Axial flux rotary electric machine

Abstract

The invention relates to an electric machine (1) intended to be attached to the rear of a reduction device (2) and including: - a stator (16) comprising a support structure (25), a plurality of teeth (19) supported by the support structure (25) and coils (22); - a rear rotor (18) and a front rotor (17) which are arranged axially on either side of the stator (16) and which are constrained to rotate with a rotor shaft (8); and - a half-casing (9) intended to be attached to a bell housing (4) of the reduction device (2); the electric machine (1) including a rear roller bearing (43) positioned between a rear portion of the rotor shaft (8) and the half-casing (9), the rotor shaft (8) including a front portion which is intended to be guided in rotation by a front roller bearing (42) intended to be supported by the reduction device (2), the support structure (25) being made of an electrically insulating material.

Description

Description Title of the invention: Axial flux rotating electric machine Technical field

[0001] The invention relates to an axial flux rotating electrical machine, in particular for an electric or hybrid vehicle, as well as an assembly comprising a reduction device and an axial flux rotating electrical machine.

[0002] The invention relates more particularly to an axial flux rotating electrical machine comprising a stator and two rotors arranged axially on either side of the stator. Technological background

[0003] Document US20220368202 discloses an axial flux rotating electrical machine comprising a stator and two rotors arranged axially on either side of the stator. The stator comprises a plurality of coils which are distributed around the X axis and which are mounted on a support structure. The stator support structure is configured to guide the rotors in rotation. To do this, two rolling bearings are respectively interposed between the stator support structure and each of the rotors. In order to have sufficient mechanical strength for guiding the rotors in rotation while limiting eddy current losses, the support structure is made of a steel alloy having a high electrical resistance.

[0004] Such an electrical machine is not fully satisfactory, particularly since the eddy current losses in the support structure remain significant. Summary of the invention

[0005] An idea underlying the invention is to propose an axial flux rotating electrical machine comprising a stator and two rotors arranged axially on either side of the stator and in which eddy current losses are further limited.

[0006] Another idea underlying the invention is to propose an axial flux rotating electrical machine of the aforementioned type which is particularly simple to manufacture, compact and / or allows the stator coils to be cooled effectively.

[0007] According to a first aspect, the invention provides an electrical machine intended to be fixed to the rear of a reduction device and comprising: - a stator comprising a support structure having an annular shape centered around an axis X, a plurality of teeth distributed around the axis X and supported by the support structure and coils which comprise a winding and which are carried by the teeth; - a rear rotor and a front rotor which are arranged axially on either side of the stator and which are integral in rotation with a rotor shaft which is mobile in rotation around the X axis, said rotor shaft passing through the support structure and comprising a front portion which is intended to be coupled to a gear system of the reduction device; and - a half-casing intended to be fixed to a bell of the reduction device and configured to form with said bell a housing space in which the stator, the front rotor and the rear rotor are housed; the support structure being fixed to said half-casing; said electrical machine being remarkable in that: - it comprises a rear rolling bearing interposed between a rear portion of the rotor shaft and the half-casing; - the front portion of the rotor shaft is intended to be guided in rotation by a front rolling bearing intended to be carried by the reduction device; and - the support structure is made of an electrically insulating material.

[0008] Thus, since the rotor shaft is guided in rotation, on the one hand, by the half-casing and, on the other hand, by the reduction device, the stator support structure no longer has to perform a function of guiding said rotor shaft. Said support structure can thus be made of a material that is less mechanically resistant than a metal and, more particularly, an electrically insulating material. Eddy current losses in the stator are thus further limited.

[0009] According to embodiments, such an electric machine may comprise one or more of the following characteristics.

[0010] According to one embodiment, the support structure is made of a polymer material.

[0011] According to one embodiment, the polymer material is chosen from polyamides, in particular long-chain polyphthalamides and polyamides 6.6, polyethersulfones and polyphenylene sulfides. The polymer material may be reinforced with fibers, in particular glass fibers.

[0012] According to one embodiment, the front rolling bearing is fitted onto the front portion of the rotor shaft and is intended to be arranged radially inside a housing provided in the bell.

