Device for supplying electrical power to a wound rotor

Abstract

Disclosed is a device for supplying electrical power to a wound rotor of an electric motor (1) of a motor vehicle, characterised in that it comprises: - a rotor shaft (6), - a bearing, in particular a rolling-contact bearing (29), and - an electrical connection element (10), the bearing being push-fitted onto on a push-fitting surface (33) of the rotor shaft, the electrical connection element comprising: - a body (20) made of an electrically insulating material, - at least one slip ring (16, 17), and - at least one conductor (23B, 24B, 23C, 24C) connected on the one hand to the at least one slip ring and intended to be connected on the other hand to a coil (5) of the wound rotor.

Description

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 in a motor vehicle. The invention also relates to an electric motor for a motor vehicle comprising 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 motors are well-known. Such electric motors consist of 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 typically includes two slip rings, each paired with a brush. 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, usually roller bearings. The bearings are arranged at the interface between the 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] Furthermore, as 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 significant stress and must have an optimal geometry, free from any deformation.

[0005] Thus, the architecture of a wound rotor shaft is complex, as it must accommodate the power supply to at least one coil while integrating roller bearings. Finally, an electric motor with 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 simple and efficient electrical power supply device for a wound rotor of an electric motor. to obtain 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, in particular a roller bearing, and - an electrical connection element, the bearing being fitted onto a mounting surface of the rotor shaft, the electrical connection element comprising: - a body made of an electrically insulating material, - at least one collector ring, and - at least one conductor connected on one side to at least one slip ring and intended to be connected on the other side to a coil of the wound rotor, said body comprising at least one arm, the at least one conductor comprising a first portion extending axially inside the at least one arm, the rotor shaft comprising at least one groove inside which extends the at least one arm, the at least one groove crossing the mounting surface, a section of the first portion of the at least one conductor comprising a radial dimension greater than or equal to a tangential dimension.

[0009] At least one slip ring may comprise a first slip ring and a second slip ring. 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. At least one arm may comprise a first arm and a second arm, the first conductor comprising a first portion extending axially inside the first arm, the second conductor comprising a first portion extending axially inside the second arm.At least one groove may include a first groove within which the first arm extends, and a second groove within which the second arm extends. A section of the first portion of the first conductor and a section of the first portion of the second conductor may include a radial dimension greater than or equal to a tangential dimension.

[0010] The first portion of at least one conductor may include a rectangular section, a long side of the rectangular section extending radially, and a short side of the rectangular section extending tangentially.

[0011] The at least one conductor may include a connector intended to be connected to the coil of the wound rotor, and a third portion, the third portion extending radially between the first portion and the connector, the first portion including a bend through which the third portion is connected to the first portion.

[0012] Alternatively, at least one conductor may include a circular section.

[0013] At least one conductor may have a cross-section greater than or equal to 4mm 2 , and at least one groove may include a width less than or equal to 8mm, preferably less than or equal to 7mm.

[0014] The power supply device may further include a third ring fixed around said body and a dynamic sealing gasket in contact with an outer perimeter of the third ring.

[0015] 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. Presentation of the figures

[0016] These objects, features and advantages of the present invention will be described in detail in the following description of various specific embodiments presented by way of non-limiting example, in relation to the accompanying figures, among which:

[0017] Fig. 1 is a schematic radial cross-sectional view of part of an electric motor according to a first embodiment.

[0018] Figure [Fig. 2] is a perspective view of part of a rotor of the electric motor in Figure [Fig. 1].

[0019] Fig. 3 is a perspective view of an electrical connection element of the electric motor of Fig. 1, the electrical connection element comprising two slip rings and two conductors connected to the slip rings.

[0020] Fig. 4 is a perspective view of two slip rings and two conductors connected to the slip rings of an electrical connection element according to a second embodiment.

[0021] Fig. 5 is a schematic axial cross-sectional view of the electrical connection element according to the first embodiment.

[0022] Fig. 6 is a schematic axial cross-sectional view of the electrical connection element according to the second embodiment.

[0023] Fig. 7 is a schematic axial cross-sectional view of the electrical connection element according to a third embodiment. Detailed description

[0024] Figure 1 illustrates, in cross-section, a portion of an electric motor 1 according to a first embodiment. 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 rigidly to the housing 2, and a rotor 4 free to rotate relative to the housing 2 and the stator 3 about an axis of rotation X.

