ROTOR FOR AN ELECTRIC MOTOR WITH COOLING CIRCUIT

Description

[0001] The invention relates to a rotor for an electric motor arranged to allow for better dissipation of the heat generated during its operation. The invention also relates to an electric motor comprising such a rotor.

[0002] In general, modern electric motors consist of a rotor attached to a shaft and a stator surrounding the rotor. The stator is mounted in a housing containing bearings for the shaft's rotation. The rotor has a body formed by a stack of laminations or claw poles held together by a suitable fastening system. The rotor body has internal cavities housing permanent magnets. The stator has a body made of a stack of laminations forming a ring, the inner face of which has teeth that define, in pairs, a plurality of slots opening towards the inside of the stator body. These slots are designed to receive phase windings. These phase windings pass through the slots in the stator body and form coils that protrude from either side of the stator body.Phase windings can, for example, consist of a plurality of U-shaped conductor segments, with the free ends of two adjacent segments joined together by welding.

[0003] In the rotor, the lamination stack is axially clamped between a front flange and a rear flange mounted coaxially to the shaft. Each flange is generally disc-shaped, extending in a radial plane perpendicular to the shaft axis. Each flange has a central hole for coaxial mounting on the shaft and several through holes for mounting screws that pass axially through the entire lamination stack. These screws are secured to the flanges with nuts. The front and rear flanges are typically made of a non-magnetic, heat-conducting material, such as a metal.

[0004] The housing typically consists of front and rear bearings assembled together. These bearings define an internal cavity in which the rotor and stator are housed. Each bearing centrally carries a ball bearing for the rotational mounting of the rotor shaft.

[0005] During motor operation, the induced magnetic flux circulating through the rotor generates significant heat that must be dissipated. Several solutions currently exist for cooling the motor. One such solution, described in French patent application FR 3 111 025, involves circulating a cooling fluid through through-holes formed within the lamination stack. These through-holes extend along the axial direction of the rotor. This solution is particularly well-suited to rotors equipped with rare-earth permanent magnets positioned on the outer periphery of the lamination stack. This outer periphery position of the permanent magnets provides sufficient space within the lamination stack for the formation of the through-holes.This solution, however, is not suitable for rotors equipped with permanent ferrite-based magnets, which, due to their large volume, leave little space available to form through cavities inside the sheet metal bundle.

[0006] In addition, US documents 2020 / 036248 A1 and US 2019 / 181709 A1 disclose prior art rotors.

[0007] The invention therefore aims to provide a rotor and an electric motor comprising such a rotor arranged to allow better dissipation of the heat generated during its operation and not presenting the disadvantages of the existing solutions described above.

[0008] To this end, the invention relates to a rotor for an electric motor comprising: a rotor shaft mounted to rotate about an axis; a lamination package mounted coaxially on the rotor shaft, said lamination package comprising internal cavities symmetrical with respect to the axis of the shaft and to each other, said internal cavities traversing axially through the entire lamination package such that they open, at one of their ends, at a front lateral face of said lamination package and, at another of their ends, at a rear lateral face of said lamination package; a plurality of permanent magnets housed inside the internal cavities of the lamination package; a front flange and a rear flange mounted coaxially on the rotor shaft and arranged axially on either side of the lamination package so as to be contiguous respectively to the front and rear lateral faces of the lamination package; in which the shaft is provided with at least one first internal channel for the circulation of a cooling fluid, called the inlet channel, and at least one second internal channel for the circulation of a cooling fluid, called the outlet channel, and in which the front flange, respectively the rear flange, is configured to form with the front side face, respectively the rear side face, of the lamination package at least one front connecting channel, respectively at least one rear connecting channel, within which a cooling fluid can circulate, said at least one front connecting channel, respectively rear, being in fluidic communication with one of said inlet and outlet channels, and in which each permanent magnet is provided with at least one longitudinal fluid circulation channel opening, on one side, into said at least one front connecting channel, and, on the other side, into said at least one rear connecting channel,said at least one longitudinal fluid circulation channel being configured to permit the circulation of a cooling fluid, and in which each permanent magnet is formed by the assembly of at least two parts, respectively at least one external part and at least one internal part, said at least one internal part being housed inside said at least one external part, and said at least one longitudinal fluid circulation channel being delimited respectively by an internal peripheral surface of said at least one external part and by an external peripheral surface of said at least one internal part.

[0009] Thus configured, the rotor of the invention can be cooled by a cooling fluid circulating successively through the rotor shaft from the inlet channel, then along one of the front and rear flanges, then through the permanent magnets, then along the other front and rear flanges, and finally exiting through the outlet channel. Due to the direct contact of the cooling fluid with the permanent magnets, improved heat dissipation from the rotor during its operation can be achieved. The solution of the invention also has the advantage of not requiring additional through-holes within the lamination stack to ensure the circulation of the cooling fluid.

