Dielectric liquid-cooled axial flux electric machine stator

Abstract

Stator of an axial flux electric machine cooled by a dielectric liquid The invention relates to an axial flux electric machine (1), comprising a stator (2), a rotor (3) secured to a rotating shaft (34), and a stator (2) comprising: - a plurality of teeth (24) projecting axially in the direction of the rotor (3), - winding supports (25) arranged on the teeth (24), and - stator windings (28) housed in the winding supports (25), the electric machine (1) further comprising a cooling chamber for the stator windings (28), and at least one of the winding supports (25) comprising at least one axial retaining wall (250, 252) comprising at least one recess (254, 256, 258) for the passage of a heat transfer liquid. (Figure 1)

Description

Title of the invention: Stator of an axial flux electric machine cooled by a dielectric liquid

[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 generally radial flux electric machines, that is to say that the stator windings of such a machine generate a magnetic field 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 the electric traction or propulsion motor of such a vehicle, it is envisaged to use, instead of a radial flux electric machine, an axial flux electric machine. This latter 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] The power density provided by an axial flux electric machine intended for automobile traction or propulsion implies that the active parts of the machine are traversed by strong currents, which cause an increase in their temperature. These active parts generally comprise stator windings, which must be efficiently cooled so that the increase in temperature due to the currents passing through them does not damage them.

[0005] Cooling of the stator windings can be achieved with a cooling jacket in which a coolant circulates, however such a jacket has a bulk around a housing of the machine which may not be compatible with certain architectures of electric or hybrid powertrains. In addition, such cooling is not very effective, the heat transfer liquid not being in direct contact with the electrical conductors of each stator winding of the electric machine.

[0006] Another solution is to spray the stator windings with a dielectric heat transfer fluid such as oil, the machine then being coupled to a cooling circuit in which the dielectric heat transfer fluid is cooled. This solution nevertheless has the disadvantage of degrading the performance of the machine due to the presence of heat transfer fluid in the air gap, which generates friction with a rotor of the axial flux electric machine.

[0007] It is also possible to confine the heat transfer fluid in a sealed stator chamber, so that the heat transfer fluid does not penetrate into the air gap. However, in a compact electrical machine, such a sealed stator chamber must be made as close as possible to the active parts of the machine and therefore to the stator teeth on which winding supports are threaded, which axially block the circulation of heat transfer fluid. Cooling by a heat transfer fluid in such a sealed chamber is therefore not uniform at least in the axial direction, which is detrimental to the performance of the electrical machine. It is also less effective if the inlet or outlet of the heat transfer fluid is axial.

[0008] The present invention aims to remedy at least in part the aforementioned drawbacks by providing an axial flux electrical machine in which the stator windings are cooled in a sealed chamber by a heat transfer liquid, and which comprises means improving the circulation of the heat transfer liquid in contact with the stator windings in the axial direction.

[0009] To this end, the invention proposes an axial flux electric machine, comprising: - a stator, - a rotor attached to a rotating shaft, and - a casing housing the stator, the casing comprising a main wall crossed by the rotating shaft, the stator comprising: - a plurality of teeth secured to the main wall and projecting axially towards the rotor, - winding supports arranged on the teeth, and - stator windings housed in the winding supports, the electric machine comprising a cooling chamber for the stator windings, the electric machine being characterized in that, at least one of the winding supports comprising on the one hand a body arranged on one of the teeth and on the other hand axial holding walls of one of the stator windings, at least one of the axial holding walls comprises at least one recess for the passage of a heat transfer liquid.

[0010] It should be noted that in this patent application, the terms "axial" (or "axial") refer, unless otherwise stated, to a direction parallel to an axis of rotation of the rotor of the electric machine. Similarly, the terms "radial" refer, unless otherwise stated, to a direction orthogonal to the axis of rotation of the rotor of the electric machine, and secant to this axis of rotation, while the terms "angular" or "ortho-radial" refer, unless otherwise stated, to a direction orthogonal to the axial direction and to a radial direction, this orthogonal direction being in fact rotating around the axis of rotation of the rotor.

