Rotor-excited electric machine

Abstract

Rotor-excited electric machine The present invention relates to an electric machine (ME) equipped with at least:- a casing (1),- a stator,- a wound rotor comprising a rotor body secured to a rotating shaft (3) about an axis of rotation (X), - a bearing (2) mounted in the casing of the electric machine (ME) and in which one end of the rotating shaft (3) is rotatably mounted, the end of the rotating shaft (3) comprising at least one electrical track (10, 16), - an excitation system comprising at least one brush (51, 52) arranged in contact with the electrical track (10, 16), the electric machine (ME) being characterized in that the electrical track (10, 16) comprises a contact surface with the brush (51, 52), arranged orthogonally to the axis of rotation (X). (Figure 1)

Description

Title of the invention: Rotor-excited electric machine

[0001] The present invention relates to the fields of mechanics and electrical engineering and concerns an electrical machine with a wound rotor using an excitation system based on rings and brushes, finding a particular application in motor vehicles.

[0002] The use of a wound rotor in an electric machine of an electric or hybrid vehicle makes it possible to do without rare earth magnets. Such a wound rotor electric machine generally uses a system of conductive rings arranged around a rotating shaft of the wound rotor, and connected to the rotor windings. These conductive rings receive an electric supply current by fixed carbon brushes arranged radially and which rub the rotating conductive rings.

[0003] However, in certain vehicle powertrains comprising an electric traction or propulsion machine, the rotor of the electric machine is connected by one end of its rotating shaft to a pinion of a gearbox which generates toothing forces which can cause the rotating shaft to enter into resonance, at speeds of the order of 5000 revolutions per minute. The ends of the rotating shaft can then, under the effect of this resonance, move radially by about twenty microns due to bending of the rotating shaft. In this case, the use of a conventional system of rings and brushes is not suitable because the brushes are no longer in continuous contact with the conductive rings, which risks generating electric arcs and deterioration of the electric machine.

[0004] Another disadvantage of conventional excitation systems based on rings and brushes is the rise in temperature of the conductive rings due to the fact that a strong current passes through them and the differential speed between the brushes and these rotating conductive rings is significant. The heat produced must be removed so as not to degrade these materials and the performance of the electrical machine.

[0005] 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.

[0006] 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.

[0007] The seal is for example arranged in an opening of a wall of the casing of the electrical 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 rotatably mounted. However, the bearing being 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 with the carbon brushes must therefore be respected, which requires a significant axial dimensioning of the rotating shaft of the wound rotor.

[0008] The present invention aims to remedy at least in part the aforementioned drawbacks by providing an electrical machine with a wound rotor, using an excitation system based on conductive rings and brushes, in which the brushes are mounted axially relative to a rotating shaft of the wound rotor.

[0009] To this end, the invention proposes an electric machine equipped with at least: - a casing, - a stator, - a wound rotor comprising a rotor body secured to a shaft rotating around an axis of rotation, - a bearing mounted in the casing of the electrical machine and in which one end of the rotating shaft is rotatably mounted, the end of the rotating shaft comprising at least one electrical track, - an excitation system comprising at least one brush arranged in contact with the electrical track, the electric machine being characterized in that the electric track comprises a contact surface with the brush, arranged orthogonally to the axis of rotation.

[0010] Thanks to the invention, the brush remains in contact with the electrical track, even when the latter is subjected to a radial displacement due to the rotating shaft entering into resonance. Indeed, in this case, the axial displacement of the ends of the rotating shaft is much less than their radial displacement. The invention makes it possible to reduce by ten the risks of deterioration of the shaft due to this resonance phenomenon.

[0011] 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 rotation of the rotor.

[0012] In the invention the brush is mounted axially or radially relative to the rotating shaft, but is in contact with the contact surface arranged orthogonally to the axis of rotation. By "orthogonally" is meant with a tolerance of a few percent relative to a direction orthogonal to the axis of rotation.

