FR3092392A1 - cooler for a battery of a motor vehicle. - Google Patents

Abstract

Cooler (1) comprising a base plate (2), and an all-metal contact plate (3) assembled against the base plate (2) and forming between them a first level (4) for the circulation of a heat transfer fluid , the contact plate (3) being in contact with an element to be cooled (5) by conduction. This cooler (1) is such that the base plate (2) comprises, in its thickness, an internal space forming a second level (6) for circulation of the heat transfer fluid, the base plate (2) being made of a thermo material. -insulator whose thermal conductivity λ is less than 2 W m − 1 K − 1 at 20 ° C. Figure to be published with the abstract: Fig. 1

Description

cooler for a motor vehicle battery.

The present invention relates to a cooler for a battery of a motor vehicle, in particular a cooler integrated in a battery pack of a hybrid or electric vehicle.

Motor vehicles, if they are electric or hybrid, include one or more traction (or propulsion) batteries connected to a power network to supply the electric traction (or propulsion) motors.

The term “battery” will be understood throughout the text of this document to mean an assembly comprising at least one battery module containing at least one electrochemical cell. This battery optionally comprises electrical or electronic means for managing the electrical energy of this at least one module. When there are several modules, they are grouped together in a casing and then form a battery pack, this battery pack being often designated by the English expression "battery pack", this casing generally containing a mounting interface, and terminals for connection.

Furthermore, the term electrochemical cell will be understood throughout the text of this document to mean cells generating current by chemical reaction, for example of the lithium-ion (or Li-ion) type, of the Ni-Mh or Ni-Cd or still lead.

The capacity and power of these batteries are constantly increasing, in particular thanks to lithium-ion “Li-ion” technology. However, this type of batteries poses problems related to the operating temperature.

Indeed, lithium-ion batteries have limited performance with negative temperatures, and high temperatures degrade them quickly.

To improve their operation when cold, it is possible to modify the materials of the electrodes, or the electrolyte, but these solutions can degrade certain performances of the batteries, in particular when hot, which reduces their service life. It is also possible to provide a larger number of cells in parallel. These different solutions significantly increase battery costs.

Another solution consists in regulating the temperature of these batteries by a cooling system traversed by a heat transfer fluid, generally glycol water, this system comprising coolers. These coolers, generally in the form of a plate in contact with the modules, are hydraulically connected to each other in series and/or in parallel, or even independent of each other.

However, the performance of the batteries (power, on-board energy, safety) causes strong constraints on the design and integration of coolers. It is therefore necessary to optimize this cooling system, in particular the coolers, to best adapt to the complexity of the batteries, with the additional objective of reducing manufacturing costs.

For example, document FR-A1-3 003 938 discloses an economical cooling plate for a battery pack, comprising a plastic base plate and a metal contact plate. If this solution is economical, it does not allow a rigid assembly of the cooler, which is therefore of limited size and not suitable for a large grouping of modules, this large grouping then requiring several coolers, and therefore several interconnecting pipes which are as much potential sources of fluid leakage.

Also known from document FR-A1-3 011 131 is a cooling plate with two levels of fluid circulation, in the opposite direction of circulation, this plate being constituted by three metallic and heat-conductive sheets, stacked, and brazed between them.

If this solution allows a homogenization of the cooling of the module, the efficiency (power) of the cooling is not optimal because part of the outgoing fluid heats up part of the incoming fluid, thus creating an internal heat loss. In addition, this solution requires metal sheets and therefore brazing, which is an assembly technology that does not allow the production of large coolers (limitation by the process). In addition, this cooler also does not have sufficient rigidity to be of large size.

The object of the invention is to remedy at least one of these drawbacks, in particular by optimizing the structure of the cooler to allow it to have both a large size and good cooling efficiency.

To this end, the subject of the invention is a cooler comprising a base plate, and an all-metal contact plate assembled against the base plate and forming between them a first level of circulation of a heat transfer fluid, the contact being in contact with an element to be cooled by conduction, this cooler being such that the base plate comprises, in its thickness, an internal space forming a second level of circulation of the heat transfer fluid, the base plate being made of a thermal material - insulating whose thermal conductivity (λ ) is less than 2 W m−1 K−1 at 20°C.

Thus the heat-insulating material, for example thermoplastic, makes it possible to avoid internal heat losses between the two levels and therefore to improve the efficiency of the cooler (better thermal efficiency). This material is also a less expensive material than metal and in particular aluminum, copper, or stainless steel.

