Storage battery module, process and tool for manufacturing said module

Abstract

The invention relates to a storage battery (1) module (20) comprising a plurality of unit cells (22) and means for maintaining said unit cells in juxtaposed positions. According to the invention, said maintaining means include at least one clip (27) which has a base from which two arms extend that are located on either side of the unit cells and are formed integrally with the base.

Description

DESCRIPTION TITLE OF THE IN ENTION: ACCUMULATOR BATTERY MODULE, METHOD AND TOOL FOR MANUFACTURING THIS MODULE TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates generally to storage batteries.

[0002] It relates more particularly to an accumulator battery module comprising several unit cells and means for holding said unit cells in a juxtaposed position.

[0003] The invention finds a particularly advantageous application in modules for traction batteries of electric or hybrid vehicles.

[0004] It also relates to a method and a tool for manufacturing such a module. STATE OF THE ART

[0005] An electrically powered motor vehicle typically consists of an electric motor and a storage battery that is specially designed to supply the electric motor with current to move the vehicle forward.

[0006] Such a storage battery typically consists of several identical modules, each of which includes a plurality of low-voltage unit cells. All of the unit cells are connected together so that the overall voltage across the battery terminals is high enough to drive the vehicle. The terminal voltage of such a battery is often in the order of 400 V or 800 V.

[0007] Each battery module is usually presented, for ease of use, in the form of a closed box housing unit cells.

[0008] Such a module can become very hot, especially when the electric motor is used intensively or when charging the unit cells. The battery modules must then be cooled. To do this, they can be positioned on a cooling wall, which incorporates, for example, coolant circulation ducts.

[0009] To ensure good heat transfer between the unit cells and the cooling wall, it is known to use two layers of foams with good thermal conductivity, one of them being sandwiched between the unit cells and a metal wall of the box, and the other being sandwiched between the metal wall of the box and the cooling wall.

[0010] The major disadvantage of this solution is that the multiplication of foam layers necessarily increases the thermal resistance of the whole and reduces consequently the performance of the cooling system.

[0011] It is in this context that document US20220085447 proposes a module whose box has an open bottom, such that the cells are exposed to the cooling wall via a single layer of foam.

[0012] In this document, to lock all the unit cells in a juxtaposed position and provide a mechanical structure to the module, the box, however, includes a crossbar that extends across the open bottom of the box. This crossbar creates a thermal barrier. Above all, it increases the distance between the unit cells and the cooling wall, which increases the required foam thickness, so that the performance of the cooling system is still not optimal. PRESENTATION OF THE INVENTION

[0013] In order to overcome the aforementioned drawback of the state of the art, the present invention proposes a new system making it possible to reduce as much as possible the distance between the unit cells and the cooling wall.

[0014] More particularly, according to the invention, a module is proposed as defined in the introduction, in which the means for holding the unit cells comprise at least one attachment which has a base from which extend two arms which are located on either side of said unit cells and which are formed from a single piece with said base.

[0015] Thus, thanks to the invention, the fasteners are open (opposite their bases), so that they do not form an interface between the unit cells and the cooling wall. The heat exchange between the cells and this wall can therefore be done optimally. In addition, thanks to this form of fastener, the assembly of the modules can be done simply and quickly, and in an automated manner.

[0016] Other advantageous and non-limiting characteristics of the module according to the invention, taken individually or in all technically possible combinations, are the following: - said holding means comprising several separate fasteners, the bases of all the fasteners are located on the same side of the unit cells; - two compression plates are provided, located on either side of said unit cells, and on either side of which the arms of each attachment are located; - an interface is provided between at least two of the unit cells which is more easily compressible than the unit cells; - the unit cells are juxtaposed in a first direction; - the arms of each attachment extend in length in a second direction orthogonal to the first direction; - at least two separate fasteners are provided, located at a distance from each other in a third direction orthogonal to the first and second directions; - these two attachments each have dimensions in the third direction which are at least ten times smaller than the dimension of the unit cells in this third direction; - each arm has at its end snap-fastening means adapted to clip onto a wall supporting the unit cells; - each unit cell being in contact with the base of the attachment by a first side and having a second side opposite the first side, the arms of the attachment have lengths such that they protrude from the second sides of the unit cells.

