FR3083036A1 - COOLING DEVICE OF AN ELECTRIC MOTOR FOR A MOTOR VEHICLE - Google Patents

Abstract

The cooling device (1) comprises a body (3) configured to support at least one electronic component. This body (3) has an interior chamber formed in the thickness of the body and configured to hermetically contain a heat transfer fluid, and the interior chamber houses a device for routing a fluid by heat pipe effect.

Description

Cooling device for an electric motor for a motor vehicle

The present invention relates to the field of electric motors for motor vehicles and more particularly to the cooling devices associated with these electric motors.

Capillary effect cooling devices are known, which can in particular be heat pipes taking the form of a tube or an evaporation chamber, and in which a fluid is contained, maintained in a sealed manner in the container and changing phase of a end to end of the device, each of these ends being associated with a hot zone or a cold zone. These specific cooling devices with capillary effect are notably known for use in the field of electronic components, tubes which can be arranged along a printed circuit board by winding between the electronic components.

In a vertical arrangement of the capillary effect cooling device, the fluid changes phase cyclically under the combined effect of zones of different heat and gravity: the fluid rises in temperature in a hot zone formed in the lower part of the device evaporates and the generated vapor rises towards the cold zone provided in the upper part of the device; this results in cooling of the fluid and condensation generating the transformation of the vapor into droplets which fall by gravity towards the lower part of the device.

In an equally common horizontal arrangement of these cooling devices, it is known to configure the tube or the evaporation chamber so as to provide at least one capillary duct (also called heat pipe) along which the droplets tend to advance from the cold zone towards the hot zone, by capillary action.

The present invention is in this context of the use of heat pipes and aims to protect in particular its application in the context of the cooling of an electric motor for a motor vehicle, by overcoming at least one of the aforementioned drawbacks.

To this end, the subject of the invention is a device for cooling an electric motor for a motor vehicle, the cooling device comprising a body configured to support at least one electronic component, the body comprising an inner chamber formed in the thickness of the body and configured to on the one hand hermetically contain a fluid, and on the other hand to house a device for routing a fluid by capillary effect.

Thanks to this last characteristic, it is possible to integrate into the volume of an electric motor radiator a capillary effect conduit, allowing the flow of a fluid configured to change phase between a cold zone and a hot zone of the inner chamber of the body. It will be understood that the hot zone is a part of the body in contact with at least the electronic component and the cold zone is a part of the body in contact with the ambient air, or that the hot zone is a part of the body in contact with one or more electronic components giving off a large amount of heat, greater than the amount of heat given off by other components in contact with a part of the body forming the cold zone. According to one embodiment of the invention, the device for routing the fluid by capillary effect and the electronic components are arranged on either side of a wall participating in defining the interior chamber and the device for routing the fluid is arranged according to the arrangement of the electronic components so as to ensure a hot zone at a first end of the tracking device and a cold zone at an opposite end of this tracking device.

The cooling device thus formed is autonomous and passive, the fluid contained in the interior chamber being used cyclically without having to be regenerated.

According to one embodiment of the invention, the body comprises a support part and a closure part which overlaps this support part and is fixed in a sealed manner to this support part, said parts being configured to form between them the interior room. Thus, by fixing a closure part on the support part, a pocket in the thickness of the body of the cooling device.

The body of the cooling device may in particular comprise a bottom wall and a peripheral side wall extending perpendicularly this bottom wall and forming a cavity in the center of the body for the reception in particular of electronic components. And in this context, it should be noted that the closure part is arranged in the cavity, between the peripheral side wall, to come opposite the interior face of the bottom wall.

In particular the support part and the closing part can respectively comprise a first face and a second face, the first face and the second face being plane and facing one another to form opposite faces participating in delimiting the chamber. interior.

The fluid routing device can be arranged on the first or second face, one or more electronic components being arranged on a face opposite to the first or second face on which the routing device is arranged with fluid by capillary effect.

Advantageously, the device for routing the fluid by capillary effect is disposed on the inner face of the closure part and at least one electronic component is disposed on the opposite face, that is to say the exterior face of the closure portion. . In this arrangement, it can be noted that the electronic components are housed in the volume of the body, between the peripheral lateral wall forming the contour of the body.

It is understood that the fluid routing device can be attached to one or the other of the opposite faces participating in delimiting the interior chamber in which the fluid is housed hermetically.

