EP4158753A1

EP4158753A1 - Rotor for an electric motor provided with a cooling circuit

Info

Publication number: EP4158753A1
Application number: EP21733498.6A
Authority: EP
Inventors: Cédric LEDIEU
Original assignee: Novares France SAS
Current assignee: Novares France SAS
Priority date: 2020-05-29
Filing date: 2021-05-20
Publication date: 2023-04-05
Also published as: CN115699521A; US20230307973A1; WO2021240100A1; FR3111025A1; FR3111025B1

Abstract

A rotor (10) comprising channels (124, 126, 175, 195) for circulating a cooling fluid, a rotor shaft (12) which is mounted for rotation about an axis (X), and a lamination stack (14) which is mounted coaxially on the shaft (12). The lamination stack (14) comprises first internal cavities (141) and second internal cavities (142) which are symmetrical relative to the axis (X) of the shaft (12) and relative to each other. The two second internal cavities (142) extend axially through the whole of the lamination stack (14) so that they open, at the first end, into a front lateral face (143) of the lamination stack (14) and, at the other end, into a rear lateral face (144). The two second internal cavities (142) are configured to allow a cooling fluid to circulate inside the lamination stack (14). A plurality of permanent magnets (15) are received inside the first internal cavities (141). A front flange (17) and a rear flange (19) which are mounted coaxially on the shaft (32) are arranged on either side of the lamination stack (14) so as to be contiguous with the front and rear lateral faces (143, 144), respectively.

Description

ROTOR FOR ELECTRIC MOTOR EQUIPPED WITH A COOLING CIRCUIT

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

In general, current electric motors include a rotor integral with a shaft and a stator which surrounds the rotor. The stator is mounted in a housing which has bearings for the rotational mounting of the shaft. The rotor comprises a body formed by a stack of sheets or pole wheels (claw pole) held in the form of a package by means of a suitable fixing system. The rotor body has internal cavities housing permanent magnets. The stator comprises a body formed by a stack of sheets forming a ring, the inner face of which is provided with teeth delimiting in pairs a plurality of notches open towards the interior of the stator body and intended to receive phase windings. These phase windings pass through the notches of the stator body and form buns projecting on either side of the stator body. The phase windings can for example consist of a plurality of U-shaped conductor segments, the free ends of two adjacent segments being connected together by welding.

In the rotor, the pack of sheets is clamped axially between a front flange and a rear flange mounted coaxially with the shaft. Each flange has the overall shape of a disc extending in a radial plane perpendicular to the axis of the shaft. Each flange comprises a central orifice for coaxial mounting on the shaft and several through holes intended to receive fixing screws axially passing through the entire package of sheets, said screws being secured to the flanges by means of nuts. The front and rear flanges are generally formed from a non-magnetic material which conducts heat, for example a metal.

The housing generally has front and rear bearings assembled together. The bearings define an internal cavity in which the rotor and the stator are housed. Each of the bearings centrally carries a ball bearing for the rotational mounting of the rotor shaft.

During motor operation, the current flowing through the phase windings of the stator generates significant heat which must be removed. To cool the engine, there are currently several solutions. One of these solutions is to circulate oil through the rotor shaft and then circulate this oil along the stator body so that it is in contact with the chignons of the phase windings. However, such a solution requires the provision of numerous modifications to the structure of the engine, which makes it difficult to implement, and therefore relatively expensive. Another existing solution consists in providing a cooling circuit inside the bearing with which the stator is shrunk, a cooling fluid circulating inside the cooling circuit making it possible to evacuate the heat generated by the stator via the bearing. . However, this solution has the drawback of being relatively expensive and complex to implement due to the use of specific bearings incorporating an internal cooling circuit.

The invention therefore aims to provide a rotor and an electric motor comprising such a rotor arranged to allow better removal of the heat generated during its operation and which does not have the drawbacks of the existing solutions described above.

