FR3118678A1 - Electricity storage battery - Google Patents

Abstract

Electricity storage battery The battery (1) comprises at least one module (3) comprising electricity storage cells (5) and at least one compartment (23) for receiving the at least one module (3), each storage cell electricity (5) having a nominal thickness E0; at least one of the transverse walls (31, 32) of the compartment being in an elastic material; when a module (3) is engaged in the compartment (23), the transverse walls (31, 32) exert on the module (3) a compressive force adapted to maintain the electricity storage cells (5) substantially at their nominal thicknesses E0. Figure for abstract: 4

Description

Electricity storage battery

The present invention generally relates to electricity storage batteries, in particular for motor vehicles.

The application filed under number FR 20 07331 discloses an electricity storage battery whose cells are cooled by direct contact with a dielectric liquid.

The use of a dielectric liquid makes it possible to directly cool the live parts, without interfering with the operation of these parts, the electric conductivity of the liquid being able to be regarded as null. Such cooling is very efficient and makes it possible to obtain good exchange densities. It can also cool large areas.

Indirect contact cooling systems, by comparison, generally do not cool the entire surface of the heat-emitting part. In such a system, it is enough to cool the most accessible part of the room. This inevitably leads to unwanted temperature gradients.

In particular, in the context of cooling by air circulation, the density of the heat exchange is very low, even by forcing convection by ventilation.

In batteries cooled by a dielectric liquid, one objective is to minimize the volume of dielectric liquid used, due to the high cost thereof.

In FR 20 07331, part of the internal volume of the battery is occupied by a low density plastic material, so as to reduce the volume of dielectric liquid used. This low density plastic material defines compartments in which the battery modules are housed. Each module consists of a stack of several electricity storage cells. The low-density plastic material is shaped in such a way as to delimit a circulation path for the dielectric liquid, allowing the greatest possible portion of each of the cells placed inside the battery to be cooled.

In FR 20 07331, provision is made for each module to present longitudinally a length greater than that of the corresponding compartment. Thus, the cells are locked in position relative to each other in the compartment due to the pressure exerted by the low density plastic material. Such an arrangement is particularly advantageous, because it is no longer necessary to provide specific means for fixing the cells of the same module to each other. In the patent application filed under number FR 19 00228, provision is made, on the contrary, to place the cells between two end plates, the plates and the cells being pressed against each other using a wound strap. around the module.

However, in order to be able to dispense with such holding means, it is necessary to comply with a large number of constraints.

In this context, the invention aims to propose an electricity storage battery respecting these constraints, and in which the modules can thus be held in place in the corresponding reception compartments without using holding means of the type described in FR 19 00228.

To this end, the invention relates to an electricity storage battery comprising:
- at least one module comprising a number N of electricity storage cells stacked in a longitudinal direction,

- an envelope, inside which is arranged at least one compartment for receiving the at least one module, the or each compartment having first and second transverse walls having external surfaces delimiting the compartment at its two opposite longitudinal ends ;

each electricity storage cell having two large transverse faces opposite each other and having, between said large faces, longitudinally, a nominal thickness E0;

at least one of the first and second transverse walls being in an elastic material;
when a module is engaged in the compartment, the first and second transverse walls longitudinally exert on the module a compressive force adapted to maintain the electricity storage cells substantially at their nominal thicknesses E0. .

Thus the first and second transverse walls exert a sufficient compressive force longitudinally on this module.

This compressive force is considered sufficient since it makes it possible to exert on each cell of the module a compressive force greater than or equal to the predetermined nominal compressive force F0 making it possible to maintain each cell substantially at its nominal thickness E0.

This is particularly important since the applicant has observed that, in the absence of such a constraint, a cell undergoes much greater and faster aging than a cell to which the predetermined nominal compression is applied. In some cases, cell aging is up to ten times faster.

This pressurization is obtained very simply, by taking advantage of the properties of the material constituting the first and/or the second transverse wall.

This result is typically obtained here by appropriately choosing at least the empty length of the compartment, taken between the first and second transverse walls, and the material constituting the first and/or second transverse walls.

This compressive force results from the fact that each cell, in the absence of compressive force applied to its large faces, tends to swell. The large faces bulge under the effect of the internal pressure of the cell, so that its thickness tends to increase.

When the module is inserted into the compartment, the internal pressure of the cells will therefore urge the first and/or second transverse walls in the direction of a separation, and slightly press the wall or walls. The compression of the elastic material of the first and/or second transverse wall will produce in reaction the compressive force.