According to a characteristic of the invention, the cooling device can comprise a closing cover attached to the body to close a cavity inside which are housed at least one electronic component, the closing part and the routing device of fluid.

Provision may be made for the inner face of the closure part and the inner face of the support part to be separated by a distance substantially equal to 3 to 4 millimeters. It should be noted that the pocket created to form this interior chamber makes it possible to lighten the body of the cooling device with a layer of 3 to 4 millimeters of metallic material, in particular aluminum, and therefore to achieve a gain in weight. more gain in cooling.

According to different embodiments of the invention, the device for routing a fluid by capillary effect can be oriented so that the fluid circulates from a cold zone to a hot zone, in the form of condensate, by gravity, and / or this tracking device may include a capillary-type routing means of the heat pipe type.

The capillary tracking means may comprise a plurality of reliefs and ridges thus forming microchannels, of small section, along which the droplets of condensed fluid circulate.

These reliefs and ridges can be grouped to form segments respectively separated from each other by a rib, two consecutive ribs forming a channel promoting the flow of the fluid in which a segment is arranged.

The ribs, the ridges and the reliefs, can in particular be parallel to each other.

According to a characteristic of the invention, a rib may have a height greater than the height of a segment. It follows that, when the closure part is pressed against the support part of the body, the ribs come to bear against the opposite face participating in delimiting the interior chamber so that the channels formed between the ribs are sealed, the fluid present in a channel flowing from a hot zone to a cold zone along one or other of the ridges and reliefs remaining in this channel.

Provision may be made for the capillary tracking means to be made from a material with the closure part or the support part from which it projects, or else it is formed from a material different from that used to make the body of the cooling device. In this case, provision may be made for the capillary tracking means to be molded onto a face participating in delimiting the interior chamber.

The fluid capillary tracking means can be formed from aluminum, the heat transfer fluid possibly being acetone.

According to characteristics of the invention, it can be provided that the ribs have a height of between three and four millimeters, and that the reliefs and ridges have a dimension in the same direction of between one and two millimeters.

The capillary tracking means may also comprise at least one porous material, either separately or in combination with the presence of the reliefs and ridges previously mentioned. The porous material can be arranged in channels delimited by two ribs.

The porous material can be obtained by sintering, and in particular by sintering copper powder. It is also possible to provide for forming the porous material by a metallic fabric.

The invention also relates to an electric motor comprising a cooling device according to the invention, and in particular to a ventilation device equipped with such an electric motor.

Other characteristics, details and advantages of the invention will emerge more clearly on reading the description given below by way of indication in relation to the drawings in which:

- Figure 1 is a perspective view of the cooling device according to the invention in which there is shown a body support part and a body closing part;

- Figure 2 is a perspective view of the cooling device of Figure 1 in an exploded representation in which there is shown the body support part and the body closing part disjoint, the routing device by capillarity of the fluid according to the invention being formed on the second face of the closing part of the body;

- Figure 3 is a view of the cooling device of Figure 2, from a different angle of perspective making visible the internal face of the support part of the body;

- Figure 4 is a perspective view of the body closing part in which we can more clearly see a plurality of ribs and reliefs participating in forming the tracking device by capillarity;

- Figure 5 is a detail view of Figure 4 in which there is shown more closely the shape of a rib and a segment formed by a series of reliefs and ridges;

- Figure 6 is a sectional view of the cooling device along the cutting plane P of Figure 1;

- Figure 7 is a detail view of Figure 6, making particularly visible the formation of an interior chamber inside the body illustrated in Figure 6;

- Figure 8A is a perspective view of the closure part of the body according to a particular embodiment of the invention in which the streaks are replaced by a porous material;

FIG. 8B is a perspective view of a detail of FIG. 8A in which the porous material has been shown in more detail,

- And Figure 9 is a perspective view of an electric motor for a motor vehicle equipped with the cooling device according to the invention.

A device for cooling an electric motor for a motor vehicle according to the invention is shown by way of example in FIG. 9. In this exploded view, one can observe an electric motor 50, comprising a stator 51 and a rotor 52 provided permanent magnets 53, mounted for rotation by means of bearings 54. The electric motor 50 is arranged in the vicinity of a radiator here forming the cooling device 1 within the meaning of the invention. The cooling device 1 has a solid body 3 allowing the evacuation of the heat released by the operation of the engine. This solid body 3 can for this purpose have cooling fins 36 facilitating the release of heat. Electronic components, not visible in Figure 9, are made integral with the radiator which also participate in the evacuation of the heat given off by these electronic components. A closing cover 40 covers this assembly to protect in particular the electronic components.

