EP2783455A1

EP2783455A1 - Vehicle drive assembly comprising cooling by means of a heat-transfer fluid and a lubricating fluid

Info

Publication number: EP2783455A1
Application number: EP12781432.5A
Authority: EP
Inventors: Daniel Walser; Bruno Fragniere
Original assignee: Michelin Recherche et Technique SA Switzerland; Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Current assignee: Michelin Recherche et Technique SA Switzerland; Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Priority date: 2011-11-22
Filing date: 2012-10-16
Publication date: 2014-10-01
Also published as: FR2983010A1; CN103959615A; US20140306557A1; CN103959615B; WO2013076536A1

Abstract

The invention relates to a drive assembly (10) for an electric vehicle, formed by an electric motor (11) mounted so as to engage with a wheel (15) of the vehicle, said electric motor comprising: a rotor (14) mounted such that it can rotate in a stator (19) via bearings (12, 13), and a magnetic assembly suitable for rotating the rotor. The rotor (14) of the motor is provided with a heat pipe (1) comprising at least one condensation zone (3) and at least one evaporation zone (2) for a heat-transfer liquid. The wheel (15) of the assembly comprises a driven shaft (17) suitable for engaging with the rotor (14) of the motor, said heat pipe (1) extending axially from the rotor (14) into the driven shaft (17).

Description

DRIVE ASSEMBLY FOR VEHICLE WITH COOLING BY LUBRICANT FLUID AND FLUID FLUID TECHNICAL FIELD OF THE INVENTION

The present invention relates to a drive assembly for an electric vehicle consisting of an electric motor mounted in cooperation with a wheel of the vehicle, for driving the latter in rotation when the motor is supplied with electrical energy.

STATE OF THE PRIOR ART

[0002] Electric motors are now commonplace, and their use is now extended to virtually all areas of activity, including the transport sector, including the automobile. Their excellent performance and therefore their low level of consumption, low noise level, compactness, etc., make them more and more attractive in an ever increasing number of applications. However, some significant disadvantages remain despite significant progress in terms of some performance. This is particularly the case of problems related to engine warming, in particular for applications requiring extended operation and / or significant power. In addition, in most electric motors, the rotors are subjected to a significant electromagnetic source heating. The motor shaft can reach very high operating temperatures. Part of the calories are removed by conduction, by the point contacts of the bearing, the engine core to the outside of the housing and by radiation. This loss of heat is even lower than what is around the rotor is very hot. It leads to a natural increase in the temperature of the rotor. In training sets for electric vehicles such as that shown for example in Figure 2, this high temperature has a negative impact on the characteristics of the permanent magnets of the engine, when equipped, but also on the reliability of certain mechanical elements such as the bearing and the seal located on the engine output side, in the interface zone with the wheel to which the engine is coupled.

The patent application WO2004 / 107535 proposes a rotating electrical machine, in particular for a motor vehicle, provided with cooling means and outward evacuation of the heat produced in the machine. The cooling and evacuation means comprise at least one device comprising a heat transfer fluid capable of absorbing heat from the environment, by a first change of state, and of restoring the environment to the heat, when another change of state, and a circulation path of this fluid between a heat generating zone and an evacuation zone thereof. This concept is usable for alternators, starters or alternator-starters for a motor vehicle. In addition, the implantations are intended in particular to evacuate the heat produced by the rectifier, including the diodes. The generators described are further provided with fans arranged to generate a cooling air circuit.

This document describes modes of implementation of a heat pipe specific to alternators or alternator-starters, which are not directly transferable to training sets for electric vehicles.

[0007] JP 2009 190578 describes a wheel in which an electric motor is integrated. The motor is connected to the wheel in order to drive it in rotation. A heat pipe is arranged in the engine. This heat pipe is arranged to capture the heat of the engine in the wheel, to transfer it to the outside of the engine and the wheel. This document only deals with an arrangement in which the motor is disposed within the wheel. To overcome these disadvantages, the invention provides different technical means. SUMMARY OF THE INVENTION

[0009] Firstly, a first object of the invention is to provide a vehicle drive assembly that promotes efficient evacuation of the thermal energy generated during operation.

Another object of the invention is to provide a drive assembly for vehicle operating in conditions favoring the service life of the interface joint between the wheel and the engine and avoiding any premature deterioration of this seal.

To do this, the invention provides a drive assembly for an electric vehicle consisting of an electric motor mounted in cooperation with a wheel of the vehicle, for driving the latter in rotation when said motor is supplied with electrical energy, the electric motor comprising a rotor rotatably mounted in a stator through bearings, and a magnetic assembly provided with a portion mounted on the stator and a portion mounted on the rotor, adapted to rotate said rotor, the rotor the engine being provided with a heat pipe comprising at least one condensation zone and at least one evaporation zone of a coolant liquid, the wheel of the assembly comprising a receiver shaft adapted to cooperate with the engine rotor, the heat pipe extending axially from the rotor into the receiving shaft, the electric motor being disposed outside the wheel and the heat pipe condensing region being aligned in the receiving shaft of the wheel.

