FR3139414A1 - BATTERY COOLED BY SPRAYING A DIELECTRIC FLUID. - Google Patents

Abstract

Battery (1) comprising: - a hermetic casing (2) delimiting an internal volume (3), and comprising a bottom (10) intended to collect by gravity a first heat transfer fluid (5) projected into this internal volume (3), - an electrochemical element (4) for storing electrical energy, housed in this internal volume (3), - a projection nozzle (9) of the first heat transfer fluid (5), housed in the internal volume (3), and intended to projecting the first heat transfer fluid (5) against the electrochemical element (4), - a cooler (14) comprising a chamber (7) intended to receive a second heat transfer fluid (8), this cooler (14) being intended to cool the first heat transfer fluid (5) by heat exchange with this second heat transfer fluid (8) by thermal conduction through a first wall (11) of the chamber (7), the bottom (10) of the casing (2) comprising this first wall ( 11). Figure 1.

Description

BATTERY COOLED BY PROJECTION OF A DIELECTRIC FLUID.

The invention relates to an electrical energy storage battery, and more particularly to a battery for an electrically powered vehicle.

By battery, throughout the text of this document, we will understand an assembly comprising at least one electrochemical cell. When there are several electrochemical cells, they are grouped into one or more modules. This battery possibly 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 tray or casing and then form a battery pack, this battery pack often being referred to by the English expression "battery pack", this casing generally containing a mounting interface, and connection terminals.

Furthermore, by electrochemical cell we will understand throughout the text of this document, cells generating current by chemical reaction, for example of the lithium-ion (or Li-ion) type, of the Ni-Mh type, or Ni-Cd or lead or fuel cells.

In this area, the chemical reactions internal to the electrochemical cells cause variations in the temperature of the cells which, to remain within an operating temperature range, must be heated and more generally cooled in a regulated manner.

We know from patent document JP-A-2021132008 a device for cooling electrochemical elements of a battery by spraying a first heat transfer fluid onto these elements. This first heat transfer fluid is itself cooled by a cooler entirely immersed in this first heat transfer fluid, this cooler being in the form of an exchanger through which a second heat transfer fluid passes. This exchanger is entirely immersed in a reserve of the first heat transfer fluid accumulated at the bottom of the battery.

Unfortunately this exchanger is very bulky and takes up the space of several cells, and therefore greatly reduces battery life. In addition, it is attached to the inside of the battery and must therefore be fixed there, which requires a delicate assembly operation due to the necessary fluid connections while the battery casing must be closed and airtight.

The aim of the invention is to remedy at least one of these shortcomings by proposing a battery presenting better integration of this exchanger.

For this purpose, the object of the invention proposes a battery comprising:
- a hermetic casing delimiting an internal volume, and comprising a bottom intended to collect by gravity a first heat transfer fluid projected into this internal volume,
- an electrochemical element for storing electrical energy, housed in this internal volume,
- a nozzle for projecting the first heat transfer fluid, housed in the internal volume, and intended to project the first heat transfer fluid against the electrochemical element,
- a cooler comprising a chamber intended to receive a second heat transfer fluid, this cooler being intended to cool the first heat transfer fluid by heat exchange with this second heat transfer fluid by thermal conduction through a first wall of the chamber,
the bottom of the casing comprising this first wall.

We will understand by "projection of the first heat transfer fluid throughout the text of this document, a projection of a fluid in the form of a spray of fine droplets and/or a mist and/or a continuous or non-continuous jet of liquid or gas.

The invention relates in particular to a spraying of fine droplets of the first heat transfer fluid.

It is implicit that the first heat transfer fluid is intended to regulate the temperature of the electrochemical element during its electrical operation and to remain within a range of operating temperatures, for example between 10°C and 50°C for a lithium type cell. -ion or Li-ion,

The electrochemical element is for example an electrochemical cell or a module comprising this electrochemical cell.

The chamber is thus perfectly integrated into the bottom of the battery casing, and this first wall can extend over a large surface of the bottom, or even the entire surface of the bottom. So :
- the cooler does not take up space in the internal volume, which can therefore contain more electrochemical elements,
- battery life is therefore increased, and
- the assembly of the battery is simplified, the cooler chamber being already integrated into the bottom of the casing.

