Casing having a heat sink provided with fins oriented at a non-zero angle of incidence

Abstract

The invention relates to a casing (5) comprising a heat sink (6) located between an inner part (10) and an outer part (11), and comprising a plurality of separate fins (8) having a body that rises from the outer face (102) of the inner part, wherein the body projects towards the outer part, and wherein these fins (8) are arranged in a plurality of rows (L) parallel to their axial direction (DA). The heat sink (6) has a plurality of separating walls (12), each extending in a plane parallel to their axial direction (DA) and defining a plurality of flow spaces (13) comprising at least one row (L) of fins comprising fins (8) whose bodies are oriented at an angle of incidence (β) with respect to their axial direction (DA), wherein (β) is non-zero for at least one fin (8) in the row (L).

Description

[0001]Casing comprising a heat sink equipped with fins oriented with a non-zero angle of incidence TECHNICAL FIELD OF THE INVENTION The technical field of the invention is that of electric motors and in particular that of electric motors with integrated electronics for aircraft. The present invention relates to an external casing for an electric motor, and in particular a casing for an electric motor with integrated electronics for an aircraft, which casing comprises fins projecting outwards. The invention finds applications in the aeronautical field, in particular for motors with integrated electronics used in the context of hybrid thermal / electric propulsion systems for aircraft, for converters intended for propulsive applications such as vertical take-off and landing (VTOL) aircraft, and for converters for non-propulsive applications such as for exampleVariable Speed ​​Constant Frequency (VSCF) current systems. TECHNOLOGICAL BACKGROUND OF THE INVENTION An example of an integrated electronics motor for aircraft according to the prior art, sometimes referred to as a smart motor, is illustrated in [Fig. 1] and [Fig. 2] and is described in patent FR3091063B1 in the name of the applicant. Integrated electronics motors 1' usually comprise an electromechanical converter 2' provided with a rotor 3' and a polyphase stator 4', a cylindrical casing 5' equipped with a heat sink 6', and an electronic control unit comprising a plurality of electronic cards 7'. In operation, these electronic cards 7' heat up considerably and need to be cooled to avoid their deterioration. Thus, an essential role of the heat sink 6' is to cool not only the casing 5', but also to cool byconduction the electronic cards 7' which are mounted on the underside of the casing 5'. The heat sink 6' is usually provided with cooling fins 8' projecting radially outwards. These fins 8' make it possible to cool the casing 5' and the electronic cards 7' with the air which circulates through the heat sink 6' when the aircraft moves. These fins 8' can be surrounded by an external casing (not shown), also designated by the English term "shroud", which serves mainly to channel the flow and to delimit the flow veins of the cooling air. They usually extend in a radial direction in which the rotor 3' and the stator 4' of the electric motor 1' extend so that the cooling air circulates through the fins 8' in an axial direction. In order to produce sufficient cooling, the 8' fins have a significant radial height, which representsdisadvantageously, high overall size, weight and cost for the electric motor 1'. There is therefore a need for a heat sink that is less bulky, less heavy and less expensive for a given thermal performance. SUMMARY OF THE INVENTION The invention offers a solution to the problems mentioned above, by providing a heat sink whose fins have a considerably reduced radial height compared to that of the prior art, while providing at least an equal cooling effect. This result is achieved by adding to at least some fins a role of deflecting the air flow in addition to their convection and conduction cooling effect. One aspect of the invention relates to an electric motor casing extending along an axis XX, comprising a hollow cylindrical portion defining an axial direction DA, a radial direction DR and a tangential direction DT, said cylindrical portion comprising: - a partcylindrical internal part, - a heat sink located on the internal part and thermally connected thereto, and comprising a plurality of separate fins each comprising a body which rises from the external face of the internal part and extends outwards, these fins being distributed in a plurality of lines L parallel to their axial direction DA, and characterized in that: - the cylindrical portion further comprises a cylindrical external part, the external part being larger than the internal part and concentric with it, the heat sink being located between the internal part and the external part; and in that - the heat sink further comprises: - a plurality of separating walls each extending in a plane P defined by their radial direction DR and their axial direction DA; - a plurality of flow volumes each delimited by the internal part and two successive separating walls; - at least one line L of finsdistinct located in at least one flow volume, fins each having a leading edge and a trailing edge, and whose body is oriented at an angle of incidence β relative to their axial direction DA, said angle of incidence β being non-zero for at least one fin of said line L. Thanks to the invention, the cooling air circulates through the fins according to a substantially helical rather than linear displacement, as illustrated in [Fig. 15] and [Fig. 16]. Indeed, the air flow is confined in flow volumes where fins oriented with a non-zero angle of incidence give it an ideally helical movement with a propeller axis substantially parallel to the axial direction, for better heat transfer taking place by radial conduction and by convection at the level of the two flanks of the fins. Thus, for an equivalent cooling effect, the conductive part of the fin can be lightened by shortening it andthinning it. In order to maintain a satisfactory exchange surface, the number of shortened and thinner fins is multiplied. Also, convective cooling on the fins is more effective near the leading edge, the cumulative lengths of which are multiplied. The separating walls are fins which do not participate in the helical movement, but delimit the air flow and can therefore extend over the entire length of the casing, maximizing its filling. The electric motor according to the invention being preferentially used in the context of propulsion systems, it will also be noted that the cooling air circulating through the fins is preferentially a forced flow which is even more capable of adopting a substantially helical movement than a cooling air flow resulting from a single natural convection. According to one aspect of the invention, the heat sink comprises at least one line L of separate fins located in at leastless a flow volume and comprising n fins 81, 82, … 8n with n ≥ 2, the body of which is oriented at an angle of incidence β1, β2, … βn relative to their axial direction DA such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 35°, more preferably such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 20°, which advantageously makes it possible to gradually deflect the air in a