[0013] Preferably, the excitation system comprises two brushes and two electrical tracks arranged at the same end of the rotating shaft, but in a variant each of the brushes and each of the tracks are arranged at different ends of the rotating shaft. In another variant, the excitation system does not use, for one of the power supply terminals, a ring and a brush, but for example a capacitive coupling.

[0014] In one embodiment of the invention, the electrical machine comprises two brushes and two electrical tracks, the end of the rotating shaft comprises a first portion of a first diameter, comprising a first axial end surface, and a second portion of a second diameter smaller than the first diameter, projecting from the first portion and comprising a second axial end surface, a first of the electrical tracks being attached to the first axial end surface and a second of the electrical tracks being attached to the second axial end surface.

[0015] This embodiment allows for a smaller footprint of the excitation system at the end of the rotating shaft. Preferably, the brushes are mounted axially relative to the rotating shaft, each axial end surface being in contact with one of the brushes.

[0016] The contact surface of the first electrical track takes for example the form of a disc with a hole in its center, the contact surface of the second electrical track then taking the form of a solid disc. It is understood that the contact surface of the first electrical track is arranged on the first axial end surface and that the contact surface of the second electrical track is arranged on the second axial end surface.

[0017] The excitation system comprises, for example, first brushes in contact with the first electrical track, and a single second brush in contact with the second electrical track. This embodiment is possible because the first electrical track is much more angularly extended than the second electrical track.

[0018] In order to ensure good maintenance of the brushes, the excitation system is for example provided with a housing comprising a first support proximal to the rotor, the first support comprising a flat annular surface facing the first electrical track, this flat annular surface being pierced by orifices for the passage of the first brushes, the first support forming in the center of the flat annular surface, a well for the passage of the second brush, the housing comprising a second support distal to the rotor on which are fixed metal cages in which the first and second brushes are mounted in translation. The supports of the housing of the excitation system are preferably made of electrically insulating material. The first support of the housing forms for example a base of the housing and the second support of the housing forms for example a cover capable of fitting into the base.

[0019] In order to supply current to the brushes, the excitation system comprises, for example, on the one hand a first electrical connector passing through the second support of the housing and in electrical contact inside the housing with a metal ring in contact with the metal cages of the first brushes, and on the other hand a second electrical connector passing through the second support of the housing and in electrical contact inside the housing with the metal cage of the second brush.

[0020] According to an optional and advantageous characteristic of this embodiment of the invention, the housing houses a heat sink and thermally conductive and electrically insulating blocks of material, in contact on the one hand with the metal cages of the first brushes and on the other hand with the heat sink. The heat sink is for example a radiator, comprising cooling fins. The blocks of material make it possible to efficiently evacuate the heat emitted by the current flowing in the first brushes and the friction of the first brushes towards the heat sink. These blocks of material are known as “thermal pads” or “thermal pastes” in the field of electronics. Some formulations are based on silicones loaded for example with graphite, some thermal pastes are synthetic based and guaranteed silicone-free. All these thermal pastes are dielectric.The blocks of material are glued or deposited on the heat sink and on the metal cages. Alternatively, they are not in direct contact with the first brushes and the heat sink, but through other elements that are good thermal conductors.

[0021] According to another optional and advantageous characteristic of this embodiment of the invention, the first support of the housing comprises at least one hole capable of allowing dust generated by at least one of the brushes to pass through, the hole being arranged under at least one of the contact surfaces of the first or second electrical tracks with the first brushes or respectively the second brush. The first support of the housing comprises for example a hole under the contact surface of the first electrical track with the first brushes, and a hole under the contact surface of the second track electric with the second brush, the latter hole being arranged in the well formed by the first support of the housing. By "under the contact surface" is meant under a horizontal plane located under this contact surface, so that the dust falls by gravity into the hole arranged under this contact surface.

