Rotor for electric motor provided with cooling circuit

Abstract

The invention relates to a rotor (10) for an electric motor (30), comprising: a rotor shaft (12) mounted for rotation about an axis (X); a lamination stack (14) coaxially mounted on the rotor shaft (12), said lamination stack (14) comprising an inner cavity (141) housing the permanent magnets (15); a front flange (17) and a rear flange (19) mounted coaxially on the rotor shaft (12) and arranged axially on both sides of the lamination stack (14) so as to abut, respectively, a front lateral face (143) and a rear lateral face (144) of the lamination stack (14); and flow channels for a cooling fluid, the flow channels being formed inside the shaft (12), the front flange (17) and the rear flange (19), and the permanent magnet (15), respectively.

Description

Technical Field

[0001] The invention relates to a rotor for an electric motor, the rotor being arranged so as to allow better removal of the heat generated during operation of the rotor. The invention also relates to an electric motor comprising such a rotor. Background of the Invention

[0003] In general, current electric motors include a rotor fixed to a shaft and a stator surrounding the rotor. The stator is mounted in a housing, which includes bearings for mounting the shaft in a rotatable manner. The rotor includes a body formed by a stack of laminations or a pole wheel (claw-shaped poles), which is held in the form of a stack by means of a suitable fastening system. The body of the rotor includes an internal cavity for accommodating permanent magnets. The stator includes a body consisting of a stack of laminations forming a crown, and the inner face of the stator is provided with teeth, which are defined in pairs with a plurality of slots, which lead to the interior of the stator body and are intended to receive phase windings. These phase windings pass through the slots of the stator body and form winding packages protruding on both sides of the stator body. For example, the phase winding can be composed of a plurality of U-shaped conductor segments, and the free ends of two adjacent segments are connected together by welding.

[0004] In the rotor, the lamination stack is clamped axially between a front flange and a rear flange mounted coaxially with the shaft. Each flange is usually shaped as a disc extending in a radial plane perpendicular to the axis of the shaft. Each flange comprises a central hole for coaxial mounting on the shaft, and a plurality of through holes intended to receive fastening screws passing axially through the entire lamination stack, the screws being fixed to the flange by means of nuts. The front and rear flanges are usually formed of a thermally conductive non-magnetic material, such as metal.

[0005] Generally speaking, the housing comprises a front support and a rear support assembled together. The support defines an internal cavity for accommodating the rotor and the stator. Each of the support carries a ball bearing at the center for rotatably mounting the shaft of the rotor.

[0006] During the operation of the motor, the induced magnetic flux flowing through the rotor generates a large amount of heat, which should be discharged. There are currently a variety of solutions for cooling the motor. One of these solutions described in French patent application FR 3 111 025 consists in making the cooling fluid flow through through cavities formed inside the lamination stack, which extend according to the axial direction of the rotor. This solution is particularly suitable for rotors provided with permanent magnets based on rare earth elements, which are arranged at the periphery of the lamination stack. In fact, this position at the periphery of the permanent magnets provides enough space inside the lamination stack for the formation of through cavities. However, this solution is not suitable for rotors provided with permanent magnets based on ferrites, because the large volume of the permanent magnets based on ferrites leaves little space inside the lamination stack to form through cavities. Summary of the invention

[0007] The present invention therefore aims to provide a rotor and an electric motor comprising such a rotor, arranged so as to be able to better discharge the heat generated during operation of the rotor and without the disadvantages of the previously described existing solutions.

[0008] To this end, the present invention relates to a rotor for an electric motor, the rotor comprising:

[0009] - a rotor shaft, which is mounted rotatably about an axis;

[0010] a lamination stack coaxially mounted on the rotor shaft, said lamination stack comprising an internal cavity symmetrical with respect to the axis of the shaft and with respect to each other and axially passing through the entire lamination stack such that the internal cavity is open at one of its ends at the level of the front lateral face of the lamination stack and at the other of its ends at the level of the rear lateral face of the lamination stack;

[0011] - a plurality of permanent magnets housed inside the interior cavity of the lamination stack;

[0012] - a front flange and a rear flange which are coaxially mounted on the rotor shaft and are arranged axially on both sides of the lamination stack so as to abut against the front and rear lateral faces of the lamination stack, respectively;

[0013] wherein the shaft is provided with at least one first internal channel for the circulation of a cooling fluid, the so-called inlet channel, and at least one second internal channel for the circulation of a cooling fluid, the so-called outlet channel, and wherein the front flange or the rear flange is configured to form with the respective front lateral face or rear lateral face of the lamination stack respectively at least one front connecting channel or at least one rear connecting channel, in which the cooling fluid can flow, the at least one front connecting channel or the at least one rear connecting channel being in fluid communication with one of the inlet channel and the outlet channel, respectively, and

[0014] wherein each permanent magnet is provided with at least one longitudinal fluid circulation channel, the at least one longitudinal fluid circulation channel leading to the at least one front connecting channel on one side and to the at least one rear connecting channel on the other side, the at least one longitudinal fluid circulation channel being configured to enable a cooling fluid circulation to circulate, and

[0015] Wherein, each permanent magnet is formed by assembling at least two parts, wherein the at least two parts are respectively at least one outer part and at least one inner part, the at least one inner part is accommodated inside the at least one outer part, and the at least one longitudinal fluid circulation channel is correspondingly delimited by the inner peripheral surface of the at least one outer part and the outer peripheral surface of the at least one inner part.

