Water cooling device for an axial flux electric machine

Abstract

Water cooling device for an axial flux electrical machine. Cooling device (10) for an axial flux electrical machine (1), the cooling device (10) being intended to cool at least one winding (6) disposed inside said electrical machine (1), the cooling device (10) being characterized in that it comprises a hollow structure (12) forming a channel within which a heat transfer fluid is intended to circulate, the hollow structure (12) comprising at least one fluid inlet (14) configured to permit the passage of the heat transfer fluid into the channel of said hollow structure (12) and at least one fluid outlet (16) configured to permit the passage of the heat transfer fluid to the outside of said hollow structure (12), and characterized in that the channel of the hollow structure (12) is delimited by at least one wall (151, 152, 153, 154), and in that at least a portion of said wall (151,152, 153, 154) is flexible. Figure for the abbreviation: Fig. 10,

Description

Title of the invention: Water cooling device for an axial flux electric machine

[0001] The invention relates to a cooling device for cooling an axial flux electric machine, and more particularly for cooling the coils of a stator magnetic circuit of such an axial flux electric machine. The invention also relates to a method for manufacturing such a cooling device. The invention further relates to an axial flux electric machine equipped with such a cooling device. The invention also relates to a motor vehicle equipped with such an axial flux electric machine and / or such a water cooling device.

[0002] Generally, two types of cooling methods are used to cool axial flux electrical machines: water cooling in the casings of the electrical machine in question and oil cooling, in which the oil is in direct contact with the active stator parts.

[0003] Each of the two types of cooling has advantages and disadvantages. Typical advantages of oil cooling include a good capacity to dissipate heat and the possibility of direct heat exchange between the cooling circuit and the heat source(s), as the oil circulates in direct contact with the active stator parts. The classic disadvantages of oil cooling are the technical complexity of its implementation, particularly in ensuring the oil circuit is sealed against the rotor. Certain components of such an oil cooling system, especially membranes and sealing plates, often require a complex design and the integration of a pump, necessary to ensure oil pressure build-up in the circuit, since oil is more viscous than water within a given temperature range.

[0004] The typical advantages of water cooling over oil cooling include the ease of implementation and the fact that pressure losses at low temperatures are more favorable with water than with oil. However, the classic disadvantages of water cooling are the significant thermal resistance between the cooling circuit and the heat source(s), as well as a lower heat dissipation capacity than oil, which means that water cooling systems are insufficient above a certain power level for axial flux electrical machines.

[0005] The object of the invention is to remedy the disadvantages described above by proposing a cooling device with a better capacity to remove heat while retaining the multiple advantages afforded by known state-of-the-art water cooling devices.

[0006] To this end, the invention relates to a cooling device for an axial flux electrical machine, the cooling device being intended to cool at least one winding disposed inside said electrical machine, the cooling device comprising a hollow structure forming a channel inside which a heat transfer fluid is intended to circulate, the hollow structure comprising at least one fluid inlet configured to allow the passage of the heat transfer fluid into the channel of said hollow structure and at least one fluid outlet configured to allow the passage of the heat transfer fluid to the outside of said hollow structure, the channel of the hollow structure being delimited by at least one wall, at least a portion of said wall being flexible.

[0007] The hollow structure may include: - an outer ring; - an inner ring concentric with the outer ring; - segments extending radially between the inner ring and the outer ring; wherein the inner ring, the outer ring and the segments are hollow inside and joined in particular by heat welds to form a continuous and sealed channel configured to convey a heat transfer fluid along a path passing from one ring to the other; the inner ring, the outer ring and the segments being arranged so as to form or delimit openings intended to surround the windings arranged inside the electrical machine.

[0008] The fluidic inlet of the hollow structure can be arranged on the outer ring and the fluidic outlet of the hollow structure can be arranged on the inner ring.

[0009] A passage section of the segments that extend radially between the inner ring and the outer ring may be less than or equal to a passage section of the inner ring and / or a passage section of the segments may be less than or equal to a passage section of the outer ring.