[0013] According to another embodiment, not shown, the gear system of the reduction device comprises an input shaft, the front rolling bearing being fitted onto said input shaft, the front portion of the rotor shaft being rotationally coupled to the input shaft and guided in rotation by the latter.

[0014] According to one embodiment, the support structure comprises a front flange and a rear flange which are fixed to each other and between which the teeth of the stator are held.

[0015] According to one embodiment, each of the front and rear flanges comprises a flank having a radial orientation, said flanks having impressions each receiving by interlocking in shape an axial end of one of the teeth.

[0016] According to one embodiment, the support structure comprises an inner periphery which is spaced from the rotor shaft by a radial gap which is devoid of a rolling bearing.

[0017] According to one embodiment, the electrical machine comprises an interconnector which is housed in the support structure and which comprises four conductive traces (U, V, W and neutral), said conductive traces connecting, on the one hand, the windings of the coils to each other and, on the other hand, connecting them to a connector intended to be connected to an electrical circuit of a vehicle.

[0018] According to one embodiment, the interconnector is housed in a housing provided in the rear flange which projects radially rearward relative to the side of the rear flange and is arranged radially outside the rear rotor.

[0019] According to one embodiment, the support structure comprises an external periphery which carries two sealing O-rings intended to cooperate with the bell of the reduction device so as to provide between said external periphery and the bell, a sealed annular chamber intended to receive a fluid of cooling, the outer periphery further comprising a plurality of spray orifices which are distributed circumferentially around the X axis and which open radially opposite the stator coils. Thus, the structure of the cooling fluid circuit is particularly simple and space-saving.

[0020] According to one embodiment, the rear rotor comprises a support disc comprising an external portion and an internal coupling portion, the external portion carrying a plurality of permanent magnets distributed around the X axis and being positioned axially opposite the stator, the internal coupling portion being rotationally coupled to the rotor shaft and being offset forwards relative to the external portion.

[0021] According to one embodiment, the internal coupling portion of the rear rotor support disc is arranged radially inside the stator.

[0022] According to one embodiment, the rear rolling bearing is arranged radially inside the outer portion.

[0023] According to one embodiment, the front rotor comprises a support disc comprising an external portion and an internal coupling portion, the external portion carrying a plurality of permanent magnets distributed around the X axis and being positioned axially opposite the stator, the internal coupling portion being rotationally coupled to the rotor shaft and being offset rearwardly relative to the external portion.

[0024] According to one embodiment, the internal coupling portion of the front rotor support disc is arranged radially inside the stator.

[0025] According to one embodiment, the front rolling bearing is arranged radially inside the outer portion of the front rotor support disc.

[0026] According to a second aspect, the invention provides an assembly comprising an electric machine of the aforementioned type as well as a reduction device comprising a bell which is fixed to the half-casing of the electric machine and which defines with the half-casing the housing space in which the stator, the front rotor and the rear rotor are housed.

[0027] According to an embodiment of the second aspect mentioned above, the reduction device comprises a bell which is fixed to the half-casing of the electric machine and defines with the half-casing the housing space in which the stator, the front rotor and the rear rotor are housed, the bell comprising a cooling fluid inlet which opens into the sealed annular chamber and a cooling fluid outlet which is in fluid communication with the sealed annular chamber. Brief description of the figures

[0028] The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly during the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes, with reference to the accompanying drawings.

[0029] [fig.1] Figure 1 is a rear perspective view of an assembly comprising an electric machine and a reduction device.

[0030] [fig.2] Figure 2 is a sectional view of the assembly of Figure 1.

[0031] [fig.3] Figure 3 is a front perspective view of the electric machine of Figure 1.

[0032] [fig.4] Figure 4 is an exploded view of the electric machine.

[0033] [fig.5] Figure 5 is a partial exploded view of the stator.

[0034] [fig.6] Figure 6 is an exploded view of a stator tooth.

