Device for cooling a contactless excitation system for a wound rotor of an electric motor for a motor vehicle

Abstract

The invention relates to a device for cooling a contactless excitation system (3) for a wound rotor (2) of an electric motor of a motor vehicle, the device comprising a lubrication circuit (4) for lubricating a bearing (6) supporting the rotor and a branch (11) of the lubrication circuit (4) in order to direct a first portion of a lubricant liquid circulating in the lubrication circuit (4) to the excitation system (3). It comprises a guide surface (13) capable of recovering a second portion of the lubricant liquid downstream of the bearing (6) and of directing this second portion to the excitation system (3).

Description

Description Title of the invention: Cooling device for an excitation system of a contactless coil rotor of an electric motor for a motor vehicle Technical field

[0001] The present invention relates to the field of cooling the parts of an electric motor and, more particularly, the optimization of the cooling circuit of a contactless excitation system of a wound rotor of an electric motor.

[0002] An application of the invention relates to the cooling of a contactless excitation system of a wound rotor of an electric motor of a motor vehicle with at least partially electric traction.

[0003] A contactless excitation system for a wound rotor performs the same function as an excitation system for an electric motor comprising a rotating commutator with a slip ring and brushes. Their function is to provide electrical power to the wound rotor. However, in a rotating commutator, the brushes rub continuously against the slip rings, which causes wear on the brushes and slip rings. A contactless excitation system thus avoids friction and therefore the risk of wear on the brushes on the rotating slip ring commutator of an electric motor.

[0004] In the automotive field, there are very few applications of wound rotor motors, and the use of a contactless excitation system for a wound rotor is non-existent. Although advantageous for limiting the risk of wear, such a system does have a significant drawback.

[0005] It requires a very high voltage for the electrical excitation of the rotor to be effective. This voltage is around 800 V, which consequently causes a significant heating of the excitation system, which risks damaging the contactless excitation system.

[0006] The problem of heating of the excitation system therefore arises more acutely in contactless excitation systems of wound rotor motors. Statement of the invention

[0007] The present invention aims to optimize the cooling of the contactless excitation system of a wound rotor of an electric motor.

[0008] The invention therefore relates to a device for cooling a contactless excitation system of a wound rotor of an electric motor of a motor vehicle, said rotor being carried by a shaft supported by a bearing lubricated by a lubrication circuit.

[0009] The device includes a bypass of the lubrication circuit to direct a first part of a lubricating liquid circulating in the lubrication circuit towards the excitation system.

[0010] This device further comprises a guide surface capable of recovering a second part of the lubricating liquid downstream of the bearing and of directing said second part of the lubricating liquid towards the excitation system.

[0011] This double projection of lubricating liquid towards the excitation system allows it to be cooled more efficiently and to enlarge the area directly in contact with the cooling liquid.

[0012] In fact, the bypass of the lubrication circuit makes it possible in particular to cool a radially external zone of the excitation system, while the lubrication liquid recovered downstream of the bearing by the guide surface makes it possible in particular to cool a radially internal zone of the excitation system.

[0013] Advantageously, the guide surface has a shape capable of directing the lubricating liquid towards the centrifugal excitation system.

[0014] According to one embodiment of the invention, the guide surface has the shape of a truncated cone.

[0015] Advantageously, the guide surface is positioned on an overmolded power bus extending between the bearing and the excitation system. Said power bus provides the electrical connection between the excitation system and the wound rotor.

[0016] According to one embodiment, the guide surface is positioned radially internally with respect to the bypass of the lubrication circuit, said bypass making it possible to direct a first portion of a lubricating liquid towards the excitation system.

[0017] Advantageously, the device comprises channels extending into the excitation system, in order to allow the circulation of the lubricating liquid.

[0018] The invention also relates to an electric motor comprising a device for cooling a contactless excitation system of a wound rotor of the electric motor as defined above.

[0019] The invention also relates to a motor vehicle comprising an electric motor as defined above equipped with a device for cooling a contactless excitation system of a wound rotor of the electric motor. Brief description of the drawings

[0020] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0021] - [Fig.l] is a partial schematic view of an electric motor of a motor vehicle equipped with a cooling device for a non-conductor excitation system. contact of a wound rotor of the motor;

[0022] - [Fig.2] is a schematic view of the coolant guide surface positioned on a wound rotor supply bus;

[0023] - [Fig.3] schematically represents the path of the lubricating liquid on the non-contact excitation system; and

[0024] - [Fig.4] schematically represents the circulation of the lubricating liquid in the contactless excitation system of the wound rotor. Detailed description

[0025] In [Fig.l], there is shown a part of an electric motor of a motor vehicle with at least partially electric traction, designated by the general numerical reference 1.

[0026] The motor comprises a wound rotor 2, a contactless excitation system 3 of the wound rotor 2 and a lubrication circuit 4.

[0027] The wound rotor 2 is carried by a shaft 5 bearing on bearings, such as bearing 6, lubricated by the lubrication circuit 4.

[0028] The excitation system 3 is intended to electrically supply the wound rotor 2. It comprises in particular an excitation part 7 fixed to the casing C of the electric motor and intended to recover an electric current and a rectifier circuit 8 intended to transmit the electric current to the wound rotor 2 via an overmolded power supply bus 9 fitted onto the shaft 5.

[0029] The power supply bus 9 has a distal end welded to an output (not shown) of the rectifier and a proximal end 9b around which the conductive wires of the wound rotor 2 are wound.

[0030] The power supply bus 9 is fitted onto the shaft 5 of the wound rotor 2, the shaft 5 immobilizing the power supply bus 9 in translation.