[0016] Thus constructed, the rotor of the invention can be cooled by a cooling fluid which flows from the inlet channel in sequence through the rotor shaft, then along one of the front flange and the rear flange, then through the permanent magnets, then along the other of the front flange and the rear flange, and finally out through the outlet channel. Due to the direct contact of the cooling fluid with the permanent magnets, a better discharge of the heat generated in the rotor during operation can be obtained. The solution of the invention also has the advantage that no additional through-cavities are required in the lamination stack to ensure the circulation of the cooling fluid.

[0017] According to other features, the rotor of the invention comprises one or more of the following optional features, considered alone or in combination:

[0018] - The inner peripheral surface of the at least one outer portion of at least one of the permanent magnets is provided with ribs, which are in contact with the outer peripheral surface of the at least one inner portion.

[0019] - The outer peripheral surface of the at least one inner portion of at least one of the permanent magnets is provided with ribs, which are in contact with the inner peripheral surface of the at least one outer portion.

[0020] For each permanent magnet, one of the inner part or the outer part is formed by a matrix made of thermoplastic material containing particles having magnetic properties and the other part is obtained by sintering, by 3D printing or by a PIM process of particles having magnetic properties.

[0021] The particles having magnetic properties used to form the at least one inner portion and / or outer portion are made of a material chosen from ferrites or rare earth elements.

[0022] The matrix made of thermoplastic material is made of a material selected from the group consisting of polyamide 6 (PA6), polyamide 6-6 (PA6-6), nylon 12 (PA12) and polyphenylene sulfide (PPS).

[0023] -The at least one front connecting channel is fluidically connected to the inlet channel, and the at least one rear connecting channel is fluidically connected to the outlet channel, so that the cooling fluid intended for cooling the rotor can flow in the rotor sequentially through the inlet channel, then flow through the at least one front connecting channel between the front flange and the front lateral face of the lamination stack, then flow through the longitudinal fluid circulation channel inside the permanent magnet, then flow through the at least one rear connecting channel between the rear lateral face of the lamination stack and the rear flange, and finally flow through the outlet channel.

[0024] - the shaft comprises a hollow front end portion and a hollow rear end portion, which is separated from the front end portion by a solid central portion, the front end portion or the rear end portion, respectively, being traversed by a cylindrical central cavity, which forms a respective inlet channel or outlet channel of the shaft, and in the interior of the front end portion or in the interior of the rear end portion, respectively, at least one hole is formed which is radially oriented with respect to the axis of the shaft so that the at least one hole leads to the inlet channel or the outlet channel, respectively, on one side and to the at least one front connecting channel, respectively, on the other side.

[0025] - the at least one rear connecting channel is in fluid communication with the inlet channel, and the at least one front connecting channel is in fluid communication with the outlet channel, so that a cooling fluid intended for cooling the rotor can flow in the rotor sequentially through the inlet channel, then through the at least one rear connecting channel between the rear flange and the rear lateral face of the lamination stack, then through the longitudinal fluid circulation channel inside the permanent magnets, then through the at least one front connecting channel between the front flange and the front lateral face, and finally through the outlet channel.

[0026] -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, the central cavity forming an inlet channel of the shaft, the front end portion being also traversed by at least one peripheral cavity coaxially aligned with the central cavity, the at least one peripheral cavity forming an outlet channel of the shaft, and at least one hole oriented radially relative to the axis of the shaft is formed inside the front end portion or inside the central portion, respectively, so that the at least one hole leads to the outlet channel or the inlet channel, respectively, on one side, and to the at least one front connecting channel or the at least one rear connecting channel, respectively, on the other side.

[0027] - the shaft comprises a body provided with a blind hole aligned according to the axis of the shaft, the blind hole comprising two adjacent sections with different internal diameters, namely a first section with a first internal diameter and a second section with a second internal diameter, and an insert made of plastic material is housed inside the blind hole at the level of the first section, the insert being formed by a tubular portion and an annular portion extending radially around one of the ends of the tubular portion, the tubular portion being aligned with the second section of the blind hole and having an internal diameter substantially equal to the second internal diameter, the annular portion being positioned at the level of the junction between the first section and the second section of the blind hole and having an external diameter substantially equal to the first internal diameter, the inlet channel of the shaft being defined jointly by the tubular portion of the insert and the second section of the blind hole, and the outlet channel of the shaft corresponding to the space delimited by the first section of the blind hole and the tubular portion and the annular portion of the insert.