[0010] The channel of the hollow structure may include a serpentine shape, said channel being intended to be arranged at least partially around the windings inside the electrical machine so as to convey a heat transfer fluid in a radial direction between two adjacent windings.

[0011] The channel of the hollow structure may have several superimposed stages along the axial direction of the electrical machine in which the cooling device is intended to be mounted.

[0012] The hollow structure may comprise at least one thermoplastic polymer material.

[0013] The cooling device may include at least one insulated conductive wire covered with a bonding adhesive, said wire being arranged between at least one wall of the channel of the hollow structure and at least one winding inside the electrical machine.

[0014] The invention also relates to an axial flux electric machine comprising at least one cooling device as defined above.

[0015] The invention also relates to a motor vehicle comprising an axial flux electric machine as defined above.

[0016] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0017] Fig. 1 illustrates a schematic cross-sectional view of an axial flux electrical machine.

[0018] [Fig.2] is a detail view of [Fig.1].

[0019] Figure 3 illustrates a first embodiment of a cooling device according to the invention.

[0020] Fig. 4 illustrates a detailed view of Fig. 3.

[0021] Figure 5 illustrates a schematic cross-sectional view of an electrical flux machine axial equipped with the cooling device of figures 3 and 4.

[0022] Fig. 6 illustrates the steps of a manufacturing process for the cooling device of Figures 3 and 4.

[0023] Fig. 7 illustrates a variant of the manufacturing process for the cooling device of Figures 3 and 4.

[0024] Fig. 8 illustrates another variant of the manufacturing process for the cooling device of Figures 3 and 4.

[0025] Fig. 9 illustrates a schematic cross-sectional view of an axial flux electrical machine equipped with a cooling device according to a second embodiment.

[0026] Fig. 10 illustrates a schematic cross-sectional view of an axial flux electric machine equipped with a cooling device according to a third embodiment.

[0027] Fig. 11 is a detailed view of the cooling device according to the third embodiment.

[0028] Fig. 12 illustrates a variant of the embodiment of Fig. 10.

[0029] Generally, an axial flux electric machine 1 comprises a stator 2, which is generally cylindrical in shape, and a rotor, also generally cylindrical in shape, disposed inside the stator 2. The rotor is intended to be driven in rotation about an axis of rotation, the axis of rotation being substantially coaxial with the axis of revolution of the stator 2. A plurality of salient poles 4 are arranged between the moving rotor and the fixed stator 2. The salient poles 4 are arranged radially so as to define an alternation of arms and slots. The arms of the salient poles 4 are intended to be surrounded by conducting wire so as to form a plurality of windings 6.

[0030] Figure 1 shows a schematic cross-sectional view of an example of an axial flux electric machine 1. As illustrated in Figure 1, the axial flux electric machine 1 comprises a stator 2 within which fifteen salient poles 4 are arranged. The arms of said salient poles 4 are surrounded by conducting wire so as to form fifteen separate windings 6. The rotor is not shown in Figure 1.

[0031] According to the invention, a cooling device 10 is provided to ensure cooling of the axial flow electrical machine 1 during operation. Common to all embodiments of the cooling device 10, it comprises a hollow structure 12 forming a channel within which a heat transfer fluid is intended to circulate.

[0032] Preferably, the heat transfer fluid is a liquid, particularly water. However, other types of fluids in liquid form, such as oil, can be considered. It is also possible to imagine a fluid in gaseous form circulating inside the channel of the hollow structure 12 of the cooling device 10.

[0033] The hollow structure 12 of the cooling device 10 comprises at least one fluid inlet 14 configured to allow the heat transfer fluid to flow into the channel of said hollow structure 12 and at least one fluid outlet 16 configured to allow the heat transfer fluid to flow out of said hollow structure 12. The hollow structure 12 of the cooling device 10 may comprise several fluid inlets 14 and / or several fluid outlets 16. Generally, the channel of the hollow structure 12 may comprise internal and external walls. The heat transfer fluid is then intended to flow between the internal and external walls that define the channel of the hollow structure 12.

