Electrically excited electric machine equipped with a cooling device

Abstract

Electrically excited electric machine provided with a cooling device The present invention relates to an electric machine (ME1) equipped with: - a casing (1), - a stator, - a wound rotor (3) comprising a rotor body secured to a rotating shaft, - a bearing (2) in which one end (32) of the rotating shaft is rotatably mounted, the end (32) of the rotating shaft comprising electrical tracks (10a, 10b) and the bearing being mounted on the casing of the electric machine (ME1), - an excitation system (4) of the wound rotor (3) comprising brushes (5) arranged in contact with the electrical tracks (10a, 10b), the electric machine (ME1) being characterized in that it comprises a block of thermally conductive and electrically insulating material (8) in thermal contact with at least one of the brushes (5) on the one hand and with a heat sink on the other hand. (Figure 1)

Description

Title of the invention: Electrically excited electric machine equipped with a cooling device

[0001] The present invention relates to the fields of mechanics and electrical engineering and more specifically concerns an electrical machine with a wound rotor provided with a rotor excitation system, requiring cooling and finding a particular application in the automotive field.

[0002] Electric or hybrid vehicles use electric machines that provide traction or propulsion torque to the wheels of these vehicles. The electrical power required to provide such torque heats up the power conductors of these electric machines in particular.

[0003] When such an electrical machine has a wound rotor, it generally uses a system of conductive rings arranged around a rotating shaft of the wound rotor, and connected to the windings of the rotor. These conductive rings receive an electric supply current through fixed carbon brushes which rub the rotating conductive rings. These conductive rings therefore rise in temperature all the more as the current they receive is strong and the differential speed between the brushes and these rotating conductive rings is significant. The heat produced must be evacuated so as not to degrade these materials and the performance of the electrical machine.

[0004] Furthermore, carbon brushes generate carbon dust which must be avoided from coming into contact with the active parts of the electrical machine. A seal is therefore generally arranged between an excitation system of the wound rotor, comprising the carbon brushes, and a body of the wound rotor. This seal rubs on the rotating shaft of the wound rotor which causes it to heat up. The heat produced by friction on the seal must also be evacuated so that it does not deteriorate too quickly.

[0005] Usually the heat produced at the carbon brushes, the conductive rings and the seal is dissipated by the natural convection of the air in thermal contact on the one hand with these elements and on the other hand with metal parts of the electrical machine, such as a metal casing which may include a cooling jacket. For this cooling to be sufficient, the quantity of material of these metal parts and in particular their thicknesses must be relatively large, which makes the wound rotor expensive.

[0006] The seal is for example arranged in an opening of a wall of the casing of the electric machine, being wedged radially in the opening between the casing and an axial extension of an inner ring of a bearing in which the rotating shaft is mounted to rotate. However, since the bearing is connected to an electrical ground via its outer ring, the carbon dust kept at a distance from the rotor body by the seal must not touch the inner ring on which it rubs, so as not to create a short circuit. A minimum electrical insulation distance from the carbon brushes must therefore be respected, which requires significant axial dimensioning of the rotating shaft of the wound rotor.

[0007] The present invention aims to remedy at least in part the aforementioned drawbacks by providing an electrical machine with a wound rotor, using a brush-based excitation system, in which the thermal evacuation of the heat from the brushes uses an electrically insulating but good thermal conductor material, which makes it possible to improve the thermal transfer, in particular between the brushes and a heat sink.

[0008] To this end, the invention proposes an electric machine equipped with: - a casing, - a stator, - a wound rotor comprising a rotor body secured to a rotating shaft, - a bearing in which one end of the rotating shaft is rotatably mounted, the end of the rotating shaft having electrical tracks and the bearing being mounted on the casing of the electrical machine, - a wound rotor excitation system comprising brushes arranged in contact with the electrical tracks, the electric machine being characterized in that it comprises a block of thermally conductive and electrically insulating material in thermal contact with on the one hand at least one of the brushes and on the other hand with a heat sink.

[0009] The thermally conductive and electrically insulating block of material is, for example, a silicone-based thermal paste. This type of dielectric block of material is known as a “thermal pad” in the field of electronics. Some formulations are based on silicones loaded with graphite, for example, while some thermal pastes are synthetic and guaranteed silicone-free. The block of material is glued or placed on the heat sink.