[0010] According to other characteristics, the rotor of the invention comprises one or more of the following optional characteristics considered alone or in combination: The inner peripheral surface of at least one external portion of at least one of the permanent magnets is provided with ribs that are in contact with the outer peripheral surface of said at least one internal portion. For each permanent magnet, one of said internal or external portions is formed of a thermoplastic matrix incorporating particles possessing magnetic properties, and the other portion is obtained by sintering or 3D printing.or by a PIM process of particles possessing magnetic properties. The particles possessing magnetic properties used for the formation of said at least one internal and / or external part are made of a material selected from ferrite or a rare earth. The thermoplastic matrix is ​​made of a material selected from polyamide 6 (PA 6), polyamide 6-6 (PA 6-6), polyamide 12 (PA 12), and polyphenylene sulfide (PPS). Said at least one forward connecting channel is in fluidic communication with said inlet channel and said at least one rear connecting channel is in fluidic communication with said outlet channel, such that a cooling fluid intended for cooling the rotor can circulate in the rotor successively through the inlet channel, then between the front flange and the front side face of the lamination pack through said at least one forward connecting channel,then inside the permanent magnets through said longitudinal fluid circulation channels, then between the rear side face of the sheet metal bundle and the rear flange through said at least one rear connecting channel, and finally through the outlet channel. The shaft comprises a hollow front end portion and a hollow rear end portion separated from the front end portion by a solid central portion, the front end portion, respectively the rear end portion, being traversed by a cylindrical central cavity, said central cavity forming the inlet channel, respectively the outlet channel, of the shaft, and in that at least one hole oriented radially with respect to the axis of the shaft is formed inside the front end portion, respectively the rear end portion, so as to open on one side into the inlet channel, respectively the outlet channel,and on the other side in said at least one forward connecting channel, respectively said at least one rear connecting channel. said at least one rear connecting channel is in fluidic communication with said inlet channel and said at least one forward connecting channel is in fluidic communication with said outlet channel, such that a cooling fluid intended for cooling the rotor can circulate in the rotor successively through the inlet channel, then between the rear flange and the rear side face of the lamination pack through said at least one rear connecting channel, then inside the permanent magnets through said longitudinal fluid circulation channels, then between the front flange and the front side face through said at least one front connecting channel,and finally through the output channel. The shaft comprises a hollow front end portion and a solid rear end portion separated from the front end portion by a hollow central portion, the front end portion and the central portion being traversed by a cylindrical central cavity, said central cavity forming the inlet channel of the shaft, the front end portion also being traversed by at least one peripheral cavity aligned coaxially with the central cavity, said at least one peripheral cavity forming the output channel of the shaft, and at least one hole oriented radially with respect to the axis of the shaft being formed inside the front end portion, respectively the central portion, so as to open on one side into the output channel, respectively the inlet channel, and on the other side into said at least one front connecting channel,respectively said at least one rear connecting channel. The shaft comprises a main body having a blind hole aligned with the axis of the shaft, said blind hole comprising two contiguous sections of different internal diameters, namely a first section having a first internal diameter and a second section having a second internal diameter, and a plastic insert being housed inside the blind hole at the level of the first section, said insert being formed of a tubular portion aligned with the second section of the blind hole and having an internal diameter that is substantially equal to the second internal diameter, and of an annular portion extending radially around one of the ends of the tubular portion, said annular portion being positioned at the interface between the first section and the second section of the blind hole and having an external diameter that is substantially equal to the first internal diameter,The shaft inlet channel is defined jointly by the tubular portion of the insert and the second section of the blind hole, and the shaft outlet channel corresponds to the space delimited by the first section of the blind hole and the tubular and annular portions of the insert. The insert comprises one or more separating fins extending radially from the outer periphery of the tubular portion, each separating fin being configured to divide the outlet channel into two or more outlet channel segments. Each of the front and rear flanges has an inner face in contact with a lateral face of the sheet metal bundle, said inner face being provided with at least one radial groove, said at least one radial groove having a proximal end opening onto a central recessed area of ​​said flange.at which at least one radial groove is in fluidic communication with the inlet or outlet channel of the shaft, and said at least one radial groove is axially aligned with one of the permanent magnets and has substantially the same general shape as said permanent magnet in a plane perpendicular to the axis, such that said at least one longitudinal fluid circulation channel of said permanent magnet opens, on one side, into said at least one radial groove of the front flange and, on the other side, into said at least one radial groove of the rear flange. at least two radial holes are formed through the shaft, each of said radial holes opening, on one side, into the inlet or outlet channel of the shaft and, on the other side, into the peripheral wall of the shaft, being in fluidic communication with the central hollowed-out area of ​​the front or rear flange.

[0011] The invention also relates to an electric motor comprising a rotor as defined above.