[0022] According to another optional and advantageous characteristic of this embodiment 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 a counterbore of the opening and arranged axially between the body of the rotor and the sealing device, the first electrical track comprising a cylindrical part, connected to the contact surface of the first electrical track on the side opposite the first brushes, and coming into contact with the sealing device.

[0023] 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 electrical machine, or in an intermediate wall of the casing of the electrical machine. The sealing device is for example a sealing gasket such as a lip seal made of elastomer material. This is for example fixed between the cylindrical part of the first electrical track and a metal ring covering an internal surface of the housing of the excitation system made of insulating material, this internal surface also being fixed in the opening of the wall of the casing. Indeed, such an elastomer sealing device must be gripped between two metal parts, preferably insulated from the ground.

[0024] Thanks to this arrangement of the sealing device, the dust generated by the brushes does not penetrate into the active parts of the electrical machine, and cannot generate a short circuit even when the brushes are close to the sealing device. Indeed, the latter is then not arranged in contact with a metal part connected to the ground, but in contact with the insulating housing or the first electrical track itself insulated from the ground. In addition, the heat generated by the friction of the seal is efficiently evacuated by the distribution of this heat in the plurality of first brushes and by the blocks of thermally conductive material in thermal contact with these first brushes and the heat sink.

[0025] In this embodiment of the invention, the end of the rotating shaft comprises, for example, a cylindrical steel end piece comprising at least two axial grooves in which are fitted branches of an electrically insulating cap on which the first and second electrical tracks are arranged, the cap including electrical conductors each connected by one of their ends to the first or second electrical track, and by the other of their ends to the windings of the rotor.

[0026] The cover overmolds, for example, the electrical conductors. This design is simple to implement, in particular it does not require any passages to be dug at the interior of the rotating shaft for the passage of electrical conductors.

[0027] The invention also relates to an electric or hybrid vehicle comprising the electric machine according to the invention. The vehicle according to the invention has advantages similar to those of the electric machine according to the invention.

[0028] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the appended schematic drawings on the other hand, in which:

[0029] [Fig.l] represents in axial section a portion of an electrical machine according to the invention, in one embodiment of the invention,

[0030] [Fig.2] is a perspective view of a cylindrical steel end piece of a shaft rotation of a rotor of the electric machine of [Fig.l],

[0031] [Fig.3] is a perspective view of an insulating cap having conductors electrical and electrical tracks and intended to be attached to the cylindrical end piece of [Fig.2], and

[0032] [Fig.4] is a perspective view of an end-mounted excitation system of the rotating shaft of the electric machine of [Fig.l], in which a cover of the excitation system has been removed.

[0033] According to an embodiment of the invention shown in [Fig.l], an electrical machine ME according to the invention is of the radial flux electrical machine type. It comprises a stator (not shown) and a wound rotor, the latter comprising a rotor body and a rotating shaft 3 to which it is secured, the wound rotor being mounted to rotate about an axis of rotation X. The stator and the wound rotor are housed in a casing 1 of which only a wall portion is shown in [Fig.l].

[0034] The rotor body is for example formed from a stack of magnetic steel sheets, shrunk onto the rotating shaft 3, the sheets forming teeth around which electrical wires are wound to form rotor poles. Of course, the wound rotor may be of a different design from that described here, the rotor body being able to be assembled onto the rotating shaft other than by shrunk, and not include a stack of sheets but a different assembly to form the rotor teeth.

[0035] In [Fig.l] only an end portion of the electrical machine ME is shown in axial section, centered at an opening in the wall of the casing 1, in which one end of the rotating shaft 3 is mounted. The wall of the casing 1 is, for example, a cover or bottom wall of the casing 1, or an intermediate wall of the casing 1, i.e., integral with a fixed part of the electrical machine ME. The casing 1 is, for example, made of aluminum.

[0036] The rotating shaft 3 comprises a steel body, and an insulating cap 12 covering a cylindrical end piece 30 of the steel body of the rotating shaft 3.