[0010] Thanks to this mass block, the heat emitted by the current flowing in the brush and the friction of the brush on one of the electric tracks is efficiently dissipated to a heat sink, which can be a dedicated device such as a radiator or a cooling plate, or else a standard component of the electric machine such as for example the housing. The housing of the electric machine is indeed generally made of aluminium. It can be in several parts, notably include a bottom and a cover, as well as possibly one or more intermediate walls.

[0011] The brushes are for example each mounted in translation in a metal cage, and the mass block is in direct contact on the one hand with the metal cage of the brush and on the other hand with the housing of the electric machine and / or a radiator.

[0012] By "direct contact" is meant that the block of material touches the metal cage and the casing and / or the radiator, or is possibly separated therefrom only by a light layer of glue. In an alternative embodiment, the block of material is in direct contact with both the casing and the radiator, the latter comprising in this alternative, a thermal conduction wall proximal to the casing and the brush.

[0013] According to an optional and advantageous characteristic of the invention, a wall of the casing separates the body of the rotor from the excitation system and comprises an opening in which is fixed a sealing device in contact with the end of the rotating shaft, the bearing being fixed in the opening and arranged axially between the body of the rotor and the sealing device, the brush being in contact with a first of the electrical tracks, the latter comprising an extension coming into contact with the sealing device.

[0014] The extension of the first electrical track makes it possible to conduct the heat generated by the friction of the sealing device against the first electrical track, towards the brush and therefore to be evacuated by the block of material in thermal contact on the one hand with the metal cage of the brush and on the other hand with the casing or a radiator. In addition, this characteristic makes it possible not to create an electrical path between the brush and the electrical mass of the electrical machine, for example due to carbon dust which would accumulate between the brush and the sealing device, since the first electrical track is electrically insulated from this electrical mass.

[0015] The opening in which the bearing is mounted is for example located in a wall of a bottom or a cover of the casing of the electric machine, or in an intermediate wall of the casing of the electric machine. Furthermore, the sealing device is for example a lip seal made of elastomeric material.

[0016] In one embodiment of the invention, the brush is mounted axially relative to the rotating shaft, and the first electrical track takes the form of a cylindrical cup with a hole in its center, comprising a cylindrical part in contact with the seal and a flat part in contact with the brush.

[0017] It should be noted that in this patent application, the term "axial" refers, unless otherwise stated, to a direction parallel to the axis of rotation of the rotor of the electric machine. Similarly, the term "radial" refers, unless otherwise stated, to a direction orthogonal to the axis of rotation of the rotor of the electric machine, and secant to this axis of rotation, while the terms "angular" or "ortho-radial" refer, unless otherwise stated, to a direction orthogonal to the axial direction and to a radial direction, this orthogonal direction being in fact rotating around the axis of rotor rotation.

[0018] Preferably in this embodiment, all the brushes are mounted axially.

[0019] Such an embodiment makes it possible, when the rotating shaft is subjected to a bending force, for example due to a mechanical connection of the rotating shaft with a pinion, not to cause the brushes to enter an excitation mode where they would no longer be constantly in contact with the electrical tracks on the end of the rotating shaft.

[0020] In this embodiment of the invention, the first electrical track is attached to a first portion of the end of the rotating shaft of a first diameter, the planar portion being attached to a first axial end surface of the rotating shaft, the end of the rotating shaft having a second portion projecting from the first portion through the central hole of the cylindrical cup formed by the first electrical track, a second of the disc-shaped electrical tracks being attached to a second axial end surface of the rotating shaft, on the second portion.

[0021] The second portion of the end of the rotating shaft is therefore of diameter strictly less than that of the first portion of the end of the rotating shaft.

[0022] Preferably in this embodiment of the invention, the brushes of the electrical machine are mounted axially, several first brushes being in contact with the first electrical track, each metal cage of these first brushes being in direct contact on the one hand with a block of thermally conductive and electrically insulating material and on the other hand with the radiator, a second brush being in contact with the second electrical track in the form of a disc.

[0023] The block of material may be the same for all of the first brushes, or separate blocks of material are used to each cool one or more of the first brushes.

