Power supply device for a wound rotor

Abstract

Power supply device for a wound rotor. Power supply device for a wound rotor of an electric motor (1) of a motor vehicle, characterized in that it comprises: - a rotor shaft (6), - a bearing housing (29), and - an electrical connection element (10), the electrical connection element comprising: - a body (20) made of an electrically insulating material, - at least one slip ring (16, 17) supported by the body, and - at least one conductor (23, 24) connected on one side to at least one slip ring and intended to be connected on the other side to a coil (5) of the wound rotor, the at least one conductor being at least partially embedded in the body, and - a metallic insert (25) integral with said body, the insert comprising a first surface (26) bearing against the rotor shaft and a second surface (27) bearing against the housing. Figure for the abbreviation: Figure 4

Description

Title of the invention: Power supply device for a wound rotor Technical field of the invention

[0001] The invention relates to a power supply device for a wound rotor of an electric motor of a motor vehicle. The invention also relates to an electric motor for a motor vehicle comprising such a power supply device. The invention further relates to a method for assembling such a power supply device. Prior art

[0002] So-called "electric" or "hybrid" motor vehicles include an electric motor capable of driving the vehicle's drive wheels. Among the various types of electric motors available, wound-rotor electric motors are known. Such electric motors include a rotor equipped with at least one coil for which an electric current flows. To supply the at least one coil with electric current, a rotor shaft generally includes two slip rings cooperating with two brushes. The two slip rings are connected by electrical conductors to the two ends of the at least one coil.

[0003] The rotor shaft is guided in rotation by bearings, generally roller bearings. The bearings are arranged at the interface between an electric motor housing and the rotor shaft. The electrical conductors connecting the slip rings to the coils pass through the central opening of an inner ring of the roller bearing.

[0004] Moreover, since the rotor shaft is likely to rotate at very high speeds, for example at more than 10,000 revolutions per minute, the bearings are under considerable stress and must have an optimal geometry, free from any deformation.

[0005] Thus, the architecture of a wound rotor shaft is complex since it must reconcile the power supply to at least one coil with the integration of roller bearings. Finally, an electric motor comprising such a wound rotor must be compact, reliable, and quiet. Presentation of the invention

[0006] The object of the invention is to provide an electric motor for a motor vehicle comprising a wound rotor remedying the above disadvantages and improving upon known electric motors of the prior art.

[0007] More specifically, a first object of the invention is a power supply device for a wound rotor of an electric motor which is both simple to manufacture and allows for reliable operation of the electric motor, even when the wound rotor rotates at high speed. Summary of the invention

[0008] The invention relates to a power supply device for a wound rotor of an electric motor of a motor vehicle, the power supply device comprising: - a rotor shaft, - a bearing, and - an electrical connection element, the electrical connection element comprising: - a body made of an electrically insulating material, - at least one slip ring supported by the body, and - at least one conductor connected on one side to the slip ring and intended to be connected on the other side to a coil of the wound rotor, the conductor being at least partially embedded in the body, and - a metallic insert, integral with said body, the insert comprising a first surface bearing against the rotor shaft and a second surface bearing against the bearing.

[0009] The at least one slip ring may comprise a first slip ring and a second slip ring. The at least one conductor may comprise a first conductor and a second conductor, the first conductor being connected on one side to the first slip ring and intended to be connected on the other side to a first end of the wound rotor coil, the second conductor being connected on one side to the second slip ring and intended to be connected on the other side to a second end of the wound rotor coil.

[0010] The insert may include a first tubular part having an inner surface and an outer surface, the inner surface and the outer surface being concentric and opposite, the inner surface comprising said first surface and the outer surface comprising said second surface.

[0011] The first part may include a face extending perpendicularly to an axis of rotation of the rotor shaft, said face being in contact against a shoulder of the rotor shaft.

[0012] The insert may include at least one opening, the at least one conductor extending through the at least one opening.

[0013] The insert may include a second part extending axially through at least one collector ring.

[0014] Said second part can extend in the axial extension of the rotor shaft.

[0015] The body can be made of plastic overmolded onto the insert.

[0016] The power supply device may include a dynamic sealing gasket, and the electrical connection element may further include a sealing ring fixed around said body, the sealing gasket cooperating with an external surface of the sealing ring.