[0011] The electrical machine according to the invention comprises at least one stator and at least one rotor, for example it comprises two stators on either side of the rotor in an axial direction. In the latter case the two stators are preferably made in a similar manner, that is to say that the electrical machine according to the invention then comprises in particular two sealed cooling chambers. Of course the cooling chamber(s) each comprise at least one heat transfer liquid inlet and one heat transfer liquid outlet. The heat transfer liquid inlet and outlet are preferably arranged in the main wall of the casing housing the stator, but alternatively one and / or the other are arranged on one or more side walls of this casing.

[0012] The casing housing the stator forms the cooling chamber in which a heat transfer liquid can circulate between the stator windings. This casing is for example a portion of a housing of the electrical machine, or a casing dedicated to the stator, the housing of the machine including for example this casing dedicated to the stator. The last option has the advantage of allowing the tightness of the cooling chamber to be tested outside a main assembly line of the electrical machine according to the invention.

[0013] The casing housing the stator comprises the main wall, generally concentric side walls, first ends of which are connected to the main wall, and a cover secured in a sealed manner to second ends of the side walls. This cover may take the form of a sealed membrane made of synthetic material, allowing the magnetic field to pass through, for example made of a polymer reinforced with glass or carbon fibers. The membrane is then, for example, glued or overmolded to the second ends of the side walls.

[0014] The main wall is for example a partition of the machine housing, arranged orthogonally to an axis of rotation of the rotor, or a support plate attached to this partition of the machine housing and on which a stator yoke is fixed, when the side walls are secured to this support plate. The teeth being secured, possibly by means of the yoke or the support plate, to the main wall, the latter is generally flat on the side of the teeth, but can of course include grooves or ribs for fixing the teeth, the yoke or the support plate. The main wall includes for example on the other side of the teeth, cooling channels using a different heat transfer fluid than that used in the cooling chamber.

[0015] The side walls of the casing are for example cylindrical or formed of several concentric cylindrical walls, for example to allow a rotor hub to be partially housed in the electric machine, in particular when the side walls are also central side walls of a housing of the electric machine.

[0016] Thanks to the invention, the heat transfer fluid between the axial holding wall and another wall of the casing orthogonal to the axis of rotation of the rotor, for example the main wall, can pass through the recess in the housing of the winding support in which the stator winding is located. Thus, the latter receives more heat transfer fluid on its surface than if this recess did not exist. In addition, this improvement in cooling uses the winding support and therefore does not require adding additional parts in the electrical machine. The recess is of course a through-hole and takes, for example, the form of an orifice or a notch in the axial holding wall. This is arranged orthogonal to the axis of rotation of the rotor and makes it possible to hold the stator winding axially.

[0017] Preferably, each stator winding support is identical and therefore comprises at least one such recess in at least one of its axial holding walls, which allows homogeneous cooling of the stator.

[0018] In one embodiment of the invention, the main wall comprises an inlet and an outlet for the heat transfer liquid arranged opposite a first of the axial holding walls, proximal to the main wall, the inlet and the outlet being arranged on either side of the tooth respectively on a first side of the tooth and on a second side of the tooth, the recess being a first recess in the first axial holding wall, which comprises a second recess, the first recess being arranged in the first axial holding wall on the first side of the tooth, and the second recess being arranged in the first axial holding wall on the second side of the tooth.

[0019] The first recess is preferably arranged opposite the heat transfer liquid inlet. Similarly, the second recess is preferably arranged opposite the heat transfer liquid outlet. Several first recesses are optionally arranged in the first axial holding wall, one of them being arranged opposite the heat transfer liquid inlet. Similarly, several second recesses are optionally arranged in the first axial holding wall, one of them being arranged opposite the heat transfer liquid outlet. These recesses are preferably arranged in portions of the first axial holding wall, centered relative to the corresponding side of the tooth.

[0020] In this embodiment of the invention, the electrical machine comprises, for example, on the one hand, a circular heat transfer liquid supply ramp communicating with as many heat transfer liquid inlet orifices arranged in the main wall as there are stator teeth, and on the other hand, a circular heat transfer liquid discharge ramp communicating with as many heat transfer liquid outlet orifices arranged in the main wall as there are stator teeth. These ramps are, for example, parts added to the main wall, opposite the stator windings. toric, or are formed by a groove in the main wall or in a partition of the electrical machine housing, when the main wall is attached to this partition.