[0035] [fig.7] Figure 7 is an exploded view of the stator. Description of the embodiments

[0036] In the description and the claims, the terms "external" and "internal" as well as the orientations "axial" and "radial" will be used to designate, according to the definitions given in the description, elements of the electrical machine and of the reduction device. By convention, the axis X of rotation of the rotors defines the "axial" orientation. The terms "external" and "internal" are used to define the relative position of one element with respect to another, with reference to the axis X. An element close to the axis X is thus qualified as internal as opposed to an external element located radially on the periphery. Furthermore, the terms "rear" and "front", respectively designated by the abbreviations "AR" and "AV" in the figures, are used to define the relative position of one element with respect to another along the axis X.By convention, the electric machine is considered to be arranged at the rear of the reduction device regardless of their relative position with respect to the front and rear of the vehicle for which they are intended.

[0037] In the example described below, the electric machine 1 is a permanent magnet synchronous machine. It can in particular be used as a motor intended to provide propulsion for an electric or hybrid vehicle and / or as a generator for such a vehicle.

[0038] Figure 1 illustrates an assembly comprising an electric machine 1, rotating with axial flux, and a reduction device 2 associated with said electric machine 1. The reduction device 2 comprises a gear system, not shown, making it possible to increase the torque delivered by the electric machine 1 towards the wheels. The reduction device 2 may have a single reduction ratio or several. In the latter case, the reduction device 2 forms a gearbox.

[0039] The reduction device 2 comprises a main enclosure 3 in which the gear system is housed. The reduction device 2 also comprises a bell 4 which projects from the main enclosure 3, towards the electric machine 1 and which is fixed thereto.

[0040] It can be seen in Figure 2 that the bell 4 has an external skirt 5 and a bottom wall 6 separating the interior of the main enclosure 3 from the interior of the bell 4. The bottom wall 6 of the bell 4 has an opening 7 allowing the passage of a rotor shaft 8 of the electrical machine 1 so that it can couple with an input shaft, not shown, of the reduction device 3.

[0041] The electric machine 1 comprises, at the rear, a half-casing 9, which is intended to be fixed to the bell 4 of the reduction device 2. The half-casing 9 comprises a base 10 of radial orientation and a peripheral rim 11 which extends axially from the external edge of the base 10 to the external skirt 5 of the bell 4.

[0042] The half-casing 9 and the bell 4 are fixed to each other by means of fixing members 12, such as fixing screws. The fixing members 12 pass through orifices provided in fixing ears 13, 14 which project radially from the external skirt 5 of the bell 4 and from the peripheral rim 11 of the half-casing 9 and which are regularly distributed around the axis X. The fixing screws are here mounted in threaded orifices provided in the fixing ears 14 of the bell 4.

[0043] In order to ensure the sealing of the housing space defined by the half-casing 9 and the bell 4, an annular seal 15 is interposed between the end of the external skirt 5 of the bell 4 and the end of the peripheral rim 11 of the half-casing 9.

[0044] The electrical machine 1 comprises a stator 16 and two rotors, namely a front rotor 17 and a rear rotor 18, arranged axially on either side of the stator 16. The front rotor 17 and the rear rotor 18 are thus respectively arranged axially opposite the front face and the rear face of the stator 16. The stator 16 as well as the front rotor 17 and the rear rotor 18 are housed inside the housing space defined by the half-casing 9 and the bell 4.

[0045] In relation to Figures 5 to 7, the stator 16 is described below. It comprises a plurality of teeth 19, one of which is shown in Figure 6. Each tooth 19 is here made in two parts 19a, 19b and has at its two ends flanges 20, 21. In the embodiment shown, the two parts 19a, 19b of the tooth 19 are assembled to each other by assembling one or more pins formed in one of the two parts 19a, 19b inside an orifice formed in the other of the two parts 19a, 19b. In a variant not shown, each tooth 19 can be made in a single part, and in this case without the flange 20.

[0046] The teeth 19 are, for example, made from a stack of electrical steel sheets. Alternatively, each tooth 19 is made from soft magnetic composite material, or "Soft Magnetic Composite (SMC)" in English, in particular obtained by sintering.

[0047] In the embodiment shown, each tooth 19 carries a coil 22. Each coil 22 comprises an insulating support 23 which comprises a sleeve fitted onto the tooth 19 and two flanges extending in vertical planes, respectively from one and the other of the two ends of the sleeve. The coils 22 also comprise a winding 24 which is made of wire, for example copper, and is wound around the sleeve of the insulating support 23 between the two flanges. In such an embodiment, the windings 24 are of the concentrated type with one winding 24 per tooth 19.

