Electric machine comprising a ventilation device

Abstract

The invention relates to an electric machine (1) comprising a stator (2) and a rotor (3) having an axis of rotation (X), one of the stator (2) or the rotor (3) coming around the other of the stator (2) or the rotor (3) such that an annular volume (4) is arranged between the stator (2) and the rotor (3), the rotor (3) comprising a ventilation device (5) movable in rotation relative to the stator (2), positioned at a first end (8a) of the electric machine (1) and configured to generate a flow of fluid in the annular volume (4) from a longitudinal inlet (6a) of the annular volume (4) positioned at the first end (8a) of the electric machine (1) to a longitudinal outlet (6b) of the annular volume (4) positioned at a second end (8b) of the electric machine (1), opposite the first end (8a).

Description

Electric machine including a ventilation device Technical Field

[0001] The invention relates to the field of cooling electrical machines and electronic components of electrical machines, such as power electronic modules. The invention also relates to an aircraft incorporating such an electrical machine. Previous technique

[0002] The present invention can be used, in particular, in the aeronautical field for electrical machines intended for propulsive or non-propulsive applications on board an aircraft, for example. The electrical machine is notably usable in an electromechanical actuation system.

[0003] An electrical machine classically comprises a stator and a rotor with an axis of rotation. The stator has a central circular opening, a plurality of teeth extending into the central circular opening in a radial direction of the stator, a plurality of power sets each comprising a coil wound around one of the teeth, and a coil support supporting the power sets.

[0004] Electrical machines are configured to reach a maximum temperature at the end of their operation very quickly, after a few minutes, for example, resulting in a limitation of the performance of these electrical machines.

[0005] Indeed, improving the torque performance of the electric machine is difficult without increasing the current, which risks raising the machine's temperature to unacceptable levels, resulting in decreased machine performance. electrical, or even its destruction. This operation at higher temperatures also increases the carbon footprint.

[0006] The electric machine also includes power electronic modules, which allow the electric machine to be supplied with electrical energy from the main network.

[0007] In order to improve the compactness and performance of electrical systems, power electronic modules can be integrated into the electrical machine, between the rotor and the stator, by being supported by an internal surface of the stator positioned opposite the rotor or by an external surface of the stator positioned opposite a housing which houses the rotor and the stator, for example.

[0008] However, power electronic modules contain heat sources that need to be cooled to prevent damage to the equipment and ensure efficient operation.

[0009] Solutions exist that utilize a heat exchanger comprising a first face mounted in contact with the power electronic modules and a second face opposite the first, defining an annular volume with the rotor through which a cooling fluid circulates by convection. The fluid can be air. The rotation of the air within the annular volume, driven by the rotor, increases the heat exchange between the air and the heat exchanger.

[0010] It is known to use annular heat exchangers with straight fins arranged perpendicular to the rotor's axis of rotation. However, straight fins are most efficient when the fluid flow is directed along the fins. During operation, the rotor induces swirling flows between the rotor and the heat exchanger. These flows can exhibit variations in inclination, which impacts the efficiency of heat exchange between the fins and the fluid. Therefore, there is a need to improve heat exchange in the context of a convective environment with a rotating fluid.

[0011] Furthermore, this solution only cools the power electronic modules and not the inside of the electrical machine.

[0012] This solution also does not allow for the cooling of power electronic modules that would be positioned on the periphery of the coils. Description of the invention

[0013] The objective of the present invention is to solve at least partially these problems and to provide an electrical machine in which the cooling between the rotor and the stator is improved, also resulting in improved cooling of the power electronic modules positioned between the rotor and the stator.

[0014] The present invention relates to an electrical machine comprising a stator and a rotor having an axis of rotation, one of the stator or the rotor surrounding the other of the stator or the rotor such that an annular volume is arranged between the stator and the rotor. The stator includes a yoke comprising a plurality of teeth extending radially within the annular volume, a plurality of power assemblies each comprising a coil wound around one of the teeth, and a coil support supporting the power assemblies, each power assembly comprising a power module positioned on a radial face of the stator, inside the annular volume, and which is configured to supply current to the coil.The rotor includes at least one movable ventilation device, rotatable relative to the stator, positioned at a first end of the electric machine and configured to generate fluid flow within the annular volume from a longitudinal inlet of the annular volume located at the first end of the electric machine to a longitudinal outlet of the annular volume located at a second end of the electric machine, opposite the first end. The electric machine includes a first bearing positioned at the first end of the electric machine, with the ventilation device positioned between the first bearing and the bearing. bearing and stator. The electric machine also includes a casing in which the stator and rotor are housed, the casing including a first housing containing the first bearing and the ventilation device.