[0037] [Fig.2] shows the cylindrical steel end piece 30 of the rotating shaft 3, and [Fig.3] represents the insulating cap 12 designed to fit onto the cylindrical end piece 30.

[0038] The cylindrical steel end piece 30 comprises respectively a first bearing and a second bearing from a central portion of larger diameter comprising grooves for hooping the stack of sheets forming the rotor body. Two axial grooves 18 are hollowed out on either side of these bearings, that is to say at 180° to each other, so as to each receive an insulating branch 120 of the insulating cap 12. Each axial groove 18 forms the same flat surface in the two bearings, on which one of the insulating branches 120 can slide.

[0039] These insulating branches 120 are flush with the surface of the second bearing and comprise a radial extension at the level of the first bearing so as to reach, at the surface of the first bearing, an insulating ring 126 of the insulating cap 12, connecting the ends of the insulating branches 120 and coming to bear against the shoulder formed by the first bearing.

[0040] The insulating cap 12 comes to bear against an axial end surface of the second bearing of the cylindrical end piece 30 made of steel, to form the end portion of the rotating shaft.

[0041] Returning to [Fig.l], the rotating shaft 3 comprises:

[0042] - the cylindrical tip 30 made of steel provided with insulating branches 120, - a first end portion 122 formed by a first cylindrical portion of the insulating cap 12 from which the insulating branches 120 extend towards the rotor body, this first end portion 122 having a first diameter equal to that of the second bearing of the steel body, and

[0043] - a second end portion 124, formed by a second portion cy lindic of the insulating cap 12 and projecting from the first end portion 122 of the rotating shaft 3, this second end portion 124 being of a second diameter strictly less than the first diameter.

[0044] The insulating cap 12 serves as a support for a first electrical track 10 and a second electrical track 16, made for example of copper. The first electrical track 10 is in the form of a cylindrical cup with a hole in its center. More precisely, the first electrical track 10 comprises a cylindrical part 101 attached to a cylindrical surface of the first end portion 122 of the rotating shaft 3, and a flat part 102 attached to an axial end surface of the first end portion 122 of the rotating shaft 3.

[0045] The second electrical track 16 is in the form of a metal disc in contact with an axial end surface of the second end portion 124 of the rotating shaft 3, this second portion 124 projecting from the first end portion 122 of the rotating shaft 3 through the central hole of the cylindrical cup. formed by the first electrical track 10.

[0046] The insulating cap 12 makes it possible to connect the ends of the rotor windings to the first and second electrical tracks 10, 16 in an electrically insulated manner relative to the steel body of the rotating shaft 3.

[0047] As visible in [Fig.l], two ends 13 of winding wires are welded, one in a positive electrical terminal 14 and the other in a negative electrical terminal 15, these electrical terminals 14, 15 projecting from the insulating ring 126, in which they are connected to electrical conductors respectively 37 and 36, each overmolded in one of the insulating branches 120 of the insulating cap 12.

[0048] The electrical conductor 37 is connected by one of its ends to the positive electrical terminal 14 and by the other of its ends to the second electrical track 16, which is therefore a positive power supply terminal of the wound rotor.

[0049] The electrical conductor 36 is connected by one of its ends to the negative electrical terminal 15 and by the other of its ends to the first electrical track 10, which is therefore a negative power supply terminal of the wound rotor. The electrical conductors 36 and 37 are for example made of copper and the insulating cap 12 for example made of polyamide.

[0050] 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 30 made of steel of the rotating shaft, on certain angular portions thereof, and against the two branches 120 of the insulating cap 12, on the other angular portions of the cylindrical portion 30 made of steel.

[0051] The electrical machine ME also comprises an excitation system housed in a housing 25 made of rigid insulating material, the latter being formed of a base 4 and a cover 5. The base 4 of the housing 25 comprises a first cylindrical wall mounted tightly in the opening of the wall of the casing 1, on the side opposite the rotor body relative to the wall of the casing 1. The ball bearing 2 is arranged axially between the rotor body and the first cylindrical wall of the base 4 of the housing 25.

