Axial flux electric machine with thermal guide between the stator coils

Abstract

The present invention relates to an axial flux electric machine comprising a housing enclosing at least one rotor and at least one stator, each stator comprising a stator body (6), teeth (7) regularly distributed circumferentially on the stator body (6), and coils (8) wound around the teeth (7), characterized in that each stator comprises thermal guides (9), each of said thermal guides (9) being fixed to the housing and comprising at least one radial portion (11) positioned between two coils (8) and in contact with said two coils (8) so as to dissipate heat from the stator to the housing by conduction, preferably, the radial portion (11) of each of the thermal guides (9) extending radially over at least the entire radial length and the entire axial length of the coils (8). Figure 4 to be published

Description

Title of the invention: Axial flux electric machine with thermal guide between the stator coils Technical field

[0001] The invention relates to the field of axial flux electrical machines.

[0002] This type of axial flux electric machine can notably find applications in electric or hybrid vehicles, such as cars, buses, trucks, construction machinery. Prior art

[0003] In recent decades, the development of electrical machines has focused mainly on radial flux electrical machines.

[0004] Radial flux electrical machines generally comprise a coaxial rotor and stator, one surrounding the other. Thus, the magnetic flux can pass radially from the rotor to the stator and vice versa, via a radial air gap which is defined as the radial clearance between the rotor and the stator.

[0005] On the contrary, axial flux machines are characterized by at least one rotor and at least one stator which are arranged successively one behind the other in the axial direction (of the axis of rotation of the rotor), so that the path of the magnetic flux between the rotor and the stator is axial. In other words, the rotor and the stator face each other and are separated by an air gap of axial thickness (or axial clearance between the rotor and the stator).

[0006] The rotor of axial flux electrical machines with permanent magnets generally comprises permanent magnets bonded to a rotor yoke or inserted into a rotor body and in this case, the permanent magnets are separated by radial arms from the rotor body. The stator generally comprises a ferromagnetic stator body with or without teeth. An electrical winding in the slots of the stator can be distributed or concentric, that is to say that each winding then surrounds a tooth.

[0007] In the context of the development of high power and torque density machines for electric or hybrid traction, particularly for electric or hybrid vehicle applications, the topology of axial flux machines is positioned among those with the highest potential, particularly due to the high axial size constraint. Axial flux electric machines are also of interest for stationary applications as well as for wind turbine applications.

[0008] Generally, axial flux electric machines allow higher power and torque densities than radial flux electric machines.

[0009] This gain is generally achievable by increasing the number of pairs of poles in the rotor, which increases the rotation frequency as well as rotor losses (i.e. losses in the magnets). In addition, the use of a tooth winding allows for a reduction in the coil heads, but increases the harmonic content in the air gap, causing increased losses in the stator iron and in the magnets.

[0010] As a result, axial flux machines tend to heat up more and controlling heating and cooling is therefore an important issue for this type of machine.

[0011] Utility model CN ​​212085909 U is known, which relates to an axial flux electric machine with two rotors and a single stator. To cool the stator, fluid circulation channels are positioned between the coils. However, the thickness of the circulation channels imposes a large space between the coils, which is detrimental to the performance of the machine. Furthermore, the circulation of the fluid is complex to achieve. In addition, since the stator is between the two rotors, the cooling of the stator is not optimal.

[0012] Patent application US 2013 / 285487 AA is also known, which relates to an axial flux electrical machine. Circulation channels are also positioned between the coils. However, cooling requires the circulation of a fluid and the space required between the coils is large, which reduces the space available for the winding. Thus, the filling coefficient and the number of turns to be inserted are limited. This reduces the electromagnetic performance of the machine in terms of torque and losses.

[0013] Thus, the technical problem that we propose to solve consists of improving the cooling of the stator, while simplifying it and maintaining the electromagnetic performance of the machine. Summary of the invention

[0014] To solve the aforementioned technical problem, the invention relates to an axial flux electrical machine comprising a casing enclosing at least one rotor and at least one stator, each stator comprising a stator body, teeth regularly distributed circumferentially on the stator body and coils wound around the teeth. In addition, the stator comprises thermal guides, each of said thermal guides being fixed, directly or indirectly, to a cold source (the casing) and comprising at least one radial portion positioned between two coils while being in contact with said two coils so as to evacuate the heat from the stator to the casing by conduction. Preferably, the radial portion of each of the thermal guides extends radially over at least the entire radial length and over the entire axial length of the coils.