There is shown in Figures 1 to 3 a cooling device 1 according to the invention formed of a body 3. The body 3 of the cooling device 1 comprises a support portion 30 and a closure portion 31 which is pressed against the support part and which is tightly fixed on this support part, in order to delimit between them a device for routing a fluid whose phase change allows the evacuation of heat produced by the electronic components attached to this body 3.

Preferably, the body 3 is formed from a metallic material. Preferably, the metallic material has properties promoting thermal conductivity. Even more preferably, the body 3 is formed by molding.

The support part 30 comprises a bottom wall 301 and a lateral peripheral wall 302 substantially extending the bottom wall 301 around it, to form together a housing 303 for receiving electronic components 2. The lateral peripheral wall 302 of the support part 30 defines a contour thereof, and the free end of this lateral peripheral wall 302 is configured to cooperate with the closure cover 40 as it has been presented in the description of FIG. 9, which covers the housing 303. It is understood from the above that the closure cover 40 and the closure portion 31 are separate parts.

The bottom wall 301 has an external face, facing the stator of the electric motor, and an opposite internal face. The internal face of the bottom wall 301 is hollowed out in its center so as to generate a cavity 305 delimited by a contour 306 forming a shoulder between a bottom face 308 of the cavity and the peripheral part 307 of the bottom wall, disposed at the direct vicinity of the side wall 302.

The closing part 31 is formed by a plate whose contour 315 is of shape corresponding to the contour of the support part 30 defined by the peripheral side wall 302, and of dimensions slightly smaller than those of this contour of the part of support 30, so that the closing part can be housed inside the housing 303 defined by the support part. The plate includes an inner face 310 and an outer face 311 opposite the inner face 310. The inner face 310 has a smooth peripheral edge 312 and a central portion 313 on which a plurality of projecting elements are formed, such as that will be described below in more detail, a fluid flow means by capillarity. When the closing part 31 is attached to the inside of the support part 30, the smooth peripheral edge comes to bear on the peripheral part 307 of the bottom wall and the ribs of the central part 313 extend in direction of the bottom face 308 of the cavity 305 of the bottom wall.

The bottom face 308 of the bottom wall and the closing part 31 brought opposite this bottom face participate in forming according to the invention a routing device 7 of a fluid formed in the thickness of the body 3. And more particularly in the embodiment shown, the projecting elements formed on the central part 313 of this closing part 31 participate in forming a means of routing by capillarity.

As shown in particular in FIGS. 6 and 7, an interior chamber 5 is then formed by a first face formed by the bottom face 308, by a second face formed by the interior face 310 of the closure part 31 and arranged opposite the first face, as well as by the contour 306 forming a shoulder around the cavity 305. As will be described below, this interior chamber 5 is sealed when the closing part 31 is assembled on the support part 30 , in order to be able to contain, without leakage, a heat transfer fluid, known as a fluid, the phase changes of which will regularly allow the cooling of the electronic components arranged near this interior chamber. By way of example, the closure part 31 can be assembled on the support part 30 by welding the contour of the closure part 31 on the peripheral side wall 302 of the support part 30.

One or more electronic components 2 are arranged against the external face 311 of the closing part 31. A single electronic component has been illustrated diagrammatically in FIG. 1, but it will be understood that several electronic components can be mounted on a circuit board printed matter 200 as illustrated in FIG. 3 which is fixed directly to the external face 311 of the closing part 31.

It is thus understood that the electronic components, heat sources which it is intended to evacuate according to the invention, are arranged on one face of the closing part 31, namely its outer face 311, while the tracking device 7 by capillary action is formed on the other side of the closure part 31.

As described above, the device 7 can comprise a capillary tracking means, which comprises, in the case illustrated in FIGS. 1 to 7, a plurality of elements formed projecting from the inner face 310 of the closure part 31, and among which we can distinguish ribs 14 between which reliefs 11 are arranged, the height of which, that is to say the protruding dimension of the inner face 310 of the closing part 31, is less than that of the ribs 14. In what follows, a preferred embodiment will be described in which the capillary tracking means is formed along the closure part, since it is this closure part which carries the electronic components on an opposite face. , and the fact that the production of the microchannels formed by these reliefs is simplified on a plate such that the closure part takes shape. It will however be understood that it could be envisaged, without departing from the context of the invention, to produce the capillary tracking means as will be described on the inner face of the support part 30.