[0015] The invention thus provides an electrical machine in which cooling between the rotor and the stator is improved. The power electronic modules positioned between the rotor and the stator are also better cooled by convection.

[0016] The air inlet is located on the side of the ventilation device in the first bearing, while the air outlet is located opposite the first bearing, on the same axis as the air inlet, at the second end of the electric machine. No additional opening is required, unlike known solutions. Furthermore, the airflow through the air gap is achieved by positive pressure, which generates more turbulence and thus better heat exchange compared to known solutions where negative pressure is created.

[0017] The torque performance of the electric machine can thus be improved by increasing the current, without the risk of raising the machine's temperature to unacceptable levels. The risk of reduced performance and machine failure is eliminated. The carbon footprint is also reduced.

[0018] According to one variant, the rotor includes a shaft around which the ventilation device is fixed.

[0019] According to one variant, the ventilation device comprises a propeller having a ring fixed to the shaft and a plurality of blades extending radially from the ring.

[0020] According to one variant, the rotor includes magnets distributed around the shaft, with the blades positioned opposite one axial end of the magnets and opposite the longitudinal inlet of the annular volume.

[0021] According to one variant, the coil support includes at least one main channel extending longitudinally in the coil support from an inlet of the main channel positioned at a first end of the coil support to an outlet of the main channel opening at a second end of the coil support, opposite the first end, the inlet being in fluidic communication with the annular volume.

[0022] Thus, a portion of the fluid circulates within the annular volume, while a second portion flows through the main channel, helping to reduce the pressure induced by the small gaps in the annular volume and improving the flow rate. This allows the coils and power modules to be cooled more efficiently by convection.

[0023] According to one variant, the main canal is positioned between two teeth.

[0024] According to one variant, the rotor comprises at least a first row of first fins extending from an external face of the rotor towards the stator. The stator comprises at least a second row of second fins extending from the radial face of the stator towards the rotor, the first fins crossing and running alongside the second fins when the rotor is moving relative to the stator.

[0025] The fins improve cooling by radiation and convection.

[0026] According to one variant, the first fins extend radially along a first plane perpendicular to the axis of rotation, the second fins extend radially along a second plane perpendicular to the axis of rotation and inclined with respect to the first plane.

[0027] According to one variant, the first and second fins are mobile in rotation relative to each other around a longitudinal axis, perpendicular to the axis of rotation, between an inclined position in which the first and second fins form an angle between them and a non-inclined position in which the first and second fins are parallel.

[0028] This solution improves the cooling of the annular volume between the stator and rotor of a moving electrical machine by 75%, both at low and high altitudes where the air is less dense. Convective cooling is favored at low altitudes, and radiative cooling is favored at high altitudes.

[0029] According to one variant, the electric machine comprises an annular heat dissipation ring fixed to an external face of the rotor and at least one dissipation plate fixed to the radial face of the stator, the heat dissipation ring comprising at least one first annular dissipation fin extending radially towards the stator, and the dissipation plate comprising at least one second dissipation fin extending radially from the radial face of the stator towards the rotor, the first dissipation fin crossing and running alongside the second dissipation fin when the rotor is moving relative to the stator.

[0030] The dissipation fins improve radiation cooling.

[0031] According to one variant, each power module is positioned on the radial face of the stator at the first end of the coil support, opposite the rotor and the ventilation device.

[0032] According to one variant, the electric machine includes a first ventilation device positioned in the first housing, upstream of the annular volume, and a second ventilation device positioned in a second housing, downstream of the annular volume.

[0033] This configuration allows for a greater airflow, improving the cooling of the electronic modules.

[0034] According to one variant, the first housing is delimited by a peripheral wall extending to a first axial face of the stator, the peripheral wall comprising a radial face of circular section having a flared shape.