[0052] A metal ring is secured to the internal surface of the first cylindrical wall of the base 4, to receive a sealing device 9. The sealing device 9, here a lip seal, is bonded by its cylindrical portion to the metal ring, and its lip comes into contact with the cylindrical part 101 of the first electrical track 10. The sealing device 9 prevents the cooling oil of the active parts of the electrical machine ME from reaching further into the housing 25 of the wound rotor excitation system.

[0053] The base 4 of the housing 25 also comprises a flat wall opposite the flat part 102 of the first electrical track 10, this flat wall comprising orifices for the passage of first brushes 51 coming into contact with the flat part 102 of the first electrical track 10. This flat wall has an overall crown shape and is connected at its center to a well formed by the base 4 of the housing 25, at the bottom of which is arranged an orifice for the passage of a second brush 52 coming into contact with the second electrical track 16. The base 4 of the housing 25 therefore has a shape generally complementary to the first and second end portions 122, 124 of the rotating shaft 3, this shape being produced at least in part by the first cylindrical wall of the base 4, the flat wall of the base 4 and the well formed by the base 4.

[0054] The base 4 also comprises a second cylindrical wall for receiving the cover 5 of the housing 25, coaxial with the first cylindrical wall and located opposite the latter relative to the flat wall of the base 4. This second cylindrical wall is open towards the outside of the casing 1.

[0055] It is therefore understood that the brushes 51, 52, which are for example carbon brushes, are arranged, in this embodiment of the invention, axially relative to an axis of rotation X of the rotating shaft.

[0056] The brushes 51, 52 are each mounted so as to move in translation in a metal cage 7, in which an axially mounted pressure spring 6 maintains contact between the brushes 51, 52 and the corresponding electrical track 10 or 16.

[0057] The metal cages 7 each comprise an axial end for attachment to the cover 5 of the housing 25 of the excitation system, on the side opposite the contact surfaces of the brushes 51, 52 with the electrical tracks 10, 16. The axial attachment ends of the metal cages 7 are conductive and each welded to one end of a metal braid 21 extending inside the pressure spring 6 present in the corresponding metal cage 7, the other end of the metal braid 21 being in contact with the corresponding carbon brush.

[0058] This fixing of the metal cages 7 to the cover 5 of the housing 25 is carried out by means of electrical connectors 23 and 24.

[0059] The first electrical connector 23 passes through the cover 5, is secured to it and forms a first power supply terminal for the excitation system. This first electrical connector 23 is itself secured, for example made in one piece, with a metal ring 22 secured to the axial fixing ends of the metal cages 7 of the first brushes 51.

[0060] Similarly, the second electrical connector 24 passes through the cover 5, is secured to it and forms a second power supply terminal of the excitation system. This second electrical connector 24 is secured, on the internal side of the housing 25, to the axial end of attachment of the metal cage 7 of the second brush 52, for example by welding. The second electrical connector 24 here takes the form of a rivet.

[0061] The fact that the brushes 51, 52 and the electrical connectors 23, 24 are integral with the cover 5 of the housing 25, greatly facilitates the assembly of the excitation system in the electrical machine ME, and in particular the positioning of the brushes 51, 52.

[0062] The contact surfaces of the electrical tracks 10, 16 with the brushes 51, 52 respectively are respectively on the one hand the flat surface facing the first brushes 51, of the flat wall 102 of the first electrical track 10, and on the other hand the flat surface of the second electrical track 16 facing the second brush 52. These contact surfaces being orthogonal to the axis of rotation X of the rotor, they allow the first brushes 51 and the second brush 52 to always be in contact with their respective electrical tracks 10 and 16, despite a possible radial displacement of the end portion of the rotating shaft 3 due to the rotating shaft 3 entering into resonance.

[0063] Furthermore, it should be noted that the electrical tracks 10, 16 are concentric but not coplanar in order to respect a minimum electrical insulation distance between them.