[0017] The invention also relates to an electric motor for a motor vehicle comprising a rotor equipped with at least one coil and an electrical power supply device as defined above, the electrical power supply device being configured to electrically supply at least one coil of the wound rotor.

[0018] The invention also relates to a method of assembling an electrical power supply device as defined above, the method comprising: - a step of assembling the electrical connection element to the rotor shaft, then - a step of machining an electrical contact surface of at least one slip ring to make the electrical contact surface coaxial with an axis of rotation of the rotor shaft. Presentation of the figures

[0019] These objects, features and advantages of the present invention will be described in detail in the following description of various particular embodiments presented by way of non-limiting agreement, in relation to the accompanying figures, among which:

[0020] Fig. 1 is a schematic radial cross-sectional view of a part of an electric motor according to an embodiment of the invention.

[0021] Fig. 2 is a perspective view of an electrical connection element of an electrical connection device according to an embodiment of the invention.

[0022] Fig. 3 is a perspective view of the electrical connection element assembled to a rotor shaft, a bearing housing, and a seal.

[0023] Fig. 4 is a perspective view of an insert, two conductors and a sealing ring of the electrical connection element.

[0024] Fig. 5 is a perspective view of the two conductors and the sealing ring of the electrical connection element. Detailed description

[0025] Figure 1 illustrates, by way of a cross-sectional view, a portion of an electric motor 1 according to an embodiment of the invention. The electric motor 1 is intended to drive the drive wheels of a motor vehicle. The electric motor 1 can, for example, be powered by an electric battery, in particular a lithium-ion battery. The electric motor 1 comprises a housing 2, a stator 3 fixed attached to the casing 2, and a rotor 4 mobile in rotation relative to the casing 2 and the stator 3 around an axis of rotation X.

[0026] At any point, an axial direction is defined as a direction parallel to the axis of rotation X. An axial direction is illustrated in particular by arrow A in Figures 1 and 2. A radial direction is defined as a direction perpendicular to the axis of rotation X and passing through the axis of rotation X. A radial direction is illustrated in particular by arrow R in Figures 1 and 2. A radial cut is a cut made parallel to the axis of rotation X. An axial cut is a cut made perpendicular to the axis of rotation X.

[0027] The rotor 4 is a wound rotor, that is, it comprises at least one coil 5, or winding of an electric wire. The coil 5 is intended to carry an electric current. The flow of an electric current in the coil 5 produces a magnetic field capable of interacting with the stator 3, leading to rotation of the rotor 4 about the axis of rotation X. The rotor 4 comprises a rotor shaft 6 and a ferromagnetic core. The ferromagnetic core may include a set of radial protrusions, in particular with a "T"-shaped cross-section, around which the coils 5A are formed.

[0028] According to the embodiment presented, the electric motor 1 is of the radial flux type, meaning that the magnetic flux between the stator 3 and the rotor 4 is oriented radially. Alternatively, the invention could be transposed to an axial flux type motor, that is to say, an electric motor in which the magnetic flux is oriented parallel to the axis of rotation X.

[0029] The rotor shaft 6 comprises two opposing ends. A first end may include a rotational drive means, for example, splines. The rotational drive means is intended to be mechanically coupled to a transmission system to drive the vehicle's drive wheels. A second end of the rotor shaft 6, particularly visible in [Fig. 1], accommodates an electrical connection element 10 configured to supply the coils 5 with electrical current.

[0030] The electrical connection element 10 is also clearly visible in [Fig. 2]. The electrical connection element 10 comprises a first slip ring 16 and a second slip ring 17. The two slip rings 16, 17 cooperate respectively with two brushes 18, 19 (visible in [Fig. 1]) to collect an electric current. The two slip rings may be, for example, copper rings. The two slip rings 16, 17 are supported by a body 20 of the electrical connection element 10. The body 20 is made of an electrically insulating material, in particular plastic. The body 20 has a tubular shape centered on the axis of rotation X.