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

- a rotor shaft rotatably mounted about an axis;

a pack of sheets mounted coaxially on the rotor shaft, said pack of sheets comprising first internal cavities and at least two second internal cavities symmetrical with respect to the axis of the shaft and between them, said at least two second internal cavities axially crossing the entire package of sheets so that they open out, at one of their ends, at a front side face of said package of sheets and, at another of their ends, at the level of a rear lateral face of said pack of sheets, said at least two second internal cavities being configured to allow the circulation of a cooling fluid inside the pack of sheets;

- a plurality of permanent magnets housed inside the first internal cavities of the package of sheets;

a front flange and a rear flange mounted coaxially on the rotor shaft and arranged axially on either side of the pack of sheets so as to be contiguous respectively to the front and rear side faces of the pack of sheets; characterized in that the shaft is provided with at least a first internal channel for circulating a cooling fluid, called the inlet channel, and at least a second internal channel for circulating a cooling fluid , said outlet channel, and in that the front flange, respectively the rear flange, is configured to form with the front side face, respectively the rear side face, of the sheet bundle at least two front connecting channels, respectively at least of them rear connection channels, inside which can circulate a cooling fluid, each of said at least two front connection channels, respectively rear, being in fluid communication with one of said inlet and outlet channels and with the one of said at least two second internal cavities.

Thus configured, the rotor of the invention will make it possible to better evacuate the heat generated during its use, due to the passage of a cooling fluid in second internal cavities formed inside the pack of sheets. Furthermore, the fact of circulating the cooling fluid through the end flanges generates few changes in the general structure of the electric motor and, therefore, offers a relatively inexpensive solution to the problem of evacuation. of heat in electric motors.

The rotor of the invention may also include one or more of the following characteristics:

- Said at least two front connection channels are in fluid communication with said inlet channel and said at least two rear connection channels are in fluid communication with said outlet channel, such that a cooling fluid intended for cooling of the rotor can circulate in the rotor successively through the inlet channel, then between the front flange and the front side face of the sheet packet through said at least two front connecting channels, then inside the sheet metal pack through said at least two second internal cavities, then between the rear flange and the rear side face of the sheet bundle through said at least two rear connecting channels, 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 crossed by a central cavity of cylindrical shape, said central cavity forming the inlet channel, respectively the outlet channel, of the shaft, and at least two holes oriented radially with respect to the axis of the shaft are formed at the interior of the front end portion, respectively of the rear end portion, so as to open out on one side into the inlet channel, respectively the outlet channel, and on the other side into said au at least two front link channels, respectively said at least two rear link channels.

- Said at least two rear connection channels are in fluid communication with said inlet channel and said at least two front connection channels are in fluid communication with said outlet channel, such that a fluid of cooling 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 stack of sheets through said at least two rear connection channels, then inside of the sheet package through said at least two second internal cavities, then between the front flange and the front side face through said at least two front connecting channels, and finally through the outlet 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 crossed by a central cavity of cylindrical shape, said central cavity forming the inlet channel of the shaft, the front end portion also being crossed by at least one peripheral cavity aligned coaxially with the central cavity, said at least one peripheral cavity forming the channel of outlet of the shaft, and at least two holes oriented radially with respect to the axis of the shaft are formed inside the front end portion, respectively of the central portion, so as to open out from a side in the output channel, respectively the input channel, and on the other side in said at least two front connection channels, respectively said at least two rear connection channels.

- the shaft comprises a main body provided with a blind hole aligned along 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 is housed within the blind hole at 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 which is substantially equal to the second internal diameter, and an annular portion extending radially around one end 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 outer diameter which is substantially equal to the first inner diameter, the inlet channel of the shaft being jointly defined by the tubular portion ire of the insert and by 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 by the tubular and annular parts of the insert.

- the insert comprises one or more separation fins extending radially from the outer periphery of the tubular part, each of the fins of separation being configured to separate the output channel into two or more output channel segments.

- Each of the front and rear flanges has an internal face in contact with a lateral face of the pack of sheets, said internal face being provided with at least two oblong-shaped grooves extending radially from a recessed central zone of said flange, at the level of which said grooves are in fluid communication with the inlet or outlet channel of the shaft, up to an intermediate zone of said flange facing one of said at least two second internal cavities of the stack of sheets.

- each of said radial grooves faces a radial hole formed through the shaft, said radial hole opening out on one side into the inlet or outlet channel of the shaft and on the other side into the peripheral wall of the tree.

- each of the front and rear flanges is provided on its internal face with a circular groove intended to house an annular-shaped seal, said seal being intended to ensure the seal between the flange and the pack of sheets .

- The front flange, respectively the rear flange, is configured to form with the front side face, respectively the rear side face, of the sheet package several groups of front connection channels, respectively several groups of rear connection channels, each of the groups comprising at least two front connection channels, respectively at least two rear connection channels, inside which can circulate a cooling fluid, each of said at least two front connection channels, respectively rear, being in fluid communication with the one of said inlet and outlet channels and with one of said at least two second internal cavities.