[0035] This flared shape improves fluid channeling from outside the electrical machine to the annular volume inside the machine. This flared shape is particularly advantageous when the ventilation device is a propeller with a diameter larger than the air gap diameter. The flared shape allows for a narrowing of the first chamber, thus compressing the air.

[0036] The invention also relates to an aircraft comprising an electrical machine as defined above. Brief description of the drawings

[0037] The invention and its advantages will be better understood upon reading the detailed description below of various embodiments of the invention, given by way of non-limiting examples. This description refers to the accompanying figures, in which:

[0038] [Fig. 1] Figure 1 schematically represents an example of an electrical machine comprising a ventilation device according to the invention,

[0039] [Fig. 2] Figure 2 schematically represents the interior of the electrical machine in Figure 1,

[0040] [Fig. 3] Figure 3 schematically represents the inside of a stator of the electrical machine in Figure 1,

[0041] [Fig. 4] Figure 4 schematically represents the interior of an electrical machine, according to another variant,

[0042] [Fig. 5] Figure 5 schematically represents the inside of a stator of the electrical machine in Figure 4,

[0043] [Fig. 6] Figure 6 schematically represents the first and second fins formed on the rotor and stator respectively, of the electric machine of Figure 4,

[0044] [Fig. 7] Figure 7 schematically represents the dissipation fins planned on the stator and rotor, according to another variant,

[0045] [Fig. 8] Figure 8 schematically represents a movable fin rotating according to air density, according to another variant,

[0046] [Fig. 9] Figure 9 schematically represents a top view of a first fin parallel to a second fin when the air density is low, in high-altitude mode, according to the variant of Figure 8,

[0047] [Fig. 10] Figure 10 schematically represents a top view of the first fin inclined relative to the second fin when the air density is higher, in low altitude mode, according to the variant of Figure 8. Description of the implementation methods

[0048] Figures 1 to 3 schematically represent an example of an electrical machine 1 comprising a stator 2 and a rotor 3 rotating about an axis of rotation X and relative to the stator 2. One of the stator 2 or of the rotor 3 comes around the other of the stator 2 or of the rotor 3 so that an annular volume 4 is arranged between the stator 2 and the rotor 3. In the example of Figure 1, the stator 2 surrounds the rotor 3.

[0049] The electric machine 1 can be used in the aeronautical field for electric machines 1 intended for propulsive or non-propulsive applications on board an aircraft, for example. The electric machine 1 is particularly usable in an electromechanical actuation system such as a rudder, a nozzle, a brake, a flap or an airbrake, for example.

[0050] As illustrated in Figures 2 and 3, the stator 2 has a central circular opening 16, a yoke 36 having a plurality of teeth 17 extending into the central circular opening 16 in a radial direction of the stator 2, a plurality of power assemblies 18 each having a coil 19 wound around one of the teeth 17, and a coil support 21 supporting the power assemblies 18. The coil support 21 encompasses at least part of the coil 19.

[0051] Each power assembly 18 comprises a power module 20 supported by the stator 2 and configured to supply current to the coil 19. The power modules 20 are positioned on a radial face 22 of the stator 2, opposite the rotor 3, and positioned at the first end 26 of the coil support 21. The radial face 22 of the stator 2 is partially formed by an internal face of the power assemblies 18. In this example, the radial face 22 is an internal radial face.

[0052] Alternatively, the radial face 22 can be an external radial face when the rotor surrounds the stator.

[0053] The power modules 20 supply electrical energy to the electric machine 1 from the main grid. The power modules 20 can advantageously be distributed circumferentially, particularly in a regular manner, around the axis of rotation X.

[0054] The electric machine 1 includes a first bearing 7a positioned at a first end 8a of the electric machine 1 and a second bearing 7b positioned at a second end 8b of the electric machine 1, opposite the first end 8a.

[0055] The electric machine 1 includes a casing 13 in which the stator 2 and the rotor 3 are housed. The casing 13 includes a first housing 14a housing the first bearing 7a and a second housing 14b housing the second bearing 7b.

[0056] The rotor 3 includes a shaft 9 passing through the first and second housings 14a, 14b.

[0057] The rotor 3 includes magnets 15 fixed to the shaft 9 and distributed circumferentially around the shaft 9. The magnets 15 are positioned inside the stator 2. The volume between the magnets 15 and the radial face 22 of the coil support 21 defines the major part of the annular volume 4.