[0012] The invention will be better understood upon reading the following non-limiting description, made with reference to the figures attached hereto. [ Fig. 1 ] is a perspective view of a rotor according to a first embodiment of the invention. Fig. 2 ] is a perspective and longitudinal cross-sectional view of the rotor shown on the figure 1 . [ Fig. 3 ] is a view similar to the figure 1 the front flange and rotor fixing screws having been removed. Fig. 4 ] is a front axial view of the rotor shown on the figure 3 . [ Fig. 5a ] is a perspective view of a permanent magnet equipping the rotor of the figure 1 . [ Fig. 5b ] is a perspective view of the internal part of the permanent magnet of the figure 5a . [ Fig. 5c ] is a perspective view of the external part of the permanent magnet of the Figure 5a . [ Fig. 6 ] is a longitudinal cross-sectional view of an electric motor incorporating the rotor of the figure 1 . [ Fig. 7 ] is a longitudinal cross-sectional view of the shaft equipping the rotor of the figure 1 . [ Fig. 8 ] is a front axial view of the tree of the figure 7 . [ Fig. 9 ] is a perspective view of the insert used in the tree of the figure 7 . [ Fig. 10 ] is a longitudinal cross-sectional view of a shaft equipping a rotor according to a second embodiment of the invention. Fig. 11 ] is a perspective view of the external face of the front flange used in the rotor of the figure 1 . [ Fig. 12 ] is a perspective view of the inner face of the flange of the figure 11 , in which one end of the tree has been truncated. Fig. 13 ] is a perspective view of the external face of the rear flange used in the rotor of the figure 1 . [ Fig. 14 ] is a perspective view of the inner face of the flange of the figure 13 , in which one end of the tree has been represented in a truncated manner.

[0013] Throughout this description and in the claims, the terms "axial" and "radial" and their derivatives are defined with respect to the rotor's axis of rotation. Thus, an axial orientation refers to an orientation parallel to the rotor's axis of rotation, and a radial orientation refers to an orientation perpendicular to the rotor's axis of rotation. Furthermore, by convention, the terms "front" and "rear" refer to separate positions along the rotor's axis of rotation. In particular, the "front" end of the rotor shaft corresponds to the end of the shaft on which a pulley, pinion, or spline can be mounted for transmitting the rotor's rotational motion to any other similar motion transmission device.

[0014] THE figures 1 à 4 represent a rotor 10 according to a first embodiment of the invention. The rotor 10 comprises a substantially cylindrical body formed by a stack of laminations 14 made of a ferromagnetic material, in particular steel, said body being rotationally fixed to a shaft 12 mounted for rotation about an axis X. The stack of laminations 14 is mounted coaxially on the shaft 12. The shaft 12 may be press-fitted into a central opening in the stack of laminations 14 so as to rotationally link the rotor body to the shaft 12.

[0015] The sheet metal stack 14 is formed by an axial stack of sheets extending in a radial plane perpendicular to the X-axis of the shaft 12. A plurality of mounting holes 11 are provided in the sheet metal stack 14 to allow the passage of screws 21 for securing the sheets in the stack. These mounting holes 11 are through holes so that a screw 21 can be passed through each hole 11. One end of the screws 21 bears against the outer face of a front end flange 17, while the other end of the screws protrudes from the outer face of a rear end flange 19 and is threaded to receive a nut which, once tightened, exerts pressure against said outer face. Thus, the sheet metal bundle 14 is axially clamped between the front end flange 17 and the rear end flange 19. These flanges 17, 19 can advantageously ensure the balancing of the rotor 10.The balancing of these flanges can be achieved by adding or removing material. Material removal can be achieved by machining, while material addition can be achieved by inserting elements into openings provided for this purpose and distributed along the circumference of the flange 17, 19.

[0016] As depicted on the figures 3 et 4 The rotor 10 further comprises a plurality of permanent magnets 15 intended to be housed in a plurality of internal cavities 141 formed within the lamination stack 14, each of the internal cavities 141 housing at least one permanent magnet 15. The cavities 141 extend radially about the X-axis and are axially through-holes. They have a substantially triangular cross-section and are uniformly distributed around the X-axis. Two directly adjacent cavities 141 are separated by a radial segment 18 of the lamination stack 14, such that the rotor body consists of alternating cavities 141 and segments 18 when following a circumference of the rotor 10. The permanent magnets 15 have an external shape substantially complementary to that of the cavities 141, so that each permanent magnet 15 is housed without play within a cavity 141.The permanent magnets 15 are orthoradially magnetized, meaning that the two end faces of each permanent magnet 15 that are adjacent to each other in the orthoradial direction are magnetized in such a way as to generate a magnetic flux in an orthoradial orientation with respect to the X-axis. The permanent magnets 15 located in two consecutive cavities 141 therefore have alternating polarities. Arranged in this way, the permanent magnets 15 generate in the stack of laminations 14 a radially oriented magnetic flux directed towards the outer periphery of the rotor body.