- the front flange, respectively the rear flange, is configured to form with the front side face, respectively the rear side face, of the sheet package several front intermediate channels, respectively several rear intermediate channels, inside which can circulate a fluid cooling, each of the front intermediate channels, respectively rear, being aligned axially with a radial segment of the packet of sheets separating two second adjacent internal cavities, each of said front intermediate channels, respectively rear, being in fluid communication with one of said channels d 'inlet and outlet and with a through hole formed through the sheet metal pack, said through hole potentially accommodating a fixing screw for securing the front and rear flanges to the sheet metal pack. The invention also relates to an electric motor comprising a rotor as defined above.

The invention will be better understood on reading the non-limiting description which follows, given with reference to the appended figures.

Figure 1 is a cutaway perspective view of a rotor according to a first embodiment of the invention,

Figure 2 is a longitudinal sectional view of the rotor according to Figure 1, Figure 3 is a rear axial view of the rotor according to Figure 1, the rear flange having been removed,

Figure 4 is a perspective view of the shaft used in the rotor of Figure 1,

Figure 5 is a longitudinal sectional view of the shaft of Figure 4,

Figure 6 is a perspective view of the outer face of the front flange used in the rotor of Figure 1,

Figure 7 is a perspective view of the internal face of the flange of Figure 6,

Figure 8 is a longitudinal sectional view of a rotor according to a second embodiment of the invention,

Figure 9 is a longitudinal sectional view of an electric motor incorporating the rotor of Figure 8,

Figure 10 is a perspective view of the shaft used in the rotor of Figure 8,

Figure 11 is a longitudinal sectional view of the shaft of Figure 10, Figure 12 is a front axial view of the shaft of Figure 10,

Figure 13 is a perspective view of the insert used in the shaft of Figure 10,

Figure 14 is a cutaway perspective view of a rotor according to a third embodiment of the invention,

Figure 15 is a rear axial view of the rotor according to Figure 14, the rear flange having been removed,

Figure 16 is a perspective view of the outer face of the front flange used in the rotor of Figure 14,

Figure 17 is a perspective view of the internal face of the front flange of Figure 16.

Throughout the description and in the claims, the terms “axial” and “radial” and their derivatives are defined with respect to the axis of rotation of the. rotor. Thus, an axial orientation refers to an orientation parallel to the axis of rotation of the rotor and a radial orientation refers to an orientation perpendicular to the axis of rotation of the rotor. Also, by convention, the terms "front" and "rear" refer to separate positions along the axis of rotation of the rotor. In particular, the "front" end of the rotor shaft corresponds to the end of the shaft on which can be fixed a pulley, a pinion, a spline intended (e) to transmit the rotational movement. rotor to any other similar device for transmitting movements.

FIGS. 1 to 3 represent a rotor 10 according to a first embodiment of the invention. The rotor 10 comprises a substantially cylindrical body formed by a pack of sheets 14 made of a ferromagnetic material, in particular steel, said body being integral in rotation with a shaft 12 mounted to rotate about an axis X. The rotor 10 comprises in besides a plurality of permanent magnets 15 intended to be housed in a plurality of first internal cavities 141 formed inside the bundle of sheets 14 and disposed obliquely to each other, each of the first internal cavities 141 accommodating a single permanent magnet 15 The magnets 15 could be made of rare earth, for example. In the embodiment shown, the magnets 15 have the shape of a parallelepiped with rectangular section and are aligned in two planes perpendicular to the X axis of the shaft 12, each of said planes respectively forming a front side face 143 and a side face rear 144 of the sheet metal package 14. The magnets 15 are distributed uniformly around the X axis and are arranged to form a star pattern with several branches. The pack of sheets 14 is mounted coaxially on the shaft 12. The shaft 12 can be force-fitted inside a central opening of the pack of sheets 14 so as to rotate the body of the rotor with the. tree 12.

