Battery tray comprising a multi-density

Abstract

The invention relates to a battery tray for a vehicle battery and a method for producing the same. The battery tray includes a multi-density foam assembly for improved battery cell collision protection wherein at least one segment of the multi-density foam assembly is designed to distribute and transfer impact loads around the battery cells and at least one segment is designed to reduce loads on the battery cells during compression of the multi-density foam assembly.

Description

Technical Field

[0001] The present invention relates to a battery tray for a vehicle battery, the battery tray including a multi-density foam assembly. The present invention also relates to a method for producing a corresponding multi-density foam assembly. Background Art

[0002] A particularly important aspect of vehicle safety is passive crash protection. This includes not only protecting the passenger compartment during a collision through an energy-absorbing structure that may deform, but also providing corresponding protection for vehicle components such as vehicle batteries or fuel tanks that may pose an increased risk in the event of damage. At the same time, these structures are required to be lightweight in order to keep the total vehicle weight low, thus enabling energy-efficient driving, whether it is a conventional fuel-driven or an electric-driven vehicle. A limiting factor on the battery side is cell damage, which must be avoided under any circumstances. Cell damage may be caused by high loads on the battery cells, which is accompanied by high deformation of the cells. It is particularly important to reduce the load level on individual battery cells if the vehicle battery is the traction battery of a hybrid or electric flatbed vehicle where the load is introduced directly into the battery in a line.

[0003] There is still a need to improve the crash protection of battery cells in a battery tray for a vehicle battery. Summary of the Invention

[0004] In a first aspect, the present disclosure relates to a battery tray for a vehicle battery, the battery tray including:

[0005] - one or more battery cells;

[0006] - at least one multi-density foam assembly having at least two integrally formed parts with different densities; and

[0007] - at least one rigid support structure;

[0008] wherein at least one multi-density foam assembly is at least partially disposed between the one or more battery cells and the at least one rigid support structure; and

[0009] the integrally formed part with a higher density is at least partially adjacent to the rigid support structure, and the integrally formed part with a lower density is at least partially adjacent to the battery cells.

[0010] Accordingly, the present disclosure provides a battery tray including a multi-density foam assembly for improved crash protection of battery cells, wherein at least one section of the multi-density foam assembly is designed to distribute an impact load and transfer it around the battery cells, and at least one section is designed to reduce the load on the battery cells during compression of the multi-density foam assembly.

[0011] When referring in this disclosure to an integral part "abutting" a structure, this should be understood as being disposed near the structure, but not necessarily in direct contact with the structure. The two corresponding surfaces may also be in partial contact or not in contact at all. For example, there may be a small gap between an integral part with a lower density and a battery cell to allow air flow for ventilation purposes. A gap of up to 5 cm (preferably, up to 3 cm or up to 1 cm) is considered an abutting structure.

[0012] At least one multi-density foam assembly has integral parts of at least two different densities. In other words, at least one multi-density foam assembly has at least one integral part that has a higher density relative to at least one other integral part. Thus, the at least one other integral part has a lower density relative to the at least one integral part. At least one multi-density foam assembly may have an integral part that has the highest density among all the integral parts of the at least one multi-density foam assembly. At least one multi-density foam assembly may have an integral part that has the lowest density among all the integral parts of the at least one multi-density foam assembly.

[0013] One or more battery cells means at least one battery cell. The battery tray may include a plurality of battery cells.

[0014] In a second aspect, the present disclosure relates to a method for producing a multi-density foam assembly having integral parts of at least two different densities, the method comprising:

[0015] (a) providing a mold having a cavity that is open on one side and corresponds to the desired outer surface of a first integral part of the multi-density foam assembly;

[0016] (b) filling the cavity of the mold with raw materials for a first foam generation process;

[0017] (c) closing the open side of the cavity of the mold with a first closing plate having a surface corresponding to the desired inner surface of the first integral part of the multi-density foam assembly, performing a foam generation process to produce the first integral part of the multi-density foam assembly, and removing the first closing plate from the cavity;

[0018] (d) filling the cavity of the mold including the first integral part with raw materials for a second foam generation process;

[0019] (e) Closing the open side of the cavity of the mold with a second closing plate having a surface corresponding to the desired inner surface and / or outer surface of the second integral part of the multi-density foam assembly, performing a foam generation process to generate the second integral part of the multi-density foam assembly, and removing the second closing plate from the cavity, wherein the outer surface of the second integral part of the multi-density foam assembly is formed by the inner surface of the first integral part and / or the inner surface of the cavity and / or the inner surface of the second closing plate; and

[0020] (f) Repeating steps (d) and (e) for each further desired integral part;

[0021] wherein the steps of filling the raw material into the cavity and closing the open side of the cavity in steps (b) / (c) and (d) / (e) can be performed in the reverse order.