[0021] The first recess is for example an orifice arranged in a clearance of the first axial retaining wall, arranged opposite the stator winding. This clearance allows the heat transfer liquid to accumulate between the first axial retaining wall and the stator winding, which then allows it to better submerge the latter.

[0022] In one embodiment of the invention, the stator winding in the winding support forms a first space between the first axial holding wall and the stator winding, in which a heat transfer liquid is able to circulate around the stator winding. This first space is for example formed solely by a staggered arrangement of the conductive wires of the stator winding. Similarly in this embodiment of the invention, the stator winding in the winding support forms a second space between a second of the axial holding walls and the stator winding, in which the heat transfer liquid is able to circulate around the stator winding.

[0023] According to an optional and advantageous characteristic of this embodiment of the invention, the body is a hollow body enveloping the tooth and comprising a surface facing the stator winding, and a channel capable of circulating the heat transfer liquid is arranged between the surface and the stator winding while being connected to the first space and / or to the second space. Thus, the heat transfer liquid can also circulate axially between the body of the winding support and the stator winding. The channel is for example arranged as close as possible to the first and / or the second recess so as to facilitate its supply with heat transfer liquid.

[0024] A stator winding support comb is optionally disposed between the surface and the stator winding, and extends axially. This comb keeps the surface and the stator winding at a distance so as to form the channel.

[0025] The surface optionally comprises at least one groove extending parallel to one of the axial retaining walls. Such grooves are preferably connected to the channel and therefore allow the heat transfer liquid to also circulate at least partially around the hollow body, between the surface and the stator winding.

[0026] Alternatively, the surface comprises stator winding support pads. Such a configuration allows the heat transfer fluid to flow in all directions, between the body of the winding support and the stator winding.

[0027] In one embodiment of the invention, the casing comprising two concentric side walls, first ends of which are connected to the main wall, and a membrane fixed to second ends of the side walls, the second wall of axial support comprises at least a third recess capable of allowing the heat transfer fluid to pass from the second space to a third space between the second axial support wall and the membrane. This third space possibly communicates with a passage located between the body of the winding support and the tooth, and allowing the heat transfer fluid to circulate axially from the third space to the main wall.

[0028] The second axial holding wall preferably comprises several third recesses, one of which is arranged on the first side of the tooth and the other on the second side of the tooth. A first channel connects, for example, the first space to the second space by being located closest to the first recess and a third recess located on the first side, and a second channel connects, for example, the first space to the second space by being located closest to the second recess and a third recess located on the second side.

[0029] In one embodiment of the invention, the second axial retaining wall comprises a free end portion of reduced thickness compared to the remainder of the second axial retaining wall, so as to form a space for circulation of the heat transfer liquid delimited in part by the membrane. The third recess(es) are then preferably arranged in this free end portion, the circulation space then corresponding to the third space between the membrane and the second axial retaining wall. This third space preferably communicates with a heat transfer liquid circulation zone located between one of the side walls of the casing and the stator windings.

[0030] The membrane is for example glued to the second axial retaining wall outside the free end portion, so as to prevent deformation of the membrane towards the air gap of the electrical machine.

[0031] The invention also relates to an electric or hybrid vehicle comprising an axial flux electric machine according to the invention.

[0032] 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 attached schematic drawings on the other hand, in which:

[0033] [Fig-1] is a half-view in axial section of a stator and a rotor mounted on a rotating shaft, of an electrical machine according to the invention, in a first embodiment of the invention,

[0034] [Fig.2] is an axial sectional view of a stator and rotor portion of an electrical machine according to the invention, in a second embodiment of the invention,

[0035] [Fig.3] is a perspective view of a stator winding in a winding support mounted on a tooth of a stator of an electrical machine according to the invention, in a third embodiment of the invention, and showing a face of the tooth located on the side of a rotor of the electric machine,

[0036] [Fig.4] is a perspective view of the winding support used in the third embodiment of the invention,

[0037] [Fig.5] is an axial sectional view of the stator winding in the winding support mounted on the tooth in the third embodiment of the invention, and

[0038] [Fig.6] is a view, from the side opposite the rotor, of a stator yoke comprising the tooth on which the winding support and the stator winding are mounted in the third embodiment of the invention.