[0064] For information purposes, the tracks 10 and 16 are axially offset from each other by approximately 9 mm (millimeters) in this embodiment of the invention, in order to reduce the risk of pollution and short-circuiting linked to wear dust from the carbon brushes 51, 52. The second electrical track 16 here has a substantially smaller surface area than the first electrical track 10, and a second diameter of approximately 8.5 mm. This is linked to the fact that the differential speed of the second electrical track 16 with the second brush 52 is lower than that of the first electrical track 10 with the first brushes 51, and to the fact that the center of the second brush 52 is always theoretically in contact with this first electrical track 10 of small surface area. The sizing of the electrical tracks 10, 16 is of course linked to the intensity of the current which passes through them, which in this embodiment is approximately 25A (amperes).

[0065] The first electrical track 10 is of larger dimensions than the second electrical track 16 since its dimensioning takes into account, in addition to the current which passes through it, the quantity of heat to be dissipated, this quantity of heat being greater than for the second electrical track 16. Indeed, the first electrical track 10 is subjected to greater friction of the brushes due to the greater differential speed between the first brushes 51 and the first electrical track 10 than between the second brush 52 and the second electrical track 16. In addition, the first electrical track 10 must also dissipate the heat due to the friction of the sealing device 9 against the cylindrical part 101 of the first electrical track 10.This sealing device makes it possible in particular to prevent the cooling oil of the electrical machine ME from mixing with the wear dust of the brushes 51, 52, such a mixture being able to give rise to a conductive paste which could generate current leaks in the excitation system.

[0066] In this embodiment, as shown [Fig.4], the excitation system comprises three first brushes 51 angularly and regularly distributed around the axis of rotation X of the rotor, in order to increase the thermal conductivity between the first electrical track 10 and a heat sink 11 arranged in the excitation system, and therefore to better dissipate the calories.

[0067] The heat sink 11 is here a radiator secured to the base 4 of the housing 25. The radiator is for example made of aluminum and comprises a cylindrical portion 110 surrounding the first brushes 51, fixed to the second cylindrical wall of the base 4 of the housing 25, and cooling fins 112 positioned between the first brushes 51.

[0068] Blocks of material 8 (visible [Fig.l]) which are thermally conductive and electrically insulating, for example made of silicone, are glued on the one hand to the metal cages 7 of the first brushes 51 and on the other hand to the cylindrical portion 110 of the heat sink 11. The glue used is for example a silicone-based glue.

[0069] The heat generated by the friction of the lip seal against the first electrical track 10 is thus evacuated via the first brushes 51 and the blocks of material 8, into the heat sink 11, itself cooled by the natural convection of the air. The second brush 52 is not cooled in a similar manner to the first brushes 51 in this embodiment of the invention, its cooling requirement being less due to the fact that the second electrical track 16 only undergoes the friction of the second brush 52. 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 52 and on the other hand with the heat sink 11 or with a cooling plate.

[0070] Furthermore, the housing 25 of the excitation system comprises two holes 19 located in a lower part of the base 4 of the housing, for the passage of wear dust from the first brushes 51 and the second brush 52. A first of the holes 19 is located under the contact surface between the first brushes 51 and the first electrical track 10, in a substantially horizontal portion of a wall of the base 4 connecting the first cylindrical wall of the base 4 to the flat wall of the base 4 comprising the passage orifices of the first brushes 51. A second of the holes 19 is located in a cylindrical wall of the base 4 forming the passage well of the second brush 52, under the contact surface between the second brush 52 and the second electrical track 16.

[0071] Finally, a reverse osmosis membrane 20 is arranged in the upper part of the cover 5 of the housing 25, to prevent the air pressure from building up in the housing while preventing water from passing into the housing.

[0072] 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 variant embodiments of the invention envisaged in this application can be combined to achieve the invention, insofar as these variants are not incompatible with each other.