[0048] In another embodiment, not shown, the windings 24 are of the distributed type, that is to say that each winding 24 is distributed over at least two of the teeth 19 of the stator 16.

[0049] Furthermore, the stator 16 comprises a support structure 25, visible in particular in FIGS. 4 and 7, which has an annular shape. The support structure 25 is made of an electrically insulating material chosen from polymer materials, such as fiber-reinforced polymer materials and in particular glass fibers. The polymers may be chosen from polyamides, including long-chain polyphthalamides (e.g. PA9T GF30) and polyamides 6.6 (e.g. PA6.6 GF50), polyethersulfones (e.g. PESU-GF30) and polyphenylene sulfides (e.g. PPS GF40). The support structure 25 supports the teeth 19 of the stator 16.

[0050] The support structure 25 comprises two flanges, namely a front flange 26 and a rear flange 27, which are fixed to each other and together define a space for housing the teeth 19 and the coils 22.

[0051] Each of the front 26 and rear 27 flanges comprises a radially oriented flank 28, an outer skirt 29 and an inner skirt 30. The outer skirt 29 of each of the front 26 and rear 27 flanges is fixed to the outer skirt 29 of the other of the front 26 and rear 27 flanges so that said outer skirts 29 define the outer periphery of the support structure 25. The inner skirt 30 of each of the front 26 and rear 27 flanges is fixed to the inner skirt 30 of the other of the front 26 and rear 27 flanges so that said inner skirts 30 define the inner periphery of the support structure 25.

[0052] As shown in Figure 7, the internal skirts 30 of the front 26 and rear 27 flanges are fixed to each other by fixing members 31, such as screws. To do this, the internal skirts 30 have at their end flanges 32 which are equipped with orifices allowing the passage of the fixing members 31. Furthermore, the orifices of one of the front 26 and rear 27 flanges, here those of the rear flange 27, have a thread allowing the screwing of the fixing members 31. According to one embodiment, the rear flange 27 has smooth orifices and the fixing members 31 are self-drilling screws for plastic material. According to another embodiment, the threads are provided in an insert, for example metallic, which is overmolded with said rear flange 27.

[0053] Furthermore, the external skirts 29 of the front 26 and rear 27 flanges are also fixed to each other by fixing members 33, such as screws, one of which is shown in FIG. 2. To do this, the external skirts 29 have at their end flanges 34 which are equipped with orifices allowing the passage of the fixing members 33. In addition, the fixing members 33 are received in a tapped bore 35, not opening, formed in the half-casing 9 and more particularly in its bottom 10. Thus, said fixing members 33 ensure both the fixing of the external skirts 29 to each other and the fixing of the stator 16 to the half-casing 9.

[0054] Furthermore, as shown in Figure 5, the flank 28 of each of the front 26 and rear 27 flanges comprises indentations 36 receiving by form fitting the axial ends of the teeth 19. This makes it possible to ensure the positioning of the teeth 19 and the coils 22 around the axis X when the front 26 and rear 27 flanges are fixed to each other. It also makes it possible to hold the teeth 19 axially. The teeth 19 can be glued to the flanks.

[0055] Furthermore, the stator 16 also comprises an interconnector 37, illustrated in particular in FIG. 5. The interconnector 37 makes it possible, on the one hand, to connect the windings of the coils 22 to each other and, on the other hand, to connect them to a connector 38, visible in FIG. 4. The connector 38 is housed in an opening provided in the half-casing 9 and is intended to be connected to the electrical circuit of the vehicle. In the embodiment shown, the interconnector 37 is housed in a space in the housing of the rear flange 27 which is provided radially between the sidewall 28 and the outer skirt 29 of said rear flange 27. Furthermore, the interconnector 37 is arranged radially outside the rear rotor 18.

[0056] The interconnector 37 comprises four annular conductive traces corresponding to the neutral and the three phases of the electrical machine 1. The conductive traces are embedded in a resin allowing them to be electrically insulated from each other. Furthermore, as shown for example in FIG. 6, the interconnector 37 also comprises three connection tabs 39 which are each connected to one of the conductive traces. The connection tabs 39 project radially outwards, outside the support structure 25 of the stator 16, in order to be connected to the connector 38.