[0015] Advantageously, the material of the thermal guide has a thermal conduction strictly greater than the thermal conduction of the material of the stator body, preferably the material of the thermal guide comprising aluminum or copper.

[0016] According to variants of the invention, each thermal guide is directly fixed to the casing or each thermal guide is directly fixed to the stator body, the stator body being fixed to the casing.

[0017] According to one configuration of the invention, the thermal guide comprises at least one means for fixing the stator to the flange.

[0018] Preferably, each thermal guide comprises a plate inserted radially between two consecutive coils.

[0019] Advantageously, each thermal guide comprises solid parts, at each radial end, the solid parts preferably extending over the entire axial length of the coils.

[0020] According to one embodiment of the invention, each thermal guide comprises a radially extending sole.

[0021] According to one configuration of the invention, the stator body comprises a groove for the passage of the sole.

[0022] According to a variant of the invention, the sole is fixed to the stator body, the stator body being fixed to the casing.

[0023] Advantageously, each thermal guide comprises two pads, one pad at each radial end of the thermal guide, each pad allowing the thermal guide to be fixed to a flange of the casing.

[0024] Advantageously, the thermal guides comprise a common outer ring and / or a common inner ring, the common outer ring and / or the common inner ring being fixed to the casing.

[0025] Preferably, the electrical machine comprises two rotors and one stator, two stators and one rotor. List of figures

[0026] Other characteristics and advantages of the electrical machine according to the invention will appear on reading the following description of non-limiting examples of embodiments, with reference to the appended figures described below. [Fig 1]

[0027] [Fig.l] represents a first variant of an axial flux machine according to the invention. [Fig 2]

[0028] [Fig.2] represents a second variant of an axial flux machine according to the invention. [Fig 3]

[0029] [Fig. 3] represents a stator in longitudinal sectional view of an axial flux machine according to the invention. [Fig 4]

[0030] [Fig.4] represents a perspective view of a stator portion of an axial flux machine according to the invention. [Fig 5]

[0031] [Fig.5] represents a first embodiment of a thermal guide of an axial flux machine according to the invention. [Fig 6]

[0032] [Fig.6] represents a second embodiment of a thermal guide of an axial flux machine according to the invention. [Fig 7]

[0033] [Fig.7] represents a third embodiment of a thermal guide of an axial flux machine according to the invention. [Fig 8]

[0034] [Fig.8] represents a first variant of a fourth embodiment of a thermal guide of an axial flux machine according to the invention. [Fig 9]

[0035] [Fig.9] represents a second variant of a fourth embodiment of a thermal guide of an axial flux machine according to the invention. [Fig 10]

[0036] [Fig. 10] represents a third variant of a fourth embodiment of a thermal guide of an axial flux machine according to the invention. Description of the embodiments

[0037] The invention relates to an axial flux electric machine comprising a casing enclosing at least one rotor and at least one stator.

[0038] The casing may comprise two flanges directly connected to each other, or two flanges and an outer cylinder (also called a "liner"), or any similar design, a flange being positioned at each axial end of the outer cylinder. Thus, the casing forms an outer envelope of the electrical machine. This outer envelope serves as protection for the stator(s) and rotor(s) which are located inside this outer envelope. The outer envelope also serves to position and fix the active parts of the electrical machine. In addition, this outer envelope may serve to cool the electrical machine, by convection with the ambient outside air or by the circulation of a heat transfer fluid in and / or around the outer envelope (in and / or around the cylinder and / or the flanges). The casing is then considered like a cold spring.

[0039] Each stator comprises a stator body, teeth regularly distributed circumferentially on the stator body, the teeth being fixed to the stator body. The teeth extend axially. The stator also comprises coils wound around the teeth.

[0040] The rotor may for example comprise a rotor disc made of metallic material and permanent magnets. Thus, when the coils of the stator of the electrical machine are crossed by an electric current, an electromagnetic torque is produced and drives the rotor of the machine in rotation, thanks to the interaction between the stator field produced by the winding and the rotor field produced by the permanent magnets. Conversely, when the rotor is driven in rotation by any rotation means (a rotation shaft for example), the permanent magnets generate a magnetic field which creates an induced voltage in the coils of the stator. This makes it possible to transform the mechanical energy of rotation of the rotor into electrical energy in the stator.Therefore, the electric machine can be used as an electric motor that transforms electricity into mechanical energy by rotating the rotor, or as an electric generator that transforms rotating mechanical energy into electrical energy.