Another advantage is that there is no longer any need to assemble the base plate and the contact plate by a conventional brazing process. This brazing process therefore no longer limits the possible size of the cooler, a limitation which was due to the limited capacity of brazing furnaces. In addition, the base plate having an internal space forming a second level of circulation of the heat transfer fluid, has improved rigidity to deformation, because it has a much larger modulus of inertia than a simple stamped plate.

Yet another advantage is that, when there are several coolers hydraulically connected in between, this base plate makes it possible to homogenize the cooling between each cooler by using the second level as a simple pipe bringing an unheated fluid to a second cooler, and therefore, to homogenize the cooling on all the modules of a battery.

According to one embodiment of the invention, the base plate comprises a first wall facing a second wall, a space preserved between the two walls forming the internal space.

According to one embodiment of the invention, the first and the second wall are made of thermoplastic materials and are assembled by welding, in particular by ultrasonic welding, heating blade, rotation, laser, or even high frequency.

According to a variant embodiment of the invention, the first and the second wall are assembled by gluing, riveting, screwing, snap-fastening, or riveting.

According to one embodiment of the invention, the base plate includes a fluid seal between the first and the second wall.

According to a variant embodiment of the invention, the base plate is made in one piece by molding.

This variant guarantees fluid tightness of the second level, while producing a one-piece base plate, and therefore a very rigid base plate, allowing large dimensions for the base plate and therefore the cooler.

According to one embodiment of the invention, the contact plate comprises at its periphery tongues crimping the base plate against the contact plate.

An advantage of this feature is the simplicity of assembly, which allows assembly of large base plates. In addition, this crimping can secure together in a single operation the contact plate, the first wall, and the second wall.

According to one embodiment of the invention, the fluid circulates according to a first flow through the first level, and a second flow at the second level, the first and the second flow being parallel and in the same direction, this cooler comprising an inlet of the fluid common to the two levels, a first outlet for the fluid from the first level, a second outlet for the fluid from the second level, the fluid inlet being the only fluid communication between the two levels.

Thus the second level replaces a fluid pipe, and the fluid entering the cooler is divided into these two flows, the freshness of the second flow being preserved thanks to the thermal insulation property of the base plate, for example to cool a second battery module. This saves space (space that would be taken up by a pipe) and pipe fittings, which are always a source of fluid leakage.

We understand by flow, throughout the text of this document, the direction of progression of the fluid from the inlet (cold fluid for a cooler) towards the outlet (hot fluid for a cooler) of the fluid for a level considered, without taking into account of the path taken by the fluid between this inlet and this outlet. The term flux is used by analogy to heat flux, the fluid heating up throughout its course and whatever the shape of this course (for example in the form of a serpentine). It is obvious that if the chiller is used as a heater, the flow is always to be considered from the fluid inlet (hot fluid) to the fluid outlet (cold fluid) for a level considered.

In addition, the second level being thermally insulated, whether the cooler is used as a cooler or a heater, the flow of this second level will always be considered from the fluid inlet of the second level to the fluid outlet of the second level, even if the heat exchange flow is zero here.

According to a variant embodiment of the invention, the fluid circulates according to the first flow through the first level, and the second flow through the second level, the first and the second flow being parallel and in opposite directions, this cooler comprising a fluid inlet of the first level, a fluid outlet of the second level, and a fluid passage between the two levels, remote from the fluid inlet.

Thus this configuration makes it possible to have the fluid inlet and the fluid outlet close to each other, for example on the same side of the battery module (which are generally parallelepipedic).

The invention also relates to a vehicle, in particular an electric or hybrid vehicle, this vehicle comprising a battery pack containing at least one battery module, this battery pack comprising a cooler as previously described, the element to be cooled by conduction being one side of the battery module.

Other characteristics, objects and advantages of the invention will appear on reading the description of the non-limiting examples of embodiment which will follow, made with reference to the appended figures 1 to 4, which represent:

shows an exploded view of a cooler according to a first embodiment of the invention, positioned under a battery module.

shows a cross-section of the chiller in Figure 1.

shows a diagram of a longitudinal section of two coolers hydraulically connected in between, and positioned under several battery modules, according to a second embodiment of the invention.

represents the diagram of a longitudinal section of a cooler, and positioned under several battery modules, according to the first embodiment of the invention of Figures 1 and 2.