[0034] At least one fluid inlet 14 supplies the channel of the hollow structure 12 with heat transfer fluid to allow cooling of the components of the axial flow electrical machine 1, while at least one fluid outlet 16 allows the heat transfer fluid, heated by the heat transfer it undergoes, to be removed in order to be replaced with cooler heat transfer fluid and / or to cool the fluid heat transfer fluid thus evacuated before being reinjected inside the channel of the hollow structure 12 of the cooling device 10.

[0035] In a manner common to all embodiments, the continuous and sealed channel of the hollow structure 12 of the cooling device 10 is delimited by at least one wall 151, 152, 153, 154. The continuous and sealed channel thus formed by the at least one wall 151, 152, 153, 154 may comprise a single conduit, or it may comprise one or more branches.

[0036] In the case where the channel of the hollow structure 12 of the cooling device 10 comprises one or more branches, the channel of the hollow structure 12 includes, in particular, a multitude of walls 151, 152, 153, 154 which are connected to one another. The connection between the different walls 151, 152, 153, 154 may, in particular, be made by heat welding in order to guarantee the sealing of the continuous channel thus formed.

[0037] In order to optimize the cooling of the components of the electrical machine 1, and in order to make this cooling as efficient as possible, it is preferable that the hollow structure 12 of the cooling device 10 have the largest possible contact surface with said components of the electrical machine 1. In particular, it is preferable that at least one wall 151, 152, 153, 154 which delimits the channel of the hollow structure 12 has the largest possible contact surface with the windings 6 around the poles 4 inside the electrical machine 1. For this purpose, and in a manner common to all embodiments, at least a portion of said at least one wall 151, 152, 153, 154 which delimits the channel of the hollow structure 12 of the cooling device 10 is flexible.

[0038] The term "flexible" here refers to the ability of at least one wall 151, 152, 153, 154, which delimits the channel of the hollow structure 12, to bend, without breaking, within a range of deformation suitable for its intended use. Thus, at least a portion of the wall 151, 152, 153, 154, which delimits the channel of the hollow structure 12 of the cooling device 10, is therefore capable of being deformed without breaking in order to adapt to the circumstances of its use. In particular, at least one flexible portion of the wall 151, 152, 153, 154 which delimits the channel of the hollow structure 12 can be deformed under the effect of the circulation of the heat transfer fluid intended to circulate in the continuous and sealed channel formed by said wall 151, 152, 153, 154 in order to be pressed against the components of the axial flux electrical machine 1 which is to be cooled.

[0039] In particular, at least one flexible portion of the wall 151, 152, 153, 154 which delimits the channel of the hollow structure 12 can be deformed to be pressed against the windings 6 around the poles 4 arranged inside the axial flux electrical machine 1 in order to maximize the exchange surface with these windings 6 in order to increase the efficiency of the cooling initiated by the circulation of the heat transfer fluid inside the hollow structure 12 of the cooling device 10. According to a preferred embodiment, the flexibility of the flexible portion of the wall 151, 152, 153, 154 can in particular allow it to conform to the shape of the wires of the windings 6 around the poles 4.

[0040] According to a preferred embodiment, the hollow structure 12 comprises at least one thermoplastic polymer material. Such materials may in particular belong to the family of polyimides, polyamide imides, polyetherimides, polyaryletherketones, polyether ether ketones, polysulfones, polyethersulfones, polytetrafluoroethylenes or any other material exhibiting high flexibility and resistance to high temperatures, i.e. temperatures above 150°C, and preferably resistance to temperatures above 200°C.

[0041] As an alternative or in addition, the flexible material(s) chosen for the hollow structure 12 of the cooling device 10 may have high thermal conductivity and / or low electrical conductivity.