The ribs 14 are parallel to each other and regularly spaced on the inner face 310, so as to delimit in pairs a channel 15 extending between two successive ribs and in which one or more reliefs 11 are arranged, promoting the path of a fluid flowing along the inner face 310 whose cyclic phase changes promote heat dissipation. Thus, between each rib, heat conduction paths operating on the model of a capillary effect conduit are formed.

Between two consecutive ribs 14, the tracking device 7 comprises one or more second reliefs 11, arranged in parallel with the ribs and the whole of which forms a segment 6 distinct from the neighboring segment. In the example illustrated and notably visible in FIG. 4, each segment 6 comprises nine reliefs 11, separated from each other by ridges 12. As is notably visible in FIG. 7, each segment 6 arranged in the vicinity of a rib is formed by a succession of reliefs 11 and streaks 12 forming a series of bumps and hollows. These reliefs and streaks form the capillary pathway, forming microchannels along which the fluid tends to progress gradually by adhesion along the walls of the reliefs.

It is understood that the arrangement of the segments 6 and of the ribs 14 is not limitative of the invention and that their respective shapes or number could be different as soon as their arrangement allows the flow of a fluid and its successive phase change as will be described below.

In Figure 5, there is shown more particularly the difference in height between the ribs 14, which each have a height Hl, and the reliefs 11 forming segments 6 and which each have a height H2. The height H2 of a relief 11 of a segment 6 is defined as being the depth of a streak 12, the streaks 12 of each segment 6 having an identical depth. The height Hl of the ribs 14 is greater than the height H2 of the segments 6. By way of nonlimiting example, provision may be made for the height Hl of the ribs, which defines the depth of the interior chamber, to be between 3 and 4 millimeters , and that the height H2 of the segments 6 is between 1 and 2 millimeters. It is thus understood that the fluid circulating by capillary effect from a hot zone to a cold zone inside a channel can pass if necessary from one streak to another in the same segment, between two ribs 14.

The segments 6 formed by reliefs 11 and streaks 12, arranged in a channel 15 between two consecutive ribs 14, form a capillary medium promoting the flow of the fluid in the direction of elongation of the channel 15 in one direction and in the other. depending on the phase in which the fluid is located.

The ribs 14 have a trapezoid-shaped section with a large base 140 formed at the junction of the inner face 310 of the closure part 31 and a free end face formed by the small substantially 141 base.

The reliefs 11 have a curved section, with a rounded upper end 110.

The support part 30 and the closing part 31 respectively comprise openings 309, 314, and it has been made visible in FIGS. 1 and 3 that these openings come into correspondence with one another when the closing part is fitted against the support part. These openings 309, 314 are mainly intended to allow passage to motor connectors between the electronic components arranged on one side of the radiator formed by the body 3 and the phases of the motor arranged on the other side of this body 3.

The edges delimiting the openings 314 of the closing part 31 are flush with the external face 311, while they extend projecting from the internal face 310, thus forming a peripheral crown 316 delimiting the corresponding opening 314. This crown 316 has a height equal to that of the ribs 14. And the openings 314 thus delimited are larger than the openings 309 of the support part 30. It is understood from the above that when the closing part 31 is pressed against the support part 30, the peripheral ring 316 delimiting each opening 314 formed in the cover part 31 comes into contact with the bottom face 308 around the openings 309 of the support part 30. As a result, each opening 309 of the part of support is inscribed inside the volume defined in the extension of a peripheral crown delimiting an opening 314 of the closing part and that the fluid housed between the bottom face 308 and the inside face 310 of the closing part 31 cannot escape through the openings because blocked by the peripheral rings in contact with the bottom face.

We will now describe the operation of the cooling device 1 according to the invention, with reference to the embodiment illustrated in Figures 1 to 7 described above.

Firstly, the body 3 of the cooling device is mounted by fixing the closing part 31 against the support part 30. The closing part is pressed into the bottom of the support part 30 by orienting the face interior 310 facing the bottom face 308 of the support part 30. The two body parts are dimensioned so that, during this assembly, the free end face of the ribs 14 and the peripheral crown support against the bottom face. There is thus defined, at least between two ribs a sealed passage defined by the bottom face 308, the inner face 310 of the closing part 31 and the two ribs 14.