The electricity storage battery may also have one or more of the characteristics below, considered individually or in all technically possible combinations:

- said elastic material is a foam of a plastic material, for example a polyurethane foam or an expanded polyphenylene ether foam;

- the external surface of at least one of the first and second transverse walls comprises a recessed zone, a protruding zone offset longitudinally towards the interior of the compartment with respect to the recessed zone (41), and an inclined intermediate zone connecting the protruding area to the recessed area;

- at least one of the first and second transverse walls comprises a part in said elastic material and at least one block comprising a second plastic material more rigid than said elastic material, said part and the at least one block being located at the level of respective zones separate from the outer surface of said wall;

- at least one block comprises a first layer of said second plastic material and a second layer of another plastic material relatively more flexible than the second plastic material, superposed longitudinally on the first layer;

- the second layer has a first thickness when the compartment is empty, and a second thickness when a module is engaged in the compartment, a compression of the second layer from the first thickness to the second thickness generating a second layer compression force:
- greater than 40% of said compressive force adapted to maintain the electricity storage cells substantially at their nominal thicknesses E0, if the first wall and the second wall each comprise said part in said elastic material and said at least one block;
- greater than 80% of said compressive force adapted to maintain the electricity storage cells substantially at their nominal thicknesses E0, if only one of the first and second transverse walls comprises said part in said elastic material and said at least one block ;

- at least one of the first and second transverse walls is covered by a skin defining the outer surface of said wall, a recessed groove being provided on at least part of the periphery of the outer surface of the at least one of the first and second transverse walls;

- the or each compartment is delimited at the bottom by a bottom and has two longitudinal walls opposite each other connected to the bottom each by an arcuate portion having a first radius of curvature, each electricity storage cell having a small bottom face facing the bottom and small side faces facing the longitudinal walls, the small side faces being connected to the small bottom face by arcuate portions having a second radius of curvature greater than the first radius of curvature of the arcuate portion;

- the compressed module between the first and second transverse walls has a compressed longitudinal length L0 = N x E0 with a tolerance of between –T1 and +T2 for 99% of the modules, the or each compartment having a vacuum between the first and second walls transverse an empty length LV less than or equal to L0 - T1.

- each cell has its nominal thickness E0 when a predetermined nominal compressive force F0 of between 20 and 200 Newtons is exerted on said large faces;

- the compressive force exerted by the first and second walls on the module is greater than or equal to N x F0;

- When a module of compressed longitudinal length L0 - T1 is engaged in the compartment, the first and second walls exert longitudinally on the module a first compressive force F1 greater than or equal to N×F0;

- When a module of compressed longitudinal length L0+T2 is engaged in the compartment, the first and second walls exert longitudinally on the module a second compressive force F2 of less than 1.5×F1;

- when said module of compressed longitudinal length L0 + T2 is engaged in the compartment, swelling of the cells resulting in an increase in the longitudinal length of the module by 1 mm leads to an increase in the compressive force applied by the first and second walls longitudinally on the modulus greater than 15%.

Other characteristics and advantages of the invention will emerge from the detailed description given below, by way of indication and in no way limiting, with reference to the appended figures, among which:

• [Fig. 1] Figure 1 is a perspective view of the casing of an electricity storage battery according to the invention, the cover being shown separated from the lower part of the casing, so as to reveal the compartments of receipt of electricity storage modules;
• [Fig. 2] Figure 2 is an enlarged perspective view of a compartment of the battery of Figure 1;
• [Fig. 3] Figure 3 is a schematic representation of one side of the compartment and of a cell, according to a cross section;
• [Fig. 4] Figure 4 is a simplified schematic representation, in side view, of an electricity storage module, and of the receiving compartment of said module;
• [Fig. 5] Figure 5 is a curve representing the compressive force F applied by the transverse walls of the compartment on the module, on the ordinate, as a function of the depression E of these walls, on the abscissa;
• [Fig. 6] Figure 6 is a sectional view, in a longitudinal plane, of the transverse wall of the compartment shown in Figures 2 and 4;
• [Fig. 7] Figure 7 is an enlarged view, in perspective, of one end of the compartment of Figures 1 and 2;
• [Fig. 8] Figure 8 is a view similar to that of Figure 7, for an alternative embodiment of the invention;
• [Fig. 9 and 10] Figures 9 and 10 are views similar to that of Figure 6, for two other variant embodiments of the invention.

The electric battery 1 represented in FIGS. 1 to 4 is intended to equip a vehicle, typically a motor vehicle such as a car, a bus or a truck.

The vehicle is for example a vehicle propelled by an electric motor, the motor being electrically powered by the electric battery. As a variant, the vehicle is of the hybrid type and thus comprises a heat engine and an electric motor powered electrically by the electric battery. According to yet another variant, the vehicle is propelled by a combustion engine, the electric battery being provided to electrically supply other equipment of the vehicle, for example the starter, the lights, etc.