[0017] In the embodiment shown in the figures 5a à 5c Each permanent magnet 15 has a general shape of a right prism with a substantially triangular base. In other embodiments (not shown) of the invention, the permanent magnets 15 may also have a general shape of a right prism with a trapezoidal or rectangular base, or be cylindrical. Each permanent magnet 15 is formed by the assembly of two parts, respectively an outer part 151 and an inner part 152, the inner part 152 being housed inside the outer part 151. In the configuration shown, the inner part 152 is solid and has the shape of a right prism with a triangular base, the vertices of the triangle being pointed, while the outer part 151 is hollow and has the shape of a right prism with a triangular base, the vertices of the triangle being rounded.The outer and inner parts 151, 152 may be joined to each other by any known means, in particular by press fitting, bonding, clipping, or welding. The outer part 151 and the inner part 152 may be formed either from a thermoplastic matrix incorporating particles possessing magnetic properties, or from particles possessing magnetic properties which are subjected to a sintering, 3D printing, or PIM (Powder Injection Molding) process. One possible configuration may, in particular, consist of using a thermoplastic matrix containing ferrite or rare-earth particles to form the outer part 151 of the permanent magnet 15, the inner part 152 being formed by sintering ferrite or rare-earth particles.Another possible configuration involves using a thermoplastic matrix containing ferrite or rare-earth particles to form the inner part 152 of the permanent magnet 15, with the outer part 151 formed by sintering ferrite or rare-earth particles. In all three possible configurations, the thermoplastic matrix of the outer part 151, and of the inner part 152 respectively, may be made of thermoplastic material such as polyamide 6 (PA 6), polyamide 6-6 (PA 6-6), polyamide 12 (PA 12), aromatic or any other type, or polyphenylene sulfide (PPS).

[0018] As depicted on the figure 5c The inner peripheral surface 151a of the outer part 151 of each permanent magnet 15 is provided with ribs 153 which are intended to come into contact with the outer peripheral surface 152a of the inner part 152, when the two parts are assembled together in the finished configuration of the permanent magnet 15 (see figure 5a These ribs 153 create interstitial spaces 154 between the outer and inner parts 151, 152, said interstitial spaces 154 extending parallel to the longitudinal direction defined by the permanent magnet 15. Each interstitial space 154 is delimited respectively by the inner peripheral surface 151a of the outer part 151 and by the outer peripheral surface 152a of the inner part 152. As explained in the following paragraphs, these interstitial spaces 154 are configured to form fluid circulation channels inside the permanent magnets 15. These fluid circulation channels 154 will thus allow a cooling fluid to circulate through the permanent magnets 15, which, ultimately, will allow the heat generated in the rotor 10 to be dissipated during its operation. The ribs 153 can have any conceivable shape.Furthermore, in other embodiments of the invention (not shown), it will be possible to form the ribs 153 at the level of the external peripheral surface 152a of the internal part 152 of the permanent magnets 15, said ribs 153 being in contact with the internal peripheral surface 151a of the external part 151.

[0019] With reference to the figure 6 It represents an electric motor 30 equipped with the rotor 10 of the figure 1 This electric motor 30 includes, in particular, a two-part housing containing the rotor 10 and an annular stator 36 which surrounds the rotor 10 coaxially with the shaft 12. The housing includes, in particular, a front bearing 32 and a rear bearing 34 connected to each other, for example, by means of fixing screws 31. The bearings 32 and 34 have a hollow shape and each centrally carries a ball bearing, 33 and 35 respectively, for the rotational mounting of the shaft 12. The front and rear bearings 32 and 34 are advantageously made of metal. Pins 37 project axially on either side of the stator body 36 and are housed in the intermediate space separating the stator 36 from the respective bearings 32 and 34.

[0020] As described previously, the lamination pack 14 of the rotor 10 incorporates permanent magnets 15, each of which defines one or more longitudinal fluid circulation channels 154. Each longitudinal channel 154 opens, at one of its ends, at the front lateral face 143 of said lamination pack 14, and, at another of its ends, at the rear lateral face 144 of said lamination pack 14. Each of the front and rear lateral faces 143, 144 faces and is directly adjacent to an inner face 173, 193 of the front and rear flanges 17, 19 respectively.

[0021] The external and internal faces 171, 173 of the front flange 17 have been shown on the figures 11 et 12 respectively, and the external and internal faces 191, 193 of the rear flange 19 were represented on the figures 13 et 14 respectively.

[0022] The front flange 17 is essentially disc-shaped. The inner face 173 of the front flange 17 is in contact with the front lateral face 143 of the sheet metal bundle 14. The inner face 173 has a series of twelve oblong grooves 175 extending radially from a central recessed area 172 of the front flange 17 to an intermediate area of ​​said flange, the twelve grooves 175 being offset by an angle of 30° from each other. The outer face 171 of the front flange 17 therefore has a series of twelve projections 178 conforming to the recessed shape of the underlying grooves 175. Furthermore, circular cavities 176 are provided at the external face 171, each of said cavities 176 being suitable for housing the head of a screw 21 intended to connect the front and rear flanges 17, 19. A bore 177 is therefore formed through the front flange 17 to allow the passage of the screw 21.