[0022] In another aspect, the present disclosure relates to a battery tray for a vehicle battery, the battery tray being configured to be provided with one or more battery cells, wherein the battery tray includes:

[0023] - at least one multi-density foam assembly having at least two integral parts of different densities; and

[0024] - at least one rigid support structure;

[0025] wherein when the battery cells are mounted on the battery tray, at least one multi-density foam assembly can be at least partially disposed between one or more battery cells and at least one rigid support structure; and

[0026] the integral part having a higher density is at least partially adjacent to the rigid support structure, and the integral part having a lower density is at least partially adjacent to the battery cells.

[0027] Details of the present disclosure

[0028] Details of the present disclosure relate to the aspects described in the Summary of the Invention. Any feature of the embodiments described below can relate to a battery tray for a vehicle battery and a method for producing a multi-density foam assembly having at least two integral parts of different densities.

[0029] In an embodiment, the vehicle battery can be a traction battery of a hybrid or electric vehicle. As described above, it is particularly important to reduce the load level of a single battery cell of such a battery, especially in the case of a flatbed vehicle where the load is directly introduced into the battery in a line. Here, the present disclosure can show the full potential of its improved protection structure. If the vehicle battery is a traction battery, the term "battery cell" should be understood to equally refer to the electronic components of these cells, which are protected from damage in the same way as the individual cells.

[0030] The present disclosure improves the crash protection of battery cells by arranging a single foam component including multiple foam densities inside a battery tray. This multi-density foam component (MDFC) is applied between the rigid support structure (e.g., side members) of the battery tray and the battery cells. The inventors have found that by using a multi-density foam component in this position, very effective load transfer and reduction can be achieved, which combines excellent protection effects and low weight. In addition, the application of the foam enables stable energy absorption throughout the deformation process without failure as in the case of plastic structures.

[0031] For a given type of foam, the stiffness and compression hardness of the foam can be considered to be substantially proportional to its density. Therefore, a specific function can be assigned to each individual foam density in the component, which is designed to reduce the load on the battery cells. To this end, the multi-density foam component is not limited to having two integral parts with different densities or a single type of foam, but can be customized according to the design requirements of the battery cells and their adjacent parts to achieve the best results in terms of force distribution and absorption.

[0032] The first integral part with a higher foam density and the resulting higher stiffness and compression hardness can be used to distribute the crash impact load and transfer it around the cell to adjacent or connected parts or the top and bottom regions of the cell. In addition, the foam can absorb impact energy during its compression. Generally, if more than two integral parts are used, the integral part with the highest foam density is used as the load transfer foam structure.

[0033] The second integral part with a lower foam density is included in the multi-density foam part that overlaps with vulnerable components (e.g., battery cells, sensitive electronics, or the like). These lower foam density parts can be used to reduce the load on the battery during the compression of the multi-density foam component, which results in a higher allowable intrusion into the battery tray without load and thus damage to the battery. They increase the total energy absorption but transfer less load to the surrounding components. However, the lower density foam parts can additionally stabilize the load transfer foam structure during compression.

[0034] In an embodiment, the overall portion of at least one multi-density foam assembly having the highest density may substantially have a C-shaped or U-shaped, pointed arch-shaped or semi-circular cross-sectional shape. "C-shaped or U-shaped" specifically refers to the rectangular shape of the letter, while "semi-circular" refers to a rounded shape. The load-transfer foam structure may have various geometries, and the common feature of these geometries is that one closed side of the shape is arranged towards the expected impact side of the rigid support structure and extends towards the open side of the shape, terminating in two separate regions which are arranged to be spaced apart from the battery cells and sensitive electronic devices. In this way, the impact load on the rigid support structure will be guided around the battery cells.