In addition, this first wall can advantageously receive the electrochemical elements and be in direct thermal contact with them.

It will be noted that the first heat transfer fluid being collected by the bottom, this bottom is at least regularly sprayed, or even immersed by the first heat transfer fluid, thus the heat exchange between the first heat transfer fluid and the second heat transfer fluid is carried out by thermal conduction at the bottom. through the first wall. It is implicit that this first wall faces the internal volume, and partly delimits this internal volume by a second face which will be explained in the description below.

According to one embodiment of the invention, the battery comprises a circulation circuit for the first heat transfer fluid, this circulation circuit comprising, fluidly connected in series:
- the projection nozzle, and
- a pump for circulating the first fluid, housed in the internal volume and intended to suck up the first heat transfer fluid collected from the bottom and to discharge this first heat transfer fluid through the nozzle.

According to one embodiment of the invention, the circulation pump is intended to be immersed in the first heat transfer fluid.

According to one embodiment of the invention, the circulation circuit comprises a filter configured to filter the first heat transfer fluid.

According to one embodiment of the invention, the circulation pump comprises a filter configured to filter the first heat transfer fluid.

It is implicit that this circulation circuit can include circulation pipes fluidly connecting the pump, the filter, the nozzle, possible non-return valves, so that the first heat transfer fluid is intended to circulate in forced flow from the bottom of the casing towards the nozzle passing through the circulation pump, so as to be projected against the electrochemical element then be collected again by the bottom of the casing, this bottom then cooling this first heat transfer fluid by thermal exchange with the second heat transfer fluid.

According to one embodiment of the invention, the bottom comprises, in its thickness:
- the first wall, this first wall delimiting part of the internal volume and
- a second wall facing the first wall, partly forming the exterior of the hermetic casing,
a space between the first wall and the second wall housing the chamber.

According to one embodiment of the invention, the first wall and the second wall form the chamber.

According to one embodiment of the invention, the first wall is thinner than the second wall.

According to one embodiment of the invention, the first wall has better thermal conductivity than the second wall. For example, the first wall is made of copper while the second wall is made of steel.

According to a variant embodiment of the invention, the first wall and the second wall are made of the same material and form a single part, in particular from a foundry.

According to one embodiment of the invention, this battery comprises the first heat transfer fluid, this first heat transfer fluid being a dielectric fluid.

The invention also relates to an electrically powered motor vehicle comprising:
- a driving wheel,
- an electric driving machine rotating the driving wheel,
- an electrical energy storage battery supplying current to the electric driving machine,
this battery being as previously described, the bottom being configured to form a reserve of the first heat transfer fluid.

Other particularities and advantages will appear on reading the following description of a particular, non-limiting embodiment of the invention, made with reference to the figures in which:

: represents a block diagram of a battery according to the invention.

: represents a diagram of a cross-sectional view of the bottom according to the invention.

: represents a diagram of a cross-sectional view according to a variant of the bottom according to the invention.

It should be kept in mind that the figures are given as examples and are not limiting to the invention. They constitute schematic representations of principle intended to facilitate the understanding of the invention and are not necessarily on the scale of practical applications. Furthermore, in what follows, reference is made to all the figures taken in combination. When reference is made to one or more specific figures, these figures must be taken in combination with the other figures for the recognition of the designated numerical references. The references of unchanged elements or having the same function are common to all the figures, and the variant embodiments.

These figures disclose a battery 1 comprising:
- a hermetic casing 2 delimiting an internal volume 3, and comprising a bottom 10 intended to collect by gravity a first heat transfer fluid 5 projected into this internal volume 3,
- an electrochemical element 4 for storing electrical energy, housed in this internal volume 3,
- a projection nozzle 9 of the first heat transfer fluid 5, housed in the internal volume 3, and intended to project the first heat transfer fluid 5 against the electrochemical element 4,
- a cooler 14 comprising a chamber 7 intended to receive a second heat transfer fluid 8, this cooler 14 being intended to cool the first heat transfer fluid 5 by heat exchange with this second heat transfer fluid 8 by thermal conduction through a first wall 11 of the chamber 7,
the bottom 10 of the casing 2 comprising this first wall 11.