[0042] At least one wall 151, 152, 153, 154 that delimits the channel of the hollow structure 12 of the cooling device 10 may have a thickness between 0.10 mm and 0.30 mm, and in particular a thickness of 0.15 mm. A wall 151, 152, 153, 154 having such a thickness may promote heat transfer between the heat transfer fluid intended to circulate inside the hollow structure 12 of the cooling device 10 and the components of the axial flux electrical machine 1 that are to be cooled.

[0043] As previously stated, the cooling device 10, and in particular its hollow structure 12, can be in various embodiments.

[0044] Thus, a first embodiment of such a cooling device 10 is illustrated in Figures 2 to 5. The cooling device 10 is arranged inside said electrical machine 1, between the stator 2 and the rotor. As illustrated in [Fig. 2], a portion of the cooling device 10 is also arranged between the windings 6 that surround the two poles 4 visible in [Fig. 2].

[0045] According to this first embodiment, the hollow structure 12 may comprise an outer ring 17 and an inner ring 18 concentric with the outer ring 17, as well as segments 19 extending radially between the inner ring 18 and the outer ring 17. In this first embodiment, the inner ring 18 of the hollow structure 12 is intended to be disposed between the rotor and the portion of the windings 6 located near said rotor, while the outer ring 17 is intended to be disposed between the stator 2 and the portion of the windings 6 facing the stator 2. The segments 19 extending radially between the inner ring 18 and the outer ring 17 are, for their part, intended to be arranged in the notches between two arms of 4 salient poles which are intended to be surrounded by conductive wire so as to form the plurality of windings 6 mentioned previously.

[0046] In this first embodiment, the inner ring 18, the outer ring 17 and the segments 19 are hollow inside and joined in particular by heat welds 20 to form the continuous and sealed channel configured to convey the heat transfer fluid along a path passing from one ring to the other.

[0047] The inner ring 18, the outer ring 17, and the segments 19 are then arranged to form or delimit openings 21 intended to surround the windings 6 located inside the axial flux electric machine 1. These openings 21 are particularly visible in [Fig. 3]. In this first embodiment, the windings 6 are thus completely surrounded by the hollow structure 12 of the cooling device 10, which maximizes the heat transfer between the heat transfer fluid intended to circulate inside the hollow structure 12 of the cooling device 10 and said windings, enabling efficient cooling of the axial flux electric machine 1 equipped with such a cooling device 10.

[0048] During the manufacture of the hollow structure 12 according to this first embodiment, different methods can be adopted to connect the inner ring 18, the outer ring 17 and the segments 19 by heat welds 20 in order to form the continuous and sealed channel inside which the heat transfer fluid is intended to circulate.

[0049] Thus, according to a first example of a manufacturing process illustrated step by step in [Fig. 6], a passage section of the channel of the hollow structure 12 can be formed using four separate walls 151, 152, 153, 154 which are connected to each other along their edges by four weld beads, in particular heat welds 21. Of these four walls 151, 152, 153, 154, two of them are arranged in a notch between two adjacent windings 6. The two walls 151, 152 are then arranged opposite each other, so that the faces of said walls which are not opposite each other are each in contact with one of the two windings 6 mentioned above. The other two walls 153, 154 allow their ends to be connected so as to form one of the segments 19 which extend radially between the inner ring 18 and the outer ring 17. As illustrated in the [Fig.[6], a section through which a segment 19 of the hollow structure 12 thus formed has a rectangular shape.

[0050] According to another example of a manufacturing process in [Fig. 7], a channel section of the hollow structure 12 can be formed using only two separate walls 151, 152 which are joined together by two heat-welding beads 20, at least in the portion of the hollow structure 12 illustrated in this [Fig. 7]. The edges of one of the two walls 151 are folded so as to adopt a "U" shape, while the other wall 152, substantially straight and flat, is intended to close the opening of the "U" in the manner of a lid in order to form a portion of the continuous and sealed channel of the hollow structure 12 of the cooling device 10. As illustrated in [Fig.7], the passage section of a segment of the hollow structure 12 thus formed also has a rectangular shape.