[0035] In an embodiment, at least one surface of the overall portion of at least one multi-density foam assembly having the highest density may include rib structures. The basic shape of the high-density load-transfer foam structure can also be strengthened by these rib structures, which can be arranged on the surface facing the inside or outside of the battery tray and in a vertical or horizontal direction. This allows for a higher geometric stiffness and compressive hardness of the entire structure in the direction of the impact towards the battery cells.

[0036] In an embodiment, the overall portion of at least one multi-density foam assembly having the highest density may substantially have a C-shaped or U-shaped, where the open side of the contour of the overall portion having the highest density faces the inside of the battery tray, and the overall portion having a lower density may be arranged inside the contour. This design is particularly useful for stabilizing the load-transfer foam structure during compression to prevent uncontrolled deformation and / or collapse.

[0037] In an embodiment, the density of at least one multi-density foam assembly may span a range from 50 g / L to 400 g / L or from 60 g / L to 375 g / L or from 75 g / L to 350 g / L. It has been found that this range provides useful foam properties for the corresponding functions to be achieved by the overall portion.

[0038] In an embodiment, the density of the overall portion having a higher density may span a range from 225 g / L to 400 g / L or from 250 g / L to 375 g / L or from 275 g / L to 350 g / L, and / or the density of the overall portion having a lower density may span a range from 50 g / L to 175 g / L or from 60 g / L to 150 g / L or from 75 g / L to 125 g / L. It has been found that these ranges provide useful foam properties for the corresponding functions to be achieved by the overall portion. In particular, it has been found that the density relationship between the two overall portions provides favorable results for the overall structure of the multi-density foam assembly.

[0039] In an embodiment, at least one multi-density foam component may include one or more of expanded polypropylene (EPP), expanded polystyrene (EPS), expanded polyethylene (EPE), polyurethane rubber (PUR), and polyethylene terephthalate (PET) foam. These types of foams have been shown to be particularly suitable for the manufacture of multi-density foam components and their different functions. As described above, multi-density foam components can also be made using different types of foams. The only limitation regarding the selection of two or more different foam types is the compatibility of the foams and their respective raw materials in the foam production process.

[0040] In an embodiment, the rocker may at least partially abut a face of at least one rigid support structure that is opposite to the face adjacent to at least one multi-density foam component. The rocker disposed on the outer surface of the battery tray that is expected to be impacted during a collision can help distribute the impact load more evenly into the multi-density foam component and thus improve the collision protection effect.

[0041] The method for producing a multi-density foam component is continuous. Individual monolithic parts of different densities are continuously produced within a mold that has a cavity that is open on one side and can be closed with different closing plates. For the first monolithic part, the outer contour is defined by the cavity of the mold and the first closing plate, and the inner contour is defined by the first closing plate. The mold is filled with the raw material for the first foam production process and closed with the first closing plate.

[0042] Any foam production reaction that can be carried out in the mold can be used for the multi-density foam component. Thus, the steps of filling the raw material into the cavity and closing the open side of the cavity with the closing plate can be carried out in the reverse order as may be required for the foam production reaction of each monolithic part. For example, the polyurethane foam reaction mixture can be poured into the cavity before closing the mold, and the injection molding process of expanded polyethylene requires closing the mold before injecting the molten polyethylene and the blowing agent.

[0043] After the foam formation process is completed, the first closing plate is removed from the cavity, and the raw material of the second integral part is filled into the mold closed by the second closing plate. Each cavity for the foam is defined on all sides by the mold and the closing plate (the first integral part), or by a combination of the surfaces of the pre-treated integral parts (the second integral part and additional integral parts). After the second foam formation process is completed, the second closing plate is removed from the mold again. Thereafter, this process is repeated for each further integral part, or the completed multi-density foam assembly can be removed from the mold.

[0044] If pressure must be applied to the raw material of the foam, the manufacturing process can proceed from the high-density part to the low-density part. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A cross-sectional side view of a battery tray according to the present disclosure is shown.

[0046] Figure 2 The results of a simulated pole intrusion test without a rocker block are shown.