[0039] According to a first embodiment of the invention, an axial flux electrical machine 1 according to the invention, represented in [Fig.l], comprises at least one stator 2 and one rotor 3 secured to a rotating shaft 34 mounted to move about an axis of rotation X. Only one half of the stator 2 and one half of the rotor 3 seen in section are represented, their other halves being symmetrical with respect to the axis of rotation X.

[0040] The electrical machine 1 also comprises a housing, not shown, housing together the stator 2, the rotor 3 and another stator, not shown, arranged axially on the other side of the rotor 3 relative to the stator 2. This other stator is arranged symmetrically to the stator 2 relative to the rotor 3 and is of a structure similar to the stator 2. However, as a variant, the electrical machine 1 comprises a single stator.

[0041] The rotor 3 takes the form of a disc with a hole in its center to allow the passage of the rotating shaft 34. It comprises a fixing hub (not shown) for the rotating shaft 34. The rotor 3 comprises a body 32 made of composite material, for example reinforced with glass or carbon fibers, this body 32 comprising a circular portion connected to the fixing hub, and branches extending radially from this circular portion to a circular hoop 36 of the rotor 3. The rotor 3 comprises magnetic poles 30 of trapezoidal shape, each housed between the branches of the body 32. These magnetic poles 30 have a surface of dimension at least equal to that of an axial end surface 240 of a tooth 24 of the stator 2 so as to receive the major part of the magnetic field created by a stator winding 28 of the stator 2, arranged around the tooth 24. Of course, if the stator teeth have a shape other than a trapezoidal shape, the magnetic poles 30 preferably have a shape identical to this different shape. The magnetic poles 30 are for example formed of small permanent magnets glued together by a resin possibly loaded with magnetic powder, or are themselves bonded magnets. The hoop 36 allows the magnetic poles 30 to be held in their housings between the branches of the body 32 despite the centrifugal force exerted by the rotation of the rotor 3 during operation of the electrical machine 1.

[0042] In this first embodiment of the invention, the stator 2 comprises a casing dedicated 22 comprising a main wall 20 arranged orthogonally to the axis of rotation X and fixed to a partition of the housing of the electric machine. This main wall 20 is a support plate in the form of a flat crown, on which is glued or welded a yoke made of magnetic steel comprising stator teeth 24 (also called stator teeth) made of magnetic steel extending axially in the direction of the rotor 3. The main wall 20 is perforated in its center for the passage of the rotating shaft 34. Alternatively, the teeth are made of the same material as the main wall 20, or are fixed by interlocking or glued or welded directly onto the main wall 20.

[0043] In this first embodiment of the invention, the teeth 24 each have a trapezoidal shape and are distributed angularly and regularly around the axis of rotation X. The teeth 24 therefore have the shape of right prisms whose height is parallel to the axial direction. On each of the teeth 24 is threaded a winding support 25 made of insulating synthetic material (for example polymer). The winding support 25 comprises a trapezoidal hollow body, of a shape complementary to the tooth 24 on which the hollow body is threaded, and comprises two axial holding walls 250, 252 of a stator winding 28, orthogonal to the axis of rotation X and each connected to a separate axial end of the hollow body. The first axial holding wall 250 is proximal to the main wall 20 while the second axial holding wall 252 is distal to the main wall 20.

[0044] A stator winding 28 is therefore arranged around each hollow body threaded onto a stator tooth 24. Each stator winding 28 is for example formed from a winding of copper wire. The ends of the stator windings 28 are each electrically connected to phase conductors, not shown, inside or outside the casing 22.

[0045] The casing 22 also comprises two concentric side walls 21, 23 secured to the main wall 20 each by a first of their ends. In this embodiment of the invention, the side walls 21, 23 are cylindrical, but may alternatively be of a different shape. The side walls 21, 23 are for example welded or made of the same material as the main wall 20. They are for example made of steel or aluminum. The first side wall 21 is distal to the rotating shaft 34 and the second side wall 23 is proximal to the rotating shaft 34. The main wall 20 and the side walls 21, 23 are dimensioned to accommodate the teeth 24, the stator windings 28 and the winding supports 25 without these elements which they accommodate extending axially beyond the second ends of the side walls 21, 23.

[0046] A membrane 27 made of glass or carbon fiber reinforced polymer, for example made of polyamide called PA6 GF35 or PA12 GF35, is fixed to the second ex ends of the side walls 21, 23 being surmounted by counterbores arranged on these second ends of the side walls 21, 23. Alternatively, the membrane 27 is glued to these counterbores. Its thickness is of the order of half a millimeter. It therefore has the shape of a flat crown.