[0051] According to another manufacturing method illustrated in [Fig. 8], a channel section of the hollow structure 12 can be formed using two separate walls 151, 152, the edges of each wall 151, 152 being folded to adopt a "U" shape. In this embodiment, the heat-sealing beads 20 that join the edges of the two walls 151, 152 are each in contact with a winding 6 between which the hollow structure 12 is arranged.

[0052] In this first embodiment of the cooling device 10, a cross-section of the segments 19 extending radially between the inner ring 18 and the outer ring 17 may be less than or equal to a cross-section of the inner ring 18. Alternatively or in addition, the cross-section of the segments 19 extending radially between the inner ring 18 and the outer ring 17 may be less than or equal to a cross-section of the outer ring 17. This embodiment is more particularly represented in [Fig. 4].

[0053] According to a preferred and optional embodiment, the cross-sections of the inner ring 18, those of the outer ring 17, and those of the segments 19 extending radially between the inner ring 18 and the outer ring 17 may be identical. This particular embodiment allows for greater homogeneity of the temperature of the heat transfer fluid intended to circulate within said channel, thus enabling homogeneous cooling of the components of the axial-flow electrical machine 1 equipped with such a cooling device 10. Such an embodiment is schematically represented in [Fig. 3].

[0054] Alternatively, and still with the aim of limiting the differences between the different passage sections when they are of different sizes, rigid parts 11 integrated into the walls 151, 152, 153, 154 of the channel of the hollow structure 12 or attached to the cooling device 10 can be used to press the walls 151, 152, 153, 154 of the channel of the hollow structure 12 against the windings 6 in order to control the size of the passage sections, in particular for the inner ring 18 and / or the outer ring 17. In contrast to the term "flexible", the term "rigid" here designates the ability of the part(s) 11 to maintain their shape within the context of the intended use, unlike the flexible wall which can bend, without breaking, within a range of deformation adapted to the intended use.

[0055] Pressing the walls 151, 152, 153, 154 of the channel of the hollow structure 12 against the windings 6 using these rigid parts 11 can also increase The contact surface between the cooling device 10 and the components of the electrical machine 1 that are to be cooled is designed to increase heat exchange and thus achieve more efficient cooling. This embodiment is illustrated in particular in [Fig. 5].

[0056] The rigid parts 11 integrated into the walls 151, 152, 153, 154 of the channel of the hollow structure 12 or attached to the cooling device 10 thus allow at least partial control of the deformation of the flexible portion of the channel of the hollow structure 12 by defining the volume that the flexible portion of the hollow structure 12 can occupy. This allows the size of the different passage sections of the hollow structure 12 to be controlled, particularly at the level of the outer ring 17 and the inner ring 18, in order to have passage sections of similar, or even identical, size between the outer ring 17, the inner ring 18 and the segments 19, so as to regulate the flow of the heat transfer fluid intended to circulate inside the hollow structure 12 of the cooling device 10 in order to homogenize the temperature of said fluid. heat transfer fluid throughout this entire cooling system 10.

[0057] In the embodiment illustrated in Figures 2 to 5, at least one fluidic inlet 14 of the hollow structure 12 can be arranged on the outer ring 17, while at least one fluidic outlet 16 of the hollow structure 12 can be arranged on the inner ring 18. This is illustrated more particularly in [Fig. 3]. In addition, or alternatively, at least one fluidic inlet 14 of the hollow structure 12 can be arranged on the inner ring 18 and at least one fluidic outlet 16 of the hollow structure 12 can be arranged on the outer ring 17.

[0058] According to an embodiment not illustrated in the figures, at least one fluidic inlet 14 of the hollow structure 12 and at least one fluidic outlet 16 of the hollow structure 12 can both be arranged on the outer ring 17 of the hollow structure 12, to facilitate the injection of the heat transfer fluid into the hollow structure 12 and its recovery when said heat transfer fluid has passed through the conduit formed by at least one wall 151, 152, 153, 154 to cool the components of the axial flux electrical machine 1.