It should be borne in mind that the figures are given by way of examples and do not limit the invention. They constitute representations of principle and are intended to facilitate understanding of the invention and are not necessarily scaled to practical applications. In particular, the dimensions of the various elements shown are not representative of reality.

In addition, to facilitate reading, the references of the elements that are unchanged or have the same function are common to all the figures, the exemplary embodiments, and the variant embodiments.

FIG. 1 illustrates a cooler 1 according to a first embodiment, comprising a base plate 2, and an all-metal contact plate 3 assembled against the base plate 2 and forming between them a first level 4 for the circulation of a heat transfer fluid, the contact plate 3 being in contact with an element to be cooled 5 by conduction, this cooler 1 being such that the base plate 2 comprises, in its thickness, an internal space forming a second level 6 for the circulation of the heat transfer fluid , the base plate 2 being made of a heat-insulating material whose thermal conductivity λ is less than 2 W·m−1·K−1 at 20°C.

Examples of possible materials are plastics, whose thermal conductivity λ oscillates between 0.15 and 0.50 W·m−1·K−1 at 20°C.

Advantageously, these materials are plastics filled with fibers, for example resins filled with glass or carbon fibers, then forming a material whose thermal conductivity will be a little higher than unfilled plastics, between 0.15 and 2 W·m−1·K−1 at 20°C depending on the orientation or not of the fibers, and the direction of propagation of the heat considered, and making it possible to increase the rigidity of the base plate 2 and therefore, d increase its size.

The base plate 2 comprises a first wall 7 facing a second wall 8, a space preserved between the two walls 7, 8 forming the internal space. In this first variant illustrated, the first wall 7 and the second wall 8 are separate plates, and the contact plate 3 comprises at its periphery tabs 9 crimping the base plate 2 against the contact plate 3 by sandwiching the first wall 7 between the second wall 8 and the contact plate 3. This crimping produces the peripheral sealing of the two levels 4, 6 by tightening the contact plate 3 and the first wall 7 and the second wall 8 between them .

The contact plate 3 comprises a first inlet 17 for the heat transfer fluid in the first level 4, this first inlet 17 being connected to an inlet pipe 21. The first wall 7 comprises a second inlet 19 of the heat transfer fluid in the second level 6, this second inlet 19 being common to the two levels and also having the function of being a first outlet orifice 19 of the heat transfer fluid from the first level 4, towards the second level 6. The first wall 7 further comprises a second outlet orifice 18 for the heat transfer fluid of the second level 6, second outlet orifice 18 connected to an outlet pipe 20, this outlet pipe 20 passing through the contact plate 3 in a sealed manner by a conduit orifice 40 made through the contact plate 3. The inlet conduit 21 and the outlet conduit 20 then both protrude from the upper face of the contact plate 3.

In a variant embodiment, not shown, it is the second wall 8 which comprises this second outlet orifice 18, the inlet pipe 21 protruding from the upper face of the contact plate 3, whereas the outlet pipe 20 protrudes from the underside of the second wall 8.

Figure 2 , which illustrates a cross section of Figure 1, and therefore of the first embodiment, discloses a first seal 10 interposed between the contact plate 3 and the first wall 7 on their periphery. Similarly, a second gasket 11 can be interposed between the first wall 7 and the second wall 8 on their periphery. These two seals 10, 11 are then compressed by crimping, between contact surfaces between the contact plate 3, the first wall 7, the second wall 8. Alternatively, these seals 10, 11 are beads made from the first wall 7 and therefore of the same material as the first wall 7, is added by a bi-injection process, on one side or both sides of the first wall 7. FIG. 2 illustrates the example where the second seal 11 is a bead of the first wall 7, while the first gasket 10 is an added gasket, for example a gasket of circular section, between the contact plate 3 and the first wall 7. It will be noted that in this section, only the contact 3 and the second wall 8 are hatched. The base plate 2 comprises the first wall 7 and the second wall 8.

Figure 2 further illustrates the tabs 9 according to their cross section, which once crimped, have a rim 14 curved against an outer face 15 of the base plate 2. This outer face 15 is the lower surface of the second wall 8.

It can be seen that the first wall 7 comprises first protuberances 12 protruding towards the contact plate 3 and going so far as to rest on the contact plate 3, in the first level 4. These first protuberances 12 are distributed over the upper surface of the first wall 7, the top being defined as the surface of the contact plate 3 which is in contact with the element to be cooled 5, and the bottom being the surface of the base plate 2 opposite to the contact plate 3 , i.e. the lower surface 15 of the second wall 8. It is also noted that the second wall 8 comprises second protuberances 13 projecting towards the first wall 7 and going so far as to rest on the lower face of the first wall 7. These first and second protrusions 12, 13 have the dual role of making it possible to support the weight of the element to be cooled 5, and to form channels for guiding the fluid in the first and second level 4, 6.