substantially helical displacement. According to another aspect of the invention, the heat sink further comprises at least one line L of separate fins located in at least one flow volume and whose body is inclined in their tangential direction DT by a non-zero angle of inclination α relative to their radial direction DR. According to a further aspect of the invention, the angle of inclination α is such that 5° ≤ |α| ≤ 60°, more preferably such that 10° ≤ |α| ≤ 45°. The combination of the angles α and β advantageously makes it possible to generate a helical movement satisfactory for the flow of air throughfins without slowing said flow excessively. These angles can advantageously be optimized so that at cruising speed, the air flow preferably makes substantially between two-thirds and one helix turn over the entire axial length of the heat sink. According to one aspect of the invention, the heat sink comprises, in at least one flow volume, at least two lines L of distinct fins, of which at least one line L of fins has a positive inclination angle α and at least one line L of fins has a negative inclination angle α. According to another aspect of the invention, the heat sink comprises, in at least one flow volume, at least one transverse row R of distinct fins comprising m successive fins with m ≥ 2 whose body is inclined in their tangential direction DT by an inclination angle α1, α2, … αm such that |α1| ≤ |α2| ≤ … ≤ |αm|. According to a further aspect ofthe invention, the heat sink further comprises at least one additional separating wall which extends in a plane PS defined by its radial direction DR and its axial direction DA and which compartmentalizes a flow volume into two flow sub-volumes. Such a wall advantageously makes it possible to compartmentalize each flow volume so as to give each flow sub-volume a geometry approaching that of a cylinder of circular section, which is the shape most suitable for generating an air flow along a helical and circular path. According to another aspect of the invention, the additional separating wall is equidistant from the two separating walls delimiting the flow volume which it compartmentalizes. Such a geometry advantageously makes it possible to have the same cooling effect in each flow sub-volume, and therefore to better control the overall cooling of the heat sink. According to one aspectAccording to an additional aspect of the invention, at least one other line L of fins is located between the two lines L of fins whose fins have a body inclined in their tangential direction DT from one line L of fins towards the other line L of fins. This configuration advantageously makes it possible to further promote the formation of a helical movement in the air flow and to fill the space with more fins with a rather homogeneous distribution. According to one aspect of the invention, at least one separating wall or one additional separating wall is connected to the external face of the internal part by a fillet connection. These fillet shapes advantageously give an at least partially rounded contour to the section of each flow volume so as to give it a shape approaching that of a cylinder of circular section. According to an additional aspect of the invention, at least one fin has at least one characteristic among thefollowing characteristics: - it has reliefs and / or hollows on at least one side; - it has a cambered profile; - it has a curved intrados and extrados with different curvatures; - it has a twist, the angle of incidence of the fin not being constant over its height; - it has a rounded trailing edge; - it has an angular trailing edge; - it has a rounded leading edge; and - it has an angular leading edge. These characteristics advantageously make it possible to increase the heat dissipation effect of the fins by reducing pressure losses. According to one aspect of the invention, at least one fin and the internal part are part of a single part made of thermally conductive material which is the product of additive manufacturing. Indeed, this manufacturing technique advantageously makes it possible to manufacture fins with a complex geometry. According to another aspect of the invention, at least one fincomprises a downstream trailing edge having at least one substantially triangular shaped notch, this notch in particular makes it possible to minimize the use of support when the fins are produced by additive manufacturing from downstream to upstream. According to an additional aspect of the invention, the cylindrical portion comprises an upstream part and a downstream part which have a different cross-sectional shape, and at least two successive fins circumferentially and located in an upstream zone of the downstream part are connected to each other by a fin whose downstream edge is inclined towards the internal part. This fin advantageously makes it possible to bring the air flow back towards the fins of the downstream part of the internal part when it encounters an obstacle due to a change in geometry between the upstream part and the downstream part of the cylindrical portion. According to one aspect of the invention, the cylindrical portion further comprises a concentric cylindrical external partwith the inner part, the heat sink being located between the inner part and the outer part, and the heat sink comprises a plurality of additional cooling fins which project towards the inner part from an inner face of the outer part. These additional fins advantageously promote the deflection of the cooling air flow, in particular when they have a geometry similar to that of the fins of the inner part. According to another aspect of the invention, the heat sink comprises at least one line L of distinct fins located in at least one flow volume, which line L of fins comprises three successive parts, namely: - a first part Z1 comprising fins whose body is oriented at an angle of incidence β1, β2, … βn relative to their axial direction DA, this angle of incidence β being non-zero for at least one fin and such that |β1| ≤ |β2| ≤ … ≤ |βn| ; - a second partZ2 comprising fins whose body is oriented at an angle of incidence βn+1, βn+2, … βm relative to their axial direction DA, this angle of incidence βn+1, βn+2, … βm being non-zero and the same for all the fins of the second part Z2; and - a third part Z3 comprising fins whose body is oriented at an angle of incidence βm+1, βm+2, … βz relative to their axial direction DA, this angle of incidence β being non-zero for at least one fin and such that |βm+1| ≥ |βm+2| ≥ … ≥ |βz|. By means of this embodiment of the invention, the cooling air circulates through the fins in a substantially helical rather than linear motion, as illustrated in [Fig. 15] and [Fig. 16]. In fact, the air flow is confined in flow volumes where fins oriented with a non-zero angle of incidence give it an ideally helical motion with a propeller axis substantially parallel to the axial direction, for betterheat transfer taking place by radial conduction and by convection at the level of the two flanks of the fins. Thus, for an equivalent cooling effect, the conductive part of the fin can be lightened by shortening and thinning it. In order to maintain a satisfactory exchange surface, the number of shortened and thinner fins is multiplied. Also, convective cooling on the fins is more effective near the leading