[0024] Indeed, in this embodiment of the invention, the need for cooling is less for the second brush and the second electrical track, which does not receive the heat generated by the friction of the sealing device against the first electrical track. The second brush therefore does not possibly benefit from cooling using a block of thermally conductive and electrically insulating material.

[0025] In an alternative embodiment, however, the metal cage of the second brush is in thermal contact with a heat dissipation device. For example, a block of thermally conductive and electrically insulating material is in direct contact on the one hand with the metal cage of the second brush and on the other hand with a heat dissipation device which may be, for example, the radiator used to cool the second brushes, or the casing of the electric machine, or even a cooling plate.

[0026] The radiator comprises for example a cylindrical portion surrounding the first brushes, and fins positioned between the first brushes. Thus one or more blocks of material are in direct contact on the one hand with the cylindrical portion of the radiator and on the other hand with one or more first brushes, to conduct the heat from the brushes towards this cylindrical portion, the heat from the cylindrical portion then being evacuated by the fins.

[0027] Furthermore, in this embodiment of the invention, the sealing device is preferably a lip seal comprising a cylindrical wall fixed to a housing of the excitation system, the cylindrical wall being extended radially by a lip coming into contact with the cylindrical part of the first electrical track. Alternatively, the cylindrical wall of the lip seal is fixed to the casing of the electrical machine.

[0028] It should be noted that the lip seal must be gripped between two metal parts. If the housing of the excitation system is made of plastic, then the cylindrical wall of the lip seal is for example fixed to the housing of the excitation system by means of a metal ring on which it is glued.

[0029] In another embodiment of the invention, the brush is mounted radially relative to the rotating shaft and is in contact with the first electrical track, the latter being cylindrical, the extension of the first electrical track also being cylindrical and enclosing an overmolding of electrical conductors connected to the electrical tracks, the thickness of the extension being less than the thickness of the first electrical track.

[0030] The thickness of the extension or of the first electrical track of course refers to thicknesses in a radial direction.

[0031] In this other embodiment of the invention, the overmolding of the electrical conductors forms, for example, a ring fitted around a steel part of the end of the rotating shaft, the electrical tracks being arranged at least partly in circular grooves of the overmolding. The conductors are flush with the bottom of the grooves and are, for example, welded to the electrical tracks there. The extension of the first electrical track is located on a bearing of the ring formed by the overmolding, the bearing being connected to the bottom of the groove which houses the main portion of the first electrical track, by a flat surface in the shape of a crown, arranged orthogonally to the axial direction. In other words, the extension of the first electrical track is located on a bearing of the overmolding, of diameter strictly greater than that of the groove housing the main portion of the first electrical track.At the bearing level, the electrical conductors are embedded in the overmolding.

[0032] This arrangement is simple to implement, in particular it does not require passages to be dug inside the rotating shaft for the passage of electrical conductors.

[0033] The invention also relates to an electric or hybrid vehicle comprising an electric machine according to the invention.

[0034] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several exemplary embodiments given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0035] [Fig-1] represents in axial section a portion of an electric machine according to the invention, in a first embodiment of the invention, and

[0036] [Fig.2] represents in axial section a portion of an electric machine according to the invention, in a second embodiment of the invention.

[0037] According to a first embodiment of the invention shown in [Fig. 1], an electrical machine ME1 according to the invention is of the radial flux electrical machine type. It comprises a stator (not shown) and a wound rotor 3, the stator and the wound rotor 3 being housed in a casing 1 of which only a wall portion is shown in [Fig.l].

[0038] The wound rotor 3 conventionally comprises a rotating shaft onto which a stack of magnetic steel sheets is shrunk, forming teeth around which electrical wires are wound to form rotor poles. This stack of sheets comprising the windings forms a rotor body. The ends of the windings are connected via electrical terminals to electrical conductors 36. These are each connected by one of their ends to an electrical terminal and by the other of their ends to an electrical track, arranged on one end 32 of the rotating shaft of the wound rotor 3.

[0039] Of course the wound rotor can be of slightly different design, in particular the rotor body can be assembled on the rotating shaft other than by shrink fitting, and not include a stack of sheets but a different assembly to form the rotor teeth.

