Electric machine comprising a centrifugal compressor

Abstract

Electric machine comprising a centrifugal compressor for cooling the exterior of a stator. The invention relates to an electric machine (1) comprising a rotor (3) and a stator (2) having an internal cavity, a yoke (5) having a plurality of teeth (35), a plurality of power assemblies (6) each having a coil (7) wound around one of the teeth and a coil support supporting the power assemblies, the electric machine comprising a housing (13) housing the stator and the rotor, a centrifugal compressor (8) positioned at a first end (9a) of the electric machine and configured to force the circulation of a fluid in a first annular cavity (11) formed at the first end, between the housing and the power assemblies and at least one cooling channel (14) connecting the first cavity to a second cavity formed at a second end (9b) of the electric machine,The cooling channel surrounding the power assemblies. Figure for the abbreviation: Fig. 1.

Description

Title of the invention: Electric machine comprising a centrifugal compressor

[0001] The invention relates to the field of cooling electrical machines and electronic components of electrical machines such as power electronic modules. The invention relates to an electrical machine and an aircraft comprising 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 having an axis of rotation. The stator has an internal cavity, a plurality of teeth extending in the internal cavity 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 in such a way that a maximum temperature is reached very quickly at the end of their operation, for example after a few minutes, which leads to a limitation of the performance of these electrical machines.

[0005] Indeed, the torque performance of the electric machine is difficult to improve without increasing the current intensity, but such an increase risks raising the temperature of the electric machine to unacceptable levels, leading to a decrease in the machine's performance, or even its destruction. Operating at higher temperatures also increases the carbon footprint.

[0006] The electric machine also includes power assemblies, each comprising a power module, which allows 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, the power 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 containing the rotor and the stator, for example.

[0008] However, the power modules may include within them heat sources which need to be cooled in order not to damage the equipment and to allow good operating efficiency.

[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 face, defining an annular volume with the rotor through which a cooling fluid circulates by convection from the second face of the exchanger. 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] Annular heat exchangers with straight fins arranged perpendicular to the rotor's axis of rotation are known to be used. However, straight fins are most effective when the fluid flow is fixed along the direction of the fins. In operation, however, the rotor induces rotating flows between the rotor and the heat exchanger, which may exhibit variations in inclination, thus impacting the efficiency of heat exchange between the fins and the fluid. Consequently, there is a need to improve heat exchange in the context of a convective environment with a rotating fluid.

[0011] Moreover, this solution allows the air gap of the electric machine to be cooled but does not allow the outside of the stator to be cooled and even less so the power modules positioned on an external surface of the stator. Description of the invention

[0012] The objective of the present invention is to solve at least partially these problems and to provide a solution for cooling the outside of the stator of the electric machine more efficiently and to improve the cooling of power modules positioned on the periphery of the stator.

[0013] 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. The stator comprises an internal cavity, a yoke having a plurality of teeth extending into the internal cavity in a radial direction of the stator, a plurality of power assemblies each comprising a coil wound around one of the teeth, a coil support supporting the power assemblies, and a power module configured to supply the coil with current.

[0014] The electric machine further comprises a housing containing the stator and rotor, a centrifugal compressor positioned at a first end of the electric machine and configured to force the circulation of a fluid in a first annular cavity formed at the first end, between the casing and the power assemblies, and at least one cooling channel connecting the first cavity to a second cavity formed at a second end of the electrical machine, between the casing and the power assemblies. The cooling channel surrounds the power assemblies. The power module is positioned on an external face of the stator and housed in either the first or second cavity.

[0015] The invention thus provides a solution for cooling the outside of the stator of the electric machine more efficiently and for improving the cooling of power modules positioned on the periphery of the stator.

[0016] The torque performance of the electric machine can thus be improved by increasing the current intensity, significantly limiting the risk of the electric machine's temperature rising to unacceptable levels. The risk of reduced performance or even destruction of the electric machine is limited. The carbon footprint is also reduced.

[0017] Alternatively, the electric machine includes a first bearing positioned at the first end of the electric machine, the centrifugal compressor being positioned between the first bearing and the stator.

[0018] Alternatively, the rotor includes a shaft around which the centrifugal compressor is fixed.

[0019] Alternatively, the stator includes magnets, the centrifugal compressor being positioned opposite an axial end of the magnets.

[0020] Alternatively, the centrifugal compressor comprises a circular hub fixed to the shaft, with first and second blades extending from the hub to a first circular flange. The hub and the first flange are arranged to form a fluid inlet downstream of the first bearing and a fluid outlet opening into the first cavity.

