FR3095077A1 - Device for regulating the temperature of a battery using a dielectric fluid and battery pack comprising such a device - Google Patents

Abstract

Device for regulating the temperature of a battery using a dielectric fluid and battery pack comprising such a device A device (4) for regulating the temperature of at least one electrical component (2) of a motor vehicle, in particular an energy storage cell, the device comprising an enclosure (6) of dielectric fluid and means for spraying the surface of said component with said dielectric fluid, said means for spraying comprising at least one stirrer (8). Figure for the abstract: Figure 1

Description

Device for regulating the temperature of a battery using a dielectric fluid and battery pack comprising such a device

The invention relates to a device for regulating the temperature of battery cells using a dielectric fluid. The invention also relates to a battery pack comprising said device as well as a plurality of battery cells. It is in particular intended to equip motor vehicles, in particular motor vehicles with electric or hybrid engines.

As the market share of electric vehicles is growing, the dielectric / heating issues of the battery packs that equip them are becoming strategic issues. The objective is to design the most efficient, efficient and economical thermal management device for batteries.

Often to meet the cooling (and / or heating) need of electric coils, “heat exchangers” are used consisting of a cold plate with circulation of a heat transfer liquid (eg mixture of water and ethylene glycol), the plates being in contact with the cells to be cooled. This type of technique can lead to uneven cooling (and / or heating) of the batteries and thus limit their life and their performance. These devices also have high thermal resistance due to the thicknesses of material present between the heat transfer liquid and the cells.

One solution proposed to respond to this problem consists of immersing the electric batteries in a dielectric coolant. This immersion can be carried out with fluid circulation or in static condition with phase change.

These two techniques are efficient from a thermal point of view in particular because of the direct contact established between the liquid and the cells but have the disadvantage of using a large quantity of dielectric liquid, which increases the cost and the weight of the pack. drums.

The invention aims to solve these technical problems by proposing a device for regulating the temperature of at least one electrical component of a motor vehicle, in particular an energy storage cell, comprising a dielectric fluid chamber and means for spraying the surface. of said component with said dielectric fluid, said means for sprinkling comprising at least one agitator.

By means for spraying is meant any type of means making it possible to bring the dielectric fluid into contact with the surface (s) of the battery cells other than by immersing said cells in said dielectric fluid.

These are in particular spraying means, spraying means or any means capable of producing a circulation of said fluid so as to bring the dielectric fluid into contact with the surface of the cells, in the form of a liquid film. , jets, droplets resulting from a misting or other.

By agitator is meant any means for setting the fluid in motion, particularly in the liquid state, and thus for agitating the fluid.

This device not only makes it possible to recover large amounts of heat and to ensure homogeneous cooling by direct contact of the dielectric fluid and the cells to be cooled, but also makes it possible to limit the amount of dielectric fluid and therefore the weight and cost of the device. eliminating the dielectric liquid bath known in previous devices.

Indeed, the volume of dielectric fluid in the liquid state can be very low, for example at most 25% of the volume of the enclosure, preferably at most 10%, preferably at most 6%. , preferably at most 4% and more preferably at least 2%. The volume of dielectric liquid used is for example 5 and 10 liters depending on the size of the battery pack. These volumes of dielectric liquid are of course understood as volumes introduced into the device in the initial state.

The invention may also include any of the following characteristics, taken individually or in any technically possible combination:

- the agitator is suitable for agitating the dielectric fluid in the liquid state and thus atomizing it;

- the agitator comprises a vibrating surface intended to vibrate and an actuator connected to this surface to make it vibrate;

- the agitator is configured to vibrate the vibrating surface at a frequency of at least 50khz and at most 1.5MHz, preferably at least 200KHz;

- the vibrating surface is a membrane;

- the actuator is of the piezoelectric type;

the device is configured such that the vibrating surface is at least partially immersed in the dielectric fluid, preferably totally immersed;

- the device is configured such that the vibrating surface is immersed under no more than 30 mm of dielectric fluid in the liquid state;

- the dielectric fluid level above the vibrating surface is at least 10mm;

- the diameter of the vibrating surface is at least 5mm and at most 35mm, preferably at least 15mm and preferably at most 25mm;

- the volume of dielectric fluid in the liquid state is at most 25%, preferably at most 10%, preferably at most 6%, preferably at most 4% of the total volume of the dielectric enclosure in which the battery cells are housed;

- the dielectric fluid has the ability to change state or phase depending on the temperature, advantageously the point of change of state is chosen according to the optimum operating temperature of the electrical device to be thermally regulated.

- the fluid is intended to vaporize on the surface of the cells, and thus to pass from a 100% liquid state to a 100% vapor state by its contact with the surface of the cells

- The dielectric fluid evolves in a closed enclosure, hermetic to said fluid regardless of its state.