The electricity storage battery 1 comprises at least one module 3 ( ) comprising a number N of electricity storage cells 5.

The number of battery modules 3 depends on the electricity storage capacity of battery 1. In the example shown, the battery comprises sixteen modules 3. However, the battery may comprise more than sixteen modules or less than sixteen. mods.

The electricity storage cells 5 are of all suitable types: lithium cells of the lithium-ion-polymer type (Li-Po), lithium-iron-phosphate (LFP), lithium-cobalt (LCO), lithium-manganese ( LMO), nickel-manganese-cobalt (NMC), or even NiMH (nickel-metal-hydride) type cells.

In the example shown in the , each module 3 comprises twelve cells 5. However, the number of cells in the same module is in a variant different from twelve, it is either greater than twelve or less than twelve.

Typically, each electricity storage cell 5 is prismatic in shape.

It thus has two large faces 7, 9 and four small faces 11, 13, 15, 17 connecting the two large faces 7, 9 to each other (FIGS. 3 and 4).

The small upper face 11 carries two electrical contacts, not shown.

In the same module 3, the electricity storage cells 5 are stacked in a longitudinal direction L, shown by an arrow in Figures 2 and 4.

The electricity storage cells 5 are juxtaposed longitudinally. They are in contact with each other by their large faces 7, 9. Typically, they are directly in contact with each other by their large faces 7, 9.

The large faces 7, 9 are thus in planes perpendicular to the longitudinal direction L.

The small faces 11 bearing the electrical contacts all face the same side and are juxtaposed. The electrical contacts of the different electricity storage cells 5 of the same module 3 are connected to each other, so as to place the electricity storage cells 5 in series and/or in parallel. The connectors making it possible to connect the electrical contacts of the electricity storage cells 5 are not shown in the figures.

Each module 3 therefore has the shape of a parallelepipedal block having an elongated shape in the longitudinal direction L.

The electricity storage battery 1 also comprises an envelope 19 ( ).

The envelope 19 internally delimits a volume 21 in which the modules 3 are housed.

At least one compartment 23 for receiving at least one module 3 is provided inside the casing 19.

More specifically, a compartment 23 is provided inside the casing 19 for each module 3.

These compartments 23 are visible in Figures 1 and 2.

The casing 19 typically comprises a lower part 25 and a cover 27. Generally, once the electricity storage battery 1 has been mounted on board the vehicle, the lower part 25 of the casing is facing downwards, that is that is to say towards the running surface of the vehicle. Cover 27 faces upwards.

In the example shown, the lower part 25 has the shape of a substantially flat plate, constituting a rigid frame supporting the modules 3. Alternatively, the lower part 25 has the shape of a tray, or any other suitable shape.

The cover 27 is concave towards the lower part 25.

The lower part 25 and the cover 27 are in contact with each other along a peripheral line. In the example shown, the lower part 25 is rectangular, and the contact line is also rectangular.

In the example shown, the lower part 25 and the cover 27 are fixed to each other by means of clamps 29 and screws not shown.

As visible in Figures 1 and 2, each compartment 23 comprises first and second transverse walls 31, 32 having respective outer surfaces 33, 34 delimiting the compartment 23 at its two opposite longitudinal ends.

Each compartment 23 is delimited at the bottom by a bottom 35 and has two longitudinal walls 37, 38 opposite each other, connected to the bottom 35.

Each compartment 23 thus has a generally parallelepipedic shape.

The first and the second transverse walls 31, 32 are parallel to each other and substantially perpendicular to the longitudinal direction L.

The longitudinal walls 37, 38 are substantially perpendicular to the transverse direction T, materialized in Figures 1 and 2. The longitudinal walls 37, 38, the transverse walls 31, 32 and the bottom 35 are substantially perpendicular to each other.

As seen on the , once the module has been inserted into the corresponding compartment 23, the small lower face 13 of each electricity storage cell 5 is placed against the bottom 35, and the small side faces 15, 17 are placed against the longitudinal walls 38, 37 respectively.

Typically, the battery 1 is of the type with electricity storage cells 5 cooled by direct circulation of a dielectric fluid in contact with the electricity storage cells 5. To do this, as visible in FIGS. 2, 7 and 8, U-shaped channels 39 are formed on the inner surface of compartment 23. Each U-shaped channel has a central branch formed on the bottom 35, and two side branches formed on the longitudinal walls 37, 38. Along the central branch, the dielectric fluid circulates in contact with the small inner face 13 of the electricity storage cell 5. In the side branches, the dielectric fluid circulates in contact with the small side faces 15 and 17 of the electricity storage cell. electricity 5.