[0041] According to the invention, each stator comprises thermal guides, each of said thermal guides being fixed, directly or indirectly (indirectly means for example by an intermediate part) to the casing (considered as being the cold source) and comprising at least one radial part positioned between two coils while being in contact with said two coils so as to evacuate the heat from the stator to the casing by thermal conduction (only by heat conduction, without requiring an exchange fluid by thermal convection). The material of the thermal guides may have a thermal conductivity for example greater than 50 W / (mK). Thus, the thermal guide captures the heat from the two coils with which it is in contact, thanks to the radial part, and it evacuates the heat to the casing, simply by conduction, thanks to the connection of the thermal guide to the casing.The casing is cooled by natural convection with the air surrounding it or by the circulation of a heat transfer fluid in circuits arranged in the casing. The invention therefore makes it possible to dispense with cooling channels with an internal fluid to capture the heat and evacuate it outside the electric machine. Thus, the cooling according to the invention is simplified. Furthermore, since the invention does not require circulation channels in the stator, the space between the coils can be reduced and the thermal guide can only fill a small empty space between the coils. As a result, the electromagnetic performance of the electric machine can be maintained.

[0042] According to the invention, the axial flux machine can thus comprise at least one rotor and at least one stator which are arranged successively one behind the other in the axial direction (of the axis of rotation of the at least one rotor), so that the path of the magnetic flux between each successive rotor and stator (i.e. which follow one another directly) is axial. In other words, each successive rotor and stator face each other and are separated by an air gap of axial thickness (or axial clearance between the rotor and the stator).

[0043] Preferably, each thermal guide can advantageously be directly fixed to the casing. In other words, there is no interface part for the connection between the thermal guide and the casing. Thus, cooling by heat conduction is improved.

[0044] Alternatively, each thermal guide may be directly attached to the stator body, which is itself attached to the casing. In other words, the stator body serves as an interface piece for the connection between the thermal guide and the casing.

[0045] According to one implementation of the invention, the thermal guide may comprise at least one means for fixing the stator to the flange.

[0046] Advantageously, the radial portion of each of the thermal guides can extend radially over at least the entire radial length and over the entire axial length of the coils. As a result, each thermal guide can capture heat by conduction over the entire possible exchange surface between the coils and the thermal guide. Cooling is thus improved.

[0047] According to one configuration, the material of the thermal guide may have a thermal conductivity strictly greater than the thermal conductivity of the material of the stator body. As a result, the thermal guide can more efficiently evacuate heat to the casing by thermal conduction.

[0048] For example, the thermal guide material may have a thermal conductivity at least 10% greater than the thermal conductivity of the stator body material.

[0049] Preferably, the material of the thermal guide may comprise aluminum or copper, for example the thermal guide may be made of aluminum or copper or an alloy of aluminum and / or copper. Thus, the heat is easily conducted to the casing. In addition, the use of these materials allows the thermal guide to be made with a plate. The choice of the material of the thermal guides and its thermal conductivity may depend on the design of the electrical machine, in particular the material of the stator, the sizing of the stator, the coils, etc.

[0050] Advantageously, the casing (the external cylinder and / or the flanges) may in particular be made of aluminum or aluminum alloy, to promote the cooling of the electric machine.

[0051] According to a variant of the invention, the thermal guide can be covered with a electrical insulation layer, especially if the thermal guide is made of an electrically conductive material (such as copper for example). The electrical insulation layer can be a coating, such as a varnish, like that which generally covers the wires of the coils.

[0052] An electrical insulation layer is understood to mean a layer of a non-conductive dielectric material. The material is conductive if there is a risk of a short circuit. For example, the electrical insulation layer may be a layer of a material whose electrical conductivity is lower than that of the material of the thermal guide. The production of this electrical insulation layer may be done simultaneously with the layer which covers the coils or separately.

[0053] According to a variant of the invention, each thermal guide may comprise a plate inserted radially between two circumferentially consecutive coils of the same stator. The plate may then form said radial portion of the thermal guide. The use of a plate makes it possible to be inserted into a restricted space between the coils, the plate having a small thickness, which makes it possible to maintain the electromagnetic performance of the electrical machine without having to increase the space between the coils in order to be able to insert the thermal guide.