edge, the cumulative lengths of which are multiplied. The separating walls are fins which do not participate in the helical movement, but delimit the air flow and can therefore extend over the entire length of the casing, maximizing its filling. In addition, thanks to the invention, the heat sink can operate bidirectionally, that is to say that it can advantageously cool the casing and the electronic cards with the same efficiency, whether the air flow circulates in one direction or the other.Thus, the same variant of the heat sink can be mounted on two different aircraft configurations: one with direct flow and the other with reverse flow. According to a further aspect of the invention, the fins of the first part Z1 are such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 35°, and more preferably such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 20°. According to one aspect of the invention, the fins of the third part Z3 are such that 35° ≥ |βm+1| ≥ |βm+2| ≥ … ≥ |βz| ≥ 0°, and more preferably such that 20° ≥ |βm+1| ≥ |βm+2| ≥ … ≥ |βz| ≥ 0°. According to another aspect of the invention, the fins of the first part Z1 are such that 0° ≤ |β1| < |β2| < … < |βn| ≤ 35°, and more preferably such that 0° ≤ |β1| < |β2| < … < |βn| ≤ 20°. According to a further aspect of the invention, the fins of the third part Z3 are such that 35° ≥ |βm+1| > |βm+2| > … > |βz| ≥ 0°, and more preferably such that 20° ≥ |βm+1| > |βm+2| > … > |βz| ≥ 0°.According to one aspect of the invention, the first part Z1 and the third part Z3 each comprise the same number of fins. According to another aspect of the invention, the first part Z1 and the third part Z3 are such that β1 = βz, β2 = βz-1, β3 = βz-2, … , βn-1 = βm+2, βn = βm+1. Another aspect of the invention relates to an electric motor equipped with a casing as described above, which advantageously has a lower weight and size than motors with integrated electronics equipped with a conventional heat sink, for an at least equivalent cooling effect. An additional aspect of the invention relates to an aircraft equipped with an electric motor as described above. The invention and its various applications will be better understood upon reading the description which follows and examining the figures which accompany it. BRIEF DESCRIPTION OF THE FIGURES The figures are presented for information purposes only and in no way limit the invention.[Fig.1] is a schematic perspective view of a motor with integrated electronics according to the prior art, the casing of which does not include an external casing. [Fig.2] is a view similar to [Fig.1] where the downstream face is open. [Fig.3] is a schematic perspective view of a motor with integrated electronics equipped with a casing according to the invention and the downstream face of which is open. [Fig.4] is a perspective view of a sector of the downstream part of a casing according to the invention, the external part of which is shown transparent. [Fig.5] is a perspective view of a detail of a sector of the downstream part of the casing of [Fig. 4] limited to a single flow volume separated into two half-volumes separated by an additional separating wall and where the external part is not shown. [Fig.6] is a front view on the downstream side of the flow volume of [Fig.5]. [Fig.7] is an external radial view of the flow volume of [Fig.5]. [Fig.8] is a sectional view of the flow volume of [Fig.5]in a plane perpendicular to the motor axis. [Fig.9] is a sectional view in an axial plane parallel to the motor axis at the root of the fins of the flow volume of [Fig.7] where the fins all have the same angle of incidence β within the same line, for example where the helical movement is established. [Fig.10] is a sectional view in an axial plane parallel to the motor axis at the root of the fins of the flow volume of [Fig. 7] where the fins have a different angle of incidence β within the same line, and increasing as one moves downstream. [Fig. 11] is a perspective view of a sector of the upstream and external part of a casing according to the invention seen from the inside, with filleted shapes in the corners of the walls delimiting the flow volumes. [Fig. 12] is a view similar to [Fig. 11] where the inner face of the outer part of the casing is equipped with additional fins in the form of folded sheets. [Fig.13] is aperspective view of a flow sub-volume of the downstream part of a casing according to the invention with fillet shapes in the corners for the external part and chamfers for the internal part of the walls delimiting said flow sub-volume. [Fig. 14] is a perspective view of a middle zone of a casing according to the invention where the helical movement is established, whose fins are equipped with a fin and where there is a change in air stream section from cylinder to plane facet. [Fig. 15] is a sectional view similar to [Fig. 8], but where the external part of the casing is shown equipped with additional fins. [Fig. 16] is a view similar to [Fig. 8] where the substantially helical movement of the cooling air is represented by white arrows. [Fig. 17] is a view similar to [Fig. 15] where the substantially helical movement of the cooling air is represented by white arrows. [Fig. 18] is a side view of an examplefin according to a preferred embodiment of the invention. [Fig. 19] is a sectional view in a radial plane along the section axis XIX-XIX perpendicular to the motor axis of the example fin of [Fig.18]. [Fig.20] is a sectional view in an axial plane parallel to the motor axis along the section axis XX-XX of the example fin of [Fig.18]. [Fig.21] is a sectional view in an axial plane parallel to the motor axis along the section axis XXI-XXI of the example fin of [Fig.18]. [Fig. 22] is a sectional view in an axial plane parallel to the motor axis at the level of the foot of the fins of the flow volume of [Fig. 7] where the fins have a variable angle of incidence β within the same line, which is increasing, then constant and finally decreasing as one moves downstream. It will be noted that [Fig.4] to [Fig.10] and [Fig.13] to [Fig.17] illustrate only the downstream part of a casing according to the invention. The upstream part of said casing is however very similar tothe downstream part, except that the internal part has a circular section in the upstream part rather than a polygonal one. DETAILED DESCRIPTION Unless otherwise specified, the same element appearing in different figures has a single reference. By convention, in the present application, the terms "upstream" and "downstream" are defined in relation to the direction of flow E of the air in the electric motor, this direction of flow E being represented by white arrows in the figures. This direction of flow E is usually parallel to the axis XX along which the casing according to the invention extends. Similarly, the terms "inner" and "outer" and "internal" and "external" are defined radially in relation to the radial direction DR of the casing. By "line" of fins, we mean an aligned set or group of fins. It will be noted that a fin is a small wing, and therefore adopts not only the general shape of a wing, but can have the samecharacteristics. These fins should therefore not be confused with any grooves or tongues that can sometimes be shaped in the mass of an engine casing to simply increase the exchange surface with the air, but