[0047] Figure 3 The results of a simulated pole intrusion test with a rocker block are shown.

[0048] Figure 4 The load transfer of an MDFC with two densities around a battery cell according to the present disclosure is shown.

[0049] Figure 5 Shows Figure 4 an MDFC with two densities.

[0050] Figure 6 Shows Figure 5 the C-shaped first integral part of an MDFC with two densities.

[0051] Figure 7 Shows Figure 5 an alternative first integral part of an MDFC with two densities having a C-shape including a rib structure.

[0052] Figure 8 Shows Figure 5 the mold, the first closing plate, and the second closing plate of the production steps of an MDFC with two densities. DETAILED DESCRIPTION

[0053] Figure 1A cross-sectional side view of a battery tray 1 according to the present disclosure is shown. Battery cells 2 grouped by a connection part 5 are located at the center of the battery tray 1. Multi-density foam assemblies 3 are arranged on the left and right sides of the battery cells 2. They are shown here as being in direct contact with the battery cells 2 and the connection part 5 respectively, but there may also be a gap between them for ventilation purposes. The first integral part 3a is a higher-density part that contacts the connection part 5, and the C-shaped horizontal part of the first integral part 3a is used to transfer impact loads into the connection part 5. The second integral part 3b is a lower-density part that contacts the battery cells 2. The C-shaped vertical part of the first integral part 3a contacts a support structure 4 of the battery tray 1. An optional rocker 6 is arranged outside the support structure 4.

[0054] Using Figure 1 the configuration shown, simulations of pole crashes have been calculated, where the pole impacts the rocker 6 from the left or directly impacts the support structure 4, i.e., the simulations are performed with and without the rocker 6 present. As a comparative example, two simulations have been performed with homogeneous foam blocks of the same shape with densities of 130 g / L and 220 g / L. An example of the multi-density foam assembly 3 according to the present disclosure has a first integral part 3a with a density of 300 g / L as a load-bearing structure and a second integral part 3b with a density of 100 g / L as a load-reducing structure.

[0055] Figure 2 The results of a simulated pole intrusion test without the rocker 6 are shown. The upper figure of the cell intrusion according to the pole intrusion shows the maximum cell intrusion, where the 2 mm marks the limit at which it is estimated that the battery cells 2 start to be damaged. For the comparative example of the 220 g / L foam, it has been observed that the load is directly transferred to the cells, while for the comparative example of the softer 130 g / L foam and the example of the multi-density foam assembly 3, significant unloading has been measured, which results in a higher allowable intrusion.

[0056] The lower figure shows the force and the absorbed energy according to the pole intrusion. The absorbed energy is determined at the start of cell damage. When compared with the comparative example of the softer 130 g / L foam and the example of the multi-density foam assembly 3, the comparative example of the 220 g / L foam shows a high force but a low energy absorption capacity. In addition, the example of the multi-density foam assembly 3 is able to absorb 10% more energy than the comparative example of the softer 130 g / L foam.

[0057] Figure 3Shows the results of the simulated pole intrusion test with the rocker block 6. Here, the multi-density foam assembly 3 according to the present disclosure demonstrates its full potential. The upper figure of the cell intrusion according to the pole intrusion shows the maximum cell intrusion again, where the 2 mm marks the limit at which it is estimated that the battery cell 2 starts to be damaged. When compared with the two homogeneous foams of the comparative examples, the multi-density foam assembly 3 according to the present disclosure shows the highest allowable pole intrusion while transferring the lowest load to the battery cells 2 of all three simulated foam assemblies.

[0058] The lower figure shows again the force and the absorbed energy according to the pole intrusion. Also in this category, the multi-density foam assembly 3 according to the present disclosure has shown the best performance. Although the homogeneous foams of the comparative examples have absorbed a considerable amount of energy until the cells are damaged, but at different force and displacement levels, the multi-density foam assembly 3 according to the present disclosure has combined an increased force level (when compared with the 130 g / L foam comparative example) with a high displacement (when compared with the 220 g / L foam comparative example). Therefore, the multi-density foam assembly 3 according to the present disclosure has achieved a significantly higher absorbed energy, increasing by 22% from 69 kJ to 84 kJ.