The sheet metal pack 14 is formed by an axial stack of sheets which extend in a radial plane perpendicular to the X axis of the shaft 12. A plurality of fixing holes 11 are made in the sheet metal pack 14 for allow the passage of fixing screws (not shown) of the sheets of the package. These fixing holes 11 are through so that it is possible to pass a screw inside each hole 11. A first end of the screws bears against the outer face of a front end flange 17, while the other end of the screws projects from the outer face of a rear end flange 19 and is threaded so as to receive a nut which, once screwed on, exerts pressure against said outer face. Thus, the packet of sheets 14 is clamped axially between the front end flange 17 and the rear end flange 19. These flanges 17, 19 may advantageously allow to ensure a balancing of the rotor 10 while allowing a good maintenance of the magnets 15 inside the first internal cavities 141. The balancing of these flanges can be carried out by adding or removing material. The material removal can be carried out by machining, while the addition of material can be carried out by implanting elements in openings provided for this purpose and distributed along the circumference of the flange 17, 19.

As illustrated in FIG. 3, the pack of sheets 14 furthermore comprises a plurality of second internal cavities 142 extending in a radial direction with respect to the X axis and are axially traversing. These second internal cavities 142 are configured to allow the circulation of a cooling fluid inside the pack of sheets. In the embodiment shown, these second internal cavities 142 are four in number, namely the cavities 142a, 142b, 142c and 142d. The cavities 142a-142d each have a section in the form of a ring portion and are distributed uniformly around the X axis. Two directly adjacent cavities 142a-142d are separated by a radial segment 18 of the sheet bundle 14 so that a central annular part of the body of the rotor consists of an alternation of second internal cavities 142a-142d and of radial segments 18. As shown in FIG. 2, each cavity 142a-142d opens, at one of its ends, to the level with the front side face 143 of said sheet metal pack 14, and, at another of its ends, at the rear side face 144 of said sheet metal pack 14. Each of the front and rear side faces 143, 144 faces and is directly adjacent to an internal face 173, 193 of the front and rear flanges 17, 19 respectively.

Referring to Figures 4 and 5, there is shown the shaft 12 fitted to the rotor of Figure 1. This shaft 12 comprises in particular a hollow front end portion 121 and a hollow rear end portion 123 separate from the hollow portion. 'front end 121 by a solid central portion 122 (the central portion 122 is delimited by dotted lines in FIG. 5). The front end portion 121 is crossed by a central cavity 124 of cylindrical shape, said cavity having a front end 124a open towards the outside and a rear end 124b closed. 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 arranged at right angles to 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, then through the radial holes 125 until it reaches the ends 125a of the holes 125. Symmetrically, the rear end portion 123 is crossed by a central cavity 126 of cylindrical shape, said cavity having a rear end 126a open to the outside and a front end 126b closed. 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 arranged at right angles to 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 level of the ends 127a of the radial holes 127, then the circulation of said cooling fluid through the radial holes 127 until it is reached. the central cavity 126, then through the central cavity 126 until reaching the rear end 126a of the central cavity 126.

In the remainder of the description, and by convention, the central cavity 124 will thus be called the inlet channel for the cooling fluid and the central cavity 126 will be called the outlet channel for the cooling fluid.

Referring to Figures 6 and 7, there is shown the front flange 17 fitted to the rotor 10 of Figure 1. The rear flange 19 having an identical structure to the front flange 17, the technical details given below will apply in a similar manner. to the rear flange 19. The front flange 17 is substantially in the form of a disc comprising in particular an outer face 171 and an inner face 173. The inner face 173 is in contact with the front lateral face 143 of the pack of sheets 14 ( on the other hand, the internal face 193 of the rear flange 19 is in contact with the rear lateral face 144 of the pack of sheets 14). The internal face 173 is provided with a series of four grooves 175 of oblong shape extending radially from a recessed central zone 172 of said flange to an intermediate zone of said flange, the four grooves 175 being arranged at right angles to each other. compared to others. The outer face 171 therefore has a protuberance 178 matching the hollow shape of the underlying grooves 175. Cavities 176 with a hexagonal section are also provided at the level of the outer face 171, each of said cavities 176 being able to house the head of a screw intended to connect the front and rear flanges 17, 19. A bore 177 is of this fact formed through the front flange 17 to allow passage of the threaded rod of said screw.

As illustrated in Figure 7, each of the grooves 175 has a distal end 175a and a proximal end 175b. In the mounted position of the front flange 17 shown in FIG. 1, the proximal end 175b opens onto the central zone 172 towards which also the ends 125a of the radial holes 125 of the shaft 12 open and the distal end 175a faces one of the second internal cavities 142a-142d of the sheet metal package 14. Thus, fluid communication takes place between the radial holes 125 of the shaft 12 and the second internal cavities 142a-142d via the grooves 175 of the front flange 17. In a similar manner , fluid communication takes place between the radial holes 127 of the shaft 12 and the second internal cavities 142a-142d via radial grooves 195 formed at the level of the internal face 193 of the rear flange 19.