[0017] The invention also proposes an accumulator battery comprising a cooling wall and at least one module as mentioned above, attached to the cooling wall by a side opposite to that where said base is located.

[0018] Preferably, the arms of the attachment are fixed by their ends to said cooling wall or to a support located against said cooling wall, opposite said module.

[0019] The invention also relates to a method for manufacturing a storage battery module as mentioned above, comprising steps of: - superposition of unit cells, - compression of unit cells, - insertion of compressed unit cells between the arms of the attachment.

[0020] The invention also relates to a tool for manufacturing a battery module having several juxtaposed unit cells, said manufacturing tool comprising two jaws which are mounted to move towards each other to compress the unit cells and which each have at least one groove for the passage of an arm of a fastener, facing the other jaw.

[0021] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. DETAILED DESCRIPTION OF THE INVENTIO

[0022] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0023] On the attached drawings:

[0024] [Fig. 1] is a schematic sectional view of an accumulator battery according to the invention;

[0025] [Fig. 2] is a schematic sectional view of a first variant embodiment of the storage battery of Figure 1;

[0026] [Fig. 3] is a schematic sectional view of a second alternative embodiment of the storage battery of Figure 1;

[0027] [Fig. 4] illustrates several steps of a manufacturing process of the storage battery of Figure 1;

[0028] [Fig. 5] is a schematic perspective view of a module of the storage battery of Figure 1 and a tool for manufacturing this module;

[0029] [Fig. 6] illustrates three variant embodiments of a clip usable in the accumulator battery of Figure 1;

[0030] [Fig. 7] illustrates three variants of the construction of a compression plate usable in the accumulator battery of Figure 1.

[0031] In Figure 1, a battery of accumulators 1 is shown.

[0032] This battery is, for example, intended to be installed on board a motor vehicle such as a car, in order to supply current to an electric traction motor of this vehicle.

[0033] This accumulator battery 1 comprises for this purpose a large number of electrochemical unit cells, distributed by modules.

[0034] Thus, each module 20 of the accumulator battery comprises several unit cells 22 (here around twenty).

[0035] Preferably, several modules are provided in the battery, although alternatively, a battery could have only one module (typically if it is a battery with a voltage at its terminals of 48V).

[0036] The unit cells 22 are preferably all identical. They generally have plate shapes.

[0037] We can represent an orthonormal reference point (X, Y, Z) in relation to these cells.

[0038] In this frame, cells extend in length along the Z axis, in width along the Y axis, and in thickness along the X axis.

[0039] The cells of each module 20 are then juxtaposed along this X axis (i.e. joined by their main faces - in other words, they are superimposed).

[0040] They are electrically connected together by 24 electrical conductors. The modules are also connected together.

[0041] During use (charging or discharging), the 22 unit cells are likely to heat up. As they age, they also tend to expand.

[0042] To reduce heating of the unit cells 22, the modules 20 are placed on a cooling wall 10.

[0043] In order for the overall volume of each module 20 to remain substantially constant, it an interface 23 is provided between at least two of the unit cells 22 of each module 20 which is more easily compressible than the unit cells 22. This interface 23 is then designed to collapse when the volume of the unit cells 22 increases.

[0044] Here, an interface 23 is provided for two unit cells 22.

[0045] Each interface 23 is for example in the form of a layer of foam of width and length identical to those of the unit cells 22.

[0046] Here, the interfaces 23 have low thermal conductivities, to form barriers in the event of thermal runaway of a cell.

[0047] When assembled, these interfaces 23 must be compressed in order to guarantee the blocking of the unit cells 22 regardless of the volume that the latter occupy.

[0048] This is why compression plates 25 are provided at the ends of the superposition of unit cells 22 and interfaces 23.

[0049] These compression plates 25 are substantially planar and they have widths and lengths identical to or greater than those of the unit cells 22. They have rigidities greater than those of the unit cells 22. In other words, these compression plates 25 deform less than the unit cells 22 when they are subjected to the same bending resistance test.

[0050] These compression plates 25 are preferably made of a polymer material, which material is preferred for its electrically insulating properties. Alternatively, a metallic material could be used but it would then be preferable to coat it with a layer of electrical insulation.