[0021] Alternatively, the second blades have a length strictly greater than the length of the first blades, the first and second blades being distributed alternately between the hub and the first flange.

[0022] Alternatively, the first cavity comprises a first portion extending radially from the fluid outlet of the centrifugal compressor to a second portion of the first cavity extending axially to an inlet of the cooling channel. The second portion has a flared shape with a second maximum annular cross-section S2 larger than a first annular cross-section SI of the first portion.

[0023] The first flared cavity generates a venturi effect to channel and accelerate the fluid to the inlet of the cooling channel.

[0024] Alternatively, the cooling channel passes through the cylinder head and / or the crankcase.

[0025] Alternatively, the crankcase comprises a first annular portion projecting from an inner face of the crankcase to a second annular portion of the cylinder head. The cooling channel passes through the first annular portion and / or the second annular portion.

[0026] Alternatively, the cooling channel has a helical shape.

[0027] Alternatively, the electric machine includes several parallel cooling channels, distributed regularly around the power assemblies.

[0028] This embodiment provides more efficient cooling of the electrical machine and the power modules positioned on the periphery of the stator in the first or second cavity.

[0029] The cooling channels allow for better heat transfer from the electrical machine to the fluid.

[0030] Alternatively, the electric machine includes a mobile ventilation device rotating relative to the stator positioned at the second end of the electric machine to facilitate the extraction of the fluid from the second cavity to the outside of the electric machine.

[0031] The present invention also relates to an aircraft comprising an electrical machine as defined above. Brief description of the drawings

[0032] The invention and its advantages will be better understood upon reading the following detailed description of various embodiments of the invention, given by way of non-limiting examples. This description refers to the accompanying figures, in which:

[0033] [Fig. 1] Fig. 1 schematically represents the interior of an electrical machine comprising a centrifugal compressor, according to one embodiment of the invention,

[0034] [Fig. 2] Fig. 2 schematically represents cooling channels surrounding power assemblies,

[0035] [Fig.3] Fig.3 schematically represents cooling channels formed in a housing,

[0036] [Fig.4] Fig.4 schematically represents the centrifugal compressor of Fig.1,

[0037] [Fig.5] Fig.5 schematically represents the interior of the centrifugal compressor of Fig.4,

[0038] [Fig.6] Figure [Fig.6] schematically represents a cooling channel, according to another embodiment,

[0039] [Fig.7] Fig.7 schematically represents the cooling channel of Fig.6 formed on a ring of the cylinder head.

[0040] Description of embodiments.

[0041] Figure 1 schematically represents 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 37 is arranged between the stator 2 and the rotor 3. In the example of Figure 1, the stator 2 surrounds the rotor 3.

[0042] 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 of an aircraft element such as a rudder, a nozzle, a brake, a flap or an airbrake, for example.

[0043] The stator 2 has an internal cavity 4, a yoke 5 having a plurality of teeth 35 extending into the internal cavity 4 in a radial direction of the stator 2, a plurality of power sets 6 each having a coil 7 wound around one of the teeth 35 and a coil support (not shown) supporting the power sets 6. The coil support at least partially encompasses the coil 7.

[0044] The reel supports are not shown in figures 1, 2 and 6 to simplify the representation.

[0045] Each power assembly 6 comprises a power module 15 supported by the stator 2 and configured to supply current to the coil 7. The power modules 15 are positioned on an external face 16 of the stator 2, opposite an internal face 34 of a housing 13 containing the stator 2 and the rotor 3. In the example, the power modules 15 are positioned at a second end 10b of the stator 2. The stator 2 includes an internal face 39, opposite the external face 16, and positioned opposite the rotor 3.

[0046] Alternatively, the power modules 15 can be positioned at a first end 10a of the stator 2, opposite the second end 10b.

[0047] The power modules 15 supply electrical energy to the electric machine 1 from the main grid. The power modules 15 can advantageously be distributed circumferentially, in particular regularly, around the axis of rotation X.

[0048] The electric machine 1 includes a first bearing 19a positioned at a first end 9a of the electric machine 1 and a second bearing 19b positioned at a second end 9b of the electric machine 1, opposite to the first end 9a.

[0049] The housing 13 includes a first housing 40a housing the first bearing 19a and a second housing 40b housing the second bearing 19b.

[0050] The rotor 3 includes a shaft 21 passing through the first and second housings 40a, 40b.

[0051] The rotor 3 includes magnets 24 fixed on the shaft 21 and distributed circumferentially around the shaft 21. The magnets 21 are positioned inside the stator 2.