[0059] According to a second embodiment of the cooling device 10 illustrated in [Fig. 9], the hollow structure 12 may comprise a continuous, sealed channel which, when arranged inside the axial flux electrical machine 1, forms an outer ring 17 and an inner ring 18 concentric with the outer ring 17. Unlike the first embodiment, the hollow structure 12 of this cooling device 10 according to the second embodiment does not have segments 19 extending radially between the inner ring 18 and the outer ring 17. In this specific second embodiment, the ring The inner part 18 of the hollow structure 12 is intended to be placed between the rotor and the part of the windings 6 located near said rotor, while the outer ring 17 is intended to be placed between the stator 2 and the part of the windings 6 facing the stator 2. This second embodiment has the advantage of being easier to manufacture, however the cooling obtained with this embodiment is potentially less efficient.

[0060] According to a third embodiment of the cooling device 10 illustrated in Figures 10 and 11, the hollow structure 12 may comprise a continuous and sealed serpentine-shaped channel. The serpentine shape is more particularly illustrated in the detail view of [Fig. 11].

[0061] In this third embodiment, the channel of the hollow structure 12 is arranged at least partially around the windings 6 inside the electrical machine 1 so as to convey the heat transfer fluid in a radial direction along the slots between two adjacent windings 6. In [Fig. 10], a dashed line indicates the path to be followed by the heat transfer fluid intended to circulate inside the continuous and sealed channel of the hollow structure 12 of the cooling device 10.

[0062] In this particular embodiment, the flexible material of the hollow structure 12 of the cooling device 10 allows said hollow structure 12 to be bent so as to dispose the continuous and sealed channel thus formed in the notches between two neighboring windings 6 and so as to partially envelop said windings 6, i.e. by passing alternately in the space between a winding 6 and the rotor or in the space between a winding 6 and the stator 2, which gives a serpentine shape to the continuous channel thus formed.

[0063] This third embodiment has the advantage of being easier to manufacture than the first embodiment; however, the cooling obtained with this cooling device is potentially less efficient than that obtained with the cooling device according to the first embodiment. Nevertheless, the cooling obtained with the cooling device according to this third embodiment may prove more efficient than that obtained with the cooling device according to the second embodiment, since the cooling device according to the third embodiment allows cooling at the slots between the windings 6 arranged inside the electrical machine 1.

[0064] In this third embodiment of the cooling device 10, the cross-sectional area of ​​the single continuous and sealed channel through which the heat transfer fluid is intended to circulate can be constant, that is to say, the cross-sectional area of ​​the continuous and sealed channel is the same at every point of the hollow structure 12, this which allows minimizing variations in the flow rate of the heat transfer fluid inside the channel of the hollow structure 12. In this way, this third embodiment allows for better homogeneity of the temperature of the heat transfer fluid intended to circulate inside said channel, thus allowing homogeneous cooling of the components of the axial flow electrical machine 1 equipped with such a cooling device 10 without having to use additional parts as in the case of the first embodiment described above.

[0065] In this third embodiment, the exchange surface between the hollow structure 12 of the cooling device 10 and the components of the axial flux electrical machine 1 that it is to be cooled is larger than for the second embodiment presented previously and illustrated in [Fig.9], but smaller than for the first embodiment described previously and illustrated in Figures 2 to 4.

[0066] According to a preferred but optional embodiment, the continuous, sealed channel of the hollow structure 12 can be divided into several superimposed stages along the axial direction of the electrical machine 1 in which the cooling device 10 is intended to be mounted. This embodiment is not illustrated in the figures. Each stage corresponds to a step or bearing in the channel; the heat transfer fluid is then intended to circulate in one stage of the channel before passing to another stage which is superimposed on the stage through which the refrigerant has just passed.