[0047] The membrane 27, the main wall 20 and the side walls 21, 23 form a sealed cooling chamber in which the active parts of the stator 2 can be bathed in a heat-transferring dielectric cooling liquid such as oil.

[0048] In order to prevent the membrane 27 from deforming, for example due to the pressure of the cooling liquid in the cooling chamber, or the vibrations of the electrical machine 1 in operation, the membrane 27 is glued to the axial end surface 240 of each tooth 24, this axial end surface 240 being arranged in contact with the membrane 27.

[0049] The heat transfer fluid enters the cooling chamber through heat transfer fluid inlets 222 and leaves the cooling chamber through heat transfer fluid outlets 224, the inlets 222 and the outlets 224 being orifices arranged in the main wall 20. The oil entering or leaving through these orifices is represented by arrows passing through these orifices in [Fig.l]. These inlets 222 and these outlets 224 communicate respectively with a first circular ramp 92 and a second circular ramp 94, connected to a cooling circuit not shown.

[0050] In this first embodiment of the invention, the circular ramps 92, 94 take the form of plastic parts with integrated seals for the inlets 222 and the outlets 224, and fixed to the main wall 20.

[0051] The first circular ramp 92 supplies each stator winding 28 with heat transfer liquid, via one of the inlets 222 arranged angularly in the main plate 20, and via first recesses 254 in each first axial holding wall 250, proximal to the inlet 222. In this first embodiment of the invention, the inlet 222 is arranged radially between a tooth 24 and the first lateral wall 21, opposite the first recesses 254 arranged in the first axial holding wall 250. The first recesses 254 and the corresponding inlet 222 are centered relative to the angular dimension of the tooth 24 but alternatively they could be arranged elsewhere on any side of the tooth 24. The arrangement of each inlet 222 of the main wall 20 is the same opposite each winding support 25.

[0052] Once the heat transfer liquid has been loaded with calories, it is evacuated through second recesses 256 in the first axial retaining wall 250, through one of the outlets 224 arranged angularly in the main plate 20 and then through the second circular ramp 94.

[0053] In this first embodiment of the invention, the outlet 224 is arranged radially between a tooth 24 and the second side wall 23, opposite second recesses 256 arranged in the first axial holding wall 250. The second recesses 256 and the outlet 224 are centered relative to the angular dimension of the tooth 24 but as a variant they could be arranged elsewhere on any side of the tooth 24. The arrangement of each outlet 224 of the main wall 20 is the same opposite each winding support 25.

[0054] The sizes of the orifices of the inlets 222 and the outlets 224 in the main plate 20 may be different to balance the pressure in the cooling chamber and efficiently cool each stator winding 28. The second circular ramp 94 is connected in the cooling circuit with an exchanger to lower the temperature of the heat transfer liquid.

[0055] It should be noted that other holes are possibly provided in the main wall 20 for the passage of the electrical connections of the stator windings or the phase conductors outside the casing 22, a sealing device being provided at these holes to prevent leaks of the heat transfer liquid contained in the cooling chamber. For example, overmolding of all the electrical connections is provided behind these holes for the passage of the electrical connections or the phase conductors, the overmolding also overmolding the periphery of these holes on the main wall 20. The electrical connections or the phase conductors can of course, as a variant, pass through one of the side walls 21, 23 of the casing 22.

[0056] Thanks to the first recesses 254 and the second recesses 256, the heat transfer liquid can circulate more easily around the stator winding 28, in particular all around the tooth 24, that is to say on the one hand between the side walls 21, 23 and the winding support 25, and on the other hand between two adjacent stator windings 28.

[0057] In order for the entire surface of the stator winding 28 to be well cooled, the stator winding 28 leaves a first space 26 between the first axial holding wall 250 and the stator winding 28, in which the heat transfer liquid can also circulate all around the tooth 24, and leaves a second space 29 between the second axial holding wall 252 and the stator winding 28, in which the heat transfer liquid can also circulate all around the tooth 24.

[0058] In addition, the surface of the hollow body, facing the stator winding 28, forms pads 255 for supporting the stator winding. These pads 255 are for example circular. They allow the heat transfer liquid to circulate from the first space 26 to the second space 29 by passing between the hollow body and the stator winding 28, around the entire periphery of the hollow body, zigzagging between the pads 255.