[0058] As illustrated in Figures 1 and 2, the rotor 3 includes a ventilation device 5 movable in rotation relative to the stator 2, positioned at the first end 8a of the electric machine 1 and configured to generate at least one flow of fluid, in particular air, in the annular volume 4 from a longitudinal inlet 6a of the annular volume 4 positioned at the first end 8a of the electric machine 1 to a longitudinal outlet 6b of the annular volume 4 positioned at the second end 8b of the electric machine 1.

[0059] The rotation of the rotor 3 causes the fluid to rotate around the axis of rotation X, in the annular volume 4. The fluid flow is represented by arrows in Figure 2. The ventilation device 5 forces the fluid through the annular volume 4 by generating a fluid overpressure at the longitudinal inlet 6a and a fluid underpressure at the longitudinal outlet 6b.

[0060] The ventilation device 5 is positioned between the first bearing 7a and the stator 2. The ventilation device 5 is also positioned between the first bearing 7a and the magnets 15 of the rotor 3. The ventilation device 5 is housed in the first housing 14a.

[0061] The ventilation device 5 forces the fluid into the annular volume 4. The fluid is drawn in from outside the electrical machine 1 and then passes through the first bearing 7a to the inlet 6a. The fluid rotates within the annular volume 4, around the axis of rotation X, and then exits the annular volume 4 through the outlet 6b. Heat exchange, primarily by convection, then occurs between the fluid and the air gap of the electrical machine 1, and in particular with the power modules 20, which are thus efficiently cooled by the circulating fluid. The heated fluid is discharged from the electrical machine 1 through the second bearing 7b.

[0062] The air inlet is located on the side of the ventilation device in the first bearing 7a, while the air outlet is located opposite the first bearing 7a, on the same axis as the air inlet, in the second bearing 7b. No additional opening is required, unlike known solutions. Furthermore, the airflow through the gap is achieved by an overpressure that generates more turbulence and thus better heat exchange compared to known solutions where a low pressure is created.

[0063] The ventilation device 5 produces a greater fluid flow in the annular volume 4, thus improving convection cooling. The fluid flow rate is approximately 0.000143 kg / s, for example, for a given rotational speed of the rotor 3.

[0064] The first housing 14a is delimited by a peripheral wall 37 extending to a first axial face 38 of the stator 2. The peripheral wall 37 includes an axial end 39 in contact with the first axial face 38 of the stator 2 so as to optimally channel the fluid from outside the electrical machine 1 to the annular volume 4. The peripheral wall 37 includes an internal face 40 with a circular cross-section and a flared shape, as illustrated in Figure 3.

[0065] The power modules 20 are positioned at the first end 26 of the coil support 21, near the first axial face 38 of the stator 2 and opposite the ventilation device 5. This position allows for more efficient cooling of the power modules 20 which are in contact with the cold fluid coming from outside the electrical machine 1.

[0066] Each power module 20 is aligned with one of the teeth 17 of the cylinder head 36 along the direction of the axis of rotation X.

[0067] The ventilation device 5 is fixed around the shaft 9, allowing its rotation around the axis of rotation X and relative to the stator 2.

[0068] The ventilation device 5 comprises a propeller 10 having a ring 11 fixed to the shaft 9 and a plurality of blades 12 extending from the ring 11. The ring 11 is press-fitted onto the shaft 9. The blades 12 are parallelepiped in shape and flat. The blades 12 are regularly distributed around the shaft 9. The blades 12 are positioned opposite the inner face 40 of the peripheral wall 37 of the first housing 14a. The blades 12 are also positioned opposite an axial end 51 of the magnets 15 and opposite the longitudinal entrance 6a of the annular volume 4.

[0069] As illustrated in Figures 2 and 3, the coil support 21 comprises at least one main channel 23 extending longitudinally in the coil support 21 from an inlet 24 of the main channel 23 positioned at the first end 26 of the coil support 21 to an outlet 25 of the main channel 23 opening at a second end 27 of the coil support 21, opposite the first end 26. The inlet 24 is in fluidic communication with the annular volume 4. The main channel 23 extends between two teeth 17.

[0070] In this example, the main channel 23 has an oblong cross-section. The cross-section of the main channel 23 could be different, such as circular, for example.