without any role in directing the air flow. Finally, the axial direction DA, the radial direction DR and the tangential direction DT, in particular for a fin, are defined in relation to the external surface of the cylindrical internal part on which said fin is located, this cylindrical internal part being for example of polygonal, circular or other section. The axial direction DA is parallel to the axis XX. The radial direction DR is a direction passing through the axis of the cylindrical internal part. For additional fins, these directions are defined in relation to the internal surface of the cylindrical external part on which these fins are located. A tangential direction DT is orthogonal to the axial directionDA and axis XX. The tangential direction DT of a fin is similar to its circumferential direction when the cylindrical internal part has an external surface of circular section. An electric motor 1 equipped with a casing 5 according to the invention is illustrated in [Fig. 3]. Its motor axis extends along the axis XX. This electric motor 1 is preferably a motor with integrated electronics. An electric motor 1 is composed of an electromechanical converter 2 and its coaxial control electronics. To simplify the industrial diagram, the electric motor 1 preferably has its own half-casing, usually cylindrical, of round section, and the electronics has its own half-casing, usually cylindrical, of polygonal section. The two half-casings are usually bolted coaxially to form the casing 5 which encloses the entire electric motor 1. Conventionally, the casing 5 is equipped with a heat sinkthermal 6 and contains an electromechanical converter 2 comprising a rotor 3 and a stator 4, and an electronic control unit comprising a plurality of electronic cards 7 located on the underside of the casing 5. The casing 5 comprises a hollow cylindrical portion 9 with a circular and / or polygonal base, forming a crown defining a radial direction DR and an axial direction DA corresponding to the axis of revolution of the cylinder when it has a circular base, this axis of revolution is preferably identical to the axis XX. The cylindrical portion 9 comprises a cylindrical internal part 10, having an internal face 101 equipped with the heat sink 6 and an external face 102. The cylindrical portion 9 may also comprise a cylindrical external part 11, having an internal face 111 and an external face 112. The external part 11 is larger than the internal part 10 and concentric with it so that the heat sink 6 is located between thesetwo parts 10, 11. According to an embodiment of the invention, the cylindrical portion 9 comprises an upstream part 9a (see [Fig. 3] where the electromechanical converter 2 is preferably housed and a downstream part 9b (see [Fig. 4]) where the electronic cards 7 are preferably housed. Conventionally, the heat sink 6 comprises a plurality of fins 8 playing a cooling role, and comprising a body which rises towards the external part 11 in a general direction A from the external face 102 of the internal part 10 (see [Fig. 5], [Fig. 6] and [Fig. 7]). The fins 8 are distinct from each other and are distributed in a plurality of lines L parallel to their axial direction DA. Each line L of fins 8 preferably comprises n fins 81, 82, … 8n with n ≥ 2. Although on the figures the fins 8 are distributed in lines and rows which intersect at right angles, they can also be arranged in a staggered pattern. Eachfin 8 has a body comprising a root 85 by which it is positioned on the external face 102 of the internal part 10, a free end 87, located opposite the root 85, a leading edge 82 located on the upstream side, a trailing edge 81 located on the downstream side and two flanks 88 delimited by these four parts 81, 82, 85, 87. The leading edge 82 is preferably rectilinear. In [Fig. 18], [Fig. 19], [Fig. 20] and [Fig. 21] is shown an example of fin 8 according to a preferred embodiment of the invention. This example of fin 8 has a base of trapezoidal section which is wider at its root 85 and which thins out substantially at mid-height to then continue with a section of constant thickness up to its free end 87 whose edge constitutes the salmon of fin 8. The first thickest part of fin 8 located closest to its root 85 has a cambered profile with a greater thickness in the middle (see [Fig.21]), whilethat the second thinnest part of the fin 8 has a rectilinear profile (see [Fig.20]). Although thin, the second thinnest part of the fin 8 can also be cambered. Like a wing, the spatial orientation of a fin 8 is also defined by its inclination angle α (alpha), by its angle of incidence β (beta) and by its sweep angle γ (gamma). By inclination angle α, we mean the angle that a fin 8 makes overall with respect to its radial direction DR (according to a rotation on the axial direction). By angle of incidence β we mean the angle that a fin 8 makes overall with respect to the axial direction DA (according to a rotation on the radial direction). Finally, by arrow angle γ is meant the angle that the leading edge 82 of a fin 8 makes overall with respect to its radial direction DR (according to a rotation on the tangential direction). The heat sink 6 comprises a plurality of separating walls 12 each extending in aplane P, substantially radial, parallel to their axial direction DA. The plane P preferably passes through the axis XX of the casing 5, it is then defined by the axial direction DA and the radial direction DR of each separating wall. The heat sink 6 comprises a plurality of flow volumes 13 each delimited between the internal part 10, the external part 11 (if present) and two successive separating walls 12. According to one embodiment of the invention, the heat sink 6 also comprises a plurality of technical volumes 16, each located between two flow volumes 13, and each delimited by the internal part 10, the external part 11 and two successive separating walls 12. Each technical volume is preferably occupied by elements making it possible to connect the internal part 10 and the external part 11. The heat sink 6 is characterized in that, in at least one flow volume, it comprises at least one line L of fins 8whose body is inclined in their tangential direction DT by a non-zero angle of inclination α relative to their radial direction DR. Preferably the angle α is such that 5° ≤ |α| ≤ 60°, more preferably such that 10° ≤ |α| ≤ 45°. According to one embodiment of the invention, the fins 8 present in at least one flow volume preferably have an angle of deflection γ such that 0° ≤ γ ≤ 45° and more preferably such that 15° ≤ γ ≤ 30°. According to one embodiment of the invention, the heat sink 6 further comprises at least one additional separating wall 14 which extends in a plane PS defined by its radial direction DR and its axial direction DA, and which compartmentalizes a flow volume 13 into two flow sub-volumes 13A, 13B, in particular in order to form flow sub-volumes 13A, 13B whose section is as close as possible to a circle. When a flow volume 13 comprises a single additional separating wall 14,the latter is preferably equidistant from the two separating walls 12 delimiting the flow volume 13 which it compartmentalizes. When a flow volume 13 comprises several additional separating walls 14, these and the two separating walls 12 delimiting the flow volume 13 which they compartmentalize are