Alternatively, the electric battery is not of the type with cells cooled by direct circulation of a dielectric fluid in contact with the cells.

Each cell 5 has, between its two large faces 7, 9, a nominal thickness E0.

Each cell 5 has, between its two large faces 7, 9, the nominal thickness E0 when a predetermined nominal compressive force F0 of between 20 and 200 Newtons is exerted on said large faces 7, 9.

This nominal compressive force F0 makes it possible to maintain the large faces 7, 9 substantially flat.

The nominal compressive force F0 depends on the internal chemistry of the electricity storage cell 5, its design, and can vary from one manufacturer to another. Typically, it is between 50 and 150 Newtons, and is typically 100 Newtons.

For an electricity storage cell 5 to operate correctly, this pressure must be applied to the large faces 7, 9, so that the electricity storage cell 5 has its nominal thickness E0.

When the large faces 7, 9 of the electricity storage cell 5 are free from external loads, the electricity storage cell 5 has a thickness notably greater than its nominal thickness E0, the large faces 7, 9 having shapes rounded to a height of up to 3 mm.

It should be noted that a new electricity storage cell 5 does not present this tendency to swell. It appears after use for a certain period of time.

When said predetermined nominal compressive force F0 is applied to the large faces 7.9 of each electricity storage cell 5, that is to say when the module 3 is compressed longitudinally with a nominal overall compressive force equal to N x F0, module 3 then has longitudinally a compressed longitudinal length L0 = N x E0, with a tolerance between -T1 and +T2 for 99% of modules 3.

The -T1 and +T2 tolerances result from the manufacturing tolerances of the electricity storage cells 5.

Indeed, each electricity storage cell 5 has a thickness tolerance of between −t1 and +t2. The theoretical maximum tolerance for module 3 is therefore -(N x t1) and +(N x t2). Statistically, however, it is almost impossible for all the electricity storage cells to be together at their maximum tolerances or at their minimum tolerances. Thus, practically, in 99% of cases, the overall tolerance for all N electricity storage cells is between -T1 and +T2, -T1 being greater than N x (- t1), and +T2 being less than N x (+t2).

An electricity storage cell 5 may for example have a thickness of 50 mm, with tolerances of −0.3 mm and +0.3 mm. For a module 3 of twelve electricity storage cells 5, the maximum tolerances are therefore -3.6 mm and +3.6 mm. In practice, in 99% of cases, the tolerances are between -1 mm and +1 mm.

Typically, the nominal thickness E0 is between 20 and 200 mm, or even preferably between 30 and 100 mm, and is for example 50 mm.

The -T1 tolerance is typically between -0.3 and -3 mm, preferably between -0.5 and -2 mm, and is for example -1 mm.

The tolerance +T2 is for example between +0.3 and +3 mm, preferably between +0.5 and +2 mm, and is for example +1 mm.

Module 3, uncompressed, has a free longitudinal length much greater than L0+T2, for example L0+N×3 mm.

As illustrated on the , the compartment 23 has empty, between its first and second transverse walls 31, 32, an empty length LV less than or equal to L0 - T1.

Typically, the empty length LV is substantially equal to L0 – T1. Alternatively, it is slightly less than L0 – T1, the difference being for example chosen so that, for a module 3, a free longitudinal length of L0 – T1 is slightly compressed. The difference must not be excessive, and remain compatible with the various criteria set out below.

The empty length LV is taken between the external surfaces 33, 34. It corresponds to the longitudinal spacing between the transverse walls 31, 32 when the compartment 23 is not occupied by the module 3, and is therefore filled with air. .

Furthermore, according to the invention, at least one of the first and second transverse walls 31, 32 is made of an elastic material.

Typically, the two transverse walls 31, 32 are in an elastic material, typically in the same elastic material.

Alternatively, only one of the first and second transverse walls 31, 32 is in an elastic material, the other being in a non-elastic material, that is to say rigid, which does not deform when module 3 is inserted in compartment 23.

According to the invention, when a module 3 is engaged in the compartment 23, the first and second transverse walls 31, 32 longitudinally exert on the module 3 a compressive force adapted to maintain the electricity storage cells 5 substantially at their thicknesses. rated E0.

This is obtained by appropriately choosing the empty length LV and the nature of the elastic material of the first and/or second transverse walls 31, 32.

More precisely, when a module 3 of compressed longitudinal length L0-T1 is engaged in the compartment 23, the first and second transverse walls 31, 32 exert longitudinally on the module 3 a first compression force F1 greater than or equal to N×F0.