[0023] Each of the radial grooves 175 of the front flange 17 is formed in particular by an orthoradial section 175a extended at each of its ends by two oblique sections 175b1 and 175b2 making an angle with said orthoradial section 175a, said oblique sections 175b1 and 175b2 meeting at a proximal end 175c which adjoins the central zone 172. Thus configured, the radial grooves 175 have substantially the same general shape as the permanent magnets 15 in a plane perpendicular to the X axis. The radial grooves 175 open at their proximal end 175c into a central zone 172 hollowed out of the front flange 17 which is in fluidic communication with holes 125 of the shaft 12 (see detailed description below). In the mounted position of the front flange 17 (shown on the figure 6 ), each radial groove 175 is axially aligned with one of the permanent magnets 15 so as to be in fluidic communication with the longitudinal channel(s) 154 of fluid circulation of said permanent magnet 15.

[0024] Similarly, the rear flange 19 is essentially disc-shaped. The inner face 193 of the rear flange 19 is in contact with the rear lateral face 144 of the sheet metal bundle 14. The inner face 193 has a series of twelve oblong grooves 195 extending radially from a central recessed area 192 of the rear flange 19 to an intermediate area of ​​said flange, the twelve grooves 195 being offset by an angle of 30° from each other. The outer face 191 of the rear flange 19 therefore has a series of twelve projections 198 conforming to the recessed shape of the underlying grooves 195. Furthermore, hexagonal cavities 196 are provided at the external face 191, each of said cavities 196 being suitable for housing the nut of the screw 21 intended to connect the front and rear flanges 17, 19. A bore 197 is therefore formed through the rear flange 19 to allow the passage of the screw 21.

[0025] Each of the radial grooves 195 of the rear flange 19 is formed in particular of an orthoradial section 195a extended at each of its ends by two oblique sections 195b1 and 195b2 making an angle with said orthoradial section 195a, said oblique sections 195b1 and 195b2 meeting at a proximal end 195c which adjoins the central zone 192. Thus configured, the radial grooves 195 have substantially the same general shape as the permanent magnets 15 in a plane perpendicular to the X axis. The radial grooves 195 open directly, at their proximal end 195c, into the central zone 192 hollowed out of the rear flange 19 which is in fluidic communication with holes 127 of the shaft 12 (see detailed description below). In the mounted position of the front flange 19 (shown on the figure 6 ), each radial groove 195 is axially aligned with one of the permanent magnets 15 so as to be in fluidic communication with the longitudinal channel(s) 154 of fluid circulation of said permanent magnet 15.

[0026] Thus, each longitudinal channel 154 of the permanent magnets 15 opens, on one side, into one of the radial grooves 175 of the front flange 17 and, on the other side, into one of the radial grooves 195 of the rear flange 19. By convention, the radial grooves 175 are thus called front linking channels and the radial grooves 195 are called rear linking channels.

[0027] As illustrated on the figure 2 The front connecting channels 175 of the front flange 17 are in fluidic communication, via the central zone 172, with radial holes 125 formed through a front end portion 121 of the shaft 12, and the rear connecting channels 195 of the rear flange 19 are in fluidic communication, via the central zone 192, with radial holes 127 formed through a rear end portion 123 of the shaft 12. Thus, fluidic communication occurs between the radial holes 125 of the shaft 12 and the longitudinal channels 154 of the permanent magnets 15 via, successively, the central zone 172 and the radial grooves 175 of the front flange 17. Similarly, fluidic communication occurs between the radial holes 127 of the shaft 12 and the longitudinal channels 154 of the permanent magnets 15 by means of, successively, the central zone 192 and the radial grooves 195 formed at the level of the inner face 193 of the rear flange 19.

[0028] The circulation of the cooling fluid inside the rotor 10 of the figure 1 will depend on the internal geometry of tree 12.