In the remainder of the description, and by convention, the grooves 175 will thus be called the front connection channels and the grooves 195 will be called the rear connection channels.

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 front flange 17 and the face. front side 143 of the sheet metal pack 14 through the front connecting channels 175, then inside the sheet metal pack 14 through the second internal cavities 142a-142d, then between the rear flange 19 and the rear side face 144 of the packet of sheets 14 through the rear connection channels 195, and finally through the outlet channel 126.

As shown in Figures 1 and 7, each of the front and rear flanges 17, 19 is advantageously provided on its internal face 173, 193 with a circular groove 174 intended to accommodate a seal 16 of annular shape, said seal d the seal 16 being intended to ensure the seal between the front or rear flange 17, 19 and the sheet metal pack 14. For this purpose, the circular groove 174 will be radially further from the central zone 172 than the distal ends 175a of the grooves 175.

FIG. 8 represents a rotor 10 according to a second embodiment of the invention. This second embodiment differs from the first embodiment described above by the shaft 12 used, which induces a cooling circuit which is also different.

In particular, as shown in Figures 10 to 12, the shaft 12 comprises a main body 120, formed of a front end portion 121 and a rear end portion 123, said end portions being separated. by a central portion 122 (the central portion 122 is delimited by dotted lines in FIG. 11). The main body 120 is provided with a blind hole 128 aligned along the X axis of the shaft 12. This blind hole 128 comprises two contiguous sections of diameters different internal ones, namely a first section 128a having an internal diameter DI and a second section 128b having an internal diameter D2. A plastic insert 13 is housed within the blind hole 128 at the first section 128a. As shown in Figure 13, this insert 13 is formed of a tubular portion 131, having an internal diameter Di substantially equal to the internal diameter D2, and an annular portion 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 Dl. Four fins 133 extend radially from the outer 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 portion 132. When the insert 13 is fixed in the main body 120, its tubular portion 131 is aligned with the second section 128b of the hole. blind 128 and its annular portion 132 is positioned at the level of 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 input channel, by which can be conveyed a cooling fluid intended to cool the rotor 10, and at least a second channel 126, said outlet channel, through which the cooling fluid can exit after having stored the heat coming from the magnets 15 and from the pack of sheets 14. The inlet channel 124 is formed jointly by the tubular part 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 part 131 of the insert 13. The outlet channel 126 is thus delimited by the internal wall of the first section 128a of the blind hole 128 and by the tubular and annular parts 131, 132 of the insert 13. This channel outlet 126 is respectively divided into four outlet 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 out, on one side, into one of the outlet channel segments 126a-126d and, on the other side, in one of the front link channels 175, as shown in FIG. 8. Similarly, four holes 127 oriented radially with respect to the X axis of the shaft 12 are formed at the interior of the central portion 122 so as to open out, on one side, into the inlet channel 124 and, on the other side, in one of the rear link channels 195.

Thus configured, the rotor 10 can be cooled by a cooling fluid, such as oil for example, said circulating cooling fluid. 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 sheet metal pack 14 at the through second internal cavities 142a-142d, 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.

Referring to Figure 9, there is shown an electric motor 30 equipped with the rotor 10 of Figure 8. This electric motor 30 comprises in particular a two-part housing housing the rotor 10 and an annular stator 36 which surrounds the rotor 10 so coaxial with the shaft 12. The housing comprises in particular a front bearing 32 and a rear bearing 34 connected to each other by means of fixing screws 31. The bearings 32, 34 are of hollow shape and each centrally carry a ball bearings, 33 and 35 respectively, for mounting the shaft 12 in rotation. Chignons 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, 34. The front and rear bearings 32, 34 will advantageously be made of metal.

FIG. 14 represents a rotor 10 according to a third embodiment of the invention. This third embodiment differs from the second embodiment by the front and rear flanges used.