[0025] At any point, an axial direction is defined as a direction parallel to the axis of rotation X. An axial direction is illustrated 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 it. A radial direction is illustrated by arrow R in Figures 1 and 2. A tangential direction is defined as a direction perpendicular to both the axial and radial directions. A tangential direction is illustrated by arrow T in Figure 2. The axial, radial, and tangential directions define an orthogonal coordinate system. This system is a local coordinate system that depends on a given point. A radial section is a section made parallel to the axis of rotation X. An axial section is a section made perpendicular to the axis of rotation X.

[0026] The rotor 4 is a wound rotor, meaning it comprises at least one coil 5, or winding of an electric wire. The coil 5 is designed 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 7, both clearly visible in [Fig. 2]. The ferromagnetic core 7 includes a set of radial protrusions 8, notably with a T-shaped cross-section, around which the coils 5 are formed. According to the embodiment illustrated in [Fig. 2], the ferromagnetic core 7 comprises four radial protrusions 8. Alternatively, this number could be different.

[0027] 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 adapted to an axial flux type motor. that is to say an electric motor whose magnetic flux is oriented parallel to the axis of rotation X.

[0028] The rotor shaft 6 comprises two opposing ends. The first end includes a rotational drive means, notably splines 9. The rotational drive means is intended to be mechanically coupled to a transmission system to drive the vehicle's drive wheels. The second end of the rotor shaft 6, particularly visible in [Fig. 1], accommodates an electrical connection element 10 configured to supply electrical current to the coils 5.

[0029] The second end of the rotor shaft 6 comprises a first portion 11, a second portion 12, and a third portion 13. The three portions 11, 12, and 13 are generally cylindrical in shape. A diameter of the first portion is strictly greater than a diameter of the second portion. A diameter of the second portion is strictly greater than a diameter of the third portion. Furthermore, the second end of the rotor shaft 6 comprises two grooves 14, 15, in particular diametrically opposed, extending parallel to the axis of rotation X along the first portion 11 and the second portion 12. The grooves 14, 15 extend radially and may have a generally rectangular cross-section. The width L1 of a groove is defined as the distance separating its two parallel edges in the tangential direction. According to this first embodiment, the width L1 of each groove 14, 15 can be approximately 10 mm.

[0030] The electrical connection element 10 is shown in isolation in [Fig. 3]. 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. These two slip rings can, for example, be made of copper. These two slip rings 16, 17 are arranged on a body 20 of the electrical connection element 10. This body 20, or housing 20, is made of an electrically insulating material, in particular plastic.

[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 from the coil 5. In [Fig. 3], 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 23A electrical conductor and a second 24A electrical conductor. The first conductor Electrical conductor 23 A electrically connects the first slip ring 16 to the first electrical connector 21. The second electrical conductor 24 A electrically connects the second slip ring 17 to the second electrical connector 22.

[0033] The body 20 comprises a tubular portion around which the two slip rings 16 and 17 are arranged. Static sealing means, in particular O-rings 25, may also be arranged around this tubular portion. The tubular portion is then extended by two arms 26, 27, in particular diametrically opposed, within which the first conductor 23A and the second conductor 24A extend respectively. The two arms 26, 27 may be connected by an annular ring 28.

[0034] The electrical connection element 10 is assembled to the rotor shaft 4 so that the two arms 26, 27 are positioned respectively in the two grooves 14, 15. Each arm 26, 27 thus has a width L2 in the tangential direction that is slightly less than the width L1 of the grooves 14, 15. In this case, the width L2 of the arms 26, 27 is therefore also approximately 10 mm. The tubular portion of the body 20 supporting the two slip rings 16 and 17 and the O-rings 25 thus extends to the height of the first portion 11 of the rotor shaft 6.

[0035] The rotor shaft 6 is supported and guided in rotation by a bearing, in particular a bearing 29. The bearing 29 is arranged at the interface between the rotor shaft 6 and the housing 2. The bearing 29 comprises an inner ring 30 mounted on a mounting surface 33 of the rotor shaft 6. The mounting surface 33 is formed in particular on the second portion 12 of the rotor shaft 6. The mounting surface 33 has a cylindrical shape of revolution and is traversed by grooves 14 and 15, i.e., interrupted by grooves 14 and 15. Thus, the inner ring 30 does not benefit from continuous support around its entire circumference. Arms 26, 27 do not support, or only in a non-significant way, the inner ring 30. Arms 26, 27 may be without contact with the inner ring 30.