[0028] The insert comprises one or more splitter fins extending radially from the outer periphery of the tubular portion, each of the splitter fins being configured to split the outlet channel into two or more outlet channel sections.

[0029] - Each of the front flange and the rear flange has an internal face in contact with the lateral face of the lamination stack, the internal face being provided with at least one radial groove, the at least one radial groove having a proximal end opening into a recessed central area of ​​the flange, at the level of the recessed central area the at least one radial groove being in fluid communication with an inlet channel or an outlet channel of the shaft, and the at least one radial groove being axially aligned with one of the permanent magnets and having substantially the same overall shape as the permanent magnet in a plane perpendicular to the axis, so that the at least one longitudinal fluid circulation channel of the permanent magnet opens on one side into the at least one radial groove of the front flange and on the other side into the at least one radial groove of the rear flange.

[0030] - at least two radial holes are formed through the shaft, each of which opens on one side to an inlet channel or an outlet channel of the shaft and on the other side to the peripheral wall of the shaft while being in fluid communication with a recessed central area of ​​the front flange or the rear flange.

[0031] The invention also relates to an electric motor comprising a rotor as described above. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The invention will be better understood by reading the following non-limiting description made with reference to the accompanying drawings.

[0033] [ Figure 1 ] is a stereoscopic view of a rotor according to a first embodiment of the present invention.

[0034] [ Figure 2 ]yes Figure 1 A longitudinal sectional perspective view of the rotor shown in FIG.

[0035] [ Figure 3 ] is similar to Figure 1 view of the rotor, with the front flange and retaining screws removed.

[0036] [ Figure 4 ]yes Figure 3 Front axial view of the rotor shown in .

[0037] [ Figure 5a ] is assembly Figure 1 A three-dimensional view of the permanent magnets of the rotor.

[0038] [ Figure 5b ]yes Figure 5a A three-dimensional view of the internal part of a permanent magnet.

[0039] [ Figure 5c ]yes Figure 5a A perspective view of the external part of a permanent magnet.

[0040] [ Figure 6 ] is combined with Figure 1 Longitudinal cross-section of a rotor of an electric motor.

[0041] [ Figure 7 ] is assembly Figure 1 Longitudinal section of the shaft of the rotor.

[0042] [ Figure 8 ]yes Figure 7 Front axial view of the shaft.

[0043] [ Fig. 9 ] is in Figure 7 A perspective view of the insert used in the shaft.

[0044] [ Fig.10 ] is a longitudinal sectional view of the shaft of the assembled rotor according to the second embodiment of the present invention.

[0045] [ Fig.11 ] is in Figure 1 A perspective view of the outer face of the front flange of a rotor used in FIG.

[0046] [ Fig.12 ]yes Fig.11 A perspective view of the inner face of a flange of , wherein one end of the shaft is shown in a truncated manner.

[0047] [ Fig.13 ] is in Figure 1 A perspective view of the outer face of the rear flange of a rotor used in FIG.

[0048] [ Fig.14 ]yes Fig.13 A perspective view of the inner face of a flange of , wherein one end of the shaft is shown in a truncated manner. DETAILED DESCRIPTION

[0049] Throughout the specification and claims, the terms "axial" and "radial" and their derivatives are defined relative to the axis of rotation of the rotor. Thus, an axial orientation relates to an orientation parallel to the axis of rotation of the rotor, and a radial orientation relates to an orientation perpendicular to the axis of rotation of the rotor. Furthermore, by convention, the terms "front" and "rear" refer to individual positions along the axis of rotation of the rotor. In particular, the "front" end of the shaft of the rotor corresponds to the end of the shaft to which a pulley, pinion, spline for transmitting the rotational motion of the rotor to any other similar motion transmitting device can be fixed.

[0050] Figures 1 to 4 A rotor 10 according to a first embodiment of the invention is shown. The rotor 10 comprises a substantially cylindrical body formed by a lamination stack 14 made of ferromagnetic material, in particular of steel, said body being rotationally fixed to a shaft 12 which is mounted rotatably about an axis X. The lamination stack 14 is coaxially mounted on the shaft 12. The shaft 12 can be force-fitted in a central opening of the lamination stack 14 in order to rotationally connect the body of the rotor to the shaft 12.