located equidistant from each other. The flow volume 13 is then compartmentalized into more than two sub-flow volumes 13A. It will be noted that a separating wall 12 or an additional separating wall 14 can be likened to a fin which would be the entire axial length of the flow volume 13 and whose plane preferably passes through the motor axis and more preferably through the axis XX. In order to form flow sub-volumes 13A, 13B whose section is as close as possible to a circle, according to one embodiment of the invention at least one separating wall 12 is connected to the external face 102 of the partinternal 10 and / or to the internal face 111 of the external part 11 by a fillet connection 121, 122 (see [Fig. 11], [Fig. 12] and [Fig. 13]). Similarly, at least one additional separating wall 14 is preferably connected to the external face 102 of the internal part 10 and / or to the internal face 111 of the external part 11 by a fillet connection 141, 142. Fillet means a surface with a partial circular section of concave shape intended to connect two surfaces forming a re-entrant angle. Each flow volume 13 or sub-flow volume 13A, 13B preferably comprises several lines L of fins, including at least one line L of fins 8 having a positive angle α and at least one line L of fins 8 having a negative angle α, that is to say that it preferably comprises at least two lines L of fins facing each other, where the body of the fins 8 of these lines L is mutually inclined from one line L towards another line L. Each flow volume 13 orflow sub-volume 13A, 13B preferably comprises at least one transverse row R of fins 8 comprising m successive fins with m ≥ 2 whose body is inclined in their tangential direction DT by an angle of inclination α1, α2, … αm such that |α1| ≤ |α2| ≤ … ≤ |αm|, that is to say that within the same row R the angle of inclination α of the fins 8 evolves, preferably linearly, from one fin 8 to another adjacent fin 8 (see [Fig.8]). In the same flow volume 13, within the same row R, the angle of inclination α of the fins 8 preferably evolves uniformly from the outside towards the center of said flow volume 13. According to one embodiment of the invention, each flow volume 13 or flow sub-volume 13A, 13B also comprises at least one line L of non-inclined fins 8. According to a preferred embodiment of the invention, each flow volume 13 or flow sub-volume 13A, 13B comprisesalso at least one line L of fins 8 have a body inclined in their tangential direction DT, and located between two other lines L of fins 8. The fins according to the invention can not only be inclined tangentially as seen previously, but they can also be oriented with a non-zero angle around their axis A, so that the general direction B of their foot 85 forms an angle of incidence β relative to the axial direction DA (see [Fig.9]). In the case where the fins are twisted, the angle of incidence of the chord of a fin 8 is not constant over its height. Due to the camber or curvature effect, the angle of incidence of the leading edge 82 and that of the trailing edge 81 differ, so the angle of incidence β then designates the average angle of incidence of the fin. Furthermore, this angle of incidence β progresses preferentially downstream, from 0° to 35°, preferentially from 0° to 20°, so that within the same line L, afin 8 has an angle of incidence β less than or equal to that of the fins 8 downstream thereof and greater than or equal to that of the fins 8 upstream thereof (see [Fig. 10]). According to a preferred embodiment of the invention, at least one line L of fins 8 comprises fins 81, 82, … 8n whose body is oriented at an angle of incidence β1, β2, … βn relative to their axial direction DA such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 35°, more preferably such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 20°. When this angle of incidence β increases from one fin to the next within a line L, this makes it possible to gradually impose a helical displacement on the air, while when this angle of incidence β remains constant from one fin to the next, this makes it possible to maintain this helical displacement. It will be noted that in the invention, a helical air flow may have a different helix pitch depending on its position within the heat sink 6. According to a variant ofthe invention, the heat sink 6 is bidirectional, that is to say that it can operate with the same efficiency, whether the air flows therein in a first flow direction E1 or in a second flow direction E2, opposite to the first, these two flow directions E1 and E2 being preferably parallel to the motor axis and more preferably parallel to the axis XX. According to this variant, at least one line L of fins 8 is divided into three parts, namely a first part Z1, a second part Z2 and a third part Z3 successively. If the air flows in the first flow direction E1, it successively passes through the parts Z1, Z2 then Z3. Conversely, if the air flows in the second flow direction E2, it successively passes through the parts Z3, Z2 then Z1. In its first part Z1, the line L of fins 8 comprises fins 81, 82, … 8n whose body is oriented according to an angle of incidence β1, β2, … βn relative to their axial direction DA, this angleof incidence β preferentially increasing from one fin to the next within a line, although two successive fins 8 may have the same angle of incidence. Within this line L, the angle of incidence β of the fins 8 is preferentially such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 35°, and more preferentially such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 20°. Within the same line L of the first part Z1, it is however preferred that the angle of incidence β increases from one fin 8 to the next, so that 0° ≤ |β1| < |β2| < … < |βn| ≤ 35°, and more preferably such that 0° ≤ |β1| < |β2| < … < |βn| ≤ 20°. In its second part Z2, the line L of fins 8 comprises fins 8n+1, 8n+2, … 8m whose body is oriented according to an angle of incidence βn+1, βn+2, … βm relative to their axial direction DA, this angle of incidence βn+1, βn+2, … βm being the same for all the fins of the second part Z2, that is to say that βn+1 = βn+2 = … = βm. In its third partZ3, the line L of fins 8 comprises fins 8m+1, 8m+2, … 8z whose body is oriented according to an angle of incidence βm+1, βm+2, … βz relative to their axial direction DA, this angle of incidence β preferentially decreasing from one fin to the next within a line L, although two successive fins 8 may have the same angle of incidence. Within this line L, the angle of incidence β of the fins 8 is preferentially such that 35° ≥ |βm+1| ≥ |βm+2| ≥ … ≥ |βz| ≥ 0°, and more preferentially such that 20° ≥ |βm+1| ≥ |βm+2| ≥ … ≥ |βz| ≥ 0°. Within the same line L of the third part Z3, it is however preferred that the angle of incidence β decreases from one fin 8 to the next, so that 35° ≥ |βm+1| > |βm+2| > … > |βz| ≥ 0°, and more preferably such that 20° ≥ |βm+1| > |βm+2| > … > |βz| ≥ 0°. According to a preferred embodiment of the bidirectional variant of the heat sink 6, within a line L, the last fin 8n of the firstpart Z1 preferably has an angle of incidence βn identical to the angle of incidence βn+1 of the first fin 8n+1 of the second part Z2. Similarly, according to a preferred embodiment of this variant, within a line L, the first fin 8m+1 of the third part Z3 