The solution advantageously provides a drive assembly whose engine comprises one or more heat pipes extending axially from the evaporation zone located internally to the bearing and the seal and extending towards the receiving shaft towards the condensing zone integrated in the receiving shaft. The heat pipes are used to collect calories in a hot zone of the engine to transmit them on the other side, in the wheel, to a cold zone. In a typically known solution, a heat pipe is arranged to capture the heat of an electric motor housed in the wheel, to transfer it to the outside of the engine and the wheel. The solution of the invention provides instead that the electric motor is disposed outside the wheel, and that the condensation zone of the heat pipe is located in the wheel receiving shaft (therefore, in the wheel).

The present solution makes it possible to cool not only the magnetic part of the motor, but also the portion of the internal bearing shaft adjacent to the wheel and internal to the seal.

This solution also improves the removal of heat from the hottest zone of the rotor by combining the rotating assembly a high-performance and reliable heat exchange means. The present solution is particularly advantageous as a means of internal cooling of motor rotors, particularly high performance, used for example in the motorization of electric vehicles. According to an advantageous embodiment, the evaporation zone is located in the portion corresponding substantially to the inner bearing of the engine.

Advantageously, the axis of the heat pipe is coaxial with the rotor axis.

The receiving shaft is advantageously cooled by an oil bath provided in an adapter. Also advantageously, the heat pipe is conical, the enlarged portion being on the side of the evaporation zone. According to another embodiment, the heat pipe comprises a heat transfer fluid reservoir provided at the evaporation zone.

According to yet another embodiment, the axis of the heat pipe forms an angle (alpha) relative to the axis of rotation of the rotor.

According to yet another embodiment, a plurality of heat pipes are distributed circumferentially along the periphery of the rotor of the engine.

According to yet another embodiment, the heat pipe is in two parts, each part being provided with an evaporation zone near the junction between the two parts and a condensing zone provided on the one hand in the external bearing sector and on the receiving shaft. According to an advantageous embodiment, the two parts of the heat pipe are substantially separated in the area of the inner bearing.

The invention also provides an electric motor for drive assembly as mentioned above, comprising a heat pipe extending axially from the rotor into the receiving shaft.

According to an advantageous embodiment, the condensation zone is located in the receiving shaft, the latter being cooled by an oil bath provided in the adapter. DESCRIPTION OF THE FIGURES

All the details of implementation are given in the description which follows, supplemented by FIGS. 1 to 6, presented solely for purposes of non-limiting examples, and in which:

FIG 1 shows a schematic representation of the operating principle of a heat pipe;

FIG 2 is a section of a drive assembly for electric vehicle;

FIG. 3 is an enlarged view of a cross section of a drive assembly comprising a heat pipe according to a first embodiment; FIG 4 is an enlarged view of a cross section of a drive assembly comprising a heat pipe according to a second embodiment;

FIG 5 is a schematic representation of a longitudinal section of a conical heat pipe comprising a heat transfer fluid reservoir;

FIG. 6 is a diagrammatic representation of a longitudinal section of an electric motor or receiving shaft rotor for a drive assembly, comprising a plurality of heat pipes distributed over the circumference of the axis.

DETAILED DESCRIPTION OF THE INVENTION

As shown schematically in Figure 1, a heat pipe 1 is a sealed enclosure containing a liquid in equilibrium with its vapor phase, generally in the absence of any other gas. The inner wall of this chamber may be lined with a microporous structure allowing the return of the liquid, by capillarity, the cold zone of the chamber where it comes to condense to the hot part where it evaporates. This microporous structure allows the return of the liquid against the gravity but in some cases, where the forces exerted on the fluid are favorable to its return to the evaporator, it is not necessary. The transfer of heat is therefore carried out by transformation of the sensible heat in latent heat. In the absence of any force other than gravity, the return of the liquid by capillarity allows use of the heat pipe in almost all positions. The heat pipe is a reliable system requiring little or no maintenance, low mass and low mechanical inertia, passive, having the ability to transmit high heat flux with a small temperature difference and whose thermal conductivity is higher several hundred times to the thermal conductivity of a copper bar. The heat pipe can operate in all positions (inclined, horizontal) and can be installed on existing engines.

The active material of the heat pipes, the one that evaporates and condenses, is chosen according to the temperature at which it is desired that the heat pipe works. For example, water, ether or alcohol is used.

The heat pipes are of preferentially cylindrical shape, consisting of a tube of good thermal conductivity and if possible metallic. Copper, a very good conductor, is one of the materials used. The heat pipes may also consist of a single hole, blind or opening with heat transfer liquid, the assembly being hermetically closed after making the vacuum air.

For implantation in the electric motor of a drive assembly according to the invention, several types of heat pipe arrangements are described in the following.

[0034] Figure 2 shows a general layout diagram of an electric motor 11 in conjunction with a wheel 15 of a vehicle, to form a drive assembly 10 for a vehicle. Such an assembly preferably comprises a coupling zone, in this example an adapter 16, in which the elements are in the presence of oil. A seal 20 is provided between the electric motor 11 and the wheel 15 to prevent the passage of oil to the engine. This seal 20 is a component likely to deteriorate if the temperature exceeds a certain threshold. In the following, various solutions are presented to allow to promote the evacuation of heat at the motor in general, but also at the area of the seal 20.