[0051] The lamination stack 14 is formed by an axial stacking of laminations extending in a radial plane perpendicular to the axis X of the shaft 12. A plurality of fastening holes 11 are formed in the lamination stack 14 to enable the passage of fastening screws 21 of the encapsulated laminations. These fastening holes 11 are through-going so that a screw 21 can be passed through each hole 11. The first end of the screw 21 bears against the outer face of the front flange 17, while the other end of the screw protrudes from the outer face of the rear flange 19 and is tapped to receive a nut which, once tightened, exerts pressure on the outer face. Thus, the lamination stack 14 is clamped axially between the front flange 17 and the rear flange 19. Advantageously, these flanges 17, 19 can allow the balancing of the rotor 10 to be ensured. The balancing of these flanges can be performed by adding material or removing material. The removal of material can be performed by machining, while the addition of material can be performed by implanting elements in openings provided for this purpose and distributing the elements along the circumference of the flanges 17, 19.

[0052] like Figure 3 and Figure 4 As shown, the rotor 10 also includes a plurality of permanent magnets 15, which are intended to be accommodated in a plurality of internal cavities 141 formed inside the lamination stack 14, each of the internal cavities 141 accommodating at least one permanent magnet 15. The cavities 141 extend according to a radial direction relative to the axis X and are axially penetrated. The cavities 141 have a substantially triangular cross-section and are evenly distributed around the axis X. Two directly adjacent cavities 141 are separated by radial segments 18 of the lamination stack 14, so that the body of the rotor is composed of cavities 141 and segments 18 alternating along the circumference of the rotor 10. The permanent magnets 15 have an outer shape that is substantially complementary to the outer shape of the cavities 141, so that each permanent magnet 15 is tightly accommodated inside the cavity 141. The permanent magnets 15 have orthogonal magnetization, that is, the two end faces of each permanent magnet 15 adjacent to each other in an orthogonal direction are magnetized so as to be able to generate a magnetic flux along an orthogonal direction relative to the axis X. Therefore, the permanent magnets 15 located in two consecutive cavities 141 have alternating polarities. Arranged in this way, the permanent magnets 15 generate a magnetic flux in the lamination stack 14 that is radially oriented and directed toward the periphery of the rotor body.

[0053] exist Figure 5a to Figure 5c In the embodiment shown, each permanent magnet 15 is generally shaped as a right prism with a substantially triangular base.

[0054] In other embodiments of the present invention (not shown), the permanent magnet 15 can also be generally shaped as a right prism with a trapezoidal or rectangular base, or have a cylindrical shape. Each permanent magnet 15 is formed by the assembly of two parts, which are an outer part 151 and an inner part 152, and the inner part 152 is accommodated in the inner part of the outer part 151. In the configuration shown, the inner part 152 is solid and has a right prism shape with a triangular base, and the vertices of the triangle are sharp, while the outer part 151 is hollow and has a shape of a right prism with a triangular base, and the vertices of the triangle are rounded. The outer part 151 and the inner part 152 can be connected together by any known means, in particular by press fit, by gluing, by clamping or by welding. The outer part 151 and the inner part 152 can be formed by a matrix made of a thermoplastic material containing particles with magnetic properties, that is, by particles with magnetic properties that will be subjected to a sintering process, a 3D printing process or PIM (powder injection molding). In particular, one possible configuration may include using a thermoplastic matrix containing particles based on ferrite or rare earth elements to form the outer part 151 of the permanent magnet 15, and the inner part 152 is formed by sintering the ferrite or rare earth particles. Another possible configuration will include using a thermoplastic matrix containing ferrite or rare earth particles to form the inner part 152 of the permanent magnet 15, and the outer part 151 is formed by sintering the ferrite or rare earth particles. Another possible configuration will include using a thermoplastic matrix containing ferrite or rare earth particles to form the inner part 152 and the outer part 151. In these three possible configurations, the thermoplastic matrix of each of the outer part 151 and the inner part 152 can be made of polyamide 6 (PA6) type, polyamide 6-6 (PA6-6) type, polyamide 12 (PA12) type, aromatic type or any other type of thermoplastic material or made of polyphenylene sulfide (PPS).

[0055] like Figure 5c As shown, 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 complete configuration of the permanent magnet 15 (see Figure 5a). These ribs 153 form an intermediate space 154 between the outer part 151 and the inner part 152, which extends parallel to the longitudinal direction defined by the permanent magnet 15. Each intermediate space 154 is delimited by the inner peripheral surface 151a of the outer part 151 and the outer peripheral surface 152a of the inner part 152, respectively. As described in the following paragraphs, these intermediate spaces 154 are configured to form fluid circulation channels inside the permanent magnet 15. Therefore, these fluid circulation channels 154 will allow the cooling fluid to flow through the permanent magnet 15, which will ultimately allow the heat generated in the rotor 10 to be discharged during the operation of the rotor 10. The rib 153 can have any possible shape. In addition, in other variations of the present invention (not shown), it can be considered to form a rib 153 at the level of the outer peripheral surface 152a of the inner part 152 of the permanent magnet 15, and the rib 153 is in contact with the inner peripheral surface 151a of the outer part 151.