- the closed enclosure is delimited by the walls of the device,

- the agitator is configured so as to spray the dielectric fluid in the form of fine drops, intended to be deposited on the surface of the cells,

- the device comprises a reservoir under the location of the battery cells, the reservoir being able to recover, in a liquid phase, the dielectric fluid sprayed by the agitator on the surface of the battery cells;

- the agitator is below the level of at least one of the battery cells

- the agitator being arranged in the tank, preferably in a bottom of the tank

- several agitators are arranged under the location of several battery cells

- the agitators are distributed over the entire tank

- the agitators are in the bottom of the tank

- the device comprises at least one means for cooling the dielectric fluid;

the means for cooling the dielectric fluid comprises a heat exchanger for exchanging heat with the dielectric fluid.

- the means for cooling the dielectric fluid comprises a heat exchanger located in the tank;

- the cooling means comprises a condenser configured so as to condense the dielectric fluid to change from vapor phase to liquid phase and to cause said fluid to flow to the reservoir;

- the condenser is configured for the circulation of a refrigerant fluid intended to exchange heat with the dielectric fluid;

- the condenser is positioned above the battery cells, preferably the condenser covers a majority of the surface occupied by the cells,

- the condenser is configured for the circulation of a refrigerant fluid intended to exchange heat with the dielectric fluid,

- the condenser forms an upper wall of the battery pack,

- the condenser covers or overhangs a majority, preferably the entire area including the battery cells.

the condenser has a face that is substantially flat and inclined relative to a horizontal direction when the battery pack is mounted on a motor vehicle,

- the condenser comprises a hydrophobic condensation surface, for example silicone, Teflon, wax or fatty acids;

the device comprises means for heating said dielectric fluid;

- the heating medium is in the tank.

The invention also relates to a battery pack comprising the above device as well as a plurality of battery cells.

The invention will be better understood and other details, characteristics and advantages of the invention will become apparent on reading the following description given by way of non-limiting example and with reference to the accompanying drawings in which:

- Figure 1 is a partial side view and in perspective of a battery pack provided with battery cells and a cooling device according to one embodiment of the invention; and

- Figure 2 is a partial sectional view of the battery pack of Figure 1.

Figure 1 illustrates a battery pack 1 comprising a plurality of battery cells 2 and a device 4 for regulating the temperature of the battery cells 2. The set of 2 battery cells forms what is called the "battery". The battery here has nine cells, but this is only a schematic example, and the battery may have a much larger number of cells.

For their correct operation, it is desired that the temperature of the cells 2 be kept within a restricted value range, for example between 20 ° C and 40 ° C. The device 4 illustrated has the precise function of effecting such a temperature regulation.

The device 4 comprises an enclosure 6 in which the cells 2 are housed as well as stirrers 8 for spraying a dielectric fluid (not shown) up to the surface of the cells 2. The enclosure 6 is delimited by the walls of the device 4. The enclosure 6 is closed so that the dielectric fluid circulates and remains within it. It has a shape of any suitable type.

The dielectric fluid settles on the surface of the cells in a liquid state and evaporates on contact with the surface of the cells 2, thereby cooling the cells 2 by absorbing heat in the dielectric fluid.

Once evaporated, the dielectric fluid rises by natural convection to a condenser intended to cool and condense the dielectric fluid from the vapor state to the liquid state by removing its heat. The dielectric fluid then returns by flowing by gravity to a reservoir 12 of dielectric fluid in the bottom of the device. The agitators 8 are housed in the bottom of the tank 12.

The stirrers 8 described are three in number, but their number is of any suitable type.

In the example illustrated, the three agitators 8 are each housed in the middle of three longitudinal sections of the reservoir 12, and, in general, the agitators 8 are preferably distributed over the entire reservoir 12.

Each agitator 8 comprises a membrane 10 intended to vibrate, forming a vibrating surface, and an actuator (not shown) connected to this vibrating surface to make it vibrate and thus spray the dielectric fluid in which each agitator 8 is bathed.

The membrane 10 is of any suitable type.

The actuator is for example of the piezoelectric type and generally suitable for causing the vibrating surface to vibrate at a frequency of at least 50khz and at most 1.5MHz, preferably at least 200KHz.

The agitator 8 is thus adapted to agitate the dielectric fluid in the liquid state and thus spray it to the surface of the battery cells.

The vibrating surface of each stirrer 8 is immersed under at least 10mm of dielectric fluid in the liquid state and at most 30mm of dielectric fluid in the liquid state. The volume of dielectric fluid in the cooling chamber is chosen so as to have these levels of dielectric fluid in the reservoir, above each stirrer 8.

The volume of liquid used is for example between 5 and 10 liters depending on the size of the battery pack, which corresponds to a percentage by volume between 2 and 4% of the volume of the enclosure. In general, the volume of dielectric liquid is at most 25%, preferably at most 10%, preferably at most 6% of the volume of the enclosure, preferably at most 4 % and preferably at least 2%.