[0057] As illustrated for example in Figure 4, the front rotor 17 and the rear rotor 18 each comprise a support disc 40 which is rotationally coupled to the rotor shaft 8 of the electrical machine 1. They further comprise a plurality of permanent magnets 41 which are fixed against the face of the support disc 40 which is opposite the stator 16, that is to say against the rear face of the support disc 40, for the front rotor 17, and against the front face of the support disc 40, for the rear rotor 18.

[0058] The rotor shaft 8 is guided in rotation on the half-casing 9 as well as on the bell 4 of the reduction device 2 by means of a pair of rolling bearings 42, 43. Thus, the support structure 25 of the stator 16 does not perform any function of guiding in rotation the front rotor 17, the rear rotor 18 and the rotor shaft 8, which allows it to be made of a less mechanically resistant and electrically insulating material, such as a polymer material.

[0059] The pair of rolling bearings comprises a front rolling bearing 42 and a rear rolling bearing 43. Each of the front rolling bearings 42 and rear rolling bearings 43 comprises an inner ring, an outer ring and rolling bodies, for example balls, interposed between the inner ring and the outer ring.

[0060] As shown in Figure 2, the rear rolling bearing 43 is interposed between the rotor shaft 8 and the bottom 10 of the half-casing 9. To do this, the rear rolling bearing 43 is, on the one hand, fitted onto the rotor shaft 8 and bears forward against a shoulder 44 provided on the rotor shaft 8. On the other hand, the rear rolling bearing 43 is fitted inside a housing 45 provided in the half-casing 9. The housing 45 is delimited by the bottom 10 of the half-casing 9 and by an annular skirt 46 which projects axially forward from the bottom 10 of the half-casing 9. The rear rolling bearing 43 is held radially inside the annular skirt 46 and bears against the bottom 10 of the half-casing 9.

[0061] As shown for example in Figure 2, the front rolling bearing 42 is fitted onto a front portion of the rotor shaft 8. The front rolling bearing 42 is intended to slide axially inside a housing 47 provided in the bell 4, when the electrical machine 1 and the reduction device 2 are fixed to each other. The front rolling bearing 42 bears rearwardly against a shoulder 48 provided on the rotor shaft 8. The housing 47 which receives the front rolling bearing 42 is delimited by the bottom wall 6 of the bell 4 and by an annular skirt 49. The annular skirt 49 projects axially rearwardly from the bottom wall 6 of the bell. The rear rolling bearing 43 is held radially inside the annular skirt 49.Furthermore, in order to ensure axial support of the front rolling bearing 42, a shim or elastic washer, not shown, is fitted onto the rotor shaft 8 and interposed axially between the bottom wall 6 of the bell 4 and the front rolling bearing 42.

[0062] In an alternative embodiment not shown, the front rolling bearing 42 is not fitted onto the rotor shaft 8. In this case, the rotational guidance of the rotor shaft 8 is achieved via the input shaft of the reduction device 3 to which it is coupled. In other words, the front rolling bearing 42 is fitted onto the input shaft of the reduction device 3. Another rolling bearing also guides the input shaft in rotation.

[0063] It is thus understood that the assembly comprising the electrical machine 1 and the reduction device 4 comprises, depending on the embodiments, three or four rolling bearings for guiding the rotor shaft and the input shaft of the reduction device 3 in rotation. When the assembly comprises three rolling bearings, two are fitted onto one of the rotor and input shafts and only one onto the other. When it comprises four rolling bearings, each of the rotor and input shafts of the reduction device 3 is guided in rotation by a pair of rolling bearings.

[0064] Furthermore, it can be seen in FIG. 2 that the support discs 40 have an external portion 50 in which the permanent magnets 41 are fixed and an internal coupling portion 51 which rotationally couples the support disc 40 to the rotor shaft 8.