In a second step, it is sought to introduce a heat transfer fluid into the interior chamber 5 thus defined between the closing part 31 and the support part 30. To this end, a first bore is made temporarily in the closing part 31 so that it opens into a channel 15, and a vacuum is made in this channel before plugging the first bore. This operation can be carried out for each channel 15, as long as they are not communicating. Then a second bore is produced to inject the heat transfer fluid there, before again sealing this second bore in order to seal the channel in which the fluid circulates.

In the example illustrated where the fluid routing device housed in the interior chamber comprises a routing means by capillarity of the fluid, the orientation of the cooling device is not important, since the channels defined by the ribs and guiding the circulation of fluid in the chamber have at one end a cold zone and at another end a hot zone. In an alternative embodiment where the faces participating in defining the interior chamber are smooth, that is to say without relief segments and ridges, provision can advantageously be made for orienting the cooling device 1 so that the channels 15 of circulation of the fluid, and therefore the ribs 14 which delimit them, are in a vertical position once the cooling device is installed on the motor vehicle, in order to benefit from the force of gravity during its operation as will be described below. after.

In this context, it should also be noted that the printed circuit board 200 may comprise separate electronic components which generate heat in a heterogeneous manner, by way of example distinguishing a first set 201 of electronic components with high heat release and a second set 202 of electronic components with less heat release than that of the first set. It is therefore sought to preferentially dissipate the heat released by the electronic components of the first assembly to avoid the formation of hot spots. This first set of electronic components 201 is then disposed in the lower part of the outer face 311 relative to the vertical direction when the cooling device 1 is in place, while the upper part of the outer face 311 is arranged on the second set of electronic components giving off less heat than the high heat given off by the first components. Equivalently, provision could be made not to have electronic components on this height part of the external face 311.

It will be understood that the lower part of the outer face 311, that is to say the part carrying the first set 201 of electronic components, corresponds to a lower part of the inner face 310 which is in contact with the fluid while the upper part of the outer face 311, that is to say the part carrying the second set 201 of electronic components, generally corresponds to an upper part of the inner face 310.

In the illustrated case where a capillary tracking means is provided, here a set of microchannels formed by the succession of reliefs and ridges on one of the faces participating in defining the interior chamber, the cooling device can be oriented indifferently, taking care that one end of the channel 15 disposed on one side of the wall corresponds to a first set of electronic components 201 giving off more heat than a second set of electronic components

202 corresponding to the opposite end of the channel.

In operation, each electronic component 2 generates heat. The heat released by the electronic component 2 is propagated by thermal conductivity from the electronic component 2 to the outer face 311 of the closing part 31. The closing part 31 of the body 3 being formed of a metallic material, the heat propagates then from the outside face 311 of the closing part 31 towards the inside face 310 of the closing part 3.

Thus, it will be understood that the heat released by the electronic component 2 is generally propagated towards the interior chamber 5 formed between the support part 30 of the body 3 and the closing part 31. It results from the difference in heat released between the first set 201 and the second set 202 of electronic components creating a hot zone and a cold zone at each end of the channels 15 formed between the ribs 14.

When the heat released by each electronic component 2 is sufficient to allow the fluid inserted into the interior chamber 5 to reach its boiling temperature, the fluid then begins an evaporation cycle.

The fluid evaporated in the interior chamber 5 moves from the end of the channel 15 corresponding to a hot zone to the end of the channel corresponding to a cold zone. It is understood that the terms cold zone and hot zone are used in comparison with the temperature differences present in said cold and hot zones.

The part of the evaporated fluid then partially transports the heat propagated by thermal conduction from the electronic component 2 to the interior chamber 5. Part of the heat propagated by thermal conduction is then transported by evaporation of the fluid from the lower part to the upper part of the inner face 310.

When the evaporated fluid reaches the part of the channel corresponding to the cold zone, the evaporated fluid then begins a condensation cycle. The fluid is then present in the upper part of the channel in the form of droplets which move, either by gravity along the walls of the channel, and advantageously along the bottom face 308, that is to say the face to the opposite of the electronic components, either by capillary action along the microchannels when a capillary tracking means is present.

In this way, the fluid circulates in the interior chamber 5 along the routing device 7 as described above.

On the side of the internal face 310 of the closing part 31, the presence of ridges 12 and of reliefs 11 makes it possible to increase the exchange surface between the internal face 310 and the liquid, and to facilitate in the lower part of the channel the rise in temperature of the liquid and its evaporation.