[0031] The electrical connection element 10 also includes a first electrical connector 21 and a second electrical connector 22. The two electrical connectors 21 and 22 are electrically connected to two ends of at least one coil 5. The electrical connectors 21 and 22 can be crimped around two ends of an electrical wire of the coil 5. In Figures 1 and 2, the electrical connectors 21 and 22 are shown in a crimping-ready state. The two electrical connectors 21 and 22 extend radially.

[0032] The electrical connection element 10 also includes a first electrical conductor 23 and a second electrical conductor 24. The first conductor 23 electrically connects the first slip ring 16 to the first electrical connector 21. The second conductor 24 electrically connects the second slip ring 17 to the second electrical connector 22. The two conductors 23 and 24 are particularly visible in Figures 4 and 5. They are at least partially embedded in the body 20 so as to be electrically insulated, in particular from the rotor shaft 4. The thickness of the plastic material surrounding the conductors 23 and 24 is sufficient to ensure effective electrical insulation. The conductors 23 and 24 may be rectangular or circular in cross-section, also known as busbars. The conductors 23 and 24 may preferably be made of copper.They may preferably include a cross-section greater than or equal to 4mm² in order to conduct a high-intensity electric current to power the rotor coils 5.

[0033] The electrical connection element 10 also includes a metal insert 25, integral with the body 20. The insert 25 can be, for example, made of steel or aluminum. It can be machined from a metal block. The insert 25 not only stiffens the electrical connection element 10, but also provides interfaces for assembling the electrical connection element 10, as will be seen later.

[0034] The insert 25 comprises a first surface 26 bearing against the rotor shaft 6. The The first surface 26 is clearly visible in [Fig. 4]. The first surface 26 is, in particular, a surface of a cylinder of revolution centered on the axis of rotation X. The first surface 26 cooperates with a portion 11 of the rotor shaft. The portion 11 is formed at the second end of the rotor shaft 6. The portion 11 is provided with a press-fit surface 39 onto which the insert 25 is pressed, in particular shrink-fitted, via its first surface 26. The press-fit surface 39 is therefore also a surface of a cylinder of revolution centered on the axis of rotation X. A certain overlap between the diameter of the first surface 26 and the diameter of the press-fit surface 39 is advantageously provided to ensure the secure retention of the electrical connection element 10 on the rotor shaft 6. This assembly also has the advantage of providing a sealed interface between the connection element electrical 10 and rotor shaft 6. Therefore, there is no need to integrate static sealing means such as O-rings at the interface between the rotor shaft 6 and the electrical connection element 10.

[0035] The rotor shaft 6, equipped with the electrical connection element 10, is supported and guided in rotation about the axis of rotation X by means of a bearing 29. The bearing 29 is arranged at the interface between the housing 2 and the electrical connection element 10. The bearing 29 may be a ball bearing. The bearing 29 may have standard dimensions. The bearing 29 includes an inner ring 30 pressed, in particular shrunk, onto a second surface 27 of the insert 25. The second surface 27 thus bears against the bearing 29. As before, a certain overlap between the diameter of the second surface 27 and the diameter of the inner ring 30 is advantageously provided to ensure the proper retention of the bearing 29 on the electrical connection element 10.This assembly also has the advantage of providing a sealed interface between the electrical connection element 10 and the bearing 29. There is therefore no need to integrate static sealing means such as O-rings at the interface between the inner ring 30 of the bearing 29 and the electrical connection element 10. Finally, the bearing 29 also includes an outer ring 31 pressed, in particular shrink-fitted, against a pressing surface formed on the housing 2.

[0036] It is therefore understood that the rotor shaft 6 is guided in rotation around the axis of rotation X by means of a bearing support, the electrical connection element 10 being interposed between the bearing support 29 and the rotor shaft 6. The bearing support 29 is therefore without radial contact with the rotor shaft 6. The insert 25 being metallic, it has a significant rigidity which efficiently transmits the forces between the bearing support 29 and the rotor shaft 6.

[0037] As can be clearly seen in [Fig. 4], the insert 25 comprises a first tubular part 28, having an inner surface and an outer surface concentric with the inner surface. The inner and outer surfaces are two opposing surfaces. The inner surface comprises the first surface 26 and the outer surface comprises the second surface 27.