In other words, a module 3 having a free longitudinal length of L0 – T1 would be weakly compressed or not compressed at all. A module 3 having a compressed longitudinal length of L0 – T1 will be strongly compressed, enough to prevent the swelling of the electricity storage cells 5 and to maintain the electricity storage cells 5 substantially at their nominal thicknesses E0.

Advantageously, when a module 3 of compressed longitudinal length L0+T2 is engaged in compartment 23, the first and second transverse walls 31, 32 exert longitudinally on the module a second compressive force F2 of less than 1.5×F1.

Again, this is obtained by appropriately choosing the empty length LV and the nature of the elastic material of the first and/or second transverse walls 31, 32.

Thus, the force required to engage in the compartment 23 a module 3 having a longitudinal length compressed to the maximum tolerance is not excessively high.

Preferably, the second compressive force F2 is less than 1.4×F1, more preferably less than 1.2×F1.

In addition, the applicant has observed that during the charging and discharging cycles of the battery, changes in temperature and internal pressure occur within the electricity storage cells 5. The electricity storage cells 5 expand and contract periodically. This can result in an increase in the longitudinal thickness of each electricity storage cell 5 and therefore an increase in the compressed longitudinal length of the module 3.

In order to limit or eliminate this increase in longitudinal length, compressed when said module 3 of compressed longitudinal length L0 + T2 is engaged in compartment 23, swelling of the electricity storage cells 5 resulting in an increase in compressed longitudinal length of the module 3 by 1 mm leads to an increase in the compressive force applied by the first and second transverse walls 31, 32 longitudinally on the module 3 greater than 15%.

Preferably, an increase in the compressed longitudinal length of the module 3 by 1 mm leads to an increase in the compressive force greater than 25%, still preferably greater than 40%.

Again, this is obtained by appropriately choosing the empty length LV and the nature of the elastic material of the first and/or second transverse walls 31, 32.

The various criteria set out above are illustrated on the .

There is a curve giving the force F applied by the first and second transverse walls 31, 32 on the module 3, as a function of the depression E. The depression E corresponds to the increase in the length separating the first and second walls transverse 31, 32 longitudinally from each other. For a depression E of 0, the length separating the first and second transverse walls 31, 32 longitudinally is the empty length LV. In other words, the depression E corresponds to the sum of the displacement of the first transverse wall 31 with respect to its position when the compartment 23 is empty, and of the displacement of the second transverse wall 32 with respect to its position when the compartment 23 is empty.

When the first and second transverse walls 31, 32 are identical to each other, the displacements of the two transverse walls 31, 32 are substantially equal to each other.

When one of the two transverse walls 31, 32 is rigid, the displacement E corresponds exclusively to the deformation of the other transverse wall 31, 32.

On the , the depression E1 corresponds to the situation where a module 3 of compressed longitudinal length L0 – T1 is engaged in the compartment 23. It occurs under the effect of the internal pressure of the electricity storage cells 5, which tends to to inflate the electricity storage cells 5 and to separate the transverse walls 31, 32 from each other. This depression E1 produces the first compressive force F1 applied by the transverse walls 31, 32 on the module 3.

The depression E2 corresponds to the case where a module 3 of compressed longitudinal length L0 + T2 is inserted into the compartment 23. Such depression E2 produces the second compressive force F2 applied by the first and second transverse walls 31, 32 on the module 3.

It also appears on the that an increase in the compressed longitudinal length of this modulus of 1 mm, that is to say a passage of the depression from E2 to E2 + 1mm, results in a concomitant increase in the compressive force from F2 to F2'.

Ideally, the passage from a depression value E1 to E2 does not lead to an excessive increase in the compression force. On the other hand, a change from E2 to E2 + 1 mm results in a much greater increase in effort. In other words, the force required to push the module 3 inside the housing 23 must not increase excessively when passing from a module 3 having the minimum length tolerance to a module 3 having the tolerance of max length. On the other hand, the swelling of the electricity storage cells 5 due to the charging and discharging cycles of the battery 1 creates an increase in the pressure exerted which is very significant, so as to limit the swelling of the electricity storage cells 5 .

These various results are preferably obtained by providing that the first and/or the second transverse walls 31, 32 comprise a foam of a plastic material, for example a polyurethane foam or an expanded polyphenylene ether foam.

According to an exemplary embodiment, the first transverse wall 31 and the second transverse wall 32 are entirely made of said plastic foam material.

As described in FR 20 07331, the lower part 25 of the casing 19 advantageously comprises beams (not shown) integral with the casing 19, generally rigidly fixed to the rigid frame supporting the modules 3. The plastic foam is molded onto beams.

In addition to the choice of the empty length LV and of the material of the first and/or of the second transverse wall 31, 32, the compressive force can be adjusted by also varying the shape of the external surfaces 33, 34 of the first and/or the second transverse wall 31, 32.