[0036] Furthermore, the electric motor 1 also includes a dynamic seal 31 arranged at an interface between the housing 2 and the inner ring 30. The inner ring 30 thus comprises, on the one hand, a raceway cooperating with the bearings of the roller bearing housing 29, and on the other hand, an external bearing surface in contact with the seal 31. The inner ring 30 of the roller bearing housing 29 is wider than the outer ring of this bearing along the axis of rotation X. Moreover, the O-rings 25 are in contact with a bore of the inner ring 30.

[0037] According to one embodiment, the outer bearing surface in contact with the sealing ring 31 could be formed on a third ring, separate from the inner ring 30. The third ring could be fitted around the body 20 of the electrical connection element 10, and cover the O-rings 25. Such an alternative would simplify the manufacture of the bearing housing 29.

[0038] Finally, secondary sealing means, in particular secondary O-rings 32, are provided at the interface between the second end of the rotor shaft 4 and a bore of the electrical connection element 10.

[0039] 23A and 24A conductors are rectangular in cross-section, also known as busbar conductors. 23A and 24A conductors are preferably made of copper. They preferably have a cross-section greater than or equal to 4 mm². 2in order to conduct a high-intensity electric current to power the rotor coils 5. The conductors 23A and 24A are embedded in the plastic body, specifically within the arms 26 and 27, so as to be electrically insulated from the rotor shaft 4 and the bearing housing 29. The thickness of the plastic material surrounding the conductors 23A and 24A is determined to ensure effective electrical insulation of the conductors. The conductors 23A and 24A each comprise a first portion 34 extending axially and a second portion 35 extending radially. Each conductor thus includes a bend 36, approximately at 90°, between its first portion 34 and its second portion 35. Similarly, the arms comprise an axial portion 37 and a radial portion 38 connected by a bend 39. The first portion 34 extends at least partially into the axial portion 37 of the corresponding arm.The second portion 35 extends at least partially into the radial part 38 of the corresponding arm.

[0040] The rectangular shape of the conductors 23A and 24A is such that the longer side of the rectangular shape always extends parallel to the tangential direction. This orientation of the rectangular shape of the conductors is particularly easy to implement since it simplifies the construction of the bends 36, simplifies the connection between the conductors 23A and 24A and their respective slip rings, and results in a reduced radial footprint.

[0041] Figure 5 clearly shows the arrangement of conductors 23A and 24A within the electrical connection element 10. At grooves 14 and 15, the tangential dimension of each conductor 23A and 24A can be approximately 4 mm, while the radial dimension can be approximately 1 mm. The rectangular orientation of conductors 23A and 24A necessitates a relatively large width L2 for arms 26 and 27. Consequently, the width L1 of grooves 14 and 15 is also relatively large, and the mounting surface 33 is correspondingly reduced. The lack of support for the inner ring 30 at grooves 14 and 15 can lead to a lack of circularity in the inner ring 30, and therefore to undesirable noise when the rotor shaft rotates at high speed. This lack of circularity of the inner ring 30 (or where applicable the third ring with which the sealing ring 31 cooperates) can lead to poor sealing of the electric motor 1.

[0042] Finally, according to this first embodiment, a simple and compact power supply device is available for the coils of a wound rotor. However, the relatively large width L1 of the grooves 14, 15 can lead to malfunctions of the electric motor 1.

[0043] Figure 4 schematically illustrates a second embodiment of the conductors, now referred to as 23B and 24B. Conductors 23B and 24B are integrated in place of the previously described conductors 23A and 24A. The shape of the body 10 is adapted accordingly to conform to the shape of conductors 23B and 24B. The shapes of conductors 23B and 24B can be symmetrical. Therefore, in the remainder of this description, we will limit ourselves to describing the shape of conductor 23B, knowing that the shape of conductor 24B can be deduced by symmetry.