[0029] Thus, in the specific configuration shown on the figure 2 The rotor 10 is equipped with a shaft 12 which is shown in detail on the figures 7 à 9 In this specific configuration, the shaft 12 includes, in particular, a main body 120 formed of a front end portion 121 and a rear end portion 123, said front and rear end portions being separated by a central portion 122 (the central portion 122 is delimited by dotted lines on the figure 7 The main body 120 has a blind hole 128 aligned along the X-axis of the shaft 12. This blind hole 128 comprises two contiguous sections with different internal diameters, namely a first section 128a having an internal diameter D1 and a second section 128b having an internal diameter D2. A plastic insert 13 is housed inside the blind hole 128 at the first section 128a. As shown in the figure 9 This insert 13 is formed of a tubular part 131, having an internal diameter Di substantially equal to the internal diameter D2, and of an annular part 132 extending radially around one of the ends of the tubular part 131, said annular part 132 having an external diameter De substantially equal to the internal diameter D1. Four fins 133 extend radially from the external periphery of the tubular part 131, said fins 133 being perpendicular to each other. Each of the fins 133 has a length such that its free end is tangent to the outer peripheral edge of the annular part 132. When the insert 13 is fixed in the main body 120, its tubular part 131 is aligned with the second section 128b of the blind hole 128 and its annular part 132 is positioned at the interface between the first section 128a and the second section 128b of the blind hole 128.Thus configured, the shaft 12 has a first channel 124, called the inlet channel, through which a cooling fluid can be conveyed to cool the rotor 10, and at least a second channel 126, called the outlet channel, through which the cooling fluid can exit after absorbing the heat from the permanent magnets 15 and the lamination pack 14. The inlet channel 124 is formed jointly by the tubular portion 131 of the insert 13 and by the second section 128b of the blind hole 128. The outlet channel 126 is defined by the peripheral space surrounding the tubular portion 131 of the insert 13. The outlet channel 126 is thus delimited by the inner wall of the first section 128a of the blind hole 128 and by the tubular and annular portions 131, 132 of the insert 13. This outlet channel 126 is divided respectively in four output channel segments 126a, 126b, 126c and 126d, two directly adjacent segments being separated by a fin 133.Furthermore, the shaft 12 is provided with four holes 125 oriented radially with respect to the X axis of the shaft 12, said holes 125 being formed inside the front end portion 121 so as to open, on one side, into one of the segments 126a-126d of the output channel 126 and, on the other side, into the central area 172 of the front flange 17 which communicates with the front connecting channels 175, as shown on the . figure 2 Similarly, four holes 127 oriented radially with respect to the X-axis of the shaft 12 are formed inside the central portion 122 (as shown in the figure 7 ) so as to open, on one side, into the inlet channel 124 and, on the other side, into the central area 192 of the rear flange 19 which communicates with the rear connecting channels 195.

[0030] Thus configured, the rotor 10 can be cooled by a cooling fluid, such as oil for example, said cooling fluid circulating in the rotor successively through the inlet channel 124, then between the rear flange 19 and the rear side face 144 of the sheet metal pack 14 through the rear connecting channels 195, then inside the permanent magnets 15 through the longitudinal channels 154, then between the front flange 17 and the front side face 143 of the sheet metal pack 14 through the front connecting channels 175, and finally through the outlet channel segments 126a-126d.

[0031] With reference to the figure 10 A variant embodiment of a shaft 12 that can be fitted to a rotor according to the invention is shown. This shaft 12 includes, in particular, a hollow front end portion 121 and a hollow rear end portion 123 separated from the front end portion 121 by a solid central portion 122 (the central portion 122 is delimited by dotted lines on the figure 10 The front end portion 121 is traversed by a cylindrical central cavity 124, said central cavity 124 having a front end 124a open to the outside and a closed rear end 124b. Near the rear end 124b is formed a series of four holes 125 oriented radially with respect to the X-axis of the shaft 12, said holes 125 being offset by 90° from each other. Each of the holes 125 has an end 125a radially distant from the central cavity 124 and open to the outside. The front end portion 121 is thus configured to allow the entry of a flow of cooling fluid at the front end 124a of the central cavity 124, then the circulation of said cooling fluid through the central cavity 124 until it reaches the radial holes 125, and then through the radial holes 125 until it reaches the ends 125a of the holes 125.Symmetrically, the rear end portion 123 is traversed by a cylindrical central cavity 126, said cavity having a rear end 126a open to the outside and a closed front end 126b. Near the front end 126b is formed a series of four holes 127 oriented radially with respect to the X-axis of the shaft 12, said holes 127 being offset by 90° from each other. Each of the holes 127 has an end 127a radially distant from the central cavity 126 and open to the outside. The rear end portion 123 is thus configured to allow the entry of a flow of cooling fluid at the ends 127a of the radial holes 127, then the circulation of said cooling fluid through the radial holes 127 until reaching the central cavity 126, then through the central cavity 126 until reaching the rear end 126a of the central cavity 126.

[0032] In the following description, and by convention, the central cavity 124 will be referred to as the cooling fluid inlet channel and the central cavity 126 will be referred to as the cooling fluid outlet channel.

[0033] By equipping rotor 10 with the figure 1 of tree 12 of the figure 10 in place of tree 12 of the figure 7 It is thus possible to modify the path followed by the cooling fluid inside the rotor 10. In particular, the cooling fluid can circulate in the rotor 10 successively through the inlet channel 124, then between the front flange 17 and the front side face 143 of the lamination pack 14 through the front connecting channels 175, then inside the permanent magnets 15 through the longitudinal fluid circulation channels 154, then between the rear side face 144 of the lamination pack 14 and the rear flange 19 through the rear connecting channels 195, and finally through the outlet channel 126 of the shaft 12.

[0034] The invention is obviously not limited to the embodiments as described above. In particular, in other embodiments (not shown) of the invention, the number of internal cavities 141, permanent magnets 15, front and rear connecting channels 175, 195 may differ from twelve and the number of radial holes 125, 127 may differ from four.