[0056] Reference Figure 6 , showing a Figure 1 The electric motor 30 is an electric motor 30 having a rotor 10. In particular, the electric motor 30 comprises a housing formed in two parts, which houses the rotor 10 and an annular stator 36 surrounding the rotor 10 coaxially with the shaft 12. In particular, the housing comprises a front support 32 and a rear support 34 connected to each other, for example by means of fastening screws 31. The supports 32, 34 have a hollow shape and each carry a ball bearing 33 and 35, respectively, at the center for rotatably mounting the shaft 12. Advantageously, the front support 32 and the rear support 34 will be made of metal. The winding package 37 protrudes axially on both sides of the stator body 36 and is accommodated in the intermediate space separating the stator 36 from the respective supports 32, 34.

[0057] As previously mentioned, the lamination stack 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 is open at one of its ends at the level of the front lateral face 143 of the lamination stack 14, and at the other of its ends at the level of the rear lateral face 144 of the lamination stack 14. Each of the front lateral faces 143 and the rear lateral faces 144 faces and is directly adjacent to the inner faces 173, 193 of the front flange 17 and the rear flange 19, respectively.

[0058] The outer surface 171 and the inner surface 173 of the front flange 17 are respectively Fig.11 and Fig.12 As shown in FIG. 1 , the outer surface 191 and the inner surface 193 of the rear flange 19 are respectively Fig.13 and Fig.14 Shown in.

[0059] The front flange 17 is substantially disc-shaped. The inner face 173 of the front flange 17 is in contact with the front lateral face 143 of the lamination stack 14. The inner face 173 is provided with a series of twelve elongated grooves 175 extending radially from a recessed central region 172 of the front flange 17 up to the middle region of said flange, the twelve grooves 175 being offset at an angle of 30° relative to one another. Thus, the outer face 171 of the front flange 17 has a series of twelve protrusions 178 matching the recessed shape of the underlying grooves 175. Furthermore, cavities 176 of circular cross section are provided at the level of the outer face 171, each of said cavities 176 being capable of accommodating the head of a screw 21 for connecting the front flange 17 to the rear flange 19. Thus, holes 177 are formed through the front flange 17 to enable the passage of the screws 21.

[0060] In particular, each of the radial grooves 175 of the front flange 17 is formed by an orthogonal section 175a, which is extended at each of its ends by two inclined sections 175b1 and 175b2 that are angled with the orthogonal section 175a, and the inclined sections 175b1 and 175b2 are combined at the level of the proximal end 175c adjacent to the central area 172. Therefore, in a plane perpendicular to the axis X, the radial groove 175 has an overall shape that is substantially the same as the permanent magnet 15. The radial groove 175 leads to the recessed central area 172 of the front flange 17 at the level of its proximal end 175c, and the recessed central area 172 is in fluid communication with the hole 125 of the shaft 12 (see detailed description later). In the installed position of the front flange 17 (such as Figure 6 As shown in the figure, each radial groove 175 is axially aligned with one of the permanent magnets 15 so as to be fluidically connected to the longitudinal fluid circulation channel 154 of the permanent magnet 15.

[0061] Similarly, the rear flange 19 is substantially disc-shaped. The inner face 193 of the rear flange 19 is in contact with the rear lateral face 144 of the lamination stack 14. The inner face 193 is provided with a series of twelve elongated grooves 195 extending radially from the recessed central region 192 of the rear flange 19 up to the middle region of said flange, the twelve grooves 195 being offset at an angle of 30° relative to each other. Thus, the outer face 191 of the rear flange 19 has a series of twelve protrusions 198 matching the shape of the recess of the underlying groove 195. Furthermore, at the level of the outer face 191, a cavity 196 with a hexagonal cross section is provided, each of said cavities 196 being capable of accommodating a nut of a screw 21 for connecting the front flange 17 to the rear flange 19. Thus, a hole 197 is formed through the rear flange 19 to enable the passage of the screw 21.

[0062] In particular, each of the radial grooves 195 of the rear flange 19 is formed by an orthogonal section 195a, which is extended at each of its ends by two inclined sections 195b1 and 195b2 at an angle to the orthogonal section 195a, which are joined at the level of the proximal end 195c adjacent to the central area 192. Therefore, in a plane perpendicular to the axis X, the radial groove 195 has a general shape that is substantially the same as the permanent magnet 15. The radial groove 195 directly opens into the recessed central area 192 of the rear flange 19 at the level of its proximal end 195c, the recessed central area 192 being in fluid communication with the hole 127 of the shaft 12 (see detailed description later). In the installed position of the rear flange 19 (at Figure 6 As shown in FIG. 1 , each radial groove 195 is axially aligned with one of the permanent magnets 15 so as to be fluidically connected to the longitudinal fluid circulation channel 154 of the permanent magnet 15 .