[0040] [Fig.l] shows only a half-view in axial section of an end portion of the electrical machine ME1 centered at an opening in the wall of the casing 1, in which the end 32 of the rotating shaft is mounted. The complete axial section view of the end portion of the electrical machine ME1 can be obtained by making this half-view axially symmetrical with respect to the axis of rotation Y of the rotating shaft. Indeed, the elements visible in the half-view of [Fig.l] can be made symmetrical, in axial section, with respect to the axis of rotation Y of the rotating shaft. In particular, the end portion of the electrical machine ME1 comprises two electrical conductors 36 arranged symmetrically to each other with respect to the Y axis of rotation of the rotating shaft.

[0041] The end 32 of the rotating shaft comprises a cylindrical portion 31 made of steel and an overmolding 35 made of electrically insulating material. The overmolding 35 forms two branches each overmolding a portion of the length of an electrical conductor 36, and a ring fitted onto the cylindrical portion 31 made of steel, the ring being distal to the rotor body relative to the two branches. These each comprise a first end from which an electrical conductor 36 projects, and a second end reaching the ring, in which the electrical conductors 36 join cylindrical electrical tracks 10a, 10b arranged on the ring of the overmolding 35. The electrical conductors 36 are flush with certain surfaces of the ring, where they are for example welded to the electrical tracks 10a, 10b, which are preferably made of the same metallic material as the electrical conductors 36, for example copper.

[0042] The two branches of the overmolding 35 are arranged in axial grooves of the cylindrical portion 31 made of steel, the latter comprising a bearing receiving the ring of the overmolding 35.

[0043] A ball bearing 2 is mounted in the opening of the wall of the casing 1, the outer ring of the bearing 2 being arranged against the casing 1 and the inner ring of the bearing 2 being arranged against the cylindrical portion 31 made of steel of the rotating shaft, on certain angular portions thereof, and against the two branches of the overmolding 35, on the other angular portions of the cylindrical portion 31 made of steel.

[0044] A sealing device 9, here a lip seal, is also mounted in the opening of the wall of the casing 1, on the side opposite the rotor body relative to the bearing 2. The lip seal is bonded by its cylindrical portion to the casing 1, the lip being in contact with an extension 11a of a first of the electrical tracks 10a. The extension 11a of the first electrical track 10a is cylindrical and extends the first electrical track 10a while being of lesser thickness than the latter. In addition, the extension 11a of the first electrical track 10a is also arranged on the ring formed by the overmolding 35.

[0045] More precisely, the main portion of the first electrical track 10a and the second electrical track 10b are arranged in circular grooves of the overmolding ring 35. One of the electrical conductors 36 is flush with the bottom of a first groove in which it is welded to the first electrical track 10a, and the other of the electrical conductors 36 is flush with the bottom of a second groove in which it is welded to the second electrical track 10b.

[0046] It is understood that the first electrical track 10a corresponds for example to a positive electrical terminal of the wound rotor 3 and that the second electrical track 10b corresponds in this example to a negative electrical terminal of the wound rotor 3.

[0047] The extension 11a of the first electrical track 10a is located on a landing of the ring formed by the overmolding 35, the bearing adjoining the groove in which the main portion of the first electrical track 10a is housed. The extension 11a of the first electrical track 10a is located axially at the level of the casing 1 of the electric machine ME1, while the main portion of the first electrical track 10a is located axially outside the casing 1 of the electric machine ME1, so as to be able to be in contact with a brush 5 of an electrical excitation system 4 of the wound rotor 3.

[0048] The excitation system 4 comprises a first brush 5 in contact with the first electrical track 10a, and a second brush 5 in contact with the second electrical track 10b. These brushes are mounted radially relative to the axis of rotation of the rotating shaft, and are for example carbon brushes.

[0049] When the end 32 of the rotating shaft rotates in the bearing 2, the lip seal rubs against the extension 11a of the first electrical track 10a, the latter being powered by the friction of the first brush 5 against the first electrical track 10a, and the second electrical track 10b being powered by the friction of the second brush 5 against the second electrical track 10b.

[0050] The brushes 5 are each mounted to move in translation in a metal cage 7, in which a pressure spring 6 maintains contact between the brushes 5 and the corresponding electrical track 10a or 10b.

[0051] A block of thermally conductive and electrically insulating material 8 is bonded on the one hand to the metal cage 7 in which the first brush is mounted, and on the other hand to the wall of the casing 1. The block of material 8 is here an adhesive thermal paste deposited between the metal cage 7 and the casing 1.