When the device is placed vertically, and the components are arranged vertically with the hot zone located in the lower part and the cold zone located in the upper part, the ridges 12 and the reliefs 11 act as pipes facilitating the circulation of the fluid from the evaporation zone to that of condensation or vice versa.

To further diffuse the heat generated by the electronic components 2 towards the internal face 310 of the closing part 31 and therefore the internal chamber 5 in which the fluid circulates, the material in which the body 3 is formed comprising the support part 30 and the closing part 31 is an aluminum-based material having good thermal conductivity.

Conventionally, the heat can also be dissipated by the support part 31 of the body 3 up to fins 36 in contact with the ambient air arranged on the external face of the peripheral lateral wall in the example illustrated.

According to any one of FIGS. 8A or 8B, another embodiment of a capillary tracking means has been shown, in which a porous material 13 provided in replacement of the relief of the reliefs has been placed in the channels 15. and streaks. This embodiment allows in particular to use the cooling device in a different orientation than that described in the embodiment described above. It will be understood that in this embodiment, the routing device 7 comprises the ribs 14, delimiting between them the channels 15, the bottom face 308 of the support part 30 and the inner face 310 of the closure part on which applies the porous material 13.

In this mode of operation, provision may in particular be made to use the cooling device in an orientation having the ribs 14 in a direction generally perpendicular to the direction of the force of gravity.

However, the invention does not exclude the use of this embodiment in an orientation identical to that of the embodiment described above.

In this embodiment, the porous material 13 allows the transport of the fluid from the cold zone to the hot zone, without it being necessary to orient the device in order to benefit from the effect of gravity. Gradually, the fluid in the form of droplets deploys through the porous material 13 to return to the hot zone, where it evaporates again to move towards the cold zone away from the porous material and vice versa.

Of course, the invention is not limited to the embodiments described and shown in the accompanying drawings. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without thereby departing from the scope of protection of the invention.

Claims (14)

1. Cooling device (1) of an electric motor for a vehicle, the cooling device (1) comprising a body (3) configured to support at least one electronic component (2), characterized in that the body (3) comprises an interior chamber (5) formed in the thickness of the body and configured to hermetically contain a heat transfer fluid, the interior chamber (5) accommodating a device (7) for routing a fluid by capillary effect. 2. Cooling device (1) according to claim 1, characterized in that the body (3) comprises a support part (30) and a closure part (31) overlapping this support part and fixed so tight to this support part, said parts being configured to form between them the interior chamber (5). 3. Cooling device (1) according to the preceding claim, characterized in that the routing device (7) is arranged on one face (308, 310) of the support part (30) or of the closing part (31 ) participating in delimiting the interior chamber (5). 4. Cooling device (1) according to the preceding claim, characterized in that the routing device (7) is arranged on an inner face (310) of the closure part (31) participating in delimiting the inner chamber (5) and in that the at least one electronic component (2) is arranged on an outer face (311) opposite this inner face (310), in the volume of the body (3). 5. Cooling device (1) according to any one of the preceding claims, in combination with claim 2, characterized in that it comprises a closure cover (40) attached to the body (3) for closing a cavity to the interior of which are housed the at least one electronic component (2), the closure part (31) and the tracking device (7). 6. Cooling device (1) according to any one of the preceding claims, characterized in that the routing device (7) of a fluid by capillary effect comprises a capillary tracking means of the heat pipe type (11, 12, 13). 7. Cooling device according to the preceding claim, characterized in that the capillary tracking means comprises a plurality of reliefs (11) and ridges (12). 8. Cooling device according to the preceding claim, characterized in that the reliefs and ridges form segments (6) respectively separated from each other by a rib (14), the ribs forming in pairs a channel (15) favoring the fluid flow. 9. Cooling device (1) according to the preceding claim, characterized in that the ribs (14) are parallel to each other. 10. Cooling device (1) according to claim 8 or 9, characterized in that a rib (14) has a height (Hl) greater than the height (H2) of a segment (6). 11. Cooling device (1) according to any one of claims 8 to 10, characterized in that the ridges (12) are parallel to the ribs (14). 12. Cooling device according to claim 6, characterized in that the capillary tracking means comprises at least one porous material (13). 13. Cooling device according to the preceding claim, characterized in that the porous material (13) is arranged in channels (15) delimited by two ribs (14). 14. Electric motor (50) for a motor vehicle comprising the cooling device according to any one of the preceding claims.