[0071] The main channel 23 has a curved shape so that it can extend from the inlet 24, which is in fluidic communication with the annular volume 4, to the outlet 25 of the main channel 23, which is positioned on the side of an external face 35 of the stator 2, opposite the annular volume 4. A portion of the main channel 23 runs along the external face 35 as it approaches the outlet 25. The main channel 23 extends globally along the direction of the axis of rotation X.

[0072] One or more secondary channels 41 extend from the main channel 23 to the second end 27 of the coil support 21. The secondary channels 41 open through a second axial face 42 of the stator 2.

[0073] In the example, the secondary channels 41 are straight and extend along the direction of the rotation axis X. The secondary channels 41 can also be curved. In the example, three secondary channels 41 are connected to the main channel 23. The length of the secondary channels 41 decreases as they approach the outer face 35 of the stator 2. The secondary channels 41 have an oblong cross-section, for example.

[0074] The main channel 23 and the secondary channels 41 are positioned between two power sets 18, or in other words between two teeth 17. Each zone between two power sets 18 includes a main channel 23 and secondary channels 41.

[0075] Thus, a first portion of the fluid circulates in the annular volume 4, and a second portion circulates in the main channel 23 and the secondary channels 41, helping to reduce the pressure induced by the small spacing in the annular volume 4 and improving the flow rate. The coils 19 and the power modules 20 are thereby cooled more efficiently by convection. The fluid flow rate increases from approximately 0.000143 kg / s for an electric machine 1 without channels 23, 41 to approximately 0.000216 kg / s for an electric machine 1 with channels 23, 41, for the same rotor speed 3.

[0076] According to a first possible variant (not shown), the coil support 21 includes a helix 10 as described previously but does not include main channels 23.

[0077] According to a second variant illustrated in Figure 7, the electric machine 1 comprises, in combination with the ventilation device 5 and optionally channels 23, 41, an annular heat dissipation ring 52 intended to be fixed to the external face 32 of the rotor 3, around the rotor 3, and heat dissipation plates 53 intended to be fixed to the radial face 22 of the stator 2. The heat dissipation plates 53 are regularly distributed around the heat dissipation ring 52. The heat dissipation ring 52 covers the power modules 20.

[0078] The heat dissipation ring 52 comprises at least one first dissipation fin 33 extending radially towards the dissipation rings 52 in a direction orthogonal to the axis of rotation X. Each dissipation plate 53 comprises at least one second dissipation fin 34 extending radially from an inner face 54 of the dissipation plate 53, towards the heat dissipation ring 52 in a direction orthogonal to the axis of rotation X. Each first dissipation fin 33 crosses and runs alongside each second dissipation fin 34 when the rotor 3 is moving relative to the stator 2.

[0079] In this example, the rotor 3 comprises two first dissipation fins 33 positioned parallel to each other and facing each other. The first two dissipation fins 33 are adjacent. Each dissipation plate 53 comprises three second dissipation fins 34 positioned parallel to each other and facing each other. The three second dissipation fins 34 are grouped together and parallel to each other.

[0080] More specifically, each first dissipation fin 33 comprises two opposing first faces 43, and each second dissipation fin 34 comprises two opposing second faces 44. The first faces 43 of the first dissipation fins 33 intersect the second faces 44 of the second dissipation fins 34 when the rotor 3 is in motion.

[0081] The second 34 dissipation fins are capable of receiving a thermal flux of 15000W / m². 2 When the 20 power modules emit a power of approximately 5W, this results in a heat flux of 15000W / m². 2 allows for the complete dissipation of calories from these 20 power modules.

[0082] The first dissipation fins 33 and the second dissipation fins 34 allow the heat emitted by the power modules 20 to be dissipated by radiation. The rotation of the rotor 3 also creates convection between the two heat sinks formed by the dissipation fins 33 and 34. Heat dissipation by convection and radiation is improved. However, in the absence of turbulent modes of convection, this dissipation remains mainly dominated by radiation.

[0083] According to a third variant illustrated in Figures 4 to 6, the rotor 3 comprises, in combination with the ventilation device 5 and optionally channels 23, 41, at least a first row 30 of first fins 28 extending from an external face 32 of the rotor 3 towards the stator 2. The stator 2 comprises at least a second row 31 of second fins 29 extending from the radial face 22 of the stator 2 towards the rotor 3. The first fins 28 cross and run alongside the second fins 29 when the rotor 3 is in motion.