In particular, as illustrated in Figures 16 and 17, there is shown the front flange 17 fitted to the rotor 10 of Figure 14. The rear flange 19 having a structure identical to the front flange 17, the technical details given below s' will apply in a similar manner to the rear flange 19. The front flange 17 is substantially in the form of a disc comprising in particular an outer face 171 and an inner face 173. The inner face 173 is in contact with the front side face 143 of the package. of sheets 14 (the internal face 193 of the rear flange 19 is on the other hand in contact with the rear lateral face 144 of the pack of sheets 14). Cavities 176 with a hexagonal section are formed at the level of the external face 171, each of said cavities 176 being able to house the head of a screw intended to connect the front and rear flanges 17, 19. In another variant embodiment, these cavities 176 can be omitted. Hexagonal section cavities may also be formed on the rear flange 19 at its outer face, each of said cavities being able to accommodate a nut intended to cooperate with one of the screws for fixing the front and rear flanges 17, 19 on the packet of sheets 14. Bores 177 are also formed through the front flange 17 to allow the passage of the threaded rods of the screws. In the mounted position of the flanges 17 and 19, these bores 17 are configured to face fixing holes 11a of the sheet metal pack 14. These fixing holes 11a are through so that it is possible to pass inside each hole 11a a screw. As illustrated in FIG. 15, the pack of sheets 14 is also provided with several other through holes 11b which are not intended to accommodate a fixing screw. The internal face 173 of the front flange 14 is further provided with a series of twelve grooves 175 of oblong shape extending radially from a recessed central zone 172 of said flange to an intermediate zone of said flange, the twelve grooves 175 being arranged according to four groups of three grooves 175, each group being separated by an intermediate groove 181 of oblong shape, said intermediate groove 181 extending radially from the central zone 172 to a distal end 181a. The outer face 171 therefore has a protuberance 178 matching the hollow shape of the underlying grooves 175 and 181.

As illustrated in FIG. 15, the sheet pack 14 comprises a plurality of second internal cavities 142 extending in a radial direction with respect to the X axis and are axially traversing. These second internal cavities 142 are configured to allow the circulation of a cooling fluid inside the pack of sheets. In the embodiment shown, these second internal cavities 142 are four in number, namely the cavities 142a, 142b, 142c and 142d. The cavities 142a-142d each have a section in the form of a ring portion and are distributed uniformly around the X axis. Two directly adjacent cavities 142a-142d are separated by a radial segment 18 of the sheet bundle 14 so that a central annular part of the body of the rotor consists of an alternation of second internal cavities 142a-142d and of radial segments 18. Each cavity 142a-142d opens out, at one of its ends, at the level of the front lateral face 143 of said sheet metal pack 14, and, at another of its ends, at the level of the rear side face 144 of said sheet metal pack 14. Each of the front and rear side faces 143, 144 faces and is directly adjacent to an internal face 173 , 193 of the front and rear flanges 17, 19 respectively.

As illustrated in Figure 17, each of the grooves 175 has a distal end 175a and a proximal end 175b. In the mounted position of the front flange 17 shown in FIG. 14, the proximal end 175b opens onto the central zone 172 towards which also the ends 125a of the radial holes 125 of the shaft 12 open and the distal end 175a faces one of the second internal cavities 142a-142d of the sheet metal pack 14. Thus, fluid communication takes place between the radial holes 125 of the shaft 12 and the second internal cavities 142a-142d via the grooves 175 of the front flange 17. Similarly, fluid communication takes place between the radial holes 127 of the shaft 12 and the second internal cavities 142a-142d by means of corresponding radial grooves formed at the level of the internal face 193 of the rear flange 19.

Furthermore, and as illustrated in Figures 15 and 17, each of the intermediate grooves 181 has a distal end 181a and a proximal end 181b. In the mounted position of the front flange 17 shown in FIG. 14, the distal 181a and proximal 181b ends are aligned with the radial segments 18 of the packet of sheets 14, the proximal end 181b opening onto the central zone 172 towards which also the end 125a of the radial holes 125 of the shaft 12 and the distal end 181a facing one of the through holes 11b of the bundle of sheets 14. Thus, fluid communication takes place between the radial holes 125 of the shaft 12 and the through holes 11b via the intermediate grooves 181 of the front flange 17. Similarly, fluid communication takes place between the radial holes 127 of the shaft 12 and the through holes 11b via the intermediate grooves 181 corresponding formed at the level of the internal face 193 of the rear flange 19. By convention, the intermediate grooves 181 formed in the front flange 17 are called "av intermediate channels. ant ”and the intermediate grooves 181 formed in the rear flange 19 are called“ rear intermediate channels ”.

Thus, in this third embodiment, the cooling fluid will be able to circulate inside the package of sheets 14 not only through the internal cavities 142a-142d, but also through the through holes 11b, thus improving the evacuation of heat in the rotor compared to the first and second embodiments.