[0051] It will be noted that these compression plates 25 also have a function of protecting the cells, particularly during the assembly of the module 20.

[0052] As shown for example in Figure 5, this protection function can further be supplemented by means of other plates 60 located against another of the cell sides. These other plates have characteristics identical to those of the compression plates 25 (apart from their widths and lengths which may differ).

[0053] Each module 20 comprises at least one fastener 27 which is designed to keep the unit cells 22 compressed and juxtaposed between the compression plates 25.

[0054] Here, as shown in Figure 5, each fastener 27 is in the form of a staple, with a base 27C and two arms 27A, 27B which are bent at right angles to the base so that they rise from the ends of the base.

[0055] This attachment is for example made by bending a metal rod (made of steel or aluminum alloy). The material used for these attachments preferably has a rigidity greater than or equal to that of the compression plates 25 (its modulus Young's plate has a higher value than compression plates 25).

[0056] Each attachment 27 is in any case manufactured in such a way that the base and the arms are formed from a single piece (they are therefore not assembled).

[0057] Here, the base 27C is rectilinear and has a uniform section, so as to be able to extend along the X axis (perpendicular to the unit cells 22) and to bear simultaneously against one of the sides of each unit cell.

[0058] In practice, the 27C bases all apply against one of the aforementioned protection plates 60.

[0059] The arms 27A, 27B are also rectilinear here and have a uniform section, so as to be able to extend along the compression plates 25, on either side of them.

[0060] Alternatively, the arms could have a non-uniform section, provided that their inner facing faces are flat. Typically, taking into account the stresses that will be exerted on them, the arms could have a section that increases from the base to their free ends. Alternatively, they could have a section that increases then decreases, so that their sections are maximum approximately at half their lengths.

[0061] In the embodiment illustrated in Figure 5, several separate fasteners 27 are provided.

[0062] Indeed, these fasteners 27 have a thickness along the Z axis which is much less than the length of the cells. Thus, several fasteners 27 are necessary along the unit cells 22 in order to ensure sufficient support for the compression plates 25 to prevent them from bending.

[0063] This thickness is illustrated in the drawings as being very low. In practice, it may be higher and represent approximately one tenth of the length of the unit cells 22. In this regard, it may be noted that the thicknesses of the two fasteners located at the ends of the cells may be identical, while the thickness of the fastener positioned in the center of the cells will be higher.

[0064] Here, three separate plates 60 are provided located at the level of the fasteners. Of course, as a variant, a single plate 60, of larger dimension, could be used.

[0065] The fasteners 27, by their shape, are open opposite their base 27C. Consequently, when they overlap the unit cells 22, they leave one side of the unit cells 22 entirely free, that is to say completely open to the outside. It is by this open side that the unit cells 22 are positioned on the cooling wall 10. In this way, the heat exchanges between the unit cells 22 and the cooling wall 10 can take place optimally.

[0066] As shown in Figure 1, the cooling wall 10 is flat and thick. It has internal conduits 11 allowing the circulation of a cooling liquid capable of evacuating to the outside the calories resulting from the heating of the unit cells 22 (this is called a “water plate”).

[0067] In Figure 1, the cooling wall 10 is shown as being positioned below the unit cells 22 (the orientation could of course be different).

[0068] In the remainder of the description, the terms “lower”, “upper”, “above”, “below” will be used taking into account the configuration illustrated in this figure 1.

[0069] The base 27C of each attachment 27 is then located above the unit cells 22.

[0070] The arms 27A, 27B of the fasteners 27 preferably have lengths greater, along the Y axis, than the width of the unit cells, so that they extend below them.

[0071] In this way, the fasteners 27 not only allow the unit cells 22 to be locked together, but they also allow these cells to be locked to the cooling wall 10.

[0072] Indeed, due to their lengths, the arms 27A, 27B of the fasteners 27 can be engaged through openings provided in the cooling wall 10 in order to attach to the latter or to an element located under this cooling wall 10.

[0073] It will further be noted that by fixing the free ends of the arms 27A, 27B to the cooling wall 10, these free ends are locked relative to each other, which prevents the arms from moving apart when the unit cells 22 expand.