[0038] The first part 28 also includes a face 32 extending perpendicularly to the axis of rotation X. The face 32 is in contact against a shoulder 33 of the rotor shaft 6. The contact between the face 32 and the shoulder 33 allows the electrical connection 10 to be positioned relative to the rotor shaft 6 along the axis of rotation X.

[0039] The insert 25, and in particular the first part 28 of the insert 25, comprises a first opening 34 and a second opening 35 through which the first conductor 23 and the second conductor 24 extend respectively. The openings 34, 35 are holes through the insert 25. The conductors 23, 24 are not in contact with the walls delimiting the openings 34, 35. Advantageously the electrically insulating material forming the body 20 extends inside the openings 34 and 35, between the conductors 23, 24 and the walls delimiting these openings 34, 35.

[0040] The openings 34, 35 lead to the face 32 of the first part 28. The second surface 27 is not interrupted by the openings 34, 35. Thus, the bearing housing 29 benefits from a completely cylindrical and uninterrupted surface in contact with its inner ring 30. This prevents deformation of the inner ring 30 when it is fitted onto the insert 25. This is important for maintaining optimal operation of the bearing housing 29 when the rotor shaft 6 rotates at very high speed. In other words, the 360° bearing span makes it possible to reduce a second-order harmonic and to avoid or reduce the deformation of the inner ring of the bearing housing 29. The openings 34, 35 also lead to the first surface 26. The first surface 26 is thus interrupted by grooves in which the conductors 23, 24 take place and which are filled by the insulating material forming the body.

[0041] As can be seen in Figures 1 and 4, the insert 25 also includes a second part 36 extending axially through the two slip rings 16, 17. The second part 36 extends along the axial length of the rotor shaft 6. The second part 36 is integral with the first part 28 and adjacent to the first part. The first part 28 and the second part form a single piece, for example, obtained by machining. The second part 36 supports the body 20 and stiffens the electrical connection element 10, particularly with respect to the radial forces that the brushes 18, 19 can exert on the slip rings 16, 17. The conductors 23, 24 extend outside the first part. Advantageously, the second part 36 includes radially extending retaining means 37, forming an axial stop for the body 20. Thus, the body 20 is not at risk of disassembling from the insert 25.

[0042] The insert 25 also includes a wall 38 extending perpendicularly to the axis of rotation X and connecting the first portion 28 to the second portion 36. The wall 38 and the first surface 26 form a blind cavity, in the shape of a cylinder of revolution, in which the portion 11 of the rotor shaft is located. The wall 38 may be without contact with the rotor shaft 6, the axial stop of the electrical connection element 10 being achieved by the cooperation of the face 32 with the shoulder 33.

[0043] Furthermore, the electric motor 1 also includes a dynamic sealing gasket 40 arranged at an interface between the housing 2 and the electrical connection element 10. Advantageously, the electrical connection element 10 includes a sealing ring 41 fixed around the body 20, the sealing gasket 40 cooperating with The outer surface of the sealing ring 41 has a revolution shape and is designed to contact a lip of the sealing gasket 40. The sealing ring 41 is adjacent to the slip rings 16 and 17. The sealing ring 41 is positioned at the level of the second part 36 of the insert 25, more precisely between the slip ring 17 and the wall 38. Advantageously, the sealing ring 41 includes an inner surface provided with grooves 42, for example, of helical shape. The body 20 is positioned in these grooves, particularly during a plastic injection molding process, which improves the ring's grip on the body 20. Advantageously, the ring 41 is electrically insulated because it is supported exclusively by the body 20, which is made of insulating material.Thus, if metallic dust from the friction of the brushes on the slip rings 16, 17 reaches the ring 41, there is no risk of generating a short circuit.

[0044] To manufacture the electrical connection element 10, the following procedure can be used. First, an insert 25 can be manufactured, in particular by machining a metal block. Advantageously, the insert 25 may include a centering hole 43 useful for centering the first surface 26 and the second surface 27 during the manufacture of the insert 25. Next, the slip rings 16, 17, the conductors 23, 24, and the sealing ring 4L can be provided. The ends of the conductors 23, 24 can be welded respectively to the conductive rings 16, 17. Then, these components 16, 17, 23, 24, 25, 41 can be placed in a mold. Molten plastic material can then be injected into the mold to form the body 20 of the electrical connection element. Thus, the body 20 is overmolded onto the insert 25. Thus, the electrical connection element 10 is simple to manufacture.Its various components 16, 17, 20, 23, 24, 25, 41 benefit from excellent cohesion with each other. The slip rings and conductors are effectively electrically insulated from their environment.