[0063] 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 therefore referred to as front connection channels and the radial grooves 195 as rear connection channels.

[0064] like Figure 2 As shown, the front connection channel 175 of the front flange 17 is in fluid communication with the radial holes 125 formed through the front end portion 121 of the shaft 12 via the central region 172, and the rear connection channel 195 of the rear flange 19 is in fluid communication with the radial holes 127 formed through the rear end portion 123 of the shaft 12 via the central region 192. Thus, fluid communication between the radial holes 125 of the shaft 12 and the longitudinal channels 154 of the permanent magnets 15 is achieved, in turn, via the central region 172 and the radial grooves 175 of the front flange 17. Similarly, fluid communication between the radial holes 127 of the shaft 12 and the longitudinal channels 154 of the permanent magnets 15 is achieved, in turn, via the central region 192 and the radial grooves 195 formed at the level of the inner face 193 of the rear flange 19.

[0065] Figure 1 The circulation of the cooling fluid inside the rotor 10 will depend on the internal geometry of the shaft 12 .

[0066] Therefore, in Figure 2 In the particular configuration shown in FIG. 1 , the rotor 10 is provided with a shaft 12 which is Figures 7 to 9In this particular configuration, the shaft 12 specifically includes a body 120 formed by a front end portion 121 and a rear end portion 123, the front end portion and the rear end portion being separated by a central portion 122 (the central portion 122 is Figure 7 The body 120 is provided with a blind hole 128 aligned according to the axis X of the shaft 12. The blind hole 128 comprises two consecutive sections with different inner diameters, namely a first section 128a with an inner diameter D1 and a second section 128b with an inner diameter D2. The insert 13 made of plastic material is housed inside the blind hole 128 at the level of the first section 128a. Fig. 9 As shown, the insert 13 is formed by a tubular portion 131, the inner diameter Di of the tubular portion 131 being substantially equal to the inner diameter D2, and an annular portion 132 extending radially around one of the ends of the tubular portion 131, the outer diameter of the annular portion 132 being substantially equal to the inner diameter D1. Four fins 133 extend radially from the outer periphery of the tubular portion 131, the fins 133 being perpendicular to each other. The length of each of the fins 133 is such that its free end is tangential to the outer peripheral edge of the annular portion 132. When the insert 13 is fastened in the body 120, its tubular portion 131 is aligned with the second section 128b of the blind hole 128, and its annular portion 132 is positioned at the level of the junction between the first section 128a and the second section 128b of the blind hole 128. Thus constructed, the shaft 12 has a first channel 124, the so-called inlet channel, through which a cooling fluid for cooling the rotor 10 can be conveyed, and at least one second channel 126, the so-called outlet channel, through which the cooling fluid can flow out after having stored the heat originating from the permanent magnets 15 and the lamination stack 14. The inlet channel 124 is formed by the tubular portion 131 of the insert 13 and 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. Therefore, the outlet channel 126 is defined by the inner wall of the first section 128a of the blind hole 128 and the tubular portion 131 and the annular portion 132 of the insert 13. The outlet channel 126 is divided into four outlet channel sections 126a, 126b, 126c and 126d, respectively, and two directly adjacent sections are separated by the fin 133. Furthermore, the shaft 12 is provided with four holes 125 oriented radially with respect to the axis X of the shaft 12, said holes 125 being formed inside the front end portion 121 so as to open on one side to one of the sections 126a to 126d of the outlet channel 126 and on the other side to a central area 172 of the front flange 17 communicating with the front connecting channel 175, as shown in FIG. Figure 2 Similarly, four holes 127 (eg, Figure 7), so that the hole 127 opens into the inlet channel 124 on one side and into the central region 192 of the rear flange 19 which communicates with the rear connecting channel 195 on the other side.

[0067] So constructed, the rotor 10 can be cooled by a cooling fluid, such as oil, which flows successively through the inlet channel 124 in the rotor, then flows through the rear connecting channel 195 between the rear flange 19 and the rear lateral surface 144 of the lamination stack 14, then flows through the longitudinal channel 154 inside the permanent magnet 15, then flows through the front connecting channel 175 between the front flange 17 and the front lateral surface 143 of the lamination stack 14, and finally flows through the outlet channel sections 126a to 126d.