[0067] The stages within the same channel may be delimited by intermediate internal walls. These intermediate internal walls may have passage openings through which the heat transfer fluid can pass from one stage to another stage above it.

[0068] The stages of the continuous and sealed channel of the hollow structure 12 thus allow the direction of circulation of the heat transfer fluid to be varied in both the radial and axial directions, which can allow for better homogeneity in terms of temperature for the cooling fluid.

[0069] Preferably, the direction of circulation of the heat transfer fluid is reversed from one stage to the next. This makes it possible to smooth out the inhomogeneities of cooling within the cooling device 10, in particular between the portions of the hollow structure 12 close to the fluid inlet 14 and the portions of the hollow structure 12 close to the fluid outlet 16.

[0070] In the particular case where the channel of the hollow structure 12 has an even number of stages, the heat transfer fluid then makes a round trip in a radial direction and changes stages in an axial direction. In this same embodiment, the fluid inlet 14 and the fluid outlet 16 can be arranged at proximity to each other, which can facilitate the arrangement of the hollow structure 12 of the cooling device 10 inside the axial flow electric machine 1.

[0071] An embodiment can be envisaged in which the cooling device 10 comprises two separate hollow structures 121, 122, each having a continuous, sealed, serpentine-shaped channel. These two hollow structures 121, 122 are then arranged one above the other along the axial direction of the electrical machine 1 intended to be equipped with such a cooling device 10. The curvatures of the serpentines formed by the continuous, sealed channels of the two hollow structures 121, 122 are opposite to each other, so as to encircle the windings 6 as a whole, as illustrated in [Fig. 12].In other words, for two neighboring windings 61, 62 considered, a first hollow structure 121 of the cooling device 10 is disposed between the stator 2 and the part of a first winding 61 which faces the stator 2, then in the notch between the first winding 61 and the second winding 62, neighbors of the first winding 61, then between the rotor and the part of the second winding 62 which faces the rotor; while a second hollow structure 122 of the cooling device 10 is arranged above the first hollow structure 121, and is positioned between the rotor and the part of the first winding 61 that faces the rotor, then in the notch between the first winding 61 and the second winding 62, then between the stator 2 and the part of the second winding 62 that faces the stator 2. This particular arrangement of the two hollow structures 121, 122 of the cooling device 10 is illustrated in detail in [Fig.12], in which a first thick dotted line indicates the path along which the first hollow structure 121 of the cooling device 10 is arranged and where a second thinner dotted line indicates the path along which the second hollow structure 122 of the cooling device 10 is arranged.

[0072] According to a preferred but optional embodiment, not shown in the figures, the cooling device 10 may include at least one insulated conductive wire coated with an additional bonding adhesive, said wire being arranged between at least one wall 151, 152, 153, 154 of the channel of the hollow structure 12 and at least one winding 6 inside the electrical machine 1. This type of wire is commonly called a "heat-adhesive wire". Such a wire can allow better contact between the wires of the windings 6 inside the electrical machine 1 and the wall 151, 152, 153, 154 of the channel of the hollow structure 12 of the cooling device 10 on which said heat-adhesive wire is arranged. Indeed, when an electric current flows through the heat-adhesive wire, the bonding adhesive surrounding this wire becomes malleable and can thus adapt to the shape of its environment.In other words, the bonding adhesive of the heat-adhesive wire can fill the hard-to-reach gaps between the wires of the windings 6 inside the electrical machine 1, thereby increasing the surface area of. contact and therefore the exchange surface between at least one wall 151, 152, 153, 154 of the channel of the hollow structure 12 and the winding(s) 6 inside the electrical machine 1. In other words, the bonding adhesive which surrounds the heat-adhesive wire can allow it to conform to the shape of the wires of the windings 6 around the poles 4.