[0059] Finally, the second axial holding wall 252 comprises third recesses 258, some being arranged between the tooth 24 and the first side wall 21, the others being arranged between the tooth 24 and the second side wall 23, so as to promote the circulation of the heat transfer liquid from the second space 29 to a third space left free between the second axial retaining wall 252 and the membrane 27.

[0060] The second axial holding wall 252 in fact comprises a reduction in thickness opposite the membrane 27, so that a first portion proximal to the tooth 24, of the second axial holding wall 252, is in contact with the membrane 27, while a second portion 253 distal to the tooth 24, of the second axial holding wall 252, forms this third space for circulation of the heat transfer liquid all around the tooth 24. The first portion proximal to the tooth 24 makes it possible to fix the membrane 27 also on this first portion in order to limit its deformation.

[0061] In this first embodiment of the invention, it is therefore understood that the heat transfer liquid arriving from an inlet 222 of the main wall 20, reaches the first space 26 between a stator winding 28 and a first axial holding wall 250 via the first recesses 254, then circulates at least on the surface of the stator winding 28 in the axial direction before reaching the second space 29, then in the third space via the third recesses 258. A portion of the heat transfer liquid arriving in the first space 26 also circulates around the tooth 24 while remaining in this first space 26 and therefore cools the stator winding 28 near the first axial holding wall 250. Similarly, a portion of the heat transfer liquid arriving in the second space 29 also circulates around the tooth 24 while remaining in this second space 29 and therefore cools the stator winding 28 near the second axial retaining wall 252.Another part of the heat transfer liquid which has reached the channel formed by the winding support studs 255 also circulates around the tooth 24 and therefore cools the stator winding 28 between the latter and the hollow body. The heat transfer liquid which has cooled the stator winding 28 and which has reached the side of the second side wall 23 is then discharged through third recesses 258 and / or second recesses 256 and then the heat transfer liquid outlet 224 located in the main wall 20.

[0062] A second embodiment of the invention of an electrical machine 1b according to the invention will now be described in relation to [Fig. 2], comprising many elements identical or similar to those of the first embodiment of the invention, and which are referenced in the same way.

[0063] This second embodiment of the invention is distinguished from the first embodiment of the invention by a stator 2b in which a winding support 25b is different from the winding support 25. The winding support 25b comprises, as in the winding support 25, a hollow body threaded onto the tooth 24 and connected at its axial ends to a first axial holding wall 250b proximal to the main wall 20, and to a second axial holding wall 252b distal to the wall main 20.

[0064] The first axial retaining wall 250b comprises first recesses 254b facing the heat transfer liquid inlet 222, and second recesses (not shown) facing a heat transfer liquid outlet. The second axial retaining wall 252b comprises third recesses 258b on the same side as the first recesses 254b and third recesses on the same side as the second recesses.

[0065] Unlike the winding support 25, however, the winding support 25b forms a channel 251b between a first recess 254b and a second recess 258b, which allows the stator winding 28 to be well cooled between the hollow body and the stator winding 28 although very little space is accessible to the heat transfer liquid between the stator winding 28 and the axial holding walls 250b, 252b. In other words, the first space between the first axial holding wall 250b and the stator winding 28 exists but is narrow, and the second space between the second axial holding wall 252b and the stator winding 28 exists but is narrow. Grooves formed around the hollow body on its surface allow the heat transfer liquid to circulate around the hollow body.

[0066] In addition, the winding support 25b forms a passage 257b between the hollow body and the tooth 24, to allow the heat transfer liquid to circulate from a space present between the first holding wall 250b and the main wall 20, to a third space present between the membrane 27 and the second holding wall 252b. This passage 257b therefore extends axially along the entire axial dimension of the winding support 25b, and angularly along a central portion on one side of the tooth 24, proximal to the first side wall 21. It does not extend beyond this central portion to allow the hollow body to fit over the tooth 24.