More generally, the cooling device is configured such that the vibrating surface is at least partially immersed in the dielectric fluid, preferably fully immersed.

The vibrating surface has a diameter of at least 5mm and at most 35mm, preferably at least 15mm and preferably at most 25mm.

As can be seen more particularly in FIG. 2, the dielectric fluid reservoir is formed by a recess in the device, under the battery cells.

The reservoir 12 is below the battery cell location, and thus being able to recover, in a liquid phase, the dielectric fluid sprayed by the agitator onto the surface of the battery cells.

In the example illustrated, the device 4 comprises in its bottom support feet 14 around the periphery and the center of the device 4.

The device 4 also includes elongated longitudinal support rails 16 extending over substantially the entire length of the battery pack. Only one of the two rails 16 is visible in the figures. The rails 16 are parallel and spaced approximately the width of the battery cells 2. These rails 16 are described purely by way of illustration and not by way of limitation. In general, the cells 2 are maintained at the height of the bottom in the device by means of any suitable type.

These rails emerge above the coolant level, but alternatively the battery cells are bathed in the dielectric liquid.

Each stirrer 8 is arranged in the bottom of the tank, under the battery cells.

In the example illustrated, the stirrers 8 are aligned and located in a midplane in the direction transverse to the direction of alignment of the cells, i.e. substantially in the middle of the cells.

In general, the arrangement and number of agitators are of any suitable type.

In the upper part of the device 4 is illustrated the condenser 18 for the dielectric fluid, that is to say intended to condense the dielectric fluid and a cover 20 closing the enclosure 6.

As visible in Figures 1 and 2, the condenser 18 comprises a cooling fluid circuit 22 passing through its thickness in several passes, so as to remove the heat of the condensation of the dielectric fluid in the cooling fluid. The cooling fluid circuit 22 is for example connected to a motor vehicle air conditioning circuit or cooled by the latter.

The condenser 18 is positioned above the battery cells 2. Preferably, the condenser 18 covers a majority of the surface occupied by the cells.

It is the condenser 18 which indirectly cools the battery cells 2 by capturing the vapor of dielectric fluid resulting from the evaporation of this fluid in contact with the surface of the cells and by condensing it. With this arrangement of the condenser, the dielectric fluid vapor is naturally guided to the condenser by an upward convective motion.

The condenser 18 forms with the cover the upper wall of the battery pack.

The condenser 18 has a face that is substantially planar and inclined relative to a horizontal direction when the battery pack is mounted on a motor vehicle. As a variant, the condenser has several inclined surfaces.

In general, the lower surface of the condenser is configured to guide the flow of liquid dielectric fluid towards the reservoir of dielectric fluid in the liquid state, the condenser comprises a condensation surface comprising a hydrophobic material, for example silicone, Teflon, wax or fatty acids. In general, this hydrophobic material can also be used on dielectric fluid condensers for which the system for spraying batteries with dielectric fluid would be different, for example spray systems.

Finally, the device comprises, in the reservoir, a means for heating the dielectric fluid, so as to heat the cells if necessary.

It should be noted that the observation windows 24 are those of a prototype and that these windows 24 are intended to be deleted in a serial version.

Claims (10)

Device (4) for regulating the temperature of at least one electrical component (2) of a motor vehicle, in particular an energy storage cell, the device (4) comprising a chamber (6) of dielectric fluid and means for watering the surface of said component with the aid of said dielectric fluid, said means for sprinkling comprising at least one stirrer (8). Device (1) according to claim 1, wherein the stirrer (8) is adapted to stir the dielectric fluid in the liquid state and thus spray it. Device (1) according to claim 1 or 2, wherein the agitator (8) comprises a vibrating surface (10) intended to vibrate and an actuator connected to this surface to make it vibrate. Device (1) according to claim 3, wherein the agitator (8) is configured to vibrate the vibrating surface at a frequency of at least 50khz and at most 1.5MHz, preferably at least 200KHz. Device (1) according to claim 3 or 4, wherein the actuator is of the piezoelectric type. Device (1) according to any one of the preceding claims, wherein the device is configured such that the vibrating surface (10) is at least partially immersed in the dielectric fluid, preferably fully submerged. Device (1) according to any one of the preceding claims, in which the device (4) comprises a reservoir (12) under the location of the battery cells, the reservoir (12) being able to recover, in liquid phase, the dielectric fluid sprayed by the agitator (8) onto the surface of the battery cells. Device (1) according to any preceding claim, wherein the agitator (8) is below the level of at least one of the battery cells. Device (1) according to claim 8 or 9, in which the agitator is arranged in the tank, preferably in a bottom of the tank. Battery pack comprising the device (1) according to one of the preceding claims as well as a plurality of battery cells arranged in the device.