Claims

Claims

1. Electrical machine (ME) equipped with at least: - a casing (1), - a stator, - a wound rotor comprising a rotor body secured to a rotating shaft (3) about an axis of rotation (X), - a bearing (2) mounted in the casing of the electrical machine (ME) and in which one end of the rotating shaft (3) is rotatably mounted, the end of the rotating shaft (3) comprising at least one electrical track (10, 16), - an excitation system comprising at least one brush (51, 52) arranged in contact with the electrical track (10, 16), the electrical machine (ME) being characterized in that the electrical track (10, 16) comprises a contact surface with the brush (51, 52), arranged orthogonally to the axis of rotation (X).

2. An electrical machine (ME) according to claim 1, comprising two brushes and two electrical tracks, wherein the end of the rotating shaft (3) comprises a first portion (122) of a first diameter, comprising a first axial end surface, and a second portion (124) of a second diameter smaller than the first diameter, projecting from the first portion (122) and comprising a second axial end surface, a first of the electrical tracks (10) being attached to the first axial end surface and a second of the electrical tracks (16) being attached to the second axial end surface.

3. Electrical machine (ME) according to claim 2, in which the contact surface of the first electrical track (10) takes the form of a disc with a hole in its center, the contact surface of the second electrical track (16) taking the form of a solid disc.

4. Electrical machine (ME) according to claim 3, in which the excitation system comprises first brushes (51) in contact with the first electrical track (10), and a single second brush (52) in contact with the second electrical track (16).

5. Electrical machine (ME) according to claim 4, in which the excitation system is provided with a housing (25) comprising a first support (4) proximal to the rotor, the first support (4) comprising a flat annular surface facing the first electrical track (10), This flat annular surface being perforated by the passage holes of the first vanes (51), the first support (4) forming at the center of the flat annular surface, a well for the passage of the second vane (52), the housing (25) comprising a second support (5) distal to the rotor on which metal cages (7) are fixed in which the first and second vanes (51, 52) are mounted for translation.

6. Electrical machine (ME) according to claim 5, in which the excitation system comprises on the one hand a first electrical connector (23) passing through the second support (5) of the housing and in electrical contact inside the housing (25) with a metal ring (22) in contact with the metal cages (7) of the first brushes (51), and on the other hand a second electrical connector (24) passing through the second support (5) of the housing and in electrical contact inside the housing (25) with the metal cage (7) of the second brush (52).

7. Electrical machine (ME) according to claim 5 or 6, in which the housing (25) houses a heat sink (11) and thermally conductive and electrically insulating blocks of material (8), in contact on the one hand with the metal cages (7) of the first brushes (51) and on the other hand with the heat sink (11).

8. Electrical machine (ME) according to any one of claims 5 to 7, in which the first support (4) of the housing comprises at least one hole (19) capable of allowing dust generated by at least one of the brushes (51, 52) to pass through, the hole (19) being arranged under at least one of the contact surfaces of the first or second electrical tracks (51, 52) with the first brushes or respectively the second brush (51, 52).

9. An electrical machine (ME) according to any one of claims 4 to 8, wherein, a wall of the casing (1) separating the rotor body from the excitation system and comprising an opening in which is fixed a sealing device (9) in contact with the end of the rotating shaft (3), the bearing (2) being fixed in a counterbore of the opening and arranged axially between the rotor body and the sealing device (9), the first electrical track (10) comprises a cylindrical part (101), connected to the contact surface of the first electrical track (10) on the side opposite the first brushes (51), and coming into contact with the sealing device (9).

10. An electrical machine (ME) according to any one of claims 2 to 9, wherein the end of the rotating shaft (3) comprises a tip cylindrical (30) made of steel comprising at least two axial grooves (18) in which are fitted branches (120) of an electrically insulating cap (12) on which the first and second electrical tracks (10, 16) are arranged, the cap (12) including electrical conductors (36, 37) each connected by one of their ends to the first or second electrical track (10, 16), and by the other of their ends to the windings of the rotor.

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