[0067] Finally, unlike the first embodiment of the invention, the third recesses 258b are made on the first portion of the second axial holding wall 252b, proximal to the tooth 24, this first portion not being glued to the membrane 27. The second portion 253b of the second axial holding wall 252b, distal to the tooth 24, allows the heat transfer liquid between the first side wall 21 and the stator winding 28 to pass into the third circulation space between the membrane 27 and the second axial holding wall 252b. Indeed, without the reduction in thickness carried out on the second portion 253b, the first side wall 21 would touch the winding support 25 with its curved end and would prevent this passage of the heat transfer liquid.

[0068] In this second embodiment also, the heat transfer liquid circulation ramps are formed by grooves 92b formed by ribs in a partition of a housing 10 of the electrical machine 1b, this partition being screwed to the main wall 20.

[0069] Figures 3 to 6 now illustrate a third embodiment, in which elements identical or very similar to those of the first embodiment are referenced in the same way.

[0070] In this third embodiment of the invention, the teeth 24 of a stator 2c of the electric machine according to the invention are made of a single material with a stator yoke 24a which is fixed to the main wall (not shown) of the casing housing the stator 2c. In [Fig.3], only a winding support 25c comprising a stator winding 28 is mounted on the stator yoke 24a, but of course when the electric machine is finished being assembled, all the teeth 24 are equipped with a winding support 25c and a stator winding 28. The winding support 25c comprises, as in the winding support 25, a hollow body threaded onto the tooth 24 and connected at its axial ends to a first axial holding wall 250c proximal to the main wall of the casing housing the stator 2c, and to a second axial holding wall 252c distal to this main wall.

[0071] The first axial holding wall 250c comprises first recesses 254c (visible [Fig.4]) facing the heat transfer liquid inlet (not shown), and a second recess 256c (visible [Fig.4]) in the form of a notch in the first axial holding wall 250c, facing a heat transfer liquid outlet. As visible [Fig.4], the first recesses 254c are three orifices arranged in a clearance 259c of the first axial holding wall 250c, arranged facing the stator winding 28.

[0072] Unlike the previous embodiments, in this third embodiment of the invention, the second axial holding wall 252c does not include third recesses, although it includes a portion 253c distal to the tooth 24, of reduced thickness compared to the rest of the second axial holding wall 252c.

[0073] In addition, the winding support 25c comprises, like the winding support 25b, a passage 257c to allow the heat transfer liquid to circulate from a space present between the first holding wall 250c and the main wall of the casing housing the stator 2c, to a third space present between the membrane 27 and the second holding wall 252c. This passage 257c extends axially along the entire axial dimension of the winding support 25c, and angularly along a portion of one side of the tooth 24 proximal to the first side wall 21. This portion extends angularly over almost the entire side of the tooth 24 except at the ends thereof. Furthermore, as visible [Fig.5], the inlet of the passage 257c, located on the side of the main wall, is of smaller radial dimension than the radial dimension of the outlet of the passage 257c, located on the side of the membrane 27. This accelerates the circulation of the heat transfer liquid in the passage 257c.

[0074] In this third embodiment of the invention, the channel arranged between the stator winding 28 and the hollow body, and making it possible to connect the first space located between the first axial holding wall 250c and the stator winding 28, to the second space located between the second axial holding wall 252c and the stator winding 28, is produced by means of two combs 4 arranged axially on the surface of the hollow body opposite the stator winding 28, and connecting angular ends of the clearance 259c to the second axial holding wall 252c. These combs make it possible to position the turns of the stator winding 28 between their teeth, at a distance from the hollow body.

[0075] The surface of the latter opposite the stator winding 28 nevertheless forms grooves 255c or ribs for positioning the turns of the stator winding 28, extending parallel to the main wall, so as to allow optimal positioning of these turns on the periphery of the hollow body outside the zone of the channel where the stator winding 28 is not in contact with the hollow body. These grooves 255c or ribs also allow the heat transfer liquid to circulate around the periphery of the hollow body so as to cool the stator winding 28 homogeneously in the radial and angular directions.

[0076] Of course, 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 the different embodiments or variants of the invention envisaged in this application can be combined to achieve the invention, to the extent that these embodiments or variants are not incompatible with each other.