This definition of top, bottom, superior, inferior, is applicable throughout the text of this document.

In this figure 2, as in all the other figures, the element to be cooled 5 is one or more battery modules 5. In all the illustrations, the top and bottom correspond to the earth's gravity and the battery module 5 rests on the cooler 1 which itself rests on a casing of a battery unit (not shown). As previously described, the cooler 1 must therefore support the weight of the battery modules 5, hence the presence of the protrusions 12, 13. But this cooler 1 can also be positioned on a vertical face of the battery module 5.

To facilitate thermal conduction between the contact plate 3 and the battery module 5, an interface thermal conduction element 16 is interposed between the two, for example a thermal paste or a thermal mat, whose ability to deform has the role of ensuring thermal conductivity over the largest possible surface between the battery module 5 and the contact plate 3.

In a variant embodiment, not illustrated, the first and the second wall 7, 8 are made of thermoplastic materials and are assembled by welding, in particular by ultrasonic welding, heating blade, rotation, laser, or else high frequency.

According to a variant embodiment of the invention, not illustrated, the first and the second wall 7, 8 are assembled by gluing, riveting, screwing, snap-fastening, or riveting.

According to a variant embodiment of the invention, not illustrated, the base plate 2 is produced in a single piece by molding, for example by injection of plastic under pressure, or rotational molding.

FIG. 4 also illustrates the first embodiment of the invention. The fluid circulates according to the first flow through the first level 4, and the second flow through the second level 6, the first and the second flow being parallel and of opposite direction. The direction of these flows is represented by arrows without reference. This cooler 1 comprises an inlet for the fluid from the first level 4 via the first inlet orifice 17, an outlet for the fluid from the second level 6 via the second outlet orifice 18, and a fluid passage between the two levels via the first orifice outlet 19 which is remote from the fluid inlet. In particular, the fluid inlet and the fluid passage between the two levels are each at an opposite end of the cooler 1.

It will be noted that, in this figure 4, the second outlet orifice 18 is moved, with respect to figure 2, and would tend to suggest that the outlet pipe 20 is orthogonal to the inlet pipe 21. Even if this configuration is quite conceivable, it is in fact an artifice to be able to represent the outlet orifice 18 in this figure 4, an orifice which would otherwise be confused with the inlet pipe 21 and would make this diagram incomprehensible.

FIG . 3 illustrates the second embodiment of the invention. The fluid circulates according to a first flow through the first level 4, and a second flow at the second level 6, the first and the second flow being parallel and in the same direction. These flows are represented by the arrows without reference. This cooler comprises a fluid inlet common to the two levels 4, 6, a first fluid outlet from the first level, a second fluid outlet from the second level, the fluid inlet being the only fluid communication between the two levels 4, 6.

The fluid inlet common to the two levels 4, 6 is produced, for example, by the same first inlet orifice 17 of the first embodiment, in combination with a third inlet orifice 22 which is common to the two levels 4 , 6, that is to say made in the first wall 7. This third inlet 22 is judiciously placed close to the fluid inlet common to the two levels 4, 6, for example opposite screw of the first inlet orifice 17. The first wall 7 then has the function of dividing the fluid coming from the first inlet orifice 17 into two distinct flows: the first flow through the first level 4, and the second flow through the second level 6. The distribution of the flow rate of the fluid between these two flows essentially depends on the difference in the fluid pressure drops between the two levels 4, 6, which is the simplest embodiment, but in a variant not illustrated, one can consider a pump for each level 4.6.

The first fluid outlet of the first level is produced by a third outlet orifice 23, distant from the first inlet orifice 17, these two orifices each being for example at an opposite end of the cooler 1. This third outlet orifice 23 is by example made in the contact plate 3 and connected to a second outlet line (not shown). The fluid leaving this first level 4 is then a hot fluid or heated by the heat of the battery modules 5, and is evacuated, via this second outlet pipe, for example to a radiator (not shown) which is part of a cooling circuit known to those skilled in the art.

It will be noted that this third outlet orifice 23, for the same reasons as the artificial representation of the second outlet orifice 18 of FIG. 4, is artificially represented in a visible manner in FIG. 3, which would not be the case if this orifice 23 was drawn through the contact plate 3. Even if this configuration of figure 3 is quite possible, it is just an artifice to be able to represent this third outlet orifice 23 on this figure 3.