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 second internal cavities 142, of radial holes 125, 127, of through holes 11b and of intermediate grooves 181 may differ from four, and the number of number of front and rear link channels 175, 195 may differ from four or twelve.

Thus, a possible configuration of the invention could consist of a rotor comprising only two second internal cavities 142 arranged symmetrically with respect to the X axis of the shaft 12.

In another possible configuration of the invention, the rotor could include three (or another odd number) second internal cavities 142, said second internal cavities 142 being distributed evenly around the X axis. so as not to create an imbalance for the rotor. In particular, the respective centers of gravity of the second internal cavities 142 may form an equilateral triangle in a plane perpendicular to the X axis and the center of gravity of this equilateral triangle will be aligned with the X axis. In another possible configuration of In accordance with the invention, the rotor 10 of FIG. 8 could include an insert 13 without separation fins 133. Therefore, the outlet channel 126 would not be divided into outlet 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. Rotor (10) for electric motor (30) comprising:

- a rotor shaft (12) mounted to rotate about an axis (X);

- a pack of sheets (14) mounted coaxially on the rotor shaft (12), said pack of sheets (14) comprising first internal cavities (141) and at least two second internal cavities (142) symmetrical with respect to the axis (X) of the shaft (12) and between them, said at least two second internal cavities (142) axially passing through the entire package of sheets (14) so that they open out, at one of their ends, at a front side face (143) of said sheet metal pack (14) and, at another of their ends, at a rear side face (144) of said sheet metal pack (14), said at least two second internal cavities (142) being configured to allow the circulation of a cooling fluid within the package of sheets (14);

- a plurality of permanent magnets (15) housed inside the first internal cavities (141) of the stack of sheets (14);

- a front flange (17) and a rear flange (19) mounted coaxially on the rotor shaft (32) and arranged axially on either side of the pack of sheets (14) so as to be contiguous respectively to the faces front and rear sides (143, 144) of the sheet metal pack (14); characterized in that the shaft (12) is provided with at least a first internal channel (124) for circulating a cooling fluid, said inlet channel, and at least a second internal channel (126) circulation of a cooling fluid, said outlet channel, and in that the front flange (17), respectively the rear flange (19), is configured to form with the front side face (143), respectively the side face rear (144), of the sheet pack (14) at least two front connection channels (175), respectively at least two rear connection channels (195), inside which can circulate a cooling fluid, each of said to at least two front (175), respectively rear (195) connecting channels, being in fluid communication with one of said inlet and outlet channels (124, 126) and with one of said at least two second internal cavities ( 142).

2. Rotor (10) according to claim 1, characterized in that said at least two front connection channels (175) are in fluid communication with said inlet channel (124) and said at least two rear connection channels (195). ) are in fluid communication with said outlet channel (126), such that fluid from cooling intended for cooling the rotor can circulate in the rotor successively through the inlet channel (124), then between the front flange (17) and the front side face (143) of the sheet pack (14) through said au at least two front connecting channels (175), then inside the packet of sheets (14) through said at least two second internal cavities (142), then between the rear flange (19) and the rear side face (144 ) of the sheet metal bundle (14) through said at least two rear connection channels (195), and finally through the outlet channel (126).

3. Rotor (10) according to claim 2, characterized in that the shaft (12) comprises a front end portion (121) hollow and a rear end portion (123) hollow separate from the end portion. front (121) by a solid central portion (122), the front end portion (121), respectively the rear end portion (123), being crossed by a central cavity of cylindrical shape, said central cavity forming the channel inlet (124), respectively the outlet channel (126), of the shaft (12), and in that at least two holes (125, 127) oriented radially with respect to the axis (X) of the shaft (12) are formed inside the front end portion (121), respectively of the rear end portion (123), so as to open out on one side into the inlet channel ( 124), respectively the outlet channel (126), and on the other side in said at least two front connection channels (175), respectively said at least two rear connection channels (195).

4. Rotor (10) according to claim 1, characterized in that said at least two rear connection channels (195) are in fluid communication with said inlet channel (124) and said at least two front connection channels (175). ) are in fluid communication with said outlet channel (126), so that a cooling fluid intended for cooling the rotor can circulate 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 said at least two rear connecting channels (195), then inside the sheet metal pack (14) through said at least two second internal cavities (142), then between the front flange (17) and the front side face (143) through said at least two front connecting channels (175), and finally through the outlet channel (126).