[0052] The heat generated by the friction of the lip seal against the first electrical track 10a is thus evacuated via the first electrical track 10a, the first brush 5 and the block of material 8, into the wall of the casing 1, itself cooled by the natural convection of the air. The second brush 5 is not cooled in a similar manner to the first brush 5 in this embodiment of the invention, its cooling requirement being less due to the fact that the second electrical track 10b only undergoes the friction of the second brush 5. As a variant, it is cooled otherwise than by natural convection of the air, for example by means of another block of thermally conductive and electrically insulating material 8 in contact on the one hand with the metal cage 7 of the second brush and on the other hand with a radiator or a cooling plate. According to a second embodiment of the invention shown in [Fig.2], an electrical machine ME2 according to the invention is of the radial flux electrical machine type. It comprises a stator (not shown) and a wound rotor 30, the stator and the wound rotor 30 being housed in a casing 10 of which only a piece of wall is re- presented in [Fig.2].

[0053] In a similar manner to the first embodiment of the invention, in this second embodiment of the invention, the wound rotor 30 comprises a rotating shaft on which is shrunk a stack of magnetic steel sheets, forming teeth around which electrical wires are wound to form rotor poles, the stack of sheets and the windings forming a body of the wound rotor 30. The ends of the windings are connected by means of electrical terminals to electrical conductors 360a, 360b. These are each connected by one of their ends to an electrical terminal and by the other of their ends to an electrical track, arranged on one end 320 of the rotating shaft of the wound rotor 30.

[0054] Of course, the wound rotor 30 may be of a different design from that described here, the rotor body being able to be assembled on the rotating shaft other than by shrink fitting, and not comprising a stack of sheets but a different assembly to form the rotor teeth.

[0055] In [Fig.2] only an end portion of the electrical machine ME2 is shown in axial section, centered at an opening in the wall of the casing 10, in which the end 320 of the rotating shaft is mounted.

[0056] The end 320 of the rotating shaft comprises a cylindrical portion 310 made of steel and a cap 34 made of electrically insulating material, covering an axial end surface of the cylindrical portion 310 made of steel. The cap 34 comprises two branches 340 each overmolding a part of the length of an electrical conductor 360a, 360b, these branches 340 each being arranged in an axial groove of the cylindrical portion 310 made of steel. The cylindrical portion 310 made of steel is extended axially by a body of the cap 34 from which the two branches 340 extend towards the rotor body.This body of the cap 34 forms a first portion 342 of the end 320 of the rotating shaft, in contact with the cylindrical portion 310 made of steel and of diameter substantially identical to that of this cylindrical portion 310 made of steel, and a second portion 344 of the end 320 of the rotating shaft, of reduced diameter compared to that of the first portion 342 of the end 320 of the rotating shaft.

[0057] The two branches 340 each comprise a first end from which an electrical conductor 360a, 360b projects, and a second end reaching the body of the cap 34, in which the electrical conductors 360a, 360b join electrical tracks 100a, 100b arranged at least in part on axial end surfaces of the cap 34, and to which the electrical conductors 360a, 360b are soldered. The electrical tracks 100a, 100b and the electrical conductors 360a, 360b are for example made of copper.

[0058] More precisely, a first of the electrical tracks 100a takes the form of a cylindrical cup with a hole in its center, comprising a cylindrical part 101a around a cylindrical surface of the first portion 342 of the end 320 of the rotating shaft, and a flat part 102a in contact with an axial end surface of the first portion 342 of the end 320 of the rotating shaft. In other words, the first electrical track 100a covers the body of the cap 34.

[0059] The second electrical track 100b is in the form of a metal disc in contact with an axial end surface of the second portion 344 of the end 320 of the rotating shaft, this second portion 344 projecting from the first portion 342, through the central hole of the cylindrical cup formed by the first electrical track 100a.

[0060] A ball bearing 20 is mounted in the opening of the wall of the casing 10, the outer ring of the bearing 20 being arranged against the casing 10 and the inner ring of the bearing 20 being arranged against the cylindrical portion 310 made of steel of the rotating shaft, on certain angular portions thereof, and against the two branches 340 of the cap 34, on the other angular portions of the cylindrical portion 310 made of steel.

