Fig-1] schematically represents in axial section a quarter of a machine axial flux electric motor according to the invention, in one embodiment of the invention,

[0038] [Fig.2] schematically represents in axial section a quarter of a pre-module assembled from active parts, a circular bus, a sealed casing and a discoidal plate of the axial flux electric machine of [Fig.l],

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

[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 of a method of mounting the axial flux electric machine of [Fig.l], in one embodiment of the invention, and

[0042] [Fig.6] is a schematic representation of early stages of the process of assembly of [Fig.5].

[0043] According to an embodiment of the invention shown in [Fig.l], an axial flux electrical 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 external cylindrical wall, and an internal cylindrical wall, the latter providing a space 215 for the passage of a rotor shaft 4 of the electrical 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 secured on the one hand to the casing 2 and on the other hand to the rotor shaft 4.

[0044] In this application, an “axial” orientation therefore refers to an orientation along the X axis of the electrical machine 1 while an ortho-radial orientation refers to an orientation orthogonal to the X axis of the electrical machine 1. The section in [Fig.l] is therefore made in a plane comprising the X axis of the electrical machine 1. Only the part above the rotor shaft 4 is shown schematically.

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

[0046] The casing 2 houses a rotor 5, secured to the rotor shaft 4 and comprising a plurality of magnetic poles 52 arranged around the rotor shaft 4. More precisely, the rotor 5 takes the form of a disc with a hole in its center so as to allow the passage of the rotor shaft 4. The latter comprises a shoulder against which a hub of the rotor is pressed, a ring being screwed, by means of bolts 80, on the other side of the rotor in the shoulder to grip the hub and thus secure the rotor 5 to the rotor shaft 4.

[0047] The hub is for example 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 between them magnetic poles 52. 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 hoop 53 around the star structure 51 and the magnetic poles 52 makes it possible to maintain 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 comprising active parts or stator coils. The stators 3a, 3b respectively comprise a circular bus 7a, 7b to which their respective stator coils are electrically connected, these circular buses 7a, 7b making it possible to electrically connect the electrical machine 1 to one or more inverters. The two stators 3a, 3b being structurally identical, only the stator 3a is now described.

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

[0050] Each stator coil comprises 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 both 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 form of a flat disc comprising a central hole 320, allowing the discoid plate 32 to be inserted between the two cylindrical walls of the casing 21. Indeed, in this embodiment of the invention, the stator coils are not directly fixed to the casing 21 to allow an assembly of the stator coils and the circular buses of the electrical machine 1 independently of the other parts of the electrical machine 1.

[0052] It is therefore the discoid plate 32 which is fixed directly to 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 orifices 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 comprise a portion curved in the axial direction, passing into an orifice 326 (the orifices 326 are referenced in FIGS. 2 and 3) of the discoid plate 32, therefore through the latter. The curved portions of the ends 340 of the stator windings 34 emerging from the discoid plate 32 are welded to the circular bus 7a. The latter 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 casing 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 envelope 38 surrounding the stator coils over the discoid plate 32 is fixed to the discoid plate 32 by screws 84, 86 (referenced [Fig.2]). It makes it possible to form, with the discoid plate 32, a sealed chamber 9 in which a heat transfer liquid 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 whose base is in the form of a flat crown. The sealed envelope 38 comprises around the base of the sealed chamber 9, a first circular sidewalk distal to the axis X of rotation of the electric machine 1, and a second circular sidewalk proximal to the axis X of rotation of the electric machine 1, the screws 84, 86 passing through these sidewalks as well as the discoid plate 32. Orifices 214, 216 allow the heads of the respective screws 84, 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 casing 21. Of course, other methods of fixing the sealed envelope 38 are conceivable, and the sealed envelope 38 can take shapes slightly different from that presented in this embodiment of the invention. It is also possible to provide several sealed envelopes each enveloping distinct stator coils of the same stator.

[0057] [Fig.2] now describes a module 37 comprising the stator coils of the stator 3a, the circular bus 7a, the discoid plate 32 and the sealed casing 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 in section along an axial plane (passing through the axis of rotation X) a stator coil in the sealed casing 38 fixed on the discoid plate 32 on which the bus 7a is also fixed. Four winding ends can be seen there to illustrate the connection of the winding ends to the circular bus but it is quite obvious that each stator coil has only two winding ends.

[0059] In this [Fig.2], it appears more visibly that the sealed envelope 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 382 over the stator coils. The sealed envelope 38 is made of synthetic material (plastic) for example polymer, the membrane 384 being thinner than the external cylindrical partitions 380 and internal 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 casing 38, an annular seal 388 is pressed axially between the external cylindrical partition 380 and the discoid plate 32, and an annular seal 386 is pressed axially between the internal cylindrical partition 382 and the discoid plate 32.

[0061] The sidewalks bordering the external 380 and internal 382 cylindrical partitions respectively each comprise several orifices 322, 324 in which inserts are integrated 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 comprise in particular:

[0063] - a winding end 348, electrically connected to a conductive bar circular 78 of the circular bus 7a. This circular conductive 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 conductive bar 76 is for example intended to form a first phase of the electrical machine 1.