[0059] When compared with the results without the rocker block 6, the improved results of the rocker block 6 can be explained by the supporting function of the integral part 3a with high-density foam for the folding of the contour of the rocker block 6, which results in a more effective compression of the extruded part.

[0060] Figure 4 Schematically shows the load transfer of the multi-density foam assembly 3 according to the present disclosure with two integral parts 3a, 3b around the battery cell 2 and into the connection part 5. The resulting main load paths are indicated by arrows. As Figure 1 shown, the multi-density foam assembly 3 has a first integral part 3a with high density as a load-bearing structure and a second integral part 3b with low density as a load-reducing structure. An impact with a high load from the left indicated by the large arrow will be reduced by the first integral part 3a and transferred into the support structure around the cell and / or the connection part 5. The battery cell 2 is protected by the second integral part 3b, which also prevents the structural collapse of the first integral part 3a.

[0061] Figure 5 Shows Figure 4 an enlarged view of the multi-density foam assembly 3 with two integral parts 3a, 3b.

[0062] In Figure 6 and Figure 7 shown are Figure 5 two alternative design variants of the first integral part 3a with high density of the multi-density foam assembly 3.Figure 6 shows a first integral part 3a of a common rectangular C-shape. Figure 7 Shows an alternative design of the first integral part 3a, where the C-shape includes a reinforcing rib structure on its inner vertical surfaces. These structures are not limited to the illustrated vertical cubic ribs, but can also be arranged horizontally and / or have a semi-cylindrical or triangular prism shape. The shape can basically be any uniform prism. Additionally, the rib structure can also be arranged on the horizontal surface additionally or alternatively.

[0063] Figure 8 Exemplarily shows Figure 5 a cross-section of a mold 7, a first closing plate 9, and a second closing plate 10 of the production steps of a multi-density foam assembly 3 having two integral parts 3a, 3b. In the first step, a first integral part 3a with a higher density is produced. The mold 7 is provided, and its cavity 8 defines the outer contour of the first integral part 3a. The cavity 8 is filled with raw materials for the first foam generation process. These raw materials can be foam raw materials such as EPP spheres or balls or foam monomers. Then the mold 7 is closed with the first closing plate 9, and the first closing plate 9 defines the inner shape of the first integral part 3a and the outer surface facing the open side of the mold 7. For example, in the case of foam monomers, the mold 7 can be closed with the first closing plate 9 before injecting them into the closed mold. If necessary, pressure can be applied to the first closing plate 9 or the mold 7 to achieve the desired foam density. Thereafter, the foam generation process is carried out, for example, by applying heat to the mold 7 to trigger the expansion and adhesion of the EPP spheres. This situation is shown on Figure 8 the left side of

[0064] After the foam generation process is completed, the first closing plate 9 is removed, and the raw materials for the second foam generation process for the second integral part 3b are filled into the cavity 8 of the mold 7 including the first integral part 3a. Thus, the outer contour of the second integral part 3b is defined by the inner contour of the first integral part 3a and its inner shape, and the outer surface facing the open side of the mold 7 is defined by the second closing plate 10 for closing the mold 7. The choice of raw materials must ensure adhesion to the integral part manufactured in the previous step. In the example shown on Figure 8 the right side of , the second integral part 3b does not have an inner contour because the multi-density foam assembly 3 to be produced has a cuboid shape and only two integral parts. Therefore, the second closing plate 10 can be a simple flat plate. After the second foam generation process is completed, the second closing plate 10 is removed, and the completed multi-density foam assembly 3 can be taken out.

[0065] If the desired multi-density foam assembly 3 has more than two integral parts, the foam generation process is repeated accordingly, with each further integral part having a corresponding closure plate. The further integral parts need not be arranged in a shell-like manner but can, for example, be arranged side by side. This can be used to adapt the load-reducing effect to the specific design of the battery cell 2 (such as the cell and the electronics).

[0066] Reference signs

[0067] 1 Battery tray

[0068] 2 Battery cell

[0069] 3 Multi-density foam assembly

[0070] 3a, 3b Integral parts

[0071] 4 Support structure

[0072] 5 Connecting part

[0073] 6 Rocker

[0074] 7 Mold

[0075] 8 Cavity

[0076] 9 First closure plate

[0077] 10 Second closure plate.