[0035] Thus, one conceivable configuration of the invention could consist of a rotor comprising two, or any multiple of two, internal cavities 141 arranged symmetrically with respect to the X axis of the shaft 12.

[0036] In another conceivable configuration of the invention, the rotor may comprise three (or another odd number) internal cavities 141, said second internal cavities 141 being distributed regularly around the X axis so as not to create imbalance for the rotor.

[0037] The number of permanent magnets 15 and front and rear connecting channels 175, 195 will preferably be chosen so as to be equal to the number of internal cavities 141.

[0038] In another possible configuration of the invention, the rotor 10 of the figure 1 could include an insert 13 without separating fins 133. As a result, the output channel 126 would not be divided into output channel segments 126a-126d, but would consist of a single peripheral cavity aligned coaxially with the central cavity 124 formed by the tubular part 131 of the insert 13.

Claims

1. A rotor (10) for an electric motor (30) comprising: - a rotor shaft (12) rotatably mounted about an axis (X); - a lamination stack (14) coaxially mounted on the rotor shaft (12), said lamination stack (14) comprising inner cavities (141) symmetrical with respect to the axis (X) of the shaft (12) and therebetween, said inner cavities (141) axially crossing the entirety of the lamination stack (14) such that they open, at one of their ends, at the level of a front lateral face (143) of said lamination stack (14) and, at another one of their ends, at the level of a rear lateral face (144) of said lamination stack (14); - a plurality of permanent magnets (15) accommodated inside the inner cavities (141) of the lamination stack (14); - a front flange (17) and a rear flange (19) coaxially mounted on the rotor shaft (12) and arranged axially on either side of the lamination stack (14) so as to be contiguous respectively with the front and rear lateral faces (143, 144) of the lamination stack (14); wherein the shaft (12) is provided with at least one first inner channel (124) for the circulation of a cooling fluid, so-called the inlet channel, and at least one second inner channel (126) for the circulation of a cooling fluid, so-called the outlet channel, and wherein the front flange (17), respectively the rear flange (19), is configured to form with the front lateral face (143), respectively the rear lateral face (144), of the lamination stack (14) at least one front connecting channel (175), respectively at least one rear connecting channel (195), inside which a cooling fluid can flow, said at least one front (175), respectively rear (195), connecting channel being in fluid communication with one of said inlet and outlet channels (124, 126), and wherein each permanent magnet (15) is provided with at least one longitudinal fluid circulation channel (154) opening, on one side, onto said at least one front connecting channel (175), and, on the other side, onto the at least one rear connecting channel (195), said at least one longitudinal fluid circulation channel (154) being configured to enable the circulation of a cooling fluid, characterized in that each permanent magnet (15) is formed by the assembly of at least two portions, respectively at least one outer portion (151) and at least one inner portion (152), said at least one inner portion (152) being accommodated inside said at least one outer portion (151), and in that said at least one longitudinal fluid circulation channel (154) is delimited respectively by an inner peripheral surface (151a) of said at least one outer portion (151) and by an outer peripheral surface (152a) of said at least one inner portion (152).

2. The rotor (10) according to claim 1, characterized in that the inner peripheral surface (151a) of said at least one outer portion (151) of at least one of the permanent magnets (15) is provided with ribs (153) which are in contact with the outer peripheral surface (152a) of said at least one inner portion (152).

3. The rotor (10) according to claim 1 or 2, characterized in that the outer peripheral surface (152a) of said at least one inner portion (152) of at least one of the permanent magnets (15) is provided with ribs which are in contact with the inner peripheral surface (151a) of said at least one outer portion (151).

4. The rotor (10) according to one of claims 1 to 3, characterized in that, for each permanent magnet (15), one of said inner (152) or outer (151) portions is formed of a matrix made of a thermoplastic material incorporating particles having magnetic properties and the other portion is obtained by sintering, or by 3D printing, or by a PIM process of particles having magnetic properties.

5. The rotor (10) according to claim 4, characterized in that the particles having magnetic properties used for the formation of said at least one inner and / or outer portion are made of a material selected from among ferrite or a rare-earth element.

6. The rotor (10) according to claim 4 or 5, characterized in that the matrix made of a thermoplastic material is made of a material selected from among polyamide 6 (PA 6), polyamide 6-6 (PA 6-6), polyamide 12 (PA 12), and polyphenylene sulfide (PPS).

7. The rotor (10) according to one of the preceding claims, characterized in that said at least one front connecting channel (175) is in fluid communication with said inlet channel (124) and said at least one rear connecting channel (195) is in fluid communication with said outlet channel (126), such that a cooling fluid intended for cooling the rotor could flow in the rotor successively throughout the inlet channel (124), then between the front flange (17) and the front lateral face (143) of the lamination stack (14) throughout said at least one front connecting channel (175), then inside the permanent magnets (15) throughout said longitudinal fluid circulation channels (154), then between the rear lateral face (144) of the lamination stack (14) and the rear flange (19) throughout said at least one rear connecting channel (195), and finally throughout the outlet channel (126).