[0065] - one end 344 of the winding, electrically connected to a conductive bar circular 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 conductive bar circular 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 of the discoid plate 32 to connect to the respective circular conductive bar 78, 76, 74 or 72. Each of these winding ends comprises, for example, a metal fork welded to one end of the copper wire of the corresponding winding, the fork being clipped onto the circular conductive bar to which the winding end is to be electrically connected, then the electrical connection is ensured by welding.

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

[0069] [Fig. 3] now shows in ortho-radial section just under the membrane 384, the stator coils fixed on the discoid plate 32 itself fixed to the casing 21. In this [Fig. 3], the stator coils are not fully drawn to simplify the figure. Only three stator coils are fully drawn, for which their winding supports 36 are visible, their magnetic cores 30 drawn in dotted lines as well as the ends of the windings 342, 344, 346, 348 projecting 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 electrical machine 1. Each orifice 326 is dedicated to one end of the winding, but as a variant, wider orifices can be provided allowing the two ends of the same stator winding to pass through at the same time, for example.

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

[0072] As a variant, in particular if the forks are carried by the circular bus, the conductive bars thereof are for example superimposed and the orifices 326 are all at the same distance from the axis X of rotation.

[0073] Two openings 92 and 94, located between stator coils, are provided on the discoid plate 32 in the sealed chamber 9, the opening 92 corresponding to a heat transfer liquid inlet and the opening 94 to a heat transfer liquid outlet. These two openings are almost diametrically opposed to properly distribute the heat transfer liquid. Of course, more than two openings can be provided if more than one heat transfer liquid inlet or outlet are provided, and depending on the configuration of the sealed casing 38, which can for example be closed between two stator coils. In other variants, these two openings 92, 94 are located between the external cylindrical partition 380 and the stator coils.

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

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

[0076] [Fig. 4] now shows the external face of the main wall of the casing 21, in which the module 37 is mounted. The circular bus 7a being overmolded on the discoid plate 32, the overmolding 70a appears in this [Fig. 4], passing through the recess 218 of the casing 21, this recess 218 being generally of the same shape as the overmolding 70a. The circular bus 7a not being closed, the main wall of the casing 21 is in a single part.

[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 to access the neutral phase of the electrical machine 1.

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

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

[0080] A first step 110 of the assembly method 100 is the fixing of the stator coils on the discoid plate 32, by inserting each of the ends 340 of the stator windings 34 through the corresponding orifices 326. The fixing of the stator coils is carried out by gluing the magnetic cores 30 on the discoid plate 32. Alternatively, other types of fixing are used, for example by welding.

[0081] A second step 120 of the assembly method 100 is the fixing of the sealed envelope 38 on the discoid plate 32. This step comprises the positioning of the inserts of the sidewalks of the sealed envelope 38, facing the orifices 322, 324, then the screwing of the screws 82, 84 into these inserts through the orifices 322 and 324 respectively.

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

[0083] A fourth step 140 of the assembly method 100 is the verification of the correct electrical operation of the stator 3a by electrically supplying the circular bus 7a. If this electrical test concludes that the stator 3a is working correctly, then the next step is a step 150 of overmolding the electrical bus 7a onto the discoid plate 32, which makes it possible to protect 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 step 160 of sealingly connecting an oil circuit to the sealed chamber 9 of the stator 3a using the openings 92, 94 in the discoidal plate 32. This step 160 is followed by a step 170 of checking the sealing of the sealed chamber 9 formed by the discoidal plate 32 and by the sealed casing 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 casing 21.

[0086] Similar steps are carried out in parallel to mount the stator 3b in the casing 22. Then the casings 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 mounting the electrical machine does not include step 140 and / or steps 160 and 170. In other alternatives, the order of the steps differs, for example the circular bus 7a is fixed to the ends 340 of the winding after fixing the discoidal plate 32 on the casing 21, or the fixing of the sealed casing 38 to the discoid plate 32 takes place after the circular bus 7a has been fixed to the winding ends 340, and / or after the discoid plate 32 has been fixed to the casing 21.

[0088] The invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the characteristics of different variant embodiments can be combined to achieve the invention, provided that these variants are not incompatible with each other.

Claims

Claims

1. An axial flux electrical 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 (3a, 3b) 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) of the rotor shaft (4), the axial flux electric 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, in which 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 for mounting (100) an axial flux electrical 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) the sealed casing (38) on the discoid plate (32), - connecting (130) the circular bus (7a, 7b) to the ends (340) of the stator windings (34), and - fixing (180) 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 (3a, 3b) by electrically supplying the circular bus (7a, 7b).

10. Method for mounting (100) an axial flux electrical machine (1) according to claim 9, in which the step of fixing (180) the discoidal plate (32) on the main face (210) of the casing (21, 22) is preceded, in the following order: - by 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), - by a step of connecting (160) an oil circuit to the discoidal plate (32) using openings (92, 94) provided for this purpose in the discoidal plate (32), and - by a step of verifying (170) the sealing of a sealed chamber (9) formed by the discoidal plate (32) and by the sealed casing (38).

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