[0052] As illustrated in Figures 1 and 2, the electrical machine 1 includes a centrifugal compressor 8 positioned at the first end 9a of the electrical machine 1 and configured to force the circulation of a fluid, in particular air, in a first annular cavity 11 formed at the first end 9a, between the casing 13 and the power assemblies 6. The electrical machine 1 also includes at least one cooling channel 14a, 14b, 14c connecting the first cavity 11 to a second cavity 12 formed at the second end 9b of the electrical machine 1, between the casing 13 and the power assemblies 6. The cooling channel 14a, 14b, 14c surrounds the power assemblies 6 and runs along at least part of an external face 16 of the power assemblies 6. The centrifugal compressor 8 is used as a compressor. The centrifugal compressor 8 draws the fluid from the outside and forces its passage towards the first cavity 11 which is under overpressure.

[0053] The centrifugal compressor 8 is positioned between the first bearing 19a and the stator 2. In other words, the centrifugal compressor 8 is positioned between the first housing 40a and the stator 2. The centrifugal compressor 8 is fixed around the shaft 21. The centrifugal compressor 8 is positioned opposite an axial end 25 of the magnets 24.

[0054] As illustrated in Figures 4 and 5, the centrifugal compressor 8 comprises a circular hub 26 fixed to the shaft 21, first blades 30 and second blades 31 extending from the hub 26 to a first circular flange 27. The hub 26 and the first flange 27 are arranged to form a fluid inlet 28 downstream of the first bearing 19a and a fluid outlet 29 opening into the first cavity 11.

[0055] The hub 26 comprises a circular base 41 press-fitted around the shaft 21 and a second circular flange 42 extending from the base 4L. The first flange 27 is opposite the second flange 42.

[0056] The first and second blades 30, 31 are distributed alternately between the first flange 27 and the second flange 42. The first and second blades 30, 31 project from an inner face 44 of the second flange 42 and each comprises a first end 43 connected to the inner face 44 of the second flange 42 and a second end 45 connected to an inner face of the first flange 27.

[0057] The second blades 31 are strictly longer than the first blades 30. The second blades 31 are curved. The shorter first blades 30 are also called "splitters," meaning they are separating fins in the inter-blade channel. The function of these first blades 30 is to prevent the formation and propagation of vortices in the inter-blade channel formed between the flanges 26, 27 when the inter-blade distance is too great. These first blades 30 are shorter than the second blades 31 and also shorter in height from their base.

[0058] The fluid inlet 28 has an annular shape and is formed between a first end 46 of the first flange 27 and the base 41 of the hub 26. The fluid outlet 29 has an annular shape and is formed between a second end 47 of the first flange 27 and an end 48 of the second flange 42.

[0059] Other shapes and structures of centrifugal compressors 8 are also possible.

[0060] The first cavity 11 comprises a first portion 22 extending radially from the fluid outlet 29 of the centrifugal compressor 8 to a second portion 23 of the first cavity 11 extending axially to an inlet 36a of the cooling channel 14a, 14b, 14c. The second portion 23 has a flared shape with a cross-section that increases from the first portion 22 to the cylinder head 5. The first portion 22 comprises a first annular section S1 formed between the inner face 34 of the housing 13 and the outer face 16 of the power assemblies 6. The second portion 23 comprises a second annular section S2 formed between the inner face 34 of the housing 13 and the outer face 16 of the power assemblies 6.

[0061] Near the breech 5, the second annular section S2 is at its maximum and is larger than the first annular section SL

[0062] The first flared cavity 11 is delimited by a flared wall 49 of the housing 13 so as to form a venturi bowl allowing the fluid to be channeled and accelerated to the inlet 36a of the cooling channel 14.

[0063] The cooling channel 14a, 14b, 14c passes through the cylinder head 5 and / or the housing 13. The housing 13 comprises a first annular portion 32 projecting from the inner face 34 of the housing 13 to a second annular portion 33 of the cylinder head 5. The cooling channel 14a, 14b, 14c passes through the first annular portion 32 and / or the second annular portion 33.

[0064] In the example, the electrical machine 1 comprises several cooling channels 14a, 14b, 14c parallel to each other, regularly distributed around the power sets 6. More specifically, the electrical machine 1 comprises several series of channels 50, each formed of three cooling channels 14a, 14b, 14c parallel to each other and regularly distributed radially in a direction perpendicular to the axis of rotation X. The series of channels 50 are distributed regularly around the power sets 6. Each series of channels 50 includes a first cooling channel 14a formed in the first annular portion 32 of the housing 13, a second cooling channel 14b comprising a first half 51 formed in the first annular portion 32 of the housing 13 and a second half 52 formed in the second annular portion 33 of the cylinder head 5, and a third cooling channel 14b formed in the second annular portion 33 of the cylinder head 5. The cooling channels 14a, 14b, 14c all have the same length.