8. The rotor (10) according to claim 7, characterized in that the shaft (12) comprises a hollow front end portion (121) and a hollow rear end portion (123) separated from the front end portion (121) by a solid central portion (122), the front end portion (121), respectively the rear end portion (123), being crossed by a cylindrical shaped central cavity, said central cavity forming the inlet channel (124), respectively the outlet channel (126), of the shaft (12), and in that at least one hole (125, 127) oriented radially with respect to the axis (X) of the shaft (12) is formed inside the front end portion (121), respectively the rear end portion (123), so as to open on one side into the inlet channel (124), respectively the outlet channel (126), and on the other side into said at least one front connecting channel (175), respectively said at least one rear connecting channel (195).

9. The rotor (10) according to one of claims 1 to 6, characterized in that said at least one rear connecting channel (195) is in fluid communication with said inlet channel (124) and said at least one front connecting channel (175) is in fluid communication with said outlet channel (126), such that a cooling fluid intended for cooling the rotor could flow in the rotor successively throughout the inlet channel (124), then between the rear flange (19) and the rear lateral face (144) of the lamination stack (14) throughout said at least one rear connecting channel (195), then inside the permanent magnets (15) throughout said longitudinal fluid circulation channels (214), then between the front flange (17) and the front lateral face (143) throughout said at least one front connecting channel (175), and finally throughout the outlet channel (126).

10. The rotor (10) according to claim 9, characterized in that the shaft (12) comprises a hollow front end portion (121) and a solid rear end portion (123) separated from the front end portion (121) by a hollow central portion (122), the front end portion (121) and the central portion (122) being crossed by a cylindrical shaped central cavity, said central cavity forming the inlet channel (124) of the shaft (12), the front end portion (121) also being crossed by at least one peripheral cavity coaxially aligned with the central cavity, said at least one peripheral cavity forming the outlet channel (126) of the shaft (12), and in that at least one hole (125, 127) oriented radially with respect to the axis (X) of the shaft (12) is formed inside the front end portion (121), respectively the central portion (122), so as to open on one side into the outlet channel (126), respectively the inlet channel (124), and on the other side into said at least one front connecting channel (175), respectively said at least one rear connecting channel (195).

11. The rotor (10) according to claim 10, characterized in that the shaft (12) comprises a main body (120) provided with a blind hole (128a, 128b) aligned according to the axis (X) of the shaft (12), said blind hole (128) comprising two contiguous sections of different inner diameters, namely a first section (128a) having a first inner diameter and a second section (128b) having a second inner diameter, and in that an insert (13) made of a plastic material is accommodated inside the blind hole at the level of the first section (128a), said insert (13) being formed of a tubular portion (131) aligned with the second section (128b) of the blind hole and having an inner diameter that is substantially equal to the second inner diameter, and an annular portion (132) extending radially around one of the ends of the tubular portion (131), said annular portion (132) being positioned at the level of the interface between the first section (128a) and the second section (128b) of the blind hole and having an outer diameter that is substantially equal to the first inner diameter, the inlet channel (124) of the shaft (12) being defined jointly by the tubular portion (131) of the insert (13) and by the second section (128b) of the blind hole and the outlet channel (126) of the shaft (12) corresponding to the space delimited by the first section (128a) of the blind hole and by the tubular and annular portions (131, 132) of the insert (13).

12. The rotor (10) according to claim 11, characterized in that the insert (13) comprises one or several splitter fin(s) (133) extending radially from the outer periphery of the tubular portion (131), each of the splitter fins (133) being configured to separate the outlet channel (126) into two or more outlet channel segment(s) (126a-126d).

13. The rotor (10) according to one of the preceding claims, characterized in that each of the front and rear flanges (17, 19) has an inner face (173, 193) in contact with a lateral face (143, 144) of the lamination stack (14), said inner face (173, 193) being provided with at least one radial groove (175, 195), said at least one radial groove (175, 195) having a proximal end (175c, 195c) opening onto a recessed central area (172) of said flange, at the level of which said at least one radial groove (175, 195) is in fluid communication with the inlet (124) or outlet (126) channel of the shaft (12), and said at least one radial groove (175, 195) being axially aligned with one of the permanent magnets (15) and having substantially the same general shape as said permanent magnet (15) in a plane perpendicular to the axis, so that said at least one longitudinal fluid circulation channel (154) of said permanent magnet (15) opens, on one side, into said at least one radial groove (175) of the front flange (17) and, on the other side, into said at least one radial groove (195) of the rear flange (19).

14. The rotor (10) according to claim 13, characterized in that at least two radial holes (125, 127) are formed throughout the shaft (12), each of said radial holes (125, 127) opens, on one side, onto the inlet (124) or outlet (126) channel of the shaft (12) and, on the other side, onto the peripheral wall of the shaft (12), while being in fluid communication with the recessed central area (172, 192) of the front (17) or rear (19) flange.

15. An electric motor (30) comprising a rotor (10) according to one of the preceding claims.