preferably has an angle of incidence βm+1 identical to the angle of incidence βm of the last fin 8m of the second part Z2. According to another preferred embodiment of the bidirectional variant of the heat sink 6, the first part Z1 and the third part Z3 are symmetrical with respect to the second part Z2, that is to say that β1 = βz, β2 = βz-1, β3 = βz-2, … , βn-1 = βm+2, βn = βm+1, and that the first part Z1 and the second part Z2 each comprise the same number of fins 8. When the air flows in the first flow direction E1, respectively in the second flow direction E2, it first passes through the first part Z1, respectively thethird part Z3, which then acts as a part for setting the air flow into helical motion, gradually imposing a helical displacement on the air which initially has a substantially rectilinear displacement parallel to the axis XX. The air then passes through the second part Z2, which is a part for maintaining the helical displacement of the air flow. Finally, the air ends up passing through the third part Z3, respectively the first part Z1, which then acts as a part for straightening the air flow, gradually imposing on the air a substantially rectilinear displacement parallel to the axis XX before it leaves the heat sink 6. In [Fig.22], where an example of the bidirectional variant of the heat sink 6 is illustrated, the first part Z1 comprises four fins 81-84, the second part Z2 comprises three fins 85-87 and the third part Z3 comprises four fins 88-811. In this example, the angle of incidence is such that β1 = β11, β2 = β10, β3 =β9, and β4 = β5 = β6 = β7 = β8. In [Fig. 22], only the foot (or root) of each of the fins 8 is schematically represented. It will be noted that when it is not necessary for the heat sink to be able to operate bidirectionally, only the first part Z1 may be sufficient - or the third part if the air must circulate in the other direction. The first part Z1 is however preferentially followed by the second third part Z3 in order to limit the pressure losses in the air flow while maintaining the helical flow of the air. According to a preferred embodiment, within the same line L of fins 8, the angle of incidence of the trailing edge 81 of an upstream fin 8n is substantially equal to the angle of incidence of the leading edge 82 of the following downstream fin 8n+1. According to a preferred embodiment of the invention, fins 8 may have reliefs and / or hollows on at least one of their flanks 88, for example in the form of undulations,shark skin scales, circular hollows distributed uniformly on the surface in the manner of an external face of a golf ball, etc. According to a preferred embodiment of the invention, at least one fin 8 and the internal part 10 are produced by additive manufacturing. This additive manufacturing is preferably carried out from downstream to upstream, in particular so as to be able to obtain fins 8 whose leading edge 82 is rectilinear. In order to allow this manufacturing, the trailing edge 81 or the leading edge 82 of the fins 8 produced by additive manufacturing may have at least one notch 86 of substantially triangular shape. According to one embodiment of the invention, fins 8 may have a cambered profile, at least in a part thereof, for example in its lower part close to the foot 85 (see [Fig. 21]) while the upper part close to the salmon has a straight profile (see [Fig. 20]). The curvature or camber, on agiven height of fin 8, can designate the angular difference between the angle of incidence at the leading edge 82 and the angle of incidence at the trailing edge 81. Formally, a curvature is the inverse of a radius of curvature therefore in 1 / distance, the radius of curvature being a distance to a considered point of a curve. Fins 8 can also have a greater thickness in the middle to generate the least possible pressure loss, where the intrados and the extrados are curved with different curvatures (see [Fig. 21]). In addition, fins 8 can have a twist, where the angle of incidence of a fin 8 may not be constant over its height. Finally, fins 8 can have a trailing edge and / or a rounded or angular leading edge, with a preferably acute angle. These characteristics, optimized between them, each make it possible to promote the helical movement of the air flow through the fins 8. Fins 8 can alsohave a greater thickness at their foot 85, which drains more calories, and a thinner thickness at their free end 87. Thus, according to a preferred embodiment of the invention, fins 8 may have a trapezoidal or triangular section. However, since the additive manufacturing of a very thin free end 87 is complicated, fins 8 may have a trapezoidal or triangular section in their part located on the side of their foot 85 and a part of constant thickness in their part located on the side of their free end 87 as illustrated by way of example in [Fig. 19]. According to one embodiment of the invention, the cylindrical portion 9 comprises an upstream part 9a and a downstream part 9b which have a different section shape, for example an upstream part 9a of circular section and a downstream part 9b of polygonal section (see [Fig. 4]), which generates a change of direction forthe flow of air passing from the upstream part 9a to the downstream part 9b. In order to correct this change of direction, a fin 15 may be provided in the flow volumes 13 or flow sub-volumes 13A, 13B (see [Fig. 14]). This fin 15 is preferably provided at the start of the downstream part 9b, that is to say in an upstream zone of the downstream part 9b. It is preferably carried by two successive fins 8 circumferentially, for example at their free end 87. Each fin is inclined so that its downstream edge is inclined towards the internal part 10. According to a preferred embodiment of the invention, the external part 11 also comprises cooling fins, designated as additional fins 80 (see [Fig. 15]). Thus, the heat sink 6 comprises a plurality of additional cooling fins 80 which protrude towards the internal part 10 from the internal face 111 of the external part 11. Theadditional fins 80 may have the same characteristics as those of the fins 8, except that they are preferably provided in axial symmetry with respect to the helical center of rotation of the air flow or with respect to the center of the air flow vein. They will therefore not be described in any further detail. It will nevertheless be noted that in one embodiment of the invention, the additional fins 80 may be obtained by folding and cutting a sheet metal (see [Fig. 12], the external part 11 is itself preferably a tubular sheet metal). The additional fins 80 are preferably fixed by welding against the internal face 111 of the external part 11, itself preferably a tubular sheet metal. The additional fins 80 may also be made in one piece with the heat sink 6 by additive manufacturing (see [Fig. 15]). The invention also relates to an electric motor 1 equipped with acasing 5 according to the invention, as well as an aircraft equipped with such an electric motor 1. Although described through a certain number of examples, variants and embodiments, the casing according to the invention includes various variants, modifications and improvements which will be obvious to those skilled in the art, it being understood that these variants, modifications and improvements are part of the scope of the invention.