This battery comprises a circulation circuit 6 of the first heat transfer fluid 5, this circulation circuit comprising, fluidly connected in series:
- the projection nozzle 9, and
- a circulation pump 13 for the first fluid 5, housed in the internal volume 3 and intended to suck up the first heat transfer fluid 5 collected by the bottom 10 and to discharge this first heat transfer fluid 5 through the nozzle 9.

The circulation pump 13 is for example intended to be immersed in the first heat transfer fluid 5.

This circulation pump 13 is for example fixed inside the internal volume 3, against the casing 2, for example against the bottom 10. But this is not obligatory, and it can also be fixed on the casing 2, at outside of casing 2.

It will be noted that on the , the circulation circuit 6 comprises pipes channeling the first heat transfer fluid 5, which are shown in strong lines. There also represents a set of seven electrochemical cells 4, or even seven modules 4, and the projection of the first heat transfer fluid 5 on these electrochemical elements 4 (the cells and/or the modules) is represented by dotted lines in seven conical envelopes of which each vertex comes from one of the seven nozzles 9 of the circulation circuit 6. These seven nozzles 9 are connected in series (relative to the direction of circulation of the first heat transfer fluid 5) along a pipe forming a branch of the circulation circuit circulation 6, but many other configurations of the circulation circuit 6 are possible, in particular with several of these branches.

There represents the battery 1 in a service position, in particular in a motor vehicle. Thus the casing 2 comprises the bottom 10 on which, for example and not illustrated on the , are housed and rest the electrochemical elements 4, and a cover closing the internal volume 3 from above. The electrochemical element(s) 4 are semi-immersed in the first heat transfer fluid 5: A reserve of this first heat transfer fluid 5 is arranged in the bottom 10 of this casing 2, and the base or bottom of the electrochemical elements 4 is immersed in this reserve, the level or free surface 17 of which is represented by a dotted line in the shape of a wave to illustrate its liquid state. Conversely, the top and/or faces of the electrochemical elements 4 are not immersed but exposed to the projection of the first heat transfer fluid 5 emanating from the nozzles 9. Alternatively, the electrochemical elements 4 may of course not be immersed in the all but entirely arranged above the free surface 17. The circulation pump 13 sucks up the first heat transfer fluid 5 by drawing near the bottom 10 of the casing 2, under the free surface 17, by the optional presence of a pipe suction 19 of the circulation circuit 6. This circulation pump 13 is shown inside the internal volume 3, and is for example immersed in the first heat transfer fluid 5, that is to say immersed in the reserve. But it could of course be external to the internal volume.

In an embodiment 1, the bottom 10 comprises, in its thickness:
- the first wall 11, this first wall 11 delimiting a part of the internal volume 3 and
- a second wall 12 facing the first wall 11, partly forming the exterior of the hermetic casing 2,
a space between the first wall 11 and the second wall 12 housing the chamber 7.

In an example 2 of embodiment according to the invention, the first wall 11 and the second wall 12 form the chamber 7.

It will be noted that the illustrates the two previous examples at the same time.

Example 1 of embodiment: chamber 7 is, in this example, identified by the sign 7a. This chamber 7a is formed inside a pipe for the second heat transfer fluid 15, this pipe for the second heat transfer fluid 15 being housed in the space between the first wall 11 and the second wall 12, for example by extending into this space by winding or forming a helicoid. Thus room 7a is housed in space. For example, this pipe for the second heat transfer fluid 15 is welded or brazed against a first face of the first wall 11, so that this first wall 11 and this pipe for the second heat transfer fluid 15 form a block directly placed or assembled with the second wall 12. For example, the first wall 11 and the pipe for the second heat transfer fluid 15 are made of a material comprising copper, in particular copper. This welding or brazing allows good heat exchange between the first wall 11 and the pipe of the second heat transfer fluid 15, this first wall 11 also being in thermal contact with the first heat transfer fluid 5 on a second face, opposite the first face, this second face partially delimiting the internal volume 3. Still in this example 1, it will be noted that the conduit of the second heat transfer fluid 15 intrinsically provides sealing between the first heat transfer fluid 5 and the second heat transfer fluid 8. Thus, a means of fixing between the two walls 11, 12 does not need to achieve this sealing, the first heat transfer fluid 5 can then be in contact directly with the outside of the pipe of the second heat transfer fluid 15. Advantageously, the first wall 11 comprises through openings in its thickness (not illustrated), so that the first heat transfer fluid 5 can be in contact with the outside of the pipe of the second heat transfer fluid 15. Advantageously, the second face of the first wall 11 receives and supports the elements electrochemical 4.