[0074] In the embodiment of Figure 1, the free ends of the arms 27A, 27B of the fasteners 27 pass completely through the cooling wall 10, at through openings. Thus, these free ends can be fixed in or under the cooling wall 10. They could typically be folded under the cooling wall 10.

[0075] Alternatively, as shown in Figure 2, the cooling wall 10 may have on its upper face projecting studs which each delimit a housing for the free end of an arm of a fastener 27. Thus, the arms 27A, 27B may be engaged in these studs and fixed there, for example by gluing.

[0076] As a further variant, as shown in Figure 3, the arms can completely pass through the cooling wall 10 and be fixed to a support wall 50 which is here placed under the cooling wall 10 and which supports the latter. In Figure 3, this support wall 50 is perforated so as not to limit the thermal performance of the cooling wall 10.

[0077] In any case, the fasteners 27 make it possible to maintain the unit cells 22 at a distance very close to the cooling wall 10. Here, a layer of a material with high thermal conductivity is then placed between the unit cells 22 and the cooling wall 10 to promote heat exchange between these elements. This is a thermal foam 40.

[0078] Figure 4 shows the main steps of the assembly process of the storage battery 1, which can now be described.

[0079] During a first step E1, the unit cells 22, the interfaces 23 and the compression plates 25 are juxtaposed and are installed between two jaws of a manufacturing tool 90. The plates 60 are then put in place.

[0080] As shown in more detail in Figure 5, the tool 90 comprises a fixed support 95 and two jaws 91, 92 which are mounted movably on this support 95 so as to be able to slide towards each other along the X axis. It further comprises actuators (not shown) making it possible to slide the two jaws towards each other or away from each other.

[0081] The support 95 has a flat face on which the unit cells 22 are installed and on which the two jaws 91, 92 slide.

[0082] The two jaws 91, 92 have facing faces which are also mostly flat and parallel to the plane (YZ).

[0083] These facing faces each have at least one hollow groove 93. More precisely, as many grooves 93 are provided in each jaw 91, 92 as there are fasteners 27 to be placed around the unit cells 22.

[0084] Thus, here, each jaw 91, 92 has three grooves 93, each located opposite one of the grooves of the other jaw. These grooves 93 are rectilinear, so that the arms 27A, 27B of the fasteners 27 can engage therein without effort. They extend along the Y axis and have a section normal to this axis which is here square and the size of which is adjusted to that of the arms of the fasteners 27.

[0085] During the first step E1, the two jaws 91, 92 are pushed by the actuators towards each other in order to compress the interfaces 23 and the unit cells 22 against each other.

[0086] Then, during a second step E2 illustrated in figures 4 and 5, the fasteners 27 are attached on either side of the compression plates 25, by engaging their arms 27A, 27B in the grooves 93 provided for this purpose in the jaws 91, 92.

[0087] These fasteners 27 are well positioned when their bases 27C bear against the upper side of the unit cells 22. Thus, the unit cells are in fact well aligned with each other.

[0088] During a third step E3 illustrated in Figure 4, the jaws are actuated to move away from each other and the modules 20 obtained are extracted from the tool 90.

[0089] In parallel with these steps E1 to E3 (before, during or after these steps), the wall cooling 10 is manufactured, with its cooling pipes 11 and with through openings 12 allowing the passage of the arms 27 A, 27B of the fasteners 27 (step E4).

[0090] During a step E5, this cooling wall 10 is covered on a part of one of its two faces with thermal foam 40. This thermal foam is here applied over the entire surface which will be occupied by the unit cells 22. It is therefore applied in strips, between the through openings 12.

[0091] Finally, during a step E6, the modules 20 are attached to these strips of thermal foam 40, by engaging the arms 27A, 27B of the fasteners 27 in the through openings 12. The free ends of these arms are then fixed to the cooling wall 10 to rigidly block the modules 20 on the latter.

[0092] During this step E6, it may be necessary to apply compressive forces to the external faces of the arms of the fasteners 27, so as to straighten these arms which tend to bend outwards so that they can engage in the through openings 12.

[0093] Finally, the modules 20 are electrically connected to each other.