Claims

CLAIMS

1. Casing (5) of an electric motor (1) extending along an axis (XX), i.e. of an electric motor comprising an electronic control unit, said casing (5) comprising a hollow cylindrical portion (9) defining an axial direction (DA), a radial direction (DR) and a tangential direction (DT), said cylindrical portion (9) comprising: - a cylindrical internal part (10), - a heat sink (6) located on the internal part (10) and thermally connected thereto, and comprising a plurality of distinct fins (8) each comprising a body which rises from the external face (102) of the internal part (10) and extends outwards, these fins (8) being distributed in a plurality of lines (L) parallel to their axial direction (DA), and characterized in that: - the cylindrical portion (9) further comprises a cylindrical external part (11),the outer part (11) being larger than the inner part (10) and concentric with it, the heat sink (6) being located between the inner part (10) and the outer part (11); and in that - the heat sink (6) further comprises: o a plurality of separating walls (12) each extending in a plane (P) defined by their radial direction (DR) and their axial direction (DA); o a plurality of flow volumes (13) each delimited by the inner part (10), the outer part (11) and two successive separating walls (12); o at least one line (L) of distinct fins (8) located in at least one flow volume (13), fins (8) each having a leading edge (82) and a trailing edge (81), and the body of which is oriented at an angle of incidence β relative to their axial direction (DA), said angle of incidence β being non-zero for at least one fin (8) of said line (L).,

2. Housing (5) according to claim 1, characterized in that the heat sink (6) comprises at least one line (L) of distinct fins (8) located in at least one flow volume (13) and comprising n fins (81, 82, … 8n) with n ≥ 2, the body of which is oriented at an angle of incidence β1, β2, … βn relative to their axial direction (DA) such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 35°, more preferably such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 20°.

3. Housing (5) according to claim 1 or 2, characterized in that the heat sink (6) further comprises at least one line (L) of distinct fins (8) located in at least one flow volume (13) and the body of which is inclined in their tangential direction (DT) by a non-zero angle of inclination α relative to their radial direction (DR).