[0065] Fig. 3 illustrates several first cooling channels 14a and several first halves 51 of second cooling channel 14b formed in the first annular portion 32 of the housing 13.

[0066] Each cooling channel 14a, 14b, 14c has a helical shape, that is, it extends around the power assemblies 6 in a general direction inclined with respect to the axis of rotation X. Each cooling channel 14a, 14b, 14c forms a portion of a spiral and has a curved shape. Each cooling channel 14a, 14b, 14c has a length less than one-quarter of the perimeter of the stator 2. Each cooling channel 14a, 14b, 14c extends around the axis of rotation X at an angle of less than 90°. Each cooling channel 14a, 14b, 14c has a circular cross-section. Other shapes are possible, such as an oblong shape, for example.

[0067] The inlet 36a of the cooling channel 14a, 14b, 14c has a larger cross-section than the outlet 36b of the cooling channel 14a, 14b, 14c in order to accelerate the fluid in the cooling channel 14a, 14b, 14c by means of the venturi effect. The inlet 36a of the cooling channel 14a, 14b, 14c has a diameter of 4 mm and the outlet 36b has a diameter of 2 mm, for example.

[0068] The diameter of the cooling channel 14a, 14b, 14c gradually decreases from the inlet 36a to the outlet 36b.

[0069] The fluid flow is represented by arrows in [Fig. 1]. The centrifugal compressor 8 draws the fluid from outside the electrical machine 1 and forces it through the first bearing 19a. The fluid enters through the fluid inlet 28 of the centrifugal compressor 8 and exits through the fluid outlet 29 of the centrifugal compressor 8. The pressurized fluid passes through the first part 22 of the first cavity 11 and then the second part 23 of the first cavity 11 in which the fluid is accelerated by the Venturi effect.

[0070] The first annular portion 32 of the housing 13 and the second annular portion 33 of the cylinder head 5 form a fluid inlet face 53, partially delimiting the first cavity 11 and comprising a multitude of inlets 36a of cooling channels 14a, 14b, 14c through which the pressurized fluid is discharged. Fluid circulation is forced through the inlets 36a. The fluid absorbs the colors transmitted by the first annular portion 32 of the housing 13 and by the second annular portion 33 of the cylinder head 5 and emerges hotter through a multitude of outlets 36b formed through a fluid outlet face 54, opposite the fluid inlet face 53 and partially delimiting the second cavity 12. The fluid outlet face 54 is formed by a portion of the first annular portion 32 of the housing 13 and by a portion of the second annular portion 33 of the cylinder head 5. The fluid then enters the second cavity 12 to exit through the second bearing 19b.

[0071] In the example, the power modules 15 are positioned on the periphery of the stator 2, and are housed in the second cavity 12.

[0072] Preferably, the power modules 15 are positioned in the first cavity 11 which benefits from an incoming fluid flow that is cooler than at the outlet 36b of the cooling channels 14a, 14b, 14c opening into the second cavity 12.

[0073] Figures 6 and 7 illustrate another embodiment in which the electrical machine 1 includes a unique helical cooling channel 14 formed in the first annular portion 32 of the housing 13 and in the second annular portion 33 of the cylinder head 5.

[0074] The helical cooling channel 14 comprises a first half 51 formed in the first annular portion 32 of the housing 13 and a second half 52 formed in the second annular portion 33 of the cylinder head 5.

[0075] Fig. 7 illustrates the second half 52 formed in the second annular portion 33 of the cylinder head 5.

[0076] The helical cooling channel 14 surrounds the teeth 35 and the power assemblies 6. The helical cooling channel 14 has a helical shape and comprises several turns surrounding the power assemblies 6 over 360°.

[0077] The helical cooling channel 14 includes an inlet 36a opening into the first cavity 11 and an outlet 36b opening into the second cavity 12.

[0078] This embodiment simplifies the design of the electric machine 1 while providing efficient cooling of the electric machine 1 and the power modules 15 positioned on the periphery of the stator 2.

[0079] In variants, the electric machine 1 may include several helical cooling channels 14, such as two or three helical cooling channels 14, for example.