[0068] Reference Fig.10 , shows a variant of a shaft 12 that can be equipped with a rotor according to the invention. In particular, the shaft 12 comprises a hollow front end portion 121 and a hollow rear end portion 123, the rear end portion 123 being separated from the front end portion 121 by a solid central portion 122 (the central portion 122 is Fig.10 124a and 125b). The front end portion 121 is traversed by a cylindrical central cavity 124 having a front end 124a opening to the outside and a closed rear end 124b. Close to the rear end 124b, a series of four holes 125 radially oriented relative to the axis X of the shaft 12 is formed, the holes 125 being offset by 90° relative to each other. Each of the holes 125 has an end 125a radially away from the central cavity 124 and opening to the outside. Thus, the front end portion 121 is configured so that a cooling fluid flow can enter at the level of the front end 124a of the central cavity 124 and then circulate through the central cavity 124 until it reaches the radial holes 125 and then circulate 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 having a rear end 126a opening to the outside and a closed front end 126b. Close to the front end 126b, a series of four holes 127 are formed, radially oriented relative to the axis X of the shaft 12, said holes 127 being offset by 90° relative to each other. Each of the holes 127 has an end 127a radially away from the central cavity 126 and opening to the outside. Thus, the rear end portion 123 is configured so that a cooling fluid flow can enter at the level of the ends 127a of the radial holes 127, then circulate through the radial holes 127 until reaching the central cavity 126, and then circulate through the central cavity 126 until reaching the rear end 126a of the central cavity 126.

[0069] In the following description, and by convention, the central cavity 124 will therefore be a so-called cooling fluid inlet passage, and the central cavity 126 will be a so-called cooling fluid outlet passage.

[0070] By Figure 1 The rotor 10 is equipped with Fig.10 Axis 12 instead of Figure 7 The shaft 12 of the rotor 10 can thus modify the path followed by the cooling fluid within the rotor 10. In particular, the cooling fluid can flow sequentially through the inlet channel 124 in the rotor 10, then flow through the front connecting channel 175 between the front flange 17 and the front lateral face 143 of the lamination stack 14, then flow through the longitudinal fluid circulation channel 154 inside the permanent magnet 15, then flow through the rear connecting channel 195 between the rear lateral face 144 of the lamination stack 14 and the rear flange 19, and finally flow through the outlet channel 126 of the shaft 12.

[0071] Of course, the present invention is not limited to the above-described embodiments. In particular, in other embodiments of the present invention (not shown), the number of the internal cavity 141, the permanent magnet 15, the front connecting channel 175 and the rear connecting channel 195 may not be twelve, and the number of the radial holes 125, 127 may not be four.

[0072] A possible configuration of the invention may therefore consist of a rotor comprising two or any multiple of two internal cavities 141 arranged symmetrically with respect to the axis X of the shaft 12 .

[0073] In another possible configuration of the invention, the rotor may comprise three (or another odd number) internal cavities 141 , which are evenly distributed around the axis X so as not to cause any imbalance to the rotor.

[0074] Preferably, the number of permanent magnets 15 and the number of front connecting channels 175 and the number of rear connecting channels 195 will be selected to be equal to the number of internal cavities 141 .

[0075] In another possible configuration of the present invention, Figure 1 The rotor 10 may include an insert 13 without the splitter fins 133. Thus, the outlet channel 126 will not be divided into outlet channel segments 126a to 126d, but will consist of a single peripheral cavity coaxially aligned with the central cavity 124 formed by the tubular portion 131 of the insert 13.

Claims

1. A rotor (10) for an electric motor (30), the rotor (10) comprising: - a rotor shaft (12) mounted rotatably about an axis (X); - a lamination stack (14) coaxially mounted on the rotor shaft (12), the lamination stack (14) comprising an inner cavity (141) symmetrical relative to the axis (X) of the shaft (12) and relative to each other, and the inner cavity (141) axially passes through the entire lamination stack (14) so ​​that the inner cavity (141) is open at one of the ends of the inner cavity at the level of the front lateral face (143) of the lamination stack (14) and is open at the other end of the end of the inner cavity at the level of the rear lateral face (144) of the lamination stack (14); - a plurality of permanent magnets (15) housed in the inner cavity (141) of the lamination stack (14); a front flange (17) and a rear flange (19) which are coaxially mounted on the rotor shaft (12) and are axially arranged on both sides of the lamination stack (14) so ​​as to abut against the front lateral face (143) and the rear lateral face (144) of the lamination stack (14), respectively; wherein the shaft (12) is provided with at least one first internal channel (124) for circulation of a cooling fluid, a so-called inlet channel, and at least one second internal channel (126) for circulation of a cooling fluid, a so-called outlet channel, and wherein the front flange (17) or the rear flange (19) is respectively configured to form at least one front connecting channel (175) or at least one rear connecting channel (195) with the corresponding front lateral surface (143) or the rear lateral surface (144) of the lamination stack (14), wherein the cooling fluid can flow in the at least one front connecting channel (175) or the at least one rear connecting channel (195), and wherein the at least one front connecting channel (175) or the at least one rear connecting channel (195) is respectively in fluid communication with one of the inlet channel (124) and the outlet channel (126), and Each permanent magnet (15) is provided with at least one longitudinal fluid circulation channel (154), the at least one longitudinal fluid circulation channel (154) leading to the at least one front connecting channel (175) on one side and leading to the at least one rear connecting channel (195) on the other side, the at least one longitudinal fluid circulation channel (154) being configured to enable circulation of a cooling fluid, It is characterized in that each permanent magnet (15) is formed by assembling at least two parts, the two parts are respectively at least one outer part (151) and at least one inner part (152), the at least one inner part (152) is accommodated inside the at least one outer part (151), and the at least one longitudinal fluid circulation channel (154) is correspondingly delimited by the inner peripheral surface (151a) of the at least one outer part (151) and the outer peripheral surface (152a) of the at least one inner part (152).