[0054] For example, each thermal guide plate may have a thickness of between 0.5 and 5 mm, preferably between 1 and 2 mm. Thus, the space between the coils can be reduced to a minimum. The continuous and transient thermal performance of the machine is thus improved thanks to the cooling induced by the thin thermal guide.

[0055] According to an advantageous embodiment of the invention, each thermal guide may comprise solid parts, a solid part at each radial end (preferably of the radial part), the solid parts being able to extend over the entire axial length of the coils. By "solid part", it is meant that the part concerned is of greater thickness than the thickness of the thermal guide between these solid parts (i.e. the thickness of the radial part in particular), the thickness being substantially taken in the circumferential direction. The solid part thus locally comprises a greater quantity of material than the part of the thermal guide located between these solid parts (the part between the solid parts being able in particular to be the radial part and preferably a plate).These massive parts allow on the one hand to capture the heat from the radial parts by increasing the mass of heat-conducting material and on the other hand to keep the stator and / or coils in position at each radial end. In addition, thanks to these massive parts, it is possible to increase the exchanges between the massive parts and the casing.

[0056] According to a first embodiment of the invention, each thermal guide may comprise a radially extending sole.

[0057] A sole has a thickness (in the axial direction) greater than the thickness of the radial portion (and preferably, than the thickness of the solid portions) to facilitate positioning of the thermal guide and its retention in position. The sole is also configured to fit into a groove of the stator body, so as to promote heat dissipation and ensure that the thermal guide is retained in position. The sole extends over the entire radial length of the thermal guide.

[0058] The surface of the sole which is opposite to that linked to the radial part rests on the stator body.

[0059] The sole is positioned at an axial end of the thermal guide so as to be able to come into contact with the stator body.

[0060] In this configuration, the stator body may advantageously comprise a groove (notch) for the passage of the base plate. Thanks to the groove in the stator body, it is possible to position the thermal guide and hold it in position. Furthermore, when the thermal guide is fixed directly to the casing (by pads of the thermal guide for example), the heat from the coils can be evacuated directly from the coils to the casing by the thermal guide. Thus, the stator body does not form a thermal resistance to this evacuation.

[0061] Alternatively, when each thermal guide comprises a radially extending sole, the stator body may not comprise a groove. The sole of the thermal guide may then be fixed to the stator body, itself fixed to the casing or the thermal guide may be fixed to the casing directly via pads of the thermal guide.

[0062] Additionally or alternatively, each thermal guide may comprise two pads, one pad at each radial end of the thermal guide, each pad allowing the thermal guide to be fixed directly to a flange of the casing (i.e. without an intermediate part, in particular without the stator body between the thermal guide and the flange).

[0063] The pads are extensions of the thermal guide in the axial direction, at the radial ends of the thermal guide, in the direction opposite to that where the rotor is located. The pads may be designed to surround the stator body. The pads may therefore preferably extend axially, preferably over at least the entire axial length of the stator body, the pads being advantageously located on either side of the stator body (one on the internal side and the other on the external side) so as to allow direct attachment to the housing flange.

[0064] The pads can also be used to lock the stator in position: in other words, the pads can serve as means for fixing the stator body to the casing. In this case, they are then configured to take up electromagnetic axial forces.

[0065] According to a variant of the invention, the thermal guides may comprise a common outer ring and / or a common inner ring, the outer and / or inner ring being fixed to the casing. In other words, the different thermal guides comprise an outer ring and / or an inner ring. And starting from at least one of these rings, the thermal guide comprises radial parts which extend between the coils. This configuration allows for simplified implementation. It also allows for fixing of the outer / inner ring to the outer cylinder and / or to the casing flange and / or for fixing of the inner ring to the casing flange.

[0066] Advantageously, the axial flux electric machine can axially comprise a succession of rotors and stators. The multiplication of rotors and / or stators makes it possible to increase performance (particularly torque and power), and this in a restricted space requirement.

[0067] Preferably, the axial flux electric machine may comprise two rotors and one stator, two stators and one rotor or a stack of alternating stators and rotors. The stators as described are particularly suitable for stators at the axial ends of the electric machine, for example for an electric machine with two stators and a central rotor, particularly when the thermal guides are fixed to the end plates of the casing. When the thermal guides can be fixed to the external cylinder of the casing (by the common external ring of the thermal guides in particular), the stator can be used anywhere, including in a machine with two rotors and a central stator.