[0061] The electrical machine ME2 also comprises an excitation system 40 housed in a housing 400 made of rigid insulating material, the latter being formed of a base 401 and a cover 402. The base 401 of the housing 400 comprises a first cylindrical wall mounted tightly in the opening of the wall of the casing 10, on the side opposite the rotor body relative to the wall of the casing 10. The ball bearing 20 is thus arranged axially between the rotor body and the first cylindrical wall of the base 401 of the housing 400.

[0062] A metal ring is secured to the internal surface of the first cylindrical wall of the base 401, to receive a sealing device 90. The sealing device 90, here a lip seal, is bonded by its cylindrical portion to the metal ring, and its lip comes into contact with the cylindrical part 101a of the first electrical track 100a.

[0063] The base 401 of the housing 400 also comprises a flat wall facing the flat part 102a of the first electrical track 100a, this flat wall comprising orifices for the passage of first brushes 50 coming into contact with the flat part 102a of the first electrical track 100a. This flat wall has the overall shape of a crown and is connected at its center to a well formed by the base 401 of the housing, at the bottom of which is arranged an orifice for the passage of a second brush 50 coming into contact with the second electrical track 100b. The base of the housing 401 therefore has a shape generally complementary to the first and second portions 342, 344 of the end 320 of the rotating shaft, this shape being produced at least in part by the first cylindrical wall of the base 401, the flat wall of the base 401 and the well formed by the base 401.

[0064] The base 401 also comprises a second cylindrical wall for receiving the cover 402 of the housing 402, coaxial with the first cylindrical wall and located at the opposite of this with respect to the flat wall of the housing 402. This second cylindrical wall is open towards the outside of the casing 10.

[0065] It is therefore understood that the brushes 50, which are for example carbon brushes, are arranged, in this second embodiment of the invention, axially relative to an axis of rotation X of the rotating shaft. The first electrical track 100a corresponds for example to a negative terminal of the wound rotor 30 and the second electrical track 100b to a positive terminal of the wound rotor 30.

[0066] The brushes 50 are each mounted so as to move in translation in a metal cage 70, in which an axially mounted pressure spring 60 maintains contact between the brushes 50 and the corresponding electrical track 100a or 100b.

[0067] The metal cages 70 each comprise an axial end for attachment to the cover 402 of the housing 400 of the excitation system 40, on the side opposite the contact surfaces of the brushes 50 with the electrical tracks 100a, 100b. This attachment of the metal cages 70 to the cover 402 of the housing is carried out by means of external connectors 406, 404.

[0068] One of the external connectors 404 passes through the cover 402, is secured to it and forms a first power supply terminal for the excitation system 40. This external connector 404 is itself secured, for example made in one piece, with a metal ring 403 secured to the axial fixing ends of the metal cages 70 of the first brushes 50.

[0069] Similarly, the other external connector 406 passing through the cover 402 is secured to the latter and forms a second power supply terminal for the excitation system 40. This other external connector 406 is secured, on the internal side of the housing 400, to the axial end of the fixing of the metal cage 70 of the second brush 50, for example by welding.

[0070] The excitation system 40 further comprises a radiator 110 secured to the base 401 of the housing 400. The radiator is for example made of aluminum and comprises a cylindrical portion surrounding the first brushes 50, fixed to the second cylindrical wall of the base 401 of the housing 400, and fins positioned between the first brushes 50.

[0071] Blocks of thermally conductive and electrically insulating material 80, for example made of silicone, are arranged between, on the one hand, the metal cages 70 of the first brushes 50 and, on the other hand, the cylindrical portion of the radiator 110.

[0072] The heat generated by the friction of the lip seal against the first electrical track 100a is thus evacuated via the first electrical track 100a, the first brushes 50 and the blocks of material 80, into the radiator 110, itself cooled by the natural convection of the air. The second brush 50 is not cooled in a similar manner to the first brushes 50 in this second embodiment of the invention, its cooling requirement being less due to the fact that the second electrical track 100b only undergoes the friction of the second brush 50. As a variant, it is cooled otherwise than by natural convection of the air, for example by means of another block of thermally conductive and electrically insulating material 80 in contact on the one hand with the metal cage 70 of the second brush 50 and on the other hand with the radiator 110 or a cooling plate.