Claims

1. A battery tray (1) for a vehicle battery, comprising: - one or more battery cells (2); - at least one multi-density foam component (3) having at least two integral parts (3a, 3b) of different density; and - at least one rigid supporting structure (4); wherein the at least one multi-density foam component (3) is at least partially arranged between the one or more battery cells (2) and the at least one rigid support structure (4); and The integral portion (3a) having a higher density at least partially adjoins the rigid support structure (4), and the integral portion (3b) having a lower density at least partially adjoins the battery cell (2).

2. The battery tray (1) according to claim 1, wherein: The vehicle battery is a traction battery of a hybrid or electric vehicle.

3. The battery tray (1) according to claim 1 or 2, wherein: The integral portion (3a) having the highest density of the at least one multi-density foam component (3) substantially has a C-shaped or U-shaped, pointed arch-shaped or semicircular cross-sectional shape.

4. The battery tray (1) according to at least one of the preceding claims, wherein: The integral portion (3a) with the highest density of the at least one multi-density foam component (3) substantially has a C-shape or a U-shape, the open side of the contour of the integral portion (3a) faces the interior of the battery tray, and the integral portion (3b) with a lower density is arranged inside the contour.

5. The battery tray (1) according to at least one of claims 3 or 4, wherein: At least one surface of the integral portion (3a) having the highest density of the at least one multi-density foam component (3) comprises a rib structure.

6. The battery tray (1) according to at least one of the preceding claims, wherein: The density of the at least one multi-density foam component (3) spans the range from 50 g / L to 400 g / L, or from 60 g / L to 375 g / L, or from 75 g / L to 350 g / L.

7. The battery tray (1) according to at least one of the preceding claims, wherein: - the density of said integral part (3a) with higher density spans the range from 225 g / L to 400 g / L or from 250 g / L to 375 g / L or from 275 g / L to 350 g / L; and / or - the density of said integral part (3b) with lower density spans the range from 50 g / L to 175 g / L or from 60 g / L to 150 g / L or from 75 g / L to 125 g / L.

8. The battery tray (1) according to at least one of the preceding claims, wherein: The at least one multi-density foam component (3) comprises one or more of expanded polypropylene (EPP), expanded polystyrene (EPS), expanded polyethylene (EPE), polyurethane rubber (PUR) and polyethylene terephthalate (PET) foam.

9. The battery tray (1) according to at least one of the preceding claims, wherein: The rocker (6) at least partially abuts a surface of the at least one rigid support structure (4) opposite to the surface abutting the at least one multi-density foam component (3).

10. A method for producing a multi-density foam component (3) having at least two integral parts (3a, 3b) of different densities, comprising: (a) providing a mold (7) having a cavity (8) which is open on one side and corresponds to the desired outer surface of the first integral portion (3a) of the multi-density foam component (3); (b) filling the raw material for the first foam generation process into the cavity (8) of the mold (7); (c) closing the open side of the cavity (8) of the mold (7) with a first closing plate (9) having a surface corresponding to the desired inner surface of the first integral part (3a) of the multi-density foam component (3), performing the foam production process to produce the first integral part (3a) of the multi-density foam component (3), and removing the first closing plate (9) from the cavity (8); (d) filling a raw material for a second foam generation process into the cavity (8) of the mold (7) including the first integral part (3a); (e) closing the open side of the cavity (8) of the mold (7) with a second closing plate (10), the second closing plate (10) having a surface corresponding to a desired inner surface and / or outer surface of the second integral part (3b) of the multi-density foam component (3), performing the foam generating process to generate the second integral part (3b) of the multi-density foam component (3), and removing the second closing plate (10) from the cavity (8), wherein the outer surface of the second integral part (3b) of the multi-density foam component (3) is formed by the inner surface of the first integral part (3a) and / or the inner surface of the cavity (8) and / or the inner surface of the second closing plate (10); and (f) repeating steps (d) and (e) for each further desired integral portion; The steps of filling the cavity (8) with the raw material and closing the open side of the cavity (8) in steps (b) / (c) and (d) / (e) can be performed in reverse order.

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