Claims

Claims

1. An axial flux electrical machine (1, 1b), comprising: - a stator (2, 2b, 2c), - a rotor (3) secured to a rotating shaft (34), and - a casing (22) housing the stator (2, 2b, 2c), the casing (22) comprising a main wall (20) through which the rotating shaft (34) passes, the stator (2, 2b, 2c) comprising: - a plurality of teeth (24) secured to the main wall (20) and projecting axially in the direction of the rotor (3), - winding supports (25, 25b, 25c) arranged on the teeth (24), and - stator windings (28) housed in the winding supports (25, 25b, 25c), the electrical machine (1, 1b) comprising a cooling chamber for the stator windings (28), the electric machine (1, 1b) being characterized in that, at least one of the winding supports (25, 25b, 25c) comprising on the one hand a body arranged on one of the teeth (24) and on the other hand axial holding walls (250, 252, 250b, 252b, 250c,252c) of one of the stator windings (28), at least one of the axial holding walls (250, 252, 250b, 252b, 250c) comprises at least one recess (254, 256, 258, 254b, 258b, 254c, 256c) for the passage of a heat transfer liquid.

2. An axial flux electrical machine (1, 1b) according to claim 1, wherein the main wall (20) comprises an inlet (222) and an outlet (224) for the heat transfer liquid arranged opposite a first of the axial holding walls (250, 250b, 250c), proximal to the main wall (20), the inlet (222) and the outlet (224) being arranged on either side of the tooth (24) respectively on a first side of the tooth (24) and on a second side of the tooth (24), the recess being a first recess (254, 254b, 254c) in the first axial holding wall (250, 250b, 250c), which comprises a second recess (256, 256c), the first recess (254, 254b, 254c) being arranged in the first axial holding wall (250, 250b, 250c) on the first side of the tooth (24), and the second recess (256, 256c) being arranged in the first axial holding wall (250, 250b, 250c) on the second side of the tooth (24).

3. An axial flux electric machine according to claim 2, wherein the first recess (254c) is an orifice arranged in a clearance (259c) of the first axial retaining wall (250c), arranged opposite the stator winding (28).

4. An axial flux electrical machine (1, 1b) according to claim 2 or 3, wherein the stator winding (28) in the winding support (25, 25b, 25c) forms a first space (26) between the first axial holding wall (250, 250b, 250c) and the stator winding (28), in which a heat transfer liquid is able to circulate around the stator winding (28).

5. An axial flux electrical machine (1, 1b) according to any one of claims 2 to 4, wherein the stator winding (28) in the winding support (25, 25b, 25c) forms a second space (29) between a second of the axial holding walls (252, 252b, 252c) and the stator winding (28), in which the heat transfer liquid is able to circulate around the stator winding (28).

6. An axial flux electrical machine (1, 1b) according to claim 4 or 5, wherein the body is a hollow body surrounding the tooth (24) and comprising a surface facing the stator winding (28), and in which a channel (251b) capable of circulating the heat transfer liquid is arranged between the surface and the stator winding (28) while being connected to the first space (26) and / or to the second space (29).

7. An axial flux electrical machine (1b) according to claim 6, wherein the surface comprises at least one groove (255c) extending parallel to one of the axial holding walls (250b, 250c).

8. An axial flux electrical machine (1) according to claim 6, wherein the surface comprises pads (255) for supporting the stator winding (28).

9. An axial flux electric machine according to claim 6 or 7, wherein a comb (4) supporting the stator winding (28) disposed between the surface and the stator winding (28) extends axially.

10. An axial flux electrical machine (1, 1b) according to any one of claims 5 to 9, wherein, the casing (22) comprising two concentric side walls (21, 23) of which first ends are connected to the main wall (20), and a membrane (27) fixed to second ends of the side walls (21, 23), the second axial retaining wall (252, 252b) comprises at least one third recess (258, 258b) capable of allowing the heat transfer liquid to pass from the second space to a third space between the second axial retaining wall (252, 252b) and the membrane (27).

11. An axial flux electrical machine (1, 1b) according to claim 10, wherein the second axial holding wall (252, 252b) comprises several third recesses (258, 258b), one of which is arranged on the first side of the tooth (24) and the other on the second side of the tooth (24).

12. An axial flux electrical machine (1, 1b) according to claim 10 or 11, wherein the second axial retaining wall (252, 252b, 252c) comprises a free end portion (253, 253b, 253c) of reduced thickness relative to the remainder of the second axial retaining wall (252, 252b, 252c), so as to form a space for circulation of the heat transfer liquid delimited in part by the membrane (27).

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