[0073] Alternatively, or in addition, a sacrificial polymer layer may be disposed on at least one wall 151, 152, 153, 154 of the channel of the hollow structure 12. This sacrificial polymer layer is configured to fill the spaces between the wires of the windings 6 under the effect of the pressure inside the hollow structure 12 and the current flowing through the coils. More specifically, the current flowing through the coils melts the sacrificial polymer layer disposed on at least one wall 151, 152, 153, 154 of the channel of the hollow structure 12, making this layer malleable, so that said layer adopts the shape of the spaces between the wires of the windings 6, thus creating thermal coupling.

[0074] With the help of these various embodiments, it is thus possible to propose a cooling device 10 for an axial flow electrical machine 1 which makes it possible to overcome the known disadvantages of the state of the art while allowing a better capacity to evacuate heat and retaining the multiple advantages allowed by the water cooling devices known in the state of the art.

Claims

Demands

1. Cooling device (10) for an axial flux electrical machine (1), the cooling device (10) being intended to cool at least one winding (6) disposed within said electrical machine (1), the cooling device (10) being characterized in that it comprises a hollow structure (12) forming a channel within which a heat transfer fluid is intended to circulate, the hollow structure (12) comprising at least one fluid inlet (14) configured to permit the passage of the heat transfer fluid into the channel of said hollow structure (12) and at least one fluid outlet (16) configured to permit the passage of the heat transfer fluid out of said hollow structure (12), and characterized in that the channel of the hollow structure (12) is delimited by at least one wall (151, 152, 153, 154), and in that at least a portion of said wall (151, 152, 153, 154) is flexible.

2. Cooling device (10) according to the preceding claim, characterized in that the hollow structure (12) comprises: - an outer ring (17); - an inner ring (18) concentric with the outer ring (17); - segments (19) which extend radially between the inner ring (18) and the outer ring (17); in which the inner ring (18), the outer ring (17) and the segments (19) are hollow inside and joined in particular by heat welds (20) to form a continuous and sealed channel configured to convey a heat transfer fluid along a path passing from one ring (17; 18) to the other; the inner ring (18), the outer ring (17) and the segments (19) being arranged so as to form or delimit openings (21) intended to surround the windings (6) arranged inside the electrical machine (1).

3. Cooling device (10) according to the preceding claim, characterized in that the fluidic inlet (14) of the hollow structure (12) is arranged on the outer ring (17) and in that the fluidic outlet (16) of the hollow structure (12) is arranged on the inner ring (18), and / or in that the fluidic inlet (14) of the hollow structure (12) is arranged on the inner ring (18) and in that the fluidic outlet (16) of the hollow structure (12) is arranged on the outer ring (17).

4. Cooling device (10) according to any one of claims 2 or 3, characterized in that a passage section of the segments (19) which extend radially between the inner ring (18) and the outer ring (17) is less than or equal to a passage section of the inner ring (18) and / or in that a passage section of the segments (19) is less than or equal to a passage section of the outer ring (17).

5. Cooling device (10) according to claim 1, characterized in that the channel of the hollow structure (12) comprises a serpentine shape, said channel being intended to be arranged at least partially around the windings (6) inside the electrical machine (1) so as to convey a heat transfer fluid in a radial direction between two adjacent windings (6).

6. Cooling device (10) according to any one of the preceding claims, characterized in that the channel of the hollow structure (12) has several superimposed stages along the axial direction of the electrical machine (1) in which the cooling device (10) is intended to be mounted.

7. Cooling device (10) according to any one of the preceding claims, characterized in that the hollow structure (12) comprises at least one thermoplastic polymer material.

8. Cooling device (10) according to any one of the preceding claims, characterized in that it comprises at least one insulated conducting wire covered with a bonding adhesive, said wire being arranged between at least one wall (151, 152, 153, 154) of the channel of the hollow structure (12) and at least one winding (6) inside the electrical machine (1).

9. Axial flux electric machine (1) characterized in that it comprises at least one cooling device (10) according to any one of claims 1 to 8.

10. Motor vehicle, characterized in that it is equipped with an axial flux electric machine (1) according to claim 9.

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