[0084] As illustrated in Figure 6, the rotor 3 comprises several rows 30 of first fins 28 projecting from the surface of the magnets 15. In this example, the rotor 3 comprises ten rows 30 of first fins 28 spaced equally apart. Within each first row 30, the first fins 28 are evenly distributed around the magnets 15. The surface of the magnets 15 is almost entirely covered by first fins 28.

[0085] The first fins 28 extend perpendicularly with respect to the outer face 32 of the rotor 3. The second fins 29 extend perpendicularly with respect to the radial face 22 of the stator 2. The first fins 28 and the second fins 29 are made of metal and have a flat shape, with an oblong cross-section, for example. Other shapes and cross-sections are possible, such as a rectangular cross-section.

[0086] As illustrated in the example in Figure 5, these second rows 31 of second fins 29 extend from a radially internal face 45 of the teeth 17. Each second row 31 comprises three second fins 29. Only one second row 31 of second fins 29 extends from a radially internal face 46 of the power modules 20. The second row 31 on the power module 20 comprises five second fins 29. The number of second rows 31 can vary on the teeth 17 and on the power modules 20 depending on the heat dissipation requirements.

[0087] The first fins 28 extend along a first plane perpendicular to the axis of rotation X. The second fins 29 extend along a second plane perpendicular to the axis of rotation X and inclined with respect to the first plane. In other words, the first fins 28 are inclined with respect to the second fins 29.

[0088] The fins 28 and 29 have a length between 5.3 mm and 7 mm, and a thickness of less than 1 mm, for example. The first fins 28 have an inclination between -10° and -60° with respect to the axis of rotation X, and the second fins 29 have an inclination between 10° and 60° with respect to the axis of rotation X. The first fins 28 are inclined relative to the second fins 29 at an angle between 20° and 70°, and preferably between 30° and 50° in absolute value.

[0089] When the first fins 28 cross the second fins 29 during the rotation of the rotor 3, a venturi channel is formed between the first and second fins 28, 29.

[0090] Figure 6 illustrates, as an example, three first rows 30 of first fins 28 intersecting three second rows 31 of second fins 29. When the first fins 28 intersect the second fins 29, an alternation of first rows 30 of first fins 28 and second rows 31 of second fins 29 is formed.

[0091] When the first and second rows of blades 30 and 31 cross, significant turbulence is created, accelerated by convection through the Venturi channel, while also promoting substantial radiative heat exchange due to the proximity and length of the blades. This situation proves particularly advantageous in the case of low air pressure, corresponding to an aircraft's cruising altitude or low rotor speed 3.

[0092] The first dissipation fins 33 and the second dissipation fins 34 illustrated in Figure 7 improve heat dissipation by convection by 60% in the case of ambient air density. The first and second inclined fins 28, 29 improve heat dissipation by convection by up to 75%, even with low air density.

[0093] According to a fourth variant illustrated in figures 8 to 10, the first and second fins 28, 29 are mobile in rotation about a longitudinal axis L between an inclined position (figure 9) in which the first and second fins 28, 29 form an angle at least when they are positioned opposite each other and a non-inclined position (figure 10) in which the first and second fins 28, 29 are substantially parallel at least when they are positioned opposite each other.

[0094] The longitudinal axis L is perpendicular to the axis of rotation X. The angle of inclination varies according to the air density and is between 0° and 80° in absolute value.

[0095] In the rest position, when the aircraft's electrical machine 1 is stopped, the first and second fins 28, 29 are initially parallel to each other.

[0096] When the electric machine 1 is running and the aircraft is moving at ambient air density, for example during takeoff, the angle between the first and second vanes 28, 29 is at its maximum. As the aircraft gains altitude, the air becomes thinner and the angle between the first and second vanes 28, 29 decreases.

[0097] As illustrated in Figure 8, the first and second fins 28, 29 each comprise a central metal portion 47 connected to two lateral portions 48. The central portion 47 is positioned between the two lateral portions 48. The two lateral portions 48 are made of a shape-memory material such as nickel-titanium, for example. Nitinole or any other type of alloy based on nickel and titanium as principal constituents, in nearly equal proportions, can be used.