[0044] As with the 23A and 24A conductors described previously, conductor 23 has a rectangular cross-section. Conductor 23B is preferably made of copper. It preferably has a cross-section greater than or equal to 4 mm². 2in order to conduct a high-intensity electric current to power the rotor coils 5. The length of the shorter side of the rectangular section is strictly less than the length of the longer side of the rectangular section. Preferably, the length of the shorter side of the rectangular section is less than or equal to 50% of the length of the longer side of the rectangular section. For example, the length of the shorter side of the rectangular section could be on the order of 1 mm, and the length of the longer side of the rectangular section could be on the order of 4 mm. The conductor 23B is embedded in the plastic body 20, and in particular inside the arm 26, so as to be electrically insulated from the rotor shaft 4 and the bearing 29. The thickness of the plastic material surrounding the conductor 23B is sufficient to ensure effective electrical insulation.

[0045] The conductor 23B can be divided into three portions 41, 42, 43. A first portion 41 extends axially inside the arm 26, in particular inside the axial part 37 of the arm 26. A second portion 42 extends axially inside the body 20, in particular inside the tubular part of the body 20. The second portion 42 extends axially between the first portion 41 and the slip ring 16. Finally, a third portion 43 also extends radially inside the arm 26, in particular in the radial part 38 of the arm.

[0046] As can also be clearly seen in [Fig. 6], the rectangular shape of the first portion 41 of conductor 23B is such that the longer side extends radially and the shorter side extends tangentially. In other words, the cross-section of the first portion 41 of conductor 23B comprises a radial dimension strictly greater than to its tangential dimension. Preferably, the cross-section of the first portion 41 of the conductor 23B has a radial dimension greater than or equal to twice its tangential dimension. Such an orientation of the rectangular shape of the first portion 41 of the conductor 23B minimizes the tangential bulk of the first portion 41 of the conductor 23B. Thus, the width L2 of the arm 26 can be reduced compared to the first embodiment. The width L1 of the groove 15 can also be reduced compared to the first embodiment. The width L1 can then be less than or equal to 8 mm, preferably less than or equal to 7 mm. Consequently, the mounting surface 33 receiving the inner ring 30 of the bearing is larger compared to the first embodiment. In particular, the area of ​​the mounting surface 33 can be increased by approximately 5% to 10% compared to the first embodiment.Therefore, the inner ring 30 is better supported and less likely to deform.

[0047] At the second section 42, the conductor 23B also has a rectangular shape. However, the longer side of the rectangular section extends tangentially, and the shorter side extends radially. This is not problematic because the second section 42 does not extend into the arm 26 but into the tubular part of the body. Therefore, this orientation does not require widening the arm 26. On the contrary, this orientation allows for a relatively thin tubular section in the radial direction.

[0048] The first portion 41 and the second portion 42 may be two separate portions in contact with each other to allow the passage of an electric current. The first portion 41 and the second portion 42 may, in particular, be nested one inside the other. The first portion 41 and the second portion 42 may each comprise a notch, the two notches being nested one inside the other. Alternatively, the first portion 41 and the second portion 42 could form a single monolithic unit.

[0049] At the third section 43, the conductor 23B also includes a rectangular shape. In this third section, the longer side of the rectangular section extends tangentially, and the shorter side extends axially. This can lead to the radial portion 38 of the arm 26 being wider tangentially than the axial portion 37. This is not problematic because the radial portion 38 of the arm extends into part of the groove 14 at the first section 11. The groove 14 can therefore be wider at the first section 11 while remaining relatively narrow at the insertion surface 33, which belongs to the second section 12. Such an orientation of the third section 43 of the conductor 23B facilitates crimping the connector 21 around one end of the coil 5.

[0050] The first portion 41 and the third portion 43 can be two separate portions in contact with each other to allow the passage of an electric current. The first portion 41 and the third portion 43 can, in particular, be nested one inside the other. The first portion 41 and the third portion 43 can each comprise a notch, the two notches being nested one inside the other. Alternatively, the first portion 41 and the third portion 43 could form a single monolithic unit.

[0051] Advantageously, the first portion includes an elbow 46 through which the third portion 43 is connected to the first portion 4L. A section of the elbow also includes a rectangular shape whose shorter side is parallel to the tangential direction and whose longer side is perpendicular to the tangential direction. In other words, the elbow 46 extends in the same radial plane as the first portion 4L.