Example 2 of production: chamber 7 is, in this example, marked by sign 7b, you must then imagine that the dotted pipe marked by sign 15 is not present. The first wall 11 and the second wall 12 form the chamber 7b. In this example 2, the sealing of the chamber 7b is achieved by the means of fixing the first wall 11 with the second wall 12. Thus, if this assembly means is for example a screwing means, it will advantageously include a seal or a sealing paste inserted between the two walls 11, 12. But other means of assembly are possible, for example by welding or gluing. In this example 2, and using the definition of first face and second face of the first wall 11 of example 1, without the conduit of the second heat transfer fluid 15, the first face is in contact with the second heat transfer fluid 8 while the second face is in contact with the first heat transfer fluid 5. Of course, in this example 2 the second face of the first wall 11 can also receive and support the electrochemical elements 4.

It will be noted that for all the examples described in this text, the second heat transfer fluid 8 is for example a fluid circulating at forced flow in the chamber 7 which it passes through. For example, this second heat transfer fluid 8 is a refrigerant of an air conditioning system, entering and leaving the chamber 7 via an inlet and outlet pipe 18 of the cooler 14. As those skilled in the art know, this system air conditioning system further comprises a condenser, and a compressor forcing the passage of the second heat transfer fluid 8 into the chamber 7, the cooler 14 having, for this air conditioning system, the function of evaporator. This cooler 14 comprises for example the first wall 11 and the second wall 12 for example 2, or comprises the first wall 11 and the pipe for the second heat transfer fluid 15 for example 1.

Likewise, it will be noted that for all the examples described in this text, an advantage of this solution is to be able to take advantage of the large surface area of the bottom 10 to optimize the efficiency of the heat exchange between the first and second heat transfer fluid 5, 8, the chamber 7, 7a, 7b, 7c, 7d extending as far as possible, within the limits of what is technically possible, over the surface of the bottom 10, thus increasing the heat exchange surface between the two heat transfer fluids 5.8. Thus the second face whose definition is common to all examples, and which is in contact with the first heat transfer fluid 5, is advantageously flat, but not necessarily, in particular if this second face receives and houses the electrochemical elements 4. In addition and optionally, for reasons of mechanical strength, the first wall 11, and therefore this second face and/or the first face, includes ribs which may individually or in combination have the functions of:
- hold the electrochemical elements 4,
- serve as a stop for the first wall 11 by bearing on the second wall 12 to prevent the chamber 7 from collapsing, for example under the effect of the weight of the electrochemical elements 5,
- increase the exchange surface between the first wall 11 and the first heat transfer fluid 5 and/or between the first wall 11 and the second heat transfer fluid 8.

For example, the first wall 11 is thinner than the second wall 12.

In fact, the desired heat exchange is between the first heat transfer fluid 5 and the second heat transfer fluid 8. Now this second heat transfer fluid 8 can be, as we have already described, a refrigerant, whose temperature is lower than the ambient temperature outside the casing 2. Thus, the heat exchange between this second heat transfer fluid 8 and the ambient air in the casing 2 is harmful. A first way of limiting this harmful exchange is to increase the thickness of the second wall 12, which increases the thermal resistance of this second wall 12. Of course, thermal insulation attached to this second wall 12 would have the same advantage, but the increase in its thickness is advantageous because it also makes it possible to increase the resistance to external mechanical attacks of the casing 2, in particular if this battery 1 is housed under a floor of a vehicle, this second wall 12 facing to the rolling surface and therefore to the projections of solid objects such as gravel or stones propelled by the wheels. In all cases, this increase in thickness can of course be supplemented by thermal insulation if necessary.

For example, and with the same objective, the first wall 11 has better thermal conductivity than the second wall 12.