[0098] The central portion 47 is not made of a shape memory material.

[0099] The two lateral portions 48 are passively deformable (without energy input) depending on the air density.

[0100] In a vacuum or near vacuum, the first and second fins 28, 29 are parallel to each other, as illustrated in Figure 9. Cooling is mainly achieved by radiation between the first and second fins 28, 29 and a temperature uniformly distributed over the first and second fins 28, 29.

[0101] In the presence of air, the first and second fins 28, 29 are tilted, as illustrated in Figure 10. A leading edge 49 of the fin 28, 29, which is the first edge in contact with the airflow, is at a different (higher) temperature than a trailing edge 50, opposite the leading edge 49. This creates a temperature difference inside the fin 28, 29, causing the leading edge 49 to rotate and deform. This rotation allows the leading edge 49 to return to lower temperatures. Nitinole transitions from the austenitic to the martensitic phase.

[0102] The deformation of the first and second fins 28, 29 occurs mainly between the ground and an altitude of about 2 km, corresponding to an air pressure varying substantially between 1000 Hpa and 800 Hpa.

[0103] The deformation of the fins 28, 29 also allows for the creation of forced convection by the formation of vortices and volutes between the fins 28, 29, improving heat transfer through an association of heat transfer by conduction, radiation and convection.

[0104] The angle of the vanes 28, 29 is at its maximum during the aircraft's low-level flight phases, such as takeoff and landing, i.e., when the electric motor 1 is under heavy load and the rotational speed of the rotor 3 increases. The electric motor 1 must then dissipate more heat. Thanks to the high air density at this altitude Near the ground, the fins 28 and 29 deform and tilt relative to each other, favoring convective cooling over radiation. At higher altitudes, due to lower air density, the fins 28 and 29 return to their initial position and become parallel to each other, maximizing radiation cooling. This cooling method is used for most of the aircraft's flight.

[0105] This solution improves the cooling of the annular volume 4 between the stator 2 and the rotor 3 of an electric machine 1 in motion by 75%, both at low altitude and at high altitude where the air is less dense.

[0106] According to another variant (not shown) which can be combined with the variants previously described, the electrical machine 1 includes a first ventilation device, as previously described, positioned in the first housing 14a, upstream of the annular volume 4, and a second ventilation device positioned in the second housing 14b, downstream of the annular volume 4.

[0107] The first ventilation device is configured to force a flow of fluid, from outside the electrical machine 1, to circulate in the annular volume 4. The second ventilation device is configured to extract the fluid from the annular volume 4 to the outside of the electrical machine 1. The airflow is then greater, improving the cooling of the electronic modules.

[0108] The first and second ventilation devices are propellers. Whether one or two ventilation devices are used, the annular volume 4 arranged between the stator 2 and the rotor 3 is under compression during cooling.

[0109] When two propeller ventilation devices are used, compression must be achieved by a vortex or whirl effect which is obtained through the first and second housings 14a, 14b, and the channels 23, 41.

[0110] Alternatively, it is possible to use a propeller that generates an annular vortex. [YES] Alternatively, the second housing 14b can be delimited by a second peripheral wall extending to the second axial face 42 of the stator 2. The second peripheral wall includes an axial end in contact with the second axial face 42 of the stator 2 so as to optimally channel the fluid from the inside of the electrical machine 1 to the outside of the electrical machine 1. The second peripheral wall includes an inner face with a circular cross-section and a flared shape (not shown).

[0112] The second flared-shaped dwelling 14b may include the second ventilation device when present or may not include the second ventilation device.