This gives additional degrees of freedom to obtain the results sought and described above.

In this case, the outer surface 33, 34 advantageously comprises a recessed zone 41, a projecting zone 43 offset longitudinally towards the interior of the compartment 23 with respect to the recessed zone 41, and an intermediate zone 45 inclined connecting the projecting zone 43 to recessed area 41 (Figures 6 and 7).

In other words, the projecting zone 43 is prominent and forms a projecting relief with respect to the recessed zone 41. The inclined zone 45 rises gradually, from the recessed zone 41 to the projecting zone 43, as shown in .

In the example shown in Figures 6 and 7, the recessed area 41 is formed at the bottom of the first and/or second transverse walls 31, 32, and adjoins the bottom 35.

In the present description, the bottom and the top are understood in a direction of elevation E substantially perpendicular to the longitudinal L and transverse directions T.

The protruding zone 43 is flat and is located at the top of the outer surface 33, 34. It covers substantially the entire transverse width of the outer surface 33, 34, and covers approximately two thirds of the height of said outer surface.

The sloped area 45 covers about a quarter of the height of the outer surface 33, 34, and is located at the bottom of the outer surface 33, 34. It extends the full transverse width of the outer surface 33, 34 .

In other words, when considering a section of the first transverse wall 31 or the second transverse wall 32 in a plane perpendicular to the longitudinal direction L, the solid area increases when moving longitudinally from the recessed area. 41 up to protruding area 43.

Such an arrangement makes it possible to modulate the pressure force exerted on the module 3 when the depression of the wall increases.

When the depression is moderate, only the protruding zone 43, possibly with a small part of the inclined intermediate zone 45, is in contact with the module 3. When the longitudinal length of the module 3 increases, for example under the effect of the swelling of the electricity storage cells 5 due to the charge and discharge cycles of the battery 1, a larger portion of the inclined intermediate zone 45 comes into contact with the module 3. This additional portion in contact with the module 3 will contribute to the compressive force exerted, which it did not do initially.

A variant embodiment will now be described, with reference to the . Only the points by which the variant of the differs from that of Figures 6 and 7 will be detailed below.

The identical elements or performing the same function will be designated by the same references.

In the variant embodiment of the , the protruding zone 43 comprises two strips 47 elongated in the direction of elevation E.

The two strips 47 are substantially parallel to each other. The inclined intermediate zone 45 comprises two lateral strips 49, arranged, in the transverse direction T, on either side of each strip 47. The lateral strips 49 are elongated in the direction of elevation E.

As seen on the , each band 47 constitutes with the two side bands 49 which adjoin it, a block of which the band 47 constitutes the top.

The recessed zone 41 comprises a central band 51 interposed transversely between the two blocks, and two outer bands 53, each interposed between a block and the longitudinal wall 37 or 38.

The protruding zone 43, the recessed zone 41 and the inclined intermediate zone 45 can be arranged in many other ways.

Another alternative embodiment of the invention will now be detailed, with reference to the .

Only the points by which the variant of the differs from that of Figures 1 to 4 will be detailed below.

The identical elements or performing the same function will be designated by the same references.

In the variant of , the first transverse wall 31 and/or the second transverse wall 32 comprises a part 57 in said elastic material, and at least one block 59 comprising a second plastic material.

Part 57 is in said plastic foam described above.

This elastic material is relatively more flexible than the second plastic material.

The second plastic material on the contrary is relatively more rigid than the elastic material.

Part 57 and block 59 are located at respective distinct areas of outer surface 33.

Typically, the or each block 59 is mounted on the beams of the lower part 25 of the casing 19 before the plastic material foam is formed, as described in FR 20 07331. After formation of the foam, the or each block 59 is completely embedded in the foam.

The or each block 59 typically has a thickness of 10 mm. It is made of PPE with a density of 0.1 kg per litre, and has a pressure of 300 kPa at 10% penetration.

The addition of such a block 59 makes it possible to modulate the characteristics of the first and/or second transverse walls 31, 32.

Another variant embodiment will now be described, with reference to the . Only the points by which the variant of the differs from that of the will be detailed below.

The identical elements or performing the same function will be designated by the same references.

On the , the or each block 59 comprises a first layer 61 of said second plastic material, and a second layer 63 of another plastic material relatively more flexible than the second plastic material, superposed longitudinally on the first layer 61.

Typically, the second layer 63 has a first thickness when the compartment 23 is empty, and a second thickness when a module is engaged in the compartment 23.

In the case where such a block 59 is provided both in the first and the second transverse walls 31, 32, it is provided that the compression of the second layer 63 from the first to the second thickness generates a compression force greater than 40 % of the compressive force adapted to maintain the electricity storage cells (5) substantially at their nominal thicknesses E0.