[0065] The internal coupling portion 51 is equipped with a splined hub which is fitted onto a splined portion of the rotor shaft 8. The internal coupling portion 51 of the support discs 40 is furthermore axially fixed onto the rotor shaft 8. In the embodiment shown, the internal coupling portion 51 of each of the support discs 40 is axially locked between a central shoulder 52 formed in the rotor shaft 8 and a nut 53 which is mounted on a threaded portion of the rotor shaft 8.

[0066] In the advantageous embodiment shown, the outer portion 50 of the support discs 40 is positioned axially opposite the stator 16 while the inner coupling portion 51 is positioned radially inside the stator 16. In other words, the inner coupling portions 51 are axially offset relative to the outer portions 50: the inner coupling portion 51 of the front rotor 17 being axially offset rearward while the inner coupling portion 51 of the rear rotor 18 is axially offset forward. As shown for example in FIG. 2, the outer portion 50 of each support disc 40 is connected to the inner coupling portion 51 by a frustoconical portion 54.

[0067] Thanks to the aforementioned geometry of the support discs 40, the rear rolling bearing 43 is, at least in part, positioned radially inside the external portion 50 of the support disc 40 of the rear rotor. Similarly, the front rolling bearing 42 is, at least in part, positioned radially inside the external portion 50 of the support disc 40 of the front rotor. Such an arrangement therefore makes it possible to limit the axial size of the electric machine 1.

[0068] A circuit for circulating a cooling fluid for cooling the electrical machine 1 will be described below. The cooling fluid is a dielectric fluid, such as oil for example. The circulation of such a cooling fluid is more particularly intended to cool the coils 22 of the stator 16 in order to prevent overheating of the electrical machine 1.

[0069] As shown in Figure 1, the bell 4 of the reduction device 2 preferably has, near its high point, a cooling fluid inlet 55. The inlet 55 here has the shape of a connection end piece which is configured to be connected to a cooling fluid supply pipe.

[0070] The inlet 55 opens into a sealed annular chamber 56, visible in Figure 2 which is arranged radially between the support structure 25 of the stator 16 and the bell 4 of the reduction device 2. To do this, as shown in Figures 3, 4 and 7, the external skirt 29 of the front flange 26 carries two sealing O-rings 57, 58 which are each mounted in a groove arranged in said external skirt 29. When the electrical machine 1 and the reduction device 2 are assembled together, said sealing O-rings 57, 58 come into radial contact against the inside of the external skirt 5 of the bell 4, which defines said sealed annular chamber 56. Furthermore, the external skirt 29 of the front flange 26 has a plurality of spray orifices 59, also visible in Figures 3, 4 and 7.The spray orifices 59 are regularly distributed around the axis X and open radially outside the coils 22 of the stator 16.

[0071] The bell 4 of the reduction device 2 also comprises a cooling fluid outlet 60, visible in FIG. 2, preferably at its lowest point. The outlet 60 communicates with a channel 61 formed in the external skirt 5 of the bell 4 and opening into the sealed annular chamber 56. The outlet 60 is intended to be connected to a cooling fluid discharge pipe. The outlet 61 also has the shape of a connecting end piece, which is received in an orifice formed in the bottom wall 6 of the bell 4.

[0072] Thus, in operation, the cooling fluid is conducted into the sealed annular chamber 60 via the fluid inlet 55. It is then sprayed onto the coils 22 via the spray orifices 59 provided in the outer skirt of the front flange 26. The cooling fluid then falls, by gravity, passing through the spray orifices 59, into a lower area of ​​the chamber sealed annular 60 from which it can be evacuated through the outlet 60 via the channel 61.

[0073] Although the invention has been described in connection with several particular embodiments, it is obvious that it is in no way limited thereto and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention, as defined by the claims.

[0074] The use of the verb "comprise", "comprise" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those set out in a claim.

[0075] In the claims, any reference sign in parentheses cannot be interpreted as a limitation of the claim.