[0068] More particularly, the invention may relate to an axial flux electric machine with permanent magnets passing through the rotor. The stator according to the invention is suitable for this type of machine and makes it possible to reduce the axial size of the machine.

[0069] A machine with two rotors and one stator can thus successively axially comprise a first rotor, a central stator (i.e. between the two rotors) and a second rotor.

[0070] A machine with two stators and one rotor can thus successively axially comprise a first stator, a central rotor (i.e. between the two stators) and a second stator.

[0071] [Fig.l] illustrates, in a schematic and non-limiting manner, a first variant of an axial flux machine according to the invention.

[0072] The axial flux machine comprises a casing 2. The casing 2 comprises an outer cylinder 5 and two flanges 3, one flange 3 at each axial (or longitudinal) end of the outer cylinder 5, so that the flanges 3 and the outer cylinder 5 form an outer casing. Inside the casing 2, the electrical machine here comprises a rotor 1 and two stators 100. The stators 100 are located on either side of the rotor 1, along the axis of rotation A of the rotor. In other words, along of the axis A of rotation of the rotor, there is a stator 100, then the rotor 1 and then another stator 100. The rotor 1 is a rotor with permanent magnets 4, passing completely through the rotor. Thus, the permanent magnets face the two stators 100, which makes it possible to reduce the axial size of the electric machine.

[0073] [Fig.2] illustrates, in a schematic and non-limiting manner, a second variant of an axial flux machine according to the invention.

[0074] The axial flux machine comprises a casing 2. The casing 2 comprises an outer cylinder 5 and two flanges 3, one flange 3 at each axial (or longitudinal) end of the outer cylinder 5, so that the flanges 3 and the outer cylinder 5 form an outer envelope. Inside the casing 2, the electrical machine here comprises a stator 100 and two rotors 1. The rotors 1 are located on either side of the stator 100, along the axis of rotation A of the rotor. In other words, along the axis A of rotation of the rotor, there is a rotor 1, then the stator 100 then another rotor 1. The rotors 1 are rotors with permanent magnets 4, completely glued to a rotor yoke, the rotor yoke being a disk, also called a rotor body, capable of receiving magnets glued to at least one of the surfaces facing a stator.

[0075] Figures 1 and 2 illustrate two variants of axial flux electric machine according to the invention but the invention is not limited to this type of electric machine. In particular, the invention could be an electric machine with a single rotor and a single stator or an electric machine with other numbers of rotors and / or stators.

[0076] [Fig. 3] illustrates, in a schematic and non-limiting manner, a longitudinal sectional view of a stator and a casing of an axial flux electric machine according to the invention.

[0077] By longitudinal section is meant a section in a plane which includes the longitudinal axis (corresponding to axis A in Figures 1 and 2).

[0078] The electric machine comprises a casing with two flanges 3 (only one is illustrated) and an external cylinder 5. The flange 3 is positioned at a longitudinal end of the external cylinder 5 to form, with the latter, an external casing.

[0079] Inside the casing, there are (at least) one stator and (at least) one rotor (not shown).

[0080] The stator comprises a stator body 6 and teeth 7 which extend axially (the axis being represented by the dot-dash line) from the stator body 6. The teeth 7 serve as a support for the winding of the coils 8 which are wound around the teeth 7.

[0081] In addition, the electrical machine comprises thermal guides which comprise at least radial portions extending between the coils and which are fixed directly to the housing, for discharging heat from the coils to the housing, solely by conduction through the thermal guides.

[0082] In the figure, part 18 corresponds to a part of the thermal guide which is fixed to the external cylinder 5 of the casing. This part could nevertheless be replaced by a part intended to be fixed directly to the flange. In other words, part 18 is only an alternative embodiment for the illustration.

[0083] [Fig.4] illustrates, in a schematic and non-limiting manner, a perspective view of a portion of stator to facilitate understanding.

[0084] The stator comprises a stator body 6, here of annular shape, defined between a cylindrical internal surface and a cylindrical external surface.

[0085] Teeth 7 are fixed to the stator body 6 and extend axially from the stator body, preferably towards the rotor which is opposite the stator. For the illustrated embodiment, the teeth have a substantially triangular or trapezoidal shape. However, other shapes can be envisaged.