Thus, for a module 3 of compressed longitudinal length L0-T1, the compression of the second layer 63 from the first to the second thickness generates a compression force greater than 40% of the first compression force F1.

In other words, the second layer 63 is chosen so as to be particularly easily compressible, and to provide an effort, once compressed, practically sufficient to reach the value making it possible to maintain the various electricity storage cells 5 of the module 3 substantially to their nominal thickness E0. The first layer 61, on the other hand, is in a material offering a much higher resistance to depression, which makes it possible to drastically limit the swelling of the electricity storage cells 5 linked to the charging and discharging cycles of the battery 1.

For example, the second layer 63 has a thickness of 2 mm, and is made of a flexible PU foam of 70 g/litre, with a pressure of only 7.9 kPa at 40% penetration. This type of foam is typically used for automotive seat upholstery.

The first layer 61 is made of a 100 g/litre rigid polyurethane foam, with a pressure of 298 kPa at 40% penetration.

In the event that only one of the two transverse walls 31, 32 comprises said block 59, the other transverse wall 31, 32 being substantially non-deformable, then provision is made for the compression of the second layer 63 from the first thickness to the second thickness to generate a compressive force greater than 80% of the compressive force adapted to maintain the electricity storage cells (5) substantially at their nominal thicknesses E0.

According to an advantageous variant of the invention, at least one of the first and second transverse walls 31, 32 is covered by a skin 65 (FIGS. 6, 9, 10) defining the outer surface 33, 34 of said wall. This is particularly advantageous when the battery 1 is of the type where the electricity storage cells 5 are cooled by circulation of a dielectric fluid directly in contact with the electricity storage cells 5.

Indeed, the skin 65 is then chosen in a material that is impervious to the dielectric fluid. This prevents the dielectric fluid from soaking the plastic material constituting the first and/or second transverse walls 31, 32.

Typically, the skin 65 covers not only the outer surfaces of the first and second walls 31, 32, but also the outer surfaces 33, 34 of the bottom 35 and the longitudinal walls 37, 38. Such a skin 65, and the method for obtain, is described in FR 20 07331.

According to an advantageous aspect of the invention, a recessed groove 67 is then provided on at least part of the periphery of the outer surface 33, 34 of the first and/or second transverse wall 31, 32.

As visible in Figures 2, 7 and 8, this recessed groove 67 extends for example on three sides of the first transverse wall 31 and / or the second transverse wall 32. It extends at the junction between the transverse wall 31, 32 and the bottom 35, and at the level of the junctions between said wall and the longitudinal walls 37, 38. The hollow groove 67 serves to provide a reserve of skin length to the transverse wall 31, 32.

Indeed, when the module 3 is pushed into the housing 23, the skin 65 covering the first and/or the second transverse wall 31, 32 is subjected to an extension force. The presence of the skin reserve, constituted by the recessed groove 67, makes it possible not to tear the skin, in particular at the corners of the recessed groove 67, which are particularly stressed areas.

It should be noted that the electricity storage cells 5 of the module 3 must also be wedged in position transversely inside the compartment 23, here by the longitudinal walls 37, 38. However, it is not necessary, according to the transverse direction T, to exert a significant compression on the small side faces 15, 17 of the electricity storage cell 5.

Each electricity storage cell 5 has a nominal width T0 in the transverse direction T, with a tolerance between -T3 and +T4. For example, each electricity storage cell 5 has between its small faces 15 and 17 a width of 144 mm, the tolerance −T3 being −0.5 mm and the tolerance +T4 being +0.5 mm.

In this case, a transverse empty width is chosen for the compartment 23 of T0-T3. The empty width LV corresponds to the spacing between the longitudinal walls 37, 38, when the module 3 is not inserted in the housing 23.

Thus, an electricity storage cell 5 having the minimum width considering the manufacturing tolerances will just enter the housing and will be in contact without pressure with the longitudinal walls 37, 38. For an electricity storage cell 5 more wide, having the maximum manufacturing tolerance, it will be necessary to slightly push the longitudinal walls 37, 38 at the time of insertion.

Advantageously, in the case where the longitudinal walls 37, 38 are covered by a skin 65 as described above, a reserve of skin is formed at the angle ensuring the junction between the bottom 35 and the longitudinal walls 37, 38 .

As partially illustrated in the , the two longitudinal walls 37, 38 are connected to the bottom 35 by an arcuate portion 71 having a first radius of curvature.

The small side faces 15, 17 of the electricity storage cell 5 are connected to the small lower face 13 by an arcuate part 73 having a second radius of curvature greater than the first radius of curvature.