Example 3: In a variant of the invention, represented in , the bottom 10 comprises in its thickness the first wall 11 and the second wall 12 which are made of the same material and form a single part, in particular from a foundry. In this example 3, from the , the chamber 7 is represented in a first form by the reference 7c, and a second form by the reference 7d. The first shape 7c is a channel having a cylindrical section, this channel forming a circulation network for the second fluid 8 in the thickness of the bottom 10. This first shape offers the advantage that the chamber 7c and the first wall 11 have good resistance mechanics making it possible to support the weight of the electrochemical elements 4 without deforming. The second form 7d is more ordinary, but of larger section: This second form is easier to obtain by foundry.

Note an example 4 of embodiment of the invention, not illustrated, which combines example 3 with example 1. Thus the first wall 11 and the second wall 12 are for example of the same material but welded together or assembled l one on the other by the waterproof fixing means, the first wall 11 being a stamped sheet comprising the partial borrowing, on its first face, of a pipe for the second heat transfer fluid. Once welded or assembled, the first wall 11 forms with the second wall 12 directly the complete conduit for the second heat transfer fluid. This first stamped wall 11 could, for example, have locally specific imprints on the second face to house the electrochemical element.

For example, this battery 1 comprises the first heat transfer fluid 5, this first heat transfer fluid 5 being a dielectric fluid. The first heat transfer fluid 5 is for example an aqueous or gaseous dielectric fluid.

This invention advantageously applies to an electrically powered motor vehicle comprising:
- a driving wheel,
- an electric driving machine rotating the driving wheel,
- the electrical energy storage battery 1, supplying current to the electric motor machine.

For example, the bottom 10 is configured to form a reserve of the first heat transfer fluid 5.

This vehicle includes for example the air conditioning system of a passenger compartment 18 previously mentioned, well known to those skilled in the art. There only represents the pipes 18 of the second refrigerant 8 connecting to the cooler 14.

For example, this motor vehicle is exclusively electric powered.

Claims (10)

Battery (1) including:
- a hermetic casing (2) delimiting an internal volume (3), and comprising a bottom (10) intended to collect by gravity a first heat transfer fluid (5) projected into this internal volume (3),
- an electrochemical element (4) for storing electrical energy, housed in this internal volume (3),
- a projection nozzle (9) of the first heat transfer fluid (5), housed in the internal volume (3), and intended to project the first heat transfer fluid (5) against the electrochemical element (4),
- a cooler (14) comprising a chamber (7) intended to receive a second heat transfer fluid (8), this cooler (14) being intended to cool the first heat transfer fluid (5) by heat exchange with this second heat transfer fluid (8) by thermal conduction through a first wall (11) of the chamber (7),
characterized in that the bottom (10) of the casing (2) comprises this first wall (11). Battery according to claim 1, comprising a circulation circuit (6) of the first heat transfer fluid (5), this circulation circuit comprising, fluidly connected in series:
- the projection nozzle 9, and
- a circulation pump (13) for the first fluid (5), housed in the internal volume (3) and intended to suck up the first heat transfer fluid (5) collected from the bottom (10) and to discharge this first heat transfer fluid (5) ) through the nozzle (9). Battery according to claim 2, the circulation pump (13) being intended to be immersed in the first heat transfer fluid (5). Battery according to one of the preceding claims, the bottom (10) comprising, in its thickness:
- the first wall (11), this first wall (11) delimiting a part of the internal volume (3) and
- a second wall (12) facing the first wall (11), partly forming the exterior of the hermetic casing (2),
a space between the first wall (11) and the second wall (12) housing the chamber (7). Battery according to claim 4, the first wall (11) and the second wall (12) forming the chamber (7). Battery according to claim 4 or 5, the first wall (11) being thinner than the second wall (12). Battery according to one of claims 4 to 6, the first wall (11) having better thermal conductivity than the second wall (12). Battery according to one of claims 4 to 6, the first wall (11) and the second wall (12) being made of the same material and forming a single piece, in particular from a foundry. Battery according to one of the preceding claims, this battery (1) comprising the first heat transfer fluid (5), this first heat transfer fluid (5) being a dielectric fluid. Electrically powered motor vehicle comprising:
- a driving wheel,
- an electric driving machine rotating the driving wheel,
- an electrical energy storage battery (1) supplying current to the electric motor machine,
characterized in that the battery (1) conforms to claim 9, the bottom (10) being configured to form a reserve of the first heat transfer fluid (5).