Claims

CLAIMS

1. Electrical machine (1) intended to be fixed to the rear of a reduction device (2) and comprising: - a stator (16) comprising a support structure (25) having an annular shape centered around an axis X, a plurality of teeth (19) distributed around the axis X and supported by the support structure (25) and coils (22) which comprise a winding (24) and which are carried by the teeth (19); - a rear rotor (18) and a front rotor (17) which are arranged axially on either side of the stator (16) and which are integral in rotation with a rotor shaft (8) movable in rotation around the axis X, said rotor shaft (8) passing through the support structure (25) and comprising a front portion which is intended to be coupled to a gear system of the reduction device (2); and - a half-casing (9) intended to be fixed to a bell (4) of the reduction device (2) and configured to form with said bell (4) a housing space in which the stator (16), the front rotor (17) and the rear rotor (18) are housed; the support structure (25) being fixed to said half-casing (9); said electrical machine (1) being characterized in that: - it comprises a rear rolling bearing (43) interposed between a rear portion of the rotor shaft (8) and the half-casing (9); - the front portion of the rotor shaft (8) is intended to be guided in rotation by a front rolling bearing (42) intended to be carried by the reduction device (2); and - the support structure (25) is made of an electrically insulating material.

2. An electrical machine (1) according to claim 1, wherein the support structure (25) is made of a polymer material.

3. Electrical machine (1) according to claim 1 or 2, in which the front rolling bearing (42) is fitted onto the front portion of the rotor shaft (8) and is intended to be arranged radially inside a housing (47) provided in the bell (4).

4. An electrical machine (1) according to any one of claims 1 to 3, wherein the support structure (25) comprises a front flange (26) and a rear flange (27) which are fixed to each other and between which the teeth (19) of the stator (16) are held.

5. An electrical machine according to claim 4, wherein each of the front (26) and rear (27) flanges has a side (28) having a radial orientation, said flanks (28) having imprints (36) each receiving by interlocking in shape an axial end of one of the teeth (19).

6. An electrical machine (1) according to any one of claims 1 to 5, wherein the support structure (25) has an inner periphery which is spaced from the rotor shaft (8) by a radial gap which is free of rolling bearings.

7. Electrical machine (1) according to any one of claims 1 to 6, in which the support structure (25) comprises an external periphery which carries two sealing O-rings (57, 58) intended to cooperate with the bell (4) of the reduction device (2) so as to provide between said external periphery and the bell (4), a sealed annular chamber (56) intended to receive a cooling fluid, the external periphery further comprising a plurality of spray orifices (59) which are distributed circumferentially around the axis X and which open radially opposite the coils (22) of the stator (16).

8. An electrical machine (1) according to any one of claims 1 to 7, wherein the rear rotor (18) comprises a support disc (40) comprising an outer portion (50) and an inner coupling portion (51), the outer portion (50) carrying a plurality of permanent magnets (41) distributed around the axis X and being positioned axially opposite the stator (16), the inner coupling portion (51) being rotatably coupled to the rotor shaft (8) and being offset forwards relative to the outer portion (50), the rear rolling bearing (43) being arranged radially inside the outer portion (50).

9. An electrical machine (1) according to any one of claims 1 to 8, wherein the front rotor (17) comprises a support disc (40) comprising an outer portion (50) and an inner coupling portion (51), the outer portion (50) carrying a plurality of permanent magnets (41) distributed around the axis X and being positioned axially opposite the stator (16), the inner coupling portion (51) being rotationally coupled to the rotor shaft (8) and being offset rearwardly relative to the outer portion (50).

10. An electrical machine (1) according to claim 9 taken in combination with claim 3, wherein the front rolling bearing (42) is arranged radially inside the outer portion (50) of the support disc (40) of the front rotor (17).

11. An assembly comprising an electrical machine (1) according to any one of claims 1 to 10 and a reduction device (2) comprising a bell (4) which is fixed to the half-casing (9) of the electric machine (1) and which defines with the half-casing the housing space in which the stator (16), the front rotor (17) and the rear rotor (18) are housed.

12. An assembly comprising an electrical machine (1) according to claim 7 and a reduction device (2) comprising a bell (4) which is fixed to the half-casing (9) of the electrical machine (1) and which defines with the half-casing (9) the housing space in which the stator (16), the front rotor (17) and the rear rotor (18) are housed, the bell (4) comprising a cooling fluid inlet (55) which opens into the sealed annular chamber (56) and a cooling fluid outlet (60) which is in fluid communication with the sealed annular chamber (56).

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