[0031] When the wound rotor 2 is powered by the power bus 9, the assembly comprising the wound rotor, the shaft 5 and the power bus 9 is rotated with the rectifier circuit 8 of the excitation system 3. While these parts are in rotary motion, the excitation part 7 of the contactless excitation system 3 is stationary, fixed to the casing C of the electric motor.

[0032] The lubrication circuit 4 comprises a set of substantially radial conduits 4a in which the lubricating liquid circulates, which make it possible to lubricate different bearings, and in particular the bearing 6 located opposite the excitation circuit 3. The lubricating liquid also ensures the cooling of certain parts of the engine, in particular the contactless excitation system 3, the filtering of impurities resulting from the rotation of the moving parts and protection against corrosion.

[0033] These conduits 4a communicate with conduits supplying lubricating liquid fication 4b substantially axial and open into an area of ​​the casing C located immediately on the periphery of the bearings.

[0034] As illustrated in [Fig.3], downstream of the bearings, considering the flow of lubricating liquid (arrows F), the rectifier circuit 8 comprises axial channels 10, for example made by drilling the casing to allow the evacuation of the lubricating liquid.

[0035] Furthermore, the lubrication circuit 4 comprises a bypass 11 of the lubrication liquid, which makes it possible to direct a first part of the lubrication liquid towards the excitation system 3, close to the channels 10 made in the rectifier 8.

[0036] As illustrated in Figures 1 and 3, the bypass 11 extends between the conduit 4a opening into the area of ​​the casing located on the periphery of the bearing 6 located in the vicinity of the excitation circuit and one of the radial faces 12 of the rectifier circuit.

[0037] The branch 11 extends in an essentially axial direction, converging towards the radially external zone of the rectifier circuit.

[0038] Furthermore, the supply bus 9 comprises a guide surface 13 which recovers the lubricating liquid downstream of the bearing 6 and which is configured to direct a second portion of the lubricating liquid towards the excitation system 3.

[0039] This guide surface extends radially internally relative to the bearing, or is located in the extension of the bearing, so as to recover the flow of lubricating liquid downstream of the bearing.

[0040] The guide surface 13 is annular and comprises a convergent frustoconical proximal surface, on the bearing side, receiving the flow of lubricating liquid downstream of the bearing, and a divergent frustoconical distal surface, on the rectifier circuit side, extending in the extension of the frustoconical proximal surface. These frustoconical surfaces make it possible, during rotation of the wound rotor and the rectifier circuit, to direct the lubricating liquid recovered downstream of the bearing towards a radially internal zone of the rectifier 8 with respect to the bypass 11.

[0041] Thus, while the bypass 11 allows cooling of a radially external zone of the rectifier circuit, the guide surface allows cooling of a radially internal zone of the rectifier circuit.

[0042] This therefore makes it possible to cool the non-contact excitation system 3 more quickly and over a larger area, particularly the rectifier circuit, the elements of which are liable to heat up.

[0043] The guide surface 13 is for example overmolded onto the power supply bus 9, and is located between the bearing 6 and the rectifier 8 of the excitation system 3.

[0044] The guide surface 13 can have different shapes, as long as this shape allows the centrifugation of the lubricating liquid towards the rectifier 8.

[0045] Referring to [Fig.3], the lubricating liquid passes through several conduits 4a before reaching the level of the bearing 6 and lubricating the ball bearings 14 of the bearing 6. The lubricating liquid then flows onto the guide surface 13, then is projected onto the radial surface 12 of the rectifier 8.

[0046] The lubricating liquid disperses over the entire surface of the rectifier 8, thus allowing the entire contactless excitation system 3 to be cooled.

[0047] With reference to [Fig. 4], after having covered the entire surface of the rectifier 8, the lubricating liquid flows into the axial channels 10 made on the sides of the surface of the rectifier circuit 8 in the vicinity of the bypass 11, passes through the rectifier circuit and is evacuated along a conduit 15 which brings the lubricating liquid back into the bottom of the motor 16.

[0048] This path of the lubricating liquid therefore makes it possible to cool the entire contactless excitation system 3 of the wound rotor 2, and thus greatly reduces the risk of overheating of the electric motor.

Claims

Claims

1. Device for cooling a contactless excitation system (3) of a wound rotor (2) of an electric motor of a motor vehicle, said rotor being carried by a shaft (5) supported by a bearing lubricated by a lubrication circuit, said device comprising a bypass (11) of the lubrication circuit (4) for directing a first part of a lubricating liquid circulating in the lubrication circuit (4) towards the excitation system (3), characterized in that it comprises a guide surface (13) capable of recovering a second part of the lubricating liquid downstream of the bearing (6) and directing said second part towards the excitation system (3).

2. Device according to claim 1, wherein the guide surface (13) has a shape capable of directing the lubricating liquid towards the excitation system (3) by centrifugation.

3. Device according to claim 2, wherein the guide surface (13) has a truncated cone shape.

4. Device according to any one of claims 1 to 3, wherein the guide surface (13) is positioned on a power bus (9) between the bearing (6) and the excitation system (3), said power bus (9) ensuring the electrical connection between the excitation system (3) and the wound rotor (2).

5. Device according to claim 1, wherein the guide surface (13) is positioned radially internally with respect to the bypass (11) of the lubrication circuit (4) directing a first portion of a lubricating liquid towards the excitation system (3).

6. A device according to claim 1, comprising channels (10) extending into the excitation system (3) to allow the lubricating liquid to circulate.

7. Electric motor comprising a device for cooling a contactless excitation system (3) of a wound rotor (2) of an electric motor according to any one of claims 1 to 6.

8. Motor vehicle comprising an electric motor according to claim 7 equipped with a device for cooling a contactless excitation system (3) of a wound rotor (2) according to any one of claims 1 to 6.

Images