The second fluid outlet from the second level 6 is produced by a fourth outlet orifice 24, preferably produced in the first wall 7 and connected to a third outlet pipe 25. This fourth outlet orifice 24 can also be produced in the second wall 8, or more generally through the base plate 2, but the advantage of making it in the first wall 7 is to be able to put the third outlet pipe 25 and the second outlet pipe in parallel and the fluid leaving in the same meaning, which is a gain in compactness for the battery pack.

It will be noted that in FIG. 3, the first wall 7 has a hook 31, this hook 31 being a wall orthogonal to the first level 4, and which closes the end of this first level 4. This configuration has the advantage of allowing the third outlet pipe 25 not having to cross the contact plate 3, and therefore avoids having to make an additional seal between this third outlet pipe 25 and the contact plate 3. But this configuration is not imperative, and in a variant not shown, this third outlet pipe 25 can, in an equivalent manner to the first outlet pipe 20, pass through the contact plate 3 in a sealed manner.

The fluid leaving this third outlet pipe 25 is an unheated or uncooled fluid, because it has traveled through the second level 6 between the first wall 7 and the second wall 8 which are made of a heat-insulating material. . This fluid leaving this third outlet pipe 25 can then be guided to a second cooler 30, the second level 6 then simply replacing a fluid pipe which would be cumbersome and a source of fluid leaks. This guidance is shown in Figure 3 by a curved arrow without reference, and is achieved by a pipe (not shown). This second cooler 30 can be of any type, but is shown here identical to the cooler 1 previously described.

The invention also relates to a vehicle (not shown), in particular an electric or hybrid vehicle, this vehicle comprising a battery pack containing at least one battery module 5, this battery pack comprising a cooler 1 as previously described, the element to be cooled by conduction being one face of the battery module 5.

Claims (10)

Cooler (1) comprising a base plate (2), and an all-metal contact plate (3) assembled against the base plate (2) and forming between them a first level (4) for the circulation of a heat transfer fluid , the contact plate (3) being in contact with an element to be cooled (5) by conduction, characterized in that the base plate (2) comprises, in its thickness, an internal space forming a second level (6) of circulation of the heat transfer fluid, the base plate (2) being made of a heat-insulating material whose thermal conductivity λ is less than 2 W · m ⁻¹ · K ⁻¹ at 20 ° C. Cooler (1) according to Claim 1, characterized in that the base plate (2) comprises a first wall (7) facing a second wall (8), a space preserved between the two walls ( 7, 8) forming the internal space. Cooler (1) according to Claim 2, characterized in that the first and the second wall (7, 8) are made of thermoplastic materials and are assembled by welding, in particular by ultrasonic welding, heating blade, rotation, laser, or even high frequency . Cooler (1) according to Claim 2, characterized in that the first and the second wall (7, 8) are assembled by gluing, riveting, screwing, snapping, or snap-fastening. Cooler (1) according to one of claims 2 to 4, characterized in that the base plate (2) comprises a fluid-tight seal (11) between the first and the second wall (7, 8). Cooler (1) according to Claim 1, characterized in that the base plate (2) is produced in one piece by molding. Cooler (1) according to one of claims 2 to 6, characterized in that the contact plate (3) comprises at its periphery tabs (9) crimping the base plate (2) against the contact plate (3). Cooler (1) according to one of the preceding claims, the fluid circulating according to a first flow through the first level (4), and a second flow through the second level (6), characterized in that the first and the second flows are parallel and in the same direction, this cooler (1) comprising a fluid inlet common to the two levels (4, 6), a first fluid outlet of the first level (4), a second fluid outlet of the second level (6 ), the fluid inlet being the only fluid communication between the two levels (4, 6). Cooler (1) according to one of claims 1 to 7, the fluid circulating in a first flow through the first level (4), and a second flow through the second level (6), characterized in that the first and the second flow are parallel and in opposite directions, this cooler (1) comprising a first level fluid inlet (4), a second level fluid outlet (6), and a fluid passage between the two levels (4, 6), distant from the fluid inlet. Vehicle, in particular an electric or hybrid vehicle, this vehicle comprising a battery pack containing at least one battery module (5), characterized in that this battery pack comprises a cooler (1) according to one of the preceding claims, the element to be cooled by conduction being one face of the battery module (5).