[0086] Coils 8 are wound around the teeth 7.

[0087] In addition, the axial flux electric machine comprises thermal guides 9 which comprise a radial portion 11 which extends radially between the coils, so as to be in contact with the two coils 8 on either side of the radial portion 9. Thus, the thermal guide can recover the heat from the two coils 8.

[0088] The radial portion 11 extends over the entire axial length of the coils 8 and over the entire radial length of the coils 8.

[0089] In addition, the thermal guide 9 comprises massive parts 10, at each radial end of the guide, on the one hand to increase the exchange surface with the coils, and on the other hand to facilitate holding the coils in position and avoid potential vibrations.

[0090] The thermal guide 9 also comprises studs 13, at each radial end, the studs serving to fix the thermal guide to the flange of the casing (not shown). Thus, the heat recovered by the thermal guide 9 can be directly transmitted to the casing, without passing through the stator body, which forms a thermal resistance.

[0091] In addition, since the pads are located on either side of the stator body, the pads serve as means for attaching the stator body to the flange.

[0092] The thermal guide here also comprises a base 12 which is intended to be inserted into a groove of the stator body 6. Alternatively, the thermal guide could not comprise a base or the rotor body could not comprise a groove.

[0093] [Fig.5] illustrates, in a schematic and non-limiting manner, a first embodiment of a thermal guide according to the invention.

[0094] The thermal guide 9 comprises a radial part 11, formed by a plate of small thickness (less than 5 mm, between 1 and 2 mm for example), and two solid parts 10 at each radial end of the plate.

[0095] The plate and the massive parts 10 extend axially over at least the entire axial length of the coils which are located on either side of the thermal guide 9.

[0096] Furthermore, the thermal guide comprises a sole 12 whose thickness (axial direction) is greater than the thickness of the radial part (and preferably, than the thickness of the solid parts 10) to facilitate the positioning of the thermal guide and its maintenance in position. The sole 12 is configured to fit into a groove of the stator body (not shown), so as to promote the evacuation of heat.

[0097] The sole 12 extends over the entire radial length of the thermal guide.

[0098] The surface of the sole 12 which is opposite to that linked to the radial part 11 rests on the stator body.

[0099] Furthermore, the thermal guide comprises two pads 13, one at each radial end of the thermal guide. The pads can advantageously go around the annular-shaped stator body, one of the pads being located on the internal side and the other on the external side. The pads are fixed, at the surfaces 14 opposite the rotor, to the end plate of the casing.

[0100] [Fig.6] illustrates, in a schematic and non-limiting manner, a second embodiment of a thermal guide according to the invention.

[0101] The thermal guide 9 comprises a radial part 11, formed by a plate of small thickness (less than 5 mm, between 1 and 2 mm for example), and two solid parts 10 at each radial end of the plate.

[0102] The plate and the solid parts 10 extend axially over at least the entire axial length of the coils which are located on either side of the thermal guide 9.

[0103] Furthermore, the thermal guide comprises two pads 13, one at each radial end of the thermal guide. The pads can advantageously go around the annular-shaped stator body, one of the pads being located on the internal side and the other on the external side. The pads are fixed, at the surfaces 14 opposite the rotor, to the end plate of the casing.

[0104] The surface 15 of the radial part 11 opposite the surface facing the rotor is placed in contact with the stator body (not shown).

[0105] [Fig.7] illustrates, in a schematic and non-limiting manner, a third embodiment of a thermal guide according to the invention.

[0106] The thermal guide 9 comprises a radial part 11, formed by a plate of small thickness (less than 5 mm, between 1 and 2 mm for example). As shown, the thermal guide 9 does not comprise solid parts at each radial end of the plate, but could of course comprise them without departing from the scope of the invention.

[0107] The plate extends axially over at least the entire axial length of the coils which are located on either side of the thermal guide 9.

[0108] Furthermore, the thermal guide comprises a sole 12 whose thickness (axial direction) is greater than the thickness of the radial part to facilitate the posi operation of the thermal guide and its holding in position. The sole 12 is configured to be able to be inserted into a groove in the stator body (not shown), so as to promote the evacuation of heat. But it can also be fixed to the stator body without the latter having a groove.

[0109] The sole 12 preferably extends, as shown, over the entire radial length of the thermal guide.

[0110] The surface of the sole 12 which is opposite that linked to the radial part 11 rests on the stator body.