[0045] To assemble the power supply device, the electrical connection element 10 can first be assembled to the rotor shaft, in particular by shrink-fitting the insert 25 onto the portion 11 of the rotor shaft 6. Next, the bearing 29 can be assembled to the electrical connection element 10. In particular, the inner ring 30 can be shrink-fitted onto the second surface 27 and positioned against the shoulder 33. The assembly thus obtained can then be assembled to the housing 2 of the electric motor 1. Finally, the electrical contact surfaces of the slip rings 16, 17 (i.e., their external surfaces) can be machined, in particular ground, to improve the coaxiality of the electrical contact surfaces of the slip rings 16, 17 with the axis of rotation X.

[0046] Finally, thanks to the invention, a simple and compact power supply device is available for the coils of a wound rotor. The power supply device allows the coils of the wound rotor to be powered without disrupting the proper operation of a bearing supporting the rotor shaft and / or a sealing means at the interface between the housing and the rotor shaft.

Claims

Demands

1. Power supply device for a wound rotor of an electric motor (1) of a motor vehicle, characterized in that it comprises: - a rotor shaft (6), - a bearing housing (29), and - an electrical connection element (10), the electrical connection element comprising: - a body (20) made of an electrically insulating material, - at least one slip ring (16, 17) supported by the body, and - at least one conductor (23, 24) connected on one side to at least one slip ring and intended to be connected on the other side to a coil (5) of the wound rotor, the at least one conductor being at least partially embedded in the body, and - a metallic insert (25) integral with said body, the insert comprising a first surface (26) bearing against the rotor shaft and a second surface (27) bearing against the housing.

2. Power supply device according to the preceding claim, characterized in that: - at least one slip ring comprises a first slip ring (16) and a second slip ring (17), and in that - at least one conductor comprises a first conductor (23) and a second conductor (24), the first conductor being connected on one side to the first slip ring and intended to be connected on the other side to a first end of the wound rotor coil, the second conductor being connected on one side to the second slip ring and intended to be connected on the other side to a second end of the wound rotor coil

3. Power supply device according to any one of the preceding claims, characterized in that the insert (25) comprises a first tubular part (28) having an inner surface and an outer surface, the inner surface and the outer surface being concentric and opposite, the inner surface comprising said first surface and the outer surface comprising said second surface.

4. Power supply device according to the preceding claim, characterized in that the first part (28) comprises a face (32) extending perpendicularly to an axis of rotation (X) of the rotor shaft (6), said face being in contact against a shoulder (33) of the rotor shaft.

5. Power supply device according to any one of the preceding claims, characterized in that the insert (25) comprises at least one opening (34, 35), at least one conductor (23, 24) extending through at least one opening.

6. Power supply device according to any one of the preceding claims, characterized in that the insert (25) comprises a second part (36) extending axially through at least one collector ring (16, 17).

7. Power supply device according to the preceding claim, characterized in that said second part (36) extends in the axial continuation of the rotor shaft (6).

8. Power supply device according to any one of the preceding claims, characterized in that the body (20) is made of a plastic overmolded on the insert (25).

9. Power supply device according to any one of the preceding claims, characterized in that it comprises a dynamic sealing gasket (40), and in that the electrical connection element (10) further comprises a sealing ring (41) fixed around said body (20), the sealing gasket cooperating with an external surface of the sealing ring.

10. Electric motor (1) for a motor vehicle comprising a rotor (4) equipped with at least one coil (5) and an electric power supply device according to any one of the preceding claims, the electric power supply device being configured to electrically supply at least one coil of the wound rotor.

11. Method of assembling an electrical power supply device according to any one of claims 1 to 9 characterized in that it comprises: - a step of assembling the electrical connection element (10) to the rotor shaft (6), then - a step of machining an electrical contact surface of at least one slip ring (16, 17) to make the electrical contact surface coaxial with an axis of rotation (X) of the rotor shaft.