[0073] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. In particular, the characteristics of the different embodiments or variants of the invention envisaged in this application can be combined to achieve the invention, to the extent that these embodiments or variants are not incompatible with each other.

Claims

Claims

1. An electrical machine (ME1, ME2) equipped with: - a casing (1, 10), - a stator, - a wound rotor (3, 30) comprising a rotor body secured to a rotating shaft, - a bearing (2, 20) in which one end (32, 320) of the rotating shaft is rotatably mounted, the end (32, 320) of the rotating shaft comprising electrical tracks (10a, 10b, 100a, 100b) and the bearing being mounted on the casing of the electrical machine (ME1, ME2), - an excitation system (4, 40) of the wound rotor (3, 30) comprising brushes (5, 50) arranged in contact with the electrical tracks (10a, 10b, 100a, 100b), the electrical machine (ME1, ME2) being characterized in that it comprises a block of thermally conductive and electrically insulating material (8, 80) in thermal contact with, on the one hand, at least one of the brushes (5, 50) and, on the other hand, with a heat sink.

2. Electric machine (ME1, ME2) according to claim 1, in which the brushes (5, 50) are each mounted in translation in a metal cage (7, 70), the block of material (8, 80) is in direct contact on the one hand with the metal cage (7, 70) of the brush and on the other hand with the casing (1, 10) of the electric machine (ME1, ME2) and / or a radiator (110).

3. An electrical machine (ME1, ME2) according to claim 1 or 2, wherein a wall of the casing (1, 10) separates the rotor body from the excitation system (4, 40) and comprises an opening in which is fixed a sealing device (9, 90) in contact with the end (32, 320) of the rotating shaft, the bearing (2, 20) being fixed in the opening and arranged axially between the rotor body and the sealing device (9, 90), the brush being in contact with a first of the electrical tracks (10a, 100a), the latter comprising an extension (11a, 101a) coming into contact with the sealing device (9, 90).

4. Electrical machine (ME2) according to claim 3, in which the brush (50) is mounted axially relative to the rotating shaft, and in which the first electrical track (100a) takes the form of a cylindrical cup with a hole in its center, comprising a cylindrical part (101a) in contact with the seal and a flat part (102a) in contact with the brush (50).

5. An electrical machine (ME2) according to claim 4, wherein the first electrical track (100a) is attached to a first portion (342) of the end (320) of the rotating shaft of a first diameter, the flat portion (102) being attached to a first axial end surface of the rotating shaft, the end (320) of the rotating shaft having a second portion (344) projecting from the first portion (342) through the central hole of the cylindrical cup formed by the first electrical track (100a), a second of the electrical tracks (100b) in the form of a disc being attached to a second axial end surface of the rotating shaft, on the second portion (344).

6. Electric machine (ME2) according to claims 2 and 5, in which the brushes of the electric machine are mounted axially, several first brushes (50) being in contact with the first electrical track (100a), each metal cage (70) of these first brushes (50) being in direct contact on the one hand with a block of thermally conductive and electrically insulating material (80) and on the other hand with the radiator (110), a second brush (50) being in contact with the second electrical track (100b) in the form of a disc.

7. Electric machine (ME2) according to claim 6, in which the metal cage (70) of the second brush (50) is in thermal contact with a heat dissipation device.

8. An electrical machine (ME2) according to claims 6 or 7, wherein the radiator (110) comprises a cylindrical portion surrounding the first brushes (50), and fins positioned between the first brushes (50).

9. Electrical machine (ME2) according to any one of claims 4 to 8, in which the sealing device (90) is a lip seal comprising a cylindrical wall fixed to a housing (402) of the excitation system (40), the cylindrical wall being extended radially by a lip coming into contact with the cylindrical part (101a) of the first electrical track (100a).

10. Electrical machine (ME1) according to any one of claims 1 to 3, in which the brush (5) is mounted radially relative to the rotating shaft and is in contact with the first electrical track (10a), the latter being cylindrical, the extension (11a) of the first electrical track also being cylindrical and enclosing an overmolding of electrical conductors (36) connected to the electrical tracks (10a, 10b), the thickness of the extension (11a) being less than the thickness of the first electrical track (10a).

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