[0094] So that the accumulator battery 1 thus obtained has optimal compactness, the through openings 12 allowing the arms of the fasteners 27 of the same module to be received are located on two lines, and these lines are merged for two neighboring modules (see figure 4, step E4). Thus, six through openings 12 are provided per line (except for the lines at the ends of the cooling wall 10). In other words, the fasteners 27 of two neighboring modules 20 engage by one of their two arms in openings which are located on the same line, which makes it possible to place these modules 20 very close to each other.

[0095] It is therefore understood that the compression plates 25 of a module 20 placed between two other modules are in contact with the fasteners of these two other modules. Thanks to this configuration, the stresses which are exerted on the fasteners 27 of this module (when the unit cells 22 swell) are partly taken up by these two other modules.

[0096] Of course, as a variant, the modules could be distributed differently on the cooling wall 10.

[0097] Typically, they could be spaced further apart. In this case, stop elements could be placed between these modules, so as to avoid any deformation of the arms during the life of the accumulator cells.

[0098] Alternatively, two modules could be placed in alignment with each other.

[0099] It may happen that once the modules 20 have been assembled, they are not immediately placed on the cooling wall 10. They are then stored. The risk in this case is that the arms of the fasteners 27 gradually move apart, and it is then no longer possible to engage them through the through openings provided in the cooling wall 10. To avoid this happening, the modules can be placed in reusable temporary boxes. Alternatively, temporary clips can be placed on the cells, in head-to-tail positions with the fasteners. In any case, the temporary boxes or clips make it possible to constrain the unit cells and prevent the arms from moving apart during storage of the modules. These temporary boxes or clips are then removed from the modules 20 before the latter are placed on the cooling wall 10.

[0100] We can better understand why we can then consider that the manufacture of a module is completed only when its fasteners 27 are fixed to the cooling wall 10.

[0101] The present invention is in no way limited to the embodiments described above, but those skilled in the art will be able to provide any variation in accordance with the invention.

[0102] Thus, as shown in Figure 6, the fasteners used to fix the unit cells 22 together could have different shapes than a simple staple.

[0103] For example, as shown in the first illustration of Figure 6, the free ends of the arms 127A, 127B of the fasteners 127 could have snap-fastening means adapted to clip onto the underside of the cooling wall 10. As shown in this Figure 6, these snap-fastening means are in the form of teeth 127D projecting from the inner faces of the free ends of the arms. These teeth have triangular shapes to allow the arms to pass through the through openings of the cooling wall 10, but to prevent their removal.

[0104] According to another variant not shown, the free ends of the arms 127A, 127B of the fasteners 127 could form eyelets. Thus, to fix the fasteners, it would suffice to pass rods through two dedicated holes in the cooling wall 10 which would pass through these eyelets and thus block the arms.

[0105] According to another variant shown in the second illustration of Figure 6, the fasteners 27 could be coupled (in pairs as shown, or in threes or even in a greater number) in order to form a single, single-piece part 227.

[0106] Here, this coupling is ensured by two rods 271 which extend respectively from one and the other of the ends of the two arms of one attachment 27 to one and the other of the ends of the two arms of another attachment 27.

[0107] According to another variant shown in the third illustration of Figure 6, the attachment 327 could extend along the Z axis over a length between half the length of the unit cells and the length of the unit cells. It could even be provided that its length is greater than that of the unit cells.

[0108] Thus, a single fastener 327 could be sufficient to assemble these unit cells. This fastener 327 thus has a plate-shaped base 327C and two arms 327A, 327B also in the form of plates. It therefore forms a sort of U-shaped tunnel.

[0109] Alternatively, if its length is greater than that of the unit cells 22, the fastener 327 could be closed at its ends and form a sort of box open on one side only. In this case, the two side walls of this box (i.e. the two arms) would preferably have notches for the passage of the jaws of the assembly tool.

[0110] In the embodiment illustrated in Figure 1, the compression plates 25 extend in height over a height greater than the unit cells 22 (here equal to the sum of the height of these cells and the thickness of the thermal foam 40). This configuration is shown in the first illustration of Figure 7.

[0111] Thus, these compression plates 25 extend from the bases 27C of the fasteners 27 to the cooling wall 10. They thus form a sort of wedge making it possible to guarantee that the distance between the bases 27C of the fasteners 27 and the cooling wall 10 is equal to the desired value.