4. Casing (5) according to claim 3, characterized in that the angle of inclination α is such that 5° ≤ |α| ≤ 60°, more preferably such that 10° ≤ |α| ≤ 45°.

5. Casing (5) according to any one of the preceding claims, characterized in that the heat sink (6) comprises, in at least one flow volume (13), at least two distinct lines (L) of fins (8), of which at least one line (L) of fins (8) has a positive angle of inclination α and at least one line (L) of fins (8) has a negative angle of inclination α.

6. Housing (5) according to any one of the preceding claims, characterized in that the heat sink (6) comprises, in at least one flow volume (13), at least one transverse row (R) of distinct fins (8) comprising m successive fins with m ≥ 2 whose body is inclined in their tangential direction (DT) by an angle of inclination α1, α2, … αm such that |α1| ≤ |α2| ≤ … ≤ |αm|.

7. Casing (5) according to any one of the preceding claims, characterized in that the heat sink (6) further comprises at least one additional separating wall (14) which extends in a plane (PS) defined by its radial direction (DR) and its axial direction (DA) and which compartmentalizes a flow volume (13) into two flow sub-volumes (13A, 13B).

8. Casing (5) according to any one of the preceding claims, characterized in that at least one separating wall (12) or one wall. additional separator (14) is connected to the external face (102) of the internal part (10) by a filleted connection (121, 141).

9. Casing (5) according to any one of the preceding claims, characterized in that at least one fin (8) has at least one characteristic among the following characteristics: - it has reliefs and / or hollows on at least one flank (88); - it has a cambered profile; - it has a curved intrados and extrados with different curvatures; - it has a twist, the angle of incidence of the fin (8) not being constant over its height; - it has a rounded trailing edge (81); it has an angular trailing edge (81); - it has a rounded leading edge (82); and - it has an angular leading edge (82).

10. Casing (5) according to the preceding claim, characterized in that at least one fin (8) and the internal part (10) are part of a single part made of thermally conductive material which is the product of additive manufacturing.

11. Casing (5) according to any one of the preceding claims, characterized in that the cylindrical portion (9) comprises an upstream part (9a) and a downstream part (9b) which have a different cross-sectional shape, and in that at least two circumferentially successive fins (8) located in an upstream zone of the downstream part (9b) are connected to each other by a fin (15) of which a downstream edge is inclined towards the internal part (10).

12. Housing (5) according to any one of the preceding claims, characterized in that the heat sink (6) comprises a plurality of additional cooling fins (80) which project towards the internal part (10) from an internal face (111) of the external part (11).

13. Housing (5) according to any one of the preceding claims, characterized in that the heat sink (6) comprises at least. a line (L) of distinct fins (8) located in at least one flow volume (13), which line (L) of fins (8) comprises three successive parts, namely: - a first part (Z1) comprising fins (81, 82, … 8n) whose body is oriented according to an angle of incidence (β1, β2, … βn) relative to their axial direction (DA), this angle of incidence (β) being non-zero for at least one fin and such that |β1| ≤ |β2| ≤ … ≤ |βn| ; - a second part (Z2) comprising fins (8n+1, 8n+2, … 8m) whose body is oriented according to an angle of incidence (βn+1, βn+2, … βm) relative to their axial direction (DA), this angle of incidence (βn+1, βn+2, … βm) being non-zero and the same for all the fins of the second part (Z2); and - a third part (Z3) comprising fins (8m+1, 8m+2, … 8z) whose body is oriented according to an angle of incidence (βm+1, βm+2, … βz) relative to their axial direction (DA),this angle of incidence (β) being non-zero for at least one fin and such that |βm+1| ≥ |βm+2| ≥ … ≥ |βz|.

14. Casing (5) according to claim 13, characterized in that the fins (81, 82, … 8n) of the first part (Z1) are such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 35°, and more preferably such that 0° ≤ |β1| ≤ |β2| ≤ … ≤ |βn| ≤ 20°.

15. Casing (5) according to claim 13 or 14, characterized in that the fins (8m+1, 8m+2, … 8z) of the third part (Z3) are such that 35° ≥ |βm+1| ≥ |βm+2| ≥ … ≥ |βz| ≥ 0°, and more preferably such that 20° ≥ |βm+1| ≥ |βm+2| ≥ … ≥ |βz| ≥ 0°.

16. Casing (5) according to any one of claims 13 to 15, characterized in that the fins (81, 82, … 8n) of the first part (Z1) are such that 0° ≤ |β1| < |β2| < … < |βn| ≤ 35°,and more preferably such that 0° ≤ |β1| < |β2| < … < |βn| ≤ 20°.

17. Casing (5) according to any one of claims 13 to 16, characterized in that the fins (8m+1, 8m+2, … 8z) of the third part (Z3) are such that 35° ≥ |βm+1| > |βm+2| > … > |βz| ≥ 0°, and more preferably such that 20° ≥ |βm+1| > |βm+2| > … > |βz| ≥ 0°.,

18. Casing (5) according to any one of claims 13 to 17, characterized in that the first part (Z1) and the third part (Z3) each comprise the same number of fins (8).

19. Casing (5) according to any one of claims 13 to 18, characterized in that the first part (Z1) and the third part (Z3) are such that β1 = βz, β2 = βz-1, β3 = βz-2, … , βn-1 = βm+2, βn = βm+1.

20. Electric motor (1), characterized in that it is equipped with a casing (5) according to any one of the preceding claims.

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