5. Rotor (10) according to claim 4, characterized in that the shaft (12) comprises a front end portion (121) hollow and a rear end portion (123) full separate from the end portion. before (121) by a portion hollow central (122), the front end portion (121) and the central portion (122) being traversed by a central cavity of cylindrical shape, 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 aligned coaxially with the central cavity, said at least one peripheral cavity forming the outlet channel (126) of the shaft (12), and in that at least two holes (125, 127) oriented radially with respect to the axis (X) of the shaft (12) are formed inside the front end portion (121), respectively of the central portion (122), so as to open out on one side into the outlet channel (126), respectively the inlet channel (124), and on the other side into said at least two front connecting channels ( 175), respectively said at least two rear connection channels (195).

6. Rotor (10) according to claim 5, characterized in that the shaft (12) comprises a main body (120) provided with a blind hole (128a, 128b) aligned along the axis (X) of the shaft (12), said blind hole (128) comprising two contiguous sections of different internal diameters, namely a first section (128a) having a first internal diameter and a second section (128b) having a second internal diameter, and in that a plastic insert (13) is housed inside the blind hole at the first section (128a), said insert (13) being formed of a tubular part (131) aligned with the second section (128b). ) of the blind hole and having an internal diameter which is substantially equal to the second internal diameter, and of an annular portion (132) extending radially around one end of the tubular portion (131), said annular portion ( 132) being positioned at the interface between the first section (128a) and the second section (1 28b) of the blind hole and having an outer diameter which is substantially equal to the first inner diameter, the inlet channel (124) of the shaft (12) being jointly defined 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 parts (131, 132) of the insert (13).

7. Rotor (10) according to claim 6, characterized in that the insert (13) comprises one or more separation fins (133) extending radially from the outer periphery of the tubular part (131), each of the fins. separator (133) being configured to separate the output channel (126) into two or more segments (126a-126d) of output channels.

8. Rotor (10) according to one of the preceding claims, characterized in that each of the front and rear flanges (17, 19) has an internal face (173, 193) in contact with a lateral face (143, 144) of the package of sheets (14), said internal face (173, 193) being provided with at least two grooves (175, 195) of oblong shape extending radially from a central region (172) recessed of said flange, at the level of which said grooves (175, 195) are in fluid communication with the inlet (124) or outlet (126) channel of the shaft (12), up to an intermediate zone of said flange facing one of said at least one at least two second internal cavities (142) of the sheet metal bundle (14).

9. A rotor (10) according to claim 8, characterized in that each of said radial grooves (175, 195) faces a radial hole (125, 127) formed through the shaft (12), said radial hole opening out. on one side on the inlet (124) or outlet (126) channel of the shaft (12) and on the other side on the peripheral wall of the shaft (12).

10. Rotor (10) according to one of the preceding claims, characterized in that each of the front and rear flanges (17, 19) is provided on its internal face (173, 193) with a circular groove (174) intended for housing a seal (16) of annular shape, said seal (16) being intended to ensure the seal between the flange (17, 19) and the pack of sheets (14).

11. Rotor (10) according to one of the preceding claims, characterized in that the front flange (17), respectively the rear flange (19), is configured to form with the front side face (143), respectively the side face. rear (144), of the packet of sheets (14), several groups of front link channels (175), respectively several groups of rear link channels (195), each of the groups comprising at least two front link channels (175), respectively at least two rear connection channels (195), inside which can circulate a cooling fluid, each of said at least two front connection channels (175), respectively rear (195), being in fluid communication with the one of said inlet and outlet channels (124, 126) and with one of said at least two second internal cavities (142).

12. Rotor (10) according to claim 11, characterized in that the front flange (17), respectively the rear flange (19), is configured to form with the front side face (143), respectively the rear side face (144 ), of the packet of sheets (14) several front intermediate channels (181), respectively several channels rear intermediate channels, inside which a cooling fluid can circulate, each of the front intermediate channels (181), respectively rear, being axially aligned with a radial segment (18) of the pack of sheets (14) separating two second internal cavities ( 142a-142d), each of said front (181), respectively rear intermediate channels being in fluid communication with one of said inlet and outlet channels (124, 126) and with a through hole (11b) formed through the sheet metal pack (14), said through hole (11b) potentially being able to receive a fixing screw intended to fix the front and rear flanges (17, 19) on the sheet metal pack (14).

13. Electric motor (30) comprising a rotor (10) according to one of the preceding claims.