[0111] In this variant, the thermal guide does not include any pads.

[0112] [Fig.8] illustrates a first variant of another embodiment of thermal guides for an axial flux electric machine according to the invention.

[0113] The thermal guides are all connected to each other via an external ring 16 common to all the thermal guides. Thus, from the common external ring 16, radial parts 11 are fixed to pass between the coils. The external ring 16 can for example be fixed with the casing for the evacuation of calories.

[0114] [Fig.9] illustrates a second variant of another embodiment of thermal guides for an axial flux electric machine according to the invention.

[0115] The thermal guides are all connected to each other via an internal ring 17 common to all the thermal guides. Thus, from the common internal ring 17, radial parts 11 are fixed to pass between the coils. The internal ring 17 can for example be fixed with the casing for the evacuation of calories.

[0116] [Fig. 10] illustrates a third variant of another embodiment of thermal guides for an axial flux electric machine according to the invention.

[0117] The thermal guides are all connected to each other via a common outer ring 16 and via a common inner ring 17 to all the thermal guides. Thus, from the common outer ring 16 and the common inner ring 17, radial parts 11 are fixed to pass between the coils. With the double fixing to the common outer and inner rings, the radial parts 11 are better maintained and the vibration phenomena can be limited.

[0118] Furthermore, for the variants of figures 8 to 10, the implementation for mounting the stator can be simplified.

[0119] For figures 8 to 10, the outer ring and / or the common inner ring can be fixed directly to the casing of the electric machine, either to the outer cylinder or to a flange. Examples

[0120] The solution of the invention according to [Fig.4] was compared to a solution of the prior art where the only difference with [Fig.4] is the absence of the thermal guides 9 (the space between the coils is left empty and the air can circulate freely by natural convection).

[0121] Thanks to the thermal guide according to the invention, the maximum temperature in the coils is reduced by 33°C for the same power level at the operating point, all other things being equal.

Claims

Claims

1. An axial flux electrical machine comprising a casing (2) enclosing at least one rotor (1) and at least one stator (100), each stator (100) comprising a stator body (6), teeth (7) regularly distributed circumferentially on the stator body (6) and coils (8) wound around the teeth (7), characterized in that each stator comprises thermal guides (9), each of said thermal guides (9) being fixed, directly or indirectly, to the casing (2) and comprising at least one radial portion (11) positioned between two coils (8) while being in contact with said two coils (8) so as to evacuate the heat from the coils to the casing (2) by conduction, and preferably, the radial portion (11) of each of the thermal guides (9) extending radially over at least the entire radial length and over the entire axial length of the coils (8).

2. An electrical machine according to claim 1, wherein the material of the thermal guide (9) has a thermal conductivity strictly greater than the thermal conductivity of the material of the stator body (6), preferably the material of the thermal guide comprising aluminum or copper.

3. An electrical machine according to any preceding claim, wherein each thermal guide is directly attached to the casing or wherein each thermal guide is directly attached to the stator body, the stator body being attached to the casing.

4. Electrical machine according to one of the preceding claims, in which the thermal guide comprises at least one means for fixing the stator to the flange.

5. Electrical machine according to one of the preceding claims, in which each thermal guide (9) comprises a plate inserted radially between two consecutive coils (8).

6. Electrical machine according to one of the preceding claims, in which each thermal guide (9) comprises solid parts (10), at each radial end, the solid parts (10) preferably extending over the entire axial length of the coils (8).

7. Electrical machine according to one of the preceding claims, in which each thermal guide (9) comprises a sole (12) extending radially.

8. An electrical machine according to claim 7, wherein the body of stator (6) includes a groove for the passage of the sole (12).

9. An electrical machine according to either of claims 7 or 8, wherein the sole is fixed to the stator body, the stator body being fixed to the casing.

10. Electrical machine according to one of the preceding claims, in which each thermal guide (9) comprises two studs (13), one stud at each radial end of the thermal guide (9), each stud (13) allowing the thermal guide (9) to be fixed to a flange (3) of the casing (2).

11. An electrical machine according to one of the preceding claims, wherein the thermal guides (9) comprise a common outer ring (16) and / or a common inner ring (17), the common outer ring (16) and / or the common inner ring (17) being fixed to the casing.

12. An axial flux electric machine according to one of the preceding claims, comprising two rotors (1) and one stator (100), or two stators (100) and one rotor (1).

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