As shown in the section of the engine of Figure 3, an insert type heat pipe 6 is trapped in two housings formed in the rotor 14 of the engine and in the receiving shaft 17. The evaporation zone of the heat pipe is placed in the substantially central portion of the rotor 14 for a heat dissipation in the condensing zone 3 provided in the receiving shaft 17, the latter being colder than the motor shaft. The calories are advantageously removed by the oil contained in the casing of the transmission. For a good heat exchange, the heat pipe / shaft connection is ensured by a special high temperature contact paste. The lateral maintenance of the heat pipe is ensured by the respective ends of the motor and receiver shafts. In the case where the evacuation of calories is not favored by the general configuration of the engine, a combination of two borehole type heat pipes 5 optimizes the yields obtained, as shown in the example of Figure 4 Two evaporation zones 2 of the heat pipes are placed in the hottest zones namely, radially inwardly at the bearing 12 and at the seal and in the rotor 14. The heat evacuation is at the rotor inlet 14 modified for better cooling efficiency, and the output of the receiving shaft 17 bathed in the crankcase oil at a lower temperature than those of the areas to be cooled. The implementation requires only the realization of two bores. Lateral positioning is ensured by the principle of mounting the two trees. For a good heat exchange the heat pipe / shaft connections are ensured by a thermal contact paste. Thanks to the presence of two evaporation zones 2 and two zones of condensation 3, this solution makes it possible to obtain very good cooling performance.

Figure 5 schematically illustrates the implementation of a conical heat pipe bore 5 at the axis of the rotor 14 of the engine to be cooled. The evaporation zone 2 comprises a tank 7 of cylindrical shape arranged at the end of the enlarged zone of the cone. The rotation and the centrifugal force of the shaft drive the liquid 9 of the reservoir against the walls of the latter. Since a large amount of liquid is available for evaporation, the efficiency of the system is thus improved.

Another embodiment shown in the layout diagram of FIG. 6 comprises a plurality of bore-type heat pipes 5 provided in the periphery of the rotor of the motor. The presence of several cooling sources distributed around the tree promotes the evacuation of calories.

The figures and their descriptions made above illustrate the invention rather than limiting it. In particular, the invention and its various variants have just been described in connection with a particular example comprising a drive assembly in which the motor is connected to the wheel at the radially outer portion of the wheel.

Nevertheless, it is obvious to a person skilled in the art that the invention may be extended to other embodiments in which, in variants, the motor cooperates with a wheel at a connection point located at another radial position, even in the center of the wheel.

The reference signs in the claims are not limiting in nature. The verbs "understand" and "include" do not exclude the presence of elements other than those listed in the claims. The word "a" preceding an element does not exclude the presence of a plurality of such elements.

Claims

A drive unit (10) for an electric vehicle consisting of an electric motor (11) mounted in cooperation with a wheel (15) of the vehicle, for driving the vehicle in rotation when said motor is supplied with electrical energy, the motor electric motor comprising a rotor (14) rotatably mounted in a stator (19) through bearings (12, 13), and a magnetic assembly provided with a portion mounted on the stator and a portion mounted on the rotor, adapted to rotate said rotor, the rotor (14) of the engine being provided with a heat pipe (1) having at least one condensing zone (3) and at least one evaporation zone (2) of a coolant , the wheel (15) of the assembly comprising a receiving shaft (17) adapted to cooperate with the rotor (14) of the engine, the heat pipe (1) extending axially from the rotor (14) into the receiving shaft ( 17), characterized in that the electric motor () is arranged externally wheel (15) and in that the condensing zone (3) of the heat pipe (1) is located in the wheel receiving shaft (17).

2. Drive assembly according to claim 1, wherein the evaporation zone (2) is located in the portion substantially corresponding to the inner bearing (12) of the engine.

3. Drive assembly according to one of claims 1 or 2, wherein the receiving shaft (17) is cooled by an oil bath provided in an adapter (16).

4. Drive assembly according to one of claims 1 to 3, wherein the axis of the heat pipe (1) is coaxial with the axis (A-A) of the rotor (14).

5. Drive assembly according to one of claims 1 to 4, wherein the heat pipe is conical, the widened portion being on the side of the evaporation zone (2).

6. Drive assembly according to one of claims 1 to 4, wherein a plurality of heat pipes (1) are distributed circumferentially along the periphery of the motor shaft.

7. Drive assembly according to one of claims 1 to 4, wherein the heat pipe is in two parts, each part being provided with an evaporation zone (2) near the junction between the two parts and a condensation zone (3) provided on the one hand in the sector of the outer bearing (13) and on the other hand on the receiving shaft (17).

8. Drive assembly according to claim 7, wherein the two parts of the heat pipe are substantially separated in the area of the inner bearing (12).

9. Electric motor (11) for drive assembly (10) according to one of claims 1 to 8, comprising a heat pipe (1) extending axially from the rotor (14) into the receiving shaft (17).

Electric motor (11) according to claim 9, in which the condensation zone (3) is located in the receiving shaft (17), the latter being cooled by an oil bath provided in the adapter (16). .