[0112] Alternatively, as shown in the second illustration of Figure 7, the lower edge of the compression plates 25 could have notches 25A, here two in number, delimiting between them a projecting tongue. This tongue is here coated on its free edge with a metal reinforcement 25B which is for example crimped or force-mounted on the compression plate and which makes it possible to ensure that the compression plate 25 does not deform. Thanks to these notches 25A, the support area of ​​the compression plates 25 on the cooling wall 10 is restricted, which prevents (for example in the event of a lack of flatness of the cooling wall 10) the support being too strong in undesired areas.

[0113] According to another variant, as shown in the third illustration of Figure 7, the lower edges of the compression plates 25 of each module 20 can be folded at right angles to each other, in order to form rims having support functions. In this variant, the bearing surface of the compression plates 25 on the cooling wall 10 is thus larger, which makes it possible to better distribute the stresses. It will be noted that in this variant, the majority of the cells are entirely supported by one of their edges against the thermal foam 40. However, this variant is not preferred since the unit cells located at the ends of the superposition of cells are not entirely so, and they therefore risk being less well cooled than the other cells.

[0114] According to another variant of the invention, the accumulator battery could comprise not a single cooling wall 10, but several. Typically, for reasons of modularity and ease of manufacture, it could comprise one cooling wall 10 per module 20.

[0115] According to yet another variant, it could be provided to glue the unit cells and the interfaces 23 together (as well as possibly the compression plates 25), so as to ensure that when the fasteners 27 are put in place, these components remain well aligned with each other.

Claims

CLAIMS

1. Module (20) of accumulator battery (1), comprising several unit cells (22) and means for holding said unit cells (22) in a juxtaposed position, characterized in that said holding means comprise at least one attachment (27) which has a base (27C) from which extend two arms (27A, 27B) which are located on either side of said unit cells (22) and which are formed from a single piece with said base (27C).

2. Module (20) according to claim 1, in which said holding means comprise several separate fasteners (27), the bases (27C) of all the fasteners (27) are located on the same side of the unit cells (22).

3. Module (20) according to claim 1 or 2, in which two compression plates (25) are provided located on either side of said unit cells (22), and on either side of which are located the arms (27A, 27B) of each attachment (27).

4. Module (20) according to one of claims 1 to 3, in which there is provided between at least two of the unit cells (22) an interface (23) more easily compressible than the unit cells (22).

5. Module (20) according to one of claims 1 to 4, in which the unit cells (22) are juxtaposed in a first direction (X), the arms (27A, 27B) of each attachment (27) extending in length in a second direction (Y) orthogonal to the first direction (X), at least two separate attachments (27) are provided, located at a distance from each other in a third direction (Z) orthogonal to the first and second directions (X, Y), which each have dimensions in the third direction (Z) which are at least ten times smaller than the dimension of the unit cells in this third direction (Z).

6. Module (20) according to one of claims 1 to 5, in which each arm (127A, 127B) has at its end snap-fastening means (127D) adapted to clip onto a wall supporting the unit cells (22).

7. Module (20) according to one of claims 1 to 6, in which, each unit cell (22) being in contact with the base (27C) of the attachment (27) by a first side and having a second side opposite the first side, the arms (27A, 27B) of the attachment (27) have lengths such that they protrude from the second sides of the unit cells (22).

8. Accumulator battery (1) comprising a cooling wall (10) and at least one module (20) according to one of claims 1 to 6, attached to the cooling wall (10) by a side opposite that where said base (27C) is located.

9. A storage battery according to claim 8, wherein the arms (27A, 27B) of the clip (27) are fixed by their ends to said cooling wall (10) or to a support (50) located against said cooling wall (10), opposite said module (20).

10. Method of manufacturing a module (20) of an accumulator battery (1) according to one of claims 1 to 7, comprising steps of: - superposition of unit cells (22), - compression of unit cells (22), - insertion of the compressed unit cells (22) between the arms (27A, 27B) of the attachment (27).

11. Manufacturing tool (90) for a module (20) of an accumulator battery (1) having several juxtaposed unit cells (22), said manufacturing tool (90) comprising two jaws (91, 92) which are mounted to move towards each other to compress the unit cells (22) and which each have at least one groove (93) for the passage of an arm of a fastener, facing the other jaw.

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