[0080] According to one variant (not shown), the rotor 3 includes, in combination with the centrifugal compressor 8, a mobile ventilation device rotating relative to the stator 2, positioned at the second end 9b of the electric machine 1 and configured to facilitate the extraction of the fluid from the second cavity 12 to the outside of the electric machine 1.

[0081] The ventilation device is positioned between the second bearing 19b and the stator 2. The ventilation device is also positioned between the second bearing 19b and the magnets 24 of the rotor 3. The ventilation device is housed in the second housing 40b.

[0082] The ventilation device is fixed around the shaft 21, allowing its rotation around the axis of rotation X and relative to the stator 2.

[0083] The ventilation device comprises a propeller having a ring fixed to the shaft 24 and a plurality of blades extending from the ring. The ring is press-fitted onto the shaft 24. The blades are parallelepiped in shape and flat. The blades are evenly distributed around the shaft 24.

[0084] 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 a restrictive sense.

[0085] It is also evident that all the characteristics described with reference to a process are transposable, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device are transposable, alone or in combination, to a process.

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) bearing around the other of the stator (2) or of the rotor (3), the stator (2) having an internal cavity (4), a yoke (5) having a plurality of teeth (35) extending within the internal cavity (4) in a radial direction from the stator (2), a plurality of power assemblies (6) each having a coil (7) wound around one of the teeth (35), a coil support supporting the power assemblies (6), and a power module (15) configured to supply current to the coil (7), the electrical machine (1) comprising: • a housing (13) accommodating the stator (2) and the rotor (3), • a centrifugal compressor (8) positioned at a first end (9a) of the electrical machine (1) and configured to force circulation of a fluid in a first annular cavity (11) formed at the first end (9a),between the housing (13) and the power assemblies (6), and • at least one cooling channel (14, 14a, 14b, 14c) connecting the first cavity (11) to a second cavity (12) formed at a second end (9b) of the electrical machine (1), between the housing (13) and the power assemblies (6), the cooling channel (14, 14a, 14b, 14c) surrounding the power assemblies (6), the power module (15) being positioned on an external face (16) of the stator (2), and housed in the first cavity (11) or the second cavity (12).

2. Electric machine (1) according to claim 1, comprising a first bearing (19a) positioned at the first end (9a) of the electric machine (1), the centrifugal compressor (8) being positioned between the first bearing (19a) and the stator (2).

3. Electric machine (1) according to any one of claims 1 or 2, wherein the rotor (3) comprises a shaft (21) around which the centrifugal compressor (8) is fixed.

4. Electric machine (1) according to claim 3, wherein the stator (2) comprises magnets (24), the centrifugal compressor (8) being positioned opposite an axial end (25) of the magnets (24).

5. An electric machine (1) according to any one of claims 3 or 4, wherein the centrifugal compressor (8) comprises a circular hub (26) fixed on the shaft (21), first blades (30) and second blades (31) extending from the hub (26) to a first circular flange (27), the hub (26) and the first flange (27) being arranged to form a fluid inlet (28) downstream of the first bearing (19a) and a fluid outlet (29) opening into the first cavity (11).

6. Electric machine (1) according to claim 5, wherein the first cavity (11) comprises a first part (22) extending radially from the fluid outlet (29) of the centrifugal compressor (8) to a second part (23) of the first cavity (11) extending axially to an inlet (36a) of the cooling channel (14, 14a, 14b, 14c), the second part (23) having a flared shape with a second maximum annular section S2 larger than a first annular section SI of the first part (22).

7. Electric machine (1) according to any one of claims 1 to 6, wherein the cooling channel (14, 14a, 14b, 14c) passes through the cylinder head (5) and / or the casing (13).

8. Electric machine (1) according to claim 7, wherein the housing (13) comprises a first annular portion (32) projecting from an inner face (34) of the housing (13) to a second annular portion (33) of the cylinder head (5), the cooling channel (14, 14a, 14b, 14c) passing through the first annular portion (32) and / or the second annular portion (33).

9. Electric machine (1) according to any one of claims 1 to 8, wherein the cooling channel (14, 14a, 14b, 14c) has a helical shape.

10. Electric machine (1) according to any one of claims 1 to 9, comprising several cooling channels (14, 14a, 14b, 14c) parallel to each other, distributed regularly around the power assemblies (6).

11. An electrical machine (1) according to any one of claims 1 to 10, comprising a movable rotating ventilation device by 13 report to the stator (2), positioned at the second end (9b) of the electrical machine (1).

12. Aircraft (1) comprising an electric machine (1) according to any one of claims 1 to 11.

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