2. The rotor (10) according to claim 1, characterized in that The inner peripheral surface (151a) of the at least one outer portion (151) of at least one of the permanent magnets (15) is provided with a rib (153), and the rib (153) is in contact with the outer peripheral surface (152a) of the 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 the at least one inner portion (152) of at least one of the permanent magnets (15) is provided with ribs, and the ribs are in contact with the inner peripheral surface (151a) of the 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 the inner part (152) or the outer part (151) is formed by a matrix made of thermoplastic material containing particles having magnetic properties, and the other part is obtained by sintering, or by 3D printing or by a powder injection molding process of particles having magnetic properties.

5. The rotor (10) according to claim 4, characterized in that The particles having magnetic properties used to form the at least one inner portion and / or the at least one outer portion are made of a material selected from ferrites or rare earth elements.

6. The rotor (10) according to claim 4 or 5, characterized in that The matrix made of thermoplastic material is made of a material selected from the group consisting of polyamide 6 (PA6), polyamide 6-6 (PA6-6), nylon 12 (PA12) and polyphenylene sulfide (PPS).

7. The rotor (10) according to one of the preceding claims, characterized in that The at least one front connecting channel (175) is fluidically connected to the inlet channel (124), and the at least one rear connecting channel (195) is fluidically connected to the outlet channel (126), so that a cooling fluid intended for cooling the rotor can flow sequentially through the inlet channel (124) in the rotor, then flow through the at least one front connecting channel (175) between the front flange (17) and the front lateral surface (143) of the lamination stack (14), then flow through the longitudinal fluid circulation channel (154) inside the permanent magnet (15), then flow through the at least one rear connecting channel (195) between the rear lateral surface (144) of the lamination stack (14) and the rear flange (19), and finally flow through 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), the rear end portion (123) being separated from the front end portion (121) by a solid central portion (122), the front end portion (121) or the rear end portion (123) being respectively traversed by a cylindrical central cavity, the central cavity forming the respective inlet channel (124) or the outlet channel (126) of the shaft (12), and at least one hole (125, 127) oriented radially relative to the axis (X) of the shaft (12) is respectively formed inside the front end portion (121) or inside the rear end portion (123) so that the at least one hole leads to the inlet channel (124) or the outlet channel (126) on one side, and to the at least one front connecting channel (175) or the at least one rear connecting channel (195) on the other side.

9. The rotor (10) according to one of claims 1 to 6, characterized in that The at least one rear connecting channel (195) is fluidically connected to the inlet channel (124), and the at least one front connecting channel (175) is fluidically connected to the outlet channel (126), so that a cooling fluid intended for cooling the rotor can flow sequentially through the inlet channel (124) in the rotor, then flow through the at least one rear connecting channel (195) between the rear flange (19) and the rear lateral surface (144) of the lamination stack (14), then flow through the longitudinal fluid circulation channel (214) inside the permanent magnet (15), then flow through the at least one front connecting channel (175) between the front flange (17) and the front lateral surface (143), and finally flow through 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), the rear end portion (123) being separated from the front end portion (121) by a hollow central portion (122), the front end portion (121) and the central portion (122) being traversed by a cylindrical central cavity, the central cavity forming the inlet passage (124) of the shaft (12), the front end portion (121) being further traversed by at least one peripheral cavity coaxially aligned with the central cavity, the at least one peripheral cavity forming the shaft The outlet channel (126) of the shaft (12) is formed in the interior of the front end portion (121) or the interior of the central portion (122), and at least one hole (125, 127) radially oriented relative to the axis (X) of the shaft (12) is formed respectively, so that the at least one hole (125, 127) leads to the outlet channel (126) or the inlet channel (124) on one side, and leads to the at least one front connecting channel (175) or the at least one rear connecting channel (195) on the other side.

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

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

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

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

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

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