[0113] Although the present invention has been described with reference to specific embodiments, it is evident that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Demands

1. An electrical machine (1) comprising a stator (2) and a rotor (3) having an axis of rotation (X), one of the stator (2) or of the rotor (3) surrounding the other of the stator (2) or of the rotor (3) such that an annular volume (4) is arranged between the stator (2) and the rotor (3), the stator (2) having a yoke (36) having a plurality of teeth (17) extending radially within the annular volume (4), a plurality of power sets (18) each having a coil (19) wound around one of the teeth (17) and a coil support (21) supporting the power sets (18), each power set (18) having a power module (20) positioned on a radial face (22) of the stator (2), inside the annular volume (4), and configured to supply current to the coil (19), in which the rotor (3) includes at least one ventilation device (5) movable in rotation relative to the stator (2),positioned at a first end (8a) of the electrical machine (1) and configured to generate a fluid flow in the annular volume (4) from a longitudinal inlet (6a) of the annular volume (4) positioned at the first end (8a) of the electrical machine (1) to a longitudinal outlet (6b) of the annular volume (4) positioned at a second end (8b) of the electrical machine (1), opposite the first end (8a), the electrical machine (1) comprising a first bearing (7a) positioned at the first end (8a) of the electrical machine (1), and a housing (13) in which the stator (2) and the rotor (3) are housed, the ventilation device (5) being positioned between the first bearing (7a) and the stator (2), the electrical machine (1) being characterized in that the housing (13) comprises a first housing (14a) housing the first bearing (7a) and the ventilation device (5).

2. Electric machine (1) according to claim 1, wherein the rotor (3) comprises a shaft (9) around which the ventilation device (5) is fixed.

3. Electric machine (1) according to claim 2, wherein the ventilation device (5) comprises a propeller (10) having a ring (11) fixed on the shaft (9) and a plurality of blades (12) extending radially from the ring (11).

4. Electric machine (1) according to claim 2 or 3, wherein the rotor (3) comprises magnets (15) distributed around the shaft (9), the blades (12) being positioned opposite an axial end (51) of the magnets (15) and opposite the longitudinal inlet (6a) of the annular volume (4).

5. An electrical machine (1) according to any one of claims 1 to 4, wherein the coil support (21) comprises at least one main channel (23) extending longitudinally in the coil support (21) from an inlet (24) of the main channel (23) positioned at a first end (26) of the coil support (21) to an outlet (25) of the main channel (23) opening at a second end (27) of the coil support (21), opposite the first end (26), the inlet (24) being in fluidic communication with the annular volume (4).

6. Electric machine (1) according to claim 5, wherein the main channel (23) is positioned between two teeth (17).

7. An electric machine (1) according to any one of claims 1 to 6, wherein the rotor (3) comprises at least a first row (30) of first vanes (28) extending from an external face (32) of the rotor (3) towards the stator (2), the stator (2) comprising at least a second row (31) of second fins (29) extending from the radial face (22) of the stator (2) towards the rotor (3), the first fins (28) crossing and running alongside the second fins (29) when the rotor (3) is moving relative to the stator (2).

8. Electric machine (1) according to claim 7, wherein the first fins (28) extend radially along a first plane perpendicular to the axis of rotation (X), the second fins (29) extend radially along a second plane perpendicular to the axis of rotation (X) and inclined with respect to the first plane.

9. Electric machine (1) according to claim 7, wherein the first and second fins (28, 29) are movable in rotation relative to each other about a longitudinal axis, perpendicular to the axis of rotation (X), between an inclined position in which the first and second fins (28, 29) form an angle between them and a non-inclined position in which the first and second fins (28, 29) are parallel.

10. An electric machine (1) according to any one of claims 1 to 6, comprising an annular heat dissipation ring (52) fixed to an external face (32) of the rotor (3) and at least one heat dissipation plate (53) fixed to the radial face (22) of the stator (2), the heat dissipation ring (52) comprising at least one first annular heat dissipation fin (33) extending radially towards the stator (2), and the heat dissipation plate (53) comprising at least one second heat dissipation fin (34) extending radially from the radial face (22) of the stator (2) towards the rotor (3), the first heat dissipation fin (33) crossing and running alongside the second heat dissipation fin (34) when the rotor (3) is moving relative to the stator (2).

11. An electrical machine (1) according to any one of claims 1 to 10, comprising a first ventilation device positioned in the first housing (14a), upstream of the annular volume (4), and a second ventilation device positioned in a second housing (14b), downstream of the annular volume (4).

12. Electric machine (1) according to any one of claims 1 to 11, wherein the first housing (14a) is delimited by a peripheral wall (37) extending to a first axial face (38) of the stator (2), the peripheral wall (37) comprising a radial face (40) of circular cross-section having a flared shape.

13. Aircraft (1) comprising an electric machine (1) according to any one of claims 1 to 12.

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