[0052] To manufacture conductor 23B, the first portion 41, the second portion 42, and the third portion 43 can be supplied as three separate sections. These three portions 41, 42, and 43 can then be joined together. Alternatively, a pattern roughly in the shape of an L can be cut from a plate of constant thickness, in particular a copper plate.

[0053] Figure 7 illustrates a third embodiment of the conductors, now designated 23C and 24C. Conductors 23C and 24C are integrated in place of the previously described conductors 23A and 24A. The shape of the body 10 is adapted accordingly to conform to the shape of conductors 23C and 24C. According to this third embodiment, conductors 23C and 24C have a circular cross-section, which is unusual for supplying an electric current to a wound rotor. Conductors 23C and 24C thus include an axial portion whose cross-section has a radial dimension equal to its tangential dimension.

[0054] Conductors 23C and 24C are also preferably made of copper. They also preferably have a cross-section greater than or equal to 4 mm². 2in order to conduct a high-intensity electric current to power the rotor coils 5. The diameter of the circular cross-section of conductors 23C and 24C can, for example, be approximately 2.3 mm. Conductors 23C and 24C are embedded in the plastic body 20, and in particular inside arms 26 and 27, so as to be electrically insulated from the rotor shaft 4 and the bearing housing 29. The thickness of the plastic material surrounding conductors 23C and 24C is sufficient to ensure effective electrical insulation. This third embodiment has the advantage of allowing a reduction in the width L2 of arms 26, 27 compared to the first embodiment, while also being simple to implement.

[0055] Finally, thanks to the invention, a simple-to-manufacture and assembly power supply device for a wound rotor of an electric motor in a motor vehicle is available. This power supply device allows the wound rotor coils to be powered without disrupting the proper functioning of a bearing supporting the rotor shaft and / or a sealing device 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, in particular a bearing with rollers (29), and - an electrical connection element (10), the bearing being fitted onto a mounting surface (33) of the rotor shaft, the electrical connection element comprising: - a body (20) made of an electrically insulating material, - at least one collector ring (16, 17), and - at least one conductor (23B, 24B, 23C, 24C) 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, said body comprising at least one arm (26, 27), the at least one conductor comprising a first portion (41) extending axially inside the at least one arm, the rotor shaft comprising at least one groove (14, 15) inside which the at least one arm extends, the at least one groove crossing the mounting surface, a section of the first portion of the at least one conductor comprising a radial dimension greater than or equal to a tangential dimension.

2. Power supply device according to the preceding claim, characterized in that: - at least one collecting ring comprises a first collecting ring (16) and a second collecting ring (17), - at least one conductor comprises a first conductor (23B, 23C) and a second conductor (24B, 24C), 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, - at least one arm comprises a first arm (26) and a second arm (27), the first conductor comprising a first portion (41) extending axially inside the first arm, the second conductor comprising a first portion extending axially inside the second arm, - at least one groove comprises a first groove (14) within which the first arm extends, and a second groove (15) within which the second arm extends, a section of the first portion of the first conductor and a section of the first portion of the second conductor comprising a radial dimension greater than or equal to a tangential dimension.

3. Power supply device according to any one of the preceding claims, characterized in that the first portion (41) of at least one conductor (23B, 24B) comprises a rectangular section, a long side of the rectangular section extending radially, and a short side of the rectangular section extending tangentially.

4. Power supply device according to the preceding claim, characterized in that at least one conductor comprises a connector (21, 22) intended to be connected to the coil (5) of the wound rotor, and a third portion (43), the third portion extending radially between the first portion (41) and the connector, the first portion comprising an elbow (46) through which the third portion is connected to the first portion.

5. Power supply device according to any one of claims 1 or 2, characterized in that at least one conductor (23C, 24C) comprises a circular section.

6. Power supply device according to any one of the preceding claims, characterized in that at least one conductor (23B, 24B, 23C, 24C) comprises a cross-section greater than or equal to 4 mm² 2, and in that at least one groove comprises a width less than or equal to 8mm, preferably less than or equal to 7mm.

7. Power supply device according to any one of the preceding claims, characterized in that it further comprises a third ring fixed around said body and a dynamic sealing gasket (31) in contact with an outer periphery of the third ring.

8. 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.

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