When the electricity storage cell 5 has substantially the same transverse width as the compartment 23, there is a clearance of reduced size between the arcuate portion 71 and the arcuate part 73. A leakage of dielectric liquid may occur in this zone. , but extremely limited throughput due to the small size of the game, and the orientation of the area.

When the electricity storage cell 5 on the contrary has a transverse width greater than that of the compartment 23, the longitudinal walls 37, 38 are pushed apart from each other at the time of the depression. The tension of the skin 65 is limited due to the skin reserve formed by the arcuate portion 71.

In all the variant embodiments, the electricity storage cells 5 of the same module 3 are held in position with respect to each other solely by the pressure exerted by the walls of the compartment 23. This pressure is strong enough for it is not necessary to provide holding straps, or any other means of holding. It is also not necessary to provide flanges at the two longitudinal ends of the module 3. The structure of the module 3 is thus considerably simplified.

Claims (9)

Electricity storage battery (1) comprising:
- at least one module (3) comprising a number N of electricity storage cells (5) stacked in a longitudinal direction (L),
- an envelope (19), inside which is formed at least one compartment (23) for receiving the at least one module (3), the or each compartment (23) having first and second transverse walls ( 31, 32) having outer surfaces (33, 34) delimiting the compartment (23) at its two opposite longitudinal ends;
each electricity storage cell (5) having two large transverse faces (7, 9) opposite one another and presenting, between said large faces (7, 9), longitudinally, a nominal thickness E0;
at least one of the first and second transverse walls (31, 32) being in an elastic material;
when a module (3) is engaged in the compartment (23), the first and second transverse walls (31, 32) longitudinally exert on the module (3) a compressive force adapted to maintain the electricity storage cells (5 ) substantially to their nominal thicknesses E0. A battery according to any preceding claim, wherein said resilient material is a foam of a plastics material, for example polyurethane foam or expanded polyphenylene ether foam. A battery according to any preceding claim, wherein the outer surface (33, 34) of the at least one of the first and second transverse walls (31, 32) comprises a recessed area (41), a protruding area ( 43) offset longitudinally towards the interior of the compartment (23) with respect to the recessed zone (41), and an inclined intermediate zone (45) connecting the protruding zone (43) to the recessed zone (41). Battery according to any of the preceding claims, wherein at least one of the first and second transverse walls (31, 32) comprises a part (57) in said elastic material and at least one block (59) comprising a second plastic material more rigid than said elastic material, said part (57) and the at least one block (59) being located at respective distinct zones of the external surface (33, 34) of said wall. Battery according to Claim 4, in which the at least one block (59) comprises a first layer (61) of said second plastic material and a second layer (63) of another plastic material which is more flexible than the second plastic material, superimposed longitudinally on the first layer (61). Battery according to Claim 5, in which the second layer (63) has a first thickness when the compartment (23) is empty, and a second thickness when a module (3) is engaged in the compartment (23), a compression of the second layer (63) from the first thickness to the second thickness generating a second layer compression force:
- greater than 40% of said compressive force adapted to maintain the electricity storage cells (5) substantially at their nominal thicknesses E0, if the first wall (31) and the second wall (32) each comprise said part (57) in said elastic material and said at least one block (59);
- greater than 80% of said compressive force adapted to maintain the electricity storage cells (5) substantially at their nominal thicknesses E0, if only one of the first and second transverse walls (31, 32) comprises said part (57 ) in said elastic material and said at least one block (59). Battery according to any one of the preceding claims, in which the at least one of the first and second transverse walls (31, 32) is covered by a skin (65) defining the external surface (33, 34) of the said wall, a recessed groove (67) being formed on at least part of the periphery of the outer surface (33, 34) of the at least one of the first and second transverse walls (31, 32). Battery according to any one of the preceding claims, in which the or each compartment (23) is delimited at the bottom by a bottom (35) and has two longitudinal walls (37, 38) opposite each other connected to the bottom (35) each by an arcuate portion (71) having a first radius of curvature, each electricity storage cell (5) having a small lower face (13) facing the bottom (35) and small side faces ( 15, 17) turned towards the longitudinal walls (37, 38), the small side faces (15, 17) being connected to the small lower face (13) by arcuate parts (73) having a second radius of curvature greater than the first radius of curvature of the arcuate portion (71). - Battery according to any one of the preceding claims, in which the module (3) compressed between the first and second transverse walls (31, 32) has a compressed longitudinal length L0 = N x E0 with a tolerance between -T1 and + T2 for 99% of the modules (3), the or each compartment (23) having, when empty between the first and second transverse walls (31, 32), an empty length LV less than or equal to L0 - T1.